mineralogy new

MINERALOGYMINERALOGY(GEO 121)(GEO 121)

Arlene E. DayaoArlene E. Dayao

MINERALOGYMINERALOGY

Also referred to as mineral scienceAlso referred to as mineral science The study of naturally occurring, crystalline substances – The study of naturally occurring, crystalline substances –

mineralsminerals Basic to an understanding of the materials largely Basic to an understanding of the materials largely

responsible for our present technologic cultureresponsible for our present technologic culture

MINERALMINERAL A naturally occurring homogeneous solid with a definite (but A naturally occurring homogeneous solid with a definite (but

not necessarily fixed) chemical composition and a highly not necessarily fixed) chemical composition and a highly ordered atomic arrangement. It is usually formed by ordered atomic arrangement. It is usually formed by inorganic processes.inorganic processes. naturally occurringnaturally occurring – formed by natural processes and not – formed by natural processes and not

in the laboratoryin the laboratory

**diamond vs. synthetic diamond vs. synthetic diamond

*CaCO*CaCO33 concentric layers in water mains concentric layers in water mains homogeneous solidhomogeneous solid – consists of a single solid substance – consists of a single solid substance

that can not be physically subdivided into simpler that can not be physically subdivided into simpler chemical compoundschemical compounds

*H*H22O - ice in glaciersO - ice in glaciers

*water*water mineraloidsmineraloids

*liquid mercury*liquid mercury

definite chemical compositiondefinite chemical composition – can be expressed by a – can be expressed by a specific chemical formulaspecific chemical formula

**Quartz – SiO – SiO22

*Dolomite – CaMg(CO*Dolomite – CaMg(CO33))2 2 or Ca(Mg,Fe,Mn)(COor Ca(Mg,Fe,Mn)(CO33))2 2

ordered atomic arrangementordered atomic arrangement – has an internal structural – has an internal structural framework of atoms or ions arranged in a regular geometric framework of atoms or ions arranged in a regular geometric pattern (crystalline)pattern (crystalline)

*glass – natural solid but amorphous - mineraloid*glass – natural solid but amorphous - mineraloid formed by inorganic processesformed by inorganic processes – includes some organically- – includes some organically-

formed compoundsformed compounds

*CaCO*CaCO33 (aragonite) of mollusk shells (aragonite) of mollusk shells

*elemental sulfur – formed by bacterial action*elemental sulfur – formed by bacterial action

*iron oxide – precipitated by iron bacteria*iron oxide – precipitated by iron bacteria

*mineral fuels - naturally formed but no definite chemical *mineral fuels - naturally formed but no definite chemical composition and no ordered atomic arrangementcomposition and no ordered atomic arrangement

*graphite – formed when coal is subjected to high temp. *graphite – formed when coal is subjected to high temp.

HISTORY OF MINERALOGYHISTORY OF MINERALOGY Recent science but the practice of mineralogical arts is as old as Recent science but the practice of mineralogical arts is as old as

human civilizationhuman civilization Cave paintings of early humans – used natural pigments such as Cave paintings of early humans – used natural pigments such as

red hematite (Fered hematite (Fe22OO33) and black manganese (Mn)) and black manganese (Mn) Stone Age – flint tools were prized possessions (paleolithic and Stone Age – flint tools were prized possessions (paleolithic and

neolithic ages)neolithic ages) Nile Valley – tomb paintings 5000 yrs. ago show busy artificers Nile Valley – tomb paintings 5000 yrs. ago show busy artificers

weighing malachite and precious metals, smelting mineral ores weighing malachite and precious metals, smelting mineral ores and making delicate gems of lapis lazuli and emeraldand making delicate gems of lapis lazuli and emerald

Bronze Age – other minerals were sought from which metals Bronze Age – other minerals were sought from which metals could be extractedcould be extracted

384-322 BC Aristotle - theorized that all the known substances 384-322 BC Aristotle - theorized that all the known substances were composed of water, air, earth, and fire and wrote were composed of water, air, earth, and fire and wrote “Meteorologica”“Meteorologica”

372-287 BC Greek Philosopher Theophrastus – 1372-287 BC Greek Philosopher Theophrastus – 1stst written work written work on minerals on minerals “De Mineralibus”“De Mineralibus”

Pliny (400 yrs. later) recorded mineralogical thought of his time Pliny (400 yrs. later) recorded mineralogical thought of his time and wrote and wrote “Naturalis Historia”“Naturalis Historia”

HISTORY OF MINERALOGYHISTORY OF MINERALOGY

1556 Georgius Agricola, German physician, Father of 1556 Georgius Agricola, German physician, Father of Mineralogy, published “De Re Metallica” – signaled the Mineralogy, published “De Re Metallica” – signaled the emergence of mineralogy as a science emergence of mineralogy as a science - Detailed account of mining practices of the time and - Detailed account of mining practices of the time and

includes the first factual account of mineralsincludes the first factual account of minerals 1912 US Pres. Herbert Hoover - translated “De Re Metallica” 1912 US Pres. Herbert Hoover - translated “De Re Metallica”

from Latin to Englishfrom Latin to English 1669 Nicholas Steno – important contribution to crystallo-1669 Nicholas Steno – important contribution to crystallo-

graphy through his study of quartz crystalsgraphy through his study of quartz crystals- Noted that despite differences in origin, size or habit, the - Noted that despite differences in origin, size or habit, the

angles between corresponding faces were constantangles between corresponding faces were constant 1780 Carangeot – invented contact goniometer to measure 1780 Carangeot – invented contact goniometer to measure

interfacial crystal anglesinterfacial crystal angles 1783 Romé de I’Lsle – made angular measurements on 1783 Romé de I’Lsle – made angular measurements on

crystals and formulated the law of consistency of interfacial crystals and formulated the law of consistency of interfacial angleangle


1784 René Haüy – showed that crystals were built by 1784 René Haüy – showed that crystals were built by stacking together tiny identical building blocks which he stacking together tiny identical building blocks which he called integral moleculescalled integral molecules

1801 Haüy – developed theory of rational indices for crystal 1801 Haüy – developed theory of rational indices for crystal facesfaces

1809 Wollaston – invented the reflecting goniometer that 1809 Wollaston – invented the reflecting goniometer that permitted highly accurate measurement of the positions of permitted highly accurate measurement of the positions of crystal facescrystal faces

1779 to 1848 Berzelius – developed the principles of our 1779 to 1848 Berzelius – developed the principles of our present chemical classification of mineralspresent chemical classification of minerals

1815 Cordier – initiated the immersion method which 1815 Cordier – initiated the immersion method which developed into an important technique for the study of optical developed into an important technique for the study of optical properties of mineral fragmentsproperties of mineral fragments

1828 William Nicol – invented a polarizing device that 1828 William Nicol – invented a polarizing device that permitted the systematic study of the behavior of light in permitted the systematic study of the behavior of light in crystalline substances crystalline substances


Late 19Late 19thth century Federov, Schoenflies and Barlow – century Federov, Schoenflies and Barlow – simultaneously developed theories for the internal symmetry simultaneously developed theories for the internal symmetry and order within crystals which became the foundations for and order within crystals which became the foundations for X-ray crystallographyX-ray crystallography

1912 Max von Laue – demonstrated that crystal could 1912 Max von Laue – demonstrated that crystal could diffract X-raysdiffract X-rays

- Proved that for the first time the regular and ordered - Proved that for the first time the regular and ordered arrangement of atoms in crystalline materialarrangement of atoms in crystalline material

1914 W.H. Bragg and W.L. Bragg – earliest crystal structure 1914 W.H. Bragg and W.L. Bragg – earliest crystal structure determinations were publisheddeterminations were published

1960s – advent of electron microprobe used in the study of 1960s – advent of electron microprobe used in the study of chemistry of minerals on a microscale chemistry of minerals on a microscale

ECONOMIC IMPORTANCE OF MINERALSECONOMIC IMPORTANCE OF MINERALS Before historic time - minerals have played a major role in Before historic time - minerals have played a major role in

man’s way of life and standard of livingman’s way of life and standard of living Present day – we depend on minerals in countless ways:Present day – we depend on minerals in countless ways:

ConstructionConstruction Manufacture of TV setsManufacture of TV sets CosmeticsCosmetics Household cleansers and abrasivesHousehold cleansers and abrasives Textile manufactureTextile manufacture Medical purposesMedical purposes Manufacture of appliances and furnitureManufacture of appliances and furniture Currency and dollar reserves (gold)Currency and dollar reserves (gold) Paint pigmentsPaint pigments Fertilizer and fertilizer carriersFertilizer and fertilizer carriers MachineriesMachineries

NAMING OF MINERALSNAMING OF MINERALS MINERAL CLASSIFICATION – based on the presence of MINERAL CLASSIFICATION – based on the presence of

major chemical component (anions or anionic complex)major chemical component (anions or anionic complex) Native elementsNative elements PhosphatesPhosphates SulfidesSulfides NitratesNitrates SulfosaltsSulfosalts BoratesBorates OxidesOxides and Hydroxidesand Hydroxides SulfatesSulfates HalidesHalides TungstatesTungstates CarbonatesCarbonates Silicates, etcSilicates, etc

- Requires chemical analysis and measurement of physical - Requires chemical analysis and measurement of physical properties such as specific gravity, optical properties and properties such as specific gravity, optical properties and x-ray parametersx-ray parameters

NAMING OF MINERALS – based on some physical property NAMING OF MINERALS – based on some physical property or chemical aspect, named after a locality, a public figure, a or chemical aspect, named after a locality, a public figure, a mineralogist or any other subject considered appropriate mineralogist or any other subject considered appropriate

NAMING OF MINERALSNAMING OF MINERALS Examples of mineral names:Examples of mineral names:

Albite (NaAlSiAlbite (NaAlSi33OO88) from Latin ) from Latin albusalbus (white) in allusion to its (white) in allusion to its colorcolor

Rhodonite (MnSiORhodonite (MnSiO33) from Greek ) from Greek rhodonrhodon ( a rose) in ( a rose) in allusion to its characteristically pink colorallusion to its characteristically pink color

Chromite (FeCrChromite (FeCr22OO44) due to presence of high amounts of ) due to presence of high amounts of chromiumchromium

Magnetite (FeMagnetite (Fe33OO44) due to its magnetic property) due to its magnetic property Franklinite (ZnFeFranklinite (ZnFe22OO44) after a locality (Franklin, New ) after a locality (Franklin, New

Jersey) where it occurs as the dominant zinc mineralJersey) where it occurs as the dominant zinc mineral Sillimanite (AlSillimanite (Al22SiOSiO33) after Professor Benjamin Silliman of ) after Professor Benjamin Silliman of

Yale University (1779-1864)Yale University (1779-1864) International Mineralogical Association (Commission on New International Mineralogical Association (Commission on New

Minerals and New Mineral Names) reviews all new mineral Minerals and New Mineral Names) reviews all new mineral descriptions and appropriateness of namesdescriptions and appropriateness of names

NAMING OF MINERALSNAMING OF MINERALS As of 2004 there are over As of 2004 there are over 4,000 species of minerals of minerals

recognized by the IMA.recognized by the IMA. 150 can be called "common,“150 can be called "common,“ 50 are "occasional,“50 are "occasional,“ the rest are "rare" to "extremely rare.“the rest are "rare" to "extremely rare.“

PHYSICAL PROPERTIES OF PHYSICAL PROPERTIES OF MINERALSMINERALS

PROPERTIES OF MINERALSPROPERTIES OF MINERALS

Dependent on:Dependent on: Chemistry of mineralsChemistry of minerals

chemical composition of mineralschemical composition of minerals Structure of mineralsStructure of minerals

geometrical arrangement of the constituent atoms or geometrical arrangement of the constituent atoms or ionsions

nature of electrical forces that bind the atoms nature of electrical forces that bind the atoms togethertogether

PHYSICAL PROPERTIES OF MINERALSPHYSICAL PROPERTIES OF MINERALS Macroscopic expression of the mineral’s internal makeup, Macroscopic expression of the mineral’s internal makeup,

specifically its crystal structure and chemical compositionspecifically its crystal structure and chemical composition

1.1. Crystal shapeCrystal shape1.1. Crystal formCrystal form2.2. Crystal habitCrystal habit

2.2. Properties based on Properties based on interaction with lightinteraction with light1.1. DiaphaneityDiaphaneity2.2. LusterLuster3.3. StreakStreak4.4. Play of colorsPlay of colors5.5. Chatoyancy and Chatoyancy and

asterismasterism6.6. LuminescenceLuminescence

3.3. Mechanical propertiesMechanical properties1.1. CleavageCleavage2.2. FractureFracture3.3. PartingParting4.4. HardnessHardness5.5. TenacityTenacity

4.4. Properties related to Properties related to massmass1.1. DensityDensity2.2. Specific gravitySpecific gravity

5.5. Other diagnostic Other diagnostic propertiesproperties

PHYSICAL PROPERTIES OF MINERALSPHYSICAL PROPERTIES OF MINERALS

6.6. Other diagnostic Other diagnostic propertiesproperties1.1. MagnetismMagnetism2.2. RadioactivityRadioactivity3.3. Solubility in acidsSolubility in acids4.4. Sensor propertiesSensor properties5.5. Electrical propertiesElectrical properties

CRYSTAL SHAPECRYSTAL SHAPE

a.a. Crystal form – the outward appearance of a mineral in a Crystal form – the outward appearance of a mineral in a regular geometric shaperegular geometric shape

- external form is the outward expression - external form is the outward expression ofof

the internal ordered atomic arrangementthe internal ordered atomic arrangement - examples: garnet – dodecahedron- examples: garnet – dodecahedron

pyrite – cubic pyrite – cubic a.a. Crystal habit – general shape of a mineral which also Crystal habit – general shape of a mineral which also

includes irregularities due to growthincludes irregularities due to growth

CRYSTAL FORMSCRYSTAL FORMS If mineral specimens display well-developed crystal forms, If mineral specimens display well-developed crystal forms,

geometric form names are used to describe a mineral’s geometric form names are used to describe a mineral’s outward appearance:outward appearance: Prismatic – a crystal with one dimension much longer Prismatic – a crystal with one dimension much longer

than the other twothan the other two Rhombohedral – having the external form of a Rhombohedral – having the external form of a

rhombohedronrhombohedron Cubic – having the external form of a cubeCubic – having the external form of a cube Octahedral – with the external form of an octahedronOctahedral – with the external form of an octahedron

CRYSTAL HABITCRYSTAL HABIT Crystal habit - typical appearance (shape and size) of Crystal habit - typical appearance (shape and size) of

crystalscrystals the many terms used by mineralogists to describe crystal the many terms used by mineralogists to describe crystal

habits are useful in communicating what specimens of a habits are useful in communicating what specimens of a particular mineral often look likeparticular mineral often look like

helps in identification of mineralshelps in identification of minerals some habits are distinctive of certain minerals, although some habits are distinctive of certain minerals, although

most minerals exhibit many differing habits (the most minerals exhibit many differing habits (the development of a particular habit is determined by the development of a particular habit is determined by the details of the conditions during the mineral formation/crystal details of the conditions during the mineral formation/crystal growth)growth)

warning: crystal habit may mislead the inexperienced as a warning: crystal habit may mislead the inexperienced as a mineral's internal crystal system can be hidden or disguisedmineral's internal crystal system can be hidden or disguised

minerals belonging to the same crystal system do not minerals belonging to the same crystal system do not necessarily exhibit the same habit necessarily exhibit the same habit

CRYSTAL HABITSCRYSTAL HABITS Factors that influence the type of Crystal Habits:Factors that influence the type of Crystal Habits:

a combination of two or more crystal formsa combination of two or more crystal forms trace impurities present during growthtrace impurities present during growth crystal twinning (occurs when two separate crystals crystal twinning (occurs when two separate crystals

share some of the same crystal lattice points in a share some of the same crystal lattice points in a symmetrical manner) symmetrical manner)

growth conditions (i.e., heat, pressure, space) growth conditions (i.e., heat, pressure, space)

HABITS OF CRYSTALS & CRYSTAL AGGREGATESHABITS OF CRYSTALS & CRYSTAL AGGREGATESHABITHABIT DESCRIPTIONDESCRIPTION EXAMPLEEXAMPLE

AcicularAcicular Needle-like, slender and/or Needle-like, slender and/or tapered, from Greek tapered, from Greek aciculaacicula meaning “root” meaning “root”

Rutile in quartz, sillimanite Rutile in quartz, sillimanite

Amygdaloidal Amygdaloidal Almond-shaped Almond-shaped Heulandite Heulandite

Anhedral Anhedral Poorly formed, external crystal Poorly formed, external crystal faces not developed faces not developed

Olivine Olivine

Bladed Bladed Individual crystals are flattened, Individual crystals are flattened, blade-like, slender and elongated blade-like, slender and elongated

Kyanite, stibniteKyanite, stibnite

Botryoidal or Botryoidal or globular globular

Grape-like, hemispherical masses, Grape-like, hemispherical masses, from Greek from Greek botrysbotrys meaning meaning “bunch” “bunch”

Smithsonite,Hemimorphite,Smithsonite,Hemimorphite,prehnite, chalcedony, prehnite, chalcedony, adamite and variscite adamite and variscite

Columnar Columnar Stout, column-like individualsStout, column-like individuals Calcite Calcite

Coxcomb Coxcomb Aggregated flaky or tabular Aggregated flaky or tabular crystals closely spacedcrystals closely spaced

Barite Barite

Dendritic or Dendritic or arborescent arborescent

Tree-like, branching in one or more Tree-like, branching in one or more direction from central point, from direction from central point, from dendrrondendrron meaning “tree” meaning “tree”

Magnesite in opal, Magnesite in opal, manganese oxides manganese oxides

CRYSTAL HABITSCRYSTAL HABITSHABITHABIT DESCRIPTIONDESCRIPTION EXAMPLEEXAMPLE

Dodecahedral Dodecahedral Dodecahedron, 12-sided Dodecahedron, 12-sided Garnet Garnet

Drusy or Drusy or encrustation encrustation

Aggregate of minute crystals Aggregate of minute crystals coating a surface coating a surface

Uvarovite Uvarovite

Enantiomorphic Enantiomorphic Mirror-image habit and optical Mirror-image habit and optical characteristics; right- and left-characteristics; right- and left-handed crystals handed crystals

Quartz Quartz

Equant, stout, Equant, stout, stubby or blocky stubby or blocky

Length, width, and breadth roughly Length, width, and breadth roughly equal equal

Zircon Zircon

Euhedral Euhedral Well-formed, external crystal faces Well-formed, external crystal faces developed developed

Spinel Spinel

Fibrous or Fibrous or columnar columnar

Extremely slender prisms that are Extremely slender prisms that are flexible thread-like grains or fibers flexible thread-like grains or fibers

Tremolite, chrysotile Tremolite, chrysotile

Filiform or Filiform or capillary capillary

Hair-like or thread-like, extremely Hair-like or thread-like, extremely fine fine

Natrolite Natrolite

Foliated or Foliated or micaceous micaceous

Layered structure, parting into thin Layered structure, parting into thin sheets easilysheets easily

Mica Mica


Granular Granular Aggregates of anhedral crystals 2-Aggregates of anhedral crystals 2-10 mm. in matrix 10 mm. in matrix

Scheelite Scheelite

Hemimorphic Hemimorphic Doubly terminated crystal with two Doubly terminated crystal with two differently shaped ends differently shaped ends

Hemimorphite Hemimorphite

Mamillary Mamillary Breast-like: surface formed by Breast-like: surface formed by intersecting partial spherical intersecting partial spherical shapes shapes

Malachite Malachite

Massive or Massive or compact compact

Shapeless, no distinctive external Shapeless, no distinctive external crystal shape, very fine grained crystal shape, very fine grained

Serpentine, goethite Serpentine, goethite

Nodular or Nodular or tuberose tuberose

Deposit of roughly spherical form Deposit of roughly spherical form with irregular protuberances with irregular protuberances

Geodes Geodes

Octahedral Octahedral Octahedron, eight-sided (two Octahedron, eight-sided (two pyramids base to base) pyramids base to base)

Diamond Diamond

Plumose Plumose Fine, feather-like scales Fine, feather-like scales Mottramite Mottramite

Prismatic Prismatic Elongate, prism-like: crystal faces Elongate, prism-like: crystal faces parallel to c-axis well-developed parallel to c-axis well-developed

Tourmaline Tourmaline


Pseudo-Pseudo-hexagonal hexagonal

hexagonal appearance due to hexagonal appearance due to cyclic twinning cyclic twinning

Aragonite Aragonite

Pseudomor-Pseudomor-phous phous

Occurring in the shape of another Occurring in the shape of another mineral through pseudomorphous mineral through pseudomorphous replacement replacement

Tiger's eye Tiger's eye

Radiating or Radiating or divergent divergent

Acicular crystals radiating outward Acicular crystals radiating outward from a central point from a central point

Pyrite suns, wavellite, Pyrite suns, wavellite, goethite goethite

Reniform or Reniform or colloform colloform

Similar to mamillary: intersecting Similar to mamillary: intersecting kidney-shaped masses kidney-shaped masses

Hematite Hematite

Reticulated Reticulated Acicular crystals forming net-like Acicular crystals forming net-like intergrowths intergrowths

Cerussite Cerussite

Rosette Rosette Platy, radiating rose-like aggregate Platy, radiating rose-like aggregate Gypsum Gypsum

Sphenoid Sphenoid Wedge-shaped Wedge-shaped Sphene Sphene

Stalactitic Stalactitic Forming as stalactites or Forming as stalactites or stalagmites: cylindrical or cone-stalagmites: cylindrical or cone-shapedshaped

Rhodochrosite Rhodochrosite


Stellate Stellate Star-like, radiating Star-like, radiating Pyrophyllite Pyrophyllite

Striated/stria-Striated/stria-tions tions

Surface growth lines parallel or Surface growth lines parallel or perpendicular to a crystallographic perpendicular to a crystallographic axis axis

Chrysoberyl Chrysoberyl

Subhedral Subhedral External crystal faces only partially External crystal faces only partially developed developed

Tabular Tabular Flat, tablet-shaped, prominent Flat, tablet-shaped, prominent pinnacoid pinnacoid

Ruby Ruby

Wheat sheaf Wheat sheaf Aggregates resembling hand-Aggregates resembling hand-reaped wheat sheaves reaped wheat sheaves

Zeolites Zeolites

LamellarLamellar Made up of layers, like the leaves Made up of layers, like the leaves in a bookin a book

Graphite, molybdeniteGraphite, molybdenite

BandedBanded Single mineral may show a thin Single mineral may show a thin and roughly parallel banding, or 2 and roughly parallel banding, or 2 or more minerals form a finely or more minerals form a finely banded intergrowth banded intergrowth

Banded malachite, chert Banded malachite, chert and hematite intergrowthand hematite intergrowth


ConcentricConcentric Bands or layers are arranged Bands or layers are arranged concentrically about one or more concentrically about one or more centerscenters

AgateAgate

GeodeGeode A rock cavity lined with mineral A rock cavity lined with mineral matter but not completely filled. matter but not completely filled. Maybe banded as in agates, Maybe banded as in agates, containing a central portion filled containing a central portion filled with euhedral crystals projecting with euhedral crystals projecting into an open spaceinto an open space

OoliticOolitic Made up of oolites, which are Made up of oolites, which are small, round or ovate accretionary small, round or ovate accretionary bodies and resemble the roe of fishbodies and resemble the roe of fish

Oolitic iron oreOolitic iron ore

PisoliticPisolitic Made up of pea-sized grains, Made up of pea-sized grains, similar to oolitic but coarser similar to oolitic but coarser

BauxiteBauxite

CRYSTAL HABITCRYSTAL HABIT Qualities of Crystal Development:

Euhedral – a mineral that is completely bounded by crystal faces (well-formed); from the Greek eu which means “good” and “hedron” meaning “plane”

Subhedral – a mineral grain that is partly bounded by crystal faces and partly by irregular surfaces; from the Greek sub which means “less than”

Anhedral – a mineral that lacks crystal faces and that may show rounded or irregular surfaces; from the Greek an meaning “without”

The qualities are a reflection of the space that was available to the crystal at the time of its growth

DIAPHANEITYDIAPHANEITY a measure of the amount of light that can be

transmitted by a mineral (light-transmitting qualities) From the Greek work diaphanes meaning “transpa-

rent” TransparentTransparent – transmits light allowing objects to

be seen through it (ulexite, gemstones) TransluscentTransluscent – capable of transmitting light

diffusely but it is not ransparent. It does not show a sharp outline of an object seen through it.

OpaqueOpaque – impervious to visible ligh, even on thin edges of the mineral

LUSTERLUSTER LusterLuster – refers to the general appearance of a mineral – refers to the general appearance of a mineral

surface in reflected lightsurface in reflected light Types of Luster:Types of Luster:

MetallicMetallic – characterized by a brilliant appearance of a – characterized by a brilliant appearance of a metalmetal

� Opaque to lightOpaque to light� Has black or very dark streakHas black or very dark streak

Sub-metallicSub-metallic – intermediate between metallic and non – intermediate between metallic and non metallic.metallic.

� Similar luster to metal, but are duller and less Similar luster to metal, but are duller and less reflectivereflective

� Often occurs in near-opaque minerals with very Often occurs in near-opaque minerals with very high refractive indices, such as sphalerite, high refractive indices, such as sphalerite, cinnabar and cupritecinnabar and cuprite

Non-metallicNon-metallic – generally light colored and transmits light – generally light colored and transmits light� colorless to very light coloredcolorless to very light colored

LUSTERLUSTER

TYPE OF NON-TYPE OF NON-METALLIC METALLIC LUSTERLUSTER

DESCRIPTIONDESCRIPTION

VitreousVitreous Luster of polished glass. One of the Luster of polished glass. One of the most common luster and occurs in most common luster and occurs in transparent or translucent minerals with transparent or translucent minerals with relatively low refractive indices (eg. relatively low refractive indices (eg. calcite, quartz and fluorite)calcite, quartz and fluorite)

ResinousResinous Has the appearance of resin, chewing Has the appearance of resin, chewing gum or smooth-surfaced plastic (eg. gum or smooth-surfaced plastic (eg. amber – a form of fossilized resin, amber – a form of fossilized resin, sphalerite and sulfur)sphalerite and sulfur)

GreasyGreasy Resembles fat or grease or with a layer Resembles fat or grease or with a layer of oil. Often occurs in minerals contai-of oil. Often occurs in minerals contai-ning a great abun-dance of microscopic ning a great abun-dance of microscopic inclusions. Many minerals with a greasy inclusions. Many minerals with a greasy lustre also lustre also feelfeel greasy (eg. opal and greasy (eg. opal and cordierite)cordierite)

LUSTERLUSTERTYPE OF NON-TYPE OF NON-

METALLIC METALLIC LUSTERLUSTER


PearlyPearly Iridescent pearl-like luster in minerals Iridescent pearl-like luster in minerals consisting of thin transparent co-planar consisting of thin transparent co-planar sheets. Light reflecting from these sheets. Light reflecting from these layers give them a luster reminiscent of layers give them a luster reminiscent of pearls. Such minerals possess perfect pearls. Such minerals possess perfect cleavage (muscovite mica and stilbite)cleavage (muscovite mica and stilbite)

SilkySilky Silk-like. Caused by the reflection of Silk-like. Caused by the reflection of light from a fine fibrous parallel aggre-light from a fine fibrous parallel aggre-gate (asbestos, ulexite, satin spar, gate (asbestos, ulexite, satin spar, chrysotile and malachite)chrysotile and malachite)

AdamantineAdamantine A hard, brilliant luster. Superlative lustre A hard, brilliant luster. Superlative lustre seen in transparent or translucent seen in transparent or translucent having a high refractive index, from having a high refractive index, from Greek Greek adamosadamos meaning “shine” (eg. meaning “shine” (eg. Cerussite,diamond, garnet and zircon)Cerussite,diamond, garnet and zircon)

LUSTERLUSTERTYPE OF NON-TYPE OF NON-

METALLIC METALLIC LUSTERLUSTER


Dull or earthyDull or earthy Exhibits little to no luster, due to coarse Exhibits little to no luster, due to coarse granulations which scatter light in all granulations which scatter light in all directions, approximating a Lambertian directions, approximating a Lambertian reflector. A distinction is sometimes reflector. A distinction is sometimes drawn between dull minerals and drawn between dull minerals and earthy minerals, with the latter being earthy minerals, with the latter being coarser, and having even less lustre coarser, and having even less lustre (eg. Kaolinite, goethite, limonite)(eg. Kaolinite, goethite, limonite)

WaxyWaxy A luster resembling appearance of wax A luster resembling appearance of wax (eg. jade and chalcedony)(eg. jade and chalcedony)

STREAKSTREAK StreakStreak – color of a finely powdered mineral – color of a finely powdered mineral

�usually constant and thus, useful in mineral usually constant and thus, useful in mineral identificationidentification�determined by rubbing the mineral on a determined by rubbing the mineral on a piece of unglazed porcelain or streak platepiece of unglazed porcelain or streak plate�if no streak seems to be made, the mineral's if no streak seems to be made, the mineral's streak is said to be white or colorlessstreak is said to be white or colorless�streak is particularly important as a streak is particularly important as a diagnostic for opaque and colored materialsdiagnostic for opaque and colored materials�less useful for silicate minerals, most of less useful for silicate minerals, most of which have a white streak and are too hard which have a white streak and are too hard to powder easily. The streak plate has a to powder easily. The streak plate has a hardness of a bout 7 and thus, it cannot be hardness of a bout 7 and thus, it cannot be used with minerals with greater hardnessused with minerals with greater hardness

STREAKSTREAK StreakStreak

�Examples:Examples:�Cinnabar (dark red color) dark red streakCinnabar (dark red color) dark red streak�Azurite (blue color) blue streakAzurite (blue color) blue streak�Fluorite (green, purple or yellow color) Fluorite (green, purple or yellow color) white streak, white streak, �Hematite (black color) red streakHematite (black color) red streak�Galena (black color) gray streakGalena (black color) gray streak�Pyrite (brass or gold yellow) green streakPyrite (brass or gold yellow) green streak�Sphalerite (dark brownish black to honey Sphalerite (dark brownish black to honey rown) pale yellow streak rown) pale yellow streak

COLORCOLOR ColorColor – directly related to the chemistry and structure of – directly related to the chemistry and structure of

mineral. When the chemical element causing the color is mineral. When the chemical element causing the color is essential to a mineral, color can be used as a diagnostic essential to a mineral, color can be used as a diagnostic tool because such a mineral has a constant colortool because such a mineral has a constant color Sulfur – yellowSulfur – yellow Malachite – greenMalachite – green Turquiose – greenish blue to blue-green Turquiose – greenish blue to blue-green

most minerals with a metallic luster vary little in color most minerals with a metallic luster vary little in color and the color of freshly broken surface of a metallic and the color of freshly broken surface of a metallic mineral is diagnosticmineral is diagnostic Galena – bright bluish lead gray color becomes dull Galena – bright bluish lead gray color becomes dull

graygray Bornite – brownish-bronze color when fresh and Bornite – brownish-bronze color when fresh and

tarnish to iridescent metallic purples and blues tarnish to iridescent metallic purples and blues (peacock ore)(peacock ore)

COLORCOLOR ColorColor – results in minerals when certain wavelengths of light – results in minerals when certain wavelengths of light

are absorbed. Color results from the combination of those are absorbed. Color results from the combination of those wavelengths that reach the eyewavelengths that reach the eye

When light strikes the surface of a mineral, part of it is When light strikes the surface of a mineral, part of it is reflected and part refracted. If light suffers no absorption, the reflected and part refracted. If light suffers no absorption, the mineral is colorlessmineral is colorless

PleochroismPleochroism – selective absorption of light by minerals – selective absorption of light by minerals resulting in a display of different colors when light is resulting in a display of different colors when light is transmitted along different crystallographic directions (eg. transmitted along different crystallographic directions (eg. Cordierite)Cordierite)

COLOR, STREAK AND OPTICAL PHENOMENACOLOR, STREAK AND OPTICAL PHENOMENA DichroismDichroism – selective absorption of light along two – selective absorption of light along two

crystallographic directions resulting in a display of crystallographic directions resulting in a display of different colors (eg. tourmaline)different colors (eg. tourmaline)

Idiochromatic minerals – minerals where color Idiochromatic minerals – minerals where color serves as an important means of identificationserves as an important means of identification Malachite – greenMalachite – green Azurite – blueAzurite – blue Rhodonite and rhodochrosite – rose red or rose Rhodonite and rhodochrosite – rose red or rose

pinkpink Chalcopyrite – brass yellowChalcopyrite – brass yellow Niccolite – copper redNiccolite – copper red Bornite – peacock oreBornite – peacock ore

Allochromatic minerals – minerals that produce no Allochromatic minerals – minerals that produce no characteristic colors and colors vary depending on characteristic colors and colors vary depending on the presence of impurities like Fethe presence of impurities like Fe

COLOR, STREAK AND OPTICAL PHENOMENACOLOR, STREAK AND OPTICAL PHENOMENA Play of ColorsPlay of Colors

the striking play of colors in minerals that result from the striking play of colors in minerals that result from the interference of light as the angle of incident light the interference of light as the angle of incident light changes either at the surface or in the interior of a changes either at the surface or in the interior of a mineralmineral

Caused by the diffraction of light from closely spaced Caused by the diffraction of light from closely spaced features such as packed spheres (opal) or fine features such as packed spheres (opal) or fine lamellae within the mineral (plagioclase), closely lamellae within the mineral (plagioclase), closely spaced fractures, cleavage planes or exsolution spaced fractures, cleavage planes or exsolution lamellaelamellae

eg. Precious opal – interference of light reflected from eg. Precious opal – interference of light reflected from sub-microscopic layers of nearly spherical particles sub-microscopic layers of nearly spherical particles arranged in a regular patternarranged in a regular pattern

COLOR, STREAK AND OPTICAL PHENOMENACOLOR, STREAK AND OPTICAL PHENOMENA Play of ColorsPlay of Colors

OpalescenceOpalescence – pearly color produced by scattering of – pearly color produced by scattering of light in common opal due to absence of microscopic light in common opal due to absence of microscopic layeringlayering

IridescenceIridescence – caused by light defracted and reflected – caused by light defracted and reflected from closely spaced fractures or cleavage planes in from closely spaced fractures or cleavage planes in parallel orientation or thin surface films (internal and parallel orientation or thin surface films (internal and surface) – bornite, hematite, limonite and sphaleritesurface) – bornite, hematite, limonite and sphalerite

SchillerSchiller - colorful iridescence that occurs when light is - colorful iridescence that occurs when light is reflected between layers (eg. moonstone and reflected between layers (eg. moonstone and labradorite), also called labradorescence labradorite), also called labradorescence

OTHER OPTICAL PHENOMENAOTHER OPTICAL PHENOMENA ChatoyancyChatoyancy

the silky appearance which results from closely packed parallel the silky appearance which results from closely packed parallel fibersfibers

a display of luminous bands, which appear to move as the specimen a display of luminous bands, which appear to move as the specimen is rotated. Such minerals are composed of parallel fibers (or contain is rotated. Such minerals are composed of parallel fibers (or contain fibrous voids or inclusions), which reflect light into a direction fibrous voids or inclusions), which reflect light into a direction perpendicular to their orientation, thus forming narrow bands of lightperpendicular to their orientation, thus forming narrow bands of light

Examples:Examples:Cat's eyeCat's eye(chrysoberyl)(chrysoberyl)CymophaneCymophaneTiger’s eyeTiger’s eye(qtz w/ amphibole) (qtz w/ amphibole)

OTHER OPTICAL PHENOMENAOTHER OPTICAL PHENOMENA AsterismAsterism

the display of a star-shaped luminous areathe display of a star-shaped luminous area triple chatoyancytriple chatoyancy Examples:Examples:

Some sapphires and rubiesSome sapphires and rubies AventurescenceAventurescence

is a reflectance effect like that of glitteris a reflectance effect like that of glitter It arises from minute, preferentially oriented mineral It arises from minute, preferentially oriented mineral

platelets within the material. These platelets are so platelets within the material. These platelets are so numerous that they also influence the material's body numerous that they also influence the material's body colorcolor

Examples:Examples:aventurine quartzaventurine quartz

LUMINESCENCELUMINESCENCE LuminescenceLuminescence – emission of light by a mineral that is not a direct – emission of light by a mineral that is not a direct

result of incandescenceresult of incandescence Occurs in minerals containing foreign ions or “activators”Occurs in minerals containing foreign ions or “activators” Usually faint and can be seen only in the darkUsually faint and can be seen only in the dark

Types of Luminescence:Types of Luminescence: FluorescenceFluorescence – luminescence that occurs during exposure of a – luminescence that occurs during exposure of a

mineral to ultraviolet light, x-rays or cathode raysmineral to ultraviolet light, x-rays or cathode raysProduced when the energy of shortwave radiation is absorbed Produced when the energy of shortwave radiation is absorbed

by impurity ions and released as longer wave radiationby impurity ions and released as longer wave radiationColor of emitted light varies considerably with wavelengths or Color of emitted light varies considerably with wavelengths or

source of ultraviolet lightsource of ultraviolet lighteg. Fluorite (blue fluorescence due to organic materials or rare eg. Fluorite (blue fluorescence due to organic materials or rare

earth ions), scheelite (pale blue fluorescence due to Mo earth ions), scheelite (pale blue fluorescence due to Mo replacing W), willemite, calcite, diamond, hyalite, scapolite, replacing W), willemite, calcite, diamond, hyalite, scapolite, eucryptite (salmon pink)eucryptite (salmon pink)

Synthetic phospors : fluorescent lamps, paints, cloth and tapesSynthetic phospors : fluorescent lamps, paints, cloth and tapes

LUMINESCENCELUMINESCENCE PhosphorescencePhosphorescence – luminescence that continues after the – luminescence that continues after the

exciting rays are cut offexciting rays are cut off Thermoluminescence Thermoluminescence – visible light emitted by some – visible light emitted by some

minerals when heated to a temperature below that of red minerals when heated to a temperature below that of red heatheatBest shown by non metallic minerals that contain Best shown by non metallic minerals that contain

foreign ions as activatorsforeign ions as activatorseg. Fluorite, chlorophane calcite, apatite, feldspareg. Fluorite, chlorophane calcite, apatite, feldspar

TriboluminescenceTriboluminescence – luminosity of some minerals after – luminosity of some minerals after having been crushed, scratched or rubbedhaving been crushed, scratched or rubbedMostly occurs in non metallic minerals that possess Mostly occurs in non metallic minerals that possess

good cleavagegood cleavageeg. Fluorite, sphalerite, lepidoliteeg. Fluorite, sphalerite, lepidolite

CLEAVAGE, PARTING AND FRACTURECLEAVAGE, PARTING AND FRACTURE CleavageCleavage - tendency of crystalline materials to split along - tendency of crystalline materials to split along

definite crystallographic structural planes (parallel to atomic definite crystallographic structural planes (parallel to atomic planes) creating smooth surfacesplanes) creating smooth surfaces

Parallel to crystal facesParallel to crystal faces Result from:Result from:

Weak type of bondWeak type of bond Greater spacing between the planesGreater spacing between the planes Combination of the 2Combination of the 2

Cleavage qualityCleavage quality PerfectPerfect GoodGood FairFair obscureobscure absentabsent

CLEAVAGE, PARTING AND FRACTURECLEAVAGE, PARTING AND FRACTURE Types of Cleavage:Types of Cleavage:

Basal or pinacoidal cleavageBasal or pinacoidal cleavage - occurs parallel to the base - occurs parallel to the base of a crystal, the {0001} crystal plane (eg. mica group, of a crystal, the {0001} crystal plane (eg. mica group, graphite)graphite)

Cubic cleavageCubic cleavage - occurs on the {001} plane parallel to the - occurs on the {001} plane parallel to the faces of a cube. This is the source of the cubic shape faces of a cube. This is the source of the cubic shape seen in crystals (eg. ground table salt, halite and galena)seen in crystals (eg. ground table salt, halite and galena)

Octahedral cleavageOctahedral cleavage - occurs on the {111} crystal plane - occurs on the {111} crystal plane forming octahedra shapes. Common semiconductors. (eg. forming octahedra shapes. Common semiconductors. (eg. diamond and fluorite)diamond and fluorite)

Dodecahedral cleavageDodecahedral cleavage - occurs on the {011} crystal - occurs on the {011} crystal planes forming dodecahedra.(eg. wulfenite and gypsum) planes forming dodecahedra.(eg. wulfenite and gypsum)

Rhombohedral cleavageRhombohedral cleavage - occurs parallel to the {1011} - occurs parallel to the {1011} faces of a rhombohedron. (eg. Calcite and other faces of a rhombohedron. (eg. Calcite and other carbonate minerals)carbonate minerals)

Prismatic cleavagePrismatic cleavage - parallel to a vertical prism {110}. (eg. - parallel to a vertical prism {110}. (eg. cerussite, tremolite and spodumene)cerussite, tremolite and spodumene)

CLEAVAGE, PARTING AND FRACTURECLEAVAGE, PARTING AND FRACTURE

CLEAVAGE, PARTING AND FRACTURECLEAVAGE, PARTING AND FRACTURE PartingParting – tendency for a mineral to break along planes of – tendency for a mineral to break along planes of

structural weakness due to external stress or along twin structural weakness due to external stress or along twin composition planescomposition planes

Result from:Result from: PressurePressure Twinning Twinning

Parting breaks are very similar in appearance to cleavageParting breaks are very similar in appearance to cleavage Types of Parting:Types of Parting:

octahedral parting (eg. Magnetite)octahedral parting (eg. Magnetite) rhombohedral parting (eg. Corundum)rhombohedral parting (eg. Corundum) basal parting (eg. Pyroxenes) basal parting (eg. Pyroxenes)

CLEAVAGE, PARTING AND FRACTURECLEAVAGE, PARTING AND FRACTURE Uses/Importance of Cleavage and Parting:Uses/Importance of Cleavage and Parting:

traditional physical property used in mineral identification traditional physical property used in mineral identification both in hand specimen and microscopic examination of both in hand specimen and microscopic examination of rock and mineral studies rock and mineral studies

technical importance in the electronics industry and in the technical importance in the electronics industry and in the cutting of gemstones cutting of gemstones

Precious stones are generally cleaved by impact as in Precious stones are generally cleaved by impact as in diamond cuttingdiamond cutting

CLEAVAGE, PARTING AND FRACTURECLEAVAGE, PARTING AND FRACTURE FractureFracture – the way a mineral breaks when it does not yield – the way a mineral breaks when it does not yield

along cleavage or parting surfacesalong cleavage or parting surfaces Types of Fracture:Types of Fracture:

Conchoidal fractureConchoidal fracture – smooth, curved fracture resembling – smooth, curved fracture resembling the interior surface of a shellthe interior surface of a shell

Fibrous or splintery fractureFibrous or splintery fracture – – Hackly fractureHackly fracture – jagged fractures with sharp edges – jagged fractures with sharp edges Uneven or irregular fractureUneven or irregular fracture – fractures producing rough – fractures producing rough

and irregular surfacesand irregular surfaces

HARDNESSHARDNESS HardnessHardness – or “scratchability” is the resistance that a – or “scratchability” is the resistance that a

smooth surface of a mineral offers to scratchingsmooth surface of a mineral offers to scratching Designated by (Designated by (H)H) Dependent on type of bonding and crystal structure Dependent on type of bonding and crystal structure Determined by observing comparative ease or Determined by observing comparative ease or

difficulty with which one mineral is scratched by difficulty with which one mineral is scratched by another mineral or by a file or a knifeanother mineral or by a file or a knife

Uses a scale of 10 Minerals (Mohs Scale)Uses a scale of 10 Minerals (Mohs Scale) Mohs Scale of HardnessMohs Scale of Hardness – introduced by F. Mohs in – introduced by F. Mohs in

18241824 arranged in an order of increasing relative hardnessarranged in an order of increasing relative hardness purely ordinal scale (eg. corundum (9) is twice as purely ordinal scale (eg. corundum (9) is twice as

hard as topaz (8), but diamond (10) is almost four hard as topaz (8), but diamond (10) is almost four times as hard as corundum)times as hard as corundum)

Absolute hardnessAbsolute hardness – measured using a sclerometer – measured using a sclerometer

HARDNESSHARDNESS There is a link between hardness and chemical There is a link between hardness and chemical

compositioncomposition Most hydrous minerals are relatively soft (H <5)Most hydrous minerals are relatively soft (H <5) Halides, carbonates, sulfates and phosphates are Halides, carbonates, sulfates and phosphates are

relatively soft (H <5.5)relatively soft (H <5.5) Most sulfides are relatively soft (H <5) with pyrite Most sulfides are relatively soft (H <5) with pyrite

being and exception (H ~6 to 6.5)being and exception (H ~6 to 6.5) Most anhydrous oxides and silicates are hard (H Most anhydrous oxides and silicates are hard (H

>5.5)>5.5)

HARDNESSHARDNESSMohs Scale of HardnessMohs Scale of Hardness

HARDNESSHARDNESS MINERALMINERAL ABSOLUTE ABSOLUTE HARDNESSHARDNESS

11 Talc Talc (Mg(Mg

33SiSi44OO1010(O(O

H)H)22) )

11

22 Gypsum Gypsum (CaSO(CaSO

44·2H·2H22

O) O)

22

33 Calcite Calcite (CaCO(CaCO

33) ) 99

44 Fluorite Fluorite (CaF(CaF

22) ) 2121

55 Apatite Apatite (Ca(Ca

55(PO(PO44))33(O(O

H-,Cl-,F-)H-,Cl-,F-)

4848

HARDNESSHARDNESS MINERALMINERAL ABSOLUTE ABSOLUTE HARDNESSHARDNESS

66 OrthoclaseOrthoclase (KAlSi(KAlSi

33OO88) ) 7272

77 QuartzQuartz (SiO(SiO

22) ) 100100

88 TopazTopaz (Al(Al

22SiOSiO44(O(O

H-,F-)H-,F-)22) )

200200

99 CorundumCorundum (Al(Al

22OO33) ) 400400

1010 DiamondDiamond (C) (C)

15001500

HARDNESSHARDNESS On the Mohs Scale:On the Mohs Scale:

pencil lead - 1pencil lead - 1 fingernail - 2.5fingernail - 2.5 copper penny - 3.5copper penny - 3.5 knife blade - 5.5knife blade - 5.5 window glass - 5.5window glass - 5.5 steel file - 6.5steel file - 6.5

Using these ordinary materials of known hardness can Using these ordinary materials of known hardness can be a simple way to approximate the position of a be a simple way to approximate the position of a mineral on the scale.mineral on the scale.

HARDNESSHARDNESS

HARDNESSHARDNESSIntermediate HardnessIntermediate Hardness

Hard-ness

Substance or Mineral

1 Talc

2.5 to 3

pure gold, silver, aluminum

3 Calcite, copper penny

4 Fluorite

4 to 4.5

Platinum

4 to 5 Iron

5 Apatite

6 Orthoclase

6 Titanium

6.5 Iron pyrite

6 to 7 Glass, Vitreous pure silica

Hard-ness

Substance or Mineral

7 Quartz

7 to 7.5

Garnet

7 to 8 Hardened steel

8 Topaz

8.5 Chrysoberyl

9 Corundum

9 to 9.5

Carborundum

<10 Ultrahard fullerite

10 Diamond

>10Aggregated diamond nanorods, Rhenium diboride

TENACITYTENACITY TenacityTenacity- the resistance that a mineral offers to - the resistance that a mineral offers to

breaking, bending, or tearingbreaking, bending, or tearing““cohesiveness” of a mineralcohesiveness” of a mineral

Types:Types: BrittlenessBrittleness – ability to break or powder easily (halite) – ability to break or powder easily (halite) MalleabilityMalleability – the ability to be hammered out into thin – the ability to be hammered out into thin

sheets (copper)sheets (copper) SectilitySectility – the ability to be cut into thin shavings with – the ability to be cut into thin shavings with

a knife (chalcocite)a knife (chalcocite) DuctilityDuctility – ability to be drawn into wires (gold) – ability to be drawn into wires (gold) FlexibilityFlexibility – can be bent but does not resume original – can be bent but does not resume original

shape when pressure is released (chlorite, talc)shape when pressure is released (chlorite, talc) ElasticityElasticity – can be bent and return to original shape – can be bent and return to original shape

upon release of pressure (mica)upon release of pressure (mica)

DENSITY AND SPECIFIC GRAVITYDENSITY AND SPECIFIC GRAVITY Density – defined as mass per unit volumeDensity – defined as mass per unit volume

Specific gravity – or “relative density”Specific gravity – or “relative density” Designated by (G)Designated by (G) A number that expresses the ratio between the A number that expresses the ratio between the

weight of a substance and the weight of an equal weight of a substance and the weight of an equal volume of water at 4°Cvolume of water at 4°C

eg. a mineral with a specific gravity of 2 weighs twice eg. a mineral with a specific gravity of 2 weighs twice as much as the same volume of wateras much as the same volume of water

Useful in fine crystal or gemstones when other test Useful in fine crystal or gemstones when other test could injure the specimencould injure the specimen

Dependent on:Dependent on:kind of atoms of which it is composed (eg. Olivine kind of atoms of which it is composed (eg. Olivine

– solid solution series between fosterite Mg– solid solution series between fosterite Mg22SiOSiO4 4

with G 3.3 and fayalite Fewith G 3.3 and fayalite Fe22SiOSiO4 4 with G 4.4)with G 4.4)

v

m

SPECIFIC GRAVITYSPECIFIC GRAVITYManner in which the atoms are packed together Manner in which the atoms are packed together

(eg. Diamond – closely packed →3.5 vs. graphite (eg. Diamond – closely packed →3.5 vs. graphite – C atoms loosely packed →2.23)– C atoms loosely packed →2.23)

Average specific gravity for non metallic minerals → G Average specific gravity for non metallic minerals → G 2.65 to G 2.75 → this is because the specific gravities 2.65 to G 2.75 → this is because the specific gravities of the most common non metallic minerals quartz is of the most common non metallic minerals quartz is 2.65, feldspar is 2.6 to 2.75 and calcite is 2.722.65, feldspar is 2.6 to 2.75 and calcite is 2.72 ulexite G 1.96 – light, barite G 4.5 – heavyulexite G 1.96 – light, barite G 4.5 – heavy

Average specific gravity for metallic minerals → G 5.0 Average specific gravity for metallic minerals → G 5.0 → this is because the specific gravities of the most → this is because the specific gravities of the most common metallic mineral pyrite is 5.0common metallic mineral pyrite is 5.0 Graphite G 2.23 – light, silver G 10.5 - heavy Graphite G 2.23 – light, silver G 10.5 - heavy

DETERMINATION OF SPECIFIC GRAVITYDETERMINATION OF SPECIFIC GRAVITY For accurate determination of specific gravity, the For accurate determination of specific gravity, the

mineral specimen must be:mineral specimen must be: homogeneous and purehomogeneous and pure compact with no cavities or cracks within which compact with no cavities or cracks within which

bubbles or films of air could be imprisonedbubbles or films of air could be imprisoned Modes of Specific Gravity Determination:Modes of Specific Gravity Determination:

Jolly balanceJolly balance PycnometerPycnometer

DETERMINATION OF SPECIFIC GRAVITY:DETERMINATION OF SPECIFIC GRAVITY: Weigh the mineral in air (Weigh the mineral in air (WWaa)).. Immerse in water and weigh again → (Immerse in water and weigh again → (WWww)). (under these . (under these

conditions it weighs less, since in water it is buoyed up by a conditions it weighs less, since in water it is buoyed up by a force equivalent to the weight of the displaced water)force equivalent to the weight of the displaced water)

(W(Wa a –– WWww)) is equal to the apparent loss of weight or equals is equal to the apparent loss of weight or equals the weight of an equal volume of waterthe weight of an equal volume of water

Specific Gravity (G) = Specific Gravity (G) = WWaa----------------------------------

WWa a –– WWw w

DETERMINATION OF SPECIFIC GRAVITY DETERMINATION OF SPECIFIC GRAVITY BY JOLLY BALANCE:BY JOLLY BALANCE: Place a fragment on the upper scale pan and record the Place a fragment on the upper scale pan and record the

elongation of the spring. This is proportional to the weight in elongation of the spring. This is proportional to the weight in air air WWaa

Transfer the fragment into the lower pan and immersed in Transfer the fragment into the lower pan and immersed in waterwater

Record the elongation of the spring. This is proportional to Record the elongation of the spring. This is proportional to the weight of the fragment in water the weight of the fragment in water WWww

Note:Note: *torsion balance used for obtaining specific *torsion balance used for obtaining specific gravities of small particles weighing less than 25 mg.gravities of small particles weighing less than 25 mg.

*because specific gravity is merely a ratio, it *because specific gravity is merely a ratio, it is not necessary to determine the absolute weight of the is not necessary to determine the absolute weight of the specimen but mere values proportional to the weights in specimen but mere values proportional to the weights in air and waterair and water

DETERMINATION OF SPECIFIC GRAVITY DETERMINATION OF SPECIFIC GRAVITY BY PYCNOMETER:BY PYCNOMETER: Dry pycnometer bottle is weighed (Dry pycnometer bottle is weighed (PP).). Mineral fragments are then introduced into the bottle and a Mineral fragments are then introduced into the bottle and a

second weighing (second weighing (MM) is made) is made ((M – PM – P) represents the weight of the sample in air) represents the weight of the sample in air The bottle containing the mineral sample is partially filled The bottle containing the mineral sample is partially filled

with distilled water and boiled for a few minutes to drive off with distilled water and boiled for a few minutes to drive off any air bubblesany air bubbles

After cooling, the pycnometer is further filled with distilled After cooling, the pycnometer is further filled with distilled water and weighed (water and weighed (SS), care being taken that the water rises ), care being taken that the water rises to the top of the capillary opening but that no excess water is to the top of the capillary opening but that no excess water is presentpresent

The last weighing is made (The last weighing is made (WW) is made after emptying the ) is made after emptying the bottle and refilling with distilled water alonebottle and refilling with distilled water alone

DETERMINATION OF SPECIFIC GRAVITY DETERMINATION OF SPECIFIC GRAVITY BY PYCNOMETER:BY PYCNOMETER: In the last step, the pycnometer contains more water than in In the last step, the pycnometer contains more water than in

the previous weighing; the volume of water added is equal to the previous weighing; the volume of water added is equal to the aggregate volume of the grains comprising the samplethe aggregate volume of the grains comprising the sample

The specific gravity is determined:The specific gravity is determined: G =G = (M – P)(M – P)

------------- ------------- W + (M – P) - SW + (M – P) - S

Where:Where: M – P = weight of sampleM – P = weight of sampleW = pycnometer + water contentW = pycnometer + water contentS = sample + pycnometer + undisplaced waterS = sample + pycnometer + undisplaced water

W + (M – P) – S = weight of water displaced by sampleW + (M – P) – S = weight of water displaced by sample

Method used when a mineral can not be obtained in a Method used when a mineral can not be obtained in a homogeneous mass large enough to permit use of the homogeneous mass large enough to permit use of the balance methodbalance method

ELECTRICAL PROPERTIESELECTRICAL PROPERTIES Conduction of electricity in crystals is related to the type Conduction of electricity in crystals is related to the type

of bondingof bonding Pure metallic bonding – excellent conductorsPure metallic bonding – excellent conductors Partially metallic – semi-conductors (some sulfide Partially metallic – semi-conductors (some sulfide

minerals)minerals) Ionic or covalent bonding – non conductorsIonic or covalent bonding – non conductors

Electrical conductivity for non isometric minerals – Electrical conductivity for non isometric minerals – vectorial property varying with crystallographic direction vectorial property varying with crystallographic direction (eg. Graphite better conductor at right angles to the c-(eg. Graphite better conductor at right angles to the c-axis than parallel to it)axis than parallel to it)

ELECTRICAL PROPERTIESELECTRICAL PROPERTIES PIEZOELECTRICITYPIEZOELECTRICITY

occurs in crystals with polar axis (polar axis is pre-occurs in crystals with polar axis (polar axis is pre-sent in crystals that lack a center of symmetry – 21 of sent in crystals that lack a center of symmetry – 21 of the 32 crystal classes have no center of symmetry)the 32 crystal classes have no center of symmetry)

A flow of electrons toward one end producing A flow of electrons toward one end producing negative electrical charge while a positive charge is negative electrical charge while a positive charge is induced at the opposite end if pressure is exerted at induced at the opposite end if pressure is exerted at the ends of the polar axisthe ends of the polar axis

First detected in quartz in 1881 by Pierre and First detected in quartz in 1881 by Pierre and Jacques CurieJacques Curie

Practical uses:Practical uses:sound waves produce by submarines could be de-sound waves produce by submarines could be de-

tected by the piezoelectric current generated when tected by the piezoelectric current generated when they impinge on a submerged quartzthey impinge on a submerged quartz


Practical uses:Practical uses:Piezoelectric property of quartz was first used in Piezoelectric property of quartz was first used in

1921 to control radio frequencies. When subjected 1921 to control radio frequencies. When subjected to an alternating current, a properly cut slice of to an alternating current, a properly cut slice of quartz is mechanically deformed and vibrates by quartz is mechanically deformed and vibrates by being flexed first one way and then the other, the being flexed first one way and then the other, the thinner the slice, the greater the frequency of thinner the slice, the greater the frequency of vibration. By placing a quartz plate in the electric vibration. By placing a quartz plate in the electric field generated by a radio circuit, the frequency of field generated by a radio circuit, the frequency of transmission or reception is controlled when the transmission or reception is controlled when the frequency of the quartz coincides with the frequency of the quartz coincides with the oscillations of the circuit oscillations of the circuit


Practical uses:Practical uses:Tiny quartz plate used in digital quartz watches Tiny quartz plate used in digital quartz watches

serves the same function as quartz oscillators serves the same function as quartz oscillators used to control radio frequencies. It mechanically used to control radio frequencies. It mechanically vibrates at a constant predetermined frequency vibrates at a constant predetermined frequency controlling accurately the radio frequency of the controlling accurately the radio frequency of the electronic circuit in the watch electronic circuit in the watch

ELECTRICAL PROPERTIESELECTRICAL PROPERTIES PYROELECTRICITYPYROELECTRICITY

Observed in crystals with polar axes (primary Observed in crystals with polar axes (primary pyroelectricity is shown in crystals that belong to 10 pyroelectricity is shown in crystals that belong to 10 crystal classes having a unique axis – eg. crystal classes having a unique axis – eg. tourmaline)tourmaline)

Simultaneous development of positive and negative Simultaneous development of positive and negative charges at opposite ends of a polar axis due to charges at opposite ends of a polar axis due to temperature changestemperature changes

MAGNETIC PROPERTIESMAGNETIC PROPERTIES MAGNETISMMAGNETISM

Being attracted to a magnetBeing attracted to a magnet Use to separate minerals by magnetic separatorUse to separate minerals by magnetic separator

Types:Types:

a.a. FerromagneticFerromagnetic• Being attracted to a small hand magnet (ie. Being attracted to a small hand magnet (ie.

magnetite Femagnetite Fe33OO44 and pyrrhotite Fe and pyrrhotite Fe-x-xSS

b.b. ParamagneticParamagnetic• Minerals containing iron being attracted in a field Minerals containing iron being attracted in a field

of powerful electromagnetof powerful electromagnet

c.c. DiamagneticDiamagnetic• Minerals repelled in a field of powerful Minerals repelled in a field of powerful

electromagnetelectromagnet

RADIOACTIVITYRADIOACTIVITY Minerals containing radioactive elements like uranium Minerals containing radioactive elements like uranium

and thorium will continually undergo decay reactions in and thorium will continually undergo decay reactions in which radioactive isotopes of U and Th for various which radioactive isotopes of U and Th for various daughter elementsdaughter elements

During decay they release energy in the form of alpha During decay they release energy in the form of alpha and beta particles and gamma radiationand beta particles and gamma radiation

Examples of radioactive minerals: uraninite, Examples of radioactive minerals: uraninite, pitchblende, thorianite and autunitepitchblende, thorianite and autunite

SOLUBLITY IN ACIDSOLUBLITY IN ACID Some minerals undergo visible reaction with dilute Some minerals undergo visible reaction with dilute

hydrochloric acidhydrochloric acid

As the calcite dissolves, it releases carbon dioxide gas As the calcite dissolves, it releases carbon dioxide gas hat bubbles in the liquid, producing the familiar “fizz”hat bubbles in the liquid, producing the familiar “fizz”

Calcite, aragonite, witherite, and strontianite as well as Calcite, aragonite, witherite, and strontianite as well as Cu-carbonates, show bubbling or effervescence when a Cu-carbonates, show bubbling or effervescence when a drop of dilute HCl is placed on the mineraldrop of dilute HCl is placed on the mineral

Other carbonates like, rhodochrosite, dolomite, Other carbonates like, rhodochrosite, dolomite, magnesite and siderite show effervescence only in hot magnesite and siderite show effervescence only in hot HClHCl

OHgasCOCaHCaCO 222

3 )(2

SENSORY PROPERTIESSENSORY PROPERTIES Odor – sulfur smells like the gas produced by rotten Odor – sulfur smells like the gas produced by rotten

egg, Clay smell earthyegg, Clay smell earthy Taste – halite taste salty, sylvite tastes salty and Taste – halite taste salty, sylvite tastes salty and

bitterbitter Feel – greasy feel for molybdenite, graphite and talc Feel – greasy feel for molybdenite, graphite and talc

CRYSTAL CHEMISTRYCRYSTAL CHEMISTRY

ATOMS AND IONS- THE BUILDING BLOCKSATOMS AND IONS- THE BUILDING BLOCKS Matter is made up of atoms. Matter is made up of atoms.

The structure of atoms dictate their properties. How The structure of atoms dictate their properties. How

atoms combine dictate what we see in the many atoms combine dictate what we see in the many

mineralsminerals in nature. in nature.

New technologies allow us to peer ever closer at the New technologies allow us to peer ever closer at the

minute structures of minerals, down to the scale of minute structures of minerals, down to the scale of

individual atomsindividual atoms

ATOMS AND IONS – THE BUILDINGBLOCKSATOMS AND IONS – THE BUILDINGBLOCKS Atom is smallest subdivision of matter that retain the Atom is smallest subdivision of matter that retain the

characteristics of the elements. characteristics of the elements. Although one can sub-Although one can sub-

divide atoms into numerous divide atoms into numerous subatomic particlessubatomic particles, we will , we will

be concerned only with be concerned only with pprotons, neutrons and rotons, neutrons and

electrons.electrons.

Protons and neutrons are together in the Protons and neutrons are together in the nucleusnucleus of an of an

atom, whereas electrons are in motion in orbits around atom, whereas electrons are in motion in orbits around

the central nucleus. Protons carry a positive electrical the central nucleus. Protons carry a positive electrical

charge, electrons carry a negative charge, and neutrons charge, electrons carry a negative charge, and neutrons

carry no charge. Neutrons work to keep nuclei together. carry no charge. Neutrons work to keep nuclei together.

Most atoms are electrically neutral, meaning that they Most atoms are electrically neutral, meaning that they

have an equal number of protons and electronshave an equal number of protons and electrons

ATOMS AND IONS – THE BUILDING BLOCKSATOMS AND IONS – THE BUILDING BLOCKS Very small massive nucleus composed of protons and Very small massive nucleus composed of protons and

neutrons surrounded by a much larger region populated neutrons surrounded by a much larger region populated by electrons, except in Hydrogenby electrons, except in Hydrogen

Not visible to naked eye and even with highest Not visible to naked eye and even with highest magnification of the electron microscopemagnification of the electron microscope

Sizes are measured as atomic radius in Å (0.46 to 2.62 Sizes are measured as atomic radius in Å (0.46 to 2.62 Å)Å)

Each electron moves in an orbit around the nucleus and Each electron moves in an orbit around the nucleus and carries negative electricity. Distance from nucleus carries negative electricity. Distance from nucleus depends on the energies of the electronsdepends on the energies of the electrons

Electrons and nuclei are both extremely small but the Electrons and nuclei are both extremely small but the electrons move very rapidly around the nuclei → give electrons move very rapidly around the nuclei → give large effective diameters (10k-20k times)large effective diameters (10k-20k times)

ATOMS AND IONSATOMS AND IONS

A schematic model of a lithium (Li) atom in the ground A schematic model of a lithium (Li) atom in the ground

state. It has 3 protons in the nucleus, and 3 electrons in state. It has 3 protons in the nucleus, and 3 electrons in

orbit. (we will get to the number of neutrons)orbit. (we will get to the number of neutrons)

ELECTRONIC AND NUCLEAR PROPERTIESELECTRONIC AND NUCLEAR PROPERTIES

Properties of atoms reflect some combination of fea-Properties of atoms reflect some combination of fea-

tures related to electrons or to the nucleus. tures related to electrons or to the nucleus.

The The electronicelectronic properties are those related to how properties are those related to how

atoms connect to one another: atoms connect to one another: bondingbonding..

The The nuclearnuclear properties include features like radioact- properties include features like radioact-

ivityivity

.

SIZE OF NUCLEISIZE OF NUCLEI

The number of neutrons tends to closely follow the number of protons. Atoms

with more of each are bigger and heavier.

A uranium atom, with 92 protons

and ~146 neutrons is gigantic

compared to dinky helium (2 + 2).

Microcosms of our solar system, atoms are dominantly empty space:

If an oxygen atom had a total radius of 100 km, the nucleus would be a

~1 m diameter sphere in the middle.

electron orbits

THE SPACIOUS ATOMTHE SPACIOUS ATOM

In a simplistic model, electrons float around the nucleus in orbits that are sometimes called shells.

As the number of

electrons increases, they

start to fill orbits farther out

from the nucleus.

In most cases, electrons

are lost or gained only

from the outermost orbits.

electron orbits

ELECTRONS IN ORBITELECTRONS IN ORBIT

CHARGED ATOMS: IONSCHARGED ATOMS: IONS

Left to their own devices, atoms are electrically neutral. Left to their own devices, atoms are electrically neutral.

That means that they have an equal number of protons That means that they have an equal number of protons

and electrons. and electrons.

During the course of most natural events, protons are During the course of most natural events, protons are

not gained or lost, but electrons may be. not gained or lost, but electrons may be.

Atoms with more or fewer electrons than protons Atoms with more or fewer electrons than protons are are

electricallyelectrically charged. They are called charged. They are called ionsions: : an atom an atom

that loses electrons takes on a positive charge (cation); that loses electrons takes on a positive charge (cation);

an atom that gains electrons takes on a negative an atom that gains electrons takes on a negative

charge (anion).charge (anion).

ATOMIC NUMBERATOMIC NUMBER

We distinguish one element from another on the basis We distinguish one element from another on the basis

of the atomic number, which is the number of of the atomic number, which is the number of protonsprotons. .

So, an atom of any element can have a variable num-So, an atom of any element can have a variable num-

ber of electrons and neutrons, but given the number of ber of electrons and neutrons, but given the number of

protons, the fundamental properties of the element are protons, the fundamental properties of the element are

unchanged. This is the basis for Dmitri Mendeleev’s unchanged. This is the basis for Dmitri Mendeleev’s

organization of the Periodic Table of the Elements. The organization of the Periodic Table of the Elements. The

table is a way of organizing elements on physical table is a way of organizing elements on physical

grounds, but also serves to group elements with grounds, but also serves to group elements with

consistent chemical properties.consistent chemical properties.

THE PERIODIC TABLETHE PERIODIC TABLE The periodic table is read from top to bottom, left to The periodic table is read from top to bottom, left to

right, as atomic number increases: 1=H, 2=He, right, as atomic number increases: 1=H, 2=He, 3=Li, 4=Be, 5=B, 6=C, and so on.3=Li, 4=Be, 5=B, 6=C, and so on.

Elements in columns (groups) have similar outer-electron configurations, and so tend to behave similarly.

THE PERIODIC TABLETHE PERIODIC TABLEa

lkal

is

alkali earths

rare earths

halogens

noble gases

transition metals

actinides

Most atoms will form the same kinds of ions all the time. For exam-Most atoms will form the same kinds of ions all the time. For exam-

ple, all the alkalis form +1 ions, and the halogens form -1 ions.ple, all the alkalis form +1 ions, and the halogens form -1 ions.

OXIDATION STATEOXIDATION STATEa

lkal

is

halogens

OXIDIZED AND REDUCED STATESOXIDIZED AND REDUCED STATES

A transition metal cation with a higher charge is more oxidized than one of lower charge. That comes from the fact that materials with high proportions of Fe+3/Fe+2 form in environments where oxygen is abundant. The opposite is also true, and we call Fe+2 reduced iron.

transition metals

The transition metals are more electronically complex. They may form ions of various charges. For example, iron (Fe) is found as +2 and +3 ions.

THE PERIODIC TABLE: THE BULK EARTHTHE PERIODIC TABLE: THE BULK EARTH

A small number of elements make up >99% of the solid Earth.

O = oxygenNa = sodium

Mg = magnesiumAl = aluminum

Si = silicon

S = sulfurCa = calcium

Fe = ironNi = nickel

THE PERIODIC TABLE: THE CRUSTTHE PERIODIC TABLE: THE CRUST

The crust is a little more elementally interesting (again, as a result of differentiation), but it is still mainly made of a small number of

elements.

C = carbonP = phosphorusK = potassiumTi = titanium

Mn = manganese

ATOMIC WEIGHT: IT’S ALL IN THE NUCLEUSATOMIC WEIGHT: IT’S ALL IN THE NUCLEUS

Since electrons weigh virtually nothing, the mass of an atom is concentrated in

its nucleus.

Each atom can be described by its atomic weight (or mass),

which is the sum of the protons and neutrons.

lithium: atomic number = 3

3 protons 4 neutrons

atomic weight = 3 + 4 = 7

BUT... although each element has a

defined number of protons,

the number of neutrons is not fixed.

Atoms with the same atomic number but

variable numbers of neutrons are called

isotopes.

STABLE AND RADIOACTIVE ISOTOPESSTABLE AND RADIOACTIVE ISOTOPES

Carbon (atomic # 6) has three natural isotopes

with atomic weights of 12, 13 and 14.

isotope #p #n======== ==

C-12 6 6 C-13 6 7

C-14 is a radioactive isotope; C-12 and C-13 are stable.

Over time the proportion of C-12/C-14 and C-13/C-14

will increase until there is no C-14.

(unless some process makes new C-14...)

C-14 6 8

ATOMS AND IONSATOMS AND IONS Atomic particles can exist only with certain energy Atomic particles can exist only with certain energy

configurations (Max Planck) → basis of Quantum Theoryconfigurations (Max Planck) → basis of Quantum Theory Quantum Theory – energy exists on an atomic scale only as Quantum Theory – energy exists on an atomic scale only as

discrete bundles and not as an infinitely divisible spectrumdiscrete bundles and not as an infinitely divisible spectrum Thus, electrons surrounding the nucleus can occupy only Thus, electrons surrounding the nucleus can occupy only

specific energy levels which differ by discrete number of specific energy levels which differ by discrete number of quantaquanta

Atomic number – the positive charge is the same as the Atomic number – the positive charge is the same as the number of protons, and this number, equal to the number of number of protons, and this number, equal to the number of electrons is called the atomic number Zelectrons is called the atomic number Z

Characteristic mass or mass number – determined by the Characteristic mass or mass number – determined by the sum of protons and neutronssum of protons and neutrons

Isotopes – atoms of the same element but with differing Isotopes – atoms of the same element but with differing numbers of neutrons (eg. O with Z=8 : Onumbers of neutrons (eg. O with Z=8 : O1616, O, O1717 and O and O1818) )

ATOMS AND IONSATOMS AND IONS Atomic weight – number expressing relative weight of an Atomic weight – number expressing relative weight of an

element in terms of the weight of the element oxygenelement in terms of the weight of the element oxygen Characteristics of an element depend on the configuration of Characteristics of an element depend on the configuration of

the electronic structure of its atomsthe electronic structure of its atoms

RADIOACTIVITY INSIDE YOURADIOACTIVITY INSIDE YOU

Concerned about radioactivity in nature?

To keep things in perspective, consider that 0.01% of all potassium is

radioactive K-40.

Potassium is an essential element in the human body.

If your body is about 1% K, this means a 70 kg

(150 pound) person contains around

1x1021 atoms (that’s one billion trillion atoms)

of radioactive K-40.

BONDING FORCES IN CRYSTALSBONDING FORCES IN CRYSTALS Forces that bind atoms or ions of crystalline solids together Forces that bind atoms or ions of crystalline solids together

are electrical in natureare electrical in nature Type and intensity of bond are responsible for physical and Type and intensity of bond are responsible for physical and

chemical properties of minerals (hardness, cleavage, chemical properties of minerals (hardness, cleavage, fusibility, electrical and thermal conductivity and coefficient of fusibility, electrical and thermal conductivity and coefficient of thermal expansion)thermal expansion) The stronger the bond → harder crystalThe stronger the bond → harder crystal

→ → higher melting pointhigher melting point

→ → smaller thermal expansion smaller thermal expansion coeff.coeff.

Diamond (C) – hardness due to very strong electrical Diamond (C) – hardness due to very strong electrical forces linking carbon atomsforces linking carbon atoms

Periclase (MgO) and halite (NaCl) – have similar structural Periclase (MgO) and halite (NaCl) – have similar structural patterns but halite melts at 801 °C while periclase at 2800 patterns but halite melts at 801 °C while periclase at 2800 °C due to stronger electrical bond requiring larger heat °C due to stronger electrical bond requiring larger heat energy to separate atomsenergy to separate atoms

BONDING FORCES IN CRYSTALSBONDING FORCES IN CRYSTALS One typical consequence of chemical reactions is One typical consequence of chemical reactions is

the formation of chemical bonds between atoms and the formation of chemical bonds between atoms and complexes. What kind of bonds form is based on the complexes. What kind of bonds form is based on the electronic configuration of the atoms involved.electronic configuration of the atoms involved.

Atoms with near-full (halogens) and near-empty Atoms with near-full (halogens) and near-empty (alkalis/alkali earths) outer electron shells, as well as (alkalis/alkali earths) outer electron shells, as well as transition metals, may form transition metals, may form ionic ionic bonds. bonds.

Covalent Covalent bonds are where atoms share outer shell bonds are where atoms share outer shell electrons. electrons.

The bulk of minerals are dominantly ionically The bulk of minerals are dominantly ionically bonded. However, many minerals have bonds with bonded. However, many minerals have bonds with some covalent and some ionic components.some covalent and some ionic components.

BONDING FORCES IN CRYSTALSBONDING FORCES IN CRYSTALS Types of Chemical Bonds:Types of Chemical Bonds:

Ionic bond (moderate hardness and SG, high melting Ionic bond (moderate hardness and SG, high melting and boiling points, poor conductors of heat and and boiling points, poor conductors of heat and electricity)electricity)

Covalent bond – strongest chemical bond (very high Covalent bond – strongest chemical bond (very high melting and boiling points, great stability) melting and boiling points, great stability)

Metallic bond (high plasticity, tenacity, ductility and Metallic bond (high plasticity, tenacity, ductility and conductivity, low hardness, low melting and boiling conductivity, low hardness, low melting and boiling points)points)

Van der Waals’ bond (weak)Van der Waals’ bond (weak)

ATOMIC STRUCTUREATOMIC STRUCTURE

• Protons and neutrons form the nucleus of an atom

– Represents tiny fraction of the volume at the center of an atom, but nearly all of

the mass

• Electrons orbit the nucleus in discrete shells or energy levels

– Shells represent nearly all of the volume of an atom, but only a tiny fraction of the

mass– Numbers of electrons and protons are

equal in a neutral atom– Ordinary chemical reactions involve only

outermost shell (valence) electrons

ELECTRONS ORGANIZE IN ENERGY LEVELSELECTRONS ORGANIZE IN ENERGY LEVELS

CHEMICAL BONDINGCHEMICAL BONDING

• Chemical bonding is controlled by outermost shell (valence) electrons

• Elements will typically be reactive unless their valence shell is full

• Atoms or groups of atoms with unequal numbers of protons and electrons, thus having a non-zero charge, are called ions. Positively charged ions are known as cations, and negative charges as anions.

• Positive and negative ions are attracted to one another and may stick or chemically bond together

IONIC BONDSIONIC BONDS

Atoms satisfy themselves

by the give and take of

outer shell electrons.

Most minerals are held

together by primarily ionic

bonds.

COVALENT BONDS: ELECTRON SHA-COVALENT BONDS: ELECTRON SHA-RINGRING

These carbon atoms are held together by sharing outer-shell

electrons.

BONDING FORCES IN CRYSTALSBONDING FORCES IN CRYSTALSPROPERTYPROPERTY IONIC BONDIONIC BOND COVALENT BONDCOVALENT BOND METALLIC BONDMETALLIC BOND VAN DER WAAL’S BONDVAN DER WAAL’S BOND

BOND STRENGTHBOND STRENGTH StrongStrong Very strongVery strong Variable strength but Variable strength but generally moderategenerally moderate

WeakWeak

MECHANICALMECHANICAL Moderate to high hardness Moderate to high hardness depending on interionic depending on interionic distance; brittledistance; brittle

Great hardness; brittleGreat hardness; brittle Low to moderate hardness; Low to moderate hardness; gliding common; high gliding common; high plasticity; sectile; ductile; plasticity; sectile; ductile; malleablemalleable

Crystal soft and somewhat Crystal soft and somewhat plasticplastic

ELECTRICALELECTRICAL Poor conductors in solid Poor conductors in solid state, melts and solutions state, melts and solutions conduct by ion transportconduct by ion transport

Insulators in solid stateInsulators in solid state Good conductors; conduction Good conductors; conduction by electron transportby electron transport

Insulators in both solid and Insulators in both solid and liquid stateliquid state

THERMAL (melting THERMAL (melting point, coefficient of point, coefficient of thermal expansion)thermal expansion)

Moderate to high MP Moderate to high MP depending on interionic depending on interionic distance; low coefficient of distance; low coefficient of thermal expansionthermal expansion

High MP, low coefficient of High MP, low coefficient of thermal expansionthermal expansion

Variable MP and coefficient Variable MP and coefficient of thermal expansionof thermal expansion

Low MP, high coefficient Low MP, high coefficient of thermal expansionof thermal expansion

SOLUBILITYSOLUBILITY Soluble in polar solventsSoluble in polar solvents Very low solubilitiesVery low solubilities Insoluble except in acids or Insoluble except in acids or alkalis by chemical reactionalkalis by chemical reaction

Soluble in organic solvents Soluble in organic solvents to yield solutionsto yield solutions

STRUCTURALSTRUCTURAL Non-directed; gives structure Non-directed; gives structure of high coordination and of high coordination and symmetrysymmetry

Highly directional; gives Highly directional; gives structures of lower structures of lower coordination and symmetrycoordination and symmetry

Non-directed; gives Non-directed; gives structures of very high structures of very high coordination and symmetrycoordination and symmetry

Non-directed; symmetry Non-directed; symmetry low because of shape of low because of shape of moleculesmolecules

EXAMPLESEXAMPLES Halite (NaCl)Halite (NaCl)Calcite (CaCOCalcite (CaCO33))

Fluorite (CaFFluorite (CaF22))

Most mineralsMost minerals

Diamond (C)Diamond (C)Sphalerite (ZnS)Sphalerite (ZnS)OO22 molecules molecules

Graphite C)Graphite C)Organic moleculesOrganic molecules

Copper (Cu)Copper (Cu)Silver (Ag)Silver (Ag)Gold (Au)Gold (Au)Most metalsMost metals

Iodine (IIodine (I22))

Organic compoundsOrganic compounds

CHEMICAL REACTIONS: ACHIEVING CHEMICAL REACTIONS: ACHIEVING STABILITYSTABILITY

Chemical reactions take place in order to achieve a Chemical reactions take place in order to achieve a more stable state (lower total energy) under given more stable state (lower total energy) under given conditions (pressure, temperature). conditions (pressure, temperature).

Unstable reactants react to form stable productsUnstable reactants react to form stable products To complicate this, the transition from unstable To complicate this, the transition from unstable

mineral to stable mineral is not necessarily automa-mineral to stable mineral is not necessarily automa-tic. Many chemical reactions require great deal of tic. Many chemical reactions require great deal of energy to run to completionenergy to run to completion

STABILITY AND METASTABILITYSTABILITY AND METASTABILITY Minerals that persist in an environment in which they are Minerals that persist in an environment in which they are

not chemically stable are said to be not chemically stable are said to be metastablemetastable. .

Most of the minerals in the rocks at the Earth’s surface are Most of the minerals in the rocks at the Earth’s surface are

metastable. Given enough energy (or enough time and the metastable. Given enough energy (or enough time and the

right conditions) they will react to form stable minerals.right conditions) they will react to form stable minerals.

graphite stable

diamond stable

tem pera ture

pre

ssur

e

Earth’s surfaceconditions

CHEMICAL COMPOSITION OF MINERALSCHEMICAL COMPOSITION OF MINERALS Most minerals have compositions corresponding to chemical compounds. Most minerals have compositions corresponding to chemical compounds.

But a few occurs as elements (native) such as native gold, native copper But a few occurs as elements (native) such as native gold, native copper and native sulfurand native sulfur

Minerals are seldom chemically pure (except quartz and kyanite), and Minerals are seldom chemically pure (except quartz and kyanite), and compositions seldom correspond to an ideal chemical formula → compositions seldom correspond to an ideal chemical formula → “characteristic chemical composition”“characteristic chemical composition”

Chemical formulas – derived from the determination of the principal Chemical formulas – derived from the determination of the principal chemical constituents of a mineral (eg. CuFeSchemical constituents of a mineral (eg. CuFeS22))

ELEMENTELEMENT ANALYSISANALYSIS

( wt. %)( wt. %)

ATOMIC ATOMIC WEIGHTWEIGHT

ATOMIC ATOMIC PROPOR-PROPOR-

TIONSTIONS

ATOMIC ATOMIC RATIORATIO

RE-RE-CALCULATED CALCULATED PERCENTAGEPERCENTAGE

CuCu 34.8934.89 63.5463.54 0.54910.5491 11 34.6234.62

FeFe 30.0430.04 55.8555.85 0.53.780.53.78 11 30.4330.43

SS 34.5134.51 32.07(2)32.07(2) 1.07681.0768 22 34.9434.94

99.4499.44 183.53183.53 100.00100.00

CHEMICAL COMPOSITION OF THE EARTH’S CHEMICAL COMPOSITION OF THE EARTH’S CRUSTCRUST

Internal structure of the earth:Internal structure of the earth: Core – 2900 to 6370 km.Core – 2900 to 6370 km.

Inner core – solid (5115 km.)Inner core – solid (5115 km.) Outer Core – liquid (2900 km.)Outer Core – liquid (2900 km.)

MantleMantle Upper mantle – 400 km.Upper mantle – 400 km. Transition Zone – 1000 km.Transition Zone – 1000 km. Lower Mantle – 2900 km. Lower Mantle – 2900 km.

Mohorovicic DiscontinuityMohorovicic Discontinuity – boundary between the crust and – boundary between the crust and the upper mantle the upper mantle

Crust - 36 km. thick (under continents), 10-13 km (under oceans)Crust - 36 km. thick (under continents), 10-13 km (under oceans) Upper part – large percentage of sedimentary rocks and Upper part – large percentage of sedimentary rocks and

unconsolidated materials forming as thin veneerunconsolidated materials forming as thin veneer Lower part – basement of igneous and metamorphic rocksLower part – basement of igneous and metamorphic rocks

Upper 10 mi. consist of 95% igneous rocks, 4% shale, 0.75% Upper 10 mi. consist of 95% igneous rocks, 4% shale, 0.75% sandstone and 0.25% limestonesandstone and 0.25% limestone

CHEMICAL COMPOSITION OF THE EARTH’S CHEMICAL COMPOSITION OF THE EARTH’S CRUSTCRUST Average composition – between basalt and graniteAverage composition – between basalt and granite Most common elements in the earth’s crust (99%):Most common elements in the earth’s crust (99%):

ELEMENTELEMENT % WEIGHT% WEIGHT % VOLUME% VOLUME

OO 46.6046.60 93.7793.77

SiSi 27.7227.72 0.860.86

AlAl 8.138.13 0.470.47

FeFe 5.005.00 0.430.43

MgMg 2.092.09 0.290.29

CaCa 3.633.63 1.031.03

NaNa 2.832.83 1.321.32

KK 2.592.59 1.831.83

ROCK-FORMING MINERALSROCK-FORMING MINERALS O constitutes >90% of the volume of the earth’s crustO constitutes >90% of the volume of the earth’s crust Earth’s crust is a packing of O anion with interstitial metal Earth’s crust is a packing of O anion with interstitial metal

ions, chiefly Si (O-containing minerals such as silicates, oxide ions, chiefly Si (O-containing minerals such as silicates, oxide and carbonates most abundant minerals)and carbonates most abundant minerals)

Rock-forming minerals are members of silicate-oxide-Rock-forming minerals are members of silicate-oxide-carbonate groupcarbonate group

Economic minerals (eg. Cu, Pb, Hg,) low abundance → locate Economic minerals (eg. Cu, Pb, Hg,) low abundance → locate areas of high concentrations (ore deposits) to make mining areas of high concentrations (ore deposits) to make mining profitable and to produce metals needed for our economyprofitable and to produce metals needed for our economy

Some elements (eg. Rubidium) are dispersed throughout Some elements (eg. Rubidium) are dispersed throughout common minerals and are never concentrated. Rb does not common minerals and are never concentrated. Rb does not form specific Rb compounds but is housed in K-rich mineralsform specific Rb compounds but is housed in K-rich minerals

Some elements are highly concentrated in some minerals: Zr Some elements are highly concentrated in some minerals: Zr in zircon (ZrSiOin zircon (ZrSiO44), Ti in rutile (TiO), Ti in rutile (TiO22) and ilmenite (FeTiO) and ilmenite (FeTiO22))

CHEMICAL COMPOSITION OF THE CHEMICAL COMPOSITION OF THE EARTHEARTH

Estimates based on composition of meteorites and the Estimates based on composition of meteorites and the volumes of the crust, mantle and corevolumes of the crust, mantle and core Core → iron meteorites (FeNi alloy)Core → iron meteorites (FeNi alloy) Lower mantle → meteorites with 50% metal and 50% silicateLower mantle → meteorites with 50% metal and 50% silicate Upper mantle and lower crust → stony silicate meteorites (with little Upper mantle and lower crust → stony silicate meteorites (with little

metal)metal)

ELEMENTELEMENT % COMPOSITION% COMPOSITION

OO 29.5329.53

SiSi 15.2015.20

AlAl 1.091.09

FeFe 34.6334.63

MgMg 12.7012.70

CaCa 1.131.13

NiNi 2.392.39

Na, K, Cr, Co, Mn, P & TiNa, K, Cr, Co, Mn, P & Ti 0.1 to 1.00.1 to 1.0

CRYSTALLOGRAPHYCRYSTALLOGRAPHY

CRYSTALLOGRAPHYCRYSTALLOGRAPHY Crystallography - study of crystalline solids and the laws that Crystallography - study of crystalline solids and the laws that

govern their growth, external shape and internal structuregovern their growth, external shape and internal structure CRYSTAL – a homogeneous solid possessing long CRYSTAL – a homogeneous solid possessing long

range, three-dimensional internal order range, three-dimensional internal order MINERALS – possess internal ordered arrangement that MINERALS – possess internal ordered arrangement that

is characteristic of crystalline solidsis characteristic of crystalline solids

- - bounded by smooth plane surfaces and assume bounded by smooth plane surfaces and assume regular geometric forms only when conditions are regular geometric forms only when conditions are favorablefavorable

CRYSTALLOGRAPHYCRYSTALLOGRAPHY Study of structure, symmetry and shape of crystals. This Study of structure, symmetry and shape of crystals. This

terminology defines the crystal lattice which provides a terminology defines the crystal lattice which provides a

mineral with its ordered internal structuremineral with its ordered internal structure CRYSTAL:CRYSTAL:

1.1. Microcrystalline – fine grained that crystalline nature can Microcrystalline – fine grained that crystalline nature can only be determined using a microscope only be determined using a microscope

2.2. Cryptocrystalline – very fine that individual crystallites Cryptocrystalline – very fine that individual crystallites cannot be resolved with microscope but can be detected cannot be resolved with microscope but can be detected by x-ray diffractionby x-ray diffraction

CRYSTAL (perfection of development)CRYSTAL (perfection of development)1.1. Euhedral – perfectly developed facesEuhedral – perfectly developed faces2.2. Subhedral – imperfectly developed facesSubhedral – imperfectly developed faces3.3. Anhedral - without facesAnhedral - without faces

AMORPHOUS – lack ordered internal atomic arrangement AMORPHOUS – lack ordered internal atomic arrangement (mineraloids)(mineraloids)

CRYSTALLIZATIONCRYSTALLIZATION Crystals form from:Crystals form from:

Solutions (evaporation of solvent, lowering temperature or Solutions (evaporation of solvent, lowering temperature or pressure)pressure)Salt dissolved in water → evaporation → solution Salt dissolved in water → evaporation → solution

contains more and more Nacontains more and more Na++ and Cl and Cl-- per unit volume per unit volume → remaining water can no longer retain all the salt in → remaining water can no longer retain all the salt in solution → salt begins to precipitatesolution → salt begins to precipitate

Slow evaporation → NaSlow evaporation → Na++ and Cl and Cl-- group together group together and form one or few large crystals with common and form one or few large crystals with common orientationorientation

Rapid evaporation → many centers of Rapid evaporation → many centers of crystallization and form many small randomly crystallization and form many small randomly oriented crystalsoriented crystals

MeltsMeltsLiquid HLiquid H22O molecules moving freely in any direction → O molecules moving freely in any direction →

temperature lowering → molecules become fixed and temperature lowering → molecules become fixed and arrange themselves in definite order → solid crystalline arrange themselves in definite order → solid crystalline mass (ice)mass (ice)

CRYSTALLIZATIONCRYSTALLIZATION MeltsMelts

Molten magma → ions of many elements in an Molten magma → ions of many elements in an uncombined state → magma cools → various ions are uncombined state → magma cools → various ions are attracted to one another to form crystal nuclei of the attracted to one another to form crystal nuclei of the different minerals → crystallization proceeds with addition different minerals → crystallization proceeds with addition of more ions to the crystal nuclei forming the mineral of more ions to the crystal nuclei forming the mineral grains of the resulting rock grains of the resulting rock

VaporsVapors Formation of snowflakes → vapor is cooled, the Formation of snowflakes → vapor is cooled, the

dissociated atoms or molecules are brought closer dissociated atoms or molecules are brought closer together, eventually locking themselves into crystalline together, eventually locking themselves into crystalline solidsolid

CRYSTALCRYSTAL A crystal consists of matter that is formed from an ordered A crystal consists of matter that is formed from an ordered

arrangement of atoms, molecules, or ions. Because there arrangement of atoms, molecules, or ions. Because there are repeated units, crystals have recognizable structures. are repeated units, crystals have recognizable structures. There are seven systems of crystal structures, which are There are seven systems of crystal structures, which are also called lattices or space lattices.also called lattices or space lattices.

A A crystal or crystalline solid is a solid material, whose is a solid material, whose constituent atoms, molecules, or ions are arranged in an constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial orderly repeating pattern extending in all three spatial dimensions. dimensions.

Crystalline structures occur in all classes of materials, with Crystalline structures occur in all classes of materials, with all types of chemical bonds all types of chemical bonds

CRYSTALLOGRAPHIC AXESCRYSTALLOGRAPHIC AXES In order to study the forms and define the In order to study the forms and define the

position of the faces occurring on crystals, position of the faces occurring on crystals, straight lines are assumed to pass through straight lines are assumed to pass through the ideal center of each crystal. These lines the ideal center of each crystal. These lines are called the are called the crystallographic axes. crystallographic axes. Intersections of crystallographic axes forms Intersections of crystallographic axes forms an an axial crossaxial cross

If the 3 crystal axes are identical (eg. If the 3 crystal axes are identical (eg. octahedron), each is referred to the same octahedron), each is referred to the same letter letter a. a. The extremities of the axes are The extremities of the axes are differentiated by the use of the plus and differentiated by the use of the plus and minus signsminus signs

If the axes are not alike, the one extending If the axes are not alike, the one extending from front to rear is termed the from front to rear is termed the aa axis, the axis, the one from left to right the one from left to right the bb axis and the axis and the vertical axis as vertical axis as cc. They are always referred . They are always referred to in the following order, to in the following order, a, ba, b, and , and cc

Grouping of crystal forms into 7 crystal Grouping of crystal forms into 7 crystal systems is aided by the crystallographic systems is aided by the crystallographic axesaxes

CRYSTALLOGRAPHIC AXESCRYSTALLOGRAPHIC AXES

ISOMETRIC HEXAGONALORTHORHOMBICTETRAGONAL

TRIGONAL MONOCLINIC TRICLINIC

CRYSTALLOGRAPHIC AXESCRYSTALLOGRAPHIC AXES crystallographic axes can be defined for the various

crystal systems. Two important points to remember:

a. The lengths of the crystallographic axes are controlled by the dimensions of the unit cell upon which the crystal is based.

b. The angles between the crystallographic axes are controlled by the shape of the unit cell.

the relative lengths of the crystallographic axes control the angular relationships between crystal faces. This is true because crystal faces can only develop along lattice points. The relative lengths of the crystallographic axes are called axial ratios.

ELEMENTS OF CRYSTALLIZATIONELEMENTS OF CRYSTALLIZATION Axial ratioAxial ratio Angles showing the inclination of the axesAngles showing the inclination of the axes

AXIAL RATIOAXIAL RATIO Axial ratio is defined as the ratio between the lengths of the Axial ratio is defined as the ratio between the lengths of the

axes of crystals. This is normally taken as relative to the axes of crystals. This is normally taken as relative to the length of the b crystallographic axis. Thus, an axial ratio is length of the b crystallographic axis. Thus, an axial ratio is defined as follows:defined as follows:

Axial Ratio = a/b : b/b : c/bAxial Ratio = a/b : b/b : c/b where a is the actual length of the a crystallographic axis, b, where a is the actual length of the a crystallographic axis, b,

is the actual length of the b crystallographic axis, and c is the is the actual length of the b crystallographic axis, and c is the actual length of the c crystallographicactual length of the c crystallographic

Axial ratios of a given substance is constantAxial ratios of a given substance is constant

AXIAL RATIOAXIAL RATIO In the In the cubic systemcubic system, where the 3 axes are identical, the ratio , where the 3 axes are identical, the ratio

is is a : a : aa : a : a or 1 : 1 : 1 (this is usually shorted to 1) or 1 : 1 : 1 (this is usually shorted to 1) In In tetragonal systemtetragonal system the lengths the length of the a and b the lengths the length of the a and b

axes are equal, this reduces to 1 : 1 : c/b (this is usually axes are equal, this reduces to 1 : 1 : c/b (this is usually shorted to 1 : c)shorted to 1 : c)

In In hexagonal crystalshexagonal crystals where there are three equal length where there are three equal length axes (aaxes (a11, a, a22, and a, and a33) perpendicular to the c axis this becomes ) perpendicular to the c axis this becomes 1 : 1 : 1: c/a (usually shortened to 1 : c) 1 : 1 : 1: c/a (usually shortened to 1 : c)

In In orthorhombicorthorhombic, , monoclinicmonoclinic and and triclinic systemstriclinic systems, there are 3 , there are 3 axes of unequal lengths axes of unequal lengths a, ba, b and and cc. This redices to a/b : 1 : . This redices to a/b : 1 : c/b (this is usually shortened to a : 1 : c)c/b (this is usually shortened to a : 1 : c)

Modern crystallographers can use x-rays to determine the Modern crystallographers can use x-rays to determine the size of the unit cell and determine the absolute value of the size of the unit cell and determine the absolute value of the crystallographic axes. For example, quartz has the following crystallographic axes. For example, quartz has the following unit cell dimensions: aunit cell dimensions: a11 = a = a22 = a = a33 = 4.913Å and c = 5.405Å = 4.913Å and c = 5.405Å

where:where: Å stands for Angstroms = 10 Å stands for Angstroms = 10-10-10 m m

AXIAL RATIOAXIAL RATIO Thus the axial ratio for quartz is 1 : 1 : 1 : 5.405/4.913 or Thus the axial ratio for quartz is 1 : 1 : 1 : 5.405/4.913 or

1: 1 : 1 : 1.1001 which simply says that the c axis is 1.1001 1: 1 : 1 : 1.1001 which simply says that the c axis is 1.1001 times longer than the a axes.times longer than the a axes.

Because crystal faces develop along lattice points, the Because crystal faces develop along lattice points, the angular relationship between faces must depend on the angular relationship between faces must depend on the relative lengths of the axes. Long before x-rays were relative lengths of the axes. Long before x-rays were invented and absolute unit cell dimensions could be invented and absolute unit cell dimensions could be obtained, crystallographers were able to determine the axial obtained, crystallographers were able to determine the axial ratios of minerals by determining the angles between crystal ratios of minerals by determining the angles between crystal faces. So, for example, in 1896 the axial ratios of faces. So, for example, in 1896 the axial ratios of orthorhombic sulfur were determined to be nearly exactly the orthorhombic sulfur were determined to be nearly exactly the same as those reported above from x-ray measurements. same as those reported above from x-ray measurements.

PARAMETERS AND PARAMETRAL RATIOSPARAMETERS AND PARAMETRAL RATIOS In order to determine the position of a face on a crystal, it In order to determine the position of a face on a crystal, it

must be referred to the crystallographic axesmust be referred to the crystallographic axes Parametral ratios differ from axial ratios which gives the Parametral ratios differ from axial ratios which gives the

numerical lengths of the axes in terms of one of them taken numerical lengths of the axes in terms of one of them taken as unity as unity

INTERCEPTS OF CRYSTAL FACES (WEISS INTERCEPTS OF CRYSTAL FACES (WEISS

PARAMETERS)PARAMETERS) Crystal faces can be defined by their intercepts on the Crystal faces can be defined by their intercepts on the

crystallographic axes. For non-hexagonal crystals, there are crystallographic axes. For non-hexagonal crystals, there are three cases:three cases:1.1. A crystal face intersects only one of the crystallographic A crystal face intersects only one of the crystallographic

axesaxes2.2. A crystal face intersects two of the crystallographic axesA crystal face intersects two of the crystallographic axes3.3. A crystal face that intersects all 3 axes A crystal face that intersects all 3 axes

Two very important points about intercepts of faces: Two very important points about intercepts of faces: The intercepts or parameters are relative values, and do The intercepts or parameters are relative values, and do

not indicate any actual cutting lengths.not indicate any actual cutting lengths. Since they are relative, a face can be moved parallel to Since they are relative, a face can be moved parallel to

itself without changing its relative intercepts or itself without changing its relative intercepts or parametersparameters

CRYSTAL FACE INTERSECTS ONLY ONE CRYSTAL FACE INTERSECTS ONLY ONE OF THE CRYSTALLOGRAPHIC AXESOF THE CRYSTALLOGRAPHIC AXES

As an example the top crystal face shown here intersects As an example the top crystal face shown here intersects the c axis but does not intersect the a or b axes. If we the c axis but does not intersect the a or b axes. If we assume that the face intercepts the c axis at a distance of 1 assume that the face intercepts the c axis at a distance of 1 unit length, then the intercepts, sometimes called Weiss unit length, then the intercepts, sometimes called Weiss Parameters, are: Parameters, are: a, a, b, 1cb, 1c

CRYSTAL FACE INTERSECTS TWO OF CRYSTAL FACE INTERSECTS TWO OF THE CRYSTALLOGRAPHIC AXES THE CRYSTALLOGRAPHIC AXES

As an example, the darker crystal face shown here As an example, the darker crystal face shown here intersects the a and b axes, but not the c axis. Assuming intersects the a and b axes, but not the c axis. Assuming the face intercepts the a and c axes at 1 unit cell length on the face intercepts the a and c axes at 1 unit cell length on each, the parameters for this face are: each, the parameters for this face are: 1 a, 1 b, 1 a, 1 b, cc

CRYSTAL FACE THAT INTERSECTS ALL CRYSTAL FACE THAT INTERSECTS ALL THREE AXESTHREE AXES In this example the darker face is assumed to intersect the In this example the darker face is assumed to intersect the

a, b, and c crystallographic axes at one unit length on each. a, b, and c crystallographic axes at one unit length on each. Thus, the parameters in this example would be: Thus, the parameters in this example would be: 1a, 1b, 1c1a, 1b, 1c

INTERCEPTS OF CRYSTAL FACESINTERCEPTS OF CRYSTAL FACES Because one does usually not know the dimensions of the Because one does usually not know the dimensions of the

unit cell, it is difficult to know what number to give the unit cell, it is difficult to know what number to give the intercept of a face, unless one face is chosen arbitrarily to intercept of a face, unless one face is chosen arbitrarily to have intercepts of 1. Thus, the convention is to assign the have intercepts of 1. Thus, the convention is to assign the largest face that intersects all 3 crystallographic axes the largest face that intersects all 3 crystallographic axes the parameters - 1a, 1b, 1c. This face is called the parameters - 1a, 1b, 1c. This face is called the unit face.unit face.

For example, in the orthorhombic crystal shown here, the For example, in the orthorhombic crystal shown here, the large dark shaded face is the largest face that cuts all three large dark shaded face is the largest face that cuts all three axes. It is the unit face, and is therefore assigned the axes. It is the unit face, and is therefore assigned the parameters 1a, 1b, 1c. parameters 1a, 1b, 1c.

INTERCEPTS OF CRYSTAL FACESINTERCEPTS OF CRYSTAL FACES Once the unit face is defined, the Once the unit face is defined, the

intercepts of the smaller face can be intercepts of the smaller face can be determined. These are 2a, 2b, determined. These are 2a, 2b, 2/3c. Note that we can divide these 2/3c. Note that we can divide these parameters by the common factor 2, parameters by the common factor 2, resulting in 1a,1b,1/3c. Again, this resulting in 1a,1b,1/3c. Again, this illustrates the point that moving a face illustrates the point that moving a face parallel to itself does not change the parallel to itself does not change the relative intercepts. Since intercepts or relative intercepts. Since intercepts or parameters are relative, they do not parameters are relative, they do not represent the actual cutting lengths on represent the actual cutting lengths on the axes.the axes.

By specifying the intercepts or parame-By specifying the intercepts or parame-ters of a crystal face, we now have a way ters of a crystal face, we now have a way to uniquely identify each face of a crys-to uniquely identify each face of a crys-tal. But, the notation is cumbersome, so tal. But, the notation is cumbersome, so crystallographers have developed crystallographers have developed another way of identifying or indexing another way of identifying or indexing faces. This conventional notation called faces. This conventional notation called the Miller Index.the Miller Index.

MILLER INDICESMILLER INDICES Miller indices are a notation system in crystallography for Miller indices are a notation system in crystallography for

planes and directions in crystal (Bravais) lattices.planes and directions in crystal (Bravais) lattices. Miller Indices are a symbolic vector representation for the Miller Indices are a symbolic vector representation for the

orientation of an atomic plane in a crystal lattice and are orientation of an atomic plane in a crystal lattice and are defined as the reciprocals of the fractional intercepts which defined as the reciprocals of the fractional intercepts which the plane makes with the crystallographic axes the plane makes with the crystallographic axes

In particular, a family of lattice planes is determined by three In particular, a family of lattice planes is determined by three integers integers aa, b, b, and , and cc, the , the Miller indicesMiller indices. They are written . They are written (abc)(abc) and each index denotes an intersection of a plane with a and each index denotes an intersection of a plane with a direction direction (a, b, c)(a, b, c) in the basis of the reciprocal lattice vectors. in the basis of the reciprocal lattice vectors. By convention, negative integers are written with a bar, as in By convention, negative integers are written with a bar, as in 3 for −3. The integers are usually written in lowest terms, i.e. 3 for −3. The integers are usually written in lowest terms, i.e. their greatest common divisor should be 1. Miller index 100 their greatest common divisor should be 1. Miller index 100 represents a plane orthogonal to directionrepresents a plane orthogonal to direction a a; index 010 ; index 010 represents a plane orthogonal to direction represents a plane orthogonal to direction bb, and index 001 , and index 001 represents a plane orthogonal to represents a plane orthogonal to cc..

MILLER INDICESMILLER INDICES

The method by which The method by which indices are determined indices are determined is best shown by is best shown by example. Recall, that example. Recall, that there are three axes in there are three axes in crystallographic crystallographic systems. Miller indices systems. Miller indices are represented by a are represented by a set of 3 integer set of 3 integer numbersnumbers

MILLER INDICESMILLER INDICES Steps to describe the Steps to describe the

orientation of a crystal face or orientation of a crystal face or a plane of atoms within a a plane of atoms within a crystal lattice:crystal lattice:

1.1. The first thing that must be The first thing that must be ascertained are the ascertained are the fractional intercepts that fractional intercepts that the plane/face makes with the plane/face makes with the crystallographic axes. the crystallographic axes. In other words, how far In other words, how far along the unit cell lengths along the unit cell lengths does the plane intersect does the plane intersect the axis. In the figure on the axis. In the figure on the right, the plane the right, the plane intercepts each axis at intercepts each axis at exact one unit length. exact one unit length.

MILLER INDICESMILLER INDICES2.2. Taking the reciprocal of the frac-Taking the reciprocal of the frac-

tional intercept of each unit length tional intercept of each unit length for each axis. In the figure on the for each axis. In the figure on the right, the values are all 1/1.right, the values are all 1/1.

3.3. Finally the fractions are cleared Finally the fractions are cleared ((i.e.,i.e., make 1 as the common make 1 as the common denominator).denominator).

4.4. These integer numbers are then These integer numbers are then parenthetically enclosed and parenthetically enclosed and designate that specific crystallo-designate that specific crystallo-graphic plane within the lattice. graphic plane within the lattice. Since the unit cell repeats in space, Since the unit cell repeats in space, the notation actually represents a the notation actually represents a family of planes, all with the same family of planes, all with the same orientation. In the figure, the Miller orientation. In the figure, the Miller indices for the plane is (111)indices for the plane is (111)

MILLER INDICESMILLER INDICES

INTERNAL ORDER AND CRYSTAL INTERNAL ORDER AND CRYSTAL MORPHOLOGYMORPHOLOGY

3-D internal order of a crystal – considered as a repetition of 3-D internal order of a crystal – considered as a repetition of a motif* in such a way that the environment of and around a motif* in such a way that the environment of and around each repeated motif is identicaleach repeated motif is identical

Motifs:Motifs: Anionic groups (SiOAnionic groups (SiO44))-4-4

molecules (Hmolecules (H22O)O) Ions (CaIons (Ca2+2+, Mg, Mg2+2+, Fe, Fe2+2+) )

Ordered arrangement provides more stable and less Ordered arrangement provides more stable and less energetic configuration. An ordered pattern is generated by energetic configuration. An ordered pattern is generated by a motif repeated in a regular sequence of new locationa motif repeated in a regular sequence of new location

Any motion that brings the original motif into coincidence Any motion that brings the original motif into coincidence with the same motif elsewhere in the pattern is referred to as with the same motif elsewhere in the pattern is referred to as an an operation. operation. Thus a homogeneous pattern can be gene-Thus a homogeneous pattern can be gene-rated from a single motif by a set of geometric operations.rated from a single motif by a set of geometric operations.

INTERNAL ORDER AND CRYSTAL INTERNAL ORDER AND CRYSTAL MORPHOLOGYMORPHOLOGY 3-D internal order of a crystal – considered as a repetition of 3-D internal order of a crystal – considered as a repetition of

a motif in such a way that the environment of and around a motif in such a way that the environment of and around each repeated motif* is identicaleach repeated motif* is identical

Motifs:Motifs: Anionic groups (SiOAnionic groups (SiO44))-4-4

molecules (Hmolecules (H22O)O) Ions (CaIons (Ca2+2+, Mg, Mg2+2+, Fe, Fe2+2+) )

Symmetry** - describes the repetition of structural featuresSymmetry** - describes the repetition of structural features1.1. Translational symmetry - describes the periodic repetition Translational symmetry - describes the periodic repetition

of a structural feature across a length or through an area of a structural feature across a length or through an area or volume or volume

2.2. Point symmetry - describes the periodic repetition of a Point symmetry - describes the periodic repetition of a structural feature around a point (reflection, rotation, structural feature around a point (reflection, rotation, inversion)inversion)

INTERNAL ORDER AND CRYSTAL INTERNAL ORDER AND CRYSTAL MORPHOLOGYMORPHOLOGY Lattice - a network or array composed of single motif which Lattice - a network or array composed of single motif which

has been translated and repeated at fixed intervals has been translated and repeated at fixed intervals throughout space (imaginary)throughout space (imaginary)- directly related to the idea of translational symmetry directly related to the idea of translational symmetry - eg. square → planar square lattice eg. square → planar square lattice

Unit cell of a lattice - the smallest unit which can be repeated Unit cell of a lattice - the smallest unit which can be repeated in three dimensions in order to construct the latticein three dimensions in order to construct the lattice- consists of a specific group of atoms which are bonded to consists of a specific group of atoms which are bonded to

one another in a set geometrical arrangement.one another in a set geometrical arrangement.- this unit and its constituent atoms are then repeated over this unit and its constituent atoms are then repeated over

and over in order to construct the crystal lattice. The and over in order to construct the crystal lattice. The surroundings in any given direction of one corner of a unit surroundings in any given direction of one corner of a unit cell must be identical to the surroundings in the same cell must be identical to the surroundings in the same direction of all the other corners. The corners of the unit direction of all the other corners. The corners of the unit cell therefore serve as points which are repeated to form cell therefore serve as points which are repeated to form a lattice array a lattice array

INTERNAL ORDER AND CRYSTAL INTERNAL ORDER AND CRYSTAL MORPHOLOGYMORPHOLOGY Lattice points - corners of the unit cell that serve as points Lattice points - corners of the unit cell that serve as points

which are repeated to form a lattice arraywhich are repeated to form a lattice array 5 possible lattices in a plane (translation)5 possible lattices in a plane (translation)

1.1. square unit cellsquare unit cell2.2. rectangular unit cellrectangular unit cell3.3. centered rectangular unit cellcentered rectangular unit cell4.4. parallelogramparallelogram5.5. hexagonal unit cell - rhombus hexagonal unit cell - rhombus

BRAVAIS LATTICESBRAVAIS LATTICES French crystallographer Auguste Bravais (1811-1863) French crystallographer Auguste Bravais (1811-1863)

established that in three-dimensional space only fourteen established that in three-dimensional space only fourteen different lattices may be constructed → 6 CRYSTAL different lattices may be constructed → 6 CRYSTAL SYSTEMSSYSTEMS

3 Types of Bravais Lattices:3 Types of Bravais Lattices: primitive lattice - has only a lattice point at each corner of primitive lattice - has only a lattice point at each corner of

the three-dimensional unit cellthe three-dimensional unit cell body-centered lattice - contains not only lattice points at body-centered lattice - contains not only lattice points at

each corner of the unit cell but also contains a lattice point each corner of the unit cell but also contains a lattice point at the center of the three-dimensional unit cellat the center of the three-dimensional unit cell

face-centered lattice - possesses not only lattice points at face-centered lattice - possesses not only lattice points at the corners of the unit cell but also at either the centers of the corners of the unit cell but also at either the centers of just one pair of faces or else at the centers of all three just one pair of faces or else at the centers of all three pairs of faces pairs of faces

BRAVAIS LATTICESBRAVAIS LATTICES 14 lattices → 6 crystal systems14 lattices → 6 crystal systems

1.1. primitive cubicprimitive cubic2.2. body-centered cubicbody-centered cubic3.3. face-centered cubicface-centered cubic4.4. primitive tetragonalprimitive tetragonal5.5. body-centered tetragonalbody-centered tetragonal6.6. primitive orthorhombicprimitive orthorhombic7.7. body-centered orthorhombicbody-centered orthorhombic8.8. single face-centered orthorhombicsingle face-centered orthorhombic9.9. multiple face-centered orthorhombicmultiple face-centered orthorhombic10.10.primitive monoclinicprimitive monoclinic11.11.single face-centered monoclinicsingle face-centered monoclinic12.12.primitive triclinicprimitive triclinic13.13.single face-centered hexagonalsingle face-centered hexagonal14.14.rhombohedral lattices (rhombohedral lattice is a subset of rhombohedral lattices (rhombohedral lattice is a subset of

the hexagonal crystal system) the hexagonal crystal system)

POINT SYMMETRYPOINT SYMMETRY Point symmetry - describes the repetition of a motif or

structural feature around a single reference point, commonly the center of a unit cell or a crystal

Point Symmetry Operations: Reflection - structural features on one side of a plane

passing through the center of a crystal are the mirror image of the structural features on the other side. The plane across which the reflection occurs is then termed a mirror plane

Rotation - structural element is rotated a fixed number of degrees about a central point and then repeated. A square, for example, possesses 4-fold rotational symmetry because it may be rotated four times by 90° about its central point before it is returned to its original position. Each time it is rotated by 90° the resultant square will be identical in appearance to the original square

POINT SYMMETRYPOINT SYMMETRY Point Symmetry Operations:

Inversion - any line which is drawn through the origin at the center of the crystal will connect two identical features on opposite sides of the crystal.

Rotoinversion - compound symmetry operation which is produced by performing a rotation followed by an inversion

reflection, rotation, inversion and rotoinversion symmetry operations → combined in different ways → 32 different possible combinations of these symmetry elements → 32 crystal classes → corresponds to a unique set of symmetry operations → each crystal class → placed into one of 6 crystal systems

CRYSTAL SYSTEMSCRYSTAL SYSTEMS1.1. Isometric or cubicIsometric or cubic

2.2. HexagonalHexagonal

1.1. hexagonalhexagonal

2.2. rhombohedralrhombohedral

3.3. TetragonalTetragonal

4.4. OrthorhombicOrthorhombic

5.5. MonoclinicMonoclinic

6.6. TriclinicTriclinic

ISOMETRIC or CUBICISOMETRIC or CUBIC the crystallographic axes used in this system are of equal the crystallographic axes used in this system are of equal

length and are mutually perpendicular, occurring at right length and are mutually perpendicular, occurring at right angles to one anotherangles to one another

all crystals of the isometric system possess four 3-fold all crystals of the isometric system possess four 3-fold axes of symmetry, each of which proceeds diagonally axes of symmetry, each of which proceeds diagonally from corner to corner through the center of the cubic unit from corner to corner through the center of the cubic unit cellcell

may also demonstrate up to three separate 4-fold axes of may also demonstrate up to three separate 4-fold axes of rotational symmetry or six 2-fold axes of symmetryrotational symmetry or six 2-fold axes of symmetry

minerals of this system may demonstrate up to nine minerals of this system may demonstrate up to nine different mirror planesdifferent mirror planes

Minerals of this system tend to produce crystals of Minerals of this system tend to produce crystals of equidimensional or equant habitequidimensional or equant habit

Examples: halite, magnetite and garnet. Examples: halite, magnetite and garnet.

CRYSTAL SYSTEMSCRYSTAL SYSTEMS

CRYSTAL SYSTEMSCRYSTAL SYSTEMS ISOMETRIC or CUBICISOMETRIC or CUBIC

CRYSTAL SYSTEMSCRYSTAL SYSTEMS HEXAGONAL HEXAGONAL

minerals of the hexagonal crystal system are referred to minerals of the hexagonal crystal system are referred to three crystallographic axes which intersect at 60° and a three crystallographic axes which intersect at 60° and a fourth which is perpendicular to the other three. This fourth fourth which is perpendicular to the other three. This fourth axis is usually depicted vertically.axis is usually depicted vertically.

crystals of the crystals of the hexagonal divisionhexagonal division possess a single 6-fold possess a single 6-fold axis of rotation. In addition to the single 6-fold axis of axis of rotation. In addition to the single 6-fold axis of rotation, crystals of the hexagonal division may possess rotation, crystals of the hexagonal division may possess up to six 2-fold axes of rotation. They may demonstrate a up to six 2-fold axes of rotation. They may demonstrate a center of inversion symmetry and up to seven mirror center of inversion symmetry and up to seven mirror planes. Crystals of the planes. Crystals of the rhombohedral divisionrhombohedral division all possess all possess a single 3-fold axis of rotation rather than the 6-fold axis of a single 3-fold axis of rotation rather than the 6-fold axis of the hexagonal division.the hexagonal division.

minerals of this division tend to produce hexagonal prisms minerals of this division tend to produce hexagonal prisms and pyramidsand pyramids

apatite, beryl and high quartz (hexagonal); calcite, apatite, beryl and high quartz (hexagonal); calcite, dolomite, low quartz and tourmaline (rhombohedral). dolomite, low quartz and tourmaline (rhombohedral).

CRYSTAL SYSTEMSCRYSTAL SYSTEMS HEXAGONALHEXAGONAL


TETRAGONAL TETRAGONAL minerals of the tetragonal crystal system are referred minerals of the tetragonal crystal system are referred

to three mutually perpendicular axes. The two to three mutually perpendicular axes. The two horizontal axes are of equal length, while the vertical horizontal axes are of equal length, while the vertical axis is of different length and may be either shorter or axis is of different length and may be either shorter or longer than the other twolonger than the other two

minerals of this system all possess a single 4-fold minerals of this system all possess a single 4-fold symmetry axis. They may possess up to four 2-fold symmetry axis. They may possess up to four 2-fold axes of rotation, a center of inversion, and up to five axes of rotation, a center of inversion, and up to five mirror planesmirror planes

minerals tend to produce short crystals of prismatic minerals tend to produce short crystals of prismatic habithabit

zircon and cassiteritezircon and cassiterite

CRYSTAL SYSTEMSCRYSTAL SYSTEMS TETRAGONAL TETRAGONAL


ORTHORHOMBIC ORTHORHOMBIC Minerals of the orthorhombic crystal system are referred to Minerals of the orthorhombic crystal system are referred to

three mutually perpendicular axes, each of which is of a three mutually perpendicular axes, each of which is of a different length than the othersdifferent length than the others

Crystals of this system uniformly possess three 2-fold Crystals of this system uniformly possess three 2-fold rotation axes and/or three mirror planes. The rotation axes and/or three mirror planes. The holomorphicholomorphic class demonstrates three 2-fold symmetry axes and three class demonstrates three 2-fold symmetry axes and three mirror planes as well as a center of inversion. Other mirror planes as well as a center of inversion. Other classes may demonstrate three 2-fold axes of rotation or classes may demonstrate three 2-fold axes of rotation or one 2-fold rotation axis and two mirror planesone 2-fold rotation axis and two mirror planes

Crystals of this system tend to be of prismatic, tabular, or Crystals of this system tend to be of prismatic, tabular, or acicular habitacicular habit

olivine and barite. olivine and barite.

CRYSTAL SYSTEMSCRYSTAL SYSTEMS ORTHORHOMBIC ORTHORHOMBIC

CRYSTAL SYSTEMSCRYSTAL SYSTEMS MONOCLINICMONOCLINIC

Crystals of the monoclinic system are referred to three Crystals of the monoclinic system are referred to three unequal axes. Two of these axes are inclined toward each unequal axes. Two of these axes are inclined toward each other at an oblique angle; these are usually depicted other at an oblique angle; these are usually depicted vertically. The third axis is perpendicular to the other two. vertically. The third axis is perpendicular to the other two. The two vertical axes therefore do not intersect one The two vertical axes therefore do not intersect one another at right angles, although both are perpendicular to another at right angles, although both are perpendicular to the horizontal axisthe horizontal axis

Monoclinic crystals demonstrate a single 2-fold rotation Monoclinic crystals demonstrate a single 2-fold rotation axis and/or a single mirror plane. The axis and/or a single mirror plane. The holomorphicholomorphic class class possesses the single 2-fold rotation axis, a mirror plane, possesses the single 2-fold rotation axis, a mirror plane, and a center of symmetry. Other classes display just the 2-and a center of symmetry. Other classes display just the 2-fold rotation axis or just the mirror planefold rotation axis or just the mirror plane

minerals of the monoclinic system tend to produce long minerals of the monoclinic system tend to produce long prismsprisms

pyroxene, amphibole, orthoclase, azurite, and malachitepyroxene, amphibole, orthoclase, azurite, and malachite

CRYSTAL SYSTEMSCRYSTAL SYSTEMS MONOCLINICMONOCLINIC


TRICLINICTRICLINIC Crystals of the triclinic system are referred to three Crystals of the triclinic system are referred to three

unequal axes, all of which intersect at oblique angles. unequal axes, all of which intersect at oblique angles. None of the axes are perpendicular to any other axisNone of the axes are perpendicular to any other axis

Crystals of the triclinic system may be said to possess Crystals of the triclinic system may be said to possess only a 1-fold symmetry axis, which is equivalent to only a 1-fold symmetry axis, which is equivalent to possessing no symmetry at all. Crystals of this system possessing no symmetry at all. Crystals of this system possess no mirror planes. The holomorphic class possess no mirror planes. The holomorphic class demonstrates a center of inversion symmetrydemonstrates a center of inversion symmetry

tend to be of tabular habittend to be of tabular habit plagioclase and axiniteplagioclase and axinite

CRYSTAL SYSTEMSCRYSTAL SYSTEMS TRICLINICTRICLINIC

CRYSTAL FORMSCRYSTAL FORMS Crystal Forms - set of faces which are geometrically Crystal Forms - set of faces which are geometrically

equivalent and whose spatial positions are related to one equivalent and whose spatial positions are related to one another according to the symmetry of the crystalanother according to the symmetry of the crystal

1.1. Monohedron or pedionMonohedron or pedion2.2. Parallelohedron or pinacoidParallelohedron or pinacoid3.3. Dihedron, or domeDihedron, or dome4.4. SphenoidSphenoid5.5. DisphenoidDisphenoid6.6. PrismPrism7.7. PyramidPyramid8.8. DipyramidDipyramid9.9. TrapezohedronTrapezohedron10.10. ScalenohedronScalenohedron11.11. RhombohedronRhombohedron12.12. TetrahedronTetrahedron13.13. 15 under the isometric system15 under the isometric system

MINERAL CLASSES ANDMINERAL CLASSES ANDMINERAL IDENTIFICATIONMINERAL IDENTIFICATION

MINERAL CLASSESMINERAL CLASSES Native elements - Native elements - eg. Aueg. Au Sulfides - Sulfides - eg. Feeg. FeSS22

Sulfosalts - Sulfosalts - eg. Cueg. Cu33AsSAsS44 OxidesOxides

Simple and multiple - Simple and multiple - eg. Cueg. Cu22OO Hydroxides - Hydroxides - eg. Mneg. MnO(OHO(OH))

Halides - Halides - eg. Naeg. NaClCl Carbonates - Carbonates - eg. Caeg. CaCoCo33 Nitrates - Nitrates - eg. Keg. KNO3NO3 Borates - Borates - eg. Naeg. Na22BB44OO55(OH)(OH)44 ·8H ·8H22O)O) Sulfates - Sulfates - eg. Baeg. BaSOSO44

Chromates - eg. Chromates - eg. PbPbCrOCrO44

Tungstates - Tungstates - eg. eg. (Fe, Mn)(Fe, Mn)WOWO44

Molybdates - eg. Molybdates - eg. PbPbMoOMoO44 Phosphates - Phosphates - eg. Caeg. Ca55(PO(PO44))33(F,Cl,OH)(F,Cl,OH) Arsenates - eg. Arsenates - eg. CoCo33(AsO(AsO44))22.2H.2H22OO Vanadates - eg. Vanadates - eg. PbPb55(VO(VO44))33ClCl Silicates - Silicates - eg. Beeg. Be33AlAl22(Si(Si66OO1818))

BASIS FOR MINERAL CLASSIFICATIONBASIS FOR MINERAL CLASSIFICATION Classification of minerals based on chemical compositionClassification of minerals based on chemical composition Dependent on the dominant anion* or anionic group (eg. Dependent on the dominant anion* or anionic group (eg.

oxides, halides, silicates etc.)oxides, halides, silicates etc.) Reasons for using chemical composition as basis for Reasons for using chemical composition as basis for

classification:classification: Minerals having the same anion or anionic group Minerals having the same anion or anionic group

dominant in their composition have unmistakable family dominant in their composition have unmistakable family resemblances, in general stronger and more clearly resemblances, in general stronger and more clearly marked than those shared by minerals containing the marked than those shared by minerals containing the same dominant cation (eg. Carbonates resemble each same dominant cation (eg. Carbonates resemble each other more closely that the minerals of copper)other more closely that the minerals of copper)

Minerals related by dominance of the same anion tend to Minerals related by dominance of the same anion tend to occur together or in the same or similar geologic occur together or in the same or similar geologic environment (eg. Sulfides occur in close mutual environment (eg. Sulfides occur in close mutual association in deposits of vein or replacement type, association in deposits of vein or replacement type, silicates make the bulk of the earth’s rocks)silicates make the bulk of the earth’s rocks)

Agrees well with current chemical practice in naming and Agrees well with current chemical practice in naming and classifying inorganic compoundsclassifying inorganic compounds

BASIS FOR MINERAL CLASSIFICATIONBASIS FOR MINERAL CLASSIFICATION Crystallochemical principles – mineral classification must be Crystallochemical principles – mineral classification must be

based on:based on: Chemical compositionChemical composition Internal structureInternal structure

Large classes are further divided into subclasses on the Large classes are further divided into subclasses on the basis of internal structure:basis of internal structure:Silicate Silicate classclass→→ { framework silicate { framework silicate subclasssubclass (structural (structural

{ chain silicate { chain silicate subclasssubclass (arrangement(arrangement

{ sheet silicate { sheet silicate subclasssubclass (of SiO(of SiO44

↓↓ familyfamily (chemical type)(chemical type)

↓↓ groupgroup (structural similarity)(structural similarity)

↓↓ speciesspecies → → seriesseries → → varietyvariety

NATIVE ELEMENTSNATIVE ELEMENTS

≈ ≈ 20 elements in native state (excluding free gasses)20 elements in native state (excluding free gasses) Types of Native Elements:Types of Native Elements:

MetalsMetals SemimetalsSemimetals NonmetalsNonmetals


Native MetalsNative Metals Usefulness of metals arose from the chance discovery of Usefulness of metals arose from the chance discovery of

nuggets and masses of goldnuggets and masses of gold Early cultures use metals in native stateEarly cultures use metals in native state Groups of Native Metals:Groups of Native Metals:

Gold GroupGold GroupPlatinum GroupPlatinum GroupIron GroupIron Group

NATIVE ELEMENTSNATIVE ELEMENTS Gold GroupGold Group

Belong to the same group in the periodic table of Belong to the same group in the periodic table of elements and have similar chemical propertieselements and have similar chemical properties

Sufficiently inert to occur in an elemental state in natureSufficiently inert to occur in an elemental state in nature Minerals are isostructural and are built on the face-Minerals are isostructural and are built on the face-

centered latticecentered lattice Common Properties:Common Properties:

Soft, malleable, ductile and sectileSoft, malleable, ductile and sectileExcellent conductors of heat and electricityExcellent conductors of heat and electricityDisplay metallic luster and hackly fractureDisplay metallic luster and hackly fractureHave low melting pointsHave low melting pointsAll are isometric hexoctahedralAll are isometric hexoctahedralHave high densities resulting from close cubic packingHave high densities resulting from close cubic packingGold (Au), silver (Ag), copper (Cu), Lead (Pb)Gold (Au), silver (Ag), copper (Cu), Lead (Pb)

Differing properties due to atomic properties (specific Differing properties due to atomic properties (specific gravity, color: yellow of Au, red of Cu and white of Ag)gravity, color: yellow of Au, red of Cu and white of Ag)

NATIVE ELEMENTSNATIVE ELEMENTS Platinum GroupPlatinum Group

IsostructuralIsostructural Platinum, palladium, iridium, osmiumPlatinum, palladium, iridium, osmium

Iron GroupIron Group IsostructuralIsostructural Iron, kamacite, taeniteIron, kamacite, taenite

NATIVE ELEMENTSNATIVE ELEMENTS Native SemimetalsNative Semimetals

Arsenic (As), antimony (Sb) and bismuth (Bi)Arsenic (As), antimony (Sb) and bismuth (Bi) Belong to an isostructural group with space group R3mBelong to an isostructural group with space group R3m Unlike native metals, these cannot be represented as a Unlike native metals, these cannot be represented as a

simple packing of spheres, because each atom is simple packing of spheres, because each atom is somewhat closer to three of its neighbors than to the somewhat closer to three of its neighbors than to the remainder of the surrounding atoms. Bonding of the 4 remainder of the surrounding atoms. Bonding of the 4 closest atoms is covalentclosest atoms is covalent

Bond type between metallic and covalent, hence, it is Bond type between metallic and covalent, hence, it is stronger and more directional than pure metallic elementsstronger and more directional than pure metallic elements

Brittle and much poorer conductors of heat and electricity Brittle and much poorer conductors of heat and electricity than the native metalsthan the native metals


Native Non MetalsNative Non Metals Sulfur (S), diamond (C) and graphite (C)Sulfur (S), diamond (C) and graphite (C) Structure very different from the native metalsStructure very different from the native metals

NATIVE ELEMENTSNATIVE ELEMENTS GOLD (Au)GOLD (Au) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system octahedral formoctahedral form Often in arborescent crystal Often in arborescent crystal

groupsgroups Crystal are irregularly Crystal are irregularly

formed from filiform to formed from filiform to reticulated to dendriticreticulated to dendritic

Seldom show crystal forms, Seldom show crystal forms, often in irregular plates, often in irregular plates, scales or masses scales or masses

Hardness: 2.5 to 3Hardness: 2.5 to 3 Specific Gravity: 19.3 (pure)Specific Gravity: 19.3 (pure) Fracture: hacklyFracture: hackly Tenacity: Malleable, ductileTenacity: Malleable, ductile Luster: metallic opaque Luster: metallic opaque


Diagnostic Features:Diagnostic Features: Distinguished from yellow Distinguished from yellow

sulfides pyrite and sulfides pyrite and chalcopyrite and from chalcopyrite and from yellow flakes of altered yellow flakes of altered micas by its sectility and micas by its sectility and high specific gravityhigh specific gravity

Fuses at 1063°CFuses at 1063°C Soluble in aqua regia (1:3 Soluble in aqua regia (1:3

volume HNOvolume HNO33 and HCl and HCl

Occurrence:Occurrence: Rare element but widely Rare element but widely

distributed in small amountsdistributed in small amounts Most commonly found in in Most commonly found in in

veins that bear genetic veins that bear genetic relation to silicic types of relation to silicic types of igneous rocksigneous rocks

GOLD (Au)GOLD (Au) Color: various shades of Color: various shades of

yellow becoming paler with yellow becoming paler with increase in silverincrease in silver

Composition and Structure:Composition and Structure: Most gold contains AgMost gold contains Ag When Ag >20% → electrum When Ag >20% → electrum Small amounts of Cu, Fe and Small amounts of Cu, Fe and

traces of Bi, Pb, Sn, Zn and traces of Bi, Pb, Sn, Zn and Platinum metalsPlatinum metals

Purity or “fineness” of gold is Purity or “fineness” of gold is expressed in “parts per 1000”expressed in “parts per 1000”

Most gold contains about 10% Most gold contains about 10% of other metals and has a of other metals and has a fineness of 900fineness of 900

Structure of gold is based on Structure of gold is based on cubic closest packing Aucubic closest packing Au


When sulfides are present in When sulfides are present in any quantity, not all gold can any quantity, not all gold can be recovered by be recovered by amalgamation → cyanide or amalgamation → cyanide or chlorination process is usedchlorination process is used

CYANIDATION → finely CYANIDATION → finely crushed ore is treated with a crushed ore is treated with a solution of potassium or solution of potassium or sodium cyanide, forming a sodium cyanide, forming a soluble cyanide. The gold is soluble cyanide. The gold is then recovered by then recovered by precipitation with zinc or by precipitation with zinc or by electrolysiselectrolysis

CHLORINATION → renders CHLORINATION → renders gold in a soluble form by gold in a soluble form by treating the crushed and treating the crushed and roasted ore with chlorine roasted ore with chlorine

GOLD (Au)GOLD (Au) Most gold occur in native Most gold occur in native

metalmetal If in combination → only with If in combination → only with

tellurium and seleniumtellurium and selenium Chief source of gold are Chief source of gold are

hydrothermal gold-quartz hydrothermal gold-quartz veins with pyrite and other veins with pyrite and other sulfides deposited from sulfides deposited from ascending mineral solutions ascending mineral solutions where gold is only where gold is only mechanically mixed with mechanically mixed with sulfides and is not in chemical sulfides and is not in chemical substitution. At or near the substitution. At or near the surface, of the earth, surface, of the earth, oxidation of the gold-bearing oxidation of the gold-bearing sulfides sets the gold free, sulfides sets the gold free, making its extraction easy by making its extraction easy by amalgamation (finely crushed amalgamation (finely crushed ore is washed over copper ore is washed over copper plates coated with mercury)plates coated with mercury)


Uses: monetary standard, Uses: monetary standard, jewelry, scientific instru-ments, jewelry, scientific instru-ments, electroplating, gold leaf, dental electroplating, gold leaf, dental appliances, small gold bars for appliances, small gold bars for investment purposes investment purposes

GOLD (Au)GOLD (Au) When gold-bearing veins are When gold-bearing veins are

weathered, the liberated gold weathered, the liberated gold either remains in the soil either remains in the soil mantle as “eluvial deposit” or mantle as “eluvial deposit” or is washed into the neighboring is washed into the neighboring streams to form “placer or streams to form “placer or alluvial gold”. Because of its alluvial gold”. Because of its high specific gravity, gold high specific gravity, gold works its way through the works its way through the lighter sands and gravels to lighter sands and gravels to lodge behind irregularities or lodge behind irregularities or in crevices in bedrock. Gold is in crevices in bedrock. Gold is recovered by panning or recovered by panning or washing through sluice boxes washing through sluice boxes where gold collects behind where gold collects behind cross-bars and amalgamates cross-bars and amalgamates with mercury placed behind with mercury placed behind the cross-barsthe cross-bars

NATIVE ELEMENTSNATIVE ELEMENTS SILVER (Ag)SILVER (Ag) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals commonly mal-Crystals commonly mal-

formed and in branching formed and in branching arborescent or reticulated arborescent or reticulated groupsgroups

Usually in irregular masses, Usually in irregular masses, plates and scales, in other plates and scales, in other places as fine or coarse places as fine or coarse wireswires

Hardness: 2.5 to 3Hardness: 2.5 to 3 Specific gravity: 10.5 (pure)Specific gravity: 10.5 (pure) Fracture: hacklyFracture: hackly Tenacity: Malleable and ductileTenacity: Malleable and ductile Luster: metallicLuster: metallic Color and streak: silver white Color and streak: silver white

and tarnish to brown or gray and tarnish to brown or gray blackblack


Occurrence: widely distributed Occurrence: widely distributed in small amounts in the oxidized in small amounts in the oxidized zones of ore depositszones of ore deposits Native silver in larger Native silver in larger

deposits is the result of deposits is the result of deposition from primary deposition from primary hydrothermal solutionshydrothermal solutions

Uses: photographic film Uses: photographic film emulsions, plating, brazing emulsions, plating, brazing alloys, tableware, electronic alloys, tableware, electronic equipment, coinageequipment, coinage

SILVER (Ag)SILVER (Ag) Composition and Structure:Composition and Structure:

Frequently contains alloyed Frequently contains alloyed Au, Hg, and Cu. Rare traces Au, Hg, and Cu. Rare traces of Pt, Sb and Biof Pt, Sb and Bi

Amalgam is a solid solution of Amalgam is a solid solution of Ag and HgAg and Hg

Structure is based on closest Structure is based on closest packing of Ag atomspacking of Ag atoms

Diagnostic features:Diagnostic features: Silver can be distinguished by Silver can be distinguished by

its malleability, color on fresh its malleability, color on fresh surface and high specific surface and high specific gravitygravity

Fusible at 960°C to a bright Fusible at 960°C to a bright globuleglobule

NATIVE ELEMENTSNATIVE ELEMENTS COPPER (Cu)COPPER (Cu) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Tetrahexahedron, cube, Tetrahexahedron, cube,

dodecahedron, octahedrondodecahedron, octahedron Usually malformed and in Usually malformed and in

branching and arborescent branching and arborescent groupsgroups

Usually occurs in irregular Usually occurs in irregular masses, plates and scales masses, plates and scales and in twisted wire-like forms and in twisted wire-like forms

Hardness: 2.5 to 3Hardness: 2.5 to 3 Specific gravity: 8.9Specific gravity: 8.9 Fracture: hacklyFracture: hackly Tenacity: highly malleable and Tenacity: highly malleable and

ductileductile Luster: metallicLuster: metallic


Occurrence:Occurrence: small amounts found in small amounts found in

oxidized zones of copper oxidized zones of copper deposits associated with deposits associated with cuprite, malachite and cuprite, malachite and azurite in many localitiesazurite in many localities

Most primary deposits of Most primary deposits of native copper are associated native copper are associated with basaltic lavas, where with basaltic lavas, where deposition of copper deposition of copper resulted from the reaction of resulted from the reaction of hydrothermal solutions with hydrothermal solutions with iron oxide mineralsiron oxide minerals

Only major deposit is found Only major deposit is found in Precambrian basic lava in Precambrian basic lava flows in the Keweenaw flows in the Keweenaw Peninsula, MichiganPeninsula, Michigan

COPPER (Cu)COPPER (Cu) Composition and Structure:Composition and Structure:

Contains small amounts of Contains small amounts of Ag, Bi, Hg, As and SbAg, Bi, Hg, As and Sb

Structure is based on cubic Structure is based on cubic closest packing of Cu atomsclosest packing of Cu atoms

Diagnostic Features:Diagnostic Features: Recognized by its red color Recognized by its red color

on fresh surfaces, hackly on fresh surfaces, hackly fracture, high specific gravity fracture, high specific gravity and malleabilityand malleability

Fuses at 1083°C to globuleFuses at 1083°C to globule Dissolves readily in nitric acid Dissolves readily in nitric acid

and the resulting solution is and the resulting solution is colored deep blue on addition colored deep blue on addition of an excess ammonium of an excess ammonium hydroxidehydroxide

NATIVE ELEMENTSNATIVE ELEMENTS COPPER (Cu)COPPER (Cu) Use: minor ore of copper, Use: minor ore of copper,

electrical purposes (wires), electrical purposes (wires), alloys:alloys: Brass (copper and zinc)Brass (copper and zinc) Bronze (copper and tin with Bronze (copper and tin with

zinc)zinc) German silver (copper, zinc German silver (copper, zinc

and nickel)and nickel)

NATIVE ELEMENTSNATIVE ELEMENTS PLATINUM (Pt)PLATINUM (Pt) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Commonly malformedCommonly malformed Usually in small grains and Usually in small grains and

scales, in some places as scales, in some places as irregular masses and nuggetsirregular masses and nuggets

Hardness: 4 to 4.5 (unusually high Hardness: 4 to 4.5 (unusually high for metal)for metal)

Specific Gravity: 21.45 (pure)Specific Gravity: 21.45 (pure) Tenacity: Malleable, ductileTenacity: Malleable, ductile Luster: bright metallicLuster: bright metallic Color: steel grayColor: steel gray Composition and Structure:Composition and Structure:

Usually alloyed with several Usually alloyed with several percent Fe (making it percent Fe (making it magnetic when iron-rich) and magnetic when iron-rich) and smallersmaller


First discovered in the United First discovered in the United States of Colombia, South States of Colombia, South AmericaAmerica

Uses: catalyst in the chemical and Uses: catalyst in the chemical and petroleum industries, chemical petroleum industries, chemical apparatus, electrical equipment, apparatus, electrical equipment, jewelry, dentistry, surgical jewelry, dentistry, surgical instruments, pyrometry and instruments, pyrometry and photographyphotography

PLATINUM (Pt)PLATINUM (Pt)amounts of Ir, Os, Rh, Pd, amounts of Ir, Os, Rh, Pd, Cu, Au, NiCu, Au, Ni

Structure of platinum is Structure of platinum is based on the cubic closest based on the cubic closest packing of Pt atomspacking of Pt atoms

Diagnostic Features:Diagnostic Features: determined by its high determined by its high

specific gravity, malleability, specific gravity, malleability, infusibility in the blowpipe infusibility in the blowpipe flame and insolubility except flame and insolubility except in aqua regiain aqua regia

Occurrence:Occurrence: most occur as native metal in most occur as native metal in

ultrabasic rocks especially ultrabasic rocks especially dunites associated with dunites associated with olivine, chromite, pyroxene olivine, chromite, pyroxene and magnetiteand magnetite

Occur as placers highly close Occur as placers highly close to the platinum-bearing to the platinum-bearing igneous parent rockigneous parent rock

NATIVE ELEMENTSNATIVE ELEMENTS IRON (Fe)IRON (Fe) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals are rareCrystals are rare Terrestrial – in blebs and Terrestrial – in blebs and

large masseslarge masses Meteoric (kamacite) – in Meteoric (kamacite) – in

plates and lamellar masses plates and lamellar masses Hardness: 4.5Hardness: 4.5 Specific Gravity: 7.3-7.9Specific Gravity: 7.3-7.9 Fracture: hacklyFracture: hackly Tenacity: malleableTenacity: malleable Luster: metallic opaqueLuster: metallic opaque Color: steel gray to blackColor: steel gray to black Magnetism: strongly magneticMagnetism: strongly magnetic Composition and Structure:Composition and Structure:

Always contains some Ni Always contains some Ni and frequently small and frequently small amounts of Co, Cu, Mn, S amounts of Co, Cu, Mn, S and Cand C


Normally present as FeNormally present as Fe2+2+ or or FeFe3+3+ in oxides in magnetite in oxides in magnetite (Fe(Fe33OO44) or hematite (Fe) or hematite (Fe22OO33) ) or goethite (FeO.OH)or goethite (FeO.OH)

Terrestrial iron regarded as Terrestrial iron regarded as primary magmatic primary magmatic constituent or a s constituent or a s asecondary product formed asecondary product formed from the reduction of iron from the reduction of iron compounds by assimlated compounds by assimlated carbonaceous materialcarbonaceous material

Most important occurrence Most important occurrence is in Disko Is., Greenlandis in Disko Is., Greenland

IRON (Fe)IRON (Fe) Kamacite contains approx. Kamacite contains approx.

5.5. weight percent Ni while 5.5. weight percent Ni while Taenite has 27-65 weight Taenite has 27-65 weight percent Nipercent Ni

Structure is based on body-Structure is based on body-centered cubic packing of centered cubic packing of atomsatoms

Diagnostic Features: Strong Diagnostic Features: Strong magnetism, malleability and the magnetism, malleability and the oxide coating on its surface. oxide coating on its surface. Infusible but soluble in HCLlInfusible but soluble in HCLl

Occurrence:Occurrence: Seldom as terrestrial iron but Seldom as terrestrial iron but

common in meteoritescommon in meteorites Elemental iron is highly Elemental iron is highly

unstable in oxidizing unstable in oxidizing conditionsconditions


Composition and Structure:Composition and Structure: Often shows limited Often shows limited

substitution by Sbsubstitution by Sb Diagnostic Features:Diagnostic Features:

Diagnostic blowpipe and Diagnostic blowpipe and chemical testschemical tests

Occurrence:Occurrence: Comparatively rare. Found Comparatively rare. Found

in veins in crystalline rocks in veins in crystalline rocks associated with Ag, Co, or associated with Ag, Co, or NiNi

Uses: very minor ore of arsenicUses: very minor ore of arsenic

ARSENIC (As)ARSENIC (As) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Pseudocubic crystals rarePseudocubic crystals rare Usually granular massive, Usually granular massive,

reniform and stalactiticreniform and stalactitic Cleavage: perfect at {0001}Cleavage: perfect at {0001} Hardness: 3.5Hardness: 3.5 Specific Gravity: 5.7Specific Gravity: 5.7 Tenacity: brittleTenacity: brittle Luster: nearly metallicLuster: nearly metallic Color: tin-white on fresh fracture, Color: tin-white on fresh fracture,

tarnishes to dark gray on tarnishes to dark gray on exposureexposure

Streak: grayStreak: gray


Structure similar to As and Structure similar to As and SbSb

Diagnostic Features:Diagnostic Features: Recognized chiefly by Recognized chiefly by

laminated nature, reddish-laminated nature, reddish-silver color, perfect cleavage silver color, perfect cleavage and sectilityand sectility

Fusible at 271°CFusible at 271°C Diagnostic blowpipe testsDiagnostic blowpipe tests

Occurrence:Occurrence: Rare, occurring with ores of Rare, occurring with ores of

Ag, Co, Ni, Pb and SnAg, Co, Ni, Pb and Sn Uses: chief ore of bismuth, used Uses: chief ore of bismuth, used

for electrical fuses and safety for electrical fuses and safety plugs in water sprinkling plugs in water sprinkling systems, medicine, cosmeticssystems, medicine, cosmetics

BISMUTH (Bi)BISMUTH (Bi) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Distinct crystals are rareDistinct crystals are rare Usually laminated and Usually laminated and

granular, maybe reticulated or granular, maybe reticulated or arborescentarborescent

Cleavage: perfect at {0001}Cleavage: perfect at {0001} Hardness: 2 to 2.5Hardness: 2 to 2.5 Specific Gravity: 9.8Specific Gravity: 9.8 Tenacity: sectile, brittleTenacity: sectile, brittle Luster: metallicLuster: metallic Color: reddish silver-whiteColor: reddish silver-white Streak: shining silver-whiteStreak: shining silver-white Composition and Structure:Composition and Structure:

Small amounts of As, S, Te Small amounts of As, S, Te and As maybe presentand As maybe present


To crack due to expansion of To crack due to expansion of surface layers due to heat from surface layers due to heat from handhand

Composition and Structure:Composition and Structure: May contain small amounts May contain small amounts

of Seof Se Diagnostic Features:Diagnostic Features:

Recognized by its yellow Recognized by its yellow color and ease with which it color and ease with which it burnsburns

Absence of good cleavage Absence of good cleavage distinguishes it from distinguishes it from orpimentorpiment

Fusible at 112.8°C and Fusible at 112.8°C and burns with a blue flame with burns with a blue flame with sulfur dioxidesulfur dioxide

Sublimates in closed tubeSublimates in closed tube Occurrence:Occurrence:

Occurs at or near crater rims Occurs at or near crater rims of active or inactive of active or inactive volcanoes where it is volcanoes where it is derivedderived

SULFUR (S)SULFUR (S) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Pyramidal habit commonPyramidal habit common Commonly found in irregular Commonly found in irregular

masses, massive, reniform, masses, massive, reniform, stalactiticstalactitic

Hardness: 1.5 to 2.5Hardness: 1.5 to 2.5 Specific Gravity: 2.05 to 2.09Specific Gravity: 2.05 to 2.09 Fracture: conchoidal to unevenFracture: conchoidal to uneven Tenacity: brittleTenacity: brittle Color: sulfur-yellow, varying with Color: sulfur-yellow, varying with

impuritiesimpurities Transparent to translucentTransparent to translucent Poor conductor of heatPoor conductor of heat When sample is held in hand When sample is held in hand

close to the ear, it can be heard close to the ear, it can be heard


rubber, preparation of wood rubber, preparation of wood pulp for paper manufacturepulp for paper manufacture

SULFUR (S)SULFUR (S)

From the gases given off in From the gases given off in fumaroles. These may furnish fumaroles. These may furnish sulfur as a direct sublimation sulfur as a direct sublimation product or by incomplete product or by incomplete oxidation of hydrogen sulfide oxidation of hydrogen sulfide gasgas

It is also formed from sulfates, It is also formed from sulfates, by the action of sulfur-forming by the action of sulfur-forming bacteriabacteria

Maybe found in veins Maybe found in veins associated with metallic associated with metallic sulfides and formed by the sulfides and formed by the oxidation of the sulfidesoxidation of the sulfides

Uses: chemical industry chiefly in Uses: chemical industry chiefly in the manufacture of sulfuric acid, the manufacture of sulfuric acid, fertilizers, insecticides, fertilizers, insecticides, explosives, coal tar products, explosives, coal tar products,


““Carbonado” is black or grayish Carbonado” is black or grayish black bort, noncleavable, black bort, noncleavable, opaque and less brittle than opaque and less brittle than crystalscrystals

Composition and Structure:Composition and Structure: Pure carbonPure carbon

Diagnostic Features:Diagnostic Features: Hardness, adamantine luster Hardness, adamantine luster

and cleavageand cleavage Insoluble in acids and alkalisInsoluble in acids and alkalis At high temperature in At high temperature in

oxygen, will burn to COoxygen, will burn to CO22 gas gas leaving no ashleaving no ash

Occurrence:Occurrence: Found in alluvial deposits, Found in alluvial deposits,

where it accumulates where it accumulates because of its inert chemical because of its inert chemical nature, great hardness and nature, great hardness and fairly high specific gravityfairly high specific gravity

In Africa and Siberia, they In Africa and Siberia, they

DIAMOND (C)DIAMOND (C) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals usually octahedral Crystals usually octahedral

but maybe cubic or but maybe cubic or dodecahedraldodecahedral

““Bort” variety has rough Bort” variety has rough exterior resulting from radial or exterior resulting from radial or cryptocrystalline aggregate cryptocrystalline aggregate (without gem value)(without gem value)

Hardness: 10Hardness: 10 Cleavage: perfect {111}Cleavage: perfect {111} Specific gravity: 3.51Specific gravity: 3.51 Luster: adamantine, uncut Luster: adamantine, uncut

crystals have a characteristic crystals have a characteristic greasy appearancegreasy appearance

Color: usually pale yellow or Color: usually pale yellow or colorless, pale red, green, bluecolorless, pale red, green, blue

NATIVE ELEMENTSNATIVE ELEMENTS DIAMOND (C)DIAMOND (C)

Occur in situ hosted in Occur in situ hosted in altered peridotite called altered peridotite called kimberlite or “diamond pipes”kimberlite or “diamond pipes”

First found in IndiaFirst found in India Uses: fragments are used to cut Uses: fragments are used to cut

glass, grinding and polishing glass, grinding and polishing diamonds and other gemstones, diamonds and other gemstones, cutting rocks, diamond drilling, cutting rocks, diamond drilling, gemstones-value depends on the gemstones-value depends on the color and purity, skill by which it color and purity, skill by which it was cut and its size (1 carat=0.2 was cut and its size (1 carat=0.2 g.) g.)


Occurrence:Occurrence: Mostly occurs in Mostly occurs in

metamorphic rocks such as metamorphic rocks such as marble, gneiss and schist marble, gneiss and schist derived from the derived from the carbonaceous material of carbonaceous material of organic origin that has been organic origin that has been converted into graphite converted into graphite during metamorphism. during metamorphism. Metamorphosed coal beds Metamorphosed coal beds may be partially converted may be partially converted into graphite during into graphite during metamorphismmetamorphism

Uses: manufacture of refractory Uses: manufacture of refractory crucibles for steel, brass and crucibles for steel, brass and bronze industries, lubricant bronze industries, lubricant (mixed with oil) pencil lead (mixed with oil) pencil lead (mixed with fine clay, protective (mixed with fine clay, protective paint for structural steel, paint for structural steel, batteries, electrodes and batteries, electrodes and generator brushes generator brushes

GRAPHITE (C)GRAPHITE (C) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Usually tabular Usually tabular

Hardness: 1-2 (readily marks Hardness: 1-2 (readily marks paper and soils fingers)paper and soils fingers)

Specific Gravity: 2.23Specific Gravity: 2.23 Fracture: hacklyFracture: hackly Luster: metallic to dullLuster: metallic to dull Color: blackColor: black Streak: blackStreak: black Greasy feelGreasy feel Composition and Structure:Composition and Structure:

CarbonCarbon Diagnostic Features:Diagnostic Features:

Color, foliated nature and Color, foliated nature and greasy feel, unattacked by greasy feel, unattacked by acids, infusible but may burn acids, infusible but may burn to COto CO22


GRAPHITE (C)GRAPHITE (C) Uses: manufacture of Uses: manufacture of

refractory crucibles for steel, refractory crucibles for steel, brass and bronze industries, brass and bronze industries, lubricant (mixed with oil) lubricant (mixed with oil) pencil lead (mixed with fine pencil lead (mixed with fine clay, protective paint for clay, protective paint for structural steel, batteries, structural steel, batteries, electrodes and generator electrodes and generator brushesbrushes

SULFIDESSULFIDES An important class of minerals that includes the majority of An important class of minerals that includes the majority of

the ore mineralsthe ore minerals Sulfide class also includes the sulfarsenides, arsenides Sulfide class also includes the sulfarsenides, arsenides

and telluridesand tellurides Most sulfides are opaque with distinctive colors and Most sulfides are opaque with distinctive colors and

characteristic colored streakscharacteristic colored streaks General formula of sulfides is XGeneral formula of sulfides is XmmZZnn in which in which XX represents represents

the metallic elements and the metallic elements and YY the nonmetallic element the nonmetallic element Many of the sulfides have ionic and covalent bonding Many of the sulfides have ionic and covalent bonding

whereas others, displaying most of the properties of whereas others, displaying most of the properties of metals, have metallic bonding metals, have metallic bonding

SULFIDESSULFIDES

Composition and Structure:Composition and Structure: Ag (87.1%), S (12.9%), Ag (87.1%), S (12.9%),

commonly contains commonly contains impurities such as calcium impurities such as calcium and magnesium sulfates and and magnesium sulfates and calcium and magnesium calcium and magnesium chlorideschlorides

Diagnostic Features:Diagnostic Features: Distinguished by its color, Distinguished by its color,

sectility and high specific sectility and high specific gravitygravity

Occurrence:Occurrence: An important primary silver An important primary silver

mineral found in veins mineral found in veins associated with native silver, associated with native silver, the ruby silvers, galena and the ruby silvers, galena and sphaleritesphalerite

ACANTHITE (AgACANTHITE (Ag22S) S) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals commonly cubicCrystals commonly cubic Most commonly massive or Most commonly massive or

as coatingas coating Hardness: 2 to 2.5Hardness: 2 to 2.5 Specific Gravity: 7.3Specific Gravity: 7.3 Tenacity: very sectile, can be cut Tenacity: very sectile, can be cut

by a knife like leadby a knife like lead Luster: metallicLuster: metallic Color: blackColor: black Streak: black, shiningStreak: black, shining Bright on fresh surface but on Bright on fresh surface but on

exposure becomes dull black, exposure becomes dull black, owing to the formation of an owing to the formation of an earthy sulfideearthy sulfide

also known as ARGENTITEalso known as ARGENTITE

SULFIDESSULFIDES ACANTHITE (AgACANTHITE (Ag22S) S)

May also occur of secondary May also occur of secondary originorigin

Uses: important ore of silverUses: important ore of silver

SULFIDESSULFIDES

Composition and Structure:Composition and Structure: Cu (79.8%), S (20.0%), may Cu (79.8%), S (20.0%), may

contain small amounts of Ag contain small amounts of Ag and Feand Fe

Diagnostic Features:Diagnostic Features: Distinguished by its lead Distinguished by its lead

gray color and sectility. gray color and sectility. When heated on charcoal it When heated on charcoal it gives odor of SOgives odor of SO22

Occurrence:Occurrence: One of the most important One of the most important

copper-ore mineralcopper-ore mineral Principal occurrence is as a Principal occurrence is as a

supergene mineral in supergene mineral in enriched zones of sulfide enriched zones of sulfide deposits (under surface deposits (under surface conditions the primary conditions the primary copper sulfides are oxidizedcopper sulfides are oxidized

CHALCOCITE (CuCHALCOCITE (Cu22S) S) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Crystals are very rareCrystals are very rare Commonly fine-grained and Commonly fine-grained and

massivemassive Cleavage: poor {110}Cleavage: poor {110} Fracture: conchoidalFracture: conchoidal Hardness: 2.5 to 3Hardness: 2.5 to 3 Specific Gravity: 5.5 to 5.8Specific Gravity: 5.5 to 5.8 Tenacity: imperfectly sectileTenacity: imperfectly sectile Luster: metallicLuster: metallic Color: shining lead gray Color: shining lead gray

tarnishing to dull black on tarnishing to dull black on exposureexposure

Streak: grayish blackStreak: grayish black Some chalcocite are soft and Some chalcocite are soft and

sootysooty

SULFIDESSULFIDES CHALCOCITE (CuCHALCOCITE (Cu22S) S)

The soluble sulfates formed The soluble sulfates formed above move downward above move downward reacting with the primary reacting with the primary minerals to form chalcocite minerals to form chalcocite and thus enriching the ore in and thus enriching the ore in copper. The water table is the copper. The water table is the lower limit of the zone of lower limit of the zone of oxidation and here a chalocite oxidation and here a chalocite blanket may form) blanket may form)

May also occur as primary May also occur as primary mineral in in veins with mineral in in veins with bornite, chalcopyrite, enargite bornite, chalcopyrite, enargite and pyriteand pyrite

Much of the world’s copper is Much of the world’s copper is produced from “porphyry produced from “porphyry copper”. In porphyry copper, copper”. In porphyry copper, primary copper minerals are primary copper minerals are disseminated through the rockdisseminated through the rock

Uses: important ore of copperUses: important ore of copper

SULFIDESSULFIDES

Diagnostic Features:Diagnostic Features: Distinguished by its Distinguished by its

characteristic bronze color characteristic bronze color on fresh fracture and by the on fresh fracture and by the purple tarnishpurple tarnish

Occurrence:Occurrence: A widely occurring copper A widely occurring copper

ore found associated with ore found associated with other sulfides (chalcocite, other sulfides (chalcocite, chalcopyrite, covellite, chalcopyrite, covellite, pyrrhotite and pyrite) in pyrrhotite and pyrite) in hypogene deposits. It is less hypogene deposits. It is less frequently found as a frequently found as a supergene mineral in the supergene mineral in the upper enriched zone of upper enriched zone of copper veinscopper veins

Occurs disseminated in Occurs disseminated in basic rocksbasic rocks

BORNITE (CuBORNITE (Cu55FeSFeS44) ) Crystallography:Crystallography:

Tetragonal crystal systemTetragonal crystal system Crystals are commonly Crystals are commonly

tetragonaltetragonal Usually massiveUsually massive

Hardness: 3Hardness: 3 Specific Gravity: 5.06 to 5.08Specific Gravity: 5.06 to 5.08 Luster: metallicLuster: metallic Color: brownish bronze on fresh Color: brownish bronze on fresh

fracture but quickly tarnishing to fracture but quickly tarnishing to variegated purple and blue hence variegated purple and blue hence called the “peacock ore” and called the “peacock ore” and finally to almost black on finally to almost black on exposureexposure

Streak: grayish blackStreak: grayish black Composition and Structure:Composition and Structure:

Cu (63.3%), Fe (11.2%) S Cu (63.3%), Fe (11.2%) S (25.5%), may contain small (25.5%), may contain small amounts of Ag and Feamounts of Ag and Fe

SULFIDESSULFIDES BORNITE (CuBORNITE (Cu55FeSFeS44))

Occurs in contact Occurs in contact metamorphic depositsmetamorphic deposits

Also in pegmatitesAlso in pegmatites Alteration: alters readily to Alteration: alters readily to

chalcocite and covellitechalcocite and covellite Uses: an ore of copperUses: an ore of copper

SULFIDESSULFIDES

Alteration: by oxidation galena is Alteration: by oxidation galena is converted into anglesite converted into anglesite (PbSO(PbSO44) and cerussite (PBCO) and cerussite (PBCO33) )

Occurrence:Occurrence: Common metallic sulfide, Common metallic sulfide,

found in veins associated found in veins associated with sphalerite, pyrite, with sphalerite, pyrite, marcasite, chalcopyrite, marcasite, chalcopyrite, cerussite, anglesite, cerussite, anglesite, dolomite, calcite, quartz, dolomite, calcite, quartz, barite and fluorite. When barite and fluorite. When found in hydrothermal veins, found in hydrothermal veins, galena is frequently galena is frequently associated with silver associated with silver mineralsminerals

Associated with sphalerite in Associated with sphalerite in veins, open space filling or veins, open space filling or replacement bodies in replacement bodies in limestones limestones

GALENA (PbS) GALENA (PbS) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals commonly cubicCrystals commonly cubic

Cleavage: perfect {001}Cleavage: perfect {001} Hardness: 2.5Hardness: 2.5 Specific Gravity: 7.4 to 7.6Specific Gravity: 7.4 to 7.6 Luster: bright metallicLuster: bright metallic Color: lead grayColor: lead gray Streak: lead grayStreak: lead gray Composition and Structure:Composition and Structure:

Pb (86.6%), S (13.4%), with Pb (86.6%), S (13.4%), with silver admixturessilver admixtures

Diagnostic Features:Diagnostic Features: Recognized by its good Recognized by its good

cleavage, high specific cleavage, high specific gravity, softness and lead gravity, softness and lead gray streakgray streak

SULFIDESSULFIDES GALENA (PbS) GALENA (PbS) Uses: only source of lead and an Uses: only source of lead and an

important ore of silver: storage important ore of silver: storage batteries, metal products (pipes, batteries, metal products (pipes, sheets, shot), litharge in glass sheets, shot), litharge in glass making, earthenware glaze, white making, earthenware glaze, white lead for paints, gasoline lead for paints, gasoline antiknock additives, shield antiknock additives, shield around radioactive materials, around radioactive materials, metal for alloys:metal for alloys: Solder – lead and tinSolder – lead and tin Type metal – lead and Type metal – lead and

antimonyantimony Low-melting alloys – lead, Low-melting alloys – lead,

bismuth, tin)bismuth, tin)

SULFIDESSULFIDES

Diagnostic Features:Diagnostic Features: Distinguished by its striking Distinguished by its striking

resinous luster and perfect resinous luster and perfect cleavagecleavage

Occurrence:Occurrence: The most important ore The most important ore

mineral of zincmineral of zinc Occurrence and origin is Occurrence and origin is

similar to that of galenasimilar to that of galena Hydrothermal veins and Hydrothermal veins and

replacement depositsreplacement deposits Veins in igneous rocks and Veins in igneous rocks and

in contact metamorphic in contact metamorphic depositsdeposits

Uses: most important ore of zinc Uses: most important ore of zinc used for metallic zinc (spelter) in used for metallic zinc (spelter) in galvanizing iron, in brass-galvanizing iron, in brass-makingmaking

SPHALERITE (ZnS) SPHALERITE (ZnS) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals are usually complex Crystals are usually complex

and malformed or in rounded and malformed or in rounded aggregates but cubes are aggregates but cubes are common common

Commonly found in cleavable Commonly found in cleavable masses, granularmasses, granular

Cleavage: perfect {001}Cleavage: perfect {001} Hardness: 3.9 to 4.1Hardness: 3.9 to 4.1 Specific Gravity: 5.5 to 5.8Specific Gravity: 5.5 to 5.8 Luster: nonmetallic and resinous Luster: nonmetallic and resinous

to submetallic, also adamantineto submetallic, also adamantine Color: colorless when pure and Color: colorless when pure and

green when nearly pure, green when nearly pure, commonly yellow, brown to blackcommonly yellow, brown to black

Streak: white to yellow and brownStreak: white to yellow and brown Composition and Structure:Composition and Structure:

Zn (67%), S (33%) when pure Zn (67%), S (33%) when pure but nearly always with Febut nearly always with Fe

SULFIDESSULFIDES SPHALERITE (ZnS) SPHALERITE (ZnS)

In electric batteries, sheet In electric batteries, sheet zinc. Zinc oxide or zinc white zinc. Zinc oxide or zinc white is used for making paint, zinc is used for making paint, zinc chloride is used as wood chloride is used as wood preservative, zinc sulfate is preservative, zinc sulfate is used in dyeing and in used in dyeing and in medicinemedicine

SULFIDESSULFIDES

black streak. Distinguished black streak. Distinguished from pyrite by being softer from pyrite by being softer than steel and from gold by than steel and from gold by being brittlebeing brittle

Also called “fool’s gold”Also called “fool’s gold” Occurrence:Occurrence:

The most widely occurring The most widely occurring copper mineral and one of copper mineral and one of the most important sources the most important sources of that metal.of that metal.

Hydrothermal veins and Hydrothermal veins and replacement depositsreplacement deposits

Porphyry copper depositsPorphyry copper deposits Original constituent in Original constituent in

igneous rocks, in igneous rocks, in pegmatites, in contact pegmatites, in contact metamorphic deposits and metamorphic deposits and disseminated in schistosedisseminated in schistose

CHALCOPYRITE (CuFeSCHALCOPYRITE (CuFeS22)) Crystallography:Crystallography:

Tetragonal crystal systemTetragonal crystal system Crystals are tetrahedralCrystals are tetrahedral Usually massiveUsually massive

Hardness: 3.5 to 4Hardness: 3.5 to 4 Specific Gravity: 4.1 to 4.3Specific Gravity: 4.1 to 4.3 Luster: metallicLuster: metallic Color: brass yellow, often Color: brass yellow, often

tarnished to bronzetarnished to bronze Streak: greenish blackStreak: greenish black Composition and Structure:Composition and Structure:

Cu (34.6%), Fe (30.4%), S Cu (34.6%), Fe (30.4%), S (35.0%), may contain small (35.0%), may contain small amounts of Ag and Feamounts of Ag and Fe

Diagnostic Features:Diagnostic Features: Recognized by its brass-Recognized by its brass-

yellow color and greenishyellow color and greenish

SULFIDESSULFIDES CHALCOPYRITE (CuFeSCHALCOPYRITE (CuFeS22))

RocksRocks Alteration: chalcopyrite is the Alteration: chalcopyrite is the

principal source of copper for the principal source of copper for the secondary minerals malachite, secondary minerals malachite, azurite, covellite, chalcocite and azurite, covellite, chalcocite and cupritecuprite

Uses: important ore of copperUses: important ore of copper

SULFIDESSULFIDES Occurrence:Occurrence:

Commonly associated with Commonly associated with basic igneous rocks, basic igneous rocks, particularly norites, occurring particularly norites, occurring as disseminated grains or as as disseminated grains or as large masses associated large masses associated with pentlandite, with pentlandite, chalcopyrite and other chalcopyrite and other sulfidessulfides

Also found in contact meta-Also found in contact meta-morphic deposits, in vein morphic deposits, in vein deposits and in pegmatitesdeposits and in pegmatites

Uses: an ore of iron and a Uses: an ore of iron and a source of sulfursource of sulfur

PYRRHOTITE (FePYRRHOTITE (Fe1-X1-XS)S) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals are hexagonal, Crystals are hexagonal,

usually tabularusually tabular Hardness: 4Hardness: 4 Specific Gravity: 4.58 to 4.65Specific Gravity: 4.58 to 4.65 Luster: metallicLuster: metallic Color: brownish to bronzeColor: brownish to bronze Streak: blackStreak: black Magnetic, but varying in intensityMagnetic, but varying in intensity Composition and Structure:Composition and Structure:

Most pyrrhotites have a Most pyrrhotites have a deficiency in iron with respect deficiency in iron with respect to sulfur as indicated by the to sulfur as indicated by the formula formula FeFe1-X1-XS, with x between 0 S, with x between 0 to 0.2to 0.2

Diagnostic Features:Diagnostic Features: Recognized by its massive Recognized by its massive

nature, bronze color and nature, bronze color and magnetismmagnetism

SULFIDESSULFIDES

Occurrence:Occurrence: Frequently occurs in, or is Frequently occurs in, or is

associated with, norites associated with, norites together with other nickel together with other nickel arsenides, sulfides, arsenides, sulfides, pyrrhotite and chalcopyritepyrrhotite and chalcopyrite

Also found in vein deposits Also found in vein deposits with cobalt and silver with cobalt and silver mineralsminerals

Uses: minor ore of nickel Uses: minor ore of nickel

NICCOLITE (NiAs)NICCOLITE (NiAs) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Rarely in tabular crystalsRarely in tabular crystals Usually massive, reniform Usually massive, reniform

with columnar structurewith columnar structure Hardness: 5 to 5.5Hardness: 5 to 5.5 Specific Gravity: 7.78Specific Gravity: 7.78 Luster: metallicLuster: metallic Color: pale copper red, with gray Color: pale copper red, with gray

to blackish tarnishto blackish tarnish Streak: brownish blackStreak: brownish black Composition and Structure:Composition and Structure:

Ni (43.9%), As (56.1%) usual-Ni (43.9%), As (56.1%) usual-ly with a little Fe, Co and Sly with a little Fe, Co and S

Diagnostic Features:Diagnostic Features: Characterized by its copper-Characterized by its copper-

red colorred color

SULFIDESSULFIDES MILLERITE (NiS)MILLERITE (NiS) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Usually in hair-like tufts and Usually in hair-like tufts and

radiating groups of slender to radiating groups of slender to capillary crystalscapillary crystals

Cleavage: good {1011}Cleavage: good {1011} Hardness: 3 to 3.5Hardness: 3 to 3.5 Specific Gravity: 5.5Specific Gravity: 5.5 Luster: metallicLuster: metallic Color: pale brass yellow with Color: pale brass yellow with

greenish tinge when in fine hair-greenish tinge when in fine hair-like masseslike masses

Streak: black, somewhat Streak: black, somewhat greenishgreenish

Composition and Structure:Composition and Structure: Ni (64.7%), S (35.3%), may Ni (64.7%), S (35.3%), may

contain small amounts of Ag contain small amounts of Ag and Feand Fe

Diagnostic Features:Diagnostic Features: Characterized by its capillary Characterized by its capillary

crystals and distinguishedcrystals and distinguished

From minerals of similar From minerals of similar colors by nickel test colors by nickel test

Occurrence:Occurrence: Forms as a low temperature Forms as a low temperature

mineral often in cavities and mineral often in cavities and as an alteration of other as an alteration of other nickel mineralsnickel minerals

Uses: a subordinate ore of Uses: a subordinate ore of nickelnickel

SULFIDESSULFIDES

Occurrence:Occurrence: Usually occurs in basic Usually occurs in basic

igneous rocks where it is igneous rocks where it is commonly associated with commonly associated with other nickel minerals and other nickel minerals and pyrrhotite probably pyrrhotite probably accumulated by magmatig accumulated by magmatig segregationsegregation

Uses: principal ore of nickel for Uses: principal ore of nickel for steel manufacture (increases steel manufacture (increases strength and toughness of strength and toughness of alloy), stainless steel alloy), stainless steel manufacture, alloys:manufacture, alloys: Monel metal (68%Ni and Monel metal (68%Ni and

32%Cu)32%Cu) Nichrome (38-85% Ni)Nichrome (38-85% Ni) German silver (Ni, Cu, Zn)German silver (Ni, Cu, Zn)

Coinage, low expansion metal Coinage, low expansion metal for watch springs and for watch springs and instruments, platinginstruments, plating

PENTLANDITE (Fe,Ni)PENTLANDITE (Fe,Ni)99SS88 Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Massive, usually granularMassive, usually granular

Hardness: 3.5 to 4Hardness: 3.5 to 4 Specific Gravity: 4.6 to 5Specific Gravity: 4.6 to 5 Tenacity: BrittleTenacity: Brittle Luster: metallicLuster: metallic Color: yellowish bronze Color: yellowish bronze Streak: light bronze brownStreak: light bronze brown NonmagneticNonmagnetic Composition and Structure:Composition and Structure:

Ratio of Fe:Ni is close to 1:1, Ratio of Fe:Ni is close to 1:1, commonly Cocommonly Co

Diagnostic Features:Diagnostic Features: Closely resembles pyrrhotite Closely resembles pyrrhotite

in appearance but in appearance but distinguished from it by lack of distinguished from it by lack of magnetismmagnetism

SULFIDESSULFIDES PENTLANDITE (Fe,Ni)PENTLANDITE (Fe,Ni)99SS88

SULFIDESSULFIDES

Plates and associations with Plates and associations with other sulfides other sulfides

Occurrence:Occurrence: Not an abundant mineral but Not an abundant mineral but

is found in most copper is found in most copper deposits as a supergene deposits as a supergene mineral, usually as a coating mineral, usually as a coating in the zone of sulfide in the zone of sulfide enrichmentenrichment

Primary covellite is known Primary covellite is known but are uncommonbut are uncommon

Uses: a minor ore of nickelUses: a minor ore of nickel

COVELLITE (CuS)COVELLITE (CuS) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Rarely in tabular crystals, Rarely in tabular crystals,

usually massive as coatings usually massive as coatings or disseminations through or disseminations through other copper mineralsother copper minerals

Cleavage: perfect {0001}Cleavage: perfect {0001} Hardness: 1.5 to 2Hardness: 1.5 to 2 Specific Gravity: 4.6 to 4.76Specific Gravity: 4.6 to 4.76 Luster: metallicLuster: metallic Color: indigo blue or darkerColor: indigo blue or darker Streak: lead gray to blackStreak: lead gray to black Often iridescentOften iridescent Composition and Structure:Composition and Structure:

Cu (66.4%), S (33.6%), may Cu (66.4%), S (33.6%), may contain small amounts of Fecontain small amounts of Fe

Diagnostic Features:Diagnostic Features: Characterized by the indigo Characterized by the indigo

blue color, micaceous blue color, micaceous cleavage yielding flexible cleavage yielding flexible

SULFIDESSULFIDES

““Metacinnabar” – has metallic Metacinnabar” – has metallic luster and grayish black colorluster and grayish black color

Composition and Structure:Composition and Structure: Hg (86.2%), S (13.8%), may Hg (86.2%), S (13.8%), may

contain small amounts of Fecontain small amounts of Fe Diagnostic Features:Diagnostic Features:

Recognized by its red color Recognized by its red color and scarlet streak, high and scarlet streak, high specific gravity and cleavagespecific gravity and cleavage

Occurrence:Occurrence: Found in quantity in Found in quantity in

comparatively few localitiescomparatively few localities Occurs as impregnations Occurs as impregnations

and as vein fillings near and as vein fillings near recent volcanic rocks and recent volcanic rocks and hot springs and evidently hot springs and evidently deposited near the surface deposited near the surface from solutions which were from solutions which were probably alkaline, probably alkaline, associatedassociated

CINNABAR (HgS)CINNABAR (HgS) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystals usually Crystals usually

rhombohedralrhombohedral Usually fine granular, massiveUsually fine granular, massive

Cleavage: perfect {1010}Cleavage: perfect {1010} Hardness: 2.5Hardness: 2.5 Specific Gravity: 8.10Specific Gravity: 8.10 Luster: adamantine when pure to Luster: adamantine when pure to

dull earthy when impuredull earthy when impure Color: vermilion-red when pure to Color: vermilion-red when pure to

brownish red when impurebrownish red when impure Streak: scarletStreak: scarlet ““Hepatic cinnabar” – inflammable Hepatic cinnabar” – inflammable

liver-brown variety with liver-brown variety with bituminous impurities, usually bituminous impurities, usually granular or compact, sometimes granular or compact, sometimes with brownish streakwith brownish streak

SULFIDESSULFIDES CINNABAR (HgS)CINNABAR (HgS)

with pyrite, marcasite, stibnite with pyrite, marcasite, stibnite and sulfides of copperand sulfides of copper

Uses: electrical apparatus, Uses: electrical apparatus, industrial control instruments, industrial control instruments, electrolytic preparation of chlorine electrolytic preparation of chlorine and caustic soda, mildew and caustic soda, mildew proofing of paint, dental proofing of paint, dental preparations, scientific preparations, scientific instruments, drugs, catalysts, in instruments, drugs, catalysts, in agriculture, amalgamation of goldagriculture, amalgamation of gold

SULFIDESSULFIDES

Occurrence:Occurrence: Found in veins of lead, Found in veins of lead,

silver, and gold oressilver, and gold ores Also as volcanic sublimation Also as volcanic sublimation

product as a deposit from product as a deposit from hot springshot springs

Uses: fireworks to give brilliant Uses: fireworks to give brilliant white light when mixed with white light when mixed with saltpeter and ignited, pigment saltpeter and ignited, pigment

REALGAR (AsS)REALGAR (AsS) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Short, vertically striated, Short, vertically striated,

prismatic crystalsprismatic crystals Frequently coarse to fine Frequently coarse to fine

granular and often earthy and granular and often earthy and as an incrustationas an incrustation

Cleavage: good {010}Cleavage: good {010} Hardness: 1.5 to 2Hardness: 1.5 to 2 Specific Gravity: 3.48Specific Gravity: 3.48 Luster: resinousLuster: resinous Color: red to orangeColor: red to orange Streak: red to orangeStreak: red to orange Composition and Structure:Composition and Structure:

As (70.1%), S (29.9%), may As (70.1%), S (29.9%), may contain small amounts of Fecontain small amounts of Fe

Diagnostic Features:Diagnostic Features: Distinguished by its red color, Distinguished by its red color,

resinous luster, orange-red resinous luster, orange-red streakstreak

SULFIDESSULFIDES

Diagnostic Features:Diagnostic Features: Distinguished from Distinguished from

chalcopyrite by its paler chalcopyrite by its paler color and greater hardnesscolor and greater hardness

Occurrence:Occurrence: Most common sulfide Most common sulfide

mineralmineral Formed both at low and high Formed both at low and high

temperaturestemperatures As magmatic segregation, As magmatic segregation,

accessory minerals in accessory minerals in igneous rocks and as igneous rocks and as contact metamorphic contact metamorphic deposits and hydrothermal deposits and hydrothermal veinsveins

Uses: Source of sulfur for Uses: Source of sulfur for sulfuric acid manufacture and sulfuric acid manufacture and ferrous sulfateferrous sulfate

PYRITE (FeSPYRITE (FeS22)) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals usually cubicCrystals usually cubic Also massive, granular, Also massive, granular,

reniform, globularreniform, globular Fracture: conchoidalFracture: conchoidal Tenacity: brittleTenacity: brittle Hardness: 6 to 6.5Hardness: 6 to 6.5 Specific Gravity: 5.02Specific Gravity: 5.02 Luster: metallic, splendentLuster: metallic, splendent Color: pale brass yellowColor: pale brass yellow Streak: greenish or brownish Streak: greenish or brownish

blackblack Composition and Structure:Composition and Structure:

Fe (46.6%), S (53.4%), may Fe (46.6%), S (53.4%), may contain small amounts of Ni contain small amounts of Ni and Coand Co

SULFIDESSULFIDES PYRITE (FeSPYRITE (FeS22))

SULFIDESSULFIDES

Diagnostic Features:Diagnostic Features: Characterized by its yellow Characterized by its yellow

color and foliated structure. color and foliated structure. Distinguished from sulfur by Distinguished from sulfur by its perfect cleavageits perfect cleavage

Occurrence:Occurrence: Rare mineral, associated Rare mineral, associated

usually with realgar and usually with realgar and formed under similar formed under similar conditionsconditions

Uses: used in dyeing and in Uses: used in dyeing and in preparation for the removal of preparation for the removal of hair from skins, previously used hair from skins, previously used as pigment but discontinued as pigment but discontinued because of poisonous naturebecause of poisonous nature

ORPIMENT (AsORPIMENT (As22SS33)) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals small tabular or short Crystals small tabular or short

prismaticprismatic Usually in foliated or columnar Usually in foliated or columnar

massesmasses Cleavage: perfect {010}Cleavage: perfect {010} Tenacity: sectileTenacity: sectile Hardness: 1.5 to 2Hardness: 1.5 to 2 Specific Gravity: 3.49Specific Gravity: 3.49 Luster: resinous, pearly on Luster: resinous, pearly on

cleavage facecleavage face Color: lemon yellowColor: lemon yellow Streak: pale yellowStreak: pale yellow Composition and Structure:Composition and Structure:

As (61%), S (39%), contains As (61%), S (39%), contains up to 2.7 % Sbup to 2.7 % Sb

SULFIDESSULFIDES ORPIMENT (AsORPIMENT (As22SS33))

SULFIDESSULFIDES

Diagnostic Features:Diagnostic Features: Characterized by its easy Characterized by its easy

fusibility, bladed habit, fusibility, bladed habit, perfect cleavage, lead gray perfect cleavage, lead gray color and soft black streakcolor and soft black streak

Occurrence:Occurrence: Found in low temperature Found in low temperature

hydrothermal veins or hydrothermal veins or replacement deposits and in replacement deposits and in hot spring depositshot spring deposits

Uses: chief ore of antimony, Uses: chief ore of antimony, metal is used in various alloys metal is used in various alloys as antimonial lead for storage as antimonial lead for storage batteries, type metal, pewter, batteries, type metal, pewter, babbitt, britannia metals and babbitt, britannia metals and anti-friction metal. Also used in anti-friction metal. Also used in fireworks, matches, vulcanizing fireworks, matches, vulcanizing rubber, medicines and pigment rubber, medicines and pigment in making glassin making glass

STIBNITE (SbSTIBNITE (Sb22SS33)) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Slender prismatic habit often Slender prismatic habit often

in radiating or in bladed formsin radiating or in bladed forms Also massive, coarse to to Also massive, coarse to to

fine granularfine granular Cleavage: perfect {010}Cleavage: perfect {010} Hardness: 2Hardness: 2 Specific Gravity: 4.52 to 4.62Specific Gravity: 4.52 to 4.62 Luster: metallic, splendent on Luster: metallic, splendent on

cleavage surfacescleavage surfaces Color: lead gray to blackColor: lead gray to black Streak: lead gray to blackStreak: lead gray to black Composition and Structure:Composition and Structure:

Sb (71.4%), S (28.6%), may Sb (71.4%), S (28.6%), may contain small amounts of Au, contain small amounts of Au, Ag, Fe, Pb and CuAg, Fe, Pb and Cu

SULFIDESSULFIDES STIBNITE (SbSTIBNITE (Sb22SS33))

SULFIDESSULFIDES

Diagnostic Features:Diagnostic Features: Distinguished from pyrite by Distinguished from pyrite by

its pale yellow color, its its pale yellow color, its crystals or its fibrous habitcrystals or its fibrous habit

Alteration: disintegrates more Alteration: disintegrates more easily than pyrite with the easily than pyrite with the formation of ferrous sulfate and formation of ferrous sulfate and sulfuric acidsulfuric acid

Occurrence:Occurrence: Found in metalliferous veins, Found in metalliferous veins,

frequently with lead an zinc frequently with lead an zinc ores. Less stable than pyrite, ores. Less stable than pyrite, easily decomposed. easily decomposed. Deposited at low tempera-Deposited at low tempera-ures from acid solutions and ures from acid solutions and commonly formed under commonly formed under surface conditions as surface conditions as supergene mineral.supergene mineral.

Frequently occurs as Frequently occurs as replacement deposits in replacement deposits in

MARCASITE (FeSMARCASITE (FeS22)) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Crystals commonly tabular Crystals commonly tabular

and less prismaticand less prismatic Usually in radiating forms or Usually in radiating forms or

stalactiticstalactitic Hardness: 6 to 6.5Hardness: 6 to 6.5 Specific Gravity: 4.89Specific Gravity: 4.89 Luster: metallicLuster: metallic Color: pale bronze-yellow to Color: pale bronze-yellow to

almost white on fresh fracturealmost white on fresh fracture Streak: grayish blackStreak: grayish black Composition and Structure:Composition and Structure:

Constant composition, Constant composition, dimorphous with pyritedimorphous with pyrite

SULFIDESSULFIDES MARCASITE (FeSMARCASITE (FeS22))

Limestone, and often in Limestone, and often in concretions embedded in concretions embedded in clays, marls and shalesclays, marls and shales

Uses: used to a slight extent as a Uses: used to a slight extent as a source of sulfur source of sulfur

SULFIDESSULFIDES

Diagnostic Features:Diagnostic Features: Resembles graphite but is Resembles graphite but is

distinguished from it by distinguished from it by higher specific gravity, by a higher specific gravity, by a blue tone of its color, where-blue tone of its color, where-as graphite has a brown as graphite has a brown tingetinge

Alteration: alters to yellow Alteration: alters to yellow ferrimolybdeniteferrimolybdenite

Occurrence:Occurrence: forms as an accessory in forms as an accessory in

certain granites, in certain granites, in pegmatites and aplitespegmatites and aplites

Commonly in high Commonly in high temperature vein deposits temperature vein deposits associated with cassiterite, associated with cassiterite, scheelite, wolframite and scheelite, wolframite and fluoritefluorite

Also in contact metamorphic Also in contact metamorphic deposits with lime silicates, deposits with lime silicates, scheelite and chalcopyritescheelite and chalcopyrite

MOLYBDENITE (MoSMOLYBDENITE (MoS22)) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystals in hexagonal platesCrystals in hexagonal plates Commonly foliated, massive Commonly foliated, massive

or in scalesor in scales Cleavage: perfect {0001}Cleavage: perfect {0001} Tenacity: laminae flexible but not Tenacity: laminae flexible but not

elastic, sectileelastic, sectile Hardness: 1 to 1.5Hardness: 1 to 1.5 Specific Gravity: 4.62 to 4.73Specific Gravity: 4.62 to 4.73 Luster: metallicLuster: metallic Color: lead grayColor: lead gray Streak: grayish blackStreak: grayish black Greasy feelGreasy feel Composition and Structure:Composition and Structure:

Mo (59.9%) S (40.1%) Mo (59.9%) S (40.1%) essentially constant essentially constant compositioncomposition

SULFIDESSULFIDES MOLYBDENITE (MoSMOLYBDENITE (MoS22))

Uses: principal ore of Uses: principal ore of molybdenummolybdenum

SULFIDESSULFIDES

Occurrence:Occurrence: Usually found in high Usually found in high

temperature depositstemperature deposits As disseminations in As disseminations in

metamorphosed rocksmetamorphosed rocks In vein deposit with other In vein deposit with other

cobalt and nickel mineralscobalt and nickel minerals Uses: an ore of cobalt Uses: an ore of cobalt

COBALTITE (Co,Fe)AsSCOBALTITE (Co,Fe)AsS Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Crystals pseudoisometricCrystals pseudoisometric Also granularAlso granular

Cleavage: pseudocubic, perfectCleavage: pseudocubic, perfect Tenacity: brittleTenacity: brittle Hardness: 5.5Hardness: 5.5 Specific Gravity: 6.33Specific Gravity: 6.33 Luster: metallicLuster: metallic Color: silver-white, inclined to redColor: silver-white, inclined to red Streak: grayish blackStreak: grayish black Composition and Structure:Composition and Structure:

Usually contains considerable Usually contains considerable Fe and lesser amounts of NiFe and lesser amounts of Ni

Diagnostic Features:Diagnostic Features: Resembles pyrite in crystal Resembles pyrite in crystal

form but is distinguished by its form but is distinguished by its silver color and cleavagesilver color and cleavage

SULFIDESSULFIDES

Occurrence:Occurrence: The most common mineral The most common mineral

containing arseniccontaining arsenic It occurs with tin and It occurs with tin and

tungsten ores in high tungsten ores in high temperature hydrothermal temperature hydrothermal deposits, associated with deposits, associated with silver and copper ores, silver and copper ores, galena, sphalerite, pyrite galena, sphalerite, pyrite and chalcopyrite. Frequently and chalcopyrite. Frequently associated with goldassociated with gold

Often found sparingly in Often found sparingly in pegmatites, in contact pegmatites, in contact metamorphic deposits, metamorphic deposits, disseminated in crystalline disseminated in crystalline limestone limestone

Uses: principal source of Uses: principal source of arsenic, metallic arsenic used in arsenic, metallic arsenic used in alloys, arsenic is used chiefly in alloys, arsenic is used chiefly in the form of white arsenic or the form of white arsenic or

ARSENOPYRITE (FeAsS)ARSENOPYRITE (FeAsS) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals commonly prismaticCrystals commonly prismatic Also granularAlso granular

Cleavage: poor {101}Cleavage: poor {101} Hardness: 5.5 to 6Hardness: 5.5 to 6 Specific Gravity: 6.07Specific Gravity: 6.07 Luster: metallicLuster: metallic Color: silver-whiteColor: silver-white Streak: blackStreak: black Composition and Structure:Composition and Structure:

Close to FeAsS with some Close to FeAsS with some variation in As and S contentsvariation in As and S contents

Diagnostic Features:Diagnostic Features: Distinguished from marcasite Distinguished from marcasite

by its silver-white colorby its silver-white color

SULFIDESSULFIDES ARSENOPYRITE (FeAsS)ARSENOPYRITE (FeAsS)

Arsenous oxide in medicine, Arsenous oxide in medicine, insecticides, preservatives, insecticides, preservatives, pigments and glass, arsenic pigments and glass, arsenic sulfides are used in paints sulfides are used in paints and fireworksand fireworks


Usually found with cobaltite Usually found with cobaltite and niccolite in veins formed and niccolite in veins formed at moderate temperature. at moderate temperature. Native silver, bismuth arse-Native silver, bismuth arse-nopyrite and calcite are also nopyrite and calcite are also commonly associated with it commonly associated with it

Uses: ore of cobalt and nickel. Uses: ore of cobalt and nickel. Cobalt is chiefly used in alloy Cobalt is chiefly used in alloy making, permanent magnets making, permanent magnets and high speed steel. Cobalt and high speed steel. Cobalt oxide is used as blue pigment in oxide is used as blue pigment in pottery and glassware pottery and glassware

SKUTTERUDITE (Co,Ni)AsSKUTTERUDITE (Co,Ni)As33 Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Common crystal forms are Common crystal forms are

cubecube Usually massive, dense to Usually massive, dense to

granulargranular Tenacity: brittleTenacity: brittle Hardness: 5.5 to 6Hardness: 5.5 to 6 Specific Gravity: 6.5Specific Gravity: 6.5 Luster: metallicLuster: metallic Color: tin-white to silver grayColor: tin-white to silver gray Streak: blackStreak: black Composition and Structure:Composition and Structure:

Essentially Essentially (Co,Ni)As(Co,Ni)As33 but Fe but Fe usually substitute for some Ni or usually substitute for some Ni or NiNi

Diagnostic Features:Diagnostic Features: Fusible at 2 to 2.5Fusible at 2 to 2.5


Usually found low tempe-Usually found low tempe-rature hydrothermal veins, rature hydrothermal veins, but also in some higher but also in some higher temperature deposits temperature deposits associated with sylvanite associated with sylvanite and other telluridesand other tellurides

Uses: ore of goldUses: ore of gold

CALAVERITE (AuTeCALAVERITE (AuTe22)) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Rarely in distinct crystalsRarely in distinct crystals Usually granularUsually granular

Tenacity: very brittleTenacity: very brittle Hardness: 2.5Hardness: 2.5 Specific Gravity: 9.35Specific Gravity: 9.35 Luster: metallicLuster: metallic Color: brass-yellow to silver-white Color: brass-yellow to silver-white Streak: yellowish to greenish grayStreak: yellowish to greenish gray Composition and Structure:Composition and Structure:

Au (44.03%) Te (55.97%)Au (44.03%) Te (55.97%) Diagnostic Features:Diagnostic Features:

Distinguished from sylvanite Distinguished from sylvanite by the presence of only a by the presence of only a small amount of Ag and by small amount of Ag and by the lack of cleavagethe lack of cleavage


Rare mineral associated Rare mineral associated with calaverite and other with calaverite and other tellurides, pyrite and other tellurides, pyrite and other sulfides in small amounts in sulfides in small amounts in veins formed at low veins formed at low temperaturestemperatures

Uses: ore of gold and silverUses: ore of gold and silver

SYLVANITE (Au,Ag)TeSYLVANITE (Au,Ag)Te22)) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Rarely in distinct crystalsRarely in distinct crystals Usually bladed or granular, Usually bladed or granular,

often in skeleton forms on often in skeleton forms on rock surface resembling rock surface resembling writings in appearancewritings in appearance

Hardness: 1.5 to 2Hardness: 1.5 to 2 Specific Gravity: 8 to 8.2Specific Gravity: 8 to 8.2 Luster: brilliant metallicLuster: brilliant metallic Color: silver-white Color: silver-white Streak: grayStreak: gray Composition and Structure:Composition and Structure:

Ratio of gold to silver variesRatio of gold to silver varies Diagnostic Features:Diagnostic Features:

Distinguished from calaverite Distinguished from calaverite by its good cleavageby its good cleavage

SULFOSALTSSULFOSALTS

are complex sulfide minerals with the general formula: are complex sulfide minerals with the general formula: AAmmBBnnSSpp; where A represents a metal such as copper, ; where A represents a metal such as copper, lead, or silver; B represents a semi-metal such as lead, or silver; B represents a semi-metal such as arsenic, antimony or bismuth; and S is sulfur or rarely arsenic, antimony or bismuth; and S is sulfur or rarely selenium. In the more simple sulfosalt formulas selenium. In the more simple sulfosalt formulas mm = = pp = 3 = 3nn is an approximationis an approximation

Sulfosalts differ from sulfides, sulfarsenides and Sulfosalts differ from sulfides, sulfarsenides and arsenides in that As and Sb play a role more or less like arsenides in that As and Sb play a role more or less like that of metals in the structure. In sulfarsenides and that of metals in the structure. In sulfarsenides and arsenides the semimetals take the place of sulfur in the arsenides the semimetals take the place of sulfur in the structurestructure

there are about 200 known sulfosalt mineralsthere are about 200 known sulfosalt minerals


Diagnostic Features:Diagnostic Features: Brilliant luster and red color. Brilliant luster and red color.

Pyrargyrite is distinguished Pyrargyrite is distinguished from proustite by darker red from proustite by darker red color and diagnostic tests for color and diagnostic tests for Sb and AsSb and As

Occurrence:Occurrence: Pyrargyrite is the more Pyrargyrite is the more

common of these two common of these two minerals. Both found in low minerals. Both found in low temperature silver veins as temperature silver veins as minerals that crystallize late minerals that crystallize late in the sequence of primary in the sequence of primary depositiondeposition

Uses:Uses: Ores of silverOres of silver

PYRARGYRITE (AgPYRARGYRITE (Ag33SbSSbS33) ) “dark “dark ruby silver”ruby silver”

Crystallography:Crystallography: Hexagonal-rhombohedral Hexagonal-rhombohedral

crystal systemcrystal system Crystals commonly prismatic Crystals commonly prismatic

with hemimorphic develop-with hemimorphic develop-mentment

Commonly massive, compact Commonly massive, compact and in disseminated grains and in disseminated grains

Cleavage: distinct {1011}Cleavage: distinct {1011} Hardness: 2 to 2.5Hardness: 2 to 2.5 Specific Gravity: 5.85 Luster: Specific Gravity: 5.85 Luster:

adamantineadamantine Color: red Color: red Streak: redStreak: red Composition and Structure:Composition and Structure:

Ag (59.7%), Sb (22.5%), S Ag (59.7%), Sb (22.5%), S (17.8%)(17.8%)

SULFOSALTSSULFOSALTS PYRARGYRITE (AgPYRARGYRITE (Ag33SbSSbS33) ) “dark “dark

ruby silver”ruby silver”

SULFOSALTSSULFOSALTS Diagnostic Features:Diagnostic Features:

Brilliant luster and red color. Brilliant luster and red color. Pyrargyrite is distinguished Pyrargyrite is distinguished from proustite by darker red from proustite by darker red color and diagnostic tests for color and diagnostic tests for Sb and AsSb and As

Occurrence:Occurrence: Pyrargyrite is the more Pyrargyrite is the more

common of these two common of these two minerals. Both found in low minerals. Both found in low temperature silver veins as temperature silver veins as minerals that crystallize late minerals that crystallize late in the sequence of primary in the sequence of primary depositiondeposition

Uses:Uses: Ores of silverOres of silver

PROUSTITE (AgPROUSTITE (Ag33AsSAsS33) ) “light “light ruby silver” ruby silver”

Crystallography:Crystallography: Hexagonal-rhombohedral Hexagonal-rhombohedral

crystal systemcrystal system Crystals commonly prismatic Crystals commonly prismatic

with hemimorphic develop-with hemimorphic develop-mentment

Commonly massive, compact Commonly massive, compact and in disseminated grains and in disseminated grains

Cleavage: distinct {1011}Cleavage: distinct {1011} Hardness: 2 to 2.5Hardness: 2 to 2.5 Specific Gravity: 5.57Specific Gravity: 5.57 Luster: adamantineLuster: adamantine Color: scarlet-vermilionColor: scarlet-vermilion Streak: scarlet-vermilionStreak: scarlet-vermilion Composition and Structure:Composition and Structure:

Ag (65.4%), As (15.2%), S Ag (65.4%), As (15.2%), S (19.4%)(19.4%)

SULFOSALTSSULFOSALTS PROUSTITE (AgPROUSTITE (Ag33AsSAsS33) ) “light “light

ruby silver” ruby silver”


Diagnostic Features:Diagnostic Features: Characterized by its color Characterized by its color

and cleavageand cleavage Occurrence:Occurrence:

Comparatively rare, found in Comparatively rare, found in vein and replacement vein and replacement deposits formed at moderate deposits formed at moderate temperatures associated temperatures associated with pyrite, sphalerite, with pyrite, sphalerite, bornite, galena, tetrahedrite, bornite, galena, tetrahedrite, covellite and chalcocitecovellite and chalcocite

Uses: ore of copperUses: ore of copper

ENARGITE (CuENARGITE (Cu33AsSAsS44) ) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Columnar, bladed to massiveColumnar, bladed to massive

Cleavage: perfect {110}Cleavage: perfect {110} Hardness: 3Hardness: 3 Specific Gravity: 4.45.Specific Gravity: 4.45. Luster: metallicLuster: metallic Color: grayish black to iron black Color: grayish black to iron black Streak: grayish black to iron blackStreak: grayish black to iron black Composition and Structure:Composition and Structure:

Cu (48.3%), As (19.1%), S Cu (48.3%), As (19.1%), S (32.6 %)(32.6 %)

Polymorph – luzonite Polymorph – luzonite (tetragonal)(tetragonal)

SULFOSALTSSULFOSALTS ENARGITE (CuENARGITE (Cu33AsSAsS44) )


Composition and Structure:Composition and Structure: Cu is the predominant metal, Cu is the predominant metal,

Fe is always present (1-Fe is always present (1-13%) and Zn (0-8%)13%) and Zn (0-8%)

Diagnostic Features:Diagnostic Features: Tetrahedral crystals. When Tetrahedral crystals. When

massive, they are brittle and massive, they are brittle and gray colored.gray colored.

Occurrence:Occurrence: Tetrahedrite, the most Tetrahedrite, the most

common sulfosalt is common sulfosalt is widespread in occurrence widespread in occurrence and varied in association in and varied in association in hydrothermal veins of hydrothermal veins of copper, silver, lead and zinc copper, silver, lead and zinc formed at low to moderate formed at low to moderate temperaturestemperatures

Uses: ore of copper and silverUses: ore of copper and silver

TETRAHEDRITE (CuTETRAHEDRITE (Cu1212SbSb44SS1313))

TENNANTITE (CuTENNANTITE (Cu1212AsAs44SS1313) )

Crystallography:Crystallography: Isometric crystal systemIsometric crystal system May occur as parallel crystalsMay occur as parallel crystals Frequently in tetrahedral Frequently in tetrahedral

crystals but may also occur as crystals but may also occur as massive, granularmassive, granular

Hardness: 3 to 4.5Hardness: 3 to 4.5 Specific Gravity: 4.6 to 5.1 Specific Gravity: 4.6 to 5.1

(tennantite harder but of lower (tennantite harder but of lower specific gravity than tetrahedrite)specific gravity than tetrahedrite)

Luster: metallic to submetallicLuster: metallic to submetallic Color: grayish black to blackColor: grayish black to black Streak: black to brownStreak: black to brown

SULFOSALTSSULFOSALTS TENNANTITE (CuTENNANTITE (Cu1212AsAs44SS1313)) TETRAHEDRITE (CuTETRAHEDRITE (Cu1212SbSb44SS1313))


Diagnostic Features:Diagnostic Features: Characteristic crystals and Characteristic crystals and

high specific gravityhigh specific gravity Occurrence:Occurrence:

Occurs typically in Occurs typically in hydrothermal veins formed hydrothermal veins formed at moderate temperaturesat moderate temperatures

Uses:Uses: Ore of copper, lead and Ore of copper, lead and

antimonyantimony

BOURNONITE (PbCuSbSBOURNONITE (PbCuSbS33) )

Crystallography:Crystallography: Orthorhombic crystal systemOrthorhombic crystal system Crystals usually short Crystals usually short

prismatic to tabularprismatic to tabular Also massive, granular to Also massive, granular to

compactcompact Called the “cogwheel ore”Called the “cogwheel ore” Cleavage: imperfectCleavage: imperfect Hardness: 2.5 to 3Hardness: 2.5 to 3 Specific Gravity: 5.8 to 5.9Specific Gravity: 5.8 to 5.9 Luster: metallicLuster: metallic Color: steel gray to blackColor: steel gray to black Streak: steel gray to blackStreak: steel gray to black Composition and Structure:Composition and Structure:

Pb (42.4%), Cu (13.0%), Sb Pb (42.4%), Cu (13.0%), Sb (24.9%) and S (19.7%)(24.9%) and S (19.7%)

SULFOSALTSSULFOSALTS BOURNONITE (PbCuSbSBOURNONITE (PbCuSbS33) )


Composition and Structure:Composition and Structure: Pb (40.16%), Fe (2.71%), Sb Pb (40.16%), Fe (2.71%), Sb

(35.39%) and S (21.74%)(35.39%) and S (21.74%) Diagnostic Features:Diagnostic Features:

Characteristic fibrous Characteristic fibrous crystals. Distinguished from crystals. Distinguished from stibnite by lack of good stibnite by lack of good lengthwise cleavagelengthwise cleavage

Occurrence:Occurrence: Occurs in hydrothermal Occurs in hydrothermal

veins formed at low to veins formed at low to moderate temperatures moderate temperatures associated with other lead associated with other lead sulfosalts, galena, stibnite sulfosalts, galena, stibnite and sphaleriteand sphalerite

Uses:Uses: Minor ore of leadMinor ore of lead

JAMESONITE (PbJAMESONITE (Pb44FeSbFeSb66SS1414) )

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Crystals usually acicular or in Crystals usually acicular or in

capillary forms with feather-capillary forms with feather-like appearancelike appearance

Also fibrous to compact Also fibrous to compact massivemassive

Called the “feather ore”Called the “feather ore” Cleavage: good {001}Cleavage: good {001} Tenacity: brittleTenacity: brittle Hardness: 2.5 to 3Hardness: 2.5 to 3 Specific Gravity: 5.63Specific Gravity: 5.63 Luster: metallicLuster: metallic Color: steel gray to grayish blackColor: steel gray to grayish black Streak: steel gray to grayish Streak: steel gray to grayish

blackblack

SULFOSALTSSULFOSALTS JAMESONITE (PbJAMESONITE (Pb44FeSbFeSb66SS1414) )

OXIDESOXIDES natural compounds in which oxygen is combined with one or more metalsnatural compounds in which oxygen is combined with one or more metals relatively hard, dense and refractory and generally occur as accessory relatively hard, dense and refractory and generally occur as accessory

minerals in igneous and metamorphic rocks and as resistant detrital grains minerals in igneous and metamorphic rocks and as resistant detrital grains in sedimentsin sediments

Groups:Groups: Simple oxidesSimple oxides (compounds of one metal and oxygen with different (compounds of one metal and oxygen with different XX:O :O

ratios as ratios as XX22O, O, XXO, O, XX22OO33))

1.1. XX22O, O, XXO Type (cuprite, zincite)O Type (cuprite, zincite)

2.2. XX22OO33 Type - Hematite Group (corundum, hematite, ilmenite) Type - Hematite Group (corundum, hematite, ilmenite)

3.3. XXOO22 Type - Rutile Group (rutile, pyrolusite, cassiterite) Type - Rutile Group (rutile, pyrolusite, cassiterite)

- Uraninite- Uraninite Multiple oxidesMultiple oxides (have two non equivalent metal atom site) (have two non equivalent metal atom site)

1.1. XYXY22OO44 Type – Spinel Group (spinel, gahnite, magnetite, franklinite, Type – Spinel Group (spinel, gahnite, magnetite, franklinite,

chromite)chromite)- ChrysoberylChrysoberyl- Columbite Columbite

chief ores of iron, chromium, manganese, tin and uraniumchief ores of iron, chromium, manganese, tin and uranium generally have strong ionic bondsgenerally have strong ionic bonds

OXIDESOXIDES

Composition and Structure:Composition and Structure: Pb (40.16%), Fe (2.71%), Sb Pb (40.16%), Fe (2.71%), Sb

(35.39%) and S (21.74%)(35.39%) and S (21.74%) Diagnostic Features:Diagnostic Features:

Characteristic fibrous Characteristic fibrous crystals. Distinguished from crystals. Distinguished from stibnite by lack of good stibnite by lack of good lengthwise cleavagelengthwise cleavage

Occurrence:Occurrence: Occurs in hydrothermal Occurs in hydrothermal

veins formed at low to veins formed at low to moderate temperatures moderate temperatures associated with other lead associated with other lead sulfosalts, galena, stibnite sulfosalts, galena, stibnite and sphaleriteand sphalerite

Uses:Uses: Minor ore of leadMinor ore of lead

CUPRITE (CuCUPRITE (Cu22O) O)

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Crystals usually acicular or in Crystals usually acicular or in

capillary forms with feather-capillary forms with feather-like appearancelike appearance

Also fibrous to compact Also fibrous to compact massivemassive

Called the “feather ore”Called the “feather ore” Cleavage: good {001}Cleavage: good {001} Tenacity: brittleTenacity: brittle Hardness: 2.5 to 3Hardness: 2.5 to 3 Specific Gravity: 5.63Specific Gravity: 5.63 Luster: metallicLuster: metallic Color: steel gray to grayish blackColor: steel gray to grayish black Streak: steel gray to grayish Streak: steel gray to grayish

blackblack

OXIDESOXIDES CUPRITE (CuCUPRITE (Cu22O) O)

OXIDESOXIDES

Diagnostic Features:Diagnostic Features: Distinguished by its red Distinguished by its red

color, orange-yellow streakcolor, orange-yellow streak InfusibleInfusible Soluble in HClSoluble in HCl

Occurrence:Occurrence: Confined almost exclusively Confined almost exclusively

to the zinc deposits of to the zinc deposits of Franklin, New JerseyFranklin, New Jersey

Uses: ore of zincUses: ore of zinc

ZINCITE (ZnO) ZINCITE (ZnO) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystals are rare, usually Crystals are rare, usually

massive with platy or granular massive with platy or granular appearanceappearance

Cleavage: perfect {1010}, parting Cleavage: perfect {1010}, parting {0001}{0001}

Hardness: 4 Hardness: 4 Specific Gravity: 5.8Specific Gravity: 5.8 Luster: subadamantineLuster: subadamantine Color: deep red to orange-yellow Color: deep red to orange-yellow Streak: orange-yellowStreak: orange-yellow Composition and Structure:Composition and Structure:

Zn (80.3%), O (19.7%)Zn (80.3%), O (19.7%) Mn often presentMn often present

OXIDESOXIDES

““emery” – black granular emery” – black granular corundumcorundum

Composition and Structure:Composition and Structure: Al (52.9%), O (47.1)Al (52.9%), O (47.1) Trace Cr in rubies give red Trace Cr in rubies give red

color, Fe or Ti give sapphire color, Fe or Ti give sapphire blue colorblue color

Diagnostic Features:Diagnostic Features: Characterized by its Characterized by its

hardness, high luster, hardness, high luster, specific gravity and partingspecific gravity and parting

InfusibleInfusible insolubleinsoluble

Occurrence:Occurrence: Common accessory mineral Common accessory mineral

in metamorphic rocks such in metamorphic rocks such as crystalline limestone, mica as crystalline limestone, mica schist and gneissschist and gneiss

CORUNDUM (AlCORUNDUM (Al22OO33) )

Crystallography:Crystallography: Hexagonal crystal systemHexagonal crystal system Crystals commonly tabular or Crystals commonly tabular or

prismaticprismatic Usually rudely crystallized or Usually rudely crystallized or

massivemassive Parting: {0001}, {1011} Parting: {0001}, {1011} Hardness: 9Hardness: 9 Specific Gravity: 4.02Specific Gravity: 4.02 Luster: adamantine to vitreousLuster: adamantine to vitreous Color: various, usually shades of Color: various, usually shades of

brown, pink or bluebrown, pink or blue Ruby – redRuby – red Sapphire - blueSapphire - blue

Rubies and sapphires have Rubies and sapphires have stellate opalescencestellate opalescence

OXIDESOXIDES

Uses: gemstone and abrasives, Uses: gemstone and abrasives, the deep red ruby is one of the the deep red ruby is one of the most valuable of gems, second most valuable of gems, second only to emeraldonly to emerald

CORUNDUM (AlCORUNDUM (Al22OO33) ) Also found as an original Also found as an original

constituent of silica-deficient constituent of silica-deficient igneous rocks as syenite and igneous rocks as syenite and nepheline syenitesnepheline syenites

May also be found in large May also be found in large masses in the zone masses in the zone separating peridotites from separating peridotites from adjacentadjacent

Also as small crystals through Also as small crystals through lamprophyric dikes and is lamprophyric dikes and is found in large crystals in found in large crystals in pegmatitespegmatites

Also be found as crystals and Also be found as crystals and rolled pebbles in detrital soil rolled pebbles in detrital soil and stream sands where it and stream sands where it has been preserved through has been preserved through its hardness and chemical its hardness and chemical inertnessinertness

OXIDESOXIDES Streak: light to dark redStreak: light to dark red Composition and Structure:Composition and Structure:

Fe (70%), O (30%)Fe (70%), O (30%) Diagnostic Features:Diagnostic Features:

Characteristic red streakCharacteristic red streak InfusibleInfusible Becomes strongly magnetic Becomes strongly magnetic

on heatingon heating Slowly soluble in HClSlowly soluble in HCl

Occurrence:Occurrence: Most abundant and important Most abundant and important

ore of ironore of iron May occur as sublimation May occur as sublimation

product in connection with product in connection with volcanic activitiesvolcanic activities

Occurs in contact Occurs in contact metamorphic deposits and as metamorphic deposits and as accessory minerals in accessory minerals in feldspathic igneous rocks feldspathic igneous rocks such as granitesuch as granite

HEMATITE (FeHEMATITE (Fe22OO33) ) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystal usually thick to thin Crystal usually thick to thin

tabulartabular Also in botryoidal (kidney ore) Also in botryoidal (kidney ore)

to reniform shapeto reniform shape Thin plates maybe grouped in Thin plates maybe grouped in

rosettes (iron roses)rosettes (iron roses) Usually earthy (martite)Usually earthy (martite)

Parting: {1011}Parting: {1011} Hardness: 5.5 to 6.5Hardness: 5.5 to 6.5 Specific Gravity: 5.26Specific Gravity: 5.26 Luster: metallic in crystals, dull in Luster: metallic in crystals, dull in

earthy varietiesearthy varieties Color: reddish brown to blackColor: reddish brown to black

Red ocher – red earthyRed ocher – red earthy Specularite – platy and Specularite – platy and

metallicmetallic

OXIDESOXIDES HEMATITE (FeHEMATITE (Fe22OO33) )

Also found in regionally Also found in regionally metamorphosed rocks where metamorphosed rocks where it may have originated by the it may have originated by the oxidation of limonite, siderite, oxidation of limonite, siderite, or magnetiteor magnetite

As cementing materials in red As cementing materials in red sandstonessandstones

As enrichment deposits in As enrichment deposits in sedimentary rocks through sedimentary rocks through leaching of associated silica leaching of associated silica by meteoric watersby meteoric waters

Irregular masses and beds as Irregular masses and beds as the result of the weathering the result of the weathering and oxidation of iron-bearing and oxidation of iron-bearing rocksrocks

Uses: most important ore of iron Uses: most important ore of iron for steel manufacture, pigments, for steel manufacture, pigments, red ocher and as polishing red ocher and as polishing powderpowder

OXIDESOXIDES Diagnostic Features:Diagnostic Features:

Distinguished from hematite Distinguished from hematite by its streak and from by its streak and from magnetite by its lack of magnetite by its lack of strong magnetismstrong magnetism

InfusibleInfusible Magnetic after heatingMagnetic after heating

Occurrence:Occurrence: Common accessory mineral Common accessory mineral

in igneous rocks. It maybe in igneous rocks. It maybe present in large masses in present in large masses in gabbros, diorites and gabbros, diorites and anorthosites as a product of anorthosites as a product of magmatic segregation magmatic segregation intimately associated with intimately associated with magnetite, rutile, zircon and magnetite, rutile, zircon and monazitemonazite

Uses: major source of titanium Uses: major source of titanium for the production of titanium for the production of titanium dioxide (paint pigment), metallic dioxide (paint pigment), metallic titanium (structural materials) titanium (structural materials)

ILMENITE (FeTiOILMENITE (FeTiO33) ) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystal are usually thick Crystal are usually thick

tabulartabular Usually massive, compactUsually massive, compact

Hardness: 5.5 to 6Hardness: 5.5 to 6 Specific Gravity: 4.7Specific Gravity: 4.7 Luster: metallic to submetallicLuster: metallic to submetallic Color: iron-blackColor: iron-black Streak: black to brownish redStreak: black to brownish red Maybe magnetic without heatingMaybe magnetic without heating Composition and Structure:Composition and Structure:

Fe (36.8%), Ti (31.6%), O Fe (36.8%), Ti (31.6%), O (31.6%)(31.6%)

Structure is very similar to Structure is very similar to that of corundumthat of corundum

OXIDESOXIDES ILMENITE (FeTiOILMENITE (FeTiO33) )


Characterized by its peculiar Characterized by its peculiar adamantine luster and red adamantine luster and red colorcolor

Lower specific gravity Lower specific gravity distinguishes it from distinguishes it from cassiteritecassiterite

InfusibleInfusible insoluble insoluble

Occurrence:Occurrence: Found in granite, granite Found in granite, granite

pegmatites, gneiss, mica pegmatites, gneiss, mica schist, metamorphic schist, metamorphic limestone and dolomitelimestone and dolomite

It maybe present as an It maybe present as an accessory mineral in the rock accessory mineral in the rock or in quartz veins traversing itor in quartz veins traversing it

Uses: coating for welding rods, Uses: coating for welding rods, alloys, electrodes in arc lights alloys, electrodes in arc lights yellow color, pain pigmentyellow color, pain pigment

RUTILE (TiORUTILE (TiO22) ) Crystallography:Crystallography:

Tetragonal crystal systemTetragonal crystal system Crystal usually prismatic, Crystal usually prismatic,

slender or acicularslender or acicular Also massive, compactAlso massive, compact

Cleavage: distinct {110}Cleavage: distinct {110} Hardness: 6 to 6.5Hardness: 6 to 6.5 Specific Gravity: 4.18 to 4.25Specific Gravity: 4.18 to 4.25 Luster: adamantine to submetallicLuster: adamantine to submetallic Color: red, reddish brown to black Color: red, reddish brown to black Streak: pale brownStreak: pale brown Composition and Structure:Composition and Structure:

Ti (60%), O (40%)Ti (60%), O (40%)

OXIDESOXIDES RUTILE (TiORUTILE (TiO22) )

OXIDESOXIDES

Diagnostic Features:Diagnostic Features: Characterized by and Characterized by and

distinguished from other distinguished from other manganese minerals by its manganese minerals by its black streak, low hardness black streak, low hardness and small amount of water and small amount of water

Occurrence:Occurrence: Manganese is present in in Manganese is present in in

small amounts in most small amounts in most crystalline rocks. When crystalline rocks. When dissolved from these rocks, it dissolved from these rocks, it maybe re-deposited as maybe re-deposited as various minerals but chiefly various minerals but chiefly as pyrolusiteas pyrolusite

Nodular deposits are found Nodular deposits are found on bogs, lake bottoms and on bogs, lake bottoms and ocean/sea floorsocean/sea floors

Nests and beds of manga-Nests and beds of manga-nese ores are found nese ores are found enclosed in residual claysenclosed in residual clays

PYROLUSITE (MnOPYROLUSITE (MnO22) ) Crystallography:Crystallography:

Tetragonal crystal systemTetragonal crystal system Rarely ion well-developed Rarely ion well-developed

crystalscrystals Usually in radiating fibers or Usually in radiating fibers or

columnscolumns Also granular, massiveAlso granular, massive

Cleavage: perfect {110}Cleavage: perfect {110} Hardness: 1 to 2 (often soils the Hardness: 1 to 2 (often soils the

fingers), 6 to 6.5 for crystallinefingers), 6 to 6.5 for crystalline Specific Gravity: 4.75Specific Gravity: 4.75 Luster: metallicLuster: metallic Color: iron-blackColor: iron-black Streak: iron-blackStreak: iron-black Composition and Structure:Composition and Structure:

Mn (63.2%), O (36.8%)Mn (63.2%), O (36.8%) Structure same as rutileStructure same as rutile

OXIDESOXIDES PYROLUSITE (MnOPYROLUSITE (MnO22) )

Derived from the decay of Derived from the decay of manganiferous limestonesmanganiferous limestones

Also found in veins with Also found in veins with quartz and various metallic quartz and various metallic mineralsminerals

Uses: most important ore of Uses: most important ore of manganese, use in the manganese, use in the manufacture of steel, alloys with manufacture of steel, alloys with copper, zinc, aluminum, tin and copper, zinc, aluminum, tin and lead, oxidizer in the manufacture lead, oxidizer in the manufacture of chlorine, bromine and oxygen, of chlorine, bromine and oxygen, drier in paints, decolorizer, drier in paints, decolorizer, coloring material in bricks and coloring material in bricks and pottery pottery

OXIDESOXIDES

Diagnostic Features:Diagnostic Features: Recognized by its high Recognized by its high

specific gravity, adamantine specific gravity, adamantine luster and light streakluster and light streak

infusibleinfusible insolubleinsoluble

Occurrence:Occurrence: Widely distributed in small Widely distributed in small

amountsamounts Original constituent of Original constituent of

igneous rocks and igneous rocks and pegmatitespegmatites

More commonly found in More commonly found in hydrothermal veins in or near hydrothermal veins in or near granitic rocks. Tin veins granitic rocks. Tin veins usually have minerals that usually have minerals that contain fluorine or boron contain fluorine or boron such as tourmaline, topazsuch as tourmaline, topaz

CASSITERITE (SnOCASSITERITE (SnO22) )

Crystallography:Crystallography: Tetragonal crystal systemTetragonal crystal system Prismatic but usually massive Prismatic but usually massive

and granularand granular Cleavage: imperfectCleavage: imperfect Hardness: 6 to 7Hardness: 6 to 7 Specific Gravity: 6.8 to 7.1 Specific Gravity: 6.8 to 7.1

(unusually high for a non metallic (unusually high for a non metallic mineral)mineral)

Luster: adamantine to submetallicLuster: adamantine to submetallic Color: usually brown or black, Color: usually brown or black,

rarely yellow or whiterarely yellow or white Streak: whiteStreak: white Composition and Structure:Composition and Structure:

Sn (78.6%), O (21.4%)Sn (78.6%), O (21.4%) Small amount of Fe Small amount of Fe

OXIDESOXIDES CASSITERITE (SnOCASSITERITE (SnO22) )

Fluorite and apatite. The Fluorite and apatite. The minerals of the wall rock are minerals of the wall rock are commonly much alteredcommonly much altered

Commonly found as rolled Commonly found as rolled pebbles in placer depositspebbles in placer deposits

Uses: principal ore of tin used in Uses: principal ore of tin used in the manufacture of tin plates and the manufacture of tin plates and tern plates (coating of tin and tern plates (coating of tin and lead instead of pure tinlead instead of pure tin) for food containers, lead ) for food containers, lead solders, babbitt metal with solders, babbitt metal with antimony and copper and in antimony and copper and in bronze and bell-metal with bronze and bell-metal with coppercopper

OXIDESOXIDES

Diagnostic Features:Diagnostic Features: Characterized by its pitchy Characterized by its pitchy

luster, high specific gravity, luster, high specific gravity, color and streak, detected by color and streak, detected by Geiger-Muller countersGeiger-Muller counters

Occurrence:Occurrence: Primary constituent of Primary constituent of

granitic rocks and pegmatitesgranitic rocks and pegmatites Also found in high Also found in high

temperature hydrothermal temperature hydrothermal veins associated with veins associated with cassiterite, chalcopyrite, cassiterite, chalcopyrite, pyrite and arsenopyritepyrite and arsenopyrite

Uses: chief ore of uranium for Uses: chief ore of uranium for nuclear energynuclear energy

URANINITE (UOURANINITE (UO22) )

Crystallography:Crystallography: Isometric crystal systemIsometric crystal system Crystals are rare, commonly Crystals are rare, commonly

massivemassive Hardness: 5.5Hardness: 5.5 Specific Gravity: 7.5 to 9.7Specific Gravity: 7.5 to 9.7 Luster: submetallic to pitchlike, Luster: submetallic to pitchlike,

dulldull Color: black Color: black Streak: brownish blackStreak: brownish black Composition and Structure:Composition and Structure:

Always partially oxidized and Always partially oxidized and composition lies between UOcomposition lies between UO22

and Uand U33OO88

OXIDESOXIDES URANINITE (UOURANINITE (UO22) )

OXIDESOXIDES

Diagnostic Features:Diagnostic Features: Recognized by its hardness, Recognized by its hardness,

octahedral crystal and octahedral crystal and vitreous luster. Distinguished vitreous luster. Distinguished from magnetite by its from magnetite by its nonmagnetic character and nonmagnetic character and white streak.white streak.

InfusibleInfusible Occurrence:Occurrence:

High temperature mineral High temperature mineral occurring in contact occurring in contact metamorphosed limestones metamorphosed limestones and metamorphic and metamorphic argillaceous rocksargillaceous rocks

Also as accessory mineral in Also as accessory mineral in many dark igneous rocksmany dark igneous rocks

Also found as rolled pebblesAlso found as rolled pebbles

SPINEL (MgAlSPINEL (MgAl22OO44) )

Crystallography:Crystallography: Isometric crystal systemIsometric crystal system Usually in octahedral crystalsUsually in octahedral crystals Also as massive, irregular grainsAlso as massive, irregular grains

Hardness: 8Hardness: 8 Specific Gravity: 3.55Specific Gravity: 3.55 Luster: vitreousLuster: vitreous Color: various (white, red, Color: various (white, red,

lavender, bule, green, brown, lavender, bule, green, brown, black) black)

Streak: whiteStreak: white Composition and Structure:Composition and Structure:

MgO (28.2%), AlMgO (28.2%), Al22OO33 (71.8%) (71.8%)

OXIDESOXIDES SPINEL (MgAlSPINEL (MgAl22OO44) )

in stream beds, where it has in stream beds, where it has been preserved because of its been preserved because of its resistant physical and resistant physical and chemical propertieschemical properties

Uses: gemstoneUses: gemstone

OXIDESOXIDES

Occurrence:Occurrence: Rare mineralRare mineral Occurs in granitic pegmatitesOccurs in granitic pegmatites Also as a contact Also as a contact

metamorphic mineral in metamorphic mineral in crystalline limestones crystalline limestones

GAHNITE (ZnAlGAHNITE (ZnAl22OO44))

Crystallography:Crystallography: Isometric crystal systemIsometric crystal system Usually in octahedral crystalsUsually in octahedral crystals

Hardness: 7.5 to 8Hardness: 7.5 to 8 Specific Gravity: 4.55Specific Gravity: 4.55 Luster: vitreousLuster: vitreous Color: dark green Color: dark green Streak: grayishStreak: grayish Composition and Structure:Composition and Structure:

FeFe2+2+ and Mn and Mn2+2+ may substitute may substitute for Zn and Fefor Zn and Fe3+3+ for Al for Al

Structure same as in spinelStructure same as in spinel Diagnostic Features:Diagnostic Features:

Characterized by its crystal Characterized by its crystal formform

infusibleinfusible


Characterized chiefly by its Characterized chiefly by its strong magnetism and black strong magnetism and black color and its hardness of 6color and its hardness of 6

Distinguished from magnetic Distinguished from magnetic franklinite by its streakfranklinite by its streak

Slowly soluble in HClSlowly soluble in HCl Occurrence:Occurrence:

Common mineral found Common mineral found disseminated as accessory disseminated as accessory mineral in most igneous mineral in most igneous rocksrocks

In certain types of rocks In certain types of rocks magnetite occur as large ore magnetite occur as large ore bodies when they become bodies when they become the chief constituent of the the chief constituent of the rock by magmatic segrega-rock by magmatic segrega-tiontion

Uses: important ore of ironUses: important ore of iron

MAGNETITE (FeMAGNETITE (Fe33OO44)) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals are frequently Crystals are frequently

octahedraloctahedral Usually granular, massiveUsually granular, massive

Hardness: 6Hardness: 6 Specific Gravity: 5.18Specific Gravity: 5.18 Luster: metallicLuster: metallic Color: iron-black Color: iron-black Streak: blackStreak: black Strongly magneticStrongly magnetic May act as a natural magnet May act as a natural magnet

(lodestone)(lodestone) Composition and Structure:Composition and Structure:

Fe (72.4%), O (27.6%)Fe (72.4%), O (27.6%) Some have few percent Mg Some have few percent Mg

and Mnand Mn

OXIDESOXIDES MAGNETITE (FeMAGNETITE (Fe33OO44))

OXIDESOXIDES Occurrence:Occurrence:

Common constituent in Common constituent in peridotites and other ultra-peridotites and other ultra-basic rocks and of serpen-basic rocks and of serpen-tines derived from them. One tines derived from them. One of the first minerals to of the first minerals to separate from a cooling separate from a cooling magma, large chromite magma, large chromite deposits are thought to have deposits are thought to have been derived by such been derived by such magmatic differentiationmagmatic differentiation

Uses: chief ore of chromiumUses: chief ore of chromium 3 groups based on chrome 3 groups based on chrome

content and Cr/Fe ratios: content and Cr/Fe ratios: refractory (bricks to line refractory (bricks to line metallurgical furnaces), metallurgical furnaces), metallurgical (ferroalloy to metallurgical (ferroalloy to give steel high hardness, give steel high hardness, great toughness and great toughness and resistance to chemical resistance to chemical attack) and chemical attack) and chemical (pigments)(pigments)

CHROMITE (FeCrCHROMITE (FeCr22OO44)) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals are rare with Crystals are rare with

octahedral habitoctahedral habit Usually massive, granular to Usually massive, granular to

compactcompact Hardness: 5.5 Hardness: 5.5 Specific Gravity: 4.6 Specific Gravity: 4.6 Luster: metallic to submetallic, Luster: metallic to submetallic,

frequently pitchyfrequently pitchy Color: iron-blackColor: iron-black Streak: dark brownStreak: dark brown Composition and Structure:Composition and Structure:

FeO (32%), CrFeO (32%), Cr22OO33 (68%) (68%) Some Mg is always presentSome Mg is always present

Diagnostic Features:Diagnostic Features: Submetallic lusterSubmetallic luster

OXIDESOXIDES CHROMITE (FeCrCHROMITE (FeCr22OO44))

OXIDESOXIDES

Diagnostic Features:Diagnostic Features: Resembles magnetite but is Resembles magnetite but is

only slightly magnetic and only slightly magnetic and has a dark brown streak. has a dark brown streak. Becomes strongly magnetic Becomes strongly magnetic on heating in reducing flameon heating in reducing flame

Occurrence:Occurrence: Confined in the zinc deposits Confined in the zinc deposits

at Franklin, New Jersey at Franklin, New Jersey where it occurs enclosed in a where it occurs enclosed in a granular limestonegranular limestone

Uses: ore of zinc and Uses: ore of zinc and manganesemanganese

FRANKLINITE (Zn, Fe, Mn) (Fe, FRANKLINITE (Zn, Fe, Mn) (Fe, Mn)Mn)22OO44

Crystallography:Crystallography: Isometric crystal systemIsometric crystal system Crystals are octahedralCrystals are octahedral Also massive, granular in Also massive, granular in

rounded grainsrounded grains Hardness: 6 Hardness: 6 Specific Gravity: 5.15 Specific Gravity: 5.15 Luster: metallicLuster: metallic Color: iron-blackColor: iron-black Streak: reddish brown to dark Streak: reddish brown to dark

brownbrown Composition and Structure:Composition and Structure:

Dominantly ZnFeDominantly ZnFe22OO44 but but always with some substitution always with some substitution of Feof Fe2+2+ and Mn and Mn2+2+ for Zn and for Zn and MnMn3+3+ for Fe for Fe3+3+

OXIDESOXIDES FRANKLINITE (Zn, Fe, Mn) (Fe, FRANKLINITE (Zn, Fe, Mn) (Fe,

Mn)Mn)22OO44

OXIDESOXIDES

Occurrence:Occurrence: Rare mineralRare mineral Occurs in granitic rocks, Occurs in granitic rocks,

pegmatites and mica schistspegmatites and mica schists Frequently in rivers sands Frequently in rivers sands

and gravels and gravels Uses: gemstoneUses: gemstone

Alexandrite – emerald green Alexandrite – emerald green in daylight but red by in daylight but red by transmitted and artificial lighttransmitted and artificial light

Cymophane (Cat’s eye) – Cymophane (Cat’s eye) – chatoyant variety of chatoyant variety of chrysoberyl when cut as an chrysoberyl when cut as an oval or or round cabochonoval or or round cabochon

CHRYSOBERYL (BeAlCHRYSOBERYL (BeAl22OO33)) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Usually in tabularUsually in tabular

Cleavage: {110}Cleavage: {110} Hardness: 8.5 Hardness: 8.5 Specific Gravity: 3.65 to 3.8 Specific Gravity: 3.65 to 3.8 Luster: vitreousLuster: vitreous Color: various shades of green, Color: various shades of green,

brown, yellowbrown, yellow Composition and Structure:Composition and Structure:

BeO (19.8%), AlBeO (19.8%), Al22OO33 (80.2%) (80.2%) Diagnostic Features:Diagnostic Features:

Characterized by its high Characterized by its high hardness, yellowish to hardness, yellowish to emerald green coloremerald green color

InfusibleInfusible InsolubleInsoluble

OXIDESOXIDES CHRYSOBERYL (BeAlCHRYSOBERYL (BeAl22OO33))

OXIDESOXIDES Occurrence:Occurrence:

Occur in granitic rocks and Occur in granitic rocks and pegmatitespegmatites

Uses: source of tantalum and Uses: source of tantalum and niobium, tantalum is employed in niobium, tantalum is employed in chemical equipment, in surgery chemical equipment, in surgery and skull plates and sutures and skull plates and sutures because of its resistance to acid because of its resistance to acid corrosion, tool steel, electronic corrosion, tool steel, electronic tubes; niobium is used in gas tubes; niobium is used in gas turbines of aircrafts, weldable turbines of aircrafts, weldable high speed steels and stainless high speed steels and stainless steels because of resistance to steels because of resistance to high temperatures. high temperatures.

COLUMBITE-TANTALITE (Fe, COLUMBITE-TANTALITE (Fe, Mn)NbMn)Nb22OO66) -) - (Fe, Mn)Ta(Fe, Mn)Ta22OO66))

Crystallography:Crystallography: Orthorhombic crystal systemOrthorhombic crystal system Usually in tabularUsually in tabular

Cleavage: good {010}Cleavage: good {010} Hardness: 6 Hardness: 6 Specific Gravity: 5.2 to 7.9 varying Specific Gravity: 5.2 to 7.9 varying

with composition with composition Luster: submetallicLuster: submetallic Color: iron-black, frequently Color: iron-black, frequently

iridescentiridescent Streak: dark red to blackStreak: dark red to black Composition and Structure:Composition and Structure:

A complete solid solution exists A complete solid solution exists from columbite to tantalitefrom columbite to tantalite

Diagnostic Features:Diagnostic Features: Recognized by black color and Recognized by black color and

red streak and high specific red streak and high specific gravitygravity

OXIDESOXIDES COLUMBITE-TANTALITE (Fe, COLUMBITE-TANTALITE (Fe,

Mn)NbMn)Nb22OO66) -) - (Fe, Mn)Ta(Fe, Mn)Ta22OO66))

HYDROXIDESHYDROXIDES

Structures are characterized by the presence of the Structures are characterized by the presence of the hydroxyl (OH)ˉ group, or Hhydroxyl (OH)ˉ group, or H22O moleculesO molecules

Presence of the (OH)ˉ groups causes the bond strengths Presence of the (OH)ˉ groups causes the bond strengths in these structures generally to be much weaker than the in these structures generally to be much weaker than the oxidesoxides

HYDROXIDESHYDROXIDES Distinguished from talc by its Distinguished from talc by its

greater hardness and lack of greater hardness and lack of greasy feel and from mica greasy feel and from mica by being inelastic, infusibleby being inelastic, infusible

Occurrence:Occurrence: Found associated with Found associated with

serpentine, dolomite, serpentine, dolomite, magnesite and chromitemagnesite and chromite

As an alteration product of As an alteration product of periclase and magnesium periclase and magnesium silicates, especially silicates, especially serpentineserpentine

Also found in crystalline Also found in crystalline limestonelimestone

Uses: used as a raw material for Uses: used as a raw material for magnesia refractories and is a magnesia refractories and is a minor source of metallic minor source of metallic magnesiummagnesium

BRUCITE Mg(OH)BRUCITE Mg(OH)22 Crystallography:Crystallography:

Hexagonal-R crystal systemHexagonal-R crystal system Crystal usually tabularCrystal usually tabular Commonly foliated, massiveCommonly foliated, massive

Cleavage: perfect {0001}Cleavage: perfect {0001} Tenacity: folia flexible but not Tenacity: folia flexible but not

elastic, sectileelastic, sectile Hardness: 2.5Hardness: 2.5 Specific Gravity: 2.39Specific Gravity: 2.39 Luster: pearly on base, vitreous Luster: pearly on base, vitreous

to waxy elsewhereto waxy elsewhere Color: white, gray, light greenColor: white, gray, light green Composition and Structure:Composition and Structure:

MgO (69.0%) HMgO (69.0%) H22O (31.0%), O (31.0%), FeFe2+2+ and Mn and Mn2+2+ may substitute may substitute for Mgfor Mg

Diagnostic Features:Diagnostic Features: Recognized by its foliated Recognized by its foliated

nature, light color and pearly nature, light color and pearly luster on cleavage faceluster on cleavage face

HYDROXIDESHYDROXIDES BRUCITE Mg(OH)BRUCITE Mg(OH)22

HYDROXIDESHYDROXIDES Black color and prismatic Black color and prismatic

crystals. Hardness and crystals. Hardness and streak distinguish it from streak distinguish it from pyrolusite, infusiblepyrolusite, infusible

Occurrence:Occurrence: Found associated with other Found associated with other

manganese oxides in depo-manganese oxides in depo-sits formed by meteoric sits formed by meteoric waterswaters

Found often in low tempera-Found often in low tempera-ture hydrothermal veins ture hydrothermal veins associated with barite, associated with barite, siderite and calcite. It fre-siderite and calcite. It fre-quently alters to pyrolusitequently alters to pyrolusite

Uses: minor ore of manganeseUses: minor ore of manganese

MANGANITE MnO(OH)MANGANITE MnO(OH) Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystal usually prismaticCrystal usually prismatic Often columnar to coarse Often columnar to coarse

fibrousfibrous Cleavage: perfect {010}, good Cleavage: perfect {010}, good

(001}(001} Hardness: 4Hardness: 4 Specific Gravity: 4.3Specific Gravity: 4.3 Luster: metallicLuster: metallic Color: steel-gray to iron-blackColor: steel-gray to iron-black Streak: dark brownStreak: dark brown Composition and Structure:Composition and Structure:

Mn (62.4%) O (27.3%) HMn (62.4%) O (27.3%) H22O O (10.3%)(10.3%)

Diagnostic Features:Diagnostic Features: Recognized chiefly by itsRecognized chiefly by its

HYDROXIDESHYDROXIDES MANGANITE MnO(OH)MANGANITE MnO(OH)

HYDROXIDESHYDROXIDES Manganese oxides by its Manganese oxides by its

greater hardness and greater hardness and botryoidal form, and from botryoidal form, and from limonite by its black streak, limonite by its black streak, infusibleinfusible

Occurrence:Occurrence: A secondary mineral, usually A secondary mineral, usually

occurs with pyrolusite and its occurs with pyrolusite and its origin and associations are origin and associations are similar to those of that similar to those of that mineralmineral

Uses: an ore of manganeseUses: an ore of manganese

PSILOMELANE PSILOMELANE (Ba(Ba2+2+,Mn,Mn2+2+))33(O,OH)(O,OH)66MnMn4+4+OO1616

Crystallography:Crystallography: Orthorhombic crystal systemOrthorhombic crystal system Massive, botryoidal, stalactiticMassive, botryoidal, stalactitic Appears amorphousAppears amorphous

Hardness: 5 to 6Hardness: 5 to 6 Specific Gravity: 3.7 to 4.7Specific Gravity: 3.7 to 4.7 Luster: submetallicLuster: submetallic Color: blackColor: black Streak: brownish blackStreak: brownish black Composition and Structure:Composition and Structure:

Small amounts of Mg, Ca, Ni, Small amounts of Mg, Ca, Ni, Co, Cu and Si may be presentCo, Cu and Si may be present

Structure is somewhat similar Structure is somewhat similar to rutileto rutile

Diagnostic Features:Diagnostic Features: Distinguished from otherDistinguished from other

HYDROXIDESHYDROXIDES PSILOMELANE PSILOMELANE

(Ba(Ba2+2+,Mn,Mn2+2+))33(O,OH)(O,OH)66MnMn4+4+OO1616

HYDROXIDESHYDROXIDES cleavage, its bladed habit, and cleavage, its bladed habit, and

its high hardness, infusible, its high hardness, infusible, insolubleinsoluble

Occurrence:Occurrence: Commonly associated with Commonly associated with

corundum in emery rock, in corundum in emery rock, in dolomite and in chlorite dolomite and in chlorite schist. In a fine grained schist. In a fine grained massive form, it is a major massive form, it is a major constituent of much bauxite constituent of much bauxite

Uses: as refractoryUses: as refractory

DIASPORE (DIASPORE (ααAlO.OH)AlO.OH) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Usually in thin crystals, Usually in thin crystals,

tabulartabular Bladed, foliated, massive, Bladed, foliated, massive,

disseminateddisseminated Cleavage: perfect {010}Cleavage: perfect {010} Hardness: 6.5 to 7Hardness: 6.5 to 7 Specific Gravity: 3.35 to 3.45Specific Gravity: 3.35 to 3.45 Luster: vitreous except on Luster: vitreous except on

cleavage face, where it is pearlycleavage face, where it is pearly Color: white, gray, yellowish, Color: white, gray, yellowish,

greenishgreenish Composition and Structure:Composition and Structure:

AlAl22OO33 (85%) H (85%) H22O (15%)O (15%) Diagnostic Features:Diagnostic Features:

Characterized by its good Characterized by its good

HYDROXIDESHYDROXIDES Streak: yellowish brownStreak: yellowish brown Composition and Structure:Composition and Structure:

Fe (62.9%) O (27%) HFe (62.9%) O (27%) H22O O (10.1%) Mn is often present (10.1%) Mn is often present in amounts of up to 5% in amounts of up to 5%

Diagnostic Features:Diagnostic Features: Distinguished from hematite Distinguished from hematite

by its streakby its streak Occurrence:Occurrence:

One of the most common One of the most common minerals and is typically minerals and is typically formed under oxidizing formed under oxidizing conditions as a weathering conditions as a weathering product of iron-bearing product of iron-bearing mineralsminerals

Also forms as a direct Also forms as a direct inorganic or biogenic inorganic or biogenic precipitate from water and is precipitate from water and is widespread as a deposit in widespread as a deposit in bogs and springs bogs and springs

GOETHITE (GOETHITE (ααFeO.FeO.OH)OH) Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Rarely in distinct prismatic, Rarely in distinct prismatic,

vertically striated crystals, in vertically striated crystals, in acicular crystalsacicular crystals

Also massive, reniform, Also massive, reniform, stalactitic in radiating fibrous stalactitic in radiating fibrous aggregatesaggregates

BOG ORE usually loose and BOG ORE usually loose and porousporous

Cleavage: perfect {010}Cleavage: perfect {010} Hardness: 5 to 5.5Hardness: 5 to 5.5 Specific Gravity: 4.37Specific Gravity: 4.37 Luster: adamantine to dull, silky Luster: adamantine to dull, silky

in certain fine, scaly or fibrous in certain fine, scaly or fibrous varietiesvarieties

Color: yellowish brown to dark Color: yellowish brown to dark brownbrown

HYDROXIDESHYDROXIDES GOETHITE (GOETHITE (ααFeO.FeO.OH)OH)

Goethite forms the GOSSAN Goethite forms the GOSSAN or IRON HAT over or IRON HAT over metalliferous veins. Large metalliferous veins. Large quantities of goethite have quantities of goethite have been found as residual been found as residual lateritic mantles resulting from lateritic mantles resulting from the weathering of serpentinethe weathering of serpentine

Uses: an ore of ironUses: an ore of iron

HYDROXIDESHYDROXIDES A rock nameA rock name

Diagnostic Features:Diagnostic Features: Can usually be recognized Can usually be recognized

by its pisolitic character, by its pisolitic character, infusible, insolubleinfusible, insoluble

Occurrence:Occurrence: Bauxite is of supergene Bauxite is of supergene

origin, commonly produced origin, commonly produced under sub-tropical to tropical under sub-tropical to tropical climatic conditions by climatic conditions by prolonged weathering and prolonged weathering and leaching of silica from leaching of silica from aluminum-bearing rocksaluminum-bearing rocks

May also be derived from May also be derived from the weathering of clay-the weathering of clay-bearing limestones bearing limestones originating as a colloidal originating as a colloidal precipitateprecipitate

In the tropics, deposits In the tropics, deposits known as LATERITESknown as LATERITES

BAUXITE (a mixture of diaspore, BAUXITE (a mixture of diaspore, gibbsite and boehmite)gibbsite and boehmite)

Crystallography:Crystallography: mixturemixture Pisolitic, in round Pisolitic, in round

concretionary grains, also concretionary grains, also massive, earthy, claylikemassive, earthy, claylike

Hardness: 1 to 3Hardness: 1 to 3 Specific Gravity: 2 to 2.5Specific Gravity: 2 to 2.5 Luster: dull to earthyLuster: dull to earthy Color: white, gray, yellow, redColor: white, gray, yellow, red Composition and Structure:Composition and Structure:

A mixture of hydrous A mixture of hydrous aluminum oxides in varying aluminum oxides in varying proportions. Some bauxites proportions. Some bauxites closely approach gibbsite, but closely approach gibbsite, but most are a mixture and most are a mixture and usually contain Fe. As a usually contain Fe. As a result, bauxite is not a mineral result, bauxite is not a mineral and should be used only asand should be used only as

HYDROXIDESHYDROXIDES BAUXITE (a mixture of diaspore, BAUXITE (a mixture of diaspore,

gibbsite and boehmite)gibbsite and boehmite) Consisting largely of hydrous Consisting largely of hydrous

aluminum and ferric oxides, aluminum and ferric oxides, are found in residual soilsare found in residual soils

Uses: the ore of aluminum. Uses: the ore of aluminum. Because of its low density and Because of its low density and great strength, aluminum is used great strength, aluminum is used as sheets and tubes. Aluminum as sheets and tubes. Aluminum castings are used in automobiles, castings are used in automobiles, airplanes and railway cars where airplanes and railway cars where light weight is desirable. Used in light weight is desirable. Used in the manufacture of cooking the manufacture of cooking utensils, food containers, utensils, food containers, household appliances and household appliances and furniture, electrical transmission furniture, electrical transmission lines. Aluminum is alloyed with lines. Aluminum is alloyed with copper, magnesium, zinc, nickel, copper, magnesium, zinc, nickel, silicon, silver and tin silicon, silver and tin

HALIDESHALIDES Characterized by the dominance of the electronegative Characterized by the dominance of the electronegative

halogen ions: Clˉ, Brˉ, Fˉ and Iˉ. These ions are large, halogen ions: Clˉ, Brˉ, Fˉ and Iˉ. These ions are large, having a charge of only ˉ1, and are easily polarized. When having a charge of only ˉ1, and are easily polarized. When they combine with relatively large, weakly polarized cations they combine with relatively large, weakly polarized cations of low valence, both cations and anions behave as almost of low valence, both cations and anions behave as almost perfectly spherical bodiesperfectly spherical bodies

Perfect pure ionicPerfect pure ionic Isometric halides all have relatively low hardness and Isometric halides all have relatively low hardness and

moderate to high melting points and are poor conductors of moderate to high melting points and are poor conductors of heat and electricity in the solid stateheat and electricity in the solid state

When halogen ions are combined with smaller and more When halogen ions are combined with smaller and more strongly polarizing cations than those of the alkali metals, strongly polarizing cations than those of the alkali metals, structures of lower symmetry result and the bond has structures of lower symmetry result and the bond has somewhat covalent properties. somewhat covalent properties.

HALIDESHALIDES

Has salty tasteHas salty taste Composition and Structure:Composition and Structure:

Na (39.3%), Cl (60.7%), Na (39.3%), Cl (60.7%), commonly contains commonly contains impurities such as calcium impurities such as calcium and magnesium sulfates and and magnesium sulfates and calcium and magnesium calcium and magnesium chlorideschlorides

Diagnostic Features:Diagnostic Features: Characterized by its cubic Characterized by its cubic

cleavage and tastecleavage and taste Occurrence:Occurrence:

Common mineralCommon mineral Often occur in extensive Often occur in extensive

beds and irregular masses, beds and irregular masses, precipitated by evaporation precipitated by evaporation with gypsum, sylvite, with gypsum, sylvite, anhydrite, calcite, clay andanhydrite, calcite, clay and

HALITE (NaCl) HALITE (NaCl) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Cubic habit, some hopper-Cubic habit, some hopper-

shapedshaped Also in granular crystalline Also in granular crystalline

masses showing cubic masses showing cubic cleavage (Rock salt)cleavage (Rock salt)

Also massive, granular to Also massive, granular to compactcompact

Cleavage: perfect {001}Cleavage: perfect {001} Hardness: 2.5Hardness: 2.5 Specific Gravity: 2.16Specific Gravity: 2.16 Luster: transparent to translucentLuster: transparent to translucent Color: colorless or white, or when Color: colorless or white, or when

impure may have shades of impure may have shades of yellow, red, blue, purpleyellow, red, blue, purple

HALIDESHALIDES

Use: chemical industry as Use: chemical industry as source of sodium and chlorine source of sodium and chlorine for the manufacture of for the manufacture of hydrochloric acid and sodium hydrochloric acid and sodium compoundscompounds

HALITE (NaCl) HALITE (NaCl) sand. Halite is dissolved in sand. Halite is dissolved in

the waters of salt springs, salt the waters of salt springs, salt lakes and the ocean. It is a lakes and the ocean. It is a major salt in playa deposits. major salt in playa deposits. The deposits of salt have The deposits of salt have been formed by the gradual been formed by the gradual evaporation and ultimate evaporation and ultimate drying up of enclosed bodies drying up of enclosed bodies of salt water and gradually of salt water and gradually buried beneath the rock strata buried beneath the rock strata formed on them.formed on them.

Also occur as salt domes Also occur as salt domes (nearly vertical pipelike (nearly vertical pipelike masses of salt) that appear to masses of salt) that appear to have punched their way have punched their way upward to the surface from an upward to the surface from an underlying salt bedunderlying salt bed

HALIDESHALIDES

Composition and Structure:Composition and Structure: K (52.4%), Cl (47.6%)K (52.4%), Cl (47.6%) May contain admixed NaClMay contain admixed NaCl Possess the same structure Possess the same structure

as haliteas halite Diagnostic Features:Diagnostic Features:

Readily soluble in waterReadily soluble in water Occurrence:Occurrence:

Has the same origin and Has the same origin and mode of occurrence as mode of occurrence as halite but is much rarerhalite but is much rarer

Uses: chief source of potassium Uses: chief source of potassium compounds for the manufacture compounds for the manufacture of fertilizersof fertilizers

SYLVITE (KCl) SYLVITE (KCl) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Cubic and octahedral habitCubic and octahedral habit Usually in granular crystalline Usually in granular crystalline

masses showing cubic masses showing cubic cleavage, compactcleavage, compact

Cleavage: perfect {001}Cleavage: perfect {001} Hardness: 2Hardness: 2 Specific Gravity: 1.99Specific Gravity: 1.99 Transparent when pureTransparent when pure Color: colorless or white, also Color: colorless or white, also

shades of yellow, red, blue from shades of yellow, red, blue from impuritiesimpurities

Readily soluble in waterReadily soluble in water Salty taste but more bitter than Salty taste but more bitter than

halitehalite

HALIDESHALIDES SYLVITE (KCl) SYLVITE (KCl)

HALIDESHALIDES

Diagnostic Features:Diagnostic Features: Distinguished chiefly by Distinguished chiefly by

wax-like appearance and its wax-like appearance and its sectilitysectility

Occurrence:Occurrence: Supergene ore of silver in Supergene ore of silver in

the upper enriched zone of the upper enriched zone of silver deposits. Found silver deposits. Found associated with native associated with native siilver, cerussite and siilver, cerussite and secondary mineralssecondary minerals

Uses: ore of silverUses: ore of silver

CERARGYRITE (AgCl) CERARGYRITE (AgCl) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Cubic habit in rare crystalsCubic habit in rare crystals Usually massive, resembling Usually massive, resembling

wax, often in plates and wax, often in plates and crustscrusts

Tenacity: sectile, can be cut with Tenacity: sectile, can be cut with a knifea knife

Hardness: 2 to 3Hardness: 2 to 3 Specific Gravity: 5.5.+/-Specific Gravity: 5.5.+/- Transparent to translucentTransparent to translucent Color: pearl gray to colorlessColor: pearl gray to colorless Readily darkens to violet-brown Readily darkens to violet-brown

on exposure to lighton exposure to light Composition and Structure:Composition and Structure:

Ag (75.3%), Cl (24.7%)Ag (75.3%), Cl (24.7%)

HALIDESHALIDES CERARGYRITE (AgCl) CERARGYRITE (AgCl)

HALIDESHALIDES

Diagnostic Features:Diagnostic Features: Distinguished by its white Distinguished by its white

color and peculiar lustercolor and peculiar luster Occurrence:Occurrence:

Occurs with granite asso-Occurs with granite asso-ciated siderite, galena and ciated siderite, galena and chalcopyritechalcopyrite

Uses: manufacture of sodium Uses: manufacture of sodium salts, manufacture of certain salts, manufacture of certain kinds of glass and porcelain, as kinds of glass and porcelain, as flux for cleansing metal surfacesflux for cleansing metal surfaces

CRYOLITE (NaCRYOLITE (Na33AlFAlF66) )

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Crystals are rareCrystals are rare Usually massiveUsually massive

Tenacity: sectile, can be cut with Tenacity: sectile, can be cut with a knifea knife

Hardness: 2.5Hardness: 2.5 Specific Gravity: 2.95 to 3.0Specific Gravity: 2.95 to 3.0 Luster: vitreous to greasyLuster: vitreous to greasy Color: colorless to snow whiteColor: colorless to snow white Transparent to translucentTransparent to translucent Composition and Structure:Composition and Structure:

Na (32.8%), Al (12.8%), F Na (32.8%), Al (12.8%), F (54.4%)(54.4%)

HALIDESHALIDES

Diagnostic Features:Diagnostic Features: Distinguished by its cubic Distinguished by its cubic

crystals, vitreous luster and crystals, vitreous luster and scratchability with a knife scratchability with a knife

Occurrence:Occurrence: Common and widely Common and widely

distributed mineral. Usually distributed mineral. Usually found in hydrothermal veins found in hydrothermal veins where it is either the chief where it is either the chief mineral or as gangue mineral or as gangue mineral with metallic ores.mineral with metallic ores.

Minor accessory mineral in Minor accessory mineral in various igneous rocks and various igneous rocks and pegmatitespegmatites

Uses: flux in making steel, Uses: flux in making steel, manufacture of opalescent manufacture of opalescent glass, enameling of cooking glass, enameling of cooking utensils, preparation of HFutensils, preparation of HF

FLUORITE (CaFFLUORITE (CaF22) ) Crystallography:Crystallography:

Isometric crystal systemIsometric crystal system Crystals usually in cubesCrystals usually in cubes Also massive, granular, Also massive, granular,

columnarcolumnar Cleavage: perfect {111}Cleavage: perfect {111} Hardness: 4Hardness: 4 Specific Gravity: 3.18Specific Gravity: 3.18 Luster: vitreousLuster: vitreous Color: varies widely but Color: varies widely but

commonly light green, yellow, commonly light green, yellow, bluish-green or purple, also bluish-green or purple, also colorless to whitecolorless to white

FluorescentFluorescent Composition and Structure:Composition and Structure:

Ca (51.3%), F (48.7%)Ca (51.3%), F (48.7%)

HALIDESHALIDES FLUORITE (CaFFLUORITE (CaF22) )

HALIDESHALIDES

Cl (16.6%), HCl (16.6%), H22O (12.65%)O (12.65%)

Diagnostic Features:Diagnostic Features: Characterized by green Characterized by green

color and granular crystalline color and granular crystalline aggregates. Distinguished aggregates. Distinguished from malachite by its lack of from malachite by its lack of effervescence in acids effervescence in acids

Occurrence:Occurrence: Rare mineralRare mineral Found in arid regions as Found in arid regions as

supergene mineral in supergene mineral in oxidized zone of copper oxidized zone of copper depositsdeposits

ATACAMITE CuATACAMITE Cu22Cl(OH)Cl(OH)33

Crystallography:Crystallography: Orthorhombic crystal systemOrthorhombic crystal system Crystals commonly slender, Crystals commonly slender,

prismaticprismatic Also tabularAlso tabular Usually in confused crystalline Usually in confused crystalline

aggregates, fibrous, granularaggregates, fibrous, granular Cleavage: perfect {010}Cleavage: perfect {010} Hardness: 3 to 3.5Hardness: 3 to 3.5 Specific Gravity: 3.75 to 3.77Specific Gravity: 3.75 to 3.77 Luster: adamantine to vitreousLuster: adamantine to vitreous Color: various shades of green Color: various shades of green Transparent to translucentTransparent to translucent Composition and Structure:Composition and Structure:

Cu (14.88%), CuO (55.87%)Cu (14.88%), CuO (55.87%)

HALIDESHALIDES ATACAMITE CuATACAMITE Cu22Cl(OH)Cl(OH)33

PHOSPHATES, ARSENATES AND PHOSPHATES, ARSENATES AND VANADATESVANADATES Phosphates contain phosphate anionic group (POPhosphates contain phosphate anionic group (PO44))-3-3 as as

fundamental building unitfundamental building unit Similar tetrahedral units, (AsOSimilar tetrahedral units, (AsO44))-3-3 and (VO and (VO44))-3-3 occur in occur in

arsenates and vanadates. Parsenates and vanadates. P5+5+, As, As5+5+ and V and V5+5+ may substitute may substitute for each other in the anionic groupfor each other in the anionic group

This mineral class, composed mostly of phosphates, is This mineral class, composed mostly of phosphates, is very large but most of its members are so rare. Only very large but most of its members are so rare. Only apatite is considered commonapatite is considered common

PHOSPHATES, ARSENATES AND PHOSPHATES, ARSENATES AND VANADATESVANADATES TRIPHYLITE Li(Fe,Mn)POTRIPHYLITE Li(Fe,Mn)PO4 4 ––

LITHIOPHYLITE Li(Mn,Fe)POLITHIOPHYLITE Li(Mn,Fe)PO44 Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Crystals are rareCrystals are rare Commonly on cleavable Commonly on cleavable

masses masses Cleavage: nearly perfect {001}Cleavage: nearly perfect {001} Hardness: 4.5 to 5 Hardness: 4.5 to 5 Specific Gravity: 3.42 to 3.56Specific Gravity: 3.42 to 3.56 Luster: vitreous to resinousLuster: vitreous to resinous Color: bluish gray in triphylite to Color: bluish gray in triphylite to

salmon-pink or clove-brown in salmon-pink or clove-brown in lithiophylitelithiophylite

Chemical composition:Chemical composition: A complete FeA complete Fe2+2+ - Mn - Mn2+2+ series series

exists between two end exists between two end membersmembers

Diagnostic Features:Diagnostic Features: Fusible at 2.5Fusible at 2.5

Occurrence:Occurrence: Pegmatite minerals Pegmatite minerals

associated with other associated with other phosphatesphosphates

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES MONAZITE (Ce,La,Y,Th)POMONAZITE (Ce,La,Y,Th)PO44 Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals are rareCrystals are rare Usually in granular masses Usually in granular masses

Cleavage: poor {100}Cleavage: poor {100} Hardness: 5 to 5.5 Hardness: 5 to 5.5 Specific Gravity: 4.6 to 5.4Specific Gravity: 4.6 to 5.4 Luster: resinousLuster: resinous Color: yellowish to reddish brownColor: yellowish to reddish brown Chemical composition:Chemical composition:

A phosphate of rare earth A phosphate of rare earth metalsmetals

Diagnostic Features:Diagnostic Features: Infusible, insoluble in HClInfusible, insoluble in HCl

Occurrence:Occurrence: rare mineral occurring as rare mineral occurring as

accessory in granites, accessory in granites, gneisses, aplites and gneisses, aplites and pegmatites pegmatites

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES APATITE CaAPATITE Ca55(PO(PO44))33(F,Cl,OH)(F,Cl,OH) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystals are long prismaticCrystals are long prismatic Also massive granular Also massive granular

Cleavage: poor {0001}Cleavage: poor {0001} Hardness: 5 Hardness: 5 Specific Gravity: 3.15 to 3.20Specific Gravity: 3.15 to 3.20 Luster: vitreous to subresinousLuster: vitreous to subresinous Color: shades of green or brown, Color: shades of green or brown,

also blue, violet, colorlessalso blue, violet, colorless Chemical composition:Chemical composition:

Fluoroapatite CaFluoroapatite Ca55(PO(PO44))33FF Chloroapatite CaChloroapatite Ca55(PO(PO44))33ClCl Hydroxylapatite CaHydroxylapatite Ca55(PO(PO44))33OHOH

Diagnostic Features:Diagnostic Features: Soluble in acidsSoluble in acids

Occurrence:Occurrence: Widely disseminated as an Widely disseminated as an

accessory constituent in all accessory constituent in all classes of rocks, igneous, classes of rocks, igneous, sedimentary, metamorphicsedimentary, metamorphic

Also found in pegamtites Also found in pegamtites and hydrothermal veins and hydrothermal veins

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES PYROMORPHITE PbPYROMORPHITE Pb55(PO(PO44))33ClCl Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystals are usually prismaticCrystals are usually prismatic Frequently globular, reniform, Frequently globular, reniform,

fibrous and granular fibrous and granular Hardness: 3.5 to 4 Hardness: 3.5 to 4 Specific Gravity: 7.04Specific Gravity: 7.04 Luster: resinous to adamantineLuster: resinous to adamantine Color: usually various shades of Color: usually various shades of

green, brown, yellowgreen, brown, yellow Chemical composition:Chemical composition:

PbO (82.2%) PPbO (82.2%) P22OO55 (15.7%) (15.7%) Cl (2.6%)Cl (2.6%)

Diagnostic Features:Diagnostic Features: Fusible at 2, characterized by Fusible at 2, characterized by

its crystal form, high luster its crystal form, high luster and high specific gravityand high specific gravity

Occurrence:Occurrence: A supergene mineral found A supergene mineral found

in oxidized portions of lead in oxidized portions of lead veinsveins

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES VANADINITE PbVANADINITE Pb55(VO(VO44))33ClCl Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Crystals are usually prismaticCrystals are usually prismatic Also in globular forms Also in globular forms

Hardness: 3 Hardness: 3 Specific Gravity: 6.9Specific Gravity: 6.9 Luster: resinous to adamantineLuster: resinous to adamantine Color: ruby-red, orange-red, Color: ruby-red, orange-red,

brown, yellow brown, yellow Chemical composition:Chemical composition:

PbO (78.7%) VPbO (78.7%) V22OO55 (19.4%) (19.4%) Cl (2.5%)Cl (2.5%)

Diagnostic Features:Diagnostic Features: characterized by its crystal characterized by its crystal

form, high luster and high form, high luster and high specific gravityspecific gravity

Occurrence:Occurrence: A rare secondary mineral A rare secondary mineral

found in the oxidized found in the oxidized portions of lead veinsportions of lead veins

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES ERYTHRITE CoERYTHRITE Co33(AsO(AsO44))22.2H.2H22OO Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals are prismatic and Crystals are prismatic and

vertically striatedvertically striated Usually as crusts in globular Usually as crusts in globular

and reniform shapes and reniform shapes Cleavage: perfect {010}Cleavage: perfect {010} Hardness: 1.5 to 2.5 Hardness: 1.5 to 2.5 Specific Gravity: 3.06Specific Gravity: 3.06 Luster: adamantine to vitreous, Luster: adamantine to vitreous,

pearly on cleavagepearly on cleavage Color: crimson to pink Color: crimson to pink Chemical composition:Chemical composition:

CoO (37.5%) AsCoO (37.5%) As22OO55 (38.4%) (38.4%) HH22O (24.1%)O (24.1%)

Diagnostic Features:Diagnostic Features: characterized by its pink characterized by its pink

color, soluble in HClcolor, soluble in HCl

Occurrence:Occurrence: A rare secondary mineral, A rare secondary mineral,

alteration product of cobalt alteration product of cobalt arsenidesarsenides

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES AMBLYGONITE (LiAlFPOAMBLYGONITE (LiAlFPO44)) Crystallography:Crystallography:

Triclinic crystal systemTriclinic crystal system Usually in coarse cleavable Usually in coarse cleavable

masses, crystals are rare masses, crystals are rare Cleavage: perfect {100}Cleavage: perfect {100} Hardness: 6 Hardness: 6 Specific Gravity: 3.0 to 3.1Specific Gravity: 3.0 to 3.1 Luster: vitreous, pearly on Luster: vitreous, pearly on

cleavagecleavage Color: white to pale green or Color: white to pale green or

blue, rarely yellow blue, rarely yellow Chemical composition:Chemical composition:

LiLi22O (10.1%) AlO (10.1%) Al22OO33 (34.4%) F (34.4%) F (12.9%) P(12.9%) P22OO55 (47.9%) (47.9%)

Diagnostic Features:Diagnostic Features: Fusible at 2, insolubleFusible at 2, insoluble

Occurrence:Occurrence: A rare mineral found in A rare mineral found in

granite pegmatitesgranite pegmatites

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES LAZULITE (Mg,Fe)AlLAZULITE (Mg,Fe)Al22(PO(PO44))22(OH)(OH)22 SCORZALITE SCORZALITE

(Fe,Mg)Al(Fe,Mg)Al22(PO(PO44))22(OH)(OH)22 Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystal rareCrystal rare Usually massive, granular Usually massive, granular

Cleavage: indistinct {110}Cleavage: indistinct {110} Hardness: 5 to 5.5 Hardness: 5 to 5.5 Specific Gravity: 3.0 to 3.1Specific Gravity: 3.0 to 3.1 Luster: vitreousLuster: vitreous Color: azure blue Color: azure blue Chemical composition:Chemical composition:

Probably a complete solid Probably a complete solid solution from lazulite to solution from lazulite to scorzalitescorzalite

Diagnostic Features:Diagnostic Features: Infusible, difficult to distinguish Infusible, difficult to distinguish

from other blue mineralsfrom other blue minerals

Occurrence:Occurrence: rare minerals found in high rare minerals found in high

grade quartz-rich grade quartz-rich metamorphic rocks and in metamorphic rocks and in pegmatitespegmatites

Use: minor gemstoneUse: minor gemstone

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES WAVELLITE AlWAVELLITE Al33(PO(PO44))22(OH)(OH)33.5H.5H22OO Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Single crystals are rareSingle crystals are rare Usually in radiating spherulitic Usually in radiating spherulitic

and globular aggregates and globular aggregates Cleavage: good {110} and {101}Cleavage: good {110} and {101} Hardness: 3.5 to 4 Hardness: 3.5 to 4 Specific Gravity: 2.36Specific Gravity: 2.36 Luster: vitreousLuster: vitreous Color: white, yellow, green, brown Color: white, yellow, green, brown Chemical composition:Chemical composition:

AlAl22OO33 (38.0%) P (38.0%) P22OO55 (35.2%) (35.2%) HH22O (26.8%)O (26.8%)

Diagnostic Features:Diagnostic Features: Infusible, radiating globular Infusible, radiating globular

aggregate formaggregate form

Occurrence:Occurrence: secondary mineral found in secondary mineral found in

small amounts in crevices small amounts in crevices in aluminous, low grade in aluminous, low grade metamorphic rocks metamorphic rocks

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES TURQUOISE TURQUOISE

CuAlCuAl66(PO(PO44))44(OH)(OH)88.4H.4H22OO Crystallography:Crystallography:

Triclinic crystal systemTriclinic crystal system Usually cryptocrystalline, Usually cryptocrystalline,

massive, compact, reniform massive, compact, reniform Cleavage: perfect {001}Cleavage: perfect {001} Hardness: 6 Hardness: 6 Specific Gravity: 2.6 to 2.8Specific Gravity: 2.6 to 2.8 Luster: wax-likeLuster: wax-like Color: blue, bluish green, green Color: blue, bluish green, green Diagnostic Features:Diagnostic Features:

Easily recognized by its color, Easily recognized by its color, harder than chrysocolla, harder than chrysocolla, infusibleinfusible

Occurrence:Occurrence: secondary mineral found in secondary mineral found in

small veins in volcanic rocks in small veins in volcanic rocks in arid regionsarid regions

Use: gemstoneUse: gemstone

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES AUTUNITE AUTUNITE

Ca(UOCa(UO22))22(PO(PO44))22(OH)(OH)88.10-12H.10-12H22OO Crystallography:Crystallography:

Tetragonal crystal systemTetragonal crystal system Crystal tabularCrystal tabular Also in foliated and scaly Also in foliated and scaly

aggregates aggregates Cleavage: perfect {001}Cleavage: perfect {001} Hardness: 2 to 2.5 Hardness: 2 to 2.5 Specific Gravity: 3.1 to 3.2Specific Gravity: 3.1 to 3.2 Luster: vitreous, pearly on Luster: vitreous, pearly on

cleavagecleavage Color: lemon yellow to pale green Color: lemon yellow to pale green Diagnostic Features:Diagnostic Features:

Characterized by yellow green Characterized by yellow green tetragonal plates, fusible at 2 tetragonal plates, fusible at 2 to 3 to 3

Occurrence:Occurrence: secondary mineral found secondary mineral found

chiefly in the zone of oxidationchiefly in the zone of oxidation

Of uraniniteOf uraninite Use: ore of uraniumUse: ore of uranium

PHOSPHATES, ARSENATES PHOSPHATES, ARSENATES AND VANADATESAND VANADATES CARNOTITE CARNOTITE

KK22(UO(UO22))22(VO(VO44))22(OH)(OH)88.3H.3H22OO Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Usually found as powder or as Usually found as powder or as

loosely coherent aggregates loosely coherent aggregates Cleavage: perfect {001}Cleavage: perfect {001} Hardness: unknown but soft Hardness: unknown but soft Specific Gravity: 4.7 to 5Specific Gravity: 4.7 to 5 Luster: dull or earthyLuster: dull or earthy Color: bright yellow to greenish Color: bright yellow to greenish

yellow yellow Diagnostic Features:Diagnostic Features:

Characterized by its yellow Characterized by its yellow color and pulverant nature, color and pulverant nature, infusible, soluble in infusible, soluble in

Occurrence:Occurrence: secondary mineral formed by secondary mineral formed by

action of water in uraniumaction of water in uranium

Use: ore of uranium and Use: ore of uranium and vanadiumvanadium

CARBONATESCARBONATES• The anionic (CO3)-2 complexes of carbonates are

strongly bonded units and do not share oxygen with each other. The triangular carbonate groups are the basic building units of all carbonate minerals and are largely responsible for the properties peculiar to the group.

• The carbonate ion is a polyatomic anion with the empirical formula CO3

2− and a molecular mass of 60.01 daltons; it consists of one central carbon atom surrounded by three identical oxygen atoms in a trigonal planar arrangement, and has D3h molecular symmetry

• In the presence of hydrogen ion, the carbonate group becomes unstable and breaks down to yield CO2 and water, according to 2H+ + CO3 → H2O + CO2. This reaction is the cause of the familiar “fizz” test with acid which is widely used in the identification of carbonates.

Ball-and-stick model of the

carbonate ion, CO32−

CARBONATESCARBONATES

Calcite GroupCalcite Group

CalciteCalcite CaCOCaCO33

MagnesiteMagnesite MgCOMgCO3 3

SideriteSiderite FeCoFeCo33

RhodocrositeRhodocrosite MnCOMnCO33

SmithsoniteSmithsonite ZnCOZnCO33

Dolomite GroupDolomite Group

DolomiteDolomite CaMg(COCaMg(CO33))22

AnkeriteAnkerite CaFe(COCaFe(CO33))22

Aragonite GroupAragonite Group

AragoniteAragonite CaCOCaCO33

Witherite Witherite BaCOBaCO33

StrontianiteStrontianite SrCOSrCO33

CerussiteCerussite PbCOPbCO33

Monoclinic Carbonates with (OH)Monoclinic Carbonates with (OH)

MalachiteMalachite CuCOCuCO33(OH)(OH)22

AzuriteAzurite Cu(COCu(CO33))22(OH)(OH)22


• CALCITE (CaCOCALCITE (CaCO33))

• Crystallography:Crystallography:

• HexagonalHexagonal

• Crystals are extremely varied in Crystals are extremely varied in habit and often highly complex. habit and often highly complex. Three important habits:Three important habits:

a.a. prismatic, in long or short prisms, prismatic, in long or short prisms, in which the prism faces are in which the prism faces are prominentprominent

b.b. rhombohedral, in which rhombohedral, in which rhombohedral forms predominaterhombohedral forms predominate

c.c. scalenohedral, in which scalenohedral, in which scalenohedrons predominate, scalenohedrons predominate, often with prism faces and often with prism faces and rhombohedral truncationsrhombohedral truncations

• usually in crystals or in coarse to usually in crystals or in coarse to fined grained aggregatesfined grained aggregates

• Cleavage: perfect {1011}Cleavage: perfect {1011}

• Hardness: 3 on cleavage, 2 ½ on Hardness: 3 on cleavage, 2 ½ on basebase

• Luster: vitreous to earthyLuster: vitreous to earthy

• Color: white to colorlessColor: white to colorless

• Composition and Structure:Composition and Structure:

• most calcites tend to be most calcites tend to be relatively close to pure relatively close to pure CaCOCaCO3 3 (CaO 56.0%, CO(CaO 56.0%, CO22

44.0%)44.0%)

• Diagnostic Features:Diagnostic Features:

• InfusibleInfusible

• fragments effervesce readily fragments effervesce readily in cold dilute HCLin cold dilute HCL

• characterized by its hardness characterized by its hardness (3), rhombohedral cleavage, (3), rhombohedral cleavage, light color, vitreous lusterlight color, vitreous luster

• Diagnostic Features:Diagnostic Features:

• distinguished from dolomite distinguished from dolomite because coarse fragments of because coarse fragments of calcite effervesce freely in HCl calcite effervesce freely in HCl and distinguished from arago-and distinguished from arago-nite by lower specific gravity and nite by lower specific gravity and rhombohedral cleavagerhombohedral cleavage

• Occurrence:Occurrence:

• iit is one of the most common and t is one of the most common and widespread minerals occuring in widespread minerals occuring in extensive sedimentary rock mas-extensive sedimentary rock mas-ses in which it is the predomi-ses in which it is the predomi-nant mineralnant mineral

• as cave deposits: water carrying as cave deposits: water carrying calcium carbonate in solution calcium carbonate in solution and evaporating in limestone and evaporating in limestone caves often deposit calcite as caves often deposit calcite as stalactites, stalagmites and stalactites, stalagmites and incrustationsincrustations


• Occurrence:Occurrence:

• it occurs as primary mineral it occurs as primary mineral in some igneous rocks such in some igneous rocks such as carbonatites and nephe-as carbonatites and nephe-line syenitesline syenites

• it is also a common mineral it is also a common mineral in hydrothermal veins in hydrothermal veins associated with sulfide oresassociated with sulfide ores

• Uses:Uses:

• the most important use for the most important use for calcite is for the manufacture calcite is for the manufacture of cements and lime for of cements and lime for mortars. Limestone is the mortars. Limestone is the chief raw material, which is chief raw material, which is when heated to about 900˚C, when heated to about 900˚C, forms forms quicklimequicklime

• IcIceland spar eland spar is valuable for is valuable for various optical instruments; various optical instruments; its best known use was in its best known use was in the form of Nicol prism to the form of Nicol prism to produce polarized light, produce polarized light, prior to the use of Polaroid prior to the use of Polaroid platesplates


• MAGNESITE (MgCOMAGNESITE (MgCO33))

• Crystal System: hexagonalCrystal System: hexagonal

• Crystal Habit: rhombohedralCrystal Habit: rhombohedral

• Cleavage: perfect {1011}Cleavage: perfect {1011}

• Hardness: 3 ½ to 5Hardness: 3 ½ to 5

• Specific Gravity: 3.0 – 3.2Specific Gravity: 3.0 – 3.2

• Luster: vitreousLuster: vitreous

• Color: white, gray, yellow, brownColor: white, gray, yellow, brown

• Composition and Structure: Composition and Structure:

• ( MgO=47.8%, CO( MgO=47.8%, CO22=52.2%)=52.2%)

• small amounts of Ca and Mn may small amounts of Ca and Mn may be present. Magnesite is be present. Magnesite is isostructural with calciteisostructural with calcite


Calcite GroupCalcite GroupMAGNESITEMAGNESITE

Diagnostic Features:Diagnostic Features: infusibleinfusible scarcely acted upon by cold scarcely acted upon by cold

HCl, but dissolve with HCl, but dissolve with effervescence in hot HCleffervescence in hot HCl

cleavable varieties are cleavable varieties are distinguished from dolomite from distinguished from dolomite from higher SG and absence of higher SG and absence of abundant calcium; white abundant calcium; white massive variety resembles chert massive variety resembles chert and is distinguished from it by and is distinguished from it by inferior hardnessinferior hardness

Occurrence:Occurrence: commonly occurs in veins and commonly occurs in veins and

irregular masses derived from irregular masses derived from the alteration of Mg-rich the alteration of Mg-rich metamorphic and igneous rocksmetamorphic and igneous rocks

beds of crystalline cleavable beds of crystalline cleavable magnesite are (1) of magnesite are (1) of metamorphic origin associated metamorphic origin associated with talc schists, chlorite with talc schists, chlorite schists and mica schists, and schists and mica schists, and (2) of sedimentary origin, (2) of sedimentary origin, formed as a primary precipitate formed as a primary precipitate or as a replacement of or as a replacement of limestones by Mg containing limestones by Mg containing solutionssolutions

Uses:Uses: dead burned magnesite is dead burned magnesite is

used in manufacturing bricks used in manufacturing bricks for furnace liningsfor furnace linings

it is the source of magnesia for it is the source of magnesia for industrial chemicalsindustrial chemicals

it has also been used as an ore it has also been used as an ore of metallic Mgof metallic Mg


SIDERITE- FeCOSIDERITE- FeCO33

Crystal System: hexagonalCrystal System: hexagonal-Crystals usually unit -Crystals usually unit

rhombohedrons, frequently with rhombohedrons, frequently with curved facescurved faces

Cleavage: perfect {1011}Cleavage: perfect {1011}Fracture: conchoidal to evenFracture: conchoidal to evenHardness: 3 ½ - 4Hardness: 3 ½ - 4Specific Gravity: 3.96 for pure FeCoSpecific Gravity: 3.96 for pure FeCo33

Color: light to dark brownColor: light to dark brownStreak: whiteStreak: whiteComposition and Structure:Composition and Structure: For pure FeCOFor pure FeCO3 3 (FeO 62.1%, (FeO 62.1%,

COCO2 2 37.9%)37.9%) Siderite is isostructural with Siderite is isostructural with

calcitecalcite

Calcite GroupCalcite GroupSIDERITESIDERITE

Diagnostic Features:Diagnostic Features: distinguished from other distinguished from other

carbonates by its color and carbonates by its color and high specific gravity, and from high specific gravity, and from sphalerite by its rhombohedral sphalerite by its rhombohedral cleavagecleavage

difficulty fusible (4 ½ to 5)difficulty fusible (4 ½ to 5) becomes strongly magnetic becomes strongly magnetic

on heatingon heating soluble in hot water w/ soluble in hot water w/

effervescenceeffervescence

Alteration:Alteration: pseudomorphs of limonite pseudomorphs of limonite

after siderite is commonafter siderite is common

Occurrence:Occurrence: frequently found as clay frequently found as clay

ironstone, impure by admixture ironstone, impure by admixture with clay materialswith clay materials

as black band ore it is found, as black band ore it is found, contaminated by carbonaceous contaminated by carbonaceous material, in extensive stratified material, in extensive stratified formations lying in shales and formations lying in shales and commonly associated with coal commonly associated with coal measuresmeasures

it is also a common constituent of it is also a common constituent of banded Precambrian iron banded Precambrian iron deposits, as in the Lake superior deposits, as in the Lake superior regionregion

Use:Use: an ore of ironan ore of iron


RHODOCROSITE- MnCORHODOCROSITE- MnCO33

Crystal System: hexagonalCrystal System: hexagonal

-only rarely in crystals of the -only rarely in crystals of the unit rhombohedronunit rhombohedron

-usually cleavable, massive; -usually cleavable, massive; granular to compactgranular to compact

Cleavage: perfect {1011}Cleavage: perfect {1011}

Fracture: uneven, conchoidalFracture: uneven, conchoidal

Hardness: 3.5 - 4Hardness: 3.5 - 4

Color: red to pink, brown to Color: red to pink, brown to yellowyellow

Streak: whiteStreak: white

Luster: vtreousLuster: vtreous

Specific Gravity: 3.5 – 3.7Specific Gravity: 3.5 – 3.7

Calcite GroupCalcite GroupRHODOCHROSITERHODOCHROSITE

Composition and Structure:Composition and Structure: (MnO 61.7%; CO(MnO 61.7%; CO22 38.3%) 38.3%) Rhodochrosite forms a complete Rhodochrosite forms a complete

solid solution series with iron solid solution series with iron carbonate (siderite)carbonate (siderite)

Calcium frequently substitutes for Calcium frequently substitutes for manganese in the structure, manganese in the structure, leading to lighter shades of red leading to lighter shades of red and pink, depending on the and pink, depending on the degree of substitution degree of substitution

Diagnostic features:Diagnostic features: characterized by its pink color characterized by its pink color

and rhombohedral cleavageand rhombohedral cleavage InfusibleInfusible the hardness (4) distinguishes it the hardness (4) distinguishes it

from rhodonite with hardnessfrom rhodonite with hardness of of (6)(6)

soluble in hot HCl with soluble in hot HCl with effervescenceeffervescence

when heated on charcoal it when heated on charcoal it turns black but it is turns black but it is nonmagneticnonmagnetic

Occurrence:Occurrence: Rhodochrosite occurs as a Rhodochrosite occurs as a

hydrothermal vein mineral hydrothermal vein mineral along with other manganese along with other manganese minerals in low temperature minerals in low temperature ore deposits as in the silver ore deposits as in the silver mines of Romania where it mines of Romania where it was first foundwas first found

Use:Use: its main use is as an ore of its main use is as an ore of

manganese. Small amounts manganese. Small amounts used for ornamental used for ornamental purposespurposes


SMITHSONITE- ZnCOSMITHSONITE- ZnCO33

Crystal System: HexagonalCrystal System: Hexagonal

Crystal Habit: Crystal Habit: massive, botryoidal massive, botryoidal to reniform to reniform

Cleavage: perfect on {1011}Cleavage: perfect on {1011}

Fracture: uneven, sub-conchoidalFracture: uneven, sub-conchoidal

Hardness: 4 -4.5Hardness: 4 -4.5


Luster: vitreousLuster: vitreous

Color: usually dirty brown, white, Color: usually dirty brown, white, green, blue or pinkgreen, blue or pink


UV fluorescence: mUV fluorescence: may fluoresce ay fluoresce pale green or pale blue under pale green or pale blue under UV UV

Calcite GroupCalcite GroupSMITHSONITESMITHSONITE

Composition and Structure:Composition and Structure: (ZnO 64.8%; CO(ZnO 64.8%; CO33 35.2%) 35.2%) forms two limited solid forms two limited solid

solution series, with solution series, with substitution of manganese substitution of manganese leading to rhodochrosite leading to rhodochrosite and with iron leading to and with iron leading to siderite siderite

small amounts of Co are small amounts of Co are found in a pink, and a small found in a pink, and a small amounts of Cu in a green-amounts of Cu in a green-blue varietyblue variety

isostructural with calciteisostructural with calciteDiagnostic Features:Diagnostic Features: infusibleinfusible soluble in cold HCl with soluble in cold HCl with

effervescenceeffervescence

when heated before the blowpipe it when heated before the blowpipe it gives bluish green streaks in the gives bluish green streaks in the flameflame

Occurrence:Occurrence: Smithsonite occurs as a secondary Smithsonite occurs as a secondary

mineral in the weathering or mineral in the weathering or oxidation zone of zinc bearing ore oxidation zone of zinc bearing ore deposits. It sometimes occurs as deposits. It sometimes occurs as replacement bodies in carbonate replacement bodies in carbonate rocks and as such may constitute rocks and as such may constitute zinc ore. It commonly occurs in zinc ore. It commonly occurs in association with hemimorphite, association with hemimorphite, willemite, hydrozincite, cerrusite, willemite, hydrozincite, cerrusite, malachite, azurite, aurichalcite and malachite, azurite, aurichalcite and anglesiteanglesite

Calcite GroupCalcite GroupSMITHSONITESMITHSONITE

Use:Use: an ore of zincan ore of zinc Zinc carbonate is used as Zinc carbonate is used as

an astringent and excipient an astringent and excipient in shampoo. It is also used in shampoo. It is also used as a fireproofing filler for as a fireproofing filler for rubber and plastics, as a rubber and plastics, as a feed additive, as a feed additive, as a pigment, in cosmetics and pigment, in cosmetics and lotions, and in the lotions, and in the manufacturing of manufacturing of porcelain, pottery, and porcelain, pottery, and rubber rubber


ARAGONITE- CaCOARAGONITE- CaCO33

Crystal System: orthorhombicCrystal System: orthorhombic 3 habits of crystallization are 3 habits of crystallization are

common:common:a. acicular pyramidala. acicular pyramidalb. tabularb. tabular

c. pseudohexagonal twinsc. pseudohexagonal twinsCleavage: distinct {010}; poor {110}Cleavage: distinct {010}; poor {110}Fracture: subconchoidalFracture: subconchoidalColor: wColor: white, red, yellow, orange, hite, red, yellow, orange,

green , blue and brown green , blue and brown Streak: whiteStreak: whiteLuster: dull or vitreousLuster: dull or vitreousHardness: 3.5 – 4Hardness: 3.5 – 4Specific Gravity: 2.95Specific Gravity: 2.95

Aragonite GroupAragonite GroupARAGONITEARAGONITE

Composition, Structure & Composition, Structure & Synthesis:Synthesis:

most aragonite is relatively most aragonite is relatively pure CaCOpure CaCO33. small into the . small into the aragonite structure by aragonite structure by extensive grinding can be extensive grinding can be transformed transformed

Aragonite is Aragonite is thermodynamically unstable thermodynamically unstable at standard temperature and at standard temperature and pressure, and tends to alter pressure, and tends to alter to calcite on scales of 10to calcite on scales of 1077 to to 101088 years years

Diagnostic Features:Diagnostic Features: infusibleinfusible decrepitates on heatingdecrepitates on heating effervesces on cold HCl effervesces on cold HCl distinguished from calcite by distinguished from calcite by

its higher SG and lack of its higher SG and lack of rhombohedral cleavagerhombohedral cleavage

distinguished from witherite distinguished from witherite and strontianite by being and strontianite by being infusible, of lower SG and in infusible, of lower SG and in lacking a distinctive flame lacking a distinctive flame colorcolor

Alteration:Alteration: CaCoCaCo33 secreted by mollusks secreted by mollusks

as aragonite is usually as aragonite is usually changed to calcite on the changed to calcite on the outer side of the shellouter side of the shell

Aragonite GroupAragonite GroupARAGONITEARAGONITE

Occurrence:Occurrence: Aragonite forms naturally in Aragonite forms naturally in

almost all mollusk shells, and almost all mollusk shells, and as the calcareous endoskeleton as the calcareous endoskeleton of warm- and cold-water corals of warm- and cold-water corals (scleractenia). (scleractenia).

also forms in the ocean and in also forms in the ocean and in caves as inorganic precipitates caves as inorganic precipitates called marine cements and called marine cements and speleothems, respectively speleothems, respectively

it is deposited by hot springs; it is deposited by hot springs; found associated with beds of found associated with beds of gypsum and deposits of iron gypsum and deposits of iron ore where it may occur in forms ore where it may occur in forms resembling coral, and is called resembling coral, and is called flos ferriflos ferri

it is found as fibrous crusts it is found as fibrous crusts on serpentine and in on serpentine and in amygdaloidal cavities in amygdaloidal cavities in basaltbasalt

Name:Name: from Aragon, Spain where from Aragon, Spain where

the pseudohexagonal twins the pseudohexagonal twins were first recognizedwere first recognized


WITHERITE- BaCOWITHERITE- BaCO33

Crystal System: orthorhombicCrystal System: orthorhombic-crystals always twinned on {110} -crystals always twinned on {110}

forming pseudohexagonal forming pseudohexagonal dipyramids by the intergrowth dipyramids by the intergrowth of three individualsof three individuals

Cleavage: {010} distinct; {110} Cleavage: {010} distinct; {110} poorpoor

Fracture: sub-conchoidal Fracture: sub-conchoidal Color: Color: colorless, white, graycolorless, white, grayStreak: whiteStreak: whiteLuster: vitreousLuster: vitreousHardness: 3- 3.5Hardness: 3- 3.5Specific Gravity: 4.3Specific Gravity: 4.3

Aragonite GroupAragonite GroupWITHERITEWITHERITE

Composition and Structure:Composition and Structure: (BaO 77.7%; CO(BaO 77.7%; CO22 22.3%) 22.3%) small amounts of Sr and Ca small amounts of Sr and Ca

may substitute for Bamay substitute for Ba Witherite is isotructural with Witherite is isotructural with

aragonitearagoniteDiagnostic Features:Diagnostic Features: high specific gravityhigh specific gravity fusible at 2 ½ -3, giving a fusible at 2 ½ -3, giving a

yellowish green flameyellowish green flame soluble in cold HCl with soluble in cold HCl with

effervescenceeffervescence all solutions, even the very all solutions, even the very

dilute, give precipitate of dilute, give precipitate of barium sulfate with sulfuric barium sulfate with sulfuric acidacid

it is distinguished from barite by it is distinguished from barite by its effervescence in acid and its effervescence in acid and from strontianite by the flame from strontianite by the flame testtest

Occurrence:Occurrence: Witherite forms in low Witherite forms in low

temperature hydrothermal temperature hydrothermal environments. It is commonly environments. It is commonly associated with flourite, associated with flourite, celestine, galena, barite, calcite celestine, galena, barite, calcite and aragoniteand aragonite

Use:Use: a minor source of Bariuma minor source of BariumName origin:Name origin: named after William Withering named after William Withering

(1741-1799). English physician (1741-1799). English physician and mineralogistand mineralogist


STRONTIANITE- SrCOSTRONTIANITE- SrCO33

Crystal System: orthorhombicCrystal System: orthorhombic

Crystal Habit: acicular; also Crystal Habit: acicular; also columnar, fibrous and granular columnar, fibrous and granular

Cleavage: {110} goodCleavage: {110} good

Color: white, gray, yellow, greenColor: white, gray, yellow, green


Hardness: 3.5- 4Hardness: 3.5- 4

Specific Gravity: 3.7Specific Gravity: 3.7

Aragonite GroupAragonite GroupSTRONTIANITESTRONTIANITE

Composition and Structure:Composition and Structure: (SrO 70.2%, CO2 29.8%) (SrO 70.2%, CO2 29.8%)

for pure SrCOfor pure SrCO33

Strontianite is isostructural Strontianite is isostructural with aragonitewith aragonite

Diagnostic Features:Diagnostic Features: infusible, but on intense infusible, but on intense

ignition swells and throws ignition swells and throws out fine branches and gives out fine branches and gives a crimson flamea crimson flame

characterized by high SG characterized by high SG and effervescence in HCland effervescence in HCl

can be distinguished from can be distinguished from witherite by flame test; from witherite by flame test; from celestite by poorer cleavage celestite by poorer cleavage and effervescence in acidand effervescence in acid

Occurrence:Occurrence: Strontianite is a low- Strontianite is a low-

temperature hydrothermal temperature hydrothermal mineral associated with barite, mineral associated with barite, celestite and calsite in veins in celestite and calsite in veins in limestone or marl and less limestone or marl and less frequently in igneous rocks and frequently in igneous rocks and as a gangue mineral in sulfide as a gangue mineral in sulfide veinsveins

Use:Use: source of strontium. Strontium source of strontium. Strontium

has no great chemical has no great chemical application; used in fireworks, application; used in fireworks, red flares, military rockets, in red flares, military rockets, in the separation of sugar from the separation of sugar from molasses and in various molasses and in various strontium compounds strontium compounds


CERUSSITE- PbCOCERUSSITE- PbCO33

Crystal System: orthorhombicCrystal System: orthorhombic

Crystal Habit: Crystal Habit: massive granular, massive granular, reticulate, tabular to equant reticulate, tabular to equant crystals crystals

Cleavage:Cleavage:Good [110] and [021] Good [110] and [021]

Fracture: Fracture: brittle conchoidal brittle conchoidal

Color: Color: colorless, white, gray, colorless, white, gray,


Luster: adamantine, vitreous, resinousLuster: adamantine, vitreous, resinous

Hardness: 3 – 3.5Hardness: 3 – 3.5


Aragonite GroupAragonite GroupCERUSSITECERUSSITE

Composition and Structure:Composition and Structure: most cerussite is very close in most cerussite is very close in

composition to PbCOcomposition to PbCO33, with , with

PbO = 83.5% and COPbO = 83.5% and CO22 = 16.5% = 16.5% it is isostructural with aragoniteit is isostructural with aragonite

Diagnostic Features:Diagnostic Features: may be readily recognized by may be readily recognized by

its characteristic twinning, in its characteristic twinning, in conjunction with the conjunction with the adamantine lustre and high adamantine lustre and high specific gravity. It dissolves specific gravity. It dissolves with effervescence in dilute with effervescence in dilute nitric acid. A blowpipe test will nitric acid. A blowpipe test will cause it to fuse very readily, cause it to fuse very readily, and gives indications for lead and gives indications for lead

Occurrence:Occurrence: important and widely important and widely

distributed supergene lead distributed supergene lead ore formed by the action of ore formed by the action of carbonated waters on galenacarbonated waters on galena

Uses:Uses: white leadwhite lead is the key is the key

ingredient in (now ingredient in (now discontinued) lead paints. discontinued) lead paints. Ingestion of lead-based paint Ingestion of lead-based paint chips is the most common chips is the most common cause of lead poisoning in cause of lead poisoning in children. Both "white lead" children. Both "white lead" and lead acetate have been and lead acetate have been used in cosmetics throughout used in cosmetics throughout history, though this practice history, though this practice has ceased in Western has ceased in Western countriescountries


DOLOMITE- CaMg(CODOLOMITE- CaMg(CO33))22


Crystal Habit: Crystal Habit: tabular crystals, tabular crystals, often with curved faces, also often with curved faces, also columnar, stalactitic, granular, columnar, stalactitic, granular, massive massive

Cleavage: rhombohedralCleavage: rhombohedral

Fracture: brittle- conchoidalFracture: brittle- conchoidal

Color: Color: white, gray to pink white, gray to pink


Luster: vitreous to pearlyLuster: vitreous to pearly



Dolomite GroupDolomite GroupDOLOMITEDOLOMITE

Composition and Structure:Composition and Structure: a solid solution series exists a solid solution series exists

between dolomite and iron between dolomite and iron rich ankerite. Small amounts rich ankerite. Small amounts of iron in the structure give the of iron in the structure give the crystals a yellow to brown tint. crystals a yellow to brown tint. Manganese substitutes in the Manganese substitutes in the structure also up to about structure also up to about three percent MnO. A high three percent MnO. A high manganese content gives the manganese content gives the crystals a rosy pink color. A crystals a rosy pink color. A series with the manganese series with the manganese rich kutnohorite may exist. rich kutnohorite may exist. Lead and zinc also substitute Lead and zinc also substitute in the structure for in the structure for magnesiummagnesium

Diagnostic Features:Diagnostic Features: it has physical properties it has physical properties

similar to those of the mineral similar to those of the mineral calcite, but does not rapidly calcite, but does not rapidly dissolve or effervesce (fizz) in dissolve or effervesce (fizz) in dilute HCl unless it is dilute HCl unless it is scratched or in powdered scratched or in powdered form form

the massive rock variety is the massive rock variety is distinguished from limestone distinguished from limestone by the less vigorous reaction by the less vigorous reaction with HClwith HCl

Dolomite GroupDolomite GroupDOLOMITEDOLOMITE

Occurrence:Occurrence: found in many parts of the found in many parts of the

world chiefly as extensive world chiefly as extensive sedimentary strata, and the sedimentary strata, and the crystallized equivalent, crystallized equivalent, dolomitic marbledolomitic marble

formed from ordinary formed from ordinary limestone by the limestone by the replacement of some of the replacement of some of the Ca by MgCa by Mg

occurs also as a occurs also as a hydrothermal vein mineral, hydrothermal vein mineral, chiefly in the lead and zinc chiefly in the lead and zinc veins that traverse limestoneveins that traverse limestone

Uses:Uses: used as an ornamental used as an ornamental

stone, a concrete aggregate stone, a concrete aggregate and as a source of and as a source of magnesium oxidemagnesium oxide

where calcite limestone is where calcite limestone is uncommon or too costly, uncommon or too costly, dolomite is sometime used in dolomite is sometime used in its place as a flux (impurity its place as a flux (impurity remover) for the smelting of remover) for the smelting of iron and steel iron and steel

in nutrition, dolomite is sold in nutrition, dolomite is sold sometimes as a dietary sometimes as a dietary supplement*supplement*

**However, laboratory experiments However, laboratory experiments conducted demonstrate that conducted demonstrate that dolomite is practically insoluble in dolomite is practically insoluble in stomach acid and is eliminated from stomach acid and is eliminated from the body before significant the body before significant magnesium or calcium can be magnesium or calcium can be absorbed absorbed


ANKERITE- CaFe(COANKERITE- CaFe(CO33))22


Crystal Habit: Crystal Habit: tabular crystalstabular crystals

Cleavage: perfectCleavage: perfect

Fracture: brittle to conchoidalFracture: brittle to conchoidal

Color: Color: white, grey or reddish to white, grey or reddish to yellowish brown yellowish brown


Luster: vitreous to pearlyLuster: vitreous to pearly


Specific Gravity: 2.9 -3.1Specific Gravity: 2.9 -3.1

Dolomite GroupDolomite GroupANKERITEANKERITE

Occurrence:Occurrence: Ankerite occurs with siderite in Ankerite occurs with siderite in

deposits of iron-ore deposits of iron-ore can result from hydrothermal or can result from hydrothermal or

direct groundwater direct groundwater precipitation. precipitation.

it can also be the result of it can also be the result of metamorphic recrystallization of metamorphic recrystallization of iron-rich sedimentary rocks. It iron-rich sedimentary rocks. It is often found as a gangue is often found as a gangue mineral associated with gold mineral associated with gold and a variety of sulfide minerals and a variety of sulfide minerals in ore depositsin ore deposits

Name:Name: it was first recognized it was first recognized

as a distinct species by as a distinct species by W. von Haidenger in W. von Haidenger in 1825, and named by 1825, and named by him after Matthias him after Matthias Joseph Anker (1771-Joseph Anker (1771-1843) of Styria, an 1843) of Styria, an Austrian mineralogistAustrian mineralogist

Monoclinic carbonates with (OH)Monoclinic carbonates with (OH)

MALACHITE- CuCOMALACHITE- CuCO33(OH)(OH)22

Crystal System: monoclinicCrystal System: monoclinic

Crystal Habit: massive, botryoidal, Crystal Habit: massive, botryoidal, stalicticstalictic

Cleavage: perfect but rarely seenCleavage: perfect but rarely seen

Fracture: conchoidal to splinteryFracture: conchoidal to splintery

Color: bright greenColor: bright green

Streak: light greenStreak: light green

Luster: adamantine to vitreous in Luster: adamantine to vitreous in crystals, dull in earthy typecrystals, dull in earthy type



Monoclinic carbonates with (OH)Monoclinic carbonates with (OH)MALACHITEMALACHITE

Structure and Composition:Structure and Composition: (CuO 71.9%, CO(CuO 71.9%, CO22 19.9%, 19.9%,

HH22O 8.2%; Cu 57.4%)O 8.2%; Cu 57.4%)

Occurrence:Occurrence: Malachite often results from Malachite often results from

weathering of copper ores weathering of copper ores and is often found together and is often found together with with azurite(Cu3(CO3)2(OH)2), azurite(Cu3(CO3)2(OH)2), goethite, and calcitegoethite, and calcite

is more common than is more common than azurite and is typically azurite and is typically associated with copper associated with copper deposits around limestonesdeposits around limestones

Diagnostic Features:Diagnostic Features: fusible at 3, giving a green flamefusible at 3, giving a green flame soluble in HCl with soluble in HCl with

effervescence, yielding a green effervescence, yielding a green solution solution

recognized by its bright green recognized by its bright green colorcolor

Uses:Uses: an ore of copperan ore of copper used for decorative purposes, used for decorative purposes,

such as in the Malachite Room such as in the Malachite Room in the Hermitage, which features in the Hermitage, which features a large malachite vasea large malachite vase

Name:Name: from Greek from Greek molochitismolochitis, “mallow-, “mallow-

green stone” green stone”

Monoclinic carbonates with (OH)Monoclinic carbonates with (OH)

AZURITE- Cu(COAZURITE- Cu(CO33))22(OH)(OH)22

Crystal System: monoclinicCrystal System: monoclinic

Crystal Habit: Crystal Habit: massive, prismatic, massive, prismatic, stalactitic, tabular stalactitic, tabular

Cleavage: perfect on {011}, fair Cleavage: perfect on {011}, fair on {100}on {100}

Fracture: concoidalFracture: concoidal

Color: Color: light blue-azure blue-dark light blue-azure blue-dark blue blue

Streak: light blueStreak: light blue




Monoclinic carbonates with (OH)Monoclinic carbonates with (OH)AZURITEAZURITE

Composition and Structure:Composition and Structure: (CuO 69.2%, CO2 25.6%, (CuO 69.2%, CO2 25.6%,

H2O 5.2%; Cu 55.3%)H2O 5.2%; Cu 55.3%) Azurite is unstable in open Azurite is unstable in open

air with respect to air with respect to malachite, and often is malachite, and often is pseudomorphically pseudomorphically replaced by malachite replaced by malachite

Diagnostic Features:Diagnostic Features: characterized chiefly by its characterized chiefly by its

azure-blue color and azure-blue color and effervescence in HCleffervescence in HCl

Occurrence: Occurrence: it is usually found in it is usually found in

association with the chemically association with the chemically very similar malachite, very similar malachite, producing a striking color producing a striking color combination of deep blue and combination of deep blue and bright green that is strongly bright green that is strongly indicative of the presence of indicative of the presence of copper orescopper ores

Use:Use: while not a major ore of copper while not a major ore of copper

itself, azurite is a good surface itself, azurite is a good surface indicator of the presence of indicator of the presence of weathered copper sulfide ores weathered copper sulfide ores

used occasionally as beads used occasionally as beads and as jewelry, and also as an and as jewelry, and also as an ornamental stone ornamental stone

was used as a blue pigment was used as a blue pigment for centuries for centuries

NITRATES AND NITRATES AND BORATESBORATES

NITRATESNITRATESThe minerals in this group are structurally similar to the The minerals in this group are structurally similar to the carbonates with plane, triangular (NOcarbonates with plane, triangular (NO33))-1 -1 groups, much like the groups, much like the (CO(CO33

)-2)-2 group, the highly charged and highly polarizing N group, the highly charged and highly polarizing N5+ 5+ ion ion binds its three coordinated oxygen's into a close-knit group in binds its three coordinated oxygen's into a close-knit group in which the strength of the oxygen-nitrogen bond is greater than which the strength of the oxygen-nitrogen bond is greater than any other possible bond in the crystal. Because of the greater any other possible bond in the crystal. Because of the greater strength of this N-O bond as compared with the C-O bond, strength of this N-O bond as compared with the C-O bond, nitrates are less readily decomposed by acids than carbonates.nitrates are less readily decomposed by acids than carbonates.

When triangular (NOWhen triangular (NO33) groups combine in one-to-one proportions ) groups combine in one-to-one proportions with monovalent cations whose radii permit 6 coordination, with monovalent cations whose radii permit 6 coordination, structure analogous to those of the calcite group result. Thus, structure analogous to those of the calcite group result. Thus, Soda Niter(NaNOSoda Niter(NaNO33), and calcite are isostructural with the same ), and calcite are isostructural with the same crystallography and cleavage. Because of the lesser charge, crystallography and cleavage. Because of the lesser charge, however, soda niter is softer than calcite and melts at a lower however, soda niter is softer than calcite and melts at a lower temperature and, because of the lower atomic weight of sodium, temperature and, because of the lower atomic weight of sodium, has a lower specific gravity. Niter(KNO3), is similarly a structural has a lower specific gravity. Niter(KNO3), is similarly a structural analogue of aragonite. Soda niter has an orthorhombic analogue of aragonite. Soda niter has an orthorhombic polymorph isostructural with niter.polymorph isostructural with niter.

EXAMPLES OF EXAMPLES OF NATURALLY OCCURING NATURALLY OCCURING

NITRATESNITRATES

SODA NITER OR SODA NITER OR NITRATINENITRATINE

PHYSICAL CHARACTERISTICS:PHYSICAL CHARACTERISTICS: ColorColor is white or gray, sometimes with tints of red-brown or is white or gray, sometimes with tints of red-brown or

yellow. yellow. LusterLuster is vitreous. is vitreous. TransparencyTransparency crystals are translucent to transparent. crystals are translucent to transparent. Crystal System Crystal System is trigonal; bar 3 2/m is trigonal; bar 3 2/m Crystal Habits Crystal Habits include masses and soil deposits in arid include masses and soil deposits in arid

and desert regions. Crystals are rare, but when found are and desert regions. Crystals are rare, but when found are in the form of rhombohedrons similar to in the form of rhombohedrons similar to calcite's crystals. crystals.

CleavageCleavage is perfect in three directions forming is perfect in three directions forming rhombohedrons. rhombohedrons.

FractureFracture is conchoidal. is conchoidal.

HardnessHardness is 1.5 - 2. is 1.5 - 2. Specific Gravity Specific Gravity is approximately 2.2 - 2.3 (below average) is approximately 2.2 - 2.3 (below average) StreakStreak is white. is white. Associated Minerals Associated Minerals gypsum, , halite and other arid region and other arid region

minerals. minerals. Other Characteristics:Other Characteristics: Deliquescent, slightly sectile, very Deliquescent, slightly sectile, very

soluble in water and gives a yellow flame test result. soluble in water and gives a yellow flame test result. Notable OccurrencesNotable Occurrences include the Tarapaca and other include the Tarapaca and other

northern Chile sites; Bolivia; Peru and Humboldt Co., Nevada, northern Chile sites; Bolivia; Peru and Humboldt Co., Nevada, San Bernardino Co., California and New Mexico, USA. San Bernardino Co., California and New Mexico, USA.

Best Field Indicators Best Field Indicators are crystal habit, flame test, solubility, are crystal habit, flame test, solubility, deliquescence, hardness, occurrence and cleavage. deliquescence, hardness, occurrence and cleavage.

Use: Use: In Chile it is quarried, purified, and used as a source of In Chile it is quarried, purified, and used as a source of nitrates. Soda niter now competes with nitrogen “fixed” from nitrates. Soda niter now competes with nitrogen “fixed” from the air. Nitrates are used in explosives and fertilizers.the air. Nitrates are used in explosives and fertilizers.

NITERNITER PHYSICAL CHARACTERISTICS:PHYSICAL CHARACTERISTICS: ColorColor is white or gray, also tinted is white or gray, also tinted

yellow or brown by impurities. yellow or brown by impurities. LusterLuster is vitreous. is vitreous. TransparencyTransparency Crystals are Crystals are

translucent to transparent only in translucent to transparent only in individual crystals. individual crystals.

Crystal System Crystal System is orthorhombic; is orthorhombic; 2/m 2/m 2/m 2/m 2/m 2/m

Crystal Habits Crystal Habits include crusts and include crusts and acicular crystals formed as acicular crystals formed as efflorescence on cave and mine efflorescence on cave and mine walls. Also as a constituent in arid walls. Also as a constituent in arid climate soils. Rarely forms crystals climate soils. Rarely forms crystals of any appreciable size but some of any appreciable size but some clusters of hexagonal shaped clusters of hexagonal shaped twinned crystals are known. crystals are known.

CleavageCleavage is good in two directions (prismatic). is good in two directions (prismatic). FractureFracture is uneven. is uneven. HardnessHardness is 2. is 2. Specific Gravity Specific Gravity is approximately 2.1 (well below is approximately 2.1 (well below

average) average) StreakStreak is white. is white. Other Characteristics:Other Characteristics: Easily soluble in water, gives a Easily soluble in water, gives a

violet flame in a flame test (potassium), is slightly sectile violet flame in a flame test (potassium), is slightly sectile and is nondeliquescent. and is nondeliquescent.

Associated Minerals Associated Minerals calcite, , dolomite and certain and certain minerals in various arid region soils. minerals in various arid region soils.

Notable Occurrences Notable Occurrences include the Persian Gulf states, include the Persian Gulf states, India; Russia; Italy; Spain; northern Chile; New Mexico, India; Russia; Italy; Spain; northern Chile; New Mexico, Kentucky and Tennessee, USA; Egypt and Bolivia. Kentucky and Tennessee, USA; Egypt and Bolivia.

Best Field Indicators Best Field Indicators are crystal habit if visible, are crystal habit if visible, solubility in water, nondeliquescent and violet flame test.solubility in water, nondeliquescent and violet flame test.

Use: Use: Used as a source of nitrogen compounds. Used as a source of nitrogen compounds.

BORATESBORATESWithin the borate group of minerals Within the borate group of minerals BOBO3 3 units are capable of units are capable of polymerization (similar to the polymerization of polymerization (similar to the polymerization of SiOSiO44 tetrahedral tetrahedral groups in the silicates) in the form of chains, sheets, and isolated groups in the silicates) in the form of chains, sheets, and isolated multiple groups. This is possible because the small multiple groups. This is possible because the small BB3+ 3+ ion, which ion, which generally coordinates three oxygen’s in a triangular group. This generally coordinates three oxygen’s in a triangular group. This permits a single oxygen to be shared between two boron ions permits a single oxygen to be shared between two boron ions linking the linking the BOBO33 triangles into expanded structural units (double triangles into expanded structural units (double triangles, triple rings, sheets, and chains). Because the triangular triangles, triple rings, sheets, and chains). Because the triangular coordination of coordination of BOBO33 is close to the upper stability limit of 3 is close to the upper stability limit of 3 coordination, boron is found also in 4 coordination in tetrahedral coordination, boron is found also in 4 coordination in tetrahedral groups. In addition to groups. In addition to BOBO33 and and BOBO44 groups, natural borates may groups, natural borates may contain complex ionic groups such as contain complex ionic groups such as [B[B33OO33(OH)(OH)55]]-2 -2 that consist that consist of one triangle and two tetrahedra. In the structure of of one triangle and two tetrahedra. In the structure of colemanitecolemanite, , CaBCaB33OO44(OH)(OH)44 ·H ·H22OO, complex infinite chains of , complex infinite chains of tetrahedra and triangles occur, and in tetrahedra and triangles occur, and in BoraxBorax, , NaNa22BB44OO55(OH)(OH)44 ·8H·8H22O, O, a complex ion, a complex ion, [B[B44OO55(OH)(OH)44]]-2 -2 consisting of two triangles is consisting of two triangles is found. Borates can be classified on the basis of the structural found. Borates can be classified on the basis of the structural anionic linking (or lack thereof) as insular, chain, sheet, and anionic linking (or lack thereof) as insular, chain, sheet, and framework structures.framework structures.

Although it is possible to prepare a three dimensional Although it is possible to prepare a three dimensional boxwork made up of boxwork made up of BOBO33 triangles only and having the triangles only and having the

composition composition BB22OO33, such a configuration has a very low , such a configuration has a very low

stability and disorders readily, yielding a glass. Because of stability and disorders readily, yielding a glass. Because of the tendency to form somewhat disordered networks of the tendency to form somewhat disordered networks of BOBO33

triangles, boron is regarded as a “network-former” in glass triangles, boron is regarded as a “network-former” in glass manufacture and is used in the preparation of special manufacture and is used in the preparation of special glasses of light weight and high transparency to energetic glasses of light weight and high transparency to energetic radiation.radiation.

Over 100 borate minerals are known but only the four most Over 100 borate minerals are known but only the four most common will be discussed:common will be discussed:

Kernite Kernite NaNa22BB44OO66(OH)(OH)22 ·3H ·3H22OO

BoraxBorax NaNa22BB44OO55(OH)(OH)44 ·8H ·8H22OO

UlexiteUlexite NaCaBNaCaB55OO66(OH)(OH)66 ·5H ·5H22OO

ColemaniteColemanite CaBCaB33OO44(OH)(OH)33 ·3H ·3H22OO

KERNITEKERNITE

PHYSICAL PHYSICAL CHARACTERISTICS:CHARACTERISTICS:

Color Color is white or gray to is white or gray to colorless. colorless.

LusterLuster is vitreous to is vitreous to greasy. greasy.

TransparencyTransparency crystals are crystals are transparent to translucent. transparent to translucent.

Crystal System Crystal System is is monoclinic; 2/m monoclinic; 2/m

Crystal Habits Crystal Habits include include short prismatic crystals, but short prismatic crystals, but is more commonly found in is more commonly found in parallel aggregates parallel aggregates resembling vein minerals. resembling vein minerals.

Cleavage Cleavage is perfect in two directions forming is perfect in two directions forming splintery fragments. splintery fragments.

FractureFracture is splintery due to cleavage. is splintery due to cleavage. Hardness Hardness is 2.5 - 3 (harder than a fingernail) is 2.5 - 3 (harder than a fingernail) Specific Gravity Specific Gravity is approximately 1.9+ (very low is approximately 1.9+ (very low

density) density) StreakStreak is white. is white. Associated Minerals Associated Minerals are are borax, , ulexite, ,

hydroboracite and other and other borate minerals. . Other Characteristics: Other Characteristics: slightly soluable in water. slightly soluable in water. Notable Occurrences Notable Occurrences include several localities in include several localities in

Kern Co., California, USA; Chile, and Turkey. Kern Co., California, USA; Chile, and Turkey. Best Field Indicators Best Field Indicators are crystal habit, associations, are crystal habit, associations,

locality, density, splintery cleavage, and hardness. locality, density, splintery cleavage, and hardness. Use: Use: As a source of borax and boron compoundsAs a source of borax and boron compounds

BORAXBORAX


ColorColor is white to clear. is white to clear. LusterLuster is vitreous. is vitreous. TransparencyTransparency crystals crystals

are transparent to are transparent to translucent. translucent.

Crystal System Crystal System is is monoclinic; 2/m monoclinic; 2/m

Crystal Habits Crystal Habits include include the blocky to prismatic the blocky to prismatic crystals with a nearly crystals with a nearly square cross section. square cross section. Also massive and as Also massive and as crusts. crusts.

Cleavage Cleavage is perfect in one direction. is perfect in one direction. Fracture Fracture is conchoidal. is conchoidal. Hardness Hardness is 2 - 2.5 is 2 - 2.5 Specific Gravity Specific Gravity is approximately 1.7 (very light) is approximately 1.7 (very light) StreakStreak is white. is white. Associated Minerals Associated Minerals are are calcite, , halite, , hanksite, , colemanite, , ulexite and other and other

borates. borates. Other Characteristics: Other Characteristics: a sweet alkaline taste, alters to chalky white tincalconite a sweet alkaline taste, alters to chalky white tincalconite

with dehydration. with dehydration. Notable Occurrences Notable Occurrences include Trona, Boron, Death Valley and other California include Trona, Boron, Death Valley and other California

localities; Andes Mountains; Turkey and Tibet. localities; Andes Mountains; Turkey and Tibet. Best Field Indicators Best Field Indicators are crystal habit, color, associations, locality, density and are crystal habit, color, associations, locality, density and

hardness. hardness. Use: Use: Although boron is obtained from several minerals, it is usually converted to Although boron is obtained from several minerals, it is usually converted to

borax, the principal commercial product. There are many uses of antiseptic and borax, the principal commercial product. There are many uses of antiseptic and preservative; in medicine; as a solvent for metallic oxides in soldering and welding; preservative; in medicine; as a solvent for metallic oxides in soldering and welding; and as a flux in various smelting and laboratory operations. Elemental boron is and as a flux in various smelting and laboratory operations. Elemental boron is used as a deoxidizer and alloy in nonferrous metals; in rectifiers and control tubes; used as a deoxidizer and alloy in nonferrous metals; in rectifiers and control tubes; and a neutron absorber in shields for atomic reactors. Boron is used in rocket fuels and a neutron absorber in shields for atomic reactors. Boron is used in rocket fuels and as an additive in motor fuel. Boron carbide, harder than corundum, is used as and as an additive in motor fuel. Boron carbide, harder than corundum, is used as an abrasivean abrasive

ULEXITEULEXITE


ColorColor is white or gray to is white or gray to colorless. colorless.

LusterLuster is silky. is silky. Transparency Transparency crystals are crystals are

transparent to translucent. transparent to translucent. Crystal System Crystal System is triclinic; is triclinic;

bar 1 bar 1 Crystal Habits Crystal Habits include include

tufts of acicular crystals tufts of acicular crystals called "cotton balls". Also as called "cotton balls". Also as vein-like masses of parallel vein-like masses of parallel fibrous crystals. fibrous crystals.

CleavageCleavage is perfect in one direction. is perfect in one direction. Fracture Fracture is fibrous. is fibrous. Hardness Hardness is 2 (softer than a fingernail) is 2 (softer than a fingernail) Specific Gravity Specific Gravity is approximately 1.97 (very low density) is approximately 1.97 (very low density) StreakStreak is white. is white. Associated Minerals Associated Minerals are are borax, , colemanite, ,

hydroboracite and other borate minerals. and other borate minerals. Other Characteristics: Other Characteristics: similar borate minerals have an similar borate minerals have an

alkaline taste, while ulexite is tasteless. alkaline taste, while ulexite is tasteless. Notable Occurrences Notable Occurrences include several localities in include several localities in

California and Nevada, USA; Tarapaca, Chile and California and Nevada, USA; Tarapaca, Chile and Kazakhstan. Kazakhstan.

Best Field Indicators Best Field Indicators are crystal habit, associations, are crystal habit, associations, locality, density, unique optical property, and locality, density, unique optical property, and hardness. hardness.

Use: Use: A source of boraxA source of borax

COLEMANITECOLEMANITE

PHYSICAL CHARACTERISTICS:PHYSICAL CHARACTERISTICS: ColorColor is white to clear. is white to clear. LusterLuster is vitreous. is vitreous. TransparencyTransparency crystals are crystals are

transparent to translucent. transparent to translucent. Crystal System Crystal System is monoclinic; 2/m is monoclinic; 2/m Crystal Habits Crystal Habits are quite variable, are quite variable,

but include the short prismatic but include the short prismatic crystals always with complicated crystals always with complicated facets. Equant crystals that appear facets. Equant crystals that appear stubby and bead-like are also stubby and bead-like are also common. The crystals are common. The crystals are sometimes flattened and can appear sometimes flattened and can appear bladed. The terminations are either bladed. The terminations are either blunted or steeply pyramidal. Also blunted or steeply pyramidal. Also massive, lamellar and granular massive, lamellar and granular habits are found. habits are found.

CleavageCleavage is perfect in one direction and distinct in another. is perfect in one direction and distinct in another. FractureFracture is uneven. is uneven. HardnessHardness is 4.5 is 4.5 Specific Gravity Specific Gravity is approximately 2.4 (somewhat lower than is approximately 2.4 (somewhat lower than

average) average) StreakStreak is white. is white. Associated Minerals Associated Minerals are are calcite, , celestite, , borax, , ulexite, ,

kernite, , hydroboracite and other borate minerals. and other borate minerals. Other Characteristics:Other Characteristics: exfoliates (peels off) upon heating. exfoliates (peels off) upon heating. Notable Occurrences Notable Occurrences include Yermo, Boron, Death Valley and include Yermo, Boron, Death Valley and

other California localities, USA; Nevada, USA; Chile and other California localities, USA; Nevada, USA; Chile and Panderma, Turkey. Panderma, Turkey.

Best Field Indicators are crystalBest Field Indicators are crystal habit, associations, locality, habit, associations, locality, density, cleavage and hardness. density, cleavage and hardness.

Use: Use: A source of borax that, at the time of the discovery of A source of borax that, at the time of the discovery of kernite, yielded over half of the world’s supplykernite, yielded over half of the world’s supply

Sulfates & ChromatesSulfates & Chromates

In partial fulfillment of the In partial fulfillment of the requirements for requirements for

MINERALOGYMINERALOGY

JEX MALTO

Sulfates & ChromatesSulfates & Chromates Sulfur- occurs as a large, divalent sulfide anionSulfur- occurs as a large, divalent sulfide anion

- this ion results from the filling by captured electrons of the - this ion results from the filling by captured electrons of the two vacancies in the outer, or valence, electron shell.two vacancies in the outer, or valence, electron shell.

- the six electrons normally present in this shell may be - the six electrons normally present in this shell may be lost, giving rise to a small, highly charged and highly polarizing lost, giving rise to a small, highly charged and highly polarizing positive ion (radius = 0.30Å).positive ion (radius = 0.30Å).

- the ratio of the radius of this S- the ratio of the radius of this S6+6+ ion to that of oxygen ion to that of oxygen (Rx:Ro =0.214) indicates that 4 coordination will be stable.(Rx:Ro =0.214) indicates that 4 coordination will be stable.

the sulfur to oxygen bond in such an ionic group is very the sulfur to oxygen bond in such an ionic group is very strong (e.v. = 1 ½; and covalent in its properties and produces strong (e.v. = 1 ½; and covalent in its properties and produces tightly bound groups that are not capable of sharing oxygens.tightly bound groups that are not capable of sharing oxygens.

- these anionic (SO- these anionic (SO44))-2-2 groups are the fundamental groups are the fundamental

structural units of the sulfate minerals.structural units of the sulfate minerals.

SULFATES AND CHROMATESSULFATES AND CHROMATES

ANHYDROUS ANHYDROUS SULFATES AND SULFATES AND CHROMATESCHROMATES

BARITE GROUPBARITE GROUP BariteBariteBaSOBaSO44

CelestiteCelestite SrSOSrSO44

AnglesiteAnglesite PbSOPbSO44

ANHYDRITEANHYDRITE CaSOCaSO44

CROCOITECROCOITE PbCrOPbCrO44

HYDROUS AND BASIC HYDROUS AND BASIC SULFATESSULFATES

GYPSUMGYPSUM CaSO CaSO44 2H 2H22OO

ANTLERITE CuANTLERITE Cu33SOSO44(OH)(OH)44

ALUNITEALUNITE KAlKAl33(SO(SO44))22(OH)(OH)66

SULFATES AND CHROMATESSULFATES AND CHROMATES

BARITE GROUPBARITE GROUP- The sulfates of Ba, Sr, and PbThe sulfates of Ba, Sr, and Pb

Form an isostructural group with space group Pama.Form an isostructural group with space group Pama.- They have closely related crystals constant and similar They have closely related crystals constant and similar

habitshabits- The members of the group are: barite, celestite, and The members of the group are: barite, celestite, and

anglesite.anglesite.

SULFATES AND CHROMATESSULFATES AND CHROMATES(ANHYDROUS SULFATES AND CHROMATES)(ANHYDROUS SULFATES AND CHROMATES)

BARITEBARITE BaSO BaSO44

Crystal SystemCrystal System: orthorhombic: orthorhombic

Crystal HabitCrystal Habit: tabular “crested : tabular “crested barite or barite roses, granularbarite or barite roses, granular

CleavageCleavage:{001}:{001}

ColorColor: colorless, white and light : colorless, white and light shades of blue, yellow, redshades of blue, yellow, red

LusterLuster : vitreous, pearly on base : vitreous, pearly on base

HardnessHardness:3 – 3.5 :3 – 3.5

Specific GravitySpecific Gravity : 4.5 (heavy for : 4.5 (heavy for a non metallic)a non metallic)


Composition and Structure:Composition and Structure:

BaO 65.7, SOBaO 65.7, SO33 34.3% for the 34.3% for the

pure baritepure barite Diagnostic Feature:Diagnostic Feature: high high

specific gravity and specific gravity and characteristic cleavage & characteristic cleavage & crystalcrystal

- fusible at 4, giving yellowish-- fusible at 4, giving yellowish-green flame (Ba). Fused w/ green flame (Ba). Fused w/ reducing mixture gives a reducing mixture gives a residue w/c, when moistened, residue w/c, when moistened, produces a dark stain of silver produces a dark stain of silver sulfide on a clean silver sulfide on a clean silver surfacesurface

Occurrence: Occurrence: -usually a -usually a gangue mineral in gangue mineral in hydrothermal veins, hydrothermal veins, associated w/ ores of silver, associated w/ ores of silver, lead, copper, cobalt, lead, copper, cobalt, manganese, and antimony.manganese, and antimony.

--in veins in limestone with in veins in limestone with calcite, or as residual masses calcite, or as residual masses in clay overlying, limestone.in clay overlying, limestone.

-also in sandstone w/ copper -also in sandstone w/ copper ores. In places acts a a ores. In places acts a a cement in sandstone. cement in sandstone. Deposited occasionally as a Deposited occasionally as a sinter by water from hot sinter by water from hot springs.springs.


- notable localities are in - notable localities are in Westmoreland, Cornwall, Westmoreland, Cornwall, Cumberland and Derbyshire, Cumberland and Derbyshire, England, Felsobanya and England, Felsobanya and other localities, Romania, etc..other localities, Romania, etc..

Use – Use – more than 80% more than 80% produced is used in oil and produced is used in oil and gas-well drilling as “heavy gas-well drilling as “heavy mud” to aid in the support of mud” to aid in the support of drill rods and to help prevent drill rods and to help prevent blowing out of gasblowing out of gas

- - Lithopone – combination of Lithopone – combination of barium sulfide and zinc barium sulfide and zinc sulfates that form an intimate sulfates that form an intimate mixture of zinc sulfide and mixture of zinc sulfide and

barium sulfate—used in the barium sulfate—used in the paint industry and to a lesser paint industry and to a lesser extent in floor coverings and extent in floor coverings and textilestextiles

-precipitated barium sulfate-precipitated barium sulfate—”blanc fixe” is employed as a —”blanc fixe” is employed as a filler in paper and cloth, in filler in paper and cloth, in cosmetics, as a paint pigment, cosmetics, as a paint pigment, and for barium meals in and for barium meals in radiology.radiology.

Name : Name : Greek word meaning Greek word meaning heavy in allusion to its high heavy in allusion to its high specific gravityspecific gravity


CELESTITE SrSOCELESTITE SrSO44

Crystal SystemCrystal System : orthorhombic : orthorhombic Crystal HabitCrystal Habit :tabular, :tabular,

radiating, fibrous; granularradiating, fibrous; granular CleavageCleavage :{001} perfect,{210} :{001} perfect,{210}

goodgood ColorColor :colorless, white often :colorless, white often

faintly blue or redfaintly blue or red StreakStreak : : LusterLuster : vitreous to pearly : vitreous to pearly HardnessHardness : 3 – 3.5 : 3 – 3.5 Specific GravitySpecific Gravity : 3.95-3.97 : 3.95-3.97


Composition and StructureComposition and Structure : : SrO56.4, SOSrO56.4, SO33 43.6% for pure 43.6% for pure

celestitecelestite

- at ordinary temperature only - at ordinary temperature only a limited series exist between a limited series exist between anhydrite, CaSOanhydrite, CaSO44, and SrSO, and SrSO44

- Celestite is isostructural w/ - Celestite is isostructural w/ barite barite

Diagnostic Feature Diagnostic Feature : closely : closely resembles barite but is resembles barite but is differentiated by lower specific differentiated by lower specific gravity and crimson flame test gravity and crimson flame test (Sr).(Sr).

- fuses at 3.5-4. usually - fuses at 3.5-4. usually decrepitates when touched w/ decrepitates when touched w/ the blowpipe flamethe blowpipe flame

- Fused with sodium carbonate - Fused with sodium carbonate gives a residue w/c when gives a residue w/c when moistened, produces on a moistened, produces on a clean silver surface a dark of clean silver surface a dark of silver sulfidesilver sulfide


Occurrence Occurrence : a common : a common supergene mineral found in the supergene mineral found in the oxidized portion of lead oxidized portion of lead deposits.deposits.

- formed through the oxidation - formed through the oxidation of galenaof galena

- is commonly associated with - is commonly associated with galena, cerussite, sphalerite, galena, cerussite, sphalerite, smithsonite, hemimorphite and smithsonite, hemimorphite and iron oxides.iron oxides.

UseUse : a minor ore o lead : a minor ore o lead NameName : Named from the : Named from the

original locality on the island of original locality on the island of Anglesey.Anglesey.


ANHYDRITE CaSOANHYDRITE CaSO44

Crystal SystemCrystal System :orthorhombic :orthorhombic Crystal HabitCrystal Habit : thick tabular, : thick tabular,

prismatic, massive or prismatic, massive or crystallinecrystalline

CleavageCleavage : {010},{100},{001} : {010},{100},{001} Fracture :Fracture : ColorColor :colorless, to bluish or :colorless, to bluish or

violet, white or tinged w/ rose, violet, white or tinged w/ rose, brown, or redbrown, or red

StreakStreak : : LusterLuster :vitreous to pearly :vitreous to pearly HardnessHardness : 3 – 3.5 : 3 – 3.5 Specific GravitySpecific Gravity : 2.89 – 2.98 : 2.89 – 2.98


Composition and StructureComposition and Structure : : - CaO 41.2, SO- CaO 41.2, SO33 58.8 %. 58.8 %.

- a metastable polymorph of - a metastable polymorph of anhydrite (yCaSOanhydrite (yCaSO44) is ) is

hexagonal and is formed as hexagonal and is formed as the result of slow dehydration the result of slow dehydration of gypsumof gypsum

Diagnostic FeatureDiagnostic Feature : - fusible : - fusible at 3. when moistened w/ HCl at 3. when moistened w/ HCl and ignited it gives an orange-and ignited it gives an orange-red flame of Cared flame of Ca

- when fused w/ reducing - when fused w/ reducing mixture it gives a residue that, mixture it gives a residue that, when moistened w/ water, when moistened w/ water, darkens silverdarkens silver

- characterized by its three - characterized by its three cleavages at right anglescleavages at right angles

- it is distinguished from calcite - it is distinguished from calcite by its higher specific gravity by its higher specific gravity and from gypsum by its greater and from gypsum by its greater hardnesshardness

- some varieties are difficult to - some varieties are difficult to recognize and one should test recognize and one should test for the sulfate radicalfor the sulfate radical

AlterationAlteration – by hydration – by hydration changes to gypsum w/ an changes to gypsum w/ an increase in volume, and in increase in volume, and in places large masses have places large masses have been alteredbeen altered


OccurrenceOccurrence : occurs in much : occurs in much as the same manner as as the same manner as gypsum and is often gypsum and is often associated w/ that mineral but associated w/ that mineral but is not nearly as common.is not nearly as common.- found in beds associated w/ - found in beds associated w/ salt deposits in the cap rock of salt deposits in the cap rock of salt domes, and in limestonessalt domes, and in limestones- found in some amygdaloidal - found in some amygdaloidal cavities in basaltcavities in basalt

UseUse : used as soil conditioner : used as soil conditioner and to minor extent as a and to minor extent as a setting retardant in Portland setting retardant in Portland cement.cement.- in Great Britain and Germany- in Great Britain and Germany

it has been used as a source it has been used as a source of sulfur for the production of of sulfur for the production of sulfuric acidsulfuric acid

NameName : from the Greek word : from the Greek word meaning meaning without waterwithout water , , in in contrast to the more common contrast to the more common hydrous calcium sulfate, hydrous calcium sulfate, gypsum.gypsum.


CROCOITE PbCrOCROCOITE PbCrO44

Crystal SystemCrystal System : Monoclinic : Monoclinic Crystal HabitCrystal Habit :slender :slender

prismatic crystals, vertically prismatic crystals, vertically striated and columnar striated and columnar aggregates, granularaggregates, granular

CleavageCleavage : {110) imperfect : {110) imperfect ColorColor :bright hyacinth-red :bright hyacinth-red StreakStreak :orange-yellow :orange-yellow LusterLuster :adamantine :adamantine HardnessHardness :2.5 - 3 :2.5 - 3 Specific GravitySpecific Gravity :5.9 – 6.1 :5.9 – 6.1


Composition and StructureComposition and Structure : :

- PbO 68.9, Cr0- PbO 68.9, Cr033 31.1 % 31.1 %

- is isostructural w/ - is isostructural w/ monazite,monazite, Diagnostic FeatureDiagnostic Feature : by its : by its

color, high luster, and high color, high luster, and high specific gravityspecific gravity

- may be confused w/ wulfenite, - may be confused w/ wulfenite, PbMo)4, but can be PbMo)4, but can be distinguished from it by its distinguished from it by its redder color, lower specific redder color, lower specific gravity and crystal formgravity and crystal form

- fusible at 1.5, fused w/ sodium - fusible at 1.5, fused w/ sodium carbonate on charcoal gives a carbonate on charcoal gives a lead globule—gives a green lead globule—gives a green (Cr) borax bead in the oxidizing (Cr) borax bead in the oxidizing flameflame

Occurrence : rare mineral Occurrence : rare mineral found in the oxidized zones of found in the oxidized zones of lead deposit in those regions lead deposit in those regions where lead veins have where lead veins have traversed rocks containing traversed rocks containing chromitechromite

- associated w/ pyromorphite - associated w/ pyromorphite cerussite and wulfenitecerussite and wulfenite

Use : not abundant enough to Use : not abundant enough to be commercial value, but of be commercial value, but of historic interest, because the historic interest, because the element chromium was first element chromium was first discovered in crocoitediscovered in crocoite

Name : from the Greek Name : from the Greek meaning meaning saffronsaffron, in allusion to , in allusion to its colorits color

SULFATES AND CHROMATESSULFATES AND CHROMATES(HYDROUS SULFATES AND CHROMATES)(HYDROUS SULFATES AND CHROMATES)

GYPSUM CaSOGYPSUM CaSO442H2H22OO

Crystal SystemCrystal System : Monoclinic : Monoclinic

Crystal HabitCrystal Habit : tabular, diamond- : tabular, diamond-shaped, swallowtail twinsshaped, swallowtail twins

CleavageCleavage : {010},{100},{011} : {010},{100},{011}

ColorColor : colorless, white, gray, : colorless, white, gray, various shades of yellow, red, various shades of yellow, red, brown, from impuritiesbrown, from impurities

Streak Streak ::

LusterLuster : usually vitreous, pearly : usually vitreous, pearly and silkyand silky

Hardness Hardness : 2: 2

Specific GravitySpecific Gravity : 2.23 : 2.23

Satin spar is a fibrous gypsum w/ silky luster

Alabaster is the fine-grained massive variety

Selenite is a variety that yields broad colorless and transparent cleavage folia



- CaO 32.6, SO- CaO 32.6, SO33 46.5 H 46.5 H22O 20.9 %O 20.9 %

-during the dehydration -during the dehydration process, between 0process, between 0oo and about and about 6565oo, 1 ½ molecule of 2H, 1 ½ molecule of 2H22O is O is

relatively lost forming a relatively lost forming a metastable phase of CaSOmetastable phase of CaSO44- ½ - ½

HH22O—with only slight changes O—with only slight changes

in the gypsum structure in the gypsum structure

- at about 70- at about 70oo the remaining ½ the remaining ½ HH220 is still retained relatively 0 is still retained relatively

strongstrong

- at about 95- at about 95oo C this is lost and C this is lost and the structure transforms to that the structure transforms to that of a polymorph of anhydriteof a polymorph of anhydrite


Diagnostic FeaturesDiagnostic Features : by its : by its softness and its three unequal softness and its three unequal cleavagescleavages

- fusible at 3 - fusible at 3

- soluble in hot, dilute HCl and - soluble in hot, dilute HCl and solution w/ barium chloride solution w/ barium chloride gives white precipitate of gives white precipitate of barium sulfatebarium sulfate

- in close tube turns white and - in close tube turns white and yields much water yields much water

- its solubility in water - its solubility in water distinguishes it from anhydritedistinguishes it from anhydrite

Occurrence Occurrence : a common : a common mineral widely distributed in mineral widely distributed in sedimentary rocks, often as sedimentary rocks, often as thick bedsthick beds

- frequently occurs - frequently occurs interstratified with limestone interstratified with limestone and shales and is usually found and shales and is usually found as a layer underlying beds of as a layer underlying beds of rock salt, having been rock salt, having been deposited there as one of the deposited there as one of the first mineral to crystallize on the first mineral to crystallize on the evaporation of salt waterevaporation of salt water

- may recrystallize in vein - may recrystallize in vein forming satin sparforming satin spar

-occurs also as lenticular -occurs also as lenticular bodies or scattered crystals in bodies or scattered crystals in clays and shalesclays and shales


- formed by the alteration of - formed by the alteration of anhydrite and under these anhydrite and under these circumstances may show circumstances may show folding because of increased folding because of increased volume volume - found in volcanic regions, - found in volcanic regions, especially where limestones especially where limestones have been acted upon by have been acted upon by sulfur vaporssulfur vapors- also common as a gangue - also common as a gangue mineral in metallic veins. mineral in metallic veins. associated w/ many different associated w/ many different minerals, the more common minerals, the more common being halite, anhydrite, being halite, anhydrite, dolomite, calcite, sulfur, pyrite dolomite, calcite, sulfur, pyrite and quartzand quartz

- is the most common sulfate and - is the most common sulfate and extensive deposit are found extensive deposit are found throughout the worldthroughout the world

UseUse : is used chiefly for the : is used chiefly for the production of plaster of paris, production of plaster of paris, “staff”, gypsum lath, wallboard “staff”, gypsum lath, wallboard and for molds and cast of all and for molds and cast of all kindskinds- adamant plaster for interior - adamant plaster for interior use, soil conditioner, use, soil conditioner, uncalcined gypsum is used as uncalcined gypsum is used as a retarder in Portland Cement.a retarder in Portland Cement.- Satin Spar and Alabaster are - Satin Spar and Alabaster are cut and polished for various cut and polished for various ornamentsornaments

NameName : Greek name for the : Greek name for the mineral, applied to the calcined mineral, applied to the calcined mineral mineral


ANTLERITEANTLERITE CuSOCuSO44(OH)(OH)44

Crystal SystemCrystal System : Orthorhombic : Orthorhombic

Crystal HabitCrystal Habit : tabular, striated, : tabular, striated, reniform, reniform, massivemassive

CleavageCleavage : {010) : {010)

ColorColor : emerald to blackish-green : emerald to blackish-green

StreakStreak :pale green :pale green

LusterLuster : vitreous : vitreous

HardnessHardness : 3.5 to 4 : 3.5 to 4

Specific GravitySpecific Gravity : 3.9 : 3.9



- CuO 67.3, SO- CuO 67.3, SO33 22.5,H 22.5,H22O O

10.2%10.2%

Diagnostic FeaturesDiagnostic Features : fusible : fusible at 3 1/2 at 3 1/2

- yields a copper globule when - yields a copper globule when fused w/ sodium carbonate on fused w/ sodium carbonate on

Occurrence Occurrence : found in the : found in the oxidized portions of copper oxidized portions of copper veins, especially in arid veins, especially in arid regions regions

- formerly considered as a rare - formerly considered as a rare mineral mineral

- may form directly as a - may form directly as a secondary mineral on secondary mineral on chalcocitechalcocite

- or the copper may go into - or the copper may go into solution and later be deposited solution and later be deposited as antlerite, filling cracksas antlerite, filling cracks

UseUse : ore of copper : ore of copper


NameName : from the Antler mine, : from the Antler mine, Arizona, from w/c locality it Arizona, from w/c locality it was originally describedwas originally described

Similar Species :Similar Species :

- Brochantite- Brochantite CuCu44SOSO44(OH)(OH)66

- Chalcantite CuSO- Chalcantite CuSO44 5H 5H22OO

- Epsomite MgSO- Epsomite MgSO44 7H 7H22OO

- Melanterite FeSO- Melanterite FeSO44 7H 7H22OO


ALUNITE ALUNITE KAlKAl33(SO(SO44))22(OH)(OH)66

Crystal SystemCrystal System : Hexagonal-R : Hexagonal-R Crystal HabitCrystal Habit : :

rhombohedrones, tabular, rhombohedrones, tabular, massive and disseminated massive and disseminated

CleavageCleavage : {0001} imperfect : {0001} imperfect Color Color :white, gray, or reddish:white, gray, or reddish StreakStreak : : Luster Luster : vitreous to pearly, in : vitreous to pearly, in

crystals, earthy in massive crystals, earthy in massive materialmaterial

Hardness Hardness : 4 : 4 Specific GravitySpecific Gravity : 2.6 to 2.8 : 2.6 to 2.8



- K- K22O 11.4, AlO 11.4, Al22OO33 37.0, SO 37.0, SO33 38.6, H38.6, H22O 13. 0%O 13. 0%

Diagnostic FeatureDiagnostic Feature : : - infusible and decrepitates - infusible and decrepitates before the blowpipe, giving a before the blowpipe, giving a potassium flamepotassium flame- heated w/ cobalt nitrate - heated w/ cobalt nitrate solution turns a fine blue colorsolution turns a fine blue color- in the closed tube gives acid - in the closed tube gives acid waterwater- soluble in sulfuric acid- soluble in sulfuric acid- usually difficult to distinguish- usually difficult to distinguishfrom similar appearing mineral from similar appearing mineral

- a positive test for acid water - a positive test for acid water will help to distinguishwill help to distinguish

Occurrence Occurrence : also called : also called alumstonealumstone- is usually formed by sulfuric - is usually formed by sulfuric acid solution acting on rock acid solution acting on rock rich in potash feldspar, and in rich in potash feldspar, and in some places large masses some places large masses have been formedhave been formed- smaller amounts about - smaller amounts about volcanic fumarolesvolcanic fumaroles

UseUse : in the Production of alum : in the Production of alum Similar SpeciesSimilar Species : :

- Iarosite KFE- Iarosite KFE33(SO(SO44))22(OH)(OH)88

-secondary mineral on -secondary mineral on ferruginous oresferruginous ores

By:By:

Mark Niño L. MiraballesMark Niño L. Miraballes

The chemistry of the tungstate (WOThe chemistry of the tungstate (WO44))-2-2 and molybdate (MoO and molybdate (MoO44) ) -2-2 ions is so similar that both are always associated. The anions ions is so similar that both are always associated. The anions are distorted tetrahedra, with the tungsten (W) or Molybdenum are distorted tetrahedra, with the tungsten (W) or Molybdenum (Mo) atom bonded to four oxygen atoms by covalent bonds.(Mo) atom bonded to four oxygen atoms by covalent bonds.

The structural unit is a tetrahedral group formed by 4 oxygen The structural unit is a tetrahedral group formed by 4 oxygen atoms at the corners of a tetrahedron surrounding a (Mo) or (W) atoms at the corners of a tetrahedron surrounding a (Mo) or (W) atom. Each MoOatom. Each MoO44 or WO or WO44 tetrahedron has a net charge of -2, tetrahedron has a net charge of -2, which is neutralized by metal ions outside the tetrahedron.which is neutralized by metal ions outside the tetrahedron.

Unlike the silicate or borate minerals, which form framework Unlike the silicate or borate minerals, which form framework structures by sharing oxygen atoms b/w adjacent tetrahedra, structures by sharing oxygen atoms b/w adjacent tetrahedra, the molybdate and tungstate minerals share none; they are the molybdate and tungstate minerals share none; they are similar in this respect to the phosphate, vanadate, arsenate, and similar in this respect to the phosphate, vanadate, arsenate, and chromate minerals. chromate minerals.

The molybdenum and tungsten ion have similar radii, they may The molybdenum and tungsten ion have similar radii, they may substitute for one another within the structure of any naturally substitute for one another within the structure of any naturally occurring example; thus, they tend to form solid solution series.occurring example; thus, they tend to form solid solution series.

Tungstates and MolydatesTungstates and Molydates

In chemistry a tungstate is a compound that contains an In chemistry a tungstate is a compound that contains an oxoanion of tungsten or is a mixed oxide containing oxoanion of tungsten or is a mixed oxide containing tungsten. The simplest tungstate ion is (WOtungsten. The simplest tungstate ion is (WO44))-2-2..

There are many other tungstate ions that contain more There are many other tungstate ions that contain more than one tungsten atom and belong to a large group of than one tungsten atom and belong to a large group of polyatomic ions that are termed polyoxometalates, polyatomic ions that are termed polyoxometalates, ("POM’s"), and specifically termed isopolyoxometalates ("POM’s"), and specifically termed isopolyoxometalates as they contain, along with oxygen and maybe hydrogen, as they contain, along with oxygen and maybe hydrogen, only one other element. only one other element.

Comparing tungsten to the other group 6 elements, the Comparing tungsten to the other group 6 elements, the large tungstate ions generally contain 6 coordinate metal large tungstate ions generally contain 6 coordinate metal atoms similar to molybdenum (molybdates) and contrast atoms similar to molybdenum (molybdates) and contrast to chromium (chromates) where 4 coordination to chromium (chromates) where 4 coordination predominates.predominates.

TungstatesTungstates

WolframiteWolframite Chemistry: (Fe, Mn)WOChemistry: (Fe, Mn)WO44, Iron manganese tungstate , Iron manganese tungstate Class: Sulfates Class: Sulfates Subclass: Tungstates Subclass: Tungstates Uses: an ore of tungsten (an important industrial Uses: an ore of tungsten (an important industrial

element) and as a mineral specimen. element) and as a mineral specimen. Occurrence: comparatively rare mineral found usually in Occurrence: comparatively rare mineral found usually in

pegmatites and high temperature quartz veins pegmatites and high temperature quartz veins associated with granites, and more rarely in sulfide associated with granites, and more rarely in sulfide veins. veins.

Wolframite is derived from an old word of German origin.Wolframite is derived from an old word of German origin. Wolframite is actually a series between two minerals; Wolframite is actually a series between two minerals;

Huebnerite and Ferberite.Huebnerite and Ferberite. Huebnerite is the Manganese rich end member while Huebnerite is the Manganese rich end member while

ferberite is the iron rich end member. ferberite is the iron rich end member. Wolframite is the name of the series and the name Wolframite is the name of the series and the name

applied to indistinguishable specimens and specimens applied to indistinguishable specimens and specimens intermediate between the two end members. intermediate between the two end members.

Most specimens found in nature fall within 20 - 80% Most specimens found in nature fall within 20 - 80% range of the series and these are termed wolframites. range of the series and these are termed wolframites.

Physical CharacteristicsPhysical Characteristics ColorColor is Black to grey or brown. is Black to grey or brown. LusterLuster is submetallic to resinous. is submetallic to resinous. TransparencyTransparency crystals are translucent to opaque. crystals are translucent to opaque. Crystal SystemCrystal System is monoclinic; 2/m is monoclinic; 2/m Crystal HabitsCrystal Habits include the flat, heavily modified, tabular include the flat, heavily modified, tabular

crystals. The crystals are elongated along the c axis and are crystals. The crystals are elongated along the c axis and are generally flattened in the a axis direction. Also as columnar generally flattened in the a axis direction. Also as columnar aggregates and lamellar masses. aggregates and lamellar masses.

CleavageCleavage is perfect in one direction parallel to the a and c is perfect in one direction parallel to the a and c axes. axes.

FractureFracture is uneven. is uneven. HardnessHardness is 4 - 4.5. is 4 - 4.5. Specific GravitySpecific Gravity is approximately 7.0 - 7.5 (heavy even for is approximately 7.0 - 7.5 (heavy even for

metallic minerals) metallic minerals) StreakStreak is brown to black. is brown to black. Associated MineralsAssociated Minerals are quartz, hematite, tourmalines, are quartz, hematite, tourmalines,

cassiterite, micas and pyrite. cassiterite, micas and pyrite.

Other Characteristics:Other Characteristics: crystals striated lengthwise. crystals striated lengthwise. Notable OccurrencesNotable Occurrences include Nanling Range, China; include Nanling Range, China;

southwest and Colorado, USA; Russia; Korea; England and southwest and Colorado, USA; Russia; Korea; England and Bolivia. Bolivia.

Best Field IndicatorsBest Field Indicators are crystal habit, color, density, are crystal habit, color, density, luster and cleavage.luster and cleavage.

HuebneriteHuebnerite Chemistry: MnWOChemistry: MnWO44, Manganese tungstate , Manganese tungstate Class: Sulfates Class: Sulfates Subclass: Tungstates Subclass: Tungstates Uses: a minor ore of tungsten (an important industrial Uses: a minor ore of tungsten (an important industrial

element) and as a mineral specimen. element) and as a mineral specimen. Huebnerite is the Manganese rich end member of Huebnerite is the Manganese rich end member of

Wolframite, but only if they are more pure than 80% Wolframite, but only if they are more pure than 80% manganese.manganese.

Huebnerite is more common than ferberite but not nearly Huebnerite is more common than ferberite but not nearly as common as wolframite. as common as wolframite.

Hubnerite tends to be light in color, with a lighter streak, Hubnerite tends to be light in color, with a lighter streak, more transparent and less dense. more transparent and less dense.

Huebnerite can make a valuable and attractive specimen Huebnerite can make a valuable and attractive specimen when associated with clear quartz clusters. when associated with clear quartz clusters.

Physical PropertiesPhysical Properties ColorColor is yellow to reddish brown. is yellow to reddish brown. LusterLuster is resinous. is resinous. TransparencyTransparency crystals are transparent to translucent. crystals are transparent to translucent. Crystal SystemCrystal System is monoclinic; 2/m is monoclinic; 2/m Crystal HabitsCrystal Habits include the flat, heavily modified, tabular include the flat, heavily modified, tabular

crystals. The crystals are elongated along the c axis and are crystals. The crystals are elongated along the c axis and are generally flattened in the a axis direction. Also as columnar generally flattened in the a axis direction. Also as columnar aggregates and lamellar masses. aggregates and lamellar masses.


FractureFracture is uneven. is uneven. HardnessHardness is 4 - 4.5. is 4 - 4.5. Specific GravitySpecific Gravity is approximately 7.0 (heavy even for is approximately 7.0 (heavy even for

metallic minerals) metallic minerals) StreakStreak is brown or grey. is brown or grey. Associated MineralsAssociated Minerals are quartz, hematite, tourmalines, are quartz, hematite, tourmalines,


Other Characteristics:Other Characteristics: crystals striated lengthwise. crystals striated lengthwise. Notable OccurrencesNotable Occurrences include Nanling Range, China; include Nanling Range, China;

France; North Carolina, Idaho and Colorado, USA; Russia; France; North Carolina, Idaho and Colorado, USA; Russia; Peru; England and Bolivia. Peru; England and Bolivia.

Best Field IndicatorsBest Field Indicators are crystal habit, color, density, are crystal habit, color, density, luster and cleavage. luster and cleavage.

FerberiteFerberite Chemistry: FeWOChemistry: FeWO44, Iron tungstate , Iron tungstate Class: Sulfates Class: Sulfates Subclass: Tungstates Subclass: Tungstates Uses: as a minor ore of tungsten (an important industrial Uses: as a minor ore of tungsten (an important industrial

element) and as a mineral specimen.element) and as a mineral specimen. Ferberite is the Iron rich end member of Wolframite, but Ferberite is the Iron rich end member of Wolframite, but

only if they are more pure than 80% iron.only if they are more pure than 80% iron. Ferberite tends to be black colored, with a black streak, is Ferberite tends to be black colored, with a black streak, is

opaque with a nearly submetallic luster, is denser, has opaque with a nearly submetallic luster, is denser, has crystals with a different elongation and can be weakly crystals with a different elongation and can be weakly magnetic. magnetic.

Ferberite is the rarer member of the series. Ferberite is the rarer member of the series.

Physical PropertiesPhysical Properties ColorColor is Black. is Black. LusterLuster is submetallic. is submetallic. TransparencyTransparency crystals are opaque. crystals are opaque. Crystal SystemCrystal System is monoclinic; 2/m is monoclinic; 2/m Crystal HabitsCrystal Habits include the flat, heavily modified, tabular include the flat, heavily modified, tabular

crystals. The crystals are elongated along the b axis and crystals. The crystals are elongated along the b axis and are generally flattened in the a axis direction. Also as are generally flattened in the a axis direction. Also as columnar aggregates and lamellar masses. columnar aggregates and lamellar masses.


FractureFracture is uneven. is uneven. HardnessHardness is 4 - 4.5. is 4 - 4.5. Specific GravitySpecific Gravity is approximately 7.6 (heavy even for is approximately 7.6 (heavy even for

metallic minerals) metallic minerals) StreakStreak is black. is black. Associated MineralsAssociated Minerals are quartz, hematite, tourmalines, are quartz, hematite, tourmalines,


Other Characteristics:Other Characteristics: crystals are often striated. crystals are often striated. Notable OccurrencesNotable Occurrences include Nanling Range, China; include Nanling Range, China;

South Dakota and Colorado, USA; Russia; Korea; England South Dakota and Colorado, USA; Russia; Korea; England and Bolivia. and Bolivia.

Best Field IndicatorsBest Field Indicators are crystal habit, color, density, are crystal habit, color, density, luster and cleavage.luster and cleavage.

ScheeliteScheelite Chemistry: CaWOChemistry: CaWO44, Calcium , Calcium

Tungstate Tungstate Class: Sulfates Class: Sulfates Subclass: Tungstates Subclass: Tungstates Uses: An important source of Uses: An important source of

tungsten, rarely cut as tungsten, rarely cut as gemstones and as mineral gemstones and as mineral specimens. specimens.

Scheelite is named for the Scheelite is named for the discoverer of tungsten, K. W. discoverer of tungsten, K. W. Scheele (1742-1786).Scheele (1742-1786).

Scheelite is an important ore Scheelite is an important ore of tungsten which is a of tungsten which is a strategically important strategically important metal, although most of the metal, although most of the world wide production of world wide production of tungsten comes from the tungsten comes from the mineral wolframite.mineral wolframite.

Physical CharacteristicsPhysical Characteristics ColorColor is white, yellow, orange or greenish grey to brown. is white, yellow, orange or greenish grey to brown. LusterLuster is adamantine to greasy. is adamantine to greasy. Transparency:Transparency: Crystals are transparent to translucent. Crystals are transparent to translucent. Crystal SystemCrystal System is tetragonal; 4/m. is tetragonal; 4/m. Crystal Habits include the pseudo-octahedral crystals that include the pseudo-octahedral crystals that

are actually tetragonal dipyramids. Also massive and are actually tetragonal dipyramids. Also massive and granular. granular.

CleavageCleavage is indistinct in two directions and good in is indistinct in two directions and good in another (dipyramidal). another (dipyramidal).

FractureFracture is conchoidal. is conchoidal. HardnessHardness is 4.5 - 5. is 4.5 - 5. Specific GravitySpecific Gravity is approximately 5.9 - 6.1 (very heavy for is approximately 5.9 - 6.1 (very heavy for

translucent minerals). translucent minerals). StreakStreak is white. is white. Other Characteristics:Other Characteristics: Fluoresces blue (yellow with Fluoresces blue (yellow with

molybdenum traces) under short wave ultraviolet light. molybdenum traces) under short wave ultraviolet light.

Associated MineralsAssociated Minerals are quartz are quartz, , garnetsgarnets, , vesuvianitevesuvianite, , epidote, topaz, schorl, apatite, gold, silver, molybdenite, epidote, topaz, schorl, apatite, gold, silver, molybdenite, cassiterite, wolframite and fluorite. cassiterite, wolframite and fluorite.

Notable OccurrencesNotable Occurrences include Hollinger Mine, Ontario, include Hollinger Mine, Ontario, Canada; Saxony, Germany; Tong Wha, Korea; Brazil; Canada; Saxony, Germany; Tong Wha, Korea; Brazil; Sonora, Mexico; Cornwall, England; New South Wales and Sonora, Mexico; Cornwall, England; New South Wales and Queensland, Australia and Mill City, Nevada, Atolia, San Queensland, Australia and Mill City, Nevada, Atolia, San Bernardino Co., California, Cochise Co., Arizona, Utah and Bernardino Co., California, Cochise Co., Arizona, Utah and Colorado, USA. Colorado, USA.

Best Field IndicatorsBest Field Indicators are crystal habit, color, density, are crystal habit, color, density, luster and especially its fluorescence. luster and especially its fluorescence.

MolybdatesMolybdates In chemistry a In chemistry a molybdatemolybdate is a compound containing an is a compound containing an

oxoanion with molybdenum in its highest oxidation state of oxoanion with molybdenum in its highest oxidation state of 6.6.

Molybdenum can form a very large range of such oxoanions Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended which can be discrete structures or polymeric extended structures, although the latter are only found in the solid structures, although the latter are only found in the solid state.state.

The larger oxoanions are members of group of compounds The larger oxoanions are members of group of compounds termed polyoxometalates, and because they contain only termed polyoxometalates, and because they contain only one type of metal atom are often called isopolymetalates. one type of metal atom are often called isopolymetalates.

The discrete molybdenum oxoanions range in size from the The discrete molybdenum oxoanions range in size from the simplest MoOsimplest MoO42−42−, found in potassium molybdate up to , found in potassium molybdate up to extremely large structures found in isopoly-molybdenum extremely large structures found in isopoly-molybdenum blues that contain for example 154 Mo atoms.blues that contain for example 154 Mo atoms.

PowellitePowellite

Chemistry:Chemistry: CaMoO CaMoO44, Calcium Molybdenate , Calcium Molybdenate Class:Class: Sulfates Sulfates Subclass:Subclass: Molybdenates Molybdenates Uses:Uses: As a minor ore of molybdenum (an important As a minor ore of molybdenum (an important

industrial metal) and as mineral specimens. industrial metal) and as mineral specimens. Occurrence: Occurrence: results from hydrothermal reactions with the results from hydrothermal reactions with the

primary sulfide mineral molybdenitesprimary sulfide mineral molybdenites, , with a formula of with a formula of MoSMoS22. . Powellite in fact, forms pseudomorphs after Powellite in fact, forms pseudomorphs after molybdenite. Powellite also is known to form as a primary molybdenite. Powellite also is known to form as a primary mineral in quartz veins. mineral in quartz veins.

Named for the American geologist, Major John Wesley Named for the American geologist, Major John Wesley Powell, a former director of the U. S. Geological Survey. Powell, a former director of the U. S. Geological Survey.

Powellite is one of only a handful of relatively common Powellite is one of only a handful of relatively common molybdenum minerals, other molybdenum minerals include molybdenum minerals, other molybdenum minerals include wulfenite, molybdenite, ferrimolybdite, molybdite and wulfenite, molybdenite, ferrimolybdite, molybdite and sidwellite. sidwellite.

Physical PropertiesPhysical Properties ColorColor is yellow, brown, grey, blue, white or black. is yellow, brown, grey, blue, white or black. LusterLuster is adamantine to greasy. is adamantine to greasy. Transparency:Transparency: Crystals are translucent to transparent. Crystals are translucent to transparent. Crystal SystemCrystal System is tetragonal; 4/m is tetragonal; 4/m Crystal HabitsCrystal Habits include small four sided pyramidal crystals include small four sided pyramidal crystals

(pseudo-octahedral) and thin plates. Commonly as crusts or (pseudo-octahedral) and thin plates. Commonly as crusts or films around altered molybdenite and as pseudomorphs films around altered molybdenite and as pseudomorphs after molybdenite. after molybdenite.

CleavageCleavage is distinct in four directions (bipyramidal). is distinct in four directions (bipyramidal). FractureFracture is uneven. is uneven. HardnessHardness is 3.5 - 4. is 3.5 - 4. Specific GravitySpecific Gravity is approximately 4.2 - 4.3 (heavy for is approximately 4.2 - 4.3 (heavy for

nonmetallic minerals). nonmetallic minerals). StreakStreak is white. is white. Other Characteristics: Other Characteristics: Fluorescent golden yellow. Fluorescent golden yellow.

Associated MineralsAssociated Minerals are quartz, zeolites, molybdenite are quartz, zeolites, molybdenite and lindgrenite. and lindgrenite.

Notable OccurrencesNotable Occurrences include the Peacock Lode, Seven include the Peacock Lode, Seven Devils district, Idaho (the type locality); Keewenaw Devils district, Idaho (the type locality); Keewenaw Peninsula, Michigan; Tungsten, Nevada; Superior, Arizona Peninsula, Michigan; Tungsten, Nevada; Superior, Arizona and Randsberg, California, USA; Nasik, India; Turkey; and Randsberg, California, USA; Nasik, India; Turkey; Russia; Scotland; Clayton Quarry, Panama Canal Zone, Russia; Scotland; Clayton Quarry, Panama Canal Zone, Panama and Morocco. Panama and Morocco.

Best Field IndicatorsBest Field Indicators are crystal habit, color, are crystal habit, color, fluorescence, association with molybdenite and cleavage. fluorescence, association with molybdenite and cleavage.

WulfeniteWulfenite Chemistry: PbMoOChemistry: PbMoO44, ,

Lead Molybdate Lead Molybdate Class: SulfatesClass: Sulfates Uses: A minor ore of Uses: A minor ore of

molybdenum and as molybdenum and as mineral specimens.mineral specimens.

Strong colors, nice luster Strong colors, nice luster and one-of-a-kind crystal and one-of-a-kind crystal habits attract the habits attract the attention of many attention of many collectors around the collectors around the world. world.

Physical PropertiesPhysical Properties ColorColor is red, orange, yellow, silver and white. is red, orange, yellow, silver and white. LusterLuster is vitreous. is vitreous. Transparency:Transparency: Crystals are transparent to translucent. Crystals are transparent to translucent. Crystal SystemCrystal System is tetragonal; 4/m or 4 is tetragonal; 4/m or 4 Crystal Habits include very thin square or octahedral include very thin square or octahedral

pinacoidal plates with pyramidal faces truncating just the pinacoidal plates with pyramidal faces truncating just the edges of the crystal. At times the pyramids become edges of the crystal. At times the pyramids become prominent and psuedo-dipyramidal crystal habits are seen, prominent and psuedo-dipyramidal crystal habits are seen, sometimes because of twinning. Prismatic faces are also sometimes because of twinning. Prismatic faces are also seen and can make psuedo-cubic crystals. Also encrusting seen and can make psuedo-cubic crystals. Also encrusting and cavernous aggregates due to intergrowth of crystal and cavernous aggregates due to intergrowth of crystal plates. plates.

CleavageCleavage is perfect in one direction. is perfect in one direction. FractureFracture is conchoidal. is conchoidal. HardnessHardness is 3. is 3. Specific GravitySpecific Gravity is approximately 6.8 (very heavy for is approximately 6.8 (very heavy for

translucent minerals) translucent minerals) StreakStreak is white. is white.

Associated MineralsAssociated Minerals are mimetite, limonite, smithsonite, are mimetite, limonite, smithsonite, vanadinite and galena.vanadinite and galena.

Other Characteristics:Other Characteristics: index of refraction is 2.28-2.40 index of refraction is 2.28-2.40 (very high, but typical of lead minerals). (very high, but typical of lead minerals).

Notable OccurencesNotable Occurences include Morocco; Tsumeb, Nambia; include Morocco; Tsumeb, Nambia; Mexico and Arizona and New Mexico, USA. Mexico and Arizona and New Mexico, USA.

Best Field IndicatorsBest Field Indicators are crystal habit, color, density and are crystal habit, color, density and luster. luster.

SILICATESSILICATES The silicate mineral class is of greater importance than any other for The silicate mineral class is of greater importance than any other for

about 25% of the known minerals and nearly 40% of the common ones about 25% of the known minerals and nearly 40% of the common ones are silicatesare silicates

Almost all the igneous rock-forming minerals are silicates and they Almost all the igneous rock-forming minerals are silicates and they constitute over 90% of the earth’s crustconstitute over 90% of the earth’s crust

Dominant minerals of the crust are silicates, oxides and other oxygen Dominant minerals of the crust are silicates, oxides and other oxygen compounds like carbonatescompounds like carbonates

The fundamental unit on which the structure of all silicates is based The fundamental unit on which the structure of all silicates is based consists of four Oconsists of four O-2-2 ions at the apices of a regular tetrahedron surrounding ions at the apices of a regular tetrahedron surrounding and coordinated by one Siand coordinated by one Si4+4+ at the centers. The bond is in part from the at the centers. The bond is in part from the attraction of oppositely charged ions, it also involves sharing of electrons attraction of oppositely charged ions, it also involves sharing of electrons (partly ionic and partly covalent)(partly ionic and partly covalent)

The sharing of oxygens may involve one, two, three or all four of the The sharing of oxygens may involve one, two, three or all four of the oxygen ions in the tetrahedron, giving rise to a diversity of structural oxygen ions in the tetrahedron, giving rise to a diversity of structural configurations configurations

SILICATESSILICATES SILICATE SUB-CLASSES:SILICATE SUB-CLASSES:

1.1. Nesosilicates or OrthosilicatesNesosilicates or Orthosilicates – silicates with independent – silicates with independent tetrahedral SiOtetrahedral SiO44 groups groups

2.2. SorosilicatesSorosilicates – silicates in which two SiO – silicates in which two SiO44 groups are linked groups are linked

3.3. Cyclosilicates or Ring silicatesCyclosilicates or Ring silicates – silicates with more than two of the – silicates with more than two of the SiOSiO44 tetrahedra are linked, forming closed ring-like structures tetrahedra are linked, forming closed ring-like structures

- Contains rings of linked SiO- Contains rings of linked SiO44 tetrahedra having a ratio of Si:O = 1:3 tetrahedra having a ratio of Si:O = 1:3

4.4. Inosilicates or Chain silicatesInosilicates or Chain silicates – tetrahedra are joined to form infinite – tetrahedra are joined to form infinite single chains with a unit composition SiOsingle chains with a unit composition SiO33 or infinite double chains or infinite double chains that give a ratio of Si:O = 4:11that give a ratio of Si:O = 4:11

5.5. Phylllosilicates or Sheet silicatesPhylllosilicates or Sheet silicates – three of the oxygens of a – three of the oxygens of a tetrahedron are shared between adjoining tetrahedra forming infinitely tetrahedron are shared between adjoining tetrahedra forming infinitely extending flat sheetsextending flat sheets

6.6. Tectosilicates or Framework silicatesTectosilicates or Framework silicates – all four oxygens of a SiO – all four oxygens of a SiO44 tetrahedron are shared by adjoining tetrahedra forming a three-tetrahedron are shared by adjoining tetrahedra forming a three-dimensional network of unit composition SiOdimensional network of unit composition SiO22

NesosilicatesNesosilicates

Nesosilicates (Greek, Nesosilicates (Greek, nesosnesos, island) are silicates where the SiO4 tetrahedra form isolated units. The silica , island) are silicates where the SiO4 tetrahedra form isolated units. The silica tetrahedra are radicals just like the carbonates or silicates. tetrahedra are radicals just like the carbonates or silicates.

The most abundant rock-forming The most abundant rock-forming minerals in the in the crust of the earth are the silicates. They are formed primarily of of the earth are the silicates. They are formed primarily of silicon and and oxygen, together with various , together with various metals. The fundamental unit of these minerals is the silicon-oxygen . The fundamental unit of these minerals is the silicon-oxygen tetrahedron. These tetrahedra have a pyramidal shape, with a relatively small, positively charged silicon cation tetrahedron. These tetrahedra have a pyramidal shape, with a relatively small, positively charged silicon cation (Si(Si+4+4) in the center and four larger, negatively charged oxygen anions (O) in the center and four larger, negatively charged oxygen anions (O−2−2) at the corners, producing a net ) at the corners, producing a net charge of −4. charge of −4. Aluminum cations (Al cations (Al+3+3) may substitute for silicon, and various anions such as hydroxyl (OH) may substitute for silicon, and various anions such as hydroxyl (OH−−) or ) or fluorine (Ffluorine (F−−) may substitute for oxygen. In order to form stable minerals, the charges that exist between ) may substitute for oxygen. In order to form stable minerals, the charges that exist between tetrahedra must be neutralized. This can be accomplished by the sharing of oxygen cations between tetrahedra, tetrahedra must be neutralized. This can be accomplished by the sharing of oxygen cations between tetrahedra, or by the binding together adjacent tetrahedra with various metal cations. This in turn creates characteristic or by the binding together adjacent tetrahedra with various metal cations. This in turn creates characteristic silicate structures that can be used to classify silicate minerals into cyclosilicates, inosilicates, nesosilicates, silicate structures that can be used to classify silicate minerals into cyclosilicates, inosilicates, nesosilicates, phyllosilicates, sorosilicates, and phyllosilicates, sorosilicates, and tectosilicates..

The simplest silicates are the nesosilicates, formed by individual silicon-oxygen tetrahedra. There is some The simplest silicates are the nesosilicates, formed by individual silicon-oxygen tetrahedra. There is some substitution of aluminum for silicon in the tetrahedra, but not as much as in other types of silicate minerals. The substitution of aluminum for silicon in the tetrahedra, but not as much as in other types of silicate minerals. The negatively charged, isolated tetrahedra in nesosilicates are held together by various metal cations. The garnet negatively charged, isolated tetrahedra in nesosilicates are held together by various metal cations. The garnet group of nesosilicates is commonly found in metamorphic rocks and more rarely in group of nesosilicates is commonly found in metamorphic rocks and more rarely in igneous rocks, and the metal , and the metal cations that are typically found in garnet minerals include aluminum, calcium, chromium, magnesium, cations that are typically found in garnet minerals include aluminum, calcium, chromium, magnesium, manganese, and manganese, and iron. Garnet minerals include almandine (Fe. Garnet minerals include almandine (Fe33AlAl22SiSi33OO1212), grossularite (Ca), grossularite (Ca33AlAl22SiSi33OO1212), and ), and uvarovite (Cauvarovite (Ca33CrCr22SiSi33OO1212). The minerals of the ). The minerals of the olivine group are nesosilicates commonly found in iron- and group are nesosilicates commonly found in iron- and magnesium-rich igneous rocks. The chemical formula of olivine is given as (Mg, Fe)magnesium-rich igneous rocks. The chemical formula of olivine is given as (Mg, Fe) 22SiOSiO44, but a complete solid , but a complete solid solution exists between the end-members forsterite (Mgsolution exists between the end-members forsterite (Mg22SiOSiO44) and fayalite (Fe) and fayalite (Fe22SiOSiO44). The nesosilicate mineral ). The nesosilicate mineral zircon (ZrSiOzircon (ZrSiO44) commonly forms in igneous rocks, and is so chemically stable that it becomes a common ) commonly forms in igneous rocks, and is so chemically stable that it becomes a common accessory mineral in many sediments and accessory mineral in many sediments and sedimentary rocks..

A group of A group of silicate minerals characterized by independent SiO minerals characterized by independent SiO44 tetrahedra with no shared oxygens. The structure with no shared oxygens. The structure is held together by bonding with interstitial cations. The group includes is held together by bonding with interstitial cations. The group includes olivine, , garnet, , sphene, , zircon, , staurolite, , chloritoid, , topaz, , chondrodite, and the Al, and the Al22SiOSiO55 polymorphs..

OlivineOlivine olivineolivine A major rock-forming A major rock-forming mineral group group

belonging to the belonging to the nesosilicates, forming a , forming a complete complete solid solution series between series between forsterite (Mgforsterite (Mg22SiOSiO44) and fayalite (Fe) and fayalite (Fe22SiOSiO44); sp. ); sp. gr. 3.22–4.39 increasing with increasing iron gr. 3.22–4.39 increasing with increasing iron content; content; hardness 6–7; 6–7; orthorhombic; usually ; usually olive-green, but white or yellowish in forsterite, olive-green, but white or yellowish in forsterite, brown or black in fayalite; colourless brown or black in fayalite; colourless streak; ; vitreous lustre; crystals rare, short, ; crystals rare, short, prismatic, , usually develops as granular aggregates; usually develops as granular aggregates; cleavage poor {010}; occurs in silica-poor, poor {010}; occurs in silica-poor, igneous rocks (e.g. rocks (e.g. basalt, , gabbro, , troctolite, , and and peridotite), extensively with ), extensively with pyroxene in in dunites, and in , and in stony meteorites and lunar and lunar basalts; alters readily to basalts; alters readily to serpentine during during weathering or weathering or hydrothermal alteration. alteration.

an iron-magnesium silicate mineral, (Mg,Fe) an iron-magnesium silicate mineral, (Mg,Fe) 22 SiO SiO 44 , crystallizing in the orthorhombic system. , crystallizing in the orthorhombic system. It is a common constituent of magnesium-rich, It is a common constituent of magnesium-rich, silica-poor igneous rocks; metamorphism of silica-poor igneous rocks; metamorphism of some high magnesium sediments also can form some high magnesium sediments also can form olivine. Dunite consists almost entirely of olivine. Dunite consists almost entirely of olivine. It also occurs in lunar rocks and olivine. It also occurs in lunar rocks and meteorites. Olivine has a characteristic yellow-meteorites. Olivine has a characteristic yellow-green to olive-green color, hence the name. green to olive-green color, hence the name. Transparent olivine of good color can be cut Transparent olivine of good color can be cut into gemstones; the gem form is known as into gemstones; the gem form is known as peridot. Sources of gem-quality olivine are St. peridot. Sources of gem-quality olivine are St. John's Island in the Red Sea, Myanmar, and John's Island in the Red Sea, Myanmar, and Arizona. Magnesium-rich olivine has a high Arizona. Magnesium-rich olivine has a high melting point and is used in the manufacture of melting point and is used in the manufacture of refractories. It was formerly called chrysolite. refractories. It was formerly called chrysolite.

Olivine structureOlivine structure At left is a polyhedral model of the At left is a polyhedral model of the

olivine structure. The oxygens are olivine structure. The oxygens are in a nearly close-packed in a nearly close-packed arrangement. Si tetrahedra cap arrangement. Si tetrahedra cap voids in the zigzag chains of Mg voids in the zigzag chains of Mg octahedra.octahedra.

Here is a ball model of the Here is a ball model of the structure. Blue atoms are oxygen, structure. Blue atoms are oxygen, magenta are silicon, and yellow are magenta are silicon, and yellow are magnesium.magnesium.

GarnetGarnet

Garnet name applied to a group of isomorphic minerals crystallizing in the cubic system. They Garnet name applied to a group of isomorphic minerals crystallizing in the cubic system. They are used chiefly as gems and as abrasives (as in garnet paper). The garnets are double are used chiefly as gems and as abrasives (as in garnet paper). The garnets are double silicates; one of the metallic elements is calcium, magnesium, ferrous iron, or manganese and silicates; one of the metallic elements is calcium, magnesium, ferrous iron, or manganese and the other aluminum, ferric iron, or chromium. Six varieties (of which there are also intermediate the other aluminum, ferric iron, or chromium. Six varieties (of which there are also intermediate forms) are distinguished according to composition—grossularite (calcium-aluminum), pyrope forms) are distinguished according to composition—grossularite (calcium-aluminum), pyrope (magnesium-aluminum), spessartite (manganese-aluminum), almandite (iron-aluminum), (magnesium-aluminum), spessartite (manganese-aluminum), almandite (iron-aluminum), andradite (calcium-iron), and uvarovite (calcium-chromium). Grossularite occurs commonly in a andradite (calcium-iron), and uvarovite (calcium-chromium). Grossularite occurs commonly in a red, green, yellow, or brown shade, depending on the impurities; if pure it would be colorless. red, green, yellow, or brown shade, depending on the impurities; if pure it would be colorless. The yellow and brown stones, coming chiefly from Sri Lanka, are used as gems under the The yellow and brown stones, coming chiefly from Sri Lanka, are used as gems under the names essonite (or hessonite) and cinnamon stone; sometimes they are miscalled hyacinth. names essonite (or hessonite) and cinnamon stone; sometimes they are miscalled hyacinth. Grossularite is found also in the Transvaal, in Mexico, and in Oregon. The most popular variety Grossularite is found also in the Transvaal, in Mexico, and in Oregon. The most popular variety of garnet is the ruby-red pyrope from Bohemia, S Africa, and Arizona, sold as Cape ruby and of garnet is the ruby-red pyrope from Bohemia, S Africa, and Arizona, sold as Cape ruby and Arizona ruby. Rhodolite, a mixture of pyrope and almandite from North Carolina, is rose-red or Arizona ruby. Rhodolite, a mixture of pyrope and almandite from North Carolina, is rose-red or purple. Spessartite, a brown to brownish-red garnet from Bavaria, Sri Lanka, and parts of the purple. Spessartite, a brown to brownish-red garnet from Bavaria, Sri Lanka, and parts of the United States, is seldom used for jewelry. Deep red, transparent almandite is the carbuncle; it United States, is seldom used for jewelry. Deep red, transparent almandite is the carbuncle; it was formerly a very popular gem. Almandites come chiefly from Brazil, India, and Sri Lanka; was formerly a very popular gem. Almandites come chiefly from Brazil, India, and Sri Lanka; Australia and parts of the United States are also important sources. Andradite, a very common Australia and parts of the United States are also important sources. Andradite, a very common variety, is usually some shade of red, black, brown, yellow, or green. Gem varieties include variety, is usually some shade of red, black, brown, yellow, or green. Gem varieties include topazolite, similar in color and transparency to topazolite, similar in color and transparency to topaz ; demantoid, a green variety with a high ; demantoid, a green variety with a high dispersion and adamantine luster, sometimes miscalled olivine and Uralian emerald; and black dispersion and adamantine luster, sometimes miscalled olivine and Uralian emerald; and black melanite. Demantoid is found in the Urals, and the other andradites come chiefly from Europe melanite. Demantoid is found in the Urals, and the other andradites come chiefly from Europe and the United States. Uvarovite, an emerald-green variety from Russia and Finland, is rarely and the United States. Uvarovite, an emerald-green variety from Russia and Finland, is rarely suitable for gem use. Garnet occurs in many different kinds of rocks—grossularite, in suitable for gem use. Garnet occurs in many different kinds of rocks—grossularite, in metamorphosed impure limestones; pyrope, in basic igneous rocks; spessartite, in granite rocks; metamorphosed impure limestones; pyrope, in basic igneous rocks; spessartite, in granite rocks; almandite, in schists and other metamorphic rocks as well as in igneous rocks; andradite, in almandite, in schists and other metamorphic rocks as well as in igneous rocks; andradite, in serpentine; and uvarovite, chiefly in serpentine. serpentine; and uvarovite, chiefly in serpentine.

The general formula of garnet is AThe general formula of garnet is A33BB22SiSi33OO1212, where A is a divalent cation (generally Mg, Fe, Mn , where A is a divalent cation (generally Mg, Fe, Mn or Ca) and B is trivalent (Usually Al, sometimes Feor Ca) and B is trivalent (Usually Al, sometimes Fe+3+3, Ti, or Cr). Since Ca is much larger in , Ti, or Cr). Since Ca is much larger in radius than the other divalent cations, there are are two series of garnets: one with calcium and radius than the other divalent cations, there are are two series of garnets: one with calcium and one without. one without.

GarnetGarnet An important rock-forming An important rock-forming mineral group, with the general formula group, with the general formula XX33YY22SiSi33OO1212, where X may be Ca, Mg, , where X may be Ca, Mg, FeFe2+2+, or Mn and Y may be Al, Fe, or Mn and Y may be Al, Fe3+3+, or , or CrCr3+3+; the main minerals are ; the main minerals are grossular (X (X =Mg, Y = Al), =Mg, Y = Al), pyrope (X = Mg, Y = Al), (X = Mg, Y = Al), almandine (X = Fe (X = Fe2+2+, Y = Al), , Y = Al), spessartine (X=Mn, Y=Al), (X=Mn, Y=Al), andradite (X (X = Ca, Y = Fe= Ca, Y = Fe3+3+), and ), and uvarovite (X = Ca, (X = Ca, Y = CrY = Cr3+3+), and there is continuous ), and there is continuous chemical variation in the group; an chemical variation in the group; an unusual variety called hydrogrossular unusual variety called hydrogrossular CaCa33AlAl22[SiO[SiO44]]22[SiO[SiO44]]1 − m1 − m (OH) (OH)4m4m has has hydroxyl ions in the structure and is hydroxyl ions in the structure and is found in the rare rock type found in the rare rock type rodingite; sp. ; sp. gr. 3.6–4.3; gr. 3.6–4.3; hardness 7.0–7.5; colour 7.0–7.5; colour very variable depending on its chemical very variable depending on its chemical composition, and can vary from shades composition, and can vary from shades of deep red-brown to almost black, of deep red-brown to almost black, green, white, yellow, and brown; usually green, white, yellow, and brown; usually vitreous lustre; ; crystals cubic, with the , with the most common form being most common form being dodecahedra; ; no no cleavage; found in high-grade ; found in high-grade metamorphic and and igneous rocks, in rocks, in beach beach sands, and , and alluvial placers. . Transparent pyrope crystals may be Transparent pyrope crystals may be used as used as gemstones, but garnet is more , but garnet is more generally used as an abrasive.generally used as an abrasive.

The Silica TetrahedraThe Silica Tetrahedra

Silica tetrahedra in the garnet unit cell. Silica tetrahedra in the garnet unit cell. Tetrahedra are darker with increasing Tetrahedra are darker with increasing distance below the plane of the diagram. distance below the plane of the diagram. With the visible face of the unit cell With the visible face of the unit cell defined as +1, and the opposite face as defined as +1, and the opposite face as zero, the tetrahedra around the four-fold zero, the tetrahedra around the four-fold screw axes have their central Si atoms screw axes have their central Si atoms at altitudes 0, 1/4, 1/2, and 3/4, and the at altitudes 0, 1/4, 1/2, and 3/4, and the pairs of tetrahedra at 3/8 and 7/8.pairs of tetrahedra at 3/8 and 7/8.

In the diagram above, it looks like there In the diagram above, it looks like there are two distinct sets of tetrahedra. In are two distinct sets of tetrahedra. In reality there are not. This diagram shows reality there are not. This diagram shows the rows of tetrahedra related by the the rows of tetrahedra related by the leftmost vertical screw axis. There are leftmost vertical screw axis. There are rows of tetrahedra parallel to all the unit rows of tetrahedra parallel to all the unit cell edges, all arranged around fourfold cell edges, all arranged around fourfold screw axes.screw axes.The apparently isolated pairs of The apparently isolated pairs of tetrahedra are really the same as those tetrahedra are really the same as those in the four-fold groups, merely viewed in the four-fold groups, merely viewed along their length instead of along their length instead of perpendicular to it.perpendicular to it.

The CationsThe Cations Divalent cations are in green, Divalent cations are in green,

trivalent in blue. As we can see from trivalent in blue. As we can see from the end-on rows, each row of the end-on rows, each row of tetrahedra lies along a twofold tetrahedra lies along a twofold symmetry axis. Divalent cations lie symmetry axis. Divalent cations lie on the twofold axes midway on the twofold axes midway between tetrahedra. For example, between tetrahedra. For example, consider the topmost two yellow consider the topmost two yellow tetrahedra, which lie on a horizontal tetrahedra, which lie on a horizontal two-fold axis. Their corresponding two-fold axis. Their corresponding divalent ion is halfway between divalent ion is halfway between them, superposed on the orange them, superposed on the orange tetrahedron.tetrahedron.

The divalent cations shown The divalent cations shown superposed on the yellow tetrahedra superposed on the yellow tetrahedra are at altitude 5/4 and are above the are at altitude 5/4 and are above the unit cell. The corresponding unit cell. The corresponding tetrahedra are not shown but they lie tetrahedra are not shown but they lie directly above the tetrahedra at directly above the tetrahedra at altitude 1/4.altitude 1/4.

The trivalent cations are between The trivalent cations are between tetrahedra at different elevations. tetrahedra at different elevations.

The Trivalent CationsThe Trivalent Cations The trivalent cations are easiest to The trivalent cations are easiest to

visualize because they are visualize because they are octahedrally coordinated with octahedrally coordinated with oxygen. Since the symmetry is oxygen. Since the symmetry is isometric, this view is isometric, this view is simultaneously a top view and a simultaneously a top view and a side view. We can see that there is side view. We can see that there is one set of trivalent ions at altitudes one set of trivalent ions at altitudes 0, 1/2 and +1, and another at 1/4 0, 1/2 and +1, and another at 1/4 and 3/4.and 3/4.

The light blue octahedra are at The light blue octahedra are at altitude 1/2, the dark blue altitude 1/2, the dark blue octahedra are at 1/4.octahedra are at 1/4.

The Divalent CationsThe Divalent Cations The coordination of the divalent The coordination of the divalent

cations is harder to see. They are cations is harder to see. They are in eight-fold coordination with in eight-fold coordination with oxygen, but the bond lengths and oxygen, but the bond lengths and angles are not uniform and the angles are not uniform and the resulting coordination polyhedra resulting coordination polyhedra are not simple. The simplest are not simple. The simplest visualization is to regard the visualization is to regard the polyhedra as cubes with warped polyhedra as cubes with warped faces.faces.

This diagram shows the distorted This diagram shows the distorted cube coordination polyhedra for cube coordination polyhedra for the divalent cations.the divalent cations.

Sphene (Titanite)Sphene (Titanite) sphene (titanite)sphene (titanite) A A nesosilicate

CaTiSiOCaTiSiO44 (O,OH,F); sp. gr. 3.45– (O,OH,F); sp. gr. 3.45–3.55; 3.55; hardness 5; 5; crystals wedge- wedge-shaped, occasionally shaped, occasionally massive; ; brown, grey, reddish brown, yellow, brown, grey, reddish brown, yellow, or black; or black; monoclinic; ; adamantine to to resinous lustre; occurs as a primary ; occurs as a primary accessory mineral in in calc-alkaline igneous rocks and alkaline igneous rocks and alkaline igneous rocks in which it may occur as a rocks in which it may occur as a major constituent along with major constituent along with apatite, , nepheline, and , and aegirine. It is . It is common in common in contact metamorphosed metamorphosed limestones, , particularly particularly skarns..

Titanite StructureTitanite Structure The structure of titanite or sphene is not too The structure of titanite or sphene is not too

complex but most mineralogy texts provide complex but most mineralogy texts provide illustrations that are unclear and overly illustrations that are unclear and overly complicated. The fundamental structure complicated. The fundamental structure consists of octahedra with titanium atoms at consists of octahedra with titanium atoms at the center and oxygens at each vertex. the center and oxygens at each vertex. They share oxygens at opposite corners. They share oxygens at opposite corners. Gaps between neighboring octahedra are Gaps between neighboring octahedra are bridged by silica tetrahedra so the bridged by silica tetrahedra so the octahedral chains zigzag.octahedral chains zigzag.For each octahedron there is a tetrahedron For each octahedron there is a tetrahedron so the number of silicon and titanium atoms so the number of silicon and titanium atoms is equal.is equal.

The calcium atoms fill the gaps between The calcium atoms fill the gaps between the chains. The interstices between the the chains. The interstices between the chains are irregular and surrounded by chains are irregular and surrounded by seven oxygen atoms (gray). Five of them seven oxygen atoms (gray). Five of them make a roughly coplanar cage and the make a roughly coplanar cage and the remaining two are above and below the remaining two are above and below the plane of the diagram. It's a cage with wide plane of the diagram. It's a cage with wide openings, but still effective. The openings, but still effective. The neighboring chains do not quite line up, so neighboring chains do not quite line up, so the mineral actually has monoclinic the mineral actually has monoclinic symmetry.symmetry.The calcium atoms are in purple with the The calcium atoms are in purple with the shade indicating two different levels.shade indicating two different levels.

ZirconZircon zirconzircon Mineral, ZrSiO Mineral, ZrSiO44; sp. gr. 4.6; ; sp. gr. 4.6; hardness 7.5; 7.5;

tetragonal; most commonly light brown or reddish-; most commonly light brown or reddish-brown, but sometimes grey, yellow, or green; vitreous brown, but sometimes grey, yellow, or green; vitreous lustre; crystals usually square ; crystals usually square prisms with bipyramidal with bipyramidal terminations; terminations; cleavage prismatic, indistinct {110} and , indistinct {110} and poor {111}; one of the most widely distributed poor {111}; one of the most widely distributed accessory minerals in in igneous rocks (e.g. rocks (e.g. granite, , syenite, and , and pegmatites), when the crystals can be ), when the crystals can be quite large, also occurs in quite large, also occurs in metamorphic rocks (e.g. (e.g. gneisses and and schists), and concentrated in ), and concentrated in detrital beach and river beach and river sands. It is the main source of . It is the main source of zirconium metal. Common zircon is used extensively zirconium metal. Common zircon is used extensively in the foundry industry.in the foundry industry.

ZirconZircon is a is a mineral belonging to the group of belonging to the group of nesosilicates. Its chemical name is . Its chemical name is zirconium silicate and its corresponding chemical formula is and its corresponding chemical formula is ZrSiO44. . Hafnium is almost always present in quantities is almost always present in quantities ranging from 1 to 4%. The crystal structure of zircon is ranging from 1 to 4%. The crystal structure of zircon is tetragonal crystal system. The natural color of zircon . The natural color of zircon varies between colorless, yellow-golden, red, brown, varies between colorless, yellow-golden, red, brown, and green. Colorless specimens that show gem and green. Colorless specimens that show gem quality are a popular substitute for quality are a popular substitute for diamond; these ; these specimens are also known as "Matura diamond". It is specimens are also known as "Matura diamond". It is not to be confused with not to be confused with cubic zirconia, a synthetic , a synthetic substance with a completely different chemical substance with a completely different chemical composition.composition.

The name either derives from the The name either derives from the Arabic word word zarqunzarqun, , meaning meaning vermilion, or from the , or from the Persian zargunzargun, , meaning golden-colored. These words are corrupted meaning golden-colored. These words are corrupted into "into "jargoon", a term applied to light-colored zircons. ", a term applied to light-colored zircons. Yellow zircon is called Yellow zircon is called hyacinthhyacinth, from the flower , from the flower hyacinthus, whose name is of Ancient Greek origin; in , whose name is of Ancient Greek origin; in the Middle Ages all yellow stones of East Indian origin the Middle Ages all yellow stones of East Indian origin were called hyacinth, but today this term is restricted were called hyacinth, but today this term is restricted to the yellow zircons.to the yellow zircons.

Zircon StructureZircon Structure The zircon structure seen from the top, The zircon structure seen from the top,

looking along the c axis. Silica tetrahedra looking along the c axis. Silica tetrahedra are in blue, zirconium atoms in orange, are in blue, zirconium atoms in orange, with darker hues for increasing distance. with darker hues for increasing distance. The coordination polyhedron for the The coordination polyhedron for the central zirconium atom is shown in central zirconium atom is shown in purple.purple.

The zircon structure seen from the side, The zircon structure seen from the side, looking perpendicular to the c axis. Silica looking perpendicular to the c axis. Silica tetrahedra are in blue, zirconium atoms tetrahedra are in blue, zirconium atoms in orange, with darker hues for increasing in orange, with darker hues for increasing distance. The silica tetrahedra are distance. The silica tetrahedra are slightly skewed for perspective, but are slightly skewed for perspective, but are really symmetrical about the faces. really symmetrical about the faces. Silicon atoms are in green .The Silicon atoms are in green .The coordination polyhedron for the central coordination polyhedron for the central zirconium atom is shown in purple. The zirconium atom is shown in purple. The central zirconium atom, which is inside central zirconium atom, which is inside the purple polyhedron, is outlined in gray.the purple polyhedron, is outlined in gray.

StauroliteStaurolite staurolitestaurolite A member of the and an important metamorphic A member of the and an important metamorphic

index mineral wit wit nesosilicates h the approximate composition h the approximate composition (Fe(Fe22+,Mg)+,Mg)22(Al,Fe(Al,Fe33+)+)99OO66[Si[Si44OO1616](O,OH)](O,OH)22; sp. gr. 3.74–3.85; ; sp. gr. 3.74–3.85; hardness

7.5; 7.5; monoclinic; ; crystals prismatic; shades of brown; occurs in ; shades of brown; occurs in regionally metamorphosed schists and and gneisses, such as iron-rich , such as iron-rich pelites, with a high Fe, with a high Fe33+/Fe+/Fe22+ ratio at moderate grades of + ratio at moderate grades of metamorphism and in association with and in association with garnet ( (almandine) and ) and kyanite; it may develop from ; it may develop from chloritoid as the metamorphic grade increases. as the metamorphic grade increases.

is a red brown to black, mostly opaque, is a red brown to black, mostly opaque, nesosilicate mineral with a with a white streak. It crystallizes in the white streak. It crystallizes in the monoclinic crystal system, has a crystal system, has a Mohs hardness of 7 to 7.5 and a rather complex chemical formula: ( of 7 to 7.5 and a rather complex chemical formula: (Fe,,Mg,,Zn))22Al99((Si,Al),Al)44O2020(O(OH))44. . Iron, , magnesium and and zinc occur in variable occur in variable

ratios.ratios. A special property of staurolite is that it often occurs A special property of staurolite is that it often occurs twinned in a in a

characteristic cross-shape. In handsamples, macroscopically visible characteristic cross-shape. In handsamples, macroscopically visible staurolite staurolite crystals are of prismatic shape. They are often larger than are of prismatic shape. They are often larger than the surrounding minerals and are then called the surrounding minerals and are then called porphyroblasts..

In In thin sections staurolite is commonly staurolite is commonly twinned and shows lower first and shows lower first order birefringence similar to order birefringence similar to quartz, with the twinning displaying , with the twinning displaying optical continuity. It can be identified in metamorphic rocks by its optical continuity. It can be identified in metamorphic rocks by its swiss cheese appearance (with appearance (with poikilitic quartz) and often manteld ) and often manteld porphyroblastic character.porphyroblastic character.

The name is derived from the The name is derived from the Greek, , staurosstauros for cross and for cross and lithoslithos for for stone in reference to the common twinning. Staurolite is a stone in reference to the common twinning. Staurolite is a regional metamorphic mineral of intermediate to high grade. It occurs mineral of intermediate to high grade. It occurs with almandine with almandine garnet, , micas, , kyanite and other metamorphic and other metamorphic minerals.minerals.

It is the It is the official state mineral of the of the U.S. state of of Georgia.. Staurolite is one of the index minerals that are used to estimate the Staurolite is one of the index minerals that are used to estimate the

temperature, depth, and pressure at which a rock undergoes temperature, depth, and pressure at which a rock undergoes metamorphism.metamorphism.

Staurolite StructureStaurolite Structure The staurolite structure consists The staurolite structure consists

of oxygen atoms in an of oxygen atoms in an approximately cubic close approximately cubic close packing. However, the cation packing. However, the cation arrangement does do not have arrangement does do not have cubic symmetry. The structure cubic symmetry. The structure consists of dioctahedral sheets consists of dioctahedral sheets joined by isolated octahedra. joined by isolated octahedra. Silica tetrahedra fill the gaps Silica tetrahedra fill the gaps between octahedra.between octahedra.

ChloritoidChloritoid chloritoid (ottrelite)chloritoid (ottrelite) A member of the A member of the

nesosilicates with the formula (Fe with the formula (Fe2+2+,Mg),Mg)(Al,Fe(Al,Fe3+3+)Al)Al33OO22[SiO[SiO44]]22(OH)(OH)44 and an and an important metamorphic important metamorphic index mineral; sp. ; sp. gr. 3.51–3.80; gr. 3.51–3.80; hardness 6.5; 6.5; monoclinic or or triclinic; ; crystals tabular, , pseudohexagonal; dark green to black; pseudohexagonal; dark green to black; occurs in occurs in regionally metamorphosed pelites with a high Fe with a high Fe3+3+: Fe: Fe2+2+ ratio at low ratio at low metamorphic grades; it develops at the metamorphic grades; it develops at the same time as same time as biotite and changes to and changes to staurolite with increasing temperature with increasing temperature and pressure.and pressure.

ChloritoidChloritoid is a is a silicate mineral of mineral of metamorphic origin. It is an origin. It is an iron magnesium manganese alumino-silicate -silicate hydroxide with formula: ( with formula: (Fe,,Mg,,Mn))22Al44Si22O

1010(O(OH))44. It occurs as greenish grey to . It occurs as greenish grey to black platy black platy micaceous triclinic crystals and and foliated masses. Its masses. Its Mohs hardness is 6.5, unusually high for a platy mineral, is 6.5, unusually high for a platy mineral, and it has a and it has a specific gravity of 3.52 to of 3.52 to 3.57. It typically occurs in 3.57. It typically occurs in phyllites, , schists and and marbles..

It was first described in 1837 from It was first described in 1837 from localities in the localities in the Ural Mountains region of region of Russia..

TopazTopaz topaztopaz A nesosilicate mineral, A nesosilicate mineral,

AlAl22SiOSiO44(OH,F)(OH,F)22; sp. gr. 3.5–3.6; ; sp. gr. 3.5–3.6; hardness 8; 8; orthorhombic; ; colourless, pale yellow, pale blue, colourless, pale yellow, pale blue, yellowish, or sometimes pink; often yellowish, or sometimes pink; often transparent; vitreous transparent; vitreous lustre; crystals ; crystals are are prismatic and often and often bipyramidal with the vertical faces striated, but it with the vertical faces striated, but it can also be can also be massive and granular; and granular; cleavage perfect basal {001}; perfect basal {001}; typically occurs in typically occurs in granite pegmatites, , rhyolite, and , and quartz veins, and veins, and extensively as an extensively as an accessory mineral in granites, associated with in granites, associated with fluorite, , tourmaline, , beryl, and , and cassiterite, , also in also in alluvial deposits. It is deposits. It is associated with pneumatolytic action associated with pneumatolytic action (see (see PNEUMATOLYSIS) and is a ) and is a constituent of greisen. The original constituent of greisen. The original cairngorms (see cairngorms (see QUARTZ) were ) were topaz crystals. It is named after topaz crystals. It is named after Topazos Island in the Red Sea.Topazos Island in the Red Sea.

Topaz StructureTopaz Structure Topaz (AlTopaz (Al22SiOSiO44(OH,F)(OH,F)22) is an ) is an

aluminosilicate with one oxygen aluminosilicate with one oxygen replaced by two hydroxyl or fluorine replaced by two hydroxyl or fluorine atoms. The structure consists of atoms. The structure consists of close-packed layers in an ABAC close-packed layers in an ABAC stacking. Zigzag aluminum stacking. Zigzag aluminum octahedral chains are joined by octahedral chains are joined by silica tetrahedra. In the polyhedral silica tetrahedra. In the polyhedral models below, the red spheres models below, the red spheres denote hydroxyl or fluorine. The denote hydroxyl or fluorine. The first model shows the zigzag first model shows the zigzag chains, the second a larger piece of chains, the second a larger piece of the structure.the structure.

chondroditechondrodite ChondroditeChondrodite is a is a nesosilicate mineral

with formula (Mg,Fe)with formula (Mg,Fe)55(F,OH)(F,OH)22(SiO(SiO44))22. . Although it is itself a fairly rare mineral Although it is itself a fairly rare mineral it is the most frequently encountered it is the most frequently encountered member of the member of the humite group of group of minerals. It is formed in minerals. It is formed in hydrothermal deposits from locally metamorphosed deposits from locally metamorphosed dolomite. It is also found associated . It is also found associated with with skarn and and serpentine..

It was discovered in 1817 on Mt It was discovered in 1817 on Mt Somma, part of the Somma, part of the Vesuvius complex complex in in Italy..

chondroditechondrodite Member of the humite Member of the humite group of minerals. The group includes group of minerals. The group includes humite, clinohumite, and norbergite; humite, clinohumite, and norbergite; general formula is general formula is nnMgMg22[SiO[SiO44]Mg(OH,F)]Mg(OH,F)22, with , with nn = 1 in = 1 in norbergite, 2 in chondrodite, 3 in norbergite, 2 in chondrodite, 3 in humite, and 4 in clinohumite; related humite, and 4 in clinohumite; related to the to the olivine group; occurs in contact group; occurs in contact metamorphic zones (see metamorphic zones (see CONTACT METAMORPHISM) of ) of limestones and and skarns..

SorosilicatesSorosilicates Sorosilicates are Sorosilicates are silicate minerals which have isolated double which have isolated double

tetrahedra groups with (Sitetrahedra groups with (Si22OO77))6−6− or a ratio of 2:7. or a ratio of 2:7. Sorosilicates are silicate minerals characterized by the linkage of two Sorosilicates are silicate minerals characterized by the linkage of two

silica tetrahedra by the sharing of one oxygen atom. The silicon:oxygen silica tetrahedra by the sharing of one oxygen atom. The silicon:oxygen ratio is 2:7.ratio is 2:7.

Sorosilicates (Greek Sorosilicates (Greek sorossoros, urn) contain units made up of two , urn) contain units made up of two tetrahedra that share an oxygen. The resulting formula for this unit is tetrahedra that share an oxygen. The resulting formula for this unit is Si2O7.Si2O7.

Sorosilicates have two silicate tetrahedrons that are linked by one Sorosilicates have two silicate tetrahedrons that are linked by one oxygen ion and thus the basic chemical unit is the anion group (Si2O7) oxygen ion and thus the basic chemical unit is the anion group (Si2O7) with a negative six charge (-6). This structure forms an unusual with a negative six charge (-6). This structure forms an unusual hourglass-like shape and it may be due to this oddball structure that hourglass-like shape and it may be due to this oddball structure that this subclass has so few common members in comparison with all the this subclass has so few common members in comparison with all the other silicate subclasses. It includes minerals that may also contain other silicate subclasses. It includes minerals that may also contain normal silicate tetrahedrons as well as the double tetrahedrons. The normal silicate tetrahedrons as well as the double tetrahedrons. The more complex members of this group, such as Epidote, contain chains more complex members of this group, such as Epidote, contain chains of aluminum oxide tetrahedrons being held together by the individual of aluminum oxide tetrahedrons being held together by the individual silicate tetrahedrons and double tetrahedrons. Most members of this silicate tetrahedrons and double tetrahedrons. Most members of this group are rare, but epidote is widespread in many metamorphic group are rare, but epidote is widespread in many metamorphic environments. environments.

SorosilicatesSorosilicates Below are the more common members of the sorosilicates:Below are the more common members of the sorosilicates: AkatoreiteAkatoreite (Manganese Iron Aluminum Silicate Hydroxide)(Manganese Iron Aluminum Silicate Hydroxide) AkermaniteAkermanite (Calcium Magnesium Silicate)(Calcium Magnesium Silicate) AminoffiteAminoffite (Calcium Beryllium Silicate Hydroxide)(Calcium Beryllium Silicate Hydroxide) AndremeyeriteAndremeyerite (Barium Iron Manganese Magnesium Silicate)(Barium Iron Manganese Magnesium Silicate) Androsite-(La)Androsite-(La) (Manganese Calcium Lanthanum Cerium Neodymium (Manganese Calcium Lanthanum Cerium Neodymium

Aluminum Silicate Oxide Hydroxide)Aluminum Silicate Oxide Hydroxide) ArdenniteArdennite (Manganese Calcium Magnesium Aluminum Iron Arsenic (Manganese Calcium Magnesium Aluminum Iron Arsenic

Vanadate Phosphate Silicate Hydroxide)Vanadate Phosphate Silicate Hydroxide) BafertisiteBafertisite (Barium Iron Manganese Titanium Silicate Oxide Hydroxide)(Barium Iron Manganese Titanium Silicate Oxide Hydroxide) BaghdaditeBaghdadite (Hydrated Calcium Zirconium Titanium Silicate)(Hydrated Calcium Zirconium Titanium Silicate) BaryliteBarylite (Barium Beryllium Silicate)(Barium Beryllium Silicate) BarysiliteBarysilite (Lead Manganese Silicate)(Lead Manganese Silicate)

BarytolamprophylliteBarytolamprophyllite (Sodium Potassium Barium Calcium (Sodium Potassium Barium Calcium Strontium Titanium Iron Silicate Hydroxide)Strontium Titanium Iron Silicate Hydroxide)

BelkoviteBelkovite (Barium Niobium Titanium Silicate Fluoride)(Barium Niobium Titanium Silicate Fluoride) Bertrandite (Beryllium Silicate Hydroxide)(Beryllium Silicate Hydroxide) BornemaniteBornemanite (Barium Sodium Titanium Niobium Silicate (Barium Sodium Titanium Niobium Silicate

Phosphate Fluoride Oxide)Phosphate Fluoride Oxide) BurpaliteBurpalite (Sodium Calcium Zirconium Silicate)(Sodium Calcium Zirconium Silicate) Chevkinite-(Ce)Chevkinite-(Ce) (Cerium Lanthanum Calcium Sodium (Cerium Lanthanum Calcium Sodium

Thorium Iron Magnesium Titanium Silicate)Thorium Iron Magnesium Titanium Silicate) ClinophosinaiteClinophosinaite (Sodium Calcium Phosphate Silicate)(Sodium Calcium Phosphate Silicate) CuspidineCuspidine (Calcium Silicate Fluoride Hydroxide)(Calcium Silicate Fluoride Hydroxide) Danburite

(Calcium Boro-Silicate)(Calcium Boro-Silicate) DavreuxiteDavreuxite (Manganese Aluminum Silicate Hydroxide)(Manganese Aluminum Silicate Hydroxide) DelindeiteDelindeite (Sodium Potassium Barium Calcium Titanium Iron (Sodium Potassium Barium Calcium Titanium Iron

Aluminum Silicate Hydroxide)Aluminum Silicate Hydroxide) EdgarbaileyiteEdgarbaileyite (Mercury Silicate)(Mercury Silicate)

AllaniteAllanite Allanite-(Ce) was first noted at Franklin by Jackson Allanite-(Ce) was first noted at Franklin by Jackson

(1850a) and later reported by Hunt (1861). (1850a) and later reported by Hunt (1861). Subsequent studies by Eakle (1894a, 1894b) Subsequent studies by Eakle (1894a, 1894b) provided much of the extant data, as reviewed by provided much of the extant data, as reviewed by Palache (1935). It has not been reported from Palache (1935). It has not been reported from Sterling Hill.Sterling Hill.

DescriptionDescription Allanite-(Ce) occurs as euhedral crystals, up to 25 Allanite-(Ce) occurs as euhedral crystals, up to 25

mm in length, and tabular or bladed (Figures 16-1 mm in length, and tabular or bladed (Figures 16-1 and 16-2). The color is invariably black; the and 16-2). The color is invariably black; the cleavages are imperfect to good; the luster is cleavages are imperfect to good; the luster is vitreous; and the density is 3.84 g/cmvitreous; and the density is 3.84 g/cm33. The crystals . The crystals are extremely brittle, and few survive attempts to are extremely brittle, and few survive attempts to extricate them from matrix. Optically, it is nearly extricate them from matrix. Optically, it is nearly opaque, brown in thin fragments, and strongly opaque, brown in thin fragments, and strongly pleochroic, with a mean index of refraction of 1.74.pleochroic, with a mean index of refraction of 1.74.

CompositionComposition Allanite-(Ce), a calcium cerium aluminum iron silicate Allanite-(Ce), a calcium cerium aluminum iron silicate

hydroxide mineral of the epidote group, has been little hydroxide mineral of the epidote group, has been little studied. The analysis of Hunt (1861) reported by studied. The analysis of Hunt (1861) reported by Palache (1935) and the partial analysis given by Palache (1935) and the partial analysis given by Frondel (1964) both show cerium (Ce) to be the Frondel (1964) both show cerium (Ce) to be the dominant REE element in Franklin material. Several dominant REE element in Franklin material. Several semi-quantitative analyses by the writer confirm this. All semi-quantitative analyses by the writer confirm this. All of these data are for the large euhedral allanites of these data are for the large euhedral allanites described below.described below.

Occurrence and paragenesisOccurrence and paragenesis Allanite, unstudied as to REE-dominance, also occurs Allanite, unstudied as to REE-dominance, also occurs

in an altered assemblage reported by Dunn in an altered assemblage reported by Dunn et al.et al. (1984a) as altered 1-3 mm crystals with burn-haloes in (1984a) as altered 1-3 mm crystals with burn-haloes in the surrounding minerals and associated with the surrounding minerals and associated with wollastonite, microcline, minehillite, margarosanite, and wollastonite, microcline, minehillite, margarosanite, and other minerals.other minerals.

Palache (1935) mentioned the occurrence of allanite on Palache (1935) mentioned the occurrence of allanite on the dumps of the local nearby iron mines; this material the dumps of the local nearby iron mines; this material has not been studied by the writer.has not been studied by the writer.

Name Allanite Name Allanite (Orthite)Chemistry (Ce,Ca,Y)2(Al,Fe3+)3[OH|(Orthite)Chemistry (Ce,Ca,Y)2(Al,Fe3+)3[OH|(SiO4)3]Hardness 5.5Lustre vitreous - (SiO4)3]Hardness 5.5Lustre vitreous - greasyColour brown, reddish brown or greasyColour brown, reddish brown or blackStreak greyish brown Density [g/cm3] 3.3 -blackStreak greyish brown Density [g/cm3] 3.3 -3.7Crystal habit monoclinic, crystals prismatic or 3.7Crystal habit monoclinic, crystals prismatic or tabularCleavage, Fracture [001], [100] imperfect, tabularCleavage, Fracture [001], [100] imperfect, fracture conchoidalother characteristics and fracture conchoidalother characteristics and occurrences accessory mineral in acid magmatic occurrences accessory mineral in acid magmatic rocks such as granites, syenites, diorites, in rocks such as granites, syenites, diorites, in pegmatites as well as in metamorphic rocks pegmatites as well as in metamorphic rocks (schists, limestone)(schists, limestone)

CLINOZOISITECLINOZOISITE CaCa22AlAl33(Si(Si22OO77)(SiO)(SiO44)(O,OH))(O,OH)22

MonoclinicMonoclinic Clinozoisite, a calcium aluminum silicate hydroxide Clinozoisite, a calcium aluminum silicate hydroxide

mineral of the epidote group, is largely unstudied. It mineral of the epidote group, is largely unstudied. It was reported from Franklin by Palache (1928a), but was reported from Franklin by Palache (1928a), but that material was later shown by Bauer and Berman that material was later shown by Bauer and Berman (1930) to be chlorophoenicite. It was subsequently (1930) to be chlorophoenicite. It was subsequently found in 1981 on the 1400 level in the Sterling Mine found in 1981 on the 1400 level in the Sterling Mine occurring as a green massive mineral, associated occurring as a green massive mineral, associated with amphibole, titanite, calcite, diopside, and a with amphibole, titanite, calcite, diopside, and a possible hydromica. Later that year it was again possible hydromica. Later that year it was again encountered at Sterling Hill, in the 935 stope, on the encountered at Sterling Hill, in the 935 stope, on the 500 level, as a pale violet mixture of clinozoisite and 500 level, as a pale violet mixture of clinozoisite and plagioclase, associated with diopside and calcite. plagioclase, associated with diopside and calcite. There are no detailed studies of these occurrences. There are no detailed studies of these occurrences.

Name Clinozoisit Name Clinozoisit Chemistry Ca2(Al,Fe)Al2[O|OH|SiO4|Chemistry Ca2(Al,Fe)Al2[O|OH|SiO4|Si2O7]Hardness 7ustre vitreousColour greenSi2O7]Hardness 7ustre vitreousColour green, grey, yellowish green, light green, , grey, yellowish green, light green, colourlessStreak greyish white Density colourlessStreak greyish white Density [g/cm3] 3.3 - 3.5Crystal habit monoclinic, [g/cm3] 3.3 - 3.5Crystal habit monoclinic, crystals prismatic, striated lengthwise, also crystals prismatic, striated lengthwise, also rounded grainsCleavage, Fracture [001] rounded grainsCleavage, Fracture [001] perfect, fracture conchoidal to splinteryother perfect, fracture conchoidal to splinteryother characteristics and occurrences characteristics and occurrences pistacitepistacite = = Fe-rich, green Fe-rich, green clinozoisiteclinozoisite = Fe-poor, grey = Fe-poor, grey contact pneumatolytic mineral, formed by contact pneumatolytic mineral, formed by thermal decay of Al- and Ca-containing thermal decay of Al- and Ca-containing silicates (feldspar, silicates (feldspar, hornblende))

EpidoteEpidote EPIDOTEEPIDOTE CaCa22(Al,Fe(Al,Fe3+3+))33(Si(Si22OO77)(SiO)(SiO44)(O,OH))(O,OH)22

MonoclinicMonoclinic Epidote, a calcium iron aluminum silicate hydroxide mineral, is relatively rare Epidote, a calcium iron aluminum silicate hydroxide mineral, is relatively rare

at Franklin. Nuttall (1822) reported it as a laminated green mineral with at Franklin. Nuttall (1822) reported it as a laminated green mineral with garnet, and Palache (1935) reported it from the contacts of the ore and garnet, and Palache (1935) reported it from the contacts of the ore and calcium silicate units. It is invariably greenish and occurs in 1-7 mm calcium silicate units. It is invariably greenish and occurs in 1-7 mm prismatic crystals, but has not been much studied.prismatic crystals, but has not been much studied.

Few assemblages have provided decent specimens or crystals. One such Few assemblages have provided decent specimens or crystals. One such occurrence consists of blackish-green hedenbergite, calcite, pyrite, occurrence consists of blackish-green hedenbergite, calcite, pyrite, andradite, ferroaxinite, and fluorapophyllite from the Palmer Shaft at andradite, ferroaxinite, and fluorapophyllite from the Palmer Shaft at Franklin, and is described under fluorapophyllite (Betancourt, 1989). A Franklin, and is described under fluorapophyllite (Betancourt, 1989). A second notable, but sparse occurrence is of superb greenish-brown, second notable, but sparse occurrence is of superb greenish-brown, euhedral 2-5 mm crystals, in sprays associated with franklinite, rhodonite, euhedral 2-5 mm crystals, in sprays associated with franklinite, rhodonite, willemite, and johannsenite, and discussed herein with the johannsenite willemite, and johannsenite, and discussed herein with the johannsenite which occurs epitactic on rhodonite from Franklin. An analysis of these latter which occurs epitactic on rhodonite from Franklin. An analysis of these latter crystals is presented in Table 7, showing minimal substitution of Mn and Zn crystals is presented in Table 7, showing minimal substitution of Mn and Zn and a composition approximating that of end-member epidote, with Al:Fe = and a composition approximating that of end-member epidote, with Al:Fe = 2:1. Specimens of epidote replacing scapolite are in some museum 2:1. Specimens of epidote replacing scapolite are in some museum collections, but their source is ambiguous. Microcline is commonly collections, but their source is ambiguous. Microcline is commonly associated. associated.

At Sterling Hill, epidote was found as 4-5 mm crystals At Sterling Hill, epidote was found as 4-5 mm crystals associated with stilbite and manganaxinite on the 1300 associated with stilbite and manganaxinite on the 1300 level, and it is locally associated with tennantite, level, and it is locally associated with tennantite, actinolite, erythrite, and other minerals in various parts actinolite, erythrite, and other minerals in various parts of the mine. An occurrence in a veinlet assemblage in of the mine. An occurrence in a veinlet assemblage in wollastonite-bearing rocks was described by Jenkins wollastonite-bearing rocks was described by Jenkins (1994). (1994).

Epidote is very common in the mines at Balls Hill, Epidote is very common in the mines at Balls Hill, especially the Gooseberry Mine, where it occurs in 10-especially the Gooseberry Mine, where it occurs in 10-cm masses associated with andradite, magnetite, and cm masses associated with andradite, magnetite, and hedenbergite.hedenbergite.

HancockiteHancockite HANCOCKITEHANCOCKITE CaPb(Al,FeCaPb(Al,Fe3+3+))33(Si(Si22OO77)(SiO)(SiO44)(O,OH))(O,OH)22

Monoclinic, Monoclinic, PP2211//mm, , aa = 8.958, = 8.958, bb = 5.665, = 5.665, c c = 10.304 = 10.304 Å, Å, b = 114.4b = 114.4oo, Z = 2., Z = 2.

Hancockite was originally described by Penfield and Hancockite was originally described by Penfield and Warren (1899). Paragenetical information was Warren (1899). Paragenetical information was provided by Hurlbut and Baum (1960). Additional provided by Hurlbut and Baum (1960). Additional chemical data, obtained on single crystals, was chemical data, obtained on single crystals, was given by Dunn (1985b). Although reported from given by Dunn (1985b). Although reported from Norway by Neumann (1985), that material has Norway by Neumann (1985), that material has insufficient Pb to be considered hancockite; a valid insufficient Pb to be considered hancockite; a valid second hancockite occurrence, from Sweden, was second hancockite occurrence, from Sweden, was reported by Holtstam and Langhof (1994).reported by Holtstam and Langhof (1994).

Crystal structureCrystal structure The crystal structure of hancockite was described and The crystal structure of hancockite was described and

the relation to epidote confirmed by Dollase (1971), the relation to epidote confirmed by Dollase (1971), who noted the diffuseness of the X-ray reflections who noted the diffuseness of the X-ray reflections from this species. Hancockite has Ca and (Pb,Sr) from this species. Hancockite has Ca and (Pb,Sr) ordered in the ordered in the AA(1) and (1) and AA(2) sites, respectively.(2) sites, respectively.

DescriptionDescription Hancockite occurs as superb euhedral 1-2 mm Hancockite occurs as superb euhedral 1-2 mm

crystals in vugs, as well as massive intergrowths with crystals in vugs, as well as massive intergrowths with other species; the latter are much more abundant. other species; the latter are much more abundant. Euhedral crystals (Figure 16-3) are composed of the Euhedral crystals (Figure 16-3) are composed of the forms {100}, {001}, {101}, {101}, and {111} and are forms {100}, {001}, {101}, {101}, and {111} and are bright and sharp. Hancockite is invariably red, bright and sharp. Hancockite is invariably red, grading to reddish brown, pinkish brown, and brown grading to reddish brown, pinkish brown, and brown when mixed with other species; the luster is vitreous when mixed with other species; the luster is vitreous to dull; and the density is 4.03 g/cmto dull; and the density is 4.03 g/cm33. Optically, . Optically, hancockite is biaxial, negative, 2V = 50hancockite is biaxial, negative, 2V = 5000, with a = , with a = 1.788, b = 1.81, and g = 1.83; pleochroism is strong; 1.788, b = 1.81, and g = 1.83; pleochroism is strong; absorption is absorption is ZZ > > XX. There is no discernible . There is no discernible fluorescence in ultraviolet.fluorescence in ultraviolet.

Occurrence and paragenesisOccurrence and paragenesis Hancockite was first found on the Parker Dump; later, in 1923, some dumps Hancockite was first found on the Parker Dump; later, in 1923, some dumps

were partly removed for reprocessing, and it was then found in quantity. The were partly removed for reprocessing, and it was then found in quantity. The best hancockite crystals (Figure 16-3) occur lining vugs in recrystallized best hancockite crystals (Figure 16-3) occur lining vugs in recrystallized assemblages composed largely of andradite, manganaxinite, mica, willemite, assemblages composed largely of andradite, manganaxinite, mica, willemite, and franklinite, together with other locally rare species, such as xonotlite. and franklinite, together with other locally rare species, such as xonotlite. Additional associated minerals were reported by Penfield and Warren (1899) to Additional associated minerals were reported by Penfield and Warren (1899) to be copper, lead, clinohedrite, vesuvianite, datolite, and barite. Fine samples are be copper, lead, clinohedrite, vesuvianite, datolite, and barite. Fine samples are prized.prized.

The bulk of the preserved hancockite is massive brick-red dull-lustered The bulk of the preserved hancockite is massive brick-red dull-lustered material, mixed with shards and remnants of the above-listed species. This material, mixed with shards and remnants of the above-listed species. This material, found in large amounts, is very inhomogeneous at the microprobe material, found in large amounts, is very inhomogeneous at the microprobe level and has not been extensively investigated. Hancockite also occurs level and has not been extensively investigated. Hancockite also occurs disseminated in feldspar. Frondel (1972) reported hancockite replacing disseminated in feldspar. Frondel (1972) reported hancockite replacing manganaxinite, a relation not investigated by this writer. Some massive manganaxinite, a relation not investigated by this writer. Some massive hancockite is severely altered; prehnite occurs in such specimens.hancockite is severely altered; prehnite occurs in such specimens.

NameName Hancockite was named in honor of Mr. Elwood P. Hancock, a mineral collector. Hancockite was named in honor of Mr. Elwood P. Hancock, a mineral collector.

He was known for his skill in relief-carving of minerals from the surrounding He was known for his skill in relief-carving of minerals from the surrounding calcite matrix (Figures 7-14 and 7-15). His collection is at Harvard University.calcite matrix (Figures 7-14 and 7-15). His collection is at Harvard University.

PiemontitePiemontite PIEMONTITEPIEMONTITE CaCa22(Mn,Fe)Al(Mn,Fe)Al22(Si(Si22OO77)(SiO)(SiO44)(O,OH))(O,OH)22

MonoclinicMonoclinic Piemontite, a calcium manganese aluminum Piemontite, a calcium manganese aluminum

silicate hydroxide mineral of the epidote group, silicate hydroxide mineral of the epidote group, was described from Sterling Hill by Jenkins was described from Sterling Hill by Jenkins (1994). It was stated to occur as pink (1994). It was stated to occur as pink microcrystals associated with johnbaumite and microcrystals associated with johnbaumite and barite. The reported analysis is grossly barite. The reported analysis is grossly inadequate for interpretation. Piemontite has not inadequate for interpretation. Piemontite has not been reported from Franklin.been reported from Franklin.

Name PiemontiteChemistry Ca2(Fe3+,MnName PiemontiteChemistry Ca2(Fe3+,Mn3+)Al2[O|OH|SiO4|Si2O7]Hardness 6 - 3+)Al2[O|OH|SiO4|Si2O7]Hardness 6 - 7Lustre vitreousColour yellow, carmine 7Lustre vitreousColour yellow, carmine red, red, reddish brown, reddish red, red, reddish brown, reddish blackStreak red Density blackStreak red Density [g/cm3] 3.7Crystal [g/cm3] 3.7Crystal habit monoclinicCleavage, Fracture [001] habit monoclinicCleavage, Fracture [001] good, [100] distinctother characteristics good, [100] distinctother characteristics and occurrences grained, dense and occurrences grained, dense aggregates, aggregates, in manganese ore deposits, which were in manganese ore deposits, which were affectes by contact metamorphismaffectes by contact metamorphism

Some pictures of Sorosilicates taken from Some pictures of Sorosilicates taken from THE BOB CAMPBELL GEOLOGY MUSEUMTHE BOB CAMPBELL GEOLOGY MUSEUM

CYCLOSILICATESCYCLOSILICATES Contains SiContains Si44OO1212 rings and rings and

BO3 groups linked by FeBO3 groups linked by Fe3+3+, , Al and Ca ionsAl and Ca ions

Diagnostic Features:Diagnostic Features: Characterized by triclinic Characterized by triclinic

crystals with very acute crystals with very acute angles angles

Occurrence:Occurrence: Occurs in cavities in granite, Occurs in cavities in granite,

in contact zones surrounding in contact zones surrounding granitic intrusionsgranitic intrusions

AXINITE (Ca,Fe AXINITE (Ca,Fe 2+2+Mn)Mn)33AlAl22(BO(BO33) ) SiSi44OO1212)(OH))(OH)

Crystallography:Crystallography: Triclinic crystal systemTriclinic crystal system Frequently in crystals with Frequently in crystals with

sharp edgessharp edges May also be massive, lamellar May also be massive, lamellar

to granularto granular Cleavage: distinct {100}Cleavage: distinct {100} Hardness: 6.5 to 7Hardness: 6.5 to 7 Specific Gravity: 3.27 to 3.35Specific Gravity: 3.27 to 3.35 Luster: vitreousLuster: vitreous Color: clove-brown, violet, gray, Color: clove-brown, violet, gray,

green, yellowgreen, yellow PyroelectricPyroelectric Composition and Structure:Composition and Structure:

Varying amounts of Ca, Fe Varying amounts of Ca, Fe and Mnand Mn

CYCLOSILICATESCYCLOSILICATES Emerald – deep green Emerald – deep green

transparent beryltransparent beryl Golden beryl – clear golden Golden beryl – clear golden

yellow berylyellow beryl Composition and Structure:Composition and Structure:

BeO (14%) AlBeO (14%) Al22OO33 (19.0%) (19.0%) SiOSiO22 (67.0%) (67.0%)

Diagnostic Features:Diagnostic Features: Usually recognized by its Usually recognized by its

hexagonal crystal form and hexagonal crystal form and color. Distinguished from color. Distinguished from apatite by greater hardness apatite by greater hardness and from quartz by higher and from quartz by higher specific gravity. Insoluble in specific gravity. Insoluble in acidsacids

Occurrence:Occurrence: Although Be is rare, beryl is Although Be is rare, beryl is

common and widely common and widely distributed distributed

BERYL BeBERYL Be33AlAl22(Si(Si66OO1818)) Crystallography:Crystallography:

Hexagonal crystal systemHexagonal crystal system Strong prismatic habit, Strong prismatic habit,

frequently vertically striated frequently vertically striated and groovedand grooved

Cleavage: imperfect {0001}Cleavage: imperfect {0001} Hardness: 7.5 to 8Hardness: 7.5 to 8 Specific Gravity: 2.65 to 2.8Specific Gravity: 2.65 to 2.8 Luster: vitreousLuster: vitreous Color: bluish green or light Color: bluish green or light

yellow, maybe deep emerald yellow, maybe deep emerald green, gold yellow, pink, white or green, gold yellow, pink, white or colorlesscolorless

Color serves as basis for several Color serves as basis for several variety names of gem beryl:variety names of gem beryl: Aquamarine- pale greenish Aquamarine- pale greenish

blue transparent varietyblue transparent variety Morganite or rose beryl – pink Morganite or rose beryl – pink

to deep roseto deep rose

CYCLOSILICATESCYCLOSILICATES BERYL (BeBERYL (Be33AlAl22(Si(Si66OO1818))

Occurs usually in granitic Occurs usually in granitic rocks or in pegmatitesrocks or in pegmatites

Also found in mica schists Also found in mica schists and associated with tin ores and associated with tin ores (South Africa and Rhodesia)(South Africa and Rhodesia)

World’s finest emeralds are World’s finest emeralds are found in Colombia in dark found in Colombia in dark bituminous limestonebituminous limestone

Uses: used as gemstone of Uses: used as gemstone of various colors. Ranks as the various colors. Ranks as the most valuable of stones and may most valuable of stones and may have a much greater value than have a much greater value than diamond. Major source of diamond. Major source of beryllium used as alloy with beryllium used as alloy with copper to increase hardness, copper to increase hardness, tensile strength and fatigue tensile strength and fatigue resistanceresistance

CYCLOSILICATESCYCLOSILICATES Diagnostic Features:Diagnostic Features:

Resemble quartz and is dis-Resemble quartz and is dis-tinguished from it with diffi-tinguished from it with diffi-culty but is fusible on thin culty but is fusible on thin edges. Distinguished from edges. Distinguished from corundum by lower hard-corundum by lower hard-ness. Pleochroicness. Pleochroic

Alteration: commonly altered to Alteration: commonly altered to mica, chlorite or talc in various mica, chlorite or talc in various shade of greenshade of green

Occurrence:Occurrence: Common constituent of con-Common constituent of con-

tact and regionally metamor-tact and regionally metamor-phosed argillaceous rocks phosed argillaceous rocks

CORDIERITE CORDIERITE (Mg,Fe)(Mg,Fe)22AlAl44SiSi55OO1818..nnHH22OO

Crystallography:Crystallography: Orthorhombic crystal systemOrthorhombic crystal system Crystals are usually short Crystals are usually short

prismaticprismatic Also found as embedded Also found as embedded

grains and massivegrains and massive Cleavage: poor {010}Cleavage: poor {010} Hardness: 7 to 7.5Hardness: 7 to 7.5 Specific Gravity: 2.6 to 2.66Specific Gravity: 2.6 to 2.66 Luster: vitreousLuster: vitreous Color: various shades of blue to Color: various shades of blue to

bluish graybluish gray PleochroicPleochroic Composition and Structure:Composition and Structure:

Most are Mg-richMost are Mg-rich Polymorph with indialitePolymorph with indialite

CYCLOSILICATESCYCLOSILICATES CORDIERITE CORDIERITE

(Mg,Fe)(Mg,Fe)22AlAl44SiSi55OO1818..nnHH22OO

CYCLOSILICATESCYCLOSILICATES by its conchoidal fracture by its conchoidal fracture

Occurrence:Occurrence: Most common occurrence is Most common occurrence is

in granite pegmatites and in in granite pegmatites and in rock immediately rock immediately surrounding themsurrounding them

Also found as accessory Also found as accessory mineral in igneous rocks and mineral in igneous rocks and metamorphic rocksmetamorphic rocks

Uses: one of the most beautiful Uses: one of the most beautiful of the semiprecious gemstones of the semiprecious gemstones having principal shades of olive-having principal shades of olive-green,pink to red and blue. green,pink to red and blue. Used in manufacture of Used in manufacture of pressure gauges due to its pressure gauges due to its strong piezoelectric properties strong piezoelectric properties

TOURMALINE (Na,Cl)(Li,Mg,Al)-TOURMALINE (Na,Cl)(Li,Mg,Al)-(Al,Fe,Mn)(Al,Fe,Mn)66(BO(BO33))33SiSi66.O.O1818(OH)(OH)44

Crystallography:Crystallography: Hexagonal-R crystal systemHexagonal-R crystal system usually in prismatic crystals usually in prismatic crystals

with prominent trigonal prismwith prominent trigonal prism Maybe massive compactMaybe massive compact

Hardness: 7 to 7.5Hardness: 7 to 7.5 Specific Gravity: 3 to 3.25Specific Gravity: 3 to 3.25 Luster: vitreous to resinousLuster: vitreous to resinous Color: varied depending on Color: varied depending on

compositioncomposition Fracture: conchoidalFracture: conchoidal Composition and Structure:Composition and Structure:

A complex silicate of B and AlA complex silicate of B and Al Diagnostic Features:Diagnostic Features:

Usually recognized by the Usually recognized by the rounded triangular cross-rounded triangular cross-section of the crystals and section of the crystals and

CYCLOSILICATESCYCLOSILICATES TOURMALINE (Na,Cl)(Li,Mg,Al)-TOURMALINE (Na,Cl)(Li,Mg,Al)-

(Al,Fe,Mn)(Al,Fe,Mn)66(BO(BO33))33SiSi66.O.O1818(OH)(OH)44

INOSILICATESINOSILICATES tetrahedra are joined to form infinite single chains with a unit composition tetrahedra are joined to form infinite single chains with a unit composition

SiOSiO33 or infinite double chains that give a ratio of Si:O = 4:11 or infinite double chains that give a ratio of Si:O = 4:11 Includes the two important groups of rock-forming minerals:Includes the two important groups of rock-forming minerals:

Pyroxenes – single chain membersPyroxenes – single chain members Amphiboles – double chain membersAmphiboles – double chain members

Similarities and differences of pyroxenes and amphiboles:Similarities and differences of pyroxenes and amphiboles: Most are monoclinic but both have orthorhombic membersMost are monoclinic but both have orthorhombic members Color, luster and specific gravity are analogousColor, luster and specific gravity are analogous Same cations are present in both groups but amphiboles have (OH) Same cations are present in both groups but amphiboles have (OH)

giving them slightly lower specific gravity and refractive indicesgiving them slightly lower specific gravity and refractive indices Pyroxenes commonly occur in stout prisms while amphiboles are Pyroxenes commonly occur in stout prisms while amphiboles are

more elongated, often acicularmore elongated, often acicular Cleavages are distinctly different due to underlying chain structureCleavages are distinctly different due to underlying chain structure Pyroxenes crystallize at higher temperatures compared to Pyroxenes crystallize at higher temperatures compared to

amphiboles and hence, are generally formed early in a cooling amphiboles and hence, are generally formed early in a cooling igneous melt and also occur in high-temperature metamorphic rocks igneous melt and also occur in high-temperature metamorphic rocks rich in Mg and Fe rich in Mg and Fe

INOSILICATESINOSILICATES Pyroxene Group:Pyroxene Group:

Enstatite-orthoferrosilite seriesEnstatite-orthoferrosilite series Enstatite, hyperstheneEnstatite, hypersthene

Diopside-hedenbergite seriesDiopside-hedenbergite series Diopside, hedenbergite, Diopside, hedenbergite,

augiteaugite Sodium pyroxene seriesSodium pyroxene series

Jadeite, aegirineJadeite, aegirine PigeonitePigeonite SpodumeneSpodumene

Amphibole Group:Amphibole Group: Cummingtonite seriesCummingtonite series

Cummingtonite, gruneriteCummingtonite, grunerite Tremolite seriesTremolite series

Tremolite, actinoliteTremolite, actinolite Sodium amphibole seriesSodium amphibole series

Glaucophane, riebeckiteGlaucophane, riebeckite HornblendeHornblende AnthophylliteAnthophyllite

Pyroxenoid Group:Pyroxenoid Group: WollastoniteWollastonite RhodoniteRhodonite PectolitePectolite

INOSILICATES (PYROXENE GROUP)INOSILICATES (PYROXENE GROUP) Varieties high in iron are Varieties high in iron are

black and difficult to distin-black and difficult to distin-guish from augite without guish from augite without optical tests optical tests

Occurrence:Occurrence: Mg-rich orthopyroxene is a Mg-rich orthopyroxene is a

common constituent of per-common constituent of per-dotites, gabbros, norites and dotites, gabbros, norites and basalts and commonly asso-basalts and commonly asso-ciated with Ca-clinopyroxeneciated with Ca-clinopyroxene

Major constituent of orthopy-Major constituent of orthopy-roxeniteroxenite

Also found in metamorphic Also found in metamorphic rocksrocks

ENSTATITE MgSiOENSTATITE MgSiO33- - HYPERSTHENE (Mg,Fe)SiOHYPERSTHENE (Mg,Fe)SiO33

Crystallography:Crystallography: Orthorhombic crystal systemOrthorhombic crystal system Prismatic crystals rarePrismatic crystals rare Usually massiveUsually massive

Cleavage: good {210}Cleavage: good {210} Hardness: 5.5 to 6Hardness: 5.5 to 6 Specific Gravity: 3.2 to 3.6Specific Gravity: 3.2 to 3.6 Luster: vitreous to pearly on Luster: vitreous to pearly on

cleavage surfacescleavage surfaces Color: grayish, yellowish or Color: grayish, yellowish or

greenish-white, olive-green and greenish-white, olive-green and brownbrown

Composition and Structure:Composition and Structure: FeFe2+2+ may substitute for Mg may substitute for Mg

Diagnostic Features:Diagnostic Features: Usual recognized by its color, Usual recognized by its color,

cleavage and unusual lustercleavage and unusual luster

INOSILICATES (PYROXENE GROUP)INOSILICATES (PYROXENE GROUP) ENSTATITE MgSiOENSTATITE MgSiO33- -

HYPERSTHENE (Mg,Fe)SiOHYPERSTHENE (Mg,Fe)SiO33

ENSTATITEENSTATITE

HYPERSTHENEHYPERSTHENE

INOSILICATES (PYROXENE GROUP)INOSILICATES (PYROXENE GROUP)

Occurrence:Occurrence: Common in high Common in high

temperature rapidly cooled temperature rapidly cooled lavas and in some intrusives lavas and in some intrusives such as diabases. Present such as diabases. Present as phenocrysts in some as phenocrysts in some volcanic rocksvolcanic rocks

PIGEONITE PIGEONITE CaCa0.250.25(Mg,Fe)(Mg,Fe)1.751.75Si2OSi2O66

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Very rarely as well-formed Very rarely as well-formed

phenocrysts with prismatic phenocrysts with prismatic habithabit

Cleavage: good {110}Cleavage: good {110} Hardness: 6Hardness: 6 Specific Gravity: 3.3 to 3.46Specific Gravity: 3.3 to 3.46 Color: brown, greenish brown to Color: brown, greenish brown to

blackblack Composition and Structure:Composition and Structure:

Calcium poor monoclinic Calcium poor monoclinic pyroxenes containing 5 to pyroxenes containing 5 to 15% molecular percent of 15% molecular percent of CaSiOCaSiO33

Diagnostic Features:Diagnostic Features: Distinguished from other Distinguished from other

pyroxenes through X-ray pyroxenes through X-ray techniquestechniques

INOSILICATES (PYROXENE GROUP)INOSILICATES (PYROXENE GROUP) Diagnostic Features:Diagnostic Features:

Characterized by crystal Characterized by crystal form and imperfect cleavageform and imperfect cleavage

Insoluble in acidsInsoluble in acids Occurrence:Occurrence:

Common in metamorphic Common in metamorphic rocksrocks

Products of igneous Products of igneous crystallizationcrystallization

DIOPSIDE CaMgSiDIOPSIDE CaMgSi22OO66 HEDENBERGITE CaFeSiHEDENBERGITE CaFeSi22OO66 AUGITE (Ca,Na)(Mg,Fe,Al)(Si,Al)AUGITE (Ca,Na)(Mg,Fe,Al)(Si,Al)22OO66

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Prismatic crystals showing Prismatic crystals showing

square or 8-sided cross-square or 8-sided cross-sectionsection

Also granular massiveAlso granular massive Cleavage: imperfect {110}Cleavage: imperfect {110} Hardness: 5 to 6Hardness: 5 to 6 Specific Gravity: 3.2 to 3.3Specific Gravity: 3.2 to 3.3 Luster: vitreousLuster: vitreous Color: white to light green, Color: white to light green,

deepens with increase of Fedeepens with increase of Fe Composition and Structure:Composition and Structure:

Mg and FeMg and Fe2+2+ substitute for substitute for each othereach other

INOSILICATES (PYROXENE GROUP)INOSILICATES (PYROXENE GROUP) DIOPSIDE CaMgSiDIOPSIDE CaMgSi22OO66

HEDENBERGITE CaFeSiHEDENBERGITE CaFeSi22OO66

AUGITE (Ca,Na)(Mg,Fe,Al)(Si,Al)AUGITE (Ca,Na)(Mg,Fe,Al)(Si,Al)22OO66

DIOPSIDEDIOPSIDE HEDENBERGITEHEDENBERGITE

AUGITEAUGITE

INOSILICATES (PYROXENE GROUP)INOSILICATES (PYROXENE GROUP) Occurrence:Occurrence:

Found only in metamorphic Found only in metamorphic rocks (high pressure and low rocks (high pressure and low temperature)temperature)

Uses: highly prized in the orient Uses: highly prized in the orient especially in China where it is especially in China where it is worked into ornaments and worked into ornaments and utensils. Also used by primitive utensils. Also used by primitive people for various weapons and people for various weapons and implements implements

JADEITE NaAlSiJADEITE NaAlSi22OO66 Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Rarely in isolated crystalsRarely in isolated crystals Usually fibrous in compact Usually fibrous in compact

massive aggregates massive aggregates Cleavage: {110}Cleavage: {110} Extremely tough and difficult to Extremely tough and difficult to

breakbreak Hardness: 6.5 to 7Hardness: 6.5 to 7 Specific Gravity: 3.3 to 3.5Specific Gravity: 3.3 to 3.5 Luster: vitreous, pearly on Luster: vitreous, pearly on

cleavage surfaces cleavage surfaces Color: apple green to emerald Color: apple green to emerald

greengreen Composition and Structure:Composition and Structure:

NaNa22O (15.4%) AlO (15.4%) Al22OO33 (25.2%) (25.2%) SiOSiO22 ( (59.4%) ( (59.4%)


Rare rock-forming mineral Rare rock-forming mineral found chiefly in igneous found chiefly in igneous rocksrocks

AEGIRINE NaFeAEGIRINE NaFe3+3+SiSi22OO66 Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals slender prismaticCrystals slender prismatic Often in fibrous aggregates Often in fibrous aggregates

Cleavage: imperfect {110}Cleavage: imperfect {110} Extremely tough and difficult to Extremely tough and difficult to

breakbreak Hardness: 6 to 6.5Hardness: 6 to 6.5 Specific Gravity: 3.4 to 3.55Specific Gravity: 3.4 to 3.55 Luster: vitreousLuster: vitreous Color: brown or green Color: brown or green Composition and Structure:Composition and Structure:

Show a wide range of Show a wide range of compositioncomposition


Rare mineral found Rare mineral found exclusively in lithium-rich exclusively in lithium-rich pegmatitespegmatites

SPODUMENE LiAlSiSPODUMENE LiAlSi22OO66 Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals prismatic, frequently Crystals prismatic, frequently

flattenedflattened Cleavage: perfect {110}Cleavage: perfect {110} Extremely tough and difficult to Extremely tough and difficult to

breakbreak Hardness: 6.6 to 7Hardness: 6.6 to 7 Specific Gravity: 3.15 to 3.20Specific Gravity: 3.15 to 3.20 Luster: vitreousLuster: vitreous Color: white, gray, pink, yellow, Color: white, gray, pink, yellow,

green green Composition and Structure:Composition and Structure:

LiLi22O (8.0%) AlO (8.0%) Al22OO33 (27.4%) (27.4%) SiO2 (64.6%)SiO2 (64.6%)

Diagnostic features:Diagnostic features: Fusible at 3.5, insolubleFusible at 3.5, insoluble

INOSILICATES (AMPHIBOLE GROUP)INOSILICATES (AMPHIBOLE GROUP) ANTHOPHYLLITE ANTHOPHYLLITE

(Mg,Fe)(Mg,Fe)77SiSi88OO2222(OH)(OH)22 Crystallography:Crystallography:

Orthorhombic crystal systemOrthorhombic crystal system Rarely on distinct crystalsRarely on distinct crystals Commonly lamellar or fibrous Commonly lamellar or fibrous

Cleavage: perfect {210}Cleavage: perfect {210} Extremely tough and difficult to Extremely tough and difficult to

breakbreak Hardness: 5.5 to 6 Hardness: 5.5 to 6 Specific Gravity: 2.85 to 3.2Specific Gravity: 2.85 to 3.2 Luster: vitreousLuster: vitreous Color: gray to various shades of Color: gray to various shades of

green and brown and beige green and brown and beige Diagnostic Features:Diagnostic Features:

Characterized by its clove Characterized by its clove brown colorbrown color

Occurrence:Occurrence: Metamorphic product of Mg-Metamorphic product of Mg-

rich rocksrich rocks

INOSILICATES (AMPHIBOLE GROUP)INOSILICATES (AMPHIBOLE GROUP) CUMMINGTONITE CUMMINGTONITE

FeFe22MgMg55SiSi88OO2222(OH)(OH)2 2 -GRUNERITE -GRUNERITE FeFe22SiSi88OO2222(OH)(OH)22

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Rarely on distinct crystalsRarely on distinct crystals Commonly fibrous or lamellar Commonly fibrous or lamellar

Cleavage: perfect {110}Cleavage: perfect {110} Hardness: 5.5 to 6 Hardness: 5.5 to 6 Specific Gravity: 3.1 to 3.6Specific Gravity: 3.1 to 3.6 Luster: silky, fibrousLuster: silky, fibrous Color: various shades of light Color: various shades of light

brownbrown Composition and Structure:Composition and Structure:

Cummingtonite-grunerite Cummingtonite-grunerite series extends from series extends from FeFe22MgMg55SiSi88OO2222(OH)(OH)2 2 to the end to the end membermember FeFe22SiSi88OO2222(OH)(OH)22

Diagnostic Features:Diagnostic Features: Characterized by its light Characterized by its light

brown color and needle-like brown color and needle-like crystalscrystals

Occurrence:Occurrence: Constituent of regionally Constituent of regionally

metamorphosed rocks and metamorphosed rocks and occurs in amphibolitesoccurs in amphibolites

Commonly co-exists with Commonly co-exists with hornblende & amphibolitehornblende & amphibolite

Use: Amosite, an asbestiform Use: Amosite, an asbestiform variety with ash gray color and variety with ash gray color and long flexible fibers is used as long flexible fibers is used as asbestos asbestos

INOSILICATES (AMPHIBOLE GROUP)INOSILICATES (AMPHIBOLE GROUP) TREMOLITE CaTREMOLITE Ca22MgMg55SiSi88OO2222(OH)(OH)2 2 - -

ACTINOLITE Ca ACTINOLITE Ca22(Mg, (Mg, Fe)Fe)55SiSi88OO2222(OH)(OH)22

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Crystals usually prismaticCrystals usually prismatic Tremolite often bladed in Tremolite often bladed in

radiating crystals radiating crystals Cleavage: perfect {110}Cleavage: perfect {110} Hardness: 5 to 6 Hardness: 5 to 6 Specific Gravity: 3.0 to 3.3Specific Gravity: 3.0 to 3.3 Luster: vitreous often with silky Luster: vitreous often with silky

sheensheen Color: varies from white to green Color: varies from white to green

in actinolitein actinolite A tough compact variety that A tough compact variety that

supplies much of jade is called supplies much of jade is called nephritenephrite

Composition and Structure:Composition and Structure: Complete solution series from Complete solution series from

tremolite to ferroactinolitetremolite to ferroactinolite

Diagnostic Features:Diagnostic Features: Characterized by slender Characterized by slender

prismsprisms Occurrence:Occurrence:

Tremolite almost frequently Tremolite almost frequently found in metamorphosed found in metamorphosed dolomitic limestonesdolomitic limestones

Actinolite is a characteristic Actinolite is a characteristic mineral of the greenschist mineral of the greenschist facies metamorphismfacies metamorphism

Use: fibrous varieties are used Use: fibrous varieties are used as asbestos, but fibrous as asbestos, but fibrous serpentine (chrysotile) is more serpentine (chrysotile) is more widely used and has better widely used and has better grade. Compact variety grade. Compact variety (nephrite) is used as jade (nephrite) is used as jade material material

INOSILICATES (AMPHIBOLE GROUP)INOSILICATES (AMPHIBOLE GROUP) TREMOLITE CaTREMOLITE Ca22MgMg55SiSi88OO2222(OH)(OH)2 2 - -

ACTINOLITE Ca ACTINOLITE Ca22(Mg, (Mg, Fe)Fe)55SiSi88OO2222(OH)(OH)22

INOSILICATES (AMPHIBOLE GROUP)INOSILICATES (AMPHIBOLE GROUP) GLAUCOPHANE GLAUCOPHANE

NaNa22MgMg33AlAl22SiSi88OO2222(OH)(OH)2 2 - - RIEBECKITE NaRIEBECKITE Na22Fe⅔Fe⅔++Fe⅔Fe⅔++ SiSi88OO2222(OH)(OH)22

Crystallography:Crystallography: Monoclinic crystal systemMonoclinic crystal system Slender acicular crystalsSlender acicular crystals Frequently aggregated, Frequently aggregated,

sometimes in asbestiform sometimes in asbestiform crystals crystals

Cleavage: perfect {110}Cleavage: perfect {110} Hardness: 6 Hardness: 6 Specific Gravity: 3.1 to 3.4Specific Gravity: 3.1 to 3.4 Luster: vitreousLuster: vitreous Color: blue to lavender-blue to Color: blue to lavender-blue to

black, darker with increasing iron black, darker with increasing iron contentcontent

Streak: white to light blueStreak: white to light blue Composition and Structure:Composition and Structure:

Partial series between Partial series between glaucophane and riebeckiteglaucophane and riebeckite

Diagnostic Features:Diagnostic Features: Characterized by fibrous Characterized by fibrous

habithabit Occurrence:Occurrence:

Glaucophane found only in Glaucophane found only in metamorphic rocks metamorphic rocks reflecting low temperature reflecting low temperature – high pressure – high pressure metamorphic conditionsmetamorphic conditions

Riebeckite occurs most Riebeckite occurs most commonly in igneous rocks commonly in igneous rocks like granites, syenites, like granites, syenites, nepheline syenites and nepheline syenites and related pegmatitesrelated pegmatites

Crocidolite occurs in Crocidolite occurs in metamorphic iron metamorphic iron formationsformations

Use: crocidolite makes up Use: crocidolite makes up about 4% of the world’s total about 4% of the world’s total asbestos production asbestos production

INOSILICATES (AMPHIBOLE GROUP)INOSILICATES (AMPHIBOLE GROUP) GLAUCOPHANE GLAUCOPHANE

NaNa22MgMg33AlAl22SiSi88OO2222(OH)(OH)2 2 - - RIEBECKITE NaRIEBECKITE Na22Fe⅔Fe⅔++Fe⅔Fe⅔++ SiSi88OO2222(OH)(OH)22

INOSILICATES (AMPHIBOLE GROUP)INOSILICATES (AMPHIBOLE GROUP) HORNBLENDE (Ca,Na)HORNBLENDE (Ca,Na)2-3 2-3

(Mg,Fe,Al)(Mg,Fe,Al)55SiSi66(Si,Al)(Si,Al)22OO2222(OH)(OH)2 2 Crystallography:Crystallography:

Monoclinic crystal systemMonoclinic crystal system Crystals prismaticCrystals prismatic Maybe columnar or fibrous Maybe columnar or fibrous

Cleavage: perfect {110}Cleavage: perfect {110} Hardness: 5 to 6 Hardness: 5 to 6 Specific Gravity: 3.0 to 3.4Specific Gravity: 3.0 to 3.4 Luster: vitreous, fibrous varieties Luster: vitreous, fibrous varieties

often silkyoften silky Color: various shades of dark Color: various shades of dark

green to blackgreen to black Diagnostic Features:Diagnostic Features:

Crystal form and cleavage Crystal form and cleavage serve to distinguish horblende serve to distinguish horblende from dark pyroxenes from dark pyroxenes

Occurrence:Occurrence: Important and widely-Important and widely-

distributed rock-forming distributed rock-forming mineral occurring in both mineral occurring in both igneous and metamorphic igneous and metamorphic rocksrocks

INOSILICATES (PYROXENOID GROUP)INOSILICATES (PYROXENOID GROUP) WOLLASTONITE (CaSiOWOLLASTONITE (CaSiO33))

Crystallography:Crystallography: Triclinic crystal systemTriclinic crystal system Rarely in tabular crystalsRarely in tabular crystals Commonly massive, Commonly massive,

cleavable to fibrous cleavable to fibrous Cleavage: perfect {001} and Cleavage: perfect {001} and

{100}{100} Hardness: 5 to 5.5 Hardness: 5 to 5.5 Specific Gravity: 2.8 to 2.9Specific Gravity: 2.8 to 2.9 Luster: vitreous, pearly on Luster: vitreous, pearly on

cleavage surfacescleavage surfaces Color: colorless, white or grayColor: colorless, white or gray Chemical composition:Chemical composition:

CaO (48.3%) SiOCaO (48.3%) SiO2 2 (51.7%) for (51.7%) for pure pure CaSiOCaSiO33

Diagnostic Features:Diagnostic Features: Fusible at 4, decomposed by Fusible at 4, decomposed by

HCl HCl

Occurrence:Occurrence: Occurs chiefly as a contact Occurs chiefly as a contact

metamorphic mineral in metamorphic mineral in crystalline limestonecrystalline limestone

Uses: manufacture of tile Uses: manufacture of tile

INOSILICATES (PYROXENOID GROUP)INOSILICATES (PYROXENOID GROUP) RHODONITE (MnSiORHODONITE (MnSiO33)) Crystallography:Crystallography:

Triclinic crystal systemTriclinic crystal system Crystals commonly tabularCrystals commonly tabular Commonly massive Commonly massive

Cleavage: perfect {110}Cleavage: perfect {110} Hardness: 5 to 6 Hardness: 5 to 6 Specific Gravity: 3.4 to 3.7Specific Gravity: 3.4 to 3.7 Luster: vitreousLuster: vitreous Color: rose red, pink, brown, Color: rose red, pink, brown,

frequently with black exterior of frequently with black exterior of manganese oxidemanganese oxide

Chemical composition:Chemical composition: Never pure MnSiONever pure MnSiO33 but but

always contains some Caalways contains some Ca Diagnostic Features:Diagnostic Features:

Fusible at 3, insoluble in HCl, Fusible at 3, insoluble in HCl, distinguished from distinguished from rhodochrosite by its greater rhodochrosite by its greater hardness and insolubilityhardness and insolubility

Occurrence:Occurrence: Occurs in manganese depo-Occurs in manganese depo-

sits and maganese-rich iron sits and maganese-rich iron formations as a result of formations as a result of metamorphic and metaso-metamorphic and metaso-matic activitymatic activity

Use: ornamental stoneUse: ornamental stone

INOSILICATES (PYROXENOID GROUP)INOSILICATES (PYROXENOID GROUP) PECTOLITE CaPECTOLITE Ca22NaH(SiONaH(SiO33))3 3 Crystallography:Crystallography:

Triclinic crystal systemTriclinic crystal system Usually in aggregates of Usually in aggregates of

acicularacicular Cleavage: perfect {001} and Cleavage: perfect {001} and

{100}{100} Hardness: 5 Hardness: 5 Specific Gravity: 2.8±Specific Gravity: 2.8± Luster: vitreous to silkyLuster: vitreous to silky Color: colorless, white or grayColor: colorless, white or gray Chemical composition:Chemical composition:

CaO (33.8%) NaCaO (33.8%) Na22O (9.3%) O (9.3%) SiOSiO22 (54.2%) H (54.2%) H22O (2.7%)O (2.7%)

Diagnostic Features:Diagnostic Features: Fuses at 2.5 to 3, Fuses at 2.5 to 3,

decomposed by HCldecomposed by HCl Occurrence:Occurrence:

Secondary mineral similar in Secondary mineral similar in occurrence to zeolites lining occurrence to zeolites lining cavities in basaltscavities in basalts

TectosilicatesTectosilicates The tectosilicates or The tectosilicates or

framework silicates have framework silicates have a structure wherein all of a structure wherein all of the 4 oxygens of SiO4-4 the 4 oxygens of SiO4-4 tetrahedra are shared tetrahedra are shared with other tetrahedra. with other tetrahedra. The ratios of Si to O is The ratios of Si to O is thus 1:2. thus 1:2. Since the Si - O bonds Since the Si - O bonds are strong covalent bonds are strong covalent bonds and since the structure is and since the structure is interlocking, the interlocking, the tectosilicate minerals tend tectosilicate minerals tend to have a high hardness. to have a high hardness.

Tectosilicate GroupTectosilicate Group SiO2 groupSiO2 group

QuartzQuartz TridymiteTridymite CrystobaliteCrystobalite Opal Opal

Feldspar groupFeldspar group K feldsparsK feldspars

MicrolineMicroline OrthoclaseOrthoclase SanidineSanidine

Plagioclase FeldsparsPlagioclase Feldspars AlbiteAlbite AnorthiteAnorthite

Danburite Danburite Feldspathoid groupFeldspathoid group

LeuciteLeucite NephelineNepheline SodaliteSodalite LazuriteLazurite PetalitePetalite

ScapoliteScapolite MarialiteMarialite MeioniteMeionite AnalcimeAnalcime

Zeolite groupZeolite group NatroliteNatrolite ChabaziteChabazite HeulanditeHeulandite StilbiteStilbite

SiO2 groupSiO2 groupNameName Crystal SystemCrystal System Density (g/cm3)Density (g/cm3) Refractive Index Refractive Index

(mean)(mean)

Stishovite Stishovite TetTet 4.35 4.35 1.81 1.81

Coesite Coesite MonMon 3.01 3.01 1.59 1.59

Low (a) Quartz Low (a) Quartz HexHex 2.65 2.65 1.55 1.55

High (b) Quartz High (b) Quartz HexHex 2.532.53 1.54 1.54

Kaetite (synthetic) Kaetite (synthetic) TetTet 2.50 2.50 1.52 1.52

Low (a) Tridymite Low (a) Tridymite Mon or OrthoMon or Ortho 2.26 2.26 1.47 1.47

High (b) Tridymite High (b) Tridymite HexHex 2.222.22 1.47 1.47

Low (a) Low (a) Cristobalite Cristobalite

MonMon 2.32 2.32 1.48 1.48

High (b) High (b) Cristobalite Cristobalite

isoiso 2.202.20 1.48 1.48

SiO2 groupSiO2 group Stishovite and Coesite are high pressure forms of SiO2, and thus Stishovite and Coesite are high pressure forms of SiO2, and thus

have much higher densities and refractive indices than the other have much higher densities and refractive indices than the other polymorphs. Stishovite is the only polymorph where the Si occurs in polymorphs. Stishovite is the only polymorph where the Si occurs in 6 fold (octahedral) coordination with Oxygen, and this occurs due to 6 fold (octahedral) coordination with Oxygen, and this occurs due to the high pressure under which the mineral forms. Both Stishovite the high pressure under which the mineral forms. Both Stishovite and Coesite have been found associated with meteorite impact and Coesite have been found associated with meteorite impact structures.structures.

At low pressure with decreasing temperature, SiO2 polymorphs At low pressure with decreasing temperature, SiO2 polymorphs change from high Cristobalite - Low Cristobalite - High Tridymite - change from high Cristobalite - Low Cristobalite - High Tridymite - Low Tridymite - High Quartz - Low Quartz. The high to low Low Tridymite - High Quartz - Low Quartz. The high to low transformations are all displacive transformations. Since displacive transformations are all displacive transformations. Since displacive transformations require little rearrangement of the crystal structure transformations require little rearrangement of the crystal structure and no change in energy, the high (a) polymorphs do not exist at the and no change in energy, the high (a) polymorphs do not exist at the surface of the earth, as they will invert to the low (b) polymorphs as surface of the earth, as they will invert to the low (b) polymorphs as temperature is lowered. temperature is lowered.

Transformations between a Cristobalite, a Tridymite, and a Quartz, Transformations between a Cristobalite, a Tridymite, and a Quartz, however, as well as between the high pressure polymorphs and however, as well as between the high pressure polymorphs and Quartz, are reconstructive transformations. Since reconstructive Quartz, are reconstructive transformations. Since reconstructive transformations require significant structural rearrangement and transformations require significant structural rearrangement and significant changes in energy, they occur slowly, and the high significant changes in energy, they occur slowly, and the high temperature and high pressure polymorphs can occur as temperature and high pressure polymorphs can occur as metastable minerals at the Earth's surface. metastable minerals at the Earth's surface.

SiO2 groupSiO2 group Quartz Quartz Crystal System: Crystal System:

Trigonal - TrapezohedralH-M Symbol H-M Symbol (3 2) Space Group: P 3121,P 3221 (3 2) Space Group: P 3121,P 3221

Cleavage: Cleavage: [0110] Indistinct [0110] Indistinct Color: Color: Brown, Colorless, Violet, Gray, Brown, Colorless, Violet, Gray,

Yellow. Yellow. Density: Density: 2.6 - 2.65, Average = 2.62 2.6 - 2.65, Average = 2.62 Diaphaniety: Diaphaniety: Transparent Transparent Fracture: Fracture: Conchoidal - Fractures Conchoidal - Fractures

developed in brittle materials developed in brittle materials characterized by smoothly curving characterized by smoothly curving surfaces, (e.g. quartz). surfaces, (e.g. quartz).

Habit: Habit: Crystalline - Coarse - Occurs Crystalline - Coarse - Occurs as well-formed coarse sized crystals. as well-formed coarse sized crystals.

Habit: Habit: Crystalline - Fine - Occurs as Crystalline - Fine - Occurs as well-formed fine sized crystals. well-formed fine sized crystals.

Habit: Habit: Druse - Crystal growth in a Druse - Crystal growth in a cavity which results in numerous cavity which results in numerous crystal tipped surfaces. crystal tipped surfaces.

Hardness: Hardness: 7 - Quartz 7 - Quartz Luminescence: Luminescence: Triboluminescent. Triboluminescent. Luster: Luster: Vitreous (Glassy) Vitreous (Glassy) Streak: Streak: white white

SiO2 groupSiO2 group TridymiteTridymite Crystal SystemCrystal System: : Triclinic – Pedial H-M H-M

Symbol (1) Space Group: F1 Symbol (1) Space Group: F1 Cleavage: Cleavage: [0001] Indistinct, [1010] [0001] Indistinct, [1010]

Imperfect Imperfect Color: Color: Colorless, White, Yellowish Colorless, White, Yellowish

white, Gray. white, Gray. Density: Density: 2.28 - 2.33, Average = 2.3 2.28 - 2.33, Average = 2.3 Diaphaniety: Diaphaniety: Transparent to Transparent to

translucent translucent Fracture: Fracture: Brittle - Conchoidal - Very Brittle - Conchoidal - Very

brittle fracture producing small, brittle fracture producing small, conchoidal fragments. conchoidal fragments.

Habit: Habit: Platy - Sheet forms (e.g. Platy - Sheet forms (e.g. micas). micas).

Habit: Habit: Spherical - Spherical, rounded Spherical - Spherical, rounded aggregates. aggregates.

Hardness: Hardness: 6.5-7 - Pyrite-Quartz 6.5-7 - Pyrite-Quartz Luminescence: Luminescence: Non-fluorescent. Non-fluorescent. Luster: Luster: Vitreous (Glassy) Vitreous (Glassy) Magnetism: Magnetism: Nonmagnetic Nonmagnetic Streak: Streak: white white

SiO2 groupSiO2 group CristobaliteCristobalite Crystal System: Crystal System:

Tetragonal - TrapezohedralH-M H-M Symbol (4 2 2) Space Group: P 41212Symbol (4 2 2) Space Group: P 41212

Cleavage: Cleavage: None None Color: Color: Blue gray, Brown, Gray, Blue gray, Brown, Gray,

Yellow, White. Yellow, White. Density: Density: 2.27 2.27 Diaphaniety: Diaphaniety: Translucent to Translucent to

transparent transparent Fracture: Fracture: Brittle - Generally displayed Brittle - Generally displayed

by glasses and most non-metallic by glasses and most non-metallic minerals. minerals.

Habit: Habit: Crystalline - Fine - Occurs as Crystalline - Fine - Occurs as well-formed fine sized crystals. well-formed fine sized crystals.

Habit: Habit: Spherical - Spherical, rounded Spherical - Spherical, rounded aggregates. aggregates.

Hardness: Hardness: 6.5 - Pyrite 6.5 - Pyrite Luminescence: Luminescence: Non-fluorescent. Non-fluorescent. Luster: Luster: Vitreous (Glassy) Vitreous (Glassy) Magnetism: Magnetism: Nonmagnetic Nonmagnetic Streak: Streak: white white

SiO2 groupSiO2 group Opal-SiO2·n(H2O)Opal-SiO2·n(H2O) Crystal System: Crystal System: Amorphous- No - No

Crystals Crystals Cleavage: Cleavage: None None Color: Color: White, Yellow, Red, Brown, White, Yellow, Red, Brown,

Blue. Blue. Density: Density: 1.9 - 2.3, Average = 2.09 1.9 - 2.3, Average = 2.09 Diaphaniety: Diaphaniety: Transparent to Transparent to

translucent to opaque translucent to opaque Fracture: Fracture: Conchoidal - Fractures Conchoidal - Fractures


Habit: Habit: Amorphous - No crystalline Amorphous - No crystalline form or imitative shape. form or imitative shape.

Habit: Habit: Massive - Uniformly Massive - Uniformly indistinguishable crystals forming indistinguishable crystals forming large masses. large masses.

Habit: Habit: Reniform - "Kidney like" in Reniform - "Kidney like" in shape (e.g.. hematite). shape (e.g.. hematite).

Hardness: Hardness: 5.5-6 - Knife Blade-5.5-6 - Knife Blade-Orthoclase Orthoclase Luminescence: Luminescence: Fluorescent, Short Fluorescent, Short

UV=greenish yellow, Long UV=white. UV=greenish yellow, Long UV=white. Luster: Luster: Vitreous - Dull Vitreous - Dull Streak: Streak: white white

Feldspar groupFeldspar group The feldspars are the most common The feldspars are the most common

minerals in the Earth's crust. They minerals in the Earth's crust. They consist of three end-members:consist of three end-members:

KAlSi3O8 - Orthoclase (or), KAlSi3O8 - Orthoclase (or), NaAlSi3O8 - Albite (ab), and NaAlSi3O8 - Albite (ab), and CaAl2Si2O8 -Anorthite (an)CaAl2Si2O8 -Anorthite (an)

KAlSi3O8 and NaAlSi3O8 form a KAlSi3O8 and NaAlSi3O8 form a complete solid solution series, known complete solid solution series, known as the alkali feldspars and NaAlSi3O8 as the alkali feldspars and NaAlSi3O8 and CaAl2Si2O8 form a complete solid and CaAl2Si2O8 form a complete solid solution series known as the solution series known as the plagioclase feldspars.plagioclase feldspars.

The feldspars have a framework The feldspars have a framework structure, consisting of SiO4 structure, consisting of SiO4 tetrahedra sharing all of the corner tetrahedra sharing all of the corner oxygens. However, in the alkali oxygens. However, in the alkali feldspars 1/4 of the Si+4 ions are feldspars 1/4 of the Si+4 ions are replaced by Al+3 and in the replaced by Al+3 and in the plagioclase feldspars 1/4 to 1/2 of the plagioclase feldspars 1/4 to 1/2 of the Si+4 ions are replaced by Al+3. This Si+4 ions are replaced by Al+3. This allows for the cations K+, Na+, and allows for the cations K+, Na+, and Ca+2 to be substituted into void Ca+2 to be substituted into void spaces to maintain charge balance. spaces to maintain charge balance.

Compositions of natural feldspars are Compositions of natural feldspars are shown in the diagram here based on the 3 shown in the diagram here based on the 3 components - NaAlSi3O8, - Albite (ab), components - NaAlSi3O8, - Albite (ab), KAlSi3O8 - Orthoclase (or) and KAlSi3O8 - Orthoclase (or) and CaAl2Si2O8. The Alkali Feldspars form a CaAl2Si2O8. The Alkali Feldspars form a complete solid solution between ab and complete solid solution between ab and or, with up to 5% of the an component. or, with up to 5% of the an component. The high temperature more K-rich variety The high temperature more K-rich variety is called Sanidine and the more Na-rich is called Sanidine and the more Na-rich variety is called anorthoclase. variety is called anorthoclase.

The plagioclase feldspars are a complete The plagioclase feldspars are a complete solid solution series between ab and an, solid solution series between ab and an, and can contain small amounts of the or and can contain small amounts of the or component. Names are given to the component. Names are given to the various ranges of composition, as shown various ranges of composition, as shown here in the diagram are: Albite - ab90 to here in the diagram are: Albite - ab90 to ab100ab100Oligoclase - ab70 to ab90Oligoclase - ab70 to ab90Andesine - ab50 to ab70Andesine - ab50 to ab70Labradorite - ab30 to ab50Labradorite - ab30 to ab50Bytownite - ab10 - ab30Bytownite - ab10 - ab30Anorthite - ab0 to an10Anorthite - ab0 to an10

K-Feldspar groupK-Feldspar group Feldspar is a group of common silicate minerals. Feldspars are the Feldspar is a group of common silicate minerals. Feldspars are the

result of one-fourth of all the silicons in SiO2 being replaced by result of one-fourth of all the silicons in SiO2 being replaced by aluminum (Si4O8 to (Si3Al)O8). When this happens, the (Si3Al)O8 has aluminum (Si4O8 to (Si3Al)O8). When this happens, the (Si3Al)O8 has a -1 electric charge. The charge is satisfied by the addition of one or a -1 electric charge. The charge is satisfied by the addition of one or more metals. The (Si3Al)O8- structure has relatively large holes, and more metals. The (Si3Al)O8- structure has relatively large holes, and the only metals that tend to stay in these holes are: K (potassium), Na the only metals that tend to stay in these holes are: K (potassium), Na (sodium), Ca (calcium), Cs (cesium), Ba (barium), Sr (strontium), and (sodium), Ca (calcium), Cs (cesium), Ba (barium), Sr (strontium), and Pb (lead). Of these, K & Na & Ca are the most common metals that Pb (lead). Of these, K & Na & Ca are the most common metals that enter the matrix. Sometimes, quite a few of the other metals enter the enter the matrix. Sometimes, quite a few of the other metals enter the structure, resulting in "garbage can minerals".structure, resulting in "garbage can minerals".

Chemical analyses of feldspars show that they range in composition Chemical analyses of feldspars show that they range in composition from from K-feldspar to Na-feldsparK-feldspar to Na-feldspar and from and from Na-feldspar to Ca-feldsparNa-feldspar to Ca-feldspar. . So, there are two "families" of feldspars. There is no chemical So, there are two "families" of feldspars. There is no chemical gradient between K-feldspar and Ca-feldspar.gradient between K-feldspar and Ca-feldspar.

The The potassium feldsparspotassium feldspars (K-feldspars) (aka alkali feldspars) are those (K-feldspars) (aka alkali feldspars) are those

that range in composition from pure K-feldspar to pure Na-feldspar that range in composition from pure K-feldspar to pure Na-feldspar (actually, feldspars with ~even & random mixes of potassium and (actually, feldspars with ~even & random mixes of potassium and sodium are rare). The feldspars with Na and/or Ca are the sodium are rare). The feldspars with Na and/or Ca are the plagioclase plagioclase feldsparsfeldspars. All feldspars have similar physical properties: a hardness . All feldspars have similar physical properties: a hardness of about 6, a whitish streak, and two cleavage planes at or very near of about 6, a whitish streak, and two cleavage planes at or very near 90º. Potassium feldspar is whitish to pinkish-orangish to salmon-90º. Potassium feldspar is whitish to pinkish-orangish to salmon-colored.colored.

K-Feldspar groupK-Feldspar group Microline KAlSi3O8Microline KAlSi3O8 Crystal System: Crystal System: Monoclinic - PrismaticH-H-

M Symbol (2/m) Space Group: C 2/mM Symbol (2/m) Space Group: C 2/m Cleavage: [001] Perfect, [010] Good Cleavage: [001] Perfect, [010] Good Color: Colorless, Greenish, Grayish Color: Colorless, Greenish, Grayish

yellow, White, Pink. yellow, White, Pink. Density: 2.56 Density: 2.56 Diaphaniety: Transparent to translucent Diaphaniety: Transparent to translucent Fracture: Uneven - Flat surfaces (not Fracture: Uneven - Flat surfaces (not

cleavage) fractured in an uneven pattern. cleavage) fractured in an uneven pattern. Habit: Blocky - Crystal shape tends to be Habit: Blocky - Crystal shape tends to be

equant (e.g. feldspars). equant (e.g. feldspars). Habit: Massive - Granular - Common Habit: Massive - Granular - Common

texture observed in granite and other texture observed in granite and other igneous rock. igneous rock.

Habit: Prismatic - Crystals Shaped like Habit: Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline). Slender Prisms (e.g. tourmaline).

Hardness: 6 - Orthoclase Hardness: 6 - Orthoclase Luminescence: None. Luminescence: None. Luster: Vitreous (Glassy) Luster: Vitreous (Glassy) Streak: white Streak: white

K-Feldspar groupK-Feldspar group Sanidine (K,Na)(Si,Al)4O8Sanidine (K,Na)(Si,Al)4O8 Crystal System: Crystal System: Monoclinic - PrismaticH-H-

M Symbol (2/m) Space Group: C 2/mM Symbol (2/m) Space Group: C 2/m Cleavage: Cleavage: [001] Perfect, [010] Good [001] Perfect, [010] Good Color: Color: Colorless, White, Gray, Yellowish Colorless, White, Gray, Yellowish

white, Reddish white. white, Reddish white. Density: Density: 2.52 2.52 Diaphaniety: Diaphaniety: Transparent to translucent Transparent to translucent Fracture: Fracture: Uneven - Flat surfaces (not Uneven - Flat surfaces (not

cleavage) fractured in an uneven pattern. cleavage) fractured in an uneven pattern. Habit: Habit: Blocky - Crystal shape tends to be Blocky - Crystal shape tends to be

equant (e.g. feldspars). equant (e.g. feldspars). Habit: Habit: Massive - Granular - Common Massive - Granular - Common

texture observed in granite and other texture observed in granite and other igneous rock. igneous rock.

Habit: Habit: Prismatic - Crystals Shaped like Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline). Slender Prisms (e.g. tourmaline).

Hardness: Hardness: 6 - Orthoclase 6 - Orthoclase Luminescence: Luminescence: Non-fluorescent. Non-fluorescent. Luster: Luster: Vitreous - Pearly Vitreous - Pearly Streak: Streak: white white

Plagioclase FeldsparsPlagioclase Feldspars Plagioclase is the most common Plagioclase is the most common

feldspar. It forms initially by feldspar. It forms initially by crystallization from magma. The crystallization from magma. The plagioclase solid solution series is plagioclase solid solution series is coupled solid solution where the coupled solid solution where the substitution is: Na+1Si+4 <=> substitution is: Na+1Si+4 <=> Ca+2Al+3 Thus, the general Ca+2Al+3 Thus, the general chemical formula for plagioclase chemical formula for plagioclase can be written as: CaxNa1-can be written as: CaxNa1-xAl1+xSi3-xO8 where x is xAl1+xSi3-xO8 where x is between 0 and 1.between 0 and 1.

The phase diagram for the The phase diagram for the plagiocalse series is shown here, plagiocalse series is shown here, and shows that the Anorthite and shows that the Anorthite component has a higher melting component has a higher melting temperature the than the Albite temperature the than the Albite component. Thus, on component. Thus, on crystallization, higher crystallization, higher temperatures will favor more An-temperatures will favor more An-rich plagioclase which will react rich plagioclase which will react with the liquid to produce more with the liquid to produce more Ab-rich plagioclase on cooling. Ab-rich plagioclase on cooling.

Plagioclase occurs in basalts, Plagioclase occurs in basalts, andesites, dacites, rhyolites, andesites, dacites, rhyolites, gabbros, diorites, granodiorites, gabbros, diorites, granodiorites, and granites. In most of these and granites. In most of these igneous rocks, it always shows the igneous rocks, it always shows the characteristic albite twinning. characteristic albite twinning. Plagioclase also occurs in a wide Plagioclase also occurs in a wide variety of metamorphic rocks, variety of metamorphic rocks, where it is usually not twinned. In where it is usually not twinned. In such rocks where the plagioclase such rocks where the plagioclase is not twinned, it is difficult to is not twinned, it is difficult to distinguish from the alkali distinguish from the alkali feldspars. Plagioclase can be a feldspars. Plagioclase can be a component of clastic sedimentary component of clastic sedimentary rocks, although it is less stable rocks, although it is less stable near the Earth's surface than alkali near the Earth's surface than alkali feldspar and quartz, and usually feldspar and quartz, and usually breaks down to clay minerals breaks down to clay minerals during weathering. during weathering.

Plagioclase FeldsparsPlagioclase Feldspars Albite NaAlSi3O8Albite NaAlSi3O8 Crystal System: Crystal System: Triclinic - PinacoidalH-M H-M

Symbol ( 1) Space Group: C1Symbol ( 1) Space Group: C1 Cleavage: Cleavage: [001] Perfect, [010] Good [001] Perfect, [010] Good Color: Color:

White, Gray, Greenish gray, Bluish green, White, Gray, Greenish gray, Bluish green, Gray. Gray.

Density: Density: 2.61 - 2.63, Average = 2.62 2.61 - 2.63, Average = 2.62 Diaphaniety: Diaphaniety: Transparent to translucent to sub Transparent to translucent to sub

translucent translucent Fracture: Fracture: Uneven - Flat surfaces (not Uneven - Flat surfaces (not

cleavage) fractured in an uneven pattern. cleavage) fractured in an uneven pattern. Habit: Habit: Blocky - Crystal shape tends to be Blocky - Crystal shape tends to be

equant (e.g. feldspars). equant (e.g. feldspars). Habit: Habit: Granular - Granular - Generally occurs as anhedral to subhedral Generally occurs as anhedral to subhedral crystals in matrix. crystals in matrix.

Habit: Habit: Striated - Parallel lines on crystal Striated - Parallel lines on crystal surface or cleavage face. surface or cleavage face.

Hardness: Hardness: 7 - Quartz 7 - Quartz Luminescence: Luminescence: None. None. Luster: Luster: Vitreous (Glassy) Vitreous (Glassy) Streak: Streak: whitewhite

Plagioclase FeldsparsPlagioclase Feldspars Anorthite CaAl2Si2O8 Anorthite CaAl2Si2O8 Crystal System: Crystal System: Triclinic - PinacoidalH-M H-M

Symbol ( 1) Space Group: P1,I1Symbol ( 1) Space Group: P1,I1 Cleavage: Cleavage: [001] Perfect, [010] Good [001] Perfect, [010] Good Color: Color: Colorless, Gray, White, Red, Reddish Colorless, Gray, White, Red, Reddish

gray. gray. Density: Density: 2.72 - 2.75, Average = 2.73 2.72 - 2.75, Average = 2.73 Diaphaniety: Diaphaniety: Transparent to Subtransparent to Transparent to Subtransparent to

translucent translucent Fracture: Fracture: Uneven - Flat surfaces (not Uneven - Flat surfaces (not

cleavage) fractured in an uneven pattern. cleavage) fractured in an uneven pattern. Habit: Habit: Euhedral Crystals - Occurs as well-Euhedral Crystals - Occurs as well-

formed crystals showing good external form. formed crystals showing good external form. Habit: Habit: Granular - Generally occurs as anhedral Granular - Generally occurs as anhedral

to subhedral crystals in matrix. to subhedral crystals in matrix. Habit: Habit: Striated - Parallel lines on crystal Striated - Parallel lines on crystal

surface or cleavage face. surface or cleavage face. Hardness: Hardness: 6 - Orthoclase 6 - Orthoclase Luminescence: Luminescence: None. None. Luster: Luster: Vitreous Vitreous

(Glassy) (Glassy) Streak: Streak: white white

Plagioclase FeldsparsPlagioclase Feldspars Danburite CaB2(SiO4)2Danburite CaB2(SiO4)2 Crystal System: Crystal System:

Orthorhombic - DipyramidalH-M H-M Symbol (2/m 2/m 2/m) Space Group: Symbol (2/m 2/m 2/m) Space Group: PnamPnam

Cleavage: Cleavage: [001] Poor [001] Poor Color: Color: Colorless, White, Gray, Brownish white, Colorless, White, Gray, Brownish white, Straw yellow. Straw yellow.

Density: Density: 2.97 - 3.02, Average = 2.99 2.97 - 3.02, Average = 2.99 Diaphaniety: Diaphaniety: Transparent to Transparent to

translucent translucent Fracture: Fracture: Sub Conchoidal - Fractures Sub Conchoidal - Fractures

developed in brittle materials developed in brittle materials characterized by semi-curving characterized by semi-curving surfaces. surfaces.

Habit: Habit: Disseminated - Occurs in small, Disseminated - Occurs in small, distinct particles dispersed in matrix. distinct particles dispersed in matrix.

Habit: Habit: Euhedral Crystals - Occurs as Euhedral Crystals - Occurs as well-formed crystals showing good well-formed crystals showing good external form. external form.


Hardness: Hardness: 7 - Quartz 7 - Quartz Luminescence: Luminescence: Fluorescent. Fluorescent. Luster: Luster: Vitreous - Greasy Vitreous - Greasy Streak: Streak: whitewhite

FeldspathoidsFeldspathoids The feldspathoid group of minerals are SiO2 poor, alkali The feldspathoid group of minerals are SiO2 poor, alkali

rich minerals that occur in low SiO2, high Na2O - K2O rich minerals that occur in low SiO2, high Na2O - K2O igneous rocks. In general, these minerals are not igneous rocks. In general, these minerals are not compatible with quartz, and therefore, are rarely, if ever, compatible with quartz, and therefore, are rarely, if ever, seen in rocks that contain quartz. They do, however, seen in rocks that contain quartz. They do, however, often occur with feldspars. Because of the alkalic nature often occur with feldspars. Because of the alkalic nature of the rocks that contain feldspathoids, associated of the rocks that contain feldspathoids, associated pyroxenes and amphiboles are of the sodic variety, i.e. pyroxenes and amphiboles are of the sodic variety, i.e. aegerine or riebeckite.aegerine or riebeckite.

The main feldspathoids are Nepheline (Na,K)AlSiO4, The main feldspathoids are Nepheline (Na,K)AlSiO4, Kalsilite KAlSi2O6, and Leucite KAlSi2O6. At high Kalsilite KAlSi2O6, and Leucite KAlSi2O6. At high temperature there is complete solid solution between temperature there is complete solid solution between Nepheline and Kalsilite, but at low temperature Nepheline and Kalsilite, but at low temperature Nepheline can contain only about 12 wt% K2O. Nepheline can contain only about 12 wt% K2O.

FeldspathoidsFeldspathoids Leucite KAlSi2O6 Leucite KAlSi2O6 Crystal System: Crystal System:

Tetragonal - DipyramidalH-M Symbol H-M Symbol (4/m) Space Group: I 41/a (4/m) Space Group: I 41/a

Cleavage: Cleavage: [110] Indistinct [110] Indistinct Color: Color: Colorless, Gray, Yellow gray, Colorless, Gray, Yellow gray,

White. White. Density: Density: 2.47 2.47 Diaphaniety: Diaphaniety: Translucent to Translucent to

transparent transparent Fracture: Fracture: Brittle - Conchoidal - Very Brittle - Conchoidal - Very


Habit: Habit: Crystalline - Coarse - Occurs as Crystalline - Coarse - Occurs as well-formed coarse sized crystals. well-formed coarse sized crystals.

Hardness: Hardness: 6 - Orthoclase 6 - Orthoclase Luminescence: Luminescence: Non-fluorescent. Non-fluorescent. Luster: Luster: Vitreous (Glassy) Vitreous (Glassy) Magnetism: Magnetism: Nonmagnetic Nonmagnetic Streak: Streak: white white

FeldspathoidsFeldspathoids Nepheline (Na,K)AlSiO4 Nepheline (Na,K)AlSiO4 Crystal System: Crystal System:

Hexagonal - PyramidalH-M Symbol (6) H-M Symbol (6) Space Group: P 63Space Group: P 63

Cleavage: Cleavage: [1010] Poor [1010] Poor Color: Color: White, Gray, Brown, Brownish White, Gray, Brown, Brownish

gray, Reddish white. gray, Reddish white. Density: Density: 2.55 - 2.65, Average = 2.59 2.55 - 2.65, Average = 2.59 Diaphaniety: Diaphaniety: Transparent to Transparent to

translucent to opaque translucent to opaque Fracture: Fracture: Sub Conchoidal - Fractures Sub Conchoidal - Fractures

developed in brittle materials developed in brittle materials characterized by semi-curving characterized by semi-curving surfaces. surfaces.

Habit: Habit: Massive - Granular - Common Massive - Granular - Common texture observed in granite and other texture observed in granite and other igneous rock. igneous rock.


Hardness: Hardness: 6 - Orthoclase 6 - Orthoclase Luminescence: Luminescence: None. None. Luster: Luster: Vitreous - Greasy Vitreous - Greasy Streak: Streak: white white

FeldspathoidsFeldspathoids Sodalite Na8Al6Si6O24Cl2 Sodalite Na8Al6Si6O24Cl2 Crystal System: Crystal System:

Isometric - HextetrahedralH-M Symbol H-M Symbol (4 3m) Space Group: P 43n (4 3m) Space Group: P 43n

Cleavage: Cleavage: [110] Poor [110] Poor Color: Color: Azure blue, White, Pink, Gray, Azure blue, White, Pink, Gray,

Green. Green. Density: Density: 2.29 2.29 Diaphaniety: Diaphaniety: Transparent to Transparent to



Habit: Habit: Disseminated - Occurs in small, Disseminated - Occurs in small, distinct particles dispersed in matrix. distinct particles dispersed in matrix.


Hardness: Hardness: 6 - Orthoclase 6 - Orthoclase Luminescence: Luminescence: None. None. Luster: Luster: Vitreous - Greasy Vitreous - Greasy Streak: Streak: white white

FeldspathoidsFeldspathoids Lazurite Na3Ca(Al3Si3O12)S Lazurite Na3Ca(Al3Si3O12)S Crystal System: Crystal System:

Isometric - HextetrahedralH-M Symbol H-M Symbol (4 3m) Space Group: P 43n (4 3m) Space Group: P 43n

Cleavage: Cleavage: [110] Imperfect [110] Imperfect Color: Color: Blue, Azure blue, Violet blue, Blue, Azure blue, Violet blue,

Greenish blue. Greenish blue. Density: Density: 2.38 - 2.42, Average = 2.4 2.38 - 2.42, Average = 2.4 Diaphaniety: Diaphaniety: Translucent Translucent Fracture: Fracture: Conchoidal - Fractures Conchoidal - Fractures



Hardness: Hardness: 5.5 - Knife Blade 5.5 - Knife Blade Luminescence: Luminescence: Fluorescent. Fluorescent. Luster: Luster: Vitreous - Dull Vitreous - Dull Streak: Streak: light blue light blue

FeldspathoidsFeldspathoids Petalite LiAlSi4O10 Petalite LiAlSi4O10 Crystal System: Crystal System:

Monoclinic - PrismaticH-M Symbol H-M Symbol (2/m) Space Group: P 2/a (2/m) Space Group: P 2/a

Cleavage: Cleavage: [001] Perfect, [???] [001] Perfect, [???] Imperfect Imperfect

Color: Color: Colorless, Gray, Yellow, Yellow Colorless, Gray, Yellow, Yellow gray, White. gray, White.

Density: Density: 2.39 - 2.46, Average = 2.42 2.39 - 2.46, Average = 2.42 Diaphaniety: Diaphaniety: Transparent to Transparent to



Habit: Habit: Massive - Uniformly Massive - Uniformly indistinguishable crystals forming large indistinguishable crystals forming large masses. masses.

Hardness: Hardness: 6-6.5 - Orthoclase-Pyrite 6-6.5 - Orthoclase-Pyrite Luminescence: Luminescence: Fluorescent. Fluorescent. Luster: Luster: Vitreous - Pearly Vitreous - Pearly SS treak: treak: colorless colorless

Scapolite seriesScapolite series Scapolite is actually the name of a series between the sodium chloride rich Scapolite is actually the name of a series between the sodium chloride rich

mineral called mineral called marialitemarialite and the calcium carbonate rich mineral and the calcium carbonate rich mineral meionitemeionite. . The structure of scapolite is similar to some feldspathoids in that it is The structure of scapolite is similar to some feldspathoids in that it is composed of large open spaces in the framework of silicate and aluminum composed of large open spaces in the framework of silicate and aluminum tetrahedrons. These open spaces are large enough to essentially cage the tetrahedrons. These open spaces are large enough to essentially cage the very large ionic groups of either Na4Cl or Ca4CO3. The sulfate ion shown in very large ionic groups of either Na4Cl or Ca4CO3. The sulfate ion shown in the formula is typically barely more than a trace, but is found in far greater the formula is typically barely more than a trace, but is found in far greater percentages than the occasional fluorine or hydroxide interlopers in the percentages than the occasional fluorine or hydroxide interlopers in the scapolite structure. Scapolite forms in metamorphic rocks from the alteration scapolite structure. Scapolite forms in metamorphic rocks from the alteration of plagioclase of plagioclase feldspars. The entire scapolite series is analogous to the . The entire scapolite series is analogous to the plagioclase series. If the formula of marialite is written as 3(Na(Al, plagioclase series. If the formula of marialite is written as 3(Na(Al, Si)4O8)NaCl it is clear how well it matches the formula of the sodium rich Si)4O8)NaCl it is clear how well it matches the formula of the sodium rich plagioclase, plagioclase, albite, NaAlSi3O8. A similar look at meionite's formula, 3(Ca(Al, , NaAlSi3O8. A similar look at meionite's formula, 3(Ca(Al, Si)4O8)CaCO3, shows that it too is near three times the formula of Si)4O8)CaCO3, shows that it too is near three times the formula of anorthite, CaAl2Si2O8. The addition of the extra sodium chloride or calcium , CaAl2Si2O8. The addition of the extra sodium chloride or calcium carbonate occurs during metamorphism as well as substantial alteration of carbonate occurs during metamorphism as well as substantial alteration of the structure. Although nearly pure albite and anorthite specimens are the structure. Although nearly pure albite and anorthite specimens are sometimes found, pure forms of meionite and marialite are unknown of in sometimes found, pure forms of meionite and marialite are unknown of in nature. nature.

Distinguishing the scapolite minerals from each other is difficult as they Distinguishing the scapolite minerals from each other is difficult as they differ only slightly in density and index of refraction, increasing in both with differ only slightly in density and index of refraction, increasing in both with increasing calcium content. It is because of this closeness in properties and increasing calcium content. It is because of this closeness in properties and yet seemingly very different chemistries that scapolite has had its share of yet seemingly very different chemistries that scapolite has had its share of pseudonyms. Wernerite was the most common alternate name for the pseudonyms. Wernerite was the most common alternate name for the scapolite series, but now it has mostly disappeared from use. A few other scapolite series, but now it has mostly disappeared from use. A few other names such as mizzonite and dipyre as well as marialite and meionite have names such as mizzonite and dipyre as well as marialite and meionite have been used as names for the entire scapolite series. Now scapolite is a name been used as names for the entire scapolite series. Now scapolite is a name recognized by most every mineralogist and rock hound the world over. recognized by most every mineralogist and rock hound the world over.

Scapolite, which is Greek for "shaft", is commonly found in stubby to long Scapolite, which is Greek for "shaft", is commonly found in stubby to long prismatic crystals, hence the name. It is tetragonal so that it will commonly prismatic crystals, hence the name. It is tetragonal so that it will commonly have a square or octahedral cross-section. It belongs to a rather exclusive have a square or octahedral cross-section. It belongs to a rather exclusive symmetry class that is shared by only two other well known minerals, symmetry class that is shared by only two other well known minerals, powellite and and scheelite. The symmetry class is called the . The symmetry class is called the Tetragonal Dipyramidal Class and is characterized by only having the one and is characterized by only having the one primary four fold axis of rotation and a perpendicular mirror plane, denoted primary four fold axis of rotation and a perpendicular mirror plane, denoted as as 4/m4/m. Unfortunately, scapolite rarely forms crystals with the complex faces . Unfortunately, scapolite rarely forms crystals with the complex faces that would be needed to see this unusual symmetry. that would be needed to see this unusual symmetry.

As a gemstone scapolite is not well known, but can be very attractive. The As a gemstone scapolite is not well known, but can be very attractive. The color of its gemstones, which is usually a nice yellow to orange, pink or color of its gemstones, which is usually a nice yellow to orange, pink or violet, is its best feature as its fire and hardness are somewhat lacking. Less violet, is its best feature as its fire and hardness are somewhat lacking. Less transparent material can often be cut as cabochons that will often exhibit a transparent material can often be cut as cabochons that will often exhibit a good Cat's Eye effect or if the "Cat's Eye" is not distinct enough it wgood Cat's Eye effect or if the "Cat's Eye" is not distinct enough it w

Scapolite seriesScapolite series Marialite Na4Al3Si9O24Cl Marialite Na4Al3Si9O24Cl Crystal System: Crystal System:

Tetragonal - DipyramidalH-M H-M Symbol (4/m) Space Group: I 4/m Symbol (4/m) Space Group: I 4/m

Cleavage: Cleavage: [100] Distinct, [110] [100] Distinct, [110] Distinct Distinct

Color: Color: Bluish, Brownish, Bluish, Brownish, Colorless, Violet, Greenish. Colorless, Violet, Greenish.

Density: Density: 2.5 - 2.62, Average = 2.5 - 2.62, Average = 2.56 2.56

Diaphaniety: Diaphaniety: Transparent to Transparent to Translucent Translucent

Fracture: Fracture: Brittle - Conchoidal - Brittle - Conchoidal - Very brittle fracture producing Very brittle fracture producing small, conchoidal fragments. small, conchoidal fragments.

Hardness: Hardness: 5.5-6 - Knife Blade-5.5-6 - Knife Blade-Orthoclase Orthoclase

Luminescence: Luminescence: Fluorescent. Fluorescent. Luster: Luster: Vitreous - Pearly Vitreous - Pearly Streak: Streak: white white

Scapolite seriesScapolite series Meionite Ca4Al6Si6O24CO3 Meionite Ca4Al6Si6O24CO3 Crystal System: Crystal System: Tetragonal - DipyramidalH-M H-M

Symbol (4/m) Space Group: P 4/mSymbol (4/m) Space Group: P 4/m Cleavage: Cleavage: [???] Distinct, [???] Indistinct [???] Distinct, [???] Indistinct Color: Color: Bluish, Brownish, Colorless, Violet, Bluish, Brownish, Colorless, Violet,

Greenish. Greenish. Density: Density: 2.66 - 2.73, Average = 2.69 2.66 - 2.73, Average = 2.69 Diaphaniety: Diaphaniety: Transparent to subtranslucent Transparent to subtranslucent Fracture: Fracture: Sub Conchoidal - Fractures Sub Conchoidal - Fractures

developed in brittle materials characterized by developed in brittle materials characterized by semi-curving surfaces. semi-curving surfaces.

Habit: Habit: Columnar - Forms columns Columnar - Forms columns Habit: Habit: Fibrous - Crystals made up of fibers. Fibrous - Crystals made up of fibers. Habit: Habit: Massive - Granular - Common texture Massive - Granular - Common texture

observed in granite and other igneous rock. observed in granite and other igneous rock. Hardness: Hardness: 5-6 - Between Apatite and 5-6 - Between Apatite and

Orthoclase Orthoclase Luminescence: Luminescence: Non-fluorescent. Non-fluorescent. Luster: Luster: Vitreous - Resinous Vitreous - Resinous Streak: Streak: colorless colorless

Scapolite seriesScapolite series Analcime NaAlSi2O6·(H2O)Analcime NaAlSi2O6·(H2O) Crystal System: Crystal System: Triclinic - PedialH-M Symbol H-M Symbol

(1) Space Group: P1 (1) Space Group: P1 Cleavage: Cleavage: [001] Indistinct, [010] Indistinct, [001] Indistinct, [010] Indistinct,

[100] Indistinct [100] Indistinct Color: Color: White, Grayish white, Greenish white, White, Grayish white, Greenish white,

Yellowish white, Reddish white. Yellowish white, Reddish white. Density: Density: 2.3 2.3 Diaphaniety: Diaphaniety: Transparent to Subtransparent to Transparent to Subtransparent to

translucent translucent Fracture: Fracture: Sub Conchoidal - Fractures Sub Conchoidal - Fractures

developed in brittle materials characterized by developed in brittle materials characterized by semi-curving surfaces. semi-curving surfaces.

Habit: Habit: Euhedral Crystals - Occurs as well-Euhedral Crystals - Occurs as well-formed crystals showing good external form. formed crystals showing good external form.

Habit: Habit: Granular - Generally occurs as anhedral Granular - Generally occurs as anhedral to subhedral crystals in matrix. to subhedral crystals in matrix.

Habit: Habit: Massive - Uniformly indistinguishable Massive - Uniformly indistinguishable crystals forming large masses. crystals forming large masses.

Hardness: Hardness: 5 - Apatite 5 - Apatite Luminescence: Luminescence: Fluorescent. Fluorescent. Luster: Luster: Vitreous (Glassy) Vitreous (Glassy) Streak: Streak: white white

Zeolite groupZeolite group The zeolites are a popular group of minerals for collectors and an important The zeolites are a popular group of minerals for collectors and an important

group of minerals for industrial and other purposes. They combine rarity, group of minerals for industrial and other purposes. They combine rarity, beauty, complexity and unique crystal habits. Typically forming in the beauty, complexity and unique crystal habits. Typically forming in the cavities, or vesicles, of volcanic rocks, zeolites are the result of very low cavities, or vesicles, of volcanic rocks, zeolites are the result of very low grade metamorphism. Some form from just subtle amounts of heat and grade metamorphism. Some form from just subtle amounts of heat and pressure and can just barely be called metamorphic while others are found pressure and can just barely be called metamorphic while others are found in obviously metamorphic regimes. Zeolite crystals have been grown on in obviously metamorphic regimes. Zeolite crystals have been grown on board the space shuttle and are undergoing extensive research into their board the space shuttle and are undergoing extensive research into their formation and unique properties. The zeolites are framework silicates formation and unique properties. The zeolites are framework silicates consisting of interlocking tetrahedrons of consisting of interlocking tetrahedrons of SiO4SiO4 and and AlO4.AlO4. In order to be a In order to be a zeolite the ratio zeolite the ratio (Si +Al)/O(Si +Al)/O must equal 1/2. The alumino-silicate structure is must equal 1/2. The alumino-silicate structure is negatively charged and attracts the positive cations that reside within. negatively charged and attracts the positive cations that reside within. Unlike most other Unlike most other tectosilicates,, zeolites have large vacant spaces or cages zeolites have large vacant spaces or cages in their structures that allow space for large cations such as sodium, in their structures that allow space for large cations such as sodium, potassium, barium and calcium and even relatively large molecules and potassium, barium and calcium and even relatively large molecules and cation groups such as water, ammonia, carbonate ions and nitrate ions. In cation groups such as water, ammonia, carbonate ions and nitrate ions. In the more useful zeolites, the spaces are interconnected and form long wide the more useful zeolites, the spaces are interconnected and form long wide channels of varying sizes depending on the mineral. These channels allow channels of varying sizes depending on the mineral. These channels allow the easy movement of the resident ions and molecules into and out of the the easy movement of the resident ions and molecules into and out of the structure. Zeolites are characterized by their ability to lose and absorb water structure. Zeolites are characterized by their ability to lose and absorb water without damage to their crystal structures. The large channels explain the without damage to their crystal structures. The large channels explain the consistent low consistent low specific gravity of these minerals. of these minerals.

Zeolites have basically three different structural variations. Zeolites have basically three different structural variations. There are chain-like structures whose minerals form acicular or needle-like There are chain-like structures whose minerals form acicular or needle-like

prismatic crystals, ie prismatic crystals, ie natrolite.. Sheet-like structures where the crystals are flattened platy or tabular with Sheet-like structures where the crystals are flattened platy or tabular with

usually good basal cleavages, ie usually good basal cleavages, ie heulandite.. And framework structures where the crystals are more equant in And framework structures where the crystals are more equant in

dimensions, ie dimensions, ie Chabazite.. A zeolite can be thought of in terms of a house, where the structure of the A zeolite can be thought of in terms of a house, where the structure of the

house (the doors, windows, walls and roof) is really the zeolite while the house (the doors, windows, walls and roof) is really the zeolite while the furniture and people are the water, ammonia and other molecules and ions furniture and people are the water, ammonia and other molecules and ions that can pass in and out of the structure. The chain-like structures can be that can pass in and out of the structure. The chain-like structures can be thought of like towers or high wire pylons. The sheet-like structures can be thought of like towers or high wire pylons. The sheet-like structures can be thought of like large office buildings with the sheets analogous to the floors thought of like large office buildings with the sheets analogous to the floors and very few walls between the floors. And the framework structures like and very few walls between the floors. And the framework structures like houses with equally solid walls and floors. All these structures are still houses with equally solid walls and floors. All these structures are still frameworks (like the true frameworks (like the true tectosilicates that zeolites are). These variations that zeolites are). These variations make the zeolite group very diverse, crystal habit-wise. Otherwise zeolites make the zeolite group very diverse, crystal habit-wise. Otherwise zeolites are typically soft to moderately hard, light in density, transparent to are typically soft to moderately hard, light in density, transparent to translucent and have similar origins. There are about 45 natural minerals translucent and have similar origins. There are about 45 natural minerals that are recognized members of the Zeolite Group. Industrially speaking, the that are recognized members of the Zeolite Group. Industrially speaking, the term zeolite includes natural silicate zeolites, synthetic materials and term zeolite includes natural silicate zeolites, synthetic materials and phosphate minerals that have a zeolite like structure. The complexity of this phosphate minerals that have a zeolite like structure. The complexity of this combined group is extensive with over 120 structural variations and more combined group is extensive with over 120 structural variations and more are being discovered are being discovered or madeor made every year. Collecting zeolites can be very every year. Collecting zeolites can be very enjoyable and fulfilling. enjoyable and fulfilling.

Zeolite groupZeolite group Natrolite Na2[Al2Si3O10]·2(H2O) Natrolite Na2[Al2Si3O10]·2(H2O) Crystal System: Crystal System: Orthorhombic - PyramidalH-H-

M Symbol (mm2) Space Group: F dd2M Symbol (mm2) Space Group: F dd2 Cleavage: Cleavage: [110] Perfect, [010] Imperfect [110] Perfect, [010] Imperfect Color: Color: White, Colorless, Red, Yellowish white, White, Colorless, Red, Yellowish white,

Reddish white. Reddish white. Density: Density: 2.25 2.25 Diaphaniety: Diaphaniety: Transparent to translucent Transparent to translucent Fracture: Fracture: Brittle - Generally displayed by Brittle - Generally displayed by

glasses and most non-metallic minerals. glasses and most non-metallic minerals. Habit: Habit: Acicular - Occurs as needle-like Acicular - Occurs as needle-like

crystals. crystals. Habit: Habit: Nodular - Tuberose forms having Nodular - Tuberose forms having

irregular protuberances over the surface. irregular protuberances over the surface. Habit: Habit: Prismatic - Crystals Shaped like Slender Prismatic - Crystals Shaped like Slender

Prisms (e.g. tourmaline). Prisms (e.g. tourmaline). Hardness: Hardness: 5.5-6 - Knife Blade-Orthoclase 5.5-6 - Knife Blade-Orthoclase Luminescence: Luminescence: None. None. Luster: Luster: Vitreous - Silky Vitreous - Silky Streak: Streak: white white

Zeolite groupZeolite group Chabazite Chabazite

(Ca0.5,Na,K)4[Al4Si8O24]·12H2O (Ca0.5,Na,K)4[Al4Si8O24]·12H2O Crystal System: Crystal System: Triclinic - Pinacoidal

H-M Symbol ( 1) Space Group: P1H-M Symbol ( 1) Space Group: P1 Cleavage: Cleavage: [1011] Imperfect [1011] Imperfect Color: Color: Colorless, Green, Yellow, Colorless, Green, Yellow,

White, Pink. White, Pink. Density: Density: 2.05 - 2.15, Average = 2.09 2.05 - 2.15, Average = 2.09 Diaphaniety: Diaphaniety: Translucent to Translucent to

transparent transparent Fracture: Fracture: Brittle - Uneven - Very brittle Brittle - Uneven - Very brittle

fracture producing uneven fragments. fracture producing uneven fragments. Habit: Habit: Druse - Crystal growth in a Druse - Crystal growth in a

cavity which results in numerous cavity which results in numerous crystal tipped surfaces. crystal tipped surfaces.

Habit: Habit: Pseudo Cubic - Crystals show a Pseudo Cubic - Crystals show a cubic outline. cubic outline.

Hardness: Hardness: 4 - Fluorite 4 - Fluorite Luster: Luster: Vitreous (Glassy) Vitreous (Glassy) Streak: Streak: white white

Zeolite groupZeolite group Heulandite (Ca,Na)2-Heulandite (Ca,Na)2-

3Al3(Al,Si)2Si13O36·12(H2O) 3Al3(Al,Si)2Si13O36·12(H2O) Crystal System: Crystal System: MonoclinicSpace Space

Group: C 2/m, Cm, C 2 Group: C 2/m, Cm, C 2 Cleavage: Cleavage: [010] Perfect [010] Perfect Color: Color: White, Reddish white, Grayish White, Reddish white, Grayish

white, Brownish white, Yellow. white, Brownish white, Yellow. Density: Density: 2.2 2.2 Diaphaniety: Diaphaniety: Transparent to Transparent to

subtranslucent subtranslucent Fracture: Fracture: Brittle - Generally displayed Brittle - Generally displayed

by glasses and most non-metallic by glasses and most non-metallic minerals. minerals.

Habit: Habit: Crystalline - Coarse - Occurs as Crystalline - Coarse - Occurs as well-formed coarse sized crystals. well-formed coarse sized crystals.

Habit: Habit: Tabular - Form dimensions are Tabular - Form dimensions are thin in one direction. thin in one direction.

Hardness: Hardness: 3-3.5 - Calcite-Copper 3-3.5 - Calcite-Copper Penny Penny

Luster: Luster: Vitreous - Pearly Vitreous - Pearly Streak: Streak: white white

Zeolite groupZeolite group Stilbite NaCa4[Al8Si28O72]·n(H2O) Stilbite NaCa4[Al8Si28O72]·n(H2O)

(n=28-32) (n=28-32) Crystal System: Crystal System: Monoclinic - Prismatic

H-M Symbol (2/m) Space Group: C 2/m H-M Symbol (2/m) Space Group: C 2/m Cleavage: Cleavage: [010] Perfect [010] Perfect Color: Color: White, Red, Yellow, Brown, White, Red, Yellow, Brown,

Cream. Cream. Density: Density: 2.1 - 2.2, Average = 2.15 2.1 - 2.2, Average = 2.15 Diaphaniety: Diaphaniety: Transparent to Transparent to

Subtransparent to translucent Subtransparent to translucent Fracture: Fracture: Brittle - Conchoidal - Very Brittle - Conchoidal - Very


Habit: Habit: Fibrous - Crystals made up of Fibrous - Crystals made up of fibers. fibers.

Habit: Habit: Globular - Spherical, or nearly Globular - Spherical, or nearly so, rounded forms (e.g. wavellite). so, rounded forms (e.g. wavellite).

Habit: Habit: Wheat Sheaf - Bundle shaped Wheat Sheaf - Bundle shaped aggregates resembling wheat sheafs aggregates resembling wheat sheafs after hand reaping wheat. after hand reaping wheat.

Hardness: Hardness: 3.5-4 - Copper Penny-3.5-4 - Copper Penny-Fluorite Fluorite

Luster: Luster: Vitreous - Pearly Vitreous - Pearly Streak: Streak: white white

Phyllosilicates @ Phyllosilicates @ TectosilicatesTectosilicates

A report by:A report by:

Paul Michael P. LlorinPaul Michael P. Llorin

BSG-1ABSG-1A

PhyllosilicatesPhyllosilicates Phyllosilicates (from Phyllosilicates (from Greek

φύλλον φύλλον phyllonphyllon, leaf), or sheet , leaf), or sheet silicates, form parallel sheets of silicates, form parallel sheets of silicate tetrahedra with Si2O5 or a silicate tetrahedra with Si2O5 or a 2:5 ratio. 2:5 ratio.

The phyllosilicates, or sheet The phyllosilicates, or sheet silicates, are an important group of silicates, are an important group of minerals that includes the micas, minerals that includes the micas, chlorite, serpentine, talc, and the chlorite, serpentine, talc, and the clay minerals. Because of the clay minerals. Because of the special importance of the clay special importance of the clay minerals as one of the primary minerals as one of the primary products of chemical weathering products of chemical weathering and one of the more abundant and one of the more abundant constituents of sedimentary rocks, constituents of sedimentary rocks, they will be discussed in more they will be discussed in more detail in the next lecture. detail in the next lecture.

Most of the Phyllosilicates, Most of the Phyllosilicates, therefore are monoclinic therefore are monoclinic structures, some are triclinic, & a structures, some are triclinic, & a few orthorhombic or trigonalfew orthorhombic or trigonal

Most phyllosilicates contain hydroxyl Most phyllosilicates contain hydroxyl ion, OH-, with the OH located at the ion, OH-, with the OH located at the center of the 6 membered rings, as center of the 6 membered rings, as shown here. Thus, the group shown here. Thus, the group becomes Si2O5(OH)-3. When other becomes Si2O5(OH)-3. When other cations are bonded to the SiO4 sheets, cations are bonded to the SiO4 sheets, they share the apical oxygens and the they share the apical oxygens and the (OH) ions which bond to the other (OH) ions which bond to the other cations in octahedral coordination. cations in octahedral coordination. This forms a layer of cations, usually This forms a layer of cations, usually Fe+2, Mg+2, or Al+3, that occur in Fe+2, Mg+2, or Al+3, that occur in octahedral coordination with the O and octahedral coordination with the O and OH ions of the tetrahedral layer. As OH ions of the tetrahedral layer. As shown, here, the triangles become the shown, here, the triangles become the faces of the octahedral groups that can faces of the octahedral groups that can bind to the tetrahedral layers. bind to the tetrahedral layers.

PhyllosilicatesPhyllosilicates Serpentine GroupSerpentine Group

AntigoriteAntigorite ChrysotileChrysotile LizarditeLizardite

Clay mineral groupClay mineral group KaoliniteKaolinite TalcTalc PyrophyllitePyrophyllite

Mica groupMica group MuscoviteMuscovite PhlogopitePhlogopite BiotiteBiotite LepidoliteLepidolite MargariteMargarite

Chlorite groupChlorite group ChloriteChlorite

Related mineralsRelated minerals ApophylliteApophyllite PrehnitePrehnite ChrysocollaChrysocolla

Serpentine GroupSerpentine Group The The serpentine groupserpentine group describes describes

a group of common rock-forming a group of common rock-forming hydrous magnesium iron phyllosilicate (( ((Mg, , Fe)3)3Si22O5(5(OH)4) )4) minerals; they may contain ; they may contain minor amounts of other elements minor amounts of other elements including including chromium, , manganese, , cobalt and and nickel. In . In mineralogy and and gemology, serpentine may , serpentine may refer to any of 20 varieties refer to any of 20 varieties belonging to the serpentine group. belonging to the serpentine group. Owing to admixture, these Owing to admixture, these varieties are not always easy to varieties are not always easy to individualize, and distinctions are individualize, and distinctions are not usually made. There are three not usually made. There are three important mineral important mineral polymorphs of of serpentine: serpentine: antigorite, , chrysotile and and lizardite. .

Serpentine GroupSerpentine Group Antigorite-Mg3Si2O5(OH)4Antigorite-Mg3Si2O5(OH)4

Named after Antigo Rio in ItalyNamed after Antigo Rio in Italy Cleavage: Cleavage: [001] Good[001] Good Color: Color: Green, Gray, Bluish Green, Gray, Bluish

gray, Brown, Black. gray, Brown, Black. Density: Density: 2.5 - 2.6, Average = 2.5 - 2.6, Average =

2.542.54 Diaphaniety: Diaphaniety: Translucent to Translucent to

SubopaqueSubopaque Fracture: Fracture: Brittle - Generally Brittle - Generally

displayed by glasses and most displayed by glasses and most non-metallic minerals.non-metallic minerals.

Habit: Habit: Massive - Uniformly Massive - Uniformly indistinguishable crystals indistinguishable crystals forming large masses.forming large masses.

Hardness: Hardness: 3.5-4 - Copper 3.5-4 - Copper Penny-FluoritePenny-Fluorite

Luster: Luster: Vitreous – GreasyVitreous – Greasy Streak: Streak: greenish whitegreenish white Crystal System: Crystal System: monoclinicmonoclinic

Serpentine GroupSerpentine Group Chrysotile- Mg 3Si 2O 5(OH) 4Chrysotile- Mg 3Si 2O 5(OH) 4

Color: Color: Green.Green. Density: Density: 2.53 2.53 Diaphaniety: Diaphaniety: Translucent Translucent Habit: Habit: Acicular - Occurs as Acicular - Occurs as

needle-like crystals. needle-like crystals. Hardness: Hardness: 2.5 - Finger Nail2.5 - Finger Nail Luster: Luster: Silky Silky Streak: Streak: white white Crtystal system: MonoclincCrtystal system: Monoclinc

Serpentine GroupSerpentine Group Lizardite- Mg3Si2O5(OH)4Lizardite- Mg3Si2O5(OH)4

Cleavage: Cleavage: [001] Perfect [001] Perfect Color: Color: Green, Green blue, Green, Green blue,

Yellow, White. Yellow, White. Density: Density: 2.55 - 2.6, Average = 2.55 - 2.6, Average =

2.57 2.57 Diaphaniety: Diaphaniety: Translucent Translucent Hardness: Hardness: 2.5 - Finger Nail2.5 - Finger Nail Streak: Streak: white white Crystal system:Crystal system: monoclinic monoclinic

Clay Mineral GroupClay Mineral Group Clay mineralsClay minerals are hydrous are hydrous

aluminium phyllosilicates, , sometimes with variable amounts sometimes with variable amounts of of iron, , magnesium, , alkali metals, , alkaline earths and other and other cations. . Clays have structures similar to Clays have structures similar to the the micas and therefore form flat and therefore form flat hexagonal sheets. Clay minerals hexagonal sheets. Clay minerals are common are common weathering products products (including weathering of (including weathering of feldspar) ) and low temperature and low temperature hydrothermal alteration products. Clay minerals alteration products. Clay minerals are very common in fine grained are very common in fine grained sedimentary rocks such as such as shale, , mudstone and and siltstone and in fine and in fine grained metamorphic grained metamorphic slate and and phyllite..

Clays are commonly referred to as Clays are commonly referred to as 1:1 or 2:1. Clays are 1:1 or 2:1. Clays are fundamentally built of tetrahedral fundamentally built of tetrahedral sheets and octahedral sheets. A sheets and octahedral sheets. A 1:1 clay would consist of one 1:1 clay would consist of one tetrahedral sheet and one tetrahedral sheet and one octahedral sheet, and examples octahedral sheet, and examples would be kaolinite and serpentine. would be kaolinite and serpentine. A 2:1 clay consists of an A 2:1 clay consists of an octahedral sheet sandwiched octahedral sheet sandwiched between two tetrahedral sheets, between two tetrahedral sheets, and examples are illite, smectite, and examples are illite, smectite, attapulgite, and chlorite (although attapulgite, and chlorite (although chlorite has an external octahedral chlorite has an external octahedral sheet often referred to as sheet often referred to as "brucite") "brucite")

Clay Mineral GroupClay Mineral Group Kaolinite- Al2Si2O5(OH)4Kaolinite- Al2Si2O5(OH)4

Crystal System: Crystal System: Triclinic Cleavage: Cleavage: [001] Perfect [001] Perfect Color: Color: White, Brownish white, White, Brownish white,

Grayish white, Yellowish white, Grayish white, Yellowish white, Grayish green. Grayish green.

Density: Density: 2.6 2.6 Diaphaniety: Diaphaniety: Transparent to Transparent to

translucent translucent Fracture: Fracture: Earthy - Dull, clay-like Earthy - Dull, clay-like

fractures with no visible crystalline fractures with no visible crystalline affinities, (e.g. howlite). affinities, (e.g. howlite).

Habit: Habit: Earthy - Dull, clay-like Earthy - Dull, clay-like texture with no visible crystalline texture with no visible crystalline affinities, (e.g. howlite). affinities, (e.g. howlite).

Hardness: Hardness: 1.5-2 - Talc-Gypsum 1.5-2 - Talc-Gypsum LuminescenceLuminescence: None. : None. Luster: Luster: Earthy (Dull)Earthy (Dull) Streak:Streak: white white

Clay Mineral GroupClay Mineral Group Talc- Mg3Si4O10(OH)2Talc- Mg3Si4O10(OH)2

Crystal System: Crystal System: Monoclinic Cleavage: [001] Perfect Cleavage: [001] Perfect Color: Pale green, White, Gray Color: Pale green, White, Gray

white, Yellowish white, white, Yellowish white, Brownish white. Brownish white.

Density: 2.7 - 2.8, Average = Density: 2.7 - 2.8, Average = 2.75 2.75

Diaphaniety: Translucent Diaphaniety: Translucent Fracture: Uneven - Flat surfaces Fracture: Uneven - Flat surfaces

(not cleavage) fractured in an (not cleavage) fractured in an uneven pattern. uneven pattern.

Habit: Massive - Uniformly Habit: Massive - Uniformly indistinguishable crystals indistinguishable crystals forming large masses. scales. forming large masses. scales.

Hardness: 1 - Talc Hardness: 1 - Talc Luminescence: Fluorescent. Luminescence: Fluorescent. Luster: Vitreous - Pearly Luster: Vitreous - Pearly Streak: whiteStreak: white

Clay Mineral GroupClay Mineral Group Pyrophyllite- Al2Si4O10(OH)2Pyrophyllite- Al2Si4O10(OH)2

Crystal System: Crystal System: Triclinic Cleavage: Cleavage: [001] Perfect [001] Perfect Color: Color: Brown green, Brownish Brown green, Brownish

yellow, Greenish, Gray green, yellow, Greenish, Gray green, Gray white. Gray white.

Density: Density: 2.8 - 2.9, Average = 2.8 - 2.9, Average = 2.84 2.84

Diaphaniety: Diaphaniety: Translucent to Translucent to opaque opaque

Fracture: Fracture: Flexible - Flexible Flexible - Flexible fragments. fragments.

Habit: Habit: Earthy - Dull, clay-like Earthy - Dull, clay-like texture with no visible texture with no visible crystalline affinities, (e.g. crystalline affinities, (e.g. howlite). howlite).

Hardness: Hardness: 1.5-2 - Talc-1.5-2 - Talc-Gypsum Gypsum

Luminescence: Luminescence: Fluorescent. Fluorescent. Luster: Luster: Pearly Pearly

Streak: Streak: white white

Mica GroupMica Group The The micamica group of sheet group of sheet silicate ( (

phyllosilicate) ) minerals includes includes several closely related materials several closely related materials having highly perfect having highly perfect basal cleavage. All are . All are monoclinic with a tendency towards pseudo-with a tendency towards pseudo-hexagonal hexagonal crystals and are similar and are similar in chemical composition. The in chemical composition. The highly perfect cleavage, which is highly perfect cleavage, which is the most prominent characteristic the most prominent characteristic of mica, is explained by the of mica, is explained by the hexagonal sheet-like arrangement sheet-like arrangement of its of its atoms..

The word "mica" is thought to be The word "mica" is thought to be derived from the derived from the Latin word word micaremicare, meaning "to glitter", in , meaning "to glitter", in reference to the brilliant reference to the brilliant appearance of this mineral appearance of this mineral (especially when in small scales).(especially when in small scales).

Mica GroupMica Group Muscovite- KAl2(Si3Al)O10(OH)2 Muscovite- KAl2(Si3Al)O10(OH)2

Crystal System: Crystal System: Monoclinic Cleavage: [001] Perfect Cleavage: [001] Perfect Color: White, Gray, Silver white, Color: White, Gray, Silver white,

Brownish white, Greenish Brownish white, Greenish white. white.


Diaphaniety: Transparent to Diaphaniety: Transparent to translucent translucent

Fracture: Brittle - Sectile - Fracture: Brittle - Sectile - Brittle fracture with slightly Brittle fracture with slightly sectile shavings possible. sectile shavings possible.

Habit: Foliated - Two Habit: Foliated - Two dimensional platy forms. dimensional platy forms.

Habit: Massive - Lamellar - Habit: Massive - Lamellar - Distinctly foliated fine-grained Distinctly foliated fine-grained forms. forms.

Habit: Micaceous - Platy texture Habit: Micaceous - Platy texture with "flexible" plates. with "flexible" plates.

Hardness: 2-2.5 - Gypsum-Hardness: 2-2.5 - Gypsum-Finger Nail Finger Nail

Luminescence: None. Luminescence: None. Luster: Vitreous (Glassy) Luster: Vitreous (Glassy) Streak: white Streak: white

Mica GroupMica Group Phlogopite- KMg3(Si3Al)O10(OH)2Phlogopite- KMg3(Si3Al)O10(OH)2

Crystal System: MonoclinicCrystal System: Monoclinic Cleavage: [001] Perfect Cleavage: [001] Perfect Color: Brown, Gray, Green, Color: Brown, Gray, Green,

Yellow, Reddish brown. Yellow, Reddish brown. Density: 2.7 - 2.9, Average = 2.8 Density: 2.7 - 2.9, Average = 2.8

Diaphaniety: Transparent to Diaphaniety: Transparent to

translucent translucent Fracture: Uneven - Flat surfaces Fracture: Uneven - Flat surfaces


Habit: Lamellar - Thin laminae Habit: Lamellar - Thin laminae producing a lamellar structure. producing a lamellar structure.

Habit: Micaceous - Platy texture Habit: Micaceous - Platy texture with "flexible" plates. Habit: with "flexible" plates. Habit:

Scaly - Morphology like fish Scaly - Morphology like fish scales. scales.

Hardness: 2-2.5 - Gypsum-Hardness: 2-2.5 - Gypsum-Finger Nail Finger Nail

Luminescence: None. Luminescence: None. Luster: Vitreous - Pearly Luster: Vitreous - Pearly Streak: whiteStreak: white

Mica GroupMica Group Biotite- K(Mg,Fe)3[AlSi3O10(OH)2 Biotite- K(Mg,Fe)3[AlSi3O10(OH)2

Crystal System: MonoclinicCrystal System: Monoclinic Cleavage: [001] Perfect Cleavage: [001] Perfect Color: Dark brown, Greenish Color: Dark brown, Greenish

brown, Blackish brown, Yellow, brown, Blackish brown, Yellow, White. White.


Diaphaniety: Transparent to Diaphaniety: Transparent to translucent to opaque translucent to opaque

Fracture: Uneven - Flat surfaces Fracture: Uneven - Flat surfaces (not cleavage) fractured in an (not cleavage) fractured in an uneven pattern. uneven pattern.


Habit: Micaceous - Platy texture Habit: Micaceous - Platy texture with "flexible" plates. with "flexible" plates.

Habit: Pseudo Hexagonal - Habit: Pseudo Hexagonal - Crystals show a hexagonal Crystals show a hexagonal outline. outline.

Hardness: 2.5-3 - Finger Nail-Hardness: 2.5-3 - Finger Nail-Calcite Luminescence: None. Calcite Luminescence: None.

Luster: Vitreous - PearlyLuster: Vitreous - Pearly Streak: gray Streak: gray

Mica GroupMica Group Lepidolite-K(Li,Al)3(Si,Al)4O10(OH)2 Lepidolite-K(Li,Al)3(Si,Al)4O10(OH)2

Crystal System: MonoclinicCrystal System: Monoclinic Cleavage: [001] Perfect Cleavage: [001] Perfect Color: Colorless, Gray white, Color: Colorless, Gray white,

Lilac, Yellowish, White. Lilac, Yellowish, White. Density: 2.8 - 2.9, Average = Density: 2.8 - 2.9, Average =

2.84 2.84 Diaphaniety: Translucent Diaphaniety: Translucent Fracture: Uneven - Flat surfaces Fracture: Uneven - Flat surfaces


Habit: Foliated - Two Habit: Foliated - Two dimensional platy forms. dimensional platy forms.

Habit: Massive - Uniformly Habit: Massive - Uniformly indistinguishable crystals indistinguishable crystals forming large masses. forming large masses.

Habit: Platy - Sheet forms (e.g. Habit: Platy - Sheet forms (e.g. micas). micas).

Hardness: 2.5-3 - Finger Nail-Hardness: 2.5-3 - Finger Nail-Calcite Calcite

Luminescence: None. Luminescence: None. Luster: Vitreous - Pearly Luster: Vitreous - Pearly Streak: white Streak: white

Mica GroupMica Group Margarite-CaAl2(Al2Si2)O10(OH)2 Margarite-CaAl2(Al2Si2)O10(OH)2

Crystal System: MonoclinicCrystal System: Monoclinic Cleavage: [001] Good Cleavage: [001] Good Color: White, Gray, Pinkish Color: White, Gray, Pinkish

gray, Yellowish gray. gray, Yellowish gray. Density: 2.99 - 3.08, Average = Density: 2.99 - 3.08, Average =

3.03 3.03 Diaphaniety: Translucent to Diaphaniety: Translucent to

subtranslucent subtranslucent Fracture: Brittle - Generally Fracture: Brittle - Generally

displayed by glasses and most displayed by glasses and most non-metallic minerals. non-metallic minerals.


Habit: Massive - Lamellar - Habit: Massive - Lamellar - Distinctly foliated fine-grained Distinctly foliated fine-grained forms. forms.

Habit: Scaly - Morphology like Habit: Scaly - Morphology like fish scales. fish scales.

Hardness: 4 - Fluorite Hardness: 4 - Fluorite Luminescence: None. Luminescence: None. Luster: Pearly Luster: Pearly Streak: whiteStreak: white

Chlorite GroupChlorite Group Chlorite- (Mg,Fe)3(Si,Al)4O10Chlorite- (Mg,Fe)3(Si,Al)4O10

(OH)2·(Mg,Fe)3(OH)6(OH)2·(Mg,Fe)3(OH)6 Color: Various shades of green; Color: Various shades of green;

rarely yellow, red, or white.rarely yellow, red, or white. Crystal habit: Foliated masses, Crystal habit: Foliated masses,

scaley aggregates, scaley aggregates, disseminated flakes.disseminated flakes.

Crystal system: Monoclinic 2/m; Crystal system: Monoclinic 2/m; with some triclinic polymorphs.with some triclinic polymorphs.

Cleavage: Perfect 001Cleavage: Perfect 001 Fracture: LamellarFracture: Lamellar Mohs Scale hardness: 2 - 2.5Mohs Scale hardness: 2 - 2.5 Luster: Vitreous, pearly, dullLuster: Vitreous, pearly, dull Refractive index: 1.57 -1.67Refractive index: 1.57 -1.67 Streak: Pale green to greyStreak: Pale green to grey Specific gravity: 2.6-3.3Specific gravity: 2.6-3.3

Related MineralsRelated Minerals Apophyllite-KCa4(Si4O10)2F·8(H2O)Apophyllite-KCa4(Si4O10)2F·8(H2O)

Crystal System: TetragonalCrystal System: Tetragonal Cleavage: [001] Perfect Cleavage: [001] Perfect Color: White, Pink, Green, Color: White, Pink, Green,

Yellow, Violet. Yellow, Violet. Density: 2.3 - 2.4, Average = Density: 2.3 - 2.4, Average =

2.34 2.34 Diaphaniety: Transparent to Diaphaniety: Transparent to

translucent translucent Fracture: Uneven - Flat surfaces Fracture: Uneven - Flat surfaces


Habit: Crystalline - Coarse - Habit: Crystalline - Coarse - Occurs as well-formed coarse Occurs as well-formed coarse sized crystals. sized crystals.

Habit: Massive - Uniformly Habit: Massive - Uniformly indistinguishable crystals indistinguishable crystals forming large masses. forming large masses.

Habit: Pseudo Cubic - Crystals Habit: Pseudo Cubic - Crystals show a cubic outline. show a cubic outline.

Hardness: 4-5 - Fluorite-Apatite Hardness: 4-5 - Fluorite-Apatite Luminescence: None. Luminescence: None.

Luster: Vitreous - Pearly Luster: Vitreous - Pearly Streak: whiteStreak: white

Related MineralsRelated Minerals Prehnite- Ca2Al2Si3O10(OH)2 Prehnite- Ca2Al2Si3O10(OH)2

Crystal System: Crystal System: OrthorhombicOrthorhombic Cleavage: Cleavage: [001] Distinct[001] Distinct Color: Color: Colorless, Gray, Yellow, Colorless, Gray, Yellow,

Yellow green, White. Yellow green, White. Density: 2.8 - 2.95, Average = Density: 2.8 - 2.95, Average =

2.87 2.87 Diaphaneity: Diaphaneity: Sub transparent to Sub transparent to

translucent translucent Fracture: Fracture: Brittle - Generally Brittle - Generally

displayed by glasses and most displayed by glasses and most non-metallic mineralsnon-metallic minerals. .

Habit: Habit: Globular - Spherical, or Globular - Spherical, or nearly so, rounded forms (e.g. nearly so, rounded forms (e.g. wavellite). wavellite).

Habit: Habit: Reniform - "Kidney like" in Reniform - "Kidney like" in shape (e.g.. hematite).shape (e.g.. hematite).

Habit: Habit: Stalactitic - Shaped like Stalactitic - Shaped like pendant columns as stalactites or pendant columns as stalactites or stalagmites (e.g. calcite).stalagmites (e.g. calcite).

Hardness: Hardness: 6-6.5 - Orthoclase-6-6.5 - Orthoclase-Pyrite Pyrite

Luminescence: Luminescence: Non-fluorescent. Non-fluorescent.

Luster: Luster: Vitreous - Pearly Vitreous - Pearly Streak: Streak: colorless colorless

Related MineralsRelated Minerals Chrysocolla- Cu4H4Si4O10(OH)8Chrysocolla- Cu4H4Si4O10(OH)8

Crystal System: OrthorhombicCrystal System: Orthorhombic Cleavage: None Cleavage: None Color: Green, Bluish green, Blue, Color: Green, Bluish green, Blue,

Blackish blue, Brown. Density: Blackish blue, Brown. Density: 1.9 - 2.4, Average = 2.15 1.9 - 2.4, Average = 2.15

Diaphaniety: Translucent to Diaphaniety: Translucent to opaque opaque

Fracture: Brittle - Sectile - Brittle Fracture: Brittle - Sectile - Brittle fracture with slightly sectile fracture with slightly sectile shavings possible. shavings possible.

Habit: Botryoidal - "Grape-like" Habit: Botryoidal - "Grape-like" rounded forms (e.g.. malachite). rounded forms (e.g.. malachite).

Habit: Earthy - Dull, clay-like Habit: Earthy - Dull, clay-like texture with no visible crystalline texture with no visible crystalline affinities, (e.g. howlite). affinities, (e.g. howlite).

Habit: Stalactitic - Shaped like Habit: Stalactitic - Shaped like pendant columns as stalactites pendant columns as stalactites or stalagmites (e.g. calcite). or stalagmites (e.g. calcite).

Hardness: 2.5-3.5 - Finger Nail-Hardness: 2.5-3.5 - Finger Nail-Copper Penny Copper Penny

Luminescence: None. Luminescence: None. Luster: Vitreous - Dull Luster: Vitreous - Dull Streak: light green Streak: light green

TectosilicatesTectosilicates The tectosilicates or framework silicates have a structure wherein all of the The tectosilicates or framework silicates have a structure wherein all of the

4 oxygens of SiO4-4 tetrahedra are shared with other tetrahedra. The ratios 4 oxygens of SiO4-4 tetrahedra are shared with other tetrahedra. The ratios of Si to O is thus 1:2. of Si to O is thus 1:2. Since the Si - O bonds are strong covalent bonds and since the structure is Since the Si - O bonds are strong covalent bonds and since the structure is interlocking, the tectosilicate minerals tend to have a high hardness. interlocking, the tectosilicate minerals tend to have a high hardness.

TectosilicatesTectosilicates

SiO2 MineralsSiO2 Minerals here are nine known here are nine known

polymorphs of SiO2, polymorphs of SiO2, one of which does not one of which does not occur naturally. These occur naturally. These are:are:

NameName Crystal Crystal SystemSystem

Density Density (g/cm(g/cm33) )

RefractivRefractive Index e Index (mean)(mean)

Stishovite Stishovite TetTet 4.35 4.35 1.81 1.81

Coesite Coesite MonMon 3.01 3.01 1.591.59

Low (Low () ) Quartz Quartz

HexHex 2.652.65 1.55 1.55

High (High () ) Quartz Quartz

HexHex 2.532.53 1.54 1.54

Kaetite Kaetite (synthetic) (synthetic)

MonMon 2.50 2.50 1.52 1.52

Low (Low () ) Tridymite Tridymite

Mon or Mon or OrthoOrtho

2.262.26 1.471.47

High (High () ) Tridymite Tridymite

HexHex 2.22 2.22 1.47 1.47

Low (Low () ) CristobalitCristobalitee

TetTet 2.322.32 1.48 1.48

High (High () ) CristobalitCristobalite e

IsoIso 2.20 2.20 1.48 1.48

TectosilicatesTectosilicates

SiO2 groupSiO2 group QuartzQuartz TridymiteTridymite CristobaliteCristobalite OpalOpal

Feldspar groupFeldspar group Feldspathoid groupFeldspathoid group ScapoliteScapolite ZeoliteZeolite

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION Phase equilibriaPhase equilibria – involves the application of physical – involves the application of physical

chemistry to the study of the origin of minerals and rockschemistry to the study of the origin of minerals and rocks PhasePhase – a homogeneous substance with well-defined set of – a homogeneous substance with well-defined set of

physical and chemical propertiesphysical and chemical properties ““phase” can be used interchangeably with “mineral” only phase” can be used interchangeably with “mineral” only

if a mineral is essentially pure (no compositional if a mineral is essentially pure (no compositional variation)variation)

Eg. Low quartz (SiOEg. Low quartz (SiO22)–low temp. phase in chem. system)–low temp. phase in chem. system

kyanite (Alkyanite (Al22SiOSiO55)–high pressure phase in the system)–high pressure phase in the system Phase regionPhase region - when a mineral exhibits solid solution - when a mineral exhibits solid solution

Eg. Solid solution series between forsterite and fayaliteEg. Solid solution series between forsterite and fayalite Phase maybe solid, liquid or gaseous as in the case of HPhase maybe solid, liquid or gaseous as in the case of H22O O

with 3 distinct phases: ice, water and steam depending on with 3 distinct phases: ice, water and steam depending on the stability in terms of pressure and temperature (P-T diag)the stability in terms of pressure and temperature (P-T diag)

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION If water and ice coexist together in constant amounts If water and ice coexist together in constant amounts

indefinitely (no water forming at the expense of ice and vice indefinitely (no water forming at the expense of ice and vice versa), then water and ice are versa), then water and ice are in equilibriumin equilibrium

In rocks, where the constituent minerals coexisted since In rocks, where the constituent minerals coexisted since their formation, one cannot always conclude whether the their formation, one cannot always conclude whether the mineral constituents are in equilibriummineral constituents are in equilibrium

If there are no reaction rims between minerals that touch If there are no reaction rims between minerals that touch each other, the minerals were in equilibrium at the time of each other, the minerals were in equilibrium at the time of formationformation

If however, rims are visible then these were not in If however, rims are visible then these were not in equilibrium (eg. garnet separated by chlorite rim from equilibrium (eg. garnet separated by chlorite rim from coexisting biotite)coexisting biotite)

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION Phase diagramsPhase diagrams – outline the stability fields of minerals (eg. – outline the stability fields of minerals (eg.

Eh-pH diagrams for iron and sulfides)Eh-pH diagrams for iron and sulfides) Liquidus diagramsLiquidus diagrams - crystallization sequence of minerals - crystallization sequence of minerals

from a liquid phase or melt (eg. SiOfrom a liquid phase or melt (eg. SiO22-KAlSiO-KAlSiO44-Mg-Mg22SiOSiO44

diagram)diagram) Mineral assemblageMineral assemblage

Granite: orthoclase-albite-quartz-biotiteGranite: orthoclase-albite-quartz-biotite Coarse texture of granite may indicate that all 4 minerals Coarse texture of granite may indicate that all 4 minerals

formed as crystallization products at about the same formed as crystallization products at about the same elevated temperatures, thus, is the mineral assemblage elevated temperatures, thus, is the mineral assemblage or mineral paragenesis of granite since they appear to or mineral paragenesis of granite since they appear to have been in equilibrium have been in equilibrium

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION MagmaMagma – masses of molten matter (900 to 1600 °C) plus – masses of molten matter (900 to 1600 °C) plus

their dissolved fluids derived from the earth’s crust and the their dissolved fluids derived from the earth’s crust and the upper mantleupper mantle

Composition of magma is not the same as that of the Composition of magma is not the same as that of the rocks from which they were derivedrocks from which they were derived

Made principally up of O, Si, Al, Fe, Ca, Mg, Na and KMade principally up of O, Si, Al, Fe, Ca, Mg, Na and K Plus volatile (gaseous) substances (water vapor, COPlus volatile (gaseous) substances (water vapor, CO22, ,

HH22S, HCl, CHS, HCl, CH44,B, F and CO) that escape or react with ,B, F and CO) that escape or react with minerals already formed before complete consolidation minerals already formed before complete consolidation occursoccurs

Volatiles play an important part in the complex series of Volatiles play an important part in the complex series of changes that take place when the temperature and changes that take place when the temperature and pressure of magma is reduced:pressure of magma is reduced:a.a. Volatiles do not enter appreciably into the minerals which Volatiles do not enter appreciably into the minerals which

crystallize first, but are concentrated in the residual material. crystallize first, but are concentrated in the residual material. The volatiles eventually form a magmatic water phase and The volatiles eventually form a magmatic water phase and finally a hydrothermal phase finally a hydrothermal phase

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION

b.b. Volatiles lower the temperature of crystallization and greatly Volatiles lower the temperature of crystallization and greatly increase the fluidity and chemical reactivity of the residual increase the fluidity and chemical reactivity of the residual magma, and the pressure of the expanding gases tend to magma, and the pressure of the expanding gases tend to force magmatic material into adjacent rocksforce magmatic material into adjacent rocks

c.c. Volatiles may be important in the reactions between the Volatiles may be important in the reactions between the magma and the country rock (contact metamorphism) and are magma and the country rock (contact metamorphism) and are also involved in the concentration of certain mineral ores. If also involved in the concentration of certain mineral ores. If near the surface, volatiles may escape and form sublimates or near the surface, volatiles may escape and form sublimates or contaminate groundwater (ie. hotsprings)contaminate groundwater (ie. hotsprings)

Pneumatolysis – Pneumatolysis – general term applied to the formation of general term applied to the formation of minerals in an igneous rock or in the fissures of the minerals in an igneous rock or in the fissures of the adjoining wall rock by gases or vapors emanating from adjoining wall rock by gases or vapors emanating from the igneous massthe igneous mass

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION Range from felsic (625°C ) to mafic (1200°C)Range from felsic (625°C ) to mafic (1200°C) Temporary features within the earth’s crust and upper Temporary features within the earth’s crust and upper

mantlemantle No continuous molten layer underlies the solid crustNo continuous molten layer underlies the solid crust Originate by partial or selective melting of the upper mantle Originate by partial or selective melting of the upper mantle

or the crustor the crust Calc-alkalic magmas from by partial melting of eclogite Calc-alkalic magmas from by partial melting of eclogite

in the upper mantlein the upper mantle Granitic magmas form in similar fashion or by partial Granitic magmas form in similar fashion or by partial

melting of sedimentary rocksmelting of sedimentary rocks Felsic magmas form crystal sedimentsFelsic magmas form crystal sediments Basaltic magmas form from upwelling of upper mantleBasaltic magmas form from upwelling of upper mantle

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION CrystallizationCrystallization – inasmuch as magmas are solutions, – inasmuch as magmas are solutions,

crystallization or precipitation of the constituent minerals will crystallization or precipitation of the constituent minerals will commence when their concentrations exceed their solubi-commence when their concentrations exceed their solubi-lities. The crystallization of minerals is not determined lities. The crystallization of minerals is not determined simply by their temperatures of fusionsimply by their temperatures of fusion**. The solution of one . The solution of one constituent lowers the melting point of another constituent. constituent lowers the melting point of another constituent. Consequently magmas remain fluid at temperatures well Consequently magmas remain fluid at temperatures well below the melting points of all its minerals. Crystallization below the melting points of all its minerals. Crystallization commences below this point. As the temperature lowers commences below this point. As the temperature lowers and the solution becomes supersaturated in specific and the solution becomes supersaturated in specific minerals, their crystallization eventually ensuesminerals, their crystallization eventually ensues

When magma cools the mineral with the highest melting When magma cools the mineral with the highest melting point does not necessarily crystallize first, but rather, the point does not necessarily crystallize first, but rather, the least soluble (basic-low SiOleast soluble (basic-low SiO22), followed by the more soluble ), followed by the more soluble

ones (acid) → fractional crystallization or magmatic ones (acid) → fractional crystallization or magmatic differentiationdifferentiation

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION The lower solubility substances crystallize first (apatite, The lower solubility substances crystallize first (apatite,

zircon, ilmenite, magnetite, chromite)zircon, ilmenite, magnetite, chromite) Olivine and orthopyroxene are among the earliest to Olivine and orthopyroxene are among the earliest to

crystallize followed by clinopyroxenes, Ca-plagioclase, crystallize followed by clinopyroxenes, Ca-plagioclase, hornblende, Na-Ca plagioclase, Na plagioclase, orthoclase, hornblende, Na-Ca plagioclase, Na plagioclase, orthoclase, mica and quartzmica and quartz

Crystallization is not in all cases a simple formation of Crystallization is not in all cases a simple formation of mineralsminerals

Certain minerals, once formed, may continue to react with Certain minerals, once formed, may continue to react with the enclosing liquid magma, with the result that their the enclosing liquid magma, with the result that their composition is continually being modified and new minerals composition is continually being modified and new minerals or solid solutions resultor solid solutions result

Reaction SeriesReaction Series – a sequence of reactions – a sequence of reactions

BOWEN’S REACTION SERIESBOWEN’S REACTION SERIES

MAGMA TYPES

Basalt

Andesite

Rhyolite

olivine

Sodium-rich

anorthite

Low temperature (late crystallization)

quartz

amphibole

pyroxene

biotite mica

potasium feldsparmuscovite mica

andesine

labradorite

bytownite

albite

oligoclase

High temperature (early crystallization)

Discontinuous series of m

afic minerals

Con

tinuo

us s

erie

s of

pla

gioc

lase

feld

spar

Calcium-rich

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION Magmatic differentiationMagmatic differentiation – process by which a variety of – process by which a variety of

rock types are produced from an originally homogeneous rock types are produced from an originally homogeneous magmamagma

Order of CrystallizationOrder of CrystallizationThe first major silicate minerals to crystallize from the The first major silicate minerals to crystallize from the magma are basic minerals, low in silica such as olivine magma are basic minerals, low in silica such as olivine and basic plagioclase. Non-silicate minerals, like sulfides and basic plagioclase. Non-silicate minerals, like sulfides and oxides of iron, copper, nickel, chromium and and oxides of iron, copper, nickel, chromium and titanium as well as platinum and diamond, maybe titanium as well as platinum and diamond, maybe associated with the basic silicate minerals. Next to associated with the basic silicate minerals. Next to crystallize are the intermediate silicates. The acidcrystallize are the intermediate silicates. The acid** minerals, such as orthoclase, mica and quartz, minerals, such as orthoclase, mica and quartz, crystallize last. This sequence of crystallization explains crystallize last. This sequence of crystallization explains the formation of different rock types from one magma.the formation of different rock types from one magma.

Complete crystallization and differentiation and no Complete crystallization and differentiation and no orogenic disturbance → zoned or layered igneous mass orogenic disturbance → zoned or layered igneous mass → ultrabasic → basic rocks → intermediate → acid rock→ ultrabasic → basic rocks → intermediate → acid rock

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION With the subtraction of the most mafic minerals from the With the subtraction of the most mafic minerals from the

magma, the residual magma in general becomes magma, the residual magma in general becomes progressively felsic. Granitic residual magmas are solutions progressively felsic. Granitic residual magmas are solutions rich in silica, alkalies, water and mineralizing fluids, some of rich in silica, alkalies, water and mineralizing fluids, some of these may be squeezed into fissures to become these may be squeezed into fissures to become pegmatitespegmatites

With progressing crystallization, the residual volatile fluids With progressing crystallization, the residual volatile fluids gather the metals possibly as complex chlorides that gather the metals possibly as complex chlorides that originally were either sparsely contained in the magma or originally were either sparsely contained in the magma or existed with connate fluids that were drawn in the magma existed with connate fluids that were drawn in the magma cupola along with the rare earths. These solutions become cupola along with the rare earths. These solutions become expelled or are deposited in the shattered of the intrusion expelled or are deposited in the shattered of the intrusion upon final crystallization and constitute the upon final crystallization and constitute the hydrothermal hydrothermal solutionssolutions that give rise to economic deposits that give rise to economic deposits

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION PEGMATITE STAGEPEGMATITE STAGE

After the major portion of the magma has crystallized , After the major portion of the magma has crystallized , the residue is greatly enriched in in the volatile the residue is greatly enriched in in the volatile constituents, the chief of which is water vapor. constituents, the chief of which is water vapor. Consequently, when the temperature is reduced Consequently, when the temperature is reduced sufficiently to allow liquid water to exist, a very hot and sufficiently to allow liquid water to exist, a very hot and highly concentrated aqueous solution (magmatic water) highly concentrated aqueous solution (magmatic water) is formed. This magmatic water still contains SiOis formed. This magmatic water still contains SiO22, Al, Al22OO33, , NaNa22O and KO and K22O plus a concentration of of many of the O plus a concentration of of many of the less common elements. The magmatic water is more less common elements. The magmatic water is more fluid than the magma, and is often injected into the fluid than the magma, and is often injected into the adjacent rocks causing vein-like bodies called adjacent rocks causing vein-like bodies called PEGMATITE DIKES that resemble granitic rocks. The PEGMATITE DIKES that resemble granitic rocks. The large crystals form because of the greater fluidity of the large crystals form because of the greater fluidity of the magmatic water compared to the viscous magma magmatic water compared to the viscous magma

MAGMATIC EVOLUTIONMAGMATIC EVOLUTION HYDROTHERMAL STAGEHYDROTHERMAL STAGE

Following the pegmatite stage, there may be a Following the pegmatite stage, there may be a hydrothermal stage of mineral deposition. Many hydrothermal stage of mineral deposition. Many important ores occur in hydrothermal veins near important ores occur in hydrothermal veins near magmatic intrusions. Hydrothermal veins are composed magmatic intrusions. Hydrothermal veins are composed entirely of non-silicate mineralsentirely of non-silicate mineralsHypothermal VeinsHypothermal Veins – great depths, high P & T of 300 to – great depths, high P & T of 300 to 500°C (cassiterite, wolframite, molybde-nite, native gold)500°C (cassiterite, wolframite, molybde-nite, native gold)Mesothermal VeinsMesothermal Veins – intermediate depths, lower P & T – intermediate depths, lower P & T of 200 to 300°C (pyrite, chalcopyrite, arsenopyrite, of 200 to 300°C (pyrite, chalcopyrite, arsenopyrite, galena, sphalerite, tetrahedrite, quarts, carbonates)galena, sphalerite, tetrahedrite, quarts, carbonates)Epithermal VeinsEpithermal Veins – near surface, 50 to 200°C (cinnabar, – near surface, 50 to 200°C (cinnabar, stibnite, marcasite, pyrite, native gold, quartz, opal, stibnite, marcasite, pyrite, native gold, quartz, opal, calcite, fluorite, barite)calcite, fluorite, barite)

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