copyright (c) 2005 pearson education canada, inc.2-1 powerpoint presentation stan hatfield....

Copyright (c) 2005 Pearson Education Canada, Inc. 2-1

PowerPoint Presentation

Stan Hatfield . Southwestern Illinois College

Ken Pinzke . Southwestern Illinois College

Charles Henderson . University of Calgary

Tark Hamilton . Camosun College

Chapter 2

Matter and Minerals

Copyright (c) 2005 Pearson Education Canada Inc. 2-2

Minerals: The Building Blocks of Rocks

Definition of a mineral:

• Naturally occurring

• Inorganic (except organic salts, Calcium Oxalate)

• Solid

• Ordered internal molecular structure

• Definite chemical composition (not exact)

Definition of a rock:

• A natural solid aggregate or mass of minerals


Lifetime Per Capita Mineral Usage

1.64 X 106 Kg all minerals 361 Kg Pb: batteries, solder261 Kg Zn: brass, cathodics, chemicals682 Kg Cu: wiring, alloys1633 Kg Al: aircraft, cans, foil, lawn chairs14864 Kg Fe: spoons nails cars ships bldgs12824 Kg NaCl: deicing, detergent, food562773 Kg: Stone, gravel, sand


The Composition of MineralsElements

• Basic building blocks of minerals• 112 are known now (92 naturally occurring)• Each element has a common standard state: g,l,s

Atoms• Smallest particles of matter• Retains all the characteristics of an element• Atoms have equal proton and electron counts

Isotopes• Atoms with same Z proton # but different n neutron #• Most isotopes are stable and present since the last Nova• Eg: 1H – Hydrogen and 2H – Deuterium both Z=1 proton• Natural Hydrogen averages 1.00079 amu (grams per mole)• 3H – Tritium is radioactive, short lived & man made

Ions• Charged “atom” with more or fewer electrons• Cations are small and positively charged (oxidized)• Anions are large and negatively charged (reduced) • Most matter in the universe occurs as ions


Fewer than 20 are Geologically Abundant


The Composition of Minerals

Atomic structure• Nucleus tiny central region consisting of:

– Protons (positive charges) whose #Z is unique to each Element

– Neutrons (no charge) ~1amu like proton gives isotope weights

– Together they account for 99% of an atom’s mass

– Most of atoms, ions and thus all matter is empty space

• Electrons– Negatively charged particles that surround the nucleus

– Electrons have very little mass but move fast and give matter most of its volume

– Located in discrete energy levels called shells & orbitals

– Some of these have particular directions accounting for bond angles and symmetries in matter as a whole


Two models of the atom.

Atoms: Building Blocks for Minerals


Heavy Atoms FormWhen Stars go Nova


Relative atomic abundances of the seven most common elements that comprise 97% of the Earth's mass..


Elements’ Cosmic Abundance

ZEven > ZOdd



Chemical bonding• Formation of a compound by combining two or

more elements

Ionic bonding• Atoms gain or lose outermost (valence) electrons to

form ions• Ionic compounds consist of an orderly

arrangement of oppositely charged ions


Chemical Bonds, Compounds & Minerals

Chemical bonding• Formation of a compound by combining two elements• Elements: H2(g) , O2(g) , C(s) , Cl2(g) , Fe(s) , Au(s) • Compounds: H2O(l), CO2(g), NaCl(s), SiO2(s) , Fe2O3(g)

Ionic bonds (most minerals)• Atoms gained or lost outermost (valence) electrons to

form ions: +Cations < -Anions• Ionic compounds consist of an orderly arrangement of

oppositely charged ionsCovalent bonds (gases and the complex anion parts of many minerals: silicates, carbonates, phosphates)Van der Waals’ bonds (weak polar bonds involving Hydrogen in ice, clays)Metallic bonding shares electrons throughout


Ionic Bonding with aPrimitive Cubic Lattice

Schematic diagrams illustrating the arrangement of sodium and chloride ions in halite.



Covalent bonding• Atoms share one or more pairs of electrons to

achieve electrical neutrality• Covalent compounds are generally stronger than

ionic bonds • Both ionic and covalent bonds typically occur in

the same compound (bonds are seldom 100% ionic or covalent in character)

• The oxy-anions: silicates, sulfates, carbonates, phosphates, borates all have some covalency

• (The cations and anions of minerals are ionic)


Illustration of the sharing of a pair of electrons in N2(g).

A Covalent Bond


Cryosphere: Ice Crystals with Hydrogen Bonding

Red negative ends of the water molecule attract Green positive ends forming hexagonal ice


Chemical Bonds in Minerals

Metallic bonding– Valence electrons are free to migrate among

atoms– Weaker and less common than ionic or covalent

bonds– Typically cubic lattices of metal cations with– Freely exchanged conduction band electrons– This accounts for Termal & Electrical

Conductivity– Au, Ag, Cu, Pt: in native metals


Isotopes and radioactive decay• Mass number is the sum of neutrons plus protons

in an atom• An isotope is an atom that exhibits variation in its

mass number• Most elements have 1-3 common isotopes• Some radioactive isotopes have unstable nuclei that

emit particles and energy in a process known as radioactive decay

• Examples: 12C >> 13C >>>> 14C ; 238U >> 235U



The Structure of Minerals

Minerals consist of an orderly array of atoms chemically bonded to form a particular crystalline structure

For ionic compounds, the atomic arrangement is primarily determined by the size of ions involved & closest packing

For covalent compounds, the atomic arrangement is primarily determined by the orbital geometry (bond shapes)


Hexagonal versus Cubic Closest Packing


Hexagonal versus Cubic Closest Packing

HCP: 2 layers ABABABA… CCP: 3 layers ABCABC…

A

B

A

A

BC

A

B


The Structure of Minerals

Polymorphs• Two or more minerals with the same chemical

composition, but different crystalline structures and physical properties

• Diamond (Cubic) and graphite (Hexagonal) are different polymorphs of the element Carbon

– The transformation of one polymorph to another is called a phase change

– Each polymorph (structure) is stable at different conditions of Pressure & Temperature


Diamond & Graphite: 2Carbon Polymorphs


Physical Properties of Minerals

Crystal Form• External expression of the orderly internal

arrangement of atoms• Crystal growth is often interrupted because of

competition for space and rapid loss of heat• Competition for space and ions with adjacent

crystals• Crystals which form in fluids like water or magma

attain ideal euhedral forms


WEB RESOURCES

http://webmineral.com/help/Forms.shtml#isometric

http://www.mindat.org/

http://www.rockhounds.com/rockshop/xtal/part1.html

http://www.klingereducational.com/

http://home.comcast.net/~eswab/ObjectThumbnails.html


Crystal Form: individual crystal shape

Habit: aggregate shapes & appearance

Lustre: appearance in reflected light

Colour: of the bulk specimen

Streak: true colour of powdered compound

Hardness: bond strength & arrangement

Cleavage: breakage on planes at some angle

Fracture: qualitative shapes & surfaces

Common Physical Properties of Minerals



Lustre• Appearance of a mineral in reflected light• This relates to the nature of the interaction of

photons with electrons in the mineral structure• Two basic categories

– Metallic always opaque

– Nonmetallic variably: transparent, transluscent, opaque

• Other terms, such as: sub-metallic, adamantine, vitreous, silky, greasy or earthy, are used to further describe particular qualities of lustre



Colour• Generally an unreliable diagnostic property to use

for mineral identification, lustre & streak better• Often highly variable for a given mineral due to

slight changes in mineral chemistry• Exotic colourations of some minerals produce

gemstones• Most metals and dense metallic sulfide and oxide

compounds appear silvery grey• Native sulfur is consistently yellow or greenish


Quartz (SiO2) exhibits a variety of colours as in the purple amethyst.



Streak• True Colour of a mineral in its powdered form• Helpful in distinguishing different forms of the

same mineral

Hardness• Resistance of a mineral to abrasion or

scratching using common impliments: fingernail, penny, knife, glass or other mineral

• All minerals are compared to a standard scale called the Mohs scale of hardness

• Depends on bonds, strength, arrangement



Cleavage• Tendency to break along planes of weak

bonding• Produces flat, shiny surfaces• Otherwise it is termed fracture• Described by resulting geometric shapes

– Number of planes

– Angles between adjacent planes


Copyright (c) 2005 Pearson Education Canada Inc. 2-35Three examples of perfect cleavage – fluorite, halite, and calcite.


Cubic 3 @ 90°3 pinacoids, (100)

Tetrahedral 4 @ 109.5°Octahedral 4 pinacoids @ 90°, (111)

Rhombohedral 3No 90° or 60°/120°


Fracture• Absence of cleavage when a mineral is broken

Specific Gravity• Ratio of the weight of a mineral to the weight of an

equal volume of water• Average value is approximately 2.7 for quartz

• S.G. = Weightair / Weightair – Weightwater

• S.G. = Densityair / Density of water



Other properties• Magnetism• Reaction to dilute hydrochloric acid• Tenacity• Malleability• Elasticity• Conductivity• Double refraction• Twinning• Taste• Smell



Classification of MineralsNearly 4000 minerals have been identified on Earth but many occur only at a very few places!

Minerals are classified by their dominant space filling anion type: oxides, silicates, sulfides…

Rock-forming minerals• Common minerals that make up most of the rocks

of Earth’s crust• Only a few dozen members• Composed mainly of the 8 elements that make up

over 98% of the continental crust


Classification of Minerals


Example Mineral Name OriginsBytownite (Ab30-10An70-90) Bytown = Ottawa

Calcite (CaCO3) calx, L. Lime

Carletonite (KNa4Ca4Si8O18(CO3)4(OH,F) H2O) Carleton U., Mont St. Hilaire

Cassiterite (SnO2) kassiteros, Gr. Tin

Labradorite (Ab50-30An50-70) Labrador

Monteregianite KCa2AlSi7O17(OH)2·6(H2O) Monteregian Hills PQ, (Hydrodelhayelite)

Sperrylite (PtAs2) F. Sperry (discoverer), ON


Silicates• Most important mineral group

– Comprise most of the rock-forming minerals

– Very abundant due to large amounts of silicon and oxygen in Earth’s crust

• Basic building block is the silicon-oxygen tetrahedron a molecule and an anion

– Four oxygen ions surrounding a much smaller silicon ion

– (SiO4)-4



Silicate structures• Single tetrahedra are linked together to form

various structures including– Isolated tetrahedra

– Double tetrahedra

– Ring structures (3, 4, 6)

– Single and double chain structures

– Sheet or layered structures

– Complex 3-dimensional network structures

– All of these molecular anions are held together by cations making ionic bonds



Common Silicate Polymeric Anions

Three types of silicate structures.


Common Silicate minerals (dark ferromagnesian silicate minerals)

• Olivine (usually pale olive green)– High temperature Fe-Mg silicate

– Individual tetrahedra, linked together by iron and magnesium ions

– Forms small, rounded crystals with no cleavage

– Most abundant mineral in Peridotite rock of Earth’s upper mantle and stony meteorites

– Gem variety is called Peridot

– (Mg,Fe)2SiO4

– Mg variety = Forsterite, Fe variety = Fayalite

Ferromagnesian Silicates



• Pyroxene Group– Single chain structures involving iron and magnesium

– Two distinctive cleavages at nearly 90 degrees

– Orthopyroxenes are the most common mineral in the pyroxene group

– (Mg,Fe)SiO3

– Mg variety = Enstatite, Fe variety = Hypersthene

– Augite/Diopside is the most common Clinopyroxene

– Ca(Mg,Fe)(SiO3)2

– Mg variety = Augite, Fe Variety = Hedenbergite




• Amphibole Group– Double chain structures involving a variety of ions

– Two perfect cleavages exhibiting angles of about 60 and 120 degrees (56° / 124° )

– Hornblende is the most common mineral in the amphibole group

– Hornblende is a Calcium ferromagnesian silicate with a complicated formula based on 23 oxygens but you won’t have to memorize this!

– Actinolite, Tremolite and Riebeckite are also common


Copyright (c) 2005 Pearson Education Canada Inc. 2-49 Hornblende crystals.

Amphiboles


Common Silicate minerals (light nonferromagnesian silicate minerals)

• Mica Group– Sheet structures that result in one direction of

perfect cleavage

– Biotite is the common dark coloured mica mineral

– Muscovite is the common light coloured mica mineral



Common Silicate minerals (light nonferromagnesian silicate minerals)

• Feldspar Group– Most common mineral group– 3-dimensional framework of tetrahedra

exhibit two directions of perfect cleavage at near 90-degree angles

– Orthoclase (potassium feldspar) and Plagioclase (sodium and calcium feldspar) are the two most common members



Potassium feldspar (orthoclase).



Plagioclase feldspar with striations.



Common Silicate minerals• Clay minerals

– Clay is a general term used to describe a variety of complex minerals

– Clay minerals all have a sheet or layered structure

– Most originate as products of chemical weathering



Important nonsilicate minerals• Several major groups exist including

– Oxides– Sulphides– Sulphates– Native Elements– Carbonates– Halides– Phosphates



Important nonsilicate minerals• Carbonate Minerals

– Primary constituents in limestone and dolostone

– Calcite (calcium carbonate) and Dolomite (calcium-magnesium carbonate) are the two most important carbonate minerals



Important nonsilicate minerals• Many nonsilicate minerals have economic value

• Examples– Hematite (oxide mined for iron ore)

– Galena (lead)

– Sphalerite (sulphide mined for zinc ore)

– Native Copper (native element mined for copper)

– Native Gold, Silver, Carbon (diamonds)

– Sylvite (Potash) (KCl salt)




Thick beds of potash at an underground mine in Saskatchewan.


End of Chapter 2

copyright (c) 2005 pearson education canada, inc.2-1 powerpoint presentation stan hatfield....

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