Systematic MineralogySystematic Mineralogy Description of how minerals are Description of how minerals are

divided into groupsdivided into groups Groups based on anionsGroups based on anions

Single anion (ClSingle anion (Cl--)) Anion group (SiOAnion group (SiO44

4-4-)) Further divided based on structuresFurther divided based on structures

DivisionsDivisions Class (anion division)Class (anion division) Family (structural division – silicates Family (structural division – silicates

mostly)mostly) Group (structural division)Group (structural division) Series (solid solution)Series (solid solution) Species (individual minerals)Species (individual minerals) Varieties (substituted elements)Varieties (substituted elements)

ExampleExample Ca-grunerite:Ca-grunerite:

A Ca-rich A Ca-rich varietyvariety Of a mineral Of a mineral speciesspecies In the cummingtonite-grunerite In the cummingtonite-grunerite seriesseries Of the amphibole Of the amphibole groupgroup Of the inosilicate Of the inosilicate familyfamily Of the silicate Of the silicate classclass

Mineral classMineral class Anion or anion Anion or anion gpgp

Native Native elementselements

N/AN/A

OxidesOxides OO2-2-

HydroxidesHydroxides OHOH--

HalidesHalides ClCl--, Br, Br--, F, F--

SulfidesSulfides SS2-2-

SulfatesSulfates SOSO442-2-

CarbonatesCarbonates COCO332-2-

PhosphatesPhosphates POPO443-3-

SilicatesSilicates SiOSiO444-4-

SilicatesSilicates The most common group of minerals The most common group of minerals

forming Earth’s crustforming Earth’s crust 25% of all minerals (~1000)25% of all minerals (~1000) 40% of rock forming minerals40% of rock forming minerals 90% of earth’s crust – i.e., those 90% of earth’s crust – i.e., those

minerals you are likely to findminerals you are likely to find

Silicate StructureSilicate Structure Basic building block: silica Basic building block: silica

tetrahedrontetrahedron SiSi4+4+ with four O with four O2-2- surrounding it surrounding it Net charge is 4-Net charge is 4- Mesodesmic, polymerizationMesodesmic, polymerization

Tetrahedron can share oxygen atomsTetrahedron can share oxygen atoms

Fig. 11-1Fig. 11-1

Silica Tetrahedron

Six groups of silicate Six groups of silicate mineralsminerals

Orthosilicates = NesosilicatesOrthosilicates = Nesosilicates Single tetrahedronSingle tetrahedron

Disilicates = SorosilicatesDisilicates = Sorosilicates Two tetrahedrons share single oxygenTwo tetrahedrons share single oxygen

Ring silicates = CyclosilicatesRing silicates = Cyclosilicates 4, 5, or 6 tetrahedron share two oxygen4, 5, or 6 tetrahedron share two oxygen

Chain silicates = InosilicatesChain silicates = Inosilicates 2 or 3 oxygen shared, arranged in single 2 or 3 oxygen shared, arranged in single

or double chainor double chain Sheet silicates = PhyllosilicatesSheet silicates = Phyllosilicates

3 oxygen shared in sheets3 oxygen shared in sheets Framework silicates = TectosilicatesFramework silicates = Tectosilicates

All 4 oxygen are sharedAll 4 oxygen are shared

Fig. 11-2Fig. 11-2

Ortho-Ortho-(Neso)(Neso)Di-Di-(Soro)(Soro)RingRing(Cyclo)(Cyclo)

Chain – Chain – double double and and singlesingle(Ino)(Ino)

Framework(Tecto)SheetSheet

(Phyllo)(Phyllo)

Z/O ratiosZ/O ratios Z = Si tetrahedral sitesZ = Si tetrahedral sites

Can be other cations, most commonly AlCan be other cations, most commonly Al Z/O ratio depends on type of silicateZ/O ratio depends on type of silicate

Ortho = 1/4Ortho = 1/4 Di = 2/7Di = 2/7 Ring = 1/3Ring = 1/3 Chain, single = 1/3; double = 4/11Chain, single = 1/3; double = 4/11 Sheet = 2/5Sheet = 2/5 Framework = 1/2Framework = 1/2

Other ionsOther ions Quartz (and polymorphs) only Quartz (and polymorphs) only

minerals with only Si and Ominerals with only Si and O All other silicates are charge All other silicates are charge

balanced by other cationsbalanced by other cations ““glue” that holds together silica glue” that holds together silica

tetrahedrontetrahedron

Degree of polymerization depends on Degree of polymerization depends on availability of Siavailability of Si Quartz and feldspars (framework): Si-Quartz and feldspars (framework): Si-

rich environmentsrich environments Si/O = ½Si/O = ½

Olivine (orthosilicate): Si-poor Olivine (orthosilicate): Si-poor environmentenvironment

Si/O = ¼Si/O = ¼

Mafic vs FelsicMafic vs Felsic MaficMafic – rich in – rich in MaMagnesium and Iron gnesium and Iron

((FeFerrum), Si-poorrrum), Si-poor E.g. biotite, amphiboles, pyroxenes, and E.g. biotite, amphiboles, pyroxenes, and

olivineolivine Commonly dark colored Commonly dark colored

FelsicFelsic – rich in Si and Al – rich in Si and Al E.g. E.g. FeFeldspars, Quartz (ldspars, Quartz (SiSiOO22), muscovite, ), muscovite,

feldspathoidsfeldspathoids Commonly light coloredCommonly light colored