List of 10 minerals (groups) you really want to know to be people Quartz, Olivine, Amphibole, Pyroxene, Feldspars, Garnet, Staurolith, Aluminosilicates, Micas, Calcite

Chemical classes of minerals Silicates – contain O and Si Carbonates – contain C and O Oxides – contain O and metallic cations Sulfides – contain S and metallic cations Sulfates – contain SO4 and metallic cations Rock-forming minerals

Chemical classes - continued Halides – contain Cl, F, I, or Br Hydroxides – contain OH Native elements – masses of all the same element metallically bonded Rock-forming minerals

Silicate ion (SiO 4 4– ) Oxygen ions (O 2– ) Silicon ion (Si 4+ ) The silicate ion forms tetrahedra. Quartz structure Rock-forming minerals Formation of silicate minerals

Rock-forming minerals Isolated silica tetrahedra have isolated [SiO4] 4− tetrahedra that are connected only by interstitial cations. Single-chain linkages have interlocking chains of silicate tetrahedra with SiO 3, 1:3 ratio, Double-chain linkages like above but Si 4 O 11, 4:11 ratio, for double chains. Sheet linkages parallel sheets of silicate tetrahedra with Si 2 O 5 or a 2:5 ratio. Frameworks have a three-dimensional framework of silicate tetrahedra with SiO 2 or a 1:2 ratio.

MineralChemical formula Cleavage planes and number of cleavage directions Silicate structure Specimen 1 plane Isolated tetrahedra Olivine(Mg, Fe) 2 SiO 4

Isolated tetrahedra (soro- and nesosilicates) Olivine group: forsterite-fayalite solid solution

MineralChemical formula Cleavage planes and number of cleavage directions Silicate structure Specimen 1 plane Isolated tetrahedra 2 planes at 90° Single chains Olivine Pyroxene (Mg, Fe) 2 SiO 4 (Mg, Fe)SiO 3

MineralChemical formula Cleavage planes and number of cleavage directions Silicate structure Specimen 1 plane Isolated tetrahedra 2 planes at 90° Single chains 2 planes at 60° and 120° Double chains Olivine Pyroxene Amphibole (Mg, Fe) 2 SiO 4 (Mg, Fe)SiO 3 Ca 2 (Mg, Fe) 5 Si 8 O 22 (OH) 2

Fig. 2.17

Fig. 3.19

Single chains of tetrahedra Pyroxene group Fig. 3.11

Double chains of tetrahedra Amphibole group

MineralChemical formula Cleavage planes and number of cleavage directions Silicate structure Specimen 1 plane Isolated tetrahedra 2 planes at 90° Single chains 2 planes at 60° and 120° Double chains 1 plane Sheets Olivine Pyroxene Amphibole Micas (Mg, Fe) 2 SiO 4 (Mg, Fe)SiO 3 Ca 2 (Mg, Fe) 5 Si 8 O 22 (OH) 2 Muscovite: KAl 2 (AlSi 3 O 10 )(OH) 2 Biotite: K(Mg, Fe) 3 AlSi 3 O 10 (OH) 2

Sheets of tetrahedra (phyllosilicates) Mica group

chrysotile

MineralChemical formula Cleavage planes and number of cleavage directions Silicate structure Specimen 1 plane Isolated tetrahedra 2 planes at 90° Single chains 2 planes at 60° and 120° Double chains 1 plane Sheets Olivine Pyroxene Amphibole Micas Feldspars 2 planes at 90° Three-dimensional framework (Mg, Fe) 2 SiO 4 (Mg, Fe)SiO 3 Ca 2 (Mg, Fe) 5 Si 8 O 22 (OH) 2 Muscovite: KAl 2 (AlSi 3 O 10 )(OH) 2 Biotite: K(Mg, Fe) 3 AlSi 3 O 10 (OH) 2 Orthoclase feldspar: KAlSi 3 O 8 Plagioclase feldspar: (Ca, Na) AlSi 3 O 8

3-D frameworks of tetrahedra (tectosilicates) Feldspar group

Feldspars

Some minerals contain water E.g., Amphiboles, Chlorite, Serpentine Water plays a crucial role in plate tectonic.

SZ-scheme

Halides Fluorite CaF 2 Halite NaCl Sylvite KCl halite x 2 fluorite x 2 sylvite

Carbonates Second most abundant group in the Earth’s crust Major component of limestone, marble, carbonatites Three major minerals: Calcite: CaCO 3 Aragonite: CaCO 3 Dolomite: (Ca,Mg)CO 3 calcite aragonite x 2

Fig. 3.12

Aragonite is the high-pressure polymorph of calcite, but it is also found in shells, hot springs, and cave deposits Temperature (C)

70% of bone is made of “hydroxyapatite:” apatite, calcite, fluorite, calcium hydroxide; 90% of tooth enamel consists of this TEM image showing apatite nano-crystals in a well-preserved dinosaur bone. Huifang Xu, Madison Phosphates Apatite: Ca 5 (PO 4 ) 3 S apatite on calcite

Sulfates GypsumCaSO 4 ·2H 2 O (anhydrite: no H 2 O) BariteBaSO 4 gypsum, gypsum, growing in mud anhydrite barite

Sulfides Pyrite FeS 2 GalenaPbS

Oxides and hydroxides MagnetiteFe 3 O 4 HematiteFe 2 O 3 CorundumAl 2 O 3 magnetite hematite x 2 corundum x 2

Pressure [kbars]