Basics of Mineralogy

Basics of Mineralogy Geology 100 Geology for Environmental Scientists Terms to Know: • Atom • Molecule • Proton • Neutron • Electron • Isotope • Ion • Bonding – ionic – covalent – metallic

The 6 Crystal Systems • All have 3 axes, except for 4 axes in Hexagonal system • Isometric -- all axes equal length, all angles 90 • Hexagonal -- 3 of 4 axes equal length, three angles @ 90, three @ 120 • Tetragonal -- two axes equal length, all angles 90 not common in rock forming minerals) • Orthorhombic -- all axes unequal length, all angles 90 • Monoclinic -- all axes unequal length, only two angles are 90 • Triclinic -- all axes unequal length, no angles @ 90

Moh’s Scale of Hardness 1. Talc 2. Gypsum 3. Calcite 4. Fluorite 5. Apatite 6. Orthoclase 7. Quartz 8. Topaz 9. Corundum (ruby) 10. Diamond

Rock Forming Minerals • Sialic Minerals • Mafic Minerals • Clay Minerals • Non-silicate Minerals

Sialic Minerals - rich in Si and Al • Feldspars – K-feldspar: KAlSi3O8 – plagioclase: NaAlSi3O8 - CaAl2Si2O8 • Quartz: SiO2 • Muscovite: KAl3Si3O10(OH)2

Mafic Minerals - rich in Mg & Fe • Olivine: (Mg,Fe)2SiO4 • Pyroxene: (Mg,Fe)SiO3 • Amphibole: Ca2(Mg,Fe)5Si8O22(OH)2 • Biotite: K(Mg,Fe)3AlSi3O10(OH)2

Clay Minerals • Form from weathering of silicate minerals; common in shale, mudstone, and soil. • Kaolinite: Al4Si4O10(OH)8 • Montmorillonite or bentonite: . (Al,Mg)8(Si4O10)3(OH)10 12H20 • Illite: more complex than montmorillonite

Non-Silicate, Sedimentary Minerals • Calcite: CaCO3 • Dolomite: CaMg(CO3)2 • Halite: NaCl . • Gypsum: CaSO4 2H2O