Earth Sciences 1022A/B Lecture Notes - Lecture 2: Calcite, Zinc Sulfide, Sphalerite
7 Dec 2015
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Document Summary
They are solid chemical compounds that are found in nature. They vary in the way that they are put together (the chemical bonding) Atomic bonding and molecular structure determine their physical characteristics. Only 20 minerals are very common in the earth"s crust. Silicon-oxygen tetrahedron (is the basic building block of the mineral) Olivine: single tetrahedra bonded to fe+2, mg+2 ions. Pyroxene: single chains of tetrahedra, ~90degree cleavage (within the chain there is very strong covalent bonding, metals come in between the chains) Amphibole: double chains, ~120degree cleavage (stronger covalent bonding within chains, weaker ionic bonding between chains) Biotite: (black mica) tetrahedral sheets with perfect (basal) cleavage (double sheet al+3 fe+2 mg+2, k+ k+ weakest bonding, al+3. Not all silicates are ferromagnesian (have iron in them) such as: Quartz: all tetrahedra (sio2), no cleavage, hardness of 7. Halite: nacl, common salt; also used for chlorine, baking soda. Gypsum: caso4 x 2h20, used to make plaster and drywall.
