Chapter 2b Mineral and Rocks Minerals A mineral is a naturally occurring homogeneous solid of definite chemical composition and ordered atomic arrangement that is usually formed by inorganic processes A Natural Crystalline Phase Minerals A mineral must occur naturally It must be chemically homogeneous down to the atomic level It must have a chemical formula eg SiO2 FeS2 It must have a defined crystal structure It must be inorganic not the result of biological processes alone Some Familiar Minerals Quartz SiO2 Pyrite FeS2 Calcite CaCO3 Gold Au Silver Ag Copper Cu Diamond C Graphite C K feldspar KAlSi3O8 Na feldspar NaAlSi3O8 Olivine Mg2SiO4 Garnet Mg3Al2Si3O12 Gypsum CaSO4H2H2O Apatite Ca5 PO4 3OH Ice H2O Some Non Mineral Solids Obsidian Glass Opal Amorphous Coal Amorphous Wood Organic Amber Organic Polymorphs Same composition different structure Graphite Diamond C Quartz Tridymite Cristobalite Coesite Calcite Aragonite CaCO3 Pyrite Marcasite FeS2 Isomorphs Same Structure Different Composition Olivine Mg2SiO4 Fe2SiO4 Calcite Rhodochrosite CaCO3 MnCO3 Apatite Ca5 PO4 3OH Ca5 PO4 3F Mineral Properties Hardness Mohs Scale Luster Color Shape A Rock is an Aggregate of Minerals Igneous Crystallized from melts Surface Volcanic Subsurface Intrusive Sedimentary Deposited from air and water on the surface Metamorphic Recrystallized from pre existing igneous or sedimentary rocks
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