Basics of MineralogyTerms to Know:The 6 Crystal SystemsMoh’s Scale of Hardness, Table 3.1Rock Forming MineralsSialic Minerals - rich in Si and AlMafic Minerals - rich in Mg & FeClay MineralsSEM photograph of clay minerals: Permian, Supai Group, Grand Canyon; x 20,900. Figure 05-D, U.S. Geological Survey ProfessionaNon-Silicate, Sedimentary MineralsBasics of MineralogyGeology 200Geology for Environmental ScientistsTerms to Know:• Bonding– ionic– covalent– metallic•Atom• Molecule•Proton•Neutron• Electron• Isotope•IonPeriodic Table of the ElementsFig. 3.3Ionic BondingFig 3.4ACovalent BondingFig 3.4BFigure 3.5 -- The effects of temperature and pressure on the physical state of matter, in this case water.The 6 Crystal Systems• All have 3 axes, except for 4 axes in Hexagonal system• Isometric -- all axes equal length, all angles 90ο• Hexagonal -- 3 of 4 axes equal length, three angles@ 90ο, three @ 120ο• Tetragonal -- two axes equal length, all angles 90ο(not common in rock forming minerals)• Orthorhombic -- all axes unequal length, all angles 90ο• Monoclinic -- all axes unequal length, only two angles are 90ο• Triclinic -- all axes unequal length, no angles @ 90οPyrite -- an example of the isometric crystal system: cubesGalena -- an example of the isometric crystal system: cubesFluorite -- an example of the isometric crystal system, octahedrons, and an example of variation in colorGarnet -- an example of the isometric crystal system: dodecahedronsGarnet in schist, a metamorphic rockLarge masses of garnet -- a source for commercial abrasivesQuartz -- an example of the hexagonal crystal system.Amethyst variety of quartz -- an example of color variation in a mineral. The purple color is caused by small amounts of iron.Agate -- appears to be a noncrystalline variety of quartz but it has microscopic fibrous crystals deposited in layers by ground water.Calcite crystals. Calcite is in the hexagonal crystal system.Tourmaline crystals grown together like this are called “twins”. Tourmaline is in the hexagonal crystal system.Andalusite -- an example of the orthorhombic crystal systemOlivine crystals in a nickel-iron matrix from a meteorite. Olivine is in the orthorhombic crystal system.Gypsum crystals -- an example of the monoclinic systemA gypsum rose. An example of different crystal habits, sheets instead of blades, for the same mineral.Orthoclase -- a K-feldspar, an example of the monoclinic systemMicrocline -- a K-feldspar, an example of the triclinic systemKyanite -- an example of the triclinic systemBauxite -- an amorphous mineral (noncrystalline). Bauxite is aluminum ore that forms by tropical weathering of aluminum silicates.Crystal systems and example minerals: Isometric - diamond, garnet, halite, pyriteHexagonal - quartz, calcite, dolomiteTetragonal - not common in rock forming mineralsOrthorhombic - anhydrite, olivine, stauroliteMonoclinic - orthoclase, biotite, muscovite, amphibole, pyroxene, gypsum, kaoliniteTriclinic - plagioclase (Na-Ca-feldspar), microcline, kyaniteChemical Classification of minerals and some examples:Native elements - gold, silver, copperSulfides - pyrite (FeS2), galena (PbS)Oxides - hematite, limonite (iron oxides)Halides - rock salt or halite, fluoriteCarbonates - calcite, dolomiteSulfates - gypsum, anhydriteSilicates - quartz, biotite, K-feldspar, plagioclase, pyroxene, amphiboleChemical Composition of MineralsMany minerals have a precise chemical formula. Examples include:quartz, SiO2calcite, CaCO3Other minerals have a variable formula because of ionic substitution, which does not change crystal structure. Examples include:olivine (Mg, Fe)2SiO4pyroxene (Mg, Fe)SiO3plagioclase NaAlSi3O8or CaAl2Si2O8Figure 3.7 -- The relative size and electrical charge of ions.Gold, a native elementCopper -- an example of a native elementHalite -- an example of a halide mineralAnhydrite -- example of a sulfate mineralMajor Silicate Mineral Groups based on tetrahedral configurations:Isolated: olivine, garnet, kyaniteDouble: uncommon in rocksRings: uncommon in rocksSingle chains: pyroxenesDouble chains: amphibolesSheets: micas, chlorite, clay mineralsFramework: feldspars and quartzFigure 3.18 -- The silicon-oxygen tetrahedronFigure 3.19 -- Silicon-oxygen tetrahedral groupsOlivine -- isolated tetrahedraAugite -- single-chain tetrahedra, a pyroxene mineralHornblende -- double-chain tetrahedra, an amphibole mineralPlagioclase feldspar – framework tetrahedra; notice the twinning striations characteristic of this mineral.These are the physical properties most useful for mineral identification: Color (be careful, not always diagnostic)Luster Transparency or Opacity Crystal SystemCrystal HabitTwinning of crystalsCleavage Fracture Hardness: Table 3.1 in TextbookSpecific Gravity or densityStreakExamples of cleavageA: biotite -- one directionB: calcite -- three directionsMoh’s Scale of Hardness, Table 3.16. Orthoclase7. Quartz8. Topaz9. Corundum (ruby)10. Diamond1. Talc2. Gypsum3. Calcite4. Fluorite5. ApatiteConchoidal fracture in quartz. Also an example of vitreous or glassy luster.Density -- some exampleswater 1 g/cm3quartz 2.65 g/ cm3olivine 3.37-4.40 g/ cm3lead 11 g/ cm3gold 20 g/ cm3Rock Forming Minerals• Sialic Minerals•Mafic Minerals•Clay Minerals• Non-silicate MineralsSialic Minerals - rich in Si and Al•Feldspars– K-feldspar: KAlSi3O8– plagioclase: NaAlSi3O8-CaAl2Si2O8•Quartz: SiO2• Muscovite: KAl3Si3O10(OH)2Mafic 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)2Clay 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 montmorilloniteSEM photograph of clay minerals: Permian, Supai Group, Grand Canyon; x 20,900. Figure 05-D, U.S. Geological Survey Professional Paper 1173.Non-Silicate, Sedimentary Minerals• Calcite: CaCO3• Dolomite: CaMg(CO3)2• Halite: NaCl• Gypsum: