Mineral Identification and Classification
Mineral Identification
Physical Properties
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Crystal habit - well formed, not well formed
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Hardness
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related to size, charge, and packing
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Mohs Hardness Scale - 1. talc, 2. gypsum, 3. calcite, 4. fluorite, 5. apatite,
6. orthoclase, 7. quartz, 8. topaz, 9. corundum, 10. diamond
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Cleavage
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cleavage direction - 1, 2, 3?
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cleavage quality - poor to excellent
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Fracture - concoidal , fibrous, splintery, etc.
Mineral Identification (cont.)
Physical and Other Properties
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Luster - vitreous, pearly, metallic, etc.
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Color (including streak)
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Specific gravity and density
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Chemical Properties
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acid test - calcite, dolomite(?)
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Optical properties - petrographic microscope
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Atomic spacing - x-ray diffraction (best)
Mineral Classification
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Common crustal elements as ions: O2-, Si4+, Al3+,
Fe2+,3+,Ca2+, Mg2+, Na+, K+
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Rock-forming minerals
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olivine, pyroxene, amphibole, mica, clay minerals, feldspar, quartz, calcite,
dolomite
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Accessory minerals -common but in small amounts; often diagnostic of origin
of rock
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e.g., chlorite, garnet, hematite, pyrite
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Classified based on anion
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Silicates - SiO44- anion
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silicon-oxygen tetrahedron - building block; interconnected or bonded by
cations
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isolated - olivine (Fe, Mg)2SiO4
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ring - beryl
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chain
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single - pyroxene (Fe, Mg)SiO3
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double - hornblende (amphibole); hydrous Fe, Mg silicate
Rock-Forming Minerals
Classification (cont.)
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sheet - biotite (mica), clay minerals
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framework
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quartz - SiO2
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feldspars - orthoclase (KAlSi3O8, plagioclase (CaAl2Si2O8
-> NaAlSi3O8)
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Non-silicates
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Native elements - gold, silver, sulfur, carbon (polymorphs graphite and
diamond)
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Carbonates (CO32-)
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polymorphs calcite and aragonite - CaCO3
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dolomite - CaMg(CO3)2-
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Oxides (O2-) - hematite (Fe2O3), spinel
(Mg2Al2O4)
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Sulfides (S2-) - pyrite (FeS2)
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Sulfates (SO42-)
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anhydrite (CaSO4)
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gypsum (CaSO4.2H2O) - hydrated