Mineral Identification
Physical Properties

• Crystal habit - well formed, not well formed
• Hardness
• related to size, charge, and packing
• Mohs Hardness Scale - 1. talc, 2. gypsum, 3. calcite, 4. fluorite, 5. apatite, 6. orthoclase, 7. quartz, 8. topaz, 9. corundum, 10. diamond
• Cleavage
• cleavage direction - 1, 2, 3?
• cleavage quality - poor to excellent
• Fracture - concoidal , fibrous, splintery, etc.

• Luster - vitreous, pearly, metallic, etc.
• Color (including streak)
• Specific gravity and density
•  

• acid test - calcite, dolomite(?)
• Optical properties - petrographic microscope
• Atomic spacing - x-ray diffraction (best)

• Common crustal elements as ions: O^2-, Si⁴⁺, Al³⁺, Fe^2+,3+,Ca²⁺, Mg²⁺, Na⁺, K⁺
• Rock-forming minerals
• olivine, pyroxene, amphibole, mica, clay minerals, feldspar, quartz, calcite, dolomite
• Accessory minerals -common but in small amounts; often diagnostic of origin of rock
• e.g., chlorite, garnet, hematite, pyrite
•  Classified based on anion
• Silicates - SiO₄^4-  anion
• silicon-oxygen tetrahedron - building block; interconnected or bonded by cations
• isolated - olivine (Fe, Mg)₂SiO₄
• ring -  beryl
• chain
• single - pyroxene (Fe, Mg)SiO₃
• double - hornblende (amphibole); hydrous Fe, Mg silicate

• sheet - biotite (mica), clay minerals
• framework
• quartz - SiO₂
• feldspars - orthoclase (KAlSi₃O₈, plagioclase (CaAl₂Si₂O₈ -> NaAlSi₃O₈)

 
• Non-silicates
• Native elements - gold, silver, sulfur, carbon (polymorphs graphite and diamond)
• Carbonates (CO₃^2-)
• polymorphs calcite and aragonite - CaCO₃
• dolomite - CaMg(CO₃)^2-
• Oxides (O^2-) - hematite (Fe₂O₃), spinel (Mg₂Al₂O₄)
• Sulfides (S^2-) - pyrite (FeS₂)
• Sulfates (SO₄^2-)
• anhydrite (CaSO₄)
• gypsum (CaSO₄.2H₂O) - hydrated