geology 102 - 3b minerals

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geology 102 - 3b minerals
2013-12-29 21:48:53
geol 102 minerals

geol 102 minerals
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  1. Major building block of silicates
    silicate tetrahedron SiO4-
  2. Silicates combine to form minerals in two ways
    1. Combine with cations (Na, K, Ca, Mg2+, Fa2+)

    2.  Can share oxygens with other Si-O tetrahedras
  3. Types of silicate linkages:
    • 1.  Isolated tetrahedra
    • 2.  Single-chain linkages
    • 3.  Double-chain linkages
    • 4.  Sheet linkages
    • 5.  Frameworks/3D frameworks
  4. Carbonates
    • -Carbonate ions
    • -Form sheets similar to sheet silicates
    • -Seperated by layers of cations
  5. Oxides
    • -O2- bonds with cations, usually metallic ions
    • -ionically bonded minerals
  6. Sulfides
    • -S2- bonds with cations
    • -almost all are opaque and metallic
  7. Sulfates
    - SO4 (2-) bonds with cations

    -Occurs primarily as precipitate from briny water
  8. Halides
    Halogen anions (Cl-, Br-, F-, I-)

    Form ionic bonds

    Most have isometric crystal forms
  9. What makes a gem? (4 characteristics)
    -Beauty - as reflected by color and luster

    • -Transparency
    • -Brilliance (enhanced by cutting and polishing)
    • -Durability (based on hardness)
    • -Rarity (and perceived rarity)
  10. Luster
    Quality and intensity of reflected light.  Metallic vs. nonmetallic.
  11. Color
    Not a reliable method for mineral ID.  Useful to distinguish dark vs light colored minerals. Color changes are due impurities.
  12. Streak
    -The color of a mineral when it is powdered.

    -Powdered mineral color is more reliable than the solid color of a mineral.
  13. Hardness
    • -A measure of the minerals resistance to scratching and abrasion.  
    • -Function of crystal structure, types of bonds, types of atoms.
  14. Cleavage
    -Tendency of a mineral to break along flat, parallel surfaces
  15. Fracture
    • -Breakage of a mineral not on planes of weakness.  
    • -Results in irregular shapes
    • -Specific type: concoidal fracture - concentric disc-shaped fracture
  16. Crystal form..
    -Geometric shape that a mineral develops when it grows in an unconfined space.  Specific shape determined by its internal atomic arrangement.