Lecture7 minerals
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Lecture7 minerals Presentation Transcript

  • 1. Minerals
  • 2. Lithosphere: the Solid Earth What’s below the surface: Rocks
  • 3. But what’s inside a rock?
  • 4. Yes, but What’s a Mineral? 1 cm Rock- a natural aggregate of minerals (and/or mineraloids)
  • 5. - a naturally occurring, inorganic, crystalline solid with a definite chemical composition and characteristic physical properties e.g., quartz, diamond, graphite, talc Mineral
  • 6. Mineralogy
    • = study of the composition, properties, & classification of minerals (Geo 321- offered in Fall)
    • Minerals id’d by
      • crystal structure
      • hardness
      • luster
      • streak
      • color
      • density
  • 7. What is a crystalline solid? Are any inorganic solids not crystalline? Glass
  • 8. How do we know a material is crystalline? Self-Similarity Halite Quartz
  • 9. How do we know a material is crystalline? X-ray diffraction
  • 10. Chemistry of the Solid Earth The Big 8 Elements
  • 11. The Earth’s Crust O 46% -2 Si 28% +4 Al 8% +3 Fe 5% +2/+3 Ca 4% +2 Mg 3% +2 Na 3% +1 K 2% +1 Element Abundance Charge 99%
  • 12. SiO 2 - Quartz
  • 13. Silica Tetrahedron SiO 4 What is the charge? Si = +4, O = -2 thus -4 How can that be?
  • 14. (Fe, Mg) 2 SiO 4 - Olivine
  • 15. How old are the oldest rocks on Earth?
    • Given: Sample from Acasta Gneiss in Canada
    • It has crystals of zircon that
    • contain 238 U.
    • 238 U is unstable.
    • It decays into 206 Pb.
    ZrSiO 4 ~Fixed chemical formula. But a few U’s can be used To substitute for Zr.
  • 16. How do Minerals Form? - Cooling from liquid (magma) to a solid
  • 17. How do Minerals Form? - Evaporation of a briny liquid - Cooling from liquid (magma) to a solid
  • 18. How do Minerals Form? - Precipitation from a fluid Section of a pipe Mineralized vein - Evaporation of a briny liquid - Cooling from liquid (magma) to a solid
  • 19. Asbestos- fibrous silicate mineral w/ fireproofing qualities Ceiling tiles
  • 20. Asbestos- commercial term, not a geological term Chrysotile- sheet structure no sharp fibres- no hazard Crocidolite- chain structure sharp fibres- BIG hazard The Cost- 50 to 150 billion $ to clean it all up >half of the asbestos is harmless Chrysotile What to Do?
  • 21. What is a rock again?
    • = assemblage of minerals (or mineraloids) in a solid state
    • 3 types
    • igneous
    • sedimentary
    • metamorphic
  • 22. Igneous Sedimentary Metamorphic Plutonic Volcanic
  • 23. 1. Igneous rocks ( fire-formed )
    • = rock that solidified from a molten state
    • majority of crustal rock (although it is often covered with sedimentary rocks)
    • consists of silicate minerals w/ metallic elements
    • “ interlocking grains”
    • e.g. granite, basalt, obsidian, pumice
    • Magma : molten rock beneath Earth’s surface
  • 24. Granite Basalt Obsidian Pumice