Lecture7 minerals

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Lecture7 minerals

  1. 1. Minerals
  2. 2. Lithosphere: the Solid Earth What’s below the surface: Rocks
  3. 3. But what’s inside a rock?
  4. 4. Yes, but What’s a Mineral? 1 cm Rock- a natural aggregate of minerals (and/or mineraloids)
  5. 5. - a naturally occurring, inorganic, crystalline solid with a definite chemical composition and characteristic physical properties e.g., quartz, diamond, graphite, talc Mineral
  6. 6. Mineralogy <ul><li>= study of the composition, properties, & classification of minerals (Geo 321- offered in Fall) </li></ul><ul><li>Minerals id’d by </li></ul><ul><ul><li>crystal structure </li></ul></ul><ul><ul><li>hardness </li></ul></ul><ul><ul><li>luster </li></ul></ul><ul><ul><li>streak </li></ul></ul><ul><ul><li>color </li></ul></ul><ul><ul><li>density </li></ul></ul>
  7. 7. What is a crystalline solid? Are any inorganic solids not crystalline? Glass
  8. 8. How do we know a material is crystalline? Self-Similarity Halite Quartz
  9. 9. How do we know a material is crystalline? X-ray diffraction
  10. 10. Chemistry of the Solid Earth The Big 8 Elements
  11. 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. 12. SiO 2 - Quartz
  13. 13. Silica Tetrahedron SiO 4 What is the charge? Si = +4, O = -2 thus -4 How can that be?
  14. 14. (Fe, Mg) 2 SiO 4 - Olivine
  15. 15. How old are the oldest rocks on Earth? <ul><li>Given: Sample from Acasta Gneiss in Canada </li></ul><ul><li>It has crystals of zircon that </li></ul><ul><li>contain 238 U. </li></ul><ul><li>238 U is unstable. </li></ul><ul><li>It decays into 206 Pb. </li></ul>ZrSiO 4 ~Fixed chemical formula. But a few U’s can be used To substitute for Zr.
  16. 16. How do Minerals Form? - Cooling from liquid (magma) to a solid
  17. 17. How do Minerals Form? - Evaporation of a briny liquid - Cooling from liquid (magma) to a solid
  18. 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. 19. Asbestos- fibrous silicate mineral w/ fireproofing qualities Ceiling tiles
  20. 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. 21. What is a rock again? <ul><li>= assemblage of minerals (or mineraloids) in a solid state </li></ul><ul><li>3 types </li></ul><ul><li>igneous </li></ul><ul><li>sedimentary </li></ul><ul><li>metamorphic </li></ul>
  22. 22. Igneous Sedimentary Metamorphic Plutonic Volcanic
  23. 23. 1. Igneous rocks ( fire-formed ) <ul><li>= rock that solidified from a molten state </li></ul><ul><li>majority of crustal rock (although it is often covered with sedimentary rocks) </li></ul><ul><li>consists of silicate minerals w/ metallic elements </li></ul><ul><li>“ interlocking grains” </li></ul><ul><li>e.g. granite, basalt, obsidian, pumice </li></ul><ul><li>Magma : molten rock beneath Earth’s surface </li></ul>
  24. 24. Granite Basalt Obsidian Pumice

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