Lecture7 minerals
- 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