Lecture7 minerals
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Lecture7 minerals

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    Lecture7 minerals Lecture7 minerals Presentation Transcript

    • Minerals
    • Lithosphere: the Solid Earth What’s below the surface: Rocks
    • But what’s inside a rock?
    • Yes, but What’s a Mineral? 1 cm Rock- a natural aggregate of minerals (and/or mineraloids)
    • - a naturally occurring, inorganic, crystalline solid with a definite chemical composition and characteristic physical properties e.g., quartz, diamond, graphite, talc Mineral
    • 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
    • What is a crystalline solid? Are any inorganic solids not crystalline? Glass
    • How do we know a material is crystalline? Self-Similarity Halite Quartz
    • How do we know a material is crystalline? X-ray diffraction
    • Chemistry of the Solid Earth The Big 8 Elements
    • 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%
    • SiO 2 - Quartz
    • Silica Tetrahedron SiO 4 What is the charge? Si = +4, O = -2 thus -4 How can that be?
    • (Fe, Mg) 2 SiO 4 - Olivine
    • 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.
    • How do Minerals Form? - Cooling from liquid (magma) to a solid
    • How do Minerals Form? - Evaporation of a briny liquid - Cooling from liquid (magma) to a solid
    • 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
    • Asbestos- fibrous silicate mineral w/ fireproofing qualities Ceiling tiles
    • 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?
    • What is a rock again?
      • = assemblage of minerals (or mineraloids) in a solid state
      • 3 types
      • igneous
      • sedimentary
      • metamorphic
    • Igneous Sedimentary Metamorphic Plutonic Volcanic
    • 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
    • Granite Basalt Obsidian Pumice