Lecture7 minerals
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Transcript of Lecture7 minerals
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Minerals
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Lithosphere: the Solid Earth
What’s below the surface:Rocks
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But what’s inside a rock?
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1 cm1 cm
Rock- Rock- a natural a natural aggregate of aggregate of mineralsminerals(and/or(and/ormineraloids)mineraloids)
Yes, but What’s a Mineral?
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- a naturally occurring, inorganic, crystalline solid with a definite chemical composition and characteristic physical properties
e.g., quartz, diamond, graphite, talc
Mineral
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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
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What is a crystalline solid?
Are any inorganic solids not crystalline?
GlassGlass
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How do we know a material is crystalline?Self-Similarity
HaliteQuartz
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How do we know a material is crystalline?
X-ray diffraction
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Chemistry of the Solid Earth
The Big 8 ElementsThe Big 8 Elements
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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%
The Earth’s Crust
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SiO2 - Quartz
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Silica Tetrahedron SiO4
What is the charge?
Si = +4, O = -2 thus
-4
How can that be?
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(Fe, Mg)2SiO4 - Olivine
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How old are the oldest rocks on Earth?Given: Sample from Acasta Gneiss in CanadaIt has crystals of zircon thatcontain 238U.238U is unstable. It decays into 206Pb.
ZrSiO4
~Fixed chemical formula.
But a few U’s can be used To substitute for Zr.
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How do Minerals Form?
- Cooling from liquid (magma) to a solid
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How do Minerals Form?
- Evaporation of a briny liquid
- Cooling from liquid (magma) to a solid
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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
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Asbestos- fibrous silicate mineral w/ fireproofing qualities
Ceiling tiles
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Asbestos- commercial term, not a geological term
Chrysotile- sheet structureno sharp fibres- no hazard
Crocidolite- chain structuresharp fibres- BIG hazard
The Cost- 50 to 150 billion $ to clean it all upThe Cost- 50 to 150 billion $ to clean it all up>half of the asbestos is harmless Chrysotile>half of the asbestos is harmless Chrysotile
What to Do?
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What is a rock again?
= assemblage of minerals (or mineraloids) in a solid state
3 types7. igneous8. sedimentary9. metamorphic
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Igneous
Sedimentary
Metamorphic
Plutonic Volcanic
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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
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GraniteBasalt
ObsidianPumice