Term
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Definition
Igneous
Granite
Intrusive phaneritic igneous rock
low color index (light color)
comprised chiefly of quartz and feldspar mineral crystals
ferromagnesian mineral crystals in granites include biotite, amphibole (hornblende)
granites rich in pink potassium feldspar appear pink |
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Term
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Definition
Igneous
Basalt
mafic, aphanitic igneous rock
extrusive equivalent of gabbro
dark gray
vesicular (bubbly) texture
comprised of plagioclase, ferromagnesian crystals (pyroxene, olivine or magnitite)
Basalt forms the floors of all modern oceans, beneath mud and sand
it is the most abundant aphanitic igneous rock on Earth. |
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Term
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Definition
Igneous
Rhyolite
a felsic, aphanitic igneous rock
extrusive equivalent of granite
light pink or gray
some rhyolites resemble andesite,
abundance of quartz and feldspar |
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Term
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Definition
Igneous
Gabbro
mafic, phaneritic igneous rock
comprised of ferromagnesian (pyroxene/augite) and plagioclase mineral crystals
quartz is absent |
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Term
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Definition
Igneous
Diorite
intrusive phaneritic igneous rock
intermediate color index
comprised of plagioclase feldspar, ferromagnesian mineral crystals (amphibole/horblende)
Quartz is only rarely present, and in small amounts |
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Term
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Definition
Igneous
Andesite
intermediate, aphanitic igneous rock
extrusive equivalent of diorite
medium to dark gray
porphyritic aphanitic texture - phenocrysts of black amphibole (hornblende) |
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Term
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Definition
Igneous
Peridotite
intrusive phaneritic igneous rock
very high color index
comprised of ferromagnesian |
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Term
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Definition
Igneous
Obsidian
extrusive igneous rock
comprised of dark glass
viscous lava cools suddenly (quenched) - hyaline texture |
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Term
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Definition
Igneous
Pumice
glassy extrusive igneous rock
generally white to dark gray
abundant adjacent vesicles
less dense than scoria-floats on water |
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