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.TOURING

COLORADO GEOLOGY

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IGNEOUS ROCKS

Minerals        Igneous         Sedimentary         Metamorphic         Fossils

INTRUSIVE

EXTRUSIVE
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Granite
an intrusive, coarse-grained igneous rock composed of primarily of quartz and feldspars.
Rhyolite
a fine-grained (extrusive) igneous rock composed primarily of quartz, potassium feldspar, plagioclase feldspars and some ferromagnesians (compare with granite)

Diorite
a coarse-grained (intrusive) igneous rock composed of plagioclase feldspars and up to 50% ferromagnesians (compare with andesite)
Andesite
a fine-grained (extrusive) igneous rock composed of plagioclase feldspars and up to 50% ferromagnesians (compare with diorite)

Gabbro
a coarse-grained (intrusive) igneous rock composed primarily of ferromagnesians with up to 50% plagioclase feldspars (compare with basalt)		 Untitled-1.JPG (94329 bytes)
Basalt
a fine-grained (extrusive) igneous rock composed primarily of ferromagnesians with up to 50% plagioclase feldspars (compare with gabbro)

Pegmatite
Pumice

Porphyry
Tuff
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Obsidian
volcanic glass
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