Igneous Textures
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Aphanitic / Fine-grained
crystals too small to be identified w/ the use of a microscope
Aphanitic Rocks are typically (e or I)___
extrusive (rapid cooling)
Examples of aphanitic rocks
rhyolite, Andesite, Basalt, Komatiite
Coarse-grained / Phaneritic Rocks
Crystals large enough to be identified w/o the use of a microscope
Where are coarse-grained rocks found?
magma chambers (outer extinguished layers)
Examples of coarse-grained and are they typically intrusive or extrusive?
intrusive; diorite, granite, gabbro, peridotite
Porphyritic (meaning)
two distinct crystal sizes (larger crystals called phenocrysts and smaller ones make up the ground mass)
How do porphyritic rocks cool?
slowly; found in dikes and other layers of the volcano on the exterior (magma stalls and cools before erupting quickly and cooling again)
types of porphyritic rocks
granite porphyr, Andesite prophryr, basalt porphyry
Vesicular Rocks (how they cool, types, and where they are located)
scoria and pumice; cool rapidly as gas bubbles escape from vesicles (upper layers of lava flows)
Glassy (same as vesicular)
rapid cooling of solidified, exploded lava; pumice and obsidian
Pyroclastic (same as vesicular)
erupted fragments; volcanic breccia, welded tuff, ignimbrite