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Basalt with columnar jointing along the Deschutes River in central Oregon.

Basalt with columnar jointing along the Deschutes River in central Oregon. Photo by Vince Cronin.


Igneous Rocks Home Page

Click on the underlined links in the tables below to obtain more information about the igneous rock, texture or mineral, including some specimen pictures.

Igneous Rocks and Glasses

andesite gabbro obsidian rhyolite
basalt granite pumice tuff
diorite

Textures associated with igneous rocks

aphanitic: very fine grained
glassy: texture of broken glass
phaneritic: mineral grains are coarse/large enough to be distinct
porphyritic: larger grains in a finer-grained matrix or ground mass
pyroclastic: "fire broken" or blasted from a volcano
scoriaceous: low-density rock with very large number of small gas-bubble voids
vesicular: with gas-bubble voids frozen in rock at time of crystallization

Minerals commonly associated with igneous rocks

alkalai feldspar biotite plagioclase feldspar quartz
amphibole olivine pyroxene

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