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Andesite is a fine-grained, extrusive igneous rock with anhedral or euhedral crystals. It's an intermediate rock and it has a medium color. It occurs when lava or magma from an andesite volcano cools underground. It usually has 55 to 65% total silica content, along with plagioclase feldspar(andesine and oligoclase), pyroxene, amphibole and biotite mica.
- OK. Whoever that was, wrong, wrong, wrong. How can it be an extrusive rock which cools underground? Really. Rolinator 05:14, 27 December 2005 (UTC)
Don't know much about geology, but I have a feeling that this article has suffered from some juvenile sabotage:
The water and initial tylerisstupid slab melts rise into the mantle wedge... The following part looks odd, too, unless it is some technical code unfamiliar to me:
Ultimately, the resultant composition of andesite and intermediate magmas is the result of fractional crystallisation, assimilation, partial melting cbnvcnvcnnbvcnbvc and contaminaton by the subducted slab.
Thin section photomicrograph
Yes, "polarised light" means nothing -- it should say whether it's plane-polarised light or between crossed polars. The image itself has metadata specifying the latter, so I've changed it. --Furrfu (talk) 20:01, 21 March 2010 (UTC)