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Diorite
What is Diorite?
Diorite is a coarse-grained, intrusive igneous rock that is intermediate in
composition between granite and gabbro.
It’s composition is very similar to the fine-grained extrusive rock known
as andesite.
Diorite is composed primarily of plagioclase feldspar, amphibole, and
pyroxine minerals with small amounts of biotite
mica. It typically contains very little quartz.
When identifying diorite look for a rock that as abundant white and dark
minerals - a “salt and pepper” appearance.
With a hand lens look for the cleavage faces of plagioclase feldspar
intersecting at oblique angles. Also, look for
vitreous cleavage faces on the dark amphibole minerals.
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