Mica

phyllosilicate

biotite

The mica group is a group of phyllosilicates (sheet silicates), including muscovite and biotite.
Mica is a common constituent of most pegmatites, granite, diorite, gabbro, andesite and gneiss.
It also may be found in quartzolite, kimberlite, clay, skarn, amphibolite and eclogite.
It is never found in the granulite facies rocks.

At Willow Springs, Pinal county, Arizona, USA, mica pseudomorphs after schorl occur in quartz (R&M 94.2.165-166).

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