![Biotite Schist (Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]) — metamorphic](https://media.rock.id/d885ae5c-385f-4eb2-9ac0-a6b173629af7-compressed.jpg)
metamorphic
Biotite Schist
Biotite-rich Schist [K(Mg,Fe)3AlSi3O10(F,OH)2]
Hardness: 2.5-3 (on mica flakes), Color: dark brown to black, Luster: vitreous to pearly, Crystal structure: monoclinic (tabular/platy), Cleavage: perfect basal cleavage
- Hardness
- 2
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Physical properties
Hardness: 2.5-3 (on mica flakes), Color: dark brown to black, Luster: vitreous to pearly, Crystal structure: monoclinic (tabular/platy), Cleavage: perfect basal cleavage
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under medium-grade temperatures and pressures. Often associated with the formation of mountain ranges during orogenic events.
Uses & applications
Used primarily for research, as an indicator mineral for metamorphic grade, and occasionally as a ground-up additive in paints, lubricants, and rubber products.
Geological facts
Biotite belongs to the mica group; it is often called 'black mica'. Its presence in schist creates a sparkling effect when light reflects off the aligned mineral grains.
Field identification & locations
Identify by its 'schistose' texture (mineral alignment) and the ability to peel off thin, dark, flexible flakes from the black mineral sections with a needle.
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