metamorphic
Biotite Schist
Biotite Mica Schist (K(Mg,Fe)3AlSi3O10(OH,F)2)
Hardness: 2.5-3, Color: Dark green to black with silvery sparkles, Luster: Vitreous to pearly, Crystal structure: Monoclinic, Cleavage: Perfect basal, Specific gravity: 2.7-3.3
- Hardness
- 2
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Physical properties
Hardness: 2.5-3, Color: Dark green to black with silvery sparkles, Luster: Vitreous to pearly, Crystal structure: Monoclinic, Cleavage: Perfect basal, Specific gravity: 2.7-3.3
Formation & geological history
Formed through regional metamorphism of shale or clay-rich sedimentary rocks under medium grade temperatures and pressures. Often found in mountain roots from the Paleozoic to Precambrian eras.
Uses & applications
Used primarily in the manufacture of glitter, roofing material, paints, and as insulation in electrical equipment. Also valued as a decorative landscape stone and for geological study.
Geological facts
The 'sparkles' seen are individual flakes of mica that reflect light. It is one of the most common minerals in the Earth's crust and was once used as a glass substitute in cold climates before modern industrialization.
Field identification & locations
Identify in the field by its distinct foliated (layered) texture and the way it easily flakes into thin sheets. Common in areas with exposed metamorphic basement rock like the Appalachians or Alps.
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