metamorphic
Biotite Mica Schist
Metamorphic Rock containing Biotite K(Mg,Fe)3AlSi3O10(OH)2
Mohs hardness of 2.5 to 3 for the mica flakes, color is dark brown to black with a yellowish-brown weathered matrix, luster is vitreous to pearly on cleavage faces, foliated crystal structure with distinct planar texture.
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Physical properties
Mohs hardness of 2.5 to 3 for the mica flakes, color is dark brown to black with a yellowish-brown weathered matrix, luster is vitreous to pearly on cleavage faces, foliated crystal structure with distinct planar texture.
Formation & geological history
Formed through regional metamorphism of argillaceous rocks such as shales and mudstones under moderate to high temperatures and pressures, typically during mountain-building (orogenic) events over millions of years.
Uses & applications
Primarily used for educational and scientific study, as well as a specimen for mineral and rock collectors.
Geological facts
Biotite is named after the French physicist Jean-Baptiste Biot and is a very common phyllosilicate mineral found in many igneous and metamorphic rocks.
Field identification & locations
Easily identified by its dark, shiny, sheet-like (micaceous) layers that flake off easily, often found in regional metamorphic terrains worldwide.
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