mineral
Biotite Mica
Biotite (K(Mg,Fe)3(AlSi3O10)(F,OH)2)
AI-generated identification · may be incorrectHardness 2.5-3 on Mohs scale, black to dark brown color, pearly to submetallic luster, monoclinic crystal structure, perfect basal cleavage (splits into thin, flexible sheets), specific gravity 2.7-3.3.
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Physical properties
Hardness 2.5-3 on Mohs scale, black to dark brown color, pearly to submetallic luster, monoclinic crystal structure, perfect basal cleavage (splits into thin, flexible sheets), specific gravity 2.7-3.3.
Formation & geological history
Forms in igneous and metamorphic rocks, often found in granites, diorites, schists, and gneisses. Can be of various geological ages.
Uses & applications
Limited industrial use due to its dark color and iron content, unlike muscovite. Sometimes used as an insulating material or a filler, but mainly of interest to mineral collectors.
Geological facts
Biotite is a common rock-forming mineral and is part of the mica group. Its perfect cleavage allows it to be peeled into incredibly thin, flexible, and elastic sheets.
Field identification & locations
Easily identified by its dark color (black to brown), micaceous habit, and perfect cleavage that forms thin, flexible flakes. Often found worldwide in granitic and metamorphic terrains.
