mineral
Biotite Mica
K(Mg,Fe)_3AlSi_3O_10(OH)_2
AI-generated identification · may be incorrectMohs hardness 2.5-3; dark brown, black, or dark green color; pearly to submetallic luster; monoclinic crystal system with perfect basal cleavage yielding thin, elastic sheets.
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Physical properties
Mohs hardness 2.5-3; dark brown, black, or dark green color; pearly to submetallic luster; monoclinic crystal system with perfect basal cleavage yielding thin, elastic sheets.
Formation & geological history
Forms in igneous rocks like granite and pegmatites, as well as metamorphic rocks like schist and gneiss, during cooling and crystallization of silicate melts or regional metamorphism.
Uses & applications
Used primarily in industrial fillers, paints, lubricants, and as an electrical insulator; occasionally collected by mineral enthusiasts.
Geological facts
Biotite is part of the mica group and is often called 'black mica' due to its high iron and magnesium content.
Field identification & locations
Easily identified by its dark color and distinctive ability to peel into thin, flexible sheets; found worldwide in granitic terrains.
