mineral

Muscovite mica schist/pegmatitic mica

Muscovite, KAl₂(AlSi₃O₁₀)(OH)₂

AI-generated identification · may be incorrect

Pale silvery-gold, translucent, pearly luster with prominent elastic sheets and perfect basal cleavage; Mohs hardness 2–2.5, monoclinic crystal structure, specific gravity about 2.8–2.9. The specimen appears to contain coarse muscovite with minor quartz or feldspar.

Identified September 16, 2026More mineral →

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Physical properties

Formation & geological history

Forms in potassium-rich igneous pegmatites and through metamorphism of clay-rich sediments; commonly Precambrian to Phanerozoic, depending on host rock. It crystallizes from late-stage, volatile-rich melts or recrystallizes under elevated temperature and pressure.

Uses & applications

Used industrially in electrical insulation, joint compound, paints, plastics, drilling fluids, and cosmetics; attractive books or crystals are collected as mineral specimens.

Geological facts

Muscovite splits into exceptionally thin, flexible transparent sheets that historically served as window material (“isinglass”) in stoves and early instruments.

Field identification & locations

Identify it by peeling, flexible, non-elastic sheets and pearly cleavage surfaces; it commonly occurs with quartz and feldspar in granite pegmatites and mica schists worldwide, especially in Brazil, India, Russia, and the United States.