mineral

Muscovite

Muscovite (KAl2(AlSi3O10)(OH)2)

Hardness: 2.0-2.5 on Mohs scale; Color: Colorless, silvery-white, or light gray; Luster: Vitreous to pearly; Crystal Structure: Monoclinic; Cleavage: Perfect basal (peels into thin sheets)

Hardness: 2
Color: Colorless, silvery-white, or light gray
Luster: Vitreous to pearly

Identified July 3, 2026More mineral →

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Physical properties

Hardness: 2.0-2.5 on Mohs scale; Color: Colorless, silvery-white, or light gray; Luster: Vitreous to pearly; Crystal Structure: Monoclinic; Cleavage: Perfect basal (peels into thin sheets)

Formation & geological history

Forms primarily in igneous rocks like granites and pegmatites, as well as metamorphic rocks such as schists and gneisses during regional metamorphism.

Uses & applications

Used as an electrical and thermal insulator in capacitors, windows for high-temperature furnaces, glitter in cosmetics, and as a filler in paints and plastics.

Geological facts

Muscovite was historically used as a glass substitute for windows in Russia, which led to its name being derived from 'Muscovy-glass'. Its thin sheets are flexible and elastic.

Field identification & locations

Identified by its extremely thin, silvery, transparent sheets and soft surface. Common in mountainous regions with metamorphic outcrops like the Appalachians or the Urals.