mineral

Muscovite Mica

Muscovite - KAl2(AlSi3O10)(OH)2

Hardness: 2.5–3 on Mohs scale; Color: Colorless, silvery, or light gray; Luster: Vitreous to pearly; Crystal structure: Monoclinic (tabular/foliated); Cleavage: Perfect basal (peels in thin, flexible sheets); Specific gravity: 2.76–3.0.

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

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous environments (pegmatites and granites) and metamorphic environments (schists and gneisses). It occurs through the cooling of silica-rich magma or the regional metamorphism of argillaceous rocks.

Uses & applications

Used as an electrical and thermal insulator in electronics, as a filler in paints and plastics, and in cosmetics (eye shadow/lipstick) for a shimmering effect. Historically used for stove windows and furnace peepholes.

Geological facts

Known as 'Muscovy glass' because it was used in medieval Russia as a cheaper, more durable alternative to glass for windows. It is highly resistant to heat and electricity.

Field identification & locations

Identify in the field by its 'book-like' layers and ability to be peeled into thin, transparent, flexible sheets with a fingernail. Common in the Appalachian Mountains (USA), Brazil, and India. Collectors look for large, undamaged 'books' or crystals.