mineral

Mica (Muscovite)

Potassium aluminum silicate - KAl2(AlSi3O10)(OH)2

Hardness: 2.5 on Mohs scale; Color: Silver-grey, white, or colorless; Luster: Vitreous to pearly; Crystal structure: Monoclinic (often appearing hexagonal); Cleavage: Perfect basal cleavage producing thin, flexible sheets; Specific gravity: 2.76-3.00.

Hardness: 2
Color: Silver-grey, white, or colorless
Luster: Vitreous to pearly

Identified March 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous environments (granites and pegmatites) and metamorphic rocks (schists and gneisses). These specimens are often hundreds of millions of years old, crystallized from cooling magma or under extreme pressure.

Uses & applications

Used as an electrical insulator, in cosmetics (glimmer effect), filler in plastics/paints, and high-temperature windows for furnaces. Collectors value well-defined books or crystals.

Geological facts

Muscovite is often called 'Isinglass' or 'Muscovy-glass' because it was used in medieval Russia as a cheaper, more durable alternative to glass for windows. Its thin sheets are transparent and fireproof.

Field identification & locations

Identify in the field by its 'book-like' formation and the ability to peel layers with a fingernail. Found globally, with notable deposits in Brazil, Russia, India, and the United States (NC, SD).

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