Muscovite Mica

Physical Properties

Hardness: 2-2.5 on Mohs scale; Color: Silvery, pearly white, or brownish; Luster: Vitreous to pearly; Crystal structure: Monoclinic (tabular/foliated); Cleavage: Perfect basal cleavage, peeling into thin flexible sheets; Specific Gravity: 2.76–3.00

Formation & Geological History

Formed primarily in igneous environments like pegmatites and granites, as well as metamorphic rocks like schists and gneisses through regional metamorphism. Common in diverse geological ages.

Uses & Applications

Used as an electrical insulator in capacitors, a heat insulator in vintage stove windows (isinglass), a glitter additive in cosmetics and paints, and as a filler in plastic and rubber.

Geological Facts

The name comes from 'Muscovy-glass', as large sheets of this mineral were used as a cheaper alternative to glass for windows in medieval Russia.

Field Identification & Locations

Identify by its 'book-like' layers and ability to peel into extremely thin, transparent, flexible sheets. Commonly found in coarse-grained igneous rocks or micaceous schists.

Identified on: 5/11/2026

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