mineral

Muscovite Mica

Muscovite - KAl2(AlSi3O10)(OH)2

Hardness: 2–2.5 Mohs scale. Color: Transparent to pearly white or light green. Luster: Vitreous to pearly. Crystal structure: Monoclinic with perfect basal cleavage, allowing it to split into thin, flexible, elastic sheets. Specific Gravity: 2.76–3.00.

Hardness: 2–2
Color: Transparent to pearly white or light green
Luster: Vitreous to pearly

Identified March 25, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous or metamorphic environments, particularly in granite pegmatites or schists. It is a common rock-forming mineral found in crustal rocks of various geological ages, often forming during the cooling of silica-rich magma or through the high-pressure metamorphism of clay-rich sediments.

Uses & applications

Used primarily as an electrical and thermal insulator in capacitors, heating elements, and soldering irons. In cosmetics, ground muscovite is used to add 'shimmer' or 'glitter' to eyeshadows and lipsticks. Historically used as a window material ('Muscovy Glass').

Geological facts

Muscovite sheets can be peeled so thin that they are transparent; it was used for windows in medieval Russia, hence its name derived from 'Muscovy'. Unlike modern glass, it doesn't shatter when hit by high temperatures, making it ideal for furnace viewing windows.

Field identification & locations

Identify in the field by its sheet-like layers (books) that can be easily peeled with a fingernail or needle. Common in mountain ranges like the Appalachians, Urals, and Alps. Collectors look for large 'books' or perfectly flat, transparent hexagonal crystals.