metamorphic

Muscovite Mica (with Schist)

Muscovite - KAl2(AlSi3O10)(OH)2

AI-generated identification · may be incorrect

Hardness: 2-2.5; Color: Silvery, brassy, or brown; Luster: Pearly to metallic; Crystal structure: Monoclinic; Cleavage: Perfect basal (peels into thin sheets); Specific Gravity: 2.76–3.00

Hardness: 2-2
Color: Silvery, brassy, or brown
Luster: Pearly to metallic

Identified April 23, 2026More metamorphic →

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Physical properties

Hardness: 2-2.5; Color: Silvery, brassy, or brown; Luster: Pearly to metallic; Crystal structure: Monoclinic; Cleavage: Perfect basal (peels into thin sheets); Specific Gravity: 2.76–3.00

Formation & geological history

Formed during regional metamorphism of clay-rich sedimentary rocks (like shale or mudstone) at medium-to-high temperatures and pressures. Most common in mica schists and pegmatites.

Uses & applications

Used as an electrical insulator in electronics, in drywall joint compounds, as a filler in plastics and paint, and in cosmetics (eye shadow/lipstick) for its pearlescent shimmer.

Geological facts

Muscovite was historically used as a replacement for glass in windows in medieval Russia, leading to its name 'Muscovy-glass'. It is highly resistant to heat and chemicals.

Field identification & locations

Identify by its 'book' of thin, flexible, transparent or silvery sheets that can be easily peeled off with a fingernail. Found globally in metamorphic belts like the Appalachians or the Himalayas.