Muscovite Mica

Physical Properties

Hardness: 2.0–2.5 Mohs (scratches with fingernail). Color: Colorless, silvery, or light green. Luster: Pearly to Vitreous. Crystal Structure: Monoclinic, typically forming thin, flexible, elastic sheets or flakes. Cleavage: Perfect basal cleavage.

Formation & Geological History

Formed as a primary mineral in igneous rocks like granite and pegmatites, as well as in metamorphic rocks like schist and phyllite during regional metamorphism.

Uses & Applications

Used as an electrical insulator in electronics, as a heat-resistant window material (Isinglass), in makeup for shimmer, and as a filler in paints and plastics.

Geological Facts

Muscovite was once used for windows in Russia because it was cheaper and more heat-resistant than glass; the name 'Muscovite' comes from 'Muscovy-glass'. Single sheets can be peeled off almost infinitely thin.

Field Identification & Locations

Identify by its ability to peel into flexible, transparent thin sheets and its pearly luster. Commonly found in coarse-grained granites and shiny schists worldwide.

Identified on: 4/16/2026

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