mineral

Muscovite (Mica) in Quartz Matrix

Muscovite (KAl2(AlSi3O10)(OH)2) and Quartz (SiO2)

Hardness: 2.5-3 (Muscovite), 7 (Quartz); Color: Silvery-white to colorless; Luster: Vitreous to pearly; Crystal structure: Monoclinic (Muscovite) and Trigonal (Quartz); Cleavage: Perfect basal (peels in sheets); Specific gravity: 2.82.

Hardness: 2
Color: Silvery-white to colorless
Luster: Vitreous to pearly

Identified March 4, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in granitic pegmatites and metamorphic rocks like schists and gneisses during regional metamorphism or the cooling of silica-rich magma bodies. Commonly found in Precambrian or Paleozoic shield regions.

Uses & applications

Used as an electrical insulator in electronics, as a filler in paints and plastics, and as the 'glitter' in cosmetics. Large sheets were historically used as stove windows (isinglass).

Geological facts

Muscovite is often called 'Moscow Glass' because it was used as a cheaper, more durable alternative to glass for windows in medieval Russia. It can withstand extremely high temperatures and high voltages without melting or conducting.

Field identification & locations

Identified in the field by its distinct 'flaky' or 'books' of silvery crystals that can be peeled into thin, flexible transparent sheets. Common in pegmatite outcroppings in Brazil, India, and the United States (Appalachians).

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