mineral

Muscovite

Muscovite (KAl2(AlSi3O10)(OH)2)

Hardness: 2.0–2.5 Mohs, Color: Colorless to silvery-white or light gray, Luster: Vitreous to pearly, Crystal structure: Monoclinic (tabular/foliated), Cleavage: Perfect basal, Specific Gravity: 2.76–3.0

Hardness: 2

Identified May 9, 2026More mineral →

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Physical properties

Formation & geological history

Formed primarily in metamorphic rocks like schist and gneiss, as well as igneous environments such as granites and pegmatites. It is the most common mica and forms through regional or contact metamorphism.

Uses & applications

Used as an electrical insulator in capacitors, in welding rods, as a filler in paints and plastics, as a lubricant, and in the glitter used in cosmetics and paper.

Geological facts

Muscovite was once used as a glass substitute for windows in medieval Russia, leading to its nickname 'Muscovy Glass.' Large 'books' of mica can be found that are several feet wide.

Field identification & locations

Identify in the field by its ability to be peeled into thin, flexible, transparent sheets. It has a silvery sheen and is found frequently in sparkling outcrops of schist or granite.