Rock Identifier
Muscovite Mica in Quartz Matrix (Muscovite (KAl2(AlSi3O10)(OH)2) in Quartz (SiO2)) — mineral
mineral

Muscovite Mica in Quartz Matrix

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

Hardness: 2-2.5 (Muscovite), 7 (Quartz). Color: Silvery-white to translucent flakes in white/clear matrix. Luster: Pearly to metallic on flakes, vitreous on quartz. Crystal Structure: Monoclinic (sheets). Cleavage: Perfect basal cleavage allowing thin, flexible sheets.

Hardness
2-2
Color
Silvery-white to translucent flakes in white/clear matrix
Luster
Pearly to metallic on flakes, vitreous on quartz
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Physical properties

Hardness: 2-2.5 (Muscovite), 7 (Quartz). Color: Silvery-white to translucent flakes in white/clear matrix. Luster: Pearly to metallic on flakes, vitreous on quartz. Crystal Structure: Monoclinic (sheets). Cleavage: Perfect basal cleavage allowing thin, flexible sheets.

Formation & geological history

Formed in granitic pegmatites and metamorphic rocks (schists/gneiss) through the cooling of silica-rich magma or through regional metamorphism. Common throughout various geological eras, especially in Precambrian shields.

Uses & applications

Used in electrical insulation, heat-resistant windows (isnglass), cosmetics for shimmer, and as a filler in paints and plastics. Quartz matrix is used in glass making and electronics.

Geological facts

Known as 'Muscovy Glass' historically because it was used as a cheaper, more durable alternative to glass for windows in Russia. Individual sheets are virtually fireproof.

Field identification & locations

Identified in the field by the 'book-like' layering of silvery flakes that can be peeled with a fingernail. Found globally, especially in Brazil, India, and the Appalachian Mountains. Collectors look for large, undamaged 'books' of mica.

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