metamorphic
Muscovite Schist with Quartz
KAl2(AlSi3O10)(OH,F)2 (Muscovite) in Schist
Hardness: 2-2.5 (mica) to 7 (quartz), Color: Silvery-gold, white, gray, Luster: Vitreous to pearly/metallic, Crystal Structure: Monoclinic (sheets), Cleavage: Perfect basal
- Hardness
- 2-2
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Physical properties
Hardness: 2-2.5 (mica) to 7 (quartz), Color: Silvery-gold, white, gray, Luster: Vitreous to pearly/metallic, Crystal Structure: Monoclinic (sheets), Cleavage: Perfect basal
Formation & geological history
Formed through the regional metamorphism of pelitic rocks (shales/mudstones) under medium-grade temperatures and pressures. The shiny flakes are muscovite mica that grew perpendicular to the direction of pressure.
Uses & applications
Muscovite is used as an electrical insulator, in cosmetics (glimmer/shimmer), and as a filler in paints and plastics. Schist is occasionally used as decorative stone.
Geological facts
Muscovite was once used as a glass substitute in Russia, known as 'Muscovy-glass'. The golden-silvery sheen in this specimen creates a 'spangle' effect typical of mica-rich schists.
Field identification & locations
Identify by its flaky, 'pagery' texture that reflects light easily. It can be scratched by a fingernail in the mica areas. Common in mountain belts like the Appalachians or Himalayas.
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