metamorphic
Mica Schist
Mica Schist (primarily Muscovite and Biotite)
AI-generated identification · may be incorrectHardness: 3.5-4; Color: Silver, gold, or grey with pearly to metallic luster; Texture: Foliated with large, visible mineral grains; Cleavage: Perfect basal cleavage in individual mica plates.
- Hardness
- 3
- Color
- Silver, gold, or grey with pearly to metallic luster
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Physical properties
Hardness: 3.5-4; Color: Silver, gold, or grey with pearly to metallic luster; Texture: Foliated with large, visible mineral grains; Cleavage: Perfect basal cleavage in individual mica plates.
Formation & geological history
Formed during medium-grade regional metamorphism of shale or clay-rich sedimentary rocks under high temperature and pressure. It often dates to Precambrian or Paleozoic eras in mountain belt regions.
Uses & applications
Occasionally used as a decorative stone in architecture or landscaping; historically used for roofing; mica itself is used in electrical insulation and cosmetics.
Geological facts
The word 'schist' comes from the Greek word 'schistos,' meaning 'cleft,' referring to the ease with which it can be split along the plane of its mica flakes. Its sparkle is due to the alignment of flat minerals reflecting light.
Field identification & locations
Identify by its 'schistosity'—a strong foliation where flat mineral grains are visible to the naked eye. Commonly found in the roots of eroded mountain ranges and metamorphic terranes. Use the 'sparkle test' in sunlight.
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