metamorphic
Mica Schist
Mica Schist (primarily Muscovite and Biotite)
Hardness: 2-2.5 on Mohs scale (for mica grains). Color: Silver-grey to dark grey/brown. Luster: Pearly to sub-metallic shimmer. Crystal Structure: Flat, platy minerals (foliated). Cleavage: Perfect basal cleavage in individual grains. Specific Gravity: 2.7-3.0.
- Hardness
- 2-2
- Color
- Silver-grey to dark grey/brown
- Luster
- Pearly to sub-metallic shimmer
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Physical properties
Hardness: 2-2.5 on Mohs scale (for mica grains). Color: Silver-grey to dark grey/brown. Luster: Pearly to sub-metallic shimmer. Crystal Structure: Flat, platy minerals (foliated). Cleavage: Perfect basal cleavage in individual grains. Specific Gravity: 2.7-3.0.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under medium-grade pressure and temperature conditions. Typically found in orogenic (mountain-building) belts.
Uses & applications
Used primarily in construction for fill and decorative stone; historically used for hearths and furnace linings due to heat resistance. Fine mica is used in electronics and cosmetics.
Geological facts
The word 'schist' comes from the Greek word 'schistos', meaning 'split', referring to the rock's tendency to split easily along mineral planes. It displays a characteristic 'schistosity' which is a profound glittery effect.
Field identification & locations
Identifiable by its distinct layered appearance and strong sparkle when rotated in light. Found commonly in mountain ranges like the Appalachians or Alps. Collectors look for garnet inclusions which are common in mica schist.
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