metamorphic
Mica Schist
Mica Schist (primarily Muscovite or Biotite Schist)
Hardness: 3.5-4 (Mohs); Color: Silvery-gray, brown, or bronze with high metallic sheen; Luster: Pearly to vitreous; Crystal structure: Monoclinic (foliated phyllosilicates); Cleavage: Perfect basal; Specific Gravity: 2.8-3.0
- Hardness
- 3
- Color
- Silvery-gray, brown, or bronze with high metallic sheen
- Luster
- Pearly to vitreous
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Physical properties
Hardness: 3.5-4 (Mohs); Color: Silvery-gray, brown, or bronze with high metallic sheen; Luster: Pearly to vitreous; Crystal structure: Monoclinic (foliated phyllosilicates); Cleavage: Perfect basal; Specific Gravity: 2.8-3.0
Formation & geological history
Formed through the regional metamorphism of shale or mudstone at intermediate temperatures and pressures. This process recrystallizes clay minerals into large, visible flakes of micas oriented perpendicularly to the direction of pressure.
Uses & applications
Primarily used as decorative stone, in construction as fill or dimension stone, and as a source of mica for electrical insulation or glitter in cosmetics when ground down.
Geological facts
The word schist comes from the Greek word 'schistos' meaning 'split', referring to the stone's tendency to split easily along its layers. It is distinguished from phyllite by having mica grains large enough to be seen with the naked eye.
Field identification & locations
Identify by its 'schistosity' or shimmering, layered appearance. It is very common in mountain belts such as the Appalachians, Alps, and Himalayas. Field identification involves looking for the 'sparkle' in the sun and its tendency to flake off in thin sheets.
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