metamorphic
Mica Schist
Mica Schist (primarily Muscovite or Biotite sheet silicates)
Hardness: 2-3 (Mohs). Color: Silvery-gray, white, or bronze. Luster: Pearly to sub-metallic. Structure: Foliated (schistose) with visible mineral grains. Cleavage: Perfect basal cleavage in individual mica grains.
- Hardness
- 2-3 (Mohs)
- Color
- Silvery-gray, white, or bronze
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 2-3 (Mohs). Color: Silvery-gray, white, or bronze. Luster: Pearly to sub-metallic. Structure: Foliated (schistose) with visible mineral grains. Cleavage: Perfect basal cleavage in individual mica grains.
Formation & geological history
Formed through the regional metamorphism of shale or clay minerals. Under high pressure and temperature, clay minerals transform into micas that align perpendicular to the direction of pressure, creating a platy texture.
Uses & applications
Used historically as a source of mica for electrical insulation and windows in wood stoves. Today, it is primarily used in landscaping, as an ornamental stone, or as a source of ground mica for gypsum wallboard joint compound and paint.
Geological facts
Mica schist is known for its 'glitter' effect due to the reflection of light off flat mica flakes. It represents a medium grade of metamorphism, falling between phyllite and gneiss.
Field identification & locations
Identify in the field by its distinct silvery sheen and tendency to flake apart into thin, flat sheets when struck. It is commonly found in mountain belts such as the Appalachians or the Alps.
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