metamorphic
Mica Schist
Mica Schist (predominantly Muscovite or Biotite sheet silicates)
Hardness: 3.5–4.0 on Mohs scale (rock scale varies); Color: Silvery-gray, brownish, or golden; Luster: Pearly to submetallic; Crystal Structure: Monoclinic (foliated mica sheets); Cleavage: Perfect basal cleavage in individual mica grains; Specific gravity: 2.7–3.0.
- Hardness
- 3
- Color
- Silvery-gray, brownish, or golden
- Luster
- Pearly to submetallic
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Physical properties
Hardness: 3.5–4.0 on Mohs scale (rock scale varies); Color: Silvery-gray, brownish, or golden; Luster: Pearly to submetallic; Crystal Structure: Monoclinic (foliated mica sheets); Cleavage: Perfect basal cleavage in individual mica grains; Specific gravity: 2.7–3.0.
Formation & geological history
Formed through regional metamorphism of shale or mudstone at intermediate temperatures and pressures. Most specimens date back to the Proterozoic or Paleozoic eras within mountain-building belts.
Uses & applications
Used historically as a construction stone for lining hearths and ovens due to heat resistance. Today, it is mostly used as a source for ground mica in paints, cosmetics, and electrical insulation components.
Geological facts
Schist is characterized by 'schistosity,' which refers to the alignment of mineral grains that allows the rock to be split into thin flakes or slabs. It is one of the most common rocks in the Earth's continental crust.
Field identification & locations
Identify in the field by its distinct glittering or 'flashy' appearance under sunlight and its tendency to flake off in thin, shiny scales when scratched. Commonly found in metamorphic terrains like the Appalachian or Himalayan Mountains.
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