metamorphic
Mica Schist
Mica Schist (primarily Muscovite or Biotite sheet silicates)
Hardness: 2-3 (on Mohs scale for the mica minerals); Color: Silvery-grey to brownish; Luster: Pearly to metallic; Structure: Foliated with visible mineral grains; Cleavage: Perfect basal cleavage in mica flakes; Specific Gravity: 2.7-3.0
- Hardness
- 2-3 (on Mohs scale for the mica minerals)
- Color
- Silvery-grey to brownish
- Luster
- Pearly to metallic
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Physical properties
Hardness: 2-3 (on Mohs scale for the mica minerals); Color: Silvery-grey to brownish; Luster: Pearly to metallic; Structure: Foliated with visible mineral grains; Cleavage: Perfect basal cleavage in mica flakes; Specific Gravity: 2.7-3.0
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. This process aligns mineral grains into parallel layers, creating a schistose texture.
Uses & applications
Used historically as a building stone (flagstone) and decorative garden stone. Ground mica is used as a filler in construction materials, paints, and cosmetics for its glittery appearance.
Geological facts
The word 'schist' is derived from the Greek word 'schizein', meaning 'to split', referring to how easily the rock can be cleaved along its foliation planes. It is the intermediate stage between phyllite and gneiss.
Field identification & locations
Identify in the field by its strong foliation (schistosity) and 'sparkly' appearance caused by large, visible flakes of mica. It is commonly found in mountain ranges such as the Appalachians or Alps.
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