metamorphic
Mica Schist
Mica Schist (primarily Muscovite or Biotite)
Hardness: 2-2.5 on Mohs scale; Color: Silvery-gray, brown, or black with metallic sheen; Luster: Pearly to sub-metallic; Crystal structure: Monoclinic (foliated phyllosilicates); Cleavage: Perfect basal cleavage leading to thin sheets; Specific gravity: 2.8-3.0.
- Hardness
- 2-2
- Color
- Silvery-gray, brown, or black with metallic sheen
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 2-2.5 on Mohs scale; Color: Silvery-gray, brown, or black with metallic sheen; Luster: Pearly to sub-metallic; Crystal structure: Monoclinic (foliated phyllosilicates); Cleavage: Perfect basal cleavage leading to thin sheets; Specific gravity: 2.8-3.0.
Formation & geological history
Formed by the regional metamorphism of clay-rich sedimentary rocks (shales) or igneous rocks. Subjected to medium-to-high pressure and temperature, typically during mountain-building events (orogeny) in the Proterozoic to Phanerozoic eras.
Uses & applications
Used as a filler in paints and plastics, as insulation in electrical equipment due to heat resistance, in roofing materials, and occasionally as decorative stone or in landscaping.
Geological facts
Mica schist is known for its 'schistosity,' a texture that allows the rock to be split into thin, wavy flakes. The word 'schist' is derived from the Greek 'schizein,' meaning 'to split.'
Field identification & locations
Identify in the field by its distinct sparkle (glitter-like appearance) and thin, flaky layers that can often be peeled with a fingernail or knife. Commonly found in metamorphic belts like the Appalachian Mountains or the Alps.
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