metamorphic
Mica Schist
Mica Schist (with Muscovite)
Hardness: 2-3 (Mohs). Color: Silvery-gray, white, or greenish. Luster: Pearly to sub-metallic. Crystal structure: Monoclinic (platy/flaky). Cleavage: Perfect basal cleavage. Specific gravity: 2.7-2.8.
- Hardness
- 2-3 (Mohs)
- Color
- Silvery-gray, white, or greenish
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 2-3 (Mohs). Color: Silvery-gray, white, or greenish. Luster: Pearly to sub-metallic. Crystal structure: Monoclinic (platy/flaky). Cleavage: Perfect basal cleavage. Specific gravity: 2.7-2.8.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under intermediate to high pressure and temperature. The heat causes clay minerals to recrystallize into larger mica crystals aligned perpendicularly to the pressure direction.
Uses & applications
Used primarily in construction for crushed stone, decorative garden stones, and historically for hearths due to its heat resistance. Low-quality mica is used as an insulator and in cosmetics.
Geological facts
The word 'schist' is derived from a Greek word meaning 'to split,' referring to its ease of splitting along the planes of mica alignment. This phenomenon is known as schistosity.
Field identification & locations
Identify in the field by its distinct 'glittery' reflection when rotated in light and the way it can be flaked off with a fingernail or pocketknife. Common in mountainous regions with a history of tectonic plate collisions.
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