metamorphic
Mica Schist
Mica Schist (KAl2(AlSi3O10)(OH)2 - Muscovite component)
Hardness: 3.5-4 on Mohs scale; Color: Silver-grey to light brown; Luster: Pearly to sub-metallic; Structure: Foliated (schistose texture); Cleavage: Perfect basal cleavage in individual mica flakes.
- Hardness
- 3
- Color
- Silver-grey to light brown
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4 on Mohs scale; Color: Silver-grey to light brown; Luster: Pearly to sub-metallic; Structure: Foliated (schistose texture); Cleavage: Perfect basal cleavage in individual mica flakes.
Formation & geological history
Formed through the regional metamorphism of shale or clay-rich sedimentary rocks under medium-grade temperatures and pressures. Most mica schists are from the Proterozoic or Paleozoic eras.
Uses & applications
Historically used for roofing and wall tiles; currently used as a filler in paints and plastics, as decorative garden stones, and as a source for ground mica in industrial lubricants.
Geological facts
The word 'schist' comes from the Greek word 'schistos,' meaning 'split,' referring to the ease with which the rock can be split into thin layers due to the parallel alignment of mica minerals.
Field identification & locations
Identify in the field by its distinct 'glittery' appearance and foliated layers that flake off easily with a fingernail or knife. Commonly found in metamorphic belts like the Appalachian Mountains (USA) or the Scottish Highlands.
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