metamorphic
Mica Schist
Mica Schist (primarily Muscovite or Biotite-rich sequence)
Hardness: 3.5-4; Color: Silver, grey, or brassy with brilliant flashes; Lustre: Metallic to pearly; Crystal Structure: Foliated/Platty; Cleavage: Perfect basal (peels in sheets)
- Hardness
- 3
- Color
- Silver, grey, or brassy with brilliant flashes
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Physical properties
Hardness: 3.5-4; Color: Silver, grey, or brassy with brilliant flashes; Lustre: Metallic to pearly; Crystal Structure: Foliated/Platty; Cleavage: Perfect basal (peels in sheets)
Formation & geological history
Formed through the regional metamorphism of clay-rich sedimentary rocks like shale at medium grades (middle of the Barrovian sequence). These rocks were subjected to high heat and pressure during mountain-building events.
Uses & applications
Historical use in furnace windows (Muscovite) and currently used as a filler in paints, plastics, and wallboards, or as decorative stone for gardens and walkways.
Geological facts
The word 'Schist' is derived from the Greek word meaning 'to split,' referring to its tendency to break easily along flaky mineral layers. It often contains garnets grown within the foliation.
Field identification & locations
Identify in the field by its distinct 'shimmer' or 'glitter' when turned in the light and the presence of visible mica flakes that can often be scraped off with a fingernail. Found in mountain ranges globally.
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