metamorphic
Mica Schist with Pyrite
Muscovite/Biotite Schist (Complex Silicate)
Hardness: 2-3 (mica), 6-6.5 (pyrite inclusions); Color: Silvery-gray, bronze, earthy brown; Luster: Pearly to metallic (submetallic); Crystal Structure: Monoclinic (foliated/platy); Cleavage: Perfect basal.
- Hardness
- 2-3 (mica), 6-6
- Color
- Silvery-gray, bronze, earthy brown
- Luster
- Pearly to metallic (submetallic)
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Physical properties
Hardness: 2-3 (mica), 6-6.5 (pyrite inclusions); Color: Silvery-gray, bronze, earthy brown; Luster: Pearly to metallic (submetallic); Crystal Structure: Monoclinic (foliated/platy); Cleavage: Perfect basal.
Formation & geological history
Formed through the regional metamorphism of shale or sedimentary mudstones under medium-grade pressure and temperature conditions (Barrovian sequence). These typically form at convergent plate boundaries and can be hundreds of millions of years old.
Uses & applications
Primarily used as a decorative stone, in garden landscaping, or as a source for mica in electrical insulation. Smaller specimens are collected for educational and hobbyist purposes.
Geological facts
The word 'schist' is derived from the Greek word 'schistos', meaning 'split', referring to the stone's tendency to flake into thin layers. The glittery 'fool's gold' often found within it is actually Pyrite or Chalcopyrite.
Field identification & locations
Identify by its distinctive flaky, 'glittery' layers (schistosity). It is commonly found in mountain ranges such as the Appalachians or the Alps. When identifying in the field, check for highly reflective surfaces that peel away in thin sheets.
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