metamorphic
Mica Schist
Mica Schist (predominantly Muscovite or Biotite sheet silicates)
Hardness: 2-4 (Mohs); Color: Silvery-gray, bronze, or brownish-gold; Luster: Pearly to metallic (glittery); Crystal structure: Monoclinic; Cleavage: Perfect basal (sheets); Specific gravity: 2.8-3.0
- Hardness
- 2-4 (Mohs)
- Color
- Silvery-gray, bronze, or brownish-gold
- Luster
- Pearly to metallic (glittery)
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Physical properties
Hardness: 2-4 (Mohs); Color: Silvery-gray, bronze, or brownish-gold; Luster: Pearly to metallic (glittery); Crystal structure: Monoclinic; Cleavage: Perfect basal (sheets); Specific gravity: 2.8-3.0
Formation & geological history
Formed through the regional metamorphism of shale or sedimentary mudstones under medium-grade pressure and temperature conditions. This process aligns mineral grains into parallel layers known as foliation.
Uses & applications
Used historically as a construction stone, in electrical insulators (for the mica content), and occasionally as a decorative stone in landscaping or architectural veneers.
Geological facts
The word 'schist' comes from the Greek 'schistos', meaning 'split', referring to the way the rock can be easily flaked into thin, flat sheets or chips due to its micaceous layers.
Field identification & locations
Identify in the field by its distinct 'glittery' reflection and foliated (layered) texture. It is common in mountain ranges like the Appalachians, Alps, and Himalayas. Collectors look for well-defined garnets which often grow within schist.
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