metamorphic
Mica Schist
Mica Schist (predominantly Muscovite or Biotite sheet silicates)
Hardness: 3.5–4 on Mohs scale; Color: Silvery-gray, greenish-gray, or brown; Luster: Silky to pearly/metallic; Structure: Foliated with visible platy minerals; Cleavage: Perfect basal cleavage in individual mica flakes.
- Hardness
- 3
- Color
- Silvery-gray, greenish-gray, or brown
- Luster
- Silky to pearly/metallic
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Physical properties
Hardness: 3.5–4 on Mohs scale; Color: Silvery-gray, greenish-gray, or brown; Luster: Silky to pearly/metallic; Structure: Foliated with visible platy minerals; Cleavage: Perfect basal cleavage in individual mica flakes.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under intermediate to high temperatures and pressures. This process aligns mica flakes perpendicular to the direction of pressure, creating the characteristic schistosity.
Uses & applications
Primarily used as a decorative stone in landscaping, flagstone for walkways, and as a source of mica for electrical insulation or glitter in cosmetics and paints.
Geological facts
The term schist is derived from the Greek word 'schistos', meaning 'split', referring to the ease with which these rocks can be flaked along the planes of the mica.
Field identification & locations
Identify in the field by its distinct 'shimmer' or 'sparkle' when rotated in sunlight and its tendency to flake into thin sheets. Common in mountain ranges like the Appalachians, Alps, and Himalayas.
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