metamorphic
Mica Schist
Mica Schist
Hardness: 3.5–4.5 (Mohs scale); Color: Silvery-gray, bronze, or golden-tan; Luster: Pearly to metallic; Structure: Foliated (schistosity); Cleavage: Perfect basal cleavage in individual mica flakes; Specific Gravity: 2.7–3.0
- Hardness
- 3
- Color
- Silvery-gray, bronze, or golden-tan
- Luster
- Pearly to metallic
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Physical properties
Hardness: 3.5–4.5 (Mohs scale); Color: Silvery-gray, bronze, or golden-tan; Luster: Pearly to metallic; Structure: Foliated (schistosity); Cleavage: Perfect basal cleavage in individual mica flakes; Specific Gravity: 2.7–3.0
Formation & geological history
Formed through the regional metamorphism of shale or clay-rich sedimentary rocks under intermediate to high temperatures and pressures. This creates a coarse-grained texture where mineral grains are visible to the naked eye.
Uses & applications
Used historically as a building stone, for paving, and in decorative garden walls. Platy micas extracted from schist are used in electrical insulators, paints, and cosmetics for their shimmer.
Geological facts
Schist is characterized by 'schistosity,' a parallel arrangement of platy minerals that causes the rock to split into thin layers. It is a common indicator of mountain-building events (orogeny).
Field identification & locations
Identify in the field by its distinct 'shimmer' or 'sparkle' when rotated in sunlight and its tendency to flake off into thin plates. Commonly found in metamorphic terranes like the Appalachian or Himalayan mountains.
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