metamorphic
Schist
Mica Schist
Hardness: 3.5-4; Color: Silver, gold, gray, to brownish-tan; Luster: Pearly to sub-metallic; Crystal Structure: Foliated with visible mica flakes causing a shimmering effect (schistosity); Specific Gravity: 2.7-2.8.
- Hardness
- 3
- Color
- Silver, gold, gray, to brownish-tan
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4; Color: Silver, gold, gray, to brownish-tan; Luster: Pearly to sub-metallic; Crystal Structure: Foliated with visible mica flakes causing a shimmering effect (schistosity); Specific Gravity: 2.7-2.8.
Formation & geological history
Formed through regional metamorphism of shale or mudstone under intermediate to high pressure and temperature conditions. This process causes clay minerals to transform into large, platy mica crystals oriented perpendicular to the direction of pressure.
Uses & applications
Used as decorative stone in landscaping, flagstone for walkways, and occasionally as a source for industrial mica. It is not generally used as a construction aggregate because of its structural weakness along foliation planes.
Geological facts
The glittering appearance of schist is due to the alignment of mica minerals like muscovite and biotite. The name 'schist' comes from the Greek word 'schistos,' meaning 'easily split,' referring to its tendency to flake into thin layers.
Field identification & locations
Identify in the field by its distinct layered appearance and characteristic 'shimmer' or 'sparkle' when rotated in sunlight. Look for the alignment of mica flakes. Found globally in mountain ranges and metamorphic shields like the Appalachians or the Alps.
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