metamorphic
Schist
Mica Schist
Hardness: 3.5-4; Color: Silvery-gray, brownish-green to black; Luster: Pearly to sub-metallic; Crystal Structure: Foliated (schistosity); Cleavage: Perfect in one direction due to mica content; Specific Gravity: 2.7-2.8
- Hardness
- 3
- Color
- Silvery-gray, brownish-green to black
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4; Color: Silvery-gray, brownish-green to black; Luster: Pearly to sub-metallic; Crystal Structure: Foliated (schistosity); Cleavage: Perfect in one direction due to mica content; Specific Gravity: 2.7-2.8
Formation & geological history
Formed from the metamorphism of shale or mudstone under intermediate pressure and temperature conditions. It typically develops in regional metamorphic zones like mountain ranges (orogenic belts). Most specimens are hundreds of millions of years old.
Uses & applications
Used in construction as a decorative stone for walls and floors (flagstone). Highly micaceous specimens are sometimes used for industrial insulation or as a source of graphite or garnet.
Geological facts
Schist is characterized by having more than 50% platy and elongated minerals, such as mica, which are large enough to be seen with the naked eye. It often contains 'porphyroblasts' like garnet.
Field identification & locations
Identify in the field by its distinct layering and 'shimmer' or 'glitter' when rotated in the light. It splits easily along parallel planes. Commonly found in the Appalachian Mountains, Alps, and Scottish Highlands.
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