metamorphic
Schist
Mica Schist (primarily Muscovite or Biotite sheet silicates)
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray, black, or greenish; Luster: Pearly to sub-metallic due to mica flakes; Structure: Foliated (schistosity); Cleavage: Distinct parallel layering along mica sheets.
- Hardness
- 3
- Color
- Silvery-gray, black, or greenish
- Luster
- Pearly to sub-metallic due to mica flakes
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Physical properties
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray, black, or greenish; Luster: Pearly to sub-metallic due to mica flakes; Structure: Foliated (schistosity); Cleavage: Distinct parallel layering along mica sheets.
Formation & geological history
Formed from the regional metamorphism of clay-rich sedimentary rocks like shale or mudstone under medium-grade temperature and pressure. It originates in mountain-building environments (orogenic belts).
Uses & applications
Used as decorative stone in gardens, thin slabs for paving or roofing, and occasionally as a source for graphite or garnets if localized. Generally too weak for heavy construction due to its fissility.
Geological facts
Schist is characterized by its 'schistosity,' which means the mineral grains have grown large enough to be seen with the naked eye and are aligned in parallel layers that cause the rock to split easily into flakes.
Field identification & locations
Identify in the field by its distinct glittering or sparkly appearance when rotated in the light ('schistose sheen'). Common in metamorphic terrains such as the Appalachian or Alpine mountains. Use a magnifying glass to see the aligned plates of mica.
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