metamorphic
Schist
Crystalline Metamorphic Schist
Hardness: 3.5-5 (Mohs), Color: Silver, gold, gray, or brown with a sparkly appearance, Luster: Vitreous to silky/metallic, Crystal structure: Foliated with visible mica flakes, Cleavage: Excellent in one direction due to mica orientation, Specific Gravity: 2.7-2.8
- Hardness
- 3
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Physical properties
Hardness: 3.5-5 (Mohs), Color: Silver, gold, gray, or brown with a sparkly appearance, Luster: Vitreous to silky/metallic, Crystal structure: Foliated with visible mica flakes, Cleavage: Excellent in one direction due to mica orientation, Specific Gravity: 2.7-2.8
Formation & geological history
Formed through the regional metamorphism of pelitic rocks like shale or mudstone under intermediate pressure and temperature conditions. It typically develops at convergent plate boundaries and can date from nearly any geological era.
Uses & applications
Historically used as a building stone, for paving, and occasionally as garden decoration. Certain types like mica-schist were used as 'glitter' in ancient pottery or as liners for ovens.
Geological facts
The word schist comes from the Greek word 'schistos,' meaning 'easy to split,' referring to its ability to be flaked apart along its foliated planes. It is the intermediate stage between phyllite and gneiss.
Field identification & locations
Identify in the field by its distinct 'schistosity'—a sparkly, foliated texture where individual mica flakes (muscovite or biotite) are large enough to be seen by the naked eye. Often found in mountainous regions or ancient eroded shield landmasses.
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