metamorphic
Schist
Mica Schist
Hardness: 3.5-4; Color: Silvery-gray to brownish; Luster: Pearly to sub-metallic due to mica; Crystal Structure: Medium-grained foliated (schistosity); Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7-2.8
- Hardness
- 3
- Color
- Silvery-gray to brownish
- Luster
- Pearly to sub-metallic due to mica
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Physical properties
Hardness: 3.5-4; Color: Silvery-gray to brownish; Luster: Pearly to sub-metallic due to mica; Crystal Structure: Medium-grained foliated (schistosity); Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7-2.8
Formation & geological history
Formed through the regional metamorphism of shale or mudstone under high pressure and temperature. The reported location (Western Caucasus) is a major tectonic belt where metamorphic rocks of Paleozoic to Mesozoic age are highly prevalent.
Uses & applications
Used historically as flagging, roof tiles, and wall stones. Low-grade specimens are often used as fill in construction; high-mica specimens are sometimes used for decorative garden stone.
Geological facts
The word 'schist' is derived from the Greek word 'schizein', meaning 'to split', referring to how easily the rock can be cleaved along its parallel mineral layers. Each layer is usually composed of platy minerals like muscovite or biotite.
Field identification & locations
Identify by its 'sparkly' appearance and distinct layering (foliation) that allows it to split into thin plates. It is extremely common in mountainous regions like the North Caucasus. Collectors look for 'garnet schist' which contains red crystals.
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