metamorphic
Schist
Mica Schist
Hardness: 3.5-4; Color: Silvery-gray to brownish; Luster: Pearly to sub-metallic due to mica; Crystal structure: Foliated with large, easily visible flakes; Cleavage: Excellent basal cleavage in individual mineral 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: Foliated with large, easily visible flakes; Cleavage: Excellent basal cleavage in individual mineral grains; Specific gravity: 2.7-2.8
Formation & geological history
Formed through regional metamorphism of shale or mudstone under intermediate to high temperature and pressure. Characterized by 'schistosity' where mineral grains align in layers.
Uses & applications
Used historically as a building stone for walls and foundations. Today, it is used for decorative garden stones, flagging, and sometimes as a source of graphite or garnet indicators.
Geological facts
The word schist is derived from the Greek word 'schizein', meaning 'to split', referring to the ease with which the rock can be split into thin layers along the mica planes.
Field identification & locations
Identify in the field by its distinct 'sparkle' or 'sheen' when rotated in sunlight and its tendency to flake off in thin, flat pieces. Finding it indicates a history of tectonic activity and regional metamorphism.
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