metamorphic
Schist
Crystalline Metamorphic Rock (Schistose)
Hardness: 3.5 - 5 (variable by mineral); Color: Grey, black, or silvery with shiny flecks; Luster: Vitreous to pearly; Crystal structure: Foliated; Cleavage: Excellent in one direction (basal) for the mica components; Specific gravity: 2.7 - 2.8
- Hardness
- 3
- Color
- Grey, black, or silvery with shiny flecks
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 3.5 - 5 (variable by mineral); Color: Grey, black, or silvery with shiny flecks; Luster: Vitreous to pearly; Crystal structure: Foliated; Cleavage: Excellent in one direction (basal) for the mica components; Specific gravity: 2.7 - 2.8
Formation & geological history
Formed through the regional metamorphism of shale, mudstone, or igneous precursors under intermediate grade (medium pressure and temperature). This occurs deep within the earth during mountain-building events.
Uses & applications
Used as decorative stone in landscaping, for garden walls, flagstones, and sometimes as a roofing material. Not strong enough for structural construction due to its tendency to flake.
Geological facts
The word 'schist' is derived from the Greek word 'schizein', meaning 'to split', referring to the way it easily parts along the plane of its mica flakes.
Field identification & locations
Identify in the field by looking for 'schistosity'—a thin, platy layering with a shiny, glittery appearance caused by large grains of mica. It is common in major mountain ranges like the Appalachians or the Alps.
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