metamorphic
Schist
Mica Schist (primarily Muscovite and Biotite)
Hardness: 3.5-4 on Mohs scale; Color: Silvery-grey to dark grey with light-colored bands; Luster: Pearly to sub-metallic due to mica; Structure: Foliated with distinct 'schistosity'; Cleavage: Basal on mica minerals; Specific Gravity: 2.7-2.8
- Hardness
- 3
- Color
- Silvery-grey to dark grey with light-colored bands
- Luster
- Pearly to sub-metallic due to mica
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Physical properties
Hardness: 3.5-4 on Mohs scale; Color: Silvery-grey to dark grey with light-colored bands; Luster: Pearly to sub-metallic due to mica; Structure: Foliated with distinct 'schistosity'; Cleavage: Basal on mica minerals; Specific Gravity: 2.7-2.8
Formation & geological history
Formed through regional metamorphism of shale or mudstone protoliths under intermediate-grade temperature and pressure. Found in tectonic plate boundaries and ancient mountain roots dating from Precambrian to Cenozoic eras.
Uses & applications
Used primarily as decorative stone in landscaping, flagstone for walkways, and as an ornamental facing stone in architecture; historically used for low-grade construction stone.
Geological facts
Schist is characterized by the alignment of platy minerals which allows it to split into thin layers. The term 'schist' comes from the Greek word 'schizein', meaning 'to split'.
Field identification & locations
Identify in the field by its distinct layered (foliated) appearance and the characteristic 'glitter' or sheen when held under light. Commonly found in mountainous regions such as the Appalachians or Alps. Collectors look for garnet inclusions frequently found within the matrix.
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