metamorphic
Mica Schist
Mica Schist (Composition: Muscovite, Biotite, Quartz, Feldspar)
Hardness: 3.5-4 (on Mohs scale); Color: Silvery-gray to brown; Luster: Pearly to submetallic; Crystal Structure: Monoclinic; Cleavage: Perfect basal (flaky); Specific Gravity: 2.7-3.0
- Hardness
- 3
- Color
- Silvery-gray to brown
- Luster
- Pearly to submetallic
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Physical properties
Hardness: 3.5-4 (on Mohs scale); Color: Silvery-gray to brown; Luster: Pearly to submetallic; Crystal Structure: Monoclinic; Cleavage: Perfect basal (flaky); Specific Gravity: 2.7-3.0
Formation & geological history
Formed through the regional metamorphism of shale or sedimentary mudstone under medium-grade pressure and temperature conditions (Barrovian sequence). It typically dates from the Proterozoic to Phanerozoic eras.
Uses & applications
Used historically as a building stone (dimension stone), in decorative landscapes, and as a source of mica for electrical insulation and cosmetic fillers.
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 layered or split along its mineral planes.
Field identification & locations
Identify in the field by its high foliation ('schistosity') and sparkling reflection. Commonly found in mountainous regions or metamorphic terrains like the Appalachian Mountains or the Alps.
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