metamorphic
Mica Schist
Mica Schist (primarily Muscovite and Biotite KAl2(AlSi3O10)(OH)2)
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray, brown, or bronze; Luster: Pearly to sub-metallic; Crystal Structure: Monoclinic (foliated); Cleavage: Perfect basal (peels in sheets); Specific Gravity: 2.8-3.0
- Hardness
- 3
- Color
- Silvery-gray, brown, or bronze
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gray, brown, or bronze; Luster: Pearly to sub-metallic; Crystal Structure: Monoclinic (foliated); Cleavage: Perfect basal (peels in sheets); Specific Gravity: 2.8-3.0
Formation & geological history
Formed through intermediate-grade regional metamorphism of shale or mudstone. It develops under high pressure and temperature (300-500°C) which causes the mica minerals to align and grow.
Uses & applications
Used primarily as decorative stone, in construction as a fill material, and historically as an electrical insulator in industrial applications due to the mica content.
Geological facts
The word schist is derived from the Greek 'schistos', meaning 'split', referring to the ease with which the rock can be cleaved into thin plates along its foliation planes.
Field identification & locations
Identify by its 'schistosity' (sparkly, wavy layers of mica). Commonly found in mountain belts and metamorphic terrains like the Appalachians or the Alps. Look for a glittery sheen in sunlight.
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