metamorphic
Mica Schist
Mica Schist (KAl2(AlSi3O10)(OH)2)
Hardness: 3.5-4 (Mohs scale); Color: Silvery-gray, brownish-black; Luster: Pearly to submetallic; Crystal Structure: Monoclinic; Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7-3.0.
- Hardness
- 3
- Color
- Silvery-gray, brownish-black
- Luster
- Pearly to submetallic
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Physical properties
Hardness: 3.5-4 (Mohs scale); Color: Silvery-gray, brownish-black; Luster: Pearly to submetallic; Crystal Structure: Monoclinic; Cleavage: Perfect basal cleavage in individual mica grains; Specific Gravity: 2.7-3.0.
Formation & geological history
Formed under medium-grade regional metamorphism of clay-rich sedimentary rocks (shale or mudstone) at higher temperatures and pressures than phyllite. Often Precambrian to Paleozoic in age.
Uses & applications
Primarily used as a decorative stone in landscaping, wall cladding, and as a filler in plaster or cement. Some specimens are kept for mineral collections.
Geological facts
The word schist is derived from the Greek word schizein, meaning 'to split,' referring to the rock's ability to be easily split into thin layers due to its foliation.
Field identification & locations
Identifiable by its distinct foliated (layered) texture and sparkly appearance from aligned mica flakes. Common in mountain ranges like the Appalachians or the Alps. Look for the 'shimmer' when rotated in sunlight.
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