metamorphic
Schist
Mica Schist
Hardness: 3.5 to 4; Color: Gray, silvery-green, or brown; Luster: Pearly to submetallic due to mica; Crystal Structure: Foliated with visible mineral grains; Cleavage: Perfect basal cleavage in individual mica minerals; SG: 2.7–2.8.
- Hardness
- 3
- Color
- Gray, silvery-green, or brown
- Luster
- Pearly to submetallic due to mica
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Physical properties
Hardness: 3.5 to 4; Color: Gray, silvery-green, or brown; Luster: Pearly to submetallic due to mica; Crystal Structure: Foliated with visible mineral grains; Cleavage: Perfect basal cleavage in individual mica minerals; SG: 2.7–2.8.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone at medium-grade temperatures and pressures. Most common in mountain belts and Precambrian shield areas.
Uses & applications
Used as decorative stone in gardens, flagstones for pathways, and occasionally as a source of graphite or garnets when present.
Geological facts
Schist is defined by 'schistosity,' which is the alignment of platy minerals like mica that allow the rock to be split into thin flakes or slabs. It is a transitional state between phyllite and gneiss.
Field identification & locations
Identify in the field by its distinct layered (foliated) appearance and the characteristic 'glitter' or shine when held under light. Look for flat, flaky surfaces. Commonly found in metamorphic terrains like the Appalachians or the Alps.
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