metamorphic
Schist
Schist (primarily mica-schist)
Hardness: 3.5-4 on the Mohs scale. Color: silvery-gray to brownish. Luster: Pearly to sub-metallic. Crystal structure: Foliated with large, visible grains (schistosity). Cleavage: Perfect mica-like basal cleavage on individual mineral grains.
- Hardness
- 3
- Color
- silvery-gray to brownish
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 3.5-4 on the Mohs scale. Color: silvery-gray to brownish. Luster: Pearly to sub-metallic. Crystal structure: Foliated with large, visible grains (schistosity). Cleavage: Perfect mica-like basal cleavage on individual mineral grains.
Formation & geological history
Formed through the regional metamorphism of shale or mudstone at medium grades of heat and pressure. Most specimens range from several hundred million to over a billion years old. Formed in convergent plate boundaries or mountain-building environments.
Uses & applications
Used primarily in construction for flagstones and decorative veneers. Historically used for roofing or paving. Occasionally used as a host rock for gemstones like garnet.
Geological facts
The term 'schist' comes from the Greek word 'schizein,' meaning 'to split,' which refers to how easily the rock breaks along its foliated planes. It is the intermediate stage between phyllite and gneiss.
Field identification & locations
Identify in the field by its distinct 'shimmer' or 'glitter' when rotated in the light and its tendency to flake into thin, uneven plates. Commonly found in metamorphic terrains like the Appalachian Mountains or the Alps.
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