metamorphic
Schist (Micaceous Schist)
Schist (containing mainly Muscovite and Quartz)
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gold, brown, or gray; Luster: Pearly to sub-metallic (shimmering); Crystal structure: Foliated (schistosity); Cleavage: Perfect in one direction (micaceous); Specific gravity: 2.7-2.8
- Hardness
- 3
- Color
- Silvery-gold, brown, or gray
- Luster
- Pearly to sub-metallic (shimmering)
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Physical properties
Hardness: 3.5-4 on Mohs scale; Color: Silvery-gold, brown, or gray; Luster: Pearly to sub-metallic (shimmering); Crystal structure: Foliated (schistosity); Cleavage: Perfect in one direction (micaceous); Specific gravity: 2.7-2.8
Formation & geological history
Formed through high-grade regional metamorphism of shale or sedimentary protoliths under intense heat and pressure. This specific specimen shows significant 'schistosity,' or the alignment of flat mineral grains, indicating it was compressed deep within the earth's crust.
Uses & applications
Used historically as a building stone, for decorative garden stones, and occasionally as a source of mica for electrical insulation or lubricants in industrial settings.
Geological facts
Schist is characterized by having more than 50% platy and elongated minerals. The term 'schist' is derived from the Greek word 'schízein', meaning 'to split', referring to the ease with which the rock can be layered or split.
Field identification & locations
Identify in the field by its distinct glittering or shimmering appearance when rotated in the sun and its layered, flaky texture. Common in mountain ranges and metamorphic terranes such as the Appalachians or the Alps.
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