metamorphic
Schist
Mica Schist
Hardness: 3.5-4 Mohs depending on mineral content. Color: Silvery-gray, greenish-black, or charcoal. Luster: Pearly to sub-metallic due to mica. Crystal structure: Foliated (schistosity). Cleavage: Near-perfect basal cleavage at a microscopic level. Specific gravity: 2.5–2.8.
- Hardness
- 3
- Color
- Silvery-gray, greenish-black, or charcoal
- Luster
- Pearly to sub-metallic due to mica
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Physical properties
Hardness: 3.5-4 Mohs depending on mineral content. Color: Silvery-gray, greenish-black, or charcoal. Luster: Pearly to sub-metallic due to mica. Crystal structure: Foliated (schistosity). Cleavage: Near-perfect basal cleavage at a microscopic level. Specific gravity: 2.5–2.8.
Formation & geological history
Formed through the regional metamorphism of shale, siltstone, or volcanic rock under intermediate pressure and temperature conditions. It typically represents a higher grade of metamorphism than slate and phyllite but lower than gneiss.
Uses & applications
Used historically as a building stone, decorative paving, and garden stone. Some schist contains industrial minerals like garnets or graphite that are extracted.
Geological facts
The word 'schist' is derived from the Greek 'schizein', meaning 'to split', referring to how the rock easily flakes into thin plates called foliation. Some schists host rare precious gemstones like emeralds.
Field identification & locations
Identify in the field by looking for a 'glittery' or 'shimmery' appearance when rotated under light. Look for visible mineral grains (larger than phyllite) and distinct platiness. Common in mountain belts like the Appalachians or the Alps.
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