metamorphic
Schist
Mica Schist (primarily Muscovite or Biotite sheet silicates)
Hardness: 3.5-4 on the Mohs scale. Color: silvery-grey to greyish-green. Lustre: Pearly to metallic (very shiny due to mica alignment). Crystal structure: Foliated (schistosity). Cleavage: Near-perfect basal cleavage on individual mica crystals.
- Hardness
- 3
- Color
- silvery-grey to greyish-green
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Physical properties
Hardness: 3.5-4 on the Mohs scale. Color: silvery-grey to greyish-green. Lustre: Pearly to metallic (very shiny due to mica alignment). Crystal structure: Foliated (schistosity). Cleavage: Near-perfect basal cleavage on individual mica crystals.
Formation & geological history
Formed from the high-grade metamorphism of clay-rich sedimentary rocks (like shale or mudstone) or medium-grade metamorphism of felsic igneous rocks under significant heat and pressure. It usually represents a medium-grade stage between phyllite and gneiss.
Uses & applications
Used primarily in construction for decorative stone (paving, roofing, flagging), garden ornaments, and occasionally as a source for certain minerals like garnets or kyanite that can occur within the rock matrix.
Geological facts
The word 'schist' is derived from the Greek word 'schizein', which means 'to split,' referring to the rock's ability to split easily along the planes of its mica flakes. It often contains inclusions of larger crystals called porphyroblasts, such as red garnets.
Field identification & locations
Identify in the field by its distinct 'sparkle' or 'sheen' and its laminated, foliated texture. It feels rough or flaky to the touch and can be easily scratched by a penknife. Look for it in mountain belts and areas of ancient continental crust.
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