metamorphic
Mica Schist
Muscovite/Biotite Schist
Hardness: 3.5-4; Color: Silvery-gray, brownish, or golden-bronze; Luster: Pearly to metallic (highly reflective); Crystal structure: Foliated/Platy; Cleavage: Perfect basal cleavage in individual mica grains; Specific gravity: 2.8-3.0
- Hardness
- 3
- Color
- Silvery-gray, brownish, or golden-bronze
- Luster
- Pearly to metallic (highly reflective)
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Physical properties
Hardness: 3.5-4; Color: Silvery-gray, brownish, or golden-bronze; Luster: Pearly to metallic (highly reflective); Crystal structure: Foliated/Platy; Cleavage: Perfect basal cleavage in individual mica grains; Specific gravity: 2.8-3.0
Formation & geological history
Formed through regional metamorphism of shale or mudstone at intermediate temperatures and pressures. This transformational process usually occurs along convergent plate boundaries.
Uses & applications
Primarily used as decorative stone in gardens, flagstones for pathways, and occasionally as a source of mica for industrial insulation or cosmetics.
Geological facts
The word schist comes from the Greek word 'schizein' meaning 'to split,' referring to how easily the rock breaks along thin layers. The sparkly appearance is due to the alignment of large mica crystals during metamorphism.
Field identification & locations
Identify by its distinct shimmering, 'glittery' reflection when rotated in light and the presence of visible, plate-like mineral grains (foliation). Common in mountain ranges like the Appalachians or the Alps.
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