metamorphic
Likely schist
Mica schist, commonly muscovite- or biotite-rich; exact identification requires testing
AI-generated identification · may be incorrectDark gray, strongly foliated, flaky texture with visible aligned mica; typically Mohs 2–3 for mica, with quartz/feldspar grains around 6–7. Luster is commonly silky to vitreous, and cleavage is prominent along mica foliation.
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Physical properties
Dark gray, strongly foliated, flaky texture with visible aligned mica; typically Mohs 2–3 for mica, with quartz/feldspar grains around 6–7. Luster is commonly silky to vitreous, and cleavage is prominent along mica foliation.
Formation & geological history
Forms when shale or other clay-rich sediment is subjected to regional metamorphism, producing mica alignment and schistosity, commonly during mountain-building hundreds of millions to billions of years ago. Common in metamorphic belts worldwide.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally building veneer; attractive pieces may be collected, though it is generally not a jewelry gemstone.
Geological facts
The specimen appears to show glittering, platy mineral grains and planar fabric characteristic of schist, but the photograph cannot distinguish it confidently from phyllite or a foliated mica-rich gneiss.
Field identification & locations
Look for layers that split into shiny flakes, unlike massive granite; a steel nail may scratch mica but not quartz-rich grains. Common localities include the Appalachians, Alps, Himalayas, Scandinavia, and Precambrian shields.
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