metamorphic
Biotite-rich schist with garnet-like inclusion
Mica schist; predominantly muscovite/biotite mica, quartz, and feldspar, with a possible garnet or weathered mafic fragment
AI-generated identification · may be incorrectVery coarse, silvery micaceous foliation with platy cleavage and vitreous-to-pearly luster; mica hardness is about 2–3, while quartz/feldspar are 6–7. The brown central piece is opaque, irregular, and may be garnet-bearing schist or an attached weathered inclusion.
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Physical properties
Very coarse, silvery micaceous foliation with platy cleavage and vitreous-to-pearly luster; mica hardness is about 2–3, while quartz/feldspar are 6–7. The brown central piece is opaque, irregular, and may be garnet-bearing schist or an attached weathered inclusion.
Formation & geological history
Formed when shale or another clay-rich protolith underwent regional metamorphism, typically during mountain building; commonly Paleozoic to Precambrian, though age depends on locality.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally dimension stone; attractive mica-rich pieces are mainly collector specimens rather than jewelry material.
Geological facts
Schistosity develops as mica crystals align under directed pressure and heat. The reflective surface is characteristic of abundant sheet silicates, especially muscovite and biotite.
Field identification & locations
Identify by its strong glitter, easy splitting along foliation, and visible mica flakes; common in metamorphic mountain belts worldwide, including the Appalachians, Alps, Himalayas, and New England. Confirm the brown center with hardness, streak, and crystal-form tests.
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