metamorphic
Mica-rich schist
Muscovite–biotite schist, commonly quartz-bearing
AI-generated identification · may be incorrectTypically medium-grained, strongly foliated, and sparkly with platy mica; gray, silvery, brown, or bronze. Quartz and feldspar are harder (Mohs 6–7), while muscovite and biotite are about Mohs 2–3; mica shows perfect basal cleavage and a pearly luster.
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Physical properties
Typically medium-grained, strongly foliated, and sparkly with platy mica; gray, silvery, brown, or bronze. Quartz and feldspar are harder (Mohs 6–7), while muscovite and biotite are about Mohs 2–3; mica shows perfect basal cleavage and a pearly luster.
Formation & geological history
Formed when shale or another clay-rich sediment was subjected to elevated temperature and pressure during regional metamorphism, commonly during mountain building. Its exact geological age cannot be determined from the photograph and varies by locality.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally dimension stone, but its pronounced foliation limits structural use. Attractive specimens are collected for their glittering mica texture.
Geological facts
The specimen’s reflective flakes and planar fabric are characteristic of schistosity, produced by alignment of mica crystals. Weathered surfaces may crumble or split readily along foliation.
Field identification & locations
Look for visible, aligned mica flakes that glitter when tilted and separate into thin sheets; a streak or hardness test can help distinguish mica-rich schist from phyllite. Common in metamorphic belts worldwide, including the Appalachians, Alps, and New England.
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