metamorphic
Likely metamorphic schist
Mica schist, probably quartz–biotite schist
AI-generated identification · may be incorrectGray to dark gray, strongly foliated with shiny mica-rich surfaces and granular quartz; Mohs hardness about 2–7 depending on mineral, vitreous to pearly luster, and no consistent cleavage as a whole, though mica has perfect basal cleavage.
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Physical properties
Gray to dark gray, strongly foliated with shiny mica-rich surfaces and granular quartz; Mohs hardness about 2–7 depending on mineral, vitreous to pearly luster, and no consistent cleavage as a whole, though mica has perfect basal cleavage.
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 precise geological age cannot be determined from the photograph.
Uses & applications
Used locally as decorative or facing stone, landscaping rock, and occasionally roofing or wall stone; attractive specimens are collected, but it is generally not a gemstone.
Geological facts
The layered texture is called schistosity and results from aligned platy minerals, especially mica. Individual layers may split readily along foliation, while quartz-rich portions remain hard and resistant.
Field identification & locations
Identify it by visible planar layering, glittering mica flakes, and an uneven, platy fracture; it differs from slate by its coarser grains and stronger sparkle. Common in metamorphic mountain belts worldwide, including the Appalachians, Alps, Himalaya, and New England.
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