metamorphic
Quartz-rich metamorphic rock, likely mica schist
Mica schist; chiefly quartz (SiO₂) with biotite/muscovite mica and possible feldspar
AI-generated identification · may be incorrectCoarse-grained, gray-brown, sparkly surface with platy aligned minerals and probable foliation; quartz has Mohs hardness 7, mica 2–3, with vitreous to pearly luster and no consistent cleavage for the whole rock.
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Physical properties
Coarse-grained, gray-brown, sparkly surface with platy aligned minerals and probable foliation; quartz has Mohs hardness 7, mica 2–3, with vitreous to pearly luster and no consistent cleavage for the whole rock.
Formation & geological history
Formed when shale or another clay-rich sediment was subjected to elevated temperature and pressure during regional metamorphism, commonly in mountain-building belts. Its precise geological age cannot be determined from the photograph.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally building veneer; attractive mica-rich pieces are collected, but it is generally not a gemstone.
Geological facts
The glitter comes mainly from reflective mica flakes, while the darker granular portions may include biotite, graphite, or amphibole. Schistosity allows the rock to split along mineral layers.
Field identification & locations
Identify it by visible foliation and abundant mica sparkle; a fresh surface should show layered, flaky texture rather than uniform glass. Common worldwide in metamorphic mountain regions, including the Appalachians, Alps, and Scandinavia.
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