metamorphic
Foliated metamorphic rock, likely mica schist
Muscovite- or biotite-bearing schist, commonly quartz–feldspar schist
AI-generated identification · may be incorrectGray, coarse-grained, sparkly and strongly foliated, with platy mica flakes and lighter quartz/feldspar. Hardness is about 2–3 for exposed mica and 6–7 for quartz; luster ranges silky to vitreous, with mica’s perfect basal cleavage.
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Physical properties
Gray, coarse-grained, sparkly and strongly foliated, with platy mica flakes and lighter quartz/feldspar. Hardness is about 2–3 for exposed mica and 6–7 for quartz; luster ranges silky to vitreous, with mica’s perfect basal cleavage.
Formation & geological history
Formed when shale or another clay-rich sediment was buried and subjected to regional heat and pressure, producing aligned mica foliation. Schists formed during ancient mountain-building events of many ages, commonly Paleozoic or older.
Uses & applications
Used locally as decorative stone, landscaping rock, and aggregate, though its foliation makes it unsuitable for major structural construction. Attractive mica-rich pieces are collected as geological specimens.
Geological facts
The visible glitter is most likely mica, which splits into thin elastic sheets; quartz grains provide the harder, pale gray portions. The small fragment may also be weathered gneiss, but its pronounced flaky texture favors schist.
Field identification & locations
Common in metamorphic belts worldwide, including the Appalachians, New England, the Alps, and parts of India. Identify it by abundant aligned flakes, foliation, uneven splitting along mica layers, and a sparkly surface; a close image or streak/acid tests would improve certainty.
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