metamorphic
Schist
Mica schist, typically muscovite–biotite quartz schist
AI-generated identification · may be incorrectUsually gray to silvery brown with pronounced foliated, flaky layers and a pearly to vitreous luster; dominated by aligned mica, quartz, and feldspar. Mohs hardness is about 2–7 depending on the tested grain, with mica cleavage and moderate-to-high specific gravity (~2.7–2.9).
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Physical properties
Usually gray to silvery brown with pronounced foliated, flaky layers and a pearly to vitreous luster; dominated by aligned mica, quartz, and feldspar. Mohs hardness is about 2–7 depending on the tested grain, with mica cleavage and moderate-to-high specific gravity (~2.7–2.9).
Formation & geological history
Forms when shale or other clay-rich sediment undergoes medium-grade regional metamorphism, commonly during mountain building; specimens may range from Precambrian to younger Paleozoic–Mesozoic ages.
Uses & applications
Used locally as decorative facing stone, paving, roofing, landscaping rock, and aggregate; attractive mica-rich pieces are collected, though generally not valuable as gemstones.
Geological facts
The visible sheen and parallel foliation result from mica crystals recrystallizing and aligning under directed pressure and heat.
Field identification & locations
Identify it by its strong planar foliation, easy splitting along mica-rich layers, and glittering flakes; common in metamorphic mountain belts worldwide, including New England, the Appalachians, the Alps, and the Himalayas.
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