metamorphic
Banded mica schist
Mica schist, chiefly muscovite/biotite with quartz and feldspar
AI-generated identification · may be incorrectTypically medium- to coarse-grained, silvery gray to brown, with glittering mica, strong foliation, and schistosity; hardness varies around 2–7 depending on mineral tested, with no uniform cleavage as a rock.
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Physical properties
Typically medium- to coarse-grained, silvery gray to brown, with glittering mica, strong foliation, and schistosity; hardness varies around 2–7 depending on mineral tested, with no uniform cleavage as a rock.
Formation & geological history
Formed when shale or other clay-rich sediment is subjected to regional metamorphism, commonly during mountain building; ages range from Precambrian to recent tectonic belts.
Uses & applications
Used locally for decorative stone, wall cladding, landscaping, and aggregate, but abundant mica and foliation limit structural use. Attractive pieces are collected as geological specimens.
Geological facts
The visible parallel layering reflects aligned platy mica crystals, which can split into thin flakes. Rusty coloration commonly indicates oxidation of iron-bearing biotite or sulfides.
Field identification & locations
Identify it by sparkling mica, wavy planar foliation, and easy splitting along schistosity; quartzite lacks abundant flaky mica, while slate is much finer-grained. Common in metamorphic mountain regions worldwide, including the Appalachians, Alps, and Himalaya.
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