metamorphic
Biotite-rich mica schist
Mica schist, likely containing biotite and quartz with possible feldspar
AI-generated identification · may be incorrectCoarse, sparkly brown-gray rock with platy mica grains and a foliated texture; biotite has Mohs hardness 2.5–3, quartz 7. Mica’s monoclinic crystals split into thin sheets; the specimen’s specific gravity cannot be determined from the image.
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Physical properties
Coarse, sparkly brown-gray rock with platy mica grains and a foliated texture; biotite has Mohs hardness 2.5–3, quartz 7. Mica’s monoclinic crystals split into thin sheets; the specimen’s specific gravity cannot be determined from the image.
Formation & geological history
Forms when clay-rich sedimentary rock or other protolith is regionally metamorphosed under heat and pressure, producing aligned mica; its age depends on the local geological setting.
Uses & applications
Schist is mainly a collector or decorative specimen; mica is used in electrical, construction, and industrial products, while quartz and feldspar are common industrial minerals.
Geological facts
The glitter comes from reflective mica flakes, and the rock’s visible alignment of minerals records metamorphic deformation.
Field identification & locations
Look for abundant shiny, flat flakes and a tendency to split along mica-rich foliation; similar schists occur in metamorphic mountain belts worldwide. A hand-sized rough specimen typically sells for about $5–$20.
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