metamorphic

Biotite-rich schist

Mica schist; predominantly biotite mica with quartz and feldspar

AI-generated identification · may be incorrect

Typically medium-hard (about Mohs 2.5–7 depending on composition), dark brown-black and silvery, with a shiny micaceous luster and strongly foliated, platy texture. Biotite has perfect basal cleavage; quartz and feldspar are harder and granular.

Identified August 16, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or other clay-rich sediment was regionally metamorphosed under elevated pressure and temperature, commonly during mountain building. The image shows a hand specimen rather than material that can be assigned a precise geological age.

Uses & applications

Used locally as decorative stone, landscaping rock, and occasionally dimension stone; its principal value is educational or as a mineralogical specimen rather than jewelry material.

Geological facts

The glittering flakes are likely biotite, which can peel into flexible sheets; light-colored bands or grains are probably quartz and feldspar. Foliation reflects alignment of platy minerals during metamorphism.

Field identification & locations

Identify it by its planar foliation, sparkly cleavage surfaces, and tendency to split along mica-rich layers; it commonly occurs in metamorphic mountain belts worldwide, including the Appalachians, Alps, and Himalaya.