metamorphic

Biotite-rich schist

Mica schist, chiefly quartz + biotite mica (locally muscovite); composition varies

AI-generated identification · may be incorrect

Dark gray to purplish, strongly foliated and sparkly, with platy mica flakes and irregular quartz-rich bands. Hardness is about 2.5–3 for biotite and 7 for quartz; mica has perfect basal cleavage, while the rock splits along foliation. Specific gravity is roughly 2.7–3.0;…

Identified September 1, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sediment was regionally metamorphosed under elevated pressure and temperature, producing aligned mica and recrystallized quartz. It is commonly Precambrian to Paleozoic, though exact age cannot be determined from the photograph.

Uses & applications

Used locally as decorative stone, landscaping material, and occasionally dimension stone, but its pronounced foliation limits structural construction use. Attractive mica-rich pieces are collected as specimens.

Geological facts

The glitter comes from aligned mica rather than abundant metal. The apparent pink-purple tones may reflect weathering, feldspar, or iron staining.

Field identification & locations

Look for planar foliation, mica sparkle, and flakes that peel or separate; a steel nail usually scratches mica but not quartz grains. The reported southeastern DRC location is geologically compatible with ancient metamorphic basement rocks, though locality confirmation requires a map or testing.