metamorphic
Mica-rich schist (likely biotite schist)
Biotite–quartz schist; typically quartz + biotite mica ± feldspar, muscovite, and garnet
AI-generated identification · may be incorrectBrown-golden, sparkly surface with abundant platy mica and pronounced schistosity; mica gives a flaky texture and vitreous to pearly luster. Hardness is roughly 2.5–3 for biotite but about 6–7 for quartz; cleavage is strong in mica, and overall specific gravity is approximately 2.7–3.1.
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Physical properties
Brown-golden, sparkly surface with abundant platy mica and pronounced schistosity; mica gives a flaky texture and vitreous to pearly luster. Hardness is roughly 2.5–3 for biotite but about 6–7 for quartz; cleavage is strong in mica, and overall specific gravity is approximately 2.7–3.1.
Formation & geological history
Formed when shale or other clay-rich sediment was buried and metamorphosed under directed pressure and elevated temperature, aligning mica into layers. Its exact age cannot be determined visually; schists commonly range from Precambrian to younger Paleozoic rocks.
Uses & applications
Used mainly as decorative stone, aggregate, landscaping material, and occasionally building stone; attractive specimens are collected, but this rough piece has modest commercial value.
Geological facts
The glitter is mainly reflective mica flakes rather than metallic mineralization. Individual mica sheets can split into thin elastic layers.
Field identification & locations
Look for glittering aligned flakes, a layered or easily splitting fabric, and a nonmetallic streak. Around 10.1°N, 2.5°W in Ghana, mica-bearing metamorphic rocks are geologically plausible, though exact identification requires a fresh surface or tests.
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