metamorphic
Likely graphite-rich schist (possibly galena-bearing metamorphic rock)
Graphite schist; chiefly quartz–mica with graphite (identification uncertain from photograph)
AI-generated identification · may be incorrectDark gray to black, metallic-to-submetallic reflective patches, irregular foliated texture, and uneven fracture. Likely hardness about 2–4 if graphite-rich; specific gravity commonly 2.6–2.9, but substantially higher if galena is present.
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Physical properties
Dark gray to black, metallic-to-submetallic reflective patches, irregular foliated texture, and uneven fracture. Likely hardness about 2–4 if graphite-rich; specific gravity commonly 2.6–2.9, but substantially higher if galena is present.
Formation & geological history
Formed when carbonaceous sedimentary material was metamorphosed under elevated temperature and pressure, producing aligned mica and graphite; graphite schists are commonly Paleozoic to Precambrian, depending on locality.
Uses & applications
Mostly a collector specimen; graphite-rich material may be used for refractory products, lubricants, and pencils, while schist can be used locally as decorative or building stone.
Geological facts
The bright reflective areas may be graphite, mica, or sulfide minerals. A streak test is useful: graphite leaves a dark, greasy streak, whereas galena produces a dark gray streak and is notably heavy.
Field identification & locations
Common in metamorphic belts worldwide, including Sri Lanka, India, Madagascar, Canada, and the United States. Check foliation, perform a streak test on unimportant surfaces, and compare density; definitive identification requires hardness, specific gravity, and mineralogical testing.
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