metamorphic
Likely graphite-rich schist (graphitic schist)
Graphitic schist; chiefly quartz, mica, and graphite (carbon), with possible pyrite or feldspar
AI-generated identification · may be incorrectDark gray to black, strongly foliated and platy, with a silvery metallic-to-submetallic sheen; graphite may mark paper and feels greasy. Typical hardness is about 1–2 for graphite but 5–7 for the rock’s silicate matrix; cleavage follows foliation, and density is commonly 2.5–2.8 g/cm³.
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Physical properties
Dark gray to black, strongly foliated and platy, with a silvery metallic-to-submetallic sheen; graphite may mark paper and feels greasy. Typical hardness is about 1–2 for graphite but 5–7 for the rock’s silicate matrix; cleavage follows foliation, and density is commonly 2.5–2.8 g/cm³.
Formation & geological history
Formed when carbon-bearing shale or mudstone underwent regional metamorphism, likely during a Paleozoic or older mountain-building event; exact age cannot be determined from the photograph.
Uses & applications
Graphitic schist is mainly a collector specimen or source rock for graphite; graphite itself is used in refractories, lubricants, batteries, pencils, and electrodes, while schist may occasionally be used as decorative stone.
Geological facts
The specimen’s layered texture and reflective gray-black surfaces are consistent with graphite aligned during metamorphism, though mica-rich schist is a close visual alternative.
Field identification & locations
Look for foliation, flaky cleavage, a gray-black streak, and a soft, greasy feel; test streak on unglazed porcelain or paper, but avoid scratching valuable specimens. Common in metamorphic mountain belts worldwide, including Canada, the United States, Brazil, India, and Madagascar.
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