metamorphic
Graphite-rich schist (probable)
Graphite schist; primarily graphite (C) with mica and quartz
AI-generated identification · may be incorrectDark gray to black, platy and strongly foliated with a metallic-to-submetallic sheen; graphite is very soft (Mohs 1–2), opaque, and leaves a gray-black streak. The specimen appears flaky and sparkly, though exact identification requires testing.
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Physical properties
Dark gray to black, platy and strongly foliated with a metallic-to-submetallic sheen; graphite is very soft (Mohs 1–2), opaque, and leaves a gray-black streak. The specimen appears flaky and sparkly, though exact identification requires testing.
Formation & geological history
Formed when carbon-rich sedimentary rocks were regionally metamorphosed, commonly during mountain building; age depends on its geologic setting and cannot be determined from the image. Graphite crystallized under elevated temperature and pressure.
Uses & applications
Used mainly as a graphite source for lubricants, refractories, batteries, pencils, and electrodes; attractive pieces may be collected, but it is generally not a jewelry gemstone.
Geological facts
Graphite is the same element as diamond but has a layered crystal structure, making it soft and electrically conductive. Schistosity develops from aligned platy minerals during metamorphism.
Field identification & locations
Look for a greasy metallic sheen, flaky foliation, gray-black streak, and easy marking of paper; it should not fizz with dilute acid. Common in metamorphic belts worldwide, including Canada, Brazil, India, Madagascar, and the United States.
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