metamorphic
Anthracite coal
Anthracite; predominantly carbon (C), with minor mineral ash
AI-generated identification · may be incorrectHardness about 2.5–3 Mohs; black to dark gray, commonly showing bright submetallic or vitreous luster and conchoidal to irregular fracture. It is lightweight relative to metallic ores, lacks visible crystals, and may leave a dark streak.
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Physical properties
Hardness about 2.5–3 Mohs; black to dark gray, commonly showing bright submetallic or vitreous luster and conchoidal to irregular fracture. It is lightweight relative to metallic ores, lacks visible crystals, and may leave a dark streak.
Formation & geological history
Formed when bituminous coal underwent intense burial, heating, and compression during regional metamorphism, typically during Paleozoic mountain-building events. It commonly occurs in layered coal seams associated with sedimentary basins.
Uses & applications
Used as a high-carbon fuel, water-filtration medium, and reductant; historically important for heating and iron production. Attractive lustrous pieces are occasionally collected, but it is not generally a gemstone.
Geological facts
Anthracite is the highest-rank coal, containing roughly 86–97% fixed carbon and burning with little smoke. The pictured sharp, shiny fragments are consistent with anthracite, though similar-looking graphite-rich rocks can overlap visually.
Field identification & locations
Commonly found in Pennsylvania, the Appalachian region, Wales, South Africa, China, and Vietnam. Identify it by its black glossy appearance, coal-like lightness, carbonaceous streak, and ability to burn; graphite is softer and marks paper more readily.
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