metamorphic
Anthracite coal
Anthracite; predominantly carbon (C), with minor mineral impurities
AI-generated identification · may be incorrectVery dark gray to black, compact, brittle, and commonly weakly foliated or layered; submetallic to vitreous luster. Mohs hardness about 2–3, low density (~1.4–1.8), and lacks visible crystals; the specimen appears somewhat shiny and cleaved.
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Physical properties
Very dark gray to black, compact, brittle, and commonly weakly foliated or layered; submetallic to vitreous luster. Mohs hardness about 2–3, low density (~1.4–1.8), and lacks visible crystals; the specimen appears somewhat shiny and cleaved.
Formation & geological history
Anthracite forms when bituminous coal is buried and subjected to elevated pressure and temperature during regional metamorphism, typically in Paleozoic coal basins roughly 250–350 million years old. It is a high-carbon, low-volatile stage of coalification.
Uses & applications
Used mainly as a high-grade fuel, in industrial heating, water filtration, and specialized metallurgy; rarely collected as a mineral specimen. It is not generally used for jewelry.
Geological facts
Anthracite contains the highest fixed-carbon content of coal, commonly about 86–98%, and burns with a short, relatively smokeless blue flame. White specks or coatings may be quartz, calcite, or clay minerals.
Field identification & locations
Identify it by its hard, black, shiny appearance, conchoidal or uneven fracture, low streak visibility, and absence of bubbling in dilute acid; it should not be confused with graphite, which is much softer and marks paper readily. Common in Pennsylvania’s Appalachian coalfields, Wales, Vietnam, China, and parts of Russia.
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