sedimentary

Likely anthracite coal

Anthracite; predominantly carbon (C), with minor mineral impurities

AI-generated identification · may be incorrect

Black to gray-black, submetallic to dull luster, layered/foliated appearance, uneven fracture, and Mohs hardness about 2–3; typically lightweight relative to crystalline rocks and may leave a dark streak.

Identified August 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed when bituminous coal underwent intense regional metamorphism, driving off volatiles and concentrating carbon, commonly during mountain-building events; ages depend on the coal basin, often Paleozoic.

Uses & applications

Used primarily as a high-carbon fuel and historically for industrial heating; attractive compact pieces are occasionally collected, but it is not generally a jewelry material.

Geological facts

Anthracite is the highest-rank coal, commonly containing roughly 86–97% fixed carbon and burning with a relatively clean, short blue flame when properly ignited.

Field identification & locations

Identify by its hard, shiny black layered surface, low density, carbonaceous streak, and ability to burn; distinguish it from graphite, which is much softer and strongly marks paper. Common in Pennsylvania and other former coal basins worldwide.