sedimentary

Likely bituminous coal or carbon-rich shale fragment

Bituminous coal; predominantly carbon with macerals and minor clay/pyrite

AI-generated identification · may be incorrect

Black, opaque, uneven to subconchoidal fracture, dull to weakly resinous luster; Mohs hardness about 2–3, low density, and no visible crystal cleavage. The image is insufficient to distinguish coal confidently from dark shale or slag.

Identified September 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Coal formed from compacted, chemically altered plant material in ancient swamp deposits, commonly Carboniferous to younger; shale formed from lithified mud. Both are sedimentary materials.

Uses & applications

Coal has historically been used as fuel and in coke production; shale may be used for aggregate or fuel. This small fragment has little practical or collector value.

Geological facts

A black streak and light weight favor coal, while a gray-black powdery streak and thin layering favor shale; metallic bubbles or glassy surfaces would suggest industrial slag instead.

Field identification & locations

Common in coal-bearing sedimentary basins worldwide, including Appalachia, the United Kingdom, China, and Australia. Estimated value: generally under $1–$5 for an ordinary fragment; labeled unusual specimens may sell for $5–$20.