sedimentary

Coal (likely bituminous coal)

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

AI-generated identification · may be incorrect

Black to dark gray, dull to subvitreous luster, layered/fibrous fracture, Mohs hardness about 2–2.5, low density, and no consistent cleavage or crystal structure. The elongated woody texture may indicate fossilized plant material or coalified wood.

Identified September 17, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by burial, compaction, and heating of ancient swamp vegetation, commonly during the Carboniferous–Permian (roughly 359–251 million years ago), though younger deposits also occur. This specimen may be coalified wood rather than ordinary bedded coal.

Uses & applications

Used primarily as fuel and for coke production; selected pieces are collected as fossils or geological curiosities, but it is generally not suitable for jewelry or construction.

Geological facts

Coal can leave a black streak, soil hands, and may show bright vitrinite bands or brassy pyrite. Coalified wood preserves original plant grain and elongated cellular textures.

Field identification & locations

Common in coal basins worldwide, including the Appalachian, Illinois, Ruhr, and Shanxi regions. Confirm with a streak test and inspect for plant structure; avoid flame tests because coal can ignite.