sedimentary

Bituminous coal

Coal; predominantly vitrinite and inertinite macerals composed chiefly of carbon, hydrogen, oxygen, nitrogen, and sulfur

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Identified August 10, 2026More sedimentary →

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Physical properties

Black to brownish-black, generally dull to vitreous or resinous luster, brittle, often showing conchoidal or blocky fracture; Mohs hardness about 2–2.5, very low density, and no visible crystal structure or cleavage. The specimen’s layered, irregular surface is consistent with coal, though image-only identification is provisional.

Formation & geological history

Formed from compacted and chemically altered swamp vegetation during burial and coalification, commonly over millions to hundreds of millions of years; bituminous rank typically develops under moderate heat and pressure from buried peat.

Uses & applications

Used mainly as fuel for electricity generation and steelmaking, and historically for heating; attractive banded pieces may be collected, but it is not typically used as jewelry.

Geological facts

A fresh surface may leave a black streak and can ignite or burn with a smoky flame; coal rank progresses from lignite to sub-bituminous, bituminous, and anthracite.

Field identification & locations

Common in coal-bearing sedimentary basins worldwide, including the Appalachian, Illinois, Powder River, and European coalfields. Distinguish it from anthracite by its softer texture and commonly less metallic luster; avoid tasting or inhaling dust.