sedimentary

Likely bituminous coal

Coal, predominantly carbon-rich organic matter; rank and composition cannot be confirmed from the image

AI-generated identification · may be incorrect

Black, opaque, with a dull-to-slightly shiny uneven surface; hardness and specific gravity are indeterminable visually. Coal has no crystal structure or cleavage; this specimen’s appearance alone is not diagnostic.

Identified October 10, 2026More sedimentary →

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Physical properties

Formation & geological history

Forms from buried plant remains altered by heat and pressure over millions of years, commonly in sedimentary basins. Geological age varies by deposit; many major coal beds formed in the Carboniferous and later periods.

Uses & applications

Used primarily as fuel and in coke production for iron and steelmaking; some coal is collected as a geological specimen.

Geological facts

Coal is an organic sedimentary rock, unlike most rocks composed mainly of minerals. The image does not establish whether this is coal or another dark rock.

Field identification & locations

Its black color and generally noncrystalline appearance are consistent with coal, but a reliable field identification may require checking streak, luster, density, and whether it soils or crumbles. Coal occurs in sedimentary basins worldwide.