sedimentary

Likely bituminous coal

Coal, predominantly carbon-rich organic matter; exact rank cannot be confirmed visually

AI-generated identification · may be incorrect

Black to dark brown, opaque, with a dull-to-subvitreous luster and irregular fracture; hardness and density vary by coal rank. The specimen appears massive and layered, but an image cannot establish its composition or hardness.

Identified September 26, 2026More sedimentary →

Explore Likely bituminous coal in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed from buried plant matter in oxygen-poor swamps, then compacted and altered by heat and pressure over geologic time, commonly during the Carboniferous and later periods.

Uses & applications

Coal is used chiefly for fuel and electricity generation; some types supply coke for iron and steelmaking. This small rough piece is mainly a collecting specimen.

Geological facts

Coal is an organic sedimentary rock rather than a mineral, and its carbon content increases with coal rank from lignite through anthracite.

Field identification & locations

The black color, layered appearance, and subdued sheen are consistent with coal, though other dark rocks can look similar. Common deposits occur in sedimentary basins worldwide; confirm by testing specific gravity, streak, and composition rather than relying on appearance alone.