sedimentary

Coal (Bituminous or Anthracite)

Carbonaceous sedimentary rock (primarily Carbon, C)

AI-generated identification · may be incorrect

Hardness: 0.5-2.5 (Mohs), Color: Black to dark brown, Luster: Dull to sub-metallic or vitreous, Structure: Amorphous/Organic, Specific Gravity: 1.1-1.5

Hardness: 0

Identified February 28, 2026More sedimentary →

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Physical properties

Hardness: 0.5-2.5 (Mohs), Color: Black to dark brown, Luster: Dull to sub-metallic or vitreous, Structure: Amorphous/Organic, Specific Gravity: 1.1-1.5

Formation & geological history

Formed from the remains of ancient plant matter in swampy environments through the process of coalification during the Carboniferous period (approx. 300 million years ago).

Uses & applications

Primarily used as a fossil fuel for electricity generation, industrial heat, and in the production of steel (coke). Polished anthracite is occasionally used for jewelry or carving.

Geological facts

Coal is the world's most abundant fossil fuel. Anthracite is the highest 'rank' of coal, containing the most carbon and burning with the least smoke.

Field identification & locations

Identified by its lightweight feel compared to stones, black streak when rubbed on porcelain, and tendency to smudge fingers. Commonly found in sedimentary basins.