sedimentary

Coal

Anthracite or Bituminous Coal (Carbon)

Hardness: 0.5-2.5 Mohs (Bituminous) or 2.5-3.0 (Anthracite); Color: Black or dark brownish-gray; Luster: Dull to sub-metallic; Structure: Amorphous; Cleavage: None/Conchoidal fracture; Specific Gravity: 1.1-1.5

Hardness: 0
Color: Black or dark brownish-gray
Luster: Dull to sub-metallic

Identified July 18, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of plant debris in ancient swamp environments (Peat) that underwent burial, heat, and pressure over millions of years (Carboniferous era).

Uses & applications

Primarily used as a fuel source for electricity generation and industrial heating; Bituminous coal is used to make coke for steel production.

Geological facts

Coal is often referred to as 'buried sunshine' because it contains energy that was originally captured by plants from sunlight millions of years ago. It is a biochemical sedimentary rock.

Field identification & locations

Identified by its low density (light weight), black streak on a porcelain plate, and ability to burn. Often found in layered beds or seams within sedimentary basins.