sedimentary

Coal

Bituminous or Anthracite Coal

Hardness: 0.5-2.5 (Mohs), Color: Black to dark brown, Luster: Dull to sub-metallic/greasy, Structure: Amorphous (non-crystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 1.1-1.5

Hardness: 0

Identified July 8, 2026More sedimentary →

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Physical properties

Hardness: 0.5-2.5 (Mohs), Color: Black to dark brown, Luster: Dull to sub-metallic/greasy, Structure: Amorphous (non-crystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 1.1-1.5

Formation & geological history

Formed from the accumulation of plant remains in swampy environments (peat), which undergo biochemical and physical changes over millions of years due to heat and pressure (coalification).

Uses & applications

Primarily used as a combustible fuel for electricity generation, industrial heat, and in the production of steel (coke). Fine specimens or jet (a form of coal) are used in jewelry.

Geological facts

Coal is the largest source of energy for the generation of electricity worldwide, though its use is declining in many regions due to environmental concerns. Jet, a dense variety of coal, was extremely popular for mourning jewelry in the Victorian era.

Field identification & locations

Identified by its black streak, lightweight feel (low density), and flammability. Found in large sedimentary basins globally, such as the Appalachian mountains and the Powder River Basin in the USA.