sedimentary

Coal (Bituminous)

Sedimentary carbonaceous rock

Hardness: 0.5-2.5 (Mohs scale); Color: Black or dark brown; Luster: Sub-metallic to dull; Structure: Amorphous/massively layered; Cleavage: None (conchoidal fracture); Specific Gravity: 1.1-1.4

Hardness: 0
Color: Black or dark brown
Luster: Sub-metallic to dull

Identified June 5, 2026More sedimentary →

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Physical properties

Hardness: 0.5-2.5 (Mohs scale); Color: Black or dark brown; Luster: Sub-metallic to dull; Structure: Amorphous/massively layered; Cleavage: None (conchoidal fracture); Specific Gravity: 1.1-1.4

Formation & geological history

Formed through the lithification and carbonization of ancient plant matter (peat) in swamp environments over millions of years, primarily during the Carboniferous period.

Uses & applications

Primarily used in electric power generation (steam coal) and in the production of steel (coking coal). Also used in cement manufacturing and various chemical processes.

Geological facts

This specimen contains distinct plant impressions or fossilized bark, which is typical for bituminous coal. It represents a middle stage of coalification between lignite and anthracite.

Field identification & locations

Identified by its black color, tendency to smudge fingers slightly, and lightweight feel compared to silicate rocks. Commonly found in massive beds in the Appalachian Basin and Interior Basin of North America.