sedimentary

Coal (Bituminous / Anthracite)

Organic Sedimentary Rock (Carbonaceous Rock)

Mohs hardness: 1.0–2.5 (Bituminous) to 2.5–3.0 (Anthracite). Color: Dark brown to black. Luster: Sub-metallic to dull or vitreous. Fracture: Conchoidal to blocky. Specific gravity: 1.1–1.5. Amorphous structure.

Hardness: 1
Color: Dark brown to black
Luster: Sub-metallic to dull or vitreous

Identified July 26, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed over millions of years (Carboniferous to Tertiary periods) from buried, decaying plant matter (peat) subjected to heat and pressure during deep burial.

Uses & applications

Historically and currently used primarily as a fossil fuel for electricity generation, industrial heating, and steel production (coking coal). Also collected as a mineral specimen.

Geological facts

Coal is an organic sedimentary rock composed mostly of carbon, along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Higher-grade coal (anthracite) burns cleaner and hotter than lower grades like lignite.

Field identification & locations

Identified by its low density (feels surprisingly light for its size), black to dark brown color, and tendency to leave a dark streak or soil hands. Found in sedimentary basins worldwide.

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