sedimentary

Coal

Carbonaceous sedimentary rock

Hardness: 0.5-2.5 on Mohs scale; Color: Jet black to brownish black; Luster: Dull to sub-vitreous; Structure: Amorphous (non-crystalline); Specific Gravity: 1.1-1.5

Hardness: 0
Color: Jet black to brownish black
Luster: Dull to sub-vitreous

Identified July 12, 2026More sedimentary →

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Physical properties

Hardness: 0.5-2.5 on Mohs scale; Color: Jet black to brownish black; Luster: Dull to sub-vitreous; Structure: Amorphous (non-crystalline); Specific Gravity: 1.1-1.5

Formation & geological history

Formed from the accumulation of plant remains in swampy environments that were buried, compressed, and subject to heat over millions of years (Carboniferous to Tertiary periods).

Uses & applications

Primary source of fuel for electricity generation, manufacture of steel (coke), and various chemical byproduct industries.

Geological facts

Coal is often referred to as 'buried sunshine' because it stores the solar energy captured by plants millions of years ago. It accounts for about 25% of the world's primary energy consumption.

Field identification & locations

Identified by its black color, light weight relative to stone, and ability to leave a black mark on rough surfaces. Commonly found in stratified layers called seams within sedimentary basins.