sedimentary
Coal (specifically Bituminous or Anthracite)
Organic sedimentary rock; primarily Carbon (C) with varying H, S, O, N
Hardness: 1-3 (Mohs scale), Color: Jet black to brownish-black, Luster: Dull to sub-metallic or vitreous, Crystal structure: Amorphous/None, Cleavage: None (conchoidal fracture), Specific gravity: 1.1-1.5
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Physical properties
Hardness: 1-3 (Mohs scale), Color: Jet black to brownish-black, Luster: Dull to sub-metallic or vitreous, Crystal structure: Amorphous/None, Cleavage: None (conchoidal fracture), Specific gravity: 1.1-1.5
Formation & geological history
Formed through the lithification and carbonization of ancient plant remains in swampy environments over millions of years (primarily Carboniferous to Tertiary periods). Formation involves heat and pressure burying peat layers.
Uses & applications
Primary use is fuel for electricity generation and industrial heating; also used in steel production (coke) and as a chemical feedstock.
Geological facts
Coal is known as a fossil fuel and is the largest source of energy for the generation of electricity worldwide, though it is the most carbon-intensive. Anthracite, the highest grade, is sometimes carved into jewelry or folk art.
Field identification & locations
Identify in the field by its low density (light feel), black streak on a porcelain plate, and ability to be easily scratched or broken. Commonly found in massive sedimentary basins or near coal mines.
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