sedimentary
Coal (Anthracite or Bituminous)
Carbo caulis / Sedimentary Carbon
Hardness: 0.5–2.5 (Mohs scale), Color: Jet black to dark brownish-black, Luster: Sub-metallic to vitreous (glassy) for anthracite; dull for bituminous, Cleavage: None (conchoidal fracture), Specific Gravity: 1.1–1.5
- Hardness
- 0
- Luster
- Sub-metallic to vitreous (glassy) for anthracite
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Physical properties
Hardness: 0.5–2.5 (Mohs scale), Color: Jet black to dark brownish-black, Luster: Sub-metallic to vitreous (glassy) for anthracite; dull for bituminous, 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 are buried and subjected to heat and pressure over millions of years (Lithification/Coalification). Most specimens are from the Carboniferous Period (360–300 million years ago).
Uses & applications
Primarily used as a combustible fuel for electricity generation and industrial heating; Bituminous coal is used in steel production (coke); higher grades like Anthracite are used for residential heating and filtration; also used jewelry (Jet).
Geological facts
Coal is often called 'buried sunshine' because it contains captured solar energy from ancient plants. It is the most abundant fossil fuel on Earth and is classified based on its carbon content and thermal value.
Field identification & locations
Identify by its low density (feels light for its size), black streak, and tendency to leave a dark residue on hands. It is brittle and often displays a blocky or layered structure. Commonly found in sedimentary basins worldwide, such as the Appalachian region or the Kuznetsk Basin.
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