sedimentary
Coal
Bituminous coal (Complex organic sedimentary rock)
Mohs hardness: 1.5 to 3; Color: Black or brownish-black; Luster: Dull to sub-vitreous; Structure: Amorphous, layered; Specific gravity: 1.1 to 1.5
- Hardness
- 1
- Color
- Black or brownish-black
- Luster
- Dull to sub-vitreous
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Physical properties
Mohs hardness: 1.5 to 3; Color: Black or brownish-black; Luster: Dull to sub-vitreous; Structure: Amorphous, layered; Specific gravity: 1.1 to 1.5
Formation & geological history
Formed from compressed plant remains in ancient swamp environments, primarily during the Carboniferous period, through the process of coalification over millions of years.
Uses & applications
Primary use is for electricity generation (thermal coal), steel production (metallurgical coal or coking coal), and previously for heating and steam locomotive fuel.
Geological facts
Coal is often called 'buried sunshine' because the energy it stores originally came from the sun via ancient photosynthesis in prehistoric swamp forests.
Field identification & locations
Identified by its relatively light weight, black streak, dark color, and tendency to soil the hands or leave a dark mark. Common in sedimentary basins worldwide.
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