sedimentary
Coal (Bituminous or Anthracite)
Organogenic Sedimentary Rock (Carbon)
Hardness: 0.5-2.5 (Mohs); Color: Black to dark brown; Luster: Sub-metallic to dull; Structure: Amorphous/Biogenic; Cleavage: None (conchoidal fracture); Specific Gravity: 1.1-1.5
- Hardness
- 0
- Color
- Black to dark brown
- Luster
- Sub-metallic to dull
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Physical properties
Hardness: 0.5-2.5 (Mohs); Color: Black to dark brown; Luster: Sub-metallic to dull; Structure: Amorphous/Biogenic; Cleavage: None (conchoidal fracture); Specific Gravity: 1.1-1.5
Formation & geological history
Formed from the accumulation of plant debris in swampy environments (peat) that underwent heat and pressure over millions of years (Coalification) during the Carboniferous period.
Uses & applications
Primarily used as a fossil fuel for electricity generation, industrial heat, and in the production of steel (coke). Minor use in carving and jewelry (Jet).
Geological facts
Coal is the largest source of energy for the generation of electricity worldwide, but also a major source of carbon dioxide emissions. The higher the rank (Anthracite), the higher the carbon content and energy density.
Field identification & locations
Identified by its deep black color, lightweight feel compared to silicate rocks, and tendency to leave a black smudge on fingers or streak plates. Found in sedimentary basins globally.
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