sedimentary
Bituminous Coal
Organic-rich sedimentary rock (Complex hydrocarbons)
Hardness: 0.5–2.5 (Mohs scale); Color: Black to dark brown; Luster: Sub-metallic to dull; Crystal structure: Amorphous (non-crystalline); Cleavage: Rectangular blocky fracturing (cleat); 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 scale); Color: Black to dark brown; Luster: Sub-metallic to dull; Crystal structure: Amorphous (non-crystalline); Cleavage: Rectangular blocky fracturing (cleat); Specific gravity: 1.1–1.5
Formation & geological history
Formed through the deep burial and lithification of peat over millions of years (diagenesis). Most deposits date to the Carboniferous or Cretaceous periods (360–66 million years ago) in swampy, coastal environments.
Uses & applications
Primarily used for electricity generation (thermal coal) and steel production (coking coal). It is also used as a raw material for synthetic fuels and various chemical industries.
Geological facts
It is the most abundant form of coal in the United States. Unlike the softer 'lignite', bituminous coal contains a high carbon content and produces more heat, though it also contains sulfur which can contribute to acid rain when burned.
Field identification & locations
Identify in the field by its blocky fracturing (cleat), dark black color, and the fact that it will leave a black streak on a porcelain plate and feels relatively light for its size. It is commonly found in basins like the Appalachian Basin or the Illinois Basin.
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