sedimentary
Bituminous Coal
Organic sedimentary rock (humic coal)
Hardness: 0.5-2.5; Color: Black or dark brown; Luster: Dull to sub-vitreous (somewhat shiny); Crystal Structure: Amorphous (non-crystalline); Specific Gravity: 1.1-1.4. Often shows banded layers.
- Hardness
- 0
- Color
- Black or dark brown
- Luster
- Dull to sub-vitreous (somewhat shiny)
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Physical properties
Hardness: 0.5-2.5; Color: Black or dark brown; Luster: Dull to sub-vitreous (somewhat shiny); Crystal Structure: Amorphous (non-crystalline); Specific Gravity: 1.1-1.4. Often shows banded layers.
Formation & geological history
Formed through the deep burial and biochemical alteration of plant matter (peat) in ancient swamp environments. Subjected to heat and pressure over millions of years, typically dating from the Carboniferous or Cretaceous periods.
Uses & applications
Primary fuel source for electric power generation, used in the manufacturing of cement, and processed into 'coke' for steel production.
Geological facts
Bituminous coal is the most abundant rank of coal. It contains roughly 60–80% carbon. It is often referred to as 'soft coal' despite being harder than lignite.
Field identification & locations
Identify by its blocky fracture, dirty smudging (black streak) when rubbed, and layered appearance. Commonly found in massive sedimentary basins (Appalachians, Midwest US). Collectors value specimens with fossil plant imprints.
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