sedimentary
Bituminous Coal
Bituminous coal (Organic Sedimentary Rock)
Hardness: 0.5–2.5 (Mohs); Color: Dark brown to black; Luster: Sub-metallic to dull; Structure: Massively bedded or blocky; Cleavage: None (has fracture); Specific Gravity: 1.1–1.5.
- Hardness
- 0
- Color
- Dark brown to black
- Luster
- Sub-metallic to dull
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Physical properties
Hardness: 0.5–2.5 (Mohs); Color: Dark brown to black; Luster: Sub-metallic to dull; Structure: Massively bedded or blocky; Cleavage: None (has fracture); Specific Gravity: 1.1–1.5.
Formation & geological history
Formed from the compression of peat layers over millions of years. It occurs when lignite coal is buried deeper, subjecting it to increased heat and pressure (coalification), typically during the Carboniferous period.
Uses & applications
Primary fuel source for electric power generation, used in the production of coke for steel manufacturing, and occasionally used as a source for decorative 'coal jewelry' in specific historic regions.
Geological facts
Bituminous coal is the most abundant rank of coal found in the United States and contains 45% to 86% carbon. It is often referred to as 'soft coal' despite being harder than lignite.
Field identification & locations
Identify by its black color, tendency to soil fingers when handled, and blocky fracture. It is commonly found in the Appalachian Basin and Interior Coal Province. Collectors should look for plant fossils often transitionally preserved within the layers.
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