sedimentary
Bituminous Coal
Organic Sedimentary Rock (composed mostly of carbon with sulfur and hydrogen)
Hardness: 1-1.5 on Mohs scale; Color: Dark brown to black; Luster: Submetallic, vitreous, or dull; Structure: Massive or banded (stratified); Cleavage: Fractures regularly, often with a blocky appearance; Specific Gravity: 1.1–1.5.
- Hardness
- 1-1
- Color
- Dark brown to black
- Luster
- Submetallic, vitreous, or dull
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Physical properties
Hardness: 1-1.5 on Mohs scale; Color: Dark brown to black; Luster: Submetallic, vitreous, or dull; Structure: Massive or banded (stratified); Cleavage: Fractures regularly, often with a blocky appearance; Specific Gravity: 1.1–1.5.
Formation & geological history
Formed through the deep burial and compression of peat and lignite over millions of years (principally during the Carboniferous period, approx. 300-360 million years ago). It occurs in anaerobic swamp environments where heat and pressure drive off water and volatiles found in lower-grade coal.
Uses & applications
Primary fuel source for electric power generation and heating; used in industry as 'coking coal' for steel manufacturing and iron production.
Geological facts
Bituminous coal is the most abundant rank of coal in the United States. It is often referred to as 'soft coal' even though it is harder than lignite, to distinguish it from 'hard coal' (anthracite).
Field identification & locations
Field Identification: Distinguished by its black color, blocky shape when broken (cleat), and layered texture; it will smudge hands and leave a dark brown/black streak. Common in Appalachia and the Midwest US. Collectors should look for 'bright coal' bands which indicate high carbon content.
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