Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality than lignite and Sub-bituminous coal, but of poorer quality than anthracite. Formation is usually the result of high pressure being exerted on lignite. Its coloration can be black or sometimes dark brown; often there are well-defined bands of bright and dull material within the seams. These distinctive sequences, which are classified according to either “dull, bright-banded” or “bright, dull-banded”, is how bituminous coals are stratigraphically identified.
Bituminous coal is an organic sedimentary rock formed by diagenetic and sub metamorphic compression of peat bog material. Its primary constituents are macerals: vitrinite, and liptinite. The carbon content of bituminous coal is around 45–86%; the rest is composed of water, air, hydrogen, and sulfur, which have not been driven off from the macerals. Bank density is approximately 1,346 kilograms per cubic metre (84.0 lb/cu ft). Bulk density typically runs to 833 kilograms per cubic metre (52.0 lb/cu ft). The heat content of bituminous coal ranges from 24 to 35 megajoules per kilogram (21 to 30 million British thermal units per short ton) on a moist, mineral-matter-free basis.
Within the coal mining industry, this type of coal is known for releasing the largest amounts of firedamp, a dangerous mixture of gases that can cause underground explosions. Extraction of bituminous coal demands the highest safety procedures involving attentive gas monitoring, good ventilation and vigilant site management.
