bituminous coal - Bronco Mine, Emery County, Utah - hand specimen
This bituminous coal is the lowest heating grade of bituminous coal. It has a shiny black surface, but not the conchoidal fracture of anthracite. Coal forms from the burial of accumulated plant material, in a series with increasing compaction from peak to lignite to bituminous coal and then anthracite. The first three are considered sedimentary. Anthracite is metamorphic, as it has undergone low-grade metamorphism, burning hotter than other coals and with a clean blue flame.
The name anthracite was derived from the Greek word anthrax, the name given to it by the philosopher Theophrastus, a pupil of Aristotle. Bituminous coal was named under the mistaken impression that it contained bitumen, a group of hydrocarbons including tar and asphalt.
This bituminous coal is from the Bronco Mine, Emery County, Utah, the former Emery Deep Mine. The coal is Upper Cretaceous in age, mined from the Ferron Sandstone member of the Mancos Shale. Its coal rank is high-volatile C bituminous, which means it has the lowest heat value of bituminous coals. This coal is low in sulfur.
This mine is Utah's oldest producing coal mine, with mining beginning in 1881. Formerly owned by Consolidation Coal Company, it was idled in 1990, reopened in 2017 after the mine's purchase by Bronco. The mine currently accesses high quality coal through a mile long tunnel under federal land to leases on state and private land.
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