bituminous coal close to anthracite - Upper Cretaceous Iles Formation near Hamilton, Colorado - hand/display specimen
This bituminous coal is close to anthracite and is fairly dense for bituminous coal. It is highly prized for burning with very little ash. It has the hard shiny surface of anthracite, but not the conchoidal fracture.
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, burns 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.
The Green River coal region's southeast arm reaches into Moffat and Routt Counties in northwest Colorado. This coal comes from the Upper Cretaceous Iles Formation of the Mesaverde Group and is ranked as high-volatile C bituminous coal. The coal beds vary from one to six meters in thickness.
This coal was collected from an exposure on Colorado Highway 13 one mile north of Hamilton, Colorado in Moffat County. Green River coal is low sulfur and is burned in steam-electric generating plants chiefly in Colorado. Generally, the older a coal the higher its rank. Deep burial and a high geothermal gradient, as in the deep basins of northwestern Colorado can significantly increase the rank of a coal. This coal appears close to anthracite.
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