Anthracite latter in two or three sizes, all three being above in (38 mm) size on round-hole screens. High grade (HG) and ultra high grade (UHG) anthracite are the highest grades of anthracite coal. They are the purest forms of coal, having the highest degree of coalification, the highest carbon count and energy content and the fewest impurities (moisture, ash and volatiles). High grade and ultra high grade anthracite are harder than standard grade anthracite, and have a higher relative density. An example of a chemical formula for high-grade anthracite would be CHONS, representing 94% carbon. UHG anthracite typically has a
Coal breaker floor and slid down a gently inclined "picker table" where breaker boys removed obvious impurities such as rocks and large pieces of slate and threw them down chutes to the culm pile. The breakers also removed obviously clean lumps of coal and sent them down a separate "clean coal" chute for crushing. Lumps intermixed with impurities would go down a third chute for crushing and further cleaning. On the second level of a typical breaker, coal would be roughly sorted. The fuel would move over sorting bars, with the various sizes of coal going down different chutes. Each type of