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
History of the iron and steel industry in the United States when coke from coal started replacing charcoal as the fuel and reducing agent. Coke has a higher crushing strength than charcoal, allowing larger smelting furnaces. Because iron and steel-making at the time consumed more coal than iron ore, the steel mills moved closer to the coal mines to minimize transportation costs. A problem of coke was that it carried impurities such as sulfur, which degraded the quality of the steel. Although coke quickly became the dominant fuel for iron-smelting, in 1884 charcoal was still used to make ten percent of iron and steel in the US. The use of charcoal