Anthracite

Anthracite, often referred to as hard coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coal. It contains more fixed carbon – 86% or greater on a dry, ash-free basis than any other form of coal and the least amount of volatile matter. It has calorific values near 35 megajoules per kilogram