Anthracite is the highest grade of coal, known for its high carbon content, low impurities, and high energy density. It is formed under conditions of high temperature and pressure, typically in geologically older formations. Anthracite is an important fuel source and has been extensively mined for its energy-rich properties, particularly in regions with significant industrial history.
Reference: Speight, J. G. (2012). The Chemistry and Technology of Coal. CRC Press.