The concept of "purest" coal typically refers to premium grades of anthracite or low-ash, low-sulfur metallurgical coking coal possessing high carbon content and maximum energy density. Regions renowned for producing some of the highest-quality, cleanest-burning bituminous and anthracite coals include the Appalachian basin in the eastern United States, specific high-grade fields in New South Wales and Queensland in Australia, and the Kuznetsk Basin in Russia. These premium deposits are highly sought after globally for specialized industrial applications and steel manufacturing.