Anthracite
Orem, Finkelman, in Treatise on Geochemistry, 2003 Coalifiion, Late Stage (Subbituminous, Bituminous, Anthracite). Later stage coalifiion (formation of subbituminous coal, bituminous coal, and anthracite) results from deeper burial and exposure of organic matter to more extreme temperatures and pressures compared to those experienced by brown coals and lignite.