The four ranks are: Anthracite: The highest rank of coal. ... Bituminous: Bituminous coal is a middle rank coal between subbituminous and anthracite. ... Subbituminous: Subbituminous coal is black in color and dull (not shiny), and has a higher heating value than lignite.
Subbituminous coal, also called black lignite, generally dark brown to black coal, intermediate in rank between lignite and bituminous coal according to the coal classification used in the United States and Canada. In many countries subbituminous coal is considered to be a brown coal.