Coal - WikipediaCoal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata .. of volatiles. However, the exact classification varies between countries. According to the German classification, coal is classified as follows:.black coal classification,subbituminous coal | coal classification | BritannicaSep 11, 2009 . Generally dark brown to black coal, intermediate in rank between lignite and bituminous coal according to the coal classification used in the.
black coal classification