Could you give me some more information about lignite and bitiminous?
Coal is generally ranked by its degree of coalification (increase in organic carbon content) attained by a given coal owing to burial and metamorphism.
Rank Fixed Carbon limits (wt. % dry and mineral and matter free basis)
Two less common grades are...
cannel coal and boghead coal
Dr Craig R. Glenn, Assistant Professor
Hawaii Institute of Geophysics and Planetology
University of Hawaii, Honolulu HI 96822