Bituminous coal is a
relatively hard containing
a tar-like substance called . It is of higher quality than but of
poorer quality than . Bituminous coal is an organic sedimentary
rock formed by diagenetic and sub metamorphic compression of bog material.
Bituminous coal has been compressed and heated so that its primary constituents
are the , , etc. The
carbon content of bituminous coal is around 60-80%; the rest is composed of
water, air, hydrogen, and , which have not been driven off from the .Bituminous coal is usually black, sometimes
dark brown, often with well-defined bands of bright and dull material.
Bituminous coal seams are strati graphically identified by the distinctive
sequence of bright and dark bands and are classified accordingly as either
"dull, bright-banded" or "bright, dull-banded" and so on.