Humic coals are banded coals. They are the most abundant type of coal. The bands of coal that comprise a humic coal are divided into four lithotypes (vitrain, clarain, durain, and fusain, Stopes, 1919) based on their general appearance. A single humic coal bed may contain all four lithotypes.
Humic Coal Lithotypes
Bright, shiny (vitreous), black bands of coal, usually brittle and cut by fissures. Vitrain tends to break into small blocky pieces. It is the shiniest of the four lithotypes.
Semi-bright, black layers composed of very finely interlayered (or inter-banded) vitrain, durian and sometimes fusain. It is brighter than durain, but not as bright as vitrain.
Dull, black to gray layers with a rough texture. Bands are not as bright as clarain or vitrain and have less fissures than vitrain. When broken, durain bands tend to break into irregular lumps, rather than small blocks.
Dull black to gray-black bands with an almost silky lustre. They may have a fine, fibrous appearance. Fusain is soft, and friable, like charcoal. Fusain bands are often responsible for the dirty hands one gets from holding a coal sample.