Fusain

fusain, macroscopically distinguishable component, or lithotype, of coal that is commonly found in silvery-black layers only a few millimetres thick and occasionally in thicker lenses. It is extremely soft and crumbles readily into a fine, sootlike powder. Fusain is composed mainly of fusinite (carbonized woody plant tissue) and semifusinite from the maceral (q.v.) inertinite (high carbon, highly reflective) group. It closely resembles charcoal in terms of both chemical and physical properties and is believed to have been formed in peat deposits swept by forest fires or by some bacterial action that generated intense heat. Compare clarain; durain; vitrain.