The Conditions of Peat Formation

Coal is an organic sediment which consists of coalifield vegetal matter. A broad distinction is made between humic and sapropelic coals of which the first type is far more frequent than the second type, which has been formed by subaquatic sedimentation of floating vegetation (algae) and allochthonous (= redeposited material, not formed in situ) organic matter. The phytogenic precursors of humic coals derived mainly from rooted autochthonous (= formed in situ) vegetation which grew in mires where they accumulated as peat. The latter is the first step in the coalification process by which the biomass is transformed into successive coal ranks which are expressed by such terms as (in order of increasing rank), brown coal, subbituminous, high, medium and low volatile bituminous coal, metabituminous coal, semi-anthracite and anthracite.