ABSTRACT
Coal is a sedimentary rock formed by the accumulation and decay of organic substances, derived from
plant tissues and exudates, which have been buried over periods of geological time, along with various
mineral inclusions. Coal is classified by type and rank. Coal type classifies coal by the plant sources from
which it was derived. Coal rank classifies coal by its degree of metamorphosis from the original plant
sources and is therefore a measure of the age of the coal. The process of metamorphosis or aging is
termed coalification.
