ABSTRACT
Coal is a natural fuel, occurring in layers in the earth’s crust composed mainly of plant material that has suffered partial decay and has been further altered by the agencies of heat and pressure to the varying degrees of completeness. This initial sediment formed by this process is, moist, spongy material, called peat, but this becomes compressed, dried and modified in both texture and composition due to diagenesis associated with burial and tectonic activity. The different kinds of plant material vary in their proportions in different coals, and the decay and subsequent alteration of the material proceeded to different degrees. As a result, coals show great variety in their chemical and physical properties and because of this, in their behaviour in practical use.
