ABSTRACT
Coal is the general descriptive term applied to a group of solid fossil fuels, black or brown in color, that consist predominantly of altered plant material and usually occur as seams within other consolidated strata (Osborne, 1988). From a geological point of view, coal is simply a sedimentary rock (it is not a mineral) consisting mainly of various organic components and with a smaller proportion of inorganic mineral constituents. The term ‘‘coal’’, therefore, does not reflect the highly heterogeneous nature of the rock. In coal processing practice, it is known that coal samples even from the same mine and the same seam are not identical in terms of their composition and properties (bulk and surface).
