Handbook of strata-bound and strataiform ore deposits. Part 4. Regional studies ans specific deposits / Практическое руководство по стратиформным месторождениям твердых полезных ископаемых. Часть 4. Региональные исследования и специфичные месторождения

Coal is one of the relatively uncommon sedimentary rocks, but it is not rare because its estimated tonnage in the crust (of the order of 1013 tonnes; Fettweis, 1979) compares favourably with such rocks as carbonatites, nepheline syenites, phosphatic rocks or even chalk.

As an economic mineral commodity, coal lithosomes are perfectly and unequivocally stratiform and in the broad context consistent and genetically uniform, being always an organic sediment. In detail there are, of course, genetic variations, such as among the autochthonous and allochthonous coals, and among the coals of coalified plant (humites, humilitйs); microorganism and bituminous plant components (sapropelites); and pollen, resin, etc. (e.g. liptobiolites, resinites), derivations. The latter two derivations, however, are rare (Murchison and Westall, 1968). <...>