Microcrystalline inclusions of pyrite as a petrographic index of types of Donetsk coals according to their degree of reduction

The results of a micropetrographic analysis and a determination of the properties of Donetsk coals confirmed the results of previous investigations on finely dispersed pyrite as an index of the reduced type of coals. Coals of the weakly reduced type contain no fine pyrite. From the indices of their properties it is possible to subdivide the Donetsk (humic) coals into only two types: weakly reduced and reduced (including transitional froms). The quantitative characteristics of the boundary between them with respect to the reflectance and the anisotropy of the reflectance of the vitrinite have been determined. It is proposed to determine the type of bed-average samples from their content of finelypyritized coal estimated from polished briquettes.