Distribution of pyrite in coal and its relation to drainage quality, Chirimiri coalfield, Chattisgarh

Abstract

The increasing environmental awareness and huge demand of coal compel us to recognize the importance of impurities and their occurrences in coal. Among various impurities, the content of pyrite in coal is a major concern, both from the environmental and economical points of view. In this paper, the mode of occurrence of pyrite in coal, its distribution and content in the three workable coal seams of Chirimiri coalfield, are studied and weathering experiment has been carried out on the physical model to establish a relation between the pyrite content and the mine drainage quality. Petrographical investigation of coal samples confirmed the occurrence of both syngenetic and epigenetic forms of pyrite. The pyrite in coal in the study area has been found to occur in different forms and morphologies. The distribution of pyrite showed both vertical and lateral variations within the seams. The vertical distribution is such that the pyrite contents are lower in the middle section and increase near the top and bottom sections of each coal seam. The simulated weathering experiment was performed in the laboratory to establish a relation between the pyrite content in coal and mine water quality. On the basis of laboratory weathering experiments, it was inferred that in the study area, pH of mine water is mainly governed by the pyrite content, geochemical character and mineralogical composition of the coal-associated rocks. © Geol. Soc. India.