MINERAL MATTER IN THE RAJMAHAL COALS - STUDY THROUGH INCIDENT LIGHT-MICROSCOPY AND SCANNING ELECTRON MICROGRAPHY

The Lower Gondwana coals of the Rajmahal group of coalfields have been studied, in detail, under the Petrological and the Scanning Electron Microscopes to elucidate the mode of occurrence of mineral matter and their microstructural relations with organic constituents. Observations of both the methods reveal the occurrence of mineral matter as massive impregnation, intimate intergrowth, superficial mounting, superficial blanketting, pore filling and solution cavity filling. The absence of microstructures, when observed via incident light microscopy, such as superficial blanketting and superficial mounting in the macerals and microlithotypes, in general, suggests their elimination during the course of grinding and polishing of the coal pellets: This suggests skewing of the mineral matter assessment through microscopic examination. The quantitative distribution of mineral matter in the coal lithotypes as observed in SEM is Durain > Clarain > Vitrain > Fusain while the ash analysis of different lithotypes shows the order of dominance of ash (equivalent to mineral matter) as Durain > Fusain > Vitrain > Clarain.