ABSTRACT
Indian Gondwana coals of drift origin, formed some 225 to 275 million years ago, are different in their physico-chemical characteristics from the carboniferous coals of Northern Hemisphere deposited 50-100 million years earlier than Gondwana coals due to environment of deposition and post-depositional features. The original plant material, which were later transformed into coal, were transported by rivers to a distance, carrying along other impurities after which coalification process took place. As a result the coal matter is finely disseminated with mineral matter causing deterioration in its quality during its formation stage itself. Hence these coals become difficult-to-wash. The extraneous ash which gets mixed with coal, mostly during mining can be removed more easily. The inherent ash of Indian coals cannot be taken off easily because it is embedded in the coal matrix and thus results into more near gravity materials.
