In Jharia and Raniganj coalfields nearly 3000 million tonnes of coal is baked due to igneous intrusives and underground fires and a part of it is converted into natural coke (Jhama). The heat-affected coals are quite heterogeneous in their physical properties and chemical composition. Due to lack of proper characterization and appropriate technology for mining, this resource was considered colliery waste till recently and has largely remained unutilized
