The significant coal seams have been found in the rocks of the Damuda Group of Lower Gondwana age. Coal seams are found within the rocks of two formations, viz. the Lower or Barakar Coal Measures and the Upper or Raniganj Coal Measures. Geographically the rocks of the Barakar Formation are more extensive and the coal is superior in quality and more in quantity than the coals of the Raniganj Formation.
The Lower Gondwana coalfields are scattered in the provinces of Andhra Pradesh, Assam, Orissa, West Bengal, Bihar Madhya Pradesh, Uttar Pradesh, Maharashtra and Sikkim.
Although Upper Gondwana coals have been found in Gujarat (Ghuneru coalfield of Kachchh), Madhya Pradesh (Hiran river valley coalfield of Jabalpur district) and Maharashtra (Kota and Chikiala coalfields), but in the field of production, the Lower Gondwana coalfields are the most important. About 98 per cent of India’s total coal production comes from the Lower Gondwana coalfields. Of these coalfields, the Jharia and Raniganj coalfields are the most important, as far as the production is concerned.