Effects of natural weathering on intrinsic properties of coal and coke quality Deepak Kumar, H.P. Tiwari, Vinod K. Saxena, Binod K. Khullar, Ranjan K. Singh and Sandip K. Bhattachryaa Metall. Res. Technol., 116 1 (2019) 111 Published online: 18 December 2018 DOI: 10.1051/metal/2018048