The coal processing methods used at the Zarand coal washery plant are the heavy medium bath,jigs,and flotation.The coal-containing materials that are fed to the plant are acquired from different mines,and they have different washability properties.In this paper,the validity of Mayer curve (M-curve),the conventional method for determining coal washability,was evaluated on blending of raw coals that are fed to the plant.Washability curves were prepared for the hand-blended samples and compared with the washability predicted by the Mayer curves.Different samples from different seams and mines were blended by hand in 50:50 ratios,and sink and float tests were performed;the resulting washability curves were in good agreement with the washability curves predicted using the Mayer method for the same blending ratio.This work resulted in the preparation of the optimum plant feed that can be achieved from the blending of different coal samples to produce the best plant yield at a given ash content. The coal processing methods used at the Zarand coal washery plant are the heavy medium bath, jigs, and flotation. The coal-containing materials that are fed to the plant are acquired from different mines, and they have different washability properties. In this paper, the validity of Mayer curve (M-curve), the conventional method for determining coal washability, was evaluated on blending of raw coals that are fed to the plant. Washability curves were prepared for the hand-blended samples and compared with the washability predicted by the Mayer curves. Different samples from different seams and mines were blended by hand in 50:50 ratios, and sink and float tests were performed; the resulting washability curves were in good agreement with the washability curves predicted using the Mayer method for the same blending ratio.This work resulted in the preparation of the optimum plant feed that can be achieved from the blending of different coal samples to produce the best plant yield at a given ash conte nt.