This study aims at investigating the possibility of cleaning of oil shales by gravitational methods. Laboratory scale Dense Medium Separation (DMS) tests were applied on Himmetoglu oil shale from Bolu, Türkiye. DMS tests were conducted at a separation specific gravity range of 1.10 to 1.80 with 0.1 increments on size fractionated oil shale samples of -30+18, -18+10, -10+0.5 and -0.5 mm. Results showed that the extent of ash rejection and improvements in calorific values increased with increasing fineness and the highest cleaning performance was achieved with DMS tests on the -0.5 mm fraction. 1.10 and 1.20 were the most effective separation specific gravities for all size fractions, implying that the organic rich portion in the Himmetoglu oil shale is relatively light. With the -0.5 mm size fraction and at 1.20 separation specific gravity, the ash of Himmetoğlu oil shale could be reduced from 34.76% to 16.65% and calorific value increased from 4312 to 5821 kCal·kg-1. Possible DMS cleaning scenarios on the entire feed at the separation specific gravities of 1.10, 1.20 and 1.30 were also assessed based on DMS results of all size fractions. It was seen that an opportunity exists for application of DMS on oil shale particularly at 1.20 and 1.30 separation specific gravities. However, it was seen that gravitational cleaning of oil shale is more difficult as compared to DMS cleaning of coals and lignites. Sharp separations with high recoveries seems to be unlikely with coarser fractions and sufficient liberation between organic matter and inorganic constituents necessitates comminution down to finer sizes
