Susceptibility to sedimentation of hard or brown coal slurries was tested by (i) optical observation of the interface between water and sediment, (ii) measuring a speed of descent of the std. rod in the suspension or (iii) detg. the ay. speed of grains of slurry. The method (ii) was the best tool for assessing the tested property, because it minimized the possibility of making errors by the operator and facilitated a comparative anal. of this type of measurement performed in various centers. The least precise course of sedimentation of both types of suspensions was detd. by the method (i).