Oil sands clay tailings settle to a gel-like sludge or slime which is still relatively low in solids content, and the tailings show extremely slow dewatering beyond this point. These characteristics imply a significant degree of structure in the slime. Based on a comparison of some of the rheological and stability characteristics of the material and those of a bentonite gel over a. range of pH, a structure is proposed which depends for its stability on the presence of residual bitumen as well as a clay-bound organic component.