Mutual coagulation tests were conducted between hexadecane droplets (with and without doping with 0.001 mol/L sodium oleate) and micrometer-sized quartz, kaolinite, and illite particles in the presence and absence of multivalent hydrolyzable metal cations. It was observed that while hexadecane did not coagulate with quartz particles in the entire pH range tested (from 3 to 11), the presence of multivalent metal ions significantly increased the mutual coagulation between the hexadecane and quartz. And this only happened when the pH was raised to the level where first-order metal hydroxyl species and/or metal hydroxides were formed. The implications of this mutual coagulation for bitumen liberation from Alberta oil sands are discussed. (C) 2007 Elsevier Inc. All rights reserved.