showed that the heavy minerals which had high resistivi-
ties (non-conductors) were also more hydrophobic, while those with lower resistivities (conductors) were hydro- philic. Furthermore, processes which produced increases in resistivity also produced increases in hydrophobicity and vice versa. Results of our tests were reported in Refs. [4,8]. They showed that for the conductors (ilmen- ite, rutile and leucoxene), sonication in water increased both the conducting and the hydrophilic properties, while sonicating with 0.1sodium carbonate solution increased these properties even more. At first, we thought that this was due to better surface cleaning.