When the same tests were carried out on the non- conductor (zircon) we found that sonicating with water increased the resistivity and the hydrophobicity, as expected. However, when we sonicated with sodium carbonate, both these properties decreased to about the same level as before sonicating with water. It should be noted that sonicating with sodium carbonate was always followed by thorough washing and a 5 s insonation with distilled water, in order to ensure that no sodium carbonate remained on the surface due to insu cient washing. Examples of changes in resistivity r for di erent treatments of products from a West Australian operation are shown in Table 2. Sonication with sodium carbonate lowers slightly the resistivity of the zircon as compared with sonicating in water. However, its e ect on enhancing the properties of the conductors is an order of magnitude greater and should more than make up for the slight decrease in zircon resistivity.