The Harmony Au deposit was completely covered by a blanket of soil and colluvium. Drilling beneath this revealed a complex regolith of weathered and partly lateritised Proterozoic basement, clay-rich valley fill sediments and colluvium. Logging the main regolith units produced a 3D regolith model which provided a valuable guide to sampling and later interpretation. The basement has been eroded and weathered and consists of mafic and ultramafic metavolcanics and fine-grained metasediments. The higher parts of this basement are of ferruginous saprolite, the axes of the palaeovalleys are largely of saprolite and mottled zone and are deeply weathered.
Lateritic residuum occupies the flanks of the palaeo-relief.
The colluvium varies from 0.5 m over parts of Harmony deposit to 20 m over the palaeovalleys and probably contained some alluvium where the cover was at its deepest. It presents a significant hindrance to exploration. The base of the colluvium is complex in places, being a mixture of saprolite blocks included in what appears to have been a palaeosol. The palaeovalleys have been infilled with smectite-kaolinite sediments, probably derived from the surrounding saprolites. All this indicates intense post-depositional weathering both at the surface and at oxidation fronts within the sedimentary pile.