Influence of mineralogy of low grade refractory Au ore on processing and blending strategy

Gold recoveries can be low when refractory gold-bearing ores are subjected to direct cyanide leaching, so pre-treatment processes may be required prior to leaching. In this study, drill core samples from a refractory gold ore deposit were mineralogically characterized and three main zones were defined as sulfide, transition, and oxide. Native gold occurs in association with pyrite in the sulfide and transition zones, while in the oxide zone it has been found to be sub-microscopic size and associated with FeOx minerals. The Au contents were determined as 1.13 ppm, 0.71 ppm and 0.76 ppm in sulfide, transition, and oxide zones, respectively. Bottle-roll tests indicated that the ore deposit can be classified as refractory with average Au recoveries for the sulfide, transition, and oxide zones of 33.1%, 40.48% and 59.5%, respectively. The flotation method was applied under different conditions for all zones and the results were evaluated in terms of gold recovery and grade. The highest gold recoveries in the sulfide and transition zones have been achieved using Aero 8045 and PAX collectors, however the synergetic effect of the collectors (PAX-strong and Aero 407-selective) has been found to be useful. The flotation concentrate was also roasted and leached, but the Au recoveries achieved were not as high as those achieved by flotation. The blending potential of the zones was evaluated, and it was concluded that sulfide and transition zones could be processed together by flotation.