Efficiency enhancement projects at the Tongon gold mine have boosted its performance significantly, and the planned expansion of the flotation process should lift the recovery rate to its feasibility study level.

Randgold Resources chief executive Mark Bristow said while Tongon had increased production, its recovery rate, while slowly improving, was still struggling to break 80% for the year. An additional 2% was achievable by optimising the existing recovery circuit, but raising the recovery rate to the targeted upper 80s will require an expansion of the flotation process to capture most of the sulphide in the ore. Initial estimates of the cost to expand the float circuit amount to US$12 million. It is targeted for completion by the end of 2014 with a forecast payback period of eight to ten months.

“The standard CIL circuit is not recovering that portion of the gold associated with arsenopyrite which is bypassing the existing flash flotation cells. The original metallurgical testwork indicated that the bulk of the Tongon ore was amenable to cyanidation, with flash flotation in the mill circuit recovering the gold associated with the sulphides. In practice, however, we’ve seen that this process is not recovering enough of the fine gold associated with arsenopyrite. The expansion of the flotation circuit will address this issue by capturing the full spectrum of sulphides,” he said.