Bioleaching shows promise at O’Brien property

Metallurgical tests on ore from the O’Brien gold mine, a former producer 45 km west of Val d’Or, Que., show that a combination of bioleaching and cyanidation can recover as much as 90% of the gold contained in sulphide concentrates.

Radisson Mining Resources (ME), which received a $10,000 grant from the National Research Council to study the process, is earning a half interest in the property from Breakwater Resources (TSE).

The research is being conducted by the Abitibi-Temiscamingue Mineral Technology Centre and the University of Quebec, Abitibi-Temiscamingue.

Sulphide ores from O’Brien are mainly arsenopyrite and were successfully pre-treated by roasting before cyanidation during the original production period, from 1933 to 1956. Roasting, however, produces air emissions that are no longer environmentally acceptable, and later attempts at extraction by direct cyanidation of the sulphide concentrates reached recovery rates of only around 75%.

Radisson says adding a bioleaching step to the process would cost relatively little, and should ensure recovery of “at least 90%.” The process is described as cost-effective, efficient, safe and environmentally clean.

Initial tests at non-optimum conditions found recovery was 82% on sulphide concentrates that had undergone bioleaching, compared with 47% on untreated concentrates. Further metallurgical tests will be completed by the end of the year, including batch and continuous-process simulations of mill conditions.

Radisson expects the process will increase the exploitable gold resource on the property, which stands at 218,500 oz. Drilling will soon get under way in an attempt to increase resources to a level justifying underground bulk sampling and a feasibility study.