Prophecy Resource Corp. (TSX VENTURE:PCY)(OTCQX:PRPCF)(FRANKFURT:1P2) has received preliminary results from its ongoing metallurgical study on the amenability of its Lynn Lake resource to the bioleach process.
The bioleach study is being conducted by Mintek in South Africa and overseen by Andy Carter, Manager of Metallurgical Engineering for Wardrop Engineering Inc., a Tetra Tech Company. Key findings of the results to date show that nickel recoveries in excess of 95% can be achieved using only a moderate grind and leach temperature, whereas high copper recoveries generally require finer grinding and higher temperatures.
In July 2010, Prophecy collected 3.7 tonnes of a representative sample of ore from Lynn Lake and shipped it to Mintek in Randburg, South Africa for study. Continuous pilot flotation tests produced a bulk concentrate containing 5.3% nickel and 3.4% copper at 89% recovery for both metals. This concentrate was used as the feed stock for the bioleaching testwork. Laboratory testwork conducted in 2008 by PRA associates showed that a separate nickel concentrate of 9.2%, and a copper concentrate of 7.5% could also be produced.
The nickel in the concentrate occurs as pentlandite and violarite, while the copper is present as chalcopyrite. Bioleach amenability test work was performed in fully-controlled continuously operated multi-stage reactor systems using microbial cultures which have been adapted at Mintek to perform optimally under the required operating conditions. The final metal extractions were calculated based on analysis of samples obtained from each of the reactor stages after achievement of steady state conditions. The process was staged over a cumulative residence time of just 6 days.
A process flowsheet is envisaged that consists of fine concentrate regrinding followed by bioleaching at either 45°C or 70°C. The parameters used for the study to date will guide the optimisation of the processing route for concentrate production and downstream processing to a saleable product.
Mintek's results show a marked improvement in nickel recoveries by as much as 6.5% compared to a previous lab bioleach study by PRA Associates in 2008. While preliminary, the results indicate that the Lynn Lake sulphide ore is highly amenable to the bioleach process. Further process optimisation is currently underway. The nine month long study is expected to be completed by June of this year. Full results will be incorporated in a feasibility study to be commenced later this year.
Lynn Lake and Bioleach Background:
The Lynn Lake mine was operated by Sherritt-Gordon from 1953 to 1976 and ranked as the third largest nickel producer in North America, after only the Sudbury and Thompson mining camps.
Wardrop Engineering Inc., a Tetra Tech company, in a National Instrument 43-101 report dated May 6, 2010, estimated Lynn Lake to contain a Measured and Indicated resource of 22.9 million tons at 0.57% nickel and 0.3% copper, and an Inferred resource of 8.1 million tons at 0.51% nickel and 0.28% copper. (0.4% nickel equivalent cutoff).
The above resource estimate does not include the recent Disco Zone discovery located within 1.5 km of the outlined resource. The Lynn Lake project has immediate access to electrical power and rail transportation and can be operated year-round.
Prophecy Resources is examining the bioleach- SX/EW option in lieu of a direct smelter take-off for its Lynn Lake nickel-copper concentrate. Bioleach SX/EW offers a proven, less expensive and greener alternative to smelting. A bioleach SX/EW process, as part of a fully integrated nickel operation will permit pure nickel to be produced on site without transportation of concentrate and costly smelter penalties. Currently bioleaching is being used with commercial success in Finland (Talvivaara), China (Laizhou) and Chile (Escondida). Owing to the exothermic nature of the reactions, cold weather has a negligible effect on the process as demonstrated at Talvivaara. In contrast to Talvivaara, which is a heap bioleaching process, Prophecy plans utilising a tank based bioleach reactor system.
Mintek is based out of South Africa and has successfully completed bioleach processes at the commercial level. They are industry leaders in the field, with 25 years experience. Commercial level implementation of this process for base-metals include the Mount Lyell copper mine in Tasmania, and a 500kg per day pilot plant at Industrias Peñoles' facility in Monterrey, Mexico, during 2001; the plant has produced more than 40 t of LME A-grade cathode copper from a complex polymetallic, chalcopyritic feed concentrate.
This news release has been reviewed and approved by Danniel Oosterman, PGeo, Prophecy Geologist who is a Qualified Person as defined in NI 43-101. The material in this news release has been reviewed and approved by Andy Carter, a Qualified Person as defined by NI 43-101.
Source: Prophecy Resource Corp.