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MINERAL PROCESSING: Simpler flowsheet increases economics for NICO plant

NORTHWEST TERRITORIES - Fortune Minerals of London, ON, says the results of a mini-pilot plant test conducted on ore from its NICO gold-cobalt-bismuth-copper project near Mazenod Lake, NT, point toward a simplified flowsheet and improved...



NORTHWEST TERRITORIES – Fortune Minerals of London, ON, says the results of a mini-pilot plant test conducted on ore from its NICO gold-cobalt-bismuth-copper project near Mazenod Lake, NT, point toward a simplified flowsheet and improved economics. The tests were conducted by SGS Lakefield.

The tests resulted in the following:

*          A simplified flowsheet with only one cyanide circuit to recover gold.

*          A corresponding decrease in capital and operating costs.

*          Average gold recovery will increase to 76% from 73%.

*          Cobalt recovery will go up to 84% from 83%.

*          The use of pressure acid leaching prior to gold recovery minimizes the affect of refractory material in the ore.

Approximately 6 tonnes of ore collected from the underground test mining program at NICO in 2006 and 2007 was tested. This test simulated most of the NICO process flowsheet, except that after recovery of bismuth from the bismuth concentrate by oxidative hydrochloric acid leach, the bismuth leach residue was blended with the cobalt concentrate for processing in the autoclave by pressure acid leach. The combined feed to the autoclave recovers cobalt and copper from the cobalt concentrate, and also recovers the minor amounts of cobalt and copper contained in the bismuth leach residue. The combined leach residue from the autoclave is then leached with cyanide to recover gold from both the cobalt and bismuth process streams instead of using duplicate cyanide circuits. Autoclave processing results in higher gold recoveries and has the added benefit of mitigating potential gold losses from gold-bismuth-tellurium alloys that can be refractory. 

The NICO mine will have an 18-year life with ore milled on site at a rate of 4,650 t/d. The mill will produce 180 t/d of a bulk concentrate that will be shipped south to a proposed metals processing plant near Saskatoon, SK.

The company’s January 2012 investor presentation is available at FortuneMinerals.com.