Gold Terra (TSXV: YGT; OTC: YGTFF) is enjoying “excellent” gold recovery from its first metallurgical tests on material from the Yellorex gold zone in the Campbell shear. The zone is part of the company’s 100%-owned Yellowknife City gold project, about 2.0 km south of the former Con gold mine in Yellowknife, N.W.T.
Total gold recovery of 92.1% was achieved in the first tests when high-grade composite samples were treated with flotation, pressure oxidation (POX), and cyanide leach. Approximately 98% of the gold reported to the flotation concentrate.
The Con mine produced over 6.0 million oz. of gold from 1938 to 2003. Ore from shallower parts of the mine (above 1,000 metres) was likely refractory. Deeper ore was free-milling, and a gravity circuit was added in 1989. At the time it was closed, the processing plant included a gravity circuit, a flotation circuit, and a POX circuit. Throughput at the plant was increased to 1,400 t/d from 800 t/d by a later owner, although recovery dropped to 80% or 90% due to ore blending.
The Yellorex zone has been drilled to 300 metres below surface. Therefore, Gold Terra expects the ore to be refractory.
The company believes it has two options: produce a saleable concentrate or produce gold on site using the POX process. Each has its advantages and disadvantages.
Processing with flotation and selling the concentrate carries a low capital investment compared to the second option. Making a high-grade concentrate for sale carries with it the expectation of lower gold recovery. There is also the potential loss on absorbing custom smelting charges.
Using flotation followed by POX and carbon-in-leach (CIL) is expected to give a higher recovery rate because it allows for higher mass pull in flotation. If a coarser primary grind can be used, there would be savings in grinding costs. A POX-CIL plant would have more flexibility to treat lower grade ore, but the plant would be more complex, thus driving up the capital cost.
Gold Terra has been granted an option to purchase 100% of Miramar Northern Mining, a subsidiary of Newmont, upon meeting certain minimum requirements. Miramar owns the Con mine as well as adjacent areas.
More details about the Yellowknife City gold project is posted on www.GoldTerraCorp.com.