Northern Freegold Resources Ltd. (NFR: TSX-V) announce preliminary results from ongoing metallurgical studies at the Revenue Cu-Au-Mo zone of the Freegold Mountain project, Yukon. The Revenue zone forms a significant part of the large, 100% owned, Freegold Mountain project. The property is accessible by a government maintained road and is located approximately 70 kilometres from the Klondike Highway which runs between Whitehorse and Dawson.
Weighted average recoveries based upon the Revenue deposit resource model as it is currently understood are as follows:
John Burges, President and CEO of Northern Freegold stated, “We are very pleased with the excellent overall recoveries of copper, gold, molybdenum and silver through the production of copper and moly concentrates and with additional gravity recovery of gold and silver. This is an important milestone for the Revenue Cu-Au-Mo deposit. These results compare favourably with many more developed copper-gold porphyry deposits in North America. Further grade and recovery optimizations are planned for the future phases of metallurgical test work. Results of similar metallurgical test work from the large adjacent Nucleus deposit where gold is the primary resource are being finalized and will be out shortly.”
Metallurgical Test Work
Metallurgical test work was completed at SGS Laboratories under the supervision of Jalal Tajadod, PhD, PEng. Sample composites of material thought to be representative of the mineralized zones were prepared from drill sample rejects from the 2011 drill program. From these, SGS prepared six variability samples. Each variability sample was blended, crushed, split and combined into three sub-composites.
The metallurgical test work was done on the assumption that metals will be recovered from a recovery process consisting of grinding, gravity separation for Au and Ag, flotation to produce a Cu concentrate and a Mo concentrate followed by cyanidation of the cleaner scavenger tails for final Au and Ag recovery. Two locked cycle gravity/flotation tests (LCT -1 & LCT-2) were undertaken, using typical and simple reagents, with material derived from granodiorite (LCT-1) and from breccia-sulphide (LCT-2) to best simulate the assumed recovery process. This was followed by cyanide leaching of the cleaner scavenger tails (CN-7 & CN-8). It is assumed that the oxide material, which only accounts for 4% of the deposit tonnage, will be stockpiled and leached. Three whole ore cyanide leach tests on the oxide samples resulted in 95.4% to 96.9% of the Au and 72.4% to 81.9% of the Ag being recovered. The remaining 96% of the deposit had recoveries as tabulated below.
The above results are based on preliminary test work and have not been optimized for recovery or concentrate grade. Locked cycle tests to produce metallurgical projections were done at a primary grind size of 120 microns. A flow sheet representing the locked cycle tests will be posted on the Company’s website shortly.
A breakdown of Au and Ag recoveries by process follows:
In order to determine whether a separate Cu and Mo concentrate could be produced, a Cu/Mo separation was completed on one sub composite of granodiorite sulphide (Cu/Mo Sep-F1). This test produced a Cu concentrate grading 20% Cu with 83% recovery and a Mo concentrate grading 47% Mo with 85% recovery. This Cu/Mo separation is the result of only one test and has not been optimized for recovery or concentrate grade. Further optimization test work could show additional improvement from the encouraging initial results.
These results conclude the first phase of the Revenue deposit metallurgical test work commenced in early 2012 and show that good recoveries of Cu, Au, Mo and Ag can be achieved in concentrates. Future metallurgical work will look at further optimizing the recoveries and concentrate grades. Importantly, notable areas of enriched tungsten have been discovered in the Revenue zone which is not included in the resource calculation. Further metallurgical review is planned to be undertaken to determine whether this too can be recovered in commercial concentrate grades.
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We acknowledge the [financial] support of the Government of Canada.