Geodex Minerals Ltd. has received initial results for the second stage metallurgical program on the tungsten-molybdenum Sisson Brook deposit in New Brunswick, Canada. This commercial scale testing confirms previous bench scale work indicating that a crushing and pre-concentrate sorting circuit ahead of the mill processing can significantly concentrate tungsten and molybdenum. This allows considerable operating cost savings as up to half the mined rock volume that is ore sorted can go directly to the waste dumps.
These results confirm the earlier bench scale results in 2009 that the Sisson Brook deposit is well suited to sorting the mineralized rock to achieve pre-concentration. The current tests used batches taken from a 400kg representative sample from drill core and were put through continuous run, commercial scale sorting equipment. Two crushed sizes were tested using different sorter settings designed to have varying quantities of the mined rock rejected. Metal recoveries ranged from 87.4% to 94.7% of the tungsten and 76.1% to 91.7% of the molybdenum for pre-concentrate product “mass pulls” (the amount of rock retained after the sorting and containing the recovered tungsten and molybdenum) that ranged from 40.8% to 69.5% of the ore sorter feed. The higher recoveries were associated with the higher percentage of mass pulls, as expected. The other critical measure is the upgrading ratio, which is the increase in grades of the pre-concentrate product over the initial feed achieved through the sorting process. The upgrading ratios resulting from these tests ranged from 1.4 to 2.4 times for the tungsten and 1.3 to 1.9 times for the molybdenum. Based on these results, it is expected that Sisson Brook may be well suited to a sorting process that has a mass pull of approximately 50%, that is about half of the material feeding the sorting process from the mine would be sorted as a first processing step, and a large percentage of the tungsten and molybdenum would be retained in this pre-concentrate product. This upgraded rock would then be processed through the mill using conventional recovery methods. The key benefit of this is that the mine would be able to significantly improve the grade of the material processed, thus improving the cost and processing efficiencies.
The main objective of the current metallurgical test program is to develop pre-concentration techniques to further improve the grades in the mill ahead of cost intensive processing steps such as grinding and flotation. Two separate testing processes are being used in the current program. The sorting test process described above and for which the initial results have now been received uses ore sorting equipment which has been increasingly used with good success in various mines. The test work was conducted by Terra Vision-Ore Sorting Solutions in Quebec and CommodasUltrasort in Germany. The second testing process, currently underway, is using well established gravity separation procedures and equipment including centrifugal gravity concentration, heavy media and spirals.
Mark Fields, President and CEO, said “Geodex is further encouraged by these sorting results. These are initial results for a commercial size unit and it is expected that further improvements in the final grades and recoveries would be achieved by using what we have learned in these tests to refine the procedures for a mine operation.”
It is expected that the final results of the full metallurgical program will be available in September.
Geodex has contracted with Bolu Consulting Engineering (“Bolu”) to oversee this metallurgical work. Bolu is a well respected firm with extensive experience working on tungsten projects around the world and directed the previous successful metallurgical work on Sisson Brook conducted in 2008 and 2009.
David Martin, B.Sc., P.Geo., CGA, Geodex’s Vice President, New Brunswick, is a qualified person under NI 43-101 and is responsible for the design and conduct of the programs carried out by the Company on the Sisson Brook project.