Kutcho Project Life of Mine Copper Recovery to 96%, Silver to 83% and Gold to 70%
VANCOUVER - Kutcho Copper Corp. reported the results of additional metallurgical testing on its 100% owned Kutcho Project in British Columbia, Canada. These latest results came from a program focused on optimizing performance from the Main Lens composite and have shown improved copper and silver recoveries versus the 2017 Prefeasibility Study. In addition, the Company has conducted leach tests on the tailings, which has shown the potential to significantly increase copper, silver and gold recovery from both the Esso and Main Lenses. Completion of this recent test program represents a significant portion of the metallurgical work required to complete the Feasibility Study for the Kutcho Project.
“We are extremely pleased with the metallurgical performance from the Kutcho project and the upside opportunities available from leaching the tailings materials for additional copper and precious metals recovery. We look forward to including these improved results in our upcoming Feasibility Study, where we believe they will have a positive impact on the economics of the Kutcho project.” said Vince Sorace, President & CEO.
The results were produced from a recent Locked Cycle Test completed on Main lens material which is contemplated to be processed at a 50:50 blended ratio with Esso lens material during the mid-years of production at the Kutcho Project. These results, in combination with those provided in the November, 2019 news release, demonstrate the robust nature of the developed Kutcho flowsheet.
The recoveries of copper and silver to the copper concentrate has improved significantly over historic test work. Given that the largest and most important contributor to the Net Smelter Return (NSR) value of Kutcho material is recoverable copper, the Company has focused efforts on maximizing this NSR value. Silver recovery was also significantly improved in this most recent testing. The copper and zinc concentrates produced from both the Main and Esso lenses are of good quality and are below threshold limits for common deleterious elements.
The flowsheet utilized for the Main material bench scale test work is the same simplified flowsheet utilized for the Esso deposit. A single stage of flotation cleaning has been used in the copper circuit and three stages of zinc cleaning were required. The current contemplated process plant design incorporates a primary grind size target of 58 microns K80 followed by sequential Cu-Zn flotation; the rougher concentrates are reground to approximately 17 microns K80 and approximately 20 microns K80 for the copper and zinc respectively. The total mass of material that will be subject to finer grinding is less than 20% of the anticipated mill feed.
Leading up to recent Locked Cycle Tests extensive mineralogical evaluations carried out on drill core composites by QEMSCAN that have been incorporated into block models to fully quantify and characterize the mineralization in terms of mineral abundance, which is important for controlling metallurgical performance. The mineralogical study allowed the Company to accurately define copper deportment and speciation (chalcopyrite and bornite) and pyrite content as well as head grades reflective of the Measured and Indicated resource grade. This gives the Company an added measure of confidence in the metallurgical results and their representation of the Main lens.
Preliminary leach test work of the cleaner tailings streams from both Main and Esso Lens material using cyanide indicates that copper, gold and silver recovery could be significantly increased and is a candidate for sulphidization-acidification-recycling-thickening (SART) treatment.
Flotation of a pyrite concentrate from the combined zinc tailings streams of the Main Lens MC4 composite was reground to approximately 25 microns K80. Cyanide leaching of the Main lens material yielded an additional 8.0% of copper recovery, 32.9% of gold recovery and 20.7% silver recovery. Similar treatment of the zinc tailings streams of the Esso Lens composite yielded an additional 2.7% of copper recovery, 27.6% of gold recovery and 11.2% silver recovery. Combined with the locked cycle test results above on approximate Life of Mine (LOM) blend comprising 75% LOM feed from the Main Lens and 25% LOM feed from the Esso Lens yields 96.4% copper, 82.9% silver and 70.4% gold recovery.
As a result of the high levels of soluble copper in the cleaner tailings streams, cyanide consumptions were very high, but copper was notably extracted to the leach liquor. This extraction result suggests that the leach liquor is a good candidate for the SART process, which can recover copper as a precipitate and regenerate cyanide for recycling.
As a result of producing a pyrite concentrate for leach, the Kutcho project benefits from generating a desulfidized tailing stream, from both Main and Esso lenses, that initial environmental analytical results suggest is potentially non-acid generating (NPAG) as determined by acid base accounting methodologies (ABA). Furthermore, preferential use of the residual pyrite concentrate for paste backfill underground may reduce, or eliminate the volume of potentially acid generating (PAG) tailings for surface storage and management that could yield benefits for the project in terms of minimizing environmental impacts. The full potential of these results will be investigated during the Feasibility Study.