New metallurgical testwork at the Youanmi Deeps gold resource within the OYG joint venture in Western Australia has achieved a 96% recovery for partners Venus Metals Corporation (ASX: VMC) and Rox Resources (ASX: RXL).
The work is believed to have improved on the deposit’s historical performance which averaged an 86.8% gold recovery and was limited by older gold extraction technology.
Advances in the past 30 years since previous owner Gold Mines of Australia built the Youanmi carbon-in-leach processing plant have made a significant difference to achievable recoveries.
The testwork forms part of development studies currently underway into potential future production at the Youanmi project.
It studies aim to establish processing pathways to optimise gold recovery prior to moving on to more extensive and detailed “feasibility study level” metallurgical testwork.
Testing included two composite samples taken from 30 individual diamond drill core intervals from historic drilling, including 14 sections from the upper part of the Hangingwall Lode domain and 16 sections from the upper part of the Main Lode domain.
The combined lodes represent over 30% of the entire Deeps mineral resource.
The tests were overseen by Orway Mineral Consultants and drew on methodologies not previously utilised in metallurgical work on the Youanmi resource.
These include a new-age pressure oxidation leach (POX) process which has indicated the possibility of boosting historical recovery figures by at least 10%.
“The tests have demonstrated a well-understood pathway to very high gold recoveries – something which was not achievable in the 1990s,” Rox said.
“Further testwork in combination with costing studies will determine the optimal and most economical feasible processing solution [and will explore] various other suitable processes.”
Perth-based Como Engineers has been engaged to conduct scoping level design and costing for the Youanmi project including capital and operating cost estimates for a processing plant solution which integrates parts of the existing 1990s circuit into a new build.
The flowsheet design is based on utilising a standard crushing and grinding circuit to 75 microns before performing conventional flotation to extract high-grade gold sulphides.
After this, float concentrates will be re-ground to 15 microns before undergoing a pressure oxidation leach process to liberate the gold at maximum recovery rates.
Float tails will also be leached to ensure highest possible overall gold recoveries.
Small processing plant
Como’s scoping work features a small processing plant with a 300,000t per annum capacity incorporating a relatively-small POX circuit as the base case option.
The size of the circuit is expected complement the low tonnage nature of a plant required to treat very high head grade material from the Deeps resource.
Other oxidation process technologies are under consideration to establish the most economically feasible solution going forward.