Manuka Resources (ASX:MKR) has started production at its Wonawinta Silver Project, one of the largest primary silver mines in Australia and globally.
Highlights:
- Initial processing of 515,000t stockpiles grading 70g/t containing 1.16Moz silver.
- New processing approach expected to significantly enhance profitability of silver production through improved head grade & materially lower tonnage of ore throughput, required to meet silver production targets.
- Wonawinta Silver Project JORC resource currently stands at 50.94moz, excluding the stockpile.
- JORC Reserve expected by mid-2022.
- Processing to continue to end-October 2022.
Following completion of the first phase of gold production from its 100% owned Mt Boppy Gold Project in March 2022, Manuka has now completed all the major capital upgrades, and wet commissioning is underway at its Wonawinta plant on the silver-bearing stockpiles included in its Mineral Resource Estimate (JORC 2012).
This is the result of a combination of extensive metallurgical trials and test-work programs as well as a not insubstantial plant upgrade, specifically to ensure a significant improvement in efficiencies, silver recoveries, and performance through the plant versus historic levels, as well as improvements in plant operational safety specific to silver production.
Metallurgical test work has continued for the past 12 months as the Company strived to develop vastly improved material handling and processing procedures for the silver oxide stockpiles trials at Wonawinta.
The knowledge gained from these trials has guided the company towards what it currently believes are the optimal means of processing the stockpiles (and also becomes highly relevant to the future mining of the oxide resource contained within the Wonawinta resource model).
The metallurgical test-work conducted utilised the internal skills and resources of the Manuka team, as well as specific expertise of AMML (Australian Minmet Metallurgical Laboratories), ALS (Australian Laboratory Services), CSIRO and COMO.
AMML helped to verify earlier findings from test work conducted by COMO and ALS. Together with QEMSCAN data from ALS and spectral core analysis performed by CSIRO based in WA, valuable geometallurgical insights were gained in terms of the silver distribution and leachability. Laboratory findings to date indicated that ultrafine clay particles reduced Ag adsorption onto carbon particles and resulted in suboptimal total recovery of silver.
This occurs as the ultrafine particles tend to clog the internal porous structure of carbon and cap maximum adsorption rates. Further analysis showed that desliming upgrades Ag and enhances dissolution and carbon recovery.
Manuka’s new approach versus that of prior operators is expected to result in an upgrading of feed grades into the plant. The finer silver particles which are not fed into the mill will either be sent to the tails or stored elsewhere for later processing.
Simply put, by screening out the clays, Manuka expects to increase average grade through the plant to >85g/t Ag while reducing ore through the plant by some 30%, which significantly improves profitability and the overall robustness of the project.
