Metallurgical Overview – Lawyers Gold-Silver Project
This overview is a summary derived from the Preliminary Economic Assessment (PEA) of September 2022.
The preliminary metallurgical testing for the Lawyers Project, focused on a bulk tonnage open pit mining scenario, commenced in Spring 2020 and concluded in mid-2021. Prior to 2020, there is limited historical information relevant to this type of operating scenario. The testing during 2020/2021 encompassed both flotation and cyanide leaching; The Lawyers material responded well to both processes. Based on the results and economic considerations, the PEA flowsheet design was directed towards whole rock cyanide leaching.
Leaching would be facilitated in aerated tanks after a gravity pre-treatment to remove coarser precious metal particles. The mined rock is categorized as moderately hard to hard. Optimization laboratory testing suggests a feed particle size to the leach at a modest grind, with 80% passing particle size (P80) of 106 µm. The laboratory data indicates a tank leach retention time of 32 hours or less. The pregnant leachate solution (PLS) would undergo washing by counter current decantation (CCD) and then proceed to zinc precipitation to produce Doré on site.
The PEA level testing was conducted on composite samples from Cliff Creek (including Dukes Ridge) and AGB zones. Gold leach dissolution recoveries consistently ranged from 91% to 97% on head grades of 0.46 g/t to 3.04 g/t. Silver recovery, influenced by changes in mineralogy related to electrum particle size and composition, varied more, showing a 50% to 92% leach dissolution recovery on composite samples with a head grade range of 3.8 g/t to 165 g/t. The average precious metal design recovery for the AGB Zone is 92.1% for gold and 60.6% for silver. For the Cliff Creek Zone, the average gold recovery is 92.5%, and for silver, it’s 83.0%.
For a more detailed understanding and additional information, please refer to the Preliminary Economic Assessment – September 2022.