"As far as recoveries go, did you hear Bruce's answer to the...

"As far as recoveries go, did you hear Bruce's answer to the question about oversize where he specifically stated that to date observations have been that they are not losing HM to oversize (33min in presentation)?"... no, he said the HM that was being lost to induration (oversize) was poor quality and not valuable HM (VHM). He said they would need to be careful about not losing too much VHM in undersize with the rejected oversize at the DMU stage.

The TB MRE has 14% oversize, reflecting the indurated sand >2mm size that got broken up but not smaller than 2mm by the drill rig. In that respect, the DFS was expecting 14% of 'poor quality' HM in indurated sand to be rejected and not recovered to the HM or final product. The 62% of product recovered from the Ore Reserve of 14.5% THM in the first few years thus takes into account HM losses to induration, HM losses to the WCP, losses to the CUP, losses to the CUP Finisher as per below diagram. The HM can only go to HM losses or product over the process... it obviously can't just disappear (accepting that HMC and final products are not 100% HM).


Sometimes it's the high-grade HM layers (black) that are more indurated than the silca layers (light) due to chemical reactions in the water table with the iron rich HM. Sometimes it's purely water table level related. Sometimes the drill bit breaks up the induration and under-reports the induration and oversize when mining because a dozer liberates less indurated sand grains than a small grinding drill bit.

We know there is a lot of indurated sand in the upper orebody, which is part of the reason why they did two test pits and trialled different mining methods besides dozer push. It's a known risk and quality issue, and they have made efforts to be ontop of it. Still, proof is in the pudding and only mining with the actual real DMU at scale will tell exactly how the oversize behaves and what HM goes to the WCP and what goes out in OS rejects. STA had lots of met work saying Coburn would be sweet but industrial scale reality didn;t deliver expected results...

Not saying SFX are doing a STA, just that I'm suspicious when certain results that are usually provided like recoveries to the WCP and tonnes of HMC produced are omitted. It's simple data the mine geo and plant mets will be monitoring, though it's always difficult to measure HM lost to OS. The most accurate measured data is HM in MRE model, HM in HMC and tails from WCP, HM in product and the rest has been lost to rejects/tails. If there is less HM in HMC and product than the model and DFS recoveries predicted, then either the MRE HM model over-called the HM grade, or losses are higher along the way to product (ie recoveries are lower).