On closer inspection, Dec and Mar Qtr mining has all been from the enlarged starter pit W_E starter pit, not out to the west or up to the north (yet). It looks like the plan is to move north and further away from the upper induration laterite, not eastwards closer to it originally planned. It may relevant for comping the 2019 vs 2022 DFS Year 1-4 grades as reported/deducted, because the current 13.5% THM grades look considerably lower than that forecast in 2019 in the same general area.
Anyway, trying to work out what's really going on so started with a simple table after the style Bridge St.
Multiply ore tonnes mined by Zir grade in ore = tonnes of Zir insitu (max possible)
Multiply contained Zir tonnes by WCP-CUP % Recovery to product = Zir tonnes in product
Divide Zir tonnes in product by % ZrO2 (+0.5% HfO2) in product = Tonnes of Zir-Con Product
To verify I ran the DFS, Year 1-3 figures into the table and cane up with between 1-10% variation in the table (under) compared to released DFS product. Obviously a lot of rounding in the DFS figures, especially over LOM, so I'm happy the table is correct. That said, if LOM average ZrO2 % is used (ie ~39-40%) instead of the 37.5% then the reported production numbers will be even higher than the table. It's possible/probable the DFS production figures used 37% ZrO2 % while describing the LOM average as 38-43% ?
HM grade from DFS years is an estimate but does not impact on the table, whose formulas run off insitu Zir grade
I believe this table helped answer the first niggles I had over Mar Qtr reported production. Mar Qtr produced 28.5% more tonnes of Zir Con Prod (~3,500t) than it should according to DFS assumptions. Dec Qtr produced 32% less tonnes of Zir Con Prod (~3,500t) than it should according to DFS assumptions. Adding the two Qtrs together, zircon-con production is approx what it should be according to DFS assumptions.
The reason imo is because the Dec Qtr reported "production of saleable product" only, meaning there was likely stockpiles of 'off-spec' product from early commissioning not reported. Over Jan when the DMU was down, it's probable any off-spec stocks were re-run through the plant and refined into salebale product. Product tonnes reported in Mar Qtr doesn;t mean it has to come from ore mined in the Mar qtr... ie only ~15,000t of Zir-con was produced from ore mined in the Mar Qtr.
If so, this is good because we know there was OS issues and lower than DFS undersize sand to the WCP per tonnes of ore mined. We also know a large amount of stockpiled ore was placed on the ore seam ahead of the first two Qtr pit mined, so not sure if that helped or hindered?
One question this raises is why Bruce says Mar Qr only produced ~85% of expected Zir product from the volume of ore mined, when at 15,000t it looks like the expected tonnes based on DFS assumptions? It could be that the zircon insitu grade is higher than I assumed in this starter pit and 15kt should be 17.5kt zir con, or that the ZrO2 5 of that 15kt of product is considerably lower than 37.5% (which might also account for lower zir-con price that expected)?
The next step is to see how product tonnes vary with different metrics such as the 75% ore to WCP, higher insitu zir, higher than DFS recoveries etc...
(20min delay)
