Ann: Robust Phase 2 Scoping Study for the Estelle Gold Project, page-101

It didn't quite answer the question, whether increasing the M&I resources would allow for the the ore sorters to be scaled up, and set to output a higher grade (as per the sensitivities analysis showing increased grade helps economics, but obviously there would be a higher CAPEX cost to consider on the sorters).


But from their answer, they're saying:
- The number of sorters matches the 6mtpa plant size (but is it also limited by the M&I resources?).
- It's set to a level where the CAPEX would not be too high (increasing ease of funding).
- Dialing up the sorting grade increases the level of waste. (Well known, but might it result in higher NPV, if having sufficient resources to do so?)
- Sorters are modular. (As long as the plant has the floor space, I expect this makes them very flexible. If M&I resources increased later, it might be easy to add more sorters, dial up the grade, have the same volume of output as previously, and not change the 6mtpa mill design at all.)
- They're considering the 'dialing up' in terms of gold price (but didn't mention volume of M&I). (So if gold price fell too low, it might be unprofitable to run the mill with 0.73g/t material. Running the sorters is cheap enough, so dial them up to have a 1g/t mill input grade, just requires some extra mining and wastage of <0.3g/t material, reducing the mine life, but increasing the mill gold output to keep cashflow positive. Compared to a mine without sorters, which might just be stuck with negative cashflow, which is dangerous/potentially dilutive.)


I'm thinking: it's not easy to adjust a constructed 6mtpa mill at a later date, but it's easy to add more sorters. If you add more sorters, then leaving them set to 0.73g/t output would mean too much material for the plant, so you'd adjust their grade up (and output down), to keep the plant throughput steady.

6mtpa seems to match the 3Moz+ of M&I resources that we currently have. So I think 5Moz of M&I (potential scenario) would allow for either: larger mill size, or more sorters and higher grade output (than SS2). Clearly they'd compare the 2 scenarios, to see which is best for NPV, but I wonder if these scenarios sound about right -

-> Increase M&I from 3Moz+ to 5Moz+ (assume same grade).
-> Can then increase plant size from 6mtpa to 8mtpa, with greater NPV.
-> OR Can increase sorters, set them to output higher grade (with higher wastage), while the mill stays at 6mtpa, resulting in higher NPV.