NVA (ASX) Ann: Mineral Resource Estimate for US listing

Originally posted by danbradster: ↑

US resource is for in-pit only.

AU global JORC is for in-pit, and everything else too.

SS2 cut the JORC down to 'in-pit JORC'.

princey37: the big change was the inclusion of Cathedral to in-pit, maybe from gold price and pit slope changes (making the mountain, and the low grade less of an issue). I can't tell if heap leach was a new factor boosting the resource estimate, or if the US resource has a different estimation method (eg. a different estimation company, and different assumptions).

Heap leach may be very applicable to Cathedral ore (if heap leach is cheaper than sorting). From memory for Korbel lately: sort out the highest grade, heap leach the rest (Cathedral may be put in with 'the rest'). Vs in SS2: sort out the medium grade, dump the rest to waste (no place for Cathedral in this scenario, unless you sort it).

"extend the life of mine"
Maybe. It depends on the balance - whether it costs much more to expand mining and heap leach for Cathedral (invest in extra trucks/staff/leach pile size), but don't really have to invest in additional sorters or plant size.

Scenario 1: early years remain unchanged (RPM focus), but the mid-years get accelerated with a larger heap leach and additional trucks to mine Cathedral faster (assumption: they don't want to spend money on more sorters, but want to enlarge the heap leach with Cathedral's bulk ore). (Lower discount from discount rate, due to it being mid-years, not late-years).

Scenario 2: they need to sort Cathedral, but don't want to invest in more sorters, so it just extends the mine life. (Higher discount from discount rate, because it's late-years).

If they can boost mid-years production with low incremental CAPEX, then it should boost NPV more than extending the mine life to >20 years (they may find ore superior to Cathedral by then anyway, then have little need for it in late years).

If agglomeration heap leach comes through, then that should help Cathedral's economics more (a margin of safety). (Assuming this resource is using the old heap leach assumptions, not some generous assumptions about recoveries).

Expand

Cathedral is still inferred and under-drilled, so I don't know how that would work for PFS (if inferred is not allowed, but the US resource assumed Cathedral has now become economic and jumped to in-pit).

If heap leach looks positive, then Cathedral would likely need more drilling. But just how much would it boost PFS NPV, so would it cause any delay while upgrading it to M&I (if little boost to NPV, then ignore it in PFS?).

Cathedral: global MRE is 0.26gt. In-pit is 0.28g/t. Korbel in-pit is 0.3g/t. Not bad grade relative to Korbel (pit slopes may have helped) - but it's very much inferred. And Cathedral's in-pit ounces actually shows quite high compared to Korbel (global MRE, Korbel is 3.3x Cathedral. In-pit, Korbel is just 2x Cathedral). So Cathedral could boost production a fair bit?

At a guess, Korbel has a lot of deep or low grade resources below the pit. So in-pit is just 2.7/6.64Moz (41%). But Cathedral shows 1.35/2.01Moz in-pit (67%). I'm not sure why Cathedral appears better. There is no Vrify pit shell to check against.

It looks to assume the mountain is all ore. So little stripping needed, just mine it all. (Needs to be proven with drilling though).

Korbel * Cathedral

It looks like RPM North and South get a combined pit, which may help the economics. This could improve more when North Uphill results get included.

Pit slope changes should help these vertical ore bodies.

There's quite a lot of new details in there, almost like a SS3 (I didn't see a new NPV, but new pit outlines etc).