Ann: Kathleen Valley - Operations Update and COVID-19 Response, page-126

This is a difficult question to answer because grades improve at depth. Because need less tonnes of ore to produce 1 tonne of 6% grade spodumene down there, the cost difference may not be as severe as one thinks. I would agree if grade was consistent throughout the deposit that with depth that costs increase, but given higher grades down there than the surface, whilst IMO costs will be in excess of US$400 per tonne, such costs become a function of underground mining techniques and higher grades. If the grade was consistent like at surface I would say costs would bewell north of US$450 per tonne down there. But that is a gut feel and the reasoning for that view is contained in these two posts below, so really a question for the DFS as I posted above, but suspect viability here depends on a 5mtpa orefeed operation to derive economies of scale.

As I said in the previous post average opex costs in the open cut section were about US$400 per tonne, meaning lower costs at surface and higher costs the deeper one goes in a open pit section. It is what happens at the switching point and how that impacts costs is the key at the underground section. Time will tell, but to put it bluntly I am a little surprised posters here haven't argued back to you with some facts around resource grade increasing at depth and impact on costs (with my own viewpoints on this question in the two posts below)
Post #: 43429490
Post #: 43351899

On strip ratio it was 7:1 in the open pit section of the mine. In terms of the underground section if the underground section follows the 'seams' could be lower than that (but might not impact overall costs around the transition stage from open cut to underground, albeit with higher grade likely to be stabilised at that point due to higher grade (or might even be slightly lower). Again from - Post #: 43351899:
"How LTR transitions (speed and rate of change hence how they do that in the DFS will be interesting) from the open cut section where the strip ratio is about 7/8:1 (which means high costs and impact on NPV/IRR and note strip ratio is different to waste ratio because waste ratio is when your actually in the pegmatite themselves as against dealing with the overburden which is strip ratio) to the underground sections, i.e. which means costs around the open cut level at that intersection point of transition to underground mining, Post #: 43055062, but IMO so that NPV/IRR is not too much adversely afffected by a reasonable price assumption is the key here in project evaluations."

Getting tired of the war between stocks as well - plenty of room in the market for decent deposits. Having said that, for LTR the main width of the pegamatite in the underground section could be mine IMO. The question is whether some of the tentacles from the underground section will be mined, and that is a question for the DFS. Certainly if the go underground mining there is resource to mine in the main sections of the pegmatite.

Others might like DYOR and thank a non-holder LOL for the response.

All IMO