Dabbler The 45Mt tonnage assumed for the high grade zone is...

Dabbler
The 45Mt tonnage assumed for the high grade zone is based on my own independent estimates (as is the 2.5% Nb2O5 grade). However tonnage is not of prime importance here - the critical variable that determines operating performance and subsequent valuation is mill throughput. It must be estimated, not calculated.
I prioritised a “long” mine life and so started with 1.50 Mtpa to give a 30 year life. I then increased it out to 2.25 Mtpa for a 20 year life and left it at that. (This throughput range is significantly less than industry rules of thumb indicate for a 45 Mt resource (e.g. Taylors Rule and Long et al later revisions specifically for open pit).
With that mill throughput range, together with assumed grade and recovery, I then calculated FeNb production. I am in the camp that recognises that the unique nature of the niobium market limits what WA1 can successfully bring to market. The calculated FeNb production range of 22 to 33 ktpa represents about 18 to 27% of current FeNb worldwide production, a big chunk. I noted that Argonaut had modelled about 30 ktpa and left it there.
I do not think that REE recoveries are relevant. I selected 55% overall recovery as the midpoint of the 50 to 60% range my research indicates as applicable to CMOC, CBMM and Magris and which I was pleased/relieved to hear supported on a Money… Mine episode.
I have run the 60% recovery case as requested: