Pacminex September 1970 Feasibility study estimated 54.5Mt of...

Pacminex September 1970 Feasibility study estimated 54.5Mt of extractable alumina "and therefore represents the minimum tonnage of ore drilled to date" p42.

BAU don't have exactly the same ground but there is overlap and other ground Pacminex didn't have. This is all pre JORC code of course. PattyP numbers on mineral endowment are ball park and conservative. Which is good.
The other point is if they operate, or sell to a bayer-sinter customer reserves roughly double.
Bx exports at around $80/t and can be higher if you're dipping into spot market.
Darling range is lower grade so maybe you won't get $80/t for DSO, but you can beneficiate. It will be gibbsitic Bx with lower reactive silica - means nice bx, low caustic cost Bx to process. Caustic prices are an issue for the industry.
As the customer using this ore as your primary ore you would want to be sure you have more than 10 years Bx. If you were just going to use it to tweak more our of a boehmite/diasopre fed plant (aka all chinese), then it would be less of an issue. BAU have alot of options as to what they could do with their Bx, but need to firm up just what they actually have.
Tom Albanese, Dick Evans and Alain Belda are all singing from the same song book in terms of forecast demand growth from developing countries. Theres a well worn trend of Al consumption versus GDP/capita. China and India (+others) have lot to catch up. If the forecast demands are realised the world will need ~30 additional 1.5Mtpa alumina production trains installed in 10-15 years. Its mind boggling. Where's that Bx going to come from? BAU could be part of the answer. DSO, beneficiate and ship Bx, or JV with a 3rd party, build a bayer/sinter plant in WA and feed it clean & cheap(ish) gas. Not fussed by the this current near-sighted dip in price.