Ann: Greater Duchess Maiden Mineral Resource, page-63

Hey plough -

Valid point on the economics of mining 0.5% Cu, of course in this case that is the minimum - rather than the average - so it could well be that the 0.5% Cu mineralisation is never mined, or that it is only mined when the Cu price makes it economically viable. (thinking the ND halo as an example).

But looking at other local reference points -
Evolution have used a cut-off of 0.7% Cu for Ernest Henry resources, and that is for a fully underground operation.
AIC have used 1.0% Cu cut-off for Eloise resources - again this is underground (to my understanding). They then have used 1.5% Cu cut-off for Eloise Deeps (looks to be ~1200m below surface based on their diagram).

All I'm saying really is I don't think CNB is doing anything outlandish with their approach here. But it also has the effect of pulling down the average grade.

Cheers,
Dingo.