1% is a respectable grade for Cu. One tonne of rock @1% would contain 1000kg x 0.01 = 10kg Cu = 22 lb Cu x $3.6/lb = $80. If the same thing is done for 1gpt Au, then that same chunk of rock would be worth an extra 1g/32 x $1700 = $53. So, the Cu "credits" in terms of AuEq would be 80/53 = 1.5 gAuEq.
It does not matter how this is looked at, Au mine with Cu credits, or the other way around, a Cu mine with Au credit the end result would be the same 1gpt Au +1% Cu = 1 +1.5 = 2.5 gpt AuEq = a nice chunk of rock.
Quite a few interesting things are noted from GQC Corporate Presentation, link below
- the appearance of drill core sample D-27493 showing very high grades of Au and Cu on Slide 17.
- I would venture that most of the nice yellowish colour belongs to the Cu, but can visible gold be seen in this sample as well, judging from the very high Au grade? There seem to be several glittering spots (visible gold?) on the sample surface, but I am no geo. Any experts out there who want to weigh in?
- Lately GQC truncated the grades for Au and Cu in their plots. Why not just plot them using the actual values which are sometimes way over the cut-off limits? IMO, this is an overly conservative way to presnt the results.