From what I understand for open pit what is most important is very large, bulk tonnage near surface and without expense of removing much barren overburden. During the last frenzy of rising gold prices I was seeing attempts to move half gram per ton deposits to open pit production.
There are all sorts of factors, whether there is a need to crush to fine size in order to get good recovery or if there is a sweet spot where the gold will leach from a course crush in a good timeframe and without too much cyanide cost. Further the type of rock, how hard, and the type of deposit particularly how fully cxidized, etc all play into it.
In today's climate where rising costs of energy, labor, machinery, and chemicals are all concerns it is likely only dominantly oxide deposits no deeper than 300 or so meters where most of that 300 meters from surface is a gram per ton or better that will be still moving forward with the projections on possible prices for gold as they are.
jmo
