jtone good thing about the mines being old is that there should...

jt

one good thing about the mines being old is that there should be some very detailed mapping and stope information etc to see how the orebody behaves and is structured as well as grade and milling information. Even if those areas are now inaccessible that info can be used to infer what is happening with new deeper or adjacent hits. This is esp important in relatively low tonnage high grade operations as you can easily waste cash chasing the wrong lead...so move a lot of tonnes that need to be hauled/moved to get to your target if you get it wrong equals a loss of profits.

with respect to surface hits, everything helps so the more the better really, as long as all the ore is free milling the blending should not be a problem......quite often a gravity circuit is installed for the higher grade material...the faster you can extract the gold the more money you make as you're not moving dirt around the mill which equates to energy which costs money....mining studies will tell.

the big bell mine will be a difficult one as it is large tonnage and relatively low grade for underground, even if you high grade it there may be stability probs that need to be addressed so the lower grade material may have to be mined in any case....so you might as well mine/haul and mill it if it carries gold(and upgrade with high grade dirt)...again mining studies will tell.

It would be interesting to see a say 1 gram envelope around the Big Bell, maybe it could become a superpit aka Kalgoorlie!