What I also find interesting is the dollar cost/oz as grade increases (assuming a fixed cost of CD$120/tonne milled):
0.3 oz/tonne => $400/oz
0.4 oz/tonne => $300/oz
0.5 oz/tonne => $240/oz
0.7 oz/tonne => $171/oz
1 oz/tonne => $120/oz
GoldCorp grades would be nice...