I was doing a little digging and rooting again (no pun intended Hog, lol) and found something that I thought is worth posting.

I took this paragraph:

Pierina is an open pit, heap leach operation, with its primary orebody very close to surface. The mine's general manager, Igor Gonzalez, told CMJ that the low cash costs are principally due to the nature of the mine--favourable ore grade, stripping ratio and mineralogy, and an economic metallurgical process. When operations first began in November 1998, executive vice-president (development) Alan Hill described the site as "a mining engineer's dream", in reference to Payback Hill, one of the first deposits to be mined at Pierina that contained an astonishing 25 grams of gold per tonne.

from this article written in June 2001

http://www.canadianminingjournal.com/issues/story.aspx?aid=1000110361&type=Print%20Archives

Then I took this paragraph;

Initial sampling from 11 pits returned an average grade of 6.84 grams gold and 31.7 grams silver per tonne, followed by eight samples from another three pits, which yielded an average of 15.4 grams gold and 47 grams silver. The mineralization was described as disseminated, with little or no sulphides.
Before long, a zone of disseminated mineralization was defined over a sizable area by 14 pits averaging 9.47 grams gold and 33.8 grams silver. A tunnel driven to provide information on geology and to test mineralization at depth returned a consistent grade of 4.85 grams gold and 180 grams silver over a length of 107 metres. A second tunnel returned 7.81 grams gold and 201 grams silver over a 38-metre length.
The first drill hole confirmed these results, returning an 88-metre intersection, starting at surface, grading an average of 6.58 grams gold per tonne

And this;

By the end of 1998, reserves stood at 114.3 million tons grading 0.063 oz. gold per ton (or roughly 7.2 million contained ounces), plus an additional resource of 61 million tons grading 0.013 oz. An attractive feature of the deposit was a starter pit dubbed "Payback Hill," which boasted gold grades exceeding 8 grams per tonne, with no overburden.

from this article;

http://agoracom.com/ir/steliasmines/forums/discussion/topics/461407-arequipa/messages/1494522

conclusion

Its interesting to see that the end mining grade turned out to be 25 grams per ton,(3 times more) when the initial average grade was just over 8 grams per ton for the "Payback Hill" portion of the property.