Thanks for the reference to the Leitch Gold mine. Here is a bit of info that  I just dug up:

 The Leitch Gold Mine -
(now on Roxmark land) was the # 1 of Ontario & Canada's
highest grade and most profitable Gold mines -
producing 860,648 ounces from 906,395 tons of ore
at an average recovered grade of 0.91 oz.Au/ton.

Even more impressively, the average recovered Gold grade -
over the last ten years of the mine’s Gold operation -
was 1.15 oz.Au/ton.