Reading: Open-Pit Mining | Geology
Gold is generally extracted in open-pit mines at 1 to 2 ppm (parts per million) but in certain cases, 0.75 ppm gold is economical. This was achieved by bulk heap leaching at the Peak Hill mine in western New South Wales, near Dubbo, Australia. Nickel, generally as laterite, is extracted via open-pit down to 0.2%.
