In 1992, 106 precious metal mines existed in the USA. A much larger number is also scattered throughout the world. The metal content of the ore in these mines is frequently very low. Many gold mines average as little as 5 grams per ton. This paper will look at the recovery techniques most commonly used. Included will be types of deposit, milling techniques, cyanidation, heap leaching, recovery from solution, bi-product recovery and bio-leaching, as well as other non-conventional techniques.

Author: Roland Loewen