Panel on Semi-Autogenous Grinding and Pebble Milling

"With todays economic trials and tribulations we have all become deeply engaged in costs and cost cutting in our field of mineral processing. Grinding is one of the most expensive unit operations. The cost of grinding media is the most expensive item in grinding costs. Therefore, it is only reasonable to attack the cost-cutting area by trying to reduce the consumption of media. This introduces the field of autogenous or rock-on-rock grinding.Rock-on-rock grinding is not new to us. It has been known for many decades;The South Africans used pebble grinding in the '20's for gold.Mr. B. Crocker was prompted for the same reasons to introduce pebble grinding at Lakeshore Mines in Kirkland Lake during the last war.The Buffalo Anchorite used beach pebbles in grinding prior to the war.Autogenous and semi-autogenous grinding is used quite successfully in the iron ore field. Base metals have their examples in Australia at Caba, in Africa at Komato and in Sweden at Aitik.Recently three mills in British Columbia and one in Arizona started with autogenous mills in their circuits. One was originally conceived to utilize a modified autogenous grind with a crusher in the circuit. All except the same mill had contingency plans for converting to semi-autogenous. All four mills have since converted to the semi-autogenous mode. These are Island Copper, Lornex, and Similkameen in B.C. and Pima Mining in Arizona."