Ore estimation problems in an erratically mineralized orebody

CIM Bulletin, Vol. 72, No. 806, 1979

GARY RAYMOND, Assistant Chief Engineer, Newmont Mines Limited, Similkameen Division, Princeton, B.C.

The Similkameen Division of Newmont Mines Limited operates a low-grade open-pit copper mine in southern British Columbia. The copper mineralization is extremely erratic. As a result, over seven years of operation, ore control methods have evolved from standard flagging based on blast-hole assays, through an in-pit grab sampling system, to the present method of mining to computer-determined ore-waste boundaries based on geostatistics.These improved ore control methods have resulted in a gain of at least 25% on ore tonnage milled, at the same grade as obtained using earlier techniques. At the same time, geostatistical ore reserve estimates are now within 7% of milled ore tonnage and grade on a yearly basis, whereas the original polygon ore reserves under-estimated mineable ore tonnage by 15% to 45% and over-estimated grade by about 20%.The author discusses why traditional ore estimation methods give poor results in erratically mineralized orebodies and describes the geostatistical approach to the problem.
Keywords: Ore estimation, Grade control, Mineralization, Open-pit mining, Similkameen Mine, Copper ore, Kriging, Geostatistics, Computers, Variograms, Sampling, Ingerbelle orebody.