Cut-off grades: statistical estimation and reality

CIM Bulletin, Vol. 80, No. 898, 1987

MICHEL DAGBERT, Geostat Systems International Inc., Montreal, Quebec

This paper illustrates the different ways grade-tonnage curves can be generated for a mineral deposit. It emphasizes systematic discrepancies between reality, estimates and actual production according to different estimation methods and grade control programs. It does not offer a universal solution to the prediction of grade-tonnage curves. Hopefully, it will inspire caution to mineral economists who use estimated grade and tonnage data in the establishment of an optimum cut-off grade for a mining operation.
Keywords: Geostatistics, Statistics, Estimation methods, Cut-off grades, Grade-tonnage curve, Grade distribution, Mining dilution, Selective mining units, Kriging.