Geological and geostatistical elements of ore-grade control at the Candelaria Mine, Mineral County, Nevada

Abstract

At the Candelaria mine, ore-grade control integrates blasthole assay data with geological information to optimize the selection of ore for selective mining. The deposit when subdivided into geologically controlled domains allows valid geostatistical evaluation of blasthole data. Detailed geological muckpile mapping is then used to interpret individual grade estimates. Check assays of blasthole samples showed a correlation coefficient of 0.98 while a comparison of blasthole assays to carefully sampled cuttings resulted in a correlation coefficient of 0.82. The mean of the check samples was 1.45 oz/ton and the mean of the carefully sampled cuttings was 2.43 oz/ton. A polygonal method of grade control when compared to one using geological and geostatistical grade estimates as well as the blasthole information designated 37% to 107% more rock as ore depending upon the geological complexity. This was verified by an exercise involving mine personnel. Comparison trials using grab samples confirmed that grade estimation was improved using kriged estimates over- blasthole data alone. This method of grade of grade control has lowered the operational costs of the mine.