Grade control in hard-rock open pit mining is the process of determining the destination for the mined material. Numerical studies are undertaken to show how grade control can be improved, that is, less ore sent to the waste dump and less waste sent to the mill. The improvements in four aspects of grade control are proposed: (1) the grade predictions should be made at a resolution of one quarter of the blasthole spacing or less depending on computational restrictions, (2) the assignment of grades should consider uncertainty to optimize the chosen destination, (3) the blast movement of rock should be considered, and (4) the destination should be optimized on the smallest unit of selection possible; ideally truck-by-truck. These improvements are developed with examples and then a case study is presented. The amount of rock sent to the wrong destination is reduced by two to five percent with the proposed improvements.
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