Mineral deposit assessment is based on estimates of the attributes within the ore body, where the sampling of these attributes is usually obtained through cores from diamond drill holes. Due to the high costs associated with drilling and sampling, the amount of drill holes is limited and their locations must be correctly defined to simultaneously maximize the uncertainty reduction related to the estimates and the confidence of the resource and reserve inventories. Having posed the problem, this article presents a methodology for defining the ideal drill-hole grids for optimizing the distribution of resources according to their measured, indicated, and inferred classes. The method combines the estimation error and geological continuity through an indicator kriging approach. This methodology is currently used as a benchmark in all the ferrous resource classification done at the Vale Ferrous mine planning department, and a comprehensive case study was conducted in two different iron ore deposits demonstrating its robustness and applicability in any mineral inventory assessment.
Sampling location; goestatistics; drilling optimization
