Progress in integrated quantitative mineral resource assessments

Three-part resource assessments, begun over 30 years ago, provide a framework for making decisions concerning mineral resources under conditions of uncertainty. The parts include general locations of undiscovered deposits that are delineated from a deposit type's geologic setting; frequency distributions of tonnages and grades of well-explored deposits that serve as models of grades and tonnages of undiscovered deposits, and number of undiscovered deposits that are estimated probabilistically by type. Recently improved deposit density models show how to make probabilistic estimates of numbers of undiscovered deposits. Significant progress has been made showing how to reduce uncertainty and risk by the practical integration of the fundamental kinds of information needed by decision-makers. The approach is founded on internally consistent mineral deposit models that help convert the output of assessments into forms helpful to decision-makers. This integration of models and methods is a source of strength that reduces the chances of biased estimates, but it is also a burden, requiring careful development of models and applications of methods. Before decisions are made on where to explore, decisions must be made about what to explore for and whether it is worth the risk.