The completeness of an exploration project is of crucial importance for making a decision to start or to give up a mining investment, or to continue the exploration to get complementary information. The authors discuss this problem on the example of the Halimba bauxite deposit, Hungary. Two-hundred thirty-seven core drills were executed on a 14 ha area. Resource calculations were carried out in 12 subsequent stages by fuzzy arithmetic with the aim to quantify the uncertainties of ore tonnage and grade. Prior information and prior probabilities were applied to complete the exploration data. Their validity was checked by the subsequent stages. Ranges of influence for the main variables were calculated by geostatistical methods (variograms). Spatial variability and spatial continuity of the orebodies were mathematically evaluated. The authors found that there is no single “overall” value to express the completeness of a mineral exploration program, but the main geological, mining, and economic factors must be evaluated separately and ranked according to their importance. The reliability of the results can be quantified by the application of new “uncertainty-oriented” mathematical methods.