In the mining industry, reconciliation can be defined as the practice of comparing the tonnage and average grade of ore predicted by the geological model with the tonnage and grade generated by the processing or metallurgical plant. This practice has shown an increasing importance, since, when correctly executed, it increases short-term planning reliability and substantially reduces losses in the operation. However, the usefulness of reconciliation relies on the quality and reliability of the input data. Successful reconciliation can be illusory. In many cases, errors at one point of the process are offset by errors at other points, resulting in excellent reconciliation results. However, this fact can hide compensating errors in the system that may surface someday. Very often sampling errors can be masked and may lead to erroneous analysis of the reconciliation system, generating serious consequences to the operation, especially when mining reaches poorer or more heterogeneous areas of the deposit. Since good estimation is only possible with correct sampling practices, the reliability in the reconciliation results depends on the representativeness of the samples that generated them. This work analyzes the sampling practices carried out at Maracá Mine for reconciliation purposes. Results show that the apparently good reconciliation between the mine and the plant is in fact illusory, consequence of the compensation of many sampling errors generated by the collection of the primary samples at the mine.
Reconciliation; sampling; representativeness
