Sampling for proactive reconciliation practices

Abstract

Reconciliation is an activity carried out at most mines around the world which can be a useful tool to evaluate sampling accuracy throughout grade control processes. The historical practice of reconciliation is based on definition of the ‘mine call factor’ and its application to resource or grade control model estimates. However, the use of correcting factors will often disguise the causes of the discrepancies between results and estimates. Reconciliation should be done in a proactive way, i.e. analysing the information behind any discrepancy and, then, adjusting methodologies and processes so that results and estimates realign. A proper reconciliation system must be based on reliable data. Therefore, the optimisation of sampling techniques is indispensable for the development of a reliable reconciliation system. This paper analyses the reconciliation practices performed at a gold mine in Brazil and suggests a new sampling protocol, intended to eliminate significant sampling biases by taking preventive action.