ORE RESERVES - ERRORS AND CLASSIFICATION

The potential sources of error that might occur during the various pha ses of an ore-reserve evaluation programme from drilling through to or ebody modelling and valuation are reviewed and the role of core recove ry in this respect is stressed. The review indicates that definitions of geological assurance as used in current or proposed classification systems are inadequate to reflect the quality of, and confidence in, r eserve-estimation procedures for a particular deposit. It is proposed that a 'resource reliability rating' system be established to attempt to quantify what is meant by geological assurance and to combine this with an estimate of the precision of estimation as gained by geostatis tical analysis. As an interim step, however, an improvement can be mad e by the incorporation of core recovery estimation into block modellin g procedures so that confidence as to whether a single block is of ore grade can be judged on this parameter as well as on whether it exceed s a specified cutoff grade.