Evaluation of gold deposits—Part 2: results of a survey of estimation methodologies applied in the Eastern Goldfields of Western Australia

Abstract

Resource-estimation methods fall into two categories: conventional and geostatistical. The choice of what method to apply must be made with regard for the local geology and statistics of the grade distribution. A survey of the application of these methods in operations in the Eastern Goldfields of Western Australia was carried out during 1997–98. Inverse distance weighting was the most popular grade estimation technique, followed by polygonal and sectional methods. Geostatistical techniques, such as ordinary and indicator kriging, were applied, but less often. The ratio of geostatistical to conventional technique usage was found to be approximately 1 : 5 at open-pits and 1 : 4 for underground operations. The dominant reason given for use of a particular conventional technique was that it could be shown to be 'historically' adequate. Company policy or the belief that insufficient data were available to generate a variogram often governed the preference for conventional techniques. Where geostatistical methods were in use their adoption was related to better understanding of geology and grade distribution.