Abstract
Before the advent of computer-aided estimation methods, the goal of a Mineral Resource statement was to estimate the in-situ tonnage and grade that might reasonably be expected to be extracted using the underground mining methods under consideration. Key items for consideration were the spatial configuration of the mineralization above-cut-off grade as well as internal diluting material, which was unavoidable during extraction by the contemplated mining method. Preparation of tonnage and grade statements were readily achieved in the pre-computer age through the use of manual methods by experienced practitioners.
Despite the transition of our industry to the use of computer-aided methods for preparing Mineral Resource estimates, the nature of mineral deposits have not changed, and neither have the fundamental realities of underground mining operations. Many Mineral Resource statements prepared using computer-aided block modelling methods are derived by applying a minimum block cut-off grade (or value) as the sole reporting criteria. This can result in materially inaccurate Mineral Resource statements, as sufficient internal dilution may not be included and spatially isolated blocks above the cut-off grade (or value) may be included in the Mineral Resources. Several techniques are currently employed by Mineral Resource estimators to ensure that the Reasonable Prospects for Eventual Economic Extraction requirement of the CIM Definition Standards for Mineral Resources are achieved.
The presentation will review the effects of application of a minimum block cut-off grade alone for preparation of Mineral Resource statements and will review some of the techniques that are being used by Mineral Resource estimators to address this challenge.