Importance of sample preparation, representivity, and reporting methologies for quantitative evaluation of precious metal mineralogy

English Abstract:

It is essential to use quantitative methods in evaluation of precious metal minerals and determining precious metal deportment, well-known to process and applied mineralogist, but this approach is under-appreciated by many, especially for those unfamiliar with study of crushed and sized representative samples. The majority of economic geology publications are still only based on study of metallic minerals in polished thin sections (PTS) that cannot be representative of the ore being described, but are then used in conjunction with bulk chemical assays to arrive at so-called mass balances and metal deportment. Precious metal mineral abundances are still being reported in terms of frequency percent or volume percent based on approximate length x width measurements. The increased access to automated SEM-based imaging systems give a false sense of reliability unless these are used by knowledgeable operators based on careful sample preparation and representivity, as well as evaluated by reconciling to chemical assays. Sample preparation, measuring techniques, and reporting of data, has been the subject of continual improvement over the last few decades. The presentation will focus on platinum-group minerals (PGM) and platinum-group elements (PGE), such as occur in mafic-ultramafic magmatic deposits.