Technical note adaptation of Pierre’s Gy theory of sampling for polished section preparation geared towards automated mineralogical analysis

Abstract

In the mining industry, mineralogical characterization using automated mineralogical devices (scanning electron microscope and reflected optical microscope) has become inescapable, especially for geometallurgical purposes. Mineralogical characterization using these techniques requires correct sampling of the material to obtain representative polished sections. This technical note proposes a method to decide the appropriate number of polished sections which need to be prepared according to the size class considered to achieve enough representability. To illustrate this method, two sampling protocols (at grain form for textural purposes and powder form) of a theoretical typical sulfide ore including a sizing preparation, are presented with the computation method of the variance of the fundamental error related to sampling. The sampling protocols are an adaptation of safety lines derived from the sampling theory of Pierre Gy and need to be adjusted according to the intrinsic properties’ knowledge of the material considered. The method can be very useful to better anticipate the lack of representativity of mineralogical data provided by automated mineralogical devices linked to the sampling preparation.