1274 In traditional modelling methodology, geologists first divide the deposit into Geological Units or GUs and obtain “representative” composites of each GU for metallurgical tests to define the respective GMUs or Geometallurgical Units (Figure 3). The main criticism of this method is related to representativeness of the composites, which according to the TOS: Theory of Sampling (Gy 1992, 1999) only become specimens, no samples, because they are obtained through selective procedures, which are not permitted under the TOS. This error is compounded when results of metallurgical tests, obtained from these composites, are boldly and recklessly extrapolated to millions of tons (GMUs), giving rise to the well-known errors traditionally associated with this methodology, which appear when the ore is being processed in industrial circuits. On the other hand, some traditional metallurgical tests like Bond Work Index (BWI), Sag Power Index (SPI), or similar, cannot be incorporated into a probabilistic database, mainly because they are based on specimens and not on systematically obtained samples. Additionally, their acquisition is both very expensive and time consuming (Canchaya 2012 and Canchaya et al. 2013). 5. IMPLEMENTATION OF THE GEO-METALLURGICAL BLOCK MODEL (GMBM) Metallurgists understand “modelling” in a different way to geologists. Metallurgical modelling aims to find a deterministic relationship between input variables (mainly mineralogical) and output variables (mainly metallurgical); which are usually performed testing composites. On the contrary, GMBM as proposed in this work, is very similar to Geological Resource Modelling. The difference being that, in addition to traditional variables like coordinates, assays, lithology and alterations, "critical" geometallurgical variables, like clays, acid consumers, cyanide consumers, minerals that contain penalizable elements, etc. should be also considered. There are two general ways to implement a Geo-Metallurgical Block Model (GMBM): (1) Based on the systematic geometallurgical logging of Mineralogical-Textural Assemblages (MTAs) and Geological Fragmentation Units (GFUs) and (2) Based on systematic quantitative analyses of critical variables. 5.1. GMBM from MTAs and GFUs Figure 4 outlines the general procedure for implementing a Geometallurgical Block Model, based on systematic logging of geometallurgical units called Mineralogical-Textural Assemblies (MTAs). The scheme corresponds to the modeling applied at the Pucamarca Mine in Tacna, Peru (Canchaya et al. 2019).
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