1270 1. INTRODUCTION Geometallurgy is a new and fascinating specialty; unfortunately, its current widespread practice, based on metallurgical tests of composites, is not yielding good results. The main reason is that composites fail to represent the inherent heterogeneity of ore deposits, and for this reason, metallurgical tests performed on them fail when their results are extrapolated to millions of tons. In this paper we will present alternatives that fully recognize the natural heterogeneity of ore deposits, proposing the Geo-Metallurgical Block Model (GMBM), a tool that is based on the Total Rock Concept (TRC), which we will explain previously. We will explain two ways to obtain a GMBM: (1) From systematic geometallurgical logging; (2) From quantitative geometallurgical data. The main objective of a GMBM is to increase recovery of ores at the lowest costs. 2. THE TOTAL ROCK CONCEPT (TRC) As defined by Canchaya (2008), a new perspective in geometallurgy is the Total Rock Concept (TRC). This concept considers rocks as a whole, since the designations of ore and waste rock are circumstantial because they are established according to requirements or needs that change over time. The TRC considers that gangue minerals are the main factors in metallurgical circuits, such as crushing, grinding, flotation, cyanidation, acid leaching, etc. Furthermore, the main problems encountered in metallurgical plants are related to gangue, especially due to its relative abundance, which in some types of ore deposits, particularly low-grade deposits, are largely predominant. For example, in Cu-(Mo and/or Au) porphyritic deposits, ores (chalcopyrite, molybdenite, chalcocite, bornite, etc.) do not exceed 2 or 3 % of the total rock, while gangue minerals are above 96 %. Even more critical is the case of high sulfidation epithermal gold deposits (such as Yanacocha and Pierina in Perú; or La Coipa and Can-Can in Chile); where gold ore is usually below 1gr/ton (1 ppm), which in percentage means only: 0.0001% of the rock; it means that 99.9999 % is gangue, composed by different types of quartz, eventually accompanied by scarce alunite, clays, pyrophyllite, jarosite, Fe-hydroxides, etc. Therefore, it is easy to deduce that any kind of problem, such as high cyanide or lime consumption, unusual resistance to crushing, or reduced recovery percentage, are mainly caused by gangue minerals. Of course, we cannot ignore the case where sulfides, sulfosalts or the same native sulfur, are also cyanide consumers; but even in these cases, we are speaking of gangues. Although it is obvious and clear that gangue minerals are the main component in low-grade deposits, the same is true for practically all types of deposits, even those with higher grades, since the proportion of ore is usually lower than that of gangue. 3. GEO-METALLURGICAL CHARACTERIZATION (GMC) To implement a Geometallurgical Model it is necessary to perform a global Geo-Metallurgical Characterization procedure. Nothing more related and committed to the TRC than the Geo-Metallurgical Characterization, which is called “global” because includes the following four analysis (Figure 1): 3.1. Chemical characterization Apart from traditional assays of both, economic and deleterious elements, should be included from exploration phase: Au and Ag cyanide analysis (CN_Au and CN_Ag); as well as “Sequential Cu analysis”: Total Cu analysis (TCu), acid-soluble Cu (AcSCu), cyanide-soluble Cu (CNSCu) and refractory Cu (RCu).
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