Abstract
Many by-product metals are classified as critical. However, they are only of marginal interest to many mining companies and are rarely part of detailed resource statements or geometallurgical assessments. As a result, there is a general lack of reliable quantitative data on the mineralogy and spatial distribution of these metals in ore deposits—hampering assessments of future availability. We propose here an innovative approach to integrate by-product metals into geometallurgical assessments. As an example, we use the distribution and deportment of indium at Neves-Corvo, a major European base-metal mine (Cu + Zn), and one of the largest and richest volcanic-hosted massive sulfide (VHMS) deposits in the world. Based on a combination of bulk-ore geochemistry and mineralogical and microanalytical data, this study is the first to develop a quantitative model of indium deportment in massive sulfide ores, demonstrating how regularities in indium partitioning between different minerals can be used to predict its mineralogical deportment in individual drill-core samples. Bulk-ore assays of As, Cu, Fe, Pb, S, Sb, Sn, Zn, and In are found to be sufficient for reasonably accurate predictions. The movement of indium through the ore processing plants is fully explained by its mineralogical deportment, allowing for specific mine and process planning. The novel methodologies implemented in this contribution for (1) the assessment of analytical uncertainties, (2) the prediction of complex mineralogical deportments from bulk geochemical data, and (3) the modeling of by-product recoveries from individual mining blocks, are of general applicability to the geometallurgical assessment of many other by-product metals in polymetallic sulfide ores, including Ga, Ge, Mo, Re, Se, Te, as well as the noble metals.
Highlights
Despite their potential to generate significant additional revenue at some mines, as well as their importance for the global economy (Wellmer et al 1990; Nassar et al 2015; EU Commission 2017), many by-product metals are only of marginal interest to most mining companies
It has long been recognized that mineralogical deportment is a key factor in the recoverability of minor and trace metals from their ores (e.g., Chryssoulis and Cabri 1990), in addition to textural and grinding properties
The mineralogical deportment of an element k present at a bulk concentration (Ck) in an ore sample consisting of N different minerals, {i}, is described by the set of percentages:
Summary
Despite their potential to generate significant additional revenue at some mines, as well as their importance for the global economy (Wellmer et al 1990; Nassar et al 2015; EU Commission 2017), many by-product metals are only of marginal interest to most mining companies. Indium is a prime example of such a metal Is it considered a critical raw material by most authors (e.g., Graedel et al 2015; NSTC 2016), but unlike other by-products, such as gallium and germanium, it is approaching its theoretical production limit (Frenzel et al 2017). It has long been recognized that mineralogical deportment is a key factor in the recoverability of minor and trace metals from their ores (e.g., Chryssoulis and Cabri 1990), in addition to textural and grinding properties. This is because it controls the proportions reporting to concentrate and waste streams.
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