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Bulk ore sorting is a preconcentration method applied to bulk streams or batches of material. The effectiveness of bulk ore sorting relies on the degree of the naturally occurring in situ grade heterogeneity of an ore deposit. The blending of ore during mining and material handling degrades the in situ grade heterogeneity initially present in an orebody and reduces the potential to apply bulk ore sorting. Block and panel cave mines experience mixing from the establishment of caves to the delivery of the caved ore to concentrators. This study focused on tracking the grade heterogeneity and quantifying the impact of mixing on the sorting potential of the Cadia East panel cave mine via the reconciliation of the grade measurements performed at different locations. The results showed that the copper and gold grades were almost fully homogenized via various mixing events identified for the mine. The tracked grade heterogeneity values revealed that the mixing during material handling, which included ore blending according to mine planning, reduced the grade variability more drastically than the mixing within the caves. As the ore travelled from its original in situ location, the grade distributions gradually transformed, and the grades eventually normalized around the mean values. Only insignificant amounts of low-grade material that could have potentially been discarded were reported to the on-belt sensor located at the surface. The results of this study are significant for cave mines exploring sorting systems for preconcentration as they highlight how mixing can impact the variability in ore grades. [ABSTRACT FROM AUTHOR]

• The potential of bulk ore sorting application at a block cave mine was investigated. • The grade heterogeneity and sortability was evaluated for different mining zones. • The relationship between ore grade heterogeneity and sortability was discussed. A block cave mine operation was investigated in terms of ore grade heterogeneity and the potential of bulk ore sorting application. The grade heterogeneity within the caved material was measured for different draw points and mining zones, in terms of Distribution Heterogeneity and Fractal Dimension. The potential of bulk ore sorting was assessed by comparing the Net Smelter Return before and after a hypothetical bulk ore sorting system was implemented. Results showed that the potential of applying bulk ore sorting was influenced greatly by the heterogeneity within the mined material. A certain level of heterogeneity was necessary in considering the mine production as 'sortable'. The sortability would also vary for different mining areas depending on heterogeneity level of the production. Peripheral zones of the orebody were considered with the highest level of heterogeneity and the most significant potential of bulk ore sorting application. [ABSTRACT FROM AUTHOR]

XRF bulk sorting is put forward as a credible intender for pre-concentration methods in mining. This paper presents a preliminary study employing a bench-scale approach to calibrate XRF surface sensing to a target concentration of interest related to its volume so as to assess the feasibility of a case barren copper ore “slots” to bulk sorting. Firstly, various top sizes, along with different operators and specimens’ weight/volumes, were examined to quantify the minimum readings needed (MRN) for XRF spot scanning at this scale. Multiple linear regression with a correlation coefficient of 0.921 was validated to be a reliable algorithm for calibrating XRF surface response to Cu volumetric concentration, owing to its consideration of elemental interacts. With the aid of graphical representations of calibrated data on recovery/grade curves, cut-off grade of 0.23% was chosen to enable 30% mass below the threshold to be discarded as waste and the remainder to go for further processing. [ABSTRACT FROM AUTHOR]

• Continuous physical, mineralogical, geochemical data recorded in waste-rock pile. • Multi-scale heterogeneities in alteration resembling hardpan formation in tailings. • Secondary mineral assemblages and weathering mechanisms in reactive and inert zones. • Mineralogical controls on leachate composition and metal mobility in waste-rock pile. Mine waste rock is typically stored on-site in large piles that are heterogeneous in terms of material composition and grain size. This leads to variable reactivity within the pile and makes prediction of drainage quality difficult. Here, we present data from two >100 m continuous boreholes through an operational waste-rock pile at the Antamina mine (Peru). Reactive zones with elevated sulfide and metal content exhibited increased temperatures, reduced oxygen content, as well as pervasive secondary mineral precipitation. Sharp contact between altered and unaltered layers at the meter to centimeter scale indicated strong variability in mineral reactivity. Unaltered waste rock persisted within high-sulfide zones due to low oxygen levels, and surface passivation and galvanic interactions between sulfide couples also limited alteration. Waste-rock layers with gradated alteration that resemble hardpans, as observed in tailings, were in direct contact with non-altered, less-permeable layers. Finally, leaching tests show that sulfate, Cu and Zn were efficiently leached from reactive and mineralogically altered zones, whereas As and Fe were retained through sorption, surface passivation, or secondary mineral formation. This study shows that, over and above bulk geochemical and lithological data, waste-rock reactivity may also be defined by mineralogical data and thereby contribute to improved drainage quality predictions. [ABSTRACT FROM AUTHOR]