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Ore grades are monitored regularly in cave mines through drawpoint sampling. Automating grade monitoring through deploying X-ray fluorescence (XRF) sensors on the buckets of production loaders has been proposed as an alternative approach to address the issues around the traditional practice of drawpoint sampling. Bucket-mounted sensors can also be employed for bulk ore sorting underground. This study is aimed at evaluating the deployment of XRF sensors on production loaders as an opportunity for grade monitoring or bulk ore sorting in caving operations. The mill feed grade prediction performances of the drawpoint sampling program and mine planning software were assessed for the Cadia East panel cave mine. The results showed that the drawpoint samples underestimated the mill feed quality during a 10-month investigation period. The cave portions with bulk ore sorting potential were linked to the extraction level layout to estimate the number of drawpoints where sensors could be situated for diverting ore and waste. Samples obtained from the mine were tested to evaluate the ability of a lab-scale proxy of a bucket-mounted XRF sensor system to measure copper and gold grades. R-squared values of 0.84 and 0.68 were achieved between the predicted and measured copper and gold grades of the samples, respectively. Sensor test results are promising in revealing the potential to utilize XRF sensors underground. Future test work is encouraged to further validate the applicability of XRF sensors in an underground mining environment. [ABSTRACT FROM AUTHOR]

Conceptual bulk ore sorting studies are essential for determining a potential improvement in mine economics before undertaking on-site sensor trials. Two approaches, block modelling and drill core compositing, are applied to simulate the bulk ore sorting performance of mining operations. While one employs the grade data of a block model, the other approach utilizes composited drill core grades. This study aimed at comparing these two approaches by estimating in-situ grade heterogeneities and simulating the bulk ore sorting performances of the currently active caves of the Cadia East panel cave mine. The results show that block modelling tends to smooth the grade variability that initially exists in the drill core grade data. Particularly in the portions of the deposit where drilling is sparse or widely spaced compared to the selected block size, block modelling leads to lower grade heterogeneity and bulk ore sorting performance estimates. However, when the drill hole data is nonrepresentative of the area of interest, block modelling can predict more realistic bulk ore sorting performances compared to drill core grades. The assessments performed with the blocks and drill core composites of various sizes showed that grade heterogeneity was adversely affected by an increased sorting scale due to averaged metal grades. [ABSTRACT FROM AUTHOR]

Amenability of mafic ores to pre-concentration was investigated with respect to ore mineralization characteristics. For the pre-concentration tests seven ores from various nickel-copper operations at Sudbury, Ontario were subjected to dense medium separation. Size assays of metal values, i.e. distribution of nickel and copper with respect to size fractions, were also determined. The ores were assessed in three categories of valuable mineralization as massive pure sulphides, coarse massive sulphide grains and disseminated sulphides. For ores with massive pure sulphides and coarse massive sulphide grains even a size classification based pre-concentration route could be sought since a clear trend of metal enrichment was identified towards finer fractions. Orebodies of similar mineralogy had similar responses to pre-concentration tests. The best results were for those ore bodies with a distinct differentiation between mineralization and gangue, i.e. the ores with massive pure sulphides, where nickel recoveries of 97% and mass rejections of 38-53% were achieved. Similar results were obtained for ores with coarse massive sulphides. For disseminated sulphide mineralogy relatively lower mass rejection was attained with acceptable recoveries of metals. Rejection of magnesium bearing gangue, such as talc, was identified as another benefit of pre-concentration. The extent of magnesium rejection occurred as a function of ore mineralogy. Clear distinction between valuable mineralization and gangue provided preferential magnesium rejection at high levels with no or minor metal losses. [ABSTRACT FROM AUTHOR]

• Nine influential factors were integrated in a mathematical framework based on fractal modelling approach. • The influence of various factors on the ore sortability were investigated. • Factors of significant influence were identified. The uptake of bulk ore sorting technology is hindered by little knowledge in assessing its applicability for certain mine operation. The applicability of the bulk ore sorting technology, referred to as 'sortability', is a multi-folded concept and is influenced by many factors. Researchers have investigated the influence of some of the various factors, but few have done this in a holistic perspective and in a quantitative manner. In this research, nine influential factors of ore sortaibility were integrated in a mathematical framework based on fractal modelling approach. Box-Behnken design was applied and 130 block cave mine operations were hypothesized under different values of the factors. The influence of the factors on the ore sortability were investigated and factors of significant influence were identified. Results showed that ore property, sorting efficiency, metal price, processing cost and operation scale were the most significant factors in affecting the sortability for a mine operation. The research is intended to improve the understanding on the bulk ore sortability for mine productions under different conditions, and to provide a holistic perspective for applying the bulk ore sorting technology. [ABSTRACT FROM AUTHOR]

• The developed fractal model was validated on mine production data. • The multifractal model was proposed for bulk ore sortability assessment. • The multifractal model was more accurate in predicting the sorting results and assessing ore sortability. A previous study demonstrated the theoretical development of a model for assessing bulk ore sortability. However, the model has not been validated with many cases. In this study, the developed model was validated using the production data from 232 draw points in a block cave copper mine. For each draw point, sorting results and mine economics were predicted using fractal modelling and compared with results based on actual data analysis. The statistical error was measured for the fractal model predictions of feed grade, mass yield, pre-concentrate grade, metal recovery, and NSR with and without bulk ore sorting. An optimised approach was developed using multifractal modelling; two sets of fractal parameters were determined to characterise the metal distribution in high- and low-grade ranges. The results showed that the multifractal model was more accurate than the fractal model in predicting the sorting results and assessing ore sortability. [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]

• Error analysis was conducted on the XRF measurements of ore materials at lab-scale. • Three main types of errors were identified associated with XRF measurements. • The applicability of XRF in bulk ore sorting applications was discussed. X-Ray Fluorescence is one of the sensing technologies with potential in bulk ore sorting application. However, its reliability is often questioned since X-Ray Fluorescence does not sufficiently penetrate and errors are associated with surface measurements representing the volumetric grade. In this paper, error analysis was conducted on the XRF measurements on bulk ore materials at lab scale. Three main sources of the errors were identified, termed as instrumental error, heterogeneity error and the sampling error. Among the errors, the heterogeneity error was identified as the most significant due to its irrelevance with measuring the concentration and the unpredictability of that value. The influence of the errors on the conventional linear regression approach was investigated in terms of the sorting results and economics. Results showed that the linear regression approach was expected suitable for cases when sufficient analysis interval time could be ensured. It this was allowed for, the applicability of XRF in the bulk ore sorting was fundamentally justified. [ABSTRACT FROM AUTHOR]

• Receiver Operating Characteristic (ROC) was applied in ore classification for bulk ore sorting. • ROC approach was found to result in more accurate classification compared to SLR. • Economics performance was enhanced by ROC approach compared to that of SLR. As high grade deposits become depleted, the mining industry is challenged by mining lower grades that require the use of non-selective bulk mining methods. Bulk ore sorting can reduce the dilution of the mined ore thereby preventing costly processing of low grade waste while improving the quality of material reporting to the processing plant. X-Ray Fluorescence (XRF) is one of the sensing technologies used for bulk ore sorting. The grade of the bulk material is predicted based on XRF measurement that is correlated to a grade using a calibrated algorithm. The effectiveness of XRF bulk sorting depends on the accuracy of the grade classification of the scanned material. False classification is attributed to poor performance of the sorting algorithm to correlate the measurements with the assay grades. The paper presents an approach to analyze XRF measurements that reduce misclassification of material. Receiver Operating Characteristic (ROC) was applied as the tool in classification of bulk materials. The performance of this approach was compared to conventional sorting algorithm, namely, simple linear regression (SLR), where XRF responses was linearly correlated to the assay grades. The ROC approach was found to result in more accurate classification and enhanced economics performance of the bulk ore sorting system. [ABSTRACT FROM AUTHOR]

• A bulk ore sorting model was developed for sortability assessment. • Metal distribution within ore deposits was recognized as a fractal structure. • The optimum cut-off grade was determined based on model calculations. Bulk ore sorting (BOS) has the potential to reduce processing costs and improve mine economics. A factor that impedes its acceptance is the lack of a method to assess ore amenability to sorting. In this study, a fractal model of metal distribution was used to assess an ore's bulk sortability. A BOS model was developed where metal distribution properties were characterised, optimum cut-off grade for sorter operation was determined, and economic potential of BOS was evaluated. For the developed model, the metal distribution within the ore deposits was recognised as a fractal structure. Two parameters were introduced, namely the grade factor and fractal dimension, to quantitatively characterise ore properties in terms of grade magnitude and heterogeneity. The mass balance of the sorter operation was modelled as a function of the characterised ore properties and the optimum cut-off grade was determined based on model calculations. The economic potential of BOS was evaluated in terms of the net smelter return and compared with that when no BOS was implemented. Based on the developed model, the bulk ore sortability of different ore properties was assessed with a hypothetical underground copper mine. The developed BOS model provided a powerful tool for ore sortability assessment and is expected to encourage academic research and industrial practices of BOS. [ABSTRACT FROM AUTHOR]

• Even with the ideal conditions, bulk ore sorting may not be applicable. • Metal losses limit the value associated with bulk ore sorting. • Good correlation between copper and gold is required for effective ore sorting. Bulk ore sorting may add significant value to block and panel cave mines where processing feed grades are constrained by limited grade selectivity. The Cadia East gold-copper mine is a panel caving operation utilizing two different on-belt bulk ore sensors to evaluate the potential benefits of the technology. To date, there is limited reported work addressing the applicability of bulk ore sorting systems at a caving mine, where two commodities drive the economics. This indicative study is aimed at investigating the importance of various key factors on the bulk ore sorting potentials of the active and future panel caves of the Cadia East mine. Results show that for only one active cave of the mine, bulk ore sorting may be applied in the ideal scenario where grades are not affected negatively by mixing and the sorting takes place at maximum efficiency. As a general trend for all the caves, when the sorting cut-off grade is increased beyond a certain threshold, a sharp decline is observed in the sorting potentials due to the significant amounts of gold and copper deporting to the sorter rejects. In the case of a significant drop in metal prices, bulk ore sorting may only provide an opportunity to improve cave economics marginally. Results obtained by investigating the spatial change in sorting potential show that the portions of the caves with low metal grades are favourable for bulk ore sorting. In the scenario where bulk ore sorting is focused on low-grade portions, it is demonstrated that improvements in the economics of the future caves may additionally be achieved. However, as the low-grade portions represent a very small volume in the orebody, applying ore sorting on the plant conveyor may not be viable. [ABSTRACT FROM AUTHOR]

Abstract: The paper reports the progress of a research project using rock samples from a large copper–gold mining project. The orebody contains a mixture of hard rock, softer material, and clays (sericite), in proportions that are expected to vary throughout the mine-life. The feasibility of a novel comminution circuit, using an autogenous (AG) mill/scrubber and parallel trains of cone crushers and high-pressure grinding rolls (HPGR) is being investigated. The process enables the application of energy-efficient HPGR to base and precious metal hard-ores containing clay, which are usually processed using SAG mill circuits. The work presented in this paper involved laboratory testwork including pilot HPGR testing, and modelling and simulation of both the HPGR-based circuit and an equivalent SAG-based circuit. The preliminary analysis reported herein includes a comparison of the energy consumption of both circuits; complete operating and capital cost comparisons will be reported in a future paper. [Copyright &y& Elsevier]