This paper presents the role of microtexture and mesotexture in the separation performance of an ore. Micro-texture analysis highlighted the influence of mineral grain size distribution in mineral liberation and separation recovery. Mesotexture analysis highlighted the contribution of vein structures in mineral liberation and provided insights of the origin of liberated particles observed during microtexture analysis. The work demonstrates the importance of the scale at which ore texture is measured and points to the way drill cores are prepared for textural analysis. Selection of the most appropriate scale of analysis also provides an effective means of acquiring textural information relevant to mineral processing for the entire deposit and consequently improving deposit characterisation.

In recent years, the Mineral Liberation Analyser (MLA) has played a pivotal role in analysing respirable and inhalable ambient air samples collected on filters from both underground coal and metalliferous mines. Leveraging backscattered electron (BSE) image analysis and X-ray mineral identification, the MLA offers automated quantitative mineral characterization. The escalating prevalence and severity of mine dust lung diseases, particularly among young miners, have reignited interest in comprehensively understanding the dust’s characterization, encompassing mineralogy, particle size, and shape. Merely measuring total respirable dust exposure and its duration based on gravimetrically determined weight is no longer deemed sufficient in addressing the evolving landscape of occupational health challenges in mining environments. Since the publication of previous studies, efforts have been dedicated to refining the Mineral Liberation Analyser (MLA) methodology for respirable dust sampling. This refinement, discussed in detail in this paper, encompasses various enhancements, such as the implementation of data checks to identify carbon contamination, backscattered electron (BSE) drift, and the misclassification of X-ray spectra. Additionally, an examination of sampling efficiency led to the exploration of using smaller samples as an alternative to the time-intensive analysis of entire filters. Furthermore, this paper presents a reanalysis of paired filter sample sets previously reported using the Sarver Group Methodology. These samples are subjected to analysis using the Mineral Liberation Analyser, providing a more detailed illustration of the outputs derived from the updated methodology and compared to previously published MLA data.

The high demand for cobalt in the global energy transition is driving the mining industry to explore alternative and more ethical cobalt sources. Reprocessing of copper flotation tailings is a potential circular economy approach to managing mine waste and supplementing global critical minerals supply. Tracking cobalt deportment from primary ore, through the concentrator and into tailings is a critical first step in assessing the valorisation potential. The mineralogy, particle liberation properties and mineral associations strongly influence the recoverability of cobalt from tailings. This research integrated Micro-X-Ray Fluorescence (mu XRF), chemical assay, Mineral Liberation Analysis (MLA) and Advanced Mineral Identification and Characterization System (AMICS) to geometallurgically track cobalt deportment throughout an operating copper flotation circuit and into the fresh tailings. Cobalt was found to be hosted in several mineral phases, including cobaltiferous sulphides and pyrite. Detailed geometallurgical characterisation and deportment studies will assist in identifying mineral processing pathways to recovering value from copper tailings.

Exposure monitoring and health surveillance of coal mine workers has been improved in Australia since coal workers’ pneumoconiosis was reidentified in 2015 in Queensland. Regional variations in the prevalence of mine dust lung disease have been observed, prompting a more detailed look into the size, shape, and mineralogical classes of the dust that workers are being exposed to. This study collected respirable samples of ambient air from three operating coal mines in Queensland and New South Wales for characterization analysis using the Mineral Liberation Analyser (MLA), a type of scanning electron microscope (SEM) that uses a combination of the backscattered electron (BSE) image and characteristic X-rays for mineral identification. This research identified 25 different minerals present in the coal samples with varying particle size distributions for the overall samples and the individual mineralogies. While Mine 8 was very consistent in mineralogy with a high carbon content, Mine 6 and 7 were found to differ more significantly by location within the mine.

The heuristic of a constant liberation by size independent of the degree of comminution has been established as a robust assumption over time. Therefore, when assessing the comminution circuit performance, achieving a final target P80 size at the lowest possible energy and cost seems to be the only concern. The introduction of higher capacity fine screening to replace hydrocyclones challenges this fixed approach due to the inherent difference in classification principles between the technologies. The impact of classification efficiency and mode on the liberation properties of a polymetallic ore ground in a production ball mill circuit are presented. It was found that the liberation properties remained constant across the comminution device but were significantly different across the circuit. The circuit closed with screens was found to improve the coarse particle liberation in comparison to the hydrocyclones. The liberation data is presented and implications for circuit performance are discussed. It is postulated that the assessment of comminution circuit design and performance should be based on the ultimate objective, recovery of the valuable minerals, and thus be based on the ore- and process-specific recovery window, not on a fixed 'grind size'.

This paper describes a geometallurgical approach for predicting separation performance of a mineral deposit that is applicable to existing operations and projects in the early stage of mine development. The method includes a class-based analysis to understand the variability in geological and mineralogical characteristics, class-based modelling to understand the influence of these characteristics on separation performance, and process performance domaining to develop domains related to separation performance and to understand the variability in separation response. The application of the approach in a copper-gold porphyry deposit has improved the prediction of copper recovery by flotation compared to the feasibility study models. The method showed that copper assay is not the only factor affecting copper recovery but has identified geological and mineralogical factors that influence flotation response. Overall, the geometallurgical approach is shown to be beneficial in assessing geological, mineralogical and processing variability within the deposit. This understanding of the variability is helpful in the design of an efficient metallurgical testwork program, and also provides valuable information for process optimisation.

Concrete corrosion, as a major issue in sewer management, has attracted considerable research. In comparison, the corrosion of reinforcing steel bar (rebar) is not well understood. Particularly, fundamental knowledge of rebar corrosion and its interactions with concrete corrosion/cracking is largely lacking. This study investigated rebar corrosion and concrete degradation using reinforced concrete coupons exposed in a pilot sewer system. The physical-chemical corrosion characteristics were investigated in local regions; the nature of rebar rusts was analyzed using the advanced mineral analytical techniques, including Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD); further, the interactions between rebar corrosion and concrete corrosion/cracking were elucidated by characterizing the microstructure and element distribution in interfacial areas using Mineral Liberation Analysis (MLA). The rebar corrosion products were found to be iron oxides, oxyhydroxides, chlorides, sulfides and sulfates. The predominant rebar corrosion reactions varied with exposure time and the development of concrete corrosion. When concrete corrosion reached rebar surface, the cracking of the concrete cover was influenced by multiple effects, including the macro-cracking induced by the corrosion products expansion, and the micro-cracking accelerated by the dissolution, diffusion and deposition of Fe derived from rebar rusts at the concrete corrosion front. A conceptual model elucidating rebar corrosion and the complex interactions between rebar corrosion and concrete degradation is proposed to support the development of corrosion prevention and refurbishment strategies for reinforced concrete sewers.

Hydrogen sulfide is a controlling factor for concrete corrosion in sewers, although its impact on sewer rebar corrosion has not been investigated to date. This study determined the corrosion mechanism of rebar in sewers by elucidating the roles of chloride ions, apart from the effects of hydrogen sulfide and biogenic sulfuric acid. The nature and distribution of rusts at the steel/concrete interface were delineated using the advanced mineral analytical techniques, including mineral liberation analysis and micro X-ray diffraction which is the first-ever use in such studies. The corrosion products were found to be mainly iron oxides or oxy-hydroxides. H2S and biogenic sulfuric acid did not directly participate in the product formation of steel partly covered by concrete or directly exposed to sewer atmosphere. Instead, chloride ions played an important role in initiating steel corrosion in sewers, supported by a thin chloride-enriched layer at the steel/rust interface. Away from the chloride-enriched layer, iron oxides accumulated on both sides of the mill-scale to form a corrosion layer and corrosion-filled paste respectively. The corrosion layer around rebar circumference was non-uniform and the rust thickness with respect to polar coordinates followed a Gaussian model. These findings support predictions of sewer service lifetime and developments of corrosion prevention strategies.

Ore texture displays the fundamental ore properties that significantly influences processing behavior of ores. Of all texture characteristics, mineral grain size and mineral association are expected to have the greatest influence. These textural features can be used to predict the separation performance of ores. To obtain such micro-scale textural information is costly and time-consuming to be applicable to the entire deposit. Recent work has shown the contribution of vein-type mineralization in the separation behavior of ores. Since veins can be identified during core logging, it provides a cost-effective means of acquiring textural information relevant to mineral processing for the entire deposit. This can then improve geometallurgical characterization of separation performance, providing better understanding of separation variability within the deposit.

This paper provides a further investigation of the role of vein structures in the ease of mineral liberation by random masking simulation of breakage. A copper porphyry ore with vein-type mineralisation underwent different methods of sample preparation for liberation analysis. A selected core was cut into semicircular slabs and another core underwent crushing. The slabs and the crushed particles were analysed in the MLA and subjected to simulated breakage from which the liberation of sulphides was determined. The result was linked with the liberation measured from particles of the same ore that have undergone actual breakage. The analysis further provided an indication of the significant contribution of veins in liberation. This information points out to a proper approach of texture and liberation analyses, and the better use of textural data from core scale logging relevant to mineral processing.

This paper describes the role of vein structures to better understand and interpret the origin of mineral liberation based on random masking simulation. An HQ half core from a copper porphyry deposit was selected and was cut into semicircular slabs of 1 cm thickness. Selected slabs were polished for MLA analysis. Classified MLA images were then subjected to image processing to identify and separate the veins from the disseminated grains. Random masking was applied on the images to simulate breakage and generate progeny particles from which liberation of sulphides was determined. Results of the simulation provided an indication of the contribution of veins in the liberation of minerals at coarser size and the increased degree of liberation. The work in this paper also suggests cutting drill cores and using slabs for texture analysis prpvides more intact textural features of the ore both at micro and mesoscale. Particularly, if veins occur to some extent, cutting the drill core into slabs is more suitable to preserve this structure providing a better understanding of the origin of mineral liberation. (C) 2016 Elsevier Ltd. All rights reserved.

The ability to optimise a concentrator from mill feed to final products requires a process simulator that integrates comminution, classification and separation stages. A key part of any such integrated process simulator is the inclusion of a model of mineral liberation in comminution to predict the particle composition distribution of the comminution products. This need was recognised by Gaudin (1939) who proposed a model of liberation based on the cubic fracture of a mineral texture composed of cubic grains of two minerals.This paper describes the development of a texture-based model of mineral liberation that builds on the method proposed by Gaudin. The approach described here, termed the JK-Gaudin Random Liberation model (JK-GRLM) uses as its basis the measured, volumetric mineral texture data that can be quantified for a given ore using X-ray micro-tomography. The textural data required as inputs for the JK-GRLM include the mineral grain size distribution. While the Gaudin model (in common with other existing liberation models) is a two-mineral (or two-phase) system, the JK-GRLM extends the approach to multimineral systems of up to 15 individual minerals, making it more widely applicable.An example of the application of the JK-GRLM to a base metal sulphide ore is provided. In the example the JK-GRLM is used to simulate the breakage of the measured ore texture and the particle composition distributions of the simulated progeny particles are compared to the measured particle composition distributions of ore that has been physically broken.The ability to calibrate this mineral liberation model with measured ore texture will allow it to be applied in greenfield situations where geometallurgical programs measure texture and in brownfield applications as a key part of integrated process simulations. The development of this model enhances our ability to simulate mineral processing operations as an integrated system.

Mineralogical characterisation is typically used to assist in the development of processing strategies for ores. This paper describes the application of mineralogical characterisation techniques in the development of flotation strategies for processing an ore from a low-grade silver deposit that contains a variety of rock types that have undergone hydrothermal alteration where zinc, lead and silver sulphides are typically the primary minerals of economic interest. Comprehensive mineralogical characterisation of the feed, concentrates and tailings from batch flotation tests was undertaken using both the mineral liberation analyser (MLA) and laser ablation inductively-coupled plasma mass spectroscopy (LA-ICP-MS). The results of mineralogical characterisation of the feed (head grade, 116 ppm) indicated that the majority of the silver occurred as solid solution in pyrite which assisted in the development of the flotation strategy used for this ore which resulted in approximately 87% of the total silver being recovered to rougher concentrate at a grade of 485 ppm. (C) 2015 Elsevier Ltd. All rights reserved.

The interaction of two clay minerals, kaolinite and bentonite with gypsum and its effects on the flotation of a copper-gold ore was investigated in this study. It was found that bentonite increased the viscosity more than kaolinite when mixed with the copper-gold ore at low shear rates. The detrimental effect of these clay minerals on flotation was attributed to the entrainment of clay particles when kaolinite was added to the ore and to a decrease in true flotation by bentonite. Bentonite formed a sponge-like structure with predominant edge-edge (E-E) interactions which might affect hydrodynamics in the flotation cell and have a detrimental effect on flotation recovery. Kaolinite did not form a particular network structure and its aggregates mostly consisted of face-face (F-F) type associations which did not affect flotation hydrodynamics. The addition of gypsum to the ore-bentonite mixture inhibited the formation of interconnected network structures. This led to lower viscosity values with flotation behaviour similar to that of mixtures with kaolinite. In this case, there was an improvement in recovery, but the grade decreased due to entrainment. The addition of gypsum to the ore-kaolinite mixture created aggregates with long strings further enhancing particle entrainment with more mass transported to the froth. (c) 2015 Elsevier Ltd. All rights reserved.

The objective of this study was to assess the effect of lime and soda ash as pH modifiers on the flotation of a copper-gold ore mixed with kaolinite at different concentrations. For the flotation experiments air flow rate, impeller speed, flotation time and other flotation reagents were kept constant, and the flotation outcomes were explained by the rheology behavior of the slurries and the type of particle aggregates formed with the addition of either lime or soda ash. Rheology measurements showed that lime increased apparent viscosities more than soda ash, but in Cryo-SEM images it was observed that the kaolinite aggregates in the slurry were similar in structure for both lime and soda ash additions. These two findings suggest that Ca2+ ions released from lime led to the formation of stronger aggregates that were more easily entrained as indicated by the changes in mass recovered to concentrate during flotation experiments. As a result, more dilution of the flotation concentrate grade occurred when adjusting pH with lime. A decrease in concentrate grade was the main negative effect in the flotation of the copper-gold ore mixed with kaolinite with the overall flotation recovery not affected. (C) 2015 Elsevier Ltd. All rights reserved.

This paper describes the results of research investigating the interaction between clay minerals and calcium bearing gangue minerals using rheological measurements. This study was motivated by the high viscosity values observed in a copper–gold ore from which the flotation response of copper and gold minerals was poor and follows on from previous research investigating the effect of pH modifiers such as lime, sodium hydroxide and soda ash on the rheology of clay minerals (Cruz et al., 2013). It was found that Ca2+ ions interacted strongly with kaolinite and illite in enhancing their rheological properties. Gypsum was found to have the highest solubility in water and released the largest quantity of Ca2+ ions resulting in a significant interaction with illite and kaolinite. Calcite and dolomite were found to be less soluble and exhibited a lower interaction with these clay minerals. This study also investigated the interaction of the three calcium bearing minerals with bentonite, a swelling clay mineral. Gypsum had the greatest interaction with bentonite as well but affected the rheological characteristics of bentonite in the opposite way to that observed with illite and kaolinite. Ca2+ ions released from gypsum dispersed bentonite slurries by preventing the swelling of this clay mineral. This study suggests that when looking at ores with clay minerals, it is important to consider the potential input from other gangue minerals for the interactions in determining the rheological behaviour.

Having knowledge of the ore mineralogy and texture can provide valuable information for effective design of a concentrator flowsheet. Specifically, these characteristics help in setting the appropriate grind size to achieve liberation and minimise overgrinding, and assist in identifying suitable flotation parameters to achieve optimum separation. This paper aims to obtain an understanding of the flotation behaviour of an ore by examining its mineralogical and textural features, particularly grain size distribution. Four samples with varying copper recoveries were obtained from different locations in a copper porphyry deposit. The samples were crushed to 4 mm and measured using a Mineral Liberation Analyser to determine the mineralogical characteristics of each. The mineralogical characteristics that were found to vary included: copper deportment and grain size and copper mineral association. This information was used to interpret batch flotation behaviour particularly copper recovery. (C) 2015 Elsevier Ltd. All rights reserved.

Recent advances at JKMRC in modelling mineral liberation required the development of a method to measure ore textural characteristics such as the mineral grain size distribution and the spatial location of mineral grains in three dimensions.This paper describes the development of this method which uses X-ray micro-tomography to provide three-dimensional (3D) measurement of the grain size distribution and spatial location of the minerals in an ore. The methodology was developed on a gold-bearing pyrite ore and used to quantify the textural characteristics which are key inputs for modelling mineral liberation in this ore during comminution. The measurement and image processing steps required to quantify the grain size distribution of the mineral of interest, pyrite, are described together with the image analysis method. The quantification of 3D mineral characteristics together with corresponding two-dimensional (2D) sections through the same particle, provided the opportunity to explore the relationship between 2D and 3D grain size data. (C) 2015 Elsevier Ltd. All rights reserved.