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By M A. Jardine, J A. Miller, M Becker, M Harris

"Although the role of texture has been increasingly recognised as a geometallurgical indicator of ore characteristics and their variability, the ability to appropriately quantify and correlate it with metallurgical performance remains an ongoing challenge. In this study, we propose the 3D characterisation and quantification of ore textures from drill core using X-ray computed tomography (XCT) with an appropriate image analysis methodology (grey level co-occurrence matrices, GLCM). This methodology has been specially customised for application of 3D XCT grey-scale volumes. This approach has potential as an online mine site analysis tool providing detailed 3D information on both quantitative texture and simple mineralogy.The approach is illustrated in this paper using drill core samples that were manually extracted from various rock types and textures representing the Nkomati Main Mineralized Zone (MMZ) sulfide nickel ore deposit. A preliminary classification of the samples was performed based on their particle size distribution after laboratory scale rod milling. Accompanying QEMSCAN analyses were also used to guide the interpretation of the grey-scale mineralogy and texture in the 3D XCT volumes. The resultant GLCM produced from quantitative 3D image analysis of the XCT volumes indicated sensitivity to ore variability and was able to capture a simple mineralogy and grain size distribution. The approach holds many possibilities for geometallurgy, of which the potential for automation is promising.CITATION:Becker, M, Jardine, M A, Miller, J A and Harris, M, 2016. X-ray Computed Tomography – a Geometallurgical Tool for 3D Textural Analysis of Drill Core?, in Proceedings The Third AusIMM International Geometallurgy Conference (GeoMet) 2016, pp 231–240 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jun 15, 2016

By P Breuer, D J. Robinson, A McFarlane, L L. Kuhar

Increasing global demand for commodity metals and capital and the greater operating costs of mining and metal production present significant challenges for the metals mining industry. Current conventional technologies may not be feasible for processing deposits of declining grade, challenging mineralogy or those that occur at increasingly greater depths. To overcome these issues, the development of a step-change technology such as in situ recovery (ISR), which reduces mining and avoids milling costs, may be vital in ensuring future economic metal production. ISR has been used extensively to treat porous soft rock deposits such as the water-soluble salts, sylvite and halite. Although ISR has typically been used for mining conventionally uneconomic uranium ores, it has also been used less frequently for the treatment of other restricted permeability hard rock deposits, such as those containing copper and gold. The reason for the limited uptake of the technology for hard rock mineralisations is primarily due to low natural rock porosity and permeability and hence poor response to available lixiviant. However, additional challenges include solution containment, management of groundwater and regulatory, ecological and societal requirements and expectations. CSIRO has focused on understanding the challenges of hard rock ISR and identifying global capabilities that can contribute to developing the essential enabling technical areas required to realise ISR. Specific focus areas include geochemistry and advanced resource characterisation; drilling and controlled rock-breaking technologies; solution chemistry and environmentally benign lixiviant systems; lixiviant delivery systems and ‘subsurface mixing’; subsurface hydrology and reactive transport mechanisms and models; downstream processing options; legal, social and environmental aspects; and techno-economic modelling. This paper will discuss ISR challenges including industry feedback focused on addressing this issue, gaps preventing ISR from being applied in practice, capabilities to overcome these gaps and the development of a collaborative approach to making hard rock ISR a reality.CITATION:Kuhar, L L, Breuer, P, Robinson, D J and McFarlane, A, 2015. Making hard rock in situ recovery a reality, in Proceedings Third International Future Mining Conference, pp 189–196 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By J Cortinez, P Vallejos, J Yianatos, M Rodriguez

Nowadays, one of the main problems in current flotation plants and new projects is the significant decrease in feed grades and changes in the mineral composition, which has an important effect on the mineral liberation and associations. Additionally, flotation plants usually operate with feed throughput higher than the original design, which has a significant impact on the feed particle size. All these conditions affect metallurgical performance, and must be evaluated and addressed, by improving control strategies for banks optimisation. For this purpose, the flotation of valuable minerals along the circuits requires better understanding, considering the compromise between performance and selectivity in flotation circuits. This paper presents a characterisation of the different minerals recovered along industrial flotation circuits. Plant sampling campaigns, performed in a copper industrial concentrator in Chile, provided the data for the study. Two rougher flotation banks consisting of cells of 130 m3 and 300 m3 were analysed. All the samples from the industrial surveys were analysed by screening and mineralogy, and the mineral recovery along the circuits was evaluated per particle size class, liberation class, type of associations, and others. Additionally, operating data on froth depth profiles complemented the evaluation of the mineral composition of concentrate streams, along the circuit. The results allowed for identifying and quantifying the main factors that affect the copper recovery and concentrate grade along the flotation banks. It was found that minerals with liberation lower than 50 per cent have a significant impact on the recovery. On the other hand, the decrease in the Cu grade in concentrates along the flotation circuits is mainly due to the relative increase of middling minerals (less liberated), non-valuable floatable minerals, such as free pyrite, and gangue entrainment. The characterisation of the gangue entrainment flow rate along the flotation banks showed a strong relationship with froth depth, which becomes more critical towards the last cells of the banks.

Aug 24, 2022

Brand se Baai, on the North-Western Cape Coastline of Southern Africa, is the site of the Namakwa Sands Limited Heavy Mineral Sands Mining Operation. The mine is a 14 000 000 tonnes per annum open-cast strip-style mining operation using truck and excavators to mine the sand. The orebody consists of relatively unconsolidated sands reworked by fluvial, marine and aeolian mechanisms. The total orebody includes three primary ore types, namely the Red Aeolian Sands, the Dorbank (a hardcap layer) and the Orange Feldspathic Sands, which forms the bulk of the resource. Mine planning and scheduling is done using a 50 m + 50 m variable bench height system with three primary bench heights. The Aeolian and Dorbank each have a bench that varies with their thickness of up to a maximum eight metres and the Orange feldspathic sand, a standard bench height of eight metres. For a number of years Namakwa Sands used a complex 2D, Datamine Based, macro system to perform the resource evaluation and mine design. As the mining operations expanded it became clear that a complete system redesign was required to cope with the increasing operational pressures coming to bear on the old system. The biggest challenges facing any replacement system are the sheer scale of the mining operation (16 km long and 7 km wide resulting in a minimum of 30 000 individual 50 m + 50 m mining blocks), the size of the geological data files (up to one gigabyte) and representing the benching system accurately (as the benches follow the topography and are not horizontal). In addition to these large-scale issues, the ability to run multiple mine design scenarios was required, an aspect which the old system was unable to perform adequately. Based upon these primary difficulties, a new business process was developed which required a complete rethink of the mine design methodology as well as the creation of a new system to deplete the resource model, produce monthly reconciliation evaluations and create a ultimate pit limit based on the operations mining cost model. Using a system based on the Earthworks Mine2-4D Mine Design and Scheduling System (with its mine design and scheduling specific tools), as well as a small, customised program, massive time-savings have been made. It is now possible to run several life of mine scenarios in the same timeframe that a single life of mine run took under the old system. This paper will present the methodology and business decisions behind the new Namakwa Sands system, and detail the restructuring and development used to deal with the large data set sizes and long processing times inherent in the old system. Future enhancements to the system that will make it more generically applicable to open-cast mining scenarios will also be dealt with.

Jan 1, 2003

By L C. P J Fonteneau, B Godel, E R. Ramanaidou

The Hamersley Province in Western Australia hosts large iron ore deposits. Each deposit displays various iron ore types that were defined on their metallurgical properties, especially in terms of porosity and mineralogy. Conventional porosity and mineralogy information on iron ore types are provided on 2D thin sections using automated image analysis with scanning electron microscopy (SEM)-based techniques combined with chemical analyses. However these techniques cannot accurately quantify the 3D porosity. High-resolution X-ray computed tomography (HRXCT) is a non-destructive technique providing a 3D image of the sample with a resolution close to 0.5 - 0.7 ¦m for samples size of up to few centimetres in length. 3D image analysis using customised algorithms now provide accurate quantitative porosity and mineralogy of iron ore types.CITATION:Fonteneau, L C P J, Godel, B and Ramanaidou, E R, 2013. Application of high-resolution x-ray computed tomography to iron ore characterisation, in Proceedings Iron Ore 2013 , pp 243-250 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By J Zhou, D M. Hunter, S M. Iveson, K P. Galvin

The recovery and concentration of ultra-fine iron ore can provide significant economic benefits. Presently, there are limited options available given the low settling rates achieved by conventional gravity separation and the relatively poor performance of reverse flotation. The Reflux Classifier is a new water-based gravity separation technology that consists of a set of parallel inclined channels positioned above a vertical fluidised section. This arrangement promotes a powerful throughput advantage compared to conventional fluidisation and a highly selective hydrodynamic basis for achieving sharp separations. A high shear rate develops within the inclined channels, which generates sufficient hydrodynamic lift to convey the lower-density particles (even if they are relatively coarse) to overflow while retaining the high-density particles (even those that are ultra-fine) for discharge to the underflow. The technology has previously been used around the world on particle sizes in excess of 0.1 mm. The present work, however, is concerned with density-based separations down to much finer particle sizes approaching 0.01 mm.A major advantage of the Reflux Classifier technology is the achievement of simultaneous gravity separation and desliming via a single-stage separation. A series of continuous experiments was conducted using an iron ore feed with head grade of 35 wt per cent FeT and nominal top size of 0.106 mm, with 59 wt per cent being below 0.038 mm in size. At a low throughput of 1.5 t/(m2 h), the Reflux Classifier produced high-grade products at a high recovery. For the entire feed, grades of 66.1 wt per cent FeT with Fe recoveries of 80 per cent were achieved in a single-stage separation. Within the 0.020–0.038 mm size fraction, grades of 68.8 per cent were achieved with iron recoveries of 94.7 per cent. Excellent recoveries of up to 57.0 per cent were achieved for the -0.020 mm size fraction. The ability of the inclined channels to retain the fine dense material further enhances the effectiveness of the Reflux Classifier by creating an autogenous dense medium effect within the vertical section. This helps to elevate large gangue particles up into the overflow.CITATION:Hunter, D M, Zhou, J, Iveson, S M and Galvin, K P, 2015. Gravity separation of ultra-fine iron ore in the reflux classifier, in Proceedings Iron Ore 2015, pp 143–148 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By D Adhikary, M Khanal, B Poulsen, H Guo

During longwall mining, the ability to reliably estimate the height of longwall mining-induced fractures is critically important in order to effectively manage mining-induced water inflows and aquifer interference. The extent of mining-induced subsurface deformation, fracture, surface subsidence and aquifer interference is largely controlled by local lithological conditions, mining methods and mine layouts. Therefore for the purpose of quantifying mining impacts it is imperative to incorporate the local geology and mine plan parameters in a mine scale model. Two different numerical models based on 3D continuum (Finite Element Method) and 2D discrete (Discrete element method) domains, respectively, are developed to incorporate the mine site parameters of a study site in Australia. Both the models are calibrated and validated with measured mine data. The continuum numerical modelling method is used to investigate the change in permeability of the overburden strata due to underground extraction considering the full 3D nature of geology and mine layout. The discrete element modelling method is used to simulate the initiation and propagation of fractures, allowing the caving of overburden strata to be represented in a realistic manner, and the permeability enhancement of the strata overlying the goaf to be calculated from first principles. Permeability enhancement in the discrete element model is a direct function of the fractures induced in the deformation/caving process; fracture location, extent, aperture and connectedness. From the numerical modelling under the simulated condition for the mine studied here, it is predicted that the permeability of the caving zone from the goaf to five times the mining height increases by almost six orders of magnitude. In the fracture zone to approximately ten times the mining height, the change in permeability is predicted to be around two to three orders of magnitude. At the height of more than ten times the mining height the magnitude of permeability increased is predicted to be one to two orders of magnitude. CITATION:Khanal, M, Poulsen, B, Adhikary, D and Guo, H, 2018. Modelling of height of connective fractures during longwall mining, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 254–265 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

By D Joshi, J Rostami, M Karakus, A Eustes

The first target of mining activities on the surface of the moon is to find and extract water from the icy regolith on the moon. A test drilling unit was designed and fabricated under a NASA Early Stage Innovation (ESI) grant. A high-frequency data acquisition system was used to record drilling responses at 1000 Hz. Parameters like weight on bit (WOB), torque, rev/min, rate of penetration (ROP), mechanical specific energy (MSE), field penetration index (FPI), and the uniaxial compressive strength (UCS) were recorded for 40 boreholes in the analog samples made of regolith simulant and specialised cement. Development of the AI system and machine learning (ML) algorithms for analysis of data to evaluate strength and hence water content of icy regolith required a large data set. In this case, the data set comprising of more than one billion data points recorded while drilling into various analogue samples and cryogenic lunar formations to optimise power consumption and make bit wear adjustment during drilling operations. The tests were also repeated in the samples of icy regolith at various water content at -190C to verify the ability of the algorithms to analyse the data and to estimate the strength of the frozen formation and hence water content. The paper will discuss the objectives and methodologies used in the project and reviews the testing program and the machine learning (ML) algorithms ability to identify various formations along the exploration boreholes.

Sep 1, 2024

By D C. Ford

The Argyle AK1 orebody was discovered in 1979 and subsequently found to be a large, economically viable reserve with high grade diamondiferous ore. Production began via an open pit operation at the end of 1985 and has continued for some 25 years to present day. This, however, will come to an end in the next few years with production moving to an underground operation via block-cave mining methods.A series of studies from 2001 - 2005 was carried out; diamond drilling commenced after approval in 2006, from an exploration drive to determine the likelihood of the current proposed block cave operation.In 2006, development of the block cave project began, in order to realise the part of the orebody below the extent of the open pit mining operation.Development of the block cave technique, comprising an undercut level beneath the target zone of the orebody with subsequent extraction level 15 - 20 m beneath, relies largely on a number of block-caving parameters (hydraulic radius, rock type, structure and orientation of stress and grade of the orebody). These all have an influence on cave ability and eventual profit of the operation. Evaluation of further potential for taking this orebody beyond the block cave phase with options such as sublevel-caving are being considered for the UG-2 portion of the resource/reserve. Diamond drilling for this work is currently under revise.The challenges faced in transitioning form the surface operations to the underground, comprising a changing workforce, converging development drives, underground aquifers, major excavations and transportation of ore via automation are intriguing.

Aug 22, 2011

By P M. Cepuritis

In hard rock mining, large-scale bulk mining methods such as block or panel caving (BC/PC) and sublevel caving (SLC) typically generate significant surface deformations such as subsidence. Surface deformations need to be considered in the project evaluation and planning stages of cave mines, for example, planning and location of critical underground mine planning infrastructure such as portals, haulage and vent shafts, access roads, or potential damage to existing infrastructure, changes to surface water management, waste dump, stockpile and tailings dam stability, and environmental impacts. Assessing the impact and risks associated with subsidence is a key component in robust mine planning and operations management.

Nov 29, 2022

Batch centrifugal gravity concentrators have become standard equipment in gold grinding circuits for recovery of gravity recoverable gold (GRG). The downstream benefits of installing a gravity circuit are well understood, and in general, if there is a reasonable amount of GRG in the ore, a gravity circuit is usually installed. The benefits of gold gravity recovery have also been well documented, with a large database of successful case studies. As well, predicting production scale gravity recovery results ahead of installing gravity has become a common practice. The missing link between lab and full scale has always been the ability to predict the recovery benefit of installing gravity ahead of actually doing so. Being able to predict the recovery benefit in advance would help an operation in assessing the economic benefit and help justify the capital costs of the gravity circuit with much less uncertainty.

Aug 1, 2010

By B Beale

Bow-tie analysis is a commonly used tool in the Major Hazard Facility sector to identify, display and control risks that have the potential to pose serious harm to personnel. It is a simple but powerful risk management tool that displays traditional risk assessment outputs as easily interpreted ‘bow-tie diagrams’. These are an effective and versatile communication format that can be applied to any type of risk (eg safety, environmental, assets etc) and as such show great benefit in managing operational hazards in mining.

May 5, 2022

The history of the down draught Dwight- Lloyd system of iron ore sintering in Australia is developed. Characterisation of the broad process is given for one plant, and regional divergences from the reference practice are noted and briefly analysed. The subject of the development of high basicity sinters is introduced, and regional differences in approach and results are Examined.

Jan 1, 1972

By H Kundapen, B R. Bolton, H Davies

The Ok Tedi porphyry copper-gold mine is located in the Star Mountains of Western Province, Papua New Guinea. Open-cut mine commenced in 1984 and is due to cease around 2010. The mine produces a total of 88 Mt of waste annually including 58 Mt overburden and 30 Mt tailings, which are discharged directly in to the Ok Tedi River. Mine derived wastes are transported downstream and deposited within the river channel in a variety of bar forms. The prevailing hydrogeological conditions including, velocity, competency, capacity, gradient, grain size and specific gravity, control the deposition and segregation of these sediments. Periodic exposure of the reactive sulfides to oxygen during fluctuations in the river discharge may result in oxidation, localised acid generation and liberation of metals into solution. To evaluate the significance of this issue, Ok Tedi Mining Limited initiated an investigation of the sediments deposited in the upper Ok Tedi River as part of its overall ARD Management Program. The specific objectives were to: evaluate the acid-forming characteristics of identified high sulfide river deposited sediments; characterise geochemically the waters in contact with sulfide-bearing river deposited sediments; map and monitor exposure areas and oxidation depth of deposited potentially acid forming (PAF) sediments; determine the depositional processes controlling sulfide distribution; and assess lag period, oxidation and metal release rates for the sediments. This work included the analysis of sediment and water samples collected on a 50 + 50 metre grid at six gravel/sand bars. The sediment samples were analysed for total sulfur, ANC, NAG, total sulfur and total copper. Water samples were tested for general water quality parameters, sulfate and a suite of dissolved metals including; Al, Ca, Cd, Cu, Fe-sol, K, Mg, Mn, Na, S and Zn. This paper presents the results of these investigations with particular emphasis on the geochemistry of the river sediments and associated contact waters.

Jan 1, 2003

Reconciliation involves the collection of tonnage, grade (quality) and contained metal (product) data from disparate and hopefully independent sources. Examples are exploration data, production sampling data from blastholes or drawpoints, and process plant data. These data may be compared by means of ratios (factors). The F1 factor usually relates short-term (ore control) model tonnages, grades and metal content to ore reserves depleted. The F2 factor usually relates received-at-mill tonnages, grades and metal content to delivered-to-mill = production tonnages, grade and metal content. The F3 factor is F1 × F2 and enables a comparison of a mineÆs ability to recover the tonnage, grade and metal content estimated in ore reserves. The F1 factor measures the accuracy of orebody knowledge in the ore reserves to the demarcation of ore and waste by ore control (short-term model). The F1 factor may be used to check and calibrate the selectivity of mineral resource models and/or planned dilution assumed in transfer from mineral resources to ore reserves. The F2 factor enables a check on unplanned dilution entering the ore stream between ore control and the mill. Using the factors it is possible to calculate a monetary value on improvements in the accuracy of orebody knowledge, selectivity and the effects of dilution and ore loss. Reconciliation should be an implicit part of the mining process, and reconciliation targets should be a key performance indicator for well-run mines.

Sep 26, 2011

By D François-Bongarçon

The link between geostatistics and Theory of Sampling (TOS) is examined again in view of new findings made while trying to compare predicted sampling variances and estimated grades (using geostatistics) on the same material, and this provides an important consistency requirement whenever calculations are made that involve both theories in a comparative way. It also briefly explores the relationship to De Wijs fractal model of mineralisation and eventually provides new support for the use of consistency theory for calibrating TOS variance formulas.CITATION:François-Bongarçon, D, 2017. Theory of Sampling and geostatistics – the ultimate link, in Proceedings Eighth World Conference on Sampling and Blending , pp 391–394 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By J Andrina, D Richar, R Smart, A Neale

The Grasberg is a large copper and gold open pit mine operated by PT Freeport Indonesia and located in the high equatorial mountains of Papua Province, Indonesia. The climate is alpine/sub-alpine with little seasonal variation in temperature and rainfall. The annual precipitation varies from about 3000 to 5000 mm over short distances around the Grasberg, but in general, an average daily precipitation of 10 mm per day applies and leaching of the overburden is continuous throughout the year. Mining commenced in 1988, and almost all of the overburden mined up to 2003 was potentially acid forming. From 2003 to the end of the Grasberg pit operation in 2014, approximately 70 per cent of the overburden will be potentially acid forming and 30 per cent limestone. A major focus of the investigations is developing strategies to maximise the beneficial use of the limestone that will be mined. Laboratory columns and field test pad investigations have been ongoing for six years examining limestone blends. Trial dumps utilising truck placement and conveyor/stacker placement and blending of limestone and acid generating rock have recently been constructed. In addition, based on initial results, investigations aimed at further evaluating the performance of limestone covers in this high rainfall environment have commenced. A significant finding has been the identification of strong armouring layers on sulfide surfaces within well-blended material and under limestone covers. These layers effectively isolate sulfides and thus progressively slow the oxidation rate to a level where the alkalinity load from the limestone exceeds the rate of acid generating. ARD is controlled and neutral low metal drainage results. The results have demonstrated that although limestone blending is effective, it is necessary to ensure that all size fractions within the blend receive adequate acid neutralising capacity to buffer the potential acidity. Because the sulfur content generally increases and the acid neutralising capacity decreases with decreasing particle size in limestone blends, the amount of limestone required greatly exceeds the stoichiometric requirement. This paper describes the development of limestone blending specifications for potentially acid forming overburden and presents the results of the ongoing limestone cover trials at the Grasberg mine.

Jan 1, 2003

By T Baumgartl, M Edraki, L Huang, D R. Mulligan

"Phytostabilisation with tolerant plant species has been advocated as a cost-effective solution for sustainable cover of tailings from metal mines and bauxite refinery. The development of sustainable plant ecosystems on such wastes requires not only tolerant plant species compatible with local climatic conditions, but also the formation of stable and functional root zones through systematic processes to develop functional soil matrix and horizons (eg A-B-C). However, the process requirements for reconstructing functional root zones in tailings are poorly understood. Based on a review of current literature and industry experience in tailings revegetation, the present paper conceptualises three key phases in the process of root zone development in amended tailings: hydro-geochemical stabilisation resulting from the interactions among tailings characteristics, amendment measures and local climatic conditions the rehabilitation of soil biological capacity the establishment of ecological (carbon and nutrient) linkages between the rehabilitated root zones and the above ground plant communities.Key research is required on: the relationship between hydro-geochemical stability and mineralogy and geochemistry of tailings, in response to rehabilitation treatments under local climatic conditions the relationship between soil biological capacity and hydro-geochemical stability in the root zone the transition of soil microbial communities specific to exogenous organic matters into those required for mineralising litters of in situ plant communities.CITATION:Huang, L, Baumgartl, T, Edraki, M and Mulligan, D R, 2012. Sustainable phytostabilisation of mine tailings - A critical analysis of system requirements and approaches, in Proceedings Life-of-Mine 2012, pp 105-116 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 10, 2012

By C Lutherborrow

The Sangdong Tungsten/Molybdenum Deposit is located in the Republic of Korea and was discovered in 1916. At this time Korea was a colony of Japan. It was mined for two years after discovery closing in 1918. Full production recommenced in 1933, and from that point until 1945, it was the major source of tungsten for armour plate for the Japanese military. After World War 2 the US government ran the mine until late 1946. The mine operation then passed to Korean ownership but production ceased during the Korean War and did not recommence until late 1953. The mine ceased operation in 1992 due to low metal prices. From the late 1960s to the time of closure, Sangdong was the largest tungsten mine in the world (Kim, 2002). An understanding of changing mining methods over time has been critical in assessing the potential of redeveloping the Sangdong Deposit.

Aug 22, 2011

By Pollard D. M

Chalcopyrite samples from two different localities were leached in oxygenated mixed chloride-sulphate lixivants at elevated temperatures and atmospheric pressure. The oxidation of chalcopyrite was found to follow predominantly linear kinetics. The slope of the major region was dependent on stirring rate, oxygen flowrate and chloride concentration while only slightly dependent on the surface area of the sample leached. This region was found to predominate only at low temperatures. The oxidised chalcopyrite releases cuprous and ferric ions into solutions. Chloride ions complex these dissolved ions to effectively move the equilibrium of the leaching reaction to the right. When the level of chloride in solution was below 6 g/l, the unstable cuprous ions were found to reprecipitate with sulphur as covellite. When no chloride was present and the lixivant was a solution of sulphuric acid then ferric sulphates precipitated. The overall leaching reaction occurring in the leaching system is: CuFeS2 + 5H+ + 1.25 02 = Cu 2+ + Fe 3+ + 2S¦ + 2.5H20

Jan 1, 1987