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By Will Callupe Arzapalo

The success of the minimization of blast induced-damage at Barrick?s Pierina Mine in Peru is the result of an effective working relationship between Mine Operations and the Geotechnical Services Department. A detailed design criteria manual is used to match the blast plan to the site?s varying rock types and slope designs. The Geotechnical Services Department has further developed a comprehensive pre- and post-blast checklist that is critical to the drilling and blasting process as it pertains to wall stability. Wall control blasts are evaluated with quality assurance field checks, vibration monitoring and frequency control, video assisted performance quantification and post excavation face profiling. These detailed observations are compiled and summarized in a blast performance evaluation that is considered to be an ?Industry Best Practice?. The information and detail provided by each performance summary allows accurate blast analysis and effective design refinement.

May 1, 2006

By A. Yaghini, Y. Pourrahimian

"Human factors (HFs) play an important role in the mining and mineral industry, affecting operational and maintenance efficiency and safety. Despite the introduction of new technologies and automation in this sector, it is well known that a significantly large proportion of total human errors occur during the operation and maintenance phase. A comprehensive literature review of HFs across several industries is provided. From this review, the impact of HFs on operation and maintenance is summarized, with a focus on what the mining industry is currently doing and what opportunities exist for additional improvements. Future research directions and themes are also identified.RÉSUMÉ Les facteurs humains (FH) jouent un rôle important dans l’industrie des mines et des minéraux, en ce qu’ils affectent l’efficacité et la sécurité de l’exploitation et de l’entretien. Malgré l’apparition de nouvelles technologies et de l’automatisation dans ce secteur, il est bien connu qu’une grande partie des erreurs humaines (EH) se produisent durant une phase d’exploitation et d’entretien. Cet article propose une analyse documentaire approfondie des FH dans plusieurs secteurs. L’impact des FH sur l’exploitation et l’entretien est résumé à partir de cette analyse, une attention particulière étant accordée à l’évolution de l’industrie minière et aux possibilités d’améliorer davantage ses activités. Sont également identifiés les futurs thèmes et voies de recherche.INTRODUCTIONDuring the past several decades, the mining industry has focused on improving equipment, machinery, and methods that have led to more advanced hardware and software, equipment with higher reliability and productivity, and other technological advancements. These actions have improved safety and productivity and have reduced casualties and maintenance workload. Although today’s mining equipment and machinery are technologically advanced and highly reliable, the risk of accidents is still relatively high and key performance indicators have not improved significantly compared to other industries (Sorensen, 2012). A prominent reason could be due to insignificant integration of human factors (HFs) as part of planning, operation, and maintenance activities. The current mining system is a people system, and inevitably HFs and human error (HE) figure prominently in all aspects of this industry. Even the most advanced technologies and innovations require operators and maintainers with significant knowledge and skill, which could increase the potential for HE."

Jan 1, 2018

By J. G. Henning

Following completion of planned mining operations at the Goldcorp Dome Open Pit Mine, a high-grade Shaft Pillar located in the pit highwall was recovered. Mining of this Shaft pillar faced numerous rock engineering design and implementation challenges due to its remote position on the highwall and the presence of mine workings within the wall. The case example presented in this paper discusses the geotechnical investigation performed at the site, novel measures undertaken for installation of ground support required for rockmass reinforcement and for worker protection, as well as operational challenges to successful mining of the Shaft Pillar.

May 1, 2009

By L. E. Djingheuzian

Introduction Cylindrical grinding mills have been used for a long time, but during many years of testing no methods were established that gave consistent results. The work by both scientific investigators and operators led very often to contradictory conclusions, and each millman was very much 'on his own' when trying to find the limits for working of his ball-mills. Fred C. Bond, in the introduction to his paper on Wear and Size Distribution of Grinding Balls, freely states that the mathematical immaturity of the grinding process "is the cause of many inefficient designs and installations as well as of much poorly oriented experimental work", and evidently he sees the solution of all our grinding problems in the discovery of the fundamental laws "which can change the empirical art into a mathematically exact science". While the writer is in complete agreement with Mr. Bond that grinding is governed by fundamental laws which can be expressed by mathematical formulae, there are so many variables in grinding, all interwoven with each other and mutually influencing each other, that the coalescing and merging of all these variables into a harmonious mathematical whole appears to be a homeric job. However, a light appeared on the horizon when it was proposed that power be used as an index of the grinding operation. It is pertinent to quote Gow, Guggenheim, Campbell, and Coghill from their paper on Ball Milling, in which they say: "Much of the past literature devoted to the subject has been concerned with the Kick-Rittinger dispute over evaluating grinding, or with dissertations on ball paths and the closely allied impact versus attrition hypotheses or with the exclusive consideration of certain specific variables, such as mill speed or circulating load, irrespectve of the other factors in operation. Such subjects may be dismissed with but little discussion in what may be called, by comparison a new philosophy in the stud of ball milling. Briefly this 'new philosophy' consists ' of using power as an index of the mill operation, and investigating grinding from the standpoint of set and induced variables with emphasis on the latter". But it is safe to assume that it was the work by E.W. Davis, H. E. T. Haultain, F. C. Dyer, A: M. Gaudin, J. Gross, S. R. Zimmerley, and others, that cleared the path for the authors of Ball Milling and induced them and A. W. Fahrenwald to look farther afield and thus to establish a far-reaching relationship between the power and capacity and the diameter of the ball-mills.

Jan 1, 1949

ABSTRACT Understanding process histories and worker exposures in nickel production operations is critical in determining the role nickel compounds play in respiratory cancer incidence. As part of a series on Vale Canada’s (previously known as Inco) nickel processing operations, this paper includes descriptions of Ni electrolytic operations at refineries in Port Colborne, Ontario (1922–1984), and Thompson, Manitoba (1961–present). Industrial hygiene measurements, by area and personal sampling, of workplace aerosols at these operations are reported.

Jan 1, 2014

By G. J. Reid, D. H. Stewart

"A diversity of structures and rock types in the Aft on pit has resulted in the occurrence of several different types of wall failure. Delivery of ore to the mill has not been affected and safety has not been compromised thanks to effective remedial 1V0rk and to a system of structural mapping, back analyses of failures, groundwater monitoring, and simple movement monitoring. Remedial measures have included artificial support, dewatering (including vacuum-assisted drainage), flattening of slopes and temporary buttressing. This paper describes six different wall failures at Afton and highlights the features of each. Examples given include rates of movement, extent and direction of movement, and piezometric responses. The practical, low-cost monitoring system was sufficient in one case to allow the prediction of date of failure. IntroductionThe Afton copper deposit is located 13 km west of Karnloops, British Columbia and has been mined for nine years out o f an expected eleven-year life. Open pit mining has reached 700 feet below sur face and is designed to proceed to 970 feet below surface by the time the pit is completed. The excavation is in a structurally and lithologically complex environment. Inevitably, some wall failures have occurred but these have been limited to small, manageable failures which have not compromised production or safety. To handle the failures it has been necessary to understand their nature. Of prim e concern has been the rate s of movement, but displacement vectors and hydrology have been monitored as well. The monitoring system is based on EDM surveys and on wire extensometers and plates set across cracks. Water levels have been read in standpipe piezometers. At Afton the emphasis has been on simple, practical, and inexpensive monitoring and because rock type s and structures play such a major role in any failure, detailed geologic al mapping is carried out."

Jan 1, 1988

By R. S. Rogers

Abstract - Forensic geology in a mineral exploration context is concerned with geology and related technical matters as they pertain to legal cases involving exploration and evaluation of mineral properties. Such cases involve the possibility of outright scams that include falsification of data and information, as well as inappropriate application of various technical procedures. Experience in forensic geology in such cases emphasizes the need for systematic quality control procedures during routine exploration/appraisal and indicates the need for more attention to ‘target hardening’ (improving security in the chain of custody of samples and assay results). A number of ‘early warning signs’ that might suggest some form of tampering or falsification of information are listed. These measures will support the work of the "Qualified Persons" (geologists and engineers) entrusted with the scientific and technical aspects of mineral exploration, and facilitate the increased attention to regulatory oversight and enforcement of securities laws recommended in the report "Setting New Standards."

Jan 1, 1998

By John Jiang, Brian R. Hart, Stamen S. Dimov, Aparup Chattopadhyay, Barun K. Gorain

"This paper presents a systematic approach to metallurgy diagnostics using an integrated gold deportment methodology developed for complex refractory gold and copper-gold ore bodies. Quantification of gold deportment for these ore bodies is a challenging task due to reasons such as lower grades, high variability of visible and invisible gold content in different sulphides and iron oxide phases, significant presence of disseminated and composite carbonaceous matters along with associations of various copper sulphide phases. Some case studies are presented in this paper to demonstrate the value of a high confidence gold deportment methodology in developing insights for problem diagnostics and to identify opportunities for metallurgical improvements. A holistic approach involving different fields of expertise is critical for successful development and delivery of solutions for complex ore bodies.INTRODUCTION Studies were initiated on various complex ore deposits and also on samples representing various process streams. These complex copper-gold single refractory, double and triple refractory gold ores are mainly composed of silicates and/or carbonates with moderate amounts of clay and mica, along with minor amounts of sulphides and organic carbonaceous matter. Variable proportions of visible gold and “invisible gold” (sub-microscopic gold) were noted in different mineral phases for various ore types and process stream samples. Invisible gold commonly occurs as solid solution or as colloidal-sized particles in different sulphides and other phases for different refractory ores. The dominance of invisible gold and presence of highly preg-robbing along with finely disseminated carbonaceous matters adversely affects gold recovery in flotation and leach circuits for most of these double and triple refractory ores. This paper discusses applications of an integrated gold deportment technique developed for different types of gold and copper-gold ores, namely, complex copper-gold, double and triple refractory gold ores (Chattopadhyay & Gorain, 2014; Chattopadhyay et al., 2016). Various process streams from flotation and gold leaching circuits were investigated. Different concentrates and tailings samples from flotation circuits whereas feed and discharges from pressure oxidation (POX) and carbon-in-leach (CIL) residues were used from gold processing circuits."

Jan 1, 2017

By Xian Jian Guo, Lei Li, Hua Wang

Direct smelting of copper concentrate to blister copper has the advantages of energy saving and environmental protection. There has been a lot of effort invested in process development including test work and theoretic analysis in the past half century. However, the process has only been applied commercially to a few smelters that treat chalcocite types of copper concentrate. The main limitation to treating chalcopyrite types of copper concentrate is high copper content in smelting slag and low direct copper recovery. Thus intensive slag cleaning is needed. In this paper, the thermodynamic analysis was mainly carried out for the multiphase equilibrium of direct to blister copper smelting for both chalcopyrite and chalcocite concentrates. The practical problems in direct to blister copper smelting, which are mainly in copper content in slag, are clarified. The operational window of slag composition for different temperatures and oxygen partial pressure for the treatment of chalcocite type concentrates is identified. The process operation optimization for the blending of chalcocite, pyrite and chalcopyrite concentrates was done. INTRODUCTION The extractive metallurgy of copper can be divided into two broad groups of processes, namely, pyrometallurgy and hydrometallurgy, and the former is dominant. About 80% of copper in the world is produced by pyrometallurgy (Christopher et al., 2006). The first stage of conventional copper pyrometallurgy processing is to smelt copper concentrate to copper matte composed of FeS and Cu2S with slagging to remove a proportion of the iron (Gargul, Boryczko, & Bukowska, 2017). The smelting processes include bath and flash smelting. The second stage of the process is to convert copper matte to blister copper. In most cases, the copper matte is converted in Peirce Smith (P-S) converters, which are batch operations (Kubiszewski, 2015). The P-S converting can be divided into two periods, slagging and copper blowing. During slagging period, FeS in copper matte is oxidized to FeO, which reacts with silica flux forming slag. When the iron content in matte is less than 1%, copper begins to oxidize and reduce to form blister copper (Kucharski, Sak, Madej, Wędrychowicz, & Mróz, 2013).

Jan 1, 2019

By W. G. Miller

An overall study was conducted to evaluate the properties and processes influencing the rate and magnitude of consolidation for oil sands fine tailings produced using different extraction processes. As part of this overall study, consolidation tests using slurry consolidometers were carried out for caustic and non-caustic fine tailings. The influence of a change in bitumen extraction process (caustic versus non-caustic) on consolidation properties, namely compressibility and hydraulic conductivity, was determined, as was the effect of adding a coagulant (calcium sulphate [CaSO4]) to caustic fine tailings. For fine tailings originating from two different oil sands ores (Ore A and Ore B), results were presented in terms of variation in average void ratio with time (settlement), void ratio with effective stress (compressibility), hydraulic conductivity with void ratio and coefficient of compressibility and hydraulic conductivity with sodium adsorption ratio. Findings indicated that chemical characteristics of fine tailings (water chemistry, degree of dispersion) do not have a significant impact on their compressibility behaviour and have only a small influence at high void ratio (low effective stress). The biggest advantage of non-caustic fine tailings and treating caustic fine tailings with coagulant is an increased initial settlement rate and slightly increased hydraulic conductivity at higher void ratios. Thereafter, compressibility and hydraulic conductivity is governed by effective stress.

Aug 1, 2010

By W. G. Miller, J. D. Scott, D. C. Sego

An overall study was conducted to evaluate the properties and processes influencing the rate and magnitude of consolidation for oil sands fine tailings produced using different extraction processes. As part of this overall study, consolidation tests using slurry consolidometers were carried out for caustic and non-caustic fine tailings. The influence of a change in bitumen extraction process (caustic versus non-caustic) on consolidation properties, namely compressibility and hydraulic conductivity, was determined, as was the effect of adding a coagulant (calcium sulphate [CaSO4]) to caustic fine tailings. For fine tailings originating from two different oil sands ores (Ore A and Ore B), results were presented in terms of variation in average void ratio with time (settlement), void ratio with effective stress (compressibility), hydraulic conductivity with void ratio and coefficient of compressibility and hydraulic conductivity with sodium adsorption ratio. Findings indicated that chemical characteristics of fine tailings (water chemistry, degree of dispersion) do not have a significant impact on their compressibility behaviour and have only a small influence at high void ratio (low effective stress). The biggest advantage of non-caustic fine tailings and treating caustic fine tailings with coagulant is an increased initial settlement rate and slightly increased hydraulic conductivity at higher void ratios. Thereafter, compressibility and hydraulic conductivity is governed by effective stress.

Jan 1, 2010

By K. Wood, R. McIvor, P. Blythe, M. Lavallee

A new analytical approach for characterizing and improving the performance of ball milling is presented. Individual ball mill circuit design and operating variables can be related to overall circuit performance through two distinct parameters for classification and breakage. The ball mill circuit functional performance equation is presented.Total mill x Classification x Test specific x Grinding power draw system efficiency grinding rate rate ratio= Production rate of new product size materialExamples from industrial plants and applications in the research and development field are discussed.

Jan 1, 1990

By Clifford R. Stanley

"Abstract - Reproducible analyses of representative samples for elements affected by the ‘nugget effect’ is vital in mineral exploration and reserve estimation. Unfortunately, a priori knowledge of what size of sample is representative from a mineral deposit or its dispersion train is commonly unavailable. Use of the simple ‘equant grain model’ and the NUGGET computer program facilitates determination of the sampling parameters that will produce appropriate samples for chemical analysis. Based on Poisson statistics, NUGGET can be used to determine: (1) the ‘effective grain size’ of nuggets in a suite of samples, (2) the level of representativity (precision) that samples with specific nugget grain sizes will exhibit, and (3) the sample size required to obtain a specific level of sample representativity. The program determines these sampling parameters for any element in any mineral, including solid solution minerals (e.g., Au, electrum, Pt-Fe alloy, diamond), and allows assumption of a variety of grain shapes (e.g., ellipsoids, cylinders, parallelepipeds, etc.). Furthermore, it outputs the effective number of nuggets expected in a sample of given size and the percentile confidence bounds on any element concentration affected by the nugget effect.Results from the software allow determination of effective sampling and analysis strategies that minimize the nugget effect in geochemical analysis/assaying used in mineral exploration and reserve estimation. This will not only improve confidence in the resulting exploration results or reserve estimate, but will facilitate estimation of the error associated with any subsequent interpretation or reserve figure."

Jan 1, 1998

By Francisco Tamargo

"This paper refers to a new process for the full recovery (above 98%) of zinc and other valuable metals (Pb, Ag, Au) accompanying zinc in its concentrates while iron is separated as a marketable product free of any harmful impurities and suitable for sale to the cement industry. The process has been especially designed to achieve the following goals: maximizing the recovery of zinc and those valuable metals that are present in most zinc concentrates (lead, silver, gold); allowing the recovery of other valuable metals such as indium or germanium that could be present in some zinc concentrates; avoiding or minimizing the need for residue disposal in safe areas as it is the common practice nowadays in the zinc industry. Finally, the process achieves the previously related goals at a competitive cost, in line with the existing more efficient operations while using conventional equipment working under atmospheric conditions. The new process can be easily implemented in those smelters using the jarosite or goethite processes as well as in those smelters using direct leaching as a part of the processing facilities. A study has already been conducted on the use of jarosite in the cement manufacturing process, in the raw mix preparation as well as for a set controller. It shows that use of clean jarosite in the manufacture of ordinary Portland cement can result in improved quality of the clinker. Jarosite showed compatibility to influence the burning characteristics of the cement raw mixes. The presence of SO3 bearing mineral phases such as natrojarosite showed the suitability of clean jarosite for use as a set controller in cement production.INTRODUCTION Iron is by far the most abundant impurity accompanying zinc in its concentrates, and consequently, iron residue disposal is a major environmental concern for many zinc smelters in the world. This is especially true during the last 30 years when environmental restrictions became more and more strict. Much research work has been carried out during the last 30 years to try to find a solution for this important issue, but with little success. Only the jarofix process represents a partial solution to this problem as jarofix is stored nearby the smelters with certain limitations as a non-contaminant residue. However, it does not avoid the need to dispose of an important amount of residues every year, representing an environmental liability. Meanwhile, the number of countries limiting or banning the disposal of iron residues generated by the zinc smelters is growing, so that the solution to this problem is becoming an urgent matter right now. At the same time, the lack of appropriate available land for iron disposal is also a major concern in many cases."

Jan 1, 2016

By Robert B. Parsons

"In this period of improved metal prices and reported profits, valuable lessons should be recalled from the 1970s when a similar cycle lured the federal and provincial governments into thinking that they could grab bigger pieces of the pie without harming the minerals industry. It took years for the industry to recover from the damage inflicted by that unprecedented scramble for higher tax revenues. It is hoped that the current policy makers will have learned from the lessons of the seventies, and will realize that mining companies need to keep a reasonable share of profits realized during the good years in order to prepare for the inevitable downturn in the cycle.INTRODUCTION"", «. We have made clear to industry that super profits... will no longer be tolerated "".With that assertion, the Honourable David Barrett , Premier and Minister of Finance of the Province of British Columbia, announced the introduction of a new mining tax regime in his February 17, 1974 bud get papers . British Columbia producers would face a basic royalty and a royalty on so-called ""super profits"", resulting in some instances in tax rates exceeding 100070 of pre-tax profits.The ball started to roll. Mining tax changes knew no political or geo graphical boundary. On April 9, 1974, Ontario's Treasurer John White stated in his budget speech:""Increased demand by major industrialized countries has resulted in sharply higher metals prices and substantial wind fall gains for the mining industry in Ontario. With the prospective demand for minerals likely to sustain current price trends into the future, it is only fair that we secure for the people a higher return from our natural resources""."

Jan 1, 1989

By W. Petruk

Mineralogical studies and concentration tests were conducted on samples from an oolitic iron deposit from the Peace River district in Alberta to determine what concentrate grades and metal recoveries could be obtained. The samples assayed 32 to 37 wt. % Fe, and consisted of goethite, nontronite, ferruginous opal, siderite , quartz, amorphous phosphate and illite . Flotation with fatty acids yielded the best over-all results. A flotation concentrate from a composite sample of the iron horizon assayed, by weight, 43.0% Fe, 12.3% SiO2 , 1.9% CaD, 0.9% MgO, 4.5% Al2O3 and 2.0% P2O5 and lost 17.2% on ignition, for an iron recovery of 48.8% and a silica rejection of 80%. When heated to drive off the water, the concentrate assayed 52 w t. % Fe and 14. 8% w t. % SiO2

Jan 1, 1977

By C. M. Campbell

IN 1902, a famous Canadian geologist made the following statement : ?'From what we know row of the iron-ore fields of the Province, we may feel that Ontario is assured of a great future as an iron-ore producing country. Judging from the extent of the territory over which the newly discovered ranges have been found, Ontario should in the not far distant future take her place as one of the chief iron producers in the world". In 1905, an official of the Department of Mines said: "In ten years Canada will have b:ecome a great metallurgical country. You will see an iron industry in this Dominion larger than in any country in the world. Canada will yet furnish the world with its iron supply. It will be the same with iron as with wheat. A decade from now Canada will outstrip all other countries in wheat growing. The production of iron at a cheaper rate than it can be made elsewhere will cause Canada to take a similar position as far as iron is concerned". In 1924, a former President of the Institute, in arguing his claim for inconceivable mineral wealth in this country, stated as a "certainty" that iron-ore deposits on the scale of the ones in Minnesota would be found "again and again" in the Canadian Precambrian. In 1930, a Minister of Mines announced that "The country surrounding Churchill holds large deposits of valuable iron and coal", and he stated that, at that place, 'We will have an industry in iron that will compare with Pittsburgh". These statements are definite promises, just as definite and important as the statement "I promise to pay" on a note, and they are not fulfilled by casually stating, as is the habit, that someday we will work our low-grade iron ores. Nor are they fulfilled by stating, as is often done, "Oh, So-and-So did not mean that ' . Due to their importance and to the prominent positions held by the men who made these statements, they were widely circulated throughout Canada. They were taken at their face value, and on the strength of them and many more of the same kind in regard to our other resources we have planned and built, at huge expense, provinces, governments, civil services, railways, and other equipment. The reserves that were to justify these expenditures have not appeared. There has not been a ton of iron ore mined in Canada for many years, and important commercial reserves are unknown. We have built the mill, but adequate ore is lacking.

Jan 1, 1937

By M. F. Goudge

BRUCITE associated with highly metamorphosed Precambrian limestone was discovered in the vicinity of Rutherglen in northern Ontario by the writer during field work on the limestones of that district in 1937, and later was identified in similar limestone at Bryson and Wakefield, Quebec. The brucite occurs as granules disseminated through the limestone (Figure 1) and comprises from 20 to 35 per cent of the rock. Such rocks may be referred to as predazzites or pencatites, depending on the proportions of the constituent minerals. In this paper, however, the general term brucitic limestone is used to designate limestone containing brucite. In none of the deposits does the magnesia content of the rock approach that of magnesite, and in the deposits near Bryson and Wakefield the magnesia content is only that of dolomite. Therefore, without some method of concentrating the brucite, the deposits would be of little or no more value as a source of magnesia than is ordinary pure dolomite, which is abundant in many parts of Canada. Investigations in the laboratories of the Bureau of Mines have, however, resulted in the development of a method whereby, from certain of the deposits, pure calcined brucite, or magnesia, in granular form can be obtained, apparently at a cost that will enable it to compete in eastern Canada with imported magnesia. The granular magnesia so obtained appears to be highly suitable for use in basic refractories, for making magnesium metal, and for various other purposes for which magnesia is commonly used. Prospecting in the neighbourhoods of the original discoveries has resulted in a number of other deposits being found in each of the three areas, and there is now apparently available s1.dficient brucitic limestone of a grade that will lend itself to commercial exploitation to supply for many years a large part of the present and prospective Canadian market for magnesia and its products. Furthermore, it is expected that additional deposits will be discovered as prospectors and others become more familiar with the appearance of brucitic limestone.

Jan 1, 1940

By R. D. Brown

Ever since British Columbia started the ball rolling in 1974 with the introduction of its now-defunct Mineral Royalties Act, all Canada's resource-based provinces have significantly altered their mining tax systems. The last resource-based province to abandon its pre -1974 mining tax structure is New Brunswick, which introduced a new mining tax regime in the summer of 1977 to take effect from April 1 1977. The new structure, which represents the outcome of considerable study and discussions with industry representatives, contains some intriguing concepts which make Nero Brunswick's new mining tax system unique among the Canadian provinces.

Jan 1, 1977

By Aleksandar N. Nikoloski, Tendekayi Tapera, Glen P. O’Malley

Chalcopyrite (CuFeS2) and enargite (Cu3AsS4) are among the most important copper sulfides. At present, many known deposits of these minerals are uneconomic to process because they are of too low grade, insufficient size or too remote to be cost effectively treated with conventional technologies that can deal with their refractory nature. Therefore, developing an effective, low cost extraction process for recovery of copper from them is important. The research presented in this paper will deal with potentially cost effective strategies involving catalysed processing, studied under conditions relevant to recycle heap leach conditions. The present account summarises some of the main findings from the research program carried out at Murdoch University between 2014 and 2018 that has investigated the effects of the common leaching parameters, major and minor species present in the leach system and additives on the rate and extent of copper extraction from low-grade ores, in which primary copper sulfide minerals such as chalcopyrite and enargite were the dominant copper minerals. The study involved batch leaching tests, detailed structural and mineralogical characterisation and thermochemical modelling under conditions relevant to heap leaching. The results have demonstrated that silver in particular has a strong catalysing effect on the extraction of copper from ore under the leach recycle conditions and, at an adequate dosage, can effectively overcome surface passivation, enabling almost complete extraction of copper from chalcopyrite as well as enargite. The aim of this paper is to present the effect of the studied additives and to briefly elaborate on the mechanism of the silver catalysed leaching process. In addition, the presence of certain secondary agents was shown to lower the critical dosage of silver and promote extraction. The data from the study allowed the development of a theory for the silver catalysed reaction mechanism, which enables further optimisation and cost-effective application of this strategy in practice. INTRODUCTION Researching the extraction of copper from chalcopyrite is important as it is the most abundant copper mineral in the earth’s crust. The majority of ores containing this mineral are processed by flotation to produce a concentrate, followed by smelting and electrorefining. However, most reserves available nowadays are of low grade or limited in size, and therefore not suitable for this conventional approach. Hydrometallurgical processing via heap leaching with or without the aid of bacteria has been shown to be potentially economical. Chalcopyrite is refractory though and suffers from slow leaching kinetics and poor overall extraction, so understanding the mechanism of how it leaches has received significant attention by researchers working in this field over the past 50 years. The refractoriness, which is the main issue with the hydrometallurgical approach, is generally described as passivation of the chalcopyrite surface whereby a surface coating is formed that blocks the reaction interface or wetting of the chalcopyrite, limiting the copper extraction. Exactly what this layer is made of or how the issue could be overcome has been the subject of intense study and debate for many years. One of the limitations of the work to date is that much of the research focus has been on typical initial leaching conditions, while there has been relatively little research into how the leaching is affected under recycle solution conditions where certain metal ions (Fe, Mg, Al) have often accumulated in the liquor. This occurs because the leach solution exiting a heap contains many species from the dissolution of gangue minerals and typically this solution is returned to irrigate the heap, once the copper has been removed, leading to an accumulation of these species.

Jan 1, 2019