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By A. V. Rasskazova

"The oxidized and mixed ores are processed by heap leaching. Primary ores with high gold content are floated. In recent years mining of primary ores with the low gold content (up to 4 ppm) has increased. Extraction of gold from these ores by floatation is technologically ineffective. Gravity concentration is ineffective for fine gold particles because of their floatability. The research objective was assessment of the viability of processing gold-bearing ore with combined gravitational and hydrometallurgical methods and testing of recovery of metals from a gold-copper oxidized ore chloride-hypochlorite leaching solution. The advantage of chloride-hypochlorite lixiviant is the low cost of reagents which is produced by the electrochemical synthesis of NaCl solution with the addition of HCl. The adsorption of chlorine compounds by a mineral matrix and its ability to oxidize the refractory ore components and allows for the application of chloride-hypochlorite systems for gold recovery for both oxidized and primary ores. The complexity and problem in using a gold–chloride system is the strong adsorption of gold–chloride complexes onto mineral surfaces, such as goethite, quartz, and alumina. In preliminary testing, gold recovery from gravity circuit gold bearing concentrates processed by agitation leaching in chloride-hypochlorite solution, gold recovery has reached up 82% after 4 hours of leaching. Chloride-hypochlorite leaching of copper-gold oxidized ore with preliminary processing by sulfuric acid provided for 94 % gold recovery to solution. Understanding of ecological hazard of cyanides is the motive power of researches in the field of search non-cyanic chemistries to provide for technologically and economically effective solvents of gold. Soluble compounds of chlorine with a suitable oxidizer are one of the alternatives to cyanides. Basic researches of gold extraction by chloride-hypochlorite solution have shown high rates of gold recovery.INTRODUCTION Because of the continued and growing environmental concern for the use of cyanide for gold processing, interest for the use of non-cyanide lixiviants, especially with halides has renewed recently (Tran et al., 2001; Ferron et al., 2003; Bhaghalha, 2007). Leaching solutions based on halides (chloride, bromide and iodide) are viable alternative to cyanide (Kwang et al., 2008). The major disadvantage of the chlorine–chloride system is the high reactivity of chlorine in reaction with sulfide and gangue carbonate minerals. It is believed that only high grade materials may be treated by chlorine–chloride systems economically (Baghalha, 2007). Another important problem of the application of gold–chloride complex is that it tends to be rather unstable and may re-precipitate upon contact with a reductant, such as sulfidic minerals of ore. It is well known that Au(III)–chloride hydrolysis species are strongly adsorbed by goethite, quartz, and alumina (Machfsky et al., 1991). To minimize adsorption of gold–chloro complexes, it works best to minimize the adsorption time."

Jan 1, 2018

By Sazol Das, Hany Ahmed, Ganesh Bhaskaran, Zhuoru Wu

"Friction stir welding (FSW) process in lap configuration for dissimilar materials has been developed and tested for steel to aluminum joining. A novel cylindrical tool was designed for improved material flow. The joining of steel to high strength 5xxx and 6xxx aluminum was carried out by FSW technique using optimized process parameters. The microstructure, micro-hardness, joint strength and corrosion properties at the weld interface have been investigated. Optical and scanning electron microscopy reveled a well layered structure at the interface and lap shear tests of the welds showed excellent fracture resistance. Neutral salt spray tests for up to 500 hours (ASTM B117) were carried out on the bare steel to aluminum FSW joints, which did not show neither evidence of corrosion at the weld interface, nor any degradation of the weld strength. The FSW lap configuration was applied to prototype commercial vehicle structural component whereby a steel stiffener insert was friction stir welded to high strength 6xxx aluminum alloy. The interface microstructure showed layered root without any steel shattering in aluminum side. A finite element study was carried out to quantify the benefits where it was found that the stiffness increases by 76% under bending loads and 36% in torsion loads.INTRODUCTION Energy preservation and environmental issues, namely carbon footprint and legislation around emission in transportation industries has led to a growing need to use of lightweight materials such as aluminum and magnesium alloys along with various grades of steel in structural application, while still maintaining their strength and crashworthiness. Assembling dissimilar materials within integrated structure is thus a stringent requirement related to optimum performance. In order to achieve an efficient technology of joining dissimilar materials such as aluminum to steel, it remains difficult to select an effective welding process for a given joint configuration. The use of aluminum in transportation industries for structural component is not exclusive in a design and is almost always used along with various steel grades for a mixed materials solution, thus dissimilar aluminum/steel lap joining is of great interest since this is widely used in the assembly of parts (e.g. pillar, frame rails, chassis, body in white (BIW), CAB, etc.)."

Jan 1, 2018

By Guy Reed, Russell Frith

"The method of determining coal pillar strength equations from databases of stable and failed case histories is more than 50 years old and has been applied in different countries by different researchers in a range of mining situations. While common wisdom sensibly limits the use of the resultant pillar strength equations and methods to design scenarios that are consistent with the founding database, there are a number of examples where failures have occurred as a direct result of applying empirical design methods to coal pillar design problems that are inconsistent with the founding database.This paper explores the reasons why empirically derived coal pillar strength equations tend to be problem-specific and should be considered as providing no more than a pillar strength “index.” These include the non-consideration of overburden horizontal stress within the mine stability problem, an inadequate definition of super-critical overburden behaviour as it applies to standing coal pillars, and the non-consideration of overburden displacement and coal pillar strain limits. All of which combine to potentially complicate and confuse the back-analysis of coal pillar strength from failed cases.A modified coal pillar design representation and model are presented based on coal pillars acting to reinforce a horizontally stressed overburden, rather than suspend an otherwise unstable self-loaded overburden or section, the latter having been at the core of historical empirical studies into coal pillar strength and stability.INTRODUCTIONThe inspiration for this paper is founded in three statements from two eminent persons in the field of coal pillar strength research, Jim Galvin and Essie Esterhuizen, as follows:Both Salamon and Munro and [the University of New South Wales] based the derivation of their pillar strength formulae on a criteria that the diameter of a panel of pillars, W, had to at least equal the depth of mining, H. This was thought to result in full tributary loading. It is now known that there are some mining environments included in both the South African and Australian databases in which mining span must exceed depth by a considerable margin in order to achieve full deadweight loading. Hence, it is logical to conclude that these data points may have contributed to pillar strength being overestimated by Salamon and Munro and UNSW (underline added by authors). Normally, this should be of no consequence because it is reflected in the probability of design success associated with any given safety factor (Galvin, 2006)."

Jan 1, 2018

By J. Coffin, M. Muinonen, D. Fragomeni, R. Multani, C. Deredin

"Rejection of pyrrhotite from pentlandite is of critical importance to the economics of nickel concentrate production and the main goal of the Strathcona milling operations. A joint team of XPS, Glencore Technology and Strathcona Mill personnel executed a comprehensive program of work to develop and implement strategies for increased Po rejection with focus on challenging ores containing high feed Po/Pn ratios (> 7) and significant hexagonal Po content (> 40% of total Po). This paper describes the team results including minerology, bench-scale flotation tests, and plant validation tests and modeling that have defined the path forward to improving the metallurgical performance and economics of the mill operation. Techniques to quantify hexagonal and monoclinic pyrrhotites were developed at XPS to assess the differences in their metallurgical behavior since their flotation responses are quite different. Mineralogical tools including QEMScan were extensively used to determine mineral liberation, associations, optimum grind size, and nickel deportment into pentlandite, pyrrhotite and non-sulphide gangue. Several reagents/strategies were evaluated during bench-scale flotation testing to significantly increase Po rejection. A significant shift in the Po-Pn selectivity and grade recovery curves was achieved using several strategies including the use of DETA and sodium metabisulfite, and regrind of the rougher concentrate and rougher cleaner/rougher tails.INTRODUCTION The Strathcona Mill is owned and operated by Glencore Nickel – Sudbury Integrated Nickel Operations and has been processing Ni-Cu ores from the Sudbury Basin since 1968 (valuable sulphides: pentlandite (Pn) – (Ni,Fe)9S8 and chalcopyrite (Cp) – CuFeS2). Currently Strathcona Mill receives ore mined from two main sources in the Sudbury area and produces two concentrate streams – a nickel-copper concentrate that is shipped to the Sudbury Smelter and a copper concentrate that is sent to the Fonderie Horne (Glencore Copper, Rouyn-Noranda). The general flowsheet currently used at Strathcona is displayed in Figure 1. It is highlighted by separate feed circuits for regular grade Ni ores and high grade copper ores. The copper circuit has a preflotation stage prior to a rougher-scavenger stage, a copper-nickel separation circuit, and a pyrrhotite (Po) rejection circuit."

Jan 1, 2018

By M. Tiedtke, T. Crary, P. MacPhail, M. Ounpuu

"The SGS carbon-in-pulp (CIP) / carbon-in-leach (CIL) model was used to evaluate and optimize the carbon circuit at Alamos Gold’s Young-Davidson Mine. Plants samples (pulp and carbon) were tested in a series of small scale batch experiments to determine rates of gold leaching and adsorption on carbon from a combined flotation concentrate/tailing product. The testwork data, along with existing plant data were then used to model the performance of the existing CIL plant and optimize the circuit to improve performance and overall recovery. The primary purpose of the modelling exercise was to determine the most cost effective way to lower solution losses at the plant. The modelling was also used to learn how the various parameters in the CIL circuit affect solution losses and the gold inventory tied up on the carbon. This resulted in recommendations for minor changes in the CIL flowsheet, which were successfully implemented in the plant. The approach, results and plant changes are presented.INTRODUCTION This paper presents the details from testwork conducted on samples from Alamos Gold’s Young- Davidson gold mine which is located near the town of Matachewan, approximately 60 km west of Kirkland Lake in Northern Ontario, within the southwestern part of the Abitibi Greenstone Belt. The objective of the test program (completed by SGS Canada in 2013) was to investigate and model the combined flotation concentrate / tailing carbon-in-leach (CIL) circuit and suggest ways to improve gold recovery. The metallurgical test program included mineralogy, rheology, and carbon modelling testwork. Plant information was provided during the test program and used in the optimization process. Upon completion of the testwork, plant changes were recommended and implemented at site (October 2014). Plant results from 2014 to 2017 confirmed the modelling results."

Jan 1, 2018

By S. Saeed, N. Coulson, P. F. Stewart

"The Mine, Health and Safety Act No. 29 of 1996, as amended, embodies worker self-regulation to advance health and safety in the workplace. An important provision for this is the Right to Refuse Dangerous Work (RRDW). This paper explores worker perspectives about the implementation of RRDW on South African mines against a backdrop of revised guidance in the sector: ‘Guideline for a Mandatory Code of Practice on the Right to Refuse Dangerous Work And Leave Dangerous Working Places’, gazetted in February 2016 by the Department of Mineral Resources (DMR). A mixed methods study conducted at mines (n = 14) included a survey of workers (n = 293), focus groups (n = 6) and in-depth interviews (n = 16). Workers reported a high level of awareness, a positive attitude, and experience of the formal RRDW. However constraints to the formal RRDW meant that informal worker resistance to dangerous work was commonplace. Evidence of informal non-confrontational consultation, cooperation, and collaboration in the event of a dangerous workplace also emerged between workers, and supervisors. The research underscores the importance of the RRDW and worker health and safety representatives to mine health and safety. The revised guidance addresses RRDW implementation gaps, but of concern is the potential partiality towards management interests. IntroductionEnsuring that mineworkers act on their duties and responsibilities for health and safety remains a concern across the globe. Article 13 of the International Labour Organization (ILO) Convention Safety and Health in Mines (176 of 1995) entrenched the Right to Refuse Dangerous Work (RRDW) as an important mechanism through which workers act in the best interests of their own occupational health and safety (OHS) and is considered a cornerstone of worker self-regulation (ILO, 1995). Countries ratifying Convention 176 are under obligation to make this right available to workers through OHS legislation that frames the circumstances, procedure, and protection of workers from discrimination in the event of a formal work refusal. The Convention has been ratified by 31 countries, with South Africa becoming a signatory in June 2000 (ILO, 2000). Worldwide studies show that workers use this right with caution (Hilgert, 2013) and cases associated with work refusal are rarely presented in court (Gunningham, 2007; Cooper, 2013). Rather, in cases of formal notification of a work refusal, issues arising out of this are addressed either in the immediate workplace or through the site OHS system and/or at industrial tribunals or similar mechanisms (Harcourt and Harcourt, 2000)."

Jan 1, 2018

By T. P. Weldum, W. Conger

"These studies address the relationship between mill media sizing and its grinding efficiency. Starting with the results from a review of the literature, the issues of initial media sizing for a new ball milling circuit, and then optimal media sizing for an existing milling operation, were studied. The Functional Performance parameters “Mill Grinding Efficiency” and cumulative “Mill Grinding Rates” from both plant and test-scale equipment were used, and provide valuable new insight into this topic. A plant media sizing diagnostic tool is presented, as are newly developed testing equipment and evaluation methods, and recent case studies. REVIEW OF MEDIA SIZING LITERATURE For a plant metallurgist to answer the question “How can I maximize plant profit by manipulating this grinding circuit variable?” she must know what effect the variable has on grinding circuit efficiency. Despite the significant cost of grinding media and its potential effect on production capacity, the ‘best’ media sizing remains ill-defined for any given ball mill circuit in the industry today. The underlying reasons for this will be discussed. But the importance of this issue drove Metcom and its industrial partners to take on the challenge of how to engineer the ball charge for an existing grinding circuit. In the absence of any proven method, the first step was a review of the literature. Sponsored by Cleveland-Cliffs, Inc., a broad review of the literature was undertaken, producing “The Effect of Media Sizing on Ball Milling Efficiency” (McIvor, 1997). Among hundreds of publications that were reviewed that discuss the topics of media sizing or wear, forty-five were studied in detail. These were grouped into: plant experiences; laboratory and pilot plant investigations; media wear studies; population balance modeling studies; and general papers on ball milling which included the topic of media sizing. The reader is encouraged to refer to that review. The findings remain unchanged, although some relevant papers have been written since (e.g. Staples et al, 1997; Banasi et al, 1999; Orford et al, 2006; LaMarsh, 2015). The main findings of the review were as follows."

Jan 1, 2018

By M. A. Stogran-Baker, S. Cole

"Fluorspar mining occurred in the St. Lawrence area from the 1930s until the mid 1980s. In 2013, CFI discovered a new ore body, the AGS vein, which proved amenable to more economic open pit mining methods. A new mill was designed to produce 200,000 tonnes per year of high quality, acid-grade fluorspar concentrate. The simple mill flowsheet includes crushing, dense medium separation (DMS), grinding, sulphide flotation, pulp thickening, fluorite flotation, thickening, and concentrate filtration. The type of flotation cell used is being installed for the first time in North America. Site clearing commenced in the spring of 2016, followed by mill building erection completed by the fall of the same year. Civil and mechanical installation as well as site-wide construction was completed by the end of September 2017. Commissioning commenced, and at the time of paper submission mill production is on track to ramp up to full capacity by the beginning of 2018. This paper will focus on the use of fluorine NMR analysis applied to fluorite and the development of on-stream analysis, flotation cell selection and the decision to install the new cells, and the water control program designed to maintain process control with the least possible environmental impact.HISTORY St. Lawrence is located on the south-eastern coast of the Burin Peninsula in Newfoundland and Labrador. The first occurrence of fluorspar in the St. Lawrence area was recorded in 1843 by British geologist J.B. Jukes (DNR 2010). Fluorspar was likely extracted in small quantities prior, however commercial fluorspar mining did not commence until 1933 at the Black Duck Mine. The Black Duck Mine operation processed ore by washing and screening – acid-grade was hand-picked from the oversize, the undersize was sold as a lower grade product. The Black Duck Mine was closed in 1941 (Wilson 2010). The American Fluorspar Limited (New Fluor) commenced operations on the Director vein in 1936, and was bought by Alcan in 1942 (Cooper 2012). Alcan also developed the Iron Springs as well as the Tarefare deposits. The Black Duck Mine mill had closed, and a new mill was built. This new mill crushed the ore prior to dense medium separation, the sinks of which were sent to Quebec for use in Alcan’s aluminum smelter (CFI 2016). Alcan shut down it’s mining operations in 1977 due to the dropping price of fluorspar as well as labour disputes. In 1986, the British-based Minworth Limited began producing ore from underground at Blue Beach North and Blue Beach South, as well as from open pits at Tarefare and Director veins (Cooper 2012). A new mill was built by Minworth in order to process the ore using flotation to produce an acid-grade concentrate. The low price of fluorspar caused Minworth to shut down operations in 1990. Whilst exploration has been ongoing, no mining had occurred in the area since 1990."

Jan 1, 2018

By N. Aslin, G. Heferen, H. DeWaal

"Mount Isa Mines (MIM) acquired a reputation for the successful application of R&D to develop break-through technologies for the mining industry starting in the 1978’s through until the early 2000’s. The ISAPROCESSTM tank-house technology has been licensed to copper refineries throughout the world, and a significant per cent of the world’s copper is refined using this technology. Since development in the late 1980’s more than 20 ISASMELTTM copper and lead smelting furnaces are now installed in countries around the world. Jameson Cell flotation technology developed jointly by Mount Isa Mines and Professor Graeme Jameson is widely used in the Australian coal mining industry and increasingly in the base-metal and gold industry. The IsaMillTM’s developed at Mount Isa and McArthur River made it possible to develop the McArthur River and George Fisher orebodies and has been successfully implemented into base metal fine grinding applications around the world. The most recent commercialised innovation is the atmospheric leach Albion ProcessTM with its supersonic HyperSpargeTM gas sparger, is being adopted as a solution to the increasing complexity of orebodies. MIM’s contribution to the industry was significant given the size and the remote location of its operations with Townsville Copper Refineries more than 1350 km and Mount Isa 1800 km from the nearest state capital of Brisbane. This paper will briefly discuss the development of each of these technologies and why MIM – now owned by Glencore - was so successful innovating and developing such technologies over a period of nearly 40 years.INTRODUCTION Mount Isa is located in the Gulf Country region of Queensland about 1800 kilometers North West of Brisbane (see Figure 1). It came into existence because of the world class mineral deposits found in the area. In 1923 the orebody containing lead, zinc and silver was discovered by the miner John Campbell Miles. Mount Isa Mines Limited (MIM) was founded in 1924 to develop the minerals discovered by Miles, but production did not begin until May 1931. It paid its first dividend in 1947 after 16 years of troubled production. In 1954 the 1100 copper orebody was discovered and with rapidly rising reserves during the 1950’s and 1960’s led to the construction of new concentrators to treat lead/zinc/silver ores in 1966 (#2 concentrator) and copper ore’s in 1973 (#4 concentrator). The difficult nature of the Mount Isa lead-zinc orebodies has meant that the company had always needed to be at the forefront of mining technology. In the 1970’s through to the 1990’s, it became a world leader in developing new mining techniques and processing technologies as a response to declining metal prices and rising costs. Mount Isa has been smelting copper since 1953 and lead since the early 1930’s. Copper Refining at Mount Isa’s fully owned subsidiary of Copper Refineries Proprietary Limited (CRL) had commenced operations in 1959."

Jan 1, 2018

By T. Holmes, S. Davison

"A surge bin at Agrium’s Vanscoy potash operations has been plagued with flow, wear, and corrosion issues since being built in 1967. The culprits? The bin’s carbon-steel construction, geometry, and the resultant funnel-flow pattern are the root causes. An investigation and cost analysis indicated that hopper redesign and retrofit would increase production and reduce maintenance and capital costs. The retrofitted bin provides safer, more reliable operation and has a much longer predicted working life. Using this example, the authors describe bulk-solids-flow theory and highlight the importance of customizing bulk-material-handling-system design using appropriate flow properties to improve reliability, safety, and cost effectiveness.RÉSUMÉ Depuis sa construction en 1967, un réservoir intermédiaire de l’exploitation de potasse Vanscoy d’Agrium connaît des problèmes de débit, d’usure et de corrosion. Les responsables ? La construction en acier ordinaire du réservoir, sa géométrie et la structure de débit en résultant au niveau de la carotte en sont les causes fondamentales. Une étude et une analyse des coûts indiquaient que la restructuration et la rénovation de la trémie permettraient d’augmenter la production et de réduire les coûts d’entretien et en capital. Un réservoir rénové permet de renforcer la sécurité ainsi que la fiabilité de l’exploitation, et sa durée d’activité prévue en est augmentée. En se fondant sur cet exemple, les auteurs de l’article décrivent la théorie du débit de matières solides en vrac et insistent sur l’importance de personnaliser la conception du système de manutention des matériaux en vrac à l’aide de propriétés rhéologiques adaptées afin d’améliorer la fiabilité, la sûreté et la rentabilité.INTRODUCTIONIn early 2013, Agrium’s Vanscoy Potash Operations (VPO) engaged Jenike & Johanson Ltd. (J&J) to provide testing, consulting, and structural engineering services related to proposed modifications to the 270 t special standard product surge bin, which Agrium planned to undertake during a two-week shutdown in August 2013. The bin, which had been plagued with flow, wear, and corrosion issues for its entire working life, was essential for the continuous operation of two of VPO’s compaction plants and for efficient dispatching to loadout. The bin often experienced product hang-ups, clumping on the walls, and plugging at the hopper outlet. Two recent unscheduled mill shutdowns had been partially attributed to flow issues in the bin due to clumping and product plugging up at the screws. These problems increased maintenance costs, limited production capacity, and degraded product quality. Holes and paper-thin sections in the bin walls discovered during a 2013 inspection revealed the potential for major hot material leaks or even structural failure. Either issue would stop plant operations until the bin could be repaired or bypassed. Clearly, the bin cone had reached the end of its life and required replacement."

Jan 1, 2018

"The most common comminution testing methods and the associated analytical procedures provide average values and do not capture the variability in breakage behaviour of ore particles. Therefore, plant designs and process performance predictions use only average values; hence, the inherent variability that exists within an ore domain translates into variation in process performance. This paper discusses the drawbacks of using the average approach to impact comminution testing and plant design. It considers breakage intensity from a single-particle testing perspective. To clearly delineate breakage behaviour of each broken particle, an experimental technique using the JK Drop Weight Tester (JKDWT) has been developed by which actual comminution energy per particle and breakage intensities were measured directly. Four different ore types in ranges of -45+37.5mm and -22.4+19mm were tested at three energy levels of 0.1, 0.25, 0.5 kWh/t and six energy levels of 0.5, 1.0, 2.0, 2.5, 3.0 and 4.0 kWh/t, respectively. Sieved results of individual particles, notionally, t5, t10 and t50 showed the presence of large variability in their breakage behaviour, which was not captured by the standard JK impact breakage testing approach. In addition, the original JKMRC model is modified by introducing a third parameter, ‘Emint10’ which describes the minimum energy required to produce the minimum percent t10 for a given ore type and its significance is tested statistically. These results suggest that the analysis of breakage variability may lead to more robust plant designs. Perhaps, the most useful insight from this work is to extend single particle breakage model developed by JKMRC to a comminution percentile envelope which may provide a more detailed picture of ore breakage variability. INTRODUCTION Rock consists of mineral grains, pores, voids and cracks that may differ markedly in size/density which make rock a heterogeneous material by nature. The degree of heterogeneity in rock affects its breakage characteristics where these variations increase local differential strain and stress within a stressed rock (Scholz, 1968) and it depends on many factors such as rock genesis, alterations, etc. One important aspect of this heterogeneous feature is presence of a large amount of experimental scatter in rock breakage results when considered from a quantitative perspective (Bieniawski, 1967; Liu, Roquete, Kou, & Lindqvist, 2004)."

Jan 1, 2018

By S. A. Lolon, J. F. Brune

"INTRODUCTION In underground longwall coal mining, the mined-out areas or gobs frequently contain methane which can form explosive methane-air mixtures. Historically, there have been many events of mine fires and explosions recorded in the United States and other countries that have demonstrated the existence of such explosive mixtures, herein referred to as Explosive Gas Zones (EGZs), inside and around the perimeter of bleeder-ventilated longwall gobs (Loane et al., 1975; Lynn et al., 1986; Elkins, et al., 2001; McKinney et al., 2001; Dziurzynski and Wasilewski, 2012; Brune, 2013). The risk of mine explosions can increase if the EGZs migrate out from the gob into the surrounding mine entries. Several factors can induce EGZs outflowing from the gob, but the most common cause is the fluctuating barometric pressure. Atmospheric pressures change regularly every day but can fluctuate abruptly and become increasingly hazardous in adverse weather conditions. Other sudden pressure changes can result from roof falls, failing ventilation controls and fan outages. Any such fluctuation of mine ventilation pressure will disturb the pressure differential between the gob and the surrounding mine workings and may cause EGZs to outgas from the gob. The correlation between major mine explosions and abrupt barometric pressure changes has been studied and confirmed for explosions in coal mining countries including the United States, South Africa, Australia, and Poland (Hosler, 1948; Boyer, 1964; Kissell et al., 1973; Fauconnier, 1992; Hemp, 1994; Wasilewski, 2014; Belle, 2014; and Lolon, 2017). Disastrous mine explosions appear to happen more frequently during stormy weather, which, in the United States, typically occurs during the late fall and winter seasons. ROOT CAUSE AND EFFECT OF GOB BREATHING Gob breathing is the result of the pressure differential between gob internal and external pressures caused by external atmospheric pressure fluctuations that occur naturally as a result of gravitational and thermal forces in the atmosphere (Lindzen and Chapman, 1969). Other major and sudden pressure changes may be caused by fan failures, failures of ventilation controls or roof falls can also cause an unexpected gob breathing. Normal barometric fluctuations occur every day but usually do not pose an explosion risk as they occur gradually so gob pressures have sufficient time to equilibrate. More extreme fluctuations associated with cyclonic weather systems and storms often result in more rapid and larger drops or rises in barometric pressure (Hosler, 1948; Fauconnier, 1992). A study by Lolon (2017) found that the timing of historical mine explosions showed consistency with the occurrence of abrupt and intense barometric variations."

Jan 1, 2018

By S. M. H. Haddad, M. Saghaeian, R. Hejazi

"Due to limited water resources in mineral processing plants, increasing the efficiency of iron tailing dewatering system in order to obtain more usable water is very important. In this research, flocculation process, as one of the best method for water recovery, was investigated by using one organic cationic and three anionic types of flocculants with different dosages (10, 20, 30 g/ton) and iron ore tailing slurry (8 % w/w solidity) in series of graduated cylinders and obtained results were compared. it is observed that for tailing sample, the anionic flocculants have a significant effect on the settling rate of solid particles compared to the cationic types. Furthermore, effects of temperature (10, 23 and 43 ºC) and pH (2, 7 and 12) on the rate of settlement and turbidity was studied by utilizing the best flocculant. Findings showed that by increasing the amount of flocculant dosage, sedimentation rate went up and turbidity decreased. Comparison the out-put data of tests indicated that at temperature 23 °C and pH=7, the best results for both of faster settling rate and producing more clear water were reached. It should be considered that lower temperature has a more negative effect on the sedimentation rate and overflow water quality. So it will be predicted that for cold seasons, the consumption of the flocculant powder would be higher than the moderate or warm seasons. Also, coagulation/flocculation was evaluated by applying organic cationic coagulant added to anionic flocculant in three different times. Different ratios of coagulant to flocculant was examined (70%:30%, 50%:50%, 30%:70%) as well. Overall, utilizing coagulant had desirable influence on sedimentation experiments and obtaining high quality water. 1- INTRODUCTION In mineral Factories, among the important processes, solid-liquid separation process due to limited resources of water is very important and operates on iron ore tailing in settling tank as thickener in order to gain clear water for preventing water loss and applying again in plant units (Ciftci and Serhat Isik, 2017). Iron ore tailing include inharmonious compounds of iron oxides, silicates and aluminum-silicates. The percentage of solid in the tailing usually changes between 5 and 10 percent (Dash et al., 2011). One of the major problem about dewatering of tailing in thickener is solid-liquid separation of slurries with high stability because of fine particles. It means that rate of sedimentation is very slow and recovered water quality is inappropriate. This issue can be solved to a large extent by factors such as pH control, ionic strength and flocculation/coagulation process which results in aggregation of particles so that settlement by gravity is happened (Dash et al., 2011)."

Jan 1, 2018

By J. B. Boisvert, D. S. Silva

"Drillhole placement involves benefits, costs, and constraints. Benefits are related to the drilling campaign value, which includes maximizing “indicated” and “measured” resources. Costs include drilling, rig movement, and access construction. Constraints include infeasible areas, maximum and minimum angles of drilling, maximum depth of drilling, and budget. Manually planning drillholes that meet these constraints is suboptimal. A framework for straight drillhole optimization that accounts for benefits, costs, and constraints is presented. The method aims to maximize the value of resources converted from “inferred” to indicated and measured. The framework is demonstrated for a Nevada gold deposit and outperforms manually selected drillholes.RÉSUMÉ Le choix de l’emplacement d’un trou de forage s’accompagne d’avantages, de coûts et de contraintes. Les avantages sont liés à la valeur d’une campagne de forage, qui comprend l’optimisation des ressources « indiquées » et « mesurées ». Les coûts englobent le forage, le déplacement de l’appareil de forage et la construction des routes d’accès. Quant aux contraintes, elles portent sur les zones impraticables, les angles maximums et minimums de forage, la profondeur maximale de forage ainsi que le budget. La planification manuelle des trous de forage répondant à ces contraintes est sous-optimale. Cet article présente un cadre relatif à l’optimisation des trous verticaux de forage tenant compte des avantages, des coûts et des contraintes. Cette méthode vise à optimiser la valeur des ressources converties de la phase « ressources présumées » à celle de « ressources indiquées et mesurées ». Ce cadre est appliqué à un gisement aurifère du Nevada et donne de meilleurs résultats que les trous de forage sélectionnés manuellement. INTRODUCTIONDetermining the optimum location of infill drilling has been studied because the high cost of drilling suggests that using fewer drillholes is preferred, and targeting locations of the deposit that are locally uncertain should result in better mine planning decisions and increased profit of the operation. Existing methods for optimizing drillhole locations consider minimizing the kriging variance (KV) as the objective and are mostly restricted to two dimensions (Soltani-Mohammadi & Hezarkhari, 2013a, b; Soltani- Mohammadi, Safa, & Mokhtari, 2016)."

Jan 1, 2018

By L. Stamenov, H. Bouzahzah, S. Gaydardzhiev, D. Naumov

"The Chelopech epithermal arsenic bearing high-sulphidation, copper-gold deposit located in Bulgaria is often referred as the richest European gold deposit currently under exploitation. Key points from the flotation circuit of the processing plant have been sampled and selected physicochemical parameters measured. Plant survey has followed with selected samples being submitted to chemical and mineral liberation analysis (MLA). Quantitative analysis has enabled to link the flotation response of the main copper bearing minerals with the physiochemical parameters (Eh, DO, EDTA extractable Cu and Fe) being measured. Data from mineral liberation analysis have highlighted an important process-relevant information explaining the variable floatability in the various granulometric classes.The low chalcopyrite recovery could be linked to the non-sufficient amount of dissolved oxygen measured in the copper selective flotation circuit. Given the finely-disseminated copper bearing minerals, the observed copper losses inside the flotation could be also explained by the insufficient degree of liberation of the mineral grains. Suggestions for improvement in metallurgical recovery are therefore proposed.INTRODUCTIONThe Chelopech deposit is a high sulphidation (HS) volcanic-hosted epithermal gold-copper one (Bonev et al., 2002; Kouzmanov et al, 2009; Strashimirov, et al. 2002). It is considered as one of the largest and economically most important ore deposits in Bulgaria, and often is referred to Europe’s largest currently mined gold resource. It is located in the Srednogorie zone which falls within the central sector of the extensive Tethyan–Eurasian copper belt formed during Mesozoic–Cenozoic time along the southern margin of Eurasia. The Srednogorie zone has the features of a subduction-related, Late Cretaceous island arc, with development of a calk-alkaline to sub-alkaline volcano-plutonic magmatism and associated hydrothermal ore deposits (Bonev et al., 2002).Ore mineralisation occurs as veins, mineralised breccia, and massive sulphide replacements and disseminations. Three mineralisation stages have been identified at Chelopech deposit. An early pyrite–marcasite mineralisation (stage I), characterised by disseminated to massive pyrite followed and partly brecciated by enargite– luzonite and tennantite–chalcopyrite–bornite (stage II) mineralisation. The gold is met in ores belonging to the stage II. Sphalerite and galena veins characterise stage III, best developed below and adjacent to the pyrite–enargite– chalcopyrite ore bodies. Advanced argillic altered volcanoclastic rocks commonly host this mineralisation (Chambefort and R. Moritz, 2014)."

Jan 1, 2018

By A. Konya

"INTRODUCTION Underground Mining and Construction projects face several challenges unique to the underground environment compared to the surface environment. The goals of an effective blasting program are the development of a blast pattern that minimizes cost, maximizes face advance, and provides the desired fragmentation and face profile. In addition to these , mines must consider the very real operational problems that occur such as drill deviation, ground vibration, and deadpressing or sympathetic detonation of explosives. These operation problems lead to increased costs and decreased production in the mine, hurting the bottom line. Combined with these problems, underground blasts can be difficult to monitor and evaluate due to tight spaces, dust during the blast obscuring video, and the need to evacuate the immediate area with no clear line of sight to observe performance. This creates an environment which most mines know that blasting can be improved in their underground operations, yet most are hesitant to change due to fears of the shot freezing, misfires occurring, and questions about how to achieve a proper design. The explosive companies and shot service providers also offer limited assistance or knowledge in the underground blasting realm, unlike with surface blasting, leaving many underground operations in the dark. It is for these reasons that most underground operations are operating decades behind the current technologies and incurring significant costs, both real and hidden, from there blasting operations. This paper discusses philosophical changes to designs that need to be made for effective design and modifications of underground blast patterns to prevent deadpressing and precompression of modern explosive products (Konya, Konya, & Worsey, Modern Blasting Method Selection, 2017). While numerous different methods of underground heading development exist, there are two types that are used in a majority of mines around the world, these are the burn cut and the V-cut. The burn cut is a parallel cut that has holes that go straight into the face and are primarily used in smaller opening (due to ability to pull deep rounds with smaller room widths) and metal mines (helps in ore dilution and greater fragmentation). The V-Cut is a cut that uses angled drilling towards the center of the face (in the traditional method) and is primarily used in underground aggregate operations due to its cheap cost but larger fragmentation sizes and greater throw of the muckpile. This paper will discuss these two forms of cuts specifically with the understanding that modifications to these can be applied to other parallel and angled underground heading techniques. BURN CUT The burn cut is one of the older forms of underground blasting, where a part of the blast (burn) of a shot is heavily loaded with additional empty (relief) holes with the goal of smashing (aka burn) and pushing/blowing all the material in the burn out to provide relief for subsequent blastholes. The relief holes in the burn cut provide a parallel relief for the holes that are firing to break too creating a second plane of relief, however these are extremely small and can cause many problems if a design is improper."

Jan 1, 2018

By O. A. Velasquez, A. R. Kumar

"Dust generated on underground mechanized coal mining faces is a health and safety hazard. Continuous miners deployed underground usually have an integrated flooded-bed dust scrubber mounted onto the machine that arrests the generated dust from close to the face and cleanses the air around it. However, the impingement screen might get clogged depending on the coal seam being worked. This necessitates the cleaning of the screen which in turn, reduces the overall availability of the scrubber and, hence the continuous miner. A novel non-clogging screen has been developed at the Department of Mining Engineering, University of Kentucky. The proposed impingement screen is built up of three individual aluminum screen units 1.5 mm thick and separated by 3 and 2 mm respectively. The screens have long vertical slits measuring 6 mm. A water spray continuously keeps the screen wet and provides for the filter element to arrest the dust particles. The slits force the dust-laden air to make sharp turns. The dust particles cannot change directions rapidly, impact one of the three screens and are separated out based on their momentum. Preliminary computational fluid dynamics (CFD) models have indicated significant cleaning efficiencies in the respirable range at the expense of much lower pressure drops. Results indicated by CFD models and supported by laboratory experiments have been discussed in this paper.ACKNOWLEDGEMENT The authors acknowledge the National Institute for Occupational Safety and Health (NIOSH) for funding this research. Dr. Thomas Novak, Professor of Mining Engineering, is also acknowledged for his continued support and encouragement. INTRODUCTION Continuous miners are ubiquitous in coal mining around the world. The miners are operated against bling headings, ensuring adequate flow of air at the face could be difficult. The minimum requirement of ventilation airflow quantities at those coal faces are legislated to dilute dust generated to harmless levels. New dust rules promulgated recently have further called for lower exposure levels of personnel working underground (Courtney) (MSHA, 2014) (NIOSH, 2010). Water sprays are also installed at strategic locations and serve as powerful air-movers. The sprays capture some amount of dust generated while cutting. In addition to this, usually, all continuous miners are equipped with a flooded-bed dust scrubber as shown in Figure 1 to capture the dust from close to the extraction drum (Chao & De-sheng, 2000) (Wala, Vytla, Huang, & Taylor, 2008) (Organiscak & Beck, 2010)."

Jan 1, 2018

By M. Somppi, Z. Yamak

"Gold producers invest significant effort in mining, processing, and creating an intermediate gold doré product. Nonetheless, equal effort should be extended to the final handling and processing of the doré bar, and managing the high-purity gold produced at the fine-gold toll refiner. This detailed attention to bullion handling and refining provides rigor and confidence that the mine site is achieving, through fair and controlled methodology, the most appropriate value for the final product. With the above in mind, the following study explores the importance of preparing a set of site best-practices for bullion handling and specifically, detailing the peculiarities of sampling methodologies and the impact on assays.INTRODUCTION Gold and silver handling practices are common place at mine sites and refineries. The practices include but are not limited to smelting, ingot casting, weighing practices, and secure transportation. Proper handling and processing of the bullion material ensures that the mine site is achieving the true value of the final product. Various handling aspects can critically impact the perceived value of the bullion. A few of these particulars include weight tracking, scale recertification and calibration, refining and melting practices, melt temperature measurement, sampling, pouring, bar cleaning, furnace technology and crucible selection, and assaying. Nevertheless, this report discusses and focuses on the importance of proper sampling and molten-metal temperature measurement and their potential impact on the final doré bar value. Refining or re-melting operations achieve a proper measure of the precious metal content of its bullion when the sample accurately represents the whole bar. At first this task appears seemly straightforward, however, taking a representative sample can be challenging and is also one of the most important tasks for valuing gold during the settlement stage at the precious metal refinery. Various bullion sampling methodologies exist; including: dip sampling, granulation, drilling, cutting, and vacuum pin sampling. The Royal Canadian Mint (2009) indicated in their technical review of refinery operations that pin sampling is one of the best methods for cases where representative sampling and accuracy are required, e.g. to determine the payable metal content. Pin sampling consists of inserting a sealed glass vacuum tube (Figure 1) into the molten metal; when the molten metal contacts a purposely-designed weak portion of the glass, the seal breaks and the metal is suctioned into the hollow centre (Figure 2)."

Jan 1, 2018

By S. Espley, T. Nyabeze, D. Beneteau

"Many mentorship programs are available to Canadian mining industry employees. Some are company-led initiatives, whereas others are provided through educational institutions or nonprofit organizations. In 2016, a national survey was launched to gain insight into perceptions of what mentorship is, learn about available programs, and collate experiences with formal and informal mentorship opportunities. This paper outlines survey findings and delivers recommendations to industry for consideration in employee mentorship programs. In addition, mining industry leaders share their mentor/mentee perspectives. The intent of this paper is to bring awareness of best practices that can help employees grow and develop in their profession.RÉSUMÉ Les employés de l’industrie minière canadienne ont accès à de nombreux programmes d’encadrement. Certains sont des initiatives menées par les sociétés, d’autres sont proposées par le biais d’établissements d’enseignement ou d’organismes à but non lucratif. En 2016, une enquête à l’échelle nationale a été lancée en vue d’obtenir des informations quant à la perception de ce qu’est réellement l’encadrement, de découvrir les programmes proposés et de comparer les expériences aux possibilités d’encadrement, officielles ou non. Cet article présente les résultats de cette enquête et fournit des recommandations à l’intention de l’industrie afin qu’elle les prenne en compte dans ses programmes d’encadrement des employés. En outre, des chefs de file de l’industrie minière partagent leurs points de vue conseillers/protégés. L’intention de cet article est de sensibiliser les employés aux meilleures pratiques, ce qui les aidera à évoluer et à se développer dans leur profession. INTRODUCTIONThis paper about mentorship in the mining industry is based on voluntary responses to a cold survey, written and circulated by the authors. In 2016, a link to an online mentorship survey was circulated to males and females in the mining industry with the belief that mentorship programs should be available to everyone. The link was delivered via the authors’ personal networks in mining, the CIM Reporter, Women in Mining (WIM) email blasts, LinkedIn, and Facebook. This paper summarizes the answers to the survey questions. The paper is a follow up to one by the same authors (Nyabeze, Espley, & Beneteau, 2010), which was written to gain insight into why women join and stay in the mining industry, and to learn why the overall representation of women is low."

Jan 1, 2018

By A. A. Rogozhin, E. G. Likhnikevich, S. I. Anufrieva, A. V. Kurkov

"Russia is among the nations holding the world's largest lithium ore reserves. Lithium is of key importance for the global economy. Therefore, it is important to review the current state of technology research aimed at finding the most effective solutions for the recovery of lithium from promising reserves in Russia. In Russia, a number of process solutions for the flotation of spodumene into salable concentrate (5% Li2O) have been implemented at the earlier existing complex low-grade ore concentration project. By applying these solutions, a sample of high-grade spodumene ore (4.7% Li2O) of the Greenbushes deposit was processed into a spodumene concentrate (7.5% Li2O) at a high recovery (~93%) of lithium. In Australia and Canada, new processes have been developed for the recovery of high-grade spodumene concentrates from high-grade ores using dense medium separation and flotation. For the recovery of mica lithium concentrates from low-grade ore, a flotation process was developed in Russia using the cationic collector ANP-2 and Oxifos-B as an additional collector. Low-grade ore containing 0.14% of lithium oxide was processed into a 2.7% Li2O concentrate. New hydrometallurgical lithium concentrate and ore processes are developed to avoid high-temperature (>1000 °C) roasting. The Sileach process (Australia) includes leaching of lithium ore with sulfuric acid in the presence of a halogen-containing component at a temperature of 95-115 °C. In the Russian process, lithium is recovered into an alkaline solution from low-grade spodumene ore in a pressure alkaline leaching environment (250 °C, NaOH concentration > 300 g/l). The developed concentration and hydrometallurgical methods will allow to design on their basis efficient processes for recovering salable products for hi-tech industries from lithium ores.INTRODUCTION Lithium has many unique and important properties. It is the least dense hard metal. Its alloys have some of the highest strength-to-weight ratios. Lithium has the lowest melting point of all known solid elements and is used as a highly-effective heat transfer medium. The high demand for lithium is due primarily to its unique electrochemical potential and low thermal expansion coefficient. It is used in the production of glass and ceramics, in petrochemicals, metals, medical and other industries. Since the late 20th century, the electronics industry has been the largest consumer of lithium. In recent years, lithium has attracted much attention also as an important component of ultra-lightweight electronic devices. It is also the preferred metal for electric batteries used in mobile electronic devices, vehicles, household power generators, making it an important resource for the development of environmentally friendly technology. Leading automotive brands have ambitious plans for the production of electric cars — Tesla Motors, VW, Toyota, GM, BYD Auto. It is expected that the production of electric vehicles alone will triple the demand for lithium by 2025. A sharp increase in the production of lithium is expected. Lithium has all the prerequisites to become a strategic resource of the 21st century. (Deutsche Bank, 2016; Bradley et al, 2017)"

Jan 1, 2018