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By A. M. Childs, R. F. Mather, K. R. Rawling

"The challenges encountered in the design and construction of mines and their process facilities today are becoming more intense and the engineering more competitive. The need to incorporate new techno1ogy to compensate for ever rising costs is always present, but its application in the harsh environment of Northern Canada increasingly requires the inclusion of new proven methods and innovative approaches to arrive at economically attractive projects.This paper deals with the development of the process design for the Cullaton Lake Gold Mine in the Northwest Territories. Particular emphasis is given to the interaction of the imposed construction and testwork schedules, and their effect on certain process decisions.The challenge that faced the project team may be defined by the following factors:1. A schedule which required that metallurgical testing, engineering, and procurement and delivery of all equipment and construction supplies should be complete within a period of ten months.2. Transportation of all personnel, equipment and supplies to the site by airlift, as no road was available or affordable.3. A six week period when transportation to the site was impossible.4. The extremes of temperature beyond the tree line in the Northwest Territories.5. A complete lack of infrastructure in the area."

Jan 1, 1983

By J. A. Meech, R. J. Tucker

"Since the establishment of froth flotation as an effective method of mineral beneficiation there has been both academic and industrial interest in the levels of the various reagents required to perform the desired separations. Academic interest was spurred by a desire to understand the mechanisms involved - industrial interest by a need to improve the efficiency of the process. These efficiency improvements can take two forms: cost reductions due to reduced reagent consumption and/or improved separation efficiencies. The latter are indicated by either improved grade-recovery relationships for removal of a valuable mineral from gangue, or improved separation of two similar valuable minerals.The processing of lower grade ore bodies at higher tonnage rates has necessitated increased interest in both reagent consumption and metal recovery. Furthermore, the development of accurate and functional on-stream analysis equipment in the 1960's and 1970's has allowed for a better understanding of the dynamic processes involved in a flotation circuit and has required a more concrete statement of the relationships and reactions between the minerals and chemicals in the flotation pulp. Development of these relationships is necessary in order to make use of on-stream analysis to control the process at, or near its more efficient level."

Jan 1, 1984

By Ertugrul Alp

Alp & Associates - Who We Are ?? Canadian consulting company (1999-?) ?? Principal Consultant: Dr. Ertugrul Alp, P.Eng. ?? Over twenty-five years experience serving the chemical, mining, pulp & paper, energy, steel, and transportation industries, and government clients. ?? Ph.D. in Mechanical Engineering, University of Waterloo ?? Experience: ?? Westinghouse Canada, Atomic Power Division, Manager, Analysis and Modelling ?? Concord Environmental (later Bovar Environmental), Principal, Manager, Air Quality and Risk Assessment ?? Arthur D. Little, Associate Director, Safety & Risk Practice Leader in Canada ?? Member: NATO CCMS Pilot Project on Disaster Preparedness (1991-1993) ?? Chair: MIACC Risk Assessment Expert Committee, 1995-1999 ?? Member: MIACC Committees on Land Use Planning and Pipelines (1993-1998) ?? Member: CSA/Q850 Risk Management Standard Technical Committee ?? Member: CSA/Z1002 OHS Risk Assessment Standard Technical Committee ?? Member: CCPA/CSChE Process Safety Management Committee (1999-?) ?? Member: ISO-31000 Risk Management Standard Canadian Advisory Committee ?? Chair: CSChE Process Safety Management Committee (2005-2006) ?? Chair: CSChE Expert Committee on Risk Assessment (1999-2005) ?? CSChE 2007 Process Safety Management Award

May 1, 2008

By I. G. Townsend, S. A. Buckley, C. I. House

"SummaryBritish Petroleum plc is developing a new gold recovery process known as coal gold agglomeration (CGA) for the recovery of gold from its ores. Liberated gold grains are recovered with high efficiency by adhering to agglomerates of coal and oil. The process is simple, can recover gold grains down to very fine sizes, avoids the large scale use of cyanide and provides the industry with an important new process option.A technical appraisal of the process has been performed on an extensive range of gold bearing materials. Ore types have been identified from which high gold recoveries can be achieved. A spreadsheet based computer program has been used to estimate the preliminary capital and operating costs of the process. Comparison with established gold production costs shows that the process costs of CGA, on the appropriate ore types, are potentially very attractive, which will enable economic treatment of lower grade ores than is currently possible using conventional cyanidation. Treatment of known placer deposits or gravity concentration plant tailings may be the most rapid means of demonstrating the process at a commercial scale prior to more widespread applications.1. INTRODUCTIONWestern world gold production for the 1980s has shown rapid growth sustained by a demand for gold at a favourable price (Fig. 1). Heap leaching and CIP/CIL operations have been responsible for the major part of new production during the 1970s and 1980s with present overall production costs averaging US$200/oz in Canada, USA and Australia and US$265/oz in South Africa [l]. A great deal of research and process development effort in the 1980s has been towards the treatment of refractory ores. Operating costs for the economic processing of these ore types by currently available routes are around US$300/oz [2]."

Jan 1, 1989

By Paul Hosford, Tim Haldane

"The paper describes the fast-track development of the project from feasibility study through to detailed design and construction, highlighting the process adaptations for handling sticky ore and water management in a tropical environment, and subsequent commissioning and operating experience of the mine. The paper discusses the geological setting, the environmental and socioeconomic considerations in developing and operating a mining operation in an underdeveloped country and the logistical challenges involved in bringing a large capital investment into Central America.INTRODUCTIONGlamis Gold Ltd. acquired the San Martin project in Honduras as a result of its merger with Mar-West Resources in late 1998. Despite the prevailing low gold price environment at the time of acquisition, Glamis anticipated rapid development of the San Martin project due to the quality of the deposit and other positive factors.Following favorable exploration and permitting activities in the first half of 1999, Glamis prepared a Feasibility study. In October 1999, Glamis decided to proceed with the development of the project and selected Hatch to provide the engineering, procurement and construction management services for the project. The San Martin project was in full-scale commercial operation approximately 14 months after the receipt of Board approval, and by July 2001 the San Martin project was operating at approximately 150% of its feasibility design capacity."

Jan 1, 2002

By Tano Balbin, Valery Astakhov, Juha Timperi, Lauri Koresaar

"Online elemental analysis is the basis of optimal flotation control in mineral concentrator plants. Traditionally XRF analyzers have been used as the online analysis method. However, online XRF analyzers struggle to measure elements below calcium in atomic number (Z=20). For many processes lighter element assays would be beneficial to improve control of grade and recovery. Processes where elements below Ca are required include P, Mg and Si in phosphate concentrators, Si, Mg and Al in iron concentrators, and S and C in gold concentrators. Laser-Induced Breakdown Spectroscopy (LIBS) based elemental analysis can readily be applied to these processes. LIBS is based on generating plasma in the slurry sample by a high energy laser and analysis of the plasma by optical emission spectroscopy. Capabilities of a new Courier® 8 analyzer based in LIBS technology are demonstrated for elemental analysis starting from lithium (Z=3). Results of a plant installation in a sulfide gold concentrator provide a good agreement with the analyzer and laboratory assays.IntroductionEffective process control can be regarded as one of the fastest paying investments for a mineral processing plant. Process optimization in flotation circuits requires constant feedback of the process state. If only manual laboratory samples are available, this optimization becomes difficult due to the long delay between taking the sample and acquiring the laboratory result. If the element grades are available in online basis, the operator or automatic process control system can make corrective actions in real time.Online X-Ray Fluorescence (XRF) analyzers have been in use at concentrators for decades. The XRF analyzers can provide a fast, accurate and precise analysis from slurry streams. However, the drawback of XRF analyzers is their lack of capability to measure elements below Ca (Z=20) in atomic number. The low energy X-rays of the low atomic number elements get absorbed by water in the sample, protective window of the analyzer, or air between the sample and spectrometer."

Jan 1, 2017

By Stephen P. Quin

One of the most prospective undeveloped greenstone belts in Canada, the Hope Bay greenstone belt extends over 80km in a north-south direction and is between 7 and 20km wide. The belt lies on the arctic coast and comprises mafic meta-volcanic and meta-sedimentary rocks that are bounded by Archean granite intrusives and gneisses. The greenstone package has been deformed during multiple events and is transected by major northsouth trending shear zones that appear to exert a significant control on the localization of mineralization. The Hope Bay belt contains a number of significant gold deposits hosted in a typical Archean greenstone belt and which occur in several geologic settings, including shear-hosted, lode-style and breccia-associated. Combined, the deposits host a measured and indicated resource of 1.6 million oz of gold averaging 15.7 g/t plus an inferred resource of 2.7 million oz of gold averaging 12.3 g/t. All deposits remain open to expansion. Exploration in the period 2000-2002 by Miramar includes more than 110,000m of drilling to more fully define the nature of the known deposits, while regional exploration has focused on identifying and evaluating new targets. In carrying out its programs, Miramar uses a number of techniques to improve its chances of exploration success. Activity in 2003 includes 43,000m of drilling focused on expanding resources in the Madrid area, testing the Boston deposit at depth and continuing the hunt for more discoveries. Meanwhile Miramar is advancing one of the deposits towards a production decision, based on a low capital, high return development scenario.

May 1, 2003

By S. Banisi, M. Pourkani, A. Kargar, D. Hamidi, M. Sarvi

"Flotation circuit of the Sarcheshmeh copper mine, which processes 40,000 t/d of ore at 0.9% Cu, consists of rougher, cleaning and recleaning stages. To study the stage recovery of copper, one of the eight identical flotation banks was selected for sampling. It was observed that 17% of copper goes to the tailings and the lowest copper recovery was for particles coarser than 105 microns. The third five-cell unit of this bank not only did not recover appreciable amount of copper but also decreased the concentrate grade. The grade of the last five cells was lower than the feed grade suggesting that mixing of the concentrates of the three units was not beneficial. To alleviate the problem, the concentrate of the first four-cell unit was directed to the cleaners feed box (i.e., by- passing the regrind mill). This increased the overall copper recovery by 1.7 %. Also rather than the current practice of adding the reagents only at the feed tank (i.e., 100-0-0%), various combinations of stage addition were examined. It was found that 75-25-0% addition regime could increase the total copper recovery by 1.3%. At the recleaning stage in order to increase the final copper concentrate grade, a froth washing system was used. To ease the maintenance of the system, a shower type washing system was installed. The optimum wash water superficial flowrate was found to be 0.06 cm/s. Continuos sampling of the recleaners with and without wash water over a period of two months showed an increase of 1.5% in the final copper concentrate grade at constant overall copper recovery.INTRODUCTIONThe Sarcheshmeh copper ore body that may rank as third or fourth largest in the world contains 1 billion tonnes averaging 0.9% copper and 0.035% molybdenum. It is located in southeastern Iran and has been processing 40 000 t/d of ore since 1982. The mine produces 100 000 tonnes of copper and 2200 tonnes of molybednite concentrate per year.After three stages of crushing, the ore with a F80 (80% passing size) of 12.7 mm is fed to eight parallel ball mills in closed circuit with cyclones to produce a product 70% finer than 75 microns. The concentrate of rougher flotation circuit is ground; rougher tails constitute the main component of the plant final tailings. A concentrate with an average grade of 31% Cu (chalcocite and chalcopyrite) is obtained after cleaning and re-cleaning stages. Total recovery of the plant varies between 83% and 87%, depending on operating conditions and ore type."

Jan 1, 2001

"At a current mining rate of 3,750 tons per day, La Mine Doyon is currently the largest gold mine in Canada. La Mine Doyon is an open pit gold mine located in the Abitibi area of Northwestern Quebec. The project is a joint venture between Soquem, a Quebec Crown Corporation in the resource development field and Lac Minerals Ltd., a publicly-held, resource development company. Lac Minerals is the managing company and operator of the project.Doyon went into production in 1980 on a very limited basis at 600 tons/day, and has seen a step wise increase to the current rate of 3,750 tons/day. Initially, all the ore was processed at Noranda Mines, Horne Division as flux for the copper smelter. The East Malartic Mill in Malartic was then upgraded and began processing Doyon ore. The third step in the progressive increase of throughput was the commissioning of the Doyon mill in November of 1982. Doyon ore is currently being processed at all three locations.During 1983, an exploration ramp was driven to explore the ore below the ultimate pit depth. Current plans indicate the sinking of a shaft and the commencement of underground mining during the next 2 or 3 years.Since its humble beginning, La Mine Doyon has always been a success; ore reserves have been extended to the east and the west and will soon be confirmed at depth, the mining and processing rates have been increased 6 fold, and the recovery has been increased from a designed recovery of 85% to over 95%. The intent of this paper is to trace the history and reasons for these rather dramatic improvements."

Jan 1, 1984

By M. Fan, M. Mankosa, G. Luttrell

"Column and other non-conventional flotation approaches continue to provide benefits where conventional flotation processes have exhibited limited success. This is particularly evident with respect to flotation of ultrafine and coarse particles. Advancements in air sparging technology have provided the ability to produce finer bubbles than previously possible. The generation of finer bubbles coupled with the froth washing capabilities of a flotation column has demonstrated improvements in ultrafine particle recovery while simultaneously producing a high-grade float product. On the other side of the spectrum, the use of these sparging technologies while applying flotation fundamentals to a fluidized-bed reactor has increased the maximum floatable particle size up to and in excess of 3 mm. Benefits of higher recoveries and reduced reagent consumption have resulted from the use of these technologies. An additional benefit includes a reduction in plant grinding requirements. As such, this paper describes the application of Cavitation-Tube sparger technology and fluidized-bed flotation (HydroFloat). A review of data from industrial and pilot-scale applications is also provided.INTRODUCTIONConventional (mechanical) froth flotation is considered the workhorse of the minerals processing industry. This low-cost process makes it possible to selectively recover minerals by exploiting the difference in surface characteristics (e.g., wettability) of the valuable component and the waste material. Unfortunately, the upper particle size limit for flotation rarely exceeds 0.600 mm, and is typically maintained at less than 0.300 mm for most industrial applications. For many commercial base metal plants, the particle size range for optimum recovery is typically between 0.01 and 0.1 mm (Lynch et al., 1981). This finding is not novel. In fact, the effect of particle size on flotation recovery was studied as early as 1931 by Gaudin et al. who showed that coarse (+0.250 mm) and extremely fine particles (-0.010 mm) are more difficult to recover than particles of an intermediate size. The loss of recovery is due to inherent limitations associated with the flotation process, including bubble-particle adhesion and collision, detachment, buoyancy, and transport."

Jan 1, 2010

By H. Agnerian

"A survey of 925 mineral property transactions worldwide was carried out between 1987 and 2004. These mineral properties with reported Mineral Resources include 457 gold properties, 322 base metal properties, and five platinum group element (PGE) properties. Based on constant Canadian dollars, the results of the survey indicate that:• In general, unit metal values in the ground (e.g. $/oz Au or $/lb Cu) have kept pace with the changes in the respective metal prices during the period of the survey.• A general decrease in unit gold values in the ground has occurred from about $57/oz Au in 1987 to about $11/oz Au in 2002 for Canadian mineral properties, with the exception of a peak of $58/oz Au in 1996.• A similar trend for mineral properties has occurred in the United States, but with lower unit values, in the range from $1/oz Au to $10/oz Au during the last three years of the survey. • Unit metal values in the ground for gold properties in Canada were higher than for those in the rest of the world.• Unit metal values in the ground for copper properties in Canada were in the mid-range compared with other countries in the rest of the world; the United States and Australia were higher and Latin America, Asia, Africa, and Europe were lower than in Canada.• Unit metal values in the ground for zinc properties in Canada were also in the mid-range compared with other countries in the rest of the world; Latin America and Europe were higher and the United States, Australia, and Asia were lower than in Canada.• Unit metal values for nickel properties in Canada were highest compared with other countries in the rest of the world, followed by the United States, Australia, Africa, and Asia.• Gold values in the ground in Canada have ranged from 6% to 14% (with an average of approximately 10%) of the gold price.• The unit values of base metals in the ground have been in the order of 2% of the quoted metal price, during the period of the survey."

Jan 1, 2006

By J. Yue

"Mount Milligan mine is located in northern British Columbia. The concentrator employs conventional SABC grinding circuit with bulk sulphide flotation processes. Commissioning started in September of 2013 and nameplate production of 60,000 TPD was reached in the fourth quarter of 2015. As is typical with many mill ramp ups, bottlenecks developed as throughput increased. Since then, plant modifications and new control philosophies in the comminution and flotation circuits have been implemented and evaluated. The mine-to-mill collaboration played a key role in reaching target throughput rates by improving blast fragmentation and implementing temporary pre-crushing. Results of the projects as well as ongoing challenges/bottlenecks and solutions will be discussed.IntroductionMount Milligan Mine is a copper-gold producer located approximately 253 km northwest of Prince George in British Columbia. Production commenced in September 2013 and reached nameplate capacity of 60,000 TPD in December 2015. Average head grades for the mine life average 0.18% Cu and 0.39 g/t Au.Circuit DesignOriginal process design began with run-of-mine ore from the pit crushed through a 60-110 gyratory crusher, conveyed to a live ore stockpile and fed to the mill via four variable apron feeders. The concentrator circuit employs SAG mill - Ball mill - Pebble Crusher (SABC) grinding configuration to grind the ore down to a target P80 of ~200µm. It is then fed to two parallel trains of flotation tanks, each consisting of five 200 m3 tank cells with the first two being roughers and last three being scavengers. Concentrate streams from roughers and scavengers are separately reground with a closed circuit Tower mill and two open circuit ISA mills operating in parallel, respectively.Three stages of cleaners upgrade roughers/scavenger products to 25% Cu followed by a cleaner scavenger stage. The final concentrate is then thickened and filtered to approximately 9% moisture and shipped off site (Figure 1)."

Jan 1, 2017

By Flavio Rojos-Tapia, Oscar Pereira-Cerda, Samuel Sánchez-Pino, Samuel Sánchez-Baquedano

"Pneumatic flotation was introduced to the Chilean Copper Mining Industry in 1993 by Ingeniería de Minerales S.A. (IDM). The technology is based on the designs of Dr. Rainer Imhof from Germany, who is the designer of several different types of pneumatic flotation cells, already sold through his Company Maelgwyn Mineral Service Limited (MMH). The company is represented by Ingenieria de Minerales S.A. (IDM) in South America.Pneumatic flotation, has been used in tough industrial applications .It has been successfully used for metallic ores such as copper sulphide and oxide minerals, copper slag, silica and silicates from iron magnetic preconcentrate (reverse flotation) and gold. It has also provided promising results when applied to molybdenum flotation. The latest applications, with ultrafine molybdenum particles in operating plants, is showing the V and G Cell (end model designed) as a real technological alternative to conventional flotation., The G Cell is an extremely high speed flotation machine with high selectivity which introduces the possibility of producing a final molybdenum concentrate with only one stage of cleaning. This is a completely new development in molybdenum flotation in the industrial circuit which has the potential to dramatically reduce the circulating load in the cleaning circuit. As a consequence the capital costs of future Molybdenum plants may also be reduced. The suitability of the G Cell will have to be determined on a case by case basis but it provides the metallurgist with an alternate flowsheet for consideration.The good performance of the G Cell can be explained by the high gas hold-up and very effective micro-turbulence which helps improve the attachment of solid particles to the bubbles. This technology may change our traditional concept of residence time in flotation. Additionally, the rotation phenomena introduced in the vessel of the G Cell ,creates radial separation forces which are critical to achieving a more rapid separation of the target minerals from the tailing. This results in a much reduced residence time requirement in the flotation machine. Some benefits associated with the use of the new G Cell are: less energy consumption, less maintenance costs, simple and reliable circuit to operate and a small area required for installing the circuits.As a result of the industrial experience in the Chile, the pneumatic flotation type G Cell can be regarded as a technology which must be considered as a replacement technology for the rougher and cleaner stages for fine particle flotation."

Jan 1, 2008

By R. C. Bryce

"Selbaie is located northwest of Joutel, in what is known as the fourth east-west volcanic sediment group in northwestern Quebec. The main metals produced are copper and zinc, with important contents of both silver and gold. Production comes from an open pit mine on the A-I zone and from two underground mines on the B zone and the A-2 zone. Each mine gave rise to important capital investment programs for construction and mine development, all of which were managed and staffed with company-hired, non-union personnel. Production from all sources now exceeds 7000 tonnes per day, with a workforce of540 regular employees. Of particular interest technically is the high recovery of B zone reserves underneath 40 m of overburden cover, the low-cost capital development of the A-2 zone, the computerized control of open pit mining, and the successful copper-zinc separation of the A-1 zone ore. Due to the low grades of the mineral deposits, efficiency in all aspects of the production process, is essential to the success of the operation.LocationThe Selbaie Mine is located 82 km northwest of the locality of Joutel in northwestern Quebec (Fig. 1). Access to the mine is by an all-weather road, 32 km of which is paved. A second road access to the site is via La Sarre, 134km to the southwest. Employee access, materials transport and haulage of copper and zinc concentrates take place over both of these roads."

Jan 1, 1990

"Mineral separation by exploiting the differences in mineral or metal specific gravities (sg) has been used since antiquity. In the modern era, this is most commonly seen in the recovery of gold by the use of centrifugal concentrators and the separation of coal (low sg) from waste rock (high sg) using heavy media cyclones and jigs. Other metals, notably oxides of tin and tungsten, are successfully recovered using some combination of jigs, spirals and shaking tables. However, many conventional gravity separation systems are limited to fairly coarse (>1 mm) to medium (>100 micron) particle separations due to the limitations of the gravitational separation forces in conventional equipment.Many of the high specific gravity minerals of interest are friable (e.g. cassiterite, wolframite, etc.) and excessive fines are generated in the grinding/comminution circuits which cannot be recovered with conventional equipment and may be lost directly to the tailings stream. Recent developments in centrifugal gravity separation equipment specifically designed for fine or ultra-fine particle separation and recovery have resulted in heavy mineral particle recoveries as fine as 10-20 microns. Ongoing research work has also identified the benefit of closed-circuit, multi-stage gravity recovery circuits using some combination of centrifugal concentrators and conventional equipment (tables, spirals, flotation, etc.) which can substantially increase overall plant recovery and final concentrate grade.This paper will provide details of the evolution of non-fluidized bed gravity concentrators for high sg mineral recoveries, correlate laboratory scale development work with plant results to confirm scale-up, and show how recent flowsheet developments have contributed to significantly improved plant performance.IntroductionGravity concentration is one of the oldest and most cost effective metal and/or mineral recovery systems, ranging from the classic hand panning of alluvial gold, through to the large scale production of a wide range of metals and minerals, including gold, silver, PGMs, black sands, coal and iron oxides. Conventional gravity recovery systems, comprised of some combination of sluices, spirals, jigs and shaking tables have limited application in fine particle (i.e. <100 microns) recovery, or where there are limited differences in particle specific gravities (sg), e.g. the separation of high sg, high value metal oxides (e.g. those of tin, tantalum or tungsten), from medium sg, lower value metal sulfides such as pyrite and pyrrhotite. These unit operations tend to have limited capacity, and while double and triple turn spirals and multi-deck tables have been developed, extensive floor space is often required in order to process the tonnages incorporated in the modern mineral processing plant."

Jan 1, 2017

By Nick D. Rose

The Dy deposit is a 21 Mt Pb-Zn-Ag-Au SEDEX-type massive sulphide resource located in the Anvil District, Faro, Yukon. This relatively unexplored orebody lies at a depth of 480 to 920m below surface, dips 20 to 35o and comprises vertical ore thicknesses of 3 to 28m at a 9% Pb + Zn cut-off grade. The deposit has been tested at depth with 63 surface diamond drillholes, but has not yet been explored or developed by underground means. Over the past decade, pre-feasibility investigations were conducted for two separate owners of the property to determine the economic viability of developing an underground mine at Dy. Following these previous studies an assessment was undertaken between 1998 and 2000 to further investigate geotechnical considerations for underground mining. The results and conclusions drawn from this study provide direction for possible future exploration at Dy.

May 1, 2002

By J Petrolito

"To improve the economic and environmental performance of underground mining operations, it is common practice to return the metallurgical waste material underground as backfill. This is called hydraulic backfill and is used to fill the mined-out areas not exposed to further mining. To provide mechanical support for underground mining a cemented backfill is normally used. Since its introduction, cemented backfill has allowed mining companies to increase their ore extraction and improve working and environmental conditions. However, cemented backfill represents up to 50% to 85% of the mine’s operating cost compared with 5% to 10% for hydraulic backfill.These economic pressures have led mining companies to carry out research into the partial or total replacement of cement using a variety of alternative materials. The materials are generally site-specific materials, readily available, and cost-effective relative to cement. Such investigations have led to reduced cost of many backfill mixes while maintaining, and in some cases improving, the physical properties of cemented backfill. However, in most cases, cement still remains an integral part of any binder combination. This can be attributed to the alternative binders investigated being either non-binding materials or capable of generating only low-strength backfills, except when used in conjunction with cement.This paper provides a historical review of backfilling binder materials and their characteristics. In particular, it reviews the many alternative materials that have been proposed to either partially or fully replace Portland cement as the main binder."

Jan 1, 2005

By Louis J. Cabri

"Mineralogical evaluation of ores containing platinum-group elements (PGE) is fraught with difficulties because of the low grades (often 1-3 g/t PGE), dispersal of PGE (usually as finegrained platinum-group minerals [PGM]), as well as occurring in solid solution in some base metal sulphides (BMS) such as pentlandite and pyrrhotite. Mineral processors not only need to know how the PGE are distributed, that is, their mineralogical distribution, but the grain sizes of the PGM, and especially the associated minerals.After obtaining a representative ground sample, common approaches include studying a large number of polished or polished thin sections, concentration of the PGM and sulphides by different gravity methods (e.g., heavy liquids, elutriation, micro-panning) and study of the produced concentrates. Unfortunately, these methods often do not produce concentrations that are sufficiently representative of a particular ore. The newly developed patented technology of hydroseparation (Rudashevsky et al., 2002) is especially effective at making concentrations of PGM over a wide range of concentrations (down to <300 ppb Pt+Pd+Au) and size fractions, including <45µm (down to a few micrometres in size), a size range not possible by other techniques. This water-based environmentally friendly laboratory technique provides a large amount of data from samples, which can range from 5 to 1000g, giving confidence to extrapolation of results to bench-scale and larger test work, especially when combined with quantitative image analysis to determine modal percent of major minerals and mineral liberation data, needed to predict the minimum (K80) and optimum (K40) grinds. INTRODUCTIONThe invention of the electron microprobe in the early 1960’s and scanning electron microscopes (SEM) with energy dispersive spectrometers (EDS) in the 1970’s presented mineralogists with powerful tools permitting them to obtain chemical and surface area data on minute amounts of minerals in situ, in a non-destructive manner. An area of process mineralogy that has very much benefited from this new technology was the characterization and understanding of PGM species, resulting in rapid growth of newly characterized species (Figure 1). Recognition of the first PGM may be ascribed to the Spanish explorer Ulloa in 1748, who described native platinum from South America. The second PGM (laurite, RuS2) was only recognised in 1866 by Wöhler in placer samples from Borneo (now Kalimantan) and the third (sperrylite, PtAs2) by Wells in 1889 from the Sudbury Ni-Cu sulphide deposits. The discovery of the important Pt-Pd deposits in the Bushveld Igneous Complex led to the characterization of the important Pt-Pd sulphides (cooperite, PtS2 in 1928 and braggite, (Pt,Pd)S2 in 1932). By the early 1960’s, only about 20 PGM were recognised, and many later proved to be poorly or incompletely characterized. Thus, the introduction of electron probe microanalysis (EPMA) led to a 50% increase of known PGM, as shown in a 1972 review on PGM (Cabri, 1972). At the time of the next review in 1981 (Cabri, 1981) the number of known PGM had grown to 75 and as of 2002, it had increased to 109 (Cabri, 2002). However, it is the author’s experience that less than about 25 PGM may be considered to be “common”, i.e., found in many different deposit types, as shown in Table 1, but usually only some of these occur in any one particular deposit."

Jan 1, 2004

By S. Banisi, J. Marois, A. R. Laplante

"This paper compares the behaviour of gold and ore in the grinding circuit of Hemlo Gold Ltd. Particular attention is given to grinding kinetics, classification behaviour, and liberation. For grinding kinetics, laboratory grinding of gold flakes and silica, 840-1200 um in size (14/20 mesh), was also performed to provide a standard for comparison and to study in a controlled environment the mechanisms of breakage, folding, smearing and impacting.Grinding kinetics were characterized at laboratory scale with breakage and selection functions. The breakage function showed that 75% of gold disappearing from the 840-1200 um class reported to the 600-840 um; this figure is much higher than for silica ( 46%) or most other minerals, and implies that comparatively fewer fine fragments are produced from the breakage of gold flakes, on account of gold's malleability. The selection function of silica was four times that of gold. At plant scale, the ratio of the selection function of ore and gold increased from 6 for at 50-100 um to 20 at 500-1000 um.Observation of original flakes and their fragments with the scanning electron microscope showed that the main mechanism of ""grinding"" from the 840-1200 um to the 600-840 um class was folding rather than actual breakage. This was confirmed by a measure of individual flake weight. The postulated breakage cycle is that relatively globular flakes become increasingly serrated through grinding; they can then regain their original shape through folding and reflattening into cylindrical and spherical shapes, as the majority does; however, some fragments will at this point undergo actual breakage. Photographic evidence is presented to support the proposed mechanisms.Smearing of gold unto silica was observed when silica was ground after a gold, and embedding of silica into gold flakes when gold was ground after a silica. Both mechanisms occur whenever gold and harder minerals are jointly ground, and result in ""unliberation"" of gold. It is postulated that smearing of gold onto other minerals plays an important role in explaining how gravity recovery can increase overall gold metallurgy, especially when used ahead of flotation.Classification of gold in the primary hydrocyclones takes place at a much finer cut-size than ore, 20 vs. 57 um. This and the slower grinding kinetics result in high gold circulating loads in the primary loop, 6700%, and a gold content in the primary cyclone underflow (PCUF) is twenty four times that of the ore. The gold size distribution for primary cyclone overflow is much finer than that of the ore, although they are essentially similar in the PCUF.Liberation, or more accurately ""gravity recoverability"", was assessed with a 7.5 cm (3"") Knelson concentrator. It varied between the thirties for the primary mill discharge and two cyclone overflows, to highs of 89 to 92% for the PCUF and secondary mill discharge, 89 and 92%, respectfully."

Jan 1, 1991

By B. S. Fee, R. R. Klimpel

"Froth flotation is the most widely used and economic means of concentrating metal sulfide ores such as those containing copper, lead, zinc, nickel, molybdenum, and pyrite. Also recoverable are other metal species that are often associated with sulfide ores such as cobalt, platinum, gold, silver, etc. Most of the initial developments made with the process of froth flotation in the early 20th century were based on the processing of metal sulfide ores. It is the relative technical and economic ease of floating metal sulfide minerals with small amounts of appropriate frothers and sulfur containing (thio) collectors that has been a major economic driving force behind the rapid expansion in the supply of metals such as copper, lead, zinc, and nickel that has occurred in the world's economy in the last 50 years. This author estimates that 1.6 billion tons of sulfide ores are processed each year (1980) in the free world based on the froth flotation process.While there has been a tendency for the quality of metal sulfide ores in any one geographic location to deteriorate over time due to mining intensity, the overall global supply of sulfide minerals is still very large. Thus, the physical supply side of sulfide ore concentrates has not been under strong technology improvement pressure with increasing metal demands. Part of this is due to the ability of capital to consistently move to new geographic locations having suitable grade sulfide ores. In these moves, the actual froth flotation technology used (including collector chemicals) has had to change little. As an illustration of this trend, of the approximately 80,000 metric tons of thio collectors used commercially (1980) in the free world, almost 98% were known and manufactured in some form 25 years ago (1). This is clearly not typical of reagent development in other process related industries. In addition, the industrial scale practice of froth flotation applied to sulfide ores has proceeded since the 1920 s with often little direct (predictive) scientific explanation due to the extreme complexity of the flotation process. Empirical testing has been a mainstay of industrial flotation reagent development and use. Even today there is often strong disagreement between researchers as to the mechanisms of chemical flotation practices that have been performed successfully at an industrial scale for many years."

Jan 1, 1987