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By M. Cai

A practical simple method is proposed to estimate the tensile strength (st) of strong brittle rocks from the strength ratio of R= sc/st = 8 sc/sci, where sc is the uniaxial compressive strength and sci is the crack initiation stress in an uniaxial compression test. 8 is the Griffith strength ratio and the term sc/sci accounts for the difference of crack growth or propagation in tension and compression in uniaxial compression tests. sci can be reliably obtained from volumetric strain measurement or acoustic emission (AE) monitoring. With the strength ratio R determined, the tensile strength can be indirectly obtained from the result of uniaxial compression tests. In addition, a practical estimate of the Hoek-Brown strength parameter mi is presented and it is suggested that mi = 12 sc/sci can be applied to strong, brittle rocks in high confinement zone and mi = 8 sc/sci can be applied to low confinement to tension zones. It is found that the predicted tensile strengths and Hoek-Brown strength parameter mi using this method are in good agreement with test data. The rock strength parameters like st and mi, which require specialty tests such as direct tensile (or Brazilian) and triaxial compression tests for their determination, can be reasonably estimated from uniaxial compression tests.

May 1, 2009

By I. Jackman

"Gold is present in different forms and associations in different ores. Flotation is used to recover gold and minerals associated with gold, but the applicability and type of flotation vary. The purpose of flotation in a gold recovery plant is largely dependent on the mineralogical association of the gold, and environmental and economic considerations. In this paper, the role of flotation in the recovery of gold is reviewed. The paper will describe examples of gold recovery by flotation including flotation of native gold, gold associated with sulphides including specifically copper sulphides, gold associated with tellurides, gold ores containing carbonaceous material and gold contained in tailings.INTRODUCTIONFlotation is widely used in the recovery of gold. However, the objectives and the mode of application are quite variable dependent on the type of ore, the gold association(s), other metal values, marketing considerations and environmental requirements. In this paper, a range of different applications of flotation incorporated in the recovery of gold are discussed. The reasons for each particular application are outlined and metallurgical results are presented.The mineralogy of the ore and the gold associations are fundamental influences on gold recovery. The use of flotation to concentrate gold is dictated by the mineralogy of the ore and gold. The fundamental factors are mineral/gold size, liberation size, association of the gold and type of gangue minerals or other valuable minerals. Gold can exhibit a range of sizes in a host from relatively large size (+50 µ) to refractory size (1 µ and sub-micron size). Similarly, the gold can occur in a number of phases in the same host. For example, the gold was present as petzite (AgAu telluride), calaverite (AuTe2) and native gold in a gold telluride ore and each of these minerals was associated with the pyrite host.Understanding the gold mineralogy and association is important in establishing the correct process route. The gold mineralogy is established by good mineralogy, use of diagnostic tools such as diagnostic leaching and assay by size fraction analyses and basic metallurgical testwork."

Jan 1, 1995

By G. Auld

"A simple method is presented whereby the additional quantity and static pressure necessary to compensate for ventilation duct leakage may be estimated using the circular reference functions of modern spreadsheets. Favourable comparisons have been made to the National Coal Board (United Kingdom) design charts and to a case study analysis. IntroductionIn mining, most ducted systems are applied to the development of access tunnels, and most of these systems leak to some extent. When the ventilation duct fails to deliver the required quantity of air to the work place, there is a significant contribution to the development costs, either directly or indirectly.Directly — More air and more pressure are required to compensate for the leakage, more capital development (ventilation shafts, parallel drives) are required because ventilation systems cannot push the fresh air far enough, and longer re-entry times to ensure toxic blast fumes to be diluted.Indirectly — There is a reduction in productivity because of the inclement atmospheric conditions, and/or closure of development ends because of unacceptable atmospheric conditions at the working place. This has been exacerbated over the last few decades because of the increased use of diesel equipment of ever increasing power, and the more stringent Occupational Health and Safety requirements demanding more air flow per kilowatt of diesel power.The leakage from a duct must, therefore, be reliably estimated in order to assess the effectiveness and construction of the system; assess the effectiveness of the maintenance or repair of the duct; appreciate the cost of the leakage, and therefore apply effective maintenance and installation procedures; and engineer safer, healthier and more cost-effective ventilation systems."

Jan 1, 2002

By P. D. R. Maltby

"1. INTRODUCTIONMy talk today will discuss a new development in the thickening of slurries and clarification of waste water - the Enviro-Clear thickener. Several industrial installations of the thickener have been made in North America in the following applications:1.,water clarification in sugar beet processing plants.2.,separation of pregnant liquors from solid wastes following acid leaching in uranium mills3.,clarification of waste water from coal treatment plants as described in a paper in the June 1975 transactions of the SME entitled ""Application and Utilization of the Enviro Clear Thickener in a U.S. Steel Coal Preparation Plant"" by A.A. Terchnik, D.T. King and J.S. Anderson.2. HISTORYThe application of the Enviro-Clear thickener can be traced back to the filing of U.S. Patent 3523889 in 1970 by the inventor F. Eis. The claims of this patent are shown in Slide 1.The new concept was developed for sugar beet processing by the Spreckels Division of Amstar Corporation, and several such thickeners have subsequently been installed in various sugar beet plants. The Enviro-Clear Co. or New York took over the world-wide manufacturing and marketing of the thickener. Experience in the sugar beet industry indicated that the Enviro-Clear thickener volume requirements could be reduced to as low as one tenth that of a conventional type thickener. Various coal samples were supplied by U.S. Steel Research Laboratories for testing. The tests indicated that feed rate loadings of 3 gpm/ft.2 could be obtained by the Enviro-Clear thickener. Such results led to several industrial applications in the coal industry. Subsequently other branches of the mineral processing industry have come to learn of the possibilities of using this thickener. Slide 2 shows a list of commercial Enviro-Clear installations at the end of 1975."

Jan 1, 1976

By J. Dong

"Xanthate is a sulfide collector that has been widely used in flotation for almost a century. It is inexpensive, easy to synthesize and apply, and produces good metallurgy in the right applications. However, a major drawback of xanthate is that it decomposes easily and generates CS2 gas in transportation, storage and operation, which can be harmful to human health. Also, excessive xanthate in tailings pond leads to toxicity of the process water and potential damages to aqua-life systems. New regulations in Ontario require that the TWA (time-weighted-average) value of CS2 in the work place is below 1 ppm, which is 1/10 of the previous limit. The stringent regulation may eventually sweep other regions of Canada with the increased awareness of healthy working conditions and environment protection. Therefore, it becomes very important to find xanthate replacements which will be “green”, i.e., environmentally friendly.In this research work, a systematic procedure is used for collector evaluation using the Sudbury nickel sulfide ores from Vale’s Ontario operations, starting with the collector properties (MSDS) evaluation, followed by batch flotation tests, miniplant tests, plant trials and economic evaluation. It is found that the most promising xanthate replacement is dithiocarbamate.INTRODUCTIONSulfide mineral flotation has been practiced since the early 20th century. Its industrial importance is well recognized as mineral concentrates from flotation can be economically smelted and refined to provide primary metals. Collectors play a vital role in froth flotation. There are reagents possessing both a polar group that binds them to the mineral surface and a nonpolar group that is oriented away from the surface to attach air bubbles. The introduction of xanthate as a sulfide collector in 1925 was a remarkable development in froth flotation (Keller, 1925). It is low cost, easy to synthesize, water soluble, simple to control in application. Most importantly, it has strong capability and usually good selectivity for sulfide mineral flotation, which have been keeping its application prominent for almost a century."

Jan 1, 2011

By Ian Bruce

Tailings and water management facilities are essential and integral components of mine and mill operations. They must be managed for the long term in order to ensure that safe and environmentally responsible stewardship is achieved. Toward this end, in 1998, The Mining Association of Canada (MAC) published A Guide to the Management of Tailings Facilities, which recommended the implementation of a tailings management framework (Figure 1) to integrate environmental and safety considerations into each stage of the life cycle of a tailings facility, from initial site selection and design, through construction and operation, to eventual decommissioning and closure. By February 2000 it was becoming apparent that while mining companies were making significant progress toward implementing and documenting tailings management systems, and integrating them with overall environmental management systems, further effort was warranted in their application at the operational level. In particular, a need was identified for further guidance in preparing manuals that outline procedures for the safe operation, maintenance and surveillance (OMS) of tailings and water management facilities.

May 1, 2002

By L. S. Urbanoski

This presentation describes a major modernization project at the Geco concentrator. The objectives of the program were to replace obsolete flotation equipment and upgrade process controls.Noranda Minerals Inc. — Gecc Division is located at Manitouwadge in Northern Ontario. The community is situated north of Lake Superior approximately equidistant from Thunder Bay and Sault Ste. Marie.Milling operations began in September, 1957. The mill processes a complex base metal ore by differential flotation techniques to produce copper, lead and zinc concentrates. To date some 43 million tons have been milled, qualifying Geco as a rather major base metal deposit.II. BACKGROUND:The Geco concentrator was designed and constructed in the mid 50's. A number of features specific to a concentrator of that vintage provided the justification for the modernization efforts described herein.Firstly, the mill was constructed without any instrumentation, not even pneumatic controls. Solid state electronics, computers and related instrumentation were unheard of, or rather primitive by today's standards.Secondly, some of the major equipment, in particular the flotation equipment, did not compare favourably to that in use today. MacIntosh flotation machines (more commonly known as Mac cells) were installed at Geco. These cells were prevalent in a number of concentrators built by Noranda, including Quemont Mining Corporation Limited, Gaspe Copper Mines Limited and Noranda — Horne Division. The Mac cells were used for copper and zinc rougher and scavenger operations. Some units were also installed for a pyrite recovery circuit that was never operated. In total, 104 Mac cells were installed in the main flotation area of the concentrator.

Jan 1, 1987

By Karina Forster

Rock mass characterisation is a critical component of effective stope design. Unexpected excessive stope dilution or uneconomic stope sizes can be the result of rock mass characterisation that is not representative of actual stope conditions. Comprehensive characterisation of the rock forming the stope hanging wall, back, ends and footwall is best done by a rock mechanics or ground control expert, however, this is time consuming and is often limited by available access. There are two general approaches for characterising a stope hanging wall for dilution estimating. Detailed classification and mapping data can be collected in local areas where good exposure is available. Personnel, exposure and time are usually not available to do a thorough analysis for all stopes. The stope hanging walls are then broken into lenses or domains and similar conditions are assumed for each area. The second approach consists of using readily available data such as RQD. Other rock mass properties which influence hanging wall behaviour are estimated based on back analysing a few case histories. Stope design is then based on the variability of the one parameter, such as RQD, that is consistently measured for the rock mass surrounding the ore body. This paper presents a third approach which looks, in depth, at the interpretation of geological core logging data for rock mass characterisation. Several rock mass properties that influence stope design, such as joint alteration, rock mass strength, joint spacing and orientations, have been linked to data collected by the mine geologists. This drill hole logging data was calibrated against underground mapping and used to back analyse the dilution prediction for mined-out stopes.

May 1, 2006

By Kim Le Roux

Cemented paste backfill (CPB) is a relatively new material that is increasingly being used in open stope mining across the world. The advantages offered by this high density tailings backfill include: a lower total cost associated with backfill placement, reduction of excess water underground; and the elimination of the need to process the tailings prior to placement. However, almost all backfill design is based on the performance of laboratory prepared samples since it is difficult to obtain undisturbed samples and conduct in situ testing due to the lack of access to backfilled stopes and the safety concerns in accessible areas. The logistical problems associated with conducting in situ testing and obtaining undisturbed samples of cemented paste backfill (CPB) has lead to the reliance in the mining industry on performance data obtained from laboratory prepared CPB samples. The degree to which these laboratory prepared samples represent the actual in situ condition is not well defined, partly because the influence of the mixing, transport and placement process on the material properties it is not well understood. Therefore, there is a need in the industry to understand how the material properties and hence the performance of the laboratory prepared CPB compares with in situ material. This paper reports the findings of an investigation into the in situ properties of CPB at a gold mine in Northern Ontario. A combination of in situ and laboratory testing, conducted on undisturbed samples, was used to quantify the in situ properties and performance of the CPB. These results were then compared to those of a laboratory based investigation of the same CPB. It is evident from this investigation that the bulk properties of the in situ CPB are different from those of the laboratory prepared CPB. The most significant observed differences are that the in situ CPB has a higher void ratio and a lower degree of saturation than the laboratory prepared material. The implication of these differences on the stability and performance of the CPB will also be explored in this paper. 1

May 1, 2002

By Christoph Müller

Information exchange for mine process optimization is essential. Today, modern mining equipment uses the IREDES standard to exchange production plans and reports for easy management and storage. To gain further benefits from process optimization, a mine wide access to real-time information is needed as e.g.: The current status of a machine, operational details etc. Presently, real-time data exchange systems are developed by machine producers. Each machine producer uses its own way of gathering, managing, and storing production data. These proprietary mining processes increase the complexity of cross platform data exchange and management for mines which involves machines produced by different vendors. Casting and unifying the data requires much effort. For this purpose, ?IREDES On-line? currently is being introduced. The standard defines an open, web based method for the exchange of volatile real time machine information. Two different principles are used: Web Services for cross platform information exchange within the IT world and the optional OPC UA for use with automation and process control systems. With such a standard information from machines of different vendors may be managed by using one common platform without spending the effort for dedicated interface development. Additionally, information management and storage will become straight forward since all the data are of the same format. The IREDES On-line standard utilizes the latest IT technologies as well as the knowledge and experiences gained from the previous IREDES standard. The paper explains the benefits, the use, as well as the technical design of the standard and gives application examples from the practice.

Oct 1, 2009

By Ludwig M. Strah

"Wear is a universal problem and is present in all cases wherein one weighted surface moves with or relative to another surface. A practical description of wear as applied to mineral processing plants is outlined.With the advent of higher material and maintenance costs, more attention is being focused on the field of wear resistant linings. The aforementioned is magnified today as the production facilities continue to be designed to handle larger daily capacities. These changes, higher costs and larger plant handling facilities have necessitated the introduction of different materials and designs to combat the never ending battle against wear.In order that wear be understood, it can be relegated to two specific types:1 - Mechanical Wear - due to movement of one loaded surface relative to another.2 - Chemical Wear - more easily defined as corrosionMechanical wearMechanical wear can be subdivided into two basic forms:A.,Material movementB.,Material impactMaterial movement Abrasion is the result of, as earlier stated, the straight move¬ment of one loaded material relative to another.Material impact Is the striking effect when a mass strikes another from various angles and at various speeds. Impact can be severe enough to permanently damage and distort the basic component installed to overcome impact."

Jan 1, 1983

By Michel Ruel

"PID loops – also known as base layers or regulatory controls – form the foundation of any plant’s control layer and it is generally accepted that PID loop health has a direct impact on the plant’s bottom line. Keeping these thousands of control loops in good health has a direct impact on the plant’s bottom line: it reduces variability, improves quality and throughput, and decreases energy costs and raw material usage. This has been well proven and documented in many articles. In the last ten years, technology has evolved: control engineers can now keep track of control loop performance and link it to the root causes of variability. However, they lack industry-wide best practices and criteria for determining what can be considered as excellent, good, fair, or poor performance. To ensure that PID control loops continue to perform well and meet their objectives, control engineers need a combination of (a) an appropriate monitoring technology and (b) best practices for doing the maintenance of base layer controls.Most plants have limited resources and operate with an increasing number of constraints; therefore, using the right tools and including reports in daily workflow is key for success. This paper suggests roles and responsibilities of key players needed to work toward control performance best practices and discuss organisational changes to succeed.INTRODUCTIONAlthough PID controllers are reliable workhorses in the process industry, they are often underrated. Since the 1980’s, computer control has evolved and the control algorithms used by control engineers have become increasingly complex. However, PID controllers still handle over 90% of the control loops in operating plants. Table 1 shows the savings that can be realized by achieving best-practice in several different process control categories (Brisk, 2004). The savings are expressed as a percentage of production costs."

Jan 1, 2011

By Elizabeth Wademan

Recessions Eventually End ??Companies aggressively cutting production and inventories ??these will come in-line with demand ??U.S. home inventories are declining ??Housing becoming more affordable ??Global trade recovering after collapsing ??Lower oil prices should act as a stimulus Protracted Deleveraging Process Beginning ??Era of leverage-driven consumption is over ??Greatest destruction of consumer wealth since WWII ??Consumers will no longer be able to substitute capital gains for savings ??Shift towards savings will be a headwind to economic growth ???Paradox of Thrift?

May 1, 2009

By Kristie Tarr

Portland cement is primarily used to solidify backfill in underground mine workings and it represents a major cost in mining operations. CANMET-MMSL has invented an alternative binder technology that does not contain any amount of Portland cement and is made using waste materials, such as development rock and smelter slag. The technology has been successfully tested with many types of base metal and ferrous slag. Research conducted in collaboration with several mining operations in Canada has shown that the CANMET-MMSL binder has considerable potential as a replacement for Portland cement in mine backfill. An integral part of the overall mining operation, backfill is used for two main purposes: safety and environmental remediation. Depending on the mining method used, backfill provides a working surface, stabilizes stope and pillar walls, as well as the surrounding rock mass, and controls caving of stope backs. There are several benefits associated with the replacement of Portland cement in backfill, including reductions in (i) the footprint by placement of slag waste underground, (ii) the environmental effects and long term liability resulting from disposal and containment of slag waste on surface such as acid rock drainage, (iii) GHG as a result of reduced Portland cement usage (the production of 1 ton of Portland cement produces 1 ton of GHG), and (iv) the significant costs associated with reduced Portland cement usage.

Oct 1, 2010

By E. W. Johnson

"The title of my paper is ""I 'Wonder Where The Yellow Went"". As you can readily guess, it is not related to an old-fashioned ""Pepsodent"" sales pitch! Rather, it concerns a situation which arises all too frequently in some gold milling operations, namely when actual ounces of gold production do not come up to estimated or projected ounces. The boss man scratches his head and wonders where the missing gold has gone and how it has disappeared. The problem, if one exists, is amplified if one forgets that an estimate is just that - an estimate - and not a hard fact - even though the numbers are produced by computers. And yet, from the point of view of engineering; financial and production planning and security; it is most desirable to tie together all data relating to production estimates, losses and actual production.In the course of this paper reference will be made to the term ""variance psychology"", to a few of the physical properties of gold and to the nature of its occurrence in Canadian ores, in relation to the topic under consideration. Activities which have a bearing on production estimates will be reviewed. These include: weighing, sampling, assaying, estimating residual losses and, in cyanide plants, gold precipitate production. Mention will be made of apparent, unaccounted for and unknown losses. In conclusion, I shall draw from personal experience and relate three examples of ""Where the Yellow Went''."

Jan 1, 1986

By Marco A. Vera

"This paper investigates the froth function in flotation and the associated upgrading process. Flotation literature has revealed that one of the main functions of the froth phase is the cleaning of bubble-particle aggregates by rejection of entrained material. The cleaning and transport processes across the froth phase exert straining forces on these aggregates on their way up to the froth surface. These forces will impact on the recovery of bubble-particle aggregates.The grade at the top of the froth (TOF) is a parameter related to the quality of particles collected by bubbles in the pulp zone (true flotation). It has recently been demonstrated that TOF corresponds to the maximum practically attainable grade described by the recovery-grade (or enrichment ratio) curve. TOF lumps all the processes experienced by the bubble-particle aggregates before reaching the launder concentrate. This paper describes a methodology for quantifying flotation performance by means of the top of the froth sample - a touch of froth.INTRODUCTIONFroth flotation may be the most important mineral processing technique, but its theory is complex and is not completely understood even though many aspects have been studied and reviewed (Teague, 1998; Wills, 1992).Two distinct particulate systems prevail in the flotation process: a pulp phase and a froth phase (Figure 1). The pulp zone had been studied extensively; however, it is only recently that techniques to measure the froth zone performance have been developed (Contini et al., 1988; Falutsu and Dobby, 1992; Feteris et al., 1987; Seaman, 2002; Vera et al., 1999b).Flotation involves a number of mass transfer processes, occurring in the pulp phase and the froth phase. The formation of the froth and its subsequent removal are considered to be two important steps of the process. Phenomena that occur in the froth phase are known to affect flotation performance significantly (Cutting et al., 1981).Because the froth has a high free surface energy (as a result of the extensive interfacial surface between liquid and air), it appears thermodynamically unstable. The foaming is a dynamic balance, as new bubbles are added continuously from the pulp, while others disappear from the top. Under steady-state conditions, the volumes of added and subtracted air are equal (Booth, 1953)."

Jan 1, 2003

By Stephen A. Gasiorowski, Frank J. Hrach, James D. Bittner

Separation Technologies, LLC (ST) has developed a processing system based on triboelectric charging and electrostatic separation that provides the mineral processing industry a means to beneficiate fine materials with an entirely dry technology. The environmentally friendly process can eliminate wet processing and required drying of the final material. The process requires little if any pre-treatment of the material other than grinding and operates at high capacity - up to 40 tonnes per hour by a compact machine. Energy consumption is low, approximately 1 kWh/tonne of material processed. Since the only potential emission of the process is dust, permitting is typically relatively easy. In contrast to the other available electrostatic separation processes that are typically limited to particles greater than 75 µm in size, the ST belt separator is ideally suited for separation of very fine (<1 µm) to moderately coarse (500 µm) materials with very high throughputs. The triboelectric particle charging is effective for a wide range of materials and only requires particle-particle contact. The small gap, high electric field, counter-current flow, vigorous particle-particle agitation and self-cleaning action of the belt on the electrodes are the critical features of the ST separator. The high efficiency multi-stage separation through charging / recharging and internal recycle results in far superior separations and is effective on fine materials that cannot be separated at all by the conventional electrostatic techniques. Since 1995, this triboelectric process has been extensively used for the beneficiation of coal fly ash with eighteen separators in place and over 100 machine-years of operation at locations in North America and Europe. The technology has been also successfully applied to the beneficiation of a variety of minerals including calcium carbonates, talc, and potash.

Jan 1, 2012

By A. Dogan Paktunc

Abstract - The Mechanic Settlement pluton is a small body of mafic and ultramafic rocks of tholeiitic affinity, occurring in the Late Neoproterozoic volcanosedimentary rocks of the Avalon terrane of the Appalachian Orogen. The lenticular-shaped intrusion is layered and consists of ultramafic and mafic lithologies in at least six cyclic units that are relatively thin or short-lived. The lowermost exposed portion of the intrusion is characterized by the cumulate sequences of olivine and olivineclinopyroxene and display relatively flat rare earth element profiles. In the overlying lithologies, plagioclase is the dominant cumulus phase following olivine in the crystallization sequence. Olivine ranges in composition from Fo73 to Fo85 and plagioclase from An62 to An89. Variations in the compositions of orthopyroxene and clinopyroxene are within Wo0-4En52-87Fs11-45 and Wo39-50En23-50Fs3-19. These mineral compositional variations in part reflect cryptic patterns and correspond to normal fractionation trends in cyclic units. Elevated Pt and Pd concentrations of up to 2.6 ppm occur in ten zones within the central cyclic series in association with both the peridotitic and gabbronoritic rock types. The mineralized zones are about several meters thick and appear to have lateral continuities over several hundred meters, suggesting that they are stratiform. Platinum-group elements (PGE) occur as discrete platinum-group minerals (PGM) including vysotskite, merenskyite, michenerite, sperrylite, stillwaterite, and hollingworthite that are associated with magmatic sulfides composed of pentlandite, pyrrhotite, and chalcopyrite. PGM grains range in size from a few micrometers to well above 20 µm. Sulfur isotope ratios and the Se/S ratios of the mineralized rocks are typically higher than the mantle values. Sulfide saturation probably occurred as a result of assimilation of crustal rocks and magma mixing during emplacement of subsequent pulses of magma. Repetition of the PGE mineralization in rather thin cyclic units suggests that the replenishing magma probably had high PGE levels and was saturated with respect to sulfide during emplacement. Ingression of the replenishing magma into the chamber in a turbulent plume and its mixing with the resident magma was probably responsible for the formation of the PGE mineralizations in the Mechanic Settlement pluton.

Jan 1, 2000

By Scott G. Honan, Wayne F. Luinstra

"Since 1992, the concentration of gold using gravity methods has progressed to become an important part of production at Hemlo Gold's Golden Giant Mine. Currently, the gravity circuit accounts for approximately 25% of the Golden Giant Mine's Gold production. This circuit consists of a 30 inch Center-Drain Knelson Concentrator and a Shaking Table. The evolution of gravity concentration will be discussed with an emphasis on the economic justification for a gravity circuit as well as the practical aspects and metallurgical impact of operating such a circuit. It will be demonstrated that the operation of a gravity circuit has definite benefits to the operation of the Golden Giant Mill and will continue to play an important role in future gold production.1.0 IntroductionHemlo Gold Mines Inc. Golden Giant Mine is a 3000 TPD underground gold mine and milling facility located 40 km east of Marathon, Ontario. Mining is accomplished by means of sublevel longhole open stoping. The ore is processed using conventional crushing, 3-stage ball milling, conventional cyanidation and CIP processes. The mill and concentrator are described in more detail in other publications1,2.Since July of 1992, the Golden Giant Mine has been using a gravity circuit for gold recovery in the mill's grinding circuit. Despite the fact that gold recovery averages over 96% using conventional cyanidation and carbon-in-pulp processes, the gravity circuit has become an integral part of milling operations. This paper will discuss the economic justification for a gravity circuit as well as the practical and metallurgical aspects of its operation."

Jan 1, 1996

By Paul Staples, Fred Woodcock, Robert Grant, Mike Cooper

"Noranda's Brunswick Mining Division, near Bathurst, New Brunswick, processes 10,500 TPD of complex Cu-Pb-Zn bearing ore. Brunswick uses conventional rod and ball milling techniques to achieve a flotation feed size of 75% passing 400 mesh. Over a two year period, testwork was performed using a Marcy pilot plant ball mill to assess the impact of several key variables on secondary grinding efficiency. Four graded mill charges were used to compare balls and slugs at 25 and 29 mm sizes. Data was evaluated by determining grinding rates using a commercially available steady state simulator. Results were critical in Brunswick's efforts to achieve finer grinds while minimizing cost per tonne.IntroductionBackgroundThe Brunswick orebody is an extremely fined grained volcanogenic massive lead, zinc, copper, silver, iron sulphide body between two metamorphosed sedimentary and felsic volcanic rock units. Pyrite content is about 60% with 20% non-sulphide minerals, mainly silica and chlorite.Size reduction at Brunswick is performed by three separate parallel lines consisting of rod mills, primary and secondary ball mill circuits, all in series. The line 3 grinding circuit is presented in Figure 1."

Jan 1, 1997