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By Edward Skolnik

The concept of using fluid dense media to separate heavy ore constituents from the lighter gangue dates back to 1858, when it was patented by Sir Henry Bessemer. Its use in coal did not begin until after 1917, however, when Chance invented a process (which bears his name) in which lighter coal floats in a suspension of fine sand in water while heavier refuse sinks. Conklin used fine magnetite in suspension as a medium for floating anthracite in 1922, DuPont designed a plant employing organic liquids in 1936, and Belknap used a solution of calcium chloride (which Bessemer had suggested, among other media) in 1937. Separation of magnetic media by magnetic separators from the suspensions in which they were carried was introduced in a Butler Brothers ore concentrator pilot plant in 1937. The media first used were crushed steel and various grades of ferrosilicon. Since 1940, when American Cyanamid used magnetic separators to recover and clean magnetite in a coal washing circuit, virtually all heavy medium circuits have been of that type. As long as static baths are employed, as they are in the processes above, coal smaller than 9.5 mm or 6.4 mm cannot be cleaned economically in heavy medium. The settling velocities of the fine material are very low, and consequently the time required to separate the lighter coal from the heavier refuse becomes excessive. In addition, stray currents in the vessel and the upward velocities induced to keep media solids in suspension affect the finer solids to the degree that physical size becomes a more important factor than specific gravity.

Jan 8, 1980

By G. Castillo, G. Thies, C. Bissue

"Newmont’s Phoenix mine began gold production in 2006 and has since experienced difficulties in reaching design throughput due to variability in ore hardness. In 2010, a debottlenecking study was conducted, generating multiple options to increase throughput of the existing Phoenix Mill through a series of phased expansions. An option was selected in early 2011 to increase the current concentrator capacity by approximately 25% through two phases. The first phase of the project was the installation of a secondary crushing and screening circuit in order to reduce SAG feed size from a P80 of 6 inches to 2 inches. The second phase focuses on downstream unit operations in the concentrator aiming to relieve existing bottlenecks such as flotation. This paper analyzes the design, commissioning, and operation of a recently installed SAG Pre-crush circuit (Phase 1). The design discussion will focus on concept development, flowsheet design, design criteria, process models, design limitations, and control philosophy. Discussion on the integration of operating data and flowsheet into design during engineering will be presented. Actual operating data of major equipment is gathered from the commissioning and operation of the circuit and compared to the initial design models. Conclusions will be drawn on equipment design factors used during engineering, and the success of model integration into operation. The paper concludes on the successes of the project and where improvements can be made during design.INTRODUCTIONThe Phoenix mine is located within 25 miles of the town of Battle Mountain, Nevada. The mill processes copper, silver, and gold ore. Production started in 2006 and has since struggled to reach the designed tonnage of 33,600 stpd due to the variability in ore hardness. In production year 2010-2011, the Phoenix mill average daily throughput of 33,000 stpd. In 2008, a larger primary crusher (FLS 60/89 gyratory crusher) was installed to operate in parallel with the originally supplied primary crusher (Metso 50/65 gyratory crusher), in order to provide additional capacity upfront in the circuit so that the primary crushing circuit could keep up with the mill.In 2010, a mill debottlenecking study was completed to assess the various options that could be implemented to increase the current mill capacity. The study was completed in late 2010 and contained four tonnages that Phoenix could achieve through various expansion scenarios. A single option was selected in early 2011 to increase the mill capacity from 33,000 stpd to 48,000 stpd. The selected option looked at a four phased expansion that would increase the capacity of the Phoenix mill and address the mill’s current bottlenecks:"

Jan 1, 2013

By R. N. Zitter

PRESENT work was done in connection with a program for obtaining a low energy gap semiconductor suitable for photodetection. The inter-metallic compound InSb, which is now being in-

Jan 1, 1959

The No. 2 Ore-shaft, at Mount Isa Mines Limited, involving the use of boreholes as ropeways for the upper portion thereof, constitutes, we believe, a unique feature in hoisting installations. The boreholes were sunk from the surface to a depth of 390 ft., thus eliminating the necessity of erecting the hoist at an underground location or construction of the shaft for this distance. Fig. 1, a diagrammatic cross-section through the shaft, shows the complete installation from the surface down to the first loading station below No. 7 haulage level.During the latter part of 1936, conditions encountered in sinking the Main Ore shaft made it impracticable and uneconomical to continue deepening it to serve haulage levels below the present No. 5-level. Plans were therefore made for an interior shaft, to serve new lower levels, that terminated above No. 5-level so that ore hoisted could be drawn off on this level and transported to the Main Ore shaft for final conveyance to the mill crude ore bin.Referring again to Fig. 1, it is apparent that the section above No. 4-level, if opened out to full shaft size, would be inoperative and would serve no useful purpose except, possibly, as a ventilation duct. Original plans therefore did not include continuation of the shaft above No. 4-level. Excavation of a hoist room upon No. 5-level; erection of sheave wheels just below No. 4-level, and a long inclined ropeway leading from the hoist to the sheaves, were incorporated in the general layout. Work on the lower sectionof the shaft had started when the idea of locating the hoist...

Jan 1, 1939

By Chulgi Suk, Hoon Park, Hyonsoo Kim, Hakman Kim, Sangho Cho

Dust emission from blast demolition and other construction activities can be a nuisance; it is widely recognized that fine particles less than 10 µm in equivalent diameter (called PM10) may cause health problems. Mist spray systems, such as rain guns, sprinklers, water/surfactant sprays (or foams) etc., are some of the most effective dust suppression methods. A large amount of research has showed that when water droplets are produced in an equal amount to that of dust particles, the airborne dust is suppressed by the agglomeration of dust and mist particles. A method for generating micro-sized mist from water, achieved by the detonation of explosives in the water tube, was suggested and is called the ‘detonationdriven water bag burst system’. There are many experimentally observed limitations of the explosioninduced water break-up process. The water bag explosion tests were simulated using the AUTODYN software, in order to investigate the aerosolization mechanisms of the detonation-driven water and water break-up process into micron-sized droplets. As a result of the numerical analyses, the diffusion direction of water when detonating in the central interior part of water tube was radioactive and significantly stronger than when detonating in the bottom exterior part; this is due to the compressive flow of the volume change inside of the water tube, which resulted from the blasting wave inside of the tube, as well as the reflected pressure on the ground. Blast tests of full-scaled reinforced concrete columns were conducted to verify the effectiveness of the suggested detonation-driven water bag burst system. The water breakdown and dispersion that occurred while blasting the reinforced concrete columns were observed using a high-speed camera, and dust generation was monitored using four density detectors. The suggested detonation-driven water bag burst system showed that the average dust density decreased by up to 7 mg/m3.

Jan 1, 2016

By Wu Liu

A modified falling ball technique for measuring the viscosity of liquids is described. It consists of recording the weight vs. time of a crucible holding the liquid of unknown viscosity, as a solid ball, or liquid drop, is let to fall through the liquid. This method does not require measurements at constant terminal velocity, as the conventional falling ball technique. Also, measurements do not depend on visual observation, which is not possible in opaque liquids or containers. The effect of process parameters on the utility of this method and its potential application to liquid systems of metallurgical interest were analyzed theoretically. The paper also com- pares the gravimetric method to the conventional falling ball technique for measuring viscosity.

Jan 1, 1992

By W. L. Hunter

The preparation of coal for the commercial market is a study both varied and wide, and can be viewed from many angles and in different ways. This short paper can but touch upon the subject and is intended to discuss briefly preparation plants which in some cases would seem to be quite inadequate. The conditions confronting most operators are similar, inasmuch as the existing plants were not built specifically to prepare a product for the market of today, but rather of yesterday. The tremendous strides made in the field of combustion in recent years require that the product be of the highest grade procurable, and in a glutted and somewhat restricted market the buyer may be more pernickety than otherwise. These would appear to be the conditions of today. Where a mine is operated individually, better all-round results seem more readily procurable than in a consolidated effort where so many different conditions are sure to arise demanding cognizance, and in many cases requiring to be incorporated in the scheme of things. In the case of a number of mines being administered to form a central source, that source not having had anything to do with the bringing into being of the institutions over which it presides, we find some of the mines well equipped with facilities to properly screen and load the coal, while in others the facilities are not so good, but are doing their share towards delivering a product that will pass muster and in such quantities that they can be counted on.

Jan 1, 1930

By Aparup Chattopadhyay, Barun K. Gorain

"Porphyry copper deposits are the most important source of copper and also gold within the orogenic belts. These deposits are characterized by low grade copper ore (0.2% to 1% copper) and host precious metals like gold, silver and platinum. A characterization tool has been developed for complex porphyry type copper-gold deposits with an aim to quantify copper and precious metal deportment. This quantification is a challenging task due to low grades and also due to the presence of both visible and invisible precious metal content in different sulphide and non-sulphide phases. Studies were initiated on various complex ore deposits and also on samples representing various processing streams such as flotation and leach products. This paper presents the development of a systematic approach to diagnostic metallurgy using state-of-the-art optical and automated mineralogy, micro-probe, dynamic SIMS and TOF-SIMS analysis for quantification of invisible and visible precious metals content in various species. The relevance of this characterization to metallurgy will also be briefly discussed in this paper.INTRODUCTIONA novel characterization tool has been developed for double refractory gold ores and complex copper-gold ores using state-of-the-art technology for quantitative gold and copper deportment study. The characterization of these ores is a challenging task due to low copper and gold grades in ores, presence of both primary and secondary copper sulphide phases and variable proportion of visible and invisible gold in different sulphides phases (pyrite, chalcopyrite, chalcocite and bornite) and iron oxide phases (magnetite, hematite and goethite). A study was initiated on various ore deposits and also on samples representing various processing streams of pilot plant batches such as flotation concentrates and tailings. This paper attempts to discuss the deportment characterization methodology through presenting results from investigations on four samples from a flotation circuit viz, Feed, Final concentrate, Cleaner Scavenger Tail and Rougher Tail samples. These four samples represent the key streams for a typical copper-gold flotation flow sheet. The key objective of this investigation was to identify and quantify visible and invisible gold along with understanding the morphology and liberation of gold associated with various sulphides, Fe- Oxides and non-sulphide gangue species. In addition, the aim of this study was also to relate this mineralogical and gold deportment information to metallurgical performance."

Jan 1, 2013

By Orr C. W

In previous papers (1, 2), the influence on the creep resistance of elements normally found in commercial lead has been recorded. The results in the present paper refer to the influence of calcium, an element which is not found naturally in lead, but which has been used commercially in the form of alloys. It was realised that calcium would act as a deoxidising agent for lead-and in fact it was with this feature in view that both calcium and magnesium were used as additions. Subsequent work (including the results given in the present paper) has tended to diminish the importance which at first seemed to be associated with the presence of oxygen in lead. The structure of the dilute calcium lead alloys has been worked out in detail (S) and the phase diagram shows the existence of limited solid solubility and a compound CaPbs.

Jan 1, 1938

By O. Leuangthong, M. Nowak

"The impact of high-grade data on resource estimation has been a longstanding topic of interest in the mining industry. Concerns related to possible over-estimation of resources in such cases have led many investigators to develop possible solutions to limit the influence of highgrade data. It is interesting to note that the risk associated with including high-grade data in estimation appears to be one of the most broadly appreciated concepts understood by the general public, and not only professionals in the resource modelling sector. Many consider grade capping or cutting as the primary approach to dealing with high-grade data; however, other methods and potentially better solutions have been proposed for different stages throughout the resource modelling workflow.This paper reviews the various methods that geomodellers have used to mitigate the impact of high-grade data on resource estimation. In particular, the methods are organized into three categories depending on the stage of the estimation workflow when they may be invoked: (1) domain determination; (2) grade capping; and (3) estimation methods and implementation. It will be emphasized in this paper that any treatment of high-grade data should not lead to undue lowering of the estimated grades, and that limiting the influence of high grades by grade capping should be considered as a last resort. A much better approach is related to domain design or invoking a proper estimation methodology. An example data-set from a gold deposit in Ontario, Canada is used to illustrate the impact of controlling high-grade data in each phase of a study. We note that the case study is by no means comprehensive; it is used to illustrate the place of each method and the manner in which it is possible to mitigate the impact of high-grade data at various stages in resource estimation."

Jan 1, 2015

By Joseph M. Kuchta

The limits of flammability and minimum autoignition temperature of a fuel are important elements in assessing fire and explosion hazards that may exist when using or handling the fuel. The limits of flammability define the range of compositions of the fuel gas or vapor mixed with an oxidant through which a flame, initiated by an outside energy source such as an electrical spark, can propagate. The minimum autoignition temperature (M.A.I.T.) is the lowest temperature at which the fuel vapors ignite spontaneously in a specified medium; in this case the ignition energy is supplied by the heat content of tae environment. This temperature is also referred to as S.I.T. value by some authors. Because the autoignition of a fuel also depends on the time interval during which the fuel is subjected to heat, ignition delays are significant. Ignition delay is defined here as the total time elapsed between the introduction of the liquid fuel into the oxidizing atmosphere and the appearance of a flame. This time interval includes both the physical and chemical processes leading to ignition. The ignition delay is usually maximum at the M.A.I.T, and decreases as the temperature of the system is increased. The flash point and the fire point are also useful in assessing the fire and explosion hazards of a fuel. The flash point is the lowest temperature at which saturated, flammable fuel vapor-air mixtures are formed at atmospheric pressure and, therefore, it is essentially the lower limit of flammability

Jan 1, 1962

By Sie A

After completing a feasibility study in 1987, Niugini Mining Limited (NML) obtained five Gold Mining Leases within PA 632, covering the Mount Victor and Clarkes Ridge gold deposits. Reserves prior to mining were 260 000t at 3.63g/t Au for Mount Victor and 40 000t at 2.8g/t Au for Clarkes Ridge. Ore was mined from the two deposits by NML from November 1987 to January 1990. A total of 645kg of gold and 346kg of silver were produced from 198 000 tonnes of ore pro- cessed. Mining and milling operations ceased in February 1990. Since then, there has been significant progress in rehabilitating and revegetating the site. Plant and workshop facilities have been dismantled and removed from site, exposed parts of the pit have been landscaped and replanted, tailings water has been neutralised and discharged, and the dam filled. All remaining personnel and equipment left the site in November 1990. It is envisaged that the replanted areas will be rapidly revegetated, leaving little evidence of mining. Niugini Mining did not recoup the initial investment for Mount Victor, but the mine produced a positive cash flow and made a significant' financial contribution to the local communities and Papua New Guinea as a Whole.

Jan 1, 1991

By Caithness SJ, Heape JMT

Following the discovery by CRA of gold at Mt Kare, and the subsequent 1988-90 gold rush, mechanised mining of the alluvial resource is now being carried by a company jointly owned by CRA (51%) and landowners of the area (49%). Mining is currently being carried out using small gravity processing plants fed by hydraulic excavators. Use of hydraulic mining techniques will be limited to over- coming difficulties related to the high clay content of the material and the soft nature of the bedrock. Current resource estimates suggest that the alluvials will have a mining life of three to four years. During this time, exploration of the hydrothermal gold mineralisation at Mt Kare will be carried out by a wholly-owned company of CRA. It is hoped that this will lead to establishment of an economic primary gold resource.

Jan 1, 1991

By Robert W. Bergwall

The $58,000,000.00 Columbia Heights Metro Station project (Section E3-a) forms a part of the Washington Metropolitan Area Transit Authority's (WMATA) Greenbelt Route - Green Line subway system. The Greenbelt route is one often segments that make up WMATA's subway system. Construction of the "cut and cover" reinforced concrete station includes 600 linear feet of an underground center platform, two ancillary service areas totaling 466 linear feet, two surface entrances, and vent shafts (See Figure No. 1). Station subgrade is approximately 60 feet below existing grade. The project can be divided into five main areas: 1. North Service Rooms and Passageway; 2. West Entrance and West Passageway; 3. East Entrance; 4. Center Platform; 5. South Service Rooms. Station dimensions are approximately 1068 feet long by 64 feet wide. Construction commenced at the site in January of 1995 and is expected to be completed by December of 1999. Franki Northwest Company, Crofton, Maryland, was awarded a subcontract by general contractor Blake Construction Company, Washington, D.C, to install the support of excavation and temporary decking systems. Franki's scope of work included the installation of 490 drilled soldier piles plus two elevator shafts totaling 29,700 linear feet of drilling; 1,150 tons of steel decking covered by 37,000. square feet of precast concrete deck planks; 120,000. square feet of timber lagging; 2,500. tons of struts and wales; and temporary support of underground utilities. In conjunction with Franki's work, Bencor Corporation of America, Dallas, Texas, constructed parallel, 600 foot long slurry walls which serve as permanent walls for the center platform portion of the station.

Jan 1, 1997

Construction of the Boddington Mine 130 km (81 miles) southeast of Perth, is about 89 percent complete. When the $2.9-billion development is finished, it will be the largest gold mine in Australia, producing 31 t/a (1 million oz/year), according to project majority owner Newmont Mining. Newmont?s acting regional group executive for Asia Pacific, Philip Stephenson, told a gold conference in Australia that the project would be ?the biggest thing for Newmont this year.? The project has been in the works for more than 10 years, but because of a three-sided ownership and fluctuating gold prices, it struggled to get started. However, Newmont is set to become the full owner of the project and is moving ahead on the low-grade project. ?We are targeting annual production of 31 t/a (1 million oz/year) for each of Boddington?s first five years. When it is in full production, Boddington will be the largest gold mine in Australia,? Stephenson said. ?The mine?s costs applicable to sales will be around US$9.64/g (US$300/oz) and that puts Boddington into the bottom quartile of the global cost curve. ?Strategically for Newmont, Boddington coming on-line will improve Newmont?s overall global geopolitical risk profile as it delivers greater exposure to an AAA-rated country.? Boddington has a projected mine life of 20 plus years. It has current total reserves of 622 t (20 million oz) and rising. Stephenson said Boddington has the largest reserve base of all gold projects in production or those that are about to go into production in A-rated countries or better. And it will be an important asset for many years to come. Newmont will acquire the remaining 33 percent share held by AngloGold Ashanti in a deal that should be concluded in the next two months. Australian miner Newcrest Mining Ltd. had exited the joint venture several years ago. Newmont had come into the project through the take-over of then Australia?s leading gold miner Normandy Mining, while AngloGold Ashanti gained entry through

Jan 1, 2009

The Australian metallurgical processing industry has shown great innovation and progressiveness over the past ten years. During the same period, exploration activity, particularly by Australian companies, has increased substantially in Indonesia. Following feasibility studies, the decision was made to establish a metallurgical laboratory and design facility in Indonesia. An Indonesian partner was selected, and legal and corporate matters were determined. The laboratory was established but proved far more difficult than a similar undertaking in Australia. Australian and Indonesian staff were recruited and training programs, including training of Indonesian staff in Australia, were implemented. Difficulties of operating in Indonesia included: ò language difficulties ò _ local pace of life ò culture ò communications. Rewards of the decision to establish the means to present the technology to Indonesia have included: ò a contribution to Australia's export of technology. ò an opportunity to expand Normet's client base. ò the opportunity to learn aspects of a foreign culture. ò the means to establish a sound long term investment. This export of technology from the Australian mining industry to Indonesia is an example of the initiatives and capabilities shown by the Australian mining service industry.

Jan 1, 1989

By W. J. Kingwell

My comments and questions are addressed to Mr. Troughton. It seems to me that the tests were very well tailored to determine long term effects on performance of bearing piles as groundwater pressures rise in the London Basin. This rise is being simulated by means of a groundwater recharge system but it would be informative to have further details of the controls of conditions simulated. Ideally the porewater pressure in Standpipes 1, 2 and 3 should be the same throughout the test. Under test conditions are there not practical dif­ficulties? Recharge Well C2 is a lesser dis­tance from the pile than the other wells. Was the rate of recharge to C2 regulated to a lesser rate than the other three? In my experience the rate of acceptance usually varies from well to well. Under a common feed pressure were mea­sures taken to compensate for this? Since the problem does not only affect London, but also Liverpool, Nottingham, Birmingham and to a lesser extent, Manchester, I question whether an ideal procedure is being used. It is well known that rates of acceptance decrease with time and often recharge wells need to be flushed out at regular intervals. Other pro­cedures may need to be adopted to accurately simulate the effect of groundwater rise, if tests of longer duration are to be considered.

Jan 1, 1991

By Kerry Lahti, Bryan Ulrich

On Feb. 11, 2005, more than 20 mining professionals gathered in Elko, NV for a day-long round-table discussion on heap leaching. Attendees included project managers, operators and environmental professionals. They represented 10 mining organizations. Knight Piésold sponsored the special event. Its seven representatives included three staff members from the company’s Elko Operation, and one each from its Denver, Cajamarca (Peru) and Vancouver offices. The roundtable format was chosen to allow people from the mining industry to share ideas and experiences in an open forum. Rather than presenting prepared talks, spontaneity was encouraged. This resulted in a lively and enjoyable discussion.

Jan 1, 2005

By Roy M. Schnabel

The Fashion Island Boulevard Bridge over the Marina Lagoon in San Mateo, California is an eight span precast, prestressed concrete girder bridge. It is approximately 495 feet in length and 61 feet in width. It is supported on 36" diameter octagonal, hollow precast-prestressed concrete pile columns. The bridge was constructed in 1968 and suffered considerable damage during the Loma Prieta Earthquake in 1989. A damage survey report prepared by the State's Office of Emergency Services (OES) recorded that sixteen of the twenty-one pile-columns sustained heavy to moderate damage from the Loma Prieta Earthquake. The damage consisted of cracking and spalling at the tops of the pile-columns. Spalls at the most heavily damaged columns exposed the prestressing strands and confinement reinforcing which also showed signs of corrosion.

Jan 1, 1993

By R. P. Smith

In 1937 the employees of the Hollinger Consolidated Gold Mines Ltd.. at Timmins. Ont., Canada, approached organized medicine for a plan to provide themselves and their families with a complete medical service including hospitalization. This approach was made because of two conditions: (1) the necessity for some organization whereby contributions could be made in instalments to offset the sudden and large expense connected with illness for which the average employee is not prepared, and (2) the need for a more cohesive quality of service to replace a contract practice then in vogue, which did not take care of the employee's family or dependents. In different parts of the United States and Canada similar plans were in force, not only for employed groups but for numbers of people in circumscribed areas. In Europe different countries had adopted various forms of health insurance plans. It then was no surprise that these employees as a group should ask for some similar plan. With the cooperation of the management, a plan was instituted. The plan has one object only—the provision of medical services, including the accessory services such as hospitaliza-tion, X-rays, nursing, and necessary drugs and medicines. It is not concerned with cash benefits, sickness and accident payments, or any form of monetary return as the result of illness, but is simply an organization to provide medical services and pay for them from a central fund. It is a nonprofit organization and the only shareholders are the employees and their families who contribute and who in turn receive services. The Hollinger plan is limited to the employees of the Hollinger mine, who live in Timmins and the immediate vicinity. At first, the membership was voluntary. In the third year, it was made a condition of employment, with the proviso that at the end of any Association financial year an employee may withdraw if he wishes to do so. After withdrawal, he cannot again become a member until the end of the next Association year, and then only by the payment of the back dues. This step was taken to ensure continuity, and to prevent employees from withdrawing when well and reentering when faced with impending illness or operations. The employee himself is subject to medical examination on application for employment, and if accepted is subject to further examination by a specialist in chest diseases under the Workmen's Compensation Board of Ontario. Thus it is possible to exclude those who have heart disease, tuberculosis, or other disabling conditions when first employed. Wives and families of employees are not subject to medical examination but other dependents of an employee—mother, father, or other relative—who are declared by the employee to be wholly dependent upon him must be examined. The employee

Jan 1, 1946