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The Pinto Valley, Arizona, plant of Cities Service Company is one of the newest copper producers in the United States, having started production in 1975. It is located a few miles west of Miami, Arizona, on the site of the Castle Dome Mine, a World War II operation which was shut down and its mill later moved and renamed the Copper Cities plant. The Pinto Valley concentrator uses six 18 ft (5. 5 m) diameter by 21 ft (6.4 m) long, 4000 hp, single-stage ball mills, taking crushed ore from four 7 ft (2. 13 m) standard and eight 7 ft shorthead crushers. It has a design capacity of 40,000 stpd but has higher tonnage capability for an expanded concentrator. The copper porphyry-ore is mined by two 15 yd and one 20 yd shovels (11.5 and 15.3 cu m) and is transported to the primary crusher by 150-ton trucks. The dump pocket is relatively shallow (14 ft or 4. 27 m deep); and because of the width necessary for the 150-ton trucks, it was designed to use the ore itself instead of manganese steel as an abrasion- resistant lining, although a heavy steel cap protects the dump pocket top edge. The pocket has a capacity of 300 tons of ore. Water sprays under the dumping positions direct a fog toward the truck being dumped for excellent dust control. Breaking of oversize is done by a hydraulic impact breaker mounted on a hydraulically operated articulated arm situated at the side of the dump pocket. Again because of the shallow pocket, no splitter is used to protect the spider of the 60 in. by 89 in. Traylor gyratory crusher, which is equipped with a hydroset mechanism. Crushed ore at 8 in. (203 mm) drops into the 360 st surge chamber lined with AR plate and then is fed directly to the 60 in. (1.52 m) stock- pile conveyor by an 84 in. by 20 ft (2. 13 m by 6.1 m) four-speed apron feeder at a rate of up to 4000 stph. Early in 1977, Cities Service will replace the four -speed electric drive with a hydraulic pump and motor with infinitely variable speed. They are also studying the replacement of the apron feeder with an 8 ft wide (2.44 m) belt feeder similar to those at Similkameen and Palabora. Peak crushing capacity would then be increased to 5000 stph. The AR plate in the crushed ore pocket was installed in large, rectangular sheets which required much less embedded metal to hold it in place than would the more conventional, smaller arid square pieces of cast manganese steel. For duty in the crushed ore pocket, where wear is not severe, the AR plate is a satisfactory material. The new Palabora Figure-8 crusher also uses this design.

Jan 1, 1978

By Darrell L. Beddard

Pile driving started October 29, 1993 and was completed on January 27, 1994. Field work included driving piling from ground surface at one site and at or near proposed footing elevations for the remainder. Piles were driven to specified tip elevations or the elevations directed by the Project Manager. In an attempt to address what installation technique(s) performed the best, several methods were used, including varied predrilled depths, open ended piles, closed ended piles, and the use of both impact and vibratory hammers. Piles were driven closed ended where possible to study the feasibility of this option to reduce construction costs associated with pile cleanout. Piles were driven to different depths to measure capacity variations. The 24-inch (610 mm) diameter piling were driven in one piece while the 42-inch (1.07 m) diameter piling was driven in two segments. A total of 79 piles were driven for the four sites, 74 of the 24-inch (610 mm) diameter and 5 of the 42-inch (1.07 m) diameter. Various hammers were used to determine which hammers provided viable solutions to the potential problems anticipated in the design phase. Hammer selection was based on the driveability studies. Equipment included a 175 ton (1.56 MN) crane, support crane for pile stabilization, crane mounted auger drill, offshore leads, Delmag D30-32, D46-32, and D62-22 diesel hammers, an HPSI 2005 single acting hydraulic hammer, a Foster IHC S-90 double acting hydraulic hammer and a Kencho VM2-25000AII vibratory hammer with the weights set to produce 17,500 pound-inch (1.98 kN-m) of eccentric moment.

Jan 1, 1996

By Gary L. Nelson

An overview is provided of Franklin Industrial Minerals mica mine and plant operations located near Velarde, New Mexico. Operated by Franklin Industrial Minerals since July of 1990, several process and product modifications have been developed and instituted to improve the operation. In addition to a brief history of site operations, descriptions of the mining, beneficiation, delamination grinding, and product classification processes are reviewed. Supportive topics discussed include equipment modifications and improvements, product application diversification, and specific product characterization. Also reviewed are the key areas of safety, environmental responsibility, and programs pertaining to process quality control and product quality assurance.

Jan 1, 1994

By S. B. Castor

Proceeds from industrial mineral mining in Nevada were approximately equal to those from metal mining during the barite boom in the late 1970s and early 1980s; however, since then the economic importance of industrial minerals has been overshadowed by gold mining (Fig. 1). The total value of industrial minerals mined in Nevada increased by about 60% during the 1980s, reaching an estimated $306 million in 1990 before falling slightly in 1991. The state's most important industrial mineral commodities, in order of estimated value, are aggregate, lithium carbonate, diatomite, lime, cement, gypsum, barite, clay, silica, and magnesia (Fig. 2). Industrial minerals produced on a smaller scale are colemanite, dimension stone, dolomite, perlite, salt, and zeolite. In 1991 industrial mineral commodities other than aggregate were produced at 39 operations in Nevada. Most of these operations are located near the two major metropolitan areas of the state, or along the major transportation routes (Fig. 3).

Jan 1, 1993

By M. P. A. Hames, D. R. Beaumont

INTRODUCTION Legend has it that when Isembard Kingdom Brunel was confronted with the cost and consequences of one of his bridges having failed, he responded cheerfully that the event had saved investors and taxpayers a fortune because it prevented him from repeating the same design at several other locations. To meet the demands of rejuvenating and expanding the transportation system in an era of industrial growth Brunel and his contemporaries introduced bold designs and many innovations. Great advances in design and construction techniques resulted, yet these too had their practical limits as the story tells. In the gold mining industry today we face the same challenge of expansion, yet designers must respond mindful of economic restraints. Is innovation the answer? It has two meanings; to bring in novelties and to make changes. Distinguishing between improvement and novelties, or simply recognizing the benefits and limitations of new ideas over proven technology is part of good design. This paper will illustrate the practical aspects of selecting appropriate solutions to a design problem by examining a variety of examples common throughout the industry. Since a variety of engineering disciplines contribute to the design of a gold processing plant, and each has some old wisdom to impart or new development to boast this paper is divided into the different areas of expertise involved.

Jan 1, 1987

By A. Desbiens, R. del Villar

"This two-part paper summarizes the design and implementation of a distributed PIbased control strategy installed at the B grinding circuit, at the Kidd Creek Division of Falconbridge Ltd. Part I details the design of the control strategy using a grinding circuit dynamic simulator (DYNAFRAG). The first step consisted of sampling campaigns and data processing to calibrate DYNAFRAG. Then, several control alternatives were designed and tested with the simulator. The main feature of these strategies is their ability to regulate or keep within an upper and lower limit five output variables (circulating load, rod mill density, cyclone feed and overflow densities and pump box level) with only three manipulated variables (rod mill water, pump box water and rod mill tonnage). By simulation on DYNAFRAG, it was possible to discriminate among several control structures. The preferred control strategy uses a saturation algorithm, which allows the adequate regulation of two measured variables with only one actuator. Controllers located in interacting loops are appropriately tuned, taking into account the existing process coupling. Part II will present the implementation of the selected control strategy.IntroductionSteady state simulators are used to predict the stationary state of a given process under specific operating conditions. Tradi - tionally, steady state simulation has been applied for process flowsheet design, for evaluating process modification benefits or for determining key operating parameters in process operation optimization. Dynamic simulators add a new dimension to process simulation since they allow the prediction of the process transient behaviour, resulting from the application of a different set of operating conditions and/or from natural disturbances or equipment failure. Dynamic simulators can also be used for the training of new operators or for the design of control strategies."

Jan 1, 1997

By J. Ritchey

This report describes the engineering feasibility and economic advantages of using a mobile bridge-type cross-pit belt conveyor system in conjunction with a large dragline to excavate and transport spoils in a typical Western surface coal mine. The studies show that such a system could be built to survive operational and climatic mining conditions, and that its implementation would offer a reduction in both acquisition and operating costs versus conventional mining units of comparable rapacity. Reclamation costs can also be significantly reduced, and the total reclamation process accelerated, making the cross-pit conveyor system attractive to mine Owners and environmentalists alike.

Jan 1, 1976

By Fred S. Mulock

THE principal operating and producing properties covered by the Western Operations of the United States Smelting Refining and Mining Company are the U. S. and Lark mine in the Bingham district of Utah, the Bayard department in the Central mining district of New Mexico, the Midvale mill and smelter near Salt Lake City, the lead refinery of its subsidiary, U. S. S. Lead Refinery, Inc., at East Chicago, Ind., and the coal operations of its subsidiary, United States Fuel Company, at Hiawatha, Utah. Operations of lesser importance at this time are conducted either on company account or by lessees in the Centennial, Bullion Beck, and Eagle and Blue Bell mines in the Tintic district of Utah, the Hidden Treasure and Ophir mines in the Ophir district of Utah, and the White Knob mine in Custer County, Idaho. The Richmond-Eureka Mining Company, in which the Company owns a controlling interest, has leased its properties near Eureka, Nev., to the Eureka Corporation Limited. The Gold-road property at Goldroad, Ariz., has been shut down since 1942, and due to high costs of labor and supplies, consideration is now being given to removal of all surface and underground improvements. The mine and mill im¬provements at the Sunnyside property in Colorado, recently purchased by the Sunbank Corporation, a subsidiary of the Company, are now being dismantled.

Jan 1, 1948

By Hannu J. Häkkinen

Metal clusters exhibit unique size-dependent physical and chemical properties that differ from those of bulk materials or large particles. Here we discuss recent theoretical investigations of the catalytic properties of free and MgO-supported gold clusters. The catalytic activity of gold clusters depends sensitively on the environment, charge state, and chemical composition of the catalyst. Relativistic bonding effects stabilize large planar structures for gas-phase gold clusters, and non-compact ?quasiplanar? structures are present as important isomers also for surface-supported clusters. The hybridization of the atomic 5d and 6s states is significantly enhanced by the relativistic effects, and large spatial variations in the nature of the local electronic structure make the low-coordinated gold atoms preferable adsorption sites for oxygen molecules. The adsorbed oxygen molecules are activated to superoxo- and peroxo-states via charge-transfer from gold, and Eley-Rideal and Langmuir-Hinshelwood reactions with CO proceed via low-barrier formation of intermediates, which do not require O-O dissociation as precursors. This facilitates the low-temperature (below 300 K) activity of gold nanocatalysts in CO oxidation. Other gold nanostructures, such as mono-atomic gold nanowires, may also become important prototype systems in chemical sensing and nanocatalysis; here we show that they are active promoters of hydrogen dissociation.

Oct 1, 2003

By Ruilin Yang

Kinematic approach of blast modeling refers to using the velocity, strain, or displacement as controlling parameters to model blasting, rather than the stress and the material constitutive relations. The rock stiffness or constitutive relations is very hard or impossible to obtain due to the complexity of the rock mass property.

Feb 1, 2020

By Gerry Roblesky

"IntroductionWestar Mining Ltd. is Canada's largest producer of metallurgical coal for the export market. It currently operates two mines, the Balmer Mine at Sparwood, British Columbia producing 6 000 000 tonnes per year and the Greenhills operation at Elkford, producing 2 100000 tonnes per year. Approximately 1600 people are employed between the two mines which operate independently but share common administrative services.Like most mining companies in Canada over the past three or four years, Westar has faced rising production costs along with flat or declining prices and demand for its products. In order to survive under these conditions it has become necessary to strive for decreased costs in any way possible. Over the past two years there has been a widespread introduction of microcomputers across the company. In order to satisfy increasing demand for accurate and pertinent information while at the same time increasing productivity, the microcomputer has become an invaluable tool.This paper describes some of the problems faced by a mine maintenance department in this operating climate and how they were solved with the help of a microcomputer. It also describes some of the problems that may be encountered both with equipment and people and recommends some ways that these might be minimized or avoided. Finally, an assessment of whether or not the move to microcomputers was a current and economical one, and a brief description of future plans and projects is given.The Maintenance OrganizationIn order to appreciate fully the role that microcomputers are playing within the Maintenance Department at Westar Mining, a little background on the organization and operating philosophies is in order. Most of the comments apply directly to the Balmer operations, however, the Greenhills operation is similar in concept.The mine maintenance organization operates on a fleet based concept with these departments reporting to the maintenance superintendent: haulage trucks, shovels and drills, loaders and Caterpillar equipment, maintenance services, and rebuild services.Each of these departments is headed by an assistant superintendent and is responsible for all maintenance on the equipment on the respective fleet. Shift foreman, planners, specialists and clerical staff are assigned to each fleet. A central engineering and administrative group consisting of one engineer and three clerical positions is responsible for maintenance engineering and centralized administrative services"

Jan 1, 1988

By I M. Platten, Y Xie

Sampling protocols that are designed to suit the mineralisation style will result in a reduction of the nugget effect and hence resource risk. The a priori need for all sampling programs is the effective characterisation of the mineralisation type(s) to support optimisation. This requires a program of sampling for sampling followed by holistic characterisation. At each end of the coarse-gold to fine-gold spectrum, the samplability of a deposit ranges from relatively simple for fine-grained disseminated gold particles, through to extremely difficult for coarse nuggety mineralisation. Many deposits contain a proportion of both particle size types. The proportion and size of coarse gold particles has a direct impact on the effectiveness of sampling, where coarser particles will require larger samples and more specialised protocols. The nature of mineralisation geology/mineralogy and associated gold particle sizing can only be determined by sampling to facilitate optimised protocols. Mineralogical studies, focusing on particle size, particle clustering and distribution in host minerals, are required as part of wider paragenetic and metallurgical investigations. This paper discusses the role of mineralogical studies in the characterisation of gold ores for sampling optimisation through a series of case studies.

Jan 1, 2008

By A. Blake Caldwell

Tyrone-a complete mining and concentrating facility built by Phelps Dodge Corp.-straddles the Continental Divide where surface water on either side flows in opposite directions although all water is taken from and returned on the northwest side of the Divide. At the outset, Tyrone was saddled with a problem of an adequate water supply, and the Gila River some 23 miles distant appeared to be the logical source. This in itself presented a major obstacle to Phelps Dodge because of the distance water had to be pumped and because of an adverse head which had to be overcome between the Gila River and the two 4-million-gal-capacity terminal water supply tanks at the mill. Having acquired water rights on the Gila River and in order to control the seasonal fluctuations in water volume, the company built the Bill Evans, off stream, earth-filled dam. This reservoir will contain 2100 acre-ft of water when full and it was constructed by the Hamilton Construction Co. for Phelps Dodge. The dam impounds fresh water for the Tyrone plant's use and four vertical turbine pumps (4500 gpm each) lift the water 275 ft from the Gila River into the reservoir. Since construction, Phelps Dodge has optioned the lake to the New Mexico State Game Commission for recreational purposes. In addition to the lake, land around the reservoir has been optioned to the State Game Commission for public use. The lake has already been stocked with trout and by next summer some keepers should be available for the taking.

Jan 12, 1969

By J. T. Lapsley, I. I. Cornet, A. E. Flanigan, R. Hultgren, J. E. Dorn

With the greatly expanding use of magnesium during the war, it appeared necessary to the War Metallurgy Committee that procedures of heat treating common magnesium casting alloys be investigated systematically. Accordingly, the National Defense Research Committee of the Office of Scientific Research and Development placed a research contract with the University of California, supervised by the War Metallurgy Committee. Research on the solution heat treatment and aging of magnesium alloy AZg2, (formerly ASTM No. 17; also known as Dowmetal C or AM26o) which was done under "Restricted" Project NRC-2I, in 1942-1943, and reported in detail in a final report to the OSRD on September 3, 1943, is the basis of this paper, which has been released for publication by the OSRD. American experience with magnesium alloys prior to World War II was limited, although some of these alloys had been in commercial use since 1909. Requirements of the aircraft industry for light alloys made it imperative to understand and utilize the advantageous strength-weight properties of magnesium castings. Magnesium casting alloys are commonly solution heat- treated to increase their ultimate tensile strength and ductility; this treatment may be followed by an age hardening at elevated temperatures, which raises the tensile yield strength but diminishes the ductility. In the present investigation, AZp was studied to determine the effects on properties of various solution heat treatment and aging schedules. The principles of heat treatment of magnesium alloys are the same as for other non-ferrous alloys. The alloy studied, AZp, has a nominal composition of 9 pct aluminum, 2 pct zinc, and minor constituents. Fig I shows, by the projection of isothermal sections on the concentration plane, the solubility surface1 of the ternary magnesium-rich solid solutions as determined by X ray 'analysis. From this figure it may be seen that above approximately 375°C (707OF), AZp alloy is a single phase alloy at equilibrium; below this temperature the equilibrium condition is a two phase alloy. The beta constituent which precipitates from the solid solution exerts a hardening effect. Because the zinc concentration is only 2 pct, ancl because of its solubility relations, AZqz resembles a binary alloy of magnesium with aluminum. The solubility curve1 of Fig 2 shows how rapidly the solubility of the beta phase decreases with decreasing temperatures. Unlike many aluminum alloys, magnesium alloys do not age harden at room temperatures; precipitation hardening of AZ² alloy is performed at about 177°C (350°F). At this temperature about 3 pct aluminum

Jan 1, 1949

By P. Peczak

A Monte Carlo simulation technique has been used to study dynamic recrystallization in polycrystals. A continuum microstructure of the polycrystal is modeled employing a discrete lattice. The response of the material to hot deformation is simulated by adding stored energy and recrystallization nuclei continuously with time. The experimentally observed nonuniform character of deformation substructures is modeled by employing a phenomenological expression for inhomogeneous distribution of the stored energy. All simulations were performed on HP-Apollo 9000 Series 700 workstations. A program written in FORTRAN with use of PHIGS graphics library calls was used to interactively monitor the current state of the matrix and all relevant parameters: deformation stress, average grain size and effective nucleation rate. Visual analysis of the simulated microstructure allows a better understanding of the data developed by averaging over a number of very long Monte Carlo runs. Since the essential features of dynamic recrystallization are accurately reproduced by the model, it is used to discuss the role of the controlling mechanisms of the dynamic recrystallization in real polycrystal.

Jan 1, 1993

By Dario Libano, Luis Carlos Tenuta, Juliano Penteado

"Subway Line Number 4 is one of the newest additions to the Rio de Janeiro subway network. Built for the 2016 Olympic Games, the 16 km (10 mi) subway line connects the south of the city, with the famous beaches Copacabana and Ipanema, to Barra da Tijuca, west of the city, where the Olympic Village and Park are located. This new line, which is estimated to cost USD 2.2 billion, is composed of six new stations: Jardim Oceanico, São Conrado, Gavea, Antero de Quintal, Jardim de Alah (JA) and Nossa Senhora da Paz Station.Brasfond participated in the construction of foundations and retaining structures for all the stations, and each presented unique challenges. This is not surprising considering the difficulties present in a highly-dense urban environment including utilities, nearby buildings, traffic limitations and noise.Of all the stations, JA Station was the most challenging to construct. It was located in the middle of an avenue between residential high rises supported on shallow foundations as well as below sea level in sands with high groundwater. The other five stations were located in small parks and squares, with no buildings in the immediate proximity.The interaction between designer, owner, and the general and foundation contractors during execution was key in safely reducing the construction schedule. This was significant given the unforeseen construction delays the client, Linha 4 Sul JV, faced due to permitting, utility and traffic relocation so that the owner could fulfill their final goal: making the line operational by the Olympic Games. The GeologyGeologically, the state of Rio de Janeiro is formed by Pre- Cambrian crystalline basement rock. Its geological formation is very old and comprises two major orogenic cycles, a Mid-Precambrian formation, called “Transamazonian” (Proterozoic Era), and an Upper-Precambrian to Cambrian called “Brasiliano” (Proterozoic-Paleozoic). The soil structure of the city of Rio de Janeiro is represented by a core of crystalline rocks, usually granite-gneiss, covered with a layer of residual soil and/or partially weathered rock.JA Station is located in a Rio de Janeiro neighborhood called Ipanema, between the Atlantic Ocean and Lagoon Rodrigo de Freitas. Local geology is composed of a superficial soil, consisting of medium to coarse grained sands. Top of rock varied significantly from 20 m (66 ft) deep on one side of the station to 33 m (108 ft) on the other. Water is at a depth of 3 m (10 ft)."

Jan 1, 2016

By M. W. BERNEWITZ

DURING my recent extended visit to Australia and New Zealand, these notes on oil and gas prospecting in that part of the world were compiled from recent reports-press and government, from conversation with one of the financial leaders in the search for oil, and from personal observation of operations of the principal importers, blenders, and distributors of oil products; also from the astonishing testimony given by them to the Petrol Commission. Australia and New Zealand have practically no petroleum production beyond a few thousand gallons a year from wells in the latter Dominion. Everything is imported, Table 1. showing the quantities for 1929-30 in Australia and for 1930 in New Zealand,

Jan 1, 1934

By J. E. Armstrong

"IntroductionT'HE PRODUCTION of gravel and sand may be considered to be the major mining operation in the Lower Fraser Valley of British Columbia. At least thirty pits are in operation with a yearly production probably in excess of two million yards and a value in excess of one million five hundred thousand dollars before crushing, washing, and sizing. The value of the finished products would probably be double the above figure.Since 1949, the writer and his co-workers have been engaged in the geological investigation of the Lower Fraser valley and adjoining Coast mountains for the Geological Survey of Canada. The study, which is not yet completed, includes both bed-rock geology and geology of the unconsolidated sediments lying above bed-rock. In a rapidly expanding industrial area, .an advance knowledge of the geology may• greatly aid in future 'planning, and in many cases may .prevent not only the wastage of large sums of money, 'but possible disaster. Some of the present and future applications in which geological information in the Lower Fraser valley should be of value are as follows: the development of domestic, irrigation, industrial, and municipal groundwater supplies; drainage for industrial sites,, roadbeds, and farmlands; flood control along the Fraser river and smaller streams in the area; the location of dam sites, of major tunnels for water supply •and sewage, of road-beds, of foundation sites for large buildings .and other engineering undertakings in which geology may aid; the evaluation of oil and gas •possibilities; the production of building stone; and the production of sand and gravel, the subject with which this paper is primarily concerned."

Jan 1, 1953

By P. H. Chang, J. E. Gould

"Solidification structures and austenite decomposition in some spot welded O.05%C - O.3%Mn steels have been studied with the aid of a numerical thermal model. The model is a one dimensional finite difference formulation, and accounts for melting, temperature dependent thermal properties, effective heat transfer in the liquid, and contact resistances. The model was used to predict solidification conditions during resolidification of the nugget. These solidification conditions were correlated with the primary dendrite spacing using available primary dendrite spacings modelling. The model was also used to predict cooling rates in the temperature regime for austenite decomposition. These cooling rates were used to interpret the underlying microstructure.INTRODUCTIONThe metallurgical transformations which occur during the spot welding of low carbon steels have traditionally been characterized only in the most general of fashions. This is most probably due to the similarity of spot welded microstructures to other welded microstructures, and that the mechanical integrity of spot welds has not been a concern. In addition, little information about the particular thermal cycles experienced during spot welding has been available. The introduction of HSLA (microalloyed) sheet steels has, however, raised new concerns about the integrity of spot welds. These steels have on occasion shown irregular weldability, as well as brittleness in the weld nugget on destructive testing l - 4 .In response to these concerns, considerable work has been done attempting to characterize thermal cycles in spot welds 5-12. This has largely taken the form of thermal modelling, with the end purpose generally to estimate the size of the nugget formed. This work uses the thermal model developed at Inland Steel 13 ,14 to try and understand, in a more fundamental way, microstructural evolution in spot welds. Two facets of this microstructural evolution are examined in detail:"

Jan 1, 1986

By Joseph C. Kieffer

THE Duquesne property of the Callahan Zinc-Lead Co. is about 20 miles east of Nogales, in southern Arizona. One mine is near the mill, but most of the mill feed is hauled in by truck from a number of small mines. The same sulphides are found in all the ores, in general, but the amounts vary considerably. All ores contain silver, copper, lead and zinc minerals but one mine ships ore high in silver and lead and low in copper and zinc; while another mine ships ore high in copper and zinc, and low in silver and lead. The common sulphides are galena, carrying most of the silver; chalcopyrite; sphalerite, carrying iron in solid solution; and pyrite, in a gangue consisting of limestone, quartz and garnet. Mineralization is fairly coarse. At the present grind of about 66 per cent minus 200 mesh most of the sulphides are liberated. A small amount of chalcopyrite is locked up with the sphalerite and cannot be liberated at an economic grind, and the copper carried into the zinc concentrate with the sphalerite accounts for the comparatively poor recovery of copper in the copper-lead concentrate. PRODUCTION OF TWO CONCENTRATES The milling problem, which was complicated by the extreme variation in the grade of the feed, was first attacked with the idea of producing a silver-copper-lead concentrate and a zinc concentrate, both with satisfactory grades and recoveries. By February I94I, it was felt that these objectives had been attained, when the grades of the various products and the recoveries were as shown in Table I. [ ] A rough outline of the flowsheet and reagents used is as follows: Minus ¾ -in. feed to a 7-ft. by 36-in. Hardinge ball mill working in closed circuit with a 36-in. Wemco classifier. The classifier overflow passes to the second cell of an 8-cell bank of No. 18 Special Denver Sub-A flotation machines (volume, 22.5 cu. ft. per cell). A rougher concentrate is removed from the second to the fifth cells inclusive, and returned to the first cell, which is the cleaner. A scavenger concentrate is removed from the sixth, seventh, and eighth cells, and returned to the third cell. Consump

Jan 1, 1942