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By John G. Payne

The Pebble deposit contains three contiguous zones. In the Pebble West zone, granodiorite stocks intrude gently warped volcanosedimentary rocks that had been intruded by diorite sills and two felsic intrusion breccias. In the Central zone, volcanosedimentary rocks are cut by diorite and granodiorite sills; the latter are genetically associated with the granodiorite stocks. In these zones, widespread potassic alteration consists of brown biotite and K-feldspar, with abundant quartz-carbonate-sulphide vein stockworks. Chalcopyrite/pyrite ratios range from 2/1 to 1/20. Diorite hosts the highest-grade mineralization, with much of it being disseminated. Patchy, later phyllic alteration is moderate and commonly depleted in copper. The Pebble East zone occupies a granodiorite stock and intruded host rocks below an eastwardly thickening wedge of barren Tertiary volcanic and sedimentary rocks up to 600 m thick. Brown biotite alteration and copper mineralization are strong, with chalcopyrite/pyrite ratios commonly over 1/1. The zone extends to a depth of at least 1200 m below surface; some drill holes bottomed in strong mineralization. Later, weak to moderate sericitic alteration removed some chalcopyrite and locally remobilized gold. The Pebble deposit has a Measured/Indicated resource of 3 billion tonnes grading 0.28% Cu, 0.32 g/t Au and 0.015% Mo (= 0.5% copper-equivalent) and an Inferred resource of 1.13 billion tonnes grading 0.30 g/t Au, 0.27% Cu and 0.015% Mo (0.55% copper-equivalent). The Pebble East zone has an Inferred resource of 2.13 billion tonnes grading 0.55% Cu, 0.34 g/t Au, and 0.037% Mo (0.97% copper-equivalent). The Pebble East zone is open to the east and to a lesser extent to the north, south, and to depth.

May 1, 2006

By Clifford S. Gibson

THESE troubled times suggest three reasons for maximum effort to control silicosis: (1) To keep to a minimum the ever-increasing burden occasioned by past deficiencies in this respect. (2) To effect the greatest production with maximum efficiency, which means at the least cost. (3) To preserve man-power in every way. Good control of the silicosis problem aids these aims. Inadequate control hampers all three. Insofar as our knowledge goes, silicosis in Ontario mines is caused by the inhalation of finely particulate quartz. It follows, therefore, that removal of dust containing this mineral automatically erases the cause. The achievement of this ideal is the aim of the mine operator. His best tool to this end is ventilation. This paper discusses mine ventilation from the viewpoint of dust control and it is hoped that in so doing there may result a better understanding of the part played by air in silicosis prevention. No attempt will be made to treat the subject fully. Instead, there will be presented certain salient aspects culled from field observations, the data in all cases referring to gold mines, unless mention to the contrary is made.

Jan 1, 1942

By R. P. D. Graham

It is almost exactly two hundred years since the foundations of the mining and metallurgical industries in Canada were laid. There '."'as nothing spectacular about this early start. It had to do with the most basic phases of these industries-the mining of coal and iron ore, and the manufacture of cast and wrought iron. At several points along the coast of Cape Breton island, coal seams may be seen outcropping quite conspicuously, and it is probable that they had been observed, and possibly worked in a small way, in very early times. However that may be, these coal seams have the distinction of being the first in North America of which there is any printed record, reference to them appearing in a volume by Nicolas Denys which was published in Paris in 1672. Regular coal mining in the district did not commence until about fifty years later, however. The metallurgists started their operations along the north shore of the St. Lawrence river. Here, at many points between Montreal and Quebec, are to be found deposits of bog iron ore, and in 1 730 a furnace for smelting such ore was established on the St. Maurice river. The St. Maurice forges continued in operation until 1880, and throughout that long period they were famed for the fine quality of castings produced, and also for a-superior wrought iron.

Jan 1, 1924

By Dayle Denton, Lloyd Buckingham, Kenneth G. Thomas, Jacques McMullen

"The dry grinding and leaching circuits of Barrick Gold’s new Roasting Facility at Goldstrike Mine in Nevada, USA incorporate well proven technologies in a unique combination. During the design of the plant, every effort was made to utilize the best available technologies from the perspective of capital, environment and operating costs.Crushing is a two stage process using gyratory and cone crusher. Ore is stockpiled and then reclaimed to two parallel dry grinding mills. The double rotator dry grinding mills include a drying chamber, coarse and fine compartments and utilize a gearless motor drive (GMD) or “wrap-around”. In-circuit product transfer is accomplished with air slides and bucket elevators. Finished product separation is performed by both static and dynamic classifiers with the final product captured in baghouses. Recycle of unfinished product utilizes cascade chutes.The final ground product reports to two 2000 ton roaster feed silos. The two-stage oxygen flu-solids roasters with their associated gas train are the subject of a separate paper.The cyanide leach circuit is a standard carbon in leach system with circular swept screens for interstage carbon retention. The loaded carbon is sent to the existing Goldstrike autoclave plant for stripping and regeneration. Tails, after cyanide destruction, are deposited in the existing tailings dam with tails from the autoclave facility.Throughout the circuit, Clean Plant Design criteria were used to assure environmental compliance, ambiental acceptability and ensure worker health and safety. The commissioning and operation of the double rotator grinding technology has been very successful at Barrick Goldstrike."

Jan 1, 2001

By G. M. Hughes, J. Ellis

"IntroductionHydraulics has been considered a science for thousands of years. Applications included water wheels, dam; and slice gates but today the term ""hydraulics"" commonly refers to ""power hydraulics"" in which fluid is used under controlled pressure to do work. The mining industry employee’s hydraulics in practically every aspect of its operations, on such equipment as trucks, front end loaders, LHD units, crushers and hydrostroke feeders. The many benefits of hydraulic drives such as ease of variable speed control, high power: weight ratio low envelope size of hydraulic actuators and ease of maintenance have been extensively developed in the pulp and paper, chemical, steel, and other basic industries, but until quite recently, concentrator operators have not taken advantage of the versatile methods of power transmission offered by hydraulic systems.After some preliminary testing at the Lynn Lake concentrator Sherritt Cordon Mines Limited installed several hydraulic system; at their Fox Mine concentrator to drive slurry pumps and conveyors. The systems used at Fox and the systems which will be installed at the Ruttan concentrator are briefly described in this paper. Since acceptance is based mainly on understanding a few basic principles of hydraulics system; including pumps, motors, circuitry and central methods are also presented in the paper.PRINCIPLES OF POWER HYDRAULICSBasicsHydraulic systems provide an uncomplicated, versatile means of power transmission. The basic system is quite simple. It consists of five main elements, as shown in Figure 1, which are:1. Prime Mover - generally an electric motor.2. Hydraulic Pump - fixed or variable positive displacement type such as a piston or vane p.mp which displaces a constant amount of fluid for ead1 revolution - this unit converts mechanical energy of the prime mover into fluid energy.3. Oil Reservoir - a standard tank to operate under atmospheric pressure which has a capacity of 2 - 3 times the maximum gpm outp.it of the hydraulic pump."

Jan 1, 1972

Geology grads mine heated job market Salaries up 44 per cent in three years ?[Geology student] passed up a $100,000-a-year job at a mining company last December when he finished his degree in geology. The 24-year-old Canadian said he?s confident he?ll get a better offer.? Rob Delaney and Stewart Bailey, Calgary Herald, Published: Saturday, March 15, 2008 Massive shortages across the mining industry > Trades and operators are a large component > Technical people are equally hard to find > Students are in an excellent positions to secure exciting jobs > Experience is at a premium. Why?

May 1, 2008

By B. Hart, J. Marois

"Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM–EDX), and Time of flight secondary ion mass spectroscopy (TOF-SIMS)were used to analyze pyrochlore grains from Niobec froth flotation plant. Samples from the mill feed, pyrochlore rougher feed, pyrochlore rougher concentrate, and tail were analyzed in order to identify a potential relationship between pyrochlore matrix composition and selective separation. SEM-EDX analyses indicate that pyrochlore grains with high Fe content appear to be less recoverable than those with a lower Fe content and that the flotation response is related to matrix Fe rather than Fe occurring as inclusions. TOF-SIMS was used to analyse the surface of high Fe and low Fe pyrochlore, in order to identify a potential relationship between pyrochlore matrix composition and the related effect on cationic collector adsorption (tallow diamine). Surface analyses of pyrochlore from a conditioning test show that species indicative of the collector favour the surface of Fe poor pyrochlore relative to the Fe rich variety. The results from the conditioning test illustrate a negative relationship between collector loading and the presence of Fe and related oxidation species. This study identifies the link between pyrochlore matrix Fe content and, the presence of surface oxidation products, to collector loading. Poor Fe rich pyrochlore recovery noted in the Niobec froth flotation plant may be partially explained by this mechanism.INTRODUCTIONPyrochlore, the most abundant niobium containing mineral (Perrault and Manker, 1981) is economically recovered in Brazil, China, and Canada (Niobec) (Kouptsidis et al., 2008). Since 1974 Niobec has been extracting niobium from the St-Honorécarbonatite deposit. Niobec is the only operating Nb extraction facility in North American and one of the three major world producers of ferroniobium (Dufresne and Goyette, 2004; Belzile, 2009).Flotation is the preferred and most cost-effective method for pyrochlore recovery (Burks, 1958; Shapolov and Polkin, 1958; Zakharov et al., 1967; Razvozzhaev and Nikiforov, 1972; Bogdanov et al., 1973; Abeidu, 1974; Raby and Desrochers, 1975; Wilson, 1979; Biss and Nadeau, 1982; Biss, 1985). With the aim of optimising the flotation process for the Niobec ore, numerous experiments were performed on the influence of surfactants and type of water to optimise pyrochlore recovery and grade during flotation (Gomez et al., 1987; Rao et al., 1988; Dufresne and Goyette, 2004; Belzile, 2009)."

Jan 1, 2013

By E. Quaquero

This article reports on the current state of an ongoing research project which is aimed at implementing intelligent models for hardly predictable hazard scenarios identification in construction sites. As past evidences showed that no programmatic action can deal with the unpredictable nature of many risk dynamics, we tried to survey on how the current approach for safety management in the construction industry could be improved. In our previous research the use of Bayesian networks elicited from subjective knowledge were preliminarily tested. Those networks might be meant as a reliable knowledge map about accident dynamics and they showed that a relevant ratio of occurrences fall in ?hardly predictable hazards? class, which cannot be warded off by programmatic safety measures. This paper reports the second outcome of our research project, which focused on the development of first elementary fragments, regarding the occurrence of a possible ?hardly predictable scenario?. Instead of experts? contributions (who, over their carrier, seldom incurred in accidents), we used ?legal cases? as an accurate source of information. They suggested which categories of ?hidden hazard scenarios? are more likely to happen. We found that the most frequent hidden hazard scenarios are linked to operator?s negligence and abnormal behavior, e.g. irregular removal of scaffolding?s components, unprotected openings, improper use of PPE, etc. Every pattern determined by legal cases has been formalized by a fragment (i.e. elementary network) of the overall Bayesian network. Finally, all the elementary networks were integrated into a comprehensive intelligent tool for realtime hardly predictable hazards prevention. The final setup, asked for interfacing these intelligent models to a low-level sensor network and used to feed them with inputs about the current state of the context, is discussed too.

Aug 1, 2013

By Dave Marsh, John Goode, Niels Verbaan, Kevin Bradley, Henrie Notzl

The mineralogy of the Avalon Nechalacho deposit is complex with significant fractions of HREEs, Zr, and Nb found in refractory minerals such as zircon and fergusonite. Sulphuric acid baking followed by water leaching can be used to extract REEs from flotation concentrates, but acid baking does not completely "crack" the zircon and fergusonite, so the extractions of Zr, Nb, and HREEs are not high. An alternative flowsheet has been developed that is able to obtain significantly improved extractions of HREEs, Zr, and Nb from flotation concentrates or acid bake residues. This is accomplished by cracking the zircon and fergusonite minerals with caustic soda at high temperatures, followed by water washing to recover excess caustic soda and soluble sodium silicates and phosphates. REEs, Zr, and Nb in the solid residue can then be solubilized with HCl or H2SO4. This paper highlights some of the findings from an extensive laboratory program and discusses several flowsheet implications.

Jan 1, 2014

By C. Larsen, E. Goodwin, E. Konigsmann

"This paper describes the development of an innovative effluent treatment process for cyanide and heavy metal removal from tailings wastewaters at Hemlo Gold Mines Inc. Golden Giant operation.The importance of minimizing dissolution of contaminants in the gold leaching circuit is discussed, as well as using recycled water in milling circuits to the fullest extent possible. Finally, a brief description of the role of natural cyanide degradation in the tailings pond is provided.Emphasis is placed on the need for overall water quality management to ensure minimum effluent treatment process costs and complexity while producing excellent quality effluents.1.0 INTRODUCTIONHemlo Gold Mines Inc. owns and operates its Golden Giant Mine located forty kilometres east of Marathon, Ontario. The Golden Giant mine is one of three gold operations exploiting the large gold orebody located in the Hemlo area. The milling facilities include two stage secondary crushing, three stage, closed circuit ball mill grinding with no reagents, thickening, cyanide leaching and carbon in pulp gold recovery unit operations. The average throughput is 3000 tonnes per day of 10 grammes per tonne gold ore. Figure 1.1 shows a schematic flowsheet of the operation."

Jan 1, 1989

By C. Guo

The Mildred Lake Settling Basin (MLSB) is the largest disposal site for mature fine tailings (MFT) at the Syncrude Canada Ltd oil sands plant. Over the past years (since 1997), there has been a marked change in the consolidation behaviour of MFT in the MLSB, which is attributed to microbial activity. Methane-producing microorganisms, known as methanogens, have become very active, and large amounts of biogas (mainly methane) have been produced. In certain regions within the MLSB, gas bubbles are released to the water surface of the tailings pond. Continued field monitoring of the MLSB has provided convincing evidence of the rapid densification process (rapid water drainage from the tailings). This phenomenon contradicts the consolidation models for MFT developed over the past 20 years. The above phenomenon has also been reported at the oil sands tailings ponds operated by Suncor Energy Ltd. in Fort McMurray. This rapid densification has caused pumping challenges in the transfer of fine tailings from the Mildred Lake Settling Basin for the creation of composite tailings. The rapid densification of the MFT may also have potential positive effects in accelerating the reclamation of the oil sands fine tailings. A field and laboratory research program is underway to study the mechanism leading to the rapid densification phenomenon. Systematic field investigations were performed to determine the distribution and characteristics of the rapidly densified MFT. Gas bubble distribution on the water surface was mapped to determine the zones of different biological activities in the pond. These field investigations provided solid ground for further experimental and theoretical research. A number of small-scale column tests were carried out to observe the gas evolution and to measure the changes of some geotechnical parameters under different microbial activity. Also, a series of gassy MFT densification tests are being conducted to study the mechanism of the rapid densification of the MFT under microbiological activity. A review and discussion of the research program is given and some preliminary research results are presented in the paper.

Apr 1, 2005

By Cameron J. Clayton

Cumberland Resources Ltd. is currently planning to develop the Meadowbank Gold Project located some 70 km north of Baker Lake, Nunavut in the eastern Canadian Arctic region. The Meadowbank Gold Project currently consists of up to 6 main gold bearing deposits within relatively close proximity to one another which are planned to be mined primarily as a truck-and-shovel open pit operation and using conventional gold milling and extraction. The mining plan indicates that approximately 20 million tonnes of ore will be mined over a mine life of 8 to 10 years. The operation will generate approximately 160 million tonnes of mine waste rock and about 20 million tonnes of tailings. The site is located in an area of continuous permafrost with mean annual average air temperature of -11 °C and average annual precipitation in the range of 100 to 200 mm. Lakes cover a large portion of the site, including some of the ore deposits. The location of the site, and the physical environment, pose challenges to development. This paper presents some of the designs considered to effectively manage and utilize the waste products of mining at the project.

May 1, 2004

Strategic Branding ? In 2006 Explore for More was created ? By industry, for industry ? Cohesive approach to career attraction ? Defines industry and employers of choice Career Kits ? Positive impression of mining: ? before seeing the brochure 31% ? after seeing the brochure 83% ? Likely to consider a career in mining: ? before seeing the brochure 12% ? after seeing the brochure 23% MARS ? Mining Attraction, Recruitment, and Retention Strategy (2007-2010) ? Attract, recruit and retain a skilled workforce ? Increase participation of under-represented groups ? Dispel myths and misconceptions of the mining industry ? Inform and educate Canadians of career opportunities ? Promote and build upon industry best practices in workforce planning

May 1, 2009

By Roland B. Hoag, Roger G. Webber

Sulphate concentration in groundwater is a good measure of the extent of oxidation of sulphides, provided that sulphide minerals are the primary source of the sulphate. A study was conducted near the Eustis Mine in Quebec to determine where and how the sulphate in groundwaters originated. Atmospheric precipitation is the only source of sulphate other than oxidation of sulphides, and in this study area it is equal to 0.01,. millimole per litre. The oxidation of sulphides can be divided into subsurface oxidation (mainly inorganic processes) and surface oxidation (including both organic and inorganic processes) . The maximum sulphate concentration due to subsurface oxidation of sulphides depends on the solubility of 0 2 in water and is 0.25 millimole per litre. Surface oxidation is, therefore, responsible for any amount greater than atmospheric plus subsurface contributions (0.29 millimole per litre). Surface inorganic oxidation occurs in waters with a pH greater than 15 and is controlled by the kinetics of the oxidation processes. Organic (bacterial) surface oxidation is dominant only in acid (pH< 1.5) waters. The bacterial action accelerates the oxidation of sulphides, and large quanttties of sulphate may be introduced into solution.

Jan 1, 1976

By R. E. Gilmore

Introduction The Sydney coal-field extends for a distance of thirty miles along the northeastern coast of Cape Breton island. At a central focal point at the tip of the south arm of Sydney harbour, seven miles or so in from the Atlantic ocean, is the city of Sydney, with Port Morien to the southeast and Sydney Mines to the north . Mining centres along the ocean coast between these points include Birchgrove, Reserve, Glace Bay, and Waterford. The field is divided into three districts or &apos;basins&apos;, namely, Morien basin to the south, Glace Bay in the centre, and the Lingan-Sydney Mines basin to the northeast. The eastern and western portions of the latter are known as the Lingan and the Sydney Mines basins, respectively. Six distinct coal seams are described as existing in the Morien basin, nine in the Glace Bay basin, and six in both the Lingan and the Sydney Mines basin. Although known by different names in the several basins, a definite continuity of the seams has been established.

Jan 1, 1933

By D. M. May

"Cut-and-fill mining is a stoping method that has been widely utilized in the mining industry over the past forty years. It took preference over shrinkage methods at Levack in the early 1930sbecause of its safety aspects; i.e., prompt support of the stope sidewalls, good working floors and better accessibility to support poor back areas. In addition, higher recoveries of ore were possible because of the flexibility of the method in that silling could take place easily at any horizon; low-grade ore could be sorted and left in the stope as fill and certain zones of rock could be left unmined. With modern techniques, a steady production rate can be established, as filling and mining can be carried out stimultaneously.AIthough there are numerous variations of cut-and-fill mining throughout the world, this paper reviews the original type of mining, with modifications and improvements through the years to present modern practices, with the Levack West operation appearing to be the most productive at this time. Stoping efficiencies have also increased substantially from the original 10 tons per manshift to the present 55 tons per manshift.The paper also outlines the many improvements that have been made with respect to mucking and ground support operations; from hand mucking in a single stope to the use of frontend loaders and haulage trucks in fully accessible stope complexes; and from timber props to roof bolts of various types. Although present methods are extremely satisfactory, experimentation is continually being conducted to improve safety and productivity for future mining.IntroductionThe major mining operations of the Ontario Division of Inco Limited are located in the Sudbury Basin (Fig. 1). Around the rim of this geological formation and within 30 miles of the City of Sudbury are nine producing mines and one &apos; open pit operated by the company .Ore production currently approximates 11.5 million tons per annum from underground and open-pit operations. Underground mining methods include sub-level caving, shrinkage, cut and fill, undercut and fill, blasthole and vertical retreat. The Levack Complex, the main plant of which is the central Levack Mine, produces 11,000 tons per day.The first prospecting in the Levack area, in 1887, was conducted by James Stobie, who examined rock cuts along the route of the Canadian Pacific Railway to the northwest of Sudbury. However, it wasn&apos;t until 1913 that operations commenced at Levack under the Mond Nickel Company."

Jan 1, 1981

By F. H. Wheeler

CONSIDERING the nature of this audience, I perhaps, in addressing you on the subject of air transportation as related to the mining industry, should speak with tongue in check or at least with some reservation. I know full well that many of you, veterans in the great mineral development in Canada, are perhaps more conversant with the overall aviation picture than I, for aviation to you has been the means to an end, and in many instances has been part and ?parcel in the success of your particular projects, in the form of the initial means of transport. I feel, however, that we in this room today have somewhat parallel geographic interests - yours in relation to what is in the ground, mine in the air - and also in the forests and in the streams - aviation, hunting, and fishing - things which have occupied my attention practically all my adult years. In the light of what has gone. before, and in view of present developments, I think you will agree with me when I say that I do not think there could be a more intriguing pursuit than playing a hand in rolling back Canada&apos;s tremendous northern frontiers, even if, at this stage, we have made but slight impression on the untold opportunities which lie in our wide-spread, undeveloped areas.

Jan 1, 1956

By Lachezar Tsotsorkov

Corporate social responsibility Is a principal trend of the corporate strategy for sustainable development of Assarel-Medet JSC ? the largest Bulgarian company for open pit mining and ore processing the production activities of which date back to 1964. Sustainable development Social responsibility is considered as one of the three pillars for sustainable development, together with the economic and environmental responsibility.

Aug 1, 2013

By S. Yalcin, S. Chang, M. Oliazadeh

"Present day ferrochrome demand is on the rise, as more steel products require this material as an alloying element. It is projected that the stainless steel demands will grow by about 6% per year to 2020; as such, the supply and demand for ferrochrome appears promising. Chromite is the only economical source of chromium, which is commonly upgraded by gravity techniques and used to produce ferrochrome. The gravity separation methods are not able to treat particles finer than 0.1 mm efficiently. Therefore, in processing chromite ore, a large quantity of fine tailings; some 25% of the mineral values have been reported as lost in slimes during processing. The chromite content of these tailings is typically 10-20% Cr2O3 and accumulates into a large stockpile/pond. A chromite concentrator project in Canada, considers a cut-off grade of 20% Cr2O3. This indicates further processing might be required to recover chromite from low-grade stockpile when the high-grade deposits are depleted. Low-grade ores normally indicates disseminated chromite ores with low liberation and consequently fine comminution. This paper reviews the techniques for treating chromite from fine material and provides some examples of successful operations in fine chromite recovery. Beneficiation techniques for fine particles include gravity separation, magnetic separation, and flotation. Several case studies are presented here that used one of the aforementioned methods or a combination of them.INTRODUCTIONChromium is one of the essential element and important material for production of ferrochrome alloys and special steel. Chromium occurs as chromium spinel, a complex mineral with chemical composition of (Fe, Mg) O (Cr, Al, Fe)2 . Chromite ore is exclusively found in ultramafic igneous rocks. Major associated gangue minerals are talc, quartz, serpentine and iron oxides.Chromite is a heavy mineral, with a specific gravity in the range of 4-5, relative to associated gangue minerals in a chromite ore, which makes gravity concentration a suitable process. This is generally true for coarse particles, ranging from 1 mm to 100 mm. Typically, the ore is prepared by crushing (and grinding if necessary) to a suitable size and the material is sized for the appropriate beneficiation techniques. It is common to use heavy medium separation (e.g. dense media drums, dense media cyclones, or Dyna Whirlpool) to treat coarse size and intermediate size particles (1 – 100 mm). Intermediate and fine particles (20 – 0.1 mm) could be treated by jigs. Spirals, shaking table, sluices, and Reichert cones can upgrade fine particles. Figure 1 shows a typical chromite beneficiation process flowsheet. As can be seen, it consists of three major sections: feed preparation (crushing, screening), de-sliming, and concentration. Beneficiation recoveries range from 80 to 85%, although the ratio of upgrading is only 2 to 3."

Jan 1, 2013

A brief description of the hydro-gen reduction of nickel from ammoniacal solutions by the Sherritt process is given, indicating how this procedure can now be used to coat a great number of materials -particularly powders -with nickel or cobalt, whereby so-called composite powders are produced. The technique for the production of composite powders is described, particularly with regard to the surface activation of noncatalytic powders, whereby it is possible to coat core powders uniformly with nickel or cobalt. The properties of some of the more interesting composite powders, such as Ni/ AI, Ni/WC, Co/WC, Ni/Graphite and i/P, are discussed as well as possible fields of application for these new products. INTRODUCTION DURING the last decade, no-table advances have been made in pressure hydrometallurgy, so that large quantities of three of the more com1r.on metals, copper, cobalt and nickel are now produced on a commercial scale by hydrometallurgical processes.

Jan 1, 1963