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By Kuniaki Murase

Cadmium telluride (CdTe) semiconductor has been well investigated as a CdS/CdTe heterojunction solar cell material since its band gap is suitable for energy conversion from sunlight into electricity. In this paper a new electrochemical processing of thin-layered CdTe using basic aqueous electrolytes is reviewed from the standpoint of thermodynamics using a potential-pH diagram. The cathodic electrodeposition of the stoichiometric CdTe with a flat surface morphology took place at more positive potentials than that of the Nernst potential for the bulk-Cd deposition and at more negative potentials than that for the hulk-To. In this potential region deviation from the stoichiometric composition of eleetrodeposited CdTe was controllable by the Cd(II)/Te(IV) concentration ratio, pH, or concentration of complexing agent for Cd2+ ions of the electrolytes, The deposition behaviors for ammoniacal media were well accounted for by the potential-pH diagram of the Cd-Te-NH3-H2O system devised by a combination of those of the Cd-NH3-H20 and the Te-H2O systems, Diagrams for other complexing agents, ethylenediamine and diethylenetriamine, were also constructed to investigate and discuss the electrodeposition conditions regarding the corresponding media.

Jan 1, 2003

By John R. Benham

In 1979 and 1980, the U.S. Bureau of Mines and U.S. Geological Survey conducted a mineral survey of the 20,500 acre Black Butte RARE II area (No. 5102) in the Los Padres National Forest (fig. 1). The work by the Bureau of Mines indicates that the potential tor mineral resources in the area is low. Samples of outcrops and stream channels contained no economic minerals. A mercury deposit near a granodiorite-sedimentary rock contact occurs 2 mi northeast of the study area, but similar deposits have not been discovered within the area. Geothermal potential exists near Tassajara Hot Springs, but no thermal springs occur in the area; nor have oil, gas, or coal resources been found.

Jan 1, 1982

By L H. Warren

The types of equipment available for generating a plasma have been reviewed. The efficiency and potential of the plasma generating equipment used in performing extractive metallurgical reactions have been determined. A general classification of the reactions that might be per-formed in a plasma has been proposed. Experimental work done on extractive metallurgical plasma reactions, heat transfer between the plasma and solids, and the quench of the products of plasma reaction has been summarized. From the preliminary results it appears that the high-intensity are or the transpiration-cooled anode plasma torch offer the most promising areas for further research. C ONSIDERABLE world-wide research effort is currently being devoted to the development of processing technologies which employ the new high-temperature generating devices that have appeared over the past few years. The plasma flames produced by these devices offer the potential for subjecting materials to any single gas or mixture of gases at temperatures up to 20,000°K. With these conditions available, many reactions in extractive metallurgy,

Jan 1, 1965

By R. F. Hüttl

The restoration of surface mining landscapes requires the (re)creation of ecosystems. In Lusatia (eastern Germany), large-scale open-cast lignite mining operations generated spoil dumps widely consisting of acidified, phytotoxic substrates. Amelioration and rehabilitation measures have been developed and applied to these substrates since the 1950s. However, it is still not clear whether these approaches are sustainable. This paper reports on collaborative research work into the ecological potential of forest ecosystem development on typical minesites in the Lusatian lignite district. At first sight, pine stands on minesites along a chronosequence comprising about 35 years did not show differences when compared with stands on non-mined sites of the general region. Furthermore, with some modification, conceptual models for flora and fauna succession in forest stands on non-mined sites seem to be applicable, at least for the early stages of forest ecosystem development. For example, soil organism abundance and activity at minesites had already reached levels typical of non-mined sites after about 20-30 years. In contrast, mine soils are very different from non-mined soils of the test region. Chemically, mine soil development is dominated by processes originating from pyrite oxidation. Geogenic, i.e. lignitic, soil organic carbon was shown to substitute for some functions of pedogenic soil organic matter. Rooting was hampered but not completely impeded in strongly acidified soil compartments. Roots and mycorrhizae are apparently able to make use of the characteristic heterogeneity of young mine soils. Considering these recent results and the knowledge accumulated during more than 30 years of research on minesite rehabilitation internationally, it can be stated that minesite restoration might be used as an ideal case study for forest ecosystem development starting at "point zero" on "terra nova".

Jan 1, 2002

By Alfred Bellows

The objective was to develop and design a remotely operated temporary roof support system that provides a safe working environment between a freshly cut coal face and the last line of permanently supported roof in which to perform roof bolting activities. This system was to take the form of a retrofit package which could be adapted to a majority of the bolters currently in service. The result is an integrated piece of hardware which will retrofit onto virtually all single boom bolters by removing the drill boom and relocating and modifying the hydraulic controls. The system is composed of three basic components: a pair of cantilevered roof supports which reach forward to the desired line of support, a mast type drill unit for drilling holes and torquing bolts, and a transverse slide assembly to carry the drill from hole to hole across the entry without relocating either the bolter or the roof support. A converted bolter not only provides a much safer operation but is projected to increase the production speed as well as reduce the manpower required to operate a section.. This improvement in productivity is shown to make the job of retrofitting a bolter cost effective in less than two months and provide a potential profit thereafter. Based on the findings presented in this report it is recommended that a proto-type be built and tested in an underground coal mine to demonstrate its effectiveness.

Jan 1, 1976

By Harry L. McNeill

The Selective Media Process was developed by the author in a laboratory provided by The Steams-Roger Manufacturing Co. It is the outcome of an investigation into the possibilities of coarse beneficiation by sink and float without using the conventional heavy media. Commercial work to date has been limited to the treatment of minus 3/8-in. iron ore at the Hill Trumbull washing plant of the Cleveland Clifis Iron Co., at Calumet, Minnesota. Two cut away prints of the machine are shown (Figs. I and 2). A rotary conical impeller is mounted within a stationary cone (Fig. 2). This impeller is adjustable vertically by a 12-ton screw jack. The speed of the impeller can be varied from 14 to 32 r.p.m. by the Reeves variable-speed motor pulley mounted on the 7½-hp. motor drive. Attached to the bottom of the stationary cone is the automatic control valve for sink product, actuated by a ¼-hp. gear motor. The sink product is dewatered in a conventional drag driven by a 7½-hp. motor and discharged onto an inclined conveyor containing from 6 to 10 per cent moisture. Two plants are operated at the Hill Trumbull property. All the ore is first treated in a typical washing plant (Fig. 3). when treating "wash ore" a finished concentrate can be produced by the log washers and Akins classifiers, as the separation involves only fine silica (minus 48-mesh) and free iron. However, when "jig ore" is led to the washing plant the coarse

Jan 1, 1947

By Harry L. McNeill

The Selective Media Process was developed by the author in a laboratory provided by The Steams-Roger Manufacturing Co. It is the outcome of an investigation into the possibilities of coarse beneficiation by sink and float without using the conventional heavy media. Commercial work to date has been limited to the treatment of minus 3/8-in. iron ore at the Hill Trumbull washing plant of the Cleveland Clifis Iron Co., at Calumet, Minnesota. Two cut away prints of the machine are shown (Figs. I and 2). A rotary conical impeller is mounted within a stationary cone (Fig. 2). This impeller is adjustable vertically by a 12-ton screw jack. The speed of the impeller can be varied from 14 to 32 r.p.m. by the Reeves variable-speed motor pulley mounted on the 7½-hp. motor drive. Attached to the bottom of the stationary cone is the automatic control valve for sink product, actuated by a ¼-hp. gear motor. The sink product is dewatered in a conventional drag driven by a 7½-hp. motor and discharged onto an inclined conveyor containing from 6 to 10 per cent moisture. Two plants are operated at the Hill Trumbull property. All the ore is first treated in a typical washing plant (Fig. 3). when treating "wash ore" a finished concentrate can be produced by the log washers and Akins classifiers, as the separation involves only fine silica (minus 48-mesh) and free iron. However, when "jig ore" is led to the washing plant the coarse

Jan 1, 1947

By Andrew T. McBride, Malcolm S. Powell, Indresan Govender

"Current empirical Semi Autogneous Grinding (SAG) mill models contain assumptions concerning the amount of energy available for particle breakage, how this energy is distributed in the mill media and the rate at which the energy is transferred. Despite these assumptions the JK SAG model is highly functional with a proven track record. DEM provides a numerical framework to greatly improve on these assumptions that were necessary due to a lack of available input data.This paper identifies key outputs of the Discrete Element Method (DEM), such as energy spectra and impact probability distribution. It describes how they can be incorporated into current mill models utilising practical rock breakage data. The rate at which energy is transferred is shown to be dependent on particle position and mill rotational speed and not once per cycle as previously assumed. Based upon this an improved energy transfer methodology is presented. The fundamental outputs of the DEM are validated against experimental three-dimensional particle tracking data, so as to establish whether the DEM produces correct energy transfer predictions on the inter-particle level, which is crucial to this work. • Effective Experimental ValidationAn automated 3D tracking technique is employed to study the motion of plastic particles deep within the charge of a 142mm diameter experimental mill. A Biplanar Angioscope is used to film the mill with X-rays in two planes simultaneously at 50 frames/s, with a shutter speed of 1/3000s. A marked ball within the charge is tracked for over 2 minutes and the resulting digital images processed by a fully automated imaging technique, which locates the 3D coordinates of the particles to within 0.2mm. With over 250 circulations, this provides statistically rigorous and accurate data for verification in the numerical modelling of mills.A series of validation techniques have been developed to compare the experimental trajectory data with the outputs of both 2D and 3D DEM simulations. The techniques describe the shape of the charge and the particle motion within mill, allowing objective comparisons to be made of key features of the charge, such as the equilibrium surface and the centre-of-circulation."

Jan 1, 2003

By H. F. Yancey

AT the annual meeting of this Institute held two years ago a new method, of estimating the grindability of coal was described, based on experimental work carried on by the Bureau of Mines at its Northwest Experiment Station. Since that time, several organizations concerned with the testing or utilization of coal as pulverized fuel have adopted and used the method in determining the grindability of several hundred samples of coal. In addition, a series of comparative tests of this method and three others has been carried out in five laboratories under the auspices of Committee D-5 of the American Society for Testing Materials. As a result the Committee has recommended that the Bureau of Mines method, designated as the "ball-mill method," and the Hardgrove method2, previously advanced, be accepted as tentative standards3. Since the ball-mill method was originally developed and published, an opportunity has been presented to apply it to a larger number of coals and to study intensively some of the principles upon which the method is based. This paper presents a resume of these further studies and includes a comparison with the Hardgrove-machine method. Trial runs were also made with another procedure recently proposed-the C.I.T. roll-test method4.

Jan 1, 1936

By T. W. Beck, J. A. Organiscak

The U.S. National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has recently studied several redirected scrubber discharge configurations in its full-scale continuous miner gallery for both dust and gas control when using an exhaust face ventilation system. Dust and gas measurements around the continuous mining machine in the laboratory showed that the conventional scrubber discharge directed outby the face with a 12.2-m (40-ft) exhaust curtain setback appeared to be one of the better configurations for controlling dust and gas. Redirecting all the air toward the face equally up both sides of the machine increased the dust and gas concentrations around the machine. When all of the air was redirected toward the face on the off-curtain side of the machine, gas accumulations tended to be reduced at the face, at the expense of increased dust levels in the return and on the curtain side of the mining machine. A 6.1-m (20-ft) exhaust curtain setback without the scrubber operating resulted in the lowest dust levels around the continuous mining machine, but this configuration resulted in some of the highest levels of dust in the return and gas on the off-curtain side of the mining face. Two field studies showed some similarities to the laboratory findings, with elevated dust levels at the rear corners of the continuous miner when all of the scrubber exhaust was redirected toward the face either up the off-tubing side or equally up both sides of the mining machine.

Jan 1, 2013

By E. A. Johnson

The Bureau of Mines determined the effect of slag additives on copper solubility and the distribution of typical impurity elements between copper-iron matte and silica-saturated fayalite (iron silicate) slag at 1,250° C, in CO-C02 atmospheres with 10 pct S02. Small additions (<10 pct) of CaO, A1203, and MgO were shown to decrease copper solubility in the slag. Additions of CaO increased the solubility of bismuth and tellurium in the slag at lower matte grades. Al 20 3 additions decreased the solubility of tellurium in the slag, but increased that of bismuth at lower matte grades. A1203 additions increased the solubility of both at lower matte grades. With no additives, matte grade did not affect the solubility of bismuth in slags, whereas increasing matte grade resulted in a slight decrease in the tellurium solubility in slag. Additions of CaO or As203 alone to the slag increased selenium and arsenic distribution to the matte, but had little or no effect on antimony distribution; whereas small MgO additions decreased antimony distribution to the matte but had no effect on arsenic and selenium distribution. In slags with no additives, selenium distribution to the matte increased with increasing matte grade, while that of antimony decreased and that of arsenic was unchanged.

Jan 1, 1982

By Tonks E. E

The earliest discovery and mining of coal in the northern area of the Greta Coal Measures at Anvil Creek in 1862 was by William Farthing, however, some official records attribute the discovery to Thomas Frost in 1864. Frost&apos;s discovery was examined by William Keen, government examiner of coalfields, and further prospecting was carried out. This was followed by the pioneering work of C S Wilkinson, government geologist in 1884. Subsequently in 1886 C S Wilkinson entrusted a detailed survey of the coalfield to the then geological surveyor, T W Edgeworth David.The outcrop of the Greta Coal Measures around the Lochinvar dome was mapped by Edgeworth David and as soon as he reported his discovery, the Department of Mines reserved in the interests of coal mining an area of 23700 acres, which extended between what became the South Greta and Abermain No I Collieries.

Jan 1, 1993

The process of refurbishment is not a precisely defined one. It is under- stood to mean an upgrading of a plant which is normally performed only once. The application of refurbishment in the field of materials hand- ling equipment poses particular problems because complex plants con- sist of individual components having quite different remaining service lives. For this reason, a systematic, proven procedure is proposed for the refurbishment of large materials handling equipment, designed to ensure economic implementation in accordance with the company goals. Rheinbraun2 has been using materials handling equipment since 1900, the largest units today being bucket-wheel excavators with a daily capacity of 240,000 bank cubic metres of overburden and a service weight of up to 13,500 t (metric tons). Since 1975, more than 50 large-scale refurbish- ment projects have been carried out in the company. In the process, refur- bishment has turned out to be the proven alternative to replacement of large materials handling equipment. Rheinbraun Engineering,3 a Rhein- braun subsidiary, carries out planning, consulting, and supervising work in the implementation of refurbishment projects in Germany and abroad. The most recent example is the refurbishment of Dredger 11 of the State Electricity Commission of Victoria in cooperation with Krupp-Australia, Melbourne.

Jan 1, 1989

By K. E. Stanfield

Asphalts from. Wyoming "black oils" are being studied at the Petroleum Experiment Station of the Bureau of Mines at Laramie, Wyo., in cooperation with the University of Wyoming. These black oils are characterized by their high-asphalt, high-sulphur, and low-gasoline content and are difficult to refine by present methods into high-octane motor fuels, burning oils, and lubricants. Accordingly, their principal use, at present, is for the manufacture of road oil and asphalt. The present production of black oil could be increased to meet a greater demand. During 1937 the daily production of these crude oils in Wyoming was slightly over 13,000 barrels, while the estimated potential production from existing wells was 56,000 barrels.

Jan 1, 1939

By Víctor R. Cabrera

Para un mayor avance en su producción, las minas de cielo abierto u "open it" de Marcona, utilizan unidades de mayor tamaño en el transporte, puesto que reduce el costo unitario del trabajo. En este aspecto, el objetivo del trabajo describe el uso de máquinas comprendidas para su uso, rendimiento de costo, pala, control de tiempo, tiempo de operaciones y el trabajo con traillas dentro de esta modalidad. etc. Como primer punto, las máquinas cargadoras, las palas mecánicas, etc, incrementan su tamaño constantemente y como tal, las operaciones de transporte cambiaron de uso de ferrocarril a de los camiones con 10,15, 20. 30 y 50 tonelajes por viaje. Posteriormente con el advenimiento de motores diesel, diseño, construcción, perforación y transporte de las máquinas cargadoras, se creó una minería de cielo abierto más económica, flexible y eficiente. En este punto, las operaciones estacionarias, sea con palas o las perforadoras de voladura, utilizaron preferiblemente la energía eléctrica que simplifica la operación y facilita el mantenimiento y las reparaciones. Mientras que las operaciones de perforación, voladura, carguío y acarreo se analiza las características de toneladas rotas por perforación, los cálculos de sobreperforación, los materiales explosivos usados, respectivamente. En cuanto la extracción de palas y volquetes, se evalúa la calidad del disparo, número de voloquetes, capacidad horaria. Finalmente en el trabajo con traillas, se evalúa la influencia del costo de las demoras relativas en las palas y los volquetes, pérdidas de la capacidad potencial de la pala cuando hay insuficiencia de volquetes, asi como las variaciones de la capacidad según la distancia de acarreo.

Jul 20, 1956

By Ryan A, Dennis R, Dekker D, Ellis W, Sowerby B

An automated facility for non-destructive elemental analysis of mine samples has been developed and tested at Mount Isa in association with the CSIRO. The analysis is based on the prompt and delayed measurement of gamma radiation emitted by the sample during and after separate fast and thermal neutron irradiation. No sub-sampling or sample preparation is required and the analyser is operated by one person that would otherwise be splitting drill core in preparation for conventional analysis. The analyser has been calibrated to measure the following (precision in parenthesis): Ag (14 ppm), Pb (0.5 wt%), Zn (0.5 wt%), Cu (0.04 wt%), Fe (0.7 wt%), S (1.1 wt%), SiO2 (0.8 wt%), A1203 (0.07 wt%), Mn (0.05 wt%), specific gravity (0.02 g cmt). Crushed or whole drill core samples that range in size between 0.5 m and 1.8 m of equivalent BQ size drill core can be analysed at a rate of six samples per hour. If required, drill core samples can be re-packed in their original configuration for storage following analysis. Standard samples are measured every day to ensure operational stability. The analyser is controlled by a personal computer which prints the results and stores them along with the raw data on the computer hard disk. This paper reports the performance of the analyser during 1992 for routine analysis of drill core from the lead ore bodies of both Mount Isa and Hilton mines.

Jan 1, 1993

By V. McLemore

New Mexico ranks 2nd in uranium reserves in the U. S., which amounts to 15 million tons ore at 0.277% U3O8 (84 million lbs U3O8) at $30/lb (EIA, 2006). The most important deposit in the state is sandstone within the Morrison Formation (Jurassic) in the Grants district. More than 340 million pounds of U3O8 have been produced from these deposits from 1948-2002, accounting for 97% of the total production in New Mexico and more than 30% of the total production in the United States. Sandstone uranium deposits are defined as epigenetic concentrations of uranium in fluvial, lacustrine, and deltaic sandstones. Three types of sandstone uranium deposits are recognized: tabular (primary, trend, blanket, black-band), roll-front (redistributed, post-fault, secondary), and fault-related (redistributed, stack, post-fault). Several companies are planning to mine these deposits by in-situ leaching.

Jan 1, 2007

By L. H. Van Vlack, T. Y. Tien, R. J. Martin

The phase relationships of the MnTe-MnS system were studied by DTA procedures. There is an eutectic at 810°C with about 10 mole pct MnS-90 mole pct MnTe. An eutectoid occurs at about 710°C with approximately 7 mole pct MnS where the MnTe(NaCl) solid solution dissociates on cooling to MnTe(NiAs) and MnS. There is very little solid solubility of MnTe in MnS. ALTHOUGH MnS may exist in three different crystal forms,&apos; only the NaC1-type phase is stable.2 Above 1040°C, MnTe also has the cubic NaC1-type structure. Below that temperature, MnTe changes to the NiAs-type structure.3 This phase transition is rapid for both heating and cooling. As a result the high-temperature crystal form of MnTe cannot be retained at room temperature. Because MnO, MnS, and MnSe are all stable with the NaC1-type structure, and MnTe has this structure at high temperatures,4 solid solution formation could be expected among these compounds. It is interesting to note, however, that a complete series of solid solutions exist only in the MnS-MnSe system,&apos; and that the solid solution is quite limited in the MnO-MnS system.&apos; The MnSe-MnTe system possesses a complete series of solid solutions at high temperatures with separation at lower temperatures.7 Although ion size may be critical in the miscibility of MnO-MnS, it is quite possible that the bond type plays a more important role with the miscibility of MnSe-MnTe. This would permit us to speculate that the miscibility gap would be extensive in the MnTe-MnS system. EXPERIMENTAL Preparation. The samples were prepared by mixing and compacting MnTe and MnS powders. The MnS was previously prepared through the sulfur reduction of Mnso4.8 The MnTe had been prepared by mixing and compacting double vacuum distilled metallic manganese and high-purity tellurium in stoichiometric ratio modified with 1 wt pct excess tellurium. The compacted powders were put in a graphite crucible which was sealed in an evacuated vycor tube. The free space in the vycor tube was made minimal to reduce the loss of tellurium. The sealed assembly was then heated slowly to about 500° C where the free manganese and tellurium reacted vigorously, melting the MnTe which formed. Only one phase, MnTe, was detected by X-ray powder patterns and metallographic techniques. Each compact of MnTe-MnS was placed in a graphite crucible and then sealed in an evacuated vycor tube. The samples were heated at 1250°C for 4 hr and furnace-cooled. Microscopic examination revealed no third phase beyond MnS and MnTe. A typical microstructure is presented in Fig. 1. Identification. X-ray powder patterns were obtained using 114.6 mm Debye-Scherrer camera and Fe-Ka radiation. Mixtures of cubic MnS and hexagonal MnTe were observed in all of the compositions prepared. No lattice parameter change was noticed among different compositions, indicating no solid solution could be retained at room temperatures between these two end-members. A lattice parameter of 5.244Å for MnS was obtained by the Nelson and Riley9 extrapolation method using the diffraction lines of (h2 + k2 + 12) equal 12, 16, 20, and 24. The values, a = 4.145Å and c = 6.708Å, for hexagonal MnTe were obtained from the (006) and (220) lines in the back-reflection region. These values agree well with the values reported by Taylor and Kag1e.10 Differential Thermal Analysis. A differential thermal analysis procedure was used to determine phase relationships since the high-temperature equilibrium conditions could not be retained for examination at room temperature, even when the sealed samples (~0.5 g) were quenched in water. The samples were sealed in an evacuated 4 mm vycor tube with a recess in the bottom to accept a thermocouple. An Al2O3 reference was similarly prepared and the two placed within a piece of insulating fire brick to dampen spurious temperature changes within the furnace. The furnace was controlled by a mechanically driven rheostat which increased the temperature at a rate of about 15°C per min. Known phase changes in the Pb-Sn system1&apos; and the a-to-ß quartz inversion12 were used for calibration

Jan 1, 1969

By Guillermo Florez Pinedo

Si bien la explotación de los recursos minerales influye en el desarrollo económico nacional, es necesario revisar el significado de la minería en el aspecto social y económico en el Perú a través de un plan maestro de desarrollo minero. En este sentido, el presente texto describe la estructura de este programa minero donde se evalúa los objetivos permanentes, las medidas de corto y mediano plazo, los recursos humanos, economía, tiempo, la estrategia de implementación y la acción empresarial del Estado respecto al desarrollo prioritario de la riqueza minera.

Nov 20, 1978

By P. Raffinot, M. Rey, V. Formanek, G. Sitia

Six years of laboratory study, followed by three years of mill operation treating more than 10,000 tons of ore, have established the flotation of oxidized zinc ores with fatty amines as an efficient process. Recently the method has been applied with success to partially oxidized sulphide ores. In this paper the authors give an account of their research and the milling results obtained in Sardinia since 1951. CONCENTRATION of oxidized copper and lead ores by flotation has been practiced for 30 years, but flotation of oxidized zinc ores has remained unsolved until a few years ago. This problem is, however, of great importance in mining districts where large tonnages of oxidized zinc ores exist in underground mines or in dumps. Some sulphide ores also possess a degree of oxidation high enough to justify recovery of oxide zinc minerals. Various attempts have been made to float the zinc carbonate, smithsonite. It is well known&apos; that smithsonite can be collected with fatty acids, but as the predominant gangue constituents, limestone and dolomite. are floatable with the same reagents, fatty acids are difficult to use. Gaudin has shown,&apos; on mixture of pure minerals, that smithsonite can be floated with higher xanthates, or better, with higher mercaptans. Another procedure, briefly mentioned by Davis," consists in sulphidizing the ore, activating the zinc carbonate with copper sulphate, and floating with ordinary xanthates. This process was attempted in the writers&apos; laboratory in 1946, but results were erratic. It has since been taken up by Italian engineers and is in operation on certain types of ores. Two other research projects should be mentioned. In 1942 Erlenmeyer and others&apos; floated synthetic mixtures of smithsonite and gangue minerals with hydroxyquinoline, an analytical reagent for zinc. On the other hand, Bunge, Fine, and Legsdin published in 19465 Some interesting results obtained on Missouri oxidized zinc ores. With sodium oleate as a collector and a combination of sodium hydroxide, sodium silicate, and citric acid as a limestone depressor, they secured, after four cleaning operations, a good grade of concentrate. With many ores this reagent combination lacks adequate selectivity. In 1939 M. Rey initiated a program of research on this important problem. Work was pursued first at the School of Mines in Liége, Belgium"&apos; and later in Paris in the laboratories of Société Miniére et Mbtallurgique de Penarroya and Société Minerais et Métaux. Reagents used in the beginning were higher xanthates and mercaptans, later fatty amines. Sulphidization with sodium sulphide was found necessary. These conditions make possible the flotation of zinc carbonate and zinc silicate. Two milling plants were put in operation in Sardinia in 1950 and several others are now contemplated." &apos; It should be mentioned that unknown to the present writers McKenna, Lessels, and Peterson were

Jan 1, 1955