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By L. B. Pankratz

Present-day interest in the rare-earth elements and their compounds, for both metallurgical and ceramic uses, makes it highly desirable to accumulate basic thermodynamic data that can be applied to theoretical considerations of the processing of these substances. Such data still are seriously lacking. This Bureau of Mines paper reports the results of high-temperature heat content measurements of the sesquioxides of four rare-earth elements--europium, gadolinium, neodymium, and samarium--and of the closely related element, yttrium. The temperature ranges covered by the measurements are as follows: Monoclinic Eu2O3, 298°-1,802° K. Cubic Eu203, 298°-1,350° K. Monoclinic Gd203, 298-1,802° K. Cubic Gd203, 298°-1,550° K. Hexagonal Nd203, 298°-1,795° K. Monoclinic Sm203 298°-1,798° K. Cubic Sm203, 298°-1,149° K. Cubic Y203, 298°-1,799° K.

Jan 1, 1962

By Forrest T. Moyer

Need for lightweight building materials was created in the latter part of the nineteenth century by a radical change in building design in which dead load or structural weight was transferred from thick, heavy, load- bearing walls of former construction practice to a load-carrying framework of beams and columns with thin walls. This new design was brought about by the introduction of structural steel followed by reinforced concrete and structural concrete as materials for the erection of the load-supporting frame. The new materials and method of construction made possible the erection of skyscrapers and the building of bridges with long spans, and made feasible additions of one or more floors to existing buildings. As size and design of the load-bearing framework are controlled chiefly by dead load, the natural result was a. search for and use of light- weight materials in partitions, floors, and exterior walls. However, these thin walls created problems of heat and sound. insulation, so that building materials which possessed good heat- and sound-insulating properties in addition to light weight were objects of extensive research. One group of materials developed to fill this need comprised lightweight concretes, of which some were obtained by the use of lightweight aggregates. Although the advantages of lightweight.materials were evident from the first skyscrapers, there was a transition.stage.between the old bearing- wall and modern skeleton-frame types of building, with the heavy and massive construction of the former superimposed upon the latter. Hence, it was not until the period between 1910 and 1930 that the new lightweight concretes were recognized and used more extensively in the erection of large, nonresidential buildings. From this type of construction, light- weight-aggregate concretes entered-fields of residential and small non- residential building; in which they were found desirable for production of prefabricated, large-size; masonry units. Although the weight of each unit was reduced sufficiently to enable one man to handle it easily, properties of the new concretes other than light weight were the principal factors in the ready acceptance of these new materials in residential building. Manufacture of precast units includes complete lines of masonry and back-up blocks, bricks; floor beams, columns and partition, roof, and floor tiles and slabs. Recent improvements in casting machinery, development of the vibration-pressure machine, and a more thorough study and knowledge of the requirements and properties of the concrete mix have all contributed materially to the rapid expansion in use of lightweight aggregates in this industry.

Jan 1, 1942

By Harry E. Krumlauf

The year 1957 was one of declining metal price and production. Many lead-zinc-copper mines were forced to close, and the remaining mines limited production to stay more in line with demand. High cost of labor, supplies, and equipment and high taxes aggravated the situation. Some operators postponed or abandoned expansion programs because of uncertain economic conditions. Output was curtailed by elimination of over- time employment and reduction of the working force. The number of employes laid off was small- reduction in the labor force was accomplished by not replacing those who left a company's employ.

Jan 2, 1958

By J. Hamisch

Climate policy regarding perfluorocarbons (PFCs) may have a significant influence on investment decisions in the production of primary aluminum. This work demonstrates an integrated analysis of the effectiveness and likely economic consequences of different climate policy options. In our study we first compare atmospheric observations to the available estimates of PFC emissions for the baseline years 1990 and 1995. We then present projections for regional emissions of PFCs from the aluminum industry using the MIT Emissions Projection and Policy Analysis model under different policy scenarios. Abatement costs for emissions of PFCs and C02 are compared in the context of the Kyoto Protocol.

Jan 1, 1999

By B. M. O'Harra

Zinc smelting is frequently termed a ba.ckward art. The term is hardly true, for great progress has been made in recent years in the design and in the thermal efficiency of the retort furnace, in the quality of retorts, in the recovery of zinc, and in the ability to treat more impure and complex ores. The fact remains, however, that the peculiar physical and chemical properties of zinc have delayed such immense advances-large smelting units, high recovery, lowunit costs, and ability to treat low-grade ores-as have been made in the metallurgy of lead and copper. In current retort-smelting practice, the ores, if carbonates, are calcined to remove carbon dioxide; or, if sulphides, are roasted to remove sulphur. The sulphur must be eliminated as completely as possible, usually to less than 1 per cent. This means that the roast must be continued for a long time at a high temperature, with resulting high cost and small capacity per furnace. The roasted ore is mixed with about 50 per cent of its weight of reducer, which may be fine coke, anthracite, or nonbituminous coal. This mixture is charged into horizontal fire-clay retorts. The retorts used in this country are about 8 inches in internal diameter by 4 feet in length and hold 50 or 60 pou~ds of ore. The diameter of the retort is limited by the tirrie required for the heat to penetrate to the center of the charge; the length by the strength of the retort, which at the high temperature employed can not support the weight of the charge if the span is more than about 50 inches. The retorts are heated externally by coal, natural gas, qr ·producer gas to a temperature of 1,200° C. or more. The zinc oxide is reduced to zinc, which is volatile at this temperature, and passes into a conical fire-clay condenser. attached to one end of the retort, where it conde_nses to liquid zinc and is removed. Twenty-four hours are required for distillation, and because of the low heat conductivity of the retort walls 11.nd of the ore charge itself, the heat efficiency even of the most modern regenerative furnacei;; is only about 12 per cent. The retorts have a short life, 30 to 6Q days, at the high temperature required-; zinc losses are heavy, usually 10 per cent or more; and the proportion of impurities in the retort charge must be carefully controlled to prevent the rapid corrosion of retorts. For these reasons, much work has been done in an e:ff ort to, find cheaper and more efficient methods o.f recovering zinc from its ores. Various methods have been proposed for smelting in the blast furnace. Some of these contemplated the production of zinc vapor and its condensation to liquid; others attempted to produce liquid zinc directly by smelting under pressure. It is now realized that fundamental difficulties render these proposals impracticable. The electric furnace for smelting offers obvious advantages in the way of the efficient utilization of energy, large units, easy attainment of high temperatures, and the possibility of treating complex ores. E. H. and A. H. Cowles first suggested a design for an electric furnace for the reduction of zinc ores and patented their process in 1885. Their attention was soon directed to other uses for their furnace and nothing further of importance was done in the electric smelting of zinc until about 1900. Several investigators then started work upon various processes and had more or less success. The chief difficulty they encountered was the impossibility of obtaining more, than a small amount of the zinc as liquid metal because most of the zinc vapor condensed as blue powder. Interest in the electrothermic metallurgy of zinc increased, many patents on processes and furnace design were taken out, and the literature on the subject grew, until in 1914 and 1915 the problem seemed to be approaching solution. About this time the hydrometallurgy of zinc, the development of which had been lagging somewhat behind that of the electrothermic metallurgy, sprang into the limelight and a commercial process was soon perfected. This rapid development, perhaps aided by the war premium on the high-grade spelter produced by electrolytic deposition, distracted attention from electric smelting to some extent, though progress continued. With the perfection and standardization of the electrolytic process has come a better realization of its limitations, especially the necessity for large-scale operation ·and the difficulty of obtaining high extraction. Because of these limitations the electrothermic metallurgy of zinc still has a field of its own and in fac-t promises to become a strong competitor of both hydrometallurgy and retort smelting except under conditions highly favorable to the latter methods. Because of the imperfections of the retort and electrolytic processes and the promise that the electric furnace offers in overcoming these imperfections, the. United States Bureau of Mines, in cooperation with the Missouri School of Mines and Metallurgy, has undertaken a study of the electrothermic metallurgy of zinc.

Jan 1, 1923

By C. C. Herrick

The vapor pressure of indium has been measured by the torque-effusion technique, as a function of temperature between 1102o and 1422oK. For liquid indium, the vapor pressure (in atmospheres) can be represented by the equation -R In P = 5.782 x104/T - 25.29from 1000o to 1422oK. Extrapolation yields a calculated normal boiling point of 2329°K and a heat of vaporization at 298 oK of 58.09 kcal per mole by the third-law method and of 58.39 kcal per mole by the second-law method. Calculations indicate that the free-energy functions of Hultgren are to be preferred to those of Guruich. BECAUSE of the potential uses of liquid metals, it is important that convenient experimental methods be developed which will lead to a sufficient body of thermodynamic data so that reasonable estimates of properties of liquid metals can be made. Indium is particularly well-suited to investigation, since it remains liquid over a long temperature interval, it alloys readily, suitable containers for it are easily procured, and relatively few investigations of its thermodynamic properties in the region above 1000°K have been made. PREVIOUS RESEARCH The first determination of the vapor pressure of indium was made by Anderson,' using the Knudsen method and silica-lines stainless-steel cells. Kohlmeyer and spandau2 determined the normal boiling point, and a mass-spectroscopic investigation has been made by Lyubimov and Lyubitov.3 (Unfortunately, only an equation representing the data of the latter investigators has been available to us.) Hultgren et al.4 and Gurvich5 have published discordant tables of the free-energy functions for indium. EXPERIMENTAL METHOD The torsion-effusion principle has been described amply in the literature.8,7 With this method, one observes the angular deflection induced by effusion of vapor from a multihole effusion cell which is suspended from a filament producing a small rotational restoring force. The pressure within the effusion cell can be computed from the relation ziaifiai where k is the torsion constant of the filament, 6 is the observed angular deflection, and ai, fi, and qi are the area, force factor, and moment arm of the ith effusion orifice. The force factor f is analogous to the Clausing factor,' and corrects for the reduction in effusive force attributable to the finite geometry of the effusion orifice. Schultz and Searcy' have tabulated the force factors for various tube geometries. EXPERIMENTAL APPARATUS The physical arrangement employed in this study is shown in Fig. 1. The furnace elements are six Globar heat rods with 15-in. hot zones. Temperature is maintained to * 1°K by a Beck mechanism driving two 26-amp Powerstats in parallel. A Pt (Pt, Rh 10 pct) thermocouple serves as the sensing element. Four inner tubes act as vibration isolators; the air pressure required for maximum isolation was determined empirically, and is maintained by a solenoid valve. The tungsten fiber, 9 by 0.002 in., is joined to an 0.008-in. tungsten wire or graphite rod via a machined lightweight chuck.

Jan 1, 1964

By John Freer

As an innovation on the annual programme, the Excursions Sub-Committee organized a social get together of the Institute's Councillors and their families on Sunday, 27th February, 1983. Asian Mining - change of date The Second Asian Mining Conference, previously announced as being held in Manila, The Philippines, from 5th to 8th November, 1984, will now be held in Manila from 11th to 14th February, 1985.

Jan 1, 1983

By J Kinal, I Mitchell

Many flotation plants use pH to adjust the pulp chemistry of their system to achieve optimum separation. For example, in a sequential lead/zinc circuit the pH during sphalerite flotation is increased to 10.5 or greater to depress galena and pyrite, thereby improving selectivity for sphalerite. However, maintaining a pulp at a particular pH value does not necessarily provide the operator with an abundance of information regarding the chemistry changes occurring within a plant. This paper provides the reader with a number of pulp chemical observations in several plants, showing that the same trends are noted over time; however, the magnitude of the measured values do change. Further, the changes in magnitude are invariably associated with a change in mineralogy. Thus, is measuring pH enough? Can the Eh, dissolved oxygen and temperature be measured at the industrial scale reliably? And, are these measurements useful?

Jan 1, 2006

By Dairo E. Chaverra, Carlos Argumedo‑Jimenez, Oscar J. Restrepo‑Baena

This paper presents the results obtained by processing a gold and silver telluride mineral concentrate from a mine in Colombia. An acid wash, also known as acidification, was carried out, followed by oxidation with nitric acid as a pretreatment. Cyanidations of the pretreatment residues were carried out and the results were compared with results from cyanidations of base materials. The removal of carbonates in the acidification, a tellurium extraction close to 90% during the pretreatment, and a 30% improvement in the gold recovery compared to the conventional process were achieved.

Nov 8, 2023

By S. Sekhar, S. Bhargava, A. K. Godugu, J. L. Porathur

Cemented backfilling has enabled underground hard rock mines to extract orebodies more safely with improved ore recovery. It is important to estimate the minimum required strength parameters for a backfill mix by optimizing the binder percentage to enable cost-effective and safe stoping operations. We conducted three-dimensional numerical modelling to study the effect of various stoping parameters on the stability of a free-standing backfill wall. A Mohr-Coulomb material model was used for the backfill material and the rock-fill interface. A strength reduction technique, excluding friction angle, was employed to arrive at a minimum stable strength value for the backfill. For a given combination of strength values, the stability state of the backfill wall could be demarcated using a displacement and yield zone tracking method. The numerical modelling results are compared to some earlier theoretical models. From the simulations, a predictive equation is developed to predict the required strength parameters for a backfill mix to ensure a stable free-standing wall. Examples are given of the successful use of the predictive equation at some underground hard rock mine sites in India.

May 2, 2022

By Clifford S. Gibson

A year ago a paper (1) was presented at the Annual Western Meeting of the Institute regarding silicosis in Ontario mines. It described the whole problem as we see it and discussed the means of prevention. The work and aims of the Technical Silicosis Research Committee of the Ontario Mining Association, and of the Committee's field engineer, were fully described also and it is suggested that reference be made to this paper in order to have a better understanding of the observations which are presented now. These observations enlarge upon parts of the dust control measures already discussed and tell of general progress in the past year. They concern fifty properties, the majority of the operating mines, which vary in size from the hopeful prospect to established producers yielding 11,000 tons of ore daily. Most of these are gold mines; a few copper-nickel. The ores range from heavy sulphides to siliceous materials and they are mined by many methods from varying types of deposits. The majority of the latter are steeply dipping and all are found in Precambrian host-rocks. Up to the present, die greatest depth to which mining has penetrated is 6,400 feet.

Jan 1, 1939

By C. P. Haller, S. J. Aresco, R. F. Abernethy

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal, expressed in British thermal units, and the composition as shown by proximate analyses. To these, when required, are added the ash- softening temperature of ash, the free-swelling index, and the hardgrove grind- ability index. Under most of these specification contracts the bidders guarantee the quality of the coal, and that guaranteed by the successful bidder becomes the standard of his contract. The deliveries are sampled in accordance with instruc- tions issued by the Bureau of Mines; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the con- tractor and, if it is not, a price adjustment is made. Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks) provide valuable data for use in evaluating future bids. In addition, the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal. The Government purchased approximately 5-1/4 million tons of coal in fiscal year 1953. In connection with these purchases, the Bureau analyzed 11,435 samples. These are published for the use of Government officials and the public. A series of publications has been completed on coal analyses by States, or, where production is small in any one State, by groups of adjacent States. In addition to analytical data showing composition and quality of coals of the States, the publications con- tain brief descriptions of the geological structure of the coal basins, typical mining conditions in the various districts, the principal economic data of the industry, and the relationship of mine or channel samples to delivered and tipple samples. The present publication covers many States but deals only with the analytical data of the coals. Previous publications in this series are: Bulletin 516, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Years 1948 to 1950 Inclusive); Report of Investigations 4934, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Year 1951); Report of In- vestigations 4972, Analyses of Tipple and Delivered Samples of Coal (Collected During the Fiscal Year 1952). Following are the Bureau of Mines technical papers published by States, with their numbers: Alabama, 347; Alaska, 682; Arizona, California, Idaho, Nevada, and Oregon, 696; Arkansas, 416; Colorado, 574; Illinois, 641; Indiana, 417; Iowa, 269 and 706; Kansas, 455; Kentucky, 308 and 652; Maryland, 465; Michigan, North Dakota, South Dakota, and Texas, 700; Missouri, 366; Montana, 529; New Mexico, 569; Ohio 344 (and Bulletin 499); Oklahoma, 411; Pennsylvania Bituminous, 590 (Supplement 645); Pennsylvania Anthracite, 659; Tennessee, 356 and 671; Utah, 345; Virginia, 365 and 656; Washington, 491 (Supplement 618); West Virginia, 405 and 626; and Wyoming, 484.

Jan 1, 1955

By Charles E. Locke

SHARP CONTRAST exists in the reports so helpfully contributed by the individual members of the Milling Committee for this review. Those engaged in the milling of gold and silver ores report great activity, of which some details will be given later. Those engaged in milling ores of base metals report continued depression and little progress. Copper production in the United States is running at about fifteen per cent of capacity. Some Arizona copper mills are closed. Anaconda is milling about 45.000 tons of copper ore per month, and the Utah Copper Co. 35,000 monthly. However, in Canada the International and Falconhridge copper-nickel mills and the Noranda copper-gold mill have increased production. Also the Climax molybdenum mill in Colorado is milling 4000 tons per day. Water shortage from the drought has caused curtailment or complete shutdown of mills in some parts of the West.

Jan 1, 1935

By R. L. Marek

An important problem in the efficient conduct of industry is that of helping the individual employee to formulate an attitude toward his work which will result in the reduction of accidents and the promotion of safety. Perhaps nowhere is the need greater for this type of Psychological training of carefully selected men than at oil refineries whore both the raw materials and the finished products are highly inflammable and explosive in nature. However, the refinery organization usually is well adapted to educational safety activities - much more so than in the producing, pipe line, and marketing departments where the personnel are more or less scattered; but the same general principles of conduct hold true in any industrial organization. This problem of directing the attention of the employees to their specific tasks or helping them to control and frequently eliminate hazards engendered by adverse mental attitude or emotion is met most satisfactorily by carefully selecting applicants and placing them at jobs for which their ability, best fits them. The subsequent training of these carefully selected employees to assure their most effective work in accident prevention mu be accomplished in a variety of ways, such as by personal supervision and instruction, inspections, drills, and by the studied use of well thought out safety pamphlets and posters. This procedure is simple in outline and not original in scope, yet the importance of selecting and training the personnel has, not been generally accepted by the petroleum industry until recent years. In 1926, the Bureau of Mines, while making a study of accidents in the petroleum industry, found that medical examinations of prospective employees were not receiving unanimous endorsement by all companies, and the point was stressed that the selection and allocation of employees was a problem requiring serious consideration in the petroleum industry.

Jan 1, 1932

By David R. Mitchell

Many of the difficult operating problems of the preparation of coal for market, of sampling coal shipments and in the utilization of coal are caused by segregation in the coal mass. Segregation may be of two kinds: i.e., "size segregation," in which particles of the same size in a mass of coal containing a range of sizes collect together and "density segregation," in which particles of the same density or specific gravity in a mass of particles of varying density gather together. Mechanics of Segregation Size segregation cannot take place with closely sized coal. As the size range increases, the tendency for size segregation increases. Similarly, cleaned coal with particles of approximately the same specific gravity have very little tendency for density segregation. The wider the density range of particles and the more particles of different density, the greater the chances are for density segregation. The following discussion deals primarily with coal of a wide size range as screenings and of wide density differences as uncleaned or run-of-mine screenings. If a mass of coal containing particles of a wide size range is subject to the stream action of a moving current of water, the small particles are transported farther than the coarser. Particles of different density in a stream of moving water are subject to the laws of classification, the heavier settling out first. The familiar sluice box of the gold miner and the action of rivers and other streams in classifying material according to

Jan 1, 1938

By David R. Mitchell

Many of the difficult operating problems of the preparation of coal for market, of sampling coal shipments and in the utilization of coal are caused by segregation in the coal mass. Segregation may be of two kinds: i.e., "size segregation," in which particles of the same size in a mass of coal containing a range of sizes collect together and "density segregation," in which particles of the same density or specific gravity in a mass of particles of varying density gather together. Mechanics of Segregation Size segregation cannot take place with closely sized coal. As the size range increases, the tendency for size segregation increases. Similarly, cleaned coal with particles of approximately the same specific gravity have very little tendency for density segregation. The wider the density range of particles and the more particles of different density, the greater the chances are for density segregation. The following discussion deals primarily with coal of a wide size range as screenings and of wide density differences as uncleaned or run-of-mine screenings. If a mass of coal containing particles of a wide size range is subject to the stream action of a moving current of water, the small particles are transported farther than the coarser. Particles of different density in a stream of moving water are subject to the laws of classification, the heavier settling out first. The familiar sluice box of the gold miner and the action of rivers and other streams in classifying material according to

Jan 1, 1938

By John Griffen

HYDRAULIC classification as explained by Rittinger and others was largely restricted to conditions wherein the free-falling velocities of the particles were conceived as governing the separations effected (see chapter 9). The laws governing classification under free-falling conditions have been summarized by Chapman and Mott as follows:

Jan 1, 1943

By Herty, C. H.

Three distinct processes take place during the conversion of iron ore to steel. First: the raw ore is reduced to metallic iron in the blast furnace and during this reduction certain constituents are dissolved in the iron, either through the solution of a solid into a liquid phase, as in the case of carbon, or by reduction of an oxide existing in the slag to the metallic element of that oxide, with subsequent solution of the metallic element in the iron. Thus by the process of solution and reduction, a pig iron results which contains about 4 per cent carbon, 1 per cent silicon, 1 to 2 per cent manganese, 0.1 to 0.4 per cent phosphorus, and 0.03 to 0.10 per cent sulfur. To obtain a sufficient yield of iron from the ore it is necessary that the reducing process be carried as far as possible, with the result that the impurities mentioned accompany the reduced iron. Second: to convert this iron into steel it is necessary to oxidize a part of the iron in eliminating the impurities to the extent desired for the particular product being made. In eliminating these impurities by oxidation a certain amount of iron oxide (FeO) dissolves in the steel. This dissolved FeO reacts with the metalloids, except sulfur, and to eliminate them to the desired extent it is necessary to leave a considerable amount of FeO in the metal. The reaction of iron oxide with silicon, manganese, and phosphorus results in the formation of the oxides of these elements. The oxides enter the slag and the extent of elimination of the elements depends on certain equilibria between the slag and the metal. The reaction of FeO with carbon results in the formation of the gases CO and CO, which, after saturating the metal, pass into the furnace gases. Third: after the iron has been purified to the desired extent as far as the elements listed are concerned, it is necessary to deoxidize the bath to remove the FeO, which is the vital factor in gas formation as the steel solidifies.

Jan 1, 1957

By Jack O. Jones

The Furnish mine, Caharrus County, W. C., was operated intermittently until 1905 as a gold mine. Scheelite was discovered by A. L. Mash in the mine dumps of the Furniss and Phoenix mines, and he later informed the Bureau of Mines of his discovery. The Bureau of Mines, in two projects at the deposit in 1948 and in drilled 12 holes totaling 1,706.6 feet, examined and sampled the underground workings, excavated by bulldozer and hand, 3,155 linear feet of trenches and collected numerous samples for assay. The best scheelite shown; was found in the underground exposure of the Furniss mine.

Jan 1, 1950

The Mount Morgan eopper-gold orebody is contained within a series of Mid-Devonian volcanics which occurs as a roof pendant within Permian granite. The ore minerals comprise pyrite, chalcopyrite, and local aggregations of magnetite and pyrrhotite. Silver-rich gold (electrum) is disseminated through the ore usually in ultrafine to sub-microscopic dimensions. Accessory minerals include marcasite, digenite, chalcocite, covellite, sphalerite, bismuthinite, molybdenite, calaverite, petzite, and cassiterite.Very minor accessories include cubanite, tetrahedrite, galena, arsenopyrite, hematiIe, goethite, and rutile. The gangue minerals are quartz, predominantly, with minor amounts of chlorite and sericite.Study of microtextures of a representative suite of specimens from Mount Morgan does not reveal any criteria indicative of metasomatic replacement but does show, in the case of pyrite, evidence strongly suggestive of annealing recrystallization. Other textures in pyrite indicate porphyroblastic growth of the iron sulphide.It is inferred that the Mount Morgan orebody is genetically related to the volcanic rocks and was later contact metamorphosed by the intrusive granite or by the series of intermediate to basic dykes that transect inmine area. On this basis the Mount Morgan orebody would be a contact metamorphosed volcanic hydrothermal deposit emplaced, according to recent studies, along a pipe-like zone of brecciation.

Jan 1, 1967