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In 2005, a total of 2,063 coal mining operations reported employment to the Mine Safety and Health Administration (MSHA). Coal mines comprised 14.1% of all mining operations. ? Bituminous mines comprised 92.6% (n=1,911) and anthracite mines 7.4% (n=152) of coal mining operations. ? Approximately 70% of all coal mines were located in three states: Kentucky (28.0%), West Virginia (21.8%), and Pennsylvania (20.6%).

Jan 1, 2008

By Michael Karmis

The International Conference on Sustainable Development Indicators in the Mineral Industries(SDIMI 2003) was held May 21-23, 2003 on the island of Milos, Greece. The objective of this international conference was to assist the mining and minerals industries in their global transition to sustainable development. The main theme of the conference was the development, monitoring and assessment of sustainable development criteria for mineral operations. Emerging technologies were also presented that can assist in the development of criteria and performance indicators.

Jan 1, 2003

By F. E. Lathe

INTRODUCTION THE present study, based largely upon phase equilibrium diagrams and other theoretical considerations but nevertheless addressed primarily to the practical metallurgist, has been undertaken with a view to discovering what light can be thrown upon the role of alumina in slags. According to Liddell (23), "alumina apparently acts as .a base if much silica is present, as an acid if the silica is low, always as a nuisance." Newton and Wilson (26) state that .alumina "is never added intentionally, as it makes the slag viscous, and is generally an undesirable constituent of slags". Camp and Francis (3) sum up their views by saying, "alumina is seldom used intentionally as a flux, but it is present in nearly all raw material, hence unavoidable". One has only to read The Function of Alumina in Slags, by Henrich (I3), and the very extensive discussion that followed the presentation of his paper, to realize that, before the days of phase equilibrium diagrams, it was a very serious question indeed as to whether alumina should be calculated as a basic, acid, or neutral constituent. Opinions then differed widely, as well they might; today, even though no categorical answer can be given to the question raised, the function of alumina can be at least partly clarified by a study of the fundamental work done by the Geophysical Laboratory in Washington and by certain universities in both America and Europe. It will be a source of gratification to Canadian metallurgists and ceramists to know that work of this type is now under way in the recently organized Physical and Crystal Chemistry Section of the Mines Branch, Ottawa, and that results of practical value have in fact already been obtained.

Jan 1, 1951

Discussion of the paper of C. M. YOUNG, presented at the St. Louis meeting, October, 1917, and printed in Bulletin No. 129, September, 1917, pp. 1369 to 1384. CARL SCHOLZ, Chicago, Ill.-Mr. Young was kind enough to' allude to the development of a mine in which I am now engaged. Several months ago the Burlington Railroad decided to open a mine in the field Which they own in Franklin County containing some 15,000 acres .(6070 ha.) of coal, ranging in thickness from 8 to 12 ft. (2 to 3.6 m.). This proposition in itself is attractive to any mining engineer, but with the backing of a large company I saw an opportunity to do some novel work in the construction line, and for several months I have been investigating and working on the problem of developing what I hope will be the largest and best equipped mine in the State of Illinois. The shaft will be sunk at a place where the coal lies at a depth of 600 ft. (182 m.) and conditions both of the surface and of the coal are ideal in every way; the seam is almost level, and we had only 7 ft. (2 m.) of surface clay to go through. We are going to hoist by skips in order to reduce the rope speed. I believe that is a long step in the direction of economy, because we not only double the output of the mine by hoisting the contents of two cars atone time, but we reduce the proportion of dead weight. In our case there will be 20 tons of coal and 18,000 lb. of skip, or 55 per cent. net and 45 per cent. tare. That, of course, necessitates less than half the rope speed for the same tonnage, and we all know that speed means power and power means cost. Skip hoisting permits the use of solid-end gate cars, which is an advantage. The cost of these cars will be in the neighborhood of $250 apiece; They are well built, with roller-bearing wheels of the most up-to-date type, spring draw-bars, and refinements of-that character which are necessary to move the loads most advantageously.

Jan 1, 1918

By J. H. Wilhelm

Continuous thickeners can be sized either from previous experience, continuous pilot-scale test results, or from batch settling tests. Although it is a relatively simple process to size full-scale thickeners when previous experience or pilot-scale operating data are available, batch testing is often the only realistic method for sizing thickeners due to time restrictions, budget limitations and availability of sample material. Many authors have, therefore, suggested means of running batch tests and analyzing the resulting data. Fundamental thickening theory had its beginning with the work o£ Coe and Clevenger(1). In order to determine the size of the thickener settling area, they proposed that a series of batch settling tests be run at various initial concentrations. The solids handling capacity at each concentration can then be determined and the lowest capacity (maximum area requirements) used to size the thickener. Kynch(2) developed a mathematical analysis in which the relationship between solids concentration and settling rate can be obtained from a single batch settling curve. Talmage and Fitch(3), Yoshioka(4)(5) and Dick(6), have enlarged upon these works to give a basis for methods of sizing thickeners.

Jan 1, 1979

By A. George Stern

The literature dealing with the drilling of oil wells has become extensive during the last few years, and oil men can find much information relating to drilling muds in the technical literature of the petroleum industry. Although large tonnages of clay are used in preparing drilling mud (also known as drilling fluid), almost no information has been published to apprise the clay industry of the types of minerals used, with their requirements and limitations. It is from this point of view that the present report has been prepared.

Jan 1, 1941

By Robert C. Merritt

Laboratory amenability studies as well as a pilot heap-leaching investigation of low-grade sandstone uranium ores from Wyoming, New Mexico, and Colorado are described. Sulfuric acid heap leaching with oxidation, for 120 days, extracted up to 98 percent, 90 percent, and 79 percent U308 from Wyoming, New Mexico, and Colorado ores, respectively.

Jan 1, 1976

By C. K. Gupta, P. K. Jena

Niobium (columbium) metal in the form of a button has been produced by calciothermic reduction of niobium pentoxide using sulfur as the heat booster. In these experiments with 50 g of niobium pentoxide per batch, the influence of percentage of calcium in excess of the stoichiometric, the percentage of sulfur by weight of the niobium oxide, and the outer-wall temperature of the bomb on the quality and yield of the metal has been studied. The maximum yield on this scale was 78 pct using 50 pct excess Ca and 20 pct of S and at a bomb-wall temperature of 600°C. In experiments conducted on 500 g of niobium pentoxide, reduction with 40 pct excess Ca and 20 pct of S, and at a bomb-wall temperature of 500°C, the.yield of the metal improved to 82 to 84 pct. Some of the reduced-metal samples have been electron-beam melted and the button melts thus obtained have been observed to be extremely ductile and capable of cold reduction to 98 pct without intermediate annealing. NIOBIUM, because of its high melting point (2468oC), its ductility, its resistance to corrosion especially in liquid metals, its high-temperature mechanical properties, and its relatively low capture cross section (1.1 barns) for thermal neutrons, has potentialities as a structural material in the field of nuclear engineering. Niobium and its alloys are also gaining importance in high-temperature technology as components in aircrafts, jet engines, and missiles, electronics, chemical engineering, and surgery. In 1904 Weiss and Aichel 1 produced niobium by reduction of its pentoxide by misch-metal. Since then a large number of investigations have been carried out for the extraction of niobium from its compounds. The various routes through which the metal niobium has been extracted from its compounds can broadely be classified into the following groups: a) reduction of its halides, oxides, and fluo-salts with metals like calcium, magnesium, sodium, and aluminum;2-10 b) reduction of its halides with hydrogen and oxides with carbon or carbides;11-18 c) electrolytic winning from its halides and fluo salts;19-25 and d) thermal decomposition and disproportion ion of its halides26-30 Among the processes in commercial use at present are sodium reduction or fused-salt electrolysis of potassium niobium fluoride, carbide or carbon reduction of the oxide, and hydrogen or metallothermic reduction of the chlorides. In 1907 Von Bolton2 prepared niobium by reducing niobium pentoxide with aluminum. Dennis and Adam-sona attempted reducing the oxide with magnesium powder in argon atmosphere and the resulting metal contained as much as 5 pct O. Mondolfo8 claimed a method for the reduction of the oxides with aluminum. In the case of both magnesium and aluminum reduction, it has been stated31 that by-product oxides such as MgO or A12O3 would involve a major separation problem. Further, in the case of alumino-thermic reduction, the solubility of aluminum in niobium and intermetallic formation have to be reckoned with. In 1922 Bridge3 produced niobium by calcium reduction of niobium pentoxide. Dennis and pdamson' obtained the metal by a similar method with an oxygen content of 0.2 pct. In most of the cases of metallothermic reduction of niobium oxides mentioned above, the metal niobium is obtained in the form of powder. In an attempt to produce massive niobium metal, lock' used iodine as the thermal booster in the bomb reduction of niobium pentoxide by calcium. Massive niobium metal was obtained with a maximum yield of 75 pct containing 0.1 pct 0. Joly32 carried out experiments on calcium reduction of niobium pentoxide on a 2-kg scale using sulfur as the heat booster in a sealed bomb filled with argon. In his experiments, the reaction was initiated by passing a current through niobium spiral wire embedded in the charge. In a typical run consisting of 2000 g of niobium pentoxide, 3100 g of calcium, and 800 g of sulfur (S/Nb2O5 = 3.3), he obtained massive metal in the form of a very uneven mass with a yield of -57 pct. With lower amounts of sulfur and calcium, powder niobium mixed with small metal globules was obtained and the yield was also poor. From these experiments he concluded that this method is not a suitable one for industrial development considering the quality and yield of metal obtainable and the possible hazards with higher ratios of sulfur to niobium pentoxide in the -~charere. In the present work, a detailed investigation on the calciothermic reduction of niobium pentoxide in a stainless-steel bomb in presence of sulfur as the heat booster was undertaken on a laboratory scale.

Jan 1, 1964

By Alan A. Campoli

The US Bureau of Mines (USBM) conducted research to develop improved guidelines for selecting the type and pattern of roof support in different geologic environments. The goal is to minimize the over and under design of mine roof support, resulting in more productive and safer mines. To obtain the necessary data on roof behavior and support performance, USBM conducted several field studies. Each study covers roof geology, stress regime, ground reaction, support interaction and mining environment. A consistent experimental design is being used. This includes measurements of roof bolt loads and roof movements. So far, 10 studies have been conducted in several geologic settings.

Jan 1, 1996

By Thomas Barkley

Mining tradition holds that a parallel round underground can not be any deeper than it’s smallest face dimension. ln other words, a mine using a 12’ (3.7 m) high by 24’ (7.3 m) wide room and pillar mine, the deepest pull that can be achieved is plus or minus 12’ (3.7 m). After experience with decking of rounds in a 12’ (3.7 m) diameter shaft to achieve more than 12’ (3.7 m) advance per round, the concept of deepening the pull on horizontal parallel rounds seemed to be a feasible concept. Tests were conducted in a conventional room and pillar metal mine with a round size of 12’ (3.7 m) high by 24’(7.3 m) wide. Standard rounds were drilled with a 16’ (4.9 m) steel as parallel rounds to an average depth of 14.5’ (4.4 m). The average depth of pull on these rounds was about 13’ (4.0 m). Using the available drilling equipment, 20’ (6.1 m) drill steel was used to drill holes to an average depth of 18’ (5.5 m). Five rounds were drilled and shot with a resulting aven$e pull of 16.2’ (4.9 m) or 90 % of drilled depth. Rounds were designed with decked bum cuts to maximize depth of pull in the cut area An innovative method of de&mining drilling accuraq was used to estimate it’s effect on depth of pull in the rounds. This method used a standard automatic 35-mm camera and scaling to determine the average drill deviation for many of the holes in the rounds.

Jan 1, 2000

By B. A. Zaharov, J. M. Shneerson, L. V. Chugaev, M. T. Zhunusov, A. M. Markelov, S. V. Drozdov

The main direction of research was the application of autoclave technology for the flotation concentrates or biooxidation feedstocks. The industry modernization also expects the possibility of increasing the yield of the flotation concentrate, to allow an increase in gold extraction in flotation circuit. This paper provides brief description of results obtained for concentrates with the yield of 4 and 8%, as well as corresponding biooxidation feedstocks. Technological efficiency of autoclave oxidation is shown for both concentrates and biooxidation feedstocks. The process has been evaluated on a laboratory and a continuous pilot plant scale. Gold extractions from POX discharge are ranging from 94-97% for each product, with only 5-7 kg/t cyanide consumed.

Jan 1, 2014

By P. R. Sahm, T. V. Pruss

Mixtures of fine GaSb and Gds as well as preal-loyed GaSbl,As, powders were hot-pressed at 690°C and 25,000 psi. Dense alloys with compositional gradients of less than 5 pct were obtained from mixtures containing about 20 mol pct GaAs. For x < 0.2, there were increasing compositional gradients, and for x > 0.2 a GaAs-rich second phase appeared in the microstructure. Densification as well as alloying wlechanisms were enhanced by dissociation and, possibly, oxidation reactions of the powders. Densification of coarse prealloyed material, however, primarily depended on plastic flow phenomena and required temperatures just below solidus and pressures of 50,000 psi Thermal and electrical properties were measured. Although in no case was the figure of merit of melt growth materials approached closer than to within 25 pct, the better overall thermoelectric properties were found in coarse-grained, prealloyed materzals which had been compacted to near theoretical density and where grain regrowth had been induced. Similar results are believed to hold in other binary 111-V compound systems if processed under similar conditions. The densification of unalloyed GaSb powders during pressure sintering (= hot pressing) was shown to depend strongly on powder particle size.&apos; Fine powders displayed a "liquid skin effect" that enhanced compaction through the presence of liquid gallium, whereas coarse powders compacted predominantly by plastic flow. The liquid skin effect, in particular, appeared attractive for alloying GaSb with other, higher-melting, III-V compounds, and to densify these in a one-step operation. This is of special interest in the case of III-V compound alloys as the conventional techniques of melt growth or long-time annealing of powders2 is very time-consuming, especially in cases where a large separation of liquidus and solidus can be expected, such as in GaSbl alloys.2 It was felt that experimentation with this system, a particularly unfavorable example, would allow us to extrapolate to several other, more favorable, cases. Uses of Ill-V alloys are most evident in thermoelectric energy conversion devices.&apos; For this reason certain thermal and electrical properties were measured and compared to those of melt-grown material and to hot-pressed prealloyed powders. EXPERIMENTAL PROCEDURE The pressure-sintering apparatus has been previously described.&apos; Using this equipment, both powder mixtures of GaSb with GaAs and prealloyed GaSbl-,As, powders were hot-pressed. The mixtures were pre- pared from cast GaSb and melt-grown GaAs. The prealloyed material was obtained from stoichiometric melts, initially heated to 1200°C in an evacuated quartz ampoule, and then annealed in the solidus-liquidus interval. A typical annealing cycle consisted of a heating to 850°C (1 hr), extended successive annealing at 750°C (65 hr), and slow stepwise cooling (25 hr) to below solidus. The GaSb, GaAs, and GaSbl-,As, materials were ground in a vibrational mill to particle sizes below 500 . A jet mill reduced these further where necessary. Fine powders were analyzed by Coulter counting for their size distribution. Average sizes by volume were calculated from the data. Mixing of the powders, where necessary, was carried out through rapid vibrational motion. The hot-pressing operation consisted of a degassing period of 15 hr, in most cases at 690°C, followed by several hours of compression, normally 25,000 psi at 690°C for powder mixtures and 50,000 psi at 710°C for prealloyed powders. The chemical compositions were confirmed by X-ray fluorescence analysis. To estimate the degree of solid solution achieved, lattice parameters were determined and interpreted according to Vegard&apos;s rule. In addition, optical microscopy helped to correlate the relative amounts of the phases present as well as the degree of porosity to the measured density. To reveal grain boundaries, polished surfaces were etched4 with H 2 O:H 2 O:HCl = 2:l:l. In several cases microscopic concentration gradients were monitored by electron-probe analysis-. RESULTS AND DISCUSSION Alloying and Densification of GaSn-GaAs Powder Mixtures. After preliminary experiments showed that no appreciable alloying took place in mixtures of coarse GaSb (22.5 p) and fine GaAs (2.5 p) powders, hot pressing of mixtures was confined to fine powders only (3.1 and 2.4 p, respectively). Alloying and densification apparently occurred simultaneously with a grain regrowth mechanism which depended on the presence of a liquid phase.&apos; The liquid phase was provided by the dissociation of GasbS particles into liquid gallium and antimony above 555°C. This not only enhanced grain regrowth and densification, as in unalloyed GaSb,&apos; but took on additional importance here for the alloying process. Alloying was speeded up by the resulting liquid-solid interaction as compared to the very slow solid-state diffusion process normally expected at these temperatures.&apos; The results obtained with a series of powder mixtures have been compiled in Table I. It is seen that for mixtures with less than 20 mol pct GaAs, x < 0.2, the compositional ranges increased and for x > 0.2 a GaAs-rich phase and free antimony appeared in the microstructure in sizable amounts.

Jan 1, 1968

By A. E. Lee

THE Blackwell Zinc Co., Inc., a subsidiary of the American Metal Co., Ltd., operates a horizontal retort zinc smelter at Blackwell, Okla. The plant has 14 furnace blocks of 800 retorts each, fired with natural gas on a 48 hr cycle. Over 13,000 tons of zinc-bearing material, chiefly sulphide flotation concentrates, are treated monthly to produce slab zinc and high lead-cadmium fume. In 1942 a program of rebuilding and modernizing the smelter was started. By 1947 furnace smelting capacity had been increased to a point where roasting and sintering facilities were inadequate, and it was necessary to purchase oxidized materials to supplement sinter production. The seven 210 ft Ropp roasters and three 42 in. x 44 ft Dwight-Lloyd machines then in use had been in service at least 20 years and were in need of major rebuilding. Thus it was entirely practical to consider all new equipment and a change of method rather than rebuilding and repairing obsolete units. A study of the problem indicated that roasting as such could be eliminated and roasting and sintering accomplished in one step by a modification of the Robson process,&apos; which had been used since the early 1930&apos;s by the National Smelting Co., Ltd., at their plants at Avonmouth, England, and Swansea Vale, South Wales. Francis P. Sinn, General Manager, Zinc Smelting Operations, The American Metal Co., Ltd., who was familiar with the practice in England, suggested the use of one large machine for the entire operation from concentrate to sinter. One step sintering appeared to best meet Blackwell&apos;s plant requirements and indicated substantial savings in labor, gas, coal, and repair costs. Choice of Machine Size The sinter machine size was set at 12x168 ft for a rated capacity of 540 tons per day. This tonnage, produced on a five day week, would meet the seven day requirements of the 14 furnace blocks. The one large machine was quoted at a lower cost than two or more 6 ft wide machines of similar total capacity. Further, the larger machine could be housed in a smaller structure and only one set of equipment for charge preparation and delivery and for disposal of sinter cake was needed. One machine on a five day week made possible a concentration of the skilled operating personnel and required less men than a plant including two or more machines and related equipment circuits. Fewer units of equipment meant less maintenance, and the two down days weekly allowed ample time to repair and, if necessary, to make up lost production. Experience had indicated better sintering quality and rates with larger masses of material, not only on wider machines, but also in deeper beds. The ratio of windbox perimeter to area for the 12x168 ft machine is 0.179, compared to 0.353 for a 6x102 ft machine and 0.617 for a 42 in. x 44 ft machine. This meant less air leakage with resulting fan power savings and less spoilage of charge along the pallet sides. Performance Initial operation of the new sinter plant was made in November 1951 and regular production attained late in December. The average product sinter output during 1952 and the first half of 1953 has been 18.2 tons per hr. The average for one month has been as high as 22.4 tons per hr. Considerable experimenting with varied operating conditions accounts in part for the below capacity — 24 tons per hr — average output, and work to further improve production rate continues. A typical sinter analyses is 66.0 pct Zn, 0.3 pct Pb, 0.1 pct Cd, 0.3 pct S, 8.0 pct Fe, 2.0 pct SiO,, 0.8 pct CaO, and 0.2 pct MgO. Use of this material has made possible increases in furnace burden and improved furnace operation over the former practice using sinter made from Ropp roasted concentrates. Better lead and cadmium elimination in sintering has permitted the furnace production of slab zinc lower in lead and cadmium. Anticipated economies of operation have largely been gained. The sinter plant is operated by seven men per 8 hr shift — one head operator, three equipment operators and three sweepers — plus one oiler on day shift only. While it has been necessary at times to operate seven days a week to produce the required sinter tonnage, the five day work week usually has been adequate. Consumption of natural gas for sinter bed ignition is 200,000 to 300,000 cu ft per day. Green Ore Sintering Practice The 30 to 31 pct sulphur content of the —200 mesh zinc concentrates is the fuel used to sinter the charge, no coal addition being required. In the feed to the machine, sufficient concentrates are added to crushed return sinter fines containing 0.3 to 0.5 pct sulphur to produce a charge averaging 5.0 to 6.5 pct sulphur. Since the return sinter used in Blackwell&apos;s practice is varied from — 1/2 to — 1/8 in., the actual sintering mixture of fine sinter and concentrates is somewhat higher in sulphur. The coarser sinter particles are too large to resinter and merely aid porosity in the sinter bed. The ratio of concentrates to return sinter in the charge ranges from about 1:4 to 1:5.5. Variations are based on the appearance of pried up bed sections, bed exit gas temperature trends, windbox suctions, and return sinter size. Sufficient sulphur must be used to obtain fritting of the charge into a soft sinter cake and to aid in the elimination of lead and cadmium. Excessive feed sulphur will result in partial slagging of the cake impairing porosity and prolonging sintering time.

Jan 1, 1954

By J. M. Mutmansky, C. Lee

"This paper outlines some of the work associated with a research study into the relationship between the characteristics of coal mine dust and the incidence of coal workers' pneumoconiosis (CWP). The project involves study of the chemical, mineralogical, and morphological characteristics of the dust. Early stages of the study have dealt primarily with the size analysis and elemental composition of airborne dust in continuous miner sections. This paper outlines the procedures and findings of the elemental analysis portion of the study.Most of the previous elemental analyses of coal were made available in the quest for information on the combustibility of coal dust or on causal agents and prevalence of CWP. However, no extensive studies have been performed to date, primarily due to the limitations of the analytical methods. A review of the analytical methods for elemental characterization of coal and coal dust particles is presented. TI1e comparisons are made based on the sample mass required, the sample preparation required, the destructivity of the test, and the capability of providing an easy multi-element analysis. The reasons for selecting the proton-induced x-ray emission spectroscopy (PIXE) method are outlined.The PIXE method was applied to both the airborne coal mine dust and channel samples collected from seven continuous miner sections in six different mines. Channel samples of the coal, roof and floor were collected and analyzed. Airborne dust sampling was performed using multi-stage cascade impactors and permissible 2.0 I/min pumps. Sampler locations were fixed in the sections with respect to the continuous miner and roof bolter or with respect to the intake and return airways. Sampling times varied from 45 minutes to 6 hours, depending on the dust concentration.The statistical analysis of the resulting elemental data is presented. Of particular importance are the analyses of the variation of elemental composition with size and the variation in elemental composition over the working section. One interesting finding is outlined showing the multivariate statistical analysis of the trace elements and its implications in the identification of the dust sources. The paper concludes with an analysis of the ramifications of the elemental data to related medical studies."

Mar 1, 1989

By Wilson Blake

Increased application and interest in the use of microseismic monitoring to deal with ground control problems, Particularly those resulting in violent failures, has brought about the need for practical guidelines with respect to all phases of microseismic monitoring. This report presents the results of an 18-month effort to review the microseismic method and develop needed practical guidelines. Microseismic activity and properties of microseismic events are treated so that these parameters can be taken into account when developing monitoring equipment. Microseismic equipment is discussed to provide familiarization with the components of monitoring systems. Factors to be considered and procedures for developing a microseismic monitoring system are presented. Both physical and electrical considerations for the installation of a monitoring system are discussed in detail. The operation of a microseismic system including data analysis procedures is presented. Field examples to illustrate use of microseismic data in evaluating ground control problems are presented in a number of case histories.

Jan 1, 1982

By Lincoln Silva Gomes

Processos metalúrgicos durante soldagem provocam tensões residuais em peças soldadas. Recentemente foi observado um efeito de redistribuição das tensões residuais de soldagem num período de até duas semanas após o termino do processo de soldagem. Existe hipótese nossa que esta redistribuição das tensões está associada a mudança na microestrutura que ocorre no material após do processo de soldagem. Para provar esta hipótese, uma simulação física dos ciclos térmicos do processo de soldagem foi realizada utilizando a simulação física termo-mecânica (GLEEBLE). Através da técnica de microscopia eletrônica de varredura associada a técnica de difração de elétrons retroespalhados (MEV–EBSD) foi observada a variação da misorientação dos grãos e mudanças na microestrutura do material nos primeiros dias após soldagem, acompanhada de redistribuição das tensões residuais.

Aug 17, 2017

By S. H. Ash

THE information obtained by examining and analyzing the core drillings from 15 diamond-drill holes shows that with the proper equipment little difficulty should be experienced while sinking the shafts at the 15 selected sites. Although a number of holes penetrated formations containing a high percentage of silica,, the health hazard from dust can be removed by using proper dust-control equipment. Methane was detected in small amounts in only one (hole 5) of the boreholes. The methane hazard should present no difficulty if adequate ventilation is employed while sinking the shafts.

Jan 1, 1952

By Ahmad-Bitar¸ Riyad N., Shadia J. Ikhmayies

"CdSi-xTex thin films with O<x<0.3 were prepared on glass substrates by the annealing of CdS:In thin films produced by the spray pyrolysis technique. The annealing was performed in nitrogen atmosphere at 400 --,C in the presence of Te vapor. The compositions of the films were determined by energy dispersive X-ray detection (EDAX) measurements. Scanning electron microscopy (SEM) was used to investigate the morphology of the films. The transmittance of the films was measured at room temperature in the wavelength range 400-1100 nm and used to produce the absorbance of the films. The first derivative of the absorbance was used to estimate the optical bandgap energy Eg by using the minima in the first derivative. The relation between the bandgap energy and the fraction x was found to fit with a parabola and bandgaps in the range 2.196: =Eg: =2.480 e V were obtained. Urbach tailing in the bandgap was also investigated.IntroductionPolycrystalline thin film CdS/CdTe solar cells are promising candidates for low cost and high efficiency photovoltaic applications. The fabrication process of these cells involves the deposition of a p-type CdTe absorber layer on top of an n-type CdS one which acts as a window. The efficiency of the solar cell is affected by the method of preparation of both layers [1, 2].Interdiffusion processes taking place at the CdS/CdTe interface have largely been realized to significantly affect the device performance [3] by changing the bandgap of both CdTe and CdS which modifies the spectral response of the solar cell [ 4]. The formation of a mixed crystal or a graded layer causes a reduction in the lattice mismatch at the CdS/CdTe junction [5] which is about 9% [ 6] and then a reduction in the number of interfacial states and recombination centers, thus enhancing the solar cell performance [7, 8]. A complete understanding of the properties of the intermixed layers CdSxTe1-x that usually constitutes the interfacial region in the CdS/CdTe solar cell is essential. According to our knowledge, a lot of research was devoted to the investigation of the diffusion of S into CdTe [3-5, 9]; but little on the direct investigation of the diffusion of Te into CdS [6]."

Jan 1, 2011

By James Norman, E. W. Gieseke

SPODUMENE is a lithium-bearing pyroxene, and is an important source of lithium compounds. Because of its high alumina and lithia content. it might be a desirable constituent of glass batches. The use of spodumene in ceramics will undoubtedly increase, as it has been shown that a mixture of the proper proportions of this mineral with soda feldspar and potash feldspar has a much lower maturing temperature upon firing than has any one of the three components.1 The mineral spodumene seldom occurs as pure mineral, but ordinarily with feldspars, mica and quartz. All spodumene-bearing rocks tested contained these minerals as gangue. Small amounts of iron and manganese oxides also were present, usually as stains on the silicate grains. Mica associated with the spodumene carried a considerable amount of lithia. This was discovered in flotation tailings, which, although virtually free of spodumene grains when examined microscopically, showed 0.4 to 0.5 per cent Li20 on chemical analysis. The lithia content of micas picked from the North Carolina spodumene rock was variable. Some samples contained little lithia, others more than 3 per cent. In 1938, under the supervision of Oliver C. Ralston, [t] the Bureau of Mines, in cooperation with the Tennessee Mineral Products Corporation, undertook to study the beneficiation of North Carolina spodumene by froth flotation. The Bureau had previously published investigations on the beneficiation of spodumene.2, 3 The methods described in the second publication3 did not give good results with badly weathered spodumene rock, so that more thorough investigation of the subject was warranted. STUDY OF METHOD OF FLOTATION SEPARATION Most of the work on concentration of spodumene was done with rock from near King&apos;s Mountain, North Carolina. Rock from two

Jan 1, 1940

By Leroy Gardner

EVERY reader of this paper is well aware of the fact that the prolonged inhalation of large amounts of free silica dust results in fibrosis of the lungs, and that other inorganic dusts, except those of asbestos and the mineral poisons, are thought to be relatively harmless. But probably few have had opportunity to visualize the effects of silica, asbestos and other minerals upon living tissues. The ideal demonstration would be based upon sections of lungs from human beings that had inhaled com-parable concentrations of different dusts for a unit period of time. Such material is generally difficult to obtain and in some instances is of ques-tionable value because the subject has been exposed to more than one kind of dust. A demonstration could be prepared from the lungs of animals. However, so many months or even years are required to com-plete the exposure to each kind of dust that enough material has not been accumulated. For a general survey of the action of different types of dust, I am therefore compelled to use the tissues of animals that have been injected with suspensions of dust particles. The injection method offers certain advantages. The quantity, the particle size and the state of dispersion can be controlled with sufficient accuracy so that the tissue responses to different minerals can be accu-rately compared. The method insures contact between the tissues and the mineral particles; protective mechanisms, which may prevent the inhalation of certain types of foreign body, never come into play. If the pathway of injection be one that minimizes nonspecific injury, the tissue responses may simulate those produced by inhalation but they develop somewhat more rapidly. It should always be remembered that injection methods merely demonstrate the capacity of various kinds of minerals to provoke reaction in the tissues; whether the same substances are inhaled from atmospheric suspension and accumulate in the lungs in dangerous quantities can be demonstrated only by inhalation.

Jan 1, 1938