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By R. E. de Barrio, M. E. Lanfranchini, R. O. Etcheverry

"The El Abuelo Ca-Fe-magnetite skarn and related hydrothermal quartz veins are located at Cerro Pepita Hill, in southwestern Chubut province of southern Argentina, 1700 km southwest of Buenos Aires. These deposits are developed in a continental magmatic arc environment linked to the Andean orogeny. Iron skarn mineralization is mainly hosted by an Upper Jurassic to Early Cretaceous sedimentary sequence interbedded with Upper Jurassic basaltic andesite, and is spatially associated with Early Cretaceous calc-alkaline dikes. Ore grades vary between 40 and 63 wt.% Fe. In addition, anomalous metal contents (>10 000 ppm Cu and up to 81 g/t Ag) are present in the hydrothermal quartz veins.At least three paragenetic mineral assemblages have been identified in the El Abuelo exoskarn: (1) amphibole > epidote ± chlorite ± quartz, formed by isochemical contact metamorphism; (2) Fe-clinopyroxene ± Ca-garnet, formed during prograde metasomatic anhydrous exoskarn formation; and (3) actinolite ± epidote ± chlorite ± quartz ± magnetite > titanite, resulting from hydrous retrograde alteration of exoskarn. Endoskarn alteration involved an early Mg-Fe-clinopyroxene ± Fe-garnet assemblage followed by retrograde actinolite replacement of pyroxene. Lower temperature hydrothermal alteration related to quartz veins was superimposed on the skarn assemblages, showing an innermost sericite ± adularia ± pyrite ± chalcopyrite assemblage and an external propylitic halo.Some metallogenic characteristics of the mineralization and the geological setting resemble those in several iron oxide copper-gold deposits elsewhere in the world."

Jan 1, 2007

By P. A. Olubambi

The leaching of zinc and copper from Nigerian bulk sulphide ore with sulphuric acid in the presence of hydrogen peroxide was studied. The aim of the study was to investigate the effectiveness of hydrogen peroxide as an oxidant for the sulphuric acid leaching of zinc and copper from a complex sulphide ore. Distribution of elementals within the various particle sizes was initially determined by ICP-OES and XRF to provide a basis for explaining the dissolution process. The effects of concentration of hydrogen peroxide, particle size, stirring speed, and leaching time at a constant temperature of 298K were studied. There were variations in elemental and mineralogical composition within the different sizes. The concentrations of zinc and copper reduced as particle size decreased while silica, sulphur, iron and lead contents increased. Dissolution results showed that the leaching rate of copper was lower than that of zinc. The highest recoveries of zinc and copper were obtained at a leaching time of 180 minutes, stirring speed of160 rpm, particle size of 75 µm and a concentration of 1M H2SO4/1MH2O2. It was observed that the leaching rate of zinc and copper increased with increasing hydrogen peroxide concentration. Increased stirring speed had a negative leaching effect as it promotes hydrogen peroxide decomposition. Keywords: Nigerian sulphide ore, zinc, copper, hydrometallurgy, sulphuric acid, hydrogen peroxide.

Jan 1, 2006

By R. Altindag

The rock brittleness is one of the most important rock properties that affect the drill-ability of rocks. It is supposed that the increase in rock brittleness causes the increase in penetration rate. The drill-ability of rocks depends on many factors. These factors can be separated as two parts depending on a machine, bit type, rotational speed, thrust, blow frequency, flushing, and rock properties, brittleness, compressive strength, structure, hardness, etc. In this paper, the relationship between brittleness and drill-ability index, which is used in the prediction analysis of the penetration rate of rotary blast hole drills, were examined using regression analysis. It is also seen that significant correlations exist between brittleness and the drill-ability index.

Jan 1, 2002

By S G. Keyte

Gravity methods of recovering alluvial gold are not very efficient at particle sizes below about 0.l mm. Whereas such gold may not have been economic to recover in the past, the same may not be true today. Centrifugal concentrators, like the Knudsen and Knelson bowls, are showing promise after an inauspicious start, at least in New Zealand. The large proportion of heavy mineral in many auriferous beach sands and the natural hydrophobicity of fine gold should make flotation an attractive contender for its recovery. The conventional mechanical flotation cell is effective, but roughing, scavenging and cleaning are necessary to achieve both high recovery and low mass Yield. More problematic is the difficulty of maintaining coarse and dense sands in suspension. The air sparged hydrocyclone is effective at recovering fine gold from a fine Colarado River sand, but is not effective for the coarse and dense beach sands of New Zealand. The flotation column shows much promise for these sands, when recoveries of over 80 per cent and mass yields of less than one per cent can be achieved in a single pass. The froth separator of the USSR and flash flotation could also be worthy contenders. It is felt that flotation could be limited to naturally and artificially de-slimed concentrates.

Jan 1, 1990

By E. R. Maize

[In %-port of Invcstiptionn 7452 ,g dcniing with roof ~wet,ent in the Cmcibla r~ine, rof&apos;erence .,as m.da to the f~ct tiwt timker decny war, bsing studied at tho tine of writing. Thic napor, written a3er completion of that ~tudy, describ~s t1l.e ~mrl&apos;: and sunlharizea the fiats obtained. Ifhen tlle stu* oi roof novement bras be,- at Cxcible tw igeas \%.ere a6-r;incsd. on decay of tiriber Q: scne of :he olficialr;: (I.) 9:la.t timber decay v:as unustmlly rapid in ,tho Ciuoiblc mins, ,m?. ((2) that timber coated with rock ri..~st deixiyad morrl mpirlly thnn those %hat vsrc not so coated. Thsx ::ore no records by which tkeso &apos;iaeas could &apos;L;e tertcc?, ard it cnpsarefi vise to make a limite6 in- vo3tiption, p~.rticu!.ai.ly of +.he effect of roc!< dusting on decny, as rock ductirg is nn importnnt mer-ns of ~rc-,rcnt?;~g cad-dust eql-osions. ]

Jan 1, 1941

By J. Matos e Silva

The paper refers five examples of executed diaphragm walls with one to five levels of anchorages. For each example a comparison is made between the results of the design using the traditional criteria and the Eurocode 7 recommendations. A comparison is also made with the behaviour of the diaphragm walls during the construction phase. From the referred examples the author presents his conclusions.

Jan 1, 2002

By J. P. Morris

"INTRODUCTION In the investigation being conducted by the Bureau of Mines concerning the production and utilization of sponge iron, it soon became evident that more information was needed regarding methods for determining the degree of reduction attained in the manufacturing process. Sponge irons made by different processes vary in physical characteristics and chemical composition, and a method of analysis that is suitable for one type is not necessarily applicable to all others. For example, the hydrogen-evolution method, which measures the volume of hydrogen evolved upon treating the sample with acid, accurately determines the oxygen content of some types of sponge iron. However, when the sponge iron contains combined carbon, hydrocarbon gases are also-evolved and large errors may result. Probably no single method will give accurate results in all instances, and for this reason it is desirable to have several reliable procedures available and to know the limitations of each.For measuring the degree of reduction, determination of either metallic iron or oxygen should suffice, although for practical application of sponge iron to the production of steel the oxygen content is more significant. After consideration of proposed methods of analysis in regard to their suitability for routine use and the probable influence of other substances, four procedures were chosen for investigation:(1) Mercuric chloride method.(2) Copper sulfate method.(3) Hydrogen-reduction method.(4) Hydrogen-evolution methods."

Sep 1, 1945

By W. C. Peters, M. W. Pullen, C. A. Bays

During the past three and a half years considerable improvement in the techniques of solution extraction of salt has been made by the use of wells which are cross-connected by hydraulic fracture at the base of the salt. Fracture is initiated by the application of hydraulic pressure. Underreaming and perforating techniques are used to control initiation. The fracture is then extended by continuous pumping until a pressure communication is obtained. Pressure communication is followed by washing-through to obtain a low-pressure connection. Well construction using non-shrinking cements that will bond with the salt and with associated strata is essential to the process. The connecting procedure described permits solution to attack the salt deposit from its base upward, thereby permitting greater recovery, fewer well repairs, better saturation of brine, and overall economy of development and operation. The fracture method of cross-connection requires special pumping of the fluid and is limited by present experience to initial well spacings up to about 1200 feet. The method has been used in bedded salts and is applicable for wells in salt domes. Since spring of 1956, new developnents in salt extraction wells have followed procedures substantially different from those in prior use. Although multiple well systems, connected either by the natural consequence of the solution process or by undercutting under protective pads, have been used previously, the past three and a half years have brought about new designs and new operation procedures based on cross-connection of the wells using hydraulic fracture. To date these techniques have been applied largely in the bedded salt deposits of Michigan, Ontario, Ohio, West Virginia, and New York. To the writers&apos; knowledge they have not been used in salt dome wells. The methods have not yet been in use for a sufficient period to permit any statistical comparison with the older methods. It is evident from experience to date that the methods result in higher recoveries, lower capital and operating costs, better saturation of produced brine, reduced well maintenance and repair, and in considerably fewer production units to insure

Jan 1, 1961

By A. G. Pasamehmetoglu, N. Celebi, K. Erarslan

A deposit evaluation system has been developed for a proposed new mine in the basin around Collolar in Turkey. It includes compositing, gridding and reserve estimation facilities and takes account of the economic value of the pit and the pit bottom elevation

Sep 1, 1991

By C. Musingwini

In the past ten to fifteen years, many organizations have applied business process re-engineering (BPR) to significantly improve their business competitiveness or stave off closures. The mining industry in Southern Africa is no exception and documented examples can be drawn from South Africa. Although the concept is superficially simple, its application has been marked by a high failure rate of about 70 per cent because it has been generally misunderstood. Shabanie mine, a chrysotile asbestos fibre producer in Zimbabwe took cognisance of this fact by cautiously embarking on a modular BPR programme in October of 2002. A year was used as a complete cycle or module for re-evaluation of the programme. Shabanie mine adopted BPR as part of management efforts to remain competitive amid serious threats to operational viability. These threats included hyper-inflation driven rising production costs, a declining world asbestos market and a possibility that Russia could take over the shrinking world asbestos market by dumping low-priced asbestos fibre. The only competitive advantage that the mine had was the high quality of its long-fibre chrysotile asbestos. The major BPR thrust was therefore to redesign processes for improved productivity and ultimately achieve a lower cost per ton of final asbestos fibre product. In addition, corporate culture change and cost-saving were also factored into the programme. This paper discusses the implementation experience of the BPR programme at the mine. The main BPR beneficial highlights are improved productivity, sizeable cost-savings, positive corporate culture change and identification of secondary projects. One of the lessons learnt from this programme is that mining companies will have to deal with the HIV/AIDS pandemic if they are to sustain high levels of productivity into the future.

Jan 1, 2005

By I. Liebman

A Bureau of Mines study is in progress to determine the effectiveness of passive water barriers in suppressing coal-dust explosions. A 2.9-ft3-capacity water-filled plastic tub was found effective in suppressing dust explosions propagating at speeds of 250 to over 1,000 ft/sec. Work directed at determining the limitations of water barriers showed that the passive water barrier technique is also feasible for the suppression of weak dust explosions propagating at speeds of 100 to 250 ft/sec. For relatively slow accelerating flames, dynamic wind forces appear to be the important quantity governing fragmentation of the plastic tub and subsequent water release and dispersion, whereas dynamic impulse appears to be the significant quantity for rapidly accelerating flames. The acoustic approximation (relation between static pressure and flame or wind speed) is shown to be valid in a long single mine entry. This relationship appears to be useful in predicting the regions within a long single entry where passive water barriers are effective in quenching a dust explosion.

Jan 1, 1974

By F. S. Crawford

"After many years of safety activity in the United States in one form or another it becomes increasingly evident to those in contact with safety work that to achieve continuous good results in accident prevention there must be an aggressive organization behind the safety movement at each mine with fairly definite plan and policy. A study of the methods used by various companies and the results they have attained will be of value to the common cause of safety promotion.A study has been made of the safety records of the Menominee iron range in the Lake Superior district, and of data from the county mine inspector's report. Several companies on this iron range that have attained a certain measure of success in their work of accident prevention have given data, and a summary of their safety methods is presented.The Menominee iron range of Michigan lies in the southern portion of the upper peninsula of Michigan, bordering on Wisconsin. It consists of two main. divisions--the West Menominee Range, situated in Iron County in the vicinity of Iron River and Crystal Palls, and the East Menominee range situated in Dickinson County in the neighborhood or iron Mountain, Mich. The mines about Iron River and Crystal Falls are peculiarly subject to fires in a carbonaceous, sulphur-bearing black slate which appears in the footwall. This gives considerable trouble because fires in this material start from spontaneous heating. The methods of mining are top slicing and open stoping, working on benches along the sides of the stopes. The character of the ground varies from medium Soft ore to relatively hard ore which permits open stoping. Approximately one-third of the operating mines are equipped with a fan for main mechanical ventilation. The remainder are ventilated by natural draft. The East Menominee range is the older, top slicing having been used there for a number of years, and the timber mats have boon well developed. In common with all districts, some companies pay more attention to safety than others, although, those which do riot have the best records do pay some attention to safety.During the past three years the annual production per man employed has remained about constant, but in many mines a general decrease is shown in the accident record. The variation in the results attained can be ascribed mainly to the earnestness with which accident-prevention work is pursued, essentially regardless of the method of mining used. This is shown to be generally true, because the record indicates a steady decrease in one mine with an active safety department, while in adjoining mines with the same kind of ground and method of mining but where not such intensive attention has been paid to safety work, the accident record is high."

Oct 1, 1931

By William A. Stickney

The zirconium-hafnium separation plant at Albany, Oreg., was the result of a chain of events that started with studies by A. R. Kaufmann at the Massachusetts Institute of Technology. Variations in the listed neutron-absorption cross-section of zirconium caused him to suspect a misprint. As a result of these discrepancies and following his suggestions, Oak Ridge scientists made studies establishing a value of 0.4 barn or lower. This meant that the potential of zirconium for reactor application was greatly enhanced. Since hafnium is invariably associated with zirconium and has a high neutron cross-section, it was necessary that an efficient hafnium-separation method be developed before the superiority of zirconium as a structural material in nuclear reactors could be realized. The Albany plant was built and operated for the Atomic Energy Commission (AEC) under Letter Agreement AT-(11-1) -140, patterned after a plant operated by the Carbide and Carbon Chemicals Corp. at Oak Ridge, Tenn. Construction was begun in April 1951. Hafnium was to be extracted preferentially as hafnium thiocyanate from an aqueous mixture of zirconyl and hafnyl chlorides in hexone (methyl isobutyl ketone) by a liquid-liquid countercurrent system.

Jan 1, 1959

By E. L. Garton

Michigan is becoming one of the important oil-producing States of the country. The amount of crude oil produced within its boundaries has increased from only 4,000 barrels in 19253/ to nearly 16 million barrels in 19935.4/ The Bureau of Mines method of crude-oil analysis and classification-indicates that the oils from the several producing fields are predominantly paraffin-intermediate-base, wax-bearing crudes. In general, they will yield 25 to 35 percent of highly paraffinic gasoline and about the t- me amount of kerosene and gas-oil combined, 7.2 to 15 percent of lubricating oil stock, and 20 percent of residuum with a carbon residue or about 6 to 7 percent. In addition, there appears to be some correlation between certain properties of the crude oils and both the geographical location and geological structure of the oil-producing areas within the State. These general conclusions are based on the analytical data presented in this report, which is one of a series of papers that record the general characteristics of crude oil from the many producing fields of the United States. This report discusses briefly the oil fields of Michigan and the characteristics of the crude oils produced from them. The analyses of 15 samples are given. These samples were obtained from 13 fields in 9 counties in the lower peninsula and represent crude oils produced from the Berea sandstone, Upper Traverse and Traverse limestones, and the

Jan 1, 1937

By A. C. Fieldner

"Gas hazards may be divided into two principal classes- namely (1) inflammation and explosions; (2) asphyxiation and poisoning. Inflammation and explosion are prevented first by adequate ventilation so that gas sufficient to propagate flame or explosion can not accumulate, and second, by avoiding sources of ignition such as open lights, flames, sparks, electrical arcs, short circuits, or sparks. Ventilation is also the best preventive measure against asphyxiation and poisoning from toxic gases. When men must enter unventilated or poorly ventilated places containing poisonous or asphyxiating gases, suitable gas masks, hose masks, or oxygen breathing apparatus should be worn. As a rule, loss of life and property from gas hazards is due to ignorance of the properties and hazards of various gases commonly used, and consequently a failure to use proper measures for eliminating and meeting these dangers. It is the purpose of this paper to describe briefly the common gases and vapors with respect to the hazards involved in their use and to discuss the necessary precautions and methods for avoiding these dangersLight, heat, and power are prime essentials of our modern industrial civilization. The combustible gases and vapors used for the production of these necessary elements of our existence comprise the largest and most common group of domestic and industrial gas hazards. Almost every individual in his daily life subject to possible danger from asphyxiation, fire, or explosion due to one or more of these gases. For evidence one need only refer to the daily newspaper where headlines such as the following are frequently seen; ""Family asphyxiated by carbon monoxide from gas heater;"" ""Schoolhouse wrecked by gas explosion in basement;"" ""Man killed by automobile exhaust fumes in his garage;"" ""Fireman overcome by smoke fumes in basement ""Woman"".""Boman severely burned by accidental ignition of gasoline used in cleaning gloves;"" and 'in recent Years we often see ""Building wrecked by explosion of still in residential district.""It will be noted that these accidents are due to inflammation, explosion, or asphyxiation. Any combustible gas or vapor, when mixed, with air or oxygen within certain limiting proportions, will explode on ignition. The violence of the explosion varies with respective proportions of air and gas, and with the degree of confinement of the mixture. For example: Mixtures of natural gas and air containing between 4.5 and 12 per cent natural gas will explode, or propagate flame throughout the mixture without the continual presence of the source of ignition that started the inflammation. The table following gives the explosive limits of the common combustible gases and air:"

Jun 1, 1926

By P. Jurovcik, D. Yantek, D. Ingram

The National Institute for Occupational Safety and Health (NIOSH) identified hearing loss as the most common job-related disease in the United States in its 1996 National Occupational Research Agenda. Previous studies by NIOSH have shown operators of surface drill rigs without cabs are commonly exposed to A-weighted sound levels exceeding 90 dB. During hammer-drilling, A-weighted sound levels exceeding 100 dB were recorded at the operator station. NIOSH collaborated with a local drilling company to design and install a partial cab between the operator and the drill steel in an effort to reduce the sound level at the operator station. Sound level measurements in the field show the partial cab reduces the A-weighted sound level by 5-9 dB at the operator’s left ear and 2-5 dB at the operator’s right ear while hammer-drilling. This paper will briefly discuss the preliminary design of a cab and the testing of materials for construction of the prototype. Explanation of the ideas behind the prototype design and fabrication will be covered. Finally, the field test method and results will be discussed in detail.

Jan 1, 2007

By Ernst M. Cohn

The demonstrations of the "Silent Sentry" by Union Carbide Corp. in 1957 and of a special tractor-plow by Allis-Chalmers in 1959 ushered in the technology era of fuel cells. The idea for direct conversion of chemical to electrical energy, first published in 1801 by Davy in England and Ritter in Germany, has been kept alive by a few people through 150 years: Grove built the first hydrogen-oxygen fuel cell in 1839; Mond and Langer made electrolyte contributions around 1890 that are still used today; Baur worked on coal-based cells from 1900; Bacon started his work in the &apos;30&apos;s, which resulted in the first multi-kilowatt unit in the &apos;50&apos;s; Davtyan studied molten-salt electrolytes in the &apos;40&apos;s, followed by Ketelaar in the &apos;50&apos;s; and Justi developed highly active electrodes in the &apos;50&apos;s, to name only some of the pioneers. Despite the tremendous increase in research and development of fuel cells, these direct energy converters are still in their infancy. They will find their functional application in space, where power density must be maximized and product water utilized. These early systems will provide valuable experience in system engineering and reliability.

Jan 9, 1964

By Charles W. Daugherty, James P. Gould, Kenneth R. Ware

INTRODUCTION As illustrated in Figure 1, the Washington Metropolitan Area Transit Authority&apos;s (WMATA) rapid transit system (METRO) ultimately will comprise 100 miles of line divided among 10 routes. At this time about 46 per cent of the system is under construction or in operation. Planning and design of an additional 38 per cent is at an advanced stage. Of the 84 miles under development or construction, about 10.4 miles consist of soft ground tunnels, and another 1600 feet of mixed face. This paper describes most of the factors considered by designers in setting grades for such tunnels. It is hoped the paper will be a useful guide to planners and engineers in developing similar transit systems. The problems faced in Washington, including those related to geology, are not so unique that the solutions cannot be applied to other systems. The paper also may be of interest to contractors who have not perceived the logic behind the selection of a particular vertical alignment. An attempt is made to explain the background constraints that make most tunnel alignments a compromise among competing alternatives. Readers might assume that the choice of alignments is largely controlled by geological conditions. In fact this is merely one of many factors to be considered.

Jan 1, 1976

By Robert B. Worthington

This investigation was undertaken to develop a more efficient copper smelting practice that would help meet the increasingly stringent antipollution standards. Continuous smelting to copper and a 0.8-to 5-percent copper slag using pure oxygen has been demonstrated for several hours at a time in a unique double furnace, which was devised to overcome the heat losses inherent in a laboratory furnace. The use of pure oxygen to effect the smelting and conversion of copper sulfide concentrate in a single unit to produce blister copper and a very high S02 concentration provides a much reduced gas volume for more economical and thorough sulfur recovery. Although the process was successfully demonstrated for several hours at a time, extended test work using longer runs will be required to balance the system and to obtain test data for adequately demonstrating its technical feasibility.

Jan 1, 1973

By A. Korchevisky

Environmental self-monitoring is one of the advanced approaches for industrial sustainability programs. Organization for Economy Cooperation and Development (OECD) defines self-monitoring as ?the system of organizational and technical measures put in place and financed by [the] regulated subject? in order to ensure their compliance with regulatory requirements?1. Self-monitoring is beneficial for industrial operators, communities, and governments. Industrial companies use self-monitoring as a central element of their compliance management that allows them to fulfill their duties, obligations, and to avoid citations. When industries control their emissions and ensure workers are not exposed above the regulated limits, communities are better. It is impossible for an EPA, OSHA, or MSHA inspectors to be close to every emission source or workplace full-time. It is much more effective for industries to self-monitor, under due supervision. Occupational conditions are a very important part of industry and health and safety self-monitoring should be highly prioritized. In this paper we will research the regulatory basis and best practice of occupational self-monitoring. We will show that not only is self-monitoring a vital element of an occupational health & safety management system, but that you need a management system for affective monitoring.

Jan 1, 2012