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By B. M. Bird

ONE of the problems studied by the U. S. Bureau of Mines in cooperation with the University of Washington has been the re-treatment of table middlings. Hydraulic classification has given the best results. Instead of using the classifier to prepare the feed to the tables, as has been the practise for many years in ore dressing, it is used to separate part of a middling product that cannot be re-treated successfully on the table. Middlings are desirable in a table plant because the separation according to specific gravity is incomplete; that is, in the products of the table there is always an overlapping of free particles of coal and refuse that can be distinguished with heavy liquids such as are used in the float-and-sink test. The causes of this overlapping may be divided into two groups, those outside the table separation itself and those inherent in the table separation. The first of these groups includes, among other causes, the following: (1) poor adjustments of the table, (2) overloading or underloading the table, (3) irregularities in the quantity and quality of the feed, (4) irregularities in the power and water supply, and (5) a vertical danc-ing motion of the table deck due to weak foundations. These causes of overlapping are largely unnecessary in a properly designed and constructed plant; but whenever they are present they materially affect the character of the middling product, and hence the problem of re-treatment. The other group includes three additional causes: (6) small differences in specific gravity between coal and impurities, (7) a size-specific-gravity relationship of the coal and refuse particles in the table feed such that the sizing action of the table opposes the separation according to the specific gravity, and (8) shapes of particles that prevent a separation. The sixth, small differences in specific gravity, may be a very important reason for an incomplete separation. The change in specific gravity from coal to shale is always gradual and the designation of one part as coal and another part as refuse is arbitrary. If some specific gravity, such as 1.45, is chosen as the dividing point between washed coal and refuse,

Jan 1, 1928

By Nickol Estrada, Jean Bueno, César Gallegos

El presente proyecto consiste en realizar la Geometalurgia en el yacimiento tipo VMS de Cerro Lindo con el fin de generar un impacto en la producción maximizando el valor operacional. Para ello fue necesario hacer una evaluación y análisis dentro y fuera de la Caja (Yacimiento VMS) con la finalidad de poder identificar y caracterizar los dominios geológicos nuevos y existentes, obteniendo como resultado los parámetros geometalúrgicos que nos ayudarán a buscar la viabilidad del proceso de extracción y tratamiento del mineral.

Sep 29, 2023

By T. Crivits, I. Bellemans, K. Verbeken

In the metallurgical industry, furnace cooling is often employed to enhance furnace lifetime. Hence, the pyrometallurgical phase comes in close contact with a non-air coolant. The proximity of the pyrometallurgical phases to the coolants may lead to dangerous situations. In case of a breach of the cooling circuit, the contact between a hot and a cold liquid may cause a vapour explosion. The outcome of this vapour explosion includes a pressure wave which could result in damage to the furnace, bodily injuries or even casualties. To prevent such dramatic events, the origin of vapour explosions is currently being studied in more detail. For this purpose, OpenFOAM was used to perform Computational Fluid Dynamics (CFD) simulations. In a first step, simulations were run to get a better idea of the influence of the compressibility on the simulations. The obtained results help in getting a better insight on the need of computational power, and possible numerical errors using compressible or incompressible solvers in future simulations. In a second step, systems without vapour explosions were simulated and compared to experimental results with mercury and aluminum. INTRODUCTION Humanity started using metals for tools around the Chalcolitic (~7400 cal BC), when copper was melted in small furnaces (Radivojevic, Rehren, Farid, Pernicka, & Camurcouglu, 2017). Nowadays, metallurgy has grown into a major industry and it has become impossible to imagine society without metals. In the pyrometallurgical industry, coolants (low temperature liquids, for example water) and pyrometallurgical phases (high temperature liquids, such as slags, mattes and alloys) are typically present in close proximity of each other. The interaction between these two phases can have catastrophic consequences (Tveit et al., 2008; Ferguson & Zsamboky, 2017). A vapour explosion may occur as the consequence of the rapid evaporation and expansion of the coolant. Whereas the volume of a gas increases linearly with the temperature (approximately a factor four by heating from 100°C to 1300°C), a simple calculation of the ratio of the two specific volumes shows that evaporation causes the volume of water to increase by a factor of 1700 at 100°C and ambient pressure (Table 1 and equation (1)), a number that was also found in literature (George, Nexhip, George-Kennedy, Foster, & Walton, 2006). The volume change occurs so fast that it resembles an explosion, hence the name vapour explosion. Such an explosion at industrial scale can cause economical losses, bodily injuries or even fatalities.

Jan 1, 2019

By R. Stefanko

In this report, the use of Penn State Ventilation Simulator (PSU/MVS) for planning and evaluating new coal mine ventilation systems is demonstrated. The simulator's application to evaluate the ventilation system of a coal mine currently under development is discussed. The ventilation system is evaluated for representing development of the mine at the end of 12, 24 and 36 months after mining has begun. The report describes the necessary steps of data input preparation, ventilation network development, analysis of results, modifications to the network, and methods to expand the computer program for networks larger than 550 branches.

Jan 1, 1977

By Graham Davis

The future of the world's minerals industries is often painted as bleak. Peter Drucker has repeatedly proposed that the demand for minerals has become "uncoupled" from world economic growth.' This implies that, while mineral demand was in the past linked to the growing demand for and consumption of goods and services, further world development will not require substantial mineral inputs. Lester Thurow noted that for these reasons the US minerals industry is diminishing in scale and economic importance.2 There is some documented evidence of such uncoupling, and the demand for minerals may indeed diminish in the future. But such announcements are, to this point, no more than speculation. For instance, is it not just as likely that renewed environmental concerns will cause increased demand for the relatively innocuous environmental properties of metals, replacing plastics? And even if the prophesied demand decreases do occur, a sufficient fall in metal prices due to technological advances could increase the quantity of minerals demanded above current levels, in spite of leftward shifting demand curves. Thus, worldwide mineral production activity may increase or decrease in the future and no one can say whether more or fewer of the earth's citizens will become involved in the extraction and processing of minerals.

Jan 1, 1994

By V. A. Ignatkina, V. A. Bocharov, T. I. Yushina, I. M. Petrov, A. A. Kayumov

"The purpose of this research was aimed at increasing recovery of metals from rebellious sulfide polymetallic ores of nonferrous and rare metal deposits. The ores under consideration have common processing features, including textural and structural complex characteristics, irregularity of impregnation and wide range of grain size, up to nanoparticle size, variable complex mineral composition, low content of precious metals etc. This all predetermines the need for advanced processing schemes with deep selective liberation and separation of minerals with intercycle release into rough concentrate and fractional products with the use of multi-stage cycles of individual dressing, based on an optimum combination of various integrated beneficiation and hydrometallurgical processes. The application of existing standard processes does not enable the production of high-grade selective concentrates without reducing the recovery rate due to incomplete separation of fine mineral intergrowths and overgrinding of brittle ore and rock minerals.The combined beneficiation processes for such type of resources, aimed at increasing recovery of nonferrous, rare, and precious metals are based on flotation methods in combination with gravity concentration to produce rich rough collective or selective concentrates, comprising readily floatable mineral fractions. At the same time, hardly recoverable and non-separable mineral associations are released into separate concentrated products for following dressing by individual processes. The proposed combined process provides for successive selective liberation of minerals with release of rich readily recoverable mineral fractions at the preparation and ore beneficiation stages. The hardly recoverable mineral associations shall be released in subsequent operations with the use of dressing, based on a combination of beneficiation and pyro- and hydrometallurgical methods."

Jan 1, 2018

By D Schwab, R M. Tosdal

The Quesnell-Stikine arcs, in the Canadian Cordillera, are host to Triassic and Early Jurassic alkalic porphyry Cu-Au and calc-alkalic porphyry Cu-(Mo-Au) deposits formed outboard of ancestralNorth America in island-arc tectonic settings (McMillan, 1991). The majority of the alkalic porphyry Cu-Au deposits are products of a discrete magmatic event at the end of the Triassic, with a second and smaller event in the Early Jurassic (Mortensen, Ghosh and Ferri, 1995). Of the Triassic complexes, the Galore Creek alkalic intrusive suite is one of the largest and most silica-undersaturated intrusive complexes, and host to the most significant undeveloped alkalic porphyry Cu-Au resource in North America (Lang, Stanley and Thompson, 1995). Because of the common presence of feldspathoidal-bearing rocks in the complex (Enns et al, 1995), Galore Creek likely represents an end member example of the alkalic porphyry Cu-Au class. The Galore Creek alkalic Cu-Au-Ag porphyry district, located in NW British Columbia (Canada), contains 12 mineralised prospects (Enns et al, 1995; Micko et al, 2007; Schwab et al, in press) with a total measured and indicated resources of 785.7 Mt at 0.52 per cent Cu, 0.29 g/t Au and 4.87 g/t Ag (NovaGold Resources Inc, February, 2008). The Central Zone is the largest and best delineated. Other economically important mineralised centres include the South-West, Bountiful, West Fork and Junction deposits. The South-West Zone, the focus of this contribution, is a Cu-Au-Ag breccia-centred deposit with a measured and indicated resource of 69 Mt grading 0.42 per cent Cu, 0.69 g/t Au, 2.67 g/t Ag. Hosted in brecciated intrusive rocks, the South-West Zone is distinctly younger than the Central Zone and most of the other mineralised centres (Enns et al, 1995; Schwab et al, in press). The South-West Zone therefore preserves the late stages of hydrothermal evolution at Galore Creek. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By Charles Bell

THE Telluride mining district of southwestern Colorado is defined by the 37° 45' and 38° parallels of latitude and 107° 45' and 108° meridians of longitude. Telluride was never a boom camp, but has had a steady growth. In recent years, notwithstanding the business depression of 1920, the business has been the same as in normal years. The first prospector is said to have appeared in 1875, in which year locations on the Smuggler vein were made. Shipments were made in 1877 and 1878, and in 1879 milling the ores was attempted. While the district produced high-grade ores, it did not become important until 1890, when the Rio Grande Southern R. R. was completed from Ridgway to Telluride. The railroad has since been extended to Durango. In the fall of 1896, 400 stamps were in operation, and the annual production was $3,000,000.00, two-thirds of which was gold. The total production from 1875 to 1923 was: Gold $58,274,527; silver 41,830,920 oz., valued at $31,016,893; copper 15,258,866 lb., valued at $2,533,291; lead 166,056,484 lb., valued at $8,324,910; zinc 18,141,182 lb. valued at $1,323,787; or a total production of $101,473,408. All: claims are held in fee. Most of them are 1500 by 300 ft. but claims located within the last few years are 1500 by 600 ft. General supplies are obtained at Telluride, Denver, and Salt Lake. The largest mines are within 6 miles of the town of Telluride. Denver is 422 miles and Salt Lake is 439 miles, by rail, from Telluride. One-half of the distance to Denver and one-sixth of the distance from Telluride to Salt Lake is by narrow-gage railroad. The labor is efficient. The best miners are Italians and Austrians, then Slavs, Greeks, and Mexicans follow in the order mentioned. There are no labor unions. There are no serious mine pumping problems, the drainage being through adits. The Tomboy and Smuggler companies pump water from their reservoirs, the former for, milling and domestic purposes and the latter for milling, power, and domestic purposes.

Jan 2, 1924

After World War I the character of my mining life changed completely. Before then adventure had been almost continuous but after the war there was lots of staying in one place, almost routine, between adventures. This was fortunate, as the life of a mining engineer is a wandering one at best, and it makes being married and raising a family a dubious enterprise. It would have been quite out of the question with the life I led before I got married at the end of the war The new sort of life made the "beaconing of adventure" intermittent. There were often long stays at home between wanderings which was fortunate as it changed the continuity of these memories. I must briefly summarize accounts of the more or less routine periods and concentrate on the occasional exciting episodes between. After a long visit with friends in Berkeley, Dorothy and I left for Arizona and three days at the Grand Canyon that were nearly too much for both of us. One beautiful day we started a short walk down the Bright Angel Trail. It was such a lovely bracing day that we kept on walking and enjoying the views until, just after noon, we reached the Colorado River. We were the only ones in sight so to enjoy the sunshine to the full we both had a good swim in the swiftly flowing river. So far, everything was wonderful. But when we started to climb back up the trail, rising nearly 6000 ft in ten miles we soon found that we had counted too much on our youth and endurance. We had to rest every few hundred feet and it seemed as though we would never reach the top. It was eight o'clock in the evening when we finally staggered into our room and collapsed. On the way to the Canyon I had seen John Greenway and Dr. Ricketts in Santa Barbara and they had little idea what would happen to them or to me. Before resuming his position as general manager of Calumet and Arizona and New Cornelia, Greenway must recover from the effects of the gas he had suffered in the war. Dr. Ricketts

Jan 1, 1976

By H. Y. Yancey, B. M. Bird

One of the problems studied by the U. S. Bureau of Mines in cooperation with the University of Washington has been the re-treatment of table middlings. Hydraulic classification has given the best results. Instead of using the classifier to prepare the feed to the tables, as has been the practice for many years in ore dressing, it is used to separate part of a middling product that cannot be re-treated successfully on the table. Middlings are desirable in a table plant because the separation according to specific gravity is incomplete; that is, in the products of the table there is always an overlapping of free particles of coal and refuse that can be distinguished with heavy liquids such as are used in the float-and-sink test. The causes of this overlapping may be divided into two groups, those outside the table separation itself and those inherent in the table separation. The first of these groups includes, among other causes, the following: (1) poor adjustments of the table, (2) overloading or underloading the table, (3) irregularities in the quantity and quality of the feed, (4) irregularities in the power and water supply, and (5) a vertical dancing motion of the table deck due to weak foundations. These causes of overlapping are largely unnecessary in a properly designed and constructed plant; but whenever they are present they materially affect the character of the middling product, and hence the problem of re-treatment. The other group includes three additional causes: (6) small differences in specific gravity between coal and impurities, (7) a size-specific-gravity relationship of the coal and refuse particles in the table feed such that the sizing action of the table opposes the separation according to the specific gravity, and (8) shapes of particles that prevent a separation. The sixth, small differences in specific gravity, may be a very important reason for an incomplete separation. The change in specific gravity from coal to shale is always gradual and the designation of one part as coal and another part as refuse is arbitrary. If some specific gravity, such as 1.45, is chosen as the dividing point between washed coal and refuse,

Jan 1, 1930

By J. U. Burger

The Elizabeth Bay aeolian deposit in Namibia comprises a sedimentary package of diamondiferous grits that have been deposited, reworked and concentrated to various degrees by dominant southerly winds. Diamond concentration in these deposits is highly variable and often unpredictable. The deposit is marginal from an economic perspective and therefore requires selective mining which in turn requires correct sampling and accurate estimation. Three methods of sampling have been used at Elizabeth Bay for mineral resource estimation: (i) pit samples utilizing an excavator to produce a sample 1 to 3 metres deep with a 10 to 20 m2 footprint, (ii)GB50 grab sampling with a 3.34 m2 footprint and (iii) a BG36 bucket auger drill with a 5 m2 footprint. Pit sampling, being easy to execute, has been the most widely used despite a limited penetration ability and, at times, questionable integrity. The GB50 grab sampling tool was tested at Elizabeth Bay and although it had better penetration ability and sample integrity, it struggled with cemented horizons. No sample optimization was conducted prior to the GB50 grab sampling. The latest phase of sampling was conducted using a BG36 bucket auger drill which is capable of penetrating thick overburden, penetrate cemented horizons and provides an acceptable sample support size. Geostatistical simulation methods were applied to establish the optimum sampling parameters required to estimate a mineral resource at an indicated level of confidence. The results show that a 5 m2 sample support size is adequate and that a 50 m 100 m sample configuration is optimal. Sample data obtained from the three methods confirms that the BG36 bucket auger tool combined with the parameters identified in this exercise produce the best results for diamond resource estimation.

Jan 1, 2009

By R. Steinitz, L. Seigle, R. Resnick

THE rates of growth of the carbide phases MC and M2C in the Ta-C and Cb-C systems have been measured at various temperatures and the results used to estimate the rate of carbon diffusion within the inter metallic phases. Sheets of high-purity tantalum (50 ppm Cb, <25 ppm Ti, 10 ppm Fe, 5 ppm Cr, <50 ppm Mo, W, and all other metals, 15-75 ppm O2, 10-30 ppm N2, and 10-30 ppm C) approximately 1/4 by 1/2 by 0.020 in. were heated to temperatures between 1800" and 2700°C in a carbon resistor furnace under an atmosphere of argon plus sufficient methane to maintain an excess of carbon at the sample surface. The thicknesses of the carbide layers, illustrated in Fig. 1, were measured with a filar micrometer and plotted logarithmically as a function of time. Fig. 2 is a typical plot for the TaC phase. The points may be represented within experimental error by lines with slope equal to 1/2; therefore the growth of the layers may be described by the usual expression X = kt1/2, where X is the layer thickness, t is the time, and k is a temperature-dependent constant. From these data and compositions at the phase boundaries, it is possible to estimate values for the diffusion coefficients of carbon in each phase, assuming that layer growth occurs by carbon diffusion alone, and that the dif-fusivity is not a function of composition within each

Jan 1, 1965

By Barry James

"This paper discusses past and current energy use patterns in the mining and manufacturing sectors of the industrial minerals industry. Information is presented on the primary energy input types as purchased by the industry, the quality and form of the energy actually required by the various production processes, and the residual form of this energy, either embodied in the product or rejected in gaseous and liquid waste heat streams. With the continuing concerns about the availability of energy combined with the rapidly increasing cost of energy as a production input, the reduction of energy usage through improved efficiency will undoubtedly be an increasing priority for the industry during the 1980s. Reduced energy consumption through investment to improve energy efficiency appears to be advantageous from both the corporate and national perspectives.IntroductionEnergy, like labour and materials, is one of the basic production input s to the various mining, processing and manufacturing production stages in the industrial minerals industry. Energy costs, as a percentage of total production costs, have been well above the average for industry in Canada, accounting for more than 50 cents out of every dollar in the most extreme cases. Consequently, energy has always been a relatively important management concern in the industrial minerals industry.The energy supply and price situation in Canada and internationally has been changing rapidly since 1973, following a long period characterized by declining real energy prices and an abundance and wide choice of energy supplies. It is generally accepted that energy prices will continue to increase rapidly, and that there will be uncertainties about the long-term continuity of supply of some energy types. In essence, a period of relative stability has been replaced by a period of relative uncertainty. In such a changing situation, a reassessment of the role of energy as a production input is appropriate.The following sections outline some of the effects of the changing energy scene on the industrial minerals industry. These effects are dealt with primarily in terms of energy costs, because, in most circumstances, a change in the cost of energy as a production input is the end result of both energy price and energy supply changes."

Jan 1, 1981

By Alan Hooper, James E. Mischler

Construction began in 1984 for a 5 megawatt hydroelectric power retrofit at the O'Shaughnessy Dam for the City of Columbus, Ohio. The construction necessitated excavation of limestone bedrock up to 27 feet below the normal water level of the river downstream of the dam. Proximity to the river and difficult terrain resulted in an interesting and challenging construction project.

Jan 1, 1986

By Alan Weakly

The Powder River Basin (PRB) of northeastern Wyoming and south-central Montana is the largest strippable reserve of compliant coal (0.6 or less lb of sulfur per million Btu) in the United States. In mining parlance, it is the Mother Lode! Wyoming’s portion of the Basin provides one fifth of the coal produced in the United States annually, and the state has been the nation’s top coal producer for the past six years. Based on 1993 production statistics and estimated strippable compliance coal reserves, Wyoming may remain the nation’s top producer for the next 76 plus years. Past articles on the PRB have focused mainly on production. After living and working in the Basin for the past five years, I have developed an appreciation for the area and its major industry that transcends size and production data. In the fall of 1993, MINING ENGINEERING’s publisher and I decided to present a series of articles that would cover many other aspects of the Basin. Ten topics were outlined, and specific individuals, selected for their knowledge and experience, were asked to contribute articles about their specialties. Although Montana has four large mines producing coal from the PRB, this series of articles will concentrate on the Wyoming portion of the Basin.

Jan 1, 1994

By Oliver Bowles

"A New Mica Company in China A report has been received from the American Consulate at Chungking, China, to the affect that a new company has been organized to operate a mica mine north of Ta-chien-lu, in the province of Ssu-Chuan. The company, which is entirely under Chinese management and control, has a working capital of $10,000. While comparatively new, the mine has been worked before, and apparently with some success. The mica is said to be of good quality. It is claimed that the deposit will supply a limited amount of mica that will cut in pieces a foot square or over, and larger quantities of smaller sizes. The chief difficulty is transportation, for it is reported that a ten days' journey, part of it over mountain trails, will be necessary to transport the mica from the mine to Yachow, the nearest practical waterway. It is probable, therefore, that the output of the mine will be limited.Necessity for Careful Trimming and Grading of MicaA recent report to the Department of Trade and Commerce, Ottawa, Canada, by Acting Trade Commissioner C. G. Venus, London, England, contains information which is of vital interest to mica producers in the United States. It is pointed out that mica exports from Canada to England show a gradual decline dur¬ing recent years, the figures being as follows: 1913- 1,383 cwt: 1914 - 1,225 cwt: 1915 - 1,864 cwt: 1S16 - 879 cwt: 1917 444 cwt: 1918 - 480 cwt. Shipments from India to England, on the other hand, show a steady increase from 40,178 cwt. in 1913 to 66,401 cwt, in 1918."

Jan 1, 1920

By NA NA

Profile of FOSROC, manufacturers and suppliers of products for the mining industry.

Jan 11, 1996

By John H. Hollomon, C. Zener

It is commonly recognized that a given material may be described as ductile or brittle only with reference to the conditions of test. Thus under the usual test conditions quartz is brittle, but under high pressures it is ductile. Salts that are brittle at room temperature become ductile at elevated temperatures. Pitch, brittle with respect to rapid loads, flows at low rates of loading. Pearlitic steel, ductile under the usual conditions of test, may be embrittled under the proper conditions of combined stresses, temperature, and rate of loading. Earlier Investigations A clear analysis of the conditions necessary for plastic flow and for fracture was first given by LudwikI1 who introduced two types of stress, the "flow stress" and the "stress at fracture." These stresses may refer to tensile or to shear stresses, or, in fact, to any type of stress. Ludwik considered these two stresses to be independent of one another, functions of the conditions of test and of the prior history of the material. For the purpose of analysis. both a Flow stress and a stress at fracture can be envisaged as functions of strain over the entire range from zero to infinite strain. Thus, the material is brittle if the stress at fracturc is less than the flow stress and ductile if the reverse is true. According to Ludwik&apos;s analysis, the problem of determining the effects of combined stresses, of temperature and of strain rate upon the behavior of metals reduces to a problem of determining the effect of these variables upon the flow stress and upon the stress at fracture. In the present paper, methods are described for determining the effects of two of these variables, temperature and strain rate, and examples are given of the dependence of tlow stress and stress at fracture, upon these two variables. The effect of combined stresses will be discussed in a succeeding paper. The flow stress may be determined from a load-diameter curve. Load-diameter curves were obtained over a wide range of temperature and over the limited range of strain rates obtainable with the lever-type Riehle machine used. The curves were then converted to an extremely wide range of strain rate by making use of the equivalence of the effects of changes in strain rate and changes in temperature, previously proposed2 and demonstrated3 by the authors. According to this principle of equivalence, strain rate e and temperature T affect the flow stress only through a single parameter-p of the form: p = eeQ/RT 111 In this equation, R is the gas constant (2 cal. per gram mol per deg. C.), and Q is a heat of activation, which varies from material to material, and may depend upon the strain, but not upon the strain rate or the temperature. There is associated with every value of p a flow-stress curve. article of strain rate and of temperature that give the same p have the same flow-stress curve. Therefore, merely by changing the temperature of test, the effect of changing the strain rate may be obtained. Thus, under isothermal conditions, the material will behave the same at

Jan 1, 1944

By C. Zener, John H. Hollomon

It is commonly recognized that a given material may be described as ductile or brittle only with reference to the conditions of test. Thus under the usual test conditions quartz is brittle, but under high pressures it is ductile. Salts that are brittle at room temperature become ductile at elevated temperatures. Pitch, brittle with respect to rapid loads, flows at low rates of loading. Pearlitic steel, ductile under the usual conditions of test, may be embrittled under the proper conditions of combined stresses, temperature, and rate of loading. Earlier Investigations A clear analysis of the conditions necessary for plastic flow and for fracture was first given by LudwikI1 who introduced two types of stress, the "flow stress" and the "stress at fracture." These stresses may refer to tensile or to shear stresses, or, in fact, to any type of stress. Ludwik considered these two stresses to be independent of one another, functions of the conditions of test and of the prior history of the material. For the purpose of analysis. both a Flow stress and a stress at fracture can be envisaged as functions of strain over the entire range from zero to infinite strain. Thus, the material is brittle if the stress at fracturc is less than the flow stress and ductile if the reverse is true. According to Ludwik&apos;s analysis, the problem of determining the effects of combined stresses, of temperature and of strain rate upon the behavior of metals reduces to a problem of determining the effect of these variables upon the flow stress and upon the stress at fracture. In the present paper, methods are described for determining the effects of two of these variables, temperature and strain rate, and examples are given of the dependence of tlow stress and stress at fracture, upon these two variables. The effect of combined stresses will be discussed in a succeeding paper. The flow stress may be determined from a load-diameter curve. Load-diameter curves were obtained over a wide range of temperature and over the limited range of strain rates obtainable with the lever-type Riehle machine used. The curves were then converted to an extremely wide range of strain rate by making use of the equivalence of the effects of changes in strain rate and changes in temperature, previously proposed2 and demonstrated3 by the authors. According to this principle of equivalence, strain rate e and temperature T affect the flow stress only through a single parameter-p of the form: p = eeQ/RT 111 In this equation, R is the gas constant (2 cal. per gram mol per deg. C.), and Q is a heat of activation, which varies from material to material, and may depend upon the strain, but not upon the strain rate or the temperature. There is associated with every value of p a flow-stress curve. article of strain rate and of temperature that give the same p have the same flow-stress curve. Therefore, merely by changing the temperature of test, the effect of changing the strain rate may be obtained. Thus, under isothermal conditions, the material will behave the same at

Jan 1, 1944

By Phillip R. Moyle

Several deposits in the Sheep Hole/Cadiz Wilderness Study Area (WSA) have small identified or potential for undiscovered gold and silver resources. One prospect area is a potential target for molybdenum. Most base and precious metals and one uranium deposit in the study area are of the fissure-filling, contact metamorphic type associated with late stage fluids of the Cretaceous Cadiz Valley batholith. Some evidence suggests limited Tertiary and Quaternary mineralization. Mineral deposits are controlled by faults, shear zones, and joints which strike northwest and dip northeast or southwest. Although undefined, calcium, sodium, lithium, and strontium brines are inferred within the study area. Some potential for oil and gas and geothermal resources is indicated by the interest private industry has shown in the eastern part of the study area. INTRODUCTION The U.S. Bureau of lines and U.S. Geological Survey conducted a mineral survey of the Sheep Hole/Cadiz Wilderness Study Area (p1. 1) which encompasses approximately 205,000 acres (83,000 ha) in south-central San Bernardino County, California. The U.S. Bureau of Mines studied the mineral resources of mines, prospects and mineralized areas; geological, geochemical, and geophysical investigations were conducted by the U.S. Geological Survey.

Jan 1, 1982