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By Yoginder P. Chugh

Elastic and viscoelastic behavior of three rocks-Tennessee sandstone, Barre granite, and Indiana limestone-was studied experimentally under uniaxial tensile stress. Cylindrical specimens of these rocks, about 1.0 in. diam and 2.0 in. long, were subjected to incremental constant stress history under uniaxial tension. The stress was held constant for a period of 40 min at each stress level. During this period, longitudinal and transverse strains on specimens were continuously monitored. The straintime history at each stress level was analyzed for elastic and viscoelastic parameters of a generalized Burger model. The viscoelastic parameters under uniaxial tensile stress were compared with those under uniaxial compressive stress. The experimental setup, experimental procedure, analysis techniques, and more significant results are described. This limited research effort clearly indicates the importance of the mechanical behavior of geologic material under tensile stresses.

Jan 1, 1975

By Gilbert Thiessen

THE purposes of this paper are (1) to show that the mineral matter content of coal is satisfactorily represented by the Parr formula; that is, Mineral matter = 1.08 Ash + 0.55 Total sulfur (2) to compare ash-to-mineral-matter ratios with factors by which ash values must be multiplied in order that dry, factor-times-ash-free values shall equal Parr unit coal values; (3) to examine such ash-correction factors and to compare them with similar factors corresponding to certain simplifications or modifications of the Parr formulas and (4) to show that ash-correction factors used for simplification in calculating approximate unit coal calorific values cannot be. correctly used for the conversion of other determined values in an analysis to the unit coal basis, but that each type of calculation requires separate treatment in simplification.

Jan 1, 1934

By A. E. Beasley, Ike McKinney

Scale is a broad term which includes many types of mineral deposits which have limited solubility in water. These mineral components precipitate when combinations of scale-forming cations and anions exceed their solubility. Scale deposits are tightly bound to each other and to the metal surfaces of a water system. Precipitates that do not readily adhere to each other or to metal surfaces are known as sludges. Sludges are easily removed from a system by flushing. For example, a sludge is formed in the internal treatment of boiler waters with orthophosphates where the calcium is purposely precipitated as hydroxyapatite. Calcium phosphate would have a tendency to adhere to the boiler tubes except for the addition of tannins or lignins. These sludge conditioners maintain the precipitated calcium phosphate as a sludge which can be readily removed by boiler blowdown.

Jan 3, 1973

By W. A. Boyer

Edward Thomas (U.S. Bureau of Mines, Washington, D. C.)—This excellent article on an ingenious and successful installation of wooden rock bolts loses much of its effectiveness through an attempt by the authors to establish the general adaptability of this type of support. Possibly because they have only local experience as a guide, they imply erroneously in the first paragraph that the Bureau of Mines has been opposed to wooden bolting, although later in the article reference is made to a Bureau publication on the subject. In 1947 the Bureau of Mines decided to sponsor experiments in roof bolting in coal mines because the experience of the St. Joseph Lead Co. had indicated that this type of roof support appeared to be a roof-fall accident-prevention measure that might be adopted and also effect economies in operating cost. Justification for this belief has been borne out, particularly in coal mining. This program has been carried out under the following general program: 1—The Roof Control Section of the Bureau of Mines has advocated and initiated underground experiments under controlled conditions with many different ideas related to rock bolting since 1947. In no instance has cooperation in developing an idea been refused, no matter how ridiculous it may have seemed at first glance, if it has been requested by a mining company. 2—The Bureau of Mines has no police powers over the selection of roof-support devices and seeks none. 3—At the request of an operator, the Bureau of Mines will make comparative tests on various types of bolts underground and will submit resultant data for the operator's consideration. 4—Wherever possible, the Bureau publicizes successful installations, so that others may benefit from this experience; however, it is careful not to discriminate between manufacturers of bolts or bolt-installation equipment. Unsuccessful experiments probably should also be publicized, but from a practical standpoint it is usually not feasible. In other words, the role of the Roof Control Section of the Bureau is in line with the original purpose for which the Bureau was first organized: to serve industry through gathering, analyzing, and disseminating factual data. It would seem to be logical that the starting point for any experimentation on roof bolts in coal mines should be the time-proved practice of the

Jan 1, 1955

CHARLES F. WILLIS,* Bisbee, Ariz. (written discussion ?).-There are few mine officials who will not say that there is, great need of vocational schools in mining communities, but the absence of success of so many of these ventures makes them wary about establishing such schools. They have neither the time nor the facilities to study the systems and to analyze the factors that have made certain schools a success and others a failure. In the first place, it is difficult to secure the proper instructors. Educators cannot make the appeal to the workmen, because of their lack of experience, and experienced men who are capable of the appeal are not usually educators, knowing nothing about the presentation of the subject. Then, too, there is ordinarily no objective in a mine school. The workman is not reached by a school that makes him merely a more valuable man to his employer, unless he can participate in the gain. An objective, as promotion or financial gain, would appeal to the man and would make for regular attendance. Usually vocational schools are run like all others-a number of subjects at a time, continued from one day to another. This is impractical for the workman, whose mind cannot work like the mind of a school boy. The school boy is spending most of his time in school work, while the man is doing it as a side issue, and he cannot be expected to pick up tonight's lesson where last night's left off. The workman is accustomed to the idea of completing a job and doing one thing at a time; his mind is trained that way, and for this reason a school that works on the principal that each lesson is a complete job, with no reference to the previous or following lesson, will go a long way toward removing one of the things that has caused many failures. The usual vocational schools .in mining communities are either very elementary, or are run by the engineering staff and, consequently, are too advanced. There is no plan between. It is believed that there is a possibility of a halfway type, but this is a subject that is large enough for a paper by itself and is entirely, too broad to be presented as a discussion.

Jan 6, 1919

By L. F. Rooney

In June 1964 the Indiana Geological Survey discovered gypsum beds more than 10 ft thick in rocks of Devonian age in La Porte County, Ind. Although the extension of the Michigan Basin evaporites into northern Indiana has been recognized for some time, the gypsum beds have been regarded as either too thin or too deep for exploitation. Current Survey research, however, indicates that exploration by industry might find commercial deposits of gypsum less than 50 miles from Chicago. In four cores taken by the Survey within 1 sq mile in La Porte County, the maximum thickness of inter-bedded gypsum and anhydrite is 35.8 ft. Both gypsum and anhydrite beds contain irregular masses of limestone and dolomite that average a few inches in cross section and total about 20% of the rock by weight. The maximum thickness of gypsum in one minable unit verified by core is 12.5 ft, and its purity is 81.3%. Chloride content of the gypsum beds is less than 0.005%. Depth to the gypsum in La Porte County is 330 to 500 ft, about the same depth as the gypsum being mined in Martin County, Ind. In June 1964 the Indiana Geological Survey discovered gypsum deposits of probable commercial thickness near La Porte, Ind. (Fig. 1). This article presents preliminary data on the distribution, thickness, depth and chemical composition of the gypsum, the possible causes of gypsification, and economic considerations of immediate interest to industry. Because of the preliminary nature of the work, only a few geologic relationships concerning the genesis of the deposits will be mentioned. DEFINITIONS The following terms used throughout this article have been restricted to the following definitions: evaporites: anyydrite (CaSO4) or gypsum (CaSO4 . 2H2O). minable evaporites: any evaporite unit which may contain more than 80% evaporites, which is more than 10 ft thick, and which in places may be completely gypsified. PREVIOUS WORK The presence of gypsum and anhydrite in the Devonian rocks of northern Indiana has been recognized for at least 70 years1-4 and can be inferred from a number of reports on the geology of Michigan. For example, in a cross section from southwestern to central Michigan, Ells5 indicated the presence of

Jan 1, 1965

By A. H. Bell

Continued low prices and restricted markets for crude oil discouraged drilling activity in Illinois oil fields during 1933. Only 36 wells were completed in the state, the smallest number since 1904, and of these the majority were scattered wildcat wells, only 10 having been drilled in producing fields (Table 2). Production was curtailed approximately 40 per cent for the first half of the year. During July, August, and the early part of September there was no restriction on production. On Sept. 8, under the "code of fair competition for the petroleum industry," the quota of allowable production for Illinois was fixed at 12,000 bbl. per day. The state's production in 1933 was 9 per cent less than in 1932. What it would have been had there been no curtailment of production and if economic conditions had permitted a normal amount of cleaning out and repairs to wells, it is not possible to estimate, but it would no doubt have been considerably more than the actual figure. No new pools or new producing horizons were discovered in 1933, but the deepening of a Robinson sand well in Crawford County to the McClosky "sand" horizon (St. Genevieve limestone of the Lower Mississippian) resulted in a production of 3 bbl. per day (Fred Patchel, Savilla Shipman No. 5, NE. 1/4, SW. 1/4, sec. 26, T.6N., R.l3W., deepened from 1122 to 1388 ft., to be tested to the McClosky horizon, and, owing to the rapid variations in porosity within short distances, as shown in the Lawrence County field to the south, one test may not be considered as proving or condemning any large area. The average price of Illinois crude oil in 1933, calculated from the posted prices as published in the Oil and Gas Journal and Oil Weekly, was $0.862 per barrel. This compares with a calculated average price of $1.032 in 1932 and 0.852 in 1931. The total value of Illinois crude oil produced in 1933 obtained by multiplying the average price (0.862) by the total production (4,227,000 bbl.) was $3,643,674. Of the 26 wildcat wells drilled in 1933, only one was drilled on known favorable structure. This was the Walmar Oil Company's William Pepple well No. 1, sec. 12, T.4N., R.12W., Hancock County, which tested

Jan 1, 1934

By W. R. Hibbard

The increased strength of a polycrystal-line metallic aggregate compared with that of its individual crystals generally has been associated with complex stress distributions at the grain boundaries resulting from atomic irregularity between grains. This disregistry, together with the necessity for adjacent crystals to deform compatibly regardless of the single crystal crystallo-graphic strain mechanism, complicates this mechanism so as to increase the metal's resistance to deformation. Although Taylor1 has shown from purely mechanical considerations the requirement for at least five active slip systems to absorb the complexities during the homogeneous deformation of polycrystalline face-centered cubic metals, experimental studies by Barrett and Levenson2 indicate that this is feasible only in a qualitative sense because of deviations from homogeneous deformation. Seitz and Read in their review3 state: " Unfortunately . . . present knowledge of the grain boundary influence is not sufficient to complement the work in single crystals and provide us with a good foundation for treating polycrystals." The purpose of this investigation was to attempt to clarify the gap between single crystals and crystalline aggregates by an analysis of the effects of dcformational stresses. Some of the results were described by C. H. Mathewson in his 1943 Campbell Memorial Lecture.zl Previous Investigations Since the performance of single crystals deformed under pure stresses has been relatively thoroughly investigated, the most significant researches are concerned primarily with deviations from single crystal behavior of large grained specimens. Qualitative grain boundary effects involving the observed amount of slip werc reported by Carpenter and Elam5 in 1921. Individual crystals in a two or three grained aluminum specimen deformed by tension acted in the normal manner described by Taylor and Elarn4 except for marked modifications at the grain boundaries. There the power to withstand deformation was considerably increased, leaving a ridge on the specimen where decreased slip occurred, often noticeable yi in. from the boundary. Adcock,6 Yamaguchi,' Seumel, Hirstg and others have also reported this phenomenon as a qualitative trend. Yet attempts by O'Neill'o and Ljunggrenll to measure a difference in hardness at grain boundaries in undeformed specimens were unsuccessful. Miller12 measured quantitatively the reduction in slip near the boundary between the single crystal and polycrystalline areas of zinc specimens. These effects consisted of two parts: I. Next to the polycrystalline interface thc distribution of stresses was so altered

Jan 1, 1949

By Gordon M. Yocom

A pRopeR consideration of the subject of this paper should include economic aspects as well as the technical phases of the metallurgy, production, and properties of the product. The metallurgical phases of the processing and properties of the product will be considered only from practical aspects and within the scope of the writer's experience with tonnage production. The Bessemer process was invented 85 years ago and became important because it put steel manufacture upon a larger and less costly basis. In America the Bessemer production has declined for many years and has not maintained its proportionate place with the rapid advances of the open hearth. The achievements in the open-hearth field were attained by the greater number of technical people attracted to that branch of the industry. The antipathy of technical students for the older and less popular Bessemer field gradually weakened the forces defending it and retarded the development of new and better methods. In Europe the economic advantage of the basic Bessemer process has not been overlooked and the tonnage usually is greater than that of the open hearth. The acid process has been the subject of renewed attention in America during the past few years and those who are more familiar with it are striving to show that the method is too valuable to abandon. A considerable tonnage of Bessemer-blown metal, in both molten and ingot forms, used in connection with the open-hearth practice makes it an important auxiliary unit to the industry. This practice aids in modifying the price level of heavy remelting scrap in addition to speeding up the open-hearth operation. The use of Bessemer steel has continued not only because of periodic economic advantages but also because of certain inherent qualities of machinability, weldability and stiffness, which are valuable for many applications. The properties of stiffness and rather high reaction to cold-work require some modification in order to meet the demands of modem methods of processing, which involve cold-reduction and cold-forming. At least one factor contributing to the stiffness of this steel is the relatively high phosphorus content of the acid product. The phosphorus content of the Thomas or basic Bessemer steel of Europe is considerably lower than the normal acid product in America. The American industry has continued the use of the acid process chiefly for the reason that the available ores are more easily adapted to this process from both metallurgical and economic standpoints. In European practice the basic process is necessary with the highly phosphoric ores available and it is sustained to some degree by the sale of the rich phosphate slag as a by-product. The basic process was used in this country at several plants many years ago, but was abandoned for economic reasons. A part of the past history of these trials is given here because the author believes it has not been published and it has some bearing on the subject of this paper. The information is authentic to the extent that he possesses chemical laboratory notebooks

Jan 1, 1941

By Gordon M. Yocom

A pRopeR consideration of the subject of this paper should include economic aspects as well as the technical phases of the metallurgy, production, and properties of the product. The metallurgical phases of the processing and properties of the product will be considered only from practical aspects and within the scope of the writer's experience with tonnage production. The Bessemer process was invented 85 years ago and became important because it put steel manufacture upon a larger and less costly basis. In America the Bessemer production has declined for many years and has not maintained its proportionate place with the rapid advances of the open hearth. The achievements in the open-hearth field were attained by the greater number of technical people attracted to that branch of the industry. The antipathy of technical students for the older and less popular Bessemer field gradually weakened the forces defending it and retarded the development of new and better methods. In Europe the economic advantage of the basic Bessemer process has not been overlooked and the tonnage usually is greater than that of the open hearth. The acid process has been the subject of renewed attention in America during the past few years and those who are more familiar with it are striving to show that the method is too valuable to abandon. A considerable tonnage of Bessemer-blown metal, in both molten and ingot forms, used in connection with the open-hearth practice makes it an important auxiliary unit to the industry. This practice aids in modifying the price level of heavy remelting scrap in addition to speeding up the open-hearth operation. The use of Bessemer steel has continued not only because of periodic economic advantages but also because of certain inherent qualities of machinability, weldability and stiffness, which are valuable for many applications. The properties of stiffness and rather high reaction to cold-work require some modification in order to meet the demands of modem methods of processing, which involve cold-reduction and cold-forming. At least one factor contributing to the stiffness of this steel is the relatively high phosphorus content of the acid product. The phosphorus content of the Thomas or basic Bessemer steel of Europe is considerably lower than the normal acid product in America. The American industry has continued the use of the acid process chiefly for the reason that the available ores are more easily adapted to this process from both metallurgical and economic standpoints. In European practice the basic process is necessary with the highly phosphoric ores available and it is sustained to some degree by the sale of the rich phosphate slag as a by-product. The basic process was used in this country at several plants many years ago, but was abandoned for economic reasons. A part of the past history of these trials is given here because the author believes it has not been published and it has some bearing on the subject of this paper. The information is authentic to the extent that he possesses chemical laboratory notebooks

Jan 1, 1941

By A. J. Williams

THE province of Saskatchewan, situated in the center of the Great Plains region of Canada, has, like most prairie areas, an essentially agricultural economy. Most of its population of about 860,000 is located in the southern half of the province in the farming and ranching areas. To the north of the prairie is a broad forested belt supporting a considerable timbering industry, and the northern one third of the province is glaciated pre-Cambrian rock formation. This latter area is relatively barren of vegetation, but the presence within it of a considerable variety of radioactive, noble and base metals, and industrial minerals has been shown by prospecting in recent years.' Glacial Geology The Keewatin ice sheet, considered to have accumulated in the country to the west of Hudson Bay in Pleistocene time, covered at its maximum advancement almost all of Saskatchewan and extended south of the international boundary. Only in the Cypress Hills in the southwest and around Wood Mountain in the south central portion of the province did the preglacial formations escape the action for this glacial period. The bedrock of the plains and forest areas therefore is overlain by moraines and modified glacial drift, which vary in thickness from a few feet to 400 or 500 ft.' Glacial action in the pre-Cambrian area of the province was largely erosional, most of the more recent formations and some of the pre-Cambrian rock being transported out of the area to the south and west. It has been estimated that about 13 pct of this area is composed of lakes and rivers not too adaptable to rail or water transportation, so that until the use of aviation for exploration purposes became general, development of the area was slow. To the south, the heavy mantle of glacial drift has to some extent deterred the discovery of industrial minerals in the bedrock underlying the forest and prairie regions3 At the same time, this drift contains numerous deposits of those most elementary and necessary industrial minerals, sand and gravel. Sedimentary Basin The major feature of the sedimentary deposits underlying the plains regions is the basinal structure known as the Moose Jaw syncline, which runs from the southeast corner of the province in a northwesterly direction. To the west of this syncline the formations curve upward, then have been faulted and further upthrust to appear at the surface in the foothills of the Rockies in Alberta; to the east and north they curve upward into Manitoba and northern Saskatchewan, but the surface contacts are covered mostly with glacial drift.238 The axis of the syncline dips to the southeast, so that there is also an upward trend of the formations along the axis to the northwest. In illustration of the regional structure underlying the province, the pre-Cambrian basement has been logged in drillholes at the following depths in several locations: Ogema (south central), 9390 ft; Gronlid (northeast), 2599 ft; Vera (northwest), 4422 ft; Big River (north northwest), 2348 ft. Fig. 1 indicates the general surface geology of the province, ignoring such glacial overburden as may overlie many of the bedrock formations. Also indicated is the approximate location of the axis of the Moose Jaw syncline.' Industrial Minerals Clays: The province is fortunate in possessing a widespread distribution of clays of ceramic value, ranging from those used for heavy structural products to the high grade pottery and china clays. Shales suitable for brick and tile production are found in the Upper Cretaceous and Tertiary formations across the south of the province where the glacial drift is thin or nonexistent. Many deposits of glacial lake clays suitable for such wares are found scattered over the rest of the province south of the pre-Cambrian area. The Whitemud formation of the Upper Cretaceous is a narrow sedimentary band of secondary clays found intermittently at points across the south of the province where glacial action did not disturb or remove them.' In the southwest corner of the province, around Eastend in the Frenchman River valley, the refractory clays of this formation are contaminated somewhat with iron compounds or other alteration products of basaltic rocks. This eliminates the use of those clays in true whitewares, as they fire to creamy buff shades at the lower temperatures and to a blue-specked grey at cone 8 to 12, (2280°F to 2390°F), the range commonly used in firing whiteware. However, for use in the production of colored artware, caneware, stoneware or crockery, and sewerpipe, this type of clay makes an excellent body that requires little or no addition of flint, feldspar, or other fluxing materials such as are required in the higher class of ware.' It is not a grade of clay that can be shipped great distances to the manufacturing centers, but a market for considerable tonnages has developed at nearby Medicine Hat, where cheap natural gas is available for the firing of the ware. Farther east in the south central portion of the province, the clays of the Whitemud formation are generally more refractory and white burning. The formation is divided into three zones, consisting of white clays, brown shale, and white sandy clays.

Jan 1, 1953

By W. R. Hibbard

THE classical work on the electrical conductivity of alloys was carried out by Matthiessen and his coworkers1 in the early 1860's. He attempted to correlate the electrical conductivity of alloys with their constitution diagrams, but the information regarding the latter was too meager for success. Guertler2 reworked Matthiessen's and other conductivity data in 1906 on the basis of volume composition (an application of Le Chatelier's principle with implications as to temperature and pressure effects), and obtained the following relationships between specific conductivity and phase diagrams (plotted as volume compositions) : 1—For two-phase regions, electrical conductivity can be considered as a linear function of volume composition, following the law of mixtures. 2—For solid solutions, except intermetallic compounds, the electrical conductivity is lowered by solute additions first very extensively and later more gradually, such that a minimum occurs in systems with complete solid solubility. This minimum forms from a catenary type of curve. Intermetallic compound formation with variable compound composition results in a maximum conductivity at the stoi-chiometric composition. Landauer" has recently considered the resistivity of binary metallic two-phase mixtures on the basis of randomly distributed spherical-shaped regions of two phases having different conductivities. His derivation predicts deviations from the law of mixtures which fit measurements on alloys of 6 systems out of 13 considered. Volency (Ionic Charge) Perhaps the first comprehensive discussion of the electrical resistivity of dilute solid-solution alloys was presented by Norbury' in 1921. He collected sufficient data to show that the change in resistance caused by 1 atomic pct binary solute additions is periodic* in character. The difference between the period and/or the group of the solvent and solute elements could be correlated with the increase in resistance. Linde5-7 determined the electrical resistivity (p) of solid solutions containing up to about 4 atomic pct of various solutes in copper, silver, and gold at several temperatures. He reported that the extrapolated"" increase in resistance per atomic percent addition is a function of the square of the difference in group number of the solute and solvent as follows: ?p= a + K(N-Ng)2 where a and K are empirical constants and N and Ng are group numbers of the constituents. This empirical relation was subsequently rationalized theoretically by Mott,8 who showed that the scattering of conduction electrons is proportional to the square of the scattering charge at lattice sites. Thus, the change in resistance of dilute alloys is propor-t,ional to the square of the difference between the ionic charge (or valence) of the solvent and solute when other factors are neglected. Mott's difficulty in evaluating the volume of the lattice near each atom site where the valency electrons tend to segre-gate: limited his calculations to proportionality relations. Recently, Robinson and Dorn" reconfirmed this relationship for dilute aluminum solid-solution alloys at 20°C, using an effective charge of 2.5 for aluminum. In terms of valence, Linde's equation becomes ?P= {K2 + K1 (Z8 -Za)2} A where K1 and K2 are coefficients, A is atomic percent solute, Z, is valence of solvent, and Zß, is valence of solute. Plots of these data for copper, silver, gold, and aluminum alloys are shown in Fig. 1. The values of K1 and K2 are constant for a given chemical period (P), but vary from period to period. The value of K, increases irregularly with increasing difference between the period of the solvent and solute element (AP), being zero when AP is zero. The value of K, appears to have no obvious periodic relationship. All factors other than valence that affect resistivity are gathered in these coefficients. Because of the nature of the coefficients, Eq. 1 is of limited use in estimating the effects of solute additions on resistivity unless a large amount of experimental data are already available on the systems involved. It is the purpose of the first part of this report to investigate the factors that may be included in the coefficients of Linde's equation. On this basis, it is hoped that the relative effects of solute additions on resistivity can be better estimated from basic data, leading to a more convenient alloy design procedure. It is well 10,11 that phenomena that decrease the perfection of the periodic field in an atomic lattice, such as the introduction of a solute atom or strain due to deformation, will also increase the electrical resistivity. Thus, in an effort to relate changes in electrical resistivity to alloy composition, it appears appropriate to consider the atomic characteristics related to solution and strain hardening

Jan 1, 1955

By Joseph Jensen

FROM Aug. 31, 1937, until Apr. 30, 1939, there were 40,872,610 bbl. of oil run to storage in California; from Apr. 30, 1939, to Aug. 31 of the same year 5,512,912 bbl. were withdrawn from storage. But from Aug. 31, 1937, to Aug. 31, 1939, the number of producing wells in the state has increased from 17,706, with a potential production of 1,323,202 bbl., to 18,910, with a potential of 2,302,282 bbl. Thus, in a period of two years, during the first 20 months stocks increased over 1/3 and during the following four months stocks decreased 1/30. In the same two years the number of productive wells increased 1/15 and potential increased 3/4. Undoubtedly, the large increase in stocks created the pressure that caused the reduction in stocks that followed; yet this has come about in spite of the larger number of wells and higher potential. Cause of the change was the adoption on May 17, 1939, by the Central Committee of California Oil Producers of a uniform method of oil curtail-ment for all wells throughout the state. Acceptance of the method in the four months following adoption by practically all fields in California indicates that producers generally are convinced of its merit and fairness. True, some operators still overproduce, but the restraint practiced by the remainder of the industry has been sufficient to turn a situation headed for chaos into one of reasonable stability. Credit for this change goes to the industry itself, because it has all been accomplished under voluntary oil curtailment.

Jan 1, 1940

Objective stockpile goals have been met for antimony, bismuth, fluorspar, and iridium, while those for bauxite, cadmium, copper, lead, zinc, manganese, mercury, platinum, tin, and vanadium have not, according to a report by the Munitions Board. Total materials under inventory and contract represent about 78 pct of entire stockpile goals, the report stated. Frobisher, Ltd., of Canada has been given permission to survey power possibilities in certain lake and river basins in the Yukon believed to have a potential of 5 million he. Canadian Resources Minister, Robert Winters, also announced that his Government has rejected a bid by Aluminum Co. of America concerning use of Canadian waters to power a proposed Alaska aluminum project. Alcoa is reported hopeful of resuming negotiations.

Jan 3, 1953

By S. J. Noesen, J. R. Hughes

Several four-inch-diameter tungsten ingots were arc melted in vacuum or in hydrogen atmospheres. Melting pressures, melt-off rates, effect of atmospheres, and other pertinent factors were examined. Two of these ingots were extruded at 1650°C. Subsequently, forging and rolling were carried out at lower temperatures. For a 60 per cent area reduction by rolling, a one-hour recrystallization temperature of 1250°C was obtained. This temperature is considerably lower than those reported in previously published work, and can probably be attributed to the extreme purity of the as-cast ingots (N, H, 0 all less than 1 ppm). EVER since W. D. Coolidge, in 1909, described his process for producing tungsten metal of high density and good workability via the powder metallurgy tech-

Jan 1, 1961

By Ronald E. Versaw

Environmental legislation, both existing and proposed, requires that mills, tailings dams, evaporation ponds, and related processing facilities be located, constructed, and operated within stringent guidelines. An early step in planning a new processing facility is performing a site selection study in which topographic, hydrologic, geotechnical, and environmental parameters are evaluated for several alternate sites. Once a site is selected, then an environmental report, including a description of the proposed action, alternatives, baseline surveys, and discussions of potential environmental impacts, mitigation measures and monitoring programs is required. The federal legislation, siting studies, and environmental studies (along with the implications of these as they affect design) are discussed. In addition, costs for performing these studies and implementing control of effluents are discussed.

Jan 1, 1978

By D. F. Strong

Most Newfoundland mineral deposits can be clearly classified as within rocks formed either as accreting plate margins (ophiolitic pyrite-chalcopyrite massive sulfides such as Betts Cove, Whalesback, York Harbour, chromite at Lewis Hills, and asbestos at Baie Verte), at consuming plate margins (Kuroko-type polymetallic massive sulfides such as Buchans and Pilleys Island, porphyry-type Mo-Cu at Rencontre, fluorite at St. Lawrence), or within plates (zinc deposits at Daniels Harbour, sedimentary iron ores at Wabana, manganese in Conception Bay.) As these metallogenic patterns can be convincingly extrapolated southward into the Appalachians and northward to the Caledonides, they provide an important means of eliminating and selecting areas for particular exploration targets. Some criteria are described for the recognition of these environments of differing economic potential.

Jan 1, 1975

By C. Richard Tinsley

INTRODUCTION The economic analysis (Chapter 3), the engineering studies (Chapter 10), the credit structure (and the consequential funding sources) - Chapter 11, and the overall feasibility structure for any venture are all directed to determining one major decision element: How much and how certain is the reward for taking these risks? Risk assessment is a surprisingly weak area of analysis and is usually addressed in a checklist fashion. It is much preferable to deal within a risk system so that the inevitable tradeoffs among risks are correctly made. DEFINITION The first step toward risk definition must be to ascertain all of the risks to which a project or a company is exposed; otherwise one will remain ignorant of the possibility of a financially crippling loss until it occurs. (Carter and Crockford, 1974). However, simply stating what "risk" is can lead to debate. For example, risk could be (adapted from Vaughan, 1982): -the chance of a loss - uncertainty of loss -possibility of loss - uncertainty -dispersion of actual from expected results - probability of an outcome different from the one expected - possibility of an occurrence of an undesirable contingency -a condition in which a possibility of a loss exists. For the minerals industry financier, the last definition is probably the most appropriate. However, from a mineral company's point of view the definition might well include the possibility of not achieving the expected financial return. RISK CLASSIFICATION Risk identification will be readily agreed as the all-important first step. There are five major "branches" of risk classification. These are: -Statistical -Modellers -Checklist -Project Financing -Insurance The Statistical set discovered probability theory and any risk discussion soon deteriorates into a mathematical jungle (Megill, 1977; Hartman, 1976; Reutlinger, 1970; and Pouliquen, 1970).Their use of terminology tells its own story: coin toss (binomial distribution), gamblers' ruin, delphi (oracle) techniques, monte-carlo simulations, random walks, etcetera. These techniques inadequately represent the judgements necessary in an increasingly complicated and interrelated world. The risk Modellers have turned to the computer to handle these inter-relationships but soon find barriers because of "simultaneity". Certainly the computer has its uses to conduct various analyses (marketed as "sensitivity" analyses) but very often one finds that this involves changing one or two variables at a time, all other things being equal. Unfortunately, in a modern and complex world all other things do not remain equal. The statisticians will, no doubt, jump to their own defence by citing this

Jan 1, 1985

By E. E. Gardner, P. A. Schumann

A description of a new four-point probe configuration which permits measurement of epitaxial layer resistivity is given. An analytic solution to the potential distribution due to a point current source on a multilayered structure is briefly described. Typical solutions for this probe configuration are presented. Probe spacing, layer thickness, substrate resistivity, and substrate thickness enter into the calculation. Correction factors for typical cases are given. A brief description of the construction of a probe which can achieve a small spacing of 15 is presented. The prohe is constructed so that all points are adjustable by micrometers and the probe spacing and configuration can be easily altered. Measurements of layer resistivity with the four-point probe are compared with those taken with the three-Point probe and diode-capacitance techniques. TWO techniques of obtaining profiles of N/N+ epitaxial structures are given. The reproducihility of the probe spacing and resistivity measurement is discussed. The effects upon the resistivity measurement of errors in the measurement of the lager thickness, substrate resistil)itv, and substrate thickness are presented. SINCE its introduction by valdes' in 1954, the four-point probe has been the most widely used tool for determining semiconductor resistivity. Its usefulness ranges from the evaluation of bulk semiconductor ingots to the characterization of impurity profiles in diffused structures. In general the four points, two current probes and two potential probes, are placed on one surface of the material being tested either in an in-line array or in a square array. Numerous correction factors1 8 have been worked out for these configurations which are dictated by the finite geometry of the sample being tested. One method of evaluating thin wafers has been proposed which has two probesg on each side of the wafer. Further modifications have added a fifth'' and a sixth" probe. One paper1' has discussed the accuracy of the four-point probe and the precautions necessary in its use. With the exception of the method where two points are placed on opposite sides of the wafer, the four-point probe is restricted to evaluation of wafers with a homogeneous resistivity or to the case where an isolating junction exists between the substrate and the layer (epitaxial or diffused) being evaluated. Due to the relative resistivities and thickness, the resistance of the epitaxial layer is much greater than that of the substrate, and consequently a majority of the current flows through the substrate. The potential distribution at relatively large distances from the current sources is determined by the substrate resistance, and hence the AV/I value is a measure of the substrate resistivity and not that of the epitaxial-layer resistivity. In the immediate vicinity of a current source the potential distribution is determined by the layer resistivity among other factors. Consequently, if the potential probe is placed very close to the current source, then with appropriate correction factors it is possible to determine the layer resistivity. This was the theoretical basis for using two closely spaced probes on opposite sides of an epitaxial wafer. However, due to mechanical problems, it is desirable to place the four probes on the same side of the wafer. This paper discusses the potential distribution in

Jan 1, 1965

By T. Cuscino, D. D. Lane, C. Cowherd, T. E. Baxter

Three types of commercially-available dust suppressants, commonly used in the surface mining industry to control fugitive particulate emissions from unpaved roads, were tested in the laboratory for cohesive strength and resistance to reduced effectiveness by large water addi¬tions. Results indicate that each product tested varies in cohesive strength with a range of 34-300 kPa (5-44 psi). Total cohesive strength depends on the aggregate moisture content and the means by which the sample is dried. Results show that laboratory testing can be used as a decision¬making tool concerning the type of dust suppressant for a particular mining operation. Also, the road surface aggre¬gate moisture content u critical to successful dust suppres¬sant performance. Large water additions to the aggregate road surface after initial suppressant application can pro¬duce nondesirable results. A modified wet sieving analysis is presented to test the effect of water addition.

Jan 1, 1984