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By F. H. Deily, Jean M. Quets, Milton E. Wadsworth, John R. 222-000-000-012 Lewis, D. S. Rowley, R. J. Howe

Samples of synthetic magnetite were reduced in hydrogen-water vapor atmospheres in the temperature range 450o to 900oC. The reaction was always surface controlled, indicating the final products of reaction are nonfirotective. Three separate cases have been identified from the kinetic results: Case I, reduction of magnetite to iron below 570°C; Case II, reduction of magnetite to iron above 570°C; and Case 111, reduction of magnetite to wustite above 570 oC. In Cases I and 111 the kinetics have been explained by the formation of oxygen anion vacancies in the magnetite surface followed by associated diffusional processes. In Case 11 the observed kinetics have been related to the concentration of iron cation vacancies in the wustite layer formed, followed by associated steady-state diffusional processes. The concentration of cation vacancies in the wustite is maintained constant by the magnetite-wustite equilibrium. THE reduction of the oxides of iron has been a subject of study and interest for many years. However, few attempts have been made to interpret the results in terms of the mechanism of reduction of an iron oxide by either hydrogen or carbon monoxide. Stalhane and Malmberg' using CO, H2, and CO-Hz mixtures, developed the rate expression: where m = mass of oxide reduced, t = time, k = a constant, s = surface area, P = partial pressure of of CO or H,, and P, = partial pressure of the reducing gas at equilibrium. The rate of reaction per unit area was proportional to the difference between the partial pressure of the reducing gas and its pressure at equilibrium. Hansen, Bitsianes, and Joseph2 studied the reduction of pellets of hematite to magnetite with mixtures of CO-CO,. They concluded that below 450°C the reaction proceeded according to a model in which CO reacts with the hematite surface producing an oxygen ion vacancy. The rate controlling step was then assumed to be oxygen ion diffusion through vacancies resulting in the formation of magnetite. They derived an expression giving the rate of reduction proportional to the cO/CO, ratio. Recently McKewan3 published results for the reduction of magnetite spheres in atmospheres below 570°C. He explained his results by an equation of the form where K, is the equilibrium constant for wustite-iron equilibrium attributed to the formation of wustite as an intermediate in the reduction of magnetite. According to McKewan, Kp is an equilibrium constant for H, -HO adsorption in which oxygen is deposited on the surface from the H,Oand subsequently acts as a poison for reduction by hydrogen. Sample Preparation and Experiments. In this work the authors used the same apparatus and experimental procedure employed in the hydrogen reduction of magnetite. Sintered disk samples weighing approximately 1.5 g and measuring 1.2 cm in diameter and 0.25 cm in thickness were prepared by a method described previously.4 Partial pressures of hydrogen and water vapor were controlled by bubbling hydrogen through a series of flasks containing distilled and deionized water maintained at constant temperature in an oil bath. The total flow rate of the reacting gases—hydrogen and water vapor—was approximately 0.5 liter per min. The entire external system was maintained at a temperature above the oil bath to prevent condensation of water vapor. This was accomplished by wrapping electrical resistance elements over all surfaces. The glass column containing the weighing system-a McBain balance suspended from a gold chain-was enclosed in an aluminum tube heated by nichrome resistance wire enclosed in an insulating material. The temperature of the glass column was held constant by means of a series of thermocouples connected in parallel to a Leeds and Northrup temperature controller. This was necessary since variations in temperature resulted in expansion and contraction of the glass column and could be readily observed with the cathetometer. The spring extensions were measured through a window with a gaertner cathe-

Jan 1, 1962

By Fred E. Wright

In a recent paper1 a detailed discussion is given of the possibilities of using polarized light in the examination of opaque substances. The factors underlying the problem are there treated from the viewpoint of the electromagnetic theory of light and the presentation is necessarily mathematical in form. The practical methods resulting from the discussion are, however, relatively simple and promise to be of value in the determination of certain ores and metals when studied in reflected light under the microscope. The results of the theoretical investigation referred to may be summarized by stating that in general the optical constants, such as refractive indices and absorption indices, cannot be satisfactorily ascertained on small, random, polished sections; that the use of polarized light enables the observer ordinarily to determine whether the crystal plate is iso-tropic or anisotropic, and also to ascertain the degree of anisotropism; that for this purpose methods based either on the contrast in intensity between the two reflected components of non-polarized light, or on the amount of rotation of the plane of polarization, on reflection, of vertically incident, plane-polarized light, may be employed; that methods based on the phase difference between the two reflected components are in general of little value because of the small differences in phase which ordinarily result for a relatively large change in birefringence or biabsorption. The measurement of the optical properties of transparent minerals, even in minute irregular grains, is a simple task with modern petrographic microscope methods and is accomplished by petrologists as part of their ordinary routine work. But the determination of the optical constants of opaque substances is difficult and is rarely attempted; all observations are necessarily made in reflected light and are restricted commonly to the determination of color, of hardness, of the character of crystallization, and of the behavior of the mineral or metal plate toward reagents and abrasives. With practice, the observer becomes expert in recognizing details of this kind and determines with a high degree of certainty the different

Jan 1, 1920

By Norikazu Hashimoto

SILICIDE coatings on refractory metals are often applied by transporting a silicon halide vapor to a hot metal surface . The coatings are usually grown by solid-state diffusion reaction. The diffusion is often slower than the vapor transport and hence may become rate-controlling.

Jan 1, 1968

By T. S. Lundy, R. E. Pawel, F. R. Winslow, C. J. McHargue

The volume-diffusion coefficients of Nb-95 and Ta-182 in niobium have been measured over the temperature range 878° to 2400°C. High-temperature specimens (T 21500°C) were sectioned by conventional lathe and grinding techniques while low-temperature specimens were sectioned by an anodizing and stripping technique previously described. Over a range of more than ten orders of magnitude in diffusivity, the self-diffusion data is well-represented by the equation: D = (1.1+ 0.2) exp [- (96,000 * 900)/RT ] cm2/sec Upward deviations from this line are explained by short-circuit diffusion in combination with the loss of resolution of the sectioning techniques. Oxygen contamination within the range 100 to 450 ppm was found to have little or no effect on the self-diffusivitj 01 niobium. In a limited number of measurements, the diffusivity of Ta-182 in niobium was found to be about half that of Nb-95 in niobium. These data may be described by D = (I.0+0.90.5)exp [- (99,300 * 2400) /RT ] PREVIOUSLY reported studies of self-diffusion in niobium were by Resnick and Castleman1 and Peart, Graham, and Tomlin.2 The data of Resnick and Castleman over a temperature range 1585" to 2120°C show considerable scatter but. can be represented by D = (12.4 *0.8) exp [-(105,000+3OOO)/RT] cm2/sec The limited data of Peart, Graham, and Tomlin follow the equation D = 1.3 exp (-95,00O/RT) cm2/sec In view of recent diffusion data for ß zirconium3 and 0 titanium4 in which Arrhenius-type plots do not yield straight lines and of the potential high- temperature uses of niobium and its alloys, we thought it important to investigate the diffusion behavior of this bcc refractory metal over a large temperature range. This has recently been done for molybdenum,5 chromium,6 vanadium,"" and tantalum.9 Niobium was a particularly suitable material for this study largely because of the development of an anodizing and stripping sectioning technique which enables diffusivities as small as l0-19' sq cm per sec to be determined accurately.10 In addition to self-diffusion data, data were obtained for the diffusion of Ta-182 in niobium and for the effect of varying oxygen content on self-diffusion. I) EXPERIMENTAL PROCEDURE Materials. The niobium was obtained from three sources: 1) melting stock from Shieldalloy Corp., 2) electron-beam melted single crystals, 1/2 in. diameter, from Semi-Elements, Inc., and 3) oxygen-doped, electron-beam melted single crystals from Materials Research Corp. The melting stock was electron-beam melted and specimens 5/8 in. diameter by 1/2 in. long were machined from the center of the bar. The analysis supplied by the vendor and an interstitial analysis of one of the specimens are given in Table I. The single crystals (type 2 above) were cut with a jeweler's saw to specimens about 3/8 in. long. The interstitial analysis of this material is given in Table 11. This material was used

Jan 1, 1965

By Merlyn B. Buhle

The value of the earth resistivity method in groundwater studies in Illinois has long been recognized. Owing to the sharp electrical contrasts between sand and gravel deposits and glacial till, alluvial silt or underlying shale, much of the earth resistivity prospecting has been of a relatively elementary nature and has been highly successful. Approximately 90 pct of earth resistivity interpretations by the State Geological Survey have been accurate for practical purposes. Four studies involving fairly simple geologic situations are presented in this paper as typical cases. FOR the past 20 years electrical earth resistivity exploration has been used in Illinois in many phases of study undertaken by the State Geological Survey, chiefly in locating and outlining deposits of water-bearing sand and gravel from which to obtain ground water for municipal and industrial supplies. At least 43 municipalities in the state derive their total water supply from deposits of sand and gravel discovered by resistivity methods. These deposits occur in both Quaternary and preglacial valleys and within much of the glacial drift which covers a large portion of the state. In recent years there has been much demand from rapidly growing municipalities for help from the Illinois Geological Survey to extend existing well fields. Water supplies for many and varied industries constitute a considerable portion of the Survey's studies. The diminishing need of water supplies for railroads has 'been accompanied by an increasing demand by the oil industry for water for secondary recovery programs. The instruments used by the Illinois Geological Survey follow closely the commutated direct current circuits developed by O. H. Gish and W. J. Rooney' using the Wenner2 electrode configuration. More recently replacement of the hand-driven commutator by a synchronous vibrator has led to increased ease of operation and accuracy. Continuing improvement of equipment and technique has led to many changes in the instruments, but the operating theory remains the same. In the field operation at a selected station, four electrodes are set at equal distances in the ground 6 to 10 in. deep, in a straight line. A 16 to 20-cycle current is applied to the two outside steel electrodes

Jan 1, 1954

By C. K. Leith

AT the outset I would like to make it clear that I do not enter this discussion in a controversial spirit, but in an attempt to contribute something helpful to an understanding of a difficult problem. I have too high regard for the sterling quality of the work of the men who have studied this subject in detail to offer anything in the way of essential contradiction to their statements of fact. Difference of opinion arises from differing valuation of the possible alternative hypothesis which these facts suggest. Some degree of recrystallization in limestone contact zones has been recognized by many investigators. Earlier investigators, for the most part, assigned an important, if not the most important, role to recrystallization in development of these zones. With the growing recognition, of introduction of ores and gangue materials into the contact zone from igneous rocks through the medium of primary magmatic solutions, there has been a tendency to ascribe to this process most, if not all, of the chemical and mineralogical characteristics of the contact zone. This has involved a correspondingly diminished emphasis on recrystallization of substances already there as a factor in the process, and in some cases even the complete elimination of this hypothesis. From detailed study of a few contacts, casual observation of others, and a general familiarity with the literature, some of us have been led in recent years to raise the question whether the pendulum has not swung too far away from recrystallization toward direct introduction from igneous sources, and to argue for more recognition of the part played by recrystallization.1 The inevitable sequence has been that those of us who have taken this view have been charged, at least by inference, with emphasizing recrys-tallization to, the total exclusion of the alternative process. Scientists, like other men, like to classify and pigeon-hole views under simple and definite designations, leaving out qualifications which would tend to make the classification more difficult to state. This has made the problem seem more definite and simple, but has tended to obscure the fact that the disagreement is primarily not one relating to essential facts, but one of

Jan 6, 1914

By Arthur F. Wendt

In the manufacture of charcoal-blooms, washing or cleansing of the ore from adhering gangue has been practiced for many years. A sluice-box is even to-day used for that purpose in the Southern Appalachian Mountains. For the Lake Champlain bloomaries hard magnetic ores are crushed with stamps and then sluiced or jigged in hand-jigs. The stamps used in the Lake Champlain region are of the most primitive kind. They consist of a trip-hammer, dropping on a perforated cast-iron plate, through which the crushed ore escapes. Only friable rock can thus be successfully treated. To render the raw ore friable, a calcining or burning in piles on a bed of cordwood is resorted to. An expense of 35 cents per ton of crude rock treated is thus incurred. The crushed ore is shovelled or otherwise fed into jigs without previous sizing, except such as is incidental to crushing through the perforated bottom of the stamping-machine. In jigging this ore, it is allowed to pass through the bedding into the "hutch." The tailings are scraped off and wasted. They contain a large percentage of fine ore. In many instances, this is regained by subsequent sluicing. Such was the condition of the industry, when the writer's attention was first called to it in 1882. No attempt had been made to introduce into thiS branch of ore-dressing the notable improvements adopted in concentrating the ores of other metals. The result of the writer's investigations was the building in 1882 of the "Crown Point Separator." At the Crown Point Mines, N. Y., lean ore unfit for the blastfurnace (containing less than 331/3 per cent. of iron), was concentrated and used in the bloomary connected with the mines. The ore was burned here as elsewhere, and treated as described. The plant designed by the writer for Crown Point, is nearly a counterpart of that since erected by Messrs. Copeland and Bacon, contractors, for the Theal mine, Putnam County, New York, which is illustrated by the accompanying plate. The only difference is in

Jan 1, 1885

By A. R. Matthews

This description of the organization of the Consolidation Coal CO. is intended to include only the portion that is charged with the responsibility of the actual operation of an individual mine, although it has seemed advisable to include several of the all-division personnel, who necessarily come in direct contact with the mine officials. The Consolidation Coal Co. has a staff and line organization and, while most of the contact between these two wings is made between officers ranking above those discussed in this paper, field representatives of several of the staff departments play such an important role in the control of certain phases of activity at the mines that a true picture of the mine organization cannot be had unless these men are included. The demands made upon the producer of large quantities of coal have certainly never been so exacting as they are today. Reductions in the number of accidents and in the cost of individual accidents has passed from the category of a desirable achievement to an unqualified necessity. Although the market price of coal today is lower than it has been in many years, consumers have never been so critical of quality. This market condition is especially severe on the producer to whom one bad shipment may mean the loss of a contract. And the battle to keep the reduction of production costs abreast with constantly dropping prices wages incessantly. For the legitimate producer this situation demands a mine-operating organization that is comprehensive, versatile, efficient and economical; and it is in an attempt to meet these conditions that our present system has been designed. To say that this line-up is incapable of being improved or that it is applicable to all conditions would be to assume a degree of presumption which certainly is not intended here, but our system does meet the conditions which we are called upon to face today with a smoothness and thoroughness which we consider reasonably satisfactory. Authority or Consultation On the chart of Fig. 1 an attempt is made to show as clearly as possible the authority and responsibility of each mine official, together with the

Jan 1, 1931

By G. C. Rauch, T. H. Courtney, J. Wulff

The superconducting behavior of Nb-Ti alloys containing 40 and higher wt pct of Nb and variable oxygen content was studied as a function of thermomechanical processing. Critical current density (Jc) us applied transverse magnetic field (H) data were obtained for 0.010 in. diam wires at 4.2° Kin steady fields up to 120 kOe. The precipitate responsible for increase in Jc in each of the alloys studied was related to niobium and oxygen content. In alloys containing 40 to 60 wt pct Nb with less than about 1600 ppm of oxygen, w precipitation in the range 350° to 450°C appears to be responsible for the maximum value of Jc observed. In alloys of higher oxygen content (-2500 ppm), the oxygen-enriched a phase which precipitates in the temperature range 450° to 550°C is a more effective fluxoid pinner. Maximum Jc in low oxygen (350 ppm) 80 wt pct Nb alloys was achieved by 600°C aging heat treatments. Measurements of resistive critical field also reflect the changes in composition accompanying precipitation in these alloys. It is well known that the superconducting critical current density, Jc, of solid solution superconducting alloys can be increased by precipitation heat treatments.1-4 The precipitate, to serve as an effective superconzlucting fluxoid pinner and increase Jc, must be of proper size and spacing.' Its electronic properties must also be different from those of the matrix.6 As in age-hardenable systems, optimum temperature and time of aging are dictated by the composition and history of the particular solid-solution alloy under consideration. The alloy diagram of Ti-Nb7-9 shown in Fig. 1 is typical of ß-stabilized Ti alloys. Precipitation to achieve high Jc in Ti-Nb and Ti-Ta alloys is usually carried out in what is believed to be a two-phase a + ß region.1,2,4,10 Previous work on Ti-Nb4,11 and on other ß-stabilized systems such as Ti-V, Ti-Mo,12-14 has shown, however, that the first precipitate to appear is not necessarily (Y. Under specific conditions the meta-stable w phase is precipitated instead. A further complication arises in such alloys from the strong influence of contained oxygen on the phase stability and on the kinetics of precipitation.15,16 The superconducting critical current density of Nb-Ti alloy containing less than 36 wt pct Nb has been studied by Vetrano and Boom1 and Kramer and Rhodes.4 The most effective aging temperature was found to be about 425°C; fluxoid pinning was attributed to the precipita- tion of a by Vetrano and Boom and of w by Kramer and Rhodes. Although the latter workers used recrystal-lized material and the former cold-worked, studies carried out in our laboratory lead us to believe that the type of precipitate responsible for increased Jc is unaffected by prior cold-work.17 That other types of precipitates may also be effective, especially in higher oxygen-containing alloys, has been demonstrated by Reuter, et al.2 in this laboratory with the aid of electron microscopy. Reuter et al. found that at an aging temperature of 600°C, fee-TiO is precipitated, resulting in high values of Jc. Even higher values of Jc were observed after heat treatment at 500°C, but the precipitate could not be indexed as fee-TiO. Whether the precipitate was oxygen-rich w or a could not be clearly distinguished. The work nevertheless indicates that appreciable amounts of oxygen alter the nature of the phases precipitated at different temperatures, at least in alloys containing more than 36 wt pct Nb. Since such compositions are more readily worked into suitable wire than lesser niobium content alloys, it was decided to study the response to aging of the alloy compositions reported in the present paper with the hope of clarifying the effect of composition on the precipitation processes responsible for high values of Jc. I. EXPERIMENTAL Nb-Ti alloys containing 40, 50, 60, and 80 wt pct Nb were prepared by are-melting 35 g ingots of iodide crystal bar titanium and electron-beam melted niobium.

Jan 1, 1969

During the war period of quicksilver activity there were a number of departures from what may be termed the classical quicksilver metallurgy. Attempts were made to beneficiate low-grade ores by gravity concentration and flotation; mechanical furnaces began to replace the Scott furnace and the vertical coarse-ore furnaces, and condensers of sewer tile and redwood tanks were used in place of the older brick and stone condensing chambers. Other developments that have occurred during the current period of quicksilver activity are mainly in the nature of improvement and further refinement of those started during the war period. Each period of quicksilver activity has been accompanied by the proposal of various new processes, including wet methods for the treatment of quicksilver ores and innovations in furnaces, retorts and condenser equipment. As far as the author knows, nothing of economic significance in the way of "new processes" has been developed. There is in fact no real need for any essentially new process for the treatment of quicksilver ores; the direct furnace treatment is simple and inexpensive. Moreover, with rare exceptions, the quicksilver industry has no complex or refractory ore problems corresponding to those which are receiving more and more attention from metallurgists in other branches of the nonferrous field. Untler these conditions improvements in quicksilver metallurgy must be looked for through the adaptation of current developments in engineering and metallurgy generally to the particular needs of quicksilver practice rather than through the invention of new processes. Preliminary Treatment of Quicksilver Ores At Sulphur Bank, in the treatment of old dump material left by the early operators, wet screening is being used as a preliminary step in concentration ahead of flotation. Power shovels and trucks are used to deliver some 400 tons of ore per day to the lower terminal of a hoist, which in turn discharges the material at the top of the screening plant. Wet screening is carried on in two stages. Depending on the character of the material, 1-in. or 2-in. punched screens are used on the first trommel.

Jan 1, 1930

By A. Sutulov

The segregation process, an alternative to benefi-ciation of oxidized and mixed sulfide-oxide copper ores, is studied here with particular emphasis placed on time, temperature, and coke and salt percentage factors. The results show that in a segregated charge, the copper assay of the coarsest fractions normally is of the same order as the copper assay of the tails obtained from grinding and flotation of the same charge. This observation suggests the possibility of limiting or even eliminating the grinding step from the flowsheet of a segregation plant. The segregation process, which offers an alternative to beneficiation of oxidized and mixed sulfide-oxide copper ores, was discovered in 1923 by Moulden and Taplin1,2 who were attempting to apply the Perkins process3'4 to a Chilean ore from the Sagasca mine. After a number of investigations and pilot plant tests,'-' the segregation process became a successful industrial operation.'r9 The process aroused considerable interest in Chile because of the existance of large reserves of oxidized copper minerals which could not be treated by conventional hydrometallurgical methods because of the high consumption and prohibitive cost of sulfuric acid. During the last two years, the Mineral Dressing Dept. of the Institute de Investigaciones Tecnology cas of University of concepci6n (Chile) has carried out a test program on 23 different ore samples representative of the national territory. These tests were carried out on a semi-continuous and batch scale with a rotary, automatically controlled and gas-fired furnace (supplied by Bartlett and Snow, Fig. 1). The results of these tests indicate that out of the 23 samples 20 can be successfully treated by this process with recoveries of copper ranging from 85 to 95%.10,11 The purpose of this paper is to treat some specific problems related to the segregation process. TIME AND TEMPERATURE FACTORS Time and temperature of calcination play an important role in the segregation process. When moderate salt and coke conditions were maintained (each of reagents was added in the quantity of 1 — % wt), systematic testing easily demonstrated the influence of these two factors on segregation and flotation recovery. The pertinent results are summarized in Fig. 2. To determine what specific changes the segregation process made on the ore, the samples, segregated at 700°C for different periods of time and under standard conditions, were granulometrically analysed and

Jan 1, 1963

The Library of the above-named Societies is open from 9 A.M. to 9 P.M. on all week-days, except holidays, from September 1 to June 30, and from 9 A.M. to 6 P.M. during July and August. The Library contains about 55,000 volumes, including sets of technical periodicals and the publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library can render valuable service through correspondence; letters requesting information will receive special attention. The Library is prepared to furnish references and copies of articles on mining and metallurgical subjects; to determine the existence of mining-maps, and to furnish general information as to the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may he what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will he saved, and the information will be sent more promptly and in more usable shape. The members of the institute can be of service to the Library by forwarding copies of mining-reports, naps privately issued, and similar material, which will be classified, indexed, and made available to other members. Suggestions for additions to the Library, either by purchase or personal solicitation as gifts, will be welcomed. It is hoped that members while in the city will use the Library freely, and assurance is given that most careful service will be rendered to them.

Jan 7, 1913

(Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) Member, mining engineer, technical education, married, 15 years' experience as foreman, superintendent, manager of examination and exploration work. Prefers Pacific Coast or Alaska, but will go anywhere. Available Nov. 25. No. 422. Mine manager or mill superintendent. U. S. A., Canada or Mexico preferred. Age, 33. Member. Five years mill superintendent, mills up to 2500 tons a day-gold, silver and lead; 6 years mining from bottom up to manager. No. 423. Member, mining engineer, technical graduate, age 40, 17 years' experience, having filled every position at a mine; superintendent of large mine at present. Familiar with all kinds of mining machinery. 'Best of reference. Available after Jan. 1, 1918. No. 424. Member, age 41, with 20 years' experience in design construction and operation of mining and smelting works and steam, electric and water-power plants, etc., who has held positions of responsibility in important concerns, desires a position requiring executive or engineering ability, or both. No. 425. Member, age 37, graduate mining engineer, with 29 years' experience in all phases of anthracite and bituminous mining, at present engaged as manager of one bituminous mine and consulting engineer for others, desires position as manager of a coal mine or consulting engineer for banking interests. No. 426.

Jan 1, 1918

Discussion of the paper of R. H. RICHARDS and BOYD DUDLEY, JR., presented at the New York meeting, February, 1915, and printed in Bulletin No. 97, January, 191.5, pp. 67 to 72. R. H. RICHARDS, Boston, Mass.-I believe that the manner of working for efficiency in almost all lines is to study the conditions of highest efficiency, and then to measure what is being clone. We can then see how near we have approached the highest efficiency. Spigots in practice often use many times the water theoretically needed. There are places where that is necessary for safety reasons. There are, however, places where it is unnecessary, and in these places it seems to me that this work of Mr. Dudley's will be a great help to the mill man to arrive at the greatest economy of water and highest efficiency. ALBERT R. LEDOUX, New York, N. Y.-A good many years ago I received a telegram from that distinguished engineer, Hamilton Smith, which simply said in substance: "I have discovered that liquids will flow faster from a square orifice than from a round orifice of the same area, under the same head." I wondered why he sent me the telegram, but some time afterward he told me that he had been making experiments along that line in Montana; that he thought the discovery was interesting

Jan 5, 1915

By N. L. Svensson

The model developed by Tuylor for the calculation of Polycrystalline yield strength has been applied to the case of an aggregate hawing a preferred orientation. In general this procedure requires the specification of texture by means of weighting factors applied to specific orientations. The problem to which the model has been applied is that of the yield-strength aniso-tropy of cold-rolled aluminum whose rolling texture was described as a combination of (110)[112] and (311) [112] In this case yield-strength anisotropy is defined by the rutio of yield strength measured at an angle 8 to the rolling direction to that measured along the rolling direction. The method of calculation of yield-strength ratio as a function of ? is described and the results show good agreement with experimental values. The orthotropic yield criterion suggested by Hill has been applied to the results and the strain ratio R also calculated as a function of ?. This has been compared with calculations using the method suggested by Elias, Heyer, and Smith which does not exhibit suck good agreement with observation. one deficietlcy of the method presented is that the strain ratios used by are those applying to iso-Irobic materials. The method should therefore be reg-clrded only as a first abbroximation to the prediction of anisotropy. THE problem of calculating the stress-strain characteristics of polycrystalline aggregates from the properties of single crystals has attracted attention for a number of years. The most important contributions to this study have been those due to: Sachs,' Cox and sopwith,2 Taylor,3 Kochendorfer,4 Batdorf and Budiansky,5 Calnan and Clews,6 Bishop and Hill,7,8 Kocks,9 Budiansky, Hashin, and sanders, 10 Kroner,11 Cyzak, Bow, and payne, 12 Budiansky and Wu,13 and Lin.14 While the earlier work has been largely superseded, recent developments tend to support Taylor's solution" within the restriction imposed by his assumptions. The essential features of Taylor's approach were: 1) the material is rigid-plastic; 2) each grain experiences the same strain components as the aggregate as a whole (the problem was that of uniaxial deformation with principal strain components in the ratio 3) all regions of each grain deform uniformly; 4) work hardening occurs equally on all slip systems. While Bishop and Hill7 have generally validated this approach, there has been some criticism offered. Kocks? as pointed out that since multiple slip must occur the single-crystal data must be determined from orientations arranged such that polyslip takes place. Boas and Hargreaves,15 and others, have shown experimentally that the strain distribution within grains is not uniform, the strains in the vicinity of grain boundaries being less than those in the center of the grains. Both of these criticisms can be largely offset by the suitable choice of single-crystal critical shear stress. However, for the problem analyzed below, the critical shear stress is not directly used and, consequently, these criticisms lose their importance. The more recent contributions have attempted to obtain a more complete analysis by considering an elas-toplastic material and considering interactions between grains of differing orientations. Lin14 has considered the early stages of yielding for a polycrystalline aggregate having specific regions of defined slip plane orientations. On the other hand, Budiansky and Wu13 have allowed for these interactions for randomly disposed grain orientations and have calculated the polycrystalline stress-strain curves for crystals exhibiting either elastic-ideally plastic or kinematic hardening characteristics. This work has shown that yielding commences when the macroscopic stress is 2.2 times the critical shear stress for slip in a single crystal (7,). The yield stress-strain curve then rises becoming asymptotic to a value of 3.072 7,. This is close to the value obtained by Bishop and Hill (3.06) in their confirmation of Taylor's method. This, of course, is to be expected since, at large strain values, the elastic strains are negligible and the rigid-plastic model is satisfactory. The results of Budiansky and Wu indicate that the result obtained by Taylor is 7.7 pct high at a plastic strain which is two times the elastic strain at the initiation of yield. By defining the anisotropy in terms of relative values, the ratio of yield strength at orientation ?, to that measured in the rolling direction, the effect of the discrepancy in Taylor's solution is considered to be of lesser consequence. Therefore, it is anticipated that an analysis based on Taylor's solution, which can be quite straightforward, should provide a reasonable estimation of the anisotropy of materials having a preferred orientation texture. OUTLINE OF TAYLOR'S METHOD In fee metals there are four possible slip planes (the octahedral planes) and in each there are three possible slip directions (the edges of the octahedron), that is a total of twelve possible slip systems. von Mises16 has shown that at least five independent slip systems must become operative in each grain of the polycrystalline aggregate in order to preserve continuity of strain. With this geometrical requirement as basis and the assumptions previously listed, Taylor determined the operative slip systems for a number of orientations of the tensile stress axis specified in the unit stereographic triangle. For the ith slip system, the critical shear stress

Jan 1, 1967

By Murray Pezim

In the good old days of the folklore of the mining industry, grizzled prospectors obtained a few loose dollars from friends and neighbours then wandered off to eventually return with the great discovery which became the core of the new corporate empires. Alternatively, merchant banking barons obtained exclusive rights to just about anything of future value over hugh nation-size territories. Some of this probably still goes on, likely with about the same ineffectiveness and waste of effort and money as in the past. CURRENT CONCERNS IN MINING In today's difficult climate in the mining industry, for that matter in all industry, effectiveness is the vital consideration. Cost effectiveness -- more bang for the buck -- is especially important in such an area of high risk as mineral exploration. And there are other factors to consider. Since minerals are depleting resources, the mining inddustry is constantly confronted with the reality that those resources extracted today must be immediately replaced if a resource enterprise is to continue. And if growth is to be achieved, even more resources must be found to support future expansion. The current and immediately foreseeable climate internationally for the mining industry creates a special need and urgency for aggressive and successful exploration, certainly in Canada, if not also in the United States. Depressed world markets and prices have turned yesterday's economic reserves into today's waste, hopefully to be converted into economic ore again in some distant time. One way of replenishing reserves and maintaining a viable mining industry is to find and develop mines which are economic under short-term depressed price and market conditions. This probably means higher grades. A new copper discovery with the right combination of characteristics to be an attractive investment even at today's pices for copper would still merit development into production. Exploration is the only way to find such mines for the difficult short-term conditions. Another important consideration is that normally many years stretch from the first thought of conducting exploration to production -- in those rare instances where an economic discovery is made. If discoveries are not made today, then there will not be any projects to develop when business conditions are more attrative. This industry and the vast number of skilled professionals who are part of mining, are faced with two key problems that underlie the need for a junior exploration segment. One consideration is how to maintain exploration during those years, indeed eras, of recession and depression. We are in such a time now. Throughout the world, major companies have sharply cut back, if not eliminated completely, exploration expenditures other than what is vitally necessary and easily and inexpensively done at the known and producing deposits. And related to that consideration, even more important today than during happier times, is how to finance such necessary ongoing exploration if major companies and governments back away because of financial stringency. CANADIAN SUCCESS In Canada, such problems are being tackled with a success which is capturing worldwide attention. The ability of mineral explorers to obtain willing, eager, high-risk capital is achieving even more outstanding results than in the past. These results are reflected in the widespread continuing exploration ativity in Canada which even spreads into the United States, with some outstanding discovery successes. The most notable exploration success from junior mining activity is the discovery of the Hemlo gold camp in northwestern Ontario, a source of gold which promises to rank with the South

Jan 1, 1985

By Howard M. Graff, Sidney C. Bouwer

The economics of mining has traditionally been viewed quite apart from the economics of blast furnace operations. It was realized, of course, that blast furnaces would operate best with good raw materials, but the shipping grade of ore, for example, was decided by a sort of collective bargaining process between the ore producers and the blast furnace operators. The mine operators had to keep their costs down, and were usually successful in convincing management that the ore in any particular deposit was endowed by nature with a certain iron content and that the mine grade could not be raised beyond a certain economic limit. The blast furnace operators would have liked a better grade, but as long as they were able to make a fairly good showing it was more or less accepted that they had to take the ore as it came. The mine operators were able to ship to the nation's blast furnaces thousands of tons of iron ore that would be completely unacceptable by present-day standards. As late as the early 1950's, the major steel companies were witnessing an actual decline in the iron content of their incoming ore supply as the mining companies mined progressively leaner material and upgraded it only enough to pass competitive market requirements

Jan 8, 1965

By V. C. Allen

THE Tri-State Zinc, Inc., Galena, Ill., was confronted with the problem of securing ore from a deposit because the hoisting shaft was several thousand feet from the mill. The orebody is several thousand feet long, averaging 200 ft in width and 60 ft in height and opened up by vertical shafts some 300 ft deep. Mining is by the room-and-pillar method. During the initial operation the ore was loaded by conventional electric 1/2-yd boom-and-dipper shovels and hauled to the shaft by 8-ton diesel trucks. This underground ore loading and hauling was well adapted to the conditions and productive of low costs per ton. However, with the mill situated as mentioned, a triple handling of all broken rock was necessary: l—from the stope to the shaft by truck, 2—up the shaft by skip br can into the surface hopper, and 3—by truck from the surface hopper to the crushing plant at the mill. In addition to the repeated handling, serious troubles were encountered during the winter because of freezing in the shaft hopper. Consideration was given to either moving the mill to the new orebody or to the construction of a second mill. The presence of other orebodies to be mined at a later date made the first alternative impractical while the capital outlay for a second mill, when the present plant of approximately 850 tons per day was deemed sufficiently large for the total reserves, made the second alternative also unwise. It was decided to retain the mill in the originals location and continue to move the ore to it. The idea of driving an inclined adit from the surface to the bottom of the orebody suitable for truck haulage and big enough to allow the passage of all mechanical equipment was conceived. Among the apparent advantages of such an incline were: 1— Direct haulage from the stope to the mill without rehandling. 2—Elimination of virtually all grizzlies. Trucking from underground to the mill would do away with all hoppers, chutes, gates, and skips and make the maximum rock size dependent solely on the size of the shovel dipper at the mine and the crusher opening at the mill. 3—Less secondary blasting would be needed. 4—Ease of transporting equipment and supplies underground. Shovels and trucks could be taken through the incline intact. 5—Equipment could be brought to the surface for repairs and servicing without loss of time. The same advantages of ease in moving would be present in the handling of men, steel, powder, and supplies. 6—There would be far less difficulty in increasing the amount of tonnage that could be moved by truck up an incline than would be found in attempting to increase the capacity of a shaft. 7—All the broken ore in the stopes would serve as bin capacity, as it would take the breakdown of all of the loading and hauling equipment to have the same effect as a delay in shaft hoisting. 8—All danger of men being trapped in the mine as a result of shaft fire or power stoppage would be eliminated. 9— Virtually all trouble from severe winter conditions would be eliminated by the direct haul underground to the mill. The decision was made to proceed with the driving of an inclined adit. The topography of the surface between the orebody and the mill was such that it was possible to locate the portal at a point 170 ft above the mine floor and 1800 ft horizontally from the central point of the orebody to the south and 2500 ft from the mill to the north. A grade of 10 pct was found to be optimum for continuous truck haulage when the various factors of speed, safety, and truck maintenance were all considered. The incline as driven was consequently 1700 ft long on 10 pct grade and 12 ft high by 17 ft wide in cross section. The tunnel-driving equipment was chosen so that it could be used in mining after the completion of the tunnel. Drilling was done with a jumbo with two Joy jibs mounting 3-in. drills, loading with an Allis-Chalmers diesel-powered, front-end loader of approximately 11/4-yd capacity, and hauling by Koehring Dumptor trucks of 8-ton capacity, diesel-powered. The width of the tunnel allowed the end loader and Dumptor to be placed abreast. Since the Dumptors can be driven either forward or backward with equal facility, loading was accomplished without turning around either machine throughout the loading operation. The crew in addition to the tunnel foreman was comprised of three men per shift at the start and in the later work, four men. Each crew could perform any part of the working cycle. If the drilling was completed and the round blasted in the middle of a shift, the same men would proceed with the loading and hauling. Since the mine already had been drained to the bottom levels, no water was encountered. At the halfway point the tunnel was widened for approximately 100 ft to permit trucks to pass. The total cost of the tunnel excluding the capital outlay for equipment, which was all continued in use in the subsequent mine operation, was $60,363.00 or $35.50 per ft. The tunnel was completed at the end of June, 1949 and has been in continuous use since that time. In the five months from July to November inclusive, 106,049 tons have been transported to the mill or an average of 835 tons per day. No unforeseen disadvantages have been encountered and the advantages which had been predicated before the adit's construction have been more than realized. As previously mentioned, the deposit is worked by the room-and-pillar system with occasional faces up to 125 ft high. Except in driving development drifts when diesel-powered, front-end loaders such as were used in the tunnel are employed, all shoveling is done by Yz-yd boom-dipper type shovels electrically driven. These units need a width of 25 ft and a height of 14 ft in which to operate. All hauling is by diesel trucks, mainly Koehring Dump-tors. Roads are maintained with caterpillar tractors and a road grader. The tonnage output from the

Jan 1, 1952

By W. M. Courtis

In compliance with the suggestion in Mr. Emmons's paper on the Genesis of Certain Ore-Deposits (Trans. xv., 125), that facts should be accumulated for study and future compilation, I wish to put on record, before the data are lost, a section of the Animikie series of rocks and the vein-phenomena exposed by the explorations at the Duncan mine, Port Arthur, Thunder Bay, Lake Superior. This may serve as a supplement to my paper on this district (Trans. v., 473). I trust this information will not be without interest at. the present time. The recent discoveries of very rich silver-ores at Rabbit and Silver Mountains, on the same belt, have brought the district once more before the public; and a study of the facts here set forth may assist some fellow-engineer in the determination of the value of property offered for sale in this neighborhood. The vein at the Duncan mine was tested to a depth of over eight hundred feet by shaft and drifts, and to nearly a thousand feet with

Jan 1, 1887

By Mark S. Childs

FRIEDENSVILLE orebody in Lehigh County, Pennsylvania, lies in the south central part of the USGS Allentown Quadrangle. Physiographically the area is located in a small reentrant-known as Saucon Valley-of the Great Valley Province into the Reading Prong of the New England uplift. Saucon Valley itself is an oval-shaped lowland eight miles long and four miles wide, surrounded by ridges except where connected with the Great Valley through a breach in the rim known as Saucon Gap. These ridges, composed of Pre-Cambrian metamorphic rocks and Cambrian quartzites, rise some 500 ft above the valley floor. They are continuous with the New Jersey Highlands. The valley lowland is immediately underlain by lower Paleozoic dolomites and limestones. This area is one of low relief having a swing of approximately 100 ft, with an average elevation of 375 ft above sea level. The entire valley, which has a water shed of about 58 sq miles, is drained by Saucon Creek. This unit flows in a northeasterly direction to the Saucon Gap, where it discharges into the Lehigh River.

Jan 1, 1957