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By J. F. Kemp

IN submitting an additional contribution to the discussion on ore-deposits in the recent volumes of the Transactions, it is my desire to adhere closely to matters of material importance as affecting the actual processes. Judging from the discussion by Professor Van Hise, and from one or two reviews or other articles by associates of his in geological work, the impression seems to prevail that, in so far as my paper* referred to ,his masterly essay,†I was guilty of misconceptions regarding both the part attributed by him in it to the igneous rocks and the ubiquitous presence of the ground-water. I should regret extremely to be wanting in these particulars or to have misunderstood one for whose great services in this and other branches of geology no one has a higher esteem than myself. I have, however, in the most careful way, and with these points in mind, read his essay again, anti, taking it as a whole, I cannot gain any different impression of relative magnitudes than the one first received. The importance of the igneous phenomena and the restrictive influence of the processes described by " cementation " in their effect upon the ground-water, as set forth in Professor Van Hise's " Discussion " (Trans., xxxi., 292), impress me as being in very marked contrast with the same things in his first essay. If the point seems to anyone of sufficient importance, it can easily be decided by reading the originals. My paper was the result of some years of observation, reading and reflection, and was meant to be an independent contribution, controversial only in some subordinate particulars. In depicting the drama of the deposition of ores, I cannot but feel that Professor Van Rise assigned to the chorus and the scene-shifters some characters which, it seems to me, should

Jan 1, 1913

By R. I. Jaffee, C. T. Sims, C. M. Craighead

The fabrication of rhenium metal by powder metallurgy techniques is discussed. The following physical and mechanical properties have been measured and are reported: lattice constants, melting point, electrical resistivity, thermal expansion, spectral emissivity, modulus of elasticity, tensile properties and ductility at room and elevated temperatures, work hardening, recrystallization, grain growth, and oxidation resistance. IT is only occasionally that a metal reaches present-day technology with as little known about its properties as element No. 75, rhenium. Relatively scarce to date, it has been studied only infrequently and used less. Previous work on rhenium has been carried out primarily by European scientists. However, realization that rhenium occurs in commercial quantities in the United States recently has focused attention on this metal. Rhenium is a very dense high melting hexagonal-close-packed metal. Like tungsten and molybdenum, its highest oxide is volatile. However, when protected by reducing or inert atmospheres, its strength at high temperatures is greater than that of tungsten. Rhenium work hardens more than any other known pure metal, but, on annealing, becomes quite soft and ductile. Its vapor pressure is approximately that of tantalum, but it does not enter into the so-called "water cycle" nearly as readily as does tungsten. (The water cycle is a deleterious phenomenon causing blackening of lamp bulbs and vacuum tubes with subsequent failure of the filaments.) These and other properties, some already known and some found as a result of the current researches, have indicated that rhenium has many potential uses, primarily of an electrical or electronic nature. Rhenium or its alloys soon may be found in service as electron-tube filaments, cathodic emitters, or as electrical contact materials. In addition, rhenium or its alloys have potential use in such devices as high temperature thermocouples, and high wear-resistant parts such as precision instrument points. Rhenium, in the form of potassium perrhenate, was made available for this study by the Kennecott Copper Corp. The potassium perrhenate was reduced to rhenium metal in two stages, accompanied by leaching to remove potassium in the form of hydroxide. This impure metal was then oxidized to rhenium heptoxide and dissolved in water. The solution was neutralized with ammonium hydroxide to produce highly purified ammonium perrhenate, a typical analysis of which is shown in Table I. The ammonium perrhenate was ground to —325 mesh in a rubber-lined ball mill with Burundum balls. This operation caused a certain amount of impurity pickup, as reflected in the rhenium analysis shown in Table I. The fine ammonium perrhenate was reduced to metal with hydrogen. Particle size of the powder ranged from 1 to 25 microns, as illustrated by Fig. 1.

Jan 1, 1956

THE Leadville tunnel, a Bureau of Mines project designed to unseal Colorado's rich but flooded lead, zinc, and manganese mines, is still being advanced, although the work is encountering severe difficulties. Work on the tunnel, begun in 1943, was dropped for lack of funds in 1945, and started again last September. The tunnel is one of the nation's toughest mining jobs. Fifty firms and individuals, who were asked to bid on the job of continuing be- yond the 6600-ft mark, didn't even answer. The work was finally taken over by the Utah Construction Co. of Salt Lake City. Since last September, the face has been moved 1000 ft closer to the flooded Leadville district mines, and to the hoped-for length of 17.300 ft. Some apparent success has already been noted, with an unusual decline in the water level in some major mine shafts reported this winter.

Jan 5, 1951

By R. E. Collins

The existence of fluid migration across fixed boundaries in oil and gas reservoirs has been known for many years. Several techniques have been developed in the past for estimating The rate of migration across fixed boundaries as an aid in planninng field development and in the valuation of oilfied properties. The principal de/errc7nt to the use of these techniques lies in the rather extensive reservoir and field data required for ca1cula1ion.s of fluid migration. For this reason, a new, simplified procedure has been developed which makes possible the calculation of fluid migration with a minimum of field and resrvoir data. This new technique is based on certain. solutions of the differential equations describing flour in the reservoir which assume, for the portion of the reservoir of interest, that the formation can be approximated by a homogeneous rock of uniforrn thickness, that only a Single mobile fluid phase exists, and {hut fluid production at the well is solely a result of expun.rioti of rile resersoir fluds. The results of the, present work are compiled in a set of curves. These curves can he used to calculate both rule and cummulative fluid migration when the abovc assumptions ore ju.r/ifiril. The only data required for such calcu1ations are the production hisrories of all wells in the field, the permeability and porosity of the reservoir., the, compressibility and viscosity of the fluid. and the shape of the reservoir, INTRODUCTION The migration of fluids across fixed boundaries in oil and gas reservoirs has long been recognized as an engineering and economic problem, but no methods for estimating the extent of migration during the development stage of a reservoir have been published. The investigation reported here has been directed toward providing a simple technique for estimating the extent of such migration and has therefore been restricted to the simple case of a homogeneous reservoir of uniform thickncss containing compressible liquids. It is assumed that only a single mobile fluid phase exists and that fluid production at the wells is solely by expansion of the reservoir fluids. Obviously, few, if any. reservoirs conform to these assumptions during their entire productive life. On the other hand, most reservoirs approximate fluid expansion reservoirs during their initial stages of primary production. Consequently, the present work should be applicable during the field development of most reservoirs, regardless of whether or not they ultimately are gas cap, dissolved-gas, or water-drive reservoirs. The mathematical analysis of this problem has been outlined in the Appendix, while the results of the investigation are presented in the following discussion. DISCUSSION OF CALCULATION PROCEDURE SLNGLE Well, Ini-iimite Reservoir The procedure for calculating fluid migrations is based on solutions of the partial differentia1 equations describing the flow of a homogeneous compressible liquid in a homogeneous reservoir of uniform thickness. This differential equation has the form of the well-known diffusion equation. The equation, as applicable to our problem, is where p is fluid density, is porosity, EL is viscosity, c is compressibility,* and k is permeability; .r, y and t are the space coordinates and time. Derivation of this equation is given in the Appendix. The analytical solution of this equation for a single well of negligible radius producing at a constant rate. q, from a reservoir of infinite areal extent for a time, 1. can he readily obtained. From this solution the rate of flow and also the cumulative flow across a straight line segment of length, 1, at a perpendicular distance. 6. from the well can be computed. One end of the line must be on the perpendicular joining the well to the

By E. H. Greener, M. E. Fine

The internal friction (1/Q) of cobalt Fig. 1 (measured by an electrostatic dynamic method1) near 250°C begins to increase rapidly on heating and continues to increase until 560°C, the highest tem- perature measured. In the plot of log of 1/Q against 1/T, above 250°C the data nearly fit two straight lines intersecting at 400°C, approximately the temperature of the hexagonal-cubic transformation. The higher temperature branch corresponds to an effective activation energy of 6500 cal per mole, the lower temperature branch 11,000 cal per mole. Young's modulus Fig. 2 increases approximately

Jan 1, 1959

By J. P. Nichols

Modern vibrating screening dates from about 1910 at which time the forerunner of the present day two bearing and four bearing circular motion inclined vibrating screens were first introduced. These simple machines consisted of a screen box holding some kind of a screening surface to which was attached an off-center shaft or a shaft with an off-center weight which was rotated. The rotation of these shafts caused a shivering motion to the screen box and produced the first vibrating screen. In the 1920's and early 30's, the box designs were improved and the mechanisms designs were also improved and by 1940, vibrating screens were an important part of most process plants. In the early days when the screen sizes were dictated by how much could be shoveled onto the screen box and by the force that a particular mechanism could produce, not much thought was given to the proper sizing of the particular units. As mechanism and body design improved the ability to predict vibrating screen capacity at various openings became more important. In the late 1930's, a set of empirical capacities came to be used. with few modifications, these capacities are still in use today, both by those companies that use a formula involving only the amount of fine material in a feed, and by those companies using a formula in which the total feed to a particular screen is used. In either method of calculation, the empirical values are based on these ideal conditions: (1) The material being fed to the screen contains 25% oversize. (2) The feed to the screen contains 40% half size material. (3) The material has a bulk density of 1.6 T/Cu.M. (100 lbs/cu.ft.). (4) The screening surface has an open area of 50%. (5) The material is dry, free flowing and relatively cubical. (6) The maximum screening efficiency required is between 90 and 95%. It is obvious that these conditions do not occur in natural or crushed size distributions. Therefore, modifications must be made to these empirical values to allow for the calculation of a vibrating screen for a particular set of conditions. Before we consider these various modifications, let us look at what happens to material as it is acted on by a vibrating screen so that we can better understand why the modifications are nec-

Jan 1, 1982

By J. B. Wagner, B. Swaroop

The atomic ratios of oxygen to iron in zlarious corn-posilions of wustite in the vicinity oj the reported p to n transformation were determined in the temperalure range between 950" and 1250°C. For these conditions, equilibrium vacancy concenrations have also been determined at vatious mixtures of C0,-CO. The data show a continuos introduction of iron vacancies as oxygen is introduced into wuistite. No phase change is observed with in the wuustite field. However, the value of n in the isothermal oxygen pressure dependence, the weight change shifts to 1ower values as the concentration of oxygen increases. WUSTITE is a metal deficit semiconductor with the majority lattice disorder being cation vacancies. Using the notation similar to that of Kroger and ink,' the dissolution of oxygen into wiistite using C02-CO mixtures is represented by, WHere v+! denotes a cation vacancy with k effective negative charges and kh • denotes k electron holes, h -. Applying the law of mass action and assuming a dilute solution of defects in the wiistite yields Where the square brackets denote concentrations. Furthermore, when k = 2 the cation vacancies are completely ionized, and both the concentration of cation vacancies and the concentration of electron holes are proportional to the third root of the ratio, PC /PCo. This analysis is valid for one particular mael based on an ideal solution at elevated temperatures (in this case t > 1000°C). At lower temperatures, it has been shown2 that the pressure dependence of the electronic conductivity changes in a manner which suggests that vacancies interact with or "trap" electron holes. At the very high concentrations of defects, 10'' to 10" per cu cm, these simple models no longer hold. Recently Tannhauser,3 Geiger et a1.' Bransky and Tannhauser; and Hillegas' have found an apparent p to n transformation in wiistite in the temperature range of 950" to 1300°C. This junction was found by thermoelectric and electronic conductivity measurements. Geiger eta1.' found that the electronic conductivity became almost independent of the oxygen pressure at high temperatures and oxygen concentrations within the experimental error. In addition, Vallet, Raccah, and coworkers6'7 have reported the existence of several "varieties" of wiistite which were reported to exist within what was heretofor presumed to be a

Jan 1, 1968

By R. M. Waterstrat, B. N. Das, Paul A. Beck

The central region of the Ti-Mn system was studied by means of x-ray diffraction and metallography. The following intermediate phases were found: an MgZn2-type Laves phase having a wide range of homogeneity, the p-phase of unknozvn structure, and the + -phase with a large tetragonal unit cell, stable at 930°C and lower temperatuves. MaYKUTH, Ogden, and jaffee1 determined the soh-inh bility limits of manganese in and titanium. They also confirmed the structure of the intermediate phase TiMn2 which was previously identified as a Laves phase of the MgZn2 type.2 In the equiatomic region they found an additional intermediate phase, y, which presumably formed by a peritectic reaction at approximately 1200°C. This last observation was disputed by Rostoker, Elliott, and McPhers0n,3 who reported the formation of TiMn by a peritectoid reaction between 900" and 1000° C, but found no evidence of any intermediate phase other than the Laves phase at higher temperatures. Elliott and Rostoker4 reported furthermore that the X-ray diffraction pattern of TiMn could be identified as that of a o phase, although their data were not consistent with this inter~retation. Margolin and Ence6 presented X-ray diffraction data for the and TiMn, phases, and obtained metallographic indications for the existence of additional intermediate phases. They concluded from metallographic observations that two Laves phases are formed, separated by another phase, designated as &. A phase diagram for the Mn-Ti system has recently been published by Savitskii and Kopetskii,' which shows considerable disagreement with the work of Hellawell and Hume-Rothery,' in particular with regard to the terminal solid solutions based on the allotropes of manganese. The present investigation was undertaken primarily to clarify the phase relationships in the equiatomic region of the Ti-Mn system. The metals used in preparing the alloy specimens Were iodide titanium and electrolytic manganese, the latter having a nominal purity of approximately 99.9 pet. The electrolytic manganese was covered with a thick coating of a brown manganese oxide which was reduced by heating the manganese flakes for several hours at a temperature of 1100°C in an atmosphere of dry hydrogen. Three alloys, see Table I, were made using sponge titanium and manganese not treated in hydrogen. The alloys were prepared by arc-melting in an atmosphere of helium or argon. The composition of each alloy was calculated by assuming that the entire weight loss during melting was due to evaporation of manganese. Subsequent chemical analysis of certain alloys indicated that the compositions calculated in this manner were usually correct within 1.4 pct, as shown in Table I. All alloy specimens were wrapped in molybdenum foil before sealing them in silica tubes containing argon at a pressure of 1 atm at the annealing temperature. After quenching in cold water, the alloy specimens were bright and clean, with no evidence of any surface reaction. The alloys listed in Table I were examined metallographically, using an etchant consisting of 20 pet HNO3, 20 pet HF, and 60 pet Glycerine. powder for X-ray diffraction examination was prepared by crushing a portion of each annealed alloy

Jan 1, 1962

By M. A. Goudie

The deposits occur in a large salt basin of Middle Devonian age. The potash, the final deposit in the salt basin, results from several interrupted cycles of evaporation and dessication. The deposits are extensive, and, at first glance, relatively undisturbed. With more and more wells being drilled, it has now become evident that salt solution has played a large part in changing the original deposits, resulting in some cases in partial to complete removal of the potash and the underlying halite. The most dominant factor in the removal of salt by solution appears to have been tectonic movement and consequent faulting, probably of relatively minor dimensions but of major importance. Evidence which indicates the tilting of the evaporite basin to the north and northwest is shown by the changing pattern of the basin during succeeding eras of potash deposition. The potash minerals of most importance economically are sylvite and carnallite. Reserve calculations indicate that 6.4 billion tons of recoverable high grade potash in K2O equivalent exist in the basin. The Devonian salt basin, which contains the Saskatchewan potash deposits, extends from just east of the foothills in Alberta, north as far as the Peace River area, across Saskatchewan and into Manitoba as far east as Range 10 west of the First Meridian and south into Montana and North Dakota (Fig. 1). The basin is closed everywhere except to the northwest. The known potash deposits are confined almost entirely to the Province of Saskatchewan, with the exception of a small area in western Manitoba bordering the Saskatchewan boundary. The following discussion will concern only the Saskatchewan part of the basin. The evaporite series in the basin is defined as the Prairie Evaporite Formation of the Elk Point Group, of Middle Devonian age. Recent work done by potassium-argon dating methods has indicated an Upper Middle Devonian (Givetian) age of from 285 to 347 million years for the potash. The Elk Point Group consists in ascending order of the Ashern, Winnipegosis, and Prairie Evaporite Formations. The Ashern formation, with an average thickness of 30 ft, sometimes called the Third Red Bed, consists of dolomitic shales and shaly dolomites. The Winnipegosis, is a reef-type dolomite, usually with good porosity, and in many cases oil-staining, although to date no production has been obtained. The thickness varies from 50 to 250 ft. The Prairie Evaporite formation, varying from 0 to 600 ft in thickness, consists of halite with interbedded anhydrite and shale, with considerable amounts of potassium salts in the upper part of the formation. The potassium salts are chiefly chlorides, although very minor occurrences of sulfates have been re- ported. The anhydrite beds do not appear to be continuous, although generally one or two bands of anhydrite underlie the lowest potash zone and are used as marker horizons. The shale occurs as seams interbedded with the salts, as large irregular inclusions in the salts and as very fine particles in intimate mixture with the salts. The Prairie Evaporite Formation is overlain by the Second Red Bed member, the Dawson Bay Formation and the First Red Bed Member of the Manitoba Group, listed in ascending order. The Red Beds are shales which vary in color from red to green, maroon, grey, grey-black, and reddish purples. They serve as marker horizons for coring the potash. The Second Red Bed averages 14 ft in thickness, the First Red Bed 35 ft. The Dawson Bay Formation, which everywhere overlies the First Red Bed and the Prairie Evaporite Formation in the area under discussion, is a reef type of carbonate, in some places limestone, in others limestone and dolomite, with vugular to pinpoint porosity averaging 130 ft in thickness. In some parts of the area, it has a salt section near the top of the formation, usually with interbedded shales and limestones. In other parts of the area, it is waterbearing and the salt is absent. Detailed mapping has indicated that the areas in which the Dawson Bay is water-bearing are areas which have been disturbed by faulting. Where the Dawson Bay is salt-bearing, the porosity has been plugged by salt. The total thickness of the salt varies from between 600 to 700 ft in the center of the basin to zero at the northern edge of the basin (Fig. 2).* The salt-free area in the center of the Province is believed to have resulted from removal of salt by solution. Evidence from several wells suggests that salt removal has been a continuing process from the time of deposition to the present day. One well drilled between the Quill Lakes for potash information encountered

Jan 1, 1961

By Grover J. Holt

In order to provide a clear picture of the development of the sink-and-float process of concentration as applied to the iron ores of Minnesota, a few pertinent facts should be brought out concerning the ores and the products of concentration. Iron ore is primarily a cheap commodity handled in immense quantities. The price of iron ore at present, based on a natural iron content of 51.5 per cent, varies from $2.55 to $2.70 per gross ton f.0.b. cars at the mine or washing plant in Minnesota. Last year 92,000,000 gross tons were shipped from the Lake Superior district (Minnesota, Michigan, and Wisconsin) to the furnaces. Concentrated iron ores have no greater value per unit of iron content than ores that can be mined and shipped direct from the shafts or open pits. For years only the higher grades of concentrating ores could be treated and sold in competition with the immense reserves of direct shipping ore available. These higher-grade "straight wash" ores required only the simplest treatment; namely, the washing out of fine sand from coarse ore particles. As the exhaustion of the " straight wash " ore is reached, rock is found replacing part of this sand, and the ore no longer responds to the former sizing treatment. Substantial tonnages of this marginal (jig ore) remained to be treated. Because of the limitations placed on concentrates by the furnaces—namely, low price of product and minimum amount of fines—iron-ore concentration oil has been and must continue to be a one-pass process. Only an increase in price or a change in structure of concentrates allowed by the ore consumer will encourage departure from this practice. Faced with the necessity of handling large tonnages, with the limitations mentioned, iron-ore research men have found their search for new and more efficient methods of treatment seriously handicapped and removed from the field of fine crushing. Sink-and-float treatment appeared to offer the best field in coarse concentration and has been proved by several plants to be well adapted to our problem. The use of ferrosilicon as a medium solid was decided upon. In our present practice, the ferrosilicon metal, carrying about 83 per cent iron, 15 per cent silicon and 2 per cent carbon and nonmagnetics, is crushed to pass 65 mesh and used without further sizing. When mixed with water the specific gravity of the medium may be controlled to within 0.02 per cent above or below the required gravity. Table I shows examples of a change in solid content of the medium for varying gravities. the I is based on clean ferrosilicon, whereas some contamination is always present in the mill circuit, tending to

Jan 1, 1947

By Grover J. Holt

In order to provide a clear picture of the development of the sink-and-float process of concentration as applied to the iron ores of Minnesota, a few pertinent facts should be brought out concerning the ores and the products of concentration. Iron ore is primarily a cheap commodity handled in immense quantities. The price of iron ore at present, based on a natural iron content of 51.5 per cent, varies from $2.55 to $2.70 per gross ton f.0.b. cars at the mine or washing plant in Minnesota. Last year 92,000,000 gross tons were shipped from the Lake Superior district (Minnesota, Michigan, and Wisconsin) to the furnaces. Concentrated iron ores have no greater value per unit of iron content than ores that can be mined and shipped direct from the shafts or open pits. For years only the higher grades of concentrating ores could be treated and sold in competition with the immense reserves of direct shipping ore available. These higher-grade "straight wash" ores required only the simplest treatment; namely, the washing out of fine sand from coarse ore particles. As the exhaustion of the " straight wash " ore is reached, rock is found replacing part of this sand, and the ore no longer responds to the former sizing treatment. Substantial tonnages of this marginal (jig ore) remained to be treated. Because of the limitations placed on concentrates by the furnaces—namely, low price of product and minimum amount of fines—iron-ore concentration oil has been and must continue to be a one-pass process. Only an increase in price or a change in structure of concentrates allowed by the ore consumer will encourage departure from this practice. Faced with the necessity of handling large tonnages, with the limitations mentioned, iron-ore research men have found their search for new and more efficient methods of treatment seriously handicapped and removed from the field of fine crushing. Sink-and-float treatment appeared to offer the best field in coarse concentration and has been proved by several plants to be well adapted to our problem. The use of ferrosilicon as a medium solid was decided upon. In our present practice, the ferrosilicon metal, carrying about 83 per cent iron, 15 per cent silicon and 2 per cent carbon and nonmagnetics, is crushed to pass 65 mesh and used without further sizing. When mixed with water the specific gravity of the medium may be controlled to within 0.02 per cent above or below the required gravity. Table I shows examples of a change in solid content of the medium for varying gravities. the I is based on clean ferrosilicon, whereas some contamination is always present in the mill circuit, tending to

Jan 1, 1947

By Ernest Gayford

THIS is a nontechnical paper on flotation, subdivided under three general headings: (1) Definition of flotation; (2) what flotation is now doing in Utah; and (3) what is the future of flotation? . DEFINITION T. A. Rickard defines flotation1 as "the act or state of floating," from the French flottaison, water-line and fitter, to float. The dictionary defines flotation as "the science of floating bodies." The flotation process is a method of concentrating ores by frothing. Weinig and Palmer 2 define flotation as follows: What is the flotation process? Briefly, it consists in the agitation of finely divided ore in water containing bubbles of air or gas, a small amount of oil and, usually, other reagents, soluble and insoluble; under these conditions the small parti- cles of native metals, sulfides, arsenides, antimonides, selenides and tellurides show a tendency to attach themselves to the 6lms of the bubbles, and are thus carried to the surface of the water. The oxidized gangue minerals, such as quartz, feldspar, limestone, hematite, etc., show much less affinity for the bubbles, are easily wetted by the water, and either remain in suspension in the water, or sink to the bottom of the vessel. If the bubbles are sufficiently stable they can be removed, carrying their load of sulfide-mineral particles with them. Thus there can be effected a separation of the two classes of minerals from each other, assuming that the grinding has been sufficient to unlock all of the particles of different composition. The separation does not depend upon differences in specific gravity of the various minerals; in fact, the sulfides are usually heavier than the oxides, and some of the heaviest sulfide minerals are the easiest to float. A particle of mineral may be so large, however, that its weight will counteract its affinity for the film of the bubble. In most cases the ore must be fine enough to pass a screen having at least 48 meshes to the linear inch. Taggart defines flotation as follows : Flotation is a method of wet concentration of ores in which separation of mineral from gangue is effected by causing the mineral to float at or above the surface of a body of liquid pulp while the gangue becomes or remains submerged. The method

Jan 1, 1928

By Waldemar Lindgren

The following pages present data accepted by many geochemists and geologists regarding the succession of minerals and the temperatures of formation in ore deposits affiliated with igneous rocks. They also present the individual views of the author on the composition of the solutions that were active and on the mode of deposition. He does not regard these views as speculations or hypotheses but as forming a well motivated and consistent theory. It is not certain, however, that all investigators will subscribe to them. Introduction The mining engineer may not always be interested in the field of stability and temperature of origin in the mineralogy of ore deposits, but he certainly is interested in the succession of minerals because this has a definite bearing on the understanding of the ores and on the best processes of extraction. It is proposed, therefore, to summarize in plain language the principal features of succession as shown in metallic ores. Chemical analyses of ores are always important, but the real knowledge of succession—sometimes called paragenesis-—of ores has been gained only in the last 20 years, by the study of polished sections. The study of hand specimens threw much light on the subject—as shown, for instance, by Breithaupt, whose "Paragenesis," written a hundred years ago, is still useful—but the results have been modified by our slowly gained understanding of the processes of replacement. Indications of Temperature Melting Points.—In the first place, a distinction must be made as to whether the ore is a product of magmatic consolidation, of pegmatitiza-tion or of hydrothermal activity. Most of the ores fall in the latter class. In any case, the melting points, although of importance, are not definite indications. In a magma the oxides and sulfides are likely to be among the earliest crystalline products (magnetite, ilmenite, zircon, corundum,

Jan 1, 1937

Would you give us a short biographical sketch including your birthplace, education and current activities? I was born Jan. 16, 1920 in Minneapolis, Minnesota, and lived there the first 22 years of my life. I also spent quite a bit of time on a farm about fifty miles north of Minneapolis owned by relatives. During the Depression, we lived off of ten cows and about fifty chickens. I'm a full-blooded Swede all along the line, and I'll be the last one in my family since my wife is not of Swedish descent. I attended Macalester College, a small school in St. Paul, to study for the ministry originally. However I soon realized that I really didn't have the talents for the ministry and I could probably do as much or more in a field where I did have some talent.

Jan 3, 1974

By R. S. Shoemaker, R. M. Darrah

Expanded markets for copper in the past few years and a consequent search for new ore bodies have revitalized the widely known but seldom applied method of producing copper called heap leaching. Heap leaching is defined here as the process applied to oxide ores which have been mined solely for the purpose of leaching. In this case, all costs of mining the ore become a part (and a substantial one, as will be shown) of the cost of the copper produced, whereas in dump leaching the mining cost has already been accounted for as a stripping cost for the sulfide ore. Of course, with newly opened ore bodies, stripping costs may be divided through accounting procedures, between the copper produced by the mill and that obtained by leaching, but in general this type of operation must be economic on the basis of the sulfide ore alone. Heap Leaching Requires Low Capitalization Heap leaching, as a beneficiation method, is unique in that it is the only process used for the recovery of a metal in which the time involved from mining the ore to metal production is measured in months instead of hours or at the most, days. Then too, after the ore body has been depleted and mining has ceased, metal production will continue for some substantial period of time. Heap leaching is also unique because unlike any other method of beneficiation, metal recovery cannot be accurately forecast ahead of time and recovery will never approach that of a conventionally milled sulfide ore or even that of a vat leached oxide ore. Counter-balancing this drawback, however, is the relatively low capital expenditure necessary to put a heap leaching operation into production and the consequence that smaller ore bodies which would not support the higher capital cost involved in a vat leaching plant can be made into producers. Stated more simply, in heap leaching the operator accepts low recovery in exchange for low capital costs and low break even point. Whether the operator chooses vat leaching with its higher recovery and higher capital costs, is a mater of economics which depends in part on the nature of the ore to decide. For instance, an ore that will vat leach in 7 to 10 days using 7 pounds of sulfuric acid per pound of copper produced might use double or triple that amount of acid during the months that are required for heap leaching.

Jan 12, 1968

By L. W. McKeehan

IT is no longer necessary, if it ever was, for your annual lecturer to apologize for including in his remarks frequent references to the arrange-ment of metal atoms in crystals and for basing his arguments that metals behave as they do upon their crystal structure. Neither will any objec-tion be raised because the large metallic crystals of which we will speak are hard to prepare and of negligible commercial interest. The particular set of physical properties we propose to discuss-ferromagnetic proper-ties-may require more justification. Very few in this audience are primarily, or even remotely, interested in the ferromagnetic behavior of the metals they handle. By no means all of you ever deal, by choice or by necessity, with metals which display any ferromagnetism at all, and even those who study or control ferrous metallurgy must usually depend upon electrical engineers for assistance in ferromagnetic applications. My excuse for talking about such an obvious specialty is, like all Gaul, divided into three parts. In the first place, the members of the com-mittee who select the annual lecturer must wish the speaker to confine himself to matters he has at least thought about before he prepares his speech. In the second place, the study of ferromagnetism in crystals has, as you will soon realize, suffered in the not-too-distant past from inade-quate metallurgy. Further progress probably depends upon proper use being made of the skill and knowledge of some members of the Institute of Metals Division who have not, before today, been asked to think about the problems presented here. Finally, there is at least a sporting chance that the ferromagnetic properties of a few metal crystals will give some insight into the more generally interesting properties which they share with nonferromagnetic metal crystals.

Jan 1, 1934

By P. K. Koh, G. C. Dunn

Si-Fe single crystals in a number of selected orientations were cold rolled 70 pct and analyzed to obtain quantitative (110) pole figures. Stable end orientations were ddetermined, and the effect of orientation on deformation behavior was investigated. WHEN single crystals are cold rolled sufficiently, they rotate into end orientations that are stable or unchanged in position with additional deformation. The end orientations of heavily cold-rolled iron crystals, positioned in holes in copper to limit lateral flow and to simulate polycrystalline conditions during deformation, were determined by Barrett and Levenson.' They found that the sum of the end orientations, a pole figure for all the crystals studied, reproduced the essential features of the cold-rolled texture of polycrystalline iron. In. an investigation of Fe-Si alloys, Barrett, Ansel, and Mehl' observed little effect of silicon content on the textures of heavily cold-rolled samples. Since alloys with less than 4 pct Si are known to have the same slip systems as iron," it seems logical to expect that they would also have the same end orientations as those for iron. Whereas Barrett and Levenson in their study of single crystals were interested in the problem of the origin of the cold-rolled texture of polycrystalline iron, the present authors are more interested in the final cold-rolled textures of single crystals of Si-Fe from the point of view of their relationship to subsequent recrystallization phenomena which will be reported in another paper. Nevertheless, such points as the tendency of an end orientation not to rotate (stability), the tendency of a pole concentration to spread out, and the tendency of the crystal to widen during cold rolling become interesting separately when the initial orientations are selected already in end orientations. Also the initial orientations having a [I101 axis parallel with the transverse direction, which include the two end orientations (111) [Ti21 and (001) [110], comprise a series that needs further clarification regarding the way such crystals rotate during deformation. Finally the present use of quantitative pole figure methods* represents an advance over the X-ray photographic method employed by Barrett and Levenson in their work on end orientations. The present investigation provides information on the cold-rolling behavior of two groups of Si-Fe crystals: 1-—crystals initially oriented in recognized end orientations for iron crystals with a [I101 direction parallel with the rolling direction, and 2— crystals initially oriented with a [I101 direction 90" to the rolling direction and in the rolling plane. For the second group, there is a 90" range between the (001) [110] orientation and the (110) [001] orientation. Since the 35" portion of this range from (110) [OOl] to (111) Di2] was included in a previous investigation," only the remaining 55" portion from (111) fii2] to (001) [I101 needs further consideration. Also, since both (111) [xi21 and (001) [I101 are end orientations for iron crystals,' there might be a critical orientation* or orientation range be- • W. W. Martin and C. G. Dunno noted that (112) [Till was such a critical orientation. tween them such that early in the deformation an orientation within this critical range splits into two orientations. Upon further deformation, these two orientations rotate to produce a final texture consisting of (001) [1101 and (111) [?i2] components. The end orientations obtained are discussed in connection with the work of Barrett and Levenson, while the observed tendency for lateral flow of crystals in these orientations is treated in terms of the theory of Hibbard and Yen.' Lateral flow according to the theory increases with deviation of the plane containing the rolling direction and the slip direction from a position perpendicular to the plane of rolling. Experimental Procedure Single crystals in sheet form with preselected orientations were prepared by methods that have been described elsewhere." Three lots designated A, B,

Jan 1, 1956

By John P. Huger

me phase diagram for the system Ag-Si has been established by thermal analysis. The diagram is a simple eutectic type with a eutectic at 3.0 pct Si and 840°C. From the liquidus curve and with the aid of regular solution theory, the thermodynamic properties of the liquid Ag-Si system at 1420 °C have been determined. Silicon exhibits positive deviations from Raoultain behavior at all compositions, while silver exhibits both positive and negative deviations. MEASUREMENTS of silicon activities in liquid iron alloys by means of distribution studies between the immiscible liquids silver and iron have been reported by Chipman, Fulton, Gokcen, and caskey.' The applicability of this technique is dependent, however, on the accuracy of the silicon activity values in the Ag-Si alloys, particularly in the dilute silicon region. Darken and Gurry2 have shown that log ?si/(1-xSi)2 is approximately linear with composition, but uncertainty exists in the extrapolation to dilute solutions. Their calculations are based on the old Ag-Si phase diagram of Arrivaut3 and any variation in the position of the liquidus curves will strongly influence the extrapolation. The purpose of this study is to redetermine the Ag-Si phase diagram and calculate the associated thermodynamic properties. EXPERIMENTAL The Ag-Si phase diagram was determined by thermal analysis of liquid alloys. The alloys were contained in a 35 mm alumina crucible under a protective stream of purified argon. The crucible was placed inside a 64 mm alumina tube fitted with a gas-tight, water-cooled, copper head. The tube and assembly were heated in a manually controlled globar furnace. The temperature was measured with a Pt, Pt + 10 pct Rh thermocouple in a high-temperature porcelain protection tube. The thermocouple calibration4 was checked against the melting point of pure silver at the start and during the course of the experiments, and against both gold and silver at the completion of the experiments. The alloys were prepared from granular silver analyzing 99.95 pct Ag and powdered silicon analyzing 99.88 pct Si and 0.026 pct Fe. Approximately 150 g of alloy were used for each run. The composition of the alloy was determined by withdrawing samples of the liquid alloy with a vycor tube-aspirator bulb device. Analysis of solidified samples agreed, for alloys containing less than 23 pct Si, within ±0.3 pct Si of the calculated composition. Duplicate samples showed a variance within 50.05 pct Si of the mean analysis. The alloy was heated to 100' to 20pC above the estimated liquidus temperature and then the furnace was adjusted to give an average cooling rate of 2" to 7°C per min. A cooling curve was obtained by taking potentiometer readings at 15-sec intervals. Several analyses were made by recording the thermocouple output on a high-speed, Stip-chart recorder, with the exception of run NO. 11, a minimum of two thermal analyses were made for each alloy and the cooling curves then obtained duplicated the liquidus and eutectic temperatures to about 1°C. RESULTS The results of the thermal analysis are given in Table 1, and are represented as the Ag-Si phase dlagram, Fig. 1. The eutectic composition was found

Jan 1, 1963

By Luis Toron, Salvador Cortes-Obregon

THE Oaxaca coal fields, shown in Fig. 1, are located in the Alta Mixteca region in the states of Oaxaca, Puebla, and Guerrero. Known outcrops are scattered over 3125 square miles. It is probable that further exploration will reveal a more extensive area of deposits. The region is of great importance to Mexico, as at present the only sources of coal are the fields near the U. S. border. Steel mills are also located in the North, and finished products must travel 600 to 800 miles to the area of consumption in central Mexico. The oaxaca coal, only 120 miles south of Mexico, D.F., lies close to several iron ore deposits. If this

Jan 1, 1955

By S. D. Baumer, P. M. Hulme

B. M. Larsen (U. S. Steel Co., Kearny, N. J.)—Could we have some sort of an estimate on the cost of calcium carbide for this treatment? Also, if you used calcium carbide on carbon-saturated iron, would some effect hold back the reaction? P. M. Hulme (authors' reply)—As far as I know we have not worked on carbon-saturated iron. About 3½ pct C is the highest we have worked on. As far as cost goes, it depends on how much sulphur You have to take out. It will run anywhere from $0.75 to $2.00 a ton overall cost including the cost of carbide per ton of metal treated. That is, using the efficiencies that we show in this paper. We are getting better efficiencies now. T. L. Joseph (University of Minnesota, Minneapolis, Minn.)—Did you say 2 lb of calcium compound? Mr. Hulme—That is based on 10 lb of calcium carbide per lb of sulphur removed. D. E. Babcock (Republic Steel Corp., Youngstown, Ohio)—We have run this type of desulphurization process at the blast furnace. We have desulphurized between 100 and 200 at the blast furnace and taken the iron right out of the furnace with an injector system. The process gave us quite varied results; stratified iron, high sulphur on the top and low sulphur on the bottom, and we decided it was impractical. Mr. Hulme Just what was the type of injection equipment? Dr. Babcock—Nitrogen gas for one injection method and we used fairly large gun equipment. We followed the same general type of pattern you show only on a larger scale. Mr. Hulme—It sounds very much like what we call the gale of wind method. We have very erratic results with that. Dr. Babcock—We have tried several types, and particle sizes. The operation was not satisfactory. Mr. Hulme—Of course, we have never tried it on that scale except on a continuous basis. That is the reason we abandoned the idea of working on 35 ton ladles on a batch principle and took it as it came out of the cupola and treated it on the fly on a continuous basis. Dr. Babcock—When you compare the relative effectiveness of the process as carried out, it does not give a very favorable comparison of that process which is already developed. We did not feel it was worth the

Jan 1, 1952