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By A. F. Brock

The cut-and-fill mining methods in use in the mines of The International Nickel Company of Canada Limited, at Falconbridge Nickel Mines Limited, in the Sudbury District, and at McIntyre Porcupine Mines Limited in the Porcupine District, are typical of the general cut-and-fill practice in both the base-metal mines and the gold mines in the Province of Ontario. The following pages describe the methods in use. HORIZONTAL CUT-AND-FILL STOPING Horizontal cut-and-fill stoping, as practiced in the mines of The International Nickel Company of Canada Limited, falls into two main classifications: (I) transverse cut-and-fill stoping, where ground conditions or wide ore bodies make it necessary to establish narrow stopes and pillars across the width of the ore body; (2) longitudinal cut-and-fill stoping where ore body widths and ground conditions allow safe mining of the full width of the ore body. Transverse Cut-and-fill StopiNg General Stoping Layouts Stope and Pillar Widths.—For transverse stoping, experience has indicated that narrow stopes and pillars, 27 ft. 6 in and 22 ft., respectively, are most satisfactory. These width are multiples of 5 ft. 6 in., which is the center to center dimension of a standard square set. Thus any stope, or block of stopes, can be readily converted from cut-and-fill to square set-and-fill if ground conditions should warrant such a change. Formerly, pillars were established 16 ft. 6 in. wide, the equivalent of the width of three square sets, with the intention of extracting the pillars by mining an overhand slice one set wide and an underhand slice two sets wide. However, subsequent experience proved that a two-set overhand slice is so much more efficiently mined than a one-set slice, and 22-ft. pillars have been made standard. Chutes.—The stope chutes are established on the longitudinal center line of the stopes and are spaced at 22-ft. centers from footwall to hanging wall. The footwall chute is usually from 5 to 10 it. from the footwall of the stope. It is offset where necessary at an angle of 52° and vertical chutes are carried from the offset at 22-ft. centers. In sections of the ore body where a flat hanging wall would cut off hanging-wall chutes within a few cuts of the sill, it has proved to be more economical to use temporary chutes or slushers, or both, for these first few cuts, rather than to el permanent chutes at the hanging wall.

Jan 1, 1946

By L. P. Davidson

ThE new electrolytic zinc plant of the American Zinc Company of Illinois commenced operation in April 1941. The simple flowsheet using the standard current density and the economic reasons that dictated it are given herewith. The Evans-Wallower Zinc Co. built an electrolytic zinc plant at Monsanto, Ill., in 1929 and operated it for about two years. The plant stood idle from 1932 and was purchased by the American Zinc Co. in 1940. Because of the condition of the equipment, excepting the motor generator set, a complete rebuilding was necessary. The Fairmont City plant of the American Zinc Co. could treat the leach residues, the purification cake and the skimmings from the melting furnace in its various plants. This possibility permitted a simple flowsheet with good economic results. The flowsheet is shown in Fig. I. The calcined concentrates are leached in mechanically agitated tanks with spent electrolyte and such ferric iron solution as necessary. When the acid has been neutralized and the iron coagulated, the fluid is discharged to settling tanks. The underflow from these thickeners is filtered on a Moore filter; the filter cake leaves the plant for retreatment and the filtrate joins the thickener overflow. Zinc dust is added to this solution until the copper and cadmium are precipitated. The pulp is filtered through Shriver presses, which deliver the purified solution to stor- age tanks, and the copper-cadmium-zinc cake is shipped for retreatment and recovery of these three metals. The purified solution is electrolyzed; the regenerated acid is returned for use in the leaching plant and the cathode zinc, after stripping, goes to the melting furnace, from which it is cast in slabs. The skimmings from the melting furnace are shipped to the Fairmont City plant for reduction to metal in the retort furnaces. The choice of this simple flowsheet was made possible only because of the facilities of the Fairmont City plant. The long leaching pried, with high acid content and high temperature which characterize the high-density process, gives a higher zinc extraction but also dissolves more impurities, which must be removed. The same is true to a lesser degree of the multi-step leaching of the western low-density plants. By the sacrifice of some initial extraction, solutions can be obtained that are relatively easy to purify and give good ampere efficiency. This loss in initial extraction is made up in the retreatment of the residues in the Waelz plant. The impurities that accompany the zinc thus extracted are inconsequential when the Waelz product is treated in a distillation plant. It was recognized that this flowsheet would require a somewhat greater amount of sulphuric acid—-eithcr as acid or as sulphate sulphur in the calcine—because of poorer washing. The sulphuric acid plant at Fairmont City could deliver 60" Bè. acid to compensate for the sulphate loss and the cost would be less than the cost of more intensive washing.

Jan 1, 1943

By L. P. Davidson

ThE new electrolytic zinc plant of the American Zinc Company of Illinois commenced operation in April 1941. The simple flowsheet using the standard current density and the economic reasons that dictated it are given herewith. The Evans-Wallower Zinc Co. built an electrolytic zinc plant at Monsanto, Ill., in 1929 and operated it for about two years. The plant stood idle from 1932 and was purchased by the American Zinc Co. in 1940. Because of the condition of the equipment, excepting the motor generator set, a complete rebuilding was necessary. The Fairmont City plant of the American Zinc Co. could treat the leach residues, the purification cake and the skimmings from the melting furnace in its various plants. This possibility permitted a simple flowsheet with good economic results. The flowsheet is shown in Fig. I. The calcined concentrates are leached in mechanically agitated tanks with spent electrolyte and such ferric iron solution as necessary. When the acid has been neutralized and the iron coagulated, the fluid is discharged to settling tanks. The underflow from these thickeners is filtered on a Moore filter; the filter cake leaves the plant for retreatment and the filtrate joins the thickener overflow. Zinc dust is added to this solution until the copper and cadmium are precipitated. The pulp is filtered through Shriver presses, which deliver the purified solution to stor- age tanks, and the copper-cadmium-zinc cake is shipped for retreatment and recovery of these three metals. The purified solution is electrolyzed; the regenerated acid is returned for use in the leaching plant and the cathode zinc, after stripping, goes to the melting furnace, from which it is cast in slabs. The skimmings from the melting furnace are shipped to the Fairmont City plant for reduction to metal in the retort furnaces. The choice of this simple flowsheet was made possible only because of the facilities of the Fairmont City plant. The long leaching pried, with high acid content and high temperature which characterize the high-density process, gives a higher zinc extraction but also dissolves more impurities, which must be removed. The same is true to a lesser degree of the multi-step leaching of the western low-density plants. By the sacrifice of some initial extraction, solutions can be obtained that are relatively easy to purify and give good ampere efficiency. This loss in initial extraction is made up in the retreatment of the residues in the Waelz plant. The impurities that accompany the zinc thus extracted are inconsequential when the Waelz product is treated in a distillation plant. It was recognized that this flowsheet would require a somewhat greater amount of sulphuric acid—-eithcr as acid or as sulphate sulphur in the calcine—because of poorer washing. The sulphuric acid plant at Fairmont City could deliver 60" Bè. acid to compensate for the sulphate loss and the cost would be less than the cost of more intensive washing.

Jan 1, 1943

By Lyon F. Terry

INCREASING domestic demand for products, a sharp reduction in exports to Europe, and a rise in imports from South America were the chief features of the economic side of the industry in 1940. As the war progressed it became evident that exports to former European customers were being cut off or drastically reduced, leaving heavy inventories of products in the hands of many American refiners who had anticipated larger demands from the belligerents. Stocks of motor fuel reached burden-some proportions early in the year for the added reason that refining operations were stimulated by heavy demand for heating oils. Excessive tanker rates for Gulf to Eastern Seaboard movements during the first part of 1940 contributed to the accumulation of products on the Gulf Coast, where refinery gasoline prices were forced to extremely low levels by midyear. Tanker rates receded to normal during the summer but have since risen again to the approximate equivalent of pipe-line tariffs from the Mid-Continent.

Jan 1, 1941

By G. Ferrara

The reserves of lead and zinc ores in the metalliferous district of Iglesias in south-western Sardinia are today estimated at about 30 million tons, grading from 4 to 10% Pb + Zn. Of these reserves, about 40% are in the mines owned by AMMI Sarda S.p.A. The working of these resources goes back to ancient times. Not infrequently, traces of old Roman workings and remains of ancient implements are come upon in the higher parts of some of the ore bodies. Exploitation of these mines on larger scale, however, dates from the middle of the 18th century. Initially, the more accessible zones of the ore bodies and the richer ores were worked - the galena and the rich oxidized ores (calamine* with 25-35% Zn), which were often found in large masses, the enormous empty cavities of which still remain. The poorer grade deposits have been gradually rendered workable by the development of technology - the perfecting of the

Jan 1, 1970

By AIME AIME

ON THE occasion of the eightieth birthday of Captain Robert W. Hunt, the Iron and Steel Committee of the Institute, desiring to commemorate the great contributions made to the steel industry by Captain Hunt during his long career, conceived the idea of a Hunt Medal to be awarded annually by the Institute for meritorious contributions to the art of making steel. The project was received enthusiastically by all to whom it was proposed, especially by Captain Hunt's partners and employees who considered it their right, and asked for the privilege of -. - raising the necessary funds within their own circle. This was agreed to, and the Institute has received from them $7500 as an endowment fund to provide an annual award, and $1000 for the expenses of providing of medal.

Jan 1, 1920

By N. V. Hansell

l. INTRODUCTION. THE last few years have shown an increasing interest in the subject of beneficiating iron-ores -in all iron-producing countries. In the United States, this movement has been slower than in certain parts of Europe, for the obvious reason that the abundance and relative cheapness of the Lake Superior iron ores has hindered the development of enterprises for the preparation of low-grade ores. Gradually, however, conditions have changed. The world's consumption of iron is increasing enormously. Being in 1900 about 40,000,000 tons, in 1910 ii was already 60,000000; and there is no reason to doubt that for the near future the increase in iron-consumption will continue at the same rapid rate, especially with, the development of China, certain parts of Africa, and other regions which have hardly been touched as yet by modern industrialism. It is. therefore, not surprising that apprehension is felt that the known available iron-ore resources of the world are gradually being depleted. Signs of this feeling are the recent investigation, under the direction of the U. S. Geological Survey, of the iron-ore resources of the United States, and the estimate presented to the last International Geological Congress, at Stockholm, Sweden, of the iron-ore resources of the world. These investigations have emphasized the fact that the known high-grade ore-deposits are limited in extent, and will, at a not distant future, be exhausted, compelling the iron industry to depend for raw material on the enormous deposits of low-grade ores which are distributed over almost all the world. The discovery of new deposits of high-grade ore, in countries not yet thoroughly explored, will not materially change this prospect. Of course, the part which such new deposits will play in the future cannot be forecast. The difficulty and cost of transportation will probably exclude many of them from use at the present centers of the iron industry.

May 1, 1912

By J. C. Fisher

Martensite transformations in steels and other alloys are characterized in part by the absence of composition changes during the growth of a new phase. Transformation occurs rapidly, and there is insufficient time for long range diffusion or partition of alloying elements to take place; martensite reactions in alloys thus are similar to phase transformations in single component systems. A fundamental understanding of martensite transformations in steels is impossible without knowledge of the free energy change upon transforming austenite (face centered cubic iron containing alloying elements) to ferrite (body centered cubic iron containing alloying elements) of the same chemical composition. The present paper assembles the best information available concerning the influence of temperature and composition on this free energy change. Most of the material has been taken from the work of Johansson,' Mehl and Wells,2 Zener3,4 and Smith;5 and indirectly, through these authors, from the work of Austin.6 In agreement with the generally accepted viewpoint, martensite is assumed to be an ordered solution of carbon in ferrite of the same composition as the parent austenite; only at high temperatures and low carbon concentrations is the carbon in ferrite distributed at random. The properties of the disordered solution are estimated by extrapolating the known properties of iron-carbon solid solutions into the range of supersaturation, and the free energy change associated with ordering is estimated from the theory developed by Zener. By incorporating Smith's recent thermodynamic measurements and Zener's theory of ordering, the present analysis modifies previous estimates of the free energy change associ- ated with martensite transformations. Consider a two component system consisting of a solvent A and a solute B. Let Na and Nb represent mol fractions of A and B respectively, let aa = raNa and ab = YbNb represent activities, and let superscripts 1 and 2 refer to phases 1 and 2. The partial molal free energies of A and B in phases 1 and 2 can be summarized as follows: free energy standard state Fa' - Fao1 = RT In an1 pure A' Fa2 - Fa2 = RT In aa2 pure A2 Fb1 - Fbo = RT In ab1 pure B Fs2 - FB2 = RT In aB2 pure B. The free energy of a gram atom of phase 1 is* AF1 = Na'Fa1 + Nb'Fb1 and that of phase 2 is AF2 = NA2FA2 + NB2Fb2. A martensite transformation from phase 1 to phase 2 requires Na1 = Na2 = Na and NB1 = NB2 = Nb, and the free energy change per gram atom accompanying transformation is AFi-2 = NA(Fa2 - Fa1) + Nb(Fb2 - Fb1) = NA[RT In (aA2/aA1) + AFa1?2] + Nb RT In (aB2/aB1) = Na[RT In (ra2/ra1) + AFa1?2] + Nb RT In (TaVTB1). [1] where yn2, yn1, yB2, yB1 are activity coefficients, and where Ma'+* is the free energy change upon transforming a gram atom of pure A from phase 1 to phase 2 at the temperature in question. For martensite transformations in plain carbon steels, A = iron (Fe), B = carbon (C), 1 = austenite (7). 2 = ferrite (a), and Eq 1 is AFr ?a= NFe[RT In (rf.a/rfer) + AFF.r?a] + TVc RT In (eca/rc1)- L2] Nothing is known concerning the values of yFea and yca for carbon concen- , trations in excess of 0.025 pct. However, the approximation rf.7 = 7f." = 1 cannot be appreciably in error for small carbon concentrations, and Eq 2 reduces to Afr-a = NfeFfer?a1 + NC RT In (rca/rcr)- [3] Johanssonl and Zenera have calculated MFfr?a from the specific heat measurements compiled by Austin.6* Their calculated values agree closely, and are summarized in Table 1. The activity coefficients relative to graphite for carbon dissolved in iron vary with temperature according to the relationships d In rcr/d(1/T) = AHcr-R dlnyca/d(l/T) = AHCa/R where AHc? and AHca are the heats of solution of graphite in y and a iron. Assuming the values of AH to be independent of carbon concentration and temperature, In rCr = AHcr/RT + I1 In rca = AHCa/RT + 12

Jan 1, 1950

By Colin J. Dixon

The full realization of the potential of computers in geological in- formation system demands new approaches to the machine representation of information. At the same time, the feasibility of such a system, particularly in commercial field, demands greater freedom in input preparation and a degree of standardization in the arrangement of subject matter system. The paper describes some of the basic notions of project "GEOSEMANTICA 70". The aim of the project is to devise means of storing real geological informations in a machine rather than the representation of the information in human language form. This is seen as the only long-term solution to the problems of the complex vocabulary of geology and the complex syntax of geological description. Effectively, a machine language is being defined, consisting of a set of symbols and a date structure for representation of geological and related information. Beyond this, is the definition of a set of rules allowing the use of constrained text as an input/output medium. The investigation is oriented primarily to the representation and handling of information about mineral deposits and the associated geographic, economic and engineering information.

Jan 1, 1969

By R. H. Wightman, G. H. Adams

In order to secure good results in the prevention of accidents, it is generally recognized that the desire for such accomplishment, as well as the aggressive and constructive action to achieve it, must emanate from the Top Management and permeate successively down through the "Chart of Authority" to the workmen. Several years ago, with the above as a basis and with full support of the Top Management, the Mining Department started a program of selling the foremen and bosses the idea that safety could be achieved and that it was desired and required. Using psychology, persistence and numerous other methods, the foremen and bosses were finally impressed with the idea that "It can be done" and "It will be done." With this in mind, new ideas were brought forth by the foremen and bosses regarding the caving operation and the specific jobs in the operation. These new ideas were taken up in round-table discussions and resulted in certain changes in the undercutting method and the actual drawing of the blocks. These changes resulted in increasing fragmentation of the blocks which prevented the usual hang-up areas in the blocks. With the rock smaller in size and within reasonable reach from the tapping drifts, accidents were prevented in the tapping section. At the same time, an enforced campaign of housekeeping throughout the mine was undertaken with very beneficial results. The foremen and bosses then, in turn, educated and trained the workers themselves to become safety conscious. In so doing, a constant reminder was given on all jobs assigned that the job was to be done safely as well as efficiently. No man is assigned a job who is not qualified for the type of work required. Efficiency and safety go hand in hand. Safety Rules To supplement and aid this safety conscious attitude, certain safety rules applicable to our operation, a modified block caving system of mining limestone, in addition to the established state regulations, were put into effect and enforced. The specific rules referred to above and which will be mentioned below are in most cases simply a means of applying and complying with the very adequate "Mine Safety Orders" issued by the Industrial Accident Commission of the State of California. Some of the safety rules and policies are as follows: All men are required to wear safety

Jan 1, 1950

By S. F. Shaw

IT IS generally recognized that the natural gas absorbed in petroleum plays the leading r6le in moving the oil through the sands to the well and supplies the energy that delivers the oil to the surface when the wells are flowing. It is the purpose of this paper to note the amount of oil that could be lifted by this gas if 100 per cent. efficiency were obtained and the efficiencies actually obtained in the use of this gas. An article in MINING AND METALLURGY,' stated that in a Wyoming field, with a pressure of 300 lb. per sq. in., there would be absorbed 65 cu. ft. of gas per barrel, or 1.55 cu. ft. per gal. of oil. The writer does not know if data have been obtained, by experiment, for pressures beyond those indicated in this article, therefore, for the purpose of illustration, he has projected this curve to obtain figures for pressures greater than 300 lb., although probably experiment will show that the extended line is not quite correct.

Jan 1, 1926

By J. Parke Channing

IT, HAS been my privilege to be Chairman of Engineering Council for very nearly three years, during which time Mr. A. D. Flinn, the. Secretary, and myself, have seen the organization develop until it is functioning smoothly and accomplishing what it can with the money at its disposal. The earliest attempt at what may be called an Engi¬neering Council, of which. I have any knowledge, was made six or seven years ago when the four Founder Societies each appointed two men, who occasionally met to discuss matters submitted to them which were of importance to, the, profession as a whole. I was one of the representatives of the American Institute of Mining Engineers.

Jan 1, 1920

By R. C. FLEMING

MINING rock asphalt for use as a paving material is an industry which has grown with the spread of the good roads movement. "Mineral Industry During 1930" reports asphaltic pavements constructed, including maintenance and repair but excluding pavement constructed with road-oil, cut-back or emulsified asphalt, as grown from 23 million square yards in 1911 to a high of 144 million in 1927. In 1930 the same source reports 106 million square yards of such paving laid and, in that year, 664,871 tons of native rock asphalt were so utilized. Many states contain rock asphalt deposits of greater or less importance but in only a few places are the de¬posits being mined commercially. In the year cited Ken¬tucky produced 305,024 tons of bituminous sandstone, Texas 270,138 tons, mostly bituminous limestone, while Alabama, Oklahoma, California and Utah produced 89,709 tons of bituminous rock for road construction. In addition Utah produced 37,906 tons of the purer asphaltic products, gilsonite, wurtzilite and ozokerite, for other uses. Speaking generally, the rock asphalt is a sandstone or limestone naturally impregnated with asphalt to an extent that makes it an ideal road surfacing material without mixing or treatment other than crushing. The asphalt content of the commercial product runs 8 to 12 per cent.

Jan 1, 1933

By B. L. Landrum, P. B. Crawford

The rise of a new laboratory model for studying tran-sient fluid flow problems, is described. The theory of he model is based on the analogy between the equa-ions which describe the flow of compressible fluids in porous media and the conduction of heal m solids. The "thermal model" is used to study the Iransient Pressure distributions during fluid displacement in five Standard well patterns. The studies indicate quantita-ively how die pressures change with lane at any poit in the reservoir. It was found that, in general, the equipressure contours are more radial about the wells early in the program than after steady-state conditions are established. In addition two studies of fractured five-spot patterns are presented to illustrate the opplicability of the model for a wide range of reservoir conditions. INTRODUCTION In reviewing the oil recovery techniques involving fluid displacement it was found that a very considerable quantity, if not all of the fluid within the pattern, mav be displaced (during a time-dependent or transient period rather than the usually applied steady-state conditions. Since the oil is displaced during a transient period, it was believed desirable to study the nature of the transients for several of the commonly used fluid displacement patterns. A literature review indicated fairly complete studies of the streamlines and isopotentials for steady-state: yet few data were available on the transient displacement process. Several simulated steady-state multiwell displacement programs were carefully mapped by Foster and Lodge on an electrical conducting sheet as early as 1875, hut the more recent work of Muskat provides the best source for steady-state phenomena having direct petroleum production applications. In order to study the transient phenomena a new lab-oratory model was developed which is based on the similarity of the equations that describe the flow of fluids and the conduction of heal. The equations describing heat flow were developed early in the nineteenth century. Regorous solutions tor most transient problems are in gcneral complex and usually limited to fairly restricted houndary conditions.2 the thermal model may be used to obtain approximate solutions for many transient problems without some of the restrictions required for analytical solution. The application of the analogy between heat conduc-. tion in solids. electrical flow and fluid flow, in a porous media has long been recognised. Techniques originally developed for the solution of heat conduction prol?lems have in many instances proved useful in ohtaining solutions to fluid flow prohlcms. Ir is not surpri5ing then that a heat conduction or thermal model might bf usefull in sludying transient fluid flow. As an example ol the problems suitable for the study with the thermal model, transient pressure distributions during fluid displacement programs are studied for the five-spot, line-drive, staggered line-diibe. seven-spot 211 two fractured patterns. A model was constructed of an iron plate of geometry similar to the reservoir patterns under study. The principle of mirror images as suggested by Bryan was employed in shaping the model. A temperature differential was obtained by soldering two sections of copper tubing to the plate at points analogous to the well location in the field. Hot and cold water was passed through the tubing. The temperature distribution, analogous to the pressure distribution in the field. was obtained a a function of time from thermocouplcs distributed over the plate.

By J. F. Elliott

PRESENT knowledge of the usual metallurgical slags indicates that they are, for the most part, rather complex in behavior and as yet there is no ready means for describing, in a simple manner, the behavior of any one of them. One of the best known slag systems is the iron oxide-silica-lime ternary which is the basic "solvent" in a number of important metallurgical refining operations, the basic open hearth being one of the most important. In this operation, the slag dissolves such components as sulphur, phosphorus, manganese oxide, and magnesia. Considerable study of this slag system and the behavior of these additions has been carried out in the past by a number of authors, as has been summarized in several critical reviews.','2 However, except for determination of the activity of iron oxide, only a limited amount of effort has been directed towards developing, from these data, an understanding of the general behavior of the basic solvent. Reported here are the results from a series of calculations based on data from the literature which permit a semiquantitative evaluation of the activities of iron oxide, silica, and lime (plus magnesia) in the ternary system at 1600°C. The preliminary results, which were reported briefly at a symposium held by AIME in 1953, have been revised and are completed. The steps in the calculation are as follows:* I—establish the activity curves and the curve of the excess molar free energy of mixing at 1600°C for each of the binary systems, 2—construct the activity surface of iron oxide for the ternary from the data on the binary systems and information available in the literature for the ternary area, 3—determine the surface of excess molar free energy of mixing for the ternary system from the activity surface of iron oxide and from the molar curves obtained for the binary system, and 4—differentiate the ternary surface of the molar excess free energy of mixing to obtain the ternary surfaces for the logarithm of the activity coefficients for silica and lime (log rslo, and log rc.~). Si0,-Fe,O: Schuhmann and Ensio have measured the activity of iron oxide in simple iron oxide-silica slags when in equilibrium with y iron. Their data recalculated to 1600°C are shown in Fig. 1. Also included is a point representing a measurement by Gokcen and Chipmana of the activity of iron oxide at 1600°C at the point of saturation with solid silica. For convenience and in accordance with other treatments,' the calculations are based on the hypothetical component, FelO, which is obtained by converting all the analyzed iron in the slag to FeO. In spite of Schuhmann and Ensio's conclusion that the activity of iron oxide in the system does not vary with temperature over the experimental range of 1258" to 1407"C, the data are corrected to 1600°C assuming that temperature does have an effect. It was felt to be most reasonable to assume that the term log rr.10 is a linear function of the reciprocal of the temperature. Reyu has indicated that an effect of temperature on the activities in this system is to be expected from the Schuhmann and Ensio data. In essence, the correction consists of multiplying the experimental value of log rf,,o by the ratio of the experimental temperature in Kelvin to 1873°K. The magnitude of the correction is not large, being approximately 11.5 pct of the experimental value of log rve10. A very minor correction was necessary to compensate for the fact that the slags were in equilibrium with y iron in the experiment, while at steel-making temperatures they would be in equilibrium with liquid iron. Data for the correction were obtained from Darken and Gurry. The standard states established are pure liquid iron oxide (FelO) in equilibrium with pure liquid iron (with the appropriate amount of oxygen in solution) and pure liquid silica. The method of plotting in Fig. 1 is convenient for the calculation of the activity of liquid silica and permits a reasonable extrapolation for the activity of Fe,O in the ranges where no experimental data are available. The uncertainty in the extrapolation to infinity at one terminal where Nvelo = 1 for the usual Gibbs-Duhem integration is reduced considerably by this method. The region of two coexisting liquid phases is estimated to range from 1.8 to 41.7 mol pct Fe,O. The nature of the activity curve for the single-phase region indicates that the activity of iron oxide across the two-phase region is very close to 0.39. Computation of the function log ~F,,o/(1— NF,,o)' for this region (dashed line) in conjunction with the curve through the adjusted experimental data indicate the best probable value of 0.382 for alPe,o in the two-phase area. The line from 0 to 0.018 Nf~~o is obtained by assuming that the component follows Henry's law. In this range, the value for log rveto is 2.59. Appropriate mathematical manipulation of the plotted linet yields the activity curves for the The curve AF", the excess molar free energy of mixing (actual minus ideal), as shown in Fig. 3 is also computed from Fig. 1. This curve is required for subsequent calculations. CaO-Fe,O: The phase diagram for the lime-iron oxide system when in equilibrium with liquid iron is not well known but there appears to be no intermediate compound present. This fact as well as the activity values for Fe,O extrapolated to the CaO-Fe,O binary from Taylor and Chipman' tend to indicate somewhat negative deviations from ideality for the activity curves for the two components. Strong indication of this is evident in Fig. 1 where are plotted the points computed from the estimated activities of Fe,O for the binary system.' It appears that the best line through the data is a horizontal straight line. Because of the general indication of the slight negative departure from ideality, the line is extrapolated horizontally to NF~,o = 0. It is con-

Jan 1, 1956

By L. Weaver

THE Tennessee Copper Co.'s mines are in the southeast corner of the state of Tennessee, Polk Co., in the well-known Ducktown copper basin. Their new circular production shaft will eventually be the only ore hoisting shaft, and is located for handling ore from Boyd, Calloway, Mary, and Cherokee mines. A circular, rather than a rectangular, shaft was decided upon because: 1-The circular shaft section is stronger when lined with concrete. Reinforcing steel was not required, thus reducing lining cost by one- quarter. 2-Water sealing was desired; it was thought it could best be done with a concrete lining followed by pressure grouting to eliminate water seeps. 3-The shaft labor saving equipment could best be used in a large opening, so the round section was made for economy, sinking, mucking, concreting and water sealing. Less shaft steel is used than could have been possible with steel sets. There are no posts required; center beams and Tee plate assembly placed at 10 ft hold the 100 lb steel guide rails.

Jan 1, 1950

By N. F. Fiore, M. F. McGuire

THIS communication describes a series of experiments in which dislocation etch pitting was used to ascertain the depth of damage in crystals which were mechanically polished or which were cut with either a commercial metallographic cut-off wheel,* a com- All specimens were cut from single crystals of American Smelting and Refining Co. 99.999+ pct pure copper which were grown from the melt by the Bridge-man technique. The test specimens were disks, with faces being (111) planes and the disk axis a (111) direction. The disks were annealed in a vacuum of 10-5 Torr for 24 hr at 950°C prior to cutting or polishing and were given a light electropolishing in an ortho-phosphoric acid bath before etch pitting. Both Youngs1 and Livingston's2 reagents were used for etch pitting and the reagents gave identical quantitative results; however Livingston's reagent produced less staining and so all photomicrographs shown are of {111) surfaces etched with this solution. The surface of the annealed crystals showed well-defined subboundaries and a density of dislocations of about 1 X 106 per sq cm excluding those present in subboundaries, Fig. 1. The depth of cold work produced during mechanical polishing was determined after an annealed specimen was mounted in a paraffin holding block to protect it from extraneous damage. The exposed (111) surface was ground on metallographic papers and then polished on billiard cloth through 0.05-p alumina abrasive. It was necessary to remove about 0.3 mm (-0.01 in.) to obtain a structure representative of the annealed sur- face, indicating that the crystal was damaged to this depth during mechanical polishing. The cold work caused by standard cutting methods was measured in another series of tests in which cuts

Jan 1, 1967

By D. P. Harris

This paper surveys a few of the quantitative exploration models that might be of interest to an ex-plorationist seeking to apply methods of operations research to mineral exploration. A general development of each model is presented, and the model is evaluated relative to the exploration activity. Finally, a philosophy of exploration and mineral resources is presented, and a possible exploration strategy incorporating concepts of some of these models consistent with this philosophy is proposed. The high cost of conducting an effective exploration program has generated an increasing interest in methods of optimizing the allocation of the resources of a firm engaged in mineral exploration. As a step towards this, mathematical models have been formulated which are designed to quantify those variables of mineral exploration in such a manner that they can be integrated with all phases of the firm's operations so as to optimize its profit objective. QUANTITATIVE MODELS General: Exploration models express at least two concepts: mineral occurrence and effectiveness of search. In simplest terms, an exploration model might be formulated mathematically as follows: P(X) = F(X) . G(X), where P(X) = the unconditional probability of discovery of X deposits, F(X) = the probability of occurrence of X deposits, and G(X) = the probability of discovery of X deposits, conditional upon their existence in the search area. With these general models as a basis of reference, some of the specific exploration models are examined below. The Allais Model: DEVELOPMENT - M. Allaisl performed the first study in which a philosophy of exploration was formulated into a probability framework. His objective was to estimate the economic profitability of the exploration of the Algerian Sahara. Allais divided the Algerian Sahara into blocks of land (called cells) 10 km square and defined the random variable, X, as the number of mining districts per cell. Thus, F(X) would describe the probability of 1, 2, or n mining districts occurring within any cell of the search area. Allais reasoned that his best information as to the form of the distribution, F(X), was the number of mining districts per cell that had been found in well explored areas in the world, such as the Western States of the U.S. He found that the Poisson function produced a reasonably good fit to the distribution of districts in these explored areas: where? is a parameter, such as the average number of districts per cell. Thus, by determining the value

Jan 1, 1968

By J. O. Betterton, D. S. Easton

A detailed investigation was made of the phase diagram of silver-zirconium, particularly in the region 0 to 36 at. pct Ag. The system was found to be characterized by two intermediate phases Zr2Ag and ZrAg and a eutectoid reaction in which the -zirconium solid solution decomposes into a-zirconium and Zr2Ag. It was found that impurities in the range 0.05 pct from the iodide-type zirconium were sufficient to introduce deviations from binary behavior, and that with partial removal of these impurities an increase in the a-phase solid solubility limit from 0.1 to 1.1 at. pct Ag was observed. The phase diagram of the silver-zirconium system is of interest as an example of alloying a transition metal from the left side of the Periodic Table with a Group IB element. Silver would normally act as a univalent metal, its filled 4d-shell remaining undisturbed during the alloying. However, there is a possibility that some of the 4d electrons might transfer to the zirconium. An insight into such a question can occasionally be obtained by comparison of phase diagrams. The silver-zirconium system forms part of a more complete review of various solutes in zirconium in which these valency effects were studied.' Earlier work on the silver-zirconium system was done by Raub and Enge1,2 who investigated the silver-rich alloys. After the start of the present experhents, work on this system was reported by Kemper3 and by Karlsson4 which for the most part agrees with the phase diagram presented here. EXPERIMENTAL PROCEDURE The alloys were prepared by arc casting on a water-cooled, copper hearth with a tungsten electrode and in a pure argon atmosphere. Uniform solute composition was attained by multiple melting on alternate sides of the same ingot. Progressive improvements in the vacuum conditions inside the apparatus during the course of the experiments reduced the Vickers hardness increase of the pure zirconium control ingot from 10 to 20 points, observed initially, to negligible amounts at the end of the experiments. Such hardness changes in zirconium are a well known indication of purity. For example, -01 wt pct additions of oxygen, nitrogen, and carbon increase hardness by 6, 10, and 3 VPN respectively. '9' Further verification that the final casting technique did not add a significant quantity of impurities was obtained when pure zirconium was arc cast and then isothermally annealed in the vicinity of the allotropic transition. The transition was always observed to take place over the same temperature range as in the original crystal bar. The alloy ingots were annealed in sealed silica capsules for times and temperatures which varied between 1 day at 1300°C and 60 days at 700°C. The best method found to prevent the reaction of the zirconium with the silica was foil wrapping of molybdenum or tantalum. With this method, samples of pure zirconium were found to be unchanged in hardness after annealing for 3 days at 1200°C. In most of the experiments the protection of these foils was supplemented by an additional layer of zirconium foil inside the molybdenum or tantalum foil. The alloys, foil, and the capsule were outgassed at pressures in the range 10 to l0-7mm Hg in the temperature range 800" to 1100°C before each anneal in order to remove hydrogen and other impurities, and to provide a suitable container for the high purity, inert atmosphere, which is essential in the annealing of zirconium. The temperature measurements were made with Pt/Pt + 10 pct Rh thermocouples calibrated frequently during the experiments against the melting points of zinc, aluminum, silver, gold, and palladium. For the longer anneals the sum of various temperature errors was generally well within ± 2°C. For short-time anneals and during thermal analysis the overall temperature error is considered to be within ± 0.5°C. The compositions of the alloys from the quenching experiments were determined by chemical analysis at Johnson Matthey and Company, Ltd., under the direction of Mr. F. M. Lever. The actual metallo-graphic samples were individually analyzed in every case, and prior to the analyses two or more sides of each specimen were examined to insure that the specimen was not segregated. The sum of the solute and solvent analyses was in each case within the range 99.9 to 100.1 pct. In the course of the experiments, minor impurities in the range 0 to 500 ppm were found to have significant effects on the zirconium-rich portion of the phase diagram. Similar effects had been encountered previously in other zirconium phase-

Jan 1, 1959

By H. L. Talbot, A. J. Hall, R. S. Young

A method for the chemical differentiation of oxidized cobalt from sulphide cobalt in complex mine and concentrator products is of considerable interest to a number of mining companies throughout the world. At Rhokana Corporation, in Northern Rhodesia, for instance, cobalt is found chiefly in the sulphide form, as carrollite, but a cobalt oxide mineral also occurs irregularly underground, and relatively small quantities in the mill feed from time to time are difficult to detect visually at the concentrator. The oxide cobalt is not amenable to the sulphide flotation process used at Rhokana and nearly all of it passes into the tailing. The occasional period when high tailing losses occur with no appreciable change in the cobalt content of the mill feed has naturally been disturbing to the concentrator staff, who had no means of determining whether an influx of cobalt oxide ore or laxity on the part of the mill flotation operators as responsible for these results. A procedure for determining oxidized copper minerals, based on their solubility in dilute sulphuric acid saturated with SO2, has been used for many years in the copper industry. In the presence of cuprite the procedure fails, but otherwise it gives results quite satisfactory for control pur- poses. Empirical methods for determining oxidized forms of zinc and lead have been proposed, but they are generally unsatisfactory except in isolated cases of a very simple ore. No published procedure for determining oxidized forms of cobalt or siinilar elements has come to the authors'notice. Experimental Procedure There are obviously two alternatives in attacking a problem of this nature. One is to employ a solvent for oxide cobalt that will not dissolve cobalt sulphide. The other is to find a substance capable of oxidizing the cobalt sulphide to sulphate, which of course is water-soluble and can then be leached from the water-insoluble oxide cobalt. A representative sample of Rhokana cobalt oxide ore was secured, ground to minus 200-mesh, and carefully rolled to furnish a standard sample for this work. The analysis of this material gave the following percentages: Co, 0.55; Cu, 1.64; Fe, 2.98; S, 0.08; SiO2, 41.42; Al2o3, 11.20; CaO, 13.82; MgO, 3.80. As a source of cobalt sulphide a similar large sample of carrollite was prepared, analyzing Co, 23.36 per cent; Cu, 27.32; and S, 31.13. This sample of course was not pure carrollite, but was the best obtainable in quantities sufficient for a standard intended for considerable work. It was a pure sulphide sample, microscopic examination showing only carrollite, a little bornite, and gangue, with no visible sign of oxidized ore present. A wide variety of reagents as used in an effort to selectively dissolve oxide cobalt or to oxidize sulphide cobalt to

Jan 1, 1949