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By Wei-Kao Lu, G. Bitsianes

An improved general rate equation for a one-ditnensional gas-solid system has been derived. Fov the veversihle interfacial chemical reaction, there are concentrations of gaseous reactant and product at the reacting zone to be considered. They have been calculated with the velations fuvnished by the constraints on the system, namely, quasi-steady state and equimolal counterdiffusion of the gases. The results of the diffusiori study of Evans, Watson, and ,Mason based on the "dusty gas" model have been applied here. The interfacial chemical reaction is taken as first-order with respect to the concentration of the gases involved. The equation has proper dependence on gas composition and on solid structure through the relative values of Knudsen and normal diffusivities. The existence of the total pressure gradient inside the specimen has been predicted and confirmed experimentally. In a previous communication' we introduced a general rate equation for gas-solid reactions by considering the contributions of chemical reaction at inter- phase boundaries and diffusion through the solid product layer simultaneously. These equations, for one-dimensional and spherical specimens, take care of the whole range continuously from purely diffusion control to purely chemical reaction control. In this paper we study only the one-dimensional system. The corresponding rate equation is reproduced here: Of the two terms on the right-hand side of Eq. [I], the first represents the contribution of interfacial chemical reaction and the second that of gaseous diffusion. The shortcomings of Eq. [I] are that in its derivation the interfacial chemical reaction was assumed to be irreversible and the diffusion rate of gaseous product was not considered. Any pressure effects building up within the porous media were also neglected. Evidently. these simplifying assumptions will limit the general applicability of these equations. The rate of reduction of iron oxide by hydrogen, for instance, is very sensitive to the concentration of water vapor in the main gas stream, as has been reported by cewan' and by Quets et a1.3 Furthermore, the gaseous phase at the reacting interface will contain an appreciable amount of the gaseous product of reaction. If this were not true, a sufficiently high concentration gradient for the outward diffusion of the gaseous product could not be maintained. With these shortcomings in mind, Eq. [1I cannot be rigorously ap-

Jan 1, 1967

By M. Deighton, R. N. Parkins

The metals Cd, ,Wg-, Sn, TI, Zn, and Zr reach a peak hardness after a criticfir1 deformation by rolling- and then soften with fwther rolling-, thereby exhibiting wovk softening. Optical metallography on Cd, Mg, and Zn shows that work softening is accompanied by a change in grain size occurring during deformation. The creep of zinc from -1l° to +60°C at stresses in the range of 7.9 to 17.3 kg per sq mm is given by € = e0 -t- Bt + Kt +at6. The third and second rate constcints are related by the equation a = K~ K6 and their stress and temperature dependence can be represented by the equations K = A, . exp - (u, - Bu)/kT. A model based upon the stress activated glide of sub-boundaries is proposed which qualitatively accounts for the metallog-raphic observations. Expressions, which are in reasonable quantitative agreement with the ex-pe~inzental observations, are derived for the creep of zinc. THE term "work softening" has been used previously by Polakowski1 and by Cottrell and stokes2 to describe phenomena where further strain of a deformed material leads to a decrease in flow stress. In both cases, however, the conditions were changed for the second straining. Here, the term "work softening" is intended to refer to a decrease in flow stress after continued straining in the same direction at the same temperature: work softening is the antithesis of "work hardening". Work softening of zinc was reported by chadwick3 and in discussion of that paper Jenkins4 indicated that cadmium also work softens. More recently work softening has been reported5 in two magnesium alloys, -99.5 pct Mg. Chadwick found that the hardness, 0.2 pct Proof Stress and the UTS of electrolytic zinc all increased with progressive cold reductions up to 30 pct and then progressively decreased with further rolling. Gay and Kelly6 used a back-reflection X-ray technique to study the effect of cold rolling zinc and found that although deformations greater than 2 to 5 pct reduction in thickness produced some recrystallized grains, deformations greater than 40 pct caused com-plete spontaneous recrystallization. At deformations greater than 60 pct the material was found to consist solely of recrystallized grains, -20 pm diam, the size of which decreased with increasing reduction and was much less than the initial grain size of the annealed material (-300 pm diam). Similar results were also reported for cadmium, tin, and lead.6 Gay, Hirsch, and Kelly' suggest that these experiments indicate recrys-tallization takes place when the dislocation density exceeds a certain value. However, no measurements of MATERIALS AND EXPERIMENTAL PROCEDURE The purity of the metals used in this work is indicated by the following figures: Zn (99.99); Cd (99.94); Mg (99.95); T1 (99.99). The zirconium was iodide crys tal bar with a probable purity of about 98 pct. The metals were obtained in the form of 0.25 in. thick strip or 0.425 in. diam rod by various fabrication methods and then annealed to ensure complete re-crystallization. Hardness-deformation curves were obtained at room temperature by rolling 4 in. thick strip under conditions which left a surface adequate for diamond pyramid hardness tests immediately after rolling. The hardness was taken as the niean of five impressions made using a 5 kg load and the time elapsing between rolling and making the last impression never exceeded 5 min. The zinc specimens for creep testing were from 3 by 3 by 4 in. cast slabs which were rolled to 0.10 in. thickness starting at 350°C and finishing cold. The resulting strip was cut into pieces 1 in. wide and annealed in batches. With suitable choices of annealing temperature between 100" arid 400°C five different grain sizes varying from 4.54 x 10' to 3.03 x l05 grains per sq cm (530 to 20 um diam) were obtained. Creep tests were done in compression using a sub-press, based on a design after Ford,8 in which the strip is compressed between dies 0.100 in. wide under conditions of plane strain. Since there is no lateral spread of the material, the area of contact between the dies and strip remains constant throughout the test and the application of a constant load, using the load maintaining device of a hydraulic testing machine, resulted in a constant stress. Covering the dies with strips of P.T.F.E. reduced frictional effects to a minimum. The creep strain was obtained by measuring the travel of the crosshead of the testing machine to a sensitivity of 0.1 pct reduction in thickness. The complete subpress assembly was contained in a steel box and for tests above the ambient this was filled with liquid paraffin and heated electrically. Temperatures below the ambient were obtained with a cooling mixture of acetone and solid carbon dioxide in the box. The liquids were stirred and the temperature of the specimen, which was controlled to ±0.5"C dur-ing a test, was measured by a thermocouple placed near the dies. Compression testing of cylindrical specimens was also carried out in the subpress using hardened flat discs separated from the test material by P.T.F.E. sheets which obviated barrelling of the specimens. Various initial strain rates were supplied by the hydraulic testing machine, and the deformation was measured by a clock dial gage resting on the cross-

Jan 1, 1970

By E. T. Turkdogan, J. H. Swisher

The solubility of oxygen in zone-refined iron was determined in the temperature range.from 881" to 1350°C. The solubility in a iron at 881°C ms found to be about 2 to 3 ppm; in y iron, the solubility was found to increase from about 2 to 3 ppm at 950°C to about 25 ppm at 1350°C. The permeability of oxygen in an iron -0.1 pct Al alloy was determined in the y iron range, using an internal oxidation technique. By combining the permeability and solubility data, the diffzisivity of oxygen in y and a iron was calculated. The oxygen diffusivity in solid iron may be s~immarized as follows: 8820 For 6 iron and IN a recent paper, Hepworth, Smith, and Turkdogan1 reported on the solubility, permeability, and diffusivity of oxygen in 6 iron, together with permeability data for oxygen in a iron. In the present investigation, similar measurements were made in the ? phase region. In addition, a solubility measurement was performed in the a phase region to permit calculation of the diffusivity of oxygen in a, iron. References to early work on this subject are given in the previous publication.' EXPERIMENTAL Solubility Measurements. The oxygen solubility was determined by equilibrating cylindrical samples 0.3 in. diam by 14 in. long of zone-refined iron in water vapor-hydrogen gas mixtures. The zone-refined iron was prepared by B. F. Oliver of this laboratory, using an apparatus and technique described elsewhere.2'3 Six zone-melting passes were used to achieve a total impurity level of about 30 ppm. Of this 30 ppm, the combined nickel and cobalt content was about 20 ppm, oxygen was 4 ppm, and all oxidizable impurities less than 1 pprn each. A vertical resistance furnace wound with molybdenum wire was used for the experiments. The temperature was measured before and after each experiment with a Pt/Pt-10 pct Rh thermocouple. In the gas train, flow rates of hydrogen and argon were measured with capillary flow meters, and the resulting mixtures were passed through a column containing 90 pct oxalic acid dihydrate and 10 pct anhydrous oxalic acid to obtain predetermined ratios of H2O to H2. The vapor pressure of H2O above this mixture as a function of temperature is well-known.4 The exit gas was ana- lyzed periodically for H2O, and good agreement (+3 pct) with the calculated composition was obtained. The zone-refined iron specimens were held in the furnace for a sufficient length of time for equilibration, e.g., 18 hr at 1350°C and 1 week at 881°C, then quenched in a brine solution. After removing the surface oxide from the samples by machining, duplicate analyses were obtained by a combined vacuum fusion-infrared method; oxygen analysis was reproducible within 2 ppm. Permeability Measurements. The permeability of oxygen in alloys containing about 0.1 pct A1 was determined by internal oxidation and measurement of the subscale thickness as a function of time. The experimental alloys were prepared by adding aluminum to electrolytic iron (grade 104A plastiron) that had previously been vacuum-carbon deoxidized. The resulting ingots contained about 20 ppm O, 100 pprn C, 40 pprn Si, 50 ppm Mo, 20 ppm P, 20 ppm S, and 20 pprn Zr as the principal impurities. After hot rolling the ingots to 1-in.-thick slabs, specimens were machined from the stock in the form of rectangular plates, 4 by 5 by 2 in. The general procedure for the permeability experiments was the same as those for the solubility measurements. The specimens were cooled in a reducing atmosphere rather than quenched, however, in order to maintain a clean surface for measurement of the sub-scale thickness. This measurement was made on a polished cross section of each specimen, using a microscope with a micrometer stage. The inclusions formed at the lowest temperature 1033°C were too small to be seen with an optical microscope. An electron micrograph showing the size and shape of individual particles is shown in Fig. 1. The dark band in the picture is a boundary between two subgrains. The subscale thickness in these samples was measured with an optical microscope after heavily etching in 2 pct nital, which gave contrast between the subscale and the unoxidized zone.

Jan 1, 1968

By J. G. Baragwanath

CUBA'S lateritic iron ores, occurring on the northern coast of that island, though known to the Spaniards. did not receive any general attention until the close of the Spanish-American War. Preliminary studies of these deposits at that time indicated that the limonite contained small percentages of nickel and chrome, and it ryas subsequently discovered that although the average nickel content was only approximately 0.6 per certain limited areas of ore were suffiniently high in nickel to be considered commercial provided a suitable process fur its recovery could be developed. Early in 1937, Pardners Mines Corp. began a series of investigations which led to the development of such a process. Coincidentally, this company acquired option' on certain properties in the Levisa Bay and Moa Bay regions and conducted a systematic campaign of exploration by test pits and hand-auger holes in the course of which an aggregate of 90.000.000 tons of ore was developed in eight deposits.

Jan 1, 1945

By C. F. Jenkins, G. V. Smith

Serrated plastic flow in stable austenitic alloys based on Fe/Ni has been shown to be related to the presence of carbon and/or chromium in the systems. Strength peaks and plateaus in the serrated-flow temperature region for a commercial alloy correlate with an increased dislocation content, arising, presumably, from enhanced multiplication as a result of a strong interaction between dislocations and solute atoms. The data generally support a mechanism controlled by migration of vacancies, with the energy for vacancy motion being modified by the presence of chromium. Chromium atom -dislocation interaction is responsible for effects above 500°C, whereas the defect interacting with dislocations between 200" and 500°C is suggested to be a carbon-vacancy Pair. ThE phenomenon of jerky flow, serrated flow, or the Portevin-le Chatelier (P-C) effect in austenitic stainless steels is usually attributed to substitutional at1,2 mospheres1,2 or to precipitates&apos;-4 which form at dislocations during plastic deformation. On the other hand, evidence exists which supports a direct inter-stitial-dislocation interaction mechanism for serrated flow in fcc Ni-C,5,6 Ni-H7-9 and in nickel-austenites containing carbon." The present work consists in a study of serrated plastic flow in stable austenitic al-loys. The effects of carbon and of chromium were investigated separately, and a commercial stainless steel with different levels of interstitial impurity concentration was studied in an attempt to delineate the combined effects of the alloying elements. EXPERIMENTAL TECHNIQUES a) Materials and Fabrication. A commercial AISI 330 stainless steel and several specially prepared aus-tenitic alloys have been studied. The experimental alloys were prepared by arc melting the constituents under purified argon. Analyses of the materials are given in Table I. The commercial alloy was obtained as 5/8 in. bar stock and rolled to 0.092 in. sq, with several intermediate anneals. At this stage some of the material was annealed in Pd-purified hydrogen at 1100°C to establish different levels of interstitial content. All other heat treatments were in vacuum (10-5 torr). The "pure" alloy ingots were swaged to 0.120-in. rod and annealed in Pd-purified hydrogen at 1100°C. The analyses for these conditions are also contained in Table I. Following the above treatment, the final wire sizes Table I. Chemical Analyses of Test Materials Hrin Hydrogen at Cr, Ni, Alloy 1lOO°C wt pct wt pct C, ppm* N, ppm* Type 330 As-received 14.78 33.25 430 300 Type 330 64 14.78 33.25 40 50 Type 330 200 14.78 33.25 27 21 Fe/35 Ni 72 - 35.10 <10 62 Fe/35 Ni 200 35.10 <I0 44 Fe/35 Nil15 Cr 72 14.95 34.94 <I0 61 Fe/35 Ni/15Cr 200 14.95 34.94 <10 45 Fe/35 Ni/C $ 35.OM 380 *Sensitivity: N t 5 ppm Ct10ppm. f Nominal Ni content. % A master NiC alloy was used in preparation of this material; courtesy of D.E. Sonon. were obtained by either swaging or cold drawing. The test results did not vary with these techniques. b) Specimen Preparation. Two sizes of specimen and two gripping systems were used. i) 0.070-in. wire with a chemically milled gage section: 0.75 in. long, 0.060 in. in diam. These were fastened into grips containing tapped grooves. ii) 0.050 in. wire, gage length 1.5 in. Ball bearings were welded to the ends of the wires and the gage length was taken to include all material between the welds. Socket-type grips were used with these specimens. With specimens of type ii), joining was performed in a specially constructed brass jig, under argon, and automatic timing was utilized in the procedure. No adverse effects of welding were noted. Specimens were encapsulated and solution treated for 1 hr at temperatures selected to produce the same average grain size, -50 µ. Annealing twin boundaries as well as normal crystal boundaries were counted. The temperatures used are listed in Table 11. Table 11. Specimen Size. Temperature of Heat Treatment and Resulting Grain Diameters for Test Materials Recrystallization Resulting Material Condition Temperature Grain Sue AISI 330 Not H purified 0.070 120O°C 45 to 55µ in, wire AlSl 330 H , pure, 0.070 in. 1150°C 45to55µ wire Fc/35Nil15Cr Pure, 0.070 in. wire 1000°C 45tossp Fe/Ni Pure. 0.070 in. wire 775°C 45 to 55µ Fe/Ni/C Pure, 0.050 in. wire 850°C 10 to 20p AlSl 330 Not purified, 0.050 1150CC 45to55p in. wire AlSl 330 ti, pure, 0.050 in. 1150°C 45to55p wire

Jan 1, 1970

By D. Harrington

WHEN the word gas is mentioned in connection with mining, almost invariably it is inferred that the explosive gas, methane, is in mind and that it must refer to coal mining. While it is true that methane occurs, or is likely to occur, in almost any or all coal mines, it is also a fact that the metal mines of the world have in them by far a greater variety of gases than have the coal mines. In many cases the gases in metal mines are as dangerous to individuals as the gases likely to be found in coal mines; in some instances the metal mine gases are even more deadly. The coal mine is more likely to have methane than the metal mine, in rare instances it may have high percentages of nitrogen or high carbon dioxide, or there may be a deficiency of oxygen where the air is confined in a blind end or in a sealed region; much more rarely there are found in coal mines in relatively small percentages, ethane, or other hydrocarbons with odor of ether, gasoline or kerosene, or there may be minute percentages of hydrogen sulfide. In time of coal mine fire or explosion, there is likely to be high carbon monoxide (4 per cent. or over in some cases) and if the coal contains much sulfur, there may be some sulfur dioxide in the fire fumes. In metal mines there are a number of cases of occurrence of methane and attendant explosions; some metal mines have appreciable percentages of the decidedly explosive hydrogen; in some metal-mining regions carbon dioxide flows into the mine, fills the workings and overflows just like water. In other regions, at many working faces there are high-temperature gases containing a mixture of gases of sulfur (sulfur dioxide, hydrogen sulfide and possibly SO3 in some cases) together with carbon dioxide and nitrogen, and the deadly hydrogen sulfide in lethal proportions is found in some high-sulfide metal mines at blasting time. Carbon monoxide constitutes a decidedly dangerous day by day hazard in connection with metal-mine blasting, because of the heavy charges of dynamite that are used and the use of fuse, which in burning gives off much carbon monoxide. The poisonous gas hazard is accentuated because of the relatively small openings where metal-mine blasting is done and to the inefficient ventilation of the usual metal mine.

Jan 1, 1930

By R. K. Datta

Eluropium -activated yttrium vanadate, excited by short- and long-wavelength ultraviolet radiations, shows enzission lines near 6100A, the principal ones correspondirzg to transitions of EU+3 ions from 5Do to the F2 energy level. The ~neclmlallistns of absorption and etnissiorz of this phosphor have been empirically studied. The absorption is caused by two separate processes in the matrix. The phosphor YVO4:Eu and tlie matrix YVO, haue essentially the same resectance spectra in the region 2500 to 4000if. There are two broat ah~o?~ption bands: natnely, around 2600 and 3600A regions. Whet? compared with the reflectance spectra of the constituent oxides, namely, Y2O3, V205, Eu2 03, the absorption bands of the tnatvix and the phosphor in the short- and long-wavelength ultraviolet regions can be interpreted as due to charge-transfer processes involving i) Y-O and ii) 17-0, respecti~~ely. The excitation spectrum&apos; of the phosphor has two broad bands with peaks at about 2600 and 3600A regions. U can be postulated that enevgy absorbed under short- crud long-wavelength ultraziolet excitatzon, respectzcely, by Y-0 and V-O parts of the niatrix is transferred by radcatio~zless process to EU+3 ions. Thzs postulate can empirically be proved on the basis of the spectra of the systems (YVO4,-YPO4,):Eu. PO? ~ons do not have&apos; any appreciable absorption in the short or long uv regions. When P0&apos;t3 ions are substitlited for v0i3 ions in YVO,:Eu phosphors, the absorption and excitation in the lo~zg uv region are gradually reduced. Ailoreover, the £«+3 emission under 3650A excitation is decreased zuitlz increase in PO^ content, lt~lzereas the emission under 253711 excitation remains esserztially constant with as IILUCIL as 60 mole pct of YPO, in YVO,:En. EUROPIUM-activated yttrium vanadate (YV04:Eu) is a well-known phosptor.&apos;-3 When excited by cathode rays, 2537, or 3650A radiations, YV04:Eu emits typical narrow-band spectrum of EU&apos;3 fluorescence in the region of 5900 to 7100A, a very strong maximum occurring at about 6190A. This emission is considered to be due to 5Do — 7F2 transition of excite: EU*3 in 4f state. Moreover, the emission under 3650A excitation increases with temperature markedly. Because of these properties, YV04:Eu phosphor finds wide application in industries, namely, in color television tube, laser, and high-pressure mercury-vapor lamps. It is the purpose of this paper 1) to present the empirical study of the mechanism of absorption and excitation of YV04:Eu phosphor by ultraviolet radiation, and 2) to offer an explanation for the process of emission. It should be mentioned that a theoretical discussion on the mechanism of absorption in terms of the crystal or ligand field theory is beyond the scope of this paper. Empirical studies presented here are based primarily on spectroscopic and crystal-chemical investigations. EXPERIMENTAL i) Preparation of Materials. The synthesis of vanadate phosphorinvolves preparation of (Yi-.tEuj^Oj, blending the mixed oxide with an oxidic compound of vanadium, such as V205 or NH4V03, and firing the mixture at about 1000°C for several hours when YVO4:Eu forms as a primary phase. (Y1-xEux)203 compositions are prepared by coprecipitation of oxalates, and igniting them at about 1000°C. The vanadium compound is added in excess of the stoichiometric proportion for fluxing purposes. The charge is cooled, ground, and the excess of vanadium is removed by a hot wash (-80°C) of alkali or ammonia. Y(VP)04:Eu samples are prepared by mixing (Yi-xEux)203 with stoichio-metric proportions of (NH4)2HP04 and the vanadium compound. The mixtures are prefired at 700" to 800°C for 1 or 2 hr, then ground and refired at 1150°C. The firings of the phosphors are done in silica crucibles, and the homogeneity of the final products checked by X-ray diffraction analysis. ii) Spectroscopic Measurements. Diffuse reflectance sqectra of the samples within the range 2500 to 7000A are obtained by using CaF2 as standard in Cary Recording Spectrophotometer, Model No. 14. The emission spectra from phosphor plaques, excited under different ultraviolet sources, are obtained by a direct-recording spectroradiometer4 adapted with a grating monochromator with nearly constant dispersion. Maximym sensitivity in the spectral region from 2500 to 7000A is obtained with a quartz-windowed, S-20 response p$otomultiplier. The total&apos; band pass is kept about 30A. The spectra are calibrated against the light from a standard tungsten filament lamp reflected from a magnesium-oxide plaque. Brightness data given throughout this report $re measured from the height of the main peak (6190A) of the emission spectra. The excitation spectra are measured using sodium salicy-late as standard. RESULTS AND DISCUSSION The diffuse reflectance spectra of both pure and activated YV04, along with their constituent components, are shown in Fig. 1. YVO4 shows two broad absorption bands, namely, around 2500 and 3600A, respectively. Since there is little difference between the reflectance spectraoof YVO4 and YVO,:Eu in the uv region (2500 to 4000A), it can be postulated that excitation of the phosphor is mainly due to absorption by the matrix, i.e., YVO4. The question, now, is whether the matrix (Yv04) is excited as a whole, or different components are responsible for the two absorption bands. The characteristic absorption spectra of molecular ions involving transition metal ions, both in aqueous solutions and in crystals, are due to electronic transi-

Jan 1, 1968

By AIME AIME

ALL sessions of the Mining Geology Committee at the Annual Meeting this year were held jointly with other groups, a plan that seemed to work out to the satisfaction of every one. Certain of these sessions are reported in this issue by others; the ones held on Wednesday are covered here. Ten papers, as published in the February M&M, were on the program for the Wednesday morning session, held jointly with the Society of Economic Geologists. Mr. Eckel made a brief presentation of his paper, on which there was no discussion, and Mr. Peoples presented that of which he was a joint author. D. M. Fraser then discussed a gravimeter survey for chromite in Cuba, which blocked out some 50,000 tons of ore, and F. G. Wells told of work on chromiferous sands in Oregon.

Jan 1, 1943

By Ross Glanville

INTRODUCTION The Optimum Production Rate (OPR) is one of the most important parameters in the evaluation of a mineral deposit. The OPR can also be expressed as the Optimum Mine Life (OML) in years since the expected mine life is determined by dividing the OPR per year into the estimated ore reserves. Unfortunately, very little time and effort has been directed towards the determination of the OPR. Instead, "rules of thumb" are often applied to select a mine life without due consideration of the economic implications of such a selection. A "justification" for a particular production rate is often based on a pre-conceived arbitrary requirement for a mine life of 5, 10, or 15 years, for example. In this paper it is demonstrated that such arbitrary selections for high-grade/low-tonnage mines (such as many underground gold/silver deposits) often lead to sub-optimal results. In fact, an apparently uneconomic deposit at an arbitrary production rate may be economic at the OPR. Consequently, investment opportunities may be overlooked if one analyzes mine properties based on arbitrary production rates. This paper analyzes the interrelationships of variables such as production rates, capital and operating costs, cut-off grades, discount rates, metal prices, etc. The analysis shows that the OML for high-grade/low-tonnage deposits is often in the range of two to four years. Although such mine lives intuitively appear too short to many individuals, it should be noted that, in the past, much of the mining industry became familiar with the economics of large scale mining operations. The rules of thumb developed for such large scale operations should not be applied to high-grade/low-tonnage mines such as many of the underground gold deposits. DEFINITION OF OPTIMUM PRODUCTION RATE The OPR is selected on the basis of maximizing the net present value of the after-tax cash flows. However, as discussed later in this paper, the production rate selected for a particular mine may be somewhat higher or lower than the theoretical OPR as a result of other variables such as: 1) the probability or expectation of additional reserves being discovered 2) the likelihood of being able to custom mill nearby deposits owned by others 3) the configuration or attitude of the orebody, which may place upper limits on the production rate 4) the residual, or salvage values, of the mine/mill facilities COMPARISON BETWEEN DIFFERENT PRODUCTION RATES For an orebody with definite physical cutoffs*, or boundaries (such as faults or unconformities), the total ore reserves at different production rates may be identical. Consequently, for such an orebody, varying production rates result in differing mine lives. Although the metallurgical recoveries, the mine dilution, and other similar physical parameters may vary slightly at different production rates, the major differences are the capital costs and operating costs per ton. The ramifications of these differences are especially important at low production rates (up to approximately 1000 tons per day), but can also be significant at higher production rates.

Jan 1, 1985

By Ernest Burchard

A RECONAISSANCE of the chrome and manganese&apos;1ore deposits of Culm was made in the spring of 191s by Albert Burch representative of the U. S. Bureau of Mines and the writer representing the U. S. Geological Survey. The object of the study was to obtain authentic information for use of the: United States Government as to the location, character, size, and availability of the Cuban deposits of the ores of these important steel-alloy metals. The Cuban Government courteously detailed Sr. E. I. Montoulieu, a mining engineer connected with the Treasury Department, to act as escort and associate throughout the work on the Island. Mr. George A. Wright, of Baracoa, Cuba, a mining engineer especially familiar with the chromite deposits of Oriente Province, was a member of the party from Feb. 25 to Mar. 20. It was possible to visit most of, the chrome-ore deposits that seemed to be of promise, but there was not sufficient time to visit all that were brought to our attention, some of which may have merit. Furthermore, no attempt was made to examine the extensive chromiferous iron-ore deposits of the Mayari, Moa, and Cubitas districts, as these deposits cannot be regarded as sources of chromium except indirectly. At the close of the field work the essential data concerning the quantity and quality of ore probably available for shipment during 1918 and 1919, in the event of the continuation of the European war, and of the tonnage of ore in reserve, were furnished to such Government bureaus as were interested, including the Shipping Board and the War Industries Board, and as soon as chemical analyses of the chrome ores could .be obtained, a press bulletin on the subject was published by the Geological Survey. In the present paper the engineering data, and tonnage estimates contained in the unpublished notes of Mr. Burch have been freely used, and their helpfulness is hereby gratefully acknowledged. Many thanks are due Senor Montoulieu and Mr. Wright for their valuable work in the field; to the officials of the Spanish American Iron Co. and of the various other companies; and to individuals holding chromite claims, for courteously facilitating the work of the party. In the study of material for the present paper, chemical analyses have been made by R. C. Wells and petrographic determinations and descriptions were furnished by Miss E. F. Bliss, both of the U. S. Geological Survey.

Jan 9, 1919

By John V. Beall

STREAM pollution caused by waste waters from mineral industry operations is a problem that has grown up with the industry. Its importance to each operator is dependent on the amount and type of waste he dumps into the rivers and streams; on whether this waste pollutes the waters sufficiently to make them unfit for potable water, irrigation, and conservation of wild life; and on whether this waste makes a safety or health hazard. Through the years our growing population and industry have made increasing demands on the mineral industries, the suppliers of the raw materials on which our industries are based; and we have met these demands at some sacrifice to the natural beauty and cleanliness of our country. However, that is often the unavoidable nature of the business, and along with the increased use of our

Jan 1, 1948

By Jay N. Fairbanks, Richard G. Robinson

This paper discusses a computer program and related formulas for fire fighting responses by coal mine personnel. The computer will interpret the mine air analysis, print reports, and provide relevant graphs allowing quick and accurate responses to coal mine fires.

Jan 1, 1983

By A. C. Wallace

THE development of the natural resources of any district of any magnitude, inevitably gives rise to many problems off title, usually due to the greatly enhanced value of the land. The development of the mining industry in the Quapaw Agency has been no exception to this general rule. Our problems, how-ever, have not been many or particularly serious. The Quapaws were allotted and patents issued by the United States Government in 1895. These patents contained a restriction against alienation for a pe-riod of twenty-five years. The effect of the restric-tion was to prevent the Indian from selling, leasing, or in any way encumbering his land. The Govern-ment, in a paternalistic spirit, sought to teach the Indian thrift and industry and to insure him a place of residence. This is evidenced by the first Leasing Act passed by Congress, which permitted only incom-petents and those physically disabled to lease their land for either agricultural or mining purposes. The able-bodied Indian was denied the right to lease. It soon became apparent to the Government, how-ever, that this was a mistaken policy, and in 1897 a General Leasing Act was passed by Congress and it was under this act that the mining industry in the Quapaw Agency was developed. The act, reads as follows: "That the allottees of land within the limits of the Qua- paw Agency, Indian Territory, are hereby authorized to lease their lands, or any part thereof, for a term not ex-ceeding three years, for farming or grazing purposes, or ten years for mining or business purposes. And said al-lottees and their lessees and tenants shall have the right to employ such assistants, laborers, and help from time to time as they may deem necessary: Provided, That when-ever it shall be made to appear to the Secretary of the Interior that, by reason of age or disability, any such allottee cannot improve or manage his allotment properly and with benefit to himself, the same may be leased, in the discretion of the Secretary, upon such terms and conditions as shall be prescribed by him. All acts and parts of acts inconsistent with this are hereby repealed." It was the interpretation of this Act that gave rise to our first serious problems. It will be noted that the Act says that "allottees of land" within the limits of the Quapaw Agency are authorized to lease their land. Thus, the first question was presented by the use of the term "allottee," and the question was as to whether or not Congress intended to limit the Quapaw Indian to the leasing of his own allotment or did Congress mean that the term "allottee" was synonym-ous with "Indian" and intend to give the Indian a right to lease both his allotment and his inherited land and was an Indian without an allotment an "allottee" even though he was a member of the Qua-paw tribe and the owner of the Quapaw land by in-heritance, and not being an allottee, could he lease his inherited Quapaw land under the authority granted in this Act?

Jan 5, 1928

By H. H. Kellogg

An invitation to address you on the occasion of the one-hundredth anniversary of AIME represents an honor, a challenge and an opportunity: an honor that you judge me worthy; a challenge that I present to you a picture of extractive metallurgy in the years ahead that contains some ideas of value; and finally, an opportunity for me to express some deeply felt beliefs about our profession and our industry. My topic concerns the technology of metal production in the future - the processes, new and old, that will be used to extract metals. The nature of these processes will be shaped by many forces - some technical, some economic, some political or social. A forecast of future technology must recognize the role of each of these forces, and I have endeavored to do this in the analysis that follows. In brief, my outline consists of an analysis of the forces (perhaps better called "problems") that will influence the future of our industry, followed by consideration of likely lines of technological development to meet them. Let me dwell for a moment on the nature of this industry and the profession that serves it. I have been engaged in the profession of extractive metallurgy - teaching, researching and consulting - for 30 years. I have always found the subject stimulating and rife with challenges of a scientific, engineering, economic and socio-political nature. It is a big subject - it encompasses most of the elements of periodic table; we measure the U. S. production of six metals in millions of tons per year; new plant costs range to $100 million and more. The supply of metals from our extractive plants plays an essential role in our modern industrial economy. We could do without DDT, or phosphate detergents or 300-page Sunday newspapers; we cannot do without a huge and increasing supply of metals. The Basic Goal of Extractive Metallurgy Understanding of some basic forces that shape this industry can be gained by consideration of the question: What determines the utility of metals to man? We think immediately of the inherent properties of metals - strength, ductility, electrical conductivity and so forth - but these tell only part of the story. Metal price and the available supply play equally

Jan 1, 1971

By HARRY H. SMITH

IT IS my understanding that, speaking broadly, the function of the engineering profession is to find how to do the thing required better for less money. Mechanical engineers, mining engineers, and the various other kinds of engineers are engaged in discovering and effectuating new and improved methods .of producing better goods and services at less cost to industry. The savings and advantages, thus, accruing ace reflected from time&apos; to time in increased productive powers of industry and lower costs to the public which consumes the goods and services.

Jan 1, 1931

By N. G. Johnson

ALL of us are only too familiar with the fact that first the defense program, and finally the war, required vastly increased production from existing sources, and the discovery and development of new sources of minerals and metals. For this vast program, the explosives industry was well prepared. I use the term "well prepared" to cover all the phases of explosives service, which include formulation, design, manufacture, distribution, and application.

Jan 1, 1944

By C. H. Mahoney, A. L. Tarr, P. E. Le Grand

Magnesium, it is now generally realized, differs in some important aspects from most other structural metals, not excepting even its close neighbors, the aluminum-base alloys. This is particularly true with respect to the effects of elevated temperatures on the two light metals when in the molten state. Aluminum, 0&apos; the one hand, should not be raised above its melting point any higher than is absolutely necessary if one is to avoid danger of gas absorption and a tendency toward grain growth in the resultant casting.&apos; Magnesium alloys, in sharp contrast, actually benefit by being heated to temperatures considerably above their melting point, It is a commonly accepted practice to establish the desired fine grain in the industrial magnesium alloys of the aluminum-hearing group by raising the temperature of the melt after the refining treatment to some 250°C (482°F.) above the melting range. To recall briefly the typical practice for magnesium alloys, the molten metal is refined by fluxing at about 730°C. (I350°F.), and after the melt has been covered with a suitable flux, the temperature is raised to between 870°C. (I600°F.) and 930°C. (1700°F.). It is then cooled as quickly as possible to the casting temperature. This superheating, as it is called, results in a fine-grained cast metal structure which has superior mechanical properties, enhanced amenability to &apos;solution heat-treatment, and better machinability than cast metal that has not been superheated. The minimum temperature of superheating varies to some extent with the composition of the alloys to be treated and usually increases with the percentage of magnesium in alloys containing the same constituent metals.&apos; It should be noted that the grain-refining effect of superheating is markedly apparent only in connection with the alloys containing aluminum as an alloying Constituent—the binary alloy containing 1.5 per cent manganese, for example, is not refined in grain to any noticeable extent by a superheating effort. While the phenomenon of superheating is well known in the magnesium industry, the mechanism of the process has remained a mystery During the superheating cycle something occurs that forces a fine grain upon the solidifying metal. The process has been controlled in an empirical manner, and occasionally, especially on large-scale melts, and for no apparent cause, no grain refinement is obtained from a superheating treatment. Only a few papers of importance have been published on the subject. Of these, one of the most helpful is the paper by Achenbach, Nipper and Piwowarski,3 which gives considerable data concerning the effect of superheating on various properties such as fluidity, shrinkage and hot crack

Jan 1, 1945

By L. A. Delano

During 1916, the St. Joseph Lead Co. milled 2,505,670 tons of ore. This is a daily operating average of 7855 tons. The economic concentration of such a large tonnage necessarily requires a plant equipped with modern machinery and operated efficiently. The milling process used in producing this output has been a gradual development through the long period of years that the company has been in existence. HISTORICAL SUMMARY OF MILLING PRACTICE Ore was first mined at Bonne Terre, Mo., in 1864. The early milling practice was crude. It consisted of breaking the ore into small pieces by hand, pulverizing in a Blake crusher and a pair of Cornish rolls to approximately minus 6 mm., and jigging in the old-fashioned hand jigs. Only the coarse heavy galena was saved, the gangue being shoveled off and discarded. The output for the first year under this method was only 240 tons of pig lead. The first mill of the company was a combination of extensions and additions built from time to time as the mines developed. It was a museum of early milling machinery, such as jigs, percussion tables, buddies, dolly tubs, log washers, etc., following no definite flow sheet. The chats, or tailings, were hauled to waste dumps by mule and ox teams, as much as 500 tons per day being moved in this manner, until a railroad was built in 1880. This mill was burned in 1883, at which time the annual output had reached approximately 7300 tons of pig lead. A new mill of 500 tons capacity was designed and built by C. B. Parsons. This mill has been admirably described by H. S. Munroe.&apos; The ore was crushed in Blake crushers, Cornish rolls, through 6-mm. screens, and treated by jigs of the Parsons type, percussion tables and log washers, or trunking machines, for cleaning the galena. The middlings were recrushed in rolls and treated on Harz jigs. The mill was operated without change, except later installing Gates crushers and en-

Jan 1, 1918

By George W. Bain

SOME problems concomitant with commercial exploitation of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service department wants defects rectified and the cause determined to avoid recurrence. The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character. GEOLOGICAL PROBLEMS The geological problems deal almost exclusively with the size of blocks. Size across the deposit is limited by thickness of individual beds, and along the strike by the space between crosscutting joints. Frequently the vertical depth of a block is reduced by exfoliation shells arising from spontaneous expansion. All these factors require consideration in developing a deposit to fill an order. Thickening of Marble Beds The limestone beds that became the marble deposits of the northern Appalachians and of the Yule locality in Colorado were seldom homo-

Jan 1, 1940

By George W. Bain

Some problems concomitant with commercial exploitalion of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service department wants defects rectified and the cause determined to avoid recurrence The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character. Geological Problems The geological problems deal almost exclusively with the size of blocks. Size across the deposit is limited by thickness of individual beds. and along the strike by the space between crosscutting joints. Frequently the vertical depth of a block is reduced by exfoliation shells arising from spontaneous expansion. All these factors require consideration in developing a deposit to fill an order. Thickening of Marble Beds The limestone beds that became the marble deposits of the northern Appalachians and of the Yule locality in Colorado were seldom homo-

Jan 1, 1941