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By F. E. Pawlek, J. K. Gerlach

The chloridizing roasting of ores is applied when metal sulfides and oxides are to be converted into soluble or volatile compounds. The chlorine required is either obtained from the admixed chlorides of sodium or calcium or added in the gaseous state. In the first part of the investigations the reaction rate of the chlorides of sodium or calcium with gas mixtures of SO,-0, or SO ,-O2 ,-SO , was measured. The rate for reactions with gas mixtures SO2-O2 is ThE chloridizing roasting of ores is applied when metal sulfides and oxides are to be converted into soluble or volatile compounds. At present the process is mainly applied to produce nonferrous metals which occur in pyrite cinders in small concentrations. Thereby the nonferrous metals are converted into water-soluble, acid-soluble, or volatile compounds whereas all the iron remains as insoluble oxide. The chlorine required is either obtained from the admixed chlorides of sodium or calcium or added in the gaseous state. The reactions occurring during the roasting process can be divided into two groups: solid-solid reaction and gas-solid reaction. The reactions between solids proceed by means of solid-state diffusion and are therefore of low velocity. The heterogeneous reactions between solids and gases of the roasting atmosphere5 are high-velocity processes and determine the velocity of the chloridizing roasting. These gas-solid reactions shall be the subject of the paper presented. In order to investigate the still little-known processes which occur during the chloridizing roasting 6-' the complex reaction is split into several partial steps. First the reactions of NaCl and CaCl, with gas mixtures of SO2 and 0, have been investigated at temperatures between 500" and 600°C by measuring the weight increase of the samples. The gas mixtures used in this series of experiments had first variable compositions, then the amount of SO 2 had been increased. Furthermore the influence of Fe 2 O3 admixtures upon these reactions, the behavior of pure Fe 2 O3 with the gaseous reactants, and the chlorination of the sulfides of lead, copper, nickel, and zinc have been investigated. FORMATION OF GASEOUS CHLORINE Pyrite cinders are never completely roasted and therefore contain still a small amount of sulfide sulfur. When heated again in air, this sulfur is converted into SO,. Accordingly the formation of chlorine can first be described by the reactions: dependent on the composition of the gas phase. If more than 1 pct SO 3 is added to the roasting gas, the reaction rate is determined only by the concentrations of the SO,. In the second part the reactions between chlorine and metal sulfides are discussed. The rate of formation of gaseous chlorine is higher by me order of magnitude than is the reaction rate between ZnS and chlorine. The reaction rate of NiS and PbS lies considerably below that of ZnS. The conversion rate of both pure Fe 2 O 3 and Fe 2 O 3 containing NaCl or CaCl2 when reacting with SO2-O2, mixtures with and without SO3 portions was measured at temperatures of 500", 550°, and 600°C. The weight increase of pressings was determined by means of a spiral balanceg and the reaction rate calculated therefrom according to Eqs. [ll to [31 and [5] to [7]. The prepared samples were suspended on a platinum filament in a vertically mounted tube of mullite (ID 4 cm, length 110 cm) which could be heated by a resistance tube furnace. The platinum filament was tied to the lower end of the spiral balance. A supremax glass tube (length 70 cm) was mounted gas-tight on top of the reaction tube. The unit was sealed up at its top by a ground-in stopper which was holding the spiral balance with the sample. The spiral balance therefore hung outside the high-temperature region of the furnace. Fig. 2 shows the experimental arrangement schematically. While lowering the sample into the reaction tube pure nitrogen was flowing through the reaction zone providing a protective atmosphere. After the sample had reached the reaction temperature within approximately 1 min, the protective gas was replaced by the sulfur dioxide-oxygen reaction mixture. It took about 30 sec until the mixture filled the tube homogeneously. A Ni/NiCr thermocouple placed in the center of the furnace where the sample hung during the measure-

Jan 1, 1968

By Arthur W. Griffith

Ozark Lead Company, a wholly owned subsidiary of Kennecott Copper Corporation, was formed in 1961 to operate in the State of Missouri. The orebody presently being mined was discovered in January of 1962, and over a quarter of a million feet of drilling was done to determine its value and extent. In addition, a development shaft, six feet in finished diameter, was drilled into the orebody by an oil field rig in order to support the results of the core drill samples and to obtain bulk samples of ore for metallurgical pilot plant testing, upon the results of which the primary flowsheet was established. The design criteria developed from the flowsheet was based upon a 6000 TPD plant throughput and the subsequent engineering and construction of the mine and concentrating plant was completed in June 1968. The plant, which is designed to mine and mill 6000 tons of ore per day and produce 60,000 tons of lead and 8000 tons of zinc in concentrate annually, is located approximately 110 air miles south- west of Saint Louis. MINERALOGY The orebody occurs in the Bonneterre dolomitic limestone formation in the form of irregular masses of disseminated sulphides in essentially horizontal beds. The Lamotte sandstone underlies the Bonneterre formation and is barren in values. Principal ore minerals include galena with lesser amounts of sphalerite and some copper minerals. Galena is found to be massive

Jan 1, 1970

By Stefan Boshkov, Malcolm T. Wane

THE validity and accuracy of velocity measurements underground have been questioned repeatedly by those in mine ventilation work. The general disagreement on the subject is well illustrated in an AIME publication.' Although the presence of errors is readily admitted, their magnitudes are not known and often are described by practical operators merely as "great," "small," or "of no importance." The belief that errors are of academic interest only prevails because of a justifiable claim that actual volumes of air circulated are well in excess of those required by law and safe mining practices. Poor understanding of the source and nature of errors inherent in velocity measurements, coupled with questionable determination of cross-sectional area, result in faulty techniques for the purpose of expediting ventilation surveys and render doubtful the calculated volume. Often consistency of readings is confused with accuracy. A succession of check readings showing a maximum deviation of 5 pct in the measured value of velocity usually signifies nothing more than diligent application of technique in a stable ventilating current. This article discusses the errors involved in air measurements underground. Where instrument errors are presented, the treatment is confined solely to the rotating-vane anemometer, recognized as a most useful ventilation measurement tool because of its simple design and easy operation. In the following pages a positive deviation is defined as one which has to be added to the registered air velocity to obtain the true air velocity.

Jan 1, 1956

By N. J. Grant, F. B. Cuff

DURING a recent investigation of high-purity aluminum,' evidence was found for grain-boundary sliding and migration at room temperature. The investigation was concerned primarily with an electron-microscopic study of a fine (approximately 1 micron) network that appeared on the surface of chemically polished aluminum. The nature of the network will not be discussed since it serves only as markers showing relative displacements in this instance. The pertinent observation, shown in Fig. 1, was made on a flat tensile specimen which had been strained about 8 pct at room temperature. As can be seen in this electron micrograph, a grain boundary has undergone a certain amount of sliding. The reason for the existence of the two differently appearing networks is given in the foregoing reference. For present purposes, however, the transition region can be disregarded. A close study of this picture reveals that in addi- tion to sliding there is a narrow band adjacent to and above the grain boundary. Fig. 2 is a schematic drawing showing the essential features of this band.

Jan 1, 1959

By W. B. Tijmann

Maintaining safe, yet economical, slope geometries in a mining operation is paramount. When design analysis and engineering judgement have dictated conservative and usually more expensive problem solutions, monitoring has often proven to be a valuable method in dealing with potential slope instability. A well planned and executed monitoring program can allow operation at a lower theoretical margin of safety. Monitoring provides a valuable check on design parameters and can measure effects of remedial improvements. Warning of impending failure can often be established well in advance. The monitoring problem situations in civil engineering works and open pit mining are much alike. Instruments used for monitoring in both industries are often the same. In this paper, geotechnical instruments for measuring deformation and groundwater pressure in rock and overburden are discussed with a broad-brush approach. Results obtained over extended time periods are presented in a graphical presentation for a case history. Descriptions of various types of instruments, mostly used to monitor stability of rock slopes, are discussed, and data analysis and approximate costs are presented.

Jan 1, 1983

By William Reynolds

THIS paper deals with the results of a study of the application and development of mining machines for cutting out and removing dirt bands in bituminous coal beds. FACE PREPARATION When one or more dirt bands1 occur in a seam of coal, the problem of elimination of impurities becomes manifest. The degree of complete-ness to which these impurities are removed at the face has an important bearing upon labor costs, haulage costs and outside cleaning costs, and often the ash content of the product is markedly affected. Yet, because the present-day miner is paid for the number of tons he loads he often lacks interest in the quality of the coal. To insure a clean product, a system of penalties for dirty coal is enforced, but control of extraneous impurity content in the loaded coal is often inadequate and ineffectual when coal and banded impurity are shot as one. It seems only logical that to reduce the amount of impurities by proper face preparation before the men are permitted to load the coal is the most efficient method of preparation.

Jan 1, 1936

By N. Brown, M. Herman

ORDERING'S effect on the creep strength and other plastic properties of metals is unknown at the present time. Sachs and Weerts' attempted to compare the mechanical properties of the ordered and disordered state by comparing a quenched specimen with one annealed for a long time at a low temperature. This experiment is unsatisfactory because it introduces a possible effect from quenching. Barrett' used a hot impact test, but his method was not sufficiently sensitive to indicate any discontinuity in plastic behavior in the neighborhood of the critical temperature. On the theoretical side, Fisher9 as suggested that short range order would strengthen an alloy, but he gives no conclusions as to the effect of long range order. Cottrell" has discussed the interaction between long range order and dislocations, but does not indicate whether slip in a completely ordered alloy without domain boundaries is appreciably more difficult than slip in the disordered state. Because order exists in so many alloy systems, it is most important to prove experimentally whether long range order weakens or strengthens a metal. This investigation used -brass because: 1) it orders

Jan 1, 1957

By E. DeGolyer

THE petroleum production of the world for 1924 again passed the billion-barrel mark, as it did in 1923. A preliminary estimate of production is 1,016,000,000 bbl., a decrease of 1,100,000 bbl., or less than 1 per cent. from the 1,017,100,000 bbl. produced in 1923, the year of greatest production. FIG. 1.-TOTAL WORLD AND UNITED STATES PRODUCTION. Production in the United States decreased 18,500,000 bbl., the. first decrease in yearly production since 1906. Mexican production decreased almost 10,000,000 bbl. Russia, Persia, Roumania, Venezuela, and Peru increased their production by an amount almost great enough to offset the decline in the United States and Mexico. The decline in the production in the United States and Mexico was considerably less than anticipated by leading geologists, economists, and statisticians; nor did the increase in consumption entirely meet the expectations of estimators. Early in the year, the statistical department of one of the most important oil companies forecast a draft on stocks, from an excess of demand over supply, of about 80,000,000 bbl. Instead of decreasing our stocks, they were increased by about 33,000,000 barrels.

Jan 3, 1925

By P. G. Salom

The manufacture of steel castings has become one of the important industries of the times. The late Mr. Alexander I,. Holley published in 1878, in the Metallurgical Review, an able paper, entitled "Solid Steel Castings," showing how all manner of castings could be made advantageously of steel. Mr. Holley had then but lately returned from the great iron and steel works of Terrenoire, France, which were engaged, I believe, almost exclusively on large castings, of a simple type, for the government,, and were repeating the same operation from day to day. These conditions are, as experience has shown, very different from those of ordinary practice in miscellaneons castings; and Mr. Holley might have been less confident if be had actually gone into the business. More than seven years have passed ; and as yet the magnificent possibilities held forth in his paper have not been realized. There are only six steelcasting establishments in the United States, and their total output of castings is certainly not as much as 20,000 tons per annum, and probably not more than 10,000 tons; whereas it should be over 200,000 tons to supply the needs of the country. A large number of so-called steel castings are made, however, which are nothing more than malleable iron. The best of these castings are made from a superior white pig, as low in silicon and

Jan 1, 1886

By A. E. Gorum, I. Cornet

Fatigrle of ionic crystals has been studied primarily in magnesinm oxide. under cyclic stress dislocations move irrreversibly; they multiply; slip bands form and grow; cracks mucleate and propagnte, and failure occurs. The use of ionic crystals such as MgO is advantageorus in such investigations because they are optically transparent. Individual dislocation Intersections with {100} surfaces may be observed with a standard microscope, using etch-pit techniques. Slip, deformation, crack .formation, and fracture in MgO crystals under cyclic stress are compared with cotrresponditzg processes in metals. ThE effect of cyclic loading in metals has been studied for many years. The appearance of slip lines is readily observed and the ensuing fracture may also be seen. From these observations it is possible to predict the behavior of a material and make an educated guess as to what is happening internally, but the actual changes taking place within the structure are not readily apparent. If one could obtain a material in which the individual glide components could be observed, it would be invaluable in determining the actual slip distribution resulting from cyclic loading as well as the distribution of slip in the neighborhood of a growing crack. Such a material is magnesium oxide. Dislocation arrays may be observed by means of etch pits

Jan 1, 1961

By R. W. Baldwin

As used in geophysical exploration, the term overvoltage applies to secondary voltages set up by a current into the earth which decay when the current is interrupted. These secondary effects may be measured by pick-up electrodes. The term induced polarization has often been employed to describe this same phenomenon. In its own operations Newmont Exploration Ltd. commonly uses the word pulse. The basis of this method in prospecting is that metallic particles, sulfides in particular, give a high response, whereas barren rock, with certain exceptions, gives a low response. Overvoltage has been tried in searching for many types of mineral occurrence but has been most successful in outlining the widespread disseminated mineralization associated with porphyry coppers. History:' Newmont Mining Corp. has been interested in overvoltage since 1946, when Radio Frequency Laboratories of Boonton, N. J.. drew the company's attention to phenomena observed in the laboratory. At the instigation of A. A. Brant further model studies were undertaken, and the first tests were performed in 1947. Tests at San Manuel, Ariz., in 1948 were very encouraging, clearly demonstrating that the method could be used to distinguish scattered sulfides at depth. H. 0. Seigel followed up the San Manuel work with a study to determine the phenomena involved.'

Jan 1, 1960

By Frederick Prime

AT the last meeting of the Institute, Mr. A. L. Holley read a paper on "Steel," in which he proposes for it a definition so opposed to the one generally received, as to call for some remarks. Until within the last five or six years there has been no dispute on the subject, and it seems worth while to investigate the matter. For not only does a proper tax on all importations depend on a proper appreciation of the term steel, but it is necessary to know whether steel, or wrought-iron, or homogeneous iron are requisite in all processes of manufacture in which malleable iron is employed, on account of cost, strength, etc. Karsteu* says : " Iron may be obtained, either as an unforgeable, unweldable metal, which melts at a high heat, termed cast-iron; or as a ductile, weldable, soft metal, which can only be melted at the * Karsten, Handbuch der Eisenhüttenkunde, 3d ed., vol. i, p. 6. Berlin, 1841.

Jan 1, 1876

Dr. Oldshue has provided a useful summary of a voluminous subject and my task will be to select and direct attention to those areas of mixing theory and practice which are germane to mineral processing in general, and to fine particle treatment in particular. Pulp mixing in impeller actuated reactors occurs in mineral processing in several different applications: (1) emulsification of reagents; (2) mixing pulp with 'reagents as in conditioning for subsequent operations (such as flotation, flocculation or agglomeration) ; (3) high intensity agitation, as in (a) disintegrating and dispersing aggregates, and (b) aggregating particles as in shear flocculation or in selective agglomeration; (4) hydrometallurgy; (5) hydrometallurgy with gas phase (e.g., Arbiter process); . (6) flotation in sub-aeration machines. Attention is invited to 3 above in which two opposite effects can be induced by proper choice of chemical treatment and hydrodynamic conditions. Successful processes for treating mineral fines require excellent aggregate dispersion in order to fully accomplish the liberation stage. Some processes depend further upon selective aggregation following dispersion. The term “dispersion” is often used in different senses which for present purposes will be clarified at the bottom of the next page.

Jan 1, 1979

By Henry Louis

THE work performed by, the Royal Commission on Mining Subsidence is likely to prove of permanent value, less perhaps for the conclusions it has reached and for the recommendations it has based upon these than for the admirable exposition which it affords of the law concerning mining subsidence and of the legal status of the person who has suffered damage by reason of such subsidence, as also of him whose working has caused the damage. The Commission was appointed by Royal Warrant in the middle of 1925 and delivered its final report in the middle of 1927. The terms of reference to the Commission were as follows: "To consider the operation of the law relating to the support of the surface of the land, and of buildings or works on or under the surface, by underlying or adjacent minerals; to enquire into the extent and gravity of the damage caused by subsidence owing to the extraction of minerals and the incidence of the resulting liability; and to report what steps should be taken, by legislation or otherwise, to remedy, equitably to all persons concerned, any defects or hardships that may be found to arise in existing conditions."

Jan 1, 1929

By C. A. Kroetz, A. J. O’Neal

The Long Island Lighting Co. has operated an extensive monitoring system for over three years. Nearly 900,000 separate pieces of information have been recorded for a land area of some 600 sq miles, 15 miles north to south by 40 miles east to west. The data are composed of about a half million sulfur dioxide measurements at various locations, 290,000 of which were by the West-Gaeke method, about 160,000 pieces of weather data, and 220,000 measurements of sulfur dioxide as emitted from each of the power plant stacks on the system, all measured on an hourly basis and stored on computor cards and tapes. The computor has been programmed to collate stack emissions, weather information, and ground level sulfur dioxide measurements. The analysis shows that emissions from tall stacks do, indeed, contribute very little to ground level sulfur dioxide. For example, LILCO shows that its Northport plant contributes less than 2 ppb, hourly annual average. They also state that the plant converted to 100% natural gas or shut down, would reduce ground level sulfur dioxide by no more than 2 ppb.

Jan 1, 1973

By S. L. Crouch, C. Fairhurst

The general term "coal mine bump" refers to the sudden and violent failure of in-situ coal. Coal bumps occur in most countries where coal is worked by underground methods. They are related to geological factors and mining techniques. Coal bumps can be characterized as unstable releases of energy associated with yielding that occurs with progressive mining. Unstable releases of energy occur when the coal is able to absorb less energy than is released by the surrounding rock mass during the yielding process. At any stage of mining, the amount of excess energy so released is governed by the mining geometry, the overburden stress, the elastic properties of the rock mass, and the stress-strain characteristics of the seam material. If the coal in the vicinity of the working face is crushed, the peak abutment pressure occurs at some distance into the intact portions of the seam, and mining takes place in essentially destressed coal. With subsequent mining, additional yielding occurs, excess energy may be released, and the peak stress is again shifted into the solid. This process continues until the mining geometry is such that the zone of peak stress is effectively surrounded by yielding coal, at which point it can be anticipated that further mining will produce dramatic redistributions of stress and be accom¬panied by large releases of energy. On this basis, the differences between several alternatives for mining a given block of coal may be pronounced.

Jan 1, 1975

By Thomas T. Read

It is natural, in reviewing the progress that has been made in mineral industry education during the three quarters of a century that has elapsed since the American Institute of Mining Engineers was organized in 1871, to seek to establish some significant correlation. Earnest endeavor along such lines, however, produces nothing more in the way of fundamental relationship than a technical economic interest in mineral production and utilization in the United States, which had been steadily increasing since 1800. This is a sound correlation, since it is unquestionable that organized and systematic mineral industry education had its origin in Germany, more than 150 years before 1871, in an economic interest in producing minerals for use with the maximum of recovery at a minimum of cost. Mineral industry became the originator* and creator of systematic technical education because of the political and economic fact that in all European (and most other) countries, prior to 1800, precious metals belonged to the ruling power, no matter upon whose land they were discovered. The practical way of working under this system was to grant to a discoverer the right to work the deposit on payment

Jan 1, 1947

By Frederic Lahee

THE purpose of this paper is to demonstrate the similarity of the oil-producing structures in the Mexia1 fault zone, and to show how the apparently very irregular well logs in these fields may be used for the practical interpretation of subsurface conditions. The Mexia oil field, in Limestone County, Tex. (Fig. 1) is closely associated with a fault that trends about 30° east of north and has a displacement of between 200 and 400 ft., with downthrow on the west. Minor slips accompany this major fault, some being roughly parallel to the main break while others are transverse to it. These faults belong to the so-called Mexia fault zone, a belt of fracturing that has been traced in its characteristic features southward to near Kosse, 15 miles south of Groesbeck, in southern Limestone County, and northward at least as far as the Trinity river at the eastern border of Navarro County, and possibly as far north as Hunt and Hopkins counties.2 The Balcones fault zone, from 30 to 40 miles west of the Mexia fault zone, differs from the latter in that its principal displacement is a down-throw on the east. In this respect, it is exactly the opposite of the Mexia displacement. Between these two zones of major faulting lies a great down-dropped block, or graben, which is broken by numerous minor faults.

Jan 2, 1925

By A. C. Halferdahl

DURING a study of reactions involving iron sulfides, it became desirable to know approxi-mately the heat of decomposition of pyrite. The values given for the heats of formation of pyrite and ferrous sulfide are 35,500 calories and 23,070 calories respectively. For the reaction 2FeS2= 2FeS+S:, the heat effect would be-24,860 calories. But pyrite gives sulfur and pyrrhotite upon heating and the latter is a solid solution of sulfur in ferrous sulfide. The only meas-urements of this decomposition are those of Allen and Lombard1 of the Geophysical Laboratory who have measured dissociation pressures of both covellite and pyrite and have carefully reviewed the literature. They give a table of values for covellite as determined by Preuner and Brockmoller2 and by Wasjuchnowa3 and compare these values with their own measurements. The conclusion is that the measurements of Preuner and Brockmoller are seriously in error, while Was-juchnowa's values fit in well with those of Allen and Lombard. Wasjuchnowa's measurements were made by a dynamic method, while Allen and Lombard em-plowed a static method on both covellite and pyrite. Tables I and II reproduce the measurements of Wasjuchnowa and of Lombard and Allen on covellite and pyrite.

Jan 11, 1927

By Irwin Roman

In addition to projects such as those reported in parts I and II above, the Section of Geo-physics of the Federal Government has undertaken a considerable amount of fundamental research. Two such field-projects may be mentioned, one a magnetometric study in the Comstock Dis-trict of Nevada, and the other a resistivity-study of snow and ice. In addition to the field-problems, there have been two classes of research of a mathematical type. One of these has been the preparation of tables, scales, and charts for the important geophysical functions already known; the other has been the extension of the relations involved in the resistivity-problem. The magnetometric study at Spring Valley, in the Comstock District, was made for the pur-pose of determining the value of the magnetometer in extending the knowledge of a region, as ob-tained by purely geological means. The variations in the vertical magnetic intensity were mea-sured with an Askania balance at intervals of 20 feet, along lines as shown in Figure I.. These lines were 100 or 500 feet apart over an area approximately a rectangle 6000 by 7500 feet. In addition to the lines shown, two areas were selected for more intensive study. In one, short

Jan 1, 1940