Search Documents

By A. J. Bartlett

Island Creek conditions are generally referred to as ideal; yet, as at all other properties, there are all known hazards of coal mining. The hardest of these hazards to combat is the human element. The basic thought in the minds of the management of these properties is to produce coal with the utmost safety, and it has impressed upon its supervisory force that it does not want a ton of coal unless it can be produced safely. This company has instituted a mine inspection department, which reports direct to the general manager, arid all matters pertaining to safety come under the direction of this department. Through the medium of the inspection department, the management is kept in touch with the actual conditions existing in general at all mines. Inspections are made regularly arid continuously; that is, at all times while the mine!: are in operation some sections of some mines are being examined. These inspections cover all active and inactive workings. Miners are contacted in their working places and other employees at their respective, work. A thorough check is made to see that the state mining laws are complied with and that company safety rules arc being observed. Night shifts receive the same attention as day shifts. All violations and dangerous practices are brought to the attention of the plant supervisory force with suggestions and recommendations; major hazards of emergency nature are taken up immediately with the management. Periodical inspections are also made of all tipples, preparation plants, dumping and hoisting equipment, to see that all machinery is properly guarded, and walkways and platforms properly fenced; conditions of equipmcnt and mechanical defects are also reported. Reports of inspection are written in letter form and in such a manner as to give the management a picture of the existing conditions at the time of inspection. Copies of inspection reports are forwarded to the superintendents with the general manager'? comments. It has been said, "There is nothing under God's heaven that justifies. your creation or your citizenship but this gospel: ' That the next greatest

Jan 1, 1938

By M. J. Langley

Zinc ores were first discovered in Tennessee in 1856 at Jefferson City where a deposit became the Mossy Creek mine. From that time until 1913, small- scale attempts at prospecting and mining were made in various parts of the district. The actual systematic development of the zinc deposit dates from 1913 when the American Zinc Co. started operations at Mascot. Mining in the Mascot-Jefferson City area today is devoted exclusively to the zinc sulfide, sphalerite. Various grades of zinc mineralization have been found intermittently through a 600-ft vertical thickness. However, the commercial ore is confined to a total thickness of about 250 ft, from which it usually is mined irregularly from four or five separate levels known locally as "ore runs." In a few places vertical thicknesses up to 150 ft have been mined where commercial material extended from one run to another.

Jan 10, 1962

By R. B. Booth, W. F. Linke

The continuous interest of the American Cyanamid Company in producing superior polymeric flocculants and dispersants for the mining industry has resulted in a broad, general study of the physical chemistry of mineral-polymer systems. The aim of this program has been to establish a sound theoretical basis on which practical problems could be analyzed, and which would lead to the development of new and improved flocculating and dispersing agents. This study has required the cooperative effort of physical, analytical, and polymer chemists, as well as engineers familiar with mining problems. This report summarizes the results of some of our investigations over the past two years. Further studies along these and other lines are in progress and will be reported in the near future. MEASURING FLOCCULATION IN THE LABORATORY The foremost problem in studying flocculation in the laboratory has been to establish reproducible methods of comparing and evaluating the effectiveness of various reagents. Previous workers have measured settling -rates 1,8 filtration rates2 , and sediment volumes3 . Direct observations of the floc size, or the clarity of the supernatant liquid, can also be used. AIthough these parameters are all interrelated, they do not always measure the same physical properties of the suspensions, and hence are not equally useful or reliable. Whatever the method of comparison selected. the testing procedure must be carefully defined and standardized. The results must be satisfactorily reproducible, and for practical purposes must accurately reflect the results obtained in mill use. In order to compare the data obtained in these various types of test, the physical nature of the flocculated system must be examined in some detail. In an unflocculated system, only the larger or denser particles (the "sands") settle at a useful rate. The sediment can be observed to build up from the bottom of the cylinder, while the fines remain in suspension for a long period of time. If the system is not disturbed, even the microscopic fines can be seen to classify themselves as they fall over a period of days. When a high molecular weight polymer is added to the system, the colloidal particles are tied together randomly in flocs, and the sands and fines settle together. The line of demarkation between solid and liquid phases moves downward from the top of the cylinder. The settling rate of the flocs depends on their size and on their effective density. For a given mineral sample, the larger the flocs, the faster the settling. Since the large flocs cannot pack as closely as small ones, they produce a sediment with more pore spaces, and hence of larger volume, which is easier to pump and to agitate. Although it is nearly impossible to measure individual floc sizes, it is relatively easy to determine settling rates and sediment volumes. Of these two, the settling rate is simpIer to measure, and hence generally more practical. Reproducible sediment volumes can only be obtained by allowing the solids to pack for a rather long period of time (e.g., hours to days), and although the volumes thus observed are directly related to the degree of flocculation (average floc size), it is often impractical to wait so long for the results.

Jan 1, 1961

By C. P. Proctor

WESTERN Pennsylvania, eastern Ohio, and Illinois are carrying out experiments wherein much more slate and other impurities are loaded with the coal in the mine and hauled to the surface preparation plant for removal. In general everything is sent to the cleaning plant although there may be some gobbing in the mine. No conclusions have been announced as to the effect of such a mining system on clean coal costs. Such factors as ability of the surface plant to handle the impurities, land and facilities for disposing of the impurities, and the transportation facilities underground should be considered.

Jan 1, 1942

By Jon J. Connor, Richard J. Ebens

The trace element geochemistry of the cherty clay-rich carbonate residuum cover in much of southern Missouri and adjacent parts of Arkansas was investigated during the earl 1970's as part of a statewide geochemical survey of Missouri.1-8 The study was environmentally oriented and focused on the character of the "natural" geochemical environment of the state. A great deal of effort was made to collect samples that would represent the geochemical variability of the near-surface environment in an unbiased way. In general, this was accomplished by use of randomization procedures in both collection and analysis. Most of the sampling sites were selected randomly to prevent personal bias from entering into sample selection. In the laboratory, samples were analyzed in a randomized sequence to circumvent the effects of any systematic bias that may have entered into the laboratory procedures. Several residuum samples contained 1000 parts per million (ppm) or more of lead, zinc, and barium. All these samples were collected in Washington County in or near the barite district. The frequency distributions shown in [Fig. 1] indicate just how unusual the residuum in Washington County is with regard to these three metals and copper. The shaded parts of the histograms represent the samples from Washington County. The histograms are based on analyses of 141 samples from 38 localities scattered over the subcrop of the Cambrian and Ordovician formations of southern Missouri and northern Arkansas. Eight localities were selected randomly from over each of four bedrock units-Bonneterre dolomite; Potosi and Erninence dolomites; Roubidoux formation; and the Jefferson City, Powell, and Cotter dolomites. Six localities were selected randomly from over the Gasconade dolomite. The geochemical "background" for these elements in residuum is defined by samples from outside of Washington County (unshaded part of the histogram); lognormal distribution curves have been fitted to the corresponding parts of each histogram. Clearly, these lognormal models (curves) describe well the background distributions of zinc, barium, and copper. The background histogram of lead concentrations is notably skewed to the right compared to the model. Lognormal distribution curves were also fitted to the data on lead, copper, and zinc in the residuum of Washington County. No model was fitted for barium in Washington County because of the distinct bimodality in the data. All samples containing more than 1000 ppm were collected in the barite mining district and obviously reflect the elevated levels of barium in the district. The frequency distributions for Washington County are clearly anomalous with respect to the background data, those for lead, zinc, and barium being exceptionally so. The models for anomalous lead, zinc, and copper seem to fit reasonably well, although the scatters in the lead and zinc anomalies are considerably larger than the scatters in the corresponding background data. The copper anomaly, although probably real, is greatly subdued compared to that of lead and zinc. Also, it has a scatter similar to that of the copper background, rather than being enhanced like the scatters of the lead and zinc anomalies. On the basis of techniques described by Miesch,4 the chemical abundance of copper, lead, and zinc in residuum in

Jan 1, 1980

By Irving M. Symonds

COMPA[N]IA Minera de Penoles, S. A., at its Avalos unit operates a lead-zinc concentrator having a capacity of about 600 short tons per day. Lead and zinc concentrates are made by flotation methods. The concentrator is at Terminal de Providencia, in the state of Zacatecas, some 70 miles south of Saltillo, Coahuila. The Pe[n]oles-Avalos railroad operating between the plant and Estacion Avalos, a distance of 6 miles, makes connections with the Coahuila and Zacatecas railroad, which in turn connects with the Nacionales de Mexico at Saltillo. The three railroads are each of different gauge, requiring the transfer of all supplies and concentrates at each junction. The mill operates on company ores, on ores from leased mines, and as a custom mill. The custom business is very small. The lead concentrates are shipped to company smelters at Monterrey, Nuevo Leon and Torréon, Coahuila. Since the European war, all zinc concentrates have been shipped to the United States. ORE TREATED The major source of ore supply is a group of four mines owned or leased by the company, some three miles south of the mill in the mountains, from which the ore is delivered to the mill by a gravity aerial tramway. Custom ore comes in by rail. The ores occur in chimneys. The upper levels contained oxidized siliceous ores of lead, copper, silver and gold, with varying amounts of zinc. These ores were direct-smelted. In the first two years of operation a good deal of the tailing loss was caused by the oxidized content of the ores milled. Much of the ore in the transition zones between the oxides and sulphides was not mined. The ores now being milled are clean, hard sulphides in a limestone gangue, with only occasional contamination of oxides. The lead and zinc sulphides are of coarse structure and are freed even above flotation sizes. The galena is usually "steel" colored, easily and quickly floated. When there is any oxidation, it is usually on the coarsest crystals. The zinc minerals vary a good deal in color; a resin sphalerite predominates but there are varying shades of brown marmatites. On an average, the zinc sulphides contain 64 per cent zinc. The only common copper mineral is chalcopyrite. Little is known of the occurrence of gold and silver. Waste minerals are mainly limestone and pyrite, both of which are barren. The ores vary from 20 to 35 per cent pyrite. Mill heads for the year 1940 and the first eight months of 1941 are given in Table I. [ ]

Jan 1, 1942

By Rollin A. Slater

This paper presents a composite of ideas on materials handling systems by describing the design of an over-all system for a hypothetical steel pellet plant located on the Great Lakes. The bulk materials handling industry has served for years as the skeleton and the central system of nerves and nourishment for the body of basic industries. During the past two decades, this body has undergone substantial growth and mutation to meet the surging demands of our national economy for more and better products. The steel industry has kept pace with spiralling demand by innovation which has resulted in new processes and improved designs which generally yield greater production from fewer units. Materials handling technology has likewise improved its techniques and currently has a new, stronger generation of equipment to perform its necessary supporting function. Drawing upon excerpts from several recent plant designs, this paper describes a basic approach to the selection and application of modern bulk materials handling systems to an entirely new steel plant. Specific details are not available for publication, and therefore the plant described herein is a composite of ideas. This imaginary plant will be located on the United States side of the Great Lakes and its owner will be called the Hypothetical Steel Corp. for purposes of discussion. TYPES OF EQUIPMENT The basic bulk materials handling systems and components required in a plant so situated are: lake boat unloaders; railroad train unloading systems; storage pile stackers and reclaimers; large bins and regulating feeders; and the conveyor systems — with their attendant controls— which connect the foregoing. PROGRAM OF DEVELOPMENT The initial work on the plant must be that of the process engineers who develop and refine the basic data, i.e., the logistics of all raw materials, waste materials and products within the plant. During this phase of study, the materials handling engineer may advance his planning only in basic areas such as movements at the dock and movements at the railroad. This initial planning work is concerned only with defining logical plant locations in the light of channels, currents, existing traffic, governmental regulations, locations of existing railroads and available rights-of-way. These systems alone have their own individual criteria which must be respected and accommodated in the final layout. All other elements, such as the arrangement of the blast furnaces, power house, coke plant, by-product plant, scrap preparation plant, BOF shop, and facilities for continuous casting, degassing, calcining, etc., are dictated by their own specific needs and their relation to each other. In the arrangement of these latter facilities, the materials handling system is secondary and must be designed to accommodate. BASIC LOGISTICS The result of the process engineer's work can be expressed in terms similar to those shown in Table I. Plants are customarily rated in terms of annual tons of ingots. Therefore, the basic size of this plant can be determined by referring to the BOF Shop wherein it is sized at 5 million tpy. From the base, the required hot metal can be traced to the blast furnace, which in turn indicates the amount of required flux, iron bearing materials and coke —which in turn establishes the demand for coal. Likewise, the total demand for flux can be determined by the combined demand of the lime plant and blast furnace. The generation of fines and waste products, which have significant value but are not usable as such, create the need for a sintering plant. From projections such as the foregoing, the complete flow of materials can be established and accommodated. The basic premise upon which this typical materials balance is predicted is that the plant will be a producer of high tonnages of non-SpecialtV- products. All basic raw materials (flux bearing, iron bearing, coal) will be prime quality. For example, the basic iron charge will be pellets, and the iron ore fraction will be sized lump, all of which

Jan 1, 1970

By Emile Rector Abadie

The picturesque little mining town of Grass Valley, nestled in the foothills of the Sierra Nevada mountains, at an altitude of 2500 feet, has been for 43 years the scene of uninterrupted activity and prosperity, as the center of a mining district which was intimately associated with the pioneer days of California, and the discovery of gold by James W. Marshall, in El Dorado county, in January, 1848. Although placer-mining was inaugurated in Nevada county as early as 1848, the first quartz ledge was not located until the summer of 1850. Discoveries made on Gold Hill and Massachusetts Hill increased the excitement in quartz-mining, and hastened the erection (during the same year) of the first mill operated in the State. At the close of 1864, the district had produced $23,000,000 in gold, and all the well-known properties of to-day had been discovered and worked. The Eureka-Idaho, the North Star, and the Empire mines were in active operation ; and to-day we still find them equipped with large crushing-plants, operating 80 per cent. of all the stamps in the immediate Grass Valley district. Of the mines just named, the North Star possesses the most recently constructed mill, a description of which, the writer believes, may prove of interest to members of the Institute engaged in the milling of goldores. During the year 1386, operations at the North Star mine (the property of the North Star Mining Company) had reached such a stage of development that the necessity of a crushing-plant at the mine became imperative, and early in October the erection of a 30stamp mill was in progress. The building designed to contain 40 stamps was speedily erected ; and within sixty days the large structure was under cover. Plate A represents the appearance of the mill 40 days after work was commenced. Late in February, 1887, the mill was in readiness, and, upon the

Jan 1, 1895

By R. H. Swallow, George Hess

Aerial photography was once a crude, uncertain tool. Today it is a precision mapping instrument which saves important time and money for strip mining and other industry. Aerial photography began in the boxkite days of aviation. The Army first used it for rough reconnaissance photographs. Then, in the early Twenties, industry began to use aerial photographs of their plants and facilities for advertising or annual reports. The quality of these pictures was not very good by today's standards, but this work began the development of better cameras, better lenses, better photographic techniques.

Jan 1, 1949

By Lewis H. Reiland

IN 1920, for the first time, the U. S. Geological Survey employed aerial photography in constructing planimetric maps. Contours were added by aerial photography and cultural details corrected. From 1925 to 1929 photogrammetric plotting machines and instruments of foreign design appeared in America for use in constructing complete topographic maps. During this period the only American technique developed was the Brock process, carried out with great success by Aero Service Corp. of Philadelphia, a pioneer in the field of photogrammetry. Between the first and second world wars the Multiplex projector, the Aerocartigraph, and the Stereoplanigraph appeared. The Multiplex projector, most popular of the three, determines three-dimensional values with very high accuracy. Many refinements have been added year by year, and it is now possible to photograph vast areas in a very short time and produce planimetric, topographic, and geologic maps of great value at very low cost per acre as compared with all methods previously known and in use. Both on the ground and in the air, however, accurate results can be produced only with highly skilled personnel and costly scientific instruments and machines. As early as 1928 the writer collected from the U. S. Army Engineers all available formulas and data on photogrammetry and personally contracted a local project of 2800 acres to be surveyed from the air. From the 10,000-ft altitude required for scale the cameras, each equipped with 4-K filters, pierced a ground haze of about 5000 ft, achieving clear, de- finable photography. The result was so gratifying, and the continuing progress in this method of surveying and mapping so great, that in the matter of economy it can hardly be surpassed. Pocahontas Land Corp., for example, constantly refers to its complete file of aero prints, covering its entire ownership in West Virginia, Virginia, and Kentucky. Photostats are enlarged or reduced from these prints to match the scale of company maps, to which various features are then added.

Jan 7, 1957

By John E. Conley

THE slate industry of the United States has shown a marked decline in value of products made annually since the peak year 1925, although there has been moderate improvement over the lean years 1932 to 1934. In 1940, the value of all slate products sold was approximately 5 3/4 million dollars for a total output of 473,450 short tons. The quantity sold was a little less and the value a great deal lower than the annual averages for the past two decades. Enormous quantities of waste materials result from the quarrying, splitting and milling of slate. Obviously, utilization of such waste material is desirable, not only from the viewpoint of economical operation but also for the purpose of conserving natural resources. One possible use is to produce expanded or puffed lightweight aggregate for use in concretes. Such concretes are strong enough for specific uses, and the advantage of lightness could be obtained in such structures as the walls and roofs of buildings, suspension-bridge roadways and various other applications where weight is a factor. Conceivably, these uses could consume an appreciable annual tonnage. USE OF WASTE SLATES FOR MAKING AGGREGATES The lightweight-aggregate industry has been discussed elsewhere4.5 and need not be covered in detail in this paper. The materials commonly utilized are naturally occurring aggregates such as volcanic cinder, tuff and pumice; by-product materials, such as ordinary cinders and air-cooled slags; and the specially manufactured products, including Haydite, Pottsco, Gravelite, Cel-seal, Superock and Waylite. Slates, however, have not been given the consideration they merit, especially in the United States. In the British Isles, some work has been done' on certain Welsh slates by the Building Research Station to stimulate the use of these wastes. REQUIREMENTS FOR RAW MATERIALS As pointed out by Hughes,4 the lightweight-aggregate industry is segregated in regions adjacent to large cities in order to localize the market and avoid the necessity of long freight haulage. Waste slate from the deposits of eastern Pennsylvania, northern Maryland, and Virginia would meet the basic requirement of any low-priced structural raw material. One apparent advantage is attained when slate waste, normally discarded, is utilized in the manufacture of a by-product. Mining or quarrying costs usually have been assessed against the main product. Some additional grinding might be desirable, but this operation would be relatively cheap, as most slates grind easily. It is believed that virtually all slates, when properly heated, will expand to some degree. However, types that will expand from 3 to 7 times their original volume are preferred. Fig. I illustrates the expansion of a Pennsylvania slate. The cube originally

Jan 1, 1942

Some 15 years ago, Dr. Adolf Schmidt, director of the Magnetic Observatory in Potsdam, Germany, developed an instrument, which was a modification of Lloyds balance, for the measurement of the vertical component of the earth's magnetism in the field. There was a keen demand for this because (1) it was desirable to have a field instrument that would measure the component of the earth's magnetism which stands in the closest and simplest relation to the configuration of the subterranean magnetic formations-the vertical component; (2) it was desirable to have an instrument that was not only more sensitive but also more reliable than the existing vertical magnetometers (the dip needle, for instance). The application of the magnetometer in oil geology demanded such an instrument, because the magnetic disturbances produced by most types of magnetic formations associated with the occurrence of oil (salt domes, faults, anticlines with crystalline core, etc.) are too small to be detected with the ordinary dip needle. The writer can prove, by some investigations recently made for the U. S. Bureau of Mines, that these instruments may be used also to very great advantage in mining, because they are capable of measuring anomalies which are as great as twice the normal strength of the earth's magnetic field. Even for such anomalies, the field balance is more advantageous than the dip needle. First, the instrument rests on a firm support and can be adjusted in the proper azimuth, which insures measurement of the vertical intensity only, without a part of the horizontal intensity, which is very important for the interpretation. The readings give the vertical intensity in linear terms and not as a function of an angle; and the field balance is insensitive to temperature when used with scale values that are adequate for the determination of large anomalies. In another phase of mining, the gold placer work, the field balance has also shown excellent results for which the dip needle is not adequate. What has been said about the dip needle holds also, though to a lesser extent, for two other types of vertical variometers recently used, the Tiberg balance and the Thomson-Thalen magnetometer.

Jan 1, 1929

By William P. Blake

The occurrence of the manganiferous variety of wolframite at a new locality in Arizona was announced in the month of May last." It occurs in the granite hills of the Dragoon mountains, in Cochise county, about 6 miles north of Dragoon Summit station, on the Southern Pacific Railway of Arizona. It is found in veins of white quartz, traversing a coarsely crystalline granitic gneiss, and, so far as yet determined, is without association with other metallic minerals in the same veins, except small quantities of scheelite. It is a very pure form of the mineral, and contains but little iron, the base being manganese oxide. The color is brownish-red; it is nearly the same as the color of the mineral originally described by E. Riotte from Mammoth District, Nevada.† Thin films or plates on the broad cleavage-surfaces, and thin cleavage-flakes, seen by transmitted light, are ruby-red, or rather more like the color of red zinc oxide or the mineral known as clintonite. By long-continued weathering the surface becomes less deeply colored, and assumes a bronze-like luster, like the dull oxidized surface of

Jan 1, 1899

By A. Moskowitz, L. S. Redmerski

The corrosion resistance of stainless steels can be strongly affected by surface treatments. Changes in corrosion resistance can relate to surface composition, integrity and stability of the passive film, and to surface profile (roughness). Operations producing oxidation at the surface, such as annealing, heat treating, and welding, can result in a chromium-rich scale and a chromium-depleted metal surface. In order to restore full corrosion resistance, chemical or mechanical clean-up techniques must remove not only the oxide, but also a very thin layer of metal. Laboratory and field test studies show that these factors are particularly significant in less highly alloyed steels. Annealing stainless in a reducing atmosphere (bright annealing) avoids chromium depletion, but as-bright-annealed material does not display optimum corrosion resistance in certain environments. Electro passiva-tion can be applied to improve pitting resistance without significantly changing bright surface appearance. Potentiometric studies show that electropassivated material also displays significantly greater resistance to breakdown of passivity in acid solutions. The application of special surface finishes for appearance purposes can affect corrosion resistance. Roughness is a key factor. Samples of related appearance but with different surface profiles can show significant differences in corrosion resistance. Thus nonreflec-tive stainless with a relatively smooth surface produced by a special rolling process is much superior to material chemically etched to a similar low reflectivity. THE corrosion resistance of a stainless steel is affected by other factors in addition to its bulk composition and metallurgical structure. These other factors include those relating to the specific chemical and physical condition of the steel's surface. This paper will consider certain aspects of surface condition in relation to corrosion resistance. In particular, studies will be described on the effects of oxidation encountered in heat treating or welding operations, of passivation after bright annealing, and of different surface finishes. EFFECTS DUE TO OXIDATION When stainless steels are exposed to high temperature in an oxidizing environment, as in annealing or welding, the oxides formed are relatively rich in chromium. As a consequence of oxidation, the metallic layer directly beneath the scale may be low in chromium to some very thin but finite depth.1"8 Such a change in chromium content could lower the corrosion resistance at the surface, whether or not the oxide layer is removed. Studies were performed relating to the effect of oxidation and chromium depletion produced during annealing and welding on the corrosion resistance of stainless steels. The nominal compositions of steels used in this study and others are given in Table I. A) Annealing Studies on 17 pet Cr Steels. 1) Effects of Pickling Treatments. Studies were performed to investigate the corrosion resistance of air annealed type 430 stainless as a function of the amount of electrolytic pickling after annealing. The material used in this study had been air annealed and electrolytically pickled in the mill. All scale had been removed, and yet the material showed unusually poor corrosion resistance. Laboratory electrolytic pickling studies were performed to determine whether additional metal removal from the surface would improve corrosion resistance. Electrolytic pickling was performed in a sulfuric acid bath using various conditions of bath acidity, temperature, time, and current density. The samples were then rated for corrosion resistance in a ferric chloride spot test. For this spot test, a solution was prepared by dissolving 10 g of FeCl3 . 6H2O, 5 g of NaCl, and 2.5 ml of concentrated HC1 in 200 ml of water. An area on a specimen was cleaned and a drop of test solution was placed on the prepared area. After 5 min, the drop was rinsed off and the area wiped dry. The spot was then rated between 1 and 5 by visual comparison with standard spots. The numerical rating of the standard spots can be described as follows: 1—No clouding of surface; 2—very slight clouding of surface; 3—slight clouding of surface; 4—moderate clouding of surface; 5—strong clouding of surface. A rating of 1 or 2 was considered to have passed the test, a rating of 4 or 5 represented failure, and a rating of 3 was considered borderline. The severity of etching in this test has been related to the actual chromium content at the surface.4 Etching (clouding) occurs on type 430 stainless (rating of 4 to 5) when the surface chromium content is 14 pct or less. The effects of current density and retention time when electrolytically repickling this material in 6 pct sulfuric acid are shown in Fig. 1. Increasing the cur-rent density or retention time improved corrosion resistance as measured by the spot test. Similarly, increasing acid concentration of the bath or bath tem-perature was found to improve corrosion resistance. The conditions making for improved spot ratings resulted in increased metal removal, regardless of specific pickling conditions used, Fig. 2.

Jan 1, 1970

By C. L. Clark

EVERY user of steel should ask himself whether or not he is taking full advantage of the discoveries of the steel metallurgists during the last few years, or is merely buying grades that looked to be the best five or ten years ago for various specific purposes and have since proved perfectly satisfactory in his plant. If he has not kept abreast of the times, then it is probable that something better has been developed, or something just as good that costs less. Though this article will have to do with steel for high-temperature applications primarily, marked advances have been made in steels for other purposes as well.

Jan 1, 1940

By C. McLean, Erickson, S. G. Kolb, S. C. Moore

The Grossschloppen vein-uranium deposit, Bavaria, West Germany, was examined with underground workings during 1980-82 by Esso Erz GmbH, an affiliate of Exxon Minerals Company (EMC). Geologic evaluation entailed dense drilling of a portion of the deposit from workings constructed specifically for the program. Discovered in 1977, the deposit was initially explored by surface diamond drillholes which allowed definition of a 30-60 m wide vein system discontinuously mineralized along a 1000 m strike length and to at least a 450 m depth. The underground program was conceives as a cost-effective procedure to answer quest ions on vein correlation, grade continuity and variability. A 1200 m decline allowed access for detailed sampling of approximately 10% of the known area of mineralization. Fanned drillholes, logged by gamma probe, were spaced to provide intersections of veins at 10 to 20 m intervals. Six cross-cuts also penetrate the pitchblende and uranophane mineralization which occurs in 0.1 to 2.5 m thick quartz veins. Detailed cross-sections and level plans were constructed for resource estimates of the intensively studied portion of the vein system. The program resulted in the discovery of local, high grade areas and an average grade in the evaluated area nearly double that expected from surface drilling.

Jan 1, 1984

By J. T. Crawford

Although nearly 10 pct of the total tonnage of coal produced annually within the United States is handled by bulk freighters on the Great Lakes, very little of the detail connected with it has been published other than occasional newspaper stories and publication of tonnage statistics. Of the total tonnage floated on the Lakes each year some 10,000,000 is stored and distributed from the port of Duluth-Superior, at the western end of Lake Superior commonly known as the Head of the Lakes. This port has the largest single area concentration of coal docks in the world. Since this area contains the largest ore docks, the largest movable material handling bridge, the largest and highest grain elevator and the largest coal bri-quetting plant in the world, it is entirely fitting and proper that here also should be located the largest coal dock and what we believe to be the world's largest clam shell. Of the sixteen coal docks operated by ten companies, five are owned and operated by the North Western-Hanna Fuel Co. which has two docks on the Superior, Wis., waterfront and three docks in Duluth, Minn. It is with these five docks that we are primarily concerned, General History In the summer of 1871 a small sailing vessel entered the harbor of Duluth-Superior with the first commercial coal cargo. All the coal brought up that first year did not amount to more than 3000 tons. During the year 1877 the first dock equipped for handling coal was built in Duluth. Coal receipts increased to 52,785 tons in 1879 the first year for which an official record was kept. Since then the volume of water-borne coal to the Head of the Lakes steadily increased to a maximum of 12,688,321 tons in the year 1923. This tonnage was nearly equalled in the year 1927 and the next highest tonnage recent year was in 1946 when 10,105,703 tons were unloaded. The average annual bring-up over a ten year period 1938 to 1947 was 8,605,231 tons. Approximately 30 pct of the coal unloaded at the Head of the Lakes is handled over the docks of the North Western-Hanna Fuel Co. Competition of other fuels coupled with expansion of coal fields in the mid-west have held coal receipts for Duluth-Superior at a relatively constant figure during the last eight years although the total tonnage of coal floated on the Great Lakes has more than doubled in the past 25 years. From the shovel and wheelbarrow method of unloading early cargoes to the horsepowered windlass derrick with a wooden tub was but a short step. The first movable coal handling, steam operated,

Jan 1, 1949

By D. L. Everhart

The search for new deposits raises two important questions: Where did the metallic ions that formed the orebodies come from? What processes and geologic factors were involved in ore replacement? A review of the wide geological variety of recent uranium discoveries tells how these questions are being answered. SOONER or later intelligent exploration for uranium leads to these questions: Where did the metallic ions that formed the orebodies come from? What processes and geologic factors were involved in ore replacement? These matters, of course, make a big difference in how best to look for orebodies. Before these questions are discussed it might be well to point out other factors bearing on the subject. The whole business of uranium exploration is only a little over ten years old, participation by the public is only about six years old, and real interest and activity by more than a few large mining companies has arisen only in the past two or three years. Throughout this short period, uranium exploration has been affected by the unique influences of necessary security measures and by division of the overall job into individual projects by a large number of specialists in diverse fields. This has meant that a normal interchange of information on the nature of uranium deposits has really only just begun. Compared to the vast amount of published studies on iron, copper, lead, zinc, and gold deposits over the past 50 to 75 years, current knowledge of uranium deposits is in its infancy and much of the pertinent information is still scattered about in a number of unpublished sources. The volume of reports on all phases of uranium exploration is now beginning to mount at a remarkable rate, and geologists with widely varying specialized backgrounds in uranium geology are engaging in spirited debates over the origin of uranium and the relative importance of geologic controls of various deposits. One of the most interesting features of known uranium deposits of the world is the wide variation, see Table I, in character and geologic environment. It should be noted that many types became prominent during 1953. The davidite-bearing veins of Radium Hill, South Australia, are almost unique, although the same mineral occurs in a different kind of deposit in Mozambique. Recent studies indicate that brannerite disseminated in the granite near Cracker's Well, South Australia, may soon constitute uranium ore. Basalt has been added to the list of favorable host rocks in the Northern Territory of Australia. Basalt is also the host of the pitchblende veins of the Martin Lake deposit, Beaverlodge district, Saskatchewan. The truly remarkable rich and extensive Steen deposit near Moab, Utah, is of the uraninite-vanadium oxide type. Secondary hydrous uranium arsenates and phosphates constitute the uranium minerals in the disseminated deposits of the Wind River Basin, Wyo., a new district discovered in the summer of 1953. Uranium minerals in shales adjacent to fractures were newly reported in New Mexico and several other parts of the world during the year. The well-known important uraninite dissemination in the Rand conglomerates of South Africa has a counterpart, as discovered in the summer of 1953, in the Mississagi quartzite and conglomerate of the Blind River district, Ontario. Gunnar deposit of the Lake Athabaska district, Saskatchewan, consists of uraninite in both granite and sedimentary gneiss beneath a granite cap, and large new orebody of the Eldorado Co. in the same general area follows a preferred stratigraphic horizon in schists. Uranium is, generally speaking, a very soluble and ubiquitous element. It occurs in at least two valency states and for this reason is not easily tied down in natural solutions. As Gruner' has pointed out, it is probable that uranium starts in the hexava-lent state in nearly all solutions instrumental in its transfer. It is believed that under oxidizing conditions the uranium moves in solution as the uranyl ion, UO. In solutions ranging in pH from 1 to 5, the uranyl ion is most commonly in association with

Jan 1, 1955

By Samuel L. Hoyt

THIS paper gives a short account of plastic deformation as observed in single crystals of zinc, zinc having been selected for the experiments described herein because the phenomena are comparatively so simple and can be studied throughout such a wide range. It is hoped that the paper will serve to show the type of information which studies of single crystals afford and will contribute toward the solution of the general problem of metallic behavior. PRODUCTION OF ZINC SINGLE CRYSTALS The method of Czochralski,1 as modified by von Gomperz,2 was used to produce the crystals studied. The equipment is shown in Fig. 1. Molten zinc is held in a crucible at a temperature which is not far above its melting point, as measured by a pyrometer. A lava disk floats on ,the melt, and is provided with a central hole about 1 mm. in diameter. A glass tube, drawn into a capillary at the lower end, is suspended from a string which is wound up by an electric drive at the speed desired. At the start, the glass capillary is let down into the melt and the hoist is started.. The capillary brings up a small quantity of molten metal with it to a point just above the lava disk. At this point, a jet of hydrogen cools it and causes it to crystallize, with the result that a small crystal forms. As the hoisting is continued, more molten metal is drawn up, in turn to be solidified by the jet of hydrogen. This additional metal continues the growth of the crystal already formed, and a long, cylindrical crystal results. The speed of hoisting used was generally between 0.1 and 0.5 mm. per sec., and the crystals were from 4 to 6 in. long and about 1 mm. in diameter. By varying the conditions, crystals of quite different orientations were obtained and were used in the study of the phenomena to be described.

Jan 1, 1927

By P. Somasundaran, D. W. Fuerstenau

This article presents the results of an analysis of grinding of 1:1 mixtures of 4x8-mesh quartz and limestone in laboratory ball and rod mills. From these experiments, the amount of energy consumed in grinding each component of the mixture was determined. In the ball mill, limestone consumes slightly more energy than quartz in the initial stages of grinding, but as the grinding proceeds quartz begins to consume a slightly greater fraction of the energy. The postulate that the fraction of energy consumed by any material in a ball mill is proportional to its volume fraction has been shown to be approximately true. On the other hand, in a rod mill energy consumption by quartz and limestone is equal only in the initial stages of grinding, with energy consumption by quartz greatly exceeding that by limestone as rod milling proceeds. Preferential energy consumption in tumbling mills has been discussed in a number of papers. For example, from an analysis of the kinetics of comminu- tion in ball mills, Arbiter and Bhrany' obtained rate equations based on the postulate that only coarse particles are ground, indicating that fine particles are protected from the action of the balls by coarser particles. In rod mills this protective action is much more pronounced than in ball mills. Recent studies on the rod milling of limestone-quartz mixtures have shown that this protective action causes the mineral with the lowest grindability (quartz in this instance) to consume the greater fraction of energy. 2 However, in the ball milling of mixtures it has been postulated that the consumption of energy by one of the constituents is determined by its volume fraction within the mill. 3 Possibly this hypothesis may be a simplification of the ball milling of mixtures since the protective action suggested by Arbiter and Bhrany may result in some preferential energy consumption by one of the constituents of a mixture. The objective of this study has been to determine preferential energy consumption in laboratory ball and rod mills by analyzing size distributions of each material in the products obtained from grinding 1:l mixtures of quartz and limestone. MATERIALS AND METHOD The procedure for carrying out the tests on wet grinding quartz-limestone mixtures has already been described.'r3 In the present investigation, 1:l mix-

Jan 1, 1963