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By George Bain

METHODS of mining building stone of any sort are planned to pro-duce as few fractures as possible, and present a strong contrast to methods of mining metallic ores, which must be crushed eventually and have fractures produced in as great profusion as possible. Shocks transmitted to a stone invariably make it more porous and more permeable and reduce its effective life, therefore methods of mining building stone involve as FIG. 1. THE SUPREME COURT BUILDING, WASHINGTON, D. C. This building illustrates the fine detail of workmanship, unprotected sharp corners and thin edges, and tall narrow columns characteristic of marble structures. These features require exceedingly coherent stone, and preservation of these features for decades or centuries demands many special quarrying precautions to keep absorption to 0.14 per cent or less, a detail not essential to stone for coarser architectural types. few shocks as possible. This is singularly true for marble because marble structures are intended to have long life, greater delicacy of line, more gracefulness and fineness of sculpture than those made from any other structural material (Fig. 1). So that delicate lines may remain in almost perfect preservation for decades, or even centuries, it is important

Jan 1, 1935

By V. L. Elliott, C. L. Meyette

The conditioning of semifinished steel products such as billets, blooms, and slabs to remove surface defects before further processing to finished products is a necessary accompaniment to steel mill rolling operations. A knowledge of the kinds of defects which occur and of the conditions in melting, teeming, and rolling that may lead to their occurrence is favorable to the production of quality products. Surface defects may be classed as either of mechanical origin such as those that occur in the heating and rolling operations and include breaks, tears, guide marks, mechanical laps and the like, or they may have been in the ingot before heating and rolling. Examples of the latter are ingot cracks, blow-holes, scabs, and inclusions which lead to the numerous known types of seams and surface flaws. Most of the common types of surface defects and methods for their identification by visual examination or by the aid of macro-etch tests are well known. The conditions which caused their formation are also appreciably understood and this knowledge has been instrumental in the establishment of methods for metallurgical control. There are, however, defects of doubtful origin. In any endeavor to trace the causes for their occurrence, the question of first concern is: I. Whether they were formed in the rolling procedure. 2. Whether they existed in the ingot prior to rolling. In the case of semifinished products which are rerolled to finished products there is also the question of whether they were formed in the primary or in the secondary rolling. In metallurgical laboratories where numerous or routine examinations of the quality of rolled products are made over the course of time, there will doubtless be many puzzling cases of defect origin. Microscopic examination of the defects may, however, reveal a characterizing condition that can be used to classify them broadly with respect to their origin. Such a condition has been observed and, after detailed investigation, is described here with the thought that it may offer a usable and relatively simple solution to a bothersome problem. Basis For Classifying In this discussion the term "mechanical type defects" will be used to designate those that have occurred as a result of the rolling operations such as in rolling from the ingot to billets, blooms, or slabs or in rerolling to finished products. The term "steel type defects" will be used to designate those that were present in the ingot prior to primary rolling or that were in the semifinished product prior to secondary rolling to finished product. The basis for distinguishing between the two types of defects lies in the relative degree of subscale formation surrounding them. Subscale is defined1 as a zone of

Jan 1, 1949

By V. L. Elliott, C. L. Meyette

The conditioning of semifinished steel products such as billets, blooms, and slabs to remove surface defects before further processing to finished products is a necessary accompaniment to steel mill rolling operations. A knowledge of the kinds of defects which occur and of the conditions in melting, teeming, and rolling that may lead to their occurrence is favorable to the production of quality products. Surface defects may be classed as either of mechanical origin such as those that occur in the heating and rolling operations and include breaks, tears, guide marks, mechanical laps and the like, or they may have been in the ingot before heating and rolling. Examples of the latter are ingot cracks, blow-holes, scabs, and inclusions which lead to the numerous known types of seams and surface flaws. Most of the common types of surface defects and methods for their identification by visual examination or by the aid of macro-etch tests are well known. The conditions which caused their formation are also appreciably understood and this knowledge has been instrumental in the establishment of methods for metallurgical control. There are, however, defects of doubtful origin. In any endeavor to trace the causes for their occurrence, the question of first concern is: I. Whether they were formed in the rolling procedure. 2. Whether they existed in the ingot prior to rolling. In the case of semifinished products which are rerolled to finished products there is also the question of whether they were formed in the primary or in the secondary rolling. In metallurgical laboratories where numerous or routine examinations of the quality of rolled products are made over the course of time, there will doubtless be many puzzling cases of defect origin. Microscopic examination of the defects may, however, reveal a characterizing condition that can be used to classify them broadly with respect to their origin. Such a condition has been observed and, after detailed investigation, is described here with the thought that it may offer a usable and relatively simple solution to a bothersome problem. Basis For Classifying In this discussion the term "mechanical type defects" will be used to designate those that have occurred as a result of the rolling operations such as in rolling from the ingot to billets, blooms, or slabs or in rerolling to finished products. The term "steel type defects" will be used to designate those that were present in the ingot prior to primary rolling or that were in the semifinished product prior to secondary rolling to finished product. The basis for distinguishing between the two types of defects lies in the relative degree of subscale formation surrounding them. Subscale is defined1 as a zone of

Jan 1, 1949

By Paul J. Sirkegian

A detail of the guide rollers is shown on Fig. I; and Fig. 2 shows a photograph of a guide roller that has been in service for several months on the haul-back cable. The former practice of supporting and guiding the haul-back cable on slusher hoists at Kimberly was accomplished by using the conventional type of snatch-block pulley, but it was found that an excessive amount of cable whipping and unreasonable wear on both rope and pulley resulted from this type of cable support. The guide, which is wholly made in the Corporation's shops, consists of two vertical and one horizontal roll assembled in a frame that is lagged to the cap timber in a slusher drift. In some slusher drifts more than one guide-roller assembly is used, depending upon the length of the drift. The installations usually are placed at 30-ft. intervals. We have found by actual experience that these rollers have increased the life of the haul-back cable approximately 200 per cent, as compared with the usage of the conventional sheave-block pulley. Cable Care The underground rigging crew and the slusher operators are trained in rope splicing. No cable clamps or knots are permitted on slusher cables and all cable "eyes" are spliced. The standard practice has been to use preformed cables of ?-in. diameter for haulage and ½-in. diameter for the haul back. The preformed cables have proved to be important factors for safety in use and speed in making splices. No external lubrication is used on the cables. It has been found that dry ropes have about 400 per cent longer life than those that were lubricated under these operating conditions. An accurate record is kept of all cable life and the tonnage moved by the slushers in each working place, and if the rope wear is excessive in any particular working place, an investigation is made to determine the reason. Wire-rope Sling for Snatch-block Anchor The rope sling is shown by Figs. 3 and 4. These slings support the snatch-block pulley for the haul-back rope. The standard practice at Kimberly is to use a roller-bearing snatch-block pulley 10 in. in diameter. The snatch-block housings are equipped with a clevis attachment in preference to swivel hooks, as it has been found that the more rigid clevis keeps the cable in better alignment. The snatch blocks are hung from the cable sling, which is wrapped around the posts of the drift sets as shown on Fig. 3. This method of anchoring the pulley provides better anchorage and flexibility than those of the rigid or spring-mounted types. When the slusher-drift headings are being advanced, the snatch blocks are hung from a "gin" pole ahead of the last set of timbers' An employee is assigned on each production shift to take care of the lubrication of all slusher hoists that are being used and he is provided with tools for minor repairs.

Jan 1, 1946

By Richard G. Warren, Michael M. Minor, Gayle J. Thomas

INTRODUCTION Los Alamos Scientific Laboratory (LASL) initiated its effort in the Hydrogeochemical and Stream Sediment Reconnaissance (HSSR), a part of the Department of Energy (DOE) National Uranium Resource Evaluation (NURE) program, in late 1975. Since that time, LASL has completed sampling of the Rocky Mountain states of New Mexico, Colorado, Wyoming, and Montana at a density of about one water or waterborne sediment sample per 10 km2 and has sampled about 85% of Alaska at a density of at least one per 25 km2. Analytical results for these samples are reported by National Topographic Map Series (NTMS) quadrangle. All collection and analytical procedures have been standardized from the outset (Sharp, 1977; Sharp and Aamodt, 1978). Until early 1979, only uranium results were reported for these samples; thereafter, results include analyses for at least 42 additional elements in the sediment samples. Each LASL HSSR report also includes a discussion of the relationship of these analytical data to known or possible uranium resources; more recently, these data have been re- examined for their relationship to resources for other metals (Beyth et al., 1980; 1980a). Analytical results for LASL HSSR sediment samples are both comprehensive, including 43 elements, and precise, allowing close inter-comparison of data between quadrangles. A recent HSSR study shows that elemental concentrations in sediment samples from the Dixon Entrance quadrangle in Alaska are insensitive to the choice of sieve size fraction and do not vary significantly between stream locations a few meters apart, except for extremely high elemental concentrations (Warren, et al., 1980). Elements that are particularly reproducible include thorium, hafnium, and the .ram earth elements. Fortunately, sensitivities for these elements, which are often associated with uranium, are excellent by the nondestructive analytical technique of neutron activation analysis that LASL employs. Wet chemical techniques may not always give reliable results for these elements in sediment samples due to the difficulty of dissolving the resistate mineral phases that normally contain these elements. LASL has recently open-filed results for a large number of NTK3 quadrangles; to date analyses have been reported for about 605 of the quadrangles within the states of the Rocky Mountain region. As a result, uranium analyses am now complete for all sediment samples collected from the state of Wyoming. We have chosen to sumnarize the analytical results for Wyoming and portions of adjoining states hereafter termed "the ~ Wyoming regionn (Fig. 1 ) ; nearly 24 000 uranium analyses and nearly 17 000 analyses for 42 additional elements are available for sediment samples collected from this area. The DOE open-file report numbers are shown in Fig. 1 for reports open filed before September 1, 1980. The Wyoming region provides an ideal area for an examination of regional geochemical patterns ex- hibited by sediment samples. It is endowed with a variety of exposed geologic units and with widely distributed uranium districts associated with host units of several ages. However, discussion will focus on rock units of Eocene and Precambrian ages because they are widely exposed and host the majority of the uranium resources within the region (Fig. 2). Miocene units are also widespread and host mineralization in the Brown's Park Formation (Fig. 2). Epigenetic uranium mineralization occurs in sand- stones of lower Eocene age such as the Wasatch, Battle Springs, and Wind River Formations whereas vein type mineralization occurs in Precambrian crystalline rocks. Precambrian rocks within the region consist of a variety of granitic and meta- morphic rocks with l .4-2.8 billion year ages, except within the Uinta Arch, where they consist of a sequence of very low grade metamorphosed or unmetamorphosed 1.0 billion year old sedimentary rocks. Precambrian rocks have served as sources for much of the clastic material comprising the lower Eocene units, and may also have provided the source for the uranium in mineralized Eocene or Miocene sandstones (Stuckless, 1979). The remainder of this paper describes the relationship of elemental concentrations in HSSR sediment samples to exposures of Eocene and Precambrian rocks. The results are used primarily to determine where these Precambrian rocks might provide the most suitable uranium source areas and to infer the direction of transport toward adjacent depositional basins during the Eocene.

Jan 1, 1980

By George C. Lipsey

FOR many years the mining of coal and other minerals occurring in sedimentary formation has been planned according to information obtained by diamond drilling. Placer mines have used churn drills for sampling and estimating deposits, and some metal mines have used the method either wholly or in part. The diamond drill method, therefore, although not entirely new, has come into more prominence in the last few years. Several large-scale developments now being planned or in the production stage have used this method in varying degree. This paper will describe the operations of the Howe Sound Exploration Co., Ltd. at Snow Lake, Manitoba, where a gold mine was developed and equipped for mining and milling wholly on the basis of diamond drilling results. The property has been in operation nearly 3 years, so that results can be compared with the estimates and assumptions made from the diamond drilling. In developing the subject it is necessary to outline as briefly as possible the normal method of mining, from discovery to production stage. Table I sets forth these various stages, the methods of financing, the percentage of total cost, and the relative time interval required for each section of the work. The plan presented in this table cannot be applied to all mining developments, but it gives a basis on which to work. In Stages 2 and 3 the investment is moderate, and if the property does not respond favorably the options or interests can be terminated. Stage 4 represents a sizeable investment, and it is more difficult to drop the property after this part of the operation is completed. Stages 2, 3, and 4 may be repeated several times by different groups or companies before Stage 5 is reached, but when Stage 5 has been started the total capital investment must be provided and there can be no turning back. It will be noted that there is a total of 116 units of investment in the overall cost if one company proceeds with Stages 2, 3, 4, and 5 in order. Stage 4, however, consumes time which is important when markets are being considered. Bringing a property into production when metal prices are low is much more difficult than when the prices are high, and if this stage can be set aside production is attained more quickly. When Stage 4 is eliminated the total becomes 86 units of cost for Stages 2, 3, and 5, but an adjustment of 14 units must be added to Stage 5. These 14 units represent the useable value of Stage 4. Thus Stage 4 represents an investment of 30 units if carried on before Stage 5, but 14 units if included with Stage 5. This is accounted for by the fact that development work can be accomplished more cheaply under Stage 5, since everything that is done is planned on a production basis with permanent services. Stage 4 must of necessity be governed by expenditures, and a great many temporary services, including housing and power plants, must be provided. The prospect shaft is a small one, and drifts,

Jan 1, 1952

By J. I. Drever, C. R. McKee

The push-pull test, which is a simple injection and pumping sequence of ground water spiked with solutes of interest, is presented as a method of determining the adsorption characteristics of a formation. Adsorption properties are necessary to predict restoration from both in situ coal gasification and in situ uranium extraction. The major problems in applying laboratory measurements to the field concern scaling the effect of particle size, and obtaining representative samples. Laboratory measurements are conducted on gram to kilogram scale samples, whereas the push-pull test evaluates a sample weighing approximately 130 to 1,000 metric tons, depending on volume injected and porosity. The problems in translating laboratory results to the field appear to be less severe for sedimentary uranium bodies than for coal. Laboratory measurements are useful in delineating possible ranges in adsorption properties, and in planning the field experiment. The adsorption properties of a formation are characterized by the cation exchange capacity (C) and the distribution coefficient measured at low concentration, (kd) 'Laboratory procedures for their measurement on coal and uranium ore are reported. Two field push-pull tests were conducted on uranium formations in Wyoming. Adsorption properties estimated from these tests on the basis of a simple cell model were compared to the laboratory values. In the first case, excellent agreement was observed between the values estimated from the field test and the values measured in the laboratory. In the second case, the value for kd determined in the laboratory was 5 times higher than the field value. It is recommended that push-pull tests be conducted on coal formations being considered for in situ gasification in view of the great uncertainty in extrapolating 1aboratory.adsorption properties to the field.

Jan 1, 1979

By K. L. Komarek, P. F. J. Landler

Synthetic polycrystals of wustite were reduced ilz H2-H2O mixtures over limited roncentration ranges wiltun the wustite. field and the weight changes were continuously followed with a McBain quartz spiral balance. The reduction was. found to be controlled by a combined surface plus solid-state diffusion reaction. The solid-state diffusion had an activation energy of 38 kcal. Self--diflusioities of iron decreased with itzcreasing vacancy concentration. The activation energy of. the surface reaction runs different tor- different samples. The surface reaction-rate constan increased with increasirzg vacancy concentration. THE reduction of the oxides of iron has been studied for many years. Edstroem' has summarized the early work and has provided much information on the reduction of magnetite and hematite by hydrogen and carbon monoxide. More recent summaries are those by smeltzer2 and Themelis and Gauvin.3 Most investigators have reported that the iron metal which forms the outer layer during gaseous reduction is rather porous. According to Kohl and Engel14 the formation of such a porous iron layer depends on the properties of the underlying wiistite layer, on the reaction of the gas with the wustite surface, and on the transport of matter through the wustite layer. McKewan, Quets, Wadsworth, and Lewis, and Knacke 10 have found that, if a porous iron layer is formed, a surface reaction between gas and wustite at the bottom of the pores controls the rate of reaction. Seth and ROSS 11 and Warner 12 have pointed out that the influence of the gaseous pore diffusion through the porous iron layer cannot be neglected. It has further been shown that the wiistite layer formed during reduction is dense and that transport of matter across the layer occurs only by solid-state diffusion of iron ions.13,14 The solid-state diffusion rates observed by Edstroem and Bitsianis 14 and the surface reaction rates observed by Quets eta1.' show that an interaction of the two steps in controlling the reaction rate has to be considered. In this investigation the reduction of wustite was studied with respect to the interaction of the two steps, isolated from any other effects, by reducing wustite within the wustite field from higher to lower oxygen concentrations with H2-H2O gas mixtures. A similar study with CO-CO2 mixtures has been performed by Levin and wagner.15 Fused synthetic wustite polycrystals were reduced in steps of 0.4 wt pct from 24.4 to 23.2 wt pct 0 and over a temperature range from 700" to 1050°C. A few tests were also conducted with reduction steps from 24.4 to 23.6 wt pct 0 and 24.5 to 23.2 wtpct0. The Fe-O phase diagram is shown in Fig. 1 where the composition of the gas phase in equilibrium with the condensed phases is plotted as pct H2 vs the temperature. A careful study of the literature led to the conclusion that the fully drawn equicomposition curves (in wt pct O) in the wustite field used by Edstroem 1,16 and other authors needed some correction. Based on results by Darken and Gurry17 (shown as open circles) and on some of our own data, four corrected curves for 23.2, 23.6, 24.0, and 24.4 wt pct O were calculated (drawn as dashed lines in Fig. 1) which should replace the fully drawn equicomposition curves. MATERIALS AND APPARATUS Materials and Specimen Preparation. Wustite was prepared from iron sulfate (Fisher Scientific Co., New York) which had a purity of over 99.92 pct, with small amounts of manganese, copper, and zinc adding up to 0.03 pct. From the aqueous solution iron oxalate was precipitated and decomposed to magnetite according to Economos. 18 The magnetite powder was pressed into cylinders and sintered in vacuum at 900°C for several hours. The sintered compacts were placed in a platinum crucible of 2.5 cm diam which was fitted into a high-purity alumina crucible and then inserted into the center of the graphite heating element of an electric resistance furnace.lg The furnace was evacuated to below 1 p Hg and the magnetite sample was slowly heated. The evolution of gases during heating deter-

Jan 1, 1967

By C. G. Fink, E. P. Polushkin

A PART of the material incorporated in this paper was derived from the studies of ancient metal objects examined by the authors from time to time for museums and art collectors, in order to verify the age of the metal. The data thus accumulated during several years were systematically surveyed and supplemented by new material obtained in examination of a set of specimens that had been generously donated by museums for this study. Altogether over 50 pieces were investigated, of which 39 are described in this paper. Every specimen is at least 1500 years old; the majority are considerably older. Exact conditions to which these bronze and copper objects were exposed in the ground are unknown, unfortunately. It is safe to say that exposure conditions did not remain constant during the long period of burial. Although the collection of specimens studied represents a wide variation in location and age of the objects, as well as in the nature and composition of the metals, it was found that fundamental changes in the metal structure were limited to a few typical cases which, therefore, may be considered as more or less general. The authors' chief aim was to study the effect of extremely long periods of corrosion on the structure of bronze and copper. Specimens Studied As the majority of specimens were very small and sometimes had a heavy coat of patina, or crust, which further reduced the amount of metal available for analysis, quantitative chemical analyses were not made. Small detached specimens were not always obtainable and studies had to be made on the statue, or other object, itself. In the description of specimens (Table I), their approximate compositions determined under the microscopc are given. The proportion of tin in bronze containing eutectoid was found by visual estimation of the area occupied by the eutectoid. It was based on the assumption that maximum solubility of tin in copper on moderately slow cooling is 7 to 8 per cent in thin castings and 9 to 10 per cent in heavy castings. When the metal was all

Jan 1, 1936

By George K. Burgess

The suggestion has often been made that it would be highly desirable, at least for certain grades of steel, to be able to control more certainly, by pyrometric measurement or otherwise, the temperatures of the operation of the open-hearth and other furnaces used in the manufacture of steel and iron. That the properties of the ingot and finally of the finished steel product are intimately related to the final temperatures attained by the metal in the furnace and to the temperature of casting, has been recognized by metallurgists for a long time, and this question has been very thoroughly treated, especially by Prof. Henry M. Howe, and by A. W. and H. Brearley.1 It is the object of this paper to demonstrate that in so far as casting temperatures of furnaces, steel ingots, and similar operations involving the temperatures of streams of iron and steel are concerned, well-known pyrometric methods may be easily applied—if certain recently determined corrections are made and precautions taken—with a relatively high degree of accuracy. Greater but not insurmountable difficulties will be encountered in the case of open-hearth furnace temperatures, while for those of the converter type a ready solution does not seem practicable. It appears that certain essential data have always been lacking in reporting observations such as those of Le Chatelier in 1892. Thus the correction to be applied for the characteristic radiation—or emissivity— has hitherto not been adequately taken into account nor the limitations of the several possible pyrometric methods clearly recognized. In view of the fact that in open-hearth practice the temperature to be measured in the furnace itself, in the stream of metal and slag and in the teeming into molds or ingots is usually above 1,500" C. (2,700" F.)

Jan 1, 1917

By O. E. Kiessling

A GROWING uneasiness in the oil fields indicates that doubts are arising as to the efficiency of the present technical, economic and legal arrangements affecting production. Recent documents of the federal government, debates in state legislatures, editorials in the daily press and statements of oil company executives re-echo the notion that the present methods of producing oil satisfy neither the business man nor the public. Such intimations are of utmost importance, since oil is a vital clement in modern industry and dependence upon it increases as new uses develop. SECTION I-PRESENT SCHEME OF COMPETITIVE EXPLOITATION IS WASTEFUL The oil industry has convinced itself, for very good reasons, that the present scheme of competitive exploitation results in losses, both in terms of quantities of oil and in terms of profits. The story of these losses is familiar enough, and it is necessary only to distinguish and summarize briefly certain factors that are of importance to the following argument. Oil pools are exploited under a competitive economic system based on private ownership and contract; the hope of profits attracts capital and enterprise, and competition is supposed to serve as a regulative factor. Whether such a scheme of industrial organization works is partially dependent on the ability of the producer to withhold or produce is commodity as he sees fit, in accordance with the dictates of market demand.

Jan 1, 1927

By Henry Siegmann

HISTORY OF PRODUCTION AND USE In 1899 the consumption of fluorspar in the United States was reported as 16,000 tons. The invention of the open-hearth method of steel manufacture, plus the beginnings of a fluorine chemical industry, pushed consumption of fluorspar to 250,000 tons by 1918. In contrast to these consumption statistics of the past, the most recent statistics available (1972) indicate a total fluorspar usage in the United States of 1.352 million st (Table 15.4D.1). Fluorspar remains the world's cheapest source of fluorine, and its unique properties make the mineral the most desirable fluxing agent for steel refining. The linking of fluorine with carbon in the late 1930s resulted in the production of fluorocarbon, and constant growth in production over the years has formed the backbone of a strong fluorine chemical industry. For example, in 1972 it is estimated that total fluorocarbon production amounted to 2.113 million tons, and that, in this process, over 1.351 million tons of acid-grade fluorspar was consumed. The producers of primary aluminum long have been concerned about the fast dwindling reserves of natural cryolite. They found the solution to their problem by utilizing fluorspar for the manufacture of synthetic cryolite and aluminum fluoride. Nuclear weapons, as well as the growing number of peaceful uses for atomic reactors, constitute a market for uranium hexafluoride. This chemical and chlorine pentafluoride, used as an oxidizer with rocket fuels, are products that are as much a novelty as fluorocarbons were 25 years ago. Judging from past success in the field of fluorine chemistry research, it is safe to assume that the market for these chemicals will grow in the future. Three major industries account for the bulk of the fluorspar consumption: steel refining, fluorine chemical, and primary aluminum production. These industries have had a pattern of fabulous growth in the past, and their future plans point to a continuation of this pattern. It seems logical that the fluorspar usage also should continue its upward trend. Considering the growth of the fluorspar industry since 1899, and the obvious dependence on imports of fluorspar as a raw material, one of the most puzzling aspects of the past has been the apparent lack of coordination between fluorspar production and fluorspar consumption. A few authoritative voices have spoken out concerning the need to expand fluorspar production in order to meet consumption of the future. During World War II, the U.S. Government took positive steps in this direction by authorizing purchases at attractive prices for its "stockpile program." As a consequence, new fluorspar producing facilities were built, not only in

Jan 1, 1976

By J. E. Lawver, J. L. Wright, H. R. Kokat

Mesabi semitaconite and oxidized taconite ores that cannot be concentrated by froth flotation can be rendered amenable to flotation through partial concentration in a high-in tensity wet magnetic separator. Since 1964, a method for accomplishing this precon-centration has been under development at the Minnesota Mines Experiment Station, where several hundred tons of ore have been successfully processed. This paper is an analysis of the performance of the separators used at the Station. At present the United States is producing about 85 million tons of iron ore a year, and nearly 55 million tons of this comes from Minnesota. Nearly half of Minnesota's production is in the form of magnetite taconite pellets —the remainder being wash ore and gravity concentrates. As the demands of the blast furnace operators become more stringent - and they are becoming more so yearly — these demands are met by improved iron ore beneficiation technology. Furthermore, there is no doubt that as magnetite taconite, gravity ores, and wash ores are exhausted, new processes will be developed to produce a product comparable to magnetite taconite pellets from Minnesota's vast reserves of oxidized taconite and semitaconite. The magnetite taconite ores are rather easily bene-ficiated by conventional, low-intensity (500- to 1400-gauss) magnetic separators, followed, in some plants, by froth flotation of the magnetic concentrates.

Jan 1, 1969

By R. S. Archer

THE name molybdena was employed by Pliny to denote various substances resembling lead. Later this name was applied to galena-the naturally occurring sulfide of lead-or substances of similar appearance. By the middle of the eighteenth century, it was applied to graphite and to the mineral sulfide of molybdenum (MoS2) now called molybdenite. This confusion is quite understand- able inasmuch as these substances look and feel very much alike. In 1778, the Swedish chemist Scheele published a treatise in which he pointed out essential differences between graphite and molybdenite. On treatment with nitric acid, molybdenite, unlike graphite, produced a peculiar white earth with acidic properties which he called molybdic acid. Since the same mineral gave off sulfurous fumes on heating, he concluded that it was a sulfide of molybdenum. In 1790, there appeared an account of the isolation by P. J. Hjelm of the new element molybdenum, as a metallic powder, by heating the oxide with carbon. It was not until Bertelius conducted the necessary experiments, about 1818 to 1825, that the foundation of the chemistry of molybdenum was laid. The only recorded use of molybdenum during the first century after its isolation was as a chemical reagent, primarily for the determination of phosphorus. It was not until the last decade of the nineteenth century that the use of molybdenum in steel appears to have been investigated. A

Jan 1, 1953

By E. P. Shea

The Anaconda Co.'s Geological Department at Butte, Mont., was started early in the Company's history because of litigation involving vein ownership and extralateral rights. The problems, some of which were resolved in courts, were many because of the large number of veins and lode locations. Defensive action was required to prove ownership and protect against illegal exploitation of the downward and extra-lateral extensions of the ore bodies. In many cases it was necessary to define the outcrop of the vein and to show that its apex was within the boundaries of the lode claim. Exhibits illustrating geology were needed to present the cases clearly, and these could be made only after careful inspection and mapping of the underground workings by competent geologists. Also, The Anaconda Co. was one of the first companies to recognize the worth of skilled mining geologists and the value of accurate records in the search for new ore. The department was organized in 1900 by H. V. Winchell who, with D. W. Brunton, worked out the methods. Reno Sales was Chief Geologist from 1906 until 1948 when he was succeeded by V. D. Perry, the present Chief Geologist. Under their direction, F. A. Linforth, M. H. Gidel, C. H. Steele, E. P. Shea, C. C. Goddard, Jr., and W. A. O'Brien enlarged the scope of the work and improved the technique.

Jan 3, 1961

By J. Howard Boyce

INTRODUCTION The Tsumeb Mine is situated in the northern part of South West Africa, approximately 335 air miles north-east of the port of Walvis Bay on the Atlantic Coast, and 240 air miles north of Windhoek, the capital of South west Africa. The mine came into operation in the early 1900's and has operated continuously since then except during the two world warm and the depression years of the thirties, Tsumeb Corporation purchased the property in 1947, installed a new plat, and ham built a modern tom. In addition to the concentrator which began operations in 1948, a copper smelter was started in 1962 and a lead smelter in 1963, Tonnage of ore treated in the concentrator has varied through the years, reaching a maximum of 70,000 tons per month with a current mined tonnage of approximately 50,000 tons per month. Copper concentrates, lead concentrates and zinc concentrates are produced, and for a number of years the production of a germanium enriched concentrate was an important feature of the operation, Both copper and lead concentrates are smelted in Tsumeb, while the zinc concentrates are shipped overseas. Ore change, and the installation of the smelters in Tsumeb have necessitated modifications in the concentrator operation. This paper will describe current plant practice in some detail and will touch briefly on the techniques used from 1954 to

Jan 1, 1970

H. H. Hill.—I believe that as petroleum engineers you are all more or less interested in geophysical prospecting. A large number of the papers that have been written on that subject are too detailed or too much involved to be of much value to a person who is not familiar with the subject, so I suggested to Mr. Fohs that he might bring us something that we could all understand. As I take it, we are interested in learning something about the different methods, the places where they have been used, their limitations and in general whether they have given satisfaction in locating oil deposits. F. J. Fohs, New York, N. Y.—I will briefly summarize some of the results as I Bee them from my practical contacts with them and my discussion of the subject with some of the more important rnen both in this country and Europe. Geophysical Methods 1. Seismographs: A. 1. Sonic refracting seismographs of Karcher, McCullom and Reiber. For rapid reconnaissance and also for detail—perhaps, the best type of instrument. 2. Mechanical refracting seismographs of the Weichert-Mintrop type. B. I. Sonic seismographs using reflected sound from contacts of sufficiently unlike beds where latter are thick enough, being used for detail of both salt domes and ordinary structures where a good reflecting key bed occurs. 2. Torsion Balances: Made in three sizes with greater portability and loss of but 20 per cent. in medium size and loss of 40 per cent. efficiency in smallest size. A. Used to best advantage in detailing salt domes, in noting anomalies of deep-seated structures of the Edgerly, La., type (but not always certain here and dependent on interpretation which involves both experience and the human equation to a large degree). R. Used to advantage in mapping faults where a lime or other denser bed occurs upthrown, and the topographic irregularities are not too involved. C. Of use where buried granite plugs and buried-hill structures occur as in the Western Texas fields. D. Believed of little use for other types of structure. 3. Magnetometers or Variometers: Now built horizontal and vertical with declinometer combined in one instrument. A. Practical in mapping granite or basic igneous rock plugs and intrusions, or of detritus therefrom. Adams has recently demonstrated definite results in mapping the well known Panhandle arch.

Jan 1, 1928

By J. Gurland

The strength variation ofWC-Co alloys with composition and particle spacing falls into two ranges. 1) Above a critical value of the mean free path, the strength follows a dispersion hardening relation; it is proportional to the volume fraction of WC and in-versely proportional to the particle size. 2) Below a critical value of the mean free path, the strength variation is based upon the Griffith criterion of fracture and is controlled by the case of crack propagation. The maximum strength is attained when the structure and load just satisfy the critical conditions for spontaneous crack propagation. THE relation between the strength and the structure of cemented carbides is of interest not only for its own sake but also for its contribution to the understanding of composite materials in general. The cemented carbides are essentially aggregates of a brittle carbide constituent and a ductile binder phase and, at certain structures of intermediate composition, the composite alloys attain strengths far higher than those of the separate constituents in bulk. It is this variation of strength with structure which will be discussed. The experimental procedures of sample preparation, mechanical testing, and quantitative metallo-graphic analysis have been described in Ref. 1. The reported strengths are the maximum fiber-stresses in bending calculated on the basis of completely elastic behavior. The plastic contribution to the over-all deformation is small and was neglected in the calculations (the elongation at fracture of the most ductile alloy, 50 pct WC-50 pct Co, is less than 0.5 pct).2 The pertinent structural parameters are: f, the volume fraction of tungsten carbide; p, the mean free path through the binder phase; the contiguity C, defined as the average fraction of surface area shared by a particle of wc with all neighboring particles of the same phase; and d, the average equivalent spherical diameter of the WC particles. The strength variation of WC-Co alloys with composition and particle spacing is shown in Fig. 1 and Table I, which are based partly on previously published data' and partly on new experimental work which extends the range to higher values of the mean free path. Each data point represents the average of five samples. For a given composition, the transverse rupture strength reaches a maximum

Jan 1, 1963

By R. J. Brison, R. D. MacDonald

This chapter is written primarily from the standpoint of development of flotation processes for treatment of specific ores. However, most of the principles and techniques discussed are equally applicable to other forms of applied flotation research such as improvement of procedures in existing plants and development of new reagents or methods without reference to specific ores. Because it is not possible to cover this subject in detail here, much of the material presented is in the form of a guide to the literature, with emphasis on readily available, English language publications. Details are included only if considered to be widely applicable or not readily accessible in the literature. Related subjects which are covered elsewhere in this volume, such as flowsheet design and statistical techniques, are not emphasized in this chapter. The material presented is intended primarily for those familiar with the theory and practice of flotation, but with limited experience in applied flotation research. It may be of value to the experienced investigator as well, by calling to his attention some useful viewpoints or techniques that he may have overlooked. It has often been said that flotation is more of an art than a science. In- deed much of the knowledge of flotation behavior is empirical. However, the unsystematic, artisan approach to flotation problems results only in an ac- cumulation of unrelated data. Like any other physical or chemical process, flotation is amenable to investigation by systematic experimental methods. The experiments should be based, as far as possible, on an understanding of the natural laws that govern the process and on good experimental procedures. SAMPLING OF A DEPOSIT In working out a flotation process for a mineral deposit, no step is more important than that of obtaining a suitable sample or samples. Experimental procedures cannot compensate for the lack of a representative sample. Methods of sampling a deposit have been published elsewhere,l-4 but a few points are of special importance from the standpoint of flotation. First, the sample should be representative of the deposit, not only in respect to chemical composition, but also in respect to mineralogical composition and degree of dissemination of the valuable minerals. To help ensure

Jan 1, 1962

By J. D. Corbett

Mining geophysics in 1967 continued to expand with greater application in the exploration and development of mineral deposits. Moreover, geophysical activity increased without the particular emphasis of a Pine Point or Timmins discovery to spur interest. This trend is expected to continue through 1968 as geophysics more and more becomes an integral part of a mineral exploration program. This past year saw the "little black box" of the old-fashioned "doodlebugger" pushed further into the background, replaced by increasingly sensitive equipment of sophisticated design. The trend also is away from the one man geophysical operation wherein the same individual is responsible for the development, design and operation of the field gear, the planning and execution of a survey and analyzing and interpreting the data. In today's technology a staff of specialists, electronics engineers, mathematicians, physicists-to name but a few- are required to back up the exploration geophysicist in the development of new methods and techniques, in the reduction of the voluminous amount of field data and in the interpretation of the anomalies which can be enhanced by various high-speed computer techniques. Obviously a full back-up staff of these varied abilities is impractical to most exploration companies. However, the equivalent function is provided to the lone staff geophysicist by the many competent geophysical contractors and individual consultants.

Jan 2, 1968