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By C. A. Wright

The average lead and zinc content of the ores mined and milled in the Joplin district is low as compared with that of other lead and zinc deposits throughout the United States. Because of this fact and of the high grade of the concentrates, the ratio of concentration is unusually high. Most of the operating companies have aimed to produce as high a grade of concentrate as possible in order to obtain the highest price for their product. They have done this at the sacrifice of the percentage of zinc recovered. The average percentage of zinc recovery is from 60 to 70 per cent. For percentage of recoveries from actual mill tests, see tables. The concentration is commonly effected by crushing the ore to ½-in. (12.7 mm.) size and subjecting it to a roughing and cleaning over two or more large Cooley jigs, of the Harz type, the finer sands being treated on the usual types of sand and slime tables. The treatment of slimes by flotation is being tested at several of the larger mills. Coarse Concentration When the ore has been hoisted from the mine it is dumped onto a chute leading to a grizzly made of iron bars, usually heavy rails, spaced 4 to 5 in. (101 to 127 mm.) apart. The oversize is caught on the grizzly, the mineralized pieces are broken with sledge hammers so as to pass through, and the boulders that are practically barren are sorted out by hand and trammed to the waste-rock pile. The proportion of waste rock thus sorted out varies from a fraction of 1 per cent. to 15 per cent., depending on the nature of the rock. Crushing The undersize material, 5 in. (127 mm.) or less in diameter, passes through the openings of the grizzly into the mill hopper below. From

Jan 1, 1918

By Waldemar Lindgren

No one would maintain that all ore deposits or all deposits of useful minerals have been formed by the same processes. Generally they have originated by special processes of concentration but these may be of many different kinds. Some deposits have their origin in chemical or biochemical processes of concentration in rivers, lakes or seas, others developed on land by means of chemical reactions of surface waters on various forms of rocks. Certain insoluble substances remained behind; others were dissolved and precipitated in favorable places. This action proceeded in the realm of the oxidizing surface waters or in the deeper zones to which the waters from the surface could find their way. Examples of the latter kind may be found in the extensive copper and vanadium deposits of some sedimentary beds or in the lead and zinc deposits of certain broad limestone strata. In these instances the evidence for any other mode of origin would seem to be very weak indeed.' Nor does it seem possible to deny that circulating waters may form deposits of the more common metals along fissures after having dissolved many constituents from paths traversed. Another very large class has been formed by magnetic processes of concentration. The last 40 years have been a period of intense activity in the investigation and description of a vast number of deposits; all modern methods have been employed and the result is an accumulation of data, difficult or impossible to master. It has been a period similar to that in petrography. The generalizations, the able deductions, have lagged behind. Evidently several geologists have become weary of this "infinite detail" and a mistrust of the microscope seems to have arisen. Although this feeling of being swamped in microscopic detail is a painful experience, nevertheless only through the detail in combination with the large features, and only by utilizing all the related sciences shall we

Jan 1, 1927

In their presentations Dr. Puddington and Dr. Stratton-Crawley have concentrated on spherical agglomeration and two-liquid extraction respectively. I should like here to complete the picture by putting these two techniques together in context with other techniques in which non-polar oils are used in the concentration and separation of minerals. Although these techniques are invariably treated separately and have been studied in isolation, there is a lot to be said for considering them together and trying to systematize their similarities and differences. This I take as a principle guideline in my introduction to this discussion. Four processes can be distinguished on the basis of the dosage of oil required: --simple flotation with collector-extender --agglomeration (emulsion) flotation --spherical agglomeration --two-liquid separation Dr. Stratton-Crawley has suggested that "pigment flushing" could find application in the treatment of ores. This is an interesting suggestion. However, the process can be regarded as a variant of two-liquid extraction, and it is convenient for me to do so in this discussion. Table 1 sets out some main features of these techniques. The first, in which the oil is used to enhance the strength and reduce the dosage of the collector is not designed for and has no special advantages in the treatment of fines, and therefore will not be further treated here. To add to the details appearing in the Table, thumbnail sketches of the other three, which all do show particular efficacy in the treatment of fine particles, are given below.

Jan 1, 1979

By John T. Thorndyke

MOST important of the naturalcalcium silicates is the meta¬silicate, CaSi03, known as wollastonite, after W. H. Wollaston. A large deposit of this mineral was dis¬covered some seven years ago near Code Siding, Rademacher mining dis¬trict, Kern County, Calif., the deposit being some 7500 ft. long and of an average width of 300 ft. It consists of a series of small domes striking north¬erly and southerly and with a dip of 81 ° to the south. This deposit was opened up by a series of small quarries showing a potential tonnage of 12,000,¬000 tons, allowing of cheap mining and transportation, the Southern Pa¬cific R.R. spur track being one mile north of the workings. Numerous sam¬ples taken from different points on the deposit, tested by Mr. Brinker, of the California Testing Laboratories, Los Angeles, showed an average as fol¬lows: Per Cent Silica (SiO2) 47.12 Lime (CaO) 41.72 Magnesia (MgO) 2.72 Alkalies (R,0) Trace Iron (Fe.,O,) 1.60 whereas the theoretical composition of of wollastonite, as given by William Shirley Bayley, is as follows: Silica 51.75 Lime 45.25 The tonnage and purity of this de¬posit led to investigations into its com¬mercial development. Early work es¬tablished the fact that wollastonite was ideal for the manufacture of a tough, almost unbreakable, glass similar to Pyrex. It also established the fact that wollastonite was particularly adapted for use in the manufacture of mineral wool, towards which further research was then directed. Briefly, the prin¬cipal advantages were the substantially unvarying chemical composition of the naturally occurring mineral and its characteristic of being relatively flexi¬ble and highly resilient when fused into a glass. A mineral wool produced therefrom is thus not only of highly uniform composition and color but is most desirable because of the high mechanical strength and length of the individual fibers constituting the wool. It is well known that mineral wool may be prepared by melting a suitable charge of raw material and then intro¬ducing a stream of a suitable fluid, such as air or steam, into a stream of the molten raw material. By this means the molten material is blown into threads or fibers, which are collected in a suitable chamber similar to a tun¬nel, from which they are removed from time to time or continuously. Com¬mercial manufacture of mineral wool has been carried on for only about 50 years, but volcanoes, specifically Kilauea in the Hawaiian Islands, have

Jan 1, 1936

By Wilson Blake

A mathematical model based on the finite element method of stress analysis has been used to describe the behavior of the western wall of the Kimbley Pit as its slope was steepened from 45° to 57°. Theoretical stress changes because of slope modification are slight except at the toe of the modified slope. Magnitudes of stress created are small when compared with the strength of a competent rock. Resulting displacement patterns point out the need for determining the in-situ state of stress at a site prior to excavation or modification. A comparison of model results with field measurements shows that, in general, the model has described the measured behavior of the west wall of the Kimbley Pit remarkably well. The Bureau of Mines and the Kennecott Copper Corp. began joint research on open-pit slope stability at the Kimbley Pit, Ely, Nev., in 1961. The initial or planning phase of this research dealt with a detailed geologic study of the Kimbley Pit, determination of in-situ stresses in the district, laboratory and field tests to determine rock properties, and the design of a full-scale experiment to study the behavior of this pit as its western wall was steepened from 45° to 57°. Fig. 1 shows a cross-section of the original pit outline, the steepened pit outline, major geologic features, and the two instrumentation adits. After the final or slope modification phase of the research began, a laboratory research program was initiated to develop a mathematical model that would analytically describe the behavior of the pit as its western slope was steepened. This theoretical model study of the slope modification at the Kimbley Pit was conducted with the finite element method of stress analysis. The results are described in this report.

Jan 1, 1969

By G. Sachs

According to Tammann,' the explanation of the effect of mechanical deformation in producing changes in the properties of metals is one of the most important problems of physical metallurgy, taking rank with the study of the constitution of alloy systems; and this problem has long attracted the attention of practitioner and scientist alike. Its solution was not advanced materially until Tammann2 set up his translation hypothesis with its crystallographic basis, while other hypotheses, such as the amorphous metal hypothesis of Beilby3 and Rosenhain,4 have been shown by more intensive studies to be less and less satisfactory. The principles of the Tammann translation hypothesis have proved to be useful even up to today and in spite of all of the recent accumulation of experimental data, while the differences of opinion which have arisen relate to the extent to which the hypothesis accounts for the observed changes Ïn properties and to what extent further assumptions are necessary. Stimulated by the proposals of Tammann, there soon developed a lively experimental activity which aimed at the elucidation of the structural or crystallographic changes produced by the mechanical deformation of metals. Parallel movements of crystal "blocks" along definite crystal slip planes had already been observed by Ewing and Rosenhain5 in 1900, in metals which had been moderately deformed but without shedding light on the crystallographic nature of the processes accompanying more severe deformation. The solution of this important problem was not advanced until a much later date, or until the methods of X-ray crystal analysis had become available. Shortly after the discovery of the diffraction of X-ray by crystals, symmetrical diffraction effects were

Jan 1, 1931

By G. Ferrara

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

Jan 1, 1970

By Benjamin C. Allen

The surface tensions of liquid chromium and manganese were determined by a modification of the dynamic drop-weight method and found to be, respectively, 1700 * 50 and 1100 * 50 dynes per cm at their melting points. Molten drops were formed LITTLE is known about the surface tension of liquid chromium and manganese, even though they are technologically important metals and widely used in steelmaking. In the past, direct determinations have been hampered by their high reactivity on the lower end of a vertically held rod inductively heated under argon. The technique essentially reproduced surface tensions reported for liquid nickel and zirconium using static drop-shape methods. and vapor pressure. In this work, surface tensions were measured by the drop-weight method, using induction heating under argon. EXPERIMENTAL WORK Chemical analyses of rods used are given in Table I. Chromium rods were prepared from iodide-process crystals which had been are-melted, hot-extruded, warm-swaged, and centerless-ground.'

Jan 1, 1964

By T. A. Rickard

RICO, in the southwestern corner of Colorado, is one of the productive mining centers of the San Juan region, so-called because its waters drain into the river of that name, which is tributary to the Colorado. The San Juan region includes the counties of Ouray, Hinsdale, San Miguel, Dolores, San Juan and Montezuma. It is traversed by a network of picturesque mountain ranges on whose lofty summits there rests perpetual snow. The region is peculiarly rugged, and, in the early days of its development, tested to the full the hardihood of the adventurers who first explored its can ions 111 search for gold and silver. A prospecting party, guided by Jim Baker, scout and trapper, penetrated in 1861 this part of the territory of Kansas. At that time the country was in the possession of the Ute Indians. In October, 1873, by the Brunot treaty, they ceded to the United States Government the richest mineral-bearing portion of their

Jan 1, 1897

By R. L. Fleischer, B. Chalmers

In order to observe size effects associated with a grain boundary, aluminum single crystals and bicrystals of various cross-sectional dimensions were deformed in tension. Typical stress-strain curves are presented in conjunction with measurements of the effects of changes in crystal dimensions. Some effects of the growth rate used in preparation of crystals are also described. It is indicated that the macroscopic constraints at a grain boundary are responsible for the most prominent grain-boundary effect, the production of multiple slip. Two measurements of the width of the region of double slip are in agreement. It is concluded that the yield stress of aluminum is affected markedly by the inherent oxide coating. THE general problem to be examined is that of dimensional effects in the plastic deformation of metal crystals. These effects will be termed "size effects" and are here defined as follows: A size effect occurs in a series of crystals if their plastic-deformation properties are a function of crystal dimensions. Clearly then size effects depend on the nature of the boundary conditions imposed on the crystal. Crystal boundaries can be of three types: interphase, inter-crystalline, and free surface. Such deformation effects as are caused by distribution of phases, grain size, lineage structure, and single crystal external geometry are specific types of size effects. This discussion will be confined primarily to grain-boundary and single-crystal size effects, though in practice most "single crystals" not only have a number of small angle boundaries but also have one or more surface phases, so that the boundary conditions appropriate to a free surface do not necessarily apply. Hence, to this extent interphase size effects will be considered. The question of size effects associated with grain boundaries (called here intercrystalline size effects)

Jan 1, 1959

By R. A. Young

Zinc metal production in the operating plants in the United States during 1948 was approximately equal to that of the year 1947, although new developments during the year assure higher output in 1949, if economic conditions are favorable. In the Western plants, the man-power shortage was almost completely overcome and new capacity has been or is in the process of being added to three plants; thus by December of 1948 daily zinc metal production had risen to the highest point since May of 1944 despite strikes in one large primary smelter and in one secondary plant.

Jan 1, 1949

By Evan Just

Throughout history mining operations have, been relatively technical in character and somewhat esoteric. In ancient times mines were places where prisoners of war or criminals were sent, to drag out short lives of hard labor, under conditions ranging from hazardous to lethal. Underground mines were damp and poorly lighted, and workers were often cramped in narrow spaces and tiresome positions. Hard rock was mined by building fires against faces and quenching with water. Combustion products from these fires and from such dim torches as were provided, plus the dampness, made the underground atmospheres quite injurious to health. During the Middle Ages, mining became less penitential and more technical. Because of the desire of sovereigns to foster production from mines, miners enjoyed special privileges as free men. Crude pumping, hoisting, and ventilation systems were introduced (Fig. 9.1). However, mining remained a relatively hardworking, hazardous occupation, separated from the lives and comprehensions of most people. With the Industrial Revolution, steam-powered pumps enabled penetration to greater depths, and the use of power-driven machinery gradually revolutionized productivity. Skill became more important than back-breaking labor. This revolution continues into the present. Mining today uses some of the largest and most complicated machinery in existence and little rock is moved by direct labor. Power drills, explosives, and boring machines penetrate and break hard rock. The modern mine, surface or underground, presents an impressive panoply of drilling, breaking, loading, and transporting equipment, facilities for power transmission, pumping, and ventilation, and expensive, complicated crushing and treatment machinery. Modern technology, machinery, and skilled workmen produce an efficiency that knows no parallel in the raw material field. Mineral substances are extracted and converted into useful forms at costs which are dwarfed by those of providing forest or agricultural products in terms of comparable weights, even though conversion of these last categories is typically much simpler. Capital investment per worker, i.e., mechanization, is greater than in nearly all other industries. Despite these features, and more than average financial risk, the mineral industries perform at modest profit. The popular concept that mines and oil fields are sources of boundless rewards is a myth, sustained by the occasional unusual episode. Before one can start actual production of minerals, he must first acquire a suitable deposit. The process of acquisition will require anything from a rather simple search to a difficult, lengthy, expensive exploration effort. After locating the desired deposit, title must be obtained by denouncement, concession, leasing, or purchase. If the deposit is solid, it can be mined in pits or underground workings. If fluid or easily fusible, it can be produced through wells. If dissolved in lake or seawater, it can be

Jan 1, 1976

Correlation between Metallography and Mechanical Testing By H F MOORE (Henry Marion Howe Memorial Lecture Trans, vol 120 11,000 words ) The lack of effective correlation between metallography and mechanical testing from the days of Reaumur to the present is noted, and two general problems of such cor¬relation are stated (1) the correlation of qualitative test results with quantitative, and (2) the correlation of average results with maximum or minimum results Some correlation has been achieved, notably in the field of heat-treatment and in the study of elastic strength of metals Correlation is in the process of being developed in several other fields, including the quantitative study of the effect of grain size of metal on mechanical properties, of grain size and type of crystalline structure on the sensitivity of metals to weakening at holes, notches and other "stress raisers," and in the study of the starting phases of spreading, "fatigue" cracks Correlation of mechanical test results and metallographic study is needed in the study of such problems as the various theories of failure of metals, the meaning of and tests for service ductility of metals, and the relative damaging effect of defects inherent in metals, such as minute cracks and segregation, as compared with the damaging effect of "imposed" stress raisers, such as screw threads, sharp shoulders, etc The neces¬sity for more correlation of metallography and mechanical testing during student days is emphasized, and also the need of a better understanding on the part of engi¬neers of the significance and limitations of metallographic apparatus and results and of X-ray diffraction This should be matched by a better understanding on the part of metallurgists of the significance and limitations of mechanical tests of metals, of testing machines and strain-measuring apparatus

Jan 1, 1937

By R. J. Schilthuis

In 1929, Coleman, Wilde, and Moore1 undertook an investigation of the theoretical decline in reservoir pressure as related to the production of oil and gas. The most important part of this work was presented in an equation defining the relationship between the reservoir pressure, the quantities of oil and gas produced, the oil and gas content of the reservoir, and the properties of the reservoir fluids. With this equation, it appeared that, with sufficient data, it would be possible to calculate the oil content of the reservoir and predict quantitatively the effect of gas-oil ratio on the decline of reservoir pressure. Needless to say, such an expression would be highly important in evaluating fields and in arriving at a choice of production methods to be used. Unfortunately, at the time these investigators published their work, there were not sufficient data available to permit application of the equation. The technique of measuring reservoir pressures had not been developed, gas measurements were uncommon, oil and water production records were in most cases inadequate, and little was known of the properties of the complex hydrocarbon mixtures making up the oil and gas in the reservoirs. For these reasons, little additional work of a similar nature could be done. However, during the past four years many data have been systematically accumulated on reservoir pressures and the properties of oil and gas, and it is now possible to use these data in furthering the studies on the behavior of oil and gas reservoirs. It is the purpose here: first, to present the derivation of a modified form of the equation given by Coleman, Wilde and Moore, which will permit the calculation of what later will be defined as the "active oil" content of a reservoir; second, to derive formulas for calculating the reservoir-energy changes that occur during the course of production, and finally, to discuss the limitations and application of the equations developed.

Jan 1, 1936

By R. J. Schilthuis

In 1929, Coleman, Wilde, and Moore1 undertook an investigation of the theoretical decline in reservoir pressure as related to the production of oil and gas. The most important part of this work was presented in an equation defining the relationship between the reservoir pressure, the quantities of oil and gas produced, the oil and gas content of the reservoir, and the properties of the reservoir fluids. With this equation, it appeared that, with sufficient data, it would be possible to calculate the oil content of the reservoir and predict quantitatively the effect of gas-oil ratio on the decline of reservoir pressure. Needless to say, such an expression would be highly important in evaluating fields and in arriving at a choice of production methods to be used. Unfortunately, at the time these investigators published their work, there were not sufficient data available to permit application of the equation. The technique of measuring reservoir pressures had not been developed, gas measurements were uncommon, oil and water production records were in most cases inadequate, and little was known of the properties of the complex hydrocarbon mixtures making up the oil and gas in the reservoirs. For these reasons, little additional work of a similar nature could be done. However, during the past four years many data have been systematically accumulated on reservoir pressures and the properties of oil and gas, and it is now possible to use these data in furthering the studies on the behavior of oil and gas reservoirs. It is the purpose here: first, to present the derivation of a modified form of the equation given by Coleman, Wilde and Moore, which will permit the calculation of what later will be defined as the "active oil" content of a reservoir; second, to derive formulas for calculating the reservoir-energy changes that occur during the course of production, and finally, to discuss the limitations and application of the equations developed.

Jan 1, 1936

By Joseph E Pogue

Over a period of years the writer has presented a number of studies1 on various aspects of proration, in a progressive attempt to analyze critically and constructively the economic complexities of this interesting institution, which in a decade has revolutionized the economics of oil production in the United States. In the course of the investigations leading to these papers, the changing nature of proration and the principles underlying its evolution have gradually become clear, so that it is now possible to depart from the analytical method and to construct a synthesis of the steps that, if furthered by the industry, should carry proration past the economic hazards that still surround it to the goal of maximizing the value of the petroleum resource to the industry and the public alike. Nature of Proration Proration literally means the allocation of demand among competing producers on a pro rata basis, but the term now carries a much broader significance for it is employed to describe the entire process by which the production of crude oil in the United States is regulated. There is naturally much confusion of thought on the subject, for proration is an evolving system of control based upon principles of conservation and equity and embracing a body of practices that are tending to adjust themselves to the needs of the situation but are subjected to varying and divergent influences in the process. As it is now constituted, proration is a planned production measure designed to prevent waste, insure ratable takings, and balance supply and demand. The procedure is administered by State regulatory bodies through use of the police power of the States under authority of State conservation laws; the practice is supported by a considerable degree of voluntary conformance on the part of operators; and the Federal Government has accorded its cooperation by providing advisory quotas, circumscribing imports, checking movements of hot

Jan 1, 1939

By Joseph E. Pogue

Over a period of years the writer has presented a number of studies1 on various aspects of proration, in a progressive attempt to analyze critically and constructively the economic complexities of this interesting institution, which in a decade has revolutionized the economics of oil production in the United States. In the course of the investigations leading to these papers, the changing nature of proration and the principles underlying its evolution have gradually become clear, so that it is now possible to depart from the analytical method and to construct a synthesis of the steps that, if furthered by the industry, should carry proration past the economic hazards that still surround it to the goal of maximizing the value of the petroleum resource to the industry and the public alike. Nature of Proration Proration literally means the allocation of demand among competing producers on a pro rata basis, but the term now carries a much broader significance for it is employed to describe the entire process by which the production of crude oil in the United States is regulated. There is naturally much confusion of thought on the subject, for proration is an evolving system of control based upon principles of conservation and equity and embracing a body of practices that are tending to adjust themselves to the needs of the situation but are subjected to varying and divergent influences in the process. As it is now constituted, proration is a planned production measure designed to prevent waste, insure ratable takings, and balance supply and demand. The procedure is administered by State regulatory bodies through use of the police power of the States under authority of State conservation laws; the practice is supported by a considerable degree of voluntary conformance on the part of operators; and the Federal Government has accorded its cooperation by providing advisory quotas, circumscribing imports, checking movements of hot

Jan 1, 1939

By J. Brett, S. Friedman

A study of the diffusion of nickel into both fibrous and recrystallized 0.065-in.-diam silica-alumina doped tungsten wire at 1200°C has been conducted. The diffusion profiles were determined by chemical dissolulion of successive circumferential layers and spectro-photometric determination of nickel in the etchant. It was shown that the diffusion of nickel into tungsten is markedly structure-sensitive. No significant amount of nickel could be introduced at 1200°C into tungsten which had first been recrystallized at temperatures of 2300°C, leading to an upper limit estimate for the bulk diffusivity of nickel in tungsten of 10-11 sq cm per sec at 1200°C. However, nickel did diffuse into initially fibrous wires, caused re crystallization, and was alsays present at the advancing recrystallization front. The accumulation of nickel in an initially fibrous region ceases when the recrystallization front arrives. The characteristics of the resulting diffusion profiles are explained in terms of the relation between diffusion processes and micro structural changes. WHILE it is well-known that the presence of nickel and certain other metals causes low-temperature recrystallization of the cold-worked fibrous structure of doped tungsten,''' the character of the phenomenon is not well understood. Recently it was shown that the recrystallization reaction can be induced at low temperatures by the presence of solid nickel on the surface of doped wire, but not by exposure to nickel vapors.3 Once recrystallization was initiated, a continued source of nickel was required for propagation of the recrystallization front. The phenomenon appeared to be a complicated solid-state reaction since, in addition to the change in structure of the tungsten from fibrous to equiaxed grains, diffusion of nickel from the surface into the recrystallized and fibrous structures was occurring with possible chemical reaction between nickel and tungsten at the surface and interaction of nickel with the dopants which ordinarily stabilize the fibrous structure within the wire. The objective of the present work was to study the diffusion of nickel into fibrous and recrystallized tungsten structures in order to clarify the relationship of the diffusion process to nickel-induced recrystallization. Studies of interdiffusion in the Ni-W system4"7 have been principally concerned with the mobility of tungsten in nickel. Information on diffusion of nickel in tungsten is meager, and there seem to be no studies of the mobility of nickel in tungsten which elucidate the structural aspects of the phenomenon. The present experiments were designed to determine the diffusivity of nickel at 1200°C in fibrous tungsten, in large-grained tungsten prerecrystallized at high tem- perature, and in tungsten recrystallized at 1200°C due to the presence of nickel. Although the concentration profiles were determined in these experiments, unexpected changes in boundary conditions or complex diffusion paths complicated the analysis of these profiles so that the interpretation could not be readily expressed in terms of simple diffusivities. EXPERIMENTAL PROCEDURE The experiments were conducted on Sylvania 0.065-in.-diam silica-alumina doped commercial tungsten wire, hereafter designated as ordinary doped wire. A special lot of 0.065-in.-diam silica-alumina doped low-nickel wire was also used. Impurity analyses of the wire are given in Table I. The experimental design is shown in Fig. 1. All heat treatments were conducted in vacuum. Two groups of ordinary doped wire were prepared for diffusion with nickel. One group in the as-received (fibrous) condition was elec-tropolished, nickel-plated, and annealed at 1200°C for 20 and 40 hr, or was exposed to nickel vapor at 1200°C for 20 and 40 hr. The second group was recrystallized to an equiaxed grain structure at 2300°C for 3 hr, electropolished, nickel-plated, or exposed to nickel vapor for anneals at 1200°C for 20 and 40 hr.

Jan 1, 1969

By Paul M. Tyler

Mineral raw materials, because they are essential to our industrial prosperity and military strength, must be made available in substantial quantities. regardless of cost. Variations in the cost of procuring minerals, as compared with the cost of obtaining other commodities, and changes in the cost of production of different minerals relative to one another, will naturally influence the quantities of a given mineral item that can be marketed readily. However, in the last analysis, the cost of winning minerals from the ground usually constitutes only a small fraction of the value of the end-use products and services derived from them. The miner's share of the cost of a typewriter, telephone circuit, or even a modem office building, is almost insignificant. Far more important to the ultimate consumer, therefore, than any minor saving in cost is the assurance of ample supplies of the minerals needed to aliment our expanding economy. To create a successful metal mining operation involves ( 1 ) the discovery and systematic development of a mineral deposit, (2) extraction of the ore, (3) the mechanical and metallurgical processing to eliminate worth- less or harmful impurities, and (4) the profitable disposal of the product. The first step of the technological process belongs chiefly in the realm of the geologist, the second is a mining engineer's job, the third is mainly up to the millmen and extractive metallurgists; whereas the fourth and equally important step poses a commercial problem that has aspects in common with the marketing of other products. Ore finding is far from being an exact science. There is no mathematical criterion for evaluating the efficiency of prospecting and exploration. Lady Luck shares the honors or assumes part of the blame along with the prospector and geologist. Marketing like- wise involves factors that seemingly defy engineering analysis. Although the other steps can be measured with some degree of mathematical accuracy, even they tend to vary so widely in basic principle, as well as in

Jan 1, 1959

By R. H. Pemberton

The principle of airborne electromagnetic prospecting is well-known. The basic geophysical texts in most cases discuss the main elements involved in electromagnetic prospecting. However, there is certainly little information available to the public concerning the present types of airborne electromagnetic systems being flown today by both contracting companies and some of the mining companies which have their own instruments. This is unfortunate since it is difficult for those people not conducting such operations to understand thoroughly the large variation in the electromagnetic instruments available.

Jan 1, 1961