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By Albert F. J. Bordeaux

The following general survey of the character and present condition of the silver-mines of Mexico, though not offered as a detailed treatise, has been prepared with care, is believed to be generally up-to-date, and is offered as a summary which may be found useful by mining engineers. For several centuries Mexico has ranked first anlong the silver-producing countries. It is now second as a copper-producer, and seventh as a gold-producer, with a fast-increasing output every year. The total amount of capital invested in its mining- and smelting-works exceeds $250,000,000, while the value of the yearly metallic production is $160,000,000. There are more than 20,000 recorded mining properties. The silver-mines of Mexico represent deposits of three principal classes: (1) veins and stock-works in eruptive rocks; (2) fissure-veins crossing the crystalline schists, granite, diorite, etc.; and (3) veins and replacement-deposits in limestone. The true fissure-veins in some districts contain (in value) vol. xxr1x.—22

Jan 1, 1909

By Arthur Redfield

THE year 1923 was marked by slight progress in exploring and developing the petroleum resources assumed to exist in Central America. Actual drilling for oil took place only in Costa Rica and Panama. The Sinclair Consolidated Oil Corpn., through its subsidiary the Costa Rica Oil Corpn., drilled in southeastern Costa Rica.. Its, Panaman subsidiary is reported to have abandoned drilling in Bocas del Toro. The Texas Co. drilled in Chiriqui, and the Panama Gulf Co. in Garachiné, Province of Darién. No oil was obtained in any of these wells;' shows of gas were met in Costa Rica. Concession hunting continued during the year. A number of concessions, several of which appear to be purely speculative, were submitted for ratification. Some confusion has been caused by overlapping concessions and claims to oil lands, caused partly by the imperfection of existing maps. A conflict between the Sinclair, and Gulf companies in Panama has been compromised. The Amory concession in central Costa Rica, held by the British Controlled Oilfields, Ltd., was voided by decision of the arbitrator, Chief -Justice Taft. Geologic exploration took-place in Guatemala and in Panama. The chief contribution of the year to Central American geology was a description by Katherine Van Winkle Palmer of Lower Miocene foraminifera and mollusks from southeastern Costa Rica. A new petroleum law was promulgated in Panama.

Jan 3, 1924

By Bai Shiwie, Li. Guangyu

This paper presents the study in situ on stress field of rock mass in a large dam site. By means of two different measure instruments and the method of stress relief, a lot of measure in situ has been done, including stress measurement of three dimensions at ten points and two deep-hole stress measurements in the perpendicular boreholes which are 59.4m and 53m deep seperately, and the basic accordant results corresponding two methods have been got. In the process of the deep-borehole stress measurement we got the stress value in critical state in which cylindrical core would become core-disking in the high stress area, which was first got in the world. The maximum principal stress was up to 650 kg/cm2. The stress value obtained by test and the thickness of rock disks all basically accord to the analysis by mechanical mechanism of core-disking The plane linear elastic finite element analysis has been completed. Results of inverse calculation all ac- cord to the measurement results in four different positions. The whole outline of the stress field of dam site was delineated clearly.

Jan 1, 1982

By Robert Mehl

IT is generally understood by workers in the field of the crystal struce ture of metallic alloys that terminal solid solutions are of two types, the substitutional and the interstitial. In reviewing the literature, the work of Weiss1 on the crystal structure of the alpha copper-tin alloys wa-encountered, in which a new type of terminal solid solution was proposed. In brief, Weiss' findings showed that the density of the alloys calculated from the side of the unit face-centered cube on the assumption of simple substitution-that is, with four atoms to the unit face-centered cell-was much higher than the density measured directly. It was suggested that the assumption of four atoms to the unit cube is not valid for these alloys, and that each unit cube contained less than four atoms; in other words, that one tin atom replaces more than one copper atom, leaving some atomic positions unoccupied. Such a structure, if verified, would have far-reaching significance in the study of the crystal structure of metallic alloys. It would indicate a complexity in terminal solid solutions not hitherto suspected and might encourage work leading to the discovery of other alloys of the same type, and perhaps to types intermediate between it and the two recognized types. It is of importance, therefore, to reinvestigate these alloys with respect to the type of solid-solution structure obtaining therein.

Jan 1, 1929

By Irnack C. Do Amaral, Mark C. Malamphy

Four magnetic fleld balances and several spare magnetic systems were purchased by the Brazilian National Department of Mineral Production from the Askania Werke A. G., of Berlin, in 1932. Preliminary field tests on this new equipment showed one of the vertical component magnetic systems to be defective. A series of measurements designed to investigate the functioning of these instruments, and particularly the defective system, showed it to have an abnormally low magnetic moment, as compared to the satisfactory systems, and a high-temperature correction that was opposite in sign to that which would be expected for a noncompensated magnetic system. Since these systems were of the "temperature compensated" type, this condition indicated an accidental overcompensation. Attempts to correct for this overcompensation by readjustment of the compensating masses on the aluminum and Invar spindles failed because the distance by which the position of the masses could be shifted was insufficient. The temperature effect was reduced by this readjustment but was not entirely eliminated, as was to be desired. Theoretical deductions indicated that the defective condition of the system could be explained as due to three possible causes: (1) considerable loss of magnetic moment of the system; (2) increase in the magnetic temperature coefficient of the laminas; (3) dislocation of the component parts of the system caused by a shock experienced after it left the factory and before it was tested in Brazil. Later information received from the factory after examination of the returned system indicated that the third cause probably played the most important role. Temperature calibrations of the defective system for various positions of the counterweights brought out an important point, which it is believed

Jan 1, 1940

By C. W. Hill, G. P. Luckey

In a previous article1 preliminary experiments were described, indicating the possibilities of a quantitative spectroscopic method for the determination of small amounts of lead in copper, which would be accurate and rapid, and could be carried out in the refining plant by one not skilled in chemical analysis. The present paper deals with the development of the method in the factory, giving the details of apparatus and its standardization, and presenting a comparison of the accuracy of the method with that of the standard electrolytic determination. (For variations and other applications of the method, the reader is referred to the first article.) A carefully weighed sample (0.4 gm.) of the copper to be tested is placed in a cavity in a graphite positive electrode. An arc capable of

Jan 1, 1919

By Cyril Smith

FOR several years an investigation has been in progress in the research laboratory of The American Brass Co. to determine the thermal and electrical conductivities of most copper alloys of commercial importance and several of scientific interest. This paper contains such data on the binary alloys of copper with silicon, aluminum, manganese and nickel, and on a large number of ternary or more complex alloys. Some inter-esting general relationships between the thermal and electrical conductivi-ties for all copper alloys at all temperatures are pointed out. The data for the copper-zinc, copper-phosphorus and copper-tin binary systems have already been published1,2 ? except for the electrical conductivity at 200° C., which is given in the appendix of this paper.

Jan 1, 1935

By R. W. Heckel, J. H. Smith, H. W. Paxton

The habit plane of proeutectoid cementute precipitated from austenite was studied using a two-trace surface (analysis coupled with a direct X-ray back-reflection determination of the orientatzon of the parent Matrix. The results were the same as those obtained by earlier workers1 - 2 who used Indirect methods to determine the orientation of the matrix. The data indicate that a range or habit planes in the parent phase is operative which is not in agreement with accepted existing theories. In 1933, Mehl, Barrett. and smith1 obtained a non-unique result in a study of the Widmanstätten habit plane of proeutectoid cementite. Their data are shown in Fig. 1. These results were verified by Greninger and Troiano,2 although they did not pre-sent any data. Both of these investigations relied upon indirect methods of determination of the matrix lattice orientation. Theoretical considerations of Widmanstatten precipitates have usually proved or assumed an orientation relationship between matrix and precipitate; the habit plane expressed relative to the matrix is generally unique, although it may be irrational.3 Opinion is divided as to the factors influencing the choice of habit plane. Mehl4 felt that a nucleus which was plate shaped to minimize strain energy and surface energy during its formation could maintain this shape by the point effect of diffusion; the

Jan 1, 1961

By C. K. Leith

In discussing the subject of mineral exploration, one is tempted to resort to reminiscence. I could tell of many missed opportunities, but I propose rather to outline certain changes in the methods and conditions of exploration which present new problems to the mineral explorers of today. Our subject might appropriately be called The Passing of the Old Time Prospector. The first question that presents itself is whether the job of mineral exploration is not already pretty well finished. The current market surplus of most minerals and the present overcapacity for production, with their attendant financial troubles, naturally raise the question whether the accumulation of reserves has not gone far enough for the present, and whether further exploration should not be left to some future time when consumption shall have caught up. Unquestionably we have gone far in the conquest of our physical environment, and the fear of shortage of minerals is less than formerly. For the time being there is no great need of further supplies for the world as a whole of many of the great essential minerals, coal, oil, copper, zinc, silver, and others. For a few minerals, such as gold and lead, the known future world supplies are not yet large enough. For all minerals the distribution is so unequal among the nations that exploration will continue in deficient areas in the attempt to make nations self-supporting.

Jan 1, 1932

By Ben E. Lusk

During the past five years, the surface mining industry in Appalachia has launched itself into a technological revolution, which has never been equaled during a similar period of time. Operators have begun to realize that effectively restoring land to a useful purpose, to the satisfaction of all concerned, has to start at the beginning of the operation and be an integrated part of it throughout. In order to insure continued mining in the mountainous areas, with protection of aesthetic beauty, things really have had to change. And so the new steep slope mining theory of "controlled placement" has been developed. Controlled placement is a broad term which means the placement of spoil in steep areas where its condition can be completely stabilized and revegetated. This includes the head of valley fill, mountain top removal, haulback, over the shoulder, block cut, and any other methods where the over-burden is technically delivered, hauled, or compacted, so that there is no adverse after effects when mining has been completed. [(Fig. 1)] Under controlled placement, our whole approach to mining has changed. Before any displacement of soil or uncovering of the coal seam transpires, a complete drainage system

Jan 1, 1977

By Moshe Sheinkin, Burke O. Trafton

This paper describes the use of a computer in analyzing the expected return on a mining venture. The computer program is designed to incorporate all aspects of a mining project, including the mine, mill, smelter, and refinery. Data input may consist of the operating variables in each phase such as the mining rate, grades, reserves at the mine, and the technical operating characteristics of the mine, mill, smelter, and refinery. Detailed tax computations are shown for a domestic operating company, for a foreign company and for a foreign subsidiary. In addition, the use of the various options that are available such as expense write-offs or deferments to create tax credits during preproduction years are considered, and its effect on the DCF. The program is also constructed to accommodate changes in metal prices, and escalation of capital requirements and operating costs. Output consists of profit and loss statements for entire projects using different methods of depreciation, cash flows, discounted cash flows, net present value and returns on investment. Returns on investment are computed for equity investment, total investment, and total investment less tax credits. Allowances are made for bank and guaranteed loans. Additional financial statements can be made for the following: a) A mine-mill segment with a concentrate selling schedule b) A mine-mill-smelter complex with a smelter product selling schedule c) Profitability of the smelter separately d) Profitability of the refinery separately

Jan 1, 1969

By H. R. Ogden, E. S. Bartlett, A. G. Imgram

THE tensile and notch tensile ductile-to-brittle transition characteristics of several refractory metals and alloys have been well documented.1-3 Electron-beam melted tantalum and columbium have been shown to retain excellent ductility at very low temperatures. Some indications of brittle behavior (low ductility and cleavage fracture) were observed with columbium tested at -253oC, but no similar effects were noticed with tantalum. Increasing the interstitial oxygen content in these two materials resulted in the detection of indications of brittle behavior at higher temperatures, although good ductility was retained in both bases at -196°C when they contained about 1 at. pet 0. Detailed descriptions of the impact transition behavior of these two materials at various purity levels have not been available. This technical note describes the effect of interstitial oxygen on the impact properties of wrought, fibered tantalum and columbium and compares the transition behavior to the previously determined tensile transition characteristics. Tantalum and columbium impact specimens with three different interstitial oxygen levels indicated in Table I were tested at temperatures ranging from -196o to 300°C. Oxygen additions were made to 1/2-in.-diam bars of electron-beam melted material in a Seiverts Apparatus. The oxygenated bars were then homogenization-annealed to obtain uniform cross-section hardnesses and swaged to

Jan 1, 1964

By L. O. Howard

Much work has been done recently on the lead-antimony system1 in connection with lead-rich alloys of commercial importance containing less than 20 per cent. antimony. Dean, Zickrick and Nix have called attention to the perpetuation in the literature of several erroneous data, such as a eutectic temperature of 228° C. at 12.5 per cent. antimony, instead of 247° at 13 per cent. The series is given as a classic example of a straight eutectiferous series in such late books as those of Heyn and Grossmann, 2 Jeffries and Archer,3 Guillet and Portevin,4 Pulsifer,5 Rosenhain,6 and Liddell,' as well as the somewhat earlier works of Hof-man (1918), Wang (1909), and Williams (1920). The work of Dean has definitely shown a solid solution of antimony in lead at about 2.5 per cent. antimony. While lecturing to a class in general metallurgy at the University of Idaho, the writer had the students prepare a series of lead-antimony alloys for the purpose of illustrating methods of thermal analysis. Proper proportions of powdered antimony (sold as C.P.) and test lead were mixed and melted in graphite crucibles under a reducing cover. Cooling

By Rossiter W. Raymond

I desire to call the attention of the Institute to an interesting experiment, which may turn out to be an indication of a valuable improvement in the manufacture of steel. As the members are aware, the addition of ordinary spiegeleisen, in the open hearth or Bessemer converter, to a bath of decarbonized iron, has a twofold object,—the recarbonization of the bath to a desired degree, and the remedy of the red shortness otherwise found to be inevitable in the final product. This red shortness is ascribed to the presence of oxide of iron in the molten metal; and it is supposed that the manganese of the spiegeleisen, uniting with the oxygen of such oxide, carries it into the slag. At the same time there is a small percentage of the manganese usually left in the cast steel, probably to the improvement of its quality. Whatever be the true explanation the effect of the manganese is acknowledged to be not only beneficial, but necessary. But the use of spiegeleisen containing high percentages of carbon limits the quantity that can be introduced, because the carbon must be limited if soft steel is desired. This inconvenience becomes so serious as to prevent the use of ordinary spiegeleisen in the manufacture of steel containing more than, say two-tenths per cent. of phosphorus; since the quality of the steel can be made tolerable only by reducing its contents of carbon in proportion as the

I TOLD you before that four things are necessary in addition to good judgment for one who wishes to practice the art of casting well. The first is to make the moulds and to have the furnace well made, the wood of a good kind, dry and seasoned, and the material disposed to melt. I have given you enlightenment on all these in detail, and on the last point as well, as you can see in the discussion on the alloys of metals where, among other things, I told you a good deal about those of copper. Therefore I wish to say but little about them in this chapter, but in order to follow the order promised you, I tell you that when you can, and if the labor or expense does not displease you, you should always alloy the whole quantity of the metals that you wish to put into one work and should make them into cakes of one kind. For, in addition to being more conveniently arranged in the furnace and mire easily handled, they all melt at one time and with much less work than they would if they were in pieces of different kinds. It is necessary to give corruption to copper, for if you decided to melt fine copper by itself in a reverberatory furnace your soul would burst before you had any honor therefrom. Then, if you wished to cast a fine thing from it, it would not succeed because it is dot fluid, on account of its viscosity; and if it should succeed, it would be all full of holes, like a

Jan 1, 1942

By John A. Church

THE Lake Superior blast-furnaces probably represent the maximum economy of fuel possible in this country. They smelt an ore which is very rich and easily reducible, and as the small amount of gangue present is not all silica, but in part a silicate, the amount of limestone required is a minimum. The average yield of the ore treated at six furnaces was 63 per cent., and the average quantity of limestone 179 pounds per ton of pig. The fuel used is charcoal, so burned as to retain most of the combustible volatile part, which, before the utilization of furnace-gas, was burned away. With these conditions it is not surprising that the Lake Superior charcoal practice is extraordinary in almost every respect. In any scientific discussion of American furnace work, the establishments there will be found at the head of the list, and they work under conditions which are extremely favorable for careful study. The Bay Furnace, near Marquette, has the honor of carrying "the broom" for the largest daily make. With a capacity of 1908 cubic feet it has, for months together, produced 29 tons of pig, graded at

Jan 1, 1876

By N. M. Saum, W. T. Caneer

Uranium may be in short supply due to the predicted energy needs in the coming years. As a result of this, a new surge of uranium exploration is underway accompanied by the refinement of numerous exploration techniques. One such technique is the monitoring of radon gas in surface soils and rocks as a guide to subsurface uranium deposits. The Colorado School of Mines Research Institute became involved in radon studies in 1967 on a project for the Atomic Energy Commission. Since that time the Institute has conducted numerous radon surveys for a large number of companies which have been active in uranium exploration. The objective of this paper is to relate the techniques utilized by the Research Institute and the results of some of the studies performed. Most of the studies performed by the Research Institute were related to roll front, sandstone-type uranium deposits. However, we have performed radon studies in various other types of rock. For those who may not be familiar with the application of radon "sniffing" in soils and rocks, a brief descriptive background should be given. The following question may be asked-why use radon as a guide to uranium mineralization? Some of the answers to this question are:

Jan 5, 1974

By M. Karmis

The development of engineering rock classification systems has received considerable at tent ion during the past few years. The purpose, application and method of assigning an index of rock quality, vary considerably between these systems. Several of them are directed toward the assessment of stability and support potential of an excavation whereas other systems are estimating a particular response of the rock, i.e. blastability or ripability. In the most widely accepted engineering rock classification systems, rock quality is expressed either in terms of meaningful descriptions or by a quantitative evaluation of a geomechanical property or properties. The application of sonic wave parameters in the engineering classification of rock mass and rock material has been the subject of considerable interest amongst investigators. The advantages of utilizing such techniques include minimal sample preparation, capabilities for large scale testing and the ability to perform non- destructive as well as reproducible tests. The purpose of the research presented in this paper was to determine the most appropriate sonic wave parameters for engineering rock classification purposes, to utilize these findings in developing new or modifying existing classification systems and, finally, to apply this information in the prediction and analysis of blasting wave characteristics.

Jan 1, 1984

By Terry E. Perkins, Len Marnewecke

Installation of a relatively simple, low-cost analog mill control system at Amax Lead Co. of Missouri's Buick concentrator has paid off handsomely. The system, which provides the capability of handling mill circuit upsets and ore changes while maintaining a desired particle size, is expected to generate annually a return on investment of several times its capital cost. In addition, the system stresses simplicity of field instrumentation and control strategy, leading to better operator acceptance and understanding, and its capital cost makes it very attractive for the specific installation when compared to more complex schemes using mass flow measurement and computers for calculating circulating load to infer particle size. This system has the advantage of utilizing an actual measurement for control, rather than a difficult-to-maintain inferred value.

Jan 2, 1978

By H. B. Charmbury, D. R. Mitchell

Everyone in the coal industry from top management to the preparation engineer is vitally interterested in recovering as much salable coal as possible from the run-of-mine product. Coal losses from a preparation plant occur in the solid refuse material being discharged from the plant and in the bleed-off slurry from the water circuit. The refuse is generally hauled from the plant in solid form by trucks, conveyors, or aerial trams to the refuse or culm banks or it may be crushed and transported by hydraulic methods to refuse ponds or dams. The loss of coal in refuse material and the extent of this problem has been covered in another paper. The loss of salable coal in the plant bleed-off slurry is one of the water circuit problems in coal preparation plants. Slurries originate at various places in the processing circuits and are usually disposed of by transportation to waste ponds known as slurry ponds. Even though the combustible material discharged as slurry and refuse from the plant is labeled a loss, the loss must only be considered temporary. There is a tendency at the present time to examine refuse and slurry losses and to reprocess these materials to recover valuable coal.

Jan 1, 1960