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By Miroslaw Hajdasinski

Estimation of the economic effectiveness of industrial development projects including mining ones is generally made on the basis of the discrete model of the value changes in time, although the character of these changes is similar to the continuous model. In this paper an attempt has been undertaken to investigate the problem of the value equivalence of both models exemplified by a construction of an underground coal mine. An effort has been made to determine the errors which for different estimation criteria appear in result of the application of the discrete model. Theoretical considerations have been supplemented with practical conclusions.

Jan 1, 1977

A plan which has just been approved by President Wilson, by, the Secretary of the Navy, and the Naval Consulting Board, provides for the active cooperation of the Associated Advertising Clubs of the World with the 30,000 engineers who will soon undertake the task of making a card index survey of American industry, so that it may be prepared for national defense, if need comes. Herbert S. Houston, President of the Associated Clubs of the World comments on the plan. "Through the great power of advertising we expect-to arouse manufacturers, workingmen, businessmen, in fact the whole country, to the vital need of making industry the basic line of defense so that, if necessity arises, it can supply munitions quickly and abundantly. "This is not a war measure, but a peace measure. The militarist will support it and so will the pacifist, as well as the great body of Americans in between. So the slogan `national defense and international peace, has been adopted believing that the two causes will be best served by linking them together. "While the primary thing, of course, is service to the country, it is manifest that this work of the engineers will be of the greatest service to industry in times of peace. If industry is mobilized for defense, it will be placed on a basis of efficiency to meet the keen competition that will surely follow the present war." Howard E. Coffin, one of the leaders of the American automobile industry, in outlining the far-reaching plans of his committee, the Committee of Industrial Preparedness of the Naval Consulting Board, said: "At the outset I wish to emphasize the absolutely non-partisan nature of this work. I am not even familiar with the political affiliations of the great majority of the members of the Board or of my committee. In setting out to, mobilize the industrial resources of the United States, we are concerned only with the benefit to the nation, and to that end we have called into being an organization made up of the best technical and business brains of the country, and that organization will work along business lines with strictly business methods. I think it reasonable to say that this is a movement perhaps unique in the history of national governments, and one geared up to the highest standards of twentieth century efficiency. "It is vitally necessary that American industry be made aware of the part it must play in the national defense. Our whole conception of warfare has been changed almost overnight. Our military heads at Washington are largely, of course, graduates of the very best technical schools, have been taught the profession of fighting, and are masters of that profession. As members of the Naval Consulting Board, we are unable to tell these men how to do their work. But while these departmental heads have lived with military problems all their adult years, we on the other hand have slept and eaten and lived with the industrial problems of the country. The two questions are wholly distinct, and the masters of one cannot possibly be the masters of the other. We are confronted then with the necessity of interlocking these two vast elements of our national life into a great working organization for the national defense. It is that which we are about to do.

Jan 5, 1916

By U. F. Kocks

SINGLE slip and a single parallel array of edge dislocations have been obtained in silicon single crystals by homogeneously bending them in a four-point dead-loading device at 1000°C around the [211] axis with [253.] as the tensile axis which encloses an angle of 40° with the glide plane. Other orientations or lower temperatures proved unsuitable. The homogeneity of the bending was checked by the method shown in Fig. 1. The chemically polished specimen was exposed to parallel light from a microscope-stage lamp. The sharpness of the focus of the reflected light is an approximate measure of the circularity of the sample. This method permitted the determination of the actual radius of bent specimens within 10 pct accuracy. The etching solution developed to show up dislocations consisted of the following volume parts: 2 HF, 1 HNO,, 2 CH,COOH, 1 a solution of 5 wt pct of CuNO, in water (Rosi'). The acetic-acid content was adjusted to produce fine well-defined etch-pits in about 2 min at room temperature. The effectiveness of the etch did not depend on the crystal-lographic orientation of the face etched. The number of etch pits produced after a given deformation was checked in the usual way against the Cahn formula' and showed good agreement. As it is to be expected from the orientation of the primary system there are slip steps on the top and bottom faces but not on the side faces (perpendicular to the bending axis), whereas etch pits appear on the side faces but not on the top and bottom faces. This is different only for occasional dislocations of a secondary glide system. All the micrographs included have been taken in places where the most of secondary glide could be seen. From this it is evident that in the homegeneously deformed region the number of secondary dislocations was less than 1 in 1000 of the primary type. Dislocation Distribution—A series of tests with varying amounts of deformation is shown in Figs. 2(a-c). An observation that can readily be made from these pictures is that the linear density of dislocations within slip lines is relatively constant and independent of the amount of deformation. "Slip line" in this context is understood to mean a line that is a straight connection of individual etch pits. The heavily pitted bands which can be seen in each of these three pictures may be resolved fairly definitely, at higher magnifications, into many "slip lines" the distance between them being of the order of 0.5p The distance between dislocations in slip lines is of the order of 2p and it is also fairly constant in going from the neutral zone outward. The higher over-all dislocation density in the outer regions of any sample and the higher total number in a more heavily deformed sample, are effected by a larger number of "slip lines." The relative constancy of the dislocation distance within an individual slip line is surprising. The absence of pile-ups" may imply, if there is no rear- rangement on unloading," that there are no substantial obstacles to slip in this case. It seems that the equilibrium distribution of the dislocations in each active slip plane under the higher external stress on

Jan 1, 1959

By S. Gstalder, J. Raynal

Consideration was given to simple tests which could be performed on rocks to give a measure of rock drillability. Various methods of breaking rocks were considered and the hardness test developed by Schreiner was selected for this study. The test involves application of an increasing load on the rock face through a flat-faced cylindrical punch until rupture occurs. Test results show that hardness is a good measure of the breaking strength of rocks. Useful relationships are shown to exist between hardness and other physical quantities such as specific disintegration, Young's modulus and sonic velocity. Specific disintegration (volume of rock broken per unit of work input) provides a possible means of comparing the effectiveness of other methods of rock breakage. The relationship between hardness and sonic velocity may be very significant for it may be possible to deduce rock drillability from sonic log data. provided that a mineralogical factor is taken into account. TO test further the results of the work, laboratory drilling tests were performed which closely simulated down-hole pressure conditions. Correlations of drilling results with rock hardness measurements were quite good. It was concluded that rock hardness, as measured in the laboratory or as deduced from sonic logs, could be used in relations for predicting rock drilling performance. INTRODUCTION Drillability of rocks cannot be defined in an absolute manner by a single quantity or measured by a single test. Resistance of rock to drilling depends to a large extent upon the means used for rock destruction. This complicates drillability classification of rocks for there may be as many classifications as there are methods of rock breakage without known functional relations between them. The objective of this work was to develop. in terms of rock destruction behavior, means of selecting the best drilling method for a given rock or the conditions for optimum output from a given drilling method. ANALYSIS OF ROCK DESTRUCTION TESTS Gauthier and Baron' have reviewed the many test methods which have been developed for determining the resistance of rocks to breakage. These include drilling tests, punch tests, scratch tests, resistance to shock, wear tests, etc. A standard drilling test might be to determine the time required to drill a standard depth (1/16 in.) in a rock using a bi-cone microbit (1 1/4-in. diameter) when a standard load (417 Ib) is applied at a standard speed of bit rotation (110 rpm). From the standpoint of similarity, the results of microbit drilling tests would seem to be most representative of the several methods suggested above. However, evaluation of drilling performance by this method is only qualitative and cannot be applied directly to actual drilling conditions. Punch tests basically measure rock hardness. Punches of various shapes and sizes, including small cones for Vickers' and Knoop's tests, the wedge for Epstein's test and the right circular cylinder for Schreiner's test, have been used. Results of these tests lead to a quantitative hardness classification which would seem to be related to the resistance of rock to bit-tooth penetration. Scratch tests are related to the resistance of rocks to abrasion such as would be encountered in drilling with diamonds. Either the width of the scratch obtained at a fixed load or the load required to give a scratch of a fixed width may be used to evaluate surface hardness of the rock. This should be related to the resistance of the rock to wear. The above tests, and probably many others. give relative measurements of the breakage or destruction characteristics of rocks. There is no direct relation between results of these tests and the drillability of rocks. Also, the tests each measure different quantities which have different dimensions and they do not permit direct comparison of numerical values. As one step in rectifying the above difficulties. it is proposed that the results of all test methods be expressed in terms of volume of rock destroyed per unit of work required; this is referred to as "specific disintegration". Test results may then be reported in a form which shows both a classification of rocks in regard to each method and a comparison of methods with regard to each rock. The disadvantage in using specific disintegration is the difficulty of measuring this quantity with accuracy. The volume of rock damage is difficult to measure. as is the true value of work input. Rock heterogeneity adds to the

Jan 1, 1967

By E. L. Tucker

IN THE metallurgy of precious metals, it has been standard practice for years to use cyanogen compounds, so it was but natural that early investigators in the field of flotation should consider these compounds as possible flotation reagents. In Australian Patent 9508, of 1913, alkali cyanides were described as suitable reagents for the separation of heavy sulfide minerals, the reagents being employed either in an alka-line or neutral circuit. In U. S. Patent 1236501, of 1917, to John M. Tibbet, the use of cyanide in conjunction with soda ash or lime is described. One of the claims of this patent reads, "An improvement in the cyanide process for the treatment of ores comprising, mixing the ore with cyanide solution and oil and alkali: emulsifying the oil in the presence of the ore, the alkali and the cyanide solution, floating a portion of the values in the pulp by producing gas bubbles in the mixture-and removing the values floated." More recently, Sheridan and Griswold, in U. S. Patents 1421585 and 1427235, describe a somewhat similar process and have, successfully introduced it in. the mill of the Timber Butte Milling Co. U. S. Patent 1429544, of 1922, to Stevens, describes the use of double cyanides of copper, zinc, and lead. The success of cyanide as a reagent in the differential flotation of lead and zinc sulfides in highly complex ores is proof that these patents have a solid foundation.. Although the technique of their application to particular ores has been worked out in many cases, no one, so far as is known, has attempted to describe the nature of the action of the cyanide or to determine the ideal conditions for its, application. It was the purpose of the present investigation to gather information on these points. Naturally this would have been an exceedingly ambitious.

Jan 8, 1925

By Strathmore R. B. Cooke, Marcus Digre

That calcium will activate quartz for flotation with anionic collectors such as soaps has been known for a number of years,12'3 and the method has been applied to the concentration of various iron ores4 5 6 as well as to other materials. Clemmer gives the permissible pH range for the activation of quartz by calcium as between 9.5 and 12.5 with an optimum value of 11.0, and Hertzog7 has determined the calcium abstraction of iron ores and of Ottawa sand, but otherwise little quantitative data are available. The purpose of the present investigation was to determine those conditions under which dilute solutions of calcium chloride will activate quartz for anionic flotation and to determine the amount of calcium ion adsorbed by quartz. Those variables, the influence of which was primary, such as calcium, sodium, and hydrogen ion concentrations, were studied. Other factors which influenced the results are discussed in the description of the experiments. Three different experimental methods were used to determine the activation of the quartz. The first method was to treat a sample of ground, deslimed quartz with solutions of calcium chloride and sodium hydroxide, and to determine the calcium adsorbed by chemical analysis of the solution. Advantages are that a direct value for the amount of calcium adsorbed is obtained, and introduction of a collector which may affect the adsorption is avoided. The difficulty is to determine the extremely small differences in the calcium concentrations before and after the abstraction. The second method was to determine the activation of the quartz by observing the contact angle obtained on pressing an air bubble against the polished surface of a piece of quartz immersed in a solution of calcium chloride, sodium hydroxide, and sodium oleate. This is the well-known "contact angle" method. The third method was to determine those conditions under which an air bubble will pick up quartz particles immersed in a solution of the desired reagents. Disadvantages common to the sec- ond and third methods are that introduction of a collector is necessary to obtain bubble contact with the mineral; very small quantities of contaminant can give erroneous results; and no information is obtainable concerning the amount of calcium adsorbed. Advantages are that tedious analyses, which at best give approximate results, are avoided, and the conditions, especially for the third method, closely simulate those of actual flotation. Although the most consistent results were obtained with the third method, this paper describes the techniques used and the results obtained from each of the three methods. Distilled water and analytical grade reagents were used throughout except where otherwise stated. Between tests all glass articles were cleaned with a chromic-sulphuric acid mixture and sodium hydroxide. Abstraction Method The raw material for the tests was Ottawa sand sized between 14 and 28 mesh. Batches of 500 g of this sand were dry ground for 1 hr in an Abbe porcelain mill with 2700 g of quartz pebbles. The batches were split down to samples weighing approximately 30 g, and the weight of each sample was adjusted to exactly this value.

Jan 1, 1950

By AIME AIME

NO FEATURE of the annual meeting is considered more important at Institute headquarters than the assembly of delegates from the various local sections and divisions. There the president of the Institute and other officials may learn at first hand what the members are thinking and doing in every part of the country, and the delegates, in turn, may find that head- quarters is not a group of more or less cold-blooded New Yorkers whose primary function is to send out annual bills for $15. This year, the section and division delegates required three sessions to thresh out the matters of common interest: Monday morning and afternoon and Thursday afternoon. They were also guests of the Institute at the Directors' dinner on Tuesday night, and at the Directors' meeting afterward.

Jan 1, 1932

By Robert Wamsley, W. E. Jones

One of the earliest problems in the life of any community is the provision of an adequate supply of water sufficiently free from all types of contamination to be suitable for domestic purposes. Generally speaking, the location of most communities is determined to a great extent by the availability of an adequate supply of satisfactory water. For a mining camp, that consideration cannot be foremost. Here, the ore takes first place, and the men who mine it must do the best they can under the existing conditions. If there is no local source of water, it must be brought from some distant source or must be found by sinking shafts or drilling wells. Fortunate indeed is the mining company that discovers a commercially valuable ore deposit beside a never failing creek full of pure water, with sufficient water rights available. because the acquisition of water in any other manner nearly always involves not only a considerable period of time but the expenditure of considerable money. The experience of Climax Molybdenum Co. demonstrates the measures that sometimes are necessary in order to provide a suitable supply of water. The Climax mine and mill are on the Continental Divide! about 13 miles northeast of Leadville. The elevation of the domestic part of the camp varies from a minimum of 11,320 ft. to a maximum of approximately 11,550 ft. above sea level, and, as is common at such altitudes, the near-by streams that might be suitable for a water supply are small and intermittent, usually flowing only during the summer months. The only streams of any size in the immediate vicinity of Climax are the Ten Mile and Arkansas Rivers The headwaters of Ten Mile River are on the Company's property, and its water has been used for the domestic supply. The headwaters of the Arkansas River are about 2 miles distant and have not been used as a source of supply by the company. During the past 11 years of the production of molybdenum at Climax, the number of families living there has increased from about 45 to 283, and the population has increased from about 200 to 1200 persons. Consequently, the capacity of the water-treatment facilities, and the amount of water available, had to be increased to meet the requirements of the camp. As early as 1932 it was recognized that the water in Ten Mile River would not continue to be adequate for domestic purposes and after considerable discussion it was decided to drive a drift through the major fault in an effort to find additional water. This drift was completed in 1935 and tapped sufficient water to make the supply adequate. This water was treated in a tank underground, where lime was added, and was then piped into the domestic supply lines. At about the time this line was completed, the presence of fluorine in harmful concentrations was discovered in the water. This problem was submitted to the International Filter Co. and in November 1937 a plant of its design was put in operation for treating the water to remove the fluorine. This plant proved entirely successful,

Jan 1, 1946

By D. M. Thayer, P. B. Linkson

High intensity wet magnetic separation methods have received much attention in the search for alternative and effective methods to treat weakly magnetic minerals. This paper examines the incorporation of such techniques in the beneficiation of a non-sliming specular Michigan Hematite. The dependence of separation efficiency and beneficiation of specular hematite on various parameters controlling the operation of such a device is investigated experimentally. Particular attention is focused on particle size limitations imposed in these separations. In light of these data, metallurgical balances are presented and an attempt made to rationalize the various models suggested in the literature.

Jan 1, 1982

By A. H. Bell

The general principles of the gas-lift will not be described in this paper. Only specific details that have not been fully discussed in previous papers, or results that do not fully coincide with conditions previously described, will be dealt with. The principal points to be emphasized and for which supporting data are furnished are as follows: 1. Gas-lift installations usually have comparatively high efficiencies as compared with standard pumping equipment, when reduced to a basis of barrels produced per horsepower installed. 2. Advantages of high-pressure plants from the standpoint of operating efficiency and for the application of the gas-lift early in the life of flowing wells. 3. Evidence of increased ultimate yield through conservation of gas by the gas-lift. 4. Possibility of development of new equipment to increase efficiency of the gas-lift. 5. Indications of the advantages of repressuring as a means of stabilizing gas-lift wells and as a means of increasing ultimate yields. TyPes of Installation The gas-lift installations of the more important companies in California have been of the central-plant type wherever field conditions would permit. This has resulted in greater flexibility and lower installation costs per well than could be obtained with individual well units. In general discussions of the gas-lift method of production, the installation costs are frequently referred to as being too high for economical operation. If the field conditions are carefully analyzed and the plant designed with the idea of obtaining high operating efficiencies, the installation cost per well can be lowered sufficiently to compare favorably with individual well-pumping units, when the operating advantages are considered. Much greater production per horsepower can be obtained with the gas-lift than is possible with pumping equipment. Table 1 shows the unit sizes and costs of gas-lift installations of three companies in the Los Angeles basin. The cost of walking beams, rods,

Jan 1, 1928

By M. Cohen, C. Wagner, J. E. Reynolds

If the total volume of a diffusion couple changes during the diffusion, the measurement of distance becomes ambiguous. Use of distance parameters as suggested by Hartley and Crank is discussed. For small concentration differences, the standard form of Fick's second law is retained with conventional length units and the in- terdiffusion coefficient D. It is shown how D can be calculated from experiments involving large concentration differences and analyzed in terms of distance parameters. 'The merits of incremental diffusion couples involving small concentration differences are emphasized. THE conventional form of Fick's second law for one-dimensional diffusion of component B in a binary solution of A and B is where c, is the concentration of component B; x, the distance; t, the time; and D, the interdiffusion coefficient which may depend on ca. Hartley and Crank' have pointed out that Eq. 1 applies only if the total volume of the diffusion couple does not change during the diffusion process; otherwise, the definition of x becomes ambiguous. No change in total volume takes place if the specific volume of the solution is a linear function of the weight fraction Wb, or if the molar volume is a linear function of the mol fraction N. In some alloys, however, these relationships do not hold, and then it is necessary to introduce a modified measure of distance, 4 in order to retain the general form of Eq. 1. The application of Hartley and Crank's suggestions to diffusion in alloys has been discussed by Wagner.' Relation Between Measure of Distance and Units of Concentration The definition of [ depends on the choice of units for the concentration c,, as follows: 1—If the concentration ca is measured as the weight fraction W, (or weight percent), [ = 5, has to be defined so that equal increments of contain equal increments of mass m of the solution, e.g., dm = pSdx = Sdw [2] where p is the local density of the solution, and S is the cross-sectional area in sq cm which is taken to be constant in this problem of one-dimensional diffusion." * da Silva and Mehla have demonstrated the constancy of the cross-sectional area in the usual type of diffusion couple. However, experiments involving diffusion into thin wires4, 5 may exhibit changes in cross-sectional area, and therefore are excluded from the present treatment. Thus and the unit of is gram per sq cm instead of cm. 2—If the concentration c, is the mol fraction N, must be defined so that equal increments of contain equal numbers of mols of solution, e.g., dn= (S/V)dx= Sd [41 where V is the local molar volume of the solution. Thus dt, = dx/V [51 and the unit of is mols per sq cm. 3—If, as may be advisable in the case of interstitial solutions, the concentration C is measured in terms of the molar ratio of components B and A (c,, = Y, = nH/nA, where n and nl are numbers of mols of B and A), = Y has to be defined so that equal increments of contain equal numbers of mols of A, e.g., dnA= (NAS/V)dx = Sdf [6]

Jan 1, 1954

By Helmut Thielsch

METALLOGRAPHIC specimens whose surfaces are to be investigated are too thick to allow either light or electrons to pass through them for microexamination by transmission. This difficulty is overcome with optical microscopes by illuminating the surface through the objective lens. For electron microscopes best results are obtained by preparing thin replicas of the surface of the specimen, placing them in the microscope and passing the electron beam through them. Since electron microscopes represent a rather recent invention, they have found little application as compared with optical microscopes. This is true because, aside from the cost of new equipment and development of new techniques, some of the older replica methods necessitated the destruction of the surface from which a thin transparent replica was obtained. In other processes in which the surface is preserved, either too tedious a procedure is required, unsuited to "mass-production " requirements of industrial laboratories, or replicas of insufficient contrast and sharpness are produced. In general, investigations with the electron microscope involve five steps: (I) polishing the surface of the metal specimen, (2) proper etching of the surface, (3) preparing the suitable replica from the surface, (4) examination and photography in electron microscope and (5) interpretation. PREPARATION OF METAL SURFACES Usual metallographic polishing is generally satisfactory. It is important though that the final polish be applied very care- fully, since otherwise evidence of a small amount of deformation might show up even on relatively deeply etched surfaces. A high-power microscope should be used to determine the suitability of the polish and etch. This, of course, is not different from optical examinations, but in these, if a deep etch is used, the problem is less serious. It is frequently difficult to detect with optical microscopes poor polishing aside from superficial scratches before etching. Figs. I and 2 show micrographs of "well" and "poorly" polished nickel etched by immersing the same for 20 min. in a solution containing 8 grams cupricsulphate in 40 C.C. of concentrated HCl and 40 C.C. of H20 (Marble's reagent). The sample shown in Fig. I was polished in its final stages for 5 min. on a carborundum wheel followed by 10 min. on a rouge wheel, whereas the sample shown in Fig. 2 was polished only I min. on the rouge wheel. Generally, this procedure does not guarantee that the surface of the specimen will be either undistorted or deformed. It was applied here merely to show the effects of good and poor polishing. To the experienced investigator, plastic deformation is

Jan 1, 1946

THERE are many kinds and varieties of earth* that are used for the loam compositions for making the moulds for casting bronze, brass, or other metals. Since this is a very necessary thing, you must try to have the best kind and one that resists the fire well. It must be disposed to receive the metals well, must make a neat casting, and must not shrink or break with cracks on drying or baking. Aside from actual trial, I believe that there is little that can help you, since the clay in itself has no color or [77] visible sign that I know of to show how satisfactory it is. Understand that their colors are no less varied than their natures, for, as you see, one is white, one black, one yellow, and another red. Perhaps none will show by its color that it is good for this work, yet it might also happen that all colors are good. But all that I can say about it is to show you by their effects how the good ones should be in their nature; and so by trial you will choose among those that come into your hands. All earths are either sandy or tufaceous, either argillaceous and lean or pasty with unctuous viscosity. The lean ones make the loam powdery and without toughness and hold together poorly by themselves when they are dry. The unctuous and viscous ones shrink and break. Becoming smaller by shrinking, they often twist the forms and they stick together badly. They swell up again in the fire and produce works that are neither exact-a nor neat. Therefore, the good ones must be those that are neither unctuous nor lean, neither wholly tender nor rough, and with a grain that is fine, without pebbles or shells. When applied to a work they easily dry out without fractures and, when dry, hold their own shape well. Above all they must resist the fire well. These are usually of a yellow or red color, but whatever their color may be, the color does not force me to say that the yellow are really better than the black, and the red than the white or gray. Their quality depends on what trial shows. Thus, to summarize, whenever you have to do this work, you must try to have the best clay that you can, because it is to be the foundation of

Jan 1, 1942

By AIME AIME

AMERICAN participation in the World Engineering Congress in Japan will be generous. Nearly seventy papers have been prepared and for- warded for printing and the A. I. M. E. is well represented in the list. At our San Francisco meeting four of these will be briefly reviewed by the authors for the benefit of those who are unable to go on to Tokyo. They constitute a group dealing with the present economic status as seen by engineers of the world's iron, coal, petroleum and non-ferrous metals. Messrs. Leith, Smith and Tryon, Requa, and Probert have written papers that constitute a notable series. Messrs. Jeffries, Sweetser and Kinney, and other Institute members have written papers dealing more closely with technologic progress. The latest list of delegates and members is printed below, names of A. I. M. E. members being set in italics.

Jan 1, 1929

By Sir Robert Hadfield

I am asked to contribute a few words to "The Book of British and American Friendship." This book of the two countries ought never to have been closed. It was a colossal mistake on the part of certain of our statesmen in the past which led to the severing of the interests of the two countries which, by the greatest of all bonds-Nature-were meant to be one. However, that is past, and a new book is opened, one full of promise for the world's future. I should imagine that outside the Kaiser-Junker classes, even the Hun himself would prefer to be under Anglo-Saxon laws and customs rather than his own. At any rate, judging from the number of Huns who have

Jan 8, 1918

R. W. Balluffi (Atomic Energy Div., Sylvania Electric Products Inc., Bayside, N. Y.)—Since porosity is known to form in the copper side of Cu-Ni couples during diffusion24,25 it is of importance to consider this factor in interpreting the large variations of chemical diffusivity with copper concentration reported for this system. The presence of porosity may affect the measurement of D in two ways: 1—density changes in the couple invalidate the usual solutions of the diffusion equation, and 2—the pores may act as short-circuiting paths when transport through the vapor or along internal surfaces is appreciable or else as open circuits when these effects are small. The error produced by the first effect may be estimated by a graphical analysis. Fig. 8 shows the porosity generated in the copper side of the Kirkendall interface of a pure nickel vs pure copper couple after diffusion for 350 hr at 1040°C in hydrogen. In Fig. 9 the actual diffusion curve which would be obtained by the usual slicing technique is shown as a solid line drawn to the same scale (from the data of da Silva and Mehl"). The amounts of porosity (obtained by lineal analysis) and of nickel are graphically represented by the hatched areas. The standard solutions of the diffusion equation are valid only when all volume elements of unit length and unit cross section contain equal numbers of atoms." It is possible to correct the experimental curve to satisfy this condition by shrinking the couple in the direction of diffusion in such a way as to eliminate the porosity.* The corrected diffusion curve obtained after

Jan 1, 1954

By Francis S. Kendorski

Caving offers the lowest cost per ton of ally large-scale mining method, but its successful application demands an ore body that conforms to several rigid requirements. The deposit must be of wide areal extent, massive and not spotty in ore values, and insensitive to ore dilution. It must also be a rock mass that breaks up readily. There are only three active caving operations in the US-Climax, Henderson, and San Manuel-but caving methods have recently-taken on new importance as deeper, lower grade mineral occurrences and ore bodies are found. These deposits are too deep for surface mining methods, and too low grade to support any type of underground mining except a bulk method such as caving.

Jan 6, 1978

By Willard L. Hunter

Four solvent extraction systems were studied to determine their efficiency jor extraction and separation of tantalum and columbium. Aqueous feed solutions of varying HF-HCl concentrations and metal content were contacted with equal volumes of cyclohexanone, 3-methyl-2-butanone, and 2-pentanone and solutions of varying HF-H2S04 concentrations were contacted with equal volumes of 2-pentanone. One multistage continuous test was made in a polyethylene pulse column using cy clohexanone as the organic phase. In each system studied, columbium and tantalum purities in excess of 95 pct with respect to each other were obtained in single-stage tests at low acidities in the feed solution. Separation factors ranging from 1700 to 2400 were obtained when rising HF-HCl mixtures in the aqueous phase. Best results were obtained when a solution of HF-H2S04 was used as the aqueous phase and 2-pentanone as the organic phase. A separation factor in excess of 6000 was obtained in one stage with aqueous solution concentrations of 2 _N HF and 2N H2S0,. When acid concentrations were increaszd to 52 HF and 10 _N H2S0,, 99.9 pct of the tantalum and 98.2 pct of the columbium initially present in the feed solution were transferred to the organic phase. The separation of columnbium and tantalum obtainable by means of the solvent extraction systems presented in this paper was found to corn -pare favorably with other systems, including the HF-H2SO4-methyl isobutyl ketone system currently used by most producers for the extraction and separation of these metals. TANTALUM and columbium are always found together in minerals of commercial significance, although the proportion of the two metals in ores varies within broad limits. Columbium is estimated to be 13 times more abundant than tantalum. Five methods generally employed for the separat:ion of these metals are: 1) fractional crystallization (the Marignac process),2 2) solvent separation, 3) fractional distillation of their chlorides, 4) ion exchange, and 5) selective reduction. Of these methods, the one currently used by industry to the greatest extent is that of solvent separation. One of the early technical developments in solvent separation of tantalum from columbium was reported by the Bureau of Mines: the HF-HC1-methyl isobutyl ketone system; data were presented for both laboratory and pilot-plant experimentation.3 Of twenty-eight organic solvents tested for their ability to extract tantalum from an HF-HC1 solution of columbium and tantalum, 3-pentanone (diethyl ke-tone), cyclohexanone, 2-pentanone, and 3-methyl-2-butanone were chosen for further study. Data on the HF-HC1-diethyl ketone system has been published4 and data describing the use of cy clohexanone, 2-pentanone, and 3-methyl-2-butanone as the organic phase are included in this report. RAW MATERIAL The source of tantalum and columbium oxides for this study was ('Geomines" tin slag from the Manono Smelter, Cie Geomines, Gelges, S.A., Congo. In order to extract the valuable Ta-Cb content, the slags were carbided, chlorinated, and the sublimate from chlo-rination was hydrolized and washed free of chloride with water. The washed material was air-dried and stored in a stoppered container. Throughout the paper, "feed material" refers to this mixture of hydrated oxides which was employed because of its high solubility in aqueous solutions. Typical analysis of the hydrated oxides is shown in Table I. I) HF-HC1-CYCLOHEXANONE SYSTEM Batch Separation. Effect of Acid Concentration. To determine the effect of varying the acid concentration upon the transfer of tantalum and columbium, a series of tests was made in which approximately 2.5 g of feed material was added to 25 ml solutions of 2, 4, 6, 8, and 10 N HF and 0 through 5 N HC1. Tantalum pentoxide concentration of the solu%ons was approximately 21 g per liter and columbium pentoxide was 14 g per liter. These starting solutions were shaken with equal volumes of cyclohexanone in 100 ml polyethylene bottles for 30 min. The phases were carefully separated in 125 ml glass separatory funnels. The time of contact of the solutions with the separatory funnels was kept at a minimum to reduce silica contamination. The measured phases were separated into 400 ml polyethylene beakers and the metal contents of each were precipitated by addition of an excess of ammonium hydroxide. Precipitate from each phase was filtered on ashless filter paper, ignited at 800" to 1000°C for 45 min, weighed, and analyzed by X-ray fluorescence.5 Data tabulated in Table I1 and illustrated in Fig. 1, show that maximum separation of tantalum from columbium for each HF concentration was obtained with no HCl present. The purest tantalum product was obtained with some HCl present. The highest separation factor was obtained at 2 N HF and

Jan 1, 1970

By G. M. Schwartz, G. A. Thiel

Dimension stone was first quarried in Minnesota in 1820 and a very active industry has grown up over the years. The main basis of the present industry is a wide variety of igneous rocks sold under the general trade name of "granite." Also of considerable importance is the Ordovician dolomite sold under the locality names, Man kato, Kasota and Winona. THE first record of the quarrying of dimension stone in Minnesota dates back to 1820 when limestone was quarried locally for part of old Fort Snel-ling. Limestone quarries were operated at Stillwater, Mankato, and Winona as early as 1854. Granite was quarried first at St. Cloud in 1868, and within a few years thousands of tons were shipped to widespread points. Rough dimension stone for large buildings furnished the first important market, but beginning in 1886 paving blocks were in demand. The largest shipment was in 1888, when 1925 cars were shipped from the St. Cloud area. Quartzite was quarried first at New Ulm in 1859 and somewhat later at Pipe-stone and elsewhere in southwestern Minnesota. The productive dolomite quarries at Kasota were opened first in 1868 and have continued as large producers of a variety of stone to the present time. At present, the industry is controlled by relatively few operators, and for that reason detailed figures on dimension stone are not released for publication. A general idea may be obtained from the data in the Minerals Yearbook for 1948. The figures for total stone produced in Minnesota are 1,804,000 tons valued at $5,090,652. Probably the largest item in the latter figure is received from dimension stone. A better idea of the situation in relation to the country as a whole may be gained by using the data for 1930 when more companies were operating in Minnesota, and complete figures were published. In that year Minnesota produced granite valued at $2,668,119 and ranked third among the states in value. Minnesota's production of granite was almost exclusively for dimension stone. In the same year Minnesota produced 300,000 tons of limestone (dolomite) valued at $840,860, and this likewise was mainly dimension stone. In finished limestone Minnesota ranked second among the states in 1930. Sandstone and minor amounts of quartzite are the only other dimension stones that have been produced in Minnesota, but the quarries are now inactive. The commercial stones of Minnesota have been described in two reports by Bowlesl and by Thiel and Dutton. The early history of quarrying in Minnesota and extensive notes on the various rocks are given by N. H. Winchell.8 Small limestone and dolomite quarries were numerous throughout the area of Paleozoic rocks in southeastern Minnesota. Early production was largely dimension stone. With the increased use of Portland cement, most of these ceased production, and today only those at Kasota and Winona remain in operation. In recent years many quarries have reopened and new ones started, but these are devoted to the production of crushed rock and agricultural lime. As the application of modern quarrying and finishing methods increased, small companies in the granite business have dropped out, and the remaining companies have modernized their plants, purchased old quarries, and opened up new ones, thus furnishing a wide variety of granites suitable for most of the customary uses. It is the purpose of this review to present notes on the geology and operations of each of the quarries now operating within the state. Granites and Related Igneous Rocks The term granite as used in this report includes granites, gneisses, diorites, gabbros, and other igneous rocks. The granites of greatest economic importance are found in three widely separated regions, see Fig. 1. 1—Central Minnesota in the region of the city of St. Cloud, 2—the upper Minnesota River valley region, 3—the northeastern portion of the state, commonly referred to as the Arrowhead region. The St. Cloud Region: The rocks of the St. Cloud region are mainly granites and related rock types such as monzonites and quartz diorites. The stones may be grouped into three major types, namely, pink granite, red granite and gray granite. Most of the pink granite occurs in the area to the southwest of St. Cloud. The rock is best described as stone with large pink crystals set in a finer grained black and white background. The minerals of the matrix occur in remarkably uniform sizes, and the pink crystals are sufficiently uniform in their dis-

Jan 1, 1953

By G. M. Schwartz, G. A. Thiel

Dimension stone was first quarried in Minnesota in 1820 and a very active industry has grown up over the years. The main basis of the present industry is a wide variety of igneous rocks sold under the general trade name of "granite." Also of considerable importance is the Ordovician dolomite sold under the locality names, Man kato, Kasota and Winona. THE first record of the quarrying of dimension stone in Minnesota dates back to 1820 when limestone was quarried locally for part of old Fort Snel-ling. Limestone quarries were operated at Stillwater, Mankato, and Winona as early as 1854. Granite was quarried first at St. Cloud in 1868, and within a few years thousands of tons were shipped to widespread points. Rough dimension stone for large buildings furnished the first important market, but beginning in 1886 paving blocks were in demand. The largest shipment was in 1888, when 1925 cars were shipped from the St. Cloud area. Quartzite was quarried first at New Ulm in 1859 and somewhat later at Pipe-stone and elsewhere in southwestern Minnesota. The productive dolomite quarries at Kasota were opened first in 1868 and have continued as large producers of a variety of stone to the present time. At present, the industry is controlled by relatively few operators, and for that reason detailed figures on dimension stone are not released for publication. A general idea may be obtained from the data in the Minerals Yearbook for 1948. The figures for total stone produced in Minnesota are 1,804,000 tons valued at $5,090,652. Probably the largest item in the latter figure is received from dimension stone. A better idea of the situation in relation to the country as a whole may be gained by using the data for 1930 when more companies were operating in Minnesota, and complete figures were published. In that year Minnesota produced granite valued at $2,668,119 and ranked third among the states in value. Minnesota's production of granite was almost exclusively for dimension stone. In the same year Minnesota produced 300,000 tons of limestone (dolomite) valued at $840,860, and this likewise was mainly dimension stone. In finished limestone Minnesota ranked second among the states in 1930. Sandstone and minor amounts of quartzite are the only other dimension stones that have been produced in Minnesota, but the quarries are now inactive. The commercial stones of Minnesota have been described in two reports by Bowlesl and by Thiel and Dutton. The early history of quarrying in Minnesota and extensive notes on the various rocks are given by N. H. Winchell.8 Small limestone and dolomite quarries were numerous throughout the area of Paleozoic rocks in southeastern Minnesota. Early production was largely dimension stone. With the increased use of Portland cement, most of these ceased production, and today only those at Kasota and Winona remain in operation. In recent years many quarries have reopened and new ones started, but these are devoted to the production of crushed rock and agricultural lime. As the application of modern quarrying and finishing methods increased, small companies in the granite business have dropped out, and the remaining companies have modernized their plants, purchased old quarries, and opened up new ones, thus furnishing a wide variety of granites suitable for most of the customary uses. It is the purpose of this review to present notes on the geology and operations of each of the quarries now operating within the state. Granites and Related Igneous Rocks The term granite as used in this report includes granites, gneisses, diorites, gabbros, and other igneous rocks. The granites of greatest economic importance are found in three widely separated regions, see Fig. 1. 1—Central Minnesota in the region of the city of St. Cloud, 2—the upper Minnesota River valley region, 3—the northeastern portion of the state, commonly referred to as the Arrowhead region. The St. Cloud Region: The rocks of the St. Cloud region are mainly granites and related rock types such as monzonites and quartz diorites. The stones may be grouped into three major types, namely, pink granite, red granite and gray granite. Most of the pink granite occurs in the area to the southwest of St. Cloud. The rock is best described as stone with large pink crystals set in a finer grained black and white background. The minerals of the matrix occur in remarkably uniform sizes, and the pink crystals are sufficiently uniform in their dis-

Jan 1, 1953