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[EXECUTIVE COMMITTEE OF THE BOARD OF DIRECTORS LOUIS S. CATES, Chairman DONALD H. NCLAUGHLIN, Vice-Chairman JOHN L. CHRISTIE JOHN R. SUMAN CLYDE E. WEED]

Jan 1, 1946

By Janshi Sen

Vertical-intensity magnetometers, for instance the Hotchkiss Superdip and the Askania vertical field balance, are now widely used, because vertical-intensity charts give definite information for the location of upper pole, dip and strike, and approximate shape of the deposit. Again, a slow and steady increase of dip over a large area indicates a large deep-lying deposit, while a large dip limited to a small area and falling away rapidly suggests a small and shallow one. The complication comes more from the richness of the ore. A large body of lean ore near the surface might produce the same vertical-intensity chart as a rich ore at depth. This paper presents a method for calculating the maximum depth of a single-pole deposit and another for a two-pole mineral body, by utilizing data of both vertical and horizontal intensities as obtained by a Thalen-Tiberg magnetometer. As shown on the left side of Fig. I, lean ore, rich ore and a single pole produce the same magnetic field. The depth of the pole, where G is the vertical intensity at point A due to the pole; F, the horizontal intensity of the same; and a, the distance from the point of maximum vertical intensity or the vertical projection of the pole on the surface to the point of observation A. If an entirely covered deposit is indicated by magnetic measurements and boring cost estimated from the calculated depth is so reasonable as to encourage drilling, the ore should be struck somewhere within the limit of the calculated depth by the borehole. A number of such points as A should be taken for calculation, erratic results should be rejected and the average figure used for cost estimation.

Jan 1, 1946

[Year of Election . 1944 .WALTER HULL ALDRIDGE New York. N. Y 1944 . SELWPN GWILLYM BLAYLOCK Trail. B.C.. Canada]

Jan 1, 1946

By Gerhard Derge

THE chemical and physical properties of slag systems are of special interest to metallurgists, for nearly all metals are in contact with molten slags during the primary reduction from their ores and then during the subsequent refining and alloying processes that determine their ultimate use, These processes are carried out at high temperatures and involve such complex chemical systems that fundamental scientific knowledge of the properties and behavior of these slags is inadequate. Various hypotheses have been proposed to explain known slag characteristics. The commonest of these regard the molten slag as constituted of compounds that are dissociated in varying degrees into their constituent oxides, as illustrated by Schenck1 and the recent papers of Chipman and co-authors.2-5 Another proposal is that these compounds dissociate by completes or partial ionization, the evidence for which has been reviewed by Martin and Derge.7 Whatever hypothesis is favored, the exact formulation of these compounds is incomplete. It is based on three principal types of information: I, Studies of solidified slag samples by X-ray diffraction, petrography, and similar methods that can be used at room temperature, The correlation of this information with the high-temperature properties of the molten slag is uncertain, 2. Studies of slag-metal equilibria, which have the advantage of providing observations on the molten slag at high temperature, However, even these data present problems of interpretation because they require a complete knowledge of the metal phase, 3, Direct measurements of properties of molten slag at the temperature of greatest metallurgical interest. Viscosity, electrical conductivity, specific heats, and similar properties have been measured, but the data of this type are widely scattered and frequently difficult to interpret, Additional direct measurements of properties of molten slag that can be interpreted in terms of chemical behavior are required, and this paper shows that the standard physical-chemical measurement of reversible electrode potentials, which measure the activity of specific constituents, is a fruitful source of such information, The purpose of this investigation, therefore, was to find an electrode combination that would yield reversible electromotive force measurements when dipped into the molten slag to be studied. Slags of the systems CaO-SiO2 and CaO-A1203-Si02 were chosen for study because graphite containers could be used and the data could be correlated with those for viscosity, conductivity, and other proper-

Jan 1, 1946

By William A. Johnson

The mathematical analysis of diffusion curves in solid metals is carried out ordinarily by analogy with the flow of heat in a continuous medium and no account is taken of the fact that the materials involved are composed of discrete particles that move discrete distances at irregular intervals. It is possible to treat the problem on the basis of simple assumed atomic mechanisms, in which case, because of the small scale of the elementary process compared to the gross effects observed experimentally, the two procedures lead to the same expression for the variation of concentration with distance. Thus, for engineering purposes, the usual methods are quite satisfactory. If, on the other hand, our purpose is to go beyond the mere collection of data, however desirable this may be, it is necessary to recognize and understand the factors that are of fundamental importance. One factor that has not hitherto been considered when dealing with solid metals is the difference in atomic weights of the isotopes of a single metal. While all the atoms of a given element are alike chemically, their weights may vary by a small but significant amount, and atoms of different weights may have different diffusion rates. With gases this variation in isotopic weight produces a change in the rate of diffusion by a factor inversely proportional to the square root of mass. While, except for the lightest gases, this is not a large effect, it is, for example, sufficient to permit a considerable concentration of one isotope at the expense of others. If metals exhibit a similar phenomenon, some modification of the analysis of the diffusion process will be required, since the different isotopes of a given metal will have different probabilities of moving and the heat-flow analogy will contain a fundamental error. This situation cannot be rectified by using a diffusion coefficient based on the average probability of moving, and it can be shown that even when the diffusion coefficient is independent of composition, the diffusion curve will not agree with the simple theory except in the rare cases where only one isotope exists; e.g., gold. If, however, the mass effect in the solid state were no larger than in the gaseous, the errors arising therefrom in the analysis of ordinary diffusion curves would be quite negligible. Nevertheless, our desire to obtain all possible information concerning the details of the diffusion process, and the possibility of diffusion in the solid state as a means for separating isotopes are cogent reasons for undertaking an experimental study to determine whether isotopes of different masses diffuse at different rates. Experimental Procedure If isotopes of different masses diffuse at different rates, the ratio of the concentration of one relative to another will vary with the distance from the diffusion inter-

Jan 1, 1946

By Frederick L. Knouse

THE south border of Espirito Santo begins about 400 km. north of Rio de Janeiro and extends along the Atlantic Coast northward some 325 km. and inland 100 to 150 km. The area under consideration, where quartz crystal of strategic grades has been mined, extends from 19° to 21° and 30" south latitude; and from 40° to 41° and 30" west longitude. This includes the central part of Espirito Santo, chiefly south of the Rio Doce from the Atlantic ocean, and west across the border into Minas Gerais near the town of Aimores, in the municipalities of Aimores, Minas Gerais; Baixo Guandu, Santa Teresa, Santa Leopoldina, Colatina, Joao Neiva, Fundao and Domingo Martines, Espirito Santo (Fig. 1). During 1943 and the first half of 1944, this region accounted for approximately 3 to 5 per cent of the quartz crystal produced in Brazil. Shipments of crystal have been made chiefly by rail to Rio de Janeiro. This region is serviced by the E. F. Minas-Vitoria and E. F. Leopoldina to Rio de Janeiro through Vitoria; and by the E. F. Minas-Vitoria and E. F. Central do Brasil through Bello Horizonte, Minas Gerais to Rio de Janeiro. The major deposits are accessible from the railheads by dirt roads, some being 5 to 30 km. off the road, reached by trail. In 1943 and the first half of 1944, the bulk of the production was from inter mountain marshes and adjoining hillside alluvial placer deposits in the zone surrounding the town of Santa Teresa. Most of these deposits were formed from the erosion of pegmatites, quartz veins and pockets in the gneiss, with minor quantities produced from miarolitic cavity fillings in the granitic rock. EARLY OPERATIONS Mining of quartz crystal in this region began in 1928, and has been stimulated by the market demand for military uses. Before 1936 little attention was given to it, either in Espirito Santo or eastern Minas Gerais. From 1936 to 1941 the Japanese sent agents to various points of production or potential production to acquire quartz through purchase. They bought crystal as small as 10 grams. Since 1941 only the United States and Great Britain have received quartz from Brazil. The United States purchases crystals of loo grams and larger for strategic purposes. The first known discoveries were made either in the municipalities of Aimores, Minas Gerais, or in Baixo Guandu, or Domingos Martines, Espirito Santo. Marketable quartz crystal was first found either in the massive quartz replacement veins of the Victor Hugo mine in the municipality of Domingo Martines, or in the large cores of quartz in the pegmatites near Baixo Guandu, extending into Minas Gerais. PRODUCTION The production of quartz in Espirito Santo from 1936 through 1941 as recorded

Jan 1, 1946

By W. I. Garms, J. L. Stevens

BECAUSE of the many conflicting opinions regarding the functioning of the ball load and the characteristics of ball wear in ball-mill grinding, the following resume of reports covering recent tests conducted at the Hayden plant of the Kennecott Copper Corporation is submitted with the view of pointing out certain salient features that should throw additional light on the subject. MILLS USED Cylindrical drum mills with trunnion feed and discharge were used. The discharge trunnion was I3 1/2 in. in diameter. Dimensions inside the lining were 6 ft. 6 in. in diameter and 9 ft. 6 in. long. The mills were Britannia-lined and nine lifter bars projected 2 in. from the lining. The mill speed was 16 2/3 r.p.m. Feed to the mill was 9 per cent on 10-mesh, 85 per cent on 100-mesh, 77 per cent solids. New balls measured 2 in. in diameter and the approximate weight of the ball load was 40,000 pounds. INITIAL TEST During a test that was being conducted to determine the relative economic value of standard cast balls vs. forged steel balls in the local grinding operation, certain observations were made in regard to the functioning of the various ball sizes and the characteristics of ball wear, which warranted a supplementary test for the purpose of confirming such observations. For the initial test, the necessity for developing a graduated load of the new forged balls before the test could be started was realized, but the time required to obtain a graduated load and the functioning of the various ball sizes was not clear. No advantage could be seen for starting out with a full load of forged balls, as this initial load, at the least, would have to be completely ground out and replaced by daily additions of balls before the graduation could be complete and a normal static condition of ball sizes reached. For a considerable period prior to exhaustion of this initial charge there would be an unusual quantity of worn balls of a certain size, which would not be typical of a normal charge and could influence the characteristics and functioning of the entire load. Therefore, it was decided to start by daily addition of the forged balls to a mill that contained a normal operating load of cast balls. After 88 days of operation the mill was shut down for inspection. By that time the load consisted of a mass of forged balls functioning around a large core of the residual material of the former cast-ball load. This core of cast slugs, locally referred to as "the kidney," was well defined from the forged-ball load.

Jan 1, 1946

By C. W. Green-Halgh

The accuracy with which grade and tonnage of a mineral deposit may be calculated from diamond-drill assays is dependent upon: (1) the reliability of core and sludge samples and (2) the validity of methods used in grade and tonnage calculations. Limitations imposed by drilling and sampling preclude elaborate methods of computation. In adjusting core and sludge assays the importance assigned the core and sludge samples may be based on either the respective weights recovered or the respective volumes represented by each. Only when core and sludge recoveries arc poor do discrepancies between adjusted assays calculated by these two methods develop, in which case the "weight" method gives emphasis to the core sample and the "volume" method gives emphasis to the sludge sample. When the sludge suffers classification within the drill hole, the weight method gives more accurate results; when the sludge sample suffers no classification, the volume method gives more accurate results. Any drilling campaign offers a compromise between desired accuracy on the one hand and expediency, limited time, money. or facilities on the other. Since the determination of grade and tonnage is an approximation at best, a proper basis for their computation requires a knowledge of the limitations imposed by all phases of work upon which the calculations depend A rational basis for coordination of these phases of work requires determination of: (I) the degree of accuracy desired, as a function of the object of examination; (2) the degree of accuracy attainable, as a function of the limitations imposed in the drilling and sampling program; and (3) the validity of method to be used in calculating grade and tonnage from core and sludge assays. This paper presents results of a comparison made between two commonly used methods of adjusting core and sludge assays, the assumptions upon which these methods are based, and the interrelationship of the phases of work upon which these calculations are dependent. Object of Examination The Purpose of prospecting any mineral deposit is to secure sufficient samples from which Ore grade and tonnage may be calculated. Any mine examination, preliminary or formal, has a definite purpose, although its scope may be limited or broad. The type of examination to be conducted is dependent, therefore, 'pan the reason for instituting the investigation; its scope and thoroughness are directly related to economic considerations. It is highly desirable, therefore, that before starting a drilling campaign a complete understanding of the extent of examination and desired degree of accuracy be determined as a means of simplifying the drilling program and unifying the relative degree of

Jan 1, 1946

Although developed primarily for sintering tantalum, the unit to be described can be used to heat-treat metals in the form ofa bar, wire or strip, by passing a current through them. The upper temperature limit with this type of heating is the melting point of the metal being heated.The unit was designed for vacuum work, but. various gases can be used if required.Briefly, the vacuum sintering furnace consists of a bell which is counter-balanced and may be lowered onto the brass base plate which holds the electrodes. A rubber ring seal is used for vacuum work. The lower flexible grips are bolted to the brass base plate which is at earth 'potential, while the other electrode passes through the plate by way of an electrically insulated vacuum seal. This upper electrode, the height of which can be altered as desired, the lower grips, and the bell are water cooled. The vacuum line to the pumps and a line to the vacuum gauges also lead from the base plate. The more important sections of the unit are described below.THE BELLThe unit was designed so that the bell could be lifted clear of the base plate and the electrodes, thus facilitating adjustment of the latter and the mounting of the specimen to be heated. A double walled steel bell, 20 in. high, with t in. cavity was used. The bell was fabricated from 10 gauge mild steel sheet using a double overlapping run of arc welding for all seams. A water inlet and outlet...

Jan 1, 1946

By M. M. Slotnick

It was once aptly said that a sign of approaching senility is ceasing work on a subject and beginning to talk about it. Perhaps that explains why, after many Years in which Part of my duties has been the training of college men in various branches of petroleum exploration geophysics, I have now begun to talk about it. In making an outline of what I believe ought to be discussed under the general heading of the title, I found it almost impossible to subdivide the ideas into an ordered set of discrete subjects. Rather, the pertinent remarks seemed to interlock almost everywhere. The consequence is that it will be necessary to start with the conclusions and then try to justify them by jumping back and forth. However, based on the types of men with whom I have had to deal, the subject naturally divides itself into two parts. In the first part, I should like to deal with the case of those undergraduates whose natural bent is toward the physical sciences and who may decide to enter the geophysical fold as a career. The other part will deal with those many men, geologists and engineers for the most part, who have drifted into exploration geophysics by one means or another, and whom it is necessary to train for geophysical work while they are occupied in their routine jobs. Here it may be in point to remark that most men in exploration geophysics at Present have been developed from precisely the latter group, and that the problem of training here is of great importance even though, in this paper, it will perforce occupy the secondary place. Training oF a Geophysicist The outstanding reason for the perplexing problem on the training of a geophysi-cist is that ideas differ on the answer to the question: "what is a geophysicistp" ln any of the scientific "specialties," like physics, for example, it is relatively simple to pigeonhole a man as being qualified to call himself a physicist. That appellation applied to an individual does not mean that he has mastered only the branches of intellectual endeavor usually associated under the broad name of "physics." we expect him also to have a more than mere acquaintance with mathematics and chemist~ and some understanding of most of the other sciences. But note this important point—we expect our physicist, whom we have chosen as an example, to be intelligently trained so that, if necessary, he can and will know how and where he can get the proper information on a subject in which he is not a specialist; he will know how to absorb that information and turn it to his uses. It seems to me that this is the outstanding characteristic of a man who can truly call himself a scientist: that he is a specialist in one of the broad branches of science in that he has enough training and discipline in the scientific approach so that, when called upon to do so, he can inteugently absorb knowledge from another bordering science (and all sciences not only border upon one another to some extent, but more often, overlap One another), and

Jan 1, 1946

By R. C. Buehl, J. P. Riott, E. P. Shoub

PILOT-PLANT tests have demonstrated that it is possible to produce low-sulphur sponge iron (0.03 to 0.05 per cent sulphur) as a continuous process in an internally fired rotary kiln from iron ore or mill scale; a solid carbonaceous reducing agent; and dolomite to control the sulphur content. The proportion of dolomite employed is small, so that it does not add materially to the cost of the sponge iron. The entire operation is carried out at temperatures well below the melting point of iron, so that the product is discharged in granular form. Compared with other methods for the production of sponge iron, the rotary-kiln method has the advantage of simplicity and low cost of equipment and; in addition, requires little labor for the operation of the process. The pilot-plant equipment used for this work was sufficiently large to demonstrate that the production of low-sulphur sponge iron in rotary kilns is feasible and that the costs are not excessive for applications in which sponge iron has distinct advantages over competing materials. This report constitutes a part of a program by the Bureau of Mines under a special Congressional appropriation for studying gaseous and solid fuel reduction of iron ores. Numerous articles on various phases of these investigations have appeared in Bureau of Mines publications or technical journals. Other articles are being prepared and will be published in the near future. The present program, which is under the supervision of Dr. R. S. Dean, Assistant Director of the Bureau of Mines, was initiated in .1942. However, a considerable portion of the work was a continuation of previous research performed by the Bureau. Previous investigators1-4 utilizing the rotary kiln for the production of sponge iron did not develop a suitable method for controlling the sulphur content. A review of the literature shows that the sulphur content in the product usually exceeded 0.2 -per cent unless reducing agents with very low sulphur contents were employed. This high sulphur value made the product generally undesirable for use as melting stock in electric or open-hearth furnaces. The production of sponge iron in an internally fired rotary kiln has been described in detail in Bureau of Mines Bulletin 2702; consequently, this article will be confined mostly to new features of the process-that is, means for controlling the sulphur content of the sponge iron. Suitable raw materials include iron ores or mill scale; coal or coke for reducing them, and sized dolomite (-20+100-mesh) as the sulphur-controlling agent. A mixture of the raw materials in granular form is fed into the elevated end of the kiln, which is fired axially from the lower or discharge end. In the reducing zone, which is approximately one third the length of the kiln measured from the dis-

Jan 1, 1946

By W. T. Irvine

Introduction The property of the Britannia Mining and Smelting Company is on the east side of Howe sound, some twenty miles north of-Vancouver. The camp is served by two settlements, one at Britannia Mines townsite, approximately three miles from the water's edge at an altitude of 2,100 feet, the other at Britannia Beach, on Howe sound. The first discovery of copper ore on the property was made in 1888, but it was not until 1905 that production started. From that year until the end of 1944, production had totalled 732,414,420 pounds of copper and 261,126 ounces of gold from six orebodies, known as the Victoria, Empress, No. 5, Fairview, Bluff, and Jane. No. 8 orebody, with which this paper is concerned, was discovered in 1937 by diamond drilling from the 4100 level, some 300 feet above sea level. Development of this orebody to the end of 1944 had included the sinking of a shaft from the 4000 to the 5250 level, and a limited amount of stoping. This work has delimited the orebody from the 3800 to the 4950 level and has indicated upwards of 1,000,000 tons of copper-zinc-gold ore. It is planned to commence production in the near future, while continuing exploration of the orebody at depth.

Jan 1, 1946

By G. Carman Ridland

In conjunction with a geological investigation of the silver-bearing veins at Contact Lake, Northwest Territories, Canada, a survey was made with a Geiger-Miiller counter of the gamma-ray emissions from the rocks in the vicinity of the mine workings. Discontinuous pitchblende veins have been encountered occasionally in the silver-bearing fissures, and the geophysical survey was undertaken with the hope that abnormally high gamma-ray intensities, if detected, might lead to larger and more continuous pitchblende discoveries. Before the instrument was used at Contact Lake, preliminary tests were made, first with laboratory specimens at Princeton University, and later over known pitchblende deposits at the Eldorado property, LaBine Point, N.W.T. The Geiger-Müller counter, as adapted for field use, is described; the technique of transporting and operating the instrument is outlined; and the general precautions to be observed are discussed. The results obtained at Great Bear Lake show that the instrument is capable of detecting not only a pitchblende ore shoot in a shear zone, but also the mildly radioactive "host rock" at a considerable distance from the ore body. Hence, use of the Geiger-Müller counter is urged, not just for the detailed search for an ore body in a shear zone, but for the detection of possible radioactive "host rocks" in large-scale reconnaissance surveys of unexplored regions made by prospectors and members of federal geological survey parties. Location.—Along the rocky eastern shores of Great Bear Lake, in the Northwest Territories of Canada, lies one of the world's great radium-producing areas. The Eldorado mine, owned and operated by the Eldorado Gold Mines, Ltd., is at LaBine Point; while the Contact Lake mine, operated by Bear Exploration and Radium, Ltd. (B.E.A.R.), lies 9 miles to the southeast of LaBine Point and 2 miles south of Echo Bay, an indentation in the eastern shore line of Great Bear Lake. Geology.—The Eldorado company obtains its radium by the mining of the mineral pitchblende, which is found associated with a complex variety of metallic and nonmetallic minerals1 in quartz-carbonate veins occurring in metamorphosed pre-Cambrian sediment aries. Most of the pitchblende is intimately associated with a brown quartz and belongs to an early hydrothermal stage of mineralization during which safflorite-rammelsbergite and minor cobalt-nickel minerals were also deposited. Some pitchblende occurs with a group of minerals belonging to a later stage of mineralization in which the gangue is mainly dolomite and sometimes ferruginous rhodochrosite. Associated with this group are native silver and lead-zinc-copper sulphide minerals. The Contact Lake property owes its existence to the mining of rich, native silver ore shoots, which are

Jan 1, 1946

By Norman Weiss

THE need for more efficient utilization of labor in the metal-mining industry has been the subject of several recent editorials in the mining press, and one attractive possibility for such improvement lies in the designing of future milling plants particularly with economy of man-power in mind. We are accustomed to think of mill design as the selection and coordinated arrangement of process equipment, but if labor is to be efficiently utilized it must be given early consideration in planning the new mill. There are three good reasons for economizing in labor: (I) to reduce costs, not only in the form of wages but also in housing, hospital, welfare, and other obligations that a company accepts when a new man is added to the payroll; (2) to prepare for recurrent periods of manpower shortage, during which a well-designed plant can manage to get along with skeleton crews; (3) because a milling plant that must depend upon an inordinately large labor force for its operation and maintenance is certain to be inefficient in other respects, for many of the shortcomings in design that make necessary the excessive use of labor are generally not corrected merely by having too many men. A simple example of this is a poorly designed ore-feeding system: if this is inadequate to the extent that one man must be constantly unclogging feed chutes, it may help the situation to put two men or three at this task instead of one, but the feed rate will still be inconstant. First of the factors that affect labor saving is the location of the mill. This is often determined by transportation costs alone, and as a result the mill may be placed close to the mine regardless of the nature of the terrain. The designer must then adapt his layout to the conditions, favorable or not. This happens often at small properties, where capital investment may seem more important than operating expense. In most instances, however, a mill site carefully selected for the advantages it gives the designer in laying out the plant is the most economical in the long run, even if it involves a slight increase in cost of ore haulage. Given some freedom of choice, the design engineer may be able to find just the piece of ground that provides the proper gradient for the needs of the flowsheet, permits installation of essential yards and trackage, and perhaps supplies an excellent site for a tailing dam. Further justification for having placed the mill not too close to the mine sometimes emerges only years later as an opportunity to treat ores from other properties. When it is known from the beginning that the new mill will serve a number of scattered mines, a free choice of mill site is naturally stimulated. The most important single factor in limiting the labor requirements of a mill is its materials-handling system for bring-

Jan 1, 1946

Jan 1, 1946

By A. W. Fahrenwald

CELL depth has been for many years a controversial question in a flotation-machine performance. In the impeller type of machine, we are really talking about impeller submergence-i.e., the depth in the pulp at which the impeller is required to produce aeration. THE FLOTATION MACHINE A COMPRESSOR A flotation machine can be considered as an air compressor or blower in which the aeration mechanism takes in air under atmospheric pressure[t] (14.7 lb. per sq. in.) and blows it into the pulp (the pulp being the receiver) against a head of 14.7 plus cell depth in feet times 0.4333 lb. per sq. inch. In commercial machines the impeller is submerged in the pulp to depths ranging from about 2 ft. in the smaller machines to as much as 5 ft. in some of the larger ones. In the 2-ft. cell, the hydrostatic head on the impeller is (2 X 1.25 =) 2.50 ft. (assuming a pulp density of 1.25), equal to (2.50 X 0.4333 =) 1.078 lb. per sq. in. For the 5-ft. cell, the hydrostatic head against which the impeller must make air is (5 X 1.25 X 0.4333 =) 2.708 lb. per sq. inch. In the small 2-ft. machine, the volume reduction is (1.078 [-] 0.147 + 0.01078 =) 6.85 per cent and in the large, 5-ft. machine, the volume reduction is (2.708 [=] 0.147 + 0.02708 =) 15.5 per cent. It is obvious that for unit volume of free air intake the larger machine receives a lesser (8.65 per cent less) volume of aeration* than the smaller machine. The bubbles in escaping from the pulp expand and are greater in volume at the surface than at the moment of their formation in the pulp; 7.33 and 18.4 per cent larger, respectively, in the small and large machines. Just how this situation affects flotation is not known. It is interesting to note, however, that the bubbles are smaller in the zone of the coarsest particles and largest in the upper zones of the finer, more easily suspended mineral particles. It would seem that the relationship might be reversed advantageously. The deep cell is at a greater disadvantage in this respect than the shallow cell. Nothing, however, presumably can be done about this situation. The shallow cell is a partial corrective. Not only does the compression ratio of aeration increase with impeller submergence but the hydrostatic head against which the impeller must operate also increases. THE FLOTATION MACHINE AS A PUMP Since, in impeller machines that rely upon their own operation to produce aeration, pulp passes through the im-

Jan 1, 1946

By Edward F. Courtney

Loss of life, loss of sight, crippling injuries, and property damage nearly always result from accidents involving explosives. The severity of such accidents has prompted lawmaking bodies to pass laws concerning the transportation, handling, and use of explosives; manufacturers of explosives publish manuals 'describing explosives and practical methods of handling then; and mining companies and others who use large quantities of explosives publish rules based on actual experience for the guidance of their employees. Careless storage of explosives by thoughtless or incompetent persons, particularly if they are left where children or saboteurs have access 'to them, has led to many serious accidents. Many contractors and mining operators who use explosives are extremely careless about storing them. It is the purpose of this paper to discuss the explosive-handling practices of a large western mining company, which are considered better than most.

Jan 1, 1946

By Robert I. Jaffee, Bruce W. Gonser

RECENT work by the authors1 established the constitutional diagram of the gold-germanium system. Of particular interest in the simple euctectiferous system was the eutectic alloy at 12 per cent Ge, which melted at the very low temperature of 356°C. and had an unusually fine eutectic structure. It was of interest to investigate the effect of third components on the melting point, microstructure, and strength of this alloy, and in this work the effect of copper is discussed rather completely, with less complete data on the effects of silver, platinum, nickel, and zinc. No reference in the literature has been found on ternary systems with gold-germanium. MATERIALS AND ALLOYING As in the work on the binary system, gold-germanium, the germanium used in this investigation was the cyanide-reduced, 99.9 per cent product, produced by the Eagle-Picher Co. Fine gold sheet from Handy and Harmon, pure platinum sheet from the American Platinum Works, copper magnet wire from Anaconda, nickel wire assaying 99.6 per cent Ni, and electrolytic zinc were used for alloying. To make the alloys, charges of the pure metals were put in a graphite crucible and melted in an atmosphere of pure hydrogen. The temperature was brought up to about 1050°C., and the metal allowed to freeze in the crucible. Except with alloys containing zinc, melting losses were consistently less than a few milligrams. When zinc was a component, weight losses up to half the weight of the zinc present were incurred, and the alloy compositions were calculated by assuming the entire weight loss to be that of zinc. In all other cases the composition of the alloys could safely be taken as that of the charge. The ingots, as solidified, were segregated, the heavier primary phases being at the bottom and sides of the ingots and the lighter primary phases at the top, but by sectioning the entire ingot vertically for microscopic examination, this factor could be evaluated. Ingots for microscopic examination weighed one gram, and those for thermal analysis weighed three grams. THERMAL ANALYSIS In this work, the eutectic line composition and thermal arrests were desired, and, after microscopic exploration had established the position of the eutectic line at a given percentage of the third component, a thermal analysis was run at that composition. The method of thermal analysis used in the work on the binary Au-Ge system,1 a method particularly well suited for a small quantity of material, was used in this work. Clearly defined arrests were obtained, although with some alloys containing platinum

Jan 1, 1946

By Haley, D. F.

WHEN operations were first started at Climax in 1917 by the Climax Molybdenum Co., they were pioneering in the molybdenum industry for little was known relative to the uses of molybdenum or the metallurgy of molybdenite concentration. Concentration of molybdenite is relatively simple today but in 1916, when the Climax deposit first attracted attention, it presented serious difficulties. Little was known, in fact, even about the assaying of such low-grade molybdenum ores. Mine samples were sent to at least a dozen of the best laboratories in the United States and average values reported varied from 0.4 per cent to 1.0 per cent MOS2. Owing to the wide variations in MoS2 content obtained from reliable chemists, the actual value of the ore was most uncertain. This variation occurred repeat¬edly over a period of six months in 1917. It was finally decided, as a last resort, to cut several tons of sample from the tunnel and have a mill test made, using the recovered MoS2 per ton as the grade of the ore, for a small error in the assaying of the concentrate would not materially affect the results. These mill tests were made by the General Engineering Co. (Callow) at Salt Lake City. The results proved an ore of commercial grade and indicated the flotation process for the best metallurgy. Based upon these tests, the decision was made to build a 200-ton flotation plant. At this time, the art of flotation was

Jan 1, 1946

By C. W. Greenhalgh

THE accuracy with which grade and tonnage of a mineral deposit may be calculated from diamond-drill assays is dependent upon: (I) the reliability of core and sludge samples and (2) the validity of methods used in grade and tonnage calculations. Limitations imposed by drilling and sampling preclude elaborate methods of computation. In adjusting core and sludge assays the importance assigned the core and sludge samples may be based on either the respective weights recovered or the respective volumes represented by each. Only when core and sludge recoveries are poor do discrepancies between adjusted assays calculated by these two methods develop, in which case the "weight" method gives emphasis to the core sample and the "volume" method gives emphasis to the sludge sample. When the sludge suffers classification within the drill hole, the weight method gives more accurate results; when the sludge sample suffers no classification, the volume method gives more accurate results. Any drilling campaign offers a compromise between desired accuracy on the one hand and expediency, limited time, money, or facilities on the other. Since the determination of grade and tonnage is an approximation at best, a proper basis for their computation requires a knowledge of the limitations imposed by all phases of work upon which the calculations depend. A rational basis for coordination of these phases of work requires determination of: (I) the degree of accuracy desired, as a function of the object of examination; (2) the degree of accuracy attainable, as a function of the limitations imposed in the drilling and sampling program; and (3) the validity of method to be used in calculating grade and tonnage from core and sludge assays. This paper presents results of a comparison made between two commonly used methods of adjusting core and sludge assays, the assumptions upon which these methods are based, and the interrelationship of the phases of work upon which these calculations are dependent. OBJECT OF EXAMINATION The purpose of prospecting any mineral deposit is to secure sufficient samples from which ore grade and tonnage may be calculated. Any mine examination, preliminary or formal, has a definite purpose, although its scope may be limited or broad. The type of examination to be conducted is dependent, therefore, upon the reason for instituting the investigation; its scope and thoroughness are directly related to economic considerations. It is highly desirable, therefore, that before starting a drilling campaign a complete understanding of the extent of examination and desired degree of accuracy be determined as a means of simplifying the drilling program and unifying the relative degree of

Jan 1, 1946