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By Charles Willis

THE time is no longer when a man can act as an independent unit; the appreciation of the interdependence of one man upon another has emphasized the importance of the social unit. Epidemics have made us recognize that even a man's health is not distinctly his own to control as he pleases. The physical examination of workmen previous to employment started with an effort to prevent the spread of tuberculosis, for tuberculosis may be .detected in its early stages and cured. But it was soon found that many other diseases were detected and the saving of lives made possible. The physical examination does not mean the elimination of the unfit-on that basis it would utterly fail- but rather the measuring of a man's physical fitness and placing the man where he can do the best for himself, his fellow worker, and the company. Industry as a whole cannot expect to live up to the standard of physical examination set for the army, nor should it expect to do so, for in all branches of industry there are types of work that do not require -the same amount of endurance as does army work, and the placing of men with physical limitations in the work for which they are' capable permits a higher average of physical fitness for the work requiring physical excellence.

Jan 7, 1919

By P. D. I. Honeyman

IN THE Southwestern copper region the event of greatest interest was the starting up of the new Hurley, N. Mex., smelter of the Chino Mines division of the Nevada Consolidated Copper Corp., which occurred in May. This plant, built as a wet-charge smelter for treating largely an all-concentrate charge, embodies in its de- sign the latest in materials-handling equipment. Noticeable around this smelter is the absence of tram cars and trackage for the handling of charge, dust and other materials. Concentrate from the mills is received in bottom- dump cars which are unloaded into a series of concentrate bins. Concentrate is then reclaimed through the bottom of the bins and discharged through a feeder on to a conveyor belt. Flux for the charge is fed on to the conveyor ahead of the concentrate charge. The belt-mixed charge is conveyed to the furnace building and discharged into the furnace charge bin ready for feeding to the reverberatory furnace. As in the McGill plant, the furnace is fed by vibrating conveyors, one down each side of the furnace.

Jan 1, 1940

By L. S. Pratt

IN 1910 the author was engaged in a qualitative study of the radio-activity of several chemical substances and a few minerals. In the course of the work he studied the mineral allanite (obtained from granite ledges at Topsham, Maine), and found it to be appreciably radio-active. Recently the fact was brought to his attention that the radio-activity of allanite is not well known, although Hon. R. J. Strutt in 1905 published a list of radio-active minerals with their analyses, including allanite from Amherst County, Virginia. In the work done, a standard ,type of electroscope was used, and the readings were made with a telescope, fitted with a scale, by means of which the rate of discharge could be readily determined. The natural "leak" of the instrument was carefully determined, and all results corrected accordingly. The method of study was as follows: The material to be tested was finely powdered, and spread over the bottom of a small, inactive pan. The electroscope was then charged, and the pan placed in position. The door of the instrument was closed, and the rate. of discharge carefully determined. All results were reduced to common form to permit of comparison. It is to be noted that the materials tested were not used in strictly comparable quantities, such as if 1 g. of. each had been used, but about the same quantity of powder was used (in the cases of the solid substances), so that the results are qualitatively accurate.

Jan 5, 1916

By L. G. Austin, R. R. Klimpel

This communication points out that serious errors exist in some current treatments of the random fracture of solids, including the prior treatments by Klimpel and Austin, Gilvarry, and Gaudin and Meloy. The problem considered in all of these papers is: what cumulative weight versus size distribution is expected for the fragments produced by fracture of a particle? The basic assumption made is that fracture surfaces propagate in random directions from weak flaws in the solid (these weak flaws being activated to fracture by applied stress), with the activated weak flaws distributed at random spatially within the solid. The previous treatments considered fracture in three dimensions, and all use similar physical models, although the mathematical techniques were somewhat different. We first noticed that these treatments were in error when we attempted to reduce the equations developed to the simple case of fracture of a one-dimensional particle, e.g. a long, thin fiber which breaks along its length. For this simple case, it is readily shown that the assumption of random fracture leads to the expression P(V) = (r/Vo) (1-V/Vo) r-1 dV (1) is the probability of occurrence of a fragment of length within the range V to V + dV; V being length dimension, from r random fractures passing through an original size of Vo to produce r + 1 fragments. This equation agreed with the one-dimensional form of an equivalent equation in the original Klimpel-Austin treatment. However, in this treatment it was then stated that, "The fractional weight below size V is [ ]

Jan 8, 1968

On request of the Commissioner of Education, a small group of administrative professors of engineering and commerce from higher institutions near St. Louis met in conference with the Specialist in Commercial Education of the Bureau of Education on Feb. 22, for the purpose of discussing ways and means whereby the business of our country may be furthered through increased opportunity in our higher institutions for the preparation of engineers with business training. One or more representatives were present at this conference from the University of Minnesota, University of Illinois, Washington -University, University of Missouri, University of Iowa, Iowa State College, University of Kansas. It was recommended at this conference: First, That the Commissioner of Education appoint immediately a committee to consider commercial engineering in its various aspects and to prepare and approve one or more curricula in commercial and industrial engineering that can be recommended by the Bureau of Education for adoption in our colleges and universities. It was suggested that the committee consider the following curricula plans: First, That a minimum number of hours in business training be required in all engineering courses. Second, That a curriculum providing for a minimum of fifteen to thirty units in business economics be incorporated in all engineering courses and offered on an elective basis. Third, That a curriculum in commercial or industrial engineering, permitting full and proper emphasis upon engineering subjects, be offered in the School of Commerce with degree to be given in that school. Fourth, That a five-year combined engineering and commercial course he prepared.

Jan 5, 1919

By D. Cubicciotti

IT has long been known that some metals are capable of being dispersed or dissolved in certain of their fused salts.' Davy' and Bunsen³ were among the first to observe that in some fused salt electrolyses, a highly colored, strongly reducing salt phase appeared in the neighborhood of the cathode. Later workers found that the current efficiency of the electrolysis was markedly reduced when such a phase appeared. It was also found that the strongly reducing salt could be made by melting the metal and normal salt together. Chemical analysis showed that in such salts the metal ion to anion ratio was always larger than in the normal salt. From such observations arose two different explanations of the nature of metal in salt solutions. When a solution of this type is quenched, it is possible to find small globules of metal in the salt. From this and other observations, Lorenz' and co-workers assumed the metal in salt solution to be a colloidal dispersion of metal in the fused salt and called it "metallnebel" or metal fog formation. They made a number of experiments to substantiate this point of view. Another school felt that when the metal dissolved it reduced the salt partially to a mixture or solution of normal salt and subsalt. Both of these ideas could explain the strong reducing character of the salt formed and the low current efficiency of the electrolysis. If either a metal colloid or a subsalt were formed at the cathode and diffused to the anode, it would be oxidized to the normal salt. Thus a cyclic process of oxidation and reduction could be set up conducting the current without giving rise to a net change in the system. These facts led the author to investigate some of the properties of metal in salt solutions with the hope of elucidating their nature further. Among the metal-salt systems that form metal in salt solutions most markedly are the alkaline earth metal-halide systems and cerium, bismuth, and cadmium halides. Other systems of halides, oxides and sulphides form such solutions to a lesser degree. The first work undertaken was a study of the temperature-composition diagrams of some of the systems." From such diagrams it would be possible to distinguish between a subhalide formation or a colloid. A subhalide should give rise to characteristic changes in the phase diagram, while a colloidal dispersion of metal in salt would not alter the freezing point of the salt. The results obtained on a number of alkaline earth metal-halide systems were all quite similar. Fig. 1 shows the barium-barium chloride system. The other

Jan 1, 1954

By A. H. Lindley, Fraizer M. Stewart

For many years large mining companies were able to finance nearly all of their capital requirements from internally generated funds. However, during the last decade, funds needed for capital expenditures, dividends, and scheduled debt retirement have grown faster than cash flow. As a result the minerals industry has had to rely increasingly on other sources of funds. Getting the capital for new mining projects is a challenge, particularly for smaller companies. New methods of financing and new variations to old methods have been developed and more are needed. Commercial banks are short-term lenders. By policy their loans are limited to low risk loans-those made solely on the borrower's general credit, and secured loans where cash flow is sufficient to provide repayment within a comparatively short term. To maintain liquidity, banks prefer to make loans of less than seven years' term. If a longer loan is needed an insurance company or pension trust may take the long-term part.

Jan 1, 1971

By C. T. Wei, A. Kelly

USING a recently developed X-ray method, reported by Schulz,2 it is possible to make a rapid survey of the perfection of a single crystal at a particular surface. This technique has the advantage of allowing a large surface of a specimen to be examined by taking a single photograph and it compares well with other X-ray methods in regard to sensitivity of detection of small angle boundaries. During the course of a survey of the perfection of large crystals of aluminum produced by a number of methods, an examination has been made of a number of single crystals produced from the melt using a soft mold (levigated alumina)." Crystals grown by this method are known, from an X-ray study carried out by Noggle and Koehler,3 to contain regions where they are highly perfect. In the present work, it has been possible to obtain photographs showing directly the distribution of low angle boundaries at a particular surface of these crystals. single crystals were grown from the melt using the modified Bridgman method with a speed of furnace travel of -1 mm per min. These were about 1/10 in. thick, 1 in. wide, and several inches long. The metal was 99.99 pct pure aluminum supplied by the Aluminum co. of America. The crystals were examined by placing them at an angle of about 25° to the X-ray beam issuing from a fine focus X-ray tube of the type described by Ehrenberg and Spear4 and constructed by A. Kelly at the University of Illinois. A photographic film was placed SO as to record the X-ray reflection from the lattice planes most nearly parallel to the crystal surface. The size of the focal spot on the X-ray tube was between 25 and 40 u, and the distance from the X-ray tube focus to the specimen (approximately equal to the specimen to film distance) was -15 cm. White X-radiation was used from a tungsten target with not more than 35 kv in order to reduce the penetration of the X-rays into the specimen. Exposure times were approximately 1 hr with tube currents between 150 and 250 microamp. The type of photograph obtained from these crystals is illustrated in Fig. 1, which shows a number of overlapping reflections from the same crystal. The large uniform central reflection is traversed by sets of horizontal white and dark lines. These two sets run mainly parallel to one another. Lines of one color are wavy in nature and often branch and run together. Large areas of the crystal surface show no evidence of these lines whatsoever. The lines are interpreted as being due to low angle boundaries in the crystal, separating regions which are tilted with respect to one another. A white line is formed when the relative tilt forms a ridge at the interface and a black line is found when a valley is formed. In a number of cases, the lines stop and start within the area of the reflection and often run into the reflection from the edge, corresponding to a low angle boundary starting from the edge of the crystal. The prominent lines run roughly parallel to the direction of growth of the crystal although narrow bands can run in a direction perpendicular to this; see Fig. 2. Although they may change their appearance slightly, the lines tend to occur in the slightly,Same place in the X-ray image and to maintain their rough parallelism when the crystals are reduced in thickness by etching. Thus the low angle boundaries can occur at any depth within the crystal. The appearance of the lines is unaffected by subjecting the crystal to rapid temperature changes, such as plunging into liquid nitrogen or rapid quenching from 620°C. From the width of the lines on the x-ray reflection, values can be found for the angular misorienta-tion of the two parts of the crystal on either side of a boundary. The values found run from 1' to 10' of arc, but values of UP to 20' have sometimes been found, e.g., the widest lines on Fig. 2. These mis-orientations are much less than those commonly found in crystals possessing a lineage structure. When a number of a and white lines occur, running in a roughly parallel direction across the image of a Crystal, the total misorientation corresponding to lines of one color is approximately equal to that corresponding to lines of the other color. The interpretation of the lines as due to low angle boundaries has been checked in a number of ways. Photographs taken with different specimen-to-film distances distinguish lines due to low angle boundaries from effects due to surface relief of the specimen. Normal Laue back-reflection photographs, taken with the beam irradiating an area of the surface showing a number of the lines, show white lines running through each Laue spot. Black lines are set to see by this method. X-ray photographs were also taken, using the set-up described by Lam-one et al.5 when the beam straddles regions giving rise to lines in the Schulz pattern, split reflections are observed within the Bragg spot. The misorienta-tions calculated from the separation of these reflections and that found from the widths of the lines on the schulz technique patterns show good agreement. An exposure was made with Lambot technique of an area of the crystal showing no evidence of low angle

Jan 1, 1956

The authors of T.P. 4179 have conducted a large number of experimental water floods, and the data are reported in a very clear manner. These data show significant variations of residual oil saturation with changes in wettability, interfacial tension, flooding rate, and oil-water viscosity ratio. Furthermore, some of the data obtained cover a range of variables not previously reported in the literature. It is our opinion that at least some of the observed variation in oil recovery can be obtained only in floods made under conditions identical with those used by the authors. There are other systems which may be said to have the same wettability, but which exhibit an entirely different qualitative dependence of oil recovery on the experimental variables. In this regard, we would like to direct attention to several items which we feel are not given sufficient consideration in the paper. The first of these items has to do with wetting equilibrium. A survey of the current literature will reveal that little is known, and even less is understood, about wetting equilibrium. This is particularly true of the relation between contact angle measurements made under static conditions, and the wettability existing under the dynamic conditions of floods carried out at relatively high rates. We feel that this is a very important consideration, particularly in the floods the authors performed under what they consider to be "water-wet" conditions. It is our opinion that wetting equilibrium did not exist in these floods, except possibly at the very lowest rates. This opinion is in part based on some flooding tests we have made which are very similar to some of those described by the authors. These floods were made in unconsolidated cores, 6 in. long and 13/4 in. in diameter, made up of carefully graded glass spheres of the approximate size of the sand grains used in the subject paper. The cores were mounted vertically, and distilled water was used to displace a refined oil equivalent to the authors Soltrol C. The glass spheres had previously been carefully cleaned so that they were strongly wet by the water. The floods were made with and without an interstitial water saturation. When interstitial water was present, the solid surfaces were mostly covered with water prior to injecting the flooding phase. Consequently, a condition very near wetting equilibrium existed throughout the flood. The data in Fig. A show that under these eircumstances, rate had no influence on residual oil at flood-out, over the range of rates studied. On the other hand, in the absence of interstitial water, the surfaces are all covered with oil before the displacement. To achieve wetting equilibrium the injected water must displace the oil from the surfaces themselves. This is not a fast process. Therefore, the effective dynamic wetting condition in floods of this type must depend upon the flooding rate. When the flood rate is very low, compared to the rate at which wetting equilibrium is attained, the residual oil saturation at flood-out is essentially the same as the residual obtained when interstitial water is present. This is shown in Fig. A, and occurs because the dynamic wetting conditions are the same in both cases. However, at moderately high flooding rates, the rate has an important bearing on the amount of oil recovered because in this case the attainment of surface equilibrium is the slow step. We believe that, in the absence of an interstitial water saturation, oil recovery varies with rate because of the reasonably slow approach to wetting equilibrium which occurs during the displacement. In fact, as the rate is increased, the oil recovery performance indicates the core is becoming progressively less water-wet. At the highest rate there is even considerable simultaneous production of oil and water after breakthrough. This does not occur at the lower flooding rates, nor is there appreciable simultaneous oil and water produc-

Jan 1, 1957

By E. H. Crabtree, T. C. King

THE ferrosilicon grinding unit at the Central Mill of the Eagle-Picher Mining & Smelting Co. near Picher, Okla., was completed in March 1947. The object of the plant was to grind pigs of ferrosilicon, having a size of approximately 1 ½ by 4 by 12 in. and an analysis of 85 pct Fe and 15 pct Si, to approximately 100 mesh by crushing and wet grinding in a ball-mill classifier circuit. The minus-loo mesh ferrosilicon had formerly been purchased, and was used as medium in the heavy media process for treatment of lead-zinc ores. From the standpoint of dollars and cents, the cost of minus-100 mesh ferrosilicon was roughly $40.00 per ton more than pigs of the corresponding alloy delivered to the mill. Estimated wet grinding costs were considerably below this figure. The possible saving in cost of make-up medium for the cone plant was particularly attractive since, at that time, the plant losses averaged over four tons of minus-100 mesh ferrosilicon per day. Aside from the probable saving on the grinding charge, the need for such a unit was twofold. First, periodic fluctuations in the differential between the top and bottom densities of the cone were thought to be detrimental to metallurgy. There was little doubt that an intermediate differential existed at which the heavy media separation was most efficient, representing a compromise between concentrate grade and tailing loss. Furthermore, if a finer, but considerably cleaner, medium could be obtained, there was the possibility that the differential could be decreased without increasing the viscosity, or conversely, the viscosity of the medium decreased without increasing the differential. Preliminary to experimental work aimed at pegging the cone differential and circulating medium viscosity at whatever values were found to be most efficient, it was essential to have control over both the non-magnetic content of the medium and the particle size of the contained ferrosilicon. The latter was possible by means of a grinding unit at the mill. Second, whereas the ferrosilicon alloys are made by a number of manufacturers, only two, to our knowledge, grind it in any quantity for use in heavy media plants. For all practical purposes, the Central Mill was limited to one source of supply, a particularly vulnerable position. In case the supply was cut off, it was thought that pigs of the 85 pct Fe, 15 pct Si alloy could be obtained elsewhere, providing means of grinding them was available. There was no published information available covering wet grinding of ferrosilicon. Dry grinding in batch mills and in continuous mills with air classification was being practiced, but the cost of grinding was excessive and the dust condition objectionable. It appeared that primary and secondary crushing was no particular problem, providing heavy duty equipment was used;

Jan 1, 1947

By Renato G. Bautista, KNona C. Liddell

A model of the reaction of chalcopyrite, CuFeS2, with Fe3+ and with 02 is considered. Homogeneous solution phase reactions are assumed to be always at equilibrium throughout the dissolution of the mineral. The dissociation of USOb- and several complexation reactions involving cu2+, Fez+ and Fe3+ are incorporated in the model equations. The relative importance of Fe3+, 02, and H+ as oxidants and the role of solution equilibria are assessed and the implications for leaching practice discussed.

Jan 1, 1981

By George H. Cook

At first sight this subject seems to belong to pure theoretical geology, but examination will soon show that it has important practical and economic interest to the mining engineer. The conclusion that all the northern portions of our country, as well as of the eastern continent, have, in the later periods of geological history, been covered with a thick bed of ice, is now accepted by geologists. This bed of ice, except in its greater magnitude, was like the modern glaciers of the Alps, and other mountains which extend above the line of perpetual snow. The marks it has left upon the surface show that it was comparatively thin on its southern edge, but that its thickness was much greater a little further north, and that it was several thousand feet thick at its kenviest parts. This variation of its surface would give it a descending slope towards the south, and cause the mass of ice, like a semifluid substance, to move in that direction,

Jan 1, 1879

The Mining Journal Annual Review. The Mining Journal, London. $1.00, 200 pp., 1952.-Contains 70 specially contributed articles reporting on events in the metalliferous mining industry throughout the world during 1951. The articles are written from the standpoints of: Economics, world mining fields, progress reports on Empire mining companies, and British mining taxation. The review has appeared for a period of 20 years. Technical developments in mining, ore treatment, refining, and metallurgy are covered. Dun & Bradstreet Reference Book. Dun & Bradstreet Inc. 4000 pp., 1952. -Changes, brought about by the expanding economy, have been made for the three million listings for the United States and Canada. Planning for the changes started more than 10 years ago. New listings have been included for the metals and mining industries on all levels. The rapid development and specialization of industry have made the old symbols used in previous editions outmoded and a new system is substituted. Atlas of World Mineral Resources, . Edited by William Van Royen and Dr. Oliver Bowles. Prentice-Hall Inc. $10.75, 180 pp., 1952.-Scheduled for publication this fall, the book contains information that has never been published in map form before, as well as much that has not been presented in map form for many years. Facts on 29 minerals most important in world trade are dealt with, along with interpretation of all data available on each mineral, discussion of the world's mineral economy from viewpoint of specific minerals related to mineral exploration, geographical distribution of world's consumption, and appraisal of the adequacy of world's mineral resources.

Jan 1, 1952

By Charteris A. Stewart

The following scanty notes on the Roumanian oil-region may serve as an introduction to more detailed future study and description. The Roumanian oil-belt follows the outer edge of the sweep of the Carpathian mountains, and may, in a broad sense, be regarded as a prolongation of the Galician belt. It is distributed over a tract of country from 300 to 400 miles in length, with a width of from 15 to 20 miles, and is believed to cover an area of at least 20,000 hectares (49,420 acres). The governmerit claims that 16,000 to 17,000 hectares of its land is petroliferous. The primary deposits of petroleum arc considered to be in the Paleogene (Oligocene) and the Neogene (the salines of the Miocene) formations. Most of the other repositories, especially those of Muntenie, are only secondary, the petroleum there having been introduced by the orogenic movements which raised the Carpathian mountains. The oil-field has been divided by the Roumanian Survey into two regions, the Flysch and the Sub-carpathian, as is shown in the accompanying sketch-map, Fig. 1. So far as is yet known, practically all the seepages and productive pits and wells are situated on anticlinals. Those which outcrop in the Flysch region (called Paleogene anticlinals), as indicated in the sketch-map, Fig. 1,are : Solontz,

Jan 1, 1907

By R. T. Hukki

The purpose of this paper is to present an analysis of the unit operation of grinding and the circulating load, of the unit operation of classification and the circulating load, and of the two superimposed into one operation to clarify the overall trend of events relating the circulating load to the capacity of the closed circuit grinding system, to the specific surface area of the final fine product, and to the energy consumption in the closed circuit grinding process. The capacity of the closed circuit is frequently, if not always, determined by the classifier, not by the mill." With these words a startling idea was expressed in 1934 by Dorr and Anable.1 Today, some 30 years later, grinding in closed circuit is universally accepted. The basic curve presenting the capacity factor versus circulating load by Dorr and Anable has obviously been so convincing that not a single authoritative investigation regarding its validity seems to have been conducted. The only major subject of discussion appears to have been the relative merits of the 'high' and 'low' circulating loads. It seems to be universally agreed that much still remains to be hoped for regarding sharpness of classification. BASIC CURVES FOR CONSTANT MILL LOADING Fig. 1 presents a series of basic curves for constant mill loadings in function of new feed rate and circulating load. The mill loading indicated by each curve is the sum of hourly tonnages of new feed and circulating load. For example, at point 0 where the new feed rate is 100 t/h and the circulating load 300%, or 300 t/h, the mill loading is 400 t/h. In closed circuit grinding, the new feed rate corresponds to the rate of finished classified material produced. Although at this stage the effect of classification is excluded in construction of the basic curves, the trend indicated by these curves is strongly in favor of closed circuit operation under relatively small circulating loads. A study of the curves reveals that, e.g., a mill operating under a load of 200 t/h at point P where the new feed rate is 50 t/h and the circulating load 300% will also operate under the same total load at point Q where the new feed rate is 100 t/h and the circulating load 100%. In other words, a reduction of circulating load from 300% to 100% would lead to doubling of the new feed rate and doubling of the rate of production of finished material, without a change in the total mill loading. The obvious question is, is it also possible by a reduction of the circulating load in a closed industrial grinding circuit to increase the production of finished classified material and, if so, how and to what extent? GRINDING TESTS BY DORR AND ANABLE In a series of open circuit grinding tests reported by Dorr and Anable1 limestone was ground at various feed rates in a 3-ft ball mill. The original data are reproduced in Table I. It can be seen that with the increased feed rate production of -65-mesh material increased and the energy consumption per unit weight of the -65-mesh product decreased in the reverse ratio. The data shown in Table I have been reproduced for our purposes in Table II for a scale corresponding to grinding in a large industrial mill. This reproduction

Jan 1, 1968

Lawrence Addicks, Perth Amboy, N. J. (communication to the Secretary*): The excellent series of photo-micrographs given in this paper shows clearly the relation between micro-structure and cuprous oxide in refined copper. The authors suggest that this method of examillation might be substituted for the " button " method now used to control the refining of cop

Jan 1, 1904

By Evert Hoek

Summarising a conference is never an easy task, but I will try to keep my comments brief and to the point. There are a number of lessons which we have learned from our deliberations together during these past three days, and I will try to give you my impressions of these lessons and of their practical implications in open pit mining. The first thing that has become increasingly obvious during these discussions is that it is no longer acceptable to offer an 'Act of God' as an excuse for a major slope or tailings dam failure. Disasters such as that at Aberfan in the United Kingdom have focussed the world's attention on the activities of the mining industry and the report of the commission set up to investigate the Aberfan disaster clearly showed that adequate knowledge was available and that failure to apply this knowledge did not qualify as an 'Act of God'. The courts and the world's press are certain to impose increasingly harsher penalties and criticism on those held responsible for major failures, particularly of tailings dams, in the future. One of the major problems in applying available knowledge to slope problems is that attempts to apply this knowledge are frequently left too late. To provide an engineering solution in the case of a slope in an advanced state of failure is an almost impossible task, and it is essential that those responsible for the stability of a slope must learn to recognise signs of distress at an early enough stage for effective remedial measures to be taken. As our ability to solve slope problems improves, the time at which slope stability problems are considered in a mining project must move forward to a stage at which these problems can be anticipated and dealt with before they arise. Conferences such as this are important in that they enable us to exchange ideas and advance our knowledge to a level at which such predictive engineering will be possible. It has been encouraging to hear of mining projects such as the Bougainville Copper operation where slope stability studies were carried out as part of the overall evaluation programme and it is hoped that this will become a more common procedure in the future. Providing a safe slope in an opencast mine obviously costs money, either in terms of the reduced ore to waste ratio given by flat slopes or because of the cost of stabilization techniques such as drainage or the use of rock anchors. An optimum slope design will provide maximum safety at minimum cost but achieving this optimum is not an easy task. Any one of us could design a slope which would be stable to the end of time, but it is probable that that slope would be so flat as to be totally uneconomic in most open pit mining situations. On the other hand, if the overall economics of a mining project are so critical as to require slope angles which the engineer responsible for these slopes considers to be unsafe, it is his duty to make us could design a slope which would be stable to the end of time, but it is probable that that slope would be so flat as to be totally uneconomic in most open pit mining situations. On the other hand, if the overall economics of a mining project are so critical as to require slope angles which the engineer responsible for these slopes considers to be unsafe, it is his duty to make

Jan 1, 1971

By Joseph E. Worthington

Many thousands of years ago when our earliest ancestor first swung out of a tree, picked up a rock, and threw it at what he hoped might be his lunch, the minerals industry, in a manner of speaking, was born. It was then a very long step indeed to the primitive metal industry of our early civilizations, for we know that precious metals were accumulated and some metal objects were produced several thousand years ago. Prospecting, or "exploration" to use the modern euphemism, consisted of little more than outcrop examination and the use of a gold pan, and it probably did not change much from our earliest civilizations until relatively recent times. In a general sense, all the early explorers of North America were also prospectors, for mineral wealth was certainly one of the goals of the first pioneers and settlers. The earliest pioneers didn't do too badly either, for they discovered copper and iron in various places in the Appalachians and Michigan, gold in the Southeast Piedmont and many mineralized areas in the Southwest. In most places these were outcropping ores or gossans, and the prospecting was incidental to the arduous task of ekeing out a living in a new land. It was the explosive discovery of rich placer gold deposits at Sutter's Mill in California that caught the public fancy and precipitated the establishment of prospecting as a full-time occupation. After the end of the Civil War in 1865, full-time prospecting became an important occupation and continued as such for almost three generations. Prospectors equipped with picks, shovels, gold pans and four-footed transportation swarmed all over what are now our Western States, discovering thousands upon thousands of mineral showings-and certainly most of today's large mining districts. Our vigorous western mining industry is a tribute to the courage and persistence of these men. The techniques of these picturesque prospectors, however, were essentially the same as those of their predecessors-examination of every outcrop and assiduous use of the gold pan. The great increase in discovery at this time was therefore due to increased activity rather than to different techniques. An important result of this in- creased prospecting was the growth of interest in geology. It was during this period that the U.S. Geological Survey began to grow. Many of the major mining districts were mapped, and geological studies and projections began to have an impact on further ore discovery. Ore search and development gradually became more geologically oriented and the geologist became a fixture in most mining camps by the 20th century. The development of mass-mining techniques in the early part of the century also changed exploration concepts.

Jan 1, 1971

PRIOR to the World War most of the barite used in the United States for manufacturing lithopone and barium chemicals was imported. Germany, by virtue of an abundance of high-grade ore and low labor costs, was in a position to dominate the world market. With the cessa-tion of imports and with the war demand for barium chemicals, the barium chemical industry and the mining of barite became well; estab-lished in the United States. This industry has continued to expand because of the increasing use of lithopone. In 1914 the sales of domestic crude barite was 52,919 tons and in 1934 it was 209,850 tons. Barite deposits of economic importance occur in at least 20 states, but the principal producers in 1934 were Missouri, Georgia, Tennessee, South Carolina, Virginia, California and Arizona. The main mining centers are located near the crude barite markets of the three principal marketing districts-the Pacific Coast, the Midwestern area, and the Eastern area. The Pacific Coast is supplied entirely by California, Nevada, and Arizona. The Midwestern area uses most of the Missouri crude and a small amount from the southern states. The eastern market is the chief competitive area. Practically all of the imported crude is marketed there; also the bulk of the southern crude and ground barite. In addition, this area absorbs a small part of the Missouri crude and 80 per cent of the ground barite. Besides the advantage of low delivered costs and purity of product, the imported barite has commanded a price differential because it is soft rather than hard, like many of the domestic ores. The inherent physical properties of the southern ores remain, but the purity can be controlled to a great extent by beneficiation. Simple washing or gravity concentra-tion has sufficed in the past, but in many cases a more efficient process now becomes imperative to remove impurities not amenable to these methods. Certain deposits now being opened are of lower, grade and require more precise milling conditions. In some ores, the kind of impurities has changed as the mining advanced.

Jan 1, 1936

By J. Nutting, D. H. Kirkwood

IT is clearly of great metallurgical interest to know the conditions of temperature and gas composition under which different products will form in sulphide roasting. A method of graphically presenting the relevant thermodynamic data will be demonstrated, such that these conditions are readily obtainable. The products of sulphide roasting may be oxide, sulphate, or oxysulphates, and the equilibria between these may be represented in the following way: 2 MSO4 = MOMSO4 + SO3 MO-MSO4 = 2 MO + SO3

Jan 1, 1961