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By G. W. Jarman

The purpose of this paper is to present briefly a description of some of the special methods of separation or concentration, either singly or in combination with others, and to give certain operating data and examples. Explanation of the usual methods of large-production mill treatment, such as flotation or wet tabling, or of chemically treating industrial minerals, is not included in the scope of this paper, although one of these methods might be, in certain instances, augmented by one or more of the special methods that will be enumerated herein. Description of these special methods will be centered on magnetic separators, electrostatic separators and air flotation or air tables. Magnetic Sepaeatohs In general, separation is achieved by exerting upon a particle some kind of force opposed to gravity, either directly or at an angle. For example, in the Wetherill or cross-belt type of magnetic separator some particles are lifted vertically from the others because they have been exposed to a force to which they respond more readily than particles of lesser magnetic susceptibility. Of course, there is a limitation to this vertical rise, for the particle must be of a high enough susceptibility to receive a magnetic force greater than the 980 dynes per gram of gravitational urge. To overcome this limitation, the induction type of magnetic separator was developed, so that it is only necessary to instill, say, 30 to 60 dynes per gram instead of the 080, to cause a deflection away from the vertical in falling, and that deflection can be used advantageously when falling by inserting a dividing knife-edge. The induction magnetic separator (Fig. 1) has become a fairly well known method of concentrating and purifying. For example, abrasive grain was among the materials that did not respond to the previously best known type of magnetic separator, such as the Wetherill type, and the development of the induction magnetic separator in the plant of a

Jan 1, 1942

By A. Becker, J. A. Slankis

Equipment has been developed to utilize natural 8 Hz electromagnetic fields to measure rock resistivities. Telluric and magnetotelluric surveys have detected resistivity variations associated with geological contacts and metallic sulfide deposits. The fundamenfa1 premises of these methods are illustrated by the results of surveys across a Pleistocene-Precambrian contact in the Ottawa Valley and a near-surface sulfide deposit in Northern Quebec. Such interfaces are characterized not only by variations in apparent resistivity, but also, unexpectedly by the spatial anisotropy of the electric fields and the presence of a strong vertical magnetic field component in their vicinity. Standard geophysical electrical and electromagnetic methods (Heiland, 1940) for the determination of the electrical properties of the ground and the search of good electrical conductors necessitate the use of a transmitter and receiver which are coupled galvanically or inductively through the ground. The electrical properties of the ground are deduced from either the transfer function, or the impulse response, of the transmitter — ground — receiver system. Where deep penetration is desired these methods require powerful transmitters whose weight and size increase the cost and reduce the speed of operation. It is possible however, to resort to another class of electrical prospecting methods which employ ambient, natural electromagnetic fields in place of a transmitter.'-' In the audio and subaudio frequency ranges, these fields are generated by thunderstorm activity. At some distance from the seat of the disturbance, the e.m. fields propagate as plane waves with a horizontal magnetic field component. The incident wave, of course, induces currents in the ground. Where the ground is homogeneous the relation between the horizontal magnetic and horizontal electric fields vectors is particularly simple:' /E/ = \[SpT/H/ (1) where: /E/ = magnitude of horizontal electric field in millivolts/kilometer (RMS) /H/ = magnitude of the orthogonal inducing magnetic field in milligammas (RMS) p = rock resistivity in ohm-meters i = frequency of measurement in c/s In practice, the ground is seldom an homogeneous half space, lateral conductivity variations exist, (in the case of base metal prospecting these are the features actually sought) and the two field vectors are no longer simply related. The ratio of E to H is still useful, however, for the determination of an "apparent" ground resistivity. From a theoretical view point, the general problem of a two dimensional fault or dyke anomaly can be separated into two distinct cases. In the first case, where the e.m. energy propagates in a direction normal to the strike, the horizontal magnetic field remains constant and is oriented along the strike of the formation.3 As shown by d'Erceville and Kunetz," all the information about the anomaly is contained in measurements of the electric field component. In fact, away from the interface, the electric fields are proportional to the square roots of the resistivities:

Jan 1, 1970

By W. H. Adams

Inasmuch as] the mining of phosphate rock and its transportation has so general a bearing on the great industries of this continent, entering as well into the problem of our trade with foreign countries, it may be useful to place on record the following list of localities from which certain products of a like nature are received by us in a business way, or in which we are interested more or less either by ownership or by competition. As a ready means of comparison, the percentages of the mine products and the deteriorating constituents are given : Coprolite (Cambridge).—This material is obtained from the Upper Greensand formation in Cambridgeshire. The phosphate runs from 50 to 60 per cent., and averages 64 per cent. It contains much carbonate of calcium, but little iron, in the ferric condition. The superphosphates manufactured from the material are permanent and little liable to a revert." They contain from 28 to 35 per cent. of soluble phosphate. Coprolite (Buckingham).—From the same formation as the Cambridge variety, and very similar in composition.. It averages 60 per cent. phosphate. Coprolite (Suffolk).—These coprolites are not so valuable for the manufacture of superphosphate as the two previous varieties, as the iron they contain is in the ferric state, and liable to "revert" the soluble phosphate. The phosphate varies from 48 to 60 per cent., but averages 54 per cent. They are of Tertiary formation. Coprolite (Potton or Bedford).—The average amount of phosphate in these coprolites is about 50 per cent. In some cases they may, however, run up to 60 per cent., and in others may not exceed 45 per cent. They belong to the Lower Greensand formation. The ferric iron frequently is as high as 4 per cent., and the alumina as much. Russian phosphate comes from the chalk, and occurs in carious rounded masses. It contains from 28 to 35 per cent. of phosphate, but may run up to 69 or 70 per cent. Curacoa phosphate is also of very high class quality, giving 80

Jan 1, 1890

By D. F. Botkin, B. H. Sage, W. N. Lacey

Joule-THomson coefficients for two natural gases were determined at pressures up to 600 lb. per sq. in. throughout the temperature interval between 70" and 310°F. From these primary data and available information relating to the isobaric heat capacities of the components at infinite volume, the heat capacities of these gases were computed throughout the above-mentioned range of pressures and temperatures. The enthalpies of the gases were computed as a function of state and the results compared with values obtained by several methods of prediction currently available. Table i .—Composition of Gas Samples Components Gas A Gas B Carbon dioxide................ 0.0090a 0 .042 0 Methane...................... 0.8255 0.8385 Ethane.......................0.0901 0 .0637 Propane....................... 0.0462 0.0374 Isobutane..................... 0.0074 0.0039 n-butane................ ...... 0. 0126 0 .0095 Isopentane.................... 0.0032 0.0016 n-pentane..................... 0.0022 0.0011 Hexanes and Heavier........... 0.003& 0.0023 Experimentally determined Joule-Thom. son coefficients for natural gases afford a satisfactory means of checking the accuracy of prediction of their thermodynamic properties from the behavior of the components in the pure state and in binary mixtures. Relatively small samples of these natural gases were available, together with their analyses, and the Joule-Thomson coeffi- The Joule-Thomson coefficients were determined by measuring the change in temperature resulting from the passage of the gas through a porous thimble with a known pressure difference and under such conditions that the process was substantially isonthalpic. The details of the apparatus employed for this purpose have been described.' It is believed that the changes in temperature and pressure were ascertained with an uncertainty of not more than 0.3 per cent. However, as a result of deviations from steady flow, it is probable that uncertainties as large as 2 per cent may exist in the measured Joule-Thomson coefficient. The gases utilized in this work were taken from high-pressure separators and were dried prior to use by passage over calcium chloride at pressures in excess of 300 lb. per sq. in. The gases were subjected to the conventional fractionation and Orsat analyses. The results are recorded in Table I. The composition is typical of gases from such sources, with the possible exception of the presence of significant quantities of carbon dioxide in each of the samples. The experimental results obtained for the two natural gases are graphically Portrayed in Figs. I and 2. The experimental

Jan 1, 1943

By W. N. Lacey, D. F. Botkin, B. H. Sage

Joule-THomson coefficients for two natural gases were determined at pressures up to 600 lb. per sq. in. throughout the temperature interval between 70" and 310°F. From these primary data and available information relating to the isobaric heat capacities of the components at infinite volume, the heat capacities of these gases were computed throughout the above-mentioned range of pressures and temperatures. The enthalpies of the gases were computed as a function of state and the results compared with values obtained by several methods of prediction currently available. Table i .—Composition of Gas Samples Components Gas A Gas B Carbon dioxide................ 0.0090a 0 .042 0 Methane...................... 0.8255 0.8385 Ethane.......................0.0901 0 .0637 Propane....................... 0.0462 0.0374 Isobutane..................... 0.0074 0.0039 n-butane................ ...... 0. 0126 0 .0095 Isopentane.................... 0.0032 0.0016 n-pentane..................... 0.0022 0.0011 Hexanes and Heavier........... 0.003& 0.0023 Experimentally determined Joule-Thom. son coefficients for natural gases afford a satisfactory means of checking the accuracy of prediction of their thermodynamic properties from the behavior of the components in the pure state and in binary mixtures. Relatively small samples of these natural gases were available, together with their analyses, and the Joule-Thomson coeffi- The Joule-Thomson coefficients were determined by measuring the change in temperature resulting from the passage of the gas through a porous thimble with a known pressure difference and under such conditions that the process was substantially isonthalpic. The details of the apparatus employed for this purpose have been described.' It is believed that the changes in temperature and pressure were ascertained with an uncertainty of not more than 0.3 per cent. However, as a result of deviations from steady flow, it is probable that uncertainties as large as 2 per cent may exist in the measured Joule-Thomson coefficient. The gases utilized in this work were taken from high-pressure separators and were dried prior to use by passage over calcium chloride at pressures in excess of 300 lb. per sq. in. The gases were subjected to the conventional fractionation and Orsat analyses. The results are recorded in Table I. The composition is typical of gases from such sources, with the possible exception of the presence of significant quantities of carbon dioxide in each of the samples. The experimental results obtained for the two natural gases are graphically Portrayed in Figs. I and 2. The experimental

Jan 1, 1943

By Joseph L. Mehaffey

A variety of chemicals offered by Armak were evaluated as dewatering aids for aqueous slurries of silica sand, sparsand and feldspar; an established commercial dewatering aid was used as a control. A number of Armak’s potential dewatering aids yielded lower moisture retention values than did the commercial product on all of the mineral samples. In addition to the chemical dewatering evaluations, some of the mechanisms involved in the removal of water from these mineral samples were examined.

Jan 1, 1984

By W. R. Crane

MINING of the red iron ores of the Birmingham district has been carried on energetically during the past 50, years, and their development has created a large iron and steel manufacturing, center, the only important one in the South. The district produces approximately 10 per cent. of all the iron ore of the United States (80 per cent. of the Alabama ore mined is red ore) ; also, 43 of the 419 blast furnaces of the country are in the district tributary to Birmingham. The rapid growth of the district has been made possible through investigations that resulted in radical changes in furnace practice, and a still greater impetus will come from the study of the low-grade, high-silica ores, as a result of which they will be made amenable to treatment by concentration. Mining practice in this district has been comparatively simple because of the occurrence of the ore; but with the-rapid extension of the work-ings and the disturbed condition of the ore bed at some distance from the outcrop, more difficult conditions are encountered and the tendency is toward worse rather than better conditions. Should the high-silica ores of the lower bench of the Big Seam become available through beneficiation, mining practice will have to be modified to meet the new conditions, which will be rendered more difficult by the increased weight of cover that will exist at considerable distances from the outcrop. Support of workings will require greater attention and the efficient and economical operation of the mines will depend largely on the successful solution of the problems of working-and handling the ore.

Jan 9, 1924

By F. W. Glaser, W. Ivanick

A pressure-sintering method was used to produce binder-free and very dense TiC specimens. Some physical properties of these TIC bodies were determined and found to compare favorably with those of certain cemented Tic grades. It was also observed that the hot transverse rupture strength of TiC bodies remained substantially the same regardless of the amount or type of binder material used. STUDIES of the structure and physical properties of refractory materials have been intensified recently because of the urgent need for nonstrategic materials that retain their strength at high temperatures. Research aimed at determining and improving the physical properties of cemented carbides and borides has been accelerated with a view toward possible use of such materials in connection with turbine blades, rocket nozzles, and other high temperature applications. On the hypothesis that the strength requirements in connection with some of the above applications could be met only by proper choice of cementing agents for such refractory materials, the literature describing the physical properties of borides or carbides was reviewed. However, with a few exceptions,'-" references were found only to compositions containing at least one or more auxiliary binder metals. Cobalt and nickel are among the most frequently employed cementing agents. The melting point of Tic (approximately 3250°C) and therefore the sintering temperature, at which notable densification of a cold pressed Tic powder compact could be expected in the absence of a liquid binder phase, is relatively high. The present study makes use of a high temperature, pressure-sintering procedure, recently described by one of the authors in connection with the sintering of binder-free ZrB,," to produce dense bodies of sintered Tic—free of any cementing agent. During the course of this sintering study, some physical properties of dense Tic bodies produced by this method will be discussed. Materials, Preparation of Samples, Testing Methods The procedure for the forming of Tic powder consisted of mixing graphite and TiH, powders in stoi-chiometric proportions, and heating this mixture in a H, atmosphere and carbon crucible by high frequency, to temperatures ranging between 1900° and 2100°C (3452" and 3812°F). The powdered carbide was then comminuted and screened to the desired particle size. Table I shows the chemical analysis of the two grades that were employed for the production of samples during this work. Bodies of Tic, approximately 2.5xlx0.5 cm were produced in graphite molds that were heated by direct conduction. Sintering was carried out at temperatures for time intervals ranging from approximately 0 to 30 sec under a constant pressure of about 1.3 tons per sq in. An alternate method for the production of samples consisted in cold pressing the individual Tic grades at pressures ranging from 4 to 10 tons per sq in. and sintering in a hydrogen atmosphere in graphite crucibles heated by high frequency induction. Sintering temperatures ranged from 2600° to 2900°C (4715° to 5255°F). Electrical testing was done by measuring potentiometrically the voltage drop over a length of 1.5 cm for a current of 10 amp at room temperature. Cross-sectional areas as well as densi-

Jan 1, 1953

By Darrel W. Hansen

Morrow Point Dam and Power Plant are principal features of the Bureau of Reclamation's Curecanti Unit of the Colorado River Storage Project. They are under construction on the Gunnison River 20 miles east of Montrose, Colo. Johnson-MK is the prime contractor, and represents a joint venture of Al Johnson Construction Co., Minneapolis, Minn., and Morrison-Knudsen Co., Inc., Boise, Idaho. The power plant will be housed in an underground chamber in the left abutment, approximately 250 ft behind the original canyon wall. The chamber is 206 ft long and 57 ft wide. The distance from the foundation to the spring line of the roof arch varies from 51 ft in the service bay to 120 ft in the control bay. The roof arch has a rise of 16 ft. The longitudinal center line of the chamber is orientated east-west with the draft tubes discharging nearly due north. Access to the power plant chamber was possible through the cable tunnel, access tunnel, two draft tube tunnels, two penstock tunnels, exploratory tunnel, which became the ventilation tunnel, or the grouting and drainage tunnel leading to the dam. (See Fig. 1.) The shortest and fastest access was through the cable and access tunnels, and the contractor drove these two tunnels simultaneously. The cable tunnel and cable gallery excavation exposed a transverse section, at the west end of the chamber, that was 15 ft wide and extended from the crown to 5 ft below spring line. It was here that arch excavation began. The first 34 ft of advance along the arch was driven on three headings, and the muck was removed through the cable tunnel. Meanwhile, the access tunnel was completed, and a raise was driven from its crown to intersect the advancing arch excavation near the longitudinal centerline

Jan 1, 1968

By Amos L. Beaty

The oil industry can prosper only if crude production is not excessive. This is true for several reasons. In the first place, the marketing branch of the business is so highly competitive that there is little room for profits in it. There are too many service stations, too many middle men or jobbers, too many refiners eager to press their products upon the market. And the battle is between the strong. If any money is being made in oil today it is by small marketers who buy products from the refining companies and sell on guaranteed margins. In the second place, refineries are overbuilt. There is a large surplus refining capacity. If refined stocks were drawn down they could and would be replenished in short time on short notice. This excessive refining capacity is not serious, however, if the supply of crude is limited to trade requirements. True, it may reflect upon the intelligence of the industry, but if there were a shortage of crude for a few years refining capacities would be readjusted. In the meantime no great harm could result from some idle capacity. It requires no computation to see that refiners could not produce surplus stocks of products from a short supply of crude. I have in mind, of course, the increased yields from cracking. Allowance must be made for that. Still, the picture is the same; less crude is required. I think we can have prosperity in the oil business if too much crude is not produced. A proper limit at this point would be felt all the way down the line. It would slow the refiner and slow the marketer inevitably. Once this constant pressure to make more and sell more is off, operations will be normal and there will be some return on investments. Peices in Relation to Production Potential production at this time is very large, and this condition has existed for many months. As a result the price of crude is low. It is below the average cost of production. Nevertheless, if restraints were withdrawn actual production would immediately increase and the situation would become even worse than it is now. Eventually, of course, the

Jan 1, 1932

By Joseph Hartshorne

This plant is situated in the borough of Pottstown, on the banks of the Schuylkill river, between the Philadelphia and Reading Railroad and the Schuylkill Division of the Pennsylvania Railroad, on a plot of about 125 acres, most of which is reserved for future extensions. About 45 acres are to be used for houses, 40 of which have already been built. The accompanying plan will give a clear idea of the general arrangement of the works. Beginning at the lower or eastern end, the first building is the basic-cinder grinding-plant. At present, it consists of a 2000 mm. Jenisch ball-mill (Kugelfallmühle) similar to those used so extensively for grinding basic cinder in Europe. It was built by Herman LÖhnert, of Bromberg. The mill is very simple in design, and efficient in execution. About 13 horse-power is required to run it, and the average output is 20,000 pounds in 10 hours. The best work we have done is 29,000 pounds in 10 hours, with perfectly dry cinder. From 95 to 98 per cent. of the product will pass through a sieve with 100 meshes to the inch, while from 70 to 75 per cent. will pass through a 150-mesh sieve. The mill has been in service since last March, part of the time on double-turn, and the renewals and repairs have been very slight. The product of the plant is sold as a fertilizer. It runs from 18 to 24 per cent. in phosphoric acid, about 14 of which is reverted. The merits of this fertilizer were explained by Mr. W. H. Morris, at the Baltimore meeting of February, 1892 (Trans., xxi., 232), and by Mr. W. B. Phillips, at the Birmingham meeting of 1888 (Trans., xvii., 84). The results obtained by its use in Europe, where over 600,000 tons were used last year, are well known. Near the cinder-grinding plant will be situated the new machineshop, which is now being erected. The next buildings contain the brick-making plant and ovens.

Jan 1, 1893

By R. F. Decker, J. R. Mihalisin

Phase transformations in a series of relatively pure nickel-titanium-aluminum binary and ternary alloys were studied. The purpose was to clarify age-hardening mechanisms, especially in predominantly titanium-hardened compositions. The micro-structures, as determined on a tirne-temperature-transformation basis by light and electron microscopy and X-ray diffraction, were correlated with room temperature and hot hardnesses. The stability of the ? phase under nonequilibrium conditions was shown to be important in this system. MANY of the alloys designed for service in the temperature range of 1200oF (649°C) to 1800°F (980°C) are austenitic iron-.nickel base alloys hardened by titanium and aluminum. The control of high-temperature properties of these alloys has been advanced by the knowledge of microstructures provided by the equilibrium diagrams of Taylor and Floyd1 and Taylor.2, 3 However, there have been notable instances in the predominantly titanium-hardened alloys where the correlation of properties with microstructure and the equilibrium diagrams has been unsuccessful. Mihalisin and carrol14 have noted in electron microscope studies of commercial alloys of this type that a fee phase precipitates and transforms to 71 (hep Ni3Ti) in stress-rupture tests. Bieber5 found that this fee phase remained in nickel-chromium-titanium alloys even when aluminum was excluded. Age hardening in iron-nickel base alloys has been attributed to 71 by Craver, Aggen, and Dyrkacz,6 ? (fee phase based on Ni3Al) by Beattie and Hagel7 and both phases by Lena,8 Yet, on the basis of the nickel-titanium-aluminum equilibrium diagram of Taylor and Floyd shown in Fig. 1, it has been difficult to understand the presence of ? in low aluminum alloys. Furthermore, the characteristic coarse dispersion of 71 has not been commensurate with the marked aging response. Also there have been anomalous grain boundary transformations in the iron-nickel base alloys which have markedly reduced notched stress rupture properties.9 These have been related to boron content and residual cold work. Recently, Golubtsova and Mashkovich,10 Buckle and Manene11 and Bogaryatskii and Tyapkin12 have noted a transition fee Ni3Ti in titanium-hardened nickel-base alloys. It was apparent from the latter studies that a transition phase was important in the nickel-titanium-aluminum system. The purpose of this study was to identify this phase, measure its transformation characteristics and kinetics, and attempt to correlate these findings with age hardening. It was believed that time-temperature-transformation studies, because of their adaptability to transition phases, would be of most value for this investigation. Accordingly, this method of study was undertaken on relatively pure nickel-titanium-aluminum alloys with controlled variations in boron content and residual cold work. EXPERIMENTAL PROCEDURES Compositions were selected from the nickel-titanium-aluminum isothermal section of Taylor and Floyd.' These compositions are plotted in Fig. 1 and were selected to obtain equal aging potential of approximately 15 pet by volume of the equilibrium precipitate. The materials were vacuum melted from

Jan 1, 1961

By A. Bar-Or, G. Hirsch, P. Wynblatt

The rates of nucleation and growth at various temperatures in U-0.45, 1.1, and 1.35 at. pet Cr alloys were determined, providing a qliantitative proo-f that the transformation under study is controlled by nucleation and diffusional growth. The linear relationship, log NV US 1/T2, suggests that the nucleation of the alloys is probably controlled by the classical law of nuclei formation. The established linear relationship, log G us 1/T, in the three alloys suggests that growth in each alloy is controlled by bidimensional nuclei formation. It was established that both the rate of growth and the rale of nucleation are retarded by chromium. Using classical formulae, sApN and sApG (the ß/a apparent interphase energies) were calculated from the nucleation and growth results, respectively. It was found that their values are of the same order of magnitude. However, why sApN is unaffected by the addition of chromium, while sApG increases with it, needs further clarification. In the last few years, an appreciable amount of research has been conducted into the mechanism of the ß —a transformation in uranium and uranium alloys. Recently, Burke1 reviewed the published work concerned with this transformation. He concluded that in dilute uranium alloys it is firmly established that, at high temperatures in the a range, ß decomposes by a diffusional process. However, he based his conclusion either on experiments dealing with the over-all transformation,2 or on qualitative results.3 It was felt that a better insight into the mechanism of transformation could be gained from the quantitative measurements of growth and nucleation rates, which we aimed to carry out in the present work. In a previous work,4 we have shown that a rim of a grains is formed during isothermal transformation at the high a range. The thickening of this rim with time was used for measuring the rate of growth in U-0.45 at. pet Cr.5 This method was also used in the present work for two more alloys. For meas- uring the rate of nucleation, a method of quenching and macroetching was developed to allow differentiation between a grains formed during isothermal transformation at the upper a range and those formed after quenching, Fig. 1. EXPERIMENTAL WORK AND RESULTS The Rate of Nucleation. The measurement of the rate of nucleation was effected by counting the num-

Jan 1, 1965

By Henry N. Doyle

Basic procedures in the mining industry have changed only slightly over the centuries since metals and fossil fuels became an essential part of man's economic and cultural life. Mining techniques of the 20th century bear a close resemblance to those of the ancients: exploration, ore breakage and removal, hoisting, and processing. The great advances, however, have been in equipment and machinery of greater size and speed which allow greater efficiency in each of these operations, with a corresponding reduction in manpower requirements. Yesteryear production was measured in pounds per man-day; today a giant and complex, but highly efficient, continuous mining machine can remove as much as eight tons of material a minute from the coal face. If our energy and metal demands of the future are to be met, and at this time it can be assumed that coal will continue to supply a significant part of the energy demand, other dramatic and spectacular technologic advances must be accomplished. Along with mechanization, however, public policy will require the industry to place greater emphasis on health and safety protection, as has been well demonstrated by recent actions of Congress. Together, fossil fuels and metals formed the basis for the industrial revolution-coal to develop power and metals to transform power into useful energy. Strangely enough, however, the mining industry the world over has lagged behind the continuous social changes brought on by the industrial revolution, such as preventive health and industrial hygiene services, and other programs directed to the well-being of the worker. In some countries this resistance, to change may have led in part to the nationalization of the coal industry. Whether this disinclination to social change in the industry of the United States reflects managerial attitudes, inept labor leadership, government neglect, or economic relationship would be the subject of an interesting study. Doubtless the mores of miners and their resistance to change, as well as their geographic isolation from other industrial groups, may have had a strong influence on these factors. In every major coal mining country the accident rate in the coal industry is substantially higher than other industrial groups, and the cost of pneumoconiosis compensation in some countries is greater than the combined costs for all other occupational diseases from all other industries. The high social cost of occupational accidents and diseases may have been a factor in the closing of the industry in at least two countries. Despite diminishing manpower needs, the industry is faced with critical manpower shortages. Miners once reared their sons to be miners; now it appears that the opposite is true. This factor alone, however, does not explain an acute labor shortage in the industry. Traditionally, the industry drew much of

Jan 1, 1976

By S. C. Geol, C. H. Page

INTRODUCTION Mining at Mindola Mine, Rokana Division of Nchanga Consolidated Copper Mines Limited is the deepest on the Zambian Copperbelt. Mining extends to 1150 metre depth so far and the present plans extend to 1500 metres, although reserves exist below this level. Mindola Mine is the major producer of copper/cobalt ore at Rokana Division and produces approximately 200,000 tonnes of copper/cobalt ore per month. A standard open stoping method is the only method used for mining with minor variations in positioning drilling drives and other development, figure 1. The standard main haulage interval is 75m but in flat dipping areas the full stope height is split into two or three panels. In 1970 severe mining problems were experienced when mining deeper than 850111 below surface. The main problems included: - Heavy support requirements in drilling drives near stope face. - Premature closure of blast holes necessitating pre-charging of the holes with explosives immediately after drilling and well before the day of blasting. - Severe bumping and spitting due to rock movements on drive surfaces and remotely within the rock mass under high stress. - Low mining efficiency due to dilution from the waste hangingwall. - These stress related factors also caused some premature detonations of precharged but unprimed blast holes which became a serious safety hazard. A number of alternatives have been considered to overcome these problems. A search for leas sensitive explosives to avoid the premature detonation problem has been partially successful, however, the need for a method of reducing stress levels at the mining face is still considered essential as the mine goes deeper. This paper describes experiments with Regional Support Pillars as a method of reducing stresses at the mining face.

Jan 1, 1981

By C. Dinis da Gama

In mining, all unit operations are closely interrelated, and the results of blasting are probably the key factor within that sequence. The drilling program prior to blasting is just as dependent upon the desired rock fragmentation as are the loading, hauling, and mechanical crushing operations which are economically and technically influenced by the results of blasting, namely, the size and scatter of the product. What is known today as optimum blasting is the process of designing a blast in order to obtain a certain degree of fragmentation so that overall mining costs are minimized. Applying this criterion often results in a different program than when an individual blasting pattern is chosen only on the basis of the lowest operational cost for that pattern, disregarding what comes before or after the blast. [Fig. 1] shows the characteristic variation of mining unit costs with the degree of fragmentation, or the maximum size of blocks obtained from blasting. From the figure, it can be seen that optimum breakage must correspond to the lowest total costs, but reducing drilling-blasting costs only does not achieve such an optimum solution. Methods of designing surface or underground blasting operations should comply with the optimization criterion, but this compliance is feasible only if a detailed mining system analysis is available. Therefore, predictions of costs of loading, transporting, and mechanical breakage of ore as a function of its size will define a narrow range of variation for drilling and blasting parameters in order to get the minimum total costs.

Jan 1, 1972

By George W. Bain

Some problems concomitant with commercial exploitalion of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service department wants defects rectified and the cause determined to avoid recurrence The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character. Geological Problems The geological problems deal almost exclusively with the size of blocks. Size across the deposit is limited by thickness of individual beds. and along the strike by the space between crosscutting joints. Frequently the vertical depth of a block is reduced by exfoliation shells arising from spontaneous expansion. All these factors require consideration in developing a deposit to fill an order. Thickening of Marble Beds The limestone beds that became the marble deposits of the northern Appalachians and of the Yule locality in Colorado were seldom homo-

Jan 1, 1941

By George W. Bain

Some problems concomitant with commercial exploitalion of marble are presented as examples of interesting, useful and profitable fields for application of scientific knowledge. The marble industry is only one such field and is selected because its varying new aspects are familiar to the author. However, what is true for marble is equally so in principle for many industrial minerals. The problems of any stone industry are to maintain markets, create new outlets for stone already in demand, and develop varied uses for varieties that are not so popular. Here the geologist has a different role from most of his colleagues in metal mining. The producing branch may ask about the expectable variation in thickness or size of a deposit as development proceeds. The stock department may call for the available amount of a given type of stone before accepting a large order. The sales force requires data on the use for stone from certain parts of deposits in order to divert grades to the most suitable use. The service department wants defects rectified and the cause determined to avoid recurrence The mills want data on durability and cutting quality of abrasives. The geologist occupies no special department; he is on general call, as may be illustrated by a few types of problems that may be classified as: (1) dominantly geological in character, (2) dominantly chemical in character, (3) dominantly physical in character. Geological Problems The geological problems deal almost exclusively with the size of blocks. Size across the deposit is limited by thickness of individual beds. and along the strike by the space between crosscutting joints. Frequently the vertical depth of a block is reduced by exfoliation shells arising from spontaneous expansion. All these factors require consideration in developing a deposit to fill an order. Thickening of Marble Beds The limestone beds that became the marble deposits of the northern Appalachians and of the Yule locality in Colorado were seldom homo-

Jan 1, 1941

By C. Schlumberger

SINCE the, beginning of the year 1928 the senior authors and their associates have applied a series of procedures which makes possible the detailed study in situ of the formations traversed by a drill hole before the casing has been landed. They have given the name "electrical coring" to the ensemble of these processes, which now replace in a large measure the mechanical coring performed by the drillers, and permit the gathering of bottom-hole data hitherto unobtainable. Three years have elapsed since the technique and interpretation of these measurements emerged from the experimental stage and entered the field of industrial application on a large scale. The total length of drill holes so far surveyed by the authors and their associates, all over the world, amounts to several millions of feet. Practical and strongly built equipment has been evolved, which permits the examination in a short time of an open hole several thousand feet long. No comprehensive paper has yet been published discussing the essential principles of the processes applied and bringing into evidence their economic interest. This is the object of the present paper.1 Numerous examples of field work performed under varied geological conditions are given, constituting a concrete illustration of the services rendered by the new methods.

Jan 1, 1932

By S. W. Miller

During the examination of welds made in steel by the oxy-acetylene and electric-arc processes, the writer has met with some unusual structures, which he has not encountered elsewhere. They seem to be quite closely associated with the welding methods used, and characteristic of them, and would seem to be worth noting, especially as the references to them in the literature are few, and their explanation not clear or complete. An introductory word or two about fusion welding may not be out of place. The oxy-acetylene process is based on the great and very local heat generated by the burning of acetylene in the presence of commercially pure oxygen, the two gases being thoroughly mixed before combustion. The theoretical temperature is somewhat under 4000" C, but on account of various losses, the actual maximum temperature is probably about 3000" C.' The electric-arc process, using a metal electrode, which is also the filling rod, generates a still higher and more local temperature. The actual temperature of the positive crater of the carbon arc is given as 3500" C.2 NO figures have been found for the temperature of the arc using a metal electrode, but it would probably not be very different from that of the carbon arc, and probably higher than that of the bxy-acetylene flame. The greater localization of the electric arc is due to the fact that it is not surrounded by a large envelope flame, as well as to its higher temperature; while the oxy-acetylene white cone, or welding flame, in which the carbon of the acetylene is burned to CO, is surrounded and preceded by a long envelope flame, itself of quite high temperature, in which the CO is burned to GO2, and the hydrogen of the acetylene to H2O. This flame spreads around and over the pieces being welded, heating them to a further distance from the weld than does the electric arc.

Jan 1, 1918