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By E. W. Greig

This paper is an account of exploration for bauxite in the Amazon Basin, Brazil, and particularly of the discovery, exploration and development of the Trombetas deposits by Alcan. A general report of the Trombetas Project has already been published in E/MJ(Anon. 1975) to which the reader is referred for details on ownership, infrastructure and construction as well as the proposal for mining and treating the bauxite. A regional account of bauxite in and around the Guyana Shield and the northern part of the Brazilian Shield is included to help explain the geology of the Trombetas deposits and their relation to other bauxites in northern South America. It is suggested that all these deposits formed during Tertiary time under similar geologic conditions.

Jan 1, 1979

By E. C. Roberts

TO facilitate some recent microscopic investigations it was necessary to devise special mounting techniques for the polishing of two quite different metallographic specimens. These techniques are extremely simple and are submitted for whatever value they may be to other investigators. The first specimen mount proved very satisfactory for the study of untempered martensite. Since it was undesirable to heat the specimen, lucite or bakelite mounting materials could not be used in the conventional manner. A cold mount was made by drilling a hole of the same diameter as the specimen in a cylindrical piece of polystyrene then press- ing the steel specimen into the hole on an ordinary vise. A prefabricated disk of lucite should work equally well. The only precautions necessary are that the hole be drilled out cleanly and the piece of steel be pressed into the plastic uniformly, otherwise the mount will crack. The second type of mount was required for the study of slag specimens by reflected light. Mounting these specimens in bakelite and then attempting to rough finish the surfaces on graded emery papers resulted in a considerable amount of chipping and breaking out of the slag particles. This made further satisfactory polishing almost impossible. It was found, however, that if the bakelite-mounted specimen was first rough finished to a point where a good specimen surface became visible, the interstices in the specimen surface could be filled and the polishing completed. This filling was accomplished by placing a small amount of lucite powder in the bottom of the steel specimen mold then reinserting the bakelite-mounted specimen on top of the lucite powder. Reheating the mold to the proper temperature and applying the required pressure resulted in the formation of a thin disk of lucite on the bottom of the bakelite specimen. By carefully grinding the lucite away a uniform surface including the slag specimen was obtained and further polishing was unhampered by slag disintegration.

Jan 1, 1951

By J. D. Lubahn, R. P. Carreker, J. G. Leschen

The formation of slip bands in crystalline solids undergoing plastic deformation has recently been treated as a problem of nu-cleation and growth.' A simplified theory was developed and shown to be qualitatively consistent with certain experimental observations reported in the literature, such as the frequent failure of slip bands to traverse the entire crystal, the effect of specimen diameter and temperature on the yield stress, and the occurrence of incubation periods in the deformation of suddenly loaded crystals. The theory further predicts the appearance of transients in the rate of strain of a crystal when the applied stress is suddenly changed from one constant value to another. A transient consists of a discontinuous change in the strain rate followed by a gradual approach to a steady-state value. Such transient behavior apparently has not been recognized in previous experimental work. The preliminary experiments reported in the present paper were undertaken to confirm the existence of the predicted transients and thus to determine whether a more detailed treatment of the nucleation theory of slip might be theoretically and experimentally fruitful. Experimental Procedure A simple creep apparatus was assembled as shown in Fig I. Very little insulation was used on the furnace in order to facilitate rapid changes of temperature. Temperature was measured with a thermometer placed in the center of the furnace and was controlled by adjusting the Variac setting. The specimens were cold-headed in split-cylinder grips. The strain was measured as total elongation by a dial gauge sensitive to I/I0,000-in movement of the weight pan. Since the specimen gauge lengths were

Jan 1, 1949

By C. A. Heiland

THE Eötvös torsion balance permits the measurement of certain second derivatives of the gravity-potential, which are known as the gradients of gravity and the curvature values for an, equipotential plane of gravity. These quantities are influenced on level ground by the configuration of the masses underneath. Hence, the torsion balance has gained great importance for the location of geological structures and thus indirectly for the discovery of oil and other mineral deposits. If the ground is not level, however, the measurements become more difficult, because the superficial mass-irregularities also produce more or less considerable disturbances. It is necessary, therefore, to determine the shape of the surrounding topography by leveling as well as by consulting topographic maps and to compute its influence upon the torsion balance. The correction thus determined is called, in general, the topographic correction; it is composed of two constituents, the terrain correction and the cartographic correction. The terrain correction would be that part of the topographic correction as derived from the direct leveling of the area surrounding the station, whereas the data for the computation of the cartographic correction are obtained from a topographic map, usually beginning with a radius of 100 meters, as under most circumstances it is difficult to level along a larger concentric circle about the station.

Jan 1, 1928

By W. L. Chen

The Batac jig was first introduced in the US for fine coal cleaning in 1973 (Tackett, 1977; Hake, 1976). Since then, a total of six such jigs of various sizes have been installed in five US plants for a total capacity of 2346 t/h. The raw coal size ranges from 19 mm x 0 to 9.5 mm x 0-fraction sizes previously fed to heavy medium cyclones, Deister tables, or water only cyclones. Growing interest in the Batac jig as a replacement for the above equipment is due to the following reasons: • Unlike heavy medium cyclones, no magnetite is required. As a result, the operating cost of the plant is reduced. • The compactness of equipment is unique on a unit ton per hour basis as compared to other equipment. • Solid state electronic control of jig stroke length, frequency, and jig bed depth makes the equipment highly efficient. Installations of Batac jigs in the US as of June 1980 are shown in [Table 1]. Use of the Batac jig is even greater outside the US (Anonymous, 1980; Chen, 1980). Its use is not limited to fine coal but is applied to coarse coal as well, with 102 mm size in the feed (Zimmerman, 1975). In countries where consumption of magnetite associated with the heavy medium system of coal cleaning is considered a waste of iron ore resource, the Batac jig is regarded as the primary choice in the selection of cleaning equipment (Chen, 1980).

Jan 1, 1981

Discussion of the paper of J. V. EMMONS, presented at the Pittsburgh meeting, October, 1914. and printed in Bulletin No. 93, September, 1914, pp. 2233 to 2248. ALBERT SAUVEUR, Cambridge, Mass.-Mr. Emmons is to be congratulated for having placed before us in so forcible and satisfactory a manner a question of much importance-that of the surface decarbonization of steel. Of course, both manufacturers and consumers have known for many years that during the heat treatment of high-carbon steel, surface deca.rbonization is always likely to occur to a greater or less degree, but the subject does not seem to have been investigated with the method and thoroughness it deserves. I am in substantial agreement with Mr. Emmons's conclusions, and I have but little to add to what he has so well said. His statement that carbon dioxide is just as effective an oxidizing agent as pure oxygen is likely to cause surprise and some will wonder whether his investigation has been carried far enough to warrant so unexpected a conclusion. The reaction C + 0 = CO, expressing the oxidation of carbon by pure oxygen, is decidedly exothermic, whereas the reaction C + C02 = 2C0, expressing the oxidation of carbon by carbon dioxide, is endothermic. Decarburization by pure oxygen, therefore, should take place much more readily than by carbon dioxide. One cannot help regretting that the author does not mention' the best way of preventing in a practical manner surface decarbonization while treating tool steel and other high-carbon steels.

Jan 4, 1915

By Howard L. Hartman

Probably no aspect of underground excavation is as important or as neglected as the environment. The Committee on Rapid Excavation, formed by the National Academy of Engineering to study the technological needs for "rapid" underground excavation in tunnels, shafts, and mines of the future, encountered a blank wall in attempting to evaluate environmental needs. In fact, so little quantitative information on the extent of present-day hazards is available that projection of future environmental-control demands must await more adequate assessment of current hazard levels. Further, there are not even accepted tolerance standards for many environmental conditions, such as heat, noise, and illumination. Only certain atmospheric contaminants have been satisfactorily catalogued. Any technical study, therefore, which purports to examine the state-of- the-art on underground environmental control must, in reality, settle for a cursory survey of a rather nebulous subject. ENVIRONMENTAL HAZARDS To contend adequately with hazards in the underground environment requires some knowledge of their nature and characteristics. In this regard, it is helpful first to identify our concern: when, where, and to whom or what may environmental conditions constitute "hazards"? Table 1 summarizes considerations that are important in this regard. For the purposes of this Conference (and book), primarily directed toward the excavation process itself, the hazards of consequence occur during excavation (item A) and primarily within the excavation (item B). However, some attention must be given to external hazards as well, since these may affect excavation. The object of concern (item C) is mainly human safety, although property security is also important. Hazards occur in a variety of forms. If one is to devise suitable control

Jan 1, 1970

By R. P. McLaughlin

IN most branches of the mining industry it is a well-recognized fact that care must be taken to protect the mineral deposit from undue physical injury. It is comparatively easy to grasp this idea when the mineral is a solid and the lives of workmen depend directly upon the care with which it is removed from its natural position, but when the product is a liquid. drawn up from pools several thousand feet beneath the surface of the ground through openings only a few inches in diameter, it requires some imagination to picture underground conditions and the changes which must often occur. The development of the petroleum deposits of California has been attended by numerous accidents, the results of which are readily noticed at the top of the wells and in the profit and loss accounts of the operators. Determination of the cause of these accidents has been the subject of considerable study, which naturally has fallen upon men familiar with technical methods. The greatest damage to the oil deposits of California has resulted from water finding its way into the oil-bearing sands, and it is the purpose of this paper to set forth briefly this phase of the oil industry. Much of the material here presented has previously appeared inn publications issued by the California State Mining Bureau, which, under the direction of State. Mineralogist Fletcher McN. Hamilton, has investigated the subject and taken steps toward improvement of conditions. The writer, having been in charge of this branch of the Bureau work, has gained considerable knowledge of existing conditions.

Jan 12, 1915

By Henry M. Howe

In my original paper, Piping and Segregation in Steel Ingots, I pointed out1 among other things that, in view of the slighter stretching (virtual expansion) of the crust, and greater opportunity for sagging, there should be less piping in broad than in narrow ingots, and less in slowly-cooled ingots, e.g., those cast in pre-heated sand molds, than in those which cool quickly, e.g., those cast in iron molds. A. A. Stevenson said that neither of these predictions agreed with his own experience. In particular, in a picture which he showed of a wide and of a narrow ingot cast from the same ladleful of steel: the wide ingot had certainly piped much more deeply than the narrow one. At the time I did not see the explanation of these discrepancies, but further reflection makes it evident. One of the most important elements in determining the depth of the pipe is the degree of " top-lag," that is, the degree to which the solidification of the top of the ingot lags behind that of the bottom. Through this lagging the steel of the upper part of the ingot is able to run down and fill the pipe below as fast as it forms. To the importance of this lagging I called attention in my original paper.' Sand us. Iron Molds.—If we compare two like ingots, one cast in an iron and the other in a sand mold, we see that the top-lag is much greater in the former than in the latter, because in the former the lower part of the ingot is cooling off fast while the metal is running into the upper part. It is perhaps easier to look at this as a case of the solidification of the hot-

Jan 1, 1910

NEW MEMBERS The following list comprises the names f those persons who became members during the period of Dec. 10, 1917, to Jan. 10, 1918. ARLUCK,- A. A., Headquarters Co., 66th Artillery Brigade, 41st Division, Care Postmaster, New York, N. Y. BUCK, LEONARD J Park & Prospect Ave., Bethlehem, Pa. BULL, FREEMAN N., Min. Engr., Robert W. Hunt & Co., 310 Wall St., Joplin, MO. BURGESS, ELISHA PAYNE JEWETT, Pres. & Mgr., Montana Consolidated Copper Co., Care Clark Dodge & Co., 51 Wall St., New York, -N. Y. CAMPBELL, THOMAS E Governor of Arizona, State House, Phoenix, Ariz. CARTWRIGHT, F. 0., Asst. Chief Clerk, The Braden Copper Co., Bancagua, Chile. CASH, FRANK E., Engr. & Asst. Supt. of Mines, Alleghany Ore & Iron Co., Lignite, Botetourt Co., Va. CRITCHLOW, EDWARD B., Pres., Conkling Min. Co., 307 McCormick Bldg., Salt Lake City, Utah.

Jan 2, 1918

By James J. Scott, John J. Reed

In a year fraught with difficulties, especially to small operators, the more stable mining organizations have shown a dynamic readiness to plunge ahead in the development of new mines, new and ingenious equipment and new tools for management to take the guesswork out of important decisions. New Mining Equipment The mining equipment display at the American Mining Congress in San Francisco demonstrated some rather radical new design concepts and a new willingness to use imagination to come up with ingenious new applications and adaptations of standard equipment.

Jan 2, 1963

By C. F. Cornell, Henderson, A. F. Dunyon, D. A. Dahlstrom

IN processing magnetic taconites several steps of crushing, grinding, classification, and magnetic separation are required to produce a 60+ pct Fe concentrate. Usually the final concentrate is in a slurry form of 55 to 70 pct solids by weight and is further characterized by a particle size of 60+ pct -325 mesh. In taconite plants already completed or under construction the conventional method used to obtain pellets suitable for blast furnaces is to filter the concentrate slurry, ball the filter cake, and then harden the green pellets in a traveling grate or in a vertical shaft furnace. Large tonnages must be handled in minimum floor space, with reduced maintenance and lowest possible operating cost. Filtration must therefore achieve two objectives: 1) high filtration rate-in terms of pounds of dry solids per hour per square foot of filtration area-at a low filtrate solids concentration, and 2) a filter cake moisture that will always permit efficient balling within the normal fluctuations of plant operating conditions. If moisture contents are too high, balling may be impossible or result in a mushy ball without enough green strength for the firing operation.

Jan 3, 1957

By Eugene P. Pfleider, Claus Freyberger

Generally, the different methods of financing new mining projects are not well understood by the engineers and supervisory personnel. Nor are the effects of these alternatives on depletion, taxes and profitability readily apparent to even the sophisticated management personnel without the aid of cash flow studies. Fortunately, with the advent of the computer it is possible now to simulate many different combinations of 1) equity, 2) loan and 3) production payment financing with little effort. A general computer program for cash flow analysis of mining ventures has been developed and applied as a case example to a 1967 feasibility study of the Underground Mining of Minnesota Taconite. The effects on profitability as measured both in rates-of-return and present value are presented for various financing combinations. In addition, percentage depletion rates were altered so as to measure the impact of this statuatory allowance. Based on the cost data as presented in the aforementioned 1967 feasibility study, and assuming 7% loans, the rates-of-return vary from 9. 9% to [00] % on equity variations and from 9. 9% to 11.4% on total invested funds.

Jan 1, 1969

By S. Frederick Ravitz

FOUR liquids are ordinarily present in the lead blast furnace during lead smelting. At the bottom is the lead bullion, which is metallic lead containing about one per cent of impurities, including gold, silver, copper, bismuth, arsenic and antimony. Above this is the speiss, which consists essentially of arsenides and antimonides of iron and copper. The speiss is followed by the matte, which consists principally of sulfides of iron, copper and lead1. The top layer is the slag, of which the major constit-uents are silica, lime, alumina, zinc oxide and iron oxide. Similar products are obtained from the dross furnace, which treats the dross obtained in decopperizing lead bullion. The distribution of gold and silver among these various products is of considerable importance in the smelting of lead. In general, the matte and speiss cannot be treated in the lead smelter, and usually are sent to a copper smelter. It is usually desirable, therefore, to keep their gold and silver contents as low as possible, and to collect the precious metals in the bullion. If the bullion, speiss, matte and slag exist together in equilibrium, the gold and silver should distribute themselves among these four liquids in a definite manner, which, other conditions being equal, should depend only on the amounts of gold and silver in the charge to the furnace. It is thus apparent that a knowledge of whether such equi-librium exists is necessary before attempting to study the effects of various compositions of matte and speiss on the distribution of gold and silver among the furnace products2. Moreover, systems consisting of four liquids in equilibrium are very rare, and are of considerable scientific interest.

Jan 1, 1936

By R. Stanford

In any discussion of steel pouring too often refractories quality assumes a high level of importance. Unfortunately when one considers the many and varied conditions to which pouring refractories are exposed, it is difficult to isolate the true role of refractories quality alone. Some of the more important, yet often overlooked, variable conditions bearing on pouring performance are heat size, tap time and temperature, steel chemistry, ladle additions, ladle height and preheat, mechanical conditions of the pouring mechanism, hot top or non hot topped ingots and, ingot size, which determine total number of shutoffs, direct or tundish pouring, ingot filling rates, metallurgical demands, etc, etc. These considerations apply for either conventional or slide gate pouring of ingots and, to a large extent, even strand casting. In any event probably the most significant factor on pouring performance in any individual shop is what is considered an "OK" pour. We find considerable variance in this qualification, not only between Republic Steel meltshops, but throughout the industry. Therefore, it is a worthless exercise to draw comparisons attributable to refractories quality alone, except for similar conditions in a single shop.

Jan 1, 1972

By H. E. Lee, P. C. Feddersen

Blast-fuRnace operation at the Bunker Hill smelter deviates somewhat from common practice. Under existing conditions it is economical to operate the furnaces at "forced" capacity. The furnace feed consists chiefly of sinter and averages close to 50 per cent lead. Experience in smelting such material favors a low charge column attended by smaller proportions of coke and a low blast pressure. Under such conditions the gain in furnace tonnage greatly overbalances the somewhat higher slag losses and increased percentage of material fumed Furnace Charge The ingredients for the blast-furnace feed are stored in a group of 24 charge bins (3600 cu. ft. capacity). Each bin has two discharge chutes. Beneath each chute is a steel weighing hopper, suspended from a Fairbanks scale. The several hoppers are kept filled with the exact amount of material required to complete a furnace charge. The weighed material is discharged into a standard-gauge, bottom-dump charge car containing two compartments, each of which holds a complete charge (approximately 1½ tons). It is hauled to the blast furnace by a 44011 electric trolley locomotive. The proportionate parts of the various constituents of a representative blast-furnace charge are shown in Table 1. Table 1.—Representative Blast-furnace Charge at Bunker Hill Smelter Material Pounds Sinter.................................................. 2500 Limerock............................................... 0- 50 Coke................................................. 250-300 Scrap iron.............................................. 0-25 Settler skulls.......................................... 75 Undried zinc-plant residue................................ 0-200 Siliceous ore............................................ 25 Baghouse dust.......................................... 0-50 By-product slag......................................... 100 A variable stock tonnage of zinc-plant residue and return by-products results in fluctuations in the percentages of these materials in the blastfurnace feed. Accompanying such variations are corresponding increases or decreases in the amounts of coke, limerock and scrap iron necessary to obtain good furnace operation and adequate reduction.

Jan 1, 1937

By Frank C. Roe

Two cogent and ubiquitous facts have supported a constant search by the ore processing industry for better wear resistant materials in equipment. First, designs and types of equipment change or improve continually to meet the economic and physical demands of different and/or leaner ores. Second, practically all equipment is subject to impact and abrasion conditions that probably are more severe and extensive than in any other industry. Development and testing by operators and equipment manufacturers alike, has produced an extensive variety of longer lasting metal alloys, rubber, plastics, ceramics and other materials to improve equipment performance under different specific conditions. The need for diversified materials becomes obvious upon the simple realization that no two beneficiation operations are identical. Among the variables in the handling of ore are: 1. Size and weight of ore particles. 2. Hardness and sharpness of ore particles. 3. Concentration of ore particles in liquid or gas suspension. 4. Velocity and direction of particle impact toward equipment surface. 5. Coefficient of friction between ore particles and equipment surface. 6. Temperature of operation. 7. Chemical environment of operation.

Jan 12, 1967

By Persifor Frazer

The section along the left bank of the Susquehanna, in Lancaster County, from Falmouth to the Maryland line, which the writer made in 1877 to accompany his report on that county, was redrawn by Professor Lesley, as stated in the prefatory'letter to Vol. CCC. (p. x.).* As then stated, neither the numerous data, nor the general features of the structure obtained by the writer, were changed ; but enough was done to make a discrepancy between the text and the section as given; and some important points were made less clear in the published section than they were in the MS. map. Amongst other portions of the section, that between the railroad stations, 1190 to 1224, gives the impression on the published maps of a much too definite superposition. A few words will be devoted to this region in the following communication. There is absolutely no room to doubt the structure for about four miles on .each side of the Tocquan axis. The dips are gentle, and in opposite directions, and the lithological characters constant within ordinary limits of variation, nor do these characters resemble those of the rocks which flank these gneisses and mica schists to the northwest and the southeast. For the same reasons it is evident that the rocks which occur within these eight miles or so, represent an horizon below the basement of the fossiliferous or palaezoic series. Not only have no fossils been found, but their lithologieal characters are unmistakably eozeic. But on the upper and lower margins of this

Jan 1, 1884

By F. W. Robinson

THE temperature coefficient of electrical resistance of pure metals is high and therefore the resistance increases rapidly with rising temperature. In 1871, Siemens suggested the use of this property as an accurate means of temperature determination. Owing to practical difficulties, particularly the contamination of the metal and consequent permanent change in its resistance and its resistance-temperature relation, this method fell into disrepute as a practical standard until revived later by Callendar and Griffiths, and subsequently by Holborn and Wien, all of whom showed that the earlier difficulties were not inherent in the method but incident to the mode of protection of the resistance coils. Following .the work of these investigators, the problem of temperature measurement by this means has been the subject of careful study and has now assumed an importance second only in practical adoption to the thermo-electric method. It is generally recognized, both here and in Europe, that the standard temperature scale should be the thermodynamic as it permits the evaluation of high temperatures on the basis of the radiation laws of Stefan and Bolzmann, of Rayleigh, and of Wien and Planck, on a scale consistent with that obtained by means of the gas thermometer at low temperatures. Lord Kelvin showed that only. a very small correction, amounting to about +0.7° at 1000° C.-almost within the limits of experimental errors-is necessary to adjust the constant-volume nitrogen thermometer to the ideal thermodynamic scale.

Jan 9, 1919

By Warren T. Smith

The Phelps Dodge Corp. Lavender pit is located in the Bisbee mining district near the town of Lowell, Ariz. A quartz monzonite porphyry exists as an intrusive stock and was the source of mineralization for the limestone replacement orebodies being mined by underground methods. Leaching of the upper portion of the stock, and precipitation of the copper as chalcocite on the finely dispersed un- oxidized pyrite in the monzonite porphyry, formed a low grade ore zone below a leached capping varying from 50 to 300 ft thick. Churn drilling starting in 1916 and supplemental churn drilling begun early in 1950 indicated a mineable area about 3100 ft long by 2400 ft wide. In general drilling was on 100-ft centers. The pit was planned with 50-ft benches and wall slopes varying from 1 to 1 to a flatter slope of 1 1/3 to 1 dependent on the character of the ground. Materials within the pit limits, using a 0.6 pct minimum grade cutoff, were estimated at 41 million tons of 1.14 pct copper ore, 31 million tons of low grade sulfides suitable for leaching with an average grade of 0.42 pct, and 70 million tons of waste.

May 1, 1956