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By S. F. Shaw

THE Sierra Mojada mining district is situated in western Coahuila, about 8 km. east of the Chihuahua state line, and about one-half way from the northern to the southern extremity of the state. It is at the terminus of the Mexican Northern R. R., 125 km. northeast of Escalón, Chihuahua; also about 240 km. due west of Monclova, Coahuila. The altitude is approximately 1500 m. above sea level. The Sierra Mojada valley is about 10 km. long, from east to west, with a width of 1 to 2 km. It is approached from the east through the Puerto del Oro, where the Mexican Northern R. R. enters the valley; the slope from west to east is gentle. The Sierra Mojada, of which about. 300 m. is an almost vertical wall, bounds the valley on the south side; on the north side, the slope to the crest of Sierra Planchada is more gradual, rising only 200 or 300 m. above the valley. Water is relatively scarce in the district, and there are no running streams. The rainy season, usually beginning at the middle of June, lasts through July, and occasionally into August or September. In some years the rains fail entirely. The slope of the ground is such that nearly all the water immediately runs off. The arroyos along 'the flanks of the mountains are not very deep, but in heavy rains, sometimes approaching cloudbursts, a tremendous volume of water rushes down them, carrying large boulders. A certain amount of seepage collects in the agglomerate, lying below the conglomerate, and is retained in the local fractures. Some shallow wells have been sunk in this agglomerate, and one well over 150 m. deep was sunk on, the Volcan ranch, supplying about 76 1. (20 gal.) per min. A considerable supply of water is collected in large earth reservoirs in and below the town of Esmeralda. In ordinary years this supply will last until January or February, after which the Volcan well has to be depended on until the next rainy season.

Jan 8, 1922

By J. R. Campbell

It is the purpose of this paper to review somewhat in detail the literature on the subject that is extant, which ought to provoke considerable beneficial discussion. The value of 1 per cent. ash in blast-furnace practice was brought to the attention of the writer when he was connected with the U. S. Steel Corpn. Various groups of blast furnaces in the Pittsburgh district compiled a statement in which the average saving was about 6 c. per ton on pig iron for every 1 per cent. of ash reduction. Later, the same groups of furnaces, when materials had reached a higher price, compiled a statement in which there was a 30-cent saving on pig iron for every 4 per cent. ash reduction in the Pittsburgh district, which was equivalent to 7½ c. for every 1 per cent. ash reduction. In the Chicago district, on long freight hauls of coal and coke from the Pocahontas district, the set-up was 30 c. per ton of pig iron for every 2 per cent. ash reduction, or 15 c. for every 1 per cent. Some years ago, Ralph H. Sweetser, of the American Rolling Mill Co., presented a paper which provoked considerable comment.' To get the matter again before this body a résumé of his computations is given below: Comparison of Pig Iron Costs Ash in Coal. Ash in CoKe, Fixed Carbon in Coke peR Ton OB PIG Iron peN Day, Per Cent. PeR CeNt. Coke. Per Cent. PIG IRon. Lb. Tons 6.00 8.70 89.80 1800 365.0 7.00 10.15 88.35 1860 353.2 Coke with 8.70 Per Cent. Ash Ore mixture, 4144 It). = 1.85 tons @ $5.50.............................. $10.17 Coke, 1800 lb. = 0.90 ton @ $6.50..................................... 5.85 Limestone, 1000 lb. = 0.50 ton @ $1.50................................. 0.75 Labor, $365 per day on 365 tons....................................... 1.00 Supplies and service, $250 per day...................................... 0.68 Overhead, $200 per day............................................... 0.55 Reserve for relining and depreciation................................... 1.00 Total............................................................. $20.00

Jan 1, 1931

By F. C. Sturges

FOR some time mining engineers have been interested in the possibility of using small diameter shafts, sunk by core drilling, as aids to ventilation and as emergency escapeways. The possibilities are interesting to contemplate, but new methods involve unknowns, and interest tends to remain passive until these unknowns are solved. Recently we have completed two 36-in. diam. core drilled shafts, and wish to make the data on these available to the industry. Both shafts were drilled for the McLain Fire Brick Co., one at its Buckeye mine and the other at its Colonial mine. Both mines are in the fireclay underlying the Lower Kittanning coal. Both mines have been in operation for a number of years [ ] and have required expensive maintenance work on return airways. It was decided that considerable savings could be effected by short-circuiting the air to the surface through small shafts. It was also realized that these holes, located near the present workings, would be of added value as emergency escapeways. Originally, 48-in. diam. shafts were considered, but actual computations showed 36-in. diam. shafts were more than ample at both mines. The shaft at the Buckeye mine is 240 ft deep, and that at the Colonial mine 258 ft deep. Both holes were started in the lower part of the Conemaugh formation and penetrated Conemaugh and Allegheny strata. The holes were started through the unconsolidated materials overlying bedrock by constructing a concrete collar with a wall thickness of 8 in. Then the shafts were drilled by the shot-core drill method. An annular groove was cut in the rock by the abrading action of chilled steel shot run under the shoe of the core barrel. The drilling was done in stages, the core barrel drilling the groove for a certain distance depending on conditions encountered, and then the cores broken off and taken out in sections. The core barrel had a 36-in. o.d. and the finished diameter of the shaft measured almost 37 in. The major questions that could not be answered until the completion of the first shaft were, (I) how much ground water would be encountered, how would it hinder the drilling, and how difficult would it be to seal off, and, (2) how would the walls of the hole stand up. The holes of course could be cased or lined, but that is considerable added expense in any shaft.

Jan 1, 1947

By Charles M. Means

A thoroughly modern coal-handling system has been installed at the Pittsburgh Terminal H. H. &. Coal Co.'s new No. 8 shaft, or Cover-dale mine, about 11 mi. (17.7 km.) from Pittsburgh on a spur of the Montour R. R. The Pittsburgh scam, which is the one worked, is reached at a depth of 342 ft. (104 m.). Power is delivered to the mine at 22,000 volts over a transmission line of the bow-arrow type of construction. A private telephone line connecting the various mines and the main office in Pittsburgh is carried on the same poles. The high-tension line is brought to an outdoor, step-down, transformer substation, where three 833-kv.-a., single-phase, 60-cycle, oil-insulated, self-cooled transformers reduce the potential to 2300 volts. The transformers are protected by electrolytic, aluminum-cell lightning arresters, horn gaps, and choke coils. High and low-tension busses, together with fuses, choke coils and air-break horn-gap switches with thcir remote-control operating mechanism are mounted on a substantial structural-steel tower 25 ft. (7.6 m.) in height. Mine Substation The transformer substation is adjacent to a. pressed-brick building that houses direct-current substation equipment together with switchboards, etc., for the control and distribution of power. This building also contains the hoist for the men and supplies. Main Switchboard The 2300-volt circuit is carried underground in a conduit from the transformer substation to an oil switch in the substation and supply hoist building. This is the main switch controlling the 2300-volt busbars mounted back to a twelve-panel black-slate switchboard. From the switchboard, 2300-volt circuits are carried to transformers feeding the street and house lighting systems and to other transformers furnishing power for the elevator and lighting circuits in the store building. Other 2300-volt circuits run from this switchboard to the main hoist building, fan house and auxiliary or man-and-supply hoist. High-tension wiring,

Jan 1, 1922

By R. Thiessen

The question whether the kind, rank and grade of coal is in any way determined by the kind or type of plant from which it originated has been a problem since coal was first studied. Some investigators claim that the kind of plants has contributed none of the attributes that characterize the differences found in the various coals; others claim that all differences are caused by the contributing plant; and others hold that only a few characteristics are inherited from the kind of plant from which the coal originated. Most coalologists, however, give this matter no thought. It can easily be shown that the kind of plant which contributed to a coal had a marked influence on its kind and type. A number of factors enter into this problem, and all unrelated ones must be carefully eliminated, including metamorphism caused by the pressure of the cover, earth movements, mountain building and higher temperature. Only the fundamental substance—the plants out of which coal was formed—• and the causative conditions that gave rise to a peat swamp and the conditions imposed upon the plant and the plant substances during the formation of the peat swamp can be considered. Everything else being equal, the question then is, how far do different classes and types of coal owe their differences to different kinds or types of plants? Geologic Age of Coal Coal has been laid down in almost every geological period since the Devonian era. Even as early as the middle Devonian some coal was formed; although of no value it has great scientific significance. The most valuable coal was deposited during the Carboniferous. The coals of England were formed during the Mississippian, and most of the valuable coals of America, Europe and China during the Mississippian and chiefly the Pennsylvanian. From the Permian come the coals of France, Saxony, Thuringia and Schwarzwald in Germany and of Bohemia and of the Ural districts of Russia. From the Mesozoic come the coals

Jan 1, 1930

By T. T. Field, M. Gell

MUCH has been learned about plastic deformation behavior in crystals through the use of dislocation and slip band etchants. Slip in nickel and nickel-base alloys has previously been revealed by various etching techniques.l-5 The techniques for nickel-base super-alloys4,5 were successful only in the Udimet 700 composition in specific heat-treated conditions. The objective of this work was to develop a more generally applicable slip-band etching procedure. The nominal compositions of the alloys used in this study are listed in Table I. The low carbon Mar-M2OO alloy referred to in the text is the same as listed in Table I with the exception that the carbon content is less than 100 ppm. Mar-M200 and Udimet 700 were solutionized at 2250" and 2150°F, respectively. The aging treatment for both cast alloys was 32 hr at 1600°F and for wrought Udimet 700 was 4 hr at 1975"F, 24 hr at 1550°F, and 16 hr at 1400°F. The new slip-band etching technique consists of a chemical etch followed by a short electropolish, Table 11. Fig. l(a) shows the best result obtained on an internal section of a plastically deformed single crystal of Mar-M2OO when using a conventional slip-band etching procedure which consists of electropolishing followed by etching. Ghostlike traces corresponding to planar slip bands are observed, but the contrast between the bands and the background is weak. Fig. l(b) shows the same field using the new slip-band etching technique. After the etching step of this technique, the same ghostlike traces of Fig. l(a) are observed, but the subsequent electropolishing accentuates the slip bands and the subgrain boundaries while the rest of the matrix is being polished. Longer electropolishing obliterates the slip bands. The new slip-band etching technique makes use of the etchants and electrolytes that are normally used for a given material. Because of this, it should be possible to slip-band etch other nickel-base superal-loys by using existing etchants and electrolytes for a material and following the procedures outlined in the "Comments" section of Table 11. All the illustrative examples given below show internal plastic deformation in single crystals of regular and low carbon Mar-M200 in the solutionized and

Jan 1, 1970

By H. J. Rahilly

Mine fires, in the Butte district, have been a source of trouble and expense for the past thirty years, for while the actual fire area in most of the mines has been comparatively small, the handling of the gas has generally been a much larger problem than the actual putting out of the fire. The chief causes of these fires have been: Defective electrical equipment, incendiarism or carelessness, and spontaneous combustion. While fires from the first two causes have been numerous, they have generally been discovered and extinguished before they became very serious. Spontaneous combustion has been the cause of most of the large fires. Sufficient heat has been generated by ground movement, high rock temperatures, and decomposition to set fire to inflammable materials (tarred ropes, canvas, dry timber, manure, and hay) left in the gobs some years ago. Also, the heat resulting from the oxidation of the fine broken sulfide ore is sometimes sufficient to set fire to the timbers. In 1906, a fire was discovered on the 1100-ft. level of the Minnie Healy mine about 400 ft. (122 m.) west of the Minnie Healy shaft, which presumably originated, in one of the upper levels, from spontaneous combustion. The fire was walled off by concrete bulkheads and a pillar of ground 100 ft. (30 m.) thick was left below and mining resumed underneath. During subsequent operations, this pillar became cracked and broken and the fire passed into the new workings. It travelled downward and spread rapidly until, in 1917, it had become necessary to wall off portions of the Tramway, Leonard, and West Colusa mines on the 1300, 1400, 1500, 1600, 1800, 1900, and 2000-ft. levels, and the tops of the 2200-ft. raises were sealed. The fire area now consists roughly of a block 1000 by 1200 ft. and from the 600-ft. to the 2200-ft. level. This block is composed largely of a series of parallel northwest-southeast nearly vertical veins and stringers that form a large orebody, with no well-defined walls but badly fractured and faulted, and known locally as "horsetail ore." These veins, or orebodies, are mined by the square-set or the rill method.

Jan 1, 1923

By N. G. W. Cook

When an excavation is made underground the original rock stresses are removed from the surfaces of the excavation. These surfaces converge to partially close the excavation and the superincumbent rock mass moves down towards the excavation. If the convergence of the surfaces of the excavation were controlled, energy generated by their motion against the controlling forces could be extracted. Since the total forces in the rock mass are not significantly affected by the excavation, stress concentrations arise around the excavation, which compensate exactly for those stresses no longer transmitted through the excavation. These phenomena give rise to two general principles which provide the basis for analyzing the effects of making any underground excavation. The first of these is that the total force resulting from the stresses across any plane in the rock, including any plane through the excavation, must be the same before and after the excavation is made. The second of these is that energy must necessarily be released as a result of making an underground excavation. It is instructive to consider the implications of these two principles for two extreme cases of material behavior between which the actual behavior of rock must lie, namely, the behavior of a fluid and the behavior of an elastic solid. For the purpose of analysis in this paper, an underground excavation is defined as an excavation in which the smaller horizontal dimension of any open void at a particular horizon is less than the depth of that horizon below surface. In the case of a fluid, any unsupported excavation would fill immediately, as a fluid cannot sustain shear stresses. For the same reason, stress concentrations could not arise and the forces across any plane would necessarily be the same before and after excavation. If the filling of the excavation were controlled by forces applied to the surfaces of the excavation, an amount of energy equal to the product of the fluid pressure

Jan 1, 1967

By V. A. Zanadvoroff

The mine and concentrator of the Howe Sound Co., Chelan Division, are at Holden, in a remote section of the Cascade Mountains of northwestern Washington. Holden is at an elevation of 3200 ft., in the narrow valley of Railroad Creek. This creek drains into Lake Chelan, at a point some 40 miles up the lake from the town of Chelan. The concentrator treats 2000 to 2500 tons of low-grade copper-gold-zinc ore per day. Concentration is achieved by the differential flotation process, with recovery of 94 per cent copper and 82 per cent gold in the copper concentrate, followed by the recovery of 65 to 70 per cent zinc in the zinc flotation circuit. The final flotation tailing is deslimed, and coarse . sands, representing 60 to 70 percent of the total, are cyanided. The tonnage of tailing material amounts to 1900 to 2370 tons per day. General Considerations The property is within the Chelan National Forest. Railroad Creek is a fishing stream, being stocked regularly with trout from State hatcheries. Consequently, in planning a milling operation, the Howe Sound Co. was obliged to avoid any pollution of the stream by tailing material, and also destruction of valuable stands of timber. Moreover, the selected tailing- disposal sites should not mar the natural beauty of the valley. In addition to these requirements, the problem of tailing disposal at Holden was complicated by topography and climatic conditions. The valley is long and narrow, averaging 1200 to 1500 ft. in width. Its walls are flaring at a steep angle. There are no extensive flat areas suitable for deposition of tailing. All valleys tributary to Railroad Creek, also the well-marked paths of snowslides, must be avoided. Finally, the direction of prevailing winds and possible dust hazard arising therefrom dictated the necessity of selecting the tailing-disposal sites downstream from the mill building and two campsites. Heavy snowfall during the winter months of November to March, inclusive, impedes building of the retaining dike, making it necessary to prepare the needed storage space during the summer months. It is inadvisable, also, to do any dike building during the freezing weather, because the dike becomes unstable with the spring thaws, producing inevitable "sloughing" of the built-up borders. Tailing-disposal Sues The existing tailing-disposal areas are near the south wall of the valley. They were developed, and put to use in the following sequence: No. I. Area.—Covers approximately 10 acres. Built up to the height of 60 ft. and abandoned. Total length of dike border is 1900 feet.

Jan 1, 1947

By W. Henry Weimer

A successful surface coal operation requires the combined efforts of engineering and operating personnel. In the planning for a mine, machines should be selected to do the best work in getting the coal uncovered, loaded, and transported to the preparation plant. The best system and extent of cleaning will be determined by the market. After the fundamentals of operation have been established, the operating personnel should see they are carried out. There is no simple solution to some of the every day problems facing the operating officials. Here the production engineer with the technical approach, time studies, control methods, past experience, and available records can help in detecting causes of inefficient phases of the operations. With these studies, a careful analysis can be made in setting up the expected standards to be followed. Management can then compare the job under study with the standards and make corrections to solve the problems. 5.2-1. Annual or Daily Coal Production. Once the production cycle has been established, it is paramount that coal sales keep the productivity of the mine as high as possible. A successful company does this by what they call "the control approach." The daily tonnage report is one of the things that is a potent control tool in attaining the goals to be achieved. If production is falling short of the goal, the daily tonnage report will reveal what has to be done in the remaining days of the month or year to achieve the expected schedule. When goals are reached or exceeded, then budgeted tonnages and costs will be reached or exceeded and thus assure attainment of a profit. Failing to keep to the scheduled pace shows up quickly and prominently, facilitating any necessary action to get things back to the projected plans. The sales target is usually set a little higher than the operating production. The sales tonnage is scheduled and sales are made accordingly, slightly

Jan 1, 1968

By Paul M. Tyler

Fully a decade ago, demand for ground mica began to exceed supplies of scrap mica from manufacturing operations and of waste block from feldspar and sheet mica mining in the United States, with the result that in recent years the market has absorbed larger and larger quantities of mica recovered as a by-product from clay washing,1 as a joint product with kyanite12 and by grinding schists. So far, only schists that contain a large percentage of mica have been utilized for making ground mica, but already there has been a good deal of wishful thinking with regard to recovering mica as an aid to the prospective working of low-grade gold ores and ores of certain base metals. With wet-ground mica selling at $60 to $100 a ton and even dry-ground mica worth over $20 a ton, many ores that could not be considered as otherwise workable under present conditions will show commercial possibilities if they can be made to yield even a relatively small percentage of salable mica. An interesting paper might be written on the coming role of industrial minerals as joint products of metal mines. It is largely a matter of markets. Many years ago I watched the mess left behind the gold dredges in the mountains of Colorado and thought of the Denver sand and gravel operators who prided themselves upon their canniness in providing devices for catching gold merely as an incident to their regular business of selling what we miners classed as "tailings." Nowadays almost every milling or mining operation near settled communities finds use for at least part of its waste for road material or concrete aggregate and several eastern iron mines have gone into the crushed-stone business. Promoters now mention fertilizer "filler" as potentially salable at all the way from $1 to $10 a ton, or whatever is needed to cover costs of mining and treating the "ore" and leave the metal values as "clear profit." In emulating the pork packers in their efforts to utilize "everything but the squeal," mining engineers may go too far; on the other hand, they should not let

Jan 1, 1942

By H. A. Buehler

LOCATION THE Ozark region occupies a large part of the southern half, of Missouri, the northern portion of Arkansas and comparatively small areas in northeast Oklahoma, southwest Kansas, and southern Illinois. . It is a roughly elliptical plateau which has been deeply dissected by stream erosion, and which slopes imperceptibly into the prairie regions to the north, east, and west, but which terminates rather abruptly along the Arkansas River on the south and Tertiary lowland to the southeast. The-Boston Mountains extending for a distance of some 200 miles (321 -km.) along the Arkansas River rise to an elevation of 2000 ft. (609 m.), forming the most prominent topographic feature of the region. The so-called St. Francois Mountains in St. Francois, Madison, and adjoining counties in southeast Missouri, form a prominent but more restricted topographic feature, the highest point rising to an elevation of 1800 ft. (548 m.).. The remainder of the region is largely a plateau area varying from 800 to 1500 ft. (243 to 457 m.) in elevation. STRATIGRAPHY The region is underlain chiefly by sedimentary formations, which outcrop in roughly concentric bands around a comparatively restricted area of igneous rocks in the St. Francois Mountain district. Although located geographically near the eastern edge of the Ozarks, the St. Francois Mountains have apparently suffered the greatest orogenic movement and the lowest formations of the succession are exposed in their immediate vicinity. The various sedimentary formations of the region do not show any considerable metamorphism and have suffered little change since consolidation. With the exception of a few basic intrusions in Ste. Genevieve County and a pegmatite dike in Camden County, Missouri, there is no evidence of igneous-action, since the first sedimentary beds were deposited.

Jan 10, 1917

By M. R. Todd, J. Szekely

THE mechanism of carbon oxidation in steelmaking processes has attracted considerable attention in recent years. The generally accepted model postulates that the reaction between carbon and oxygen occurs at the surface of CO bubbles that originate at the suitable nucleation points and subsequently rise through the metal bath.1-4 Although this model describes adequately the behavior of open-hearth type operations, it is not a satisfactory representation of carbon oxidation in oxygen steelmaking processes since it cannot account for either: i) the very high rate of oxidation per unit bath area,or ii) the commonly reported shapes of the curves showing the dependenie of the oxidation rate on the carbon concentration. The very high decarburization rates commonly encountered in oxygen steelmaking processes need no further elaboration; some typical plots of the rate of carbon removal against carbon concentration, taken from a publication by Li, Dukelow, and smith,' are reproduced in Fig. 1. It is seen from the curves that the decarburization tends to decrease from a peak or a plateau once the carbon concentration falls below a certain value; in the experiments reported, this critical value ranged from 1.2 to 0.2 wt pct C. The apparent dependence of the decarburization rate on the carbon concentration indicates that within this region phenomena associated with the transfer of car- bon must play an important if not predominant role. Since the concentration of oxygen in molten iron at steelmaking temperatures (removed from the immediate impact zone) is only about 0.1 wt pct,6 it is clear that simple simultaneous diffusion of carbon and oxygen to the surface of CO bubbles could not account for the rate of carbon transfer being the controlling step at carbon concentrations as high as 1.0 wt pct. The purpose of this communication is to present an alternative model which may explain at least qualitatively the apparent anomalies mentioned and may stimulate further experimental work. The Physical Model. It is suggested that the principal mechanism of decarburization is the reaction between CO bubbles and an emulsion consisting of molten iron and molten iron oxide particles in the vicinity of the "slag-metal interface9'.* This mech-

Jan 1, 1968

By Thomas Egleston

The uncertainty of finding the exact equivalents fortechnical expressions in different languages has led me to think that a glossary of furnace-terms would be useful to members of the profession. I was led, some years ago, to prepare a small one, which has been found so very useful, that I have arranged one for presentation to the Institute, for four different 'types of furnaces, in the hope that it may prove of use to those who are in the habit of consulting foreign technical journals, I was further induced to make the attempt in the hope that it might tend to make the terminology less complicated than it now is, and also to make it more uniform over larger districts. The idea of referring to a drawing which expresses exactly what is meant, resulted from the necessity of presenting such subjects to students, and will, it is hoped, prove much more useful than the mere dictionary arrangement in alphabetical order. The drawing of the blast-furnace was prepared for me by Mr. J. P. Witherow, of Pitsburgh ; the drawing of the open-hearth furnace by Mr. S. T. Wellman, of Cleveland, and the reverberatory furnace by Mr. John Fritz, of Bethlehem. The bloomary-furnace is taken from my own paper* on Bloomaries, but, in order to have a complete furnace, I have introduced into the drawing of those used at Saranac the guard-plate used at Ironville. The interest which has been taken in the preparation of this paper by those gentlemen who have contributed the drawings, has been supplemented by gentlemen in Europe who have taken the trouble to read the proof. In France it has been read by Mr. Lodin, of the School of Mines, and by Mr. Chaper, of Paris, and in Germany by Dr. Wedding, of Berlin, and Mr. Luhrman, of Osnabruck. The preparation of the paper has been much more difficult than was anticipated, and its value has been very much enhanced by Dr. Raymond's kind assistance and cooperation; and to him, as well as to all the other gentlemen, Iam very much indebted. It was at first proposed to add to the paper the names of all the tools used in these various furnaces. It was found, however, that this would make such

Jan 1, 1888

By E. R. Parker, T. H. Hazlett

An understanding of the mechanism of creep of metals requires an accurate knowledge of shape of the time-deformation curve. An expression is developed which accurately expresses the creep curve for a number of structurally stable metals and alloys. VAST strides have been made in the development of high temperature creep resistant alloys; however, no sound understanding of the physical mechanism of creep exists to date. Consequently, creep resistant alloys are still developed by "cut and try" methods formerly so successful but now yielding returns at a continuously diminishing rate. It is apparent to all workers in the field that if the mechanism of creep were understood, much fruitless labor could be avoided. The dirth of fundamental knowledge has not discouraged the theorists. Speculation has flourished and numerous theories of creep have been proposed. A critical review of these theories reveals that, even though there are some general areas of agreement between the majority of the workers, there are many basic questions yet to be resolved.' It is generally conceded that theoretical speculation is far in advance of experimental evidence. The shortage of reliable creep data greatly hinders more rapid progress in this field. It is essential that the effects of different stresses and temperatures on the creep characteristics of metals be quantitatively determined. Once this has been accomplished, it will then be possible to evaluate the effects of alloying additions and, it is hoped, to provide a firm basis of facts for theoretical treatment of the creep phenomenon. The work reported herein was undertaken to determine the effects of such variables as stress, temperature, alloying, and structure on the creep characteristics of some metals. Material and Equipment Nickel was selected as the base material for the current investigation and an experimental program was initiated to determine the effects of temperature and stress on the creep characteristics of this material. Since a large quantity of high purity nickel was required for the proposed program and such material was not commercially available, it was decided to refine, cast, and prepare the required metal in our own laboratory. The resulting nickel test bars had the following composition, given in percentage by weight: Fe, 0.030 (1); Si, 0.003 (2); Ca, 0.001 (1); Mg, 0.020 (2); and S, 0.002 (2); to make total impurities of 0.056. The nickel (balance by difference) is 99.944 pct. The details of the purification process are described elsewhere.' This

Jan 1, 1954

By H. B. Muller

Single stage autogenous grinding of run-of-mine ore was selected by Broken Hill South Ltd., parent Company of Cobar Mines Pty. Ltd. for the concentrator to treat 60,000 tons per four weekly period of copper and complex copper-lead-zinc sulphide ores from the C.S.A. Mine at Cobar, Australia. Ore is mined by mechanised horizontal cut-and-fill stoping and is prepared for grinding by crushing under- ground in a 60 in. x 48 in. jaw-crusher set at 5 in. closed side setting. The ore is reduced to 80% minus 76 microns in two parallel sections each of one 22 ft. dim. x 7 ft. long autogenous grinding mill, powered by a 1,250 H.P. motor, operating in closed circuit with a single stage 20 in. dim. cyclone. Broken Hill South's original concept of the concentrator required the maximum use of reliable instrumentation, centralised control, and the minimum of manning. To achieve this objective the control room, housing the process recorders, alarms, closed circuit television monitors and all the control equipment, overlooks the grinding and flotation sections, and the whole plant is serviced by a public address system. The grinding units and associated equipment are located in the open and are serviced with the aid of a mobile crane and a mobile hydraulically-operated liner lifting device.

Jan 1, 1970

By K. D. Snyder

Barite deposits occur in the Iglesiente-Sulcis district of southwestern Sardinia, an historically important lead-silver-zinc district. Barite, often genetically associated with the base metal deposits, has become an independently important economic commodity. Barite deposition in southwestern Sardinia was related to Caledonian, Hercynian, and Alpine orogenic cycles. A model is presented that relates synsedimentary, karstic, vein, and residual deposits. Synsedimentary deposits are widespread, have common depositional characteristics, and act as sources, along with hydrothermal systems, for other barite deposit types. Caledonian-, Hercynian-, and Alpine-related secondary enrichment processes resulted in residual and karstic deposits that are complex in terms of their geometry and texture, but are more economically important than those of synsedimentary or hydrothermal origin.

Jan 1, 1985

By S. Usui, I. Matsuoka, H. Sasaki, J. Shimoiizaka

Depression of galena by sulfite or chromate ion in xanthate flotation was investigated by means of adsorption measurements, electron diffraction and flotation tests. Flotation of galena was depressed by sulfite ion only when galena had been oxidized; no depression took place with unoxidized clean galena. A similar behavior was found when chromate ion was used as a depressant, with the exception that the chromate ion depressed unoxidized clean galena around neutral pH. Depression was attained with galena on which xanthate still remained in appreciable amounts, indicating that the depression is not due to a decrease in xanthate adsorption. The galena surface produced sparingly soluble films under conditions in which depression of galena took place. These films were identified by electron diffraction as lead sulfite and lead chromate on oxidized galena and as chromic oxide on unoxidized clean galena. These observations in conjunction with contact angle measurements, indicate that the depressing action of sulfite or chromate ion arises primarily from film deposition resulting from the reaction between depressants and the galena surface. The thickness of the film was analyzed by means of electrochemical polarization.

Jan 1, 1976

By James E. Reynolds, Duane N. Goens, Charles W. Kenney

A process for recovery of lead and silver from high-grade lead sulfide concentrates by dry chlorination and fused salt electrolysis was developed by Hazen Research, Inc., for Cyprus Metallurgical Processes Corporation (Cymet). A pilot plant was designed to handle mixed sulfide concentrates and to produce high purity lead in a 2,000- ampere capacity fused salt cell. Design of the dry chlorinator and fused salt cell is discussed. Integration of modern chlorine caustic cells for reagent generation was evaluated in the pilot plant program. Also included in the paper will be process chemistry; pilot plant flowsheet, equipment and data: by-product and impurity removal: and scaleup and economic considerations for the process.

Jan 1, 1977

By John W. King

Uranium ore was first discovered in the Edgemont district of the southern Black Hills in the summer of 1951. The discovery was not made known for some time, but after the news leaked out prospecting became intense, and several hundred claims were staked in the spring of 1952. The Hot Springs Sub Office of the Atomic Energy Commission was established at that time and airborne radiometric surveys were commenced by the Government and by private companies. During the succeeding summer another important discovery was made by private airborne surveys in the northern Black Hills, and the area favorable for uranium ore was expanded many times. Between that summer of 1952 and the present, many individuals and groups have explored, developed, and exploited their claims until now uranium ore is produced in significant quantities and substantial reserves have been developed. The Black Hills portion of the geologic map of the U. S. issued by the U. S. Geological Survey is shown in Fig. 1. Sedimentary formations are exposed as a series of cuestas and hogbacks in a roughly annular pattern with the older sediments resting on the pre-Cambrian core, which is exposed in the eastern and southern portions of the dome.

Jan 1, 1956