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By N. J. Grant, A. W. Mullendore, Y. Ishida

Creep tests were performed at 500°F on polished specimens of A1-3 pct Cu at stresses of 2000, 4000, and 6000 psi. The effects of the size and distnbution of the second phase were studied in connection with the mechanisms of deformation, especially grain boundary sliding. Although the amount of grain boundary sliding varied considerably for the different heat treatments, yestriction of grain boundary sliding is not due primarily to precipitate on the grain boundary. NUMEROUS prior investigations of grain boundary sliding, notably those of McLean, 1 Rachinger, 2 Rhines, Bond, and Kissel, 3 and Brunner and Grant,4 have established the importance of this phenomenon in the deformation of pure aluminum and its solid-solution alloys at elevated temperatures. An extension of this kind of study to the case of a simple two-phase structure is an important step towards understanding the deformation behavior of more complex alloys. A two-phase A1-3 pct Cu alloy was selected for this study. The creep behavior of alloys in this system has been studied by Sully and Hardy,5 by Underwood, Marsh, and Manning,' and by Pelloux, Chaudhuri, and Grant.7 In these studies, the prior heat treatments were such that some precipitation took place during the tests in most cases. Pelloux, Chaudhuri, and Grant7 studied the creep of A1-2 and 3 pct Cu alloys in the overaged condition. Their results indicated that the structure most effective in promoting high-temperature strength consisted of a fine, closely spaced grain precipitate and large, widely spaced particles on the grain boundary. The present work consists of quantitative meas- urements of grain boundary sliding during creep of an A1-3 pct CU alloy with four different precipitate distributions. The aims were to quantitatively define the role of the second phase on grain boundary sliding, and to obtain information regarding the mechanism of grain boundary sliding. MATERIALS AND PROCEDURE A high-purity A1-3 pct Cu alloy, kindly supplied by Alcoa, was used in this investigation. The composition of the alloy in weight percent was as shown in Table I. This composition is such that A12Cu exists as a second phase at temperatures below 850°F. A homogeneous grain size of 0.6 to 0.8 mm was obtained by annealing the machined test bars for 5 min at 1000°F, furnace cooling to 930°F, and homogenizing for 5 hr. Following the recrystalli-zation and homogenizing anneal, four different heat treatments shown in Fig. 1 were utilized. The F7 and F5 treatments utilize a furnace cool to the aging temperature while Q7 and Q5 have a water quench from the homogenization temperature before aging. Figs. 2 to 5, and Table 11, show the size and shape of precipitate dispersions obtained with the above heat treatments. The heat treatments produce variations in the dispersion both in the grains and along the grain boundaries. Precipitate particles along the grain boundaries are rounded and large (about 1.5 p diameter) in the F5 and F7 structures (Figs. 3 and 5). The grain boundary precipitate was somewhat smaller (0.9 p diameter) in the Q7 structure and no grain boundary precipitate was detected in the Q5 structure using light microscopy. The pre-

Jan 1, 1964

By Dr. O’Neil Thomas J., Donald W. Gentry

There are mines that make us happy, There are mines that make us blue, There are mines that steal away the tear-drops As the sunbeams steal away the dew. There are mines that have lost the ore chute faulted, When the ore's forever lost to view, But the mines that fill my heart with sunshine, Are the mines that I sold to you. -Anonymous INTRODUCTION The preceding chapters have discussed, in various degrees of detail, the primary considerations necessary to perform a cash flow analysis of a mining-related investment opportunity. Although the previous discussions regarding the manipulations, calculations, and interrelationships of the various components of the pro forma income statement were illustrated in the text, many individuals are un- familiar with the format and appearance of a final spread sheet for the evaluation of a mining property. As a result, it seems appropriate to conclude this book with an abbreviated case study of an actual mine property (currently in production) showing the cash flow analysis and some back-up data. Obviously all of the supporting data and calculations for the case study presented cannot be provided; however, reference is made to the major assumptions utilized and to the appropriate procedures employed in the calculations, as described elsewhere in the text. The problem associated with using any case study for illustrative purposes is that one tends to be overwhelmed by detail. For instance, specific costs, prices, expenditure timings, and other variable values may be challenged because they either do not conform to one's expectations or are not consistent with specific operating experiences. When this occurs the instructional value of the problem becomes obscured. The purpose of most case studies, and particularly the one presented in this chapter, is to expose the student to the methodology, procedure, and format associated with performing a cash flow analysis of a mining property. It is not to laboriously wade through the specific details associated with operating and capital cost development, mine plans, or equipment schedules. It should be noted, how- ever, that the values represented in this case study result from specific mine plans, operating procedures, equipment spreads, manpower requirements, and other en-

Jan 1, 1984

By D. Jenkins

The Franklin Laboratory was designed mainly for the analysis of the products from the two concentrating mills situated at Franklin and Sterling Hill, the most important determinations being the zinc, iron, manganese, lime, moisture, and silica contents of the ores. Within the last 4 years, however, it has been found advisable to examine most of our supplies, and therefore additional space and equipment was allotted for the examination of such substances as oils, greases, soaps, alloys, fuels, paints, explosives, and water. The building as shown in elevation (Fig. 1) and plan (Fig. 2) consists of a main or routine laboratory, an experimental laboratory, a water analysis room, and the other accessories such as stock room, library, sampling and drying rooms, and office. The main laboratory is further divided into a balance room and zinc analysis room. As the greater part of our determinations are volumetric, good light is a very important factor and with this in view the interior malls of the building were constructed of white enameled brick laid in Keene cement. These also have the additional advantage that they give a clean and attractive appearance to the room. The windows are large, being 76 by 44 in. and even on very dark days the light is good throughout the whole laboratory. Our zinc titration requires a constant light and as, on many days, especially in winter, the light is variable, we installed two Artificial

Jan 1, 1918

By S. F. Shaw

IN 1913, the Tiro General mine, at Charcas, S.L.P., Mexico, which had been making from 125 to 150 gal. of water per min., was allowed to become flooded, after all the pumps had been removed, and in 1918 the problem of unwatering it came up for solution. There are two vertical shafts, the Tiro General, 1390 ft., and the San Fernando, 1225 ft. in depth, with five connecting levels between them. The San Fernando shaft had been partly retimbered, while the Tiro General had been newly timbered from the collar to, 1090 ft. in depth. It had been possible to place guides in only one compartment of the Tiro General, from the collar to the seventh or 850-ft. level, to which it was necessary to lower the water before station pumps could be installed. Soundings indicated that compartments in the Tiro General were open to 1082 and 428 ft., and in the San Fernando shaft to 471, 488, and 586 ft. The water had risen to a point 140 ft. below the collar of the Tiro General shaft. PUMPING EQUIPMENT The steam plant at the Tiro General shaft includes one 300-hp., one 150-hp. and one 100-hp. Erie City water-tube boiler, and two 160-hp. Heine water-tube boilers. All but one of these boilers were supposed to be in good shape, but it was soon discovered that six years of idleness in a climate that is foggy for several months of the year had left them in poor condition. The compressed-air plant comprises one Nordberg cross-compound compressor with piston displacement of approximately 2500 cu. ft. of free air compressed to 96 lb. per sq. in.; and another Nordberg cross-compound with piston displacement of 1235 cu. ft. of free air, to the same pressure.

Jan 2, 1920

By R. B. Roof, J. J. Lombardo

DURING the course of investigations on U-Cb alloys by X-ray diffraction techniques, an impurity or an additional phase was observed in severa1 alloys of various compositions. The X-ray dif-

Jan 1, 1959

By W. N. Poundstone

The mining and ventilating system used in development work in the Pittsburgh Seam in northern West Virginia is discussed. The seam conditions and the nature of the accompanying methane gas are described. The type of equipment and the mining cycle will be discussed, showing how they are well suited for very gaseous development work. Face ventilation in development work is possibly the fastest growing problem of the industry. The coal mines of the future will be faced with the prospect of mining from under increasing depths of cover. Consequently, larger and larger amounts of methane gas probably will be found. The Pittsburgh Seam, in northern West Virginia, is an example of an area already faced with this problem. At the present time, most of the development work being done in this seam lies beneath 500 to 1200 ft of cover. The Pittsburgh Seam in this area has always been very gassy—even near the outcrop—and the recent development work has been accompanied with extremely large volumes of gas. In many cases, a single development section has liberated in excess of 1,000,000 cfm in 24 hr. This problem of heavy gas liberation was the chief concern, several years ago, when continuous mining equipment was first considered at Christopher Coal Co. All of us were apprehensive about the liberation that would accompany rapid extraction in a single working place. However, the experience during the past few years has shown that this ability to mine only one place at a time, is actually the key to working this type of coal. With all of the mining or advancement concentrated in one place, the ventilation can also be concentrated. By this it is meant that continuous mining permits the active working place to be ventilated with a maximum amount of fresh air, taken directly from the intake source without first passing another working place. Continuous mining (and a good ventilating system) also permits a much greater concentration of attention or vigilance to the actual working place. There are two things that are very important to the mining of coal having high rates of liberation. First, adequate volumes of air are necessary. Second, and perhaps more important, a mining and ventilating system must be used that will provide an uninterrupted flow of air to every portion of the working section. Liberations of this magnitude take only a few seconds of interruption for a dangerous accumulation of gas to occur. With adequate volumes of air available, the ability to concentrate ventilation more than offsets the concentration of gas emission that is inherent with continuous mining. The mining system used with continuous mining equipment at Humphrey Mine is similar to the system used at many mines in the area for development work. This system is designed to favor ventilation, realizing that other efficiencies are meaningless if the equipment must stop because of ventilation difficulties. This plan is especially well suited to minimizing ventilation interruptions. Basically, the overall plan of mining is to develop headings into virgin coal and encircle or block out large areas. These blocks are generally at least 2000 ft sq. The purpose of this blocking out is to bleed gas from the area before pillaring. Experience has shown this method to be quite effective, even in the most gassy areas. The gas in this field seems to migrate or flow readily from the solid coal into the outside return headings of the development work. The numerous clay veins and slips that are found in the area are extremely good avenues for gas flow. A block of coal, surrounded with development headings, usually bleeds off readily; and since it is cut off from the virgin coal, it is not subject to gas migration, through the seam, from this source. However, the outside return of the encircling development work, adjacent to the virgin coal, may liberate gas for years. This liberation from the outside ribs in the virgin coal is the reason split ventilation is used in development work. If split ventilation were not used, there would, in many cases, be a serious build-up of gas in the intake before it could reach the working face. Fig. 1 shows a typical development section having seven headings. The two outside places on each side are returns, and the three center headings serve as intakes. This section is equipped with a ripper-type continuous mining machine. An off-track loading machine is used to load from a surge pile on the

Jan 1, 1961

By H. A. Dierks

PENNSYLVANIA's anthracite region lies in the heart of the richest and most densely populated area of the U. S. Nearly 70 million people live within a radius of 500 miles, in which 130,000 manufacturing plants employ more than 8 million workers. The region comprises some 3000 sq miles and contains 484 sq miles of coal measures, which folding and erosion have divided into four separate and distinct fields, known as the Northern, Eastern Middle, Western Middle, and Southern. One million people live in the anthracite region proper, and their prosperity depends to a great extent on the anthracite industry, which produces more than $200 million in new wealth for the U. S. each year. Nearly 80 pct of the tonnage shipped out of the region is handled by nine railroads, which depend on this traffic for a large part of their revenue. It follows that the economic health and the very existence 0: this industry is of real concern not only to the region itself but also to the state of Pennsylvania and the country as a whole. Anthracite mining is one of the oldest mineral industries in America. About 1760 burning rock or stone coal was discovered on the hillsides of northeastern Pennsylvania. Within a few years a systematic search for coal bed outcrops was under way, and hand mining was begun. At first production was very limited, since anthracite was difficult to burn and was not readily accepted as a fuel. Pennsylvania anthracite is one of the densest and hardest of all coals, and its content of volatile matter is low. Consequently it does not ignite easily and it burns without smoke. About 1808 Judge Fell of Wilkes-Barre burned anthracite in an open grate fireplace and demonstrated proper handling of an anthracite fire. From

Jan 1, 1958

By Charles M. Rolker

The Allouez Mine is situated in section 31, town 57, north of range 32 west, Michigan. The mine is being worked in a conglomerate bed, which conglomerate is generally conceded to be the continuation of the Albany and Boston conglomerate of Honghton County. Besides the well-known Calumet and Hecla with the adjoining Osceola, both working on the same bed, and the new location, the Seneca, now being tried on the Kearsarge conglomerate, the Allouez Mine is the only one working on a conglomerate bed. The Albany and Boston, in Houghton County, of which, as said before, the Allouez is supposed to be the continuation, shares with all the remaining conglomerate beds, near and around Portage Lake, the property of being non-quartziferous, while the conglomerates of Keweenaw County are all highly quartziferons in character. This change takes place, according to Professor Pumpelly, about six miles northeast of Portage Lake. The Allouez conglomerate, with a dip of 38" 15' and a general course of about 36' east of north, is overlaid by a trap, and has as its footwall an amygdaloid. The trap is followed by a series of amygdaloidal melaphyres and true amygdaloids, further on by the greenstone and ashbed; towards the lake shore alternating traps and conglomerates are found. At the footwall of the Allouez conglomerate, an amygdaloid lies, the thickness of which is not known, which is also the case with the other formations, accurate surveys and geologiwl researches of this district having, as I was informed, never been made. About 198 meters (650 feet), horizontally measured, from the Allouez conglomerate another amygdaloid bed can be traced, on which the present rockhouse stands, further on a melaphyre is exposed, and then follow the diverse conglomerates, the Calumet, the Kearsarge, and Kingston, which, according to the last geological report, are at about the re-

By T. E. Seidel, A. U. MacRae

The dependence of the electrical and crystalline properties of silicon containing ion implanted boron atoms have been studied as a function of the incident dose, substrate temperature, and annealing tempera-ture. Hall effect studies show that the compensation due to defects is negligible after annealing at and above 500°C for a dose of 1013 ions per sq cm. Steps occur in the isochronal annealing curve for the sheet resistance at 300°C and 800°C and the mechanisms responsible for these steps are discussed. The range of the ions at 150 kev is 3500 * 5001. Electron diffraction studies on samples implanted with 150 ker ions show the existence of damaged (polycrystalline) silicon closer to the surface than the range of the ions. Etching and subsequent annealing of etched and unetched specimens suggest that the poly crystalline silicon is closer to the surface than the bulk of the distribution of ions. THE purpose of this study is to investigate some electrical and crystalline properties of ion implanted boron in silicon. Sheet resistance, Hall measurement, depth distribution by chemical staining, thermal probe and electron diffraction have been used to study the properties of samples implanted in a random direction with ions having energy up to 150 kev. The boron-silicon system has been the subject of considerable study'-7 due to its possible application in the fabrication of electronic devices. The implanted ions produce considerable crystalline damage to the substrate crystal before they lose most of their primary energy and come to rest. Fortunately, most, if not all, of this damage can be removed by subsequent annealing or by holding the substrate at an elevated temperature during the implantation process. Sheet resistivity measurements of the p-type layers produced by boron implantation into room-temperature silicon, reveal that the annealing occurs in a two-step process: the first occurring at -300°C and the second at -800°C.' Electron-microscope and low-angle electron diffraction studies of this damaged material indicate that the bombarding ions produce an amorphous silicon region about the trajectory of each ion.' At high doses, these damaged regions overlap and an amorphous surface layer results. Furthermore, the 800°C annealing step, appears to be associated with the elimination of this gross damage. The depth distribution of the as-implanted and also the annealed samples have been studied by an angle lap and staining technique as well as by Hall measurements.3-7 We find the experimentally determined ranges of the boron are less than those calculated by the Lindhard-Scharff-Schiott theorys (hereafter referred to as the LSS theory). Our results are in essential agreement with pre- vious results. In addition, we have made Hall measurements on samples bombarded with a low dose (2 x 1013 ions per sq cm) to minimize impurity banding effects, and find that deep ionized levels influence the carrier concentration and room-temperature hole mobility until the sample is annealed at temperatures above 500°C. Above this temperature, the data corresponds to that obtained when silicon is doped with boron by conventional techniques. We have also made a depth distribution determination of the crystalline damage due to the implanted boron by using glancing angle electron diffraction techniques. It was found that the gross damage depth distribution of heavily implanted samples is closer to the surface than the depth distribution of the electrically active boron. By removing this gross damage, without affecting the distribution of the implanted boron, we have determined that the 800°C annealing stage is not exclusively due to the improvement in the crystalline perfection of the amorphous material but also appears to be associated with the annealing of some point defects. These results and their relation to previous results are discussed in the following sections. IMPLANTATIONS Boron ions were implanted into silicon samples using an accelerator capable of operating from 10 to 150

Jan 1, 1970

By John E. Miller

Unit Rig & Equipment Co., manufacturer of Lectra Haul trucks, is continually studying methods of reducing the operating costs of large haulage trucks. Reduction of haulage system operating costs is an important goal that equipment operators and equipment manufacturers constantly try to improve on. One of the most variable and important factors affecting operating costs is actual truck operating practices. An examination was centered on methods to optimize truck utilization. It was found that a very effective method of accomplishing this goal would be an automatic truck control (ATC) system to automatically control a fleet of haulage trucks in a predetermined pattern. Economic studies were conducted which showed a very favorable reduction in mine operating costs by use of an ATC system. In 1970, Unit Rig & Equipment Co., in conjunction with SAAB-SCANIA began preliminary development of adapting, for truck use, a proven automated control system, previously used for train systems, small trucks, and military target vehicles. In 1974, the first prototype system was installed on a Lectra Haul M-100 and tested extensively at Unit Rig's test track in Tulsa, OK. This truck and system were then displayed publicly at the 1974 convention in Las Vegas. In 1976, the system was redesigned for production to maximize reliability, ease maintenance, and to accommodate future control and-status reporting developments proposed for haulage trucks. The new design equipment was manufactured, and a full system test will be conducted in an actual open-pit mine for an extended period to evaluate reliability, compile economic data, and obtain application information to evaluate complete mine haulage system conversions to ATC. System Description The ATC system is designed to provide automatic control of all the vehicle functions normally accomplished by the vehicle operator. The basic system consists of the on-board control equipment and the wayside control equipment. The on-board equipment receives commands from the wayside equipment and controls all the truck functions. In addition, on-board sensors monitor all critical truck functions and provide instructions to the truck and system to assure safe operation. The wayside equipment consists of a buried guidewire, block control units and a central controller which provides predetermined signals to the on-board equipment for speed control, steering, and for auxiliary functions (dumping, horn, etc.) through the guidewire located in the truck's path. The wayside equipment also controls vehicle separation, system status, and provides truck location to a central display panel. The central control panel can vary the speed level signals over any segment and can also command an emergency stop to halt all the units. [Fig. 1] illustrates a typical ATC installation. If ATC is used in operations which require flexibility and mobility at the end of the ATC guidance network, the trucks can then be operated by either radio remote control or manually to complete their assigned functions.

Jan 1, 1982

By Chase Palmer

INTRODUCTION. WHILE the reducing action of organic matter, of ferrous sulphate, and of hydrogen sulphide has frequently been invoked to account for the deposition of native gold and silver from ore-forming solutions, the high efficiency in this respect of certain of the metallic minerals which form the ore itself has not been sufficiently recognized. If a little finely powdered chalcocite is placed. in a test-tube and 2 or 3 cc. of a dilute solution of gold chloride are poured over it, two or three shakes of the tube suffice to remove all the gold from the solution. The color of the solution changes from yellow to pale green, showing that copper is dissolved simultaneously with the precipitation of metallic gold. If a piece of chalcocite is hung in a dilute aqueous solution of silver sulphate (1 normal), a coating of silver begins immediately to form on the mineral, and within a few moments a beautiful silver tree has developed, similar to that formed when metallic zinc is immersed in a similar solution.

Jan 5, 1913

By Alfred Brooks

THE only oil produced in Alaska in 1923 was obtained from a dozen small wells, one of which was drilled during the year on the single patented tract of petroleum land in Alaska, in the Katalla field. These wells are owned by the Chilkat Oil Co., which finds a ready local market for its product in the form of gasoline produced in its own refinery. The search for oil has been continued, but except in the Cold Bay field there has been no drilling in new fields during the year. Drilling was in progress during 1923 at Pearl Dome, 18 miles from the coast. Here the Associated Oil Co. sank two wells, about 500 and 950 ft. deep, but suspended drilling in June. The Standard Oil Co., drilling on the same structure, reached a depth of 300 ft. by August and is reported to have reached about 700 ft. by November. The company began the, installation of a second drill in August. George C. Martin, who hastily examined the Chignik region, south of the Cold Bay field, reports that what is known of the geology near Chignik is not favorable to the presence of petroleum. Kirtley Mather, who made a geologic survey of the northern part of the Alaska Peninsula, reports that some of the structures and the formations are favorable to the presence of oil. A small seepage has long been known in the region near the mouth of Douglas River, which flows into Cook Inlet. Sidney Paige last summer made an examination .of the oil seepages which have long been known near Cape Simpson, 50 miles southeast of Point Barrow, the northernmost point of Alaska. He reports that there are two very large seepages emanating from small ridges about a mile apart and several miles from the coast. These are marked by flowing petroleum, and cover many acres. There is a very large accumulation of petroleum residue at these seepages. The surface exposures consist of clay shales with hard thin partings of calcareous shale which lie nearly horizontal, and are probably, of Jurassic age. Mr. Paige and his two sub-parties explored a large area inland from the Arctic coast between Cape Beaufort on the south and Point Barrow and Cape Simpson on the north. He himself ascended the Meade River for 150 miles. These surveys indicate a wide distribution of what is believed to be the formation from which the Cape Simpson seepages emerge, which is probably of Jurassic age. These rocks near the north Arctic coast are little disturbed, but are increasingly folded to the south, toward the mountains. No other seepages have been found, but what is known of the geology is not unfavorable to an oil field. This entire region lies in Naval Petroleum Reserve No. 4, and it was examined by the Geological Survey at the request and expense of the Department of the Navy.

Jan 3, 1924

By Charles W. Oxford, R. L. Huntington

During the past 20 years (1932-1952), many condensate reservoirs have been discovered in the United States, particularly in the Gulf Coast region. Most of these reservoirs have been produced by a combination of gas cycling and slow pressure depletion in order to recover the liquefiable components from the single-phase fluids originally existing within the Although a record of the composition of the produced fluids has been kept on some of these reservoirs, very little laboratory work has been done on small scale replicas so as to obtain some idea of the effect of such variables as fluid flow withdrawal and cycling rates, pressure, temperature, percentage of liquid hydrocarbon and water saturation within the reservoir. Weinaug and Cordell have shown experimentally that condensates can be revaporized within a sand reservoir; however, they studied only the effect of fluid withdrawal rate. In this investigation the above mentioned variables were studied experimentally in small scale reservoirs both in the case of vaporization of condensate by batchwise pressure deple-

Jan 1, 1953

By F. G. Tickell, R. C. McCurdy, O. E. Mechem

The behavior of fluids in the voids of a rock is fundamental to the study of many of the problems of oil-field development and production. For it is by virtue of these openings between grains that oil and gas are able to move through the rock, to be contained by the rock, and to pass from the rock into the well. The capacity to contain fluids is measured by the porosity of the rock, and the ease of fluid movement is governed by the permeability. When the engineer wishes to estimate the amounts of oil and gas in an underground reservoir he is often concerned with the porosities of the rocks and, when dealing with problems relating to rate of production, he is more likely to be interested in the permeabilities of the rocks. Rocks are permeable because they are porous, but they may be porous without being permeable. Clays are very porous, and yet they are impermeable from a practical standpoint. Attempts have been made1 to correlate permeability with porosity for certain rock members but, where a definite relationship between these two properties is found to hold, it is purely fortuitous and local. Porosity and permeability do not necessarily bear any quantitative relationship to one another. The porosity of a substance is the percentage of void volume to bulk volume. The petroleum engineer is usually interested only in the inter-granular voids that are accessible to fluids. In measuring porosity he does not wish to include scaled openings. The measurement he desires is one of "available porosity," otherwise called "apparent porosity." The porosity of a natural aggregate of solid grains, such as a sandstone or clay, is governed by: (1) Grain-size distribution, (2) angularity of grain, (3) colloidal content, (4) degree of compaction. It is not difficult, for unconsolidated rocks, to measure the effect of any one of these when it alone is varied, and then to predict what the effects on porosity will be for such single variables. It is very difficult, however, if not

Jan 1, 1933

By W. A., Wasley

THE EL TIGRE MINE is a highgrade silver and gold producer located in the northern part of Sonora, Mexico. It has been worked continuously since 1903, producing 50,000.000 oz. of silver and returning handsome dividends. During 1930 and 1931 falling silver prices compelled the Tigre company to make representations before the Department of Labor in Mexico City showing the necessity for drastic reductions in wages and personnel. The delays in obtaining permission from the Federal Labor Board to make these readjustments caused the company to suffer considerable financial loss during those years. After the reduction in operations was finally effected, the Sonora state government headed by Señor Francisco Elias (former Governor, now Secretary of Agriculture) and Señor Rodolfo Elias Calles (present Governor and eldest son of Señor Plutarco Elias Calles, recently Secretary of War and former President of Mexico) have cooperated with the company to make continued operation possible by revising downward certain state taxes that would have been a factor in forcing the closing of this mine. Also, permission to change our workmen over to another system of mining was essential to continued operation.

Jan 1, 1933

By H. W. Hitzrot

SEPARATING a mixture of particle sizes of material suspended in a liquid medium is by no means an exact science. Selecting machines for individual classifying operations is even more difficult. The plant operator's own background is of course invaluable, and considerable help may be obtained from technical articles, talks with sales engineers, and handbooks on ore dressing. These several sources of information, however, are difficult to marshal in proper perspective for the major decision on classification units that an operator may be called upon to make. To the present writer's knowledge this assembly of facts is not available in handbooks, and technical papers are scarce on classification equipment developed in the past five or six years. It is believed that this paper will be helpful to users of classification equipment at this particular period in the development of hydro-classification. For easy reference the following classification units now available and in use in metallurgical and industrial operations are listed below, with a brief description of each. Unit-type classifiers, bowl classifiers, and bowl desiltors are all rectangular tanks, slightly tilted, with reciprocating rakes or screws to remove settled sands. The unit-type classifier, Figs. 1 and 2, is available in widths from 14 in. to 20 ft and lengths up to 40 ft. The shallow bowl of the bowl classifier, Fig. 3, equipped with rotating rakes, is superimposed on the lower end of the tank. Reciprocating rake compartments for this design range from 18 in. to 20 ft wide. Bowl diameters vary from 4 to 28 ft. The flat-bottomed bowl of the desiltor, Fig. 4, of relatively large diameter, is equipped with rakes rotating outward and partly over a pit, which is created by extension of the rectangular tank into and under the bowl section. Bowl desiltors are available with reciprocating rake sections 4 to 20 ft wide and bowls from 20 to 50 ft in diam. The bowl desiltor is used for applications beyond the range of the bowl classifier. The hydroseparator, Figs. 5 and 6, is a circular tank equipped with slowly rotating rake arms, set on a slope, with interrupted rake or spiral blades to move the settled solids to a central discharge cone. Tank diameters vary from 4 to 250 ft. Tank depths at center are 2 to 3 ft for small units and up to 25 ft for larger units. Hydraulic classifiers of the sizer and super-sorter types, Figs. 7 and 8, are narrow, deep, rectangular tanks divided by vertical baffles into a series of pockets. Hydraulic water is added near the bottom of each pocket. Perforated constriction plates, spiral flow arrangements, or jets are used to disseminate the water under pressure (hydraulic water) throughout the bed of material in the pocket. Discharge valves on each pocket are operated automatically by a pneumatic mechanism, a pincer-type mechanism, or a pressure control and motor combination actuated by a hydrostatic tube within the pocket. Hydraulic classifiers are available in 4, 5, 6, and 8-pocket units of varying constriction plate areas to suit conditions. There is now a jet sizer of unit pocket design that can be made up in 1 to 25 sections or more to accommodate sizing requirements. The hydroscillator, Fig. 9, is a rectangular tank set on a slope of 3 to 4 in. per ft. A bowl is superimposed on the lower end. The bowl bottom is an oscillating rubber-covered disk, perforated to allow hydraulic water introduced beneath the disk to set up a teeter bed and thus produce an oversize or rake product exceptionally free of slimes, and material minus the mesh of separation. A shallow dam at the periphery of the bowl allows the coarse or oversize fraction to spill over and drop down into the tank compartment, where it is moved up the deck by reciprocating rakes. The material, minus the mesh of separation, overflows a circular and stationary weir which is several inches higher than the dam on the oscillating disk. It is carried off in a circular launder in the usual manner. These units are available in bowl diameters from 4 to 14 ft and with reciprocating rake compartment widths to suit the tons per hour to be handled. Centrifugal classifiers include the solid bowl centrifuge and the cyclone classifier. The solid bowl centrifuge, Fig. 10, consists of a truncated cone fixed to a horizontal shaft and rotating at high speed. An internal spiral rotating at slightly less speed continuously removes solids deposited on the inner surface of the cone, or bowl. Feed enters the cone by means of the hollow center shaft. Overflow leaves through ports at the large end of the cone, and oversize solids, moved by the spiral, exit through ports at the small end. Centrifugal classifiers of this type are available in cone diameters from 18 to 54 in. The cyclone classifier, Fig. 11, is a stationary cone having a cylindrical upper section and a lower cone section. Feed is introduced tangentially into the upper cylindrical section under pressure from a hydrostatic head or by means of a pump. Centrifugal force thus induced effects a classification within the cone, the fine sizes being carried off in the overflow through an opening at the top of the cylindrical section. Coarse solids at relatively high pulp density exit through a control valve at the apex of the lower cone section. Cyclone classifiers are available in 3, 6, 12, 14, 24, and 30-in. diam. The cone classifier, Fig. 12, is a steel-plate cone with sides usually about 60" from horizontal. It contains no rotating mechanism. Feed enters a feed-well at center and classification is effected by gravity and pulp density. Fines are carried off in the flow over a peripheral weir at the top of the cone. Settled solids exit through an opening at the apex. An apex valve actuated through levers and rods by the pulp density in the lower cone section is usually supplied. Diameters are usually maximum at 8 ft.

Jan 1, 1955

By Lennart Bergstedt, Olov Fägremo

Boliden Metall Aktiebolag, the prime base metal mining company of Sweden, treats some 10-10.9 t/y (11-12 stpy) of sulphide ore in nine concentrators. During the years considerable effort has been devoted to the development of all phases of the technology of ore prospecting, mining, milling, smelting and refining. This has been necessary due to the complex and low grade ores. The autogenous grinding technique was first studied within the company as early as 1945. Basic test work commenced during the early fifties, whereby the merits of pebble grinding could be evaluated.

Jan 2, 1978

By Donald A. Brobst

The minerals barite (BaSO4 barium sulfate) and witherite (BaCO3 barium carbonate) are the chief commercial sources of the element barium and its compounds whose many uses are nearly hidden among the technical complexities of modern industrial processes and products. Barite, the major ore mineral, is extremely vital to the petroleum industry which in 1973 consumed at least 80% of the world's produc¬tion of 4.4 million tons as a major ingredient of the heavy fluid, called mud, that is circulated in rotary drilling of oil and gas wells. The re¬maining 20% of the barite production was consumed chiefly in the manufacture of barium chemicals and glass and as a pigment, filler, and extender. Barite occurs throughout much of the world and is available from three major geologic types of deposits-vein and cavity fill¬ing, residual, and bedded-in sufficient quantity at competitive prices to meet current demands. The world's demand for barite is expected to increase, and geologic circumstances are favor¬able for the discovery of new deposits of com¬mercial value. Witherite is much less common and abun¬dant than barite, although it is more desirable in many ways as a raw material for the pro¬duction of barium chemicals. The United States has not produced witherite since about 1950; England is currently the chief producer of witherite. End Uses Most of the world's barite production since 1926 has been used as a weighting agent for the muds circulated in rotary drilling of oil and gas wells. The muds fundamentally are mixtures of water, clay, and barite in different proportions that vary according to local reservoir condi¬tions. Muds with a specific gravity as great as 2.5 are used. The mud is pumped down the hollow drill stem, passes through the bit at the bottom of the hole, and rises to the surface in the space between the drill stem and the wall of the hole. In the course of this circulation the drill bit is cooled, cuttings are removed, the drill stem is lubricated, the walls of the hole are sealed, and the hydrostatic head of the column of weighted fluid helps to confine high oil and gas pressures. The latter feature aids in prevention of gushers, thus reducing both environmental pollution and waste of oil and gas resources as well as conserving the natural reservoir pressure for greater production and rate of recovery of the products contained in the rocks. Barite is particularly well suited for drilling mud because it is clean, easy to handle, soft (nonabrasive), heavy, virtually inert chemi¬cally, and relatively inexpensive compared to many other available heavy materials. Barite is used in the manufacture of glass in continuous tanks. The addition of barite ho¬mogenizes the melt and gives greater brilliance and clarity to the finished glass. Ground barite, both unbleached and bleached by sulfuric acid, is a common industrial filler, extender, and weighting agent. The rubber in¬dustry is a major consumer of barite as a filler. Barite also is added to bristolboard, heavy printing paper, playing cards, rope finishes, brake linings, clutch facings, plastics, and li¬noleum, to name but a few uses. Bleached barite has long been an extender in white lead paint because of its weight. The low index of refraction of barite, however, makes its ability to cover marks poorer than some other sub¬stances, but its low capacity for absorption of oil is a good feature. Off-color or unbleached barite can be used as a filler in colored paints. In the construction industry, some lump barite is used in concrete aggregate to weight down pipelines buried in marshy areas and to shield nuclear reactors. Because barite absorbs gamma radiation well, its use reduces the amount of expensive lead shielding otherwise

Jan 1, 1975

By F. G. Miller

The washabilities of typical bituminous coals are discussed in an effort to illustrate the importance of determining, by a complete washability study, the sulfur forms and their distribution in a coal. This study will then show the extent to which the sulfur can be removed. It should be emphasized that each potential application requires a thorough study because of the varying amounts of sulfur in different coals. It is not the intent of this paper to show the best results that flotation can produce, but rather to illustrate the potential of this process and point out the importance of improved flotation techniques where sulfur reduction is involved. It is generally accepted that sulfur exists in coal in three forms: (1) pyritic, (2) organic, and (3) sulfate sulfur. Sulfate sulfur usually makes up less than 1% of the total sulfur content. Pyritic and organic sulfur make up almost all of the total sulfur content, occur in varying amounts in different coals, and can vary greatly in coal of the same seam. Pyritic sulfurs of 20% to 80% of the total sulfur have been reported. Other authors have shown that it is not possible to remove the organic sulfur without chemically altering the coal. Chapman and ones' state: "Organic sulfur, unlike pyritic sulfur does not exist as discrete particles, but is intimately associated with the coal structure, and as such it is not possible to remove it or reduce its concentration by physical means." Any success in removing sulfur has come about by removing pyritic sulfur by physical means; therefore, removal of sulfur in the pyritic form is the subject of this investigation. The extent to which any impurities can be removed from a particular coal can be determined by a washability study. Outside of crushing coal to finer sizes or chemically altering the coal, there are no known methods of changing this inherent washability characteristic. The efficiency of various methods used to remove impurities can be determined by comparison of results produced at a yield to the results as shown by a washability study. In recent years heavy media processes have proven their ability to wash plus 28 mesh coal and nearly produce results shown to be theoretically possible by the washability study. Therefore, it is the objective of this paper to show various methods of treating the finer fractions of the coal, in the hope of developing

Jan 1, 1964

By B. Ancker, E. R. Parker

The small-angle dislocation-boundary density of nickel and some of its alloys was investigated as a function of strength. It was found that the strength is a linear function of the density for pure nickel and for Ni-Ti alloys, but not for Ni-Co alloys. The results are interpreted in terms of dislocation theory. THE processes by which metals deform are still poorly understood, even though there has been a concentrated research effort in this field during the past fifteen years. Single crystals and individual grains in polycrystalline aggregates often develop a subgrain structure when deformed. Substructure formation occurs as a result of local plastic bending and its development is augmented by annealing at moderate temperatures.' Investigations made to date, largely qualitative in nature, have shown that the substructure is composed of a network of small-angle boundaries. The purpose of the present paper is to present some quantitative data on substructure (obtained by X-ray techniques) and to correlate the results with the strength of the metal in which the substructure existed. Nickel and some of its alloys were used for the experiments. The presence of certain kinds of foreign atoms greatly alters the formation and effect of the substructure. Polycrystalline tensile specimens were prepared from high purity nickel, two Ni-Ti alloys, and two Ni-Co alloys; the composition of these materials is given in Table I. Tensile specimens having a reduced section 1/4 in. diam by 3 in. long were machined from materials which were refined, cast, forged, and swaged in the authors' laboratories. The specimens were annealed for 1/2 hr at 1150°C, a treatment which produced grains having a diameter of approximately 0.5 mm. This rather large grain size was used to facilitate later examination of the substructure. Duplicate specimens of pure nickel and of each alloy were strained various controlled amounts in tension at room temperature and recovered for 1 hr at 800°C. (This strain induced prior to recovery will be referred to hereafter as the "prestrain.") One of each of the recovered specimens was pulled in tension at room temperature to obtain the stress-strain curves. The other bar was cross-sectioned in the gage length, carefully polished, and deeply etched to remove all cold-worked material. This specimen was then examined by the X-ray microscopic technique2 to determine the nature and magnitude of the substructure. The use of duplicate specimens permitted a direct correlation between tensile properties and substructure characteristics. X-ray microscopic studies were made with an apparatus constructed to have an average resolving power of about 4 microns. The monochromatic radiation reflected from grains which were oriented favorably was recorded on fine-grain photographic plates. These were examined at Xl00 which represents the true magnification, since there was essentially none in the X-ray system. This permitted detection of angular differences between subgrains of as little as 10 min. A very large number (over 100) of grains for each specimen was examined at this magnification and the number of substructure boundaries per grain was tabulated. An accurate relative measure was obtained under fixed experimental conditions, e.g., same grain size, resolving power, magnification, etc. The greatest source of error lay in counting the subboundaries, but this proved to be surprisingly small when repeated counts were made by different investigators. Furthermore, as the subsequent analysis indicates, whatever human error was introduced was not significant. Analysis of the Substructure Data When the number of substructure boundaries per grain was plotted against the frequency, skew (asymmetrical) distribution curves of the type shown in Fig. 1 were obtained. These are smoothed curves for the 1 atomic pct Ti in nickel alloy subjected to various prestrains and are representative of the curves obtained with all the metals. Since skew-distribution curves cannot be analyzed by elementary statistical methods, detailed investigations were undertaken in order to 1—test the consistency

Jan 1, 1955