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By Charles Austin

IT has long been known that plain high-carbon steels may be susceptible to graphiti-zation below the A, critical, but no data have been available to indicate what factors cause and tend to inhibit graphite formation. Two recent publications1,2 have shown that the factors controlling graphitization below the A, are different from those operating above the A, inversion where commercial graphitization of malleable iron begins. Furthermore, for plain high-carbon steels graphitization below the critical point does not appear to be related to ordinary chemi-cal analyses. Many years ago it was recorded' that the rate of graphitization at subeutectoid tem-perature is not a maximum just below the A, critical, but at some lower temperature, which Austin and Norris have shown to be about 670°C. Indeed, work done in our laboratory has demonstrated that it is im-possible to spheroidize certain steels in the temperature range of 650° to 710°C. with-out the formation of considerable amounts of graphite. However, if the temperature is maintained just below the A, (720°°C,) these same steels may be completely sphe-roidized at constant temperature. In previous studies1,2,4 on 1 per cent plain carbon steels graphitization was en-countered during prolonged tempering. The limited number of steels studied did not provide sufficient data to permit adequate study of the factors controlling this graphi-tization. Accordingly, a limited statistical investigation was undertaken, utilizing 18 steels of similar chemical analyses, fur-nished by four steel companies, who also supplied information regarding the history of manufacture.

Jan 1, 1940

Victor G. Hills, Cripple Creek, Colo. (communication to the Secretary): In continuation of the subject of the perform ance of "baby machine-drills," presented by Mr. Thane, I sub mit the following records of work done with these drills in the Cripple Creek district of Colorado. Two years ago, the Anchoria-Leland mine began to use baby drills ; and, to make the experiment more complete, began by purchasing two machines, of the same size, but of different make. The little drills were first used for stoping and up raising, in which they achieved at once an unqualified success. Soon after, they began to be used for the smaller branch-drifts and prospecting cross-cuts, while the large two-man drills were still used for the main drifts. Now they have almost entirely superseded the large drills, since it has been found that they will do any ordinary work in the mine at less cost, both for labor and for powder, per ton of rock broken. The large drills, of course, make more rapid progress; but it is only where time is a specially important factor that they are now used. The Portland mine, where, until within a year, only the large machines were used, is now using some small drills for stoping, and also for drifting. Mr. Thane speaks of having two men to operate a baby-drill; but in this district the baby-machine is always worked by one man without help. Again, in Prof. Christy's postscript, the quoted extract from a letter of Mr. L. T. Seymour, the South African engineer, mentions a " 2 1/2-inch Little Giant," as though that were the smallest machine used in that region. These statements leave some doubt as to just what Mr. Thane means by a " baby-drill." To avoid any such uncertainty as to the present communication, I will say that the large or two-man drill in common use at Cripple Creek has a 3 1/8-inch cylinder; while a few mines employ a 3-inch, and a few, in running large tunnels, a 3 1/2-inch drill. What we call a baby-drill here has a

Jan 1, 1900

By R. W. Raymond

That the death of Martin Coryell, which occurred at Lambertville, New Jersey, on Monday morning, November 29th, touched the sympathies of a wide circle of professional associates and personal friends, was amply testified by the gathering at the funeral services on Friday. Like his distinguished friend and neighbor, the late Ashbel Welch, Mr. Coryell was one of those pioneers in American engineering to whom we owe the great railway and canal systems which lie at the base of our national prosperity, and who have consequently enjoyed the respect and esteem of their successors of the present generation. Martin Coryell was born July 20th, 1815, at New ope, Rucks County, Pa., and was educated principally in the schools of his native town arid of Lambertville, New Jersey, to which place he returned for permanent residence fifty years later. With the exception of a brief period in youth, during which, to restore his failing health, he learned and practiced for a few months the carpenter's trade, and another brief period, later in life, when he read law for a time in the office of B. H. Brewster, of Philadelphia, afterwards Attorney-General of the United States, Mr. Coryell may be said to have spent his life as an active civil and mining engineer. Even these two episodes can scarcely be said to have been deviations from that profession, since they served to give him more thorough preparation for constructive and administrative work. The Delaware Division Canal, the Raritan Canal, and the Brunswick Canal, are among those upon which Mr. Coryell was employed. For the Raritan Canal Company, under the superintendence of Ashbel Welch, he located the greater part of the Belvidere Railroad (now the Belvidere division of the Pennsylvania Railroad), and directed its construction from Trenton to Lambertville. He was also active as a mining engineer, being one of the early pioneers of mining in the Lake Superior copper region, and had much to do with the development of the Hazleton coalfield and the railroad which has since expanded into the Lehigh Valley system. In 1862, he removed to Wilkes-Barre, where, in 1864, he became manager of the Warrior Run Mining Company. One of the editors

Jan 1, 1887

By J. E. McConnell

No. 1 Electric Furnace and Billet Casting Shop, located in Plant No. 4 adjacent to our new 12 inch merchant bar mill, represents Inland Steel Company's first venture into both electric furnace steelmaking and continuous casting. Construction of the shop began in September, 1968 with excavation and foundation work, followed by awarding of general construction and major equipment contracts from December, 1968 to April, 1969. The first heat was tapped from No. 90 furnace on December 18, 1970, and the first cast attempted on December 29, 1970. The rated shop capacity is 500,000 tons per year of semi-finished billets and blooms, and was justified on the basis of approximately 85 percent of the product mix falling into the special bar quality category of steel grades. Auxiliary equipment has been designed into the shop to pursue free machining steels, including leaded and tellurized grades. The start-up and operation of the shop for the first year was essentially based on a two-part philosophy: 1. Initially operate with the "open stream" casting technique to accomplish machine shakedown and operator familiarization and training. 2. Operate with special bar quality, or "submerged casting", practices, make necessary refinements and gain customer acceptance

Jan 1, 1972

By WM. HUFF WAGNER

Computations and allowances for mine depletion for Federal income tax purposes depend upon the meaning of certain terms in the pertinent provisions of section 114(b) 4 of the Internal Revenue Code. Unfortunately, but one of these terms is defined in the Code. Congress left it to the Commissioner to define the other terms in the Regulations. Even though the Commissioner, through his staff, labored long and earnestly to draft these definitions they have not been satisfactory to the mining industry, because the definitions in the Regulations and the interpretation placed thereon by the Commissioner do not state what the industry believes to be the clear and obvious intent of Congress. Consequently serious and prolonged disputes, unduly delaying the settlement of Federal tax returns involving percentage depletion deductions are continually arising between taxpayers and the Commissioner.

Jan 1, 1949

By E. P. Chapman

In May 1957 a diamond drill hole intersected 40 ft of magnetite and chalcopyrite assaying 2.55% copper and 51.6% iron on the claims of Craigmont Mines Ltd. near Merritt, southern British Columbia. The subsequent drilling indicated the presence of a multi-million ton orebody averaging over 2% copper and 18% iron, the latter present for the most part as magnetite and specular hematite in approximately equal proportions. This orebody, although under shallow cover at its eastern extremity, did not come to the surface and the early drilling was done on the basis of strong coinciding magnetic and geochemical anomalies. After 4 ½ years of intensive exploration and development the property was put into production in September 1961. The new ultramodern concentrator has a design capacity of 4000 tpd but is consistently treating well over this amount. Production is currently coming from that portion of the deposit which is amenable to open-pit mining methods. By mid-1958 information regarding the importance of the Craigmont find became fairly wide- spread, and exploration in the Merritt area was greatly intensified. Numerous magnetic and geochemical anomalies have been tested by drilling with notable lack of success. Detailed geological studies of the deposit and of the area have been made by Government agencies and by private companies and such studies are continuing. Many types of geophysical methods have been employed over the Craigmont deposit in an effort to develop knowledge which would assist in the search for similar mineral concentrations in the environment in which it occurs. This paper will discuss the results of the various geophysical surveys in relation to geological conditions and ore outlines insofar as they are now known.

Jan 7, 1962

By J. A. Ryder

TRANSIM II is a general purpose mining-oriented transport simulation program. It features the accurate modelling of locomotive tramming systems involving interferences and queue build- ups, as well as inter-level transport facilities linking bunkers of finite capacity. Features of the program are described, and a number of practical applications briefly reviewed including studies of optimal train capacities, pulling schedules, tip and bunker capacities, and operation of simple traffic-light systems.

Jan 1, 1977

PHILIP D. BLOCK, JR., vice president of Inland Steel Co., visualizes a fine future for the Menominee Range of the Upper Peninsula of Michigan. He sees a future unclouded by threat from foreign ore imports or the development of low grade ore processing in Minnesota. The statement was made during the opening of Inland's new Cayia mine near Crystal Falls. Inland, according to the vice president, is planning to use an increased amount of the high phosphorous ores found on the Menominee Range. He said that other steel companies will probably do the same, because the steel industry has learned how to use ores of high phosphorous content. He said: "I do not mean to imply that we can use an unlimited amount of high phosphorous ores or that we can burden our blast, furnaces with 100 pct high phosphorous ores, but we have reached the point where we can absorb a much larger percentage of these ores without any detrimental effects. Foreign ores and lowgrade Minnesota ores cost too much to offer real competition, Block said. Transportation costs from the Menominee range to steel producing centers in Chicago and on Lake Erie are less than for any other range in this country. In the meantime, the American operators of the Bomi Hills iron ore mine in Liberia, have reportedly signed a new agreement with the Government. Several months ago, President Tubman of Liberia expressed a definite dissatisfaction with the original contract. Informants state that the agreement only needs the approval of the Export-Import Bank, which loaned Liberian Mining Co. $4 million to develop the iron ore properties. Majority stockholder of the Liberian Mining is Republic steel, with 61.57 pct of the stock. Under the new contract, the Liberian Government will start to share in the profits when the indebtedness is liquidated and the return of invested capital accomplished, or April 1, 1957, whichever is earlier. Under the old agreement the Liberian Government received a 5 cent per ton royalty and an additional sum based on the price of pig iron. The royalty rate reached more than 17 cents per ton this year. After debt liquidation the Liberian Government will receive 25 pct of net profits for the first five years; 35 pct for the next ten years; and 50 pct thereafter. Until the Government starts to share in profits it will receive a royalty of $1.50 per ton in U. S. currency, in addition to royalties provided for in the old agreement.

Jan 1, 1952

By R. L. Robinson, P. DeFrank, R. F. Hatfield

Production equal to or greater than open-hole completions is possible through perforated completions if the flow paths throughout the perforations are free of obstructions.' Previous investigations have indicated that, in some cases, maximum productivity is not obtained due to plugging of the perforations with debris from the wellbore fluid and/or debris from the perforating process. Control of wellbore fluid and proper well completion techniques are very important in the elimination of perforation plugging.' Selection of properly designed perforating equipment also is quite important for maximum well productivity. Studies made with the use of the perforation flow laboratory, in which perforating tests are run under simulated well conditions, have shown that perforation plugging occasionally occurs. Plugs in perforations result from various causes. One of the contributors to plugging that can be controlled by the perforating device is the slug or carrot resulting from jet perforating. This condition has undergone extensive study, and previous developments have resulted in a decrease in carrot size—but not in complete elimination. It was felt that, if a method of completely eliminating the carrot could be found (with charge performance equal or better than previously obtained), a significant contribution would have been made. Such a charge has been developed and is reviewed in this paper. THEORETICAL CONSIDERATIONS OF CARROT ELIMINATION There are several popular theories of how a shaped charge jet is formed."," One of these is the hydrodynamic theory, wherein the liner is treated as a fluid under the impact of the explosive forces. Another is the spalling theory, where the interaction of shock waves in the liner causes small particles to be torn from the inner surface of the liner and projected at high velocity toward a common focal line to form the jet. It is not unreasonable to assume that both of these theories may be partially correct. For purposes of our discussion, it is simpler to use the second theory. Generally speaking, when a plate of metal is attacked by an explosive shock pulse, the pulse is transmitted through the metal at high velocity, as shown in Fig. 1(A). Pressures at the shock front may be 6 X 10' psi or higher. This shock wave (a compression wave) upon striking a free surface, Fig. 1(B), is partially reflected back as a tension wave. The interaction of the tension wave with the decaying compression wave causes a stress concentration in the metal; when this stress becomes great enough, a failure occurs and a small particle flies off and is projected away from the metal surface, as shown in Fig. 1(C). A new free surface is then presented to the shocks; the process repeats itself until there is no longer enough energy to cause failure, leaving a portion of the metal relativcly untouched. See Fig. 1(D). To apply this theory to a perforating shaped charge, consider the flat plate to be folded into a somewhat conical shape, with a column of explosive placed in intimate contact with the cone (Fig. 2). An explosive initiator detonates the charge, creating a shock wave

By W. J. Feuerstein

STRUCTURAL imperfections in crystals, in recent years, have received the attention of metallurgists concerned with single-crystal properties. Certain etching solutions cause local variations in the rate of etching at dislocations.' Dislocations are expected to be preferred segregation sites for impurities' and Dash" has shown that precipitation of copper occurs preferentially at edge-type dislocations in silicon. Diffusion rates along dislocations are probably higher than rates through more perfect crystalline regions.' These and other phenomena which may be influenced by dislocations may be studied by revealing dislocations as etch pits. This study was undertaken to develop an etch solution for silicon crystals to reveal low-angle grain boundaries associated with dislocation arrays and also etch pits with good contour definition. Additional etches have been reported by Dash," Vogel and Lovell.T rystals were sectioned on crystal lographic planes at various angles from the growth direction for microscopic examination of the etch pits. Experimental Crystals of 75-100 g mass and 3 cm diam were oriented and cut on crystallographic planes. Crystals were grown by Czochralski technique from a quartz crucible. Lapped wafers were chemically polished in a modified CP-4 etch for 1 min (bromine was deleted from the etch solution). The polished wafer was then etched* at room temperature for 5 min. The use of larger amounts of H2O and/or CH2COOH slows the reaction. The Cu(NO3),.3H2O was added to increase the reaction rate and give more definition to the etch pits developed. Some pertinent features concerning the attack of this etch on silicon can be summarized as follows:

Jan 1, 1959

By Pierre de P. Ricketts

Having had occasion while in Europe during the past summer to visit some of the foreign mints and assay offices connected with the same, I thought a brief description of the general process of coining employed, and such items connected with assaying as were new, might prove interesting to the Institute. The principal foreign mints are: the Royal Mint, London; and the mints in Paris, Brussels, Utrecht, Berlin, Vienna, Copenhagen, St. Petersburg, Stockholm, Madrid, Milan, Rome, and Constantinople. My time only permitted my visiting a few of the principal and largest given in the list, and for a description of the remainder I am indebted to the kindness of Mr. James M. Napier, who in company with the deputy master, and chemist of the Royal Mint, made a complete inspection of all the European Mints in 1870.

By Pierre de P. E. M. Ricketts

HAVING had occasion while in Europe during the past summer to visit some of the foreign mints and assay offices connected with the same, I thought a brief description of the general process of coining employed, and such items connected with assaying as were new, might prove interesting to the Institute. The principal foreign mints are: the Royal Mint, London; and the mints in Paris, Brussels, Utrecht, Berlin, Vienna, Copenhagen, St. Petersburg, Stockholm, Madrid, Milan, Rome, and Constantinople. My time only permitted my visiting a few of the principal and largest given in the list, and for a description of the remainder I am indebted to the kindness of Mr. James M. Napier, who in company with the deputy master, and chemist of the Royal Mint, made a complete inspection of all the European Mints in 1870.

Jan 1, 1876

M. G. CORSON.'-I am not going to discuss any of the papers presented but merely the question of season cracking of brass in general. Alpha brass has been known for nearly 500 yr. and from the very beginning a number of articles were made from sheets of this alloy by the process of spinning. Metal turning lathes were not yet known but wood turning lathes already existed and the wood turners used to make the mandrils and do the brass spinning themselves. Cases of season cracking were known even then. In 1915 I was connected with a small company doing a certain amount of brass spinning. Before the war its products never gave cause for complaint but their war-time products were cracking too frequently. The reason was, that due to the exigencies of war an excessive speed-up was attempted and the material simply could not take it. Today corrosion cracking of brass is most important in the case of cartridges for small arms ammunition and shell cases for large guns. The cracking takes place in storage and too frequently it is explained by the hypothetical presence of vapors of ammonia. However, I had the experience of purchasing some 20,000 rounds for the old Vetterli rifle from the Swiss government in 1905. The rifle and the cartridges were obsolete for many years and those which I bought were stored for at least 10 yr. None of them was found to be cracked or to crack in use. And the reason again was in the amount of work used in manufacturing the cartridges between anneals. The machinery today is more powerful and the amount of

Jan 1, 1945

We note with sincere regret the death of H. T. Chen,, who was killed by forest fire in the mountainous re-ion of Kokiu-Chang where he had been operating as Engineer in Chief of the Yunnan Tin Trading Co. Mr. Chen graduated in 1911 from the Department, of Mines, .University of California, being the first Chinese Government scholar in mining to attend that institution; and one of the first in America. He came of a distinguished family, many members of Which are in official life in Peking and in his native province of Hunan, all of whom are noted for their classical scholarship. He was himself a Hsiao-tsai or Bachelor of Arts, a coveted degree of the old literati class, Which he won under the Manchu regime when he was still a stripling. His mining work in Yunnan was carried on with only the most primitive facilities and in a distant province, but was, nevertheless, attended with great success and profit for his company. The region is infested with brigands and rebellious troops. who frequently turn marauders and prey upon the countryside, and Mr. Chen has had to go to the mines always with a large armed guard sometimes aggregating 150 men and some hundreds of miners, also armed. Two armed squads of men keep in touch with his base 'at Kokiu-Chang every day to get supplies and food, and it is feared that the brigands who have thus been prevented from plundering and mobbing his parties have started 'he fires to burn him out, with the disastrous result reported. Mr. Chen has thus given his life to his country in the attempt to win for modern China and Chinese civilization the raw materials of her new industrial life. He did so cheerfully and with full appreciation of the dangers that beset him, and China regards this as one of the most noble sacrifices of her young sons on the altar of patriotism. He is survived by a daughter of two years and by his widow who was also a graduate of the University of California and will be remembered by her classmates as Lucy Kong, 1912.

Jan 7, 1917

By AIME AIME

THE best meeting ever held, was the opinion expressed by a number of those who attended the annual meeting of the Institute in New York, Feb. 18 to 21, and there was an atmosphere of friendliness and good fellowship about it that fully justified the feeling. In numbers it was not quite so large as last year and unless the Engineering Societies should build for themselves a new building it is probable that no meeting can be larger, in respect to numbers, than that held in 1928, which was only made possible by the circumstance that the eighth floor of the building happened to be, temporarily vacant at the time. The number of rooms available for -sessions that were provided when the building was built long ago proved inadequate, and it is only by the expedient of obtaining the temporary use of the board and committee rooms of other societies that it is possible to arrange for the over 40 sessions that must be spread over the four days of the meeting. The-fifth floor, where. a buffet lunch is served each-day, has reached its full capacity and it seems quite evident that any future development of Institute meetings must be along the lines of quality, not size.

Jan 1, 1929

By M. T. Melvin, N. P. Kripakov

The practical application of a post-processing modeling procedure to simulate progressive rock failure around the periphery of coal mine entries is presented. This numerical scheme utilizes a simple rock model that incorporates easily obtainable input parameters consistent with basic rock mechanics principles. These parameters include the cohesion, angle of internal friction, modulus of elasticity, and Poisson's ratio of the bedded deposits that comprise the imediate roof, coal seam, and immediate floor. The geometry of the entry, along with the in situ stresses existing at a mine site prior to mining, are also considered in the analysis. The potential of this procedure as a predictive tool in determining the extent of pillar rib fracturing and yielding of the immediate roof and floor is evaluated assuming a Mohr- Coulomb failure criterion. The procedure is designed to be user oriented and is adaptable to any finite element code with linear elastic capability, making it particularly attractive to users with limited budgets and computer size.

Jan 1, 1983

By G. W. Doepel, W. P. Sibley

A three-dimensional, multilayer, mathematical model has been developed for predicting performance by mis-c.ible displacement. Areal and vertical coverage, total gas-oil ratio, propane-oil ratio and oil-recovery factor for the multilayer system are computed as functions of hydrocarbon pore volumes of solvent injected. The technique has been programed for use on the IBM-7090 digital computer and was used in calculating perfortnance for continuous miscible displacement of a five-spot, 50-layer .system. Results reported are based on the use of published laboratory data for a single, uniform five-spot layer. However, the technique is sufficiently generalized to calculate performance of any system of layers of any pattern configuration and mobility ratio, provided data are available to describe perfortilance of a single layer. The technique has also been adapted for predicting oil recovery resulting from various gas-driven slug sizes. The results presented for both continuous and slug-type injection show, that permeability variation has 0 significant effect on oil recovery but that solvent composition, within the range studied, has a lesser effect on oil recovery. INTRODUCTION Experience from many of the miscible-phase displacement projects currently in operation indicates that the injected solvent flows preferentially through the more permeable zones in the reservoir. This preferential solvent flow in the high-permeability streaks results in a reduction of vertical coverage (C,) and an attendant decrease in oil recovery. The multilayer technique presented in this paper uses areal coverage (C.,) data for a single layer from the literature and from laboratory measurements of displacement efficiency (herein referred to as microscopic coverage, C,,) to calculate areal coverage (C,) and vertical coverage (C,) for the multilayer system. Oil recovery for the multilayer system is obtained as the product of (Ca) (Cm) (Cv). It is assumed that C, in a single layer is 100 per cent; therefore, (C,) (Cm) is a measure of oil recovery from that layer. Data presented in the literature for a single layer generally deal only with areal coverage and/or microscopic coverage —but seldom specifically with oil recovery. Nevertheless, this technique is flexible in that either Ca and C,, of an individual layer or a direct measurement of oil recovery for the layer may be used. In developing this technique, the problem arose concerning a method of determining the relative amounts of solvent that will enter each layer during any increment of solvent injected. To solve the problem, a dimensionless equation was derived for expressing solvent injected into each layer as a fraction of total injection. A finite-difference method was applied in integrating the equation to determine oil recovery for the system of layers as a function of pore volumes injected. The technique subsequently was programed for solution on a digital computer. The method was applied to predict performance of a deep California reservoir under continuous miscible displacement and has been extended for calculating oil recovery as a function of slug size for gas-driven slug injection. The technique may be applied to any petroleum reservoir that can be adequately represented as a layered system, by considering permeability variation,1-3 permeability range and average permeability. Each layer is then assigned its appropriate permeability, porosity and hydrocarbon saturation. RESERVOIR VOLUME CONTACTED BY SOLVENT It has been recognized for some time that high microscopic coverage (C,) can be obtained by injecting a miscible agent, such as propane, into an oil reservoir. These high values of C,,, have been demonstrated in the laboratory and are normally between 80 and 100 per cent, depending on solvent and reservoir oil composition as well as on reservoir temperature and pressure. In miscible-phase displacement, because there is no interface between solvent and oil, effective permeability to solvent is the same as that to oil. (This assumes that oil saturation has not changed and that water is immobile.) Consequently, mobility ratio (M) simply reduces to that of viscosity ratio . Perrine4 and Habermann5 have shown that large

By S. F. Ravitz, S. R. Zimmerley

High-grade cobalt concentrates were produced from the complex Blackbird ore with very good recovery in continuous pilot-plant operations in which a low-grade bulk cobaltite-pyrite flotation concentrate was roasted in a multiple-hearth furnace to oxidize the pyrite selectively. The cobaltite was floated from the resulting calcine. THE existence of the cobalt-copper deposits in the Blackbird district, Lemhi County, Idaho, has been known for many years. However, these deposits have not yet been exploited successfully because of the low grade of the ore, absence of information on ore reserves, and lack of feasible methods for concentrating and recovering cobalt from the ore. In 1941, when it appeared that World War II might interfere seriously with imports of cobalt from overseas, the U. S. Bureau of Mines started an extensive mining and metallurgical investigation of the Blackbird deposits. Exploration by trenching and drilling1 indicated that ore reserves were adequate to warrant consideration of large-scale exploitation. A process for producing high-grade cobalt concentrates from the ore was developed at the Salt Lake City Station of the Bureau,2 and hydrometallurgical procedures for producing cobalt metal or oxide from the concentrates were developed at the Boulder City Station.3 The Howe Sound Co., through a subsidiary, the Calera Mining Co., carried out further exploratory work, which increased probable ore reserves to a tonnage commensurate with a large investment in mine, mill, transportation facilities, and refinery. Simultaneously, the metallurgical staff of the company, working in cooperation with the Bureau of Mines, further investigated the metallurgical problems. It was the opinion of both groups that pilot-plant testing was required to translate laboratory results into plant operation. In general, the Blackbird ore has a high content of pyrite and some pyrrhotite and contains 0.5 to 1 pet cobalt and 1 to 2 pet copper, which are present essentially as cobaltite and chalcopyrite. The copper can be recovered readily as a high-grade concentrate by selective notation. The cobalt then can be recovered as a bulk sulphide concentrate assaying 4 to 5 pct cobalt, but no satisfactory procedure for separating the cobalt from the pyrite and pyrrhotite directly by flotation had been found. The method developed by the Bureau for producing a high-grade cobalt concentrate is essentially an application of the old Horwood process of selective roasting.4 The bulk sulphide concentrate is roasted to form an oxide coating on the iron mineral particles, and the calcine is then treated by flotation. The oxide coating prevents the iron minerals from floating so that it is possible to obtain a high recovery of cobalt in concentrates assaying more than 20 pct cobalt. Laboratory tests by metallurgists of both the Bureau and the Howe Sound Co. had indicated the optimum roasting temperature to be 425° to 450°C. At lower temperatures the rate of oxidation of the iron minerals is too low, whereas at higher temperatures substantial quantities of cobalt are rendered water-soluble. Because of its high sulphur content (35 to 40 pct), the bulk concentrate tends to continue to burn after it has reached the optimum roasting temperature. Although excessive temperatures could be avoided in the small-scale laboratory furnaces, there was considerable doubt that the temperature could be controlled properly in industrial equipment. To provide material for the pilot-plant tests, the Calera Mining Co. installed a small, temporary flotation mill at the Blackbird property and treated

Jan 1, 1951

By S. R. Zimmerley, S. F. Ravitz

High-grade cobalt concentrates were produced from the complex Blackbird ore with very good recovery in continuous pilot-plant operations in which a low-grade bulk cobaltite-pyrite flotation concentrate was roasted in a multiple-hearth furnace to oxidize the pyrite selectively. The cobaltite was floated from the resulting calcine. THE existence of the cobalt-copper deposits in the Blackbird district, Lemhi County, Idaho, has been known for many years. However, these deposits have not yet been exploited successfully because of the low grade of the ore, absence of information on ore reserves, and lack of feasible methods for concentrating and recovering cobalt from the ore. In 1941, when it appeared that World War II might interfere seriously with imports of cobalt from overseas, the U. S. Bureau of Mines started an extensive mining and metallurgical investigation of the Blackbird deposits. Exploration by trenching and drilling1 indicated that ore reserves were adequate to warrant consideration of large-scale exploitation. A process for producing high-grade cobalt concentrates from the ore was developed at the Salt Lake City Station of the Bureau,2 and hydrometallurgical procedures for producing cobalt metal or oxide from the concentrates were developed at the Boulder City Station.3 The Howe Sound Co., through a subsidiary, the Calera Mining Co., carried out further exploratory work, which increased probable ore reserves to a tonnage commensurate with a large investment in mine, mill, transportation facilities, and refinery. Simultaneously, the metallurgical staff of the company, working in cooperation with the Bureau of Mines, further investigated the metallurgical problems. It was the opinion of both groups that pilot-plant testing was required to translate laboratory results into plant operation. In general, the Blackbird ore has a high content of pyrite and some pyrrhotite and contains 0.5 to 1 pet cobalt and 1 to 2 pet copper, which are present essentially as cobaltite and chalcopyrite. The copper can be recovered readily as a high-grade concentrate by selective notation. The cobalt then can be recovered as a bulk sulphide concentrate assaying 4 to 5 pct cobalt, but no satisfactory procedure for separating the cobalt from the pyrite and pyrrhotite directly by flotation had been found. The method developed by the Bureau for producing a high-grade cobalt concentrate is essentially an application of the old Horwood process of selective roasting.4 The bulk sulphide concentrate is roasted to form an oxide coating on the iron mineral particles, and the calcine is then treated by flotation. The oxide coating prevents the iron minerals from floating so that it is possible to obtain a high recovery of cobalt in concentrates assaying more than 20 pct cobalt. Laboratory tests by metallurgists of both the Bureau and the Howe Sound Co. had indicated the optimum roasting temperature to be 425° to 450°C. At lower temperatures the rate of oxidation of the iron minerals is too low, whereas at higher temperatures substantial quantities of cobalt are rendered water-soluble. Because of its high sulphur content (35 to 40 pct), the bulk concentrate tends to continue to burn after it has reached the optimum roasting temperature. Although excessive temperatures could be avoided in the small-scale laboratory furnaces, there was considerable doubt that the temperature could be controlled properly in industrial equipment. To provide material for the pilot-plant tests, the Calera Mining Co. installed a small, temporary flotation mill at the Blackbird property and treated

Jan 1, 1951

By Dever C. Ashmead

Coal companies in the anthracite region are studying various methods of mining, seeking one that will shorten considerably the life of the gangway and thus decrease the maintenance charges. In steep pitching measures, the maintenance charges of the gangways are high because of the cost of replacing timbers and cleaning up falls. Therefore, if the length of the gangways can be decreased and the mining made more concentrated, the life of the coal gangways will be decreased and the maintenance charges per ton of coal produced will be smaller. The practice in the anthracite region is to drive long coal gangways and to work the breasts as the gangway from which they were driven is advanced. In many cases these gangways are from 4000 to 6000 ft. in length; and some are even longer. As these must be maintained not only until they have reached their limit but until second mining begins (which may be some years later), the maintenance charges are high. If the gangway is allowed to close, when the time comes to remove the pillars the cost of re-opening it may be as expensive as the original driving cost. The Lehigh and Wilkes-Barre Coal Co., at its Wanamie Colliery at Wanamie, Pa., has been using a system of mining that, as far as the writer knows, is not used in any other place in the anthracite fields. The

Jan 1, 1925