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By Mark C. Malamphy

During colonial times, Brazil was famous for the richness of her alluvial gold deposits. Paul Ferrand has estimated that the gold produced during the period from 1700 to 1820 was the equivalent of some 64 million pounds sterling. Since that time, most of the more prolific alluvial deposits have been exhausted. A few gold mines are still functioning, notably the Morro Velho mine, which is one of the deepest mines in the world. Today, the gold production of Brazil is insignificant when compared with world figures, but there are still many gold-bearing regions and it is probable that in at least some of them profitable returns would result from an exploitation program taking advantage of all the most modern innovations in gold mining and ore treatment on a large scale. In order to demonstrate the value of some of these abandoned prospects and stir up interest in increasing the national gold production, the government has stimulated research. Experimental plants have been and are being established in various places, and tests on large quantities of ores are being carried out on a semicommercial basis. The Geological Survey of the State of Minas Geraes is very active in this line and the Federal Institution is also showing an increased interest in the matter. One of the lesser known gold-bearing regions of Brazil is in the vicinity of Lavras, in the State of Rio Grande do Sul. Gold was first reported from this region in the early part of the nineteenth century. In 1811, D. João VI sent an experienced prospector from Minas Geraes to investigate the validity of the reports. According to the reports of Baron Eschwege, he succeeded in extracting some 30,000 Oitavos (about 105 kg.) during the first few years, but the production costs exceeded the value of the gold obtained.

Jan 1, 1934

By H. Van F. Furman

TO those engaged in the purchase and sale of gold- and silverores, mattes and bullion, the frequent differences in the gold- and silver-contents, as reported by different assayers, is a source of much annoyance and expense. The desirability of uniform methods of assay has long been recognized by certain refiners who specify in their bullion-contracts the method to be adopted in assaying the bullion. One large producer of base bullion employs at each refining-works with whom it has a bullion contract an assayer whose duty it is to see that the bullion is sampled and assayed according to contract-specifications. For the assay of gold- and silver-bullion, standard methods are now generally adopted; the reeult being that differences seldom occur. While we cannot hope for anything near perfection from fireassay methods for ores, mattes and base bullion, as carried out cornmercially, such methods may be made to yield results which answer all commercial requirements, and they will probably be retained for obvious reasons. The object of the present paper is to point out some of the sources of error and to show the importance of more uniform methods of assay and close attention to the details of the work. The sources of error in the assay of ores and mattes are: improper sampling; losses of the precious metals during fusion, scorification and cupellation; imperfect elimination of the base metals on the cupel and imperfect extraction of the silver during the parting in nitric acid. It is not the object of the present paper to enter upon the subject of sampling; but a few remarks may be of value. There has been considerable discussion recently in Colorado upon the frequent differences which occur in the assays of Cripple Creek gold-ores, and these differences have been attributed to various causes. The writer is informed by two of our most prominent smelters that since they have adopted 100-mesh screens (the general practice is 80-mesh) the

Jan 1, 1895

By William Wraith

1. INTRODUCTION. AT the Washoe smelter,. Anaconda, Mont., the blister-copper from the converters is transferred, by means of a crane, to a refining-furnace,, in which it is brought to proper pitch by means of air and poles. From this furnace the refined copper, containing gold and silver, is poured into cast-iron molds placed on a platform-conveyor, giving an anode 36.75 in. long, 28 in. wide, and 21 in. thick. By reason of a disagreement between the smelter and the refinery, in reference to the silver-content of the anodes, it became necessary to investigate the methods of sampling used. II. SMELTER METHOD OF SAMPLING. At the smelter the sampling is done by " spotting " into water a small portion of the molten stream of copper as it flows from the furnace, by batting" the stream with a wooden paddle. The first sample is taken 30, min. after the pouring is started, three. other samples being taken at 1-hr. intervals, each sample weighing from 4 to 6 oz. The samples are dried, examined for particle's of burnt wood, screened on a 10-mesh screen of No. 8 wire to remove the fines, the oversize then screened on a 4-mesh screen of No. 20 wire to remove the coarse, the undersize of this screen being taken as the sample. Teh four portions thus obtained are thoroughly mixed and spli in half by passing over a 16-slot splitting-device, slots being 0.5 in. wide. One-half of the sample is sent to the laboratory for analysis and one-half kept as a duplicate. III. REFINERY METHOD OF SAMPLING. The method used at the refinery and also used in this investigation is the one developed by Dr. Edward Seller, of

Mar 1, 1910

By Mark Malamphy

DURING the latter part of the year 1932, the Servico Geologico e Mineralogico do Brasil ordered four magnetic field balances with tem-perature-compensated magnetic systems and a photographic recording apparatus for the registration of the diurnal variation. These instru-ments were delivered during the early part of the year 1933 and a short time later were taken to Santa Catherina for use in the field. Before the field work was begun, a series of experiments was carried out to determine the behavior of these new instruments under existing field conditions. The recording instruments were mounted in an under-ground chamber and their sensitivities checked by means of a Helmholtz coil. The field instruments were then mounted at fixed stations and readings were taken to determine the diurnal variation and compare it with the photographic records. The data obtained with the horizontal field balances were concordant but that obtained with the vertical component instruments showed a considerable divergence. This divergence was of such a magnitude that it was necessary to spend considerable time in determining its cause and finding a means of improving the functioning of the instruments. This paper presents the results of our observations on these systems and the conclusions at which we arrived; also the means we took to partly elimi-nate the difficulty until new systems could be ordered from Germany.

Jan 1, 1935

By Frank H. Probert

The mining laws relating to winding-ropes in some of the German provinces are very strict, and severe tests have to be periodically made to see that the ropes in use come up to the prescribed standard. A few notes on the method of testing the ropes and the results obtained may be of interest to the members of the Institute. Permission must be given by the Inspector of Mines to put up a winding-plant; and previous to installation a full report made by the manager, clearly setting forth all details of the shaft, the pit-head, engines and appliances appertaining thereto has to be sent to the mining officials. Accompanying each subsequent report, further details, such as the name of the firm supplying the rope, construction, quality of steel, date of installment, weight per meter, length, particulars of the safetycatches, cages, etc., must be given. At least one spare rope must be kept at ever? shaft ready for use in case of emergency. The rope must hang in the shaft, with cage attached, not less than twenty-four hours before it is used for winding; and it must have undergone a severe test in the manner hereafter described. The laws prescribe that when a rope is continually in use it must be tested every three months; but if the rope is only used every few days it must be tested at least every six months, in the presence of the superior officer; and notification of the date of testing has to be sent to the Bergrath two days before the test is made, in order that he can personally superintend the operation if he chooses. Should winding have been stopped for a long time, it is not necessary to test every six months; but before the rope can be used again it must be tested.

Jan 1, 1901

Jan 1, 1954

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Jan 1, 1942

Jan 1, 1888

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Jan 1, 1938

Jan 1, 1908

Michigan College of Mining and Technology, Houghton, Mich W. O Hotchkiss, President. Copies of the Engineering Research Bulletins of the College of Mining and Metallurgy are sent free upon request to those who ask to be placed on the mailing list. From the complete list

Jan 1, 1933

By E. D. Gardner

Introduction Oil shale deposits have been exploited in various countries throughout the world, but generally with government aid. The oil-shale industry of Scotland perhaps is the oldest and best-known; the largest was conducted in Manchuria by the Japanese during World war 11 as a source of liquid fuels for military uses. In general, foreign oil-shale deposits that have been exploited are much lower grade than those in the western United States. Considerable interest began to be shown in western oil shales in 1916; the peak of activities was in 1923. The catlin operation, near Elko, Nevada, perhaps was the nearest approach in this country to an oil-shale enterprise on a commercial scale. Over 100 companies were formed, ostensibly for exploiting the oil shale; a large number of them, however, proved to be stock promotions only, which gave the embryo industry a black eye. The Bureau of Mines operated an experi-mental oil-shale retort plant near Rifle, Colorado, from September 1926 to June 1927 and again from April 1928 to July 1929, after which the plant was dismantled. By this time the East Texas oil fields had come ill and the country lost interest in substitute liquid fuels. During World War II the Nation again became concerned about the magnitude of its petroleum reserves. Congress (April 1944) directed the Bureau of Mines to build and operate demonstration plants to produce synthetic liquid fuels from coal, oil shales, and agricultural and other products; a five-year Program was authorized. *' a part of this program the Bureau of Mines has built, at Anvil Points near Rifle, Colorado, a retort plant and develOped an experimental mine to supply the plant with oil shale. An important part of the mining work at Rifle is to devise methods and select practices for mining the oil shale on a commercial scale at the lowest practicable cost. The product to be mined has a relatively low value, a fact that must be kept in in mind. The combined aim of those in charge of the mining and those in charge of retorting is to demonstrate that the shale oil can be produced at a cost per barrel corresponding to the current quotation for crude petroleum —or at least very close to it. Plans call for an uninterrupted flow of broken oil shale from the lace in the mine, through crushers, through the retorts and thence to the disposal dump. The disposal of the spent shale in the Ride area should present no unusual problem. Mining research has consisted so far of Paper studies of the general phases of the probleml determination of the widest Span that the roof Stone will stand safely unsupported, and drilling problems. underground development has not proceeded far

Jan 1, 1949

By Luis A. Fierino, M. Ashraf Mahtab

This paper reviews the background of, and solution techniques for, the major geomechanics problems affecting caving operations, including prediction of cavability, defining size distribution of or fragments, stability and support of production openings, and control of rock bursts and subsidence. Further research is also suggested in the solution of the various geomechanics problems.

Jan 1, 1984

Jan 1, 1902

Jan 1, 1940

By R. N. Stevens

Any consideration of the errors involved in determination of ?gb by previous workers should discuss their experimental methods in terms of the appropriate theoretical equation; this the authors have not done in a number of cases. To facilitate the present

Jan 1, 1969

Jan 1, 1940

By J. F. Mahoney, P. B. Hobsbawn, N. Arbiter, C. C. Harris

Current trends in flotation applications are reviewed and effects of increased cell sizes and automation of circuits considered. The role of laboratory and pilot plant investigations in establishing design criteria and project feasibility are assessed and illustrated.

Jan 1, 1978

All manuscripts intended for presentation at the February meeting of the Institute must be in the hands of the Secretary of the Institute not later than Monday, Nov. 23, 1914. This is the date at which the manuscript must be in the hands of the Secretary, and is not the mailing date upon which it leaves the author's hands. In case manuscripts are sent to members of Technical Committees, they must be in the hands of the Technical Committee a sufficient time in advance of Nov. 23 so that they may be in the hands of the Secretary on the date indicated.

Jan 10, 1914