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By N. S. Dalal, X. Shi, V. Vallyathan

"Correlated spectroscopic and cytotoxicity measurements were made on newly crushed silica to find whether the fracture-induced, silicon related (Si-0· or Si· type) free radicals play a direct role in the mechanism of hemolysis by silica particles. The free radical content of the silica particles was controlled through the radical decay, thermal annealing, and boiling processes, and was followed with electron spin resonance spectroscopy. Portions of the same sample were evaluated for their hemolytic potential, employing sheep erthyrocyte and optical absorption techniques. The results indicate little, if any, correlation between the amount of the silicon-based radicals and the hemolytic potential of the fresh dusts, but these or related radical sites might be contributors to silica cytoxicity and fibrogenicity via peroxidative pathways .INTRODUCTIONIn an earlier convnunication (1.) from our laboratory it was reported that mechanical crushing of coal and quartz under normal air atmosphere generates free rad;cals on the particle surfaces, and that these radicals decay with time, hence pointing to a higher toxicity of fresh dusts in relationship to pneumoconiosis and silicosis. More recently Fubin; et al.(2) have also reported the detection by electron spin resonance (ESR) of the formation of SiO· and Si·-type of radicals from quartz particles crushed under atmospheric conditions. In agreement with earlier ESR studies on single crystals of quartz crushed under high vacuum (10-10 torr) (3) and subsequent exposure to air (3), and to other gases (4), these radicals were identified (2) as being formed by the hemolytic cleavage of the Si-0-Si bonds and the reactions of the Si· and SiO· ,radical with atmosphere. Fubin; et al. (2) also suggested that these radicals might be involved in the mechanism of the fibrotic action by silica, either by transforming the particle surface into a selective oxidating agent or as an initiator of a sequence of reactions leading to fibrosis. Earlier Gabor and Anea (5) had reported that lipid peroxidation caused by free radicals on the silica surface might be involved in the red blood cell membrane damage. Thus far, however, no parallel cytotoxicity, fibrogenicity, and free radical studies on a given Quartz dust sample have been reported, except for some earlier work from our laboratory (1,6,7). We now present more recent results obtained from parallel cytotoxicity, fibrogenicity, and free radical measurements on a freshly made quartz dust. The dust’s free radical content was measured using ESR spectroscopy while its cytotoxicity poteni1al was estimated via hemolysis. Hemolysis was employed as the tox1c1ty test because it 1s a widely used method for estimating the potential of a dust for disrupting the cell membrane (8). The f1brotic potential was followed.by measuring the dust-induced lipid perox1dat1on. us1ng linole1c ac1d as a model lipid. As discussed below, the results obtained suggest new clues.to the mechanism of the Quartz-related cytotoxicity and fibrogenicity."

Jan 1, 1988

By T. M. Ruff

A prototype mucking machine designed to operate in narrow-vein stopes was developed by Foster-Miller, Inc., Waltham, MA, under contract with the U.S. Bureau of Mines. The machine, called a compact loader-trammer, or minimucker, was designed to replace slusher muckers in narrow-vein underground mines. The minimucker is a six-wheel-drive, skid-steered, load-haul-dump (LHD) machine that loads muck at the front with a novel slide-bucket system and ejects it out the rear so that the machine does not have to be turned around. To correct deficiencies of the tether-remote-control system, a computer-based, radio-remote-control system was retrofitted to the minimucker. Initial tests indicated a need to assist the operator in guiding the machine in narrow stopes. An automatic guidance system that used ultrasonic ranging sensors and a wall-following algorithm was installed. Additional tests in a simulated test stope showed that these changes improved the operation of the minimucker. The design and functions of the minimucker and its computer-based, remote-control system are reviewed, and an ultrasonic-sensor-based guidance system is described.

Jan 1, 2010

By N. E. Hanna

Experience with the current version of gallery test 4, in use since 1913 to evaluate the incendivity of permissible explosives in the presence of coal dust, has shown the procedure to have inadequate discrimination. Consequently the Bureau of Mines used the up-and-down method of statistical design to investigate the incendivity of permissible explosives in the presence of coal dust and gas. A suitable device was developed to measure coal dust concentrations in the air-gas mixtures and to disperse the dust in the gallery atmosphere. A proposed testing method which uses suspended shots in a predispersed coal dust-gas-air mixture was evaluated. The new method can discriminate between different explosives with respect to their incendivity. Maximum ignitibility of the coal dust cloud by permissible explosives occurred in the vicinity of 0.3 oz/cu ft. About 10% sodium chloride in permissible explosive formulations had a very significant effect in reducing the probability of igniting coal dust. Bundled charges were more incendive than column charges.

Jan 1, 1966

By T. F. Dumm, O. Trass, V. R. Koka, L. G. Austin

"The size distributions of carefully screened 2 size fractions of ground materials were determined using a Microtrac laser dif-fractometer. The size distributions were fitted to the empirical function P(x) = 1/[1 + (x50/x)1] where P(x) is cumulative mass fraction less than Microtrac size, x. The standard deviation of A for a 50 second test time was approximately 0.5, so that seventeen test times give a mean with an estimated error within t 0.25 (95% confidence level). Values of were 5.44, 4.82, 4.40 for a coal ground under different conditions, indicating statistically different shape distributions; the average value for mica was 2.91 owing to the high aspect ratio of the particles. The ratio of x50 to the geometric mean sieve size was 1.2 for the coal and 0.70 for mica.1 IntroductionKoka and Trass have presented evidence [1,2] that materials ground in the Szego mill [3] give different shapes depending on the milling conditions. The variations in shape were deduced qualitatively by viewing SEM photomicrographs of selected 1/2 screen fractions. This paper quantifies their observed differences in shape by using measurements of the size distributions of screen fractions examined in a laser diffractometer [4] (Microtrac, Model 7991). The basic concept is that particles of 'a given ""screen"" size will give a wider distribution of ""Microtrac"" size when the particles are flaky with high aspect ratios, and a narrower distribution when the particles approach the cubical and spherical geometries.2 TheoryAustin and Shah [5] have shown that coal screened within a 1. 1/2 upper-to-lower sieve size range will give rise to a much wider distribution of Microtrac size. They found that the screen interval of irregular fragments of comminuted coals or quartz gave Microtrac size distributions which could be described by the simple function"

Jan 1, 1988

By THEO L. JOHNSTON

In preparing for war , Japan built an iron and steel industry that ranked high with other industrial nations . Deficient in raw materials for making iron and steel , it had to acquire the bulk of its iron ore and much of its coal and scrap iron from foreign sources . Steel manufacture, and fabrication , however , were reserved mostly for the Home Islands , where modern integrated plants produced the implements of war . The vulnerability of relying on imports during the war was recognized early, and steps were taken to exploit iron-ore deposits and develop treatment processes on the Home Islands in order to be as self - sufficient as possible . Although the industry had expanded considerably, the capacity of the large plants still was insufficient for military requirements, so other meth- ods of producing iron and steel were adopted, which in some ways illustrate the desperate effort made to supply the war machine. In developing the iron and steel industry, modern practices of other countries were studied and followed with modifications to suit Japanese con- Aitions. German and American technical ability and equipment played a large part in the program; however, the Japanese had competent furnace technologists capable of obtaining proper equipment performance. For the most part, the standard practice consisted of smelting iron ores in blast furnaces and then refining the pig iron to make steel in open-hearth furnaces. Electric furnaces played an important part, especially in the manu- facture of alloy steels. Various other methods yielded minor but significant production. Among the various other treatment processes used, the production of sponge iron in rotary kilns 'probably was the most important in producing melt- ing stock for steel making. Of special importance was the fact that sponge iron made from low-grade ores contained critical metals, such as nickel and chromium, so that the results were more significant than was generally believed.'

Mar 1, 1948

By Thomas F. Tomb

The penetration characteristics of a horizontal plate elutriator and of a 10-mm nylon cyclone were evaluated. The test aerosols were polydisperse coal-dust particles ranging from less than 0.3 to 15 micrometers in diameter. Particle densities ranged from 1.3 to 1.4 grams per cubic centimeter. Equivalent Stokes diameters were measured using Coulter counter analytical techniques. Experimental results indicate that the penetration characteristics of the horizontal plate elutriator closely approximate the sampling efficiency curve defining the respirable fraction of the dust cloud recommended and adopted by the Johannesburg Pneumoconiosis Conference in 1959. Penetration characteris-tics of the 10-mm cyclone were evaluated at flow rates of 1.4, 1.5, 2.0, 2.5, and 2.8 liters of air per minute. The data indicate that the penetration curve obtained at 2.0 liters per minute most closely approximates the sampling efficiency curve for respirable dust recommended at a meeting sponsored by the U.S. Atomic Energy Commission in 1961.

Jan 1, 1970

By John Jordan, Tesarik, Steven J. Knoll, Theodore J. Williams, David K. Denton, Douglas F. Scott

Highly stressed rock in stopes continues to be a primary safety risk for miners in underground mines because this condition can result in failures of ground that lead to both injuries and death. Personnel from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health studied two methods for identifying stress in rock. A seismic tomographic survey, finite-difference analysis, laboratory measurements of compression wave (ultrasonic) velocities in rock cores, and site geology were integrated to evaluate the use of seismic tomography for identifying induced pressures in an underground pillar at the Edgar Mine, Idaho Springs, CO. Electromagnetic (EM) emissions were also investigated in the Galena Mine, a deep underground mine in Idaho, in an effort to determine if these emissions could be used as indicators of impending catastrophic ground failure. Results of this research indicated that (1) seismic tomography appears to be a useful tool for determining relative stress in underground pillars, while (2) EM emissions do not appear to be significant precursors of impending catastrophic ground failure.

Jan 1, 2004

By K. K. Kelley, L. B. Pankratz, W. W. Weller

The heat capacity of columbium (niobium) carbide (CbC ) was measured over the temperature range from 51 ° to 298 ° K, and the entropy at 298.15° K was evaluated . Also , the heat content above 298.15 ° K of columbium carbide was measured to 1,800 ° K. The results were combined with the known heat of formation at 298.15 ° K to obtain values of the heat and free energy of formation over the temperature range from 298.15 ° K to 2,000 ° K.

Jan 1, 1964

By J. W. Paul

"The economic features of coal mining must take into account the drain on the man power. Study over a recent 5-year period reveals an average yearly loss of 2,125 underground men, of whom 1,182 are killed by falls of roof and coal, and according to recent data compiled by the Bureau of Mines it is estimated that 54,000 men sustain lost—time disabling injuries from the same cause.Under normal activity of the mines approximately 50 lives are taken by falls of roof during every 10 days the mines are operated, or 5 persons are killed per day, which, at a compensation charge of $5,000 each, amounts to $25,000 per day. Add to this the similar number killed by causes other than by falls of roof and we have $50,000 as an approximate daily fatality charge for each day the mines operate. On the basis of 200 working days per year, this amounts to the alarming figure of $10,000,000 annually. An investment at 5 per cent to yield this amount would require $200,000,000, which is equivalent to a capital investment of $0.40 per ton of coal, produced annually, on the basis of 500 million tons. These figures apply only to fatalities for which a fixed or stated amount is paid for compensation and do not include the compensation and hospitalization paid for the approximately 103,000 upon whom idleness is enforced by a lost-time disability injury. In one State having an annual production equal to approximately 30 per cent of the total bituminous production of the United States, the most recent data shows that for each fatality there are eight serious injuries causing 60 days or more lost time. The frequency rate of accidents for that State is less than the average for the United States, and so a conservative comparison may be made by using the figures of that State in estimating the total serious injuries, which gives 16,000 as losing 60 days or more. The average number of underground employees in the coal mines of the United States for the past 10 years has been approximately 570,000; the annual underground fatalities amount to approximately 2,000 and non-fatalities to 108,000, or a total of 110,000, which means that one out of every 5.17 employees ,or 19.3 per cent, receives an injury which results in either a fatality or a lost-time disability; this figure in a little over five years will reach a number equivalent to 100 per cent of all underground workmen. Against this is the record of many miners who have worked 25 years or more without a lost—time disability injury, indicating that coal mining is not necessarily productive of injury or death to workers.In the matter of falls of roof, it is found that 85 to 87 per cent of all fatalities occur at the working face, face of a room or entry, or in pillar work. It is at the working face that the greatest roof hazards are encountered, and when about 75 per cent of the underground employees spend approximately 90 per cent of their working hours at the face, it is logical that there is where injury is most likely to occur.Although the roof hazards may vary in different beds of coal, experience has proved that roof hazards can be successfully controlled in all coal mines, essentially regardless of the character of the roof if constant care and attention are given by the management and employees in applying the principle of safety. In almost every mining district some companies maintain an extremely low frequency rate of injury, whereas in the same district with essentially the same roof conditions the opposite is true.A study has recently been made of a number of reports upon fatalities in one district of one of the principal coal—producing States and it showed that 50 lives had been lost at 23 mines as the result of falls of roof or sides. These reports were made by the mine officials, safety engineers, and safety committees and an attempt was made to give both the cause and the person or factor responsible for the fatality. A summary of the items of responsibility is as follows:"

Feb 1, 1932

By R. S. Dean

The principle of explosive crushing depends upon the fact that an expandable substance contained within the pores of a solid body will disrupt such a body upon expansion. Such expansion may be obtained by the detonation of an explosive or by the sudden release of pressure of a superheated liquid. That this principle of disruption may be applied to minerals rests on the fact that cracks, cleavage planes, and pores exist in all mineral to an extent hardly conceived possible heretofore. Crushing by this method takes advantage of force applied from within the mineral rather than from forces applied from without. The application of a force from within would appear to be more effective. A consideration of the possibilities of such a method for crushing led to some experimental work of a preliminary nature, the results of which are embodied in this paper. No systematic program was followed in the work and the results are, therefore, not final and far from complete. The success attained so far, with the mediocre apparatus available seems to warrant a preliminary report, with the expressed hope that the work may be carried on as well-outline program covering such phases as have been impossible to investigate at this time.

Jan 1, 1931

By J. B. Stephenson

The Bureau of Mines, under an interagency agreement with the Department of Energy (DOE), investigated the feasibility of hardfacing the critical surfaces of valves and similar devices by chemical vapor deposition. The purpose of this research was to increase the wear resistance of these components for use in the abrasive and erosive environment of coal gasification units. Tungsten and molybdenum coatings were produced on nickel-plated carbon steels and stain-less steels by hydrogen reduction of the metal hexafluoride at 325° to 600° C. Titanium nitride coatings were produced on low-carbon steels by the reaction of titanium tetrachloride, hydrogen, and nitrogen at 1,000° C. Titanium carbonitride coatings were produced on low-carbon steels by the reaction of nitrogen, hydrogen, and methane at 900° C. Tungsten, molybdenum and titanium nitride coatings were formed on 6-, 10-, and l2-inch (0.15-, 0.25-, and 0.30-meter) ball valve seats for evaluation in the low-Btu coal gasification pilot plant at the Morgantown Energy Research Center, Morgantown, W. Va.

Jan 1, 1979

By Bruce Cantrell, K. L. Rubow

"INTRODOCTIONMeasurement of the contribution of diesel exhaust to respirable aerosol in mine environments has become increasingly important because of current concerns over the occupational health effects resulting from exposure to diesel emissions. In response to this, the U.S. Bureau of Mines is developing and evaluating new sampling methods for measuring diesel aerosol in underground mines. Two such techniques are being studied by the Bureau, size selective sampling and Chemical Mass Balance (CMB) modeling. These techniques use measurable physical or chemical characteristics of a mine aerosol sample to infer the amount of diesel particulate material contained in the sample.Size selective sampling is being adapted for measurement of diesel aerosol by the Particle Technology Laboratory (PTL) of the University of Minnesota under sponsorship by the Bureau. 1 It is based on the premise that diesel and mineral dust aerosol can be physically separated by size and collected during sampling using inertial impaction. An independent effort by the National Institute for Occupational Safety and Health to develop a size selective sampling technique was also sponsored by the Bureau.The second technique, CMB modeling, is being developed by the Bureau as an alternative measurement technique to referee the results obtained using size selective sampling.3 It compares measured trace element ""finger prints"" of aerosol sources with similar profiles of mine aerosol samples. From these, the portions of the sample contributed by each source can be determined. Results of these investigations in underground coal mines have confirmed that diesel and coal dust aerosol are of different size and can be measured separately using size selective sampling techniques.A major difference in diesel usage among underground mines is the requirement for exhaust gas cooling systems in coal and gassy noncoal mines. Nongassy mines usually employ limited exhaust conditioning in the form of catalytic converters, which have limited effect on primary exhaust particulate. The cooling system in most general use in gassy mines is the water scrubber. This device has little effect on most of the gases but removes particulate material from the exhaust. 5 Because of this, exhaust aerosol characteristics in nongassy mines are expected to be different. To see if size selective sampling techniques can be used in such mines, the Bureau and the University of Minnesota conducted a second study in three metal and nonmetal mines, two nongassy and one rated as gassy."

Jan 1, 1990

By J. Mutmansky, C. Lee

"The size distribution of coal mine dust is one of its most important characteristics because the particle size is known to govern the region of deposition of dust within the human respiratory tract. In addition, dust characteristics, particle settling rate, transportability of the dust and the efficiency of dust control measures are all affected by the particle size. As a result, particle size distribution of the airborne dust in a coal mine is a fundamental property that impacts on the health of underground workers.This paper deals with some basic findings on the size distribution of cool mine dust based upon the results of data collection in six underground coal mines using continuous miners. All airborne dust sampling was performed on development sections using eight stage cascade impactors and permissible 2. O l / min pumps. Samplers locations were fixed in the sections with respect to the continuous miner and roofbolter or with respect to the intake and return airways • Sampling times varied from 45 minutes to 6 hours , depending upon the dust concentration. The first topic of analysis was the test to determine whether the commonly used lognonnal distribution is valid when applied to airborne coal mine dust. Secondly, the conventional method of representing the· distribution using two parameters, the geometric mean and the geometric standard deviation, is questioned. Since almost all size data were found to show some degree of bimodality, the two parameter lognonnal distribution may not represent the total airborne coal mine dust size , quite adequately. Bimodal lognonnal distribution was tested to be a good approximation in the case with two modes in the size distribution.The final topic discussed in this paper is the 'locational variation of the airborne dust size distributions within the continuous mining section. The size distributions varied considerably at the different sampling locations with the continuous miner and roofbolter producing the coarser distributions. Fine size modes in the range of 2 to 4µ m including mostly respirable dust particles were present in almost all samples • Second dust generating sources such as the shuttle car movement were found to be major causes of high respirable dust concentrations in some cases ."

Jan 1, 1988

By Oliver Bowles

From the most remote periods of civilization stone has been used to perpetuate the memory of individuals or to immortalize their noble achievements. Ancient memorials ranged from simple piles of stone (cairns), or single markers, to great obelisks and pyramids or magnificent mausoleums. The Taj Mahal at Agra, India, built of white marble by Shah Jehan in memory of the Empress Mumtaz Mahal, is one of the most beautiful and costly memorials ever built. It was erected between 1632 and 1650 at an estimated cost of $50,000,000 or more and is today an object of unusual interest for travelers. Other magnificent memorials both ancient and modern are to be found in many lands. No sharp line can be drawn between buildings and monuments, because the larger types of memorials such as the Bok Singing Tower, Lincoln and Jefferson Memorials, and mausoleums of various types have features in common with buildings. However, great care must be exercised in selecting a site for a quarry that will produce acceptable monumental stone because appearance as well as quality is of prime importance. The deposit must be of uniform texture and attractive color and must be notably free of knots, hairlines, impurities, incipient seams, or other defects. Many memorials are of polished stone, and spots or streaks that might be virtually Invisible on a natural rock face will appear distinctly on a polished surface. Hence, stone to be polished must be selected with unusual care. However, less flawless stone may be used for hammered surfaces.

Jan 1, 1955

By L. B. Berger

In this investigation, the ampoule type of carbon-monoxide (CO) detector which is manufactured under license of U. S. Patent 1,644,014 (October 4, 1927) was tested for sensitivity and reliability. This detector was devised primarily for examining the air of manholes and sewers for possible dangerous contamination with CO before workman enter those places, but dine to the simplicity of the device it may have a more general usage for examination of atmospheres which are known or suspected to be contaminated with CO. Some of the suggested uses are the examination of the air in garages, tunnels, mines, around blast furnaces, gas plants, and in the home.

Jan 1, 1930

By L. F. Willmott

Pulverized high-volatile A bituminous coal was gasified with oxygen and superheated steam in a pressure-gasification pilot plant equipped for slurry feeding. The minimum ratio of water to pulverized coal that could be pumped satisfactorily as a slurry was about 1 to 1. Heating this slurry produced a suspension of coal in superheated steam having a steam-to-coal ratio greater than the 0.3 to 1 proportion that is considered optimum for pressure gasification of pulverized coal. A steam separator removed enough steam to provide ratios down to about 0.5 to 1, but a 0.3 to 1 ratio was not achieved. Gasification of Sewickley coal produced a synthesis gas containing about 36 percent H2, 46 percent CO, and 13 percent CO2, Gas output, gas composition, and coal and oxygen requirements were Virtually the same as for a pilot plant equipped for fluidized-coal feeding. Typical results from the slurry-fed plant at 300 psig were carbon gasified, 95 percent; coal requirement, 34 lb/M (thousand) std cu ft CO + H2 produced; oxygen requirement, 365 std cu ft/M std cu ft CO + H2 produced. The results showed that the two feeding methods are equally satisfactory from the standpoint of gasification. A choice between a fluidized-coal gasification process or a slurry gasification process depends on considerations relating to the coal-feeding phase itself, including capital and operating costs, manpower requirements, safety, and flexibility of operation.

Jan 1, 1962

By W. A. Jacob, E. W. Dean

The Pittsburgh petroleum laboratory of the Bureau of lines has recently developed an improved method for the determination of water in pctroleum emulsions. It has been described in detail in an article entitled "A convenient method for the determination of water in petroloum and other organic emulsions" by E. W. Dean and D. D. Stark (Jour. Ind., and Enc. Chem. Vol. 12, ſay, 1920, page 436). It is essentially a modification of the familiar procedure of "distillation with an iniscible solvent", the improvement consisting in the use of apparatus that is rºck more convenient than any previously employed. The method has been used with marked success in the Bureau's laboratories for a period of about a year and has also been tried with equal satisfaction by a number of other laboratories. It has been most extensively employed for determining the water content of heavy fuel oils but has been applied also to several other types of emulsions, including shale oils, tars derived from coal, greases, and mixtures of powdered coal, oil and water. The Bureau has received a number of requests for information regarding commercial sources for the apparatus used, and having been assured of the value of the method, has taken steps to render it available for general use. - The equipment is, with the exception of two items, made of parts that are obtainable from the ordinary stock of chemical supply houses. The two exceptions are (1) the so-called "distilling tube receiver" and (2) the electric heater. The former is an essential part of the equipment; the latter is a convenient ac cessory but it can if necessary be roplaced by a gas burner. Efforts on the part of the Bureau staff to ronder these two items of apparatus available for purchase from supply houses, or for production by the user are hero described.

Sep 1, 1920

By Perry G. Cotter

The objective of this investigation was to synthesize and investigate the properties of a high-temperature refractory material based on a combination of boron, silica, and magnesium. A magnesium-thermic reaction was used for the synthesis. X-ray examination of the product indicates that the crystalline portion of the composition is a combination of magnesium borides, magnesium silicate, and magnesium orthoborate. Chemical analysis of a representative sample shows, in weight-percent, boron 17.6, silicon 23.9, magnesium 17.8, and chromium 0.5. The balance is largely oxygen. The composition is resistant to high temperatures under oxidizing conditions and is stable in water, hydrochloric acid, and hydrogen. It has a low density (less than 3 grams per cubic centimeter) and a hardness value in the range of quartz. It has a melting point above 1,700° C. and can be hot-pressed to shape in the temperature range between 1,200° and 1,350° C. The properties described in this paper indicate that the material may have some uses as a high-temperature refractory, and because of its boron content it may have some value as a thermal-neutron-absorption material.

Jan 1, 1961

By R. V. Lundquist

The Bureau of Mines made a laboratory study of the amenability of anorthosite rock ( from the San Gabriel Mountains , Los Angeles County , Calif . ) to treatment by the lime soda sinter process for the extraction of alumina . The study was done under a cooperative agreement with the California Division of Mines and Geology . This report presents the results of the investigation , and it includes a review of the geology of the deposit ( 7 ) by Dr. Gordon B. Oakeshott . Interest in the recovery of alumina from submarginal aluminum silicate ores is stimulated by the fact that the domestic aluminum industry depends on imports of bauxite for its alumina requirements . Of the 8.0 million long dry tons of high - grade bauxite consumed in 1961 for producing metallurgicalgrade alumina , only 0.9 million long tons , or 11 percent , was mined in this country . During past years many organizations have carried out research programs to determine if alumina could be extracted economically from such domestic ores as clays ( 3 , 4 ) , anorthosite ( 8 ) , and other silicate sources . Successful alumina extraction is the ultimate objective of the Bureau of Mines program.

Jan 1, 1963

By R. B. Schluter

The Bureau of Mines investigated the flotation responses of two copper-nickel ore samples from the Duluth Complex with the objective of recovering bulk sulfide concentrates. One of the ores studied was taken from a test pit; the other was taken from a test shaft. The samples were quite similar except that the pit sample analyzed 0.35 pct Cu and 0.11 pct Ni and the shaft sample analyzed 0.69 pct Cu and 0.14 pct Ni. Flotation responses were studied in both laboratory and pilot plant tests. Pilot plant flotation responses were similar for both samples resulting in grades of 12.2 pct Cu and 2.5 pct Ni for the pit sample and 12.2 pct Cu and 2.1 pct Ni for the shaft sample. Weight recoveries were 2.5 pct for the pit sample and 5.2 pct for the shaft sample. Copper and nickel recoveries for the pit sample were 87 and 62 pct, respectively, and 92 and 73 pct for the shaft sample. Both concentrates contained small but significant values of cobalt and precious metals. Cobalt recoveries were low--less than 40 pct for both concentrates. Precious metals contents of the concentrates were 1.59 oz/ton for the pit sample and 0.99 oz/ton for the shaft sample. Silver was the predominant precious metal by weight, but platinum and palladium represented the highest values.

Jan 1, 1980