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Possible consequences of continuing internal political unrest and the imposition of foreign sanctions raise concerns about the traditional reliability of the Republic of South Africa as a major world supplier of important minerals. A recent Bureau of Mines' technical report (Open File Report 76-86) examined the impacts of temporary peacetime disruption scenarios for six key materials and mitigating options. Because of South Africa's dominant producer position for these minerals (except for cobalt), expansion of primary production capacity outside of South Africa is not a short term mitigative option. However, prospects of a longer term disruption would likely spur investment in capacity expansion in alternative Market Economy Country supply sources. This report identifies the resources, production costs, and burdens that would be placed on alternative MEC producers of chromium, cobalt, gold, manganese, and platinum-group minerals if South Africa's production were subject to a long term; disruption. When long term supplies from South African deposits are discounted, more than a few years reserves were found only for cobalt and manganese. Even for these two minerals, higher sustained prices would be required to increase manganese production capacity and to support means of cobalt transportation not through South Africa.

Jan 1, 1986

By B. M. O'Harra

The residues resulting from the retort distillation of zinc ores have from 40 to 75 per cent of the weight of the original ore and contain from 5 to 15 per cent zinc . A rough estimate indicates that approximately 450,000 tons of residues are produced annually in the United States , containing about 36,000 tons of zinc . Besides the current production of residues there are at many smelter sites large accumulations from past operations which are available for treatment if this can be done profitably . In addition to their zinc content the residues contain much unconsumed coal , which has been carbonized during the distillation process , and those from most western ores also contain lead and silver . In this paper is summarized the information obtained in a survey , recently made by the Bureau of Mines , in cooperation with the Missouri School of Mines and Metallurgy , of processes which are in use or which have been suggested for the treatment of retort residues . The complete report of the survey is to be published as a Technical Paper of the Bureau of Mines .

Apr 1, 1923

By G. W. Reimers

Conditions in the underground mine environment can cause self-heating of sulfide ores as a result of exothermic oxidation reactions, which may result in mine fires. This Bureau of Mines report describes thermal analyses of finely ground chalcopyrite, chalcocite, galena, pyrrhotite, marcasite, and arsenopyrite, to characterize their responses under oxidizing conditions. Thermal gravimetric analysis (TGA) and differential thermal analysis (DTA) were used, in the temperature range 1000 to 5000 C. Chalcopyrite showed an initial weight gain, due to formation of sul-fates, a weight loss, caused by ignition of iron sulfide to iron oxide, and a final weight gain, indicating the conversion of copper sulfide to sulfate. Chalcocite did not ignite in the temperature range studied but exhibited a rapid weight gain, because of the rapid conversion of copper sulfide to sulfate. Likewise, galena failed to ignite but underwent a steady weight gain when oxidized in a moist atmosphere, showing conver-sion of lead sulfide to sulfate below the ignition point. Marcasite underwent a rapid weight loss, indicating ignition, at 2000 C. Moisture in the oxidizing atmosphere lowered the ignition point of marcasite and arsenopyrite but not that of pyrrhotite. All the sulfides exhibited exothermic behavior at temperatures below the ignition point.

Jan 1, 1987

By Willard L. Hunter

The Bureau of Mines studied the effect of temperature upon the reduction of chromite by carbon and the relative reducibility of chromites as a function of their composition. Ferric oxide was also studied to provide comparative data. Pellets weighing approximately 1 gram and containing 70 percent ferric oxide, chromic oxide, or chromite and 30 percent graphite were subjected to closely controlled temperatures under a flow of argon for 15 minutes. The amount of CO and CO2 evolved was measured, and the reduced sample was analyzed by X-ray diffraction techniques. The reduction of Fe2O3 was studied over a temperature range of 600° to 1,400° C, while the reduction of Cr2O5 and chromite was conducted from 9000 to 1,621° C. The temperature above which appreciable reduction of Cr203 by graphite took place was 1,125° C. The temperature at which significant reduction started for three of the four chromite samples was approximately the same, indicating that there was concurrent reduction of iron and chromium oxides in the chromite mineral rather than selective reduction of iron oxides followed by reduction of chromic oxide. Rhodesian chromite appeared to dissociate at a lower temperature with concurrent reduction of iron. Based on the temperature at Which chromite was 50 percent reduced in 15 minutes, Transvaal chromite reduced most easily, followed by Mouat, then by Kampersian, and finally by Rhodesian DFC material. Statistical analysis of test results indicated that the ferric iron content of chromites affects their reduction behavior more than any other constituent.

Jan 1, 1966

By Sidney Katell

This study presents the economics of the hot-carbonate purification process for removing C02. It considers three variations of the process in order to meet the design specifications, which call for a feed-gas flow of 10 million standard cubic feet per hour (std.c.f.h.) with C02 inlet concentrations of 10, 20, and 30 percent and exit C02 values of 5, 2, 1, 0.5, and 0.1 percent. Inlet pressure and temperature are 350 pounds per square inch [e] (p.s.i.g.) and 300° F., respectively. Estimated capital and operating costs are shown in the following to tabulations: [ ]

Jan 1, 1960

By P. D. Kovscek

The performance of a novel prototype kerf-cutting impact mining machine was evaluated under a cooperative agreement between the U.S. Bureau of Mines and RAMEX Systems, Bellevue, WA, while operating under conditions typical of normal tunnel entry development. Selected operating parameters were monitored concurrently to determine baseline operating conditions and to study relationships between operating parameters. Using the data obtained, the specific energy requirements of the impact mining machine were calculated and compared to specific energy requirements of tunnel boring machines cutting in rock having similar hardness. Tests results indicate that the kerf-cutting impact mining machine can provide a mechanical means for mining very hard rock that cannot be effectively mined using commercially available mechanical excavators.

Jan 1, 2010

By Robert M. Cox

The U. S. Bureau of Mines (USBM) MULSIM/NL modeling technique has been used to analyze anticipated stress distributions for a proposed alternative longwall gate road design for a western Colorado coal mine. The model analyses indicated that the alternative gate road design would reduce stresses in the tailgate entry without increasing stresses in the headgate entry. To test the validity of the alternative gate road design under actual mining conditions, a test section of the alternative system was incorporated into a subsequent set of gate roads developed at the mine. The alternative gate road test section was instrumented with borehole pressure cells, as part of an ongoing USBM research project, to monitor ground pressure changes as longwall mining progressed. During the excavation of the adjacent longwall panels, the behavior of the alternative gate road system was monitored continuously using the USBM computer-assisted Ground Control Management System. During these field tests, the alternative gate road system was first monitored and evaluated as a headgate, and later monitored and evaluated as a tailgate. The results of the field tests confirmed the validity of using the MULSIM/NL modeling technique to evaluate mine designs.

Jan 1, 2010

By Joseph S. Coffman

The Bureau of Mines investigated the availability of barite (BaSO4) from 35 U.S. and 41 non-U.S. mines and deposits in 17 market economy countries (MEC's). This evaluation assesses the availability of mud-grade barite, and concentrates consumed by the chemicals and fillers industries. The demonstrated resources defined in this analysis totaled 130 million metric tons (Mmt) of barite (contained BaSO4), yielding a potential 115 Mmt of recoverable barite concentrates. At the 1984 MEC production rate, the evaluated resources would last about 30 yr; however, this would include production costs of up to $100/mt concentrate. An average price needed to cover all costs of production over the life of each operation was determined for both mud-grade and chemical- and filler-grade barite products. Including a 0-pct discounted-cash-flow rate of return (DCFROR), regional weighted- average total production cost ranged from $38/mt for barite concentrates in Asia to $71/mt for U.S. operations. Transportation costs have the greatest impact, contributing up to 60 pct of the total cost of production. Rail transportation costs from the mines to U.S. markets are generally significantly higher than ocean shipping rates on imports.

Jan 1, 1986

By A. C. Fieldner

The Bureau of Mines has recently conducted a study of results obtained in analyzing similar samples of coal and coke by 25 laboratories throughout then country, in comparison with results obtained in the Bureau's coal laboratory at Pittsburgh. The purpose of this work was primarily to obtain a comparison of the methods of coal analysis used by the laboratories of the American Gas Association. Therefore, four standard samples of coal end one of coke ware prepared in the Bureau of Mines coal laboratory at Pittsburgh, and portions sent to each laboratory. At the same time, a like number of standard samples were submitted to 12 commercial laboratories rot affiliated with the Association, for the purpose of comparing their analyses with the results is obtained by the U. S. Bureau of Mines and the American Gas Association. Tire comparison is based on the average of 24 analyses by the Bureau of Mines on each kind of coal, and the accompanying curves show the deviation from this average analysis, together with deviations from the check limits of the American Society for Testing Materials.

Jan 1, 1923

By Peter F. Steidl

Seven degasification wells have been completed in the Pittsburgh coalbed at the new Emerald mine near Waynesburg, Pa. Funding was provided by the Bureau of Mines to perform stimulation treatments on five of the wells, to show that this is a feasible and economical means of degasifying part of a coalbed. The seven wells ranged in depth from 590 to 910 feet. Stimulation treatments used 25,260 to 42,660 gallons of foam and 7,400 to 12,800 pounds of 20/40-mesh prop sand. Pumping rates were 10.8 to 11.6 bbl/min and treating pressures were from 1,050 to 1,600 psig. On the day following stimulation, gas production ranged from a few hundred cubic feet per day to more than 100,000 cu ft/day.

Jan 1, 1978

By L. L. Oden

The Bureau of Mines is conducting research to develop methanation catalysts for converting synthesis gas derived from coal to synthetic natural gas. This report describes a method to prepare supported Raney nickel coatings by dipping screen-covered nickel sheet in molten aluminum-nickel alloy. Coatings were formed at 1,050° C that were comparable in thickness, composition, microstructure, and catalytic properties to flame-sprayed commercially pre-pared Raney nickel. A molten salt comprising cryolite-8 wt-pct LiF was employed over the molten metal bath to clean and preheat the substrates, to protect the metal bath from oxidation, and to heattreat the coated specimens. Immediately following heat treatment, specimens were quenched to 700° C in a molten salt bath containing CaC12-34.5 wt-pct NaCl, which also functioned to remove the insoluble occluded fluoride salt.

Jan 1, 1976

By William M. McKewan

The U.S. Bureau of Mines has established a wire rope research laboratory to examine the factors that affect the life of wire rope. Ropes of sizes ranging from 3/4 to 2 in. in diameter and from 2 to 35 ft in length were tested to determine their breaking strength, elongation, and torque. This was done to characterize the test equipment on ropes used in mine hoisting systems.

Jan 1, 1990

By F. E. Block, Stephen D. Hill

The necessity for measuring radiation dose is encountered in studying both the beneficial and damaging effects of ionizing radiation on materials . It is also necessary to know the radiation dose absorbed by the reactants in order to evaluate the efficiency of reactions or processes that are promoted by radiation . Thus , a significant effort was made at the Albany cobalt 60 facility to investigate techniques by which the exposure radiation dose can be determined . Methods including ferrous sulfate , ceric sulfate , and methyl methacrylate chemical dosimeters , ion chamber dosimetry , and an absolute radiation calorimeter were investigated . Isodose curves were constructed for several standard source configurations using the dosimetry techniques which were investigated .

Jan 1, 1964

By Jr. Sharkey

The Bureau of Mines investigated gases from flash and laser irradiation of Pittsburgh seam (hvab) coal to determine the action of high temperatures on coal. Temperatures in excess of l,000° C were reached with both types of irradiation. Craters about 300 microns in diameter were produced in the coal with millisecond pulses from the laser unit rated at 1.7 joules' output. Gaseous products from laser and flash irradiations in vacuum contained 21 and 8 percent acetylene, respectively. Diacetylene, vinylacetylene, and other products to molecular weight 130 were indicated in the mass spectrum of the gas from the laser study. Single experiments were also conducted in which the laser energy, particle size of the coal, and atmosphere were varied. The results indicated that the distributions of products obtained from the flash and laser irradiations of coal were different from that produced in high-temperature carbonization.

Jan 1, 1966

The Bureau of Mines, U.S. Department of the Interior, devised a flotation technique for upgrading chromite in chromium ores and gravity concentrates. The technique consisted of cationic flotation of chromite from a slime-free pulp acidified to pH 2.5 or lower using H2S04 modifier. Flotation results showed that ore containing serpentine as the primary gangue mineral was more amenable to concentration by this technique than ore containing the readily floatable olivine as the primary gangue mineral. Rougher flotation of a chromite ore containing abundant serpertine increased the grade form 19 to 41 percent Cra03 at a chromite recovery of 89.6 percent. Rougher flotation of ore containing abundant olivine upgraded the chromite from 23.4 to 29.6 percent Cr203 at a recovery of 89.4 percent. The technique was also applied to chromite gravity concentrates to further upgrade chromite and to reject silicates. Flotation of a gravity concentrate containing 40.9 percent Cr203 and 4.4 percent SiO2 recovered 90 percent of the chromite in cleaner products containing 44.9 percent Cr203 and 0.63 percent Si02. The combined recovery by gravity and flotation was 87 percent. An economic evaluation of this technique will be undertaken to deter-mine its feasibility for commercial use.

Jan 1, 1980

By Lung Cheng

Based on earlier tests that showed steel to be much more likely to cause frictional ignition than tungsten carbide, the Bureau of Mines redesigned coal-cutting bits to reduce the hazard of face ignitions. Two bit designs--a mushroom-shaped bit with a conical shank and a dove-tail bit with a rectangular shank--are described, as well as bit wear tests conducted in the laboratory and in an operating coal mine. In laboratory tests, for 1/8-, 1/4-, and 1/2-in-deep cuts and cutting speeds of 280, 500, and 660 ft/min, the mushroom bit had significantly longer tip wear life than the conventional bit; the dovetail bit was also superior to the conventional bit. Results of in-mine tests on the mushroom bit agree well with laboratory results. In-mine tests of the dovetail bit are underway.

Jan 1, 1983

By R. A. Meyer

A table that greatly simplifies determination of metastable transitions in mass spectra has been prepared. All the mathematically possible metastable transitions of any compound whose molecular weight lies between 26 and 150 can be determined from the table without calculation. The method of utilizing the table is described, using selected peaks from the spectrum of normal butane for illustration. In the mass spectrometer, ions are formed in the isatron and accelerated through a series of slits. Most of these ions reach the collector without further change, but a few dissociate in transit to form new ions. These ions appear in the mass spectrum at neither the mass--to-charge ratio (m/e) of the original ion nor that of the new ion. A formula that relates the appearance of these new ions to the ion from which they were formed is: [ ]

Jan 1, 1957

By Fred N. Kissell

This U.S. Bureau of Mines report is a guide for the control of air contaminants during tunnel construction. Topics discussed are calculating air quantity requirements, types of ventilation systems, planning ventilation systems, control of methane gas, control of dust, control of diesel emission, ventilation to remove blasting fumes, measuring airflow, and measuring gases. This report does not provide detailed design information, but seeks to answer practical questions on air contamination issues.

Jan 1, 1995

By R. Stefanko

The industrial hygiene and safety aspects with internal combustion engine in mining systems is truly interdisciplinary and encompasses many fields such as mine ventilation, exhaust gas and particulate analyses, mine atmospheric environment monitoring, mathematical modeling of generation, dilution and dispersion of pollutants in ventilation systems, and engine testing and approval. Mathematical models of the dilution and dispersion of diesel exhaust contaminants can be useful only if these models can be validated. In this research report, experiments that were specially designed for the above purpose are described. These experiments were conducted in the U.S. Bureau of Mines, Safety Research Coal Mine, in Bruceton, Pa. On the basis of this study, the data collected, and further review of available literature, it is concluded that mathematical models of dilution and dispersion are useful tools for mine ventilation planning. Additional objectives of this study about which conclusions and recommendations are reported here include: (a) evaluation of mine atmosphere contaminant monitoring systems; (b) optimum sampling site locations; (c) model sensitivity and error analyses; (d) computer coding of mathematical models; and (e) development of a diesel bibliography. While an extensive bibliography on diesels is provided in this report, Volume II of this final report has 511 references.

Jan 1, 1977

By W. P. Yant

The widespread use of toluene in industry and the importance of air analysis in industrial-hygiene surveys have created a need for a simple and accurate method for determining toluene vapor in air. Most of the methods used to determine small quantities of toluene in liquid or vapor form are based on the measurement of its physical properties. Methods based on fractional distillation, determination of specific gravity, use of the interferometer, use of the spectrograph, and sorption on solid sorbents with subsequent determination of gain in weight have been employed. Distillation and specific-gravity methods are not applicable to the small quantities of toluene found in the air, and use of the interferometer, spectrograph, and sorption methods either are not specific for toluene in the presence of other volatile substances or require expensive equipment.

Jan 1, 1936