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Underground coal mining continues to evolve in the U.S., and more reserves are being mined under deeper cover, with worse roof, or with interactions from previous workings. At the same time, the mining community is responding to higher safety standards and intense competitive pressures. The need for effective ground control design has never been greater. Ground control safety issues that have been addressed by recent the National Institute for Occupational Safety and Health (NIOSH) research include: Improving roof support performance; Maintaining safe tailgate escapeways from longwalls; Optimizing pillar design for retreat mining; Controlling multiple seam interactions; Predicting roof conditions during extended cuts, and; Preventing massive pillar collapses. As funding from both government and the private sector has diminished, the emphasis in research has focused on providing the mining community with practical techniques for improved ground control design. Many projects have successfully employed empirical methods that emphasize the statistical analysis of case histories from underground mines. Other projects have employed numerical models and large-scale laboratory testing of roof support elements. Using these data, NIOSH has developed an entire toolbox of computer programs that have been effectively transferred to the mining community.

By R. H. Fernald, C. D. Smith

When the United States Geological Survey began operations at the coal-testing plant erected at the Louisiana Purchase Exposition at St. Louis, Mo., in 1904, it had already outlined a comprehensive plan for the systematic study of coals, lignites, and other mineral fuels with reference to their suitability for particular purposes and the methods by which they could be utilized most efficiently. Recognizing the need of information on the relative economy of producer gas as compared with steam for power purposes and the lack of comparable tests of American coals in the gas producer, the Geological Survey undertook investigations of the merits of different coals as producer fuel for the purpose of promoting efficiency in the utilization of the nation's fuel supplies. These investigations were carried on at St. Louis, Mo., and, later, at Norfolk, Va., and Pittsburg, Pa. The aet of Congress approved May 16, 1910, transferred the fueltesting work being carried on by the Geological Survey to the Bureau of Mines. This bureau is conducting producer-gas tests at P~ttsburg, Pa., and is publishing and distributing reports relating to all the fuel tests made by the Survey. These investigations into the possibility of generating producer gas in a commercial way for power purposes from the various fuels of the country have been associated with steaming, briquetting, coking, and other tests, all of which supplemented an examination into the nature, extent, and distribution of the fuels. The tests have all been made with carefully selected representative samples and carload lots of materials procured specially for the purpose by experienced collectors.

Jan 1, 1911

Productivity in underground metal and nonmetal mines is contingent upon work methods, mine layout, and ore handling techniques. One of the most important factors impacting productivity is the efficient movement of men, materials and supplies from the surface into and throughout the mine. Various transportation systems such as man-trains, service shafts, rubber-tired diesel equipment, etc. are currently used to transport men and supplies in underground mines. In many underground mines, it is not uncommon for a worker to spend 25% of his eight-hour working day traveling from the surface to his work area and returning to the surface.

Jan 1, 1975

By S. D. Hill

To help insure the continued viability of the minerals and materials sector of the U.S. economy, the Bureau of Mines is conducting research and disseminating technology that will result in more efficient minerals extraction. As part of this effort, a process is being investigated that involves an aqueous chlorine-oxygen leaching procedure to treat complex sulfide concentrates to produce ZnCl2. Subsequent fused-salt electrolysis of the ZnCI2 produces high-purity zinc metal. Previous reports described preliminary, small-scale research on the chlorine-oxygen leaching system and fused-salt electrolysis of ZnCl2. This report discusses the details of design, construction, and longterm, continuous operation of both monopolar and bipolar fused-salt cells. The effects of temperature, electrode gap, current density, electrolyte composition, and electrode configuration on current efficiency and energy consumption were determined for a ZnCl2-KC1-NaCl electrolyte system. Zinc metal was produced at the rate of about 50 lb/day in a monopolar cell which was operated continuously for 60 days with current efficiencies from 85.8 to 98.6 pct and an average power consumption of 2.1 kwhr/lb. Bipolar cells with several different electrode configurations were operated for 90 days. A current efficiency of about 70 pct and power consumption of about 1.7 kwhr/lb of zinc were achieved using a three-electrode-pair, bipolar assembly with a chlorine gas lift pump to circulate electrolyte.

Jan 1, 1981

By Stephen D. Smith

This chapter summarizes data on crude nonfuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rim. Also included are tables that show the principal nonfuel mineral commodities exported from and imported into the United States and that compare world and U.S. mineral production. The detailed data from which these tables were derived are contained in the individual commodity chapters of Volume I and in the State chapters of Volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing, the stage of measurement used in this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the output from auxiliary processing at or near the mines.

Jan 1, 1988

By R. Blickensderfer

The sparking and gas-igniting tendency of steels and alloys were evaluated my measuring the radiance of spark showers produced by grinding a sample on an abrasive wheel in air, the time required for a spark shower generated on an abrasive wheel to produce an ignition in an explosive gas mixture, and the energy and speed required for impacts between various materials to ignite an explosive gas mixture. Mixtures of air-methane were found quite resistant to ignition by showers of sparks. A mixture of air-9.S pct hydrogen was used to increase the sensitivity of the tests and to thereby extend the range of materials that could be evaluated. The results of the spark-shower tests indicate that carbon steels and the alloy steels found in coal-cutter tools are among the most sparking and most incendive of any materials tested. Stainless steels, nickel alloys, and tungsten carbide are among the least sparking and least incendive. The brightness of the spark showers depended upon the degree of oxidation of the abraded particles. Impact tests against hard rocks such as solid quartz and sandstone, showed that high-carbon steel was more inc endive in the hydrogen mixture than were the softer steels or the alloy steels found in coal cutters. Ignitions were found much less likely to occur at speeds somewhat lower than the speeds currently in use in continuous mining machines.

Jan 1, 1972

By Larman J. Heath

Wellbore enlargement was tested using hydrazine hydrate in a gas-storage well in Ohio to increase the well productivity. The wellbore was to be enlarged by chemical disaggregation of the sandstone adjacent to the wellbore. Productivity immediately declined 49.1 percent and gradually declined to zero in 7 months. A down-hole camera survey showed a white-to-gray precipitate covering the entire wellbore surface. The precipitate was chemically analyzed and identified as mostly carbazic acid, a hydrazine derivative of carbonic acid. Formation of this precipitate was not anticipated; this viscous sub-stance caused the gradual loss in productivity of the well. The wellbore was not enlarged. Laboratory tests were run to determine what clay stabilization measures could be taken in sandstone cores to prevent clay swelling and particle migration caused by hydrazine hydrate. Normal clay stabilization methods did not prevent the virtually complete loss in permeability to hydrazine hydrate. Other laboratory tests using natural gas diluted with small amounts of carbon dioxide confirmed the ease with which carbazic acid could be formed in a hydrazine hydrate-saturated environment within and adjacent to the wellbore.

Jan 1, 1970

By LaMar G. Evans

The rapid determination of uranium in ores by radiometric means was investigated by the Bureau of Mines. Among the various procedures and schemes tested, two showed most promise. They were the ratio scheme developed in the Bureau's Tucson, Ariz., laboratory and the equilibrium method developed by the Canadian Department of Mines and Technical Surveys. The ratio method is a simple, empirical procedure for classifying the state of equilibrium in ores by measuring their radioactivity by means of a Geiger-Muller counter under three different conditions, using filters. The principal merit of the method is in providing a clue as to the reliability of equivalent uranium determinations.

Jan 1, 1958

By W. H. Young

The thickness of the coal seam is one of the more important items influencing the productivity and general overall efficiency of operation of a coal mine. The average thickness of coal seams mined in the United States has changed very little in the past 40 years. The first measurement of thickness of bituminous coal and lignite seams was made for 1920, when the average thickness was 5.3 feet.4/ The average thickness for later years was as follows: 1945, 5.4 feet; 1950, 5.3 feet; 1955, 5.2 feet; and 1960, 5.5 feet.5/ Table 1 includes data on number and production of bituminous coal and lignite mines classified by I-foot intervals of seam thickness mined in 1920, 1945, 1950, 1955, and 1960. Though bituminous coal and lignite are mined today from seams of exceedingly variable thickness -less than 2 feet to more than 50 feet - a large majority of the production, 62 percent in 1960, came from seams 3 to 6 feet thick. This is not surprising since the coal seam of moderate thickness presents the least mining difficulties.

Jan 1, 1962

By Fred Leighton

The Bureau of Mines has developed rock noise source location techniques that may be used to obtain precise and practical source locations from micro-seismic field data. These techniques enable one to monitor all or any part of a rock structure and map progressive stress buildup or rock movement. Thus, the microseismic method of determining instability in rock structures is becoming an invaluable engineering tool for the mining or civil engineer engaged in rock excavation and construction.

Jan 1, 1970

By Stanley C. Rhoads

The Bureau of Mines investigated the complete ternary system K2 HfF6¬K2ZrF6-l.25 weight-percent HF at 40° C. In addition, solubility curves have been established at 25°, 30°, 500, 60°, and 70° C. These solubility data implemented a study of hafnium enrichment in feed solutions for liquid-liquid extraction processes.. Selected K2HfF6-K2 ZrF6-1.25 weight-percent HF mixtures were equilibrated in a constant temperature bath. Compositions of the equilibrated solutions and wet residues were established from combined hafnium and zirconium oxide and total fluorine analyses. All solubility curves were essentially parallel on triangular coordinates. At 40° C, the solid phase of the K2HfF6-K2ZrF6-1.25 percent HF system is a series of solid solution hydrates with K2HfF6-H20 and K2ZrF6.3H2O segments existing at the respective extremes. Since this system contains K2HfF6-H20 and K2ZrF6.3H20 segments, it is not ideal for simple separation of high-purity K2HfF6 from K2HfF6-K2ZrF6 mixtures by recrystallization. However, it would be useful for producing hafnium-enriched feed solutions from zircon concentrates for liquid-liquid extraction of hafnium from zirconium.

Jan 1, 1973

By Gary E. Sherman

This report presents a Bureau of Mines study on the cost of mine permitting and compliance with environmental regulations in Alaska. It discusses permitting requirements and procedures for placer and lode mines. Placer miners must comply with recently established (1988) water quality regulations and effluent treatment requirements. To estimate the impact differing treatment options (no recycle, 100% recycling, and flocculation) have on a placer mine's rate of return, three models (1,500, 1,000, and 500 yd3/d) were simulated. Rates of return for these models show a marked decrease as effluent treatment is increased. The incremental increase in operating cost from one treatment option to the next is relatively small; however the opportunity cost of lost production if' significant and accounts for the decreasing rate of return with increased effluent treatment. Lode mines face greater costs for permitting and compliance than similarly sized placer mines as a result of the impact of the operation. Direct permitting costs for lode mines range from 2 to 6% of total project cost, with 4% the most common figure cited by industry. Total costs for permitting and compliance are approximately double those for permitting. Indirect costs associated with compliance include mitigation, monitoring, and reclamation.

Jan 1, 1991

By G. R. Fitterer

In the manufacture of steel by any process the refining period involves the partial elimination of the metalloids carbon, manganese, phosphorus, and silicon, by virtue of their reactions with ferrous oxide. At the end of this refining stage the metal consists chiefly of iron in which small amounts of these materials are dissolved. Unless some deoxidizer is added to the steel at this time, the reaction between carbon and ferrous oxide will continue with such force that it is impossible to form sound steal in the ingot molds. Instead, the product will exhibit a marked porosity due to the formation and trapping of carbon monoxide-the product of the reaction mentioned. However, if deoxidizers are added, steel may be obtained which is dense and free from gas bubbles. At the same time the deoxidation products will remain in the steal as impurities. For example, silicon additions form Si02 or combinations of Si02 and FeO. Additions of manganese form deoxidation products consisting of various proportions of MnO and FeO. It is also quite obvious that simultaneous additions of manganese and silicon will form oxide combinations either in the binary system MnO-SiO2 or in the ternary system FeO-MnO-SiO2. Work at the Pittsburgh Experiment Station of the United States Bureau of Mines, in cooperation with the Carnegie Institute of Technology and the Metallurgical Advisory Board, involved the study of such deoxidizing reactions and their products. In this connection considerable information is necessary concerning FeO, MeO, Si02, and Al 203, and their various combinations. Some of the most needed data are the melting points of all of these materials. At the outset of this work ordinary methods of melting point determinations were found to be inadequate for various reasons, and the procedure finally selected involved the use of the micropyrometer with occasional corroboration by quenching methods, The reasons for this selection, together with a description of the apparatus, are given in the following pages.

Jan 1, 1932

By Robert W. Metcalf

Corundum, natural alumina, or aluminum oxide (A1203) is the hardest mineral known except diamond. Theoretical composition is Al 52.9 percent and 0 17.1 percent, but it always contains small quantities of impurities, chiefly silica, iron, and lime. The melting point of corundum is above 1950° C., and it is insoluble in the strongest acids. Its hardness (9 on the Mohs scale) varies slightly according to purity, and its specific Gravity ranges from 3.95 to 4.10, 4 being a fair average. The index of refraction is 1.760 to 1.768 and its streak is white. Luster is adamantine to Vitreous, come specimens pearly, and color varies widely from white, gray, pink, and blue to black, brown, or bronze. Gem varieties are transparent or translucent, and of more brilliant coloring - red, blue, yellow, purple, or green. Corundum occurs in opaque massive or block structure with parting planes little developed or only roughly delineated and in granular form as minute crystals or small, irregular grains interspersed throughout the contact zones of schists and gneisses.

Jan 1, 1944

By Virgil A. Marple

The objective of this contract was to conduct characterization, evaluation and/or calibration studies of instrumentation used for measuring the quantity of respirable dust in mining atmospheres. Initially, this work involved the upgrading and detailed evaluation of the aerosol test chamber and the development of impactors with respirable classification characteristics. These were used as standards in the chamber for measuring the quantity of respirable dust based on either the ACGIH or BMRC respirable dust criteria. A program was then conducted to calibrate several photometers. In addition, the mass sensitivity of the GCA RAM-1 photometer to water droplets in the respirable size range was determined. Three additional studies were also made in this program. First, an experimental study was performed to ascertain the effect of crosswind, cyclone orientation and particle size on particle sampling and penetration through the 10 mm Dorr-Oliver cyclone. Second, a theoretical study was conducted to refine the theory used to predict the particle collection characteristics of impactors. Third, filter samples with known quantities of diesel and coal particles were produced and delivered to the B. of Mines for testing a Raman scattering analysis technique to discriminate diesel particles in the presence of coal dust.

Jan 1, 1984

By R. H. Hiltz

One of the major hazards in underground coal mining is fire. The inherent hazard of fire is exaggerated by the nature of coal mining restricted areas, the highly combustible nature of coal itself, and a potential for explosive concentrations or dust and gas in the air it becomes imperative therefore to make every effort to eliminate the causes of fires, while providing the most effective means possible to control and extinguish those fires which may occur it has been demonstrated by prior work that the problem of control increases in proportion to the time necessary to institute control procedures. There are several areas of underground coal mining with obvious fire potential. Some of these, like belt heads, have reliantly undergone improvements in standby fire control devices Others, although having fire suppression systems available to them, have not received as complete a systematic study of their problems. Face machinery, particularly those without a water supply, falls in this latter category.

Jan 1, 1973

By J. A. Kosek

Work has been carried out under Bureau of Mines Contract No. HO395132 to develop and fabricate gas sensors for mining applications. Promising new instruments have been designed, developed, tested and supplied to meet BuMines requirements. These instruments include prototype 1) remote-sensing, diffusion-type CO monitors for mine operation which can be operated in conjunction with a surface computer, 2) control modules for alternate in-mine readout of the remote diffusion type CO monitors, 3) personal CO diffusion-type dosimeters and 4) personal NO diffusion-type dosimeters. In addition, retrofit modifications were made to update and optimize operation of CO and NO2 direct-reading type detectors provided under a previous contract. Studies were conducted to evaluate and demonstrate the availability of stable, portable N02 calibration sources for NO2 instrumentation. The use of selected, commercially available cylinder sources for NO2 instrument calibration were recommended. Additional studies were also conducted to investigate the feasibility of instrumentation for rapidly monitoring CO, NO and NO2 in diesel exhaust.

Jan 1, 1981

By Thomas E. Finch

This report is a continuation and expansion of a previous USBM grant (No. G0254004) which examined alternative methods of handling the parting between two coal seams in a surface mining operation. The alternative methods consist of equipment implementation in either a stowing or haulback technique. Following a typical strip mine conformation, the parting is directly stowed or hauled back and placed in the pit bottom after second seam removal. The objectives are to produce an environmentally sound material placement technique and to increase prime stripping machine utilization. This report contains the engineering philosophy behind two computer programs created to evaluate parting handling methods over d wide range of coal and parting thickness ratios. The nature of the computer approach allows cost sensitivity analysis and quick updating of costs. The two programs are clearly presented with documentation and examples such that consumers may apply then to their own operations.

Jan 1, 1977

By L. A. Stewart

This paper describes all occurrences of barite in Arizona that were known or reported to the authors. The history, ownership, production, and geologic setting are discussed for most of the deposits. The uses and specifications of product grades are briefly discussed. Seventy-five deposits were examined in 9 of the 14 counties of the State. The descriptions are given under county headings. No occurrences were reported in the four northeastern counties of Coconino, Navajo, Apache, and Greenlee, nor in Santa Cruz in the southern part of the State. From about half of the deposits examined, 55 samples were taken; of these, 45 were for chemical analysis, and 8 larger samples, ranging from 100 to 350 pounds, for beneficiation tests. A 30-ton bulk sample was taken for pilot-plant tests. Bench-scale flotation tests of the eight samples employing several different procedures and reagent combinations yielded marketable-grade barite products with barite recoveries ranging from 60 to 97 percent. Five of the samples contained enough fluorspar to warrant its recovery. Acid-grade concentrates, which accounted for fluorspar recoveries of 45 to 70 percent, were obtained from three of these ores. Batch laboratory tests of a representative portion of the 30-ton bulk sample revealed that acid-grade fluorspar and high-grade barite concentrates could be recovered. Results of the laboratory and continuous pilot-plant tests of this ore will be presented in a separate report.

Jan 1, 1960

By K. L. Whitehead

An examination of 60 mines, 11 illumination hardware manufacturers, and Q mobile face-equipment manufacturers was conducted to determine the state of the art of mine-illumination hardware, define lighting system installation and maintenance problems, and assess personnel acceptance of lighting. Longwall and mobile face-machine illumination were studied. Major problems on room and pillar installations include damage of exposed components, electrical failures, and reduced lamp life, with extreme variability in the degree of these problems. Most longwall systems had low or moderate maintenance requirements, cable damage being the most significant problem. Most mobile face-equipment operators liked their machines' lighting systems, but many complained of glare and other problems. Longwall lighting was unanimously accepted by face personnel, and most complaints were minor. Based on the survey, general installation and maintenance guidelines have been established, addressing hardware design aspects, approaches proved effective to minimize problems, and improper practices noted which are detrimental to effective lighting.

Jan 1, 1981