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By Michael D. Fenton

Bauxite resources were primarily in Africa, Asia, Oceania, and South America. Only five countries combined, Australia, Brazil, Guinea, India, and Jamaica, contained most of the total world reserves available for extraction under current economic conditions and accounted for nearly 80 % of world production of bauxite. World bauxite and alumina production declined and prices for smelter-grade alumina remained below the $200/mt level during 1993 because of growing aluminum inventories on international markets and declining worldwide demand. The United States imported bauxite primarily from Australia, Brazil, Guinea, and Jamaica. U.S. alumina plant capacity remained essentially unchanged throughout 1993, but apparent capacity utilization decreased by the close of 1993. Chromium Most of the world's known resources and reserves of chromite are located in India, Kazakhstan, South Africa, and Zimbabwe. India, Kazakhstan, and South Africa accounted for 73 % of world production of chromite. The two largest producers of chromite, Kazakhstan and South Africa, were in the process of major economic and political change during 1993. South Africa's production and exports of chromite continued to fall during 1993, because of weak international demand and a flood of cheap metal from the former U.S.S.R. and China into world markets. Despite a significant increase in production, South Africa's ferrochrome producers continued to operate below capacity in 1993. Prior o the dissolution of the U.S.S.R., Kazakhstan was a major internal supplier of chromite ore to the U.S.S.R. consumer, but subsequent decline in demand led to a downward trend of chromite production in Kazakhstan and increasing exports to Europe during 1992 and 1993. The United States consumed, about 10% of world chromite ore production in various forms of imported materials. The United States imported nearly one-half of its required chromium contained in chromite ore and chromium ferroalloys and metal from South Africa; the remainder was from the minor producers Turkey, Yugoslavia, Zimbabwe, and others.

Jan 1, 1995

By Verne S. Mutton, William A. Slivensky, Eric S. Weiss, Kenneth L. Cashdollar, Deepak R. Kohli

The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Laboratory, cooperated with Tecrete Industries Pty. Ltd. and BHP Australia Coal in a research program to evaluate the strength characteristics and air leakage of four seal and two stopping designs for use in underground coal mines. A fundamental safety research area for NIOSH is to eliminate the occurrence of coal mine explosions or to mitigate their effects. One approach to achieve this goal is to develop new and innovative seal designs that provide increased explosion isolation protection for the mining personnel against ignitions that originate from within the gob or. other worked-out areas of the mine Full-scale seals and stoppings were constructed in the Experimental Mine at Lake Lynn Laboratory near Fairchance, Fayette County, PA. They were ail--leakage tested, then subjected to a series of explosions with average pressure pulses ranging from 25 to 500 kPa (3.5 to 72 psi). Instrumentation measured seal displacement and acceleration as a function of time, providing data to assist in the development of numerical models 1'01- future seal design. All three seals designed with Meshblock wire forlnwo~-k ant1 a lnonolithic shotcrete core withstood the first explosion test, which generated an avcr-age rnaximu~n pressure of - 140 kPa (-20 psi) while maintaining acceptable air leakage rates. These seals I-anged from 175 to 325 mm thick. They included a 2.7-m-high by 325-mm-thick seal that was tesled 27 hr after completion against this - 140-kPa explosion pressure, a special requirement of the test program. This seal survived explosions with pressure pulses up to 300 kPa (43 psi). The 2.3-m-high by 325-mm-thick Meshblock seal survived three explosion tests with overpressures up to 455 kPa (66 psi) and satisfied the air leakage criteria. A I ,200-mm-thick plug seal was constructed of two Gunmesh formwork walls in-filled with shotcrete and a 3,450-kPa (500-psi) strength Aquablend core. This plug seal survived three explosions with pressure pulses ranging 11-om 150 lo 430 kPa (-22 to 62.5 psi) with no measurable postexplosion air leakage. Two Gunmesh stoppings with thicknesses 01' 40 and 75 inln withstood explosion overpressures of 23 and 115 kPa, respectively. Anchoring all seal and stopping designs into the roof, ribs, and floor with steel "rootbolts" provided very effective boundary constraint that is critical to the performanceofstructures subject to explosion overpressures.

Jan 8, 1999

By J. C. Franklin

An experiment was conducted by the U.S. Bureau of Mines and the Canada Centre for Mineral and Energy Technology (CANMET) to measure the emanation rate of radon from cemented unclassified mill tailings in two dewatered stopes of a uranium mine at Elliot Lake, Ontario, Canada. The radon was monitored upstream and downstream and in both stopes to determine the concentration in the stopes and the amount exhausted from both stopes. The emanation rate was determined to be 0.55 pCi/cm2 sec-1 from the mill tailings, which is approximately 1,000 times higher than the average flux in the mine before backfilling.

Jan 1, 1982

Improve ground control in longwall gate entries by developing a practical method for evaluating longwall pillar designs. Background Longwalls have emerged as the most important technology to be applied to underground mining since the continuous mining machine. Longwall mines currently produce more than 30 pct of all the underground coal mined in the United States, up from less than 5 pct just 15 years ago. Safe longwall mining depends on maintaining ground control in the gate entries, the lifelines that provide access to the longwall face. In multientry retreat mining as practiced in the United States, rows of chain pillars are left to protect the gate entries (see figure 1). Chain pillars are subject to severe and complex abutment loads during the process of longwall panel extraction. The design of these pillars is often the single most important element in gate entry ground control and has been the subject of intensive Bureau of Mines research.

Jan 1, 1991

By H. W. Leavenworth

Research was conducted by the Bureau of Mines to develop a technique to grow metallic fibers from a sulfide mineral. In this research, chalcopyrite (CuFeS2) was made sulfur deficient, and the remaining sulfur partitioned to the iron in the mineral to liberate metallic copper, or to the copper to liberate metallic iron. The metals formed on the surface as fibers and in the interior as spherical particles. Fiber growth is very fast. Lengths of 3 to 4 cm form in a matter of minutes, and the diameter of individual fibers is less than 1 µm. The mechanism of fiber growth is explained, and the reactions are reversible as predicted. Copper fibers can be made to grow from the surface at 400° C or to dissolve back onto the solid surface and be replaced by iron fibers at 625° C. Growth and dissolution can also be controlled to form copper/iron duplex fibers.

Jan 1, 1974

By R. B. Tippin

Research investigations conducted on five ore samples show the applicability of heavy liquid separation (HLS) techniques to mineral processing. Under proper operating conditions, semicontinuous tests in small fluid cyclones yielded 90 percent sink-float concentrates with recoveries exceeding 90 percent on minus 35-mesh ore samples of kyanite, potash, spodumene, fluorspar, and beryl. Although none of the ores were examined in detail, their response to this novel concentration method provides basic examples that are typical of the process. Various aspects of cyclone design and operational characteristics of heavy liquid cyclone circuits were studied which demonstrated the flexibility of HLS by using multiple units connected in series. A comparison of two heavy liquid solutions, tetrabromoethane and methylene bromide, exhibited their individual advantages and limitations. Unique problems relative to this process are discussed including liquid viscosity, mineral composition of the ore, toxicity, and material handling hazards.

Jan 1, 1968

By G. M. Molinda, J. P. Ulery

Since 1970, abnormally high methane emissions have been observed in eastern sections of the Federal No. 2 Mine operating in the Pittsburgh Coalbed in northern West Virginia. The nature and volume of these emissions indicate a source other than the coalbed. An investigation was undertaken to delineate probable methane sources. Gas well information and stratigraphic correlation of corehole data indicates that a sandstone directly above the main coalbed is an additional source of methane emissions. The sandstone body appears to be an ancient stream channel, infilled with fine-grained sand and organic matter. Coalification of the organic matter produced methane as a byproduct. Additional methane presumably migrated into the sandstone unit from the subjacent coalbeds. The methane became trapped in the porous clasticunit by the surrounding impermeable strata. Mine development near this unit creates a significant pressure gradient, triggering abnormal methane emissions into the mine along naturally occurring fractures. Pre-development methane drainage of the sandstone could be accomplished by completing vertical boreholes along its trend.

Jan 1, 1984

By H. B. Brunot, L. C. IlsLey

The chief object of the Electrical Section of the United States Bureau of Mines is the study of causes and means of preventing accidents resulting from the use of electricity in mines . A large part of this work for the last 20 years has been the inspection and testing of mining equipment under the provisions of schedules which give the minimum requirements considered essential for the safety of equipment intended for use at or near the working faces of dusty or gassy mines . During the first few years of this work , particular attention was paid to the explosionproof features of the various accessories such as motors , controllers , and other parts . The knowledge of the essentials necessary for safe designs of enclosures has since been augmented by field experience and by data obtained in testing a large number and variety of designs . With our present knowledge it would seem that a disproportionate stress was placed on making the various enclosures explosionproof , but not enough thought was given to the danger from wiring and connections outside of explosionproof enclosures . The list of equipment that has met minimum requirements for safety and has been approved as permissible by the Bureau of Mines includes storage - battery locomotives , power trucks , drills , loading machines , conveyors , cutting machines , room hoists , pumps , concrete mixers , and rock-dusting machines . The wiring on some of the machines is comparatively simple and sometimes , except for the trailing cable , may be entirely within the explosionproof enclosures . In general , there is outside wiring between enclosures , and on the larger machines the wiring may be extensive and complicated . In considering the safety of wiring for mining machinery , attention must be given the severe service and unfavorable surroundings imposed by mining conditions . Some of the matters that require consideration are : ground . The lack of care of the exterior wiring to be expected in the average mine . The lack of adequate periodic inspection of the wiring . The absence of adequate facilities for satisfactory inspection and repairs under- The severe conditions of moisture , dirt , mechanical injury , and low voltage encountered in mining service .

Apr 1, 1931

By H. R. Shell

Variations between laboratories on the silica and alumina content of calcined kyanite led to this Bureau of Mines study of the extent and nature of the differences. In particular, Bureau scientists hoped the study would lead to correction of the causes of the dissimilarities. A sample of calcined Kenya kyanite was analyzed by seven different laboratories familiar with silicate analysis. The compiled data indicated differences originating from lack of recovery of silica after two acidic dehydrations, from high alumina caused by several factors, from loss or gain of iron during sample fusion, and from indifference regarding the accurate determination of minor constituents.

Jan 1, 1959

By F. L. Klinger

CRUDE OIL refining continued to be the foremost industry of Bahrain in 1963. This island, the largest of a group 30 kilometers off the Saudi Arabian coast, is the site of the first petroleum discovery in the Persian Gulf and in the Arabian peninsular region. The island's only oilfield was discovered in 1932; exports of crude began in 1934 and the refinery was built in 1936. Although its crude oil has been less than 1 percent of annual Middle East output in recent years, Bahrain has been an important refining center for many years, processing a substantial portion of Saudi Arabian petroleum as well as all local production. The Bahrain refinery annually accounts for 17 percent 0 the petroleum products produced in the Middle East and 25 percent of the exports. Bahrain's mineral resources consist of oil, gas, and basic construction materials. Petroleum production and refining are the important mineral industries and contribute most of the national income by payments for taxes, wages, and local services including construction and material supply. The petroleum industry has supported a large share of local business and extensive indirect employment, and its early establishment also helped Bahrain to strengthen its position as a trading center in the Persian Gulf. The country's entrepôt trade produces about 20 percent of Government revenue, and Bahrain is somewhat less dependent on the petroleum industry than are the neighboring States to the west.

Jan 1, 1964

By D. B. Starkey

Investigation into the expressions of the field produced by a loop over a conducting half space or in an infinite conducting half space are well documented. Reasonably complex descriptions of the effects of stratification also are reported. However, a model which must contain all of these complexities because of transmission to depths of 15,000 feet and also include the pertibation of the field by a verticle cylindrical steel casing loses its facility in the field or for quick, accurate approximation to field magnitudes and phase. This paper describes the results of two field tests to determine the attenuation and phase versus depth and frequency of an electromagnetic wave (induction field). A simple two-layer model is postulated to predict the magnitude and phase of the induced field which does not require sophisticated computing tools. Correlation of the model with experimental results show agreement of most amplitude measurements to within 3 db and most phase measurements to within five degrees. The tests were conducted in a 7400 foot deep well in Nevada and an 11,000 foot deep well in Wyoming which had conductivities ranging from .0025 mhos/m to .25 mhos/m. The surface transmitting dipole had an area of ~ 10 6 feet squared and constant frequency signals of 1.5 Hz to 20 Hz were transmitted through the earth utilizing less than 65 watts of power. Model Description The magnetic field intensity components generated by a magnetic dipole immersed in an infinite homogeneous medium can be expressed in spherical coordinates as: [ ] where N, I, and (p a ) are the transmitting antenna turns, current, and effective area, respectively, and r is the range from the loops circumference to the measurement point. The case of interest for these experiments, however, is the special case of coaxial dipoles, i.e., ? = 180° . For this case H?= 0 and H reduces to: [ ]

Jan 1, 1973

Provide reliable, early-warning fire detection instruments, telemetry, and control systems for noncoal underground mines. Approach Industrial-grade fire detection instruments and signal telemetry equipment were modified for long-term exposure to harsh underground mine conditions, then were installed in four mines to evaluate long-term performance and reliability. How It Works The elapsed time between the onset of a fire and its detection is critical because fires tend to grow in size and intensity with time. Early fire detection and warning permit the initiation of a mine's emergency plan (evacuation, fire fighting, etc.) while the fire is still small, or ideally, while it is still in the incipient stage. Fire detection and warning systems, utilizing sensitive heat, flame, smoke, and gas analyzers, provide the most rapid and reliable indication of a developing fire.

Jan 1, 1987

By R. V. Ramani, V. T. Burgos, J. A. McClay

Cost Data Library The data retained in the Cost Data Library is of a semi¬permanent nature in that it is held in storage for immediate use with the program although its contents may require periodic evaluation to maintain it in a current status. The library is composed of six arrays containing both technical and cost data. The following description of the library input system provides the information necessary to maintain an active storage file. Array POWERA: FORMAT (8F10.0) - contains the step groupings of the power rate schedule for power cost computations. Four input data cards are required to fill this storage area. Card Column 1 1 - 10 Demand in Kilowatts for the First Step of the Demand Rate Schedule 11 - 20 Demand in Kilowatts for the Second Step of the Demand Rate Schedule y 41 - 50 Demand in Kilowatts for Fifth Step of the Demand Rate Schedule 51 - 60 Maximum Demand Level for this Rate Schedule 61 - 70 Percent Power Factor for this Rate Schedule 71 - 80 Unassigned 2 1 - 10 First Step Demand Charge, $/Kw 11 - 20 Second Step Demand Charge, $/Kw 4¬ 41 - 50 Fifth Step Demand Charge, $/Kw

Jan 1, 1975

By Lewis C. Karrick

This paper is based on data obtained in the course of the oil - shale investigations of the U. S. Bureau of Mines , conducted in cooperation with the State of Utah . The amount and quality of oil that can be produced from any shale may be made to vary to an important degree by changing the temperature relations existing in the shale charge during destructive distillation . The rate at which the oil is formed from the shale is affected by the rate of heat supply , and therefore by the temperature of the shale during its thermal de composition . The quality of the oil formed may be controlled by altering the temperature of the shale , and therefore , the rate of formation of the oil . Variations in the yield and quality of shale oils may be caused by inherent properties of the retort used , but in any event the properties of the crude oil and yield are very largely the result of the extent to which the thermal de composition has progressed . Recognition of these principles will aid in explaining to a large degree the reasons for the wide variations in oils produced from the same shales by different " processes " . These principles also may be applied in the operation of different types of retorts in order that crude oils of a type most profitable to the operator may be produced . The Bureau of Mines has conducted an extended series of tests in the dee structive distillation of oil shales , in order to determine the wide variations that may be effected in the quality and yield of shale oil by changing the rate and temperature at which the oil is formed . These tests furnished interesting information on the four related points : yield of oil , quality of oil , temperatures required to distill shales , and time required for distillation .

Mar 1, 1923

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

7. Hoisting Systems Hoists used solely for emergency escape use should above all, be simple and dependable. The hoist systems' motive power should be independent of all other mine equipment so that only an emergency in the immediate vicinity of the hoist will render it inoperative. The hoist should receive the same high level of inspection as is normal with any other man hoisting system. It should be operated at regular intervals, and must include sufficient safety devices to ensure safe operation when hoisting men. Of equal importance, however, safety devices must be included to safeguard the hoist system from in¬advertant damage due to inspection, maintenance or operator error In an emergency situation the hoist operator will be under considerable stress and the system must be simple and foolproof to operate. Under normal circumstances the hoist will only be operated during the regular inspection cycle. Because of this very low operational use rate, certain requirements, normally associated with man hoisting, can be relaxed. In particular the wire rope installation requirements, in terms of drum and sheave diameter and fleet angles, can be reduced provided that rope inspection during the system life is maintained at a high level. The following section includes recommended guidelines for emergency hoist system design, installation, operation, maintenance and inspection A summary of available hoisting equipment and components is included in Appendix C. Emergency Hoist Guidelines All hoists designated as part of a mine emergency escape system shall meet the requirements of the Emergency Hoist Guidelines. Where these hoists are also utilized for hoisting other than emergency hoisting, the requirements of Title 30, Code of

Jan 1, 1976

By W. G. Bradley

THIS PAPER describing the quarrying, mining, and crushing of gypsum at the Blue Diamond mine, 11 miles from Arden, Nev., on the Union Pacific Railway, is one of a series on gypsum mining being prepared for and published by the Bureau of Mines. These papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating expenditures only and not total costs. It is recognized that publication of total production costs might in some instances cause embarrassment to individual producers as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue.

Jan 1, 1932

By Philip B. Lorenz

A Bureau of Mines feasibility study on the use of tracer pulses to assess the degree of fracturing in an underground formation consisted of three phases: 1. A laboratory study on sand packs and open tubes, which developed a correlation between dispersion of the pulse and size of the flow channels. 2. A test on a retort, 11 feet in diameter and 45 feet high, packed with shale rubble. Void volume was measured, but evaluation of channel size was not possible because of interference from the space unoccupied by the matrix. 3. A field test on an explosively fractured shale formation. Pressure, flow, and transit time led to qualitative estimates of fracture pattern, but quantitative detection of dispersion in the formation was overwhelmed by dispersion effects in the well.

Jan 1, 1973

By Lloyd A. Morley, Robert Stefanko

1. Anonymous (Berggewerkshaftliche Versuchsstrecke), "75 Jahre Berggewerkshaftliche Versuchsstrecke, 1894-1969," 1969. 2. Anonymous, British Symposium on Flameproofing and Intrinsic Safety, IEEE Conf. Report Series No. 3, 1962. 3. Anonymous (Ministry of Fuel and Power), "A Review of Electrical Research and Testing with Regard to Flame-Proof Enclosure and Intrinsic Safety of Electrical Apparatus and Circuits," 1943. 4. Australian Standard Specification, ASC-98, "Electrical Equipment for Explosive Atmospheres," 1970. 5. Belgium Standard Specification, Norme NBM 286, "concernant la protection par enveloppe antideflagrante," 1965. 6. Bossert, J.A., "Approval for Electrical Equipment for Hazard Locations," paper PCI 66-33, IEEE 16th Annual Petrol. and Chem. Ind. Conf., L. A., California, Sept. 15-17, 1969. 7. Bossert, J.A., "Intrinsic Safety in Canada," Electrical Safety Practices, ISA Monogram, vn. 112, 1969. ,8. British Standards, BS229, "Flameproof Enclosure of Electrical Apparatus," 1957. 9. British Standards, BS4683 Part 1, "Classification of Maximum Surface Temperatures," 1971. 10. British Standards, BS4683 Part 2, "The Construction and Testing of Flameproof Enclosures of Electrical Apparatus," 1971. 11. Brown, G.R., and Silver, S., "An Explosion Hazard Due to Inflam¬mation of Aluminum Particles in Flat Flanges of Flameproof Enclosures," CEAL No. 197, Canadian Explosive Atmospheres Labor¬atory, 1969. 12. Campbell, J.D., and Chudleigh, J.P., "Problems Encountered in Designing Electrical Systems for Hazardous Areas," paper PCI-69¬31, IEEE 16th Annual Petrol. and Chem. Ind. Conf., L. A., California, Sept. 15-17, 1969. 13. Canadian Standards Association, C22.2 No. 30, "Explosion-Proof Enclosures for Use in Class I Hazardous Locations." 14. Dainty, E.D., and Brown, G.R., "Explosion Gas Temperatures at the Entrance to Flanges of Enclosures Containing 8.5% Methane-Air Mixtures," CEAL No. 196, 1969.

Jan 1, 1974

By J. W. Eckerd

Metal production rates of 42 to 45 tons per day were obtained with hollow-core anthracite briquets in an experimental blast furnace. Tuyere pressures were about the same for both coke and briquet operations, but from 150 to 175 pounds more of briquets were required per ton of metal than were needed with coke. Furnace operations were comparatively smooth, furnace hanging occurring less often than in previous tests with anthracite briquets. Dust production was substantially higher than with coke, however, and metal quality could not be controlled by corrective burdening and moisture control.

Jan 1, 1968

Treat contaminated coal mine drainage to meet EPA and State water quality requirements. Approach A model (fig. 1) is presented for selecting, designing, and sizing one or several passive mine drainage treatment systems that can be used in remediation of abandoned mine lands (AML). The three principal types of passive mine drainage technologies for the treatment of coal mine drainage are an aerobic system, a compost wetland, and an anoxic limestone drain. The multistep approach presented here provides a simplified method to characterize the type and magnitude of the water quality problem and then to select either a single treatment system or a combination of treatment systems to address the specific site situation. How It Works Step 1. Discharge Characterization. Characterization of the discharge consists of measuring the discharge flow rate and collecting water samples at the point of discharge for chemical analysis. Both the flow rate and chemistry of a discharge can vary seasonally and in response to storm events. It is important to account for this variability by determining flow rates and water chemistry under various conditions.

Jan 1, 1992