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Table 1.-Salient aluminum statistics (Thousand short tons and thousand dollars) [ ]

Jan 1, 1967

To investigate mine ventilation problems which do not lend themselves to conventional anemometer and smoke study techniques by use of SF6 (sulfur hexafluoride) tracer gas. Approach SF6 tracer gas is released in-to the air at a given mine location. By collecting air samples at various other locations and analyzing these samples for SF6, the amount of air traveling from the release location to each sampling location can be quantitatively determined. Travel time between these locations can also be deter-mined. How It Works SF6 is ideal as a mine tracer gas. It is safe, odorless, chemically and thermally stable, and it generally has no background concentration. Furthermore, it is instrument detectable at concentrations as low as 10 parts per trillion. The SF6 is generally released from a pressurized lecture bottle, and air samples are taken in syringes or evacuated bottles. During the past several years, SF6 tracer gas has been employed to study a wide variety of mine ventilation problems such as: recirculation of return air into In-take airways, air leakage from adjacent mines and gob areas, air transit times through stoped areas, airflow patterns during a mine fire, leakage of gases from an underground oil shale retort into mine workings, face area ventilation patterns, methane flows in metal/nonmetal mines following a methane out-burst, and many other problem areas. Examples of some recent uses of SF6 follow.

Jan 1, 1982

During the summer of 1973 we were asked to perform a theoretical investigation of the propagation of low frequency (LF) radio waves down deep (10,000 feet) hoistshafts* for the case where the hoist cable ("rope") is the only metal conductor present. Propagation is by means of the TEM coaxial mode of transmission in which the hoist cable serves as the inner conductor and the surrounding rock acts as the outer conductor. Since the rock is a relatively poor electrical conductor the current in the outer conductor of the coaxial line is not confined to a very thin surface layer as in a metal coaxial cable, but spreads radially to a distance that is generally many times the shaft diameter. This feature of the wave propagation requires a more sophisticated theoretical treatment than the approximate skin-depth theory that is adequate for metal coaxial lines. In this Part we treat the hoist shaft wave propagation loss, characteristic impedance, and the field current distributions in the surrounding rock medium. We also show that the large penetration of the wave into the rock outer conductor does not present a difficult problem with regard to coupling the transmitter or receiver to the transmission line with a minimum of insertion loss, but that the large impedance mismatch caused by the capacitance termination between the cage and shaft wall may well be the most significant contribution to overall system loss. Inductive coupling and impedance matching to the hoist rope/shaft transmission line are also treated briefly. Preliminary results indicate that a broad minimum in overall system loss should occur between 100 kHz and 1 MHz, possibly centered around 300 kHz. Further work is needed to better quantify this signal loss behavior, compare it with hoist shaft electromagnetic noise spectral data recently acquired by NBS, and identify the most favorable operating frequencies.

Jan 1, 1974

By J. W. Paul

Withdrawing timber in coal mines is done for the purpose of inducing the roof to cave in the mined-out areas and thereby relieve stresses in the immediate roof material over the working places adjacent to the breakline of the roof, thus preventing the crushing of the ends of pillars and adding to the safety of those engaged in pillar extraction. A secondary purpose is the recovery of timber for further use either as prop-, crossbars, lagging, sprags or cap pieces. At some mines timber is withdrawn as a precaution against fire which may he of spontaneous origin, because wood always aids a fire of any origin. With some of the power-driven types of machines now in use a greater proportion of mine timber may be recovered, and in mines where pillars are left too narrow for their removal some of the timber in rooms might be salvaged for further use.

Jan 1, 1933

By Robert C. Steckley

The Bureau of Mines performed a fragmentation experiment in cooperation with Duval Corporation in a porphyry copper-molybdenum deposit near the Sierrita pit south of Tucson, Ariz. This experiment evaluated the fragmentation created in a 10-hole test blast having blasthole spacings of 25, 20, and 15 feet. The 10 blastholes were 9 inches in diameter and contained a total of 17,400 pounds of aluminized slurry blasting agent in 50-foot columns with 60 feet of stemming. Diamond drill core examination was the primary method used to determine the condition of the rock before and after blasting. These core examinations included study of length recovery, rock quality designation (RQD), weight recovery, and size distribution. Topographic surveys were used to measure the rock swell produced by the blast and a fragment size distribution was obtained for the broken material on the surface. Fragmentation to depths of 110 feet was excellent from the 15-to 20-foot blasthole spacing patterns. Good breakage was also produced by the 25-foot pattern although the effects of the blast were not so obvious. In situ leaching tests were not conducted. However, based only on size consideration, all three blasting patterns produced adequate breakage for successful leaching.

Jan 1, 1975

By J. S. Dunning

A primary goal of the Federal Bureau of Mines is to minimize the requirements for scarce mineral commodities through conservation and substitution of more abundant elements, such as iron and molybdenum. One example of this is the research effort to devise substitute materials for specialty alloys, thereby conserving nickel and chromium in high-volume stainless steels. As a possible substitute for the solid solution strengthening of chromium and nickel, the precipitation hardening characteristics of a number of binary iron-based systems in which Laves phase precipitates, such as Fe2Mo, are formed were investigated. Several hardening responses were observed, but none were ideal. The Fe-Ta binary system had the highest magnitude of hardening, even with low alloy additions, and the Fe-Mo system had unique stability at temperature. Accordingly, the Fe-Mo-Ta system was selected for study to determine if a ternary Laves phase could combine high hardening with long-term stability at elevated temperature. Hardening and stability were reflected in excellent elevated temperature, tensile, and stress rupture strengths. Future research will study ternary systems based on more abundant resource materials, such as the Fe-Mo-Ti system, together with additions, such as aluminum and minimal chromium, to provide oxidation resistance.

Jan 1, 1979

By D. Bienstock

A rig was constructed to burn 100 to 125 lb of coal per hour at 4,000° F in a cyclone burner with oxygen-enriched air preheated to 1,500° F to ascertain the problems in the coal-fired MHD generation of power. Potassium carbonate was added to the coal at several concentrations up to 1.23 g-moles/kg of coal (17 lb K2C03/100 lb coal). Boiler-tube materials maintained at wall temperatures of 800° to 1,500° F were exposed to the combustion effluent of 1,800° to 2,500° F. Practically complete removal of sulfur dioxide from the stack gas was achieved with the seed addition. Nitric oxide formation followed theoretical expectations at combustion temperatures with some decomposition of the NO occurring as the gas cooled flowing through the system. Nitrates in the fly ash were less than 1.7 percent of the total fixed nitrogen. With aqueous extraction of the fly ash a maximum recovery of 75 percent of the potassium was obtained. Haynes 25 was unattacked at a wall temperature of 1,500° F in combustion gas at 2,500° F; the stainless steels 310, 316, and 446 were resist-ant at a metal temperature of 1,100° F in gas at 2,100° F.

Jan 1, 1970

By David C. Byrne

PURPOSE: Evaluate practical technological advances in level-dependent hearing protectors and inexpensive personal acoustic monitors. RESEARCH SUMMARY: The results of previous NIOSH research show that miners develop hearing loss much more quickly than nonoccupationally noise-exposed individuals and that miners experience a greater severity of hearing loss than would be expected for nonoccupational noise-exposed persons of the same age and gender. Using hearing thresholds at 4,000 Hz as an indicator, coal miners experience hearing loss 2.5 to 3 times greater than would be expected for persons not exposed to occupational noise. At age 50, 90% of coal miners and 49% of metal/nonmetal miners were found to have a hearing impairment. In comparison, only 9% of a nonoccupationally exposed control group had a hearing impairment at age 50. There are numerous barriers to the prevention of hearing loss among miners. In an effort to overcome some of these obstacles, this work was initiated to evaluate practical technological advances in level-dependent hearing protectors and inexpensive personal acoustic monitors. Experiments will involve analysis of this new technology under both laboratory and field conditions. Laboratory components will consist of controlled studies using an anthropometrically correct test fixture as well as human subjects to evaluate the adequacy/effectiveness of various hearing protective devices. Electroacoustical performance testing of new noise monitors will also be conducted in a laboratory setting. Subsequent field studies will determine the actual usefulness and practicality of the personal protective/monitoring equipment as used in different mining situations. It is anticipated that increased on-the-spot awareness of hazardous noise levels and the availability of better-suited hearing protectors will provide a degree of protection beyond what is currently attained in different mining environments. Therefore, the intent of this project is to identify and adapt new acoustical technologies and products that have a direct application to individual mine workers. With increased knowledge of these technological advances, a greater demand for similar devices will likely occur, which, in turn, will lead to a better understanding and awareness of hearing loss prevention methods throughout the mining community. The ultimate goal is for widespread integration of useful hearing loss prevention products and devices into the daily routines of miners

Jan 2, 2000

By d&apos, Kathleen J. Amico

THIS SUAMMARY is shown in Minerals Yearbook volumes I and III of this series on mineral production in the United States, its island possessions, the Canal Zone, and the Commonwealth of Puerto Rico, and on the principal minerals imported into and ex- ported from the United States. The several commodity and area chapters contain further details on production. A summary table comparing world and U.S. mineral production also is included. Mineral production may be measured at any of several stages of extraction and processing. The stage of measurement used in the chapter is normally what is termed "mine output." It usually refers to minerals in the form in which they are first extracted from the ground, but customarily includes for some minerals the product of auxiliary processing operations at or near mines.

Jan 1, 1962

By William J. Wuest

The technical analysis of parameters that can influence roof and rib reinforcement is important to the operation of safe and profitable underground mines. One such parameter, studied in this U.S. Bureau of Mines investigation, is the effect of time on untensioned, resin-grouted bolt anchorage characteristics. A group of seventy-three 4-ft-long bolts with three different grout column lengths were I installed in a stable coal mine roof. The bolts were then subjected to standardized pull tests at various intervals throughout a 37-month period. For each test, load-deformation data were reduced to determine axial stiffness and yield point. The magnitudes of these two anchorage characteristics at the time of installation were compared with results from subsequent pull tests to determine if anchorage capacity deteriorated. Bolts with 18-in grout columns were studied over 9 months, and no measurable loss occurred. Bolts with 48-and 24-in grout columns were studied over 37 months and also exhibited no measurable loss.

Jan 1, 2010

By R. V. Ramani, J. Qin

"In this paper, the results of a research study on airborne dust transport in a full scale simulated longwall face are presented. The simulated longwall face was set up in the Lake Lynn Laboratory mine of the U.S. Bureau of Mines to conduct experiments under controlled conditions. The controlled parameters in the experiments were the dust dispersion rate, dust size distribution, density of the dust, air velocity, and the rate of travel of the dust generating source. The analyses of the experimental results on mass concentrations, particle size distributions, and real-time respirable dust concentrations are discussed. There are definite spatio-temporal trends between the location of the shearer, the concentration at any location in the face, and the dust generation rates. The size-consist and density characteristics of the source dust, the air velocity in the face, and the air leakage into the gobs all affect the concentration. INTRODUCTIONA detailed experimental study on the characteristics of longwall dust cloud in operating longwall faces has been reported by Ramani, Qin, and Jankowski (1991). The study indicated that there are several important factors whose effects on dust transport in longwall faces need to be further investigated. In an operating longwall face, the effect of these parameters could not be easily isolated as control over the affecting parameters is not readily possible. In a simulated longwall face, however, these parameters can be controlled. Therefore, as a follow-up to the field study, a series of controlled experiments were conducted in a full scale simulated longwall face in the Lake Lynn Laboratory mine of the U.S. Bureau of Mines [Qin, 1992]. Specific aspects which were addressed during the experimental design phase included determining the types of samples to be collected, selecting proper instruments to collect these samples, and developing detailed sampling and time-study plans to correlate the dust concentrations with face activities. Two types of dust--anthracite and bituminous--were used. Dust dispersion rate into the air as well as the source dust particle size distribution were documented. Control was exercised over both air velocity at the face and air leakage along the longwall face. During experiments, the dust source was moved to simulate the shearer movement at operating longwall faces. Detailed descriptions of the design of experiments, experimental results, and data analyses follow in the subsequent sections."

Dec 1, 1996

By J. H. Weber

This Bureau of Mines publication describes the hardware system and software package for the semiautomatic acquisition and automatic processing of high-resolution mass spectrographic plates. The semiautomatic data acquisition allows a tenfold saving of time compared with manual data acquisition. Automatic processing of the high-resolution data to yield exact masses, intensity, and the corresponding empirical formulas is accomplished by efficient programming on a small, inexpensive, programmable calculator system.

Jan 1, 1974

By R. W. Dalzell

The performance characteristics, efficiency, and operating pressure of jute line-brattice systems were studied under varying underground conditions; various fabric grades and installation methods were used. The test results indicate that line-brattice system efficiency is dependent upon the method of ventilation the method of installation, porosity of fabric, and size of tight rib area.

Jan 1, 1966

By R. Craig Smith

The Bureau of Mines conducted a study of production costs for the secondary lead industry and determined costs for present, pending, and proposed environmental legislation. Operating costs for smelters by capacity groups range from 16.8 to 19.6 ¢!lb of refined lead. Present regulatory compliance costs for these groups range from 2.2 to 2.4 ¢!lb. Pending compliance costs could add 3.5 ¢!lb of refined lead, and proposed regulations could add another 1.3 ¢!lb. The individual capital costs necessary to comply with pending environmental regulations are estimated to be $1.8 million for small smelters and $10.4 million for large smelters. Proposed regulations could require additional expenditures from $1.9 million for small smelters to $4.9 million for large smelters. These cost estimates, based on average 1985 dollars, indicate that pending and proposed legislation could add significantly to capital and operating costs of the secondary lead industry. These regulatory compliance costs may result in a loss of up to 40 pet of secondary lead production capacity.

Jan 1, 1987

By Carl Rampacek

Recent research by the Bureau of Mines has demonstrated that the segregation process has merit for treating oxidized and mixed oxide-sulfide copper ores. The process comprises heating the crushed ore with salt and coke or other carbonaceous materials at about 700° C. to produce fine flake copper, which then is recovered by conventional copper-flotation methods. Bench-scale laboratory tests of a number of oxidized and mixed copper ores assaying 0.78 to 5 percent Cu gave copper recoveries of 73 to 96 percent. The flotation concentrates assayed 21 to 76 percent Cu, depending on the ore being treated.

Jan 1, 1959

By Seth C. Schaefer

As part of the Bureau of Mines, U.S. Department of the Interior, effort to provide thermodynamic data for the advancement of minerals technology, the Gibbs energy of formation of sphalerite (zinc sulfide) was investigated with a high-temperature galvanic cell employing stabilized zirconia as the electrolyte. In the temperature range 948 to 1,210 K, potential measurements were obtained for the cell Pt, ZnS + ZnO, S02 = 1 atm // Zr02 // Cu20 + Cu, Pt, with the overall cell reaction ZnS(c) + 3 Cu20(c) = ZnO(c) + 6 Cu(c) + S02(g). (1) These results, combined with the best available values of ?Gf° for ZnO, S02, and Cu20 from the literature, give the Gibbs energy of formation of zinc sulfide for the reaction Zn(l,v) + 1/2 S2(g) = ZnS© (2) ?Gf° = -64.223 + 24.02 X 10-3T ± 0.650 kcal/mole (3) (948-1,180 K; standard states - pure liquid zinc and S2 gas at 1 atm), and ?Gf° = -92.720 + 48.17 X 10-3 ± 0.650 kcal/mole (1,180-1,210 K; standard states - pure zinc vapor and S2 gas at 1 atm). A third law analysis yields for the formation reaction Zn(1) + 1/2 S2(g) = ZnS(c), (5) a standard enthalpy of formation as follows: ?Hf298.15 = -63.64 ± 0.700 kcal/mole.

Jan 1, 1978

By Oliver Bowles

From remote antiquity stone has been employed for structural, ornamental, and memorial purposes. It was, and still is, so used because of its availability in innumerable localities and its architectural adaptability, dignity, substantiality, and durability. The principal varieties of stone used are granite, marble, limestone, sandstone, and slate. This report deals with granite. OCCURRENCE AND CHARACTER OF GRANITE Granites usually have been classed as igneous rocks derived from molten masses or magmas, but there is wide evidence that the origin of some granites may be attributed to regional metamorphism of preexisting rocks, rearrangement and recrystallization taking place without a liquid or molten stage. In any event granitization is a slow, deep-seated process.

Jan 1, 1956

By D. S. Kimmel

The Bureau of Mines sponsored development of a system to remotely energize and de-energize the trolley wire in a section in response to demands from vehicles as they enter and leave the controlled section. The system developed utilizes a detector/actuator that controls a dc contactor at the outby end, and a 3 kHz oscillator at the inby end. A prototype system has been built and installed at the Bureau's trolley test site at Bruceton, Pennsylvania which has demonstrated the ability to also provide load discrimination for faults of 300 amperes or more. The system could readily be modified by locating the oscillator on the vehicle to provide automatic de-energizing of the trolley wire when the vehicle's pole is removed or the vehicle leaves the section.

Jan 1, 1978

By Michael D. Fenton

Detailed comprehensive assessment of the performance of Afghanistan's mineral industry during 1987 is virtually impossible, owing to the paucity of reliable published information. It was evident, however, that the level of civil disorder, now in its eighth year since the arrival of significant numbers of Soviet troops, was in actuality little removed from open civil war. Insurgents controlled substantial areas of the country and imperiled any industrial activity in many places. Assistance programs by the U.S.S.R. and other Eastern European nations were directed at developing the country's meager mineral industry, but the economy was generally viewed as chaotic. The inflation rate was somewhere between 20% and 30%; major food shortages contributed to the discontent of the population, and numerous villages were devastated by Soviet and Afghan Government campaigns to destroy the insurgents and cut their supply routes. Moreover, proposals by the Soviets and the Kabul Government aimed at reducing tensions with the rebels and scaling down the warfare seemingly were taken by the opposition as signs of weakening by the Soviet-backed Government, and rather than reducing aggressions, seemed to heighten insurrectionist activities. Efforts to entice the substantial number of Afghans who have fled to nearby areas of Pakistan and Iran to return to their country seemingly were failures, and indications near yearend that the Soviet Union might soon begin withdrawal of its occupation force of nearly 120,000 did little if any to reduce disorder.

Jan 1, 1989

By H. D. Jacobs

The Bureau of Mines developed a concentration method to upgrade and utilize marginal natural or direct-shipping iron ores and fine-grained lean iron ores. Presently these ores receive little beneficiation and accordingly have low iron-silica (Fe-Si02) ratios. Ore samples were roasted with equal weights of solid reductant at 1,100° C for 1 hour to metallize the iron and for an additional hour at 1,200° C to promote grain growth. Concentration was effected by crushing and screening techniques and/or wet magnetic separation. Sized concentrates (minus 4 plus 35 mesh) derived from crushing-screening processes contained from 80 to 85 percent iron that was 90 percent metallized. Iron-silica ratios as high as 12:1 and iron recoveries from 75 to 94 percent were obtained. The sized concentrates were judged suitable for use as blast furnace feed. Minus 200-mesh metallized concentrates derived from roasted minus I-inch plus 8-mesh ore fractions and magnetically concentrated contained 90 percent Fe and 4 percent or less Si02, chemically qualifying them as feed for electric furnaces. Roasting minus 8-mesh ore with hydrogen, then magnetically concentrating it, produced iron concentrates containing 57 percent to 67 percent Fe and 3.6 percent to 8.4 percent Si02. The concentrates having Fe-Si02 ratios ranging from 8:1 to 12:1 were considered adequate for use as blast furnace feed. Overall iron recoveries for the 12 ores tested ranged from 56 percent to 94 percent with an average iron recovery of 86 percent.

Jan 1, 1969