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By Charles L. Kimbell

For a study such as this, which summarizes and amalgamates much information collected, compiled, and utilized by the numerous U.S. Bureau of Mines country specialists and branch chiefs for inclusion in their country and regional reports that comprise the five other volumes of the international studies of the Minerals Yearbook, it is clearly impossible to cite all sources of information used in its presentation, but some recognition seems due. Generally speaking, this study and its related detailed studies on countries and areas would be much more difficult, if not impossible, without the efforts of the personnel of our counterpart agencies throughout the world. Information they collect, compile, and then publish, either in their own volumes or those of central statistical agencies in their countries, are the foundations on which this work rests. Thus, we must begin by expressing our appreciation to the multitude of persons employed by these agencies for their contributions.

Jan 1, 1993

By Christopher Mark

Roof bolt system design means the selection of the type, length, capacity, and pattern of bolts for a particular application. Despite research efforts dating back 50 years, no design methodology has found wide acceptance. This paper begins by identifying four mechanisms that roof bolts use to reinforce the ground. It argues that the reinforcement mechanism is determined by the roof geology and stress level, not by the type of bolt. Next, the attributes of roof bolts are discussed in the light of recent research, including anchorage mechanism, installed tension, length, capacity, timing of installation, and installation quality. Several significant areas of controversy are identified. Design methods from around the world are discussed, including those based on empirical research, numerical modeling, and roof monitoring. Finally, some simple guidelines for preliminary design of roof bolt systems are proposed based on statistical analysis of roof support performance at 37 U.S. mines.

Jan 10, 2000

By S. J. Schatzel

In an effort to increase productivity, many longwall mining operations in the U.S. have continually increased face lengths. Unfortunately, the mining of larger panels may increase methane emissions. The National Institute for Occupational Safety and Health (NIOSH) conducted a mine safety research study to characterize and quantify the methane emissions resulting from increasing face lengths in the Pittsburgh Coal-bed. The goal of this research effort was to provide the mine operator with a method to predict the increase in methane emissions from the longer faces for incorporation of additional methane control capacity into the mine planning process, if necessary. Based on measured methane emission rates of 0.066 m3/s (140 cfm) for a 315 m (1032 ft) face, projected longwall face methane emission rates were 0.090 m3/s (191 cfm) for a 366 m (1200 ft) face, 0.106 m3/s (225 cfm) for a 426 m (1400 ft) face, and 0.124 m3/s (263 cfm) 488 m (1600 ft) face.

Jan 1, 2006

By P. A. Wasson

Drill cores from 15 holes in the West Central Mesabi Range were studied as part of the Lake Superior iron resource investigation begun in 1957 by the Bureau of Mines. Chemical, petrographic, and metallurgical analyses were made to determine grade, mineralogy, magnetic characteristics, and response to beneficiation. Data in this report were developed to provide a better under-standing of the nature and character of low-grade iron ore occurrences, to measure potential of usable ore, and to provide a basis for comparison with bank samples previously taken in the same general area. The average iron content of 4,445 feet of core was 31.8 percent. Iron oxides present were hematite, goethite, and magnetite; the gangue minerals were chiefly quartz, iron silicate, and iron-bearing carbonates.

Jan 1, 1962

By Steven J. Page, William A. Heitbrink, Andrew B. Cecala, Edward D. Thimons, John A. Organiscak

Miners at noncoal surface mining operations are often exposed to high levels of respirable dust. In an effort to lower the respirable dust exposure of these surface miners, the National Institute for Occupational Safety and Health (NIOSH) has been conducting research to address this problem in a practical and economically viable manner. One successful effort deals with lowering the dust exposure of equipment operators in enclosed cabs. Many types of surface mining equipment utilize enclosed cabs to protect equipment operators from dust exposure. Normally when the equipment is new, the cabs are fairly airtight. These tightly sealed cabs, combined with good filtration systems, generally provide the operator with good dust protection. However, most mining equipment is older, and as aging occurs, many components of the enclosure deteriorate. The structural integrity of the cab diminishes and the effectiveness of the air filtration system fails. NIOSH has been successfully researching costs-effective methods to improve both filtration effectiveness and cab integrity of these older cabs in order to provide a healthier work environment for equipment operators. Dust sampling records indicate that drill operators and helpers have the highest dust exposure of all workers at surface mining operations. Since much of the overburden contains a high percentage of silica, the health hazard associated with this dust can be even more serious. NIOSH research is addressing techniques to lower respirable dust levels at surface drilling operations. INTRODUCTION NIOSH's mission is to assure a safe and healthy work environment for the working men and women of this nation. The primary emphasis of NIOSH's Pittsburgh Research Laboratory (PRL) is mining health and safety research. This report focuses on two areas of research

California's coal resources are estimated to be 100 million tons, of which 50 percent is lignite, 40 percent subbituminous, and 10 percent bituminous. The occurrence of coal in California is rather limited and is restricted generally to the foothill regions of the western slopes of the Sierra Nevada Mountains. Significant quantities of coal have been mined in five areas: Ione in Amador County, Alberhill in Riverside County, Stone Canyon in Monterey County, CorralHollow in Alarneda County, and Mount Diablo in Contra Costa County. Most of the coal was rnined in the early 1900s and was used locally for fuel. Current mining operations are located in Amador County near the city of Ione. The two producing mines supply fuel to a mine-mouth co-generation power plant. The fuel coal is processed prior to burning to extract montan wax. Because California does not have primacy, coal mining in the state is regulated by the Office of Surface Mining's Albuquerque, New Mexico, Field Office.

Jan 1, 1992

By W. W. Simpson

During cyanidation of mercury-bearing gold-silver ores, significant amounts of mercury are extracted. The presence of mercury decreases. gold loading and increases mercury stripping time on activated carbon, complicates fire refining of the gold cathodes, and creates a potential health hazard. Addition of calcium sulfide (CaS) to the cyanide leach slurry precipitates the solubilized mercury but also some silver. The Bureau of Mines investigated silver loss during CaS precipitation of mercury. Addition of 0.1 lb CaS per short ton ore to a mercury-bearing gold-silver ore precipitated both mercury and silver. However, if copper was added with CaS, or if the ore contained copper, much of the sil-ver loss was prevented. Addition of 235 ppm Cu with 0.1 lb/st CaS, prior to carbon-in-pulp adsorption, resulted in 89-to 97-pct, 80-to 91-pct, and O-pct adsorption of the solubilized gold, silver, and mer-cury, respectively, on the activated carbon.

Jan 1, 1986

By George A. Morgan

Mineral production was confined to out-put of cement and gravel. However, exploration was being conducted by the U.S.S.R. and the United Nations Development Program. Development of a domestic limestone deposit and crude oil from an offshore oilfield was underway. Benin's currency remained fixed to the French franc. The gross domestic product (GDP) was $977 million in 1981, the latest year for which information was available. 2 COMMODITY REVIEW Cement.-Construction of a cement plant with 500,000 tons per year capacity neared completion at Pobé. The operator of the plant, using locally produced limestone, was the Societe des Ciments d'Onigbolo, a joint venture between Benin and Nigeria. Nigeria was expected to utilize most of the cement produced. Equipment for the plant included a 1,600-ton-per-day, oil-fired pre-heater.

Jan 1, 1984

By H. B. Cooke

In connection with its researches on the crude petroleums of the United States, the Bureau of Mines has made a particular study of apparatus for the distillation of hydrocarbon mixtures. While this study is still incomplete it has already resulted in the development of considerable laboratory and semi-plant equipment, motet of which has been described in various publications of the Bureau. The laboratory apparatus (Hempel distillation) and method gives satisfactory comparative results in the laboratory examination of crudes and have been found applicable to crudes of all types, but the agreement of laboratory and plant distillations is not as close as might be desired. This is due, in part, to limitations in size and construction of the laboratory apparatus. Some refiners claim that the Bureau of Mines' laboratory method (Hempel distillation3) for distilling crude petroleum, does not show the full gasoline content of the oil, while others have stated that it indicates more gasoline than can be obtained from the crude commercially. This difference of opinion among refiners results largely from the great variation in stills used and methods of operating them. The Bureau's experience has shown that crude oils from different fields vary widely in character; in fact, that it is not yet possible to classify crude's adequately on the basis of their Down chemical and physical characteristics. As a result of the differences that exist among crudes, and of the difficulty of designing refinery equipment, no standard practice has yet been adopted for the commercial distillation of petroleum, and ma" types of stills are used in the refineries of this country. Although many factors enter into the design of equipment and the development of commercial practice in refining of crude oil, there

Jan 1, 1924

By Paul R. Thimas, Edward H. Boyle

"The Bureau of Mines evaluated the long-term cost and availability of primary gold production from 135 mines and deposits worldwide. Collectively, the evaluated countries represent 93 pct of world gold production. Total recoverable gold available (as of January 1984) from a subset of 111 significant producing mines and developing deposits in 13 market economy countries (MEC's) is estimated at 810 million tr oz. The Republic of South Africa is estimated to account for 87 pct of total recoverable gold. The United States and Canada account for 4 and 4.5 pct of the total, respectively. Eighty-three percent of total recoverable gold is available at a constant 1984 break-even price of $400/tr oz, and 70 pct is available at $300/tr oz. South Africa accounts for 90 pct of the gold available at $400/tr oz or less.Major conclusions are that (1) South Africa should remain the largest world producer through the year 2000, (2) annual MEC output in 2000 should not be significantly different than current output given constant 1984 gold prices of more than $300/tr oz, and (3) there may be a significant decline in production after 2010 in the absence of major new discoveries and continued development of new mines to offset the depletion of the South African mines. INTRODUCTIONSince the late 1970's the world gold mining industry has been characterized by dynamic growth in production and volatility in price. World production in 1983 was almost 15 pct greater than in 1980, and the short-term trend continues upward. Annual dollar-based price changes since the early 1970's have been unprecedented in both magnitude and volatility. This commodity, which sold for $35/tr oz3 for over a third of a century, reached an annual average $612/tr oz in 1980. Until 1980, the future price of gold seemed set on an upward trend. Since that year, however, world gold prices have fallen by over 50 pct to slightly over $300/tr oz at the end of 1984.Against this background, this study was undertaken to determine (1) the level of world demonstrated gold resources, (2) total and annual availability of gold mine production, (3) long-run production costs per operation and by national aggregates, (4) the economic and technical factors that impact upon cost and availability, and (5) probable future mine production and cost trends."

Jan 1, 1985

By Joseph Cervik

Coal is a soft and brittle material. Drilling rates in the Pittsburgh coalbed using a drag bit exceed 3 ft/min at 2,500-pound thrust. However, maintaining the bit on a horizontal trajectory or parallel to bedding planes to attain lengths of 1,000 feet is difficult. This Bureau of Mines report presents a drill string configuration that can be guided through the coalbed. The angle of the borehole is measured periodically and by proper combinations of bit thrust and rotational speed (r/min), bit trajectory can be lifted or dropped to keep the bit in the coalbed. An example of a hole drilled to 2,126 feet is presented to show levels of thrust and rotational speed used to lift or drop the bit, the seemingly unexplainable events that occur, and the strategy used during drilling. Thrust levels during drilling range from 600 to 2,500 pounds. Hydraulic motors powered by a 30-hp, 440-volt motor provide ample power for drilling horizontal holes 2,000 feet long.

Jan 1, 1975

By G. Nuñez, M. A. Pathak, C. F. Stanley

"Holographic interferometry is a non-destructive technique to detect small deformations1 of an object. It is a whole-field technique· with an accuracy of a few microns. An adaptation of holographic interferometry is time-averaged holographic interferometry which is particularly useful in detecting small vibration amplitudes of an object under investigation. Its application to biological tissue is especially difficult due to the combination of (a) the high sensitivity of the technique, and (b) the tendency of these objects to deform excessively, or move during the testing period. (This is also compounded by the changing moisture content of the tissue surface.)Ideally, a pulsed laser and fast-acting thermoplastic film camera could be chosen to overcome these difficulties, but the total equipment cost could exceed $75,000. In this paper we describe our relatively economical method to apply time· averaged holographic interferometry to an excised animal lung, utilizing holographic plates and a mechanically-shuttered continuous-wave Argon laser.EXPERIMENTAL METHODThe schematic of the experimental setup is shown in Fig. 1. The holographic equipment, including the laser, is fixed on a 3 ft x 6 ft x 4 in. honeycomb holographic table. This table is functionally similar to one described by Mark and Horsch2 which can be constructed for about one thousand dollars. The holographic table itself rests on six inner tubes to absorb floor vibrations. All unnecessary vibrations must be reduced to preserve the quality of the holograms. A laser beam from a 0.5-watt continuous-wave Argon laser is split by a circular variable beamsplitter (Newport Corporation Model 50GOOAV.1) into two beams, i.e., an object beam and a reference beam. The object beam is again split into two beams of equal intensity by a 50150 beamsplitter (Newport ·Corporation Model BS.1). These beams are optically filtered and expanded by spatial filters (Newport Corporation Model 910) to cover as much area of the object as possible. Soft biological tissues exhibit low reflectives, resulting in a relatively high reference to object beam ratio of roughly 5 : 1 at the holographic plate."

Jan 1, 1989

By N. S. Dalal, Xianglin Shi

"INTRODUCTIONEpidemiologic studies of workers in chromate-ore related industries, 1-3 and stainless steel welding and related occupations4 have shown that they have about 20-40 times higher risk of throat or respiratory track cancer than controls. Although the actual carcinogenic substances were not identified in these statistical studies, Cr(VI) compounds (for example, calcium chromate, zinc chromate, and lead chromate) were implicated as the causative agents, whereas Cr(III) compounds were not suspected as carcinogens. s These suggestions were supporte4 by laboratory studies wherein many Cr(VI) compounds produced sarcomas at the implant or injection sites.1,5 Squamous cell carcinomas and adenocarcinomas closely resembling human lung cancer were induced by intrabronchial implants of calcium chromate in rats, 6·7 whereas Cr(DI) oxide and Cr(lll) sulfate did not induce any tumor formation.6,7While the mechanism of the chromate-induced carcinogenicity is not fully understood, it is generally thought8 that it involves some damage to DNA. Specifically, it has been reported that: a) the chromate ion, henceforth referred to as chromate, can pass through the cell membrane and enter the cell while CR(DI) does not, 9 b) chromate does not interact with either native or denatured DNA 10 while Cr(III) does, 11 and c) the final Cr-DNA complex isolated from cellular reactions of chromate is Cr(III)-DNA, with Cr(III) binding to the phosphate groups.12,13 Thus the important question is: since Cr(DI) cannot pass through the membranes, how does Cr(III)-DNA complex form? For this to happen, Cr(VI) must be reduced to its lower oxidation states, 14 ultimately to Cr(III), by some reductants in the cellular environment. Unless this reduction occurs, the DNA would not be damaged and therefore no chromate carcinogenicity would ensue. Thus the reduction of chromate to its lower oxidation states seems to be a key step in the chromate carcinogenicity .1s One of the major reductants in cellular environments is thought to be glutathione (GSH), both outside and inside the cells.16-lB Some evidence for the role of GSH in the chromate toxicity was provided by recent studies showing that exposure of hamster cells to non-toxic levels of added selemite increases the levels of GSH as well as the Cr(VI)-induced DNA strand breaks,19 and that such DNA strand breaks in hepatocytes also change in direct proportion to the GSH content. 20,21 These observations were interpreted as implying that the reduction of chromate by GSH to some reactive intennediate is an important step in the chromate carcinogenicity. 20.21 In · the present undenaking22 we have used electron spin resonance (ESR) and spin-trap methodology to investigate the reduction of chromate by GSH and find evidence for the involvement of the glutathionyl radical (GS ·) as well as Cr(V)-intermediates."

Jan 1, 1990

By Thomas M. Barczak

The success of longwall mining can largely be traced to the development of powered roof support systems. The most significant improvement in powered support design has been the shield support, which improved kinematic stability and promoted the application of longwall mining in difficult-to- control caving conditions where chock and frame supports were inadequate. The most obvious trend in shield design has been an increase in shield size and capacity. This U.S. Bureau of Mines report examines shield design and operation practices and their consequences for the utilization of high-capacity shield support systems. An optimization goal is to minimize support loading by selecting an active shield setting force that is compatible with strata behavior and shield loading characteristics. Shield stiffness is an important design parameter that is often overlooked. A consequence of increasing shield capacity by incorporating larger diameter leg cylinders is a proportional increase in shield stiffness. Setting forces have also increased in direct proportion to the increase in shield capacity. The increased stiffness and higher setting force cause the available capacity to be consumed more quickly, severely limiting the ability of high-capacity supports to last longer and provide reserve capacity for difficult mining conditions.

Jan 1, 1992

By T. Ruff

Researchers at the National Institute for Occupational Safety and Health, Spokane Research Laboratory, studied technology and methods that could reduce accidents involving surface mining equipment that collides with other vehicles or workers, or drives over an unseen road edge. These accidents are partially attributed to the lack of full visibility around these large pieces of equipment. Blind areas can be extensive and this report presents plots of blind areas for five pieces of surface mining equipment. Several technologies designed for detecting obstacles in blind areas and providing a warning to the operator were evaluated on off-highway dump trucks. These proximity warning systems included radar, sonar, GPS, radio transceiver tags, and combinations of radar and cameras. A summary of test results is presented in this report, along with guidance on effective proximity warning technology, installation and maintenance considerations, and recommendations for effective implementation. This study found several commercially available systems that could effectively warn an equipment operator of an impending collision. Several new technologies also show promise for reducing these accidents. In most applications, it is recommended that sensor-based systems be combined with video cameras to provide important alarming functions along with an actual view of the blind area.

Jan 6, 2007

By V. Castranova, K. VanDyke

"INTRODUCTION A soluble mediator has been described which is released from activated rabbit leukocytes and induces histamine secretion from rabbit platelets (Barbaro and Zvaifler, 1966; Siraganian and Osler, 1971). This factor has been isolated, characterized and named platelet activating factor, PAF (Bcnveniste et. al., 1972). PAF has since been chemically identified as l-0-alkyl-2-acetyl-sn-glyceryl-3-phosphocholine (Benveniste et. al., 1979; Demopoulous et. al., 1979).PAF is a lipid mediator of broad biological activity. It causes smooth muscle contraction, contraction of lung tissue and decreased FEV 1; while enhancing capillary permeability thus causing edema (Pinkard, 1983). In addition, PAF is a chemoattractant and can lead to inflammation.PAF has been reported to stimulate the release of lysosomal enzymes, leukotriene B,, and lipid metabolites from neutrophils (Smith et. al., 1983; Shaw et. al., 1981; Lin et. al., 1982; O'Flaherty et. al., 1984). The objective of the present investigation was to further characterize PAP-induced stimulation of granulocytes and to develop a bioassay, i.e. chemiluminescence, for screening PAF receptor antagonists and inhibitors of PAP-induced activation of granulocytes. The possible use of the chemiluminescence assay to monitor PAF synthesis by human granulocytes is also described.METHODSBlood was drawn from healthy volunteers into a blood storage bag containing CPD anticoagulant. Granulocytes were partially purified by dextran sedimentation and further purified by centrifugal elutriation as described previously (Jones et. al., 1980). Granulocytes obtained by this procedure were approximately 95 percent pure. The number of granulocytes in this preparation was determined using an electronic cell counter (Coulter Model Z1, Coulter Instrument Co., Hialeah, FL). Isolated granulocytes were used to monitor membrane potential, hydrogen peroxide and superoxide release, oxygen consumption, calcium uptake and, in some cases, chemiluminescence. Studies of PAF receptor antagonists were conducted using neutrophils isolated by density centrifugation. Briefly, blood was layered onto Mono-Poly-Resolving Medium (Flow Laboratories, McLean, VA) and centrifuged at 22 °C and 300 g for 30 min. Neutrophils collected from the second band of this gradient were at least 90 percent pure."

Jan 1, 1989

By Carl R. Peterson

This report describes the development and testing of a prototype tunneling machine. Principal efforts were aimed at testing of the fragmentation subsystem of a continuous drill and blast hard rock excavation machine suitable for use in underground mining and tunneling applications. The concept utilizes a unique self -shielding spiral blasting pattern that permits efficient performance with relatively small single shots, while at the same time directing major blast fragments at right angles to the tunnel axis. A major accomplishement was the development of a remote controlled, loading and initiation system in which explosive slurry and a detonator are Simultaneously placed (pumped) into the blasthole via a loading hose. The special electric long-delay detonator is inductively ignited upon emplacement, and the machine remains at the face during the blast.

Jan 1, 1976

By Thomas M. Barczak, Christopher Mark

Roof supports can only be understood in conjunction with the rock structure that they support. The strength of the rock depends on geology, and the loads are applied primarily by the in situ and mining-induced stresses. Other factors, such as wider spans and retreat or multiple-seam mining, can also reduce the stability of mine openings. Roof supports are used to help stabilize these openings, but their performance characteristics must be properly matched to the loading environment and ground behavior if they are to succeed. Roof supports include both intrinsic supports, such as roof bolts, and standing supports. The key characteristics of any support include its maximum load-carrying capacity, stiffness, and residual strength. Other important factors are the timing of installation, the stability of the support as it is loaded, and the capability of the support system to provide skin control. This paper explains in practical terms how supports work and the important factors in ensuring that a good support design and application strategy are developed.

Jan 10, 2000

In 2006, a total of 280 metal mining operations reported employment to the Mine Safety and Health Administration (MSHA).1 Metal mines were the smallest mining commodity sector, comprising 1.9% of all mining operations. ? Gold mines comprised 46.8% (n=131) of all metal mining operations. Other common types of metal mines were copper ore (n=34; 12.1%), and iron ore (n=33; 11.8%). Nevada had the largest number of metal mines (n=53; 18.9%), followed by Alaska (n=31; 11.1%).

Sep 1, 2008

By Sidney A. Suhler

A field operable, breadboard model, borehole radar was developed for the detection of hazardous geological anomalies in and above a coal seam in advance of mining. A four-inch diameter downhole probe was fabricated and tested in several environments. The radar transmitter was also employed in a cross-hole or through transmission mode to determine natural geotechnical and man-made conditions between boreholes. Sensitivity to underground conditions in both modes of operation were indicated.

Jan 1, 1978