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1. In 2002, a total of 256 metal mining operations reported employment to the Mine Safety and Health Administration (MSHA). Metal mines were the smallest mining sector,1 comprising 1.8% of all mining operations. • Gold mines comprised 44.1% (n = 113) of all metal mining operations. Other types of metal mines were copper ore (n = 31; 12.1%), iron ore (n = 25; 9.8%), and lead and/or zinc ore (n = 21; 8.2%). • Nevada is the state with the largest number of metal mines (n = 53; 20.7%).

Jan 1, 2004

By Arnold B. Hubbard

Automatic control instruments were utilized by the Bureau of Mines for routine assays of large numbers of oil shale samples and other bituminous materials. The standard Fischer assay method was automated by automatically controlling the heating cycles of a battery of 12 electric heaters with electronic controllers and programmers. The condensers were cooled with a modified automatically controlled refrigeration bath. The complete assembly consisted of 12 retort units, necessary control instruments, and the refrigeration bath. This equipment was capable of producing more consistent results than those previously obtained with the gas-heated retorts and of increasing the output of assays substantially with no increase in operating personnel.

Jan 1, 1965

By E. S. Shedd

Misch metal was electrowon from a treated bastnasite concentrate in a REF3-LiF-BaF2 electrolyte at 950° C. The metal was prepared and tapped from a 1,000-ampere cell, and nearly 100-percent utilization of the rare-earth oxide was achieved. Prolonged operation in a smaller cell (40 amperes) indicated that the composition of the misch metal product was reasonably constant, and no significant increase of impurities, with the exception of carbon, was noted.

Jan 1, 1970

By John E. Miller

Supercompressibility factors, Fpv, were derived from experimental compressibility data for five helium-nitrogen mixtures containing from 50 to 100 pct helium. These Fpv values are required as volumetric correction factors for or if ice meter measurement of "crude helium" (helium-nitrogen) purchased by the Government in a program of helium conservation. Although compressibility measurements were made by the Burnett method (2)3 - for pressures from 100 to 3,400 psia and temperatures from 40° to 100° F, Fpv values were needed only for pressures from 400 to 2,000 psia. Consequently, values at increments of 2° F, 2 pct helium, and 10 psia were tabulated only for the required pressure range. Values for pressures outside this range can be calculated from information shown in the tables. Values for the second, third, and fourth coefficients in the equation Z = 1 + BP + CP2 + DP3 are also included.

Jan 1, 1963

By R. L. Montgomery

Heats of solution of yttrium chloride and oxide in hydrochloric acid were measured by Bureau of Mines researchers. Using the heat of combustion of yttrium mentioned in the literature, the Bureau calculated the heat of formation of yttrium chloride to be -239.16 + 0.50 kcal./mole. The Bureau experiments gave evidence that the heats of solution of yttrium chloride from the literature are mostly too low because of water and/or oxychloride impurities. Heat of combustion of yttrium (8)3/ and its heat of solution in hydrochloric acid (2, 14) have been measured. The earlier heat of solution measurement (2) is unreliable because of possible potassium contamination (4). Heat of solution of yttrium chloride has been measured by three researchers (3, 9, 15), who obtained widely different results. Spedding and Flynn (14) report the heat of formation of yttrium chloride as -232.69 kcal./mole from their solution studies. The present work was designed to check the reported heats of solution of yttrium chloride and to determine the heat of solution of yttrium oxide. The latter measurement would allow the results of solution and combustion data for yttrium to be intercompared.

Jan 1, 1960

By Jack G. Croeni

A study was made by the Bureau of Mines to determine the influence of high energy-rate deformation on the structures and properties of low-carbon steel, stainless steel, titanium, titanium-6 percent aluminum-4 percent vanadium, beryllium, molybdenum, and tungsten. The purpose of this study was to determine relative formability, the effect of energy and temperature on metalworking parameters and resulting structures, and the properties of materials formed by this technique. Forming techniques were limited to upset forging and direct extrusion on pneumatic-mechanical forming machines. Results show that considerable grain refinement can be achieved by careful control of deformation and forming temperature by high energy-rate techniques. Significant improvements in strength were observed as a result of this refined structure. Approximate deformation resistance as a function of temperature was determined for a variety of materials.

Jan 1, 1966

By H. E. Powell

This Bureau of Mines study describes two processes for recovering zinc, copper, silver, and iron from the magnetic fraction of a waste generated by the primary smelting of zinc in horizontal retort distillation furnaces. The laboratory-scale procedures include reduction melting to produce a high-copper iron and matte smelting to produce a copper-silver-iron matte and metallic iron. Zinc is fumed in each process and recovered as the oxide. Direct reduction melting yields a metallic iron high in copper and a small rich matte from the sulfur contained in the waste. The products of the second process are a matte containing essentially all of the silver, about 80 pct of the copper and 37 pet of the iron, and an iron-copper alloy containing all of the remaining copper. Extraction with metallic lead or sodium sulfate recovers essentially all of the copper from the molten high-copper iron and yields an acceptable foundry iron.

Jan 1, 1973

By Alan R. Buehler

The Bureau of Mines conducted a mineral investigation of the 10,500-hectare Cache Peak study area in 1992; the area had been proposed as wilderness. Bureau personnel examined and sampled prospect workings; 14 rock and 20 placer samples were taken during the investigation. The study area is centered about 40 km south-southeast of Burley. Idaho, in the Sawtooth National Forest. There were seven mining claims located inside the study area, and one additional historical mining claim location. Gold, silver, copper, lead, zinc: Possible resource, poor exposure precludes estimate. Marble: Several million tonnes may be suitable for a variety of uses; markets too distant to favor mining. Sand and Gravel: Several million m3, but markets and transportation costs do not favor mining. Quartzite: Several million tonnes may be suitable for metallurgical purposes; however, markets are too limited to mine. Slabs have been quarried at three localities adjacent to the study area, for decorative stone. Production: In 1979, two tonnes of ore were produced and a plan of operations was submitted calling for approximately 5 km of access road for the Last Chance mine. Decorative stone production was not recorded.

Jan 1, 1993

By Frank L. Wideman

This information circular describes methods used in mining inclined beds of phosphate rock in mines operated by San Francisco Chemical Co. in Rich County, Utah. The mines are on the western flank of the Crawford Mountains, a short, narrow range in northern Utah near the Idaho-Wyoming corner (fig. 1). The western front of the range is a conspicuous wall of folded and faulted sedimentary rocks that rises abruptly 300 to 600 feet above the floor of the adjacent Bear River Valley. Rex Peak, highest point in the range, is approximately 8,000 feet above sea level. The area surrounding the mines is sparsely populated. Randolph, the county seat of Rich County, has a population of 650. It is 10 miles southwest of the mines by road and the only town in their vicinity.

Jan 1, 1958

By Alexander May

The U.S. Bureau of Mines investigated the application of oxidation-reduction potential (ORP) and pH measurements to environmental studies of mining and mineral processing wastes, and developed a computer program to estimate the concentrations of species of lead present in samples from a lead processing waste site. The methods and techniques for the ORP-pH measurements were investigated using known standard solutions made in the laboratory, samples from a ferric oxide waste disposal pond at a rutile production plant, and samples of well water and stream water from the lead processing waste site. ORP values were measured from 5 to 80 °C, from pH 1 to pH 12, and at various ratios of oxidant to reductant. The ORP-pH values can help identify valence values and species of ions present, including those of major, minor, and trace concentrations, and also indicate possible reactions at various pH values. The ORP measurements versus temperature yield data from which thermodynamic values can be calculated. The application and limitations of these measurements are discussed, and a brief discussion of the computational program to identify species of lead is presented.

Jan 1, 2010

By Marcia L. Harris

The National Institute for Occupational Safety and Health (NIOSH), as part of its continuing research program for evaluating coal dust explosion hazards, has investigated several areas in which current practices may need to be updated in order to adequately protect mines against coal dust propagated explosions. In the United States, current rock dusting requirements remained largely unchanged since 1969. US Title 30 Code of Federal Regulations Section 75.403 is based on a coal dust particle size survey performed in the 1920s and later was supplemented by full-scale testing of the rock dust ability to inert a coal dust explosion. NIOSH recently conducted a comprehensive survey of US underground coal mines to determine the range of coal particle sizes found in dust samples collected from the mine entries. Due to advancements in technology and modern coal mining techniques, the current coal dust particles in intake airways are significantly finer than those found in the mines in the 1920s. According to past full-scale dust explosion test results, the current rock dusting practices used in today?s mines to inert a coal dust explosion may not be adequate. Other closely related issues such as rock dust testing methods and sampling procedures are discussed.

Jan 1, 2009

Objective: To continuously monitor, display, and record concentration levels of respirable coal mine dust in mines to an accuracy of ±25% with a 95% confidence level for at least 30 days without servicing.

Jul 1, 1997

By Robert W. Smith

In a certain application2/ it was necessary to compute the beta function B(p, q) for a certain set of values p and q. Since t he set of p and q values was much mo re finely spaced than those in any published tables, the authors decided to make their results available in this report. In connection with this application the functionB(p, q) was needed at various points in the p, q plane at intervals of 0.05, 0.05<p = q< 10.00. Fletcher, Miller, and Rosenhead2/ state that the only tables available in the desired range are those of Rearson.4/ However, the interval used by Pearson was not small enough for the present application. For this reason it was decided to calculate B(p, q) for p = q =0.05 (0.05) 10. 00.2/ This table is published because of the fundamental importance in mathematical analysis of the complete beta function.

Jan 1, 1953

By James R. McVey

Tests during pillar robbing, longwall operations, and other mining activities indicate that roof-floor convergence rates can be used as an indicator of imminent roof failure. A large number of electrical-mechanical devices have been built to measure convergence as well as convergence rates, but most obstruct mine traffic and are costly and time consuming to install. The Bureau of Mines has designed and is evaluating three types of small ultrasonic units to make these measurements. The new instruments provide nonobstructing measurements up to 35 ft away. The ultrasonic transducers can be attached to a roof bolt, placed in an unsupported area (by means of a toss basket), or handheld. Total distance to the target and rate of closure are displayed digitally to 0.001 ft and 0.01 ft/min, respectively.

Jan 1, 1984

By R. G. Knickerbocker

[The Electrornetal~.1~~1c~.l T,:tt31~tn~ir of the Bureau of Miner,, 3oulder City, !.Tev. , invsst:&apos;.~:es 1:h .-inc.z-.l ci.c;,oritr, in 51-3 regon around Boulder Dam, i~d. this papei- ?i*esmt; tvr) cl-c~;ef.o!~~ilcinl;$ of n s5siqn of atufiies on boron ninerala GB~O 3;; tlir t ~t;s?,Lo:]

Jan 1, 1940

By A. T. Iannacchione, D. G. Puglio

The Bureau of Mines established geologic factors affecting the mining of the Lower Kittanning coalbed to aid in coalbed minability studies and examined the occurrence of "wants" (places where coal is missing) and types of unstable roof rock strata. Trends established from mapping, including prediction of areas of high methane emissions, were extrapolated to unmined areas. "Wants" in the coalbed are of two types: Erosional and depositional. Erosional features occur where north-south-trending sand-filled channels cut into the coalbed. Variations in depositional environments have caused the coalbed to "split" into several thinner units. Slickensides, commonly indicative of unstable roof, are adjacent to and on the underside of sandstone channels; they were caused by differential compaction and by soft sediment sliding along the contact between the sandstone and adjacent shale. The frequency of unstable roof also increases where the interval between the Middle and Lower Kittanning coalbed is less than 30 feet. The zones of weakness at the contacts above and below the Middle Kittanning coalbed are the controlling factors for unstable roof in these strata. Methane emissions from the coalbed are controlled primarily by depth, fracture permeability, and rank of coal. Local geologic factors are coalbed thickness, associated rock strata, structure, and proximity to outcrop.

Jan 1, 1979

By T. T. Campbell

This report traces the development of techniques for the preparation of high-purity rare-earth metals. Rare-earth metals, excepting samarium, europium, and ytterbium, were prepared by converting their oxides to anhydrous chlorides or fluorides and reducing the rare-earth halides with active metals such as lithium or calcium. High-purity, anhydrous rare-earth chlorides were prepared by dissolving the rare-earth oxides in hydrochloric acid to form hydrated chlorides and by subsequently dehydrating the hydrated salts in the presence of ammonium chloride at temperatures ranging from 70° to 360° C. while under reduced pressure (50 microns to 1 inch Hg). The chlorides were also prepared by direct chlorination of rare-earth oxide-carbon mixtures. Reaction efficiencies in excess of 95 percent were obtained by either method; however, purer chlorides were prepared by the aqueous ammonium chloride conversion method. Purification of yttrium chloride by high-temperature vacuum distillation proved to be an effective method of separating, oxygen-bearing compounds from the chloride. Yttrium metal prepared from purified chloride contained significantly smaller amounts of oxygen (990 p.p.m. oxygen in yttrium metal prepared from raw chloride and 200 p.p.m. in that prepared from distilled chloride).

Jan 1, 1961

By Walter W. Kaufman

This report summarizes a study conducted to determine the state of the art of various rock removal systems and their capabilities. The Objective of the study was to determine if currently manufactured equipment can adequately accomplish rock removal in surface mine reclamation applications. Evaluations of state reclamation regulations, with regard to topsoil rock content, were made to determine the rock removal requirements. The major categories of equipment studied are rock pickers and rock rakes. The impact of rock removal implementation on the reclamation operations is discussed in detail.

Jan 1, 1979

By R. W. Van Dolah

An important function of stemming used to confine explosives in shot holes in underground coal mines is to minimize the chance of ignition of firedamp or coal dust by the detonation products. Until 1952, the Bureau of Mines approved only the use of fireclay or similar incombustible material for stemming permissible explosives. At least 2 feet of stemming were required except in holes less than 4 feet deep; in such short holes the stemming was required to be half the depth of the hole. Over the years, several special stemming devices have been proposed in the United States as substitutes for fireclay. Many economic and safety advantages were claimed for these devices, but only one approved device has been marketed in this country. Bureau requirements for stemming explosives in coal mines were modified at that time to permit the approved stemming device to be used as a substitute for the required fireclay.

Jan 1, 1961

By J. M. Stuve

Thermodynamic properties were determined by the Bureau of Mines for the intermetallic compound, TiA13. Heat capacities were obtained from 5 to 303 K by adiabatic calorimetry. The derived value of S2 1s is 22.08±0.07 cal/deg¬mole. Enthalpies relative to 298 K were obtained from 298 to 1,413 K by copper-block drop calorimetry. No anomalous thermal behavior was noted in the temperature ranges investigated. Low- and high-temperature data were combined with a known enthalpy of formation at 298 K to give values of enthalpy of formation and Gibbs energy formation, 0 to 1,400 K.

Jan 1, 1974