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By Zsuzsanna Zborovszky

Study of the energy transfer from an inductive circuit to the discharge under the conditions of the minimum discharge voltage being smaller than the source voltage. Analysis of the effect of the electrode separation speed on the duration and maximum power amplitude of the discharge. Recommendation for optimal electrode setting. Experimental data on the variation of maximum discharge power required for ignition as a function of volumetric gas content for methane-air and propane-air mixtures. Experimental determination of the ignition limit for discharges derived from a 24, 15, 10 and 6v inductive-resistive circuit in 8.3% methane-air mixture by using the PTB breakflash with Cd disc and W wires, and also with Cu disc and BeCu wires. Method for calculating ignition limits for other source voltages.

Jan 1, 1978

By H .. B. HUMPHREY, F. E. Cash

Sixty-one fatal accidents were reported in the mines of Alabama during 1930. This number is a decrease of 15 per cent as compared with 1929; however, production was 13 per cent and the man-hours worked were 16 per cent less than in the previous year. There were 21,731 men employed inside and 3,386 outside. Table 1 gives the comparative rates per million tons and per million man-hours for the United States and for Alabama for 1929 and 1930. These rates are based on figures published by the State and by the United States Bureau of Mines, with preliminary figures for 1930. (These sources of data are used throughout this paper.)

Oct 1, 1931

By Chas. F. Jackson

This paper is one of a series dealing with special mining problems and forming part of a general study of mining, methods and costs being conducted under direction of the Bureau of Mines. A considerable part of the material assembled and discussed in this paper has been gathered from articles on individual mines written by consulting engineers to the bureau who are engaged in active mine operation at the properties described, while other data have been taken from the technical press or gathered from personal observations. OBJECT AND SCOPE OF PAPER C. F. Jackson4 ha[-] pointed out that underground transportation (tramming, haulage, and hoisting) absorbs an appreciable percentage of the total underground cost of most mines, averaging for different methods of mining 12.9 to 28.4 per cent of the total underground cost. In general the percentage of cost accounted for by transportation was shown to be highest for the low-cost mining methods.

Jan 1, 1931

By Oliver Bowles

"Asbestos" is not the name of a distinct mineral species but is rather a commercial term applied to fibrous varieties of several minerals. The origin and significance of names applied to asbestos by early writers are discussed in the section devoted to sources of supply and terms employed in ancient times. VARIETIES The most useful variety of asbestos is chrysotile, a fibrous serpentine the composition of which is expressed by the formula H4Mg3Si209. Chrysotile is characterized by a strength and flexibility that permit the use of the longer fibers for spinning. The bulk of the world production of both long and short fibers, is of this variety.

Jan 1, 1935

After more than 20 years dependence on bituminous coal as a primary fuel for generating electricity, the Pennsylvania Power and Light Company initiated a one-year study on the economics of building an electric generating station using anthracite as a fuel. The study will be completed in December 1976. If the feasibility study so indicates, PP&L will consider installing four 400,000 kilowatt generating units for scheduled commercial operation in 1985. Each unit would consume up to one million tons of anthracite annually. Anthracite generally is more difficult and expensive to extract than bituminous coal, but it has a significantly lower sulfur content than the bituminous coal currently being used by PP&L, thereby eliminating the costs of installing sulfur emission controls at generating stations. Moreover, significant reductions in transportation costs may be realized because the utility's operating territory is situated in the center of the anthracite region in northeastern Pennsylvania. These advantages may indicate that the use of anthracite is more economical than bituminous coal to PP&L. ASBESTOS -Asbestos production in the U.S. dropped again in 1975 until it was just two-thirds of that in 1973. This was in spite of the very strong demand caused by the Quebec strike. The 7-month strike of the asbestos miners in Thetford Mines, Quebec cut off 55 percent of the normal supply of U.S. consumers. Apparent domestic consumption was less than 75 percent of that in 1974. The wage settlement will probably result in a 20 percent increase in asbestos prices.

Jan 1, 1975

By D. A. Paice

A power supply to operate fluorescent or mercury vapor lamps from 300 volt dc coal mine trolley wires has been developed for the Bureau of Mines. A high frequency regulated inverter unit incorporates ballasts for a mix of lamp loads up to 650 watts. For 600 volt trolley systems an additional power converter unit was developed to step down the dc voltage to 300 volts for the inverter unit. Both units have operated in a working coal mine for over 12 months without need for servicing. The lamp load in these tests included two 100 watt mercury vapor head lamps and six 75 watt fluorescent lamps.

Jan 1, 1979

By A. L. Engel

Production of chromite in California has been from many small, high-grade mines. The opening of the Purchase Depot at Grants Pass, Oreg., in 1951 has stimulated chromite mining in California, and a large number of properties are being reexamined as there is a possibility that some low-grade ores from many of these properties can be beneficiated to meet the purchasing schedule. The Bureau of Mines in its program of conservation is continuing ore-dressing tests on chromite ores to better evaluate their potential. This report is a compilation of preliminary concentration tests on samples from five different properties in California. The concentration tests were made on ores from the David mine, Butte County, the Seiad Creek mine, Siskiyou County, the High Plateau mine, Del Norte County, Bud's mine, Tuolumne County, and tailings from the Miller concentration plant in San Luis Obispo County, Calif., to determine the possibility of beneficiating these ores so that they will meet the specifications for the Government stockpile.

Jan 1, 1956

By James R. Boyle

The mining methods and practices used at the Young zinc mine, American Zinc Co. of Tennessee, have resulted in a low-cost, high-yield operation. Zinc ore (sphalerite) occurs in limestone-dolomite beds of the Kingsport Formation and is mined by modified room and pillar method. Utilizing trackless mining equipment which incorporates a high degree of flexibility, this operation has had a steady increase in productivity.

Jan 1, 1965

By Anil Mahyera

Towards the goal of achieving uniform-high-tensions in roofbolts to provide superior roof support[1-7] for extended periods, Terra Tek installed mechanical-anchor bolts in a mine in eight different ways -- under torque/thrust control with and without hardened washers, belleville washers and tension equalization; in a conventional manner with and without a hardened washer. The various bolt groups were analyzed in terms of their tension uniformity and mean tension levels. Installing the bolts accurately with ? a hardened washer under the bolthead, and ? proper torque/thrust control resulted in the mast uniformly tensioned bolts -- with a coefficient of variation of only 14%, an improvement of 3 times over a conventional installation. Also, these bolts maintained a high tension level -- 80% of the installation tension, compared to 50% achieved conventionally.

Jan 1, 1982

By R. H. Nicholas

Shuttle cars have undeniably proved their worth as a means of transporting coal underground; however, several factors have arisen in connection with their possible improvement. This report .discusses the effect of shuttle cars that employ rough-tread and smooth-tread tires on mine roadbed, the amount of dust thrown into suspension by the use of such tire treads, and the service rendered by each type of tire. Involved, also, in this study are observations on the use of different amounts of calcium chloride on the haulageways.

Jan 1, 1949

By R. B. Ladoo

"Present Situation:At the beginning of 1920 a general feeling of optimism was noted in many talc-producing districts. The industry seems to have recovered from the temporary depression of the first half of 1919 and many mills are running at capacity production with their entire output for 1920 contracted for. The imports of talc for 1919 were only slightly larger than in 1918 by weight and probably no more by value. Thus foreign competition has not begun to be seriously felt. Several new companies in this country have been organized, some to operate new deposits and others to continue the work done by others.An interesting phase of the present situation is the possibility of increased use of talc in paint. There is a shortage of barium sulfate used as a paint filler. Since, for some uses, talc is considered second only to BaSo4 as a filler for paint, it is possible that part of the shortage could be relieved by an increased use of talc.A series of physical tests upon all pigment materials used in the manufacture of paints is being conducted for the Paint Manufacturers Association of the United States. It is important that all types of talc be represented in these tests. Producers of finely ground talc, 200 mesh and finer, are urged to submit samples of at least two pounds each of these grades that are available to paint makers with trade name and quality data, to the Institute of Industrial Research, 19th & B Streets, N. W., Washington, D. C., where the tests are being conducted."

Jan 1, 1920

By J. E. Chilton

Interim performance specifications are presented for carbon monoxide, methane, and air velocity transducers used in the Bureau of Mines intrinsically safe mine monitoring system. These specifications give quantitative values or qualitative descriptions of the transducers, including environmental parameters and monitoring system measurement and maintenance requirements as recommended by the Bureau of Mines. Commercially available transducer modules and prototype modules are listed together with selected characteristics.

Jan 1, 1983

By John Ward Smith

Aragonite, co-occurring with calcite and dolomite as matrix minerals, has been discovered in Mahogany zone oil shales of Colorado's Eocene Green River Formation, posing puzzles on the geochemical patterns of their separate origins, reasons for their simultaneous existence, and their interrelation. The presence of aragonite is demonstrated by X-ray diffraction. Amounts of aragonite and dolomite are significantly and inversely related, but the calcite quantity is essentially independent of either aragonite or dolomite quantity. A geochemical pattern outlining the deposition conditions that created the Green River Formation oil shale is postulated from characteristics of the oil shale. The development of the three separate carbonates--aragonite, calcite, and dolomite--the inverse relationship between aragonite and dolomite, and the independence of amounts of calcite and the other two carbonates are shown to be natural consequences of this oil-shale genesis pattern.

Jan 1, 1973

By W. H. Eddy

The Bureau of Mines used several laboratory batch flotation schemes combined with magnetic separation to investigate the feasibility of recovering potash feldspar and glass sands from molybdenite tailings. Four molybdenite tailings or prospective tailings were used as test samples. Feldspar concentrates containing from 10.7 pct to 12.0 pct K2O were recovered from three of the four samples. The alkali content of the fourth sample met the grade for a mixed feldspar. All the feldspar concentrates contained iron in excess of the 0.10-pct-Fe203 specification for most uses. Electron-beam microprobe examination of the feldspar concentrates showed the presence of an iron-bearing potash feldspar in quantities that were excessive with respect to most iron specifications. However, a high-quality glass sand was produced from all of the samples.

Jan 1, 1980

By Laurence A. Dahners

As part of the strategic minerals program, the Bureau of Mines conducted a diamond-drilling project on three barite properties in eastern Tennessee and western North Carolina during the summer and fall of 1944. These properties, the Moccasin Gap prospect and the Krebs property in Cocke County, Tenn., and the Sandy Bottom mine of the Stackhouse group in Madison County, N. C. (fig. 1), are known to have produced some barite. The Bureau of' Mines project was planned to prospect for extensions of the ore bodies. A total of 3,169 feet of diamond drilling was done in 15 holes on the three properties. Tabulations of sample analyses and drill-hole logs are presented in this report. Two other mines of interest in the area are the McCoy and the Williams in Cocke County, Tenn. The Williams adjoins the Krebs. No drilling was done by the bureau in either of these properties.

Jan 1, 1949

By G. R. Hopkins

Crude-petroleum pipe lines in the United States on May 1, 1941, had a total length of 118,350 miles - an increase of 7,770 miles since Jun, 30, 1936, then the last previous survey was made by the Bureau of Mines. The expansion was due almost entirely to trunk-line construction, as the mileage of gathering lines was virtually unchanged from 1936. The greatest mileage of gathering lines, 53,640, was recorded in the survey of May 1, 1931. Both trunk and gathering-line mileage decreased moderately, in the interval from 1531 to 1936, but the present survey indicates that trunk-line facilities have expanded since 1936 to new high levels. Truck-line mileage equaled 55 percent of the total mileage of all crude lines on May 1, 1941, and 52 percent is 1936. The total length of gasoline pipe lines on May 1, 1941, was 9,001 miles this does not include several hundred miles of life under construction at that time or several hundred additional miles now being laid. No detailed surveys of gasoline mileage were made for 1, 1931, and June 30, 1936, but the mileage for those dates was about 1,400 and 4,600, respectively.

Jan 1, 1941

By E. J. Matson

Under the investigation for critical and strategic minerals the Kaiser mine, formerly the Baxter fluorspar property, in northeastern Mineral County, Nev., was explored. The work comprised excavating 32 trenches averaging 90 feet in length, 8 feet in width, and 1 1/2 feet in depth. The trenches were excavated across the strike of the ore body to enable the engineer to spot the diamond-drill holes; 7 such holes were drilled, aggregating 3,276 linear feet. A total of 20 core samples and 107 sludge samples was taken. The work under this program indicated that the fluorspar southwest of the deposit extended laterally and also at depth at least 250 feet below the 400-foot level. INTRODUCTION The Kaiser fluorspar deposit is in the northeastern portion of Mineral County, Nev. Mining was begun about 1928, and the property has been a consistent producer of both Acid- and Metallurgical-grade fluorspar. The mineralized zone has been developed along a strike length of about 2,000 feet and to a depth of over 700 feet along the dip.

Jan 1, 1957

By Jr. Holmes

"The Riley tungsten property of the Northern Nevada Mining Co. was examined by the Bureau of Mines in August 1943, and from February 22 to August 22, 1945, the property was explored by the Bureau.Riley mine, which comprises 60 acres, is in sec. 9, T. 38 N., R. 42 E., Mount Diablo base and meridian, in the Potosi Mining District, on the east slope of the Osgood Range in eastern Humboldt County, Nevada. J. S. Riley is president of Northern Nevada Mining Co., the general offices of which are at 29 East First Street, Reno, Nev.Winnemucca, Nev., 42 miles southwest of the mine and on the main line of the Southern Pacific and Western Pacific Railroads and U. S. Highway 40, is the nearest supply center. The post office for the Potosi district is 15 miles south at Red House, Nev., a station on the Southern Pacific and Western Pacific Railroads. A good dirt road, which leaves U. S Highway 40 about 15 miles east of Winnemucca, extends northeast to the property.Tungsten occurs as scheelite in a characteristic Nevada contact-metamorphic tactite deposit between limestone and granodiorite Fifteen diamond-drill holes were completed for a total length of 2,630 feet.In its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources, to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work, and prepares the final report. The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples and performs beneficiation tests. Both these branches are under the supervision of Dr. R. S. Dean, assistant director.Special acknowledgment is made to A. C. Johnson, chief, :Reno Division, Mining Branch; E. O. Binyon, mining engineer, Reno Division; S. F. Clabaugh and S. Warren Hobbs of the Federal Geological Survey, who made available the un¬published Geological Survey report ""Tungsten Deposits of Osgood Range, Humboldt County, Nevada;"" and S. P. Zimmerley, chief, Salt Lake City Division, Metallurgical Branch, Salt Lake City, Utah.The Riley tungsten property comprises 60 acres of patented land owned by the Northern Nevada Mining Co. of Reno,,a partnership comprising J. E. Riley, H. H. Luce, Phyllis Riley, Beatrice Knight, Gene Crosby, and M. R. Wilson.The property is part of a federal land grant to the Southern Pacific Railroad, from which it was acquired by Tom Dernan many years ago. Two short adits and several shallow pits were excavated in a search for silver ore, but no record of precious metal production exists."

Sep 1, 1946

By William A. Beck

"INTRODUCTION Mica is found in Georgia from the Fall Line in the central part of the State to the Valley and Ridge Province in the northwest. During the past 3 years, Georgia has been one of the chief producers of dielectric mica in the United States. Since January 1945, when prices were reduced, mining has decreased until practically no sheet mica is being recovered at present.The main mica-bearing regions in the State may be classified into three districts: The Thomaston district comprising Upson, Lamar, and Monroe Counties; the Ball Ground district, comprising Cherokee and Pickens Counties; and the Hartwell district, comprising Hart and Elbert Counties. There are numerous mines and prospects in all of these districts. All have been visited from time to time by engineers of the Bureau of Mines and by members of the Federal Geological Survey. The Federal Survey has made detailed maps and reports on all of the most important ones.This report will deal with five of these properties on which the Bureau of Mines has diamond-drilled.ACKNOWLEDGMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy. It is the policy of the Bureau to publish the facts developed by each project as soon as practicable after its conclusion. The Mining Division, I. B. Moon, chief, conducts preliminary examinations, does the actual investigative work, and prepares the final report. The Metallurgical Division, O. C. Ralston, chief, analyzes samples and makes beneficiation tests."

Apr 1, 1948

By H. H. Schrenk

One phase of Bureau of Mines work in health and safety, is promotion of the use of safe, satisfactory, and reliable respiratory protective devices. To insure that such devices will be available, the Bureau has established schedules of minimum requirements for self-contained breathing apparatus,3/ gas masks, supplied-air respirators (hose masks, air-line respirators, and abrasive blasting helmets, hoods, or masks),2 dispersoid (dust, fume, and mist) respirators, and nonemergency gas respirators (chemical cartridge respirators). Approval tests of self-contained breathing apparatus are conducted by the Safety Branch, approval tests of other types of respira- tory protective equipment are conducted by the Health Branch, These branches are in the Health and Safety Division.

Mar 1, 1948