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By George J. Carter

Data obtained from field and laboratory examinations were used by the Bureau of Mines to evaluate 82 silica deposits in the Pacific Northwest. A total of 94 field samples was taken from 64 deposits, and an additional 18 deposits were investigated that did not warrant sampling. Of the 37 deposits found to be of high quality, only 16 were large enough to be classified as industrial silica resources. Another 27 deposits did not meet quality requirements. Methods of simple low-cost beneficiation and rapid classification of a large number of samples were investigated in the laboratory. These tests indicated that high-intensity electromagnetic separation was equal or superior to either high-or low-intensity electrostatic separation. In general, the electromagnetic method gave higher recoveries and produced equal or better grade concentrates. A glass button method developed for estimating iron oxide content of silica samples proved to be highly satisfactory as a means of classifying field samples and evaluating beneficiation tests.

Jan 1, 1962

By Alan H. Goode

Glass wool meeting requirements for commercial use was made from glassy fractions of urban solid wastes by the Bureau of Mines. This research was a part of the Bureau's program to develop building products and other usable materials from reclaimed urban waste materials. Mixes of molten glass were fiberized into glass wool during laboratory studies by impingement of a jet of compressed air on a stream of the molten glass. The principal test variable studied was composition of the melt; this was varied by adding dolomite and alumina to obtain molten glass with the handling characteristics required for producing final wool products of the desired composition and physical characteristics. When no charge is made for the waste glass and approximately $75 per ton can be obtained for the wool product, an interest rate of return on investment after taxes of about 12 percent can be obtained. If a charge of $5 per ton is required for the waste glass, a selling price of about $78 per ton would be necessary to obtain a l2-percent-interest rate of return on investment after taxes.

Jan 1, 1972

By E. F. Divers

This Bureau of Mines report describes the results of a program to develop small, rugged mechanical dust collectors (scrubbers) with high dust collection efficiency and low energy comsumption for controlling dust in coal mining operations. All of the scrubbers described are similar in configuration and are powered by 6-hp, 2,000-ft3/min vane axial fans. Air pressure differential is less than 6 inches water column. Height of the scrubbers? including fan is less than 14 inches, width is less than 16 inches, and length is less than 45 inches. The flooded fibrous-bed scrubber achieved respirable (less than approximatey 7 µm) dust collection efficiencies of 95 percent. The small-diameter-cyclone scrubbers showed about 92 percent efficiency and can be best where excess water is a problem. The wetted brush scrubber showed 88 percent efficiency at low cost, and the wetted fan scrubber showed a slightly lower efficiency (87 percent) but offered the smallest size and cost. A suitable water droplet eliminator is described.

Jan 1, 1978

By Mary Cocklan-Vendl

Regulatory processes associated with development of a world class lead-zinc mine, Red Dog Mine, in northwestern Alaska were reviewed and evaluated. Informal interviews with key project personnel, consultants, and agency field and permitting specialists provided perspective on the regulatory successes and failures of the project. Due to potential impacts to air quality, water quality, wetlands, and National Park lands, an Environmental Impact Statement was required. By developing a comprehensive baseline of information on the existing environment to aid in minimizing impacts during project siting/design and through regular coordination of evolving project plans with regulatory agencies, the mine developers were able to acquire necessary permits in a timely and cost effective manner. The only major exceptions occurred when inadequate information was collected on dispersal of airborne particulates, rates of surface water run-off, and groundwater quality. These deficiencies resulted in the need for design changes, unscheduled construction, additional environmental monitoring costs, and delays in issuance of the NPDES permit.

Jan 1, 1992

To develop more accurate means of measuring low ventilating air velocities in underground mines to facilitate compliance with ventilation standards. The Approach: A commercially available vane anemometer which produces an electrical, rather than a mechanical, output was coupled to electronic circuitry to produce the Bureau's Digital Low Velocity Anemometer (see photo). [ ] How It Works: The experimental instrument has a vane anemometer head which produces an electrical output signal with a frequency directly proportional to the rotating speed of the vane anemometer shaft. The commercially available ABBIRKO FLOWMASTER anemometer head was used in this instrument. In the signal conditioning circuits the electrical signal from the anemometer is converted into pulses, which are counted during either 3-second or 1-minute intervals, depending on the position of the operator's control switch. (Readout is either "instantaneous" or averaged for a period of one minute.) The number of pulses counted is then translated (integrated and divided by a constant) in the logic circuits to get average speed. Average air velocity in feet per minute is displayed in illuminated digits. (See simplified diagram of circuitry.)

Jan 1, 1975

By James Westfield

A brief résumé follows of recent activities of the Division of Coal-Mine Inspection that have had a favorable effect on health, safety, and the reduction of injuries at coal mines: 1. The Federal Mine Safety Code for Bituminous Coal and Lignite Mines of the United States was issued originally by the Director of the Bureau of Mines on July 24, 1946, after consulting with management and labor representatives of the coal-mining industry. The code has been used by Federal coal-mine inspectors while inspecting bituminous-coal and lignite mines as a basis for determining the existence of unhealthful and unsafe conditions and practices in these mines. A revised code was issued by the Secretary of the Interior on October 8, 1953, after further consultations with representatives of management and mine workers and was incorporated by reference in the 1952 and subsequent bituminous-coal wage agreements. The agreement of May 29, 1946, between the Secretary of the Interior, acting as Coal Mines Administrator under authority of Executive Order 9728, and the United Mine Workers of America, covering bituminous-coal and lignite mines in Government possession, charged Federal coal-mine inspectors with the responsibility of making periodic investigations of the mines and reporting to the Coal Mines Administrator any violations of the Federal Mine Safety Code. Federal coal-mine inspectors also had temporary authority to close mines found to be imminently dangerous, but such authority (under Executive Order 9728) was removed on June 30, 1947, when Government control of the mines was terminated.

Jan 1, 1958

By A. C. Fieldner

"INTRODUCTION In a previous report3 prepared for the American Gas Association, the influence of washing coal on coke properties and on gas and by-product yields was discussed on the basis of answers to questionnaires sent to coke-oven superintendents and a review of the literature on the subject. This review indicated that the elimination of free impurities by cleaning coal improved coke quality by (a) reducing ash and sulphur, (b) decreasing clinker trouble in burning the coke, (c) diminishing cross fractures in the coke, resulting in greater resistance to breakage on handling, and less small coke and breeze, and (d) greater uniformity in chemical composition and physical properties of coke. Washing also reduced the sulphur in coke and gas and increased the yield of gas and by-products per ton of dry coal charged.This paper is supplementary to the previous report and presents some experimental data obtained with Pittsburgh bed coal from Pennsylvania and Mary Lee bed coal from Alabama.ACKNOWLEDGMENTSGrateful acknowledgment is made to F. J. Pfluke, of the Rochester Gas and Electric Cc., of Rochester, N. Y., for the plant test data on screened lump and washed coal; and to Ray W. Arms, Manager of the Coal Cleaning Department, of Roberts & Schaefer Co., of Chicago, for the data on effect of air cleaning."

May 1, 1931

By John K. Alley

Despite the extensive use of fluorphlogopite, investigators do not agree as to its exact melting temperature. Data on other fluormicas and on related fluorsilicate systems are largely nonexistent. A knowledge of the melting temperature is necessary for the effective synthesis and use of fluorphlogo¬pite or other fluormicas. The increasing use of two- and three-mica systems to yield polycrystalline ceramics has made more urgent the need for melting temperature information concerning these other fluormicas. This report is part of a program by the Bureau of Mines to synthesize large-size or large-crystal fluorphlogopite and develop a usable reconstituted fluormica sheet. The melting temperature of fluorphlogopite, K2Mg6A12Si6020F4, was found to be 1,383° ±2° C. This temperature was found by studying single crystals of fluorphlogopite, heating behavior of glass of fluorphlogopite composition, and the actual crystallization of fluorphlogopite from a melt that had been heated above 1,430° C. The formation of forsterite or norbergite was directly proportional to the loss of volatiles during the experimentation. Many trials revealed that the only reliable seal was a thick platinum sheet with welded seams. If no volatiles were lost, neither norbergite nor forsterite were formed; fluormica was then the only product. Excellently formed crystals of forsterite with an optical sign different from ordinary forsterite were obtained during the single crystal melting experiments. These crystals resulted from a slow loss of volatiles. A congruent melting of fluorphlogopite is indicated by the data of this report; however, incongruency within a small temperature range is not precluded. A more refined method using phase equilibria-quench methods would be necessary to settle the question absolutely.

Jan 1, 1962

By D. E. Larson

The U.S. Bureau of Mines investigated Fe-base alloys containing 8 pet Crwith Ni, AI, and Si additions as substitutes for standard AISI Type 304 stainless steel (SS) in high-temperature oxidizing applications. The objective of this study was to reduce the amount of Cr required to make an austenitic stainless steel while retaining satisfactory workability, mechanical properties, and oxidation resistance. Alloys prepared in this investigation had a composition of Fe-8Cr-lMn-0.07C with varying amounts of Ni, AI, and Si. A minimum of 10 pet Ni was required to achieve an austenitic composition. The microstructures of the austenitic alloys were very susceptible to room-temperature, deformation-induced martensitic transformations. When the alloys were cold worked or stressed, the materials had far greater tensile strengths than Type 304 SS at room temperature. At higher temperatures, tensile strengths and workability of several of the alloys were comparable to that of Type 304 SS. Although martensitic transformation caused the room-temperature properties of the experimental alloys to be quite different than those of Type 304 SS, the superior oxidation resistance and similar hot workability of several alloys encourage their use as replacements for Type 304 SS.

Jan 1, 1989

By Alla D. Mah

The heat of formation of scandium sesquioxide (Sc203) has not been measured previously, and existing values for gallium sesquioxide (Ga203) are subject to large uncertainties. As a consequence, thermodynamic calculations involving these oxides hare lacked scientific exactness. This paper reports newly determined values of the heats of formation of gallium and scandium sesquioxides at 298.15° K., by combustion calorimetry. The corresponding free energies of formation are derived from heat and entropy data.

Jan 1, 1962

By I. Liebman

A Bureau of Mines study is in progress to determine the effectiveness of passive water barriers in suppressing coal-dust explosions. A 2.9-ft3-capacity water-filled plastic tub was found effective in suppressing dust explosions propagating at speeds of 250 to over 1,000 ft/sec. Work directed at determining the limitations of water barriers showed that the passive water barrier technique is also feasible for the suppression of weak dust explosions propagating at speeds of 100 to 250 ft/sec. For relatively slow accelerating flames, dynamic wind forces appear to be the important quantity governing fragmentation of the plastic tub and subsequent water release and dispersion, whereas dynamic impulse appears to be the significant quantity for rapidly accelerating flames. The acoustic approximation (relation between static pressure and flame or wind speed) is shown to be valid in a long single mine entry. This relationship appears to be useful in predicting the regions within a long single entry where passive water barriers are effective in quenching a dust explosion.

Jan 1, 1974

Sixteen papers concerned with the technology and utilization of low-rank fossil fuels are presented as the proceedings of the 1973 lignite symposium. This symposium, the seventh in a series of biennial meetings, was cosponsored by the Bureau of Mines and the University of North Dakota.

Jan 1, 1974

By V. E. Edlund

As part of a research program for recovering alumina from domestic nonbauxitic resources, the Bureau of Mines investigated a lime-sinter, caustic leach technology for anorthosite. This report discusses the unit operations--feed preparation, sintering, and leaching. Acceptable pellets for the bench-scale sintering studies were prepared from mixtures of minus 200-mesh anorthosite and limestone using water alone as the pelletizing agent. Heating pellets at 1,270° to 1,360° C for periods of 0.5 to 2 hr, followed by a 15-min soaking period at 700° C and cooling to room temperature, produced a sinter that dusted to more than 90 pct minus 65 mesh. The weight ratio of limestone to anorthnsite was critical in producing sinter exhibiting good dusting and leaching characteristics. A ratio of 2.0 was optimum for the bulk samples of anorthosite and limestone used in this research. Leach solutions from lower ratio sinters were unstable; gelation became progressively more severe with higher ratio sinters. Leaching the dusted sinter with 10-pct Na2CO3 at 60° C extracted 85 to 90 pct of the alumina in a product solution containing about 50 g/l A1203. Leach residue in contact with pregnant solution tended to set up as a rigid gel as a result of cementation, comp action, and gelation. The presence of a calcium-sodium zeolite [(Cn,Na2)6?(Al2Si04)12?27-3OH20] in the ungelled residues seemed to be the main difference between gelled and ungelled residues.

Jan 1, 1982

By Alan A. Campoli

The U.S. Bureau of Mines evaluated two different conventionallongwall gate entry systems in the Southern Appalachian Basin, where mining and geologic conditions are conducive for coal pillar bumps. These gate entry systems were in a coal mine located in the Pocahontas No.3 Coalbed under approximately 2,000 ft of overburden and a massive quartzite sandstone member, and both employed a center abutment pillar flanked by yield pillars. The 8O-ft-square tailgate abutment pillars within the first study area began bumping 500 ft in advance of mining. This was accompanied by face bumps on the tailgate corner of the longwall face. The 120-by 180-ft tailgate abutment pillars within the second study area did not begin to bump until mining was approximately 100 ft past. Coalbed stress change and abutment pillar dilation data demonstrated that a 15-ft-wide perimeter of yielded coal surrounded a highly stressed core in both sizes of abutment pillars. The 62 pet more core area per foot of gate entry in the larger abutment pillars prevented excessive load transfer to the corner of the tailgate panel and eliminated the face bumps experienced with the original gate entry design.

Jan 1, 1990

By F. D. Everett

This report summarizes the results of a nationwide investigation completed in 1964 to determine the nonferrous base metal ore reserves and potential sources of ore and to evaluate criteria for their ultimate exploitation. Engineers of the Bureau of Mines contacted mining company officials, reviewed reports and Government records, and where necessary made personal appraisals in arriving at the results. The estimates are presented by metals in ores in geographic regions and include some of the problems affecting the reserves and potential sources. The recoverable metal in the measured ore category and in the total ore reserves was estimated as follows: [ ] At the 1963 rate of domestic mine production these total reserves would be adequate to provide copper for 62 years, lead for 121 years, and zinc for 42 years. Data also are given for gold, silver, and other coproducts. Reserve estimates greatly exceed those of previous investigations; some prior estimates of copper reserves are included for comparison (table 23). Projections of requirements for base metals indicated the United States will need approximately 45 percent more copper in 1970 and 110 percent more by 1980 than was consumed in 1960; similar projections for lead indicate increases of 20 percent by 1970 and 45 percent by 1980; zinc projections are 40 percent more by 1970 and 90 percent by 1980. Much of the production of gold and silver is a coproduct of base metals recovery and the projected need for the precious metals exceeds all the United States can produce. Some problems of the industry are mentioned. A graphic evaluation of the economic availability of the reserve and potential sources is shown.

Jan 1, 1967

By W. M. Bangert, F. S. Boericke

"INTRODUCTION Determination of the thermodynamic properties of metallurgically important compounds of chromium has been one of the activities of the Pacific Experiment Station of the Bureau of Mines. Earlier reports have dealt with the entropies 4/ 5/ of chromium, chromic oxide, and chromous and chromic chlorides, with the thermodynamic properties of the chlorides of chromium, 6/ and wits the thermodynamic properties of the carbides and oxide of chromium. 7/ Evaluation of the thermodynamic properties of chromite, FeO.Cr2O3, is desirable, as this material in impure form constitutes the only natural source of chromium of any consequence.Two general methods are available for directly determining heats of formation - (1) measurement of heats of combustion and (2) measurement of heats of solution. Neither of these methods is directly applicable at present to ferrous chromite, which accounts for the lack of previous data. Combustion of a stoichiometrical mixture of iron and chromium under conditions prevailing in a calorimetric bomb yields a mixture of iron and chromium oxides rather than chromite. None of the usual calorimetric solution media dissolve chromite at temperatures low enough for solution calorimetry. Sulfuric acid and an oxidizing agent, such as MnO2 or CrO3, are known to dissolve chromite, but the possible calorimetric use of t is medium would require long preliminary investigation. Consequently, recourse must be taken to some indirect method. At the start of the present work, the most promising method appeared to be the determination of equilibria in the selective, reduction of the iron in chromite by hydrogen;"

Jun 1, 1945

By W. E. Robinson

Differences in the composition or chemical structure of the organic material in samples of Uinta Basin (Utah) oil shale were studied relative to stratigraphic position within the Green River Formation. This involved a systematic study of the soluble organic material and the insoluble organic material (kerogen) present in the samples. Emphasis was placed upon the distribution of the alkanes (normal and isoprenoid compounds) in the soluble extracts and upon the aromaticity of the kerogen. Significant differences exist in the chemical composition of the organic material from various strata within the Uinta Basin, some of which were related to burial depth but most were related to source material variations, environmental differences, or other factors. The Uinta Basin samples differed significantly from Piceance Creek Basin and Green River Basin samples in the large amount of soluble extract they contained.

Jan 1, 1975

By Winton J. Gale

Coal pillar design has been based on generalized formulas of the strength of the coal in a pillar and experience in localized situations. Stress measurements above and in coal pillars indicate that the actual strength and deformation of pillars vary much more than predicted by formulas. This variation is due to failure of strata surrounding coal. The pillar strength and deformation of the adjacent roadways is a function of failure in the coal and the strata about the coal. When the pillar is viewed as a system in which failure also occurs inthe strata rather than the coal only, the wide range of pillar strength characteristics found in the United Kingdom, United States, Republic of South Africa, Australia, People's Republic of China, Japan, and other countries are simply variations due to different strata-coal combinations, not different coal strengths. This paper presents the measured range of pillar strength characteristics and explains the reasons. Methods to design pillar layouts with regard to the potential strength variations due to the strata strength characteristics surrounding the seam are also presented.

Jan 5, 1999

By d&apos, Kathleen J. Amico

This summary appears in Minerals Year-book volumes I and III, which cover mineral production in the United States, its island possessions, the Canal Zone, and the Commonwealth of Puerto Rico, as well as the principal minerals imported into and exported 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, 1966

By David A. Hill

This volume contains a summary of the results of past analyses on U.S. Bureau of Mines Contract No. 80122061 which are relevant to electromagnetic location in mine rescue situations. The analytical results indicated that detection of a trapped miner equipped with a special transmitter is feasible in most situations. Location of the miner by surface measurements is also generally feasible within certain errors. The feasibility of miner detection and the accuracy of miner location have been examined theoretically for a wide variety of situations. Agreement with experimental results is generally good in cases where measurements are available. Personnel involved in the investigation include J.R. Wait (Principal Investigator), D.A. Hill (Co-Principal Investigator), K.P. Spies, A.Q. Howard, and Lana Slusher (Administrative Assistant).

Jan 1, 1974