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By d&apos, Kathleen J. Amico

THIS SUMMARY appears in Minerals Yearbook 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 operatons at or near mines.

Jan 1, 1963

By d&apos, Kathleen J. Amico

THIS SUMMARY appears in Minerals Yearbook 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, 1965

By S. H. Ash

California leads the Nation in the number of operating metal mines and the small number of persons employed at individual mines, which reached a minimum irk 1932 with an average of seven men. The mines are scattered over the entire State, which is the second largest in area (155,562 square miles) in the United States. The mines are situated at various altitudes, with portals ranging from approximately 300 feet below sea level to almost 12,000 feet above. Many of the mines can be reached only during the summer, while at others the heat of the regions adds so the difficulties during the summer months Supplied of explosives the use (or, probably more correctly, the misuse) of which constitutes one of California's gravest mining problems; are handled and stored under condition that contribute many hazards. The problem of providing medical care is serious and complicated, especially at small mines and more particularly in the almost inaccessible mountainous regions; instances in which a knowledge of first aid would have been beneficial but was lacking, or when first aid was instrumental in saving life or limb because it was available are too numerous to be mentioned.

Jan 1, 1936

By F. W. Lee

Operating engineers and mining executives are interested in the science of applied geophysics, but are looking for a simple and understandable exposition of its problems, instead of dissertations which are becoming more and more involved and increasingly difficult to comprehend. It may be well to discuss the goal, the attempted methods of reaching it and the psychological motive, if any, tack of the science. Where does the subject of applied geophysics stand from the viewpoint of (1) the physicist, (2) the mathematician, and (3) the geologist? Fundamentally, the science aims at a differentiation of subterranean geology with the object of finding useful mineral products by the study of gravitational, magnetic, seismic, electric, and other fields which may be associated with the materials naturally or which may be applied to them. The more skillfully these fields are recognized, applied, and analyzed the greater will be the possibility of interpreting results in a way that will be remunerative both economically and scientifically.

Oct 1, 1931

By W. M. Myers

The U. S. Bureau of Mines conducted an investigation to determine the cause of the deterioration of Portland cement during storage and transportation , and to discover a means of preventing it . All available printed sources of information on this subject have been examined and a bibliography has been compiled . The subject has also been discussed with the leaders in the cement industry ; the present report is the result of their cooperation , and is based principally on information thus obtained . Deterioration of Portland cement during storage over any considerable period of time has long been noted ; closely related to it is deterioration of cement during transportation, which involves not only the time factor of storage but also exposure to varied climatic conditions . Deterioration in both cases is due to hydration of the cement by absorption of moisture from a humid atmosphere , or by exposure to actual rain-fall . After hydration cement possesses no cohesive power ; the degree of deterioration is directly proportional to the degree of hydration . The amount of deterioration of Portland cement during storage has been accurately determined in an investigation by the Structural Materials Research Laboratory , in cooperation with the Portland Cement Association . Cement stored in a shed in cloth sacks retained 80 per cent of its original strength after three months storage ; 71 per cent after six months ; 61 per cent after one year ; and 40 per cent after two years . The deterioration of Portland cement during storage and transportation was noted particularly in France during the World War . Information concerning cement used by the American Expeditionary Forces was furnished by Lt. Col. H. S. Spackman and Major E. C. Eckel , U. S. R. , who had charge of practically all matters concerning cement used by the A. E. F. The cement used by the A. E. F. came from the following sources : 42,000 tons was French , Swiss , and Spanish cements ; 120,000 tons was English cement ; 55,000 tons made in plants operated by the A.E.F .; 500 tons ( Not over) from America . Deterioration was most marked in cement from the first source .

Jun 1, 1922

By Lloyd A. Morley, Alan M. Christman

General Six open-pit metal mines, five copper and one molybdenum, were visited during the course of the research. Four were investigated twice, in summer and in winter, in order to determine the effects of seasonal variations In temperature and moisture upon the measured parameters, Permission to enter the fifth mine was received too late to make an examination during the summer months. The sixth mine was visited to confirm the results obtained from the other five and specifically, to observe how the project recommendations (as will be presented in this chapter) would apply to open-pit metal mines in general. Information gathered during the ten plant visits is sufficient to form an adequate data base for the report. A complete presentation of all field trip data is given in Appendix 1. Further, a detailed description of the electrical distribution and grounding practices at each mine is also contained there. Typical System. At a typical mine as shown schematically in Figure 62, one or more substations with resistance-grounded secondaries are employed to transform the incoming utility-voltage to the lower potential used by the mining machines, generally three-phase 4160 V. At this level, pit distribution is carried on overhead lines, supported by wooden poles, to supply switchhouses located in benches near the particular piece of equipment. A switchhouse is a small portable (often skid-mounted) structure at the termination of an overhead line which contains disconnect

Jan 1, 1976

By David C. Byrne

PURPOSE: Evaluate practical technological advances in hearing protective devices for use in different mining environments. RESEARCH SUMMARY: Previous NIOSH research shows that miners develop hearing loss much more quickly than nonoccupationally noise-exposed individuals. Also, miners experience a greater severity of hearing loss than would be expected for nonoccupational noise-exposed persons of the same age and sex. As described in the National Occupational Research Agenda, problems created by occupational hearing loss include (1) the reduced quality of life due to social isolation and unrelenting tinnitus, (2) impaired communication with family members, the public, and coworkers,(3) a diminished ability to monitor the work environment (e.g., warning signals, equipment sounds, etc.), (4) lost productivity and increased accidents resulting from impaired communication and isolation, and (5) expenses for workers’ compensation and hearing aids. Although the elimination of hazardous noise is the ideal long-term solution to the noise problem, miners will likely need to rely on personal hearing protection in certain situations for quite some time. However, it is well known that noise attenuation provided by hearing protectors as they are worn during everyday use in the workplace is usually worse than when tested under laboratory conditions. Additionally, workers may refuse to wear their hearing protection for any number of reasons. Therefore, this project was initiated to evaluate practical technological advances in hearing protectors, with an emphasis toward optimizing the balance between effectiveness, comfort, overprotection, and communication ability. Currently, the necessary in-house laboratory facilities and research techniques are being finalized. Individual experiments are planned that involve analysis of new hearing protector technology under both laboratory and field conditions. The laboratory components are to consist of con-trolled studies using human subjects and/or an anthropometrically correct artificial test fixture to evaluate the adequacy/effectiveness of various hearing protective devices. Field studies are planned to determine the actual usefulness and practicality of the hearing protectors as used in diferent mining environments. Recommendations can then be offered to the mining community regarding correct earplug/earmuff usage that maximizes recognition of hazard/warning sounds while adequately protecting the miners’ hearing.

Jan 12, 2000

By Thomas Varley

Data on the consumption of reagents used in .flotation during the year 1925, in metallurgical plants in the United States, are presented in this paper. Previous reports have covered the same subject for the years 1916, 1919, 1923 and 1924. The data contained herein show departures most radical from even the 1924 practice. Flotation has developed rapidly and on a more scientific basis than ever before. Perhaps more fundamental and useful data have been uncovered during the past two years than in all the years the art has been practiced.

Jan 1, 1926

By Hylton R. Brown

Advertisements and articles in technical and trade journals announce the approach of a new age, in which plastics, light metals, laminated wood, and numerous other products or byproducts will be used in the construction of automobiles, airplanes, and furniture and equipment used in our factories, offices, and homes. Undoubtedly, after the war there will be many such developments which will introduce new manufacturing methods and new hazards to challenge the safety engineer. Already we know, from experience in laboratories and pilot plants where these new products are being tested, that there will be many fire and explosion hazards to be overcome. The danger of dust explosions may be one of the principal hazards, because thetic resins and other materials used in the plastics industry, as well as metal powders, wood dust, and other finely divided substances, are capable of forming explosive mixtures in air. Heavy losses of life and property have been caused by dust explosions in flour and feed mills, starch factories, and grain elevators, and it will be well to consider the possibilities that such losses may occur in any new industry and to provide all possible safeguards against hazards. Fortunately, we have learned something about the behavior of dust explosions and know something about the ease of ignition, limits of Explosive concentration, end pressure developed. Our efforts should now be directed toward the application of this knowledge in the development of safe operating practices.

Jan 1, 1945

Develop an environmentally feasible method of mining shallow oil sands without removing overburden. Approach Oil sands are extracted through a single borehole by cutting into the sands around the borehole with a high pressure water jet, and pumping the resulting slurry to the surface. Although oil can be extracted from shallow fields by open-pit mining methods, this type of mining may create significant environmental impacts, including; (1) disruption of the surface, (2) accumulation of waste rock piles, (3) accumulation of tailings, (4) damage to the ground water quality, and (5) surface water pollution. The borehole mining system developed and successfully field tested by the Bureau of Mines offers a method for extracting oil from oil sand with minimal disturbance to environmental quality. (For examples of other applications of borehole mining, see Technology News Nos. 95, 63 56, and 48.) How It Works Prior to the start of mining operations, baseline conditions for ground subsidence and ground water quality are established at the test site so that the degree of subsidence and changes in ground water quality can later be determined. Oil sands mining is conducted using the Bureau of Mines borehole mining system. The borehole mining tool consists of a 12-inch-diameter pipe string and accessories capped with a three passage swivel terminated with a mining section. The mining section has an auger at the bottom. Four slurry inlet holes and an eductor are located above the auger, and a single cutting nozzle is located near the top of the mining section. The tool generates a high velocity water jet that erodes and slurrifies ores. The slurry is drawn into the inlet of the eductor which lifts the slurry to the surface where it is deposited into a slurry discharge sump. To detect evidence of subsidence, surveys of the land surface are made at regular intervals during, and until 30 days after, the termination of the mining operations. Samples of ground water from the borehole and two adjacent monitor holes are taken on alternate days during the mining operations, and are later analyzed to determine if any ground water contamination has occurred.

Jan 1, 1981

By L. C. George

The Bureau of Mines measured the vapor pressures of selected mixtures in the binary systems CdCl2 ?SnCl2, CdCl2 -ZnC12, PbCl2 ?SnCl2, and PbCl2 -ZnCl2 by the static pressure method. These data were evaluated by the second-law (sigma-plot) method. Equations expressing the vapor pressures and the heats and free energies of vaporization as functions of temperature are given.

Jan 1, 1969

By G. R. Hopkins

One of the largest items in the expense of operating a refinery is the cost of the fuel used in distillation and for miscellaneous purposes such as in the heating of buildings and in the generation of electricity, On a B. t. u. basis, the average refinery consumes approximately one-tenth as much fuel as it produces. Theoretically, the fuel consumption at refineries should be much smaller than this, but furnaces can riot be designed to be 100 per cent efficient' and, in addition, a large part of the waste heat is low-temperature heat which would not pay for the expense of recovering it. Annual surveys of fuel consumption at refineries have been made by the United States Bureau of Mines, beginning with 1925. During the 5-year period, 1925-1929, the refineries made steady progress in fuel economy. This is evidenced by the Computed figures of heat requirement Per barrel of crude oil refined, which show a decline from 829,000 B. t. u. in 1925 to 639,000 B. t. u. in 1929 (see fig. 1). In 1930, however, the trend in fuel economy was reversed and the quantity of heat utilized in refining the average barrel of crude oil rose to 672,000 B. t. u. There were undoubtedly a number of reasons for the apparent decrease in fuel economy at refineries in 1930, chief of which were the tendency to carry the distillation farther instead of merely topping the crude and a gain in the consumption of waste oils, such as acid sludge, which in actual practice yield less heat per unit consumed than has been theoretically assigned to oil. The consumption of natural as fuel at refineries has declined since 1927, but this has been more than compensated by a rapid increase in the use of refinery or still gas. The total consumption of oil as refinery fuel in 1930 was not much below the 1925 total, but the consumption of coal has declined rapidly, so that in 1930 liquid and solid fuels contributed only 56 per cent of the total heat units- utilized at refineries as compared with 77 per cent in 1925 (see fig. 2).

Jan 1, 1931

This chapter presents MSHA data on mine employment and active mining operations during 1986-1995. Figures 3-1 through 3-10 show, for each commodity, the location of mine operations in 1995, and employee hours and active mining operations by year during 1986-1995 for mine operators. For coal and nonmetal operators, the number of active mining operations and the number of employee hours decreased over the 10-year period. For metal operators, the number of active operations decreased, while the number of employee hours increased. For stone and sand and gravel operators, the number of active operations and the number of employee hours remained about the same. Figures 3-11 and 3-12 show that over the 10-year period, there was an increase in the proportion of hours worked by contractors in coal mining, while the overall employment decreased. For metal, nonmetal, stone, and sand and gravel combined, the proportion of contractor hours increased, with overall employment also increasing. Table 3-1 shows the distribution of hours worked during 1986-1995 by commodity and type of operation. For coal, the majority of hours worked were in underground mines. For metal, nonmetal, and stone, the largest number of hours worked were in mills and preparation plants. For sand and gravel, all work hours other than office were in surface mines. [ ]

Jan 5, 2000

By Edward D. Thimons

A remote-actuated stench gas fire-warning system has been designed and tested by the Bureau of Mines. This system makes use of the hard-wire network for the mine's phone pager system, thus greatly reducing the system cost. By locating stench gas canisters with remote-actuation release capabilities near working sections, the fire-warning time can be greatly reduced. In a test of the system in a Missouri lead mine, the time required to warn miners of a fire at two working faces was reduced from about 20min with the conventional system to less than 4 min with the remote-actuated system.

Jan 1, 1984

By L. B. Pankratz

Heat contents were measured for Na2CaSi04 and Na2Ca2S02 between 298° and 1,300° K, for Na2Ca2Si309 between 298° and 1,500° K, and for Na4CaSi3O9 between 298° and 1,350° K. Copper-block drop calorimetry was employed. Reversible, first-order transitions were found for Na2CaSi04 and Na2Ca2Si309. The transition for Na2CaSi04 is at 830° K with a heat absorption of 160 cal/mole; that for Na2CagSi309 occurs at 750° K with a heat absorption of 1,550 cal/mole. Results for the other two silicates showed no irregularities. A table of heat content and entropy increments above 298.15° K and heat con-tent equations are included for use in thermodynamic calculations.

Jan 1, 1968

By Robert A. Jankowski

Through laboratory and underground studies, the Bureau of Mines has evaluated the use of passive barriers (dust shields) to help confine dust generated by longwall shearers to the face area. Laboratory studies focused first on selection of the optimum barrier design, which proved to be a simple, gobside barrier (made of conveyor belting), coupled with a headgate splitter arm, which was found necessary to prevent the dust cloud from entering the walkway at the headgate end of the shearer when cutting tail to head. Further laboratory testing was done to determine whether using passive barriers in combination with different water-spray dust-reduction methods, including the shearer-clearer system developed by the Bureau, would improve dust reduction over that from using the water sprays alone. It was found that the combination of gobs ide passive barriers plus the full shearer-clearer system was most effective, and surmised that this would be especially useful in thicker seams. However, underground testing revealed that the shearer-clearer system alone was 35 pct more effective in reducing dust contamination than when used with the gobside passive barriers, and far more effective than using passive barriers with a conventional water spray system. For such an effective system as the shearer-clearer; the reduction in avail-able space over the top of the machine actually impeded system performance; this was shom1 in both eastern and western mines. But when used with comparatively inefficient water spray systems, the passive barriers, used in combination with a headgate splitter arm, provide consider-able help in reducing dust levels in the walkway.

Jan 1, 1986

By C. J. Tsai, K. Olson, R. Caldow, B. Cantrell, D. Y. H. Pui

"The amount of new surface generated during fracture of coal and rock has been found to be directly proportional to the amount of energy associated with the fracture. To confirm this and study the relationship between the new surface and dust aerosol formed during fracture the U.S. Bureau of Mines has conducted experiments simulating fracture as it occurs during mining operations. In addition to fracture energy measurements, fragment size distributions were determined over a size range of 0.5 microns to 1 inch. The size measurements accounted for the mass of the original sample. Material studied was Illinois No. 6 coal, coal from the Taggart seam of Virginia, and Berea Sandstone. The experiment employed a chamber to confine sample fracture fragments and a combination of particle measuring systems. Measurement methods included aerodynamic sizing of entrained dust aerosol with optical counting and inertial impaction techniques, physical sizing of non-airborne fragments by sieving, and optical sizing of fragments using optical counting and scanning electron microscopy.Results of the size distribution measurements indicate that a single size distribution law does not adequately describe the entire fragment size distribution. A combination of two size distribution laws, such as the Rosin-Rammler and log-normal distributions, is necessary to describe this size distribution. New surface created by fracture is primarily found 1n particulate between 2 and 50 microns with a mean size of 12 microns. It was also found that the specific energy of fracture can be linearly related to the .concentration of aerosol in this size range.Only a .small fraction, between 0.02 and 0.16 pct, of the dust particles .generated during fracture become airborne. The remainder adhere to the new surface created during fracture. An entrainment fraction, defined for a given particle size is the ratio of the mass of airborne particles to that of the total particles generated in that size range. This experimental entrainment fraction is related to the Van der Waals adhesion force and the electrostatic forces operating during fracture and is used to derive empirical parameters to model these two processes."

Jan 1, 1989

Coal is found in the northeast comer of Georgia, in Dade, Chattooga, Walker, and Floyd Counties. Five seams, which underlie all of Lookout, Sand, and Pigeon Mountains, have produced most of the coal mined in the state. Representative analyses of Georgia coals show that they are typically low sulfur (less than one to one percent), low-to-medium volatile, bituminous deposits. Although there is no active mining in the state, reclamation continues on several permitted areas. In 1983 the State of Georgia relinquished primacy to the Office of Surface Mining. Since that time permits have been issued and mining completed. All the sites are presently in the process of bond release.

Jan 1, 1992

By Jr. Oitto

A polyester-type resin and deformed-steel reinforcing bars (rebars) were used in to strengthen and to stabilize bolted, fractured wall rock along pas 1:'y. in a western gold mine. Reinforcing bars were placed in boreholes drilled into fractured rock and then were surrounded by resin pumped under pressure into the holes and intersecting fractures until the wall rock was thoroughly impregnated. Pumping and injection equipment and infusion procedures are described. Visual examinations for movement in bonded and adjacent unbonded rock were made for 3 years. Fractured walls containing resin-rebar installations were strengthened. The results suggest that resin-rebar support can be used advantageously and economically in repairing fractured or broken rock when compared with rock bolting or timbering.

Jan 1, 1965

By J. D. Davis

Coke Since the beginning of manufacturing of metallurgical coke in the United States, which dates from about 1859, Pennsylvania has main tamed supremacy in coke production Available statistics for the year 1880 show an output of 3,338,300 short tons, which was neatly trebled by the end of the succeeding 10 years. From this time on the increase was steady, though not rapid, and in 1922 the total production was 13,991,892 tons, which is approximately 37 per cent of the total coke production of the United States. The main reason for the rapid development of the coke industry in Pennsylvania lies in the abundance of coals particularly adapted to beehive coking, for which purpose the Pittsburgh bed in the Connellsville district has long been looked upon as standard At first practically all metallurgical coke was made in beehive ovens, the only exception being the short lived and wasteful method of coking in piles, byproduct owns did not make then appearance until after 1893 The suitability of a beehive coking coal cannot be accurately predicted from its chemical analysis, but it can be said, perhaps, that the volatile matter should be about 32 per cent, and that the oxygen content should not be mole than 10 pet cent or less than 4 per cent The sulphur and phosphorus content should be small-not over 1 25 per cent sulphur and under 0 02 pen cent phosphorus-and the ash content should not be over 7 per cent The Pittsburgh bed at Connellsvnlle fills these requirements well, as may be seen from the following representative analysis. Analysts of coal from Pittsburgh bed Moisture 1 70 Volatile matter 31 10 Fixed carbon 59 80 Ash 7 40 Sulphur 0 85 B t u 13,990

Jan 1, 1928