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By Michael G. Pojar, John K. Ahlness

"The copper industry has had a long and interesting history associated with leaching, involving vat, dump, heap, and in situ methods. The Bureau of Mines has also had an interest in copper leaching and has researched the techniques of solution recovery, particularly concentrating on in situ methods. In situ mining is a relatively low cost method and has been proven commercially successful by nine operations. It has been most commonly used for final recovery in old workings at the conclusion of conventional mining operations.This report brings together information about 10 commercial in situ operations as well as 14 experimental projects. These 24 sites comprise most of the in situ copper mining activities that have taken place in the United States. Background information, geology, ore preparation, solution application, and recovery and processing are provided for each operation. Production data and tables summarizing the engineering statistics for each operation and an extensive in situ mining bibliography are included. INTRODUCTIONThe purpose of this Bureau of Mines report is to summarize the documented in situ copper leach mining activities that have taken place in the United States. It was prepared to provide a source of engineering and operating data upon which future in situ copper mining activities can be based. Twenty-four different sites are discussed. These are all of the sites that are known to the authors from the extensive in situ copper leach mining bibliography developed at the Bureau's Twin Cities (MN) Research Center (Appendix B).In situ copper leach mining activities fall into the following categories:1. Commercial operations with ore body preparation.2. Commercial operations in old mine workings.3. Experimental programs.Ore body preparation includes such activities as blasting, block caving, and hydraulic fracturing (hydrofracing) specifically to fragment the ore body. Operations in old mine workings include those done in open pits, worked out block caved areas, and backfilled stopes where leaching is done as an afterthought to conventional mining. Experimental programs are small-scale tests of the feasibility of a commercial operation. Some of these programs did not progress to the point where leach solutions were applied to the ore.Each operation (locations shown in figure 1) will be discussed in terms of background information, geology, ore preparation, solution application, recovery and processing, and engineering and production data. Information was collected from published reports, communications with company personnel, and site visits."

Jan 1, 1982

By Carl E. Norman

An investigation of geologic structure on macroscopic, mesoscopic, and microscopic scales was conducted on near-surface igneous and metamorphic rocks in which the existing stress field was determined by in situ methods. A consistent NE-SW orientation of the maximum compressive stress in the horizontal plane at four of five test localities appears due to the intrusion of NW-trending diabase dikes. Structural features at the mesoscopic scale show no consistent directional relationship to determined stress directions. Petrofabric diagrams of open microfractures show preferred orientations, but these are not consistently related to the orientations of larger structural features, such as joints, foliation, or mineralized shear zones. However, at five of six test sites the preferred direction of microfractures occurs nearly perpendicular to the maximum principal stress directions; an anomalous parallel relationship exists at a test site in an intrusive rock body. The results suggest that the open microfracture subfabric may provide a means for gaining information on the directional properties of stress fields. Such information can be obtained from oriented cores taken from holes which exceed the approximate 100-foot depth to which other in situ methods are presently limited.

Jan 1, 1970

By James C. Barker

Gold placer deposits along the upper Yukon River, in the region between the river villages of Circle and Eagle, were investigated by the Bureau of Mines. The investigation was conducted intermittently between 1976 and 1985 as part of an evaluation of mineral resources on lands proposed for inclusion in the National Park System. At least 230,000 troy ounces (tr oz) of gold has been produced in the region, principally from Woodchopper, Goal, and Fourth of July Greeks. The placers are underlain by, or occur downstream of, early Tertiary sediments that have been deposited in the Eagle Trough. Strike-slip displacement along the Tintina Fault is responsible for creation of the trough and may have been a factor in the formation of the present placers. Placers were found to have a close spatial correlation to certain altered fault lineaments of the Tintina Fault trench. Placer concentrates contain several different textural forms of gold, suggesting multiple origins. Geological studies and a survey of 162 panned concentrates throughout the region indicated previously unreported sites of placer gold, and potential exists for the discovery of additional placer and lode gold. Because of nearly continuous soil and vegetation cover, further evaluation of the region will require subsurface sampling.

Jan 1, 1986

By Charles L. Kimbell

While the statistical summary focuses on 1991 data, this update and outlook section draws on information available to the author as of the date of final preparation in early 1993. For all the press notoriety associated with the shift in the Near East crisis from the defensive posture of Desert Shield to the restoration of Kuwaiti sovereignty through Desert Storm, this was not the dominant event governing global economic thinking in 1991 and the first half and more of 1992. From the global perspective, the momentous political changes in the area that was the U.S.S.R. and in the smaller emerging transitional economy states of Eastern Europe will have even greater current and long-lasting effects on world mineral industry activities than the crisis in the Near East.

Jan 1, 1993

By Edward D. Thimons

Several types of inflatable stoppings, developed under Bureau of Mines contract for use as mine air barriers during underground production, have been tested by the Bureau. All of the stoppings tested showed significant internal leakage initially but, in all but one stopping, the leaks were sealed with limited effort The stoppings were tested underground in two western noncoal mines under production conditions. The results from the Colorado molybdenum mine showed the stoppings to be generally unsatisfactory for daily mine usage if they are deployed near blasting areas or in locations where near-perfect air seals are required. They were very susceptible to blast damage and seldom were better than 90 percent efficient as air barriers. However, stoppings tested in the New Mexico uranium mine were located substantially distant from any blasting. Because slight leakage past the stoppings was acceptable, they proved very satisfactory in that application.

Jan 1, 1976

By Thomas R. Bur

Symmetry theory, based on ground work established in the study of single crystals and experimental procedures utilizing ultrasonic pulse velocities of spherical specimens plotted on equal area polar projections, enables the direct identification of a material's elastic symmetry system and the determination of its orientation, as well as the position of the elastic coordinate axes. The method is especially useful for elasticity studies of polycrystalline and amorphous materials for which this knowledge of symmetry is a prerequisite in determining the independent elastic constants. Projections based on theoretically derived velocities are given for a single crystal from each of the major crystallographic symmetry systems except the triclinic. Projections based on experimentally derived velocities are given for one brass and several rock spheres.

Jan 1, 1969

By J. Wade Watkins

One potential peaceful application of nuclear explosives is stimulating the production of liquid or gaseous hydrocarbons from essentially nonproductive deposits of petroleum, natural gas, oil shale, and tar sands. Within the United States the appreciable difference between producible proved reserves and ultimate reserves and resources of hydrocarbon deposits is of such magnitude that much petroleum, natural gas, shale oil, and bitumen will not be produced unless significant technological progress is made in production techniques. The shattering effect of contained nuclear explosives and, to a lesser extent, the heat produced, have been considered as stimulative forces when the thickness, depth, and nature of such deposits permit considering the use of nuclear devices. Mechanical production problems would be less in an oil or gas reservoir than in an oil-shale or tar-sands deposit. Also, tar-sands resources in the United States may not be adequate to warrant serious consideration of applying nuclear-explosives stimulation. Gas reservoirs should present the least- radioactive-contamination problem. The technical feasibility of using nuclear explosives cannot be evaluated fully at present. Additional information is needed on the effects of pressure, heat, and radioactivity on the solids and fluids of hydrocarbon deposits, the nature and extent of induced fractures in different rock media, and the possibility of isolating and confining or removing radioactive contaminants. Final technical feasibility can only be determined by a field test. If technical feasibility is established, economic feasibility will depend upon the comparative cost of producing hydrocarbons by nuclear explosives and by conventional means. It is probable that an economic comparison would favor nuclear stimulation only where devices of relatively high yield could be used practicably and safely.

Jan 1, 1964

By E. J. Gleim

In April 1932, the Bureau of Mines published Information Circular 6595, entitled "Data in Reference to Installation of Cables in Shafts and Boreholes", in which were described methods followed in various sections of the United States when electrical circuits are taken into mines by means of cables suspended in shafts and boreholes. In view of the present tendency to extend high-tension cables along entries and passageways from the bottom of the shaft, borehole, or other point of entrance to coal mines rather than over the surface, it is deemed that the various methods of installing such cables deserve careful consideration, particularly in mines in which gas and coal dust contribute to explosion hazards. This is especially true of localities where there is an inclination to restrict the extension of 2,300- and 4,000-volt circuits into the mines. Probably it is feared that accidental contact with the cables of such circuits may result in more serious shock than with lower voltages; also, it is possible that new circuits are regarded merely as explosion hazards additional to those already existing, regardless of the manner in which the new circuits may be installed. It is the firm belief of some engineers that the circuits can be installed so that they will not be damaged by wrecks or roof falls, thereby eliminating the hazard of explosion from this source while at the same time making the chance of accidental contact remote if not impossible. Moreover, some believe that fire hazards from direct-current systems can be reduced by keeping motor-generator sets close to load centers. Thus, although the alternating-current circuits would be lengthened, the size and extent of direct-current circuits would be kept to a minimum.

Jan 1, 1939

By Oliver Bowles

Slate possesses many admirable qualities, not only as a roofing material, but for blackboards, electrical switch boards, and for various structural uses such as stair trends, floor tile, baseboards, and sanitary enclosures. The American slate industry was established manor years ago, and has made remarkable progress, particularly during the past five years. One of the chief drawbacks to more rapid expansion is the high percentage of waste which reaches 75 to 94 per cent of gross production. Much of this waste is duo to rock imperfections over which man has no control, but a careful study of tae industry by the Bureau of Mines over a period of years indicates that an undesirably large percentage of the marketable slate is wasted in the processes of quarrying and manufacture. The initial step in quarrying slate is to separate from the solid ledge masses of a size that ray be conveniently removed from the quarry. This first step entails a greater waste of material than any subsequent process, and, therefore, invites the most earnest effort toward waste reduction. Attention has consequently been directed toward possible improvements in methods of making primary cuts in the quarry floor. A study of European practice with the wire saw, together with theoretical consideration of its advantages, convinced the writer that it possessed sufficient merit to justify its use as a primary slate cutter in American quarries. No practical conclusion in this matter could be reached except by experiment. Therefore, the desirability of obtaining equipment and trying it out under actual conditions of operation was urged upon operators. While no doubt the equipment could be readily manufactured in America, it had already been developed to the point of practical use in Europe; therefore the writer urged the desirability of purchasing one completely equipped wire saw in Europe, and determining through tests whether it gave sufficient promise of success to warrant its manufacture in America.

Jan 1, 1927

By V. E. Erwin, W. W. Adams

"INTRODUCTION This report presents statistics of accidents at coke ovens in the United States during the calendar years as 1933, the twenty-first year for which data of this kind are available, 1913 being the first year for which accident reports were collected from the operating companies by the Bureau of Mines. The present report is presented in mimeograph form because insufficient funds are available for printing it. The first report of the Bureau of Mines that contained statistics of accidents for the coke-mining industry in the United States covered the two calendar years, 1913 and 1914. While the figures presented therein related both to beehive and by-product ovens, the original returns from the operating companies were not classified so as to permit the presentation of accident statistics for each class of ovens separately. Beginning with 1915, the accident reports from the operating companies have shown the general type of ovens to which the reports related; therefore, since that year, separate statistics for each of the two classes of ovens have been given in the Bureau's yearly reports of accidents at coke ovens.The coke-making industry in the United States established a safety record in 1933 almost equal in merit to that which it achieved in 1932, when the accident-frequency rate was the lowest and therefore the most favorable that the industry has known. Credit for the achievement is due almost entirely to companies operating byproduct ovens. (See table 8.)"

Mar 1, 1935

By H. R. Beard

The Bureau of Mines investigated the absorption of radium and thorium from waste uranium leach liquor by clays and other materials. This work was conducted in support of the Bureau's goal of minimizing the environmental conflicts, impacts, and occupational hazards associated with mining and milling operations. Tailing and soil samples from New Mexico were evaluated for their potential to absorb radium and thorium from tailing liquors. Absorption ranged from 0 to 97 pct for radium and 0 to 60 pct for thorium. Some samples that readily absorbed radium were contacted with various salt solutions that could be present in tailing solutions to determine whether desorption would be a potential problem. The desorption of radium ranged from 0 to 75 pct. An alpha spectrometric method was used to determine the radium and thorium concentrations in the solutions and solids.

Jan 1, 1980

By D. D. Dornenburg

The effect of changes of atmospheric pressure on methane emissions from extensive worked-out areas of coal mines in several Midwestern States has lone caused concern to State and Federal mining departments, as well as to the operating companies involved. Common mining and ventilation methods employed in mines in these States have resulted in large sealed and unsealed worked-out areas in which considerable quantities of methane are emitted alone both intake-and return-air courses. The common practice is to watch barometric changes very closely and take special precautionary measurer during periods of low barometric pressure. Although the hazard is recognized, mining officials have different opinions concerning the effect of barometric pressure variations on the emission of mine gases. These opinions are based upon scattered personal observations, as no records exist of actual studies to establish such effects.

Jan 1, 1955

By Andrew B. Cecala

The Bureau of Mines conducted laboratory and in-mine tests on the Racal airstream helmet (Model #AR21) to evaluate its protection efficiency. Laboratory tests indicated that as ambient air velocity increased, the protection offered by the helmet decreased. In tests conducted at several coal mine long-wall sections with face velocities under 400 fpm, the helmet was 84 pct effective at reducing respirable dust in the miner's breathing zone. However, at a high-velocity section, 1,200 fpm, the efficiency of the helmet was significantly reduced, confirming our laboratory results.

Jan 1, 1981

By H. P. Greenwald

About mid-December 1936, the safety director of a large coal corporation visited the authors at the Bureau's Experimental coal mine to discuss a rock-dust barrier he had invented primarily for use in trackless entries of coal mines. The rock dust in this device was carried in its original paper containers and means were provided for ripping these open so that the dust might be scattered in the path of an explosion. The inventor termed the device a "bag barrier", and this term has been adopted in the present paper for convenience. At that time the device was in an early stage of development, and the inventor felt that the barrier should be tested to determine whether it had enough promise of being successful to justify further development. The matter was taken under consideration and finally three tests were made during the week of February 15, 1937. It was concluded that while the device did stop an explosion in two of the three tests, it was much loss effective than ordinary rock dusting, and that too few data were obtained to permit direct comparison with tests of other barriers. Apparently, the conditions under which the device could, be successful 'Were somewhat limited, out the limits could not be defined without additional tests.

Jan 1, 1938

By R. W. Stahl

"This study by the Federal Bureau of Mines was confined to pillaring with continuous mining machines and to mines where total extraction is practiced. Many different conditions and practices in as many coalbeds as possible in Pennsylvania were observed.Pillar extraction or pillaring can be the most productive part of coal mining if done properly; but it also can be the most dangerous if done improperly.Because of the need for more careful planning before and caution during pillaring, many mining companies resort to the undesirable practice of stumping or hogging of pillars with subsequent unnecessary waste of valuable natural resources. Pillaring can be done at reasonable cost and safely, as proven at many mines where complete extraction is practiced and enviable cost and accident records are maintained.Although continuous mining machines are bulky and sometimes difficult to maneuver, they have been used with great success in pillaring. Occasionally, however, a machine is caught, or men are injured by a fall during pillar recovery. This Bureau survey was conducted to ascertain how safe and successful pillaring (especially the removal of final stumps in lifts or the final stump of a pillar), is accomplished in some mines, while others have considerable difficulty under similar conditions.The Bureau hopes the information to be presented in this publication will prove beneficial to those who wish to recover more pillar coal and to improve their accident record during such procedures."

Dec 1, 1959

By Earl L. Phillips

The Bureau of Mines conducted laboratory tests on samples of pozzolanic-cement concrete to develop a low-strength backfill. Results show that support costs can be lowered by replacing a portion of the portland cement in mine backfill with pozzolan (fly ash) and lime. Unconfined compression tests on various ratios of fly ash to cement in 84 samples produced compressive-strength curves that can be used to estimate the best backfill mix for any mine.

Jan 1, 1981

By Joseph N. Harstead

This Bureau of Mines report provides information on the first 49 water-flood projects (or units) in Nebraska. All injection was in the ?D? or "J" Cretaceous sands of western Nebraska. Specific data presented include location, map, discovery and development, water supply and injection, oil and water production, estimates of oil in place, primary and secondary recoveries. The 49 projects studied) including four dual-zone projects, should recover about 126.5 million barrels of oil. Eighty-six percent of the estimated oil had been recovered by the end of 1966. Abundant water was found near most projects.

Jan 1, 1967

By Paul M. Tyler

Graphite is chemically identical with diamond, both being crystallized allotropic forms of carbon. Graphite obviously differs greatly from diamond in physical properties and is easily recognized by its blackness, its softness (1 to 2 on Mohs' scale), and its slick feel when rubbed between the fingers. Strictly speaking, all graphite is crystalline, but grades in which the individual grains cannot be distinguished with the naked eye are commercially classed as amorphous. Natural mixtures of the two varieties occur in all proportions, and the classification of a given sample as "amorphous" or "crystalline" graphite is based largely upon trade practice. Until recently different varieties of vegetable or animal charcoal, lamp black, soot, gas carbon, and coal ware considered strictly amorphous, but modern examination by X-ray methods indicates that even these materials possess the same internal crystalline structure as graphite, differences in physical properties being perhaps explained by porosity or presence of combined hydrogen or other impurities.

Jan 1, 1941

By Foster Fraas

The dielectric constant .has been frequently referred to as an important property in electrostatic separation whore the particles are in an air ambient. Hatfield (1) has studied the problem on the basis of fundamental theory, with the conclusion that separations in air dependent on the differences in dielectric constant, in conjunction with a nonhomogeneous field, are not feasible, because of the low dielectric strength of the air. Although Hatfield has made the statement without showing the calculation or data, calculated values substantiating this under certain conditions of the problem will be given in the following text. However, under other Conditions, these conclusions do not hold, and it is probable that the dielectric constant is indirectly influential.

Jan 1, 1948

By B. H. Eccleston

Experimental work is reported showing the effects of gasoline characteristics on auto emissions. Fuel volatility is shown to influence evaporative losses, with the higher losses associated with higher volatility. Fuel front-end olefin is shown to contribute significantly to reactivity of emissions. Large vehicle-to-vehicle differences were found. The study was conducted by the Bureau of Mines at its Bartlesville Energy Research Center in cooperation with the Coordinating Research Council Air Pollution Research Advisory Committee. The work was done using 15 1968-70 model autos and eight fuels were tested at ambients ranging from 20° to 95° F. Data on emissions from each vehicle-fuel-temperature combination are presented. Also included are calculated photochemical reactivity data and the distribution of hydrocarbon and nitrogen oxides during the test cycle.

Jan 1, 1972