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By Richard F. Link

The principal procedures for the statistical analysis of gold assay and other trace-element data depend on applying either the normal frequency distribution or the lognormal frequency distribution. The consequences of applying both methods are examined through reference to example data from United States and South African gold mines. It is concluded that for estimation of average grades, except for certain data with a very high coefficient of variation (ratio of standard deviation to mean), use of the lognormal distribution is ordinarily undesirable because bias may be introduced and little efficiency can be gained. However, if biased average grades can be tolerated, as in the examination of data from surveys in exploration geochemistry, use of the log-normal distribution may be desirable. Various statistical analyses are detailed, and the tables presented to implement the analyses are more complete than those previously published.

Jan 1, 1971

By Thomas M. Barczak, Christopher Mark

Roof supports can only be understood in conjunction with the rock structure that they support. The strength of the rock depends on geology, and the loads are applied primarily by the in situ and mining-induced stresses. Other factors, such as wider spans and retreat or multiple-seam mining, can also reduce the stability of mine openings. Roof supports are used to help stabilize these openings, but their performance characteristics must be properly matched to the loading environment and ground behavior if they are to succeed. Roof supports include both intrinsic supports, such as roof bolts, and standing supports. The key characteristics of any support include its maximum load-carrying capacity, stiffness, and residual strength. Other important factors are the timing of installation, the stability of the support as it is loaded, and the capability of the support system to provide skin control. This paper explains in practical terms how supports work and the important factors in ensuring that a good support design and application strategy are developed.

Jan 10, 2000

By C. O. Hawk

As an exploratory effort to produce useful products from coal by a new path, the Bureau has made a few experiments on the fast heating of finely ground coal particles by irradiation with a flash of high intensity light. The flash was produced by an electrical discharge at high voltage through a xenon-filled tube. The flashes lasted from 2 to 3 milliseconds. The reaction took place in small sample tubes, ½ inch-dimeter by 4 inches long, and with small amounts of coal (total amount charged 0.1 gram, probable effective amount not more than 20 milligrams). Average particle size of the coal, estimated on a numerical basis, was 20 microns. Temperatures reached were evidently quite high, because all products obtained in quantity were characteristic of high temperature pyrolysis. Apparently, conversion of the coal was extensive where isolated particles received the full benefit of a flash. It seems particularly significant that acetylene was present in appreciable amounts--comprising almost 3 percent of the total gaseous product in one case. This is good evidence of a short heating period to very high temperature (well above 1,000° C) followed by rapid quenching. Although the results are interesting, they do not suggest any immediate practical application.

Jan 1, 1963

By Richard C. Ballance

Fly ash from four sources and in certain proportions was shown to assist chemical coagulation of turbid water and settling of chemically induced floc. Fly ash reduced the time required to form the first visible floc, promoted more uniform flocs about 2 mm in diameter, and increased the mean settling rate of floc particles. Also, the addition of fly ash produced denser sludges than those obtained with alum alone. Final turbidities were independent of fly ash particle size and carbon content. Optimum proportions of fly ash additive are given.

Jan 1, 1966

By James L. Konchesky

Crushed coal, consisting of a wide range of sizes, was effectively blended by recycling it through a bin equipped with a particle distributor. Vertical blending was accomplished by simply recycling the coal; it was not significantly influenced by the horizontal blending that was achieved by the distributor. The method was effective, even though the coal was wet and possessed poor flowing characteristics. Recirculation appears capable of providing uniform blends of solids that can be more efficiently processed. Recirculation also appears useful, preceding packaging operations, to insure for blending of solids into specification products. Continuous measurement of the bulk density of the coal by a gamma ray meter proved to be an effective monitor of vertical blending effectiveness.

Jan 1, 1972

By D. E. Hirsch

The Bureau of Mines, as a part of American Petroleum Institute Research Project 60, Characterization of the Heavy Ends of Petroleum, has made extensive use of gel permeation chromatography (GPC). Data developed in this study were used to develop several correlations that greatly expanded the usefulness of GPC and the data have been used as an aid in the interpretation of mass spectra (MS). GPC retention volume data on pure compounds were used with molecular structure to develop correlations that can be used to accurately predict retention volumes, molecular volumes, densities, chain lengths, and ring numbers of many components of petroleum without resorting to further laboratory experimentation. Conversely, the correlation can be used to select or reject some compounds from several possible compounds that are indicated on the basis of MS analysis. The utility of these correlations in compound type characterization is demonstrated by showing their application to 330° to 550° C fractions from a low-sulfur and a high-sulfur crude oil.

Jan 1, 1974

By James V. Kelly

During the spring and summer of 1947, the Bureau of Mines conducted an investigation and core-drilling program in the vicinity of the Rodham mine, approximately 4 miles north of Shullsburg, Wis. This work was undertaken as a part of a general study of the zinc and lead-producing area of southwestern Wisconsin. Work in the Rodham-mine area was done to investigate further a mineralized area frilled in part by the Puritan Exploration Co., a Delaware corporation, with offices in Galena, Ill. Some significant lead-bearing samples were obtained, but no continuous ore body was disclosed as a result of the Bureau of Mines work.

Jan 1, 1949

By G. S. Price

This paper, which describes the milling practice at the Page concentrator of the Federal Mining and Smelting Co., is one of a series being prepared by the Bureau of Mines. The Page mine and mill are located on Silver Creek, 3 miles west of Kellogg, Idaho, and 1 mile south of United States Highway No. 10. Supplies and concentrates are hauled by truck over an automobile road which connects Highway No. 10 with the property. The concentrator has capacity to treat 300 tons of ore per day and utilizes all-flotation methods of treatment. Power is supplied from the main line of the Washington Water Power Co. which runs from Spokane, Wash., to Kellogg, Idaho. Water is obtained from the mine and also from a well which is situated 1 mile distant from the concentrator and about 600 feet in elevation below the concentrator.

Jan 1, 1932

By Wesley A. Grosh

The Valzinco mine, Spotsylvania County, Va., is a lead-zinc deposit with minor quantities of copper. The property was reopened n 1942 by Panaminas, Inc. The Bureau of. Mines, in an effort to increase the reserves of the deposit to justify greater production, diamond-drilled nine holes totaling 4,213 feet during 1943. Drilling by the Bureau delimited the original ore body and discovered another ore body on the hanging-wall side, which was being developed by the company at the close of the project.

Jan 1, 1949

By J. B. Janus

This report continues a series of analyses of coal samples made by the Bureau of Mines in connection with the yearly purchase of several million tons of coal for various Government agencies. Listed are the analytical data on the composition and quality of tipple and de livered samples of coal collected during fiscal year 1974.

Jan 1, 1975

By R. V. Subramanian

This project financed by the Bureau of Mines investigated the use of polymers to achieve rock bonding and reinforce coal mine structures for better or permanent ground support. Support was achieved by pumping the polymers into the rock interstices to bond the mass together for increased structural competence. Holes were drilled in the mine roof, after which the polymers were injected at about 100 psi to permeate the cracks. Initial laboratory work indicated that of all the resin systems tested, the epoxy resins could most likely be modified to be suitable for rock injection. This was confirmed when several potentially suitable resin systems underwent intensive evaluation. In a series of three field tests, two conducted in a copper mine with coal mine-type shale and the third in a coal mine, it was shown that the polymers penetrated cracks less than 0.005 inch wide. The fast-setting epoxy systems, cured out in thin films under mine conditions, produced a bond exceeding the strength of the uncracked virgin rock.

Jan 1, 1974

By R. L. Grayson, W. E. Wallace, T. Simonyi, J. C. Harrison

"Application of an SEM-based methodology suggests a reason for past contradictory results on the relationship between quartz and coal workers' pneumoconiosis (CWP). Results indicate that coal seams with the same bulk analysis of quartz may have different amounts of surface-availablequartz. Our research shows that the amounts of pure and surface-available quartz in a respirable dust vary directly with the rank of a coal seam, except in the case where rock materials are mined. The estimated amount of surface-available quartz therefore provides a measure of the quartz-related fibrogenic potential of a respirable dust.INTRODUCTIONFrom our previous work (Grayson, 1991), we have shown that the amount of pure quartz in a respirable coal mine dust sample appears to vary directly with the rank of the seam (using fixed carbon as the basis for comparison), except when a substantial rock parting, roof or floor are mined. Our other work (Wallace et al., 1989) showed that high-silica particles in a clay mine may generally be coated with clay, rendering the quartz core non-available for surface reaction in the lung. The combination of these findings led us to hypothesize that the coating phenomenon may indeed be present in coal mines as well, and that a rank relationship may be present regarding this phenomenon. Thus higher rank coal seams may have more surface-available quartz as well as more pure quartz particles in their respirable dusts. The scientific protocol for testing this hypothesis and the results obtained to date are discussed in this paper. Thus far, there is no reason to doubt that the relationship holds."

Mar 1, 1992

By W. H. Ode, W. A. Selvig

Low-temperature distillation tests at 200°, 350°, and 500° C. were made on a subbituminous coal from Boulder County, Colo., and a subbituminous coal from Weld County Colo., in connection with a survey of carbonizing properties of American coals 4/ and investigations of their chemical and physical properties. 5/ The coal represented by the sample from Weld County was reported to give off combustible volatile matter at unusually low temperatures when placed on a fuel bed. The yields of tar and oil and the composition of the as from this coal, as obtained in the distillation tests, did not confirm this report. These yields and the gas composition of the Weld County coal differed but little from those obtained from the coal from Boulder County. Both coals yielded tar and gas in amounts considered to be normal for coals of their rank.

May 1, 1937

By C. C. Merrill

Studies were made to determine the amenability of yttrium to fused-salt electrorefining in a controlled atmosphere. Tests were conducted in a LiCl- YCl3 electrolyte system at 710° C. The major variables studied were the YCl3 content of the electrolyte, from l.7 to 13.4 mol percent, and the initial cathode current density, from 410 to 1,630 amperes per square foot. Vacuum distillation was employed to remove salt from the deposited metal. Metallic impurities, except for lithium, could be reduced to near or below their lower analytical limits, ranging from 10 ppm for Cu to 300 ppm for Ta; reduction of oxygen content, however, was accomplished only in metal produced from electrolytes with 5.4 mol percent YCl3 or less. Initial cathode current density had little effect on the purity of the product.

Jan 1, 1967

By Jack R. Woodyard

Bonding angles, promotion energies, and relative atomic sizes can be estimated through the solution of a set of algebraic equations generated from simple atomic models, and quantum mechanical parameters such as bond strength can be estimated from simple, hydrogenic form-wave functions. The precepts of The Engel-Brewer Theory are melded with the "Crystal Approximation Model" to produce atomic-structure models making these predictions, The two-valence-electron case is presented in this report. For the candidate atoms Be, Mg, Ca, Sr, and Ba the calculated promotion energies agreed within a few percent of their experimental values. These atomic parameters determine the possible crystal structure of the candidate atoms when alloyed. This is part of the effort at the U.S. Bureau of Mines to develop methods for alloy design in response to requirements for new high-performance alloys that conserve critical or rare materials.

Jan 1, 2010

By John H. Soule

Appreciable quantities of sine and lead orus have been produced from the West. Pinos Altos district of Grant County, N. sex. This area was visited many times by engineers of the Bureau of ines. D. H. Johnson and 4. R. Storms visited the district in haren 1943 in connection with an acrenu road to toe wines. M. H. Storma again visited the area in July 1943 in connection with a hetals Feserve Corporation loan on the Routen-Thomas

Apr 1, 1948

By McHenry Mosier

Mercury is one of the strategic metals the supply of which has been raised from critical uncertainty to more than enough for essential demands. Work by the Bureau of Mines has contributes substantially to increased production of mercury in the United States and to consequent accumulation of Governments stock. Other contributing factors were higher prices for mercury and Government loans to operators. The Bureau has undertaken 15 exploration projects, 13 of which have been completed. This work comprised 40,307 feet of drilling arid 35,082 linear feet of sure ace trenching and has indicated commercial ore containing 37,400 flasks of mercury and marginal ore contain¬ing 29,200 flasks - a total of 66,600 flask , equivalent, respectively, to domestic production at 50,000 flasks per year for 9 months , 7 months, and 16 months. Early in 1944, as Government stocks had become adequate, domestic production was gradually curtailed cancellation of Government contracts for the purchase of mercury and Government control of labor and operating supplies.

Jan 1, 1944

By R. F. Stewart

A sedimentation method involving the use of the Palo-Travis apparatus was found satisfactory for rapid determination of the size distribution of coal particles ranging from 10 microns in diameter to those passing an 840-micron opening (20-mesh sieve), The method is most useful for comparing the size distributions of samples of pulverized coal where the actual size of the particles is not required and is applicable to sieve and subsieve sizes of a wide variety of coals and chars that can be wetted and are heavier than water. An analysis, including all calculations, can be completed in 1/2 to 10 hours, depending on the time required for the finely divided coal to settle. A typical analysis requires about an hour, making this a rapid, precise method for routine size-distribution analysis of powdered coals. When used with coal particles smaller than 400 microns, the method is precise within 15 microns for wide variations in test conditions and within 5 microns for identical test conditions. The precision decreases as particle size increases, becoming unsatisfactory for particles larger than 400 microns (40-mesh). For precision within 15 microns, the samples must be equal in weight. Greater precision is obtained with 4-gram samples, but samples as small as l gram may be used.

Jan 1, 1961

By W. G. Bradley

THIS PAPER describing the quarrying, mining, and crushing of gypsum at the Blue Diamond mine, 11 miles from Arden, Nev., on the Union Pacific Railway, is one of a series on gypsum mining being prepared for and published by the Bureau of Mines. These papers are designed to disseminate technical information regarding the methods used. The cost tabulations represent operating expenditures only and not total costs. It is recognized that publication of total production costs might in some instances cause embarrassment to individual producers as well as to the industry as a whole. On the other hand, operating costs are essential to the technical discussion and study of the methods employed. The attention of the reader is specifically called to this differentiation in order that no misunderstanding of the scope of the cost tabulations shall ensue.

Jan 1, 1932

By S. D. Maksimovic

The use of vertical surface degasification boreholes with bleeder systems and the use of a timbered bleeder system to degasify gob areas were studied by the Bureau of Mines. This report describes three gob degasification studies conducted in the Pittsburgh coalbed. One study was conducted to determine the number of panels degasified with one large borehole. The study showed that the borehole provided degasification for three panels. Another study was conducted during the retreat of a 35-acre panel with a single-entry and a two-entry bleeder system and a large surface borehole. A major portion of methane emitted from the panel was carried away by the bore-hole, leaving the bleeder entries relatively free of methane. The last study was made to determine the effectiveness of a timbered bleeder system. The bleeder entries successfully degasified the gob area when enough entries were available and adequate pressure was available to force the air through roof falls.

Jan 1, 1980