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By Albert L. Toenges

[During the past few years there has beer trend away from locomotive haulage of coal from the loading point to the preparation plant of bituminous-coal strip, miner to motorized. haulage. The question has arisen whether this is always economical, and the purposes of this investigation is to determine, if possible the economic limit for motorized haulage. The operators of strip coal mines and of open-pit ore mines have shown great interest in this problem, and it is thought that the findings of this investigation will. Provo helpful to them.]

Jan 1, 1938

By Kevin Malone

Chrysotile asbestos occurs in many counties in California, and a small production had been reported at times, but development of deposits had been disappointing. A reconnaissance survey by the Bureau of Mines indicated that several deposits in the serpentine belt in Shasta, Trinity, and Siskiyou Counties might contain enough asbestos of filler grade to supply the growing demand on the west coast. Accordingly from 1956 to 1958 parts of the Mount Eddy and Shasta View deposits were investigated by trenching and diamond drilling to determine their potential. The work comprised construction of roads, bulldozer trenching, excavation of areas for diamond drilling, sampling, and upping. The trenches were excavated to expose the surface extent of some of the asbestos-bearing areas, To determine the downward continuation of asbestos-bearing sections and to secure samples for test purposes, six diamond drill holes, totaling 1,738 linear feet, were drilled in two selected areas. The trenching and core-drilling indicated that the asbestos-bearing material occurs as ribs and lenses of varying thicknesses in a broad belt of serpentine, about 600 feet wide and several miles long,

Jan 1, 1962

By M. J. Beus

The U.S. Bureau of Mines is conducting investigations to improve design methods for mining volcano-genic massive-sulfide (VMS) type deposits in environmentally sensitive regions. This study was conducted at the Greens Creek Mine, which is typical of many VMS-type deposits throughout southeast Alaska, and served as a case history for computer modeling and structural analysis. Results indicated that the finite-element design method provided reasonable comparisons with both the anticipated regional stress regime and the measured deformational response of the underground accessways. Investigators concluded that reasonable accuracy can be expected for stability analyses of proposed mine design scenarios at this mine using the results of this preliminary study.

Jan 1, 2010

By J. R. Thoenen

The objective of this circular is threefold: First, to describe briefly the various modes of occurrence of sand and gravel. Second, to emphasize the need for adequate prospect¬ ing and exploration prior to the expenditure of funds for development and plant construction. Third, to describe various methods of prospecting and exploration and their application to the several modes of occurrence of sand and gravel. Sand and gravel may be found in nearly every county or township in the United States. Commercial deposits, however, are by no means so widespread. The introduction of concrete and the consequent impetus given to consumption of gravel and sand aggregates has seriously depleted deposits in some congested areas. Increasing re¬ strictions in the specification requirements for marketing sands and gravels have further narrowed the economic areas. On the other hand, the combination of increasing transportation costs and decreasing selling prices has forced the decentralization of gravel production. As a result smaller, intermittently operated, and widely scattered portable or semiportable unit plants have been encroaching on the territory formerly supplied from centrally located pits with large tr.atment plants. Generally speaking, the small portable plant can not produce any great variety of ma¬ terials to as exacting specifications nor as economically as the large permanent plant.

Dec 1, 1932

By D. A. Wilson

A laboratory method for processing lead battery scrap has been developed that eliminates virtually all of the S02 emission that normally is produced when a reverberatory or blast furnace is used. The method employs a hydrometallurgical step to convert the PbS04 to PbO and CaS04 by mixing the battery scrap with a slurry of Ca(OH)2. The reaction is exothermic and goes to completion in 2 to 5 minutes at room temperature. The dried product is mixed with a KC1-NaC1 flux and carbon and reduced at 6500 C. A minimum charge ratio of 3 parts of carbon to 100 parts of battery scrap is required for reduction. The process produces lead reductions and recoveries as high as 97.0 and 94.9 percent, respectively. The KCI-NaCl flux is recovered using a standard counter-current water leach followed by evaporation.

Jan 1, 1976

By Dennis R. Dolinar

The National Institute for Occupational Safety and Health?s Pittsburgh Research Laboratory conducted a full-scale test of a composite polyurethane-aggregate seal in a hydrostatic chamber at the Lake Lynn Experimental Mine. This composite seal consisted of a polyurethane and limestone aggregate core that was formed between two concrete block walls. In the hydro-static chamber test, water is used to pressurize the seal. During the test, the maximum average water pressure the seal was able to withstand was 18.9 psi. Further, the seal began to yield at an average water pressure of only 17 psi. At the time of the test, the minimum seal design requirement was 20 psi under 30 CFR4 75.335 (2005). Therefore, based on this test, the seal did not meet the regulatory minimum design requirement. Uniaxial compressive tests conducted on samples from the polyurethane-aggregate core revealed that both the compressive strength and the elastic modulus of the material were much less than that for polyurethane only with a density of 10.0?12.0 lb/ft3. The significant reduction in the strength and stiffness of the polyurethane-aggregate mixture results from the formation of a soft polyurethane foam around each piece of aggregate. The formation of the soft foam seems to be caused by residual moisture from the aggregate. The moisture also caused the density of the polyurethane in the polyurethane-aggregate mixture to be less than the design requirements. The lower density of the polyurethane in the mixture, along with the formation of zones of pure polyurethane only, resulted in the overall seal density being less than the design requirements. During seal construction, steps were taken to control the moisture, but were not successful. An analysis of the seal failure showed that the calculated shear stresses at failure and the estimated shear strength of the polyurethane-aggregate mixture are fairly close. This suggests that the strength properties of the polyurethane-aggregate mixture along with a weak zone of poorly bonded aggregate controlled the maximum pressure the seal could withstand. At the time of the seal testing, the minimum design requirement was 20 psi, as specified at 30 CFR 75.335 (2005). New emergency temporary standards for seal designs were promulgated on May 22, 2007, with a minimum requirement of 50 psi under specified conditions. However, it will be shown that the evaluation of the polyurethane seal performance as designed to meet the older 20-psi criterion can be relevant to the design requirements under the new standards.

Jan 1, 2008

By Arel B. McMahan

The U.S. Bureau of Mines investigated mines, prospects, and mineralized areas in the Owlshead Mountains Wilderness Study Area (WSA) in 1982. Within the WSA, subeconomic manganese, iron, zinc, and lead resources were identified at two mines; sample analyses indicate five other mines and prospects may have gold, silver, iron, manganese, and copper resources. Three mines examined adjacent to the WSA have identified manganese and iron resources; and sample analyses indicate manganese, iron, and gypsum resources may exist at two prospects. Greatest likelihood for future identification of mineral reserves is for manganese at the Black Magic Mine in the southeast part of the WSA. The southern half of the WSA contains nearly all identified mineral resources, and properties at which sample analyses indicate additional resources. The most significant are manganese and iron resources at the Black Magic Mine in the southeastern part of the WSA; and the Ellie, New Deal, and Owl Hole Mines adjacent to that part of the area. Manganese and iron minerals filled fractures and replaced limestone in brecciated and faulted contacts with intrusive granitic rocks. In the southwest corner of the WSA, sample analyses indicate four prospects may have gold and silver resources. These precious metals are in gouge zones along contacts where diorite has intruded volcanic rocks. A small identified resource at the Kennedy Boys Lead Mine in the western part of the WSA consists of quartz veins with zinc and lead minerals along a brecciated contact between granite and limestone roof pendants.

Jan 1, 1985

In 2005, a total of 2,063 coal mining operations reported employment to the Mine Safety and Health Administration (MSHA). Coal mines comprised 14.1% of all mining operations. ? Bituminous mines comprised 92.6% (n=1,911) and anthracite mines 7.4% (n=152) of coal mining operations. ? Approximately 70% of all coal mines were located in three states: Kentucky (28.0%), West Virginia (21.8%), and Pennsylvania (20.6%).

Jan 1, 2008

By William G. Pariseau

A small displacement-small strain finite element technique utilizing the constant strain triangle and incremental constitutive equations for elastic-plastic media that are nonhardening and obey a Coulomb yield condition has been applied to the analysis of gravity flow initiation in a V-shaped hopper containing a powder under lunar environmental conditions. Three methods of loading were examined. Of the three, the method of computing the initial state of stress in a filled hopper prior to drawdown by adding material to the hopper layer-by-layer is superior (as expected). Results of the analysis of a typical hopper problem show that the initial state of stress, the elastic moduli, and the strength parameters have an important influence on material response subsequent to the opening of the hopper outlet.

Jan 1, 1971

By J. M. Singer

Thermal, mechanical, and physical properties of virgin and heat-treated Pittsburgh seam coal were determined as part of a comprehensive study of combustion of monolithic coal block. The information was sought to help characterize pyrolysis and combustion processes in underground coal mine fires but should also prove useful in the study of in situ and surface coal gasifiers. Measured properties include thermal conductivity, specific heat, thermal expansion, density, compressive and tensile strength, porosity, and permeability. The transport property data were obtained (when feasible) in two mutually perpendicular directions of the anisotropic virgin coal material, and coal samples carbonized for 5 hours at temperatures of 350° C, 475° C, 500° C, 650° C, and 850° C. Other coals (Pocahontas No. 3, Sewell, and Illinois No. 6 seams) were investigated for porosity and relative permeability. Interdependence among all properties was evident from the results; however, only a few correlations could be developed owing to inhomogeneity of coal material and specimen variation, which had the effect of reducing the accuracy of measurement and increasing data scatter.

Jan 1, 1979

By H. F. Feldmann

This Bureau of Mines report presents a method for the computer solution of the equilibrium compositions of any complex, multiphase, chemical system for which appropriate thermodynamic data are available. The method describes in detail the computation of systems in which solid or liquid species can form by heterogeneous chemical reactions where these species do not occur in any equilibrium equations. Also described are the calculation of phases formed by condensation (pure or solutions) and the inclusion of other system restrictions such as electroneutrality. The method is being used to compute the equilibrium composition of mixtures of an electrically conductive plasma and a liquid slag phase arising from the high-temperature combustion of coal for magnetohydrodynamic power generation. These mixtures can contain up to 65 species including gases, liquids, free electrons, and ions.

Jan 1, 1969

By Mark S. Sanders

The purpose of the present study was to develop and test improved Type V workvests for use on dredge operations. The goal was to design workvests that would be more comfortable to wear, would interfere less with task performance, and would better meet the needs of dredge workers. It was hypothesized that by attaining these goals, the resulting vests would be worn more often and would be kept buckled more of the time than traditional vests. The study involved three major phases. In Phase I, visits were made to dredge operations and a definition of the problem was developed. Problems with current vests were identified and working conditions and tasks surveyed In Phase II, prototype vests were developed and laboratory tests were per-formed to assess comfort and interference. In Phase III, the prototypes were modified and field tested with actual dredge operators and workers.

Jan 1, 1985

By Donald S. Colby

This Bureau of Mines report is essentially a handbook, or manual, for making the type of mineral resource valuation commonly required for such public policy problems as mineral leasing. The principle of resource valuation through the capitalization of cash flow is well established. A mathematical procedure, based on a simplified accounting system, is detailed for calculating cash flow from revenue, plant costs, and operating expense. Variations of procedure cover cost depletion, percentage depletion, and depletion limited to 50 percent of net income. The influence of the depletion provisions of the tax regulations on the value of a resource to an owner and to an operator is analyzed. The relationship of royalty, bonus payments, and sales price to resource value is also described, and methods for approximating resource values using these payments as input data are developed.

Jan 1, 1969

By James S. Browning

For the past several years, the Bureau of Mines has conducted laboratory and continuous process development work on weathered mica pegmatites and micaceous schist ores to determine the feasibility of recovering commercial-grade mica concentrates by flotation. The research has resulted in the development of two processes for flotadon of mica: an acid cationic method for recovery of coarse mica, and an alkaline anionic-cationic method for recovery of fine mica. The research indicated that the two processes may be effectively utilized separately or in combination for flotation of mica from weathered pegmatites and micaceous schists. Concentrates containing over 98 percent mica, with recoveries ranging from 77 to 92 percent, were obtained from the pegmatite ores. The micaceous schist ores yielded concentrates containing 95 to 98 percent mica, with recoveries ranging from 70 to 83 percent. Part 1 of this report summarizes the process development work and demonstrates the feasibility of producing commercial- grade mica concentrates. The report also includes details of commercial beneficiation and grinding of .mica.

Jan 1, 1973

By David P. Lindroth

The objective of this research by the Bureau of Mines was to determine the technical feasibility and associated pilot data for drying minus 1/4-in coal with microwave energy at a frequency of 2.45 GHz. The drying data were obtained experimentally on three coal types: bituminous, subbituminous, and lignite. The experiments were performed with a custom-designed conveyorized microwave oven having a continuous power capability of 12 kW. Drying efficiencies near the theoretical maximum of 1.54 kg of water per kilowatt hour of energy input were achieved for two coals and two sizes; overall drying efficiencies averaged 77 pct.

Jan 1, 1986

By W. L. Falke

Research was conducted to develop methods on a laboratory scale for recovering manganese from manganiferous slimes and limestones . The procedure is a low- temperature modification of the carbamate process , in which manganese is dissolved and the valence reduced by treating slimes and limestones with controlled amounts of sulfurous acid . Manganese ( II) hydroxide is precipitated and leached with ammonium carbamate solution , and manganese carbonate is separated by warming the leach solution . A major portion of the reagents is regenerated and recirculated . About 75 percent of the total manganese in manganiferous slimes , and from 50 to 75 percent of the total manganese in manganiferous limestones , are recovered as manganese carbonate containing 45 percent manganese .

Jan 1, 1964

By R. L. Solmer

During 1959-61, the Bureau of Mines investigated the strain and deformation induced in rock and concrete linings around mine openings by retreat panel caving at the Climax Molybdenum mine. Two concrete-lined slusher drifts on the Phillipson level of the mine were instrumented with both electrical strain gages and extensometers. Changes in strain and deformation were recorded over an 18-month period during the undercutting and caving of the mining panel. General agreement was found between the strain and deformation measurements and the hypothesis that the vertical component of the stress field on the openings is almost completely removed by undercutting. This phenomenon is a possible explanation for the structural failures that occur in the slusher drifts during the undercutting cycle.

Jan 1, 1965

By R. G. Dressler

The design and operation of the Koppers powdered-coal gasifier and its auxiliaries at Louisiana, Mo., are described. This unit was designed to convert 1 ton of coal per hour with oxygen and superheated steam into synthesis gas - primarily carbon monoxide and hydrogen. The first run was made on May 4, 1949. After this, 44 short runs (less than 8 hours each) and 1 long run (lasting 11 days) were made. Total gasification time was 420 hours. The gasifier was not cooled down during the year when these runs were made. After an initial period of test operations and equipment proving, during which 12 runs were made, the effect of numerous variables on gasifier performance was studied. The long run was made primarily to check the equipment in sustained operation. Detailed data from these runs are presented.

Jan 1, 1954

By Kenneth P. V. Lei

The Bureau of Mines investigated a silver-catalyzed oxidative procedure for leaching an arsenical copper sulfide concentrate containing 10 pct As and 32 pct Cu_ Currently, there are no environmentally safe means to treat arsenical copper concentrates in the United States. Leaching was conducted in a 2-L autoclave reactor. The effects of catalyst concentration, O2 pressure, temperature, and H2S04, Cu, As, and Fe concentrations in the leaching solution on extractions of metals from the concentrate were determined. The best leaching conditions for extracting 95 pet eu and As and less than 21 pct Fe were 260 g/L concentrate, 0.007 mol/L (1.0 g/L) AgCI, 3.0 mol/L (294 gIL) H2S04, 1000 C, 60 psig 02, and 6 h. Copper as CuS04-5H20 was recovered by crystallization from the pregnant solution. Arsenic, as AS203, was recovered from the copper mother liquor by solvent extraction, with tributyl phosphate, S02 reduction of As5+ to As3+ in the strip solution, and crystallization of the As3+. The silver catalyst was recovered by contacting the leached residue with a brine solution. A conceptual scheme is proposed for treating arsenical copper sulfide concentrates.

Jan 1, 1987

By P. G. Guest

"INTRODUCTION Need for More information on Spark IgnitionMany questions have yet to be answered more completely concerning the ignition of flammable gases and vapors by electric sparks. Among these one might mention the following: How do the mixture limits for ignition by sparks and by other means compare? Are the most explosive mixtures of the gases the most easily ignited? How ""hot"" must the spark be or what is the minimum energy required for ignition? Does the electric spark act merely as a source of thermal energy or do aggregations of ions, electrons, and metastable atoms formed during and just before the spark play an important part in promoting chemical reactions that ultimately lead to ignition? It is possible for ignition to occur as a result of a silent or brush discharge? How do the ignition energies with single and rapidly recurring sparks differ? What is the relative effectiveness of long, tenuous sparks in ignition as compared with intense, short-gap sparks of equal energy? What is the influence of the material, size, and shape of the spark electrodes? Does the energy for ignition change noticeably with moderate changes in pressure and temperature of an enclosed gas mixture? What order of lag exists between the occurrence of an incendiary spark and the first evidence of flame propagation? What part of a spark in space and time is most effective in producing ignition? Answers to these questions bear directly on the general problem of flame initiation and propagation and, if sufficiently comprehensive, should contribute much to an understanding of the actual mechanism of combustion."

May 1, 1944