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By P. W. Jeran, C. M. McCulloch, Maurice Deul

The natural vertical fracture sys tem in bituminous coalbeds is called cleat. Cleat orientation commonly controls the direction of mining with major development paralleling the face cleat. Previous researchers have categorized the origin of cleat as endogenetic, relating the origin of cleat to compaction and coalification, and exogenetic, relating the origin of cleat to tectonic forces. In the coalbeds studied for this report it was found that tectonic forces were the controlling factor of cleat formation. Face cleats were formed as extension fractures during structural deformation, and butt cleats, as release fractures during erosion and uplift. The face cleat of the Pittsburgh coalbed rotates from N 80° W in north- western West Virginia to N 57° W in southwestern Pennsylvania ; the face cleat maintains a perpendicular orientation to the shifting axial trend of local structures . Cleat orientation in other bituminous coalbeds in Virginia, Utah, Oklahoma, and Central Pennsylvania showed a similar relationship to local structure. Directional permeability of coal is directly related to cleat. Holes drilled perpendicular to the face cleat yield from 2.5 to 10 times the amount of gas released as compared with holes drilled perpendicular to the butt cleat.

Jan 1, 1974

By J. B. Littlefield

The term "konimeter" is used generally to designate a type of dust-sampling instrument that collects the dust from a small volume of air by impingement on a glass plate prepared aced with an adhesive film. The konimeter was first developed by Sir R. N. Kotze about 20 years ago and was followed a few years later by the circular-type konimeter, by which a number of samples may be collected on a glass disk. The present discussion will be confined to the circular type, as it is used most. Various techniques have been developed for using the konimeter, and many materials, such as petrolatum, mineral oil, and glycerine jelly, have been used in preparing the adhesive film. In South Africa, Australia, and Canada, where the konimeter has been employed most widely, dust samples are treated by ignition and washing before being counted. In Canada the dust samples are collected on a disk of special heat-resistant glass prepared with a film of mineral oil; the disk is then heated to a dull cherry-red in a muffle-furnace to remove the film and organic matter, cooled, and washed with a few drops of 50-percent hydrochloric acid followed by distilled water and alcohol, and then heated again to remove residue left by evaporation of the alcohol. After this treatment, the dust samples are counted under a magnification of 150 diameters with dark field illumination.

Jan 1, 1938

By Sathit Tandanand

Massive roof overlying the working seam in longwall operations can cause hazards if it does not cave readily behind the face supports. The overhang thus formed can overload the supports and endanger personnel when it collapses suddenly as a large rock mass. This Bureau of Mines report proposes the use of a concentrated load, either strip or point loading, applied onto the roof with the help of the upward thrust of the face supports. An experiment was conducted in the laboratory to obtain information about break characteristics and the values of significant parameters of three sedimentary rocks. The results were used to determine the breaking load requirement for a strong roof possibly encountered in typical longwall operations. The results show that the roof slab of moderate thickness can be fractured within the load capacity of off-the-shelf powered supports.

Jan 1, 1979

By Oliver Bowles

"A Product from Mica Mines.Mica commonly occurs in pegmatites which consist of large crystals of feldspar and quartz, mica constituting but a small proportion of the total rockMuch of the feldspar thus thro n out during the process of mining is pure and of high quality, end the Bureau of Mines has suggested that much of it could be utilized for ceramic purposes. Encouragement is given to such utilization by the fact that several mines now worked for mica were formerly operated for the production of feldspar. ""'here mines are not readily accessible to railroads feldspar utilization might not be feasible, for it is a much lower priced product than mica and cannot therefore bear as heavy transportation expense. '""here mines ire located close to railroads, however, such utilization would tend to reduce the cost of mica mining, and at the same time assist in the solution of the waste disposal problem.The Bureau has recently been informed that some of the feldspar from mica mines near Spruce Pine, N.C., is now being sold and shipped away. An extension of this by-product industry is to be recommended.A Mica Deposit in New York City.The Bureau recently received a mica specimen obtained from a. building excavation at 157th St. and Riverside Drive, New York City. The specimen was about 2 by 4 inches in size, and fairly clear though containing numerous hair cracks. It was obtained only 7 or 8 feet below street level. At greater depth and with more careful methods of excavation material of much better quality might be obtained. The material submitted could be used for mica washers but not for sheet mica. It is stated by an official of a prominent mica company that many such fragments are obtainable in this locality and the possibility of the occurrence of a good mica vein is thereby suggested."

Jun 1, 1920

By Aarne Visnapuu

Experimental modifications have been made by the Bureau of Mines on standard pneumatic rock drills to reduce the noise of the air exhaust, drill steel resonance noise, and noise radiated by the drill body. A close-fitting case and muffler around the drill body, consisting of a metallic honeycomb skeleton filled with viscoelastic absorber on the inside and a durable outer shell, provide both exhaust and drill body noise muffling and absorption. Drill steel resonance noise is reduced by a constrained-layer treatment consisting of a tubular metal cover bonded to the ouside of the rod by a viscoelastic filler. Damping alloy components have been developed to reduce metallic resonance noise. Combined, these modifications have reduced the drilling noise level in granite from 115 dbA to 97 dbA. Data are presented on the individual and combined effects of these modifications on drilling noise and performance.

Jan 1, 1975

By Donald O. Capstick

A mineral survey of a 13,525-acre portion of the 21,875-acre Owyhee Canyon Wilderness Study Area in northern Nevada was conducted by the U.S. Bureau of Mines in 1984. Two samples from sand and gravel deposits in the study area contained minor placer gold typical of the Owyhee River area. The gold-bearing gravels are too low grade or of insufficient volume to support commercial placer mining operations. The sand and gravel deposits might have minor local construction uses.

Jan 1, 1986

By T. H. Jeffers

Significant amounts of cobalt, a strategic and critical metal, are present in readily accessible spent copper leach solutions. For example, recovery of cobalt at two major u.S. copper operations could produce about 1,300,000 lb Co annually, about 13 pct of domestic consumption. However, techniques such as solvent extraction and precipitation have not proven cost effective in separating and recovering the cobalt from these low-grade domestic sources. The Bureau of Mines has devised a procedure using a chelating ion-exchange resin to extract cobalt from a pH 3.0 copper leach solution containing 30 mg/L Co. Cyclic tests in 4-ft-high by 1-in-diam columns gave an average cobalt extraction of 95 pct when 65 bed volumes of solu-tion were processed at a flow rate of 4 gpm/ft2 of resin area. After an impurity scrub, eluates contained, in grams per liter, 0.4 Co, 0.2 Ni, <0.001 Cu, 1.3 Fe, 2.8 Zn, and 0.008 AI. Solvent extraction procedures to remove impurities, reject nickel, and concentrate cobalt produced a cobalt sulfate solution containing 80 g/L Co, 0.05 g/L Ni, and not more than 1 mg/L Cu, Fe, Zn, or AI. Based on data from commercial electro-winning operations, this solution appears suitable for production of metallic cobalt.

Jan 1, 1985

By A. L. Engel

The sample of ore on which the work described in this paper was done came from Mina Oriente, Carrizal Bajo, Provincia de Atacama, Chile, South America, and was sent at the request of the Chil.ean Government through the Foreign Minerals Division of the Bureau of Mines. This ore had been tested locally for treatment by flotation and cyanidation without satisfactory results. An additional difficulty was the absence of water near the ore deposits, so that in any treatment method considered the water requirements would have to be very low. It was desired to develop a practical method of recovering the gold and, if possible, the copper in the area. No data of previous investigations were made available. The sample received was mostly quartz, highly brecciated, with limonite and hematite in the fractures. Copper occurred as malachite and azurite, also in the fracture s and to a slight extent as a stain in the quartz. Some fine-grained pyrite with a little arsenopyrite occurred within the quartz. An occasional grain of chalcopyrite was observed. No free gold was seen during examinations of the ore, but amalgamation indicated that some was present.

Jan 1, 1949

By Jeffrey B. Osmint

The Bureau of Mines Information and Analysis Directorate collects worldwide data on virtually every commercially important nonfuel mineral commodity. These data form the base for tracking and assessing the health of the minerals sector of the U.S. economy. The Bureau&apos;s data collection activity was instituted by the 47th Congress in an appropriations act of August 7, 1882 (22 Stat. 329), which placed the collection of mineral statistics on an annual basis. The most recent authority fur the Bureau of Mines survey activity is the National Materials and Minerals Policy, Research and Development Act of 1980 (Public Law 96479, 96th Congress), which strengthens protection fur proprietary data provided to the U.S. Department of the Interior by persons or firms engaged in any phase of mineral or mineral-material production or consumption.

Jan 1, 1991

By Charles C. Boley

The Bureau of Mines dried and carbonized two wood wastes, one softwood (redwood) and one hardwood (oak), using continuous, vertical entrainment techniques previously developed for use with coal. It was demonstrated that these techniques are readily applicable to wood waste and that appreciable changes in the yields of carbonization products can be obtained by varying operating conditions. A limited amount of experimental work was done on briquetting the char-coals. Firm briquets were formed with oak charcoal, although greater quantities of starch binder than used commercially for kiln-produced charcoal were required. Redwood charcoal did not briquet successfully under the test conditions employed.

Jan 1, 1969

By J. Roger Loebenstein

ASARCO Incorporated, the only domestic arsenic producer, terminated copper-smelting operations and the associated recovery of byproduct arsenic trioxide at Tacoma, W A. in 1985. It still shipped small quantities of trioxide from its remaining stocks in 1987. Imports for consumption of arsenic trioxide were slightly higher than in 1986. Domestic Data Coverage.-Shipments of small amounts of arsenic trioxide from remaining stocks by Asarco were reported voluntarily to the Bureau of Mines.

Jan 1, 1989

By Laurance L. Oden

The Bureau of Mines studied three processes for preparing NaAl(OH)2C03) the intermediate compound which is calcined to produce alkalized alumina: (1) Mixing of Na2 C03 and of A12 (S04)3 solutions, (2) digestion of aluminum hydroxide in solutions of Na2C03 and NaHC03 at 90° C, and (3) addition of CO2 at 25° C to caustic solutions of aluminum to precipitate aluminum hydroxide followed by digestion at 90° C. The first process had the highest raw material consumption and washing requirements, and successful application of process 2 depended upon the availability of active aluminum hydroxide. Process 3 was the most effective, considering both process technology and raw material requirements. Procedures were also investigated for washing, filtering, drying, and calcining precipitates. Analytical methods included X-ray diffraction, atomic absorption spectroscopy, differential thermal analysis, and thermogravimetric analysis.

Jan 1, 1969

Use instantaneous sampling to pinpoint dust sources and to Improve dust control on longwalls. Approach Use a dust monitor developed under a Bureau contract. How It Works Sampling can be done by either a moving or a stationary method. In the "moving&apos; method, the dust monitor is carried by a survey engineer walking at the midpoint of the shearer Dust levels and face position (support number) are taken during all phases of the mining cycle while the shearer is cutting. These measurements can show how changes in airflow along the face, face specific; (rock partings) and cutting sequence (cutting the wedge) variables affect dust levels. In the "stationary sampling" method, the survey engineer stands with the RAM at a fixed location on the face. As the shearer approaches, the dust level and the distance to the shearer are recorded at 10-second intervals. Typically measurements start when the shearer is 20 feet from the sampling position and continue as the shearer passes the position until it is 20 feet away on the other side. Dust profiles around the machine are obtained at several fixed locations along the face only while the shearer is cutting.

Jan 1, 1982

Provide respiratory protection and a clean work environment for stationary or semimobile workers at minerals processing plants. Approach An Overhead Air Supply Island (OASIS) was developed which filters, conditions, and evenly disperses an envelope of clean air over a worker&apos;s head, thereby insuring reduced dust levels and a clean work environment. How It Works The concept for the OASIS derives from an earlier Bureau development of a canopy air curtain for continuous mining machines (see Technology News #21). In this application, the benefits of a reliable, self-contained, self-cleaning industrial-duty air filtration and distribution system are extended to the minerals processing field. The OASIS draws dust-laden room air into a filtration system, removing the dust and delivering clean air to a specific 16-square-foot area. It consists of: ? a self-cleaning primary filter ? a heater (cooling coil optional) ? an airflow distributor and secondary filter (combined)

Jan 1, 1985

By Charles P. Lazzara, Charles D. Litton, Frank J. Perzak

This U.S. Bureau of Mines report details the results of a series of large-scale experiments where small coal fires were used to ignite the conveyor belt at air velocities ranging from 0.76 to 6.1 m/s. In the tests, electrical strip heaters imbedded within a pile of coal were used to heat the coal to a point of flaming ignition. The flaming coal subsequently ignited the conveyor belt located approximately 5 to 10 cm above the coal pile. During the tests, temperature, CO, and smoke levels were continuously measured in order to determine both alarm time and level as the fire intensity progressed through the stages of smoldering coal, flaming coal, and flaming coal plus flaming belt. Analysis of the data leads to certain conditions of air velocity and sensor alarm levels that are required for early detection of conveyor belt entry fires. Two nomographs are presented, which define sensor alarm levels and sensor spacings as a function of belt entry cross-sectional area and belt entry air velocity.

Jan 1, 1991

By James P. Bennett

To improve construction materials for emerging chemical and metallurgical technologies, the Bureau of Mines is investigating the acid resistance of ceramic materials. In the study described here, eight commercial ceramic materials comprising two red shale, two fire clay, a silica, a silicon carbide, a carbon, and a high-alumina brick were evaluated. Samples were exposed to 20 wt-pct HC1 at 50° C for 110 days. The test apparatus designed to evaluate the materials is described. Changes in chemical and mineralogical composition, cold crushing strength, volume, and weight, and leach rates of AI, Ca, Fe, K, Mg, Na, Si, and Ti ions were monitored. In general, the statistically significant physical property changes that occurred were small. In many cases, no changes were detected.

Jan 1, 1982

By I. A. Jacobson

In a closely controlled laboratory retorting system for oil shale, a relationship was developed by the Bureau of Mines between the temperature in the retort and the weight ratio of ethylene to ethane in the gases produced. Reciprocal temperature was shown to be directly proportional to the log ([ethylene]/[ethane]). From this relationship a number, called retorting index, was developed. The retorting index has the dimension of temperature, but its magnitude depends on both temperature and residence time for the reactants in the heated zone in the oil-shale retort. The slopes of the lines relating reciprocal temperature and the logarithm of the ethylene-ethane ratios are nearly constant for each of the retorting processes for which data have been presented. The retorting index should be a valuable tool to control the operation of oil-shale retorts, either aboveground or in situ. If an optimum operating condition can be established, the maintenance of the optimum or the departure from it should be easily monitored by use of the index.

Jan 1, 1974

By Jerry L. Huiatt

An accurate and reproducible procedure was developed using the gas-liquid chromatograph to quantitatively measure oleic acid on flotation products and in flotation water phases. The method comprised extraction of the oleic acid from the mineral surfaces with alcoholic NaOH, esterification of the extracted oleate, and chromatography of the methyl ester with an internal standard. Quantitative analysis of oleic acid on flotation products from test tube and bench-scale flotation tests with pure minerals and with natural ores proved the applicability of the method on a variety of minerals. The accountability of oleic acid added was 100 percent, ±5 percent.

Jan 1, 1968

By D. Z. Hobbs

Because an economic method for preparing pure boron has not been developed, a program was started by the Bureau of Mines to evaluate existing techniques or to develop new methods for preparing the pure element. This report describes investigations directed toward the development of techniques for the preparation of pure boron by fused-salt electrolysis. Only two of the several fused-salt baths tested were satisfactory for the preparation of boron. These baths contained (1) potassium fluoride, lithium fluoride, potassium fluoborate and boron trioxide; and (2) potassium fluoride, potassium chloride, and boron trioxide. Of these two mixtures, the latter was more satisfactory. Elemental boron of from 90- to 95-percent purity and, in isolated cases, as high as 98-percent purity, was prepared from these two types of fused-salt baths. There appeared to be no distinct differences either in the yields or the purity of boron prepared at current densities ranging from 795 to 1,000 amperes per square foot. Current efficiencies were as high as 85 percent.

Jan 1, 1961

By Roy Greenfield

Estimates are given for the distance from a seismometer at which a miner can probably be detected. The procedure in making these estimates was to first establish the natural noise levels at the output of a surface seismometer for the 25 to 100 Hz frequency passband. The noise levels give the range of values which may be expected in areas with no man-made noise. For each noise level, we give the detection threshold which, when exceeded, indicates that a signal has been received. Based on the signals recorded by Westinghouse, curves are given which show the peak signal amplitude as a function of source- to-receiver distance (slant range). Curves are given for the Westinghouse seismic thumper, a 50-pound timber, and a sledge. For a given type of source, the receive signal strength depends more strongly on slant range than on any other factor. However, there is approximately a five-to-one scatter in the amplitudes. Thus, further study of factors affecting the signal amplitude might allow better estimates to be made for any particular geological setting. Combining the signal amplitude with the detection thresholds for the different noise conditions gives the distances at which a miner should be detected. These are given in Table l* below. [ ] The text also gives the increase in detection ranges which should occur if steps are taken to increase S/N by 10 dB. We feel that 10 dB is a conservative estimate of the improvement possible. During an actual rescue operation, the seismic crew and system should be capable of making on-site estimates of their detection capability, based on measurements of the site noise, and upon the best available estimates of the

Jan 1, 1974