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By M. C. McCall

When electric current of any appreciable magnitude flows from a power line into the earth, a change sometimes takes place in the conditions of resistivity immediately surrounding the electrode or medium of contact. If the conducting medium is composed of moist earth or clay the effect is to increase rapidly the resistance. If the conducting medium is coal or a coal bed, the effect is one of slowly decreasing resistance as the coal is carbonized, If, however, the flow of current is not enough to carbonize the coal, it will dry slowly, with a resultant increase in resistance. Measuring ground resistance, or impedance, with conventional commercial ground testers does not always indicate the current that will flow in the earth circuit from a direct-current or an alternating-current power circuit. The exact reason for this has not been determined however, it is thought to be due to the comparatively minute currents used for such testing. A typical ground, tester used by the authors for this work indicated a maximum current of 25 milli-amperes. The frequency of this testing current also has an effect on the readings in all probability. While the possibilities of the effects of varying frequencies has by no means been fully explored in this investigation, there are very definite indications that the impedance of a circuit through a section of earth will vary in some inverse relationship to the frequency of the applied voltages. This is evident at ordinary power-line frequencies ns well as at higher frequencies up to 200 kilocycles, which was the highest frequency available for tests in this investigation. This report is written in the hope that it will stimulate further investigation of the possibilities suggested for communication and the development of safety devices for increased electrical safety in coal mining.

Jan 1, 1952

By Hugh Haddow

This paper describing the methods of recovery and treatment of a sand and gravel deposit and the preparation of these materials for a number of special markets is one of a series being prepared by the U. S. Bureau of Mines. It is of particular interest to those sand and gravel operators who have a surplus of fine sand which must be sent to waste, both from the point of view of, equipment and the variety. of markets supplied, and in that it describes one of the few sand and gravel plants which have resorted to hydraulic classification for sizing fine sand. ACKNOWLEDGMENTS The author wishes to acknowledge the assistance of J. R. Thoenen, mining engineer of the Bureau of Mines, in the preparation of this paper.

Jan 1, 1931

By Patrick D. Plumb

The Bureau of Mines (BOM) has begun a project to increase the understanding of the relationships between ecosystem health and its functions, and minerals development. The BOM, Juneau Branch, Alaska Field Operations Center, is providing support for ecosystem based land-management decision-making and the development of ecosystem based regulations by documenting the effects of mining on ecosystems and demonstrating the tools used to assess and analyze those effects. This is done by reviewing the data available on ecosystems and the environment at a mining site, the Greens Creek Mine near Juneau, Alaska, and applying available Geographic Information System modeling tools to assess the impacts of the mine on components of the pristine ecosystem. Habitat Capability Models for wildlife indicator species are used in this examination. Wildlife indicator species are used as indicators of ecosystem health by the U.S. Forest Service and the Alaska Department of Fish and Game, who developed these models for southeast Alaska. Analysis techniques from the U.S. Fish and Wildlife Service's Habitat Evaluation Procedures (HEP) are also used in this report. By applying available models and analytical techniques to the Greens Creek area, the benefits gained through mitigation of potential impacts become apparent. These or similar techniques are useful for cost/benefit analysis of mitigation alternatives. Also apparent from this analysis is that the degree to which potential impacts are observable will depend upon the ecosystem scale considered. This demonstrates the importance of defining the ecosystem and scale before performing impact and cost/benefit analysis. The watershed scale is found to be useful for assessing impacts to ecosystem components at the Greens Creek Mine. Much progress remains to be made in the modeling and prediction of impacts to ecosystems from mining activity.

Jan 1, 1994

By Thomas J. Peters

In 1987, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied a 12,564-acre portion of the 34,795-acre Rockhouse Wilderness Study Area (CA-010-029) in order to evaluate its identified mineral resources. The study area is located in Kern and Tulare Counties, CA, about 60 air mi northeast of Bakersfield at the south end of the Sierra Nevada. A review of the geologic and mining literature, and a field examination identified a turquoise and a gold prospect in the study area, and another gold prospect and a feldspar prospect within a mile of the study area boundary. Thirty-three rock and 16 alluvial samples were taken.

Jan 1, 1988

By David C. Oyler

Three long horizontal holes were drilled from a directionally drilled surface hole at the Emerald Mine near Waynesburg, Pa. The purpose was to adapt the technique of directional drilling for use in draining methane from coalbeds. A 504-m (1,652-ft) long, 76-mm (3-in) diameter, circular arc pilot hole was drilled, using a downhole mud motor, to enter the Pittsburgh coalbed at a vertical depth of 305 m (1,000 ft). The hole was reamed to 222 mm (8-3/4 in) and was cased to a measured depth of 486 m (1,595 ft). Three 76-mm (3-in) diameter horizontal drainage holes were then drilled, totaling 2,909 m (9,544 ft) of horizontal hole. Improvements in drilling methods increased the average drilling rate from 20.4 ill (67 ft) to 64.9 m (213 ft) per day. The cost of drilling the directional and horizontal holes (using a Government-owned drill rig) was $1,169,530, a figure inflated by inexperience and by delays caused by lost-circulation problems and fishing operations. An estimated total drilling cost of $960,000 (including rental of a drill rig) for an improved system, was determined by a detailed cost analysis. Initial gas and water production from November 1979 through May 1980 was low because of caving of the horizontal holes drilled in shale near the bottom of the casing.

Jan 1, 1982

By C. H. Elder

Two degasification test boreholes were drilled to depths of 1,238 and 1,212 feet on Bureau of Mines property at Bruceton, Pa., as part of the Bureau's long-range coal degasification program. The holes provided detailed geologic information and geologic sections, which were correlated with regional stratigraphic cross sections prepared by the Pennsylvania Geological Survey. Gas content determinations and coal analyses were made on the Upper Freeport, Middle Kittanning, Clarion, Brookville, and Mercer coalbeds; gas content of the coalbeds ranged from 53 to 165 cubic feet per ton. Formation pressure and gas flow tests were conducted on selected coalbed intervals in borehole 1; formation pressures ranged from 292 to 473 psig. The middle Kittanning coalbed was hydraulically stimulated using very heavy gelled water, but gas production remained low because gel residue and formation water inhibited the flow of gas. Gas contents in the Clarion, Upper Brookville, and Mercer coalbeds were anomalously low owing to the proximity of porous sand-stones which act as reservoirs for gas migrating from coalbeds.

Jan 1, 1977

By Robert S. Warfield

The Bureau of Mines investigated a geologically favorable area in the Beluga River coalfield in south-central Alaska to determine if there were sufficient minable coal reserves for onsite utilization to meet the projected thermal power needs of the Anchorage area. A program of diamond core drilling and sampling delimited a shallow saucerlike structure estimated to contain indicated reserves of more than 20 million tons of subbitminous coal in a seam over 50 feet thick that could be mined by opencut methods. A large sample of fresh coal was taken across the full width of the seam for washability studies. This sample, with 4 volume-percent of clay partings eliminated, contained 24.4 percent moisture and 16.8 percent ash and had a calorific value of 7,162 Btu per pound. The studies indicated that mechanical cleaning would be of doubtful value.

Jan 1, 1963

By Richard A. Allwes

This U.S. Bureau of Mines report presents the results of structural analyses and full-scale physical tests conducted on a steel-set arch and tri-set. The purpose of the analyses and tests was to evaluate the suitability of these structures for use in roof-fall prone areas. The arch canopy test and design procedures previously developed by the Bureau were utilized in this evaluation. Theoretical resistance functions were established for the steel-set arch and tri-set and were representative of the experimental behavior of the structures. The resistance functions were used to determine the energy absorption capacity of the structures and to predict their dynamic response to impact loading. The dynamic tests demonstrated that the arch canopy design procedure is appropriate for tri-sets and yields conservative designs for both steel-set arches and tri-sets. As a result of this work, it is recommended that these two structures may be considered for use in roof-fall prone areas and for rehabilitation work, provided the arch canopy design procedure is utilized for each application and the principles underlying the design procedure are understood.

Jan 1, 2010

By Gary A. Kingston

Chromium resources in the United States are estimated at 1.8 million tons of recoverable chromium contained in 22.5 million tons of chromite-bearing material. Additional resource is presumed existent in large, but as yet undetermined, quantities of material containing less than 10 percent Cr203. No domestic resources are being mined presently (1969). Excluding transportation charges to domestic consuming areas, the total 1.8 million tons of chromim is estimated to be available, in ore or concentrate, at costs up to $0.64 per pound; 63 percent of the total is available under $0.11 per pound; and 38 percent under $0.08 per pound. It is judged that transportation from the resource areas to the existing market centers would add nearly $0.05 to the cost of a pound of chromium contained in ore or concentrate. Technically effective beneficiation methods have been developed for much of the known domestic resource, and further development might reduce costs of processing these materials. However, at present, domestic chromium resources are noncompetitive with foreign sources.

Jan 1, 1970

By I. D. Shah

The Bureau of Mines investigated the sequence of principal chemical reactions taking place during the roasting of covellite (CuS). Practically all covellite is converted to digenite (Cul.SS) before oxidation to Cu20 begins. Part of the Cu2O is then converted to CuO, which in turn forms CuS04 through CuO?CuS04 as an intermediary. CuS04 and CuO'CuS04 decompose at 600° to 700° C to yield CuO and S03 (g) as final products. An overall mechanism is proposed for chemical reactions occurring at different interfaces of partially oxidized CuS pellets.

Jan 1, 1970

By Fun-Den Wang

This report presents the results of two large scale field coal pillar strength tests (80 ft by 80 ft), the results of a series of laboratory small core sample tests, and the correlation between those field and laboratory tests. The concept of applying laboratory coal sample strength data to predict the in situ coal pillar strength appears to be feasible. The deformation property of large pillars can be obtained successfully by testing the coal sample in the laboratory within acceptable accuracy. There are prevailing directional strength and deformation properties in coal pillars along the butt and face cleat system.

Jan 1, 1976

By Phillip R. Moyle

A mineral survey of 19,350 acres of the Gooding City of Rocks Wilderness Study Areas (WSAs) in the north-central Snake River Plain was conducted by the U.S. Bureau of Mines in 1984. No formal mining districts are known in or near the study area. Forty-two placer claims within and adjacent to the study areas cover the Clover Creek diatomite deposit. Minor production from four pits was reported by the owners. The diatomaceous sediments are underlain by dacitic welded tuff and capped with basalt. Five exposures or blocks totaling 416 million tons of the diatomaceous material comprise the Clover Creek deposit; four of the blocks are in the study areas, out are predominantly covered by basalt. The North Clover block, just west of the areas, is only partially capped, and could be mined by open pit methods on the western flank of the exposure. The minable wedge contains an inferred marginal reserve of 35 million tons of diatomite possibly suitable for filter aid, filler, insulation, and other applications. At a production rate of 150,000 tons/year, total mining and milling costs for high-grade filter aid diatomite would be about $100/ton. The deposit is classed as marginal because products from this deposit may be inferior to currently marketed diatomite products. The market is well supplied by developed sources.

Jan 1, 1985

By Rolf S. Paine

The Bureau of Mines studied the presplitting technique used for control-ling overbreakage in the walls of a vertical shaft at the U.S. Army Corps of Engineers Littleville Dam project near Huntington, Mass. The periphery of the shaft, the dimensions of which were 16-1/2 feet wide by 21 feet long and 52 feet deep, was presplit (cracked) in the solid to a depth of 48 feet prior to full-depth sinking. Presplitting prevented overbreak in a fairly soft schist and provided sound self-supporting walls which required very little scaling.

Jan 1, 1965

By Rolf S. Paine

The Bureau of Mines studied the presplitting technique used for control-ling overbreakage in the walls of a vertical shaft at the U.S. Army Corps of Engineers Littleville Dam project near Huntington, Mass. The periphery of the shaft, the dimensions of which were 16-1/2 feet wide by 21 feet long and 52 feet deep, was presplit (cracked) in the solid to a depth of 48 feet prior to full-depth sinking. Presplitting prevented overbreak in a fairly soft schist and provided sound self-supporting walls which required very little scaling.

Jan 1, 1965

By Thomas J. Peters

The Danskin/South Fork Boise River study area is 40 air km southeast of Boise, Idaho. The 16,000-hectare, two-segment area is mainly underlain by Cretaceous-age granodiorite and an aplitic and pegmatitic complex of the Idaho batholith, Miocene-age rhyolitic tuffs and lavas, and late Tertiary-age basalt flows. No mineral resources were identified in the study area. One mine, The Flat Creek mine, which produced several ounces of gold and silver, was found in the study area. It is geologically similar to deposits in the Neal mining district, adjacent to the northwest corner of the area; gold mineralization occurs along east-northeast-trending faults and associated quartz veins, which dip moderately to steeply southeast, and within adjacent Cretaceous granitic rock. Samples indicate the Flat Creek deposit is not rich enough to mine underground, and near surface, open-pit-mineable deposit areas could not be identified. However, exploration is warranted there and also in the 7-km interval to mines in the Neal district, and for extensions of those mines. No evidence of geothermal activity was observed, although there are hot springs in the vicinity. Some alluvial (placer) samples from the interior of the study area contained free gold, but no substantial gravel deposits were seen.

Jan 1, 1993

By Michael L. Clar

This volume is an annotated bibliography of published literature pertaining to the occurrence and control of surface and groundwater in underground coal mines. This literature was used to develop Volume 1 of this report, which assesses the feasibility of water diversion and overburden dewatering for underground coal mines in the Appalachian Region. Each abstract is followed by subject descriptors. the abstracts are listed alphabetically by title and are numbered consecutively. These numbers are used in the subject index to help the reader locate the appropriate articles.

Jan 1, 1981

By Richard J. Kline

The underground mining industry is presently using the fluid network analyzer and digital computer to analyze ventilation systems. The availability of the digital computer and ventilation programs to mining companies has escalated its use, permitting the design and modification of new or existing mine ventilation systems to be projected completely and thoroughly with consistent precision. Because the analog computer has been analyzing ventilation systems accurately for many years, a comparison of the analog and digital methods was warranted. This report summarizes a detailed comparison for one mine, based on parallel analyses by the two computer systems.

Jan 1, 1972

A construction material based on plasticized sulfur and mineral aggregate, that is superior in corrosion resistance and strength to portland cement concrete. The material can be used in the chemical, metallurgical, and fertilizer industries, and will also provide an attractive market for by-product sulfur resulting from compliance with pollution regulations. How It Is Made Sulfur concrete is thermoplastic material. Plasticized sulfur is mixed with sand and gravel aggregate heated to 375-400° F. The sulfur melts and acts as the binder or cement. The sulfur concrete is poured hot and sets at a temperature of 200° F. Full strength is attained in a few hours, compared to several days for portland cement concretes. Sulfur concrete even pours and sets in freezing weather. Although unmodified sulfur with aggregate will produce a sulfur concrete with good initial properties, it undergoes crystallographic modifications, and deteriorates with time, particularly when exposed to moisture or freeze-thaw conditions. The Bureau of Mines has developed plasticizers which, when reacted with the sulfur, give sulfur concretes with excellent moisture and freeze-thaw resistance. The plasticizers are based on mixtures of dicyclopentadlene (DCPD) and ollgomers of cyclopentadiene. About 5 percent by weight of the plasticizers is reacted with molten sui fur for several hours. The sulfur cement can be used directly or allowed to solidify for easier handling and storage.

Jan 1, 1981

By E. J. Matson

"SUMMARYThe Bureau of Mines has been investigating deposits of critical and essential minerals in the United States since 1939. Projects were set up on only the most promising properties. A preliminary examination of the Rio Grande property was made by Bureau of Mines engineers in July 1942 and the property was examined again in July 1943.The Geophysical Branch of the Bureau undertook a Geophysical survey of the area in November 1943 and was intermittently active in the district until June 1946. The major portion of their work was done from June 191 to November 1945. Favorable areas for exploration were recommended by the Geophysical Branch of the Geological Survey, 3/ and all holes were drilled in them.Two projects were set up by the mining branch in an endeavor to find ore bodies on the strength of the geophysical information."

Sep 1, 1947

By H. D. Kline

Manganese ores have been mined in the Batesville district since 1849. Although not continuous over the intervening years, production had totaled approximately 432,000 tons of manganese ore and ferruginous manganese ore to the end of 1953. The ores occur in deposits, essentially low in manganese content, distributed over an east-west belt 24 miles long and 4 to 8 miles wide, the core of which is about 6 miles north of Batesville, Independence County. Although the reserves of high-grade ores in the district are comparatively small, the large deposits of subgrade ores and low-grade manganiferous material comprise potential sources of supply of manganese that may have increasing future importance. The manganese occurs as primary oxide and carbonate minerals in relatively flat-lying limestone and shale formations in which they were originally deposited and as oxides in residual clays resulting from decomposition of the shale and lime-stone. Most of the deposits underlie from a few to over a hundred feet of sedimentary chert, but many occur in the residual clays on exposed slopes of chert-covered hills.

Jan 1, 1956