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By Terry J. Close

From 1981-84, Bureau of Mines personnel examined and evaluated mines and prospects in the highly mineralized 62,400 acre Inyo Mountains U. S. Bureau of Land Management (BLM) Wilderness Study Area (WSA), located east of Lone Pine, CA. The 62,400 acres studied is the part of the 87,145 acre WSA designated as suitable prior to February 28, 1983. The WSA is underlain principally by quartz monzonite and quartz diorite that have intruded sedimentary and volcanic rocks. Three types of mineral deposits are present: 1) gold in fissure veins, 2) silver in fissure and replacement veins, and 3) talc in metasomatic lenses. Of the 84 nines, mills, and prospects examined, 54 are significant: 1) 5 in the intrusive rocks total about 4.4 million tons of inferred marginal gold reserves averaging 0.24 oz gold and 0.74 oz silver/ton; 2) three associated with intrusive-sedimentary rock contact zones total about 280,000 tons of inferred subeconomic silver resources averaging 7 oz silver/ton; 3) 27 gold and silver occurrences in the intrusive and sedimentary rocks total about 1.2 million tons of material in poorly defined bodies too small or low grade to be resources; 4) 15 gold and silver occurrences in the intrusive and sedimentary rocks are too poorly exposed to estimate tonnage and grade; and 5) four talc deposits along intrusive-sedimentary contact zones have inferred marginal reserves totaling about 640,000 tons. The marginal gold reserves at $450/oz might be profitably mined (reserve) at a gold price of about $600/oz and the subeconomic silver resources at a silver price in excess of about $27/oz. The marginal talc reserves might become minable at prices of about $50/ton and $80/ton for unprocessed and processed talc, respectively, after present supply sources are depleted. At most of the 54 significant mines and prospects, additional reserves or resources would likely be disclosed by trenching or drilling. Present in the WSA are 13 gold mills, numerous small pits and cuts, 270 underground workings totaling about 36,000 ft, and 80 mining benches totaling about 11,000 ft. Gold, silver, or talc were produced from most of the workings. A total of 1,561 lode and 18 placer samples were taken.

Jan 1, 1985

By S. P. Godby, S. P. Sharples

Wind-tunnel tests were carried out of the conditions under which nuisance dust particles (100-1 000 micrometres) become entrained by wind. A laser entrainment monitoring system (LEMS) was used, and was found to provide an accurate means of assessing nuisance dust emissions from a surface. Accurate determination of the threshold entrainment velocity of dusts using the LEMS gives a baseline against which the performance of dust control techniques can be evaluated. Minerals tested included coal, petroleum coke, limestone, sand and pulverised fuel ash. Pilot field trials of a portable wind tunnel equipped with the LEMS have been successfully completed, providing a means of validating laboratory results in the field

Jun 19, 1905

By Vinit Mody

The belt conveyor is one of the major pieces of equipment for transferring bulk material in mining operations. However, considerable amount of respirable dust may be generated whenever the bulk material is loaded, dumped, or transferred. This report identifies and evaluates various dust control technolgies applicable to belt conveyors, and describes how an integrated systems approach can reduce dust emissions at a transfer point. Phase I of the program consisted of literature search and a critical evaluation of various dust control technologies. The work established that a comprehensive approach to calculating exhaust volumes for dust collection system does not exist. The parameters that affect the wet dust suppression efficiency were also reviewed. Based on the Phase I work, bulk material handling system and dry dust collection or wet dust suppression systems were designed and installed at a number of transfer points in a limestone processing facility, a surface mine selected as a field test site. Field test data were used to determine the validity of various exhaust volume calculations at the different transfer points. The field test data also formed the basis for the evaluations of the relative effectiveness of commercially available and wet dust suppression systems in controlling respirable dust emissions.

Jan 1, 1984

By D. Bienstock

The use of alkalized alumina in removing sulfur dioxide from a coal-combustion flue gas at 625° F was investigated on a pilot plant scale. The absorber was 26 feet long and 1.6 inches ED. Counter-current gas-solids flow at gas velocities of 8 to 15 ft/sec in the presence and absence of baffles, as well as solids entrainment at gas velocities of 20 to 23 ft/sec with solids recycle, were employed. The spent absorbent as regenerated as fixed bed with the reducing gases--reformed natural .7.7d hydrogen. Of absorption-regeneration were successful completed using the alkalized alumina rolled into spherical granules 10 to 16 mesh. There was no loss in activity of absorbent toward SO2 with a modest attrition equivalent to 0.l percent of the solids feed. Supporting studies were conducted on the effect of the sodium content in the absorbent, the composition of the reducing gas, thermal treatment to increase absorbent hardness, and removal of absorbed chlorine from the absorbent. A mathematical model was formulated to describe the removal of SO2 by alkalized aluminum from fixed and falling beds.

Jan 1, 1967

By Philip R. Whitney

Precipitation of hydrous manganese/iron oxides in streams can be readily observed in much of the northeastern United States, and is apparently a common phenomenon in other glaciated areas (1,2,3,4). Deposition occurs when Mn-enriched ground or surface water enters the stream environment and encounters conditions of higher Eh and pH. The preferred location for deposition is in shallow, fast-flowing segments of stream; the oxides usually form as coatings on detrital material. The experimental studies of Hem(5) and a considerable amount of work on marine and lacustrine manganese nodules(6,7,8) suggest that given an appropriate substrate, deposition of manganese oxides may occur even when the water is undersaturated in Mn with respect to the oxides, due to catalysis by organisms or by silicate, carbonate, or ferric hydroxide surfaces. Once begun, manganese oxide deposition is autocatalytic (9). Studies of the distribution of oxides in various size fractions of stream sediments indicate that the thickness and prevalence of the coatings commonly increases with increasing particle size in the coarse sand and gravel size ranges. Figures 1 and 2 show a fairly typical distribution of leachable metals over nine size fractions from 62 microns up to 8-16 mm. The leaching solution used was neutral ammonium citrate with hydroxylamine hydrochloride, which effectively removes the oxide coatings without significantly attacking most silicates, carbonates or sulfides. Figure 1 shows metal content as ppm of the total sample; figure 2 shows' the same data as micrograms of metal per square millimeter of surface area.

Jan 1, 1975

By John J. S. Sebastian

A laboratory-scale investigation was made of the basic problems involved in developing a ceramic heat exchanger to operate at high temperatures for using nuclear heat from gas-cooled process-heat reactors. Technical data were obtained on transferring heat by forced-convection from helium to air in a single-tube vitreous-alumina heat exchanger. Coolant air was passed through the annulus parallel with, and either concurrently or counter to, the flow of helium inside the tube. The data obtained pertain to removing heat from the helium. Average inside film coefficients were determined at mean surface temperatures of 200° to 1,570° F., inlet-gas temperatures of 1,450° to 2,665° F., and Reynolds numbers up to 560. The gas-to-surface temperature ratios were varied from 1.05 to 7.6. The tabulated results are shown in the appendix at the end of this report. The film coefficients of heat transfer were correlated by taking into account the physical properties of the helium at the average fluid temperature. With experimental conditions pointing to a laminar flow, the Nusselt number was found to decrease as the ratio of gas-to-wall temperature was increased to a value of 3. However, within the range tested, gas-to-wall temperature ratios above 3 did not affect the Nusselt number, regardless of the value of the Graetz number. Thus, beyond this point any increase in this ratio ceased to influence the heat-transfer relationship.

Jan 1, 1962

By James S. Graham

Foundation pile driving hammers used in New York City in the past 100 years have been drop, steam, compressed air, diesel, and hydraulic. In 1992, the first hydraulic hammer in the New York City area was purchased by Norwalk Marine Contractors, Inc. from Junttan in Finland. It was bought because of its variable energy and ease of mobilization, not because of its higher transferred energy. Heller and Johnsen engineers instrumented hydraulic hammers on nine jobs. The measured transferred energy for the nine jobs was found to average approximately 80 percent. There is no clear consensus regarding the reasons for the hydraulic hammer being more efficient in delivering energy to the pile as compared to single-acting steam/air impact hammers. To minimize pile damage during installation, and to minimize footage overruns, an up-to-date version of the wave equation software that includes an efficiency value of 0.95 for hydraulic hammers is now used.

Jan 1, 2000

By L. E. Cardwell

This publication contains routine analyses and related source data for 475 natural gas samples from 17 States and two foreign countries. Of this total, 454 samples were collected during calendar year 1971. The remaining 21 samples were collected during previous years, but releases granting permission to publish the analyses were not received until 1971. All samples were collected as part of a continuous survey of the free world for occurrences of helium in natural gas. This survey has been conducted in the United States by the Bureau of Mines since 1917. In late 1965, the survey was expanded to include foreign gasfields. The analyses published herein were made by mass spectrometer and a special helium analysis apparatus, which are described in Bureau of Mines Bulletins 4863 and 576.4 Thirteen previous publications have presented the results of 9,427 gas analyses prior to 1971. The first three, Bulletins 486,5 576,6 and 617,7 contain analyses and related source data on 5,218 gas samples collected from

Jan 1, 1972

This report describes the work performed by Mine Research Company in developing a prototype mobile roof shield during 1971-1972 for the U. S. Bureau of Mines, along with background information leading to the design decisions adopted for the project. In addition, the report evaluates the choice of design and analysis and the results of the project in terms of future possibilities of mobile roof support systems. The report begins with the discussion of the problems of designing, building, and using mechanical and hydraulic roof support in coal mines. It then gives a historical summary of past work with discussions of the design choices made for previous roof support systems.

Jan 1, 1973

By Clayton M. Rumsey

The U.S. Bureau of Mines conducted a mineral resource survey of the Cinder Cones Wilderness Study Area (WSA) (CDCA-239), 10 miles east of Baker, CA, in 1983. The 44,299-acre WSA is underlain by Precambrian granite gneiss, Upper Cretaceous or lower Tertiary Teutonia quartz monzonite, and Quaternary basalt flows and alluvium. This mineral survey included an examination of two volcanic cinder mines, five lode prospects, two volcanic cinder prospects, and reconnaissance sampling in and near the WSA. The seven prospects are in the WSA; the two volcanic cinder mines are adjacent. No mines are in the WSA. In 1981, there were 61 placer and 3 lode mining claims in the WSA. Sample results from two prospects within the WSA contained significant gold and silver values; however, the mineralized rock is of limited extent and no resources were apparent. Alluvial samples taken throughout the WSA contained only traces of gold. Two volcanic cinder cones within the WSA contain an estimated 30 million tons of cinders. There are sufficient cinders outside the WSA to satisfy demand in the foreseeable future. Stone, sand, and gravel deposits are not resources because similar material is closer to markets. No evidence of energy minerals or geothermal resources was found.

Jan 1, 1985

By L. You

Theoretical and analytical analyses of three mitigative measures- plane fitting method, trenching, and tension cable led to the development of a total protection plan to eliminate or reduce damages to the residential structures subjected to surface movements caused by underground longwall mining. The protection plan was applied to twelve residential houses and two external garages. The success rate is overwhelming. This paper describes the methods employed for protection and results of those case studies.

Jan 1, 1986

By M. Onifade, B. Genc, P. O. Akinseye, M. Fourie, K. O. Said

Coal is mined by both surface and underground methods and its extraction is normally characterized by numerous hazards that can lead to catastrophic accidents, which result in devastating effects such as injuries or fatalities, damage to mining assets, and destruction of mineral resources. These hazards exist due to the ability of coal to support combustion and its association with toxic, flammable, and explosive gases. Underground coal mining entails higher safety risks than opencast coal mining, chiefly because of issues relating to mine ventilation and mine collapse. Furthermore, coal mine collapses mostly occur due to crumbling of mining supports, especially in room and pillar mining systems. To avoid such adverse occurrences, safety management systems need to be in place. This study reviews the various technological safety systems and principles that are used for safe-rescue and self-escape of miners in underground coal fires, particularly in South Africa, using data obtained from Mines Rescue Services in Carltonville, South Africa. The outcome of the review shows that practising safety culture has been given priority across many South African underground coal mines through setting up safety management systems and encouraging workers to stay committed to safety principles.

May 2, 2022

By Pierre Rocque

The Red Lake Mine is located approximately 600 km northwest of Thunder Bay. This 545 tpd (600 tons/day) underground narrow vein gold operation is set to produce in excess of 14.8 tonnes (475,000 ounces) in 2001 at a cash operating cost below 75 U$/oz. The high-grade nature of this deposit (>55 g/t or >1.6 opt) coupled with its complex geological environment and relatively deep location dictated the choice of a very selective primary mining method, Mechanized Overhand Cut and Fill. In addition to geological challenges, mine design issues such as material handling, ground stability and requirements for yieldable ground support are also discussed in this paper.

Oct 1, 2001

By J. D. Davis

THIS REPORT gives results of an investi¬gation of the carbonizing properties of coals from Pittsburgh bed, Jamison No. 9 mine, Marion County, W. Va., and from Upper Freeport bed, Bull Run No. 1 mine, Preston County, W. Va. The study included Bureau of Mines-American Gas Association tests at 800° and 900° C. and various chemical and physical tests designed to evaluate the plastic, expanding, and agglutinating properties of coal. A blend of each coal was carbonized in the 500-pound slot oven. The carbonization sample of Pittsburgh coal contained 2.7 percent moisture, 35.8 percent volatile matter, 54.4 percent fixed carbon, 7.1 percent ash, and 0.9 percent sulfur. It contained 60.9 percent fixed carbon on the dry, mineral-matter-free basis and had a heating value of 14,780 B. t. u. per pound on the moist, mineral-matter-free basis. It therefore ranks as high-volatile A bituminous and was blended with low-volatile Pocahontas No. 3 coal. Upper Freeport coal contained 2.8 percent moisture, 27.7 percent volatile matter, 60.9 percent fixed carbon, 8.6 percent ash, and 1.0 percent sulfur, as carbonized. It contained 69.5 percent fixed carbon on the dry, mineral-matter-free basis and therefore ranks as medium-volatile bituminous. It was blended with high-volatile A Pittsburgh coal from Allegheny County Pa.

Jan 1, 1952

By J. C. Franklin

A data-acquisition system was designed by the Bureau of Mines to monitor five detectors with radon continuously flowing through each. These detectors could be monitored up to 12 times an hour, but were only monitored according to a preset time, thus allowing radon to be monitored continuously in a uranium mine. The counter can be set to monitor each detector for any period of time up to 16.5 minutes. This allows very low concentrations to be monitored longer to reduce statistical error. There would be no upper limit in radon concentration that could be monitored, but there would be a lower limit of 50 picocuries per liter (pCi/l). Each detector was cylibrated in the laboratory by the Lucas flask method. Multiple samples were taken at two different concentrations, and the correction factor for each detector was determined by a least squares fit of the data. To verify the calibrations, a series of measurements at several concentrations were made against a constant source. Our agreement at low radon concentrations (300 pCi/i) with the two-filter method as within 3 percent; thus, the total error would be this difference plus the two-filter error. At high concentrations the coefficient of variation ranged between 2.1 and 9.8 percent for the five different detector units.

Jan 1, 1976

By Jon G. Bredeson

The electromagnetic noise that exists in a mining environment is quite severe and was shown to have been reasonably well documented by a number of researchers in the Phase I Report. The noise levels are such that prudent communication design requires the careful use of all the electromagnetic noise data available. A comprehensive survey was undertaken to determine techniques used in various industrial environments to achieve secure communications in the presence of electromagnetic interference. The techniques were given in the Phase I Report and are rudimentary, but have produced reasonably good results. A number of these techniques could be applied to the mining environment.

Jan 1, 1980

By B Whittaker

The paper examines the role of chain pillars in longwall mining layouts as used in several countries. The application of chain pillars in relation to their expected design role is discussed. An important feature is the specification of the pillar design to meet strata loading conditions as imposed by the mining and geological setting. The paper relates longwall width and chain pillar configurations to pillar size to satisfy anticipated loading and strength expectations. Laboratory work is referred to which examines criteria for pillar stability. Comments are made regarding the application of the findings presented in the paper, to different situations involving the use of chain pillars in longwall and shortwall mining systems.

Jan 1, 1987

Gangue-cemented paste backfill (GCPB), is a well-established green mining technology and significantly improves the recovery rate of mineral resources, prevents mine dynamic disasters, reduces surface subsidence, and consumes a considerable amount of solid waste. The addition of an early strength agent as an additive in cement-based materials provides several security, technical, and economic advantages. In this study, the early strength agent on the early age (3, 7 and 28 days) strength of GCPB is evaluated experimentally. The GCPB specimens have an initial sodium sulfate early strength agent concentration of 0%, 1%, 2%, 3%, and 4%, and the obtained samples were analyzed by testing for uniaxial compressive strength (UCS) and scanning electron microscopy (SEM). The test results show that the UCS of the GCPB specimens with sodium sulfate is much higher than that of the blank specimens. When cured for 3 days and 7 days, the strength of GCPB with 2% sodium sulfate increased the most, by 131% and 116% respectively. When cured for 28 days, the strength of GCPB with 1% sodium sulfate increased by 135%. Scanning electron microscopy (SEM) results showed that the GCPB with 1% and 2% sodium sulfate had better internal structure compactness, thicker acicular crystals, and more flocs. As a kind of early strength agent, sodium sulfate can react with calcium hydroxide to generate calcium dihydrate sulfate and then react with calcium aluminate; the hydration product (C3A) quickly generates calcium sulfoaluminate hydrate (AFt) needle-shaped crystals, forming an early skeleton and improving the early strength.

Jan 7, 2020

By Scott A. Stebbins

This Bureau of Mines publication presents a method for estimating capital and operating costs associated with the exploration, mining, and processing of placer deposits. To ensure representative cost estimates, operational parameters for placering equipment and basic principles of placer mining techniques are detailed.

Jan 1, 1987

By P. A. Rossouw, G. A. Fourie

Several attempts have been made over the latter half of the twentieth century to devise a system for the classification of underground mining methods. None of these are found to be totally successful. A revised classification is suggested with three main categories being identified by reference to fill requirements, steep stopes and stratified geological environments. Methods always needing lasting mass or structure fill include methods with timber-structured stopes and those with mass-filled (or cut-and-fill) stopes. Methods associated with steep stopes are subdivided into steep-stope-specific caving and steep-stope-specific non-caving (or self-supporting) methods. Methods not in the first two categories, often used in stratified geological situations, are not necessarily restricted to stratified environments and include caving as well as non-caving varieties. This category is further divided into room-and-pillar mining, longwall and shortwall coal mining and the type of open stoping found in gold or platinum reefs comprising overhand, underhand and breast-stoping variations

Dec 1, 1996