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By N. Greninger

The Bureau of Mines conducted a laboratory study of the measurement of the water and rock dust (RD) contents of synthetic mine-type coal dust (CD) mixtures using a commercial unit for measuring water content and several prototype radiometric units for measuring the RD content. The RD content ranged from 50 to 100 wt pct and the added water (AW) ranged from 0 to 15 wt pct. The total water (TW) content (intrinsic (IW) and AW) of a small dust sample could be readily measured automatically by essentially untrained personnel using a commercial unit. The RD content of a sample containing only IW could readily be measured by moderately trained personnel using several radiometric units. With gamma-ray devices, about 300 g of sample is needed. With the improved beta-ray device, about 25 g of sample is needed. With dry mine dust samples, the estimated RD error range for gamma-ray devices is 0.8 to 2.3 pct and 0.5 to 1.0 pct for beta-ray devices. However, the radiometric measurement of RD content was questionable if the dust mixture also contained AW or if it was uncertain whether the dust mixture contained AW.

Jan 1, 1988

By R. R. McLellan

The Brown Derby pegmatites are in Gunnison County, Colo., about 18 miles east of Gunnison. Approximately 860 tons of lepidolite concentrates, with smaller amounts of microlite and beryl, was produced from 3 dikes of the Brown Derby group from 1943 through 1947. No mining was done from 1948 until December 1950, when production of lepidolite and beryl was resumed by the Poston Mining & Milling Co. Mining was intermittent during 1951 and 1952. The dikes were mapped and studied by the Federal Geological Survey during the field seasons of 1942 to 1944, and in May 1950 the Bureau of Mines initiated a diamond-drilling project to test the three dikes for lepidolite and beryl. After being recessed twice, the project was terminated indefinitely July 1951. Seven drill holes were completed for a total of 1,841.6 feet of drilling.

Jan 1, 1956

By A. T. Iannacchione

The Bureau of Mines established geologic factors affecting the mining of the Lower Kittanning coalbed to aid in coalbed minability studies and examined the occurrence of "wants" (places where coal is missing) and types of unstable roof rock strata. Trends established from mapping, including prediction of areas of high methane emissions, were extrapolated to unmined areas. 'Wants' in the coalbed are of two types: Erosional and depositional. Erosional features occur where north-south-trending sand-filled channels cut into the coalbed. Variations in depositional environments have caused the coalbed to "split" into several thinner units. Slickensides, commonly indicative of unstable roof, are adjacent to and on the underside of sandstone channels; they were caused by differential compaction and by soft sediment sliding along the contact between the sandstone and adjacent shale. The frequency of unstable roof also increases where the interval between the Middle and Lower Kittanning coalbed is less than 30 feet. The zones of weakness at the contacts above and below the Middle Kittanning coalbed are the controlling factors for unstable roof in these strata. Methane emissions from the coalbed are controlled primarily by depth, fracture permeability, and rank of coal. Local geologic factors are coalbed thickness, associated rock strata, structure, and proximity to outcrop.

Jan 1, 1979

By G. S. Rice, H. P. Greenwald, H. C. Howarth

"Stoppings in coal mines serve, important and. vital functions, such as coursing the ventilating current, sealing off abandoned or dangerous workings, sealing fire areas, and separating mines at boundaries. Stoppings may hold back water, but normally that is not their function; their design is, or should be very different from that of a hydraulic dap which is designed to a definite load, often a very heavy one, from one direction over an indefinitely long period. Hence, a dam usually requires an arched structure to resist hydraulic pressure, and it must be massive to meet vertical stresses due to heavy ground pressure.Stoppings are designed primarily to resist a pressure applied laterally through air or gases. Their strength cannot be stated without specifying the direction of applied load. A stopping may be placed in stress by proof pressure subsequent to erection, through extraction of pillars in the vicinity which may act direct, or by squeezing the ribs or heaving the floor. These forces act more or less parallel to the faces of the stopping and may be very great but measures must be taken suitable to each case, and it is impossible to allow for these in general specifications other than to call for normally good construction. A stopping is principally designed to resist the action of forces at right angles to its face, such as the shocks of blasting, the pressure of gas from instantaneous violent out bursts such as have occurred in certain British Columbia coal mines, sudden compression of the air by great falls of roof in closed spaces, and at time pressures that accompany an explosion of either fire damp or coal dust or both. This paper deals with the tests of pressures of explosions only."

Sep 1, 1930

By A. C. Fieldner

The Sectional Committee on Classification of Coals, functioning under the sponsorship of the American Society for Testing Materials and the rules of the American Standards Association, in its 1934 report recommended to the American Society for Testing-Materials5 that Specifications for Classification of Coals by Rank be adopted as tentative. These specifications, slightly modified as recommended by the Sectional Committee, in its 1935 report,6 wore approved as tentative standards by the society in 1935. The specifications rover the classification of coals according to their degree of metamorphism, or progressive alteration, in the natural eerie s from lignite to anthracite. The basic scheme of classification is according to fired carbon and calorific value (expressed in B.t.u.) calculated to the mineral-matter-free basis. The higher-rank coals are classified according to fixed carbon on the dry basis, and the lower-ran]: coals according; to B.t.u. on the moist basis, that is, containing its natural bed moisture but free of visible surface moisture. Agglutinating and weathering indices arc used to differentiate between certain adjacent groups.

Jan 1, 1935

By E. P. Hayes

This report supplements the date contained in Bureau of Mines Information Circular 6156, "Special features of core drilling in the salt beds of Western Texas and New Mexico," by J. S. Wroth. That circular dealt with the drilling of the first 12 of the 24 potash tests made by the U. S. Bureau of Mines in cooperation with the U. S. Geological Survey; this report is concerned with the drilling of the last 12 tests. ACKNOWLEDGMENTS The writer is indebted to R. E. Heithecker, the Bureau of Mines engineer who had charge of the drilling of tests 13 to 17, for his well-prepared records on the drilling of these tests.

Jan 1, 1933

By Denise A. Herzog

The U.S. Bureau of Mines conducted a study of cyanide leach technology used in Alaska's mineral industry from 1987 through 1990. Literature and cost data were obtained for mines in the contiguous United States, Canada, and Alaska that use cyanide to recover gold and silver. The data was compiled in an effort to evaluate the economics and conditions associated with cyanide use in Alaska. This report discusses heap leaching methodology and evaluates a "typical" heap leach operation in Nevada and compares the results of the Nevada operation to an analogous hypothetical mine in Interior Alaska. Five daily tonnage rates were analyzed for both the Nevada and the Alaska operations to evaluate the spectrum of economic possibilities. The discounted cash flow rate of return (DCFROR) for each production rate was then evaluated in terms of recoverable metal value (RMV). The Nevada RMV for each production rate was then compared with its Alaskan counterpart, and the results averaged. The Alaskan production costs are an average of 1.71 times greater than costs associated with mining in Nevada at a 0% DCFROR. At 15% DCFROR, costs in Alaska are 2.01 times greater than those in Nevada. Costs are higher in Alaska because of the shorter leaching season, increased labor and transportation costs, and heavier precipitation and vegetation.

Jan 1, 1991

By R. H. Sprute

The Federal Bureau of Mines conducted full-scale field tests in electro-kinetic dewatering and consolidation of slimes in cooperation with the Hecla Mining Co. at two of the firm's underground mines in north Idaho. To test the technique on new deposits, 4,000 ft3 of slimes from a collection sump, pumped into a watertight stope equipped with electrodes, were treated in two steps. Immediately after placement, direct current was applied using a floating electrode to hasten settlement of suspended fine particles. After removal of clarified water, the residue was further dewatered and hardened with electrokinetic treatment. In 25 hours, the material had become firm and dense with a surface capable of supporting workmen. In testing old deposits, 10,000 ft3 of slimes, placed in an unused tail drift 10 to 12 months previously, were treated. This material was sufficiently consolidated by electrokinetics to allow its removal from the mine with standard ore-handling equipment. In both tests, electrokinetic treatment densified slimes in a relatively short time with moderate power consumption.

Jan 1, 1976

By A. M. Evans

Because of an urgent national need for manganese, the deposits in the Little Florida Mountains of Lune County N. Mex., were visited by O.H. Metzger, an engineer of the Bureau of Mines, on June 12 and 13, 1940, accompanied on the second day by S. G. Lasky, a geologist of the Federal Geological Survey. After this preliminary examination, it was recommended that exploratory work be done by the Bureau of Mines on several properties in the district. An exploratory project of trenching, sampling, and core drilling was started by the Bureau of Mines in September 1940 and completed in May 1941.2/ Work was done on three properties - the Luna mine, the American group of claims, and the Manganese Valley mine. The Little Florida manganese district is situated on the eastern slope of the Little Florida Mountains about 2 miles south of U. S. Highway 80-90, 12 to 14 miles southeast of Deming, Luna County, N. Mex. The principal claims comprise the Luna Manganese, American, and Manganese Valley groups.

Jan 1, 1949

By McClelland. John J.

This Bureau of Mines report discusses recent applications of water in-fusion technology to control dust in U.S coal mines and presents recommended guidelines for determining coal seam infusibility. The techniques required to use water infusion are presented in detail. A Bureau case study indicated that water infusion reduced dust levels by 68 pct along a longwall plow face, bringing this section into compliance with the Z.0-mg/m3 Federal dust standard. Similar studies conducted by Occidental Research Corp. under a Bureau contract show water infusion at two longwall double-drum shearer operations produced dust reductions ranging from 38 to 50 pct. Water infusion was found to be cost effective, aver-aging 5 cents per ton.

Jan 1, 1987

By Rodney D. Rosenkranz

Energy consumption in domes tic copper production has increased nearly 60 percent in the last 10 years, reaching approximately 175 trillion Btu in 1973. Energy required to produce 1 pound of copper rose from nearly 41,000 Btu in 1963 to nearly 50,000 Btu in 1973. Production from lower grade ores and strict pollution control regulations have contributed to this increase. Each stage of copper production has been analyzed to determine total energy consumed, energy mix required, cost of the energy, and recent or proposed changes in operations which may affect the consumption of energy by the copper industry. Data have been gathered from a recent Bureau of Mines canvass of the industry, from visits to copper operations, and from conversations with copper industry officials.

Jan 1, 1976

By M. J. Sheridan

"INTRODUCTION In December 1942, the-Bureau of Mines reported favorably on a proposal to grant Government assistance-in constructing an access road (consisting principally of a timber-pile bridge across the Rio Grande at Hot Springs, N. Mex.) to the property under lease to the United States Fluorspar Co. At that time the property was being developed actively, and there appeared to be no immediate-need for exploratory or metallurgical assistance by the Bureau of Mines.Because milling facilities were inadequate; the access-read project was eventually disapproved, but prior to disapproval the company had discontinued operations. In June 1943, exploration was resumed by the Humphreys Gold Corporation of Denver, which had subleased the property. Difficulty of access continued to interfere with exploratory progress. In July 1945, at the request of the lessee, the Bureau of Mines directed sampling, using company employees.At the completion of this sampling program, the Bureau of Mines concluded that the property was potentially a important source of fluorite but that further development for production appeared to depend largely on the establishment, by exploration, of adequate reserves. Because of the relatively easy position-of metallurgical-grade concentrate and ores, it also was deemed advisable to investigate the possibility of producing acid-grade concentrate from the ore, for which a demand was becoming evident. Accordingly, a program of trenching, diamond drilling, and metallurgical testing was undertaken by the Bureau. The results of its investigation are reported herein."

Feb 1, 1947

The Mateen deposit comprises two large spodumene-bearing pegmatite dikes that outcrop along the, side and crest of a hill overlooking 'Rill City in the southern Black Hills of South Dakota. The Bureau of Mines investigated the Mateen deposit as part of a comprehensive study of the lithium mineral-production possibilities in the Black Hills area. The work was undertaken during the second World War, when the demand for certain lithium salts and compounds exceeded the small productive capacity of the industry. During the course of the investigation, the Bureau of Mines took 61 large channel samples from surface trenches, 4 channel samples from a shaft, and 3 from the face of an open cut. In addition, 8 diamond core-drill holes were completed to investigate the attitude of one of the dikes at depth. Metallurgical tests were conducted by the Bureau of Mines to determine the feasibility of beneficiating spodumene-bearing ores from the Mateen dikes.

Jan 1, 1948

By P. L. Weston

The Bureau of Mines used high-temperature reduction roasting, magnetic separation, acid-leaching, and autoclave precipitation processes to recover iron and manganese from brown Cuyana range ores of Minnesota. Wet magnetic separation concentrated over 90 percent of the iron in 3 of 4 ores as high grade products analyzing 74 to 85 percent iron, 2.5 to 6 percent manganese, and 3 to 10 percent SiO2. The nonmagnetic fractions were leached with dilute sulfuric acid extracting 83 to 93 percent of the contained manganese and small amounts of iron. The leach solutions contained Mn-to-Fe and Mn-to-SiO2 ratios favorable enough for possible consumption in metallurgical mane operations. Exceptionally pure Mn solutions were achieved by pressure precipitation of the remaining iron in an autoclave followed by lime precipitation of silica and alumina.

Jan 1, 1966

By Frank J. Weibelt

In accordance with provisions of the Strategic Minerals Act of 1939, the Bureau of Mines surveyed the chromite occurrences in California. The Seiad Creek deposit afforded excellent opportunity for developing reserves that could be used by the nation in case of critical shortages of the mineral. Subsequently an exploration and development program was undertaken in April 1941, which was concluded in October of the same year. Work included road construction, diamond drilling, drifting and crosscutting, surface trenching, and sampling.

Jan 1, 1949

By G. W. Jones

From evidence made available during the investigation, it was concluded that the first of a series of explosions occurred at 1:15 to 1:20 p.m. September 21, 1951, in an underground vault that housed pressure regulators on the gas-distribution lines that served Brighten. This explosion damaged the pressure regulators and permitted high-pressure gas to enter the distributing mains and individual-service lines. As a part of the gas-distribution system was not provided with means for protection against such excessive pressures, gas gained access to the interiors of many residences in this area and caused a series of disastrous explosions and fires, which took place during a period of approximately 2 hours after the initial explosion in the pressure-regulator vault. Two persons were killed in the first explosion in a residence, and a third person died of a heart attack attributed to the excitement that prevailed during the explosions and fires, Twenty-three persons were listed as injured. Forty-one residences were either destroyed or damaged - 11 by explosion and the remainder by fires, which developed as a result of gas leakage into residences. Fifteen residences were listed as "completely down" or "gutted." Unofficial estimates of property damage ranged from $1,000,000 to $1,500,000. In view of observations made and information obtained during the investigation, recommendations are presented in this report relative to the natural-gas distribution system in Brighton, which may be helpful in the prevention of similar accidents in this and other communities.

Jan 1, 1952

By A. Visnapuu

The U.S. Bureau of Mines investigated the oxidation of American Iron and Steel Institute (AISI) Type 304 stainless steel (SS) during annealing in simulated combustion products from several air-CH4 fuel ratios. Atmospheres representing air-CH4 ratios of 14:1 and 18:1 contained free 02, while atmospheres representing 10:1 air-CH, ratio did not. A Cr203 layer formed on SS samples annealed in atmospheres containing free 0, while a Cr-Fe spinel layer formed in atmospheres with no free 02. The Cr203 layer was adherent and presented a protective barrier to metal diffusion, effectively limiting oxidation of the metal substrate. The Cr-Fe spinel was not protective and allowed the diffusion of Fe through the spinel to the gas-oxide interface where it was oxidized to magnetite, which spalled from the surface. This resulted in thick scale layers on samples annealed in atmospheres containing no free 02, as compared to layers formed on samples annealed in atmospheres containing free 02. These results confirmed and explained industrial operators' observations that thick, smoky (fine spalled magnetite) scales form on SS annealed in low free-02 atmospheres, while thin protective oxide layers form on sheets in atmospheres containing free 02.

Jan 1, 2010

By S. M. Shelton

[The widespread occurrence of domestic manganese deposits and the shortage of ferromanganese-grade ore have been sources of much speculation and investigative effort for many years. The present emergency has intensified the search by the Bureau of Mines for methods of producing ferromanganese-grade concentrates4/ from low-grade ores.]

Jan 1, 1941

By A. B. Campbell

The Bureau of Mines is developing alloys using ion implantation as an alternative to bulk alloys that consume large quantities of strategic materials such as chromium and nickel. These alloys are formed at the outer layer of relatively common materials. To more fully understand the corrosion characteristics and physical properties of this outer layer, it was necessary to deter-mine the alloy concentration as a function of depth into the substrate material. Also, since many of the ion-implanted alloys would be utilized at elevated temperatures, it was necessary to determine the diffusion behavior of the implanted element. Proton-induced X-ray emission and inert gas ion sputtering have been utilized to generate composition depth profiles for Fe-Cr, Fe-Ni, and Fe-AI ion implanted alloys fabricated by implanting 25-kev Cr+, Ni+, or AI+ into iron substrates. The data were fitted (utilizing a computer program) with symmetrical Gaussian profiles yielding values for the range and range straggle of the ions. These parameters were then compared with those calculated from theory. Changes in the profiles due to annealing were investigated and values for the diffusion coefficient were obtained assuming diffusion according to Fick's Law. For the Cr+ and Ni+ implantation, the profiles as-implanted agree reason-ably well with theory and exhibit ?norrmal" diffusion characteristics at 500° C. For the Al+ implantation, the profile as-implanted is much broader than predicted and exhibits substantial enhanced diffusion at temperatures up to 500° C.

Jan 1, 1979

By Richard F. Link, George S. Koch

Through the use of statistical methods, estimates of metal content and tonnage of an ore body made by using data from 18 diamond-drill holes are compared with actual values established with data from 1,829 drift samples. The reliability of the estimates made from the drill holes is assessed in several ways. The relationship of metal content (assay-width product) to grade is explained. It is concluded that useful estimates can be made from 18 drill holes provided that reasonable assumptions are made and certain risks accepted. The ore body investigated is the Don Tomas vein of the Frisco mine, San Francisco del Oro, Chihuahua, Mexico.

Jan 1, 1964