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By Everett A. Sondreal

Material and energy balances for stockpiled lignite were calculated by computer simulation techniques to determine the occurrence of spontaneous heating. Data on properties of lignite which affect spontaneous heating were required. In some cases, best values from reported data were utilized; in other cases, new data were developed. These include specific studies on the rate and conditions that influence oxidation, heat of oxidation, heat of wetting, specific heat, thermal conductivity, and permeability of stockpiles to air. These data are presented and discussed in detail for possible application to other studies. Results of computer simulations confirm past field experience on the storage of lignite containing as-mined moisture, and predict a greater risk of heat occurrence in stockpiles of dried lignite where experience is lacking. Successful storage was predicted for dried lignite of 20 pct moisture content, if it were cooled after drying and compacted to an interparticle void fraction of 9 pct (bulk density of 67 lb/cu ft) compared to 10 pet void fraction (72 lb/cu ft) for as-mined lignite.

Jan 1, 1974

By Kelly C. Strebig

Laboratory tests were conducted by the Bureau of Mines to determine the effect of depth of cut and bit type on respirable coal dust generation. Apparatuses were constructed to contain the coal samples, measure the linear cutting forces, and analyze the dust generated. Single-bit tests were conducted in Illinois No. 5 and Pittsburgh seam coals with five bit types at four depths of cut. The results showed that bit type did not significantly influence dust production. On the other hand, deep-cutting bits were more efficient and generated substantially less respirable dust per pound of coal broke than shallow-cutting bits.

Jan 1, 1975

By A. D. Garman

The mining ordinance of Costa Rica dates from 1830. In spite of the numerous attempts to enact a new ordinance , it has been so much amended and reamended during the hundred years of its existence either expressly or , more often , by implication , and sometimes by Executive Decrees of which the validity has been called in question - that in most cases no one but a lawyer thoroughly conversant with Costa Rican mining practice could properly advise with reference to it . The present attempt at a digest of these laws is based on the 1929 edition of Bolandi and Johanning - the only source available in Washington . Apparently this edition has no official character , and the editors themselves often made surmises although one would think that definite facts would be available in Costa Rica where it was published .

Jul 1, 1930

By C. W. Smith

Research was conducted by the Bureau of Mines to determine the effectiveness of various types of crushers for use with the Bureau-developed pneumatic concentration technique for mica. Three types of crushers were investigated in this study, a roll crusher, a jaw crusher, and a hammer mill. All the mica concentrates produced contained over 82 percent mica, but recoveries varied considerably. The roll crusher gave the lowest recovery of 46 percent of the mica followed by the jaw crusher with a recovery of 50 percent of the mica. The hammer mill proved the most effective, producing four concentrates with recoveries of at least 70 percent.

Jan 1, 1981

By D. E. Wolfson

Destructive distillation (carbonization) was shown to be a feasible method of disposing of scrap tires. The Bureau of Mines conducted tests under a variety of conditions. Solid, liquid, and gaseous products were produced, recovered, and analyzed. The quantities of the various products were shown to be quite dependent on the test temperature. Variability in composition of the liquid and gaseous products with changes in test temperature was also significant.

Jan 1, 1969

By John A. Breslin

Three scale models of coal mine entries and mining machines were constructed by the Bureau of Mines to study the effects of ventilation parameters on dust concentrations where mining personnel would be working. A one-fifth-scale model of a coal mine entry with a drum-type continuous-mining machine and a one-sixth-scale model of an entry with a twin-borer-type machine were used as well as a one-fifth-scale model of a longwall face with a double-drum shearer. Methane was used as a tracer gas to simulate respirable dust in the models. The distance of the end of the brattice or tubing from the face was found to be more important than the airflow rate for the drum-type machine. Dust reductions greater than 90 pct were shown to be possible with a secondary ventilation system used with the twin borer and a dust collector mounted on the longwall shearer. Cutting-head speed had a significant effect on concentrations at typical positions of miners with the drum-type machine and longwall shearer but not for the twin borer.

Jan 1, 1976

By J. P. Baur

The sensitivity of radiochemical techniques makes possible the study of the initial-stage sulfuric acid leaching kinetics of chalcopyrite and other copper sulfide minerals. This Bureau of Mines study of the initial leaching of chalcopyrite used techniques to evaluate the molecular and electrochemical processes. High-grade Transvaal chalcopyrite was neutron-irradiated in a TRIGA reactor4 to produce radioisotopes copper-64, iron-59, and sulfur-35. Dissolution rates were measured in the time interval zero to 60 minutes, during which time significant anomalies were observed. First was an initial period of rapid dissolution lasting a few minutes; second, an arrest or ?plateau? region usually lasting from 6 to 10 minutes; third, a second period of dissolution of lesser rate than the first. The effects of solution variables such as pH, oxygen partial pressure, and ferric ion concentration at different temperatures were measured.

Jan 1, 1974

RI 9527. Effective Hazard Recognition Training Using a Latent-Image, Three-Dimensional Slide Simulation Exercise, by E.A. Barrett and K.M. Kowalski. Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, 1995. NTIS stock number: PB95-170379. Rl 9531). Computer Modeling and Analysis of The Greens Creek Mine, Admiralty Island, AK, by MJ. Beus and T.J. Orr. Spokane. WA. -U.S. Department of the Interior, Bureau of Mines. 1995. NTIS stock number: PB95-176418. RI 9600. Application of Field Measurements and Computer Modeling to Evaluate Deep Mine Shaft Stability in Northern Idaho, by M, J. Beus, T. J. Orr and J. K Whyatt. Spokane, WA: U.S. Department of the Inferior. Bureau of Minus. 1996. NTIS stock number: PB96-140181. [ ]

Jan 1, 1995

By E. D. Gardner

"The Bureau of Mines receives many inquiries concerning favorable areas in which to prospect for gold, procedure to be followed, equipment required, and allied subjects. This circular has been prepared for use in reply to these inquiries.Interest in gold mining and prospecting for gold remains steady. From time to time many people take to the field to search for new gold deposits. A large percentage of them have had no previous experience in prospecting for lode gold; this paper has been written with the hope that it might assist these newcomers.A majority of the metal mines in the United States have been discovered by qualified prospectors who were searching for valuable minerals at the time. Chance, however, always has played a large part in finding mineral deposits. Some of the discoveries of the past were made by men on other errands, such as rounding up burros or hunting game. Accidental discoveries of ore bodies have been made in building roads and trails and in excavating for mine struc¬tures. Evidence of ore has been brought to the surface by burrowing animals and by ants; gold found in the craws of fowl has led to discoveries of deposits. Important discoveries have been made by men who had no knowledge of rocks or minerals; on the other hand, many ore bodies have been found by experienced prospectors, sometimes after hundreds of untrained men had already passed over the ground.The prospector who carries on his work diligently and intelligently is of course more likely to be rewarded for his efforts than the lazy or unintelligent worker; nevertheless, it is obvious that if valuable deposits are not present at the place being prospected none will be found. Conscientious and painstaking efforts to trace gold to its source usually disclose nothing more valuable than some narrow, unworkable seams; however, many deposits that were developed into profitable mines were found by this method of prospecting. Although some prospectors have made several lucky strikes, many others have spent their working lives searching for gold without finding anything worth while. Probably only one prospector out of several thousand ever finds anything worth developing. Moreover, only 1 out of every 300 or 400 properties developed becomes a profitable mine.Prospecting was begun in the Western States in the fifties as the miners looked for the source of gold found in placers. The search for gold has been continuous since that time; the number of prospectors in the field at any one time, however, has varied greatly. Except in some desert regions, practicallyall of the placer fields now being worked were discovered by old timers; more-over, most of the important gold districts were found by early prospectors. Important discoveries of lode mines, however, have been made from time to time. Most of the area in the mining regions of the West has been searched many times by prospectors, and nearly all of the easily found deposits have been located, but it is reasonable to expect that new gold mines will continue to be found. Most of the future discoveries undoubtedly will be of deposits that do not outcrop. Prospecting for such deposits requires considerable digging.Several important discoveries were made in 1934. One of these, the Rogers-Gentry gold mine at the edge of Antelope Valley in Los Angeles County, Calif., was found by an experienced prospector on an old patented homestead a number of miles from the nearest producing mine. The initial discovery at this mine was an iron-stained, decomposed, silicous limestone outcrop, with no vein structure evident at the surface, near a small, barren quartz outcrop and a water seep. Another discovery, the Silver Queen gold mine, in the same general region and near Mojave, Calif., was found by an experienced miner on an open fraction 400 by 1,400 feet in size between two old properties that were thought to have been worked out years ago. The Silver Queen discovery was made as the result of finding a"

Feb 1, 1950

By M. E. Tyrrell

Work in this investigation was undertaken by the Bureau of Mines to demonstrate how waste glass might be utilized to lower the required firing temperature and firing time of structural clay products. Mixtures of waste glass and common clays were formed by stiff-mud extrusion and fired to the temperature required to produce a body having 6 to 7 percent absorption. Substitution of glass for one-half of the clay in a red body reduced the firing temperature 500° F, which made possible a 30-percent increase in production; in a tan body, the firing temperature was reduced 400° F, which made possible a 23-percent increase in production.

Jan 1, 1972

By A. L. Engel

Simple treatment methods, employing the least possible equipment, can sometimes be established for marginal ores and economical results achieved. In continuation of a long-established part of the hydrometallurgical and ore-dressing program of the Reno Station of the Bureau of Mines, typical ores from newly discovered or recently explored mining districts have been investigated. The purpose of such investigations is to encourage the search for and development of mineral resources and particularly to assist in the economical exploitation of low-grade and marginal ores, as well as the conservation and recovery of values in products from former operations that were discarded because of past inability to treat them economically. Several of these investigations have been limited to preliminary tests of samples from prospecting operations, whereas some involved samples of old dumps or tailings piles. The test, work in these cases was not extensive enough to warrant publication as individual reports, but is of considerable interest inasmuch as it indicates the possibilities as well as the limitations of treating the respective materials; and because, inasmuch as the samples were representative of the districts from which they were obtained, this in-formation should be helpful in the future development of these districts. The present report is a compilation of results of brief preliminary tests on oxide ores only, which contained gold and silver and in some cases base metals. The methods of treatment used include gravity concentration, amalgamation, flotation, and cyanidation. For the most part, only standard laboratory procedures were employed. No attempts were made to develop new methods for the low-grade refractory ores in this group of samples if simple treatment was not successful, as the stage of development of the properties did not warrant extensive experimentation on the samples submitted.

Jan 1, 1951

By G. F. Kuncir

The funding tables included in this report were defined in support of an evaluation of the Advancing Oil Sale Mining Technology Program undertaken by The Aerospace Corporation. Because of the sensitive nature of the fiscal planning information, the tables have been separated from the main analysis report and given a limited distribution.

Jan 1, 1977

By R. Karl Zipf

The sudden, violent collapse of large areas of room-and-pillar mines poses a special hazard for miners and mine operators. This type of failure, termed a 'cascading pillar failure' (CPF), occurs when one pillar in a mine layout fails, transferring its load to neighbouring pillars, which causes them to fail, and so forth. Recent examples of this kind of failure in coal, metal and nonmetal mines in the U.S.A. are documented. Mining engineers can limit the danger presented by these failures through improved mine design practices. Whether failure occurs in a slow, non-violent manner or in a rapid, violent manner is governed by the local mine stiffness stability criterion. This stability criterion is used as the basis for three design approaches to control cascading pillar failure in room-and-pillar mines-the containment approach, the prevention approach and the full extraction mining approach. These design approaches are illustrated with practical examples for coal mining at shallow depth. Cascading pillar failure {CPF) in room-and-pillar mines can go by many other names, such as `progressive pillar failure', `massive pillar collapse', 'domino-type failure' or 'pillar run'. In this kind of failure when one pillar collapses the load that it carried transfers rapidly to its neighbours, causing them to fail, and so forth. This failure mechanism can lead to the rapid collapse of very large mine areas. In mild cases only a few tens of pillars might fail; in extreme cases, however, hundreds, even thousands, of pillars can fail. CPF can have catastrophic effects on a mine, and sometimes these effects pose a greater risk to health and safety than the underlying ground-control problem. Usually, the CPF induces a devastating air blast as a consequence of the displacement of air from the collapse area. An air blast can disrupt the ventilation system totally by destroying ventilation stoppings, seals and fan housings. Flying debris can seriously injure or kill mining personnel. The CPF might also fracture a large volume of rock in the pillars and immediate roof and floor. In coal mines and certain other mines this can lead to the sudden release of large quantities of methane gas into the mine atmosphere; a methane explosion might result from the CPF. CPF is at the far end of the spectrum of unstable pillar failure. At the other end are slow `squeezes' that develop over days to weeks and, because of their slow progress, do not pose an immediate danger to mining personnel. There is ample warning time for men and machinery to get out of the way of the failure. In a CPF, however, the failure progresses so rapidly that men and equipment cannot be evacuated in time. Significant seismic energy is released as a consequence of the rapid failure and collapse. CPF should not be confused, however, with coal-mine bumps and rockbursts. In some cases the damage can appear similar, but the underlying mechanics are completely different. As will he shown later, the mechanics of CPF depend on the applied vertical stress and the post-failure, i.e. strain-softening, behaviour of the pillars. In a CPF pillars shed their applied load rapidly and have very little residual strength after failure. The collapse itself may release significant seismic energy, but otherwise the mine is seismically quiet. Alter a CPF the openings in the affected mine workings have usually closed completely. In contrast, coal-mine bumps and rockbursts occur in seismically active mines. Research has shown that coal-mine bumps and rockbursts are seismic events induced by mining that damage underground mine workings. Bumps and bursts are thus a subset of a much larger set of mining-induced seismic events.[ Only some of these seismic events damage mine workings; fortunately, most do not. The mechanisms by which a mining-induced seismic event can lead to a damaging coal-mine bump or rockburst is still a significant research area.2 After a bump or rockhursr the affected mine workings may or may not be completely closed. For example, in the coal-mine bump described by Soler and co-workers2 the mine workings remained open even though the pillars were destroyed during the bump event. Because CPF differs from a coal-mine bump or rockburst, the design approaches to control their occurrence also differ. The design recommendations developed here apply to CPF and not to bump- or burst-prone mines. Cascading pillar failure examples Unfortunately, CPF has occurred in room-and-pillar coal, metal and non-metal mines. The most infamous example is the Coalbrooke colliery in South Africa, where 437 miners perished where [si >1 3at1ttsumsus7car kky vArtMixiL7i nesafr tramwsamn ures] on 21 January, 1960.1 Table I summarizes the mining dimensions of 13 examples of rapid pillar collapse in U.S. coal mines. All occurred during the 1980s and 1990s, and all happened suddenly or without significant warning. Most resulted in air blasts and damage to the ventilation system. Table 2 gives the mining dimensions of six room-and-pillar metal and non-metal mines in the U.S.A. where failure occurred in all probability by the CPF mechanism. The collapse areas can be huge. Fortunately, some of these failures gave advance warning. At the lead-zinc mine slabbing from pillars and roof falls began four weeks prior to the main collapse.3 At the copper mine considerable rock noise and smaller failures preceded the main collapse by five days.5 At the copper-silver mine it is not known if nature provided a warning.6 Evidently, the trona mine collapsed without warning.7,8 Rock noise and other failure warnings preceded the silica mine collapse by three weeks. v The presence or absence of warnings at the salt mint is not known. to Most of these collapses induced a substantial air blast; damage to the ventilation systems was limited, however, to bent airdoors and a few downed stoppings, except at the trona mine where extensive damage to the ventilation system resulted.

By Gregory M. Molinda

The Bureau of Mines conducted an investigation into the occurrence of outbursts of salt known to be responsible for explosions, fatalities, and damage in domal salt mines. The purpose of the investigation was to develop a basis for predicting these outbursts based on geologic and associated physical properties of salt. The investigation was conducted at the Cote Blanche salt mine in southern Louisiana. Because outbursts are the primary mode of methane emission into the mine, more than 80 outbursts, ranging in size from 1 to 50 ft in diameter have been mapped. These outbursts generally are aligned and elongate parallel to the direction of salt layering. More than 200 salt samples, both random and selected, were tested for methane content. It was found that outburst zones are well correlated with high methane content. Detailed mapping also revealed that the zones are well defined, with salt crystal size abruptly increasing upon entry into the zone. The intensity of folding and kinking of the salt layering within the outburst zone also appears to increase. An interbedded sand layer occurring throughout the mine does not appear to be a significant source of methane. However, fine-grained salt may be related to outburst occurrence.

Jan 1, 1988

By Charles Prasky

This report describes bench-scale studies and pilot-plant development of the Bureau of Mines process for roasting iron ores with a ferrous scrap reductant, such as discarded automobile hulks, to yield artificial magnetite. Quality magnetic concentrates containing about 66 percent iron and 6 percent silica with iron recoveries of over 90 percent were obtained after roasting fine-grained oxidized or nonmagnetic taconite with unburned, sheared automobile hulks in a rotary kiln. The relatively complete oxidation of the lighter gage metal in the automobile during roasting resulted in a metallic byproduct consisting of the unconsumed heavier gage metal scrap. This residual or tailored scrap is potentially useful as heavy melting stock and has more value than the original automobile hulk.

Jan 1, 1970

By G. B. Shea

The accident experience of the California petroleum industry for 1927 was characterized by a decrease it .the number of fatalities. The year closed with a total of 41 fatal accidents, as compared with a total of 54 for the preceding year. 3 In percentage, the figure for 1927 represents a decrease of 24 per cent from that of 1926 and evidences the promising results of organized safety work, in which the industry in California has taken an absorbing interest. The percentage of decrease for 1927 is the largest recorded in any one year since the compilation of the fatality record in the California petroleum industry was begun. Although good progress has been made during the past few years, much remains to be done to reduce still further the human and economic waste caused by accidents. This review is intended to show the employee, as well as the employer, the proximate and contributing cause of accidents. To increase the value of the report, preventive measures in various instances are suggested, on the theory that accidents of a similar nature will occur unless remedial action in taken to remove the cause.

Jan 1, 1928

By Noel N. Moebs

Coal mine roof failure is categorized according to character, trend, or pattern of occurrence. Two principal categories of failure are proposed--geology related and stress related. Geology-related failure includes both lithology and structure. Each of several subcategories reflects the probable cause of failure and thereby provides a basis for the selection of appropriate techniques for reducing the incidence of failure. These control techniques, depending on local conditions, may include supplementary support, destressing, reduction of mine air humidity, or a change in the customary support methods.

Jan 1, 1986

By R. H. Thompson

Six different types of blasting caps, mainly of the type used in coal mines, were evaluated to determine both their 1lF and DC characteristics. Two of the caps were of foreign manufacture. All the American made caps had "no-fire" (0.1% firing probability with 95% confidence, as determined by the Bruceton test) levels above 0.04 watts. One of the caps of foreign manufacture had a "no-fire" level of 0.023 watts. A worst case analysis of blasting cap pick up of RF power in coal mines was performed and safe distance curves were generated.

Jan 8, 1973

By R. J. Hundhausen

The continued worldwide shortage and strategic value of nickel place great importance upon the continued development and exploitation of new sources of nickel in the United States, The deposits of nickel-bearing minerals in Oregon and Washington have attracted considerable attention, particularly since the Hanna Development Co. has engaged in development work aimed at producing ferronickel from the Nickel Mountain deposit, near Riddle, Douglas County, Greg. The Red Flats nickel deposit in Curry County, Oreg., was first examined by the Bureau of Mines in dune 1945, but it was not until 1952 that the deposit was drilled and sampled. In 1953, a 15-ton sample of Red Flats material was procured and subjected to continuous smelting tests in the Bureau's Northwest Electrodevelopment Laboratory, Albany, Greg.

Jan 1, 1954

By A. H. Warner

Sphalerite crystals occur sparingly in minor faults and pockets in a coarsely crystalline dolomite on the Brown-Tipton farm near Greenville in Greene County, Tenn. After several visits by U. S. Bureau of Mines engineers and U.S. Geological Survey geologists, a survey was r: the in the fall of 1944. Upon their recommendations, trenches on the Brown farm under Bureau of Mines supervision. In each case, the bed most favorable for zinc deposition was exposed. In the finished trench bottoms no zinc minerals are visible.

Jan 1, 1950