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By E. S. Leaver

The mineral value in the ores from the Mother Lode mining districts of California is almost entirely gold, Although many mines have produced extremely high-grade ore the usual mill grade averages approximately $7.00 gold per ton. Fully 80 per cent of the gold has been and is now being recovered by amalgamation. Various methods have been introduced to recover the gold that was not obtained by the amalgamation processes. They include vari¬ous kinds of gravity concentration which in some cases were followed by chlorination or cyanidation. The usual practice includes only stamp battery, plate-amalgamation, and vanner concentration. In the very early practice the tails were run to waste through the main drainage streams of the different mining districts. During later years very large storage dumps have been impounded. These old tails, together with those being saved from present mills, furnish the problem discussed in this article. The clean sand portion of these mill tails is amenable to the usual cyanidation. The slime portion contains the major amount of the gold lost, but it also contains 1-1/2 to 3 per cent carbon, which precludes direct cyanidation of this part of these low-grade waste tails. The black carbonaceous slime portion is the particular problem considered in this report.

Jan 1, 1930

By Wm. W. Odell

A study of certain gas making and fuel problems peculiar to the gas industry of California has been made by the Bureau of Mines. The work was done at the request of, and in cooperation with The California Gas Research Council 2, for the purpose of obtaining basic information on the gas-making fuels available to California, and their applicability to the present and future needs of the gas industry in that State. The data obtained have been applied in outlining a construction program, and indicate the possibilities in efficiently utilizing fuels in making gas by other than the oil-gas process. This paper presents an outline of the study and a summary of the principal results obtained, with some of the more important conclusions and recommendations based on this data. Gas is produced in California by processes which are both unique and different from those common to other parts of the United States. The bulk of the manufactured gas is made in and distributed from two main districts which are centers of population - namely, the Los Angeles district and the San Francisco Bay district. The gas manufactured in the Bay district is, almost exclusively oil-gas, whereas that produced in the southern part of the State, where natural gas is available, is mostly mixed natural gas and reformed-gas, but oil-gas is the chief product when the supply of natural gas is inadequate. Practically all of the gas companies are equipped with oil-gas generating apparatus, and anticipate using it in the future. As the continued use of the oil-gas process to the exclusion of all other processes, depends upon a continued supply of oil at a low cost, and the prospect of obtaining such low-priced oil in the future is somewhat uncertain, the questions have arisen: What will the future gas-making process or processes be? When will it be necessary to make plans for the installation of different gas generating equipment, and what will that equipment comprise?

Jan 1, 1926

By George S. Rice

"It is well known that the lost coal left in the ground in mining, under such conditions that recovery is practically impossible, constitutes a large proportion of the coal in the beds worked. A recent estimate, in a paper on ""The World's Fuel Supply"" presented by Prof. L. P. Breckinridge, of Yale University, before the Annual Meeting of the. American Society of Mechanical Engineers, places the average loss in bituminous coal mining as one-third left in the ground.The bald statement that there is a loss of one ton of coal for every two recovered may seem to those not familiar with coal mining to imply inexcusable and wanton waste. Perhaps a better way of expression is in terms of total recovery rather than in terms of losses. Many mine superintendents and mine owners will readily concede that their total recovery may be only 60 to 75 per cent, but to state that they are wasting 25 to 40 per cent arouses antagonism. The suggestion is of willful waste, whereas the majority of the operators try to the best of their ability to get a high recovery under the adverse and complex conditions that confront them. These involve natural, commercial, and labor conditions, and the requirement in many cases of boundary pillars under railroads and buildings, which may be called for in the deed or lease, or in the absence of specific exemption in the deed or lease, the common law requirement that a surface owner is entitled to the support of the surface."

Apr 1, 1921

By Frank J. Wiebelt

In its efforts to maintain production of tungsten during the recent war period, the Bureau of Mines explored certain parts of the properties of the Atolia Mining Co. in San Bernardino County, Calif., by diamond drilling. Owing to past production record and other available data, the area was considered attractive for possible development of new ore bodies. Scheelite occurs in narrow veins ranging in width from a fraction of an inch to several feet. The veins are in quartz monzonite in a zone 2 miles long and 500 feet wide. Production from the district was reported to have been over 1,000,000 units of W03. Twelve diamond-drill holes, totaling 5,056 feet, were drilled by the Bureau of Mines in the vicinity of the Papoose, Papoose No. 5, Amity, and Union mines, the tailings pond, and the "Old Spud Patch." The work began in August 1943 and was completed in June 1944. This publication briefly describes the history and deposits of the district and gives full details of the work performed by the Bureau.

Jan 1, 1950

By J. M. Kuchta

The Bureau of Mines used laminar hot air jets of l/8- to 3/4-inch diam-eter to determine the hot gas ignition temperatures of various combustible vapor-air mixtures. The combustibles were n-hexane, n-octane, n-decane, a hydrocarbon jet fuel (JP-6), and an adipate ester aircraft engine oil (MIL-L- 7808). Minimum ignition temperatures occurred at a fuel to air weight ratio of about 0.5 and were not greatly sensitive to variations of fuel concentra¬tion. Moderate variations of jet velocity also had little influence on these ignition temperatures. However, these temperatures decreased with increase in heat source dimensions (jet diameter). The hot gas ignition temperatures of the combustibles were not necessarily much greater than corresponding autoignition and wire ignition temperatures when the size (,F the heat source and the ignition criterion were the same.

Jan 1, 1966

By G. S. Rice

[This paper describes preliminary tests at the Bureau's Experimental Mine to determine, under conditions that may prevail ira bituminous coal-mine heading, how small a quantity of fire damp may bring coal-dust into suspension and ignite to it. The results show that the explosion of as little as 150 cubic feet of an explosive mixture of gas and air containing 9 per cent natural gas may start a disastrous explosion Of coal-dust. This is a very small volume, of gas, to cause such a result. Let us suppose that this amount of exclusive mixture, was at the face of an entry which was 10 feet wide and the face was overcut to a depth of 6 foot and an upper layer of coal 2 1/2 feet thick had been removed, the recess so made would save a volume of 150 cubic feet. Furthermore, only 13 cubic feet of pure methane is needed in this volume to produce this 9 per cent explosive mixture.]

Jan 1, 1930

By Fred N. Kissell

Air recirculation caused by dust scrubbers at coal mine working faces was examined by the Federal Bureau of Mines with regard to the potential hazards caused by a possible buildup of methane gas. A theoretical analysis indicated that there was no apriori way to predict the effect of scrubber recirculation on methane concentration levels. Experiments conducted in a full-scale model of a working face area indicated that methane levels were dependent to a great extent on the location of the scrubber exhaust, but that the scrubber recirculation did not substantially increase the methane concentration above those levels that would have prevailed were the scrubber not in operation. An analysis of two underground scrubber trials showed that the scrubbers had no significant effect on methane levels, and a review of explosions attributed to recirculation showed that these were characterized by a lack of fresh air as well as recirculation. It was concluded that high methane levels are due more to a lack of fresh air than to recirculation.

Jan 1, 1975

By R. V. Ramani, R. Bhaskar

"While the National Academy of Sciences has stated that gravimetric sampling technology for compliance purposes is adequate, research into various aspects of respirable dust control require data on many other parameters of airborne dust. These, in turn, have created the need to use many instruments, other than personal gravimetric samplers, in mi ne environments for dust measurement. There is a need to evaluate the performance of these instruments under conditions of potential use.As part of research in the Generic Technology Center for Respirable Dust, cascade impactors, gravimetric personal samplers and gravimetric samplers collecting dust using isokinetic sampling principles were employed for dust measurements under identical conditions in a mine airway. During the course of the experiments, 8-stage cascade impactors and gravimetric samplers drawing air isokinetically were located in the center of a mine airway at various stations. Two types of data were examined - concentration of dust and size distribution of the dust collected in the samplers. The data show that the amount of dust collected by an impactor is less than half the amount collected isokinetically. The size distributions of the dusts collected from the two instruments, though comparable, show a consistent difference in median diameters. The cause for this bias is examined.The paper presents and discusses the results of the tests, including the concentrations and size distributions obtained from the two instruments for different experimental conditions. There is a need to document the performance of various dust measuring devices in mine airflow conditions.INTRODUCTIONThe sampling of airborne dust in mines can be done for several purposes. Traditionally, dust sampling has been restricted to the gravimetric measurement of airborne respirable dust to comply with the regulations governing the mining industry. Instruments such as the MRE gravimetric sampler, and personal gravimetric samplers that have collection characteristics similar to the human respiratory system have been in use for the last two decades. Presently available instrumentation for the purpose of regulation have been considered adequate by the Committee on the Measurement and Control of Respirable Dust in Mines (National Academy of Sciences, 1980),"

Jan 1, 1989

By H. M. Smith

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Jan 1, 1927

By Webster S. Anderson

Bureau of Mines planer mining tests on the phosphate bed of the Douglas mine, near Drummond, Mont., indicated that a competent bed with a Mohs' scale hardness of 3 to 4 cannot be mined economically with the planer. Although planer mining was feasible where the bed was fractured enough for a 4-inch depth of cut to be consistently maintained, the depth of cut in the competent beds at the Douglas mine did not exceed 0.5 inch. Average production rates were 0.15 ton per minute and 9 tons per man-shift.

Jan 1, 1966

By E. D. Gardner

This paper is one of a series on mining methods and costs being published by the United States Bureau of Mines. In April 19.74 the St. Joseph Lead Co., at Atlanta, Elmore County, Idaho, was mining and milling about 225 tons of gold ore daily with a total force of 150 men. The mine, which comprises the old Boise-Rochester and Monarch properties, is at an elevation of about 6,000 feet. Snow lies on the ground about 5 months each year but does net interfere greatly with local operations. However, the road to Mountain Home, the shipping point 80 miles distant, passes over a high range and usually is closed by snow from about November 15 to June 15. Heavy supplies are brought in and concentrates trucked out during the summer. In winter the district is served by a biweekly mail plane and a passenger and express plane making 4 to 6 trips weekly. Mine timber is cut locally. A plentiful supply of water is obtained from a stream brought to the property through 7,500 feet of plume.

Jan 1, 1935

By N. S. Dalal, V. Castranova, K. Van Dyke, V. Vallyathan, J. H. Kang

"We have reported previously that crushing or grinding crystalline silica results in the generation of silica-based radicals on the particulate surface and that these radicals can generate hydroxyl radicals in aqueous solution. Data in the present study indicate that freshly ground silica is more cytotoxic and is a more potent activator of alveolar macrophages than comparably sized aged silica. That is, compared to aged silica, fresh silica is 4.2-fold more potent in decreasing the membrane integrity of macro· phages; is 50% more potent in activating hydrogen peroxide secretion by macro· phages; and is 4.frfold more potent in stimulating cellular chemiluminescence. Prosil 28, an organosilane material, is an effective coating agent for fresh silica. It decreases the cytotoxicity of fresh silica by as much as 78% and decreases the ability of fresh silica to induce chemiluminescence from alveolar macrophages by 58%. The data suggest that surface radicals associated with freshly cleaved dust may be an important factor in the induction of pulmonary disease. Furthermore, treating dust with coating agents may substantially decrease toxicity. INTRODUCTIONThe U.S. Department of Labor estimates that over 1.25 million American workers may be exposed to crystalline silica and that nearly 60,000 may be at risk of developing some degree of occupational lung disease (Parkes, 1982; Peters, 1986). Occupations of concern include miners, stone quarry workers, sand and gravel workers, sandblasters, foundry workers, and glass workers. Acute silicosis is characterized by inflammation, alveolar lipoproteinosis, and the rapid development of respiratory disability (Banks, 1986). In contrast, chronic silicosis develops 20-40 yr after initial exposure and is characterized by the appearance of concentric hyalinized nodular lesions and the progressive development of dyspnea (Parkes, 1982; Ziskind et al., 1976)."

Mar 1, 1992

By Roger L. King

The Bureau of Mines has developed probes to be used in emergency mine rescue operations by being lowered through a borehole drilled into an underground mine. Various probes can provide two-way voice communication with trapped miners, continuous mine atmosphere monitoring, temperature indication, and television searching capability. At present, an infrared imaging probe is being developed for "seeing" through coal smoke.

Jan 1, 1976

By L. G. Marshall

The geology, mining, beneficiating, types of products, and costs in terms of percent of total costs and of labor, power, and supplies of two crushed-limestone operations in Madison County, Iowa, are described in this paper. The operations are basically similar, differing in refinements in mining, product types, and markets. The operations are comparable as to personnel and as to weighted costs in terms of percent of total costs and in terms of man-hours, power, and sup-plies. The waste-to-stone stripping ratio is 1 to 0.8 at both operations, the powder factor is 0.29 pound of explosives per ton of stone, and daily production is 95 tons per man-shift. Both companies use crawler-mounted diesel shovels for loading, truck transportation, wagon drills, and dry screening.

Jan 1, 1963

By M. J. Ankeny

This is a study of 58 fatal haulage accidents investigated by Federal coal-mine inspectors during the period January - June 1951. The information presented in this circular was obtained by analyzing fatal haulage accidents in 33 bituminous-coal producing counties representing 11 States. The physical conditions represent a cross section off producing coal beds. Mining and transportation methods vary, from those of small hand-loading mines to those of large modern mechanized operations. These data are thought to be representative of haulage conditions within the bituminous-coal mining industry and are submitted to follow up the Information Circular 7604 ?Analysis of Haulage Fatalities in Bituminous-Coal Mines - 1950.? Coal-mine haulage ranks second as a cause of coal-mine fatalities, and the problem of haulage safety is complex. It is subject to constant change and is comprised of numerous influencing variables, which are not always obvious. The solution to this problem will not come through the application of any standard formula or mechanical approach since the inherent factors are strongly influenced by the human equation, and the chain of circumstances is further affected by expediency.

Jan 1, 1951

By D. Harrington

Springing or chambering of deep drill holes is common practice in some quarries. It involves definite hazards from premature explosion during placing of the springing charges or the final charge due chiefly to heating of the bottom of the holes by the successive exploding of the springing charges or, in some instances, from burning of paper or other material following detonation of the explosives The danger is either unknown or disregarded in many instances by those who place the charges in the holes. Disregard of this hazard probably is, at least in part, responsible for the far too high fatality and injury rate due to charging explosives and premature slots in quarry work. Awareness of the danger' should result in elimination or at least of material decrease in injuries from this cause.

Jan 1, 1941

By James P. Bennett

In this Bureau of Mines study, portions of four acidproof bricks (two red shale and two fireclay) were exposed to 20 wt pct RCI at 900 C for periods of 30 days. Three different techniques were selected to deter-mine volume expansion of these materials after exposure. Linear expansions ranging from about 0.02 to 0.12 pct were noted from Ta pin and dilatometer measurements. The use of strain gages to measure expansions was not successful. The red shale and fireclay brick with the lowest apparent porosities had the lowest expansions. Expansion data obtained by direct measurement of samples exposed for 30-day periods or by dilatometric measurement of autoclaved samples ex-posed for 2 h were comparable. This suggests the use of an accelerated autoclave exposure procedure for determining volume expansion effects of ceramic materials in acid environments.

Jan 1, 1985

By David E. Siskind

The Bureau of Mines recorded particle accelerations in the mine roof produced by three types of explosives in the Pilot Knob Pellet Co. mine, Pilot Knob, Mo. Examined were the effectiveness of cube root, square root, and two-thirds power scaling in grouping the underground blast vibration data, and the effects of mine geometry, rock type, explosive type, and charge size on blast vibration levels. A propagation law for this mine was determined. The scaling factor of the square root of the charge weight was developed from previous Bureau studies of vibrations from quarry blasts, and in under-ground blasting both square root and cube root scaling were found applicable for scaling particle vibration data. The vibrations from the Pilot Knob blasts were best grouped by a square-root scaling factor. The empirical propagation equation AW1/2 = 76,250 (R/W1/2)-2.61 where A is the peak acceleration in g's, W is the charge weight in pounds, and R is the distance from the blast in feet, may be used to describe vibration amplitudes from charges fired with zero delay caps or with a single cap at Pilot Knob. Statistically significant differences were found in the vibration levels generated by the different explosives. The Power Primer (75-percent weight-strength ammonia gelatin dynamite) produced levels of vibration of 1.7 to 2.4 times those of AN-FO and slurry explosives; the latter two are approximately equal.

Jan 1, 1973

By R. P. Vinson

The Bureau of Mines examined the effects of high humidity and water droplets on the GCA Corp. real-time aerosol monitor (RAM--l). which uses a lO4mm cyclone preseparator. Tests were conducted both in a laboratory and in a full-scale model mine entry. The laboratory tests were conducted in a test chamber saturated with moisture and water droplets. Under these extreme conditions. the RAM-I responded by indicating dust concentrations of 1-1/2 to 2 mg/m3? although the air was dust free. Within the first 2 h of each test. water accumulated in the cyclone and affected the cyclone particle separation characteristics. resulting in readings of 3 to 4 mg/m3. In addition. condensation formed inside the RAM-I case and affected the liquid crystal display (LCD). However. the full-scale mine entry tests revealed that the RAM-I can function ac-ceptably in an atmosphere of water vapor and water droplets similar to the most severe conditions found in an underground mine.

Jan 1, 1984

By R. S. Conti

This U.S. Bureau of Mines (USBM) report discusses the results of research conducted in the USBM experimental mine at its Lake Lynn Laboratory to determine the alarm times of smoke and carbon monoxide (CO) sensors, and a point type heat sensor (PTIIS) to slowly developing coal-conveyor belt fires. The tests were conducted at air velocities of 0.44 and 0.97 m/s, The data clearly indicate that smoke sensors provide earlier warning of fire than 10 ppm CO sensors, and that 10 ppm CO sensors provide earlier warning than PTHS, A success rate of 1.0 (indicating detection of every test fire) was obtained for both smoke and C8 sensors. For the PTHS, the success rate was 0.57 at the lower air velocity, decreasing to 0 at the higher air velocity, Data are also presented showing the sequence of fire events and detection events at the two air velocities as a function of time. Results show that early detection and warning of underground mine fires will improve the probability of miners' escape.

Jan 1, 2010