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By Peter G. Chamberlain

The surge in gold and silver prices during the 1970's attracted many new mining operators and has rekindled interest among experienced ones. With its low capital investment requirements and fast payout, leaching has attracted many operators--particularly those with small or low- grade deposits. Although in certain situations leaching offers many advantages over conventional mining methods, many operators are uncertain how these relatively new techniques should be implemented. Consequently the Bureau of Mines has prepared this circular to disseminate information on gold and silver leaching practices, techniques, and problem. Engineering data gathered from 26 operations indicate that most ores are leached in heaps following crushing and distribution on pads. Metal values are recovered from cyanide leach solutions using either zinc precipitation or charcoal adsorption. Potential problems that my hamper on block development of a leaching operation are poor percolation characteristics of the ore, calcium salt buildup, low temperatures, and solution losses. An extensive bibliography on gold and silver leaching is appended.

Jan 1, 1984

By M. A. Mahtab

This report presents the geometric parameters (attitude, spacing, extent, and aperture) of fracture patterns in a selected portion (study area) of San Manuel copper mine, Arizona. The geometric parameters are quantified for input to structural analyses for studies of the influence of fractures on cavability of ores. Using an orientation analysis procedure developed earlier by the Bureau, three prominent and nearly orthogonal sets of fracture orientations were delineated in the study area. Sets 1 and 2 dip nearly vertically, and generally strike east-west and north-south, respectively, whereas set 3 is nearly horizontal. Both a horizontal rotation (of 14° to 26° for sets 1 and 2, respectively) and a tilt (of 20° for set 3) is shown to occur between the 1415 and 2015 levels of the mine. Gomparison of the three major rock types present in the study area (quartz monzonite, monzonite porphyry, and rhyolite) show that the rhyolite is characterized by short extent, small spacing, and tightness of fractures as well as the general absence of fracture set 3, which may account for its generally observed strong resistance to caving.

Jan 1, 1973

By H. H. Heady

A naphtha obtained by destructive, recycle hydrogenation of crude shale oil, produced by gas-combustion retorting of Colorado oil shale, was found by the Bureau of Mines to contain 49.1 percent paraffins, 20.3 percent cycloparaffins, 7.8 percent olefins, and 22.8 percent aromatics. The naphtha contained only minor amounts of sulfur, nitrogen, and oxygen compounds. Compounds containing less than 5 carbon-atoms per molecule were removed by distillation before analysis. The paraffins where predominantly straight-chain compounds; n-Hexane was present in the largest quantity, and the other straight-chain paraffins decreased in amount as the molecular weight increased. The cycloparaffins, which contained both cyclopentanes and cyclohexanes, were evenly distributed throughout the boiling range. Although the naphtha had been produced by hydrogenation, it contained a small quantity of olefins. Straight-chain olefins with a terminal double bond comprised about two-thirds of these compounds. Among olefins with an internal double bond, those having trans configuration were present in three times the quantity of those in the cis form. In the aromatics all but one of the alkylbenzenes having nine or less carbon-atoms per molecule were identified; toluene was present in the greatest quantity. Only a few of the higher molecular-weight homologs were identified. The composition of the naphtha was computed from analyses of 105 narrow¬boiling distillation fractions. Volume, density, refractive indices, bromine number, and an ultraviolet spectrum were determined on each fraction. From these data the hydrocarbon-group composition of each fraction was estimated. A silica gel adsorption analysis was used to check the values of nearly one-third of the fraction calculated from physical-property data. Mass and infrared spectra were obtained on some fractions for identifying individual compounds or types of compounds, such as terminal olefins.

Jan 1, 1960

As part of the Phase I study activity, a questionnaire was sent to a representative sampling of mining companies to obtain information on the uses, use conditions, personnel policies and other user concerns associated with front-end loaders. On-site visits to several of the mining companies were also parried out and the questionnaire was used during these visits as well. Five major areas were dealt with in the user questionnaire. These included: 1) Front-End Loader Critique - An open-ended form was employed to permit the mining companies to describe the particular things they liked and disliked about front-end loaders, in general, and/ or specific models in particular. 2) Usage - A form indicating the functions performed by front-end loaders and the numbers, makes and models of front-end loaders being used by mining companies. 3) Environment - A form where the user indicated the various types of conditions encountered in their use of front-end loaders. 4) Personnel - A form for describing factors pertaining to the qualifications of front-end loader operators. 5) Miscellaneous and Comments - A form permitting the user to comment on his feelings toward standardization of front-end loader operator stations.

Jan 1, 1973

By T. A. Lang

The objective was to develop a Program Plan of analytical studies and tests for determining ( 1) the optimum installation tension of a coal mine roof bolt, (2) the most valid bolt support theory or theories, and ( 3) the most valid roof failure theory or theories. On this basis a comprehensive literature search was made and significant material dealing with coal mine roof behavior, roof bolting and roof support was collected, reviewed, classified and analyzed. Emphasis was given to the influence of rock reinforcement on the control of deformation, stress field modification and mine roof stability. An assessment was made of the effect of various parameters including bolt tension, bolt pattern and time of installation, on the effectiveness of rock reinforcement systems, and equations developed for bolt tension as a function of these parameters, and rock properties. From these studies, a major program plan of tests and studies was developed for verifying and validating the most tenable theories of roof behavior and roof support and for determining optimum bolt installation tension.

Jan 1, 1979

By W. W. Adams

The safety record established by the coal-mining industry of the United States during 1934, although not as favorable as that for the previous year, was better than the record for any other year during the period 1930-34 for which complete figures covering fatal and nonfatal accidents at the mines are available. The number of accidents was 89.98 per million man-hours of employment compared with 86.74 for the year 1933, the latter being the lowest rate in any of the 5 years referred to. The rate was 105.60 for 1930, the first year covered by available data. Employment increased in 1934; the number of workers represented an increase of 8 percent over the year 1933, man-shifts of labor increased 16 percent, and the number of man-hours of labor increased 7 percent. The total number of man-hours of employment also exceeded the number reported for 1932, and was almost equal to the record for 1931.

Jan 1, 1936

By Oliver Bowles

"General.The term mica is probably derived from the Latin ""micare"", meaning to shine or glitter, for the brilliant reflection from mica flakes in rocks has directed more than ordinary attention to this group of minerals. Mica includes a group of several minerals all characterized by a perfect basal cleavage, by virtue of which they may be split into exceedingly thin plates. The minerals are of very common occurrence in all countries, constituting about 4 per cent of the igneous rocks of the world The term ""isinglass"" is sometimes applied to glazing mica, but this is incorrect, for true isinglass is a soluble combustible material made from the air bladders of certain fish. As a constituent of granites and schists, mica is present as flakes too small for commercial use. Mica occurs also as small scales in many sandstones. When granites decompose, the quartz and the white mica are the most resistant to weathering, and so remain when the other constituents have been decomposed and carried away. A secondary white mica known as sericite is formed by the metamorphosis of clay-bearing rocks, and thus, in extremely fine-grained form it constitutes an important constituent of slates and related rocks. Some schists contain a high percentage of mica, but the presence of large amounts of quartz and other minerals has up to the present time rendered them useless as commercial sources of mica for grinding. It is possible, however, that certain mica or seri-cite schists which are composed almost wholly of mica with very little quartz may be utilized for ground mica if found in large enough entity. Considerable micais sometimes found mixed with the residual kaolin that results from decomposition of pegmatites, and in one locality at least it has been recovered as a by-product in a clay purification plant."

May 1, 1922

By William E. Wallace, S. J. Page, B. L. Razzaboni, C. A. Hill, Pamela Mike, P. Bolsaitis, M. J. Keane, Val Vallyathan

"Respirable quartz cytotoxicity, as measured by erythrocyte hemolysis and pulmonary macrophage release of lactate dehydrogenase in vitro, is neutralized by boiling in water in glass test tubes for 10 to 40 minutes. The cytotoxicity is reduced to near zero by boiling l to IO mg quartz per milliliter water. For greater concentrations of quartz in water the hemolytic potential after 40 minutes of boiling approaches that of native quartz. Replacing the medium with fresh water midway through boiling results in full detoxification through 20 mg quartz per milliliter water. Pre-boiling the medium with silica reduces the detoxification effect. Detoxification persists after mild drying at l 10°C for 8 hours, and persists after three days of resuspension in water at room temperature.INTRODCJCTIONResearch underway to determine interactions of quartz and other mineral dust surfaces with pulmonary fluids and alveolar macrophages in culture led to the observation that when dusts were autoclaved in aqueous suspension, their cytotoxic effects on macrophages were suppressed, in some cases fully and even after several days incubation with the cells. This finding was in direct contradiction to earlier results from both short term macrophage lysosmal enzyme release assays, as well as longer term cytotoxicity assays from macrophages in culture; in those studies, dusts were steam autoclaved at 121°C with no liquid water but with steam present. 1.2 However detoxification under boiling conditions has been reported in other research. 3 It was decided to use the hemolysis assay to further investigate these findings, because of its sensitivity simplicity and cost.RESCULTS AND DISCCISSIONRespirable quartz dust used in this study was taken from a stock of crystalline silica, Min-U-Sil; obtained from Pennsylvania Sand Glass Corporation, fractionated in air with a particle classifier. The small size fraction retained for use was 80% less than S micrometer particle diameter, with an area equivalent median diameter of 1.24 micrometers as estimated by automated image analysis. The silica was at least 98.S mass percent silica as determined by X-ray energy spectrometric analysis; and the crystalline form was alpha-quartz as determined by X-ray diffraction. It's specific surface area was 3.97 square meters per gram as determined by nitrogen adsorption isotherm methods. I"

Jan 1, 1990

By Richard H. Spencer, Thomas E. Doerfler, Robert L. Lagace, James M. Dobbie, William S. Hawes

This report assesses the expected detectability, on the surface above mines, of electromagnetic signals produced in the frequency band of 630 to 3030 Hz by a rescue transmitter activated by miners trapped underground. This assessment is based on a statistical analysis of experimental signal and noise data taken at a representative sample of coal mine sites well distributed over the United States underground coal fields. Regression analyses are performed to characterize the signal transmission behavior of overburdens as a function of depth and frequency. The predicted signal behavior is then combined with experimentally based distributions of the background noise, and aural detection characteristics of signals in noise, to generate curves of the expected probability of detection for trapped miner signals versus overburden depth and operating frequency. The implications of these results, and associated recommendations, are presented regarding the detectability of trapped miners, sensitivity analyses and confirmatory tests, and operational utilization considerations for the trapped miners and the search and rescue team on the surface.

Jan 7, 1980

By M. C. Malamphy

A general description of the activities and results of bauxite investigation by the Bureau of Mines at its bauxite project in Saline and Pulaski Counties, Ark., has been given in Report of Investigations 4251. The factual data obtained during the project are reported in a series of Reports of Investigations beginning with No. 4251, of which this is the fifteenth. The data are accompanied by maps showing the location of holes drilled and the deposits developed. Each area upon which work was done is reported by halt townships. Each bauxite deposit investigated was assigned a name and a number for ready reference and identification and its location and name are shown on the appropriate half-township map. The description of each half township is followed by a description of each deposit developed in that half township. The 14 halt-township maps and 77 detail maps of the bauxite deposits in this series of reports give the locations and numbers of all the holes drilled on the project except the deep holes drilled to test the geophysical anomalies. The locations of those holes show on figure 13 in volume 1. The Descriptions of the deposits developed are followed by complete detailed logs of the drill holes. Many of the widely spaced exploratory holes did not discover bauxite of minable thickness and grade. The pertinent information obtained from the widely spaced exploratory drill holes has been summarized and tabulated, and a table for each halt township is given with the discussion covering that area.

Jan 1, 1948

By E. H. Denny

This paper discusses accident experience and costs in 150 Colorado coal mines for the 5 years 1929-33; these mines produced 62 percent of Colorado's coal tonnage during this period. This and similar studies by the United states Bureau of Mines in other States (listed in the appendix to this report) make available comparable information on mine-accident costs and bring out clearly the importance of accident reduction from the humanitarian as well as from the economic standpoint. Compensation insurance costs constitute a considerable part of the cost of coal output. The tendency toward greater liberalization of workmen's compensation laws and increased benefits thereunder may mitigate to some extent the seriousness of an accident to a worker and his dependents, but no compensation is paid ultimately, not by an insurance fund but by the mine operator and the general public, which includes the miner. The one really effective method of reducing compensation costs is to reduce the number and severity of accidents.

Jan 1, 1935

By K. P. Wang

SIGNIFICANT general developments took place in the Far East during 1964, with far-reaching repercussions on the mineral and industrial economies of individual countries and the region as a whole. Japan, during this, "the Year of the Open Door," ushered in the era of industrial maturity, greater independence in economic policy, and expanded technical assistance to less developed countries. Symbolic of its dynamic economic growth is the fact that Japan out-produced the Federal Republic of Germany in steel during 1964 to take over a third-ranking world position. Mainland China, recovering from the "Leap Forward" debacle, made significant gains in industrial output. Mainland Chinese trade with Japan was on the upswing, and discussions were held between the Chinese and the Soviets for possibly resuming Soviet aid in industrial and mineral development. Meanwhile, United States aid to Taiwan was being phased out because of progress achieved. Rapprochement between South Korea and Japan was imminent late in 1964, a factor which may well affect South Korean mineral development. The Indonesian-Malaysian confrontation created economic difficulties in both countries. The war in Viet-Nam seriously disrupted industrial activities, particularly in the south.

Jan 1, 1966

By Robert L. Marovelli

The thermal conductivities of six rocks were measured by the transient line source method over the temperature range of -850 to 1,500° F. Close-fitting ceramic probes were used in 0.065-inch-diameter holes drilled through 5-to 6-inch-thick rock specimens. Taconite, granite, quartzite, and basalt were used in the tests. The method yields absolute data and is applicable to both laboratory and in situ measurements.

Jan 1, 1965

By F. W. Smith

This paper is based largely on a study of experimental data obtained by the Bureau of Mines in its comprehensive 25-year survey of the carbonizing properties of American coals. Although the Bureau was interested in and conducted carbonization research-from time to time ever since it was organized in 1910 (1),4/ no systematic studies of the coke-, gas-, and byproduct-making properties of American coals were undertaken until 1927, when the American Gas Association appointed an advisory committee (2) to cooperate with the Bureau in developing equipment and techniques to obtain-data for the accurate assessment of the behavior of coals on carbonization. It was found, in general, that small-scale laboratory tests were unsuitable for the complete evaluation of the coking properties of coal; hence, larger pilot-plant-scale equipment was designed and used (3). It was decided that the scale of the test should be large enough to determine both the yield and quality of the products and yet small enough to maintain adequate control of the process variables (4). These considerations led to development of a carbonizing retort and furnace-of 80 to 200 pounds of coal capacity, suitable for operation at various temperatures up to 1,100° C. (2,0120 F.) and equipment for recovery and measurement of gas and byproducts. This apparatus and the standardized procedure for its operation became known as the Bureau of Mines-American Gas Association (EM-AGA) method or retort (5).

Jan 1, 1955

By S. Benedict Levin

In the spring of 1944, during the emergency In the supply of strategic mica, the Bureau core-drilled six aggregating 913 feet, at the Blister mica Trim. Cheshire County, N.H. These holes indicated a downward extension or the mica shoot which was being mined at that time and developed information essential for economic mining of the deposit.

Jan 1, 1949

By L. Nahai

COAL, salt, lapis lazuli, and construction materials such as lime, gypsum, slate and stone were the only mineral commodities produced in Afghanistan during 1963. Beryl has been produced sporadically. Small deposits of chromite and lead-zinc are known but remained unexploited because there were no domestic markets for the two commodities and transportation costs from Afghanistan to world markets were too high. Oil fields of sufficient magnitude to justify exploitation have not been discovered, but known natural gas reserves are substantial and have potential significance. There is evidence of large high-grade iron ore resources, but these are in an unfavorable location. The contribution of the mineral industry to the economy was small, although precise figures are not available. The reported value of mineral production in 1963 (excluding barite) was 181.6 million afghanis (about US$4 million). Employment in the industry, including cement plants and quarries, was estimated to be no more than about 2,000.

Jan 1, 1964

During the first quarter of 1973 ADL worked closely with PMSRC staff, under an extremely compressed time schedule, on all aspects of the detailed planning, organization and overall coordination and preparation of the lectures and in-mine demonstrations for the Bureau's Technology Transfer Seminar on Mine Communications given in March of 1973 to representatives of the mining industry. Our efforts centered on the detailed organization and preparation of each of the five technical seminar lectures and associated supporting material, and the coordination of tasks assigned to ADL and other seminar participants. Revised and expanded drafts of the seminar papers were prepared from rough draft versions obtained from PMSRC, Collins Radio and ADL staff. Measurements were made to gather key data on the operation and performance of each of the following systems installed in the Bruceton Safety Research Mine; call alert paging, roof bolt paging, section wireless radio, and guided wireless radio systems. These data were analyzed, manufacturer's equipment specifications utilized, and calculations made to provide performance curves and data for each of the above systems. A substantial amount of artwork was conceived and prepared for 35 m slides, system identification posters in the mine, and seminar handouts. This artwork included some forty 8-1/2" x 11" line sketches, graphs, block diagrams, circuit diagrams, coverage maps, and other line drawings; five 30" x 40" block diagram system identification posters suitable for in-mine use; a 20" x 30" detail perspective illustration of a representative coal mine layout; forty viewgraphs; and seventy 35 m slides of the artwork and word charts. Conferences, discussions and review sessions were held with conference participants to help coordinate the various efforts, obtain technical information, and make final plans regarding the lecture presentations, associated visual aids, and the communication system installations to be demonstrated in the Bruceton mine. These meetings included final systems checkouts and dry run presentations and reviews of the lectures and mine demonstrations. This phase of the seminar effort concluded with R. Lagace and R. Spencer of ADL participating in two days of seminar presentations in the lecture hall and in the Bruceton mine.

Jan 1, 1974

By D. Harrington

The record of fatalities from mine explosions during the past 2 fiscal years has been anything but encouraging; more men were killed by explosions (379) than were killed from the ante cause during to' preceding 6 years combined (368). The reason for the large increase in the number of explosion fatalities during the past 2 years as compared with the previous 6 years is not entirely clear. In some instances, there has been laxity in the enforcement of State mining laws; in others, both workers and operating officials is have failed to observe recognized precautionary measures to prevent explosions. In many of the explosions that lave occurred within the asst few years in mechanized mines it has been evident that speed of operation and a demand for maximum tonnage at minimum cost resulted in neglect of ordinary safety measures.

Jan 1, 1942

By G. W. Grove

The wearing of self-contained oxygen breathing apparatus, although relatively safe if proper precautions are taken, is dangerous if defective apparatus -is worn, if men with inadequate training, experience, and physical requirements are used, or if improper procedure is followed. This is proved by the fact that at least 26 men are known to have lost their lives while wearing-oxygen breathing apparatus since its introduction in this country about 35 years ago. Self-contained oxygen breathing apparatus, commonly called "mine rescue apparatus" and sometimes improperly referred to as "oxygen helmets," is the only equipment that can be used for respiratory protection against poisonous mine gases, regardless of concentration or against an atmosphere containing little or no oxygen.3/ Apparatus of this type was introduced in this country in 1907, and since that time it has been widely used in conducting rescue and recovery work after mine fires and explosions and in some other work. All oxygen breathing apparatus used in this country before 1918 was imported from Europe, and although this equipment provided safer, more rapid means of conducting recovery work after mine disasters, there were many mechanical deficiencies in the apparatus which resulted in the death of some of the wearers. This led to the research and experimental work by the Bureau of Mines that resulted in the development and manufacture of more reliable and efficient types of apparatus in this country.

Jan 1, 1944

By C. J. Wilhelm

The disposal of brines produced with crude petroleum and natural gas has been a long-continuing problem to oil and gas operators as well as to farmers and stock-raisers in the vicinity of producing fields. .An impartial appraisal of conditions pertaining to the problem of brine disposal lead to the conclusion that study of the technical considerations, with proper weight given to the economic and social factors, is the most desirable approach to this problem . Brine disposal is a problem of such magnitude 1n certain areas in the State of Kansas that in August 1934 a cooperative agreement w s made between the Kansas State Board of Health and the U. S. Bureau of Mines for a cooperative technical study of methods of brine disposal.

Jan 1, 1935