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By M. R. Geer

Full-seam mining with continuous mining machines in dirty coal beds may increase loss of coal in the washery refuse. At one mine mentioned in this report the loss of salable coal was increased sixfold. Cleaning trials were made on three samples of jig refuse in a dense-medium pilot plant to demonstrate the application of this process to the recovery of coal from waste. These tests demonstrated that coal could be separated from impurity with the same degree of sharpness obtained in treating raw coal by dense medium. However, the recovery efficiency achieved in treating refuse averaged distinctly lower than that possible with raw coal because of the greater proportion of intermediate-density material in the feed and the lower yield of clean coal.

Jan 1, 1955

By C. T. Sheeran

The Bureau of Mines investigated a microprocessor-based real-time control and monitoring system for uranium mining applications. The system is capable of controlling and monitoring up to 768 stations within 3 km of the central processor on a common four-wire cable. It can be used in conjunction with detectors to continuously monitor and display radiation working levels at points throughout the mine. Surface alarms are sounded for critical situations such as rapid radiation buildup, loss of power to monitors or fans, and changes in air door position. Permanent records of all changes are automatically printed out with their time of occurrence. Printouts can also be obtained for shift reports or trend logs. The system can be used to remotely control fan startup and shut-down, and also can alert miners of underground conditions by blowing horns or turning on lights. Battery backup keeps the system operative for up to 4 h in case of a mine power outage. A special software feature permits automatic, time-delayed, sequential restart of fans.

Jan 1, 1984

By L. C. George, J. W. Jensen

A new system for precisely counterbalancing and measuring vapor pressure operates by servomechanical principles . It was developed with the objective of determining the vapor - pressure equations of metal halides . The system is isolated from the vapor - pressure bulb by a diaphragm transducer that signals a pressure regulator to null any pressure difference that is detected . Pressure measurement and readout are continuously performed by a servomanometer , accurate to ±0.003 cm Hg for the range of 0.1 to 200 cm Hg . High response rate and sensitivity are obtained . Methods of use are described , and results for CdC1 and PbC1 , in agreement with data of other investigators , are given as examples .

Jan 1, 1964

By Harold J. Barnett

In January 1948 , the Secretary of the Interior directed that a study be made of energy resources and requirements that would provide a basis for continuing appraisal of the adequacy of the Department's programs in the energy field . That this instruction was timely has been demonstrated by the increasing interest being evidenced by Congress , industry , labor , and the public in the future of the energy segment of our national economy . Several studies of individual energy sectors have appeared . Various legislative proposals have been made in Congress for obtaining more information on this subject . Substantial interest in energy projections is not , of course , a recent innovation . Energy availability and consumption are strategic factors in peacetime prosperity and growth and in our national defense as well . The past generation's literature of earnest public discussion and of legislative consideration of matters involving energy projections is very extensive . This is an exploratory study produced in the Program Staff of the Office of the Secretary of the Interior in the first half of 1949 and revised recently to take account of certain of the preliminary energy data from the 1947 Census of Manufactures and critical comments . It is offered at this time solely as a technical contribution in economic research technique . As the Bureau of Mines has recently undertaken to revise this preliminary study , critical and other comments are invited .

Oct 1, 1950

By A. R. Kirchner

This paper describing the practice at the concentrator of the Minas de Matahambre, S. A., is one of a series being; prepared by the Bureau f Mines on milling methods and costs. The Minas de Matahambre, S. A., concentrator treats the production of the Matahambre mine and has a capacity of 1,300 tons of copper ore per day by selective flotation. During the year 1930 the heads averaged 4.55 per cent copper, the concentrates 29.20 per cent copper and the recovery was 95.96 per cent.

Jan 1, 1931

By Carl Rampacek

The conversion of dilute sulfur dioxide gas into sulfuric acid by autoxidation in mechanical cells of the flotation or gas absorber types was investigated. Bench-scale tests were made with sulfur dioxide-air mixtures to determine the influence of several factors on autoxidation of sulfur dioxide, using iron and manganese salts as catalysts. The laboratory investigation subsequently was extended to pilot plant acid-making tests, using a modified turbomixer gas absorber having a 12-inch-diameter impeller. Sulfur dioxide gas was produced for the tests by roasting pyrite in a fluidized-bed reactor. In the better tests, made with manganese sulfate as the catalyst, the equivalent of 1,000 pounds of anhydrous H2SO4 was produced per 24 hours as a 10-percent solution; power consumption was 0.2 kwhr per pound of equivalent anhydrous acid synthesized. The batch and continuous tests demonstrated the technical feasibility of producing dilute sulfuric acid by autoxidation of sulfur dioxide gas in mechanical cells when converting pyrite roaster or waste smelter gases.

Jan 1, 1963

By Raymond B. Ladoo

Deposits of talc are known in many districts in Canada but at the present time active mining operations are reported only in Ontario . Here three companies are now operating, two of which, George H. Gillespie & Co. , Ltd. , and the Anglo- American Talc Co. , are at Madoc . The operations of the former company are probably the largest and best known in Canada . The writer , in his capacity as an engineer of the U. S. Bureau of Mines , was permitted by this company to make an inspection of its mine and mill in June, 1920 , and study the methods employed . This information was desired for comparison with methods employed in the United States . The following description is based on observation made during this visit , supplemented by data supplied by the company .

Sep 1, 1920

By J. Drew Potts

In this U.S. Bureau of Mines study, four underground respirable dust surveys were conducted to determine factors affecting belt entry dust levels and how using belt air to ventilate work areas affected dust exposures. Belt entry dust levels on the surveyed longwall and continuous miner sections averaged 0.59 and 0.26 mg/m3, respectively. The stageloader-crusher contributed an additional 0.5 to 0.9 mg/m3 of dust to belt air, while the feeder-breaker contributed 0 to 0.2 mg/m3 of dust. A 1,000-ft increase in belt entry length or a 200-to 500-st-per-shift increase in production resulted in roughly a 0.1-mg/m3 increase in dust. Using the belt entry as an intake entry on the continuous miner section appeared to reduce dust levels by 0.1 to 0.3 mg/m3 during cutting. Belt air was not used to ventilate the face on the longwall section.

Jan 1, 2010

By Richard F. Link

A statistical technique, useful to analyze assay and other data characterized by location in three dimensions, is described in this Bureau of Mines report. If present, trends in the data are defined for the purposes of improving ore estimation, predicting ore beyond existing workings, and aiding geological interpretation. The technique is to fit linear and quadratic polynomial equations to the data through the statistical method of regression analysis. The fitted linear equations have the geometric form of hyperplanes; the fitted quadratic equations have the geometric form of ellipsoids or elliptic hyperboloids of one or two sheets. To visualize these three-dimensional forms, contour maps of a series of plane sections through the fitted surfaces are plotted. Both the fitting of the polynomial equations and the plotting of the con-tour maps are done by electronic computer to facilitate calculations and to obtain accurate results. Computer programs are described in appendixes. Methods employed are illustrated by an example analysis) based on data from a part of the Fresnillo mine) Zacatecas, Mexico.

Jan 1, 1966

By C. S. Compton, T. E. Marshall, D. R. Dolinar, R. Grau, L. J. Prosser, A. T. Iannacchione, D. C. Oyler

Unrecognized roof beam failures resulted in 69% of the falls of ground injuries occurring in underground U.S. stone mines from 1990 to 1996. Field investigations at 45 underground stone mines suggest that excessive beam sag or deflection is the principal unstable roof behavior characteristics associated with miner injuries. Laminated roof structures, common in most underground stone mines, allow the immediate roof to separate into distinct beams. The timely determination of roof beam deflection could provide stone miners with advanced knowledge of potentially hazardous roof. Existing methods to assess roof conditions consist of observational and monitoring techniques. Observational techniques include open drillholes, sounding, wedging, and borescopes. Monitoring techniques include scratch tools, extensometers, telltales, Miners Helpers, and Guardian Angels'. Miners have difficulty utilizing these techniques because roof beams are located an average of 8 m (26.5 ft) above the miner's head in environments that are dark, dusty and noisy and these deflections are measured in millimeters of movement. To help mitigate the potential for falls of ground injuries to underground stone miners, the National Institute for Occupational Safety and Health (NIOSH) has developed the Roof Monitoring Safety System (RMSS) to aid in monitoring dangerous levels of roof beam deflection. If enough site-specific information is collected and placed on highly visible maps, individual mining operations could establish general guidelines for responding to specific roof beam deflection occurrences. This would help in implementing a pro-active, comprehensive roof control plan for reducing falls of ground injuries.

By W. L. Dare

This information circular is one of a series, published by the Federal Bureau of Mines, on methods and costs of mining uranium ore on the Colorado Plateau. This report describes the relatively small-scale operations of the Salt Wash miner: The mining method followed, the equipment used, and the production costs. It describes 10 lease-operated mines of Union Carbide: Nuclear Co. that are typical of Salt Wash operations on the plateau. These mines lie within the Uravan mineral belt3/ and arc in the Gateway, Bull Canyon, and Uravan mining districts. (See fig. 1.) Generally the ore bodies occur as irregular, discontinuous layers of ore minerals within sandstone beds in the Salt Wash member of the Jurassic Morrison formation. The ore bodies sometimes occur as rolls, pod associat with carbonaceous trash, or tabular masses. Their size and erratic distribution preclude the use of a prearranged and uniform stoping system. The mining method is simply to follow the ore and leave open scopes behind.

Jan 1, 1959

By R. B. McElwaine

From November 1943 to April 1944, the Bureau of Mines put down 18 churn-drill holes aggregating 2,571 feet of bore in an investigation of the virtually abandoned zinc deposits of the north-central Arkansas district, principally in Marion, Boone, Searcy, and Newton Counties. The ore of this area occurs in flat-lying sedimentaries of the Mississippian and Ordovician ages. Much of the zinc is in the form of carbonate and silicate, although some sulfide has been produced. Preliminary studies resulted in selection for investigation of the Big Hurricane mine in northwest Searcy County, the Spies mine in northeast Newton County, and the Coon Hollow mine in eastern Boone County The comparatively large production of th.ese properties in the past was a factor in the selection. This report describes the work accomplished in the investigation and presents the data obtained.

Jan 1, 1948

By Zsuzsanna Zborovszky

Experimental study directed toward gaining improved understanding of the exact mechanisms causing ignition in the PTB breakflash. Investigation and comparison of tungsten and copper wires as to their ability to cause hot wire ignition. Evaluation of the importance of discharge duration in the ignition process. Study of the parameters influencing the duration of a discharge (minimum discharge voltage, purity of electrode materials, purity and properties of the gaseous atmosphere contaminations, deposits on the electrode surface).

Jan 1, 1976

By Gennaro G. Marino

The Bureau of Mines and the University of Illinois investigated surface characteristics and damage to structures from mine subsidence over a room-and-pillar coal mine in Hegeler, IL. Data on three adjacent subsidence sags and associated structural damage were collected, summarized and evaluated. The subsidence sags developed over a 10-year period and took place above a modified room-and-pillar operation mining the Herrin (No. 6) coal at a depth of 130 to 135 ft. Surface vertical displacements of 3.0 to 3.5 ft resulted from extracting 6.1 to 6.4 ft of coal. Ground movements associated with sag formation severely damaged three houses and a radio station building, broke numerous utility lines, and structurally distorted three radio transmission towers. The radio station was remodeled and the towers repaired, but the three houses were subsequently demolished. Surface waters collecting in the subsidence depressions caused failure of radial ground transmission systems. The following subsidence profile characteristics were determined at the radio station and one of the houses, respectively: profile slopes, 0.02 and 0.07; maximum curvatures, 2.3 x 10-4 ft-1 and 3.0 x 10-4 ft-1; and angular distortions, 6.6 x 10-3 and 62.0 x 10-3. Although the house was more severely damaged than the radio station, both structures are classified as severely to very severely damaged.

Jan 1, 1986

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 E. R. Palowitch

A centrifugal float-and-sink test procedure has been developed by the Bureau of Mines to reduce the time for the gravimetric separation of coals finer than l4-mesh from as long as 24 hours to less than 1 hour. Comparative tests indicated that centrifuging a minus 14-mesh Pittsburgh-bed coal for 20 minutes at 1,500 revolutions per minute produced results that compared favorably with static float-and-sink test results. Standard deviations of the mean recovery and ash content of the float obtained centrifugally ranged from 1.31 and 0.04 percent, respectively, at 1.30 specific gravity to 0.21 and 0.05 percent, respectively, at 1.60 specific gravity. As in static separations, retreatment of the products separated at low specific gravities was required.

Jan 1, 1961

By G. M. Molinda

The U.S. Bureau of Mines conducted an investigation to determine the nature and frequency of coal mine roof failure beneath valleys. A mechanism for this failure and suggestions for controlling this problem are presented. Hazardous roof conditions identified in some mines were positively correlated with mining activities beneath stream valleys. Mine maps with overlays of unstable roof and locations of stream valleys show that 52 pct of the instances of all unstable roof in the surveyed mines occurred directly beneath the bottom-most part of the valley. The survey also showed that broad, flat-bottomed valleys were more likely to be sites of hazardous roof than narrow-bottomed valleys. Evidence of valley stress relief was found beneath several valleys in the form of bedding plane faults and low-angle thrust faults. This type of failure, previously believed to be only a shallow phenomena, was found at mining depths as great as 300 ft. In situ, horizontal stress measurements beneath a valley and the adjacent hillsides, confirmed valley stress relief. Numerical analysis of 13 valleys overlying one mine property showed the effect of the valley excavation on horizontal and vertical stress.

Jan 1, 2010

By Radford Schantz

In 1990, the Bureau of Mines (BOM) conducted a mineral investigation of the mines and prospects in the East Mojave National Scenic Area (EMNSA). San Bernardino County. California During field work. BOM identified 701 mines and prospects in EMNSA for which the geology, mineral resources, and mining history were compiled and summarized. Analytical results for 1.188 rock samples collected are tabulated. Total value of identified resources in EMNSA is $5.0 billion. Twenty-four mines and prospects were deemed profitable under current economic conditions. Development could generate considerable economic benefits to San Bernardino County. Potential economic benefits from mining the deposits were evaluated under the following access restrictions for EMNSA: 1) fun access, 2) HR 3460, and 3) S 11/HR 780. Under the full access scenario, cumulative mine revenues are $3.0 billion, cumulative personal earnings at mines and supporting industries are $0.94 billion, and annual jobs at mines and supporting industries are 2,379. Under HR 3460, mine revenues, personal earnings, and annual jobs are $2.9 billion. $0.88 billion, and 2,165, respectively. Under S 11/HR 780, mine revenues, personal earnings, and annual jobs are $1.0 billion, $0.32 billion, and 936, respectively.

Jan 1, 1990

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

By J. H. Wiggins

The evaporation of crude oil without doubt causes one of the largest single losses to which the oil is subjected after it is taken from the ground. The few days during which crude oil is stored on the lease before being taken by the pipe line, causes an aggregate loss per year from evaporation estimated at 122,100,000 gallons of gasoline in the Mid-Continent field alone. This has a value, at 22 cents per gallon, of $26,880,000 and represents about 3 per cent of the total gasoline produced in the United States from all fields and all sources. The following table shows this in more detail:

May 1, 1920