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By S. J. Hussey

The Bureau of Mines investigated the applicability of carbon-in-pulp pro-cess for recovering silver from low-grade ores. The reasons for the research were (1) to illustrate a practical procedure for the process design of carbon-in-pulp adsorption circuits using leach slurries and simple equipment; and (2) to illustrate how equations of adsorption theory relating rate data and equilibrium adsorption curves can be helpful in process design. Carbon-in-pulp silver adsorption tests were made on Banner, Idaho; mine-run ore samples with silver contents ranging from 2.0 to 8.5 oz/ton and variations in cyanide leach extraction from 48 to 93 pet. The lower recoveries were attributed to the presence of complex silver sulfide minerals. Carbon-in-pulp batch adsorption tests provided rate data for the estimation of a silver equilibrium adsorption curve. Process design procedures in which the rate data were related to an equilibrium adsorption curvey by equations of adsorption theory were used to plan a four-stage pilot plant cascade. The pilot plant was successfully operated for 45 hr of countercurrent flow, producing a carbon product containing a mean silver loading of 571 oz/ton from a pregnant solution of 1.7 oz/ton of silver. Virtually all of the dissolved silver was recovered on the carbon.

Jan 1, 1978

By S. J. Page, J. A. Organiscak

Dust surveys were conducted around small truck-mounted rock drills operating at surface coal mines to assess their airborne respirable dust generation and in-service dust control methods. Of four out of seven drills sampled, respirable dust concentrations measured around the drill deck ranged from 8.68 to 95.15 mg/m with3concentrations ranging from 1.37 to 2.69 mg/m at distances 12.2 to 30.5 m downwind of these drills. The other3drills had noticeably lower respirable dust concentrations measured around the drill deck at or below 1.30 mg/m.3Rotoclone-type dry dust collectors were commonly used with dust being emitted from around the drill deck shroud, collector exhaust, and collector fines dumping. Wind speed and direction was also a factor in the dust concentrations measured on the bench. Dust control modifications were made to three rock drills to reduce their airborne dust emissions. Dust controls tested included water injection into the Rotoclone exhaust, Rotoclone exhaust extension, improved sealing of drilling deck shroud, shrouding the Rotoclone hopper dump process, and wet drilling. These control techniques showed noticeable improvement in dust concentrations measured around the drills. Finally, repositioning the drill operator showed that operator dust exposure can be improved by avoiding the dust cloud around the drill.

Jan 1, 1995

By W. E. Lamont

The Federal Bureau of Mines conducted research to develop methods of removing phosphorus from the earthy, calcareous hematite ores of the Birmingham, Ala., iron district while simultaneously improving the grade and recovery of the iron values prior to furnacing. An attempt was also made to identify the phosphorus minerals present in the ores. The ores contained about 36 percent iron, 12 to 16 percent CaO, 15 to 20 percent hydrochloric acid insolubles, and 0.30 to 0.36 percent phosphorus. Fractions containing 5 to 15 percent phosphorus were isolated from the ores. Collophanite, Ca3P2O3?nH2O, a member of the apatite group, was the only phosphate mineral identified. Beneficiation methods using flotation and reduction roasting with magnetic separation yielded good grade iron concentrates, but were not as effective for reducing the phosphorus content of concentrates. Reduction roasting followed by fine grinding, magnetic separation, and acid leaching gave iron concentrates containing 62.5 percent iron and 0.04 percent phosphorus with an iron recovery of 82.9 percent and a phosphorus rejection of 93.7 percent. Reoxidation of reduced magnetic concentrates followed by acid treatment gave iron concentrates containing 58.1 percent iron and 0.02 percent phosphorus with 89.6 percent recovery of the iron and 96.5 percent rejection of the phosphorus.

Jan 1, 1973

By H. Robert Ensminger

The Belizean economy had an estimated annual growth of about 3.4% over that of 1986. Economic growth during the 2 previous years was slower and was characterized by a negative trade balance. The gross domestic product (GDP) was an estimated $200 millioni2 in current dollars. Limited natural resources and scarce finances continued to make the Government's task a difficult one. Belize and China signed an economic cooperation agreement in April under which the Chinese Government is to provide technical assistance, a cash grant of $60.000, and a long-term, interest-free loan of approximately $1.5 million. In May, it was reported that gold was discovered in a remote area of the Maya Mountains in western Belize. An estimated unassayed value of $400 million has been placed on the deposit by one of its discoverers. However, the government in Belmopan has played down the discovery. Two U.S. oil companies. Seahawk Oil International of California and Alston Oil Co. of Texas, were granted licenses to explore for oil. Seahawk Oil will explore a large area of the Orange and Corozal Districts, while Alston Oil will prospect a 90,000-acre area of the western Cayo District. Another U.S. oil company, Pecten Oil Co., recently completed seismic studies off-shore of Belize City. Pecten Oil has made plans to start drilling in 1988.

Jan 1, 1989

To improve the reliability of the Bureau developed bore-hole gage now widely used to determine the absolute state of stress in rock. Approach Use the knowledge gained by extensive field tests to design a more rugged and reliable Instrument using lighter and stronger materials. How It Works The original gage consisted of a stainless steel cylinder 1-3/8 Inches In diameter and 10-1/2 inches long. The new gage is made from titanium. This lighter material reduces the weight of the gage by 43 percent, which enhances the gage placement and depth of overcoring in vertical up? holes. For added strength, the titanium case and placement end are now threaded to the gage body instead of using screw fasteners. Three pairs of strain gaged transducers are positioned to measure the diametral deformation of a 1-1/2 diameter borehole at 60-degree intervals around the Inner surface of the borehole. Each transducer consists of a beryllium copper cantilever with a strain gage cemented on each side. These transducers are secured Into the gage body by a tapered shank for minimal creep. The transducers opposite each other are wired together to form a 4-arm external bridge circuit. A pair of transducers is referred to as a component. Any deformation of the borehole, which occurs during overcoring, is detected by pistons which translate the motion to the components. Each

Jan 1, 1982

By Maria I. De Rosa, Charles D. Litton

The National Institute for Occupational Safety and Health (NIOSH/PRL) con­ducted a series of large-scale experiments to evaluate the effectiveness and safety of various concentrations of an inert gas mixture (CO2,8%;N2, 50%; Ar, 42%) for preventing and sup­pressing cab ?res. Comparison of concentrations effectiveness in yielding safe times has led to the choice of an optimum gas mixture concentration, discharged in the cab through a muf?ed nozzle system, for the development of a dual cab ?re inerting system. Of note is that safety training programs, including the synchronization of performed tasks, need to accompany this technology to enhance operator’s ef?ciency and safety during ?re emergencies within the safe times yielded by the cab ?re inerting system. Cab ?res are caused by the ignition of ?ammable vapors and mists (ball of ?re) that penetrate the cab during prolonged hydraulic ?uid and fuel ?res, and electrical malfunctions involving other cab combustible materials. Often, these ?res force the operator to exit the cab under hazardous conditions during a time needed to perform emergency tasks. Hence, it is important to provide the operator, not only with an engine fire suppression system (dry chemical powder), but also with a cab ?re protection system, effective both in preventing the ignition of ?ammable vapors in the cab, and suppressing cab material ?res.

By Travis Q. Lyday

Ecuador's economy continued to slow in 1982 due, in part, to declining foreign demand for oil, depressed world oil prices, and high international interest rates. Real growth of the gross domestic product (GDP) was estimated to be in the 2% to 3% range, down from the revised 4.3% recorded in 1981 and the 4.5% anticipated officially. In current prices, the GDP in 1982 was estimated at $12.1 billion.2 Inflation abated slightly from that of 1981 to an estimated 13.9% annual rate. The sucre was devalued in May by 32%, the first time in more than a decade, as a result of the pervasive flow of capital abroad. Ecuador's production of petroleum increased an estimated 1.9% in 1982 compared with that of 1981. The consortium of Corporación Estatal Petrolera Ecuatoriana (CEPE), the state oil company holding a 62.5% interest, and Texaco Inc. (37.5%) produced an estimated 98%, or approximately 211,000 barrels per day, of the total from the northern part of El Oriente, the eastern jungle region, where a Texaco-Gulf Oil Corp. partnership discovered oil in 1967. Gulf subsequently sold out to CEPE in 1977 for $117 million, Remaining production was from the Santa Elena Peninsula Fields on the Pacific coast where production has been steadily declining for several years.

Jan 1, 1984

By J. A. Organiscak

The U.S. Bureau of Mines recently conducted an investigation into the amount of respirable and quartz dust generated while mining rock in coal mines by continuous and conventional methods. The study was made at two mines that use both continuous and conventional mining. Results show that continuous mining produces 1.2 to 3 times more respirable dust, and 6.7 to nearly 15 times more quartz dust than conventional mining.

Jan 1, 1989

In 2001, a total of 2,144 coal mining operations reported employment to the Mine Safety and Health Administration (MSHA). Coal mines comprised 14.7% of all mining operations. • Bituminous mines comprised 92.0% (n=1,972) and anthracite mines 8.0% (n=172) of coal mining operations. • More than 71% of coal mines were located in three states: Kentucky (29.5%), West Virginia (21.3%), and Pennsylvania (20.6%).

Apr 1, 2003

By Robert F. Chaiken, Thomas H. Dubaniewicz, Gregory M. Green, Kenneth L. Cashdollar

Optical technologies have progressed rapidly in the past 15 years. One application of laser technology in underground coal mines currently under evaluation is the remote measurement of explosive methane gas. Federal regulations require that atmospheric monitoring systems used in gassy underground mines where permissible equipment is required shall be intrinsically safe. Mine Safety and Health Administration criteria for the evaluation and testing of intrinsically safe apparatus and associated apparatus contain no specific guidance for optoelectronic components such as diode lasers. The National Institute for Occupational Safety and Health is conducting a study to help provide a scientific basis for developing appropriate safety guidelines for optical equipment in under- ground coal mines. Results of experiments involving ignition of methane-air mixtures by collections of small heated particles of Pittsburgh seam coal and black iron oxide are reported. The inert but more strongly absorbing iron oxide targets consistently ignited methane-air mixtures at lower powers than the coal targets. Minimum observed igniting powers for laser energy delivered by 200, 400 and 800 pm core fiber optic cables and directed onto iron oxide targets in methane-air atmospheres were 0.6, 1.1, and 2.2 W, respectively. Comparisons with the results of other researchers are made. A thermal layer theoretical approach to describing the process is included as an appendix.

By Mark S. Stagg, Virgil J. Stachura, John W. Kopp, David E. Siskind

The Bureau of Mines studied airblast from surface mining to assess its damage and annoyance potential, and to determine safe levels and appropriate measurement techniques. Research results obtained from direct measurements of airblast-produced structure responses, damage, and analysis of instrument characteristics were combined with studies of sonic booms and human response to transient overpressures. Safe levels of airblast were found to be 134 dBL (0.1 Hz), 133 dBL (2 Hz), 129 dBL (6 Hz), and 105 dB C-slow. These four air- blast levels and measurement methods are equivalent in terms of structure response, and any one could be used as a safe-level criterion. Of the four methods, only the 0.1-Hz high-pass linear method accurately measures the total airblast energy present; however, the other three were found to adequately quantify the structure response and also represent techniques that are readily available to industry. Where a single airblast measuring system must be used, the 2-Hz linear peak response is the best overall compromise. The human response and annoyance problem from airblast is probably caused primarily by wall rattling and the resulting secondary noises. Although these will not entirely be precluded by the recommended levels, they are low enough to pre- clude damage to residential structures and any possible human injury over the long term.

Jan 1, 1965

By Lloyd A. Morley, Robert Stefanko

In addition to explosion-proof enclosures, the IEC has published recommendations: 1. 79-2 Pressurized Enclosures, 2. 79-3 Intrinsic Safety, 3. 79-5 Sand-Filled Apparatus, 4. 79-6 Oil-Immersed Apparatus, and 5. 79-7 Increased Safety. All these are valid methods of electrical hazard reduction and find wide use in industries other than mining. Magison (52) discusses in detail each technique and, therefore, such an examination will not be repeated. Two other systems, lamina and labyrinth, are but variations of common explosion-proof enclosures and, therefore, will not be cov¬ered. (34,35,46,53,54,61) By examining other national authorities' opinion, the following will investigate each system's applicability to coal mining. Intrinsic safety applies to any system which is incapable of re¬leasing sufficient energy to be an electrical hazard. (49) Not one foreign country contacted disagreed with the concept, and they find these systems totally acceptable. Only South Africa does not accept oil-immersed apparatus, but no reasons were given. (62) Healy (27) stated that Queenlands, Austrailia would accept all techniques, yet some were still to be employed. Japan specifications allow for all but sand filled. (42,43) Increased safety or Protection Type "e" is an approach in hazard reduction in which special design considerations are applied to ensure an extremely low probability of electrical or mechanical breakdown

Jan 1, 1974

To recover metals as sulfide concentrates from contaminated waste streams using hydrogen sulfide (H2S) generated by the bacterial digestion of waste organic materials. Approach The goal of this research is to develop a treatment method for metal mine effluents that will rival the cost and convenience of conventional lime treatment, and that will provide better effluent water quality, result in less expensive sludge disposal, and allow for the selective recovery of metals.

Jan 1, 1993

By J. P. Morris

This paper describes a gas-transport method for measuring vapor pressures of liquid metals. Vapor pressures of iron and nickel were determined at temperatures between 1,540° and 1,620° C. The results can be represented by the following equations: log Pmm (iron) -19,460/T + 9.147, log Pmm (nickel) -2l,030/T + 9.689. The study was undertaken as part of a program to determine thermodynamic activities in liquid iron alloys.

Jan 1, 1957

In 2006, a total of 741 nonmetal mining operations reported employment to the Mine Safety and Health Administration (MSHA).1 These mines (e.g., potash, gypsum, salt) comprised 5.0% of all operations. ? Mines producing common clay comprised 25.2% (n=187) of all nonmetal mining operations. ? Nonmetal mining operations were located in all states and territories except Alaska, Delaware, Hawaii, Maine, New Hampshire, Rhode Island, Puerto Rico, and the Virgin Islands.

Jan 1, 2008

By John G. Kovac

A computer simulation has been developed by the US. Bureau of Mines to estimate the chances of a miner making a successful escape while wearing a self-contained self-rescuer (SCSR). The model takes into account (1) training in the use of SCSR's, (2) apparatus integrity, and (3) oxygen cost of a mine escape. This report examines survival odds for a prototypical escape, and illustrates how these odds change when SCSR training is improved.

Jan 1, 2009

By T. J. Ballard

"The Hog Creek mine, in lot 92 of the 17th district in Towns County, Georgia, was examined in 1890 by F. P. King, who reported the existence there of a 4-foot vein of corundum. The mine is about 2 miles west of Hiawassee, on the southern side of Ramey Mountain. Ed Burch, of Hog Creek, holds the surface rights, and the mineral rights appear to be vested in the heirs of William R. McConnell, who formerly owned and prospected the property.Examination by the Bureau of Mines showed the workings to be caved, but it was thought advisable to open the mine and uncover the reported vein. The Bureau's work consisted, of trenching and cleaning out the pits and shaft.William R. McConnell, the former owner, prospected the property in about 1890. At some tine during that operation, the prospect was visited by Francis P. Kings a geologist with the Georgia Geological Survey.3/King reported that a 4-foot vein of corundum was exposed g feet below the surface in the main cut and was opened for 20 feet along the strike. He also reported that the so-called ""Georgia rubies"" were taken from this mine.The main mine is about 2,000 feet- north of Hoc Creek on a timbered southern slope of Ramey Mountain. It lies at an altitude of about 2,100 feet, approximately 100 feet above the high-water level of the Catuga reservoir, which floods Hog Creek to a quarter of a mile above its confluence with the Hiawassee River. The nearest water is a small branch about 1,000 feet to the west.Chlorite schist is the principal host rock. It has been intruded by irregular masses of a very herd periodtite rock possibly troctolite. The schist near the surface is extremely weathered, presenting white and red laminations parallel to the schistosity. At a depth of 40 feet in the cross-cut it appears as a fine-grained green-chlorite schist. The schist strikes about N. 350 E. and dips 800 to the southeast.No corundum vein was found, and if any existed it must have been mined out after King's visit. In the pit, about 15 feet west of the shaft, approximately 150 pounds of zoisite and an occasiona1 small crystal of corundum were found imbedded in schist about 18 feet below the surface, near hard, dense troctolite."

Mar 1, 1946

By N. H. Snyder

Coal analyses help to describe the character of coal as it lies in the ground of as it may he delivered to the user Analyses of samples of coal collected from the face of the bed in mines are plentiful, but available analyses of delivered coal are relatively few, and there is a distinct difference between "mine samples" and "delivered samples.” Mine samples are collected actor drag to a standard method. 13 The sampler cuts a channel. 2 by 6 or 3 by 4 inches from roof to, floor in the face of the bed, and excludes from the sample all partings more than 3/8 inch thick, and any lenses or concretions of sulphur or other impurities more than 2 inches in maximum diameter and 2 inch thick. Analyses of mine samples form a permanent and scientific record of the coal bed at the point sampled, they ale important in determining the character of the coal in any given mine or district These analyses, when the samples are taken by a standard method, are valuable to the operator When compared with analyses of delivered coal they show him whether his mine is being worked efficiently or whether the coal is being properly prepared, which involves the ques¬tion ii Nether he has suitable mechanical appliances for separating the impurities sties. In the purchase of coal, mine samples may serve as a sufficient guide for the experienced buyer who has knowledge of the impurities in the bed, and the degree to which these are eliminated in mining and preparing the coal To the average purchaser, however, unacquainted with these details, dependence on mine samples may be misleading The quality of coal indicated by the base samples call rarely, if ever, be attained in the delivered coal Certain impurities that are eliminated from the formally prepared mine sample may not be eliminated by the miner Some of the roof and floor may also be included if these are soft or flaky When coal prices are high and competition is lessened it is easy for the miner and the management to lower the standards of preparation, and a return to rigid stand¬ards is always difficult. In sampling delivered coal the Bureau of Mines follows a definite procedure. 14 A sample of not leas than 1000 pounds is systematically

Jan 1, 1928

By John M. Gomes

In the repetitive electrowinning of tungsten from scheelite, the calcium impurity buildup in the molten electrolyte results in decreased metal purity, metal recovery, and current efficiency. Periodic addition of B2O3, which reacts with the lime liberated from the scheelite, more than tripled the life of the electrolyte in winning 99.9-percent-pure tungsten and also reduced the number of units of electrolyte required per unit of tungsten recovered from six to four.

Jan 1, 1966

By J. M. Stuve

Low-temperature heat capacities of chiolite (Na5Al3F14) were determined by adiabatic calorimetry in the temperature range 5.8 to 300 K. The derived standard entropy (S°, 298.15) was 115.6 ± 0.2 cal/deg-mole. High temperature enthalpies relative to 298.15 K were obtained by precision drop calorimetry up to 1,000 K. Tables of experimental data and related thermodynamic functions are given for the temperature range of experimental observations.

Jan 1, 1980