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By Ralph B. Adair

The Bureau of Mines conducted laboratory and small-scale, continuous tests of weathered mica-pegmatite ores from Randolph County, Ala., to determine the feasibility of recovering commercial-grade mica concentrates by flotation. Two flotation methods were used in continuous tests for recovery of mica. One method utilized acid-cationic flotation for the recovery of coarse mica and alkaline-anionic-cationic flotation for recovering fine mica. This method yielded mica concentrates containing 98.6 percent mica with a recovery of 85.9 percent. The other method was based on the Bureau-developed alkaline-anionic-cationic method, and yielded concentrates containing 97.5 percent mica with a recovery of over 90 percent. In both methods, preconcentration of the ground ore on a Humphreys spiral was employed to reject over half of the feed in a product virtually free of mica.

Jan 1, 1968

By Eugene Frey

The Romur is one of several properties in the Copper Mountain mining district, Fremont County, Wyo., that contain scheelite deposits. The district lies on the southern slope of the Bridger Mountains, 18 miles northeast of Shoshoni and 15 miles from the rail point at Bonneville on the Chicago, Burlington & Quincy Railroad (figs. 1 and 2). The tungsten deposits occur in a zone of pre-Cambrian schists and gneisses that have been cut by numerous basic dikes and granite pegmatite dikes. Scheelite occurs in lenses and pods that lie parallel to the foliation and bedding in the metamorphic rocks. The more important deposits are found in a lime-silicate rock consisting primarily of zoisite but with small quantities of quartz and carbonate. Scheelite was found in December 1941, and the area was mapped by the U. S. Geological Survey early in 1942. In November 1942 the Bureau of Mines commenced work on the Stardust-Comet group for the purpose of developing reserves for war requirements. The initial work consisted of driving an alit in the ore zone a distance of 109 feet. This zone was sampled during the progress of the work, and subsequently surface and underground exposures on adjoining properties also were sampled (figs: 5, 6, 7, and 8). One hundred twenty-four samples were obtained. Sample and assay data are shown in tables 2, 3, and 4.

Jan 1, 1950

By R. Havens, B. K. Shilber

"INTRODUCTION In the course of the investigation of the occurrence of manganese deposits in the western United States, ore-dressing tests were made on three samples procured by Bureau of Mines engineers from two properties in southeastern Juah County, Utah, each of which is known by the name Black Jack. To avoid confusion, the tests will be described under the names of the owners Kendall-Duvall and the Empire Mines.None of the samples were amenable to ore dressing for the production of high-grade manganese sinter.Ores from the Kendall-Duvall deposit represent an interesting metallurgical phase of low-grade manganese occurrence, as the occurrence of manganese as silicate (braunite) automatically governs the extent to which they can be beneficiated by mechanical methods of treatment. As less than 50 percent of the total manganese was recoverable by complex methods of treatment in a 40- percent-manganese sinter, attempts were made to recover most of the manganese in a low-calcite, intermediate-grade product that might be acceptable for subsequent metallurgical treatment. By selective flotation of calcite and manganese, up to 68 percent recoveries were obtained in plus 20-percent manganese products..No encouragement can be given for successful ore-dressing of Empire ores as represented by samples received for testing, as no products were obtained that would meet minimum marketing specifications. Empire ore contained only 1 percent lime and might be high enough in grade (19 percent manganese) for direct hydrometallurgical treatment."

Nov 1, 1947

By M. J. Ferrante

Enthalpy and entropy increments above 298.15° K were determined for cop-per sulfate between 298° and 1,000° K and for copper oxysulfate between 2980 and 1,146° K by the method of copper-block drop calorimetry. Enthalpies, entropies, and heat capacities are tabulated for both compounds. In addition, free-energy functions are tabulated for the sulfate. Equations representing the enthalpies are given for each compound.

Jan 1, 1972

By F. P. Haver

Primary lead is produced in the United States by the pyrometallurgical smelting of lead sulfide (galena, PbS) concentrates, which poses sulfur dioxide and lead air pollution control problems. The Federal Bureau of Mines has investigated an alternative hydrometallurgy procedure that does not generate gaseous sulfur oxides and diminishes the potential for the escape of lead into the atmosphere. The procedure involves leaching galena flotation concentrates with ferric chloride (FeC13) solution to obtain lead chloride (PbC12) and elemental sulfur as expressed by the following chemical reaction: PbS + 2FeC13 ? PbC12 + 2FeCl2 + S°. At 100° C, over 99 pct of the PbS in the concentrate is converted to PbCl2 in less than 15 min. The leach solution, composed of brine (NaCl) containing slightly more than the theoretical required amount of FeC13, dissolves the PbC12 as it is formed, leaving a residue of elemental sulfur plus gangue. High-purity PbC12 (>99.9 pct) crystallizes from the leach filtrate on cooling and is electrolyzed in a low-temperature, fused-salt cell to obtain corroding-grade metal (>99.94 pct Pb). Spent leach solution (FeC12) is regenerated for further use by reaction with the chlorine obtained in the electrolysis of lead chloride. Other values, such as Ag, Cu, Zn, and S°, are recovered by additional treatment of either the leach solution or leach residue.

Jan 1, 1976

This report describes a U.S. Bureau of Mines investigation into the removal of gate road chain pillars in conjunction with longwall retreat mining. The research objective was to determine, through evaluations of the loads imposed on the gate road pillars and supplemental support elements in the entries, how the pillars, supplemental support, and entries were affected by the longwall abutment pressure. To achieve this goal, vibrating wire stressmeters and hydraulic flat jack pressure cells were installed in the support elements to monitor stress change caused by abutment pressure as a function of longwall face advance. The findings documented in this report are the result of information collected from instrumentation and observation at the mine. Pillar and support loading measurements and stability observations revealed that the roof and the support elements remained stable during panel retreat, while the face progressed at a normal rate of advance. The ability to safely and efficiently mine chain pillars during panel retreat increases resource recovery and can provide several other benefits described in this report.

Jan 1, 2010

By E. G. King

Cerium and thorium sulfides have found use as crucible materials for melting certain radioactive metals. However, thermodynamic treatment of these sulfides has been hampered by lack of experimentally derived entropy values. This Bureau of Mines report describes heat-capacity measurements between 51° and 298° K, and entropy evaluations at 298.15° K, for cerium monosulfide (CeS), cerium sesquisulfide (Ce2S3), and thorium disulfide (THS2). The entropy values, with Literature results for the heats of formation, are used to obtain free energies of formation at 298.15°K. MATERIALS The samples used in this work were supplied by Prof, Leo Brewer of the Department of Chemistry, University of California. The methods of preparation and some of the physical and chemical properties of these sulfides were given by Eastman and coworkers.3 4/ Chemical analyses, conducted in our laboratory, gave the following results:

Jan 1, 1959

By J. M. Stuve

Low-temperature adiabatic heat-capacity determinations were made by the Bureau of Mines in the temperature range from 5 to 300 K for the two crystalline modifications of zinc sulfide, sphalerite (ß) and wurtzite (a). The entropy at 298.15 K of sphalerite was evaluated as l4.02±0.04 cal/deg mole and wurtzite, l4.06±0.04 cal/deg mole.

Jan 1, 1974

By D. E. Fogelson

In a factorial experiment, blasting caps were detonated in three sizes of shotholes in mortar with three types of stemming--dry sand, wet sand, and hydrostone. Free-surface displacement pulses were recorded with a capacitive-displacement gage at a distance of 15 inches. The effects of decoupling and the type of stemming on the amplitude and the duration of the displacement pulse were determined. Both the amplitude and the duration of the displacement pulse were significantly decreased by increasing the decoupling, but they were little affected by the type of stemming.

Jan 1, 1965

By Alfred E. Schwaneke

A versatile torsion creep tester was instrumented with electromechanical and servomechanical components to operate automatically and unattended, producing digital printed outputs. The apparatus uses an electrical system for applying torsional stresses, and a unique angular transducer as a null detector operating a servocontrolled strain measuring system with the digital readout. The tester is designed to measure the creep in single-crystal or polycrystalline zinc, zinc alloys, magnesium, magnesium alloys, or other metals and alloys. Applied stresses may be varied from zero up to 2,000 psi in the outermost fibers of a 1/8-inch-diameter, 4-inch-long specimen. Strain readings to 0.001 degree, equivalent to a strain of 2.73 X 10-7, may be made automatically from one every 5 seconds to one per month. The apparatus has provisions for programed temperature control and special atmospheres or vacuum operation. A discussion of applications of the system to other mechanical testing apparatus is included.

Jan 1, 1970

By G. W. Groove, E. E. Quenon

"INTRODUCTION Uncontrolled mine fires originating in exposed coal beds through the acts of careless or irresponsible persons present a serious threat to buildings, surface property, and the life and health of persons near the affected area. Apparently, the seriousness of such fires is not fully understood by property owners or those residing in the vicinity, as practically nothing has been done to alleviate conditions. In many instances, such fires have been active for several years before property owners or civic organizations have shown any interest toward having the fire extinguished. Recommendations by Bureau of Mines investigators in the interest of controlling such fires are seldom followed, as the Bureau cannot provide the funds for doing the work.Several uncontrolled and widespread fires are burning along the outcrop of coal beds and in underground abandoned mine workings within a 25-mile radius of Pittsburgh, Allegheny County, Pa. If these fires are permitted to continue to burn unabated, the ultimate results may be far-reaching. Most of the outcrop fires investigated are believed to have originated from burning rubbish, forest fires, or workmen, hunters, or others building fires near the outcrop of ,the coal beds. In other instances, smoke and fumes have suddenly appeared in the vicinity of abandoned coal-mine openings, indicating that a fire has either burned its way along the outcrop of the coal bed or has traveled through the abandoned mine from another location. An underground or outcrop coal-mine fire will be very likely to continue to burn as long as an oxygen supply is present.; and, so far as is known, such fires do not stop burning automatically until virtually all combustible matter is consumed."

Feb 1, 1948

By Martin H. Stanczyk

Freezing to dewater typical Florida phosphate rock slime as demonstrated in laboratory tests appeared to have potential commercial use because of indicated moderate energy requirements, good compaction of dewatered solids, and effective recovery of usable water. After freezing, thawing, decanting, and filtering, batch freezing of gallon-size 13.7 percent solids slime samples yielded 42 percent solids products. Cationic amine, used as a process additive, yielded 46.8 percent solids product with significant filter area reduction. Semicontinuous 8 stage freezing tests also produced thickened slimes. Cooling and freezing 13.7 percent solids slime from 30° to minus 10° C required removal of 183 Btu per pound of slime; Carnot cycle calculation indicated that the theoretical minimum energy to transfer this heat was 27.8 Btu per pound. To produce 1 ton of 44 percent solids slime from 13.7 percent sol-ids slime, the calculated theoretical energy required for cooling and freezing was 52.3 kilowatt-hours. During the research heat capacity and heat of fusion data were determined for the slime at various percent solids.

Jan 1, 1971

By Albert E. Schreck

THIS CHAPTER concerns such minor nonmetals as greensand, meerschaum, mineral wool, staurolite, and wollastonite. GREENSAND Output of greensand (glauconite) was slightly higher than in 1958. Open pits of The Kaylorite Corp. (Calvert County, Md.), National Soil Conservation, Inc. (Burlington County, N.J.), and Inversand Co." (Gloucester County, N.J.) accounted for the entire production. Soil conditioning used about 72 percent of the greensand sold. The remainder was used as a water-softening agent. Prices for greensand, f.o.b. mine, ranged from $13 to $70 per short ton.

Jan 1, 1960

By Kenneth L. Cashdollar

This paper is an overview of and introduction to the subject of dust explosions. The purpose is to provide information on the explosibility and ignitability properties of dust clouds that can be used to improve safety in industries that generate, process, use, or transport combustible dusts. The requirements for a dust explosion are: a combustible dust, dispersed in air, a concentration above the flammable limit, the presence of a sufficiently energetic ignition source, and some confinement. An explosion of a fuel in air involves the rapid oxidation of combustible material, leading to a rapid increase in temperature and pressure. The violence of an explosion is related to the rate of energy release due to chemical reactions relative to the degree of confinement and heat losses. The combustion properties of a dust depend on its chemical and physical characteristics, especially its particle size distribution. In this paper, the explosion characteristics of combustible dusts will be compared and contrasted with those of flammable gases using methane as an example. These characteristics include minimum explosible concentration, maximum explosion pressure, maximum rate of pressure rise, limiting oxygen concentration, ignition temperature, and amount of inert dust necessary to prevent flame propagation. The parameters considered include the effects of dust volatility, dust particle size, turbulence, initial pressure, initial temperature, and oxygen concentration. Both carbonaceous and metal dusts will be used as examples. The goal of this research is to better understand the fundamental aspects of dust explosions.

By E. C. Lane

Although motor gasoline marketed in the United States in January of this year was, on the average, slightly more volatile than that sold in January 1925, the improvement in quality is too small to be of importance. In other words, there is no evidence that any radical change in the quality of gasoline is being made at the present time. During the past six years the Bureau of Mines has made semi-annual surveys of the gasoline marketed in the United States, the survey just completed being the thirteenth in the series. The cities in which samples have been collected have been chosen as representative of the more important marketing territories as it is obviously impracticable to obtain a sample of every gasoline sold in the entire country.

Jan 1, 1926

By L. E. Schultze

As part of the Bureau of Mines research program on recovering alumina from domestic resources, methods for extracting iron from aluminum sulfate solutions (obtained by leaching kaolinitic clay with dilute sulfuric ,acid) were investigated. In countercurrent extraction experiments at a l-gal/hr flow rate of aluminum sulfate leach liquor, the iron concentration 'was decreased from 1.4 g/l to 0.01 g/l after four stages of using a primary amine extractant. The iron-loaded amine solution was regenerated in five stages using 3[N] sulfuric acid or in four stages using 6[N] sulfuric acid. The aluminum sulfate solution obtained was suitable for the preparation of alumina meeting cell-grade standards of less than 0.01 pct iron.

Jan 1, 1979

By Siavoljub D. Maksimovic

The Bureau of Mines, through a cooperative agreement with Duquesne Light Co. of Pennsylvania, field tested a method of using pneumatic stowing of crushed limestone to construct seals in long-abandoned mine openings that were part of an active mine closed shortly before sealing. A total of 13 openings at 11 sites were backfilled. In pneumatic stowing, material is conveyed through a pipeline and into the mine opening under low air pressure. The stowing equipment consists of a power sup-ply, a blower, a feeder to inject material into the pipeline, and a nozzle for directing the placement. Material is ejected from the nozzle at high velocity, creating a high-compaction fill upon impact. The fill material used was well-graded limestone aggregate up to 1-1/2 inches in diameter, with sufficient fines. This fill was modified at five locations by the addition of portland cement, expansive cement, and/or bentonite. The pneumatic stowing method is safer and faster than conventional methods, is cost competitive, and eliminates or reduces the exposure of workers to possible hazards since the nozzle can be kept outside the mine opening. The equipment is mobile, but some modifications in the technique would improve performance. The technique was used at remote locations where other methods could not be used without disturbing the environment.

Jan 1, 1982

By Manuel Gomez

Published experimental coke data from a pilot plant slot-type oven were examined by statistical regression analysis. Quantitative relationships were found to exist between the coking rate, bulk density, and fine grinding of the coal, sole-oven expansion, volatile matter, moisture, ash, and carbon con-tent of the coal and coke parameters indicative of size and strength. Regression equations developed from coke data were shown to yield computed values that were in good agreement with experimental results for 11 coke properties. Prediction equations developed were evaluated with an independent set of data. Present results indicate that the variables cited undergo much interaction and the sum of these interactions determines coke size and strength.

Jan 1, 1967

By Mark I. Copeland

Bureau of Mines researchers investigated the combined effect of copper and tin additions on the mechanical properties of hot-rolled steels. Wrought steels containing 0.2 wt-pct C and up to 0.2 and 1.0 wt-pct Sn and Cu, respectively, were made and evaluated by conducting tensile and impact tests and electron-beam microprobe and electron microscopy examination. Tin additions did not significantly affect the tensile properties of steel at different copper contents in the hot-rolled condition. Tin lowered the copper content at which strengthening by copper precipitation normally starts, 0.8 wt-pct, and decreased the strength of steel aged at 1,022° F (550° C). The most adverse effect of tin was lowering the notch toughness of steels at most copper contents.

Jan 1, 1976

By Richard C. Ballance

Fly ash from four sources and in certain proportions was shown to assist chemical coagulation of turbid water and settling of chemically induced floc. Fly ash reduced the time required to form the first visible floc, promoted more uniform flocs about 2 mm in diameter, and increased the mean settling rate of floc particles. Also, the addition of fly ash produced denser sludges than those obtained with alum alone. Final turbidities were independent of fly ash particle size and carbon content. Optimum proportions of fly ash additive are given.

Jan 1, 1966