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By Frederick Felder

The paper point out the Angostura deposit is located in Colombia. The Angostura deposit, located within the Eastern Cordillera of Colombia is hosted by Triassic-Jurassic quartz monzonite and quartz diorite porphyries emplaced into Precambrian gneisses of the Bucaramanga Group. Silicification, pyritization, sericitization, alunite and pyrophyllite and other alteration and indicator minerals suggest a high sulfidation origin for the strong hydrothermal alteration. Major faults and shear zones occur in the area with NE, E-NE, E-W, WNW, NW and N-S directions. Analysis of geological results and structural modeling has also demonstrated that there is potential for additional high-grade ore shoots within the presently known mineralized structures. Delineating these structures should result in an increase of overall grade and contained ounces.

Apr 22, 2003

By J. C. Johnson

High-grade ore found in a shaft pillar at the Homestake Mine prompted a request for a Bureau of Mines study to determine if selected areas of the shaft pillar could be mined without jeopardizing the shaft. The design approach was to perform a finite-element study of the shaft pillar. Plan view and vertical sections were developed using two-dimensional, elastic, plane strain assumptions. Input into the model consisted of in situ stress measurements geologic mapping rock mass properties, and previous mining history. Results from the study indicated that ore-beating sections of the shaft pillar could be removed within the displacement tolerances acceptable for the shaft. Homestake engineers, using the results of the finite-element study and considering other factors, have designed and are beginning to mine the shaft pillar.

Jan 1, 1989

By A. C. Fieldner

This report is the fourth of a series of annual summaries of research and technologic work on coal by the Technologic Branch of the Bureau of Mines. The coal research program of the Bureau has been broadened and made more flexible to adapt it to changing conditions and needs of the coal industry, and as a result information as to the properties and composition of coal has been increased and new and improved practices in mining, preparation, and utilization of coal have been devised. The present

Jan 1, 1940

By J. B. Rosenbaum

Prolonged laboratory and limited pilot plant tests have shown that the Bureau of Mines buffered S02 -H2S process is capable of removing 95 to 99 percent of the S02 from industrial waste gases. Most of the S02 is converted to elemental sulfur; only about I percent converted to sulfate The process comprises (1) washing the flue gas to remove particulates and S03, (2) absorption of the S02 in citric acid or other carboxylate solution, (3) reaction of the loaded solution with H2S in a closed vessel to precipitate the absorbed S02 as elemental sulfur, and (4) separation of the sulfur from the regenerated solution by oil flotation and melting. Two-thirds of the molten sulfur is converted to H2S for use in the sulfur precipitation step by reacting sulfur vapor with natural gas and steam in the presence of an alumina catalyst. The chemistry and mechanism of the process are described, initial laboratory and pilot plant data are summarized, and second-generation laboratory operation and pilot plant design are reviewed. Preliminary cost estimates are presented for recovering sulfur from copper smelter gas, powerplant flue gas, and Claus plant tail gas.

Jan 1, 1973

By d&apos, Kathleen J. Amico

This summary appears in Minerals Year-book volumes I and III, which cover mineral production in the United States, its island possessions, the Canal Zone, and the Commonwealth of Puerto Rico, as well as the principal minerals imported into and exported from the United States. The several commodity and area chapters contain further details on production. A summary table comparing world and U.S. mineral production also is included. Mineral production may be measured at any of several stages of extraction and processing. The stage of measurement used in the chapter is normally what is termed "mine output." It usually refers to minerals in the form in which they are first extracted from the ground, but customarily includes for some minerals the product of auxiliary processing operations at or near mines.

Jan 1, 1966

By A. G. Pasamehmetoglu, N. Celebi, K. Erarslan

A deposit evaluation system has been developed for a proposed new mine in the basin around Collolar in Turkey. It includes compositing, gridding and reserve estimation facilities and takes account of the economic value of the pit and the pit bottom elevation

Sep 1, 1991

By X. Cui, H. Ding, J. Wen, Q. Gu

This study is a continuation of previous work designed to further explore the mechanism of the bioleaching of sulfide concentrate at neutral pH by heterotrophic bacteria Bacillus megaterium QM B1551. The concentrate contained 13.2 percent nickel (Ni) and 0.2 percent cobalt (Co), which presented primarily as pentlandite and pyrrhotite. Contact and noncontact bioleaching experiments were conducted with finely ground ore at an initial pH of 6, resulting in 44.7 percent of Ni and 38.2 percent of Co leached in the contact-bioleaching treatment. Oxidation experiments of sulfur, thiosulfate (S2O32−) and ferrous ions (Fe2+) by cell membrane were performed to verify whether sulfur transferase, thiosulfate quinone reductase and enzyme cytochrome B558 on the surface of the bacteria could be expressed to oxidize the sulfide. The results show that thiosulfate quinone reductase and cytochrome B558 could be expressed to oxidize S2O32− and Fe2+ to SO42− and Fe3+, respectively.

By Hideki Shimando

Periodic weighting and windblast which are caused by the dynamic effects of overburden in a longwall panel significantly affect longwall mining This study describes past experience with wind blast at Miike Colliery, proposes a new loosening system using hydraulic fracturing and moistening, and also discusses strength deterioration in hard-to-collapse roof rocks due to water in order to solve the problems caused by the effects of dynamic roof rocks behavior in a longwall face

Jan 1, 1998

Particles of a complex nickel sulphide concentrate (containing pyrite, pyrrhotite, pentIandite, and violarite as the major mineralogical constituents) were entrained in a stream of hot gas the temperature of which was varied from 500 to -1000°C. Chemical analysis of the particulates collected from the furnace was used to detect the rapid change in sulphur content which accompanied the ignition temperature jump. X-ray diffraction analysis was used to characterize the oxidized material.These techniques showed that ignition was dependent on the mineralogical composition and occurred over the temperature range 500-900°C. Pyrite ignited first in the range 500-600°C; pyrrhotite was the least reactivemineral and required temperatures in excess of 800°C for ignition. The nickel minerals <pentIandite and violarite decomposed before ignition and ignited at temperatures intermediate to those required for the pyrite and pyrrhotite. The ignition temperature for the pyrite was found to be independent of particle size and concentration of oxygen in the atmosphere.Ignition temperatures determined by the simulated flash smelting method were compared with the results of differential thermal analysis (DTA) measurements performed on the same concentrate. Temperaturesdetermined in the DTA test as corresponding to the start of exothermic activity were shown to be at least 100°C below those determined by the simulation test.

Jan 1, 1978

By Gordon R. Sima

This contract is concerned with the construction of a Time Resolved Audio Dosimeter System consisting of one readout unit and several dosimeter units. The Time Resolved Audio Dosimeter System was designed and developed by the Bureau of Mines with the purpose of this contract aimed at obtaining additional units for further field testing and evaluation. All construction was in accordance with the Bureau of Mines design and/or Bureau approved drawings produced during the course of this contract. This report contains a summary of the construction efforts, problems encountered, recommendations and all drawings produced under this contract.

Jan 1, 1977

By Daniel E. Walsh, P. D. Rao

"A four-inch compound water cyclone (CWC) was tested to evaluate its gold recovery characteristics when processing -4.8 mm run-or-pit, placer material. Neutron activated placer gold particles (840 to 37 microns) were used as radiotracers (/98Au) in a closed circuit ewe test loop to determine concentrator recovery; a procedure believed unique to this study. The effect on gold recovery of gold size and shape, feed pulp density, feed pressure, vortex finder clearance (VFC), ewe cone type, top-size of the feed solids, presence or absence of heavy minerals in the feed, and the quantity of-37 micron slimes in the feed was investigated in over 300 tests.CWC concentration ratio and the top-size of the underflow solids were both affected by cone type, VFC, and feed pressure. Gold recovery was significantly affected by gold size, gold shape, and concentration ratio. These effects are complex, because significant size-concentration ratio and size-shape interactions exist. Radiotracer techniques showed gold particles had a residence time within the ewe of approximately one second. This study suggests ewe gold recovery is a concentration. This work suggests ewe gold recovery is a function of particle size and shape, and the flow rate through the cyclone. CWC cone ""bed density"" is considered important only as a thin, protective layer, which shields coarser gold particles from the entraining currents and facilitates their movement through the CWC.IntroductionCompound water cyclones (CWC), or automedium cyclones, are enhanced gravity concentrators for the beneficiation for slurries of sand, coal, and ground ore (Fig. 1). They are called compound water cyclones because of the compound slopes of their basal cones (Fig. 2) and are operated to suppress classification phenomena in favour of gravity concentration effects. The compound water cyclone is not a new wet concentrator. It was developed in the late 1950s by Dr. Jan Visman through research sponsored by Canada's Department of Energy, Mines, and Resources. Since that time, it has become a common unit in coal washeries for cleaning fine coal. CWCs and other versions of concentrating cyclones have also shown promise for heavy minerals and precious metals recovery."

Jan 1, 1988

By William J. Campbell

Three types of X-ray analytical instrumentation were compared for applications in the secondary brass and bronze industry. The instruments were a conventional X-ray spectrograph, a portable X-ray spectrograph, and a radioiso-topic X-ray analyzer using balanced filters. The following two general applications were considered: Rapid identification for sorting scrap metals and quantitative analyses to provide guidance in the melting and casting of alloys. Twenty-three analyzed copper-base alloys were used as standards. Although the alloys varied widely in composition, matrix correction procedures were not necessary except for copper. The conventional X-ray spectrograph provides positive identification of the alloys and quantitative values for the six elements investigated--aluminum, copper, iron, lead, tin, and zinc. Equivalent results were obtained with the portable X-ray spectrograph for those elements whose characteristic X-rays are in the wavelength range of the instrument. The radioisotopic X-ray analyzer distinguishes certain groups of alloys and provides quantitative determinations for copper, lead, tin, and zinc. The sensitivity of the analyzer was marginal for the determination of small concentrations of elements of atomic number 26 or lower.

Jan 1, 1972

In order to reach a large, untapped reserve of high-quality coal, D8 Cloverlick mine proposed to mine a corridor nearly 2,000 ft deep beneath the Benham Spur of Black Mountain, Kentucky’s highest peak. D8 Cloverlick mine was extracting the Owl seam, but the corridor’s route lay approximately 70 ft above century-old mine workings in the C–(Darby) seam. Adding to the concern, three serious coal bursts had recently occurred in nearby Owl seam workings.

Jan 7, 2020

By J. S. Miller

The Bureau of Mines conducted surface tests to determine the feasibility of using liquid explosives for underground rock fracturing. The effects of configuration, confinement, length, critical layer thickness, and fracture-propping sand on detonation and explosive propagation velocity of desensitized nitroglycerin were studied, using polymethyl methacrylate and glass-plate reservoirs through lengths from 3 to 12 ft, with explosive-layer thicknesses from 0.1875 to 0.0312 in and in aluminum tubes 8 ft long with diameters from 2.000 to 0.125 in. Interval and continuous detonation velocity data were obtained. Under the test conditions detonation velocity was dependent upon explosive confinement and fracture-propping sand. The detonation velocity of a confined nitroglycerin explosion in aluminum tubes can be reduced by as much as 85 percent, when the tube contains fracture-propping sand. The shape of the reservoir, whether triangular or rectangular, has little effect on the detonation velocity or explosive propagation. The critical or minimum explosive-layer thickness between glass plates, capable of supporting propagation, was 0.0312 in. The presence of a fracture-propping sand in the sheetlike layers increased the critical explosive layer thickness to 0.0625 in. In nitroglycerin-filled and nitroglycerin-sand filled tubes, the minimum tube diameters successfully tested were 0.125 in and 0.375 in, respectively.

Jan 1, 1969

By Arthur Notman

TO present some idea of the magnitude of the gold-mining industry of Canada and the world, the records of 106 gold-mining companies currently paying dividends have been studied. Forty of these are in Canada, and 37 on the Rand in South Africa, these being all the straight gold-mining companies that paid dividends in the two areas in 1938. None of the base-metal companies that produce gold as a by- product, or even as a major fraction of the value of their total product, have beezl included. In addition, a group of 29 similar companies from Southern Rhodesia and the Gold Coast in Africa, India, Australia, Manchuria, Philippine Islands, the

Jan 1, 1939

By W. H. Young

The thickness of the coal seam is one of the more important items influencing the productivity and general overall efficiency of operation of a coal mine. The average thickness of coal seams mined in the United States has changed very little in the past 40 years. The first measurement of thickness of bituminous coal and lignite seams was made for 1920, when the average thickness was 5.3 feet.4/ The average thickness for later years was as follows: 1945, 5.4 feet; 1950, 5.3 feet; 1955, 5.2 feet; and 1960, 5.5 feet.5/ Table 1 includes data on number and production of bituminous coal and lignite mines classified by I-foot intervals of seam thickness mined in 1920, 1945, 1950, 1955, and 1960. Though bituminous coal and lignite are mined today from seams of exceedingly variable thickness -less than 2 feet to more than 50 feet - a large majority of the production, 62 percent in 1960, came from seams 3 to 6 feet thick. This is not surprising since the coal seam of moderate thickness presents the least mining difficulties.

Jan 1, 1962

At the Orieco mine quartz veins carrying sulphides were localized in parts of an extensive fault zone in the Mathinna Beds during late Middle Palaeozoic mineralization.These deposits were subsequently exposed, and oxidation of the sulphides by percolating groundwaters resulted in the formation of gossans at the surface, and replacement close to the permanent water table of the more soluble sulphides by copper sulphides (chalcocite, coveIlite). A restricted zone containing copper oxides (cuprite, tenorite), copper carbonates (malachite, azurite), iron arsenates (scorodite, pharmacosiderite) and possibly rare copper sulphates occurred above the water table.The renewed oxidation of these deposits following mine development has been facilitated by the ready circulation of air and water combined with the formation of large free surfaces ideal for evaporation of aqueous solutions. Under these new conditions of high initial sulphate concentration, low pH, and relatively high Eh, the previously formed mineral assemblage is unstable and numerous Cu (Fe,Zn)-sulphates and Fe (Cu,Pb)-arsenates are presently forming in fractures in the fault zone and on the adit and stope surfaces for some considerable distance from the Sulphide-rich ore shoots. The observed spatial sequence of the major sulphates with respect to the sulphide-rich zones (Le. chalcanthite-antleritebrochantite and langite) is consistent with decreasing sulphate concentration and increasing pH away from the oxidizing sulphides.

Jan 1, 1970

By P. J. Bethell

Background Increasingly complex geological conditions, with the presence of high ash binders in the mining horizon were encountered at the A.C. I. Dugout Mine near Price, Utah. This led to the production of high ash coal from the Dugout Mine during 2003 and 2004. This material had poor marketability and posed operating issues for the utilities burning the coal. Ash levels increased from typical levels in the 9-12% range to between 15 and 25%. etween 15 and 25%. Reviews of the mine plan and expected geological conditions indicated that further periods of high ash production could be expected. Action Plan Detailed sampling of the mine high ash production was carried out. The majority of the coal from the Dugout Mine is trucked to the Savage Coal Terminal (SCT) at Wellington, Utah where it is stored in multiple piles by quality. Coal at the mine is segregated by a CoalScan 2600, on-line analyzer into high ash, low ash and rock chute (waste material). From these piles, the material is crushed prior to shipment to SCT. The samples obtained from the various high ash piles were subjected to detailed sizing and washability analysis. Once this information was obtained, alternative circuit configurations were evaluated to process this material into a salable product. Water supplies in the arid terrain where the plant is located are scarce. This factor played a part in the final circuit design.

Jan 1, 2008

By J. W. Adams

This report surveys the efforts of six contractors to the U.S. Bureau of Mines with regard to their electromagnetic noise measurement programs. What has been done, what is planned, and evaluations and recommendations are given for each contractor. The main observation is that to date there is not sufficient knowledge of electromagnetic interference in mine environments to design a reliable communication system. This knowledge should be available by the end of June 1972 if certain planned programs are completed successfully. A major effort of this report is to establish parameters to be measured, units to be used, and workable formats for data presentation. This is given in Appendix A. Some details concerning equipment, procedures, locations, and sample data are included in Appendix B.

Jan 1, 1971

By J. R. Ross

A reconnaissance for sources of scandium and a metallurgical investigation of recovery methods for byproduct scandium from uranium mill solutions were conducted by the Bureau of Mines. The work on scandium was undertaken to obtain information on domestic resources and to explore and develop recovery procedures in consonance with the Bureau's long-range program for conservation and wise utilization of mineral resources. The element scandium is widely distributed in the earth's crust in trace amounts, but it seldom occurs as an important constituent in any mineral. An exception is thortveitite, (Sc,Y)2 Si207) a rare mineral that contains various amounts of scandium and yttrium and may contain up to 42 percent scandium oxide (SC203). Knowledge of the chemistry of scandium has expanded rapidly in recent years (1, 4, 9)4 but only fragmentary information is available about the metal because it is still largely a laboratory curiosity without established uses (2, 3). A recent study shows some of the physical proper-ties of the metal are (1) density of 3.05 grams per cubic centimeter) (2) melting point of 1,540° C, (3) hexagonal close-packed structure) (4) hardness of about 50 Brinell (500-kilogram load), and (5) an alloy behavior similar to yttrium and rare-earth metals (2). The price of $2,850 a pound for scandium oxide of 99.9 percent purity and $2,700 a pound for oxide of 99 percent purity reflects the scarcity and complex chemistry of the element.

Jan 1, 1962