Search Documents

By R. A. Cattell

The Bureau of Mines actively conducted a well-coordinated research pro- gram during the past fiscal year on problems dealing with the production of oil and gas, transportation of natural gas, chemistry and refining of petrole- um, thermodynamic properties of hydrocarbons, and the processing and utiliza- tion of incombustible helium gas. These particular reserach phases, compris- ing the presently scheduled activities, are integral parts of a broad program selected soon after the war as suitable for Bureau of Mines study, to meet immediate needs for specific information on petroleum and natural-gas problems of national scope. Important progress was made and many technical reports were finished during the year. Several reports were published on gas-condensate production problems, one giving the results of laboratory tests of relative merits of various steels and alloys for rosisting the corrosion that occurs in high-pressure gas- condensate wells. Research was continued, using the Bureau's windowed cell, to determine the characteristics of gas-condensate fluids, and an important paper on the phase relations of these fluids at low temperatures was published. An important part of the Bureau of Mines petroleum production research program for many yoars has been the engineering study of type oil fields. This year reports waro completed on the Lake Creek, Sheridan, and West Rod River fields, Tex.; the Atlanta field, Ark.; and the Bogge field, W.V. Othor fields under study and for which reports will be issued are the Carthage and Now Hope fields, Tex., and the Weber pool, Okla. Spocial studios to determine the characteristics of the oil-gas solutions as they exist within the native reservoir rocks have been in progress in the North Lindsay field, Okla.; the Elk Basin field, Wyo. and Mont.; and the Rangely field, Colo. The North Lindsay study brought to light several un- usual physical proporties of the oil as it is found in this deep-seated reservoir. For instance, its viscosity is less than that of water, and more than 2 barrels of the initial reservoir oil must be produced to yield 1 barrel of "stock-tank oil." In the Elk Basin and Rangoly fields the oil-gas solution varies in composition within the reservoir, depending upon structural location. Engineering studies were continued on woll spacing and on drilling fluids with special emphasis on obtaining uncontaminated cores, or coros for which the flushing action of the drilling fluid can be dotormined accurately. In connection with research on production of oil by secondary recovery methods, progress was made in studies of conditioning water for subsurface injoction, of input ratos and pressures for water-flooding oil sands, and of the selective plugging the more permeable mediurs to prevent or retard channel- ing of the injected fluid. The availability of fuels for all types of internal-combustion engines still is tho primary resoarch project in potroleum chomistry and refining. This rosearch program is subdivided into a sorios of problems under four main topics: (1) Raw-material studios; (2) relationships of fuel consumption, proporties, and performanco; (3) utilization of potroleum products; and (4) analytical mothods, which include chomical and physical property detorminations.

Dec 1, 1949

By Raymond O. Dannenberg

The gas-combustion retort developed by the Federal Bureau of Mines at the Rifle Oil Shale Project near Rifle, Colo., is a continuous, gravity-feed retort. The heat required to convert the kerogen in the oil shale to liquid oil is generated by the combustion of product gas and carbonaceous residue remaining on the retorted shale after the kerogen has been converted to oil, gas, and residue. A study of the effects of the process variables on retort operation, product yields, and product properties is important to the successful solution of the problems encountered in the development of a satisfactory process. Statistical methods were used to design the experiments and analyze the effects of the rate of shale throughput, the composition of dilution gas, the height of the shale bed above the air entry, air-gas distributor design, shale size range, and the ratios of the flow rates of the various gas streams entering the retort to the rate of shale throughput.

Jan 1, 1960

By M Malec, J Szczerbinski

Hazards in underground mines are concomitant with the mining of mineral deposits and have their source in a minerÆs work environment. The authors of the paper have undertaken a trial classification of these hazards into three groups, depending on the sphere of their occurrence:lithosphere, ie rock mass, atmosphere, ie air in mine workings, and technosphere, ie machines, equipment and facilities in mine workings. The lithosphere creates such hazards as bumps, rock outbursts, the atmosphere is a factor causing fires, methane explosions and climatic hazards, whereas accidents concomitant with an operation of machines and equipment occur in the technosphere. Assuming that the number of accidents in the mining industry, concomitant with hazards, reflects the degree of safety, it has been shown, that in Poland they are under control to a large extent.

Jan 1, 1999

By J. HUNER

Twenty-four new fields were found in Louisiana during 1945. Of this number 15 were oil fields, eight were gas condensate, and one a dry gas field. None of these fields, with the exception of West Delhi, is as yet of any great consequence. The Weeks Island field in Iberia Parish may eventually develop into a considerable reserve.

Jan 1, 1946

By S. Makni, S. Koppalkar, A. Bouajila

ABSTRACT This paper briefly reviews the gravity recovery between conventional and centrifugal gravity separators. The advantages of semicontinuous gravity separators will be discussed, as will techniques for upgrading the gravity concentrates. The research efforts in optimizing semicontinuous gravity separators will be recalled. An innovative gravity circuit for eliminating or minimizing the use of complex processing schemes will be reviewed. Ongoing gold gravity research has revealed that gold particle shape transformation is one of the main factors explaining the lower recoveries of the plant units. Efforts to devise possible remedies for improving plant gravity recovery will be discussed.

Jan 1, 2013

By Edwin T. Myskowski, Alfred H. Hesse

THE development by the U. S. Bureau of Mines of a process for purifying manganese by electrolysis has stimulated interest in manganese alloys. While recent publications have shown some alloys of manganese and copper to possess rather unusual properties, none have included information on tensile properties, which have an important bearing on the usefulness of the alloys. Manganese-copper alloys can be heat-treated, since the single phases that exist at high temperatures may be retained by quenching. According to Persson,1 when quenched alloys containing from about 30 to nearly i00 per cent manganese are reheated, alpha manganese is precipitated (Fig. I). Calculations based on Persson's X-ray data indicate that this decomposi¬tion is accompanied by a change in volume of as much as S per cent. The reason that this large volume change has not been noted probably is the slow rate at which equilibrium is reached by these alloys. In an investigation on hardening by cold-work and heat-treatment, Dean and Anderson3 found that quenched alloys increase in hardness with manganese content and that high-manganese alloys harden very slowly with cold-work, while high-copper alloys harden much more rapidly. Heat-treatment has little effect on manganese-copper alloys containing less than 40 per cent Mn, and affects those alloys containing more than 40 per cent in accordance with their manganese content and heat-treating temperature. Dean and Anderson4 also found that cold-work increased electrical resistance of alloys containing from 50 to 80 per cent Mn, and that heat-treatment of alloys containing from 40 to 96 per cent Mn altered the electrical resistance considerably. Dean, Anderson and Potters have shown that the high vibration damping capacity that characterizes manganese-copper alloys containing 40 to g0 per cent Mn. is affected by cold-work and heat-treatments. Highest vibration damping capacity at low stresses was obtained by heating for 2 hr. at 450°C. (842°F.) after quenching from solution temperatures. Preparation of Alloys.-The alloys for these tests were melted in a 17-lb. basic-lined high-frequency induction furnace using electrolytic manganese, grade A ingot copper and a 70-30 Cu-Mn master alloy (69.80 per cent Cu, 0.12 Fe, 0.04 Si, 0.006 S, 0.07 C, balance Mn). The manganese was heated slowly to expel excess dissolved gases and melted before the addition of copper. No fluxes or covers were used. The melts were cast in tapered iron molds and the ingots were reduced go per cent when forged to ½ in. rounds. These rods were given 2-hr. solution treatments at temperatures that depended upon the composition (Table I). Tensile Tests.-The tensile specimens, 0.313-in. diameter (1.25-in. gauge length), which were enclosed in evacuated Pyrex

Jan 1, 1942

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 Ronald D. Hill, Elmore C. Grim

Coal-haul and mine access roads are defined as any road constructed, improved or used by the operator (except public roads) that ends at the pit or bench. These roads constitute approximately 10% of the total area directly disturbed by the surface mining operation(l). In some cases, the land disturbed by haul roads exceeds the area included in the mining operation. Studies (2 and 3) of the U. S. Forest Service in eastern Kentucky show that typical contour mining roads exhibit poor alignment, excessive grades, insufficient strength and durability, and poor drainage. Mine roads in other Appalachian- States, particularly where contour mining is practiced, appear much the same as those in Kentucky. Access roads(4) were also found to be a large source of sediment. It is possible that of the sediment that finds its way into the streams as much (or even more) originates from the haul roads as from the mining operation. Most roads are built as cheaply as possible, and good road-building design and practice are ignored. Maintenance schedules are generally inadequate, and upon completion of mining, haul roads are usually abandoned, with little or no attempt made to bed them down(5 ) . Such roads deteriorate very rapidly (Figure 68). Area mining, which is practiced in flat to gently rolling terrain, presents fewer haul road related environmental problems. These roads through necessity are generally well engineered because of the heavy equipment using them, such as 240 ton (217 metric ton) haul trucks. They must have wide beds, good alignment, and adequate drainage to permit coal haulers to run at top speed during all seasons of the year. Excessive dust can be a public nuisance and a driving hazard, and it is hard on equipment. Calcium chloride and sodium chloride have proven to be effective materials for controlling dust. Two applications during the summer when the ground surface is moist at the rate of 1/2 pound per square yard (.26 kilograms per square meter) (3 1 have been suggested. Th4 most common procedure is to keep the roads wet by using water trucks. Sediment that reaches the streams can be traced to one or more of the following five basic phases of haul-road life:

Jan 1, 1974

By Evelyn Dayrell Lopes Júnior

A capacidade de alimentação de sistemas de fundição é uma das características tecnológicas que está correlacionada a resultados qualitativos negativos, como porosidades e deformações geométricas dos produtos fundidos. As ligas com suas características são parte fundamental do processo de alimentação. A metodologia de caracterização da capacidade de alimentação por meio da coquilha Tatur foi utilizada nesse trabalho, para a qual foram desenvolvidos novos processos de dosagem da liga líquida, com o objetivo de prover maior repetitividade, e consequentemente, maior coerência morfológica das amostras produzidas. Para isso, foram desenvolvidos dois novos métodos de dosagem, chamados “método de dosagem dinâmica” e “método de pré-dosagem”. Esses foram testados e analisados, sendo suas amostras avaliadas comparativamente com o padrão morfológico teórico. O objetivo da obtenção de amostras coerentes foi atingido, sendo evidenciadas a grande influência das variáveis presentes na etapa de vazamento sobre os resultados das amostras obtidas.

Aug 17, 2017

By Thomas C. Wilder

ALTHOUGH there is an abundance of thermodynamic information available in the literature today, no experimental data on the standard molar properties of formation of zinc oxide have ever been reported for the temperature range 419.5" to 908°C. This is the temperature range for which zinc metal is a liquid. so that the formation reaction is: Data have been reported for Reaction [I] where zinc is a solid or a gas. Maier. Parks, and nderson' measured the electromotive force of the cell: in order to obtain the free energy of the reaction: over a limited temperature range. With the known properties of H2O, those of ZnO were calculated. These workers found that t;j of ZnO is -75,930 ± 150 cal per gfw and Mtf is-83,000 300 cal per gfw at 25°C. akolkin made similar measurements to obtain ilF7 and AH; of -75,870 and -82,540 cal per dw respectively at the same temperature. Truesdale and arirlg and Kitchener and 1gnatowicz4 measured the equilibrium of the reactions: respectively, in order to determine Ff of ZnO from the known values of CO, CO2, and H/X The thermodynamic properties of ZnO, presumably taken from the above investigations, are tabulated by Kubaschewski and vans' and Wicks and Block" The latter reference also gives values for the range where zinc is a liquid. These numbers are probably acquired from the known extremities of the range plus Cp data of the components. In the present work the electromotive force of the cell: was measured in order to calculate the properties of ZnO from the well known values of NiO for the temperature range where zinc is a liquid. In Cell [B] the cathode reaction is: and at the anode: The overall reaction is: for which the free energy change is: where is the electromotive force in volts of cell [B] after correction for the Pt-Ta thermocouple. The standard molar free energy of formation of NiO is very well known as a function of temperature. Kiukkola and agner's data are used in most tabulations. The error is probably less than I00 cal per gfw, The latter authors were the first to use solid mixed oxide electrolytes in galvanic cells. Their work with NiO and other oxides was performed with cells similar to Cell [B] using a variety of reference electrodes of fixed oxygen potential. There may be a small composition range for which either NiO, ZnO or both exist. If nonstoichiometry does exist for these oxides, then the properties described herein are those for the metal saturated compositions. The simple cell design was the same as described elsewheres except that the molten metal electrode was about 125 g of pure zinc including a small (0.25 to 0.50 g) amount of ZnO. The mixture of pure nickel and NiO powders making up the reference electrode was contained in a tube of the ZrOl + CaO electrolyte which was immersed in the molten zinc. A platinum contact was made to the reference electrode; tantalum to the zinc. A refractory cement plug was necessary at the open end of the electrolyte tube in order to prevent zinc vapor from contaminating the reference electrode. Experimental details such as the vessel containing the cell, furnace, temperature control and measurement, and electromotive force determinations of the cell have all been outlined previously. The temperature was varied randomly in the range between the freezing and boiling points of zinc. After each temperature change, time was allowed for the drift at the new temperature to be less than +;"c whereupon a series of three cell readings was taken at least 10

Jan 1, 1970

By D. J. Hallbom

The ?yield plastic? rheological model describes the flow behaviour of a variety of non-settling suspensions, including many types of mineral slurry. The current paper presents the laminar flow relationship (pressure gradient vs. flow rate) for a yield plastic fluid flowing through a pipe or cylinder. Simplified algebraic equations, suitable for engineering purposes, are presented for yield plastic fluids with values of the scaling factor in the range that includes most industrially important slurries. The laminar pipe flow relationship is one of the most important fluids engineering calculations. It may be used to determine the rheological parameters of a material in a capillary rheometer or flow loop. If the rheology is known, these relationships may be used to determine the laminar flow pressure gradient in pipelines of various sizes.

Jan 1, 2014

By K. R. Price, M. Gauna

A high seam geologic condition exists at Jim Walter Resources No. 4 mine that requires immediate rib support after a continuous miner cuts a place. High seam mining heights are typically 2.4 to 2.6 m (8 to 9 ft) and a thick rock layer is present in the upper portion of the coal rib side. The 610-m (2000 ft) mining depth at No. 4 mine induces horizontal rib line movement after excavating an entry. Horizontal rib movement greater than 305 mm (12 in.) have been noted. When lateral movement occurs in the high seam areas, the thick rock layer, and the coal above the rock layer, become fractured and tend to roll into the entry. If not adequately supported, large rib rolls develop in the place being bolted as well as in previously mined areas that endanger men and equipment. To control this, rib support must be installed in the roof bolting operation as the bolting crew works toward the face. A rib control system has been developed for this high seam mining condition using a mechanical anchor bolt placed at an angle in the rib and installed with a modified Fletcher DDM-15 bolting machine. More than 120 km (75 miles) of entry have been supported with angle rib bolts. These angle bolts constitute 43% to 60% of the total roof and rib bolt footage in the high seam portions of No. 4 mine. The angle rib bolting system has proven safer, more effective, and more efficient than the earlier support method using bolts installed horizontally into the rib. No rib roll accidents have occurred since the angle drill bolting machines were placed in service in 1981. By securing the broken rib material with an angle bolt anchored above the coal pillar, a more effective means of rib control is achieved. Angle rib bolting does not interfere with continuous miner productivity. In addition, bolting crews are now reduced from three to two people. Total drilling supply costs are about 60% the previous cost, when compared to the previous support method using horizontal rib bolts:

Jan 1, 1985

By Robert H. Peters

Several significant problems associated with employee turnover among underground miners are described in this Bureau of Mines report. Although a vast amount of research has been conducted on turnover among employees in nonmining industries, there has never been an attempt to empirically investigate the causes of turnover among underground miners. This report presents the results of empirical research on employee turnover in other industries and describes and critiques the research methods that have been used to investigate turnover. Using the findings on employee turnover in other industries and known data about miners and the mining industry, a conceptual model of the factors that cause turnover among miners was generated. This model, which is expected to provide a basis for later empirical studies, is presented. Several recommendations for controlling miner turnover are also presented.

Jan 1, 1986

By J. W. Leonard, J. C. Anderson, C. T. Holland

PREPARATION CONTROL IN UNDERGROUND MINING Selective Mining According to district Depending upon the particular geographic loca- tion or seam characteristics, modern raw coal preparation practices can be used to obtain improved product quality and uniformity. Nevertheless, certain coal markets may require only marginal quality while others may require very high quality, and these objectives may be sought by commencing the preparation of coal underground at the "working face." Under- ground preparation involves choosing those portions of the seam which can be cleaned to satisfy predetermined market requirements involving ( 1 ) maintenance of uniformity in chemical quality, (2) elimination of removable impurities, (3) control of sizes and size ratios, and (4) control of moisture. The methods employed to attain these objectives vary widely with the (1 ) seam under development, (2) mining equipment available, and (3) changing trends in the consuming markets. When a mining property is opened and development progresses from one section to another, the (1) petrography of the coal in the seam does not remain uniform, (2) character of roof and floor are subject to change, and (3) character and prevalence of mineral impurities are subject to considerable variation. The quality of coal shipped to market from any mine depends upon intelligent foresight, planning, execution, and supervision. Mining becomes a highly technical art. The quality of coal as determined by chemical and petrographic analysis is without question one of the most important considerations in the development and life of any coal-mining property. Variations in such proper- ties as volatile matter, ash, sulfur, Btu content, and petrography are of considerable interest, and to a limited extent so are such properties as phosphorous content, free swelling index, plasticity, hardness, pressure formation during coking, and ash composition. The maximum and minimum specifications of these characteristics as established by competitive market conditions place definite limits on the marketability of a coal.

Jan 1, 1979

By D. G. C. Robertson

The thermodynamics and kinetics of the reactions involved in fuming zinc from oxide slags using coal or coke were first studied in 1955 and have been the subject of many investigations since that time. The key reaction is ZnO(in slag) + CO Zn(g) + COl. This paper will review the some of the recent work, and will add new insights obtained in experiments carried out by the authors. In the first series of experiments it was shown that the reaction 2Fe2+ + ZnO = 2Fe3+ + Zn(g) or 2FeO + ZnO = Fe2O3 + Zn(g) does not occur at an appreciable rate, as is expected from thermodynamic considerations. In the second series of experiments it was shown that zinc does not fume from the slag at a significant rate unless a reductant has been added. This again is in accord with thermodynamic considerations, but is in contradiction to some of the experimental results reported in the literature. A third series of experiments was carried out with excess coke being present, so that the rate of supply of reductant was not in any way controlling the rate. The kinetics of zinc oxide reaction were then found to be independent of the zinc oxide concentration, but increased with increasing basicity, and temperature. The presence of high concentrations of FeO in the slag also improves the kinetics. At low zinc oxide concentrations iron oxide reduction occurred in parallel with zinc oxide reduction. We propose that (under the conditions of this work) the kinetics were controlled by a chemical step, namely the rate of desorption of an adsorbed CO2 species. This is the same mechanism as reported by Belton and co-workers for the kinetics of the reduction of FeO. This explains why the reduction of metal oxides in slags by hydrogen is often faster than by CO.

Jan 1, 2003

By Michael Kelly

Longwall mining is the principal method of underground coal mining in Australia, with 70 million tonnes being produced by longwall mines in 1999. However, the mechanisms that control longwall geomechanics are still not clearly understood resulting in stoppages costing several hundred million dollars per annum The CSIRO has been investigating longwall geomechanics with consultant groups and minesites through several ACARP supported projects since 1994. The research has aimed to improve longwall support design and control methods by defining strata failure mechanisms and their occurrence about underground extraction panels, It also aimed to develop better predictive tools bur a broad range of underground environments. As a result of site studies at more than 8 locations some of the aspects that have been touted to control longwall geomechanics, especially from a 3D aspect are highlighted. These aspects include stress controls, geometry, faulting, depth. longwall width and changes in lithology.

Jan 1, 2000

By A. Perry Thompson

I. GENERAL DISTRIBUTIONS APPEARANCE, AND RELATIONS MINING in Butte has seldom encountered covellite in commercial quantities. The notable occurrences, extending vertically and laterally perhaps several hundred feet, presented scattered, bladed lenses of this mineral in a matrix of quartz, pyrite, enargite, bornite, and chalcocite. But under the microscope covellite is seen to be widespread in the Butte ores, though in such small quantity that megascopic examination will not discover it. In early mining operations covellite was found in the Gray Rock vein, a member of the Blue vein system. As described by Sales,1 it persisted as an occasional ore mineral, associated with quartz, pyrite, tetrahedrite, bornite, chalcocite, and minor amounts of sphalerite, from the 700-ft. to the 1,200-ft. level of the East Gray Rock and Diamond mines. Crushed quartz-monzonite and later quartz completed the vein filling between

Jan 4, 1915

By R. R. French

The industrial minerals industry in the Atlanta, Ga., area was studied in order to better understand problems associated with exploiting mineral resources in and near metropolitan areas. A method for delineating the Atlanta urban area and its component parts was developed so that the factors affecting the location of the minerals industry could be viewed mere objectively in the urban context. Major attention is focused on the area's dominant crushed stone subindustry Demographic and socioeconomic analysis of the Atlanta, Ga., area shows that expansion of the metropolis and its environs will probably eliminate potential mineral resources from the mineral resource base in the area, and that the expanding metropolis will be the primary determinant of future mining sites. Competition for land is accentuated to varying degrees by the incompatibility of wining operations with residential and other environmental requirements. Areas of consideration are suggested to provide maximum development of land and resources for greatest economic benefits it minimum social cost. Further research is recommended to determine market locations in urban areas, optimum operating levels for industrial minerals plants, and alternatives to surface mining.

Jan 1, 1970

By J Rayner, R P. Langmead, J A. R Coote

Gosowong is situated within the Neogene magmatic arc of Halmahera island in the Maluku province of eastern Indonesia. It was discovered as the result of a rigorous ground reconnaissance program in an area with no previous mining activity. The broad structural setting in the Gosowong District comprises an elongate dome formed by the forceful upward intrusion of magma along a deep-seated structure, resulting in associated tensional fracturing trending parallel to the long axis of the dome. Four copper-gold porphyries and numerous low-grade epithermal veins occur within this mineralised corridor, with the Gosowong Deposit being the only economic occurrence discovered to-date. Gold mineralisation is hosted within multiphase epithermal quartz-adularia and quartz-chlorite fissure veins, breccias, and stockworks. High-grade gold mineralisation is emplaced in two gently south-plunging ore shoots along a 400 m section of the north-striking, east-dipping, Gosowong Fault, the primary control on mineralisation. The Gosowong Fault is believed to be a tensional fracture associated with uplift of the dome. Lithological variation and structural intersections play a large role in grade distribution within the vein zone. Host rocks comprise a wide range of shallow marine, intermediate-basic volcanic and volcaniclastic rocks of ?late Miocene age. The Gosowong gold deposit is a classic example of a low-sulphidation epithermal gold deposit, based on the abundance of adularia and illite in the alteration assemblage, and low base-metal sulphide content within quartz-adularia veins. The indicated resource is estimated at 0.99 Mt at 27 g/t Au and 38 g/t Ag for a total of 870 000 ounces Au, using a cut-off grade of 2 g/t Au.

Jan 1, 1999

By T. A. Sullivan

The Bureau of Mines investigated modified sulfur concretes as one part of a program for utilizing sulfur in construction materials. The use of modified sulfur was studied as a means of preventing the stressing action in the concretes caused by the allotropic transformation of sulfur on solidification. Unmodified sulfur concretes have been prepared that have compression, flexural, and tensile strengths equivalent or better than Portland concretes. However, most of these concretes have been vulnerable to deterioration by weathering, temperature fluctuations, and freeze-thaw cycling. The sulfur was modified by reaction with dicyclopentadiene or dipentene before use as an aggregate binder. Sulfur concretes and modified sulfur concretes were pre-pared from acidic and basic type aggregates. Physical properties of the optimum mixtures were determined and compared with each other and with Portland cement concretes. The best results were obtained by reacting sulfur with 5 pct dicyclopentadiene to prepare modified sulfur concretes. Field testing of the concretes are in progress. Present results show that modified sulfur concretes are superior to unmodified sulfur concretes and equal or better than Portland concretes in compressive, flexural, and tensile strengths. Long-term aging characteristics of both modified and unmodified sulfur concretes are being determined.

Jan 1, 1976