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By R. D. Saltsman

Under contract with the Federal Bureau of Mines, Bituminous Coal Research, Inc., performed a statistical study to find less expensive and time-consuming methods of monitoring the noncombustible content of coal mine dust. Calculations based on thermodynamic considerations verified the reasonableness of Federal rock-dusting requirements. The results of extensive sampling in southwestern Pennsylvania mines indicated that, at the 95-percent confidence level, the present system of sampling at 200-foot intervals may be replaced by sampling at 500-foot intervals, and that a 1-inch scoop floor sampler may replace the standard 6-inch scoop for floor sampling. Further field testing is recommended.

Jan 1, 1975

By T. R. Raponi, D. Barnes

The Williams Mine mines and mills 6000 t/d (6600 stp’d) of gold ore using SAG/ball milling, leaching and CIP, electrowinning and refining. Electrowinning, high-pressure cathode washing, filtering, retorting and refining are based around the use of knitted stainless steel mesh cathodes. Their primary advantage over conventional steel wool cathodes is that electrowon gold can be washed off and the cathode can then be reused. Typically, the knitted cathodes have a useful life of up to 15 months. Gold production of up to15 t/month (50,000 oz/month) is easily processed with this system. Presented is a description of this operation, including a review of the equipment and performance data.

Jan 1, 1992

By Chenxi Ding, Chenglong Xiao, Guoli Shi, Zhiwei Zhao

This study investigates the directional blasting of a 90° slit charge structure using laboratory experiments and field tests. A 90° slit charge suitable for the corner of roadway is proposed. After the slit charge blasting, two long main cracks along the slit, and several short secondary cracks in other directions. The slit charge not only significantly reduces damage to the surrounding rock, but also improves the quality of the roadway contour. In addition, a comprehensive damage evaluation system of the roadway contour and the surrounding rock is constructed using digital image analysis, borehole televiewer, and CT scanning.

May 23, 2024

By Waynw P. Myers

Electricity, as normally thought of by a layman's definition, is a man- made force that has no color, no odor, is not visible, cannot be heard, yet man can control it and make it perform his work for him. A person dare not cheat on it, for it then will master him. It has laws, rules, and regulations that must be strictly adhered to if it is to perform in the safest, most reliable, and economical manner. In the early days of coal mining the power source was man himself. Later man employed steam and compressed air to reduce his muscle power requirements needed in the extraction of coal. By the turn of the 20th century, electricity had become the most common source of power for the coal industry. Steam and compressed air are still found in use in isolated cases today for specific applications; however, they are rapidly being replaced by electricity. Electrical laws and regulations are quite extensive and somewhat complex for the proper generation and use of electricity. Man-made laws, rules, and regulations for the care and handling of electricity, designed for man's safety, are rigidly enforced by Mine Safety and Health Ad- ministration (MSHA), as well as the various state departments of mines. BACKGROUND Until recent years most underground coal mines used direct current exclusively for all movable and for some stationary equipment. Exceptions were for permanent pumps, tipple, fan, and outside buildings where alternating current was normally employed. However, over 60 years ago there were mines with dual systems. Alternating current was used for cutting machines, drills, and pumps ; direct current for locomotives. There were no other machines as these were hand-loading mines. Later, during early mechanization in the 1920s, alternating current was also applied to loading machines at some mines. Use of dual electric systems then declined until fairly recently when

Jan 1, 1981

By C. E. Siebenthal

produce attractive and consequently more salable products. It would seem, however, that if solder and babbitt were cast in closed molds, just as good practical results would be obtained by the user, without his being able to give preference to solders of unnecessarily higher grade on account of their appearance. It would be hopeless for any one. manufacturer of solder to undertake a change of this kind, but if all manufacturers of solder agreed upon it, they would be able, in my opinion, to get the users of solder to take, and to approve by their practical tests, metals containing less tin than they have been accustomed to. The same is true with regard to babbitt metals. An illustration of how, in the use of an alloy, appearance sometimes is deceptive, is to be found in the case of what may be called intermediate grades of babbitt. I am thoroughly convinced that high-tin or high-lead babbitts are better than those containing both lead and tin with relatively high percentages of each. A high-tin babbitt should not contain more than about 10 per cent. of lead, and a high-lead babbitt should not contain more than 10 per cent. of tin, unless the percentage of antimony can be correspondingly increased. The intermediate babbitts, such as those that contain from 30 to 70 per cent. of lead or tin, may give nice appearing castings that flow easily, but they have not the serviceability of the high-lead or high-tin babbitts. Their hardness diminishes very rapidly as the temperature rises, and they have a relatively low softening point due to the eutectic components present. The Cadmium Supply of the united States* C. E. Siebenthal, † Washington., D. C.—From being one of the most maligned of metals—a veritable bugaboo—cadmium has almost overnight become respectable, though its slender claim to respectability rests almost wholly on the possibility of its substitution for tin. Preliminary to any campaign for such substitution, particularly for enforced substitution, the possible supply of cadmium should be determined as closely as possible; for that reason the statistical inquiry of which this paper embodies the results was undertaken. Production Cadmium is marketed in two forms, as metallic cadmium, in sticks or bars, and as cadmium sulfide, the pigment. The metal has found its greatest field of use in this country as a component of an easily fusible alloy that is used in automatic fire extinguishers. The sulfide is used to some extent in paints but chiefly to give color and luster to glass and porcelain. The metal was first made in this country by the Grasselli Chemical

Jan 1, 1919

By E. Chin

Bangladesh, whose population probably passed 100 million by yearend, remained one of the poorest countries in the world, with a per capita gross domestic product (GDP) of $126.2 Its only economically significant mineral production was natural gas. A few other minerals or mineral-based commodities were also produced, generally for local consumption. These included cement, clays, nitrogenous fertilizers, limestone, salt, steel, and pilot plant production of ilmenite and rutile. Exploration for oil was a continuing quest, which was hindered by a lack of funding and a hesitancy on the part of foreign petroleum companies to make long-term or expensive exploration commitments. PODUCTION AND TRADE Production of natural gas continued to increase as more use was being made of the abundant gas reserves variously put at between 7 and 16 trillion cubic feet. The main consumers were nitrogenous fertilizer producers and electric powerplants, but other industries were converting to natural gas from imported coal or fuel oil wherever possible.

Jan 1, 1986

By Joseph Blake Smith

Coal resource data from published sources and company files were used by the Bureau of Mines to determine the location and extent of strippable coal reserves in Wyoming. Total strippable reserves of 23 billion tons were estimated in seven major coal areas. Seven large strip mining operations were active in 1969, and their production totaled 45 million tons of coal. Cutoffs used to define strippable reserves were (1) minimum coalbed thicknesses of 5 feet; (2) overburden-to-coal ratios of less than 10 cubic yards of over- burden per ton of coal; and (3) total overburden thicknesses of less than 120 feet, except where reserves occur in multiple beds or a single thick bed. Tertiary rocks along margins of the Powder River basin contain most of the strippable coal reserves in Wyoming. The Wyodak beds, ranging in combined thickness from 30 to 1.30 feet, crop out on the east flank of the basin and contain an estimated 19 billion tons of strippable subbituminous C-rank coals under less than 200 feet of overburden. Partings between these beds total less than 60 feet. The 100- to 200-foot-thick. Healy bed on the western flank of the basin and the 35-foot-thick School and 20-foot-thick Badger beds on the south also contain large strippable reserves. Elsewhere in Wyoming, strippable reserves. Elsewhere in Wyoming, strippable deposits are subbituminous coal of Late Cretaceous and Tertiary ages, mostly in the Hanna and Great Divide basins in the south-central portion of the State and in the Kemmerer-Hamms Fork region in the southwestern corner.

Jan 1, 1972

By S. E. Khalafalla

A method for preparing ferrochromium alloys containing less than 2 pct carbon has been devised in a single vacuum furnace reactor. This method can conserve chromium and should reduce the capital and energy requirements relative to chromite electrothermal reduction. Reduced products containing less than 2 and as low as 0.01 wt pct carbon were obtained by reacting pellets of chromite and carbonaceous reductant mixtures at pressures of 0.1 to 1 ton and temperatures of 1,230° to 1,320° C. The extent of reduction increased with increased temperature and decreased pressure; however, operating conditions were limited due to the onset of significant chromium vaporization at higher temperatures and lower pressures. Foundry coke, anthracite, and carbon black were found to be superior to graphite as reductants. The reduction of chromite to metallics was found to proceed via the carbide intermediates Fe3C or Cr3C2. Lime accelerates the. rate of solid state reduction of chromite and can shorten the furnacin1r time at 1,3000 C under vacuum from 13 hours to less than three hours. Additional lime and silica are added to the hot reduced chromite after releasing the vacuum and raising the furnace. temperature to 1, 700° C. Soaking the charge for about 20 minutes gave a button of low carbon ferrochromium alloy beneath a well-defined slag layer.

Jan 1, 1985

By L. Russell, van Wert

During an investigation in which the solubility relations of the phases in Muntz metal (60 per cent. copper, 40 per cent. zinc) were under study, certain phenomena that had no immediate connection with the main problem were observed, which were thought sufficiently interesting to study further. Because of lack of time, only a preliminary survey was made of two of these; namely, the cleavage structure developed under certain conditions in a 60:40 brass and abnormal grain growth in this alloy. Cleavage Structure in Heat-treated Muntz Metal Carpenter noted many years ago that cold-working a brass of the Muntz metal type, which had been quenched previously from within the beta field, results in a partial breakdown of the supersaturated beta solution and the precipitation of the solute (the alpha solution) in the cleavage planes of the beta grains. This manner of rejection of a solute from a metastable solid solution is not peculiar to this particular alloy, for among others, it occurs in the cold-working of certain austenitic steels; for example, the austenitic nickel steels. In these ferrous alloys, cold deformation produces a partial decornposition of the austenite, with the formation of martensitic "needles" and zigzags in the austenitic poly-hedra. It is interesting to note that while the two solid solutions— austenite and quenched Muntz metal— are metastable and in their mode of decomposition behave quite alike when deformed in the cold, the metastability of each results from a different cause; viz., that of the austenite from the fact that it is a supercooled solution (its solvent. gamma iron, at ordinary temperatures is below its normal stable range whereas the metastability of the quenched Muntz metal is the result of supersaturation. When a 60:40 brass is quenched from above 800" C.—that is, from within the field where the beta phase alone is stable—this solution is retained practically intact and the alloy so cooled is found to consist almost entirely of polyhedra of this solution with only a little alpha present ordinarily at the boundaries of the beta grains—the result of a slight

Jan 1, 1929

By van Wert, L. Russell

During an investigation in which the solubility relations of the phases in Muntz metal (60 per cent. copper, 40 per cent. zinc) were under study, certain phenomena that had no immediate connection with the main problem were observed, which were thought sufficiently interesting to study further. Because of lack of time, only a preliminary survey was made of two of these; namely, the cleavage structure developed under certain conditions in a 60:40 brass and abnormal grain growth in this alloy. Cleavage Structure in Heat-treated Muntz Metal Carpenter noted many years ago that cold-working a brass of the Muntz metal type, which had been quenched previously from within the beta field, results in a partial breakdown of the supersaturated beta solution and the precipitation of the solute (the alpha solution) in the cleavage planes of the beta grains. This manner of rejection of a solute from a metastable solid solution is not peculiar to this particular alloy, for among others, it occurs in the cold-working of certain austenitic steels; for example, the austenitic nickel steels. In these ferrous alloys, cold deformation produces a partial decornposition of the austenite, with the formation of martensitic "needles" and zigzags in the austenitic poly-hedra. It is interesting to note that while the two solid solutions— austenite and quenched Muntz metal— are metastable and in their mode of decomposition behave quite alike when deformed in the cold, the metastability of each results from a different cause; viz., that of the austenite from the fact that it is a supercooled solution (its solvent. gamma iron, at ordinary temperatures is below its normal stable range whereas the metastability of the quenched Muntz metal is the result of supersaturation. When a 60:40 brass is quenched from above 800" C.—that is, from within the field where the beta phase alone is stable—this solution is retained practically intact and the alloy so cooled is found to consist almost entirely of polyhedra of this solution with only a little alpha present ordinarily at the boundaries of the beta grains—the result of a slight

Jan 1, 1929

By J. Chipman, N. J. Grant, H. L. Bishop, H. N. Lander

Data of several studies on the equilibrium between molten iron and open hearth-type slags have been combined to determine some of the chemical reactions involved in steel-making. Effects of slag composition and temperature on the iron oxide activity, distribution of sulfur between slag and metal, and the carbon content of the metal are discussed. Also, an overall reaction for the equilibrium between sulfur and oxygen is presented. DURING the past 15 years, a number of significant equilibrium studies have been carried out between liquid iron and simple basic and acid slags in an effort to throw light on the chemical reactions involved in steelmaking. This paper is a summary of the experimental reports on investigations which have been conducted at the Massachusetts Institute of Technology, and of related work in other laboratories. The investigations summarized in this paper include the works of Fetters and Chipman1 and Taylor and Chipman,' which dealt with simple slags that are similar to those found in the open hearth. The sulfur determinations of the slag-metal tests of Fetters and Chipman as reported by Grant and Chip-man" are included. Also, the investigations by Win-kler and Chipman' and Grant and ChipmanQ f more complex slag systems are included in this summary. The experimental procedure is described in detail in each of these papers and will not be discussed. Since the previous reports have been somewhat independent, it is desirable to review and combine the data of the various investigations to determine, as accurately as possible, the reactions in the slag-metal systems of the open hearth. It is the object of this report to present the combined data in such a way as to enhance their utility and applicability. Oxidizing Power of Slags of the System (CaO+MgO)-Si0,-FeO in Equilibrium with Carbon-Free lron The slags selected to determine the iron oxide activity in equilibrium with pure liquid iron were those containing less than 2 pct each of P,O,, MnO, or A1,0, on a weight percentage basis. The method used to calculate activities of iron oxide in liquid slags was that developed by Taylor and Chipman.' The solubility of oxygen in molten carbon-free iron under pure iron oxide slags can be expressed by the following eauation —6320 log (pctO)-------------— + 2.734 [1] where T is the absolute temperature. The oxygen solubility values as determined from Eq. 1 were used throughout this study to calculate the iron oxide activity. The iron oxide activities of slags of various iron oxide contents are plotted in Fig. 1 as a function of the basicity, which is defined as the ratio (pct CaO + pct MgO)/pct SiO,, and are based on molecular percentage values of the components. The percent (FeO), is the total iron content in the slag calculated to FeO. Fig. 1 shows that as the basicity increases at constant mol pct (FeO),, the iron oxide activity increases rapidly and reaches a plateau which extends on the basicity scale from about 1.3 to 2.3; the iron oxide activity then decreases rapidly until a basicity of about 3.0 is reached, where it tends to level off. The solid portions of the curves represent the experimental data of Fetters and Chipman and Win-kler and Chipman. Their experimental heats were made in magnesia crucibles, and hence the slags were saturated with magnesia. The broken lines on the left represent the experimental data of Taylor and Chipman, who used a rotating crucible. In general, these slags contained less than 3 pct MgO. The absence of data for slags containing less than about 40 mol pct (FeO), and basicity ratios greater than about 2.5 made it necessary to calculate curves using ionic concepts of slags. The broken lines on the right, which disregard the solubility limits of di and tricalcium silicate and lime, were obtained by following the treatment of Flood and Grjotheim,"

Jan 1, 1957

By Russell P

Polyurethane resin (PUR) is extensively used in almost all coal producing countries. On the local scene, PUR components suitable for underground application were selected and subsequently, trials were carried out at several coal mines. This paper describes the work at Pikes Gully Colliery (B.P.3Coal), where water flow rates of up to 4.5 m (1000 gallons) per minute, were reduced to 1-1.5 m /minute at the tirst stage of application. Subsequent trials were carried out at West Cliff Colliery (Kembla Coal and Coke). A variety of PUR chemical mixtures were tested in coal ribs and in the roof of intersections and roadways. The trial results are presented with all particular details. Using the PUR injection method, the roof, at the most difficult intersection, was stabilised and 'de-bonded' roof bolts were re-sealed. At Pikes Gully and West Cliff Collieries, 2 tonnes and 3 tonnes of PUR chemicals were injected, respectively. The technique, primarily based on German experience (Bergwerksverband), was used by Delta Control Systems Pty. Ltd. ACIRL was closely associated with the trials, which were monitored by installation of the measuring Stations.

Jan 1, 1986

By A. A. Ruitenberg, C. J. Morrissy

"The Lake George antimony deposit comprises a system of stibnite-bearing quartz veins that cut Silurian greywacke and slate. The stibnite-bearing ore zone is in part enveloped by a uraniferous zone.The ore-bearing quartz vein system occupies an easterly striking, gently north-dipping fracture system that cuts across north-northeasterly trending gently southwest-plunging, tight Acadian (early Middle Devonian) folds. This vein system continues at depth into a siliceous skarn zone intruded by altered granite porphyry dykes, which constitute probably a late phase of the Hawkshaw granitoid intrusion to the north.Most of the ore occurs in a northeast-plunging, trough shaped vein structure that formed where the vein system (gently north-dipping) intersects the axial surf ace zone (steeply northwest-dipping) of an Acadian synform. The trough shaped structure resulted from deflection of the fracture zone (containing the vein system) by competent beds.Emplacement of the quartz-stibnite veins was preceded by, and is in part penecontemporaneous with, the formation ofa micaceous-argillaceous alteration halo, which in turn intersects a patchy biotite alteration zone.The hypabyssal intrusions associated with the Lake George deposit probably represent a late phase (early Carboniferousr) of the nearby Hawkshaw intrusive granitoid complex. IntroductionThe Lake George Antimony Mine is situated 40 km southwest of Fredericton and 2.5 kin north of Lake George, New Brunswick (Fig. 1). The mine is owned by Consolidated Durham Mines and Resources Ltd.Shaw (1940) described the early history and development of the mine. In subsequent years, available drill cores were relogged by several geologists. Much new information became available when an extensive diamond drilling program (Kidd , 1970) was started by Consolidated Durham Mines and Resources Ltd. in 1970. A study of the geology and economic potential of the deposit was made by Glover (1973). Abbott and Watson (1975) made a study of the ore mineralogy. Available drill cores were relogged and a preliminary study of the fracture system in the mine was made by G.A. Pierce and A.A. Ruitenberg during 1976. Outcrops in the area sur rounding the mine are extremely sparse.Between 1976 and 1979 the present authors made a detailed study of the mine workings, available drill core and regional structure in the vicinity of the mine, with results set forth in this paper. The regional geologic setting of the deposit, the geometry and structural controls of the ore zones, and the mineral zonation and rock alteration are emphasized."

Jan 1, 1980

By Alexander R. Troiano, Eugene P. Klier

SINCE the very early work on quenched structures, where the products of the martensite transformation had been recognized, this transformation has provoked much interest and study. Theoretically it was desirable to account for the extreme changes in physical properties resulting from the formation of martensite, as that information might lead to results of practical importance. Desirable information, therefore, was on the kinetics of transformation from austenite to martensite as well as on the physical constitution of the martensite. It has been known for years that certain steels quenched to room temperature will contain persistent austenite as well as martensite. Other important and now well- established features of the martensite reaction are the progress of the reaction on cooling only and the independence of Ar" with cooling velocities exceeding the critical velocity. These facts have been experimentally determined by various methods and investigators. Notable among the early investigators were Tammann and Scheill and Wever and Engel.2 Unfortunately, all investigators did not fully interpret their results, which, coupled with several investigations that yielded conficting results, caused a state of confusion that was not clarified until quite recently. X-ray investigations of martensite in steels3-6 indicate it to be a supersaturated solid solution of carbon in alpha iron. This supersaturation is evident from the appearance of a body-centered tetragonal structure with the addition of sufficient carbon. The dimensions of this tetragonal structure are alinear function of the carbon content within the limits of accuracy of the determinations. Slight tempering of tetragonal martensite leads to the destruction of the tetragonal structure, which is converted to a body-centered cubic structure. This phenomenon has precipitated a controversy concerning the nature and mechanism of the tempering of martensite. The facts in the case have been outlined by Epstein7 and more recently by Antia, Fletcher, and Cohen.8 The significance of Ar" on theoretical grounds is not clear, however, although considerable study has been devoted to its determination. The precise position of Ar" as a function of carbon content was first stated by Greninger and Troianos for steels covering a range of approximately 0.7 to 1.8 per cent carbon. The effect of alloying elements on Ar" has recently been the subject matter of investigation by various methods.

Jan 1, 1945

By Harry A. Wahl

Precent fracture design procedures are bared on the total fracture area created. A method to distinguish beI,,.ecn total area and [he propped or effective fracture area has not been available. This paper presents a solution to this problem, applicable to horizontal fractures. The difierences between effective fracture area and torn] area are demonstrared in example calculations. This work is hayed on experimentally determined transport efficiencier of solids in sand-liquid slurries. Newtonian and non-Ne~vtoninn systems are considered. INTRODUCTION Fifteen years after commercial introduction, hydraulic fracturing remains the most successful stimulation technique in the oil field. This success is primarily due to ability of induced fractures to penetrate and alter permeabilities deep within formations. Many fields producing today could not have been developed without the hydraulic fracturing process. Because of wide usage, fracture-treatment design has received a great deal of engineering and research effort. This work, resulting in improved equipment and materials, has increased the benefits from fracture treatments as well as the applicability of the process. A major contribution was the development of fluid-loss additives. Necessarily, the number of parameters to be considered in treatment design has steadily increased, resulting in more complicated design techniques. Almost all present design procedures are based on the precepts set forth by Howard and Fast. Relating the fluid volume lost into the formation, the volume required in extending the fracture, and the total slurry volume injected, they developed an expression for the total fracture area created in terms of pertinent treatment parameters. Fluid loss during treatment was expressed as a function of time for three flow mechanisms. Although modifications of fluid loss equations have been made, the total fracture area concept has remained unaltered. A vast amount of field data indicate that induced fractures must be propped and held open to be effective. A notable exception is the Mesa Verde formation in the San Juan basin. However, analysis of these treatments shows that improved well productivities are obtained when propping agents are incorporated in the treating fluid. Although propped fracture area has been recognized as an important design parameter, a method to distinguish between total area and effective fracture area has not been available. The necessary information on slurry-sand transport in fractures has been lacking. Interest in the propped region of induced fractures is not restricted to areal extent alone. The distribution of sand within fractures is important from the standpoint of fracture flow capacities. Flow capacity affects the increase in well productivity after stimulation. The work of Huitt and Darin4 hows that partial monolayers of sand have large flow capacities compared to thick* dense sand packs. It has been postulated that gelled fluids have the ability to transport sand within the fractures at the deired low concentrations. An early contribution in the area of sand placement in fractures was made by Kern et al.' They studied sand movement in a transparent vertical fracture model. It was observed that the sand tended to settle out in the bottom of the model before moving very far. When the fluid velocity exceeded a certain critical value, all of the sand injected began moving through the crack even though it settled to the bottom. This critical velocity was determined under several flow conditions. Some work on sand movement in horizontal fractures has been reported in Russian publications. Sand movement was studied by Izyumova and Shan'gin' using a transparent "pie-shaped" flow model to simulate a horizontal radial flow system. However, the data were limited, especially in a quantitative sense. Dorozhkin, Zheltov and Zheltow studied the behavior of sand-liquid slurries in a horizontal linear flow model. The quantitative data were restricted primarily to the thickness of sand deposits formed at the bottom of the fracture. An earlier paper provided basic data on the flow of sand in horizontal fractures. This study was designed to yield specific quantitative information on rate of advance of sand particles and pressure behavior under various flow conditions. A comprehensive photographic study was undertaken in a 10-ft windowed flow cell to provide the necessary qualitative and quantitative data. Since the number of potential variables far exceeded the capacity of the initial study, emphasis was placed on the effects of sand concentration, oil viscosity and oil flow rate. A detailed description of these experiments and the results are described in Ref. 9. However. the implications of this work on the fracture design calculations were not discussed. An analysis of these data as well as new data is provided in the following sections. EXPERIMENTAL RESULTS The primary objective of the experimental investigation was to provide information on the rate of advance of the solids in sand-liquid sturries. A 10%-ft long transparent

Jan 1, 1966

By Vernon O. Markworth

This report contains the results of tests performed on three large diesel engines to determine their ability to meet selected criteria of the Mining Enforcement and Safety Administration Regulations for equipment used in gassy, non-coal mines. Study efforts were first directed toward determining the types of equipment expected to be used in underground oil shale mines. Three typical engines in the 800-1200 horsepower range were then selected for testing. Intake flame arresters, exhaust scrubbers, and water jacketed exhaust system were designed and built for each engine. During testing, each engine was evaluated for its gaseous emissions output, adequacy of the exhaust gas cooling system, ability to withstand internal explosions, and adequacy of the flame arresters. Surface temperatures of the engine and exhaust cooling system were determined under full load operation.

Jan 1, 1978

By R. C. Gifkins, A. Gittins

A. Gittins and R. C. Gifkins (University of Mel-houvne)— Evidence from somewhat similar experiments to those described in this paper has led us to the conclusion that possibility 2) of the four listed on p. 319 is a description of what happens in grain boundary sliding. That is, sliding is limited by accommodation deformation, it being necessary to the Continuance of sliding that this accommodation should take place. An example of such accommodation, though probably not the most important, is fold formation at triple points. The evidence and arguments for this point of view are set out in Refs. 14 to 16. In particular, an experiment with a lead bicrys-tall5 seems to support point 2) rather than 3). In creep of this specimen it was found that at least 90 pct of the extension of a zone 0.3 mm wide at the boundary was supplied by sliding at the boundary. The sliding was localized in a region at the boundary very much smaller than 0.3 mm, in fact, in a region too narrow to resolve optically. In poly crystalline Specimens&apos; there appears to be a surface effect, as found by Rachinger," but it appears that this may not manifest itself at low strains. "Low strains" means <10 pct for a Pb-TI alloy, <2.5 pct for magnesium or "Magnox" A12 alloy, or <40 pct for a 0 brass. Up to this extension the sliding, measured by the mean vertical step at boundaries, is proportional to extension. We are able to say this with some confidence, since the error bars on our points are statistically derived. Our results would lead us to think that the error bars on other work, including that of Mullendore and Grant, are much too large at low strains to show this

Jan 1, 1963

By David K. Denton

There are no active mines in the Mt. Eddy RARE II area. Chromite, gold, and stone prospects were examined. The RARE II area contains no identified mineral resources; however, a sample of a 260 ton occurrence contained 38.1 percent chromium oxide (Cr203) at the Ratero Prospect (fig. 1, no. 3), which has low potential for chromium resources. The Johnson Mine (fig. 1, no. 6) produced a small unrecorded amount of chromite during World War IT, but only a low potential exists for chromium resources. A low potential exists for gold resources at the Half Century Prospect (fig. 1, no. 2). At a borrow pit northwest of the study area (fig. 1, no. 1), sheared serpentinite is quarried for road metal; similar rock occurs in the RARE II area, but better material is more readily available elsewhere. Sand and gravel occurrences are too inaccessible and distant from markets to be considered resources. Mineral fuels and geothermal resources were not evaluated during this Bureau of Mines study. There currently are three unpatented lode mining claims in the study area. INTRODUCTION The Mt. Eddy RARE II area is 7 air-mi west of Mt. Shasta City, California, and straddles the Siskiyou-Trinity county line. The roadless area includes 7,200 acres of rugged, glacially carved, ridges and drainages which comprise Mt. Eddy. Elevations vary from 6,000 ft along the North Fork Sacramento River to 9,025 ft at the summit of Mt. Eddy. The area is covered with conifer forest below 8,000 ft elevation.

Jan 1, 1983

By J Vann

The key functions of project evaluation are to assess potential profitability and to develop an effective operational design. For mining projects, design aspects include mining methodology, ore treatment methodology and production rates. All of these characteristics impact on project economics and overall value. Resource models, which form the ultimate basis of project evaluation, typically consist of tonnes above cut-off, grade above cut-off and the spatial distribution (connectivity) of tonnes/grade above cut-off, for one or more variables. Dilution, ore loss and metallurgical recovery are all modifying factors applied to the resource model during evaluation and determination of profitability. A key issue is: how is the value determined? In addition to traditional combination of in situ tonnes/grade, the following merit serious consideration: the concentration of deleterious elements, throughput rates, mining/processing costs and û importantly û metallurgical recovery. Geometallurgy is an emerging field targeted at integrating these issues by identifying either direct measures or proxies for throughput (hardness, grindability), recovery (liberation, mineral shape/texture, etc) and concentrate quality from easily collected macro-, meso- and microscopic data. These ægeometallurgical variablesÆ drive project costs and revenues in a fundamental way. For geometallurgical characterisation to have a real impact on business design, it must enable improved mine planning. When creating spatial estimates for such variables, it is preferable to find proxies that can be measured as close to the intact rock mass as possible. However, spatial estimation of proxies for geometallurgical properties and responses is complex and requires special consideration. Unlike grades, both proxies and absolute measures of geometallurgical variables are not necessarily linear or additive and therefore require very careful geostatistical consideration. In some cases, models must predict extreme values of geometallurgical attributes rather than averages. Incorrect characterisation of metallurgical recovery/throughput can (and has) led to misspecification of the scale of projects, and thus can be seriously value destructive. Aspects of geometallurgy have long been important in iron, bauxite, manganese and coal deposits and are increasingly on the radar for base and precious metal miners. However, as more metallurgically complex deposits are developed and mining of large-scale, low-grade deposits becomes more commonplace, the importance of characterising the metallurgical response in order to generate properly optimised projects will rapidly increase. It is possible that in many ætraditionalÆ (ie grades and tonnes) reserve models, the variables that drive the project are missing!

Jan 1, 2007

By A. Mykytiuk, I. E. Puddington, W. D. Macleod, F. W. Meadus

"A laboratory-scale continuous procedure for the up-grading of naturally occurring tin ores, based on the principle of spherical agglomeration, is described. High recoveries are indicated. A proposed second stage suggests useful fractionation steps.IntroductionA LABORATORY-SCALE batch process for the upgrading of a tin ore using the principles of spherical agglomeration has already been described (1). This procedure consisted of milling, for about an hour, a precrushed ore with at least 200 per cent water, 0.2 per cent of a reagent such as tall oil (to render the de-sired ore particles hydrophobic) and about 3 per cent of a viscous petroleum oil. The feed material passed an 8-mesh Tyler sieve, and the percentages of re-agents are based on the dry weight of the feed. Du-ring the grinding, the hydrophobic particles transfer into the oil phase to produce coherent semi-solid bodies while the gangue stays preferentially in the aqueous phase. The concentrate can be separated from the gangue easily by a mechanical operation. Using an ore containing about 0.3 -0.5 per cent tin, grades of from 1.5 to 7.0 per cent were obtained by varying the pH of the system. Recoveries fell from about 80 per cent to as low as 50 per cent as the grade in-creased."

Jan 1, 1966