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In the screening process, used to prepare particles for many applications, shape is known to have a significant effect. The degree of flakiness of construction aggregates has been considered particularly important. The objective of this research was to find values of operating parameters that optimize the separation of flaky from non-flaky particles by slotted screens. Thus an investigation was conducted to experimentally determine the influence of the particle size and thickness on the screening process. The Response surface method was employed for modelling and analysis of the data. Experiments employing a central composite design were performed on a pilot-scale, rectangular-aperture, vibrating screen to examine the effects of the screening variables the mass recovery of flaky and non-flaky particles to the oversize product. The SAS statistics package was used to fit a second-order model to each response and to analyze the fitted surface to determine the optimum levels. The optimization associated with a dual response system was then considered. The results of this study should provide a basis for optimizing screening conditions to obtain maximum recovery of non-flaky particles to the screen oversize while minimizing the recovery of flaky particles, which should be of interest to the aggregate industries.

Jan 1, 1999

By Farrel W. Lytle

An X-ray emission spectrographic method of analysis is presented for determining rare-earth elements in fractions obtained from bastnaesite ore. The method includes determination of yttrium, thorium, lanthanum, and the rare-earth elements in various complex mixtures. The analysis technique is based upon comparing the samples with synthetic standards approximating the composition of the samples. Working curves are plotted on an absolute-intensity basis, with no correction for back-ground. Examples of working curves and the analyses of typical rare-earth concentrates are included. The selection of spectral lines for the various sample matrices is discussed. A special technique is used for samples in which rapid hydration and carbonation occurred. By analyzing synthetic samples of known composition, the accuracy of the method was determined. The average error of analysis was about 3 percent of the amount present in the range from 5 to 100 percent and about 7 percent in the 0.2-to 5-percent range. A maximum of about 40 samples per day may be analyzed for 7 elements each.

Jan 1, 1957

By J. A. Broggi

América es un continente geológico que contiene riquezas minerales descubiertas, pero que a su vez devela otros valores ocultos en su interior. En este aspecto se requiere la realización de un afloramiento mineralizado en condiciones de visibilidad, a fin de percibir mejor las particularidades que se encuentran ellas y evaluar si los carácteres favorales de tal superficie persistirán en profundidad. Por tal motivo, el objetivo del trabajo es resaltar la importancia de este procedimiento en relación a la demanda industrial, asi como revisar los afloramientos de carácter primario y secundario, en tanto ofrezca un tipo de alteración química en su interior y exterior respectivamente. Asimismo, señale la necesidad de registrar las incidencias de una explotación, como documentos de gran valor para el desenvolvimiento de la geología económica y progreso de la minería.

Jul 20, 1955

By You-Hai Wen, Yinkai Lei, Tian-Le Cheng

A phase field model is developed to simulate the performance of SOFC electrodes. By solving the conduction equations on both the electrolyte and electrode phases, and incorporating the three-dimensional microstructure and reaction front at triple phase boundaries, the current-voltage relation of an electrode is directly simulated. By further coupling it to our recently developed coarsening model, we are able to investigate the effect of initial microstructure on the performance degradation in SOFC electrode. This model is applied to LSM-YSZ cathodes with different LSM volume fraction. The volume fraction effect on the electrode performance and its degradation rate has been analyzed and discussed.

Mar 1, 2018

By Carlos Varela Castillo

El texto describe el proceso de ensayo de fabricación de arrabio en los hornos eléctricos de reducción de Chimbote, utilizando la escoria de acería eléctrica. Para ello, se muestran los resultados de los cálculos de la escoria, cuadros de análisis de arrabio, escoria y gas de reducción, así como el consumo mensual de materías primas, producción, arrabio, potencia promedio y porcentaje de marcha del horno de reducción. Concluyendo que el uso de escoria elimina el empleo del manganeso y reduce de un 30 a 40% el consumo de piedra caliza por tonelada de arrabio, aumentando la producción del mismo y solucionando el problema de almacenamiento. De otro lado, las dificultades en el uso de la escoria de aceración eléctrica son su falta de homogenidad química y física, y contenido de fósforo que limita su mayor utilización.

Jul 20, 1961

By Douglas M. Smith

The town of Tayoltita, Durango is located at the bottom of the 2000 m. deep Rio Piaxtla canyon on the axis of the rugged Sierra Madre Occidental mountain range. Throughout most of the year access to the town is restricted to travel by mule or STOL aircraft. Silver and gold have been produced from epithermal veins in the north side of the canyon since 1757. During the last seventy-three years more than 4,588,000 kg. of silver and 76,322 kg. of gold have been produced from approximately 6,000,000 metric tons of ore. The Tayoltita mine is developed within a fault block bounded by normal faults which strike north-northwest and have opposing dips. A thickness of at least 1300 meters of late Cretaceous or early Tertiary volcanic rocks is exposed in the mine. These range in composition from andesite to rhyolite. Andesite predominates in the upper 750 meters of the section. The volcanic rocks were passively intruded by quartz-monzonite and andesite stocks during middle (?) Tertiary time. Mineralization spatially and temporally (?) related to the stocks occurs along the east boundary fault and in intersecting footwall fissures which strike east-west and northeast. Ore was deposited over a vertical range of up to 600 m. prior to tilting of the volcanic rocks 35 to 45° to the east. With few exceptions, the ore bodies are found within the lower 400 to 500 m. of the andesite. Argentite (acanthite), stromeyerite, jalpaite, electrum and native silver are the principal ore minerals. They occur in gangue composed of one or more of the following: quartz, calcite, bustamite, adularia, chlorite, and albite. Base-metal sulfides make up less than 1.5 percent by weight of the ore.

Jan 1, 1974

By Michael A. Poling

Ladies and gentlemen, I appreciate this opportunity to be with you, and to share my outlook on the future of Federal coal leasing. I'm told that you wanted the best speaker on this subject in the world. Perhaps it's a reflection of these trying financial times, but I'm glad you finally agreed to settle for the best speaker your budget would afford. I have been asked to give you some insight on the status of Federal coal leasing, and how the budget problems facing the Department will affect the coal program. So I've polished up my crystal ball, and I'll try to give you a peek at the future. Before I do that, however, let me first go back in time - to when this Administration took office in 1981. We had a coal program then, after a hiatus of ten years. But that program was untested and - for reasons well known to all of you - did not work well in practice once we began operating the program. We went back to the drawing board and redesigned the program so that it can do what it is intended to do. We've made the program more predictable. That means that when future lease sales are scheduled, those sales will be reflective and reactive to the need to lease coal. On February 26, Secretary Hodel unveiled a framework for resumption of Federal leasing program activities, ending a more than two-year suspension of regional coal sales. The new program will provide the opportunity to satisfy market demand for acquiring and developing new leases, assure the government of fair market value for its coal reserves, and provide a stable supply of coal for this country's energy needs. The new program grew out of the Department's response to recommendations of the Linowes Commission and the Office of Technology Assessment, coupled with a supplemental environmental study. The Linowes Report, issued in 1984, contained 36 recommendations and three Judgments on leasing levels, tract selection, sale procedures, appraisal methods, key statutory and related factors, and organization and management of the leasing program. Major changes in the new leasing program reflect these concerns. We have developed a definition for captive tracts and devised procedures to appraise their value to the adjacent coal or mine owner. Other steps include a coal lease appraisal guide which describes our appraisal methodology and is available to the public. Improvements have also been made in the gathering of lease assignment information to help in estimating the value of potential lease tracts. To improve market analysis, a three-tiered system will be used to ensure that steps of the lease sale decision process are undertaken in the context of coal supply and demand. Regional Coal Teams will thus have the advantage of long range, regional and tract specific market studies to help them determine whether sufficient demand is expected first to warrant the initiation of activity planning, then to set regional leasing levels, and finally to actually offer specific tracts for lease sale. Sale procedures will also be improved in many ways to encourage competition, improve the chances for receiving adequate bids, and to evaluate whether bids represent fair market value. We made additional modifications to the program in response to the OTA recommendations. Regional Coal Teams have been given a larger role in recommending key decisions concerning the amounts of coal to be studied and the actual selection and scheduling of tracts for lease sale. These recommendations will be accepted unless the Secretary can cite an overriding national interest factor, or a governor's request to modify the recommendations. Smaller, more frequent sales will be held, to better judge market conditions and prevent over- or under-leasing. Public participation guidelines have been written, to document all opportunities for the public to comment at various stages in the planning process. We also decided that resource management plans prepared after the passage of FLPMA in 1976 must be completed, in order for a new round of lease sale planning to begin. The BLM will also beef up its procedures for consulting with affected Federal agencies during the planning process, to assure that the purposes and values of those agencies are considered and factored into land use decisions. To assure consistent use of an adequate data base in coal lease decision-making, Regional Coal Teams will develop standards and guidelines for data adequacy, and document the use of these standards. These procedures will also be applied to the unsuitability criteria screening process. Thus, the new leasing system announced by Secretary Hodel: is fully responsive to recommendations made by the Linowes Commission and the Office of Technology Assessment for improving environmental planning and fair market value procedures; gives the regional coal teams a major say in determining leasing levels, and on the timing,

Jan 1, 1986

By C. Mattich, A. L. Beyzavi

The Waelz Plant at Taiwan Steel Union Co. Ltd. (TSU) was erected within nine months from September 1, 1998 to May 15, 1999. The nominal capacity of the plant is 50,000 tonnes per year of electric are furnace dust (EAFD). The plant, consisting of material handling, a waelz kiln, a waste gas cleaning system, waelz oxide leaching and waste water treatment, was commissioned within three months from July 1, 1999 until October 12, 1999. The specific problem of the plant is the high chlorine content in the EAFD pellets which is up to 6 %. Lurgi Metallurgie GmbH, Frankfurt, Germany was responsible for the engineering erection and commissioning of the plant.

Jan 1, 2000

By Emad Farouz, Roger Failmezger

"The proposed reconstruction of I-75 downtown consists of widening an approximately 2.46 Km section of IR-75 through the northern section of downtown Dayton, OH, USA. Bridge B-13 is a 9-span continuos prestressed concrete I-beam, 319.0-meter (1,048-foot) long bridge with a stub abutment on MSE walls for the rear abutment, and a stub abutment with spill-through slopes for the forward abutment. The piers in the river were located parallel to the Great Miami River, and are full-height reinforced concrete walls. PRESSUREMETER TEST PROCEDUREThe driller advanced either casing or augers approximately 1 meter above the pressuremeter test. Steel casing was used to advance borings performed in the river, and augers were used for borings on land. Mud rotary drilling with a large diameter roller bit was used to remove all of the gravel and cobble fragments inside the casing or augers.At the pressuremeter test elevation the driller used a 63.5-mm (2.5-inch) carbide button bi-cone bit, using a rotation rate of about 60 rpm, a mud fl ow rate of about 10 gallons per minute (40 liters per minute), and an advance rate of 6 to 10 minutes per meter (2 to 3 minutes per foot). To minimize vibrations, advance rates were slower where excessive cobbles were encountered. The 63.5-mm (2.5-inch) O.D. slotted casing pressuremeter was lowered to the test elevation, often requiring either pushing or hammering into the test zone. We believe that the test zone was not perfectly straight, or that gravel or cobble fragments jutted into the test zone and had to be displaced to advance the pressuremeter into the test zone. The slotted casing prevented membrane damage during insertion. A photograph of the slotted casing being lowered into the borehole is shown below.The pressuremeter was calibrated for system compressibility and membrane resistance. At full expansion of 800 cm3, the membrane resistance of the slotted casing was about 2.5 bars.Strain-controlled tests were performed using a Texam control unit with a monocell probe. Volume increments of 20 cm3 were injected into the probe and corresponding pressures were measured. Near the end of the elastic portion of the test, an unload-reload cycle was done. A creep test was performed for 10 minutes at the next volume increment. The test continued until either 800 cm3 were injected or the membrane burst."

Jan 1, 2007

By Emad Farouz, Roger Failmezger

"The proposed reconstruction of I-75 downtown consists of widening an approximately 2.46 Km section of IR-75 through the northern section of downtown Dayton, OH, USA. Bridge B-13 is a 9-span continuos prestressed concrete I-beam, 319.0-meter (1,048-foot) long bridge with a stub abutment on MSE walls for the rear abutment, and a stub abutment with spill-through slopes for the forward abutment. The piers in the river were located parallel to the Great Miami River, and are full-height reinforced concrete wallsPRESSUREMETER TEST PROCEDUREThe driller advanced either casing or augers approximately 1 meter above the pressuremeter test. Steel casing was used to advance borings performed in the river, and augers were used for borings on land. Mud rotary drilling with a large diameter roller bit was used to remove all of the gravel and cobble fragments inside the casing or augers.At the pressuremeter test elevation the driller used a 63.5-mm (2.5-inch) carbide button bi-cone bit, using a rotation rate of about 60 rpm, a mud fl ow rate of about 10 gallons per minute (40 liters per minute), and an advance rate of 6 to 10 minutes per meter (2 to 3 minutes per foot). To minimize vibrations, advance rates were slower where excessive cobbles were encountered. The 63.5-mm (2.5-inch) O.D. slotted casing pressuremeter was lowered to the test elevation, often requiring either pushing or hammering into the test zone. We believe that the test zone was not perfectly straight, or that gravel or cobble fragments jutted into the test zone and had to be displaced to advance the pressuremeter into the test zone. The slotted casing prevented membrane damage during insertion. A photograph of the slotted casing being lowered into the borehole is shown below.The pressuremeter was calibrated for system compressibility and membrane resistance. At full expansion of 800 cm3, the membrane resistance of the slotted casing was about 2.5 bars.Strain-controlled tests were performed using a Texam control unit with a monocell probe. Volume increments of 20 cm3 were injected into the probe and corresponding pressures were measured. Near the end of the elastic portion of the test, an unload-reload cycle was done. A creep test was performed for 10 minutes at the next volume increment. The test continued until either 800 cm3 were injected or the membrane burst."

Jan 1, 2007

By Carl F. Cline, Richard R. Vandervoort, Willis L. Barmore

THE objective of this investigation was to determine the high-temperature plastic deformation behavior of stoichiometric uranium mononitride as a function of stress and temperature. Interest in the properties of this material stems from its potential use in high-temperature nuclear reactor systems. The creep of other refractory compounds containing uranium (e.g., U02, UC) has been studied by various investigators.1"4 Fassler et al.4 have studied the creep of UN in vacuum from 1100° to 1350°C at stresses of 6000 and 8000 psi. In the present work, the creep of stoichiometric UN was investigated from 1500° to 1800°C at stresses from 2000 to 5000 psi in a partial pressure of 200 mm of nitrogen. The specimens were prepared by hot isostatic pressing of UN powder into cylinders of $ in. diam by about 1 in. high. After pressing, the specimens were heat-treated in nitrogen at 1900°C for 50 hr. The densities of individual specimens were determined by the water displacement method. All specimens were theoretically dense, based on a value of 14.32 g per cu cm.5 Principal metallic impurities in ppm by weight were: Ca, 50; Cu, 5; Fe, 30; Mg, 5; Ni, 10; and Si, 20. Oxygen content was 400 ± 50 pprn and carbon content was 100 i25 ppm. The nitrogen content was 5.56 ±0.05 wt pct. The average grain size for five specimens, as determined by the intercept method, was 0.14 i 0.01 mm. One specimen had a grain size of 2.0 mm. This large grain size is an anomaly, since all specimens had the same chemical and thermal histories. Specimens of 1/4 in. diam by 1/2 in. high were creep-tested in compression in a clam shell furnace heated by W-25 pct Re sheet elements. Temperature was measured to ilODC by an optical pyrometer which had been calibrated by a standard source. The distance between fiducial marks on the specimen was measured before placement into the furnace. The furnace chamber was evacuated to 10-5 Torr and back-filled to 200 mm N2. After heating rapidly to temperature, the load was applied and controlled to ±2 pct by an Instron testing machine. Upon initial loading, the specimen was deformed until a constant crosshead rate was obtained, then quenched to room temperature, remeasured, and replaced in the furnace. Upon subsequent reloading at temperature, the crosshead rate was constant for the selected condition indicating steady-state creep.

Jan 1, 1969

By I. A. Ibrahim, A. K. Ismail, A. A. I. Afifi

"Synthetic rutile for paints industry is conventionally produced by a combined smelting and leaching process. Smelting process is an energy intensive step and represents economic burden in view of the increasing energy costs. Egyptian ilmenite ore containing 40% TiO2 and 38% total Fe was thus directly leached with sulphuric acid to produce eventually synthetic rutile. The process-involves digestion of the ore with sulphuric acid whereby both TiO2 and Fe are dissolved. The solution was then treated with iron powder to convert Fe3+ to Fe2+ to avoid co-precipitation of iron during the hydrolysis step. After solid/liquid separation and clarification, Fe was crystallized as ferrous sulphate hydrate by chilling. The titanium pregnant liquor was concentrated by evaporation and then hydrolyzed to precipitate hydrated titanium dioxide which was then calcined to produce synthetic rutile containing 98.6 TiO2 and 0.58% Fe2O 3. The optimum conditions of all the processing stages were determined.IntroductionSynthetic rutile for paints, welding rods and other industries could be produced from ilmenite ore by sulfuric acid leaching process. This process is a batch process and nearly 80% of all TiO2 produced in the world is made by this process [1]. Figure l shows simple block flowsheet of the process. The process involves the following stages.Digestion: In this stage, ilmenite ore is treated with concentrated sulfuric acid where both iron and titanium are converted to their respective sulfates according to the following equations:"

Jan 1, 2000

By Harry E. Holzschuh

The two Agrico Chemical Company self unloading Phosphate Rock barges put into service in 1976 operate at over their design carrying capacity. Each barge now carries 26,000 short ton instead of the planned 25,000 short ton at 32 foot of draft. They are in service between Agrico's Tampa, Florida Terminal and the Donaldsonville, Louisiana Fertilizer Complex, moving a total of 2,500,000 short tons each year. This was the first use of the Parascrew design for a marine application. The barges, with their 3,000 STPH unloading and matching loading rate is the vital link in this total transportation and handling system. Rock is moved from the Pierce, Florida Mines through the Tampa Big Bend Terminal, across the Gulf of Mexico, and up the Mississippi to the Agrico Faustina Phosphoric Acid Plant 30 miles below Bacon Rouge, Louisiana. The trip from the terminal to the plant is 600 miles and the turnaround time is just about six days. Seven years operating experience has proved that the system works. Fittingly, the two barges are named the "Faustina" and the "Pierce". They have a beam of 85-feet and are 495 feet long. folded depth is 43 feet, with a ballasted light draft of 19 feet and a typical loaded draft of 32 feet. There are four separated holds with the machinery room located forward of 101 hold. Each hold is 51 feet wide at the coamings with an 18 foot straight section on the side, and a 24 foot long, 600 slope sheet for a 23 foot clear reclaim width at the bottom. The Parascrew in each of the holds is 37 feet long between the bearings and is supported on a 14 inch diameter hollow shaft. The screw pitch varies and the diameter of the flights step up from l'-9" diameter to 2'-6" diameter on the discharge end. By sloping the centerline, a minimum four inch bottom clearance is maintained across the hold. Some bending of the tube does take place.

Jan 1, 1983

By W. J. Fene

Ventilation is undoubtedly the greatest single safety factor in the operation of a coal mine. Any condition or occurrence that interrupts the ventilating current or changes its normal course through the mine workings is a distinct hazard and should be considered as such by every coal-mine owner, operator, and worker. The hazard, of course, is much greater in a mine that is emitting gas, as an explosive mixture can accumulate in a very short period if the ventilating current is interrupted. It is common to find one or more entries producing 600 cubic feet or more of methane per hour. If the ventilating current were short-circuited from these entries for 15 minutes, there would be an accumulation of 150 cubic feet of methane, which, when mixed with enough air to dilute it to the lowest explosive point, would make about 3,000 cubic feet of explosive mixture; this gas could be ignited in almost any normally operated mine by a cutting machine or other electrical equipment. The ignition of this quantity of an explosive gas-air mixture can readily cause an explosion of coal dust that would completely wreck the underground workings and possibly some of the surface structures. In fact, the ignition of one-tenth of the above quantity of an explosive mixture of gas and air might readily start an explosion that would, extend through every part of a large mine. The possibility of occurrence of interruptions to the ventilating current has received comparatively little consideration from mine owners, operators, and workers in many parts of the United States. Such a possibility should be considered in connection with every mine that gives off explosive gas, and steps should be taken to prevent it.

Jan 1, 1943

By M. Shamsi, M. Nehring

One of the most challenging aspects in semi-mobile in-pit crushing and conveying (SMIPCC) system design is determining the optimum depth at which to change from a purely truck-based haulage system to a conveyor-based haulage system. We used scenario analysis to determine the optimum transition depth between a truck and shovel (TS) system and a SMIPCC system. Traditional pit-limit algorithms were used to generate the final pit limit on a copper deposit, which was then divided into four pushbacks. The final operating pushbacks (phases) were designed for both TS and SMIPCC. The end depths for each phase are viewed as candidate transition points to switch from the TS to SMIPCC haulage system. Economic calculations were applied for five different scenarios, including adopting SMIPCC from the outset (pure SMIPCC), after the first, second, and third phases, and finally not using the SMIPCC system (pure TS) at all. The analysis indicates that the second scenario, at a depth of 335 m, results in the lowest cumulative discounted cost (CDC). In this case, the CDC is 17.6% lower than that for the pure TS scenario and 10.7% lower than for the pure SMIPCC system scenario.

Sep 1, 2021

By Tracy Brettmann, Shailendra Endley, Jason Leary, Shashank Valluru

"Augered Cast-in-Place (ACIP) piles have long been used for deep foundation support in sands due to their high capacity and speed of installation. Very little information exists on the effects on capacity if the auger needs to be withdrawn from the hole prior to grouting. This condition can occur due to various reasons including grout plug ups, equipment issues, and grout supply delivery problems. It can become a major problem for the project team if this happens during production because the capacity of that pile is then in question, potentially resulting in re-design, installation of replacement piles and/or schedule delays. This paper compares the results of two high capacity test piles installed into a dense sand where one test pile was installed by first completely withdrawing the auger from the hole after drilling to the pile tip depth and the other test pile was installed utilizing conventional industry standard methods. Identical load tests were then performed on both piles to compare the effects of the two different installation procedures. The load test results were surprisingly similar in this case although the grout take required for the test pile installed in the pre-drilled hole was significantly higher to produce a similar grout return depth.IntroductionAugered Cast-in-Place (ACIP) piles are used extensively along the Texas Gulf Coast due to their combination of high capacity and speed of installation resulting in one of the most cost effective deep foundation systems relative to other options. Soil conditions in this region typically consist of alternating layers of sand and clay in the upper several hundred feet. ACIP piles are routinely installed to depths of over 100-ft to achieve the required capacity depending on the site specific soil conditions and therefore typically extend through and tip into sand layers. Occasionally, due to various reasons like equipment issues and plug-ups, the auger is withdrawn from the hole without grouting. Significant sand in the soil profile could lead to questions about the effect of the auger withdrawal on the pile capacity and load deflection relationship.This paper summarizes the results of two identical pile load tests performed on adjacent piles of the same length with the main difference being one was installed using the standard installation procedure and the other was installed by first completely withdrawing the auger from the hole after drilling to the pile tip depth. The load test results were then evaluated using load transfer analyses to estimate the effect of the withdrawal of the auger on the load-deflection characteristics and capacity."

Jan 1, 2017

By Luis Hochschild

"El presente texto señala las posibilidades y problemas de la minería en el Perú. Para ello, primero se revisa los factores que afectan la pequeña y gran minería tales como: los impuestos, agua, agilización de la mina, desarrollo zonal, carreteras, denuncios, permisos para reinversiones adecuadas. Asímismo, se debe analizar este poder de inversión y actualizarlo cuando se le utilice para fines específicos como: construcción de campamentos, colegios, hospitales, etc y esto debe regir para la pequeña, mediana y gran minería, ya que la inversión que haga cualquiera de ellas será en beneficio del trabajador peruano. "

Jul 1, 1969

By V. Maseko, C. Musingwini

"When considered collectively, Mineral Resources and Mineral Reserves are arguably a key asset for any mining company. Mineral Reserves are the economically mineable portions of Mineral Resources. They therefore provide a good indication of the economic prospects in the short to medium term and associated non-financial impairments for mining companies, hence a focus on Mineral Reserves. An assessment of modifying factors for converting Mineral Resources to Mineral Reserves revealed that Mineral Reserves were most sensitive to long-term commodity prices, hence the focus on long-term commodity prices. The justification for selecting gold and platinum mines is that they collectively make a significant contribution to South Africa’s earnings from mining.The introduction of the South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves (SAMREC Code) in 2000 informed the basis for analysing long-term commodity price assumptions for major South African gold and platinum mining companies between 2000 and 2016. The analysis revealed that the least number of non-financial impairments occurred when long-term commodity prices were within ±5% of spot prices. This finding suggests that this range is the ideal range for long-term commodity price assumptions to improve confidence in Mineral Reserve declarations and minimize impairments. Introduction The South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves (SAMREC Code) defines a Mineral Resource as ‘a concentration or occurrence of solid material of economic interest in or on the Earth’s crust in such form, grade or quality and quantity that there are reasonable prospects for eventual economic extraction’ (SAMREC, 2016, p. 18). Mineral Resources are categorized according to increasing levels of geoscientific confidence or knowledge, from Inferred to Indicated and lastly, Measured categories. The SAMREC Code defines a Mineral Reserve as ‘the economically mineable part of a Measured and/or Indicated Mineral Resource’ (SAMREC, 2016, p. 25). In some of the other reporting codes such as the Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (the JORC Code), a Mineral Reserve is synonymous with an Ore Reserve. The conversion of Mineral Resources to Mineral Reserves involves applying modifying factors, which are non-resource considerations. The modifying factors used in the Mineral Reserve estimation process include mining, metallurgical, processing, infrastructure, economic, marketing, legal, environmental, social, and governmental factors. Each of these modifying factors consists of several components which require due consideration in the estimation of Mineral Reserves. Table I shows some of the components typically considered for each of the modifying factors."

Mar 1, 2019

By O. M. Bishop

"SUMMARYAs a result of the increased demand for fluorspar during the war, the Bureau of Mines investigated numerous fluorspar properties in the southern Illinois field, which is centered in Rosiclare. Among these the J. J. Shelby 40-acre tract on the western edge of the district presented favorable factors that caused it to be chosen /or exploration.H. G. Spiller, formen lessee of the property, had explored the Shelby vein by means of an adit level and winze, and showed it to contain goad values in zinc and fluorspar at the depth explored. A diamond-drill hole with which Spiller explored the vein 78 feet southwest of the winze, however, failed to cut ore. After studying the field evidence, the Bureau concluded that the vein merited further exploration, particularly at a depth of about 440 feet, where the Fredonia limestone would form the foot-wall of the vein and the hanging wall would be the competent Cypress sandstone.Between October 17, 1944, and March 26, 1945, three diamond-drill holes were bored for a total inclined depth of 1,592 feet. Holes 1 and spaced approximately 500 feet apart, explored the vein at 440 feet 4 below the surface. The economic mineralization existed in the vein where cut. Hole 3 cut the fault at approximately 300 feet below the outcrop but failed to find any vein matter except stringers of calcite with small amounts of pyrite."

Apr 1, 1947

By Hallet R. Robbins

KOREA, the ancient " Hermit Kingdom," is a peninsula jutting out from the coast of eastern Asia. By the natives it is called " Chosen," which, translated, means " Land of the Morning Calm." It lies between the Yellow sea and the Sea of Japan. On the north it is separated from Manchuria and the Russian province of Primorsk by the Yalu and Tiumen rivers ; on the south the Korean straits interpose a rough voyage of 120 miles to the nearest point in Japan. The entire country is situated between the parallels of 34° and 42° N. latitude. The surface of the country is made up of successive ranges of unglaciated mountains, separated by narrow, fertile, and more or less densely populated, valleys. Through all the obscure centuries of its history, Korea has succeeded in maintaining a monastic seclusion, over which, from time immemorial until the late Chino-Japanese war in 1894, China exercised a shadowy sovereignty. Although Korea had been forced into slight foreign contact previously, her first foreign treaty was signed with Japan in 1876. Under the restraining guardianship of China, the Japanese treaty bore but insignificant innovations for Korea; but when, in 1883, a treaty was made with the United States, the first of the western nations, a decade after the American gunboats, under Commodore Rodgers and Lieutenant Schley, forced their way up the Salee river, shooting daylight through the ancient walls and fastnesses, Korea awoke from her sleep of 4,000 years. The Korean peninsula suddenly became the arena where rival nations' enterprises and individuals met in fiercest conflict. Out of this struggle grew two singularly successful American

Jan 7, 1908