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By Ch. Houston

El presente estudio refiere los factores que afectan el desarrollo minero mundial a partir de una política minera canadiense. En este sentido, la presencia de riquezas naturales, el fácil acceso, la continua predisposición a las inversiones de propietarios extranjeros, las buenas relaciones entre el comercio y el gobierno y el acceso a los mercados se constituyen como factores esenciales en el desarrollo de la producción minera del país norteamericano. Cabe agregar que la educación y la tecnología son los pilares de la conducción de este desaroollo minero, ofreciendo beneficios a los países que esten preparados en torno al conocimiento minero.

Nov 20, 1972

By Peter Zamora

Dado que ya no es posible confiar en el incremento industrial de las materias primas de las especies minerales y no metálicos de la tierra -en tanto estas son caracterizadas por condiciones minero-geológicas favorables-, el presente texto refiere posibles soluciones a través de yacimientos de grandes profundidades, condiciones desfavorables y de ley más baja que el mineral y así proceder a la explotación de los llamados yacimientos pequeños que hasta ahora han sido registrados y balanceados en el marco de la llamada "riqueza metálica" de tal o cual Estado, pero que no fueron considerados como industrialmente explotables a título de la explotación económica y técnicamente poco efectiva. Asimismo, la explotación de yacimientos minerales pequeños por los métodos clásicos de explotación masiva con utilización de la mecanización minera automóvil libre de carriles y la aplicación de los métodos geotecnológicos, elimina los procedimientos clásicos de afloramiento, trae el elemento de movilidad a los equipos de extracción y de beneficio. De esta forma reduce asimismo los costos de inversión de la explotación y permite así su explotación efectiva.

Sep 1, 1981

By Julio Aníbal Morales Pereira

Sabe-se dos problemas associados com as inclusões não metálicas, os quais afetam não somente a operação de fabricação, como também a qualidade do produto final. Por esses motivos, muitos estudos têm sido realizados para melhorar o controle do tamanho, quantidade, forma, distribuição e composição das inclusões. Especificamente para as inclusões de espinélio MgO·Al2O3, ainda é preciso melhorar o entendimento dos fenômenos sobre a formação e modificação destas inclusões para um melhor controle ao longo do processo de fabricação do aço e obter maior limpidez inclusionária nos aços. Assim, neste trabalho, foram revisados tópicos reportados na literatura relacionados com: a formação, influência da composição da escória e modificação com cálcio das inclusões de espinélio.

Aug 16, 2017

By Elliot Gillerman

The title of this paper implies the presence of silver, nickel, and cobalt minerals at, the Alhambra mine. Perhaps this should be amplified to include uranium, as pitchblende also occurs, possibly in mineable quantifies. A brief history of the Alhambra mine is of interest, both from a historical angle and as pointing up the importance of geology in the-present development. The Alhambra is one of several mines in the Bullards Peak or Black Hawk dis¬trict, ass it is more familiarly known, in southwestern. New Mexico, which was mined for silver in the 1880?s and 18901s, Silver valued between $500,000 and $1,000,000 was extracted from the mine in the 10 years prior to 1893, when operations ceased. Almost all the silver mined was native silver, although a small quantity of argentite was produced. Nickel and cobalt were recognized in the ores, but they were thought to be of no consequence.

Jan 1, 1959

By J. Bhattacharya

In many different ways industrial raw materials resources industry as a whole has accepted the principles of sustainable development and has made a commitment to move toward this goal. The critical question now is ?how?? While many companies have adopted policies and are implementing community relations programs, sustainability is not always ?lived? throughout the organization. While traditional programs and commitment from the top are critical, employees within all functional areas can advance sustainability. Individuals can make difference at all organizational levels, and it is this collective action that is so critical for enhanced financial performance as well as the preservation of the industry. Keywords: value chains, sustainability, legislation, auditing process

Sep 1, 2012

By L Tolmay, L Nair

Investor confidence can be compromised when one observes large discrepancies between the SAMREC reserves and the mining plan. It is therefore up to the responsible persons to ensure that all contributing factors get taken into account when determining a reserve declaration. Confounding factors could be further aggravated by large oscillations in the commodity price thus resulting in major changes to the mining plan, if the accepted price was either too optimistic or pessimistic. Additional factors that must receive our attention are, uncertainty in geological facies type, mining practices, geology and grade estimation. The paper outlines (in the authors? opinion) some of the important factors that need to be taken into account, in order to ensure proper alignment between the estimates of the life of mine (LOM) reserve grades, and the corresponding actualisation of the mining plan. These parameters provide an historical insight into what actually happens when attempts are made to implement the mining envisaged in the LOM plan. In turn these allow judicious application of discount factors that enable a realistic estimate of SAMREC reserve classification and declaration. Some of the factors that will be covered are: - 1) Flexibility of developed reserves and the ability to maintain this. 2) Mining control mechanisms and their overall efficacy. 3) The ability to extrapolate facies types and its effect on grade control. 4) The ability to control the mining mix and value variation. 5) Finding a happy medium between optimism and pragmatism.

Jan 1, 2007

The fundamental objective of mine plans are usually to maximize the mine profit by extracting ore at the lowest possible cost over the mine life while some technical constraints are satisfied. Since the costs associated with the operation of trucks and shovels as resources are significant, determining the optimum number and allocation of these resources is an essential issue. This paper presents a Mixed Integer Linear Programming (MILP) model to determine the optimum number of shovels and trucks required to meet the short-term plan?s goals. Also, the model takes into account the allocation of trucks and shovels to mining faces. This model minimizes operational costs, while attempting to meet the production demand and to satisfy technological constraints. This paper also analyzes the operations of trucks and shovels in an open pit mine using ARENA simulation software.

Jan 1, 2012

By Andrew G. Patton

The Alimak mining method was introduced at the David Bell mine in 1998 to extract an otherwise uneconomic and inaccessible reserve. The success associated with the extraction of these reserves led to major expansion of the method. To date, results have been extremely positive in terms of grade control, reduced dilution, stope recoveries, productivities and mining costs. It is hoped that through further development of the method at David Bell mine we will continue to see positive results in these areas and be able to increase mineable reserves to include proven resources that do not currently meet the criteria of our current stoping plan.

Oct 1, 2001

By J. T. Vehkala, S. S. Kerr, D. E. Robertson

"Since the late 1970s, extensive work has been carried out at Placer Dome Inc. 's Dome Mine to develop new mining methods and equipment to improve the productivity of narrow vein mining (Mining Magazine, Oct. 1986, pp. 308-317; Mar. 1988, pp. 176-/79). This work has been focused on mining veintype deposits varying from 0.9 m to 1.5 m in width using open stoping and cut-and-fill mining methods.In 1989, the Dome Mine entered into a contract with Ram Raising Ltd., a joint venture company of Angus Martin and I.S. Redpath Ltd., to develop and mine a narrow vein test stope using an Alimak Raise Climber. Early results have been favourable, indicating that Alimak methods can be used successfully to mine narrow vein are.HistoryThe Dome Mine, which has been in continuous operation since 1910, is located in South Porcupine, part of the city of Timmins, Ontario. The mine is wholly-owned and operated by Placer Dome Inc. and is part of Placer Dome Inc.'s international stable of of 19 mines."

Jan 1, 1990

By Bee R. Waples

The Alimak Raise Method, using the Alimak Climber, has proven to be a new, fast, economical method of driving raises at the Iron King Branch of Shat-tuck Denn Mining Corporation, Humboldt, Arizona. In order to fully understand the advantages of the Alimak Raise Climber, it is necessary first to describe the basic machine; second, a complete cycle of a raise round; and third, the comparative speed and economy afforded the Iron King operation by using this new method of raise driving: The raise climber consists of a drilling platform that is raised and lowered by two 6.2 HP compressed air motors that drive, through roller chains and sprockets, three worm gears connected in series. These worm gears drive pinions which grip the guide rail rack. The worm gems are fitted with spring-loaded couplings so that a small rock or grit in the rack is passed over without disturbing the mesh between the rack and the other pinions.

Jan 1, 1961

Martin Mining and Tunnelling Pty Ltd is a mining contractor with offices in Kalgoorlie, WA, Australia and Timmins, Ontario, Canada.Martin Mining and Tunnelling Pty Ltd offers services in mine contracting which include shaft raising, raise enlarging, excavation of rock passes and ventilating systems. It also offers the mining industry a unique mining method using the Alimak raise climber system.The Alimak raise climber system may be utilised in various types of orebodies, as the system is flexible to change. Sloping widths, drill hole patterns and changes in dip can all be accommodated with this method.This system allows for a highly productive, cost-efficient alternative to conventional longholing methods. This paper will focus on various aspects of the Alimak system which inherently make it a safe, viable method of ore extraction.

Jan 1, 1993

By Alex Salvador

El Comisionamiento de una planta concentradora es un proceso secuencial ordenado y adecuadamente organizado de pruebas de operación con carga, que permite llevar a los diferentes equipos a su capacidad de diseño. Consiste en un proceso de arranque de equipos, seguido de un incremento progresivo de tonelaje de acuerdo a los criterios y protocolos del fabricante.

Sep 29, 2023

By T Connor

Alkali emissions are one of the environmental challenges facing alumina refineries. Queensland Alumina Limited (QAL) is undertaking a number of initiatives to continuously improve its environmental performance. One of these is a program aimed at the reduction of alkali emissions. Alkali emissions originate from a number of sources (eg elevated open tanks), and its level depends on a number of process parameters/ mechanisms (ie splash filling, thermal currents in tanks, streams discharged from a pipe, tank temperatures, atomisation) and climatic conditions (eg wind speed and direction, rain, etc). Under normal operating conditions, there is a continuous low level of alkali emissions from the plant. Certain vessels within the plant have been identified as major contributors to this level of emission, while certain activities within the plant contribute to a temporary elevation (æspikeÆ) of alkali emissions. QAL developed a method using phenolphthalein-treated pads to measure emissions within and outside QAL boundaries. These provide no information about mass emission rates but are important for detecting if alkali material is present. Since mass emission rates are important for determining if improvements in emissions are made, QAL identified the need to design an improved sampling method. Following the development and implementation of a sampling and analysis method to monitor alkali emission concentrations, QAL is conducting a number of feasibility studies evaluating a range of alkali emission reduction options. The alkali measurement method will be used to track and demonstrate progress in this environmental initiative. This paper will discuss the measurement method and emission reduction options being evaluated.

Jan 1, 2005

By Leopoldo Gutierrez

Eight oil sand ores with the bitumen content ranging between 3.6 and 15 wt.% and the fines content (-44 micrometers size fraction) between 9 and 69 vol.% were subjected to the standard alkali extraction test used to measure the degree of oxidation of metallurgical coals. The results showed that there is a strong correlation between the absorbance of extracted solutions at a wavelength of 520 nm and the ratio of the fines content to the bitumen content. The latter factor is directly relevant to assessing the extractability of bitumen from oil sand ores. Bitumen extraction tests showed that the bitumen recovery decreased from 90 % to 30 % when the absorbance at 520 nm increased from 0.23 to 0.64. A comparison of the UV/visible spectra of solutions obtained from the alkali extraction tests with solutions of Aldrich Humic Acids suggest that low bitumen/high fines oil sand ores release substantial amounts of organic matter very similar, if not identical, to humic acids. In contrast, high-bitumen and low-fines ores do not release as much of the organic matter, and UV spectra of these leached substances are quite different from those of humic acids. Overall, the results show that chemical composition of bitumen in the tested ores varies greatly with ore type and oxidation, and that the alkali extraction test is a promising technique to quickly assess the extractability of bitumen from a given ore type.

Sep 1, 2012

By M. Elbert Nigri

Radioactive wastewaters from nuclear source of electrical energy production need to be treated and disposed of properly. Sr, Ca, Mg and Ba are common elements in this effluent, which can cause incrustation in process equipments and being unsafe to human health (90Sr). Fixation of CO2 can be applied to remove the ions mentioned before and to provide a solution where CO2 is sequestered and the deleterious elements precipitated, becoming one of the possible steps to reuse the water into the process. Moreover, removal of several metals from distinct wastewater has been evaluated using bone char through adsorption. The chemical similarity between calcium and strontium makes the exchange of these two metals favorable in the hydroxyapatite structure contained in bone char. This paper evaluated the combined action of precipitation and adsorption process with injection of CO2 and bone char addition in simulated nuclear wastewater. Removal levels of 89.0% (Sr) and 83.3% (Ca) were obtained in the combined process. The presence of bone char as seed increased the precipitation kinetics, allowing a Sr removal of 85.2% in five minutes, higher than 75.3% obtained in absence of seeds. However, removal of 91.6% (Sr) and 89.8% (Ca) were obtained in absence of seeds at 24 h. Analysis of solids have evidenced that CO2 was consumed to precipitate the metals as carbonates, since the hydroxides are formed at higher pH’s.

By Jiayao Wang, Jian Chen, Leiting Shen, Hongyang Wang, Zeping Cao, Ziru Wang

Large amounts of by-products, including coal gangue, circulating fluidized bed (CFB) slag, and coal fly ash (CFA), are generated during mining, washing and burning of high alumina coal (HAC). The stockpile of these by-products of HAC will cause the pollution of air, water and soil. Meanwhile, the unbalanced regional distribution of bauxite and alumina production has been a critical challenge for the sustainability of world alumina refineries, especially for China. Therefore, economical extraction of alumina from by-products of HAC not only resolves the environmental pollution problems caused by stockpile but also decreases the dependence degree of import bauxite in China. Considering the fact that powder alumina can only be produced by alkali methods, the alkali extraction of alumina from by-products of HAC is summarized in this paper. Based on the formation process of by-products of HAC, the principle, research status, and problem of existing methods were analyzed and discussed, as well as the forecast of research trend. The analyses indicate that simplex recovery of alumina from byproducts of HAC generates large amounts of leaching residue (red mud) with difficulty for disposing, while comprehensive extraction of alumina and silica meets the research trend for clean and high-value utilization.

Aug 25, 2023

By William Y. Holland, Roger H. Cook

In view of the increasingly widespread deterioration of concrete structures as the result of the interaction of the alkalies sodium and potassium released by hydration of portland cement and susceptible rocks and minerals in aggregates, it is believed that a paper summarizing the geographic distribution of these aggregates will be of interest to producers and users of concrete, concrete products, and concrete-making materials.

Jan 10, 1953

By Lawson F

Chrome chemicals are commercially produced by the alkali roasting of chromite ores with sodium carbonate. Results of tests conducted in a laboratory furnace indicated that the sodium carbonate reacted rapidly with part of the gangue material to form a metastable intermediate that later reacted further with the chromite. For the conditions used, the recovery of water-soluble sodium chromate was able to be described empirically as yield % = a tn with a = 0.24 T - 241.3; n = 3.90 - 3.12 × 10-3 T and t is the reaction time in hours.The major rate limiting step in the overall reaction sequence appears to be the rate at which oxygen can get to the reaction sites across the liquid film coating the solid reactants.Sodium sulfate alone was found to be an unsatisfactory source of alkali for reaction with chromite. However when limestone also was added in quantities sufficient to allow the reaction CaCO3 + Na2SO4 + H20 ? Ca SO4 + 2NaOH + CO2 to take place, the results obtained were comparable to those found when sodium car-bonate was used.For chromite particles in the size range -124 + 105 µm, the use of stoichiometric excess of sodium carbonate did not appear to increase the yield or the reaction rate significantly. However, with smaller sized particles, - 53 µm, increased yields of water-soluble chromate were obtained when roasted with more than the theoretical quantity of sodium carbonate.

Jan 1, 1984

By R. E. Whitehead

"Abstract - Alkali-alumina and MgO-alumina plots are an effective instrument for displaying chemical and mineralogical compositions of altered and unaltered rhyolites and rhyodacites. They reveal that most supposedly unaltered rhyolites, apart from those of Cenozoic age, have undergone losses in Na2O and gains in K2O. The extreme loss of Na2O from highly altered rhyolites immediately adjacent to VMS deposits is strikingly illustrated by alkali-alumina plots. MgO/Al2O3 vs. K2O/Al2O3 diagrams display a strong negative correlation between MgO and K2O that results from the conversion of sericite to chlorite. A similar negative correlation between MgO and whole-rock d18O is apparent on plots of these two parameters. Alkali-alumina plots underscore problems in selecting appropriate precursor compositions required for mass-balance calculations. Molar ratio plots are a viable alternative to such calculations. Sommaire -Les diagrammes alcali-alumine et MgO-alumine constituent un instrument efficace pour la représentation des compositions chimiques et minéralogiques des rhyolites et rhyodacites altérées et fraîches.Ces diagrammes révèlent qu’à l'exception de celles d’âge Cénozoïque, la plupart des rhyolites qualifiées de fraîches ont subi une perte de Na2O et un gain de K2O. L’intense perte en Na2O que l’on note dans les rhyolites fortement altérées associées aux gîtes de type SMV est particulièrement bien mise en évidence par le diagramme alcali-alumine. Le diagramme MgO/Al2O3 vs. K2O/Al2O3 montre une forte corrélation inverse entre le MgO et le K2O due à la conversion de la séricite en chlorite. Une corrélation inverse analogue entre le MgO et le d18O de la roche totale s’observe sur un graphe comparant ces deux paramètres. L’usage du diagramme alcali-alumine fait ressortir combien il peut être difficile de choisir un précurseur de composition appropriée pour des calculs de balance de masse. Les diagrammes de rapport molaire constituent une alternative à de tels calculs."

Jan 1, 2006

By M. L. Leming

Introduction In the decades since silica gel was first identified in material exuding from cracked concrete, a great deal of research has been conducted regarding the chemical reactions between the alkalies found in portland cement and silica found in aggregates. The reaction is complex and one that is not yet completely predictable, especially from the point of view of developing specifications that are appropriate to all situations. This paper is not intended to be a rigorous review of the research findings but is an attempt to provide a simplified review of the mechanisms of the alkali-silica reaction (ASR), so that one can better understand the implications of the specifications, test results and effects on structures. In addition, the contractual relationships between the aggregate supplier and one of their major clients, the concrete supplier, will be examined with regard to the ASR. ASR basics Silica. Silica (silicon oxide) may exist in naturally occurring aggregates in various forms and in combination with a number of other elements. When the silica is completely crystalline, such as in quartz, it is chemically and mechanically stable. Quartz silica is impermeable and reacts only on the surface of the crystal, where the silicon and oxygen bonds are broken. Because the surface area per unit volume of most quartz is low, the reactivity is also low. Completely amorphous (noncrystalline) silica is, on the other hand, more porous and very reactive. The less "crystalline" the silica is in the aggregate, the more reactive. Silica that has melted and cooled quickly without recrystallizing, creating a glassy material (such as in certain volcanic aggregates), has a very low state of crystallization and will be much more reactive in an alkaline solution. Crystalline silica that has been transformed by heat and pressure may have a large quantity of strain energy stored in the crystal lattice. The presence of this higher energy will make the silica more likely to react. The "strained quartz" found in many metamorphic aggregates means that these aggregates are potentially susceptible to deleterious alkali silica reactivity, although the rate of reaction is typically much slower than with aggregates composed of or containing glassy or amorphous silicas. Another problem may exist with aggregates in which the silica is primarily crystalline. In aggregates such as chert, in which the silica exists as very fine crystals (i.e., crypto- or microcrystalline), the very high surface energies between the crystals contribute to alkali sensitivity. Therefore, the potential reactivity of an aggregate is seen to be a function of both the degree of crystallization of the silica in the aggregate and the amount of energy stored in the crystal structure, whether due to a large quantity of microcrystalline silica, a high strain energy stored in the crystals or some combination of these factors. The surface area per unit volume of the reactive silica will also affect the rate of reaction, because a larger surface area of reactive silica will have more opportunity to react. Obviously, the reactivity of the aggregate is also affected by the silica content. However, in this case, the results are not quite so obvious. A discussion of the effect of silica content will be postponed until after a discussion of the contribution of the cement paste. Paste characteristics. Hydrated portland cement is a very alkaline material with a pore solution pH typically in excess of 12. The alkaline environment of moist concrete provides an ideal place for noncrystalline or cryptocrystalline silica to react. However, not all alkalies are equal in their effects. Calcium compounds react with glassy silica to form calcium silicate hydrate, commonly abbreviated C-S-H a poorly crystalline material that can occur in several forms and chemical compositions. C-S-H was at one time called tobermorite gel, because it was chemically similar to the naturally occurring crystalline mineral tobermorite and because it had a gel-like (noncrystalline) structure when viewed under an optical microscope. The formation of C-S-H is the basis for both portland cement hydration and reaction with, for example, fly ash. C-S-H is relatively stable. Although drying will cause some shrinkage and rewetting will cause some expansion, the volume stability of the C-S-H is very good compared to the volume stability of most alkali silica gels. Alkali silica gels with high sodium contents, for example, are nonstable compared to C-S-H.

Jan 1, 1997