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By R. R. Irrinki

Abstract -The Key Anacon deposit consists of four sulfide zones called, from south to north : Key Anacon No. 1, Key Anacon No. 2, Key Anacon No. 3, and Key Anacon Copper Zone. Massive sulfides of zones 1, 2, and 3 are underlain by rocks correlated with the Nepisiguit Falls Formation and are overlain by matie volcanic rocks correlative with the Boucher Brook Formation. In contrast to zones 1, 2, and 3, narrow northwesterly-trend.ing, copper-rich fracture zones occur within the Patrick Brook Formation. Sulfides in zone 2 occur as three mineralogical associations, namely: pyrite-chalcopyrite, pyrite-sphalerite-galerta, and pyrrhotite-sphalerite-galerta. The distribution of lithologies and en-echelon patterns of the three sulfide lenses of Key Anacon No. 2 zone are the result of F1 and F2 folding. Zone 2 is the most promising economically, with proven reserves of 1.11 million tonnes grading 0.2207o Cu, 3.47% Pb, 8.41% Zn, and 96 g/t Ag; the zone is open below a depth of 427 m.

Jan 1, 1992

By A. J. Pearce

MOST mines have a model of some kind to illustrate either geological structure, mining operation, or some special condition or feature of the property. The type used depends on the particular feature or use for which it is intended. At Dome Mines we have developed an interesting and practical application of the horizontal-type model. This model shows the workings of each level horizon plotted on glass. These glass panes are set in frames which, in turn, rest on drawers equipped with rollers which can be pulled out as desired into a light chamber. The features of this model are its rigid steel construction and that any desired number of level plans can be pulled out, eliminating any other interference from other levels. Figures 1 and 2 are photographs of the model cabinet and show its construction and general features. The cabinet is of steel construction with the following overall dimensions: width, 6 ft. 5 in.; depth, 6 ft. 7 in.; height, 5 ft. 2 in. When not in use it can be completely closed-in, making the cabinet practically dustproof. There are 30 drawers, one for each of the 29 levels and one for the surface. The glass in each drawer is divided into two panes, 36 in. by 36 in., of flatdrawn double-diamond 'lustraglass' with about l/32 in. between adjacent edges. The panes are held rigidly in the frames, which are lined with felt strips, and may be adjusted by set screws, four of which on each drawer are shown in Figures 1 and 2. The level workings, on a scale of 1 inch equals 100 feet, are traced in ivory black Windsor & Newtons artist oil paint. Co-ordinate lines are shown in crimson lake, and main geological contacts are shown in their respective colours. Figure 3 is a photograph looking down on one of the levels. The lighting consists of 14 30-watt fluorescent bulbs, with reflectors, under frosted glass. These lamps are much more satisfactory when operated by 60-cycle rather than 25-cycle and, as we had available nearby a source of direct current, this was used. The electrical unit consists of a rotary converter from d.c. to 60-cycle. This arrangement gives perfect lighting, allowing most colours to be easily distinguished. Figure 1 was photographed using this source of light, Figure 2 using an outside floodlight.

Jan 1, 1945

By P. Garritsen, J .. A. Blanco, M. C. Bell

"By 1994, Inco Limited will lower sulphur dioxide emissions from the Copper Cliffsmelter by 60% to 265 000 tonnes/year, primarily through implementing two key process changes. First, new milling technology will permit economic rejection of additonal pyrrhotite prior to smelting. Second, a bulk coppernickel concentrate will be oxygen flash-smelted, thereby eliminating the existing multi-hearth roasters and reverberatory furnaces . All copper will be recovered in the matte separation plant as a nickeliferous chalcocite, and will be oxygen flash-smelted for blister production. This paper outlines the development of the project and describes the process, including the flash furnaces, new sulphuric acid plant and additional oxygen plant.IntroductionInco 's SO2 Abatement Program will lower sulphur dioxide emissions at Sudbury from the current levels of 685 000 tonnes per year to 265 000 tonnes per year by 1994 as required by Ontario' s countdown on acid rain regulations.It is the high tonnage of sulphur mined that creates the magnitude of the SO2 emission problem at Sudbury. At a production rate of 240 million pounds of nickel per year, Inco mines 12 million tonnes of ore. At 10% sulphur it mines 1.2 million tonnes per year of sulphur. If Inco did not fix any of this sulphur it would be emitting 2.4 million tonnes per year of sulphur dioxide-about as much as all other Canadian emissions. Today, however, Inco is already fixing 70% of the SO2 in ore, in several ways : mostly as sulphur in pyrrhotite rejected to tailings in the milling operations; as acid from the roasting of pyrrhotite and some nickel concentrate at the Iron Ore Recovery Plant (lORP) and some as liquid S02 from the copper flash smelting furnace. By fixing 70% of the sulphur the current allowable SO2 emission levels of 685 000 tonnes per year is met. Total sulphuric acid production is currently 450 000 tonnes per year and in fact, the 10RP operation is being continued only to maintain established acid markets.Historically emissions have been reduced from the 2 000 000 tonne per year level to the current level of 685 000 tonnes per year by rejecting pyrrhotite from the smelter feed, and 70% of the SO2 containment problem at Sudbury has already been addressed.While Inco's profits are large at current nickel prices, most people have forgotten that back in 1982 Inco was losing a million dollars a day. Inco did make a dramatic response to this economic stimulus. The Ontario Division increased productivity by 65% and lowered costs to become the lowest cost nickel producer."

Jan 1, 1990

By Andrea R. Gerson, Roger St. C. Smart, Russell Schumann, Joan E. Thomas, Warwick Stewart, Stuart Miller

Sequential Net Acid Generation (NAG) accelerated oxidation testing using peroxide was carried out on single sulfide mineral samples. The calculation of the nett acid production potential (NAPP) assumes that all the sulfide is present as pyrite and that dissolution results in a 2:1 ratio of H+:SO42-. NAPP as kg H2SO4/t is calculated as 30.6 x wt.% S present. To test whether this calculation is valid a NAPP* value was defined in which instead of using the wt.% S present for the calculation the wt.% S dissolved is used. Stoichiometric analysis of the dissolution products of the sulfide minerals as they would occur at pH 7 indicates, that in all cases, the ratio of H+:SO42- of 2:1 is viable. The NAG to pH 7 and NAPP* closely coincided for pyrite, bornite, chalcocite and covellite. For the three Cu-containing minerals, the NAG to pH 4.5 value was 0 as is predicted on the basis of the speciation likely to be present at pH 4.5. Acid generation is due to hydroxylation of the dissolved Cu between pH 4.5 and 7.0. The NAG to pH 7 and NAPP* values for chalcopyrite, arsenopyrite and pyrrhotite were in reasonable agreement but were not for either sphalerite or galena. Zn is not completely hydroxylated at pH 7 as is assumed by the calculation. For galena, surface analysis identified polysulfide formation on of the leach residue polysulfide. The formation of polysulfide is an acid consuming reaction. Therefore under conditions of accelerated oxidation the NAPP value is a reasonable estimate of the possible acid production in all cases except for sphalerite and galena. However, under conditions of less intense oxidation, for instance in columns, waste rock and tailings dumps, the formation of polysulfides is likely to be more widespread thus reducing the correlation between NAPP and the maximum possible acid production.

Jan 1, 2004

By D. M. Cruden

"When two discontinuities form a tetrahedral wedge in a rock slope, a factor of safety for the wedge can be simply calculated (if motion is driven only by gravity and resisted only by friction) from plots of the normals to discontinuities on an overlay of a polar, equal-area spherical projection to which the great circles of a similar equatorial projection have been added.IntroductionThe stability of slopes in rock masses is often controlled by the discontinuities that exist in the masses. In particular, the geometry of the discontinuities constrains the ways in which the mass may fail. Displaying the orientation of the discontinuities on a spherical projection has been found to be a useful way of identifying possible failure modes. The most concise display shows the orientation of the normals (or poles) to the discontinuities that compose the fabric of the rock mass. Computer processing of large samples of discontinuity orientations is necessary if the sampling biases identified by Terzaghi (1965) are to be routinely corrected. Fortunately, displays of the poles to discontinuities (or pi diagrams) are relatively easily produced on the line printer of a computer or by a computer plotter (Cruden , 1978; Ramsden and Cruden, 1979). Unfortunately, further analysis of the stability of a rock mass has tended to use traces of typical discontinuities on a spherical projection rather than pi diagrams; examples may be seen in Hoek and Bray's book (1981)."

Jan 1, 1990

By Q. Han

Irradiation of high energy ultrasonic vibration in metals and alloys generates oscillating strain and stress fields in solids, and introduces nonlinear effects such as cavitation, acoustic streaming, and radiation pressure in molten materials. These nonlinear effects can be utilized to assist conventional material processing processes. This article describes recent research at Oak Ridge National Labs (ORNL) and Purdue University on using high intensity ultrasonic vibrations for degassing molten aluminum, processing particulate reinforced metal matrix composites, refining metals and alloys during solidification process, welding, and producing bulk nanostructures in solid metals and alloys.

Jan 1, 2014

By Sadough vanini Ali

The silicon anisotropic wet chemical etching technique is widely employed for fabricating various microelectromechanical system (MEMS) structures for advantages such as simple etching equipment and its capability to fabricate special microstructures. In this paper, we consider a complete theoretical derivation of the analytical solution based on geometrical and kinetic aspects of step flow on any surface and with a mathematical method we derive new equation for calculating the microscopic etch rates of surface atoms for a new range of concentrations and temperatures. Furthermore, a novel equation is presented for the calculation of the microscopic activation energies for some typical surface atoms and a new comparison of activation energies between some atoms is made that divides atoms into three categories. The results demonstrate agreement with the experimental results.

Oct 1, 2011

By Lucas G. Thompson

My topic, "The Administration of Mineral Rights'.' is possibly an unusual one, as it deals with a subject upon which many of us have a more than passing interest, I thought ?it might prove consistent with the objects of this meeting, more especially as I propose to deal, not with those broad subjects of nation-wide importance which are often the subject'? of learned (and sometimes futile) academic discussion, but rather with problems in their practical light. To the scientist, the important question is What is it? to the technician, Can it be utilized? to the business-man, Will it pay? All three questions are important, and so quick has been the march of business on the heels of science? that the one question follows the other with astonishing rapidity and all three must be considered in the modern management of a mineral estate. A .good illustration of the force of this can be found in the recent advance of our knowledge of the element helium in which we have advanced from a solution of the first question to the last question in the short period of 55 years. It is to be borne in mind, however, that in the administration of mineral rights, the question "Will it pay?:' is of primary importance. What forms a mineral estate ? A former practice in western Canada in selling lands was to sell the hair with the hide. All transactions sold the lands in fee simple, which included all mines, minerals and rights and privileges whatsoever, excluding only the royal metals, gold and silver, which by imputation, though not by specific reference, in deeds. of title are reserved to the Crown. At that time the country was in the first ?stages of settlement and the value of our mineral resources was hardly appreciated and little understood.

Jan 1, 1923

By A. Singh

Two alloys Mg96.9Zn2.7Ho0.4 and Mg93Zn6Ho have been processed by direct extrusion at 300°C and 200/230°C to produce various microstructures containing icosahedral quasicrystalline phase with different grain sizes. The alloys were mechanically tested in tension and compression. The mechanical properties were related to the grain size and microstructures studied by transmission electron microscopy. The extruded alloys showed a mixture of nano-sized icosahedral and monoclinic Mg4Zn7 phase, as well as icosahedral phase particles a few hundred nanometers in size distributed in the matrix. Coarse icosahedral phase particles several micron in size also remained after extrusion. The alloys Mg96.9Zn2.7Ho0.4 and Mg93Zn6Ho extruded at the same temperature of 300°C produced very different grain sizes of 15 and 3 µm, respectively. The alloy Mg96.9Zn2.7Ho0.4 extruded at 200°C and Mg93Zn6Ho extruded at 230°C produced grain sizes of 0.7 µm and 1.5 µm, respectively. Both the alloys showed yield stresses of about 300 MPa in both tension and compression with elongations of about 18%. Hall-Petch parameters are calculated for the alloys.

Jan 1, 2006

New Millennium Capital Corp. shall not be liable or responsible for any claim or damage, direct or indirect, special or consequential, incurred by the user arising out of the interpretation, reliance upon or other use of the information. Users should not rely on information for any purpose other than for gaining general knowledge of New Millennium Capital Corp. Although New Millennium Capital Corp. believes that its expectations reflected in these forward-looking statements are reasonable, such statements involve risks and uncertainties and no assurance can be given that actual results will be consistent with these forward-looking statements.

May 1, 2011

By G. Bimpilas, G. N. Anastassakis

"Today, one of the most intense problems in mineral processing systems is referred to the treatment of fine (–100 µm), and even smaller size, particles. Fine mineral particles possess specific properties (small mass, high specific surface area, and high surface energy per unit area) that render their separation inefficient with conventional methods (physical, physicochemical) and equipment. As a result, it is not feasible to obtain a concentrate both of high grade and recovery in mineral value and a considerable amount of mineral fine particles is lost to the tailings. As evidence, we could cite numerous examples from industrial practice with considerable loss of mineral values to the tailings because of the fine particles size, e.g. phosphate, tungsten, tin, etc.The objective of the current paper is to investigate the possibility to separate magnetic gangue minerals and rocks (serpentine, ilmenite, and olivine) from magnesite by co-agglomerating all the gangue components and subsequent magnetic separation of the agglomerates.To meet the target, hydrophobic agglomeration tests were initially carried out on single minerals to define the favorable conditions for selective hydrophobic co-agglomeration of the gangue minerals. In this respect, the effect of the following factors was examined: pH, collector dose, conditioning time, and settling time of the agglomerates. Among the combinations examined, the most favorable proved that with amine in the basic pH region. The use of non-polar oil proved beneficial. The preliminary results were confirmed by tests on mineral mixtures. The application of magnetic separation resulted in the removal of gangue minerals and the recovery of magnesite concentrates of commercial grade (magnesite content 95% approximately) and high yield.The current paper contributes to the development of mineral processing, since it successfully copes with a very important problem of mineral processing, such as the efficient separation of fine particles."

Jan 1, 2016

By P. Farsangi, A. Hara

"Kidd Creek Mines places approximately 10 000 tonnes of consolidated rockfill on a daily basis. Consolidated rockfill is comprised of sized aggregate mixed with different ratio and amounts of binders. Consolidated rockfill, with closely controlled specification, is employed for subsequent pillar recovery and improved passive active/ ground support. With the same amount of cementing agents consolidated rockfill mass yields a higher, compressive strength, modulus of elasticity, cohesion, and angle of friction compared to a typical cemented hydraulic fill mass.The consolidated rockfill at Kidd Creek Mines is designed to sustain not only the gravitational loading of the overlaying fill material, but also to some extent the dynamic loading applied during blasting of the adjacent stopes and/or pillars.The quality control of materials used in Kidd Creek's rockfill system could be effected in three stages of handling: (1) at the surface backfill plant; (2) during transportation; and (3) placement of the fill.The emphasis in this paper is placed on individual stope backfill design and quality control measures at Kidd Creek Mines to place fill in large-scale open stopes which eventually could be exposed on all four walls during pillar recoveries."

Jan 1, 1993

By C. R. Hocott

"IntroductionRESEARCH in petroleum production consists primarily in investigations related to the drilling for and recovery of oil. As an organized activity of individual oil companies, production research is now 30 to 35 years old, and the petroleum industry may point with justifiable pride to the achievements of this third of a •century. Emphasis on research has grown through the years until at the present time many of the larger companies operating in the United States •have well-organized production research staffs.In addition to the efforts of the oil companies, significant research and development in petroleum production technology have been performed by oilfield service companies and others. Valuable contributions have been made through fundamental research carried on by the U. S. Bureau of Mines and by various colleges and universities, both in their own programmes and in programmes sponsored by industry, such as those of the American Petroleum Institute. However, the total effort of these groups is small when compared to the sum of the effort devoted to research by the individual .oil companies. In contrast to some industries which conduct the major portion of their research through co-operative, sponsored research at universities or research institutions, research by the petroleum industry is done predominantly by individual company research staffs. These industrial research groups have usually been organized in such a way as to provide liaison and co-ordination with operating technical staffs. In this way, the research groups are kept aware of the major problems confronting the operating departments and, correspondingly, the operating technical people •are able to keep informed on research activity and progress. This type of close contact generally results in prompt testing of research developments in actual operations."

Jan 1, 1953

By P. A. Riveros

This paper describes the leaching of the common copper minerals tennantite (Cu12As4S13), tetrahedrite (Cu12Sb4S13) and enargite (Cu3AsS4) in acidic media using Fe(SO4)1.5, FeC13 or 02 as oxidizing agents. At temperatures <100°C, tennantite dissolves slowly in Fe(SO4)1.5-H2SO4 media, and the rate is directly proportional to the area of the sized tennantite. The rate increases sharply with increasing temperature and the apparent activation energy is 69 kJ/mol. Increasing Fe(SO4)1.5 concentrations slightly increase the tennantite leaching rate. The kinetics of dissolution of disks of synthetic iron-bearing tetrahedrite in Fe(SO4)1.5-H2SO4 media are linear; the leaching rates are slow but increase significantly with increasing temperature, with an apparent activation energy of 120 kJ/mol. The dissolution of sized particles of natural Ag-bearing tetrahedrite in FeC13- HC1 solutions proceeds according to the shrinking core model, and both Cu and Ag dissolve at about the same rate, provided that the total chloride concentration of the solution is sufficiently high to solubilize the AgC1 reaction product. The leaching rates are slow, and the apparent activation energy is 116 kJ/mol. The addition of sulphate ions to the FeC13-HC1 system reduces the tetrahedrite leaching rate to values similar to those realized in the Fe(SO4)1.5-H2SO4 system. At <100°C, enargite dissolves slowly in either Fe(SO4)1.5 or FeC13 media, and the dissolution rate obeys the shrinking core model. The rate increases with increasing temperature and the apparent activation energies are 50-64 kJ/mol. The rate increases slightly with increasing FeC13 concentrations in 0.3 M HC1 media. The leaching of enargite at elevated temperatures and pressures was also investigated. Potentially useful leaching rates are achieved above 170°C, at which temperature sulphate, rather than sulphur, is produced. Lower temperatures (130-160°C) lead to fast initial leaching rates, but the dissolution of the enargite is incomplete because of the coating of the enargite particles by elemental sulphur.

Jan 1, 2007

By Peter A. Hacquebard

"The early history of the Geological Survey of Canada is closely connected with coal geology investigations in the Atlantic Provinces. In 1843, Sir William Logan, the first director of the Geological Survey, measured the 4441m thick shore section at Joggins in Nova Scotia. Detailed mapping of the coalfields were subsequently carried out by H. Fletcher during the latter part of the nineteenth and first part of the present century. During the 1920-1940 period, the stratigraphy of the carboniferous WIZS&apos; established by WA. Bell, who later also became a diretor of the Survey. Bell&apos;s work WIZS&apos; followed by coal geology investigations of A.A. Hayes, W.S. Dyer, EA. Goranson, G. W.H. Norman, J.E. Muller, T.B. Haites and P.A. Hacquebord.The activities and accomplishments of the Survey geologists during the past 150 years are presented in this paper.General Outline of Survey Activities in Coal Geology During the Past 150 YearsIn 1842, when the Geological Survey of Canada (GSC) was established, the industrialization of the major countries of Western Europe and North America was actively persued. The energy required for this industrialization was obtained from the only fossil fuel then available, namely coal. The measure of a country&apos;s major mineral wealth at that time was the availability of mineable resources of coal. Eastern Canada, where mining had been carried out since 1720, was known to be well endowed with valuable coal deposits. In the major fields of Nova Scotia (Fig. I) several large-scale operations had been started during the middle and latter part of the nineteenth century.The significance of coal, therefore, was well understood, and exploration surveys specifically oriented toward coal were carried out by the Geological Survey from its earliest beginning. The first report of a detailed geological description of the coal measures of eastern Canada was prepared in 1843 by Sir William Logan (1845), the founder and first director of the Geological Survey of Canada. This early work was continued and complemented in 1896 by H. fletcher (1906), who during the latter part of the nineteenth century and first part of the present century systematically mapped the coal-bearing regions of Nova Scotia, which he considered all to be of approximately the same age."

Jan 1, 1992

By Arnold Blaisonneau, Théophile Guillon, Xavier Rachez, Sylvie Gentier

"L’étude présentée ici vise à étudier l’influence, lors de stimulation hydraulique de puits dans les réservoirs géothermiques de type Enhanced Geothermal System (EGS), du comportement mécanique des zones de failles recoupant le puits sur la réponse hydraulique du réseau de fractures 3D. Dans ce but, un modèle 3D, basé sur la méthode des éléments distincts et dans lequel les zones de failles recoupant le puits sont modélisées par des fractures numériques 2D, est mis en oeuvre. Les modélisations présentées ici visent à caractériser l’influence du comportement mécanique (type de comportement, hétérogénéité) sur la cinétique de la stimulation hydraulique, ainsi que sur son effet spatial autour du puits. INTRODUCTIONPour le développement de l’exploitation géothermique de type Enhanced Geothermal System (EGS), la phase de stimulation conditionne grandement le succés du projet ; en effet, elle a pour objectif d’augmenter l’injectivité et la productivité des puits et doit permettre d’assurer la connexion entre les puits d’injection et de production garantissant ainsi la viabilité technique et économique de l’échangeur. Pour le site EGS de Soultz-sous-Forêts (France), parmi différentes techniques de stimulation, la stimulation hydraulique a été utilisée à cette fin en provoquant une augmentation irréversible de la perméabilité autour des puits. Dans ce type de réservoirs fracturés, le but des stimulations hydrauliques est de réactiver, plus spécifiquement en cisaillement, des structures hydrauliques pré-existantes (fractures, zones de failles etc.) dans le socle cristallin. La compréhension des phénomènes physiques durant la stimulation hydraulique est cruciale pour optimiser cette technologie et pour contrôler/limiter les risques associés (viabilité technique et économique des puits, sismicité induite etc.). C’est notamment le cas pour la relation entre le comportement mécanique des structures stimulées et les conséquences sur le comportement hydraulique dans un contexte tectonique spécifique."

Jan 1, 2015

By I. Silin, M. Stapelmann, H. Wotruba, K. M. Hahn, C. Gerold, J. Katzmarzyk

New deposits are often characterized as low-grade and complex ore bodies. To date, processing of fine grained ore deposits implies complex processing routes with high energy consumption. For that reason, the investigation of dry grinding, e.g. with vertical roller mills (VRM), is an approach to save energy reserves. It is already proven that dry grinding can influence subsequent processing steps. In terms of flotation, the surface characteristics of the minerals are crucial for a successful flotation process, e.g. the sufficient adhesion of mineral particles and air bubbles. Wet grinding results in different surface properties of the product entering the conditioning stage than dry grinding, which has direct influences on the subsequent flotation process. To investigate the consequences for flotation, processing of a copper sulfide ore containing chalcopyrite and bornite was investigated, including grinding and rougher flotation. The effects of wet tumbling mill and dry VRM grinding on the degree of liberation of valuable minerals are characterized using mineral liberation analysis by scanning electron microscopy. The obtained flotation results, as well as the recorded flotation parameters such as dissolved oxygen, oxidation reduction potential and conductivity are presented and discussed. INTRODUCTION Copper production is mainly connected to porphyry copper deposits as main source for copper sulfides such as chalcopyrite and bornite. State-of-the-art processing of these deposits is already established worldwide for decades, combining crushing, fine grinding and subsequent flotation with rougher, cleaner and scavenger stages (del Villar, Desbiens, & Maldonado, Bouchard, 2010). While the demand for copper is increasing, copper grades of the deposits are decreasing and the remaining ore bodies have more complex mineralogy and finer particle size distribution. This implies processing routes with high water and – due to the liberation of fine grained valuable minerals – high energy consumption by fine grinding. One of the main energy consumers in processing plants is the grinding section, which accounts for more than 50% of the energy consumption in processing plants and even 4% of the worldwide energy consumption (Jeswiet, & Szekeres, 2016). Therefore, dry fine grinding alternatives are applied to enhance the overall energy consumption of mineral processing plants: high pressure grinding rolls (HPGR) and vertical roller mills (VRM).

Jan 1, 2019

By R. Lodha, C. Oprea, G. Oprea, H. Zargar, T. Troczynski

"The basic refractories used in non-ferrous industry contain chrome ore for improving the thermal shock resistance, thus reducing the penetration of molten metal and fayalite-type slags into the lining. The current study aims to replace chrome ore with Me4+ ions along with Fe3+ ions in order to form MgO-Al2O3- FeOx-Me4+O2 based complex spinel systems that could perform similar to the complex chromia-bearing spinel in the magnesia-chrome refractories. This system allows for lower temperatures of synthesis and sintering. In our study, compositions with 60% MgO were fired below 1500°C and resulted in complete formation of complex spinel, and open porosity less than 5%. The in-situ formation of the complex spinel from the fine mix of oxides in the MgO-Al2O3-FeOx-Me4+O2 system offers a suitable alternative of binding system to produce basic refractories at lower temperatures and of similar physical and mechanical properties with magnesia-chrome bricks fired above 1750ºC. INTRODUCTIONThe synthesis of magnesium aluminate spinel (MgAl2O4) (Maschio, Fabbri, & Fiori, 1988) or magnesium chromate spinel (MgCr2O4) from their respective oxides is diffusion controlled resulting in a sluggish reaction even at high temperatures. For instance, the diffusion of Mg2+ and Al3+ ions in the intermediate spinel layer during reaction is slower than the diffusion of Mg2+ in corundum and Al3+ in periclase. The interfacial layer of spinel formed during the reaction increases the diffusion path for the spinel forming cations. This accompanied by ~8% volume expansion retards further reaction resulting in incomplete spinel forming reaction during sintering and hence densification during the reaction cannot be achieved. In order to assess sintering studies with fine particulate oxides that would result in a lower diffusion path, a mechanical mixture of the hydroxides of aluminium and magnesium calcined at 1400ºC to 1600ºC for 1 hour does not result in complete spinel formation (Sarkar, Das, & Banerjee, 2003), which indicates that reaction sintering of stoichiometric magnesium aluminate spinel is retarded by initial reaction forming the interfacial spinel layer. The basic bricks used as linings in non-ferrous pyro-metallurgical convertors are manufactured using magnesia and chrome ore, the sintering of which produce spinel solid solution. This solid solution is a mix of both normal and inverse spinel structures that sinters at temperatures in excess of 1800ºC in air."

Jan 1, 2012

By R. A. Frith

"Belts of Yellowknife Supergroup volcanic and sedimentary strata in the Slave Structural Province are separated by granitoid complexes. The strata and most intrusive rocks are 2.7 and 2.5 Ga old, but rocks around 3.1 Ga have been recognized in some of the complexes and are believed to represent a once-extensive sialic crust. Volcanics were erupted along rifts in this crust and the rifts became sites of crustal foundering and the development of troughs that filled with turbidites of volcanic and granitoid provenance. Present margins of the granitoid complexes may be close to the original margins of deposition of volcanics, with associated mineral deposits, and close to the thickest parts of basins of sedimentation.The Hackett River volcanic belt extends 100 kilometres between Mara River and Back River and is crudely S-shaped, with a northern sector surrounding a core of granitoid basement rocks, a northeasterly facin g central sector and a southerly facing southern sector. Up to 8 kilometres of andesitic volcanics with intercalated felsi c volcanic rocks are preserved within the central sector. The f elsic rocks include thick lenses of volcaniclastics with large, quartz-eye-bearing clasts, but the known metal deposits are not associated with these. Both of the deposit areas, the Hackett River area in the northern domal sector and the &apos;A itch &apos; Lake area 40 kilometres to the south in the central sector, are near the tops of relatively thin atypical volcanic sequences above suspected basement rocks. The Yava deposit near &apos;A itch , Lake overlies a unit of subaerially deposited, welded, andesit ic ash flows and the Hack ett River deposits overlie highly metamorphosed volcaniclastic rocks that include suspected ignimbrites.The deposits are notably argentijerous and lead-rich. They consist of stratigraphically zoned sheet-like bodies of iron sulphides, sphalerite, galena and chalcopyrite underlain by altered rocks containing chalcopyrite stringers. The Yava deposit was formed where hydrothermal fluids exuded through the fractured floor of a flooded caldera basin. The Hackett River deposits may have been formed in a similar setting and it is not inconceivable that all the known deposits in the belt were formed in a single large caldera basin, although there is no independent evidence for the required major fault separation between the Hackett River dome and the &apos;Aitch&apos; Lake area."

Jan 1, 1980

By Sergio Romo, Gerardo Fuentes, Adriana Garcés

Refractory ores with gold entrapped in a sulfide matrix, must be processed in a first stage with chemical or physical treatment in order to liberate the gold for a subsequent step with cyanide. The goal of this research was to compare the refractory behavior of a gold concentrate treated using two pretreatment methods: pressure oxidation and fine grinding. Gold concentrate from Viacha Mining in Bolivia, assaying 50.11 gpt, with a P80 of 131 ?m was used. The concentrate contains arsenopyrite and pyrite as main sulphides in the matrix. A preliminary test with cyanide resulted only 13.5% of gold extraction with 4 hours of stirred leaching. Using an autoclave oxidation with sulphuric acid and 12 bar oxygen pressure at 220°C pretreatment, the cyanide gold extraction increased to 69.0% in 4 hours. When material was ground in a pulverizer, producing a P80 of 20 ?m and the product directly cyanided, stirred leaching gave a gold extraction of 65% in 4 hours. For both techniques, the effect of temperature, sulfur produced in autoclave oxidation, optimization of the cyanide and the nature of residues were also studied.

Jan 1, 2014