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Records of ex-solution intergrowths with tetrahedrite as a component are rare. Intergrowths of this nature of tetrahedrite with galena have been described by Guild (1917) and Schneiderhohn (1922), and in Broken Hill ore by Stillwell (1926), but both Schneiderhohn (1922) and Gruner (1929) have commented specifically on the apparent absence of exsolution intergrowths of tetrahedrite and chalcopyrite, despite their frequent association in ores, and their related atomic structures. Schwartz (1942), reviewing the literaturerelating to ex-solution among ore minerals, lists only two instances of such intergrowths, one an occurrence of lamellae of chalcopyrite oriented along the octahedral planes of tentantite (the arsenical isomorph of tetrahedrite), the other of blebs of tetrahedrite in stannite. The only other possible instance of such intergrowths known to the author is the record of "pseudoeutectic" intergrowths of tetrahedrite with chalcopyrite and with bornite in a silver pitchblende ore from the Great Bear Lake district of Canada (Furnival,1939).Some interest attaches, therefore, to the two occurrences described below of tetrahedrite showing ex-solution relationship, in one instance with chalcopyrite, and in the other with bornite.TETRAHEDRITE-CHALCOPYRITEAn intimate intergrowth of tetrahedrite and chalcopy-rite, apparently the product of unmixing of a solid solution of...

Jan 1, 1946

By J. L. Jambor

Previous crystal-structure determination of magnesian annabergite (Ni,MgMAsO4)2 8H2O indicated that ordering of Ni and Mg occurs in non-equivalent octahedral sites; such ordering supports the possibility of miscibility gaps on the Ni3(AsO4)2 8H2O -MgiAs04)2 8H2O. (annabergite-hornesite) join. In a predecessor study based on analyses of natural specimens, it was proposed that solid solution is incomplete both for annabergite-hornesite and annabergite-erythrite [Co, (AsO4)2 8H2O]. In the current study, syntheses by use of a slow-addition technique and aging of the precipitates indicated that the annabergite-erythrite solid solution is complete, and that no miscibility gap is present on the annabergite-hornesite join to at least 58 mol % Mg. Thus, interpretation of the compositions of these phases in oxidized mill-tailings impoundments can be done with the normal precautions for homogeneity, and without the added concern of the possible presence of miscibility gaps in the ternary system.

Jan 1, 1995

By C Ferron, R Massimi

There is approximately 240 000 tonnes of arsenic trioxide dust stored in underground chambers at the Giant Mine in Yellowknife, Northwest Territories, Canada. To minimise the amount of arsenic released to the environment, a number of closure alternatives are being considered. One alternative is to mine the dust, encapsulate it and dispose the mixture into a secured landfill. The potential leaching behaviour of the encapsulated dust was examined in a laboratory programme. Cylinders of arsenic trioxide dust mixed with cement/aggregate and bitumen were prepared. The dust content varied between zero per cent and 60 per cent of dry weight charge. The cement cylinders were tested for strength, leaching and freeze/thaw durability. The bitumen cylinders were tested for leaching only. The results show that increasing dust content in the cement cylinders negatively impacts the strength and the freeze/thaw durability of the samples. A contributing factor is likely the high water to cement ratio in the samples. Leaching tests show that arsenic release from cement cylinders increase with increasing dust content. Arsenic concentrations in leachates do reach a plateau at a certain point in time. Arsenic release from bitumen cylinders was significantly lower compared to cement cylinders. Arsenic concentrations eventually were less than 0.05 mg/L in samples containing up to 25 per cent arsenic trioxide dust. Arsenic leaching rates were found to decrease by an order of magnitude over the course of three months.

Jan 1, 2003

By Stephen C. Britten

An in-situ amperometric slag sensor for measuring the concentration of easily dissociable oxides in slags at temperatures between 1200-1600°C is being developed. The sensor provides the same information as potentiometric sensors while also providing data on the concentration of the transition metal species and the diffision kinetics within the slag. The electrochemical technique utilized in the sensor is similar to methods utilized in aqueous voltammetry.

Jan 1, 1998

By Strathmore R. B. Cooke, Robert E. Brandt

EARLIER work1,2 has shown that the strength developed by fired magnetite pellets containing silica or silicates is due to three separate effects. Two of these are associated with the formation of slag in the interior of each pellet at temperatures above 1000°C, where the atmosphere is substantially though temporarily neutral. The third is independent of the silica content and is responsible for the development of a hard shell around the pellet during the initial stages of firing, a condition which permits the pellet to assume the increasing load of the overlying burden and prevents extrusion of the slagged and semi-liquid interior. Pellets made from hematite concentrates do not show these effects unless specific additives are incorporated, and it is these differences in behavior which in large part account for the difficulty in producing satisfactory pellets from such concentrates. Elsewhere it has been stated that "the most important factor responsible for the development of strength in fired magnetite pellets containing no additive is the oxidation of magnetite to hematite and the subsequent recrystallization and grain growth of this constituent."1 The object of the investigation reported in the present paper was to study in detail the mechanism described above and to evaluate its contribution to the strength of the fired pellet compared with other possible mechanisms, excluding slag bonding. This was effected by placing together polished faces of two cubes prepared from specific minerals and then heating them under constant pressure at different temperatures both in air and in nitrogen.

Jan 4, 1954

By M. Sibanda

The diffusion of carbon in Co-5% Fe alloy was studied in a belt-type pressure system at temperatures of up to 1330°C and press loads or nominal pressures of 7 020 tons or 42±3 kbar. Under these conditions, this alloy is in the solid state. Discs of graphite and prealloyed Co-5%Fe were used to make up the diffusion couple. The diffusion coefficient increased with increasing press load due to the tendency of the low density graphite to dissolve in the metallic phase reducing the overall volume and increasing the density of the system. Furthermore, inhomogeneous plastic deformation may have promoted diffusion by creating defects in the alloy. Diffusion couples treated at atmospheric pressure exhibited graphite particles in the metal, while those treated at high pressures exhibited carbide in the form of Widmanstatten laths. Carbon analyses indicated increased carbon solubility with increasing pressure. This was confirmed from calculated high-pressure phase diagrams.

Jan 1, 2005

By Jun Sugiyama, Hiroyuki Sano, Toshiharu Fujisawa, Hideki Takeuchi, Chikabiuni Yamauchi

"The solid .state electrotransport (SSE) is one of the most promising methods for the elimination of gaseous impurities from chemically active metals, such as rare earth metals. . In the present work, the SSE process was applied for the oxygen removal from praseodymium. The SSE factors, such as effective valence, were measured under the various temperatures, electric field intensities and initial oxygen contents, and the effects of those conditions on the SSE process were discussed. Furthermore, the solubility of oxygen in .solid praseodyillium was also measured·, by using the SSE method and metal-oxide equilibrium method.IntroductionWhen a direct current is passed through a solid alloy, not only electrons but also solute atoms are transported as charge carriers toward the anode or cathode. This phenomenon is referred to as an electrotransport or electromigration. The solid state electrotransport (SSE) is the application technique, based on this principle, to the pUrification of the solid metallic materials.Rare earth metals are used for various functional materials, such as magnetic, optical or electronic materials, therefore their high purity metals are required [l ,2]. However, rare earth metals are chemically active and have a strong affinity with gaseous elements (e.g. oxygen, nitrogen, hydrogen and carbon). In many cases, eliminating operations of gaseous elements have not been always made commercially, because these impurity elements could not be eliminated by usual treatments applied to the purification of ·common metals. As an alternative method, authors have proposed the· application of the SSE process to the elimination of gaseous impurities from rare earth metals. Investigations have been carried out on the yttrium-oxygen and neodymium-oxygen systems and the results were already reported[3,4]."

Jan 1, 2000

By Johnston R. F

The factors which influence the reduction of chromite are investigated with special reference to Coobina chromite. This was compared with a South African chromite ore. The reduction characteristics are outlined and the reduction kinetics studied Temperature has the most significant effect, followed by particle size, silica addition and type of coal.Electron microprobe analysis of the products indicates that iron in the chromite is first reduced at temperatures above 1100°C, followed by chromium at around 1200°C. At temperatures greater than 1200°C metallic iron and chromium are formed simultaneously and subsequently give an iron-chromium-carbon alloy. It was observed that the metallic carbide contains a small amount of silicon. The decomposition of the chromite spinel was observed to pass through the FeO.Cr2O3, MgO.Cr2O3 and MgO.AI2O3 forms before slag formation. It is concluded that Coobina chromite is suitable for the production of ferrochrome if direct prereduction followed by intensive bath smelting is used.

Jan 1, 1994

By M. Reuter, C. Schuffeneger, T. Seppälä, L. Holappa

Reaction kinetics of solid-state reduction of chromite pellets (laboratory made and industrial) and lumpy ore was investigated by the thermogravimetric analysis (TGA) technique. Carbon monoxide was used as the reducing agent, with the presence of graphite in proximity to chromite. The experiments were carried out at both rising temperature and constant temperature in the range of 1450 - 1550°C. Scanning electron microscopy was employed to observe and analyse the structure and composition changes of the chromite samples. For the lab-made chromite pellets, the effects of particle size and bentonite addition on the reduction behaviour were studied. The pellet with smaller particle size gave a higher reduction rate. Bentonite addition had slightly negative effect on the reduction rate. When reducing industrial pellets, temperature and CO flow rate had positive influence on the reduction rate. Reduction of lumpy ore took place slower than reduction of a pellet. In all samples, chromite reduction proceeded longer in the outer part of the sample than in the centre part. The porosity of the chromite samples was determined before and after the experiments. The porosity of lumpy chromite increased significantly during the reduction. However, the porosity of lab-made chromite pellet decreases due to sintering effect. The reaction mechanism is discussed on the basis of experimental results and earlier investigations.

Jan 1, 2004

By R. H. Eric, P. Taskinen, A. Bhalla, P. Halli

Sustainable development requires less energy consumption with lower carbon footprint. In this review the solid state reduction behaviour of three oxide ores using methane gas are briefly summarized based on experimental work conducted in our laboratories. The discussion concentrates mainly on mechanisms of the reduction studied through SEM-EDAX and X-ray diffraction techniques. Limited preliminary kinetic input is also mentioned. Iron ore containing titanium and vanadium could be reduced significantly in the solid state with methane-hydrogen mixture up to 400 °C lower than is needed in ordinary solid state carbothermic process. The reduction of chromite and manganese ores were possible similarly at lower temperatures with potential energy savings lower carbon footprint.

Mar 1, 2017

By A. Kenneth Schellinger

THE terms surface tension .and surface energy are well known when applied to liquids and are generally described by referring to the excess energy of the air: liquid interface as a result of unsaturated molecular forces surrounding the surface molecules of the liquid due to the presence of the air phase on one side. Such unbalanced forces produce the familiar water droplet of spherical form and are generally summed up as a surface tension measured in dynes per centimeter which can be shown mathematically to be equal numerically to a corresponding surface energy expressed in ergs per square centimeter. A specific surface energy, however, is best thought of as the energy necessary to produce one unit of new surface on a substance. Hence, in producing a bubble in a flotation cell the impeller must supply surface energy corresponding to the air: liquid interfacial area on the interior of the bubble. Inasmuch as it is relatively easy to extend or contract the surface of a liquid, there are a number of successful methods for liquid surface tension, or energy, measurement based upon surface deformation. This happy state of affairs does not, however, extend to solids, which are considered to possess surface energies for the same reasons as do liquids, i.e. because of unsaturated ionic bonds at the solid gas interface. As in the case of the flotation cell producing surface on liquids as new bubbles, it takes energy to produce new surface on solids as new particles. As every mill man knows, this surface is produced on mineral solids in a grinding mill by the action of a tumbling mass of iron balls. But here so much energy usually is wasted by the inefficient action of these balls that a large amount of heat is generated, and the surface energy production may be easily confused with the energy necessary to produce this ineffective heat. The tumbling balls and fracturing minerals ultimately take their energy from a rather large electric motor. It has been variously estimated that from 10 to 20 pct" only of this energy from the motor does not appear as heat and may be presumed to appear as surface energy on the minerals present.. Such a production of new surface on the mineral phases is accompanied, of course, by a size reduction that is inevitable as more and more mineral interior molecules become surface molecules by the fracture exposure. This size reduction of mineral particles, although the most obvious feature and perhaps the sole object of the milling operation, is from this energy viewpoint the outward manifestation of the production of surface energy only. Measurement of the characteristic surface energies of pure minerals and their various mixtures in ores would be a step towards understanding of the energetics of the commercial grinding operation. In addition, the characteristic surface energy of a mineral is probably a physical property specific for that mineral, and therefore, from a scientific standpoint, should be measured. It is interesting to note that, in contrast to the large body of work on the surface tensions of liquid systems and biological systems, the field of solid surface energies has been neglected. Prior to. 1920 it is difficult to find more than one or two references to work on solid surface energies in Chemical Abstracts. Since 1920 such references number somewhat less than 100, while those on liquid systems are numbered in the thousands. Much of this apparent neglect of the field of solid surface energies (the term is intended to be somewhat inclusive at this point and refers both to the solid: gas, and the solid: liquid interface) is because of the lack of a reliable method of measurement rather than any lack of scientific curiosity. It was, and still is, difficult to produce new surface on a solid without the simultaneous production of interior changes in the same solid which may consume part of the energy used. The extension in the surface area can be measured, but the interior crystal-

Jan 1, 1952

By Ronald D. Hill, Janet L. Auerbach

It is estimated that the mining industry generates over 2.1 petrograms per year of solid waste. These wastes are overburden, waste rock, low grade ore, concentrate (tailing), sludges from treatment facilities and wastes from support facilities. Concentrate wastes present the greatest environmental problem. Three recent federal laws impact the disposal of waste from mining: Resource Conservation and Recovery Act of 1976 (RCRA), Surface Mining Control and Reclamation Act of 1977, and Uranium Mill Tailings Radiation Control Act of 1978. RCRA specified a special study on mining waste which was to include an analysis of: (1) sources and volumes of waste produced, (2) present disposal practices, (3) potential dangers to health and the environment, (4) alternate disposal methods, (5) cost of disposal, and (6) potential for use of waste.

Jan 1, 1980

By David B. Crouch

Wastes in various forms have always been a part of mining, and management of mine waste has evolved from the early days of "push it over the side and down the creek" to today's highly engineered waste facilities. Changes have been brought about not only by technological advances in the ?3M?s? - mining, milling, and metallurgy - but also by environmental awareness and changing social values that have been manifested in an ever-growing maze of regulations. This is a dynamic era, and the debate goes on. So it is that planners have to anticipate permit and regulatory requirements in the site-selection process along with the traditional criteria. The McLaughlin gold project is an example of how one company, Homestake, has met this planning challenge. In August of 1980, Homestake Mining Company announced a major gold discovery in northern California known as the McLaughlin Project. The property is approximately 80 air miles northeast of San Francisco near the junction of Lake, Napa, and Yolo Counties. This is an area where mercury has been mined off and on for over 100 years; gold has never been mined in the area. The gold is microscopic and finely dispersed in a complex geologic setting. Reserves are estimated at approximately 20 million tons at a grade of approximately 0.16 ounces per ton.

Jan 1, 1983

By D. B. Crouch, D. A. Poulter

The engineering and metallurgical assessment of the McLaughlin Project ore body concluded that an open-pit mine and cyanide leach mill process would be feasible, producing both waste rock and residual mill tailings. As a part of the planning and permitting process, site selection studies were conducted for the tailings and waste rock disposal. The site selection process began with a regional identification of potential disposal sites and proceeded through 1) regional screening, 2) elimination of sites with obvious fatal flaws, 3) qualitative ranking of site evaluation criteria, 4) quantitative ranking of sites, 5) field investigation, 6) evaluations of field data, and 7) selection of preferred sites. Based on this approach of site rankings and field evaluations, tailings and waste rock disposal sites were selected and recommended for the preliminary design phase of the permitting and project development process. The site selection study provided the documentation necessary to justify the use of these sites for waste disposal and enabled Homestake Mining Co. to anticipate and integrate environmental concerns with agency requirements into the planning process.

Jan 1, 1986

By David E. Jones

In any manufacturing process, the generation of secondary, associated or waste products along with the primary product is inevitable. Today there is great emphasis on the concept of waste minimisation. As part of that overall strategy, the search .for markets for these materials formally regarded as wastes, can mean the development of whole new industries. This paper examines some of the work necessary to develop recycling and markets for associated products with particular reference to iron and steelmaking slags.

Jan 1, 1994

By Ray D. Peterson

The hydrothermal enrichment of chalcopyrite by CuSO, occurs in the absence of oxidizing or reducing reagants. Kinetics of the enrichment process were determined under autoclave conditions in the temperature range of 398°K (125°C) to 473°K (200°C). Covellite (CuS) formed first, followed by digenite (Cu,,,S), with rejection of iron to the solution. The kinetics have been explained by a model which includes diffusion during the first stage formation of covellite followed by surface reaction rate control when digenite be. The effects of particle size, temperature, pH, and cupric and ferrous ion concentrations on the leaching kinetics were examined. Additions of ferrous ion to solution markedly increased the rate of reaction.

Jan 1, 1994

"Geological investigation in the Appalachian region of Canada began more than 150 years ago. The distribution of rock formations, and their ages and regional structure are today reasonably well known in most parts of the region to 1-or 2-mile scale. Most Newfoundland geology is known only to 4-mile scale. About 200 earth scientists carry out research in the region, of whom about 25 per cent are government employees, 50 per cent university staff and graduate students, and 25 per cent industry employees.Increased activity is needed toward both regional analyses and problem studies through the efforts of multi-disciplinary teams. The ultimate objectives of earth science must be the discovery and development of mineral re•-sources and the use and conservation of natural material in the environment, all for the benefit of the local in-habitants. To accomplish this, the scientific community must carry out an array of research projects ranging from the technical products of geological, geophysical and geochemical surveys through to the research products de-signed to renew theories and hypotheses bearing on natural processes. Some scientific sub-objectives are listed.Recommended is the increase and broadening of communication among Appalachian scientists, specifically those resident in the Atlantic Provinces. It is proposed that an Appalachian Division of the Geological Association of Canada be formed to provide a forum for discussion of Appalachian topics. In addition, a committee or council of university, industry and government earth scientists should be formed to examine the state of the science in the region, to identify programs of investigation and individual projects of research, and to recommend methods of approach. If the committee succeeds and the scientific community acts upon the recommendations, the quantity, quality and pertinence of research will increase, and earth science will better serve Appalachian society."

Jan 1, 1970

By D. Forbes

The results of a fundamental study involving zeta-potential and turbidity determinations of solid suspensions are discussed. Illustrations of how these results are utilized to design field applications of solid-grade polymers to clarify mine-drainage water are presented. Operational and economical advantages are examined.

Jan 1, 1997

By N. Karapinar

Ferrihydrite, a member of iron oxides family, has been used as an adsorbent for the removal of heavy metal ions from industrial wastewater. The success of the operation depends mainly on the efficient removal of ferrihydrite from the aqueous phase. Hence, the emphasis of this study was given on the separation of ferrihydrite by high gradient magnetic separation (HGMS) method to overcome solid-liquid separation difficulties of ferrihydrite. Magnetic seeding technique in which the magnetite mineral was chosen as a seeding reagent was used to make magnetic separation available. The method clearly involves the attachment of ferrihydrite to a magnetic seed material and subsequent magnetic separation of ferrihydrite ? magnetite coagulates. Seeding of ferrihydrite with magnetic particles was achieved by exceeding the solubility limit of the ions in the presence of dispersed magnetite. Magnetic separation results of seeded ferrihydrite showed that maximum seeding performance is obtained in the pH range of 7.0~10.0. Iron/magnetite ratio had a marked effect on the separation of seeded iron oxide precipitate by HGMS. This ratio determines the operation parameters such as magnetic field strength and flow rate. It was concluded that when used with magnetic seeding technique, HGMS can be used to surpass separation difficulties of ferrihydrite used in adsorption-based treatment techniques.

Jan 1, 2014

By Gary L. Hundley

The Bureau of Mines has devised and demonstrated a process for recovering Ni and Co from low-grade domestic laterites. The process consists of four major steps: (1) reduction roast, (2) ammoniacal leach, (3) solvent extraction, and (4) electrowinning. Several solid-liquid separation steps are required that affect the economics of the overall pro-cess. In this study, two techniques for solid-liquid separation, centrifugation and thickening, were investigated. This report presents the results of (1) laboratory and pilot plant studies to determine parameters for sizing centrifuges and thickeners and (2) an economic study of the two techniques, based on the requirements of a commercial-size (5,OOO-tpd) laterite processing plant. Sizing and other equipment-related recommendations, based on data from the Bureau's studies, were obtained from commercial manufacturers. The costs of thickening and centrifugation, including all the unit operations affected, were determined by the Bureau's process evaluation group. The total operating costs ~or separation using the two techniques (including depreciation on the capital cost of equipment) were found to be quite close: $17.26 per ton of laterite for centrifugation and $18.15 per ton of laterite for thickening. For centrifugal separation, the greatest cost was found to be the initial capital cost for the separation equipment; using thickeners, the greatest cost was for re-agent recovery.

Jan 1, 1984