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By J. E. Shigley

The gemological properties that allow natural emeralds and blue sapphires to be distinguished from other gemstones are summarized in this paper. A variety of synthetic and laboratory-treated emeralds and blue sapphires are also encountered in the jewelry industry today. Gemologists distinguish these latter materials from their natural counterparts based primarily upon features seen with magnification, such as inclusions and/or growth zoning. In some cases, however, these observations and standard gem-testing methods are insufficient, and the use of non-destructive analytical methods, such as optical spectroscopy and chemical analysis, are required for positive identification. The commercial value of synthetic and treated gems are much less, and can be insignificant in comparison to that of an important untreated natural gemstone. Identification of synthetic and treated gem material is essential to maintaining integrity in the jewelry industry. Loss of consumer confidence in the gemstones sold at the jewelry counter could have a negative impact on the exploration and mining of natural emerald and blue sapphire.

Jan 1, 1998

By X. Cao, A. Birur, R. R. Chromik, J. Cuddy, P. Wanjara, J. Gholipour Baradari, T. Shariff

In this study, 3.1 mm thick Ti-5553 (Ti-5Al-5V-5Mo-3Cr) butt joints were autogenously welded using a 4 kW continuous wave Nd:YAG laser. The effect of welding speed and defocusing distance on the weld quality was investigated in terms of the surface morphology, welding defects, microstructure and hardness. Welds with full penetration were achieved at a defocusing distance ranging from -1 mm to 0 mm and welding speeds from 2.25 to 6.0 m/min. Underfill and porosity were the two main defects most frequently observed but within the optimum process window these defects could be maintained to meet aerospace specification tolerances. The fusion zone (FZ) consisted entirely of retained beta with a refined dendritic morphology. Compared to the bimodal alpha (a) + beta (ß) microstructure of the base metal (BM), the dissolution of the a phase was observed in the heat affected zone (HAZ), which led to an 11 % decrease in hardness from the BM to the FZ. To determine the tensile properties of the welded samples, an automated 3D deformation measurement system was used to measure the local strain in the weld region. The yield strength (YS) and ultimate tensile strength (UTS) increased with increasing welding speed with a highest joint efficiency of 75 % being achieved, albeit with a concomitant reduction in the ductility.

Jan 1, 2010

By Omkar N. S. Beruar

Extraction of sill pillars has always been problematic because of high risk of seismicity and rockburst. Depending on a number of factors, a sill pillar can undergo different failure modes and cause problems in the mine. Of these, sudden and uncontrolled failure of part(s) of the pillar leading to highenergy seismic events and rockbursts is a main concern because it is not possible to predict the location and time of a rockburst apart from its potential to cause extensive damage to the mine structures. To date, a comprehensive technique for sill pillar design and recovery does not exist. Conventional methods of pillar design, such as the pillar stability graph method, are utilized to design stiff sill pillars. In these design approaches, the post-peak response of the pillar-rock system is not considered. This is in part due to a lack of clear and comprehensive understanding of the post-peak behaviour and failure mechanism of sill pillars. In general, the strength of a rockmass is described using a failure criterion. When stresses reach the strength of the rockmass, the rockmass does not necessarily become unstable and knowledge of the loads alone is not enough to assess the instability conditions accurately. In fact, it is not possible to predict instability of rockmass based on the strength/stress ratio alone because instability depends not only on this ratio but also on the loading condition and loading system characteristics. The loading system can dictate whether the sill pillar will go through a stable or unstable failure process. This paper examines the influence of various parameters such as the pillar width to height ratio, the extraction rate, and placement of backfill on the Loading System Stiffness (LSS) and the Pillar Stiffness (PSS). The ultimate goal is to design yielding sill pillars that would yield in a stable manner and will reduce the risk of pillar rockburst. Plane strain finite element analysis is conducted using the generalized Hoek-Brown failure criterion with elastic-brittle-plastic parameters. Examples are given to demonstrate how to calculate these stiffness values and assess the stability condition of sill pillars. It is found that increasing the rate of extraction increases the likelihood of unstable yielding of the pillar as has been found in other studies. Placement of backfill in a timely fashion in the stopes above and below the sill pillars increases the stiffness of the loading system. This indicates that backfilling of stopes while creating the sill pillar increases the likelihood of stable yielding of the sill pillar.

Aug 1, 2013

By R. Matusewicz, A. Kaye

Ausmelt Top Submerged Lancing (TSL) Technology has gained widespread commercial acceptance in non-ferrous applications, including the processing of lead and zinc primary concentrates and secondary (post-consumer) materials. TSL is highly flexible and efficient, and is one of the few technologies which can process primary and secondary feeds, and use varying fuels, to deliver high recoveries and excellent environmental performance. With the recent high value of both lead and zinc, and an escalating awareness of the sustainable use of resources, focus on the processing of secondary feed material sources has surged. Ausmelt Technology has proven to be well suited to the economic recovery of values, with twenty-two (22) Ausmelt furnaces processing lead and zinc bearing feed sources now in operation, under design or construction. This paper describes Ausmelt's progress in the fields of lead and zinc processing, and developments in new processing areas such as EAF dust processing and linking to innovative hydrometallurgical technology. Ausmelt has recently committed to the Whyalla Zinc project as the owner/operator of a facility for the treatment of zinc bearing secondary feeds. This project is due for start up in the first quarter of 2008.

Jan 1, 2008

By M. R. Coffin

Since the plant startup in 1972, the leaching and jarosite precipitation circuits at the zinc plant of the Kidd Metallurgical Division have been reconfigured several times to improve overall performance, and/or to respond to market conditions. For the most part, the circuit changes have been driven by two market factors: the price of zinc and the price of silver. Until recently, circuit modifications undertaken to improve zinc extraction and recovery came at the expense of silver recovery, and vice versa. In 2004, the plant was modified once again to produce a precious metals-bearing residue, but additional leaching circuits were added to ensure that zinc extraction and recovery did not suffer as a consequence. The development of the zinc plant of the Kidd Metallurgical Division is updated in this paper, with a focus on the recent circuit modifications and associated control strategies that were implemented to maximize zinc and precious metals recoveries, and control the quality of the jarosite residue.

Jan 1, 2006

By J. R. Rau

While refuge chambers are common place in most underground mining projects, there are different philosophies as to what life support systems are to be considered and how these systems are to be applied. Case studies in the underground mining industry have examples of emergencies where the external compressed air and power supply to the refuge chamber were compromised due to proximity of services to the fire location. In 2005, The Department of Industry and Resources, Western Australia, drafted guidelines that listed specific requirements for refuge chambers which included a secondary life support system that would operate independently of external sources. The objective of this document is to examine what critical life support systems are essential for safe entrapment in the event of an emergency and to examine considerations for their application.

Aug 1, 2013

By Yoginder P. Chugh

This paper discusses an ongoing field study in southern Illinois (USA) that focuses on: 1) Identifying mechanisms of instability in the set-up rooms (SR) and their T-junctions with headgate and tailgate entries, 2) Developing alternate 3-entry and 4-entry set-up rooms geometry using 3-D numerical analyses, 3) Implementing developed geometries in cooperation with mining professionals and regulatory agencies, and 4) Demonstrating performance of implemented geometries through field monitoring. Illinois longwall mining operations typically experience ground control problems (roof falls, rib sloughing, floor heave, etc.) within SR layouts and around the T-junctions of SR. These occur around the areas where the SR for adjacent longwall face (to be mined) connect with the SR of the previously mined face, and around the tail-gate entries of the mined-out longwall face and around the T-junctions of SR. The problems manifest as highly fractured immediate roof strata, major shear zones in the roof, horizontal displacements within the excavations that result in shearing off the heads of the bolts, floor heave and severe rib sloughing. Similar observations have also been made in longwall mining in Utah.

Aug 1, 2013

By Sazol Das, Hany Ahmed, Ganesh Bhaskaran, Zhuoru Wu

"Friction stir welding (FSW) process in lap configuration for dissimilar materials has been developed and tested for steel to aluminum joining. A novel cylindrical tool was designed for improved material flow. The joining of steel to high strength 5xxx and 6xxx aluminum was carried out by FSW technique using optimized process parameters. The microstructure, micro-hardness, joint strength and corrosion properties at the weld interface have been investigated. Optical and scanning electron microscopy reveled a well layered structure at the interface and lap shear tests of the welds showed excellent fracture resistance. Neutral salt spray tests for up to 500 hours (ASTM B117) were carried out on the bare steel to aluminum FSW joints, which did not show neither evidence of corrosion at the weld interface, nor any degradation of the weld strength. The FSW lap configuration was applied to prototype commercial vehicle structural component whereby a steel stiffener insert was friction stir welded to high strength 6xxx aluminum alloy. The interface microstructure showed layered root without any steel shattering in aluminum side. A finite element study was carried out to quantify the benefits where it was found that the stiffness increases by 76% under bending loads and 36% in torsion loads.INTRODUCTION Energy preservation and environmental issues, namely carbon footprint and legislation around emission in transportation industries has led to a growing need to use of lightweight materials such as aluminum and magnesium alloys along with various grades of steel in structural application, while still maintaining their strength and crashworthiness. Assembling dissimilar materials within integrated structure is thus a stringent requirement related to optimum performance. In order to achieve an efficient technology of joining dissimilar materials such as aluminum to steel, it remains difficult to select an effective welding process for a given joint configuration. The use of aluminum in transportation industries for structural component is not exclusive in a design and is almost always used along with various steel grades for a mixed materials solution, thus dissimilar aluminum/steel lap joining is of great interest since this is widely used in the assembly of parts (e.g. pillar, frame rails, chassis, body in white (BIW), CAB, etc.)."

Jan 1, 2018

By W. R. Middagh, R. M. Garvey

"Phosphate rock is shipped by boat from Florida to Vancouver, B.C., where it is unloaded and stored in a 50,000-ton silo. It is shipped from Vancouver in 100-ton hopper cars in 80-car trains to Fort Saskatchewan. Both the ship and the hopper cars are on a back-haul with potash. The rock cars are unloaded at Fort Saskatchewan at a rate of approximately 4 cars per hour. The rock is stored in three concrete silos, 40 ft in diameter by 110 ft high, which hold 18,000 tons of recoverable rock with 2,000 tons dead space. The rock is reclaimed from the silos by gravity and fed to the phosphoric acid plant by remotely operated conveying equipment.Problems encountered in the operation include scheduling the rock shipments, contamination of the rock with potash, and handling the 80-car trains both in Vancouver and Fort Saskatchewan."

Jan 1, 1968

By S. Ivanova

The results presented in this paper show that the gold solution dilution is a key parameter to control the dispersion of gold on ?-Al2O3 the selected support. The variation of concentration leads to changes in pH which modify the nature of gold complexes from HAuCl4 formed in the solution. These complexes are presented. Some of them (AuCl3(OH)- and AuCl2(OH)2 -) react with the surface of alumina and give interesting interaction. AuCl2(OH)2 complex has been considered as an ideal complex because of the strong anchorage of a bidentate species on the alumina. This complex is formed mainly in a solution of gold with a concentration of 10-4 M giving a pH of 3.5-4.5. The nature of the anchorage and the amount of chlorine, has an influence upon the formation of Au-Cl bridges which modify the dispersion of the gold on alumina of the final catalyst as shown by TEM.

Oct 1, 2003

By F. Henríquez, V. Iriarte, L. Vinnett, J. Yianatos, F. Díaz

Metallurgical characterizations of the collective (Cu/Mo) and selective flotation plants were carried out in Minera Los Pelambres, Chile. The selective plant allows the valuable minerals of Cu and Mo to be separated. The evaluation involved two surveys consisting of metallurgical sampling as well as residence time distribution (RTD) measurements to determine load distribution. The RTD data were obtained in real-time by means of the radioactive tracer technique. In addition, metallurgical data was reconciled and supported by effective residence times. In the collective plant, a performance comparison of parallel rougher circuits was carried out, which included a bank of six mechanical cells of 250 m3 and banks of nine mechanical cells of 130 m3. In the selective plant, the Cu and Mo evolution along the plant was evaluated. The results in the selective plant allowed for performance evaluation of mechanical and pneumatic cells in primary flotation. In both plants, mineral losses were evaluated and their relationship with circuit configuration (cell types and circuit layout) was determined. The metallurgical characterization was a powerful tool to evaluate circuit performance and to detect improvement opportunities at industrial scale.

Jan 1, 2015

By Y. A. Topkaya

In this research work, a process was described for the recovery of copper and zinc in copper converter flue dust from the Black Sea Copper Works' Samsun Smelter Plant. After characterization of a representative flue dust sample, the process included roasting of the flue dust and then leaching in dilute sulfuric acid solution. Roasting time and temperature were studied to determine the optimum roasting conditions. Sulphuric acid concentration, duration, temperature of leaching and solid to liquid ratio were the parameters studied in the bench scale laboratory leaching experiments.

Jan 1, 2007

By E. Ghali, B. Arsenault

Aluminum alloys play an important role in the manufacturing of air and ground vehicles. However, with such alloys, corrosion damage is often found on structural components subjected to fatigue loading. The alloying provides large benefit in terms of the high specific tensile strength (ultimate strength/density ratio) to the aluminum alloy but causes the aluminum alloy to be more sensitive to localized corrosion due to complex microscopic heterogeneities such as secondary phases. This paper investigates thermal spray coating namely arc spraying to evaluate the protection against environmentally assisted cracking (EAC) and localized corrosion on Aircraft structural 7075 T651 aluminum alloys. In particular, EAC and pitting corrosion at the interface coating-substrate are a challenge for thermal spray protective coatings on aluminum alloys under cyclic load and immersion. To address these issues, different surface preparation techniques prior to arc spraying were considered such as chemical de-oxidation, laser ablation, shot peening and grit blasting. Results indicate that surface preparation and improved coating process parameters play an important role to provide a coating conferring a protection against both localized corrosion and EAC.

Jan 1, 2006

By Y. X. Li, L. R. Xiao, S. Gong, S. S. He

Porous copper and porous copper based alloys with controllable pore structure have been manufactured successfully by sintering evaporation process. This process consisted of mixing copper or copper based alloys with NaCl powders, hot pressing and final high-temperature sintering to evaporate the filler material of NaCl powders. NaCl was eliminated completely during vacuum sintering, and strong metallurgical bonding in the walls was achieved. The pores’ structural parameter (pore size, shape, and direction) and porosity can be controlled effectively. These porous copper and porous copper based alloys with controllable pore structure have great potential in many fields. Including heat dissipating materials, heat absorbing materials, chemical catalyst carriers, electromagnetic shielding materials, filtering materials, damping materials, silencing materials, battery electrode materials. INTRODUCTION The development of porous materials began in the 1960s. The research of activated carbon with high specific surface area made porous materials enter the stage of material research (Belyakov et al., 2008; Ferey et al., 2008). With the rapid development of science and technology, porous materials play an important role in material research, and gradually become an indispensable part of the material research field (Wu et al., 2012). The research of porous materials has gradually extended to metal, ceramics, plastics and glass and other fields. It has been successfully applied in many fields, such as functional materials, industrial production, aviation, medical materials, biochemistry and electronics, which fully shows that porous materials have considerable development prospects. Porous silicon, plastic porous materials and glass porous materials are the most widely used in the field of non-metallic porous materials (Capelle et al., 2012). Compared with non-metallic porous materials, metal porous materials have developed rapidly in the late 1980s and become new materials with good mechanical properties and excellent physical properties. Porous metal materials have many advantages, such as large specific surface, small specific gravity, good silencing effect, high stiffness, high electromagnetic shielding performance, good shock absorption performance, etc (Li et al., 1999; Ferey et al., 2008). Among its many applications, metal porous materials can be used as both functional materials and structural materials. In some cases, metal porous materials have dual functions and structures. It is a multi-purpose engineering material with excellent performance. At present, porous copper, porous aluminium and porous nickel are the most concerned materials (Chen et al., 2002; Yang et al., 2017; Liu et al., 2018). The preparation methods of porous copper and copper-based alloys mainly include self-propagating high temperature synthesis (SHS), capsule-free hot isostatic pressing (CF-HIP), spark plasma sintering (SPS) (Kvanin et al., 2008; Takahashi et al., 2008; Zhang et al., 2014). However, these methods can not accurately control pore structure parameters (including pore size, shape, orientation, distribution, etc.). In porous materials, pore structure plays an important role in the overall performance of materials. In order to control pore structure parameters accurately and optimize material performance, it is necessary to explore and develop new preparation technology. In this paper, the sintering evaporation process (SEP) was introduced for the preparation of porous copper and copper-based alloys. The core process of the preparation method is hot pressing and evaporative desalination. Hot pressing can make the pore orientation consistent. Evaporative desalination can ensure the complete removal of NaCl in the form of vapor in a short time, thus eliminating the corrosion of residual NaCl on the matrix metal (Gong et al., 2011).

Jan 1, 2019

By J. E. Armstrong

THE Pinchi Lake mercury belt is in central British Columbia, about fifty miles north of the Prince Rupert branch of the Canadian National railway (Figure 1). Until 1936 little was known about the geology of this area. Jn 19~6 and 1937, J. G. Gray and the writer mapped the Fort Fraser area (G.S.C. maps 630A and 631A) for the Geological Survey of Canada. During the field season of 1937, cinnabar was discovered by J. G. Gray in the Permian limestones on the north shore of Pinchi lake on what have since proved to be the main showings of the Pinchi Lake mercury mine. Claims were staked in the spring of 1938 and later that year were optioned to the Consolidated Mining and Smelting Company. Development work revealed cinnabar deposits of commercial size and grade, and a small reduction plant was erected, production of mercury commencing in June, 1940. Since 1940, this plant has been enlarged by additional units. The ore treated is reported to contain between 0.5 and 0.75 per cent mercury. The production of mercury from this deposit is now far in excess of Canadian requirements and this country is able to supply the United Kingdom with part of its needs. In 1940 and 1941, several other occurrences of cinnabar were found northwest of Pinchi lake. During 1941, the writer made a geological investigation of the known cinnabar occurrences and of the belt of country in which they are located. The present paper summarizes the results of this work. The writer is indebted to officials of the Consolidated Mining and Smelting Company, and to Mr. E. Bronlund of the Pinchi Lake mine in particular, for their generous co-operation in the work.

Jan 1, 1942

By T. C. Murphy, W. Taciuk

In 1966, the Iron Ore Company of Canada commissioned a wet magnetic scavanging plant for the recovery of fine magnetite values p.resent in spiral tailings discharged from a spiral gravity separation process. The plant includes dewatering, grinding, classification, thickening, mini-wedge screening, and primary, secondary and tertiary wet magnetic separation stages. The source of feed varies in quantity and quality, so the original design included variable operational procedures to deal with these conditions.

Jan 1, 1972

By D. L. Cramp

The Direct-Connected Electric Hoist In the latter part of 1931 a new electric hoist was installed at the Lake Shore mine. A number of interesting features were incorporated in this machine, which is the first direct-connected, direct-current-operated hoist to be placed in service in the Kirkland Lake district. Many factors requiring care and study enter into the selection of hoisting-engine drive. In this instance, conditions warranted the selection of the generator voltage control system (Ward-Leonard), utilizing a direct-current driving motor and a separate motor generator unit. It was further deter-mined that additional economies could be secured by the selection of a motor generator unit with a flywheel, and consequently the Ilgner-Ward Leonard flywheel set was adopted. Some of the advantages of this system are: 1) Greater accuracy of control, resulting in increased flexibility in hand-ling with increased precision and safety; especially desirable in large, important installations where the rope-speed is high or where frequent shifting is necessary. (2) Reduced energy consumption. (3) Feasibility of load equalization, without which, in some cases, the power system would be unable to carry the fluctuating load imposed on it by the operation of the hoist. ( 4) Elimination of reduction gearing in the construction of the hoist. The hoist is located on the surface and is used for skip operation at the main shaft, hoisting ore from a present maximum depth of 4,200 feet.

Jan 1, 1933

By L. R. Wilkinson, W. J. Howarth, G. J. Wenk

Over a period of three years, a cooperative program in Australia has resulted in the development of radioisotope immersion probes for the on-stream analysis of mineral slurries. Two basic probe types are now available on a commercial basis - fluorescence and absorption probes - and within each type there are a number of variations so that optimum sensitivities can be obtained for elements with atomic number greater than titanium (22), thus covering most metals of interest to modern metallurgy.

Jan 1, 1973

By van der Meer. F. P.

High Pressure Grinding Roll (?HPGR?) technology is applied in a broadening range of minerals processing applications for relatively wet or moist materials. HPGR grinding of dry material or involving drying and air classification is more common, for example in cement manufacturing. A number of minerals processing plants are also operating with dry material, either due to process reasons, such as considerations of preceding or subsequent process stages, or as dictated by local conditions of arid areas and scarcity of water. The present world-wide expectation of decreasing availability of water supply urges us to look for alternatives that minimize water consumption. Recently established and envisaged future HPGR applications with dry ores have indicated that the technology of dry crushing and classification as practiced in cement and limestone grinding can be applied in minerals processing. Moreover, dry technology could very well be applied for generating a final fine product at sizes near or below 100 microns, as may be required for beneficiation by, for instance, flotation, magnetic separation or tank leaching. Dry HPGR grinding requires special attention in maintaining suitable process economics, when considering power input in grinding, drying and classification. In some cases, HPGR capacity and roll surface wear life may be negatively affected by a lack of moisture in the feed. This publication summarizes some of the features of, and experiences in dry HPGR applications. This includes design aspects of the classification system and discussion of the wear protection of the roll surfaces. The paper also includes examples of operational experiences of dry practices in minerals processing and cement plants.

Jan 1, 2012

By M. L. F. Paullo, S. Cristian Mejia, D. Roehl

"Rock fracture simulation most often presents non-linear behaviour due to loss of material integrity and strain concentration in the fracture zone. These strains generate local instabilities that propagate to the global system of equilibrium equations, generating convergence problems of the numerical solution. Often, in such cases, analyses in the post-critical regime are unfeasible. To overcome the numerical difficulties associated with problems of stiffness loss in the post-critical regime control methods, also called continuation methods, are employed. Among them are the arc-length method, the energy control method and the indirect displacement control method. These methods are employed in conjunction with a Newton- Raphson scheme for the solution of non-linear systems of equations. However, depending on the system instability, convergence in not guaranteed even with very small increments. In the present work these control techniques are investigated in combination with cohesive elements to simulate rock fracture. The constitutive model employed with the cohesive elements represents stiffness degradation through a damage law, which leads to serious convergence difficulties as reported in the literature. Here the continuation methods mentioned are applied to a Mode I rock fracture problem and to hydraulic fracture simulations. The effectiveness of the different continuation methods is compared.INTRODUCTIONThe process of rock fracture induced by the fluid pressure is called hydraulic fracturing. The propagation of a hydraulic fracture is a complex process, which is basically defined by the mechanical deformation of the rock, the fluid flow within the fracture and the fracture propagation itself (Mokryakov, 2011). In the works of Bendezu et al. (2013), Chen (2012) and Carrier et al. (2012), vertical hydraulic fracture propagation is modeled by cohesive elements with traction-separation law. The softening behavior of rock in post-critical regime is demonstrated by experimental testing and is characterized mainly by high strains and low stresses (Crowder and Bawden, 2004). This nonlinear behaviour can arise due to material nonlinearity, such as micro-cracking and damage, leading to softening behaviour (Chandrakant, S.D., 2012). The cohesive fracture model considers in its formulation the softening behaviour that most rocks present in post-critical regime with propagation criteria."

Jan 1, 2015