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By M. Arlandi, J. C. Monge

In this paper, the finite element method is used to obtain deformations of a rock tunnel. More than 3,000 numerical simulations and calculations were carried out. The analysis of this results has allowed to achieve mathematical formulations and graphs, to obtain in advance support monitored displacements in tunnelling construction, so they can be predicted before excavation and supporting woks. The application of the presented formulations and charts will aid engineers to control tunnel monitoring, reducing decision time when problems occur. The analysis is limited to cases involving elastic behaviour of the terrain for tunnels of average to good quality in rock, and to excavation sections of average or smaller dimensions for road tunnels. The results show that, in all cases, mathematical expressions to obtain induced displacements around tunnel excavations, have similar pattern than Kirsch (1898) expressions for circular excavations. As corollary of the achieved results, a method to estimate in situ natural geostress ratio K0=sh/sv , by means of convergence measurements, is presented. In diesem Beitrag wurden die Verschiebungen eines Tunnels durch die Methode de Finiten Elemente berechnet. Mehr als 3000 numerische Simulationen und Berechnungen wurden ausgeführt. Die Analyse dieser Resultate hat es ermöglicht, mathematische Formeln und Grafiken zu entwickeln, die zur Voraussage der Verschiebungen in Tunnel dienen, auch unter Betrachtung der verschiedenartigen Abstützungen. So können die Verschiebungen vor den Erdarbeiten und dem Bau der Abstützung abgeschätzt werden. Die abgeleiteten Formeln und Grafiken werden vor allem einen grossen Dienst für Ingenieure bei der Mithilfe zu zeitsparenden Entscheidungen im Tunnelbau und bei der Tunnelkontrolle leisten. Die analysierten Fälle sind auf eine elastische Modellierung des Baugrunds beschränkt, sowie auf eine mittlere bis gute Qualität des Felsens und auf die Aushebung von Abtragungsabschnitten mittlerer oder geringer Grösse für den Strassenverkehr. Die Resultate zeigen, dass in allen Fällen die hergeleiteten Formeln zur Berechnung der durch den Tunnelbau verursachten Verschiebungen um den Tunnel die gleiche mathematische Struktur haben wie diejenigen von Kirsch (1898) für kreisförmigen Bodenaushub. Als Korollarium der ausgeführten Berechnungen wird eine Methode zur Abschätzung der vorherrschenden in situ Geospannungs-Verhälniss K0=sh/sv angegeben, die von den Messungen der Verschiebungen im Tunnel ausgeht. Dans cet article, la méthode des éléments finis est utilisée pour obtenir les déformations d’un tunnel creusé dans la roche. Plus de 3000 simulations numériques et calculs ont été effectuées. L’analyse de ces résultats a permis de définir des modèles mathématiques et des abaques afin de prédire, avant l’excavation et les travaux de soutènement, les déplacements auscultés pendant la construction du tunnel. L’application de ces modèles et abaques permettra donc aux ingénieurs de contrôler les déplacements durant l’auscultation du tunnel et de réduire le temps de décision lorsque des problèmes surviennent. L’analyse est limitée au cas du comportement élastique du terrain pour des tunnels creusés dans de la roche de moyenne a bonne qualité, et à de sections d’excavation de petites à moyennes dimensions pour des tunnels routiers. Les résultats montrent que, dans tous les cas, les expressions mathématiques permettant d’obtenir les déplacements induits autour des excavations de tunnel, présentent des similitudes avec celles de Kirsch (1898) pour des excavations circulaires. Comme corollaire aux résultats obtenus, une méthode pour estimer le rapport des

Jan 1, 2003

By S. Bellec, A. Berton

"Usually, steady state mass balances are used for the design of mineral processing plants. However, this tool does not take into account the impact of process inputs variability nor does it evaluate process transient behaviours between stationary states, such as mill start-up and shutdown. The use of advanced simulations enables the integration of dynamic behaviours in process design decision-making by highlighting situations that are undetectable by using only steady state mass balances. Applying these simulation tools to brown field projects allows the simulator performances to be calibrated and validated on actual plant data before it is used as a prediction tool for the modified plant.Three (3) simulators were implemented at the design stage of a major upgrade project for an ore processing plant in order to assess process behaviours under different production scenarios. These simulators were built to evaluate the impacts on major elements such as mine production, ore stockpile, concentrator production as well as water demand. A validation of individual equipment models was performed whenever sufficient measured data was available. The simulators were then used to study the impact of ore variability (grade, hardness, throughput), to assess day-to-day production special events, and to evaluate the true stockpiles live capacity.The use of a stochastic simulator for equipment sizing allowed a more precise sizing of many pieces of equipment and avoided important expenses in the fresh water pumping system. The dynamic simulator also confirmed that the water in place system would suffice, even in the most demanding production scenario. Finally, the stockpile simulator allowed an important production bottleneck to be quantified and then made possible the assessment of various practical solutions for the stockpiling-reclaiming issues.Post start-up, process data underlines the fact that using advanced simulation tools was useful to mitigate process-related risks associated to the plant expansion, showing generally accurate prediction and adequate equipment sizing, leading to smooth process commissioning. The presented methods are part of what is now routine in Soutex’s participation in both greenfield and brownfield projects."

Jan 1, 2015

By Michael A. Piepenburg

The East Side Access (ESA) Project will extend Long Island Rail Road (LIRR) into midtown Manhattan via 11 km of tunnels, a new terminal station and associated support facilities. In addition to the hard-rock tunneling currently underway in Manhattan, soft-ground tunnels in Queens will traverse beneath Amtrak?s Sunnyside Yard and Harold Interlocking, the busiest rail interlocking in North America. This paper details ESA?s coordinated approach to interfacing with both Amtrak and LIRR with regard to the planned tunnels, shafts and related construction beneath or adjacent to the operating railroads. This interface includes integration of railroad staff, extensive presentations, reviews and agreements with the railroads regarding settlement mitigation, real-time automated geo-instrumentation monitoring, ground improvement, and geotechnical/environmental controls.

By J. V. Ghelarducci, M. A. Sharpe, D. G. Chedgy

This article presents a novel design, called the Climax, High Capacity Processor (HCP), for pre-combustion cleaning of coal. This design is particularly suitable for the plant capacities of 400 ~ 660 TPH. The HCP is different from the conventional designs with an equivalent throughput in three major aspects: 1) the use of one large capacity HM cyclone to separate coarse and intermediate raw coal in a single circuit; 2) the elimination of the conventional secondary magnetics recovery system by use of the high efficiency Climax, magnetic separators; 3) the use of "single line" piping with a minimum requirement of ancillary devices. In comparison with conventional designs with similar capacity, the HCP plant costs much less in capital investment, operation and maintenance.

Feb 24, 1997

Well designed and maintained haul roads are the key to minimising truck haulage on-road hazards and costs, as well as increasing productivity. However, practically designing and managing a haul road for optimal performance is often diff cult to achieve. Poorly designed and built roads exhibit high rolling resistance - a one per cent increase in road rolling resistance can typically reduce speed on ramp by as much as ten per cent - and on the f at by up to 26 per cent. In the current economic climates, investment and operating decisions come under scrutiny. In the long run, this scrutiny returns improved efficiencies and leaner, healthier operations. The focus of this evolving evaluation process should and will certainly fall on haulage operations - simply by virtue of their contribution to overall cost of operations - often in excess of 50 per cent of total costs for deep open-pit mines. Whilst the end result - improved efficiency and reduced cost per ton hauled - is not in itself problematic, it is the route, or process followed to achieve these savings that needs to be carefully managed. We can be guided on this journey by our understanding of how a road is designed, and, critically, the interplay between a good design and safe, cost efficient haulage.This paper brief y summarises the evolution of mine haul road design, from the seminal USBM work of Kaufman and Ault in 1977, through to current geometric, structural, functional and maintenance management design components. These augmented design and management guidelines have been developed over the past decade, both in response to the requirements of mine operators for more safe and efficient haulage systems, and the truck manufacturers' requirements for a more predictable and controlled operating environment. These developments have been paralleled by the need to minimise haulage hazards, both from a health and safety perspective. Generally, both objectives have been achieved, but with some specific areas of design and operation still presenting ongoing potential health and safety hazards.The paper then summarises current design guidelines for these safety-critical issues, both from a road-design 'best-practice' and road management perspectives. Implementation of the approach is seen as a basis for reducing the potential of an under-designed mine road to lead to health and safety defects and secondly as a means of giving haul road safety and performance issues greater prominence in the minds of the road-user, operator, mine planner and designer alike.

Dec 6, 2010

By Cory J. E. Yacyshyn

Anchored steel pipe piles are being used more frequently in British Columbia for shoreline projects such as public ferries, cruise ship docks, containership terminals and locally in the expansion of the Vancouver waterfront convention center. While a 36? diameter driven pile may provide adequate compression loads it will not always achieve enough penetration to provide the required tension loading. That is why bundles of threaded anchors or strands are drilled through the center, past the pile tip, and anchored into the underlying strata. Drilling up to 250 feet deep through the piles in variable water bearing strata presents challenges. Southwest Contacting Ltd. (SWC) recently completed the three largest anchored pile projects in BC; Vancouver Port and Convention Center Expansion, Vanterm Container Terminal and the new Prince Rupert Cruise Ship Terminal. This paper will present the separate challenges encountered drilling the anchors. At Prince Rupert, the recently completed Northland Cruise Ship Dock ultimately required a cased system to drill and install triple thread bar anchors. When 200 foot long steel pipe piling was unable to penetrate the highly fractured gneiss/schist bedrock to obtain a seal and consolidation grouting was unsuccessful, a modified cased system was advanced deep enough into the rock to eventually seal. The 3-#20 bars were changed to 12-strands since the bars wouldn?t fit through the smaller cased hole. The options were limited because each dolphin only had enough room for a small hydraulic drill rig that wouldn?t have the power to fully case the holes. The Canada Place Pier Extension in Vancouver?s Harbor led to the development of an innovative tip design used later at Vanterm. The 36? diameter steel pipe piles were driven closed end but modified to permit drilling through a concrete plug at the base. The driving of the piles at Canada Place often knocked out the plug so we were faced with 50 feet of sand up inside the pile when the drilling started. This led to discussions on how to safely remove the sand, solidify the tip, and continue drilling to get past the tip without undermining the pile. Finally, Vanterm Berth Extension was completed with a unique drilling system because the pile tips stopped in hydraulic sands, as opposed to the native till. We were faced with advancing the casing to the till without undermining the base of the pile. With 100 psi water pressure at the pile base after we broke through the concrete plug, the trick was to prevent charging the sand with our 250 psi air which liquefies it and forced it up our drill casing. And of course, it has to happen just before Christmas holidays!

Jan 1, 2004

By Louis W. Cope

Many Americans have seen Greenland while flying over it on their way to or from Europe. Few have visited this largest island in the world. Portions of the 20 percent of the territory that are not ice-covered are highly mineralized. Greenland could become very productive if the present interest in exploration increases. The people and Greenland’s history The population of Greenland is 57,000. Twenty percent are Europeans, mainly of Danish decent, while 80percent are native Greenlandic or mixed Greenlandic-European. The native population is the same as the Inuit of the Canadian Arctic. They speak the same language.

Jan 1, 2004

By R Ratlou

Increased contamination due to sand in spiral feed has had a negative effect on the efficiency of spiral concentrators at Navigation Plant. The no. 1 seam at Kromdraai opencast, which was previously mined by underground bord and pillar methods, is now susceptible to spontaneous combustion because of air ingress into the old workings which are exposed in the opencast high wall. This posed a risk in the loss of reserves to burnt coal. As solutions, buffer blasting of the preceding cut to collapse bords and soft overburden dressing of un-collapsed bords were implemented to prevent air entering the workings. The latter remedy resulted in increased contamination due to addition of sand in Run of Mine. After evaluating alternatives, a low capital option was selected. The 110t/hr Teetered Bed Separator (TBS) has been installed, primarily to desand and upgrade the feed to the spiral concentrators. The unit indicated an upgrade with a yield increase of 0.4% during test work and is currently showing an overall plant yield increase of 0.97%.

Jan 1, 2006

By D Thorburn

This paper reviews the history of environmental assessment in New Zealand with reference to mineral developments. Emphasis is given to larger more controversial projects particularly metal mines. The changing role and application of the Environmental Protection and Enhancement Procedures is examined in the context of changes in the government's environmental administration and the response of the Ministry of Energy's resource allocation group. Conclusions are drawn on the effectiveness of the present environmental assessment activities and on the allocation of administration of priorities in the Ministry. The Ministry of Energy has effectively ceased to exist.

Jan 1, 1990

By Lawrence H. Van Vlack, Alfred S. Keh

The distribution of sulfur in iron was found to be dependent upon the time and temperature of the treatment as well as the chemical composition of the sulfide. With higher temperatures, the sulfide phase spreads more extensively between the iron grains. A complete network, however, does not form until approximately 1300°C (2372°F), ot which temperature the dihedral angle approaches zero. Silicon has little effect on this change. Aluminum, oxygen, and manganese all modify the temperature of sulfide network formation to a higher value. The microstructures which result and have significance in relation to hot-shortness are discussed. SULFIDE inclusions in steel were recognized by metallurgists before the turn of the century. Considerable attention has been paid to them, and numerous studies have been made on the working properties of steel as affected by them. It has been suggested that ho t-shortness of steel is due to the presence of an enveloping liquid sulfide film at the grain boundaries of the steel in the range of the hot-working temperatures. However, several facts have been observed in commercial steels which do not seem to be completely consistent with this explanation: 1) the frequent absence of continuous films of sulfide as observed under the microscope, 2) the absence of hot-shortness in some high sulfur and resulfurized steels, and 3) the limitation of hot-shortness to a definite temperature range. The role that manganese plays in steel to eliminate hot-shortness is well known, but the theory behind it is still under question. Moreover, the effect of de-oxidizers such as aluminum and silicon, and the effect of oxygen are still not clearly known. In this study, the effect of heat treatments and of additions of manganese, aluminum, silicon, and oxygen upon the distribution of sulfide inclusions in iron was investigated. Both the as-cast and the heat treated structures were studied, using microscopic and autoradiographic techniques. Part of the results were interpreted in terms of Smith's' concept of microstructure. Review of Literature Metallurgists used to consider sulfide inclusions as suspended particles. It was Wohrman' who first pointed out that sulfide inclusions are soluble in liquid iron. Many observed facts may be understood on the basis of this concept of solubility. Wohrman found that small castings contain small inclusions. and larger castings contain larger ones. Also, inclusion sizes are smaller near the chilled surface. For the same size ingot, the average inclusion size in a given heat of steel depends upon the rate of solidification. That is, with slow solidification, enough time for precipitation and agglomeration of these

Jan 1, 1957

By Katsuyoshi Kondoh

The utilization of silica particles originated in rice husks as reinforcements of magnesium composites was discussed. By using the solid state reaction of rice husk silica particles with magnesium powder, P/M magnesium based composites dispersed with the magnesium silicide (Mg2Si) and magnesium oxide (MgO) were fabricated. High-purity silica particles were originated from rice husks, one of the major agricultural wastes, via the citric acid leaching treatment and combustion in air. The effects of the silica particle characteristics such as size, crystalline and porous structures, on the reactivity of silica and magnesium to synthesize Mg2Si intermetallic were discussed. Amorphous silica was more useful for this reaction than crystalline one. The reactivity of rice husk silica was superior to that of the conventional mineral silica particles because of not only its amorphous structure but the larger specific surface area due to their pore structures. In the case of the green compact of the mixture of the rice husk silica and Mg powder, the silica particle size was not effective on the reactivity because the coarse particles were fractured into fine ones by cold compaction. The distribution of Mg2Si intermetallics of magnesium powder composites consolidated by SPS process was investigated by XRD and SEM-EDS analysis. Their mechanical and physical properties were also evaluated in detail.

Jan 1, 2009

By M. Dworzanowski

The physical beneficiation of iron ore that has a wide particle-size distribution is problematic, regardless of the process applied, whether dense medium separation, gravity concentration, magnetic separation, or flotation. The problem of particle size is further compounded when there is a significant -10 µm fraction. Generally the approach to a wide particle-size distribution is to split into narrower size ranges and treat each separately. More often than not the -10 µm fraction is not treated but discarded. This approach results in a more complicated and expensive flow sheet and the loss of any potential value in the -10 µm fraction. Wet high-intensity magnetic separation (WHIMS) bench-scale test work was conducted on a haematite-rich material with a particle size of -200 µm. What made this material different was that it contained a 60% -10 µm fraction, hence discarding the -10 µm material was not an option. The objective of the test work was to determine how to maximize the recovery of the haematite across the full particle size range. Given the unusual particle size distribution, it was concluded that WHIMS would be the only practical beneficiation route. The -200 +10 µm and -10 µm fractions were treated separately and together under varying WHIMS conditions. For a given concentrate grade, the mass yield obtained was greater when the total particle-size distribution was treated. The inferred optimum conditions, using the same material, were tested on a pilot-scale WHIMS and similar results were obtained.

Jan 1, 2014

By E. Ringdalen

Keywords: Pyrometallurgy, research, Norway, SINTEF, NTNU The Norwegian Ferro-alloy Industry and the model for research cooperation between SINTEF, NTNU, and the Norwegian ferro-alloy industry is presented as an introduction. The research within pyrometallurgy is illustrated by examples from characterisation of Mn-ores and characterisation of carbon materials. Examples from studies of reaction mechanisms in laboratory- and pilot-scale experiments are presented, in addition to an example of industrial off-gas measurements. Education possibilities at NTNU are also described.

Jan 1, 2011

By A J. Cornah

Critical decisions in iron ore project evaluation and production are based on global and local spatial estimates of primary mineral deposit properties (such as in situ geochemical grades) and geometallurgical responses (such as screened, washed or concentrated product yields and grades), which are derived from limited sample data. These spatial estimates are typically made using classical geostatistical techniques, which fundamentally assume that the attributes of interest behave additively. This assumption is generally appropriate for æprimaryÆ variables but æresponseÆ variables may behave non-additively and therefore their direct linear estimates may be biased.In this paper an existing additivity testing mechanism is used to quantify the bias resulting from direct linear estimation of a non-additive iron ore attribute. Data from a magnetite project are used to determine the circumstances under which such biases may be of material impact. The implications for iron ore resource estimation, geometallurgical modelling and grade control are outlined and discussed.CITATION:Cornah, A J, 2013. Assessment of the impact of non-additivity in the estimation of iron ore attributes, in Proceedings Iron Ore 2013 , pp 129-136 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By Panshi Xie, Xicai Gao, Yi Luo, Youfu Zeng, Yongping Wu, Shenghu Luo

This research investigates roof deformation and failure characteristics, as well as mechanical interaction between the panels of the roof strata above two adjacent working faces in a steeply inclined coal seam. Physical modeling with photogrammetry measurement method has been employed in this investigation. The movement of roof strata and section pillar, as well as the stratum morphological characteristics, was quantitatively analyzed. Results show that the roof movement direction above the two panels has zoning characteristics, especially in the lower panel. Roof migration in the lower panel of the working face is larger than that in the upper panel. The roof to floor closure perpendicular to the seam direction is larger than the sliding along the seam. The maximum roof concave and convex bending occurred at the middle and upper parts of both panels; the roof bending in the upper panel mining area indicates a larger mining disturbance induced by lower panel mining. The void ratio contour of the lower panel is an asymmetrically arched shape, which is different from that of the upper panel area. The higher roof strata above the upper panel exhibit separation and breaking, whereas the lower roof exhibits compression due to mining in lower panel. The section pillar is compressed and slides slightly, which aggravates the mechanical interaction between the panels and increases the caving height of the roof over the lower panel and the periodic weighting intensity

By Panshi Xie, Xicai Gao, Yi Luo, Youfu Zeng, Yongping Wu, Shenghu Luo

This research investigates roof deformation and failure characteristics, as well as mechanical interaction between the panels of the roof strata above two adjacent working faces in a steeply inclined coal seam. Physical modeling with photogrammetry measurement method has been employed in this investigation. The movement of roof strata and section pillar, as well as the stratum morphological characteristics, was quantitatively analyzed. Results show that the roof movement direction above the two panels has zoning characteristics, especially in the lower panel. Roof migration in the lower panel of the working face is larger than that in the upper panel. The roof to floor closure perpendicular to the seam direction is larger than the sliding along the seam. The maximum roof concave and convex bending occurred at the middle and upper parts of both panels; the roof bending in the upper panel mining area indicates a larger mining disturbance induced by lower panel mining. The void ratio contour of the lower panel is an asymmetrically arched shape, which is different from that of the upper panel area. The higher roof strata above the upper panel exhibit separation and breaking, whereas the lower roof exhibits compression due to mining in lower panel. The section pillar is compressed and slides slightly, which aggravates the mechanical interaction between the panels and increases the caving height of the roof over the lower panel and the periodic weighting intensity

7253. Arkhangelsky, A. D. Geological Results of the General Magnetometric and Gravimetric Surveys of the U.S.S.R. (in Russian). Internat. Geol. Cong., Rep. of the 17th Sess., Moscow-Leningrad, 1937, vol. 1, Moscow, 1939, pp. 241-250. Geophysical methods have been used in the U.S.S.R. to study geological problems. Such is the case of the general magnetometric and gravimetric surveys made jointly by the Main Physical Observatory, Main Office of Geodesy and Cartography, Institute of Terrestrial Magnetism, and Main Office of Geophysical Prospecting. Some institutions supplied the data, others processed them. Geological interpretation was made by the author. (1) Regional magnetic anomalies in the plains of the U.S.S.R. are traceable to the folded substratum overlain by sedimentary rocks; these anomalies promise to yield data characterizing the substratum in respect to strike and depth. Anomalies in European U.S.S.R. suggest that the pre-Cambrian -substratum of the East European plateau consists of elements of different ages. In the most ancient of them, the main strike of the folding is almost latitudinal; in the younger ones, the folding is oriented in the meridian. (2) The Faye and Bouguer gravity anomalies are caused primarily by differences in the density of rocks composing the upper crust and by unknown processes producing changes of density at depth; these processes are not connected with isosiatic movements. The anomalies in the European and adjoining Asiatic U.S.S.R. promise to indicate the volume of the pre-Cambrian massif of the east-European plateau and to clarify the interrelations between the Ural, Tian-Shan, and Donetz Basin folding systems, as well as between the Dnieper-Donetz depression and the mid-European depression. - V. S.

Jan 1, 1944

By M. Bhandari, D. Norval

The bulk of plain carbon steel is produced through conventional Basic Oxygen or Electric Arc Furnace routes where the development of the AC Ladle Furnace has made it possible to also produce alloy steels. Smaller Ladle Furnaces have limitations such as lower efficiency; high electrode consumption and diminutive yields rendering them uneconomical to operate and making the processing of low carbon steel grades difficult due to carbon pick up. The demand for special steels and alloys with strict specifications is increasing while commodity prices remain competitive. The production of special steels and alloys have specific process control requirements and the development of the induction melting furnace (IMF) has made it possible to produce smaller batches economically. Refining and alloying of the melt in the IMF further enhance the efficiency. The INDUREF furnace offers increased productivity and flexibility through increased thermal efficiency and can be utilised for holding molten metal for further processing such as granulating, atomising, nitriding, alloy additions and desulphurisation of Ferro-alloys and steels. The system utilises a specially engineered ladle which is placed in an induction-heating assembly comprised of a stationary water-cooled copper coil and lamination packs. The addition of equipment for vacuum degassing and decarburisation of steels and alloys is also feasible. Benefits are: ? No electrode consumption or carbon pick-up ? Lower installation, operation and maintenance cost. ? No line-flicker facilitates operation on a weak power grid. ? Good power factor and balanced load ? No skull formation and reduced refractory consumption ? Higher yield of Fe-alloys ? Automatic controlled stirring

Jan 1, 2004

Six simulations by the Mpnte Carlo method employing both classical and geostatistical techniques are presented for the determination of the probability distribution of the in situ value of a coal seam. To avoid the problem of qualitative estimation of parameter variability in the calculation of an arbitrary seam value, only data values from borehole information were used to quantify the variation in four coai seam parameters.The method which is suggested as being the most appropriate is a particular geostatistical approach that employs the best linear unbiased estimate and the error of estimation for a number of two dimensional blocks. The results indicate that the variance of the coal seam unit value may be much higher than that indicated by the classical approach because of the spatial variability that is properly incorporated in the geostatistical approach.The model used in the Monte Carlo simulation to determine the economic value of a coal seam can be extended to incorporate all those parameters which are necessary for a true estimation of the probability distribution of the coal seam value. A time value concept for discounting can also be incorporated to optimize the economic return of a coal mining project.

Jan 1, 1983

By M Shaffer, D C. Grant, D J. Goudie, P Sylvester, C Voisey

Scanning electron microscope–Mineral Liberation Analyser SEM-MLA can be used to discriminate between hematite/magnetite in iron ores, but achieving backscattered electron (BSE) segmentation between the two minerals is difficult for particles =75 µm using typical preparation and analysis methods for the MLA based on a tungsten filament SEM (Quanta 400) with 25 kV high voltage. Preparing iron ore sample mounts using a slow-speed polishing method, and conducting the experiment on a field emission gun SEM-MLA (Quanta 650) with the high voltage (HV) setting lowered to 15 kV reduces instrument noise and results in very clean BSE images and segmentation. This method requires new X-ray standards to be acquired for each mineral identity at 15 kV because of major changes in the spectra at lower kV. However, once these X-rays are added to the mineral reference list, effective segmentation can be achieved and a proper analysis obtained.CITATION:Grant, D C, Goudie, D J, Voisey, C, Shaffer, M and Sylvester, P, 2017. Discriminating hematite/magnetite via scanning electron microscope–mineral liberation analyser in the - mesh size fraction of iron ores, in Proceedings Iron Ore 2017, pp 541–548 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017