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By R. Drummond

The fourth Teetered Bed Separator (TBS) has just been installed in Australia, and trials have been run in many sites. There is a growing recognition of the potential advantages of using TBS technology to treat coal in the ?3+0.25 mm size range, at cut points below 1.60. From these activities, there has been a substantial growth in knowledge with respect to application engineering and operational functions. The paper briefly describes the installations, including flowsheets, and so provides a background to the potential deployment of TBS technology. There are a large number of potential applications for TBS technology, including treatment of fine ROM coal in new plants, or in upgrade situations for re-processing of spiral product, or scavenging coal from coarse tailings. As well, cost effective capacity upgrades are possible by using TBS units for treating the sands size fraction. Issues arising from Australian TBS installations and application engineering are also discussed.

Jan 1, 2002

By J. N. Van der Merwe, D. P. Roberts

The two components of pillar design formula being used in South Africa are pillar strength and pillar load. While considerable effort has been directed to the determination of pillar strength, the other half of the safety factor equation, the load, has not received the same amount of attention. The load acting on pillars has always been calculated using the Tributary Area Theory (TAT). This paper summarises the recent studies on coal pillar loading using various numerical models. It concludes that although there are meaningful differences under certain circumstances, there is still a compelling argument to use the TAT in coal pillar design. Les deux parties composantes de la formule de conception de pilier généralement utilisée en Afrique du Sud sont la résistance de pilier et la charge de pilier. Tandis que des efforts considérables on été dirigés vers la détermination de la résistance de pilier, l’autre moitié du facteur de sécurité n’a pas reçu la même attention. La charge agissant sur les piliers a toujours été calculée avec la Théorie d’Aire Tributaire (TAT). L’étude présente résume les études récentes sur la charge de pilier de charbon utilisant des modèles numériques variés. La conclusion est que bien qu’il y ait des différences significatives selon les circonstances, il y a toujours un argument puissant pour utiliser le TAT dans la conception de pilier de charbon. Die in Südafrika für die Auslegung von Pfeilern verwendeten zwei Formelkomponenten sind Pfeilerstärke und Pfeilerbelastung. Während beträchtlicher Aufwand zur Bestimmung der Pfeilerstärke gemacht wurde, wurde der anderen Hälfte der Sicherheitsfaktorsgleichung nicht die gleiche Aufmerksamkeit gewidmet. Die auf die Pfeiler wirkende Last wurde immer unter Verwendung der Tributary Area Theory (TAT) berechnet. Diese Arbeit fast neuere Studien betreffend der Belastung von Kohlepfeilern unter Verwendung verschiedener numerischer Modelle zusammen. Die Schlussfolderung ist, daß obwohl unter bestimmten Vorraussetzungen bedeutende Unterschiede existieren, nach wie vor ein bezwingendes Argument besteht TAT in der Kohlepfeilerauslegung zu verwenden.

Jan 1, 2003

By I. M. Wolf, S. A. Usmar, L. A. Cornish

The limiting criterion in the use of stainless steel for certain forming operations such as coining is its hardness, which determines parameters such as required striking pressure, wear on dies, and integrity of pattern detail. Attention is given here to the development of ultra-soft ferritic stainless steels for coinage. In the first instance, the influence of carbon content on the striking properties of a series of commercial and experimental 17%Cr alloys was evaluated. It was found that a lower carbon content permitted the striking of relatively highly profiled and intricate patterns, provided that the hardness did not exceed 125 HV. Hardnesses as low as 115 HV were achieved in the fully annealed condition, but these alloys required high striking pressures. In a further study, three grades of experimental 14%Cr ferritic stainless steels were produced with a view to optimizing the ductility. When the residual impurities were minimized, hardness values of about 100 HV and lower were achieved. Micro-alloying additions allowed the heat-treatment response and grain size to be controlled. Excellent tensile properties, with elongations of up to 42 per cent, were achieved in the fuly annealed condition, and highly profiled patterns were produced in coining trials.

Jan 1, 1993

By Z. Saw, C. Poveda, N. L. Mai

Optimising the throughput of a mining network comprising all equipment from shovels to semi-autogenous grinding (SAG) mills is a complicated task, yet the potential benefits can be significant. Key modelling challenges stem from the sheer number of possible routes which material can travel, different equipment operating under different constraints, and the rate of SAG mills being calculated through a nonlinear function of the blended materials’ rock attributes. Nevertheless, this is an ideal onapplication area of mathematical programming, a branch of operations research. This paper describes an application of mixed integer linear programming (MILP) to optimise the mining equipment network of one of the world’s largest copper mines.The model takes as input a year-long monthly mine schedule of shovels in different pits, pushbacks, sequences and faces which produce material to be moved through a network of crushers, conveyors, silos, distributors, stockpiles and SAG mills, ultimately outputting a daily operational plan for all equipment that maximises the throughput of the network. All operational constraints and business rules are considered, including three quality attributes of copper ore. Comparing model results with actual data shows an improvement of 4.47% in network throughput tonnage. Additionally, although the model is solved using a free, open-source solver, optimal solutions are still achieved within a practical timeframe.

Sep 1, 2021

By S. Pule, Z. Ndabezimbi, A. Hefer, E. Cupido

This article outlines various projects implemented at Rand Refinery to reduce effluent generation and freshwater consumption. The refinery generates about 2800 m³ of effluent annually and has initiated projects such as granulation water recycle and silver leach optimisation to address these issues. The granulation water recycle project has successfully reduced effluent volumes, while the silver leach optimisation has further decreased effluent by implementing stoichiometric addition of HCl and NaClO3. The vibratory shear enhanced processing (VSEP) trial showed promising results for gold recovery from wastewater, though further trials are recommended. The water savings of the effluent reduction projects are monitored by measuring the amount of effluent pumped to service yard effluent storage facilities with the use of flow meters connected on SCADA. Since the effluent reduction initiative of granulation effluent recycle in FY23, the effluent reduced to 2676 m³. In FY24, the stoichiometric addition of HCl and NaClO3 was implemented in the silver leach process, further reducing the effluent to 2083 m³.

Mar 5, 2025

By J. Morkel

During research on mainly the weathering of kimberlite, it became evident that its mineralogical composition is an important factor in the complex process of physical and chemical disintegration. The mineralogy of tuffisitic kimberlite breccias from two localities, the Cullinan and Venetia mines, is compared with special reference to the occurrence of associated clay minerals. The clay mineral composition influences the engineering properties of these rock types. It is illustrated how the presence of swelling clay components can be confirmed by ethylene glycol treatment and chlorite minerals by heat treatment using X-ray diffraction. Smectites are present in both tuffisitic kimberlites, dominant at Venetia while chlorite is more frequent at Cullinan. More tuffisitic kimberlite breccias samples from venetia were also characterized. It was found that kimberlite disintegration is correlated with the presence and abundance of smectite.

Jan 1, 2006

By J. W. van der Merwe, A. S. Bolokang, M. J. Phasha, V. J. Matjeke, C. Moopanar

"Excessive wear rates on railway wheels can result in rolling-stock derailments. If wear is detected early the possible derailments can be prevented by prematurely replacing wheelsets, although the inventory cost and maintenance downtime remain a challenge. In the current study, wheels were introduced and monitored in-service for two years to investigate the cause of excessive wear rates. The wear rates and stresses were calculated for the wheels suitable for a maximum load of 26 t per axle. Microstructural and mechanical properties were analysed. As expected, the general microstructure of all the wheels tested was pearlitic. Although all the wheels complied with the tensile strength requirements, stress calculations confirmed material distortion on excessively worn wheels whereas trial wheels revealed yield strength exceeding the yield criterion. High wear rates observed on the wheels were a result of low yield strength relative to the load per axle. The typical wear mechanism found was due to a combination of rolling contact fatigue and abrasive brake wear. Despite compliance of the wheels with existing requirements regarding material and mechanical properties (hardness, ultimate tensile strength), it is recommended that the yield strength must also be taken into consideration as a critical parameter.IntroductionRailway wheels are used to support the wagon mass and guide the wagon along the tracks (Park, 1974). The wheels and rails must be able to tolerate the applied tangential forces in order to effect wagon dynamic performance and reduce material deformation (Ghidini et al., 1994; RSE_TE_SPC_0045, 2011; AAR M107/M 208 Specification, 2011. Over the past ten years, the South African coal wagon maintenance depot has experienced excessive hollow wheel wear rates on the heavy haul line wheels. The maximum load of Jumbo wagons on the coal line is 104 t, or 26 t per axle. Although the maintenance intervention cycle for wheelsets was two years, between February 2011 and August 2012 some wheels experienced excessive hollow wear. Hollow wear is regarded as wear exceeding 2 mm on the central portion of the wheel tread (RSE_TE_SPC_0045, 2011). This happened despite the fact that these wheels were manufactured and certified according to the requirements of AAR M107/208 standard for carbon steel wheels (AAR M107/M 208 Specification,. 2011) and the local wheel RS/ME/SP 021 standard specification (RS / ME / SP / 021 REV 5 (2013). The AAR standard only specifies a minimum hardness as a required mechanical property and the local standard specifies hardness and minimum tensile strength only. In general, an increase in hardness will improve the rolling/sliding wear resistance of steel. This relationship of hardness and wear resistance was found to be true only in a situation where solid and similar alloys are in contact (Singh, Khatirkar and Sapate, 2015). The sliding wear resistance of a material is usually estimated using Archard’s equation (Liu and Li, 2001)."

Jan 1, 2016

By B. Elevli

This paper deals with the selection of alternative accesses to a podiform chromite orebody in Turkey. The most important alternatives studied in a related project have been stated as a new vertical shaft and a ramp system. The comparison of these alternatives have been carried out on the basis of total investment costs, ore transport unit cost and net present value (NPV) of overall project for various depth. The results show that up to the depth of 700 m, the total investment cost and NPV favours the ramp access while unit ore transport cost make the shaft access preferable.

Jan 1, 2002

By M. Salimov, J. Sattarvand

The conventional visualisation method of remote equipment is through the installation of one or more cameras on the machine, and sending a live feed to the operator’s flat display. However, the performance of the teleoperation can be enhanced using better visualisation through virtual reality (VR). This paper presents the process of the design and manufacturing of a robotic platform that will be used in the next phase of the project for a VR-assisted teleoperated excavator. The robot consists of a loading boom and arm arrangement installed on the undercarriage of a CAT300-9D. All hydraulic cylinders are replaced with electric actuators, and crawling motors are substituted by electric motors. The pieces of the boom and the arm, as well as the bucket were designed in Autodesk Inventor, and manufactured from aluminium sheets using a desktop and CNC machine. Parts are joined by pins and welding as needed. An Arduino-based control system is developed for the robot, and motor controllers are used to convert the power commands from the microcontroller to the high-amperage actuators. The control system is capable of communicating with a wireless Play Station controller to operate remotely. The manufactured robotic excavator is planned to be utilised in multiple autonomy research projects.

Sep 1, 2021

By H Möller

The purpose of this paper is to give an overview of the corrosion behaviour of steel in seawater. It is shown that the corrosion products (oxy-hydroxides and calcareous deposits) that are formed during corrosion in seawater have a significant effect on the corrosion behaviour of steel. The chemical composition of the steel determines how protective the oxy-hydroxide corrosion product is. The composition of the seawater influences the nature of the calcareous deposits. This needs to be considered when artificial solutions are used to simulate the corrosion behaviour of steel in seawater. A 3.5% NaCl solution is used frequently for this purpose, but because no calcareous deposits can be formed in this solution, erroneous results in terms of corrosion rates are obtained. The more complex ASTM D1141 artificial solution can be used to include the effects of ions other than Na+ and Cl- in synthetic seawaters. The importance of these other ions on the formation of calcareous deposits is discussed. Keywords: Steel, corrosion, seawater, calcareous deposits, oxy-hydroxides

Jan 1, 2006

By S. Heukelman

Zinc or, a zinc refinery in South Africa, uses oxygen enrichment of up to 26% O2 in its fluidizing air to increase concentrate-throughput in its fluidized bed roasters. The aim of the study is to determine whether O2 enrichment can be reduced by introducing micro-pelletized concentrate into the feed blend, while maintaining concentrate throughput rates and calcine quality. A laboratory scale fluidized roaster was used to determine the strength and oxidation kinetics of suitable micro-pellets. The strength of the pellets was determined by the extent of attrition during roasting. It was found that micro-pelletization decreases the fines in the feed to the roasters; the ?500 µm fraction decreased from 87% to 10%. The micro-pelletized particles do break down during roasting, which increases the -500 µm fraction to 31%. The general morphologies of the roasted particles are similar to those found by previous workers. Micro-pelletized concentrate particles require more time than non-pelletized concentrate particles to oxidize in the roasting step, although this is less than the mean residence time of the Zincor roasters. Roasting micro-pellets in O2-enriched fluidizing air increased the reaction rate.

Jan 1, 2011

By Jo Katembo, Patty Bwando, Patient K. Ilunga, Yves Kalubi, Emman Mulaj

"From 2010, the dolomite concentration in the ore fed to the Usoke Plant increased, resulting in a significant increase in the gangue acid consumption and Mg build-up in the circuit, and thus an increase in the Mg:Co ratio in the plant solutions. This affected the Co salt grade, reagent consumption, filtration and drying capacity. Efforts were put in place to minimise the acid consumption and consequently the Mg dissolution (such as use of pre-diluted acid), but the benefits were negligible. Various efforts were then initiated by CHEMAF to improve the cobalt plant productivity (quantity and quality) by process changes, dual precipitation and seed recycle. The positive results obtained in the laboratory were successfully implemented on plant scale. A change in the process from a single-stage precipitation with Na2CO3 to dual precipitation using a combination of Na2CO3 and NaOH improved the capacity of the Co salt filtration by 30%, the Co salt grade and drying capacity by 50%, and reduced the reagent consumption by 22%. Implementation of precipitate seed recycle increased Mg rejection by 40%, improving the Co salt grade from 20% to 25%, and yielding a further drop in reagent consumption. INTRODUCTION CHEMAF (Chemicals of Africa), a mining company located in Katanga province of Democratic Republic of Congo (DRC), has been operating since 2003. The Usoke hydrometallurgical plant treats the Cu-Co ore from the Etoile pit to produce Cu cathodes via a leach–solvent-extraction (SX)–electrowinning (EW) circuit and Co salt via a selective precipitation process. The plant was designed to treat run-of-mine (ROM) ore grading 6% Cu and 1.5% Co; but, in 2008, due to a decline in grades, a heavy-media separation (HMS) plant was commissioned to enrich the low-grade ROM (3.5% Cu and 0.5% Co) up to 8% Cu and 1% Co before feeding it to the hydrometallurgical plant. Co is recovered by precipitation of Fe and Al with limestone, followed by Co precipitation as Co carbonate using sodium carbonate (Na2CO3), also known as soda ash. 85% of the final effluent from cobalt precipitation is recycled back to the plant as process water; the balance, 15%, is bled out and compensated for by fresh water top up to control and retard the rate of sodium sulfate build up."

Jan 1, 2015

The key aspects of process metallurgy that distinguish platinum group metal (PGM) concentrate smelting from that of other base metal sulphide concentrates are presented. These differences include considerably higher input chrome and magnesia contents that directly raise the slag liquidus temperature and have the potential to increase accumulations of refractory spinels. Most importantly, the higher processing temperature required for PGM smelting, and the resulting very high matte superheat lead to considerably more onerous smelting conditions than those typical of other smelting operations. This has presented challenges to furnace design and integrity, especially when coupled with the progressive intensification of smelting, involving doubling, and then redoubling, of furnace power input over the past 20 years. These power increases have been enabled by increasingly more advanced furnace cooling and structural technologies. Key technologies include strong constant-force spring-loaded bindings acting in three dimensions to minimize infiltration of superheated matte into brick joints, and robust well-cooled tapholes for reliably tapping the superheated matte. The result has been substantially improved productivity, and reduced smelting capital cost outlay per unit of production. A significant challenge that was not anticipated, presented itself in the form of insidious corrosion of the furnace lining, and especially high-intensity copper cooling elements. Investigation of corrosion in related industries eventually identified 'chloride-accelerated sulphidation', and this term has been retained as it generically describes the most pertinent aspects of the accelerated low-temperature wear of copper coolers observed in PGM smelting. In addition to discussing the corrosion mechanism, this paper describes a number of solutions that were developed jointly by Anglo American Platinum and Hatch to address the copper corrosion problem. First, new monitoring technologies allowed furnaces to be operated more safely for a longer period of time. Second, a system for replacing corroded coolers from outside the furnace during a fast 'hot' shutdown minimized the impact on furnace operating factor and hearth life. Finally, a corrosion-resistant graphite-protected cooler design significantly improved furnace campaign life, and heralds a more lasting solution to cooler corrosion in PGM furnaces.

Jan 1, 2012

By L. Andrews

Mineralogy, traditionally associated with concentrator studies, is being increasingly applied to problems in pyrometallurgy. Such investigations commonly make use of a number of techniques, and the results are combined for a meaningful interpretation, which can lead to a successful solution for the problem. Mineralogical techniques are described for various pyrometallurgical operations. Examples are given of studies and investigations involving mineralogy in chemical-looping combustion, feed monitoring to platinum-smelting furnaces, and losses to slag in base metal and platinum smelting.

Jan 1, 2011

By F. Rwere, A. Masasire, P. Dzomba, M. Mupa

Accurate determination of platinum group metals (PGMs) and gold (Au) has always proven to be a difficult task, due to their low concentrations in platiniferous ores. The most common preconcentration technique used in analysis of these metals is fire assay with a flux containing nickel or lead. This technique can be improved by using co-collectors. Here we hypothesise that Fe, Co, and Cu can be used as co-collectors to enhance separation and preconcentration of PMGs and gold by fire assay. To test this hypothesis, geological exploration samples from Siyanda Union Mine (Northam, South Africa) were analysed by an inductively coupled plasma-optical emission spectrometer (ICP-OES) for PGMs (Pt, Pd, and Rh) and Au. A control sample (certified reference material AMIS 0426) was also analysed by the same technique. The PGM and Au recoveries from the control sample ranged from 83% to 105% for all three co-collectors, with relative standard deviations less than 10% for the control sample and 7% for the geological samples. The PGM and Au recoveries by Fe and Co co-collectors were modestly higher than that of the Cu-collector. These results indicate that Fe and Co are better co-collectors than Cu, presumably due to the loss of analyte when using Cu. Taken together, Fe and Co co-collectors can be viable alternatives for analysis of PGMs and gold using the fire assay method.

Jan 2, 2022

By B. Simser

Rockbursting around underground excavations continues to be a core risk for many deep mining operations. Numerous advancements in mine design, preconditioning, monitoring, mining equipment, exclusion zones, and ground support have significantly lowered the risk to mine workers. As mining continues in deeper, more challenging environments, a multitiered approach to rockburst risk mitigation, starting with mine design, is required. Both the overall mine sequence, for example, avoiding converging mining fronts, and local design “stick handling” can play an important role in risk reduction. Rockburst case studies dating back to the late 1990s up until 2024 are used to highlight risk factors and risk mitigation (tactical and strategic). Examples from several deep hard rock mines are used, generally in high horizontal stress fields (k ratios 1.5 to 2), and strong brittle rock (> 200 MPa unconfined compressive strength). Mining induced stresses as well as high in situ stress due to depth are discussed. The context is Canadian mining, which typically has highly mechanised operations, large openings and equipment. Examples from a narrow vein mine and shaft sinking are also given because neither environment is simple to mechanise, highlighting the need for other risk mitigations. A “sieve” analysis based on mine incident reports is used to show how a multi-tiered risk management plan can lower exposure to violent ground failures. A few incidents still make their way through the “sieve,” indicating a need for further improvements. Thoughts on future/ current developments, and their strategic importance are given. Ground support is the last line of defence. The proliferation of multiple styles of yielding tendons and support systems has made many choices available to rock engineering professionals. Despite the increased availability of dynamic ground support components, there are still difficulties getting clean load transfer to bolts, determining support demand, monitoring loss of capacity over time/mining, and evaluating true system capacity. Virgin development in deep high stress brittle rock can result in high strainburst exposure prior to any stoping operations. The mining process must reduce worker exposure to unsupported rockmasses. Successful preconditioning in a shaft sinking operation, the use of high early strength shotcrete, and mechanised equipment are also discussed.

Nov 24, 2025

The optimum cut-off grade policy maximizes the net present value (NPV) of an open pit mining operation subject to the mining, processing, and refining capacity constraints. The traditional approaches to cut-off grade determination ignore the escalation of the economic parameters such as metal price and operating costs during life of an operation, and consequently lead to unrealistically higher values of the objective function. Further, the NPV of a mining operation declines due to the depletion of the available reserves, causing a decline in the optimum cut-off grade, i.e. higher cut-off grades in the early years of an operation and lower cut-off grades during the later years. Hence, low grade material mined in the earlier years may be stockpiled for processing during later years to offset the effect of escalating economic parameters on NPV. This paper demonstrates the combined impact of introducing economic parameters, escalation and stockpiling options into the cut-off grade optimization model. The model promises an enhancement in NPV as illustrated in a case study incorporating practical aspects of an open pit mining operation.

Jan 1, 2011

What is a nugget effect? In the early development of geostatistics, the term ?nugget effect? was coined for the apparent discontinuity at the beginning of many semivariogram graphs. This name was chosen to reflect the large differences found between neighbouring samples in ?nuggety? mineralizations such as Wits gold reefs. Geostatistical theory assumes that the difference between a sampled value and a potential repeat sample at the same location is actually zero. Included in this ?nugget effect? would be true variation between contiguous samples due to the nature of the mineralization, micro-fracturing, nugget or crystal size, and so on. Also included in the nugget effect would be any ?random? sampling variation which might occur due to the method in which the sample was taken, the adequacy of the sample size, the assaying process, etc. Arguments were put forward that ?sampling errors? actually exist at zero distance. Some geostatistical schools actually maintain that the ?nugget effect? is all sampling error. This would imply that ?perfect? sampling would eliminate the nugget effect entirely. There is now a dichotomy both in the geostatistical world and in the software packages provided for geostatistical analyses. It may seem academic to argue over whether the semivariogram model should take a value of zero, a value equal to the nugget effect, or a partial value at distance zero. However, the decision can have a profound effect on both the estimated resource and in our confidence on that resource. Whereas most geostatistical texts define the semivariogram model as taking the value of zero at zero distance, others imply that the full nugget effect should be used at zero distance. For example: ?The nugget effect refers to the nonzero intercept of the variogram and is an overall estimate of error caused by measurement inaccuracy and environmental variability occurring at fine enough scales to be unresolved by the sampling interval3 ?Christensen4 has shown that the ?nugget effect?, or non-zero variance at the origin of the sernivariogram, can be reproduced by a measurement error model ?The nugget effect is considered random noise and may represent short-scale variability, measurement error, sample rate, etc.5. In many training texts and Web courses, the definition of the semivariogram is ambiguous as the formulae for semivariogram models is not actually specified at zero distance6,7,8.

Jan 1, 2010

By H. Copur

Experimental studies for quantification of force and brittleness indices relevant to rock cutting performance are presented. A simple interpretation method is developed, which quantifies the force-penetration response obtained from indentation tests. Basic parameters of the quantification are force increment and decrementrates, force increment and decrement periods, and number of increment and decrement data points. Blocks of eleven different rock samples were collected from different operating mines in Turkey and subjected to indentation tests to calculate the indices. The samples included harzburgite, serpentinite, trona, limestone, claystone, two different sandstone samples, siltstone and three different chromite ore samples. The concept was validated by a set of full-scale linear cutting tests using a conical cutter for measuring the cutting performance in relieved and unrelieved conditions, i.e. cutter forces, specific energy, size distribution of rock cuttings. The rock cuttings were sieved to determine coarseness index, indicates coarse chip generation characteristics, and size distribution. The force index is moderately correlated with the cutting performance and mechanical properties of the rocks, and poorly correlated with the coarseness index and size distribution of cuttings. A general and moderate trend is observed between the brittleness index and the coarseness index, cutting performance for unrelieved cutting conditions and mechanical properties of the rocks. However, additional data is required to fill the data gaps and to potentially establish relationship between the brittleness index and all other parameters.

Jan 1, 2003

By Basson. J., L. R. Nelson, L. A. Cramer

The South African based platinum mines produce the world?s majority of platinum metal that is used in autocatalysts and jewellery. As the platinum market is forecast to grow at healthy rates into the future, the South African producers, Anglo Platinum, Impala, Lonmin and Northam are planning to expand in the next decade. Furthermore a number of smaller producers who are accessing other mineral rights are entering the buoyant market. The South African platinum mines have traditionally exploited the Merensky reef of the Bushveld Igneous Complex (BIC); however, the mining of this reef is reaching depths that require significant vertical shaft systems and costly refrigeration for access to the ore bodies at deeper levels. In the past decade all of the producers have begun to mine the less attractive UG2 reef because of its cheaper mining costs. This UG2 reef contains significant quantities of chromite with typically a chrome-to-iron (Cr/Fe) ratio of 1.35. UG2 ores can contain between 10 and 25% Cr2O3 depending upon the reef width and the selected mining method. It is relatively cheap and easy to extract a portion of the chromite from a platinum concentrator tailings stream at a grade of between 40-42% Cr2O3. However it is only in recent years that some ferrochrome producers have begun to source some of their chromite from the tailings of platinum producers. South Africa is also the world?s largest single producer of ferrochrome and supplies much of the world?s stainless steel producers and thus the growing market for their product. As the traditional sources of high Cr/Fe ratio ores have been depleted at the shallow economic depths and thus have become more expensive sources of chromite, technical developments have improved the ability to use fine chromite economically to make acceptable grades of ferrochrome. Thus UG2 fines are now becoming possible cheap sources of acceptable feed to the ferrochrome industry. The abundance of feedstock for ferrochrome production and the lessening dependence on mined material will impact upon the structure of the ferrochrome business in South Africa. With continued platinum mining from UG2 reefs, South Africa is set to remain highly competitive in the world?s ferrochrome/stainless steel industry.

Jan 1, 2004