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Work undertaken in the field of cut-off grade optimization has not advanced much beyond the work undertaken by Lane in 1988. His definitive work is based on the calculus of the Net Present Value criterion which is the most widely understood, consistent, and appropriate method by which sequential cash flows arising from the extraction of mineral reserves from an exhaustible resource can be represented. Although the mathematics is not complex Lane’s method is not a widely appreciated or applied approach to maximizing the value of a mining operation through selection and balancing of operational cut-off grades. Three stages in a mining operation namely, mining, processing and marketing were defined by Lane and the economics of each stage are identified and isolated to provide an optimum cut-off for each stage. Points of intersection along the present value curves for each stage of a mining operation are used to identify balancing cut-off grades at points where the capacity of the mining, processing and marketing stages is fully utilized and the Net Present Value of the operation is optimized. Data that simulate a small, deep-level Witwatersrand-type gold mine with an average grade of 6 g/t Au and a logrithmic variance of 1.2,are applied to the model to illustrate the benefits of representing cut-off grades in terms of present value curves for different segments of a mining operation. Keywords: Cut-off grade, Net Present Value, grade-tonnage curve, balancing cut-off grade, mining, processing, marketing.

Jan 1, 2003

By C. Dixon

This paper is based on the assumption of some knowledge of the National Water Act. It will consider the question of how that Act fits in with: a) existing laws which overlap on the subject matter b) new laws either in draft or in the process of being compiled c) policies which will eventually find their provisions included in new legislation (e.g. minerals policy) d) international practices. The focus will be specifically on the interaction of legislation relating to water use and water pollution in the mining sector as well as the role of the Department of Water Affairs in mining matters. Hence the title of the presentation.

Jan 1, 1999

By R. P. H. Willis

For technology transfer to be successful a process, from research to full scale application, has to be followed. This paper describes such a process and how it is applied in practice. Some of the ?do?s? and ?don?ts? are highlighted. Recommendations are made on how to communicate existing knowledge and to ensure that a framework exists to effectively plan future projects with final technology transfer objectives firmly in place. The Impact Ripper System is used as a case study to illustrate lessons learned. Key words: Technology transfer, implementation

Jan 1, 2002

Council for 2001/2002 President A.A.B. Douglas President-elect S.J. Ramokgopa Vice-presidents Senior F.M.G. Egerton Junior Prof. T.R. Stacey Immediate Past-president Dr L.A. Cramer Honorary Treasurer J.A. Cruise

Jan 1, 2002

Tracey Khanna, Assistant Editor of UK?s Mining Magazine discusses some of the new and important environmental challenges, physical and social, that are facing mining companies. The tide of public opinion has turned strongly against those companies which are unable to show that they are practising responsible environmental stewardship. This is, no doubt, in part due to the recent focus of the international media on environmental issues and constantly improving means of communications, which has brought the whole subject of mining and the environment to those who, in the past, had only a limited awareness of the industry. Mining companies today face new and important challenges with regard to the environment, both physical and social. New technology and a greater understanding of waste management techniques has helped to bring about improved handling and disposal of mines wastes, so reducing some of the impacts. However, improved technology has also brought about the economic viability of exploiting increasingly lower-grade ore from open pits, resulting in a greater visual impact.

Jan 1, 2000

By M. Ng

As part of a long-term study of titanium minerals processing being undertaken by the Julius Kruttschnitt Mineral Research Centre, techniques have been developed to measure the resistivity of ilmenite, rutile, zircon and other associated minerals. The techniques have proven reproducible and have allowed the measurement of resistivity under conditions of varying temperature, surface condition and surface moisture adsorption. The measured values can be linked to the separability of the minerals in the dry plant, and hence are useful as a diagnostic test for existing plants when performance deteriorates, or for greenfield sites to investigate potential problems. One of the major problems in electrical separation of titanium minerals is surface coating on the mineral grains. Coatings can make normally conductive minerals such as ilmenite and leucoxene behave much more like non-conductors. Electrical separation of surface contaminated ilmenite from non-conductors then becomes extremely difficult unless the surface contaminant is first removed. The resistivity measurement technique was used to evaluate the effect of surface cleaning on the resistivity of ilmenite and zircon from a Western Australian deposit which will shortly be in production. Ten different attritioning methods were evaluated, ranging from simple rinsing inwater to chemical attritioning in sulphuric acid combined with ultrasonic leaching. A roasting and quenching step was also investigated. As would be expected, the gentler treatments, such as rinsing in water or Calgon, had only amoderate effect on the ilmenite surface coatings. Ilmenite resistivity decreased by about 1 order of magnitude from 5.6 x108?m to between 2.5 and 4.4 x107?m. More intense treatments had a much more pronounced effect. The most effective, reduced ilmenite resistivity to 6.5 x105?m or three orders of magnitude. Zircon was relatively unaffected by any of the attritioning methods, with only a small increase in resistivity observed from 8.0 x1012?m to 2 x1013 ?m. The results show that measurement of mineral resistivity allows the effect of surface treatments to be easily quantified in a way that has benefits for greenfield site development where only small samples are available for testing. The effect of surface moisture has also been investigated using resistivity measurements. Measurements were made on zircon in an environmental chamber in which both humidity and temperature could be closely controlled. Zircon resistivity at 60 deg C decreased from 6 x1011?m at 5% relative humidity to 8 x108?m at 95% humidity. Moisture content and moisture re-adsorption from dry of zircon and number of other minerals were measured using a Mettler moisture analyser. Zircon adsorbed the least amount of surface moisture (0.05–0.09%) but re-adsorbed moisture from dry the fastest, reaching 98% of the original level in 10 minutes. Leucoxene adsorbed the most moisture (0.67%), but was much slower re-adsorbing this moisture from the dry state, reaching only 63% of the original level in 10 minutes. The difference was attributed to the surface characteristics of the grains, the leucoxene being much more porous than the zircon examined. The resistivities and differing rates of moisture adsorption can be used to quantify the effects of changes in atmospheric conditions of the performance of electrical separation in dry plants.

Jan 1, 2003

The excavation of ramps and tunnels often requires high-speed development with (or without) the use of high-energy mining equipment such as loaders, dump trucks, TBMs and roadheaders. This high-speed development creates a challenge in terms of providing a safe and productive working environment. For example, heat from continuously exposed surrounding rock, heat from broken rock, heat generated by mining equipment, potential in flows of hot ground water, pollution from associated diesel equipment and the distance of the advancing face from fresh through-ventilation all have to be taken into account when designing ventilation systems for high-speed ramp and tunnel developments. This paper discusses methods of achieving acceptable environments at the face and along the length of the tunnel. The methodology has been successfully implemented in the development of long (up to 20 km) TBM drives in the Lesotho Highlands Project and in mining projects in hot rock using drill and blast methods as well as mechanized methods using continuous miners and roadheaders. The determination of heat loads includes calculation of the heat flow within the surrounding rock, evaluation of the operating cycle of the equipment and the contribution to the overall heat load of the broken rock as it travels out of the tunnel. The determination of heat loads from surrounding rock in new tunnels required a modification of the algorithms generally used for established excavations. The paper also examines the use of, for example, mobile duct and fan systems to ensure that fresh air is delivered to the specific areas where workers are located.

Jan 1, 2000

By D. François-Bongarçon

When it comes to sampling theory, a bad sampler is a bad sampler, no matter what, and a sampler is either bad or good. It also is of critical economic importance to tell and understand the difference, especially in a metallurgical plant. In this paper, the grand principles of Sampling Theory are first recalled, then the most popular types of sample cutters for plants are critically reviewed. It is concluded that the industry has a lot of progresses to make in that direction, although improvements usually pay for themselves very quickly.

Jan 1, 2002

By W. C. A. van Niekerk, M. H. Fourie

The carcinogenic potential of chromium (VI) has been the subject of numerous environmental and occupational studies, from which many regulatory efforts emanated. Besides the regulation of levels of known toxic substances (e.g. Cr (VI)), the classification of dusts for regulatory purposes has thus far depended on broad definitions of particle size, mainly used to distinguish only between inhalable and respirable particles. In the past, ultrafine particles (less than 0.1 µm diameter) (PM0.1) were often regarded as a non-issue, because it was believed that significant doses would not deposit in the lungs. A growing body of scientific data is indicating that ultrafine particles are more toxic than their coarse counterparts. Increased toxicity can be related to the unique dosimetric aspects of the deposition and disposition of inhaled ultrafine particles. Secondly, ultrafine particles have a larger surface area per given mass. The increased surface area can act as a carrier for co-pollutants, specifically transition metals (including chromium) that could form a coat on the particle surfaces during particle formation. This suggests that the presence of ?inert? ultrafine particles in the environment may enhance the potential for exposure to reactive airborne compounds, including Cr (VI). These factors are particularly important when information on occupational epidemiology is interpreted. It is desirable to consider the particle size distribution, for example when occupational exposure to hexavalent chromium compounds is assessed. Since ultrafine particles are more toxic than coarse particles with the same chemical composition, it could be speculated that cancer slope factors might be related to particle size distribution. This is relevant not only to carcinogenic chromium compounds, but also basically for any particle-associated toxicants. In general, the probability of developing health effects associated with occupational toxicants is likely to be higher when these are associated with the ultrafine particle range.

Jan 1, 2004

By B. W. Lee, P. O?Shaughnessy

The practice of manganese ferroalloy smelting has traditionally been based on utilising oxide ores which typically contain a high level of manganese. This preference for oxides has even been extended to the modification of natural carbonates into nodulized oxides. However smelting practices developed over the past 30 years have created a market for natural manganese carbonate ores, driven in part by the unique properties that this type of ore can offer. An understanding of the mineralogy of carbonate ore and its thermal properties has provided important information which enables furnace operators to take full advantage of the chemical differences. However changes to traditional operating practices have been necessary. Once furnace operations using natural and unmodified carbonate ore have been mastered, the unique chemical features of manganese carbonate ore are able to contribute, not only to new product development, but also to cost savings. The use of natural manganese carbonate ore is now a well-established aspect of the industry. The sustained increase in demand for carbonate ore worldwide over the past several years confirms acceptance of its quality. There are effectively few limits to its successful use.

Jan 1, 2004

By Onuralp Yücel, Süheyla Aydin, Erçin Ersundu

Turkish iron and steel sector, the base of which was established in the 1930?s, plays an important role in the industrialization and development of the country?s economy. In Türkiye this sector is the major consumer of ferroalloys. There had been a great improvement in Turkish Iron and Steel industry, especially after the 1980?sand as a result, 20.9 million tons of yearly crude steel production placed Türkiye 11th in the global steel output and 3rd in Europe. 15 % of steel produced in Türkiye is flat products, while the long products make the rest. The product composition and the general characteristics of steel production process led to an increase in ferroalloy consumption. Domestically consumed ferroalloys are especially ferromanganese, silicomanganese, and ferrosilicon. As of today, ferroalloy production capacity of Türkiye is 173,800 tons/year; 161,500 tons of which is ferrochrome with high and low carbon grades, 7,300 tons of ferrosilicochrome and the rest is ferrosilicon (5,000 tons/year). Türkiye is one of leading ferrochrome producers in the world considering the above mentioned production figures. However, this production is mainly exported since Türkiye?s stainless steel production level is modest requiring low amounts of ferrochrome. The products of iron and steel industry in Türkiye require large quantities of other ferroalloys, which make Türkiye a major importer and exporter of ferroalloys. The aim of this work is to present production, consumption, import and export quantities of: ferrochrome, ferromanganese, ferrosilicon, ferromolybdenum, ferrotungsten, ferrotitanium and ferrovanadium of Türkiye, between 1990 and 2006.

Jan 1, 2007

This is an abstract from Environmental Service and Technology (Vol 32 No 20 1998) which will be o finterest to South African Mining and Metallurgical Scientists, involved in chromium mining and Metallurgical processing. Maybe the scourge of our dams and reservoirs?the water hyacinth can be put to good use! The novel technology of phytoremediation embraces plant accumulation processes for the cleanup of toxic heavy metals and organic chemicals. Several plant species have been identified that are excellent hyperaccumulators of a number of heavy metals, e.g., Brassica juncea (Indian mustard) and Thlaspe caerulescens (Alpine pennycress). Other speciesincluding Myriophyllum brasiliense(Parrot?s feather), Salixsp. (willow), and Popullussp. (poplar) have also demonstrated phytoremediating abilities.

Jan 1, 1999

By M. A. W. Bryson

Platinum group metals are extracted almost exclusively in South Africa from three very different zones in the Bushveld Igneous Complex, called the Plat, Merensky, and the UG-2 reefs. The Plat reef is currently being exploited only by Anglo American Platinum, whereas the Merensky reef is exploited by them, Impala Platinum, Northam, and Lonplats. The UG-2 reef, on the other hand, is also processed by these producers, but Kroondal and Barplats have operations that exclusively treat ore from this reef. At present the extraction of pgms from ores in South Africa follows the traditional route of upgrading to a concentrate in a minerals processing circuit, further upgrading to a matte in a smelter, and final upgrading and separation of the individual metals in a refinery. Thus all operations that extract pgms require a minerals processing circuit, the design and performance of which is a topic of much interest, as it is a poorly understood and not a very efficient process in relative terms, compared to the other processes. Recoveries across the minerals processing circuit of between 75 and 90% are the norm.

Jan 1, 2004

By S. A. Scott

Mintek developed the MinataurTM leach-solvent extraction-precipitation technology as a cost effective, easily operated alternative to conventional gold refining processes. The technology was first commercialized at the Harmony Gold Refinery in 1997 to produce 99.99 per cent gold product and has subsequently led to development of various value-addition steps including the casting of various investment bars, gold wire drawing and gold potassium cyanide powder production. In addition to refining gold to high purity, if an appreciable amount of silver is present in the feed material it is also refined to 99.99 per cent purity. The major advantage that the Minataur? technology has over other gold refining processes is the relatively low gold lock-up and reduced operating costs. The operating cost1as at April 2001 for the expanded Harmony refinery (24-ton per annum gold production) was approximately half that of conventional smelting and toll refining. The extractant employed for solvent extraction is relatively cheap and highly selective for gold, making the technology attractive in situations where significant quantities of platinum group metals or base metals are present.

Jan 1, 2004

By B. J. Vorster

AngloGold South Africa region currently consists of twelve gold plants. These plants use a combined total of $20 million of cyanide per annum. Of this, the major portion (60%) is consumed at two Ergo dump retreatment plants. Historically the primary motivation for cyanide control at Ergo has been one of leach/cost optimization. However, more recently, with the increased public awareness of cyanide in the environment, a secondary but increasingly important motivation for control has been to ensure that only the minimum amount of cyanide is added to the process whilst not compromising leach performance. Following a brief overview of the Ergo process, the methodology in determining the amount of cyanide to be added is described. The paper then traces the developments in cyanide control from very basic manual systems to the current automated control system. In line with the increasingly sophisticated control systems, developments also took place in regards to the method of cyanide analysis. The development of these analysers is also discussed. Whilst cyanide is one of the major drivers, if not the major driver of gold dissolution, it cannot be viewed in isolation particularly with respect to the relationship between cyanide and oxygen as ascertained from the Elsner?s well-known equation. Consequently, in order to control cyanide addition, knowledge of the relative cyanide/oxygen profiles is necessary. Various means investigated at Ergo for pulp oxygenation have therefore been included for the sake of completeness. Finally a comparison is made of the control achieved from the current system compared to the original manual system. The knowledge and experience gained at Ergo is now being used to draw up guidelines for the installation and optimization work at the other AngloGold plants. The net effect of this will be reduced cyanide consumption for the region, which also, apart from the obvious economic benefit, translates into a reduced environ-mental risk.

Jan 1, 2001

By R. J. Durrheim

The DEEPMINE Collaborative Research Programme was established to create the technological and human resources platform that would make it possible to mine gold safely and profitably at depths of 3 to 5 km. The DEEPMINE Programme has four goals: to acquire knowledge of and develop appropriate technology for new ultra-deep level mines, to stimulate education and training, to establish a culture of innovation, and to encourage rapid technology transfer and implementation. The research programme was launched in July1998 and will be completed in March 2002, with the final year focusing on the transfer of knowledge to the industrial partners. DEEPMINE represents a new model for conducting mining research: it is driven by industry needs; emphasizes collaboration between industrial partners, research organizations and tertiary education institutions; and has a novel joint-funding mechanism. DEEPMINE has employed a range of vehicles to transfer knowledge to its industrial partners. Novel aspects include: (a) electronic publication of Summary Reports and Guideline Handbooks that seek to consolidate the huge body of knowledge comprehensively and concisely, (b) a series of DEEPMINE Schools designed to enable industry practitioners to apply the knowledge to their current work situation, and (c) Consultancy Reviews, where DEEPMINE specialists seek to apply knowledge to specific real problems on mines.

Jan 1, 2002

INFACON conjures up many things for many people. For the fortunate few who have been actively involved with this event since its inception, it brings back memories of far places, stimulating debates and above all, the people who have over the years contributed to the outstanding success of the Congress and who have added to the wealth of knowledge on all aspects of ferroalloys. The International Ferroalloy Congress (INFACON) has been held every three years since 1974. INFACON X will be held in Cape Town in February 2004. Simple arithmetic shows that next year?s Congress should in fact be INFACON XI. Thus, one Congress was skipped. INFACON 74, as the name implies, was held in 1974, in Johannesburg, South Africa. The event was sponsored by the Ferro Alloy Producers? Association of South Africa (FAPA), the National Institute for Metallurgy (NIM - Mintek as it is known today) and the South African Institute of Mining and Metallurgy (SAIMM). You will see some of the same sponsors involved in INFACON X. Dr. Robbie Robinson, renowned academic and past president of the SAIMM, was the Chairman of the Organising Committee. The editor was Dr. Helen Glen. Anyone fortunate enough to possess a copy of the proceedings of this first Congress will agree that from a literary and technical perspective, it is still the benchmark for subsequent events. A unique feature of INFACON 74 was the use of rapporteurs (my first duty) to ensure that the discussions following the presentations were recorded (in direct speech) as accurately as possible. This involved time-consuming correspondence (can you imagine life before e-mail?) to all parts of the world between the author and the person posing the question, with the rapporteurs acting as go-betweens. It is understandable that the much-awaited proceedings only saw the light in 1975. The names recorded in the proceedings as the members of all six committees read like the who?s-who of the South African ferroalloy industry at the time: Dr. Peter Jochens, Mr. Harvey Reid, Mr. Piet Streicher, Prof David Howat, Mr. Sigurd Selmer-Olsen - to name but a few. The Congress was held in the new, very fashionable and upmarket Carlton Hotel in the CBD. In the Foreword of the proceedings, Dr. Robinson provides an insight into the event. Three hundred and thirty six delegates from twenty two countries attended the Congress, which was opened by the Honourable P.G.J. Koornhof, Minister of Mines. Again, the opening address makes fascinating reading. During the Congress an ad hoc committee was convened as the first International Committee on the Organisation of Ferroalloys Congresses, with representation from the main ferroalloy associations of the world. The following decisions were recorded: ? The Congress would be continued at three-yearly intervals under the name of INFACON ? Every third Congress would be held in South Africa ? NIM (Mintek) would provide the permanent secretariat. Six technical sessions were held, each preceded by a plenary address with a closing address by the session chairman. In all, thirty technical papers were presented. Prior to the closing address, a panel discussion on factors affecting the future of the ferrochromium industry provided stimulating debate in the form of a question-and-answer session. The hosting country for the next INFACON would be announced. Eventually, word got round that the next INFACON would be held in Japan. However, due to unforeseen circumstances, the event was cancelled ? thus no INFACON 77. INFACON 80 was subsequently held in Lausanne, Switzerland from 12th to 16th October 1980. The event was organised by IFPEO, Institut des Producteurs de Ferro-Alliages d?Europe Occidentale. The Congress was officially opened by the President of IPFEO, Mr. R. Björklund, who was also President of the Organising Committee. The technical sessions were held in the Palais de Beaulieu. The Congress was well attended by 400 participants from 28 countries as well as 100 accompanying ladies. A total of four plenary addresses and 18 technical papers were presented. As with the first event, an international panel discussion (questions and answers) preceded the closing address. In his closing address, Dr. Louw Alberts, Chairman of the International Committee on Ferroalloys and President of NIM, presented an insight into the factors affecting growth in the industry and where growth was likely to take place. Twelve exhibitors had stands at the Congress. Attendees could choose from four post-event tours to Belguim/France (SADACEM/Compagnie Universelle d?Acetylene et d?Electro-Metallurgie), France (CUAEM), Finland (Outokumpu Oy) and Norway (Elkem Fiskaa plant).

Jan 1, 2004

By F. T. Cawood

One of the consequences of globalizing mine finance is a necessity to apply uniform accountancy and valuation standards that are clearly understood and consistently applied by the global investment community. However, each country has unique circumstances, which sometimes make it difficult to align domestic practice with international requirements. South Africa is no exception and issues such as its political history, a taxation regime enforcing different rules on different mineral producers and a unique mineral rights ownership distribution, are barriers to internationalization. The economy is in a transitional phase as a result of the many and diverse policy documents following the change in political dispensation in 1994. Many of these documents have recently been implemented through new legislation and, in the case of mining, negotiations are continuing in order to ensure an acceptable outcome. This paper discusses the challenges that the South African minerals industry faces in the field of mineral property valuation. It draws on international experience and includes a discussion on the unique considerations that the South African mineral property market must take into account in establishing a code for this purpose, as such a code could later be aligned with international practice.

Jan 1, 2004

The typical reactions which the reductants undergo during ferroalloy production are reviewed, and identified as reaction with CO2 and with SiO, and dissolution in metal. Available reactivity tests for these three reactions are reviewed. It is proposed that it is worthwhile considering dissolution kinetics as a reactivity parameter. Greater crystallinity of the reductant decreases CO2 and SiO reactivity, but increases dissolution rates.

Jan 1, 2002

By H. G. Denkhaus

Please allow me the temerity to reply to your reply to my contribution as follows: A fracture is brittle if plastic deformation is absent or, conversely a fracture is ductile if plastic deformation is present. Consequently, brittleness is specified by the degree of plastic deformation at fracture. This is the generally accepted definition. If other material properties (e.g. the quorient or the product of the uniaxial compressive and tensile strengths) under certain conditions are influenced by brittleness, or brittleness by them, these should not be called brittleness. If the one or the other author does that, he simply uses imprecise language. Even your remark, that ?Inyang and Pitt (1990) stated that the ratio of the compressive strength (sc/st) is directly proportional to brittleness?, confirms that the two quantities are not considered the same. For example:? The well known definition that a material is linear?elastic if the strain is directly proportional to the stress?does not mean that stress (measured in MPa) and strain (measured in %) are the same thing.

Jan 1, 2003