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Advances in extractive metallurgy, 1977. Proceedings of the third symposium organised by the Institution of Mining and Metallurgy held from 18-20th April 1977. London, the Institution of Mining and Metallurgy, 1977. 244 pp. £18,50. Coal preparation A meeting of the Organising Committee of the Eighth International Coal Preparation Congress took place in Moscow on 24th and 25th May, 1977. Representatives NIM reports Report no. 1906 An automated instrument for measuring the effects of impurities on cathodic-current efficiency during the electrowinning of zinc. (2nd Sep., 1977). Report no. 1908 An analysis of the replies to a questionnaire on materials of construction for ore hoppers. (16th Sep., 1977). Report no. 1913 The mechanism and rate of reduction of Mamatwan manganese-ore fines by carbon. (2nd Sep., 1977). Report no. 1914 The thermodynamics of the formation of sulphate complexes of iron (111), cobalt (11), iron (11), manganese (11), and copper (11) in perchlorate medium. (15th Sep., 1977). Report no. 1924 The composition of chromite grains from varwUB Witwatersrand reefs. (23rd Sep., 1977). Atomic absorption The Perkin-Elmer Corporation of South Africa is planning to hold an Atomic Absorption Autumn School in Cape Town from 10th to 13th April, 1978. Travel bursaries Two Atlas Cop co travel bursaries for study tours of Swedish mines may be awarded annually to young mining graduates. Stability in coal mining The First International Symposium on the above subject is to be held in Vancouver (Canada) on 5th to 7th April, 1978.

Jan 1, 1978

By E. J. Magri, D. M. Hawkins

This paper deals with an experimental programme carried out with a gold analyser in the period June to September 1979 at Loraine Gold Mines. The results were found to be reproducible, with no overall or conditional bias when the measurements were compared with those obtained from chip samples. The standard error of estimation of a 3 m reef exposure, which was the sampling interval, can be reduced by a factor of 2,5 if the complete stretch is scanned, rather than the taking of one chip sample in its centre. Complete statistical and computational procedures were developed for the fitting of the normal-Iognormal model to observed analyser data and for the determination of the most likely gold grade for a particular analyser measurement. (This corection procedure is necessary since a significant number of negative analyser measurements can be observed.) Panel averages of uncorrected scans showed a small conditional bias relative to those of corrected scans. However, uncorrected panel averages can be used for on-the-spot decisions regarding whole panels. For standard calculations of ore reserves, use should be made of corrected scans. Under reasonable assumptions, the use of the detector in the selective mining of low-grade narrow reefs such as the Basal Reef at Loraine Gold Mines, when compared with the conventional chip-sampling method, can result in a saving of as high as R40 million in present-money terms over the life of a project. The difference could be even larger in a highly variable reef like the B Reef at Loraine Gold Mines.

Jan 1, 1987

By P. R. Jochens, D. D. Howat, R. B. Atmore

INTRODUCTION The Miller chlorination process has assumed a preeminent position in the refining of gold bullion, a position it has maintained for over half a century. In the early sixties considerable interest was aroused by the idea of producing a consistently high grade bullion at the mine smelthouses themselves. However, as the use of chlorine in industrial plants is associated with considerable hazards, oxygen was considered a natural alternative, apart from bing less expensive than chlorine. Partial refining at the mine smelthouses would considerably decrease the requirements made on Rand Refinery Limited as well as indicating the possibility of reducing final refining costs. An added factor would be the purer silver chloride obtainable, after prior removal of the base metals by oxygen injection, which would facilitate the production of high-purity silver. The free energies of formation of the oxides of the metals;- silver, copper, lead, zinc, iron and bismuth indicate that, with the exception of silver, these metals should be capable of removal as oxides by oxygen injection. Rose1 had shown that during injection of gold bullion, considerable loss of silver to the boraxsilver slag occurred and, furthermore, that copper removal was not efficient and oxide attack on the refractories was severe. Plant test work2 had confirmed the difficulty of copper removal, but had shown that zinc and lead were almost completely removed. The difficulty of copper removal by oxygen injection warranted further investigation. Also, the high decomposition pressure of silver oxide suggested that by suitable control of the slag composition it might be possible to reduce to very small proportions the silver carried into the slag as oxide. The oxidation of copper by oxygen injection and subsequent dissolution of the oxide in a slag may occur according to the following reactions; Reactions 4 and 5 were considered because of the relatively high solubility of oxygen in molten silver and silver alloys. Thermodynamic data indicate that there is little possibility of any reaction involving the formation of CuO occurring at temperatures above 1 000 °C. To ensure that the operative reactions 1 and 4 take place to the maximum extent, the following factors He significant. (a) an increase in the activity of the copper in the bullion, (b) an increase in the partial pressure of oxygen in the system, (c) an increase in the activity of the oxygen in solution in the metal, (d) a decrease in the activity of cuprous oxide in the slag. From practical considerations, the operative variable most easily susceptible to control is the composition of the slag. SOLUBILITY OF COPPER OXIDES IN BOROSILICATE SLAGS Very scanty information exists on systems containing copper oxides but the indications are that slags containing considerable amounts of boric oxide would possibly prove to be the best solvents for cuprous and cupric oxides. This is attributed to the fact that the activities of copper oxides are much lower in boric oxide slags than in slags in which silica is the main network former. The number of possible slags containing boric oxide was limited by consideration of liquidus temperature, viscosity, corrosive action on refractories, volatilization, and ultimately cost (for industrial application). Slags in the systems soda-boric oxide-silica and lime-boric oxide-silica were selected paying due attention to the above limitations. Additions of 5, 10 and 15 per cent cupric oxide were made to the finely ground, premelted slags. These mixtures were then reground and 2g quantities held in re crystallized alumina crucibles at temperatures of 1150°C and 1 250°C respectively for 30 minutes. The crucibles were removed from the furnace, rapidly cooled, cut in half longitudinally, and a thin section taken from one half was subjected to microscopic examination.

O.F.S. Branch Proceedings of the Annual General Meeting on Wednesday, 30th July, 1975 The Aromal General Meeting of the Branch was held at the St. Helena Club on Wednesday, 30th July, 1975 at 7.45 p.m. Mr D. A. Smith (Chairman) was in the Chair. There was also present: Professor R. P. Plewman, President of the S.A. Institute of Mining and Metallurgy. Conference on Vacuum Metallurgy The Fifth International Conference on Vacuum Metallurgy is to be held in Munich from 11th to 15th October, 1976. Excavation and tunnelling A conference on 'Rapid Excavation and Tunneling' is to be held in Las Vegas from 14th to 17th June, 1976. Book reviews Mine filling. Queensland (Australia), Mt. Isa Mines, Limited, ] 973. 293 pp. $A20,00 incl. postage. Young, R. S. Cheml:cal phase analysis. London, Charles Griffin, 1974. 126 pp. £4.50. NIM reports Report no. 1714 The efficiency of the fire-assay procedure with nickel sulphide as the collector in the determination of platinum,silver, gold, and iridium. Report no. 1721 A preliminary investigation into the mechanism of depression in the flotation of sulphide minerals at the Prieska Copper Mine. Report no. 1725 The determination of silica in fluorspar by 14 Me V neutron-activation analysis. Report no. 1736 The determination, by atomic- absorption spectrophotometry and liquid extraction, of antimony (parts per million) in ores and concentrates. Report no. 1741 South African costs of equipment for the metall'urgical industry(1975}. Report no. 1744 The refining of the platinum-group metals . Report no. 1746 The determination, by atomic-absorption spectrophotometry, of minor elements in zinc, lead, and copper sulphide concentrates. Report no. 1747 Magnetohydrostatic separation of gold from gravity concentrates. Report no. 1750 A review of the present and future development of sulphur production in South Africa. Report no. 1754 A new three-dimensional anodic electrode for reduced power consumption du,ring the electrowinning of metals. Report no. 139 A preliminary survey of goldrecovery problems arising in the production of pyrite. (9th Feb., 1967, re-issued Jun. 1975.) 16 pp. Report no. 140 A preliminary mineralogical investigation of pyrite from the K imberley and the Main Reefs, VogelstruisbuU Gold Mine. (13th Feb., 1967, re-issued Jut 1975.) 11 pp. Report no. 165 Gold recovery from pyrite flotation mill products by cyanidation. Progress made up to 1st May, 1967. (5th May, 1967, re-issued Jun. 1975.) 8 pp. Report no. 133 Gold recovery by cyanidation from mill products obtained after pyrite flotation. Progress made up to ht July, 1967. (18th Jul., 1967, reissued Jun. 1975.) 14 pp. Report no. 219 A review of some of the mineralogical factors influencing the flotation of pyrite. (29th Nov., 1967 reissued Jun. 1975.) 20 pp. Report no. 278 Gold recovery by cyanidation from mill products obtained after pyrite flotation. (24th Jan., 1968, re-issued Sep. 1975.) 51 pp. Report no. 306 The effect of preaeration on two samples of thickener under flow from the Venterspost Gold Mine. (30th Mar., 1968, re-issued Jul. 1975.) 14 pp. Report no. 317 Results of tests carried out at the Loraine Gold Mine during the period 5th to 7th February, 1968. (21st Mar., 1968, re-issued Jul. 1975.) 11 pp. Report no. 321 Aeration of ore from the Loraine Gold Mine before theaddition of cyanide.(17th Apr., 1968, reissued Jul. 1975.) 30 pp. Report no. 380 The effect of aeration, before cyanidation, of pulps of gold ores containing xanthate. (14th Aug., 1968, re-issued Jul. 1975.) 44 pp.

Jan 10, 1975

1. Book reviews Tungsten: 1982. London, Mining Journal Books Ltd, 1982. 179 pp. Reviewer: G.A. Brown The geology of industrial minerals in Canada, edited by G.R. Guillet and Wendy Martin. Canadian Institute of Mining and Metallurgy, special volume 29. Reviewer: R.W.O. Kersten Foam flotation - theory and applications, by Ann N. Clarke and David J. Wilson. New York, Marcel Dekker, 1984. 418 pp. Reviewer: B.K. Loveday Industrial and financial indicators of the steel industry, by Patrick Genevaz. Paris, La Chambre des Cartes, 1982. 2 vols. Vol I: Analysis and conclusions, FF3500. Vol. 11: Tables, FF4000. Reviewer: R.J. Dippenaar An encyclopaedia of metallurgy and materials, by C.R. Tottle. Plymouth, Macdonald and Evans and The Metals Society, 1984. 481 pp. RI44,50. Reviewer: P. T. Wedepohl The role of crack growth in metal fatigue, by LP. Pook. London, The Metals Society. Reviewer: C.A. Boothroyd Hydraulic coalmining - new technology and its geological and industrial significance, by H.C. Siebert. Hamm, Zentraldruckerei BAG, 1984. 33 pp. Hydraulic coalmining - hydromining update: potential impact on coal deposits and coal mining industry, by H.C. Siebert. Hamm, Zentraldruckerei BAG, 1984. 130 pp. Victoria's brown coal. A huge fortune in chancery, edited by J .T. Woodcock. The Australasian Institute of Mining and Metallurgy, 1984. 204 pp. Reviewer: J.J. Versluis 2. Canadian publications The following reviews of the activity and developments during 1982 in respect to the chief minerals produced or consumed in Canada are now available. Zirconium. An important mineral commodity. Mineral Policy Sector, Mineral Bulletin MR 202, $6.60. Canadian minerals yearbook 1982. Mineral Policy Sector, Mineral Report 32, $40.75. Canadian reserves of copper, nickel lead, zinc, molybdenum, silver and gold as of January 1, 1983, by W.H. Laughin. $4.20. Mineral Policy Sector, Mineral Bulletin MR 201. Sulphur market profile, by B.W. Boyd. Mineral Policy Sector, MRI 84/5. 3. Mintek publications Report M123 The use of of activated charcoal in a NIMCIX column for the recovery of gold from cyanide solutions. Report M150 Energy transfer in the hearths of submerged-arc furnaces. Report M151 A preliminary investigation of the initiation of pitting corrosion in austenitic stainless steels and nickel-based alloys. Report M154 The reduction of Winterveld chrome spinel at 1300°C under an argon atmosphere in the presence of carbon. Report M165 The development of an improved on-line gold analyser. Report MI67 three nebulizers for use with an inductively coupled plasma spectrometer. 4. New publications Mineral Industry Consultants Association (as at 31st March, 1984). Parkville (Australia), The Australasian Institute of Mining and Metallurgy, 1984. 112 pp. Philosophical and procedural guidelines for the planning professions. Johannesburg, the Environmental Planning Professions Interdisciplinary Committee (EPPIC, P.O. Box 61019, Marshalltown 2107), R2.50. Directiona//y solidified materials for high temperature service, by M. McLean. London, the Metals Society, 1983. 337 pp. Tin and its uses no. 142. Greenford (England), International Tin Research Institute, 1984. Metals engineering International Symposia & Exhibitions Ltd - a subsidiary of Industrial Newspapers PLC - are pleased to announce that they will be organizing a mammoth engineering event, entitled Metals Engineering 86, comprising five important exhibitions in 1986:. Agglomeration A major symposium on agglomeration is being organized in Toronto for the 2nd to 5th of June, 1985. Speakers from around the world (Canada, U.S.A., Brazil, Australia, Japan, West Germany, Italy, India, China, Switzerland, Poland, Yugoslavia, and France) will address delegates on various aspects of agglomeration relative to iron ore, coal, coke, and fuels. Plenary theme papers will also be presented by speakers from Japan, the U.K., and the Netherlands.

Jan 1, 1985

By S. Banisi, S. Zare, M. Mahmoudi, M. Maleki-Moghaddam, M. Yahyaei

As the orebodies become more complex and lower grade, there is an increasing demand from crushing circuits for a finer product. When the product from a crushing circuit does not satisfy the requirements of the downstream processes, the cost of production increases. Thus, enhancing the performance of cone crushers through optimisation of their operating factors becomes important. One of the key factors affecting performance of cone crushers is the filling of the crushing chamber during the operation. The effect of varying the filling of the crushing chamber of a cone crusher was investigated. To assess the crusher performance, parameters such as crusher capacity, power utilisation, and reduction ratio were used. Extensive plant trials were conducted to obtain samples and operational data when the crusher chamber was 50% full (half-full) and 100% full, which is 300 mm above the top of the crusher chamber (super-choked condition). The results indicated a 62% difference in the crushing capacity when the crusher was operated in a super-choked condition compared to the half-full chamber level. In the super-choked condition, the size-specific energy at 12.7 mm was 20 % lower than that of the half-full condition. The Bond ball mill work index (BBWI) of crusher product indicated that the BBWI of the product of the super choked condition is 5.6% less than that of the product of half-full condition. This can be attributed to the generation of micro cracks in particles due to increase in the interparticle breakage when the crusher was operated in the super-choked mode. Keywords: Cone crushers, crushing efficiency, crushing chamber filling

Jan 1, 2020

Mixtures of MnO and graphite were reacted under argon at temperatures ranging from 1200 to 1425°C, and the loss in mass of the mixture was recorded continuously. The results showed that the rate of reduction of MnO increased as the temperature increased and the ratio of MnO to C decreased. The effect of the particle size of MnO and of graphite on the rate of reduction at I350°C was very small in the range 63 to 250 µm for MnO and 45 to 355 µm for graphite. The rate of reduction at I350°C was increased markedly by the addition of Na2CO2 and K2CO3, was slightly increased by the addition of Fe2O3, was unaffected by the addition of CaO, MgO, and AI2O., and was decreased by the addition of SiO2. Some CO2 was always present in the effluent gas, and this was taken as evidence that the reduction of MnO occurred by way of CO2 as an intermediate product. The activation energy of the ratecontrolling step was 57,5 kcal, and this was similar to the measured activation energy for the gasification of graphite by CO., namely, 61,S kcal per mole of graphite. A simple kinetic model was derived on the assumption that the gasification of graphite was the ratecontrolling step, and the results over the temperature range 1200 to I425°C, when plotted in the appropriate form, yielded straight lines as predicted by the model.

Jan 1, 1980

By D. D. Aksenova, V. A. Ignatkina, L. A. Samatova, A. V. Lygach, E. D. Shepeta

Calcium minerals such as scheelite, phosphate, apatite are valuable minerals, which have similar flotation properties to the calcium gangue minerals. An additional problem is the fine dispersion and close mineral association of valuable and other minerals. Low polar compounds (non-ionic surfactant), such as fatty iso alcohols, neonol and phosphol, and their combinations with sodium oleate have been studied using flotation of monominerals and ore flotation; ATR IR spectroscopy and TEM for study surface of minerals; UV spectroscopy for control solubility, aggregation and de-aggregation processes. Increase in solubility of fatty acid collectors was confirmed by low soluble (heteropolar) compounds. Oxyethylated esters of phosphoric acid are adsorbed on phosphorite by -O2PO2R2 and on other rock minerals by donation of OH bond. Same effect shows difference of adsorption of fatty iso alcohols on calcite and scheelite. The different forms of adsorption of ionic and nonionic compound on a sparingly-soluble mineral surface creates distinction of the flotation kinetics and technological balance of ore flotation. The results of the separation of flotation of scheelite from calcite depend on the order of pouring into pulp of fatty iso alcohols and oleate, and their ratio in the mixture. Increasing scheelite recovery into rougher scheelite concentrate by 3.6% for both the flotation and sludge classes was obtained. Calcite recovery varied slightly upwards or downwards by 0.8-2.4%. The use of the non-ionic surfactant phosphol in combination with a fatty acid soap allows for obtaining a phosphate concentrate with more than 28% P2O5 content and almost 80% recovery in flotation operation. It is not obtainable with other reagent regimes. Keywords: Flotation, calcium minerals, oleate, fatty isoalcols, neonol, oxyethylated esters, adsorption

Jan 1, 2020

By B. Geelhoed

Gy's formula for the variance of the fundamental sampling error (FSE) is based on a model that assumes independent selections of particles. A generalization of this model, which can theoretically lead to more realistic representation of actual sampling processes, was, for the first time, experimentally verified by repeated sampling from a well-mixed batch consisting of particles of zirconium silicate of two different sizes. The predictions for the sampling variance made in Gy?s theory and in the more general model were compared with the experimentally observed sampling variance. During the experiment performed here, the variance prediction made in the theory of Gy ranges from 0.96 × 10?7(g2/g2) to 0.95 × 10?7(g2/g2), which is approximately a factor 60 lower than the experimentally observed variance (5.76 × 10?6(g2/g2)). The difference between the Gy prediction and the experimentally observed variance cannot be fully explained by the uncertainty in the experimentally obtained variance due to the finite number of degrees of freedom. Therefore, the difference is likely to be a significant effect. This shows that, under the experimental conditions, Gy?s formula for the variance of the FSE probably undervalues the sampling variance, unless an empirical correction factor for grouping and segregation is applied in the theory of Gy. The new theory resulted in a variance prediction of 6.00 × 10?6(g2/g2), which is much closer to the observed variance than the Gy prediction. This indicates that the generalization of Gy?s theory offers an outlook for providing a better variance prediction than the Gy predictor in the case of dependencies between particle selections. The results are discussed. Keywords: sampling, variance, parameter for the dependent selection of particles, Gy, experiment.

Jan 1, 2009

By J. Ojeda, R. Kuyvenhoven, M. Ziemski M

This paper focusses on the identification of operational opportunities in a 1100 tph pellet plant to reduce the specific energy consumption in its comminution circuit, which is designed to process magnetite ore and produce pellets to be used as raw material in the iron and steel industry. The assessment is carried out through a frequency analysis for three of the four processing lines of the plant, consisting of one ball mill each with an installed power of 4.5 MW and 280 tph of mill throughput design capacity. The methodology, as described in this paper, facilitates the visualisation and quantification of plant performance and provides a good first approach to prioritise alternatives for optimisation. In a pellet plant, grinding is a critical stage due to its high energy consumption and its major impact on the physical properties of the iron pellets, which quality depends to a large extent on grind size and Blaine index. From the evaluation that was performed it can be concluded that production line 2 has the lowest specific energy consumption of 15.1 kWh/t, while line 1 has the highest with an average of 16.6 kWh/t for the same type of ore. On the basis of the results and current operational practices, it is recommended to increase the average mill throughput from 240 tph to 265 tph, translating into specific energy reduction of 10%, without affecting the chemical and physical properties of the final product. The implementation of an HPGR for regrinding the magnetic concentrate is proposed to assure adequate specific surface area in case grinding coarser becomes an alternative, which would also be beneficial for the subsequent water recovery stages. Keywords: Iron ore pelletisation, grinding circuit, energy efficiency, particle size, frequency analysis

Jan 1, 2020

By T. Könighofer

Processing of copper-cobalt orebodies in Africa?s Copper Belt has received much recent attention with various flowsheet options being developed specifically for the refining of cobalt. The upfront leach and copper refining routes are well understood whereas the refining of cobalt is more complex, requiring numerous impurity removal steps to produce high purity metal. This paper describes an investigation into one of the possible processing steps in the refining of cobalt, namely, cobalt solvent extraction. The paper emphasizes the importance of upstream impurity removal to achieve the required cobalt solvent extraction feed composition. 18% (v/v) Cyanex 272 in an aliphatic diluent is used as the organic phase. The pH profiles in the various stages are evaluated in order to obtain a raffinate containing <10 mg/[l] cobalt and with a low magnesium content reporting to the stripping section. The pH profile is also used to minimize the impurity deportment to the cobalt electrolyte. The effect of adding a preneutralization stage before feeding the organic phase to the extraction circuit is investigated. Zinc build-up in the stripping stages is also looked at. It is recommended for the purpose of this study that four extraction stages at an O:A ratio of 1 with a pH profile from 4.9 to 5.7 be employed. The pH is controlled with 40 g/[l] NaOH. A preneutralization stage is required, where the organic phase is contacted with 10 M NaOH. Two scrubbing stages are recommended at an O:A ratio of 40, using the cobalt electrowinning advance electrolyte as the scrub liquor. Three strip stages are to be employed at an O:A ratio of 0.67.

Jan 1, 2009

By E. J. Magri, A. Couble

Kriging estimates of geological resources are sometimes conditionally biased because the kriging plan contains too few samples. This may be done purposely in order to match the variance of the estimates to the true block dispersion variance. This work aims at evaluating the influence of conditional bias over the ultimate optimum pit design in relation to its shape, size and NPV (Net Present Value of profits). It has been restricted to two real case studies: a ‘carrot shaped’ gold porphyry in northern Greece and a manto-typeexotic copper deposit located in northern Chile. The methodology applied to each deposit consisted of generating a ‘real block model’ and four resource estimates by the use of conditional simulation and the application of four different kriging plans to the drillhole databases respectively. The estimation models vary in smoothness and conditional bias. Ultimate optimum pits were determined for the ‘real’ and the four different kriging models. Pit comparisons lead to the following conclusions: •In the worst case, conditional bias overestimated the project&apos;s NPV by 32% and 5% for the gold and copper deposits respectively. •The overestimation of high grades is more relevant than the underestimation of low grades. This resulted in a tonnage over-extraction of 148% and 1% for the gold and copper deposit respectively. This difference was attributable to the vastly different geometry of the deposits. •The smoothing effect of kriging, without or very little conditional bias, produced open pits that were different to the ‘true’ (ideal) ones and furthermore, underestimated the project&apos;s NPV by 10% and 6% for the gold and the copper deposits respectively. •Other factors that influence the optimum open pit design and to some extent control the effect of conditional bias are: the cut-off grade, the orebody geometry and distribution of grades within it and the amount of over-burden. Keywords: conditional bias, ultimate pit design

Jan 1, 2003

By C. I. Ware

The phrase ?back to basics? is used to describe the fundamental principles and philosophies on which a successful mining operation is based. At Richards Bay Minerals (RBM), ?back-to-basics? (BTB) has been implemented as a continuous process to probe operational functions with a view to increase production without capital expenditure. It also ensures that the fundamentals of dredge mining are understood and adhered to. BTB is based on the principle that people drive organizations, necessitating an interactive implementation approach. At the RBM mine this entails a three-pronged approach, namely practical training, teamwork initiatives and the use of lean Six Sigma methodology. It is the latter on which this paper will focus. The lean Six Sigma methodology is successful in identifying, managing and documenting BTB projects, while team work initiatives are integral to successful project implementation. This paper describes two examples of how the Six Sigma methodology can be applied to a dredge mining operation. The first example focuses on the improvement of Mining Pond Echo (MPE) plant throughput by reducing the lost opportunity (non-production) due to tails downtime. The project was successful in increasing plant throughput by 4.5%. This was achieved by increasing the tails disposal system availability by running MPE as a four tails lines operation and focusing on causes of tails production downtime. Subsequently, the tails system at MPE is no longer the production bottleneck. Second, the Six Sigma methodology was successfully applied at Mining Pond Charlie (MPC) to increase the primary dredger throughput by 4.6% through focusing on the dredging technique and maintenance issues. This project highlighted the need for trend analyses to ensure an effective dredging technique, coupled with simple production documentation, which also ensures a focus on maintenance. Keywords: Back to basics, Six Sigma, training, teamwork, throughput improvement, tails, dredger.

Jan 1, 2007

Interpretation of Leached Outcrops, by Roland Blanchard. Published by Nevada Bureau of Mines, University of Nevada, Reno, Nevada, 89507, 1968, 188 pages. Price $7.50 (R5.40). This book contains a summary of the author&apos;s knowledge of leached outcrops, derived from some 30 years&apos; experience as a geologist operating mainly in the United States of America and Australia. Part 1 of the book provides a comprehensive coverage of the various processes and substances involved in the oxidation of many minerals, under different climatic conditions, to form the final leached products. In Part 2, details are given of the appearance and composition of the oxidation products of the following minerals: pyrite, pyrrhotite, arsenopyrite, cha1copyrite, cha1cocite, bornite, tetrahedrite, oxidized copper minerals, galena, cerussite, sphalerite, molybdenite, chromite, hematite, magnetite, manganite, pyrolusite, calcite, siderite, fluorite, salite and supergene silica. The illustrations, the black and white photographs and the colour plates of oxidation products are of a high standard. The material is presented in a logical order and in terms which are not over-technical; hence it is useful to persons other than trained geologists. Despite the advances in geophysical and geochemical prospecting, the location and interpretation of gossans remains an important method of discovering ore bodies, particularly so since the correct interpretation of a leached material can prevent the fruitless and expensive prospecting of an underlying body of uneconomic concentration. Therefore it is considered that this volume will be a valuable addition to the libraries of universities, exploration companies and geologists. It is of interest to note that the author, who died in 1966, presented a paper, under the same title as this book, to the Chemical, Metallurgical and Mining Society of South Africa in 1939. For this work he was awarded the Society&apos;s Gold Medal. W.T.S.

By G. Y. Nisbet

The contribution made to the economy of South Africa by the-minerals industry is discussed according to four of its aspects. Firstly, the industry supports both students and lecturers in technical and academic institutions. This support covers virtually the whole range of courses available at the universities and technikons, although most is obviously devoted to the engineering and science faculties. Secondly, the industry makes a direct financial contribution to the State in that it contributes about40 per cent of the State&apos;s receipts from direct tax paid on incomes and 30 per cent of the contributions to the total State revenue. It provides employment for 28 per cent of the total active labour force, and contributes 24 per cent directly to the gross domestic product. Thirdly, the industry is responsible for over 65 per cent of the country&apos;s foreign earnings in spite of the significant rise in exports from the manufacturing sector. South African minerals are of crucial importance to the word, since the country has the world&apos;s largest reserves of seven minerals and features very prominently in many others. Finally, the industry makes an indirect contribution, referred to as the multiplier effect. This is the ripple effect on the economy made by a large injection of momey by which that money acquires an added effective value. A study made of the total production of the mining industry in 1978, for instance, showed this multiplier to havea value of 1,5. Thus, if this effect is included, the industry&apos;s contribution to the gross domestic product is 44,S per cent. Similarly, the industry is responsible for the creation of jobs both within itself and in other industries, which could amount to 100000 for the period 1981 to 1935.

Jan 1, 1981

1. Book review Economics of mineral exploration in Australia, by Brian W. Mackenzie and Michel L. Bilodeau. Australian Mineral Foundation (Private Bag 97, Glenside, South Australia 5065). 198pp. $A58. $A45 for students. Reviewer: D.G. Krige 2. Recent publications Combustion of coal liquid mixtures, by G.F. Morrison. London, lEA Coal Research, 1983, 52 pp. Hafnium: physico-chemical properties of its compounds and alloys. Vienna, International Atomic Energy Agency, 1981. 408 pp. 620 Austrian schillings. Canadian mines handbook 1984-85, edited by CD. Gardiner. Toronto, The Northern Miner, 1984. 500 pp. $24. Drilling equipment in Canadian mining and exploration- opportunities for the industry, by AJ. Jakubek. Toronto, Micromedia Limited (144 Front Street, Toronto M5J IG2, Canada), 1984. Research report 1984. Port Melbourne, Division Mineral Chemistry, Commonwealth Scientific and Industrial Research Organization, 1984. 190 pp. Surface engineering Wear is an unavoidable problem in virtually all products of the engineering industry, from the minute bearings of instruments to the cutting surfaces of earth-moving plant. Safety in mines About 50 papers will be presented at the 21st International Conference of Safety in Mines Research Institutes at Sydney from 21st to 25th October, 1985. Some 250 delegates from 30 nations are expected to attend. Professional development seminars March 18th-21st, 1985 Underground Blast-hole Mining May Ist-3rd, 1985 Mineral Processing of Gold Ores May 6th-10th, 1985 Mineral Comminution Systems May 13th-15th, 1985 Processing of Metallurgical Residues Analytical chemistry The Second Symposium on Analytical Chemistry in the Mining, Exploration and Processing of Materials is to be held in Pretoria from 15th to 19th April, 1985.

Jan 1, 1985

By M. Coetzee

The susceptibility of experimental low-nickel Cr-Mn-N stainless steels to hot cracking, sensitization, and pitting corrosion in the as-welded condition was investigated. These steels were developed for deep-drawing applications and are similar in composition to type 201 stainless steel. In order to obtain good formability, the rapid rate of work-hardening (characteristic of the 200-series steels) was decreased by the addition of copper. The behaviour of two sets of alloys during fusion welding was investigated: 17Cr-7Mn-4Ni-o.5Cu steels containing 0.001 to 0.27 per cent nitrogen, and 17Cr-7Mn-2Ni-o.1N steels with copper contents varying between 0.01 and 3.11 per cent. Al the steels in these two sets initially solidify as d-ferrite, which transforms partially to austenite during cooling. As the nitrogen level increases, the microstructure of an autogenous-weld metal ranges from large amounts of d -ferrite, martensite, and Widmanstätten austenite, to austenitic structures with small amounts of vermicular d -ferrite. The formation of d -ferrite during solidification and the presence of ferrite retained in the weld metal indicate that the experimental alloys will not be susceptible to hot cracking during welding. Except for the alloy with 0.27 per cent nitrogen, the resistance to pitting corrosion of the experimental steels in the as-welded condition is inferior to that of type 304 stainless steel. None of the experimental steels is susceptible to intergranular attack in the as welded condition. The alloys with 0.19 and 0.27 per cent nitrogen have properties (corrosion and microstructure) similar to those of type 304 stainless steel in the as-welded condition.

Jan 1, 1996

By H. M. Krieg, M. J. Ungerer, C. G. C. E. van Sittert, D. J. van der Westhuizen

"The transition metals tantalum (Ta) and niobium (Nb) are of significant importance, for example in the nuclear energy sector where they are used as cladding materials, as well as in capacitors and specialized materials. For these applications a high-purity metal is needed. The separation of Ta and Nb is always a challenge since they are found together in nature and have similar chemical and physical properties, resulting in costly and laborious separation processes. A technology that has been used successfully for the separation of these metals entails solvent extraction (SX)1. While separation was achieved in a previous SX study using a sulphuric acid (H2SO4) medium with the extractants diiso-octyl phosphinic acid (PA) and di-(2-ethylhexyl) phosphoric acid (D2EHPA), due to the absence of speciation data for Ta and Nb it is not clear how the separation occurred.One method that might be suitable for determining the speciation of a reaction is molecular modelling. Calculations based on the densityfunctional theory (DFT) are now used not only for light elements and small molecules, but also metal complexes, heavy metals, and especially metal separation in SX2. In this study the aqueous phase used during SX was investigated by studying periodic systems of Ta, as a metal and in salt form, when it is in contact with H2O and H2SO4. The results were used to predict the reaction mechanism occurring during SX. Results showed that (i) in a 1:1 acid-water ratio, the deprotonation of H2SO4 was endothermic, (ii) in a 1:5 ratio deprotonation was exothermic forming HSO4 -, and (iii) in a 1:10 ratio double deprotonation occurred to form SO42- exothermically."

Jan 1, 2017

By B. M. Munyungano

Rössing Uranium Mine operates a recovery circuit with continuous ion exchange followed by solvent extraction. Serious organic degradation problems were encountered during 1985/6, 2000 and 2005 in the solvent extraction plant. The preferential loss of the tertiary amine extractant was observed during the above-mentioned period. Previous investigations revealed that the tertiary amine was breaking down to nitrosamine, which cannot take part in the exchange reaction with U3O8. A reduction in the redox potential of the solvent extraction plant feed to below 500 mV halted this preferential loss. A lot of effort has been made to try and understand the actual mechanism for nitrosamine formation. Current understanding for the degradation is that formation is due to high nitrates on the strip side of the circuit emanating from nitrates from the precipitation process using ammonia. It is the current belief that pH lower than 3.7 on the strip side results in loading of nitrates onto the solvent. If oxidizing conditions prevail on the extraction side of the solvent extraction circuit, the tertiary alamine will then degrade into nitrosamine. This phenomenon is yet to be established and verified. It has, however, been established that the above process is brought about the following conditions ?High redox potential greater than 550 mV predominately caused by a high Fe3+/Fe2+ratio (4:1) ?Perception that if Fe2+<0.5 g/lit will contribute to high redox ?High concentrations of NO-3 in the conc eluate (feed to SX)/ammonium sulphate (NO-3> 4 g/l based on historic values) ?Presence of Mo as a catalyst ?Tests also have proved that the presence of nitrous acid in a concentration of 1 g/lat 550 mV leads to formation of nitrosamines from alamine.

Jan 1, 2007

By K. Forsberg, Ş. Kaya, C. Dittrich, M. Svärd, E. M. Peters

Scandium can be recovered from waste streams of other metallurgical processes such as red mud from the Bayer process and titanium dioxide acid waste. This is accomplished by an integrated process comprising leaching using acidic media, solvent extraction using organic solvents and stripping of Sc from the organic phase using NH4F solutions. The precipitation of scandium as (NH4)3ScF6 from NH4F strip liquors has been demonstrated at lab-scale with recoveries and purities greater than 98% and 98.3%, respectively. It is desired to assess the possibility of recovering the solvents for re-use in the process to improve its economy and environmental friendliness. Investigations have been conducted to recover alcohol by simple distillation from strip liquor-alcohol mixtures containing about 50 v/v% alcohol. The mixtures were obtained after anti-solvent precipitation of (NH4)3ScF6 using an alcohol to strip liquor volumetric ratio of 1:1. The starting strip liquor contained about 2000 mg/L scandium in 3 mol/L NH4F solution. In the recovery of methanol, the first distillate product collected had a purity of about 87 v/v% and this decreased slightly with time over two hours. The methanol distillate collected in the first 30 minutes with a purity of ca. 85 v/v% was re-used in anti-solvent crystallisation of (NH4)3ScF6 from the initial strip liquor, and the scandium recovery attained was about 98.6 w/w%, almost similar to that of 99.2 w/w% obtained using 100 v/v% methanol. For ethanol recovery, the first distillate product collected was approx. 84 v/v% pure and the distillate collected in the first 30 minutes with a purity of about 75 v/v% achieved a scandium recovery of about 97.2 w/w% in comparison to 98.5 w/w% obtained using 100 v/v% ethanol during anti-solvent crystallisation. Keywords: Alcohol recovery, methanol, ethanol, anti-solvent crystallisation, (NH4)3ScF6

Jan 1, 2020