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By J. J. Taute, N. B. du Preez

"A well-performing solvent-extraction circuit is a key part of producing good quality copper cathode. To ensure consistent operation, a good understanding of the circuit’s operation and an ability to rapidly troubleshoot key parameters is required. This paper briefly discusses the modeling of solventextraction circuits. The paper then goes on to discuss the determination of key performance parameters from plant data and comparing these with the circuit models to quantify circuit performance. The identification and troubleshooting of circuit issues is presented with a worked example. INTRODUCTIONA well-performing solvent-extraction (SX) circuit is a key part of producing good quality copper cathode. To ensure a consistent, high-quality operation, a good understanding of the circuit performance is required. Evaluating the performance of an SX circuit is an extensive topic. The objective of this paper is to focus on the evaluation that the metallurgist should be performing on a regular basis using flow and concentration data. This paper does not cover important topics, such as crud management, phase continuity, or organic management. Some basic SX modeling concepts are first be presented. The calculation of the parameters is then presented with a brief discussion and recommended ranges (where applicable). A worked example is used to provide a basis for further discussion on the evaluation of the calculated parameters and use of data collected.BASIC SOLVENT-EXTRACTION MODELING CONCEPTSThis section presents the basic modeling concepts used in SX simulation packages currently available. SX reagent suppliers have invested significant time and effort into collecting data on the performance of their reagents under different conditions. Based on these data, suppliers have developed packages which they normally make available to their clients for free. These are typically used for process design and plant optimization studies. For example, BASF developed ISOCALCTM and CYTEC Industries developed MINCHEM® and MEUMTM.Chemistry of Copper Solvent ExtractionLiquid–liquid extraction involves the selective transfer of a substance between two immiscible liquid phases by controlling the relative solubility in each phase. In the case of copper SX, the exchange is typically achieved by an oxime-based chelating mechanism. In particular, mixtures of aldoxime and ketoxime are normally used in conjunction with modifiers. More detail on this extensive topic can be found in Schlesinger et al. (2011)."

Jan 1, 2015

By W. K. Loftus, H. S. Simpson

Discussion I. R. M. Cheston (Visitor): I should like to congratulate the authors on this interesting paper which graphically illustrates the overall effects of the gradual developments in diamond concentrating processes which have taken place over the past few years. These final stages of diamond concentration represent only a minor factor in the cost of diamond production but because of the shortage of highly trained people for this work, any easing of the burden on the sorting staff has an importance far beyond the immediate economic sphere. The search for the solution of problems posed by the economic and social conditions of industry is never-ending. The Diamond Research Laboratory is, even now, carrying out further work to improve still more the operation of general diamond recovery processes as described in the paper. Before looking at some of the latest developments in this field of final recovery, there are a few points arising from the paper on which I would like to comment. On page 321, reference is made to the X-ray sorters originally developed by the DRL. The paper gives a figure of 100 per cent recovery of diamonds from +7 mesh concentrates in two passes through the prototype machine. Not wishing to claim miraculous powers for our group, I would prefer to see this given as virtually 100 per cent recovery of all fluorescing diamonds. Firstly however much care is taken, there is bound to be an occasional operating loss. In the test work, 100 per cent recovery was made on many occasions but this was not always so. Secondly, although most diamonds fluoresce strongly under X-rays, some diamonds only fluoresce weakly. Type IIB diamonds, in fact hardly fluoresce at all, but the incidence of this special type of diamond is very low in most deposits. However, in operating the commercial X-ray machines, there is a certain background level of reflected radiation from other feed particles. Unless the diamond fluorescence is several times greater than this, it is not possible to achieve sufficient sensitivity in ejection. A certain small but variable proportion of diamonds from each deposit is always found to fluoresce too weakly to be recovered by the X-ray machine. Tests have shown, that for the De Beers mines, this proportion is considerably less than I per cent. These diamonds are nearly all dark brown or black in colour and therefore of low value. The degree of fluorescence does not, however, depend entirely on the colour or quality of the diamond and some of the brightest fluorescence comes from the lowest quality of boart diamonds. Investigations into the property of the diamond which causes this low fluorescence are being carried out. On page 322 it is suggested that zircon fluoresces in the same colour spectrum as the diamond. This is not quite accurate. The total light given out by zircon under X-rays is of the same order as that of diamond. However the zircon radiation has a much wider spectrum band than the diamond fluorescence. Reference is also made on page 322 to the effect of selective milling in small laboratory mills on diamonds. Perfect diamonds are very hard and very strong and are extremely difficult to break. Imperfect diamonds, which form the majority of diamonds recovered from most deposits, although hard, can be very brittle. Even under slight impact some of these diamonds may shatter to powder. Milling conditions must therefore be extremely closely controlled to minimize breakage, and even so, some breakage will always occur. As suggested in the paper, the necessary conditions are: the use of small balls, slow speed mills and very limited water addition. Tests elsewhere have suggested that the water content of the pulp in such a mill must be less than 25 per cent by weight of pulp to prevent diamond breakage reaching significant proportions. The skin flotation techniques described on page 323 operate on a very small scale. It is of interest to note that in West Africa a large-scale continuous skin flotation machine is used to recover the fine diamonds. In this operation the feed is dried and, after standing, is mixed with water and fed in a single layer onto a woven phosphor-bronze conveyor belt. This belt runs at a shallow angle into a water bath and as the particles are carried through the air-water-interface, the diamonds float off and over a weir into a collecting box. The bulk of the particles, being wettable, sink to the bottom of the tank and are continuously removed. If treated without prior drying, the diamond recovery is poor. If material is treated immediately after drying, a lot of the gangue particles also float. During standing, in the hot and humid atmosphere of West Africa, it is found that the gangue particles recover their wettability much faster than the diamond particles. Optimum selectivity is obtained after standing for approximately 24 hours. At the DRL we have been experimenting with optical filters to differentiate between the fluorescence of diamonds and zircon. By limiting the light transmission to the fairly narrow range emitted by diamonds, it is

Jan 4, 1970

By J. H. Viljoen, J. F. Morrison, C. H. Wyndham

SYNOPSIS Heart rates, oral temperatures, shovels/min and number of 3/4 ton cars/hour trammed over distances of up to 350 ft were measured in samples of 6-10 miners, engaged in tram-shovelling, at 76°, 84°, 86°, and 89°F wet bulb temperatures in stopes in a mine. From the results it has been concluded that a man with an 'average' maximum oxygen intake capacity of about 2. 8 litres/min should be able to work: at 6 shovels/min, or 30 cars/shift per two men, at 76°-84°F; at 5 shovels/min, or 27 cars/shift per two men, at 86°F; and at 4 shovels/min, or 24 cars/shift per two men, at 89°F wet bulb air temperatures. INTRODUCTION A number of gold mines in South Africa still use tram-shovelling extensively. In this method of rock removal from the face of the stope, Bantu mine workers load rock into cars and tram the cars to a centre gulley where they are emptied. Previous studies from this Laboratory3 have shown that tram-shovelling is one of the most arduous tasks underground. The rate of energy expenditure is relatively high, being an oxygen consumption of about 1.4 litres/min over a period of some hours. In cool air conditions the upper limit to the rate of production of the well-motivated men employed on tram-shovelling has been shown1 to depend upon their capacities for physical work of an endurance nature (as measured by their maximum oxygen intakes). However, in hot conditions the factors which set the upper limit to the rate of production are different. They are primarily the ability of the body to maintain a heat balance between the rate of heat production, due to physical work, and the hot atmosphere, so that the men do not develop excessively high body temperatures8. In order to give mine managers guidance on the 'optimum' rate of production of Bantu mine workers engaged upon tram-shovelling under different temperature conditions underground a study was carried out in a mine. The number of shovels per minute and cars per hour were recorded and heart rates and oral temperatures were measured throughout the duration of the shift on samples of 6-10 Bantu mine workers in different air conditions. The results of the study are recorded in this paper and conclusions are drawn as to the number of shovels per minute and cars per hour which Bantu mine workers of 'average' maximum oxygen intake capacity should be able to produce at wet bulb air temperatures of between 76° and 89°F without either excessive fatigue or danger of heat illness.

1. New books Specialty steels and hard materials, edited by N. R. Comins and J. B. Clark. Oxford, Pergamon, 1983.482 pp. Hardcover £55.50. Papers presented at an international conference on advances in flow measurement techniques, edited by H. S. Stephens and B. Jarvis. BHRA Fluid Engineering (Cranfield, Bedford, MK43 OAJ, England), 1982. £36. Papers presented at Fourth European Conference on Mixing, edited by H. S. Stephens and D. Goodes. BHRA Fluid Engineering (Cranfield, Bedford, MK43 OAJ, England), 1982. £36. Papers presented at an international conference on hydrocyclones, edited by H. S. Stephens and G. Priestley. BHRA Fluid Engineering (Cranfield, Bedford, MK43, OAJ, England), 1982. 248 pp. £27. Controlled atmospheres for heat treatment, by R. Nemenyi. Oxford, Pergamon, 1983. 225 pp. Hardcover 20, flexicover £7.50. Electrochemical techniques in corrosion testing and research, edited by J. S. Scully. Oxford, Pergamon, 1983. 150 pp. Flexicover £9.45 2. Book reviews Off highway truck haulage, by the Newman Combined Group. Parkvine (Victoria), Australasian Institute of Mining and Metanurgy, 1982. Reviewer: B. J. Vorster Elsevier's mineral and rock table, compiled by P. Lof. Reviewer: A. Wedepohl Field geologists' manual, by B. A. Berkman. Monograph Series No. 9, Australasian Institute of Mining and Metanurgy, 1982.295 pp. Reviewer: R. A. G. Cuipers 3. Mintek reports Report M56 A computer programme for the evaluation of process routes in the production of ferrochromium. Report M61 An atomic-absorption programme for the Apple 11 Plus computer. Report M63 A general-purpose data logger. Report M65 A preliminary survey of the corrosivity of water in gold mines. Report M66 A review of corrosion inhibitors: theory and practice. Report M67 The determination of total cyanide in solutions containing uranium and gold. Report M68 The suitability of Doppler flowmeters for use in the minerals-processing industry. Report M70 The preparation and certification of two reference materials of South African manganese ore. Report M78 A n evaluation of the Leeds laboratory-scale flotation cell. Report M79 The determination, by X-ray-fluorescence spectrometry, of gold and uranium on resin. Report M80 The installation and commissioning of a Siemens SRS200 sequential X-ray-fluorescence spectrometer. Report M81 The application of the inductively coupled plasma system to the simultaneous determination of precious metals. Open-pit and strip mines The South African Institute of Mining and Metallurgy and the Mining Alumni Society of the University of Pretoria are organizing an International Conference on The Planning and Operation of Open Pit and Strip Mines in Pretoria from 9th to 13th April, 1984. Other Institutes co-sponsoring the Conference are The Canadian Institute of Mining and Metallurgy, The Institution of Mining and Metallurgy, and The Society of Mining Engineers of AIME.

Jan 1, 1983

By M. D. Raganya

The Kriel Colliery is an Anglo Coal mine which is contracted with Eskom to produce No. 4 seam for Kriel power station. The mine previously found it uneconomical to mine No. 5 seam due to the low qualities and tonnages of the seam, both at the opencast and underground sections. An area has been encountered for the first time at Kriel Colliery opencast pit 5, where the tonnage and qualities of No. 5 seam warrant further investigation. The primary reason for the investi¬gation of No. 5 seam by Kriel Colliery is because of the advantage of the high selling price (R450/t) that the market is currently prepared to pay for the No. 5 seam. The aim of this project is to mine No. 5 seam economically without interrupting No. 4 seam mining operations. The problem is that the equipments that are currently being used at the mine belong to Eskom and are dedicated to mining No. 4 seam only, not No. 5 seam. Through geology investigation, it is found that the whole No. 5 seam (No. 5 seam upper and lower) has an average thickness of 1.8 m. It also contains a parting of carbonaceous shale which divides the seam into two parts. No. 5 seam upper contains less tonnage compared to No. 5 seam lower. The calorific value and ash content of No. 5 seam lower is far better than No. 5 seam upper, but would still require washing the coal. This makes No. 5 seam lower the preferred seam to mine because it meets the requirements of the customer which is Highveld Steel. It is a coincidence that the area containing No. 5 seam under investigation encounters high overburden problems. The problem of drilling to No. 4 seam was going to be encountered because the thickness of the overburden ranges from 35 to 39 m. The Gardner Denver at the mine can drill blastholes only to a depth of 34.5 m, meaning the full overburden will not be drilled at once. This means the mining of No. 5 seam will do favours for Eskom because the overburden thickness will be minimized. This then led to an agreement between Anglo Coal and Eskom to mine No. 5 seam because both companies benefit from the project. In order to identify a suitable mining method for No. 5 seam lower, literature studies took place. It is found that San Juan mine from the USA has similar geological features to Kriel Colliery's No. 5 seam. Through comparisons, it is found that truck and shovel mining would suit the geology of Kriel Colliery's No. 5 seam since San Juan mine is using it. The sequence of mining No. 5 seam lower allows for a clearance of two cuts between the truck and shovel operation and the dragline. The mining sequence of No. 5 and 4 seam will be in the order of top soil removal; soft overburden pre-stripping; pre-strip drilling; pre-strip hard overburden; No. 5 seam lower coaling; interburden drilling and blasting; interburden stripping and No. 4 seam coaling. Financial evaluation of the project shows that a contractor will charge Kriel Colliery (Anglo Coal) approximately R 102.2 million to mine No. 5 seam successfully. The sales of No. 5 seam lower will provide a profit of R99.4 million at a yield of 70% from the washing plant. The project is beneficial to both Eskom and Anglo Coal because Eskom will have eliminated the problem of pre-stripping and Anglo Coal will generate additional profit. Through investigation and analyses of the project, it is proven to be viable and should take place. This is after looking at the advantages that the project has for Anglo Coal and Eskom. Keywords No. 5 seam, truck and shovel mining, Kriel Colliery, No. 5 seam mining at Kriel Colliery opencast, Anglo Coal and Eskom, No. 5 seam upper and lower, top soil removal, soft overburden pre-stripping, pre-strip drilling, pre-strip hard overburden, No. 5 seam lower coaling, interburden drilling and blasting, interburden stripping, No. 4 seam coaling.

Jan 1, 2011

By J. H. Bulloch

This paper describes detailed fractographic analyses of several specimens that had undergone corrosion-fatigue tests at high stress ratios in simulated pressurized water-reactor environments. The distribution and morphology of non-metallic manganese sulphide inclusions are shown to strongly affect the growth of environmentally assisted cracks (EAC), and certain features suggest that a hydrogen-assisted mechanism is responsible for the observed EAC growth. The incidence of transient EAC growth in isolated regions suggests that the critical conditions that trigger this type of growth are the 'right' local chemistry at the crack tips and imposed mechanical conditions.

Jan 1, 1987

By D. Duncanson, R. J. Davidson, C. G. S. Schmidt, G. A. Brown, J. D. Taylor, N. W. Hanf

The development of a cyanidation route for the treatment of gold-plant gravity concentrates is described. This work was carried out as a natural consequence of earlier improvements to the recovery of gold in the gravity sections of existing gold plants. Concern about the environmental aspects of the conventional amalgamation process was further motivation in the development of an alternative procedure. It was found that the partial pressure of oxygen in solution was the most critical reactionrate determining factor. The rate of gold dissolution was shown to be controlled by the reaction rate below approximately 25°C and by diffusion above that temperature. Thus, the efficiency of pulp agitation and oxygen partial pressure permitted a high degree of control over the rate of gold dissolution. The use of oxygen rather than air significantly increased the dissolution rate of both gold and silver. The solubilities of sodium, calcium, and potassium aurocyanide complexes under simulated reaction conditions were studied, and it was established that the values for the sodium and calcium complexes were limited, requiring the use of lower pulp densities and higher reaction temperatures for the treatment of very high-grade concentrates. The presence of excessive amounts of tramp iron in such concentrates of up to 25 per cent by mass was found to result in poor gold dissolution owing to the cementation of gold under certain reaction conditions. The maintenance of high oxygen partial pressures, together with high cyanide concentrations, high pH levels, and the presence of calcium in the system, all aided in passivating the tramp iron. Copper, gold, and iron were shown to be the main cyanide-consuming elements. Optimum gold dissolution was obtained in a closed bench-scale reactor incorporating a flotation-machine type of agitator for effective pulp agitation and oxygenation, the oxygen being recirculated. The reactor was designed to operate under a very small positive pressure. After reaction times of 2 to 6 hours at temperatures in the region of 30°C, both the gold and the silver dissolution averaged 99,S per cent. In the case of very high-grade concentrates, it was shown that gold could be floated in the same reactor by drawing off the flotation concentrate through a port in the reactor. A flotation recovery of 87,4 per cent of the gold in 3,9 per cent by mass was obtained. The recovery of osmiridium from cyanide-leach residues and the electrowinning of gold from the pregnant liquors were also considered as processing aspects in the treatment of gold-plant belt concentrates. Final table tailings with a gold concentration of 10to 12 gft were obtained. The results of the investigation strongly suggested that an alternative cyanidation route for the treatment of gold-plant concentrates was technically feasible, provided the system included effective agitation and oxygenation. In the case of lower-grade concentrates, cyanidation followed by the electrowinning of gold appears to be the simplest route, while, for high-grade concentrates, flotation and smelting of the concentrate followed by cyanidation of the flotation tailings are suggested. The use of oxygen rather than air for sparging the pulp would depend largely on the grade of material to be treated. A preliminary comparison of the costs related to the amalgamation and cyanidation processes for the recovery of gold from such concentrates indicated very similar capital and operating costs. It was concluded that other considerations, e.g. toxicity, safety, and lower labour requirements, were more important than such small cost differences. Furthermore, the 'opening' of the gold-plant gravity circuit, which would be made possible by a cyanidation route, would further reduce the operating costs because of the subsequent decrease in the tonnage to be treated.

Jan 1, 1978

The 96th Annual General Meeting of The South African Institute of Mining and Metallurgy was held in the Gold Room of the Transvaal Automobile Club in Johannesburg on Wednesday, 11th August, 1993. OBITUARIES The President announced the deaths of the following members of the Institute during the past year. Life Fellow E.F. Laschinger. Other Members R.K. Boright, J.S. Jacobi, R.D. Power, J.H. Cannon, C.J. du Plooy, L.B. Mcrae, C.P. Rossouw, A.L. Sillars, A.W. Heugh, R.K. Briggs, P.J. Stark, and C.S. Stott. As a mark of respect to the memory of the deceased and in sympathy with the bereaved, all rose and observed a moment of silence.

Jan 1, 1993

By S. Kauchali, J. van Dyk, J. Feris, S. Pershad, M. van der Riet, D. Love, J. Brand, C. A. Strydom

"This paper offers an introduction to and strategic context for the other papers included in this special UCG edition of the Journal of the Southern African Institute of Mining and Metallurgy. South Africa is facing long-term energy security challenges, brought about by a myriad of factors that are somewhat unique or exacerbated in the global context. Underground coal gasification (UCG) is a process used to produce synthesis gas from coal in situ, that is, in the coal seam. UCG is an emerging, advanced clean coal technology that offers a potential solution for these challenges, as it can cost-effectively and cleanly liberate vast coal resources in the country that currently cannot be economically exploited using traditional mining technologies. One of the tasks of the South African Underground Coal Gasification Association (SAUCGA) is to advance the development of UCG in South Africa by compiling a technology roadmap. This paper presents the initial findings of the SAUCGA Roadmap (Draft), and contextualizes the technology opportunities and challenges, stakeholders, and provides a basis from which to progress further plans for technology development. Firm development plans and deadlines are not yet possible due to the reliance of the UCG Roadmap on the higher level South African energy policy and regulatory framework. However, the draft roadmap has taken the first step of identifying these policies and stakeholders, and should be seen as the seed from which this embryonic technology and industry can be further developed. IntroductionSouth Africa’s long-term energy security challenges include energy access and affordability, dwindling reserves of accessible bulk primary energy, mounting environmental concerns with all forms of energy generation (especially coal and nuclear), balancing the electricity grid by incorporating an increasing proportion of non-despatchable renewable energy sources, mounting environmental liabilities regarding defunct mining operations, and lastly but by no means less important, fluctuating exchange rates and energy commodity prices.Correctly managed underground coal gasification (UCG) is an emerging, advanced clean coal technology that offers a potential solution for these challenges, as it has been shown to have the potential to cost-effectively and cleanly liberate vast coal resources in the country that currently cannot be economically exploited using traditional mining technologies."

Jan 1, 2019

By R. M. Stroh, D. F. H. Grave

In this paper ventilation planning methods are discussed, with particular reference to the application of computer techniques to the solving of the many problems associated with the forecasting of ventilation and refrigeration requirements in mines of high production rates going to depths and rock temperatures higher than previously experienced. The use of the Starfield-Dickson programmes for calculating heat flow into airways and advancing stopes is demonstrated in the case of ventilation planning on a large mine extending to a brief depth of over 3 km below the surface. The possible effects of new mining methods on ventilation requirements in the future is briefly discussed.

By A. Montini

The problems encountered in the design of control systems for milling cir- cuits when the model of the system and the model parameters are uncertain are discussed. Considering these uncertainty factors has led to the development of a technique that gives a quantitative assessment of real system stability, reveals the trade-offs between performance and stability and helps the designer in deciding what level of model complexity to use in the controller design. Furthermore, it allows for on- or off-line optimization of the milling circuit performance as it provides the base for the design of a controller which is stable over the plant operating range.

Jan 1, 1987

By H. Wagner

It is a great privilege for me to have been asked to present the closing address to this most successful symposium on backfill in the South African mining industry. When I accepted this invitation I did not fully appreciate the tremendous progress made on most aspects of backfilling in the last few years. The number and quality of papers presented at this symposium bear testimony to the mining industry's determination and success in introducing backfill in underground mines to improve strata control and environmental conditions, and to provide better protection to mineworkers against the hazards of rockbursts and rockfalls. Many contributions demonstrated that these benefits can be achieved at a reasonable cost, and in some instances improved grade and higher rate of face advance result in improved economics. In my closing address I will attempt to summarize the progress made in the various aspects of backfilling underground workings and to identify those areas which, in my opinion, require further attention and effort. I will undertake this review under the following main headings: ? fundamentals of backfilling; ? design of backfill systems; ? operation of backfill systems; ? control of backfill systems; and other aspects of backfill systems.

Jan 1, 1988

The 95th Annual General Meeting of the South African Institute of Mining and Metallurgy was held in the Gold Room of the Transvaal Automobile Club in Johannesburg on Wednesday, 12th August, 1992.

Jan 1, 1992

The possibility that type 430 stainless steel can become sensitized during annealing after hot-rolling was studied by simulated cycles of continuous-annealing heat treatments, and by calculation of the carbon solubility. It was found that the lower-carbon steel could be sensitized at lower annealing temperatures than the higher-carbon steel, which is in line with plant experience. The difference in sensitization behaviour is ascribed to the lower rate of recovery of the lower-carbon steel during cooling, since recovery is sensitive to the grain size. At practical heat-treatment temperatures, austenite formation does not play a role.

Jan 1, 1996

By D. Rankin, H. J. Stucke, W. K. B. Loftus

SYNOPSIS Planning for the Finsch opencast mine is described with particular reference to the proposed stages of mining, the method used to determine the limits of surface waste rock stripping and the derivation of the waste rock mining rate. Actual mining practice is described and the possibility of installing a skipway into the open mine at a later date is discussed. In addition, the waste dumping policy is referred to: this includes the cutting of slots through the hill on the west side of the pipe to increase tramming speeds. The crushing, washing and recovery sections of the treatment plant are described together with the various changes being made to the circuit. The most important of these are the installation of X-ray sorters for the final recovery of + 7 mesh diamonds, and the vibrating grease belt for the recovery of - 7 mesh diamonds. INTRODUCTION The Finsch Mine, a subsidiary of De Beers Consolidated Mines, Limited, is situated approximately 90 miles west of Kimberley, and some two miles from the village of Lime Acres, in the Northern Cape. Lime Acres is a company village shared with the Northern Lime Company which operates a limestone quarry and works near the township. The mine is near the southern end of a well mineralized belt producing limestone, asbestos, diamonds, manganese and iron ore, and the whole area has developed rapidly in the last 20 years. Power for mining operations is drawn from the Electricity Supply Commission. The mine is conveniently close to the main Kimberley-Postmasburg railway line. Water is drawn from the Vaal River through a 57 mile State-owned pipeline at present temporarily operated by mine staff. DISCOVERY AND PROSPECTING OPERATIONS The diamondiferous orebody is situated on the farm Brits, which is State-owned ground that has been leased to the Company for the period of mining operations. There are indications of interest in the area by prospectors (Richter, de Bruin and others) over a period of some 30 years and the discovery would possibly have been made years earlier but for a law preventing prospecting for precious stones on State-owned land. Although the pipe formed a clear depression on the hill where it was situated, it was overlain by some 5 to 40 ft of banded ironstone rubble which was washed into the depression from the hillside above the pipe and obscured the deposit. In 1958, Mr Allister Thornton Fincham applied for, and was granted, the right to prospect for base minerals on the farm Brits. Asbestos is known to occur in the area and, initially, was Mr Fincham's primary interest. However, during the prospecting operations, garnets were discovered and it was realised that diamonds might be present. In 1960, when the Precious Stones Amendment Act was passed, a company

By R. W. Ottermann, N. D. L. Burger, A. J. von Wielligh, P. R. de Wet, J. L. Steyn

Underwind and overwind protection system concepts for mine hoist shafts were developed in conjunction with and for the Safety in Mines Research Advisory Committee (SIMRAC). End-of-wind operation of mine hoists is the most hazardous aspect of mine hoisting, carrying the highest risk of loss of life, injuries to workers and loss of production. Systems operating mechanically and with local actuation were developed. This was done in order to remove the increased risk associated with dependency on remote or external energy and information supply associated with most existing protection systems. The proposed underwind protection system concept absorbs the energy of motion of a conveyance overrunning the design lower limit of travel by drawing a metal strip through a set of rollers. This action causes dynamic cyclic plastic bending of the strip material that converts the kinetic and potential energy of the conveyance into strain energy of the metal. In the concept design a pair of cable slings attached to the strips catch the overrunning conveyance and transfer the retardation force. The proposed overwind protection system concept absorbs the energy of motion of a conveyance overrunning the design upper limit of travel by early detaching of the conveyance from the hoist cable. This detaching is carried out via an additional humble hook activation mechanism fitted at a sufficient height below the spectacle plate to allow the conveyance to retard to standstill under gravity before it would crash into the spectacle plate. The conveyance so brought to rest is prevented from falling by means of jack catches on the conveyance interacting with a rack (toothed profile) fitted on the guide rails in the retardation zone. Scale models (1:10 scale) of both protection systems were designed for conformance with established retardation standards. The retardation standards were limited by the requirement of passenger safety in retarding cages. The models were then built and tested in a 1:10 scale shaft model. Retardation performance close to the required levels was achieved. The retardation distance required should allow such systems to be retrofitted to most existing shafts. Given the simplicity and robustness of the designs

Jan 1, 2003

By F. H. Deist, R. P. Plewman

The history of development of analytical techniques for the determination of elastic behaviour around tabular excavations, is examined briefly. The design of a completely digital system, which appears to afford considerable improvements in speed, accuracy and versatility compared with existing analogue methods, is described in detail. The practical application of this system is illustrated by means of an actual underground problem. The results are presented, not in the form of specific solutions to the mine's problems, but as indications of the versatility and scope of the new method.

By H. Wagner

The paper points out that bord-and-pillar mining is the most important method of coal extraction in South African underground coal mines, and advocates that pillar design procedures should be refined to make more rational allowance for the differences in strength properties between various coal seams and roof and floor strata. However, any deviations from well-established design procedures must be based on sound engineering principles and reliable data on the strength properties of the seams and strata concerned. Recent information indicates that practices for the protection of surface structures against underground mining should be revised.

Jan 1, 1980

By P. Geldenhuys, D. J. C. Taylor, D. C. Page

This paper gives a technical review of the history, occurrence, mining, and metallurgy of iron in South Africa. The reserves of iron ore worldwide and in South Africa are reviewed, and potential new developments In the iron-and-steel industry in South Africa are examined. The paper concludes that the exploitation of lower-grade iron deposits will probably supplement the reserves of high-grade hematite ore in the distant future, and that, accepting this scenario. South Africa will be well placed to provide iron ore for its expected internal steel requirements, as well as supplying quality Iron ore for the export market.

Jan 1, 1988

By John Taylor

?Introduction to Black Mountain ?Historical metal accounting practice ?Metal accounting audit ?Feed measurement ?Sample precision ?Concentrate measurment ?Current metal accounting practice ?Further refinements to the metal accounting practice

Jan 1, 2005