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By M. A. von Below, I. C. Robinson

A mineral economic analysis of South Africa's mineral-beneficiation industry, comprising both economic theory and case studies, suggests that the domestic market has proved to be a more effective vehicle for promoting the establishment of advanced beneficiation projects than the availability of domestic raw materials. Although the domestic market plays an important role in the promotion of beneficiation by providing a secure outlet for sales, its most vital role is in the development of technological and marketing know-how that may give South African beneficiated products the competitive advantage required to penetrate export markets. The real wealth of a country lies primarily in the skills of its people rather than in its natural resources, and the domestic market plays a pivotal role in the development of these skills.

Jan 1, 1990

By O. A. W. Strydom, J. C. M. Wethmar, P. R. Jochens, D. D. Howat

Liquidus temperatures in the Cr-Fe-Si system in the composition range representative of ferrochromium-silicide produced in South Africa J. C. M. Wethmar, B.Se. (Eng.) Rand D. D. Howat,U B.Se. (Glas.), Ph.D.. F.I.M. P. R. Joehens, Pr.Eng., M.Sc. (Eng.) Rand, Ph.D., A.I.M. O. A. W. Strydom, M.Sc., Ph.D. Alloys in the composition range of chromium, 20 to 50 per cent, iron, 10 to 30 per cent, and silicon, 25 to 55 per cent, were subjected to both differential thermal analysis and the classical quench method so that the liquidus temperatures of ferrochromium-silicide alloys could be determined. The results are presented as liquidus curves on pseudo-binary sections at various ratios of chromium to iron and as liquidus isotherms in the ternary section.

By A. J. Jager, J. A. Ryder, M. U. Ozbay

This paper deals with procedures used for designing pillar systems in hard-rock tabular mines operating at shallow depths, typically less than 1000 m. A comprehensive review if current practice identifies four types if pillars, namely non-yield, yield, crush and barrier pillars, and the main principles for designing these pillars are outlined. It is shown that the current design methods for pillar systems in South Africa are mainly empirical, each mine developing its pillar-design methods based largely on practical experience. This results in varying pillar layouts, even between neighbouring mines, despite similarities in geology, and depth if mining. It is suggested that some current layouts may fall short if being the best as regards safety, the maximum safe extraction percentages, or flexibility in accommodating future mining scenarios in deeper or otherwise different geological conditions.

Jan 1, 1995

By J. R. de Wet

The behaviour of mild steel in aqueous cyanide solutions similar to caustic cyanide elution solutions was investigated at high temperature in electrochemical experiments. The anodic polarization diagrams of mild steel indicated that steel may undergo active dissolution under these conditions. The rare occurrence of gold plating in practice is the result of the limiting of the anodic dissolution of the steel by the presence of a passive layer on the steel. This passive layer is stable only in a certain potential range, and the free corrosion potential attained determines whether the steel will be passive or active. For conditions typical of elution columns, several corrosion potentials are possible, depending primarily on the initial condition of the steel and the concentration of oxygen in the solution. If these conditions result in the formation of a passive layer on the steel, changes in concentration and temperature will not necessarily result in plating since the layer may exist in a metastable form.

Jan 1, 1993

By J. H. Bulloch

The paper gives an assessment of the available data on the linear elastic fracture mechanics involved in stress corrosion cracking and in the behaviour of reactor pressure-vessel materials exposed to a simulated pressurized water-reactor environment. As a result of the different experimental techniques used in the various studies mentioned, only a few detailed conclusions can be drawn. The data from constant-displacement wedge-opening loading (WOL) tests, with the exception of one study, exhibited very limited or no crack extension during exposure periods of up to 14000 hours. The data from constant-load tests indicated evidence of crack extension, but the nature and extent of the crack extension are still unclear. When crack extension did occur, it was exclusively transgranular in nature. Certain differences in the available test data are tentatively explained in terms of the experimental procedures used, and the need for a consistent code of experimental techniques is highlighted.

Jan 1, 1987

By R. B. MacGillivray

The No. 2 Seam at Van Dyks Drift Colliery was found to be made up of six easily recognizable bands or plies of differing qualities. Not only did the plies differ from one another in quality, but their thickness and quality varied laterally across the mine. The economic production of a Iow-ash blendcoking coal for supply to the Japanese Steel Mills called for the mining of different portions of the seam. The portions that could be extracted economically varied in thickness and position within the No. 2 Seam across the mine. A unique system of selective mining had to be developed involving the dispatch of two separate streams of coal out of the mine. Conventional American mechanized pillarand-stall mining was used, and the productivity was improved by the installation of twin conveyor belts into a double-header section. The method of grade control that was instituted to ensure efficient extraction of the available coal reserves is described.

Jan 1, 1985

By C. J. Fauconnier

The main purpose of the paper is to determine the contribution of fluctuations in barometric pressure to flammable gas explosions in South African mines. For this purpose, the barometric-pressure patterns preceding each of the 59 major explosions in South African gold and coal mines over the past 20 years were analysed. It is concluded that diurnal fluctuations in pressure do not have a major influence on the accumulation of gas in the underground workings, but that pressure drops associated with cyclonic weather systems moving across the country over a number of days are the major factor contributing to gas explosions in mines. To illustrate some of the points made in the paper, the Hlobane Colliery explosion of September 1983 is used as a case study. In the final section, several general conclusions are drawn and recommendations put forward as to how mines should recognize and react to meteorological phenomena that may lead to an increased probability of gas explosions in underground workings.

Jan 1, 1992

By B. B. Mamba, J Ndalamo

The existence of an impressive reserve of oxidized cobalt-copper bearing ores in the African copper belt area lead the GECAMINES (DRC) to develop specific and adapted mineral processing routes (Mulaba-Bafubiandi, 2001). During the conventional diluted sulphuric acid leaching of oxidized cobalt-copper bearing ores commonly referred to as ?heterogenite?, more than 10% cobalt dissolution yield increase was observed in a plant situation (Mwema et al., 2002) when SO2(g) was flushed into the acidified cobalt leaching solution. The present paper attempts to elucidate mechanisms involved which lead to the increase of total cobalt as SO2 is flushed during the leaching of oxidized cobalt bearing minerals. The kinetics of cobalt dissolution as SO2 is flushed into the acidic solution as well as a full characterization, using UV-Visible spectroscopy, of Co2+ and Co3+ species present in the collected leachate are presented while possible effects of the presence of Cu and Fe on the leachability of cobalt bearing minerals present in the oxidised ore will be discussed. In the view of speeding up the leaching process, the mixed cobalt-copper oxidised ores were microwaves pre-processed. Preliminary results were also discussed.

Jan 1, 2007

By R. W. O. Kersten

Backfilling is one of the options available to the mining engineer in mine design. The decision as to the type of backfill is dependent on the purpose for which it will be used. For example, in a situation where high-grade, steeply dipping multiple reefs are to be mined, the purpose would be the following: ? to facilitate maximum extraction; a ? to minimize loss of fines; ? to allow closely spaced multiple reefs to be mined; and a ? to create a working platform. The physical properties required which will satisfy the abovementioned requirements can then be defined; the design of the fill plant, as well as the transport of the fill, will be governed by these considerations. The same procedure is also adopted in deciding on backfill in single- reef gold mines. The first question to be asked is the purpose of the fill. It may be to reduce the energy release rate, for environmental reasons, to reduce timber usage, to improve productivity, to reduce stoping costs, to obtain higher mining extraction, and so on. Only after one, or a combination, of these factors has been selected, can the specifications for the fill be decided on, and the plant designed accordingly. The introduction of backfill at Sheba Gold Mine will be used to illustrate the procedure adopted by Anglovaal in determining the type of fill required.

Jan 1, 1988

By P. J. F. Fourie

The purpose and frequency of comprehensive performance testing and the types of tests to be included are discussed. The results obtained from a series of such tests are reviewed.

Jan 1, 1980

By I. M. Wolff, M. B. Cortie

The Stainless Steels '91 Conference, which was held in Chiba, Japan in June 1991, was the fourth in a series of related international conferences on this theme. These conferences have a high profile and currently constitute a premier forum for exchange between researchers and industrialists active in stainless-steel technology.

Jan 1, 1991

By N. Gibson

The application of oxygen in a copper smelter by N. GIBSON* (Visitor) This paper describes how the problem of increasing the capacity of the Rokana copper smelter was handled, and how oxygen was found to be technically and economically the best solution. The first phase of its implementation is outlined.

Jan 3, 1974

By P. J. Nel, A. Täuber

SYNOPSIS A method is described whereby finely ground glassy granulated blastfurnace slag mixed with small quantities of clay, whiting and quartz has been used for making ceramic tiles in the laboratory. The tiles were semi-dry pressed and devitrification as well as sintering occurred during firing. The properties of the resulting product compared favourably in many respects with ordinary ceramic flooring materials.

The 94th Annual General Meeting of The South Mrican Institute of Mining and metallurgy was held in the Gold Room of the Transvaal Automobile Club in Johannesburg on Wednesday, 14th August, 1991. Obituaries The President announced the deaths of the following members of the Institute: Honorary Life Fellow and Past President

Jan 1, 1991

The 87th Annual General Meeting of the South African Institute of Mining and Metallurgy was held at Kelvin House, Johannesburg, on Wednesday, 15th August, 1984. Professor R.P. King (President) was in the chair, and declared the meeting open at 16h00.

Jan 1, 1984

By J. B. Parry

Three types of high-strength cold-rolled steels are discussed. Two are currently being developed at Iscor: rephos phorized steel and niobium microalloyed steel. Heat treatment after cold rolling is carried out in batch annealing furnaces. A third type, dual-phase steel, which requires a continuous annealing treatment for economic production, is also described. The properties, strengthening mechanisms, and applications of these three steels are examined.

Jan 1, 1983

Carbon-concentration Meter The latest of these, the ultrasound-based carbon concentration meter, was developed by Mintek with original sponsorship by the Chamber of Mines Research Organization, and is now being manufactured and marketed worldwide by Debex Electronics in Johannesburg. Testing of detonators* The Chief Mining Engineer has asked the South African Bureau of Standards to monitor locally manufactured, as well as imported, detonators. This could ensure greater safety in fiery mines.

Jan 1, 1990

The 91st Annual General Meeting of The South African Institute of Mining and Metallurgy was held at Kelvin House, Johannesburg, on 17th August, 1988. Mr B.c. Alberts (President) was in the Chair, and declared the meeting open at 16hOO. Obituaries The President announced the deaths of the following members of the Institute:

Jan 1, 1988

I am a partner in a minerals' development company called A.B.F. Limited, that does minerals development in Africa and Asia. I have read your very fine magazine often at the Colorado School of Mines Library in Golden, Colorado. I would like to ask your assistance in trying to locate a South African smelter; preferably on the coast, but not totally necessary for the project, that can separate the first four metals (Au, Ag, Cu, and Pb).

Jan 1, 1980

The finite element method of stress analysis is nowadays widely used in the fields of mining, mechanical and civil engineering. This paper presents a short description of the three-dimensional method, in which the elements used are arbitrary hexahedrons. Two examples of the application of the method are presented, namely, calculation of the elastic stress distributions in a coal pillar and in an opencast mine.