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By G. C. Howell, H. A. D. Kirsten

The mining-induced effects around narrow tabular stopes have traditionally been evaluated in terms of elastic continuum analyses. An understanding of the phenomenological behaviour of the rock surrounding deep-level gold mines has accordingly been developed on the basis of such analyses. However, elastic analyses do not afford reliable representations of the behaviour of rock in which failure may occur on discontinuities. This paper describes investigations that show how the stress and stiffness characteristics of a rockmass are affected under such circumstances for representative ranges of values for the relevant parameters (depth, span, support stiffness, field stress ratio, and discontinuity strength). These investigations afford a substantially different understanding of the mechanical behaviour of rock that is subject to failure. Instead of forming an arch across the abutments, the rock in the hangingwall bears directly across the stope onto the footwall and, instead of being subjected to tension, the nether hangingwall is clamped in compression in the horizontal direction.

Jan 1, 1993

By M. C. J. van der Merwe

"Carboxymethyl cellulose is an organic binder used in the iron ore pelletizing industry. The basic principles of how carboxymethyl cellulose (CMC) solutions behave during the pelletizing process and how these principles affect the drop and compression strengths of the pellets are poorly understood. The aim of the investigation was therefore to gain knowledge on the behaviour of CMC during the pelletizing of haematite concentrate.Haematite pellets with different additions of CMC (0.1–0.4 wt%), were subjected to drop tests, compression tests, and free moisture content analysis. The relationship between the drop strength, compression strength, free moisture content, elapsed time, and CMC concentration was analysed.The drop strength had a strong correlation with the free moisture content of the haematite pellets, with a correlation coefficient of 0.94. The compression strength of the CMC-bonded haematite pellets increased as the free moisture content decreased, reaching a maximum upon depletion of the free moisture content. Haematite pellets with CMC concentrations of 0.1 and 0.2 wt% developed most of their strength within the first day after pelletizing, whereas pellets with concentrations of 0.3 and 0.4 wt% developed most of their strength between one and two days after pelletizing. The time within which CMC-bonded haematite pellets develop most of their strength is therefore dependent on the CMC concentration. IntroductionFines are produced during the beneficiation of iron ore. These fines are separated from the lump ore and can be upgraded to produce a concentrate, which is used as a raw material for the production of pellets. Pellets in turn form a key burden material for direct reduction processes as well as the blast furnace (Zhu et al., 2015).Inorganic binders such as bentonite have been used predominantly in the iron ore pelletizing process to obtain pellets with suitable properties (Eisele and Kawatra, 2003). These binders, however, have the disadvantage of introducing impurities into the pellets. This has resulted in organic binders being pursued as suitable replacements for inorganic binders, of which carboxymethyl cellulose (CMC) shows good potential. Although CMC has been used as an organic binder in iron ore pelletizing, the fundamental principles of how it behaves during pelletizing and how these impact on pellet properties are poorly understood."

Jan 1, 2017

The structural design of a pavement relates to the ability of the road to carry the imposed loads without the need for excessive maintenance or rehabilitation. Current techniques for the structural design of haulage roads are empirical and based primarily on the previous experience of personnel assigned to pavement design, both in terms of the strength of the structure and the quality of the wearing course material. This has the potential for unwarranted expenditure on too thick a structure or, conversely, premature deformation leading to the need for excessive expenditure on maintenance. Furthermore, the effect of larger haulage vehicles on the structural performance of a pavement cannot be predicted. Thus, there is a need to develop a portable and practical method of structural design. This paper presents an overview of structural design methods for mine haulage roads and, through an analysis and quantification of the structural performance of existing pavements, recommends the mechanistic design procedure, together with a revised structural design and associated limiting design criteria. It is concluded that the application of the mechanistic method to a design project can reduce the costs of haulage roads construction and accrue additional benefit in terms of reduced operating and maintenance costs.

Jan 1, 1996

By N. A. Barcza

This paper describes the development of large-scale thermal-plasma systems, which was motivated, in general, by the potential cost savings that could be achieved by their use as a replacement for the more conventional methods used in the generation of thermal energy. The anticipated cost savings arise not only from the use of plasma-generating devices but from the manner in which they have been interfaced with a furnace to process particular materials, mostly as fines. Thermal-plasma systems fall into two categories: non-transferred-arc and transferred-arc devices. In general, transferred-arc devices have been interfaced with open-bath furnaces in which melting or smelting processes carried out, while non-transferred-arc devices have normally been applied to shaft furnaces. Water-cooled transferred-arc devices are somewhat limited in power (about 5 MW) because of the relatively voltages (300 to 500 V) that can be attained in open-bath furnaces, where very long arcs are undesirable, and because only relatively low levels of current can be carried. Graphite electrodes can overcome the restriction current, and power levels of 30 to 50 MW seem feasible, even with one electrode, if direct current is used. Multiple water-cooled devices are capable of attaining similar power levels, but the capital costs are much higher. Costs due to electrode wear are lower for water-cooled systems, but expensive gases are needed for transferred-arc devices. Mintek conducted extensive pilot-plant work in which water-cooled devices were used initially but graphite electrodes were used subsequently to produce ferochromium from fines. Transferred-arc open-bath configurations were used. This work led to a decision by Middelburg Steel & Alloys (MS&A) to install a 16 MVA furnace of semindustrial scale to produce ferochromium aloys based on the ASEA d.c. arc furnace developed for the Elred process. Non-transferred-arc devices have atained reasonable scale-up to the 6 to8 MW power level, and high-voltage operation, which is inherent in such devices, has enabled lower currents to be used. Nevertheless, multiple systems are still necessary to accommodate large-scale applications, and this can be costly from a capital point of view. The cooling requirements are large, and can represent a considerable loss of electric energy. Shaft furnaces equipped with non-transferred-arc devices are suitable for the processing of materials that have volatile species, e.g. silica or manganese, or where the shaft is used to prereduce oxides that are amenable to gas-solid reactions. It is probably in the treatment of light and refractory metals that plasma technology will achieve its greatest development in the years to come. The energy requirements for the production of these metals are high, and very low oxygen potentials are necessary. These are factors that favour thermal plasma. Much developmental work is still needed in this interesting field. It should be remembered that electrically generated thermal energy is a unique temperature source that, in many instances, cannot be replaced technically or economically by the combustion of a fuel.

Jan 1, 1986

The following contributions were received to the paper entitled 'Safety in South African mines: An analysis of accident statistics', by H.S. Eisner and J.P. Leger, which appeared in the J. S. Afr. Inst. Min. Metal., vol. 88, no. 1, Jan. 1988, pp. 1-7. Contribution by H. WAGNER* The paper by Dr H.S. Eisner and Mr J.P. Leger is critical of the safety situation on South African mines and portrays the industry as having little concern for the health and safety of its workers. Moreover, the casual reader gains the impression of deliberate misinformation by the industry to the public concerning safety maters. Furthermore, certain socio-economic reasons are advanced for the apparent differences between the fatality and injury rates reported for coal mines in South Africa and those for the United Kingdom. Contribution by S.A. WATTS. Authors Eisner and Leger are to be commended on their paper, which highlights, according to their interpretation, various shortcomings of both the Chamber of Mines accident statistics and those published by the Department of Mineral and Energy Affairs. Authors' Reply We gratefully acknowledge Dr Wagner's contribution to the discussion on our paper. For convenience, we shal use his sequence of comments in our reply. Before doing so, however, it may be useful to explain how our paper came to be written. After the explosion at Hlobane Colliery in 1983, one of us (HSE), in February 1984, was retained by the lawyers acting for some of the dependants of the victims to advise on technical maters relating to the explosion. Contribution by Ms S.A. Wats Some of the points made by Ms Wats have already been answered in our comments on Dr Wagner's contribution. We are fully aware that the number of accidents leading to absences of less than 4 days would be much greater than shown in our bar chart, and are grateful to Ms Wats for drawing attention to the specific exceptions that can make a 1-3 day accident compensable and that are clearly responsible for the relatively low count in that category of the chart.

Jan 1, 1988

By I. D. Wood

Deposition of gold-bearing deposits in the Witwatersrand Basin was controlled by hydraulic processes. These resulted in the formation of independent sedimentological facies areas having different statistics and semivariograms. Consequently, when there are indications that data are a mixture of statistical populations, it is important to decompose them into statistical subpopulations and analyse these independently. However, in the case of actual mining, physical position and extent of sub- populations are important and, as a consequence, any decomposition of data must take space into account if it is to be of use. An algorithm for the spatial decomposition of data into its sub-populations is described and is applied to real data taken from the Witwatersrand. Two distinct areas with completely different geostatistical parameters were revealed.

Jan 1, 1987

The refractoriness of the gold in many of the pyritic ores from the eastern Transvaal is due mainly to the association between the gold and the sulphides, but it can be due to the presence of graphltlc carbonaceous material, which complicates the recovery of the gold by virtue of its adsorption activity. In an examination of the roasting characteristics of three flotation concentrates from the Barberton area, It was found that the gold in the concentrates occurred mostly in two forms: in very fine gold particles distributed within the arsenopyrite, and in a slightly coarser form loosely associated with the pyrite. Direct cyanidation of the concentrates gave gold extractions of from 16 to 30 per cent. After the concentrates had been roasted at temperatures of 650 to 700°C for 20 minutes with rabbling, the extractions varied from 86 to over 90 per cent. Examination of the residues after cyanidation indicated that gold was present in the porous calcines or in the calcined sulphide product. This observation, together with porosity measurements, suggests that physical encapsulation of the gold particles is the main reason for the refractory behaviour of the gold in the calcines.

Jan 1, 1988

By D. Nardini

The need to move towards faster and safer mine development is a key priority in mining houses globally. In addition to this, South Africa faces an array of challenges introduced by labour-intensive operations; hence a study was conducted to look into improving development rates and labour productivity, specifically in the areas where trackbound flat-end development is required. The aim of the study was to propose a method to deliver fit-for-purpose tracked tunnels that advanced at a rate of one blast per end every single working day. A major part of the study was to optimize the selection of an appropriate trackless fleet and mitigate any constraints introduced with the mechanization. This was done by creating scenarios, based on a typical case study, looking into the aspects around safety, mine design, mine activity cycling, men and machine requirements, service installations, and trackless-trackbound interfaces. The case study was based on a deep-level gold mine developing twin headings with connectings; however, with the move to extend and deepen platinum operations it is foreseen that twin end development will become more prevalent due to ventilation, logistical, and other requirements. With the introduction of the trackless mechanized system suggested, development rates of 56 m of system advance are expected (189 m total development), with on an average of three headings and fixed blast times. Scenarios run with multi-blast conditions yield expectations of 75 m/month advance of the system, significantly higher than the conventional performance seen today.

Jan 1, 2012

By G. D. Schena

The issue of evaluating the economic impact of large mineral projects in developing countries was studied by the use of econometric models. The evaluating system is demonstrated by its application to an example from Namibia. Three-dimensional graphics are used to illustrate the procedures leading to an assessment of the economic effects of the mineral development. The analysis allows the assessment of the overall economic consequences of mineral developments where there is a need to incorporate in the evaluation issues that are broader in scope than the pure financial objectives. Sets of technical coefficients are exploited for the development of input-output models of the productive structure of an economy. The models are refined to incorporate country-specific behaviours. The increased flexibility of the enhanced semi-input-output model permits a more confident investigation of the economy wide effects associated with a new project in the mineral sector of a developing country. Synthetic measures of profitability at market and shadow prices are introduced, and the cost/benefit ratio is used to rank mineral projects according to their economic profitability. The cost is the capital mobilized for the development of the project and for increasing the productive capacity of the related satellite industries. The benefits are identified with the economy-wide increase in value added induced by the project. 80th costs and benefits are initially valued at market prices. Their ratio is likely to be an index of economic profitability superior to measures that concentrate exclusively on the benefit side of projects. To allow for market distortions, the concept of shadow prices is introduced, and accordingly project-related costs and benefits are re-evaluated. A new cost/benefit ratio at shadow prices is recalculated, which is more meaningful to the policy-maker than decision-making based on socio-economic issues.

Jan 1, 1993

By M. Mathey

The application of the Monte Carlo technique to production planning and everyday economic decisionmaking in mine production management is demonstrated. The logic is detailed using an example of underground production with continuous miners (CMs) and truck haulage. It is argued that availability of equipment and personnel are the predominant variables influencing mine output and productivity and that those availabilities may be well represented by binomial probability distributions. The probabilistic model is implemented in a standard Excel® spreadsheet with Palisade’s @Risk add-on to facilitate simulations. Starting from model calibration against data obtained from a mine’s annual reports, some general interdependencies of availability, utilization, productivity, and costs of production processes are outlined. Finally, several possible options and their consequences as regards production improvements are explored.

Dec 13, 2022

By M. Gershon

During the exploration phase of mine development, drilling location is in the hands of the geologist, and drilling is spread over the entire domain of the property or deposit boundary. During the mine planning and production phases, however, the mining engineer also needs to use the information obtained from the drilling program. Thus it is important that he/she have some input into the selection of the drillhole locations. Usually, when exploitation will center on one portion of the property for the immediate future, the mine engineer will want to have more of the drilling performed in this area. In the early stages, the purpose of the drilling was to make a decision concerning whether or not to develop a mine. Once the decision is made to proceed with this development, the mine engineer needs to know, with as much confidence as possible, the estimate of the ore grade at each location where mining will occur. This paper addresses the problem of drillhole location for the needs of the mining engineer. The goal is to compare a variety of approaches to drillhole location with a new approach developed by the author. This approach is based on the theory of geostatistics, with the estimation variance used as the quantitative measure of the confidence attained. The goal of the algorithm is to select those locations that minimize the estimation variance subject to constraints on the number of drillholes and the total cost of the drilling program. The kriging equations are used as another set of constraints. The resulting nonlinear optimization model is expressed in terms of binary (0 - 1) decision variables leading to a solution by the branch-and-bound procedure. The algorithm has been applied at a number of operating properties, and practical results and suggestions for implementation are provided.

Jan 1, 1987

By M. Berjak, D. M. Hawlins, R. B. MacGillivray

SYNOPSIS The paper describes a method of producing iso line plans using a mathematical technique for interpolating between boreholes, and its computer application. The iso line plans are used for assessing the value parameters of an ore body. The computer programme also produces means and standard deviations to supplement these iso line plans. The mathematical techniques tested for the production of a satisfactory fit of the data were the polynomial, Fourier and moving average technique. The iso line plans are used for assessing the quality of the ore and other salient features such as depth to the floor of the ore body at different points, with a view to deciding how best the ore may be mined. The plans are plotted by the computer to any scale required. INTRODUCTION To assess the economic exploitability of an ore body many tedious and repetitive calculations must be carried out. Observations of borehole or development samples have to be processed yielding measures of ore reserve and quality in each sampled area, and also measures of the worth of the ore body as a whole and of variation in quality from section to section of the ore body. The observations made on the ore (which we shall term 'value parameters') may embrace a variety of characteristics of the ore. Obvious value parameters are those directly related to the economics of mining, viz. assay values, ore body thickness and depth below surface. Other value parameters however may be almost as important. In the case of coal for example a purchasing contract may specify limits of acceptability on other value parameters such as calorific value, ash content or the percentage of volatile matter. In this case, a detailed study of these value parameters will also be crucial. This detailed study must include an assessment, not only of the body as a whole, but also the regional variation in value of the parameter. An obvious and satisfactory way of displaying this variation is by drawing iso lines of constant value parameter on a map of the ore body and supplementing this with the means and standard deviations of the value parameters taken over all boreholes. Such plans, considered together, show up the zones of significance. The relatively stereotyped nature of the operations involved in this process makes it amenable to computer solution. In order to produce iso line plans on the computer we require some mathematical formula for producing a 'valuation surface'-a mathematical

By C. Holck, J. Yarmuch, J. Read

"Steepening of slopes provides the means to reduce waste extraction and increase ore recovery in open pit mines; however, it may also adversely affect safety by posing a higher risk of slope failure. The implementation of slope monitoring programmes is recommended to manage this risk inherent in steeper slopes. In this paper, the design and evaluation of monitoring campaigns to measure subsurface deformation and groundwater pore pressure in open pit mines is presented. The monitoring programmes were applied to a theoretical case of an open pit mine designed using DeepMine software (BOAMine SpA, 2015). Mine plans were developed based on the initial base case scenario with monitoring programmes considered for four types of monitoring instrumentation: two established technologies, in-place inclinometers (IPIs) and vibrating wire piezometers (VWPs); one emerging technology, the ShapeAccelArray (SAA); and a novel technology under development, the Enhanced Networked Smart Markers (ENSMs). Technical and economic appraisals of the monitoring programmes and sensitivity analysis of the developed mine plans showed that using ENSMs spaced every 4 m had the lowest cost per unit of data gathered. IntroductionSeveral open pit mines have already exceeded their design life and, as they become deeper and reach depths over 1000 m, they face higher rock stress levels and tensile deformations (Stacey and Xianbin, 2004; Stacey et al., 2003). The more complex the conditions in modern open pit mines, the more difficult it is to achieve long-lasting, stable pit slopes and to meet the mine’s economic needs: maximize financial returns, minimize risks to operational safety, achieve optimal ore recovery, and minimize waste extraction (Stacey, 2009). Steepening of slopes provides the means to reduce waste extraction and increase ore recovery (Stacey, 2009; Calderon and Tapia, 2006; Bye and Bell, 2001; Jefferies, Lorig, and Alvarez, 2008); however, it may adversely affect operational safety, as steeper slopes are less stable than shallow slopes (Steffen et al., 2008; Mphathiwa and Cawood, 2014)."

Nov 1, 2018

By M. Holuzko, Y. R. Zhang, J. Alexander

The use of dual-energy X-ray transmission (DE-XRT) technology in the mining industry has been developing rapidly in the past decade. In many projects, DE-XRT images are analysed to classify ore and waste in sulphide deposits where the sulphides and non-sulphides have distinct characteristics in density. In the current practice of DE-XRT image processing, every pixel in the image gets classified into two categories, depending on the intensity of the pixel from both low and high energy X-ray response. If the pixel’s intensity is above the threshold curve generated in the high-energy and lowenergy scatter plot, it is classified as “higher density” material, and the remaining pixels are classified as “lower density” material. This paper elaborates on an alternative approach to DE-XRT image processing for in-depth characterisation of samples from a lead-zinc sulphide deposit. The detailed characterisation is achieved by providing density distribution of individual rock using DE-XRT laboratory sorting unit (COMEX) located at the University of British Columbia. Instead of classifying the X-ray images into two different classes from one threshold curve, multiple density classes are created between two threshold curves to generate the density distribution. By manipulating the two threshold curves, we can analyse images of samples obtained at different resolutions of density distribution. If the two threshold curves become infinitely close to each other, it will create a single-threshold scenario similar to the current methods being used in the industry. This method provides the ability to change the threshold curves, hence providing more flexibility on material characterisation based on the needs of the operation. Furthermore, the DE-XRT images from individual rock specimens are compared to the test results from hand-held X-ray fluorescence (XRF) analyser as well as assays of various elements for the same set of samples. The data analysis will provide information regarding ore characteristics and also the theoretical performance of the sensor-based sorting. Keywords: Dual-energy X-ray Transmission (DE-XRT), X-ray fluorescence (XRF), ore characterisation, density distribution

Jan 1, 2020

By I. Soto, E. Córdova, A. Anani

The new caving megaprojects that are planned to go into production in the next decade have scheduled horizontal developments at very high rates, which are difficult to achieve. Research has been conducted that seeks to model the construction times for underground developments to determine the feasibility of achieving the planned rates. However, these previous attempts do not consider all the operational aspects that make up the mine development cycle. Here, we present a discrete event simulation (DES) model that individualizes each unit operation of the development cycle to determine the construction rates that new projects will be able to attain. The developed model was applied to the New Mine Level (NML) of the El Teniente Division (DET). The results indicate that it would be impractical to achieve the advance rates scheduled in the original plans if the unit operations of the mine continue to be executed using the status quo. The metres developed after six years in the sections analysed can be significantly improved by changing the maintenance strategy for the equipment (457 metres increase), orepass availability (194 metres increase), and the initial planning sequence (1 598 metres increase). It is recommended that the mine implements a flexible maintenance strategy, defines a strategy to ensure and increase orepass availability to contractors, and makes use of current simulation tools for a more robust development sequence planning.

Oct 1, 2022

By D. Hu, J. Xu, N. Liao, C. Wu, J. Ye

The vertical stirring mill’s fine grinding equipment is affected by the operating conditions during the grinding process. The grinding media has a great influence on the energy consumption and particle size distribution. This paper investigates the fine grinding performance of nano-ceramic balls and steel balls of the same weight for magnetite by a wet grinding process in a vertical stirring mill, where 15 mm nano-ceramic balls and 12 mm steel balls are used as grinding media to carry out batch grinding tests. We have observed that the newly qualified particle content of the nano-ceramic balls is higher than steel balls of the same weight at the same specific energy. The reason may be the advantage of a greater surface area and volume filling rate with the nano-ceramic balls. Moreover, the specific energy of nanoceramic balls is less than steel balls of the same weight under the same grinding fineness. In addition, energy efficiency indicates that the nano-ceramic ball has a higher energy efficiency than a steel ball of the same weight. This is due to the light bulk density of nano-ceramic balls. The application of a nanoceramic ball in a vertical stirring mill will improve iron ore grinding performance. Keywords: Steel balls, nano-ceramic balls, vertical stirring mills, fine grinding, particle size distribution, energy consumption

Jan 1, 2020

By T. A. Claasen

Exceptionally low yields in the coking-coal fields of the Soutpansberg area in the northern Transvaal, are taxing the skill and ingenuity of preparation engineers. The coals are highly intergrown, and a series of crushing and washing steps may be required to extract the maximum usable tonnage. In addition, novel preparation techniques may have to be employed. This paper, which is a case study of work recently undertaken, gives a general account of raw coal properties, emphasizing those related to maximum recoveries, and outlines the steps involved in the design of appropriate flow sheets based on laboratory studies.

Jan 1, 1980

By J. M. Czaplicki

The problems connected with deep mine hoisting and the increasing complexity of this process can be analysed through the application of such mathematical tools as stochastic modelling to study the effectiveness, reliability or safety of hoist methods. To relate these theoretical investigations to real practice, knowledge about components, their stochastic nature and stochastic order of appearance is necessary. This paper presents results obtained during the ten-year (1976-85) period of research undertaken in the Polish mining industry by the Mining Mechanisation Institute of the Silesian Technical University, Gliwice, Poland.

Jan 1, 1987

By D. Pienaar, D. Stanton

This paper provides an overview of possible approaches for structuring the ventilation systems for mines that will become operational within the next decade. Features addressed in the paper include: aspects of airway design and layout in the absence of centralized vertical return shafts, the impact of using diesel-powered trackless equipment in conjunction with conveyor belts in the development and production phases of the project, and the need to balance increasing electrical power costs against the requirement for reduced capital expenditure. The paper provides brief descriptions of the strategies employed in real-life situations and presents an overview of various operational parameters affecting the design of ventilation systems that will be used as ?platforms? for much deeper mines in the future.

Jan 1, 2006

The Institute was founded in 1894 as the Chemical and Metallurgical Society of South Africa. In 1904 it was reconstituted as the Chemical Metallurgical and Mining Society of South Africa and in 1956 it became the South African Institute of Mining and Metallurgy. The objects of the Institute are to advance the science and practice of mining and metallurgy, to afford opportunities for the interchange and recording of knowledge of mining and metallurgy and to ensure high standards of professional conduct and competence. Membership benefits include monthly issues of the Journal of the Institute, monthly General Meetings at which papers are read, symposia, excursions to mining and industrial concerns and the use of club facilities at Kelvin House. Technical journals received on an exchange basis are available to members at the Johannesburg Public Library. The current membership of the Institute is over 1,400. Membership applications are accepted from suitably qualified persons and the requirements for entrance to the various grades of membership are summarised below. Members shall be not be less than 30 years of age, shall be university graduates in pure or applied science or shall produce evidence to the satisfaction of the Council that they have successfully completed a co-ordinated course of study in pure or applied science of at least three years' duration at an approved university or institution deemed by the Council to be of equivalent status. Members shall have been employed in senior technical positions in important mining or metallurgical undertakings for at least five years or they shall have practised as mining or metallurgical consultants for at least five years. They shall be practising their profession at the time of application. Entrance fee R4.00; Annual subscription R14.00 (town), R12.00 (country). Letters of designation: M.S.A.INST.M.M. Associate Members shall be not less than 25 years of age and shall be university graduates in pure or applied science, or shall have successfully completed co-ordinated courses of study in pure or applied science of at least three years' duration. They shall have been engaged in work of an approved technical character in the mining or metallurgical industries, of which not less than two years shall have been in positions of responsibility. A candidate shall be practising his profession at the time of his application. Entrance fee R2.00; Annual subscription R12.00 (town), R10.00(country). Letters of designation: A.M.S.INST.M.M. Affiliates shall be not less than twenty-five years of age, and shall have been engaged in positions of responsibility in, or associated with, the mining or metallurgical industries for periods of not less than three years. If, however, the candidate for admission to the higher grade of Affiliate, is at the time of his application, already a Student member, he need satisfy the Council only that he is, at the time of his application, engaged in a position of responsibility in or associated with the mining or metallurgical industries. In all cases the applicants shall satisfy the Council that they are fit and proper persons to become Affiliates. Entrance fee R2.00; Annual subscription R12.00 (town), R10.00(country). Graduate Members shall be not less than 21 years of age and shall be university graduates in pure or applied science, or have completed co-ordinated courses of study in pure or applied science of at least three years' duration at an approved university or institution. They shall not remain Graduate members after attaining the age of 30 years without the permission of Council. Entrance fee R1.00; Annual subscription R7.00 (town), R6.00 (country). Students shall be persons not less than 18 years of age who are being educated or trained in a manner approved by the Council, to occupy a technical position in or associated with the mining or metallurgical industries and who, furthermore, shall not have attained the qualification required for a higher grade of membership. They may remain Students until they have obtained the necessary qualifications for transfer to a higher grade of membership, but not after the end of the Institute's financial year in which they attain the age of 28 (twenty-eight) years. They shall then transfer to a higher grade to retain membership of the Institute. The Council may relax the provisions of this clause in such cases as it considers appropriate. Entrance fee nil; Annual subscription R3.00 (town), R3.00 (country). Other. The Council has the power to elect to the grade of Member or Associate Member candidates who may not fulfil all the requirements for entrance to these grades but whose status, professional achievements and practical experience in mining or metallurgy justify such election. Applications. Requests for membership application forms should be addressed to the Secretary: South African Institute of Mining and Metallurgy, P.D. Box 1183, Johannesburg.