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By P. R. Jochens

SYNOPSIS This review article first highlights the past performance of the industry and discusses the manner in which the development of the industry has followed a logical progression from mining to the production of mineral and metal products of specification purity. Then the numerous constraints against a greater contribution by the industry are enumerated. Attention is drawn to the extent of further processing that can be undertaken in the context of mining and metallurgical processing, not only to indicate the benefits that can be derived from the added-value conferred on a mineral or metal commodity during each stage of its further processing, but also to point out some important corollaries of further processing. The many opportunities and challenges for an increased contribution by the minerals and metals industry are then reviewed. This major section includes a list of commodities for which increased penetration of export markets could be sought because the increasing resistance level (a term developed in this paper) has not been attained; a list of commodities that are imported at present, many of which could be produced locally on the basis of identified resources and expertise; a list of commodities for which additional uses should be developed so that South Africa, which possesses the largest reserves and is the largest exporter, can increase its production rate; and examples of commodities for which further processing is still at an early stag*..

Jan 1, 1985

By Z. Zitron, G. J. de Korte, D. W. Horsfall

This paper summarizes work carried out on the treatment of fine coal, nominally classified as minus 0,5 mm (wedge-wire screen), which is removed from the raw coal prior to the treatment of the plus 0,5 mm sizes. The minus 0,5 mm coal divides, for treatment purposes, into fines, nominally between 500 and 150 !tm, and ultrafines, nominally minus 150 !tm. Studies on processes for the treatment of minus 0,5 mm coal are discussed, and the lower size limit beneficiated is indicated for each process. The installation and operational results from a pilot froth-flotation plant treating minus 150!tm coal are described.

Jan 1, 1986

By D. P. Power

The development of an accounting code for the metallurgical industry has been debated for many years. Following the series of tumultuous economic events in the nineties and earlier this century that have affected business, there was much need for legislation to be passed to minimize potential risk. One of the consequences to affect the mining industry was the enhancement of existing geological codes for reporting. In parallel the sponsors of AMIRA have taken the brave step to develop a generic code for metal accounting that embraces the full gamut of industry. In this paper the code will be reviewed in the context of metallurgical accounting as it applies to coal preparation. This paper provides the background for this development and an insight into the mechanism for the debate for the generation of this code. The key elements of the code as it applies to the coal industry are explained but most importantly the key opportunities are highlighted.

Jan 1, 2010

By Q. G. Reynolds

The problem of direct-current plasma arc behaviour, interaction, and dynamics is considered in the context of metallurgical DC arc furnace applications. Particular attention is paid to the transient flow behaviour of arc systems. A mathematical formulation of the physics used to describe the arc system is presented, and includes the spatial and temporal evolution of fluid flow, heat transfer, and electromagnetism. Based on this formulation, a numerical model is developed using a finite difference approach on a regular cartesian grid in both two and three dimensions, with a special focus on robust stability, high resolution modelling, and high performance. A collection of results produced using the numerical model to study pilot plant-scale furnaces is then presented. These address a range of process and design variables and their effect on the numerical model?s results. Where possible, the qualitative behaviour of the model is compared to available experimental data. A number of novel effects and phenomena are seen in the dynamic behaviour of the DC plasma arc model for both single and multiple arc systems, which may lead to improved understanding, control, and manipulation of such systems where they occur in industrial applications. Keywords Pyrometallurgy, direct-current furnace, plasma arc, modelling.

Jan 1, 2010

By C. Musingwini, A. S. Nhleko, M. J. Mahase

"In an environment like the mining industry, which is characterized by different stakeholders with multiple objectives, multi-criteria decision analysis (MCDA) is a useful approach for optimal decision-making. The application of MCDA techniques in the mining industry has predominantly been in mine planning and related problems, although no comprehensive survey has previously been undertaken to establish the application trends. A survey of the use of MCDA techniques was therefore conducted using case studies from the literature. It was noted that often two or more methods are applied to the same problem in order to increase confidence in the solution derived. As the number of criteria and alternatives increases, some methods become inefficient. A combination of the analytic hierarchy process (AHP) method with other MCDA techniques was the most frequently used approach, indicating the efficiency of the AHP method, especially when evaluating problems with more criteria and fewer alternatives. A combination of fuzzy theory with AHP or other methods incorporates uncertainty. The findings from the survey will benefit users applying MCDA techniques to solve mine planning and related problems.IntroductionA country’s natural resources serve the needs of different groups of people within the country. These different groups are collectively known as stakeholders (Herath and Prato, 2006). Stakeholders have different needs, preferences, and expectations, which describe and define the criteria to be considered in decision-making. The options available as solutions describe the alternatives in decisionmaking theory. The criteria and alternatives have to be evaluated simultaneously when making decisions, and this is when multicriteria decision analysis (MCDA) techniques become invaluable (Herath and Prato, 2006) because the human mind is considered to be limited when solving complex and intangible problems with several criteria and alternatives (Saaty, 2007). MCDA techniques belong to a broad group of techniques called multi-criteria decision-making (MCDM) techniques. The other group of techniques within MCDM comprises the multi-objective decision-making (MODM) techniques. MODM techniques are generally used to solve problems with an infinite number of alternatives, while MCDA techniques are generally used to solve problems with a finite number of alternatives (Musingwini, 2010)."

Jan 1, 2016

By H. Von Michaelis

The world is rapidly becoming more ?green? i.e. energy conscious. Since mining and mineral processing are massive energy users, the mining industry is seeking ways to reduce its energy footprint. In mining and mineral processing operations, energy is often the most expensive cost item. Comminution, i.e. grinding, is frequently the most energy-intensive step between mine and metal. High pressure grinding rolls (HPGR) are being installed in a rapidly growing number of ?hard rock? mineral processing operations. In the energy conscious cement industry, HPGR grinding has been standard practice for decades. HPGR is known to be energy-efficient; the question is how energy efficient? How can the energy efficiency of HPGR be enhanced? This paper reviews recent HPGR applications for the processing particularly of copper, gold, platinum, PGM-Ni-Cu and iron ores. HPGR technology is discussed with respect to energy efficiency. The harder the ore the greater the energy savings are likely to be. Typical energy savings of 10?20% can be expected when installing HPGR vs. a SAG mill. Wipf(2005) showed why conventional Bond Work index tests on HPGR product is likely to under-estimate the energy savings that can be achieved by installing HPGR. Energy efficiency of HPGR is, however, ore-specific. The biggest energy savings of HPGR tested thus far is 9.5 kWh/tonne claimed for Vista Gold?s Mt. Todd gold ore from Western Australia, a savings of over one-third of conventional SABC comminution energy. Several commercial scale iron-ore pellet feed plants install HPGR for fine-grinding of concentrate to increase the surface area of pellet feed in a manner that reduces overall energy consumption. Energy-consumption in comminution is, however, only part of the energy savings benefit story. HPGR typically also reduces the amount of steel lost through wear of mill liners and media. Marsden(2008) showed that when the energy that would have been consumed to produce the steel that is saved by applying HPGR is factored in, then the overall energy savings of HPGR is considerably greater. Johnson et al.(1988, 2005) tested HPGR in a flowsheet in which energy savings of around 50% can be expected if HPGR product screen oversize is recirculated to the HPGR. Innovative flowsheets have been proposed by Rule et al.(2008) and by Morley (2008) which are expected to result in significantly increased energy savings. HPGR applied in flowsheets in conjunction with coarse ore separation devices, e.g. ore sorting or DMS to remove barren waste from HPGR feed promises significantly greater energy efficiencies. Fine-grinding and ultra-fine grinding of ore or concentrates in conventional ball mills results in energy consumptions that increase exponentially with product fineness. Wipf (2009) presented a flowsheet in which he proposed the installation of HPGR ahead of the Aerosion ?Disintegrator? for ultra-fine grinding of ores and/or concentrates. This dry grinding arrangement is expected to achieve ap80 = 7 µm using up to 100 kWh/t less energy than could be achieved by wet ball milling. Using conventional comminution, an ore might require grinding to p80 = 45µm (? 325 mesh), for example, to liberate the valuable components, e.g. magnetite, from gangue, e.g. silica. Inter-particle comminution in HPGR may break some ores along grain boundaries thereby liberating valuable minerals from gangue at a much coarser particle sizes. Early magnetic separation rejection of silica gangue liberated from magnetite by HPGR at coarser grain sizes could further reduce downstream comminution energy consumption.

Jan 1, 2009

By K. R. Vost

Variation in air temperature in a cross-section of an underground airway by K. R. VOST, B.Sc. (Glas.), M.Sc. (N.S.W.) (Visitor) Measurements of air temperatures in underground airways are normally made at only one point in a cross-section, and the air tem peratures at other points in the cross-section are assumed not to differ significantly from this. This paper discusses measurements made at a number of points in fifty crosssections in airways with different air velocities and wetness of floor. These measurements show that significant variations of air temperature can occur in a given cross-section at a given time. The effects of such variations on the accuracy of measurement of rises in air temperature as air passes along an airway are discussed. The importance of considering experimental error in the measured rises in air temperature when attempting to validate theoretical and empirical methods of predicting such rises is also discussed.

Jan 7, 1976

By A. Dabbagh

The aim of this research was to investigate the effect of coke particle size on the thermal profile of the charge bed in the sintering process of iron ore. Six different ranges of coke particle size that could be used in practice in the sintering line of Esfahan Steel Company (ESCO) were used while parameters such as ratios and particle sizes of other ingredients, ignition temperature, and suction power were kept constant. Thermal profiles were obtained by measuring the temperature changes at three points in the sintering bed. The influence of coke particle size on rate of temperature rise, maximum temperature of the sintering bed, and the flame front velocity of the sintering bed was determined by analysing the thermal profiles. Moreover, the cold strengths of the sinters were measured using the Tumbler method. The results indicated that the coke particle size has a significant impact on the thermal properties of the sintering bed. Based on the results, a coke particle size between 0.212 mm and 3.350 mm was determined as the optimal range for the specific conditions in the sintering line of ESCO. Keywords iron ore sintering, coke particle size, thermal profile, flame front velocity, Tumbler index.

Dec 1, 2013

By R. J. Davidson

The mechanism of gold adsorption on activated charcoal by R. J. DAVIDSON: M.Se., Ph.D. (Rhodes) (Visitor) The adsorption of gold onto activated charcoal is most dependent on the concentration and character of the 'spectator' cations present in the adsorption medium. In the presence of calcium ions, gold is adsorbed as the calcium aurocyanide complex. The degree to which the aurocyanide complexes are adsorbed follows the series Ca> Mt:> H> Li> Na> K, calcium aurocyanide being the most stable complex and potassium aurocyanide the least firmly bound. If a loaded charcoal, where the gold is present as the calcium complex, is treated initially with either sodium carbonate or potassium carbonate solutions, the gold can subsequently be eluted from the charcoal with hot deionized water as either the sodium or the potassium complex respectively. The elution of gold with deionized water appears to be most attractive practically and economically, and has several potential applications in the recovery of gold from dilute solutions.

Jan 10, 1974

By M. Le Roux

The dewatering of coal, and particularly fine coal, continues to challenge coal prepatration engineers to find a cost-effective solution. With known world oil reserves being depleted daily, it is envisaged that the future price of coal may justify the use of thermal drying to achieve lower coal product moisture levels. The effect of exposure of the coal to elevated toemperatures on the mechanical strength of the coal was investigated. It was found that temperature does not play a major role in determining the volume breakage of a particle and that other variables such as orientation during impact has a much greater influence. A double breakage mechanism was reported during the grindability tests. Surface, as well as volume breakage, occurs for the first 4 minutes while only surface breakage takes place thereafter. Due to this double breakage action, it was found that exposure to temperature does play a role in the amount of breakage and breakage rates during grindability tests. It was also concluded that a particle will break to an optimum size due to impact, after which only its surface will grind away as it is subjected to breakage forces.

Jan 1, 2008

Notices EIGHTH WORLD MINING CONGRESS The Eighth World Mining Congress will be held in Lima, Peru, from 3rd to 8th November, 1974. The theme of the Congress is 'Prognosis of mining development up to the year 2000', with the following subthemes: INF ACON 74 Readers are reminded of the International Ferro-alloys Congress being organized by the National Institute for Metallurgy, in conjunction with the Ferro Alloy Producers' Association of South Africa and the South African Institute of Mining and Metallurgy.

By J. M. Eriksen, T. Rosenqvist, H. Elstad, S. Seim, A. Hildal

The titanium industry demands high titanium feedstock for their processes. As rutile resources are limited, ilmenite has become the most important titanium source. Ilmenite smelting is an important part of upgrading ilmenite to high titanium feedstock. In the year 2005, upgrading of ilmenite by smelting, producing a slag with 80-90% Ti02, accounted for approximately 40% of the feedstock to the Ti02 pigment industry. In ilmenite smelting molten iron is produced together with a slag, which in addition to titanium oxide contains iron oxide as well as various impurity oxides of manganese, magnesium, silicon, aluminium, etc. Titanium is present mainly as Ti02 but partly also as Ti203. It is known that the concentration of Ti203 increases with decreasing concentration of FeO, but this dependency is affected by the nature of the impurity oxides. Sigurdson and Moore1 showed that slags high in CaO and MgO had a lower concentration of Ti203 than slags high in Si02 for the same amount of FeO. Pistorius2 showed in 2002 that if the impurity oxides MnO and MgO are counted, on a molar basis, as FeO, and Cr203, V203 and part of the A1203*), as Ti203, industrial slags will have a composition close to that of the M305 phase, where M denotes the elements Ti, Fe, Mn, etc, and which has the pseudobrookite structure. However, for equilibrium with liquid metallic iron he computed, by means of a computer program FACT, that the slag equilibrium composition is represented by a curved line in the ternary phase diagram FeTi03-TiO2-Ti2O3, but with a significantly higher concentration of trivalent titanium than actually observed in the industrial slags, and he discussed various mechanisms by which the slag during solidification could change its composition to a lower Ti203 content, but the possibility that the computed compositions might be wrong was not mentioned. Trane113 found in her research on titaniferous silicate slags a lower Ti3+/ Ti4+ ratio than that which is computed by the FACT program. The purpose of the present investigation was to study the equilibrium composition of Fe-Ti-O slag in equilibrium with liquid metallic iron, as well as the effects of impurities such as Si02, CaO and MgO on the slag composition. Industrial slags from TINFOS Titan and Iron KS (TTI) will also be discussed and their compositions will be plotted in the ternary phase diagram. These are slags produced from Tellnes ilmenite, quite high in magnesium and iron. Experimental In the past, equilibrium studies of the Fe-Ti-O slag system were difficult when it came to producing the slag. It was difficult to find a suitable crucible for the meltings. The highly corrosive slag would attack all known refractories, and the metal would attack metallic crucibles such as those made of platinum and molybdenum. In the present investigations the slag-metal combination was prepared in a high-frequency induction furnace with a vertically segmented water-cooled copper crucible. The crucible is shown in Figures 1 a and 1b. It was designed by the Australian Nuclear Science and Technology Organisation (ANSTO) with power from a 75 kVA high-frequency generator (750 kHz) supplied by Farfield Electronics Pty, Ltd, Australia. This enabled the slag-metal combination to be melted with turbulent stirring and is expected to be isothermal. The entire temperature gradient

Jan 1, 2007

By I. Serepa, N. C. Steenkamp

Investigations were conducted to determine the condition and stability of the existing decline at amine in the Kalahari Manganese Field, Northern Cape Province, South Africa. During the inspection of the decline, voids were identified behind the concrete lining on the hangingwall and sidewalls over a total linear distance of 230 m. The voids did not provide confinement and, as a result, self-mining was occurring behind the lining. Water was flowing into the decline, over a total linear distance of 100 m, at areas where the decline intersected incompetent rock units, causing softening of the concrete lining and deterioration of the surrounding rock mass. Further damage to the concrete lining was caused by expansion and contraction of the wet red clay unit. Remedial work comprised void filling and water sealing to prevent further deterioration of the decline and ensure that it remained operable for the remainder of the life of mine. Void filling was accomplished by drilling rows of holes along the decline to access the voids and filling the voids with foam. This was followed by the sealing with polymer fluids. Telescopic pipes were also installed to allow water to drain off. A visual inspection was conducted and check-holes were drilled to assess the quality of the remedial work. The void filling material had penetrated cracks in the concrete lining, and areas where voids were intersected by check-holes were re-filled. Additional holes were drilled to re-seal areas that were still wet. The remedial work was completed successfully, as all voids were filled and stability achieved without compromising the concrete lining. The ingress of groundwater was also reduced to some residual dampness.

Mar 2, 2022

By R. N. Guest

The Tromp distribution curve was used in an evaluation of gravity separators treating a synthetic ore made up of silica and marker minerals of various relative densities. The results pinpoint differences in the concentration of particles of different sizes, and indicate how the grade of a concentrate is likely to vary with particle size. An increase in the feed rate increased the efficiency of the 'waterless' spiral concentrator that was tested, but the multiport spiral concentrator tested was more efficient. Both spiral concentrators were found to be more efficient than the pinched sluice and the shaking table that were tested. The method was found to be a useful way of evaluating gravity concentrators, but, for ease of analysis, care must be taken in the choice of marker minerals.

Jan 1, 1985

By C. A. Green, M. A. T. Cocquerel, R. T. Gates

"Engineering studies by Selection Trust, Limited, initially in connection with the development of a copper and nickel deposit for Bamangwato Concessions, Limited, and subsequently for several other clients, have required a large number of metallurgical design calculations. The flash smelting process, developed by Outokumpu Oy in Finland, has been selected as the most suitable method for these projects and the computer programs described in this paper have been developed to facilitate the computation.The data required by the programs arc the chemical and mineralogical analyses of the concentrate, gangue and flux materials and the specification of possible fuels. The required grade of furnace matte is set as the main design parameter and the programs calculate detailed heat and material balances for the smelting process."

Jan 1, 2014

By J. Levin

The Bond standard grindability test provides a Work Index that is widely used to estimate the energy required for grinding, but the test cannot be applied to fine materials such as plant tailings and middlings. For such materials, a comparative grinding test must be used in which a reference material from an operating plant is ground in a laboratory mill to determine the 'equivalent' energy consumption per revolution of the laboratory mill. As the Bond grindability test mill and its operating conditions are specified, its equivalent energy consumption per revolution should be a constant, here designated as B. Once B has been determined, the mill can be used to estimate the grindability of fine materials without the need for reference materials. A value of B can be calculated from any Bond grindability test, and 245 tests that were conducted at Mintek were examined to determine its value. A wide range of values was found, but most of them were grouped around 198 x 10- 7 kWh/rev, which is taken as the best estimate of B that is available at present. Values of B that are not close to this figure are obtained from materials for which the Bond grindability test gives misleading or 'spurious' Work Indexes. These spurious Work Indexes lead to the apparent departure of B from its true value. Some limitations of the Bond grindability test arise from its use of a mill without litters and of screening, instead of classification, to close the circuit.

Jan 1, 1989

By O. K. H. Sheff

An editorial in the April 1990 edition of Mining Magazine is worth a wider audience in South Africa, particularly as the SAIMM enters its own centenary decade and the process of change in the minerals industry world-wide makes increasing demands on the professionalism of its leaders. The editorial considers the changing status of engineers, who up to the 1880s had been held in high regard by society. Alumina and bauxite Economists forecast a slower economic growth rate in 1990, but expect continued increase in demand for aluminum at a 3 per cent annual rate during the decade. Structural and numerical analysis Struceng & Femcad (structural analysis and finiteelement method) is a conference and exhibition that is to be held in Grenoble (France) on 17th and 18th October, 1990. It is sponsored by the Institute for Industrial Technology Transfer (ITT-International).

Jan 1, 1990

By Y. Fan, D. H. Zhang, J. Y. Xu

The hydrogeological conditions in the Chambishi mine area in Zambia. were investigated. Chambishi is a very wet mine and groundwater discharge costs are high. The research goal was to identify methods to reduce the discharge costs without greatly affecting the mining process. Hydrogeological data was obtained from measurements in drill-holes and from drill cores. The differences in structural deformation in different areas determine whether a layer of rock is an aquifer. In the mine region, the Lower Roan Group ore shale and quartz-sandstone unconformably lie on the basal schist and granite aquifuge. The Upper Roan Group dolomite is continuously distributed over a large area around the orebody. This dolomite is the main target of groundwater control efforts, and its water yield is also influenced by the deformation intensity. Based on the observations, backfilling was gradually adopted to appropriately safeguard the integrity of the aquifuge above the orebody. The overlapping relationship between the aquifer and aquifuge has been utilized to increase mine drainage efficiency. This measure has not only greatly reduced the costs of mine drainage, but also improced protection of the groundwater environment. The old drill-holes that were not sealed after exploration drilling were grouted. Further, possible water-conducting fracture zones were investigated. Cover drilling towards the suspected zone was conducted to prevent the high-pressure groundwater from shallower aquifers from entering stopes in deep areas of the mine.

Jun 10, 2024

By J. K. E. Douglas

PRESIDENTIAL ADDRESS Given by Mr J. K. E. DOUGLAS, M.Se. (Eng.) (Rand) SYNOPSIS Lime is the most widely used and the cheapest chemical alkali known to man and virtually every product we use or eat has required lime in some phase of its manufacture. Its use goes back to the earliest days of man and many ancient buildings and writings bear testimony to this. The manufacture of lime involves quarrying, crushing and screening of limestone and the burning of the sized stone in kilns of which there are several types. The earliest kilns were of very crude design and only in comparatively recent times have large capacity, automated and scientifically controlled kilns been developed. The history of the South African lime industry is largely that of the three main lime companies and their story is briefly told. No other material used in industry has a greater diversity of uses or more varied functions and lime has applications in most South African industries. The main applications are in the production of gold and uranium, iron, steel and ferrochrome, carbide, sugar and paper and for water treatment, agriculture and building. The Republic is well endowed with high quality limestone and the conclusion is drawn that many other minerals will have been exhausted before we run out of limestone with which to process them. The expansion of the lime industry has in the past kept pace with the requirements of industry and the future demand is expected to grow in parallel with the growth of these industries. Since the war this growth has been phenomenal and with our expanding populations and abundance of raw materials it should continue in the years ahead. Limiting factors are the shortage of skilled labour and the distance from export markets. Confidence is expressed that the challenges of the future will be met and that the lime industry will continue to make an important contribution to the growth and prosperity of South Africa. INTRODUCTION Lime, gentlemen, is known to all of you. Like myself, most of you have undoubtedly found it to be, on the appropriate occasion, a most pleasant flavouring for gin. But this lime, or rather its juice, was in earlier days more than just a flavouring. In the days of sail it was vital to the health of sailors as a deterrant against the scourge of all sea-going men-scurvy. It thus played a small but important role in the opening-up of trade routes around the world on which was based the original wealth of many of today's more advanced nations. I propose to address you on the subject of lime this evening, not the citrus variety I have just mentioned, but the most widely-used and cheapest alkali known to man, which, largely unsung, plays an even more vital part in modern industry than did its namesake in the development of inter-continental trade. In the time at my disposal, I propose to tell you something of the history, geology and technology of lime manufacture. Then I will briefly sketch for you the development of this industry in South Africa and indicate the role it plays in supplying the requirements of many of our important industries. Finally we will attempt to look into the future. The importance of this chemical alkali to our modern civilization is seldom fully appreciated-virtually every product we use or eat has required lime in some phase of its manufacture, either directly or indirectly. It is one of those basic materials, along with iron, coal, sulphur, salt and petroleum without which industry and, in fact, our modern way of living could not exist. Fortunately, nature has endowed the world with a plentiful supply of the limestone from which lime is derived and most countries have deposits adequate for their requirements. As a result, not only has there been little trade in lime products between countries but in the past the widespread occurrences of limestone have set a pattern of numerous small plants each serving a limited area. These plants were generally crude affairs incapable of producing a quality product. It is not surprising that, in an industry comprised of small producers with limited financial resources and in fierce competition with each other, there was little interchange of information. Technological development was therefore slow and the industry tended to be regarded as a backyard operation. Its popularity was not enhanced by the fact that lime is difficult and unpleasant to handle if proper facilities are not provided. In recent years the lime industry has undergone very radical changes to meet the more exacting requirements of today's more sophisticated consumers. Only since the war have the larger companies emerged with proper management, highly mechanized plants and a scientific approach. HISTORY Lime was one of the first chemical reagents used by man and consequently lime burning is one of the oldest of the chemical industries. The use of limestone dates back to the stone age when primitive man used limestone to build fireplaces, construct shelters and make crude tools and weapons. It is probable that lime was first discovered by him when the stone in these fireplaces disintegrated to a white powder which he could use for decorative purposes. The first recorded use of limestone was when huge blocks of limestone were used to build the pyramids of Egypt in 4,000 to 2,000 RC. It was not long after this that the beauty of marble, which is in fact a limestone, came to be appreciated and it found wide application in sculpturing and for decorative wall construction. Originally lime, mixed with sand, was used mainly as a mortar for building purposes, the earliest record of its use for chemical purposes being in 350 B.C. in a report of the wreck near Marseilles of a ship carrying a cargo of linen and lime 'for its bleaching'1. Cato mentioned the burning of lime kilns in 184 B.C. and the Romans made extensive use of both limestone and lime for highway construction. A treatise on architecture by Vitruvius who had an official position in the rebuilding of Rome under the Emperor Augustus remained for nearly two thousand

By D. G. Wymer, A. G. du Plessis, N. C. Joughin

The use of a dense hangingwal-support configuration extending right up to the face would enable greater levels of safety and productivity to be achieved in stopes, and becomes a practical proposition if water jets are used for stope cleaning. Such an arrangement opens the way for extending the use of water hydraulic power to the whole stoping operation. This, in turn, can provide further productivity benefits and significant savings in working costs. With al the necessary equipment being available, such a system could be introduced immediately, although the designs of props and rockdrills are not yet ideal.

Jan 1, 1989