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By J. P. Ress

In 1903, seventeen years after mining of the Witwatersrand gold-bearing reefs started, the findings erf the Miners' Phthisis Commission (Transvaal) resulted in the initiation of measures with the object of controlling dust production. The substance of these measures was as follows: Removal of persons from places where they would be exposed to blasting fumes; use of water to suppress dust made in drilling and in other operations; supply and control of air to working-places; filtration of dusty air; and determination of the amount of the dust in the air. Broadly speaking, progress in dust control has followed these four lines with increasing success as the nature of the problem has become better known. Complete success has not, however, been achieved, partly because increasing mechanization of mining has intensified the problem and partly because the application of these measures is not infallible, being subject, in many cases, to human control. A brief summary of the development of these measures will lead to a description of present-day practice.

Jan 1, 1947

The mineralogical composition of the ore was determined and the mineral phases with which nickel is associated were identified. The ore was prepared by grinding to -420 micrometres and classification into granulometric fractions. Prior to the main series of experiments the effect of agitation rate on nickel recovery was investigated. The influence of sulphuric acid concentration, temperature and particle size on the kinetics of nickel extraction was then studied, both quantitatively and qualitatively, over fixed value intervals. Application of the initial rate method enabled determination both of the order of reaction with respect to sulphuric acid concentration and the activation energy for the dissolution of nickel. The results indicate that a physical mechanism can be ruled out as the rate-determining step in the extraction of nickel from the ore and that a chemical mechanism is more likely

Dec 1, 1991

By V. E. Ross

A comparison was made of three methods for determining the contributions of true flotation and entrainment during batch flotation tests. In the first method size-by-size recoveries are measured in both the presence and the absence of a collector, a frother being present in both tests. In the second method the mass of solids and water recovered after a chosen time of flotation is varied by changing the rate of froth removal and the depth of the froth. The third method uses a transfer factor to describe the classification of solids and water, and hence the changes in the composition of the pulp, during a single flotation test. Batch flotation tests were carried out with artificial mixtures of pyrite and gangue, the amount of floated material recovered being calculated according to each of the three methods. The discrepancies betweeen the calculated amounts are analysed in terms of the assumptions that are made for the various methods and the most suitable conditions for the application of each method are identified

Dec 1, 1991

By J. H. E. Jeffes, K. T. Jacob

The activity coefficients of oxygen in liquid Pb-Sn alloys have been measured between 550 and 1100°C by use of solid oxide galvanic cells: Pt, Ni-NiO | Zr02 Solid electrolyte | O (Pb + Sn), Cermet, Pt; and Pt, Fe-FeO | Zr02 Solid electrolyte | 0(Pb + Sn), Cermet, Pt. Alcock and Richardson's quasi-chemical equation, with the coordination number of atoms set to 2, is found to predict successfully the activity coefficients of oxygen in these alloys. The relative partial molar enthalpy and entropy of oxygen at 1 atom per cent in the alloys have been calculated from the variation of the activity coefficient with temperature. The addition of Sn to an unsaturated solution of O in Pb is shown to decrease significantly both the partial molar enthalpy and entropy of O. As the measurements were restricted to a narrow range between 750 and 1100°C in Pb-rich alloys, however, the pronounced variation of the partial molar enthalpy of O with temperature at constant alloy composition predicted by the quasi-chemical model could not be verified.

Dec 1, 1971

By K. El-Barawi, Hussein M. Kamal

Chlorination was performed of iron-rich chromite ore from Barramyia, United Arab Republic (UAR), together with its concentrate. The effects of change of grain size, chlorine gas flow rate, time and temperature were studied. The extent and mechanism of chlorination were followed through chemical and structural analyses of the feeds and complete chemical analysis of the chlorination products. By conducting the chlorination process for short periods at 600°C or lower temperatures, products having high Cr-Fe ratios suitable for ferrochrome production can be obtained.

Dec 1, 1971

By L. J. Barnes, R. O. Koch, J. H. Versteegh, P. J. H. Scheeren, F. J. Janssen

Following two years of laboratory research with bench scale reactors, a 9 m3 experimental process demonstration reactor was installed at Budelco's zinc refinery to treat their underlying groundwater. A 600-fold scale-up was successfully achieved. It has demonstrated that this anaerobic microbial process can remove a wide range of heavy metals and sulphate to the required levels. Extended operation of the demonstration unit has shown that the process is robust, can withstand wide variations in feed composition, rapidly recovers from operational upsets and is easy to start up and shut down. The metal sludge produced can be processed in a metal refinery to recover both metals and sulphur.

Jan 12, 1992

"Prior to the publication of the General Report of the Miners' Phthisis Prevention Committee of South Africa in 1916 little attention was paid to the dust hazard and the necessity for its suppression in the underground workings of the Broken Hill mines. Such precautions as were observed for the elimination of dust were related rather to the prevention of lead poisoning, which, in the early days of Broken Hill when large tonnages of lead carbonate ore were being won, was rather prevalent. Ventilation and hygiene followed the general practice in this and most foreign countries.This paper covers incidence and action since 1918, considering medical aspects and operating aspects. "

Jan 1, 1947

By G Fakes

This paper describes the history of civil engineering tunnelling and developments in soft ground techniques during the 19th and 20th centuries, culminating in the design and use of high speed tunnelling machines for all types of ground conditions. Some of the problems encountered are outlined, and descriptions are given of some contemporary developments in rock tunnelling techniques, with comparisons of methods used in the mining industry.

Jan 5, 1996

By A. G. Waters, N. J. Bristow

A comparative study was made of an untreated and a heated haematite ore and a sinter produced from a feed consisting of 100% ore, to study the influence on reduction behaviour of sinter bonding phases such as SFCA (silico-ferrite of calcium and alumina). Under low-temperature reduction conditions the order of increasing reducibility followed that of increasing porosity and surface area but under similar conditions at 900 degrees C the sinter exhibited higher reducibility than the ores even though the total porosity and chemical reducibility of the individual phases were lower. This behaviour can be explained in terms of the higher total porosity of the natural ore at low temperatures and the higher level of fine pores in the sinter at high temperatures due to the presence of SFCA, which acts to support the fine (c.0.1 micrometre) pores created by the reduction process. This leads to the conclusion that the main role of SFCA in sinter during high-temperature reduction is to maintain a high level of fine porosity. Some implications of this work for granule design and sintering practice are discussed

Apr 1, 1991

By L. Wade, R. Wang, M. A. Horton

Laboratory methods to find the mechanical properties of rock are inherently biased towards stronger strata, which best survive the sample preparation process. Geophysical techniques are not subject to such bias and may be used to predict mechanical properties rapidly and cheaply. Samples (151) were obtained from a borehole that had been comprehensively geophysically logged. The mechanical properties of the samples were established in the laboratory and correlated with the geophysical responses of the strata from which they came. The results indicate that, for homogeneous strata at least, it is possible to predict the unconfined compressive strength reasonably well from sonic travel time measurements made in the field. Predictions of static Young's modulus may also be made from this data source, but with a lesser degree of confidence. A multivariate regression equation is presented which relates down-hole sonic travel time to unconfined compressive strength, depth and the frequency of fractures in the rock mass. This equation may offer potential for the prediction of the mechanical rock properties of fractured and layered strata.

Jan 4, 1993

By R. Trueman, D. B. Tyler

Numerical modelling was used to determine the magnitude and direction of stresses around drives both adjacent to and distant from open stopes in the South Crofty tin mine. Modelling predicted that drives near the stopes are situated in a stress-relaxed zone. The peripheries of drives that are sited in solid rock away from the influence of stoping are in compression. Key-block modelling was used to determine the typical geometries of critical blocks and distinct element modelling was used to determine block stability. The conclusions derived from modelling fitted the observational data. This indicated that key-block theory is a valid tool for analysing the stability of roadways in the South Crofty mine. The support requirements for drives located next to stoped-out areas were formulated using a risk analysis approach to key-block formation. The results were compared with support guidelines derived using empirical design methods. Good agreement was obtained for the roofs of the drives but not for the sidewalls. The concept of a critical excavation width was formulated: once an excavation is larger than the critical size the length of rockbolts need not be increased as the excavtion dimensions increase. This may be the case in all rock mases.

Jan 4, 1993

By D. Mireku-Gyimah, R. S. Suglo

Ghana contains auriferous belts which cover 51 800 km2 of its small area of 239 400 km2. From 1493 to 1600 35.5% of the world gold production was from the Gold Coast (renamed Ghana in 1957). This dropped to 8.9% from 1701-1800. For the past fifteen years annual production has averaged less than 2% of the world total. By 1985 only four gold mines were operating, compared with 45 in 1934 and 11 in 1945. Since 1987 Ghana has experienced a boom in gold mining activities. By 1991, 83 new companies had acquired prospecting licences. At least five new companies have started large-scale production. About 650 licensed small-scale mining groups are in operation. The economic and technological factors that have contributed to the decline of gold production in Ghana are discussed. A summary is given of the methods used to mine and recover gold. These cover small-scale workings, dredging, open cast operations and underground mining. The advantages and disadvantages of these technologies and the future of gold mining in Ghana are considered.

Jan 4, 1993

By L Zhang

The Chinese coal industry is the largest coal producer in the world. The total production in I995 was 1.28 bnt. On the way towards introducing a market economic system, this mature industry is facing major challenges. The main problems are a large surplus of manpower, shortage of current assets and capital, low productivity, high casualties and a huge deficit. This paper discusses the present situation and the future developments in the Chinese coal industry. The current policy can be stated as ‘rapidly developing the state collieries and improving the village and private mines; integrated development to achieve an economic operating scale and encouraging a diversified economy; rapidly exploiting and developing in the North west and South west; promoting productivity and efficiency; welcoming multi-sources and types of investment; setting up coal exchange markets; and the careful control of resources and the environment'.

Jan 11, 1996

By A. Paulin, A. W. D. Hills

The work has shown that packed-bed behaviour can be predicted from the results of single-particle experiments, total reaction times being predicted somewhat more accurately than gas and solid temperatures and gas compositions. A small laboratory packed-bed reactor was built and used to study the decomposition of beds of specially prepared CaCO3 spheres, steps being taken to minimise the effects exerted by the walls of the bed on processes occurring within the bed. Gas and solid temperatures and gas compositions were measured at various points in the bed and compared with theoretical predictions based on kinetic data determined in previous single-particle experiments. The measured solid temperatures and total reaction times agreed remarkably well with the values predicted theoretically. Gas and solid temperatures measured after the reaction had finished at any point in the bed did not agree with the theory. This was because solid temperatures in the bed rose very rapidly once the reaction was completed and the walls of the bed could not be heated at a sufficient rate for their temperatures to rise as rapidly; thus some loss of heat from the bed to the walls was inevitable, and this could not be accounted for in the theory. In addition, the theory did not allow for the conduction of heat within the bed, and this resulted in some further slight discrepancy between the measured and predicted values, particularly after the reaction was completed. Gas compositions measured in the bed were rather scattered, but, even so, they agreed moderately well with the predictions of the theory.

Dec 1, 1971

By R. W. Ruddle

The advent of new methods of roasting, “flash roasting and fluidisation”, which are now under development, combined with the use of oxygen-enriched air, may markedly increase the SO2 content of roaster smokes. Skogmo suggests that the production of smokes containing as much as 50 per cent SO2 should be feasible. The use of flash smelting processes may well enable a similar increase in the SO2 content of smelter smokes to be made. In this event the recovery of sulphur would be greatly cheapened and the process might well be much more economic, even if allowance is made for the cost of generating the oxygen

Jan 1, 1953

By A. H. G. Mitchell

Gold-poor and gold-rich porphyry and epithermal gold-silver deposits of Caenozoic and Cretaceous age in the western Pacific and central and eastern Europe are confined to predominantly andesitic continental margins and island arcs. The arc volcanic rocks overlie a complex non-oceanic basement of stacked nappes, the uppermost of which is often ophiolitic. The emplacement of ophiolite triggered a reversal of tectonic polarity, subduction and arc magmatism. Andesitic volcanism and the formation of a strato-volcano were followed by the ascent of magma and porphyry copper mineralisation. Regional propylitic alteration came from convecting, predominantly meteoric fluids. Magmatic degassing caused advanced argillic alteration. This is commonly unmineralised in perched water tables, but may sometimes host high sulphidation gold or enargite gold at deeper levels within the propylitic zone. The onset of extensional stress after the andesitic volcanism allowed meteoric water to circulate to depths of 5 km or more, with consequent cooling of an ascending magma body at depth and the development of low sulphidation epithermal gold mineralisation near and immediately above the sub-volcanic basement surface. All andesitic arcs are mineralised. Regional controls on their ore potential include the level of erosion and geological features in the basement that focus the ascent of fluids. Differences between the mineralisation of the European and the western Pacific arcs may reflect the presence of older, more granitic basements in many of the European arcs.

Jan 12, 1992

By A. B. Holland-Batt

Two graphical techniques which are commonly used to assess batch separations are analysed in terms of reaction kinetics to provide a more powerful method of evaluation. An alternative and more general approach, based on the selection and application of suitable efficiency criteria, is also presented. The method proposed distinguishes between selection and collection efficiency in flotation and can be used to estimate the degree of liberation in the feed. Two examples are given: table concentration of monazite and ilmenite from a beach sand, and flotation of a pyrite-haematite ore

Dec 1, 1971

By R. Patel, J. Ephraim

The production of titanium dioxide (TiO2) from its minerals such as ilmenite is challenging, and subsequent isolation of titanium from TiO2 is even more difficult because of the metal-oxygen bond strength. Currently, titanium sponge is mainly produced via the Kroll process, which is energy intensive and generates large quantities of waste. A number of international research groups have come up with technologies for the production of titanium metal. However, none of them have been commercialised, because of engineering or economic issues. The team at Bradford have confirmed that ultra-pure titanium powders can be separated from TiO2 powder through metallothermic reduction and are working to scale up the process.

May 1, 2015

By D. L. Buchanan, ed. sci.

The issue comprises 10 contributions on PGE mineralisation, of which 9 were presented at the symposium organised by the IAGOD Commission on Ore Deposits in Mafic and Ultramafic Rocks and the BRGM-CNRS University of Orleans research group. The editor's introduction and summary of the papers is presented together with the title page, contents list and cover photograph of a harzburgite ridge, dunite boundary and chromite quarry in the Shetland ophiolite on Unst

Apr 1, 1994

By Garforth W.

The chairman announced the new government duties of the out-going President, Sir Thomas Holland, and the formation of a new standing committee on mining to advise the Advisory Council for Scientific and Industrial Research on suitable projects for grants. Some of the potential lines for investigation into the best methods of winning and presenting coal in the best commercial condition include wasteful practices in operating steam boilers, national loss due to neglecting recovery of coal by-products, and the leaving of large areas of coal for fear of spontaneous combustion or as boundary pillars and support

Dec 1, 1916