Search Documents

By Z. Sawlowicz

Finely dispersed, primary sulphide mineralisation in the Cu-Fe sulphide zones of copper-bearing shale of the Polish part of the Permian Kupferschiefer is mainly present in the form of framboids and spherules. This type of mineralisation is especially well preserved in organic-rich shale, where it often dominates over a later diagenetic mineralisation that consists of large grains and veins. In microscopic observations special attention was paid to composite grains of copper and iron sulphides. The results suggest that the Cu-Fe and Cu sulphides precipitated in the Kupferschiefer sediment before pyritisation of the framboids had ceased and that they replaced metastable precursors of pyrite. The precipitation of copper sulphides could have been delayed owing to the formation of Cu-organic complexes.

Jan 4, 1992

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. T. Matthews, C. E. Loo

During sintering, porous ore particles are easily assimilated by liquid melt. Two simple models of the process are considered: the dissolution of a solid by a liquid and the penetration of a liquid into a porous solid. Laboratory sintering studies covering a range of experimental conditions were undertaken to characterise the assimilation of large particles of ore and flux by melts formed from different mixes of fines. For ores, the process appeared to be complicated by the detachment of fines from the ore surface prior to melt formation, according to the mass of adhering fines and surface roughness of the particle. This delayed the onset of assimilation and sometimes reduced it, although melt penetration was fast and effective. Studies using different temperature profiles suggested that the assimilation of haematite was controlled by the transport of Fe2O3 away from the surface of ore particles. The assimilation of limestone depended more on thermal conditions than on the three magnesia-bearing minerals considered. Changing the composition of the initial melt significantly altered the extent of assimilation of ores and limestone, but again had a less marked effect on the magnesia-bearing fluxes.

Jan 8, 1992

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 Fearnsides W. G.

Discussion at the The Midland Institute of Mining, Civil and Mechanical Engineers' general meeting held in Doncaster on 27th May 1916, on the paper published in Trans. I.Min.E., vol.LI, 1916, p.409-448, included oral contributions by Lupton A. on the mechanisms of subsidence and water egress and by Kendall P.F. on the validity and accuracy of the contour extrapolation technique and the effect of major faults, together with the author's response

Dec 1, 1916

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 J. M. Smith

This resume provides an account of the work of the Bureau and it's establishment by an Act of Parliament in August 1916. The Medical Bureau is concerned solely with the administration of the medical provisions of the Act. Its main functions are to conduct and to direct or control the medical examinations provided for in the Act. The paper covers the changes in type of silicosis, classification into the three legal stages of silicosis, cancer of the lung and tuberculosis.

Jan 1, 1947

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

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. 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 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 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. G. Skinner, J. H. Griffiths, F. T. Williams, A. G. Withers

"The absence of homogeneity, in dust-clouds underground indicates the use of a method in which the volume of air sampled is an appreciable proportion of the total volume under consideration. Of the available methods, only the impinger and gravimetric techniques seem to comply with this requirement. In practice, greater efficiency of collection of the smaller particles is possible by the use of a gravimetric filter than with the impinger. For this reason if, as seems desirable, a standard method of sampling be sought, the adoption of a gravimetric technique is to be recommended.Provided that the amount of dust collected is reasonably large, the paper filter would seem to be preferable to the solid crystal type of filter on account of its greater convenience in use.Alternative methods of sampling are desirable to cover the wide range of practical conditions."

Jan 1, 1947

By N T. Byrom

This paper is essentially in two parts. It describes how risk assessment fits into the overall framework of the activities required to control risk effectively within an occupational health and safety (OH&S) management system. It then goes on to describe the assessment of an OH&S system by the process of auditing.

Jan 7, 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 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 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 Briggs H.

Initial discussion of the paper presented at the Mining Institute of Scotland's general meeting held in Edinburgh, 12 February 1916, with D.W. Mowat, president, in the chair, included comments by Masterton J. (HM Inspector of Mines) and Sim J., and the author's reply

Dec 1, 1916

By J. R. Hammond, I. C. Herbert

Report of discussion at October, 1970, IMM general meeting (Chairman: M. J. Cahalan, President) and contributed remarks on the paper published in Transactions/Section C (Mineral Processing & Extractive Metallurgy), vol. 79, June, 1970, pp. C128-36 and introduced by I.C. Herbert. Contributors were von Struve G., on the application of balling discs and the use of basic additives; Young P.A., asking for details of the drying, grinding, balling, induration and specification testing equipment and processes; Davison J. on pellet swelling properties and Carter G.C. on disc operation, refractories and green ball properties.

Dec 1, 1971

By S. Y. Ezz

Report of discussion at February, 1971, IMM general meeting (Chairman : M. J. Cahalan, President) of a paper published in Transactions/ Section C (Mineral Processing & Extractive Metallurgy), vol. 79, September, 1970, pp. C226-C233 with contributions by Wild R. and Astier J. on fluidised bed reduction of iron ore fines

Dec 1, 1971