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Jan 1, 1947

By I. A. Scott, T. J. Napier-Munn

Size-by-size partition curves for mineral separation in dense-medium cyclones pivot about a single characteristic point. This is defined for stable, non-segregating media by the medium density and the proportion of the medium reporting to the underflow. The pivot point departs from these values for unstable, conventional media. The phenomenon can be represented by an equation with two parameters defining pivot point coordinates and two the Ep value. On the basis of experiments in a 200 mm cyclone using ferrosilicon media, simple regression equations were developed for the separation parameters in terms of operating conditions (the coefficients were likely to be site-specific). The experiments successfully decoupled the effects of medium density and viscosity and showed that the value of Ep was independent of the former but strongly dependent on the latter. A classification model was used to predict the density of the underflow medium, a knowledge of which is required to determine the pivot parameters. The model correctly reflects the performance trends observed in dense-medium cyclone operation and has the potential to be generalised to a wide range of industrial practice.

Jan 8, 1992

By NA NA

Reports of discussion at sessions held in Keyworth, UK, on 22-23 April 1992.

Jan 12, 1992

By S. Vardy

The paper notes that the extraction of 22% of the remaining workable reserves in the north western area involves a risk of spontaneous combustion higher than is normal in Britain. Mining systems have been tailor made in order to minimize the risk of spontaneous heatings, and these systems are described. Well-proved methods of combating spontaneous combustion are referred to, as well as the limitations which now apply to them as the result of the introduction of modern mining techniques. A substantial part of the paper is devoted to the circumstances in which spontaneous combustion occurs underground in the north western area. Several actual incidents which have occurred in the last few years, along with the practical application of the lessons learned, are described. Of particular note are: a) the procedure adopted in the north western area to equalize pressure differences across stoppings using pressure chambers, and b) a retreat mining system, primarily designed to deal with high methane emission and steep gradients, which also affords some protection against spontaneous combustion.

May 23, 1905

By Gibson J.

Written discussion contributions to the paper presented at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 12th February 1916, with Mr. T.Y. Greener, President, in the chair, comprise comments by Kilpatrick W.M., Routledge W.H., Watson J. and Smith W., along with the author's reply. Also briefly noted are the demonstration of two pieces of equipment, an incline chock and a cage arrestor

Dec 1, 1916

By A. W. Fletcher

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, December, 1970, pp. C247-52, and contributed remarks. Contributions are included from: Cahalan M.J., giving figures related to leaching Cu from pyrite at Rio Tinto 1880-1910; Noakes F.D.L.; Embling P.M.K.; Bradshaw A.V.; Le Roux N.W.; Kelly D.P.; and Tuovinen O.H. Questions were raised regarding impurity removal, effects of light and ultraviolet light on the bacteria, the economics of solvent extraction and the possibilities for other organisms or other metals

Dec 1, 1971

Discussions of the papers with a written contribution on Paper No. 11 and authors' written replies. Also brief obituary of Dr. T. David Jones on p146.

Jan 1, 1947

By H. B. Bell, L. C. Smith

Measurements have been made of the activity of 'FeO' in 'Fe0'-Mn0-Ti02 melts at 1475 degrees C. The results obtained are discussed in terms of ideal mixing of titanates and in terms of a regular solution model. On the basis of the regular solution model activities of Ti02 and MnO in the Fe0-Mn0-Ti02 and Mn0-Ti02 systems have been derived. The data have been shown to be consistent with the liquidus lines in the phase systems. Examples are given of the application of the data to slag-metal equilibria, being used to derive slag-metal data between liquid iron and Fe0-Mn0-Ti02 slags

Dec 1, 1971

By Gibson J.

Further discussion at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 3rd June 1916, on the paper published in Trans. I.Min.E., vol.LI, 1916, p.72-84, included a written contribution by Parfitt I.C. and the author's written replies to this and previous discussion

Dec 1, 1916

By E R. Hassall

Discussiong the importance of minerals and mining, impacts on the environment and remediation, and the need to foster interest in science among young people.

Jan 8, 1997

By R. W. Schultz

Mineral exploration carried out in Ireland since the mid-1950s has resulted in the discovery of ore deposits that are now in production atTynagh (Pb-Zn-Cu-Ag), Silvermines (Zn-Pb) and nearby Ballynoe (barite), and Gortdrum (Cu-Ag-Hg); a major Zn-Pb deposit at Navan that is now being drilled prior to development; potentially productive deposits at Keel (Zn-Cd-Pb), Ballinalack (Zn-Pb) and Aherlow (Cu-Ag); and a number of interesting prospects, including one of spodumene. Underground exploration of a formerly extensively mined copper deposit at Allihies has outlined new, albeit currently uneconomic, reserves at depth. The copper and pyrite deposits at Avoca have in recent years been re-explored and are now again being worked. Most Irish ore deposits are in the lower half of the Lower Carboniferous succession of limestones and subordinate shales and sandstones, and this stratigraphic zone is being most intensively explored at present. Other geological units under active exploration are Ordovician sediments-volcanics belts, Caledonian granites, and parts of the Old Red Sandstone and Dalradian series. Surface prospecting is made difficult in many places by glacial and other superficial deposits, including peat and alluvium. Geochemical prospecting methods have been outstandingly successful and primarily responsible for most new discoveries. Boulder hunting and outcrop prospecting have proved effective in detailed investigations of geochemically anomalous areas. Some parts of the country have been covered by three separate airborne geophysical surveys, albeit without success so far. The induced polarisation technique, the most widely used ground geophysical method, has contributed to several discoveries. The scope of application of electromagnetic surveys is more restricted than that of induced polarisation, but the method has been effective in a few cases and has contributed to the Tynagh discovery. To date, the resistivity and self-potential methods have found little application. Magnetic surveys are not applicable directly in the search for ore deposits of the various known types, but can be helpful in outlining geological structures in some areas. The gravity method has been used successfully in a survey over the Zn—Pb deposit at Navan ; it has also proved effective in trials over a blind sulphide deposit at Tynagh that cannot be detected with geoelectrical methods. An appendix lists summary descriptions of 15 Irish deposits and occurrences

Dec 1, 1971

By E. A. C. Chamberlain

New techniques for the continuous sampling and analysis of mine air are expected to replace traditional methods used for the early detection of spontaneous combustion. It has been established that the rate of evolution of carbon monoxide is the earliest indicator of incipient spontaneous combustion. Two methods of continuous monitoring of this gas are available and are now in use in the UK collieries. The first is the UNOR infra-red gas analyser, which is flameproof and may be used underground; the second is a system of tube bundles, which permits air to be drawn from any critical point in a colliery and analysed on the surface. Each system has its advantages and disadvantages but both provide the colliery manager with far more information on the condition of his pit than could previously be obtained by spot sampling and laboratory analysis. This paper describes the two systems presently in use and assesses likely future developments.

May 23, 1905

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

"The sulphide nickel resources of Australia are concentrated in the Western Australian Shield. This shield is considered to have developed by extensive, but incomplete, Proterozoic reworking of once-continuous Archaean crust. It now constitutes relic Archaean cratons and intervening orogenic mobile belts transected by narrow, curvilinear tectono-thermal mobile belts of younger Proterozoic age. Remnants of the Archaean cratons are exposed in the Yilgarn and Pilbara Blocks. In the former an ancient (to ca 3600 m.y.) high-grade gneiss terrain (Western Gneiss Terrain) occurs along the western margin of the block and is interpreted to flank younger (ca3000-2800 m.y.) greenstone belts to the east. Ancient (to ca3500 m.y.) granitoid-greenstone terrains dominate the Pilbara Block.Proterozoic mobile belts contain only traces of nickel mineralization, except for one locality in the Halls Creek Province. The Archaean high-grade gneiss terrains contain no important mineralization, and the Pilbara granitoid-greenstone terrains contain only scattered examples of less important types of mineralization.The important deposits (e.g. Kambalda, Windarra, Agnew, Mt Keith) are all of komatiitic affinity and are best developed in the youngest greenstone belts of the eastern part of the Yilgarn Block. In particular, they are concentrated within, and adjacent to, the Norseman-Wiluna Belt, which contrasts in age, lithofacies and structural style with all other greenstone belts in the shield. It is interpreted to have been a rift zone. Within this belt the two main deposit types—the volcanic peridotite-associated and intrusive dunite-associated deposits—are concentrated into spatially separate zones. Precise controls on this heterogeneous distribution cannot be determined unequivocally from available data. One possibility is that the major volcanic peridotite-associated deposits were developed selectively in the actively subsiding axial part of the rift zone during the early extensional phase, whereas intrusive dunite-associated deposits were formed during a subsequent (less active?) stage of volcanic basin development. Distinctive sub-types (facies) of the volcanic peridotite-associated deposits form clusters that are generally within the rift zone. These may represent deposits related to discrete eruption centres, and at least part of their variation is due to relative position within extensive, topographically confined, linear flows."

Jan 1, 1984

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 L. J. Barnes, R. O. Koch, J. H. Versteegh, C. J. N. Buisman, P. J. H. Scheeren

Several water treatment options have been studied and piloted. A process based on activity of sulphate reducing bacteria combines sulphate removal and heavy metal removal in one process step. The anaerobic bacteria reduce the sulphate to sulphide and consequently metal sulphides will precipitate. The final design for the commercial scale plant is described.

Jan 12, 1992

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

Solid oxide galvanic cells, of the type: Pt,Ni-NiO | Solid electrolyte | O(metal),Cermet,Pt, were used to measure the activity coefficient of oxygen in liquid Cu at 1 100 and 1 300°C and in Pb at 1 100°C. Similar cells were used to study the activity coefficient of oxygen in the whole range of Cu + Pb alloys at 1 100°C and in Pb-rich alloys at 900 and 750°C. The results obtained are discussed in terms of proposed solution models. An equation based on the formation of 'species' of the form M(2)O in solutions of oxygen in binary alloys is shown to fit the experimental data

Dec 1, 1971

"The Archaean komatiite-associated nickel sulphide deposits at Kambalda, Western Australia, exhibit a number of stratigraphic features that are indicative of a strong volcanic control on ore localization, including (1) a restriction to specific basal cumulate metakomatiite host units, (2) confinement within distinctive synvolcanic embayments in the footwall and (3) variations in the internal structure and composition of overlying and adjacent barren metakomatiite flow's and the distribution of interflow metasediments with proximity to the ore zones.The high magnesium content of the host units (up to 45% MgO volatile-free) in comparison with that of aphyric or spinifex- textured lavas (16-32% MgO) has been considered previously to indicate either magmas/lavas rich in intratelluric olivine or selective accumulation of olivine phenocrysts. The marked linear trend of the oreshoots, basal host units, footwall embayments and the volcanic stratigraphic relationships have been used as evidence for local linear feeding fissures. Rare relict igneous olivine in some host units is, however, demonstrably not intratelluric, and there is no direct or indirect evidence of a proximal eruptive site (e.g. footwall feeders, pyroclastic breccias, ultramafic intrusives) at Kambalda such as at some other deposits of this type. Kambalda is interpreted as a distal rather than proximal volcanic environment.Emplacement of the komatiite sequence at Kambalda was probably controlled by the locations of a few specific eruptive sites relative to regional topographic gradients and influenced by the topography of the pre-existing volcanic surface. Olivine enrichment in the basal host units occurred by in-situ fractionation and cumulus crystallization of olivine during longitudinal lava flow within linear lava conduits, possibly centralized on depressions between non-overlapping footwall basalt flows. The distinctive stratigraphic relationships are attributed to localization of lava conduits along the volcanic pitchline, flanked by more slowly moving parts of the flows. There are analogies with the physical volcanology of Modern basaltic and Proterozoic komatiitic lava flows.A corollary of this model is that the lava conduits thermally eroded and assimilated sulphidic sediments, contributing additional sulphur to sulphur-saturated komatiites or possibly inducing sulphide separation in originally sulphur-undersaturated komatiites. The latter would account for the restriction of ores to linear cumulate komatiite host units (thermally active lava conduits) and the locally mutually exclusive, but stratigraphically equivalent, relationship between the ores and sulphidic metasediments at Kambalda."

Jan 1, 1984

By R. F. Bell, Schultz

The paper briefly discusses the nature of spontaneous heating in mines in the Doncaster area, in the period immediately before 1967 and steps taken to prevent and treat such outbreaks. The changes that led to the increased rates of advice of Barnsley Seam faces since 1967 are listed and the effects of these increased rates on the frequency and location of spontaneous combustion are discussed. The change in methods of control required by the increased rate of advance of the faces and the changes in location of outbreaks are described. Some typical heating situations are evaluated. The methods described include the use of air sealants, water gels for filling of voids in wastes, the balancing of pressures across heating areas by pressure chambers, booster fans, and the resiting of air separation doors, and the sealing of air-ways by flooding. The authors discuss the influence of mine layouts on the risks of spontaneous combustion and advocate that future plans should be designed to limit the number of districts at risk when heatings occur.

May 23, 1905

By G. P. . RiddIer

The ninth symposium in the series 'Prospecting in areas of glaciated terrain' was organized by the Institution of Mining and Metallurgy in association with the British Geological Survey and was held in Edinburgh from 2 to 4 September, 1991. Dicussions of sessions are presented.

Jan 4, 1992