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By Kallioinen J

This paper discusses different possibilities to enhance coarse particle flotation using forth manipulation and improved flotation cell design. Experiments were carried out in laboratory, pilot and industrial scale ranging from 0.0015 to 100 m3/axle. During the work it could be shown that the conventional idea of one single flotation cell type for both fine, immediate and coarse flotation of coarse and fine particles need different impeller tip speeds and a different froth control objective for effective operation. For optimal operation for coarse feeds the tip speed must be reduced and the froth vertical velocity must be increased to compensate the respective drainage velocity and also the water film thickness must be taken care of. Turbulent eddies below the froth interface should be suppressed. The paper discusses the effects of different froth manipulation variables like froth vertical velocity and froth residence time to the recovery and selectivity. A function has been developed, between the residence time of the froth and the flotation cell's ability to produce an improved concentrate grade as a function of different operating and froth manipulation variables.

Jan 1, 1993

Gold Fields Ghana Ltd (GF Ghana) currently operates an underground mine at Tarkwa, in south--west Ghana. The mine was operated by Tarkwa Goldfields Limited, a wholly owned subsidiary of the State Gold Mining Corporation of Ghana (SGMC). The mine was making operating losses and in a poor state of repair. Tarkwa Goldfields retrenched all the staff and GF Ghana assumed management responsibility for its own account on I July 1993.

Jan 1, 1997

By Dight P. M, Dugan K. J

Design approaches for the artificial support of open pit walls have been reviewed and the main factors affecting support performance have been identified. An example of passive support in a potentially unstable pit wall has been used to demonstrate the importance of slope displacement as part of the support design process.

Jan 1, 1989

By R Farnf, M Pegden, S Hosein, T White

A number of theoretical papers have been published outlining the use of electronic detonators to limit peak particle vibrations levels, but few empirical studies have been undertaken and even fewer examples have been published of the use of such technology in the aggregates industry. This paper gives a summary of the research work carried out at two limestone quarries in the North of England, where a series of blasts were used to compare and contrast the use of electronic and non-electric detonators. The majority of blasts were carried out using the same burden, spacing and decked charge weight loadings. A methodology was established that could be used to reduce the peak particle velocities (PPVs) at two or more specific locations by using single-hole blast vibration signatures in conjunction with specific electronic detonator timing intervals. The initial study concluded that this was only possible if single-hole signature blasts were periodically recorded to establish the shape of the correct vibration envelopes as properties were approached. These wave envelopes could then be used as the basis for choosing the specific electronic detonator timing intervals to give the lowest PPV for the properties or locations concerned. This methodology was then used in the second study to access a large volume of aggregates adjacent to a working railway tunnel. The financial benefit for the company was to convert these additional tonnages of rock from being a resource to an exploitable reserve. The project involved careful blast design and the instrumentation of a number of boreholes to enable the results of blast monitoring exercises to be compared with predicted PPV results. The iterative process involved the vibration results being uploaded into æBlast LogÆ (an expert blasting database system developed by the Blasting and Environmental Research Group at the University of Leeds) and analysed to produce predictions ready for the next blast.

Jan 1, 2007

By S F. Simmons, A McOnie, J L. Mauk

Three cross sections, 200 m apart, display the distribution of indicator hydrothermal minerals across the Empire zone of the Golden Cross epithermal Au-Ag deposit, Waihi, New Zealand. These minerals are used to interpret the temperature and composition of hydrothermal fluids. The distribution of interstratified illite-montmorillonite and illite indicate that temperatures ranged from 140 to >220¦C, with temperatures above 220¦C predominating. The mineral assemblage of quartz-adularia-chlorite-illite-calcite-pyrite envelops the Empire vein system and stockwork, and reflects formation from an alkali chloride water whereas the mineral assemblage of replacement calcite-interstratified illite û montmorillonite-kaolinite forms a carapace and reflects formation from a CO2-rich steam-heated water. Alkali chloride waters appear responsible for the epithermal Au-Ag mineralisation.

Jan 1, 1995

By I Thin, I Sheppard

Resin encapsulated rock bolting practices have been adopted by Mount Isa Mines since the early-1980s. Fully encapsulated rock bolt systems meet designated requirements for long-term ground support in the mines. A variety of rock bolts, resins and installation methods have been utilised over this period in underground mining. As a parallel to this evolving application, Mount Isa Mines have tested various resin encapsulated rock bolt systems. Testing has included routine underground pull testing and the development and implementation of the push test for the entire encapsulated bolt length. The latter test enables a greater understanding and representation to be had of the overall mixing, level of encapsulation and capacity of the system. Rock mechanics at Mount Isa Mines undertake evaluation of new bolt systems that become available, in addition to the maintenance of compliance with quality control measures for the existing systems. Improved methods of installation and systems are also investigated to further the cost-effective nature and minimise risks associated with resin rock bolt practices.

Jan 1, 2002

By Dickin FJ

Advances in the development and application of in situ imaging of mineral processing operations using electrical tomography techniques are reviewed and illustrated with case studies relating to pneumatic conveying, mixing and centrifugal separation processes. The potential for applying these methods to full three-dimensional visualisation of the dynamic behaviour of flow in pipelines and separators, and the resulting consequences for process-modelling strategies, are discussed.

Jan 1, 1993

Alcoa of Australia's Western Australian bauxite mining operations in the Darling Ranges, south east of Perth, present major challenges in the control of air blast. The close proximity of rural communities and the face profile make the traditional methods of air blast control difficult. An extensive blast noise monitoring programme has been established. The develop- ment of a computerised blast noise prediction model and the establishment of a radiosonde weather balloon facility have reduced blast induced complaints by a factor of ten. The meteorological factors affecting blast noise transmission are discussed and examples are given of adverse weather condit- ions for the south west region of Western Australia.

Jan 1, 1982

By Rozman L. I

This paper describes the latest open pit optimisation techniques,which now go beyond merely finding an optimal outline. The paper starts by briefly reviewing pit design techniques before optimsation. It then goes on to describe the pit optimisation procedure and the extensions to it which allow the automatic generation of nested families of pits. Next, the properties of families of nested pits are examined and the paper explains how they can be used to simulate certain mining sequences and schedules. Finally, we describe an actual study which was done using this kind of Software.

Jan 1, 1991

By Pease JD

This paper reviews the changes in operating practices made in the heavy medium plant to meet the objectives of increased silver, lead and zinc production at lower operating cost. The effects of medium quality, screen- ing efficiency, medium consumption, equipment service life and plant availability on these objectives are described.

Jan 1, 1988

By Quemard D, Troncoso J

The Gordonstone Project with a capital cost in excess of $500 million will become the largest underground coal mine in Australia. The project development decision was taken on 31 July, 1990 and at 31 May, 1991 construction was approximately 35 per cent complete. The first train of processed product coal will be railed to Gladstone during December 1992. The general theme of this paper therefore will address the planning and development processes at Gordonstone particularly the interrelatedness of technical, production, construction and environmental disciplines to ensure success during operations.

Jan 1, 1991

The nickel ores mined in New Caledonia for one century are mainly silicate ores. These ores are nickel enriched saprolites, formed by partial weathering of peridotites (predominantly harzburgites and some dunites), serpentinised to varying degrees. Saprolites constitute the lower horizon of lateritic soils, sometimes up to 100 metres thick, developed on peneplains now greatly modified by erosion. Saprolites are generally overlain by laterites, a more weathered horizon, where the main components are iron oxy-hydroxides with a low nickel grade. The structure of saprolites depends essentially on the serpentine content of peridotites and, on the other hand, serpentine minerals may have a high nickel content and, so, represent important nickel bearing minerals in silicate ores. Two types of serpentines can be found in nickel ores from New Caledonia: ò primary serpentines, formed by hydration of olivine at temperatures below 400¦C, during overthrusting of peridotites in late-Eocene (Paris, Andreieff and Coudray, 1979), are generally very abundant; ò secondary nickeliferous serpentines, associated with other sheet silicates in garnierites, are now relatively scarce but garnierites were selectively mined one century ago, because of their high nickel grade.

Jan 1, 1996

By Quast K. B

The effects of metal ion addition rates and contact time on the activation of synthetic sphalerite using copper, cadmium and silver ions were determined in order to investigate the exchange characteristics at the mineral surface. The stoichiometry of the adsorption indicated that the activation of sphalerite involved both a simple ion exchange and redox process in which the activating ion and oxygen were reduced, and the mixed-sulphide surface was oxidised to produce elemental sulphur and a metal-deficient sulphide surface. Unactivated sphalerite was shown to be relatively hydrophilic, with recoveries usually less than 20 per cent for a five-minute float. Activated sphalerite could be readily floated without the use of a conventional collector. This inherent flotability of the activated sphalerite had previously been associated with the formation of a metal-deficient sulphide layer; however, this study emphasizses the significance of the surface oxidation processes occurring.

Jan 1, 1993

By Ryan CG, Both RA, Mernagh TP, Large RR, Hunns SR, Gemmell JB

The Hellyer and Mt. Chalmers deposits are mound-style volcanic-hosted massive sulphide (VHMS) deposits in Australia. Textural, petrographic and microthermometric investigations of fluid inclusions in the Hellyer stringer system indicate that Type I, primary, liquid-vapour inclusions are 10-15 pm in size, and yield homogenisation temperatures of 170-220¦C in early 2A veins, 165-322¦C in main-stage 2B veins and 190-256¦C in late-stage 2C veins. These data suggest a waxing and waning thermal history. However, the average salinity remained between 8-11 NaCl equiv. wt % in all Stage 2 veins. At Mt. Chalmers, Type I inclusions up to 20 ¦m are found in quartz from the mineralised zone, and these inclusions yielded homogenisation temperatures of 160-268¦C and salinities of 5-8 NaCl equiv. wt %. Laser Raman spectroscopic (LRS) analysis indicates the presence of CO2 (

Jan 1, 1995

By Monette J. C, Nulty J. H

High temperatures and pressures are required to obtain acceptable stripping rates. Higher chemically induced stripping rates could reduce the need for higher temperatures which lead to cyanide losses. The higher rates could lead to lower carbon inventories and higher gold production. This paper reports laboratory and continuous test unit data which strongly suggest that the preceding can be achieved. New stripping agents demonstrate efficient stripping under conditions of cyanide depletion such as after carbon acid washing. Stripping times for gold and silver can be reduced by at least half compared to caustic cyanide through the use of these novel substances.

Jan 1, 1991

By Warren L. J

In the mineral processing industry solid-liquid separation within a thickener usually requires the addition of a synthetic flocculant to enhance the settling rate of fine particles. The characteristics of the resulting flocculated suspensions may vary considerably depending upon the physical and chemical conditions which prevail during the flocculation process. For example, parameters such as flocculant type, dosage and solution concentration, surface chemical characteristics of particles and the suspension agitation conditions can influence the degree to which the particles aggregate. Aggregated suspensions exhibit various structures, and range from those composed of small, dense aggregates to those containing large, voluminous aggregates. The size distribution and structural type of the aggregates which form within the feed-well of a thickener can have a dramatic effect upon overall thickener performance. Thickener performance cannot be optimized without optimization of the aggregate structure produced in the feed by synthetic flocculant addition. This has required the development of new techniques to quantify the nature of aggregated suspensions, details of which are presented in this paper.

Jan 1, 1989

By Ma F, Yang Q, Ujihira M

The effect of stresses and acoustic emissions on the gas permeability of coal was investigated in the field and the laboratory in order to find an estimative method of the practicability of gas drainage. In the field, acoustic emissions and gas emissions during gas drainage drilling were monitored tentatively at some coal mines in Japan and China.In the laboratory, acoustic emissions from coal specimens in addition to gas permeability were measured during the triaxial compression loading in order to interpret the results monitored in the field. Besides, the opening of gas permeation channels in coal was considered on the basis of the experimental results.

Jan 1, 1991

Congratulations on your considerable enterprise in securing the opportunity to have this international conference here in Brisbane - and congratulations on your success in attracting such a distinguished audience from so many nations, with such a broad selection of papers. It is a notable achievement that in the year in which Australia is celebrating two hundred years since settlers first came fran Britain, The Australasian Institute of Mining and Metallurgy is responsible for some ten major conferences, of which at least four are specifically international, or have a very strong international involvement.

Jan 1, 1988

Samples weighing 0·5 g are fused with potassium hydrogen sulphate, leached with 4 ml. of 4 M nitric acid and diluted to 10 ml. with water. An aliquot of the clear solution is treated with EDTA, adjusted with ammonia to give a pH value between 5 and 6 treated with cyanide, ammonia, and sodium diethyldithiocarbamate then bismuth diethyldithiocarbamate is extracted with chloroform and the yellow colour is compared visually with a standard series. Alternatively, the bismuth complex may be filtered on a "Millipore" filter and subjected to x-ray fluorescence spectrometry.

Jan 1, 1971

Preparing for automated sample preparation has two facets; the need for better procedures as seen by the laboratory Manager and the approach to be adopted as envisaged by the equipment manufacturer. Both have many options and during the 1990s some at least of these options will be tried. As automation of sample preparation is only just beginning, can it be said that there is a real need for better procedures. What does automated sample preparation have to offer? Does it have real advantages or is it just a marketing tool to sell equipment?

Jan 1, 1976