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By G H. Luttrell

The use of secondary desliming cyclones ahead of froth flotation cells to reject ultrafine (-45 ¦m) particles has become a popular option in the United States for preparing fine coal feeds for froth flotation circuits. In light of this popularity, several experimental studies have been performed at industrial plant sites to develop a better understanding of the impacts of ultrafine desliming on froth cell performance and, ultimately, overall plant performance. These studies included an evaluation of various circuit configurations incorporating different flotation technologies (conventional machines and column cells) as well as different dewatering systems (disc filters, screen-bowl centrifuges, and thermal dryers). The data obtained from these studies indicate that deslime circuits offer several important benefits including lower product ash, reduced product moisture, better froth handling characteristics, and lower capital and operating costs. In addition, case studies conducted as part of this investigation have been used to develop generic guidelines for how deslime circuits may be successfully applied to improve the overall profitability of fine coal flotation circuits for both the metallurgical and steam coal markets.

Jan 1, 2005

By D Giles

We present plate tectonic reconstructions, showing that porphyry-type ore deposits are spatially and temporally linked to ridge subduction. A reconstruction of the Peruvian subduction system reveals an immediate metallogenic response to the arrival of the Nazca Ridge at the subduction trench, followed by southward migration of the zone of metallogenic activity due to the lateral migration of the zone of ridge subduction. A similar pattern is recognised in central Chile , where the spatio-temporal distribution of giant ore deposits coincides with the arrival of the Juan Fernandez hotspot chain at the subduction zone. We conclude that there is a spatial and temporal link between ridge subduction and ore deposit formation, with high metal fluxes concentrated in zones of ridge subduction. Thus, the recognition of tectonic patterns associated with ridge subduction can provide insights into predictive mineral discovery by enhancing our ability to predict the position of large mineral deposits in other modern and ancient orogens. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

The mIning operations of Bougainville Copper Pty. Limited are located at Panguna on the Island of Bougainville which is part of the Territory of Papua and New Guinea.C.R.A. Exploration Pty. Limited first established mineralization in the Panguna area in 1964. Exploration work since then has established ore reserves estimated to be 900,000,000 long tons of ore assaying 0·48 per cent copper and 0·36 dwt/ton gold. An economic feasibility study completed in July, 1969 enabled a decision to be made to proceed with a major mining operation. The ore will be mined by open cut methods and will be treated in a conventional concentrator with a nominal capacity of 90,000 short tons/day. The concentrate will be pnmped as a slurry through a 16 mile long pipeline to a port established on the east coast where it will be filtered and dried ready for export. Other supporting facilities for the mine include two towns, a 135 MW steam power station, and access roads.

Jan 1, 1971

A methodology for the fatigue life estimation of load haul dumpers, employed in underground platinum mines, has been developed and applied. This method entails the quantification of operating conditions by means of stress measurements. The measurements are then translated into a fatigue loading factor for a finite element model. The results of this analysis are then used to compare all the critical connections in the structure to detail categories in relevant fatigue codes, and predict a life in operating hours for the vehicle structure. The method was applied on a specific model and the results of this analysis were compared to actual failure occurrences with reasonable accuracy. It is intended that the methodology be embedded into performance specifications and purchasing contracts and that technology transfer to OEMs be achieved. Based on the experience of this project and other similar exercises it is estimated that structural life expectancies may be increased across a typical fleet of trackless mining vehicles (LHDs, drill rigs, utility vehicles, dump trucks) by at least 20 per cent.

Jan 1, 2005

By Reeve JS

Heap leaching is a low capital cost alternative to conventional processing techniques for gold recovery from areas that contain small gold particles in a porous host rock.For successful heap leaching the ores to be leached must maintain good permeability after being stacked into heaps so that the leach solutions can percolate evenly through them.The presence of clays, slimes or excessive amounts of fines can hamper the flow of leach solutions causing channelling and producing dormant or unleached areas within the heaps. This results in unreasonably long leach periods and poor extractions. In extreme cases the clays or fines completely seal ore heaps, causing leach solutions to run off the sides of t'he heaps rather than penetrate the ore.The Northern Queensland Company uses the Agglomeration Heap Leach technique (AHL) to overcome the difficulties associated with clays or fines. This technique involves cementing the fines, by using readily available binders, into a rigid, porous network that greatly enhances uniform flow of cyanide leach solutions through the ore heaps.

Jan 1, 1986

MR JOHN S Foxall wrote: Mr Clayton in his paper on the above subject (Proceedings, N.S. No. 34) made an assertion which should not be allowed to remain unchallenged. On the top of page 10 appears the following statement;- "By viewing the box at adepression angle of 45°, all the dimensions are disclosed and the box may be projected on isometric co-ordinates" and lower down on the same page:- "An isometric plan, being virtually a projection on a plane inclined at 45°, the nearer the dip approaches this figure so is the outline of the stoping more truly shown." Those statements embody an inaccuracy which would be misleading were an isometric plan to be constructed to suit a special case, ie the case of a mine whose lode dipped at 45°, or approximately 45° and it would be found that in such a plan the outline of the stoping would not be truly shown. The reason for this is that the depression angle at which an object is viewed in order to...

Jan 1, 1920

By R MacGillivray

The Golden Cross mine was an open-pit and underground gold and silver operation from December 1991 to April 1998. Closure of the mine has been based on an approach agreed among stakeholders. The initial phase was the release of a closure plan which was regarded as the blueprint for the following phases and the closure works required to implement the plan. The second phase involved lodgment of consent applications and their granting for the final water management configuration. The final phase is monitoring, confirmation that the site is performing as required by the closure plan and consents and settlement of final ownership, management and surety arrangements. Industry best practice modelling techniques have been used to finalise closure design and have been shown to be good predictors of site water management and discharge performance. Site discharges are in compliance with toxicology based water quality criteria for the protection of aquatic life and most discharges from the site, including those from the closed cyanide-tailings facility, can now be discharged without further active intervention or treatment.

Jan 1, 2002

By M I. Jeffrey, J A. Rumbal, D M. Hewitt

Ion chromatography utilising an anion exchange column and UV detection has facilitated an improved understanding of sulfide mineral leaching in cyanide solutions. By analysing for sulfide, sulfite, thiocyanate, thiosulfate and metal cyanides it is possible to show that chalcocite dissolution is a non-oxidative process in which copper cyanide and sulfide ions are formed in solution. Further, the homogeneous oxidation of the sulfide ions by dissolved oxygen is slow, but catalysed by a surface of lead sulfide or pyrite. Polysulfides may also be formed as an intermediate oxidation product and these undergo further reaction to produce thiocyanate, thiosulfate and sulfite. The leaching of copper from a pyrite concentrate sample is shown to be rapid, and accompanied by significant iron dissolution; however, the iron is not believed to be from pyrite, pyrrhotite or chalcopyrite. The rate of iron leaching and cyanide consumption is reduced by maintaining low cyanide and high oxygen concentrations. Preoxidation or the addition of lead(II) ions does not reduce the iron dissolution from this pyrite concentrate.

Jan 1, 2007

This short paper outlines the authorÆs views regarding the present ability of the resources industry to manage its mining assets. It represents a personal view û but one founded in fact-based observations of mining companies and of the mining industry in general. It contends that whilst a great deal has been learnt about the management of mines over the last 500 years since the seminal work of Agricola, observations suggest that best practice management is the exception rather than the rule across our industry. Although insights regarding the successful management of mines have become apparent, we still witness unnecessary errors in our industry that lead to the loss of shareholdersÆ funds. By highlighting some aspects of current best practice, particularly in the arena of operations improvement, it is hoped that this short paper contributes a small step along the next 500-year-long learning curve. At a time of key skill shortages in our industry as mineral producers attempt to ramp-up production to capture historically high commodity prices, achieving best practice operations management has seldom been more critical.

Jan 1, 2006

By S A. Johnson, J Cassidy, J L. Mauk

Geophysical anomalies at Puhipuhi reflect both diverse lithologies and different degrees of hydrothermal alteration. Most significant is a strong negative gravity anomaly (up to 50 g.u.), encompassing but extending beyond areas of known alteration, which is modelled as a deep zone (up to 3 km) of reduced density in the host greywacke basement. This zone, interpreted as being due to alteration (at least in part), closely correlates with the extent of overlying basalt flows. The gravity data indicate that the most intense alteration occurs below the basalts and correlates with the location of previously inferred hydrothermal upflow zones. These observations suggest that the basalt may have acted as a cap rock to a mineralising geothermal system. Aeromagnetic data identify highly variable but typically low magnetisations in the basalts which suggests that alteration may have been contemporaneous with volcanism. These geophysical data at Puhipuhi confirm the locations of centres of known alteration and suggest potential exploration targets below the basalt cap where there is no surface manifestation of alteration. Further implications of these results are discussed in Locke et al. (1999).

Jan 1, 1999

By Oliveira JF

Thiourea is an alternative reagent for cyanide in gold leaching. The recovery of gold from acidic thiourea solutions by adsorption on activated carbon is based on methods similar to those applied for the extracting of gold from cyanide solutions, but the mechanism involved in the process is not completely understood. In the present work, studies were carried out to evaluate the adsorption of gold onto activated carbon. Experimental data showed good agreement with both the Freundlich and Langmuir isotherms. The adsorption of gold from acidic thiourea solutions proved to be an endothermic process, while the adsorption from cyanide is known to be exothermic. The isosteric heat of adsorption of -11.3 kcal/mol in the early stages of the adsorption is an indication of a process involving chemisorption. The effect of temperature was studied between 15¦C and 55¦C. An activation energy of 3.5 kcal/mol was determined by the Arrhenius plot, which indicates that the controlling step in the kinetics of adsorption is the diffusion onto the porous structure of the activated carbon.

Jan 1, 1993

By Tyler MA

If the record of maj or proj ects in Australia is taken into account, it is apparent, the proper planning of an industrial relations strategy for many such projects has been ill considered by project developers. The recognition of the need to develop a plan from the initial feasibility study has been forced on those promoting new projects by the publicity given to the Australian industrial relations record. The delays in delivery caused by factors supposedly out of the project's control are often given for non-performance of contract and used as an excuse for limiting further development. Many of the problems experienced in project development can be overcome with sound industrial relations planning. The promises given in the euphoria of the early stages of a project relating to price and delivery often become a burden for the future because the complexities of the Australian Industrial Relations Systems are not understood or considered. The recognition by senior executives of their responsibilities in this area will contribute greatly to a new era of project development.

Jan 1, 1983

Bougainville Copper Limited (BCL) ships about 600,000 dry tonnes of copper concentrate per annum to Japan, Germany and Spain, with some spot sales to other countries. Concentrate sales value for 1984 was 335 million US$, representing almost half of PNG exports. Contained metal determination is based on physical and chemical measurements on representative samples. The entire procedure is subject to statistical uncertainties and possible systematic errors; losses as high as several percent of contained copper or gold are common and frequently are regarded as unavoidable. In this context, the function of the chemical laboratory is to identify and eliminate such errors and recommend correct technical procedures for possible inclusion in sales contracts. BCL's marketing management has encouraged this approach and the close buyer versus seller agreement is beneficial for all parties involved. BCL participates in the respective technical committees of the Standards Association of Australia (SAA) and the International Standards Organisation (ISO). Standard methods for sampling and analysis of copper, lead and zinc ores and concentrates are in course of preparation, some being due for publication shortly.

Jan 1, 1986

Workplace Centred Learning, (WCL), is a learning strategy which helps organisations cope with the constant change in skill requirements that is part of business today. WCL focusses on the specific needs of the workplace and provides the structure and sets the standard whereby the required competencies can be transferred between individuals. Learning is considered part of the job and ownership is achieved by involving individuals in all aspects of the learning system. Each individual in a WCL system is considered both a learner and a teacher. A significant advantage of WCL over conventional training systems is that it responds quickly to changing requirements, and once in place, becomes self-sustaining. That is, once implemented, the system provides mechanisms to detect and respond to changes in skill requirements as they arise. WCL is a competency-based system with multiple levels of validation. It provides a flexible approach to skills development that recognises both the needs of the workplace and the needs of the individual. WCL was developed in collaboration with ALCAN Aust Ltd and is currently being implemented by companies within Australia and overseas.

Jan 1, 1995

By Twemlow GL

The accounting profession in Australia and overseas has taken up the responsibility of setting standards specifically relating to the minerals and energy industries. Australia led the way with AAS7 Accounting for the Extractive Industries. This statement was issued in 1976 and amended 1977..It largely deals with accounting for preproduction expenditure and uses the term "economically recoverable reserves". It does not require disclosure of reserve quantities or values in balance sheets or as supplementary information in financial statements. The United States accounting profession in 1982 finally resolved an accounting standard in the same area as AAS7-SFAS69 Disclosures About Oil and Gas Producing Activities. It applies only to oil and gas producers, but has extensive disclosure requirements, including proved oil and gas reserve quantities. Current developments indicate that Great Britain is about to follow the US example. At this time in Australia, AAS7 or some other statement relating to the extractive industries has not been issued as an approved accounting standard by the ASRB. Standards issued by the ASRB are binding in law.

Jan 1, 1987

INCREASE OF THE OIL CONSUMPTIONIt is of the greatest interest to study the prospects open today for the petroleum industry by looking back to the past years.The' results for the past 15,years can be said. to be- satisfying; - the develop-ment of the petroleum industry has sustained a very fast tempo and the world consumption of energy has around the years 1960-1961 - reached aòpeak figure.Undoubtedly, the petroleum industry is the principal beneficiary of the growth of world, energy demand. For the caning years a slackening of the rate of expansion is'. likely to be expected; but will. not alter the general trend. This ' slackening of expansion may be explained, partly by a better use of the energy consumed and by the increased use of new types of energy, mainly natural gas.Although.the development of world energy demands follow structural and tech-nical modifications".,-At. can be foreseen, without any doubt, that the petroleum products. consumption. vri 11 be less affected than any other type of energy by this limited reduction in the rate of increase.

Jan 1, 1962

By S M. Mousavi

The issue of estimating evaporation in soils is central to the design of engineered soil caps for mine waste and landfill applications. In general, because evaporation from the soil is difficult to measure in the field, laboratory experiments and empirical methods have been used. Much of the earlier work has been conducted in soil science, although in recent years, geotechnical and geoenvironmental engineers have given great deal effort to this work. The result of this increased interest is the development of numerical models, such as UNSATH and SoilCover for estimating evaporation. In this study laboratory-measured evaporation from soil columns was compared with evaporation predicted using the computer program SoilCover, and the analytical method proposed by Gardner and Hillel. Good agreement among the results was observed. Also the sensitivity of the predicted evaporation to soil hydraulic and geotechnical properties, such as saturated hydraulic conductivity and coefficient of volume change was discussed and the practical implication of the sensitivity were highlighted. The work has application in the design and construction of soil covers over sulfide-bearing mine waste and landfills.

Jan 1, 2003

By Somasundaran P

Controlled modification of mineral/liquid interfacial properties by adsorption is critical for mineral processing operations such as flotation, filtration, dispersion and flocculation. Ionic/nonionic surfactant mixtures usually show enhanced surface activity and salt tolerance over ionic surfactants, and this is especially beneficial for flotation of salt type minerals in which case dissolved multivalent cations in high concentrations usually cause loss of anionic surfactants by precipitation. Adsorption of nonionic/anionic surfactant mixtures on kaolinite has been studied with sodium dodecylsulfate as the anionic surfactant and octaethyleneglycol mono-n-dodecylether as the nonionic surfactant. Synergistic interaction between these surfactants was found to cause adsorption of the nonionic surfactant with its hydrophilic chains protruding into the bulk, leading to substantial changes in flotability and dispersion characteristics of kaolinite. Similarly, hydrophobicity changes are observed also' for silica particles upon adsorption of nonionic ethoxylated alcohols owing to possible changes in the orientation of the adsorbed surfactant species at the interface. Also, based on the results obtained with surfactant adsorption, a hydrophobically modified polymer was used successfully to disperse graphite particles in aqueous solution.

Jan 1, 1993

The drilling and evaluation of bore cores provides the best available statistical basis for characterizing a coal prospect. Important, long-term decisions by management frequently must be based on the results. The majority of coal mined presently is used for steam raising or the production of metallurgical coke. Common bore core tests and analyses appropriate to this usage can be cate- gorized as non-destructive, chemical, physical, petrographic, caking/plastometric and propert- ies of non-coal material. The major tests within each category are described. Certain specific information from the bore cores is required by the coal geologist, mining engineer, coal preparation engineer and the user, either individually or as a group. The optimal bore core evaluation test pro- gramme is the one which satisfies the needs of all the professional disciplines with the grtatest speed and at minimal cost. The principal steps in such a programme are listed. There is an urgent need for a bold new Australian standard to provide the necessary guidelines to an industry which at present lacks uniformity in its approach to the task.

Jan 1, 1977

Computers are playing an increasing role in the management of technical data in mines. Companies are re-assessing the role of their data processing departments as users demand computer resources in non-accounting areas. Data of all kinds is now being seen as a, company resource, and the role of computing professionals is to help to manage the data flow, not merely to manage computers. The concept of distributed data bases puts the responsibility for data entry, editing and updating with the user. This challenges conservative views of centralized control of computing, suggesting, instead, centralized co-ordination. A survey of the possible applications of computers in technical areas points up the special requirements of handling raw, processed and consolidated technical data. Technical data bases have become flexible as mini- computer hardware and software have rapidly developed. Management has the ultimate responsibility for efficiently administering corporate data bases, and it must ensure suitable policies are developed for this purpose, with enough flexibility to cope with the impact of fast changing technology.

Jan 1, 1980