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In this paper the reactions which may lead to particle hydrophobicity/hydrophilicity as a function of grinding environment-are reviewed. The results of pulp chemical investigations related to a Cu-Pb-Zn ore on a pilot plant scale and laboratory tests with a Pb-Zn ore to evaluate the effect of some inhibitors on grinding/flotation are presented. The flotation recoveries of the ores treated by conventional and autogenous grinding methods show only a marginal difference and the results favour autogenous grinding. Iron originating from several sources manifests in the form of insoluble hydroxy complexes in the pulps. Such metal hydroxy complexes are hydrophilic and coat the mineral surfaces indiscriminately. On the other hand, selectivity is a problem for pulps ground by autogenous milling. Some corrosion inhibitors used in the laboratory grinding/flotation tests on a Pb-Zn ore showed maximum reduction in the wear of the grinding media ranging from 25 - 36 per cent, depending on the type and concentration of the inhibitor.

Jan 1, 1993

By Carlie JC

Many low sulphidation epizonal gold and zinc-lead vein deposits within magmatic arcs are situated on basement highs, and post-date both the main volcanic episode and porphyry copper (gold) mineralization. These features are best explained by emplacement of a flat batholith a few kilometres beneath each mineral district, as recently demonstrated by geophysical data in the Baia Mare district of Romania. The batholith provides heat for the hydrothermal system, and results in extensional faulting both through up-doming of the overlying rocks, and in some arcs through incipient collapse of the thermally weakened crust under regional extensional stress. More water-rich magmas emplaced at greater depths could explain some deep epizonal and mesothermal gold deposits situated outside magmatic arcs.

Jan 1, 1995

The Newmont Waihi Operations mill has undergone significant growth over its life. Initially designed as a single SAG mill operation, the circuit has been progressively upgraded since 1988 from a nameplate capacity of 600 000 tonnes per annum to the current rate of 1.3 million tonnes per annum. With future mining potential there is renewed interest to increase the processing rate even further. Over the next twelve months five sustaining capital projects will be undertaken and two major eco-efficiency projects will be completed. With the exception of the large grinding mills, most equipment on a gold treatment plant is replaced after 10-15 years. Waihi Gold mine has been operating for 14 years and has just recently received approval to replace equipment in five main areas; carbon elution, carbon regeneration, scats crushing, intertank screens and variable speed drives. Each project has been justified on improved process efficiencies and operating/maintenance cost savings. The two eco-efficiency projects involve a water balance model and a cyanide optimisation project, both of which are Corporate key performance indicators (KPI).

Jan 1, 2002

By Gelding P. W, van Herk H

The Cattlegrid copper orebody is a concealed thin, tabular sheet localised near an unconformity between two sub- horizontal Precambrian sandstone units. It extends over an area of 1,000 m by 500 m within a wider area of mineral- isation. The ore consists of complex sulphides and is neither massive nor disseminated. It consists mainly of irregular fillings in pore space developed between clasts in sandstone breccias, in fault zones and joints and along stratification planes. Its habit is unique amongst Australian base metal ore bodies. During the pre-development period ore was outlined by percussion holes but in studies leading to investment decisions ore reserves were manually calculated from intercepts and assay results of cores from diamond drill holes. The methods used for estimating reserves in the pre-production and production periods are described and evaluated by comparing mine production during the first five ore production years with the forecasts made.

Jan 1, 1979

By Swanson AR, Nicol SK

A study has been made into the influence of feed size distribution on the flotation response of coal. The results show that a full description of the flotation response of a coal must not only consider the inherent floatability of the coal, but also, the size distribution of the feed to flotation. The performances of a number of flotation circuits were compared using a coal which was "poorly floating" because of its size distribution. Split feed flotation, two stage reagent addition, and reflotation of classified tailings all gave better yields than that obtained by conventional single stage flotation. The optimum flotation circuit for the washing of the coal in question, was reflotation of classified tailings.

Jan 1, 1978

By McKee DJ

Many workers have observed an inverse relationship between final concentrate grade and valuable component recovery achieved by a flotation circuit, i.e. an increase in either grade or recovery may only be achieved at the expense of the other. The relationship is termed a "grade-recovery" curve and, in theory, limits the separation obtained by the circuit. However, circuit surveys in a nickel concentrator indicate that the operating "grade-recovery" curve of a circuit is not only determined by the nature of the ore and the circuit operating conditions, but also by the circuit design, particularly in terms of stage capacities. The surveys show that different capacity circuits can produce different operating curves for the same ore, and that capacity reallocation between stages has the potential to improve both grade and recovery. In particular, the relationship between circuit design and operating curve position is shown to be a function of the circulating loads generated by the circuit design, balancing the beneficial effects of recycling material against the proportion of plant capacity consumed by recycling.

Jan 1, 1986

With the proclamation of the Environmental Protection Act, 1971-80, the Environmental Protection Authority and Department of Conser- vation and Environment were established to enhance the quality of the environment. Proposed gold developments of all scales can be referred to the Authority in the form of a Notice of Intent. Environmentally significant projects might then require preparation of an Environmental Review and Management Programme. Current environmental issues include the'effects of clearing by prospectors,, mine dewatering and tailings disposal. INTRODUCTION In the past, the environmental aspects of gold industry related activities have received little attention. However, with the proclamation of the Environmental Protection Act, 1971-80, mechanisms were instituted which allowed both for referral of projects to the Environmental Protection Authority (EPA) and establishment of the Department of Conservation and Environment. As well as providing assistance to the EPA on referred projects, the Department is concerned about a number of environmental issues associated with the gold mining industry.

Jan 1, 1982

A wide range of models are available to computer process simulators that require a large number of parameters which often are physical measurements, coefficients, calibration factors and functional forms. This makes it intuitively difficult in the majority of cases, to tune the parameters in order to simulate a circuit in agreement with experimental results. Unit calibrators operating on the principle of least squares minimisation of the difference between predicted and observed plant data, are relatively successful when the parameters are unconstrained and independent of each other. In the case of constrained parameters, a set of carefully chosen transforms is presented which map the unconstrained variables being minimised into the constrained parameters required for the model. This technique has been used successfully with the Powell minimisation algorithm and it may also be applied to other unconstrained minimisation methods. Necessary model characteristics are discussed to enable these transforms to be applied to interdependent model parameters such as points of a graph. Examples of the calibration of several unit models using these transforms are presented. KEYWORDS: Calibration, optimisation, transforms, process simulation.

Jan 1, 1993

Deep lead mining by methods other thanconventional open-cut techniques has not been effectively employed in Australia in -the second half of this century. The reasons for this are essentially economic, and are related particularly to the labour intensive nature of the methods involved as well as the high consumption of support materials. These methods have been adapted in recent times to undertake bulk sampling programmes in deep leads. Although some consideration is given to surface-oriented hydraulic and solution mining applications, the prime function of this paper is to investigate the possible application of modern underground methods to deep lead exploitation. As deep leads are not currently being worked (with the exception of some minor operations on the Eastern seaboard), these applications remain essentially untested. They have, however, been conceptually developed following several years of small scale deep lead development. Current mineral economics, particularly with respect to gold, combined with the known extent of partially - or totally - unexploited mineralised leads demonstrates the necessity to investigate all possible means of ore extraction.

Jan 1, 1985

By D Millette, F Gay

Surface tailings are finely ground waste materials produced in all mines after the mineral or metal has been removed from the metallurgical process. Current methods for disposal of tailings involve constructing dams, dumping into existing waterways, and depositing as backfill underground. Each method has its drawbacks in terms of cost, level of complexity, safety and environmental concerns. Backfilling is the process whereby waste material (generally metallurgical tailings, prepared aggregates or a combination) is placed from the surface back underground into open mine workings via conveyor belts, hydraulic or pneumatic pipes or gravity. In the backfill process common difficulties are expensive placement costs, equipment wear and the ability to meet early and long-term strength requirements. Traditional tailings transportation in pipes involves the use of water as the transport medium. Foam technology involves the introduction of micro-air bubbles that replace the water as the main transport medium. This air can be removed after placement if necessary, by the addition of a defoaming agent. This could produce an under-saturated stable cake. Foam technology has the potential to revolutionise surface tailings disposal and backfilling by providing a less expensive and environmentally safe alternative to those just described.

Jan 1, 2000

By M A. Faizulin, N G. Stukalova

The present till now practice of averaging of ore by metal content at mining-dressing enterprises does not allow evaluating objectively really existing regularities of dressing process. The processing of large statistical data by specially designed methods has revealed the relationships of extracted mass of metals into concentrates when processing of ore at preparation plants. The analysis of the obtained relationships points to necessity of timely control by flows of ore with due account of different sorts of metal. For this problem solving it is offered to use specially designed methods on carrying out of calendar planning of a mining and shipment of ore at open casts, based on ranked arriving of flows of different sorts ores to preparation plant. The given methods includes economic-mathematical model forming and its implementing by worked out method. The formed model allows taking into account different technological and organisation limits, typical operation conditions of open cast and preparation plants. Using this methods of control of mining operations and designed on its basis the complex of software allows increasing volume of metals, extracting into concentrate, up to two per cent without any additional costs and saving of the existing technological schemes at preparation plant.

Jan 1, 2003

By H R. Watli, K L. Davies, J A. Johnson

Novel microbial isolates that readily oxidise iron and sulfur were recovered from samples collected from a spent chalcopyrite/pyrite test heap. Methods were developed to enrich and isolate microbes that thrive in low pH environments and utilise iron and/or sulfur as sources of energy. Screening of these isolates revealed diverse substrate utilization (sulfur, ferrous ion, chalcopyrite, pyrite, glucose) as well as growth at temperatures between 30 - 50¦C. When native isolates were employed, shake flask leaching tests of chalcopyrite concentrate resulted in higher copper yields in comparison to laboratory reference strains Acidithiobacillus ferrooxidans (DSM 583) and Sulfobacillus thermosulfidooxidans (DSM 9293). After 700 hours several native isolates had leached between 20 - 30 per cent more copper than laboratory reference strains during experiments conducted at 45¦C. This research has established a unique culture collection of mining microbes that readily adapt to Australian conditions. Exploitation of these microbes may result in improved leaching kinetics and copper recovery from Australian chalcopyrite ores as demonstrated from shake flask leaching tests. Whilst this research provides a capability for Australian mineral sulfide ores, this technology can be easily adapted to suit ores of any origin resulting in more effective and efficient microbial leaching.

Jan 1, 2004

By A Saghafi, S Day

The control of spontaneous combustion in spoil piles is an area of concern for a number of open cut coal mines. Spontaneous combustion in spoil may occur when carbonaceous waste materials are exposed to air. In large piles, the relatively high voidage within the pile may allow sufficient movement of air through the pile to sustain oxidation and heat generation. Over the past decade, ACARP and CSIRO have funded a number of projects aimed at providing a better understanding of the causes of spontaneous combustion in spoil piles and the development of control strategies. Work has focused on prevention measures but has also considered measures available to deal with well-developed fires. Field, laboratory and numerical modelling methods have been brought to bear on the issues. Individual projects have addressed: causes of spontaneous combustion including the relative reactivities of mine waste materials; the use of cover layers to prevent spontaneous combustion; the use of flyash grout to control an active fire; the emissions of air pollutants; and the emission of greenhouse gases. This paper provides a description of the work carried out to date with an emphasis on the major findings of the research and its application to open cut mines.

Jan 1, 2005

A feasibility study will fail its objective if it does not identify and then correctly assess, all the risks which could have a substantial impact on the financial viability of a project. Before this assessment can be undertaken, one needs to understand the risk profile of the entity which is making the decision about the project. Some of the commonly encountered issues when assessing project risk are related to the problem of not being able to see the wood for the trees. In any risk analysis it is important that conservatism does not strangle a viable project; that the variables are internally consistent with each other, that reality checks are carried out and that appropriate expertise is used. Sensitivity analysis forms a part of the overall project risk assessment; however, it can only test those variables which have already been identified in the financial model. The most useful tool in performing a sensitivity analysis is Monte Carlo simulation. When properly used, it provides a more real world scenario than the simple adjustment of key variables by ¦ 10 per cent one at a time. Monte Carlo can provide valuable information about the robustness of a project. Project risk and sensitivity assessment is prone to the analysis paralysis syndrome. The focus should be on quality rather than quantity.

Jan 1, 1997

It has become increasingly clear in recent years that human kind has developed the capacity to alter the environment of the Earth on a global scale. The changes are often subtle. This is particularly true in the case of stratospheric ozone. Ozone is produced primarily in the stratosphere, at altitudes in excess of 20 km, initially through the action of ultraviolet sunlight dissociating molecular oxygen. According to theory as it existed up to a few years ago, ozone is removed mainly by reaction with atomic oxygen. In the unperturbed environment, this reaction proceeds both directly, and by paths catalyzed by trace quantities of nitrogen radicals. Molina and Rowland [Nature, 249, 810, 1974] pointed out that decomposition of industrial chloroflurocarbons could in-troduce an additional source of radicals to the strato-sphere. Chlorine radicals are even more efficient than nitrogen in catalyzing recombination of oxygen atoms with ozone; models suggested that we might expect reductions in the vertical column density of ozone of as much as a few per cent over the next several decades. A reduction in ozone of x¦/a, by increasing the flux of ultraviolet sunlight reaching the surface, was predicted to result in an increase of about 2x% in the number of cases of skin cancer, with other less well defined impacts on the non-human environment for life.

Jan 1, 1990

When Australian voters elected a Labor Government in March 1983 the value of the Jabiluka uranium deposit as an asset of Pancontinental Mining Limited effectively evaporated overnight. The day before the election, Jabiluka was Pancon's principal asset, with the Company's 65% stake in the deposit having a market value of the order of $US1 billion. This value had been set by an agreement reached with a potential customer, who was prepared to pay $US150 million for 10% of Jabiluka. The months before the election had been the culmination of ten years of unremitting effort to bring what was then the world's largest reserve of high'grade uranium ore into production. These efforts had included two and a half years of negotiations with the local aborigines, as well as exhaustive environmental studies and conceptual mine planning. All domestic approvals required to develop the Jabiluka deposit had been given to Pancontinental and marketing efforts had successfully placed about 50% of the expected uranium production with overseas utilities. It appeared that Jabiluka was about to emerge as one of the world's great mining enterprises. The election of a government with an anti-uranium policy stopped Jabiluka dead in its tracks. Pancontinental's largest asset had effectively become worthless and the Company appeared to be facing a bleak future.

Jan 1, 1987

MR. E. J. HORWOOD wrote: In view of the difficulty of obtaining accurate results when using plumb lines in shafts, owing to the effect of currents of air, the writer, over M years ago, devised a method of transferring oearings from the surface to, the underground workings independently of plumb lines.An attachment was procured for the theodolite consisting of a 45° prism enabling a view of a fine line stretched across the shaft at the surface to be observed from the bottom of the shaft. The instrument was set up in such a position that.a view of the portion of the surface line could be obtained as close as possible to the shaft timbers.By candle light signals an assistant at the surface moved his line so that the portion close to the side or end of the shaft coincided with the cross wires of the theodolite. The theodolite was then swung to enable the crosswires to traverse the surface line. It was a simple matter to transfer the bearing of the surface line to points in the drive extending from the shaft. Similarly the relation of the bearing of the surface line to the shaft, with which a connection was intended, was easily obtained.The success of this method was demonstrated at Broken Hill in making connections many hundreds of feet from the shafts from which these were driven.

Jan 1, 1940

German coal mining suffers from rock temperatures up to 600C which are the same as in South Africa at 3000 - 4000 m of depth. Therefore cooling plants have increased in the last decade and today a cooling power of nearly 200 MW is installed in the total Ruhr District. Cooling a mine is a little bit different from cooling a bottle of beer in a refrigerator in the kitchen because the heat taken from the bottle of beer is delivered to the kitchen some centimetres away; in mining the cooling-problem is more difficult: here the bottle of beer corresponds to the airflow at the coal face and the kitchen to the surface, So it is necessary to transport the heat or the "coldness" a long distance. In the address by Ieuan Morris some systems for transporting heat from the coalface to the evaporator of the cooling machine and further from the condenser of the machine to a return airflow were described. The following is a short idea of the way this problem is treated in Germany.

Jan 1, 1983

By Rogers R, Kinnane T

In a typical open cast mining operation, investigation of how existing truck performance compares with the highest achievable truck performance is largely neglected. This paper addresses this issue by proposing a computerised system that will provide a systematic method for comparing existing truck operational performance to the highest performance considered achievable. Through analyses of existing versus achievable performances, various inefficiencies associated with truck operations can be identified. These inefficiencies could occur due to machine configurations, haul route design and conditions or operator skill level. Remedial action should then be taken in a timely fashion to better manage these factors and to ensure the fleet is always operating at its peak efficiency.

Jan 1, 1994

By A D. Bugarski, B R. Conard, G H. Sc

The objective, of the Diesel Emissions Evaluation Program (DEEP)-sponsored project at IncoÆs Stobie mine, was to conduct a long-term field evaluation of selected diesel particulate filter (DPF) systems, available to the underground mining industry. Nine state-of-the-art DPF systems were retrofitted to heavy-duty and light-duty vehicles and were subjected to extensive long-term in-mine evaluation. Periodic efficiency tests were conducted at various stages of the study (in 2001, 2002 and 2004) to establish in-use efficiencies and durabilities of the tested DPF systems. During efficiency tests, the vehicles/engines were operated over several steady-state operating conditions. Various instruments were used to measure particulate and gaseous emissions upstream and downstream of the filter systems. The results were used to assess the effects of the filter systems on the concentrations of diesel particulate matter (DPM), nitric oxide, nitrogen dioxide and carbon monoxide in the vehicle exhaust. Experience with the operational issues related to deployment of the filter systems on underground mining vehicles, coupled with the assessment of the filtration efficiencies, were the primary objectives of the study. The variety of filtration systems and regeneration concepts used in this study offered the opportunity to investigate the advantages and disadvantages of the various types. Some of the major issues studied were criteria for selecting the filter media, means of regeneration, the long-term operational reliability, and the occurrence of unwanted secondary emissions.

Jan 1, 2005