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By Li G, Dean-Jones G. L, She T

Highwall mining is a specialised and largely automated mining method developed in the United States for the extraction of coal left under a shallow overburden cover after cessation of economical open cut mining operations. As the name indicates, coal is extracted from the seam exposed along a highwall by a remotely controlled continuous miner operating in a single unsupported opening and brought to the surface by a string of conveyor segments. The single entries are separated by coal .pillars and driven normal to the highwall, over areas where the thickness of cover and volume of recoverable coal is insufficient to allow or justify conventional underground mining. An additional highwall mining method is augering. The success of high wall mining operations depends significantly on geological features, notably the stability of the working roof, determined by the type and mechanical properties of the immediate roof strata. Stability of the ribs, absence of floor heave, faults and dykes are further important prerequisites for profitable highwall mining. The geometric relationship between the spatial attitudes of existing joint systems, the direction (azimuth) of the single entry opening and its vertical profile determine the unimpeded depth of penetration into the coal and thus its economic success. The mechanical implications of the lithological transition zone from a coal seam to either primary or original roof strata, compared to an interface between the coal seam and overlying strata, characterised by a sharp erosional boundary between coal and a secondary immediate roof stratum, are very significant. The compatibility between the response to mining by the geological system (floor-seam-roof) and the capability of the mining equipment to prevent the development of instability are essential requirements from a mechanical viewpoint. The minimisation of vibrations, very good horizon control, an ability to vary the profile of the opening, and the maintenance of consistently high advance and retreat rates, are also important aspects of profitable highwall mining.

Jan 1, 1995

Mr Chairperson, respected leaders of the mining industry, ladies and gentlemen;   Good morning, Kiora, Nihao.   I am very honoured to give a speech to the 2005 New Zealand minerals conference. I would like to take this opportunity to express my sincere thanks to the Ministry of Economic Development to invite me to be part of this important event.   Today, I am going to talk about two themes: a brief introduction of ChinaÆs economic development, including ChinaÆs energy strategy; the good bilateral relations between China and New Zealand, its potential for further development and its relevance to our cooperation in the field of minerals and energy.   It is a well-known story that over the past 27 years, great changes have taken place in China. In 1978 when ChinaÆs reform and opening up just started, its gdp was near to only 150 billion usd dollars. By the year of 2004 it reached to 1.6 trillion usd, an average of yearly growth rate 9.4 per cent.   ChinaÆs great achievements are widely appreciated both in China and abroad. ChinaÆs development has not only improved the living standard of its own people, but also produced a huge market and brought about great opportunities for the world. Since ChinaÆs entry into WTO in 2001, China has imported near to 1.8 trillion usd dollars of goods, averaging a yearly imports of 500 billion usd dollars, creating for other countries and regions more than ten million jobs.   Our prediction is that in the next five years, ChinaÆs imports will be well over three trillion usd dollars. China will continue to serve as one of the leading growth engines for the future world economic development. Now China is on its great strive to achieve the goals of improving living standard for all the Chinese people. We are trying to reach a quadruple gdp of 2000 by the year of 2020, namely to reach gdp four trillion usd, a gdp per capita 3000 usd dollars.

Jan 1, 2005

By J Tuma

Technical measurements are an integral part of research and development of new technical devices. Now they are also an integral part of production too, especially as a part of quality control systems. More new problems started with they applications up, like storing and following preservation of big data files. Many problems are also with processing of the measurement results, especially to be up to standards of ISO 9000 normative. It includes basic data about the measurement (structured data) and measurement outputs (huge data streams). Using database systems looks as good idea, because of structured measurement data and they processing. They were developed more concepts of database measurement system support during the research project MSM 272300012. It was decided to develop specialised measurement systems, on the base of experiments and experiences with they use in operating conditions. It proved to be wrong to develop general system, because of compound operating and long response of the system. And it is not possible to use these systems for mass production systems. The problem of data storing is not as easy to be answered, because of dependence on used technical devices. During realisation the measurement system for gearbox noise measurement are data stored to the database, because used analyser system PULSE (Brnel and Kjµr Co) is open structure and can cooperate with other software systems. Anyhow the data streams are not longer (after compression) than the Memo data type, in practical use increases the data file too fast (about hundreds MB daily). Therefore we must include a special supervisory system for administration and creating data files to the system. Nevertheless the used system MS-Access supports data files up to 1 GB, for practical application is better if the file size do not exceed the capacity of CD-ROM disc.

Jan 1, 2003

In order to maintain an accurate survey underground, it is first necessary to connect all shafts used for the transferring of the survey to the levels below by a precise surface survey.This has been achieved at Mount Isa by a careful triangulation survey with stations adjacent to those shafts most suitably located for transferring the survey below.The precedure used is described herein.The Weisbach triangle commonly used is obtained by reading to swingirig wires, the theodolite being placed in line with them as nearly as is possible. The surveyor at the surface places the wires in the shaft as far apart as the size of the shaft will permit, with sufficient space between the wires and walls to ensure their swinging freely. The far wire is fixed in position, while the near one is movable by means of fine adjusting screws to facilitate its being brought into line with the fixed wire and the theodolite. When this is done the surveyor at the lower level is advised by pre-arranged signals and the survey can then commence.The surface portion of the survey is simple; all that is necessary being to read the angle from the backsight to the wires, measure their distance from the theodolite, and keep a check on them throughout the survey to make sure that no movement takes place.The lower portion of the survey is more difficult, the surveyor first qf all having to place his theodolite as nearly as possible in line with the wires.

Jan 1, 1953

In general the iron ore industry has been slow to adopt the Whittle Pit optimising software in the evaluation of iron ore deposits. The reasons for this are two-fold:the iron ore industry has developed techniques, usually bespoke software residing in the corporate offices of the respective iron ore companies, to establish their final pit limits; and the fact that the Whittle software doesnÆt easily lend itself to estimating a sales product of constant quality without maximising grade (metal content). The Whittle software is based on the work done by Lerch and Grossman (in the early 1970s), which proposed that graph theory be used to establish an optimal surface that maximises the revenue from a deposit. The maximised surface created in the pit optimiser is translated into a proposed optimal final pit shape that can be used by the mine design engineers as a target outline to lay out the final practical pit. By treating a geological and ore resources model that was created for an iron ore deposit as a subset of the recoverable resources estimation (RRE) type of geological models, the evaluation of an iron ore deposit and establishing the final pit is greatly simplified in the Whittle 4-X optimiser. Instead of trying to optimise the iron content of the deposit, the emphasis swings to maximising the extraction of a finished and saleable iron ore product. This is achieved by treating the finished saleable iron ore as an element in the multi-element Whittle optimiser. The quality of the finished sales product is represented, and the material that cannot be used in the blended product is also shown. Proposals for enhancing the functionality in the Whittle 4-X optimiser to make the evaluation of iron (and coal) deposits easier includes the creation of a new reporting function that will allow the user to specify which field(s) can be used as the divisor(s) for the reporting of the element grades in the model.

Jan 1, 2007

Delivered by K. B. Gross at the First Ordinary Meeting of the Australasian Institute of Mining and Metallurgy, August 18th, 1952.Mr. President, Ladies and Gentlemen:Confronted with the task of reviewing the progress of Mount Isa Mines Limited, since the inception of the Company 28 years ago, I soon found that effective coverage was a task beyohd me, if I were to confine the address within the limits of time allowable. Faced with the alternative, a summary, that could only fail to -do justice to the subject, I turned elsewherl? for inspiration and found it in Chester Wilmot's book "The Struggle for Europe". Those of you who have read this masterly contribution to the literature of World War II will recall that he takes us, most dramatically, behind the scenes and we learn of the thoughts and ideas that were uppermost in the minds of both allied and enemy leaders at times when decision's that profoundly influenced the course of the war were taken. I felt I could safely follow this rather novel approach to my own problem. Strengthened by the realisation that the technical achievements of the Company have largely been covered over the years, and that the results of our labours are mainly here before you, I have attempted to liven up my modest canvas by going behind the scenes, and have sought to deal with ideas and the reasons for important decisions, rather. than to embark upon a purely descriptive essay.If then, you will bear with me, we shall skip back through the years to the days of struggle that our President's address has so aptly covered, and find that one man's ideas and faith stand out beyond all others. W. H. Corbould must always be credited with having founded the enterprise, for he correctly appraised the potential of the struggling prospect and foresaw what could be done, despite the handicaps of geography, climate and need for heavy expenditure.

Jan 1, 1953

At many locations in Australia the decommissioning of mining operations will require the disposal of excess water. If the water is contaminated its disposal may be restricted by government guidelines. The timing of water disposal may be critical to the schedule of close-out. The uncertainty of the annual rainfall input to the water storage and disposal system may determine the success or failure of close-out. The uncertainty associated with any outcome can be used to determine the reliability of the system, or inversely its risk. The technique of Monte Carlo simulation, using the uncertainty in annual rainfall, is applied to quantify the risks associated with water disposal as part of the requirements for close-out in two case studies. In both case studies it is assumed that water disposal is via evaporation only. The first case study is the Nabarlek operation, located about 270 km east of Darwin. This project is required to complete the engineering work associated with its close-out by December 1995. The second study investigates the situation of close-out for the Ranger Uranium Mine, about 250 km east of Darwin. It should be noted that the Ranger mine was examined as part of the annual update of its contingency rehabilitation plan and the probability of implementing the plan is extremely small. The probability of success for the Nabarlek case varied from less than ten per cent to greater than 95 per cent depending on the management strategy. Four possible strategies were investigated for the Ranger mine with the chance of success varying between 20 and 95 per cent. The estimation of the evaporation rate and the area allocated to evaporation was critical in both cases. By applying seasonally based evaporation pan coefficients determined on site, rather than an average monthly value of 0.75, the chance of success was improved by up to 35 per cent for Ranger. Simulation modelling is able to provide information on the likely response of mine water management systems and the level of risk. This information is required to efficiently plan and manage the disposal of water for close-out.

Jan 1, 1994

By Kershaw M. G

At the Risdon plant of the Electrolytic Zinc Company of Australasia Limited, impurities toxic to the electrolytic production of zinc metal, notably arsenic and antimony, have traditionally been coprecipitated when precipitating iron as ferric hydroxide. With the development of a new lead/zinc mine at Elura, New South Wales, it was anticipated that the concentration of impurities, particularly arsenic, in the zinc sulphide concentrates treated at Risdon would increase. This suggested that an increase in the capacity of the iron purification step in the Risdon plant would be required to cope with the higher input of these impurities.Laboratory investigations showed that the additional capacity would be achieved, either by a large increase in the amount of iron used as the "collector" in the process, or by a two-stage process. The latter approach was preferred as a increase in the amount of iron precipitated would lead to much higher operating costs and overloading of the existing equipment.In the two stage procedure, acidic iron bearing solution is added to solution feeding the first stage and most of the arsenic removed from solution when iron is precipitated from solution by neutralisation with limestone. Mter separation of the precipitated solids, acidic iron bearing solution is added to the solution, and remaining arsenic removed almost completely following neutralisation by limestone.This paper describes the laboratory and pilot plant results and the plant modifications required. Abrief account is also given of the operator training and acceptance in the use of the digital control facilities installed in the new plant.The new plant is working well and good solution purity is being maintained despite a substantial increase in the concentration of impurities in the raw materials.

Jan 1, 1990

Agitation leaching data has generally not been analysed to extract the maximum amount of information that is available. Analysis of heap leaching systems has been developing over the last five years to include the underlying rate determining process. This has been found to be diffusion control for all copper leaching; irrespective of whether they are oxide or sulfide minerals. Extension of the diffusion model has enabled better scale-up protocols to be developed. Acid consumption in copper heap leaching operations has been found to be a first-order chemical controlled system. The analysis of the data is relatively straightforward. However the interpretation and scale-up is not as direct as for agitation leaching. The differences in the residence time distributions (RTDs) are required to properly account for the scale-up between test columns and field. The leaching of oxide copper in agitated systems has also been found to be diffusion controlled. However, there are significant differences in the control mechanisms. Initially the leaching control is the supply of acid to the mineral surface. This is limited by the diffusion through the surface boundary layer and is thus subject to the level of agitation. Higher agitation provides thinner boundary layers and faster diffusion rates. Similarly, higher grade material creates a thicker concentration boundary layer and relatively slower leaching. Acid consumption in agitated leach systems is also a first-order system. However, the interpretation of the RTD is easier from batch testing to continuous multiple CSTR series plant operations. Altering the method of acid delivery can significantly reduce acid consumption rates. Predilution of the acid minimises the local acid concentration near the addition point and can reduce the consumption by up to 50 per cent. Modelling of the combined leach rate(s) and acid consumption rates in agitated systems allows comparison of various leaching strategies and selection of the most appropriate. Similarly, the model allows the identification of economic limits to leach recovery; where the cost of acid consumption is greater than the value of the copper recovered. From this analysis selection of residence times for agitation leaching can be determined. The modelling tools are useful in identifying optimum conditions for the leaching process.

Jan 1, 2005

In November 1992, the Internal Revenue Commission (IRC) was formed from the rperggr of the Papua New Guinea Taxation Of- fice (PNGTO) and the Bureau of Customs, and now has the re- sponsibility for the administration of direct and indirect taxes on a national basis in Papua New Guinea (PNG). Since that date we have undertaken many initiatives to make the new organisation more efficient and responsive to clients' needs. Income Tax The mining industry is catered for, in respect of income tax, un- der a separate taxation regime within the Income Tax Act (ITA), Division 10, as well as some general provisions within that Act as may be applicable. Division 10 is itself broken up into subdi- visions to cover the different types of mining leases, namely Spe- cial Mining Leases (SMLs) and Mining Leases (MLs), and peri- ods of time during which those sub-divisions apply. Ring Fencing Income tax assessed on the mining industry, with the exception of Mining Leases (these will be explained later), has a project basis of assessment, that is, each project is assessed separately as if the taxable income of the taxpayer from operations attributable to the project was the only assessable income derived by that taxpayer. This is often referred to as "ring fencing". This is an important point to consider because losses from unsuccessful projects cannot be set off against income from those that are suc- cessful, except in very limited specific circumstances, such as where an unsuccessful exploration licence is cancelled or surren- dered. The project basis of assessment applies to both resident and non-resident companies. A relaxation in the 'ring fence' provisions was applied from 1st January 1995, where ten percent of exploration expenditure, in- curred in areas outside of Special Mining Leases and Petroleum Development Licences in a particular year of income, can be claimed as an outright deduction which is limited to ten percent of the tax otherwise payable in that year. This was introduced to encourage exploration in PNG.

Jan 1, 1997

By J Rostami, D Tadic

While hard rock tunnel boring machines (TBMs) have an established track record in the tunnelling industry, accurate estimation of TBM performance for each specific project remains critical. Machine performance prediction is required to assist planning activities, including costing and schedule preparation, machine specification and effective planning of maintenance and repairs. In addition, monitoring machine performance during the construction period is required to assess and manage excavation progress, and to achieve optimal advance rates based on specific geotechnical conditions exposed during excavation. TBM performance analysis can also contribute to the development of more accurate performance prediction models for future applications. Rock mass characteristics play a dominant role in machine performance. This paper offers a review of the impact of rock mass characteristics on TBM penetration rates for two specific tunnelling projects. A discussion is provided on the results of statistical analysis of available field data, including geological back mapping, rock properties and measured rates of penetration (ROP). The analysis offers a comparison of the achieved and predicted ROPs to provide a better understanding of the influence of rock mass properties on the performance of hard rock TBMs. A new rock mass adjustment factor is introduced to enhance the accuracy of an existing prognosis model for use in jointed rock masses.

Jan 1, 2008

By D A. Shushkov

Analcime-bearing rocks are one of the varieties of raw zeolite material, although the characteristics of analcime are not as good as other kinds of zeolites such as clinoptilolite or mordenite. However, some fields of application of analcime-bearing rock have been found, eg a method of water purification has been developed and patented. Analcime-bearing rocks are rather widespread in the Timan region of the Komi Republic of the Russian Federation. They are represented by Upper Permian siltstones and mudstones. The analcime-bearing rocks have the following mineral composition (per cent): clay minerals (50 - 70 per cent), quartz (ten to 30 per cent), analcime (one to 30 per cent), feldspars (two to ten per cent), carbonates (two to five per cent) and pyroclastic material. Analcime aggregates encrust cavities and infill microfissures in rock. Both microcrystalline (crystals <0.01 mm in size) and medium-crystalline (~0.5 mm) aggregates are observed. The mechanical, gravitational, magnetic, sorption and ion-exchange properties of analcime-bearing rocks have been studied. They are characterised by a high index of grindability and a low index of abradability and crush resistance, low values of the benzol-based pore volume and toluene-based specific surface area, and a medium porosity value. The magnesium based ion-exchange capacity (IEC) ranges from 28.7 to 196 mg+equiv/100 g. Analcime-bearing rocks of the Timan region are characterised by low beneficiation potential. Preliminary ultrasonic treatment of the analcime- bearing rocks is efficient for the destruction of intergrowths along their boundaries and production of free analcime aggregates. The proposed beneficiation procedure yields 95 per cent analcime concentrate. In the Komi Republic, analcime-bearing rocks are utilised in agriculture. They are also used for domestic needs (eg as biotoilets for domestic animals) and the solution of ecological problems (regeneration of soil polluted by oil). We have completed experiments on the purification of potable and industrial water using analcime-bearing rock subjected to thermal treatment. The experiments demonstrated that it was possible to decrease water colouration by 20 per cent, turbidity by 79 per cent, permanganate oxidation by 30 per cent and total iron content by 70 per cent.

Jan 1, 2008

By I Ametov, G Levay

It is now common practice to use substantial amounts of recycled water in mineral processing plants to minimise both environmental discharge and withdrawal of fresh water from often limited water resources. Recycled water additions to process water are frequently obtained from sources such as tailings dams, tailings thickeners and concentrate dewatering. It has been suggested for some time that addition of recycled water to process water will impact the quality of the process water and that changes in water quality may influence flotation performance. To date, investigations of process water quality changes as a result of water recycling have been limited and as a consequence there are very few data available to substantiate these ideas. Thus the impact of recycling on process water quality remains largely unquantified. Over recent years we have conducted water quality studies at a number of mineral flotation plants with varying degrees of water recycle. This paper describes the results of these investigations, including data which suggest that build up of salinity due to recycling while it occurs, is reduced by fresh water make-up. The fate of flotation reagents such as collectors, promoters, frothers and flocculants during process water recycling has also been investigated. Results show that process water concentrations of these reagents vary from plant to plant, but that, with the exception of frothers, most reagents are generally removed from the system through mineral adsorption. In general, the results of these investigations suggest that recycling process water will not result in continuous increase in solute concentrations as appears to be the commonly held view.The effects of changing water quality on flotation can vary. In many cases, flotation conditions can be optimised to suit the water quality, while in others, treatment of the water may be necessary to obtain acceptable plant performance.

Jan 1, 2009

In the 1890s, The Goldfields Water Supply Department in Western Australia commissioned the diamond drilling of two deep artesian exploratory water bores near Coolgardie (Blatchford, 1899). At the time, in spite of strongly-worded advice to the contrary from the Government geologists, there was a wide popular belief that you could obtain artesian groundwater virtually anywhere providing you drilled deep enough. The first Coolgardie hole was drilled to over 900 m, despite the fact that the bore penetrated granite from a depth of 5 m below the surface. Drilling proceeded for more than 16 months, between July 1896 and November 1897. A small quantity of salt water was struck at a depth of 36 m. The second bore was mercifully terminated at a depth of 50 m, also in granite, with again only a small inflow of salt water. Such were the desperate lengths that were pursued to obtain a reliable water supply for the influx of people in the Eastern Goldfields gold rush. The WA Goldfields continued to rely on huge condensers for water supply until that great engineering feat, the construction of a water pipeline from Mundaring Weir to Coolgardie, was completed in 1903. An enormous network of rail tracks penetrated outwards from Kalgoorlie and Coolgardie for the collection of timber, principally to feed the condensers. Remnants of the rail network are still visible today. The acute shortage of fresh water led to great deprivation, disease and death among the early miners. Today, the water problems faced by the mining industry are thankfully not as severe, but they are nevertheless no less challenging. The southern part of the WA Goldfields is a notoriously difficult area for finding potable quality groundwater. Even as recently as the 1990s, there were occasional serious efforts to find potable groundwater in that area, some very imaginative and innovative. One mining company, working south of Southern Cross, spent many months experimenting with recovery of potable quality water from a shallow freshwater lens overlying hypersaline water in a low permeability weathered granite aquifer. They used very low capacity pumps manufactured from car windscreen washer pumps powered by solar panels.

Jan 1, 2000

By D Mather

The Resources Boom of the 1960s in Australia provided a strong foundation for AustraliaÆs economic prosperity for the remainder of the twentieth century. In combination with sound economic management, our world-class minerals and energy sector has played a key role in the nationÆs competitiveness, and it has been the major source of our exports since the early 1970s. Even with the emergence since 1990 of major mineral provinces in Latin America and elsewhere, Australia has increased its percentage of world production of several minerals. Between 1990 and 2002, our share of iron ore production rose from 13 per cent to 20 per cent, nickel mine production from eight per cent to 17 per cent, copper mine production from four per cent to seven per cent and zinc mine production from 13 per cent to 17 per cent. Whether this situation will continue during the coming decades motivates the discussion of this reflective paper. The approach is to consider fundamental supply-side and demand-side issues in arriving at a view about the state of the world, the world minerals sector and the Australian resources sector in the coming decades. The argument draws from the experiences of other mature mineral producing countries such as Canada and the United States. In such nations, efficient producers have often sustained competitiveness for extended periods, despite falling grades and other challenging operating conditions. Yet several forces are changing the economic geography of the minerals industry in significant ways. These include the re-emergence of major global mining corporations, the revision of mineral policy in over 100 nations since 1985, the mobility of technology and more efficient transport both for mineral productions and mining professionals. Given these trends the paper argues that the Australian mining industry must continue to change and evolve significantly in the foreseeable future. Its leaders will need to be even more internationally focused if it is to maintain its strong competitive position.

Jan 1, 2006

By D A. Williams

The conventional method of transporting mine tailings from a process plant to a tailings storage facility (TSF) is in the form of a low to medium density1 slurry, which can be pumped using centrifugal pumps. Over the past several decades, therefore, mine operators have generally adopted this default approach. There are, however, some convincing arguments why consideration should be given to thickening the tailings slurry to a higher density paste consistency. In particular, the minimisation of environmental impacts, the reduction in water consumption and the cost savings relating to TSF closure make paste an attractive option for the life of mine tailings disposal. There are several environmental impacts that are associated with a conventional slurry TSF, such as land sterilisation, aesthetics, dust, seepage and acid mine drainage. Some of these impacts, such as dusting, may be difficult to mitigate while the TSF is in operation. Others can be influenced by adjustments made to the tailings slurry density at the plant. Unplanned fluctuations in slurry density and/or viscosity can have a significant influence on TSF performance and can exacerbate the environmental impacts relating to the facility. Relatively minor changes in the solids content of the slurry can affect tailings beaching behaviour, degree of segregation, position of the phreatic surface, amount of freeboard, consolidation behaviour, placed (settled) density (and hence TSF capacity) and in situ strength of the tailings. Paste is a non segregating slurry and many of these effects can be minimised at the TSF when the tailings slurry is thickened to a paste. These improvements are manifested by reduced seepage, flexibility in selecting an appropriate final landform, ability to rehabilitate progressively and reductions in plant water usage. It is possible to minimise environmental impacts of a TSF through the use of tailings paste. Ideally the paste production plant should be part of the initial design of the process plant. However, significant benefits can be gained by adding a paste production plant at some time later in the operational life of the mine to reduce environmental impacts and facilitate an environmentally acceptable TSF closure.

Jan 1, 2002

By Edmonds G. A

The power station went into operation in 1931, when the installed capacity was 12,500 kVA. with a loading of 4,000 kVA. In 1936 the loading increased to 6,750 kVA. which necessitated the addition of a third set which went into operation in 1937, the installed capacity at that date being 18,750 kvA. with a loading of 7,000 kVA. This remained fairly constant until 1945, when a gradual increase was noticed, the loading in 1952 being 10,598 kVA.With the addition of the copper plant, additional generating capacity was required and it was decided to raise the installed capacity by the addition of a fourth set to 34,375 kVA. with an expected loading, when producing copper, of 20,000 kViA.MAIN POWER PLANTThis consists of three GiE.e. alternators of 6,250 kVA. or 5,000 kW. at 0.8 P.F. rating and one G.E.C. alternator of 15,625 kVA. or 12,500 kW. at 0.8 P.F. rating, making a total generating capacity of 34,375 kVA.Each alternator is driven by Fraser and Chalmers turbines at 3,000 r.p.m.SYSTEMThe main 3 phase 3 wire 3,300 volt distribution system has the neutral point of alternators earthed through by one or two earthing resistors designed to limit earth fault current to 3,000 amp. for 20 seconds, in the case of the large machine, and to 1,100 amp. for 10 seconds, in the case of the smaller machines, or full load of either size machine at rated voltage.

Jan 1, 1953

The perception of the mining industry in the Australian community has changed considerably over the last four decades. This has been partly brought about by changing values and expectations of the Australian community as well as by global factors. The legal environment for the Australian mining industry has undergone significant changes. Among them, the High Court's Mabo decision which confirmed native title rights as part of the common law and environmental legal developments are dealt with particularly. It is suggested that the Australian legal environment is not necessarily the prime cause for Australian mining companies taking their investment off shore. This is a summary on how native title impacts on land tenements and some of the major issues that emerged since the `Mabo decision' and the Native Title Act 1993 are discussed. Environmental legal developments have resulted in liability facing directors and senior management in compliance matters .and in operating mining and other businesses because of changes in community expectations. In the next decade it is suggested there will be many drivers for more changes in the legal environment. Some of these are touched on including the changing roles of the Commonwealth and State Governments, the High Court as -law-makers and the changing relationships with indigenous people in Australia and in overseas countries. The changing legal environment for mining demands a national approach in many areas on the proposition that resource based industries are part of a national industry. The uniform law approach among the States has been taking place but this needs to further. An appropriate task force should be forward to review the entire legal structure and regulations affecting mining on a national rather than a State basis . The mining industry will need to work with expectations of a changing community which have powerful, but sometimes contradictory, interest groups.

Jan 1, 1997

By Fountain C. R

In April 1987, Mount Isa Mines Limited (MIM) commissioned an ISASMELT reactor to smelt 15t/h of copper concentrate at the Mount Isa Copper Smelter. This unit was based on the Sirosmelt lance technology and incorporated features proven in the Lead ISASMELT plant which has been operating in the MIM Lead Smelter since 1983. From April 1987 to June 1989, the copper smelting plant treated 167000 tonnes. Concentrate, coal and fluxes are fed continuously to the furnace. Oxygen enriched air is injected through a lance which is submerged in the slag bath. Matte and slag are tapped together through a single taphole into a reverberatory furnace, and from there are treated with normal reverberatory furnace production. Advantages of the process include its ability to eliminate most lead and arsenic in feed, its flexibility with respect to feed composition, sizing and moisture, and the plant's low capital cost. Acceptable refractory life has also been demonstrated. The commissioning of a 70 t/day oxygen plant has rerated the plant from 15t/h to 18t/h while allowing a reduction in fuel usage of one third. A trial using 150 t/day oxygen was carried out in May 1989, and showed that the furnace could treat 48 t/h chalcopyrite concentrate while maintaining a very low fuel requirement. The oxygen trial results have given considerable confidence for plant scale-up. Detailed project evaluation is currently underway for the replacement of the roaster and reverberatory furnaces at Mount Isa with a single 110 t/h ISASMELT reactor.

Jan 1, 1989

By T Leach, I Pringle

The Bowdens Silver Deposit is a low sulfidation epithermal silver-base metal deposit that has formed on the northern margin of a hydrothermal system within air-fall breccias, ignimbrites and crystal tuffs of rhyolitic composition. The deposit lies near the north-eastern margin of the Lachlan Fold Belt and the rhyolitic host rocks are of Early Permian age. The silver mineralisation occurs as flat-lying zones of disseminations and silicic fracture-filling within the Rylstone Volcanics and is closely associated with sulfides of iron, arsenic, lead and zinc. High-grade silver mineralisation is also found in steeply-dipping fracture zones which host banded sulfide veins. Studies of the alteration products indicate that high temperature fluids, flowing from south of the current project area, resulted in quartz (¦adularia) û illite/sericite alteration. Cool, low pH steam-heated waters on the northern and eastern margins of the prospect area resulted in siderite û smectite-illite clay û Fe-carbonate û marcasite û kaolinite alteration. Mixing of the two fluid types resulted in the deposition of iron and base metal sulfides, a decrease in both sulfur activity and pH of the mineralising fluid, and subsequent silver mineralisation.

Jan 1, 2004