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Every estimate of ore reserves necessarily contains an assumption in regard to the specific gravity of the ore. This assumed figure may be based on experimental data, on textbook data, or on a reconciliation of past tonnage estimates and production figures. Not infrequently it is simply a guess - shrewd or otherwise.Errors in the density factor are not likely to be serious in gold-quartz mines-or, at least, not so serious as in base metal mines. It is to the closer determination of ore density in the latter that this paper is devoted. Moreover, the remarks apply to ores which show no appreciable pore space.Not many ore bodies are sufficiently homogeneous to allow of a truly representative factor being obtained by the simple testing of a few specimens of ore, or by the weighing, after breaking, of a carefully measured block. The empirical figure derived from a comparison of past ore reserves and actual production can never truly describe conditions other than those now past; no real link with ore as yet unmined is provided. The dilution of heavy ore by waste is not exposed by this method, but is effectively cloaked. Anyerrors in past estimations of ore reserves are transmitted, by way of the density factor, as a source of error in all future estimates.ObjectIons may be raised to the practice of weighing measured blocks of ore in the case of any but a very homogeneous ore body. Even then, the exact composition of the block weighed, and an indication of whether its moisture content is representative of the whole, are difficult to determine.

Jan 1, 1940

Landscape interpretation, geology and mining history are being successfully used to explore options for sustainable community tourism product development. Recent work by the author in Europe and Australia has indicated the value of adding and producing interpretive information about mine and quarry locations û both active and inactive. This work has allowed for the branding and development of new sustainable community tourism products based on the landscape, folklore, mine and geological heritage. Communities in rural areas are seeking new opportunities to sustain their local economies. Using a relatively new phenomenon called geotourism as a starting point, they have developed themed products connected to walking/cycling guides, interpretive panels and visitor centres. These themes can be linked to geology, archaeology, botany, local history and to industrial heritage sites such as old mines, to generate local employment. This new geotourism approach has successfully brought a new and greater audience to discover the value of geology and mining history. Communities have established a unique place for themselves within the tourism marketplace using the geotourism brand. Other communities with an established tourism product are also now using geological and mine heritage via geotourism to rebrand and meet changing global trends. The geotourism approach has allowed for positive collaboration among communities, service providers, local and government authorities to channel tourist revenues into rural communities. The pooling of resources under the banner of geotourism has led to cost-effective marketing, targeting and promotion of products using multimedia and web sites. Geotourism has emerged strongly in Europe, North America and China in the last decade. The Australian minerals industry now has an opportunity to implement this new branding concept to assist and benefit the communities in which they run their activities. Communities can also take advantage of the potential to develop a sustainable geotourism business around a past or present mineral industry in their vicinity.

Jan 1, 2009

By P Cepuritis, G Chitombo a, I Brunton

There is a significant amount of past evidence that links blasting and occurrences of slope failure. Particularly of great concern at Telfer Gold Mine is the effect of open pit blasting on the stability of the footwall slope above the underground portal and the stability of underground structures. For this reason, Newcrest Mining Ltd invited JKMRC to conduct necessary field measurements and numerical modelling with the following objectives:assess the dynamic stability of the footwall slope above the portal; assess the characteristics of current and future blasts in the open pit; and prepare open pit blasting guidelines that will minimise the detrimental effect of blasting on slope stability. To achieve these tasks it was necessary to develop a scaled distance attenuation curve for blast vibrations. In order to validate the developed vibration attenuation curves it was necessary to monitor vibrations from a production blast. Using JKMRC blast design software tools, the vibration of the production blast was also modelled from the blast design and vibration results from single hole blasts. The intention was, assuming that the observed and modelled vibrations were close in terms of frequency and amplitude, to use the software tools to model the vibrations of future blasts and assess their likely effect on slope stability. Numerical modelling of the dynamic stability of the footwall slope was done using the FLAC finite difference code and the UDEC distinct element code. The results of the numerical modelling and of the field measurements of the blast induced ground vibrations were combined into the blast design rules that relate distance between the slope and the blast, charge weight per delay and number of blasts necessary to cause failure of the slope.

Jan 1, 1999

By H Waterer, L Zheng, T Kalinowski

The Hunter Valley Coal Chain (HVCC) consists of mining companies, rail operators, rail track owners and terminal operators, together forming the worldÆs largest coal exporting facility. In 2008, the throughput of HVCC was about 92 million tonnes, or more than ten per cent of the worldÆs total trade in coal for that year. The coal export operation generates around $15 billion in annual export income for Australia. As demand has increased significantly in recent years, and is expected to increase further in the future, efficient supply chain management is crucial. The Hunter Valley Coal Chain Coordinator Limited (HVCCC) was founded to enable integrated planning and coordination of the interests of all parties, thus improving the efficiency of the system as a whole. One of the many planning challenges faced by the HVCCC is that of annual maintenance planning. Different supply chain elements, such as trains, railway track, terminal equipment and load points, must undergo regular preventive and corrective maintenance, leading to significant reductions in system capacity (up to 15 per cent). However good alignment of the maintenance tasks can reduce their impact, and the HVCCC undertakes an annual process to ensure the impact of maintenance on the supply chain capacity is as small as possible. This is achieved in an iterative negotiation process between HVCCC and individual service providers. In the past, maintenance schedule optimisation was largely manual, which for the more than 1000 tasks involved is quite labour-intensive.In this paper the authors describe an approach developed at the University of Newcastle in partnership with the HVCCC to automate this schedule optimisation process. We will discuss our experience in applying exact (mixed integer programming) and heuristic techniques from mathematics and computer science to address the problem. This work is anticipated to lead to new decision-support tools for the HVCCCÆs capacity planning team.

Sep 26, 2011

By R Dunne, D Yan

In flotation where a bulk flotation concentrate is produced or a gangue sulfide such as pyrite contaminates a concentrate, residual collector has to be removed from the sulfide surfaces to allow selective separation in a subsequent flotation step. Depending on the sulfide mineral, the main species that needs to be removed when using a xanthate collector is either a metal xanthate or dixanthogen. For the identification of surface species, specific solvents may be used to remove each species û metal xanthates are known to be soluble in acetone whilst dixanthogens are known to be soluble in non-polar solvents such as diethyl ether. Xanthates break down with time, temperature and pH into various decomposition products. The major decomposition product is dixanthogen which can aid flotation but other products such as perxanthate and carbon disulfide can have an adverse effect on flotation. Various analytical techniques can be employed to monitor the formation of decomposition products on the surface of the mineral and in solution. The best of these is ultraviolet spectroscopy as it has diagnostic peaks for decomposition product determination. In this work two approaches were taken to understand the relationship between the flotation of a chalcopyrite and pyrite from an ore containing these two minerals. One approach was to remove the xanthate species with an organic solvent and then use ultraviolet spectroscopy to determine the concentration of dissolved species. The second method involved measuring xanthate decomposition in solution by measuring the residual xanthate concentration using ultraviolet spectroscopy. These experiments confirmed the species adsorb at the surface of the mineral and how these species affect the recovery and grade of the valuable mineral. In both cases pH and temperature were varied and two xanthate collectors (SEX and PAX) were used to study these relationships. These relationships could be applied to industrial flotation systems and allow for more accurate determination of optimal xanthate dosage and hence save on reagent costs.

Jan 1, 2005

By Boehme PW, Gregory OR

The results presented here show quite definitely that in the system investigated the intensity of dispersion is enhanced by switching the flow entry from bottom to sides of the packed trough. Since there is no reason to suppose that this would not be true generally then it is not surprising that the blast furnace dispersion data of Standish and Polthier lie above the data for packed columns with bottom fluid entry. In fact, on the basis of the present results, blast furnace dispersion results can never equal standard packed column behaviour but must always be above these. The result that the intensity of dispersion in the trough model is higher closer to the side ports than away from them is at variance with that of Standish and Polthier blast furnace results. Aside from the obvious structural differences between these two systems, it is thought that the presence of raceways and the tortuous path of the gas flow in the furnace may provide an answer. Clearly this is an important difference in the behaviour of the two systems and further investigations designed to clarify the position would have significant practical value. This would also give an indication of how the furnace D/ud values may be decreased along the whole height - assuming of course that this result gives the best overall performance of the furnace. However, there is to date no knowledge whatsoever about this aspect of blast furnace Technology.

Jan 1, 1975

By M Kuruppu

The paper explores the sustainability of the Australian mining industry, and the potential for application of a substitute fuel into existing mining operations. This alternative fuel biodiesel is produced from biological oils and not from refined hydrocarbons like the transport fuel diesel (petrodiesel). The fuel is compatible with all current diesel equipment with little to no modification and has many superior properties. As biodiesel is derived from biological sources it is æcarbon neutralÆ meaning there is no net carbon addition to the atmosphere when the fuel is burned. The current fuel, petrodiesel releases long stored carbon dioxide (CO2) and is of concern to Australian government targets which seek to reduce these emissions. The mining industryÆs unique reliance on petrodiesel is of particular interest when assessing the substitution of biodiesel into underground and open cut operations. The underground benefits of biodiesel see a reduction in the noxious emissions of carbon monoxide and diesel particulate matter, both contaminants which require extensive diluting ventilation to ensure safe levels. As biodiesel is both safer to store due to its higher flash point and produces less exhaust emissions, its occupational health and safety benefits in underground mines is clear. The use of biodiesel in open cut mines benefits the environmental sustainability aspects of the project. The formulation of national targets relating to carbon dioxide emission reductions promotes any measure to reduce CO2 within the mining environment. As the diesel engine is one of the least emission efficient (kWh/tonne CO2) energy sources on-site, its potential for reduction in CO2 at minimal cost is the greatest. By substituting the fuel, significant quantities of site emissions are reduced, thereby achieving the goals of improved site sustainability and the governmentÆs targets to reduce emissions. This aspect of gauging mutually beneficial relationship regarding government interests and mining industry profitability is the underlying outcome for this paper.

Jan 1, 2009

COAL constitutes such a gigantic item in modern industry, either for direct heating, production of coke for smelting, or for the generation of power, that its quality and price play a very significant part in economic industrial progress. Australia is still a very young country industrially, and is groaning under many disabilities compared with competitors overseas, not the least of which is the quality of coal. Linked with the word "quality" should be that of "utility," for high-ash content prevents efficient utilization of the fuel.The marketing of good quality coal is a very important matter indeed, and if industry in Australia is to progress in the way that it should, this matter must receive keen attention.New South Wales, above all the other Australian States, has been blessed by nature with vast coal-fields, from which fuel is shipped to every State, and provides the base for power for most of our railroads and industries.Experts frequently refer to the fact that in some districts only partial extraction of thick seam coal is being made, without a care or thought for the future. Ranking next in importance to this is the fact that much of the coal is being carelessly marketed.Very few collieries in Australia are equipped with coal-washing plants for dealing more particularly with small coal grading which most industries require, and to which coal producers as a whole pay the least attention. In England each year nearly20,000,000 tons of coal is being water-washed before sale, and is marketed as a fuel of far greater utility once it has been freed from extraneous ash.Investigation proves that a great many pits in New South Wales are marketing coal (more particularly small coal) containing a considerable quantity of extraneous ash, due to the admixture...

Jan 1, 1926

The GDR has extensive lignite deposits at its disposal, which formed the basis for the development of an independent energy source after 1945 and which will retain their significance well beyond the year 2000 (see fig. 1). In 1946 lignite output was about 110 x 106 t. In 1985 312x 106 t was produced and in 1988 the planned output will be ca. 315 x 106 t. Thus, the domestic produc- tion of lignite covers ca. 75% of the GDR's primary energy requirements. More than 80% of the electrical energy is gener- ated by the use of lignite and about 12% by nuclear energy. In addition to this, about 18 x 106 t/a mineral oil and about 6 x 109, m3/a natural gas are imported, predominantly from the Soviet Union. The lignite deposits of the GDR are of Tertiary origin and are recovered exclusively by opencast mining. There are two large regions (fig. 2): - in the region east of the river Elbe (Cottbus/Senftenberg- "Niederlausitz") and - in the region west of the river Elbe (Halle/Leip- zig/Magdeburg). These deposits differ in geological age and conditions of depo- sition, consequently there are differences in their chemical and physical composition and, thus, in their uses. The younger Mio- cene coals of the main region in the East of the river Elbe belong to the epirogenetic type and have a low content of ash and sul- phur. Among other things, they are suitable for the production of brown coal high-temperature coke (Lauchhammer and Schwarze Pumpe). The older Oligocene coals of the Halle/Leip- zig region are bitumenous in certain areas. Therefore, they form the basis for production in low-temperature carbonizing and chemical plants. In the Halle-Magdeburg region, where the lig- nite is in contact with the underlying Zechstein subdivision, so- called "salt coals" are found.

Jan 1, 1989

Having worked as a consultant for most of his 40-year working life, mostly as a mineral property valuer, the author has seen many poor valuations. Most were valuations of exploration tenements where the selection of the rather subjective, but necessary, geological inputs raised the main concerns. Those valuations involving iron ore prospects raise particular problems due to the special characteristics of such deposits. Iron ore is more like an industrial mineral rather than precious or base metals and Reserves are determined not by a traditional cut-off grade but by customer specifications. This is intended to be an overview/keynote paper on the current state of the growing (yet consolidating) Australian Iron Ore industry. It has now moved beyond Western AustraliaÆs æPilbara Big TwoÆ of Rio/BHPB (with the emergence of the irrepressible FMG and Hancock Prospecting) to include the YilgarnÆs æMidwest ManyÆ (including US re-entrant Cleveland Cliffs through Portman) and projects in other States. Ore types have moved from haematite Brockman to martite-goethite Marra Mamba (including the RobeÆs mesas and below water table Yandicoogina CIDs) and magnetite ore types. There are DSOs and secondary process feed. Mineral valuers have to reflect today upon these and many other determinants of value when choosing the most appropriate methodologies to adopt when technically assessing and valuing exploration tenements containing iron ore. Set against a frame work of the JORC Code (2004) and VALMIN Code (2005), the general valuation issues involved in using the cost methods (eg multiple of exploration expenditure), market methods (eg comparable sales, rules-of-thumb and joint venture terms) and income methods (eg synthetic discounted cash flow (DCF)/net present value (NPV) modelling) are discussed. Relevant factors when valuing iron ore properties are discussed, eg ore type, lump/fines ratio, stripping ratio, water table, impurities and grade, particularly the JORC confidence category of the identified mineralisation. Remoteness and access to existing rail infrastructure is a key consideration.

Jan 1, 2007

Bauxitic laterite of variable thickness and grade is best developed in the Darling Range but covers a large part of the southwest corner of Western Australia. Its limits are defined by the rainfall isohyets to which jarrah forest is confined. Within this broad belt there is an increase in arable land southwards concomitant with a thinning of the laterite layer.Bauxite quality and perhaps thickness as well are dependent on the type of source rock, and are influenced by topography. Economic deposits occur over a vertical range in altitude of about 1200 ft. Some bauxite orebodies appear shoot-like in character, and analogy is suggested with the ore shoots of syngenetic metalliferous deposits.The alumina is in the form of gibbsite enabling low temperature digestion in treatment.INTRODUCTIONAlthough the existence of bauxite in Australia has been known for many years it is only recently that exploitation has commenced of the two most important deposits, strangely at almost diagonally opposite tips of the continent (Fig. 1).Recognition of the importance of the bauxite in the southwest corner came about initially through the efforts of Western Aluminium N.L. which, with some outside financial help, tackled the early exploration with commendable foresight and courage. Subsequent investigations around the periphery of the original reserves (now held by Alcoa of Australia) were undertaken by several companies, including Bauxite Exploration Pty. Ltd.ORIGIN OF BAUXITEThe genesis of bauxite is stilI somewhat controversial.Owing to its common association with kaolin some investigators have been led to believe that it has been derived from the latter; others believe the process has been vice versa.From a recent study of the Arkansas bauxite region in the...

Jan 1, 1964

By Mann LD

The Haveluck gold deposit, located 2.5km north of Meekatharra, contained 1,284,000 tonnes at an average grade of 1.8 g/t gold of drill delineated proved and probable ore prior to commencement of production. Following successful laboratory and pilot scale testing a decision was made to establish a 300,000 tonnes per year heap leaching operation. The ore, crushed to minus 100mm was stacked on an impermeable membrane and irrigated with a dilute cyanide solution. Gold was recovered from the resulting pregnant solutions by adsorption onto activated carbon and gold bullion produced in a modified Zadra process desorption plant. From the commencement of mining it was obvious that a high percentage of fine material was being produced which would adversely affect the percolation of the cyanide solution-through the leach heaps. A screening plant was incorporated into the crushing circuit which provided an oversize product satisfactory for heap leaching and an undersize for carbon-in-pulp treatment. Plant design provided for the slurrying of minus 0.8mm ore before feeding to the pachuca tanks. Initial practice was to use four tanks for gold dissolution and two for carbon contact. Vibrating screens were used through- out for the carbon-ore separation and the loaded carbon was stripped in the existing desorption plant.

Jan 1, 1982

By E Ahern

In exchange for issuing minerals rights from the Crown Mineral Estate to explorers and miners, the Crown expects a æfair returnÆ on this investment, ultimately for the benefit of all New Zealanders. In the case of mining permits, this return is in the form of a tangible asset û royalties from mining activities. But for exploration activity, the return sought by the Crown is an intangible asset û information. The information obtained serves three purposes û in helping Crown Minerals to set work programme conditions during permit allocation, for monitoring the performance of permit holders in accordance with permit conditions, and for archiving and making available for future interested explorers and other parties. Difficulties can arise during the allocation and monitoring process when either party has more information than the other that is not shared. To date not enough emphasis has been placed on the intrinsic value and content of the information generated by explorers and the importance this information can have in the exploration process leading to new mineral discoveries. For attracting exploration investment, the quality and availability of such information, combined with other geoscientific data, is a fundamental determinant for potential explorers when choosing to explore in a global market, and strongly defines the mineral prospectivity for a country. This is something the Australian States and other jurisdictions seeking mineral investment learnt long ago, and who now provide substantial amounts of cheaply or freely available packaged geoscientific datasets, increasingly over the Internet. To have a vibrant mineral exploration industry so that the benefits from the mineral estate can be realised for all New Zealanders, a shift in emphasis to the value of its mineral information base itself is required. Such an approach is befitting of a true Knowledge Economy, and would enable the Crown to make better-informed decisions regarding utilisation of its natural resources.

Jan 1, 2002

By P Lamberg, M Lyyr, S Heimala, J Liipo

Since the introduction of froth flotation for industrial practice, the process has long been developed and improved by making cultivated guesses or by using trial and error methods to a varying degree. Fresh possibilities have emerged after development of new surface sensitive analysing methods and in situ electrochemical methods. Having had the possibility to combine different findings between science and everyday plant practice, Outokumpu has been able to develop a catch-all procedure to manage a flotation process taking into account the specific requirements set by different minerals in a slurry. A number of these procedures are available and offered globally to clients as part of a Plant Audit service. The Outokumpu Plant Process Audit (Process ef-X) concept comprises of mineralogical determinations from process samples and plant data analysis together with electrochemical process measurements using mineral electrodes. Automatic control loop analysis can also be included. The objective is to combine the results for a basis of flotation process improvement. Since this methodology has earlier been an in-house practice, it follows that the results are also reflected in the development and design of the OutokumpuÆs processing equipment. An increasing number of ores have a very intimate fine-grained texture and it may be physically impossible to combine high grade with acceptable recovery by a flotation process alone. For such cases, combinations of different hydrometallurgical û mineral separation û pyrometallurgical processes are available. Mineral specific information and chemical expertise of flotation technology can be utilised in development of other processes, as well.

Jan 1, 2005

By P D. Munro

The spatial distribution of ore with similar processing properties or domains within an orebody may be identified early in the assessment of an orebody to provide a sound basis for later development of the orebody. The assignment of domains in the primary sulfide portion of an orebody is often more difficult than recognition of the oxidised, supergene and related domains usually located towards the top of the mineralised volume. This paper will discuss some approaches to assigning domains within the primary sulfide portion of an orebody. The processing properties of each mining block will be known if the contained domain(s) and their proportions are known. The use of both physical and chemical ore properties to assign the domains is discussed. The domains based on similar processing properties do not necessarily coincide with geological zones assigned by geoscientists. As part of assessing the physical properties of ore, the modal analysis of the ore with respect to the valuable sulfide minerals and the sulfide and non sulfide gangue minerals has to be known, along with the traditionally used elemental assays for valuable and penalty elements. Two scales for determining other physical ore properties will be considered: the mesoscopic scale (examined by human eye) and the microscopic scale (examined via a microscope under high magnification). The strengths and weaknesses of the data obtained at the two scales are discussed in the paper. Broadly, data collected at the mesoscopic scale are much less expensive but the types of data available are more limited. Methods for evaluation of chemical ore properties are also discussed. After establishing a basis for establishing the spatial distribution of domains, variability testing is required to verify the integrity of the designated domains. In contrast, each block of ore in some orebodies has been assessed principally via the results of a laboratory separation on a number of drill core samples or composites from throughout the block, with minimal or no attention to the concept of domains.

Jan 1, 2008

Australian wheat belt agriculture is causing a decline of its natural resource base. The major problem, salinity, arises from a small reduction in water consumption by agricultural crops compared to what prevailed under the prior native vegetation. This causes groundwater accumulation which, in the low relief landscapes of the wheat belt, is leading to extensive surface saturation in low landscape positions and dramatic, destructive change in the hydrological behaviour and habitat of streams and rivers. The ability of agriculture to invest in salinity control is severely limited by its long-term decline in its terms of trade. Extensive planting of perennial vegetation has the potential to increase water use and arrest the salinisation process. If these perennials were also commercially attractive, the cost of salinity treatment could be minimised. Given the difficult commercial position of food commodities, it is logical to develop ænon-foodÆ perennial crops, in particular woody crops suitable for industrial products. This paper looks at the example of Sweden, where there has been a generation of investment in developing forest harvest residue recovery, and short cycle woody crops for bioenergy, but with only limited success. In contrast, secondary residues (processing wastes) from forestry industry are readily saleable for low value uses like bioenergy. This suggests that the model woody crop must have a higher value fraction to facilitate delivery and commercial use of its lower value fractions. This model is being emulated in the development of native mallee eucalypts as short cycle woody crops in Western Australia. Some $50 million has been expended on mallee development in the past decade and this has culminated in an engineering demonstration of integrated processing. The putative high value products are activated carbon and eucalyptus oil and the residue (plus waste heat) will be converted to electricity. The potential scale on which crops of this type would be required to achieve salinity control means that many more high value and residue products will have to be developed. Metallurgical charcoal appears to be a promising product option.

Jan 1, 2006

By M Reisi, H Waterer, M Savelsbergh, F Engineer

The Hunter Valley Coal Chain Coordinator (HVCCC) Limited is the primary planning organisation responsible for the export of coal through the Port of Newcastle, Australia. HVCCC stakeholders include producers (mining companies), rail track owners, above rail operators, and terminal operators. The HVCCC is tasked with coordinating the activities of all the corresponding parts of the coal export supply chain so as to maximise the system efficiency. The HVCCC also has a forward looking planning role: with demand for coal expected to double in the next decade, strategic capacity planning is a core activity for the HVCCC. Optimisation and simulation models are key aids in such activity. They are used to suggest and evaluate infrastructure expansions and operating policy changes. These models require input data in the form of shipping stems, which are arrival streams of ships at the port, together with their cargo types and composition, and date and time of arrival.Although everyone is familiar with the expression ægarbage in equals garbage outÆ, relatively little research is dedicated to the issues surrounding input data generation. In this research we seek to redress this, and have developed a method for generating high quality shipping data. Shipping stems used as input should be realistic, reflecting key characteristics of historical patterns. They should accurately represent future demand scenarios. Yet they should also have controllable parameters that can be used to test what-if scenarios, such as are required by the HVCCC to answer questions about future infrastructure or operational plans.Here we review our process for achieving this, and give a case study analysing the effects of different shipping stems on the performance of the coal chain, as measured by a capacity assessment tool. The latter is an optimisation model that takes shipping stem and infrastructure data as input, and calculates key supply chain performance metrics. The potential benefits of alternative demand management strategies are analysed by measuring the performance of the coal chain given different shipping stems obtained via the stem generatorÆs controllable parameters.

Sep 26, 2011

The first 12 m diameter rakeless thickener in the Australian gold mining industry was installed to treat plant tailings at the St Ives gold plant in April 2000. The plant processes approximately 3.2 M tonnes of ore producing about 430 000 oz of gold per annum using conventional crushing, grinding, gravity and carbon in pulp processing methods.The main benefit sought from the thickener was to improve water recovery in the plant and provide water for a 55 000 oz per annum heap leach operation. The thickener design indicated that more than 128 m3/h of overflow water could be returned directly into the plantÆs water circuit, relieving the demand on the borefields. The resultant surplus in the water circuit would then be available for the heap leach project. Based on laboratory and pilot plant scale tests conducted by EIMCO the thickener was designed to handle up to 700 m3/h of tailings slurry (450 tph of solids) with a 40 per cent oxide component in the ore blend. The normal plant throughput is 565 m3/h of slurry (400 tph of solids). Gold mineralisation in most areas at St Ives comprises quartz-sulphide vein and breccia lodes with common albite-biotite-chlorite alteration assemblages. There are well developed supergene gold horizons in the clay-oxide profile above most of the deposits (Osborne, 2002). This results in a wide variety of ore types being treated. At times 40 - 50 per cent of the ore may be oxide in nature. After some commissioning difficulties associated with instrumentation, the thickener has performed satisfactorily although it has not reached its design capacity. The maximum density achieved under normal operating conditions with 20 per cent oxide ore is about two per cent below the design. The thickenerÆs performance deteriorates further with increasing amounts of oxide ore in the blend. The thickener has provided sufficient water for the successful operation of the heap leach and has also provided some down stream benefits for the gold plant by way of pH and cyanide conditioned thickener overflow water.

Jan 1, 2002

By P Licence, M Stevens, P Atkinson, J L. Mauk

The Rahu and Ascot epithermal Au-Ag prospects are two km north of the Karangahake deposit in the Hauraki Goldfield, and all occur in an approximately 6 km2 north-south elongated magnetic æquietÆ zone. The prospects are hosted by andesitic flows, lithic-crystal tuffs and local sedimentary rocks; local silica sinter occurs at Ascot. These host rocks are intensely altered by quartz, adularia, albite, chlorite, pyrite, illite, interstratified illite-smectite and calcite. Several minerals show zoned distributions, such as widespread adularia that overlies more localised and deeper albite. Illite is the only dioctahedral phyllosilicate in several drill holes, but elsewhere it forms a shallow carapace underlain by interstratified illite-smectite with 50 to 90 percent illite. Veins are common with quartz dominating near the surface and calcite becoming more abundant at depth. Local laumontite-calcite veins also occur. Pseudosecondary and secondary fluid inclusions in quartz and calcite at Rahu and Ascot have homogenisation temperatures (Th) that range from 162¦ to 268¦C and 128¦ to 243¦C, respectively. Most inclusions have trapped dilute fluids with salinities of less than 1.9 weight percent NaCl equivalent, but 20 percent of the inclusions have salinities of 2.0 to 10.5 weight percent NaCl equivalent. Calculated paleowater table elevations suggest that the water table at Rahu occurred at 440 m above sea level (asl). At Ascot, silica sinter formed from discharging geothermal fluids (=100¦C) at the paleosurface at ~135 m asl. However the sinter also contains comb quartz with pseudosecondary inclusions that have a Th average of 229¦C, corresponding to a paleowater table at ~430 m asl during inclusion entrapment. Taken together, these results suggest that the Ascot sinter was buried by approximately 300 m of cover material during a major volcanic or tectonic event, and that subsequent hydrothermal fluids formed veins and alteration at Rahu and deposited comb quartz at Ascot.

Jan 1, 2007

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