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Remnants of Plio-Pleistocene hot spring systems in Northland, New Zealand contain sulfide minerals, principally pyrite, marcasite and cinnabar. The climate is warm temperate to subtropical, with up to 3 m of rainfall per annum, and rocks are deeply weathered. Decomposition of the iron sulfides in natural outcrops and human excavations results in acid rock drainage with pH typically between 2 and 5, and locally down to pH 1. Deeply weathered basement greywacke is clay-rich and has negligible neutralisation capacity. Some overlying volcanic flows have resisted weathering, and pH is kept near neutral by relict secondary calcite in small areas. Natural rainforest soils commonly have pH between 4 and 5 over mineralised and unmineralised greywacke. Mineralised zones are enriched in arsenic, which occurs in solid solution (up to 1 wt per cent) in sulfides and phosphate minerals. Mercury also occurs in solid solution in some of these minerals, as well as in cinnabar. Base metals are present in low (background) concentrations only. Decomposition of the iron sulfides and phosphates releases the solid solution arsenic and mercury into the acid rock drainage solutions. Arsenic is readily adsorbed on to iron oxyhydroxides formed in acid rock drainage situations, and can be effectively removed from the biosphere. However, this arsenic is released back into the environment if the pH rises, as adsorbed oxyanions become less strongly bound and are displaced by hydroxyl ions. Behaviour of dissolved mercury is similar to that of arsenic but less well understood in these settings. Both arsenic and mercury are readily leached into pH 6 solutions from solid material collected from acid rock drainage sites. These observations suggest that neutralisation of acid rock drainage sites is undesirable in this setting, as arsenic and mercury will become more mobile in the environment. The naturally low pH of 4 to 5 of the forest floor, or even lower pH of natural acid rock drainage, is a preferable management option.

Jan 1, 2003

The major coalfields of Australia are almost unique in the occurrence in some areas of CO partly or almost completely replacing CH4,t1e normal seam gas from metamorphism of coal due to time and depth of burial. This CO2 situation has some benefits but mostly it introduces particular safety problems result- ing from the high density of CO2 relative to air, magnifying problems of gas dilution in ventilation, and the greater affinity which coal has for CO2 than for CH4 increasing proneness to gas-dynamic phenomena. The occurrence of most CO2 seam gas can be directly related to igneous intrusion and to its associated pneumatolytic injections. Whilst intrusions locally increase the rank of coal by their contact metamorphic effect, normal coal metamorphism due to time and depth of burial continues after intrusion and injection together with the ongoing metamorph- ic production of CH . This new CH slowly displaces any CO to leave some present-day intruded coals with seam gas with reduced CO2 or even without any significant CO2 associat- ions. The seam gas maps of the Bowen and Sydney Basins and more detailed maps of specific areas exemplify these situations. Mining progress, plus more searching studies of igneous-coal relationships provide improved understanding of the factors involved.

Jan 1, 1986

By E Bouchard March, F Lavoie, B Legare, K Bourassa

Quebec Iron Ore (QIO), a subsidiary of Champion Iron Limited (Champion), completed the restart of the Bloom Lake iron ore mine located in the heart of the Labrador Trough region of Northern Quebec, Canada in February 2018. Prior to its restart, the concentrator flow sheet underwent major upgrades which brought the iron recovery to the highest of all Labrador Trough operations. After two profitable years of production, QIO, supported by Soutex, started to look at technologies to improve its current performance and integrate into its expansion project flow sheet. From the lessons learned while optimising Phase 1, the addition of a scavenger-cleaner processing stage was identified as an improvement opportunity to increase recovery, produce a higher-grade product, and further improve the stability of concentrate quality. In 2019, the NI-43101 feasibility study for the Phase 2 expansion, aiming to double the production of high-grade iron ore concentrate, was published. Based on the metallurgical test work, the hydraulic classifier was selected to perform the scavenger-cleaning duty for its well-established performance and known behaviour at the cleaning step in the Phase 1 plant. To validate laboratory results, a pilot scavenger-cleaning hydraulic classifier was installed in Phase 1. Although the hydraulic classifier was selected for the feasibility study, metallurgical test work performed with the REFLUX® classifier showed interesting potential. It was thus decided to also install a pilot RC300 Reflux classifier at the scavenger-cleaning stage in Phase 1. Despite their apparent great similarities, the metallurgical performance was significantly different, and many dozens of sampling campaigns highlighted the different performance of both pieces of equipment considering the feed material particle size. This article presents the pilot plant results in terms of recovery, selectivity and stability for both the Reflux classifier and the hydraulic classifier operated in a scavenger-cleaner stage at the Bloom Lake iron ore concentrator.

Nov 8, 2021

By W L. Daniels, C Stilson, C Zimmerman

Mineral sands mining for ilmenite, rutile and zircon has disturbed over 1000 ha of prime farmland in Virginia (USA) since 1997 and additional areas are likely to be disturbed in Virginia and North Carolina (USA) over the next 15 years. Full-scale mining operations at the Old Hickory Project in Virginia were initiated in 1997 by Iluka Resources Inc. and restoration protocols have continued to evolve in response to a variety of economic, technical and social issues. Early on, the return of these lands to agricultural row-crop production was complicated by vertical stratification of tails + slimes and lateral variability in soil physical conditions in the reclaimed pits and by limited topsoil return. Virginia Tech and Iluka have worked cooperatively with all stakeholders for over 20 years to review the pre-existing research base, conduct new and innovative site-specific research and thereby provide reasonable expectations of post-mining soil productivity levels. In 2004, Virginia Tech, Iluka Resources and a local leaseholder (Carraway-Winn family) agreed to jointly manage a 45 ha research demonstration farm where the long-term effects of alternative soil reconstruction practices are being rigorously monitored for both row crops (corn and wheat) and forage production. All mined land crop yields are also compared to an adjacent undisturbed exceptional quality prime farmland soil. Row crop yields between 2005 and 2010 were significantly above county average yields (regulatory target level) and approximately 75 - 80 per cent of undisturbed adjacent prime farmlands. The state regulatory authority has recently relaxed its position on the necessity of topsoil return versus use of topsoil substitutes based on appropriate on-site research results and the ability of the reclaimed soils to meet comparative local county crop yield targets. This cooperative effort allows all clientele groups to objectively assess the post-mining productivity of these mined lands while providing an invaluable educational opportunity for the mining industry. CITATION:Daniels, W L, Stilson, C and Zimmerman, C, 2012. Development of effective rehabilitation protocols for mineral sands mining in Virginia, USA, in Proceedings Life-of-Mine 2012 , pp 97-104 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By Porter I, Singh RN

An advanced elasto-plastic finite element model adopting a modified Von Mises yielding criterion was used to simulate progressive failure of the rock strata surrounding a room and pillar mine structure. The model conformed to the strain-softening behaviour of rock and accounted for post-failure residual strength. The simulation was achieved in such a way that material values were updated after each FE run, according to the stress criterion until the solution reached the final equilibrium steady state of the mine structure. The suggested structural stability analysis approach accounted for the main features of the structure degradations produced during loading through changes in rock material stiffness and subsequent evolution of stresses. Comprehensive parametric analysis was performed and the inevitable effect of interaction of the roof, pillar and floor on the overall mine stability limit was investigated. The numerical results clearly showed that linear models could not realistically represent the true behaviour of the mine structure. The results obtained are in good agreement with that predicted in the field.

Jan 1, 1992

By A M. Lechner, S Arnold, M J. Gillespie, P D. Erskine, D R. Mulligan, A T. Fletcher, A Gordon

Mine ecological monitoring schemes are often conducted only to address compliance and in some cases do not have the sufficient statistical power or understanding of ecological systems to assess, quantitatively, the meeting of rehabilitation targets or mine impacts. Monitoring schemes for rehabilitation commonly rely on analogue sites or premining baselines (reference sites) to assess whether rehabilitation sites are ecologically similar and thus successfully rehabilitated. In the case of monitoring for mine impacts, if the impacted sites diverge from reference data, the site is considered to be impacted. Fundamental to any monitoring scheme is testing the sampling design to ensure that it can detect these differences if they are present through adequate sample sizes (ie statistical power). However, a good understanding of the ecological system is required to ensure that differences detected are ecologically significant. Modelling ecosystem properties can provide a quantitative understanding of how ecosystems change over time and space, in response to natural environmental variations and thus aid in determining significant ecological differences. Furthermore, modelling methods can be used to predict future ecosystem states. Within the ecological literature, guidelines for robust statistical monitoring designs and modelling methods exist but are not routinely being used in the mining industry. This paper uses simple examples to discuss: problems with current compliance monitoring methods; importance of robust statistical techniques; and how modelling can assist rehabilitation assessment and guide monitoring schemes. The aim of this paper is to describe general monitoring and modelling methods that could be potentially used for mine site monitoring and closure assessment. These methods are often considered by mining companies as an extra expense that provide little practical benefit, and the domain of academia; however, engaging these methods may be more cost-effective in the long-run than conducting untargeted monitoring schemes that give no confidence to regulators on whether rehabilitation criteria have been met. Furthermore, monitoring programs in mining contexts provide a good opportunity to better understand long-term ecological patterns and test the application of more rigorous modelling approaches as the life of many mines tends to be greater than ten years.CITATION:Lechner, A M, Arnold, S, Fletcher, A T, Gordon, A, Erskine, P D, Gillespie, M J and Mulligan, D R, 2012. Embracing modern ecological methods - Monitoring and modelling for mine closure, not compliance, in Proceedings Life-of-Mine 2012 , pp 25-32 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By B Morey, J Gordon, P Mackenzie

Mount Tom Price Mine is peerless amongst Rio Tinto iron ore resources around the world. It has provided Hamersley Iron with premium quality, high lump yield haematite ore over the last four decades. The Brockman type bedded ore, containing bands of haematite and shale of varying thicknesses has been traditionally bulk mined to either high-grade or low-grade based on alumina cut-off grades. As open pit mining has progressed deeper into the orebody approaching the keels of the megastructure, increased structural complexity, chemical and physical variations in the ore, unfavourable ore presentation and reduced blending options have become an issue for grade control and may have serious impacts on product stockpiles. The grade blocks and boundaries must be accurately defined according to geological contacts and where identified, selective mining may be applied. Therefore in-pit geological mapping is the definite and ultimate guide to achieve target grades and grade predictions. Under this scenario, it is absolutely vital that the mine geology team ensures this geological knowledge is passed onto the related departments including mining crews as well as to the short- and long-term planners.

Jan 1, 2002

By S Gulati, N Sarkar, T Vink, S Battersby, L Okada

This paper examines a successful project implemented by BHP Mitsubishi Alliance (BMA) and the Polymathian team at Deswik, aimed at enhancing short-term scheduling processes to reduce vessel turn times in the BMA Central Queensland coal value chain. The project’s objective was to digitalise the planning process to enable planners to make data-driven insights to improve the profitability of the value chain. The strategy involved developing a digital mining system that incorporates data storage, cloud computing, and the ability to meet the integration needs of both internal and external business systems. This was complemented by a sophisticated, optimisation-based, decision-support tool to enhance the planning teams’ ability to make timely and effective decisions.

Sep 1, 2024

By M Allen

By its nature, the mining industry is energy and emissions intensive. In the future, the world will still require the outputs of mining but the industry will need to adapt to the low emissions economy. Understanding the risks of climate change to a particular site or at a company level is key to managing this transition.CITATION:Allen, M, 2018. Assessment of climate risk in the Australian mining industry, in Proceedings Life-of-Mine 2018, pp 13–16 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By D Kentwell

A resource model serves two main purposes depending on the stage of a project. The first is to provide an early indication of likely tonnages and grades at certain cut-offs so that decisions can be made on whether continued spending on the project is justified. The second is to provide a basis for mine planning, feasibility studies and reserves. Resource models are not designed for selection of actual blocks in the ground for processing. This is the purpose of a grade control model, which is created at a stage beyond both resources and reserves.Inferred, Indicated and Measured Resources contain different levels of uncertainty with respect to the accuracy of the resulting grade and tonnage curves. These uncertainties arise from three broad areas: quality of information, geological assumptions and estimation technique. This paper focuses on known problems with the ordinary kriging (OK) estimation technique. Resource estimates often produce smoothed block grade distributions with much lower block grade variability than true selective mining unit (SMU) block grade distributions. There are two main factors that are involved in this smoothing. Firstly, where the block size used for estimation is larger than the SMU block size, this will smooth the block grade distribution and move the grade and tonnage curves away from the true SMU block grade and tonnage curves. Secondly, and less well recognised, is that smoothing is inherent in the OK estimator. This also moves the grade and tonnage curves away from the true SMU grade and tonnage curves, even when the estimate is done at the SMU block size. There are a number of techniques, such as simulation, uniform conditioning and degraded search neighbourhoods that can provide a better approximation of the true SMU block grade and tonnage curves at the expense of individual block accuracy.This paper aims to explore the extent to which OK resource estimates designed to maximise individual block accuracy can differ from (an estimate of) the true resource at SMU block size in terms of grade and tonnage curves. The differences at economic cut-offs and above are examined. In some cases these differences are significant. Both the OK estimation technique and block size play a part in the differences observed. To do this we will examine a number of commodities and deposit types using real project data.The conclusion is that the current industry standard default practice of targeting maximum individual block accuracy (conditional unbiasedness) using OK at resource stage, without consideration or evaluation of the extent of associated smoothing at SMU scale, can lead to significant errors in fundamental mine planning decisions. This then has implications for resource classification if the classifications are based heavily on the OK quality without consideration of the true SMU distribution.CITATION:Kentwell, D, 2014. Aligning resource estimates with mine planning, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 185–192 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By S Hancock, B H. Brady, H Muhlhaus

The aims of this paper are to present the governing science, verify the performance and demonstrate the potential engineering applications of a computational simulator for in situ leach mining of non-ferrous minerals. Assuming that the target mineral is deposited either uniformly within rock matrixes (matrix-hosted) or on fracture walls (fracture-hosted), in situ leaching can be treated as reactive flow and transport in geological media (porous media for matrix-hosted ore deposits and fractured media for fracture-hosted ore deposits). Under this treatment, the processes of in situ leach mining for non-ferrous minerals can be quantified through several sets of equations and these coupled equations have been numerically solved. The computational simulator has been applied to the simulations of one-, two-, and three-dimensional in situ leaching cases. The computational simulator, together with laboratory and in situ leaching tests, can be used to:optimise the leaching chemistry; optimise the in situ scale mining operations; scale up the in situ scale test operation to a full-scale mining operation; and evaluate the post-mining environmental restoration plan.

Jan 1, 2000

Reduction of Iron Content from Silica by Gravitational Processes In this research work, it was attempted to reduce the iron contents (Fe2O3) in silica sample which was provided from Shenin silica mine using gravitational processes including jig machine, multi gravity separator (MGS), shaking table and spiral. The silica sample contains 93.75 per cent SiO2, 0.44 per cent Fe2O3, 2.78 per cent Al2O3, and 0.08 per cent TiO2 and the Fe2O3 has to be reduced to about 0.1 per cent or less than 0.02 per cent. Mineralogical studies and XRD analysis indicated the presence of haematite, pyrite and goethite as the major iron impurity phases. Mineralogical studies of polished and thin sections yielded that the degree of freedom of silica is more than 80 per cent in the range of -300 +212 mm. After elimination of fine particles, at first nine tests were carried out on crusher product (in two size fractions), wet rod mil product and scrubber product by means of Jig Machine. The best results were obtained with about 0.15 per cent Fe2O3 on rod mill and scrubber product which was not desirable. Thereafter 7 tests were carried out using shaking table; the best results were obtained with about 0.14 per cent Fe2O3 on rod mill and scrubber product which was not desirable. MGS showed the worst result in order to iron removal from silica which was not desirable. Finally 9 testes were carried out using spiral whish is the best gravitational separator for elimination of iron impurities from silica. The best result of spiral tests were achieved on scrubber product. In this test concentrate weight percent and its Fe2O3 grade were 82.32 per cent and 0.085 per cent respectively. Finally a test was carried out using 2 stages of spiral in order to develop flow sheet. In this test concentrate weight percent and its Fe2O3 grade were 78.8 per cent and 0.1 per cent respectively. This product can be used to produce float (clear flat) glass.

Sep 13, 2010

By Willis GM

The matte-metal-equilibria in the system Pb-Cu-S have been studied at temperatures between 720 and 920¦C by direct sampling and D.T.A. methods. These results are compared with those of other workers. The applications of such data to a continuous copper drossing process, and to a number of other metallurgical processes are discussed.

Jan 1, 1975

By R-H Yoon

The thin film pressure balance (TFPB) technique was used to measure the kinetics of thinning of single foam films and disjoining pressures in the presence of sodium dodecyl sulfate (SDS) and electrolyte (NaCl). The results were analysed in view of the Reynolds equation to determine the role of surface forces in film thinning. It was found that film thinning is controlled by surface forces at thicknesses below approximately 200 nm. It was also found that hydrophobic force plays an important role particularly at low SDS and NaCl concentrations. The values of the hydrophobic force constant (K232) estimated from the film thinning experiments were used to predict the disjoining pressure isotherm using the extended DLVO theory, which were found to be in excellent agreement with experiment. The TFPB technique was also used to measure the equilibrium thicknesses (He) of the foam films stabilised by a non-ionic surfactant, n-octanol, in the presence of NaCl. At a given ionic strength, He increased noticeably with increasing octanol concentration at very low concentrations. This observation suggests that hydrophobic force is at its maximum level in the absence of surfactant and decreases with increasing surfactant concentration. The results obtained with the single foam films were used to explain the stability of the three-dimensional foams.

Jan 1, 2005

ABSTRACT' The first references to gold in New Guinea were by the Portuguese in 1525. The first significant discovery and gold rush was on Sudest Island in 1888 and was a natural extension of the rush that surged up Australia's eastern coast and ended at cook- town. Prospectors made a series of minor discoveries in coastal regions before the first large discovery at Wau/Edie Creek/Bulolo in 1925. Major post war gold discoveries were made at Bougainville, Frieda River, Porgera and Ok Tedi. On Misima Island a large bulk low grade deposit has been recognised surrounding old gold workings. Gold exploration has increased drama- tically since the lifting of a 3 year moritorium on new exploration areas in Noverrber 1982. A new bulk low grade gold discovery has been made on Lihir Island, north of Bougainville and a number of other promising areas are being drilled. Gold production is also expanding dramatically from current levels of 600,000 ounces to an anticipated 1.3 million ounces in 1985 with the opening of Ok Tedi. Other potential developments are likely to increase output above 2 million ounces by 1990. Papua New Guinea's world ranking as a producer is likely to move from 9th to 7th in 1985 reflecting the favourable geological potential, stable political environment and attractive development terms offered by the Government.

Jan 1, 1984

By P Worsey, B Lane

The recommended maximum explosive weight for boulder blasting using internal charges is 0.15 kg/m 3 (Olofsson, 1988). Normally this charge results in excessive scattering and flyrock, creating increased liability for the operator, especially in congested areas. An alternative technique using smaller explosive charges is being developed at the University of Missouri-Rolla (UMR). It is designed to reduce boulder scatter, flyrock and fumes and allows shooting in close proximity, using common blasting products. The method comprises drilling a hole into the top of the boulder, inserting a small primer, filling the hole with water and shooting it. The hole is drilled approximately two thirds into the boulder and the charge (10 g/m 3 ) is placed half way into the hole filled with water. Upon initiation the primer produces a small volume of gas at extremely high pressure which acts upon the surrounding (relatively incompressible) water. The water transmits this pressure to the surrounding blasthole, hydraulically fracturing the rock. As the fractures propagate and the boulder expands a rapid increase in the blasthole volume occurs. Because of the small charge the gas pressure quickly dissipates reducing rock movement, resulting in a fractured boulder with minimal material leaving the immediate vicinity. The current work includes both laboratory and field testing programs. The laboratory program is focussed on determining optimum parameters at reduced scale using concrete cubes. The field program focuses on determining a minimum powder factor and includes shooting smaller boulders up to 1 m 3 underground and 1.5 to 5 m 3 boulders in a surface quarry. In both cases the boulders were obtained as oversize from regular production blasts.

Jan 1, 1999

In the early ages man contented himself with the use of such tools and appliances as would assist him in the enlightenment of his labours. With the advancement of science, numerous motives, with modifications and adaptations, have been introduced to enlighten labours, and in many cases have taken the place of man, but it can hardly be said that this applies to shovels, although one of the oldest implements of labour; certainly, with the introduction of the steam shovel the labours of man have been considerably reduced, but the hand shovel of today is used similarly to that of years ago.If the principle of the hand shovel has not been improved upon, it must not be suggested that the manufacturers of this article are not endeavouring to improve its quality, and the main point with which the manufacturers have to contend is the production of an article which will give a maximum of durability combined with a minimum of lightness. In order to accomplish this they must select suitable material, and subject it to such heat treatment process that will produce a shovel having a maximum of hardness and toughness without being unduly brittle, and which will withstand the excessive wear to which it is subjected.In this article an endeavour will be made to explain (a) the manufacture of shovels; (b) the defects commonly met with-the cause of same and measures which are necessary to remedy them.Before doing so a brief description will be given of the class of steel used for shovels; this is an important factor, and a steel which is admirably suitable is a plain carbon one containing approximately 55 - 70% C., and closely resembles that used for the manufacture of railway rails. This plain carbon steel is very extensively used, although at present alloy steels are being utilised to a certain extent for shovel manufacture, and with suitable heat-treatment.

Jan 1, 1926

By A Boucher, M Baudin, P Androszczuk, I Minniakhmetov, A Rigby, P Machado, M Wright, B Van Dijken

IGO Ltd’s (IGO’s) Nova Operation (Nova), which is 160 km east-north-east of the town of Norseman in Western Australia (WA), mines and processes nickel-copper-cobalt (Ni-Cu-Co) sulfide ore from the magmatic Nova-Bollinger Deposit (Nova-Bollinger), which is hosted by the Mesoproterozoic age high-grade metamorphic rocks of the Albany Fraser Orogen. Over its 56-month life-of-mine (LOM) operations to 31 December 2020, Nova has processed 5.63 Mt of ore grading 2.04 per cent Ni, 0.86 per cent Cu and 0.07 per cent Co from its underground mine. At the end of 2020, both the Nova-Bollinger JORC Code reportable Mineral Resource estimate (MRE) and Ore Reserve estimate (ORE) were >90 per cent classified in the highest JORC Code confidence categories of Measured Mineral Resource and Proved Ore Reserve respectively. The high JORC Code classification confidences assigned to the Nova-Bollinger MRE and ORE results from the 386 km of surface and underground diamond drill testing of the deposit to a nominal 12.5 by 12.5 m pierce point spacing in mineralisation. The close spaced high-quality drilling and bulk mining method employed at Nova has effectively removed the need for any grade control modelling outside of the MRE process. Importantly, having only the one fully drilled out deposit being mined and only the one process plant, Nova’s reconciliation process is in the fortunate situation of not being confounded by issues such as external ore sources and constant updates as new grade control information becomes available. IGO’s Nova reconciliation processes are focused on reconciliation ratios that quantify operational period differences between the MRE and ORE head grade and tonnage forecasts and the process plant head actuals. These metrics have been used to identify key reconciliation issues and have initiated several studies into the causes for specific reconciliation results, which are discussed in the paper. In late 2020, a period of sustained poor reconciliation results led to the recognition that increasing the understanding of risk between the MRE and ORE should be investigated. To assist with modelling stope level risk within the mine plan and subsequent reconciliation, an attempt was made to develop a formula to quantify ‘stope risk’ from MRE metrics such as sample spacing, kriging efficiency and so on

Mar 22, 2022

By L McCarthy, B W. Cuffley, O K. Thomas an

The Central Victorian Goldfield is a world-class field located in Victoria, Australia. It is currently undergoing a revival through activities in the Bendigo, Ballarat, Tarnagulla, Maldon, Castlemaine and other fields. Sediment-hosted auriferous gold-quartz reefs that are structurally and geometrically complex dominate the region. To date, no remote methods have been developed to assist in the targeting of the discrete high-grade oreshoots that characterise the mineralisation. An understanding of the structural setting and controls, and thus likely frequency of repetition of oreshoots remains the main exploration tool. Gold within the reefs is generally characterised by both its coarse nature (>100 up to 10 000 microns) and erratic distribution; as a result, most of the Victorian deposits are classed as high- to extreme-nugget effect systems. This characteristic ensures that mineralisation is very challenging to explore, evaluate and exploit. The key issues facing the explorer and miner are related to effective sampling, and definition of geological and grade continuity, and ultimately grade and tonnage. Tonnage can often be estimated to a reasonable level of confidence, whereas the grade estimate generally carries a medium- to high-level of uncertainty. In these deposits, surface diamond drilling alone is generally only able to define an Inferred Mineral Resource, with underground development, closely spaced in-fill drilling and bulk sampling/trial mining required to define Ore Reserves. The extraction of gold from ores is relatively simple, based on the coarse nature and hence amenability to gravity recovery. Ground conditions and the need for in-stope grade control (eg mapping, sampling etc), generally point toward mechanised cut-and-fill as the primary stoping method in the region. To potential investors this style of mineralisation has been viewed as high risk, because of the associated low confidence in the grade estimate, general paucity of Ore Reserves at mining start-up and need for underground development at the Feasibility Stage.

Jan 1, 2004

Societal influences, needs, and uses for recyclable materials are becoming increasingly important business and economic factors in the traditional natural resource companies. Several metals (such as steel, aluminium, zinc, lead and cadmium) are amenable ro recycle which eliminates solid waste generation and decreases the depletion of natural resources. In recent years, the non-ferrous industries have begun to recycle more materials and the next decade will see even larger recycle efforts. In addition to the traditonal recyclable materials, existing metallurgical plants are, or should be, able to handle and recycle materials viewed as 'hazardous'. Unfortunately, some national and regional regulations hinder, and in some cases prevent, the recycling of certain materials. Zinc Corporation of America (ZCA) is currently the largest producer of zinc metal in the USA and one of the world's largest producers of value-added zinc products. Over the last few years, ZCA has become one of the world's largest recyclers of zinc from various diverse materials. ZCA considers these recyclable materials as valuable 'land mines' that provide economic alternatives to the depletion of natural resources while serving society in the minimisation of solid waste disposal. Using the current production facilities of ZCA as a model, this paper overviews the recycling of zinc-bearing materials with special emphasis on: 1. the amenability for recycle within ZCA's pyrometallurgical and hydrometallurgical operations, 2. the quantities and economics of recycle, 3. the problems of recycling hindered by current national and regional regulations, 4. the concepts of total recycle rather than just recovering zinc while generating a modified solid waste, and 5. the motivators for recycling.

Jan 1, 1993