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The importance of good winding rope practice is stressed. Details of the ropes used for various duties in the four shafts of The Zinc Corporation, Limited (ZC) and New Broken Hill Consolidated Limited (NBHC) are given. Inspection, testing (including non destructive methods), maintenance and rope discard criteria are discussed. There are sane catments about rope installation methods and an appendix is included which outlines the appropriate statutory requirements for winding ropes in New South Wales (NSW).

Jan 1, 1983

By Hill J. R M, McDonald M. M

A prediction technique for support perfor- mance of hydraulic backfill in narrow stopes is applied to two stopes separated vertically by a sill pillar. Predicted stope wall closures and fill pressures compare favorably with field measurements taken over a period of several years at two mines in the Coeur d'Alene dis- trict. Stope wall closure and peak pillar stress can be substantially reduced by improved fill quality within a practicable range of fill and rock properties.

Jan 1, 1973

The difference between a hypothetical and a theoretical approach is considered and the advantages in using a hypothesis is discussed. Virgin horizontal stresses play an important role in stabilising strata which bridge across an excavation, and reduces the tensile stresses which develop in a beam subjected to bending. Simple formulae are deduced for the bridging of a thick massive stratum under such conditions. At shallow depths, tensile failure on the upper side of the beam is the most likely cause of fracture, but below a certain depth this gives place to compressive failure on the underside, with the possible incidence of rock bumps. The presence of strong massive beds delay the onset of subsidence and may restrict the width of the subsidence trough. If the material involved in the caving is strong, this will reduce the final subsidence, especially at shallow depths. The British regulations for the control of aquifers and their dependence on the strain developed at the seabed are discussed. As an alternative, the concept of a disturbance factor is introduced to permit the consider- ation of aquifers at depth, leading to an explanation of the make of water on the first faces to be mined in the Selby Coalfield. 'Elie paper closes with a brief consideration of the different roles played by longwall face supports in the control of readily cavable strata, and the control of strong beds which hold up in the waste.

Jan 1, 1986

By A Coelho, D Bruce, H Grosser, C Parken, M Xia

Carrapateena is a new underground sublevel cave mine and was officially opened in 2020. It has a mine life of 20 years. Development began in 2016, and with the rare opportunity to start a with a blank canvas and having a long mine life, an effort was made to explore how to incorporate innovative and leading-edge technologies. The Ventilation on Demand (VoD) system was designed with the objective to optimise power consumption and ventilation delivery through the primary and secondary ventilation systems. Primary fans controlled by Variable Speed Drives (VSDs) and dualwinding secondary fans with multiple setpoints control the delivery of overall quantity. Automated butterfly dampeners control the regulation of air to individual production crosscuts, and automated louvres control the exhaust quantities from the mining levels. Ultra-sonic flow sensors are installed to measure air quantity and environmental stations are installed to measure air quality. Both are designed to play a key role in control and calibration of the system. It was quickly identified that no one vendor could provide a holistic solution to meet the design requirements. A strategy was derived to use multiple vendors, harnessing the specific strengths of each. A control system has been developed to allow the Site Operations Control Centre (SOCC) to oversee and control real-time delivery of ventilation as required by operations. The first full level installation of the VoD system was completed in September 2020.

Mar 15, 2021

By R Coleman

The flotation mechanism plays a key role in the flotation process. It is used to provide the contact between solid particles and bubbles and also the energy for these particles and bubbles to attach. The mechanism must therefore provide sufficient mixing to keep the solids in suspension so that they can be transported into the froth and recovered to the concentrate. The design of the mechanism is critical and over the past decade Outotec has developed and optimised a new mechanism design to improve metallurgical and energy performance. The FloatForce® mechanism consists of a rotor and stator arrangement and has been specifically designed to provide sustained mixing at higher air flows and lower power inputs.Over 500 FloatForce® mechanisms have been installed in existing and new operations. This paper outlines the technological aspects of the FloatForce® mechanism and provides metallurgical, operational and energy performance results from a number of flotation circuits in which these have been installed.

Aug 8, 2011

By A Horn

Mineral processing is characterised by a constant adaptation to changing raw materials and market conditions. It is the link between the mined raw material and a marketable product. As a lot of high-grade reserves are exploited, a steady deterioration of raw material quality can be observed. At the same time, the customer’s requirement for product purity and consistent quality increases.Over recent years beneficiation techniques for iron ore fines have become more important in order to achieve a maximised utilisation of ore resources and to produce competitive products according to international standards.Many high capacity iron ore beneficiation plants that target the production of fines focus on gravity separation processes using fluidised bed classifiers and spirals or wet high intensity magnetic separators as an alternative. This paper demonstrates the suitability of utilising the allflux® two-stage fluidised bed classifiers to treat iron ore particles up to 2 mm in size as well as showing how the high capacity gaustec® wet high intensity magnetic separation (WHIMS) technology offers several advantages compared to other WHIMS technology.The combination of the allflux® and gaustec® technologies offer the following benefits:The two-stage fluidised bed classification extracts a significant amount of concentrate from the feed. This in turn reduces the feed capacity required for the gaustec® WHIMS located downstream.The second classification stage produces a -0.5 + 0.1 mm product and a -0.1 mm product. The efficiency of the magnetic separation on these classifi ed products is high due to optimised settings for each size fraction.

Jul 11, 2011

By J Araya, O Leiva

The mine evaluation process, composed of the designing, planning and valuation of a mine project, is, among other variables, based on an estimated orebody model. However, as the information from the drill holes is limited, it is impossible to know with certainty the mineral content in each block within the estimated block model. Consequently, uncertainty about the value of metal grades, or other geological attributes, arises because of the lack of information at unsampled locations. This is one of the reasons why, in any mine operation, there will always exist a divergence between estimated and real values. Cut-off grade optimisation is the process used to determine the operating mining strategy (long-term production scheduling) that will maximise the total profit value (normally referred as the net present value (NPV)) of a mine operation. This is done by defining a dynamic cut-off grade policy which is constrained by the production capacity of the mining, mill and refining.Real options is a type of contract, written on real assets such as mining, oil and other natural resource industries, that gives you the right but not the obligation to exercise the contract. It is based on operational and managerial flexibility, which allow mine decision makers to react to either good or bad operational and economic events in the future. But, what do geostatistics and cut-off grade optimisation have to do with the application of real options in a mine project evaluation process? The objective of this paper is to answer the previous question by showing how geostatistics combined with cut-off grade optimisation are key tools for corporate/managerial decision makers, which allow them not only to analyse the resource/reserves of their projects, but also to generate operational strategies that can maximise project value by minimising the downside risk due to ore tonnes and grade uncertainties, while achieving operational and physical constraints such as mining and processing capacities. A real copper grade open pit mine project is used as a case study.

Sep 26, 2011

By G Williams

Somewhat to the surprise of many heavy mineral sands (TiO2 and zircon) producers, there are important geological structures within their typical placers and aeolian sands deposits that affect plant metallurgical performance. After many years of operations, even experienced producers have encountered unexpected changes in production, product quality and recovery. After looking in all the obvious (but wrong) places, it is recognised that the mine has advanced into ore with different separation characteristics. Metallurgical process response can vary significantly between ore sourced from different geological domains. The mineral characteristics that are exploited for effective separation may be associated with differences in the depositional environment, or be post-depositional in origin. Surface coatings that interfere with electrostatic separation might be associated with paleo-water table movements. Major storm events in the deposition history can also leave distorted mineral assemblage through stranded formations or incisions in older deposits.Apart from the influence on capital and operating costs, geometallurgical variances add another dimension to orebody modelling. Each domain could have specific recovery, mineral assemblage and product quality values to be considered in the value model. Project success is often directly dependent on understanding the geometallurgy of the resource. Tailoring the exploration and early process flow sheet development programs to account for such variances should be standard practice. Such practices have had a chequered history in the mineral sands industry, with sophisticated processes having been developed, only to be shelved for ‘economic’ reasons, and then once again ‘discovered’ when problems re-emerge.It is clear that knowledge gained through a higher level understanding of the changing mineral separation characteristics and advance warning of mineral behavioural differences can mean the difference between lost recoveries and disappointed customers or well timed capital plans and maximised revenues.

Oct 5, 2011

By D Blair, L Fergusson, G Barros

"The purpose of this paper is to present the findings of a waste rock remediation program conducted at a gold mine in New South Wales (NSW) over a six-year period. The treatment of waste rock dumps included the longitudinal results of one-off applications using: ViroMine Technology, including the application of a chemical reagent called Terra B, which is a benign, clay-like substance derived from processed bauxite and other sources lime and biosolids (added for nutrient value) clay capping and topsoil compared treatment outcomes from these three approaches to a control.Parameters measured in the program included leachate pH, total actual acidity (TAA) and chromium reducible sulfur (CRS), Al, Cd, Cu, Fe, Mn, Ni, Pb, Zn, and tree height and vegetative cover density with data collected at regular intervals over a six-year monitoring period. Findings over the life of the study indicated, for example, that leachate pH in the control area was 4.5 in year 1 falling to 4.0 by year 6; pH in the lime and capping treated waste rock was initially raised to about 5.5 after treatment but fell to 5.0 within 24 months and remained a low 4.7 by year 6; pH in the Terra B waste rock was 6.8 in year 1 immediately after treatment, and actually increased to 7.3 by year 6 with no further treatment. This finding is of relevance because it effectively profiles the acidity curves of waste rock control, lime, and capping applications, and shows that they decline over time, despite an initial æpH shockÆ to the solids as measured by TAA and CRS in the case of lime. Similar treatment curves were observed for heavy metal leachates. Tree height and vegetative cover density indicated that with increasing acidity in the waste rock dump, the lime and capping options did not allow healthy revegetation, but in the Terra B treated areas tree growth and density were comparable to background, undisturbed forest levels.is needed with respect to tailings management, based on a novel integrated research framework.CITATION:Fergusson, L, Blair, D and Barros, G, 2012. Sustainable waste rock remediation and revegetation - A real-world longitudinal study comparing ViroMine technology to standard applications and doing nothing, in Proceedings Life-of-Mine 2012 , pp 249-258 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 10, 2012

By J Butler, N Patel, S Narendranathan, S Rastogi

The Yallourn Mine (YM) commenced mining of brown coal in the 1920s under operation by the State Electricity Commission of Victoria (SECV), prior to it becoming privatised in 1996. The present owners of the YM, Energy Australia Yallourn (EAY), acquired the site in 2000 and intend to continue operations until scheduled closure in 2028. Brown coal extracted from the YM is fed into the Yallourn Power Station which supplies approximately 22 per cent of Victoria’s electricity. Water within the YM is collected and stored in the Township Field Fire Service Pond. Water levels within the Fire Service Pond (FSP) may fluctuate considerably depending on the requirement for storage at the site. With due consideration to the stability performance of mine batters adjoining the FSP, the authors performed slope stability assessments to evaluate the risk and consequence of batter instability during the potential pond filling as it approaches the ‘critical pool’. The critical pond is defined as the level at which the driving forces (destabilising forces) are at their greatest and the resisting forces (lake forces, friction) are at their lowest. This assessment was undertaken using the Mine Geotechnical Risk Index (MGRI) approach.

Aug 2, 2023

By S Schwarz, D Alexander

The mining industry, and in fact the world, has undergone significant changes in the past five to ten years, ranging from the metals boom, the global financial crisis and the rise and fall of national economies, to name just a few. There has been a focus on sustainable development for projects and operations in the mining industry, mainly pushed onto the industry by communities, governments and other agencies. While sustainable development and operation is a worthy priority for mining operations, discussions with mining industry personnel (with a strong slant on the mineral processing perspective) have shown other issues have surpassed the typical issues of water resources, energy availability and the environment. These include staff turnover and skills shortages, extracting metal from more complex orebodies and the uptake of new step-change technology.A number of key operating mineral processing personnel were interviewed to determine their perspective on the current issues facing the mining industry. This paper details the findings of this survey and highlights some of the topics that have been identified as the top issues from a mineral processing perspective.CITATION:Schwarz, S and Alexander, D, 2012. Current issues in the mining industry - From the operational mineral processorÆs perspective, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 369-372 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By Somerville M, Muray A, Bocking M

Australia has an extremely large total hot dry rock (HDR) resource above a depth of 5 km, equivalent to 7500 times its present annual energy consumption, of which 80 per cent underlies the Great Artesian Basin. The resources most likely to be exploited first are those residing in homogeneous granitic bodies beneath sedimentary basins containing insulating rocks such as shales and coal measures. In the Sydney Basin south of Muswellbrook, an area of high geothermal gradient corresponds to a gravity low thought to be a buried granite body at a temperature of possibly 250¦C. This locality is suspected to have the ideal geological characteristics for Australia's first hot rock test facility. Australia's high HDR potential is possibly unique in the world, in that the potential sites satisfy four independent, geological conditions, each considered as favourable for the creation of a resource, and for the ease of extracting that resource. They are: ò Higher crustal heat generating capacity than that of normal continental crust. ò Much of the Australian continent is covered by sedimentary basins which contain a high proportion of shales and coal measures that have low thermal conductivities, thus providing an insulating blanket for the heat being generated beneath. ò The sedimentary basins are in many places underlain by large untectonised granitic bodies that are not only a major contributor to heat generation, but also ideally suited to the establishment of HDR reservoirs. ò The crustal shortening stress field that is found in the majority of the Australian continental crust results in a vertical minimum principal stress orientation which should result in the development of favourably oriented horizontal stimulation cells necessary for maximising an HDR resource.

Jan 1, 1995

By R H. Knight

Production mine geology must be accurate and efficient in order to reduce risk and ensure that ore value and mining operation revenue are maximised. Present grade control practices are commonly based on outmoded and inaccurate 2D geological mapping techniques where spatial relationships are estimated by eye, sketched by hand and projected to arbitrary reference planes. The 3D mapping approach outlined in this paper integrates 3D photogrammetric imagery with implicit modelling techniques to enable more accurate grade control and reconciliation in underground mines. High-resolution stereo photographs are taken of daily ore development headings. Ore contacts are traced directly on a 2D face photo using a stylus and rugged tablet. Area-weighted face grades are estimated and calculated on mapped 2D face planes. In the office, a 3D photorealistic mesh is processed and georeferenced. 2D face mapping data is transformed into its actual 3D location and true 3D mine mapping is performed by digitising oriented 3D polylines representing ore contacts and other geological features directly onto the image surface. Three-dimensional spatial relationships are fixed, eliminating the projection error of traditional 2D methods. Ore envelope and waste solids are modelled within the closed, drift-round mesh. Volume-weighted ore envelope and round grades, as well as round volume and tonnage, are calculated. Ore/waste classifications, grade, tonnage and per cent dilution are quantified per round, visually assessed in 3D and reconciled with short- and long-term models on a daily basis. Updated geological continuity models provide geological guidance in development headings under geological control and accurate 3D structural and form-line mapping improves definition drilling and stope planning. Three-dimensional imagery provides a permanent detailed survey and geological record of mine workings that can be revisited virtually to reinterpret geological ore controls in light of new observations and insights. In addition images can be used to monitor daily production performance, create training scenarios for miners, engineers and geologists and prepare management presentations. This approach adds value to underground mines by improving the accuracy and efficiency of mine geology practices. The method is particularly effective in mines with visually distinct and geometrically complex orebodies, such as those in the Balmat zinc mine located in New York State, USA, which are used to illustrate the method.CITATION:Knight, R H, 2017. 3D mine mapping – improving grade control and reconciliation in underground mines using photogrammetric imagery and implicit modelling techniques, in Proceedings Tenth International Mining Geology Conference 2017, pp 203–212 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By B E. McCarthy

Red Dome Mine was a highly complex gold copper operation developed over a number of phases between mid-1986 to October 1997. With only three years of production ahead at any time, a proactive practical approach to mine closure was necessary. In 1989 the Domains Concept to life-of-mine planning and mine closure was created as a response to the proposed changes to legislation.The Domains Concept, a relatively simple idea developed to integrate mine closure during production at Red Dome, has been broadly adopted by both government agencies and industry in the intervening 20 year period. Over time the author has observed that the concept has been poorly applied, misunderstood and in some cases even misrepresented. As a consequence, the potential opportunities from applying the concept, including the optimisation and minimisation of life-of-mine costs, mitigation of long-term financial liability exposures and building credibility with the general community, have been missed.This paper examines the many benefits, advantages, applications and perceived barriers to developing and integrating a fully costed life-of-mine plan. Integrating the Domains Concept early in the project, within the operational budgeting, allows the production of a meaningful and useful document, representative of a whole life-of-mine, cradle to grave, with measurable rehabilitation and closure outcomes when the concept is used to full effect.The Domains Concept serves to optimise cost-effective, whole of mine, life cycle planning which provides beneficial outcomes for the community, significantly mitigates legacy issues and contributes to the attainment of compliance and sustainability principle objectives.CITATION:McCarthy, B E, 2014. The domains concept – 20 years on retrospective, obstacles and opportunities for effective life-of-mine implementation, in Proceedings Life-of-Mine 2014 , pp 621–636 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By B Laidens, D Souza, W Bielefeldt

The CaO-MgO-SiO2-Al2O3 system, characterised by its intricate phases and thermodynamic properties, plays a pivotal role in steel secondary refining processes, encompassing desulfurisation, non-metallic inclusion capture, and refractory protection. Accurate predictions for diverse industrial applications, including metallurgy, ceramics, and materials science, are imperative. To address this challenge, a combination of machine learning techniques will be specifically applied to model the liquid fraction of the slag and the solid fraction of MgO. The development of an artificial intelligence (AI) system, leveraging various machine learning techniques, has gained momentum in this project. The focus of this work is on constructing an AI model, based on machine learning techniques, within the CaO-MgO-SiO2-Al2O3 system, utilising simulation results from FactSage™, version 8.1 (by GTT Technologies). The primary objective is to train the AI model using these simulation outputs to predict the percentage of liquid fraction and MgO saturation based on chemical composition parameters. The AI model will undergo training with a comprehensive data set of simulations within the CaOMgO- SiO2-Al2O3 system, covering a diverse range of compositional at 1873 K. These simulations, conducted through FactSage™ 8.1 software, provide a robust foundation for AI model training, ensuring generalisability and precise predictions for the liquid fraction of the slag and the solid fraction of MgO, the solid fraction of MgO in this case is determined by the difference between the total MgO and the MgO in the liquid fraction, so it is not the objective of this study to determine which phase of MgO is in the solid state.. The predictive capabilities of this AI model hold significant implications for process optimisation, quality control, and decision-making in CaO-MgO-SiO2-Al2O3- dependent industries. Precise estimations of the liquid fraction and MgO saturation empower researchers and engineers to enhance operational efficiency and quality. This paper explores the methodologies employed for AI model creation and training, achieved results in terms of prediction accuracy, and potential applications in the field. The development of this AI system signifies a notable advancement in utilising machine learning for better comprehension and control of complex chemical systems. Furthermore, to align the study with real-world steel production, we introduce FeO and MnO at concentrations of 2 per cent and 1 per cent at 1873 K, respectively, following the validation of model results using the CaO-MgO-SiO2-Al2O3 system. This adjustment aims to bring the study closer to the observed reality in steel mills globally.

Jun 19, 2024

By P Stewart, S Cowie, A Offer, J Carpenter, E Jones

The Ban Houayxai Gold-Silver Operation is a producing asset for Australian-based copper and gold producer, PanAust Limited. The Operation lies within PanAust’s 2600 square-kilometre Phu Bia Contract Area in northern Laos. Commencing production in 2012, Ban Houayxai is operated by PanAust’s Lao-registered company, Phu Bia Mining. PanAust owns a 90 per cent interest in Phu Bia Mining. The Government of Laos owns the remaining 10 per cent. The Operation mines an intermediate sulphidation epithermal gold-silver deposit and comprises an open-pit feeding ore to a conventional carbon-in-leach process plant. Metallurgical recoveries for gold and silver are approximately 75-85 per cent and 55 per cent respectively. To year-end 2017, the Operation had poured 0.65 million ounces (oz) of gold and 4.7 million oz of silver. The Ban Houayxai Ore Reserve supports a mine life of approximately four years from the end of 2017. The Ban Houayxai deposit is in an early Permian volcano-sedimentary unit which is part of a late Carboniferous to early Permian (310–270 million years ago) volcanic-plutonic sequence of the Truong Son Fold Belt. The deposit formed when hot saline (240–415°C, 2.7–13.0 weight per cent NaCl equivalent) fluids ascended from a geologically fertile island arc porphyry into overlying volcanics along a fault or faults in the early Permian (290–256 million years ago) (Manaka et al, 2014). CITATION: Carpenter, J, Cowie, S, Stewart, P, Jones E, and Offer, A, 2018. Machine learning at a gold-silver mine: a case study from the Ban Houayxai Gold-Silver Operation, in Proceedings Complex Orebodies Conference 2018, pp 82–85 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

By P G. Bourke, A Yáñez, G J. Jameson, N M. L Kupka

The kinetics of fine and ultrafine particles in conventional mechanical flotation cells are limited (Feng and Aldrich, 1999; Trahar, 1981; Wang et al, 2016). Accordingly, even limited recoveries with such machines require long residence times. Theoretical investigations into the rate of capture of fine particles by flotation, have indicated that a key parameter is the rate of shear in the fluid surrounding the bubbles and the particles. Achieving fast flotation rates of ultrafines requires a new method of bringing the particles and bubbles into contact, utilising the beneficial properties of highly dissipative flows to break through the water boundary layer. In 2010, a new type of flotation cell known as the Concorde Cell was described, in which bubbles and particles are brought together in a sonic shock wave (Jameson, 2010). Earlier research had shown that when a dispersion of fine bubbles in liquid passed through a converging nozzle at the local speed of sound, the resulting shock wave downstream generates a mass of even finer bubbles in the flow as it passes through the shock wave. The fluid within the shock wave is highly turbulent, and an environment is created that is very favourable to particle-bubble collision and capture. In this paper, we briefly describe the Concorde Flotation Cell and give examples of its use.

Aug 24, 2022

This paper presents a review of heat illness in mining, including reference to several recent investigations by the author. Heat illness is a collective term, covering the conditions of heat stroke, heat exhaustion, heat cramps and miliaria rubra. Heat stroke is life-threatening and is by far the most serious condition. It is rare in mining, if appropriate control measures are instituted. Heat exhaustion is primarily due to hypohydration, following prolonged sweating in hot conditions. Symptoms include fatigue, headaches, dizziness, anorexia, nausea, vomiting, shortness of breath, or brief syncope. Confusion, ataxia, prolonged unconsciousness or convulsions are strongly suggestive of heat stroke. Heat cramps are painful involuntary contractions of skeletal muscle associated with work in hot conditions. The limbs are usually involved and the spasms typically last a few minutes, during which the affected part of the body is incapacitated. Heat cramps tend to occur in heat exhaustion, when hypohydration becomes marked. Miliaria rubra is a skin rash caused by extravasation of sweat into the skin, as a result of obstruction of the sweat glands. It occurs after prolonged and profuse sweating in hot environments. It can take three to four weeks of sedentary duties, in an air-conditioned surface environment, for the condition to resolve. Heat illness would be unlikely in underground mining, if the thermal environment was sufficiently well controlled by ventilation and refrigeration. This is however, often not practicable. Where engineering controls alone cannot provide sufficient control of risk, the residual risk can be assessed using an appropriate heat stress index. While procedural controls may further reduce the residual risk, it is important to remember that these are less reliable than engineering controls and cases of heat illness may still occur. Procedural controls include the application of heat stress limits, education, hydration, self-pacing, early symptom reporting, medical advice, acclimatisation procedures, air conditioned accommodation, support to achieve a healthy body mass index, and an effective emergency response capacity.

Jan 1, 2005

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 J Gould, T Elkington

Mine operation strategies are commonly optimised with a net present value (NPV) maximisation objective. There are well known properties of a typical mining project optimised for NPV, including high production rates and declining cut-off grade schedules. In practice, however, frequently there are operations that diverge from such NPV-maximising properties. Although a range of reasons for this can be at play, one possible explanation is that operators intuitively adjust their strategies to compensate for the flaws inherent to NPV maximisation. In particular, NPV analysis does not reflect the benefits of managerial flexibility inherent in a mining plan. Real options valuation (ROV) is an alternative approach that addresses this issue. We compare the properties of NPV and ROV optimisation solutions generated for the same scenario. Our simple case study demonstrates that the presence of real operating options in the optimisation model not only entails increased project value as expected, but also tends to encourage lower processing capacity (with lower associated capital cost), higher cut-off grades and greater use of stockpiles.CITATION:Elkington, T and Gould, J, 2012. Real option value optimisation, in Proceedings Project Evaluation 2012 , pp 35-40 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012