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By W Zirima

A detailed, mine scale non-linear numerical model of Rosebery mine has been built for the purpose of simulating life-of-mine global deformations. The model was calibrated using observations of displacement and damage, and was then used to investigate the correlation between dissipated plastic energy (DPE) and seismic event occurrence. The study is unique because the seismic data was collected over a relatively short period using a temporary portable seismic system. It is the intent to undertake significantly more work, but the analysis of limited data shows that a very good, non-linear relation between DPE and event probability is present. The observed correlation is consistent with measurements from other mines where more data was available. With more data, the strength of the correlation will allow the DPE analysis to be used during the design and sequencing phase of planning to better design the mine to minimise seismic hazards.

Jan 1, 2008

By D A. Williams, J C. J Boshoff

The properties of tailings that emanate from laterite nickel processing plants are significantly different to most other mine tailings. They typically comprise a mixture of fine materials that are made up of altered clays, chemical residues and salts. Neutralisation processes that are undertaken prior to tailings discharge result in a high proportion of gypsum in the tailings. The salinity of the pore fluid is commonly higher than 140 g/L of salts, dominated by magnesium sulfate. Hydraulically-placed tailings that undergo solar evaporation typically reach dry densities of less than 1 t/m3 of insoluble solids. In situ water contents after many months of drying may be as high as 80 per cent, and peak undrained shear strengths are unlikely to be greater than 20 kPa.This type of material is not conducive to upstream raising, from both a practicality and overall slope stability perspective. Even at rates of rise of less than 1 m/a, it is difficult to effect upstream raising on unaltered laterite nickel tailings. However, the authors have successfully designed and implemented upstream-raised laterite nickel tailings storage facilities. The upstream raises have been formed from both imported natural materials and air-dried and compacted tailings borrowed from the tailings beaches.Drying and associated strength gain has been achieved through various means of mechanical intervention, repeatedly exposing a zone of tailings to the atmosphere for evaporation. Field trials have been undertaken to optimise the approach, and the findings from the trials have been implemented in practice to allow stable upstream raises to be constructed. The cost savings and reduced environmental impact compared to high-volume downstream raises have been significant.CITATION:Williams, D A and Boshoff, J C J, 2015. Upstream raising of laterite nickel tailings storage facilities, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 271–280 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By D Finn, D Kentwell

Experience has shown that the E-Type multiple indicator kriging (MIK) estimation technique often works well for resource estimation in stockwork mineralisation that contains a mixture of high and low-grade mineralisation types that are difficult or impossible to separate spatially. E-Type MIK, like ordinary kriging (OK) is a smoothing estimator and where data is sparse can result in estimates of grade tonnage curves that do not reflect the true block variability at selective mining unit (SMU) scale. The rank and replace (RR) estimation methodology is designed to reproduce both local block accuracy and true block variability at SMU scale and has shown good results when used with highly skewed unimodal diffusive style mineralisation. This paper examines the use of RR with mosaic style mineralisation typically found in stockworks via a case study using real data from Newcrest’s Telfer West Dome deposit. Resource level estimation results for ordinary kriging (OK), E-Type MIK and RR are compared to close spaced grade control models as the reference reality.Results show that stationarity requirements and declustering can severely impact on the usefulness of the rank and replace technique and that it should only be used where trends are not too strong and data are relatively uniformly spaced. This does not rule out its application to stockwork or mosaic style deposits. However, in this case, the presence of trends and different data densities requires the non-stationary domain to be further broken down into sub domains for the RR technique to be effective.CITATION:Kentwell, D and Finn, D, 2017. Testing new estimation techniques – rank and replace: a stockwork case study, in Proceedings Tenth International Mining Geology Conference 2017, pp 365–374 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 20, 2017

By S Sullivan

A recent review of resource reports lodged to statutory bodies found geological models with oversmoothed or unrealistic lithological boundaries, many of which do not represent geological appearance in the field, pit or underground drive. The underlying data is often too complex or messy to be incorporated into the resource model and is thus a simplification of reality, to the detriment of the mining operation and its shareholders. Volumes can be over- or underestimated and subsequent grade predictions can be misplaced, combining to cause over- or understatement in resource reporting to stakeholders and statutory authorities. Domain models can be improved with new modelling techniques such as machine learning. However, with poor data or improper use of machine learning techniques, the conclusions can be just as misleading as with current techniques. Machine learning rarely offers a single ‘right’ outcome, rather a range of possible outcomes from the data provided. But importantly it can take advantage of the full richness of data for more informed models. Machine learning also provides confidence in its predictions so that uncertainty in the resultant models can be quantified and passed through for risk assessment during mine planning and operation. This paper will discuss the factors accentuating complexity in deposit modelling: data diversity, structural controls, chemistry, data volumes, process workflows and external non-geological constraints. A case study illustrates the risk of reducing or ignoring complexity, which can result in an overly simplified geological model.

Mar 22, 2022

The Pacific Rim countries ofAustralia, New Zealand, Papua New Guinea, Indonesia, Fiji, Philippines and Solomon Islands will be reviewed from an equity investors perspective.   The following areas will be covered: Country risks Exploration spending and activity Project development Taxation Relative cost of doing business Environmental considerations Political/bureaucratic situations Capital raising Equity markets as a source of funds Developing market funds The aim of the paper will be to outline the most attractive areas for investment by equity and private funds plus documenting the changes needed in the less favourable countries if they are to attract investors.

Jan 1, 1995

By J Lombardi

OZ Minerals' Prominent Hill copper-gold concentrator is located 130 kilometres south east of the town of Coober Pedy in the Gawler Craton of South Australia. The concentrator was built in 2008 and commenced commercial production in early 2009. The Prominent Hill concentrator is comprised of a conventional grinding and flotation processing plant with a 9.6Mtpa ore throughput capacity. The flotation circuit includes six rougher cells, an IsaMill for regrinding the rougher concentrate and a Jameson cell heading up the three stage conventional cell cleaner circuit. In total there are four level controllers in the rougher train and ten level controllers in the cleaning circuit for eighteen cells.Generic proportional – integral and derivative (PID) control used on the level controllers alone propagated any disturbances downstream in the circuit that were generated from the grinding circuit, hoppers, between cells and interconnected banks of cells, having a negative impact on plant performance. To better control such disturbances, FloatStar level stabiliser was selected for installation on the flotation circuit to account for the interaction between the cells. Multivariable control was also installed on the five concentrate hoppers to maintain consistent feed to the cells and to the IsaMill. An additional area identified for optimisation in the flotation circuit was the mass pull rate from the rougher cells. FloatStar flow optimiser was selected to be installed subsequent to the FloatStar level stabiliser. This allowed for a unified, consistent and optimal approach to running the rougher circuit. This paper describes the improvement in the stabilisation of the circuit achieved by the FloatStar level stabiliser by using the interaction matrix between cell level controllers and the results and benefits of implementing the FloatStar flow optimiser on the rougher train.

Aug 8, 2011

By H Fukaya T Miki, J Gamutan

Molybdenum disilicide (MoSi2) is a promising material for thermal applications due to its excellent heat and oxidation resistance. It can operate at temperatures of up to 1800°C as furnace heating elements and protect refractory metals such as molybdenum from rapidly reacting with air to form volatile molybdenum oxides at elevated temperature. In this work, the feasibility of forming MoSi2 on a molybdenum substrate by hot dipping in a silicon-saturated molten metal bath was investigated. This method is simple, predictable and can be used to coat large components and complex parts. It was found that tetragonal MoSi2 can be successfully synthesised on the surface of the substrate after dipping for 15 mins at 1000°C using molten tin (Sn), bismuth (Bi) and copper (Cu) baths. The growth of the MoSi2 layer was fast within the first 15 mins and then gradually slowed down with time. After dipping for 60 mins at 1000°C, the thickness of the MoSi2 layer were measured as 441.5, 19.5 and 13.1 μm for the copper, tin, and bismuth baths, respectively. The MoSi2 coating synthesised in this study provided oxidation resistance at 1150°C by forming a protective SiO2 layer on the surface. The SiO2 layer prevented the sample from rapidly oxidising by inhibiting direct contact between the molybdenum substrate and oxygen in the atmosphere. Compared to conventional methods, the proposed hot dipping method produces a MoSi2 layer more rapidly and at much lower operating temperatures. This makes it a more attractive option for coating large and complex components, with the potential to enable the use of MoSi2 in a wider range of applications.

Jun 19, 2024

In an area north of Mowit Ica chip sampling of limonitic outcrops on a regional scale led to the investigation of a number of areas considered to be geochemically anomalous for copper and zinc. These areas were closely gridded,end where geochemical results were favourable, they were subsequently drilled or ro¦titeaned Che results indicated that for copper Lne anomalies were mainly associated wiL_ ironstone formed in areas of faulting. is suggested that copper is able to move considerable distances by ground water movement and is likely to be fixed under conditions of low pH. The movement of zinc is more difficult to explain but it appears to have an affinity for iron and is only deposited in areas having a high pH (i.e. doioiirific scdimet=Cs).

Jan 1, 1973

RME has a vision for a new mill operational paradigm made possible by RMEÆs fast, safe Mill Relining System. This vision can be moved forward into reality at any time with or without guidance from recent development in measurement and predictive modelling tools.Some new liner designs can degrade SAG mill performance because of mill volume loss, ball strike (rotational speed limitations) and other issues often brought about by optimising liners for life and without a backward glance at metallurgical consequences. Freshly relined mills can initially produce as little as 80 per cent of their maximum throughput, that maximum occurring toward the end of the linersÆ wear life. RMEÆs proposition is to design new liners for maximum commercial performance. This may mean more frequent changes of liners but with liners designed to yield optimum grinding, metallurgical and profitability performance. In other words, mill liner profiles and mill relining speed become key operational controls and not simply æmust doÆ maintenance functions. Taken to the extreme, liner profiles may prove capable of ætuningÆ a grinding plant for maximum profitability in any metal price environment. This paper provides an update regarding RMEÆs fast, safe Mill Relining System technologies and outlines RMEÆs vision of a æliner profile versus profitabilityÆ model as a function of metal price, developed intuitively or by using a combination of new measurement and modelling technologies. These new measurement and modelling tools provide the opportunity to predict the optimum commercial outcome, off-line in the virtual world, before committing to an expensive liner experiment.

Jan 1, 2006

By J Hartog, V Beehan, D Beeson

Treating an ore blend from five different deposits at Newgold’s Peak Gold Mine (PGM) has always been a challenge due to the inherent variability between each of the orebodies.Operating the processing plant at PGM with a ‘normal’ level of process control and a good operations and metallurgical team has allowed the processing plant to achieve above the name plate design at 102 t/h and recoveries in the order of 92.8 per cent for gold and 88.4 per cent for copper.With a company value and culture of striving for continuous improvement, PGM implemented the Manta Cube® system, an advanced process control system, for the semi-autogenous grinding (SAG) mill, gold leach circuit and tailings thickener over a 12-month period throughout 2012 and 2013.The overall benefits of implementing the Manta Cube® system has led to an increase in mill throughput of at least two per cent, improved SAG mill liner life, a ten per cent decrease in cyanide consumption and a reduction in flocculant of at least 30 per cent with no detriment to the gold and copper recoveries.The entire project had a payback period of less than two months, and the combined benefits resulted in an overall increase in revenue of at least $5 million per annum. This is quite significant for a processing plant the size of PGM.This paper describes the methodology, overall results and economic benefit of applying the Manta Cube® system on-site at Newgold’s PGM.CITATION:Hartog, J, Beehan, V, Karageorgos, J and Beeson, D, 2014. Optimisation of the Peak Gold Mine’s processing plant through advanced process control, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 335–344 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

Development of the Davcra flotation cell has continued over the past seven years. Preliminary testwork on single cells has now been extended to a com- plete Davcra flotation circuit, to cells ranging from 5 to 400 tons per hour capacity and to cells operating on a variety of materials. Operation of both test and production units has shown the Davcra cell to be competitive with conventional flotation machines. It offers a lower capital cost installation than conventional cells and in addition has a number of. operating advantages, particularly in its adaptability to automatic control.'

Jan 1, 1971

By L Drowley

The Adelaide Desalination Plant (ADP) draws raw sea water into the facility and returns saline concentrate to the Gulf St Vincent via subsea conduits. This paper describes the detailed design and construction methodologies developed for the cross connection tunnel excavation. The paper concentrates on key design elements which include:· lateral breakout support of the segmental tunnel lining,· ground improvement grouting in the zone of the cross connection tunnels due to extremely variable and weak ground conditions, and· excavation methodologies and proposed support types of the riser to tunnel cross connections.The design process consisted of developing concepts, detailed risk assessment, three-dimensional (3D) finite element modelling and structural analysis for temporary support of tunnel lining; functional design of the ground improvement grouting and the temporary support; and permanent lining design of tunnel to ocean riser connections in a mixed soft ground/hard rock environment.The paper also presents conclusions of the design based on construction data available, and highlights the close collaboration between the design team and construction team.

Mar 8, 2011

By F Ramos

Conventional techniques for resource estimation generally involve the laborious analysis of variograms and the specification of parameters for covariance functions. In large deposits, construction of resource models and their update require significant amount of manual work, expert knowledge and time. In this paper we take a machine learning view to the problem of resource estimation. This is a non-parametric Bayesian method, leading to automatic parameter estimation (learning). Through Bayesian learning, the parameters of the model can be obtained by optimising a quantity known as the marginal likelihood. The main advantage of this approach over conventional maximum likelihood estimators is that the objective function incorporates the OccamÆs razor principle. This allows the comparison of different statistical models û for example, models designed with different covariance functions û and naturally penalises complexity, thus avoiding overfitting. Our technique presents significant flexibility for the definition of mean and covariance functions and permits the usage of more sophisticated models.The second contribution of this work is the formulation of a data fusion mechanism that continuously updates the resource model. As mining progresses, more information becomes available. For example, the hardness of the rocks can be measured while drilling blast holes, grades of ore and contaminants are obtained from cone logging. This information is in general available at a finer spatial resolution but can be more uncertain. The data fusion mechanism can seamlessly estimate the uncertainties of the different types of information and fuse them as new measurements are acquired. This procedure can significantly improve the quality of the resource model, defining new grounds for stochastic mine planning. We demonstrate the effectiveness of our approach in estimating iron ore deposits by integrating information about different grades.

Sep 26, 2011

Mining operations in the Obuasi mine of AngloGold Ashanti Limited began in 1897 using mainly gravity concentration and amalgamation to recover the gold from predominantly high-grade quartz ores. The mine is primarily an underground operation, although some surface mining still takes place. Ore is currently processed by two main treatment plants: the Sulfide Treatment Plant (STP) for underground ore and the tailings treatment plant for tailings reclamation operations. STP was commissioned in February 1994 to treat 180 000 t/m of double refractory gold ore and it hosted the then world's largest commercial scale bacterial oxidation plant which uses Gencor's BIOX« technology. Gold is recovered by gravity and flotation, with the regrinding of the sulfide concentrate before bio-oxidation to liberate locked gold in sulfi de minerals. The BIOX« product is leached using the carbon in leach (CIL) process. Gravity gold recovery is a major component of STP operations and its contribution to overall plant recovery is about ten to 13 per cent. Gravity recovery has undergone series of technological upgrading, since the very first circuit which consisted of a Knelson concentrator and a Gemeni shaking table which was incorporated into the milling circuit at the start of the plant. Presently, each of the gravity circuits which consists of Knelson concentrator(s), cyclones and Gekko InLine Reactors (ILR), are located at the Milling and BIOX« circuits. More recently a new gravity recovery facility comprising of four 48 inch Knelson concentrators and cluster of ten inch cyclones have been incorporated at the tail of the flotation circuit. An additional ILR will be commissioned in 2010 to treat the concentrate generated from the new Semi Autogenous Mill #2 (SAG 2) Knelson: concentrator tower under construction. Since the inception of STP, significant gravity recoverable gold has been recovered via Knelson concentrators and the employed circuits have seen a number of modifications and upgrades, motivated by ore mineralogical changes and recovery concerns. The pioneering adoption of the ILR technology in 2001 and 2003 was a critical factor in enhancing the improved recovery benefit of the gravity circuits. Therefore the objective of this paper is to highlight the mine's experience in the gravity recoverable gold process with emphasis on plant modifications and gravity equipment upgrade. Operational challenges and the contribution of gravity gold to overall plant recovery are also discussed.

Aug 1, 2010

Alluvial mining even of shallow deposits is often economically a marginal proposition and causes significant disruption of the land surface through the need for large scale excavation. In-situ leaching using chlorine-based solutions eliminates the need for excavation, the disruption of surface activities, and may greatly reduce processing costs and improve recovery especially of fine gold. A spreadsheet model has been developed to design and analyse the economics of in-situ leaching of alluvial deposits. In-situ leaching of shallow deposits may be achieved in a number of ways including solution infiltration via perimeter ditches or the use of injection and production wells. In most instances deeper alluvials may only be processed using well systems. Two deposits are analysed in this paper. The first consists of one metre of payable wash beneath one metre of overburden. Some thirty fields per year are treated processing 450 000 BCM per year at a cut-off grade of around $4/tonne ($8/rn3 or the gold value equivalent of 0.26 gh or 0.52 g/m3). The principal costs are well drilling and labour. Sensitivity analysis indicates that doubling the throughput halves the cost. The economics of the project are relatively insensitive to reagent costs and consumptions, and halving the recovery doubles the cut-off grade. Shallow deposits treated using the infiltration ditch system may be marginally cheaper and more conveniently managed although this depends on the relative cost of digging the perimeter ditches. In a second example, deep leads with one metre of wash beneath 30 metres of overburden necessitate significant drilling and feature reduced throughputs as a consequence. In the example chosen 30 fields a year are processed for an annual throughput of 65 000 tonnes costed at around $20/tonne (1.4 g/t Au equivalent, $40 /m3). Sensitivity analysis indicates that throughput, and drilling cost per metre are not important but there is a high sensitivity to recovery and to the depth to payable wash.

Jan 1, 1992

By M Z. Abzalov

Drilling mineral sand deposits has specific challenges, which are different from drilling hard rock deposits: Drilled sequences are represented by non-consolidated free-flowing sands to semi-consolidated clayey sands and indurated layers. Valuable heavy minerals (ilmenite, rutile, zircon, leucoxene) have an average density of 4.6 g/cm3, which is significantly heavier than the hosting sand matrix; mainly represented by quartz (density = 2.6 g/cm3). The large difference in the mineral densities can result in sample segregation in the drilling rods and capturing devices causing biased composition of the recovered samples. The drilled strata can contain beds of consolidated sediments, hard pan lenses and concretions. Therefore, chosen drilling equipment should be flexible and permit a switch from drilling the free-flowing sands to hard rock drilling. Thickness of the sand hosted mineralisation varies from several metres to more than 170 m. Mineralisation is distributed above and below the water table. Evaluation of the mineral sands deposits is based on hundreds of drill holes and many thousands of samples, therefore drilling methods should be fast and cost effective. The drilling methods commonly used for mineral sand deposit evaluation, include aircore, triple tube diamond and sonic; including its variants, such as vibrocore drilling technique. The ability of the studied drilling techniques to properly address the above listed challenges in mineral sand deposits, whilst maximising the quality of the obtained samples has been compared in three deposits: Corridor Sands (Mozambique), Richards Bay (Republic of South Africa) and Fort-Dauphin (Madagascar).This study has shown that aircore samples tend to be negatively grade biased, underestimating the heavy minerals content, in particular when drilled intervals are located below the water table. Triple tube diamond core method can produce non-biased samples. However, results can be marred by incorrectly chosen drilling mud. Sonic drilling is a relatively new technique based on a high frequency vibratory technology. It is the only production drilling technique that allows a continuous relatively undisturbed sample of unlithified sands to be obtained. The main limitations of this technology preventing its wider use for developing mineral sand resources are the relatively high drilling costs, in particular when the depth of drilling exceeds 100 m, and speed of drilling advance.

Oct 5, 2011

Bolivia, due to its turbulent past with a history of constant military coups, has given an image of complete instability to the foreign investor. The effects of this have been several fold, the major one resulting in a complete lack of exploration in modern terms since their revolution in 1952. What was overlooked by the foreign investor was the fact that revolution produced Agrarian Reform which is the foundation of the stability which Bolivia enjoys today. Another factor that is overlooked is the fact that its past history is one of vast mining fortunes having being made. Their political problems resulted in economic chaos in 1985 with an annual inflation rate of 26,000 percent. This resulted in the collapse of the government but the democratic process continued. Then came the so-called"South American Miracle" in 1986 when the government of Dr. Paz Estenssoro enacted an extremely harsh austerity program which consisted of the abolition of wage and price controls, the abolition of monopolies, the right to hire and fire, the weekly auctions of dollars and the free convertibility of currency which yielded a stable government with 8 percent inflation. This was followed by massive personnel reductions in the various mines and other industries.

Jan 1, 1991

By Fuerstenau DW

The flotation of pyrite in ethyl xanthate solutions is presented along with electrokinetic results. The results have been analysed in view of recently published thermodynamic calculations as well as other published data on the pyrite-xanthate system including adsorption and voltarnmetry studies. The flotation response of pyrite in xanthate solutions is characterised by two maxima, one at pH 4 and the other at pH 8-9. The acidic maxima is also associated with a reversal in the electrophoretic mobility of pyrite, probably due to the formation of ferric xanthate on the pyrite surface through chemisorption of xanthate ions while the basic maxima is not associated with major changes in the mobility and flotation at this pH can probably be attributed the adsorption of dixanthogen. It is concluded that there is not sufficient experimental evidence to conclusively attribute the lack of flotation response in solutions at near neutral pH to any particular phenomena, either kinetic or thermodynamic.

Jan 1, 1993

By C Boyle

Brockman 2 mine is located in the Pilbara of Western Australia and is operated by Rio Tinto Iron Ore. Mineralisation is hosted by synclines where there is structural complexity to focus fluid flow. Mineralisation is hosted by the Brockman Iron Formation. Mining is on 10 m benches and blastholes spaced at 6 - 8 m apart are geologically logged, sampled by shovel cuts, and assayed using X-ray fluorescence for ten chemical variables. Blast blocks are digitised by mine geologists to assign destinations of material within blasts. Resource evaluation drilling is on a spacing of 50 m × 50 m across known mineralisation and consists of recent reverse circulation drilling and older open hole percussion drilling. Sampling of resource evaluation drilling is by rotary splitters or riffle splitters, and assaying is by X-ray fluorescence for ten chemical variables. Ordinary kriging of resource evaluation produces a long-term resource model. This study examines whether mine planning would be improved by using a blasthole estimate to extrapolate grades into deeper benches and merging the blasthole estimate with the long-term model made using resource evaluation drilling. The two estimates are merged into one model using an inverse weighting based on kriging variance. However, reconciliation results in a test bench show the original estimate made using resource evaluation drilling more closely matches mine geology block outs than does the merged model. This is due to a local trend of more high grade and higher iron grades of high grade in the area. The blasthole estimate of deeper benches must use extrapolation and it is diffi cult to take local trends into account. In contrast, the estimation using resource evaluation drilling is mainly interpolation and is better able to handle local trends.

Jul 11, 2011

By C E. Woolley, A Hosseini, J Foster

Northern Star’s Thunderbox Open Pit C-Zone cutback was designed to maximise extraction in a short life excavation; In fresh rock on the western wall this included 20 m to 30 m bench heights with 6.5 m to 10 m berm widths and a 90° pre-split angle. Rock mass quality in this area is generally fair to good, however, there are sections where the dominant foliation runs parallel with the designed pit wall, and more closely spaced, altered, foliation is present: these areas are difficult to predict and prone to failure. Stringent controls and monitoring were required in order to safely access below these areas, in particular the use of slope stability monitoring radar, Trigger Action Response Plans (TARPs), re-entry procedures, visual inspections, drone inspections and day-to-day personnel awareness of the hazard. Robust and comprehensively planned remediation was also required after two significant slope failure events where long reach equipment and rope access techniques were utilised to remediate the areas in question safely, but also in a timely manner, such that expected production targets were impacted as little as reasonably practicable. This combination of rigorous risk management and well planned remediation resulted in a successful and complete extraction of the C-Zone cutback with no impact to operational safety.

Jun 22, 2022