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In February 1995, Falconbridge Limited approved the construction of a nickel mining and milling facility on its Raglan property situated in the Nunavik region of northern Quebec, Canada. The construction period successfully terminated with the commissioning and start-up of the plant and concentrator in early-December 1997. The estimated life of the project is 20 years with an annual mining rate of 800 000 tonnes of ore, producing 21 000 tonnes of nickel per year. This paper discusses the subject of æRemote Mining in the Canadian ArcticÆ as it applies to the Raglan mine process and people. During the feasibility stage of the project, many assumptions were made which influenced the design and operating parameters of the facilities and the equipment. Transportation, communication, remote logistics techniques and standard industry practices required to support a æfly-in/fly-outÆ operation were reviewed and either adopted or rejected for use at Raglan. These assumptions were æmade to fitÆ the uniqueness of our planned operation. It was also acknowledged that many of them would ultimately impact on the people required to staff the operation following construction. Therefore, their suitability and applicability were examined from an economic, operational and human perspective. In a continuing effort to improve the quality of life for Raglan employees, as well as the economics of our mine operations, these assumptions are under constant review and scrutiny. There is no doubt that experiences gained, and willingly shared by other North American arctic mining operations, proved invaluable and are a big reason for RaglanÆs overall success thus far. The mining industry is being challenged technically to develop lower grade orebodies at the lowest possible cost. In addition to environmental constraints, serious social, political and moral questions are being asked and added to this list of challenges. Miners throughout the world must improve their operating standards and public image if we want to attract the best possible employees. Remote mining operations provide a unique opportunity to experiment with various human resource concepts as well as demonstrate the industryÆs commitment to environmental and community concerns.

Jan 1, 1998

By M Allen

Energetics has been in the business of climate change for more than twenty years. This experience has only served to cement the understanding that decisions taken during design define the environmental and economic performance of any project. The 80-20 rule definitely applies, with 80% of a project’s performance being set through the first 20% of design decisions. This in depth knowledge is used for determining energy price forecasts, future carbon markets and carbon costs, current and future energy technologies, as well as giving a thorough understanding of the processes and technologies in place in the mining industry to work out what the most carbon and energy sensitive decisions during design are. Project selection and design is a gated process where decisions are taken in line with the information available at that point in the evolution of the project. Design decisions are, by their nature, dominated by uncertainty. In order to ensure that robust decisions are taken, it is necessary to ensure that the correct information is brought to bear at the correct decision point. This then defines and supplies the necessary carbon and energy information for design decisions to be correctly made. One of the most significant risks facing design engineers and decision makers in the mining industry is the future cost of energy. Part of this risk is associated with a future cost of carbon, however, a significant part of this risk is the cost, and variability in this cost, of the energy itself. This paper investigates the information required to support good decision taking during the design process.Project Managers and MetPlant Operators accept poor quality evaluations because they are generally unaware of what they should expect.The 2010 draft AusIMM ‘Guidelines for Techno-Economic Evaluations’ were collated by a subcommittee of practitioners and are regarded as best practice.They apply directly to projects and metallurgical plant evaluations, including those with a heavy technical basis. They can be applied to technical problem solving where there are no monetary computations.Project Managers and MetPlant Operators should demand that economic models and evaluations follow the six principles. They should become working tools which are easy to understand, fit for purpose, consistent, rigorous, record sources of input data, have key graphs and are rapid to audit.

Aug 8, 2011

By P D. Munro

On the occasion of the 14th Mill Operators’ Conference and marking 40 years since the first one was held in Mount Isa in 1978, it is fitting to review the history of the Conference and its development over that time.The first 10 Conferences were irregularly held at three to four year intervals, with 9 of these in regional centres of Australasia. It is only since 2012 that the Mill Operators’ Conference has become a regular biennial event, alternating with the MetPlant Conference.The number of people attending the Conference has more than doubled to 470 delegates at the 13th one in 2016. It has outgrown its regional beginnings.Papers presented to the previous Conferences have been analysed according to commodity, country of origin, technology and theme plus the affiliation of the authors to discern any trends that may assist in planning the future events.Suggestions are made as to how the AusIMM might wish to arrange its mineral processing/metallurgical conferences.Recent changes to the structure of the Conference providing a more meaningful experience for the delegates and increasing their interaction and involvement should be vigorously pursued.CITATION:Munro, P D, 2018. Mill Operators’ conferences – a 40-year retrospective and a vision for the future, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 5–14 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By L Snyman, S Webster and J Samosir

Northparkes is located 27 km north of the township of Parkes in central New South Wales, Australia. The operations consist of underground block cave mines and an ore processing plant, which produces high-grade copper and gold concentrate. Production is currently sourced from the E48 Lift 1 block cave mine and open cut stockpiles. Mining commenced at Northparkes in 1994 as an open cut operation. Underground block cave mining began in 1997. Northparkes was the first mine in Australia to use the highly efficient block cave mining method, which relies on gravity and natural rock stresses to fragment and recover the ore.The E48 extraction level is located approximately 581 m below surface and consists of ten extraction drives and 214 drawpoints. Several stress measurements carried out at various levels in both E26 and E48 indicated a low underground regional stress environment and a low to moderate stress state in the E48 orebody. The E48 block used a post undercut strategy that was initiated in 2009, with production commencing in September 2010 and cave-through to the surface occurring approximately four months later in January 2011. Changes to the cut-off grade and fixed prices meant that Northparkes was able to develop an additional two drives to the north of the existing cave and one additional drive to the south. Modelling of the cavability of the additional drives indicated that the cave would not readily propagate to sufficient height of draw to mobilise the ore and tended to arch over to the existing cave shape. Based on modelling and a desire to reduce the risk of the project, preconditioning was adopted. Along with the requirement of safely hydrofracturing an active cave, a measure of the success of the preconditioning was desired. Few block cave operations have developed extension drives adjacent to existing caves.This paper summarises the lessons learnt from the development of this extension project, with a specific focus on ground control and monitoring.CITATION:Snyman, L, Webster, S and Samosir, J, 2016. E48 cave extension at Northparkes, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 111–118 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Nakahiro Y, Wakamatsu T

In the present study, from experimental results, a new concept of possibility of flotation separation of quartz from feldspar is presented. The effect of the nonionic surfactant Brij 58 on the flotation behaviour of quartz and feldspar has been investigated. The effect of the surfactant adsorption at the solid-liquid interface was also studied. The results demonstrate that maximum flotability of quartz occurred at low concentration of surfactant. Feldspar is not collected by this surfactant. Flotation tests with feldspar that had previously been subjected to leaching by hydrochloric acid yielded similar flotation response as that of quartz. The effect of removal of alkali cations from feldspar surface on its flotability was investigated. The effects of inorganic and organic additives on the flotation recovery of quartz are discussed in terms of the slating-out or salting-in properties of these additives. KEYWORDS: Alkyl polyoxyethylene; feldspar; flotation; nonionic surfactant; quartz; salting-in; salting-out; separation; silanol groups.

Jan 1, 1993

By M Dean, M Nehring, P Knights, M S. Kizil

Integrated continuous mining techniques such as fully mobile in-pit crusher and conveyor (FMIPCC) systems offer inherent labour, energy and environmental benefits to deep pit metalliferous mines. However, before such systems become commonplace, a number of barriers must be overcome.This paper outlines a number of commonly perceived barriers to FMIPCC application, together with a number of suggested solutions. The paper advances a design approach for specifying FMIPCC systems for deep pit metalliferous applications. A novel FMIPCC configuration is advanced using a hydraulic excavator in backhoe configuration. Because of the requirement to minimise belt extensions, a mine planning approach is presented based on a series of parallel and radial belt conveyor moves.The FMIPCC system does not fully replace truck-shovel systems. In the proposed mine plan, sinking is undertaken with truck-shovel systems using a series of box cuts, whereas pit ‘widening’ activities are accomplished via the FMIPCC system. Because of inherent differences in mine sequencing, the net present value derived from the FMIPCC mine will differ markedly from that derived from traditional, nested-pit, truck-shovel mining approaches. Therefore, any comparison of the FMIPCC and truck-shovel approaches must take into account radically different mine planning approaches.CITATION:Dean, M, Knights, P, Kizil, M S and Nehring, M, 2015. Selection and planning of fully mobile in-pit crusher and conveyor systems for deep open pit metalliferous applications, in Proceedings Third International Future Mining Conference, pp 219–226 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By D R. Venkatesulu, N K. Nanda

Due to increased production of steel in India, the thrust is now on iron ore producers not only to enhance productivity from existing mines, but to look also into alternative resources, like lean grade iron ores such as banded haematite quartz (BHQ)/banded haematite jasper (BHJ), which are available in abundance but not yet utilised for want of suitable process technology. In this context, BHJ ore from the Bellary-Hospet sector was collected and subjected to detailed physical, chemical and mineralogical characterisation and beneficiation studies. The as-received sample was found to occur physically as alternating layers of haematite and jasper. The chemical analysis of the sample was 41.20 per cent Fe, 39.10 per cent SiO2 and 0.86 per cent Al2O3. Based on the mineralogical observation, haematite was found to be the lone ore mineral and jasper was the major gangue mineral. The microscopic observations revealed that the ore minerals liberate at a top size of 0.150 mm. Guided by the characterisation results, indicative tests were conducted using gravity and magnetic separation equipment, namely, Floatex«, gravity slime table and wet high intensity magnetic separator (WHIMS). The results indicate that it is possible to upgrade the sample by both gravity and magnetic separation techniques. However, the WHIMS results indicate that jasper grains report to the concentrate at higher gauss intensities. Therefore, based on the encouraging gravity separation results and the availability of new design spirals for treating fine particles, the applicability of gravity spirals for beneficiating BHJ in the liberation size range of -0.150 mm was studied. The sample was ground to a top size of 0.150 mm and was subjected to preconcentration using wash waterless spirals. Tests were conducted at different feed rates, pulp densities and splitter positions. The results indicate that it is possible to upgrade the sample from a feed grade of 41.20 per cent Fe to a preconcentrate ranging from 46 per cent to 62 per cent Fe with a yield ranging from 19 per cent to 55 per cent. The obtained preconcentrate was then subjected to a cleaning stage by using a combination of wash water and wash waterless spirals. The test results indicate that it is possible to obtain a final concentrate assaying 65.75 per cent Fe and 4.75 per cent SiO2 with a yield of 25.9 per cent and an iron recovery of 41.31 per cent. It was concluded that further test work is necessary to increase the recovery and improve the product specification.

Jan 1, 2009

By J Herrmann, J Richards, B Hutchison

An extensive trial of laser-based survey and monitoring systems at Hillgrove Resources Kanmantoo Copper Mine in the Adelaide Hills, South Australia, has proved the capabilities of the system in monitoring rock movements on open pit walls. Initially, the trial involved deploying a Maptek I-Site 8820 laser scanner and the proof-of-concept Maptek Sentry software in the Nugent Pit to monitor ductile rock movements located up to 260 m away. The system was proven to be capable of monitoring various rock movements from 1.5 tonne rockfalls up to a 40 m high toppling wall failure. Data collected from smaller rockfalls was used to help build a database for Hillgrove’s rockfall management program. As part of the trial, the laser scanner was deployed to monitor a ramp movement event, as well as the toppling failure, adjacent to an IBIS slope stability radar. Both devices monitored the slump and the slowly developing toppling movements, with similar results. Although the radar was used as the successful ‘critical alarm’ device for the toppling failure, post-failure analysis showed the laser-based system to be capable of performing a similar role in the ductile rock regime; albeit over much shorter distances than the radar capability. A second laser scanner was deployed to monitor Kanmantoo’s Emily Pit in early December 2014, where it successfully provided critical alarm warnings for a block topple event. Sentry software, which takes advantage of Maptek I-Site 3D spatial imaging technology, was first released in November 2014 to meet industry demand for a cost effective, flexible system to detect movement. Sentry has now been re-launched as a fully transportable monitoring system. Deployed in a custom trailer, the system offers a power and communications module, cellular and Wi-Fi networking and a stable bollard for the I-Site laser scanner and Sentry software. This paper will present rock wall movement data from the Sentry trial and a subsequent two years of monitoring of the open pit walls at the Kanmantoo Copper Mine, at distances out to 750m. In addition, examples of remote geological mapping and small rockfall detection, using the laser scans, will be described. The Sentry system has proven to be beneficial for the continual improvement of slope monitoring and risk management at hard rock mines. CITATION:Hutchison, B, Richards, J, Richards, J and Herrmann, J, 2018. Mine rockfall and rock wall failures – proven digital laser-based approach for monitoring slopes at the Kanmantoo Copper Mine, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 463–472 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

Located 350 km west of Sydney and 20 km outside Orange, NSW, lies the Ridgeway Gold Mine û NewcrestÆs flagship Underground Gold Mine. Key to success at Ridgeway has been the fast tracked development of the 3.8 km, 1 in 5.3 conveyor decline which houses the 850 t/hr conveying system feeding the dedicated Ridgeway Concentrator, built adjacent to the existing Cadia Hill Concentrator. Eroc was contracted to develop the steep conveyor decline, drawing on its personnel and experience from past metalliferous, tunnelling and coal mining projects to complete the ambitious schedule within 12 months. This paper deals with the complexities and experiences in safely delivering what is understood to be one of AustraliaÆs steepest declines of any substantial length in a metalliferous mine.

Jan 1, 2002

By G J. Harbort, V Lawson, L Reemeyer

The Jameson Cell is a high intensity flotation device, which utilises induced air from the atmosphere. It was developed jointly by Mount Isa Mines and Professor Graeme Jameson of the University of Newcastle in the 1980s. It is proven to generate fine bubbles, in the order of 300 to 500 ¦m, in a high intensity, high shear and compact zone contained in the downcomer. This aerated mixture exits the downcomer into the pulp zone, which is the quiescent mineral and gangue separation zone. A number of Australian base metal flotation circuits feature a reverse flotation stage at the head of the circuit. Testwork and plant operating data has shown that the use of a Jameson Cell in the prefloat cleaner application has further improved prefloat gangue recovery and selectivity. Operation of a Jameson Cell in a carbonaceous/pyrite prefloat cleaner duty at the Mt Isa copper concentrator increased copper recovery and reduced pyrite in the copper concentrate. Testwork at Zinifex Century Zinc Mine showed a decrease in zinc losses by the utilisation of Jameson Cell prefloat cleaner. Appraisal of a Jameson Cell in a scalping role within the Mt Isa Copper Concentrator indicated significant benefits could be achieved.

Jan 1, 2005

The Cannington silver lead zinc deposit is located near Mt Isa in North West Queensland. This world class orebody is owned by BHP World Minerals (BHP) and is estimated to contain 45 million tonnes of ore at an average grade of 11 per cent lead, four per cent zinc and 500 grams/tonne silver. At BHPÆs planned 1.5 Mtpa extraction rate, the mine life will exceed 20 years. Construction of the underground mine, which commenced in August 1993, was carried out by Peabody Resources Ltd (Mining Services Division) (PRL) for BHP Minerals Pty Limited (BHP) under contract packages totalling approximately $100 M using several innovative techniques to deliver safety, quality and time related project goals. Client/Contractor Partnering, resulting in harmonious working relationships, a combined commitment to the achievement of an excellent safety record, and a seamless transition from the construction phase to operation of the mine, has been a feature of the project.

Jan 1, 1998

The transition from low stress to high stress conditions is a challenge eventually faced by most mines in Australia that extend to depths greater than (generally) about 1000 m. In areas with strongly adverse 'stress versus depth' gradients, such as some parts of Western Australia, significant stress-related problems have occurred at depths as shallow as 300 m below surface. The actual depth at which the 'transition' occurs is a function of the local pre-mining stress field, the strengths of the various rock types hosting the deposit and the layout and sequencing adopted in the mine. Stress-related damage can result in increased support costs, and delays associated with rehabilitation and disruption to production. In the worst case, where strong seismicity and associated damage occurs in active mining areas, 'exclusion' zones and 're-entry' protocols may be required. These can severely disrupt production. A key aspect of managing the transition is the recognition of the onset of stress-related ground behaviour. Damage mapping can be used to develop understanding of the relationships between mining activities and the local and regional response to them. Carefully documented case histories provide a basis for calibrating numerical models. This paper discusses some of the typical styles of ground behaviour observed in higher stress conditions in underground mines. A simple damage classification scheme is described to assist in 'damage mapping' of mine tunnels. An example of damage mapping is presented to illustrate an approach commonly used for recording stress-related damage.

Nov 25, 2010

By D J. A Van Zyl, J C. Cunning

Technological advances associated with the expanded application of paste technology in underground mine backfilling are now stimulating an interest in the disposal of process tailings as paste in the surface environment. Concurrent with the development of alternative surface tailings disposal practices is the requirement to fully understand the consolidation behaviour of tailings in paste form, and to relate this understanding to the significant body of data and operating experience from decades of study of the performance of hydraulically placed tailings. One effective method for demonstrating the benefits derived from handling and placement of tailings as paste is to review tailings slurry consolidation theory from the perspective of the changes which take place in the material as it makes its transition from a loose slurry to a dense, stable deposit resulting from managed thin-layer deposition. For a typical process tailings, an example is provided which illustrates the effect which mechanical dewatering has in accelerating the consolidation process and thereby providing a range of benefits from the perspective of surface disposal. Increased rates of filling (rise), expanded use of upstream embankment construction methods and elimination of impounded surface solutions are some quantifiable benefits which can be assembled on a site-specific basis to allow for valid comparisons with more traditional approaches to tailings disposal.

Jan 1, 1998

By J Carrillo, A King

Gravity recoverable gold (GRG) is largely distinguished from other gold by its non-mineralised, metallic form, its high degree of liberation from the ore and its appreciable particle size. The gold mining industry has so widely accepted the use of batch centrifugal concentrators (BCC) and intensive cyanidation (IC) systems for the recovery of GRG that these may well be considered requirements of any plant processing ore containing appreciable GRG. The recovery of gold by gravity is quick, easy and cheap by comparison to alternatives. However, there are cases where attributes of the ore make recovery of gold by gravity and IC unusually challenging. This paper describes three examples where such challenges have been encountered and met, including those where the ore contains cyanide soluble base metals and where fine GRG is to be recovered from flotation concentrate.CITATION:King, A and Carrillo, J, 2018. Addressing challenging applications of intensive cyanidation in gravity gold recovery, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 283–290 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By A Finch, C Pridmore

The Cosmo Project falls within the Archaean to Palaeo-Proterozoic Pine Creek Orogen, one of the major mineral provinces of Australia.The Cosmo Deposit is interpreted to be a series of steep north-west-plunging gold mineralised vein, breccia and shear systems within the tight Howley Anticline and hosted within interbedded siltstones, mudstones, banded iron, phyllites, dolerite sills and greywacke.A folded environment poses a number of technical challenges, particularly for estimation.Handling of tightly folded and in some cases narrow domains might include subdomaining for orientation, omni-directional three-dimensional (3D) estimation within constrained domains or software-enabled unfolding/un-wrinkling procedures (transformation of the data and estimate space into a two-dimensional environment). Each technique has its own unique set of advantages and disadvantages.A further method (one applied at Cosmo) is where the estimation parameters (specifically search and variography orientation) are modified in a frequent or ‘dynamic’ sense to suit the orientation of the domain whilst maintaining 3D space. Control of the resource estimation orientation can be done in several ways, including the use of sectional panels of a specific size or, alternatively, orientation sector divisions. The sector approach provides some significant reductions in processing time over the panel technique and could be applied in a number of software packages.Three-dimensional ‘dynamic’ interpolation reconciles well with production data from Cosmo, whilst the sector method provides a practical technique that can be executed without the complications of transformation or the need for labour-intensive orientation subdomaining and with acceptable resource estimation run time.CITATION:Finch, A and Pridmore, C, 2014. Dynamic interpolation – estimation in a folded environment at the Cosmo Deposit, Northern Territory, Australia, in Proceedings Ninth International Mining Geology Conference 2014 , pp 107–114 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By G Booth

Whilst communications systems in the mining industry have evolved over the years, the premise remains consistent that reliable communication is vital for safety and operational efficiency. TodayÆs open pit mines are benefiting from advanced developmental efforts based on mesh networking hardware and software technology. This paper highlights Rajant CorporationÆs adaptation of technology, originally developed for the defence and first responder industries, to provide wireless network connectivity in open pit mining applications. Featured is the large-scale deployment of over 300 mobile, meshing access points in the Bingham Canyon Copper mine near Salt Lake City, Utah, the worldÆs largest open pit copper mine. Many companies have positioned themselves, their technology and their product line in the arena of rugged outdoor wireless broadband mesh networking infrastructure. However, Rajant Corporation has combined specialised command and control software and portable networks which offer network extensibility and redundancy that are not available in any other networking solution. Rajant CorporationÆs BreadCrumb« offers unique traits in portability and non-line-of-site networking nodes which intelligently route and broadcast in standard 802.11 protocol. The advantage of RajantÆs solution is especially valuable for users needing equipment moved easily and rapidly into and out of the theatre of operations with uninterrupted network availability. The main differentiators that set the BreadCrumb« network apart from the competitors are mobility (continuous availability), simplicity, ability to properly load balance and power options. In 2007, RajantÆs BreadCrumb« wireless mesh system was selected by the Kennecott Utah Copper Corporation (KUCC), a wholly owned subsidiary of Rio Tinto, as its primary communications platform for operations within the Bingham Canyon Copper mine, the worldÆs largest open pit copper mine. The Rajant BreadCrumb« technology enables KUCC to gain additional operational efficiencies by tracking, monitoring and managing its copper mining operations. The primary goal of using the BreadCrumb« wireless mesh system Kennecott was to streamline its complex mining operations. KUCC required a high number of moving wireless nodes for improving mine monitoring and control. The Rajant InstaMesh« software running on the wireless BreadCrumb« units connects hundreds of devices to each other while rapidly transporting critical operational data. Kennecott has successfully implemented a large number of BreadCrumb« radios in an interconnected network that allows loader trucks, shovels, pumps, laptops and other production equipment to communicate with each other in real-time. These systems are a mix of secure access nodes that enable data and voice communications across a meshed, self-healing network for fleet dispatch, health monitoring and other critical mining applications. Many of the devices that require wireless communications are moving at all times throughout the wireless mining infrastructure. The BreadCrumb« nodes rapidly adapt to any changes in the network topology, assuring that IP traffic uptime and bandwidth are maximised. The installation layout and data network specifics, as well as maps and data network efficiencies will be detailed in the paper.

Jan 1, 2008

By D Henderson, M Germain

The beneficiation of iron ore deposits to yield haematite and magnetite concentrates for steel making processes typically require the use of one or a combination of wet processing techniques based on gravity, magnetic or froth flotation processes. With the need for more cost-effective technologies with a lower water demand, a re-examination of dry processing techniques has been initiated. For example, a dry processing capability may offer an advantage where suitable quality and quantity of process water hinders the development of a particular resource. This paper describes recent laboratory test work for the production of high grade concentrates using dry electrostatic techniques for -300 ¦m haematite and magnetite ores and compares them with magnetic separation techniques.

Jan 1, 2009

By R Bertuzzi

"This paper presents preliminary results of ongoing research being carried out at the University of New South Wales Australia (UNSW) into improved methods for estimating rock mass strength. In this paper the rock mass strength of Hawkesbury Sandstone is assessed. An estimate is first made based on an extensive database of intact rock strength data being collated by the author and the assumption that rock mass strength can be determined following the geological strength-index (GSI) approach. The resulting strength envelope is then compared with nine documented case studies where stress induced failure has occurred in tunnels excavated within Hawkesbury Sandstone. The case studies cover a range of conditions: construction dates from 1880s to 2006 spans from 3.2 to 12.5 m depths from 17 to 124 m excavation methods of drill and blast, roadheader and tunnel boring machine (TBM).Finite element modelling is used to assess the likely magnitudes of the principal stresses that were present at the time of the failures. The finite element models are interrogated to provide the values of major and minor principal stresses in and around the mapped failure zones. Failure and stable points are then compared to the proposed strength envelope(s) of Hawkesbury Sandstone derived using the Hoek-Brown and the spalling criteria. The ability of the Hoek-Brown rock mass strength criterion to differentiate between the ‘failed’ and ‘stable’ zones is considered to be remarkable.CITATION:Bertuzzi, R, 2014. Estimating the rock mass strength of Hawkesbury Sandstone, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference, pp 417–424 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 5, 2014

By J E. Everett

Ore selection is generally a highly subjective task, with emphasis on producing product with a consistent target grade matching a perceived market requirement. A composite selection criterion ‘Comp’ (a linear function of the grade vector) can be used to maximise ore tonnage at a specified target grade (in Fe and contaminants) extractable from a block model. The blocks correspond to the selective mining units, with grades interpolated from diamond drill hole data. An iterative procedure has been developed to identify the coefficients and cut-off value for the composite function ‘Comp’, maximising potential ore tonnage at target grade.Commonly, target grade is predetermined by marketing; however, there is no guarantee that maximising ore tonnage at a specified target grade maximises the potential value of the mine. If the value of ore could be expressed as a linear function of the grade components, then these coefficients would be appropriate for the selection criterion ‘Comp’. The cut-off value for ‘Comp’ would correspond to the marginal cost of production; all blocks with a ‘Comp’ score above the cut-off would be classified as ore; and the cumulative grade of these ore blocks would be the average product grade over the life of the mine.Unfortunately, no such value function for iron ore is generally available. Methods for estimating the value function are discussed, using the spot price and sensitivities based either upon operational tolerances for Fe and the contaminants or upon published price differentials. This approach has been applied to an anonymous Pilbara deposit with about one million blocks averaging 1.1 kt. It is shown how the optimal target grade, cut-off grade and maximum tonnage can all be explored as a function of marginal cost and iron ore price. Alternatively, given marginal cost and an iron ore price, the effects of changing the tolerances (and therefore the relative costs of the contaminants) can also be explored.It is suggested this procedure can enable informed decision-making for an iron ore mine. Rather than setting final policy for the entire life-of-mine, the method enables target grades and tonnage estimates to be revised by re-computation as the mine life proceeds to recognise changes in market conditions and knowledge about the resource.It should be emphasised that this paper is concerned with ore selection rather than ore sequencing. Appropriate ore selection is a necessary but not sufficient condition for maximising value. Having identified the set of blocks that potentially maximise value, the sequence in which they are mined will present a trade-off between producing at constant grade and extracting high value ore early. The sequencing issue is not considered here. It is shown that optimum ore selection for an open pit mine is independent of any consideration of discount rates, although ore sequencing will depend upon the time value of money if the product grade is to vary across time.CITATION:Everett, J E, 2015. Ore selection to maximise value, in Proceedings Iron Ore 2015, pp 443–448 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By P Myers, T Elkington, S Wonday

Sierra Rutile LimitedÆs (SRL) heavy mineral sand mining operation in Sierra Leone, West Africa, is embarking on a new phase of its life. After confronting many challenges during the 1990s and 2000s, SRL is embarking on a strategy of growth to recover maximum value from the mine over the rest of its life. Sophisticated linear programming techniques have been used to develop an optimum strategy for extracting SRLÆs many known deposits of economic grade, while considering options for expansion and for a variety of mining and processing methods and combinations. CITATION:Myers, P, Elkington, T and Wonday, S, 2012. Strategic optimisation at Sierra Rutile - A case study in maximising project value, in Proceedings Project Evaluation 2012 , pp 59-66 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012