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By A Jankovic, D David, P Payne

Although the majority of current steel production is supported by iron ore sourced from high-grade haematite deposits, the long-term growing demand for steel has led to higher raw material prices and opened the way for many new magnetite deposits to also be developed. There is a rich and long history of magnetite ore processing in Western countries, including large operations such as Cleveland Cliffs in the USA and LKAB in Sweden, as well as smaller operations like Savage River in Tasmania. The challenge for virtually all magnetite operations is to minimise operating costs, which is dominated by the cost of power required to fine grind the ore in order to achieve acceptable concentrate iron grade together with low impurity content. This remains the case today and will be even more important in the future when a carbon tax is expected to become a significant addition to the operating costs for magnetite deposits. Historically, the lowest operating cost was achieved by multistage fully autogenous grinding with integrated magnetic separation steps between the stages. The major benefit of fully autogenous grinding is the elimination of steel grinding media costs and the need to discriminate between steel and magnetite in coarse magnetic separation. The separation step between grinding stages progressively reduces the amount of material to be ground. Application of more efficient grinding technologies developed in the last 20 years, including high pressure grinding rolls (HPGR) for fine crushing and stirred milling for fine grinding, has provided opportunities to further reduce the operating costs associated with comminution. Both technologies are already implemented in some magnetite processing operations, although in limited capacity. The results of a theoretical option study for high capacity processing of a hard, fine-grained silica-rich magnetite ore is presented in this paper, with the emphasis on comminution circuit options. Several circuit options are ranked based on a net present value analysis incorporating an estimate of carbon tax added in the operating cost. The study demonstrates the significant advantages of applying more efficient autogenous grinding technologies.

Jan 1, 2009

By L Köresaar, J Moilanen

With lower and increasingly variable Fe grades in iron ore resources, the monitoring of Si, Al, Mg and other light elements to meet quality requirements is gaining importance in the iron ore beneficiation industry. The high cost per manual assay and associated manpower requirements often limit the frequency of shift composite samples and laboratory assays. Furthermore, the shift composite assays represent past performance of a plant but are not useful for immediate reactions to feed variations, detection of equipment malfunctions or process control. Automated online analysis of light elements radically reduces the cost per assay and provides repeatable, timely data for process analysis, control and optimisation.A light element online slurry analyser, based on laser-induced breakdown spectroscopy (LIBS) optical emission technique, will be presented. This paper discusses the analyser design for the iron ore industry and also reviews the performance of the analyser against the manual laboratory. Additionally operator safety, user friendliness and maintenance requirements are discussed.A case study will also be discussed in this paper. The sophisticated measurement technique has been implemented in an industrial automated analyser and sampling system to allow for slurry measurement for up to 12 sampling points. However, careful selection of the sampling points and implementation of the sampling system is required for smooth operation.CITATION:Köresaar, L, Timperi, J and Moilanen, J, 2015. Optimised process control in iron ore via online analysis of light elements, in Proceedings Iron Ore 2015, pp 511–518 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By E A. G Marques, P M. Dight, T A. V Costa, K Mercer

Brazilian banded iron formation (BIF), known as ‘itabirite’, is the main host rock for iron ore in the Iron Quadrangle mines, Brazil. Their geneses are controversial and it is agreed that diagenetic, metamorphic and tectonic events, as well as weathering processes, were responsible for the iron concentration. In addition, it is understood that weathering processes are mainly responsible for reducing the original high intact rock strength, and for generating deep weathered profiles with low strength rocks commonly observed in Vale’s mines.A considerable amount of work has been done to correlate the macro and micro aspects of the itabirites as physical, chemical and geotechnical characteristics that directly or indirectly affect the intact rock strength; however, it is not yet clearly understood what effects the weathering processes have on the strength reduction of these rocks and its associated impact on pit slope stability. This forms a key focus of the lead author’s current research work.This paper presents a review of the geological, geotechnical and weathering characteristics of the itabirites, and early results for the evaluations of fresh itabirites from the PhD thesis research being undertaken by the authors at the Australian Centre for Geomechanics, School of Civil, Environmental and Mining Engineering, The University of Western Australia, sponsored by Vale SA.The results showed that to evaluate the density and unconfined compressive strength (UCS) correlation, not only the porosity but also the geological features should be considered, as they are responsible for data dispersion; however, the presented data suggested a trend that provides the confidence to develop advanced studies and a data population increment to establish proper correlations to support a reliable UCS method.CITATION:Costa, T A V, Dight, P M, Mercer, K and Marques, E A G, 2015. An overview of the weathering process, preliminary density and unconfined compressive strength correlations for fresh itabirites in vale mines on the western side of the Iron Quadrangle, Brazil, in Proceedings Iron Ore 2015, pp 241–254 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By J Joy, A Bye, G V. Kizil

This paper presents an application of the newly developed risk-cost-benefit (RCB) framework to support risk management decisions for the selection of wall monitoring technologies at an open cut mine site. The RCB framework quantitatively assessed the risk of unstable slope-induced wall failure and its impact on both loss of life and coal recovery. The RCB framework was utilised in the selection of an optimum group of risk-controls to effectively manage the risk of wall failure to ensure safety and optimal production occurred. The RCB framework incorporates mathematical modules that integrated RCB calculations and risk-control effectiveness assessments to determine the risk reduction and financial impact of the examined safety initiatives.This paper provides an overview of the five-staged RCB framework, incorporating the RCB decision support tools, RCBGEN (Risk-Cost-Benefit Generator) and RCEMETHOD (Risk-Control Effectiveness Method), and demonstrates its application to slope stability risk management at the case study site. The RCB charts are designed to display a balance between risk, cost and benefit for easy interpretation by decision makers to support the objective selection of an optimum suite of risk-controls. The RCB analysis revealed that a combination of ævisual inspections, automatic extensometers and radarÆ for fast- and slow-wall failures with structure were sufficient to reduce the probability of loss of life (PLoL) to the æModerateÆ zone as defined by the Australian Geomechanics Society (AGS, 2007) for the case study site. The new framework presented in this paper provides a method to effectively determine the suitability of risk-controls and supports industry efforts to reduce risk to as low as reasonably practicable (ALARP).CITATION:Kizil, G V, Bye, A and Joy, J, 2012. Risk-cost-benefit analysis of early warning technologies impact for wall failure risk management in surface mines, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 55-64 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012

By J A. van Niekerk, J G. Jardine, J W. Olivier

The Runruno Gold Project is located on the island of Luzon, approximately 200 miles north of Manilla in the Philippines. The mine is an open cut operation and uses the proven BIOX® and carbon-in-leach (CIL) processes to recover gold, and the ASTER™ process for detoxification of the CIL residue prior to discharge to the Residue Storage Impoundment (RSI). Work to date has defined a mineral resource of 1.39 million ounces (Moz) of gold, and the operation will produce 96 700 oz of gold per annum over a mine life of 10.4 years. The BIOX circuit is designed to treat 140 000 t/y of concentrate with a design capacity of 404 t/d of concentrate at a design sulfide sulfur grade of 17% S2-.The Runruno BIOX Plant is the first application of the Outotec BIOX Generation III design principles, focussing on ease of operation and maintainability. During development and implementation, the project team focussed on identifying opportunities to optimise the capital efficiency while not compromising on the operability or overall efficiency of the process or the equipment. The BIOX plant also incorporates the latest developments in the design of the BIOX agitators for more efficient mixing and gas dispersion. This paper will discuss some of the critical aspects and decisions taken during the development and implementation of the BIOX Process at the Runruno Gold Project. The paper will highlight some of the factors affecting the commissioning process as well as the improvements seen through the introduction of the Generation III BIOX design principles. CITATION:van Niekerk, J A, Olivier, J W and Jardine, J G, 2017. Implementation of the BIOX® process at the Runruno Gold project, in Proceedings MetPlant 2017, pp 218–228 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 11, 2017

By F P. van der Meer, E Lessing, E Matthies

High pressure grinding rolls (HPGR) technology is growing to be a common comminution tool in iron ore processing. The technology finds a wide acceptance and presents specific benefits in coarse ore grinding and closed-circuit grinding in preparation of ball mill feed, right down to the other end of the particle size spectrum for iron ore pellet feed preparation.A growing number of minerals processing plants are facing higher operating costs and difficulties due to a scarcity of process water, which in some cases is a result of more stringent environmental constraints. In addition, many new iron ore deposits are located in more arid regions of the world. These challenges have led to operators taking a new look at dry processing of iron ores.The use of dry crushing and classification technology in cement production from blast furnace slag, clinker material or limestone feed stocks indicates that the technology may be applied in minerals processing. In addition, dry processing provides the possibility of generating a final product from finely disseminated and inter-grown ores at sizes near or well below 100 µm, as may be required for beneficiation techniques such as in fine magnetic separation, flotation or magnetic flocculation.Dry grinding by HPGR has a number of specific features, challenges and opportunities, including balancing power input, moisture content requirements and classification efficiency in the process design. HPGR parameters and the latest HPGR design and sizing capabilities indicate considerable potential benefits from this dry processing technology.This paper highlights some of the specific issues that play a role in dry HPGR application, with respect to energy and materials balances. Examples of dry HPGR practices and process studies in iron ore mineral processing are discussed.CITATION:van der Meer, F P, Lessing, E and Matthies, E, 2015. Iron ore final grinding by high pressure grinding rolls and air classification, in Proceedings Iron Ore 2015, pp 197–204 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

The Kalgoorlie Golden Mile is proposed as an Archaean volcanogenic-type deposit, modified and redistributed along later-developed structures. Rich pyritctelluride and Green Leader gold mineralization is associated with the end phase of basic volcanism and, in a general sense, is confined to a broad interface zone between the products of marine basic volcanism and later acid volcanism. There is virtualIy no ore associated with the main body of acid volcanics.Green Leader is the local name of a type of ore that occurs at some igneous rock contacts in association with graphitic sediments and layered acidic tuffs. It is characteristicalIy green, of various shades, and commonly yields very high gold assays, the reasons for which are not apparent in hand specimen.Carbonates, carbonaceous shales, tuffites, rich gold ores, and acid and intermediate dykes, alI indicating a common heritage, are features common to the main ore hosts, viz. the Paringa Basalt (Calc Schist) and theGolden Mile Dolerite ("Quartz Dolerite Greenstone").Several probably related fracture systems have reconstituted most, but not all, of the original deposits into a large number of steep tabular lodes.Includes two sets of discussions and comments from later Proceedings volumes.

Jan 1, 1974

No paper available.

Jan 1, 1996

By D Morgan, K Jones

"In March 2015 Northparkes Mines (NPM) installed a process mineralogy facility on-site. The laboratory included a TESCAN TIMA scanning electron microscope (SEM) and was the first SEM facility to be commissioned on a mine site in Australia. While the initial intent of the quantitative mineralogy laboratory was to provide information to drive processing plant improvements, in practice, it has been utilised for so much more and is now serving as an integral link between departments on-site. This multidisciplinary approach to orebody knowledge is a new strategy for NPM whereby all parts of the value chain are aligned towards the common goal of achieving process efficiency and stability while still maintaining high throughputs. The NPM experience is presented as a case study to illustrate how on-site process mineralogy can drive a realignment in business strategy with a common goal of mill optimisation, stability and more realistic forecasting through orebody knowledge and information sharing between disciplines.Citation:Jones, K and Morgan, D, 2016. On-site Process Mineralogy - Linking Departments and Disciplines with the Common Goal of Increasing Plant Performance, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 149–156 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By D Laurence

Mining cycles have come and gone and with them there have been dramatic swings in the levels of interest and student entry into minerals-related education programs, hence graduate supply to the industry. So what is the problem? These trends will keep happening and the industry will keep on keeping on – or will it?This paper discusses recent trends in Australian minerals education programs and some international examples, together with some of the more recent initiatives taken by both the minerals education sector and the industry, such as the Minerals Tertiary Education Council (MTEC) and MEA. The real problem is that things will not just keep going the way they have over recent decades – there will come a time when there is no longer a supply of minerals academics available to provide the educational programs; and universities will simply shut down subcritical mass mining programs and invest in the much more lucrative programs such as commerce, law, medicine, etc. By the time this starts to happen it will be at least ten years too late for any last-minute reactive response by industry, if they were to try and avert such a consequence. International experience with mining programs bears out this scenario quite clearly.It is therefore timely for industry individual mines and mine management to take a much more strategic look at their role in the education sector. Sustainable mining also means sustainable minerals education – without one, the other will not function over the long-term. There is a pressing need for long-term strategic buy-in by industry into the education sector – not just for the good times, but also through the tough times. This means much more than a scholarship here or there, but includes such commitments as major industry-university research partnerships; collaborative recruitment initiatives and much more. The paper will discuss a range of such issues, problems and opportunities to address these important issues through strategic, comprehensive, long-term commitments by industry and equally significant and appropriate responses by the education sector. We care – do you?

Mar 21, 2011

By Scoble M, Peck J

This paper reviews the instrumentation and monitoring of blasthole drills and electric mining shovels at a surface coal mine in western Canada. The drill monitoring component involved the development and implementation of microprocessor-based hardware on Bucyrus-Erie 45R and 60R drills. Over a two year period 3800 metres of blasthole drilling were monitored The drill data was subsequently correlated with core and geophysical logs towards identifying unique and reproducible ranges of performance parameter data for the different rock types penetrated. Using this technique, the geology of the study area benches was characterized in detail. Once these same benches had been blasted, the performance of a P&H 2800XP shovel was monitored as it worked through the blasted ground. In this regard, the influence of different digging conditions on shovel performance were identified in a range of blast and geological environments within the study area. The precise nature of these environments was confirmed by a correlation with the interpreted drill monitored data and muckpile size distributions obtained from a digital photo-analysis study. The excavation of 500 000 bcm of waste was thus monitored and a digging index derived which reflected variations in muckpile diggability. The paper concludes by proposing an integrated monitoring approach which, as a first step, uses interpreted drill data for explosive loading. This capability would permit greater accuracy in explosives loading ie. charge placement within higher strength lithologies, while avoiding weaker units. The performance of an instrumented shovel would then be monitored as it works through the resulting muckpile. Interpretation of the shovel performance data would determine the overall quality of the blast in terms of a digging index (DI), providing an indication of the relative digging effort and the effectiveness of the blast design.

Jan 1, 1990

By Leahey T. A

The variability of gold mineralization in the Warrego Gold Pod is described by classical statistical techniques using sample distrib- utions and analysis of variance; and by the use of geostatistical variogram analysis to define the spatial variability and anisotropy of the mineralization. Comparison is made between declared mine production from the Nineteen Stope and a series of ore reserve estimates derived by manual, numerical and disjunctive kriging methods.

Jan 1, 1979

By J D. Grobler

In the heavy minerals industry wet high intensity magnetic separators (WHIMS) are widely applied for primary magnetic separation of magnetic minerals and non-magnetic minerals. This piece of equipment is well known for its robustness to handle a wide range of feed conditions and still produce stable product qualities and yields. A heavy mineral production plant aimed to increase production through their WHIMS plant containing 11 duties and 26 units. Instead of adding new units an alternative approach was followed to firstly maximise the efficiency of the current circuit and secondly to consider possible reconfiguration of the circuit to produce additional product tons for minimal capital investment. In order to characterise the current circuit’s efficiency, identify pockets of excellence and determine the areas for improvement the whole circuit was surveyed several times and mineral mass balances were drawn up.This paper aims to: discuss the modelling process of the WHIMS circuit,explain the calibration and validation process followed to ensure the accuracy, anddemonstrate the sensitivity analysis performed on the different options. From this analysis an efficiency criteria was developed to compare different circuit configurations that enabled the production plant personnel to make an informed decision on the way forward.

Oct 5, 2011

The problem of stability of the development working at the great depths of coal winning is of great seriousness. Numerous researches of the problem were carried out in the USSR, the results of which determined that raising of resistance of existing support will not lead to a considerable rise of working output. It is necessary to try to find ways at the expense of heightening the support ability of rock massif. For these purposes it is necessary to direct it correctly and in proper time. While carrying the development working the most intensive deformations of rock occur at a depth of 30m from the entry face. The zone of destruction of rock around the work is realised here for 60 to 70 percent. These facts show that in influence zone of entry face a kind of embryo of the working steadiness is forming, which greatly determines its following conditions. Therefore, it is necessary to begin direction of mining pressure around the work directly in a face.Complex research of the mechanism was carried out starting with the effect of moving face upon the surrounding rock massif. It was ascertained, that the zone influenced by the face is a section of 5 equivalent diameters of the work by the length within which the rock of the sides, roof and floor, experience the cyclical influence of stresses at the time of cyclical shift of the face. The elastoplastec deformation is occurring with it at the moments of rock removal and the deformation of creeping takes place at such intervals.

Jan 1, 1991

By D W. Nisbet

Today Hudson Bay Mining and SmeltingÆs 777 Project is the largest mining construction project under way in Canada. The project comprises six components: construction of the new 777 zinc-copper mine; construction of the new Chisel North zinc mine that will truck ore out from 600 metres below surface; expansion of the Flin Flon ore concentrator; expansion of the zinc plant to increase throughput by 15 per cent; a spill gas project that will reduce fugitive gas emissions by some 90 per cent; and infrastructure improvements including construction of a new electrical substation. Total investment in The 777 Project is over $US 260 million. Seven years ago, the Flin Flon, Manitoba-based company was fighting for its very existence. How does a company go from down-for-the-count to robust contender in just seven years? Contributing reasons are many, but all have their root in a process HBMS calls æTransformationÆ. It is transformation that has taken HBMS, a very traditional company, through a very non-traditional turnaround (Figure 1).

Jan 1, 2000

By I Gray

While in some cases it is vitally important to measure the virgin stress in rock prior to tunnelling there are a number of cases where such stress measurement is really not required. The concept of having to have a number to put in a numerical model representing a continuum is often quite inappropriate. This paper discusses the cases when virgin stress measurement is required and the most appropriate means to measure it. The techniques discussed cover all of the overcoring systems, hydrofracture and borehole breakout measurements. It also covers the use of rock surface stress measurement, which is easy to perform and should be used to check for changing stress conditions. Unfortunately this technique has been ignored in recent times because engineers are addicted to numerical models requiring far field stresses rather than measuring the real values that exist where they matter – at the tunnel wall. A case is presented in which the measurement of surface stress in a tunnel boring machine tunnel enabled the far field stress to be determined in what must be the world’s largest overcore.CITATION:Gray, I, 2014. The measurement of rock stress for tunnelling, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 153–160 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By A Deakin

It has been almost a decade since the release of the International Council of Mining and Metals (ICMM) Health and Safety Critical Control Management: Good Practice Guide (2015a). During this time the ICMM member companies, along with many others across industry, have been busy designing, deploying and enhancing their own critical control management (CCM) programs. So, what have we learnt? This paper discusses the scope, application and learnings from the implementation of CCM within the mining industry. What’s going well? What are the common challenges? What are the opportunities to strengthen the approach? What are the threats to successful implementation? The paper draws on the author’s experience as one of the key contributors to the development of the CCM Good Practice Guide and an adviser to many mining companies, including six of the ICMM members. The paper focuses on the practical (operational) application of CCM and the cycle of identifying, defining, implementing, verifying and improving critical controls at the frontline. The paper also includes a discussion on the safety performance of the ICMM member companies over the past decade and provides a recommendation for how CCM can be incorporated into a more proactive model to measure safety performance. The paper concludes with practical recommendations that mining companies, regardless of their CCM maturity, can consider as they look ahead. They are supplemented by three additional recommendations for consideration at the industry level.

Apr 16, 2024

By R Wheeler, E Stalenberg, J Lemon, M S. Crowther, D Lunney, K Ross

Gunnedah, in north-western New South Wales (NSW), including the town, the surrounding Liverpool Plains and the Pilliga forests to the west, are currently the subject of intense mining interest for coal and coal seam gas. Achieving positive outcomes for koala conservation on mined landscapes will require a sound grasp of koala ecology; and local knowledge of koala movements, tree choice and associated threats to the continued survival of koalas, particularly roadkill from increased mining infrastructure. This requires a research-oriented approach to testing ideas applicable to the long-term survival of koala populations. Our recent koala research in NSW has shown that, in 2006, Gunnedah had the largest koala population west of the Great Dividing Range, and the only population in NSW that was expanding. That prompted us to instigate a detailed study in 2008 - 2011 to determine, inter alia, whether the koalas were using trees that were planted in the 1990s to cope with rising soil salinity. Our GPS-tracking has shown that regrowth trees as young as ten years old can attract koalas. In 2009, the demise of about a quarter of the local koala population from an intense heatwave gave us a foretaste of how habitat and climate change interrelate at the landscape scale. We are now examining the optimal combinations of tree choice, and patch size and shape, for habitat restoration. This will be relevant to local coal seam gas and coal mine proposals, and ongoing mitigation actions. The Senate enquiry of September 2011 on the koala and demonstrated the intense public interest in the survival of this iconic species. Its subsequent listing for Queensland and NSW under the Commonwealth Environmental Protection and Biodiversity Conservation Act 1999 further raises its profile and obligations for management of koalas and their habitat. It will take considerable effort to manage the Liverpool Plains koala population for the next 50 years in the face of extensive land-use changes from mining, and the attendant threats from road kill, compounded by the new threat of climate change manifesting itself as an increased frequency of heatwaves and more severe droughts. This paper describes the research that underpins these conclusions, identifies some of the research approaches needed, argues for working strategically now, rather than try to patch up matters after the event, and presents a set of guides for environmental plantings. CITATION:Lunney, D, Lemon, J, Crowther, M S, Stalenberg, E, Ross, K and Wheeler, R, 2012. An ecological approach to koala conservation in a mined landscape, in Proceedings Life-of-Mine 2012 , pp 343-352 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By L Abrahamsson

This paper describes results from a gender study for a new mine in Pajala, a small community in northern Sweden. Using a gender perspective, the study examines migration, education, local culture, the labour market, and work organisation as problems and opportunities in the regional context for the planned mine. The most obvious ‘gender issue’ for the Swedish mining industry is the very low percentage of employed women, which is even lower among mining workers. To recruit the best people, a company actively needs to attract both women and men; however, the mining companies find it difficult to recruit women as cultural, labour market and educational traditions as well as the mining companies’ own cultures often make it difficult for women to find work in the mining industry.The Torneå river valley, the region surrounding Pajala, has a gender-segregated labour market and gender-stereotyped culture and few young women live in this traditional and oldish region. Many young people leave the region and this is especially true for women. Compared to the rest of Sweden, there is a low educational level, especially among the men. In the mining companies, as in many other male homosocial workplaces, the workplace culture has strong connections to a certain type of traditional masculinity (laddishness, a kind of ‘macho-style’) and for a long time this has excluded women. ‘Gender’, however, is not only a question of recruiting women to a male-dominated industry. An organisation that discriminates according to gender can become inflexible, hindering communication, learning, innovations and change processes. In mining companies, this can manifest itself in hesitant attitudes among the miners about safety as well as organisational and technological development.This study found that companies establishing a presence in this region should develop a strategy for how to deal with and manage the risks and opportunities in the surrounding society (the regional culture) as well as inside the company (the mining culture). This need to be strategic will also be required of future mining companies as they will face higher demands on safety, gender equality, and technology to become modern, efficient and lean organisations.

Nov 22, 2011

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