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DML Resources Limited - Mining Division produced over 50 000 oz of alluvial gold in the 1995 - 1996 year from five operations located in the West Coast and Otago Regions on the South Island of New Zealand. DML Resources Limited - Mining Division have a twenty year history of alluvial gold mining development in New Zealand. Recent expansions have seen the establishment of two operations in Chile whilst exploration continues in Bolivia, Peru and Argentina. The overseas growth is based on a stable production base in New Zealand focussed on the West Coast and Southland/Otago present and future operations. DML Resources consider that the mining potential in the Arahura Valley on the West coast will be fundamental to their New Zealand operations for some time. Collectively the plants operating in this catchment are referred to as the Poutini Project. Recent and late Pleistocene gravels derived from the erosion of the Alpine Schists running parallel to the Alpine Fault located on the Pacific/Australian Plant boundary are thought to be the sources of the alluvial gold in the Arahura and adjacent catchments. These gravels have been extensively mined for the past 130 years yielding some six million ounces over this period. Production from the Poutini Project started in 1989 and stood at approximately 35 000 oz for the 1995 - 1996 year. This production was split among three plants each working different areas of the deposit. Recovery techniques from each of the plants are fundamentally the same. Gravels are fed to a floating treatment plant where, following screening, the gold is recovered using jig plants and knudsen bowls. Overburden to wash stripping ratios vary between zero and seven to one with plants treating between 80 and 250 cubic metres per hour. Restoration of the land following mining is undertaken progressively. All land in the Poutini Project area mined to date has been restored to a standard suitable for dairy farming purposes. The Poutini Project is a cooperative venture between the Maori landowners and DML Resources Ltd. The Arahura River has particular cultural significance to the Maori as it is the source of the much valued greenstone or pounamu a type of jade valued for jewellery and tools. The Poutini Agreement was signed in 1989 setting out the role of each party in the mining of the Arahura and adjacent lands. Current exploration and development should extend the resource to allow mining to continue on the Poutini project for an additional three to five years at current gold prices. Production within new Zealand beyond this point may be compromised by increasing difficulty in gaining access to prospective areas within New Zealand, lowered margins due to high New Zealand dollar exchange rates and the overall lowering of alluvial headgrades throughout the West Coast and Otago/Southland regions. To counter these effects DML has continued to improve on operational efficiency and performance monitoring to optimise the mining practices used. This paper detains the background to the Poutini Project, the geology, plant and equipment used together with descriptions of the current mining methods employed.

Jan 1, 1996

By A Bennett, S Arndt

Minerals and Metals Group Pty Ltd (Golden Grove Mine) commissioned a comprehensive study of the life of mine using advanced 3D stress modelling. Essential input into the modelling was the proposed mining sequence, itself the culmination of years of planning and geotechnical experience gained in comparing actual performance to predictions. The modelling approach addressed the whole of mine at a scale of 5 km. There were however several magnitudes of scale to address, from the scale of laboratory testing (0.05 m), to drive size (5 m), extraction size (50 m) and stope size (500 m). Scaling was therefore an integral part of the procedure. The constitutive rock properties in terms of peak and post-peak behaviour varied with the scale. At the laboratory scale, the constitutive relationships for all the main rock units were determined in 3D as well as recovering the in situ stress using the rock memory technique, deformation rate analysis (DRA), whereas at the larger scale the properties were varied to match observations.The modelling, using non-linear analysis to account for rock mass yield and peak-residual strength, demonstrated that if the planned extraction sequence and stope geometry had been pursued there was a high probability of large volumes of excess shear stress being released. However, it was not possible to identify whether the excess shear stress (ESS) will release as one large event or many smaller events. The mining approach was to modify the extraction sequence/stope geometry to manage the hazard. This is where the economic advantage can be realised.Alternatively or in combination with further modelling, the volume identified with the predicted high ESS or energy release could be intensively explored for structures having adverse orientation to the stress change and with sufficient areal extent to release the ESS. The microseismic data can be interrogated for the likelihood of a large event to support the hypothesis of a singular release versus multiple releases of smaller events. If the initial planned extraction sequence had to proceed as designed, changes to dimensioned stopes would be recommended for risk mitigation. Mine planning could as an option, modify the sequence and the extraction could then be remodelled.CITATION:Bennett, A, Arndt, S and Dight, P M, 2014. The economic advantages of detailed geotechnical assessments for extraction sequencing, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 243–250 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

Bacteria can play a key role in the processing of 'difficult' ores. Bioleaching opens the way to potentially extract copper from vast amounts of otherwise hard to process refractory low-grade chalcopyrite. In my talk I will outline our research philosophy to develop bioleaching as a Precision Processing unit process step. In our view, Precision Processing is a sophisticated approach to mineral processing where the ultimate goal is to measure and characterise the ore body in-ground and in real time during mining, allowing the down-stream unit processes (bioleaching, in this case) to be continuously tailored and tuned via feedback and feed-forward controls to obtain the highest possible recoveries at the lowest possible cost and environmental impact. I will describe some of the work that we are undertaking to better understand the interfacial phenomena underlying the fundamental bioleaching process with the aim of coming to a Precision Processing approach. We use techniques such as interfacial electrochemistry (scanning electrochemical microscopy, SECM), AFM, zeta potential measurement, and synchrotron science to elucidate the parameters that drive bacterial selectivity and adhesion, bacterial metabolism, and dissolution and precipitation processes for model systems and real chalcopyrite ores. As examples of our research, I will discuss in some detail our method to produce and characterise micro-patterned CuxS - silica thin films as model substrates for electrochemical and bacterial adhesion work and our approach to the interfacial chemical characterisation of extracellular polymeric substances of bio-active bacterial cells. I will also cover some of our recent findings relating to measurement and interpretation of bacterial adhesion on sulfidic substrates and its implications for bacterial adhesion and substrate selectivity. After having identified and discussed crucial leaching parameters, such as pH, Eh, T, [Cu2+], and [O2], the talk will go on addressing some of the early achievements and challenges encountered in our work to design and prepare low-cost, rugged sensing devices that allow the in-situ (in this case, in-dump or in-heap) localised measurement of these parameters. I will conclude my talk by painting the picture of how the work of our group might contribute to realising the dream of transforming bioleaching into genuine high-tech Precision Processing of minerals. This is an ABSTRACT ONLY. A full-length paper was not prepared for this presentation.

Sep 13, 2010

By U Singh

This paper presents the evolution of the studies and strategic plans to extend the life of operations at the Savage River iron ore project in north-western Tasmania. The current Life-of-Mine (LOM) plan for the Savage River operations is based on a series of open pits. Drilling has confirmed high-grade extensions of the magnetite resource at depths that exceed practical limits for open pit mining. Grange Resources Limited, the owner of the operation, is investigating underground options – not only to extend the LOM plan but also to maintain peak production at a reduced operating cost while reducing greenhouse gas emissions into the future. What makes this project unique is that it requires introducing a productive and cost-effective mining method to exploit a challenging geotechnical and geometrical orebody in an area of high rainfall. To support the study efforts, the development of an exploration decline, underground drilling programs, and an exploratory drive excavated into the orebody for geotechnical investigation was key to providing the necessary data for a pre-feasibility study (PFS). This paper describes the pragmatic approach and processes to developing the underground mining options study through data collection and then integrating these options into the open pit plans to optimise an overall strategic plan for the Savage River operations. The learnings for operators from this experience are how the technical and pragmatic approaches were aligned to develop the strategic plans, and the importance of timely investment in gathering the necessary data.

Mar 29, 2023

Use of Impact Crushing for the Enrichment of Low-Grade Colemanite Concentrates This paper presents the results of an investigation into the enrichment of -25+3 mm low grade colemanite concentrates exploiting differential breakage properties of various minerals associated within the ore sample. Boric acid production process requires concentrates containing at least 42 per cent B2O3, hence concentrates below this grade either stock piled or further treated to increase B2O3 content. The low grade concentrate is obtained as a by-product of Emet Colemanite Concentrator and the B2O3 content may vary around 37 - 38 per cent. The sample used in the experimental studies assays 37.52 per cent B2O3. In the experimental procedures the sample was crushed using a laboratory size horizontal shaft impact crusher and the products were classified into different size fractions by screening so that any improvement by size could be observed. In the tests the effects of parameters such as the revolution speed of the crusher and heat treatment was checked. Test results prove that boron contents show a tendency to increase as the particle size decreases. As a result of the experimental studies a colemanite concentrate assaying 42.13 per cent B2O3 is produced with 76.55  per cent recovery. Arsenic content is seen to change inversely proportional with the B2O3 content of the concentrate such that it drops from 1016 ppm from the as received sample to 676 ppm in the concentrate.

Sep 13, 2010

The Myra Falls minesite, of Westmin Resources Limited, is located at the geographic centre of Vancouver Island, within the confines of Strathcona Provincial Park. The operation includes two active underground mines, II-W and Lynx, together with a modem 3650 1/d milling facility. Recent exploration successes will lead to the commissioning of a third mining area in late-1993 - The Battle/Gap Mine. These ore deposits are complexly metal-zoned volcanogenic massive sulphides of Devonian age, hosted in the Myra Formation of the Sicker Group volcanic assemblage. Three distinct felsic volcanic units are defined within the 450 metre thick Myra Formation. They are, from oldest to youngest, the H-W Horizon, the LMP Horizon and the Upper Rhyolite Unit. Massive sulphide mineralisation occurs throughout the property in the H-W and LMP Horizons. There are a number of orebody types, including polymetallic massive sulphides, polymetallic disseminated sulphides, zoned pyritic massive sulphides, elastic sulphide zones and stringer sulphide zones. Individual orebodies range in size from 10 000 tonne zinc-rich polymetallic lenses to the ten million tonne, zoned massive sulphide H-W main lens. The property has been in continuous operation for 26 years, producing over 13 Mt of ore averaging 2.2 g/t Au, 64.0 g/t Ag, 1.9 per cent Cu, 0.6 per cent Pb, and 5.6 per cent Zn. Current geological reserves stand at 12.5 Mt at a comparable grade, including 4 Mt of recently discovered high grade ore in the Battle and Gap Zones. Mining and milling methods have evolved over time to enable successful extraction and milling of these complex ores. Change is on-going with the recent conversion of the H-W Mine to large-scale bulk mining methods, and the development of effective computerised ore reserve calculation and mine planning tools. These changes, in concert with successful exploration techniques that led to recent high grade ore discoveries, have breathed new life into the operation and should assure its present and future viability.

Jan 1, 1993

By G F. Johansen

The erratic and localised occurrence of economic gold grades is a common feature of high-nugget effect gold veins. The nugget effect is a consequence of small-scale geologically controlled enrichment, and the inclusion or exclusion of sparse gold particles because of the sampling process. Such deposits do not always contain visible or coarse gold, and can be characterised by fine gold particles. Economic grade accumulations are generally contained within discrete oreshoots, which are surrounded by barren to low-grade material. Problems are often encountered where small sample types (eg drill core or channel samples) often vastly understate in situ grade, due to their general inability to intersect rare gold particles. As a result, the definition of grade and its distribution is often challenging, and leads to substantial resource uncertainty. Proxies, or indicators for grade, can help the geologist gain a better understanding of grade distribution and grade potential. These are based upon geological (eg mineralogical, textural, etc) and/or geochemical (eg specific elemental ratios, fluid inclusion compositions, elemental correlations, etc) criteria. The paper discusses the use and application of such proxies through three case studies.

Jan 1, 2004

By E Widzyk-Capehart, C Hölck Teuber, S Steffen, V Rivero, O Fredes, E Sanchez, I Pedemonte, N Gonzalez

This paper summarises the research, development and initial application of a sensing platform that has the potential to monitor subsurface deformations, pore pressure and other variables simultaneously to gain a better understanding of rock mass behaviour. The platform is based on Networked Smart Markers (NSMs) devices, which, with their ability for wireless communication between individual sensors and the possibility of real-time data acquisition and processing, will assist in the development of predictive tools to better assess rock mass behaviour.A good opportunity to implement this technology is in the specific application of transitioning from an open pit mine to an underground caving operation. One of the key elements to maintaining the mining business during such a transition is having a good understanding of the unique geotechnical conditions of mutual influence created during the open pit to underground interaction. The knowledge acquisition will require the implementation of a robust platform for geotechnical monitoring, which could be enhanced by incorporating the NSMs. The integration of sensors within the NSMs would enable the collection of additional data about rock mass behaviour (ie caving propagation and crown pillar fracturing), which could be used to improve the management of mining operations and, specifically, allow the development of reliable predictive tools based on the data collected.CITATION:Widzyk-Capehart, E, Hölck Teuber, C, Fredes, O, Rivero, V, Sanchez, E, Pedemonte, I, Gonzalez, N and Steffen, S, 2016. Understanding rock mass behaviour through the development of an integrated sensing platform, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 275–284 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By J Lainé, M Badawi, A C. de Araujo, Y Foucaud, C Veloso

Flotation is the one of the most used techniques for the mineral separation of non-ferrous ores worldwide. However, the increase of the complexness along with the decrease of ores liberation sizes ought to become important challenges for mineral processing, including flotation. It now appears necessary to better understand the fundamentals of the flotation process, particularly the adsorption of flotation reagents at the liquid/mineral interfaces, to propose further improvements. Flotation relies on different phenomena: surfactants adsorption, on one hand, and collision, adhesion, and transport of particles with bubbles, on the other hand. For acknowledging the reagents adsorption mechanisms, molecular modelling tools borrowed from chemical and material sciences, are increasingly used. Atomistic simulations were successfully applied to study the flotation reagents interaction with various mineral surfaces, eg of two common minerals from iron ores, kaolinite, and magnetite surfaces, or with fluorite surface, a tungsten ores common gangue mineral.

Aug 24, 2022

By S Nkwanyana, I Govender

Batch experiments in a 0.6 m diameter mill have shown that improvements of about 13 per cent in the efficiency of energy utilisation can be realised in ball mills by replacing 25 per cent of the ball charge by an equivalent volume of cost-free critical size pebbles from AG/SAG mills. For a mill of a given size, speed and charge filling, the rate of size reduction of ore particles depends on (i) the frequency of grinding media collisions (ii) the probability of capture of ore particles between the colliding grinding media (iii) the probability of fracture of the captured particles. The probability of fracture depends on the magnitude of collision energy. The distribution of collision energy into shear and impact events determines the relative strengths of attrition breakage and impact breakage. The efficiency of energy utilisation depends on which of the two mechanisms of breakage is more desirable in a particular milling stage. In this paper collision data from a series of DEM simulations of a mill charged with steel media and a mixture of steel media and pebbles is presented in energy spectra and spatial distribution maps. The data provides the necessary detail to elucidate the improvements in the efficiency of energy utilisation in ball mills when using a mixture of pebbles and steel media.

Aug 24, 2022

By J Zhou, D M. Hunter, S M. Iveson, K P. Galvin

The REFLUX Classifier is used to perform particle separations on the basis of density utilising a set of parallel inclined channels positioned above a vertical fluidised section. In continuous mode, feed enters part way up the vertical section, while fluidisation water is introduced from below. Lower density particles are conveyed upwards and collected in an overflow stream, while high density particles segregate onto the inclined surfaces, settle to the base of the system and empty via an underflow stream. Pressure transducers are used to measure the suspension density in the vertical section. This suspension density is maintained by a pneumatically controlled underflow valve to maintain a target suspension density or ‘set point’.Previously, Galvin et al (2010) demonstrated the significant improvement achieved via a new laminar-shear separation mechanism, achieved by utilising closely spaced inclined channels in the REFLUX Classifier. For the separation of low-density coal particles from mineral matter, a channel spacing of 6 mm proved effective; however, for the separation of gangue minerals from much higher density minerals such as iron ore, the shear-induced lift needs to be even higher. In this paper, we examine the influence of two different channel widths on the continuous processing of an industrial iron ore feed in the REFLUX Classifier. It was found that when moving from 6.0 mm to 3.0 mm channels, the ability of the system to reject coarser gangue material and retain finer high density material across a particle size range from 0.125 to 1.0 mm was increased, resulting in a higher grade product.CITATION:Hunter, D M, Zhou, J, Iveson, S M and Galvin, K P, 2017. Influence of shear rate on separation of iron ore fines using the REFLUXTM Classifier, in Proceedings Iron Ore 2017, pp 205–210 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By A M. Nyembwe, A M. Garbers-Craig, R Cromarty

With the depletion of high-grade lump iron ore, concentrates have been identified as an alternative material for sinter making. Adding concentrates to the sinter mixture reduces sinter bed porosity and gas flow through the sinter bed. This will result in lower sinter strand productivity. A potential solution to this problem is to add concentrate in the form of micropellets. This study investigates the effect of concentrate and micropellet additions on the permeability of the sinter mixture. Permeability was measured on sinter mixtures containing ten to 40 per cent concentrates and micropellets at various moisture contents. The effect of concentrate and micropellet addition on the permeability–moisture relationship was examined. The results confirmed that the addition of concentrates into the sinter mix decreases the maximum permeability of the sinter bed. The incorporation of micropellets into the sinter mix reduced the permeability less than concentrate addition. The study also showed that the maximum permeability of sinter mixes containing concentrate is reached at the same moisture content as the sinter mixture without concentrate addition. For sinter mixes containing micropellets, additional water must be added to obtain maximum permeability. Parameters including the granule size, void fraction and angle of repose were also investigated to evaluate their effects on the sinter bed permeability.CITATION:Nyembwe, A M, Cromarty, R and Garbers-Craig, A M, 2015. Effect of concentrate and micropellet addition on iron ore sinter bed permeability, in Proceedings Iron Ore 2015, pp 69–76 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By A D. Campbell

The sublevel caving (SLC) mining method is becoming more widely adopted as an underground mining method as mines become deeper and target lower grade mineralisation. SLC has been successfully adopted in increasingly complex and wide-ranging conditions in the past 10–20 years, demonstrating the flexibility of the method. Various challenges encountered at SLC mines around the world have led to significant differences in operating practices, mine performance and mine productivity. Unfortunately, aspects related to productivity, operational performance and best practice are not widely published and remain with individual companies. Limited information is publicly available to compare operational performance of SLC mines in the various conditions where the mining method is now being applied. To overcome this shortcoming, a global review of SLC operations was undertaken over a three-year period as part of the Cave Mining 2040 research consortium. The purpose of the review was to document technical and operational practices, hazard management strategies and key benchmarking metrics at SLC mines around the world. A total of 21 mines spread over four continents and 17 different mining companies were included in the project. The main outcome of the project was a manual of operational and technical practices, benchmarking of key metrics and documentation of the current state-of-the-art for each aspect of SLC mining. This paper describes the main findings from the benchmark in terms of mine productivity, including mine development, production and mining costs. The implications of mine scale, depth and ground conditions on operational performance at each of the benchmarked mines is described and charts are provided comparing key productivity metrics.

Mar 29, 2023

By W J. Rankin, D R. Swinbourne

There are large tonnages of low-grade manganese ores in India fromwhich it is uneconomic to produce ferroalloys by conventionalsubmerged arc furnace smelting. A possible way to utilise these ores is to smelt them with carbon to produce pig iron and a manganese-rich slag, then to metallothermically reduce the molten slag to silicomanganese. Thermodynamic modelling of the metallothermic reduction stage using aluminium, silicon or aluminium-silicon alloy as the reductant at 1450¦C showed that an acceptable grade of silicomanganese could be produced. Manganese recoveries were predicted to be about 80 per cent. Heat balances indicated that silicothermic reduction may not produce enough heat to maintain reaction temperature. Small-scale laboratory experiments showed that the manganese grade of the alloys, and the manganese recoveries, were close to those predicted, but those for silicon were muchlower. Aluminothermic reduction produced the highest grade manganesealloy. The slag-metal equilibrium involving manganese, silicon and their oxides was investigated and it was found that equilibrium was not attained in any of the experiments, due probably to the very low rate of reactions involving silicon. This could be used to advantage in practice to achieve higher manganese levels in the alloys.

Jan 1, 1998

By J M. Marwan, B Tang

Strain-type rockbursts, or strainbursts, are characterised by a localised violent failure. Their cause is attributed primarily to the sudden release of strain energy, which accumulates in a volume of highly stressed rock as a result of mining activities. Examples of such phenomena are crown/sill pillar bursts created in the mining process, pillar crush in room-and-pillar mining, face ejection in drift development headings at depth, and floor bursts associated with deep shaft sinking. The paper describes a simple method for the assessment of crown pillar bursts in steeply dipping ore deposits which are extracted by the overhand cut-and-fill method. The method is based on a theory previously established by the author to help assess the need for a remedial solution such as pillar destress blasting. Basically, the mining-induced energy storage rate (ESR) in the pillar is compared with the critical strain energy to come up with the so-called burst potential index (BPI).

Jan 1, 2001

Good morning and thanks for the chance to talk to you. It's really pleasing to see so many industry representatives here I want to spend a few minutes talking about issues relating to your industry. At the end of today I would like to leave you with three strong messages from government. The first is that this government supports environmentally responsible mining and the endeavours of the mining industry. The second is that explorers and developers are wanted and welcomed in New Zealand. And the last is that it is up to the industry to keep the public properly informed about how your industry and to constantly work on improving your public image. The mining industry is a high-tech industry which fits snugly with our concept of a growing knowledge-based economy. It has particular value for regional development, the gold mining industry alone provides more than 4,000 jobs û mostly outside of the main cities. The industrial minerals industry is twice as large as that. As well as those people directly employed by the industry there are greater downstream effects for the community. One example from the broader extraction industry of this is of the local pie shop down the road from one of Taranaki's petroleum industry locations. The shop sells over $4,000 worth of pies a week to workers in the industry. That's just one example of the positive benefits the industry brings to its local community and is the sort of real positive benefit you need to be telling people about  

Jan 1, 2000

By K B. Quast

Changes in feed size distribution can have significant effects in rod mill grinding. The product sizing resulting from wet batch milling of a tin ore showed little influence on fines production after truncating the feed at either the coarse or fine end. The addition of fine material caused a less amount of fines to be produced and a possible increase in grinding at coarse sizes, although this is complicated by the changing feed size distribution. The changes in feed size distribution caused no tendency for preferential grinding of the cassiterite.

Jan 1, 1998

By C Parihar, R Garg, A Bhandari, S Bhandari

Blasting can impact the efficiency of entire downstream mining operation. Individual technology solutions for blasting have been available in the industry for many years but all of them only cater for certain aspects of blasting. Many of them are based on individual research and/or experiences. Some of the available software solutions are not suitable to be used in the field as that they need advanced skills or tools. Also, most do not take technology advancements like mobility, advanced data analytics, web solutions and integration into consideration. Hence, no technology platform is currently present in the industry that addresses all potential needs a blaster may need in an integrated manner.This paper presents an integrated solution that takes care of all aspects of blasting – design blasts according to mine plan; collect data after drilling has been carried out (as there is often difference in designed and actual drilled hole locations in the field); predict blast results in terms of fragmentation, flyrock, ground and air vibrations, wave front reinforcement and flyrock distance; and after assessment, allows changes in charging, delay timing and sequence. The technology solution is a secure, cloud-hosted, web-based software-as-a-service solution that can be accessed from anywhere. Also it has a mobile app, which is available for both Android and iPhone/iPad. The mobile app is also integrated with the web-based solution using application programming interface calls to the central data repository.Case studies for two limestone mines are presented where this solution is being used in its initial format. This software platform enabled analysis of the outcome from a previous blast pattern and then subsequently allowed optimisation of blasting operations based on historical data. Uses of this platform have resulted in improved key performance indicators in these two limestone mines. The mobile app as part of this platform enables extensive field blast data capture and analysis and also various predictions before a blast. Data collected include blast parameters, individual hole charging, initiation pattern, videos, photographs and vibration records for analysis/reporting. The key features of the solution are a blast designer, a detailed blast data collection/analysis and a series of environmental predictors. These predictors give blast results in terms of fragmentation, flyrock, ground and air vibrations and wave front reinforcement and take remedial steps before blasting to optimise and control adverse environmental impact. Many features, such as fragmentation predictor and mobility solution, are completely unique features that are not available elsewhere in such a field personnel-friendly manner.CITATION:Bhandari, S, Parihar, C, Garg, R and Bhandari, A, 2015. An integrated technology solution for optimised and environmentally-controlled blasts, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 393–400 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By G Love, S Maher

In Victoria’s onshore Gippsland Basin, geology is driving brown coal developments, and geologists are key decision-makers. Prompted by volatile energy prices and the likelihood of a carbon constrained future, significant work has been carried out on the next generation of technologies to be applied to this giant resource. These include new-generation gasification technologies, coal conversion processes yielding products as diverse as diesel and fertiliser, drying technologies producing thermal and metallurgical coals and in situ conversion processes. However, coals aren’t coals, and brown coal available for new projects will have different quality parameters and mining economics from that currently mined.New projects are likely to be developed on coals with moisture contents averaging 60 per cent and corresponding low energy values. Whilst ash values will be low, averaging just 5 per cent (dry basis), this will at times approach 10 per cent, which is a level that would challenge the installed-generation technologies. Sulfur values will average 0.4 per cent (dry basis), but at times exceed 0.6 per cent, requiring technologies that address the potential for sulfur dioxide emissions. Whilst localised high levels of the fluxes iron (>1 per cent dry basis) and sodium (>0.3 per cent dry basis) would increase fouling of installed technologies, they may be suitable for selected next-generation technologies.Project viability for this next generation of technologies will be strongly influenced by mining cost, and geologists are playing a role in identifying higher-value coal. At its simplest, this is being achieved for open cut mines through regional, vertical strip ratio assessments, which are considered a first-order proxy for mining cost. Follow up assessments are incorporating mining and processing cost, coal quality penalties and product revenues. At a regional scale, it is informing the likely location and relative timing of future mine developments, as well as thinking around rehabilitation strategies, infrastructure and land-use planning.For deeper coal, factors like macro permeability, the ability to isolate seams from aquifers, groundwater chemistry, pressure temperature conditions, connection with groundwater recharge and in situ biota are being used as vectors to in situ coal conversion opportunities.Matching coal to the next generation of technologies has benefited from regional-scale geological studies of coal quality and mining economics, and has benefited from early engagement between geologists, technology developers and project proponents.CITATION:Maher, S and Love, G, 2014. Matching brown coal to the next generation of Latrobe Valley projects, in Proceedings Ninth International Mining Geology Conference 2014 , pp 77–84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By G Gosson

An important requirement in every geological quality control program is that the identity and grades of the control samples (duplicates, certified reference materials (CRMs), and blanks) must remain æblindÆ to the analytical laboratory. Once the entity to be controlled is aware of relevant details of the control process, such as the identity of the control samples, the objectivity may be lost and the control may no longer be completely valid. Whereas the blind insertion of field duplicates and coarse blanks can be easily conducted at site, simultaneously with the sampling process, the rest of the control samples should be inserted into the batches during or after sample preparation and prior to assaying, in order to ensure a proper assessment of precision, accuracy and assay contamination, independent of the internal quality control of the laboratory. Such a procedure raises the concern that blind insertion of crushed or pulverised material in sample batches prior to assaying could represent a breach in the chain of custody principle, as samples would have to be temporarily returned to the custody of a non-laboratory person in charge of the insertions. In this seemingly conflict scenario, what should we give up? Do we maintain the strict chain of custody, knowing that the laboratory will be aware of the identity of some of the control samples, or that some duplicates will not be true same-batch duplicates? Do we ignore chain of custody issues to maintain the anonymity of the control samples and insert blind same-batch duplicates, CRMs and blanks? Is it possible to do blind insertions without breaching the chain of custody? Current NI 43-101 and JORC requirements, as well as real-world QA/QC and sample security practices, are discussed in light of AMECÆs approach to the solution of this apparent dilemma.

Jan 1, 2008