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By D G. Rantucci

Organic carbon is a major ore contaminant at MMG’s Century mine. This carbonaceous matter is associated with shale hosted sphalerite mineralisation. It occurs as elongated lamellae and as inclusions in porous sphalerite aggregates which are fine grained and difficult to liberate from sphalerite. The carbon prefloat circuit was designed to remove the liberated organic carbon in order to mitigate excessive reagent consumption, contamination of the lead and zinc concentrates and poor flotation performance in the primary zinc circuit. The consequence of organic carbon removal is that sphalerite and galena minerals are lost to the prefloat concentrate. A Jameson Cell was installed in late 2005 as a prefloat cleaner cell. Operational experience showed that the cell became capacity limited during periods of high amounts of organic carbon in the feed and was subsequently bypassed.Reactive style operating strategies were implemented to manage the effects of insufficient organic carbon removal by the prefloat circuit but due to the relatively large circuit residence time, upstream changes meant hours before the downstream circuits were stabilised following a disturbance from excess carbon.This paper describes the modifications and testwork undertaken to enable the Jameson Cell to be operated during periods of high organic carbon in the float feed and the implementation of process control initiatives to proactively remove the required prefloat mass from the float feed to eliminate the reactive style operating strategy.The process control modifications centred on dynamically targeting a prefloat mass recovery determined by an equation relating the carbon to zinc ratio to the carbon prefloat mass as a percentage of the float feed. The equation was developed by analysing historical data. These improvements served to optimise the prefloat circuit and consequently stabilise the downstream lead and zinc circuits.

Aug 8, 2011

By P A. Kirsch, A Hine

Mining is a major global industry that requires the moving of considerable volumes of earth and rock (overburden) to win the valuable ore prior to mineral extraction and processing. As a result of this process, new landscapes are created, both extracted voids and overburden piles, as well as infrastructure for management of mine operations, wastewater, tailings, other raw materials, transportation and extreme rainfall events. Resource companies must develop and obtain regulatory approval for detailed plans that manage this displaced material through all phases of the life-of-mine and rehabilitate the site at the time of closure (including landform stability, revegetation and ongoing management).Individual mine sites operate in long time frames (ten to 50 years), with several mines often operating in the same region, generating cumulative overburden volumes and heavily altering the original landscape. These impacts are universally framed as a negative consequence of the industry, especially by modern society that values natural (and some agricultural) landscapes as pristine and almost sacred. Overburden and tailings are also seen as a problem, and are a significant business cost to mining practice.This paper looks to investigate perceptions of mining and post-mining landscapes, questioning the aesthetically driven emphasis on the ‘natural’. It proposes instead an opportunity to reframe the way we look at overburden and landscape impacts from mining, exploring the possibility of imagined post-mine landscapes unburdened by traditional aesthetic expectations. These landscapes, to be conceived by regional stakeholder roundtables, have the capacity to be built by regional mining consortia as a foundation for sustainable post-mining economies.Post-mine regeneration offers both the motivation and the basic materials to create an altogether new environment from a blank slate. Few circumstances allow the opportunity to truly explore a re-envisioning of the land on a huge scale, and the possibilities merit serious consideration.CITATION:Hine, A?and Kirsch, P?A, 2014. Dreams of futures past – curating post-mining landscapes, in Proceedings Life-of-Mine 2014 , pp 121–138 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By T Huynh, K Tungpalan, E Wightman, M Edraki, S Palaniandy

Most preventive environmental management practices promote proactive integrated approaches to waste management. For example, life cycle assessment is often used to find the ‘hot spots’ of environmental burdens. This kind of approach is often based on generic data and has rarely been used for tailings. Besides, life cycle assessments are less useful for designing operations or simulating changes in the process and consequent environmental outcomes. It is evident that an integrated approach for tailings research linked to better processing options is needed.The aim of this Nextmine™ project is to develop new tailings management models by streamlining orebody characterisation, process optimisation and rehabilitation. We present an integrated tailings management approach and preliminary results from a case study. Combined grinding and flotation models were developed using geometallurgical data from the orebody, to predict the properties of tailings produced under various processing conditions. The modelling scenarios based on the case study data provide the capacity to predict the composition of tailings and the resulting environmental management implications. For example, the type and content of clay minerals in tailings will affect the geotechnical stability and water recovery. Clay content will also influence decisions made for paste or thickened tailings and underground backfilling.CITATION:Edraki, M, Huynh, T, Wightman, E, Tungpalan, K and Palaniandy, S, 2015. An integrated approach to proactive tailings management, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 323–332 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By F Ouchterlony

Soviet precursors to Cunningham’s Kuz-Ram model from 1983 are described. They are rooted in the mean fragment size and Rosin-Rammler (RR) fits to sieving data and rely on approximations. Three versions of the Kuz-Ram model are presented and all three are de facto based on the median fragment size x50, even if the term mean is used in the papers. This discrepancy caused Spathis in 2004 to suggest a correction procedure for the Kuz-Ram rock factor A, which was said to explain some of the missing fines in the model. This correction, while applicable to Cunningham’s 1983 paper, does not apply to his 1987 paper, in which he presents his own A factor.Common fixes of the Kuz-Ram model’s fines issue are fragmentation models where the fines are mainly generated in a crushed zone around a blasthole. This is contradicted by careful model blasting tests. The lack of a largest block size in the RR function may lead to spurious values of the uniformity coefficient n, eg in conjunction with image-based fragmentation measurements or crusher modelling. These issues may be solved by using the transformed RR function, which has a largest block size xmax or its replacement by the Swebrec function, such as in the KCO model.The mean to median issue is investigated in some detail and it is found that using x50 instead of the mean:has a sounder theoretical backgroundis less prone to errorsis not contradicted by the original Soviet data.It is finally suggested that future work on fragmentation prediction equations focus on the use of distribution independent quantities like percentiles, eg x50, x20 and x80. Some previous work in this direction is briefly analysed and one consequence is that the n-value of the Kuz-Ram model should depend on specific charge.CITATION:Ouchterlony, F, 2015. The median versus the mean fragment size and other issues with the Kuz-Ram model, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 109–120 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By D Gagnon, P Bouchard, F Vanier, E Soares de Lima Filho, J El-Haddad, M Sabsabi, G J. Wilkie, A Beauchesne, A Hamel, A Blouin, T Vaillancourt, F Boismenu, A Harhira, A Plugatyr, C Padioleau

Quantitative mineralogy is an established discipline in the geosciences and is aimed at providing mineral grade and texture information for geological and mineral processing applications. The two core technologies underpinning Quantitative Mineralogical Analysis (QMA) are Scanning Electron Microscopy (SEM) in combination with Energy-dispersive X-ray Spectroscopy (EDS). Technologies such as QEMSCAN and MLA are now routinely used to optimise the performance of large-scale mineral processing plants in the base and precious metal sectors. One of the major disadvantages of the QMA methods used today is extensive sample preparation requirements which make application of this technique to real-time mineralogical characterization not feasible. A breakthrough has been achieved by the National Research Council Canada in collaboration with CRC ORE by developing a novel Laser Induced Breakdown Spectroscopy (LIBS) based technology capable of real-time mineralogical characterization of process streams without sample preparation. The potential applications of this technology include, but not limited to, in-pit muck piles, underground draw points, cross-belt analysis as well as slurries. This paper describes the development of the LIBS-based technology from a proof-of-concept (TRL2) to the construction of a prototype sensor and its validation in a simulated environment (TRL5). Future work is being planned to test and further validate the LIBS sensor on a mine-site which will progress the technology to its next readiness level (TRL6).

Nov 10, 2020

By M Watson, A V. Engelbrecht, E Murray-Hayden

Whereas mine reconciliation is a well-established month-end process for most modern mining operations, the resource sector has yet to endorse uniform reporting factors against which model accuracy and metal recovery can be formally assessed. Logically, any comprehensive reconciliation framework should facilitate comparison between period reserve, mine and mill and production figures. Historically, Parker’s F Series ratios (Parker, 2012) are often used in some form by mine operators, although they are rarely shared externally, as formal definitions have yet to be accepted. This paper presents a structural extension to the reconciliation process, wherein resource ratios (R Series factors) are used to quantify the long-term impact of the information effect, together with dilution and ore loss. A case study from the El Limón Guajes (ELG) Mine Complex in Mexico is used to demonstrate how an R Factor Series can be implemented to facilitate operation optimisation, over and above conventional F Series reconciliation treatments. This approach is applicable to any mining operation.

Mar 22, 2022

By R Norris, M Dunne

Mining and mineral processing is expected by society and obliged by law to operate in an environmentally friendly fashion, minimising the impact on and avoiding damage to the environment. Substantial efforts by the industry, as well as by process and equipment designers have resulted in many innovative developments, which show that operating in an environmentally responsible manner can be achieved in a cost-effective way. This paper showcases five emerging equipment best practices in industry including installation examples. Flip-flow screening machines are proven worldwide in the dry classification of coal and other minerals, reducing the size of beneficiation plants whilst reducing energy, water demand and media consumption. They also allow the screening of wet/sticky materials not able to be sized using conventional screens. The belt press filter is a small fraction of the operating and capital cost of alternative dry tailings technologies. This gives operators who must dry their tailings a competitive advantage and makes such ægreenÆ operations much more sustainable. The filtercake is disposed with other plant rejects, eliminating the need for tailings dams to be constructed and thus also often increasing mine reserves. Mining applications include coal tailings, sand tailings, sinter plant waste and power station fly ash. Screen-scroll and vibrating centrifuges are widely used in the coal, potash and salt industries to dewater the product to low surface moistures. Inclined plate Lamella separators are used for toxic water clarification and/or sludge thickening in many downstream metal industries with the underflow often dewatered in a belt filter press. Such low cost, high capacity thickeners could also be used instead of conventional thickeners at smaller mines. The simple and reliable continuous washing upward flow (CWUF) sand filters have been used for treatment of waste water from coal preparation plants and steel works as well as in the worldwide production of potable water. The filtered waste water from mining processes can then either be reused or discharged from site. Other installations include cleaning mine water to prevent the blocking of dust suppression spray nozzles.

Jan 1, 2006

By D Semini, B Newcombe

Base-metal sulfide refractory gold ores often contain a portion of ‘free’ gold that is amenable to recovery using gravity concentration methods, whilst the refractory portion of the gold is better recovered using flotation. The decision as to whether a plant treating a refractory gold ore should utilise gravity concentration or a flash flotation circuit (or a combination of both) within the grinding circuit is usually made at the design stage of flow sheet development. Very limited data is available in the published literature which provides an industrial scale comparison on which to base such a decision and conventional laboratory testing methods are often the only way of obtaining such data. The optimum processing route will also be mineralogy dependent.This paper presents the findings of operating a refractory gold plant with either flash flotation (normal operation) or a combination of flash and gravity recovery methods treating the cyclone underflow stream and will demonstrate the regions of the recovery profile that each contributes to. Size-by-assay analysis has been performed on a number of streams around the operating plant to gain an insight into the changes that occur when the gravity circuit is in operation in addition to the flash flotation circuit. A discussion around the implications to overall plant operation in combining the use of a batch process (gravity concentration) with a continuous process (flotation) is presented.CITATION:Newcombe, B and Semini, D, 2014. Interactions between flash flotation and gravity concentration – an industrial case study of a refractory gold concentrator, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 427–436 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

By S Robinson, R Perkins, D Barrett, D Kepert, C Fowers

The discovery and delineation of significant mineralisation in the Eliwana region continues Fortescue Metals Group’s strong exploration success. In the decade after the first hole was drilled into Christmas Creek in mid-2004 a total of over 11 Bt of hematite-goethite mineralisation have been delineated supporting the raising of $13 B, construction of five mines, 620 km of rail and a five-berth port. As of June 2014, Fortescue was shipping at the rate of 155 Mt/a. The area including the Eliwana and Flying Fish deposits is one of a number of future growth opportunities that Fortescue is currently evaluating.The Eliwana and Flying Fish deposits occur on the south dipping limb of the Brockman Syncline/Jeerinah Anticline. The Eliwana group of deposits are hosted by the Brockman Iron Formation with the Flying Fish/Broadway group hosted by the Marra Mamba Iron Formation.Structurally the area is dominated by moderate southerly dips of the regional dome and keel style folding. The regional limb is locally cross-cut at a small angle by asymmetric north facing Ophthalmian folds trending 110°. These fold sets, in part, preferentially host subsequent supergene mineralisation. Faulting is only locally apparent.Early phases of exploration commenced in 2006, with mapping of Flying Fish and reconnaissance drilling in 2007. However, due to the concurrent discovery (Clarke et al, 2009) and subsequent fast tracked development of Solomon channel iron deposit and Firetail bedded iron deposit (Simpson et al, 2011) priority was placed on developing Solomon due to its relative proximity to existing Fortescue infrastructure. Staged follow-up drilling of both Marra Mamba and Brockman targets at Eliwana was progressively undertaken from 2008 onward.As of 20 May 2014 a total of 1494 reverse circulation (RC) holes for 54 248 m and 13 diamond holes had been completed, resulting in the delineation of a Mineral Resource of 740 Mt. Exploration via mapping, drilling and metallurgical evaluation of adjacent prospects continues with additional resources expected in the future.CITATION:Barrett, D, Perkins, R, Kepert, D, Robinson, S and Fowers, C, 2015. Geological setting of Eliwana and Flying Fish deposits along the north limb of the Brockman Syncline, Hamersley Province, Western Australia, in Proceedings Iron Ore 2015, pp 219–228 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 13, 2015

By D Connelly

Silver and gold bearing ore from the Troy Resources NL Casposo Gold-Silver Project, located within the San Juan Province of Argentina contains a complex mix of gold, silver, electrum and silver sulphides in the ore. Casposo is a typical low sulphidation epithermal style gold–silver deposit where mineralisation is hosted within rhyolite – andesite flows and breccias. Veins are typically banded quartz–chalcedony colloform - crustiform banded with quartz - carbonate infill. Mineralisation is associated with an assemblage consisting of quartz, chalcedony, adularia, calcite, illite, sericite and trace sulphides. Gold and silver occur as electrum, native silver, sulfosalts and silver sulphides. This paper presents a case study that describes the process selection, development and engineering of a tailored process plant for the recovery of gold and silver from this ore.The original feasibility study, modelling, metallurgical testwork and engineering studies are outlined. The final flowsheet was based on minimising capital cost, operability, recovery and minimising technical risk.The process flowsheet uses the traditional Merrill Crowe route because of the high silver to gold ratio in the feed and achieves maximum gold and silver recovery while providing a common facility for future ore body treatment.

Aug 8, 2011

By R L. Koenig

The rediscovery and recognition of the magnetite potential of the iron mineralisation at the Hawsons Project area 60 km south of Broken Hill has the potential for the development of a new series of magnetite iron-ore operations across the Braemar Iron Formation in New South Wales and South Australia. Despite the low-grade of 16 per cent magnetite, the Hawsons project feasibility studies are indicating a positive business case for a large-scale 20 Mt/a of magnetite project for the following reasons:• The mineralisation is on a huge scale, with a major potential for increases beyond the already very large established resource of 1.4 Bt.• The mineralisation is particularly soft for crushing and grinding, with a Bond work index of 6.3 and an overall comminution power requirement of 6.7 kWh/t of ore. This equates to 39 kWh/t of concentrate which is significantly less than for similar projects.• The mineralisation fractures easily, preferentially along grain boundaries.• Location is close to mining infrastructure and a skilled workforce at Broken Hill, 60 km to the northeast.• It is close to road and rail infrastructure for access to the resource.• A high-grade, clean magnetic concentrate can be produced, with the only contaminant being silica.The deposit is a sedimentary siltstone which is considerably different to other known magnetite deposits. This caused significant differences in Davis Tube Recovery (DTR) results between laboratories so that the softness of the ore has required a close focus on, and changes to the laboratory procedures. A DTR procedure has been developed to provide consistent results across the deposit.Crushing and grinding test work has established a clear advantage in the use of the high-pressure grinding rolls (HPGR) crushing and grinding circuit for this particular ore. The power required for comminution using the HPGR crushing circuit is about half the power required for the Autogenous milling circuit.Therefore, despite the low magnetite grades, the Braemar Iron Formation in New South Wales and South Australia has the potential be a new magnetite iron ore province.

Jul 11, 2011

The Yanacocha district hosts the largest and most significant acid-sulphate, high-sulphidation deposits in Per· with total production, reserves and resources of over 27 million ounces of gold. Several other smaller high-sulphidation systems are also recognised in the Cajamarca region including La Zanja, Sipßn, Tantahuatay, and San Nicolas. These each have reserves/resources of between 640 000 and 800 000 ounces of gold. Gold deposits in the Yanacocha district are hosted in an extensive volcanic field. Flow domes have intruded precursor pyroclastic rocks and flows that are interpreted as part of an earlier intermediate multi-vent volcanic complex. The larger, contiguous Yanacocha Norte - Sur and Encajon gold deposits are spatially associated with late-stage diatreme breccias. At La Zanja extensive acid-sulphate alteration is associated with the margins of the small San Pedro caldera (6 +4.5 km), nested within the larger, less well-defined La Zanja caldera (19 +24 km). The inner caldera is resurgent with abundant magmatism expressed as several flow dome complexes located on the caldera rim, and shallow level intrusive stocks. Gold mineralisation is associated with a WNW-trending structural corridor that transects the southern margin of the San Pedro caldera. On the eastern side of the La Zanja caldera there are a series of younger andesitic eruptive centres, some associated with acid-sulphate alteration and gold mineralisation. The Sipßn deposit occurs in one such centre with structurally-controlled gold associated with a NE-trending silicified structure developed within a sequence of andesitic tuffs. In conclusion, although a number of high-sulphidation deposits are recognised in northern Per·, their settings and styles of mineralisation are all quite different. Smaller deposits generally have strong and obvious structural controls. In the larger Yanacocha deposits the structural controls are less obvious, and mineralisation is disseminated in porous or strongly fractured and brecciated silica. Erosional levels are probably a significant factor, with disseminated mineralisation at higher levels, and structurally-controlled mineralisation in more deeply eroded deposits.

Jan 1, 1999

By P Hawke, J Hurst, B KrapeP

Hancock Prospecting Pty Ltd (HPPL) drilled two deep diamond stratigraphic holes (ECD0001 and RHD0296) within the eastern Fortescue Valley in the Pilbara of Western Australia. Located south of the Roy Hill Iron Ore project, the holes aimed to define the stratigraphy of the Marra Mamba Iron Formation (MMIF) of the Chichester Range and its south-dipping extensions below recent cover. Previous attempts to define the MMIF of the Chichester Range have resulted in differing interpretations due to the data available at the time.The unweathered MMIF beneath the Fortescue Valley in the HPPL drill holes is characterised by dolomitic carbonate interbedded with stilpnomelane-rich shales, chert and banded iron formation (BIF) with hematite staining. This intersection equates to ~75 m of carbonate-facies iron formation, as opposed to the ~230 m thick oxide-facies BIF and shale sequence encountered south of the Fortescue Valley.Various detailed geological core analyses and interpretations from ECD0001 and RHD0296 were integrated with regional diamond and reverse circulation (RC) holes from across the Fortescue Valley. Interpretation of the data indicates that the eastern Fortescue Valley MMIF represents a thinned thickness sequence of the whole formation. The MMIF of the Chichester Range and Fortescue Valley has gamma logs that correlate strongly in parts to the type section used for MMIF south of the Fortescue Valley. Therefore, the outcropping MMIF in the Chichester Range represents an eroded equivalent of the æreducedÆ thickness MMIF observed in ECD0001 and RHD0296.Data from deep diamond drill holes across the valley, from the Hamersley Basin to the Carawine Basin, were correlated. The correlation shows that the depositional site of the MMIF in the HPPL diamond drill holes is consistent with a proximal ramp setting, in which iron-rich shales wedge up-palaeoslope and shelf-derived carbonate turbidites wedge down-palaeoslope. Not only is it the occurrence of these shales that define the MMIF, but they also determine the northward potential to develop orebodies, as they are the source of iron from which iron-rich oxides and carbonates of metamorphic or diagenetic origin form.CITATION:Hurst, J, KrapeP, B and Hawke, P, 2013. Stratigraphy of the Marra Mamba iron formation within the Chichester Range and its implications for iron ore genesis at Roy Hill - evidence from deep diamond drill holes within the East Fortescue Valley, in Proceedings Iron Ore 2013 , pp 91-106 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By K J ROSENGREN

Underground rock mechanics was initiated as a formal discipline in Australia by early studies for underground structures for the Snowy Mountains Scheme in the 1950s. These techniques were quickly embraced by underground mining and there has been steady development to the present time. The paper reviews the status of current techniques for rock mechanics studies and discusses some important issues such as ground support, mine filling and caving. It concludes that a considerable degree of engineering judgement is still required for the practical application of rock mechanics to underground mine design.

Jan 1, 1992

Bacterial leaching of sulfide minerals are fairly well established in heap, dump and in situ leaching and the primary bacterial treatment of refractory gold concentrate using CSTR have gained industrial prominence in recent years. Three cultures, a mesophile T ferrooxidans (DSM583), a moderate thermophile Sulfobacillus acidophilus (strain YTF1) and a extreme thermophile (Sulfolobus strain BC65) were used for the biooxidation (pre-treatment) of the Porgera gold-bearing pyrite concentrate under optimum O2 and CO2 enriched air (30 per cent O2 and ten per cent CO2) based on volume ratios. The positive effect of using oxygen and carbon dioxide enriched air for the biooxidation of gold-bearing pyrite mineral was clearly demonstrated where an increase in Fe release rate by a factor of 2.8, 1.8 and 1.5 for DSM583, YTF1 and Sulfolobus respectively were observed compared with the shake flask tests. The lag phase observed with the other test conditions such as in shake flask or with air decreased by about 80 per cent for all three cultures. The average observed dissolved oxygen concentrations in the pulp for these tests were 8.7, 5.8 and 5.0 mg/L for DSM583, YTF1 and Sulfolobus respectively, indicating that O2 was not limiting in these tests. The pulp redox potential was observed to increase with time for all tests coincident with the leaching rate and reaching a maximum of 663 mV, however the maximum value differs for each strain, with DSM583 exhibiting the highest followed by YTF1 and Sulfolobus. Biooxidation of pyrite under optimum gas enrichment at different pulp densities showed near total Iron extraction occurred for pulp densities of three, ten and 20 per cent (w/v). At high pulp densities, more so at 40 per cent than 30 per cent (w/v), the leaching rate decreased rapidly for tests with YTF1 and Sulfolobus. Monitoring of dissolved O2 shows that O2 demand increased with increasing pulp density and the average dissolved O2 concentration observed for YTF1 and Sulfolobus at 40 per cent solids concentration was 1.0 mg/L and below, suggesting limiting oxygen and carbon dioxide conditions for these two cultures. The decrease in leaching rate observed at high pulp densities (30 and 40 per cent) under optimum gas enrichment was accompanied by low metal dissolution and low redox potential values which was attributed to shear stress due to attrition of cells by high solids concentration, toxicity of metal ions especially Ag and Fe and the formation of precipitates and jarosites as confirmed from XRD analysis of leach residues hence impeding the leaching process. Limiting conditions due to high pulp density and viscosity were only observed for YTF1 and Sulfolobus. The subsequent cyanide leaching for precious metals from the pre-treated pyrite concentrate in all cases shows the extent of gold and silver recovery increased with the degree of pyrite oxidation and Au and Ag recoveries in excess of 80 per cent were achieved compared with only 18.1 per cent and 35.9 per cent for gold and silver respectively when treated by direct cyanide leaching on the original, untreated concentrate.

Jan 1, 2004

By R Norris, M Dunne

Substantial efforts by the industry, as well as by process and equipment designers, have resulted in many innovative developments that provide cost effective reductions in water usage. This paper showcases four emerging best practices in industry including examples of recent installations. Belt press filters are a small fraction of the operating and capital cost of alternative ædryÆ tailings technologies. This gives operators who must ædryÆ their tailings a competitive advantage and makes such operations much more sustainable. The new generation of belt filter presses use less energy, produces lower cake moistures and better disposal stacking properties. The need for tailings storage facilities may be eliminated or in some cases high-grade tailings can be dewatered and sold as a low value product. Mining applications include sand tailings, sinter plant waste, coal tailings and power station fly ash. Flip-flow screening machines are proven worldwide in the dry classification of coal and other minerals, reducing the size of beneficiation plants, whilst reducing energy, water demand and media consumption. They also allow the screening of wet/sticky materials not able to be sized using conventional screens. Lamella separators are used for toxic water clarification and/or sludge thickening in many downstream metal industries with the underflow often dewatered in a belt filter press. Such low cost, high capacity thickeners could also be used instead of conventional thickeners at smaller mines. The simple and reliable continuous washing upward flow (CWUF) sand filters have been used for treatment of waste water from coal preparation plants and steel works as well as in the production of potable water. The filtered waste water from mining processes can then either be reused or discharged from site. Other installations include cleaning mine water to prevent the blocking of dust suppression spray nozzles.

Jan 1, 2006

By K Le Bron

Fatalities that occurred because of rock falls in off-reef excavations (excluding shafts) over the last three years range between ten per cent and 20 per cent of the total number of fatalities that have occurred due to rock falls in the South African mining industry. These rock falls, mostly exacerbated by blasting practices, occur because of failure on discontinuities within the rock mass. Among other reasons of their occurrence is insufficient support installation or the incorrect assessment of rock mass conditions. This report presents qualitative analysis intended to outline rock stability conditions in tunnels subjected to dynamic loading. Seismic waves including those created by firing an explosive charge in tunnel rocks are considered. The rock behaviour is monitored using geophones and extensometers variably installed to record the near and far effects of roof bolt support units on a dynamically loaded rock. The paper discusses the results of field investigations.

Jan 1, 1999

By H Arvidson, J Vann

When only wide-spaced drilling is available, for example at concept, prefeasibility and feasibility stages, properly implemented linear estimation (including ordinary kriging) predicts grade tonnage relationships that are over-smoothed compared to final production estimates (and production). Non-linear estimation and conditional simulation are alternative geostatistical approaches that can provide more reliable estimates of the recoverable tonnage and grade from wide-spaced drilling. Non-linear estimation and conditional simulation have been rarely used on iron ore deposits. However, these techniques have had wide application in other commodities such as gold and base metals. Conditional simulation has been used in the iron ore industry (eg Guibal et al, 1997); however, its use here is outlined as a means of generating non-linear estimates, not just its use for variability and drill spacing analysis. As a rule, regardless of commodity, the decision to use non-linear geostatistics will necessitate increased skills and require more time. This decision must therefore be justified in terms of cost-benefit. Such cost-benefit analysis is not straightforward, and to help an approach for determining when linear estimates are inadequate is presented. Recommend in this paper is a well-established non-linear geostatistical approach, the global ædiscrete Gaussian modelÆ (DGM) of change of support, as a tool to establish whether moving from linear to non-linear estimates will materially improve estimate results. Also discussed is the additional use of DGM as a block model validation tool. One specific factor contributing to the lack of application of non-linear geostatistical methods in iron is the added difficulties that arise when conditional simulation and non-linear estimates are required to reproduce the numerous and often important correlations between variables in iron ore deposits. Consequently, presented in the paper is a synoptic review of non-linear estimation and simulation methodologies applicable to correlated variables.

Jan 1, 2007

By S C. Dominy

For any gold deposit-based geometallurgical study, the collection and processing of representative samples for gold grade and recovery tests is critical. Sampling protocols should be designed to suit the style of orebody in question. The proportion and size of gold particles has a direct impact on the effectiveness of sampling protocols and metallurgical recovery processes employed. Studies focussing on ore mineralogy and gold particle deportment, size and distribution are required. Key issues are the presence of gold particle clustering (important for sampling optimisation) and proportion of coarse versus fine to refractory gold. X-ray computed tomography (CT) is a radiographic technique that produces high-resolution 3D computerised models of objects based on density distribution. The ‘virtual’ specimens are made up of voxels, the 3D equivalent of pixels each assigned a grey value based on X-ray absorption. This paper presents the results of recent research on the imaging of in situ gold particles in a coarse gold-bearing ore. The technique shows promise as a rapid non-destructive method for preliminary characterisation to facilitate more detailed studies. Early and rapid gold particle determination enables sampling protocol optimisation and metallurgical recovery parameters to be defined prior to detailed feasibility studies

Sep 5, 2011

By D J. Bradshaw, E M. Wightman, C L. Evans, B Triffett

During the commissioning phase of Prominent Hill, periods of reduced recovery were experienced with higher-grade ore blends. This was unexpected and as part of the process to identify the cause, surveys were conducted in May 2009, with two different ore blends (copper grades: 1.94 per cent Cu (blend 1) and 2.49 per cent Cu (blend 2)). Metallurgical performance was assessed in terms of rougher recovery and grade with consideration of both pulp and froth effects. In addition, hydrodynamic measurements (gas hold up, bubble size, superficial gas velocity) as well as measurements of bubble load and top-of-froth grade were taken during the surveys and full mineralogical assessment of selected streams completed to characterise the nature of the differences. The metallurgical results showed that the lower performance was obtained with blend 2 which contained the higher amount of chalcocite and was higher-grade. Analysis of the survey data showed that for both ore blends more than half of the copper loss occurred in the +38 ¦m size fractions. Almost 30 per cent of the copper in the +38 ¦m fractions that reported to the rougher tails during processing of blend 2 was liberated compared to less than five per cent for blend 1. Additionally almost 60 per cent of the copper in the +38 ¦m fraction of blend 2 was chalcocite compared with approximately 20 per cent in blend 1. This paper discusses the sensitivity of the chalcocite-to-surface chemistry effects causing marked reductions in recovery either through reduced pulp recovery or froth phase (detachment) effects. The reagent suite and operating conditions were subsequently changed and the recoveries increased substantially and the sensitivity to ore changes eliminated. It should be noted that subsequent optimisation work, which focused on recovery improvement, has led to copper recoveries of over 90 per cent being achieved.CITATION:Bradshaw, D J, Wightman, E M, Evans, C L and Triffett, B, 2012. Characterising the reasons for the difference in performance of two ore blends in early processing at OZ Minerals Prominent Hill Operation, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 273-278 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012