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By B Crowdey, J Wall

The particular underground operation relating to this paper is a gold producer and has an orebody predominately consisting of rhyolite and marcasites pyrite. The ore has been identified as being reactive to nitrates.Operations currently utilise two twin boom Tamrock™ Super-Drill Jumbos for development mining. Capital (waste) headings have a nominal size of 7 m wide × 6 m high, while ore headings are designed at 5 m wide × 5 m high, with the lower reaches of the mine narrowing down to a 4.5 m × 5 m design. Production drilling is currently undertaken with an Atlas-Copco L6 Solo. Due to the reactivity of the ore, inhibited emulsion phase bulk explosives are used for all blasting activities, with electronic detonators utilised in the production sequence.Sublevel shrinkage stoping is utilised when the orebody is stronger than the host rock. After blasting the ore, and during extraction, the surrounding host rock cannot maintain integrity and it ‘collapses’ on top of the ore. Gravity forces this collapsing rock to follow the blasted ore through the drawpoints.The highest risk involved with sublevel shrinkage stoping is the necessity for charge crews to work upon ‘rills’ at the drawpoints, which are occasionally unstable, to charge the next blast ring to be fired. To overcome this issue a loading technique called ‘precharging’ is used whereby two to three rings are charged, but only the first ring is fired. This technique can minimise risks by taking the charge crew away from the rill and brow.As this mine contains hot and reactive ground, strict guidelines from the Australian Explosives Industry and Safety Group Inc (AEISG) are adhered to. These guidelines relate to the sleep time for the precharged rings.This paper describes the issues faced with precharging in hot and reactive ground, the monitoring required and the systems and procedures that were put in place to enable a successful outcome.CITATION:Crowdey, B and Wall, J, 2014. Precharging sublevel shrinkage production rings in hot and reactive ground with electronic blasting systems, in Proceedings 12th AusIMM Underground Operators’ Conference 2014 , pp 283–288 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 24, 2014

By E R. Ramanaidou, M Wells

The aim of this paper is to summarise all known Phanerozoic ooidal ironstone deposits worldwide, including Australian deposits such as the well-known channel iron deposits (CID). Nearly 400 occurrences have been catalogued based on stratigraphy, geographical coordinates, facies, grade, tonnage and iron bearing ore minerals. The description also includes details on the geochemistry, genetic models and main references. Brief statistical analysis provides an overview of the variation between these deposits. This compilation offers a basis for better understanding of the ooidal ironstone deposits and a global evaluation of this important resource worldwide.

Jan 1, 2009

In recent years there have been many changes in mine ownership due to the on-going rationalisation towards larger mining companies. Larger companies inevitably find it hard to manage small mining operations and in many cases smaller mines do not fit corporate resource, production and profit criteria. Smaller companies are more suited to managing these medium or small scale mines and are tendering for the purchase or lease of mines that larger companies wish to dispose of. In addition to these factors there has also been a trend (especially in Western Australia) for mines to continue operating at ever increasing depths. This in turn has led to more mines operating in high stress environments and experiencing damaging seismicity. Assessing the viability of seismically active mines from a takeover or purchase point of view should involve analysing the risk profile of every aspect on mining that could be affected by adverse seismicity. This includes assessing current and alternative mining methods, mine designs, support systems, extraction sequencing, monitoring and blasting. This paper includes discussion on items that need to be assessed when considering the purchase of seismically active mines, with experience gained from some recent studies in Western Australia. In these cases it was apparent that quantification of previous seismic history on itÆs own was a totally inadequate method of assessing minewide seismic risk potential. A more holistic approach is required, taking into account all aspects of relevant data, all the minewide effects of seismic activity and all possible means of mitigating those effects.

Jan 1, 2002

By A D. Campbell

Conversion of Mineral Resources to Ore Reserves requires a multidisciplinary approach and application of a number of Modifying Factors. The Modifying Factors for mining, particularly dilution and recovery in a caving mine are complex and can be difficult to determine. Cave flow modelling software is widely used for mine planning, scheduling and forecasting metal production. However, the conversion of Mineral Resources to Ore Reserves remains a difficult and subjective process and a consistent approach to convert Mineral Resources to Ore Reserves as part of the cave flow modelling process is not published in the literature. This is due to the difficulty in estimating the Ore Reserve that remains as cave stocks at a particular point in the mine schedule, the recovered tonnage and grade of the diluting material at various stages in the mine life, as well as the Mineral Resource classification of both the recovered and diluting material that forms the Ore Reserve. The key principle of this paper is the tracking of the Mineral Resource classification in the flow model used to estimate the Ore Reserves. This is critical to defining the Ore Reserve as Proved or Probable and enabling transparency in the reporting process. An approach for dealing with mineralised external dilution in the Ore Reserve estimation process is also provided.This paper outlines the approach to convert Mineral Resources into Ore Reserves developed at the Ernest Henry mine sublevel cave (EHM SLC). The same method could be used in any cave mine and applied at any stage of the mine life. The process replaces broad-brush assumptions for the mining Modifying Factors, such as dilution and recovery, as these are determined numerically as part of the model computation. This paper explains the Ore Reserve estimation method with a worked example to enable the reader to adopt the process at any caving mine. Mineral Resource classification within the block model is embedded in the cave flow model and the flow model results used to attribute tonnes, grade and the mixed proportions of the Mineral Resource classification for material extracted from each drawpoint. This information is then used to convert planned mine production into the appropriate Ore Reserve classification. Since the flow model simulation follows the mine schedule, it can be used to predict depletion and cave stocks at any stage of the mine life, and can calculate a residual block model at the end of the mine life. The accuracy of the flow model is checked by validating the forecast ore grade and metal tonne with reconciliation data from the concentrator which is also used to calibrate the flow model.CITATION:Campbell, A D, 2017. A simple and accurate method for Ore Reserve estimation and Mineral Resource depletion in caving mines, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 253–260 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By M Recabarren, A Echeverria, J Ronda, J I. Guzman, R Dodds, G Juarez, E Vila-Echague

A strategic mine plan is a fundamental part of any mining operation. It must provide a realistic and operative extraction and processing schedule, and yield the highest value for the business. For open pit mines, the problem can be modelled as a set of blocks representing the deposit, for each of which we need to decide if it is going to be mined, if so, when and where it will be sent (process, stock or dump).This problem can be proven to be of NP-Hard complexity. The traditional approach used by mining engineers to tackle this complexity is to separate the problem into more tractable components, solving each separately. The first step is to use the Lerchs-Grossman (LG) algorithm to obtain the final pit limit, as well as a set of optimised pit shells (nested pits), using different input prices. Then, using this input, operational phases are designed. Third, the set of phases can be used as an input for a phase-bench style optimisation, usually using a mathematical programming-based algorithm.There are, however, several problems with this approach. First, dividing the problem into simpler parts has the consequence that any compromises made at early stages limit the potential value left for the following steps. Second, LG is a static algorithm, with no concept of the time-value of money, capacity limits, opportunity costs, etc. Phase design is essentially a manual step, for which nested pits provide insufficient information in practice, and therefore the quality of the result in terms of potential net present value (NPV) depends strongly on the experience and expertise of the designer. This means that key input data such as commodity prices, different processes capacities and mine movement limits, are considered only at scheduling, when there is little room for optimisation. This sequential approach limits the potential value in each step, where a simplified problem is addressed, instead of addressing the real, and more complex problem, which is dynamic and should be solved as a whole.We present in this paper an algorithm, and its commercial software implementation, that addresses the dynamic problem as a whole, simultaneously and automatically creating a high-value strategic mine plan that adheres to basic operational constraints, determining dynamic cut-off grades and delivering a set of phases which can serve as a much stronger guide than nested pits for the final design. We discuss some of the key elements of the algorithm and propose a new methodology for strategic mine planning, where phase design dynamically responds to mining strategy definition. Results using different mining and operational parameters on a fictitious copper deposit are used as a demonstrative example.CITATION:Juarez, G, Dodds, R, Echeverria, A, Guzman, J I, Recabarren, M, Ronda, J and Vila-Echague, E, 2014. Open pit strategic mine planning with automatic phase generation, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 147–154 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

The green field discovery of a two million ounce high-grade refractory gold ore deposit in the Indonesian Province of Sulawesi Utara, led Newmont to utilise its proven technical expertise in dry grinding and whole ore roasting to develop a 2000 tonne per day, 160 000 ounce per year operation in this remote and picturesque location.Located at an elevation of 250 in above sea level and ten kilometres to a deep water natural harbour, the hard rock open pit mine, process plant and infrastructure facilities were built to budget at a capital cost of US$132 million. The plant was commissioned with oxide ore, with the first gold poured in March 1996 and with refractory ore in January 1997. The operation rapidly met its production targets because of extensive forward planning and training programs developed for the local workforce. The presence of steep topography, fertile coastal plains, high rainfall, high seismicity of this location led to the decision to dispose of neutralised tailings in deep water off the coast instead of impounding tailings in a dam. This paper describes the development of the project and the challenges in developing a gold operation in a remote location which lacked infrastructure, the steps taken to ensure a smooth commissioning, and the selection of the workforce to operate a technically sophisticated facility.

Jan 1, 1997

By J Seppelt

The Kanmantoo Copper Project is owned and operated by Hillgrove Resources Limited and is situated in the Adelaide Hills region in South Australia. Mining in the area has taken place off and on over the last 140 years to recover metal from both copper and lead-zinc ores. This paper focuses on the commissioning, ramp up and future outlook for the copper concentrator at the Kanmantoo Copper Project with major focus on issues encountered and operating performance achieved to date.CITATION:Seppelt, J, 2012. Commissioning of the Kanmantoo Copper Concentrator, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 127-136 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By J Penman, N Turner, H Liu

This paper aims to present a snapshot of the risk profile for tailings storage facilities within Western Australia by comparing the spatial distribution of known facilities against common geohazards such as cyclonic activity, climate, and peak ground accelerations from earthquakes. The analysis also includes an assessment of proximity to populations at risk including towns and sensitive receptors including significant river systems and wetlands.

Jul 1, 2021

By J F. C L Costa, J C. Koppe

It is recognised by the major international codes that resource classification involves the interaction of numerous qualitative and quantitative criteria such as data quality, geological and grade continuity, etc. However, the difficulty in quantifying the degree of uncertainty associated with mineral resources estimation has led to the creation of a large suite of methodologies, terms and definitions, with almost every mining company having its own set of standards. It is also intuitively known that several traditionally used methods to evaluate resources do not take into account the spatial continuity of the grades, being unable to provide a reliable measure of the error associated with their estimates. Since they do not provide an error assessment, these methods are inappropriate to assess local or global uncertainty associated with an estimate. Faced with these problems, this work aims at developing a methodology for either quantitative or qualitative analysis of mineral resources estimation, through incorporation of uncertainty and the correct definition of the associated risk or error. The proposed methodology includes the development of a software code incorporating all the main classification techniques used by the mineral industry. A comprehensive study about each technique was conducted allowing a comparison of the parameters affecting mineral inventory assessment. A case study was conducted with a typical iron ore deposit data set from the Conceitpo mine of the Itabira Complex in the Iron Quadrangle, Brazil. The results showed the specific limitations of each classification system and the influence in selecting their key parameters, always based on subjective choices.

Jan 1, 2009

By Ellson I. G

Shay Gap was created for the sincrular purpose of housing, in comfort, the workforce that would be required to mine iron ore, from leases held by Goldsworthy Mining Limited, in hill country, approximately 170 kilometres east of Port Hedland in the Pilbara region of Western Australia. To combat the and environment, the Company ultimately decided to adopt a novel planning concept for the town, which had not been attempted before in Western Australia. The special problems encountered during planning, and the reservations that were expressed during construction and early settle ment, are now part of the dim past. During the three years of occupation now achieved, there has been accumulated a story of success in the provision of an acceptable alternative to modern suburbia. Not only may this be claimed, but it can also be argued that the Shay Gap concept has been a more successful solution to a real environmental problem in our arid Pilbara region than has been seen in other similar settlements.

Jan 1, 1976

By H Ishikawa, R Halomoan, S Palaniandy

The Karara iron ore project is a magnetite operation consist of open pit mining and concentrator to produce high-grade magnetite concentrate. The concentrator has adopted three stages of comminution, ie fine crushing in the high pressure grinding rolls (HPGR), primary ball milling and fine grinding in the TowerMill plus magnetic separation in between these comminution devices. Since 2014, the concentrator has increased the plant feed rate by 18 per cent. Meanwhile, the ore hardness has increased by 13 per cent to a Bond work index value of 15 kWh/t that led to a coarser flotation feed. Karara Mine has decided to shift the comminution workload from the primary ball mill to the TowerMill circuit by bypassing the 100 µm fine screen in between the ball mill and TowerMill circuits. This action has increased the circuit feed particle size distribution with a top size close to 1 mm. The specific energy consumption of the TowerMill circuit was approximately 3.4 kWh/t, and the circuit product sizes (P80) were ranged between 38 and 45 µm. A joint process improvement exercise was carried out to reduce the circuit product size closer to the magnetite liberation size, ie 35 µm. Among the activities were circuit audit, recommendation for improvement, modelling and simulation, multicomponent analysis, implementation of recommendations and quantification of the improvement. One of the key findings was the density effect of multicomponent minerals in the hydrocyclone. The analysis revealed that the low density coarser gangue minerals were bypassed to the hydrocyclone overflow stream that has resulted in a coarser particle size distribution. Meanwhile, more than 20 per cent of fine (-35 µm) high-density magnetite particles were recycled back to the mill through the hydrocyclone underflow stream and increased the circulating load. Based on these outcomes, several recommendations such as conversion to bottom feed configuration, use of smaller grinding media, high operating hydrocyclone pressure and additional grinding power to the TowerMill circuit were made to improve the overall circuit performances. Karara Mine has prioritised to implement those recommendations that have a minimal financial implication. Full-scale plant trials with bottom feed configuration and 17 mm grinding media were conducted to evaluate its performances. These trials have indicated that the grinding efficiency in the TowerMill was enhanced by 10 – 30 per cent. In May 2017, all the five TowerMills were converted to the bottom feed configuration. This paper discusses the impact of shifting the comminution workload load from the primary ball mills to TowerMill circuit and the performances enhancement of the TowerMill circuit. CITATION:Palaniandy, S, Halomoan, R and Ishikawa, H, 2018. Shifting the comminution workload from the primary ball mill to TowerMill circuit, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 163–176 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By T Isaksson, J Anderson

The procurement process for underground construction contracts, in particular those contacts involving tunnel boring machines (TBMs), is subject to many complex and inter-related variables, including national and local politics, public policy, community involvement and media attention û as well as strict environmental and legal requirements. Other restrictions include the time available to adequately investigate geotechnical conditions and viable technical options to determine the best construction methodologies û including selection of tunnel boring machine characteristics and, those construction means and methods suitable for the specific geotechnical and environmental conditions. The latter are, most often, quite imperfectly understood. æGetting it rightÆ implies that an optimal configuration û of machine type, characteristics and associated methodologies û can be found and successfully implemented for a particular project. æFrom the beginningÆ implies that the lack of time issue can be successfully resolved. Within an international context this paper highlights a number of issues of concern which relate to tunnel procurement systems and the ways in which certain key processes are managed during planning, design and construction. The authors argue that there is considerable room for improvement in the way tunnelling projects are undertaken and an approach is discussed which has the potential for substantial gains in cost and schedule and reduction of risk. Savings, however, may only be fully realised if the new methods can be fully implemented by all parties involved. This, we believe, will require the rejection of ætraditionalÆ forms of management and procurement with associated changes in the roles and responsibilities of owner, engineer and contractor. Additionally, risk identification, assessment and mitigation are essential cost and schedule control process which have, to this point, been underutilised by the underground construction industry.

Jan 1, 1999

By T Goswami, G Brent

In response to concerns over greenhouse gas (GHG) emissions and an imposed cost in some jurisdictions, many mining houses have committed to reductions in their GHG emissions. However, mining faces particular challenges in this regard, notably from increasing strip ratios. Furthermore, mining activity around the globe is not expected to decrease in the foreseeable future as mineral demand is driven up by the aspirations of rapidly-developing nations. Novel approaches will thus be needed if any reductions in energy consumption and GHG emissions of mining are to be achieved.This paper presents some directions for the mining industry to pursue in reducing their GHG impact, focusing on the difference that blasting methods can make. Importantly, large productivity and revenue gains can also be realised from these methods.Key directions considered here include optimising resource recovery and quality through:reducing coal damage and loss from throw blastingrecovering thin coal seamsproducing cleaner coal with less dilution.Blast design can also significantly improve the productivity of surface mining by:improving muck pile shapingimproving mine equipment productivityimproving scheduling.We show how a particular blasting method can eliminate coal loss in overburden throw blasting and can lead to large increases in coalmine profitability. Thin seams that were previously wasted can also be recovered with this method. Furthermore, the method has been implemented to combine several separate drill and blast cycles into a single cycle, leading to productivity gains.An illustrative example is given to show how increased coal recovery can increase revenues and more than offset any potential GHG emissions liabilities. Overall mine energy and GHG emission intensities can thus be reduced.CITATION:Goswami, T and Brent, G, 2015. Blasting approaches to increase mine productivity and reduce greenhouse gas emissions in surface coal mining, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 635–644 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By B Beale

Bow-tie analysis is a commonly used tool to identify and display risks that have the potential for an undesired hazardous event. The output of the analysis are bow-tie diagrams, which are an effective and versatile communication format that can be applied to any type of risk. Contrary to their simplicity, a proper bow-tie diagram that maintains its usefulness and clear communication is difficult to build. Over two decades assisting Major Hazard Facilities with bow-tie analysis for Safety Cases, several common mistakes have been identified. This paper aims to highlight those issues with examples and provide improvement strategies. A sample of the most common mistakes are: - overly complicated risk analysis - poorly scoped and defined terms - poor descriptions and justifications - identifying too many dependent controls. Overly complicated risk analysis leads to wasted time in obtaining data for little gain. The bow-tie diagram is only a model. Effort should be redirected into identifying and managing controls that will make a tangible difference to site risk. Broad scopes lead to enormous and confusing bow-tie diagrams for both the user and the workshop team. Defining the scope of the study, the consequence severity of interest and critical control characteristics creates focused workshops and targeted analysis. With more definitive scope, there may be more bow-tie diagrams, however, they are succinct and specific. Well described causes are imperative for clear communication to users, regulators and future bowtie review workshop groups. It is best to use common wording structures and explain the event stepby- step. Also, clearly document any likelihood calculations and use data references where applicable. Identifying all possible controls creates a false sense of security that there are many layers of protection. In reality, most controls are dependent on a single system or person and could all be compromised from a single failure. A definition of a ‘bow-tie’ control is required whereby it must be independent from other controls. Improving the bow-tie analysis process will assist operators in developing meaningful and ‘operational’ bow-tie diagrams to support risk management systems and practices.

Apr 16, 2024

By E J. B van Etten

This paper reports on the results of several years of monitoring rehabilitation at a silica sand mine on the Swan Coastal Plain, south of Perth. Mining here occurs below the regional watertable and leaves a post-mine landscape of dredge pond voids (pit lakes) with surrounding battered slopes. The restoration we recommended was to develop the pit lakes as wetlands of regional analogue and value. Several different restoration techniques have been applied to re-vegetate pit lake slopes over many years which have enabled an evaluation of reasons for success/failure of different restoration approaches. Learning acquired clearly showed the benefits of using fresh topsoil for restoration over topsoil that has been stockpiled for several years. Most topsoil used in restoration was from seasonal wetlands and consequently restoration was most successful in the riparian zone from the edge of pit lakes to about 2 m vertically above the water table. Topsoil restored areas above this level remained poor in plant species and cover. Conversely, remedial seeding/planting proved largely unsuccessful. Permanently and seasonally flooded pit lake margins recolonised relatively quickly and successfully with native sedges and rushes. Development of rehabilitated upper slope plant communities over time was evident with loss of typical wetland species and greater growth and survivorship of upland and dampland plant species on mid to upper rehabilitated slopes. Plant communities of lower slopes showed a converse pattern of development, with a shift towards a more typical wetland composition. We believe matching topsoil to site and development of topographic profiles similar to natural wetlands of the region are the keys to optimising restoration success of sand mines with shallow water tables.

Oct 5, 2011

By J P. Sykes, T C. McCuaig, J E. Vann

Resources added to the global metal inventory through exploration over the past 15 years have been generally of poor quality (declining grades, recoveries and lack of acceptable financial return). Similarly, companies opting for an acquisitions-based strategy have had to pick from a group of poorer quality resources left from previous exploration booms, and will struggle to deliver this metal to market economically. Increasing difficulty in obtaining sufficient social and community acceptance of mining projects and potentially an energy-constrained future may exacerbate this problem, redefining what is considered ‘ore’. There will need to be more focus on deposit quality, defined as sustainable margin in the future business environment.Traditionally there has been a lack of translation of ‘mineralisation quality’ back to mineral project design and mineral exploration. This disconnect is due to two main factors: the first is technical – inherent deposit variability; and the second is organisational and socio-psychological –the mindset of explorers and project managers themselves.There are four elements to value realisation for a mineral deposit: (1) social licence to operate; (2) geological factors (depth, geometry, water and geotechnical, and geometallurgy – influenced by texture, mineralogy, chemistry and grades); (3) financial engineering (capex, opex, future commodity prices, future energy prices), and (4) operating factors (production rate, recovery, energy consumption). These elements are strongly interdependent, and geology underpins and drives linkages between them. A quality deposit addresses all of these elements and thus can be developed in a time frame that allows acceptable returns to the owners of the invested capital.Geological drivers of the above elements can be measured and mapped throughout a deposit. Moreover, when viewed in the context of mineral systems, a predictive understanding of the common causative processes of quality (despite deposit-scale variability) is emerging, and with it the ability to target quality of mineralisation, not just quantity of mineralisation.The second factor is a ‘heuristic software problem’. Current lines of education (and consequently organisational and professional structures) are discipline-based, producing ‘silos’ that do not speak each other’s language and work with different ‘mental models’. People who effectively recognise systemic links between these silos are called ‘boundary spanners’, of which we propose two distinct types: outside-insiders and inside-outsiders. Outside-insiders are people who are within a community, but recognise advances in outside fields and effectively integrate them into the community. Inside-outsiders start outside of a community, and successfully bring new ideas into it. Common traits in boundary spanners are: they seek exposure to (and embrace) key ideas that are outside of the framework of their own specialisation; they have high mental processing ability (MPA) – the ability to connect systems that are currently not perceived to be connected; and they introduce ideas from outside a field into a new context in a way that re-frames the field.The challenge is to identify and nurture potential boundary spanners that can build critical links, in particular between the (largely geoscientific) mineral exploration mindset and the (largely non-geoscientific) project development mindset. Critical linkages to be built are between mineral system science, targeting science, and whole of value chain modelling.CITATION:McCuaig, T C, Vann, J E and Sykes, J P, 2014. Mines versus mineralisation – deposit quality, mineral exploration strategy and the role of ‘boundary spanners’, in Proceedings Ninth International Mining Geology Conference 2014 , pp 33–42 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By A J. Weston

Block or panel caving technology is far removed from that of the top slicing and block caving of the late nineteenth or early twentieth centuries. The rapid mechanisation and expansion of these methods in the late twentieth century was as much a result of the change of the technology of the unit operations of development, ground support, drilling and blasting and transport as it was of the advances in geotechnical understanding and practice. The small footprint gravity and scraper block caving mines with boundary weakening, rail transport and shaft hoisting of the early to mid-twentieth century have been replaced by massive high lift panel caves using preconditioning of the ore, large load-haul-dump units, adjacent crushers and conveyors to surface. The technology changes in the unit operations are described and the drivers for these changes examined.CITATION:Weston, A J, 2016. The evolution of block caving technology, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 265–274 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By V Mutton, L Potts, D Joyce

This paper describes the method of extracting sill pillars within the underground operation from under unconsolidated mullock fill at the Cracow Gold Mine. This pillar recovery method was initially successfully used to recover sill pillars at Crusader Mine, Western Australia in 2001. Globally significant resources have been sterilised due to the placement of loose rock fill above crown pillars and within adjacent stopes. The method described here offers significant opportunities to increase recovery of sill pillar recoveries.The royal orebody sill pillars at Cracow Gold Mine form a significant resource. Extraction of these pillars needed to be undertaken with minimal ore dilution and maximum ore recovery. The application that was selected to consolidate the loose mullock fill above each pillar used an injection grouting process (Minova FB200).Cracow Gold Mine mining method is bottom up bench mining. The pillars were left within the orebody to allow for stoping to commence whilst the decline was being developed. Due to the remainder of the orebody being extracted the only access to consolidate the backfill was from the sill pillar extraction level. Numerous problems were encountered and overcome from product selection and trial, system of injection to extraction.This pillar recovery process achieved a 95 per cent recovery of the sill pillar compared with an estimated 60 per cent typical for other mining options.CITATION:Potts, L, Mutton, V and Joyce, D, 2012. Pillar recovery at Cracow gold mine using grouted consolidated mullock, in Proceedings Narrow Vein Mining 2012 , pp 179-184 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Mar 26, 2012

By D Kentwell

IGO Ltd’s (IGO) Nova Operation (Nova) is 160 km east-north-east of the town of Norseman in Western Australia (WA). Discovered by Sirius Resources NL (Sirius) in 2012 and acquired by IGO in 2015, the Nova-Bollinger Deposit (Nova-Bollinger) occurs within the Fraser Zone of the AlbanyFraser Orogen. Nova-Bollinger is a complex nickel-copper-cobalt (Ni-Cu-Co) magmatic intrusive sulfide deposit, which is characterised by high-grade folded and undulating breccia lodes that host the bulk of the payable metals. Significant sulfide mineralisation is also found in several magmatic intrusive styles including net-textured, disseminated and blebby styles. A smaller but material volume of sulfides has also been remobilised into the deposit’s footwall rocks as ‘stringer’ bands in metasediments, or as discrete massive sulfide lenses. When interpolating Mineral Resource estimate (MRE) block grades in the presence of locally varying grade connectivity trends, such as folds or undulations, the sample search neighbourhood, which is used to identify the composites subset that is used for each block estimate, should be oriented to match the local trends. In theory, the most robust method of estimation where locally varying angles (LVAs) are applied to search neighbourhoods, are techniques where the composites and the blocks to be estimated are transformed to an unfolded coordinate system (UCS). However, UCS methods can be tedious to implement and require subjective decisions to be made that cannot always be fully defended. An alternative LVA method commonly used in the industry is dynamic anisotropy (DA), which is much simpler to implement and is often assumed (but not that often demonstrated) to result in similar results to UCS-style estimation. In 2018, Nova’s Mine Geology team (MGT) estimated the grades and density of the Nova-Bollinger MRE using the UCS approach. For the 2020 MRE update, Nova’s MGT tested and compared the USC grade interpolation method with the DA approach. As applied to the Nova-Bollinger’s 2020 MRE, the comparison, advantages and disadvantages of the two estimation methods are the subject of this paper

Mar 22, 2022

By T Takayama, M Matsumura, Y Konno

The steel industry accounts for 14 per cent of domestic CO2 emission in Japan, and iron ore sintering process occupies approximately three per cent. While Fe content in iron ore is gradually decreasing. So, the amount of concentrated iron ore will increase in the future. We have focused on magnetite concentrate as sinter materials, because magnetite can be easily magnetically beneficiated. However, it is experienced that blending magnetite ore resulted in increasing Fe2+ component in the iron ore sinter, which results in lower reducibility. Therefore, promoting the oxidation reaction from magnetite to hematite in the sintering process is countermeasure for reducibility. In addition, this promotion causes increase of oxidation heat, which results in high sinter strength and reduction of coke. It is assumed that the oxidation of magnetite tends to proceed in the cooling stage, where the oxygen partial pressure increases after the combustion of fine coke, but there are few studies on the effect of heat profile, especially cooling path. The purpose of this study is to design the effective sintering heat profile to promote oxidation of magnetite ore, especially, to investigate the effect of cooling path on sintered ore microstructure. In this study, magnetite ore and magnetite reagent were respectively mixed with calcium carbonate reagent. Then the mixed samples were pressed and formed into cylindrical tablets for simulating the adhesive layer of a pseudo particle. Through examining influence of maximum temperature and cooking rate on oxidation reaction of magnetite, we confirmed that the oxidation reaction of magnetite is suppressed at above 1350°C for maximum temperature, compared to 1300°C. Sintering at lower temperature is desirable because hematite is stable below 1350°C in the Fe2O3-CaO phase diagram.

Nov 8, 2021