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By Magne L, Barria J, Castro O, Menacho J, Gonzalez GD

An extensive experimental campaign was developed in a continuous 6 x 2' (D x L) pilot scale SAG mill. The effect of the feed flow rate, feed solids concentration, ball filling fraction and feed size distribution, over the mill performance was investigated. The residence time distribution (RTD) for the fine material was measured in every test, in order to detect changes in the mixing characteristics of the mill under different operating conditions. Based on phenomenological considerations a state model of the SAG mill was developed, which independently incorporates mechanisms such as: grinding, mass transport and classification in the grate discharge. These can be parametrised using information and optimisation software. This comminution model extends the compensation condition, which is a conventional hypothesis for ball milling, to the semi-autogenous mill grinding. The mathematical analysis of this hypothesis, applied to SAG mills, allow the reduction of the number of parameters in the model, using the relationship Ki = (1-bii)Si, where b and S have the conventional meaning. Therefore, the distribution fracture matrix bij and the specific fracture rate SIE are grouped in just a single diagonal matrix Ki.

Jan 1, 1993

By R Morrison, P Walters, B Adair, V Jokovic

‘Grade Engineering<sub>®</sub> is an integrated approach to coarse rejection that matches a suite of separation technologies to ore specific characteristics and compares the net value of rejecting low value components in current feed streams to existing mine plans as part of a system-view’ (Walters, 2017). Two of these technologies are directly recoverable through screening stages: Natural Deportment and Induced Deportment. The potential for taking advantage of “Natural Deportment” by size following blasting and crushing has been demonstrated for a range of ore types. Simple and low cost screening can in some cases generate a fine product with improved grade and a lower grade oversize which can be directed to leach or to waste. Where an ore body consists of many different ore types, the traditional approach of blending to metal grade will often add to complexity of treatment, which will reduce the effect of “natural deportment” by size.CITATION: Jokovic, V, Walters, P, Adair, B and Morrison, R, 2018. Applying enhanced grade engineering to complex ore bodies, in Proceedings Complex Orebodies Conference 2018, pp 21–23 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 21, 2018

By T Belligoi

Diamond cores and drill chips provide the only direct physical evidence for ore containing rocks. Early characterisation of cores and drill chips is important as it provides critical information for downstream processing. Traditional characterisation techniques include visual logging by a geologist or analytic and spectroscopic methods but they are time consuming and can miss some important textural or geomechanical features.The goal of this work is to evaluate the application of image analysis to iron ore cores and drill chips and to suggest improvements to existing core-scanning and chip monitoring systems. Two samples of massive ore differing by their mineralogy and texture, as well as two different batches of drill chips, have been imaged and analysed. Results are compared in function of the imaging system and the classification algorithms.As a conclusion, despite the necessity for more testing and improvements in calibration and lighting, it is obvious that image analysis technologies can bring a lot of useful information in the perspective of a geometallurgical mapping of the deposit.

Jul 11, 2011

By J Pearce, R Ramanathan

hortly after the World Health Organization declared COVID-19 a pandemic, the words ‘social distancing’ entered the global lexicon. The effects on the public of social distancing, lockdowns and travel bans are well documented. They also present unique challenges to the mining industry. For Hexagon’s Mining division, this posed a significant challenge. We have built our business – our reputation – on regional, customer-focused service and support. True to Hexagon’s values of being professional, engaged and customer-focused, we innovated to overcome the distance dilemma. Making automation a reality for our customers by implementing and supporting technology projects from a distance has helped deepen partnerships by making it easier to tap into our global experts’ knowledge. For example: • Body cameras were at the heart of a successful safety installation at a mine in Ghana. Despite the pandemic lockdown preventing travel by our South Africa staff into Ghana, the project was completed with minimal delays. • Traditionally, implementation and training for our Blast Movement Technology solution is done physically at the mine site. With COVID-19 travel restrictions in place, we have developed and successfully employed a remote deployment methodology. • Using RealWearTM headsets in the field and utilising the knowledge management platform from HINDSITE, Hexagon workshop technicians have been able to support hardware repairs in local offices, which once would have been undertaken in our overseas offices. • The same headset is being utilised to provide clients with remote mentoring sessions by our skilled team members who are based in our regional locations and unable to travel to their site without extensive quarantine commitments. • In instances where our team members have had to travel to site, we have provided consumer technology such as VR headsets to help them cope with long periods of quarantine to and from site. Post-pandemic, Hexagon will continue to refine and improve this method of working. INTRODUCTION Shortly after the World Health Organization (WHO) declared COVID-19 (COVID) a pandemic, the words ‘social distancing’ entered the global lexicon. As governments, healthcare organisations and the public scrambled to respond to the crisis, one thing became abundantly clear: isolation was and, for most of us, still is the key to maintaining our health. Hexagon, a leader in sensor, software and autonomous solutions, was well positioned to pivot and assist in the global response to the crisis. From simulations of the effects of social distancing to mapping the spread of COVID in real time, to drone technology delivering COVID tests, to providing communities with transparent geospatial information, Hexagon solutions continue to help ensure that innovation is readily available to those who need it most during uncertain times. The effects on the public of social distancing, lockdowns and travel bans are well documented. They also present unique challenges to the mining industry.

Jun 22, 2022

By M Steinberg, M Amarant

Upstream Classifier are well-known in the iron ore industry for at least 15 years. At present, more than 60 units are in operation in Western Australia. The advantage of this technology is their capability to produce three products with one equipment – iron ore concentrate, iron ore middlings for further processing and slimes (tailings). The principal of this beneficiation process – upstream classification and upstream separation – will always remain. However, the optimisation of the classification and separation efficiency of the equipment itself is a continuous process driven by enhanced automation and instrumentation, design changes and the use of upstream and downstream information and requirements. Besides efficiency, the safety, maintenance and replacement conditions are very important subjects for the operation of an iron ore mine. The aim of this paper is to present a new allflux® upstream classifier design, which has been developed together with several iron ore producer from Western Australia. The new design benefits from its sustainability approach by dividing the entire equipment into small reusable parts. As a result, maintenance is minor, replacement much faster, lifetime much longer and costs much lower. Furthermore, it demonstrates new features to prevent hazardous working conditions such as confined space as well as new fixing devices to speed up the replacement of certain items and parts.

Sep 18, 2023

By M A. Harrington-Baker, J M. Trudnowski

Sulfate-reducing bacteria (SRB) have the ability to immobilise dissolved metals by precipitating them as sulfides, provided that a favourable biochemical environment is created. Such an environment includes the presence of sulfate, anaerobic conditions and the availability of organic carbon. If such conditions are engineered within a reactive barrier or field-bioreactor, most metals can be effectively removed. To demonstrate this concept, three passive SRB field-bioreactors were constructed in 1998 at an abandoned mine site in the vicinity of Butte, Montana, USA to treat acid mine drainage with characteristic elevated concentration of metals and low pH. Performance of the field-bioreactors, using aqueous samples, was monitored over 32 months until the project was terminated, field-bioreactors were decommissioned and solid matrix sampling of the reactive matter was performed. The most important analytical results are presented in this paper together with conclusions regarding the appropriateness of the field-bioreactors construction features. Only Zn, Cu, and Cd were being removed as sulfides due to SRB activities. Changes in concentrations of other metals (Fe, Mn, Al, As), which do not necessarily precipitate as sulfide, seemed to be affected by SRB only in an indirect manner by responding to increased pH caused by SRB activity. An innovative cellular containment system used for placing organic matter worked very well in preventing settling of the organic matter and ensuring uniform flow of AMD throughout the entire cross-section of the organic carbon with no preferential flow paths This demonstration was funded by the US EPA and was jointly administered by the EPA and the US DOE under DOE contract number DE-AC22-96EW96405. The project was implemented by MSE Technology Applications, Inc, Butte, Montana, USA.

Jan 1, 2003

By J L. Merritt

Contour banks and waterways are standard soil conservation measures to assist farmers reduce the impact of gully erosion on sloping cropping land by reducing the slope length to the interval between the banks. The Universal Soil Loss Equation (USLE) developed by the USA Department of Agriculture Soil Conservation Service in 1930s predicts the long-term average annual soil loss (A).The equation is the product of the rainfall erosivity factor (R), the soil erodibility factor (K), the topographic factors of slope length and angle (L and S) and the cropping management factors (C and P). Contour banks reduce the slope length (L) only.Contour banks are a constructed earth embankment, incorporating a channel on the upslope side, typically traversing a slope on or close to the contour to control and/or prevent the erosion of that slope. The banks are also referred to as graded banks, terraces, or bunds (DSITI 2015). Contour banks are either broad based or narrow based. Broad based banks allow the passage of the machinery over the banks whilst narrow based bank batters are too steep preventing the passage of machinery. Waterways are a stable, longitudinally sloping water disposal area of sufficient capacity used to discharge surplus runoff from the contour bank and to allow it to flow to a lower level without causing erosion (DSITI 2015).The mining industry must decide what the role for contour banks and waterways is in each operation’s rehabilitation and closure plan.CITATION:Merritt, J L, 2018. Contour banks in spoil rehabilitation – a matter of timing, in Proceedings Life-of-Mine 2018, pp 147–149 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 25, 2018

By L M. Zhang, X Y. Li

Surface displacements are routinely monitored at multiple points during slope excavation. The monitoring data reveals the safety status of the slope under current loading conditions. They can be used to enhance the prediction of the future performance of the slope by reducing the uncertainties of the prediction model and its model parameters. In a multistage excavation, the observed displacements in the current stage can be used to update the prediction of the displacements in subsequent stages. Besides, due to the spatial correlation of the slope parameters, the prediction of the displacement at one location can also be updated using the monitored displacements at adjacent locations. This study aims to develop a multistep updating method to enhance the prediction of the future performance of the slope using time-series monitoring data at multiple points. This method integrates the theoretical computational model with observational evidence. It considers the inherent uncertainty of the slope, model uncertainty and measurement uncertainty. With more monitoring information being incorporated, the prediction becomes closer to the actual performance of the slope. A case study of a multistage excavation of an extremely high rock slope in south-west China is presented for illustration.CITATION:Li, X Y and Zhang, L M, 2014. Better prediction of performance of a slope using time-series monitoring data at multiple points in a multistep excavation, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 183–188 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By Marshall T. E, Finfinger G. L

Gulf Coast domal salt mining operations have had sporadic encounters with methane gas emitted without any warning. In virtually all confirmed cases, the methane was localized in methane enriched zones. In a few cases large quantities of methane were expelled rapidly with salt outbursts, resulting in dangerous methane concentrations. Estimates of methane liberated by face blasts in methane-enriched areas is needed in determining how much air should be supplied to the face for proper dilution. A relationship between the gas content of salt samples collected from the face and the amount of methane liberated would be helpful in estimating how much methane will be produced by a face blast. Little is known about the layering or stratification of methane in large area-low velocity airways. This publication reports on three tests conducted by the Bureau of Mines which monitored the immediate return air of four faces during blasting. The test locations were in a methane gas-enriched section that had previously experienced two large outbursts and many smaller ones. A comparison was made between gas content values of face salt samples from the dissolution test and the gas liberation quantities. The characteristic movements of the methane in a large room with low air velocities were charted. This will help to better understand the factors involved in proper placement of methane sensors as a warning system.

Jan 1, 1988

By M Sparrow

The Victoria Park Tunnel project is an inner-city alliance project in central Auckland, New Zealand. The existing two-directional viaduct will be modified to single-direction flow, and a new northbound 440 m cut and cover tunnel will be constructed beneath Victoria Park. Three-dimensional (3D) visualisation media were used to communicate key design innovations to stakeholders and the general public. The 3D visual material has proven a useful tool for informing motorists of a new safety barrier method adopted for traffic management.This presentation will explain how 3D visualisation was incorporated in the project and will showcase the 3D visualisation media created for the project.

Mar 8, 2011

By S Brochot, M-V Durance

In many cases, current metallurgical accounting practice does not consider the errors associated with the measurements used in obtaining the metal balance. Considering all measurement errors, including errors associated at each step of the process - from sampling and analytical errors to measurement errors in circuit instrumentation, can improve the accuracy of the final metal balance - assisting in the improvement of process performance, optimisation and control.The consequences of the inclusion of measurement errors on metal balance for different circuit configurations and typical metallurgical accounting practice (two product and three product formulae) will be discussed in this paper.Examples of the tools, methodology of implementation, and periodical metal balance tasks are presented to illustrate the advantage of this approach in meeting the different requirements of each department.CITATION:Brochot, S and Durance, M-V, 2012. A new approach to metallurgical accounting, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 217-224 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By S Tierney, D Cumming-Potvin, I Thin, Y Potvin, D Grant

The preliminary modifying factors for future stope design in the Southern Mine Area of Olympic Dam consisted of only a single, arbitrary value of Equivalent Linear Overbreak/Sloughing (ELOS). In order to improve this, a study was conducted which developed a more comprehensive methodology for assigning ELOS, Equivalent Linear Lost Ore (ELLO) and Equivalent Linear Fill Overbreak (ELFO) to individual stope faces based on geotechnical and mining parameters. The approach used was to look at the simple cases, which were classed as vertical stope walls in good ground (RQD 80-100%), divided into wall orientations (North, South, East, West). The stope walls were also split based on the blasting practice used (toeing, parallel or a combination of the two). The expected ELOS and ELLO from these ‘base cases’ are then modified by parameters which have historically been found to affect stope performance (Hydraulic Radius and Q’). The size of the effect found in the historical data determines the ELOS / ELLO applied. The methodology was summarised in an easy to use flow chart and was applied to all of the proposed stope shapes for the Southern Mine Area and summarised per mining block. This allowed each iteration of the mine plan to be assessed in terms of overbreak (both rock and vertical fill exposures) and underbreak.

Mar 15, 2021

By M I. Pownceby, A Guiraud, S Purohit

Sticking and breakage of iron ore pellets during high temperature reduction can result in several operational challenges during shaft furnace ironmaking. With the shift to H2-based DRI processes and decreasing iron ore quality, this issue becomes more prominent. It is therefore important to understand how the iron ore chemistry and mineralogy affects the sticking and breakage of pellets inside the shaft furnace. This study provides a review of the mechanisms that lead to sticking and breakage of pellets inside the shaft furnace. The sticking index of pellets is related to the rate of metallic iron production as well as the precipitation morphology of product iron. Sticking of pellets is also enhanced by the formation of low-melting slag phases. The breakage of pellets inside the shaft furnace is often associated with the mechanical load of burden and pellet swelling, which is caused due to iron whisker or protruded iron formation. This paper investigates how the composition of iron ore, particularly the presence of different impurity oxides such as SiO2, Al2O3, MgO, CaO and alkali oxides in the pellets, influences the sticking and swelling indices. The effect of ore mineralogy on these adverse behaviours is also discussed.

Sep 18, 2023

By J R. Taylor, J A. Muchan, S M. Pape, B S. Davis

Acid and metalliferous drainage (AMD) is routinely derived from waste rock, tailings, pit wall rock, underground mine voids, heap leach pads, ore stockpiles, concentrate stockpiles and even slag piles. In many jurisdictions, there is an assumption that tailings materials represent the highest AMD risk. This is likely due to their highly sulfidic and ultra-fine grained nature, and the fact that they occur in large tonnage, partially unsaturated deposits. These characteristics are not unreasonably associated with reactive and therefore highly polluting mine waste materials. Interestingly, however, the high sulfide content and highly reactive nature of tailings achieves the rapid consumption of oxygen in tailings pore spaces. This oxygen depletion can limit or halt sulfide oxidation throughout much of the tailings pile. Oxygen can only be resupplied to the tailings via atmospheric exchange at the air-tailings interface. The grain size of most tailings materials limits this resupply to a diffusion related process that only affects the uppermost 100–2000 mm. Hence sulfide oxidation in tailings can be inherently self-limiting. Unfortunately, the same cannot be concluded for waste rock materials.Using a unique site assessment strategy that focuses on quantifying acidity fluxes from various domains at a mine site, it has become increasingly evident that sulfidic waste rock produces the majority (typically 60–80 per cent) of the soluble acid and metalliferous pollution at most active and decommissioned sulfide-bearing mine sites. Whether sulfidic waste rock is disposed in engineered above ground facilities, backfilled into pits or even underground voids, it remains the primary source of pollutants for decades to centuries.Conventional end-dumping waste rock practices result in angle-of-repose pathways for air and water, and these internal fabrics exacerbate sulfide oxidation (ie pollution generation) and discharge from waste rock materials. The primary aim of many cover systems is to retard the access of air and water to these conduits. Recent thinking is that more emphasis needs to be directed at strategic waste rock pile construction practices, and less reliance placed on thin soil cover systems to prevent AMD.Waste rock pile construction approaches that minimise porosity and permeability but raise the retained moisture content and enhance water residence times have the potential to lower sulfide oxidation rates and thereby improve water quality outcomes. For example, innovative base-up, layered and compacted (BULC) waste rock piles have the potential to avoid or minimise the generation of AMD, supersede the need for treatment and facilitate successful closure and relinquishment across the mining sector (Figure 1).CITATION:Taylor, J R, Pape, S M, Davis, B S and Muchan, J A, 2016. Waste rock pile construction to lower closure and relinquishment costs, in Proceedings Life-of-Mine 2016 Conference, pp 97–99 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 28, 2016

By A-M Fleury

There has been much progress on the issue of acid drainage over the past 20 years; however, significant challenges remain. The International Network for Acid Prevention (INAP) is attempting to address them by globally coordinating acid drainage information sharing and research. INAP pursues three branches of activities: it links AD research, practice, and people; it organises, sponsors, and participates in regional workshops as a forum for technology transfer; and it instigates and funds key acid drainage research projects. Through these activities INAP is helping the industry deal with what is arguably its most serious legacy issue.

Jan 1, 2003

A hidden asset in most exploration and mining activities is data. Common practice involves the spending of large amounts of money to discover, define and prove the viability of a mining project. Some organisations have used operations research analysis and internal costing methods to allocate a value to their data and to compare the costs of data maintenance to other more tangible activities like plant and equipment maintenance. Those organisations, which do not undertake such an analysis often, have little knowledge or understanding of the extent and the worth of their data. Often the organisations lack of knowledge and understanding of the data is indicated by their failure to fully exploit or realise their opportunities. The focus of this paper is to discuss new technologies that optimise the management and security of collected and derived data. The technologies discussed are components of the software systems acQuire and MineSight.

Jan 1, 1999

By R H. Sibson

Magmatic and/or hydrothermal fluid systems in island or mountain arcs self-organise to critical states subject to perturbation by changes in the regional stress, which plays a controlling role in the containment of overpressured fluids. Whether the magmatic arc is under compression (eg Andes, northern Honshu) or extension (eg Taupo Volcanic Zone, New Zealand) is a key factor controlling the ease of magmatic or hydrothermal fluid ascent. Abrupt changes in the stress regime have the potential to induce major episodes of fluid redistribution. Large earthquake ruptures along plate boundaries may induce such changes over broad areas, also contributing to fluid redistribution by renewing fault permeability along the causative rupture zone or reactivating distant fault-fracture permeability by shaking from radiated waves. High-resolution geophysical investigations of active arc systems and the subduction thrust interface underlying their fore-arcs reveal repositories of overpressured hydrothermal fluids. In active magmatic arcs under compression such as NE Honshu or Cascadia, there is evidence for a heterogeneous distribution of overpressured hydrothermal fluids in the middle-to-lower crust trapped around the base of the upper crustal seismogenic zone. Investigations of the subduction thrust interface responsible for great (Mw = 8.0) ‘megathrust’ earthquake ruptures has revealed in some instances (Cascadia, SW Japan) the existence of a belt of non-volcanic tremor (NVT) with accompanying slow slip episodes defining the base of the megathrust interface at 40 ± 5 km and 350°C??-??550°C. Aqueous fluid at these depths is likely derived from dehydration reactions accompanying the basalt-eclogite transition in subducted oceanic crust. NVT sequences in the hanging-wall above the interface may be defining migration pathways into the overlying crust.The potential for eruptive episodes in magmatic arcs and redistribution of hydrothermal fluids is assessed in the light of the stress changes that followed the 2011 Mw9.0 Tohoku subduction thrust rupture which extended along strike for over 500 km and down-dip for over 150 km, with maximum slip of c 50 m.

Aug 22, 2011

By S Hanrahan, S McLaughlin

A case study is presented that details the safety journey at a North American project involving two major contracts: a 1000 m shaft recovery and rehabilitation, and the development of a drainage gallery in a large open pit operation. In the early stages of the contracts, there were a number of incidents that created tension between the owner and contractor, which resulted in the contractor being placed on a final warning with almost imminent potential termination. As a result of this, it was agreed to initiate a focused safety recovery plan as a ‘last chance’.Over a period of two years, the engagement and consequent performance of the contractor was turned around, steadily working to set it up for success such that in one of the contract work areas, a record of ‘one year LTI (lost time injury) free’ was achieved. The journey involved the owner and the contractor teams working cohesively to educate all parties in the safety requirements and, most importantly, providing the context and understanding for certain requirements being put in place. Early on in the process, it was recognised that the owner team unknowingly was an impediment in that they did not fully understand the safety requirements and so was not able to lead the way for the contractor effectively. The journey to rectify the situation was supported and followed up by focused engagement with the project team, which generated a progressive improvement in a very challenging environment.In particular, the contractor turnaround was significant and of enough value for the contractor to ultimately export some of the safety systems from this site to other contract sites. This demonstrated the ultimate benefit of the contractor understanding and buying into a safety culture and system.CITATION:Hanrahan, S and McLaughlin, S, 2016. Winning the safety battle, in Proceedings International Mine Management Conference, pp 181-186 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jun 22, 2016

By B Waldon, M Valastro

A coal dust explosion is one of the most significant risks in the harsh and complex environment of an Underground Coal Mine (UCM). Reviewing literature, regulations and existing systems surrounding explosive dust management shows that there have been few advancements in managing this risk over the past 90 years. Legislation has remained relatively stagnant and minimal systems are implemented in the real world that can simplify, standardise and improve the effectiveness of UCM explosive dust management. To help bridge this gap, Corehesion, in collaboration with an UCM has designed, developed and implement an Explosive Dust Risk Mitigation System (EDRMS) utilising components of Business Intelligence (BI) that is capable of real-world use in industry. To do this the existing explosive dust management process at the associated research mine was evaluated to form high-level and detailed design requirements, focusing on digitally simplifying the procedure, not replicating it. The system was then iteratively and incrementally developed and implemented at the research mine to commence real-world use. The developed BI platform is compared with the existing process to highlight the advancements in performance transparency, efficiency and optimisation of UCM explosion mitigation. This comparison and evaluation of the real-world system implementation at the research mine demonstrate its success in automating procedure steps, providing a readily accessible source of data and enabling a proactive approach to planning and managing explosion risk mitigation. In addition to improvements just for the research mine, this EDRMS created directly address many Queensland regulatory audit findings. By finalising the total system and making the highlighted changes for standardisation, this BI system will have the adaptable capabilities for implementation across the UCM industry. As accurate data availability improves at UCMs, further work can be done to improve the systems’ optimisation techniques and integration of other risks.

Apr 16, 2024

By J Ireland, S Rose

The main outcomes of mining grade control include defining the boundary between ore and waste and then categorising the ore according to which stockpile it should be sent. A typical workflow includes using general mine planning software (GMP) – such as SurpacTM, VulcanTM or CAE StudioTM – to create three-dimensional wireframes of mineralisation domains, which are used to flag the relevant samples of interest and constrain estimation during block modelling. Creating the wireframes is a time-consuming process, requiring reasonable software skills, patience and an eye for detail. The interpretations can be subjective; indeed, even the same geologist will give different shapes if presented with the same data at different times. The process can become particularly tedious when trying to carry out updates due to new data. It can also be difficult to test the effect of alternative interpretations or grade thresholds because of the time constraints in production.There are now several implicit modelling tools available, either as standalone programs or as add-on modules to existing GMP. In this paper, the authors develop a workflow using implicit modelling methods to show how grades and geology can be rapidly interpreted to provide effective domains for grade estimation. The paper includes case studies from open pit gold mines. The implicit modelling approach can save several days of interpretation work for each grade control drilling campaign.CITATION:Rose, S and Ireland, J, 2014. Implicit modelling applied to grade control data, in Proceedings Ninth International Mining Geology Conference 2014 , pp 115–122 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014