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By D Chalmers, C C. Harb

The detection and control of gas levels in mining is a continuing challenge for the industry. Standard detectors have many problems that could be overcome with laser based spectroscopic instruments, but to date these systems have not been suitable for mining conditions. This paper reports the development of a new digital data extraction scheme to modernise traditional cavity ring down spectroscopy (CRDS). CRDS is a direct cavity enhanced laser based absorption technique, which is used to allow the identification of an unknown substance by their molecular fingerprint; this unknown substance is identified by analysing the ring downtime of the light exiting the optical cavity. Traditional CRDS has many issues when analysing substances in hostile environments, or when multiple species may be present. This presents an alternative approach, called real-time CRDS (rtCRDS) that has the potential to overcome many of these issues and produces systems that could be used in the mining industry. The system utilises newly developed widely tuning quantum cascade lasers combined with improved optical cavities and novel digital data extraction to produce spectra over a 1500 nm range in a few seconds. The ring downtime measurements produced are accurate and have high sensitivity and maximum signal to noise ratio. This paper discusses the technique, illustrating the advantages compared to traditional systems and show real-time spectra for a set of molecules of interest to the mining industry. This paper also provided an analogy between this approach and that used in digital communications systems, and shows that this scheme is ideally suited to provide a network of sensors in hostile environments.CITATION:Harb, C C and Chalmers, D, 2015. Real-time methane detection – modern digital laser spectroscopy for hostile environments, in Proceedings The Australian Mine Ventilation Conference, pp 161–166 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

Sublevel open stoping (S.L.O.S.) was introduced at Rosebery in 1972 in the wider ore blocks below 14 level, largely replacing cut and fill methods which had been in use up till that time. During 1973/74 the method produced 10% of primary stoping tonnes, and by 1981/82 it increased to 65%. Because of the increasing reliance placed on sublevel open stoping for primary stoping production, every effort was made in both planning and operating to: - maximise ore recovery and reduce dilution - increase productivity - reduce costs.

Jan 1, 1982

By B Yang, L Wang, C Y. Ng

Flotation process intensification is often achieved through changing chemical reagent scheme or flotation machine or both, which likely brings a hefty burden to the flotation plants in terms of capital or operating expenditure. A novel approach to flotation process intensification is the use of acoustic sound, which has been demonstrated to be effective in improving the flotation of various mineral systems with different type of flotation cells. This approach was based on the dynamic stabilisation effect of acoustic sound on the flotation froth. The present work aims to understand the influence of various experimental conditions on the effectiveness of the approach. First, the effects of sound frequency and amplitude were studied with column flotation of silica particles. Results showed that the flotation performance was improved only within a certain range of frequencies and above certain amplitude. The study was then extended to the mechanical flotation of quartz particles with various size ranges and at two solids concentrations. With sound, the recoveries of different size fractions within the range of 20–212 μm were all increased. In particular, the recovery of 150–212 µm particles was increased from 0 per cent to approximately 25 per cent, demonstrating the potential for extending the upper limit of particle size in flotation by using acoustic sound. Furthermore, mechanical flotation of chalcopyrite particles at various collector dosages (50–150 g/t) was carried out with and without sound. Results showed that the increment of the final flotation recovery was increased with sound at different collector dosages. Overall, acoustic sound has the potential to be used as an effective and versatile method for flotation process intensification.

Aug 24, 2022

By E Amini, N Beaton

Application of ore pre-treatment technologies such as Grade Engineering and in-pit ore treatment require comprehensive analysis to show proven value is being generated by switching away from the current practices. Considering most mining operations last several decades; the pre-treatment technologies must be investigated over life of mine (LOM) to truly show value was generated or lost. Therefore, a value chain flowsheet model has been usually developed to run those analysis/simulations over LOM using a set of defined ore characteristics and the operating equipment capacities. The Integrated Extraction Simulator (IES) has been used for this type of LOM simulations as it has the necessary flexibility to accommodate the whole mining value chain flowsheet in one platform and provide essential computation power to run mass simulations for the given scenarios using the resource block model. This allows to forecast the value chain response over the LOM for all given scenarios in a feasible amount of time. The traditionally developed flowsheets for the analysis/simulations are usually limited to the mineral processing plant and were developed based on a single audit conducted on the plant in a very short time, e.g. several hours. The process plant is being operated with a certain ore at a certain condition during the short audits which would not reveal the true capacity of the operation equipment when ore characteristics changes. Therefore, it would be impossible to define the true capacity of the equipment and identify the constraints along the value chain. In this study, a methodology was developed to identify the constraints along the value chain and implement those in the IES flowsheet using process information. Also, the equipment models were fine-tuned to represent the true capacity of the equipment in the flowsheet using the same data set. The methodology was tested over five process plant in two operations and showed the performance forecast was significantly improved over the traditional methods being used so far. Then those high-fidelity flowsheets were used to evaluate the ore pre-treatment technologies proposed by the relevant resource company experts.

Nov 10, 2020

By C X. Zhang, W K. Ru, S C. Hu

To study the creep properties and the energy evolution characteristics of the weakly cemented rock (WCR) in western China, the creep deformation damage law of weakly cemented mudstone (WCM) under graded loading and the energy evolution characteristics of each creep stage were analysed based on the triaxial graded loading creep test of WCR. The results showed that as the confining pressure increased, the creep failure strength of the WCM increased from 9.5 to 24.8 MPa, and the relative displacement of the mineral particles in the mudstone increased gradually, resulting in a reduction in the fracture angle from 79.7° to 58.3°. At the same stress level, the strain energy Ue, the total energy U, and the dissipation energy Ud all increased as the confining pressure increased, but the growth rates of U and Ud decreased gradually, while the growth rate of Ue remained high. At the end of the stable creep stage, Ue increased slowly with the confining pressure, while U and Ud increased rapidly with the confining pressure, and their growth rates were basically the same. At the end of the accelerated creep stage, the growth trends of these three energies were all positively correlated with the confining pressure, Ue was significantly lower than that at the end of the stable creep stage, and Ud and U were further increased. These results revealed the unique creep properties and energy evolution characteristics of the WCR, providing a theoretical basis for long-term stability control of roadways that are built with WCR.

Nov 29, 2022

By G Fergus, M Hart, S W. Weeks

Rio Tinto Alcan has undertaken feasibility level assessments into the expansion of its bauxite mining operation in an area south of the Embley River in far north Queensland. The project has the potential to extend their Weipa operations by approximately 40 years.The construction and operation of two additional mineral ore processing plants are proposed for the South of Embley project. Golder Associates was engaged to develop and conduct modelling assessments of potential sources of water supply required by mineral ore processing.Two models were developed using GoldSim: a dam yield model and a water balance model. GoldSim is a graphical object-oriented modelling environment with a capacity to carry out dynamic probabilistic simulations. Originally developed by Golder, GoldSim has been applied successfully in a decision support role to a range of mine water management operations.The dam yield model was used to provide estimates of reliability and volume of annual water supply of several potential surface water dams. This information was then used to determine a hierarchy of water supply options for processing plant operations. The water balance model dynamically simulated the water demands of the two production plants and the consequential response in water supply, with respect to the timing and discharges provided by the various source options.Use of the model provided a preliminary operational tool to assist with water supply management decisions. Water quality issues required a blending of water from separate sources and attention paid to scheduling to ensure water supply through the dry season. The model also helped identify risks to water supply in the event of underperformance of one or more water supply sources. This allowed the operational rules to be refined to minimise those risks.The dynamic and stochastic modelling approach provided a method for identification of water supply issues susceptible to seasonal climate variability.CITATION:Weeks, S W, Hart, M and Fergus, G, 2013. A dynamic evaluation of water supply security susceptible to climate seasonality, in Proceedings Water in Mining 2013, pp 197-208 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By J V. Mehrabani, A R. Sayadi

Adequate estimation of equipment costs is a key factor in a feasibility study and in evaluation of design alternatives for mining and mineral processing projects. Inaccurate early cost estimation could lead to the elimination of investment benefits. However, this estimation is complex and time consuming because of data accessibility problems and consequently access to a rapid, up-to-date and accurate tool is desirable for carrying out cost estimations.This paper describes the development of models for estimating capital and operating costs for a jaw crusher, which is used as the primary crusher for a wide variety of mineral beneficiation plants, applying single and multivariate regression analyses, together with the design of experiment approach, based on principal component analysis. Explanatory variables include gape size, length of feed opening and power as numeric (quantitative) variables and toggle type (single or double) and the existence of extra heavy duty construction as categorical (qualitative) variables. The performance of each model has been investigated and comparing the estimated R-squared (R2) of each model, the best was selected and its validity examined. The cost models include the capital and operating costs along with the operating cost components. The results indicate that the suggested best cost model is sufficiently accurate for use in feasibility studies.

Sep 26, 2011

By J Wen, P Hou, W Yu, M Hu, Z Jiang, C Bai

Vanadium titano-magnetite (VTM) is one of the important iron ore resources in the world. High viscosity and low fluidity are the basic characteristics of hot metal containing vanadium and titanium during the ironmaking process. Clarifying the influencing mechanism of the melt viscosity would be a significant issue for the high efficiency smelting of VTM. In this paper, a self-developed melt viscometer based on the principle of torsional vibration theory was employed to measure the viscosity of hot metal accurately. Simultaneously, the thermodynamic calculations and some modern detection methods were also used to investigate the precipitation behaviour of high-melting-point phases in hot metal containing vanadium and titanium. The measuring results show that the viscosity of molten iron gradually increases with the increase of titanium content when the mass fraction of titanium is between 0.09 wt per cent – 0.50 wt per cent. Meanwhile, the viscosity of the hot metal was affected significantly by the vanadium content. When the vanadium mass fraction was higher than 0.30 wt per cent, the viscosity of hot metal increased sharply, which will have a serious impact on the fluidity of the hot metal. Furthermore, it was revealed by thermodynamic calculations that an increase in titanium and vanadium content would result in the precipitation of high melting point phases such as TiC, TiN, VC, and VN in the molten iron, ultimately resulting in a decrease in its fluidity. Meanwhile, it was confirmed by Scanning Electron Microscope (SEM) observation that the precipitates in the hot metal were compounds consisting of V, Ti, C, and N elements, which agrees well with the thermodynamic analysis results.

Aug 21, 2024

By J Kuva, M Parian, B I. Pålsson

One of the main factors affecting the suitability of an ore for autogenous grinding is the ore’s competency, ie providing enough critical stones for the grinding process. Several experimental test routines exist and are used for assessing the viability of the ore for autogenous grinding. However, very little attention is given to the generation of fatigue in large stones experiencing repeated shocks in the mill. To investigate this, large pebbles sampled from an industrial autogenous grinding mill running hard and soft ores were categorised based on the grinding energy. From the pebbles, small drill core samples were prepared and went through a series of fatigue cycle tests. Both hard and soft ores showed similar average resistance to failure in compression tests, but the hard ore had a consistent resistance with lower variations. The cores were scanned by XCT before and in-between fatigue tests at the highest reachable resolution, 1.5 µm voxel size. The outcome showed that a higher number of micro-cracks were visible in the soft ore compared to the hard ore. The frequency of micro-crack development in the soft ore may be the reason for its lower specific grinding energy compared to the hard ore. It is obvious that for realistic conditions in an autogenous grinding mill, stones are pre-weakened by fatigue before they fracture. Therefore, shortcut methods focusing only on running tests on fresh and small samples may operate in unrealistic conditions by ignoring the fatigue phenomenon. This is even more important for ores that are on the borderline to be considered as competent for autogenous milling.

Aug 24, 2022

By S Flanagan, M M. Mete, A R. Tiryaki, M Guresci

First Quantum Minerals (FQM) operates the Cayeli underground copper mine in Turkey. In response to a lost time incident (LTI) that occurred at the mine in 2022, the mine management decided to introduce a new safety approach on-site. The initiative began with a comprehensive safety culture analysis conducted by Arti Consulting, involving focus group studies. Employees actively participated in candid discussions, sharing their insights on safety issues and offering solutions. These conversations were meticulously audio recorded, resulting in over 150 000 words collected from more than 100 employees. These transcribed narratives then underwent rigorous semantic analysis, with the assistance of a sociologist, to identify and dissect patterns of unsafe behaviour. This analysis found areas for improvement, particularly in near-miss and incident reporting, quality of safety toolbox talks and effectiveness of pre-work risk assessments. Subsequently, mine management deliberated on these insights and devised corrective actions. An emphasis was placed on involving all employees in the corrective actions through communication training, empowering them to own the decisions and changes made. These impactful measures were seamlessly integrated into FQM’s Think! Safety Program, which embodies FQM’s sensible health and safety strategy. FQM partnered with Strika Entertainment (Strika) to develop innovative visual-first safety communication tools that use illustration, animation and graphic design to simplify complex messaging into easy-to-understand edutainment. As part of this approach to safety communications, Cayeli and Strika revamped the safety toolbox talks to encourage employees to voice their concerns and receive feedback when their suggestions were implemented. The response from employees has been positive, with over 200 unsafe behaviours and conditions reported within the initial two months of launching the Think! Safety Program. Remarkably, the Cayeli Mine has not experienced any LTIs for the past 500 days as of 9 December 2023. This paper encapsulates the dedicated efforts to transform Cayeli into a safer mining operation.

Apr 16, 2024

Copper-Cobalt hydrometallurgy has seen a resurgence in recent years with the development of projects in Zambia and the DRC. Many of the flow sheets are unique in their use of hydrometallurgical techniques to improve performance compared to the older types in current use. The emphasis has moved from direct copper electrowinning/stripping, with multiple stages of precipitation for removal of impurities and concentration of cobalt, to innovative use of solvent extraction and ion exchange with higher cobalt recoveries to final product. The poor quality direct electro-won copper has been supplanted with solvent extraction-electrowinning; with consequent production of LME 'A' quality metal. Many of the precipitation steps in cobalt recovery and concentration, have been replaced with solvent extraction; while the remaining precipitation stages have been enhanced with use of oxidants to improve impurity removal. Operating experience from two of these circuits has shown the benefits of the new technologies and the improved overall recovery of both copper and cobalt into higher quality products.

Jan 1, 2008

By J Paradis, K Dudgeon, M Topping

At Newmont’s Jundee Operation, exploration and resource geologists collaborated to produce an open pit resource model. Using a variety of modelling and estimation techniques but no new data, an uneconomic underground target was converted into a potentially economic open pit evaluation. During an industry downturn, it is more important than ever to efficiently share expertise, ideas and resources to problem solve and produce meaningful project outcomes. The two departments brought together different methods and ideas, and the process showed that certain methods worked better than others in different situations, thus the appropriate method was applied to each part of the evaluation. The results were used to create new procedures and improved lithology modelling and resource model estimations. Adaptability of the geology departments and collaboration such as this are key to ongoing improvements and future mine life at Jundee.CITATION:Dudgeon, K, Paradis, J and Topping, M, 2014. Cook open pit model – the hurdles: how we leapt, lunged, stumbled and overcame them, in Proceedings Ninth International Mining Geology Conference 2014 , pp 169–174 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By M Wortley, J McKay, D La Rosa, O Guyo

It has been a generally held concept that crushing operations were, by their nature, too simple to benefit from the implementation of advanced process control. The commissioning of an OCS¬ expert control system and image-based oversize detection system, VisioRock, at the Pilbara Iron Tom Price facility are dispelling these notions. A constraint-based OCS¬ expert control system has been designed and commissioned on the high-grade crushing and screening plant along with a vision-based oversize detection system functioning on six product conveyor belts. To date, the expert control has demonstrated the ability to increase production by maximising dynamic constraint utilisation. Dynamic constraint utilisation is a concept developed by Rio Tinto Technical Services for effectively evaluating constraint-based control logic performance. The VisioRock system has been installed and configured and has been operating for a period of several months. Currently, Tom Price and Metso personnel are working to define correct oversize detection thresholds. Details of the plant implementation are discussed.

Jan 1, 2006

By B Smith, R Gelson

Springvale Colliery is an underground longwall mine situated approximately 10 km north-west of Lithgow in the western coalfields of New South Wales. Following a full-scale review of the mineÆs ventilation system in mid-2010, it was clear that the mine by early 2013 would become ventilation constrained as a result of the increasing size of the mine workings, the predicted worsening tailgate conditions and plans to introduce a fourth continuous miner unit. This realisation led Springvale to embark on a major upgrade of the mine ventilation system that would meet short-term and life-of-mine (LOM) requirements.Included in the upgrade project was the installation of a new high pressure centrifugal main exhaust fan that is capable of overcoming the high resistances imposed frequently on the circuit by restrictions in the tailgate airway. The new fan featuring a 2.5 MW motor is designed to be capable of operating at a quantity of 250 m3/s at a pressure of 7.9 kPa, a substantial improvement over the previous system, which had an operating duty of approximately 145 m3/s at 1.9 kPa. The new fan is of a centre hung design and features a backup diesel motor to maintain ventilation in the event of a power outage.Structural engineering analysis determined that under the operation of the new main fan the existing standard of ventilation control devices (VCDs) at Springvale would not be adequate to withstand the increase in differential pressures. As such, an upgrade of critical VCDs was undertaken utilising a novel high flexural strength (9 MPa) shotcrete and thin spray-on liner, which help serve to safeguard the structural integrity of the appliances and prevent increased leakage as roadway conditions at VCD sites deteriorate over time (a serious problem in many areas of the workings at Springvale).In addition to the main ventilation system upgrade, a separate upgrade focusing on improving development face ventilation was also undertaken. This upgrade included the purchase of two high capacity (22 m3/s) variable inlet vane (VIV) auxiliary fans to facilitate comfortable development face ventilation.The upgrade of the mine ventilation system at Springvale has been three years in the making, but has removed a major business risk in that it has afforded mine planning and operational flexibility (a fourth unit can now be introduced) for the LOM, and importantly provided unprecedented levels of comfort to operators at the working faces where previously ventilation and heat issues were frequently reported. The impact of this on the morale of the workforce, and hence their output, should not be underestimated.CITATION:Gelson, R and Smith, B, 2013. Life-of-mine ventilation system upgrade at Springvale Colliery - A case study, in Proceedings The Australian Mine Ventilation Conference , pp 79-86 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By W Y. Guo, L X. Chen, D X. Zhang

To obtain the rock type-I crack propagation process accurately, a novel fixture is used to make the prefabricated crack of rock propagation along the predetermined direction. In this study, the crack propagation process of rock is monitored with the digital image correlation method (DICM), and a mechanical model of crack directional propagation was established. The results show that the simple crack directional propagation device can effectively realise the stable propagation of type-I crack along the predetermined direction, the crack initiation angle is less than 10°, and the deviation between the peak strength of crack propagation calculated by a simplified mechanical model and the tensile strength of Brazilian splitting is 22.76 per cent and 7.53 per cent, respectively. According to the deformation field evolution law, crack propagation can be divided into three stages: microcrack development, main crack propagation, and main crack propagation. As for the rock type-I crack initiation and propagation mechanism, before reaching the peak strength, the prefabricated crack tip is subjected to maximum tensile stress; the elastic energy increases rapidly, and the dissipation energy increases slowly; after the peak strength, elastic energy exceeds its energy storage limit and released rapidly, and most of the input energy is converted into dissipation energy, which makes the crack propagation rapidly. The crack directional propagation device will be further optimised and improved, and it is expected to provide a new method for the study of crack propagation mechanism, rock failure precursor information and crack arrest principle, etc. It will also provide theoretical references for the optimisation of coal strata directional blasting, fracturing, fracture arrest, and other related technologies in geotechnical engineering.

Nov 29, 2022

By B E. De Gee, N Viviers, A Naidoo

In 2013 the Mopani Copper Mine Mufulira plant in Zambia embarked on a project that was aimed at improving concentrator recoveries. The project commenced with the automation of the milling and flotation circuits. This involved the installation of new instrumentation, namely measurement devices and actuators, and the connection of these to new programmable logic controllers (PLCs).The infrastructure changes were followed by the implementation of basic proportional-integral-derivative (PID) controllers on the PLCs. Supervisory control and data acquisition (SCADA) interfaces were also implemented to allow for switching between controller modes, inputting of setpoint variables and to provide a visual display for process monitoring. The final phase of the project involved the installation and commissioning of advanced process control (APC) solutions on the milling and flotation circuits. This work was carried out by Mintek over 21 on-site days. The APC solutions included the MillStar and FloatStar suites of advanced controllers.The MillStar control suite focused on stabilising the mill feed and mill discharge on the two primary mills as well as the flotation circuit feed. Mintek’s CyLas instruments, which provide a measurement of the hydrocyclone underflow angle, were also installed. The measurements were incorporated into the discharge stabilisation control on both milling circuits. The FloatStar level stabiliser controller provided flotation cell pulp level control on fourteen cells, including two columns.Performance tests showed that the Mintek APC system stabilised the mill feed and mill discharge while ensuring the process remained within operational constraints. The MillStar control system utilised the CyLas instrument to prevent roping on the hydrocyclone underflow. This was not always achieved under normal operation. Additionally, the flotation section was stabilised as a result of improved level control by the FloatStar control system.Performance comparisons showed that the Mintek control system improved the operation of the milling and flotation circuits resulting in a greater copper recovery.CITATION:Naidoo, A, De Gee, B E and Viviers, N, 2014. Implementation of an advanced milling and flotation control system at Mopani Mufulira copper mine, in Proceedings 12th AusIMM Mill Operators’ Conference 2014 , pp 363–368 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 1, 2014

Technological advances evolve in different ways; many are the result of years of application of scientific method. i.e. Observation Deduction Hypothesis Proof In the mining industry, better explosives, drill bits or reagents are likely to evolve in this way. The scientific method is suited to the application of conventional management structures. Other advances are simply the result of a "brainstorm", or building a better mousetrap. Such inspiration probably resulted in "Split Set" rock bolts, or the first use of a vacuum cleaner principle for shaft mucking. Individual consultants can apply lateral thinking to generate such inspiration. In gathering material for the presentation of this paper, I sent a.letter to all members of the Mineral Industry Consultants Association asking them to nominate problems in the industry requiring investigation. The answers have been divided into two classifications - contract research underway and identified problems requiring solutions.

Jan 1, 1986

By O Dominguez

Significant value can be added to ore supplied from the mine to the mill by measuring its quality in real time and performing grade control additional to that within the mine. Responsibility for ore quality between the mine and mill stockpiles is not always clear due to operational siloes so geologists and mining engineers need to be involved collaboratively with metallurgists to optimise ore value prior to processing. Sensors, such as the GEOSCAN-M which utilises high specification Prompt Gamma Neutron Activation Analysis (PGNAA), that measure conveyed ore flow representatively (continuous and fully penetrative) and in real time have been used in the minerals sector since 2003 and have been successfully applied in multiple commodities. Quality can be measured within the mine where material is conveyed underground or in-pit. Bulk ore sorting is used to divert increments of waste from the ore stream to upgrade material sent to the crushed ore stockpile (COS) as well as to create run-of-mine (ROM) stockpiles of different qualities to maximise blending opportunities and accommodate processing priorities, eg blending out deleterious content. The real time composition measurement can be combined with moisture and fragmentation analysis data for improved ore type characterisation, to control ore blending, for feedback to the mining schedule and block model reconciliation, and feed forward control for grinding and processing operations. The paper discusses various parameters measured and derived in existing operations that are used to maximise coarse waste rejection and metal recovery, optimise plant feed quality consistency, and reduce consumables; power, grinding media, water, reagents, and minimise fine tailings generation. Innovative geometallurgy applications are also discussed.

Mar 22, 2022

By A B. Jahed, Ö Aydan, T Ito

In this study, the authors compiled some case history data and present some typical examples of rock slope stability issues in Afghanistan with a special emphasis on Kandahar region and categorise rock slope failures according to the principles of modern rock slope engineering. The slopes considered involve rock-cut, natural rock slopes mainly. The effect of structural geology and discontinuous nature of rock mass on both slope-cuts and natural rock slopes is taken into account and some preliminary assessments on the stable and unstable rock slopes are presented. Furthermore, the seismic effect on their stability is also considered. It is also pointed out that similar issues could be observed in open pit mines, which may be exploited in years to come.

Nov 29, 2022

By D François-Bongarçon

After a review of the progresses made on the liberation factor theory since its inception by Gy (1982), a new and surprising result of great practical importance is presented: the liberation factor. First introduced simply as a number between 0 and 1, then shown to be the ratio of two variances, is now shown to be well approximated by the proportion of liberated mineral.CITATION:François-Bongarçon, D, 2017. Evolution of the concept of the liberation factor and a surprising new result, in Proceedings Eighth World Conference on Sampling and Blending , pp 307–310 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017