Julius Kruttschnitt Mineral Research Centre Research Articles

A 3D cellular automata ore stockpile model – Part 2: Simulation and industrial validation of dynamic discharging and trajectory segregation mechanisms

This paper describes a 3D cellular automaton (CA) for dynamically modelling ore piles with continuous feeding and discharging and incorporating two separate size segregation mechanisms. Stockpiles are an integral part of materials handling and storage, and their operation plays an important role in the overall performance of the mineral processing plant. Size segregation can create fluctuations and cause processing units to receive uneven feeds. However, this issue has not received enough attention. Therefore, a three-dimensional dynamic stockpile model has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC), which can model the dynamic response of a wide-size-range stockpile. A Continuous Cellular Automata was developed, dividing the volume of the stockpile into a three-dimensional grid of cells with each cell containing an independent set of properties that are tracked throughout the simulation. Modelling size segregation during material flow was presented in Part 1. The variation in the stockpile surface profile and size distribution of the stockpile can be predicted. In this paper, the stockpile model with size segregation extends to the discharging and migration for real-time simulation. The model structure and industrial validation are discussed in this paper, which will show the application of the dynamic model, including the particle size distribution and the height variation of the stockpile. The three-dimensional dynamic stockpile model can contribute to the control of the comminution circuit because different operational strategies can be predicted using the model.

Classification performance of semi-inverted hydrocyclones

Researchers have reported in the past that inclined hydrocyclone operation can provide a lower water split to underflow and much coarser cut sizes. However, semi-inverted hydrocyclones (inclined higher than the horizontal position) have not been investigated in detail. This paper presents the results of a comprehensive study that was carried out at the Julius Kruttschnitt Mineral Research Centre (JKMRC) using a semi-inverted (SIV) hydrocyclone. A 250 mm hydrocyclone was tested with a modified cone. The modified cone extended the operational range of the hydrocyclone. The SIV hydrocyclone was tested at different inclinations and operating feed pressure using three different slurry feeds. A significant reduction in the water split (WS) to coarse was achieved at semi-inverted positions. WS values of 3–5% at 135° inclination were achieved. The change in WS did not influence the sharpness of separation (α). Stable operation and sharpness of separation were achieved, despite the appearance of roping-like underflow discharge in semi-inverted operation.

MW heating of rock particles and their cross-dependencies

Microwave heating inside a cavity is not uniform and depends on various factors such as: cavity geometry, properties of treated material and frequency. In most applications of microwave (MW) heating there is only a small variation in the nature of the feed. However, this is not the case for the MW/Infra-Red (IR) ore sorting. As microwaves are electromagnetic waves, the microwave field around a given ore particle is influenced by its dielectric and magnetic properties and the modified field should also influence the heating of neighbouring particles. While influence is reciprocal it is clear that particles with high dielectric properties will dominate field effects. Understanding of this process is important in the particle-by-particle ore sorting process where the accept/reject decision is based on the temperature of the ore particle.A series of experiments were conducted at the Julius Kruttschnitt Mineral Research Centre to investigate the impact of particle size and its (highly) electromagnetic properties upon the heating of other nearby particles. The results suggest that magnetic and/or MW responsive particles that are prone to heat strongly during MW heating will have an impact on the heating of neighbouring particles of intermediate responsiveness. The heating of particles which is influenced by other highly responsive particles is very likely to lead to misclassification during the sorting process.

A review of development of better prediction equations for blast fragmentation

Abstract The paper reviews the development of prediction formulas for the fragmentation from bench blasting. Much attention has been paid to the Kuz-Ram model, its development and errors, and the mean vs. median misunderstanding. The work by the US Bureau of Mines (USBM) and Chung and Katsabanis are also reviewed, as well as the two Julius Kruttschnitt Mineral Research Centre (JKMRC) models, i.e. the crush zone model (CZM) and the two-component model (TCM), which were developed to cope with the underestimation of blasting fines. The change brought by the Swebrec distribution and the associated Kuznetsov-Cunningham-Ouchterlony (KCO) model is described. Studying distribution-free fragment sizes x P for an arbitrary mass passing P led to the discovery of the fragmentation-energy fan, and with the help of dimensional analysis, to the new fragmentation prediction model x P -frag, which has much lower errors than those of the Kuz-Ram and CZM models.

Selective breakage of mineralised synthetic particles by high voltage pulses. Part 1: Metalliferous grain-induced breakage in a two-particle paired system

The propensity of high voltage pulse (HVP) towards mineral-enriched ore particles during treatment has been reported by researchers at the Julius Kruttschnitt Mineral Research Centre. However, the fundamentals of HVP selective breakage between particles remains unclear due to complex mechanical and electrical properties of the natural ores. An experimental study of HVP selective breakage was conducted using fabricated synthetic particles embedded with various metalliferous minerals of different conductivities/permittivities. HVP tests were performed by placing the mineralised and the barren synthetic particles in the pulse discharge zone, which were then treated with one pulse loading. Part 1 of this study presents evidence of metalliferous grain-induced breakage in a two-particle paired system, with barren particles remaining intact. High-resolution images of the mineralised fragments showed that the electrical breakdown channel exerted detrimental effects upon the integrity of all the metalliferous grains tested, resulting in complete disintegration and heavy surface oxidation of the metalliferous grains, rather than liberating the metalliferous grain along its boundaries as reported in the literature. In addition, the influence of metalliferous grain locality in a particle on HVP breakage selectivity is also investigated.

Extending the application of JKFBC for gravity induced stirred mills feed ore characterisation

Although stirred mills have been used widely in the mineral processing concentrators for fine grinding purposes, till date a standard ore characterisation test is not available for this technology. Advanced process modelling requires ore hardness index and ore specific breakage functions for accurate predictive capability. The Julius Kruttschnitt Mineral Research Centre (JKMRC) has pioneered the initiative to develop a practical ore characterisation test for the fine particles (within stirred mill regime). The JKFBC (JK fine-particle breakage characteriser) was used to develop an index that represents the ore hardness of the stirred mill feed. The index is called Stirred mill index (SMi). This index measures the particles hardness and generate a generic tn-family curve (to establish energy base breakage function). Four types of materials were chosen for the test work i.e. Au-Cu ore, limestone, Fe ore and Au ore. The JKFBC test works were carried out by varying the applied vertical load, mill rotational speed and number of revolutions to achieve various levels of energies. The energy regimes chosen in this test work were within the typical operational conditions of the industrial scale gravity induced stirred mills. The test was modified from the original Shi’s test methodology by reducing the thickness of the particles bed in the mill and specific energy consumption. The volume of the material in the mill is kept constant to avoid the particle density effect. A new t10 function that incorporates the size effect was used to describe the breakage in the JKFBC. Ore hardness of the fine particles (between 1180 and 53μm) was quantified through SMi. A preliminary tn-t10 family curves was developed that responds based on the hardness of the samples - SMi and energy. Further work in extending this procedure with other types of ores are essential for a more robust model parameters. This preliminary development has enabled a more predictive stirred mill process model development that incorporates the ore characteristics in the selection function.

Ore particle breakage behaviour in a pilot scale high voltage pulse machine

SELFRAG AG has developed a flexible pilot scale Pre-Weakening Testing Station (PWTS) using high voltage pulses (HVP). This provides a unique opportunity to investigate the machine setting conditions on ore breakage behaviour. A joint campaign was undertaken by the Julius Kruttschnitt Mineral Research Centre and SELFRAG AG to investigate the breakage behaviour of two copper–gold ores and one iron ore in the PWTS. The effects of specific energy, pulse voltage, cumulative discharges, feed particle size and ore particle breakage pattern (body breakage or surface breakage) were investigated. The investigation revealed that the mass-specific energy of HVP was the most significant factor affecting the breakage behaviour in the PWTS. This effect was compounded with the effects of ore properties and particle size. Comparison between the PWTS and a laboratory HVP machine indicates that there is considerable scope for optimisation of HVP performance based on processing zone design.

Modelling of vertical spindle mills. Part 1: Sub-models for comminution and classification

A new mechanistic model for vertical spindle mills (VSM) has been developed by Julius Kruttschnitt Mineral Research Centre (JKMRC) at the University of Queensland. Unlike the previous work in the literature, which treats the VSM as a “black box”, the present work incorporates two sets of variables in the model: (1) the coal specific property, and (2) the machine specific variables. The VSM model is presented in two parts/papers. The first part presents the sub-models for comminution and classification in the VSM. The second part describes the integration of the sub-models to simulate industrial scale E-Mill, MPS and CKP mills. The sub-models include mill power prediction, size specific energy calculation, size dependent breakage function, product size distribution estimation, elutriation classification and gas cyclone classification. The coal breakage property was measured with a JKFBC grinding device and modelled using a size-dependent breakage function. The machine specific variables include mill geometry, air classifier geometry, coal feed rate, primary air flow rate, air temperature, air pressure, grinding table rotational speed, mill spider hydraulic load and mill power draw. These variables are incorporated in the comminution and classification functions based on physical principles.

Coal breakage characterisation – Part 2: Multi-component breakage modelling

A multi-component breakage model has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC) to describe the energy–size reduction in relation to particle size and density for coal breakage characterisation. The model takes the following form: t10=M(RD/RDmin)c·{1-exp[-fmat·x·E]}. The model incorporates four parameters and fits 60 JKFBC (JK Fine-particle Breakage Characteriser) test data for each of the Australian coal and Chinese coal samples, with R2=0.982 and 0.978 respectively. The multi-component model can be switched into a single component model by setting c=0.A set of tn-family of curves for coals ground in the JKFBC are presented. It was found that the data from various particle sizes and densities of the two coal samples, collected from the Australian and Chinese power stations, all fall on similar tn-curve trend lines. These tn-family of curves can be used in the multi-component model to estimate the product size distribution from the predicted t10 values. A procedure has been developed to calibrate the multi-component model with seven tests based on a combination of various particle sizes, coal densities and grinding energy levels, using the JKFBC device. Over 100 sets of data have been used to validate the calibration procedure.

Coal breakage characterisation – Part 1: Breakage testing with the JKFBC

An improved method for coal breakage characterisation has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC). Part 1 of this paper presents the breakage testing method and results, Part 2 gives a breakage model that determines the energy-size reduction relationship for multi-components of particle size and coal density, and Part 3 demonstrates the applications of the model for HGI predictions and coal breakage simulations.The new method incorporates hardware for a fine particle breakage characterisation test, the JKFBC (JK Fine-particle Breakage Characteriser), a device modified from the standard HGI mill, which has a precision torquemeter installed to record energy utilisation during the experiments. Distinguished from the traditional HGI test, which is based on a single particle size with a single energy, the new characterisation test offers the flexibility to grind coal particles at various sizes, or various densities, or indeed (various components) with a range of energy levels. Energy consumption during the grinding was recorded. Using an Australian and a Chinese coal sample collected from power stations, this paper demonstrates the effects of particle size and density on coal breakage, and elucidates the deficiencies associated with the traditional HGI test.

A modeling approach using back-calculated induction times to predict recoveries in flotation

The current modeling flotation approach of the Julius Kruttschnitt Mineral Research Centre (JKMRC) predicts recoveries in a flotation circuit using a lumped parameter called the floatability of mineral particles (P) which has no direct physical meaning and is assumed to be conserved in flotation circuits in the absence of regrinding or change in chemical environment. In this paper, the original definition of P as the efficiency of collection was resurrected. Fundamental models of particle collection by bubbles were applied to an industrial data set from a down-the-bank flotation survey of the first four cells of the galena rougher circuit at BHP Billiton's Cannington operation in Australia. The floatability of mineral particles P was no longer treated as a lumped parameter but described by the physical measurable inputs of the models. Induction time as a model parameter was back-calculated from knowledge of the experimental data and application of the collection model. The assumption that the induction time of a size-by-liberation class at fixed chemistry was conserved allowed prediction of galena recoveries in the circuit. An extensive error analysis was conducted on the new modeling approach and it was found to be very sensitive to the value of the bubble rise velocity. Finally, since the variation in the key flotation variables down the bank at the BHP Billiton Cannington's lead rougher circuit was not significant, the two approaches predicted similar flotation kinetics down the bank.

Preface to the Proceedings of the Mathematics in Industry Study Group 2011

MISG 2011 Melbourne, Australia 6--11 February 2011 This Special Section of the ANZIAM Journal (Electronic Supplement) contains the refereed papers from the 2011 Mathematics and Statistics in Industry Study Group (MISG 2011) held at RMIT University in 6--11 February 2011. The MISG is a special interest meeting of ANZIAM, the Australia and New Zealand Industrial and Applied Mathematics (ANZIAM) division of the Australian Mathematics Society. The MISG meetings take place annually and provide a forum where problems proposed by industry can be worked on intensively, by high profile scientists in the fields of Applied Mathematics, Statistics and Operations Research, from Australia, New Zealand and the world beyond, along with representatives from the industries proposing the problems. Five problems were presented from diverse industries, with 73 delegates participating. All the papers were written by the problem moderators in consultation with the company representatives. The manuscripts were submitted to the editors; Associate Professor John Shepherd, Dr Andrew Stacey and Professor Tony Roberts; and were subsequently refereed by two expert referees. On the advice of the referees manuscripts were accepted for publication, subject to the recommended revisions, and formally approved by the editorial committee. Director: Associate Professor John Shepherd Deputy Directors: Dr John Gear and Dr Lynne McArthur Administrative Officer: Ms Leanne O'Doherty Two invited speakers presented at the conference: Rheometric Analysis of Non-Newtonian Sheet Flow Professor Paul Slatter, Rheology & Materials Processing Centre, RMIT University Unknown, Inconsistent and a Million Dollars Professor W Whiten, Julius Kruttschnitt Mineral Research Centre, The University of Queensland Acknowledgements We gratefully acknowledge support from the following organisations: EPA Victoria; Defence Science and Technology Organization; New Zealand Steel; Transpower; Fonterra; ANZIAM; AMSI; RMIT University. We are also grateful to Dr Geoff Prince, Director AMSI, for his opening address, and to Dr Bob Anderssen of CSIRO for his closing remarks. Equation free summaries Allowing for ‘worst case’ wind farms correlations in delivering secure power system operations Vanadium recovery during steel production from iron sand Test procedure equivalence Setting Water Quality Objectives to Ensure the Health of Freshwater Fish Capability management, fleet management and sustainability

Characterising chalcopyrite liberation and flotation potential: Examples from an IOCG deposit

A critical aspect of geometallurgy is quantifying mineralogical and textural relationships that affect mineral processing (e.g., liberation and recovery) and it is vital that this information is included in the planning process for both mining and mineral processing. However, to date, this has been an expensive and time consuming venture and only minimal amounts of this type of data are available to be included in the planning process. Our research is focused on developing new methods that will produce the required mineralogical and textural data rapidly and inexpensively. These include obtaining quantified textural data, such as the size and distribution of the valuable phase and its association with other minerals, by extracting it directly from mineral maps. In addition, simulated breakage of drill core samples was used as a rapid way of looking at various particle sizes to determine potential liberation behaviour. The predicted liberation parameter compares favourably with results obtained from typical MLA recovery analysis, is spatially coherent and can be used to recognise domains of high and low liberation potential that are expected to affect the grade recovery curve. The flotation response was evaluated and the technique validated using a small scale test being developed at the Julius Kruttschnitt Mineral Research Centre, i.e. the JKMSI (mineral separability indicator).

Designing and testing the representative samplers for sampling a milling circuit at Nkana copper/cobalt concentrator

The primary objective in any ore processing method, is to prepare the ore for economical and effective extraction the valuable minerals. Milling circuits are extremely energy intensive, making them very expensive operations and it is very pertinent to optimise their operationto be economically viable. Therefore, their design is very critical and this can only be achieve by adopting new control strategies to improve energy utilisation. Nkana Mine concentrator of the Zambia Consolidated Copper Mines Limited (ZCCM) has been experiencing problems inestablishing the optimum mesh of grind for the various ores, to achieve effective separation of the cobalt minerals from those of copper. This prompted the designing and testing of representative samplers for sampling the milling circuit at Nkana Concentrator. In the design of the samplers, use was made of the Gy’s formula to determine the minimum weight of the sample to be extracted from various process streams. The particle size distribution of the streams was conducted to determinethe size of the largest particle in each stream. Samplers were designed on the basis of theoretical and practical applications and a factor of three was built in the normal sampler width opening. This enabled that the entire stream had equal chance of entering the sampler.The milling circuit on which a sampling campaign was conducted consisted of a 2.7m by 3.6m (9ft, 12ft) Rod Mill in open circuit with a 760mm (30inch) hydrocyclone which was in closed circuit with a Ball Mill of thesame dimension as the Rod Mill. Samples were taken from the feed to the Rod Mill, Rod Mill discharge, Cyclone underflow( feed to the Ball Mill), Ball Mill discharge and the cyclone overflow using appropriate sampling techniques for a complete shift at equally spaced intervals. Sampling was only started when it was established that steady state operation of the plant was attained. Important operating parameters were established which included the throughput of the material tothe Rod Mill, the pulp densities of the streams in the milling circuit, the particle size distribution of the streams, volumetric flow rates of the streams and the rate at which dilution water was added. These parameters were then used to carry out Mass balancing using a mineral processing simulation software called JKSimMet which has been developed by the Julius Kruttschnitt Mineral Research Centre at the University of Queensland in Australia. The simulator can be used to predict the possible alternatives to optimising the circuit performance and physical modifications which can be made to the plant with confidence. The correlation between the measured and the calculatedparameters was found to be fairly satisfactorily. This showed that the designed samplers and the sampling techniques used were suitable for obtaining representative samples from the milling circuit. This paper describes the method used in designing the samplers, the sampling techniques used and the results obtained from the JKSimMet software.

Gas dispersion measurements in industrial flotation cells

For nearly 100 years, the flotation plant metallurgist has often wondered what is happening ‘beneath the froth’. To assist in unravelling this mystery, new technology has been developed as part of the Australian Mineral Industries Research Association (AMIRA) P9 project, to measure gas dispersion characteristics (such as gas hold-up, superficial gas velocity and bubble size) in industrial flotation cells. These measurements have been conducted in a large number of cells of different types and sizes by researchers from the Julius Kruttschnitt Mineral Research Centre (JKMRC) and JKTech. A large database has been developed and the contents of this database are described in this paper. Typical cell characterization measurements show a wide spread in values, even in the same cell types and sizes performing similar duties. In conventional flotation cells, the typical gas hold-up values range from 3% to 20%, bubble sizes range between 1 and 2 mm, and superficial gas velocity ranges from 1 to 2.5 cm/s. The ranges of cell characterization measurements given in this paper will enable plant personnel to compare their operation to other similar types of operations from around Australia and the rest of the world, giving opportunities for further improvement to flotation plant operations.

Estimation of fines generated by blasting – applications for the mining and quarrying industries

This paper introduces an engineering approach to estimate the proportion of fines generated during the blasting process. The proposed framework is based on the combination of two Rosin-Rammler based distribution functions to model the full range of fragments expected to be produced during this process. This particular approach, which has been successfully applied for a number of years by the Julius Kruttschnitt Mineral Research Centre (JKMRC), has been improved with the introduction of a new model to predict the potential volume of crushed material resulting from the crushing and shearing stages of blasting. Other sources of fines including liberation of infilling from discontinuities, particle collisions and post-blast processes have been excluded to simplify the modelling process. Validation analysis of the proposed framework has shown that there is good agreement between model predictions and the measured distribution of fines. In three distinct cases, results verified the hypothesis that a single index of uniformity can be used to describe the distribution of fragments in the range of 1 mm through to the expected post-blast mean fragment size (x50). Although some limitations have been noted, the approach appears to provide useful approximations for continuous improvement analysis and applications. The practical application of the proposed modelling framework is demonstrated with an engineering study aimed at assessing the impact of blast fragmentation on the overall production of fines in a hard rock quarry. Results from simulations showed that less crushing requirements due to an overall increase in fragmentation contribute to a decrease in the specific crushing energy and hence a reduction in power consumption requirements. This analysis helped demonstrate the importance of addressing the impact of blast fragmentation distribution on overall quarry productivity requirements; and highlights the importance of adopting a holistic approach when addressing the blast optimisation problem.

Engineering Tools for Design, Analysis and Information Management Applied to Underground Drilling and Blasting

In underground mining, the often unpredictable variability in ground conditions may lead to the application of suboptimal drilling and blasting patterns, resulting in poor performance. Experience and pertinent information to develop and implement improved drilling and blasting strategies can be easily lost due to the lack of means to help engineers store, access and manage this information. The Julius Kruttschnitt Mineral Research Centre (JKMRC) through a series of industry funded applied research projects has been developing a system that can facilitate the drill and blast design, analysis, auditing, documentation and data management processes. The system is a hybrid between an information management software module called BMS (Blast Management System) and two design and analysis modules, 2DRing for underground production blasting activities and 2DFace for development blasting activities. A concise description of the software tools and its applications are given in this paper. Opportunities to further develop the software are also highlighted, they include options to integrate these tools to existing drilling and blasting automation systems and portable computing technology to facilitate the design, implementation and continuous improvement processes.

The JK three-product cyclone—performance and potential applications

In spite of their wide application in comminution circuits, hydrocyclones have at least one significant disadvantage in that their operation inherently tends to return the fine denser liberated minerals to the grinding mill. This results in unnecessary overgrinding which adds to the milling cost and can adversely affect the efficiency of downstream processes. In an attempt to solve this problem, a three-product cyclone has been developed at the Julius Kruttschnitt Mineral Research Centre (JKMRC) to generate a second overflow in which the fine dense liberated minerals can be selectively concentrated for further treatment. In this paper, the design and operation of the three-product cyclone are described. The influence of the length of the second vortex finder on the performance of a 150-mm unit treating a mixture of magnetite and silica is investigated. Conventional cyclone tests were also conducted under similar conditions. Using the operational performance data of the three-product and conventional cyclones, it is shown that by optimising the length of the second vortex finder, the amount of fine dense mineral particles that reports to the three-product cyclone underflow can be reduced. In addition, the three-product cyclone can be used to generate middlings stream that may be more suitable for flash flotation than the conventional cyclone underflow, or alternatively, could be classified with a microscreen to separate the valuables from the gangue. At the same time, a fines stream having similar properties to those of the conventional overflow can be obtained. Hence, if the middlings stream was used as feed for flash flotation or microscreening, the fines stream could be used in lieu of the conventional overflow without compromising the feed requirements for the conventional flotation circuit. Some of the other potential applications of the new cyclone are described.

Critical Comparison of Julius Kruttschnitt Mineral Research Centre (JKMRC) Blast Fragmentation Models

Blast fragmentation can have a significant impact on the profitability of a mine. An optimum run of mine (ROM) size distribution is required to maximise the performance of downstream processes. If this fragmentation size distribution can be modelled and controlled, the operation will have made a significant advancement towards improving its performance. Blast fragmentation modelling is an important step in Mine to Mill™ optimisation. It allows the estimation of blast fragmentation distributions for a number of different rock mass, blast geometry, and explosive parameters. These distributions can then be modelled in downstream mining and milling processes to determine the optimum blast design. When a blast hole is detonated rock breakage occurs in two different stress regions - compressive and tensile. In the-first region, compressive stress waves form a ‘crushed zone’ directly adjacent to the blast hole. The second region, termed the ‘cracked zone’, occurs outside the crush one. The widely used Kuz-Ram model does not recognise these two blast regions. In the Kuz-Ram model the mean fragment size from the blast is approximated and is then used to estimate the remaining size distribution. Experience has shown that this model predicts the coarse end reasonably accurately, but it can significantly underestimate the amount of fines generated. As part of the Australian Mineral Industries Research Association (AMIRA) P483A Mine to Mill™ project, the Two-Component Model (TCM) and Crush Zone Model (CZM), developed by the Julius Kruttschnitt Mineral Research Centre (JKMRC), were compared and evaluated to measured ROM fragmentation distributions. An important criteria for this comparison was the variation of model results from measured ROM in the-fine to intermediate section (1-100 mm) of the fragmentation curve. This region of the distribution is important for Mine to Mill™ optimisation. The comparison of modelled and Split ROM fragmentation distributions has been conducted in harder ores (UCS greater than 80 MPa). Further work involves modelling softer ores. The comparisons will be continued with future site surveys to increase confidence in the comparison of the CZM and TCM to Split results. Stochastic fragmentation modelling will then be conducted to take into account variation of input parameters. A window of possible fragmentation distributions can be compared to those obtained by Split. Following this work, an improved fragmentation model will be developed in response to these findings.

Origin of blast-induced fines

The generation of fines during blasting has intrigued researchers and practitioners for some considerable time. Fines are generally considered to be fragments smaller than 10 mm, but in some applications the cutoff size is more explicit. In the case of iron ore fines are considered to be particles less than 6.3 mm, and in the case of coal less than 1 mm. There is thus a need for a more general definition of fines. It is considered here that fines are particles that are much smaller than the median or mean fragment size produced by blasting and that they are also created predominantly by shear failure of the rock mass, whereas coarser particles are created by tensile failure of the rock. Tensile failure tends to be the dominant mode of blast-induced rock mass fragmentation on account of the inherently low tensile strength of a rock mass. The Kuz–Ram model for prediction of blast-induced fragmentation does not consider fines separately from the coarse particles.1 As result, its application almost always results in a significant underestimate of the amount of fines. The literature on blasting describes models that aim to predict the amount of fines. Some of these models are based on calculation of the extent of failure around the blasthole, using equations from the theory of elasticity for a thick-wall cylinder under static internal pressure2 combined with the Kuz–Ram model for coarse fragments. Another method is based on the testing of large rock lumps in a blast chamber.3 The fraction of fines is defined from the change of slope of the fragment size distribution when the distribution is presented in a double logarithm coordinate system. Extrapolation to in-situ conditions is based on the amount and type of explosive employed in the laboratory relative to that used in practice and makes use of the concept of strain energy factor coupled with the empirically derived part of the Kuz–Ram model. Although this approach clearly provides a sounder base for modelling, it also frequently underestimates the amount of fines found after blasting. The principal reason is associated with the representativeness of a large rock lump in relation to the in-situ rock mass. As part of blast fragmentation research projects the Julius Kruttschnitt Mineral Research Centre conducted a large number of small-scale blasting tests on rock and concrete samples. In the course of that work numerical modelling of the rock fragmentation process was also carried out with the continuum finite-difference code FLAC and discrete-element modelling code PFC3D.