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By D K. Weatherley, G R. Ballantyne, S Ali, M Yahyaei, M S. Powell

This paper explores development of a novel ore characterisation method for the precise measurement of practical minimum comminution energy. A monolayer of particles with a narrow size distribution is broken using a precision rolls crusher (PRC); an ore characterisation device developed to overcome the shortcomings of conventional tests. For energy measurement, PRC uses two shaftmounted rotary torque transducers. These transducers acquire precise torque and angular speed data in response to the load applied to the rotating shafts during breakage events, which is converted into energy. The test progressively crushes feed particles down to final product size in many controlled breakage stages. The generation of fines in each breakage stage is then plotted as a function of input energy. The inverse of the gradient of this plot provides the size specific energy (SSE) in kWh/t of material generated below a predefined marker size; -75 μm in this case. The PRC has potential to evolve as a geometallurgical ore characterisation test—it is simple, fast, requires small sample mass (200–300 g), covers a wide feed particle size range (10 mm to 115 µm), and provides ideal SSE measurements that can be used for the calibration of on-site production equipment.

Aug 24, 2022

Grey River Gold Mining Limited (GRGML) has constructed and largely completed the commissioning of an alluvial gold dredge designed to recover gold from a low grade gold deposit in the Grey River Valley, New Zealand. The most important resource that GRGML has are the people who are employed by the organisation. The low grade of the deposit necessitates the requirement to operate the dredge at optimum efficiency, which in turn requires the work force to be of high calibre and continually motivated. The primary prerequisite for employment at GRGML is for employees to be receptive to new ideas and have the adaptability to develop new skills and apply those skills to the changing demands of the workplace.   A continually changing organisational structure is utilised to meet the needs of a changing work environment. The adoption of an innovative site employment agreement allowing for flexible working hours has aided the achievement of good employee productivity and attendance.   Employees gain a higher quality of life by working a roster pattern involving twelve hour shifts and a four day on, four day off pattern.   Employees and management are communicating very well and working together to achieve organisational goals which will ultimately benefit the employees, the shareholders, the local community and the mining industry generally.

Jan 1, 1989

By C De-Vitry

In skewed distributions seen in many geochemical data sets, samples at the extreme ends of the distribution are often termed ‘outliers’. Samples considered as outliers can often make exploratory data analysis and resource estimation more difficult and less reliable. Such outlier samples may be legitimate because they are part of a natural high- or low-grade tail in the distribution. How these samples are identified and dealt with in resource estimation can often be a material issue for the Competent Person, particularly under the latest edition of the JORC Code (JORC, 2012). This paper discusses the identification and characterisation of outliers and high- and low-grade tails and proposes methods to deal with them in estimation.For dealing with outliers and high-grade tails ,very simple approaches, such as top-cutting through to more advanced geostatistical approaches, are discussed. The strengths and weaknesses of each approach are also outlined. Some examples of how the underlying geological understanding of a deposit influences the view of outliers and low-/high-grade tails is provided. The importance of documenting, communicating and challenging a given geological model is also discussed. Finally, some ideas for dealing with the uncertainty created by outliers are outlined.CITATION:De-Vitry, C, 2014. Identifying and dealing with outliers in resource estimation, in Proceedings Ninth International Mining Geology Conference 2014 , pp 159–168 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By K Ehrig, C Lower, V Liebezeit, M Smith, E Macmillan

"Minerals, minerals, minerals. Elements occur in the earth as minerals. If local physical, chemical and structural conditions are conducive to concentrating these minerals to sufficiently high abundances in the earth’s crust, a mineral deposit will form. If technology is available to extract metals from the minerals economically, then you have a mineral resource that will be mined and processed. Determining which minerals are present and quantifying their abundances, textural characteristics (grain size and shape) and how they are intergrown with each other is the realm of the mineralogist. Geologists use this mineralogical data to understand how the mineral deposit formed, how to find high-grade zones within the deposit and where to find other mineral deposits. Metallurgists use this data to design, operate and optimise processing facilities to extract metals from the minerals. The types, quantity and precision/resolution of the mineralogical data required by geologists and metallurgists are different, but are not mutually exclusive of each other. Fortunately, measurement technology is available that is relatively rapid, high volume and low cost, thus enabling ore and gangue mineral characterisation at a historically unprecedented scale of a mineral resource.CITATION:Ehrig, K, Liebezeit, V, Smith, M, Macmillan, E and Lower, C, 2014. Geologists and the value chain – how material characterisation by modern mineralogy can optimise design and operation of processing facilities, in Proceedings Ninth International Mining Geology Conference 2014, pp 5–14 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 18, 2014

By B L. Sainsbury, M F. Lee, A Penney

For most practical rock engineering purposes, stress versus strength conditions around underground openings for which rock masses fail and their various modes of failure, are reasonably well-understood and predictable. Some rock masses and particular rock types fail slowly and relatively quietly. However, others can fail rapidly, violently and maybe with the ejection of significant broken rock. In some countries and in some mines, the latter style of violent fracturing and failure of the rock mass is referred to as ‘strain bursting’. It can be alarming and extremely hazardous to nearby miners and machines. For such situations, the design and installation of appropriate ground support, to provide a safe work place, can be challenging. At any particular mine site, it’s often generally understood which local rock masses (rock types) are prone to strain bursting. Competent and strong siliceous rocks and some massive sulphides are often the main offenders. While some neighbouring, equally-competent and strong rocks might also fail, they do so more quietly and without ejection. To understand this contrast, a better understanding of the fracturing process is required other than simple and standard strength versus stress considerations. Suites of standard intact rock properties from numerous Australian mines have been used to define and help understand different high-stress failure styles for component intact rock; especially those prone to violent fracturing (strain bursting). Simple considerations of micro-fracturing (defects in the intact material), plus the available energy at failure versus the energy consumed during fracturing, distinguishes between over-stressed and competent rock types that fracture violently and those that don’t. CITATION:Lee, M F, Penney, A and Sainsbury, B L, 2018. Proneness of competent over-stressed intact rock to violent fracturing, in Proceedings The Fourth Australasian Ground Control in Mining Conference (AusRock), pp 170–184 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 30, 2018

This paper presents an overview of a program PC-BC developed for application to the design and evaluation of block cave operations. Conventional mine planning software tools are not well suited to the evaluation of this type of deposit. The paper looks at the modelling approach as applied to a block cave mining project. The following steps are described:Initial preparation of data including block models, draw point footprint geometry and draw cone geometry. Computation of individual draw point reserves. Procedure for modelling of vertical mixing of material within each draw point and subsequent determination of the best height of draw for each draw point based upon an economic cut-off value. Smoothing of draw heights amongst neighbouring draw points to produce a realistic draw envelope. Mineable reserves within the envelope are then computed. Tools for preparation and evaluation of various production schedules. This includes definition of draw rates, and rates for commissioning new draw points. In an operating mine, the capture and analysis of daily draw tonnages is important. How PC-BC accommodates this is described as well as the processes for depleting the draw column reserves. In the 12 years since the program was first developed, it has been used on a number of projects for feasibility studies and operating mines. Some practical examples of the use of the program in these projects are presented. Finally, some commentary on the sensitivity of various parameters is presented. Particular emphasis is placed on the overall footprint design.

Jan 1, 2000

Review on Some Research Methods of Mineral Crystal Chemistry and Computer Simulation on Flotation

Sep 13, 2010

By P Holtham, K Duffy, B, W Valery, E Tabosa, rade

Pre-concentration has potential to significantly improve Mineral Resource efficiency by removing gangue early in the process, before energy intensive and expensive comminution and fine processing. However, there are numerous options for pre-concentration and the performance and benefits of these are very case specific. To determine the best option for a particular deposit and to successfully integrate it into the overall mining and processing operations requires comprehensive evaluation. This needs to consider orebody suitability, technology capability and economic viability. The in-situ variability of a deposit and how it is influenced by mining methods and the liberation size of gangue are key factors which are generally not well understood. Geostatistical methods provide an insight into orebody variability, and the overall selection of any pre-concentration solution must be an integrated approach between geology, mining and processing. Many pre-concentration evaluations investigate the potential of just one option. Technology selection should start wide and may include: selective mining, pre-screening (with or without selective blasting), sorting (bulk and or particle), coarse gravity separation (e.g. jigging, DMS), coarse particle flotation, magnetic separation, etc. The upgrade performance of these processes is very ore specific and should be determined from testing, with detailed multi-component modelling used to determine the overall process performance. Many of these pre-concentration processes require significant ancillary equipment, feed preparation and materials handling. It is important to realistically estimate all costs to understand overall economics and select the best option. Some examples showing evaluation and comparison of pre-concentration options are presented in this paper. These include assessments of in-situ variability using geostatistical tools, process modelling of pre-concentration options and overall performance, preliminary layouts and cost estimates, and economic evaluations.

Nov 10, 2020

By G B. Smith, D Hillier, T Gibbons, D B. Donato, M D. Adams, S Davies, R S. Schulz

Responsible management of cyanide solutions and tailings on gold processing plants worldwide is an important aspect to these operations and is regulated via guidelines provided by the International Cyanide Management Code, an industry initiative designed to minimise cyanide risk to operators and the environment. Here we demonstrate the unprecedented causal relationships surrounding the saline (>14 000 mg/L total dissolved solids - TDS) and hypersaline (>50 000 mg/L TDS) cyanide solutions in gold plant tailings in the Central Goldfields of Western Australia, resulting in zero wildlife mortalities on three sites over the study period of almost one year. Wildlife interaction and ingestion is significantly lower than that experienced at other gold mine sites, with more rapid degradation of weak-acid dissociable (WAD) cyanide within the tailings storage facility (TSF). A rigorous chemical sampling using a novel æminimal accessÆ robotic sampler device and wildlife observation exercise was carried out at two hypersaline mine sites: Barrick Kanowna Belle (BKB) and Gold Fields St Ives (GSI) and one saline site, Barrick Granny Smith (BGS). The data was compared with available reported chemical sampling and wildlife observation data from a previously operational fresh water site (<2000 mg/L TDS) that had experienced wildlife mortalities, Case Study D (CSD). The comprehensive body of work, along with cyanide degradation test work carried out in the laboratory, was analysed via hypothesis development and testing, causation analysis and dynamic chemical modelling. The non-mortality effect on these sites appears to hold over a further four years of routine wildlife and cyanide monitoring by site personnel. This study has helped these three mine sites achieve and maintain full Compliance Cyanide Code status over a significant period while removing the need for operating the detoxification plants they would otherwise have required.CITATION:Adams, M D, Donato, D B, Schulz, R S, Smith, G B, Gibbons, T, Davies, S and Hillier, D, 2013. Hypersaline-induced reduction in cyanide ecotoxicity at gold operations, thereby obviating detoxification plants, in Proceedings World Gold 2013, pp 489-502 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By J Harding, S Munro, R A. Bearman

Despite the importance of the primary crushing stage, performance optimisation is not well analysed with sufficient focus to give improvement opportunities. At the Newcrest owned Telfer operation, liner life plays an important part in scheduling planned maintenance. Major consideration is given to monitoring crusher performance, as the highly abrasive nature of the feed significantly impacts the liner wear life. A study was undertaken by the lead author which focused on establishing a strong baseline of accurate data pertaining to the performance of the crusher, in terms of, operating parameters, liner life and key machine design factors. As part of the study, mining feed materials were examined for a particular set of liners and this revealed that improved methods should be pursued. Due to the competitive nature of the mining industry, the business solution to complex problems with long shutdown cycles should be streamlined to incorporate a non-operational modelling approach that is significantly more efficient than traditional online trial and error methods. In order to dramatically reduce the time and business risks, it was decided to engage services to model and simulate the liner life by varying main operational and mechanical factors. The key to all simulation work is gathering high quality baseline data. Such data allowed deployment of the Kinematic Crusher Model and validation of the model against worn 2D wear liner profiles. The proven model was then successfully deployed to predict operational values that defined crusher performance. To enhance the study, further investigation into a set of mechanical and operational simulations generated a sensitivity matrix measuring key performance parameters throughout the wear life of the liners. The study revealed throughput as a highly sensitive parameter and a change in eccentric throw provided the greatest improvement in extending liner wear life.

Aug 24, 2022

By G Smart, D Ward, J Grace

Ridgeway Gold Mine is part of Cadia Valley Operations which is wholly owned and managed by Newcrest Mining Limited. It is an underground sublevel cave (SLC) operation mining approximately 5 Mt per annum. Ore control systems at Ridgeway have been designed to deliver gold and copper metal production through focussing on the ore characteristics that impact on mine and mill performance and ultimately metal delivery. This is achieved using data collection and management systems which allow data to be collected digitally with æat captureÆ validation routines. These data form the basis for forecasting and on-going systems analysis which aim to accurately assess local in situ and drawn ore characteristics. Physical attributes of ore such as draw characteristics, brow conditions, visual grade estimates and draw point sampling are routinely recorded. Ore tracking and accounting systems monitor gold and copper grades, copper mineralogy, host lithology and ore sizing. These factors have material impacts on concentrator throughput and metal recovery. Draw point recovered grades are routinely reconciled back to design data to monitor and assess draw performance. Statistical variance controls are also employed to analyse mine and plant performance and guide actions.

Jan 1, 2003

By E Topal

Stopes are used in several underground mining methods. Boundary determination of these stopes is generally based on simple rules of thumb. While several stope boundary optimisation techniques are available, they fail to guarantee true optimum results. The first part of this paper reviews some important stope boundary optimisation studies and proposes a new algorithm to optimise stope boundaries and layouts for underground operations. The second part applies the proposed algorithm to a block model to test its ability to produce optimum results and demonstrate its applicability in a number of different scenarios. The results demonstrate that the proposed algorithm can find optimum stope boundaries and layouts in three dimensions for different stope sizes and economic conditions.

Jan 1, 2009

The profitability of individual ore blocks can be classed as clearly profitable, clearly not profitable, and those in between which are by nature quite sensitive to their major cost and revenue drivers. It is often the case that the most effort goes into the least profitable ore blocks to ensure that these will in fact not generate a loss. In these cases a cut-off grade policy is often not sufficiently live to separate individual sources given the volatility of financial markets and individual circumstances of some sources particularly in remnant operations such as Mount Isa MinesÆ Lead Mine. Standard sensitivity analysis can determine which factors stope profitability is most sensitive to. However, this does not usually indicate the likelihood of any input change, nor the combined effect of multiple inputs changing. The author attempted to modify the Lead Stream financial model that determines cash margin by inserting probability distribution functions and then using Monte Carlo simulations to determine the probability of any particular ore block making a profit. This effectively demonstrates the combined effect of varying a number of inputs simultaneously to provide a probability of making a profit. The limitations of this analysis lie in the accuracy that individual probability distributions can be specified. Attempts to generate valid functions from first principles have proved difficult for a number of reasons and these are discussed along with some practical alternatives.

Jan 1, 2002

By P Esteves, J L. Bechir, R Galery, C Senna, V Souto

The current moment experienced by the mineral industry is marked by a series of economic, social and environmental challenges. Among the main challenges, it is important to highlight the decreasing in ore grades with the gradual depletion of the existing deposits, the high volatility in international commodity prices and the operational inefficiencies in the mine, beneficiation, and metallurgical plants. In this context, mining companies are continuously looking for alternatives that minimize production costs and maximize overall production. In addition, recent tragedies involving tailings dam collapses in Brazil, reinforced the need for a more responsible, sustainable, and conscious mining, such as aiming the preservation and rehabilitation of the land environment. In this scenario, the Sensor-Based Sorting (SBS) technology is currently getting more space into the mining market. This separation technology aims the removal of gangue material in coarse particle size fractions, prior to comminution and concentration stages. As a consequence, the technology allows a smaller consumption of energy, water, chemical reagents and other inputs. Moreover, the sensor-based sorting is a dry processing technology and favors the reduction of fine material to be sent to the tailings. The aim of this paper is to provide information regarding the technical and economical evaluation of SBS technology applicability to a zinc silicate mining in Brazil. The project evaluation was performed in two stages: laboratory test work and the execution of a pilot plant. The execution of a pilot plant allowed the technology optimization, quantification of downstream process effects, such as a proper economic evaluation about the technology benefits. Keywords: Sensor-Based Sorting; Particle Sorting; Ore Sorting; Preconcentration; capital expenditure (CAPEX); operating expenditure (OPEX); zinc; comminution; dry processing.

Nov 10, 2020

By S R. Pecover

AustraliaÆs opal and sapphire mining industry has fallen from its peak in the 1980s and 1990s into a significant low today. This is not due to exhaustion of the resource, but instead an over-reliance of the Australian miner on achieving a fair price for the gemstone product from offshore middlemen dealers. Gemstone and geological research is also at a low as Federal higher education expenditure has fallen with research institutions relying increasingly on private funding in an environment of restricted autonomy and flexibility for researchers. What little remaining research skills the universities have is being bled into the private sector as a result of the mining boom and encouraged by lower than average academic salaries. Nevertheless, some highly innovative research has been taking place, often by self-funded individuals and retired academics simply with a desire to advance the understanding of the particular branch of science in which they are interested. New models for the formation of sapphire and opal are now beginning to be applied to the exploration for these gemstone commodities. This research, together with well thought out plans for managing the gemstone product through its value-adding steps to the jewellery retail level, has the potential to bring about a resurgence in the Australian gemstone industry.

Jan 1, 2008

By C Harrison, A Bowskill

The Ambuklao hydroelectric dam was originally constructed in the 1950s in the remote and mountainous region of the northern Philippines. Following its construction the dam has suffered heavily due to siltation and a partial collapse of the intake structure due to a 7.8 magnitude earthquake that struck the region in 1990. Between the years 1990 and 1999 the power station progressively lost its capacity to generate power. In 1999 the owner took the power station out of commission. The power station remained idle over the next 12 years. In 2008 the power station was sold to a new owner who commissioned the rehabilitation works.The rehabilitation project restored the operating status of the power station in June 2011 and increased its capacity from 75 MW to 105 MW. The civil contract of the rehabilitation project required the construction of a new intake structure behind an in situ rock coffer dam on the edge of the existing reservoir, new 6.2?m diameter × 124?m deep blind sunk shaft behind the intake structure, which connects to a new 6.8?m horseshoe profile headrace tunnel that ultimately connected onto the existing vertical penstocks which feed three No 35 MW Horizontal Turbines rated at 155?m head.The unique challenge in rehabilitating this existing hydropower station involved finding solutions that would conclusively deal with the challenging geological and hydrogeological conditions associated with excavating new tunnels and a drop shaft beneath a live dam.McConnell Dowell was awarded the civil works package for the rehabilitation works in August 2008. The Ambuklao rehabilitation program took 33 months to complete.Over 600?m of tunnels were excavated in highly weathered and often challenging geotechnical conditions via drill and blast with the extensive use of high-pressure fissure grouting to control groundwater ingress that was surcharged by the dam.This paper focuses on the use of high-pressure fissure grouting that took place to enable the excavation of the new waterway system and intake structure.CITATION:Bowskill, A and Harrison, C, 2014. High-pressure fissure grouting for drill and blast tunnelling, Ambuklao, Philippines, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 141–152 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By S Gillies, H W. Wu

A study has been undertaken into mine ventilation systems currently in use within Australian modern coal longwall (LW) extraction mines. It reviews systems and discusses evolving changes being adopted to address the more complex challenges. There is a strong move to longer panels, wider faces, greater extraction heights, increased production rates, more efficient ventilation and decreased personnel. Each of these changes is motivated by improvement in productivity and generally leads to cost reduction. In addition, mine workings are moving deeper, which results in increased ventilation control issues such as higher total and respirable dust levels, greater seam gas contents in parallel with lower in situ permeabilities, spontaneous combustion and heat management issues. A comprehensive database of Australian LW ventilation practice is analysed. Currently there are a variety of LW panel ventilation circuits used in Australian underground coal mines due to various combinations of seam characteristics, gas emission rates, spontaneous combustion, geological features and surface constraints. The main issues usually addressed in the designing and planning of ventilation circuits for LW panels are airway velocity, gas concentrations, LW cutting methods (eg Bi-di, Uni-di or half web), ventilation of control devices, pressure differentials and leakage paths and understanding gas concentrations across the length and width of the goaf. If the ventilation circuit can manage the applied contaminant load (gases, heat and dust) at an acceptable cost and circuit duty, then supplementary controls, such as gas drainage, refrigeration and dust sprays and scrubbers, may not be required. CITATION:Gillies, S and Wu, H W, 2013. Review of Australian longwall panel ventilation practices, in Proceedings The Australian Mine Ventilation Conference , pp 87-94 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By M G. Aylmore, L W. de Klerk

Roasting of refractory gold ores has been a commercial process for many years. Improvements in design of fluidised bed roasting technologies and low capital and operating costs compared with other refractory treatment processes can potentially make roasting a viable option.However, gold extraction from roasted ores carried out on laboratory scale equipment often invariably yields lower recoveries than other processes such as bio-oxidation or pressure oxidation. Non-optimal laboratory roasting conditions can incorrectly write roasting off as a process option.Low gold recoveries from the cyanidation of calcine products from roasting can often be attributed to roasting conditions not favouring gold liberation and agglomeration processes, particularly if lockups of elements such as arsenic are being pursued for environmental reasons.This paper reviews the conditions favoured for gold agglomeration and accessibility of gold to cyanide, test conditions to achieve gold liberation and agglomeration on laboratory scale and designs that incorporate staged decomposition and roasting to make roasting a more commercial option.CITATION:Aylmore, M G and de Klerk, L W, 2013. Conditions and design considerations for maximising recoverable gold in roasting of refractory gold ores, in Proceedings World Gold 2013 , pp 375-388 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

This paper on the relation of Granite and Sedimentary Contacts to Victorian Mining will, it is hoped, be of interest to members of the Institute.The broad fact that gold often occurs' at or near the junction of granite with sedimentary silurian or metamorphic rocks has been noted by some Victorian geologists, miners, and prospectors; but the fuq practical value -of the fact does not seem to have been fully realised by prospectors. Glancing at the Geological" Map of Victoria, one can see that many of our goldfields 'are situated at or near the junction of granite with Palceozoic sedimentary formations, and that some of our alluvial fields are on granite. Many prospectors are possessed of this knowledge but when prospecting a contact locality, they would be just as likely to confine their search for auriferous matrices to spots a quarter of a mile on the sedimentary side, as on the actual contact line of two formations.

By M P. Simpson

Forty one whole rock samples from the Gold Cross low-sulfidation epithermal Au-Ag deposit have d18O values that range from 4.4 to 9.3 per mil, with an average value of 7.0 per mil. Unaltered and weakly altered rocks have d18O values greater than eight per mil, and the orebody is surrounded by samples that are depleted in 18O. A strongly silicified sample adjacent to the Empire Vein System has a d18O value of 9.0 per mil, similar to previously reported analyses of vein quartz (7.0 to 11.7ë, average 9.4ë). This suggests that, in detail, Golden Cross may have a zone of 18O-enriched wall rocks in the core of the deposit, adjacent to the main underground veins. Although some workers have suggested that stable isotope geochemistry may provide useful information for epithermal mineral deposit exploration, at Golden Cross this is not the case. Alteration minerals, major elements and trace elements all define larger, less ambiguous halos than the zone of 18O-depleted wall rocks.

Jan 1, 2001