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By G Haywood

This paper presents the evolution of the planning, scheduling and mining practices at the Yilgarn Star underground. The paper will concentrate on the principals of æjust in timeÆ and the impact of such practices on mine planning and scheduling and subsequent development and production. The principals of æjust in timeÆ were developed to minimise the impact of creep and time dependent failure of the ground in the ore and hangingwall zones. These zones are characterised by altered schistose material with inherent weak rock strengths compounded, at depth, by the maximum principal stress of the virgin stress field approaching the UCS of the rock mass. Yilgarn Star underground has and continues to develop the æjust in timeÆ methodology to ensure the continued viability of the mine. The mine continues to use longhole open stoping mining methods to ensure high levels of productivity with minimal dilution and at an acceptable cost of production.

Jan 1, 2002

By J Loeb, D Thornton

Blast movement measurement is a key component of grade control, enabling mines to carry all of the precision involved in locating ore blocks, through a chaotic blast, to production. A monitoring system was developed about ten years ago so that mine operation personnel can measure three dimensional movement in every production blast. Research has shown that blast movement is always highly variable with a significant non-deterministic component. The consequence is that modelling will be inaccurate and therefore optimal ore recovery can only be achieved by direct measurement of blast movement.Three dimensional movement vectors are measured at discrete locations in the blast. If blast movement is only measured at one location in a blast pattern, data is severely limited and has all of the inherent inaccuracies of modelling a variable population. It is intuitive that the accuracy of defining the post-blast ore block mark-ups are proportional to the number of movement measurement locations, however increasing the number of monitoring locations causes increases to the direct operating costs of the mine.A cost-benefit analysis is used to explore the optimal number of monitoring locations. Using the method described in this paper, an automated selection of the number and location of blast movement monitors are analysed against the value of recovered ore compared to the control, for each trial.CITATION:Loeb, J and Thornton, D, 2014. A cost benefit analysis to explore the optimal number of blast movement monitoring locations, in Proceedings Ninth International Mining Geology Conference 2014 , pp 441–450 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By B Yang, S M. Aminossadati

Transporting coal by means of conveyor belts is very common in Australian underground coal mines. Major conveyor belt-related mining incidents are now relatively infrequent as a result of recent improvements in engineering standards and use of fire-resistance materials. However, conveyor belts have the potential for incidents capable of causing either personal or structural damage. In addition, any unexpected break down of rolling components or failure of belts creates a significant interruption to the production that is a major concern for operators whose responsibility is to achieve the optimum mining production.Currently, underground coal conveyor belts are examined for the presence of any overheating, smouldering or unsafe conditions likely to cause a fire. Periodic inspection of operating conveyor belts is carried out with the aim of detecting any local heat sources in an early stage. This includes temperature measurements of the driving head, idlers and rollers using hand-held temperature sensors such as infrared cameras or laser temperature sensors. The disadvantages of current conveyor belt temperature monitoring systems include high labour and equipment costs, safety risk to personnel who are in close proximity to moving conveyors, the ability to take line of site measurements only and potential for missed overheated idlers. Some of the conveyor idlers in underground coal operations cannot be accessed for traditional temperature measurements. This introduces a significant risk to the operation of critical infrastructure.A distributed temperature sensing (DTS) system can be used to develop an advanced conveyor belt temperature monitoring system that provides real-time, accurate and continuous temperature measurements along a conveyor belt particularly at the rolling components. The DTS system comprises of fibre optic detection cable, DTS controller and interfacing module. The advantages of the system include the accuracy, low-cost, easy installation, robustness, safety, immunity to radio frequency and electromagnetic interference, real-time data collection, and secure data transmission. This paper presents a scoping study on the development and utilisation of a fibre optic-based DTS system for underground coal conveyor belts. The mechanism of heat generation, the operation temperature range and the installation issues of fibre optic cable along the conveyor belt particularly in close proximity to each end of the spindle on every idler will be discussed.CITATION:Aminossadati, S M and Yang, B, 2013. A scoping study on fibre optic-based temperature monitoring of underground coal conveyor belts, in Proceedings The Australian Mine Ventilation Conference , pp 35-42 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By C Preston, T Williams, D Roy

The easiest way to mine valuable orebodies is through the use of explosives and well-planned blasting layouts that produce fragmentation profiles designed specifically for conveyance equipment in underground mines. The design of blasting patterns is specific to not only the explosives being used but also the rock or ore type being fragmented. Many blasting designs are based solely on the experience of those developed for similar orebodies in terms of properties and orientation or individuals that have some blasting experience.The primary technical objective of this paper is to outline a unique methodology for determining underground blasting methodologies (developing specific blasting parameters) commensurate with explosive energies and rock/ore equations of state for a narrow-vein gold property located in Northern Quebec and for underground mines in general.The procedures developed are to define the desired fragmentation specification so that a specific thermodynamic break is generated, taking into account powder factor, energy factor, tonnages, explosive energies and distribution along with blasthole diameter and orebody orientation for a specific set of explosive and dynamic rock/ore properties. Determining dynamic modulus values for the ore using seismic sensors to measure P- and S-wave velocities, the aforementioned parameters will be utilised to set the design constraints to maximise recovery and minimise overbreak and dilution.New underground blasting software (AEGIS) will use thermodynamic break in conjunction with defined fragmentation profiles to create an array of blasting parameters used to design and plan ring layouts. This software will also allow mining planners, prior to drilling and loading a production blast, to appraise future intended blasting patterns to minimise the potential of diluting ore with host rock and the likelihood of damaging mine support structures.CITATION:Roy, D, Williams, T and Preston, C, 2015. Underground stope drill and blast designs optimisation program, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 137–148 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By G Tsatouhas, R Newell, K Y. Wong

A sulfide ion selective electrode was used to control sulfidiser addition in the flotation testing of a synthetic and a naturally occurring ore containing malachite in order to compare the behaviour of sodium sulfide and calcium polysulfide. Both slug and controlled potential sulfidisation methods of addition were used. Under defined optimum CPS conditions, calcium polysulfide was a more effective sulfidising agent than sodium sulfide on the basis of both capital and operating costs. Surface and solution studies were used to compare the mechanism of each sulfidiser. For calcium polysulfide, XPS showed that polysulfide ions are adsorbed, whereas for sodium sulfide it is the hydrosulfide ions that are adsorbed on the mineral surface. For calcium polysulfide, the CuSx layer was believed to form on the malachite surface, which promoted the flotation of the malachite, by xanthate. Studies of surface morphology of the sulfidised malachite showed that a fairly uniform sulfidised layer is formed with both reagents. The use of sodium sulfide resulted in a thinner initial sulfidised layer compared to polysulfide at equivalent initial sulfur concentration.

Jan 1, 2005

By K Friese, H P÷llmann

Clinoptilolites, modified with sodium, produced a material which has been tested for the ability to remove Hg (II) from aqueous nitric acid. The amount of adsorption depends on contact time, acid concentration of aqueous solution and initial mercury concentration. The study of the kinetics of mercury uptake revealed that all sorbents exhibit a fast rate of sorption. The highest sorption capacities were observed for sodium forms, and were up to five times higher than for the unmodified zeolite. The maximum sorption capacity toward mercury is determined as 0.093 ¦g/g at an initial concentration of 10.0 ¦g/L for a clinoptilolite from Tsagaantsav deposit (Mongolia). The sorption of Hg (II) has an ion-exchange nature and consists of three stages, ie the adsorption on the surface of microcrystals, the inversion stage and the ion exchange in the interior of the microcrystal. Sorption capacity decreases with the increase of mercury concentration. The presence of other metal ions such as Cd (II), Cu (II), Ni (II) and Zn (II) increases Hg (II) uptake capacity. Finally, sorption for Hg (II) was investigated in batch systems to evaluate the short-term stability of the sorption properties.

Jan 1, 2008

By I Treloar, T Elenbaas, E Isaaks

Critical reviews of grade control generally focus on blasthole sampling and the estimation of ore control block model (OCM) grades, with little or no attention given to dig-line design. For example, the estimation of block grades is deemed important as estimation errors lead to the misclassification of ore types and subsequent dollar loss. Recognition of the problem that the underestimation of block grades may be more or less costly than overestimation led to the application of loss functions to the classification of individual OCM blocks by ore type. The method is known as maximum profit selection (MPS). However, each OCM block may be misclassified a second time by dig-line design. Although each block may initially be assigned an optimum ore type by MPS, OCM blocks are seldom individually mineable by ore type. As a result, a common solution to this problem is the design of mineable polygons or dig lines loosely constrained by a minimum mining width. All material within a properly designed dig-line polygon can be mined and sent to a single destination such as the mill, stockpile or waste dump. These dig lines are often designed manually or by simple variations of computer-generated contour lines. They are generally suboptimal and result in additional misclassifications of ore types. This paper provides an algorithm for constrained optimum dig-line design where dig-line misclassifications are also evaluated through loss functions or MPS. Constrained optimum dig-line designs minimise the dollars lost by dig line misclassifications for a given minimum mining width constraint. A case study is provided illustrating constrained optimum dig-line design and subsequent benefits.CITATION:Isaaks, E, Treloar, I and Elenbaas, T, 2014. Optimum dig lines for open pit grade control, in Proceedings Ninth International Mining Geology Conference 2014 , pp 425–432 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By G K. N Subasinghe

Metallurgists operating Knelson Concentrators (KC) often rely on manufacturerÆs recommendations for selecting operating parameters, such as fluidising water flow rate and cycle time. Recent studies have shown that these parameters are not only dependent on the machine parameters but also on the feed characteristics, such as size distribution of the gold and gangue particles and the composition of its constituent minerals. It is known that a particle entering a KC initially traverses a circular path within the bowl. For a particle to maintain a given orbit, the required centripetal force must be supplied by external means. It has been argued that this centripetal force, which is dependent on the mass of the particle, its radial position and the rotational speed of the bowl, is provided by the fluid drag force created by inwardly moving fluidising water and the BagnoldÆs force created by the particle/particle collisions. Depending on the fluidising water flow rate, one of two situations can occur where the porosity of the bed increases or decreases, which influences the amount of material retained within the bowl. The amount of material of a given size and density retained in the bowl is thus dependent on the extent of the centripetal force provided. Based on the above concept, a criterion that can be used to predict the amount of material recovered in the bowl has been derived and validated by experimental data. It may also be construed that this criterion demarcates the transition of the bed from a packed-bed state to a fluidised state. By identifying the transition values for the different constituent mineral particles in the feed, it is possible to estimate the optimal fluidising water flow rate that would maximise gold recovery while minimising gangue recovery. In addition, the kinetics of gangue displacement by incoming heavy mineral particles were also studied using synthetic mineral mixtures. The experimental data suggests that this process follows first order kinetics and that the build-up of heavy mineral reaches a maximum. A model has been proposed to predict the optimal batch cycle time for a KC in terms of the feed characteristics and machine operating parameters.

Jan 1, 2006

By B Levasseur, C Olsen, E Ghasemian Langeroudi, F Larachi, F Safizadeh, C Gagnon

Gold recovery by the cyanidation process is often accompanied by the leaching of other species. This leads to the depletion of the level of free cyanide and oxygen available for gold cyanidation. The largest proportion of the consumed cyanide is diverted by the cyanicides (eg S, Cu, Zn, Fe, etc) into non-valuable complexes.COREMÆs Extractive Metallurgy team has been conducting a research program on the improvement of the gold cyanidation process. As a part of this program, the current study aims to investigate the effect of certain operating parameters on the reactions involved during preoxidation and cyanidation. Flotation tailings and single mineral samples such as pyrite, sphalerite and chalcopyrite, along with their different combinations, were analysed to highlight the influence of ore mineralogy on the operating conditions. The effects of different kinds of oxidants (oxygen, hydrogen peroxide, ferricyanide and ozone) and chemical additives (ammonium sulfate) were investigated.Experiments conducted in alkaline solutions reveal that mineralogy is a key parameter since pyrite, chalcopyrite and sphalerite react quite differently during preoxidation and cyanidation. A significant increase in sulfur dissolution, especially on pyrite, was observed by applying preoxidation. H2O2 preoxidation showed a positive effect on increasing sulfate formation, a desirable by-product from the cyanide consumption point of view. Preoxidation of synthetic ores with ferricyanide resulted in boosting thiosulfate formation. Tests conducted on flotation tailings from a polymetallic mine revealed that a short preoxidation increases the dissolution of the ore leading to higher gold recovery and lower cyanide consumption. Regarding the formation of thiocyanate, the most undesirable by-product of the cyanidation, ferricyanide and ozone were found particularly efficient to hinder their formation. Finally, the addition of ammonium sulfate during the cyanidation process showed some promising results in terms of both gold dissolution and cyanide consumption.CITATION:Ghasemian Langeroudi, E, Levasseur, B, Safizadeh, F, Olsen, C, Larachi, F and Gagnon, C, 2013. Optimisation of operating parameters for cyanidation of sulfide-bearing gold flotation tailings in order to prevent the impact of cyanicides, in Proceedings World Gold 2013 , pp 111-120 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

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

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

Jan 1, 2009

By G Gilchrist, S C. Dominy, T Jashashvili, R C. A Minnitt

The grouping and segregation error is one of Gy’s seven errors that cannot be measured in any qualitative manner because of its transient and changing characteristics each time the sample is handled mechanically. Attempts to calculate the mean and variance of the segregation error is considered by some as ‘an exercise in futility’ that would not help us achieve representative sampling. This research is aimed at understanding the process of segregation of dense, finely divided and dilute particulate materials supported in a clean quartz substrate during intense agitation. Several mixtures of fine-grained materials including steel, tungsten carbide and gold grains were used in these experiments. Four hundred grains of each of the minerals and metals at a top size of 2 mm were mixed with approximately 600 g of finely ground quartz material (95 per cent passing 2000 microns) in a 500 ml plastic jar with a sealable lid. The mineral–?metal mixtures were analysed in three steps using microfocus X-ray computed tomography. Step one consisted of rolling the containers on a flat surface in an attempt to concentrate the mineral and metal grains in the core of the supporting substrate; this is a base case that can be reconstructed after each session of analysis. The second step involved gentle and vigorous shaking of the mixtures in order to segregate the denser minerals and metals from the supporting quartz substrate. In some cases, a third step involved splitting the sample through a riffle splitter. Three-?dimensional images of the surface of each grain, its volume and its X-, Y- and Z-coordinates, before and after intense agitation of the container, were interpreted from the reconstruction of the tomographic X-ray data. The spatial analysis of grains using cell declustering and 3D variography provided a useful means of characterising the distribution of the grains in space and the extent to which they had become segregated during the process of agitation. Spatial analysis indicates that in general, grouping and continuity of grains is weakly developed. The modelled nugget effect remains high for most tests, indicating that grains of similar size did not group together strongly. Agitation through rolling provided the best continuity, although not consistently in the long axis of the plastic jar. The nugget effect was consistently highest, and the range of continuity shortest in samples that had been split, indicating that the grouping and continuity were reduced through splitting the sample. Initial results indicate that very little segregation of the minerals and metals occurs in the quartz substrate. This is somewhat counter-intuitive, but suggests that the effects of agitation on mixtures of dense minerals and metals in substrates of lower density do not lead to excessive segregation. Differences in behaviour between dense materials in response to agitation are evident. Grains of different composition and shape did not group and segregate in a predictable manner in response to the agitation methods. Initial results indicate that the degree to which a material groups and segregates relates more to the characteristics of the denser material itself, rather than the agitation method employed.CITATION:Minnitt, R C A, Jashashvili, T, Gilchrist, G and Dominy, S C, 2017. Quantifying segregation of minerals and metals in particulate materials using computed X-ray tomography and variography, in Proceedings Eighth World Conference on Sampling and Blending , pp 173–182 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By B Upton, J Mitchell

The use of hydro scaling and in-cycle shotcrete to replace conventional jumbo scaling, mesh and bolting as the primary method of ground control for run of mine development has been investigated through extensive trials at the Waroonga mine, Agnew Gold Mining Company.These trials have progressed from investigating the productivity aspects of the method through to a three month mine-wide trial, which may yet lead to the adoption of this potentially best practice ground control technique at Agnew.Ov erseas trials and research have shown that hydro scaling results in a significant improvement in the shotcrete-rock bond strength. Good adhesive bond strength ensures that the shear strength of the shotcrete layer rather than itÆs flexural or tensile strength is fully mobilised as rock mass reinforcement.This maximises shotcretes ground reinforcement capability and it is suggested that a bolt-less fibrecrete support design is feasible using the hydro scaling technique.

Jan 1, 2005

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

By A N. Parry

In May 2018 Kasbah Resources Limited (“Kasbah”) completed an ore sorting test work program which was a precursor to releasing in July 2018 an updated Definitive Feasibility Study (“DFS”) for the Achmmach Tin Project in Morocco, which it is proposing to develop along with its joint venture partners. The testwork program evaluated ore sorting as a pre-concentration option to achieve early elimination of gangue and the low-grade component of ROM feed, thereby potentially:  Significantly upgrading the head grade of tin to the downstream processing plant.  Significantly reducing the required throughput capacity (and projected capital expenditure) of the downstream processing plant.  Reducing total consumables, power and water requirements in downstream processing.  Increasing the recovery of tin in the gravity and flotation circuit due to the higher feed grade achievable with ore sorting.  Reducing tailings tonnage, tailings cost and environmental footprint.  Using sorter rejects for mine backfill or road base applications. Key aspects of the design of the metallurgical testwork program centred around the need to ensure that samples representative of ROM ore feed (including projected mining dilution) were selected for the ore sorting testwork. The design and implementation of the ore sorting bulk testwork program is described, as well as a summary of the test work results and a discussion of the enhancement of the project economics reported by Kasbah, which led the company to adopt ore sorting as part of the proposed processing circuit in the updated 2018 DFS.

Nov 10, 2020

The Mineragraphic Section of the Council for Scientific and Industrial Research has had occasion from time to time to examine rocks, ores and concentrates from the Yatukoula goldfield, Fiji. The results of the examinations have been supplied as Mineragraphic Reports and have been supplementary to various investigations carried out by the mining companies on ore treatment, or by visiting geologists on the nature of the rocks and lodes. The presence of tellurides was determined in 1935, though incorrectly as nagyagite. The general absence of lead, except in traces, was soon afterwards discovered, and it came to be recognised as the mines were opened up that the chief telluride minerals on the field were sylvanite and native tellurium. Specimens of the tellurides have been provided from time to time by E. G. Theodore, Managing Director of the Emperor Mines Ltd., and of the Loloma (Fiji) Gold Mines N.L., and further material was recently obtained, as the result of a visit to the field at the invitation of Mr. Theodore.The aim of this paper is to describe the occurrence of the tellurides in these specimens. The work has been carried out as part of the programme of research of the Mineragraphic Section.THE VATUKOULA GOLDFIELDThe Emperor, Loloma and Dolphin mines are situated at Vatukoula, six miles, south of Tavua, on the north coast...

Jan 1, 1949

By P Brown, M Nagarajan, A Green, P Dare-Bryan

Coal loss is an important issue at many coalmines, with losses of five per cent being common. The type of loss varies from mine to mine but is dependent on mine strata, the drilling and blasting processes applied and the mining method used. Typical coal loss mechanisms from the drill and blast process are coal roof damage and edge loss. Usually a reduction in coal loss is in direct competition with the need to provide material that is well-fragmented and a muck pile that has the required cast percentage. These competing issues were addressed over a two-year period at a mine in the New South Wales Coalfields by implementing a five-step approach. This was centred around building an understanding of the coal loss mechanisms utilising proprietary heave- modelling software, measuring coal losses by comparing survey to drill and/or gamma logs and implementing appropriate coal loss reduction processes. The end result exceeded expectations with a 95 per cent reduction in coal loss. Mine excavation productivity was maintained and coal loss minimised to less than one per cent of the in situ coal block.CITATION:Nagarajan, M, Green, A, Brown, P and Dare-Bryan, P, 2015. Managing coal loss using blast models and field measurement, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 429–436 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

Quantitative probabilistic ecological risk assessment has been used to evaluate the likely effect on fish diversity and abundance of filtered and bioavailable metals in streamwater affected by acid drainage from the abandoned and remediated Rum Jungle U/Cu mine in the Northern Territory of Australia. The water quality was determined using monitoring data from a gauging station on the East Branch of the Finniss River, downstream of the mine site, and modelled assuming a number of potential water quality management options. The management options ranged from no action, through some flushing options to full catch and treatment of contaminated seepage from the waste rock heaps. The computer code AQUARISK was used to undertake the analyses. Critical criteria for contaminant water concentrations at the site, derived from probability density functions of available fish ecotoxicology data, were found to closely approximate the regulatory trigger values for the contaminants of concern. Modelled predictions of reduced diversity and abundance were also in good agreement with in situ biodiversity measures. Based on a reasonable target of 67 per cent species tolerance for this heavy impacted site, it was found that none of the low cost options for wastewater management was acceptable. Combinations of two of the options approached acceptability. Both of the catch and treat options exceeded the arbitrary acceptability target well. This implied that the more expensive option of liming to pH 10 might be unnecessary at this site. Thus, the use of ecological risk assessment modelling has proven useful in undertaking cost-benefit analyses for this site. The approach provides a management decision-making tool that can be economically used to link expensive on-site environmental engineering options with site-specific ecological goals rather than the previous nebulous aims of æreduced contaminant loadÆ or æimproved biodiversityÆ that often resulted in excessive expenditure without achieving successful environmental benefit.

Jan 1, 2003

By Robertson K. S, Hunter T. C

AEG-Elotherm's electromagnetic dosing channel, or Eldomet, is a recent invention enabling the transport and metering of molten metals. The development of a reliable refract- ory lining, and the use of suitable construct- ion and operating techniques has led to the successful application of the Eldomet for casting copper anodes at Copper Refineries Pty. Ltd.

Jan 1, 1974

The general principles of technical due diligence best practice that are involved in assessing a mineral property in the early stages of its development are described and a bibliography of relevant papers is attached. The issues specific to the evaluation of gold deposits are highlighted. The Australasian Institute of Mining and Metallurgy's (The AusIMM) initiatives in this area, dealing with the proper public reporting of Reserve/Resource information (JORC Code) and property assessment/valuation (VALMIN Code), will be used as a framework against which the illegal tampering with drilling samples to artificially boost their gold content (salting) from the Busang gold deposit (Kalimantan, Indonesia), owned by Bre-X Minerals Limited (Calgary, Canada), will be reviewed. While the Busang saga was based upon fraud, through salting the samples, the general lessons to learn from such a scam are worth documenting. In Australia, most of those working in the mineral industry belong to long established professional institutes and consultant associations (eg The AusIMM or Mineral Industry Consultants Association [MICA]) that require their members to work within their technical limits and to comply with best practice guidelines, or risk being judged and found wanting by their peers in the context of strong Ethics Codes. There is also a strong interface between such representative professional bodies and the corporate and financial market regulators (ASC/ASX), which closes the monitoring loop. Canada has only now seen the wisdom of having this type of early warning system in place. Fraud and deliberate deception will be always possible, but deception on the enormous scale that occurred at Busang is most unlikely with proper surveillance systems in place and the use of accredited technical professionals. There should have been more hard data available about so big and rich a deposit owned by a C$6Bn company.

Jan 1, 1997

By M Randall, P Ebzery, F Burns, C Aisthorpe, P Blanz

SAG Mill process control classically maintains the SAG mill volumetric filling within a set operating range. Typically a SAG mill weight measurement, by either bearing pressure transducers or load cells, is used as an inferred measurement of volumetric filling. To maintain volumetric filling within a set operating range the SAG weight setpoint use for process control requires regular review due to changes in SAG mill charge density (rock:ball ratio) and the wearing of mill liners. At Lihir Gold Mine in Papua New Guinea, the use of SAG mill weight for process control is additionally complicated by compromised load cells and drifting bearing pressure measurements. The need for an improved method of measuring and controlling volumetric filling led to the recent installation of the Outotec MillSense, a SAG mill toe angle instrument. This paper presents the integration of the toe angle control in to the Lihir SAG mill process control philosophy as replacement for the traditional mill weight control.CITATION:Burns, F, Aisthorpe, C, Blanz, P, Randall, M and Ebzery, P, 2018. Toe angle measurement for SAG mill control at Lihir gold mine, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 59–76 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018