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By Hunter TC

Metals Refining Operations Pty. Ltd. (NMO), PNG's only gold and silver refinery is operated by Golden West Refining Corporation Ltd (GWR), a member of the Rothschilds group and has a strong PNG ownership link through statutory shareholders. Located in Waigani, MRO has been successful in substantially increasing production through toll refining for Porgera, Misima, Tolukuma, Wapolu and, more recently, at Lihir as well as treatment of alluvial gold from smaller operations. This increased throughput has resulted in the need to constantly upgrade equipment, techniques and practices, particularly to continue quality improvements and meet market demands. The evolution of these changes are documented and discussed and the probable future development plans are detailed.

Jan 1, 1997

By Bonsall EM, Schwabe MR, Hamlyn DA

Historically, most of the gold produced from Kalgoorlie has been derived from the gold and gold telluride Golden Mile lode systems dominantly hosted within the Golden Mile Doler-ite and to a lesser extent, Paringa Basalt. In more recent times the gold-quartz stockwork ore bodies within Unit 8 of the Golden Mile Dolerite at Mt Charlotte have become increasingly imp-ortant.Extensive low grade gold mineralisation has now been defined to the north and east of Kalgoorlie within rock units of the Golden Mile sequence not generally considered to be highly prospective.Two main types of mineralisation have been defined. The first comprises variably mineralised and altered quartz-albite porphyr-ies emplaced within talc-carbonated Hannans Lake Serpentinite (Mystery deposit). There is intense fuchsitic, pyritic and carbonate alter-ation of the serpentinite adjacent to the porphyry bodies. Gold mineralisation is assoc-iated with fine-grained disseminations and veinlets of pyrite and narrow quartz and quartz-tourmaline veining within the porphyry and adjacent fuchsite-carbonate rock. Several sets of vein directions are present, some of which typically exhibit sulphide alteration haloesnnA H] rhina_

Jan 1, 1984

By J E. Everett

When ore is being selected from a regularised block model, a common procedure is to accept as ore any block whose iron content exceeds a cut-off value, and whose content in each contaminant analyte is below an appropriate cut-off value. This method defines a quadrant within the multidimensional analyte space, such that any block lying within the quadrant is accepted as ore and any block lying outside the quadrant is rejected as waste. The cut-off levels can be adjusted to maximise ore tonnage at a target grade (or analyte vector). When the method is applied to a project comprising multiple pits with systematically differing grades, it is found that ore tonnage at target grade is maximised if different cut-off quadrants are used for the different pits. This is apparently illogical, because it implies that an ore block from one pit may be accepted as ore, but an identical block from another pit is rejected as waste, even when ore from both pits is to be blended into the same product and there are no production cost differences between the pits. The paradox is an example of the ætheory of the second bestÆ: if there are multiple conditions for optimality and one condition is broken, then obeying the other conditions may not be the best policy. The problem lies with the quadrant cut-off method, which is shown to be inconsistent even for selecting ore from a single pit. A criterion that is inconsistent cannot be optimal. It is shown that a linear composite cut-off function provides maximum ore tonnage, and that a single composite cut-off criterion is consistent and optimal over multiple pits. Further, it is shown that a composite cut-off function not only maximises ore tonnage at a specified composition, but also can be used to select ore so as to maximise project value, if marginal costs and values are available.CITATION:Everett, J E, 2013. Selection of ore from multiple pits, in Proceedings Iron Ore 2013 , pp 185-192 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 12, 2013

By Owen D

A central part of mine planning is to ensure the protection of the beneficial uses of water. Integrated mining software does not generally provide tools to help the mining engineer to achieve this objective. This paper identifies some of the requirements which are desirable for such a tool and discusses how object oriented modelling can help achieve an effective design.

Jan 1, 1995

By Junpeng L, Huiguo Q

Field instrumentation was installed to monitor ground and lining behaviour during and after construction of the Mount Shaughnessy Tunnel (Rogers Pass Short Tunnel) in Canada. The instrumentation was placed in a soft ground section of the tunnel at its crossing with the Trans Canada Highway. The tunnel was excavated through a dense bouldery soil. Presentation of the field data and inter- pretation of the tunnel performance from a geological-geotechnical point of view form the basis of this paper. The loss of ground due to the tunnel excavation was found to be exceptionally small. This has been attributed to the unusually high strength and stiffness of the host soil. Evaluation using the Boundary Element Method, together with a simplified analytical technique, were applied to assess the relevant soil parameters and their influence on the tunnel performance.

Jan 1, 1987

Ventilation challenges are often encountered when an underground mine expands to new zones and it often is the case to make a thorough review of the existing system and assess immediate and future airflow needs at the desired quantity and quality. An unexpected mine plan change that calls for increased development and production from new areas can impose a strain on the existing ventilation system. Budgetary constraints can also demand creativity in design on the mine ventilation engineerÆs part. Since the addition of several mining horizons it had become obvious at the Meikle mine that something had to be done to increase airflow quantity and quality in the old main zones because most of the ventilation resources had been channelled for development in the new mining horizons. An airflow assessment of the existing system had to be performed and it was determined that the airflow quantity had to be increased by at least 30 per cent and the quality of the air had to be improved by reducing nuisance and respirable dust and at the same time reducing the airflow temperature before it was used in a few mining zones. At the conclusion of the airflow assessment it was determined that a third centrifugal fan would be installed on a new 3.05 m diameter borehole from surface to underground. By a careful study of temperature conditions over time it was determined that an evaporative cooling spray chamber would be sufficient to cool the airflow down from the high dry bulb temperatures observed down to saturation at the wet bulb temperature. At the same time excessive nuisance dust generated as a result of the airflow travelling a long way in a haulage drift will be knocked down in the spray chamber resulting in cool, clean air in the mining districts. Expansion of the existing surface ammonia refrigeration plant was out of the question for several reasons. The fact that the airflow was hot and dry meant that evaporative cooling spray chambers could achieve lower working temperatures at a very low cost compared to the expansion of the chilled water plant. The expansion of the ventilation system at Meikle mine and the use of evaporative cooling spray chambers were demonstrated to be very successful and the information presented in this paper can be of benefit to other mines experiencing the same ventilation problems as was the case at the Meikle mine.

Jan 1, 2005

By Mutton B. K

A systematic approach to the collection, presentation and application of structural geology data is employed in the extraction of narrow en echelon Ag-Pb-Zn orebodies by rut and fill stoping at Mount Isa. The aim is to locate, document and predict areas of adverse ground thereby enabling adequate ground support to be installed in advance of production mining. The important structural features are identified and their relevance illustrated by case histories of previous failures. The methods of collection, documentation and application of data are discussed.

Jan 1, 1977

By Lee M. F, Guilfoyle K

A large hard rock rib pillar was recently preconditioned at Mt Charlotte mine using a novel blasting technique. The motivation for trialling this procedure was a history of past pillar failures, with associated seismicity. Design studies had shown that a new proposed pillar would be at risk of violent failure, and preconditioning was used in an attempt to reduce this risk. Preconditioning by blasting involves physically modifying a selected zone of ground in advance of mining, then forming the pillar so that it incorporates that zone of ground. The modified rock in the zone is intended to allow extra closure (yield) of the pillar in response to mining-induced stress changes. The ground modification was done by tight firing a blasthole array to fracture the rock. The blast design comprised pairs of pre-split blastholes to create a series of short cracks across the target zone, followed by main blastholes to fracture the rockmass between each pair of cracks. A monitoring program was used to establish whether or not the preconditioning was effective. It included conventional extensometers, stress change cells and closure stations, plus a seismic monitoring system. To-date, stoping is complete on one side of the pillar and has just commenced on the other. Results show significant movements within the preconditioned zone and on geological structures in the pillar, as well as lower stress in the pillar compared to an adjacent non-preconditioned site. The preconditioning technique can be applied elsewhere, provided its purpose, mechanism and side effects are understood. Benefits are likely to include more assured production, and successful pillar recovery even in high stress situations.

Jan 1, 1995

By Nilmani M, Fountain CR

Injection of gases into slag-melt mixtures produces various zones as a result of bubble formation and disintegration within the melt. The extent of these zones depends on the type of reactor used. When compared with ferrous processes, non ferrous processes are character- ised by large bubbles formed adjacent to the tuyeres, low flowrates and shallow tuyere sub- mergence. These features can result in a greater proportion of reaction occurring above the bath, more refractory wear and tuyere blockage with more splashing. The large bubble zone adjacent to the tuyeres has been investigated using the tech- niques of physical modelling, mathematical modelling and plant trials. Large bubble form- ation in physical models was recorded using a high speed camera and a rapid response pressure transducer coupled to an oscilloscope and data recorder. It was found that the bubble volume (Vb) could be correlated at low flowrates using the single bubble model Vb = 1.378 Q6/5 g-3/5 Deviations from this correlation occurred with increasing gas jet momentum. Plant trials were carried out on a copper converter at Mount Isa Mines during five different charges. Pressure measurements were made through the tuyeres during the slag blow and commencement of the copper blow. The power spectrum density showed that the dominant pulse amplitude occurred at a frequency of approximately 3 pulses/sec. Plant data from this and other converters were correlated using the same relationship as for physical modelling. De- viations occurred due to the state of the re- fractory, bath composition or bath circulation effects.

Jan 1, 1984

By Skaviniak M

Some better perspectives applying to the exploitation and dressing of polymetallic ores in the Banskfa. gtiavnica-Hod- rusea Ore District are supposed to be achieved after a suc- cessful investigation and proving there the existence of deep-seated mineralization as well as due to increasing de- mand for non-ferrous metals and consequently to higher mar- ket prices of those recently noticed. With respect to the present situation in mining and to the further technical development as well, a several times higher exploitation may be in this region expected, especially in the deeper .eated parts of the deposit. When solving the tasks of a complex economic exploitation over the whole region, consi- derable attention is paid to regional relations and impact studies (due to expected exploitation and ore dressing but also to very difficult problems of dewatering (drainage pro- blems-). It will be first of all necessary to find there an equilibrium between the consequences resulting from the re- naissance of mining industry and environmental requests un- dispensable for the city of Banska 9tiavnica and the other neighbouring towns in the vicinity of mining plants.

Jan 1, 1988

By Johnson N. W, Quast K. B

Over the years there have been occasional references in the literature to the activating effect of cyanide in galena flotation with xanthates. These have usually been associated with the processing of lead-zinc or copper-lead-zinc ores. Bubble contact curves for the pure galena-xanthate system show a flotation edge at pH 10.4 independent of sodium cyanide concentration which was thought due to hydroxyl ion, not cyanide ion.Flotation tests were conducted on samples of Mount Isa lead-zinc ore using varying concentrations of sodium ethyl xanthate and sodium cyanide. At low collector concentrations, galena recovery kinetics improved with sodium cyanide addition, and the higher the cyanide concentration, the higher the galena recovery rate. At higher collector concentrations, galena recovery rate was independent of sodium cyanide addition.For a given collector addition, the lead grade-recovery curve shifted to an improved position with increasing sodium cyanide level. For the same recovery there was an increase in the lead grade with increased sodium cyanide addition, and this increase was most dramatic at high sodium cyanide concentrations.The presence of sodium cyanide during the grinding of Mount Isa ore caused surface passivation of the iron sulphides and possibly the sphalerite.These sulphides, therefore, reacted with less of the oxygen present in the pulp, hence more oxygen was directed to the surface of the galena. This resulted in an enhancement in the total amount of xanthate adsorbed on the galena that is reflected in the improved flotation response of that mineral.

Jan 1, 1990

Experience in evaluating grade control at operating mines has shown that a number of similar errors re-occur in diverse settings. These can be broadly classed as technical errors, and procedural or grade contra management errors. Examples of typical errors are presented a; generalised case studies. A brief explanation of why the recommender solution worked is also presented for each case.

Jan 1, 1993

By Warren L. J

The recovery of phosphate minerals from the Mt Weld deposit by froth flotation has been studied by many researchers. Most of the flotation experiments were carried out with a tall oil fatty acid as collector and sodium silicate as dispersant and gangue depressant at pH about 10. Several rougher stages and cleaner stages and, sometimes, a desliming stage were included. The major difficulty was to reduce the Fe2O3 impurities in the concentrate to the required level. We used QEM*SEM (Quantitative Evaluation of Materials by Scanning Electron Microscopy) to provide a comprehensive and accurate mineralogical analysis of the flotation products. The analysis indicated that the Fe2O3 impurities were mainly recovered in the second concentrate, owing partly to the incomplete depression of the liberated iron oxides by the sodium silicate and partly to composite particles containing iron oxides. The selective depressing action of sodium silicate was improved by adjusting the variables such as the modulus (SiO2/Na2O), pH and time of standing of the stock sodium silicate solutions or by adding some polyvalent metal salts into sodium silicate solution. The flotation process was optimised to produce a phosphate concentrate with the required grade and recovery (38.6 per cent P2O5, 2.67 per cent Fe2O3, 13.7 for P2O5/(Fe2O3 + A1203), at P2O5 recovery of 81.5 per cent). The possibility of recovering the rare-earth phosphate, monazite, from the Mt Weld deposit by flotation was also studied.

Jan 1, 1991

By Toop G. W, Martin M. T

At the Cominco Ltd plant in Trail, British Columbia, the Betts lead electrorefining operation requires that antimony and arsenic be present in the lead bullion for anode slimes stability control. Until 1986 the antimony and arsenic inputs from concentrates to the Lead Smelter needed to be supplemented with high antimony and arsenic content recycles from the Silver Refinery operation to maintain a satisfactory composition. Subsequently the antimony and arsenic inputs have increased as a result of increasing levels of antimony in Sullivan lead concentrate and the purchase of larger quantities of silver/gold bearing concentrates that inherently have higher antimony and arsenic levels. The increase has exceeded the limits required by the Betts process. It therefore became necessary to install a partial softening process downstream of the Continuous Drossing Furnace to satisfactorily control the bullion composition. Process control and oxygen injection techniques used in the partial softening process are reviewed. Approximately 8 tonnes/day of softening slag are produced having a combined antimony and arsenic content of 25 percent. This slag is reduced in a recently commissioned short rotary furnace followed by vacuum distillation of the metal for recovery of the antimony and arsenic values.

Jan 1, 1989

By J Moncrieff, P Bellairs

The Black Star Open Cut is located immediately adjacent to the township of Mt Isa and is situated in the middle of extensive pre-existing infrastructure including two concentrators, two smelters, a wet fill plant and two shafts. At any one time there are in excess of 500 people working on the surface within an industry-accepted 600 m exclusion zone from Black Star blasts. Apart from the surface operations there are also the underground operations including the lead mine (closed in December 2005) and the Enterprise and X-41 mines that must clear for all Black Star blasts. The application of industry standard blasting exclusion zones (600 m) was risk assessed as imposing operationally prohibitive constraints which could cause significant business interruption due to the logistical challenges required to ensure that all personnel from surface plants were evacuated for each blast and potential for lost production whilst these personnel were not operating the plant. In was therefore an imperative for the blast exclusion zone to be reduced. This was achieved by the: use of a QA/QC team to ensure that relevant drill and blast implementation is within an acceptable tolerance (KPIs) from design; use of high-quality stemming material called HMR, which is a by- product of the concentrating process and is generally sized at -14 mm with very little fines; implementation of appropriate training and support to Black StarÆs own blast crews, reinforcing the need to achieve the designed amount of stemming in every hole; and provision of appropriate support from Black StarÆs management for additional resources to ensure that every blast achieves design within the KPIs but especially in high-risk areas. The blast exclusion zone was successfully reduced after monitoring the flyrock results from more than 176 blasts. Black Star Open Cut now maintains a minimum blast exclusion of 200 m in critical areas; however, general blasting currently uses a 250 m exclusion as this provides additional risk management whilst still minimising the logistics associated with clearing and securing the slightly increased area.

Jan 1, 2007

By Tronson K

Improvements in technology do not necessarily lead to higher profits: the benefit of lower costs can be captured by coal buyers, governments and workforce rather than by the colliery operators. The economic impact of longwall mining in Australia has been critically assessed to provide lessons for the future. For a variety of reasons, companies investing in longwall equipment in the past five years have generally not achieved an adequate return on the funds invested. The effect of technological innovation must be examined in the light of competitive forces operating in the market. Projections of cost reduction trends in the coal industry have been applied to a world cost model to provide a picture of the coal industry in the year 2000.

Jan 1, 1988

By Craw D

Quaternary warping and uplift of antiformal schist ranges in Central Otago, New Zealand, has resulted in recycling of alluvial gold from widespread, generally weakly auriferous, Miocene fluvial gravels that unconformably overlie the schist, into aprons of fan sediments along the range margins. Basement erosion during uplift has been limited and so gold input from sparse gold-bearing quartz veins in the schist has been relatively minor. In an eluvial cycle on the slopes of the ranges, chemical remobilization of gold occurs during oxidation and erosion of the Miocene sediments. The typically fine-grained (300-400¦m) gold undergoes chemical modification and grain size enhancement of up to two orders of magnitude, and much of it is redeposited in a large number of relatively small alluvial fans along the range margins. Groundwater mobility within the fans results in minor additional gold mobility and grain size Enhancement.

Jan 1, 1995

An investigation was made into the mineralogical characteristics of the upper portions of the 650 and 750 copper lodes. The investigation was based on a comprehensive suite of geological specimens representing all types of mineralization encountered during mining until the end of 1954 and the chief aims of the investigation were to determine (a) the minerals present and their textures and associations, (b) the paragenetic sequence of deposition of minerals in the orebodies, (c) significant changes, if any, which could be found in the orebodies with depth, and (d) the nature and mode of occurrence of nickel in the ore. The general structure of the orebodies is outlined and their mineral composition given. 10 textures exhibited by the ore minerals are described and a paragenetic sequence of events in the formation of the copper orebodies is outlined. No decrease in the complexity of the sulphide mineral textures with depth could be seen and no evidence was found to suggest that the tenor of the ore would decrease with depth although some factors which may eventually limit the extent of the orebodies are noted. The mode of occurrence of minor elements in the orebodies is described. Notes on the occurrence of pyrite, aikinite and berthierite in the orebodies is given and the orebodies are considered to be identified with LiIidgren's mesothermal type of sulphide ore deposit in which considerable replacement of older by younger generations of sulphide minerals occurred.INTRODUCTIONA mineragraphic study was made by Stillwell and Edwards (1945) of a suite of specimens submitted by Mount Isa Mines Limited from the Mount Isa Black Star copper orebodies with a view to determining 1. the nature, extent and association of arsenic, antimonyand bismuth minerals, 2. the mode of occurrence of silver and 3. whether galena and sphalerite occurred in minute forms and below the sizes readily observed in hand specimens.

Jan 1, 1961

By S Shipard

Filters are used in water treatment and hydrometallurgical process plants for objectives such as generating a dry spadable solid, pumpable high density slurry or high purity filtrate. The priority objective of every polishing filter, sometimes also termed clarifying filters is high purity filtrate and these are found in many diverse industries and even different applications within the same industry.To generate a high purity filtrate, process designers have the choice of many different polishing filter products, but in reality very few polishing filters are based on fundamentally different filtering concepts.This paper reviews the technology merits of well-known and the more recently developed polishing filter products and aims to assist metallurgists and engineers with the selection of an appropriate polishing filtration technology for pregnant liquor filtration and other process applications, plus a guide to best practice.CITATION:Shipard, S, 2013. Polishing filters for mineral processing plants, in Proceedings MetPlant 2013 , pp 118-125 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

In the stability assessment of open pit walls, geotechnical engineers have to deal with uncertainty related to structural geology, rock mechanical parameters, groundwater and so on. This uncertainty will immediately and significantly impact on wall stability assessment and therefore. influence mineral recovery and ultimately the financial return of open pit mining. However, the conventional factor of safety applied to measure the stability of slopes and the relevant analytical computer packages cannot quantitatively consider the variability or uncertainty of the input data. As a supplement, therefore, geotechnical engineers have begun to apply probability to the stability assessment of open pit walls over the last two decades. To-date unfortunately, no powerful computer package is available to geotechnical engineers to conduct the probability analysis of slope stability. This paper presents a computer package of probability analysis for rock and soil slope stability. In this computer package, the strength parameters of rock and/or soil material such as cohesion, friction angle and unit weight of the different rock and/or soil type domain in a complex structural geology environment can be considered as the basic input random variables. Groundwater level can also be taken into account as a random variable in this package. Two `rigorous' limit equilibrium solutions, the Morgenstern/Price method and the Sarma method, can be used to calculate the factor of safety during Monte Carlo Simulation applied in this program. Five types of probability distribution are included in this package for the user to simulate basic input random variables. Two realistic cases from BHP Iron Ore are used to illustrate this package.

Jan 1, 1997