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By Tam Tran

Over the last decade, halide (chloride, bromide and iodide) systems have been evaluated as alternative lixiviants for the processing of gold to replace cyanidation which has been widely used in commercial practice. This paper first reviews the development of processes promoted by Kaljas Ltd / Lachlan Resources (Australia) and Great Lakes Corp (USA) using different bromide/bromine systems in the early 1990's. Several research groups subsequently evaluated the use of iodide/iodine and chloride/chlorine for gold extraction, showing similar characteristics of gold/silver dissolution and recovery. A critique is :given on the advantages and the ,shortfalls of halide systems as alternative lixiviants. The stability of gold? halide complexes is discussed, based on practical experience and thermodynamic modelling of their speciation, The iodide system provides the most stable gold / silver complex for easier handling. However, the cost of iodide inhibits its application for are processing. In this critique, emphasis is given on the cheapest system, which involves the use of chloride for leaching (in conjunction with an appropriate oxidant). However the chloride-base leachant has a major drawback which is related to the unstable nature of gold chloride in a reducing environment.

Jan 1, 1998

By M. A. Giralico

A new generation of hydraulic efficient pumper and auxiliary impeller designs is the result of an extensive research program focused on improving the overall performance of optimized SX/EW plants. Combined with the proper scale-up, these optimized designs will greatly reduce aqueous and organic entrainment losses, reduce or eliminate air entrainment and crud formation, enhance mass-transfer and maximize the overall copper yield. Currently, these new pumper and auxiliary impellers are installed full-scale in numerous plants ranging in flow rates from 90 to 15000 G.P.M. and developed heads up to 51 inches. Operational results reported by the independent metallurgist at each processing plant are reporting the lowest entrainment results in the industry. Further R&D has just been completed on a new mixing configuration that separates the systems mixing and pumping requirements. Results from the system pilot test document further improvements in reduction of both chemical entrainment and crud formation, while keeping mass transfer stage efficiencies.

Jan 1, 1998

By W. M. Lewis

Product losses to tailings ponds have long been a source of frustration for the mining and utilities industries. The utilization -of the Lewis Econosizer to recover lost products has proven to be very cost effective through reduced acreage requirements, cleaning costs and increased production. The unit is successfully operating in coal, aggregates, industrial minerals, clay, fly ash, heavy minerals and many other ores. Utilizing an upward flow of slurry in a free settling environment, particles stratify within the unit according to settling velocities and are removed as sized products. Ultra fines or clarified water is removed off the top of the unit. The Econosizer requires no power and only minimal maintenance.

Jan 1, 1998

By G. C. Allen

Selective flocculation is used for the purification of clay minerals. Here we present data from a surface spectroscopic investigation into the polyacrylamides mediated selective flocculation of kaolin from an impure matrix. Use of X-ray photoelectron spectroscopy (XPS) was shown to offer a useful approach for investigating the observed selective separations. In particular, a new small area XPS technique was used to characterize, in situ, the differential competitive, f1occulant adsorption onto mixed kaolin/gangue systems.

Jan 1, 1998

By Waijun Cheng, Guilin Xie

A microcomputer control system prototype of a Switched Reluctance drive for storage battery electric vehicle in coal mines is developed. The paper introduces the hardware components, the control strategy and the software unit. It is shown that

Jan 1, 1998

Mining projects frequently fail to meet their financial objectives. A significant area of poor performance lies in the areas of resource estimation, reserve definitions, selective mining and metal accounting. The processes leading to the exploi

Jan 1, 1998

By K Timtner

As shown in former publications there are problems in load sharing of backstops in multiple drives of conveyors. Therefore, detailed calculation methods and design recommendations are required. In this paper various designs of load sharing methods are described and a dynamic torque calculation method will be presented. With this method the loadsharing properties for low and high speed backstops are calculated and compared. These properties depend on the spring characteristic of the drive train between backstop and load. Furthermore, the properties depend on the method of torquearm support and shock absorber configuration. Remarkable differences for external and internal backstops are shown

Jan 1, 1998

By Daniel Mageau

Ground freezing has been used for over 100 years to provide shoring and ground water cutoffs for hundreds of projects worldwide, including drilled shafts, tunnels and cofferdams. Typically, these cases involved difficult soil/water problems where ground freezing was likely the only solution. This paper discusses a recent ground freezing project where a frozen soil wall was used for a more conventional problem. A 4-foot-thick frozen soil wall was used to provide shoring and groundwater cutoff for a 20-foot-deep excavation during construction of a cast-in-place concrete storm water detention vault. The site is located along the northbound on-ramp to I405 from westbound SR522 in Woodinville, Washington. The frozen soil wall was successfully formed in soils consisting of till fill over soft organic silt and loose saturated sand in about 3 weeks. The depth to ground water varied from about 4 to 8 feet over the site. The unfrozen soil inside the frozen soil wall was excavated vertically to the frozen soil boundary. The vertical excavation remained open for approximately 2 months with no dewatering required. On one side, fully-loaded dump trucks and other construction equipment operated within 6 feet of the wall face with zero wall movement. This paper addresses the construction issues related to installation and operation of ground freezing shoring. The overall wall performance of the frozen soil wall as well as basic geotechnical design issues are also discussed.

Jan 1, 1998

By S. J. Swart

This paper discusses the principles and application of risk assessment and management as the basis for environmental management within the mining industry. Unlike in other industries, mines are required to obtain closure certificates in terms of section12 of the Minerals Act, which should ultimately release them from further environmental responsibilities. It is emphasized that the concept of environmental risk assessment and management, when applied correctly will mean that the mine will be identifying and managing environmental issues beyond those set by current legal requirements and management strategies. The focus shifts from conventional minimum legal compliance management to management of real environmental risks. The advantage of this approach is that the perceived ?shifting of legal and management goal posts? due to changing environmental laws or management principles, will not influence or dictate the mine?s short or long-term management objectives or actions, mine closure funds can be more accurately determined and mine closure should become a relatively simple procedure. The risk assessment approach has been applied to the planning of mine closure at Iscor?s Durban Navigation Collieries (Durnacol) in Kwa-Zulu Natal and certain key risk issues such as the long-term risk of water pollution from coal discard dumps have already progressed to fully quantitative risk assessment. This paper will discuss the process, which has been followed to date, with particular emphasis on the most recent phase, namely quantitative risk assessment and management of pollution from coal discard dumps. It is believed that the approach that is being pioneered at Durnacol and which overcomes some of the more obvious deficiencies of both the EMPR and the traditional IEM process will ultimately serve as the model for all responsible mines in South Africa. It is also believed that this approach will enable the authorities to issue closure certificates with the confidence that there will be no unforeseen surprises in the years after closure.

Jan 1, 1998

By Joseph Trocino, John Anderson, Stephen Murray

This paper describes the development of LEXFOAM® (Liquid EXplosive FOAM) as a unique low density explosive, and its successful application as an effective tool for "in-place" demolition of landmines and unexploded ordnance. Explosives research using aerosol technology led to the development of LEXFOAM whose components are safely transported and stored as flammable liquids. These components are mixed on site to produce an explosive foam, which enhances safety and minimizes logistical problems. Hand-held, Backpack and Palletized Delivery Systems form a versatile family of dispensing systems to suit any application.

Jan 1, 1998

By C. Blais, G. L’Espérance

Characterization of second phase particles is important with regard to their influence on mechanical properties of materials. Analytical electron microscopy offers the possibility to achieve complete characterization of inclusions. Complete characterization of inclusions means quantitative evaluation of their chemistry and the stereological parameters. A characterization technique based on integrated microscopy and involving scanning electron microscopy, image analysis and energy dispersive X-ray spectrometry is presented. A discussion of the use of transmission electron microscopy and electron energy loss spectroscopy is also presented for the characterization of very small particles and compounds (>100 nm).

Jan 1, 1998

For the past 40 years, underground trucking using diesel powered or electric wheel driven vehicles, either conversions of surface trucks, or purpose built, has been the preferred means of ore and waste transport in underground mining. The relatively low capital cost, flexibility and requirement for minimal infrastructure means that trucking systems are selected in the early stages of a mining operation. An increase in the carrying capacity of trucking systems with dimensions to operate within existing development excavations is the solution to long term ore and waste underground haulage systems using trucks. The next generation of underground trucks will be low profile articulated trucks with carrying capacities up to 60 t.

Jan 1, 1998

By J. W. Merks

Applied statistics provides scores of powerful tests and techniques that are widely used and abused in science and engineering. The variance is the basic measure for variability, precision and risk. The formulas for the variances of the arithmetic mean and the weighted average are derived from the variance of a general function, as defined in probability theory. The requirement of functional or mathematical independence in probability theory translates into the concept of degrees of freedom in applied statistics. Geostatistics is the only variant of statistics in which functional dependence and degrees of freedom are irrelevant. This paper examines whether such basic elements of probability and statistics can be ignored with impunity.

Jan 1, 1998

By A McDowell

Pound Road Quarry is an alluvial gravel quarry owned and operated by Fulton Hogan Ltd. for the supply of aggregate in Canterbury, and is the largest quarry in the South Island in terms of production. It has evolved from three separate quarries, as a result of which extraction has occurred sporadically in a number of areas. Due to this factor, and the need to manage environmental impacts, a detailed quarry management plan was completed in 1995 which formed the basis for implementation of a certified environmental management system.   In December 1997, the quarry was the first in New Zealand to achieve ISO 14001 (TELARC) accreditation for implementation of an environmental management system. The main potential environmental impacts arising from the quarry operation include dust, noise and groundwater contamination, and visual landscape effects associated with gravel extraction, the mitigation of which is achieved by means of æbest practiceÆ methods. All quarry operations are controlled in terms of the environmental management system by means of regular (monthly and yearly) environmental reviews, appropriate auditing of environmental documents, and monitoring of environmental targets in accordance with consent and statutory requirements.

Jan 1, 1998

By André Chagnon, Michel Malo, Benoît Dubé, Chantal Pelchat

"Abstract- In the southern Gaspé Appalachians, gold mineralization is spatially associated with the Acadian dextral strike-slip Grand Pabos-Restigouche fault system. Two different structurally-controlled gold prospects, the Lac Arsenault and the Saint-André-de-Ristigouche, are described to unravel the genesis of gold mineralization in this part of the Canadian Appalachians.At the Lac Arsenault gold prospect, gold mineralization consists of Au-As-Pb-Zn-Cu-(Ag) polymetallic fault-filled quartz veins with laminated textures emplaced in brittle-ductile sinistral X shear fractures. Mineralized veins are hosted by Middle Ordovician graywacke of the Arsenault Formation, belonging to the Dunnage Zone, the Early Paleozoic oceanic domain of the Appalachians. Terrigeneous rocks of the Arsenault are regionally metamorphosed at the lower greenshist facies and the mineralized veins are included in a zone of Fe-carbonate alteration.The Sb-Au-As mineralization of the Saint-André-de-Ristigouche gold prospect, in the southwestern Gaspé area, comprises extension veins in the extension direction emplaced in brittle conditions. Mineralized veins are hosted by calcilutite and laminated silty and argillaceous limestone of the Early Silurian part of the White Head Formation, which belongs to the Gaspé Belt, the Middle Paleozoic successor basin in the Gaspé Appalachians. Metamorphic grade of the White Head Formation in the southwestern Gaspé area is very low, but the gold mineralization is included in a zone of hydrothermal propylitic alteration which includes two Cu-skarn mineral occurrences. The Lac Arsenault gold prospect has many characteristics of "greenstone-hosted quartz-carbonate vein" deposits whereas the southwestern Gaspé area, which includes the Saint-André-de- Ristigouche gold prospect, shows affinities with the geological setting of sediment-hosted gold deposits (Carlin-like deposits). The two gold prospects are controlled by the Grand Pabos- Restigouche fault system but they were not emplaced at the same level in the crust. Acadian strikeslip fauting played a major role in their respective genesis in providing channelways for ore-bearing fluids. The recognition of the analogy of the geological setting of the southwestern Gaspé area with that of Carlin-like mineralization gives new ideas for exploration in the area and elsewhere in the Appalachians.Résumé - Dans le sud des Appalaches de la Gaspésie, on trouve des minéralisations aurifères spatialement associées au système de failles de coulissage dextre acadien de Grand Pabos-Restigouche. Deux indices très différents, Lac Arsenault et Saint-André-de-Ristigouche, sont décrits pour évaluer la genèse des minéralisations aurifères à contrôle structural de cette partie des Appalaches canadiennes. Au Lac Arsenault, la minéralisation aurifère comprend des veines polymétalliques à Au-As-Pb- Zn-Cu-(Ag) en remplissage de failles. Ces veines à texture laminaire se retrouvent dans des zones de cisaillement fragiles-ductiles senestres de type X. Les veines minéralisées sont encaissées dans les grauwackes d’âge Ordovicien moyen de la Formation d’Arsenault appartenant à la zone de Dunnage, le domaine océanique du Paléozoïque précoce des Appalaches canadiennes. Les roches terrigènes de l’Arsenault sont métamorphisées régionalement au faciès inférieur des schistes verts et les veines aurifères sont dans de larges zones d’altération dolomitique (Fe-carbonate).Dans le sud-ouest de la Gaspésie, la minéralisation à Sb-Au-As de Saint-André-de-Ristigouche est dans des veines d’extension comprises dans la direction d’extension et mises en place dans des conditions de déformation fragile. Les veines minéralisées sont encaissées dans les calcaires argileux et les calcilutites de la partie silurienne de la Formation de White Head qui appartient à la ceinture de Gaspé, le bassin successeur du Paléozoïque moyen des Appalaches de la Gaspésie. Le degré métamorphique des roches du White Head est très bas, mais"

Jan 1, 1998

It is very rare in the underground hard rock environment to find a deposit that is ideally suited to a specific mining method. Usually the irregular shape of the orebody will allow the deposit to be extracted by more than one mining method. During the prefeasibility stage, a number of conceptual mine designs are generally evaluated to see which offers the best method of extraction for the deposit. The selected method is usually based on key decision criteria such as the overall extraction of the orebody, the amount of metal produced annually and the unit cost of production. Often the prefeasibility study document will state that the project has an NPV of æxÆ million dollars. This statement can be made without any quantitative consideration of the likely risks of the mining methods reviewed or the level of confidence in the estimation of the NPV. By assigning a probability of failure to each component of the mining cycle a measure of the risk for each method can be determined. One mining method may provide the highest NPV when it is performing well, however, there may be a higher risk of a major failure impacting on the performance of that method, eg the failure of a mass blast of a crown or rib pillar. This paper will present a flowsheet approach to the use of risk analysis for determining the likely production rates of different mining methods. This framework allows the annual metal output to be estimated and from this the NPV for each method. A level of confidence can be applied to the estimated NPV for each option. An example will be presented on how this technique has been used within the Normandy Group.

Jan 1, 1998

By Jacobs M

After a methane explosion in a coal mine a pre-determined crisis management procedure is instigated. As the process rapidly evolves the inevitable question arises - are personnel trapped underground, are they alive and can they be rescued without putting the lives of the rescue crew at risk? This is a very emotive question with many sub-questions such as; could anybody have survived, is there the potential for a secondary explosion and is there a `window of opportunity' before that secondary explosion occurs?To determine if that window of opportunity exists two fundamental elements must be in place; a method of determining the atmosphere at key points in the mine and a method of predicting the course of change of that atmosphere with respect to time. The first element can be achieved if the tube bundle system is intact and drawing samples from known points, alternatively boreholes can be drilled from the surface. The second element can be realised by utilising a sequence of computer generated control charts which have a time axis, a percentage combustibles axis, the upper and lower explosive limits of the current atmosphere and a prediction option which allows the user to look at the potential changes in the atmosphere over a set period of time. These control charts would be part of the mines on-going crisis management system rather than a tool to be used after an explosion had occurred.

Jan 1, 1998

By Barry A. Hillman

The rapid evolution of computer and field sensor technology is now providing the ability to integrate mine and office operations. Digital maps and mine plans as well as CAD and GIS can be transferred to ruggedized field computers for development of real-time mine surveys and real-time GPS machine navigation and monitoring. Surveyors can insure that their surveys are accurate before returning to the office. Engineers and surveyors are also able to upload field computer-based surveys to mine planning software and directly to mine equipment including shovels, drills, and dozers providing the operator of the equipment with a real-time view of their work space. Production information can be transmitted through dispatch and/or centralized mine servers to update mine plans with mining progress and production data. Static mine models then become a dynamic element of operations, providing greater use of information that emphasizes the spatial aspects of the mine by providing real-time maps, productivity charts, and graphs. This information can be disseminated through various mine communication systems to provide operators and management with real-time feedback as well as daily and weekly reports. Integrated systems now being used in extensive trials are reporting productivity increases of 4 -7% or more thereby providing rapid payback to the mine.

Jan 1, 1998

By G K. Searle

In Australia, coal mines have generally not adopted filling to increase mining recovery. The aim of this project, entitled æImproved recovery in highwall mining using backfillÆ, was to examine the feasibility of using fill to improve recovery in highwall mining. Current fill practice was reviewed for metalliferous as well as coal mining, both here in Australia and overseas, for its applicability to highwall mining. Studies were then made at a conceptual level to determine whether fill could be economically used, to determine appropriate sources for fill and to trial key aspects of fill behaviour. A review of filling methods led to conceptual studies being undertaken on seven filling methods and these studies demonstrated that fill could be used to improve recovery. These studies were then further refined. Selected filling materials have been reviewed and laboratory tests have been made on these to assess their suitability.

Jan 1, 1998

By M. G. Rylatt, G. M. Popplewell

"Production from Canada's first diamond mine is planned for the last quarter of 1998. The climatic conditions and the variation in kimberlite types to be treated have lead to the development of a compact and flexible processing plant.High kimberlite moisture contents and winter temperatures below -40°C have dictated a process flowsheet with limited in-circuit storage to reduce materials handling difficulties. The latest developments in High Pressure Grinding Roll technology will be used to liberate the valuable diamond, reduce diamond breakage, and increase fines production to reduce the amount of material for down stream processing in the Heavy Medium Separation section.A varying heavy mineral concentrate yield has lead to the development of a final Recovery section that will incorporate Attrition Milling and Wet High Intensity Magnetic Separation for concentrate reduction. The latest developments in diamond X-ray sorting will be used to produce a final diamond concentrate for mechanical sizing, weighing and packing.Fine tailings thickening will utilise Deep Bed Compression type thickeners. This relatively new technology can produce;i) high underflow densities at low flocculant dosage rates, andii) clear overflowswith a smaller thickening area than conventional high-rate thickeners."

Jan 1, 1998