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A survey of leaching systems for the dissolution of gold has been undertaken and their advantages and disadvantages evaluated both from their effectiveness at leaching and their compatibility with carbon- in-pulp (CIP) and resin-in-pulp recovery. In the near future it is almost certain that cyanidation in some form will remain the leaching system of.choice although economic and environmental pressures could see the introduction of other leaching systems particularly for treating refractory gold ores. The most likely alternative leaching systems appear to be acid chlorine, acid thiourea and ammoniacal thiosulphate. INTRODUCTION High grade reserves of readily recoverable gold ores are gradually being depleted which, inevitably, must create a greater awareness amongst gold producers, of the efficiency and, in some cases, the suitability of present day metallurgical processes for treating low grade, complex and refractory deposits. One of the key steps in the extraction of gold is the dissolution of the metal using chemical reagents which, ideally, should be cheap or recyclable, selective, non-toxic and compatible with down-stream recovery processes. In practice, meeting all these critera is difficult - if not impossible - particularly in view of the stringent environmental impact requirements which must be met Nowadays.

Jan 1, 1982

ABSTRACT- I Chemotrophic bacteria, capable of oxidising inorganic species such as Fe(II) and S(-]I) for their metabolic energy, have been known for many decades and interest in these bacterial species has increased since their ability oxidise auriferous arsenopyrite ores has been demonstrated. The rate at which bacterial cultures can oxidise a solid sulphide ore is of importance but a number of difficulties arise when attempting to evaluate this oxidative activity. The two major problems are counting the number of viable bacteria present in the reactor and identifying the types of bacteria that are active in both the solid and liquid phases. Enumerating the numbers of bacteria responsible for an observed change is necessary to compare the activity of different isolates. For selection and identification of bacteria during the development stages of a project, and for monitoring an operational process, the recognition of different species will be of importance. Methods for the taxonomic discrimination of bacterial species rely on observations, different culturing techniques, and the degree of DNA base homology between isolates. A method reported recently uses IR spectroscopy for comparisons between isolates. This spectroscopic method and its application is discussed.

Jan 1, 1991

A system for rapid on-line determination of weight percentage coal in slurry and weight percentage ash in coal has been developed at the Julius Kruttschnitt Mineral Research Centre, University of Queensland. The gauging system is suitable for use with coal flotation slurries or slurries having a maximum particle size of about 1 millimeter. The system is based upon measurement of gamma ray transmission; radioisotope sources emitting photons of two widely different energies are employed. The inaccuracies of measurement that would normally result from variable amounts of air entrained in the slurry are substantially reduced by pressurising the slurry to approximately 2MPa (300 psi) using a Mono pump. The equipment can be used to make measurements on more than one slurry stream by pumping streams sequent- ially. The system is being tested at the Peak Downs Mine of the Utah Development Company in Central Queensland. This paper describes the theoretical principles of the gauge design, the experience gained to date in the commissioning of the equipment, including the installation of a PDP 11/03 computer, and the progress made in developing satisfactory interpretations of the gauge count-rate output.

Jan 1, 1978

By McKenzie C. K

During a programme of explosive performance evaluation at Hamersley Iron, Mount Tom Price Mining Operations, the relative performances of a range of heavy ANFO explosives were compared during normal production blasting operations. In addition, a number of heavily instrumented single hole blasting trials were conducted with each product type. The blasts were monitored in terms of blasthole velocity of detonation (VOD), measured using multi-point plasma conductivity probes with up to 16 measurements per blasthole. Up to 16 blastholes were monitored in each production blast. The results of measurements show a marked difference in performance of all heavy ANFO products between single blastholes and full production blasts, indicating a significant degree of interaction between blastholes in production blasting. The interaction is shown to result in a loss of detonation pressure of explosive, and considered to lead to a loss of fragmentation. The degree of interaction is seen to increase with increasing emulsion content in the products, and is more pronounced in some explosive types than others. The paper presents the methods of measurement and analysis, and the results of monitoring, together with implications on blast design and application of heavy ANFO products.

Jan 1, 1990

Today the application of computer programs for planning of mine-ventilation and for safety- analysis of ventilation systems is widespread practice in German mining. The computer program for network calculat- ion, developed at the "Mine Ventilation Testing Centre of the Westfalische Berggewerkschaft- skasse" allows the distribution of airflow and pressure in mines to be calculated. In a physically well founded manner it takes into account the natural ventilation as well as changes of volume-flow in the mine, which both are dependent on pressure and temperature. Compared to an incompressible treatment of the mine air these circumstances are of increasing importance with the increase of depth, air temperatures and fan-pressures'. This especial- ly holds for the calculation of airflows during failures of fans or for assessing the influence of open mine-fires on ventilation. The application of the program is very easy and its structure is made to fit the requirements of practice. For instance it takes into account the fan characteristics of all fans. For each planning calculated air- flows in all mine workings are compared to those of an eligible basic calculation or to measured airflows. In addition for the

Jan 1, 1983

Since 1958 there have been 16 major coal mine explosions in the U.S. claiming 323 lives. Whilst the exact cause of a number of these incidents has not been determined, the majority has involved gas ignitions in one way or another. In addition there have been fatal gas explosions in salt mines and vapor explosions in oil mines. Furthermore, many of the oil shale mines in the U.S. have proven to be gassy giving cause for concern. Compounding these problems is the fact that frictional ignition of methane in coal mines has dramatically increased over the past several years; over 100 such ignitions were reported in 1979. While, no fatalities have been attributed to frictional ignition in the U.S. since early 1978, a recent mine explosion in Nova Scotia which resulted in 11 fatalities was attributed to a frictional face ignition. Research being conducted at the Bureau of Mines is aimed at the prevention and suppression of gas explosions. Emphasis is placed on new coal cutter bits for reducing ignition frequency, machine-mounted water sprays for preventing frictional face ignitions and automatic devices for quenching incipient ignitions and fully developed gas explosions.

Jan 1, 1981

By Wygralk A, Hallenstein CP

On a world scale, many Mid-Proterozoic fluvial sediments are prospective for low grade, large-tonnage gold deposits. A significant area of the Northern Territory is covered by such Mid-Proterozoic sediments, the gold potential of which has been barely tested. The geological knowledge of these sediments is summarised. The Westmoreland Conglomerate, the basal Mid-Proterozoic formation of the McArthur Basin, has been subjected to detailed sedimentological studies in order to determine the paleoenvironments and to assess the possibility of paleoplacer occurrences. The results indicate that the sandstones and conglomerates of the formation were deposited by braided rivers and debris flows as an alluvial fan which originated in source areas to the north east. The formation contains several upward-fining cycles of sedimentation, which are related to repeated periods of uplift in the source areas. The formation of placer-type gold occurrences is possible in such depositional environments. Very limited heavy mineral sampling has indicated a cassiterite- wolframite-gold suite in the sediments of the Westmoreland Conglomerate. Disconformities at the base of sedimentation cycles are deemed to be the most likely sites for large-tonnage paleoplacer concentrations.

Jan 1, 1984

By Warner N. A

There is an inherent problem in producing simultaneously lead, zinc and copper as metals in a single polymetallic smelting furnace. It relates to the condensation of lead and zinc from the gas phase under vacuum conditions such that metals in bulk form, either solid or liquid, are obtained as products rather than a fume or dust containing both metallic and non-metallic components. To understand this phenomenon, it has been necessary to establish mathematical models with computer simulation to identify the process requirements for effecting the objective of maximum bulk metal production with minimum fog formation. The theoretical framework of simultaneous heat and mass transfer involved in condensation from gas mixtures containing a non-condensable gas has been extended to the high temperature and reduced pressure conditions. These apply to new technology for polymetallic smelting now being developed in a project currently funded jointly by the Commission of the European Communities and the Mineral Industry Research Organisation. Under the right conditions it is theoretically possible to condense out both lead and zinc with minimal fume formation, but in all practical cases it is anticipated that some circulating load for reversion back to the smelter will be needed.

Jan 1, 1989

By Watson DF

Calculation of the amount of metal in an ore deposit or mining block should be approached by multiplication and integration of appropriate numerical manifolds describing the spatial distribution of the relevant variables, viz. grade, specific gravity and also thickness for bivariate data. Construction of a numerical manifold necessarily involves some form of interpolation but detailed characteristics of this are often not specified in various automatic methods, some of which even provide manifolds with discontinuities. A manifold used in calculations should describe in a geologically plausible way the spatial distribution of the variable of interest. Different approaches to the problem are discussed and compared. Particular computational inconsistencies emerge when "accumulation" is used as a variable in calculations of average grade. If an ore deposit is variable in relation to its sampling and especially if selection of mining blocks according to grade cut-off is a necessary operational decision, the biases introduced by accumulation methods can bring about serious problems of over-evaluation. Modern computational techniques make unnecessary the use of accumulations; because of potential inconsistencies it would seem unwise to use them in any ore reserve computation.

Jan 1, 1987

ADDRESS BY THE PRESIDENT OF THE INSTITUTE (MR. J. G. SYMONS) IN PRESENTING THE CERTIFICATE TO ROBERT COLVILLE BRADSHAW, O.B.E.Today it is my privilege and pleasure to introduce to you, Robert Colville Bradshaw. O.B.E., the third New Zealander to be honoured with Honorary Membership of The Institute. Sir William Hudson and Mr. C. H. Benney were the others.Mr. Bradshaw has been an Affiliate Member of The Institute since the formation of the New Zealand Branch in 1966. Like his friend Matt Benney. Bob Bradshaw is an accountant by training. Last June he retired as senior partner of the firm of chartered accountants, now known as Wilkinson Wilberfoss, with which he served from January 1929.Mr. Bradshaw grew up in New Zealand attending the Terrace School in Wellington, the New Plymouth Boys' High School where he was a boarder, and completing a Bachelor of Commerce at the university now known as the Victoria University of Wellington. He is an elected Fellow of the New Zealand Society of Accountants and an Associate of the United Kingdom Institute of Cost and Works Accountants.

Jan 1, 1977

By Hagan T. N

Quite apart from economic considerations, the following performance parameters must be considered when selecting an explosive for a particular blasting operation. 1. total energy yield/kg, and more particularly, strain energy/kg and bubble energy/kg of charge 2. charge weight/m of blasthole 3. sensitivity of the charge 4. water resistance of the charge The effective division of an explosive's total energy into strain energy (SE) and bubble energy (BE) is explained as is the influence of each energy component on blast results. Because some rocks require a high strain energy for effective breakage, while others are most satisfactorily fragmented by bubble energy, values of SE and BE are more meaningful than those of total energy. Unfortunately, our extensive knowledge of the effects of certain variables on total energy has not yet been completely supplanted by the influence of these variables on SE and BE values. Relative SE/kg and BE/kg values are presented for a range of explosives. The 'charge density of ammonium nitrate/ fuel oil (ANFO)-type explosives is essentially constant throughout the length of the charge; because of their compressibility, slurry

Jan 1, 1974

New Zealand contract mining has been well established for close to 50 years. The opencast industry has grown from mining quantities of less than 1 million bcm per year in the 1950s to around 20 million bcm in the late 1990s. Trends here are following those in other countries with mining companies looking to contract out more of the so called traditional mining work. The key driver behind this trend is not unique to the mining industry, but is simply a matter of concentrating on doing a few things well. In the case of the mining company this has come to mean owning and developing orebodies and where appropriate, marketing mining products, and leaving owning and operating of mining fleets to the contractor. This has the effect of reducing risk to the mining company as well as lowering costs. Both can be achieved without losing control of the key elements of the operation. Optimising performance is simply a matter of identifying the key drivers behind performance, having the right plant and the right people at the right place and providing these people with the information they need to manage the operation.

Jan 1, 1997

By Yaniuk DW

The sampling of non-ferrous concentrates from trucks and trains has long been carried out either manually or by automatic spears. Very little use has been made of conventional sampling systems for sampling concentrates at transfer points, or cross-belt samplers for sampling from the belt as the concentrate moves along the conveyor.Due to the high value of base metal concentrates and the often extremely heterogeneous nature of the material it is imperative that the sampling procedures adopted are accurate and precise. The basic principle that all particles in the stream have an equal opportunity to be included in the final sample is not fulfilled by accepted traditional concentrate sampling procedures such as the spearing of wagons, trucks or streams. This may lead to significant bias being introduced into the final sample.Consequently, the application of correct sampling procedures, either with conventional cross-stream samplers or the newer cross-belt samplers, is of prime importance.SGS Australia has recently installed a number of cross-belt samplers for the sampling of base metal concentrates both in Australia and overseas. The application of these samplers will be discussed with emphasis on the benefits of their use.

Jan 1, 1976

Gold mineralisation at the Macraes Gold Project is hosted in the Hyde-Macraes shear zone and can be traced for ~30km along strike, although economic resources are confined to a 7 km section in the vicinity of the Macraes township. The shear zone, which typically dips at a low angle (~20 o ) to the NE, is bounded by an upper hanging wall shear and a lower footwall fault. Mineralisation occurs along the hangingwall of the shear zone as well as in low angle concordant shears and stockworks. Ore types include graphitic cataclasites with variable amounts of quartz veining, ælode schistsÆ and quartz-vein stockworks. Rehabilitation at the mine has focused on creating an environmentally benign site dominated by pasture to allow continuation of the traditional pre-mine farming economy. Changing regional economics, continued urbanisation and a reduction in traditional employment opportunities has seen a rethink in the long-term rehabilitation outcomes. The community has recognised that the rehabilitated site will provide the basis of a viable tourism venture and the creation of a Heritage and Art Park (working title æGolden Point ParkÆ) is the culmination of that process.

Jan 1, 2002

By Gyasi-Agyei Y

In recent years rapid advances have been made in the technology used for hydrology and erosion modelling of rural catchments. These advances have been driven by the growing availability of digital terrain maps that can be used to automatically define catchment properties that previously had to be manually extracted from contour maps. In addition, these models have, in principle at least, more powerful predictive capability. The author is involved in a number of projects to migrate and further develop these models for application to mine rehabilitation assessment. Current technologies for hydrology and erosion assessment (eg CREAMS, ANSWERS) are reviewed, underlying principles highlighted and deficiencies in the context of mine rehabilitation design assessment addressed. The advantages and disadvantages of the new digital terrain map tools (eg WEPP, SIBERIA) are discussed. Current work integrating these new models with existing rehabilitation design tools (eg ACIRL's ARGUS computer package) highlights the advantages of an integrated approach using digital terrain maps; cheaper, faster, lower impact and more flexible rehabilitation design. The use of novel visualisation tools to aid the design process is discussed. The paper is illustrated by applications to mine sites in Queensland and the Northern Territory.

Jan 1, 1995

By Muir D. M

Highly saline process water has a number of implications for the CIP process during the leaching, adsorption and recovery of gold. The reduced oxygen solubility in saline water can seriously reduce the rate of gold leaching, while dissolved oxygen meters do not necessarily reveal actual oxygen concentrations in saline water. High levels of magnesium in the ground water necessitate operation at lower pH (-9), with the potential for greater cyanide loss via HCN stripping. In addition increasing salinity renders viscosity modifiers largely ineffective.The adsorption capacity of aurocyanide onto activated carbon is improved with increasing salinity, but misleading results can be obtained in assessment of gold loading kinetics of plant carbon samples already loaded, or partially loaded, in saline water if subsequently tested in fresh water. Elevated chloride levels in the Zadra elution process can cause severe anode corrosion in the elecuowinning cell. The Anglo elution process is tolerant to only slight increases in water salinity, but elution times can be reduced by ethanol addition. Care is required in carbon regeneration, as salts can catalyse carbon decomposition as well as increase kiln corrosion.

Jan 1, 1994

The Favona Underground Project is located approximately two kilometres east of Martha Mine Open Pit in Waihi, 150 km south east of Auckland, New Zealand.   The underground reserve of 354 koz Au contained in resources of almost 600 koz lies within 600 m of the existing process plant presenting an attractive development target in a challenging environment.   The Martha Mine Open Pit is surrounded by urban housing on the north western edge of Waihi township and the Favona Underground abuts residences on the eastern edge of town. Environmental, community and social licence aspects influence project strategies as the new underground mine extends mining in a town that is planning for closure of current open pit operations in late 2006.   The Favona Underground Project has successfully passed through a detailed feasibility study, the third stage of the five stage Newmont project appraisal system. Methodologies used in the feasibility study and parallel permitting draw on a high level of stakeholder involvement to streamline the development and permitting phases.   This paper discusses the project appraisal process and design innovation required for developing an underground mine adjacent to town.

Jan 1, 2004

By J O. Okonkwo

AngloGold operates various gold mines in South Africa, the largest of which are situated in the North West province. The impact of AngloGold Vaal River mining operations on the environment and, specifically, on aquifers and groundwater is assessed. The location of such aquifers and plumes is determined by remote-sensing and ground-sensing operations, followed up with the correct placement of monitoring boreholes from which information such as water rest levels, chemistry and geological data is gathered. This study utilises an integrated approach consisting of the following mutually reinforcing phases: Phase 1: Airborne multi spectral scanning; Phase 2: Airborne thermal remote sensing; Phase 3: Ground resistivity survey; Phase 4: Borehole placement; and Phase 5: Sampling and monitoring. The integration of the investigation tools and phases in use at AngloGold Vaal River has been found to be very useful in determining the exact sources of contamination, the direction of flow of such contamination, the positioning of interceptive measures and the analysis of such contamination. This adopted approach will enable the development of flow transport models that will further enhance our knowledge of contaminants in aquifers at the mine and enable management to conduct educated interventions.

Jan 1, 2003

By M McGeough

Following the success of calcrete sampling at Challenger, calcrete sampling has been widely adopted as the primary exploration technique for gold exploration, in the Gawler Craton. Calcrete is uniformly distributed over large areas and produces discrete gold anomalies. This allows drilling to focus on specific gold anomalous targets. However, despite widespread use of calcrete sampling, very little is known of the origin of calcrete in the Gawler Craton, and the link between calcrete gold anomalies and primary mineralisation. In an attempt to understand this association Lisa Gibbons recently completed an honours project at the Old Well Prospect approximately 45 km SSE of Tarcoola. Her work is part of a collaboration between CRCLEME, MESA and MIM Exploration. At Old Well, a calcrete anomaly (>10 ppb Au)covers an area approximately 7 km x 2 km with a peak value of 97 ppb Au. The study looked at the regolith as a whole, processes of its formation and nature of mineralisation within it. She was able to combine previous calcrete and drilling results with her own observations. The results from this study highlighted problems in relating surface calcrete anomalies to in situ gold mineralisation.

Jan 1, 1998

By Vernon PN

The Eossing Uranium Mine is a high tonnage low grade open pit operation using acid leaching for uranium extraction and ion exchange and solvent extraction for solution purification. Advanced technology, much of it computer based, has led to major economies that have contained operating unit costs over the last four years in the face of double figure inflation. An improved ore reserve block model and mine planning system have achieved a considerable reduction in the stripping ratio. Drilling and blasting costs have decreased some 25%, mainly by the introduction of heavy ANFO explosive. A centralised computer control centre for the metallurgical plant has increased labour productivity resulting in improved process control. The all-staff workforce is united with management in the objectives of creating a safe, healthy, working and living environment and a prosperous company, capable of contributing to the wellbeing of the nation and the shareholders. This situation has been brought into being by an equal opportunity policy coupled with a management system emphasising open two-way communication through all levels in the organisation. The success of this policy is highly apparent in the morale and productivity of the workforce.

Jan 1, 1986