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By Bangerter PJ

The use of gravity concentration is, and has always been, the conventional primary method for gold recovery from alluvial deposits. The development of high capacity cone concentrators and metallurgically efficient wash-waterless spiral separators has had some impact in the technology for alluvial gold processing, but perhaps more significantly has led to the relatively recent use of this gravity concentration technology in grinding circuits of hard rock ore for "coarse" gold removal and for scavenging gold locked in sulphides from cyanidation tailings streams.Gravity concentration systems are relatively low-cost, non-polluting and energy efficient; and their judicial use in gold treatment plants can significantly reduce overall capital and operating costs.The application of modern gravity concentration technology to hard-rock and alluvial gold ore treatment is discussed. Flowsheets and test and operating data from a number of gold processing operations incorporating gravity concentration treatment are presented.

Jan 1, 1984

By Potter DJ, Firkin GR

The Imperial Smelting Furnace operated by Sulphide Corporation Pty. Limited at its Cockle Creek zinc-lead smelter was recently equipped with tuyeres angled at 25 degrees instead of the usual 10 degrees. This change was prompted by the results of model studies undertaken by tha Research Department of Imperial Smelting Processes Limited, at Avonmouth in the United Kingdom, and by the favourable results of operating trials on the Cockle Creek furnace using bent-tip tuyeres to simulate 25 degree inclination. The use of 25 degree angle tuyeres has made it possible to operate with lower zinc values in discard slag and has improved hearth stability over a wider range of sinter quality and composition.

Jan 1, 1981

By DAVID C LAURENCE

The richer, shallower sapphire deposits of the New England region of New South Wales which have been traditionally mined by the small miner are almost worked out. Larger mining and exploration companies are replacing the small miner and exploring for the primary source of sapphire or lower grade alluvial deposits.Although in recent years considerable exploration effort has been directed at locating the primary source, commercial exploitation of sapphire is still restricted to the working of alluvial deposits.If the Australian industry is to compete against Asian and African producers it must use cost effective exploration, mining, processing and marketing methods.

Jan 1, 1990

By P Dare-Bryan

Many mines have an interest in improving fragmentation at their sublevel caving operations in order to produce better ore recovery, lower dilution and less overbreak. The primary requirement for the extraction phase is to understand and optimise the flow of the fragmented rock in the rings including interactions with the caved material. Rock fragment formation is critically controlled by the blasting phase and can potentially be improved by optimising the dynamic energy distribution throughout the ring through the crafting of explosive charging, priming position and initiation timing. The modelling of fragmentation and damage due to explosive loading of complete rings is inherently and irrevocably a three dimensional problem that is difficult to address. We have therefore initially utilised an analytical code to predict vector peak particle velocities and energies that are restricted to the plane of a ring. Dynamic energy distributions based on common timing and priming practice have been compared with other possibilities using conventional pyrotechnic detonators as well as initiation designs based on accurate electronic detonators. The energy distribution can be quite subtly tailored to increase energy in appropriate regions or to decrease energy in the brow region for example to potentially reduce instability and the probability of misfires. We have also recently developed the capability to efficiently model particle flow using four-sided polygonal elements. Despite the 2D limitations of such a model this results in more realistic fragment interaction and stacking than can be achieved using conventional rigid circular elements. Modelling of a typical sublevel caving ring utilising these elements activated by the correct dynamics offers considerable potential for understanding the influence of the blasting energetics and timing on the complex flow and extraction process.

Jan 1, 2005

By Hustwick I

New Zealand Steel Mining Limited operates two independent sand mining operations on the West Coast of the North Island of New Zealand. (Fig. 1)Waikato North Head 30km south of Auckland supplies ironsand concentrate as the raw feed for New Zealand Steel's works at Glenbrook, and Taharoa 70km further south, exports ironsand concentrate to Japan. Taharoa uses two sets of six low pressure Warman centrifugal pumps in series to load bulk ore carriers 3km off shore through two underwater pipelines.Waikato North Head delivers the ironsand to Glenbrook l8kms through a 200mm ID buried pipeline using two stages of high pressure positive displacement (HPPD) pumping.A high level of operating and maintenance expertise has been developed since commissioning the two systems which are proving to be reliable, efficient and of minimal impact environmentally.

Jan 1, 1990

By Chugh Y. P

A generalized void diffusion model for subsidence prediction has been developed based on theoretical concepts and physical principles. The general form of the model is a three-dimensional differential equation. With a few assumptions on the characteristics of overburden strata overlying typical room-and-pillar mining or longwall mining systems, specific solutions for the differential equation were obtained. A brief description of these solutions and their applications in the United States and China are presented in this paper.

Jan 1, 1992

By Bradford NL

The Isa Mine of Mount Isa Mines Limited produces 5.1 million tonnes of copper ore and 2.2 million tonnes of silver-lead-zinc ore from sublevel open stopes annually. Extraction of the narrow, steeply dipping silver-lead-zinc orebodies requires a strategy quite different to that used in the massive copper orebodies. A range of blasthole diameters, explosive types and initiation systems gives the flexibility needed to adapt open stoping to a variety of situations. Hole diameters from 70 mm to 200 mm are being used, with lengths of up to 100 m common for the latter.

Jan 1, 1982

The New South Wales coal industry is a highly mechanised well organised industry which has developed from an annual production of slightly less than 13 million tons in 1950 to over 33 million tons in 1969. Although continuous miners were not introduced into the mines until 1950, by June 1969 the percentage of coal won by these units was 87.3. The paper describes mining conditions in the various coalfields of the State, their complexities and problems and how these have been dealt with. The introduction of fully mechanised longwall faces has presented a challenge which has been accepted and descriptions of systems in use are discussed. Major expansion of the industry is anticipated to meet the requirements of the growing Australian steel industry, for local power generation and to meet the increasing demands of overseas markets.

Jan 1, 1980

By Das S. C

A detailed study was undertaken on the effect of Fe+3 in combination with LIX64N during copper electrowinning from sulphate electrolytes. The results show that the presence of Fe+3 not only affects the current efficiency during copper electrowinning but also affects the cathode quality. The effect is enhanced by electrolysis parameters like temperature, circulation rate, current density, etc. No significant effect was found from the presence of Fe+2. The presence of Fe+3 along with LIX64N causes a synergistic effect and results in a drastic fall in current efficiency. Moreover, cathode quality is also affected. A pyramidal structure is favoured in the presence of Fe+3 but the presence of LIX64N along with Fe+3 promotes a ridge structure. Addition of thiourea not only causes modification of cathode deposits, but also a rise in current Efficiency.

Jan 1, 1992

The South Wall Base Case Design for Mt Whaleback indicated that along portion of the South Wall a cigar shaped synclinal keel, contain- ing 14 800 m', of Dales Gorge Member ore, would be unkeyed and bed- ding undercut. The dry "ore lobe" slope would be 60m high, unbenched and approximately 170 m long. Stability analyses using specific design parameters established that artificial reinforcement could stabilise the slope and be economically justifiable. To implement the slope design reinforcement for such a complex geo- logical structure it was necessary that all functions pertaining to slope excavation be integrated and co-ordinated within the Mine Geotechnical Section. The objective being to minimise slope damage and thereby optimise the effect of design reinforcement. The successful excavation of the ore lobe in 1988, three years after the introduction of artificial reinforcement, was achieved by strictly main- taining the following parameters. 1. Accurate Geological Model 2. Controlled Perimeter Blasting 3. Controlled Excavation Techniques 4. Quality control -Reinforcement Installation 5. Additional Reinforcement.

Jan 1, 1989

By P A. Dowd

This paper describes an integrated approach to the evaluation of ore loss and ore dilution via geostatistical simulation of in situ geology and grade characteristics, simulation of blasting mechanisms and simulation of loading from a blast muck pile. The approach is demonstrated on a case study. The sequential Gaussian method is used to simulate in situ bench grades on the scale of the smallest selectable volume within a blast muck pile. The simulated grades of these component volumes are interpreted as the reality that would be available with exhaustive sampling. The simulated bench is subjected to a blast simulator, based on the SCRAMBLE model, which effectively moves each of the component model volumes to its final resting place in the blast muck pile. Ore/waste delineation and selective loading processes are applied to the simulated muck pile to determine the degree of selectivity that can be achieved by various sizes of loader and types of loading and to quantify ore dilution and ore loss. An in situ model representing the reality of knowing only the data and information that are available from specific grade control drilling and sampling grids is obtained by sampling the geostatistically simulated model on a specified grid. The volumes comprising the in situ model are then populated by estimates based only on the data and from the specified grade control drilling and sampling grids. Different drilling and sampling grids are used to generate different models, each reflecting the levels of data and information available. Selectivity is assessed as a function of the drilling and sampling grids as well as the size and type of loader. Performance is assessed against the ideal selectivity that could be achieved on the perfect knowledge model comprising the simulated values of each component volume. Costs, prices and financial criteria enable an optimal selection of the grade control drilling grid, size of loader, type of loading and blast design.

Jan 1, 2004

Alluvial gold exploration is aimed at recognizing areas of anomalous gold content as evidenced by the nature of the drainage system, its age, geomorphic history and other features of the geological environment including the provenances. Subsequent studies to quantify the findings are governed by the need for accurate data based upon precise measurements. Computerization allows the use of more complicated mathematical procedures than are feasible manually, thus promoting the development of more advanced technological aids. Data banks provide the means of storing vast quantities of information for instant recall.Sample representivity is a major problem and a clear understanding of both sampling and analytical requirements is essential for dealing with problems arising from variations in sample size and particle size distribution. Field samples must always be large enough to ensure adequate representivity or the sampling has failed in its purpose.

Jan 1, 1984

By Stewart A. M, Price D

This paper presents recent findings concerning longwall caving mechanisms relating to Australian mining conditions and their effect upon longwall support requirements and behaviour. The findings are based on a program of intensive hydraulic support monitoring in a variety of Australian mining conditions coupled with geotechnical observations.

Jan 1, 1992

By Denby B, Miles N. J

The underlying theory behind the construction of an on-line size analysis system is described together with an introduction to the Artificial Intelligent techniques that it is founded on. Previous systems based on more traditional technology such as edge detection and dilation algorithms have been restricted by the significant processing power they require, this has resulted in the production of systems with either reduced functionality or severe hardware requirements. A neural network approach offered a new perspective to the problem of size analysis; the ability of a network to learn and recognise subtle patterns in training data before on-line processing is initiated opened up the possibility for the production of a fully functioning practical system. The format of the training data had to be carefully analysed prior to its implementation in a neural network as the capability of a neural network solution depends as much upon a suitable data preparation as it does on the system architecture. To facilitate experimentation with various profile quantification techniques such as fourier and fractal analysis an Image Profile Analysis System was constructed (IPAS) in software on a personal computer. The IPAS system was produced with the aim of pre-processing image data to create data sets for experimenting with external neural network packages. The system allows the analysis of both real images obtained by image capture and simulated images created by an in-built in simulator. A measurement comparison scheme is also included together with a case study concerned with the frequency analysis of simulated images. The power of neural networks combined with the data compression provided by profiling removes the need for direct measurement of individual particles. This has obvious implications on the level of hardware necessary, and ultimately the expense of a stand alone system. The extrusive nature of data collection via an image analysis system will also permit simple installation of a shipped system; eliminating any requirement for interference with existing machinery.

Jan 1, 1995

By Gross A. E, Neville P. C

Over the last decade heap leaching with a cement binder has allowed the economical leaching of low grade gold ores of less than 2 grams/tonne. Despite the continued use of cement as an agglomeration aid, numerous leaching operations continue to experience channelling and blinding problems. This paper describes the development of polymeric agglomeration aids, Extract Ore 9760 and 9960, which when used as a partial cement or lime replacement can result in a higher rate of and/or a higher total gold recovery in plant evaluations. Extract Ore in combination with cement acts to produce a stronger agglomerate which results in reduced fines migration during leaching and helps prevent blinding of the heap. Both of these changes will give a more even flow of cyanide solution throughout the heap and improve solution contact efficiency within the ore. Polymeric agglomeration aid programs are now being used by heap leaching operations in three different countries. A summary of benefits identified at some of these operations are presented in this paper.

Jan 1, 1994

By T Laurencont, C Unger

The Mount Morgan minesite, located approximately 40 km SW of Rockhampton in Central Queensland, comprises 270 ha of unrehabilitated land which is the currently the major source of acid mine drainage run-off and seepage to the adjacent Dee River. Additionally, the minesite hosts an Open Cut Pit which contains 9000 ML of acidic and metal-rich water. In the absence of active management of water in the pit, there is a 50 per cent probability of an uncontrolled spill occurring in future years. The development of a contingency plan for management of overflow from the pit in the short term, has incorporated findings from numerous studies relevant to the Open Cut Pit including, but not limited to, water balance, contaminant source identification, toxicity testing, water quality profiling and limnological modelling, and estimates of probability of overflow. Extensive stakeholder consultation and peer review were also undertaken during the formulation of the contingency plan. The medium-term goal of lowering the water level in the pit to reduce the current high probability (50 per cent) of uncontrolled overflow to acceptable levels of risk is proposed to be achieved by a campaign of chemical water treatment. The treated water will be discharged to the Dee River, and sludge returned to the pit. The methodologies used for the selection and development of the water treatment process, that is proposed to involve treatment with lime, are described. Water treatment is the short- to medium-term component of a long range rehabilitation plan for achieving a negative pit water balance, and sustainable management of acidic water across the whole site. Achieving this ultimate goal will involve: reducing the inputs of water to the Open Cut Pit such that the annual water balance is zero or net negative, thus removing the need for water treatment in perpetuity; maximising, by surface rehabilitation works, the quality of run-off reporting to the Dee River; and minimising the volume of acidic seepage reporting to the seepage interception system. Possible strategies for achieving this long range goal consistent with overall site rehabilitation objectives are currently being developed and costed.

Jan 1, 2003

By Ranklin W. J

The mechanism and rate-limiting step of carbonaceous reduction of zinc from slags was investigated in the laboratory. Disks of graphite were rotated in ZnO-containing slags at various speeds for fixed periods at 1250 to 1325¦C. The mass loss was used as a measure of the amount of ZnO reduced. Application of the Levich equation indicated that at rotation speeds at which it is valid, the reduction was chemically controlled with an activation energy of 27 kcal/mol. At zero rotation speed the reduction of ZnO by carbon appeared to be slag-phase mass transfer controlled with an activation energy of 38 kcal/mol. An increase in the FeO content of the slag increased the rate of reduction while an increase in sulphur content decreased the rate of reduction. When FeO was present in the slag, reduction appeared to occur by a combination of indirect reduction of ZnO by carbon and by reduction by FeO with reduction of Fe203 back to FeO by carbon. The effect of sulphur was consistent with a surface blockage mechanism due to the surface active nature of sulphur in slags.

Jan 1, 1993

By Townsend IJ

The Upper Triassic Leigh Creek Coal Measures which include a number of seams of sub-bituminous black coal are preserved in four small intramontane basins. The largest is Telford Basin, 1,000 m in thickness. The coals, of variable thickness and quality, are mined by open cast mining methods and utilised for generation of electricity at Port Augusta. The combined proven and indicated reserves are about 100 million tonnes.

Jan 1, 1975

Electromagnetic methods used in geo- physical prospecting for conductive ore bodies have proved successful in Canada,Sweden and other countries. In Australia however the depth of weathering generally exceeds 30 metres. This introduces a problem of highly conductive overburden and renders equipment useful elsewhere virtually ineffective. A discussion of several EM prospecting techniques is presented and a new system under development at James Cook University using V.L.F. transmissions capable of indicating changes in impedance (not only highly conducting media) is outlined.

Jan 1, 1974

The geology and mineral deposits of the West Pilbara Goldfield are described and comparison is made with the Pilbara Goldfield,, In the West Pilbai'a Goldfield two adjacent environments are represented by a predominantly clastic succession and a predominantly volcanic succession. These two successions are lateral equivalents and lithologically they are similar to the classical successions at Warrdiwdbna and Mosquito Creek. How- ever, no evidence of a significant erosional break has been found. It is suggested that the Archaean rocks of: the Pilbara Block represent a single geosynclinal cycle, which culminated in orogenesis, within which-local disconformities have been developed in various places: and that the sub-Mosquito; Creek unconformity at Eastern Creek may be the most widespread of these disconformities, Widespread evidence of'preconsolidation movement, aid the intrusion of igneous rock into. unconsolidated sediment, suggest that tectonism and igneous activity began at a very early stage, This was localised along lines of fracture in an unidentified basement.,.Moveme.nt was primarily vertical and persisted into the older Proterozoic, The sediments were enriched in metal by vulcanicity, chemical sedimentation, and possibly detrit`1' contribution. Diagenesis and metamorphism caused the remobòliyation of the metallic constituents of igneous and sedimentary, rocks which were then localised-in loci of dislocation-formed both before and after consolidation.,.. . . , . .

Jan 1, 1964