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Gold occurs at Mt. Charlotte associated with a stockwork of pyritised quartz veins in Unit 8 of the Golden Mile Dolerite. The ore- body is massive, 200m long and 40m wide and has been proved to over 600m below surface. Mining is by sublevel ring drill stoping with the ore recovered by diesel powered equipment. Ore reserves are based on traverses of diamond drill holes oriented to produce an equal intersection width on the two principal sets of quartz veins. Assay and geological boundaries are marked on each drill section and this boundary is transferred to mine plans and cross sections. Ring-drilling patterns are based on the cross sections and the resulting mining outline is transferred back to the drilling sections. The mine ore reserve is calculated from the mining outline.

Jan 1, 1979

The basic rule for correct design of a sample plant is that all parts of the material being sampled must have an equal probability of being collected and becoming part of the final sample for analysis. However, this rule is often ignored in the design of sample plants to save capital costs. This is false economy, because the samples taken are likely to be seriously biased and the precision may be compromised. The introduction of bias is particularly serious, because no amount of replicate sampling and analysis will reduce bias once it is present and it is often quite difficult and expensive to subsequently rectify the problem due to space limitations around the primary sampling location. This is also true of secondary and tertiary sampling stages, particularly in terms of the relationship between particle size and retained sample mass. The best strategy is to seek expert sampling advice and design the sample plant correctly at the outset.

Jan 1, 2005

By Hindmarsh G

The colliery is owned by the BHP Collieries Proprietary Ltd., the principal shareholders being the Broken Hill Pty. Company Ltd. and Hebburn Limited.It is situated due west of Newcastle and 6 south-east of Cessnock, N.S.W., and is conneeted by 36 miles of railway to the port of Neweastle. Of this mileage, 3 miles are owned by the Company, 3 by Hebburn Limited, 9 by the South Maitland Railways Ltd., and 21miles by the Government Railways.The seam worked is known as the Main Greta Seam of the Greta Coal Measures and is on the southern slope of the Lochinvar anticline.At the shaft, the seam is 1190 ft. below the surface, and the section of the coal measures is:-Upper or Main Seam, . 24 ft. 0 in.Conglomerate and shale 70 ft. 0 in.'Middle Seam 8 in.Conglomerate 25 ft. 0 in,Bottom Seam 1 ft. 2 in.These lie between two marine measures, and are the lower coal series of the permo-carboniferous period.Only the upper seam is workable in this area, the lower seams being too thin for eompetitive working. The section of the workable seam at the shafts is as shown on Fig. 1.Unfortunately, only the lower 12 ft. 5 in. of the seam is saleable.

Jan 1, 1935

A novel approach to validate size distributions obtained from bubble sizing techniques is introduced. The experimental rationale consists in verifying whether the output features the anticipated bi-modality when two uni-modal populations (ca. 0.5 and 5 mm) are mixed in a bubble column. The degree of deviation is quantified by comparing the calculated and real proportions on a volumetric basis. A sampling-followed-by-imaging technique was used to proof the concept. The results showed the anticipated bi-modality in which the real and calculated proportions corresponded with a deviation of less than 15 per cent, considered good given the severity of the test. However, the deviation was correlated to the superficial gas velocity (Jg) in the column and was consistently against smaller bubbles. Possible sources of bias are suggested.

Jan 1, 2005

By Mozley R

Contaminated sediments are a multinational problem. A crucial factor in solving an environmental problem is knowledge of, not only the amounts of polluted soil, the contaminants involved and their concentration, but also the historical background of the problem. Processing polluted soil is a tailor made activity based on rational decisions resulting from a detailed treatability study. Lack of information about characteristic properties of a specific sludge/pollution combination is the main obstacle in the route from first ascertaining that a particular harbour subsoil is polluted, to final identification of the full scale treatment plant. In the first instance, information must be generated regarding the distribution of pollutants in relation to the distribution of the original geophysical components. Based on this information rational decisions can be made on separation at a particular cutpoint and what sequential techniques should be involved for a certain fraction. For this purpose a `fingerprint method' is presented especially developed for investigation of polluted soil and sediments. The heart of the fingerprint method is a series of sequential hydrocyclone separations, by which a series of products is generated. The objective of the fingerprint method is to select an optimised treatment procedure in which the pollutants are concentrated in as small a volume of material as possible, leaving the bulk of the material clean. The pollutants can then readily be destroyed or isolated from the environment. The philosophy and advantages of the fingerprint method are demonstrated for a harbour sludge containing heavy metals as main pollutants. Hydrocyclone separation combined with flotation of both the coarse and fine fraction resulted in reusable and dischargeable products. Flotation of the fraction of fines was carried out by means of an experimental flotation cyclone enabling the selective recovery of mineral particles with diameters less than 10 microns. The overall conclusion is that design and engineering of treatment flow schemes for polluted dredged materials is a tailor made activity based on rational decisions resulting from the fingerprint information.

Jan 1, 1993

By T Muri

The drying operation of materials from particulate solids, through slurries and suspensions, to continuous sheets represents an important part of several processes in the chemical and mineral industries. The increasing demand of high productivity at low cost and minimal environmental impact makes it complex to evaluate and choose the best available drying technology for each industrial application. The drying technologies are mainly characterised on the basis of how the wet product is related to the drying medium, namely: direct and indirect drying. In the direct drying method (convection drying), the product is brought into direct contact with the drying medium, which may be hot gas or air. Large quantities of gas are necessary for transfer of the required energy. A special case of the direct dryer is the fluid bed dryer, in which the product floats on a cushion of air or gas. The process air is supplied to the bed through a perforated distributor plate and flows through the bed of solids at a velocity sufficient to support the weight of particles. Very high heat and mass transfer values are obtained as a result of the intimate contact with the solids and the relative velocities between individual particles and the fluidising gas. In the indirect drying method (conduction or contact drying), the wet product is separated from the drying medium. The drying unit can consist of a rotor forming the indirect contact heating surface mounted in a stationary or rotating shell. The indirect method uses saturated or superheated steam resulting in low energy consumption and minimal environmental impact. In this paper, a review is given of the technologies available on the market based on different drying methods. The advantages and the disadvantages are summarised with respect to issues such as investment and operating cost, maintenance, product capacity, product handling and environmental impact.

Jan 1, 2006

Historical exploration of the Ballarat East goldfield defined two primary quartz vein lode types. Tracking the intersection of these lodes with vertical lines of enrichment (or so-called æindicatorsÆ) was the basic practice for historical mining. This strategy proved highly successful in terms of identifying quartz veins associated with mineralisation. However, it provides little understanding of the timing or processes involved in the formation of these veins, or the associated emplacement of gold. Current underground mapping shows the Ballarat East gold deposit can be subdivided into four stages of vein formation. The earliest veins (V1 and V2) strike north-south and formed during bedding flexural slip and limb thrust fault propagation in parasitic chevron folds. V3 veins are subhorizontal and relate to further fold tightening involving a transition from east-west compression to north-south extension that initiated re-shear of bedded slip surfaces and additional strike-slip faults. Sporadic V4 veins overprint the shallow-dipping sections of V2 and V3 veins and are associated with weak north-south compression. The V4 veins mineralogy is distinguished by a high carbonate content and sphalerite-galena sulfide assemblage. Vein sampling indicates a significant increase in gold mineralisation where overprinting by the later deformation/veining has occurred. As a result of these observations, a new model is emerging that identifies the chronology, structural control and spatial distribution of respective quartz vein types. This is a major advance in terms of exploration targeting, resource modelling and mine planning.

Jan 1, 2008

Surface oxidation is one of the most important factors that influence the flotation selectivity and recovery in the processing of complex sulphide ores. It is an inherent part of surface chemical reactions that determine whether the surface film formed on a sulphide mineral will act as a hydrophobic or hydrophilic one. Because of the highly complex surface chemistry and mineralogy involved the results of flotation tests may often be difficult to interpret. In this paper, the flotation behaviour of nickel-copper ores processed in the Sudbury area is discussed with emphasis on the effect of oxidation on individual minerals, primarily pyrrhotite. In general, moderate oxidation of a freshly ground ore promotes the flotability of all principal sulphides in the ore leading to a bulk flotation concentrate. The ease of individual mineral flotability under normal aeration conditions, which is chalcopyrite > pentlandite > pyrrotite, changes to pentlandite > chalcopyrite > pyrrhotite under oxygen-deficient conditions. This behaviour is correlated with the catalytic activity of these minerals for oxygen reduction. On the other hand, preferential oxidation of pyrrhotite may lead to a selectivity increase in flotation. Such a behaviour has been noted in the flotation of a pyrrhotite-rich process stream. The results have been discussed in the light of fundamental electrochemical interactions involving pentlandite, chalcopyrite, pyrrhotite, pyrite and grinding media and a mechanism has been proposed to explain the selectivity.

Jan 1, 1993

By Anderson RJ

Tower Mills are used at Aberfoyle's newly commissioned Hellyer base metal sulphide concentrator. Hellyer ore is particularly fine grained. To achieve adequate liberation fine grinding is necessary. Three Tower Mills are used on regrind duties, grinding to less than 20 microns. The physical arrangement, material flows and grinding characteristics for the Hellyer Tower Mills are described. The mills have performed satisfactorily, both in size reduction and power efficiency. Wear parts must be inspected and changed more often than with ball Mills. To date, 92 per cent availability has been achieved. As parts and maintenance routines are rationalised, this is expected to improve to 96 per cent. Modifications to wear parts for the Hellyer Tower Mills are discussed.lhc Tower Mill grinding environment is highly reducing. The impact of Tower Mill regrind on downstream flotation is discussed.

Jan 1, 1991

By F Clark, B Catto

The Mako domain comprises the Mako lodes at Sunrise Dam Gold Mine, Western Australia. This domain was initially bulk or æbucketÆ domained for the open pit resource in 2000, due to complexity in defining the lodes as a result of low drill density. Negative ore tonnage and positive grade and ounce reconciliations were experienced during mining of the domain in the mega-pit, though only small volumes of the domain were mined. Significant amounts of exploration and underground grade control drilling has been completed since the initial bulk domain interpretation and greater geological understanding of the mineralisation controls and geology of the lodes now exists. Mako provides approximately 50 per cent of the ore tonnes and ounces for the North Wall Cut-back, the latest open pit phase of mining at Sunrise Dam. The importance of Mako to mill supply and life-of-mine planning, as well as past reconciliation performance necessitated a reinterpretation of the domain to increase confidence for mining. Historic exploration drilling, underground grade control drilling and detailed pit-wall mapping were used to build mineralised subdomains within the confines of the original domain. These reflect more closely the spatial extents and geological controls on the mineralisation. A new resource model using the multiple indicator kriging (MIK) technique was generated using the new domains. It resulted in a decrease in tonnes and ounces but increase in grade for the sum total of the new domains compared to the old æbucketÆ domain. This is attributed to the increased selectivity and structural constraints imposed by the new domains. A retrospective comparison of the Mako grade control from the mega-pit versus the new resource model was conducted, which æreconciledÆ 103 per cent tonnes, 106 per cent grade and 110 per cent ounces. This has provided confidence that the new model is a better estimate of the lodes. Qualitatively, the new model is a better representation of the geology and extent of the mineralised structures with significant areas of change identifiable. Grade-tonnage plots comparing the 2006 and 2008 models show that most tonnes have been shed from the low-grade û subeconomic grade cut-offs. This is mostly attributable to the volume reduction of æoreÆ in the 2008 model compared to the 2006 model, where the true mineralised zones are captured by the new domains. The reinterpretation and remodelling of Mako is an example of an evolved domain model and shows that mineralised zones need to be differentiated adhering to the geology and geological controls on mineralisation, which are understood largely due to increased drilling density coupled with mapping.

Jan 1, 2009

By G E. Holt

Active EM subsurface imaging is a proprietary technique developed by Marschall Acoustics Instruments Pty Limited (MAI) to image subsurface features at depths useful for the mining industry. Similar in field operations to high resolution seismic surveying, the Active EM technique employs electromagnetic energy rather than elastic wave energy. Received backscattered energy in the Active EM technique is thus due to differences and contrasts in electromagnetic permeability and permittivity in the subsurface, analogous to LamTÆs constants in elastic wave imaging. Carrying the analogy to seismic imaging even further, the Active EM method employs high power transmissions of very wide-band coded signals of a controlled polarisation. Likewise, the array pattern and polarisation of the receiving transducers is also tightly controlled. Thus, in a certain mathematical sense, Active EM is the electromagnetic equivalent of high power high resolution vibroseis seismic surveying. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

By J Andrina, D Richards

The Grasberg is a large copper and gold open pit mine operated by PT Freeport Indonesia and located in the high equatorial mountains of Papua Province, Indonesia. The climate is alpine/sub-alpine with little seasonal variation in temperature and rainfall. The annual precipitation varies from about 3000 to 5000 mm over short distances around the Grasberg, but in general, an average daily precipitation of 10 mm per day applies and leaching of the overburden is continuous throughout the year. Mining commenced in 1988, and almost all of the overburden mined up to 2003 was potentially acid forming. The current acid drainage from this overburden is being collected and treated. From 2004 to the end of the Grasberg pit operation in 2014, approximately 70 per cent of the overburden will be potentially acid forming and 30 per cent limestone. A program of laboratory leach columns, field test pads and an instrumented full-scale dump was developed with the objective of defining scale up factors to quantify the acid and metal leaching rates and to evaluate the stockpile geochemistry and control options. The results of an ongoing seven year program have demonstrated feasible scale up between laboratory columns, field test pads and the trial dump in relation to material geochemistry and ARD evolution trends at Grasberg. The potentially acid forming waste types are highly reactive and maximum acid generation rate occurs within two to three years and that maximum copper release occurs within one to two years of exposure. The results also show that the net acid generation (NAG) test provides a good estimate for the potential acid load from overburden types. The chemistry, temperature and oxygen data from the trial dump suggest that oxidation and acid generation is occurring throughout the dump but at a decreasing mass rate with increasing distance from the toe of the dump. It is apparent that convection and/or advection are important mechanisms for the transport of oxygen into and within the dump. Key results and findings of the investigations carried out are presented and the implications of the findings for long-term ARD management at the Grasberg mine are outlined.

Jan 1, 2003

The paper is aimed at mining engineers and other mining practitioners in the metalliferous mining industry who are considering the use of roadheaders and wish to understand the basic geomechanical and operational principles controlling their performance. The paper aims to address metalliferous minersÆ general unfamiliarity with roadheader technology, which is one of the factors which has limited the application of these machines in such mines. The historical development of drag tool mechanical excavation machines is briefly discussed, and factors affecting the application of roadheaders are mentioned. The mechanics of cutting with drag tools is then reviewed as are the effects of these and tool wear on tool performance. The implications of tool performance to roadheader performance are mentioned, the potential benefits of high pressure waterjet assistance are discussed and the relative performances of different tool types and materials are compared. Roadheader performance factors including productivity and utilisation are mentioned, and the state-of-the-art of conventional roadheaders is discussed in the context of machine weight, power and cutting head configuration. The influence of these and rock strength on machine productivity is analysed. Alternative, developing technologies are discussed which may extend the effective use of mechanical excavation into stronger rock masses which are beyond the range of conventional roadheaders. Finally, conclusions on these discussions are presented, along with recommendations for continuing research and development.

Jan 1, 1997

By Eckersley J, Boyd G

A brief review is presented of the mechanisms and causes of spoil pile failures which have occurred at the Goonyella Mine. In particular, the results of a recent geo- technical investigation of the spoil dumps in the Cleanskin pit are briefly presented. Spoil pile hydrology is discussed in relation to the use of effective stress concepts in the analysis of spoil pile stability. Experience in relation to stabilisation of dragline dumps is discussed as well as the likelihood of current techniques being success- ful in the prevention of gross failures if prestrip material is placed in existing spoil piles. Parameters exerting a major control on dump stability are outlined.

Jan 1, 1981

By Kavetsky A

A new model of flotation is presented which allows predictive calculations of total solids flows and metal grades and recoveries to be made for industrial flowsheets. A method of making these calculations is presented and illustrated with examples. The problem of determining sufficient flotability characteristics from a sample of circuit feed to predict the behaviour of that specific ground ore in the flotation circuit (ie performing flotometric analysis) is addressed, and some suggestions are made for its solution. A feature of the flotation model is its practical technological orientation, allowing determination of a small number of ore flotability parameters by fitting observed batch kinetic flotation data. The unit model explicitly includes the cell aeration as total bubble area per unit pulp volume, and pulp residence time. Although more complex unit models are feasible, it is thought that this model is sufficiently realistic to illustrate the points made. The modelling approach is illustrated by application to flotation data from a Kambalda ickel circuit. The model is parameterised and ore flotability parameters are back-calculated from batch kinetic data. These parameters are then used to fit the observed behaviour of the industrial circuit by numerically adjusting the unit aerations. Finally, it is shown how the model may be used to predict the effect of circuit and ore changes on the circuit's technological indices.

Jan 1, 1992

By Fernando N, Guang LX

Brown coal in Victoria in spite of its substantial reserves is not utilized greatly because of its high moisture content(-65% w/w). Transportation and handling costs of raw brown coal, on an available energy basis are so expensive that 93% of production is burnt for electricity generation on or adjacent to the coal deposit in Victoria. With direct firing of moist brown coal in power stations, approximately 20% of the gross calorific value of the fuse is used to evaporate the water contained in the coal. This energy is lost as vapour with the flue gas which is vented to the atmosphere. Also there is a 25% increase in flue gas volume and the size and cost of most of the units through which it passes must be appropriately larger. Since there are large quantities of water present the flame temperature is significantly reduced. For zero excess air and no air pre-heating the theoretical flame temperatures are: 609'o wow moisture 1450¦C 40% ª ª ª 1790¦C ZOO ª ª ª 1990¦C As a result of this there is a reduction in radiant heat transfer leading to a requirement for a two fold increase in radiant tube area. A boiler of much greater size and cost is thus required to house the additional tubes. Figure 1 illustrates the relative sizes of a boiler fired with 60% moisture brown coal with a boiler or similar output fed with a British bituminous coal, 14% moisture.

Jan 1, 1989

By Lyman G. J, Ka

The use of images to determine blast fragmentation is the only feasible technique when one does not want to disturb the production cycle. However, three major problems exist with the use of images. The first is determining real size from a two-dimensional particle, the second is estimating the fines which are missing due to image resolution and particle size range, and the third is proper sampling such that a statistical probability can be calculated for the distribution. Once these problems are resolved, the tedious process of digitizing images by hand may be automated. This paper describes the present techniques used at the JKMRC to "size" blast fragmentation, estimate the missing fines using the Rosin-Rammler equation, determine the sampling error using Gy's sampling equations, and extract the particles from an image using an IBM-AT computer.

Jan 1, 1990

The Australian Mineral Industry has to compete on world markets, so its mineral research has to be aware of overseas developments, it must be of world class, and it must utilise as many ideas as possible in order to solve those problems that uniquely affect Australian minerals processing. North American mineral and resource research may be taken as a guide to world government, industrial, contract, and entrepreneurial research trends and ideas. A number of interesting findings are noted that may guide Australian developments and strategies for the future, in minerals research and exploitation.

Jan 1, 1986

By B Petrie, D J. MacKenzie

The Macraes mine is producing 175 000 ounces Au/year from a mesothermal deposit with total resource of at least five million ounces. The deposit is hosted in greenschist facies Otago Schist, a widespread Mesozoic metasedimentary sequence that forms the basement of the South Island of New Zealand. Mineralisation was controlled by a late metamorphic shear zone which had both brittle and ductile structures accompanying mineralisation. The shear zone dips shallowly (about 15¦), subparallel to the shallow-dipping regional foliation, and mineralization occurred during southwesterly-directed thrust motion. Mineralisation occurred under greenschist facies conditions (about 350¦C) during uplift of the Otago Schist in the late Jurassic. No syn- or late-metamorphic igneous bodies occur within the schist belt. The hosting shear zone is up to 120 m thick, and is traceable for more than 30 km along strike. The shear zone is truncated by an underlying low angle normal fault that juxtaposes mineralised lower greenschist facies rocks on to unmineralised upper greenschist facies rocks.

Jan 1, 2004

By Paley N, Cameron A, Townson P

Although blasthole deviation is a problem which can seriously affect blasting operations, there is little practical emphasis on controlling this deviation and no practical emphasis on understanding its practical behaviour. The most common way of dealing with it involves tight control over drill set up and surveying hole paths. The surveying might involve simple collar location and inclination measurement to estimate the hole's actual path. At best, some operations routinely survey hole paths after all holes in a stope have been drilled. In addition, although there is an expectation that holes will deviate, there is no planning for this behaviour in order to reduce its impact on the blast. Design decisions are invariably made with the assumption that holes are straight. If and when surveys reveal problems it is possible only to adjust charging and initiation to 'work around them'. In extreme cases the drill might be recalled to fill in gaps. The lack of planning and the lack of understanding are doubtlessly linked.A model is presented that will predict the expected path of a drill hole. By knowing how a selected few holes deviated it is possible to make a good estimate of the deviation of other holes in the same rock mass. After minimal calibration the model can be used to increase the amount of information for a given amount of surveying or the amount of surveying can be reduced while maintaining the same level of knowledge of blasthole deviation. Equally important is the ability to plan for the deviation in future drilling through altering the initial collar angles or drilling from different locations. It is the authors' hope that planning for hole deviation becomes as much a part of the design process as planning for detonator delay scatter and explosive performance variation.

Jan 1, 1992