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The mining of mineral sands in coastal aquifers is often constrained by other land use conflicts and inappropriate controls imposed through a lack of understanding of environmental interactions and processes. The recent experience with the Tea Gardens mining operation illustrates how increasing our knowledge and understanding leads to more effective management of environmental problems. As well as a source of heavy minerals, the Tea Gardens sand bed serves as a town water supply source. From past experience it was believed that mining could cause undesirable increases in dissolved iron concentrations in the aquifer, but the reasons and mechanisms for this phenomenon were not clear. A water monitoring program was therefore designed for the mining operation which was aimed at protecting the water supply borefield from any detremental effects. After one year the results of the monitoring program were assessed in the light of new knowledge and understanding of iron hydrochemistry. It was found that the existing program was not achieving some of its major aims, and was therefore modified to a more effective and cost efficient program.

Jan 1, 1988

By Huntington J. F, Green A. A

The quality of a photointerpreter's anno- tation of an image may be displayed by writing maps in which the pixels are shaded according to the number of times a pixel was seen to be on a feature. The map of grey tones is more valuable, if, for each grey level, a measure of quality is determined, which is the probability that a feature exists in a pixel of a given grey tone. From repeated annotations (at least four) of the same image by a single observer, it is possible to formulate a perception model which describes stochastic processes in the observer. From that model, it is possible to assign estimates of data quality for each observer to each grey tone. For two observers on the same scene, the 'mean' method of quantifying the grey levels is to assign a value equal to the mean of the ii,:lities for each of the two observers separately. For this example, the grey tones arr thus quantified at probability levels of 0.70, 0.80, 0.90 and 0.95.

Jan 1, 1977

By Grano S. R, Lauder D. W

Investigations on the oxidation behaviour of chalcocite and its rejuvenation by hydrogen sulphide ion have been undertaken. Chalcocite oxidation was measured using X-ray photoelectron spectroscopy (XPS), zeta-potential and by dissolution in et

Jan 1, 1997

By Large RR

Underlying the 15 million tonne, high grade Hellyer volcanogenic massive sulphide deposit of western Tasmania is an extensive, well developed, and well preserved stringer system. Pervasive alteration of the footwall mafic volcanics occurred as the hydrothermal system initiated. Mineralogical zoning exists within the footwall alteration pipe, with a central siliceous core giving way to zones of chlorite, chlorite-carbonate, sericite-chlorite, and finally sericite-quartz on the margins (stringer envelope zone). However, the alteration morphology and zonation is not symmetrical around the central siliceous core; eastward the alteration zones are steeply dipping and terminate abruptly under the massive sulphide, while westward they extend out under the ore body in a blanket fashion. Geologic evidence indicates that the pervasive alteration started with the development of sericite-quartz which was subsequently overprinted by chlorite and finally quartz-sericite as the hydrothermal system became focused towards the centre of the stringer system.

Jan 1, 1990

The Rosebery Mine on the west coast of Tasmania is a world class polymetallic base metal deposit, containing six major minerals: galena, sphalerite, chalcopyrite, gold, silver and pyrite. This resource has been exploited for nearly a century, yet a reliable estimate of the reserve continues to present a challenge.Over the past twenty years, the operation has changed from relatively low productivity cut and fill timber-support scraper mining, to higher productivity bulk mechanised open stoping. At the same time, economic constraints have changed and grades have fallen, which have increased the pressure to refine the resource/reserve estimating processes. This paper compares the restrictions of the polygonal section method of the past with the advantages of a kriged block model. The limitations of Mine Call Factors, the problems involved in converting decades of diamond drilling data on paper into a computer data base, and the effect of this new methodology at Rosebery, are described.

Jan 1, 1990

Lime is the common reagent used for pH control in cyanide gold circuits. Lime can be supplied as either quicklime (CaO) or 'hydrated lime(Ca(OH)2). Both are dry powders with variable flow properties. These properties demand special attention when designing machin- ery to handle them.

Jan 1, 1987

By N DavT

Pyritic tailings from the Quirke mine waste management area in Elliot Lake, Ontario were subjected to long-term column leaching experiments in two PVC columns measuring 122 cm in height and 15.2 cm in diameter. At the end of the leaching experiments, the columns were taken apart and sampled at 5 cm intervals for quantitative mineralogical and geochemical characterisation. Each column is represented by a total of ten samples. Polished sections, prepared from the samples, were studied by optical microscopy, scanning electron microscopy, electron microprobe and X-ray diffraction techniques. Mineral quantities were determined based on linear mixing models of whole rock and mineral compositions. Pyrite particle sizes were measured by image analysis interfaced to an electron microprobe. The tailings are coarse-grained (ie 96 per cent passing 75 ¦m) and composed of quartz, K-feldspar, muscovite and pyrite. Pyrite is homogenous and occurs as liberated particles displaying angular to subangular boundaries with strong dissolution features at the end of the leaching experiments. Based on up to 3518 particles measured in a sample, pyrite particle sizes range from 1.7 to 78.6 ¦m. Pyrite concentrations vary from 0.1 to 7.8 wt per cent, depending upon their location from the top of the columns. These correspond to pyrite losses of up to 99 per cent from their original level of 7.2 wt per cent in the upper half of the columns. Pyrite oxidation rates in terms of moles of pyrite oxidised per mole of pyrite per square metre per second were calculated from the effluent data and the measured pyrite particle sizes. The rates vary from 1.71+10-12 to 5.78+10-10 mole+m-2+s-1 within the 1.5 to 3.5 pH range for 10 ¦m particles. These results are comparable with the published oxidation rates at pH 2 where the dissolved oxygen is the only oxidant.

Jan 1, 2003

By Aguirre E, Chitombo G

The magnitude of stress variations associated with a blast wave near production pillars is analysed by modelling blast vibrations measured in the surrounding rockmass. The results indicate a wide variation in stress which is thought to contribute to the observed damage in pillars adjacent to the draw points.

Jan 1, 1995

By Lee H. G, El-Rahaiby S. K

The literature relating to reduction of sulphides by carbon using lime as sulphur-absorbent is reviewed. A stage-wise thermodynamic model is employed to evaluate the practical feasibility of the direct reduction smelting of galena (PbS) concentrates with a carbon reductant in the presence of lime; a coke-rate of 65 kg/ton Pb is predicted by the model. The experimental data on the reduction of PbS:4CaO:4C mixtures under nitrogen were correlated by means of a finite difference numerical method and the values of the intrinsic rate constant I1 were derived. The results for the uncatalysed reduction are represented satisfactorily with log I1 = 1.247(±0.522) - 5540(±610)T-1.The catalysed PbS:4CaO:4C mixtures contained 2.5 wt% of ternary (K, Li, Na)2CO3 catalyst. For the catalysed reduction it was found that log I1 = 3.981 (±0.301) -7790(±353)T-1, where I1 (in both relations) is expressed in moles.(g.C.)-1.atm-1.s -I. The catalytic enhancement faclor was found to be quite large in the 1068 to 1262°K temperature range investigated here.

Jan 1, 1991

By Gibbons S. L, Ritchie I. M, Murr D. M

Fundamental studies on the transformations of iron oxides have been carried out and related to the solution conditions in the Becher process. The results show that a number of iron oxide interconversion reactions occur in the aeration reactor with the products depending on the pH, temperature and oxidation potential of the aeration liquor. It is concluded that the lack of process control in the aeration reactor of the Becher process significantly hinders the ability to predict and produce high quality single phase iron oxides of a consistent colour.

Jan 1, 1990

By Wang S

Fragmentation is the basic concern in rock blasting and serves as the main measure of blasting effectiveness. A good estimation of fragment size distribution before blasting is very useful and helpful for selecting the proper equipment for loading, transporting, and crushing rocks. A fragmentation model is presented that is based on a hole by hole analysis and correlates the rock properties, burden, spacing, and explosive column with the blasted volume and fragmentation obtained. The drill bench is divided into three separate areas corresponding to different breakage mechanisms. They are: 1) a main breakage or casting area, 2) a secondary breaking area, and 3) an overbreak area. The boundary of the main breakage area is found from the magnitudes of strains in the stress waves and the tensile strength of the rock. The secondary breaking area is determined by stress wave reflections at discontinuities and interactions between colliding stress waves from adjacent boreholes. The overbreak area is that beyond the main breakage area "where the reflected tensile waves no longer break the rock. This analysis is applied on a hole by hole basis to locate the breaking points. Then connecting the breaking points on each side of a borehole forms the triangle of the main breakage area. This is repeated for the next hole and the remaining area is the secondary breakage area. After the angle and area for each hole are found the Kuz-Ram model is used to predict the fragmentation size distribution for each hole. Then summing up the size distribution for each hole gives the total fragmentation distribution. This analysis has been successfully applied to field tests performed in a limestone bench where the entire spoil pile was screened to determine the fragment size distribution. Knowing the explosive and rock properties the breaking area was found for each hole, the strain and stress values, the breaking point, and angle of breakage (104 degrees). The fragmentation size distribution was then calculated and compared to the field data with excellent agreement.

Jan 1, 1990

By M R. Davidson, M P. Schwarz

A model for column bioleaching is investigated to identify and understand aspects of bacteria in bioleaching applications, which have implications in heap bioleaching operations. The model is used to simulate scenarios that would otherwise be time consuming to perform experimentally. This study uses a model of bacterial transport and attachment/detachment to ore particles, with a bioleaching model for the depletion of a copper-sulfide, also accounting for liquid and gas flow and gas/liquid oxygen mass transfer. The model includes aspects such as oxygen and ferrous ion consumption, coupled with leaching of a copper-sulfide via the shrinking core model. The model is used to investigate how the rate of leaching is affected by the bacterial concentration in the columns, by the bacterial regeneration of the leaching oxidant ferric ions. The model is also used to assess the impact of oxygen limitation and inoculation method on the copper leaching. Some comparison of the model with experimental data will be shown.

Jan 1, 2004

By Wright G. A

The objective of refining in steelmaking is to reduce the concentration of impurity atoms, e.g. sulphur, phosphorus, from an initially high level to a specified low concentration. A two-film theory of refining is presented in which the rate of

Jan 1, 1980

By A Sinuhaji, H Kalangi, T B. Setyoko

Ore fragmentation at the DOZ block cave mine is highly variable, both as a function of rock type and column height of draw. Initially, the mine was constructed and equipped with limited capability to handle drawpoint oversize material. Significant issues with drawpoint availability and achieving overall mine production targets resulted. A suite of secondary sizing tools was added to the mine equipment fleet over a one-year time frame. Although significant oversize continues to be experienced, use of the correct secondary breakage tool for each particular oversize or hang-up occurrence has resulted in increased drawpoint availability, production rate, draw compliance, and operator safety. Currently, a range of secondary breakage techniques is being utilised to size material for delivery to the primary crusher. Run-of-mine material (3) is directly mucked to ore passes fitted with grizzlys that have one-metre square openings. Ore containing small boulders (>1 m3, 3) is loader-trammed to ore passes fitted with rockbreakers. Medium-sized boulders (>2 m3) accessible from the drawpoint are drilled with Sandvik Tamrock Commando drills. Boulders hung-up within the drawbell are drilled and charged with a Sandvik Tamrock Secondary Breakage Unit. Compacted, fine-grained muck is blasted utilising 55 mm cartridge powder concussion bombs.

Jan 1, 2005

After extensive testing and a period of plant trials to establish the benefits of Caro's acid (H2S05) as an alternative oxidant, Queensland Mines Limited (QML) decided to replace pyrolusite with Caro's acid in its acid leach uranium treatment plant at Nabarlek. The decision was based on the reagent savings and environmental gains associated with the removal of manganese from the process liquors, as well as the labour savings and improved oxidation reduction potential control possible in leaching using the Caro's acid system. The permanent Caro's acid generating plant was designed by Interox Chemicals Pty Ltd of Australia (IC) to suit QML's require- ments and differed from the unit used during the plant trials. Commissioning of the plant was completed in April 1983 and it has been continuously used since that date.

Jan 1, 1984

The paper describes the design of the dilute medium and medium recovery circuits installed at the coal preparation plants at the Cornwall Coal Company's Fingal Mine, and the BP Coal Australia's Howick Mine. These circuits maximize the use of clarified water for rinsing to improve the mass transfer of adhering medium from the coal surface into the carrying liquid, and have been combined with the use of a two stage magnetic separator. The separator utilizes a conventional concurrent first stage and a counter-rotation second stage. This combination results in high medium recoveries during both normal operation, and start up and shut down phases when large quantities of medium can be lost from a conventional circuit. Overall losses using this circuit have been estimated to be, 200g/t, over a twelve month period. Further advantages in plant operation are also obtained, especially steady operating conditions in the centre-tube pump tank, lower slimes contamination of the product, and lower quantities of non magnetics trapped in the separator concentrates. The techniques are particularly suited to incorporation in circuits treating coals containing high percentages of sticky and difficult clays, as are found in the Walloon coal measures.

Jan 1, 1987

By S Hapugoda, A Edenton, M Adam, R J. Holmes, J R. Manuel, R Smyth

Lump ore is one of the key ferrous feeds used in the blast furnace ironmaking process, normally accounting for ten to 20 per cent of the blast furnace burden. Like other feeds, the characteristics of lump ore have an important impact on the stable operation and productivity of the blast furnace. Lump ore is usually assessed chemically, physically and mineralogically to establish its likely blast furnace performance. The physical characteristics of lump ore are strongly related to the chemistry, mineralogy and texture of the ore involved. In this paper, the blast furnace ironmaking process is reviewed, with particular emphasis on the key quality requirements for the ferrous burden material. A variety of key physical characteristics of lump ore measured using standard and non-standard methods are then described and subsequently correlated with the chemical and mineralogical characteristics of the ore wherever possible. Finally, the impact of these physical characteristics on blast furnace operation is assessed.

Jan 1, 2009

The economic significance of a fundamental understanding of the mineral pyrrhotite is dis- cussed. Particular emphasis is placed on the relationship of other sulphide minerals to the pyrrhotite when it is the major sulphide mineral present in an ore body. Studies of the Kambalda nickel deposit are used to give a better under- standing of (a) the genesis and other character- istics of a particular ore body (b) the textural relationships between pyrrhotite and other sul- phide minerals (c) magnetic properties of natural pyrrhotite, and (e) the oxidation and supergene processes that take place in a sulphide ore body.

Jan 1, 1972

The screening of iron ores, sinter and coke, and investigations undertaken to improve screening efficiency and cloth life are discussed. The major modifications to coke screening proposed with the construction of No. 7 coke ovens battery are briefly described. The major problem areas were identified as screen cloth blinding and pegging, feed presentation and screen overloading. Blinding and pegging have had a significant effect upon screening efficiency with the screening of sinter, coke breeze and wet iron ores in particular. Pegging can be reduced or eliminated by the correct selection of aperture size and shape, screen excitation and slope, and screening medium. Blinding encountered with wet coke breeze was a particular problem in which no significant progress was made.

Jan 1, 1984

Gold at Renco occurs in association with pyrite, pyrrhotite, chalcopyrite and quartz and is confined to a series of brittle fractures and fault breccias (reefs) preferentially developed within an anastomosing ductile shear zone. During late Archaean crustal movements both the orebody and the enclosing host rocks were deformed within a series of east-north-east striking, southerly dipping, shear zones. The reefs within these shear zones are now texturally different to those away from the shear zones, and this difference is reflected by differences in the way the gold is distributed in the two reef types. These differences are not taken irto account by the software package currently being used to generate kriged plans of gold grade and reef thickness and this may explain some of the inaccuracies found in these plans.

Jan 1, 1990