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The originally estimated mine life at Kidston (starting 1984) was 12 years. Through a continuing process of re-evaluation and improvement in the operation and by expanding the geological knowledge in the region, the mine life has been considerably extended. With falling grades and harder ore, the additional reserves have come with increasing risk - not only in an economic sense associated with diminishing profit margins but also operationally, requiring innovative milling technology and geotechnical designs to provide a lower cost environment for continued profitable mine production.

Jan 1, 1994

By Zingano A, Costa J. F

Brazilian amethyst production is mostly obtained from underground mines in the southernmost part of the country, involving approximately 6000 miners and generating an income of US$ 20 million per year. Amethyst-bearing geodes are hosted by Cretaceous continental flood basalts of the Serra Geral Formation. The economic zone occurs in the massive (colonnade) intermediary section of the Sao Gabriel Basalto. The tunnels and stopes follow the occurrence of geodes leading to an erratic and complex layout. A ground control survey revealed excessive roof convergence. Topographic results show excessive roof deformation and some roof falls have already been reported. To understand the ground conditions, prevent roof falls and better define the pillar dimensions detailed geomechanical mapping was carried out using the scanline method. Uniaxial compressive strength tests provided complementary information for rock mass classification. Results of the geomechanical classification were used to modify the mining layout taking into account the roof and pillar geomechanical characteristics. Retreat pillar mining minimised ground instability.

Jan 1, 1997

Oxygen is required for the leaching of gold ores in cyanide solutions. The source of this oxygen demand and the effect of dissolved oxygen concentration on the rate of the process are briefly reviewed.A method of measuring the oxygen consumption rate is described and some experimental results reported.Fundamental aeration theory and rating of aerators is summarised to show how this type of experimental work provides the basis for full-scale design of aeration equipment.

Jan 1, 1984

Recent work has shown that, in at least some instances of regional metamorphism, metamorphic diffusion has been restricted to such relatively minute distances (of the order of 1.0 mm and much less), that there is no clear, direct evidence of prograde metamorphic mineral reactions, and that metamorphic equilibrium does not appear to have been attained through even very small domains.A number of stratiform orebodies and their immediate metapelitic environments exhibit very large, seemingly "disequilibrium", assemblages of regional metamorphic index materials. One such, in north-eastern Australia, includes laumontite, prehnite, chamosite, stilpnomelane and related hydrous iron silicates, primary chlorite, sericite-muscovite, epidote, actinolite, biotite, almandine, andradite, metamorphic hornblende and clinopyroxene, scapolite, staurolite and sillimanite, all within a 20 metres length of a single diamond drill core. In this and several related occurrences it appears that metamorphism has involved very small scale in situ transformation of pre-existing materials rather than large-scale diffusion and reaction, and hence that the observed metamorphic minerals have probably been derived directly from precursor materials of sedimentary/diagenetic origin.It is concluded that the fluctuating seafloor interplay between warm, acid, concentrated hydrothermal waters with cold, alkaline, dilute seawater during stratiform ore formation, together with diagenetic processes, leads to the formation of a wide range of clay, chlorite, mixed-layer clay and clay/chlorite, and zeolite precursor materials and hence, later, to the complex assemblages of metamorphic minerals closely associated with some stratiform ores. Commonly included in highly localized assemblages of this kind are various minerals which, in conventional regional metamorphic studies, are generally regarded as indicating widely different grades of metamorphism.

Jan 1, 1982

By Quast K. B

Samples of limestone and micaceous hematite have been ground in a laboratory batch mill using equal weights of either rods or balls. Values of the Schuhmann distribution modulus, a, have been shown to depend on grind time and do not remain constant as often reported. The linear reduction in a with grind time was attributed to a change in grinding mechanisms with time. The product sizing from ball milling limestone showed a bimodal distribution, but rod milling produced a unimodal size distribution. The product sizing from milling micaceous hematite was difficult to interpret due to the major influence of the shape factor on the transition from screen sizing to cyclosizing.

Jan 1, 1995

By L Torckler, J Hobbins

Favona is a blind low-sulfidation epithermal vein deposit in the Waihi Vein System approximately two kilometres east of the world class Martha Hill deposit that has produced nearly 6.8 M oz Au to date. The Favona epithermal system has surface expression in variously altered and mineralised hydrothermal eruption breccias forming a series of low hills that are windows through post mineral dacites and ignimbrites. The tip line of the Favona vein is about 50 û 100 m below surface with a steeply east dipping principal vein structure carrying numerous hanging wall splays in the upper flatter section and thickening down dip where the vein steepens. Host rocks comprise feldspar phyric andesite flows with minor pyroclastics. Although Favona has a strike length in excess of 1000 m and vein widths up to 25 m over a vertical range in excess of 400 m it was only recently discovered after nearly thirty years of exploration by various companies involved in the Martha Hill joint venture that operates the Martha Mine. Since discovery in 2001 a feasibility study based on 27.5 km of diamond drilling in 83 holes has been completed reporting a reserve of 1 Mt @ 10 g/t Au against a resource of 1.8 Mt @ 10.3 g/t Au. Exploration is continuing with a further 20.5km of diamond drilling completed to date on nearby prospects.

Jan 1, 2004

By Sehic O. A

Geology can be the root of evil or a source of bliss; there is a choice; to ignore geology is at a mine's peril.Risk can be minimised and profitability maximised by the application of a detailed understanding of geology, alteration, structure, mineralogy, chemistry, fabric and texture.Geology is dynamic, not static.The impact of geology is pervasive.The integration of ore quality control with grade control is one strategy for improving the utilisation of both the mineable reserves and existing plant and equipment. Grade maintenance is but one constraint on the problem of how best to blend the ore. Other ore characteristics such as mineralogy, hardness for grinding, and pulp fluidity or density for slurry size classification can be included to explore alternative blending Strategies.

Jan 1, 1993

There are two mechanisms in the flo- tation process by which particles are transported from the pulp to the con- centrate: bubble-mineral aggregation and entrainment. It is the chemical processes which occur in the pulp which are critical to the success of flotation since they control the floatability of different min- erals and the selectivity which can be obtained. However, these chemical pro- cesses are so complex that metallurgists are still limited in their ability to predict the floatability of particles in industrial circuits by consideration of the minerals present and the chemical environment. The alternative approach to understand- ing flotation is to examine the behaviour of minerals in industrial flotation pro- cesses, to recognise similarities and differences, and to define the "laws" which appear to apply. Using this ap- proach it has been found that minerals float at a rate which is proportional to their concentration in the pulp, and that the rate of flotation of different min- erals is influenced by variables which' affect the pulp or the froth phase. The ultimate application of this approach is the use of models for circuit simulation purposes. It is this alternative approach which is the theme of this paper. One of the most important problems in understanding the technology of flotation has been in defining the characteristics of the particles being floated. Particles entering flotation vary widely in size and mineral composition, and different par- ticle types float at different rates. These rates do not change uniformly as operating variables change. It has been conventional practice to assess flotation performance in terms of the metal contents of total streams because no better method has been available, and this procedure has obscured important effects which occur in

Jan 1, 1984

By S Miller, A Neale

As part of a long-term acid rock drainage (ARD) mitigation study, PT Freeport Indonesia has completed the construction of a highly instrumented, full-scale, experimental, overburden stockpile to further evaluate the behaviour of the waste rock system at Grasberg mine. A total of 24 lysimeters, 30 sets of thermistor strings and 48 oxygen-sampling ports were installed at select locations during stockpile construction. ARD flow rates and chemistry have been recorded since the start of overburden rock placement in April 2000. Measurements of in situ temperatures and oxygen concentrations quantify reaction rates and the oxygen pathways that control oxidation kinetics deep within the waste rock profile. Direct field observations show the significance of advective oxygen flow with respect to the onset of oxidation kinetics. Oxygen measurements show that the rubble zone that forms at the base of a waste rock bench provides a critical pathway for oxygen entry to the waste rock profile. Furthermore, rapid oxidation as evidenced by measured temperature increases deep within the panels of waste rock is observed to occur. The observations presented in this paper provide critical insight for understanding the mechanisms and behaviour of full-scale waste rock stockpiles with respect to ARD generation. The results of this program will assist in the future selection, testing and evaluation of appropriate mitigation measures with respect to surface and face treatments to reduce long-term ARD generation. This project is a work in progress, and at least another two-years will be required to fully understand site-specific ARD generation and ARD mitigation mechanisms. This paper will discuss various design and construction considerations, provide an overview of results achieved to date, and some preliminary interpretation of what is happening within the overburden stockpiles.

Jan 1, 2003

The mineralogy, maero- and micro-textures of Thackaringa ore are simple and have many counterparts among base metal-quartz-siderite vein type deposits elsewhere.The ore consists predominantly of galena, sphalerlte, chalcopyrite, tetrahedrite, and arsenopyrite in a quartz and siderite gangue. Silver minerals, as such, appear to be lacking and silver values are no higher than in other sulphide ores of this type. These features contrast very markedly with those of the A.B.H. Consols Lode which appears to have emanated from the north end of the Broken Hill Main Lode Horizon during high grade regional metamorphism. The Consols Lode has been regarded as of Thackaringa type, and both are regarded as possibly arising from the remobilization of Main Lode Horizon ore. Whilst this may yet prove to be so it appears that the marked differences in mineral composition between the Consols and the Thackaringa types, would require somewhat different modes of regeneration.Thackaringa ore, as well as A.B.H. Consols ore, on this basis, would necessitate the development of a metahydrothermal ore fluid to account for their present apparently hydrothermal (or pseudo-hydrothermal) constitution...

Jan 1, 1967

By G Harbort, V Lawson

Mount Isa Mines Limited operates one of the worldÆs largest underground mines in North West Queensland. ItÆs mining and smelting complex produces copper anode, crude lead bullion (containing silver), and zinc concentrate. Copper is recovered in the Copper Concentrator from chalcopyrite ore, converter smelter slag and rotary holding furnace (RHF) slag via grinding and flotation operations. During 2002 a project to optimise cleaner circuit capacity was commenced. Its aims were to minimise copper losses and minimise slag/chalcopyrite cross contamination by reconfiguring existing flotation equipment and the addition of new flotation capacity. To minimise cross contamination a Jameson Cell was installed and dedicated to cleaning of slag concentrates, which had formerly been conducted by three flotation columns operating in series. The flotation columns were re-configured to operate in parallel and dedicated to upgrading chalcopyrite concentrate. In addition a Jameson Cell was installed to reject entrained copper from a prefloat concentrate consisting of talc and carbonaceous pyrite. This paper discusses the logic behind the cleaner circuit expansion, recent test work relating to the Jameson Cell and the installation and commissioning phases. Difficulties relating to the commissioning are reviewed and the solutions to problems are highlighted. The benefits the reconfigured circuit has provided to Mount Isa Mines are also discussed.

Jan 1, 2003

By Katsuyama K, Nag DK

Three aspects of rock mechanics, namely, in-situ stress estimation by acoustic emission (AE) method, strength of rock mass and role of chemicals to reduce the strength are covered. It is possible to detect the previously applied maximum stress by stressing a rock specimen to the point where there is a substantial increase in AE activity. This is known as Kaiser effect. From the AE signatures in the second and subsequent loadings, AE take-off point was identified more easily than in the first loading. In determining the compressive strength of rock mass, two factors have to be considered, namely, the size effect on the compressive strength of intact rock and the effect of discontinuities on the compressive strength of rock mass. Although a modified Bieniawski criterion gives best agreement with the triaxial test data, modifications have been suggested to Hoek-Brown criterion due to its popularity. It is possible to reduce the tensile strength of sandstone by saturating it with weak chemical solutions made with dodecyltrimethyl ammonium bromide, polyethylene oxide and aluminium chloride by up to 30%. In the case of compressive strength, there is no appreciable effect. The possible explanation is that the chemical solutions produce an effect on the strength of sandstone only when the failure mechanism is dominated by tensile mode.

Jan 1, 1998

By Moxon N. T

A series of low shock energy water resistant emlulsion based explosives have been developed by combining inert materials, such as Perlite P500, into the formulation. The material handling, water resistance and explosive properties of these mixtures were determined as a function of inert additive type, density, charge diameter and emulsion base. Of the emulsion bases tested Emulite produced the best and most stable low density mixtures ranging in density from 0.8 to 1.35 g/cm3 producing velocity of detonations (unconfined) ranging from 3000 to 5500 nits. The mixtures could be detonated successfully at these densities at diameters as low as 25mm. Low shock mixtures formed by combining Emulite with Perlite P500 were successfully trailed at the Cadjebut zinc mine in Western Australia. The performance of the explosive, at three densities, was monitored using both continuous and point to point VOD techniques. The fragmentation produced by the blasts were compared by photographic analysis. During this trial the low shock emulsion mixtures were shown to be as effective as the currently used explosives (packaged emulsion) at a significantly reduced cost.

Jan 1, 1990

By R N. Humphries

The aim of this paper is to question the need to develop bespoke monitoring and assessment methodologies and criteria, thereby ‘reinventing the wheel’, when designing and assessing the success of important natural habitat and ecosystem restoration schemes at mine sites in the UK and Australia. It draws attention to the existence and applicability of the Phase I Habitat, National Vegetation Classification (NVC) and Condition Monitoring methods in the UK and similar approaches used in Australia. These are long accepted established methodologies and have published accounts for describing, assessing and managing natural vegetation communities, habitats and ecosystems. They are often used at the environmental impact stage, but seemingly rarely, if at all, in restoration design and management at mine closure. Their application to mine restoration and closure is illustrated and discussed by reference to a surface coalmine in South Wales, UK.It is concluded that the application of a combination of the Phase I Habitat, NVC and Condition Monitoring methods is highly relevant to the expectations of the Convention on Biological Diversity (CBD) and its implementation in the UK, and probably in Australia too. The methodology and criteria described could be incorporated into the guidance and specified in the mining permits so that there is clarity as to the expectations and requirements for monitoring and assessment for bond release. Their use could be of wider application where there is a requirement to assess the success of restored CBD assets and ecosystems.CITATION:Humphries, R N, 2014. Why reinvent the wheel when there are established methodologies to aid the design and assessment of restored natural ecosystems on mined land?, in Proceedings Life-of-Mine 2014 , pp 675–692 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

Mt Todd lies towards the south end of the Pine Creek Geosyncline, sandwiched between the Cullen Batholith and the Edith Falls Basin, in an area of regionally metamorphosed sandstones, siltstones and shales. The Batman deposit, some 3 km west of Mt Todd is a sheeted quartz vein system hosted within greywackes of the Palaeoproterozoic Burrell Creek Formation (Finniss River Group). The gold-bearing quartz veins, trending 010¦-020¦ and dipping 60¦-70¦E, are commonly 0.5 to 5 cm wide and occur at intervals which are from 10 cm to 1 m apart. Gold tends to be restricted to the quartz veinlets and immediately adjacent country rock. Grade Control utilises two 4 m 'collar' samples which are collected from each 8 m production blasthole. The irregular distribution of the quartz veins and erratic gold mineralisation has resulted in a disseminated 'salt and pepper' type of gold occurrence, with only a poorly defined footwall. Delineation of ore and waste blocks for mining uses an approach which combines the smoothing effect of kriging with a pragmatic view of the raw data. Large ore blocks with simple geometry help to minimise mining dilution, reduce block variance and give good reconciliations to interpreted ore tonnes and grade. Daily mine face advance is reported against truck counts and provides continual comparison with budgeted production. All data processing uses Gemcom software, together with Lotus spreadsheets.

Jan 1, 1994

The paper first outlines the conceptual basis for evaluating and controlling geological risk. Geological risk, the economic reflection of the uncertainties associated with tonnage, grade, and other pertinent deposit parameters, is evaluated in terms of economic risk criteria. Delineation provides the deposit information required to appraise and control this risk. The improved reliability of geological estimates resulting from additional delineation reduces the economic risk associated with mine development and production decisions. However, the benefits of delineation, subject to diminishing returns, have to be weighed up against the direct and time costs involved. These costs decrease base case economic values and shift the probability distributions of possible outcomes towards, lower values. The optimum amount of delineation normally is achieved short of the point where economic risk is minimised, depending on the mining company's relative preference for a higher base case value or a lower economic risk. Then, two open pit copper mine examples, based on actual situations, are analysed to illustrate the application of the concepts presented. The first case concerns the extension of ore reserves at an operating mine. Finally, a new mine development opportunity is considered.

Jan 1, 1994

By Readett D. J

Soluble salts can be removed from Bowmans lignite by water and acid leaching. The success of the removal of water soluble or acid exchangeable impurities is directly associated with the efficiency of dewatering these slurries. The filtration characteristics of a slurry at its natural pH (4.0) were poor, with a filter cake moisture of 65%. Acid treatment of the slurry at pH2 caused the filter cake moisture content to drop to 61 %. Various oils, oily surfactants and a flocculant were tested to determine the conditions for minimum filter cake moisture. A series of pilot scale filtration tests were conducted on flocculant dosed slurries with and without washing on a horizontal test unit. Moisture contents of 54% were obtained in laboratory testing using high additions of oily surfactant. For the pilot scale test work, moisture levels close to 60% were obtained with low flocculant additions, similar to results obtained in laboratory studies. Removal of soluble salts could be correlated directly to the final moisture content of the filter cake. This process of leaching followed by filtration resulted in the removal of approximately 75% (more than 80% with washing on the cloth) of the sodium chloride originally present in the lignite.

Jan 1, 1989

Working thick coal seams in Poland is a very serious problem. Nearly 40 per cent of all coal is extracted from seams more than 3 m. thick. In absolute figures this represents about 70 million tons of coal per year. Working seams with thicknesses up to 3.5 m. does not present, at present, major difficul- ties. Working thicker seams calls for a steady improvement in order to increase the degree of utilization of the deposit and to enlarge the concentration of output. The problem is sometimes more difficult because, in many cases, the seams are worked under protected surface structures which compels the mines to use hydraulic stowing with all its advantages and disadvantages. Rock burst hazard, the control of which is the basic problem hindering the mining, is a further problem. The mining systems used in Poland are adapted to these natural and technical conditions.

Jan 1, 1976

By D Craw

Quaternary warping and uplift of antiformal schist ranges in Central Otago, New Zealand, has resulted in recycling of alluvial gold from widespread, generally weakly auriferous, Miocene fluvial gravels that unconformably overlie the schist, into aprons of fan sediments along the range margins. Basement erosion during uplift has been limited and so gold input from sparse gold-bearing quartz veins in the schist has been relatively minor. In an eluvial cycle on the slopes of the ranges, chemical remobilization of gold occurs during oxidation and erosion of the Miocene sediments. The typically fine-grained (300 - 400 ¦m) gold undergoes chemical modification and grain size enhancement of up to two orders of magnitude, and much of it is redeposited in a large number of relatively small alluvial fans along the range margins. Groundwater mobility within the fans results in minor additional gold mobility and grain size enhancement. During range uplift, a small number of relatively large axial streams and rivers have developed in structural lows between growing antiformal folds. Axial streams 'gather' their flow from consequent streams draining the folds, and flow parallel to a range axis for some distance before cutting across it in an antecedent gorge. The axial streams rework alluvial fan sediments along the range margins, and transport mainly fine-grained gold from the fans along the ranges. This gold is redeposited where the axial streams emerge from a range in the neighbouring structural basin. Axial streams drain relatively large areas of range surface, and thus reconcentrate significant quantities of gold in a small number of relatively large fans and fluvial deposits. The processes of gold collection and re-deposition by axial streams are essentially the same, regardless of stream size. Coarse-grained gold produced by chemical remobilization, is more difficult to transport in fluvial systems, and thus remains in close proximity to eluvial environment where it was formed.

Jan 1, 1995

By Cotton P. L

Although the terms "pipe" and "tube" are normally considered synonymous, a distinction is often drawn, the former term being applied to the hot finished product and the latter to cold finished material. It is, considered that the title of this paper includes hot finished seamless, and continuous-weld pipe, cold drawn seamless tubing, and electrically welded tubing.The continuous-weld process will be reviewed first, passing to the various methods of seamless manufacturing, which, in addition to meeting the demand for hot finished seamless pipe, also supply the raw material for cold drawn tubing, the manufacture of which will then be described. Finally the electric resistance-weld process will be Considered, and the paper will conclude with a brief review of the processes described and trends in present-day manufacture.CONTINUOUS-WELD PIPEThe raw material for this process is delivered in the form of coiled, hot finished, strip steel, generally referred to as "skelp". The end of one coil is electrically buttwelded to that of'the next, so forming an unbroken strip. This continuous ribbon of 'steel is fed into a skelp heating furnace, and brought to the correct temperature for the forming and welding operations which follow. This temperature is usually about 1,350°C.The heated skelp issues from the furnace into 'a multistand mill, in which the first pair of rolls is designed to form the skelp into tubular shape, the edges being in close proximity to, but not touching each' other. These edges...

Jan 1, 1951