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By Gupta A, Hall ST

The grinding characteristics of quartz which is normally associated with gold bearing ores in Kalgoorlie area was examined in a stainless steel laboratory size ball-mill in the presence of inorganic and organic surface active reagents. The cationic species considered were Fe3+, Cu2+ and Ca2+, and the anions were CO? and S2 as these are normally present during the process of grinding of gold ores in the region. The organic surfactants examined were K-amyl- xanthate, dodecylamine-hydrochloride and the Grinding Aid XFS-4272 manufactured by Dow Chemical The study was primarily based on an examination of the electrokinetic properties of quartz surface in the presence of the grinding reagents. Zeta potential at different reagent additions and pH values in the presence of individual reagents were examined and the corresponding grinding charcteristics determined. A correlation has been indicated between the grinding characteristics, as measured by the -53um size fraction produced, and the surface energy of quartz. It was observed that an

Jan 1, 1978

Mount Isa Mines Limited has been mining copper ore for 50 years. In recent years, this production has been entirely by open stoping methods with cemented backfill, mostly in the large 1100 orebody.This has been the major ore source for 20 years, with smaller amounts coming from the 400, 500, 650 and 1900 orebodies. At present, the 1100 orebody is the only source, and this situation will continue until the deep 3000 and 3500 orebodies begin producing in late 1992/93. Production rates have increased to almost 6 Mt/yr, and are planned to rise to 7 Mt/yr by 1995/96. In the future, there will be a move towards variations of the open stoping system as production moves to more lensy zones of the southern 1100 orebody and to the deeper 3000 and 3500 orebodies. This paper describes current operations in the 1100 Orebody, with some indications of future directions.

Jan 1, 1993

The planned extraction of deeper copper ore at Isa Mine has necessitated a review of existing equipment and methods to contain costs and improve working conditions. Mining is in progress for a crushing-conveying system to serve the deeper southern areas of the 1100 Orebody. This system will permit direct tipping of ore to the crushers and conveying of the crushed ore by cable belt conveyor to existing shaft loading facilities, a distance of about 2 km. To develop part of the conveyor drive a new machine will be used, the Robbins MM120 Mobile Miner, a joint development project between The Robbins Company and Mount Isa Mines Limited. The Mobile Miner uses a rotating cutting wheel to excavate headings 3.7 m high and from 4.7 m to 7.5 m wide. To ventilate the deep crusher complexes and associated development at high virgin rock temperatures, a refrigeration plant will be built on surface to reticulate chilled water underground. Bulk cooling of air to the 3000/3500 Orebodies and the southern crushers will be combined with the reticulation of chilled service water to the lower workings of the mine.

Jan 1, 1984

Syferfontein Colliery, part of the Sasol group of companies which specialises in the field of petro-chemical production, was established in 1990. The mine is situated about 150 km east of Johannesburg, South Africa. Two coal seams are mined, utilising two 75 m3 draglines, shovels and a fleet of 177 ton rear dump trucks. The mine will reach its full production capacity of seven million tonnes per annum in 1992. During the planning period, prior to the establishment of the mine, management were confronted with the unstable socio-political environment in South Africa which could jeopardise the eventual success of the mine. They consequently conducted a strategic planning exercise to determine guidelines for mine planning to improve the chances of success in this unstable third world environment.The strategic guidelines formed the basis for specific actions taken during the planning and commissioning of the mine. Specific actions were taken in the field of operating cost, labour relations, working environment, logistics and the general environment. First results indicate that these actions have played a major role in the success of the mine to-date. This process can be utilised by others facing similar or even totally different uncertainties.

Jan 1, 1992

In south-eastern King Island, sediments and lavas of possible Upper Proterozoic to Lower Cambrian age have been intruded by Lower Carboniferous granitic rocks.Within the contact aureole of the Bold Head adamellite north of Grassy the sediments and lavas have been metamorphosed to hornblende hornfels facies grade. The thermal gradient within the contact aureole was small, as the hornfelses exhibit no mineral zoning over a distance of 700 ft from the adamellite.Skarns occur both within the adamellite near its contact with the country rocks, and within the country rocks as partial replacements of three dolomitic limestone horizons. The latter type, the exoskarns, commonly have an andradite-salite mineralogy and carry economic concentrations of scheelite. These resulted from the replacement of carbonate beds due to both diffusion and infiltration metasomatism. Silica, tungsten, minor sulphides, and water were introduced from the adamellite, while aluminium and iron diffused from the enclosing pelitic sediments. Calcium released during marble replacement countered the loss of iron and aluminium in the pelitic hornfelses transforming them to diopside-rich rocks.Endoskarns within the adamellite are the result of two way diffusion across the contact; calcium, aluminium, and iron diffused from sediment to adamellite as silica, potassium, sodium, and water diffused from adamellite to the sediments. From estimates of the lithostatic pressure and mole fraction of CO2, the mineral assemblages of the hornfelses imply that the temperature of metamorphism lay between 530° and 710°C. This temperature range is in good agreement with minimum temperatures, between 610° and 710°C, for the recrystallization of the marbles of the contact aureole, calculated from the determinations of the solid solution of the magnesite molecule in calcite.

Jan 1, 1971

The late Carboniferous to early Permian Featherbed Volcanics cover an area of about 3000km near the western margin of the Hodgkinson Basin, in northeastern Queensland. The dominantly ignimbritic volcanic rocks are mostly confined to a single, composite, volcano-tectonic depression, but, along with the associated intrusive rocks, may be divided into two main groups: late Carboniferous I- type rocks and early Permian A-type rocks. Late Carboniferous I-type andesitic to rhyolitic ignimbrites and minor andesite lava crop out in the southeastern, southern, and southwestern parts of the complex, mostly confined to a basin-like depression, or "sag" structure, and are associated with coeval dioritic (and rare gabbroic) to granitic intrusive rocks. Extensive Sn, W and base- metal, and some Au, mineralisation are associated with these rocks, particularly in the southeast. The main part of the complex is of early Permian age, and consists almost entirely of A-type rhyolitic ignimbrite and relatively minor volumes of lava intruded by a peripheral ring dyke of porphyritic microgranite and by resurgent-type plutons of porphyritic microgranite and microgranodiorite. These rocks are associated with sparse base-metal, Au, U, W, and Sn mineralisation.

Jan 1, 1987

Particles finer than 10 um often cause problems in flotation. The current under- standing of the nature of the following effects is discussed: slime coatings on particles, carrier flotation, increased froth stability, entrainment of ultrafine gangue, excess reagent consumption, slower rate of flotation, more reactive surfaces. The review emphasizes the principles underlying these effects rather than details of progress in practical solutions to the problems they cause. The princi- ples of selective flocculation and floc flotation and the various approaches to achieving selectivity are discussed. Hydrodynamic effects on floc growth are reviewed. The evidence suggests that satisfactory performance in the ultrafines fraction will be achieved only by simul- taneously increasing the rate of flotation of the ultrafine valuable mineral and de- creasing the rate of entrainment of ultra- fine gangue.

Jan 1, 1984

In the past ten years or so there has been a renewed interest worldwide in the processing of refractory gold ores. The Archean province of Western Australia contains both numerous and major gold deposits, and has a long history in the development and practise of treating refractory ores (eg Blaskett and Woodcock, 1953). Depletion of shallow oxidised ores in recent years has re-focused attention on deeper sulphidic ores, and as a consequence has renewed interest in treatment methods for those ores which are refractory. Mineralogical factors he at the heart of reasons as to why these ores are refractory, and are the key to designing and improving treatment options in the longer term. This paper presents an overview of mineralogical factors that are relevant to the processing of refractory gold ores in the Archean of Western Australia. It is based on a number of research projects and other work on a variety of gold deposits, mainly in the Eastern Goldfields region, carried out over the past five years or so.

Jan 1, 1991

By Sibson RH

The gold province of Otago occupies an area of upwarped basement, the Otago Schist, comprising predominantly quartzofeldspathic and volcanogenic metasediments. This assemblage is the product of collisional tectonic deformation and associated metamorphism, mainly to lower greenschist facies, during the Rangitata Orogeny (200-100 Ma). Historically this region has produced 240 tonnes of gold, 4% (10 t.) of which was from the mining of Cretaceous gold- quartz mineralised vein systems. Auriferous vein systems in the Otago Schist are mainly hosted within NW trending normal fault-fracture arrays, however NW trending reverse fault-hosted vein systems also occur. We propose that the Late Cretaceous-mid Tertiary Otago Schist structure represents a regional anticlinorium containing flexural folds of at least two wavelengths. The anticlinorium structure has been quantified by determining variations in angular discordance between schistosity and the Otago Peneplain, a Late Cretaceous-mid Tertiary erosion surface covering most of the Otago district. A structural model for the evolution of the post-collisional anticlinorium requires the cooling surficial zone (carapace) of a retrograding metamorphic belt to behave as an elastic lid. Erosion of topographic load on the carapace drove isostatic uplift, which was greatest in the tectonically thickened core of the orogen. In this way differential uplift produced flexural deformation in the elastic carapace, expressed as a large scale arching of the orogenic belt. Flexure created tangential longitudinal strains in the outer-arc, leading to extension and the formation of mineralised normal faults. These structures are separated by a neutral surface from shortening and associated mineralised reverse faults in the inner-arc. Our structural model predicts that the distribution of auriferous lodes should be localised about zones of maximum flexural curvature, where the tangential longitudinal strains are highest. As a result, NW-SE hinge regions separating schistosity dip domains in the Otago gold province may have new found significance as potential exploration targets.

Jan 1, 1995

By J Kok

"In some underground mines it has been observed that the primary focus during feasibility studies is to determine the best way to mine the defined orebody. Some studies have been conducted without sufficient consideration of the ventilation and cooling requirements or the risk from exposure to associated airborne pollutants caused by the mining operations.Following the hierarchy of control to manage risk, numerous problems of the ventilation systems in some underground mines could have been avoided if sufficient consideration was given to the ventilation requirements to manage heat, airborne pollutants and leakage during the feasibility study phase. If the constraints and hazards were well defined and understood at the time of the study, efforts could have been made to eliminate or substitute the hazards to decrease the risk. Some of these problems include but are not limited to: primary fan locations heat loads diesel exhaust ventilation design based on the production requirement fire/emergency response strategies.This paper highlights areas in the ventilation discipline that are sometimes overlooked during feasibility studies. It will also highlight the importance of the Ventilation Specialist during these studies. Experience and knowledge of best ventilation practices must be applied in feasibility studies.As a result of adequate consideration to all ventilation aspects in the feasibility study phase, risks will become lower in terms of health, safety, production loss and equipment downtime caused by heat.CITATION:Kok, J, 2014. Feasibility studies – what should be considered in terms of ventilation, in Proceedings 12th AusIMM Underground Operators’ Conference 2014, pp 197–204 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 24, 2014

By E Ferrow, R Herbert, M E. Malmstr, M Fuchs

The study of microbial sulfide oxidation and oxidation rates of tailings requires the use of sterile control samples in laboratory experiments for comparison purposes. The need for sterile tailings sand is also apparent in the study of microbial communities and processes. This study compares six different methods with regard to sterilisation efficiency and investigates chemical and mineralogical changes in the samples as the result of sample treatment. In addition, the effect of sterilisation on mineral weathering rates is also studied. The efficiency of the different methods with regard to sterility is estimated by most probable numbers (MPN) of both sulfur and iron oxidising bacteria. The sterilisation methods that were compared are: washing with sterile water, washing with ethanol, applying antibiotics, repeated heating to 70¦C, autoclaving, and γ-irradiation. There are several possible drawbacks with the different methods, including the risk of an applied chemical acting as a substrate for micro-organisms in the system, and the risk of altering the tailings. The results show a substantial difference in sterilisation efficiency between the treatments. For example, autoclaving, repeated heating, ethanol and irradiation efficiently kill micro-organisms, rendering an undetectable amount of bacteria after one month of incubation, whilst washing with water exhibits virtually no microbiological effect, with a bacterial content comparable to the control. The use of antibiotics for sterilisation ranks intermediate: the lag-phase was twice as long in the antibiotics treatment compared with the controls. X-ray diffraction, optical and electron microscopy, M÷ssbauer spectroscopy, and mineral magnetism indicate no significant change in the bulk mineralogical composition. However, X-ray photoelectron spectroscopy analyses show that with some of the treatments, sulfides are partially oxidised, as indicated by the formation of sulfate and partially û oxidised sulfur species at the tailings surfaces. Aerated batch weathering experiments performed on sterilised tailings samples and untreated controls indicated that while the initial rates of element (S, Fe, Cu, Zn, Mg, Na, K, Ca) release may differ between the samples, over the course of ~100 days of experiment at pH 2 and room temperature, the rates declined toward a similar value for all samples. To conclude, there does not appear to be one perfect method for tailings sterilisation. Autoclaving and heating damage the mineral grain structure and oxidise the sulfide surfaces. Ethanol, antibiotics and rinsing greatly alter the pore water chemistry through the washing procedure. In addition, ethanol and denatured antibiotics might serve as a substrate and also, in the case of antibiotics, adhere to mineral surfaces thus obstructing chemical reactions. Irradiation seems to be the preferable method on an overall basis, although the formation of surface Fe3+ was suggested by M÷ssbauer spectroscopy.

Jan 1, 2003

By R Piper

The Yabulu Nickel Refinery commissioned in 1974, processes lateritic ore via a modified Caron process to produce high quality nickel and cobalt products. The Greenvale orebody provided the sole source of feed to the plant until 1990 and with well-blended mineralogy, it resulted in stable and predictable plant performance, allowing the operating focus to be on reducing energy consumption and increasing ore throughput. This approach provided better economics than pursuing increased reduction efficiency. From 1990, increasing quantities of lateritic ore were imported from Indonesia, Philippines and New Caledonia. This introduced considerable variation in ore blends and instability in plant operation but also provided the opportunity to treat higher grade ore blends which yielded higher reduction efficiencies. Ore reduction is conducted using 12 Herreshoff multiple hearth reduction furnaces, using heavy fuel oil as reductant. The æROASTERÆ Project was approved in November 2000 with the primary objective of improving Nickel reduction efficiency by: Stabilising Roaster Operation via a structured program including focused maintenance efforts, capital equipment upgrades, new process measurements, process re-design and improvements to operating skills and process troubleshooting. A structured technical program including laboratory and plant studies using one plant furnace as a pilot unit to develop improved knowledge of how the reduction process proceeds in the Herreshoff furnace. Armed with this knowledge, optimised process conditions and a reduction process model were developed contributing to a significant demonstrated reduction efficiency improvement. Technical input to the project was provided by QNI with Hatch providing the engineering and project management for the $8.5 M capital work. Execution of the work included extensive consultation with the plant operators and close cooperation between the Hatch project team and QNI operations personnel ensuring installations were completed with minimal production disruption. A strong focus on safety management resulted in a number of brownfields project relevant safety initiatives being implemented resulting in project completion without a serious injury.

Jan 1, 2002

An enormous capital outlay is required to bring a new deep level (¦ 4 000 m deep) Witwatersrand gold mine into production. In addition, future mining methods must cater for rapidly rising working costs of which labour costs make up the largest portion. South African mining engineers are therefore being forced to challenge accepted design and valuation principles when planning these high risk ventures. New mining methods must be sought to satisfy the ever increasing need for productivity improvement. The technological problems posed by such changes cover a wide range of disciplines. Aspects of shaft design and configuration, besides being examined in the light of productivity, must also consider the rock mechanics implications at depth. Mining methods must anticipate and prepare for extremely hostile conditions due to seis- micity and virgin rock temperatures.

Jan 1, 1986

For the last decade Australia has been the leading exporter of both steam and coking coal. In the ten-year period 1989 - 1998 steam coal exports increased by 93 per cent and metallurgical coal exports increased by 50 per cent. However, profitability of the steam coal sector has been disappointing. The coking coal sector, especially the hard coking coal segment, has fared better but its profitability was more because of its ability to maintain relatively high prices rather than its inherent productivity. Until quite recently the Australian coking coal sector was widely expected to be able to maintain this comfortable state without undue effort for the three major æpartnersÆ; the companies, the State Government and the unions. But coking coal could now be heading down the path followed by steam coal that ends with long-term over-supply and, despite steady improvements in productivity, poor profitability. Steam coal entered the ænewÆ era of long-term over-supply some years ago. Over-supply was due to the rapid increase in production in Indonesia, often from new mines and Australia. AustraliaÆs production rise was underlain by the apparent belief that the best way to lower costs was to increase production. In the first couple of years costs didnÆt fall much but the additional tonnage was sold at lower and lower prices into the spot market. By mid-1998 the difference between the contract price set with Japanese utilities and spot sales was often in excess of $US12 per tonne. Japanese contract prices and tonnages have since fallen significantly. Steam coal has moved from being a product to being a commodity. Any profits are due more to the low Australian dollar rather than inherent mine productivity. Seaborne coking coal trade has been dominated by Australia, Canada and the USA, with the USA becoming less competitive. Unfortunately, when the Queensland capacity expansion was well down the pipeline, the Asian financial crisis occurred and the Japanese economy entered what appears to be a long-term recession. Contract prices fell 18 per cent, tonnages decreased and some mines have been reclassified as supplying lower priced coking coal. The paper analyses past and expected future trends in labour and mine productivity, rail freight and FOB export port cash and total costs of the Australian steam coal and coking coal sectors and discusses the market outlook for Australia. The future economic viability of the industry is analysed and discussed in the light of the rapidly changing global environment.

Jan 1, 2000

By Hoberg H, Schnieder FU

The disposal of residues from coal preparation and processing will to an increasing extent require investigation and consideration of the environmental problems resulting as a consequence of this. Different authors (Diingelhoff and Plankert, 1983; Hasenpatt, 1985; Szczepanska and Twardowska, 1987) have concentrated primarily on the content and the mobilisation of inorganic contaminants such as chlorides, metals and heavy metals from spoil tips, while no publications have yet been found on the question of a possible emission of organic contaminants (PCB, PAH, HC HC) from processing residues. Here the flotation residues in particular are able to bind larger quantities of organic contaminants by physi-sorptive means because of their large specific surface and, after disposal, to be re-emitt than into the environment. The flotation agents used in coal flotation are mixtures of technical distillation products with a correspondingly fluctuating composition. As Hey, 1986 showed, they may contain, in addition to the main components (n-alkanes, alcohols, surfactants), over 50 individual trace substances. In conjunction with the structural-chemical similarity of the individual components, this complicates the quantitative analysis of individual components considerably. For the analysis of hydrocarbon content of flotation products by means of extraction with organic solvents in accordance with DIN 38408, H18, the difficulty arises, besides the insufficient sensitivity at low concentrations, that geogeonic hydrocarbons are extracted from the coal as. well and the analysis results are thus falsified. These problems were overcome by the application of the 14C radiotracer method where certain components of the flotation agents are marked with radioactive carbon (14C). By measurement of the radioactivity of solid and liquid samples, the concentration of the marked substance can be measured very sensitively and precisely, whereby the accumulative measurement of similar organic substances is ruled out. Thus the reaction path of certain substances in complex reagent mixtures such as flotation agents can be traced excellently and the conceivable environment burden resulting from flotation tailings disposal can be estimated. In this paper, the adsorption behaviour of typical components of coal flotation agents are investigated for different coals and types of gangue material, the reagent content of flotation concentrates and tailings, as well as the mobility of the reagents adsorbed onto solids. The knowledge of adsorption and desorption mechanisms of unpolar hydrocarbons emulsified in water to solids are also of particular interest for the understanding of processes of organic soil contamination and for the further development of washing processes for oil-contaminated soils.

Jan 1, 1993

Fission track thermochronology is a well established method for reconstructing the thermal histories of rocks with particularly important applications in tectonic studies, detecting low-grade thermal events, sedimentary basin analysis and resource exploration. These applications take advantage of the limited stability of fission tracks, especially in apatite, when exposed to the temperatures found in the upper 3-4 km of the crust. Apparent fission track ages in apatites can define an invisible 'stratigraphy' in otherwise homogeneous rock masses that can give valuable information on thermal, tectonic and erosional events. Quantitative modelling of the thermal annealing of tracks in apatite shows that distinctive profiles of apparent fission track age can be related to a number of simple thermal history styles. The main types of profile observed tend to be either an essentially linear decrease of apparent age with increasing depth, which relates to continuous uplift and denudation, or a concave-upwards profile produced by partial annealing in environments of tectonic stability or burial. More complex thermal histories produce compound profiles which are essentially just combinations of these two elements. Track length information allows the apparent age profiles to be interpreted in much greater detail. Examples of the major profile types have now been identified in various geological environments and can be analysed to give information about, for example, uplift and denudation rates, the timing of uplift or low-grade thermal events and maximum palaeotemperatures experienced during burial.

Jan 1, 1990

By Floyd JM

Conventional smelting reactor systems were designed to recover only one main element from their feedstocks. They did not possess sufficient flexibility to allow optimisation of co-production of multiple values from a complex feed.New reactors such as Sirosmelt and Top Blown Rotary Converters are providing new possibilities for making separation between components and this is of great significance for the complex feeds which are becoming prevalent in the metal extraction industry.Process routes using chemical procedures which take advantage of the flexibility of these reactors will be discussed in relation to a number of possible feedstocks.

Jan 1, 1985

Organic dyes such as nigrosine and sun yellow act as depressants for carbonaceous particles in the, flotation of sulphide ores. Depression is achieved when initially hydrophobic organic surfaces are made hydrophilic by preferential adsorption of dye molecules. Experimental studies, mainly on Mount Isa ores, indicate that dyes are adsorbed as planar anionic micelles attached to carbonaceous surfaces by van der Waals and ion exchange attractive interactions. Relationships appear to exist between the amount of organic matter on the surface of ground particles, the surface area of the particles, the "saturation" adsorptions of dyes, and the degree of difficulty experienced during froth flotation.

Jan 1, 1975

The areas of impact when employing high productivity long wall systems are reviewed and the financial implications of the most significant areas highlighted. A distinction has been made between availability and utilization. The need for more efficient delay recording, together with increasing control and utilization of the systems has been identified and the measurability of the latter discussed. The increased use of electronic delay reporting direct from the operating unit as the basis for operational control and a pre-emptive maintenance philosophy is seen as an important area of achieving higher performances from existing long wall production systems and Configurations.

Jan 1, 1988

By Hayes P. C

In commercial mineral processing operations it has been found that the conditions in the drier have a considerable effect on the subsequent electrostatic separation of nttile and zircon. Laboratory scale studies simulating these heat treatment processes have shown that the electrical conductivity of nitile varies markedly with treatment temperature, time and gas composition. The zircon on the other hand is unaffected. By increasing the electrical conductivity of the rutile, significant increases in separation efficiency can be achieved. Electron microscope investigations have shown the increase in electrical conductivity to be associated with the production of planar defects in the crystal lattice.

Jan 1, 1991