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Investigation on Sheelite Floatability by Particle Size Fraction

Sep 13, 2010

Material sampling theory is well established in mineral process monitoring, improvement and control. It has been much enhanced by fundamental contributions due to Gy. When GyÆs sampling theory is applied to sampling inspection and monitoring, it provides estimates of average quality or extent of contamination. It also provides estimates of uncertainty, but these often ignore uncertainty in estimated variograms or other measures of variability. Risk assessment is often an implied task in sampling inspection and quality monitoring. A valid technique of risk assessment needs to take into account the uncertainty in the variational measures themselves. Standard statistical tolerance limit calculations which do take such uncertainty into account can be adapted to develop a technique for handling uncertainty in variational measures such as the variogram. Data from a published example is used to illustrate the technique.

Jan 1, 2005

By A Grice

AMC has completed a number of backfill options studies, including several in recent years for large, three-dimensional orebodies involving total extraction by longhole open stoping with backfill. This has led to the development of a thorough review methodology that assists in the selection of the most appropriate backfill system and the most economic mixes to achieve the required performance. A recently developed design tool has simplified the calculation of backfill strengths for various exposure dimensions and automatically determines strengths incrementally over the height of a stope. Using a generic orebody with a plan dimension of 120 m wide by 360 m long, several different stoping layouts have been analysed to determine the effect of stope dimensions and sequencing on backfill strength requirements. This has been done for stope heights from 50 m to 300 m, in 50 m increments. The required strengths have been calculated in slices and summarised for each stope in four equal layers. The average strength requirement for each layout at each stope height has been compared graphically. For all stope heights, a panel stope layout that minimises the proportion of primary stopes results in a lower average strength requirement than grid layouts on a checkerboard pattern. However, for very high stopes, smaller plan dimensions become more economic. The increase in required strength with stope height is non-linear, making taller stopes potentially more attractive. The main cost factor in most backfills is the rate of binder addition, which is closely related to the strength required. By choosing a layout that minimises the backfill strength requirement, significant savings in binder addition rates and overall costs can be achieved. These must, of course, be weighed against other factors to determine the optimum stoping layout and backfill system.

Jan 1, 2000

By A Reid

The Late Archaean of South AustraliaÆs Gawler Craton contains significant potential for gold resources. The main targets of interest are migmatised gold style systems of which the Challenger deposit is the best known example. This deposit is one of the lower cost gold producers in Australia due to the high-grade, low-tonnage nature of the mineralisation. Structurally controlled, metamorphosed deposit styles are also possible throughout the Archaean of the Gawler Craton, including occurrences within reactivated shear zones. More typical, lower metamorphic grade orogenic gold styles are also possible within greenstone host sequences identified in the central and southern parts of the Gawler Craton.

Jan 1, 2007

The problems arising in the excavation of hard rocks with the use of mechanical tools consist chiefly in a slow advance rate accompanied by an intensive wear due to the toughness and abrasiveness of the rock. In order to allow the further extension of mechanical excavation beyond the limits of the presently available technology, the assistance of waterjet aiming at improving the performance of the equipment while reducing the wear rate of the tools, has been recognised as one of the most interesting technical solutions. The paper illustrates the improvement of the performance of both disk cutters and picks obtained with the waterjet assistance at the Waterjet Laboratory of the University of Cagliari on a medium-hard rock.

Dec 6, 2010

By R Brown

The Singapore Land Transport Authority Contract C917A is for the design, construction and completion of all outstanding works under the original Contract 917, including taking over the design and construction responsibility for the works carried out by previous contractor. Construction works connect the bored tunnels between the stations at King Albert Park and Sixth Avenue on the Downtown Line two in Singapore.The original contractor became insolvent leaving the works incomplete. On 29 August 2013 McConnell Dowell were awarded the completion contract following a fast-tracked tender process. The completion contract required a quick start and therefore the recruitment of some of the original workforce. A large majority of the original workforce was from Malaysia, Indonesia, China, Philippines, Bangladesh, India and Thailand. In order to ensure that the safety standards were upheld, and that the new workforce embraced a safety culture, a behaviour based safety (BBS) approach was implemented.The BBS approach was implemented to overcome the existing poor cultural safety behaviours, and to ensure that high standards and expectations for safety were implemented. This ensured that the workforce were comfortable in identifying hazards, avoiding shortcuts, and changing poor safety behaviours.This article outlines how a BBS program was delivered on the C917A project, containing defined goals, communication tools, and assessment and feedback models.CITATION:Brown, R, 2014. Behaviour-based safety with a foreign-based workforce, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 65–68 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Pollard DM, Willis GM

The removal of bismuth from liquid copper in a vacuum furnace was studied over a range of pressures. The rate determining step changes from diffusion in the gas at pressures above 0.2 Torr to approach the Langmuir evaporation rate at pressures of 10-2 Torr. Oxygen and sulphur were found to have a negligible effect on the rate. Bismuth removal from copper sulphide was found to be considerably slower than from copper. This is consistent with the known thermodynamic properties of ternary sulphide melts.

Jan 1, 1980

By Swanson AR, Nicol SK

A study has been made into the influence of feed size distribution on the flotation response of coal. The results show that a full description of the flotation response of a coal must not only consider the inherent floatability of the coal, but also, the size distribution of the feed to flotation. The performances of a number of flotation circuits were compared using a coal which was "poorly floating" because of its size distribution. Split feed flotation, two stage reagent addition, and reflotation of classified tailings all gave better yields than that obtained by conventional single stage flotation. The optimum flotation circuit for the washing of the coal in question, was reflotation of classified tailings.

Jan 1, 1978

An airlift pump is fitted to the screw conveyor of a decanter type centrifuge in order to pump out soft cakes which are difficult to discharge from a standard decanter. The new patented2 design improves separation performance and allows more stable operation, particularly when operating the decanter as a thickener.

Jan 1, 1989

The control of industrial grinding circuits in Australian concentrators has been practised for many years in one form or another. Some have established simple feedback loops in areas such as fine ore bin feeders (tonnage control), mill pump sump levels (flow control) and water additions (density control). There are also some sophisticated systems which infer circuit product size using complex measurements of mass flaws and water additions in the circuit and attempts are made to control those flaws to produce a constant circuit product size. The inferred size method in Australian concentrators has become firmly entrenched in the last ten years and control techniques involving the use of direct size measurements with reliable on-stream sizers have been Ignored.

Jan 1, 1983

By R Lastra, Y Choi, C Hamilton, P Kondos

Hydroseparation (http://www.cnt-mc.com) was used to concentrate sized fractions (from <38 ¦m to 150 ¦m) of various ore products ahead of carbon-in-pulp (CIP)-treatment. The resulting size-by-size concentrates were mounted as monolayer polished sections and subjected to automated unattended precious metal searches by image analysis (see Lastra, Wilson and Cabri, 1999). Systematic variations in Au-deportment permit quantification of Au reporting as discrete grains from fresh-feed through to pressure oxidation (POX)- and CIP-feed. Application of hydroseparation, image analysis and assays to characterising tailings (from <10 ¦m to 106 ¦m) from four mine sites is also described. Results are encouraging enough to predict that the combination of hydroseparation (HS) and automated image analysis could become a standard methodology for study of precious metal ores and metallurgical products.

Jan 1, 2008

By F J. van Zyl, C A. S Thomson

"Anglo American Thermal Coal conducted a high level study of all of its underground collieriesto determine if there were electrical power saving opportunities at the main fan stations.A systems approach to electrical power savings was used to identify potential savings in the various components of a primary ventilation system. Furthermore, only technological interventions were considered to obtain electrical power savings. From generic technological driven electrical power saving strategies four energy savings strategies were identifi ed, namely potential overall reduction in ventilation volume, improved underground air utilisation, optimisation of fan-set effi ciency and potential fan drift design optimisation. The study indicated the colliery (say Colliery D, Shaft A) that showed most potential in the four technology driven energy savings strategies. A detail study was undertaken at Colliery D, Shaft A to increase the confi dence level and the study confi rmed that up to 45 per cent of the main fan absorbed power can be saved (475 kW) with an estimated capital payback period of 18 months. The study clearly showed that an integrated approach to optimise the entire mine ventilation system has great potential for power saving, and that a clear, well -defi ned methodology will be applicable to similar underground collieries. This paper discusses the background to the study and the process followed to implement the energy savings initiative at Colliery D, Shaft A."

Jun 1, 2012

A review is given of the development of the author's ideas on the relationship of ore occurrence to regional dislocations in the earth's crust, presently identifiable in particular areas as linear discontinuities in patterns of geological and geophysical data. Ideas originating from field observations in Broken Hill were developed in conjunction with three-dimensional kinematic deformation models which were devised to simulate rock structures, and to illustrate their response to assumed linear and planar movements at the scale of mine and regional geology. These led to the study of linear features in the pattern of Broken Hill district geology, and to the observation that the Broken Hill lode occupies a "cross-roads" position at the intersection of regional geological lineaments where they cross through and deflect the host rocks. A genetic association was therefore proposed. The recognition of significant regional lineaments requires special techniques and treatments of field data originally developed for the Broken Hill situation. The subsequent application of the work to the Western Australian shield revealed that known major nickel and gold deposits also occur where the host rocks are crossed by one or more regional lineaments. These lineaments were recognised as part of a continental tectonic pattern of major linear trends with which major ore deposits are associated. The ideas were later used in exploration leading to the discovery of the Olympic Dam deposit at Roxby Downs, South Australia, which is related to regional lineaments.

Jan 1, 1983

By Lawrence L. J

The Australian Broken Hill Consols Mine, situated some 600 yd east of the main Broken Hill line of lode, is noted for its rich ores of silver. In contrast to the vast conformable orebodies of the Broken Hill field, the Consols lode occupies a narrow fissure dipping to the south west at angles increasing from 240 through to vertical and transgressing the strike of the metamorphosed country rock at an oblique angle. This feature, together with the abundance of calcite and siderite and the virtual absence of silicate minerals in the gangue, has led to its classification as an orebody of the Thackeringa type (King, 1953). Recorded production during the period 1890 to 1903 is given as 845,000 oz of silver and 20 tons of lead.The unusually rich silver values of the Consols lode were concentrated at the intersection of the fissure with beds of amphibolite, whereas in the adjacent schists and gneisses the lode became markedly impoverished. From the surface to a depth of some 120 ft extensive surface oxidation had occurred, resulting in the breakdown of siderite and its replacement by limonite and associated manganese oxides.Silver halides, dyscrasite, acanthite and partly oxidised tetrahedrite were the main silver minerals in this zone. With increasing depth the lode material gradually reverted to minerals representative of the hypogene zone.The only previous work specifically on the mineralogy of the Consols lode is that by Smith (1922), one time manager of the mine. His zeal as a mineral collector resulted in much valuable information being available on the distribution of the minerals. More recently, Garretty (1943) noted the...

Jan 1, 1962

By McDougall I, Claoue-Long J

A combination of high precision 40Ar/39Ar and U-Pb dating has been used to determine the age of hydrothermal minerals and host rocks in a number of Lachlan Fold Belt (LFB) gold deposits in New South Wales, Au4 ralii In particular, this investigation demonstrates that the UAr/ Ar technique of K-Ar dating can be used to determine the timing of mineralization in Palaeozoic systems.A close temporal link between mineralization and Late Ordovician to Early Silurian magmatism is indicated by the dating work. Hydrothermal sericite from the Goonumbla p8rph gy Cu deposit and Glendale Au prospect yieldsAt/ Ar step heating ages between 437.9 ¦ 1.1 and 441.2 ¦ 1.1 Ma (16), and4 minjrnum age of about 425 Ma has been obtained by Ar/ Ar dating of hydrothermal amphibole from the Browns Creek Au-Cu skarn deposit. Hydrothermal aluniI8 frog the Gidginbung epithermal Au deposit yields reset 44 Ar/ Ar ages of 401.0 ¦ 1.3 to 417.3 ¦ 1.3 Ma (16). U-Pb dating by ion microprobe on magmatic zircons from the vicinity of the Goonumbla and Gidginbung deposits gives ages of 438 ¦ 3.5 Ma (2 6), and 435 ¦ 2.5 Ma (2 (7) respectimly, W a minimum age of 435 Ma has been obtained by Ar/ Ar dating of magmatic phases from volcanic rocks adjacent to the Browns Creek skarn deposit. Magmatic episodes near the Sheahan-Grants gold skarnpost give ages of 479.2 ¦ 1.1 and 467.9 ¦ 4o1 by 'Ar/ 9Ar dating of magmatic amphibole. Most Ar/3yAr age spectra show the effects of partial Ar loss at between 360-420 Ma, probably due to heating caused by granitoid emplacement.The radiometric dating work in this paper suggests a restricted metallogenic epoch in the Late Ordovician-Early Silurian LFB, NSW, of similar duration to that found in the Andean margin and the western Pacific island arcs around the Pacific Rini.

Jan 1, 1990

By Moore J

Gunpowder Copper Ltd is using in-situ leaching to extract copper from the Mammoth sulphide ore deposit in north-west Queensland. To increase metal recovery, ore is fragmented using conventional underground longhole drilling and blasting techniques. Although the upper levels of the orebody had previously been mined by open cut and underground methods, significant reserves of copper existed around old workings. To safely and economically recover this resource, a decision was made to fire the remaining pillars in the upper part of the mine by a single 1.37 million tonne mass blast in February 1992.This paper records the planning, design, and implementation of the Mammoth mass blast. Geological and geotechnical aspects are summarised, to explain the reasons for such a large blast. Drilling, charging and blast initiation are discussed in detail, to show how standard equipment and products were applied to a unique task.

Jan 1, 1992

By Baafi EY, Sun Y, Tague I

Field trials at three New South Wales and one Queensland coal mines were carried out to gather data on oxygen "run out" times of Self-Contained Self Rescuers (SCSRs), time taken to escape from the mine, distances travelled and the average heart rate of subjects wearing SCSRs. The study has led to a method of predicting the duration of oxygen supply from a SCSR as a function of the wearer's body weight, physical fitness and the prevailing environmental conditions. Escapeway design, planning for emergencies, familiarity with SCSRs and experiential escape training are critical to control panic and maximise the likelihood of survival of a person attempting to escape in an emergency involving fire or explosion.

Jan 1, 1998

Roadheaders have had a chequered history in hard rock excavation in Australia since their introduction into the country in 1972. This has resulted in a poor reputation among both clients and contractors and subsequent reluctance to design tunnels and underground space around their performance characteristics.This has now changed because of the introduction into Australia of a new breed of Roadheader, the Mitsui. This paper sets out the history of development of the Mitsui range of Roadheaders. It describes the process which resulted in the introduction of this new machine, its performance to-date and the characteristics which have contributed to the success of the machine. The combination of these factors have led to a change in attitude to the use of Roadheaders in underground excavations.

Jan 1, 1993

China has been producing gold for more than 4000 years with gold production increasing substantially since the 1980s, from about 25 tonnes in 1980 to some 160 tonnes in 1998. More than 80 per cent of the gold production is from East China. However, complete information on eastern China gold has been rarely reported internationally. This is a general overview on the tectonics and metallogeny of gold deposits in East China. The geology of these gold deposits is compiled mainly from data and information reported in China, and is also based on the authorÆs work in China from 1974 to 1986 and a recent visit to China.

Jan 1, 1999

The Professional Standards Act responds to the growing problem of professional liability by introducing a mechanism whereby professional associations can have schemes approved. Those schemes include a cap on liability; a requirement for compulsory insurance; the development of risk management strategies; and the establishment of a complaints and disciplinary system. The Act is also designed to support and develop the concept of self-regulation by the members of occupational associations who provide services to the community by providing them with those tools. It implicitly accepts that self-regulation is preferable to statutory regulation and that self-regulation serves the interest of the community and of the providers of services. The Act arose from a review of professional liability commenced in 1988. The Attorney General's Department produced an Issues Paper, released in September 1989, which outlined in detail the extent of the problem. This was widely circulated and an extensive number of comment were received.

Jan 1, 1995