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Gold mineralization like other low concentration high value commodities has gained the notoriety of being difficult to sample. This adversely affects the confidence that can be placed in resource estimates and ore reserves. As an example, it is not uncommon to find differences of the order of 30% between duplicates of a single sample sent to two different commercial laborartories. Two halves of drill core generally show marked differences in grade. Again differences of 50% are not uncommon in halved core. In the context of this type of "error" within the base data used for the resource estimate, many of the subtleties of computation methods and expert judgement of resource categories, are almost a case of shutting the gate after the horse has bolted. Managers, financiers and consultants must question the quality of the base data upon which resource estimates are made. They must insist that standard and duplicate samples are used to measure the accuracy and precision of commercial analytical laboratories, that sampling practices have been checked for possible bias and give tolerable repeatability. Further they must ensure there can be a realistic confidence in the estimates by correctly using these measures of data quality to quantify risk.

Jan 1, 1990

The introduction of large diameter holes to underground mining has provided the first opportunity to apply near spherical charges in production scale blasts instead of the convent- ional long cylindrical charges generally used in stope and pillar mining. A modified version of the cratering prin- ciple was applied in the blast design in extrac- ting ore across a horizontal area of a stope or pillar. The new rock breaking technique has developed into the Vertical Crater Retreat (VCR) mining system and eliminated raise boring, slot cutting and dilution of the ore by back- fill material. Furthermore it has reduced labour and time requirements thus becoming not only a low cost method of mining but the safest method of underground mining known today. Exceptionally fine muck is provided with a minimum of damage by blasts to walls and re- treating backs of the stope or pillar. The VCR method can also be used for drop- raising, and for the excavation of underground cavities for almost any purpose . The proper explanation of the breakage mechanism of the near spherical charges opposite to the cylindrical charges yet to be found. The mining industry has quickly recognis- ed the value of the VCR mining method which is being adopted by an increasing number of mines

Jan 1, 1978

The winning and upgrading of mineral raw materials necessarily includes size reduction, which serves the liberation and production of marketable products from highly valuable and bulk materials. For crushing, the following factors can be duly accounted for depending on material type and the selection of the suitable machine: ò producing a particular size distribution, ò producing a particular grain shape, ò selective comminution, ò gentle comminution, and ò producing a size range required by a specific process and/or for a specific product.

Jan 1, 1993

By Yamada K, Abe H

Magnetic scanning type mass spectrometers have been given improved sensitivity with a large dynamic range and considerable resolution by the addition of a computer-controlled electric equipment. A mass spectrometer equipped with this newly developed electric system was applied to studies of the activities of liquid iron-silicon alloys and of liquid iron-phosphorus alloys at 1600¦C. The range of silicon concentration was 5.8at%-51.1 Si= at%, and values of ySi -3.1+0.15 and es 11.5 +1.5 were obtained. The concentration range of phosphorus was 1.3at%-5.7at% and a value of eP=7.3+0.1 was obtained.

Jan 1, 1980

By Hustwick I

New Zealand Steel Mining Limited operates two independent sand mining operations on the West Coast of the North Island of New Zealand. (Fig. 1)Waikato North Head 30km south of Auckland supplies ironsand concentrate as the raw feed for New Zealand Steel's works at Glenbrook, and Taharoa 70km further south, exports ironsand concentrate to Japan. Taharoa uses two sets of six low pressure Warman centrifugal pumps in series to load bulk ore carriers 3km off shore through two underwater pipelines.Waikato North Head delivers the ironsand to Glenbrook l8kms through a 200mm ID buried pipeline using two stages of high pressure positive displacement (HPPD) pumping.A high level of operating and maintenance expertise has been developed since commissioning the two systems which are proving to be reliable, efficient and of minimal impact environmentally.

Jan 1, 1990

By Murphy A. S, Budod A

The Philex concentrator represents the first time Jameson Cells have been used in a cleaner scavenger application or in large scale flotation in roughing and scavenging. This necessitated a major change in Jameson cell design as well as a chan

Jan 1, 1997

By Dyson NF

Nickel sulphide precipitated from waste liquors at the Yabulu plant of Queensland Nickel Pty Ltd was pressure leached under various conditions. Leaching at 130¦C and 700 kPa of air dissolved 95 per cent of the nickel as the sulphate in less than 2 h. Leaching at 130¦C and 350 kPa of oxygen dis- solved 95 per cent of the nickel in less than 1 h. Dissolution was faster with oxygen than with the equivalent pressure of air. Crystallization of hydrated nickel sul- phate from the resulting clarified leachate is readily achieved. Because the sulphide pre- cipitate also contains minor amounts of iron, copper and cobalt, the crystallization product contains these metals in excess of the amounts required for electrolytic-grade nickel sul- phate. This grade of product could only be produced if the contaminants were removed prior to crystallization. Alternatively, the "crude" nickel sulphate could find a market as a feed for the electrolytic production of Ni-Fe coatings.

Jan 1, 1984

By Corrans I. J

A wide variety of copper-bearing gold ores exist throughout the world which have yet to be processed economically for gold recovery. The copper minerals present in these ores can be many and varied and usually result in high cyanide consumptions and problematical levels of copper in leach solutions. The copper content is often assessed as being of nuisance value as the ores are generally of the grade or type which can support neither a copper project nor a straight gold project, due to the interference of copper. Many of these problematical gold-copper ores could possibly be processed economically for gold recovery using a novel ammoniacal cyanide leaching system which utilises a copper-ammonia-cyanide complex as an effective lixiviant for gold, yet limits copper dissolution and conserves cyanide. Results from recent testing have promoted a re-evaluation of the economics of treating some gold-copper ores. This paper describes the novel leaching process and discusses the conditions employed to treat a variety of gold-copper ores.

Jan 1, 1992

Having provided basic data in the main paper I would now like to move on to discuss these areas in broader terms and to examine the various coalfields in terms of their tectonic setting and depositional environment and ultimately to make some brief comments on the factors which may have controlled deposition.

Jan 1, 1975

It is no longer satisfactory to assess the value of a coking coal on its intrinsic properties alone, its value depends upon its behaviour as a component in a blend. No single test can be used to make this assessment, it can only be made by carrying out a suite of tests. The quality parameters which are considered desirable, and which have widespread acceptance, have been discussed and their application to the blending of coals from New South Wales and New Zealand has been reported and discussed. Blending can be utilised to offset deficiencies, or capitalise on advantages, of the individual coals making up a blend. Coals can be blended, which alone are poorly coking, but which have compensating features. Blending also allows better exploitation of coking coal Reserves..

Jan 1, 1980

By Hoberg H, Schneider FU

Flotation tests were conducted with galena, quartz and with synthetic mixtures of the two, in different ranges of grain size, and with different process parameter variants. Physico-chemical analyses were also carried out on surface energy and on xanthate adsorption on galena with different grain sizes. Reference will also be made to hydrodynamics, interfacial chemistry and the influence exerted by grain size in flotation.

Jan 1, 1993

By Colwell JB, Cronan DS

Manganese nodules cover great areas of deep ocean floor far from land, and have long been considered a major potential resource of nickel, copper, cobalt and perhaps manganese. A decade ago there was a period of intense evaluation of nodule fields, especially those lying between the Clarion and Clipperton Fracture Zones in international waters southeast of Hawaii. There, nodules are abundant and of high grade (average of 2.4% Ni+Cu+Co). The evaluation activity has since declined, but a recent agreement on lease boundaries among all interested parties may lead to a resurgence of work. Indeed, French and Japanese groups have pushed ahead with field and economic assessments.The Southwest Pacific, where there are large nodule fields in the waters of the Cook Islands and Kiribati, has seen considerable assessment of resources in the last ten years, especially through a major field programme of the Japanese Metal Mining Agency. The best prospect appears to be in the South Penrhyn Basin, in Cook Islands waters, where nodules are very abundant but of only moderate grade (1% Ni+Cu+Co). Using a cut-off of 5 kg of wet nodules per m2, Cronan (1989) and Cronan et al. (1989) have estimated the total resource to be a huge 110 million tonnes of Ni+Cu+Co.

Jan 1, 1990

By Demin SS

Slow seismotectonic movements along the in-clined deep fault zone under the compressional horizontal stresses are supposed to be the prin-cipal mechanism controlling the structure and processes in the active ocean margins. Within the scope of the plane strain problem a simple 2-D geomechanical model for the evolution of an island arc system is investigated. We consider a homogeneous elastic half-plane with a shea-ring surface crack. The key element of the model is viscous interaction between the crack sides, the viscisity varying with depth. The model dif-fers from the classical steady-state mode of subduction by nonstationary creep processes on deep faults and by possibly cyclical development of the transition zone.A numerical modeling of the stress-strain state within the island arc system through time was carried out using a semianalytical approach. The results of simulation are in good agreement with geological, geophysical, and seismological data.

Jan 1, 1990

The results of laboratory grindability tests on coal are of primary importance to the designers and operators of coal grinding mills, and coal handling plants in general. However, the potential industrial application of these test results have not been fully realised due to a lack of laboratory-test/field data correlations. This paper focuses on the grindability characteristics of Queensland coals, and provides a new look at an old problem in terms of (i) a more rigorous characterisation of the grindability properties of coal and its associated mineral impurities, and (ii) the correlation of laboratory grindability test results with the size characteristics of run-of-plant thermal coals, and their pulverising characteristics in full-scale mills. A new grindability test is also proposed based on the Yancey, Geer and Price laboratory abrasion-test mill.

Jan 1, 1991

By G Gibson, B Bessen

In coal preparation, large dense medium cyclones (DMC) at low pressure heads (typically 9D where D = cyclone diameter) are the norm. This contrasts with high density mineral applications where, largely for historical reasons, smaller cyclones at high heads are the standard. There are advantages in preferring large diameter cyclones at low heads, assuming that metallurgical performance does not suffer significantly. These include simpler plant layouts, easier maintenance, smaller spares inventories, reduced wear, reduced medium pumping demands, smaller buildings and overall lower capital and operating costs. In 2008, therefore, Xstrata Zinc decided to trial a single DSM-design 800 mm cyclone in one of its four DMC lines at Mt Isa, replacing the four 400 mm cyclones previously installed. Circumstances allowed a low head of 9.5 D to be trialled, compared with the existing 400 mm head of 21.5 D. This paper describes the trial, including tests using painted ore particles as tracers, estimates of yield and metal recovery, and wear monitoring. The larger unit performed well. There was no evidence that metallurgical performance in terms of metal recovery and waste reject rate suffered, and there was some evidence that it may have improved. Cyclone life increased, and preliminary data suggest that the replacement cost of the 800 mm cyclones is less than half that of the 400 mm units, and this is expected to improve. The plant layout and operability have also improved significantly. Xstrata has therefore decided to convert the whole plant to four low head 800 mm units, replacing the original 16 high head 400 mm units. The paper includes an explanation of the effect of static head on DMC separating force. It also reviews earlier research on diamond applications, and applies a general DMC process model to the Xstrata case, both of which confirm that large, low head cyclones are appropriate in mineral applications, contrary to conventional practice. Such units could significantly reduce both the capital and operating costs of DMC plants in mineral applications.

Jan 1, 2009

The 1980's have produced an outstanding revival of the Australian gold industry. In contrast to some previous mining booms, the economic aspects of the growth in gold production are soundly based. In general the new developments have been highly profitable and this is beneficial to all parties- whether they be government, shareholders employees or suppliers. Mining companies are showing a large commitment to gold exploration with approximately 50% of Australian exploration budgets now being directed towards gold. An increasing proportion of this expenditure is being channelled towards the eastern States with Queensland 'being the major centre of interest. Further strong growth in production is expected with some 50 projects likely to come on stream before 1990. A very significant aspect of the foundation for this growth is a continuation of the existing tax status of the industry.

Jan 1, 1987

By Watt JS

The ash content of coal can be determined using radioisotope X-ray techniques. A number of overseas applications of X-ray techniques are described; however these suffer from the disadvantage of either not compensating for iron variations or, if compensation is used, using X-rays of low penetration with consequent sampling difficulties. Current Australian Atomic Energy Commiss- ion (AAEC) research on X-ray techniques is aimed at overcoming the limitations of these methods. The AAEC method involves making measurements proportional to mass absorption coefficients of X-rays in coal at two energies. Calculations and experiments with X-rays up to 35 keV have shown that ash content can be determined to about 1 wt.%. This work is being extended to higher X-ray energies to enable the technique to be used directly on a conveyor belt or in a hopper. Neutron techniques can be used to measure the concentration of specific elements such as carbon, hydrogen and silicon in coal. Their con- centration is correlated to the coal parameters of interest. Methods of moisture determination based on hydrogen measurement and ash determina- tion based on silicon and aluminium measurement are described. Energy content can be determined accurate- ly by analysing the carbon content of coal

Jan 1, 1978

During the past 18 months a rock mechanics project has been in operation at Renison Limited. The project was established to identify and investigate key problem areas that would affect future production at the Renison mine. An in-house approach was adopted, using shall compact equignent, to investigate ground behaviour. Information on the rock stress field was considered to be particularly important for an understanding of ground behaviour. A high horizontal stress component exists, which enables large flat dipping spans of hanging wall to be opened up, with support being provided by post pillars. The amount of support provided by these post pillars has been found to be low.

Jan 1, 1982

Two independent sets of observations from rifted con-tinental margins suggest a way to reach a quantitative under-standing of how the topography of rifted margins erodes. First, a prominent erosional escarpment, which demarcates an elevated, inland region of low relief from rugged, deeply-incised terrain on the seaward side, is the main feature of the geomorphology of many rifted continental margins. Second, apatite fission track ages from the southeast Australian and southwest Saudi Arabian margins scatter about constant Paleozoic ages over the higher elevations inland from the escarpment, but decrease systematically seaward of the escarpment to near-rifting ages approaching the coastlines. We have developed erosion models based on conservation of mass principles to explain these observations. These models seek to explain the "rejuvenation" of erosion at the time of rifting, initiation of the observed erosional escarpment, and its migration inland with time at a rate on the order of 1 km/10 yr. We find from the modeling that erosion at rift flanks and passive margins is fundamentally a non-linear pro-cess. The erosional development of passive margin topogra-phy has much is common with travelling wave solutions to non-linear diffusion-type problems, and to self-similar sto-chastic processes, such as diffusion-limited aggregation. We suggest that the fission track data record the thermal effects of erosional unroofing at rift flanks and passive continental margins. Models intended to explain the erosional develop-ment of continental margins must explain both the geomor-phology and the fission track observations as well.

Jan 1, 1990

By Hebblewhite B, Humphreys D

An experimental mining project has been carried out in the Collie Basin to demonstrate the safe operation of total extraction mining techniques in the underground mines of the basin. To achieve this, it was necessary to design and install a means of controlling or removing groundwater so that goafing of the overlying strata could be safely achieved as part of the mining operation. The site chosen for the experiment was a triangular panel adjacent to Western No 6 (WD6) underground mine, which includes the 3 to 4 m thick Wyvern Seam beneath 130 to 180 m of overburden. The test area abuts a major fault on the downdip side. The overburden and underburden sequences include several horizons of permeable sandstones which form major aquifers. Water problems have long been recognized in all underground mines in the Collie Basin, and have previously prevented the successful application of total extraction mining. Following extensive hydrological investigations, dewatering and depressurization systems were designed to dewater the immediate roof aquifers and to depressurize aquifers higher in the sequence and in the floor. This would enable stable roof conditions to develop and controlled goafing to be achieved. The roof dewatering/depressurization procedure involved a combination of in-mine vertical roof drainage holes and conventional dewatering bores constructed from the ground surface above the mining trial area. The dewatering system was installed and operated for 29 months before the commencement of mining. Mining was eventually successfully completed in two trial panels using a retreat Wongawilli extraction system using bridge conveyors and continuous miners. Water inflow into the mine workings was channelled to a constructed sump area at the lowermost corner of the panel and pumped to the surface via vertical sump bores. The dewatering and depressurization measures adopted were successful in permitting the first controlled and systematic total extraction recovery of coal from the Collie Basin. This trial mining exercise demonstrated the potential for increasing substantially the recovery of coal from the Collie Basin, where previously recovery rates of around 30 percent from underground mining were commonplace, using only bord and pillar methods.

Jan 1, 1988