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The Century zinc-lead-silver deposit has a geological resource of 118 million tonnes averaging 10.2% zinc, 1.5% lead and 36 g/t silver. It lies approximately 250 krn NNW of Mt Isa in NW Queensland, Australia, and is hosted by middle Proterozoic age siltstones and shales of the Lawn Hill Formation. Within the orebody, most mineralisation occurs selectively within black shale units as fine grained sphalerite and galena lamellae with minor pyrite and siderite. The black shale units are separated by weakly mineralised sideritic siltstone horizons. The deposit is unmetamorphosed and only weakly deformed, displaying excellent lateral stratigraphic and grade continuity. The deposit is mostly overlain by younger Proterozoic sediments and later Cambrian age limestone cover and only a small proportion of the mineralisation crops out. Mineralisation has a subtle surface expression without a classic gossan profile, probably due to the low iron sulphide content of the ore. These factors contributed materially to the length of time between the first recognition of lead-zinc-silver mineralisation in the area by prospectors in the 1880s, to the discovery of the orebody by CRA Exploration Pty Ltd (CRAE) in April 1990.   Small scale prospecting and mining continued in the area from the date of the first mining lease in 1887. Post 1950, the deposit area was also included within nine separate regional exploration titles prior to CRAE's title acquisition in 1987. CRAE's original exploration strategy was partly pragmatically and partly conceptually inspired, but the eventual discovery only partly conformed to the original conceptual model. The deposit was found higher in the stratigraphy than the original target position, with unexpectedly low total sulphide content relative to other known deposits.   The discovery soil anomaly was located by the CRAE's first regional orientation traverse line in the area, but was not drill tested for three years. The discovery sequence at Century has strong elements of persistence, technical competence and some luck. It demonstrates that even in well explored terrains (by conventional standards) the exploration story can never be said to be over. The foreshadowed development of an economic resource at Century will hopefully inspire continued commitment to 'brownfields' exploration by mining companies, and demonstrate to external regulators the importance of genuine multiple land use strategies and the need for continued access to land for exploration and mining purposes.

Jan 1, 1995

By Miller F. S

The famous Golden Mile of Kalgoorlie in Western Australia was, between 1888 and 19ft, one of the richest and most important gold camps in the world. Annual production, which reached a peak of nearly 1,300,000 oz. in 1903, however dropped to below 400,000 oz. after 1920.Depression seized the camp, and many mines closed down. The output from this old field is now steadily mounting under the stimulus. of a higher price for gold. In 1935 300,000 oz. of precious metal were recovered and the future is bright. Total production from the field is 21,400,000 oz., whereas something like £23,600,000 have been paid in dividends.The Golden Mile has been studied by many geologists. Their somewhat diverse findings were published for the most part in the Australian technical press which, unfortunately, is not sufficiently represented in foreign libraries.The following article is based on an eighteen months' study in the district for Gold Mines of Kalgoorlie Ltd., preceded by four years' experience with almost identical rock types in the, Porcupine district of Ontario. The excellent record of observed fact left by previous invesigators, augmented by talks with observant mining men...

Jan 1, 1937

A survey has been undertaken of the petrography of North Island greywackes with a particular focus on the occurrence in them of smectite (swelling clay) and chlorite, two minerals that are closely associated, chemically similar, and commonly interlayered with each other. Smectite is the mineral which is a major cause of greywacke aggregatesÆ poor performance. Smectite occurs in post-metamorphic shear zones and in surface weathering profiles over greywackes. This study focuses on the petrography of fresh greywacke rocks.   The occurrence and abundance of smectite and chlorite and their relationship in greywackes is largely a function of the chemistry of the sediment and the maximum temperature that the sediment has been subjected to during diagenesis and/or very low grade (anchizone) metamorphism. Rock chemistry, particularly total iron and MgO, determines the smectite and/or chlorite content in fine-grained greywackes (argillites and siltstones) but chemistry is less influential in sandstones, where at low grades of metamorphism much of the Fe and Mg of the rock is held in unreacted detrital minerals and the mineral constituents of lithic grains.   Four zones which represent different levels of diagenesis and very low grade metamorphism, based on the crystallinity of illite and chlorite in the greywackes, and the proportion of smectite interlayered with chlorite, have been mapped in the North Island. In the anchizone smectite does not appear as a discrete mineral, it is always interlayered with chlorite. In the upper anchizone chlorite contains approximately ten per cent of smectite interlayered with chlorite. In the lower anchizone about 30 per cent smectite can occur in chlorite.   In addition to the smectite and chlorite inherent in the greywackes as the result of the thermal overprint, smectite as a discrete mineral and smectite-chlorite interlayered minerals with high levels of smectite, occur in abundance on shear zone surfaces and in alteration zones adjacent to shear zones; these are the main contributers to the high levels of smectite recorded in many greywacke aggregates.

Jan 1, 2006

By K Ehrig

You are a geologist, geometallurgist, or metallurgist/process engineer and are fortunate enough to work for an organisation who asks you to design/execute a geometallurgy program. What seems like a simple request is actually not a trivial exercise. æRecipeÆ style manuals are not readily available. However, many æexpertsÆ are lurking around willing to deliver solutions which will solve all of your problems. Even though similar ore deposit styles (e.g. porphyry Cu, IOCG, Ni-laterites, calcrete hosted U, etc.) have many similar characteristics, each ore deposit is unique. Hence your geometallurgy program needs to be æfit-for-purposeÆ. This paper offers some insights gained via designing and executing geometallurgy programs from exploration through to production, and working at a mine where you are held accountable for your metallurgical performance predictors.CITATION:Ehrig, K, 2013. Geometallurgy - What do you really need to know from exploration through to production?, in Proceedings MetPlant 2013 , pp 28-33 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By W B. Edgar, I M. Platten, C A. J Towsey, B W. Cuffley

The evaluation of historical goldfields has been common over the past 15 years, reflecting changing economic conditions, improvements in knowledge and technology and lack of greenfield sites. Many goldfields comprise narrow gold-quartz veins, which are structurally complex with an irregular distribution of gold, have variable geometry and architecture and display late deformational effects. The study of historical mine records can be an important tool during early and advanced project evaluation, since it contributes to understanding the orebody, exploration target size and setting expectations. Mine records include documents such as plans, sections, reports, news cuttings, production tabulations, etc. A major advantage for the modern explorer is the capability of computer modelling to display this data in 3D. Historical records can give the explorer substantial information on various deposit characteristics, not least grade and geological continuity, geometry and architecture, mineralogy, metallurgical properties, bulk density and ground conditions. From an evaluation perspective, historical records can be used to support a Mineral Resource estimate, though its application will depend upon the quality and quantity of the data and judgement of the Competent Person. Effectively used, historical records can reduce geological uncertainty and focus evaluation efforts û thus reducing project risk.

Jan 1, 2009

THE method depends upon:--1. The position of the mill.2. The space available for stacking the residue.3. The nature of the residue as discharged from the mill.4. The value of the residue for re-treatment.5. The requirement of the residue for underground filling.Originally the conditions in this district varied mainly in the position of the mill, some mills having an elevated site with plenty of dumping space for the time being, whilst others had a flat site, and very little dumping space near at hand; but in most cases the residue discharged was in the form of filter-press cakes, suitable for conveying on belts, or in trucks, and stacking in a high clump; and, while a portion of the residue was used for underground filling, the dump was regarded as a valuable asset, to be re-treated later. Under these conditions, conveyor belts, electric trams, aerial trams, and hose trucks, all gave satisfactory results, and the following figures, taken from "'West Australian Metallurgical Practice," will show how these methods compared as regards costs...

Jan 1, 1909

In, one stage of the purification sequence of the zinc sulphate electrolyte used at Risdon, cobalt is, precipitated as cobalt nitroso-,B-naphtholate, which is separated from the solution by filtration. Owing to the method of conducting the purification the filter cake contains much gypsum, unconsumed calcium hydroxide, basic zinc sulphate, and entrained zinc sulphate solution, Small amounts of iron and copper that have escaped previous purification steps are also precipitated with the cobalt as nitroso-,B-naphtholate. Thisprecipitate, normally carrying about 18% cobalt, is the raw material for the production of cobalt oxide, cobalt sulphate and cobalt metal.COBALT OXIDEThe main problem in the preparation of a reasonable grade of cobalt oxide from the filter cake is the economic separation ,of the cobalt nitroso-,B-naphtholate from the gypsum. This was solved by the application of flotation. It was discovered that the cobalt nitroso-,B-naphtholate, under correct conditions, would float without any addition agent, giving a relatively high grade concentrate. A plant, was built and has been in operation since 1936. The filter cake is pulped with water and pumped to one of two mechanically agitated tanks, eath capable of holding one day's output. Sulphuric acid is added until the free acid concentration reaches about 3 gm. per litre. Basic zinc sulphate is dissolved and calcium hydroxide converted to gypsum. The pulp, carrying about 2t lb. of solids per gallon, is pumped at a suitable rate to the first of a series of 10 flotation, boxes.. Each box is 3 ft. by 2 ft. 9 in. by 5 ft. deep, and, all have a common, pulp level, since the...

Jan 1, 1949

By D O’Dea, B Godel, T Honeyands, B Ellis, T Harvey

X-ray computed tomography (XCT) is a non-destructive technique that allows the exploration of the internal structure of solid objects in 3D. Over the past ten years, the combination of XCT with more conventional 2D techniques and quantitative 3D image processing and analysis (commonly referred to as digital rocks) has allowed us to address some of the most challenging problems in ore deposit studies. The range of X-ray energies used in XCT allows the X-rays to be transmitted through complex and dense materials including iron ores (eg sinters, lumps, granules). Recent high-resolution XCT scanners have the ability to generate multiscale (25 down to 0.3 µm voxel size) imaging of a given sample enabling the characterisation of 3D textures across a range of scales. This paper will focus on the application of digital rocks to iron ore sinter particles (using filtered polychromatic X-ray beam). The paper is divided into three parts and includes: i) details on the methodologies including their benefits and limitations and the effect of spatial resolution; (ii) the quantification of pore network topology and pore characteristics (eg open versus closed pores, pore size distribution and pore morphologies; degree of connectivity of the pore network and its tortuosity); and (iii) the evaluation of the technique to characterise various phases within the material and quantify 3D mineral textures.CITATION:Godel, B, Ellis, B, O’Dea, D, Honeyands, T and Harvey, T, 2017. Digital rocks for iron ore sinters – towards a D quantification of sinter textures, in Proceedings Iron Ore 2017, pp 529–534 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

By G P. Taylor

Mining Lease SML 57 was registered to Mount Kasi on 5 January, 1995. The Mount Kasi gold mine is located in Vanua Levu, Fiji's second largest island and operated from 1932 to 1946 producing 261,000t of ore at an average grade of 7.5g/t Au. The deposit represents a structurally controlled style of high sulphidation copper gold mineralisation with peripheral low sulphidation mesothermal vein type gold mineralisation. The resource consists of 1,048,000 tonnes of residual soils (eluvium) containing 1.9 g/t Au at 0.5 g/t Au cut off and 1,240,000 tonnes of hard rock at 3.0 g/t Au and 1.0 g/t Au cut. 94 drill holes, 298 auger holes and 85 pits were modelled to outline the resource. 29% of the pits bottomed in mineralisation and it is likely the full thickness of eluvium has been understated. The pit is scheduled to produce 500,000 tonnes of ore per annum to yield 35,000 ounces of gold with an initial 2 years of eluvial ore followed by a further 2 years of hard rock ore. Total capital costs are estimated to be less than 10.0 million dollars with construction planned to commence in 1995. The likelihood of locating further ore is high.

Jan 1, 1995

Last evening, in Auckland, I heard the Chairman of Heinz US, Dr Tony O'Reilly (who, in addition to Heinz's ownership of our largest food processor, also has substantial personal investments in this country), advocate New Zealand as a 'regional corporate capital'.   Why would someone like Dr O'Reilly hold that view? No doubt, as one of Ireland's great rugby players of the 50s and 60s, he admires at least one thing that we do very well (confirmed again in Dublin over the past weekend). But that's not sufficient to support such a view.   He cited many reasons for preferring New Zealand over, say, Sydney, Australia, calling this 'the most rational in which to locate [an] international headquarters', including û +         we have no capital gains tax; +         a more 'pro-business environment'; +         a 'first class' legal and banking system; and +         a 'simple political system'.   I can find no better 'text for today's address.

Jan 1, 1997

Much of the coal and gold mining industry of New Zealand is small scale. Funding is tight and mechanisation limited. The country has many well documented small coalfields (some with significant outcropping) and alluvial gold deposits. These are generally remote, difficult to access (physically and otherwise) and of submarginal value (largely a consequence of size when viewed for extraction by traditional techniques). The industry is also burdened by environmental and bureaucratic constraints. The above over simplified setting suggests to the Author, a newcomer to New Zealand, the opportunity to consider some novel concepts based on technology and techniques developed overseas or borrowed from other industry sectors. The objective being to make viable in economic and environmental terms projects that might otherwise be stillborn if considered for exploitation by conventional means. The paper mainly discusses 2 concepts focusing on the application of augers for exposed high wall or outcrop coal and micro-tunnelling augers for alluvial gold extraction. These may be considered high mobility 'container' (as in shipping container) packaged, or 'non invasive' mining systems. It is stressed that these are but concepts and have yet to be subjected to rigorous financial or engineering scrutiny. This could only follow their acceptance by, and input from, New Zealand miners. There will also be brief mention of a new modular conveyor system which might have application within the concepts or existing small scale mineral extraction operations and mention of a project currently in progress to apply tangible 'sustainability' to underground coal mining.

Jan 1, 1996

During August, 1926, with the consent of Mr. Schell, mine manager, the writer conducted a mill test on this company's concentrators. Mr. Schell not only gave him his permission, but rendered all possible assistance. Although it was impossible to take all the samples one could have wished to obtain, yet the salient points of the mill flow-sheet were sampled for a continuous period of eight hours, and from these samples and separate data supplied by the manager, valuable information was collected.THE MINEThis is a true vein-type of mine; the lode formations, striking almost due north-south, cut the large porphyritic intrusion at right angles. There are three distinct veins on this property - parallel, persistent, and dipping at an angle varying between 40° - 50° to the horizontal.The country rock is very sound, and timber, save for the small amount required for ore chutes, is entirely absent from all mine workings.The lode varies from a width of 1 in. to 8 in., but the stopes are carried forward with a minimurn width of about 30 in.The mine is particularly dry for a West Coast property, and conditions underground are very favourable. Air drills are used...

Jan 1, 1928

High Pressure Grinding Rolls Scale-Up and Experiences

Sep 13, 2010

The Barmac autogenous crushing mill is one of the most successful new comminution technologies to become available to the mining and industrial minerals industries in this decade.   The Barmac autogenous crushing mill is an innovative Vertical Shaft Impactor which operates in essence like a high intensity dry ore centrifugal pump with the reduction occurring primarily as a result of high velocity rock to rock impact in a fully rock lined crushing chamber.   With applications in a wide range of mining and industrial minerals operations the Barmac autogenous crushing mill presents an opportunity to enhance reduction and liberation whilst providing many cost savings and production increases in new and existing plants.   This paper briefly describes the operation of the Barmac autogenous crushing mill and reviews its benefits.

Jan 1, 1990

By A D. Stewart Gillies

Resource rent taxes are taxes which only become effective at such a time as a pre-determined rate of return has been achieved by an operation. Resource Rent Taxes have from time to time been considered for implementation in bothAustralia and New Zealand. The offshore petroleum industry in Australia is already subject to RRT as is the Roxby Downs (Olympic Dam) Mine in South Australia. Both the mining and petroleum taxation regimes in Papua New Guinea include a resource rent tax component called Additional Profits Tax.   The implications of the current form of additional profits tax for shareholder cash returns are that the tax burden on the operation may suddenly increase at some stage in the life of the mine if and when the threshold level of profitability for the tax to be triggered is exceeded. From that point in time onwards the cash return to the shareholders on the capital invested is greatly diminished. For mining companies in Papua New Guinea, the effective tax rate increases from 35% to 57.75% as a result of the onset of additional profits tax. This tax rate penalty is so severe that there appears to be merit in considering the concept of managing profitability through time rather than purely maximising annual pre-tax profits as is currently the case in most mining operations. This would have the benefit of deferring or perhaps preventing altogether the onset of the tax. One possible method for the effective management of profitability is through the control of average mining grade by cutoff grade manipulation.   Traditional cutoff grade theory has usually considered taxation as a direct cost at a fixed or variable percentage of annual profits. As a result of this most analyses are conducted on a pre-tax basis. If tax is included in analyses it is usually present as a time independent function of gross profit. Additional profits tax is both time, and rate of return dependent and therefore not adequately accommodated by currently accepted cutoff grade theory.   A review has been made of the effects of resource rent taxes on both the investment decision-making process as well as possible development and mining strategies which may be employed by mining companies faced with resource rent taxes. The review includes examples based on the structure of additional profits tax which is levied in Papua New Guinea.

Jan 1, 1995

Experiments on High Efficiency Separation of Mixed Plastic Wastes by Vortex-Tube Separator

Sep 13, 2010

An experimental study of the soil mechanics of brown coal showed that brown coal consolidates in the same manner as does a clay and that the theory of consolidation for soils may be applied to brown coals. Moisture content is a function of the coal type, the existing effective stress, and the stress history of the coal.The effective stress in a brown coal seam is a function of the overburden pressure, the pore stress and tectonic stresses. Stress history may be deduced from geological evidence and determined by consolidation tests. Application of these principles to the brown coal seams of the Latrobe Valley shows that the distributions of natural moisture contents are consistent with consolidation.INTRODUCTIONThe nature and geology of the brown coals of Victoria, particularly of the Latrobe Valley, were discussed in some detail by Edwards (1945, 1948), Thomas and Baragwanath (1949) and Gloe (1960). A salient feature of these studies was the distribution of moisture contents in the brown coal seams. Recent experimental work, part of a soil mechanics study of the structure and strength of brown coal, showed that moisture content variation is a reflection of consolidation phenomena in brown coal and application of the results to .field condItions verified and modified the conclusions of Edwards in his pioneer work. Further detail of this experimental work is recorded elsewhere (Rosengren, 1961).EFFECTIVE STRESS AND CONSOLIDATIONEffective stresses in soilsA saturated soil is a two-phase system, consisting of a compressible skeleton of rigid soil particles and pores filled with water, an incompressible fluid. (In this context, the terms compressible, incompressible, and rigid are relative only and refer to orders of magnitude). If this system is subjected to stress we define...

Jan 1, 1963

Tumbling mills and some theoretical and practical aspects of milling are discussed. Attention is directed towards the difficulty of relating the dynamical analyses of the motions of particles within mills to the existing treatments of breakage processes. This synthesis may be advanced by a study of milling that utilizes the matrix analysis of breakage processes. Application of the matrix analysis to results obtained on (i) grinding in open-circuit a zinc ore in a conical pebble mill and in a modified conical mill, (ii) "grinding of cement clinker in a compound mill, and (iii) to some drop-weight grindability tests is discussed. It is shown that the 'IT-breakage model adequately describes the breakage processes of each of the tests. (The proportion broken in each breakage cycle is given by 'IT and is independent of particle size.)The size distributions of the products are accurately predicted in the cases considered. Matrix analyses of the breakage of coals, various ores and a cement clinker have been made. Appendices give an elementary account of the matrix methods and give the equations fully describing reverse order closed circuit operations. The matrix analyses of breakage processes and the survey are used to examine briefly closed circuit grinding.INTRODUCTIONTumbling mills are slow-speed crushing and grinding machines which have been developed from some fairly simple types into many widely differing forms. Many of these versatile mills have proved extremely useful in ore dressing and mineral beneficiation, whereas others have been used in the cement industry and less extensively in the coal industry.The performance of even the simplest tumbling mill is very imperfectly understood, whilst the more difficult problems associated with the balancing of complex milling circuits and with the establishment of the optimum operating conditions for the whole of a complex circuit are even less well apprehended.Our knowledge of the performance of tumbling mills is rather sharply divided into two categories: the first consists...

Jan 1, 1957

By Lancucki C. J, Nickson N. M

X-ray diffraction and differential thermal methods were used to determine the mineralogy of some clays used by the heavy clay industry in the Adelaide area. A detailed analysis was made of the mineralogy and particle size distribution of eighteen samples from beds in two pits in the Recent sediments in the Adelaide plains, of six white clays developed from the weathering of the Adelaide series of sediments, and of four Recent alluvial clays from a pit in the Mount Lofty ranges south of Adelaide. Structural clay products in the Adelaide area are manufactured from mixtures of these clays, so the mineralogy and particle size distribution was determined of eighteen clay mixtures used to make red bricks, cream bricks, facing bricks, pipes and tiles.Knowledge of this mineralogy is important in understanding the ceramic behaviour of the clays.INTRODUCTIONIn this investigation an account is given of the clay mineralogy and particle size distribution of some ceramic clays from the Adelaide area. The clays are used in the manufacture of structura,l clay products and the results to 'be described are part of an overall 'plan of study covering the heavy industrial clays and shales of Australia. Previous work has been published (Cole and Carthew, 1953; Ferguson, 1954; Ferguson and Hosking, 1955; Cole and Nielsen, 1958/59).In this work no attempt has been made to examine clays from all pits engaged in supplying materials for the structural clay industry. However, in 1954 the senior author collected detailed samples from two pits working in Recent alluvial clays in the Allenby·Gardens and Beverley areas near...

Jan 1, 1963

In the course of work being carried out in the Lubricants and Bearings Section of the Council lor Scientific and Industrial Research on the production of copper4ead 'bearings for 'use in aircraft, it has been found necessary to develop special metallographic methods. For proper control of the production of steel-backed copper-lead bearings it is necessary to adhere to rigidly controlled conditions, and it is essential that a method of examination be adopted which will readily detect actual defects or any variations in quality. Some defects can be observed with the naked eye, whilst others are detected by radiographic examination. This latter method is invaluable as a rapid, reliable test in the production of aircraft bearings, but it is necessary to observe the structure of the alloys under the microscope, both to be able to interpret the radiograph correctly and to determine what has occurred to the metal during and after solidification. The use of a sound metallographic technique is'particularly important in developmental work and research connected with these bearings.Polishing TechniqueCopper and lead are practically immiscible in the solid state, but whilst they are miscible only in certain limited proportions in the liquid state; consequently "alloys" of copper and lead consist of a mixture of the constituent metals. The metallographic difficulties are obvious. Copper is a relatively tough metal, although it readily scratches, whilst lead is extremely soft and easily deformed. It wouId be expected if any normal polishing technique were applied that the lead would be readily torn out of the surface being prepared, and, in addition, that the lead would tarnish very easily.Grange(2) has described a method by which these difficulties can be overcome. The method involves an etch-polish procedure using "chrome regia" as an etchant for the copper. The chrome regia was a solution of chromium trioxide and hydrochloric acid in water. This type of etchant has been adopted, but it was found necessary to make certain changes.The method now adopted in this laboratory is as follows: The specimen (which is usually mounted in bakelite) is wet ground in a series of successively finer Hydro-Durexsil emery papers down to 60.0· grit paper.The specimen is then etched in the chrome regis, etchant (the composition of this etchant will pe discussed later) for approximately five seconds.Most efficient etching is obtained by swabbing the surface of the specimen...

Jan 1, 1944