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Experimental results are presented for the anode overvoltage as a function of current density for different alumina concentrations in an alumina reduction cell. Voltage changes due to the electrolyte resistance and also the decomposition voltage, have been evaluated as a function of alumina concentration and anode current density. From these values of voltage, changes in the total cell voltage have been derived for changes in alumina concentration for different anode current densities. The results show that for each operating current density there exists a discrete alumina concentration that defines a minimum reduction cell voltage. Discussion is made about potential savings in power consumption when the alumina concentration is controlled.INTRODUCTIONThe standard procedure in the aluminium industry when analysing the cell-voltage required for the Hall-Heroult process for reduction of alumina, is to subdivide the total voltage into the following components (e.g. Pearson, 1955; Maritell, 1960).1. ohmic drop through busbars and joints2. ohmic drop through cathode lining3. ohmic drop through anode4. ohmic drop through electrolyte5. overvoltage at anode6. electrolytic decomposition voltage.(Overvoltages ,at the cathode are of negligible magnitude at all practical current densities.)It is understandable that the voltages assigned for each factor invariably differ for different workers...

Jan 1, 1965

By D Crequer

Land rehabilitation at Golden Cross is reviewed, 8 years after mine closure in 1997/98, from the perspectives of a Peer Reviewer (land rehabilitation) and a Regional Council Officer (Resource Consents compliance). Land rehabilitation items we discuss include: management of restored pastures, native plantings (on-site riparian and block plantings and off-site environmental riparian enhancement plantings), wetlands (on-site tailings lake and sediment ponds littoral zone plantings, and basement of the open pit; and off-site wetlands enhancement plantings), pine plantations on-site and on surrounding land, stabilization of the Tailings Lake Embankment (landslide) and Open Pit capping, capping of acid-mine-rock, stability of discharge channels, buildings and amenities, public access for recreation, educational uses, and future management of the site. Pest control has helped to conserve the rare and endangered HochstetterÆs (Leiopelma hochstetteri) and ArcheyÆs (L. archeyi) frogs, and a regionally significant stand of rare swamp maire (Syzygium maire) has been conserved and fenced.

Jan 1, 2006

The projection of operating costs for mining, processing, and other site operating costs is an exercise which can be fraught with considerable peril. Not only are the physical characteristics of each mineral property unique, but a range of other factors will influence the consultant's approach to compiling cash flow estimates. This paper details some of the techniques used in estimating operating costs for use in order-of-magnitude cost studies and feasibility studies, and describes how to avoid common areas of difficulty. A series of examples relating to open pit gold mining and processing cost estimates illustrate these problems, and various corrective methods are described. The mining and treatment processes, and their associated cost elements, are followed in sequence of operation from on-going ore delineation through to disposal of the product. In addition the problem of assigning management, administration and overhead costs along with taxation allowances is addressed. Of critical importance is the application or possible misapplication of accrual procedures to the cost elements. In many cases such misapplication can introduce more pronounced errors with projects of short duration, such as the typical open pit/C.I.P. gold operation commenced in the last decade. The importance of providing verification of estimates depending upon the standard of the cost study is also investigated, and opinion is provided upon the minimum levels of verification necessary at various stages. Finally, the amalgamation of the various individual cost elements into a coherent whole is reviewed.

Jan 1, 1990

In New York City, on the walls of the library of the United Engineering Societies are these words:"Engineering-the art of organising and directing men and of controlling the forces and materials of nature for the benefit of the human race," but who, reading the schedules of even our best engineering schools, would infer that engineering is an art or that it should always havejn mind the benefit of the human race? While it must be remembered that our engineering schools exemplify the British cult of the amateur, that cult which lets men who have never attended a lecture on "Education" or perhaps nevereven read a book on it, become enginering teachers by profession (and so educators by inference), the root of the matter is to be found in the fact that our educational aims, and consequently our educational practice, seem suited much better to the position engineering held in the community in 1900 than to the position it holds to-day. This civilization of ours has developed, !;loth for good and for ill, into one based largely on engineering achievement; technical progress is so continuous and so rapid that thevalue of descriptive knowledge of current practice is ever lessening; enough must be imparted to make the young graduate immediately employable, and this amount is sufficient for illustrating the principles on which practice is based and on which its advance depends, but the young graduate's technical progress depends much less on his having acquired additional knowledge than on his ability to acquire knowledge, so, paradoxically, the more useful knowledge there is availabJe the less of it the student should be taught.Less conspicuous but fully as important is the enlargement of the field of work of engineering graduates, especially its extension to the initiating of policies and to the broader problems of administration. At present the road to such positions lies normally through a considerable period of professional work, but it is by no means unlikely that the field will soon include much that requires little professional expel'ience. At all events it is safe to say that the changed. and changing position of engineering in the communitydemands the attention of the engineering schools and that profitable discussion of engineering education demands some understanding of the real nature of education and of the part which engineering plays in the life of the community.THE NATURE OF EDUCATIONUnfortunately "to educate" supplies an example of how words degenerate in meaning; most people regard it as the equivalent of "to instruct"; a small number feel they have gone to. the root of the matter when they say...

Jan 1, 1941

G. R. Compton (Gold Mines of Kalgoorlie (Australia) Ltd., Fimiston, W. A.) : In congratulating Mr. Hooker upon his resume of Mr Parry's paper I have in mind the fact that he carried out the research into pipe pressures. Hydraulic filling as practised in Kalgoorlie has created world wide interest, with these pressures and percolation being vital points.Early in the 1950s, representatives of the Kolar field were conduGted over the local mines where stopes at depths below 2,000 ft were being filled. The problems of pipe pressures were their main consideration since depths of up to 10,000 ft were envisaged.Mr Krishnaiah and Mr Murthy from the same field are with us today and perhaps we may hear of their experiences with depths of 6,000 ft and long lateral lines.J. Holly (Lake View and Star Ltd., Fimiston, W.A.): There is one phase, which I would like to mention myself, that has been very evident in Kalgoorlie operations. That is, we do not get the percolation properties that are obtained on many other fields in the world, and our tendency here has been to assess the quality of our fill more by its settling rate, i.e. the rate at which we can draw off clear water at the surface of the filling levels, rather than the rate that this water percolates down through the fill before it consolidates.We are tending now to measure the quality of our fill as a settling rate rather than as a percolation rate.Americans talk about percolation rates being the important property: If anyone has any experience on operating with fills with different percolation rates, I think their views would be very interesting to the meeting art this stage. Mr ...

Jan 1, 1965

By B S. Utting, W J. Cowie

The alluvial gold industry of New Zealand is based on the placer deposits in Otago and on the West Coast. Production from these since discovery in the 1850s has been an estimated 480 t (15 Moz) of gold. Annual output has expanded continuously since 1980 and is expected to be over 2 t of gold for 1989. Following a historical review, the characteristics of typical operations, which use hydraulic excavators and mobile trommel units are discussed. Descriptions are then given of alluvial activities in Otago and on the West Coast.

Jan 1, 1990

To many Australian Mining Engineers, we take it, the singular features of banket deposits are not as familiarly known as they would wish, possibly because in the majority of instances they are not in touch with the South African milling world, and have had little opportunity of studying the development of the banket beds, either from correspondence or literature. The writer hazards this opinion feelingly, because, when in Australia and before he had visited Africa, the utmost knowledge he was able to obtnin was a mass of conflicting theoretic discussion as to the agencies which formed the banket bed, without any practical hints as to their geological horizon, the rocks with which they are associated, the usual appearance and character of the ore, in fine, without that everyday detailed description which the miner requires when seeking information regarding mineral or metal deposit foreign in character to any that he has yet studied, or as yet had any opportunity of studying in his own country.The writer recognised that many more able men than he have from time to time discussed the features and formation of the banket beds of the land, notwithstanding which and feeling that many of his Australian colleagues have found themselves in a similar position regarding accurate detailed information respecting these African banket deposits as he himself was, he hopes that the present paper on the said deposits, as found on the fields under notice, will prove useful to some and of interest to all.

By Lavers G

Factors governing the dissolution of nickel and iron in pentlandite and pyrrhotite concentrates from Mt. Windarra were studied for aqueous solutions at normal temperatures and pressures. The effects of dissolved dioxygen, carbon dioxide, hydrogen ions, and chloride ions are described. The direct reaction of aerated water wiili pyrrhotite is much faster than with pentlandite, and reaction rates are proportional to the dissolved dioxygen concentration. In both cases divalent metal sulphates are produced initially. The subsequent oxidation of iron(II) to iron(III) and its oxolation produces acid solutions which rapidly attack both minerals. The presence of carbon dioxide or chloride ion has little effect on these rates.

Jan 1, 1976

When the mining and milling of 1100 copper orebody commenced at Mount Isa a satisfactory grade of copper concentrate was difficult to produce. The major concentrate contaminants were fine pyrite and silica, particularly in the minus 10 microns fraction. Studies of the 1100 orebody showed that much of the fine grained pyrite and a proportion of the silica present in the ore contained carbonaceous matter in the form of complete or partial rims and as internal carbon films disseminated throughout grains. The hydrophobic surface property of the carbonaceous material resulted in inherently flotable fine pyrite and siliceous particles.The addition of a 60:40 mixture of nigrosine and dextrine, initially to a prefloat concentrate of the inherently flotable carbonaceous material and finally to the total copper flotation feed, successfully controlled the flotation rates of the carbonaceous pyrite and silica. The objective of a 25 per cent Cu concentrate grade was then achieved without decreasing copper recovery.

Jan 1, 1971

Residual aeolian placers (RAPs) are formed by the wind, by preferential entrainment and removal of small and low-density detritusfrom a pre-existing, typically sedimentary sequence containing heavy minerals. Heavy minerals that are resistant to chemical alteration and either soft and malleable (gold), or extremely hard (diamond, sapphire, ruby, etc), are concentrated as a residual on the wind deflation surface, typically in the interstices between larger resistant clasts. RAPs form preferentially in arid or semi arid areas, where the vegetation is sparse or absent, and where topography and surface gradients are low, but may also form on beaches and in periglacial environments. RAPs consist of a continuous or discontinuous, planar or gently undulating horizon of heavy minerals in a single-clast-thick pavement of resistant pebbles, cobbles, or boulders, which mantles the present topography or palaeo-topography. Extreme wind erosion and surface deflation may condense the full pre-existing sequence into a layer of heavy minerals only. The grade of RAPs is substantially higher than in the precursor deposit, and commonly much higher than those typically found in most other placer types. Aside from their general occurrence as a thin pavement of resistant clasts, the best indicators of residual aeolian gold placers are the presence of wind-eroded stones (ventifacts) on the pavement, and the distinctive and unique shapes of aeolian gold grains themselves. The shape of the gold grains is progressively transformed by sand blasting during placer development, from grains with thickened rims, to toroidal grains on which the rims are æsplitÆ and peened inward toward the grain centre on one or both of the grain sides, to hemispherical or sub-spherical grains that are fully encapsulated by the in-turned rims. Gold that has undergone aeolian shape transformation is difficult to entrain and transport away from the site of aeolian concentration by anything other than mass movement or glacial processes. It is also easily retained by commercial recovery plants of any configuration.

Jan 1, 2004

By B Leisemann, M Watkinson

Coal augering is an ideal method for recovering coal from the highwalls of open cut coalmines. Coal augering is a simple process whereby additional flights are added to the auger cutting head and auger holes are drilled at 1.9 m diameter up to 200 metres deep. Traditional monitoring was located at the mouth of the hole and if methane was encountered above two per cent, inert gas was delivered into the mouth of the hole to deplete the oxygen content at the auger cutting head below 12 per cent. The auger operator was asked the question ‘how do you know that this is the case?’ Trials were undertaken to prove that the oxygen content at the cutting head did drop below 12 per cent (the lowest limit for methane to ignite, also known as the oxygen nose point). Initial trials showed that the oxygen content in the mouth of the hole did not drop below 12 per cent and modifications were made to hold the inert gases in the mouth of the hole so that the auger flights could take this inert gas into the hole. In-hole monitoring, after completion of mining and after extracting the auger flights, showed that the atmosphere quickly returned to fresh air. In-hole monitoring was also tried during the augering process and yielded valuable results. This paper will discuss the results of the monitoring, information on the gas results obtained and the methodologies used to optimise the oxygen content at the auger face.CITATION:Watkinson, M and Leisemann, B, 2017. Inertisation of coal augering holes, in Proceedings Australian Mine Vent Conference 2017, pp 293–298 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

IN the underground department of a mine, we may fairly say that "good management is based upon three elementals: first, sound engineering; second, proper coordination and efficiency of every human unit; third, economy in the purchase and consumption: of supplies.This paper is practically an analysis of the second element; which stands out prominently as the most important in the winning of successful results. The human units are divided into officers and men. The officers intermesh. One man takes responsibility where another throws it down; incessantly new conditions are arising where they may be doubtful of their powers; and always, on account of the three shifts, varying methods of work are coming into conflict. This very often results in disorganization. What is most necessary to guard against this is an esprit de corps, which would influence officers to stifle personal feelings for the general welfare of the department, To secure co-operation and loyalty of the staff, the writer recommends for the mines of the field a system of profit-sharing. Distributed on a salary basis, together with liberal holidays (not less than three weeks in each year) on full pay...

Jan 1, 1912

By P L. McCarthy

To design and operate a successful mine the technical specialists must agree on what is ore, what is not ore, and how quickly the orebody is to be mined and processed. These seemingly simple questions defy easy analysis and can push mining engineers, geologists, metallurgists and others to the limit of their capabilities. The questions are rarely addressed adequately in feasibility studies or in operational planning. To optimise the mine and processing plant requires proper determination of cut-off grades or values, prediction of feed variability on an hourly, daily or longer basis, right-sizing the mining rate for optimum product quality, understanding the cost of capital and the expectations of investors, and many other considerations that involve geology, geotechnical engineering, mining, metallurgy, environmental effects and economics. This paper addresses the key matters that should be considered as inputs to the practical issues of metallurgical plant design and operation.CITATION:McCarthy, P L, 2015. Integrated mining and metallurgical planning and operation, in Proceedings MetPlant 2015, pp 35–45 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

Thirty mixed cultures of microorganisms from soil, water and mineral samples from the Groote Eylandt Mining Company mine site were approximately three times more effective in biodegrading manganese dioxide (34± 18 mg Mn++/1/day) than sixteen purified strains (11 ± 10 mg Mn++/1/day) isolated from the primary enrichment cultures. Two pure bacterial genera identified as a Pseudomonad and a Bacillus, with an excess MnOz and nutrient, were able to dissolve 106 mg Mn++/litre/day in mixed culture compared with 29 mg Mn++/litre/day when grown separately.

Jan 1, 1983

THE furnace described in this paper was installed and has been used by the writer for the melting of rich gold-bearing material, and has given complete satisfaction. It may, therefore, prove of interest to other metallurgists who are faced with a similarproblem. A furnace of this type should be most suitable for the reduction of "cyanide preeipitate," "charcoal ash," "anode sludge," &c. formerly the melting was done in fire-clay crucibles, using coke or crude oil as fuel, but this method is costly, slow, and unsatisfactory. A small water-jacketed blastfurnace was also tried on this material after briquetting it, but was discarded in favour of the electric furnace. The furnace may be described as a simple form of the Heroult resistance furnace, with an adjustable upper electrode and a fixed bottom electrode. This is in accordanee with Stansfield's classification of electric furnaces. The heating is mostly due to the resistance offered the current by the molten slag. The melting chamber consists of a steel drum 14 in. in diameter and 21 in. high, and is lined with silica bricks specially made to fit the shell. The internal diameter is G in. The bricks contain 92 % silica, are made from calcined quartzite bonded with fireclay, and are similar in composition to those used for lining steel converters. They are set in a mixture of finely-ground quartzite and clay, and well dried out. The shell is bolted to a steel plate, which forms the decking of a truck running on rails, so that the furnace can be moved under ahood for carrying off the fumes. A cast-iron slag spout is bolted to the shell below the tapping hole, which is 4 in. from the bottom of the shell. Opposite this another hole 1 in. in diameter is drilled through the shell and lining for the passage of the lower...

Jan 1, 1918

By M Shaffer, D C. Grant, D J. Goudie, P Sylvester, C Voisey

Scanning electron microscope–Mineral Liberation Analyser SEM-MLA can be used to discriminate between hematite/magnetite in iron ores, but achieving backscattered electron (BSE) segmentation between the two minerals is difficult for particles =75 µm using typical preparation and analysis methods for the MLA based on a tungsten filament SEM (Quanta 400) with 25 kV high voltage. Preparing iron ore sample mounts using a slow-speed polishing method, and conducting the experiment on a field emission gun SEM-MLA (Quanta 650) with the high voltage (HV) setting lowered to 15 kV reduces instrument noise and results in very clean BSE images and segmentation. This method requires new X-ray standards to be acquired for each mineral identity at 15 kV because of major changes in the spectra at lower kV. However, once these X-rays are added to the mineral reference list, effective segmentation can be achieved and a proper analysis obtained.CITATION:Grant, D C, Goudie, D J, Voisey, C, Shaffer, M and Sylvester, P, 2017. Discriminating hematite/magnetite via scanning electron microscope–mineral liberation analyser in the - mesh size fraction of iron ores, in Proceedings Iron Ore 2017, pp 541–548 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017

MR. W. E. WAINWRIGHT occupied the chair, and in introducing the lecturer said, on account of the absence of the vice-president, it fell to his lot to introduce the lecturer. Mr. Tennberg, he said, was visiting Australia, and those present might wonder who he was.He understood that the lecturer w~s a reputable practising geophysicist, associated with a reputable company! It was rather desirable perhaps to say that the Institute had made some inquiries with regard to his status. Geophysics was a comparatively newscience, and had suffered several hard knocks in Australia and elsewhere. Most of those knocks had been the result of undue optimism of a number of people who did not understand what they were talking about. It had been claimed that geophysics was a...

Jan 1, 1930

In 1953, Dr. N. H. Fisher of the Bureau of Mineral Resources, acting on behalf of the Society of Economic Geologists, which is considering the sponsoring of a uniform system of nomenclature for ore reserves, enquired from the Australasian Institute of Mining and Metallurgy whether it had ever considered this subject and particularly whether it had ever set up any standard definitions or specifications with regard to ore reserves.As this had not been done, but was thought to be desirable, the Council of the Institute appointed a Committee consisting of H. H. Dunkin, Associate, Professor of Mining Engineering, University of Melbourne (Convenor), E. A. Rudd, Professor of Economic Geology, University of Adelaide, I. N. Campbell, Chief Geologist of Western Mining Corporation; and the writer to consider and report on this supject.In December 1953, the Committee submitted its first report to the council and this report (reproduced here as an Appendix) was widely circulated among member companies, and engineers, with an invitation to comment on the proposal. A large number of, replies was received and studied.After studying the replies the Committee issued a second report in part as follows:-From these replies we have learned that the suggestions made in the first teport of the Committee are unacceptable to most of those interested, on one or all, of the following grounds;-(a) number of categories,(b) definition of categories;(c) nomenclature.

Jan 1, 1955

Rare-earth permanent magnetic roll separators, pioneered by our group a few years ago, have distinctly different operation characteristics compared to prior art electromagnetic separators of various types. Many new applications for dry high-intensity (or better: high-force) magnetic separation have been developed in a short time period. It has also been found that the new generation of separators generally are more efficient with regards to removal of weakly magnetic contaminants in glass and ceramic raw materials with minimum loss of valuable product compared to induced magnetic roll (lMR) separators. The latest development is in the area of production of clean magnetic concentrates at high recoveries. It is likely that the PERMROLLR magnetic separator will replace cross-belt and lift-type magnetic separators as a result of this most recent advance.   The paper will review the features of the PERMROLLR magnetic separator in comparison with other types of magnetic separators on the market and give examples on applications.

Jan 1, 1990

Differentiation of a basaltic (?) magma occurred in an active volcanic area during the late Miocene and Pliocene, and a change in the general mode of extrusion from fissure flow for the basalt to explosion for the andesite reflects an accompanying increasing magmatic viscosity. A caldera formed after the flow phase was completed and was filled with coarse agglomerate, much of which has a fused appearance. After an erosion interval its shape was modified and it became gradually deeper as repeated explosions from growing andesitic volcanoes caused large quantities of pyroclastic material to be deposited. At the close of this phase the floor abruptly collapsed when a, large block of the underlying crust was engulfed. The incompetent pyroclastics filling the caldera steepened in dip and the ensuing fractures were filled by the rising magma as dykes and sills and a chonolith formed below the caldera at a shallow depth. The ensuing activity reveals a further stage in differentiation and biotite is an important new ferromagnesian to be observed in the new rocks.Fracturing of the surrounding basalts was most intense in the rocks forming the periphery of the caldera where steeply and flatly dipping faults resulted from increasing horizontal pressure directed towards the caldera.Further differentiation resulted in the increased crystallization of orthoclase felspar, as evidenced by the numerous intrusives of trachy andesitic composition. Magmatic freezing caused mineralizers to accumulate at the top of the chonolith. These eventually escaped and auriferous pyrites, tellurides, quartz, and calcite were deposited in the surrounding rocks.The flatly dipping fractures are the most important and can be expected at various depths in a zone about 4,000 ft wide surrounding the caldera. Latest movement along these was controlled by magmatic consolidation rather than the shape of the caldera. Some flat faults were able to remain open during mineralization and acted as a feeder for the shallower fractures, thus limiting the depths to which the steeper dipping fractures were mineralized with the possible exception of one particular Nw.-striking lode (the Crown-Crescent).INTRODUCTIONThe gold deposits of the Tavua district were discovered in 1932 and from 1935 to June, 1961, 1,985,041 fine ounces of gold were produced from 4,202,504 tons of ore. Of the original three producers, only the Emperor remains active in the...

Jan 1, 1962