Search Documents

A process was developed, on a laboratory scale, for the removal of iron oxides from Weipa pisolitic bauxite. The technique involves the chemical reduction ofthe iron oxides by carbon, followed by selective removal of the iron species by acid leaching or chlorination.To remove more than 90 per cent of the iron it is necessary to reduce the iron oxides substantially to iron metal by heating the bauxite, pre-calcined at 650-800°C, with reactive carbon at 1040-1100°C. Reduction proceeds via the intermediate formation of hercynite (FeO.Al2O3) and difficulties have been encountered in reducing hercynite formed under less favourable reduction conditions.Following reduction, efficient selective removal of iron species is readily effected by acid leaching using dilute hydrochloric acid at 100°C, or chlorination at 500-750°C using Cl2, Cl2/N2, or Cl2/N2/CO mixtures.After removal of unreacted carbon, the final products contain 0·5-1.0 per cent Fe203 and 87-92 per cent Al203.

Jan 1, 1971

TIMBER supports for large underground cavities are temporary expedients until the permanent filling can be put in. Nevertheless, timber supports are very necessary in some form. The general problem is to support the cavity in all directions withthe minimum of timber, disposed in the strongest way. The simplest way of filling an irregular space with timber sets is to form triangles.The right-angled isosceles triangle (Fig. 1) leads to the true square set, in which caps are equal to struts. The right-angled unequal-sided triangle and the scalene isosceles triangle (Fig. 2) lead to the oblong square set, where caps are longer than struts.The scalene triangle (Fig. 4) leads to the rhombic or oblique set. The equilateral triangle leads to the hexagon set (Fig. 3), in which the caps and struts are all equal. These five plane figures, the triangle, square, rectangle, rhomb and hexagon, are the only figures that will completely fill any irregular plane figure, without interstices. Hexagon sets were first suggested by the writer in 1902 to a mine manager at Broken Hill, who did not see his way to use them.

Jan 1, 1912

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

OWING to the gradual depletion of the hitherto plentiful supply of firewood in the immediate vieinity of Queenstown and Gormanston, which caused a steady increase in the cost of fuel for domestic purposes, the Mount Lyell Company took steps several years ago to make available as a substitute electric current from its Lake Margaret hydro-electric supply. In order to make this practicable it was necessary that the cost of electric power for heating purposes should compare favourably with the cost, of fuel, and the installation of domestic appliances brought within reach of the average householder, and efforts have been continuously directed towards this end since the year 1928.WATER HEATERSThe installation of electrical apparatus in local dwellings began with hot-water services, the heating elements being the types then procurable on the market and adapted to meet requirements.These, however, did not prove satisfactory, but the study of their bilure resulted in a type being developed locally which has overcome all difficulties. The first type of water heater evolved was an outside circulation one the element of which consisted of an iron pipe through which the water passed, insulated with micanite and wound with nichrome wire, the latter being covered with alundun cement to keep it in position and prevent oxidation. This was insulated on its outside surface with a layer of asbestos flour, and connected to the hot-water container as shown in Fig. 1. It was found, however, that the iron pipe had a short life, due to a certain amount of acidity in the water, and a copper pipe was substituted which proved very durable. Some heaters with this improved type of element are still operating after six years of use. The resistance wire is run at a very low current density, which ensures durability.

Jan 1, 1927

The additional information that Clarke and Taylor (1982) provide about the important but poorly documented Ardlethan deposit is, of course, very welcome. However their contention that structural considerations, in conjunction with petrology, alter the interpretation of the mineralogical and geochemical data presented previously (Scott, 1981) is not accompanied by adequate supporting evidence. Indeed characteristics of the orebodies studied invalidate their arguments.Heterogeneity between matrix and fragments is not a problem in the South Cherry and Ardwest orebodies because most samples are comprised entirely of interlocking hydrothermal assemblages with a fabric and mineralogy that is uniform through both former breccia fragments and matrix. In hand specimen, the rock superficially resembles altered granite and, as indicated by Clarke and Taylor (1982), a brecciated texture is difficult to discern. In thin section, relict brecciated textures can be observed as localized changes in the grainsize or in the distribution of minerals that outline former breccia fragments (P. J. Eadington, 1982, personal communication).Because of the intense brecciation and comminution of rocks (fragments < 10 mm are usual) in the South Cherry and Ardwest breccia bodies, hydrothermal recrystallization was complete, resulting in homogenization of fragments and matrix. Furthermore, the amount of sample analysed (-100 g for drill core and 2-3 kg for hand specimens) is sufficiently large to be representative of both former breccia fragments and matrix. The Carpathia and Stackpool orebodies, with their abundance of sedimentary fragments, have alteration superimposed on a heterogeneous fabric, and were not studied. Thus the problems of differentiating between fragments and matrix (Clarke and Taylor, 1982) are irrelevant to the particular orebodies described in my paper.Within the alteration halo, which is several hundred metres wide (Paterson, 1976), the very uniformity of the alteration assemblages implies that subsequent, postmineralization brecciation is of only minor significance.Indeed tourmaline pipes in the Ardwest pit are less than several metres across (Clarke, 1979) and produce minimal alteration in the surrounding rocks. Therefore the interpretation of the mineralogical zonation is not compromised by the recognition of several periods of brecciation.

Jan 1, 1982

By Parker A. J, Muir D. M

Solutions of acetonitrile in water dissolve water soluble copper(I) chloride. Removal of volatile acetonitrile from the resulting solutions, by distillation with low grade steam, precipitates pure copper(I) chloride. This is used to purify a crude copper chloride sublimate from the chlorination of nickel matte but is applicable to other sources of copper(I) chloride. The pure product can be converted to pure copper(I) oxide, copper(II) oxychloride or pure copper metal directly.

Jan 1, 1980

Mount Read is 'situated in the county of Montagu, on 'the west coast of Tasmania, about 20 miles inland from. Remine in an easterly direction, 15 miles northerly from Mount. Lyell, and 30 miles south-east from Mount Bischoff, and is one of the mountains forming the west coast range; it rises to a height of 3890 ft. above sea level.About eleven years ago the first mineral section was taken up on Mount Read by a Hobart company, known as the Mount Reid Silver Mining Company, consisting of 25,000 shares its holding consisted of one section of 80 acres, held under mineral lease. Prospecting was carried on for some months under great disadvantages, as all supplies had to be carried up the mount from Dundas, a distance of nine miles, on men's backs, until a pack track for horses was made.The track rises 2500 ft. in the first five miles, and then falls 200 ft. from that point to the mines, which are at an altitude of 3000 ft. above sea level, and at a point about two miles westward from the summit of the mountain, approximately midway between Mounts Read and Dundas.

Jan 1, 1901

Taking the third meridian as the eastern boundary of proved payable auriferous country, there is a stretch of country, nearly 600 miles in width, in which no appreciable amount of gold has yet been discovered. Many prospectors have attempted to .penetrate or traverse it, but comparatively few have thought it worth while proceeding with the examination.The desolate stretch of waterless desert-the very few and insignificant outcrops through the sand and the almost total absence of feed for horses have, combined, presented such a barrier as to preclude prospecting. The few who have traversed the country are eloquent in denunciation, yet their investigations, necessarily hurried, are not quite satisfactory. The absence of water utterly debars a thorough examination being made. Gold may exist in quantity, yet it would have to be extraordinarily plentiful to render its obtaining profitable. Too fantastic is the idea of its ever being a mining district; shifting sand to traverse, utter absence of wood and water render the notion absurd. Likely looking belts occur, but these in all "cases are small and remote from water. Gold has been obtained from likely look ing quartz reefs, but only by fire assay, and then but a few do to the ton. Without wishing to be pessimistic, I would unhesitatingly declare that east of the third meridian, and between the parallels 25 and 30 degrees in West Australia, there is no gold in payable quantities.

Jan 1, 1901

Throughout history, many of the world's achievements, conflicts and problems can be traced to the demand for minerals. With the rapid expansion of our industrialised society in recent years the demand for minerals has grown to such an extent that uncertainties about availability and cost have arisen, especially in the case of energy minerals.Minerals have acquired a new dimension for governments as the availability of these resources is interwoven with the ability of governments to achieve their developmental goals on national and international levels. Accordingly, the supply of minerals will increasingly be affected by social and political factors.

Jan 1, 1986

A poured slag bottom is universally considered to be the best type bottom for copper reverberatory furnaces. It is impervious to molten matte and ready for immediate use.When molten slag is not available a monolithic silica bottom is the second best; such a bottom has been adopted at Mount Morgan. The laying of such a bottom is a phase of smelter construction on which so little real information is obtainable that a day to day record of such a recent example as Mt. Morgan's 19 ft. x 40 ft. reverberatory may be of interest. The work was done under the direction of E. Pesout, of McGill Smelter, Nevada. PREPARATION OF THE BOTTOMA 26-inch bed of closely packed firebrick with sand-filled joints was first laid on the clean, dry concrete foundation and the whole dried out by small fires maintained on the brickwork for several days. Ninety tons of silica sand was meantime thoroughly dried and stored in clean drums. This sand must be low in FeO and CaO and contain about 95% Si02 , the majority of which should be present as tridymite. This form of silica shows little expansion at high temperatures, for it is the form stable between 870° and 1470° C.Its presence thus minimises disturbance to the bottom by the expansion which, during the burning in, would mark the transformation of quartz to tridymite.

Jan 1, 1939

Gas well tests were performed on 17 wells in the Roma area. The procedure used in the test programme incorporates an initial isochronal test followed by what is described as the "two flow drawdown" technique. The second flow of the two flow drawdown test was conducted for sufficient time to allow transient investigation of the surrounding reservoir. This combination of tests allows the evaluation of stabilized production capacity in addition to the determination ,of several important reservoir characteristics.It also provides a qualitative indication of reserves, by reflecting the presence or absence of reservoir boundaries within the drainage area affected during the test.

Jan 1, 1968

The ultraviolet spectrum of isopropyl ethylthionocarbamate (the principal constituent of Dow flotation collector Z-200) in water and of Z-200 itself in water was found to have an absorption peak at 242 nanometers(nm). The height of this peak was found to be directly proportional to isopropyl ethylthionocarbamate concentrations up to 15 p.p.m. Z-200 contains about 90 per cent isopropyl ethylthionocarbamate and the heightof the peak was proportionately lower, but obeyed the straight line relationship up to 15 p.p.m. This showed the potential value of spectrophotometric measurements for the determination of Z-200 residuals in flotation liquors.Methyl ethyldithiocarbamate (an impurity in Z-200) increased the peak height slightly, but other impurities in Z-200, xanthates, and most inorganic salts present in flotation liquors do not interfere. However nitrate ion and thiosulphate ion have absorption peaks which overlap the isopropyl ethylthionocarbamate peak.The simplest general method to overcome this effect is to extract the isopropyl ethylthionocarbamate into cyclohexane and to measure the absorbance of the extract.The maximum absorbance of the cydohexane extract was at 247 nm and the peak height at this wavelength was found to be directly proportional to the isopropyl ethylthionocarbamate or Z-200 concentration in the original aqueous solution. An alternative method is to measure the spectrum of the original aqueous solution using the aqueous raffinate from extraction as a reference solution. This gives the spectrum due to isopropyl ethylthionocarbamate alone and measurement of the absorbance at 242 nm gives the concentration in the original aqueous solution. Both methods give the same value for the concentration of isopropyl ethylthionocarbamate in the original solution.

Jan 1, 1969

Same-batch and non-blind as well as blind pulp duplicates are often submitted as quality assurance/quality control (QA/QC) control samples to a routine laboratory along with routine assays (and other control samples such as reference material samples). The current ways of interpreting the results of duplicate assays to derive QA/QC conclusions and decisions, however, has not yet been formalised in a scientific manner. The current, prevailing approach and its limitations are reviewed and a new method is proposed as a substitute tool. This new tool should allow for operational error detection on a batch per batch basis (ie batch rejection) as well as laboratory performance assessment with time on reproducibility.

Jan 1, 2008

IN concentrating mills, where several millerals are recovered for realisation in more than one product, various systems are used to express the relative economic value of the work done, and, in the hope that it may prove of use to other operators, the writer will describe a system which, in his opinion, is more complete than any other that he has seen published.The controlling factor in all mill work must be based on the economic result represented by the greatest margin possible between the realizable value of the products and the cost of obtaining same.From a mill-man's point of view these are affected by the following factors:1. Metal contents of ore.2. Grade of products.3. Recoveries.4. Working costs.The grade of ore milled is usually outside the mill-man's control, but this may exercise a considerable influence on the grade of his products, metal recoveries, and revenue per ton of ore. Higher grades or recoveries may be obtained by using a more expensive process, or by additional grinding or reagents, and the economic comparison can only be arrived at by obtaining an analysis showing the monetary value of each variation within the possible limits.In the system to be described, the value of unit variations of metal contents of the ore, grade of products and recoveries are calculated in terms of a monetary unit per ton of ore with the returning charges ruling, and any suitable metal prices. To do this it is necessary to assume what, for convenience, is termed a "standard" set of results from the mill, preferably representing about average conditions, and having calculated the effect of unit...

Jan 1, 1931

During the past Two years in reef gold mining, "indicators" have received great attention at the hands at the Victorian gold seekers. Many years ago, what was caned the" indicator lode," was struck in Ballarat East, on the course of which extremely rich deposits of gold were discovered but as to its being a .qeneral experience in reefs or leaders no one ever dreamed. Now, however, we find that these "indicators" are frequently to be met with, though they differ very much in different localities, making it, therefore, a difficult matter for other than a careful minel' to follow them. The necessity of following "indicators" for the purpose of developing gold is now recognized, and the policy of following them up has been attended with much success in this field. In the case of Messrs Shaw and Sons, at Wedderburn, those gentlemen began to work on an "indicator" here five years ago, and immediately thereafter more by accident than anything else they being at that time inexperienced as regards "indicators " came upon gold bearing quartz, which continued payable so long as the" indicator" aud the stone were in conjunction with each other, but as soon as they parted company the stone ceasedto be of any value then, by following the" indicator," as the latter intersected fresh bodies of stone they proved again more or less payable, until a fortnight or so ago the Messrs. Shaw turned out 4 tons of stone, which yielded £1,825, with also profitable workingup to the present moment. Where they are now working is a mile north of their original find thus proving that "indicators" travel considerable distances and have something to do with the gold deposits found in reefs. On the direct course of Shaw's "indicator," as high as hundreds of ozs to the ton was obtained from the stone but, just a few inches from either side in the same" leader," not a colour could be got. Whatever the cause-whether by electricity or some unknown force in nature-the gold is found on the course of these" indicators" and nowhere else, and-as each of the Victorian Government Geologists admit-their value to the gold-seeker as a means of leading to' gold cannot be over-estimated.

A numerical method for discriminating between replacement and sedimentary processes is applied to a folded stratiform sulphide occurrence. It is shown that numerical treatment of chemical analyses from a single diamond drill hole allowed a rapid assignment of the ore to the syngenetic sedimentary class and thereby enabled a revision of the evaluation program concerned with consequent reduction in costs.

Jan 1, 1973

By Lewis PJ, Halfpenny R, Craighead GA

Exploration drilling by Joint Venture partners CRA Exploration Pty Ltd and Elders Mining PNG Pty Ltd has discovered a signif- icant copper and gold deposit at the Wafi River prospect, 60km WSW of Lae in Papua New Guinea. An indicated resource of 18Mt at 2.5g/t Au using a lg/t cutoff has been delineated in Zone A. No estimate has been determined for the separate copper occurr- ence at Rafferty's Zone but the copper will be significant to the project. Metallurgical studies on the gold indicate that the primary ore is refractory to direct cyanidation giving a highly variable and inadequate response. All conventional refractory ore oxidation techniques perform well on both ore and pyrite concentrate and oxidation occurs rapidly. No metallurgical studies on the copper mineralisation have been undertaken. Hypogene covellite and chalcocite copper mineralisation is associated with an intensely quartz-stockworked, and quartz and alunite-altered intrusive. Economically significant gold mineralisation occurs in distal subhorizontal lenses, within a sedimentary host, that plunge toward the intrusive. These lenses are sandwiched between overlying quartz and alunite-altered zones and underlying quartz and smectite zones in a mixed zone of quartz, dickite, kaolinite and illite alteration. The alteration and mineralisation is classified as a high sulphidation, epithermal style resulting from the influx of hot, acid magmatic fluids. Preliminary land ownership, road access, power supply and mine infrastructure studies are in progress. The project is currently at an advanced exploration stage.

Jan 1, 1991

By Peddie F, Low K, Madgwick J, Rajoka M. I, Gutierrez N, Lim C

Percolation irrigation of low-grade quartz feldspar porphyry ore with pH 2.0 H2SO4 at 510 litres/m2/day using particle sizes 1.7 - 6.7 mm in columns measuring 5 cm dia × 126 cm long was used to study effects of interrupted irrigation ('rest' periods) on metal ion release and leaching bacteria. Copper tenors increased approximately 16 fold and bacterial iron oxidation activity three fold following a 14 day 'rest'. A linear relationship between copper tenor and bacterial activity demonstrated that this experimental system was effective for quantitative studies of bacterial leaching in ore colums.

Jan 1, 1981

Antimony ore samples (mean assay 18·7 per cent antimony) from Endeavour Inlet, Marlborough Sounds New Zealand, were tested for upgrading by flotation to a saleable product (60 per cent antimony).The effects of activating agents, collectors, frothers, pH, conditioning time, and particle size on the recovery and grade of a stibnite flotation concentrate were determined using HaIlimond tube and laboratory flotationcell test apparatus. Optimum flotation conditions for the ore were thereby established. A stibnite concentrate grading 63 per cent antimony and an overall recovery of 90 per cent is obtainable in a two-stage process.

Jan 1, 1977

By C Barton, B Randall, T Weldon, M Lefler

FLSmidth-Summit Valley Technologies has been a leader in gold processing equipment for nearly two decades. Over the past several years an extensive research and development effort has led to improvements in Mercury Abatement systems and process efficiency in Adsorption Desorption and Regeneration (ADR) or "Carbon" plant operations. Two technologies will be discussed that are focused on efficiency improvements followed by an explanation of Mercury Abatement systems. Gold and silver can be desorbed from carbon in several ways. FLSmidth has made significant improvements to the Pressure ZADRA process allowing for lower energy consumption and lower capital costs. This patented process is known as the Split-ZADRA Strip method. Split-ZADRA allows a plant to elute loaded carbon in a semi-continuous fashion. This increases the grade of the Pregnant Strip Solution, improves electrowinning efficiency, reduces capital equipment costs, and reduces energy requirements. During desorption and electrowinning for the Pressure ZADRA process, the pressure and temperature of the circulating strip solution is changed multiple times. A self-contained heating and cooling system has been developed which decreases the energy requirements for elution. Mercury Abatement technology has become increasingly important in recent years. Along with FLSmidth Summit Valley Technologies' complete Mercury Retorting Systems, FLS-SVT has developed systems for the capture and removal of mercury from electrowinning cell and strip solution exhaust, Carbon Regeneration exhaust, and the dore furnace exhaust. This paper describes each of the technologies introduced above and their success in operational gold and silver mines. Case studies will be discussed showing the advantages of each specific technology as it applies to operations around the world. CITATION:Lefler, M, Weldon, T, Barton, C and Randall, B, 2013. Improvements in the mercury abatement and process efficiency of adsorption, desorption and regeneration gold processing operations, in Proceedings MetPlant 2013 , pp 468-478 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013