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Up to 19 chemical parameters were studied in flotation pulps in six Australian lead-zinc concentrators with the aim of obtaining a better understanding of the nature of, and changes in, the chemical environment. This paperdiscusses collector residuals, metal concentrations in solution, and other parameters.Collectors used in the plants studied were various xanthates, Z-200, and Aerofloats. Xanthate residuals varied in different ways in most plants. However the general trend was for residuals to be at the O· 5-2 p.p.m. level in lead flotation and O· 5 p.p.m. or less in zinc flotation.Aerofloat residuals were also variable but in the plant concerned were at a much higher level (8-10 p.p.m.) than xanthate residuals. Z-200 residuals were in the 10-20 p.p.m. range and it was found that the Z-200 added to zinc flotation was reporting in dam return water and entering lead flotation.Copper concentrations in solution were negligibly low in those plants where cyanide was not used. When cyanide was used, copper was at the 5-20 p.p.m. level and appeared to be present as Cu(CN)-2. However the hiocyanatepresent may be important. Xanthate was also present in these solutions.Zinc concentrations ranged from 0·1 to 800 p.p.m. in different plants. The general trend was for the zinc level to be highest in the grinding circuit and to drop during flotation. However there was always an increase in zinc concentration when copper sulphate was added, even tho.ugh this incre.ase was not permanent, and the increase was greater with higher copper sulphate additions.The manganese concentration also increased appreciably during copper-activation of marmatite. In some plants lead concentrations increased from 0·1 to 1 p.p.m. during activation of marmatite.Calcium concentrations (20-1200 p.p.m.) and magnesium concentrations (10-600 p.p.m.) tended to be fairly stable in each circuit.

Jan 1, 1970

GENERALTHE coal deposit, where it is being worked, consists of a bed of brown coal varying in thickness from 120 ft. to 200 ft., covered by an overburden of clay, drift, loam, etc., of a thickness of 22 ft. to 40 ft., and averaging 28 ft.The overburden is first entirely removed from the coal, and then the coal is excavated by. large revolving shovels which work at the bottom of the hole or open cut in the coal and deliver it in shovel bucketfuls to the transport system. The shovels owned by the Commission and available for this coal excavation are two Bucyrus steam revolving shovels, one being type 150B, weighing 150 tons, having a 21-cub. yd. bucket, and capable of digging a 47-ft. face; and the other being type 175B, weighing200 tons, having a 31-cub. yd. bucket, and capable of digging a 61-ft. face.In addition to these two steam shovels, the Commission has recently obtained a No. 250 Ruston electric revolving shovel weighing 340 tons, and having a bucket of 10 cub. yd. capacity, and capable of digging a 75-ft. face. When this electric shovel has been erected it will replace the steam shovels on the coal excavation, and the permanent transport system has been designed to take delivery of the coal from its bucket.The duty to be performed by the transport system is to take the coal from the shovels, elevate it out of the open cut, transport it to the screening house, deliver it iuto the hoppers at the top of this building, then to take the coal after it has passed over the screens and distribute the required grades to the power house and to the briquetting plant.

Jan 1, 1924

Mining has long been an important activity for the people of Australia . The Aboriginals used rocks and minerals in their culture many thousand years before European settlement. It was not until 1840 that silver-lead ore was discovered in the Mount Lofty Ranges , and developed as Australia's first metalliferous mine. The mining industry contributes significantly to all aspects of the Australian economy, generating substantial employment opportunities, investment and income, export earnings and royalties for Governments. While the mining industry in South Australia is small by comparison with Western Australia, Queensland and New South Wales, it is nevertheless a very important industry in the State.   With the discovery of the world's third largest Cu-Au-U-Ag resource at Olympic Dam in 1975, the State saw a period of intense exploration activity through the early to mid-1980s. However, failure to locate additional world class deposits saw a dramatic reduction in exploration activity during the late 1980s. A perceived lack of prospectivity was compounded by the recognition that exploration for such deposits was neither easy nor inexpensive in South Australia because more than 80% of the State is masked by surficial sand and silt.

Jan 1, 1995

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

Mining at Waihi on the Martha Hill commenced in 1878 and between 1892 and 1953 produced 35 million ounces of bullion from some 13.5 million short tons of ore from 40 named quartz reefs. The general geology of the ore is recorded in detail with differing interpretations by Bell and Fraser (1912) and Morgan (1924). The reefs and stringers have formed by fissure filling and replacement in mainly quartz andesite dacite flows within the Waihi 'Graben'. The host rocks are extensively propylitised with intense alteration forming zones of kaolin adjacent to the main reefs.

Jan 1, 1979

Development of New Comminution Testing Methodologies for Geometallurgical Mapping of Ore Hardness and Throughput The emerging discipline of 'geometallurgy' is becoming increasingly recognised as a discrete and high-value activity that reflects an ongoing trend towards more effective mine site integration and optimisation. Constrained sampling that reflects and defines inherent ore body variability is a key geometallurgical requirement. This requires use of larger numbers of low-cost physical testing which can be applied to small sample volumes suitable for defining natural variability. The AMIRA P843 'GeMIII' project (Geometallurgical Mapping and Mine Modelling) is a major industry-supported research initiative designed to develop new tools, methods and protocols to support geometallurgical integration. As part of this integrated research a new more rapid low-cost comminution test (GeM Comminution index) has been developed which can be employed as a front line tool for geometallurgical mapping purposes and predictive throughput modelling. The test has been designed to be inserted into routine assay sample preparation and is based on constrained jaw crushing protocols linked to analysis of resultant size distributions. Extensive validation and modelling has shown the GeM Comminution Index (Ci) is correlated with the Drop Weight index A*b and Bond Mill Work Index (BMWi). Large scale trials have been conducted within a commercial assay laboratory to demonstrate and optimise incorporation of the Ci test into routine sample preparation protocols. While Ci based estimates of A*b and BMWi are not as precise compared to larger volume more expensive test-work, the ability to undertake large numbers of tests typically in a systematic down-hole manner, provides a high level of data support through adjacency. A Ci based approach is highly suitable for variability mapping, domaining and selecting large composite samples for more precise testing. Within the context of the AMIRA P843 project this forms part of an integrated work flow designed to support geometallurgical integration. The development of a comminution test linked to routine assay sample preparation represents significant value adding to a process that in most cases is already going to be carried out. This paper introduces the Ci test concept and application to geometallurgical testing for throughput modelling

Sep 13, 2010

By P Mitchell, J Proffett, I Munajat

Batu Hijau is an island arc porphyry copper-gold deposit located in the southwest corner of Sumbawa Island in the Sunda-Banda archipelago of Indonesia. Southwest Sumbawa Island is underlain by Early Tertiary, low-K calc-alkaline to weakly alkaline volcanic and intrusive rocks. Within the mine area the oldest exposed rocks are medium- to thick-bedded, medium to coarse andesite volcanic lithic breccia, thin bedded, fine-grained volcaniclastic sandstones and mudstones and hypabyssal porphyritic andesite. In the eastern portion of the mine area there is a thick sequence of quartz diorite that postdates the andesites. A small stock of Equigranualar Quartz Diorite predates the Batu Hijau deposit and occupies the contact between the andesitic volcaniclastic sequence of rocks and the Porphyritic Quartz Diorite. Batu Hijau is a world-class copper-gold deposit that has a drill indicated mineable reserve of 914 million metric tonnes grading 0.525 per cent copper (10.58 billion pounds copper) and 0.403 g/t gold (11.8 million ounces gold). Mineralised material not in reserve accounts for an additional 580 million metric tonnes at 0.328 per cent Cu (4.19 billion pounds copper) and 0.171 g Au/T (3.19 million ounces gold), and including an oxide copper resource of 57 million tonnes at 0.37 per cent Cu and 0.12 g Au/T. Copper and gold mineralisation is directly related to quartz veining and wall rock alteration that developed with multiple tonalite porphyry intrusions. The tonalites were emplaced along the contact between the andesitic volcaniclastic rocks and quartz diorite intrusives. Copper and gold are zoned around the porphyry intrusions, which are designated by their contact-age relationships and other features as Old Tonalite, Intermediate Tonalite(s), and Young Tonalite(s). The Old Tonalite was the first copper-bearing intrusion, and although it is the smallest intrusion it has the highest quartz vein density, the strongest alteration and the highest grade. At least two tonalite porphyry intrusions followed the emplacement of the Old Tonalite. Each of these intrusions was associated with less quartz veining, weaker hydrothermal alteration and lower grade copper and gold than the previous intrusion. The intrusive cycle culminated with the emplacement of the Young Tonalite, which contains relatively few quartz veins, is weakly altered and mineralised. Hypogene hydrothermal alteration and sulphide mineralisation developed in five temporally and spatially overlapping stages. These stages consist of Early, Transitional, Late, Very Late, and I Zeolite alteration. Early alteration and sulphide mineralisation accompanied each tonalite porphyry intrusion, but with diminished intensity in each subsequent intrusion. Transitional and later stages of alteration and mineralisation postdate the tonalite porphyries and overprint Early stage alteration and mineralisation. Early alteration and mineralisation consisted of biotisation, secondary magnetite and plagioclase development, fine porphyry-style stockwork veining and ore mineralisation. Magnetite-biotite????quartz stringers and dark micaceous (biotite-sericite) veinlets were developed. The veinlets were accompanied by biotisation of magmatic mafic minerals and groundmass. Thin, irregular and discontinuous æAÆ type quartz veinlets and fine-grained chalcocite, digenite and bornite mineralisation accompanies the Early alteration. It is hypothesized that most of the copper mineralisation was originally deposited as bornite, digenite and chalcocite. Secondary plagioclase was added along the selvages of the early quartz veinlets. Early alteration is pervasive within and proximal to the tonalite porphyries. In the distal portions of the deposit, andalusite and anthophyllite formed at intermediate to shallow depths, and in the deeper portions of the deposit, respectively. The andalusite and anthophyllite probably developed at the same time as the early magnetite-biotite-quartz alteration in the core of the deposit. Transitional-age alteration consists of oligioclase/albite-sericite-chlorite- quartz-¦vermiculite and is associated with æBÆ quartz veins. Through-going planar æBÆ veins are thicker than æAÆ and æA-familyÆ veinlets and have chalcopyrite????bornite along vuggy centrelines and narrow oligioclase????albite alteration envelopes. Rare æCÆ chalcopyite¦quartz veinlets were also formed during Transitional alteration. During Transitional alteration early copper sulphide minerals (chalcocite, digenite and bornite) are converted to bornite and chalcopyrite. The majority of the copper (50 - 70 per cent) in the deposit is contained in ores in which chalcopyrite is the predominant sulphide. Late alteration consists of feldspar destruction and replacement by sericite and other minerals. The late alteration is accompanied by the development of æDÆ sulphide veinlets and veins. These veins consist of pyrite and quartz????chalcopyrite. Within the halos of the late pyritic veinlets biotite is replaced by sericite, quartz-sericite, quartz-andalusite, or quartz-pyrophyllite+kaolinite replace plagioclase, and magnetite is converted to specularite and/or pyrite. In the periphery of the deposit, the feldspar destructive alteration, together with outer zones of Transitional-age alteration, constitutes what is commonly referred to as a æpropylitic zoneÆ. Very Late hydrothermal alteration is also characterised by feldspar destruction, but differs from Late alteration in that feldspar is replaced by smectite in association with sericite and chlorite. Sulphide mineralisation in this stage consists of sphalerite, galena, tennantite, pyrite and chalcopyrite. The last stage or I Zeolite alteration consists of low-temperature, open space filling consisting of stilbite or laumontite¦calcite. Supergene oxidisation of the orebody extends to a maximum depth of 210m. Isolated deep oxidation occurs along open fracture zones to depths of ~400 metres along æDÆ vein filled fracture zones. Weak supergene copper enrichment occurs in a thin horizon (15 to 60 m thick) that blankets the top of the deposit. The main supergene copper mineral is secondary æsootyÆ chalcocite replacement of sulphide grains and as veins.

Jan 1, 1999

By P K. Wong, D A. F Oliveira, F M. Azad

In situations where foundation piles are located in proximity to existing or future tunnels, it is typical for the tunnel owner to require that sleeving of the piles be carried out to at least the invert of the tunnels to minimise any load transfer to the tunnel lining. In competent rock, this practice may be sometimes unnecessary, thus uneconomical. This paper presents an assessment of the effect of pile loading from one of the multi-storey buildings at Barangaroo South in Sydney on the adjacent future Sydney Metro tunnels. It was originally required by Transport for NSW (TfNSW) that the piles be sleeved below the tunnel invert level; however, the building developer wanted to reduce the pile sleeving depth to achieve a more economical solution due to the large number of load transfer piles being required for the project. To assess this feasibility, a full 3D commercial numerical code, FLAC3D, was used to carry out this complex soil-structure interaction analyses. Based on these assessments, it was demonstrated successfully to the TfNSW that the pile sleeving may be terminated at 2 m above the tunnel invert level. For this arrangement, the investigations found that the loading on the piles should have negligible adverse impact on the tunnel lining design. As a result of such an assessment, the proposed pile sleeving level was approved by TfNSW, thus offering an economical foundation solution for the project.CITATION:Azad, F M, Oliveira, D A F and Wong, P K, 2014. The impact of pile loading on adjacent metro tunnels – Barangaroo South, Australia, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 355–360 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

The small scale alluvial gold mining industry in Papua New Guinea (PNG) is c.irrently the only form of small scale mining carried out in this country. It already contributes significantly to the economy with current production estimated at 2 000-2 500kg per year. Until recently, small scale alluvial gold mining has been confined to simple panning and sluicing of high grade alluvial and colluvial deposits. Traditionally the small scale miner in PNG has only worked gravels with gold grades in excess of 500mg/m3. Grades of this order are required to justify the hard physical labour involved ~n hand operated small scale mining methods. .he introduction of higher throughput technologies such as trommels fed by hydraulic excavators has the effect of altering what constitutes an economically viable deposit. Mechanised techniques allow for the consideration of grades of almost half that level. The potential and opportunities for utilising this type of small scale mechanised mining in PNG are enormous with large areas of ground with gold grades running in excess of 250mg/m3 and often up to 2000mg/m3 throughout the country. An assessment of the current operating economics of this technology in the PNG context is the principal objective of this paper. Small to medium scale mechanised mining can potentially contribute significantly to the PNG economy particularly as it lies within the react-, of many PNG businessmen. Its potential is currently somewhat limited by a general lack of infrastructure and is also constrained by socio-political factors.

Jan 1, 1991

By Morabito J, Harrop D. W

Uranium exploration was commenced in 1973 and carried out at a regional scale over a wide area of the northern part of the Camarvon Basin of Western Australia by Minatome Australia Pty Limited and their joint-venture partners. As a result, pervasive uranium mineralization has been found in the Cretaceous sandstones near Manyingee Hills in the Onslow Region, which were probably deposited in a near-shore, fluvia deltaic palaeo-environment.Mineralization is generally found in poorly sorted argillaceous sandstones and siltstones near redox fronts formed by oxidizing waters circulating in reduced sediments. The principal minerals found in the two Manyingee deposits delineated so far are coffinite, uraninite with associated pyrite in the reduced zones, and phosphuranylite, siderite and limonite in the oxidized zones. The presence of dissolved uranium in the superficial aquifers, of secondary uranium minerals as coatings on granitic rocks, and of recent uranium-bearing calcrete sediments, suggest that the whole Cretaceous-Precambrian system has been subjected to the formation ofroll-front type uranium deposits since the Cretaceous. Continuing exploration is locating additional uranium occurrences. The deposits outlined so far are being evaluated for their amenability to in situ leaching tests planned for 1982-1983.

Jan 1, 1981

By Tellis D. A

An outline is given of the general position of earthsciences information in Australia, the background to development of the Australian Earth Sciences Information System (AESIS) and the role of the Australian Mineral Foundation in developing and co-ordinating the projeot in co-operation with the CSIRO, BMR, National Library of Australia, AGIA, and many companies.Details 'of the system, method and anticipated rate of input (especially of unpublished material at which the System particularly aims), mode of dissemination, and use of the data base are discussed. Information on theAustralian Thesaurus of Earth Sciences and Related Terms and brief details of some 30 earth sciences information collections in Australia is given.

Jan 1, 1977

Essential features of the role of the fill material in mechanized cut and fill mining are discussed, with particular emphasis on its dewatering and strength development after emplacement. The fill material is regarded as a chemically-reactive porous medium, the most important property of which is permeability. Methods are described for measurement of permeability and other fill properties and results of such measurements applied to develop an orderly approach to the operation.

Jan 1, 1966

Advances in Thickener Feedwell Design via Computational Fluid Dynamics Modelling

Sep 13, 2010

Shortly after Denny, Robson, and Irwin published their first paper in 1937, on the prevention of silicosis by metallic aluminium, experiments were begun on the practical application of the discovery.It was thought at that time that aluminium powder, to be effective in aluminium therapy, would have to be intimately admixed with siliceous dust at the latter's source. There followed several years of experimental work underground, during which the application of aluminium powder was tested in:(1) Speakers on machine columns, vibrated by drills.(2) Vials placed in drill holes to be blasted.(3) Both homogeneous and heterogeneous mixture with explosives.(4) Packages with tamping.(5) Compressed-air lines.(6) Special compressed-air ejectors for use while drilling and after blasting.(7) The discharge of ventilation fans.(8) The filters of respirators.It was concluded from this research that any adequate method of introducing aluminium powder into a mine atmosphere would require too much extra gear, supervision, and aluminium p;wder, and would interfere unduly with underground routine.Later, animal experiments by Denny, Robson, and Irwin2 showed that aluminium powder provided effective therapy when inhaled independent of silica dust. Therefore, some means of surface treatment was deemed more practical.APPARATUS USED IN THE DEVELOPMENT OF ALUMINIUM PROPHYLAXIS SAMPLINGA basic requirement was a method of sampling to assess accurately the particle-size concentrations of dispersed aluminium powder. Konimetry, though regularly practised at McIrityre, was inadequate for the research in mind. On the other hand, the efficiency of the thermal precipitator was recognized as being very high. Accordingly, the latter instrument was chosen as best suited to our needs. Through the courtesy of the Ontario...

Jan 1, 1945

This paper firstly reviews the requirements for container and hopper design for reliable discharge. Discussion is then directed to the evaluation of the consolidation stresses acting in both in both the cylinder and hopper sections during both initial and flow conditions. Here the vast difference, especially in vicinity of the bin outlet, between the initial or filling and flow conditions is highlighted. This vast difference has major design and operation implications. A further major implication is that all bulk solids must dilate to flow. The opportunity to simultaneously attain reliable discharge and partial moisture removal is also examined.The selection of design parameters to maximise the consolidation stresses in both the cylindrical and hopper sections is detailed. In regard to the latter, it is recommended fine coal bins be discharged using low friction lined transition hoppers with large outlet spans. Such outlets will discharge fine coal in a relatively compacted state. This compaction state should exhibit minimum water retention and short term moisture uptake.

Jan 1, 1998

By H Hutchinson

Froth flotation is applied to mineral sand concentrates in order to produce commercially viable xenotime concentrates. Experiments indicate that a xenotime product containing 38% Y2O3 at 47% recovery or 34% Y2O3 at 83% recovery can be obtained from a 27% Y2O3 feed. The process involves a primary stage of reverse flotation at which oxide and silicate gangue is floated, and secondary stage of direct flotation at which xenotime is floated. Of the various collectors screened an amphoteric compound was found to be effective at both stages. This was made possible by the addition of sodium silicate at the second stage, which acted as depressant for the remainder of the gangue. Similar studies on a low grade feed material were somewhat unsatisfactory as the grade achieved fell short of what was targeted.

Jan 1, 1990

By J Mercuri, S Dunford, P Rothman, E Bartsch, J Snyder, D Newton, R Maron, D Cirulis

The purpose of a mineral comminution circuit with a ball mill running in closed-loop with a hydrocyclone classification cluster is to feed the downstream process with the target particle size. Maintaining the optimal particle size in the flotation feed can significantly improve plant cash flow. In particular, reducing the amount of coarse material is often a major challenge. Existing instrumentation to provide particle size measurement is considered standard equipment in most modern concentrator plants. However, availability is often very low, mainly owing to high maintenance requirements of the analyser and associated sampling system.CiDRA Minerals Processing has developed two novel and robust technologies that address this challenge by providing high reliability and very low maintenance systems for on-line measurement of coarse material in the overflow of individual hydrocyclones. The first system is non-invasive and measures pebbles and rocks greater than 6 mm. This paper focuses on the second system, which is a ruggedized wetted sensor design with no moving parts and provides a real-time trend of the desired target grind size parameter, such as percentage above 150 micron.Both systems have simple robust designs and measure in the primary overflow stream of the individual hydrocyclone. Individual hydrocyclone measurement enables identification of poor performing hydrocyclones in addition to providing a representative measurement of the whole hydrocyclone cluster. The systems do not require sampling and associated sample transfer piping circuits that are prone to plugging, thus avoiding high maintenance requirements.The wetted sensor will be described in detail along with its implementation in a robust control scheme in a major copper concentrator in North America. Plant data shows very high availability, achieved with very low maintenance, has enabled improved process control, thereby maintaining throughput and ball mill target power while reducing grind size.CITATION:Cirulis, D, Dunford, S, Snyder, J, Bartsch, E, Rothman, P, Maron, R, Newton, D, O’Keefe, C and Mercuri, J, 2015. Process optimisation using real-time tracking of coarse material in individual cyclone overflow streams, in Proceedings MetPlant 2015, pp 93–109 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

The process of electrostatic separation was developed in the late 19th century, but did not make much headway for about 25 years. High dc voltages, of the order of 20 kilovolts, are involved, and the only means of obtaining such voltages at that time were by the use of frictional machines, such as the Wimshurst. These were not reliable, for two reasons:-a. If a spark discharge occurred it took an appreciable time before a steady voltage was again attained.b. In damp weather the machines were almost useless.In the first 20 years of the 20th century the advent of mechanical and vacuum-tube rectifiers led to promising developments of 'the process. In the early 1920's flotation became widely used commercially, and proved to be more reliable, and capable of wider application, than electrostatic separation. During the last 15 years or so, with a better knowledge of the fundamentals forming the basis of the process, electrostatic separation is beginning to compete with flotation, especially in the treatment of smallsizedgranular material, such as beach sands. Electrostatic separation can be, and is, widely used in many cases where flotation is impossible, such as in the cleaning of food products which must be kept dry.

Jan 1, 1950

By A Simmons, J Chan, A Li, Q Gu, D M. Brett

The paper presents an example of field density achievements using thin layer deposition and solar drying and compares this with compaction data from laboratory testing and field trials of mechanical densification processes.

Jul 1, 2021

By D C. McPhail, S L. Rogers, J Brugger

Using iron- and sulfur-oxidising bacteria to catalyse the breakdown of sulfides that host the gold is an important biological method for the pretreatment of refractory gold ores. Following this biological treatment a combination of chemical and physical methods are used for leaching (such as the cyanide process) and concentration (such as carbon-in-pulp or electrowinning) of gold. Although these methods are well accepted by industry, they harbour limitations in the processing of low-grade refractory ores, and regulatory agency/public acceptance of cyanide use. Thus, it is beneficial to industry to develop environmentally friendly, cost-efficient leaching and concentration techniques that are based on micro-organisms. This may soon be possible by adapting the results of recent regolith geoscience research, which has shown that micro- organisms are capable of driving a biogeochemical cycle of gold dispersion, transport and reconcentration in the supergene environment. The indigenous microbiota in biologically active soil microcosms from a number of Australian sites are capable of solubilising up to 80 wt per cent of the gold contained in these materials during 50 days of incubation. Studies using molecular microbial techniques have shown that a metallophilic bacterium, Ralstonia metallidurans, is present in biofilms on gold grains from a number of Australian sites. R metallidurans is capable of actively accumulating gold from solution, suggesting that the bacterium may contribute to the formation of secondary gold grains and nuggets. Identifying the biochemical and physiological pathways that lead to the dispersion and accumulation of gold in regolith, and quantifying the reaction kinetics of these processes may thus lead to the development of industrial bio-processing capacities for gold-containing ores.

Jan 1, 2007