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Silver and gold bearing ore from the Palmarejo mine, located within the Mexican state of Chihuahua, contains a complex mix of electrum, native silver, silver sulfides and silver chlorides. This paper presents a case study that describes the selection, development and engineering of a tailored process plant for the recovery of silver and gold from this ore. Process circuit feasibility study modelling, metallurgical test work and engineering studies are outlined. Options considered to optimise the recovery of the contained silver and gold are compared, based upon cost, operability, recovery and engineering aspects. Concentration by flotation was found to be the preferred primary recovery route. Intensive leaching of the flotation concentrate resulted in solution grades sufficient to allow direct electrowinning to be evaluated against the more traditional Merrill Crowe process. The flotation tailings stream is processed through a separate leaching stage as there is sufficient economic metal extractable from this stream. The processing flow sheet, which is designed to maximise the recovery from both the flotation concentrate and tailings, and to utilise a common metal production facility, is presented.

Jan 1, 2009

Gold was discovered in the Bendigo area of Victoria in 1851 (Willman and Wilkinson, 1993), and all the early gold mining of any note involved washing (puddling) the gold out of the regolith or alluvium. The waste material from this process was a semi-fluid mixture of rock debris, soil and water, referred to as `sludge'. Puddling machines were gradually introduced to speed up the puddling process (Cole, 1994), and by 1855 an estimated 2000 machines were in the district (Anderson, 1978). In 1859 it was estimated that approximately 2 293 000 m3 of material was puddled annually by the machines on the eastern side of the goldfield, whose waste drained into Bendigo Creek and its tributary gullies. It was also estimated that after the gold was removed, approximately one-quarter of the residue/sludge consisted of the heavier, coarse-grained material which settled out fairly quickly, while the remainder, approximately 1 720 000 m3, was the fine-grained material which flowed downstream for some distance (VPP, 1859 - 60). From these figures it can be assumed that for the ten years during which this volume of puddling was maintained (1854 - 1864) over 5 700 000 m3 of gravels and sands and 17 200 000 m3 of fine-grained sludge had been discharged into and around Bendigo Creek. This was enough to cover an area of over 400 km2 to a depth of 5 cm. By 1859 the problems associated with the sheer volume of sludge being discharged were such that a Royal Commission was appointed to `Enquire into the Best Method of Removing the Sludge from the Gold Fields' (VPP, 1859 - 60). The goldfields referred to were those in the Bendigo area around the township of Sandhurst (now known as Bendigo). The Report of the Commission (VPP, 1859 - 60) stated that: `... inspection of the country bordering upon the course of the Bendigo Creek, to a distance of about fifty miles from Sandhurst . . . ' had revealed that the sludge had ' . . . filled up watercourses and flooded pasture lands . . . '. It also noted that ' . . . even on the plains, thirty or forty miles away from Sandhurst, where the sludge flows thin, and is relieved from its heavier particles, we found it baked into a perfect concrete, and in thicknesses varying up to two feet or more . . . '. The italics were used for emphasis in the original text. As it was considered unlikely that the physical evidence for such widespread inundation would have disappeared completely over the intervening 130 or so years, a project was initiated to locate any evidence of the inundation in the current landscape. If such evidence were to be found, then an estimate could be made of both its extent and its effects on the topography, drainage, and land-use of the inundated area. Extensive field work has determined that over 700 km2 to the north of Bendigo was inundated by the sludge. The area has not been uniformly covered, but has occasional `inliers' which have obviously escaped inundation by being slightly higher than the surrounding areas. Today the sludge is readily identified as a very fine-grained, hard-setting, concrete-like `capping' overlying a well-developed, well-structured, pedal horizon, or in some instances, the gravels and sands of a creek bed. The thickness of the sludge capping varies between a few centimetres and three metres (Peterson, 1996). The buried topography was gently undulating, in direct contrast with the almost unnatural flatness of

Jan 1, 1997

By Lee G, Stitt P

The term "industrial minerals" covers a vary wide field. However in Australia this field tends to be characterised by the follow- ing: (1) Relatively low unit values. (2) Product specifications can be exacting compared to the metalliferous field. (3) Product specifications often have to be tailored to the needs of the end user. (4) Beneficiation plants tend to involve low capital outlays relative to the metalliferous field. However they often have to produce products'to a range of specifications. (5) Technology often influences what can be considered as reserves. (6) Because of low unit values industrial minerals tend to be relatively cost sensitive. This is particularly the case in regard to transport. (7) Location of deposits near to major urban areas (markets) dictates a greater pressure on ecological aspects. (8) In Australia there has been a tendency to vertical integration largely due to the restricted market available. Reserves assessment is shown to be critically dependent upon the above Factors.

Jan 1, 1979

By P O. Andersson

Mining of sill pillars is more difficult than the ordinary mining. The sill pillar mining is performed under more difficult conditions and the mining of the sill pillar itself produces more problems; failure of the rock due to high stresses, difficulties in controlling the fill above, overall stability of the stope and special requirements on the technique for backfilling. Altogether this makes sill pillar mining technically difficult and often not profitable. A project was therefore initiated with the aim to increase the mineable ore reserve by making sill pillars mineable, both technically and economically. The project aimed at developing technique for already existing sill pillars as well as planned sill pillars. For the existing sill pillars a technique would have to be developed for mining beneath unstabilised fill. For sill pillars that would be created in the future, the most suitable mining method and methods of supporting or stabilising the fill in the stope above was to be chosen within the project.

Jan 1, 1998

By Thompson IR, Solomons SS

Underground mining with the cut and fill method has been declining during the past decade or so, being replaced mostly by sublevel open stoping methods. During 1983 the Australian Mineral Industries Research Association Ltd. (AMIRA) commissioned a review of the method, with the aim of compiling the state-of-the-art, indicating future trends and recommending topics for research that would be needed to support this future mining. Mines using the cut and fill method in Australia and three other countries were visited to compile current practices and expected developments.Cut and fill is mostly used where geological and ground conditions are unsuitable for open or caving methods. These range from narrow, irregular orebodies to wide, massive orebodies where pillars are retained in ore. There is significant potential for improvement and further development of the method. It may then be used in a broader range of conditions and for orebodies that may not otherwise be viable to mine.

Jan 1, 1985

Close spatial relationships between the deposits of the Etheridge Goldfield (23,000 kg of bullion) and various regional geological and geophysical features suggest that genesis of the ore deposits was a multi-stage process that started with magmatic and metamorphic stages in the mid-Proterozoic, climaxed with structural and hydrothermal stages in the late Palaeozoic and terminated with an oxidation enrichment stage in the Cainozoic. Acceptance of this hypothesis permits classification of the Georgetown region into areas likely to contain deposits of the Etheridge type and those unlikely to do so. Consequently there is little scop- for the discovery of extensions of this field. However, the stratigraphic interval between the source rocks of the Etheridge field and stratigraphically higher host rocks of the Croydon field may contain disseminated replacement gold deposits of the Carlin type. The potential host (pyritic carbonaceous, and locally dolomitic siltstone of the Candlow Formation) is locally faulted and cut by granitoids and the extension of a mineralised, long-standing zone of structural weakness.

Jan 1, 1980

By A McCarthy

Spatial modelling has been used to determine potential locations of granite-related nickel skarn mineralisation throughout eastern Australia. It is believed that during granite intrusion, fluid can leach nickel from nearby mafic lithologies and combine with sulfur to form nickel sulfides. Currently exploration for this style of deposit has been limited to the region around the Avebury Deposit in western Tasmania. As the lithologies near Avebury are not unique it is feasible that similar deposits could exist elsewhere in Australia. The weights of evidence spatial data modelling technique was used to evaluate the wealth of geological data available over eastern Australia and included known economic deposits as training data to weight the themes of the model. These weighted themes were combined to create a prospectivity map showing areas favourable for granite-related nickel deposits. Several regions were identified by the model to have good potential to host nickel mineralisation similar to the Avebury deposit. These include areas located throughout New South Wales, Victoria, Tasmania, the Tasman District of New Zealand and, in particular, the Rockhampton region of eastern Queensland. An EXTENDED ABSTRACT is available for download. A full-length paper was not prepared for this presentation.

Jan 1, 2008

The mineral sands deposit of Australia pose a number of unique, and quite unusual problems for the explorationist. Most concentrations of heavy minerals have been found in the unconsolidated sediments of the east and west coasts. Mineral sands mines open larger areas per tonne of concentrate than most other mines. This is because of the shallow depth of the sands containing the heavy mineral concentrations. Obtaining tenure can, by mining industry norms, be a massive operation due to the large areas to be examined and, particularly on the east coast, the large number of land holders encountered. A commercial development can still emanate from anything ranging from a small high grade body to a massive low grade deposit, the prices currently being obtained for rutile, zircon, ilmenite and monazite, although still modest when the remarkable properties and applications of these minerals are considered, is nevertheless attractive when compared to the prices being obtained for the base metals with the exception of gold. The current interest in the location and definition of new reserves of heavy minerals reflects this relative price attractiveness. The discovery of heavy mineral concentrates does not necessarily ensure the early establishment of a mine. Because of the cyclical nature of market prices, the average returns likely over the life of the mine permit the employment of only relatively simple, low cost, mining, concentration, and separation processes. If difficult mining conditions are encountered or the removal of small contaminants by complex metallurgical processes are required, then higher market prices must be obtained. Until the market is prepared to pay more for the commodities so produced, the resource will not be economic and lower cost reserves will be mined in preference. The Australian mineral sands industry has seen many closed mines because of past failures to properly assess the data base collected during the exploration and development phases of the failed projects.

Jan 1, 1987

The operation of cyclones and cylinders is briefly described and com- pared, and a number of recent applications in mineral, gold and coal plants discussed. The capacity of an existing pump and cyclone in a circuit can be sig- nificantly increased by retrofitting a cylinder in series to predensify the cyclone feed. The cyclone overflow product size can also be adjusted and controlled using a variable aperture valve between the cylinder and the cyclone. This predensifier-cyclone system has been used at plant scale to con- trol the pulp density of the feed to cyanidation in gold plants, to size flotation feeds before split conditioning and to deslime and classify in gravity plants. Application in a typical regrind circuit is considered. Cylinders and cyclones also have numerous applications in water management systems, e.g., degritting mine and plant waters to protect pumps, sprays and other equipment. Screen undersize and flotation con- centrate dewatering circuits are described to illustrate how suitable stream recycles can reduce water consumption, optimize fresh water use and improve efficiency.

Jan 1, 1988

This study introduces a new probabilistic approach to seismic stability analysis of embankments and slopes. The approach is based on Sarma's solution, which is modified through presentation of the seismic force by its horizontal and vertical components; i.e. the force may have an arbitrary inclination. The probabilistic modelling includes Monte Carlo simulation of the shear strength parameters of the soil mass, which are assumed to have a normal distribution. The probability of failure is determined based on the seismic co-efficient, which is treated as a random quantity. The probabilistic approach is illustrated through a solution of a numerical example from an opencast coal Mine.

Jan 1, 1992

The late Carboniferous to early Permian Featherbed Volcanics cover an area of about 3000km near the western margin of the Hodgkinson Basin, in northeastern Queensland. The dominantly ignimbritic volcanic rocks are mostly confined to a single, composite, volcano-tectonic depression, but, along with the associated intrusive rocks, may be divided into two main groups: late Carboniferous I- type rocks and early Permian A-type rocks. Late Carboniferous I-type andesitic to rhyolitic ignimbrites and minor andesite lava crop out in the southeastern, southern, and southwestern parts of the complex, mostly confined to a basin-like depression, or "sag" structure, and are associated with coeval dioritic (and rare gabbroic) to granitic intrusive rocks. Extensive Sn, W and base- metal, and some Au, mineralisation are associated with these rocks, particularly in the southeast. The main part of the complex is of early Permian age, and consists almost entirely of A-type rhyolitic ignimbrite and relatively minor volumes of lava intruded by a peripheral ring dyke of porphyritic microgranite and by resurgent-type plutons of porphyritic microgranite and microgranodiorite. These rocks are associated with sparse base-metal, Au, U, W, and Sn mineralisation.

Jan 1, 1987

The primary object of this paper is to describe the present metallurgical practice of the Emperor Combined Mill, wherein ores from the adjoining and Associated Mining Companies, Emperor Gold Mining Company Ltd., Loloma (Fiji) Gold Mines, N.L., and Dolphin Mines, Ltd., are treated for the recovery of gold and silver.The mining field is located in the foothills, five miles from the sea, on the northern side of Viti Levu, the largest and most important island of the Fiji group.The orebodies occur in basalt and associated ash beds overlain by andesite, tuffs and sediments. The basalt is a dark greenish-black rock and in much of the ore mined is weathered with alteration of the olivine to serpentine and iron oxides, of the augite to chlorite and of the minute included crystals of iron ore to other iron oxides. Into the basalt intrudes a considerable number of andesite dykes, and the lodes occur as veins in these dykes, as "flatmakes" along fissures or, ash beds extending horizontally from the dykes and at the contact of the basalt and the andesite dices.The Emperor orebody is the largest and most important, and consists essentially of massive, shattered, well altered and mineralized basalt.Little or no free gold occurs in the ore at present being milled, the most important host minerals for gold being the tellurides sylvanite and hessite, next in importance being the sulphides, pyrite, marcasite and arsenopyrite. Chalcopyrite is present in quantities large enough to be troublesome in the subsequent concentrate treatment section, while sphalerite, tetrahedrite, bornite, galena and native tellurium are present in small quantities.Unimportant occurrences of native copper have been observed in both Dolphin and Emperor orebodies.

Jan 1, 1953

By M Fisher, P Bradley, D Rogers

New England Antimony Mines has operated the Hillgrove Gold Plant at Hillgrove in New South Wales since 1969, producing stibnite and arsenopyrite products by selective flotation. Gold is present in the ore as fine free gold, gold associated with stibnite and gold associated with arsenopyrite, with some ten to 20 per cent of the gold reporting to the antimony stream and 35 - 50 per cent reporting to the arsenopyrite stream. Opportunity to process the arsenopyrite concentrate for onsite recovery of the gold values to improve upon the ten per cent recovery achieved by conventional cyanidation was recognised and subject to comparison with biological oxidation, roasting, nitric acid oxidation, low temperature oxidation (Activox«) and conventional pressure oxidation. Following further testwork and a feasibility study, a 7500 tonnes per annum concentrate feed pressure oxidation autoclave circuit was constructed at Hillgrove and commissioned in October 1999. The plant has operated at the close to design capacity since commissioning whilst optimising various operational and metallurgical aspects. The last three years has seen the process achieve an overall gold recovery of greater than 90 per cent for oxidised concentrates.

Jan 1, 2002

Taxation is a major factor in evaluating mining project developments. The availability or otherwise of effective tax relief for project expenditures can have a crucial bearing on the decision to proceed with a project. The special position of the mining industry is recognised within the Income Tax Assessment Act (the "Tax Act") by special legislation, namely Divisions 10, 1OAAA and 10AA. The legislation both extends the scope of items which are eligible for deduction and affects the timing of deductions. Generally, the legislation separates expenditure into 3 categories: 1. Expenditure on exploration 2. Capital expenditure on the development and the running of the mine; and 3. Facilities used in the transport of minerals. Companies evaluating a project should carefully analyse their proposed expenditures, allocating them between these categories so as to identify potentially non-deductible expenditures and to determine the period over which tax relief will be Obtained.

Jan 1, 1983

By Finch W, Dunne R

Understanding how liberated and unliberated minerals behave in comminution and classification circuits is of vital importance to ensure that maximum liberation occurs without unnecessary and costly overgrinding. This paper presents the results of a study carried out by the Julius Kruttschnitt Mineral Research Centre and Newcrest Mining of the liberation performance of Newcrest Mining's New Celebration grinding circuit. Using data from surveys of the circuit, together with QEM*SEM analyses of individual streams, a detailed picture of the liberation and classification of gold-associated pyrite is presented. In addition the relationship between the QEM*SEM analyses and results from laboratory leach tests are also discussed. Using the survey and QEM*SEM data, mathematical models were constructed of the performance of the ball mill and cyclones, and simulations carried out to investigate ways of improving the performance of the circuit. The results from the more promising scenarios are Reviewed.

Jan 1, 1993

Depletion of shallow ore reserves is forcing the South African gold mining industry to exploit reefs at ever-increasing depths. By 2010 around 30 per cent of South African gold production probably will come from depths greater than 3 km (Johnson and Schweitzer, 1996). At such depths, virgin stresses will rise significantly, producing complex rock engineering problems (Malan and Basson, 1998). Concern over structural instability at depth has led planners to seek a technology capable of ædetection of geological structures with a displacement of 2 m or greater (or as appropriate to the mining technique) 200 m ahead of mining at an acceptable costÆ. Borehole radar probably is such a technology. Cover holes are drilled routinely ahead of development. The evaluation of its candidacy for a tactical role in ultra-deep gold mining dependsùamong other thingsùupon establishing the electromagnetic characteristics of the environment hosting significant gold reefs. The Ventersdorp Contact Reef (VCR) is one such reef. Recent borehole radar field trials, presented here, suggest that the VCRÆs overburden is a remarkably translucent, clutter-free dielectric with a Q of ~35 and that the VCR itself is the dominant radar reflector.

Jan 1, 2002

The New Guinea Mobile Belt is the northern zone of the Melanesian Orogeny (Dow and Sukamto, 1984), which consists of a complex zone ofupthrusted and accreted, regionally metamorphosed geosynclinal sediments and volcanics of Mesozoic to Eocene age and the overlying sediments. On the northern margin of this accreted terrane, formed an Eocene to Middle Miocene island arc. The North New Guinea Basin formed during the Upper Oligocene on the accreted margin. The depositional history of this basin is complicated by major crustal movements during the Upper Miocene to Holocene. During the Middle to Upper Miocene two magmatic arcs were emplaced. The northern magmatic arc is in part, spatically and genetically related to the Eocene to Middle Miocene island arc. The Maramuni-Utawa Magmatic Arc (southern) is a result of the Oligocene accretion and regional metamorphism. Coincident witt these magmatic arcs are belts of mineralization containing porphyry Cu-Au, epithermal/hydrothermal Au, Ag + Cu-Pb-Zn, exhalative Cu-Pb-Zn + Ag-Au, lateritic Ni-Cr-Co + PGE and alluvial Au, PGE, Cr occurrences and deposits. An intergrated tectonic model is presented for these and other data for the northern zone of the Melanesian Orogeny.

Jan 1, 1990

This paper considers three aspects of cemented fill practice and research in Mount Isa. Firstly, an account is given of the use of Portland cemented hydraulic fill, considering mainly the role and specifications of the fill used but including brief description of fill preparation and placement. Data resulting from a Portland cemented hydraulic fill sampling, curing and cesting campaign covering about 18 months of operating practice are presented, analysed and discussed. These yield information indicating the mode of operation of a fully-automated fill preparation station, as well as a means of comparing field and laboratory strength results. A technique with potential for use as a fill quality control without actual strength testing is also described. Results of a fill research programme conducted by the author in Mount Isa since early 1968 are presented, involving both Portland cemented hydraulic fill and altei._acive, cheaper, additives for cementing hydraulic Fill.

Jan 1, 1980

By Han Kook-Nam, Lawson F

The recoveries of the three cobalt minerals in the Mount Cobalt deposit, cobaltite CoAsS, erythrite CO3(AS04)8H20, and new cobalt mineral with a composition approximating 2CoO.CaO.Fe203.2As205.11H2O were investigated using physical and surface-chemical processes.Over 80 per cent cobalt recovery was achieved by tabling a cobaltite-mineralized sample, while about 76 per cent cobalt recovery was obtained by dry feed magnetic separation of a sample containing erythrite and the new cobalt mineral. The resultant primary magnetic concentrate with a cobalt grade of 5.5 per cent, was able to be upgraded to 14.4 per cent cobalt by regrinding .and a further magnetic separation.Electrophoretic mobility - pH responses for each of the three cobalt minerals were found to be similar. Each mineral remained negative over the pH range 3 to 11 and was most negative at mildly alkaline pH values.Cobaltite was floated effectively with amyl and ethyl xanthate collectors under acidic conditions at collector concentrations of 10-2M to 10-5M. Erythrite showed a similar flotation response using 10-sM amyl xanthate. The practical application of these laboratory separations to an industrial process is suggested.

Jan 1, 1976

THE MORWELL BROWN COAL DEPOSITSTHIS deposits of brown coal in the neighbourhood of Morwell, are of tertiary age, and are represented on several horizons, but, owing to lack of evidence, the exact age cannot be fixed definitely. It is chiefly by reference to the basalt flows of the Older Volcanic series that the brown coal beds have been classified as of Pre-Volcanic and of Post-Volcanic age. The Pre-Volcanic brown coals are less widely distributed, and the seams generally are thin, though near Thorpdale a thickness of 40 tt. has been recorded, and from 10 ft. to 12 ft. in the vicinity of Narracan. Both of these localities lie to the south-west of Yallourn, and it has not been proven as yet whether these older coals and accompanying basaltic flows pass under the Morwell beds.The brown coal deposits have accumulated in an area where extensive faulting in early tertiary times has taken place with oscillations of elevation and depression of the land surface. In the vicinity of Yallourn, Paheozoic strata (probably Silurian) are exposed on either bank of the Latrobe River about a mile above the powerhouse weir, where the river flows through steep banks rising a couple of hundred feet on either side. The Silurian strata are highly inclined, and consist mostly of slates and Illudstones. Resting unconformably on the upturned edges of the Silurian is a conglomerate bed of Mesozoic age, above which occur beds clipping to the south-east of felspathic sandstones, with alternating mudstones at times carbonaceous, and containing thin seams of black coal.The brown coal seams and associated lignitic Clays, sands, gravels, etc, rest on the Mesozoic strata (as proved in the vicinity of the power-house and by boring north of the Latrobe River, near the old open cut), but do not appear on the surface of the Mesozoic, where these beds attain an altitude of more than 50 ft. above the present level of the Latrobe River.Half a mile upstream from the power-house a layer of basalt of the Older Volcanic series, almost resting upon the Silurian strata, is...

Jan 1, 1924