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By C. A. Pickles, J. M. Toguri

The refining of two molten Ag-Cu alloys, containing 7.5 and 11.2 mass% Cu, with a borosilicate slag was investigated using both air and pure O2 to determine the effects of the following variables: flow rate of oxidising gas; injection time; mass of sodium borosilicate flux; and injection of the oxidising gas into either the slag or the metal. The results demonstrate that more than 90% of the Cu can be removed with Ag losses of less than 5% and that refined metal with a Cu content of less than 0.5 mass% can be produced. Ag losses to the slag increased with the amount of Cu removed, and a mechanism is proposed to account for this

Dec 1, 1995

By J. S. Duval

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). The compilation of the National Uranium Resource Evaluation aerial gamma-ray data to produce maps of the apparent surface concentrations of potassium, uranium and thorium for the conterminous USA has resulted in a reasonably accurate representation of the distribution of these elements in the surface rocks and soils. This claim is supported by the general agreement between the mapped geology and the patterns seen in the data

Jul 1, 1991

By P. H. Davenport, L. W. Nolan

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Geochemical mapping provides a direct approach to delineating areas of epigenetic mineralisation and for relating the regional distribution of this mineralisation to an overall tectonostratigraphic and structural framework, as well as to extensive areas of hydrothermal alteration. Organic lake sediment is a widely available and effective sampling medium for regional geochemical mapping in Newfoundland, that has proved to be valuable in Au, Sb and W exploration

Jul 1, 1991

By A. R. Biggart

Twenty-sixth Sir Julius Wernher memorial lecture, presented at the Tunnelling '94 symposium held in London, 5-7 July 1994. In describing 18 projects with which he has been involved over a period of 36 years, the author aims to illustrate how technological change and an increase in scientific knowledge have influenced tunnelling practice, which he nevertheless maintains does continue to be an art. Tunnels discussed are: the Silver Street, Blackfriars, Whitechapel, St. Paul's and Waterloo Post Office tunnels, 1958-1969; metro tunnels on the Victoria Line, London, 1962-1970; the introduction of tunnel boring machines (TBMs), 1971-1978, in the Empingham reservoir diversion tunnels in Rutland, the bentonite tunnelling machine experiment at New Cross, the Southern tunnel water main section of the London Ring Main and the Warrington sewer in Cheshire; tunnels in rock 1975-1981, for the Lune Wyre and Megget Manor aquaducts, Weymouth sea outfall and Bristol interceptor sewer; Priestley TBM tunnels 1969-1982; the Greater Cairo wastewater project 1983-1987; Anacostia River crossing, Washington DC 1985-1987; the Channel Tunnel 1987-1992; and the Storebaelt eastern tunnel in Denmark, 1992-1994.

Dec 1, 1994

By R. M. Cooper, H. K. Herbert, D. N. Phillips

A study was carried out to determine the effects of adding CaCO3, Fe, Al and CaSi2 to the ladle, rather than to the raw materials, in order to increase the concentration of Ca, Fe and Al in the final product to meet customer specifications at Simcoa's Kemerton plant in Western Australia. LA-ICP-MS, SEM-EDXRA and ICP-AES analysis of samples and controls showed that the technique is suitable for controlling minor element concentrations. Iron was successfully added, while calcium silicide with aluminium proved better than limestone with aluminium for controlling Ca and Al concentrations in the silicon

Jun 19, 1905

By A. Berckmans

The key variables in the financial analysis of a mining project include the metal price and the quantities of ore and metal. In general, if the metal price drops, the cutoff grade is increased so as to increase the average grade. This causes recovered tonnages of ore and metal to drop. Discussion is presented of the development of a new method to evaluate the relationship between the cutoff grade, z, the ore tonnage above cutoff, T, and the metal quantity above cutoff, Q. Detailed information is provided on the QTz curves for lognormal and inverse gaussian (Sichel's) distributions. Both these distributions are used as models for the grades in different types of ore bodies, and they are both T-symmetric. The geometry of the QTz curves is simplified, making it easier to work out the impact of minor variation in the parameter values for each distribution

Dec 1, 1996

By P. H. Morris

The profile of a delta formed by fine-grained mineral processing wastes, disposed of as aqueous slurries by subaerial deposition from a pipeline, has a significant bearing on the volume that is available for waste and water storage in a given containment structure. Earlier field data and laboratory experiments suggested that mine waste delta profiles could be predicted with high levels of accuracy using data from small-scale laboratory deposition tests. The relationships between the profiles of full-size and laboratory-model deltas were analysed using the principles of kinematic similarity and a recent theory of delta formation based on engineering hydraulics. Measured profiles of full-size and model coal-mine tailings deltas are compared and the prediction of full-size profiles discussed. It is shown that the data-derived laboratory-model deltas are insufficient to allow accurate prediction of full-size delta profiles. Initial slope data or other, equivalent data for the full-size delta are also required

Apr 1, 1996

By G. Zhan, P. Mousset-Jones, G. Danko, J. J. K. Daemen, C. Mezei

Paper presented at the conference Risk assessment in the extractive industries, held in Exeter, 23-24 March 1994, and first published London: IMM, 1994, preprint volume. 18pp., 12 refs. (Originally entitled: Tunnel roof diagnosis using a robotic sensor test bed.) An integral roof diagnosis method is proposed to assist in assessment of risk regarding the stability of an excavation. A Robotic Sensor Test Bed (RSTB) is being developed for the characterisation of roof stability. The sensor test bed consists of a sonic/ultrasonic wave response sensor, a laser surface profiler and a surface temperature sensor. These sensors are mounted on an articulated robot manipulator for performing remote-controlled or fully automated diagnoses. A number of laboratory and field sonic/ultrasonic tests were conducted. A high-energy ultrasonic transducer and an impact device were used to resonate rock slabs. The fracture depths of the slabs were found to be inversely related to the measured resonance frequencies. The agreement between identified and actual dimensions was acceptable. Field tests also showed that loose rock on the surface can be clearly distinguished from solid formation by comparing their wave responses. The robotic laser profiler part of the RSTB was used to measure surface geometry. Different scanning methods are being developed to achieve the fastest and most precise measurements and to provide pertinent information about rock joints and major fractures

Dec 1, 1994

By P. H. Morris

Nineteen field trials of the co-disposal of fine coal tailings and coarse coal wastes were conducted at the dual Goonyella-Riverside mine in Queensland and at the Hunter Valley No. 1 and Warkworth mines in New South Wales, Australia. The profiles of and the sorting that occurred on the co-disposal deltas are described and an existing theory of subaerial deposition, originally developed for mine tailings alone, is shown to apply to the co-disposed wastes. This enables the dimensionless profiles of large deltas, which may take years to deposit, to be predicted from data obtained from a small delta formed in a few days or even hours

Jun 19, 1905

By J. M. Jimenez, G. D. Schena, A. J. Cazorla

A full-scale Deister column was operated in parallel with the conventional cleaning bank of cells and a pilot Jameson cell in parallel with the conventional rougher cells. Flotation column performance was appreciably enhanced by use of an improved washing system and an internal launder. The performance of the rougher bank of cells, Jameson cells, cleaner cell bank and column were described by simple linear functions. These allowed calculation of overall circuit recoveries and evaluation of alternative circuits. An evaluation procedure based on a financial criterion is demonstrated with a simplified example, illustrating how revenues and operating margins are often of more concern than concentrate grade and recovery

Jun 18, 1905

By S. Kelebek, J. A. Finch, Zhenghe Xu, S. R. (Ram) Rao

To improve SO2 emission compliance, pyrrhotite from Sudbury copper-nickel ores is being depressed with DETA. To understand the mechanism of depression, the role of complexing in controlling metal-ion activation of pyrrhotite was investigated. DETA was found to remove Cu and Ni ions but leave hydrophilic ferric species on the pyrrhotite surface. The metal:DETA ratio appeared to be 1:2. Cu was more readily removed than Ni, but the combination of DETA with sulphur dioxide was equally effective for both metal ions. Certain combinations of DETA, Ni ions, xanthate and dithionite (S2O4) or dithionate (S2O6), as representative derivatives of SO2 in water, produced hydrophilic precipitates. These may enhance pyrrhotite depression

Jun 19, 1905

By I. W. Farmer

High horizontal stresses and high horizontal to vertical in-situ principal stress ratios in the plane of underground drifts and entries can damage weakly laminated roof rocks quite severely. Such stresses are difficult to measure accurately, as illustrated by case histories of in-situ stress measurement at Wistow and Lea Hall mines, in the UK. Their direction and relative magnitude can, however, be estimated from the absolute velocity vectors of continental plates. With the preliminary results from the World Stress Map project now available it is possible to indicate mining areas where regional horizontal stresses are low, such as Europe, and high, such as Australia and Asia

Jun 19, 1905

By R. J. Gochin, G. D. Schena, R. Spencer

The impact of a mineral project in a developing country is evaluated in the broad context of its economy using input-output models. Minimum economic theory is used to develop simple numerical models. Sets of technical coefficients are exploited in the development of linear models of the productive element of an economy. The analysis allows assessment of the overall economic consequences of a mineral development in which issues broader in scope than financial objectives need to be incorporated in the evaluation. In part 1, the framework for the development of the input-output model is presented. The model is refined to incorporate country-specific behaviour. The increased flexibility of the enhanced semi-input-output model permits a more confident investigation of the economy-wide effects associated with a new project in the mineral sector of a developing country. The relevance of the models is illustrated using an example from Namibia

Sep 1, 1991

Paper presented at the UK minerals industry conference and published in: Minerals extraction towards the millennium. UK minerals industry conference, 3-5 April 1995, University of Leeds. London: Institution of Mining and Metallurgy, 1995. The various types of risks that arise in minerals industry projects are usually financial, technical, or environmental, and the key to valid risk analysis is complete integration of all risks, both within and between categories. Geographical information systems (GIS) and geostatistical simulation methods can provide a means of integrating data and conducting realistic risk analyses. Risk can be quantified but there are limitations to numerical approaches to risk assessment. Realistic quantification requires adequate models of the processes that give rise to risk. Risk perception must also be taken into account when conducting risk assessment and reporting the results, especially in public forums. The modelling and visualisation capabilities of a combined GIS/simulation system can provide the means of dealing with perception in risk analysis

Jun 19, 1905

By S. Babendererde

The twenty-ninth Sir Julius Wernher memorial lecture of the IMM, presented at Tunnelling '97, London, 2-4 September 1997. The tunnelling industry is well prepared to face the challenge from the population explosion in urban areas in the near future. Many well-established yet redundant concepts are still impeding progress, however, including the prediction of excessive surface ground settlements. The correct selection of TBM can minimise these, and ground deformations can be avoided completely if the appropriate techniques are applied. Advanced techniques have been used in the Tokyo Bay Crossing, where the tunnel lining was installed by robots. Other advanced techniques include the use of a sliding slip form to give temporary support to an extruded tunnel lining, the chemical processing of ground by polymers during earth-pressure balanced tunnelling and the use of electronic monitoring and steering devices in TBMs. There will be challenges to tunnelling in urban environments, as open cut techniques will no longer be tolerated. Two examples of mined stations are briefly discussed

Jun 19, 1905

By E. Niehuis, J. Y. Kim, H. G. Cramer, S. L. Chryssoulis, K. G. Stowe, C. Bendel

TOF-SIMS was used to detect, identify from parent molecular ions and determine the relative concentrations of collectors sorbed on the surface of mineral particles in concentrate and tailings samples from three Canadian concentrators. In the Kidd Creek Zn circuit, sphalerite lost to tailings carried on average a quarter of the amount of isobutyl xanthate present on that recovered to Zn concentrate; amyl xanthate, which is not reported as added to the circuit, was also detected on floated sphalerite and pyrite. At Brunswick, sphalerite particles lost to the scavenger tailings had ten times less amyl xanthate and isobutyl xanthate than those recovered to the Zn final concentrate, while both xanthates were detected on sphalerite floated to the Cu-Pb cleaner circuit. At Matagami, significantly more isopropyl xanthate and isopropyl dithiophosphate were detected on sphalerite recovered to the final Zn concentrate than on that lost to the Zn rougher tailings

Dec 1, 1995

By A Cox

It has been demonstrated that all the cadmium from spent batteries, typically 4 g per battery, can be recovered by burning polyvinyl chloride waste to yield hydrogen chloride; this reacts to produce volatile calcium chloride, which can then be condensed and collected in a separate reactor. Alternatively, chlorine may be used to chlorinate the cadmium with equal efficiency. There is also a prospect of using very low concentrations of these gases, less than 1%, to effect the separation. The Cd was recovered more quickly when exposed to sustained, controlled flow rates of chlorinating gases, whereas when PVC was burnt most of the gas was produced in a very short time, not allowing complete reaction. This problem can be overcome by recirculation of the gas into the reactor. The technology is efficient and clean and the equipment used is simple, enhancing the prospects for a pilot-scale version of the process

Jun 21, 1905

By H. K. Taylor, B. Denby, L. D. Smith

Contributions by H.K. Taylor and G.A. Davis discuss the three papers published in Transactions IMM A, vols. 103 and 104, with responses by Smith and Dowd

Dec 1, 1995

By Boorder De, B. S. Panov, A. B. Westerhof, V. A. Korcemagin

Paper presented at the conference on Economic geology in Europe and beyond II, models for <mineral deposits> in sedimentary <basins>, held in Keyworth, UK, 13-14 April 1994. The Hg and Sb deposits of the Mediterranean and Circum-Pacific Belts are often found at elevated structural levels, suggesting that their preferential occurrence in young orogenic belts is not a fundamental metallogenic feature but merely reflects their chances of surviving post-orogenic peneplanation. In western Europe their emplacement appears often to be related to late orogenic extensional events accompanied by a notable increase in heat flow. Although Nikitovka and Almaden have quite different settings, both appear to be related to deep-reaching shears. Together with brittle fault zones at higher levels, these provided pathways for fluid phases that originated at least partially within the mantle. The Nikitovka deposits are located in the Donets segment of the 2 000 km Pripyat-Dniepr-Donets palaeorift in the East European Platform. Initiated in the mid-Devonian with a possible Precambrian precursor, its listric boundary faults displace the Moho from a depth of about 50 km north and south of the rift to 35 km along the axes of the Pripyat and Dniepr segments. The steep central anticline of the Donets segment, within which the main Hg-Sb district is located, is interpreted to be associated with a reactivated fault reaching into the upper mantle. The Almaden syncline, formed during the Variscan Orogeny, may be an older pull-apart basin or half-graben associated with the collapse of the Cadomian Orogenic Belt. It is situated on a major ENE-WSW-striking shear zone which may represent a Late Cadomian transfer zone reaching into the mantle

Apr 1, 1995

By D. M. Milne, P. J. Lunder, R. C. Pakalnis

During the mining of an open stope, deformation of the hanging-wall and the potential for dilution generally increase with the size of the exposed hanging-wall. Excluding discrete structures that may delineate unstable blocks, the mechanisms that drive hanging-wall deformation and possible dilution comprise several factors which can include elastic, plastic and discontinuum deformation. These stages of deformation are not mutually exclusive and at any point during mining all three of these mechanisms may be acting on the hanging-wall rock mass. Computer modelling techniques are available to analyse the three stages of deformation, but the difficulty lies in trying to obtain realistic rock mass properties for input and in determining when each stage of deformation is acting. Instrumentation data can be used to predict the effect of continued mining. However, it is often difficult to calibrate numerical models against field data owing to the large number of input parameters required. An empirical approach is recommended that uses two new parameters, the radius factor and the effective radius factor. A method is proposed for predicting the effect of continued mining from existing deformation and dilution data for a given hanging-wall

Apr 1, 1996