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By S Durucan, A Korre

The application of simple methods of statistical analysis, coupled with geostatistical analysis and geographic information systems, can only summarise and give an outline of the spatial distribution of the parameters measured. Spatial analysis of the components or factors calculated, through principal component analysis or factor analysis, allows assessment of the geographical distribution of the dominant processes contributing to soil composition and/or contamination. Neither of these tools, however, distinguishes between the different sources of pollution. The application of canonical correlation to the data, driven by expert appraisal of the potential pollution sources, allows their quantitative and spatial assessment while GIS provides the environment in which to organise and present the results. The methodology is illustrated by its application to soil-contamination data from the Lavrio area in Greece, where silver-bearing orebodies have been mined for more than 25 centuries

Jun 21, 1905

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 J. A. Finch, Zhenghe Xu

The competitive adsorption of xanthates on sulphide minerals in a binary mineral system (pentlandite and pyrrhotite) was studied using the pseudo-in-situ technique of attenuated total-reflectance FTIR spectroscopy. The minerals were placed in the same collector solutions, either separated by a glass wall or in direct contact with each other before magnetic separation and separate analysis. The effect of mineral interaction on xanthate adsorption was clearly demonstrated spectroscopically for the first time. At low concentrations of xanthate, its adsorption on pentlandite was activated by physical contact with pyrrhotite; the effect may be attributed to the enhancement of electron transfer through electrical contact between the two minerals. The results emphasise the need for caution in extrapolating results obtained from single-mineral studies to flotation practice

Jun 18, 1905

By R. J. Pine, J. S. Coggan

Distinct-element modelling has been used to study the mechanisms associated with observed deformation of the western face of the quarry. A complex failure mechanism involving distinct planar surfaces that was proposed for a slope failure in 1967 has been modelled and shown to be plausible. In addition, deep-seated flexural toppling may contribute to the slope instability. Modelling has confirmed the detrimental influence of a raised water-table on the stability of the slope and also indicates that the observed cyclic opening and closing of tension cracks may be attributed to seasonal rise and fall of the groundwater level

Apr 1, 1996

By A. E. Tercan, D. Mamurekli

Ordinary kriging on the assumption of a gaussian error distribution and indicator kriging were used to derive the probability that a given calorific value would or would not be exceeded by coal from an area of a deposit. The two techniques led to similar probability maps despite local differences; the lack of an absolute reference makes it impossible to judge which method is better for this particular application

Jun 19, 1905

By V. A. Melezhik, P. K. Skufin, L. P. Nilsson

these factors into account. Theoretical and

Aug 1, 1994

By J. H. Morris, G. M. Steed

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. Oxygen isotope analysis indicates that quartz, carbonates and muscovite could all have formed in near-isotopic equilibrium with the mildly saline H2O-CO2 ore fluid at 330 degrees C. Calculated values for O, C and S in the ore fluids imply derivation from a deep, homogeneous source region and are consistent with formation either as a direct or an indirect result of igneous processes. Values for delta-O18 plot a little outside the accepted magmatic range, but have almost certainly been modified by exchange reactions with wall rocks. These reactions were also the most likely cause of deposition of the ore constituents. The chemical and isotopic character of the fluid was similar to that in many Archaean and later mesothermal auriferous vein systems, especially the Mother Lode region of California. If the Southern Uplands-Longford Down accretionary complex conceals an Ordovician arc, the tectonic setting was also broadly comparable

Jun 19, 1905

A production drill rig at a site in Sweden was equipped with a monitoring system to estimate production statistics. Drill running times, drill hole depths, penetration rate, rotation speed, thrust, air percussive pressure and torque pressure were recorded for every 10 mm of hole length for a period of 5 months. Operational activities (rock penetration, tube handling, moving and set-up time) accounted for almost 62% of the time consumed, the remaining 38% being different types of stoppage. Drilling itself, as opposed to handling, took less than 24% of the total time. The results give an indication of how the overall drilling capacity can be increased and which activity should be emphasised. The impacts of automation, new developments and reorganisation on production can also be predicted. Average production was found to be around 100 m/day, but varied between 50 and 160 m/d. The company's specification for the drill rig, before purchase, was that an average production rate of 130 m/d be attained over two consecutive months of drilling - a rate which monitoring shows will not be achieved

Jun 19, 1905

By S. L. R. Lenharo, H. Kahn, H. Born

Different ore types result from the irregular spatial distribution of the associated alkaline/carbonatite rocks and the zoned alteration profile within which apatite may have undergone reprecipitation. Different flotation responses are caused by their mineralogy, iron oxide impregnation and grain-size characteristics. Samples from seven deposits were crushed, screened and separated before being studied by chemical analysis, optical microscopy, X-ray diffraction, FTIR spectroscopy, cathodoluminescence and scanning electron microscopy. Two main apatite varieties with peculiar crystal morphology were identified: hydroxy-fluorapatite as the primary phase and carbonate-fluorapatite as the reprecipitated phase. The former occurs as prismatic or ovoid grains and the latter as polycrystalline aggregates or crusts on the primary grains; both are associated with iron oxide coatings (primary) or intergrowths (secondary). Microflotation tests showed variations in flotability for particular apatite associations as well as intensity of iron oxide coatings. The differences in flotation behaviour can be related to morphological properties and chemical substitution in the apatite structure

Aug 1, 1996

By F. C. Gennari, D. M. Pasquevich

With the gradual exhaustion of natural rutile, there has been extensive research into its synthesising from lower-grade titanium minerals. The removal of Fe from pseudobrookite (Fe2TiO5) by chlorination was studied, using both isothermal and non-isothermal thermogravimetric measurements. Correlation of the results obtained from element distribution maps, scanning electron microscopy, energy-dispersive X-ray analysis and phases detected by X-ray diffraction in the chlorinated samples showed clearly two associated processes. First, the pseudobrookite particles reacted with chlorine and iron was removed selectively as FeCl3(g), leaving a solid residue rich in the TiO2 phases anatile and rutile, separated from an inner layer of unreacted pseudobrookite by a distinct interphase boundary. Second, chlorine allowed TiCl4(g) to form in the reaction bed, where it removed iron from the Fe2O3 crystals as FeCl3(g) and substituted Ti through a pseudomorphic reaction

Jun 21, 1905

By R. Sankey, L. Gatty, F. Bizzozero, G. F. Shannon, F. Savaglio, L. McDonald

State mining regulations in Queensland stipulate that a mine be provided with an earth installed on surface and that all underground equipment that needs to be earthed should be connected via a copper conductor to this surface grounding point. The regulations further require that all exposed metal surfaces in underground substations be connected to an earth. In a study of earthing conditions at Mount Isa mine it was found that the physical anchoring of metal work at substations (with rockbolts and associated steel mesh) also provides an excellent electrical connection to the country rock. It was established that not only is the mine's earthing system grounded at numerous underground locations but also that such anchor points offer, in general, a path to ground with lower resistance than does the legally required grounding point on the surface. It is recommended that metalliferous mines should utilise a multiple-earth system and not a run earth connected to a single, above-ground earth point

May 1, 1991

By G. B. Harris, A. R. Laplante

Fine tungsten was used to mimic gold and fine and coarse silica and magnetite to mimic gangue. The optimum flow rate of fluidisation water varied from 1.7 l/min for fine silica to 5.6 l/min for coarse magnetite. Overloading at optimum flow rate was then investigated. With fine silica gangue no overload occurred under any of the conditions studied, and there was very little overload with fine magnetite. Coarse silica caused appreciable overload, but only after a significant bed of tungsten had been formed; with fine magnetite gangue the onset of overloading occurred earlier. Finally, with coarse magnetite severe overloading occurred almost immediately. Overloading was modelled using a first-order kinetic rate constant for erosion of the concentrate bed and a critical mass of constant above which it takes place. The results clearly demonstrate the importance of removing oversize to maximise recovery, particularly with a high-density gangue

Jun 18, 1905

By R. H. T. Garnett

N.B. This paper provoked much (positive!) discussion in later issues, with responses from the author (and thanks also for the many private contributions he had received) - see under Garnett R.H.T. Expanded version of a paper originally presented at the Alluvial mining conference, London, 11-13 November 1991 and published in Alluvial mining, Barking: Elsevier Applied Science for IMM, 1991, p.115-156. The usual measure of performance in gold and tin dredging is the R/E factor. It compares actual production or recovered grade for a given period with that estimated from the original sampling. The factor is a multiple of four component factors, each ideally approaching 1.00. The factors are concerned with estimation, selection, excavation and treatment. The estimation factor reflects the errors involved in determining the grade and depth of single drill-holes or pits. An optimum selection factor is achieved by a higher drilling density. The excavation factor is affected by failure of the dredge to excavate the total volume contained within its course. The required dredge throughput rate influences not only the success in digging recovery but also the treatment factor. No two alluvial deposits are the same, but, in general, the greatest divergence from 1.00 is invariably demonstrated by the estimation factor. A major divergence in one of the other factors may also be the cause of the R/E factor being significantly different from 1.00. The component factors are examined in detail and historical trends in R/E factors are discussed

Sep 1, 1991

By J. A. Finch, D. Lin

The robustness of the large-sections correction procedure, Hill's fast approximation, Barbery's correction and the PARGEN correction was examined by comparing their ability to reconstruct the true liberation distribution using sectioning data from computer-generated spheres. The results indicate that the flexibility of a correction procedure is related to the assumptions it makes about the continuity of the liberation distribution, locked-particle characteristics and ore texture. Overall, the large-sections procedure appeared to be the most generally applicable. The Hill fast approximation performed well, but this was probably because it partially incorporates the sphere model; the performance of the PARGEN and Barbery corrections varied from case to case.

Dec 1, 1995

By Xiao Min You, D. R. Swonbourne

Smelting of Cu anode slimes involves the use of a slag to hold the oxidised Cu, but some Ag is also inevitably oxidised to the slag. The solubility of Ag in sodium silicate slags at 1 100 and 1 150 degrees C has now been determined over a very wide range of oxygen partial pressures. Silver was found to be present in the slags both as neutral atoms and as AgO(0.5). The activity coefficient for atomic Ag was a very strong function of slag composition and temperature, whereas that for AgO(0.5) was much less affected by slag composition and was almost independent of temperature over the limited range examined. The results reveal that the dissolved Ag cannot be fully recovered by reduction of the slag with very reducing gases

Jun 21, 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

By F. Tailoka

Bi was electrorefined from alloys containing 10-90 wt% Pb, together with Cu and Ag as minor impurities, in a basic cell and in a recessed-channel cell with 27.5:72.5 NaCl-PbCl electrolyte at 450-470 degrees C and 10 000-20 000 A/m2. The voltage in the basic cell was as high as 9 V, with some carryover of Bi to the cathode observed, whereas in the recessed-channel cell it was as low as 285-635 mV. Flow patterns observed in a room-temperature model indicated that the recesses provide both static liquid hold-up and good mixing of the alloy, enhancing cell performance in combination with the reduced anode-cathode distance of 0.90 mm. The purity of the resulting anode product is as high as 99.9%

Aug 1, 1995

By J Parnell, B Manson

Bitumen occurs in the basins in reservoir sandstones, in veinlets close to hydrocarbon source rocks, in veins through lava beds and in sulphide-mineralised veins where it is closely associated with, but predates, the sulphides. The role of organic matter was probably in enhancing metal reduction by creating a low-Eh environment rather than in metal transport. Coeval euhedral quartz crystals or albite in sulphide-bearing carbonate veins provide evidence of an aqueous component to the hydrocarbon fluid

Aug 1, 1995

By J. S. Mason

Paper presented at Mineralisation in the Caledonides, the Mike Gallagher memorial meeting held in Edinburgh, 27-28 June 1996. Detailed paragenetic studies of the post-tectonic fracture-hosted vein mineralisation have demonstrated a complex paragenesis, reflecting a multi-phase combination of regional metallogenesis and tectonics through time. Previously published work regarding paragenesis and zoning was oversimplified. Two major epochs of mineralisation resulted in the emplacement of the A1 group of assemblages, from which lead, copper and silver were the main metals mined, and the A2 group, whose galena is only moderately argentiferous but which were major sources of lead and zinc. Tectonic and tentative isotopic evidence points to post-orogenic relaxation as the mechanism for development of the A1 assemblages in the early Devonian, whereas the A2 assemblages are believed to reflect Variscan extensional regimes and regional metallogenesis in the early Carboniferous and Permian

Jun 19, 1905

By M. W. Grabinsky, M. S. Diederichs, E. Hoek

Provided that they are used correctly, numerical models can be of considerable assistance to mining engineers in designing underground excavations. Guidance is given to the engineer or geologist who is not a specialist in numerical analysis but who is interested in using numerical modelling tools or in employing someone to analyse the stresses, displacements and failure in the rock surrounding underground excavations. A description of the theoretical background to a number of these numerical models and discussion of the advantages and disadvantages of each are followed by guidelines on the selection of appropriate models for each stage in the development of a mine, from exploration to the completion of mining

Jan 1, 1991