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By R. R. Tatiya

The following procedure was used to determine cut-off grades: define the orebody profile; plan the stope layout and quantify the work involved; formulate equipment-performance norms; calculate unit costs; input process recoveries and metal prices; and calculate the cut-off grade. Use of the method is illustrated using data from a copper mining complex in India. Results from the study led to the following conclusions for underground mines in general. Cut-off dependent costs vary significantly with the stoping method employed, orebody thickness, the degree of mechanisation and the working efficiencies of the workforce and equipment. This applies even within the same deposit. Sub-level stoping and its variants can be operated at a lower cut-off grade than cut-and-fill and its variants. Thinner orebodies affect cut-off grades adversely, but with thinner orebodies very little further reduction in cut-off grade can be achieved once a certain minimum width has been exceeded. For the same stoping method and in the same mine the cut-off grade varies with the degree of mechanisation. Labour-intensive methods require higher cut-off grades. An allowance for working efficiency should be made when calculating cut-off grades. Higher process recoveries allow a significant lowering of cut-off grades

Jul 1, 1996

Jan 1, 1984

By M. D. Pritzker

Shrinking-core models are used to describe the physico-chemical processes that are associated with many metallurgical gas-solid and liquid-solid reactions. The models can be used to evaluate rate constants and effective diffusion coefficients from experimental data. This work generalises the model for diffusion through a product layer to cases where the transport of more than one species is rate-controlling

Jul 1, 1991

By Eric Forssberg, Vigen Zeng

During mechanical grinding high intensity vibration is emitted that contains information on the mill's operating state. Tests, using a laboratory ball mill, studied the influence of operating parameters on the vibration signature. The parameters studied were: mill speed; powder filling; pulp density; grinding period; and pulp temperature. Vibration signals were detected by an accelerometer, amplified by a vibrometer and recorded onto digital audio tape. A digital oscilloscope converted the signals into IBM-compatible data format. Digital signal processing and multivariate data analysis were carried out with specially developed software. The power spectral density was estimated from the time-domain vibration signal. Four new latent variables were used to describe changes in the vibration spectra. A relationship was established between operating parameters and latent variables which could form the basis of a quick and automatic method of monitoring operating parameters in ball mill grinding.

Jan 4, 1993

By R. Scheepers, J. E. Misiewicz, A. C. Fitzgerald

Discussion by A.C. Fitzgerald of the paper, published in Trans. IMM A, vol.104, 1995, p.B121-B135, is presented together with the authors' response. Fitzgerald points out a number of problems with the idea of mineralising fluids leaving no trace in the large volumes of rock traversed before depositing all minerals of value in a particular horizon or rock type with which the required isobaric or isothermic surface also coincides. He suggested that in the case of the Rooiberg tin deposits, the Lebowa Granites may be batholiths that reached the surface and were capped by sheets of their own volcanics. The authors agree that they had considered a possible syngenetic origin for the stratabound deposits, explain that no conclusive evidence for this could be found, discuss the relative ages of the sediments and volcanics of the Rooiberg Fragment and explain the role of its low-intensity deformation and flat dip in the coincidence of an isobaric-isothermic surface with the lithological stratification

Jun 18, 1905

By A. G. Royle

Sampling formulae for in-situ material, hard rock sampling and alluvial sampling are briefly discussed

May 1, 1991

By R. N. Pryor, S. H. Shaw, D. L. Dowie, S. H. U. Bowie, M. J. Cahalan, S. F. Gandar

It is concluded that land-based mineral resources will be adequate for most minerals in the immediate future, but in the long term more minerals will come from offshore locations. Because the oceans are international and can transport pollution, international control of offshore workings will be necessary. In the UK and similarly highly developed areas, the working of low-value bulk minerals will create increasing problems in urban development and countryside preservation. Much more information should be published on standards to be adopted and their costs, if emotional social pressures founded on ignorance are to be avoided. The Town and Country Planning Acts have greatly improved the environmental quality in Britain in relation to mineral working. In the long term conservation of some minerals in short supply may be necessary on a national or international basis. Much research is required for the determination of adequate criteria and standards for the preservation of environmental quality in the mineral industry. New local, national and international legislation will be required and the adoption of voluntary standards by trade associations should be encouraged wherever appropriate

Dec 1, 1971

By M. A. Bussell, G. S. Camm

The study included lode zones at Wheal Pendarves, South Crofty and Rosevale tin mines. Fluid inclusion-containing microfractures are a common feature of the granites and typically show a preferred orientation over quite a large area. The close proximity of a dominant vein or fault controls their density and orientation. They are important pathways for fluids and provide a marker for palaeo-fluid flow. Overprinting provides a reliable representation of the evolution of the hydrothermal fluids in a vein system from early magmatic fluids to late-stage meteoric and basinal brine input. Measurement of microfracture orientation allows estimation of the regional stress regime during a specific hydrothermal event. Since micro- and macro-structures can generally be reliably correlated, these studies assist in modelling the detailed development of complex vein systems. Microfracture density is a good measure of palaeo-permeability, with implications for control of wallrock alteration. The determination of the location and density of microfractures can assist the mine geologist in identifying the location of potentially economic vein structures where macroscopic markers are absent

Aug 1, 1996

By A. W. Fletcher

Report of discussion at February, 1971, IMM general meeting (Chairman: M. J, Cahalan President) of a paper published in Transactions/Section C (Mineral Processing & Extractive Metallurgy), vol. 79, December, 1970, pp. C247-52, and contributed remarks. Contributions are included from: Cahalan M.J., giving figures related to leaching Cu from pyrite at Rio Tinto 1880-1910; Noakes F.D.L.; Embling P.M.K.; Bradshaw A.V.; Le Roux N.W.; Kelly D.P.; and Tuovinen O.H. Questions were raised regarding impurity removal, effects of light and ultraviolet light on the bacteria, the economics of solvent extraction and the possibilities for other organisms or other metals

Dec 1, 1971

By C. A. Pickles, S. J. Splinter, J. Cameron

The addition of copper oxide to a borosilicate slag resulted in the breakdown of the silicate network and a dramatic decrease in viscosity. With increasing borax to silica ratio the viscosity was reduced by two mechanisms. First, rising sodium oxide content promoted cleavage of the Si-O bonds. Second, increasing boric oxide (B2O3) content increased the number of trigonal borate units that were converted to tetrahedral borate units by sodium oxide and copper oxide. The BO4(4-) tetrahedra decreased the local silicate symmetry, thus disrupting the silicate network and lowering the viscosity. The activation energy decreased with increasing temperature and increasing copper oxide content

Jun 13, 1905

By Winmill T. F.

(Paper presented at the Institution of Mining Engineers' general meeting held in London on 8th June 1916.) The conclusions reached in this paper may be summarized briefly as follows: (1) The method of estimating moisture in coal by determining the loss in weight of a sample heated to 105°-110° Cent, in an air-bath for an hour is untrustworthy, the results so obtained being too low. (2) Dried coal has a very considerable power of absorbing moisture, and a sample, after being dried, must be protected instantly if it is to remain free from moisture. (3) A fairly accurate estimation may be made by heating the coal in a current of dry air at 105° to 110° Cent., and collecting the moisture evolved. (4) In cases in which it is proposed to use the dried coal for any further experiments, the drying must be done in the absence of oxygen, and this can be done simply and quickly by the vacuum method now described

Dec 1, 1916

By W. J. Whiten, D. W. Grinsberg

Most cluster analysis techniques are not well suited to the analysis of engineering data as they have been designed for more qualitative data that tend to produce compact clusters. A clustering technique is described which develops and uses local cluster shapes to build clusters that are suitable for use in engineering applications. The technique is finding application in the analysis of many types of data, particularly where multiple trends and outlying points occur in multiple dimensions. Applications of particular interest are the calibration of on-stream analytical equipment and the analysis of data on plant performance. In both cases the multidimensional nature of the data renders manual analysis very difficult

Dec 1, 1991

By N. T. Moxon, D. Mead, S. B. Richardson

A laboratory and theoretical study of air decks was carried out to assess the effects of the size and location of air-decks on fragmentation. The degree of fragmentation was found to depend on both factors. As the size of the air-deck increases the degree of fragmentation is reduced relative to a full column charge. However, the reduction is relatively small until a critical size is exceeded. The critical size depends on the strength and structure of the surrounding material. A critical air-deck length of 30-35% of the original explosive column was determined for the model materials used in the study. A theoretical explanation of the results was derived based on pressure decay rate relationships. The location of the air-deck also influences fragmentation. The interaction and oscillation of the two shock fronts from the top and bottom charges mean that mid-column air-decks produce better fragmentation for the same air-deck length and explosive loading as top-column or bottom-column air-decks.

Jan 4, 1993

By F. Reich, S. L. Chryssoulis, K. G. Stowe

The surface chemistry of particulates from mineral processing streams can be determined by laser-probe microanalysis. The small area of analysis (2-30 micrometres) enables the surfaces of individual grains to be characterised. Conclusions are based on data acquired from a statistically significant number of grains of a given type. Maps showing the distribution of elements on the surface of mineral particulates can be obtained by time-of-flight secondary ion mass spectrometry. The importance of such analyses in understanding the response of minerals to beneficiation practices is discussed with reference to three examples. The first relates to the loss of selectivity in the differential flotation of a base-metal ore, the second to the different flotabilities of coarse- and fine-grained pentlandite from a Cu-Ni ore and the third concerns the preg-robbing effects of organic matter in a carbonaceous gold ore.

Jan 4, 1992

By D. D. Lei, H. Sevim

Long-term production planning in open-pit mines requires the determination of cut-off grade, mining and milling production rates, a mining sequence, mine life and ultimate pit limits. Since these variables interact in a circular fashion, a genuine solution to the problem necessitates their simultaneous determination. A methodology with this capability is described. This comprises a group of heuristic algorithms and an unconventional dynamic programming algorithm. The method is demonstrated using data for a gold deposit in the western USA

Jul 1, 1996

By D. J. Esdale, D. F. Pridmore, F. W. Lindman, J. H. Coggon

Almost all the presently viable nickel reserves in the Yilgarn Block contain nickel in a sulphide phase. Both volcanic peridotite- associated (VPA) deposits and intrusive dunite-associated (IDA) deposits are characterized by massive, matrix and disseminated sulphides (typically, pyrrhotite, pentlandite, pyrite, chalcopyrite, magnetite and other spinels), though in the IDA deposits the volume of disseminated sulphides is far greater than that in the VPA deposits. Potentially all geophysical techniques have application in the direct detection of these deposits'gravity for the detection of the dense massive and matrix ore; magnetics for the detection of magnetite and pyrrhotite in the ores; electromagnetics for the detection of the massive and matrix ore; and induced polarization for the detection of disseminated and to some extent matrix and massive ore. In practice the application of geophysical techniques is limited to a varying extent by (1) the relatively small size of an economic accumulation of sulphides, particularly the VPA deposits, (2) the extreme depth of weathering and lack of outcrop on the Yilgarn Block and (3) the abundance of geological noise or anomalous responses caused by sources other than economic mineralization.

Jan 1, 1984

By H. L. Shergold, O. Mellgren

The conditions of amine concentration and pH necessary for the concentration of fine haematite particles at the iso-octane-water interface have been determined. Results obtained from the related studies on the effect of pH and dodecylamine concentration on the adsorption density, electrokinetic potential, contact angle and concentration of various amine species in the system are included. A good correlation was obtained between these different variables. Maximum concentration of haematite at the oil-water interface was obtained when the haematite zeta-potential was small or equal to zero

Dec 1, 1971

Summary of the morning's events with a Written Contribution to Paper No. 4 and author responses

Jan 1, 1947

By E. H. W. Hornbrook, P. W. B. Friske

Paper presented at the 28th International Geological Congress, Washington DC, July 1989 (International geochemical mapping sessions). The objective of the programme is to establish and maintain a nationally consistent geochemical drainage database. Towards this end systematic surveys have been conducted since 1973. To date more than 200 surveys have been completed to the required standards, representing 180 000 sites and covering about 2 100 000 km2 throughout Canada

Jun 13, 1905

By R. G. Jones

Chris Hinde talks us through his career from BSc in Mining Engineering to roles with Golder Associates, Schroder Securities, Mining Journal and SNL. He discusses the issues facing the mining industry.

May 1, 2015