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By M. Lombardero, J. Garcia-Guinea, J. Taboada, B. W. Roberts

The structural, textural and mineralogical properties of the slate formations of NW Spain make it the most important district in the world for quarrying roofing slates. Over the past 10 years the introduction of new methods has increased yields from 2 to 13%. The main factors affecting quality are quartz grain size less than 75 micrometres, homogeneity of slaty cleavage and S0-S1 intersection angle, very low metamorphic grade, absence of secondary foliation, beds 10-12 m thick and low content of oxidisable Fe sulphides. The two main controls on fissility are lithology and deformation accompanied by metamorphism. The minimum natural block size should be 0.6 m3 but this volume can be reduced for modern cutting tools such as diamond wire, chain and circular saws. Structural analysis is crucial in exploration and quarrying, as shown by the prospecting methodology applied at Dominio de Truchas in central Spain and the computer analysis of rock mass discontinuities at Casaio quarry

Jun 19, 1905

By C. E. Dunn

Paper presented at the 28th International Geological Congress held in Washington DC, July 1989 (International geochemical mapping sessions). Evidence is accumulating that reconnaissance-level biogeochemical sampling can provide valuable insight into the chemistry of the substrate. Problems such as seasonal variations in plant chemistry and the lack of a universal biogeochemical sample medium may be circumvented by adopting normalising procedures. The planet can be divided into a few climatic zones, each of which is characterised by one or two common plant genera. If it can be demonstrated that the chemical differences between certain species of a single genus are small - as is suggested by studies of boreal forests - it would seem feasible to apply biogeochemistry as a low-density geochemical mapping tool. The technique could prove particularly useful for assessing the substrate chemistry of areas of dense forest, rugged terrain and difficult access by employing airborne sampling of trees from helicopters

Jul 1, 1991

By P wade

This is the first Presidential Address given to the Nottinghamshire Branch of The Institution following the merger of the Nottinghamshire and North Derbyshire Branch of The Institution of Mining Engineers (IMinE) and the Midland Branch of The Institution of Mining Electrical and Mining Mechanical Engineers (IMEMME). I intend to review the formation of the individual institutions as well as what has been achieved by mining related institutions over the years and finally I intend to look to our future.

Jan 11, 1996

By C. P. Summerhayes, J. W. G. Gilbey, S. Henley, G. P. Glasby, J. J. T. Harvey, J. Larsson, O. Akiman, A. G. Brown

Abstracts are presented from six University of London, one University of Nottingham and one University of Durham PhD theses

Dec 1, 1971

By R. Phillips

The low concentration of diamond in workable deposits requires very large samples for grade estimation, and results, even then, may be erratic and difficult to interpret. Although the Poisson probability distribution cannot accurately describe the occurrence of diamond, it is suggested that it gives a better estimate of grade than conventional methods, even from single samples. Examples illustrate the simple calculation required.

Dec 1, 1971

By B. M. England, L. C. Mackey

Magnesia minerals are included in most iron ore sinter mixes to provide the MgO requirements of blast furnace slag. The properties of these minerals have an influence on the eventual sintering properties of the mixes. A detailed study was undertaken of serpentine and dolomite and the use of limestone, olivine and magnesite was also investigated. A consideration of particle properties indicated that as these materials calcine a reduction in size can occur together with cracking and changes in surface properties. These changes could affect the permeability of the sintering bed and sintering performance. Studies of sintering reactions showed that magnesium and calcium, formed from the calcination of dolomite, are extremely mobile before the formation of melt. Evidence suggests that the movement of these oxides into surrounding areas is via a solid-state diffusion process. The diffusion of Ca into the surrounding hematite particles is faster than that of Mg, resulting in the formation of dicalcium ferrite and magnetite or magnesioferrite, the last two subsequently being converted to dicalcium ferrite in the presence of Ca with removal of Mg from the structure as ferroan periclase. Studies of pilot-plant sinters indicated that reaction mechanisms formulated from the bench-scale studies were occurring in actual sintering processes. The differences in sintering reactions between dolomite and serpentine were considered to be the major cause of differences in the availability of lime for bonding phase formation. Pilot-scale studies indicated that the sintering properties of a mix containing dolomite could be improved by increasing the basicity of the sinter mix while keeping the MgO level constant

Jun 18, 1905

By W. P. C. Duyvesteyn, B. J. Sabacky

Reprinted with revisions from Extractive metallurgy of copper, nickel and cobalt, volume I: Fundamental aspects. ed. Reddy R.G., Weizenbach R.N. Warrendale, Pennsylvania: The Minerals, Metals and Materials Society, 1993. Development work on the Escondida process, concluding with the successful operation of an integrated leach-SX-EW pilot plant and a pilot flotation plant for the upgrading of leach residues, demonstrated that all major process objectives could be achieved. Extraction of 40% of copper in concentrates containing monovalent copper was achieved with essentially no oxidation of sulphide sulphur. The Cu contents of leach residues from four different types of concentrate were successfully upgraded to the original feed grades, giving a product that has potential as a high-quality concentrate for the smelter market. A compact solvent extraction section effectively recovered the ammonia lixiviant for recycling to leaching and selectively transferred Cu into a conventional acid sulphate electrowinning system. High-quality "six-nines" copper cathode was produced on commercial-scale stainless steel blanks, demonstrating that the process will be able to compete effectively in the premium cathode market

Dec 1, 1995

By G. Kill

Although other energy commodities have developed successful futures contracts, long-term contracts still dominate the coal market. To establish whether coal markets will develop in the same way, coal price and volume data are tested against a set of criteria considered to represent some of the factors contributing to the development of a successful futures contract. Coal meets only some of the criteria: market players are subject to little risk in quite a stable market, have strong preferences for the specific nature of long-term contracts and profit from product uniqueness, each trade being individually negotiated. Potential structural changes in the western European market are not felt to be sufficient to create demand for a coal futures contract, but an empirical model has been developed that could form the basis of a further study to predict the potential for success

Aug 1, 1994

By F. J. Tavera, J. A. Finch

A probe suitable for on-line measurements of gas hold-up in industrial flotation systems has been developed. It is based on an open cell for measurement of slurry-gas conductivity and a novel syphon cell for measurement of slurry-only conductivity. The desired behaviour of the two cells was demonstrated and estimates of gas hold-up were shown to be in good agreement with independent measurements. The gas hold-up probe was used as a diagnostic tool to assess the operation of flotation columns. Differences in gas hold-up between baffled sections in two industrial columns were detected

Jun 18, 1905

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 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 A. T. Iannacchione

Underground mining of stone in the US is increasing, as is the depth of overburden above the mines. Data gathered from mine visits, maps, discussion with operators and numerical simulation have been used to investigate pillar design and recommend safe practice. Many pillars have slender shapes with relatively large adjacent mine openings: width-to-height ratios range from 0.54 to 3.13 and extraction ratios from 0.56 to 0.91. The pillar material is often very strong and average overburden only 80 m, but occasional failure due to excessive local stress has occurred where pillar size had been unintentionally reduced, overburdens were greater than 200 m, width-to-height ratios were less than 1.25 or extraction ratios were greater than 0.83. Pillars with width-to-height ratios of less than 1.5 appear more likely to fail under excessive stress. When width-to-height ratios fall below 1.0, defects such as through-running discontinuities can have a significant influence on stability. Dip, orientation and material properties are also important

Jun 21, 1905

By T. Piirainen, T. Alapieti

"The Koillismaa layered igneous complex is the result of igneous activity that occurred 2436±5 m.y. ago. Its crystallization took place in three separate but connected magma chambers, the total volume of which is estimated at more than 2000 km'. These chambers were located partly in a feeder system within Archaean granitoids and partly in an unconformity between these grani­ toids and Early Proterozoic supracrustal rocks. The composition of the parental magma that initially filled the chambers is thought to have been that of a relatively MgO-rich tholeiite. Sulphides and platinum-group minerals are mainly concentrated in the marginal series of the western part, where they are encountered over a distance of 25 km. This marginal series is an originally nearly horizontal series of rock types that displays a reversed differentiation trend, grading inwards from gabbroic to ultramafic rocks, followed bv rocks of the layered series. The chilled margin is not encountered anywhere in its original position at the contact, probably as a consequence of magmatic erosion, but remnants are to be found in the form of elongated xenoliths. Partly melted siliceous fragments from gneissic country rock typical of the lower part of the marginal series indicate pronounced contamination.Chalcopyrite, pentlandite and pyrrhotite±pyrite are the predominant sulphides. The accessory sulphide minerals include covellite, violarite, marcasite, mackinawite, sphalerite and argentian pentlandite. Platinum-group minerals are represented by froodite, michenerite, merenskyite and sperrylite. Other accessories that have been identified are electrum and native copper and gold. The mean of the Cu/(Cu+Ni) ratio in the mineralizations is 0.67 and Pt/(Pt+Pd) 0.31.It is suggested that the sulphide phase was formed in the marginal series as the solubility of sulphur in the basic magma was lowered by contamination, possibly assisted by some other factors. The sulphur isotope data support the juvenile origin of the sulphur."

Jan 1, 1984

By A. R. Naderian

Laboratory strength and deformation testing of freshly blasted sandstone and claystone overburden from Jeebropilly colliery in Queensland and in-situ plate-bearing tests on four backfills of different ages showed that the bearing capacity of backfill is a function mainly of compaction, not of age. The modulus or stiffness of the backfill is significantly increased by previous loading, in some cases up to threefold. Backfill material experiences some compaction through the passage of mining vehicles, likely to provide a bearing capacity that will support normal construction activities; the limited testing performed suggested that completed backfills are capable of supporting loads of up to 200 kN/m2 while sustaining displacements acceptable for a wide range of residential and industrial uses, but may be susceptible to collapse settlements due to saturation in the long term

Jun 19, 1905

By I. Marklund, W. Hustrulid

Sublevel caving is likely to remain the dominant system at both Malmberget and Kiruna for the foreseeable future. The sub-level interval has increased from 12 m in 1983 to 30 m, requiring more effective drifting and the development of a contour blasting technique to reduce requirements for rock reinforcement. Production drilling is mainly by hydraulic hammers or water-powered in-the-hole machines drilling 115 m diameter holes. Loading operations are undertaken 7 days/week with 15-25 tonne capacity electric shovels. Production has increased by nearly 70% since 1983 and productivity has risen threefold

Dec 1, 1995

By R. R. Tatiya

Data obtained from a copper mine were used in a comparative study of the reserve estimates generated by applying geostatistical methods to surface borehole data, underground core drilling results and assay values from chip sampling. Global estimation of the deposit performed by kriging of the low-density sampling data from the surface boreholes did not provide reliable results, but could identify the potentially mineralised zones. The reserve generated from core drilling results correlated well with that estimated from chip sample data and with that estimated by the conventional methods used at the mine. A satisfactory reserve evaluation could, therefore, be obtained by kriging of the data from the underground core drilling alone, provided that a systematic sampling procedure was adopted. Estimates based on chip sampling information could be used as a check, which could avoid the current practice of chip sampling of most of the mine workings. The aim should be to develop a semi-variogram for the deposit, which could be used to estimate the reserves by kriging

Jun 19, 1905

By P Shead, M A. Tuck

Both climate and methane control have been a prime concern in the development of the workings within the Deep Soft seam at Harworth Colliery. This paper describes the numerous methods employed over the past 15 years to effect control over these two major environmental pollutants at Harworth and describes a future method of working which will enable the output levels required to be achieved, whilst effecting the required level of both climatic and methane control. Firstly, the paper gives a broad historical overview of the steps taken since 1981, when production started in the Deep Soft seam at Harworth Colliery, to effect control over the main environmental pollutants in the seam. Secondly, the paper details the results of planning exercises undertaken to assess the various options with respect to panel layout, to achieve environmental control in future production districts. Finally, the recommended method of panel design to achieve the levels of production required is detailed.

Jan 7, 1997

By C. H. J. Beaven, M. P. Jones

Since the various new techniques of automation and computing have enabled vast numbers of mineralogical observations of relatively small samples to be made cheaply and rapidly, the statistical assessment of these measurements has become of vital importance. Much of the theory and most of the procedures of sampling that are used in the mineral industry are based on Gaussian statistics, but modern measuring techniques show that many mineralogical parameters do not necessarily follow the Gaussian distribution function. Consequently, it has become necessary to examine the application of other, more suitable statistical methods in order to derive the maximum amount of useful information from the examination of mineralogical samples. Some of the errors that can be introduced by the use of incorrect distribution functions are discussed and the value of determining the function that is appropriate to the particular parameter that is being measured is shown. Examples are provided of non-Gaussian distribution functions in mineralogical materials that were encountered during prospecting and during mineral treatment operations: a Canadian uranium ore, a Thai tin ore, and gold ore tailings.

Dec 1, 1971

By P Cochrane

Our ability to generate information and transport it about the planet on super highways of optical fibre is about to change the way in which we communicate, work and live. There is not a single aspect of our future that will go untouched by the communication and computing revolution that Is now upon us. The change we are about to witness will overshadow the impact of the printed word, industrial revolution and physical transport. The next major wave of information technology (TT) development will focus on the delivery of information and experience on demand, in the right form, at the right time, at the right price, to fixed or mobile terminals anywhere, over networks of optical fibre, radio, satellite and optical wireless. Bandwidth, distance and time will no longer be significant cost elements as service and access become dominant.

Jan 7, 1996

Carbon anode cells were studied by two-dimensional computer simulation to evaluate their suitability for alumina electrolysis at high superficial current densities. The most efficient anode arrangement was needed to overcome the electrochemical disadvantages of alumina's low solubility in chlorides. Cells with packed-bed anodes might provide practical superficial current densities greater than 0.67 A/cm2 when the granule size was less than 1 cm, but in the process of electrolysis the granules within the active zone would be consumed and become smaller, affecting alumina concentration transport. For zones of very small granules a concentration-dependent model should be considered; for more complete consideration a time-dependent model can be introduced to describe the variation of granule size and its influence on mass transfer and polarisation

Jun 19, 1905