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1994 estimates for Porgera are probable and proven reserves of 58 200 000 t of ore grading 5 g/t Au. Gold mineralisation is related to an intrusive complex emplaced at shallow levels in poorly consolidated sedimentary rocks. The complex is located in a zone of fold-and-thrust deformation, whose formation may have been initiated shortly before emplacement and continues locally today. Abundant primary magnetite in the complex gives an intense, 5 km wide aeromagnetic anomaly. The deposit formed during two main stages of mineralisation, the first related to early magmatic-hydrothermal activity and the second representing later epithermal overprinting centred on the Roamane fault. Hydrothermal alteration followed closely on emplacement indicating a close genetic relationship between magmatism and mineralisation. Both stages of hydrothermal activity post-date and overprint early propylitic alteration. Several factors have acted in unison or sequentially to concentrate metals at the deposit, including an extensional or trans-tensional tectonic setting within an arc or collisional environment, the exsolution of a magmatic hydrothermal fluid prior to sulphur saturation in the melt, the development of the hydrothermal system into one favourable for transporting gold, the action of late-stage faulting in focusing epithermal fluid flow, and the role of dissolved gases in promoting fluid phase separation and high-grade ore deposition

Jun 19, 1905

A study of the thermodynamic properties of magnesium chloride ammines was carried out with the ultimate objective that the thermal decomposition of the hexammine MgCl2.6NH3 may prove successful on a commercial scale for the manufacture of anhydrous magnesium chloride, which is required for the efficient electrolytic production of magnesium. The experimental data are presented in the form of an equilibrium diagram that aids the understanding of the conditions associated with the thermal decomposition of ammines

Jun 13, 1905

By D. R. Hudson, M. J. Donaldson

"Study of gravity concentrates from the gold-recovery circuit of the Kambalda nickel mill has enabled an assessment to be made of the nature, relative abundance and compositional variability of platinum group element (PGE) minerals and other associated heavy minerals that are present in the Kambalda nickel deposits. The major platinum minerals are sperrylite, PtAs2, and nioncheite, (Pt. Pd, Ni)(Te, Bi)2, and the major palladium minerals are sudburvite, (Pd, Pt, Ni)(Sb, Te, Bi), stibiopalladinite, Pd6Sb2, and palladoarsenide, Pd2 (As, Sb), together with a palladium antimonide and a palladium arsenide that have not been fully characterized. Palladian melonites, which contain up to 10 wt% Pd, and palladian nickeline are also important PGE hosts. Sperrylite and sudburyite are by far the most abundant discrete minerals in the gravity concentrates.Gold occurs as argentian, cuprian and nickeloan—cuprian gold, and as the tellurides calaverite, petzite and auriferous hessite. Silver is present in petzite, hessite and volynskite. Other rare phases contained in the gravity concentrates include native bismuth, altaite, frohbergite, breithauptite, gersdorffite, parkerite, scheelite, tantalite, cassiterite, rutile, bunsenite, gahnite, barite and uvarovite.Descriptions of in-situ occurrences of PGE minerals at Kambalda are rare. Michenerite, PdBiTe, and testibiopalladite, PdSbTe, have been described from a telluride-rich quartz-carbonate vein that intersects massive sulphide ore in Lunnon Shoot. Moncheite has been observed in chalcopyrite-rich stringers, and sudburyite occurs as inclusions in nickeline in a quartz- carbonate veinlet. No discrete PGE minerals have been found within the massive and matrix ore zones in the Kambalda ore- shoots, and the geochemical distribution of PGE suggests that the formation of discrete PGE phases may be related to post- magmatic processes—in particular, metamorphic segregation of sulphides, and the interaction of the ore sulphides, containing PGE in solid solution, with younger hydrothermal fluids. This has led to local redistribution of the PGE, with concentration in footwall stringers and veins, and in reaction zones."

Jan 1, 1984

By W. H. McAllister

The paper considers the geology and the coalfields that comprise the Scottish south area. It traces the history of known sources of spontaneous combustion and indicates the collieries concerned, with the position of the seams in the geological series where heatings have occurred. The methods of work over the years are described. It relates in detail the circumstances surrounding a fire at Bilston Glen Colliery in the Lothian Coalfield, and the heating at Killoch Colliery in the Ayrshire Coalfield, and the steps taken to deal with them. It also describes some of the difficulties in steep seam working. Methods adopted to prevent spontaneous combustion throughout the area are discussed, and some detail of the UNOR gas analyser is given. Finally, it comments on the present techniques in use in the area, particularly at Bilston Glen Colliery, to prevent spontaneous combustion.

May 23, 1905

By A. C. Dunham, Y. D. Drakapoulos, P. W. Scott

The Pt and Pd occur alloyed with copper in small, irregularly-shaped grains, 0.25-5.0 micrometers in maximum dimensions. Grains of unalloyed native copper are also present. The grains are completely surrounded by or marginal to magnetite with inclusions of Ni-Fe-Co sulphides and native Ni-Fe, which is apparently a product of the serpentinisation process. Crystallisation of the Pt-Pd-enriched copper probably occurred at the same time, at low temperature, but the previous form of the Pt and Pd is unknown as no earlier PGE phases have been found. While Pt and Pd minerals are usually important in early-magmatic base-metal sulphides, Pt alloyed with Cu is extremely rare and apparently occurs only very late in the paragenetic sequence. A Cu alloy with Pd dominant over Pt and only minor amounts of other elements appears not to have been reported

Jun 14, 1905

By E. C. I. Hammerbeck

"Geological controls and constraints in space and time define the milieu of the nickel deposits of Southern Africa. Primary, magmatic deposits are of two types, e.g. synvolcanic or syntectonic deposits confined to certain orogenic domains, and those related to intracratonic, post-orogenic magmatism, e.g. the Great Dyke, the Bushveld Complex and the Insizwa intrusion. Epigenetic and supergene deposits form a separate, unrelated group and are of minor economic importance.The metallogenic evolution of syntectonic nickel deposits is particularly well illustrated in the Zimbabwean Province, where the relationships between Archaean greenstone development and nickel mineralization are best illustrated. Volumetrically subordinate, nickel-poor greenstones in the 3500 m.y. old Sebakwian Group are followed by more common komatiite development in the Lower Greenstones (3000 m.y.), and, finally, by very significant komatiites with important nickel mineralization in the 2700 m.y. old Upper Greenstones of the Bulawayan Group. Comparable nickel mineralization is not known in the Raapvaal Province, in spite of ubiquitous komatiitic magmatism of the Onverwacht Group (3500 m.y.) and other greenstone sequences. No komatiitic rocks younger than about 3200 m.y. are known in this region, orogenic activity in the Kaapvaal tectonic province having ceased at about 3100 m.y., whereas the Zimbabwe Province remained tectonically active until at least 2600 m.y.The tectonic environment, host-rock petrology and mode of emplacement, as well as some details of the nickel mineralization, are the parameters employed to classify the Southern African magmatic nickel deposits. A rating of the deposits is introduced that reflects the original resources of the deposit, its average nickel content, its mining history and potential to facilitate ready comparison with and assessment of the nickel deposits listed in the classification, as well as some important nickel deposits worldwide."

Jan 1, 1984

By A. J. Naldrett

"Synorogenic mafic intrusions are a common feature of the northern Appalachians. Two sulphide-bearing intrusions in central Maine that have been investigated revealed a number of important features that illustrate sulphide-silicate interaction that relates to magmatic sulphides. The Moxie Pluton is a large mafic intrusion emplaced during the Devonian Acadian orogeny. The Katahdin gabbro is a small mafic body that is probably genetically and temporally related to the Moxie Pluton. Both intrusions were formed bv the intrusion of variably fractionated magmas into irregular chambers and feeder zones. The southern half of the Moxie Pluton contains three small sulphide accumulations, whereas the Katahdin gabbro hosts a large, predominantly massive, sulphide body. Textural evidence clearly documents the magmatic origin of these sulphides.The three Moxie Pluton sulphide bodies are located at or very close to the intersection between the intrusion and the sulphidebearing Hildreths Formation. Sulphur assimilation, suggested by this relationship, is supported by the isotopically light (634S = —8 to —25) and the selenium-poor (S/Se - 25 000-48 000) character of the Moxie sulphides and correlation with the Hildreths Formation sulphides (S34S = —25, S/Se = 25 000-48 000). Isotopically light sulphur (534S = —20 to —21) and high S/Se ratios indicate that the majority of sulphur in the Katahdin sulphide body was also derived from an unexposed country rock source. The volume of sulphide in this example illustrates the potential efficiency of the sulphur assimilation process—so efficient in this case that marked dilution of the economic chalcophile elements resulted from the addition of so much external sulphur.The three Moxie Pluton sulphide occurrences are all impoverished in Ni and Cu (1.87-0.44% Ni; 0.72—0.32% Cu in massive sulphide), but contain normal Co contents (0.22-0.13%) relative to typical magmatic sulphides. The Katahdin sulphides show a greater Ni and Cu impoverishment (0.2% Ni; 0.1% Cu in massive sulphide) with similar Co (0.17%). The Ni content of the Moxie Pluton olivines document the fractional removal of sulphides during crystallization of the host magma, which resulted in the progressive depletion of the chalcophile metals in this magma. Modelling that involved the fractional crystallization of the magma coupled with the fractional removal of a specified proportion of sulphide has successfully duplicated the Moxie Pluton sulphide compositions. A similar magmatic model has been postulated for the Katahdin sulphides with a greater degree of sulphide fractionation. This latter model is again supported by extremely low Ni/forsterite ratios in olivines, though the compositional range is insufficient to document fractionation. These magmatic models are not unique, but they provide a relatively constrained and consistent explanation for the sulphide compositions.The Ni contents of olivines are the most important indicator of sulphide-silicate interaction in mafic magmas and have exploration potential. They provide a means of assessing the timing and extent of sulphur saturation in an intrusion and are a guide to the Ni content of a sulphide accumulation in equilibrium with olivine. In the Maine examples they provide strong evidence of the magmatic origin of the sulphide accumulations and justification for magmatic modelling."

Jan 1, 1984

The mineralogical composition of the ore was determined and the mineral phases with which nickel is associated were identified. The ore was prepared by grinding to -420 micrometres and classification into granulometric fractions. Prior to the main series of experiments the effect of agitation rate on nickel recovery was investigated. The influence of sulphuric acid concentration, temperature and particle size on the kinetics of nickel extraction was then studied, both quantitatively and qualitatively, over fixed value intervals. Application of the initial rate method enabled determination both of the order of reaction with respect to sulphuric acid concentration and the activation energy for the dissolution of nickel. The results indicate that a physical mechanism can be ruled out as the rate-determining step in the extraction of nickel from the ore and that a chemical mechanism is more likely

Dec 1, 1991

By Dean S.

Further discussion at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 12th February 1916, with Mr. T.Y. Greener, President, in the chair, of the paper published in Trans. I.Min.E. vol.L, 1915, p.179 and 388. Written contributions to discussion included Mr. Dean's reply to earlier discussion (p.35-44), further written contributions by Tate S. (p.44-54) and Brown E.O.F. (p.54-56), and oral comments by Hare S., Merivale J.H., Greener T.Y. and Tate S. Particularly debated were the causes of the difference in output between American and British coal miners

Dec 1, 1916

By W. Petruk, M. J. Matos

An aplite ore from Guarda in northern Portugal, containing albite, microcline and quartz and muscovite gangue was studied to identify conditions for extracting the feldspar minerals. The large amounts of quantitative mineralogical data needed to evaluate grinding behaviour were provided by automated image analysis. The images were acquired on polished surfaces by measuring back-scattered electron signals produced with a microprobe. Minerals were identified from X-ray spectra and discriminated by grey level and element-characteristic X-rays. The quantities and size distributions of the minerals were determined by measuring thin sections of unbroken ore to predict the grind required to liberate the feldspars. The ore was then ground to -1.7 mm, polished sections were prepared from sieved fractions and the quantities of mineral species and apparent total liberation were determined by analysis. The predicted and measured liberations were compared and the grinding behaviour of the ore interpreted. In an appended correction, the correct version of Equation 1 is represented and Tables 3 and 6 are revised to consider all size fractions, including those coarser than 300 micrometres, in calculating the total liberation from King's fractional liberation

Jun 18, 1905

The paper, presented at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 8th April 1916, presents experimental work undertaken to observe the quenching effect of different substances, to find the most efficient of these substances, and to arrive at a possible explanation of their preventive action. The coal-dusts experimented with were such as passed through a 100-mesh sieve (10,000 holes to the square inch), and were obtained by grinding the coals. The quenching substances, used in as fine a state of division as possible, included gypsum, dried Chance mud, quicklime, magnesia, magnesia alba (levis), anhydrous sodium carbonate, sodium bicarbonate, soda-crystals, Glauber salts, ground shale and boiler-ashes

Dec 1, 1916

By R. F. Bell, Schultz

The paper briefly discusses the nature of spontaneous heating in mines in the Doncaster area, in the period immediately before 1967 and steps taken to prevent and treat such outbreaks. The changes that led to the increased rates of advice of Barnsley Seam faces since 1967 are listed and the effects of these increased rates on the frequency and location of spontaneous combustion are discussed. The change in methods of control required by the increased rate of advance of the faces and the changes in location of outbreaks are described. Some typical heating situations are evaluated. The methods described include the use of air sealants, water gels for filling of voids in wastes, the balancing of pressures across heating areas by pressure chambers, booster fans, and the resiting of air separation doors, and the sealing of air-ways by flooding. The authors discuss the influence of mine layouts on the risks of spontaneous combustion and advocate that future plans should be designed to limit the number of districts at risk when heatings occur.

May 23, 1905

By Schwartz M.

Respect for mining in Botswana is long-standing. This article looks at Africa's most transparent mining regime and some of its ambitious plans. Botswana's mining industry value is forecast to average 5.2% growth from 2014-2018 with solid growth for the diamond sector and acceleration of coal production. Respect for the country's mining regime is maintained in the Fraser Institute 2014 annual survey where Botswana occupies the 26th position of 122 administrations. Botswana's transparency is illustrated by Mupane gold mine near Francistown, Ghaghoo diamond mine in the Gope area and the Morupule coal mine

Mar 1, 2015

By C. J. V. Wheatley

Recent studies of the mineralisation at Avoca in southeast Ireland, Parys Mountain in Anglesey, and Coniston in the Lake District result in the proposal of a new metallogenetic model for mineral deposits in the Southern Caledonides. A regional pattern of metal zoning exists, an axial belt, including the major copper deposits, being bordered by areas with lead-zinc deposits. Conformable lenticular pyritic zones occur in the central belt, closely associated with acid volcanic sequences and, often, post-dating them. These zones are thought to have been formed in a marine environment, mineral growth taking place below the sediment-water interface, whereas magnetite-rich zones developed under different Eh and pH conditions. Stockworks containing appreciable copper and, in some cases, lead and zinc were developed at a later date, stratigraphically below the pyritic zones, by migrating hydrothermal chloride and metal-rich fluids. Complex lead-zinc-pyrite mineralisation resulted from the reaction between pyritic zones and the final fraction of the hydrothermal fluids. Crosscutting vein-type fissure infilling mineralisation occurs in every mineral field. These deposits apparently comprise a pulsatory metasomatic sequence, closely related to tectono-stratigraphic controls, ore localisation being influenced by the coincidence of suitable structures and pyritic shale horizons. The implications for mineral exploration are considered and it is concluded that the model offers an explanation for the existing pattern of metal zoning; and it may have wide applicability to mineral deposition in geosynclinal sequences.

Dec 1, 1971

By J R. Leeming

The paper describes a technique that has been developed by the Health and Safety Executive (USE) to make an assessment of the effectiveness of Health and Safety (H and S) management at complex sites. The paper then describes how the technique was adapted and used for the first time at a large coal mine. The results highlighted certain deficiencies in the safety management system, allowing directed advice to he given to management.

Jan 4, 1997

By R. W. Ruddle

The present state of knowledge on this subject may briefly be summarized as follows: (1) The copper content of the slag increases with the grade of the matte in contact with it; on the other hand, the proportion of copper lost decreases as the matte grade increases, because as a general rule a smaller volume of slag is produced when a high-grade matte is made. (2) The presence of CaO and MgO in the slag decreases the copper content of the slag, and the presence of ZnO increases it; the presence of A1203 seems to have little effect. The influence of the silicate degree is not yet clarified, but on theoretical grounds it seems likely that the copper content increases with the silicate degree of the slag. (3) High slag viscosity, high magnetite contents and low density difference between matte and slag all tend to increase the copper loss. The volume of slag is also an important factor. (4) The effect of bath temperature on the copper loss is not clear and further investigation of this point is needed. (5) It appears possible to recover a large part of the copper in the slag by adding FeS, CaS and other sulphides

Jan 1, 1953

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

By J. Ivon Graham, T. D. Jones

This paper presents methods in use in British coal-mines for the suppression of dust. While the effect of present-day treatment will not be apparent for several years, in pits in South Wales, concentrations as high as 50 gm./1,000 cu. ft. were some years ago fairly common in various operations at or near the coal-face, with an average concentration of 20 gm./1,000 cu. ft. Now the average concentration in what were previously dusty pits is probably not greater than 3 gm./1,000 cu. ft.Nevertheless, every effort must be made to improve conditions still further. In South Wales it is claimed that 99% of the coal-faces requiring treatment have been dealt with either by wet cutting, infusion, or hand-spraying. The extent of the treatment by these methods can be gauged by the fact that the total length of coal-faces now being treated by water infusion in Cardiff and Swansea areas is about 33,000 yds., by wet cutting 25,000 yds., and by hand-spraying nearly 14,000 yds. The influence of methods of mining upon dust production is only mentioned very briefly in this review, and there is no doubt that much more is to be learned concerning this aspect. It can be stated, however, that good mining practice is essential to prevent unnecessary dust production, and the problem of dust in mines will be solved only by the closest co-operation between mine managers, workmen, and scientists.

Jan 1, 1947

Discussion at the North of England Institute of Mining and Mechanical Engineers' general meeting held in Newcastle-upon-Tyne, 8th April 1916, on the paper published in Trans. I.Min.E., vol.LI, 1916, p.72-90, included written contributions on size and gauge standardisation by Lupton A., Peck W.R., Dean S., Mayer R.W. and Ashworth J., with the author's written response, and by Bulman H.F. and Brown M.

Dec 1, 1916

By G W. Clamp

The most traum atic event within the lUK coal industry during the last 30 years was its privatisation. Who were the relatively unknown people from RJB: white knights or robber barons? This paper highlights the strong safety and progressive engineering cultures th at existed and continues within the company. A long-term view of the business coupled with proven professionalism is amply developed. Quite dearly, to revert to private ownership is not a return to Victorian values but ‘back to the future’.

Jan 8, 1997