Search Documents

By M. E. Wilson

"The property of McWatters Gold Mines, Limited, is in the east-central part of Rouyn township and about 6 miles east-southeast of the town of Rouyn. It includes 35 claims, the group of 5, staked originally, and 30 claims acquired in later years. The Rouyn-Val d'Or road and the Noranda Senneterre branch of the Canadian National railway both pass within a few hundred feet of the mine.The group of claims in which the mine occurs was first staked in 1922, but gold was not discovered until August 1932 when a schistose zone including veins of quartz carrying considerable free gold was laid bare in a stripped area in the northeastern part of claim R.11604. Diamond drilling undertaken in 1932, and continued into 1933, shouwd that the gold extended for at least 1,000 feet along the strike. A 3-compartment shaft was sunk to 418 feet in 1933. A mill having a capacity of 50 tons a day was constructed in 1934, and enlarged to 150 tons in 1935. Production began in 1934 and continued without interruption to June 1944. Except for a few diamond drill holes, there have been no operations on the property since that time. The maximum depth of the mine workings is 1,50) feet. A total of 368,013 tons of ore having a value of $3,946,752 and an average grade of $11.04 was mined during the years of operation.GEOLOGYThe ore mined from the property occurred within the south limb of an eastward plunging syncline of volcanics and sediments cut off on the north by the Cadillac-Bouzan Lake fault. Because the rock formations within the syncline have been severed from those outside with which they were originally continuous, their correlation is based almost wholly on lithological similarity. They include an irregular middle zone of conglomerate and greywacke underlain by north and south bands of andesite agglomerate and andesite tuff, in which lenticular bands of pillowed andesite are included."

Jan 1, 1954

By Yvon T. Maurice

Under the auspices of the Federal-Provincial Uranium Reconnaissance Program, a geochemical orientation survey was undertaken in an area of uraniferous Lower Proterozoic (Aphebian) rocks near Cape Dorset in southwest Baffin Island. The main objective of this study was to establish a methodology for a future reconnaissance geochemical program using lake samples over a 300-mile Lower Proterozoic rock belt that occurs along the southern coast of Baffin Island. Mineralogical and chemical studies of known radioactive occurrences, combined with detailed sampling of secondary environment media in the vicinity of the showings. indicate that uranium is the most significant pathfinder, despite considerable enrichment of other metals in the uraniferous rocks, Significant geochemical patterns produced by uranium in lake waters and uranium in lake sediments have been obtained, but their relative usefulness depends on the distribution of carbonate bedrock, which in turn affect the bicarbonate content of lake waters. In southern Baffin Island, because of erratic variation in lake-water alkalinity, it is recommended that both water s and sediments be sampled on a routine basis. The need for lake-water acidification to prevent depletion of soluble metal ions in samples resulting from adsorption on the walls of the containers and/or suspended solid matter is discussed briefly. The base metal potential of the area was examined in some detail and found to be significant, particularly for a Lower Proterozoic gossanous formation that occurs throughout southern Baffin Island.

Jan 1, 1977

By Eurípides do Amaral Vargas Jr., J. A. de Mello Franco

"It is frequently necessary to excavate a tunnel for Civil Engineering purposes, or wells for petroleum exploitation, in laminated rock mass like schists or phyllites or in highly foliated gneisses. The determination of the pre-existing in situ stresses is essential, in order to assure the stability of these excavations. In most cases, the pre-existing triaxial stress field is arbitrary in relation to the tunnel or well axis. For these rock masses the concept of Generalised Plane Strain can be correctly utilized.There are closed form solutions for the calculation of stresses in anisotropic rock masses under Generalised Plane Strain conditions (Lehknitskii, 1981 and Hong , 1994). Based on these analytical solutions, established for the cases of Generalised Plane Strain, a synthetic problem will be formulated: the theoretical in situ stress tensor acting on this rock mass will be determined, with the aid of Bayesian Inverse Problem Techniques, as developed by de Mello Franco (2009). Additionally, the reliability of results obtained will be evaluated, in accordance with the research performed by this author. INTRODUCTIONThe Inverse Problem Technique, as developed in the paper, is based on the definitions and concepts obtained from the current literature and used for the solution of Inverse Problems, but the innovation to be presented is the utilisation of Bayesian Techniques and the determination of the reliability of the results obtained. This will be shown in a synthetic example where the determination of the in situ stress tensor, from strain measurements in a drill hole is supposedly performed. It is assumed that this drill has its axis arbitrarily placed in relation to the rock mass. Generalised Plane Strain conditions will hold for use with problem. The equations of Beltrami – Mitchel, in agreement to Lekhnitskii (1981) and Ong (1994), will be used in this synthetic case, for calculating strains, hypothetically measured in the hole before the final excavations. Finally a synthetic example for the determination of the in situ stress in a fully anisotropic rock mass, based on Bayesian Techniques and its reliability, developed in de Mello Franco (2009) is presented."

Jan 1, 2015

By Toivo Toivanen

The paper begins with a brief history of the nickel industry in Finland, and then deals with the introduction of the flash smelting process. The main part of the paper is devoted to nickel refining, which is studied under four main headings -grinding, leaching, electrolyte precipitation, and nickel electrowinning. Flowsheets are illustrated, and the equipment used is described. Analyses of the material in the various stages, from concentrate to high-grade nickel matte, are also presented. N ICKEL made its appearance in the Finnish mining industry forty years ago, when a nickel deposit was discovered at Petsamo in Lapland. Mond Nickel Co. received the concession for this deposit from the Finnish Government, and the Petsamon Nikkeli Company constructed a mine and a nickel smelter (1), the completion of which was prevented by the 1939 Winter War. The mine and smelter were, however, completed soon afterwards in spite of World War II,

Jan 1, 1964

By Euler De Souza

"Underground operation ventilation energy requirements constitute a significant portion of mine energy consumption (40–50%) and total energy costs (25–40%). In general, mine ventilation systems are energy inefficient; the author has found several systems that operate at efficiencies below 65%. This paper presents how engineering design principles can improve the performance and efficiency of ventilation appliances, resulting in reduced power consumption and operating costs. Case studies demonstrate that, by retrofitting ventilation appliances using proper engineering concepts, systems will operate at efficiencies well above common operating efficiencies, resulting in a drastic reduction in costs and base electrical and energy loads.RÉSUMÉ Les besoins énergétiques nécessaires à l’aérage d’une exploitation souterraine représentent une part considérable de la consommation d’énergie d’une mine (de 40 à 50 %) ainsi que des coûts totaux liés à l’énergie (de 25 à 40 %). De manière générale, les systèmes d’aérage d’une mine sont loin d’être écoénergétiques ; l’auteur a trouvé plusieurs systèmes fonctionnant à des rendements inférieurs à 65 %. Cet article présente les principes de conception technique qui peuvent améliorer la performance et l’efficacité des systèmes d’aérage, entraînant une réduction de la consommation d’électricité et des coûts d’exploitation. Des études de cas montrent qu’en les rénovant à l’aide de concepts techniques adéquats, les systèmes d’aérage fonctionneront à des rendements bien supérieurs aux rendements habituels d’une exploitation. Ces rénovations donneront lieu à une réduction considérable des coûts ainsi que des charges électriques et énergétiques de base.INTRODUCTIONIncreasing electricity supply problems in North America have encouraged an industry-wide evaluation of energy consumption, resulting in a more urgent emphasis on energy-efficient design and operation for all energy-consuming systems. Electricity is the main mode of energy supply and the mining industry is affected by the increasing cost of this commodity (Natural Resources Canada, 2017). Ventilation systems normally operate 24 hours per day, 365 days per year, and account for 25–40% of the total energy costs and 40–50% of the electrical consumption of a mine operation (De Souza, 2013). Ventilation engineers are under ever-increasing pressure to reduce ventilation energy consumption and be cost effective."

Jan 1, 2018

By E. Ghali, A. D. Bas

"Treatment of oxide, e.g. roasted gold ores has received relatively less attention than sulphidic ones and recently, handling of oxide gold ores is becoming essential. In this study, the influence of roasted gold ore (RGO) slurry (at 35% solid ratio) on the electrochemical dissolution of gold has been examined using pure gold and iron oxide minerals (hematite, maghemite, and magnetite) as disc electrodes by zeroresistance ammeter mode either in one or two separate containers. The presence of slurry decreased galvanic currents, i.e. corrosion rates due to the release and increase in the amount of soluble and/or insoluble species that could retard further the anodic behaviour of gold. Higher galvanic currents were observed in two separate containers than that in one container indicating the primary importance of galvanic interactions. SEM-EDS results observed iron hydro/oxide coatings on gold surface in case of magnetite test. However, in case of RGO electrode it is not a perfect passivation, although somewhat decreasing trend was observed on gold dissolution. These findings have revealed that passivation is not only a laboratory phenomenon, but also it could be responsible for the slowdown of gold dissolution in industrial practice.INTRODUCTIONThe cyanidation of gold is an electrochemical corrosion process thus; the dissolution of gold can readily be studied by electrochemical techniques. The outcome/summary of previous electrochemical studies of gold leaching can partially be summarized as follows: Filmer (1982) and Lorenzen and van Deventer (1992) reported the negative effect of pyrite and pyrrhotite on gold leaching due to the galvanic interactions; Aghamirian and Yen (2005) studied gold galvanic corrosion in presence of sulphide mineral electrodes only in one cell using zero-resistance ammeter (ZRA) mode; Dai and Jeffrey (2006) discussed, individually, the anodic and cathodic behaviours between gold and sulphide minerals, and Azizi et al. (2010, 2011) used a bed reactor to examine the influence of sulphide minerals on gold dissolution in one and two separate cells. Accordingly, a slowdown in gold leaching has generally been attributed to the passivation phenomenon, although the indication of this phenomenon is still an undergoing debate. For instance, Mrkusic and Paynter (1970) identified the passivation as the film formation of dissolved species from calcine, Crundwell (2014) explained passivation, in the case of corrosion of metals, as the formation of a layer which is composed of a new chemical species on the mineral surface and this layer inhibits or blocks further reactions. He suggested that passivation is related to the oxidation of the metal, and the formation of a passive layer that retards the rate of dissolution by several orders of magnitude. Consequently, galvanic interactions, passivation phenomena, or combinations of them are considered significant electrochemical factors affecting gold dissolution (van Deventer, Reuter, Lorenzen, & Hoff, 1990; Azizi, Petre, & Larachi, 2012). It is important to note that generalizing the influence of a mineral/metal on gold dissolution may not be correct in all cases, since contrary behaviours/results (for pyrite) have been observed (Aghamirian & Yen, 2005). Therefore, electrochemical study of gold is still a subject of research and need to be examined further in detail."

Jan 1, 2016

By H. T. Fargey

This paper considers the social, economic and political factors and their influence on future production and marketing of Western Canadian minerals. Among the subjects discussed are inflation, taxation, anti-combines legislation, unstable international currency relationships, economic nationalism and protectionism, the European Common Market and environmentalism.

Jan 1, 1973

By B. Kruger

The Dundee Precious Metals Tsumeb Smelter has evolved over the last decade to meet the challenges and opportunities brought about by a changing copper concentrate market, technological advances, environmental legislation as well as social and political changes. The paper discusses some of the challenges, successes and lessons learnt through the expansion and modernization of its smelter complex. It considers the details and impact of the transition from slag granulation to that of slag slow cooling as well as the improvement program that was implemented to more than double the refractory campaign life of the Ausmelt furnace from around 6–9 months to 15–18 months. In addition, given the evolving world we live in, it considers the challenges that the smelter faces today, not the least of it being how to remain relevant in an age of digital and other 4th Industrial Revolution disruptions. INTRODUCTION Dundee Precious Metals Tsumeb (DPMT) Smelter is located just outside the town of Tsumeb, in the Oshikoto region of Namibia. It is the largest town in the region with a population of approximately 45,000. The smelter was built in the early 1960s to treat concentrate from the nearby Tsumeb copper mines. Construction of the site was completed in 1962 and the smelter was officially commissioned in 1963 by Tsumeb Corporation Limited (TCL). At the time the smelter consisted of a lead section (including a refinery), a copper section and plants that produced cadmium, sodium antimonite and arsenic trioxide. Production commenced in early 1964, with 3,500 tonnes of copper and 6,000 tonnes of lead being produced per month. TCL was acquired by Gold Fields South Africa in 1988, and a few years later the lead section was shut down due to reduced lead content of the mined ore. In mid-1996, all mining and smelting operations were halted due to labour strikes. Ongopolo Mining and Processing Limited (OMPL) re-opened the mines and the smelter in 2000, only operating the copper section of the smelter. At the end of 2008, all mining operations were halted by the new owner of OMPL, Weatherly Mining International, while the smelter continued to operate. The closure of the Weatherly owned mines in Namibia, the primary feed source to the Tsumeb Smelter, meant that the smelter had to transition its business model from operating as a ‘captive smelter’ to that of a ‘toll smelter’. Its Ausmelt Top Submerged Lance (TSL) smelting technology and various ancillary plants made it especially suitable for accepting and treating complex concentrates that were available on the global market.

Jan 1, 2019

By V. A. James

The new electrolytic copper refinery situated at Copper Cliff, Ontario, has been in operation for over a year and a half. This plant is operated by the Ontario Refining Company, Limited. The associated companies behind the enterprise are the International Nickel ?company of Canada, Limited, the American Metals Company, Consolidated Mining and Smelting Company of Canada, Limited, and Ventures, Limited. The plant was an outgrowth of the rapid development of copper resources in the nickel-copper ores of the Frood and other great mines in the Sudbury district, and of the desire to have all primary production units grouped together as compactly as possible. Starting anode furnace operations in June, 1930, and electrolytic refining on July 1st of that year, after a record-breaking construction programme completed in only fifteen months, the plant soon settled into its stride and the usual starting-up difficulties were .rapidly overcome. The rated capacity of the plant, namely, twenty million pounds of refined copper per month, has, of course, never been reached, due to depressed business conditions and latterly to the world copper agreement limiting production. It may be said, however, that the present installation has proved its ability to produce in excess of its rated capacity, and with relatively minor additions to plant and equipment that capacity can be doubled. Owing to the severity of the winters, when temperatures of from 20 to 40 degrees below zero are to be expected, the building of this refinery involved a number of problems in insulation, layout, ventilation, etc., which were rather unusual in copper-refinery construction.

Jan 1, 1932

By Antonio Segatori, Bjørn Holmedal, Kai Zhang, Trond Aukrust, Knut Marthinsen

"The visual appearance and mechanical properties of aluminium alloy extrusions are strongly dependent on the microstructure and texture of the extruded profiles, where the desired microstructure and texture may depend on the specific applications. In the present work, the evolution of deformation, as well as recrystallization textures during extrusion of AA6xxx aluminium alloys, have been experimentally and numerically investigated. Extrusion trials were performed in a laboratory extrusion set-up, which enabled immediate water-quenching of the profiles at the exit of the die, and thus the possibility to capture the deformation texture prior to post-extrusion recrystallization. The textures and their through-thickness variations were experimentally measured by the electron back-scatter diffraction technique (EBSD, and the deformation textures numerically modelled by coupling FEM flow simulations and crystal plasticity (CP) simulations. Different CP models as well as different choices of model parameters were employed and evaluated for texture predictions. With an appropriate choice of crystal plasticity model and model parameters, the deformation texture can mainly be predicted, although the accurate intensities are hard to reproduce. The corresponding recrystallization textures, either generated through spontaneous recrystallization of the extruded profiles or through post-extrusion annealing, are far more challenging to reproduce with available recrystallization models.INTRODUCTION Extrusion is a widely applied thermal-mechanical process to produce aluminium profiles. The properties of the profiles, for example mechanical, fatigue, fracture, corrosion as well surface appearance, are strongly dependent on the underlying microstructure and texture, and the requirements with respect to these aspects may vary with applications (Ralston et al., 2010; Dumoulin et al., 2012; Donati et al., 2013). Moreover, it is often a challenge to produce extrusions with a consistent and homogenous grain structure and texture along as well as through the cross section of the profiles. It is thus vital to understand and be able to predict (model) how different microstructures and textures are formed and how they evolve during and after extrusion, as basis for controlling the final appearance and properties of extruded profiles."

Jan 1, 2018

By M. B. Mansur, A. S. Guimarães, A. J. M. Santanilla, D. C. R. Espinosa, J. A. S. Tenório, R. A. Pini

The separation of Ni and Co from sulphate medium containing Mn, Mg, Cu and Ca was carried out by solvent extraction. The object of this study was to investigate the synergistic effect using phosphinic acid (Cyanex 272) and carboxylic acid (Versatic 10) and their mixtures in kerosene. The extraction percent of each metal ion was found to increase with increasing pH and extractant concentration. Co was preferentially extracted over Ni under the same extraction conditions. The separation factors of Ni/Co increased with the use of the synergistic systems investigated.

Jan 1, 2014

By A. Brown

IN INTRODUCING the subject of rock pressures, it may safely be assumed that mining men are only too familiar with the physical effects of strata stresses that accompany the extraction of minerals. It may be further assumed that they have, as individuals, arrived at certain conclusions regarding their nature, based upon years spent in observing such phenomena and in learning how to continue mining in spite of them. Such hardly won experience forms the core of what is often referred to as 'pit sense'. This essential type of knowledge is not ?based on theoretical considerations, nor can it be found in text books. It is highly individualistic in nature and almost impossible to pass on from one generation to another in terms of precise rules for guidance. It is this aspect of individual judgment based on practical experience that has led to the significant phrase The Art of Mining.

Jan 1, 1956

By S. W. Marcuson

In the late 1960's concerns about the natural environment reached high levels within North America and provided activists with suitable platforms for exerting influence over the general public and politicians. In response a host of regulatory mechanisms were developed, statutes, voluntary measures, land grants, codes of practices etc. Emerging environmental awareness from the era provided impetus for rapid technological change that encompassed all industries, especially the base metal business. The resulting clean up impacted all aspects of copper production, dealing with issues such as waste disposal, water and air quality with specific impact on emissions of sulfur dioxide and particulate. This paper provides a perspective of these changes reviewing the macro-economic impact of environmental movement in mining with its specific implications to the copper smelting industry. The fundamental challenges that were faced by the old, but capital-intensive North American plants and the approaches taken to deal with the changing times are reviewed with special emphasis on the conceptual approach to smelter S02 abatement and different paths taken in the USA and Canada. The role of economics, sustainable R&D and presence of technical infrastructure that facilitated the change process is elucidated, and speculations are made about the future state of pyrometallurgy and the natural environment. Cu2007 -

Jan 1, 2007

IN 1932, the No. 4 shaft at Wright-Hargreaves mine was completed to a depth of 4,000 feet, and the lowest operating level at that time was at 3,900 feet. It was realized that the existing pumping system, using triplex plunger pumps at somewhat irregular depths in the mine, would be in-adequate to take care of the increasing volume of water that would have to be handled as mining operations expanded. Accordingly, in February, 1932, after a thorough study of the whole matter, it was decided to instal an entirely new, automatically controlled, system of pumping, employing centrifugal pumps, with their characteristically trouble-free performance, operated by off-peak power.

Jan 1, 1939

By William E. Roscoe

"Mineral exploration properties are those on which an economically viable mineral deposit has not yet been discovered. Such properties are bought, sold, optioned and joint ventured on the basis of their perceived potential for the existence and discovery of a viable mineral deposit. The intrinsic value of an exploration property is therefore based on the exploration potential. One measure of the exploration potential is the amount that can be justified to spend on exploration for a viable deposit.The appraised value method uses a cost approach to value exploration properties. It is based on the premise that an exploration property is worth the meaningful past exploration expenditures plus warranted future costs to test remaining exploration potential. Results of past exploration work are analyzed in order to retain only those past expenditures that are productive in terms of identifying remaining potential. Warranted future costs comprise a reasonable exploration budget to test that potential.INTRODUCTIONThe purpose of this paper is to describe a cost approach to the valuation of mineral exploration properties and to provide some valuation examples. The particular cost approach described is the Appraised Value Method, which is best applied to mineral properties at the exploration stage.At present there are no comprehensive regulations or guidelines in Canada which specify what approaches and methods to use for the valuation of mineral properties. In this paper, the Appraised Value Method described is one method that the writer considers to be accepted industry practice for mineral properties at the exploration stage.Mineral properties are valued for a number of reasons, including mergers and acquisitions, non arm's length transactions, pricing of initial public offering of stock, support for property agreements, litigation, expropriation, and insurance claims."

Jan 1, 2003

By J. S. Redpath, W. R. Dengler

"A description of the equipment used and the electrical-mechanical problems encountered in sinking a deep shaft is given. This shaft is currently being sunk to a depth of 7,115 feet. Some of the features of the sinking plant are a 6,500-hp double-drum hoist, a Blair stage hoist, special high-capacity mucking gear, a Galloway stage, high-tensile stage suspension ropes and 12-ton sinking buckets.INTRODUCTIONIN THE EARLY FALL OF 1965, a contract was let, by The International Nickel Company of Canada, Limited, to Shaft Sinkers (Canada) Limited -J. S. Redpath Limited -Joint Venture, • to sink and equip the Creighton No. 9 shaft at their Creighton Mine proper-ty in Ontario. This paper describes the electrical and mechanical equipment used by the contractor on this project, and details various problems that were en-countered.The shaft itself is circular in section and is lined with monolithic concrete. Upon completion, it will feature twin skip compartments, a cage compartment, counterweight compartment, manway and pipe compartment. The finished diameter of this opening will be 21 feet and the shaft will bottom 7,115 feet below the collar. The present depth of the shaft (April, 1968) is 5,400 feet. The opening is concrete lined as excavation takes place and the steel will be placed in the shaft upon completion of sinking. Hoisting is done on rope guides which are part of the stage suspension system."

Jan 1, 1968

By Hang Zhao, Xinping Li, Pingan Wu, Yi Luo

"The deep-buried rock surrounding the Jinping II Hydro-power Station was taken as the engineering background. Using model specimens of classified rock materials to simulate fractured rock mass under high in-situ stress conditions, the test about acoustic propagation law on single fracture model of specimen under different pressures and different angles were carried out. The variation of p-wave velocity in fractured rock mass and axial stress-strain relationship in the whole test procedure was also studied. Based on damage mechanics principle and the acoustic wave propagation in cracked rock mass, comparative study on damage constitutive relation of fractured rock mass under high in-situ stress in consideration of equivalent strain and equivalent energy was performed. As the results showed, with the change of axial stress level under constant confining pressure, the change in wave velocity can be divided into three stages: slow increase (small variation in amplitude), rapid reduce (large variation in amplitude ) and accelerate reduction. When the confining pressure is constant, the maximum p-wave velocity and the peak strength of specimens increases with the decrease of the crack angle.When the crack angle is constant, the maximum p-wave velocity and the peak strength of specimens increases with the increase of confining pressure.It is identified that the theoretical calculation results of constitutive relation about elasto-plastic damage model containing variable wave velocity in the fractured rock mass is consistent with the model test results.Therefore,the constitutive relation can provide reasonable suggestions for engineering practice. INTRODUCTIONThere are a lot of joints and fractures in surrounding rock mass of deep-lying in the Jinping-II hydropower station, which has a great influence on the physical and mechanical properties of rocks and effects the acoustic wave propagation and attenuation law in rock. Many previous research and project examples has proved that sound propagation parameters are closely related to crack and stress condition. Thus, it has certain theoretical significance and practical application value to carry out researches on sound propagation characteristics and establish damage constitutive model of fractured rock mass which is related to sound propagation parameters."

Jan 1, 2015

By O`Donnell. P. J.

THE modern coal cutter is a highly developed, and to a certain extent a somewhat complicated, machine. The requisite power to cope with conditions as found must be generated by the motor with due regard to limitations in the matter of dimensions and weight. This imposes the necessity of relatively high speeds of rotation. Any factor external to the machine proper which tends to reduce the load on the motor and gearing is most important. Experience has proved that close attention to the question of cutter-chain details undoubtedly results, in practically every coal-cutting operation, in increased efficiency and reduction of power and maintenance costs. The chain is the unit of the coal cutter which most greatly affects the economical operation of the machine, and only by due consideration of conditions and by the proper selection of the right chain can best results be expected; also, intelligent care of the chain while in operation is essential if it is to give its best service. The chain is the part of the machine that carries the pick boxes or blocks, which are connected to each other by a pair of chain links. The power to drive the chain is trans-mitted by a sprocket. The chain runs in guides supported by a rigid member called a 'jib'. Figure 1 shows the various parts mentioned. The first requirement of a chain is that it cut the coal as fast as possible. The second is that it do so economically. Economy of cutting can conveniently be divided as follows: (1) Economy in power used. (2) Economy in pick life. (3) Economy ' in chain life. ( 4) Economy in jib life. (5) Economy in labour for maintenance.

Jan 1, 1936

By G. S. Hume

In the transformation of carbonaceous materials, such as peat, to coals of various grades, the changes are known to be both physical and chemical and the grade of coal finally produced depends on the stage to which alteration proceeded. Those changes, which are frequently spoken of as the results of metamorphism, are due to pressure with accompanying heat and, according to the amount of metamorphism to which the sediments with the included carbonaceous beds have been subjected, there is a gradation from peat to anthracite coal, and even to graphite. The improvement in the quality of the coal as a result of metamorphism is due to an increase of the carbon content of the coal and a corresponding loss of the volatile materials. This rise in the quality of the coal according to the degree of metamorphism is well illustrated by the coals of western Canada. In the Plains area, where the deformation and the attendant metamorphism of the sediments is comparatively small, the coals are lignites, whereas in the mountains, where deformation has been severe, the coals are semi-anthracites. Sub-bituminous and bituminous coals occur in the intervening areas. The same general relationship between the quality of the coal and the degree of metamorphism holds true for the Appalachian basin of the United States, where there is a progressive improvement in the quality of the coals from west to east, that is, from an area of comparatively slight metamorphism to an area of marked deformation in the Appalachian Mountain region. But while it is true that this relationship holds in a general way, it has been found that the improvement in the quality of the coal is not always uniformly progressive, and there may be local variations such that an area containing coal with a carbon content indicating low or medium metamorphism may be surrounded by areas in which the coals are of higher grade. These local variations in many cases can be explained, and they in no way detract from the general rule that, in a region exhibiting a progressive betterment in the quality of the coal from an area of low metamorphism to one of more marked deformation, the quality of the coal, i.e., the amount of fixed carbon in the coal, may be taken as an index of the degree of metamorphism of the coal as well as of the sediments in which it occurs, It has been pointed out (') that certain coals, such as cannels, are unreliable indicators of the varying degree of metamorphism because of the nature of the material from which such coal was derived. Such coals, however, are not known in western Canada and their behaviour need not here be discussed.

Jan 1, 1927

By A. Ignatieff

"Excavation, the principal mining process, 'which hitherto has been based largely on the intuition and logic of mining men, is increasingly receiving the attention of engineers and scientists versed in rock mechanics. The paper intro-duce the principles of this science in simplified form, directed both to underground and open-pit mining. Reference is made to the large annual tonnage from ore and rock excavations, which in 1967 were responsible for 250 million tons of mineral production in Canada.The urge to transform excavation into a continuous instead of an interrupted process is discussed with references to the various types of energies employed or proposed in rock breakage or excavation. Due to the rapid decay of applied energy in the discontinuous and heterogeneous rock environment, large confined blasts proposed for in-situ mining do not give much expectation of success as yet. Raises and ventilating shafts are already bored in reasonably hard rock. Tunnelling machines will be used for drifting and cross-cutting in the future, but continuous mining machines of the cuttmg and shearing type are not 'around the corner' for stoping typical orebodies. On the other hand, bed mining, particularly of coal, has led the way in continuous mining, and Remotely Operated Long-wall Face (ROLF) experiments are progressing in an encouraging way. Some reflections on the mining environment in relation to the human element are made."

Jan 1, 1970