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By R. Cammack

"A fundamental component of the Hoek–Brown empirical rock failure criterion is assessing an appropriate mi constant. In developing their empirical criterion Hoek and Brown normalised triaxial test results by dividing the principal stresses at failure by the uniaxial compressive strength to provide mi values for typical rock types. Experience shows that Hoek triaxial tests for individual lithology types commonly have a large inherent scatter. In addition, tests are often conducted on core from random locations, which although being of one parent rock type, display variations in density as well as minor variations in grain size and alteration.This paper presents experience from projects the authors have been involved in which large sample populations of triaxial and UCS tests on similar rock types were available. Geophysical logging data was also available for some projects. The methods used to estimate the compressive strength for each sample and the effects on normalising the data sets are described. The variability of the data and uncertainties and assumptions involved in the process of assigning a mi value from the normalised data are also discussed."

Jan 1, 2015

By R. C. Rowe

THIS paper is an endeavour to analyse the ideal and practical functions of government technical mining services, and their relationship to the National Domain, as well as to one another. its spirit is not critical, even though at times it may appear to besoin fact. It is a serious effort to divert a trend in public thought which delights in calling itself practical whereas it is really merely short-sighted. The author refers particularly to the idea that governmental research is a luxury which should be curtailed in the interests of economy, and turned over to private enterprise or the provinces. In order that we obtain the proper perspective of the question, it is advisable to indulge in a little history. In the year 1842, the Geological Survey of Canada was formed under the guidance of William (later Sir William) Edmund Logan. The literature on the founding and history of the Geological Survey of Canada is extensive, and therefore it is unnecessary to go into detail here regarding it. It might be mentioned, however, that the Geological Survey of Canada is only seven years younger than the Geological Survey of Great Britain (founded in 1835), and is only exceeded in age on the American continent by the State Geological Surveys of New York, Pennsylvania, Massachusetts, and Michigan, which were founded between 1833 and 1836. In 1877, the Geological Survey became a permanent government institution as a branch of the Department of the Interior. It should be noted, however, that the Director of the Survey ranked as a Deputy Minister and reported direct to the Minister. This continued until 1907. In 1886, the Mineral Resources and Statistics Division of the Geological Survey was formed. Some years later, the Canadian Institute of Mining and Metallurgy (then the Canadian Mining Institute), backed by the mining press, began to agitate for the establishment of a Dominion Department of Mines, and in 1907 such a department was founded by the Geology and Mines Act of that year, with a separate Cabinet portfolio for the position of Minister of Mines.

Jan 1, 1939

By The Staff

IT is a high compliment to be invited to present a pap::r on the subject of "Mining in the National Economy". To cover it adequately would need the knowledge of the economic geologist and of the technical mining engineer, together with the arts of the statistician and of the economist in general, allied with generous psychic powers. Further, one should embellish the tale with a touch of drama. It is comforting that the subject is so broad that whatever may be said within the compass of a paper like the present, can hardly be criticized as going beyond the terms of reference. A conventional approach would be to begin with the noteworthy statistics of the mining industry of yesterday and today. But in the present company this would be "carrying coals to Newcastle"-or to give the venerable metaphor local colour, "nickel to Sudbury". Such statistics are available in all their stimulating detail in our official publications. Let us tackle at once, therefore, as a less hackneyed theme, the relationship of mining to other phases of the Canadian economy. RELATION TO TOTAL PRODUCTION While mining occupies a position of less importance than manufacturing or agriculture in Canada, its relative contribution has greatly increased during the post-war period. Due to the fall in wholesale prices, the net value of production in Canada has shown a decrease averaging about 1.5 per cent per year during the post-war period, though its volume of course has gone up. Mineral production on a value basis, on the other hand, showed a gain of 2.8 per cent per year. Mineral production was only 5.14 per cent of the net value of production of all kinds of commodities in 1919, bur from 1929 to 1936 the proportion rose steadily rill it reached no less than 12. 76 per cent in the latter year.

Jan 1, 1937

By J. R. Rau

While refuge chambers are common place in most underground mining projects, there are different philosophies as to what life support systems are to be considered and how these systems are to be applied. Case studies in the underground mining industry have examples of emergencies where the external compressed air and power supply to the refuge chamber were compromised due to proximity of services to the fire location. In 2005, The Department of Industry and Resources, Western Australia, drafted guidelines that listed specific requirements for refuge chambers which included a secondary life support system that would operate independently of external sources. The objective of this document is to examine what critical life support systems are essential for safe entrapment in the event of an emergency and to examine considerations for their application.

Aug 1, 2013

By Roy S. Celland, K. H. Singh

The introduction of 'post' pillar mining at the Strathcona mine represents a new approach to ground support in cut-and-fill applications. The method has also shown significant economic advantages. It is believed that the development of this concept is one of the few examples where rock mechanics principles have successfully been applied in the development of a stoping method. The paper describes the evolution of this method and contains discussions on the theoretical analysis of the technical, operational and economics aspects of the system. Pillar design procedures and field observations on the practical application of theoretical analysis are also outlined.

Jan 1, 1973

By J. F. Boux

"The study of the total utilization of fly ash has involved all of the known technology in the processing of this waste material into useful products. In addition, a complete knowledge of all the possible uses of fly ash and its products in the market area was probably the most important factor in evaluating the theory and practical feasibility of the total utilization of fly ash from a single large supplyLaboratory tests carried out on the separation of fly ash into different fractions were shown to improve its value and utilization. Four main fractions were studied: a fine pozzolanic low-carbon fraction; a coarse fraction for light-weight aggregate production by pelletizing and sintering; a high-iron fraction; and a carbon-rich fraction. The term ""beneficiation"" here refers to a process of separating fly ash into more useful components.Laboratory and pilot sinter strand tests were employed to optimize the sintering capability and the quality of the heat-hardened pellets through a study of the agglomeration cycle in four principal heat zones, under controlled conditions of air flow, temperature and atmosphere, and including the controlled sizing of pellets.The suitability of the heat-hardened pellets as light-weight aggregate was evaluated in test batches of concrete, which were compared with concrete containing commercial lightweight aggregate of established quality.A study of beneficiated fly ash pozzolan as a partial cementitious binder component in normal and high-temperature cured concrete was reported in a paper at the re-cent Second International Fly Ash Symposium.Samples of raw and beneficiated Lakeview ash were compared with samples of other established high-quality fly ash pozzolans. The evaluation indicated the usefulness of beneficiated Lakeview ash as a pozzolan. Economic studies indicated that to accomplish the primary objective of total utilization of any single source of fly ash (in this case. fly ash from the Lakeview Generating Station, producing approximately 400,000 tons per year), a broad knowledge of the technology of various mineral processes was essential.The design of the fly ash processing plant had to be based on the disposal of all the raw fly ash produced by the generating station. This is contrary to the normal design of a processing plant in which raw materials are supplied and produced according to product demand. The design, therefore, had to be of such flexibility as to pro-duce as wide a variety of products as possible, and the ability to market them had to be well researched and understood."

Jan 1, 1970

By B. Qiu

The large surface ground movements induced by underground mining could threaten the safety of the pipelines laid across the subsidence-prone area. Existing analytical methods for the stress analysis of buried pipeline over mine subsidence area were based on the assumption of ?thin? pipeline, which limited their applicability. This paper presents the improved model with the capability to determine the stress distribution of the ?thick? pipeline. The pipe-soil interaction in this model was also updated to adapt various pipe soil contact conditions. In addition, the time-dependent effects of dynamic subsidence effects were also added to the model. A case of protecting a long section of a buried large-diameter pipeline over two longwall panels in a shallow mine is shown. The stress distribution along the pipeline is determined and the overstressed sections are identified. A partial uncovering plan was developed based on the predicted stress and complicated terrain at the site.

Aug 1, 2013

By J. E. Armstrong

THE Pinchi Lake mercury belt is in central British Columbia, about fifty miles north of the Prince Rupert branch of the Canadian National railway (Figure 1). Until 1936 little was known about the geology of this area. Jn 19~6 and 1937, J. G. Gray and the writer mapped the Fort Fraser area (G.S.C. maps 630A and 631A) for the Geological Survey of Canada. During the field season of 1937, cinnabar was discovered by J. G. Gray in the Permian limestones on the north shore of Pinchi lake on what have since proved to be the main showings of the Pinchi Lake mercury mine. Claims were staked in the spring of 1938 and later that year were optioned to the Consolidated Mining and Smelting Company. Development work revealed cinnabar deposits of commercial size and grade, and a small reduction plant was erected, production of mercury commencing in June, 1940. Since 1940, this plant has been enlarged by additional units. The ore treated is reported to contain between 0.5 and 0.75 per cent mercury. The production of mercury from this deposit is now far in excess of Canadian requirements and this country is able to supply the United Kingdom with part of its needs. In 1940 and 1941, several other occurrences of cinnabar were found northwest of Pinchi lake. During 1941, the writer made a geological investigation of the known cinnabar occurrences and of the belt of country in which they are located. The present paper summarizes the results of this work. The writer is indebted to officials of the Consolidated Mining and Smelting Company, and to Mr. E. Bronlund of the Pinchi Lake mine in particular, for their generous co-operation in the work.

Jan 1, 1942

By J. D. Christian

WHEN mining development began in the Kirkland Lake camp, twenty-five years ago, there was very little information obtainable from surface showings as to the nature of the ore deposits. A length of almost a mile of the main 'break' lay under the south arm of the lake, and elsewhere most of the outcrops were covered with glacial drift. Shafts were sunk on ore-bodies of uncertain value, either on the outcrop of the veins or-because of the lake to the north-in the south or hanging-wall. In the second year of the camp's development, the Great War broke out and retarded progress for its duration. He would have been a real optimist who, in those early years, could have foreseen mining at depths of more than a mile.

Jan 1, 1939

By T. G. Joseph, A. Chamanara

ABSTRACT: The chicken and egg scenario — where adverse truck motions cause ground deterioration and poor ground profiles cause adverse truck motions — is a downward deterioration spiral dominating our industry. If we remove one action, the reaction stops. A simple truck to excavator load data analysis and wireless communication system is outlined, which will provide visual assistance to the excavator operator in achieving improved load placement and balance in a truck body. This will reduce subsequent hauler duty cycle adverse motions and g levels that contribute to structural fatigue, higher tkph, reduced tire life, and ongoing maintenance of haul roads.

Jan 1, 2012

By Omkar N. S. Beruar

Extraction of sill pillars has always been problematic because of high risk of seismicity and rockburst. Depending on a number of factors, a sill pillar can undergo different failure modes and cause problems in the mine. Of these, sudden and uncontrolled failure of part(s) of the pillar leading to highenergy seismic events and rockbursts is a main concern because it is not possible to predict the location and time of a rockburst apart from its potential to cause extensive damage to the mine structures. To date, a comprehensive technique for sill pillar design and recovery does not exist. Conventional methods of pillar design, such as the pillar stability graph method, are utilized to design stiff sill pillars. In these design approaches, the post-peak response of the pillar-rock system is not considered. This is in part due to a lack of clear and comprehensive understanding of the post-peak behaviour and failure mechanism of sill pillars. In general, the strength of a rockmass is described using a failure criterion. When stresses reach the strength of the rockmass, the rockmass does not necessarily become unstable and knowledge of the loads alone is not enough to assess the instability conditions accurately. In fact, it is not possible to predict instability of rockmass based on the strength/stress ratio alone because instability depends not only on this ratio but also on the loading condition and loading system characteristics. The loading system can dictate whether the sill pillar will go through a stable or unstable failure process. This paper examines the influence of various parameters such as the pillar width to height ratio, the extraction rate, and placement of backfill on the Loading System Stiffness (LSS) and the Pillar Stiffness (PSS). The ultimate goal is to design yielding sill pillars that would yield in a stable manner and will reduce the risk of pillar rockburst. Plane strain finite element analysis is conducted using the generalized Hoek-Brown failure criterion with elastic-brittle-plastic parameters. Examples are given to demonstrate how to calculate these stiffness values and assess the stability condition of sill pillars. It is found that increasing the rate of extraction increases the likelihood of unstable yielding of the pillar as has been found in other studies. Placement of backfill in a timely fashion in the stopes above and below the sill pillars increases the stiffness of the loading system. This indicates that backfilling of stopes while creating the sill pillar increases the likelihood of stable yielding of the sill pillar.

Aug 1, 2013

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 Tim J. Carew, Dennis C. Martin

"One approach to stabilization of rock slopes is to place a buttress at the toe of the slope to provide additional resisting forces and increase the length and strength properties along the failure surface. This paper describes the rock mechanics and mine planning aspects of incorporating a buttress of intact rock in the lower part of the slope as part of the slope design for the south wall of the final pit at Cassiar Mine. Stability analysis techniques and results are described. Analyses results have indicated that, in order to maintain steep over-all slopes in the final pit, a buttress of intact rock shoud be incorporated into the lower section of the slope until late in mine life. The effect of the buttress is to flatten the slope and reduce the slope height thereby improving slope stability. The mining plans would be such that the buttress would be mined out during the last four months of mining when the consequences of instability would be least severe.IntroductionThe concept of using a buttress to stabilize slopes has been used in mining and civil engineering construction in may locations (Richards and Stimpson, 1977). Most buttresses involve placement of coarse rock fill timber cribs or other material as a load at the toe of an already unstable slope to provide forces which resist failure by counteracting driving forces and increasing the length and strength of the failure path.This paper describes the geotechnical and mine planning aspects of incorporating a buttress of intact rock in the design of the south wall of Cassiar Mine. The effect of an intact rock buttress is to flatten the slope and reduce the slope height, thereby improving slope stability. No actual construction is required other than normal excavation of the slope. The ""mine plans would be such that the buttress would be mined out at the end of mine life when the impact of instability would be less severe and additional ore might possibly be recovered from the slopes. Mining of the buttress could induce instability at the very end of mine life at a time when maximum ore extraction has been achieved."

Jan 1, 1986

By Sazol Das, Hany Ahmed, Ganesh Bhaskaran, Zhuoru Wu

"Friction stir welding (FSW) process in lap configuration for dissimilar materials has been developed and tested for steel to aluminum joining. A novel cylindrical tool was designed for improved material flow. The joining of steel to high strength 5xxx and 6xxx aluminum was carried out by FSW technique using optimized process parameters. The microstructure, micro-hardness, joint strength and corrosion properties at the weld interface have been investigated. Optical and scanning electron microscopy reveled a well layered structure at the interface and lap shear tests of the welds showed excellent fracture resistance. Neutral salt spray tests for up to 500 hours (ASTM B117) were carried out on the bare steel to aluminum FSW joints, which did not show neither evidence of corrosion at the weld interface, nor any degradation of the weld strength. The FSW lap configuration was applied to prototype commercial vehicle structural component whereby a steel stiffener insert was friction stir welded to high strength 6xxx aluminum alloy. The interface microstructure showed layered root without any steel shattering in aluminum side. A finite element study was carried out to quantify the benefits where it was found that the stiffness increases by 76% under bending loads and 36% in torsion loads.INTRODUCTION Energy preservation and environmental issues, namely carbon footprint and legislation around emission in transportation industries has led to a growing need to use of lightweight materials such as aluminum and magnesium alloys along with various grades of steel in structural application, while still maintaining their strength and crashworthiness. Assembling dissimilar materials within integrated structure is thus a stringent requirement related to optimum performance. In order to achieve an efficient technology of joining dissimilar materials such as aluminum to steel, it remains difficult to select an effective welding process for a given joint configuration. The use of aluminum in transportation industries for structural component is not exclusive in a design and is almost always used along with various steel grades for a mixed materials solution, thus dissimilar aluminum/steel lap joining is of great interest since this is widely used in the assembly of parts (e.g. pillar, frame rails, chassis, body in white (BIW), CAB, etc.)."

Jan 1, 2018

By Gordon MacVean

The object of this paper is to present for your consideration some of the present-day trends of safety practice in the coal mines in the United States and Canada. Coal mining at its best is a hazardous occupation. Men must be experienced miners in order to appreciate the existing hazards and must remain ever conscious of them if they are to work safely. The question is often asked whether our efforts for increased safety are showing results. So often it appears that strides are made for a period of a few years in the reduction of fatalities and lost-time accidents only to have all ground lost by an unfortunate year, after which progress is commenced again only to have a repetition of the same thing. Table No. 1 is an answer to this question. It shows the fatality rates over the last two decades in the coal mines of the United States and Canada. These are given in divisions of five years. The general trend is noticeably downward, exceptions being due to explosions or disasters which claimed an unusually heavy toll of life. These last are certainly not as common today as they have been in the past. It is only reasonable to suppose that this trend towards a lower fatality rate is the result of well directed safety effort. Reliable statistical organizations have offered figures to the effect that only 15 per cent of all accidents can be eliminated by the use of mechanical safeguards. The state of mind of the man involved, or his attitude towards safety, commonly called 'safety-consciousness,' is the controlling factor in the prevention of 85 per cent of our accidents.

Jan 1, 1931

By Arthur Laing

"IT is indeed a pleasure to have the opportunity of addressing this group today. Not only does it give me the opportunity of meeting with representatives of what is considered by many to be the most dynamic segment of industry in Canada today, but it also allows me to talk about a subject of para-mount interest to myself, the development of the North, and to explain, if even only briefly, some of our beliefs and hopes in this regard.It is inconceivable that all lands north of the 60th parallel, representing 35 per cent of Canada's total land area, which we believe contain a great natural resource potential, will remain as an undeveloped portion of Canada. The re-sources are there, although the people and private industry are as yet not there in sufficient numbers.It has been estimated that in the west and north of Canada there are 1.6 million cubic miles of sedimentary rocks. Of this figure, 342,-000 are thought to lie in Alberta, 115,000 in British Columbia and about 1 million cubic miles are thought to lie in Canada's northern regions, the bulk in the Arctic Islands. On the basis of apparent volumes of sedimentary rock, we estimate that as much as 13 billion barrels of petroleum may lie beneath the permafrost of the North-west Territories, another 3 billion barrels in the Yukon Territory and 33 billion barrels in the Arctic Islands. This is, indeed, a rich and elusive prize, and one which must be sought with a view to fulfilling demands on the production of petroleum."

Jan 1, 1966

By J. Fellowes, V. Landais, J. Robson, J. Carr

"Aerospace Al-Zn-Mg-Cu (7xxx) alloys are known to be susceptible to environmentally assisted cracking (EAC). This phenomenon has been studied intensively for many decades, leading to empirically adopted methods to mitigate this problem through overaging and composition design. In parallel, many theories have been developed to explain EAC in 7xxx, but none is yet universally accepted. Today, a number of emerging techniques offer potential to shed new light on EAC in 7xxx. The purpose of the present paper is to demonstrate how X-ray tomography (XCT) combined with electron microscopy can be used to identify the true crack path in 3-dimensions, and hence identify material for site specific electron microscopy analysis. Composition mapping over large areas to high accuracy has been performed using a modern electron microprobe analysis system. This has been combined with transmission electron microscopy to investigate local composition in matrix and precipitates at high resolution. This combination of techniques across length scales offers the potential to provide new insights into the links between local composition, microstructure, and EAC resistance.INTRODUCTION Environmentally-assisted cracking (EAC) is a phenomenon which dramatically decreases the performance of metals and can cause premature failure of large structures. Observed in situations where components were not subjected to critical loads and no widespread corrosion was involved, this type of brittle failure is extremely difficult to predict. The EAC designation covers a number of phenomena, e.g. stress corrosion cracking (SCC), hydrogen embrittlement (HE), corrosion fatigue (CF), etc. Initially identified in steels, EAC can also affect other metals such as high-performance aerospace aluminium alloys, and this phenomenon has been a concern for industries for decades. Extensive research has been conducted on the effects of various environments (moist air, saline water, dry hydrogen gas, etc.) on microstructures and crack propagation, however no consensus has been reached and the exact nature of the mechanisms that control EAC is still being debated (Birnbaum & Sofronis, 1994; Gangloff, 2007; Holroyd & Scamans, 2013; Lynch, 2012; Oriani, 1972; Scamans, Alani & Swann, 1976, Young & Scully, 2002)."

Jan 1, 2018

By K. Horikawa, S. Kitahata, H. Kobayashi

"It has been clarified that the Al-5%Mg alloys containing 200 mass ppm of sodium showed grain boundary (GB) fracture, even when tested at room temperature, as well as at high temperatures (~500°C). SEM/EDX study revealed that the GB fracture was associated with the segregation of sodium on grain boundaries of the Al-Mg base alloys. Differential scanning calorimetry (DSC) revealed that the GB fracture at room temperature of Al-Mg alloys was caused by sodium segregation in the solid state. It was also shown that the tendency of the GB fracture strongly depended on the heat treatment; the alloys after the solution heat treatment showed severe GB fracture compared with the alloys after the homogenizing treatment. Moreover, it was shown that the GB fracture at room temperature by sodium segregation was suppressed by the addition of bismuth or indium. The suppression of the GB fracture by the additional elements was believed to be the scavenging effects by forming the sodium bearing compounds in grains.INTRODUCTIONIt is widely known that Al-Mg base alloys containing high amount of magnesium(~5 mass%)show better workability at room temperature, while that the alloys show grain boundary (GB) embrittlement at higher temperatures ranging from 200 to 500°C, depending on grain size(Otsuka, 1984), sodium impurity level(Ransley, 1959, Okada, 1997, Horikawa, 2001)and testing strain rate(Yamada, 2012). In the case of coarse-grained Al-5%Mg alloys (~300 ?m), 2 mass ppm of sodium causes severe GB fracture around 300°C, however, the Al-5%Mg-2ppm alloy does not show GB fracture at room temperature. It has also been shown that the GB embrittlement caused by 2ppm of sodium was suppressed by the additional elements, such as bismuth (Talbot, 1995), antimony (Ueda, 1997) and indium (Horikawa, 2012). Basedon these facts, we have concluded that the GB embrittlement at higher temperatures of Al-Mg alloys is attributed to the synergy effects of GB segregation of atomic sodium and GB sliding. For the GB embrittlement mechanism of Al-Mg alloys, involvement of low melting point metallic phases has been pointed out (Lynch, 2002),since the GB embrittlement appeared only at high temperatures. Up to date, the effects of high amount of sodium addition more than 2 ppm on GB fracture were not fully investigated in Al-Mg alloys. In the present study, the effect of 100 ppm ordered sodium impurity on GB fracture of Al-5%Mg alloys was examined, together with the effect of another additional elements."

Jan 1, 2017

By D. S. Evans

Major Project Blues Over the last two decades, almost every major project has suffered significant cost overruns, significant schedule delays, and/or poor quality work. Exceptions are rare and most projects that tout being ?On Time and Under Budget? have re-cast schedules, significantly modified scope or revised base estimates. The problem isn?t new. In the late 1980?s the Rand Corporation published a study showing that 80% of all major projects had significant cost and schedule overruns. The problem is not restricted to the Canadian environment, or to a specific industry. It is a global problem.

May 1, 2013

By Harry V. Warren

THE Dolly Varden Mine is situated in the Kitsault River valley, eighteen miles from the head of Alice arm, in the Nass River mining division of British Columbia. During the years 1919-21 it was operated by the Taylor Engineering Company, Limited, and produced 1,300,000 oz. silver from about 36,000 tons of ore. The ore was transported by narrow-gauge railway to Alice arm, and shipped to the smelter at Anyox for treatment. During recent years, a small quantity of high-grade ore has been extracted by leasers and shipped to the smelter at Tacoma, Wash. Unfortunately, the bonanza ores which occurred near the surface did nor persist to depth, and two hundred feet below the exposures only rare and unimportant patches of ridi ore have been found. Two opinions exist as to the origin of this rich silver ore. One, advanced by V. Delmage (1, 2), is that the ores are hypogene, and the other, by G. Hanson(3, 4, S), is that the ores are the result of supergene enrichment. It is true that Dolmage first advanced his view that the ores are primary because they appeared to be analagous to Premier ore, which he had studied in detail and which he considered to be primary. The present authors have had access to excellent suites of material from both mines and consider the comparison well taken, the only essential mineralogical difference being the presence at the Premier mine, in addition to the silver minerals, of gold and electrum. Although the arguments put forward by Delmage have, in the opinion of the authors, never been refuted, nevertheless R. P. D. Graham(6), in a reference to the mine published in 1924, describes the ore as of supergene origin, and since then nobody appears to have challenged this statement. Indeed, in 1935, Hanson re-affirmed his earlier conclusion(5).

Jan 1, 1942