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By Y. M. Zhao, C. L. Duan, Z. F. Luo, X. L. Yang

"Fine coal beneficiation in a dry way is considerably imperative for the efficient utilization and conservation of coal resource in drought regions, especially for China. In this study, a continuous vibrated gas-fluidized bed separator was established and developed based on the results of laboratory batch separation results. The fluidization behavior and the effects of several main parameters including superficial air velocity, vibrational parameters, bed height and separating time were systematically investigated. The results showed that the bed expansion increased linearly with the superficial air velocity and theoretically, higher bed expansion benefited the hindered settling process of fine coal particles. However, larger superficial air velocity would induce intense fluctuation in bed surface and a poor performance of density segregation. The conveying velocity of particles was mainly determined by the vibration angle and a predicted model was established by the nonlinear regression analysis. A theoretical model of bed height distribution was established and this model fitted the measured value well. The beneficiation performance of this separator was evaluated by separating -3+1 mm Wuhai fine coal. The results showed that the probable error, E, is 0.225, indicating a continuous vibrated gas-fluidized bed separator could achieve a satisfactory performance.INTRODUCTIONFine coal beneficiation in a dry way is considerably imperative for the efficient utilization and conservation of coal resource in drought regions, especially for China. Meanwhile, it is also conducive to environment protect and low-carbon, green development of coal sector. In recent years, the increasing academic interest in the field of fine coal dry beneficiation has been aroused in most of big coal countries. In summary, recent processes of fine coal dry beneficiation are, according to their processing principles, mainly classified into two categories: dense medium beneficiation (Dong et al., 2015; Fan, Chen, Zhao, & Luo, 2001; Luo et al., 2008; Macpherson, Iveson, & Galvin, 2011) and improved pneumatic beneficiation (Patil & Parekh, 2011; Yang, Zhao, Luo, Song, & Chen, 2013; Yang, Zhao, Luo, Song, Duan, et al., 2013; Zhao, Zhao, Chen, & Luo, 2015). The former deploys artificial dense medium, such as magnetite powder and fine sand, to form a stable gas-solid suspension with certain density under the function of the upward fluidizing air flow and in some case, the external force field like vibration and magnetic field. Generally, it is believed that the process of air dense medium fluidized bed (ADMFB) is suitable for separation of coarse coal (-50+6 mm) and can't obtain a satisfactory result for fine coal separation (Luo, Chen, & Zhao, 2002; Luo et al., 2008). However, some recent laboratory efforts (Patil & Parekh, 2011; Zhang et al., 2014) attempt to find an improved performance for fine coal beneficiation in ADMFB with some modifications. The point of these works is to use a comparatively shallow bed and finer magnetite powder with appropriate size distribution. It is known that fluidization of finer magnetite powder is prone to arouse adverse fluidization properties such as channeling and slugging. Thus, the external force is introduced to an ADMFB in order to improve the fluidization quality of a magnetite powder bed. Some recent literature on air dense medium magnetically stabilized fluidized beds (Fan et al., 2001; Luo, Zhao, Chen, Fan, & Tao, 2002; Song, Zhao, Luo, & Tang, 2012), air dense medium vibrated fluidized beds (Luo et al., 2008) and Reflux Classifier (Macpherson, Iveson, & Galvin, 2010) reports that the separation efficiency, namely the probably error E value, of dense medium separation of fine coal ranges from 0.066 to 0.07, indicating a good separation performance. But, the main unresolved problems of dense medium beneficiation are located in the processes of product purification and medium recovery and are urgent to be solved befor"

Jan 1, 2016

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 P .. H. Grimley, N. Champigny

"Fourteen companies (Appendix) representing senior mining organizations in Canada were canvassed in order to assess: (1) the current usage and trends, and (2) the usefulness of computer applications in ore reserve estimation and grade control. The results of the questionnaire suggest that:• computers are unsurprisingly, predominant in the mining industry for calculating reserves and performing grade control;• time and cost savings are realized;• computer-based approaches are applicable to underground situations;• geological information is incorporated to the computerization process; and• computer usage does not hinder the collaboration of geologist and mining engineer.A clear need is identified for case histories comparing computer-calculated ore reserves and actual production data.IntroductionAmong the management and technical staff of some mining companies there is a perception that the application of computer based technology for the estimation of ore reserves and grade control, has as many drawbacks as benefits. Some of the objections raised against the utilization of computers for ore reserve estimation are that:• computer-based reserve models work for large open pit mines but not for underground situations;• computer-generated reserves ignore the geologist's knowledge base; they are strictly a number crunching exercise; and• the use of computers for ore reserves hinders collaboration between the geologist and mining engineer.In order to determine (I) the extent of current computer usage and future trends and (2) whether the objections noted above are borne out by experience, a number of senior Canadian mining companies were canvassed.The respondents were asked to provide:• an assessment of the importance of the computer in the ore reserve estimation and grade control process;• the level of involvement of individuals and staff groups with computer-based ore reserve estimation;• the advantages perceived and realized from the utilization of computer-based ore reserve approaches;• the current and future human resources requirements for the evaluation, implementation, maintenance and development of computer-based ore reserve systems;• the hardware and software resources presently used and planned; and• the developments needed to increase the use and acceptance of computer-based ore reserves."

Jan 1, 1990

By M. Lindgren, M. Latva-Kokko

Process performance can be significantly influenced by proper design of hydrometallurgical reactors. Optimal reactor configuration is case specific and depends on process requirements such as reaction rate limiting factor and particle size distribution. Choice of materials and manufacturing methods also play important roles in highly corrosive and abrasive environment often involved in hydrometallurgical industry. In this paper performance of different reactor designs has been compared in some typical hydrometallurgical applications. Results show that significant improvement in energy consumption, gas utilization efficiency and equipment lifetime can be achieved with process specific reactor design.

Jan 1, 2014

By Donald E. Wakefeld

"The pace at which mining will occur in Northern regions and Arctic lands will depend on the answers to a number of questions. Who are the local aboriginal participants? What land uses are they pursuing? What are their objectives? What is their understanding of the process of mining development? This paper will focus on the last question, communicating the process of mineral development to local aboriginal communities.IntroductionIn the environmental impact hearings for the BHP-DiaMet diamond mine, the smaller Dene Treaty 8 Nation argued for the settlement of its Land Claims as a pre-condition to development. However, the larger Dene Treaty 11 Nation were prepared to permit the mine to proceed on the basis that their people would receive benefits during the construction and operation of the mine.Wherever mining is the significant basis for tax revenues and economic development expectations may be encouraged beyond the realities of the situation. Izok Lake has been known for several decades as a significant mineral deposit but because of its size and the transportation costs involved, it is now a “frozen” ore body. The extent of its mineralization at current metal prices will not support the mining and processing costs without substantial government support for infrastructure and roads. At the opposite side of Canada, Voisey’s Bay clearly satisfies all technical criteria but, nonetheless, two Inuit groups, the Innu, and Métis, have all made LandClaims relating to the mine area.Contrasting the mineral deposits at Voisey’s Bay and Izok Lake emphasizes that the timing of production is dependent on factors such as the grade and amount of reserves, their market price, location and availability of government support. Nonetheless, it is this author’s thesis that given an economic orebody the next most important factor is good communications. It is his view that Arctic mineral development will occur quickly only where good communication has resulted in the trust and mutual respect necessary to implement the mammoth cultural changes required."

Jan 1, 1996

By D Maschemeyer

The cobalt production of the Chemical Metallurgical Division of Sherritt Gordon Mines Limited was supplemented, from May, 1962, to June, 1964, by processing 3,500 tons of a calcined cobalt-nickel concentrate. This paper describes the reduction roast -aqueous sulphuric acid leach process and the operating practices employed in recovering cobalt, nickel and copper from this oxidized by-product of a lead-copper operation. Incorporated in this paper is a description of how this process was integrated with the existing ammonia leach -hydrogen reduction process for the recovery of nickel and with the soluble cobaltic ammine process for the recovery of cobalt. Introduction T HE Chemical Metallurgical Division of Sherritt Gordon Mines Limited at Fort Saskatchewan, Alberta, has recently completed ten years of operation utilizing the ammonia leach process for the recovery of nickel, cobalt and copper from sulphide concentrates, matte and other materials amenable to this process. A continuing development program, along with the expansion of certain facilities, has enabled the refinery to attain a production rate of 31, 000,-000 pounds of nickel per year by hydrogen reduction. This represents an increase of approximately 85 per cent over the original design capacity of the plant.

Jan 1, 1965

By J. P. Grau, J. Z. Lu

"Thickeners/clarifiers are widely used in coal preparation plants, potash processing and other mineral processing facilities. Thickeners play a very important role in slurry treatment systems to accomplish solid/liquid separation. The demand for larger plants and the increased thickener handling capacities sometime require thickener diameters as large as 200m. The development and use of high capacity thickeners makes it possible to increase the handling capacity of these thickeners by several to more than 10 times compared to conventional thickeners. Hence, for a given slurry rate, selection of a high capacity thickener will significantly reduce the footprint of the thickener. Much higher handling rate, higher concentration of underflow, clearer overflow and lower capital cost are obvious advantages of high capacity thickeners; however, some process requirements and the concerns of operational cost, especially the flocculant cost of a high capacity thickener operation, keep some engineers selecting conventional thickeners and staying away from the high capacity thickeners. Forty years after the first high capacity thickener was developed, there are still arguments in the selection of conventional thickeners or high capacity thickeners in mineral processing. The arguments will continue unless there is a clear picture of capital cost vs. operational cost for each of the thickener types. The purpose of this paper is to analyze these costs and to provide guidelines for selection of thickeners. INTRODUCTIONThickeners/clarifiers are widely used in various slurry treatment systems. For mining and mineral processing, thickeners are an integral part of the solid/liquid separation system. The feed to the thickeners are processing slurries. The fundamental mechanism for the solids/liquid separation is for the solid particles in the slurry to gravity settle inside the thickener tank. The clear water overflows from the top of the thickener tank and is typically reused in the processing circuit, and the concentrated underflow is discharged to different downstream process systems depending on the application of the thickeners. The general requirements for a thickener operation include high density of underflow and clear overflow. Since thickener operation consists of continuous feeding, overflow and discharge of underflow, the solid particles will gravity settle against an upward flow with its velocity dependent on the feed rate and the underflow discharge rate. Higher feed rates to a given thickener produce higher upward velocities. Underflow discharge is typically relatively small compared to the amount of overflow. The upward flow tends to take particles up to the overflow. Only those particles having a settling velocity greater than the upward flow velocity will possibly settle out. Hence, thickener feed rate has to be controlled so that the required overflow water clarity can be achieved."

Jan 1, 2012

By Eugene Larochelle

The serpentine of the Eastern Townships of Quebec is more or less seamed and impregnated with chrysotile asbestos, of which we note two types: the cross-fibre and the disseminated fibre. The cross-fibre type always appears in fibres or crystals arranged parallel to one another, and disposed at right angles to the walls of the matrix serpentine. The length of fibre of these veins, which run in every conceivable direction, even crossing ?one another, varies from microscopie dimensions to three and sometimes four and even five inches. It is the principal form of asbestos found in the serpentine of Thetford Mines, Black Lake, Coleraine, and Asbestos. The disseminated-fibre type, which is the main product of the serpentine of Broughton township, in which ate located the mines at East Broughton, does not form veins, but occurs in the serpentine without any definite arrangement. There is a difference in the toughness and hardness of the rock of the two types, the Broughton serpentine being softer than that at Thetford. The disseminated-fibre section of the serpentine belt is probably more regular in its content than is the cross-fibre section. Nevertheless, it contains no 'crude,' which is the most valuable of asbestos, and the fibre is usually shorter than the cross-fibre average.

Jan 1, 1928

By C. H. van Eendenburg

"Installation of a 3.6 km long raw coal conveyor in the Balmer open pit was undertaken to improve over-all haulage efficiency. This paper covers the rationale behind this project, system design and construction aspects and initial operating experiences. The majority of the construction work was performed by our own personnel. Where feasible, used equipment was installed to reduce capital cost and facilitate a tight construction schedule.BackgroundWestar Mining Ltd's Balmer Mine is located in the British Columbia Rockies, just outside of the town of Sparwood in the southeastern corner of British Columbia. The open pit mine, which has been in operation since 1969, currently produces about 6 million clean tonnes of coal per year, mostly for the metallurgical coal export market. Run-of-mine coal tonnages total between 9 and 9.5 million annually and waste removal volumes exceed 30 million bank cubic metres.The mine is a truck/shovel operation; loading equipment includes nine electric shovels, five front-end loaders and a hydraulic backhoe. The truck fleet consists of 40 units of 154-tonne, 181-tonne and 315-tonne capacity. The newer 154-tonne trucks are used for coal haulage for which they have been equipped , with tailgates to maximize their coal carrying capacity."

Jan 1, 1990

By Staff

This paper contains an outline of the history of the Sullivan mine, now owned and operated by the Consolidated Mining & Smelting Company of Canada, Ltd.; some account of the various methods by which the ore has been treated in efforts to solve the metallurgical problems which its complex character presents, and, finally, to give, as concisely as possible, an outline of the present mining and metallurgical practice along with a description of the mining and milling plant at Kimberley and the smelter and refineries at Trail, in British Columbia. EARLY HISTORY In May, 1892, Pat Sullivan, John Cleaver and Mike Holland left the Coeur d'Alene country, in the State of Idaho, to seek their fortunes in the Kootenay lake district in British Columbia. They were aided in their venture by James Cronin, afterwards locator and owner of the St. Eugene mine at Moyie. Two months later the party broke up, Sullivan and Cleaver crossing the mountains from Crawford bay on Kootenay lake to the head waters of the St. Mary's river, the course of which they followed down to Fort Steele. Here they found a good deal of excitement about the North Star mine, and, joined by "Ed." Smith, who was familiar with this part of the country, they determined to return and prospect in its vicinity.

Jan 1, 1924

By Kazuhide Nakaniwa

In this research, we devised a measurement method using total stations (TSs) which have ?the Baum? which is a concentric circle reticle, as substitute for crosshairs. The Baum owes its name to the similarity between the concentric circles and trees (Baum in German). By setting one circle on both of edges of cylinders, operators can set their sights on points on the center line of the cylinders, and also can measure positional coordinates of the points. Also, by measuring two different points on the center line, operators can measure the position and tilt of the axes of the cylinders. Furthermore, we developed a pile driving navigation system. Foundation piles are used for various structures, and their forms are generally cylindrical. Especially, although it is difficult to drive tilted pile foundations, their usage are expected to expand due to their high earthquake resistance. Yet, a method to accurately measure the tilts of piles has not been established. However, we proved that operators can obtain adequate accuracy to control foundation piles through the measurement experiment using this system. Using this system, the information of the pile is measured using a TS, transferred to a PDA, and displayed from the operator?s view of the piling machine.

Aug 1, 2013

By André Piché

"Over the last ten years, several developments have been undertaken to conceive a machine capable of carrying out simultaneously all the mining tasks in hard rock deposits: cutting, mucking, hauling, ground support and dust control.The main advantages of continuous mining over conventional drill and blast is the elimination of the cyclical nature of the actual methods. Other advantages sought are improved stability of mine openings, higher productivity, lower costs, and a cleaner and safer mining environment. Noranda has con-tributed to these developments in a major way. As a member of HDRK, Noranda participated in the development of two mechanical continuous mining machines; the TM60 and the Wirth. Noranda also undertook a development of its own based on the utilization of electricity to break rock. This technology is called plasma blasting (PBT). The concept of plasma blasting is illustrated in Figure 1.When the operating voltage is reached (18kV), the energy is released through a high current switch (500k A) into a coaxial powercable. It is then delivered to the tip of an electrode inserted into a drill hole which is filled with an electrolyte (water). When the energy reaches the electrolyte, it is instantaneously transformed into a high temperature, high pres-sure plasma that produces a shock wave capable of breaking rock(1).After initial testing of the plasma blasting technology in the lab and in the feld, two experimental platforms were constructed. The first one, a test bench, was erected at the Noranda Technology Centre in Pointe Claire, Quebec.(2)The second one is a rock breaker prototype based on a standard diesel-powered carrier (Fig. 2). Each platform was equipped with a 300 kJ pulsed-power module.In 1993, the rock breaker prototype was used for an extensive series of tests in the field. During that campaign, over 700 oversized boulders were blasted. The results of the tests demonstrated that more durable components for PBT were needed. The test bench was then used to successfully develop and test long-lasting components (probe, switch, cable, connector) that can be adapted to industrial platforms leading to the commercialization of the technology."

Jan 1, 1996

By Alfredo Bambaren

First Encounters between Communities and Mining 1. Importance, meaning and process 2. Antamina?s study case 3. ?Self-organization? theory (NLP) 4. The story we tell, the values we live 1. Importance, Meaning and Process ? First encounter stays in mind as a model. ? First encounter means foundation. ? First encounter builds the story.

May 1, 2010

By M. Pearson, W. Bristowe, A. Hanson

"There's no such thing as quality assurance; only quality control ... by inspection. "(1) A common misunderstanding in the procurement and construction of custom designed, fabricated pressure vessels and piping systems is that quality assurance can be achieved by simply referencing codes, standards, ISO 9002, QMS or other such programs in the contract documents. In the authors' experience, nothing could be further from the truth, not detrimental to the performance of the equipment than the exclusion of inspection activities and reliance upon warranties and "fit-for-purpose" clauses. Likewise, the expectation that fabricators, suppliers, or third party inspectors can provide such assurances is also unrealistic where they have limited knowledge of the process, material selection criteria, or limited technical resources. The development and successful execution of a quality assurance program is a collaborative effort by engineers, designers, material suppliers, equipment fabricators, and field inspectors with the full understanding and support of the end user.This paper presents an outline of the quality control activities undertaken by the authors for several recently completed and on-going hydrometallurgical projects. The activities include: prequalification of fabricators and sub-vendors, shop audits, material validation testing, material source control and verification, positive material identification of weld metal overlay, specialised welding inspection, contamination control for titanium and titanium-clad fabrication, eddy current and mass spectrometer (helium) leak testing of shell-and-tube heat exchangers, hot cycle testing of titanium clad equipment, tolerance verification for refractory lined equipment, final inspection and cleaning.

Jan 1, 2004

By P. Condori

Palabora Mining Copper (PMC) has two autogenous mills that have been in operation since 1976. The mills were originally designed to treat 30 000 t/d of open cast copper ore in a closed circuit with cyclones. As the ore body went deeper the open cast method of mining was changed to block caving, a consequence of this was the dolerite content (hardest barren material) increased significantly, increasing the production rate of pebbles and thus reducing the milling capacity. In order to cope with the increased ore hardness and to increase mill capacity, a second ball milling stage and pebble crushing were incorporated to the circuit. The above actions created new challenges to the circuit operation and bottlenecks in different areas of the milling circuit. This paper reports the holistic work performed on the Palabora autogenous milling circuit including the implementation of a mill constraint control scheme, the implementation of a pebble removal system from the circuit and a new circuit configuration. The achieved plant stability and increment of ore throughput are also reported in this paper.

Jan 1, 2012

By M. Hitch, M. B. Lytle

Resource development conflicts arise largely due to differences in worldview between those who support and those who oppose development. This paper illustrates how societies and civilizations with different worldviews produce different levels of creative and economic energy. A questionnaire was created to build a database of responses to test whether worldview and resource development are correlated. Factor and multivariate regression analysis determined correlations for respondent groupings. Results showed a positive correlation between the respondents\u2019 worldviews and their attitudes toward resource development. Correlations became stronger as the homogeneity of the sample subgroups increased.

Jan 1, 2017

By L. Ferland, D. LaRonde, J. C. Caron

"The free-world production of columbium ore concentrates has doubled in the last five years. St. Lawrence Columbium and Metals. Corporation has contributed largely to this expansion, its production rate increasing from 720 tons of concentrates per year in 1961 to 2 200 tons in 1965.To follow the normal market development, the Company initiated an engineering study aimed at establishing the most economical mining methods, thus permitting it to increase its milling rate from 1,000 tpd in 1964 to 2,000 tpd in 1967 and possibly to 3,000 tpd in 1968. The results of this study pointed out the advantages to be gained in converting from an open pit to an under-ground operation. This paper describes how the mining engineering department has successfully developed ""stopes"" from the walls of its No. 2 open pit, in order to assure continuity of its operation during the interval required to develop its underground mine."

Jan 1, 1967

By James A. Robertson

"The Pronto Mine located at the east end of Lake Lauzon, Long Township, some 12 miles east of Blind River is of historic note being the discovery locality and the first producing mine of the Elliot Lake uranium camp. Radioactive bedrock was discovered in 1949, a commercial deposit was verified in 1953 and production commenced in 1955. Production continued to April 1960: total tons milled 2,264,404 from which 4,643,835 pounds U,O, were recovered at a recovered grade of 2.05 pounds U3O8 per short ton.The orebody is in a bed of pyritic quartz pebble conglomerate at the base of the Matinenda Formation of the Elliot Lake Group of the Huronian Supergroup. The rocks strike east and dip 15 degrees to 20 degrees south and unconformably overlie Early Precambrian granite, the upper surface of which is marked by a regolith. Several diabase dykes cut the orebody which is also affected by albite, chlorite, and carbonate-rich alterations. To the south the orebody is cut by a fault. The orebody is 6to 10 feet but locally 10 to 15 feet thick, has a strike length of 3,500 feet and extends down dip for 3,600 feet to a depth of 1,000feet. Some 300,000 tons of ore grade mineralization remain in the deeper portion of the mine.IntroductionThe Pronto Mine, (Photo I) at the east end of Lake Lauzon in Long Township some 12 miles east of Blind River, is of particular interest as being the discovery site and the first producing mine of the Elliot Lake camp.Production at the Pronto Mine commenced in 1955 and continued until 1960 when the mill was converted to treat copper ore from the nearby Pater Mine at Spragge. A description of both mines, based on material provided by the mine staff, was given in the report on ""Geology of the Spragge Area"" (Robertson, 1970).As little study has been done on Pronto geology or petrology since mine closure, the earlier description of exploration and geology is essentially repeated, but shortened, here- the main change being that the stratigraphic terminology has been amended as recommended by the Federal-Provincial Committee on Huronian Stratigraphy (Robertson et al., 1969)."

Jan 1, 1986

By Robert D. Brown, Robert B. Parsons

"The mining industry may have survived the October 28 federal budget relatively unscathed, but the same certainly cannot be said of the petroleum sector-and many mining men are left wondering if their industry will be the next one to be singled out for special attention, as federal and provincial governments seek additional revenues and pursue nationalistic or provincial policies.Higher taxes, higher prices, a potpourri of ""incentives"", and a -""Canadianization"" policy mark the principal features of the new National Energy Program released by the government along with Finance Minister MacEachen's budget address.This month, Tax Notes examines the federal budget. with appropriate emphasis on the National Energy Program and its possible future implications forthe Canadian resource industries.IntroductionMost of the Canadian mining industry (tar sands miners excepted) heaved a sigh of relief on the evening of October 28, 1980, as Finance Minister MacEachen confounded the prophets in his budget address by not raising personal or corporation taxes and by making only relatively modest changes in the general tax system. Instead, he concentrated on a sweeping new energy policy. Unfortunately for that important sector of Canada's mining industry which is involved in mining the country's vast tar sands reserves, either now or in the future, the National Energy Program that was introduced along with the budget 'has serious implications."

Jan 1, 1981

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