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By A-A. Bogno, M. Rappaz, J. Valloton, H. Henein

"Rapid solidification of Al-Cu droplets of eutectic composition was carried out using Impulse Atomization in an argon atmosphere, to study the microstructures forming at different cooling rates and undercoolings. Two distinct morphologies were observed within the investigated Al-33wt%Cu droplets microstructures: (i) A regular lamellar morphology and (ii) an undulated morphology. The volume fraction of each type of morphology was measured as a function of the droplet size and the nucleation undercooling was deduced using the hypercooling limit equation. The scale of the microstructures was determined through measurements of inter-lamellar spacing across and along the growth direction. Growth velocity and undercooling were deduced using Jackson and Hunt (1966) eutectic growth theory. Finally, mechanical properties were estimated through micro-hardness analysis using a Vickers hardness tester, revealing exceptional properties for an aluminum-copper alloy. Indeed, the hardness values, increasing with growth rate and undercooling, were 3 times higher than the values obtained in hypo-eutectic Al-Cu alloys.INTRODUCTION Eutectic alloys are very attractive due to their good fluidity allowing ready shaping of parts in casting processes as well as in thermal spray deposition. In addition, they yield microstructures with high mechanical properties, by the virtue of their scale/size which is defined by the solidification parameters and the thermodynamic and thermophysical properties of the given alloy. Therefore, it is important to understand the relationship between the microstructures and the solidification parameters of eutectic alloys in order to control their solidification path and mechanical properties. The latter could be improved by either adding an appropriate strengthening component to a base eutectic material (Böyük, MaraslI, Kaya, ÇadIrlI, & Keslioglu, 2009) or by refining the microstructures for more effective dislocation pinning (Campbell & Campbell, 2003). Tailoring the microstructure can also be beneficial to chemical (Freitas, Osório, Spinelli, & Garcia, 2014; Osório, Freire, Caram, & Garcia, 2012) or electrical (Kaya, 2012) properties of the material. Eutectic-type microstructures, usually formed from liquid (eutectic transformation) or solid (eutectoid transformation), are made up of two or more different phases, generally of lamellar or fibrous (rod like) morphologies (Kurz & Fisher, 1998). In general, a binary eutectic structure can be regular (when both phases are non-faceted) or irregular (one of the two phases is faceted), the two solid phases having roughly the composition of the liquid from which they are formed."

Jan 1, 2017

By J B. McConnell

The Thompson smelter has three unique features which form the basis ~f its design: fluid bed roasters which treat nickel concentrate filter cake from the mill, as well as the flux, in order to achieve partial desulphurization; the use of electric furnaces for the smelting of the partially desulphurized, preheated roaster product; and the disposal of slag by water granulation and slag slurry pumping. The installation consists of three fluid bed roasters, each feeding an electric furnace. Nickel concentrate is received at the smelter via pipe line. It is thickened and filtered, and the filter cake, together with siliceous flux, is fed through rotary bin feeders and reciprocating double-gate seals into the fluid bed roasters. Air injected into the roasters through club-head tuyeres oxidizes part of the sulphur and associated iron in the concentrate. The heat of reaction dries and heats the charge. Roaster product is recovered from the gas stream in cyclones and from the roaster bed through automatic valves.

Jan 1, 1963

By E. G. Joe

"Recent trends in Canadian mineral processing were reported in seven areas of interest covered by seventeen technical papers at the 1976 Annual Meeting of the Canadian Mineral Processors, held at Energy, Mines and Resources' Camsell Hall, Ottawa. New milling equipment included the Enviro-Clear thickener, large-volume Outokumpu flotation machines and abrasion-resistant polyurethane screens. Grinding experiences from a variety of milling operations were reported. Opportunities for increased sizing and grinding efficiency were presented. Flotation control by digital computer and by chemical additions were described in two mill operations. Slurry pumping and sampling techniques were described for various operations. Environmental control in milling was reported concerning dust suppression, arsenic removal and tailings disposal. Several aspects of gold milling were described by the most recently commissioned gold mine and by CANMET. Potash operations were reported showing the similarity of processing and process control to that of metallic minerals."

Jan 1, 1976

By G. Ellie, D. F. Coates

"The mining of coal in thick and inclined seams is difficult, and there are only a few countries in the world that are really interested in the problems associated with their exploitation. In France a considerable amount of investment has been made in the mechanization of systems appropriate for such conditions.For seams inclined up to 50 degrees, of normal thickness, a new system was introduced in 1967. It consists of a longwall advancing to the rise with walking props, a shearer and hydraulic backfill. During the first two years the panel productivity was an average of 25 TN/MS, and they foresee the possibility of reaching an average of 30 TN/MS.A system for thick beds, both horizontal and inclined, is in p•rocess of being mechanized. In 1969 they started with a method consisting of a longwall in a footwall slice, or sub-level drifts with walking props, and caving and drawing up to a height of 20 m of coal. Recent experiments with a shearer have produced panel productivities between 9 and 11 TN /MS, and there is hope that with experience an average of 16 TN/MS will be obtained.In 1964 a method was initiated for beds inclined from 60 to 90 degrees, based on a mechanical cutter designed by the collieries in Lorraine. An overhand slice of 4.2 m in height is taken with a drum cutter mounted on the end of a boom. Hydraulic fill is placed at the completion of a slice. The face productivity, which has been from 13-20 TN /MS, can be perhaps increased to an average of 22 TN/MS. For those companies with important reserves in inclined and thick seams, these French systems may be worth the trouble of examining in some detail."

Jan 1, 1972

By Sherwin F. Kelly

"THE TITLE I have chosen is certainly not one of those self-explanatory ones. I shall endeavour to make its significance clear during my remarks but, in the hope of minimizing that inevitable exodus which follows a good lunch such as this, I am going to withhold the final key to its meaning until the very last sentence of this talk.Some explanation is due at the beginning, however, so for those of you unfamiliar with Spanish I will explain that casa means house, or home. The casa about which I am going to talk necessitates a wide .and generous interpretation of the word, because I am using it to indicate principally that portion of the North American continent which is the home, in the western hemisphere, of British and American ideals of justice and freedom, the dignity of the individual and his right to exercise private initiative .and engage in private enterprise. In a wider sense, I am including the entire western hemisphere, which may yet stand as the last bulwark of political and industrial democracy.As for the treasures of which I am about to speak, may I remind you that there are no• material treasures but those derived from the earth, and they are derived by one of two processes, -mining and farming. These two fundamental industries are the basis, and the sole material basis, of our welfare, our wealth, our very existence. From farming, whether it be farming of the land. or farming of the sea, we obtain the food to keep us alive, healthy and able to work."

Jan 1, 1955

By Alfred Guenkel, Kyle Marte, K. Nikolaisen

"The INCO SO2/air process was patented by INCO in 1985 (Borbely, Devuyst, Ettel, Mosoiu & Schitka, 1985). Well over 80 mining operations worldwide are using this process to oxidize cyanides to cyanates in the tailings from gold, silver and copper mining operations. Though it is possible to supply sulphur dioxide (SO2) in either gas or liquid form, the majority of these SO2/air operations use sulphite-based salts as the ‘SO2’ equivalent reducing agent. This is probably due to the lower capital cost, safety concerns with, and availability of liquid SO2. Sodium metabisulphite (SMBS) is commonly employed, and its cost is an order of magnitude higher than that of sulphur. The increased capital expenditures (CAPEX) for a sulphur-burning SO2 gas plant could have a pay-back of less than two years. In addition, a SO2 gas plant offers potential for significant heat recovery from the sulphur burning process. In terms of safety, the SO2 gas plant only requires the storage of relatively benign sulphur and the site inventory of SO2 will be limited to the plant gas inventory. Furthermore, a SO2 gas plant will not trigger the US Clean Air Act Section 112(r) accident prevention regulations, as may be the case for liquid SO2.Most existing mining operations using ‘SO2’ are gold operations, but in recent years there has been an increased interest in larger sulphur dioxide gas plants for hydrometallurgical facilities that employ leaching of cobalt/manganese minerals or precipitation of manganese/iron (e.g. Tenke Fungurume and Boleo).This paper discusses the different processes which require SO2 as a reducing agent and compares the capital and operational costs of a SO2 gas plant to conventional process alternatives using sulphite-based salts or liquid SO2.The heart of the SO2 gas plant is the sulphur furnace. The most economical way to produce SO2 is by combustion of sulphur in air producing up to 19.5 vol% SO2. Examples of large and small sulphur furnaces are discussed in terms of design, operation, and impacts on operational costs.The SO2 gas produced in a sulphur-burning plant has to be contacted with the liquor to be reduced. The choice of gas-liquid contacting device is important, and two contacting devices are discussed: 1) Gas sparging into the bottom of leach tanks (high, nearly constant, back pressure due to liquid head) and 2) absorption columns (low gas-side pressure drop)."

Jan 1, 2014

By Nehad Elsafty

It is always necessary to expand existing buildings, so that they could meet the growing societal needs. Compared with demolishing them and then constructing new ones, the expansion of existing buildings could not only reduce project cost, but also save the use of energy and raw materials in projects. Therefore, it is widely adopted in most under-developed countries. However, the expansion of existing buildings is not an easy task. It has been involved with a lot of issues in defining the scope of work, planning landscape, managing construction activities, etc. This paper investigates the potential challenges in expanding existing buildings. The project of expanding the Al-Agoza Hospital, one of the biggest and oldest hospitals in Cairo, Egypt, is selected as a case study. In the case study, the project documents have been carefully reviewed. The project engineers and the health-care professionals working in the hospital have been interviewed. This way, the point of views from the owner, the architect/engineer, and the contractor have been taken into account. Several lessons are learned through the discussion with these people. The results from this paper are expected to provide pieces of useful advice and suggestion for the expansion of existing buildings in the future.

Aug 1, 2013

By O. Hall

DISCUSSION AT QUEBEC MEETING MR. A. V. CORLETT: With drill holes radiating from a common point, is loading carried to the collars, and do you undertake to distribute the powder evenly? MR. R. V. PORRITT: When the collars of the holes, particularly the diamond-drill holes, are close together, two out of three holes are loaded only to within six or seven feet of the collars, and the intervening holes are loaded close to the collars. When the collars are farther apart, the holes are loaded close to the collars. No spacers are used, and the holes are filled solid with powder, this applying particularly to the diamond-drill holes, except, of course, where the collars are close together and some holes are not loaded close to the collars. MR. J. G. L. McCREA: I would like to enquire in respect to the various efforts made to reduce the cost of diamond drilling to the lowest point, what is. the relative cost of the solid bit to the standard bit? It would seem that the solid bit has the higher cost. MR. PORRITT: The non-coring or solid bit gives a slightly lower diamond cost than the coring bit. With the coring bit, the greatest diamond loss is on the inside stones, apparently due partly to vibration, but mainly to the core blocking against these stones. This condition, of course, does not apply with the non-coring bit. Our experience is that the non-coring bit, which drills out a much greater area, has a diamond consumption slightly less than the coring bit. The non-coring bit is sturdier, and is far less liable to damage in starting holes and in drilling through cracked or broken ground.

Jan 1, 1939

By M. B. Shongwe, R. K. K. Mbaya, C. K. Thubakgale, P. Mendonidis

"A low-grade nickel-bearing ore was pre-concentrated on a SB40 laboratory model Falcon Concentrator. Three size fractions, -212+125, -125+75 and -75 µm were tested with the intent to upgrade the nickel content by reducing their content of fine silica, which becomes amorphous during leaching. Separation of silica from nickel-bearing magnesium silicate minerals; hornblende, clinochlore and talc, was more efficient in the finer particle sizes, -125+75 and -75 µm, and at high G-forces. For these two size fractions, nickel was upgraded from 0.06 to 0.07%, with a reduction in silica content from 52.12 to 50.71%. Leaching of feed samples prior to pre-concentration resulted in the formation of amorphous silica, indicative of the presence of fine silica in the samples. Leaching of nickel from the -125+75 µm fraction increased with increasing G-force and feed pulp percent solids, while that of -75 µm was not influenced. The optimum nickel recovery was 15.68% to the Falcon underflow, using the feed size fraction of -75 µm, 30 G and a feed pulp solids content of 10% solids, after 120 minutes of treatment.INTRODUCTION A low-grade South African nickel-bearing ore with about 0.06% Ni was previously studied for atmospheric pressure acid leaching using sulphuric acid. The study was motivated by the continuing search for methods to treat of low-grade ores, which appear to be an increasingly important source of valuable metals as a result of a declining production from rich sulphide ores. Nickel is a base metal that is used as an alloy in steelmaking and chemical industries because of its resistance to corrosion (Haudet et al., 2015). Nickel laterite ores with grades lower than 1.50% Ni are considered to be complex ores, accounting for 70% of the global nickel reserves (MacCarthy et al., 2016). Their complex nature may be attributed to the indefinite mineralogy of these ores, in which nickel may occur in more than one mineral host. In some cases, nickel may be finely disseminated in the ore. The grade of such an ore and complex mineralogy do not justify the application of pyrometallurgical methods for extraction of nickel (Zhu et al., 2012). This suggests that there is a need for less expensive alternative methods of extraction. This study investigates the application of centrifugal gravity concentration, using the Falcon concentrator, followed by leaching to determine the effect of pre-concentration of the ore prior to extraction by atmospheric pressure leaching with sulphuric acid."

Jan 1, 2017

By M. Myllymäki

"Pre-treatment of mill feed in a minerals processing plant enables for higher production efficiency per ton of product, reduction of consumables and diverting mineral feed types. Sensor based particle sorting allows for pre-concentration of the run-of-mine (ROM) material prior to other concentrating process. Various sensors provide different responses from the minerals in measured particles. The capability of “accepting” or “rejecting” particles based on sensor responses is investigated in specific test work for each project. Modern sorting machines use pneumatic actuators to divert the reject particles from the material stream. This paper discusses the incorporation of ore sorting test work in processing and plant design. When taking the effects of a sorting circuit into account early in the process planning phase, the downstream process can be adequately sized and impacts evaluated. Potential benefits include but are not limited to increased head grade, lower tonnage to the mill, increased mining operations, removal of deleterious elements and changed properties in the process feed. In a case study we present the Keliber lithium project in central Finland. The plant will produce 9000 tons of lithium carbonate per year from a spodumene ore. Ore sorting and flotation tests were carried out in laboratory and pilot scale. Process models were designed and simulations performed using Outotec’s HSC Chemistry Simulation software. Changes in the flotation performance (grade, recovery, impurity levels) were simulated with and without the pre-concentration of the ROM material. The metallurgical performance and mine economics of the different operational scenarios were evaluated using the Ore-Met optimizer module of the simulation software.INTRODUCTION Challenges in the recent years such as declining ore grades, increasing energy prices, scarcity of water and increasing environmental regulations raise the demand for more efficient processing technologies. Sensor based sorting offers a method for pre-concentration or waste rejection at an early process stage. The technology analyzes each rock particle separately for their unique physical and chemical properties, and diverts the particles into separate material streams by high pressure air jets. Successful implementation relies on ore heterogeneity, differential sensor response and suitable feed preparation."

Jan 1, 2018

By P. Dauphin

"CANMET’s Mining and Mineral Sciences Laboratories have developed the Canadian Mining Technology Network (CMT-Net), a website to provide industry with up to date information on technologies in several areas. This paper gives background on the Mineral and Metal Processing sector, describes the steps leading to the development of the websites strategy and gives a tour of CMT-Net. IntroductionThe government of Canada is developing a strategy aimed at fostering the development of value-added activities in the area of mineral and metal processing (MMP). Natural Resources Canada (NRCan) and Industry Canada will partner in delivering on this strategy. Instrumental in defining the main thrusts of the value-added strategy was a series of consultations held across Canada with representatives of companies and organizations active in the sector. The objective of the consultations was to identify barriers to the development of activities which add value in the sector, as well as point to positive factors.Following the consultations, a discussion paper was produced, “From Mineral Resources to Manufactured Products: Towards a Value- Added Mineral and Metal Strategy for Canada” (Natural Resources Canada, 1998). The paper reviews the sector’s structure and main statistical information, lists some of the positive factors and barriers to value-added activities and defines a new partnership between industry and government that will lead to more valueadded activities. The main objective of the paper is to serve as a discussion document between stakeholders during the development of the strategy."

Jan 1, 1999

By B. M. Hamilton

"IntroductionTHE PROCEDURE and technique for drilling holes has probably undergone as great a change during the past ten years as any one of the other operations conducted in hard-rock mining. During this period, we have seen a change from the heavy leyners and drifters to the light jackleg type of drill machine; from steels that were forged and hardened on the bit end to the inserted •carbide-tipped rod, from the necessity of providing special bit-end fabrication and beat treatment of shank steels to the simple grinding or turning of a plain section on a shank with no heat treatment required for bit attachment.When the steel maker was first called upon to manufacture a hollow drill rod, it was required that the steel must not only have sufficient strength and fatigue resistance to cope with the stresses of service, but also must be capable of being heat treated on the bit end to a high hardness for resistance to wear and abrasion . Little was known at that time about alloy steels and the beneficial effects to be gained from additions of chromium, nickel , and molybdenum. So it was that the plain 0.80 per cent carbon analysis was selected, since it had already proven to be a suitable grade for chisels, hammers, and other such shock tools. This grade has long endured the test of time and is still used in considerable tonnage today, particularly by the construction industry.As the metallurgist learned more about the influence of alloying elements, a new hollow drill analysis was placed on the market in the early 'thirties'."

Jan 1, 1954

By M. D. Lawton, P. Steen

"Drilling results from the established levels at AngloRouyn Mines Limited had indicated inadequate tonnages to meet the planning schedule. It was decided to develop the main zone of the orebody below the bottom working level of the mine. The orebody dips north at an average of 50 degrees and plunges to the west at about 10 degrees. Due to the need for rapid development of this area, a decision was made to use trackless equipment.This paper describes the method used and highlights the use of small 5-ton diesel trucks as carriers for the 2-cu.yd LHD machine. The method achieved advances of about 1,000 feet per month, at a dip of 12 degrees over a length of close to 2,000 feet, using as few as 20 men per day."

Jan 1, 1971

By S. Hunt, S. Jayasekera, J. Kyle, N. Perera, K. Stone

A preliminary investigation has been conducted to determine the conditions for the precipitation of phosphate from the liquor produced after a hydrochloric acid pre-leach and rare-earth recovery from a rare earth containing fluorapatite concentrate from the Nolans rare earth deposit in the Northern Territory of Australia. The results show that at 50oC the phosphate can be precipitated in two stages using limestone to produce a Stage 1 precipitate containing most of the impurities including iron (94%), aluminium (92%), fluoride (98%), uranium (84%) and thorium (94%), followed by a relatively pure Stage 2 dicalcium phosphate precipitate (DCP) containing only 0.05% Fe, 0.05% Al, 0.1% F, 0.01% U, and <0.01% Th. The initial Stage 1 precipitate contained about 25% of the phosphate while the remaining 75% reported to the Stage 2 phosphate precipitate. Depending on the required radioactivity specifications, the amount of phosphate in the Stage 1 precipitate could be reduced. Reagent requirements were 11.4 kg limestone (as pure CaCO3) per cubic metre of solution for the Stage 1 precipitate and 39.7 kg limestone (as pure CaCO3) per cubic metre for Stage 2. The analysis of radionuclide balance indicated that radionuclides deported mainly to the final filtrate (86.4%) compared to Stage 1 precipitate (5.4%) and Stage 2 precipitate (8.2%). Settling and pressure filtration tests indicated the precipitates were both readily settled and filtered. The final moisture contents of the Stage 1 and Stage 2 precipitates were 62.5% and 49.3%, respectively.

Jan 1, 2014

By T. Verdel, Y. Gunzburger

Rockfalls are major and essentially unpredictable sources of danger, particularly along transportation routes (roads and railways). Thus, the assessment of their probability of occurrence is a major challenge for risk management. From a qualitative perspective, it is known that rockfalls occur mainly during periods of rain, snowmelt, or freeze-thaw. Nevertheless, from a quantitative perspective, these generally assumed correlations between rockfalls and their possible meteorological triggering events are often difficult to identify because i) rockfalls are too rare for the use of classical statistical analysis techniques and ii) all intensities of triggering factors do not have the same probability. In this study, we propose a new approach to investigate the correlation of rockfalls with rain, freezing periods, and strong temperature variations. This approach is tested on three French rockfall databases, the first of which exhibits an outstandingly high frequency of rockfalls (approximately 950 events over 11 years), whereas the other two databases are more typical (approximately 140 events over 11 years). These databases come from (1) the national highway RN1 on La Réunion Island, (2) a railway in the Bourgogne-Franche Comté region, and (3) a railway in the Auvergne region. Whereas a basic correlation analysis is only able to highlight an already obvious correlation in the case of the “rich” database, the newly suggested method appears to detect correlations even in the “poor” ones. Indeed, the use of this method confirms the positive correlation between rainfalls and rockfalls on La Réunion Island database. This method highlights a correlation between cumulative rainfalls and rockfalls in the Bourgogne region, and it detects a correlation between the daily minimum temperature and rockfalls in the Auvergne region. This new approach is easy to use and also serves to determine the conditional probability of rockfall function of a given meteorological factor. This approach will help to optimize risk management in the studied areas based on their meteorological conditions. Nevertheless, even if some rockfalls are correlated to meteorological factors, other seems to occur independently of these factors, which highlights the unpredictability of rockfall hazard.

Jan 1, 2015

By C R. Crook

A brief outline of production methods and processes is given to show how maintenance fits into the picture at this plant. The work force, and the tools needed to carry out this function, are then described. Preventive maintenance practices, scheduled annual shutdowns and routine check-downs are explained, especially as related to planning and to the materials and labour involved for a mini-mum downtime. A brief explanation of the materials, sup-plies and spare parts program, as well as the part played by the Stores Department in conjunction with the Maintenance Department, is given. Cost control and equipment expenditure indicators are explained. Some specific examples of maintenance jobs are described in order to show the flexibility of the program. S HERRITT GORDON Mines Limited has been in continuous production, except for the planned downtimes needed for expansion tie-ins, or the annual shutdown check-over periods, since the first shipment of nickel on a commercial basis in July of 1954.

Jan 1, 1964

By John H. Nicholls

In this paper, Imperial Oil Limited reports briefly on the drilling by contract rigs of twenty-nine slim holes in the Virden, Smiley, and Souris Valley areas. The investigations showed that slim-hole penetration rates, as a result of careful control of drilling variables, can approach those achieved with 7 7/8-inch bits. It is concluded that slim-hole drilling is acceptable for development or exploratory work. Imperial also reports on the completion techniques and equipment that have been developed on twenty-seven tubingless 2 1/2-inch casing completions. Indications are that the method is economically desirable where excessive gas or water production is not anticipated.

Jan 1, 1958

By R. E. Bou Serhal

Many miners are exposed to dangerously high levels of noise on a daily basis. Over the past 15 years, a continually increasing number of occupational hearing loss has been reported from the mining community in the United States, of which, more than 95% is attributed to prolonged noise exposure. Although the noise exposure levels may differ between coal miners and metal and non-metal miners, in the absence of noise control at the source, the solution is the same: use of personal hearing protection devices (HPD). While protecting the miners? hearing it is also essential to no longer hinder their ability to communicate. With access to an advanced HPD that is customized to the miners? ears we are able to combine these two requirements. Using an intra-aural instantly custom molded HPD miners are protected from high levels of noise. The HPD is equipped with wireless capabilities, and contains both a speaker and an In-Ear Microphone (IEM). Therefore, the miners? speech may be captured from inside the ear and transmitted to the remote listener. This IEM signal is relatively noise-free since it is isolated from the background noise. The IEM speech signal, however, is ?boomy? and is missing some high frequency content, making fricative consonants hard to understand. Nonetheless, the IEM speech signal is correlated with the natural speech signal and may be manipulated through statistical techniques to more closely resemble natural speech. By improving the intelligibility and quality of the IEM signal, numerous applications may be enabled. One use of the enhanced IEM signal will be for radio communication. Using wireless radio communication in a noisy mining environment is sometimes the only practical and affordable solution to allow communication between miners equipped with personal hearing protection devices. Traditionally, one of the weaknesses of such wireless radio communication lies in the lack of designating receivers: whether they are the intended receiver or not, all those carrying a radio receiver are subjected to the broadcasted signal. The current work will detail a new concept of a "radio-acoustical virtual environment" where the radio signal will only be received by miners within a given spatial range, such range depending on the user?s vocal effort as well as the ambient and perceived background noise levels.

Aug 1, 2013

By The Satff

"TEXADA Island is situated in the Strait of Georgia, about 100 miles northwest of Vancouver. The property of Texada Mines Ltd. lies on the southwest coast of the northern end of the Island. A part of the ""Sunshine Coast,"" the climate is moderate, with about 30 inches of rain during winter months and relatively dry summers. Texada has been shipping high-grade magnetite concentrate continuously since 1952 to Japanese ore buyers. In 1959, a 3,000-foot tunnel was driven just above sea level to explore the possible downward extension of known orebodies then being mined by open pit. In January of 1961, because the open-pit operations had a limited life, C. C. Huston and Associates were brought in as mining consultants to do a feasibility study on the possibility of going underground for production. This study was completed in March, 1961. With the completion of the report, the Company went to Japan seeking a ,long-term contract to justify the capital outlay necessary for setting up an underground operation. Concurrently, underground diamond drilling revealed more ore, and the Company planned some modifications to the concentrator for increasing the copper recovery. By November, 1961, a ten-year contract was signed with Japanese ore buyers for the sale of 450,-000 long tons of concentrates beginning in October, 1963. Since that time, the Company has built its own 65 000-ton ore carrier and an additional three-year contract has been negotiated, with an annual tonnage increase of from 450,000 to 550,000 tons."

Jan 1, 1967

By Cedric E. Gregory

"A study of model rectangular mine shafts has been made in the wind tunnel, with the aim of reducing air-flow resistance elements to a practicable minimum. An analysis of Table 7 shows an indicated average decrease in resistance of 28 per cent by adopting the over-all modifications involved in the configurations actually tested. Much greater reductions (up to 68 per cent) are indicated by extrapolating beyond the test results directly achieved. Intermediate partial reductions in aerodynamic resistance are shown for individual modifications, such as: (1) about 3 per cent for locating the lagging in the No. 4 (inside flush) position as against the No. 1 position - 8 per cent as against the No. 2 position - and 23 per cent as compared with position No. 3; (2) about 12 per cent for using lagging instead of steel meshwork along the divider separating the skipway from the service compartment; (3) about 14 per cent for using steel gridwork ladder stagings at 3-set intervals instead of similarly spaced wooden stagings; (4) about 12 per cent for using steel gridwork ladder stagings at 3-set instead of at 1-set intervals; (5) about 13 per cent for fitting a streamlined fairing (see Fig. 5) to the upstream face of the skipway divider. Contrary to expectations, an advantage of only 3 per cent is indicated for lagging in the inside flush (No. 4) position over the outside position (No. 1). This slight gain does not appear to warrant the cost of moving the lagging. However, if the lagging is already in the No. 2 or No. 3 position, there is an 8 and 23 per cent advantage respectively."

Jan 1, 1973