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By Miguel A. Cuba

Resource models are generally constructed using data of different types and/or from different sources. A common issue is the consistency of scale in the information that often leads to a requirement to composite the data prior to model construction. For the purposes of mine planning, development and/or resource assessment, this model may then be upscaled to a relevant selective mining unit. It is well established that the geostatistical parameters for resource model construction is scale dependent. In particular, the volume variance of integrating these various scales has a direct impact on the variogram that should be used in model construction and/or the assessment of volume variance relations as it affects resource estimation. The scaling laws are a set of guidelines that detail how the variogram should change as a result of a change in the volume; these laws are empirically derived and involve some simplifying assumptions, not the least of which is an assumption of shape invariance in the variogram structure. An alternative approach was proposed to directly upscale the variogram via numerical integration, which demonstrates that the assumption of shape invariance is not required and we can directly access the new variogram shape given any volume of interest. This paper compares these two different approaches to variogram upscaling by considering two applications: the first corresponds to a 2D synthetic case and the second looks at a 3D case with data from a porphyry copper deposit. The simulation studies in these cases show that the direct upscaling approach performs better than the scaling laws in fitting the average experimental variogram values at any block size. This is based on a mean absolute error criterion. Moreover, it is also shown that with an increase in the block size, direct variogram upscaling significantly outperforms the scaling laws approach.

Oct 1, 2009

By Rodrigo A. Marinho

Erratic high grade values are as common in Nature as they are a source of problems for resource estimators. In some highly erratic metal deposits, less than 2% of the drilling samples can represent more than 10% of the total metal in the blocks and they are associated with a high risk level. There is a risk of local overestimation but also of global overestimation, with the high grades being projected over too large a volume. Capping or restriction of these outliers control is being widely used in the industry and commonly applied in resource estimation for the last three decades. The primary purpose of this paper is to present and describe the most applied methodologies for restricting the extrapolation of high grade samples and discuss the results based on a theoretical simulated model. Additionally, this paper demonstrates the economical impact associated with the high-grade and the project risk profile associated with each method.

Oct 1, 2009

By L. Zhu, S. Kaierle, M. Dahmen, C. Zimmermann, T. Haubold, I. Kelbassa, C. Mattern

Application of integrally bladed disks (blisks) is of increasing interest in compressors of aero engines. Blisks are preferred due to their potential for size and weight reduction, for increased performance and for reduced manufacturing costs compared to conventionally bladed disks. In case of a damage the blisk aerofoils cannot be simply replaced. If the damage is beyond acceptance or blending limits refurbishment is possible only by scrapping the whole blisk assembly, or more cost effective by the application of advanced weld repair methods. Weld repair of blisk aerofoils is challenging as it affects a critical part with specific requirements regarding its mechanical integrity, and as the accessibility is usually limited. The paper describes the ongoing development of advanced weld repair processes as part of a comprehensive repair strategy which have been developed for small-sized blisk assembly to give competitive maintenance cost.

Jan 1, 2006

By E. T. Turner

Introduction 1n assembling material for this paper on Wood Refuse Burning 1 turned first to the records of our early studies of the problem in order to learn how and why certain basic decisions were arrived at and also how it came about that the completed central steam plant differed so much from the original plans. It may be of interest, therefore, to outline the engineering problems as they presented themselves in the early part of 1948, and to indicate the economies involved. Although the principle of using wood refuse as boiler fuel instead of burning it to waste was quite sound, and in fact the practice had been in use for a long time in the boilers of many lumber companies, there was some guesswork as far as Hollinger was concerned in deciding how best to handle the large quantities of wood refuse involved and as to the type of boiler equipment necessary to .burn it efficiently. These problems will be examined first. Hollinger Boiler Equipment in 1948 Hollinger had four separate boiler houses, at Main, No. II, and No. 19 shafts, and a small unit at the compressor plant for heating purposes. Main and No. Il boiler houses operated all the year round; No. 19 and the compressor plant only in the winter. At Main there were four 36-year-old HRT boilers with total available h.p. of 500, at No. II, three 30-year-old HRT boilers with 195 available h.p., and at No. 19 two old field-type locomotive boilers capable of producing 95 h.p.

Jan 1, 1951

By Avi Nanda, Robert Brandt, Alex Piatkiewicz, David M. Jones

In 2010 the United States Environmental Protection Agency (UESPA) revised the National Ambient Air Quality Standards (NAAQS) by lowering the permissible value to a 1-hour average SO2 concentration of 75 ppb. In 2012, the USEPA designated the Miami area as non-attaining for the new SO2 NAAQS. A number of options were studied to assist in bringing the Miami smelter into attainment with the new standard. The chosen solution included: Installation of a large tertiary hooding system over the converter aisle; Hooding of the anode vessels and treatment of the anode gas in a baghouse; Installation of a large 2,325,212 Nm3/hr caustic scrubber to treat the captured converter fugitives and anode off-gases; Installation of a secondary ESP for the tapping fugitive off-gas treatment system; and the continuous scrubbing of all acid plant tail stack gases. The modifications have reduced smelter SO2 emissions by 85%, achieving a world class SO2 stack emissions rate of 0.45 kg of SO2/tonne Cu. INTRODUCTION The Freeport McMoRan Miami smelter has been previously described in literature (Steinborn, Pasca, Sallee, Binegar, Bhappu). For the sake of brevity a brief description is given here. The Miami smelter is located 129 km east of Phoenix, Arizona near the town of Miami, Arizona. The smelter was established in 1915 and has undergone a number of process upgrades and modernizations over the years. The present smelter consists of an Isasmelt furnace, an electric settling furnace, four Hoboken converters, two anode refining vessels & one casting wheel; and one double contact sulfuric acid plant. Concentrates are railed & trucked to Miami from four Freeport McMoRan mines located in Arizona & New Mexico. The wet concentrates, typically containing 10% H2O with a Cu/S ratio of 0.85, are smelted in an Isasmelt furnace to a matte grade of 58%. The entire output from the Isasmelt is laundered into an Elkem electric furnace (originally installed in 1972 as the primary smelting furnace) for separation into matte and slag. Slag containing 0.85% Cu is skimmed from the electric furnace and discarded. Molten matte, containing 60% Cu, is tapped from the electric furnace and processed in one of four Hoboken converters to produce blister copper. Two anode refining vessels further refine the blister copper before the final product is cast on a single, 30 mold, casting wheel. All of the anodes produced at Miami are shipped to the Freeport McMoRan electrolytic refinery in El Paso Texas for refining into cathode copper. Smelter off-gases from the Isasmelt, electric furnace and Hoboken converters are combined and treated in a double contact acid plant to produce sulfuric acid. Acid produced at Miami is internally consumed at Freeport McMoRan mines in the region.

Jan 1, 2019

By J. Mcdvcka

Sustainable development has become a driving imperative for the resource industry as it is for the rest of the global business world. Being unsustainable is a risk no business can afford. Yet implementation of sustainable development practices beyond satisfaction of compulsory reporting is still sporadic. The current standard approaches to problem analysis and decision making are too narrow to capture the complexity of the issues at stake. Hence it is necessary to develop innovation in thinking and in doing. Those who search for ways to implement sustainable development use concepts such as Whole Systems Thinking and Eco-efficiency as well as tools like Life Cycle Analysis. Others develop their own instruments. In their effort to innovate they face both resistance and support within their organisation as well as within the industry or the wider context. This paper explores the factors that support, hinder and shape the sustainable development drive of the industry and proposes a comprehensive decision-making framework that links the goal of sustainability with the tools of sustainable development. This exploration is illustrated by a case study used in a doctoral research conducted on an engineering firm providing services to our industry.

Jan 1, 2007

By A. Dahi Taleghani, Amir Shojaei

A continuum damage mechanics (CDM) based constitutive model has been developed to describe elastic, plastic and damage behavior of rock during drilling. In addition to inelastic deformations, this model incorporates rock anisotropies like toughness anisotropy due to the bedding planes orientation that is a common observation in soft Shales. The pressure sensitive inelastic deformation of porous rocks together with their damage mechanisms are studied for drained and undrained conditions. Fracture mechanics of microcrack and micro-void nucleation and their coalescence are incorporated into the formulation of the CDM models to accurately capture different rock failure modes. The performance of the developed elastoplastic and CDM models are compared with the available single cutter test data of a specific shale play and then the models are introduced into a commercial finite element package through user-defined subroutines. A workflow to derive the required model parameters is presented through inverse modelling of the single cutter test data. The developed CDM model outperforms the traditional discrete element and fracture mechanics approaches by removing stress singularities at the fracture tips and simulation of progressive fractures like formation of the cuttings ribbon without any essential need for remeshing. This model would provide a robust tool for modeling bit performance and rate of penetration using conventional elements of FEA with a reliable results and a computational cost less than similar computational techniques like discrete element methods.

Jan 1, 2015

By J. Hendry, K. Brady, J. Yorzyk

Drawing from the experience of nickel, copper, aluminum and mineral borates, this paper illustrates the business value that the mining, minerals and metals industry as a whole can gain from applying life cycle assessment (LCA) to products and operations. Through the use of case studies, the paper explores how companies and industry associations have used LCA to their advantage: from evaluating capital investments, meeting customer information needs, supporting new product applications, and developing credible marketing information on the environmental performance of their products. It also explores the dynamics of LCA adoption and integration within companies, and provides recommendations to further strengthen institutionalization of LCA.

Jan 1, 2010

Grinding with an electrochemically inert grinding media (i.e. high chrome white iron, or Magotteaux’s Duromax® alloys) shifts the pulp potentials to more oxidising conditions, increases the dissolved oxygen content and reduces the EDTA extractable iron concentration when compared with milling with electrochemically active grinding media (forged steel). These changes in pulp chemistry produce cleaner particle surfaces, reduce reagent consumption and increase concentrate grades and recoveries. This paper presents a robust laboratory test program that is able to not only demonstrates these effects but also provide an indication of the magnitude of the improvements that are possible. While laboratory studies are interesting, the proof is in the pudding! So, the paper provides an overview of plant trials conducted at a number of operations around the world, including: Newcrest’s Cadia Operation, Oz Minerals’ Prominent Hill Mine and Glencore’s Ernest Henry Mine. These successful plant trials clearly demonstrate that selection of the right grinding media alloy will yield savings in grinding media consumption and reagent consumption as well as increases in revenue through improved copper, gold and molybdenum recoveries. INTRODUCTION The key to a successful separation in mineral processing is the preparation of particles with adequate liberation under the correct pulp chemical conditions. While the importance of liberation on flotation separations is generally understood and well documented in the literature (Johnson, 1987; Jackson, Sutherland, Gottlieb & Quittner, 1989; Young, Pease, Johnson, & Munro, 1997; Greet and Freeman, 2000), the importance of pulp chemistry is more nebulous, particularly with regard to the impact of grinding media. Extensive work examining the electrochemical interactions between grinding media and sulphide minerals has been completed (for example, Iwasaki, Reid, Lex & Smith, 1983; Natarajan and Iwasaki, 1984; Yelloji Rao and Natarajan, 1989(a); Yelloji Rao and Natarajan, 1989(b)). Broadly, these studies indicate that most sulphide minerals are more noble than the grinding media used during comminution, therefore a galvanic couple between the media and the sulphide mineral(s) exists, which increases the corrosion rate of the grinding media. The corrosion products of the grinding media, iron oxy-hydroxide species, invariably precipitate on to the surfaces of the sulphide minerals thereby affecting their floatability (Johnson, 2002).

Jan 1, 2019

By Charles Graham

For hundreds of years the standard vertical mine shaft was rectangular shaped and timber lined. There are many advantages to rectangular shafts but as mines became deeper the circular shaft became more popular. The chief advantages of circular, concrete lined shafts are their ability to resist lateral pressure and they offer less resistance to ventilation air. A number of elliptical shafts have been sunk in an attempt to realize the advantages of both the rectangular and the circular shaft. A concrete lined elliptical shaft provides better space utilization than a circular shaft, would allow for shaft sinking with two double drum hoists, as well as concurrent level development. The design also makes one sided stations possible and provides for a simple headframe design.

Feb 1, 2008

By Jörgen Appelgren

Atlas Copco, a leading supplier of equipment and services to the mining and construction industries, is consistently pursuing its strategy to offer the most productive and economical solutions by continuously offering new innovative products. These are in most cases developed and tested in close cooperation with demanding end users before being officially launched on the international market. The demands for higher productivity and improved overall economy have resulted in systems for automation of the drilling cycle and also tools for integrating the Drilling equipment to the production control system used by the customer. In terms of improving the blasted material quality, Atlas Copco has placed emphasis on hole straightness and the need for hole logging and positioning. By applying state of the art technology to today?s computerized drilling rigs, major steps in improving overall drilling and blasting performance have been achieved. This paper will give some examples derived from the latest development of solutions for the Rotary drilling product line.

Oct 1, 2009

By J. Gillies

"Extraction of Gold in Ketone from a suitably prepared sample of sulphide or siliceous ore or concentrate permits a rapid and accurate determination by Atomic Absorption. Mill test products and exploration development samples are acid-treated to effect complete dissolution of silver, copper, zinc, lead, molybdenum and iron present. Interferences in the determination of molybdenum are described. Results by Atomic Absorption are comparable to those afforded by other acceptable methods.INTRODUCTIONDuring recent years much has been written and discussed concerning Atomic Absorption Spectrometry as a technique for determining the concentration of metallic elements. We would, however, recommend a perusal of the paper presented by J. C. Ingles at the annual meeting of Canadian Gold Metallurgists held in Ottawa, January, 1966. The paper was published in the August, 1966, issue of the Canadian Mining Journal, and contains general information on Atomic Absorption.The purpose of our paper is to present certain specific method procedures for the determination of several precious and base metals normally present in Mine, Mill and Smelter products. Of necessity, analytical results should be as accurate as the most suitable available method permits, whether for metallurgical balance, settlement purpose, ore beneficiation programs, or exploration property development. The success of such programs is relative to the accuracy, speed and economics of the analysis. It is obvious, therefore, that in presenting our paper we consider the technique has achieved the desired evaluation."

Jan 1, 1968

By J. W. Stickney

"On July 1, 1977 Hudson Bay Mining and Smelting Company Limited announced the commencement of construction of a 3800 ton per day concentrator at Snow Lake, Manitoba. Snow Lake, a community of 2200 people, is located 130 road miles from the main metallurgical plants at Flin Flon.The design, detailed engineering and equipment selection for the project was awarded to Wright Engineers Limited of Vancouver, B.C., who would be working in close liason with Hudson Bay Mining personnel throughout the project.The feasibility of constructing a metallurgical plant in the Snow Lake area, in addition to the concentrator at Flin Flon, had been under study since 1964 with plants of varying capacities and designs being considered. Each successive study recommended a plant of increased capacity and sophistication and finally upon an in-depth study in 1976 of ore reserves, freight rates and operational benefits, the construction of a 3800 ton per day copper-lead-zinc concentrator appeared highly benificial."

Jan 1, 1981

By L Thompson, R C. West, T S. Kho

In 1978, the Outotec direct to blister flash (DBF) smelting process was commercialized with the commissioning of the Glogow 2 smelting facility in Poland. Since then four further DBF facilities have been constructed, two at Olympic Dam, one in Zambia and most recently one at Glogow 1 in Poland. The DBF smelting process differs considerably from conventional smelting process in both chemistry and unit operations, presenting opportunities for flowsheet capital and operating cost savings particularly when the concentrate copper grade is high. WorleyParsons has amassed considerable expertise in the Direct to Blister process and in this paper the process is compared to the modern two stage Double Flash process. The processes are modeled, and the key operating parameters, consumables and production metrics are directly compared. Subsequent flowsheets, key equipment lists and capital costs are also presented for comparison and discussion. The results show the range of concentrates which are most economically treated by the DBF process relative to those best treated in conventional processes along with those concentrates which could be treated by either process. INTRODUCTION The Outotec Direct to Blister (DBF) process was developed and installed at Glogow in 1978 (Czernecki et al., 2006). Currently there are a total of five DBFs built on three sites: Glogow No.2, Olympic Dam No.1, Olympic Dam No.2, KCM Zambia and Glogow No.1, being the most recently constructed. The DBF process was the first flash furnace process to produce blister copper and paved the way for the subsequent development of the flash converter and other continuous converting processes. Today four flash converters are in operation taking the total number of flash furnaces producing blister copper to eight. In all DBF operations it is the unique ore and concentrate composition which made selection of the DBF process the most attractive. In all cases, the concentrate is relatively high in copper but low in iron because chalcopyrite is not the major constituent. When considering smelting options for high copper, low iron concentrates a key question is then often asked, “At what point does it become economic to switch from two stage smelting and converting process to the DBF process?”

Jan 1, 2019

By Chen Feng

Compared to widespread successful deployment of robotic manipulators for repetitive and hazardous tasks in related industries such as manufacturing, the construction industry has achieved relatively limited benefits from robotics and soft automation. Unlike manufacturing, where robotic solutions benefit from the structured layout of the environment (e.g., factory assembly line), construction robots face unique challenges that arise from the rugged, dynamic, and unstructured environment of the work site, as well as the uncertainty and evolving sequence of occurring on-site events. This challenges any intended construction robots to not only replicate basic human motion, but also be capable of sensing and adapting to environmental changes, and making decisions based on the evolving state of the environment. Building upon recent advancements in robotic mapping, computer vision, and object recognition, the authors propose to introduce autonomous behavior at the basic task level for on-site construction robots to address these challenges in a flexible and extensible manner. This paper reports the outcome of the first phase of this research - a structured methodology for improved design and development of basic task automations - and focuses on algorithms developed for mobile robot navigation and relative pose estimation. The algorithms are implemented on a prototype mobile robotic platform, and evaluated in several experimental scenarios.

Aug 1, 2013

By H. Hejny

Economy needs mineral raw materials in almost each sector of modern life. They can only be provided by mining activities. An increasing share of the total mining production will be by underground mining. The mineral deposits will be found at gradually greater depths, including all problems associated with them. It involves an increase in overburden pressure with subsequent rock stability problems and risks of structural collapse. There is a need for new and safe technologies for almost all parts of a modern mine. The mining industry faces a number of challenges which require technical solutions that encompass the entire network and include the economic, social and environmental issues. The industry needs a new image based on pioneering solutions and a modern structure that can exploit minerals at greater depths and promote both high productivity and safe working conditions. Funding has been secured from the European Commission for the I²Mine project. Work started in November, 2011. This initiative is designed to focus on the technological challenges that the mining industry is currently facing including the exploitation of ever deeper deposits and the aspiration for an invisible, safe, zero impact mine. The project comprises a consortium of 27 organisations from 10 European countries. I²Mine marks the start of a series of development activities aimed at realising the concept of an invisible, zero impact, deep mine. The extractive sector, still seen as being old fashioned and environmentally unfriendly, will show that mineral extraction and processing can be done in a highly innovative and sustainable manner with low impact underground and zero impact above ground. The concept of I²Mine is to develop innovative methods, technologies, machines and equipment necessary for the efficient exploitation of minerals and disposal of waste, all of which will be carried out underground. This will dramatically reduce the volume of surface transportation of both minerals and waste, minimising above ground installations and reducing the environmental impact. New eco-efficient technologies will be applied in order to make the entire mining process more efficient and environmentally sound. The concept is for an integrated mine, with the majority of the installations underground, and only the final product will be transported above ground to be shipped to the customer. Production waste will be treated and stored underground and gaseous emissions will be managed underground as far as practical. I²Mine will also focus on ideas and concepts that increase energy efficiency and decrease waste. The core of the project will be to develop breakthrough technologies for autonomous, highly selective, continuous mineral extraction processes and machinery based on new sensor technologies, face front separation as well as innovative concepts for mass flow management and transportation integrating state of the art technologies. The concept of an invisible, zero impact mine requires a refined process underground that selectively extracts the mineral thereby reducing waste. For this reason, improved extraction machines and near to face processing methods, including backfill procedures, need to be developed. These developments include rock mechanics and ground control solutions, incorporating health, safety and environmental issues.

Aug 1, 2013

By Lifeng Yang, Xiang Zhang, Liang Yuan, Yonghui Wang, Bing Hou, Mian Chen, Rixing Zhang

Large-scale hydraulic fracturing technique has been widely applied to the development of shale gas reservoirs, where the interaction between natural fractures and critical fracture zones has substantial impact on the propagation of hydraulic fractures. Therefore, it is of significant importance to understand and experimentally verify such mechanism. To reach this end, tri-axial fracturing tests were implemented on 400mm×400mm×400mm block samples collected from Longmaxi shale outcrops. The interplay between hydraulic and natural fractures was investigated during the tests, factoring in the role of pump rate in affecting the created fracture network. Based on the experimental results, the critical fracture zone, defined as the weak formation zone nearby the wellbore created by staged pressure implementation that is observed rapid fracture propagation upon next stage of pressure increase, was thoroughly investigated. The analysis illustrates that given the high brittleness of the shale formation, abundant critical fracture zones are generated around natural fractures with pressure building up at a relatively low pump rate. As the pump rate increases, hydraulic fractures initiate and come into play with critical fracture zones, implying emergence of a large number of micro-cracks. A changing pump rate modifies the way of interaction between hydraulic and natural fractures and the subsequent formation of fracture network. Long term fracturing fluid injection with relatively low pump rate below the activation of critical zones is suggested. Also proposed is appropriate timing when applying a specific pump rate that will contribute to the improvement of hydraulic fracture propagation.

Jan 1, 2015

By D. G. Eskin

"It is well known that it takes some time for the solid phase to completely dissolve upon melting, especially inside the defects of insoluble particles, e.g. oxides. Until then the oxides remain active solidification substrates in the case of subsequent solidification. It is also known that ultrasonic melt treatment causes grain refinement through activation and dispersion of solidification substrates (one of the mechanisms) and also accelerates the dissolution of solid metal in the melt. In this study we combine these effects and demonstrate that the introduction of an alloy rod into the matrix melt of the same composition results in significant grain refinement, this effect being increased by the ultrasonic vibration of the rod. The achieved grain size is comparable to that obtained by a standard Al–Ti–B grain refiner. All samples were cast using a standard TP-1 mould to enable correct comparison. The effect of the temperature range of the rod introduction, as well as the effect of ultrasonic vibrations are discussed.INTRODUCTION The fact that by introducing solid metal into the melt one can achieve structure refinement is rather well known. As early as in the 1930s–1950s a series of papers and patents have been published, showing the benefits for grain refinement when dissolving solid metal in the melt before solidification (Danilov and Neimark, 1938; Scheil, 1956). Later on this way of structure refinement was developed further and dubbed “suspension casting” or introduction of “internal chills” (Madyanov, 1969; Zatulovsky, 1981). The solid metal was added in a form of cut wire, cut sheet, or powder, with the resulting grain refining, elimination of columnar grain structure in ingots and castings of steel, copper and aluminium alloys. The underlying mechanisms have been suggested as (1) rapid cooling of the melt due to the latent heat consumption upon melting of the solid metal with the resultant melt undercooling and (2) introduction of many solidification substrates in the form of crystal fragments and active non-metallic inclusions (Danilov & Neimark, 1938; Balandin, 1973). A number of patents have been filed where either the same solid alloy or a master alloy with additions (e.g. Ti for Al alloy) is introduced in the amounts up to 50% (typically less than 10%) into the melt close to the liquidus temperature (Schmidt, 1966; Talbot & Soller, 1973, Krupp, 1974; Bondarev, 1979). The main reason that this technique is not widely used in industry is the possible incomplete dissolution of the solid parts introduced into the melt with ensuing inhomogeneous as-cast structure and potential defects. Also the selection of the temperature range where the technology works the best is not clear."

Jan 1, 2018

By E. W. Lucht

THE term "high pressure", as used in industry today, is applied rather loosely. Generally, it refers to pressures that are higher than those encountered in most industrial processes although no definite limits are normally stated. For the purpose of this talk I should like to set rather arbitrary limits to the term "high pressure", and in ab-solute figures this would be the range from 1000 psi to perhaps 40,000 or 50,000 p.s.i. The scope of high pressure technology is very broad, and it would take more time than we have avail-able here today to cover fully even one aspect of the field. Therefore, I should like to discuss just some of the techniques used and problems en-countered in high pressure operations. Research work into the high pressure region dates back about 150 years, but it was not until 1910 that the first commercial application of high pressure technology was made in the production of ammonia.

Jan 1, 1962

By Roderick C. McDonald

Great Bear lake, the fourth largest body of water on this continent, comprises an area of approximately 12,000 square miles, and is set astride the Arctic circle, with a large portion of it witnessing both the Arctic winter night, and the Arctic summer day with its midnight sun. The very name itself, Great Bear, suggests an Arctic region. The seasonal contrasts at Great Bear lake are very marked by the cold and darkness of winter, and the warmth and brightness of summer. Signs of winter such as low clouds, snow, sleet, fog, and night frosts, generally appear the latter part of August, while ice forming on bays during the last two weeks in September ends boat travel on the lake about September 30th.Early in June the ice leaves the river mouths, during the last ten days of the month it disappears from small bays, and at some time during the last two weeks of July the main body of the lake becomes navigable. In 1916, the ice disappeared earlier than usual, and the lake was navigable on July 5th. Great Bear river generally breaks up about June 1st, but, on account of ice cliffs and floes, it is not navigable with safety until early in July. Even then, the traveller is confronted with the Charles rapids, but these might be overcome by a wagon or motor road, such as the one from Fitzgerald to Fort Smith: However, in 1931, Mr. A. W. Boland, Fort Norman, N.W.T., carried with scow and motorboat practically all freight between Fort Norman and LaBine point and Hunter bay, at the east end of the lake. During July and August, two types of clothing are required, for, although the days are mainly ones of warm sunshine, the nights are cloudy and cold. In the winter season, fur clothing is used exclusively. Considerable timber, mainly white spruce, suitable for fuel and building purposes, borders the lake and extends eastward to the Coppermine river. North of the lake, no timber is found except in the river valleys, but with oil and coal possibilities near Fort Norman, the fuel situation might be solved.

Jan 1, 1932