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By K. S. Coley, G. A. Irons, T. Kaneyasu

"It is very important to reveal the lime dissolution mechanism in steelmaking slag, to promote its dissolution without calcium fluoride, which is now almost forbidden for use in most industrialized countries. In this research, the purpose was focused on the development of an experimental method to measure the mutual diffusivity of Ca2+ under the condition of lime dissolution into slag. By forming diffusion couples using a ""vacuum slag aspirating technique"", the method was established. The following mutual diffusivities of Ca2+, in CaO-SiO2-FeO slag systems, imitating oxygen steelmaking slag, were determined using this method:4.1*10-10 m2/s at 1400°C for 27wt.%CaO-53wt.%SiO2-20wt.%FeO slag,4.3* 10-10 m2/s and at 1400°C for 20wt.%CaO-40wt.%SiO2-40wt.%FeO slag, and 1.3*10-10 m2/s at 1250°C for 20wt.%CaO-40wt.%SiO2-40wt.%FeO slag.It was also verified that, if the basicity and ferrite content of the bulk slag are low, then a calcium silicate film forms on the lime surface, and drastically deters the lime dissolution."

Jan 1, 2004

By R. H. Fett

T HE APPROACH to maintenance must always be ?completely positive: there must be no question of putting off difficult problems until it is more convenient to tackle them. By this it is meant that a piece of machinery or equipment which, by experience, is known to be due for a check should not, merely because it appears to be operating satisfactorily, be left until it reaches a critical .condition and breaks down. The mentality of the Maintenance Manager must be completely orderly and methodical and he should, in fact, possess a ledger-book mind, having a debit and credit outlook. The debit side would be that applying to time out of service, cost in wages, material, personnel involved, etc., and the credit side that relating to continuous operational time of the locomotive and therefore to the ultimate benefit of the mine and the personnel who work there. The Maintenance Manager is not concerned with design problems, and although he and the personnel under his jurisdiction are not engaged in productive work, he and his staff do, nevertheless, add greatly to or detract from the overall efficiency of the organization. Provided the machinery placed in his care is good to start with, he must take the best steps he possibly can to keep it running. However, he may, on occasion, be forced to improvise and this is where the ingenuity of a clever man rises to the occasion.

Jan 1, 1956

By J. J. O?Neill

Introduction The Beattie mine is the first of its character to be exploited in Quebec. It is primarily a large low-grade gold deposit containing values which a few years ago would not have been considered as ore. Much interest is attached to this development as its success may mean a greatly enlarged scope to gold mining in Canada on deposits which have formerly been considered worthless. Because of its potential importance as a pioneer in low-grade gold mining, the Quebec Bureau of Mines decided to make a careful detailed study of the Beattie in the hope not only of assisting in its development, but of stimulating the search for similar essential geological conditions in other parts of the Province. This paper is a summary of the results obtained during two months on the property in 1932, supplemented by a few trips underground in 1933. The full report will appear in the Annual Report of the Quebec Bureau of Mines for 1932, Part C. Location and Means of Access: The Beattie ore-body is situated two miles west and one half mile north of the centre of Duparquet township, and approximately 22 miles north 28° west of the town of Noranda. Until the fall of 1932, access to the property was from LaSarre, on the Canadian National railway, over a thirty-mile water route with one portage 600 feet long; about 2,000 tons of machinery and supplies were taken in by that route. An automobile road, nine miles long, now connects the property with the Makamik highway, and a narrow-gauge railway, without ballast, gives outlet for concentrates from the mill to the C.N.R. tracks of the Rouyn-Taschereau line, nineteen miles distant.

Jan 1, 1934

By G. McIsaac

This paper discusses the formulation of a linear program with the objective of maximizing the cash flow of the long-term plan of an underground operation. A mine is split into eleven independent ore zones, each characterized by its reserves, required development, and mining method. Based on practical considerations, maximum rates are set for each zone?s development and production capacity. For the total mine plan, a minimum daily production rate is set along with a minimum feed grade to the mill. A maximum daily development capacity is set based on the equipment and labour available. Proven and probable ore is mined preferentially over possible ore in the early years of the plan. Also, the fixed cost of operating the mine is taken into consideration whenever mining activities take place. Once the linear program is solved, it can be critically reviewed, and unrealistic results can be identified. Some resource allocations constraints can then be changed in certain sectors, and new results can be analyzed. ?Whatif? scenarios can also be examined, such as determining the impact of hiring a contractor to develop a given sector, or dropping an ore zone completely from the plan.

Sep 1, 2005

"An innovative concept is proposed whereby the operating power for haul trucks in certain areas of an underground mine are reduced in order to lower ventilation costs. Airflow that must be provided for diesel-powered equipment in most jurisdictions are regulated based on engine peak power capability and engine emissions, both of which can be lowered by artificially reducing the capacity of the engine through the engine control unit. Advances in asset tracking and ventilation on demand enable this methodology and this study demonstrates that it could represent significant value for mine operators. An examination of haul truck duty cycle indicates that de-rating of engine operating power based on the truck’s location in the mine can enable a step change in ventilation rates, often with no material impact on working conditions. Methods for implementation and estimate of cost savings will be defined.INTRODUCTION Ventilation of underground workings remains a significant operating cost burden for modern mine operators. In particular, ventilation rates for underground diesel mining equipment are often defined by local regulatory bodies and are assumed to present minimal opportunity for optimization or savings, at least until battery propulsion systems can be adopted. Commonly, the quantity of air flow required is defined by the peak rated engine output power of diesel equipment. For example, Ontario Regulation 854 SS 183.1 (3) states that “The flow of air must be at least 0.06 cubic metres per second for each kilowatt of power of the diesel-powered equipment operating in the workplace”. Jurisdictions that define air flow using the prescribed CANMET or MSHA ratings use peak engine emissions to calculate air flow required for dilution ventilation. These approaches are similar in that the maximum power capability of a vehicle’s engine is used to define the ventilation rate in all areas where it travels, regardless of what power output is actually used in any of those areas. Examination of the duty cycle of a typical underground haul truck identifies a large variance in the power output of the vehicle depending on its location in the mine and the activities undertaken at these locations. For example, travel on a mining sub-level requires a fraction of the truck’s peak power due to the minimal grade and significantly reduced travel speed. So if we can reliably reduce the peak engine power capacity and engine emissions in areas where peak power is not required, we can logically cut the ventilation rates for those areas."

Jan 1, 2017

By J. A. Folinsbee, Andre Robitaille, Tony Y. Chong

"Conventional crushing and grinding is followed by gravity concentration to recover free milling gold. Refractory gold, finely disseminated within the pyrite and arsenopyrite matrix, is recovered by flotation followed by pressure oxidation, cyanidation, and cementation. Non-refractory gold is recovered by cyanidation/CIP processing.A comprehensive test program aimed at improving flotation recovery was initiated in June 1995. Plant testing indicated that flotation tails value could be significantly reduced using mechanical flotation cells. Based on these test results, a flotation circuit that incorporates one of the three existing flotation columns followed by mechanical scavenging and cleaning was developed. Detailed engineering was completed in September 1996. Construction started in February 1997 and was completed in 3 months at a cost of $3.2 million. An on-stream X-ray analyzer was installed to provide real-time arsenic and iron analyses and inferred sulphur value on some of the flotation streams.The new flotation circuit proved to be an instant success. Flotation tails values were reduced by 27%. Final tails solids and solution was reduced from 0.035 to 0 023, and 0.0014 to 0.0006 oz/ton Au, respectively. Based on a mill throughput of 1,620 stpd this decrease in tails value will result in an increased gold production of 7,500 ounces per year. The payback for the project is estimated to be around one year.This paper describes the evolution of the project from bench scale testing to commissioning. Also, the operational and economic impacts on down stream processing are highlighted"

Jan 1, 1998

By E. V. Konopleva, H. J. McQueen

Steels in high variety have been providing strength and ductility for more than a century mainly through complex heat treatments following hot shaping. The economical and sustainable goal was a steel with the two operations combined through applying knowledge of dislocations and strengthening mechanisms aided by new mechanical and microstructural techniques. Primary hot reversing-mill rolling produced static recrystallization (SRX) between every pass to significantly finer grain size. Hot torsion showed that with lay-on temperature and rate of reduction suited to gradual precipitation of minor additions of Nb, the austenite grains would become highly pancaked; the existence of very fine subgrains along the grain boundaries (GB) could be deduced from tests on stainless austenite. The HSLA strip had to be water-jet cooled immediately to prevent SRX at austenite GB and ensuring complete transformation to ferrite avoiding grain growth after coiling. Confirmation on old mills and successful product led to the design of more flexible mills for wider range of compositions and products. A significant one was auto bumpers that reduced crash damage. More crack-resisting compositions were developed for strip welding into line pipe for arctic oil transport. Lower metal consumption and easier fabrication has resulted in more sustainable welded bridging.

Jan 1, 2015

By Farid Mirahadi

Forecasting productivity of construction operations is a difficult but crucial task in planning construction projects. Over the past decades, many models have been developed to forecast productivity for different construction operations. Models made up of several functional relations and controlled by a specific number of control rules are more in line with human reasoning and logic. Neural-Network-Driven Fuzzy Reasoning (NNDFR) structure as one of these models shows a great performance for modeling datasets among which clear clusters are recognizable. Lack of the compatibility of conventional NNDFR with fuzzy clustering algorithms besides the insufficient attention paid to the optimization of number of clusters in this model, created a potential area for further research. The main contribution of the proposed model is to develop a modified NNDFR system to model construction data. To this end, Fuzzy C-Means (FCM) algorithm is substituted for K-means in NNDFR structure, and its parameters such as the number of clusters and weighting exponent are optimized through genetic algorithm. The proposed model is further verified through simulation of a construction operation in which several qualitative and quantitative factors are considered. Its implementation to the case study shows a considerable improvement of model performance with lower Mean Squared Error (MSE). The developed model assists researchers and practitioners in utilizing historical construction data to forecast productivity of construction operations with a high accuracy that could not be obtained by traditional techniques.

Aug 1, 2013

By Guocheng Pan

Geostatistics has been widely accepted as a standard tool for reserve estimation and mine planning. Kriging has been adopted as the best estimator of grade. Although many discussions have been conducted in the use of kriging in the mining industry, insufficient attention has been given to solutions for over-smoothing. This effect has been frequently encountered in many mines. The so-called over-smearing refers to two facts: (1) over-reduction of grade variabilities and (2) over-estimation of low-grade ore tonnages. This study attempts to link over-smoothing effects with several other practical aspects in kriging. These include the weight independence of data values, variogram modeling, and search strategy used in estimation. All solutions recommended here are suited for precious metal deposits (e.g. gold) in open-pit mining.

Jan 1, 1995

By David Forrester

"At the 95th CIM Annual General Meeting in Calgary, 1993, a paper entitled “Progress on Futuristic Mining Technologies” was presented(Matthews and Sarin), in which they outlined the goal of continuous excavation of hard rock and some of the technologies being developed to achieve it. The subject continues to be featured in periodic reviews and articles in the literature, (Gertsch, 1994; E&MJ, 1995). Matthews and Sarin note the considerable success of the development and application of continuous mining technologies in the soft rock under-ground mining industry, especially those in coal and potash, with major benefit to overall production, productivity and economic viability. It is the belief that similar achievements can be realised in the underground hard rock mining which continues to drive the development of hardrock continuous mining technology.This overview has been prepared specifically for this issue of the CIM Bulletin. It attempts to tie together current advancements in continuous mining in soft rock (where remote control and automation are already well established) with the background and status of development in hard rock continuous mining. Following a brief review of key factors and machine types, soft rock aspects are discussed, then a more detailed review is given of hard rock technology, with particular reference to Canada’s HRDK Mining Research Ltd. and their key role.The mining industry has long been at the forefront of technology development, for example, the application of the early steam engine to reach reserves at greater depth for dewatering mines in the industrial revolution. By necessity, the individual characteristics of seams and orebodies dictate the mining method, continually presenting mining engineers with new challenges. One of these is the extraction process itself and the goal of replacement of the drill-blast-muck cycle by continuous excavation. Very soft rocks have always been mineable using some form of cutting, even with primative tools. However, as the challenge has been taken up, technologies have evolved to steadily increase the hardness of rock that can be mechanically excavated. It may surprise some readers that at least three machines have successfully cut and loaded rock with an unconfined compressive strength (UCS) of 250 Mpa to 300 MPa (36 000 to 43 500 psi) in field trials (Table 1)."

Jan 1, 1996

By A. J. R. Smith

"CANADA'S ECONOMY TODAY is about two-fifths larger than it was six years ago, as measured by the total volume of production of goods and services. Such an achievement has been a rare phenomenon in Canada's first one hundred years. Excluding the forced-draft expansions which took place under war-time conditions, perhaps only the first decade of this century recorded a performance of greater dimensions, when, with massive immigration, the opening up of the West and a powerful array of well-de-signed development policies, the country was looking forward confidently to a great future of nation-building in the twentieth century.What makes Canada's over-all economic advance since 1961 all the more remarkable is that six years ago there was virtually no one in this country who anticipated an expansion of such dimensions. Back in the buoyant conditions of 1956-57, perhaps such an achievement would not have seemed beyond our grasp. After 1957, however, Canada stumbled through an extended period of slow economic growth, high unemployment and substantial and widespread under-utilization of its productive capacity. By the early 1960's, conditioned by the emergence of substantial, persistent and pervasive slack in the economy, t h e r e were few Canadians bold enough to anticipate that their economy was about to embark on a Great Expansion. However, this •is, in fact, what occurred. Beginning early in 1961, Canada moved forward into a sweeping advance which grew into the longest and largest peacetime business expansion in Canada's first century as a nation -a truly great expansion by any standard of measurement. This strong thrust has moved Canada into the front ranks of over-all economic expansion among the industrially advanced nations in the 1960's."

Jan 1, 1970

By C. H. Madsen

THE Hard Rock gold mine is in the Little Long Lac mining area, Thunder Bay district, northwestern Ontario. It is four miles by road from the town of Geraldton, which is on the Canadian National railway, 180 miles northeast of Port Arthur. The original discovery of gold-bearing quartz veins on the property was made in 1931. Shaft sinking began in the fall of 1934 and approximately 7,400 feet of lateral development on four levels was completed. In 1935, further discoveries were made half a mile west of the early workings, and the No. 2 shaft was sunk in this area in a porphyry zone. In January, 1938, a 20C-ton cyanide plant was completed and began drilling ore from the gold-bearing porphyry orebody. The daily feed was increased gradually to 300 tons in the next six months and a recovery of 97.5 per cent was effected. During the summer of the same year, a new and larger orebody was discovered to the north of the porphyry zone. It occurs in a band of iron formation and contains a high percentage of pyrite and arsenopyrite. Extensive tests were rr.ace on this sulphide ore in the Mines Branch ore dressing laboratory at Ottawa, in the laboratory of Canadian Industries, limited, at Toronto, and later at the mine, to find a suitable method of treatrr.ent. As a result of this research, a Potation plant was added to the original cyanide mill and on November 7th, 1938, differential flotation was used to separate the pyrite from the arsenopyrite fraction of the ore. The pyrite concentrate was re-ground and cyanide:l, and the arsenopyrire concentrate was stored for subsequent treatment. Differential flotation was discontinued in April, 1939, in favour of bulk formation of all the sulphides, and the whole cyanide residue was stored. On March 15th, 1939, a 10-ton pilot roaster was completed and rests were conducted on the arsenopyrite concentrate and the bulk concentrate. The results obtained led to the building of two roasters of the same type, large enough to roast all the concentrates. These roasters were put in operation on September 24th, 1939, and the calcines were cyanided in the original circuit.

Jan 1, 1941

By M. D. Gerst

The degree to which copper will continue to be in an integral part of the world economy in the future will depend largely on the dynamics of global economic development, the primary and secondary copper resource stock, technological change, and potential environmental constraints. We have characterized the copper cycle of 1994 for all of Earth's regions and for the planet itself (T. Graedel et al., Environmental Science & Technology, 38, 1242-1252, 2004) and recently updated that cycle to year 2000. In this paper, we compare various features of the 1994 and 2000 cycles. The three largest-using regions, Asia, Europe, and North America, all increased their absolute rate of copper use between 1994 and 2000, and all increased the per-capita rate of copper use as well. Globally, the use of copper increased by about 32%, from 11.7 to 15.3 million metric tons, while population increased by only 8%. Various changes are seen in scrap trade, finished products trade, and other parameters of the cycle. We conclude by considering how the rates of technological change and growth in demand, especially in Asia, may influence the copper cycle in the years ahead.

Jan 1, 2007

By G. Eaton

Safety management is an important mortal and business function in construction. Contractors have traditionally tracked and reported lagging indicators, e.g. fatalities and lost-time accident rates, to measure their safety performance and stay in compliance with relevant regulations. Over the last several decades, contractors became more proactive in their approach to safety and developed programs that track leading indicators, e.g. safety audits and safety climate. In particular, safety climate measures workers? perception of safety management and its effectiveness in the workplace. Past literatures indicated that, while some industrial construction contractors ignore safety climate measures, others are limited by a lack of a formal means to measure safety climate. In this study, a survey approach is used to measure an industrial construction contractor?s safety climate through three key areas: management commitment, job control, and general safety climate. As a pilot study, a total of 214 individuals at a fabrication facility participated in the survey to verify the validity and effectiveness of the proposed survey approach. This survey study also confirms that job control and management commitment have a positive correlation and that worker demographics have an effect on respondents? perceptions of management commitment.

Aug 1, 2013

By A. M. King, J. M. Neilsen

"Roughness at varying scales is an important component of the shear strength of discontinuities. Small scale roughness can be assessed in drillcore and through laboratory testing of drillcore derived samples. Large scale roughness, or waviness, also plays an important part in peak shear strength and a number of methods for its incorporation into defect plane strength models are presented.A number of methods for capturing waviness data from exposed faces are reviewed. A method is presented for deriving waviness from downhole televiewer data, which is shown to be significantly more accurate than structural data derived from core logging. The method is based on work undertaken in the highly anisotropic bedded units of the Hamersley Province, Western Australia where televiewer surveys are routinely undertaken. Values of waviness are derived through a review of variation in dip resolved in the direction of the slope face. This method allows design engineers to incorporate large scale roughness in defect plane shear strengths at the design stage.INTRODUCTIONThere are a number of constitutive models currently being applied by rock mechanics practitioners in calculating defect plane shear strength parameters, such as Patton, Barton – Bandis and Hencher [1, 2, 3]. Most of these shear strength determinations are typically undertaken by determining the base or residual friction angle, and applying corrections for small and large scale surface roughness."

Jan 1, 2015

By Stephen B. Cheeseman

The quantity of data available and the rate at which we access such data are rapidly increasing. Electronic data capture systems, fleet management systems and a host of other technological advancements have created a constant stream of real-time, tactical data. However, are we taking advantage of this data? Are we converting data into useful information to aid in efficient decision-making? Mining operations are struggling with ?information overload?, finding it difficult to extract the benefits from vast stores of data. Without the necessary tools to facilitate a data filtering and information reporting process, most operations revert to old practises such as re-entering data into multiple spreadsheet reports. As a result, the ability to make effective use of data still eludes many mining operations. Some operations have taken audacious steps to rectify this situation. The De Beers Venetia mine in South Africa has implemented an integrated mining information technology solution that transforms their data into practical, usable information allowing staff and management to make decisions that improve efficiencies and reduce costs. In the absence of quantitative justification or ROI, De Beers took a risk in implementing change. Today, they are realising the benefits. This paper will unearth the information technology issues that surfaced during the Venetia implementation, then identify the benefits De Beers has obtained from deploying an integrated mining information technology solution at the Venetia mine.

May 1, 2002

By M. Turner-Jones, N. Steenekamp

"The Lonmin Base Metal Refinery treats converter matte from the Lonmin Smelter to produce nickel sulphate crystals, copper cathode as well as a concentrate containing the platinum group (PGM) metals. The original process employed a Sherritt design and utilizes atmospheric and pressure leaches for the dissolution of base metals. This paper describes the original flow sheet and the improvements made to enhance PGM recoveries, product quality and to increase capacity. Changes include the introduction of flash recycle cooling on the autoclave, batch leaches to improve the quality of the PGM concentrate and the implementation of solid-liquid separation with centrifuges. INTRODUCTIONThe Lonmin Base Metal Refinery (BMR) is about 100 km north-west of Johannesburg and treats converter matte from the Lonmin Smelter to produce nickel sulphate crystals, copper cathode and a concentrate containing the PGMs. The plant was commissioned in 1985 based on a Sherritt design to treat 12 tonnes converter matte per day. The original flow sheet consists of a milling circuit, an atmospheric leach and a pressure leach to produce a PGM concentrate which is despatched by helicopter to the Lonmin Platinum refinery in Brakpan, about 40 km east of Johannesburg. The liquor from the atmospheric leach is treated by crystallization to produce a nickel sulphate hexa-hydrate crystal. The leach liquor from the pressure leach is treated by a selenium removal step followed by electro-winning to produce copper cathode. The spent solution from the copper electro-winning is recycled to both the atmospheric and pressure leach steps to provide sulphuric acid for the leaching reactions.Modifications were made to the original circuit to increase the plant capacity, to improve the PGM recoveries and to improve the quality of the PGM concentrate. Capacity increases included all the unit operations, new mill, new first stage, additional autoclaves, additional nickel sulphate crystallizers, new copper electro-winning and new batch leach reactors for upgrading the PGM concentrate. The current circuit is described in this paper and not the detailed history of each plant change."

Jan 1, 2012

By G. Marchand, R. H. Hay, E. C. Pearson

"AbstractA polishing .technique is described together with two anodic etching methods for aluminum and its alloys. Some of the optical and structural characteristics of the film formed by •these etching methods are discussed and it is shown to what degree these properties of the film are related to the crystallographic orientation of the metallic substrate. Applications to the study of recrystallization and twinning phenomena and to the study of plastic deformation, banding, and texture estimation are discussed. Micrographs are shown .to illustrate the manner in which the technique is particularly well suited to the study of such phenomena.IntroductionThe physical metallurgist is constantly faced with the problem of polishing and etching of metallic sections. Mechanical polishing is tedious, time consuming, and not applicable whenever a surface entirely free from plastic deformation is required. Etchants are generally required to reveal the grain structure in order to determine its size, shape, and regularity, or to bring up constituents. In the case of aluminum, the .most common etchant to reveal grains is a mixture of three acids: HC1, HN03, and HF. This etchant is fairly satisfactory on certain alloys and for certain metallurgical conditions but in general fails to give a good definition of the grain on castings, on highly alloyed products, and whenever the grain is smaller than 100 microns in diameter. Besides size and shape, a grain, or crystal, has an orientation and may be endowed with several types of imperfections."

Jan 1, 1952

By C. F. Chung, F. P. Agterberg

"Prediction of a variable sulphur content in Cape Breton seams is important for planning the production of a highgrade metallurgical coal. Two extrapolation methods (Kriging and a version of Universal Kriging) to predict sulphur content in blocks of coal before mining are presented and applied to the New Lingan Mine reserves in the Harbour seam. The uncertainty of the predicted values is expressed by using standard deviations. Some statistical results for the Phalen seam, which occurs about 400 ft below the Harbour seam, are presented for comparison. The two mathematical models consist of two sets of equations which have been used in computer algorithms. Some limitations of the present approach and possibilities for further statistical work are indicated."

Jan 1, 1973

By D. Campbell Mackenzie

THIS paper is submitted primarily to put on record the results of a number of experiments carried out at the Wingdam mine of Consolidated Gold Alluvials of B.C., Ltd., with the object of establishing a reliable method of concentration of 'wash' and a maximum recovery of gold from the concentrate. It will be generally admitted that, during the last two decades, a tremendous amount of research work has been carried out, both by private companies and Government departments, with a view to improving the technique of the recovery of gold .from quartz veins or lodes. So thorough have been these investigations that milling practice at a modern quartz gold mine is almost an exact science, carried out with meticulous accuracy. In placer mining, on the other hand, very little departure from old traditional methods can be noted, with the exception perhaps of the more modern gold dredges. This may be due to the fact that the concentration of placer gravels, up to a certain point, is comparatively easy. Only a simple equipment of sluice box and riffies seems necessary where the gold is coarse and the gravel free from clay. In the early days of placer mining, when claims were rich and fairly 5hallow, nobody worried very much about fine gold; and, if clay was present, an enlarged dump box was constructed in which the gravel was subjected to a rather desultory puddling. That large quantities of gold are lost in normal placer practice is generally admitted. Some 26 years ago, I had inspectorial charge of many bucket dredges on the Ovens river, in Australia. Occasionally it was necessary for a dredge to work through its own tailing to reach a new section, and almost without exception enough gold was recovered from these tailings to defray the total cost of moving the dredge. Since those days, the technique of gold recovery in dredging has been considerably improved and it is still receiving close attention. Outside of dredge mining, most placer operations, deep or otherwise, are as they were-notorious gold losers, paying little attention to the recovery of fine gold and taking an absurd amount of time over each clean-up. In the Cariboo district of British Columbia, the alluvial gold is usual y associated with varying quantities of black sand (magnetic) and grey sand (non-magnetic); and it can be taken as axiomatic that, if you save all the black sand and grey sand, you save practically all the gold. It is on this hypothesis that we have carried out our research work and brought our recovery system up to its present highly satisfactory standard.

Jan 1, 1937