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By Longjiang Li, Song Mao, Zhengyang Qiao, Qin Zhang, Guizhou University, Ling Wang

"After a study on the advantages and disadvantages of flotation column, according to the limitation of ordinary flotation column only is used for a flotation of microgranular minerals, the paper designed a new kind of layered convection coarse particle flotation column.Using a bauxite to test the rationality of the flotation column.The test results show that the new layered convection coarse particle flotation column is feasible.It has certain advantages about coarse particles flotation.INTRODUCTIONFlotation column has many advantages, for example,a simple structure, high efficiency and energy saving, the obvious advantage of fine particles flotation , the index superior and so on. The advantages gradually getting people's recognition. Research of flotation column has been a breakthrough, however, due to it only is used for the flotation of microgranular minerals, and the microgranular mineral particles will lead to a series of problems, and makes the processing cost is increased. Due to increase grinding fineness can save the grinding time and reduce the cost of grinding, also can avoid the disadvantage of fairly granular mineral particles cause a deterioration in the flotation. So it is necessary to research a kind of coarse particle flotation column.After a research on the advantages and disadvantages of flotation column, the authors designed and manufactured a new layered convection coarse particle flotation column, the flotation column both in theory and operation is better than flotation machine.DESIGN OF THE LAYERED CONVECTION COARSE PARTICLE FLOTATION COLUMNAdvantages and Disadvantages of the Traditional Flotation ColumnIn the field of mineral processing, as the increasing proportion of ore that has low grade, fine dissemination size, complex mineral composition characteristics. The limitations of traditional flotation machine is increasing[1],for instance, the high energy consumption, severe wear, inconvenient configuration , large amount of maintenance and so on. Compared with flotation machine, the flotation column with high separation efficiency, low investment and production cost, covers a less area low installation cost, less reagent dosage, more suitable for separation of fine particles and can automatically control, etc[2]. At present, the ore is facing the world energy crisis situation, and becoming increasingly difficult to flotation. So it is important to invent a coarse particle flotation column."

Jan 1, 2016

By O. G. Olvera

"Refractory sulfidic ores consist of materials in which gold occurs finely disseminated within metallic sulfides or forming solid solutions, with pyrite and arsenopyrite being the two sulfides most commonly associated with gold. Typical cyanide operations show poor performance and require oxidative pretreatments to increase gold recovery. Pretreatment alternatives include roasting, pre-aeration, acidic and alkaline high pressure oxidation, and bacterial oxidation. The presence of arsenic, however, introduces a serious disadvantage to the use of roasting and bacterial leaching, while high pressure oxidation involves high capital costs. This work focuses on evaluating the effect of the addition of a carbon resin as a sulfur collector on the oxidation of different arsenopyrite concentrates under atmospheric tank leaching (ATL) conditions. The addition of the resin improved the oxidation of sulfides and favored the formation of elemental sulfur over the generation of sulfate. The use of AF5 in ATL resulted in higher gold recoveries under standard cyanide carbon-in-leach and thiosulfate leaching.INTRODUCTION Refractory sulfidic ores consist of materials in which gold occurs finely disseminated within metallic sulfides or forming solid solutions, with pyrite and arsenopyrite being the two sulfides most commonly associated with gold. Gold is not readily accessible to solutions in these types of ores and typical cyanide operations show poor performance, thus making the use of oxidative pretreatments a requirement to increase gold recovery. Pretreatment alternatives include roasting, pre-aeration, acidic and alkaline high pressure oxidation, and bacterial oxidation. The presence of arsenic, however, introduces a serious disadvantage to the use of roasting and bacterial leaching, while high pressure oxidation involves high capital costs. The use of carbonaceous materials to enhance the dissolution of sulfides is not novel, and leaching additives such as coal, activated carbon and carbon powder have been considered for the improvement of bioleaching, atmospheric leaching, and pressure oxidation leaching processes. However, this type of technology has been focused mainly on the recovery of copper from copper concentrates containing chalcopyrite with less attention paid to other sulfides."

Jan 1, 2017

By L. Vollert

"The application of pneumatically-assisted fluidized bed flotation, specifically the ERIEZ HydroFloatTM technology, has found widespread use in non-sulphide processing (particularly phosphate, potash and coal) for the recovery of coarse particles. In gold processing, centrifugal gravity circuits and flash flotation cells are typically employed for the recovery of coarse and near-size liberated gold which tends to accumulate in recycled grinding streams due to bypass to the classifying cyclone underflow streams owing to the higher specific gravity of these gold particles. Early removal of this gold from the grinding circuits contributes toward the reduction of downstream processing losses as a result of overgrinding and particle shape deformation in the case of flotation processing, longer leach residence times in the case of extractive processing, and surface occlusions in the case of both flotation and extractive processing. Furthermore, recovery to bullion attracts higher payment terms by way of comparison to concentrate sales in the case of copper-gold concentrators. This paper assesses the application of pneumatically assisted fluidized bed flotation for the recovery of coarse liberated gold through the analysis of piloting data generated from the operation of a continuously operated 16 inch ERIEZ HydroFloatTM unit treating a sized coarse grinding circuit stream. The paper presents the stage recovery by size performance of the ERIEZ HydroFloatTM unit together with quantitative gold deportment analysis to demonstrate the efficiency with which gold was recovered during this pilot campaign and then compared to more conventional processing units – centrifugal gravity and conventional flotation.INTRODUCTION Newcrest Mining Limited (NML) has identified that an opportunity exists for improving the recovery of coarse composite particles at its current operations, both as a means for improving overall recovery and as an opportunity for early gangue rejection. As such, Newcrest Mining Limited has taken an interest in the application of pneumatically-assisted, fluidized-bed flotation i.e. ERIEZ HydroFloatTM technology. This interest dates back to 2011 with sighter testwork carried out on their Australian-held ore bodies (Kohmuench et al, 2013). Newcrest continues to assess ERIEZ HydroFloatTM potential for coarse composite recovery and, in the case of the topic of this paper, coarse gold recovery based on examples in the literature which demonstrate the efficiency of this technology in this regard (Carmona Franco et al., (2015); Miller et al., (2016); and Kohmuench et al, 2013)."

Jan 1, 2017

By H. Tetu, F. Pells

"The copper-molybdenum property of Brenda Mines Limited is located in the Okanagan district of British Columbia, approximately 25 miles west of Kelowna. The Okanagan Valley is a resort and fruit-growing area, and therefore pollution control measures are more stringent than in some remote areas.The Brenda plant began production in April 1970 and is operated at a rate of 24,000 tons per day. The plant site is located at an elevation of 4,800 feet, which is approximately 3,600 feet above the level of Okanagan Lake. The site is in the Okanagan drainage basin.The major consideration in the design of the system was the prohibition of any downstream discharge. It was therefore necessary to redaim as much water as possible and to minimize the addition of fresh water to the system. The maintenance of a water balance is of critical importance.This paper will outline the major design criteria for the systems and the site investigations which were carried out. The design and construction of the facilities will be de-scribed and current operating experience will be outlined."

Jan 1, 1971

By P. C. Thurston, T. Setterfield, D. H. Watkinson

"The Maybrun copper deposit IS In a succession of pillowed basaltic flows in the Wabigoon sub-province, northwestern Ontario. The rocks have primary flow morphologies and remarkably well-preserved crystallization textures, including quench-textured plagioclase, in spite of metamorphism to the amphibolite facies. The sulphide assemblage chalcopyrite-pyrrhotite-cubanite with minor sphalerite and pyrite is primarily in interpillow spaces and is stratabound. Basaltic rocks immediately enclosing the copper sulphide minerals have an enrichment in Fe, Mg and K and depletion in Ca and Na relative to surrounding flows. The Maybrun deposit is interpreted to have formed contemporaneously with volcanism and alteration, and was subsequently metamorphosed with the enclosing basalts.IntroductionThe association o f significant base metal accumulations with mafic submarine flows in the Archean is as yet poorly documented. Such deposits, where noted, have typically been small, and are therefore commonly over looked. The Maybrun Mine, a 2.6 x 106-tonne copper deposit in pillowed basalt, has many similarities with large, well-documented volcanogenic deposits. Given the interpretation of the Maybrun Mine to be volcanogenic in origin, there is n o reason why similar processes could not produce large deposit s. This is an important realization in an area where Archean submarine mafic rock s are very common, but frequently are examined only superficially. As gold commonly occurs in deposits such as Maybrun, even modest-sized deposits may be economic. The basalts at Maybrun are remarkable for amphibolite-facies rocks because of their extremely well-preserved delicate volcanic textures, including quench textures.The Maybrun Mine is one kilometre south of Atikwa Lake, in the Wabigoon sub-province of the Superior structural province, 75 km southeast of Kenora, northwestern Ontario, at longitude 93°35'W, latitude 49°25'N (Davies, 1973). Archean metavolcanic and metasedimentary rocks and intrusions underlie the area. Goodwin (1970) concluded that the mafic and minor felsic metavolcanic rocks, as well as the overlying metasedimentary rock s, were an eastward extension of the lower cycle of the Keewatin type section for the Lake of the Woods area. He estimated that the stratigraphic thickness of Keewatin rock s in this area is about 6900 m, of which 87% is basalt. The flows contain numerous interlayered sills, predominantly of basaltic composition; they have been extensively folded, faulted, metamorphosed to amphibolite facies and intruded by numerous felsic bodies, most importantly the Atikwa Batholith."

Jan 1, 1983

By R. E. G. Caines, P. Alport

"Operating heavy equipment in Labrador, where the winters are 8 months long and the temperature frequently drops below -40°F (-40°C) for days and sometimes weeks presents unique problems in both the operation and maintenance junctions. Winterization programs must be well designed and implemented at the proper time. These programs must include the proper selection of fuel oil, engine oil, hydraulic oils, greases, cooling system fluids, etc. More often than not, modifications have to be made to the original equipment in order that it can be operated safely and economically in the Canadian North. Manufacturers usually design equipment for a less harsh environment and the user makes adaptations by trial and error.Operators have to be trained for the proper operation on ice- and snow-covered roads in an open-pit mine. Special emphasis must be put on haulage road conditions. In this paper, the authors will cover some specific maintenance procedures, equipment modifications and operator training problems experienced by the Iron Ore Company of Canada in its open-pit operation in Labrador.IntroductionT he Iron Ore Company of Canada is engaged in open-pit mining , concentrating and pelletizing of iron ore. The company operates in two provinces, Quebec and Newfoundland (Fig . 1) . The Knob Lake operation "", based in Schefferville, Quebec, has mine sites located both in Labrador and Quebec . The Caro l Lake Project is situated in Labrador, 25 kilometres east o f the Quebec border at Labrador City. The Carol operation mines, concentrates and pelletizes it s o re before rail transportation to the seaport o f Sept-lies via the Quebec North Shore and Labrador Railway."

Jan 1, 1984

By Y. J. Yu, C. D. Zhang, Y. S. Zhao, W. G. Liang, Y. D. Geng, J. L. Bi

"In this study, the coefficient of thermal expansion (CTE) and thermal conductivity (TC) of shale in two perpendicular directions, vertical and parallel to the bedding of the rock, are firstly measured by experiment. The experimental results show that the CTE of the shale in the vertical direction is 1.69 times as much as that in the parallel direction, while the TC in the parallel direction is 1.83 times larger than that of the vertical direction. Based on the no initial strain assumptions, numerical simulations for the thermal cracking in shale are carried out with the obtained coefficients. Using finite element method and thermal-mechanical coupling theory, two fracture mechanical parameters, KI and J-integral of the shale are also analyzed for the shale thermal fracturing. The simulation results show that both KI and J-integral reach the maximum when the fracturing angle equals to 0° in the shale, namely parallel to the bedding direciton. It is also found that the two fracture parameters decrease with the fracturing angle increasing. Additionally, the thermal fracturing effect of the shale is evaluated under a given scenario. The study is significant for shale oil or gas recovery by in situ pyrolyzing method.INTRODUCTIONOil shale is regarded as a kind of unconventional resource that can contribute to production of shale oil and hydrocarbon gases (Rahm & Dianne, 2011). As is known that there is a large deposit of oil shale in China, and present technology for exploiting oil shale still concentrates on open-pit mining, obtaining shale oil by retorting shale on the ground (Li, Tang, Xue, Zheng, & Du, 2014; Qian, Yin, 2008). However, this technology has a bad effect on the environment and leads to severe resource waste for utilizing oil shale. Exploiting oil shale by in-situ method for ‘green mining’ is widely necessary in China (Kang, Wang, Cao, Liang, Chang, & Liu, 2013; Waters, Dean, Downie, Kerrihard, Austbo, & McPherson, 2009; Zoback, Kohli, Das, & McClure, 2012). One of effective method to exploit shale oil is heating oil shale in-situ underground. For instance, the in-situ conversion process (ICP technique) from Shell Company etc. used a direct heating method, and convectional heating oil shale underground by injecting superheated steam from Mining Technology Institute, Taiyuan University of Technology and constructing horizontal fracture in vertical wellbore from Chevron Company use indirect heating method (Chaudhary, Ehlig, & Wattenbarger, 2011; Hazra, Lee, Economides, & Moridis, 2013; Zhao et al., 2010). The convectional heating method contains complicated procedures with phase transition in double-media of fracture-matrix of oil shale subjected to multi-physical fields coupling including stress, fluid and temperature (Zhao et al., 2010). The characteristics of thermodynamics, solid mechanics and seepage of oil shale have been investigated separately (Hopkins, Rosen, & Hill,1998; Kang, Zhao, & Yang, 2008; Yang, Zhao, Kang, 2010; Zhao, Yang, Feng, Liang, & Kang, 2008; Zhao, Cao, Zhao, Lin, & Wang, 2008). However, it is quite difficult to solve constrained problem of each physical parameter in multi-physical fields coupling for oil shale pyrolysis."

Jan 1, 2015

By Arthur Dubé

An account is given of the developments brought about in the last fifteen years by metallurgical research in the field of heat treatment of steels. The practical aspects of these developments are especially emphasized. Methods of representation of the phase-change during austenitizing and sub-critical transformation of austenite are described and the importance of time-temperature-transformation charts for the planning of heat treatment cycles is shown. Special copies such as retained austenite and internal stresses developed on quenching are also discussed in some detail. Due to the interest shown currently in these problems, it has been thought advisable to describe briefly the underlying principles and present some of the results already available.

Jan 1, 1945

By D. -A Tremblay

Dynamic wetting spread factors and interfacial heat transfer coefficients were determined for aluminum droplets solidifying on copper substrates, The spread factors were determined from the droplet geometries while the heat transfer coefficients were obtained by solving inverse heat conduction problems, 1-D and 2-D heat transfer models are presented and the results they provided are compared, For the latter, a sensitivity analysis was also performed to determine the influence of thermophysical properties and boundary conditions. Experiments were alternatively carried out with three different gaseous atmospheres and the dynamic wetting spread factors were correlated to the interfacial heat transfer coefficients.

Jan 1, 2005

By Ralph W. Edie

"IntroductionTHE GOLDFIELDS AREA in northern Saskatchewan has be-come important in recent years because of numerous discoveries of pitchblende. The area is underlain by rocks of Precambrian age and, because of metamorphism and hydrothermal alteration, the geology in the vicinity of the pitchblende deposits is exceedingly complex and presents a challenge to all geologists •working in the district. This paper is a contribution to the geological literature of the area and presents a description of rock types, supplemented with petrographic, chemical, and spectrochemical data.Field work in connection with this paper was carried out during the summers of 1948, 1949, and 1950 while the writer was employed as assistant geologist for the Crown Corporation, Eldorado Mining and Refining ( 1944), Limited, Gold-fields area. Laboratory work was undertaken at the Massachusetts Institute of Technology during the winter months of 1949-50 and 1950-51 and extended through the summer of 1951.With the exception of SiO2and FeO, all of the new analyses ( 1) presented were carried out by quantitative spectrographic techniques under the supervision of Dr. L. H. Ahrens at M.I.T. Many of the techniques have only recently been developed at that Institute and detailed laboratory procedures have not yet been published."

Jan 1, 1952

By J. Worden, D. Hughes, S. Smart, H. Zughbi

The enterprise wide optimization (EWO) of steelmaking and manufacturing is a multi-level, hierarchical problem which spans higher level corporate planning and scheduling through to the lower level operations of processes that produce and manufacture steel. External and internal system dynamics combined with process unit co-ordination create complex changing circumstances for the enterprise. This paper presents a scoping study as a prelude to enterprise wide considerations at an integrated steelworks to help inform the choice of appropriate model types and optimization techniques. The hierarchical, multi-level structure of the enterprise and the important spatial-temporal scales to consider are defined. Insights into the system were gained by analyzing a large set of dynamic operational data. Over two years of data were subject to both univariate and multivariate analysis with the intent of understanding the complex interrelations of energy flows on site, the inherent system dynamics of the energy network, system operational modes, aspects of planning and scheduling and the coordination between major processing units. This analysis was further used to evaluate the performance of the system in regards to energy utilization and understand the potential economic benefits derived from improved operational decisions.

Jan 1, 2015

By Jeanne B. Percival, Paul Ramaekers, Charles W. Jefferson, Pat A. Hunt, Eric G. Potter, Katherine E. Venance, William Davis, Sean A. Bosman

"A 10-cm thick clay-rich layer near the top of the Manitou Falls Formation of the Athabasca Group is unusual in its breccia texture, alteration, and detrital mineral composition relative to the adjacent overlying and underlying sedimentary beds. This layer is composed of angular quartz grains set in an illite >> kaolinite + dickite matrix. Deformed clay-rich fragments within the layer have very similar mineral assemblages. The presence of euhedral accessory minerals including Ti-oxides and aluminophosphatesulphate minerals points to a diagenetic/hydrothermal origin. The presence of individual grains of Kfeldspar and amphibole is unusual relative to the typical Athabasca quartz arenite; originally, these minerals were probably included in detrital quartz and subsequently liberated during fracturing. The textures and alteration characteristics suggest that this layer is a hydraulically-fractured unit, which has experienced hydrothermal fluid alteration - a possible pathway distally related to uranium mineralization Une couche argileuse de 10 cm d’epaisseur pres du sommet de la Formation de Manitou Falls du Groupe d'Athabasca est remarquable par sa texture brechique, son alteration et la composition de ses mineraux detritiques qui different de ceux des couches sedimentaires sus- et sous-jacente. Cette couche est composee de grains de quartz angulaires dans une matrice composee d’illite >> kaolinite + dickite. Des fragments deformes riches en argile dans cette couche presentent des assemblages mineraux tres similaires. La presence de mineraux accessoires idiomorphes dont des oxydes de titane et des aluminophosphates-sulphates suggere que ces derniers ont une origine diagenetique / hydrothermale. La presence de grains de feldspath-K et d'amphibole est inhabituelle comparativement aux arenites quartziques typiques de l’Athabasca; initialement, ces mineraux constituaient probablement des inclusions dans le quartz detritique qui ont ete subsequemment liberees pendant la fracturation. Les textures et les caracteristiques de l'alteration suggerent que cette unite a subi une fracturation hydraulique et a ete alteree par un fluide hydrothermal - possiblement en lien avec les effets distaux de mise en place de la mineralisation en l'uranium."

Jan 1, 2013

By G. E. Norman, A. L. Mckague

"The new smelting process commenced operation in 1978. The pelletizing and sinter plants were replaced with slurry-fed roasters and the blast furnaces with electric furnaces. The existing converter aisle and matte handling facilities remained unchanged.Process DescriptionNickel-copper concentrate is partially roasted in two slurry-fed fluid bed roasters. After gas cleaning, the sulphur dioxide gas is transferred to the acid plant. The roaster product is conveyed to two electric furnaces for smelting to produce a waste slag and furnace matte. The slag goes to the disposal area and furnace matte containing the metal values is processed in the converters for further removal of iron and sulphur.The final matte containing about 75 per cent metal values is shipped to the refinery in Norway.The commercial smelter was designed for 2135 tonnes per day of concentrate, with an availability of 85% . Roasters and electric furnaces were sized at 117 per cent of design, or 1250 tonnes per day on each of two lines. Concentrate storage capacity in the plant is sufficient for two to three days' plant operation.The new smelting process will be discussed under the following headings:Concentrate Slurry HandlingFeed PreparationRoaster OperationRoaster Gas CleaningCalcine TransferElectric Furnace Operation and Process Control Converting and Matte HandlingUnder these headings, process control , equipment changes, and plant performance after three years' operation is reviewed. A brief discussion of accident prevention , and working environment is also included ."

Jan 1, 1984

By W. M. Goodwin

"IntroductionIN THE preceding paper we have learned about Canada's resources of metallurgical coal. There is an adequate amount in Nova Scotia, a very large reserve on the eastern flank of the Rocky mountains, and a strictly limited supply on the Pacific coast. Added to these is an unknown quantity of coking coal in the Peace River district, at present rather isolated but possibly capable of industrial development in the future.The chief use of metallurgical coal is to make iron and steel. For this, an adequate supply of iron ore is required. So we should now scan the Canadian supply of iron ore, the possibility of its increasing use at home, and the probable markets abroad.Trade in iron ore tends to be international, as is the case with many other raw materials. The present tendency with iron and steel, in contrast, is to keep its manufacture within national boundaries, and there is no evidence that this will change much in the years to come. We should keep these two points clearly in mind when considering the disposal of iron ore from Canadian mines. We should remember, also, that the modern blast furnace and steel plant has such a large output that a correspondingly large population, reasonably compact, is needed to consume its products.Large Ore Supply in East, Small in WestCanada has now four major iron ore fields, well situated to serve adequately the eastern half of the country. Wabana .and Labrador are well placed to serve overseas markets and plants on the eastern seaboard and eastern interior of the United States and Canada."

Jan 1, 1952

By J. Suarez Condezo, E. Herrera Alarcon

The Ilo Smelter Modernization Project will require treating the slag from the Peirce Smith converters in Slag Cleaning Furnaces using pig iron technology. Currently the slags from the converters show variable magnetite contents. The copper contained in this slag is recovered in Reverberatory Furnaces, where the smelting rate was improved due to the high silica content of the converter slag. Preliminary industrial tests where developed to clean the slag from converters using pig iron. The results showed that the magnetite content has a significant influence in this process. This work describes the actions that are being implemented in the converter operation to control the magnetite content in the slag in order to maintain the high copper recovery of the smelter when the new facilities are commissioned. This task will demand a strong control of both the slag chemistry and converter practices in order to get the copper recovery considered as the design criteria (~97.4%).

Jan 1, 2007

By Helmut Ehnes

Over 330 million accidents at work happen world wide every year, only counting those leading to more than four days absence. More than 350,000 end fatal. Two million people more die every year due to work-related diseases. To sum this up: around 2.4 million people die every year because of work conditions. Among many risky industries, mining stands out. While mining represents just 1% of employees globally, it unfortunately represents 8% of all occupational fatalities. Mining operations go along with a variety of hazards. Not only in large operations, as they first come to mind, but also in the manifold small scale mines, with an estimated 13 million labourers worldwide exposed to substances such as dust, mercury and other chemicals, while also dealing with poor ventilation, inadequate space and overexertion. But is the number of severe accidents and diseases inevitable or can we change this situation? We can make mining sustainably safer, but we need a successful strategy to do so. A high potential lies in Vision Zero. Vision Zero is a prevention strategy for a safe future without fatal or serious occupational diseases, work accidents and traffic accidents. First defined as early as in the 19th century by Eleuthère Irénée du Pont, its very successful elements were adopted by many European countries first aiming at road safety, then extended to safety and health at work. Vision Zero?s holistic elements cover technology, workplaces, rules, and people as fields of action. By focussing on severe and fatal accidents, its application increases the level of safety and health overall.

Aug 1, 2013

By S. Orzecki

The KGHM Copper Refinery Plant, Glogów 1, has operated for 35 years and -increased its capacity almost ten times.Cathode quality, expressed in terms of the total impurity content, has undergone a five-fold improvement. The present refining capacity is equivalent to 240,000 metric tonnes of copper cathode, with a total impurity content of 20 ppm, inclusive of 10 ppm Ag. These accomplishments result from combined implementation of current technological progress in electrolytic refining and KGHM's own solutions applied to the Glogów Refinery. The quality improvement measures feature both lowering actual current density, despite an increase in nominal current density, and diminishing the role of non-ion mechanisms which transfer impurities to cathodes. The paper contains a detailed discussion of these issues and outlines possible measures aimed at further production and quality improvements.

Jan 1, 2007

By W. Rostoker

Packing Experiments The porosity and most of the other physical properties of a coherent mass of any material built up by the packing together of discrete particles will obviously vary with, and be governed by, the manner of association of the particles. The relation of packing to powder metallurgy has been discussed in some detail by at least two authors. Packing Theory Theories of particle packing have been put forward by C. C. Furnas and A. E. R. Westman. Although their approach to the problem is not the same, their conclusions are similar. In the process of packing, they visualize the voids of a uniformly sized material becoming filled with particles of a smaller size, and the voids between these being filled in turn with still finer particles. Obviously, if this process is carried ad infinitum, the resultant mass will have the same density as the constituent particles. In practice, of course, such a density of packing is never attained. In addition, the premise is made that successive particle sizes must fit into the voids left by the immediately larger particles- an assumption requiring definite size gradations and also particle shapes. It remained, then, for theory to correlate relative diameter ratios, and proportions and numbers of sizes of particles, for requisite packed densities. Briefly, the following principles were postulated: (a) For an infinite diameter ratio between largest and smallest sizes, an infinite number of particle sizes in proper proportion is required to give natural density. (b) For a given diameter ratio, there is a maximum number of permissible particle sizes for maximum packed density (Furnas). (c) Provided the particle shape is spherical, or approximately so, the proportions o particle sizes can be calculated. (d) The ratios of successive diameters of particles are in geometric progression.

Jan 1, 1947

By Donald Carlisle

"IntroductionTHE OPINION is held by many persons outside the mining industry, and by some within it, that mine •operators customarily find it advantageous to mine •only the richer parts of orebodies and to leave behind, perhaps permanently, leaner material which could be mined only at a lesser profit. This opinion and the inference which might be drawn from it that 'gutting' of mineral resources is a common feruture• of the mining industry are prejudicial to the intertsts of the industry and deserve careful scrutiny. Oddly enough, a theory of mine economics which gives much support for the opinion was advanced first by members of the mining profession itself, has been repeated •several times in mining literature, and to my knowledge has never been adequately refoted.According to the theory, selective mining of the rich ore first on a large scale will yield substantial gains and these gains do not merely reflect the desire of 'money minded investors' for a quick return but derive from the logical application of compound interest rates and the concept of ;present value. W. O. Hotchkiss and R. D. Parks (1) illustrate the reasoning with a hypothetical example in which an orebody of 4,000,000 tons may be mined either in its entirety in forty years at $1.00 per ton profit or selectively with the recovery of only the richest half in twenty years at $1.50 per ton profit. They show that, with Hoskold rates of 4 and 8 per cent, the present value of profits from mining only the richer 2,000,000 tons exceeds the present value of profits :from mining the whole orebody by about 20 per cent."

Jan 1, 1953

By A. K. Chetin, W. W. Fitkin

"The reservoirs of Mississippian Mi-dale beds and Frobisher beds found in the Weyburn field lie at the north-western termination of a broad productive belt extending 120 miles along the northeastern rim of the Williston basin. These carbonates, and inter-bedded evaporites, originated during cycles of marine transgression and regression, and were deposited as rock types characteristic of shoal, lagoon, and basinward shelf environments. The Frobisher-Alida Beds, which form a secondary reservoir to the main Midale Beds of producing zone are composed of oolit1c, fragmental-bioclastic, vugular limestone capped by an impervious dolomitic mudstone. Production is controlled by localized structural features resulting from de-positional build-up. Excellent reservoir conditions are accompanied by an active water drive. The Frobisher Evaporite, consisting of massive primary anhydrite with dolomitic veinlets, forms the floor seal for the Midale beds oil accumulation. A significant facies transition into an oolitic, bioclastic, vugular limestone characterizes this unit. Beyond the depositional margin of the evaporitic facies, marked increases in porosity and permeability of the en-tire reservoir are noted. Carbonate units overlying the areal extent of the Frobisher Evaporite exhibit a greater degree of metasomatism, dolomitization, and more abundant secondary anhydrite.Porous carbonates comprising the producing zone of the Midale beds are divided into an oolitic, fragmental bioclastic, vugular limestone, and an overlying granular marly lime-stone unit, capped, by the Midale Evaporite. Oil is accumulated in a stratigraphic trap bounded above and be-low by primary anhydrite and truncated by the post-Mississippian erosional surface. Mississippian strata dip basinward from this erosional surface in a broad homocline exhibiting only minor irregularities. Rapid lateral and vertical porosity and permeability variations are common. Localized, separated, porous lenticles contain interstitial water in areas where the Midale beds are underlain by the Frobisher Evaporite. The major portion of the field, however, is capable of water-free production. Bottom and edge waters are found in certain portions of the field. Productive limits are tentatively defined around most of the present field perimeter. A large area along foe southern edge of the field remains open to future development. Probable ultimate remaining recoverable crude oil reserves, as of September 30th, 1958, were estimated by Mc-Daniel Consultants Ltd. to be in excess of 330 million barrels."

Jan 1, 1959