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By B. W. Frazier

IN the numbers of the Engineering and Mining Journal of June 27th and July 11th, 1874, there appeared some very complete statistics of the working of some anthracite blast-furnaces belonging to a large establishment in this country, followed by calculations of the heat requirements of the furnaces, similar to those which have been made for European furnaces by Mr. I. Lowthian Bell, Prof. Gruner, Prof. Akerman and others. To the author of these valuable papers, Mr. John A. Church, of New York, the thanks of American iron metallurgists are due for this attempt (the first, to my knowledge at least), to attack systematically and scientifically the problem of economy of fuel in our anthracite blast-furnaces, by applying the formulas obtained from European practice and from the experiments of European metallurgists, to the determination of the amounts and the modes of distribution of the heat production and absorption in our furnaces. In order to facilitate a comparison of the results thus obtained for the anthracite furnaces in question with those obtained for the best types of European coke furnaces, I have reduced to the same standard of heat units (the product of the ton and the degree Centigrade), and placed side by side, the calculations of the heat requirements of one of the furnaces of the Clarence works, as given by Mr. Bell, of a furnace at Pouzin, on the banks of the Rhone, given by Prof. Gruner, and of the anthracite furnaces for 1869-73, as given -by Mr. Church. Table I shows the different conditions of working of the three furnaces, of which Table II gives the respective heat requirements. I have made this latter table in such a manner as to give for each furnace its heat requirements, both according to the views of Mr. Bell and those of Prof. Gruner. Mr. Bell assumes that all the carbonic acid produced by the decomposition of the carbonate of lime of the charge, is reduced to carbonic oxide by contact with solid carbon ; also, that the carbon of the pig iron is a portion of that deposited in the ore in the upper part of the furnace, by the dissociation of carbonic oxide. Prof. Gruner, on the other hand, assumes that all the carbonic acid of the carbonates of the charge escapes unreduced, and that the carbon deposited in the upper part of the furnace, by the dissocia¬tion of carbonic oxide, is again converted into carbonic oxide or

Jan 1, 1875

By C. V. Corless

We are living at a period of the world's history in which social phenomena are on so vast a scale, are of so profoundly soul-searching a nature, and are occurring in such rapid succession in the great world drama in which we are both actors and spectators, that, in our efforts to obtain a rational point of view in relation to them, our minds may fail to discern the simple in the complex and our understanding is liable to become confused or even overwhelmed. To the social student whose: scientific training has convinced him of the truth of the evolutionary law, Natura non facit salium, it is neither the vast scale of the events, their deeply soul-stirring nature, nor their rapid succession that matters so much, as the discovery of the underlying principle or law in accordance with which the disintegration and reintegration, which are the two aspects of social evolution, or indeed of evolution everywhere, are occurring. He is most deeply concerned in seeking an answer to the question: Have we in the present great and perplexing upheavals in human society, whether regarded in Central Europe, in Russia, in Great Britain, or in America, a really new cause at work, or, have we, though on a very large scale, merely new manifestations of the working out of an old principle? When we think of the appalling struggle in Europe, into which the world's greatest exemplar of democracy was finally drawn, no one has any hesitation in admitting that the great conflict was fundamentally a life-and-death struggle for self-preservation and self-propagation on the part of autocracy. The variations we meet with in the statement of the cause of the war arise mainly from differing distances of perspective; but in the last analysis all agree that the autocratic system of political gov ernment, which found its very soul and center in Prussian despotism, was consciously arrayed in a final "world-power-or-downf all" struggle against a love of freedom which was steadily widening and deepening throughout the world, and particularly throughout those parts of the world where this love of freedom and justice hasfound expressionin democratic institutions. It is not irrelevant to our discussion to recall in passing that this most imposing structure ever conceived by the human mind as an instrument of tyranny is lying today an irretrievable mass of ruins, completely over-

Jan 1, 1920

By Edgar R. Kendall

A knowledge of the fundamental principles of locating, sampling, testing and evaluating materials is essential in prospecting for mineral aggregates. In this discussion, mineral aggregates will be considered sand, gravel, crushed stone and slag that are used as materials of construction. The quantity of mineral aggregates produced in the United States during the year 1935 for such purposes was roughly 165,000,000 tons, about 60 per cent of which was sand and gravel, 37 per cent crushed stone and 3 per cent crushed slag. The total value of this material was approximately $100,000,000. It is apparent therefore that the prospecting for suitable mineral aggregates is of considerable economic importance. In prospecting for mineral aggregates, the methods employed are the same whether the organization is large or small. In the large organization there may be available geologists for locating sources of supply, a land acquisition department to arrange for the necessary options or permits, engineers to do the sampling, a laboratory for testing, and a board of consulting materials engineers to make the final selection. Even small organizations must follow the same general procedure, though the responsibility for the selection of aggregates may rest with one man, who may or may not be an engineer, but who must depend entirely upon his own judgment. Locating the Supply The initial step in prospecting for mineral aggregates is the locating of suitable, adequate and economic sources of supply for the project in mind. Commercial plants in the vicinity should be investigated and a survey made of the existing structures that have been built of aggregates from these sources. If the structures are rather old and show no signs of deterioration, it is fairly good evidence that the aggregate is satisfactory. If materials of the proper quality can be obtained from commercial sources in sufficient quantity, and delivered to the job economically, it

Jan 1, 1942

By F. O. Garrabrant, F. S. McNicholas, Robert Henderson, R. U. King

Several years ago, it was decided to experiment with the use of high-pressure water to bring in finger hangups and reduce the amount of secondary blasting necessary. It was argued that the velocity effect of the high-pressure water would bring down hangups without unduly wetting the ore. Water under a head of about 550 ft. was installed in certain slusher drifts. Ordinary ¾ in. water hose, with a nozzle opening of % in., was used, and water was impinged on the fines under a hangup. Results were excellent. About half the total number of hangups were brought in with high-pressure water without blasting and the cost of this part of the slushing operation was reduced about 50 per cent. Operations were speeded up, dust counts and safety hazards were reduced, and a more desirable working place was secured. The additional water added to the ore was under one per cent and caused no inconvenience in slushing, haulage, or crushing operations. Usually the ore would absorb all of the water, so that none of it would enter the loading drifts. The entire mine, developed by slusher drifts, is being equipped with high-pressure water. Heating Mine by Compressor Cooling Water Several years ago, the problem of heating certain sections of the mine during freezing weather became important. It was calculated that there was sufficient heat in the compressor cooling water to heat the incoming ventilating air current to above freezing, if such heat could be transferred from the water to the air. All schemes of radiation from pipe were rejected as too cumbersome, costly and impractical. It was thought that by spraying the heated water from the compressor cooling system into the incoming air, a satisfactory heat exchange could be accomplished. The only objection was that the sprayed water would freeze and might fill the air-intake drift. However, when water at about 75° to 80°F. was sprayed at the rate of 200 gal. per minute through a bank of sprays into the incoming and freezing air current, this air was thereby heated to above freezing; and although some ice was built up in the air drift, the amount was not objectionable. Occasionally the built-up ice was picked down into the outgoing water stream, which removed it. The entire south and westerly parts of the mine were prevented from freezing. Concreting for Hangups Considerable trouble was experienced in securing hangups of fine ore in slusher fingers that needed repairing. Regular methods of timbering were unsatisfactory. Now, a slab of concrete is poured over the top of the muck by Pumperete machine, almost filling a finger, which gives a satisfactory slab to work under for making the needed repairs. Derailers Some trouble has been caused by motor-men not observing safety lights and

Jan 1, 1946

By B. W. Frazer

In the numbers of the Engineering and Mining Journal of June 27th and July llth, 1874, there appeared some very complete statistics of the working of some anthracite blast-furnaces belonging to a large establishment in this country, followed by calculations of the heat requirements of the furnaces, similar to those which have been made for European furnaces by Mr. I. Lowthian Bell, Prof. Gruner, Prof. Akerman and others. To the author of these valuable papers, Mr. John A. Church, of New York, the thanks of American iron metallurgists are due for this attempt (the first, to my knowledge at least), to attack systematically and scientifically the problem of economy of fuel in our anthracite blast-furnaces, by applying the formulas obtained from European practice and from the experiments of European metallurgists, to the determination of the amounts and the modes of distribution of the heat production and absorption in our furnaces. In order to facilitate a comparison of the results thus obtained for the anthracite furnaces in question with those obtained for the best types of European coke furnaces, I have reduced 60 the same standad of heat units (the product of the ton and the degree Centigrade), and placed side by side, the calculations of the heat requirements of one of the furnaces of the Clarence works, as given by Mr. Bell, of a furnace at Pouzin, on the banks of the Rhone, given by Prof. Gruner, and of the anthracite furnaces for 1869-73, as given by Mr. Church. Table I shows the different conditions of working of the three furnaces, of which Table II gives the respective heat requirements. I have made this latter table in such a manner as to give for each furnace its heat requirements, both according to the views of Mr. Bell and those of Prof. Gruner. Mr. Bell assumes that all the carbonic acid produced by the decomposition of the carbonate of lime of the charge, is reduced to carbonic oxide by contact with solid carbon ; also, that the carbon of t,he pig iron is a portion of that deposited in the ore in the upper part of the furnace, by the dissociation of carbonic oxide. Prof. Gruner, on the other hand, assumes that all the carbonic acid of the carbonates of the charge escapes unreduced, and that the carbon deposited in the upper part. of the furnace, by the dissociation of carbonic oxide, is again converted into carbonic oxide or

By Dan Crackel, G. G. Ramos, Mark Heisel

INTRODUCTION Feasibility studies indicated that a cratering type stoping method was best suited to the character of the first ore block at Carr Fork. This method known as vertical crater retreat (VCR) has since been modified to a combination cratering and deck blasting using VCR drop raises for initial undercut development . The modified form retains many of the advantages of VCR while allowing high tonnage production blasts which have offset many of the disadvantages. FIRST CONCEPTS AND PREMISES Geologic Considerations The Steep Highland Boy (SHB) skarn orebody, the first of several blocks being developed, is a steeply dipping 70° to 90° limb of a syncline, with a width averaging 25 m (82 ft). The bed has a consistent east-west strike length of over 400 m (1300 ft) and extends from the surface to depths of over 1000 m (3300 ft). The footwall is highly fractured quartzite and the hanging wall grades from garneti te to limes tone and hornfe 1s. Because of the limestone in the hanging wall, the hanging wall appears more competent than the footwall. The ore is garnetite with lenses of massive sulphide and magnetite. The quartzite footwall is highly fractured not only because of the bedding but also due to the folding and intrusion of the quartz monzonite. This irregular footwall outline of some stopes in- creases the likelihood of excessive dilution. The principal ore mineral is chalcopyrite with some bornite. The garnetite ore is quite variable in terms of compressive strength and drillability. In addition to the sulphide and magnetite lenses, it is transected by clay- altered dikes and major and minor north-east faults. TABLE (1) gives the range and mean strengths of the rocks. Investigating Mining Methods Initial consideration of a suitable mining method centered around maximum safety and efficiency with minimum potential dilution. The following major methods were considered and investigated. Cut and fill mining was eliminated because of low productivity, the cost and problems associated with providing fill, and the relatively unsafe nature of the method. Sublevel caving was rejected due to the unpredictable cavability of the waste and the geometry of the ore body. Conventional sublevel or blasthole methods require excessive development, as fan and ring drills are limited to efficient drilling in the 18 to 25 m range (60 to 80 ft). Mining downdip with equipment drilling small diameter holes would have required eight separate extraction/drill horizons with crosscuts and associated excavation in the main ore block. The use of down the hole (DTH) machines cap- able of drilling 165 m (6g in) diameter holes

Jan 1, 1981

By Benjamin Lustman, Robert F. Mehl

THE study of the high-temperature oxidation of pure metals, intensively pursued experimentally since the pioneer work of Pilling and Bedworth1 and supplemented by the recent theoretical work of Wagner2 is now well advanced. The important field of low-temperature oxidation-i.e., oxidation extending only through the temper color range of thicknesses with the formation of thin oxide layers in the range from o to 1000-2000 Angstroms-has not, however, reached so satisfactory a state, owing largely to the experimental difficulties that attend the formation and study of thin films; most of the work has been performed on abraded specimens whose surface irregularities approximated the thickness of the films formed. It has been pointed out that the rates of oxidation of different crystal faces are different and that the difference may be related to the orientation relationships that obtain between the metal crystal and the superimposed oxide crystal; it has also been suggested that this orientation dependence should manifest itself in rates of oxidation and perhaps also of corrosion in aggregates bearing preferred orientations. 3,4 An attempt to measure the rates of oxidation of different crystal faces of alpha iron demonstrated this difference in rate,4 but the dependence of rate on orientation was not simple; the method of measuring thickness, consisting of a color comparison with barium stearate multi-films of known thickness, was not wholly satisfactory. For these reasons it was felt that a study of the rate of oxidation of single crystals prepared with surfaces as smooth as possible, using a sensitive method giving true film thickness, should be profitable. Copper was chosen because of the ease of reduction of the primary oxide film and because the orientation relationships between metal and oxide and the composition of the oxide films formed at low temperatures are known; for thin films formed at low temperatures, Cu2O alone occurs.22-24 EXPERIMENTAL PROCEDURE Various methods of surface preparation were attempted in order to obtain a surface that would oxidize uniformly and reproducibly. Electrolytic polishing by the method of Jacquet5 and electrolytic and mechanical polishing followed by annealing in vacuum and in purified hydrogen at various temperatures were tested. The procedure finally adopted consisted in a fine metallographic polish followed by an anneal in purified hydrogen at temperatures of 900º to 1000°C. for 12 hr. or more. The surface so produced was very bright and smooth, with no trace of specular etching (though some grain-boundary etching was observed); indeed, fine scratches produced by the final polish were entirely removed by the high-temperature anneal.

Jan 1, 1941

MODERN mining is based on drilling--everything else stems from that. U. S. and Canadian mining companies and suppliers of mining equipment are constantly seeking new techniques and tools for increased drilling efficiency. Ultimate goal is increased bit-against-rock time. Just how important their efforts are can be seen through a legitimate extension of available statistics. In Canada some 70 million ft of drilling per year is required. While the number of feet actually drilled in the U. S. is unknown, it is possible to compare U. S. and Canadian mineral production, excluding oil and coal. In the U. S. mineral value was $4200 million and across the border $836 million. Taking into account the number of drilled feet required to produce Canada's total, the U. S. total would be 365 million ft in 1953. A saving of 14 per ft would reduce over- all metal and nonmetal mining costs some $3.65 million per year. This does not take into account other indirect savings. Methods have changed and there have been structural and metallurgical advances in blasthole practice in the last ten years. The Editors of MINING ENGINEERING in the articles on the following pages present the most significant innovations coupled with results in the field. Environment plays an important role in selection of materials and equipment -but while unanimity does not exist throughout the industry in reference to drilling problems, a definite trend is evident. For the story of that trend read the articles on the following pages.

Jan 9, 1954

By Samuel Shallcross

TO principal function of the Bell limestone mine, of the American Lime & Stone Co., at Bellefonte, Pa., is to supply raw material to the company's modern rotary kiln plant at Bellefonte. Because mining costs are naturally higher than many open quarries with more favorably lying strata, it cannot compete, except to a limited extent, in the markets for road material and fluxing stone. In the broad sense, mining does have an advantage over the average open quarry when the end products are designed for and controlled by process and final inspection for the exacting demands of the industrial and chemical markets. Approximately 80 per cent of the output of the Bell mine is sold in the industrial and chemical markets. And as higher standards are set each year for construction and agricultural work, the remainder of the mine output goes to these two classes. Mining produces more fines than open quarries, and these fines are difficult to market; on the other hand, owing to absence of contaminating clay and impure rock, a greater percentage of the output of a mine is marketable. Because of the great production of fines, rotary kilns for lime burning are necessary when the stone must be mined. In 1921 the American Lime & Stone Co. operated 19 quarries and 72 lime shaft kilns spread over an area of 40 miles between Bellefonte and Altoona, Pa. At that time the lime-production capacity of the 72 kilns amounted to approximately 700 tons per day. After 15 years the company operates three rotary kilns and six shaft kilns, with a combined output of approximately 500 tons of lime per day, concentrated in its single Bellefonte plant (Fig. 1). Its only stone-producing plants are now the limestone mine at Bellefonte and a construction-stone open quarry at Union Furnace, near Tyrone, Pennsylvania.

Jan 1, 1936

By Jack M. Swales

Kermac Potash Co., the newest American entry in a rapidly expanding industry, has come on the scene with notable variations in conventional shaft-sinking and mining techniques. Located in the famed potash producing district east of Carlsbad, N. Mex., Kermac started up its mine in November, 1965, to supply ore to the company's 500,000-tpy potash crystallization refinery. In so doing, the company (1) drilled the first large diameter mine shaft in the potash industry and (2) has employed new continuous miners especially adapted for use in thin potash beds. REACHING THE ORE ZONE In its initial mine planning, Kermac, a partnership owned jointly by Kerr-McGee Corp. and the National Farmers Union Development Corp., considered it imperative that the shafts be sunk and equipped as soon as possible and that the mine be developed sufficiently to insure a constant ore feed to the mill when the unit was placed on stream. After examining the alternative sinking techniques available to it, the company decided to accept a proposal by Big Hole Drillers, Inc., to drill the shaft from the surface through various formations of sandstones, siltstone, shales, anhydrite, limestones, dolomite and salts to the potash ore zone.

Jan 12, 1966

By RUSSELL C. FLEMING

THE important advances that have been made of recent years in mining and milling methods and in mechanical equipment at mines need no re- telling, but there has been a remarkable growth in one type of equipment which has gone nearly unnoticed. That is the increasing use of storage-battery locomotives underground. Since the war the number of these locomotives and their field of use have increased tremendously; their growing acceptance represents an al- most complete reversal of opinion from an earlier period when they were generally looked upon as in- adequate for the strain of mine service. At the time when storage-battery powered units were first making their bid for recognition, the use of power in haulage had already passed through several phases; hand tramming, rope haulage, compressed air locomotives, even gasoline locomotives, had all been used, ending finally in the general adoption of the electric trolley locomotive for practically all power-haulage requirements. It was, and is, conceded that the trolley loco- motive met more adequately the varied and severe conditions of mine service than any previous type of haul- age unit. Subsequent developments have had to endure comparison and surpass in performance that type of haulage before changes would be considered.

Jan 1, 1930

By NEWTON B. KNOX

PERU, lying south of Ecuador and having common frontiers with Brazil, Chile, and Bolivia, includes over a thousand miles of the Andean mountains. The coastal plain is arid and narrow and the Amazonian jungle region is of interest only on account of its oil and gold placer possibilities. The mountain zone, however, here forms one of the world's most highly mineralized regions. The Peruvian Andes, like their Bolivian and Ecuadorian counterparts, form two distinct chains separated by the great Apurimac and Maralion valleys; but these rivers cut through the Eastern range to join the Amazon drainage, and the central valley is missing north of the passes thus formed by these rivers; the localities where the ranges are joined are aptly called knots. In addition, in central Peru, there exists a third range lying to the east of the first two and separated from them by the Urubamba and Huallaga Rivers. The Eastern range, however, is of little importance to the miner for few metal deposits are to be found therein except for the gold mineralization in the South. In general, deposition of metals in the Peruvian Andes accompanied igneous intrusions which invaded the folded Paleozoic and Mesozoic rocks during the Tertiary; thus the ore bodies are all typical of shallow or moderate depths.

Jan 1, 1945

By R. T. Hukki

IT is no great exaggeration to say that present grinding practice and economics are largely determined by lining design. A record of outstanding liner wear can be achieved with any liner surface pattern that will positively lock the outer layer or layers of grinding media. With no slippage, lining wear is bound to be slight. At the same time, popular practice calls for tumbling loads of about 50 pct of mill volume to obtain maximum grinding capacity. Innumerable parallel grinding investigations have verified that optimum speed for such a mill lies within 70 to 85 pct of theoretical critical speed. If the mill is speeded up to 100 pct of critical, little or no grinding can be accomplished. Earlier Work on Supercritical Grinding: First investigations concerning grinding at supercritical speeds seem to be very old. Remarkable work on the subject has been performed by White,&apos; and his experiments have been described and summarized by Richards.&apos; White&apos;s contributions seem to have passed unnoticed by Fahrenwald,2,3 whose extensive experiments have been well presented, yet apparently very little appreciated. Additional work on grinding at supercritical speed has been reported, e.g., by Lewenson and Tscherny,&apos; USSR; Anselm and Grunder,&apos;, Germany: and Rose and Evans." Great Britain. Subcritical and Supercritical Speeds: In the formula of the critical speed given in the textbooks of mineral dressing, no factor indicating the coefficient of friction is generally included. If this factor = 1.0, which is equivalent to grinding conditions in a mill provided with heavily ribbed lining, the formula of the critical speed holds as such and grinding is possible at subcritical speeds only. In a mill equipped with a smooth or relatively smooth lining, the numerical value of the friction factor in the denominator of the formula becomes <1.0, indicating that grinding at supercritical speeds should be possible in such mills. It has been recently shown by the author&apos; that a wide supercritical speed range will become available for grinding—and especially for fine grinding—if the basic conditions within the mill have been selected properly. Mathematical analysis of mill dynamics at supercritical speeds&apos; has indicated that the mill speed may be increased if: 1) total mass of grinding medium decreases, 2) mass of the individual grinding piece increases, and 3) the coefficient of friction between the outer layer of medium and the mill lining decreases. It is obvious that the mass of the individual grinding piece will be affected by its shape and by its specific gravity. The coefficient of friction decreases with: 1) increasing smoothness of liner surface, 2) increasing roundness of the grinding piece, 3) increasing fineness of material to be ground, 4) decreasing pulp density, and 5) decreasing hardness (abrasiveness) of the mineral to be ground. In a mill equipped with heavily ribbed lining, practically no size reduction will take place between the lining and the outer layer of tumbling medium, because slippage is prevented. In the overwhelming majority of today&apos;s mills the grinding accomplished is by virtue of cataracting and/or cascading media with some action within the tumbling charge. Sub-critical speeds only can be applied. In grate-type or peripheral discharge mills equipped with a smooth lining a tumbling load of any kind of common medium occupying about 50 pct of mill volume will behave in such a way that practically no slippage will take place. This has been verified in experiments run by the author in the laboratory and in pilot plant mills&apos; equipped with smooth lining. Again, the operation is limited to the subcritical range. In a mill with a smooth lining, grinding will be possible either at subcritical speeds or within a wide supercritical speed range as soon as the basic requirements for a desired speed are fulfilled. In a mill operated at supercritical speed, any point on the liner surface proceeds at a speed greater than that indicated by the formula of the critical speed, while any grinding piece situated in the outer layer of the medium against the lining proceeds in the same direction at a speed less than that indicated by the critical speed. This speed difference produces a very effective attrition grinding zone between the liner surface and the outer layer of the medium. The share of attrition grinding of the total grinding accomplished increases rapidly with increasing speed in the supercritical speed range. The smooth surface of the mill lining may be well illustrated by the surface of a bucking board. The outer ball layer may be similarly represented by the lower surface of a muller. If the bucking board, the material to be ground, and the muller all proceed in the same direction at the same speed, no grinding will result. This is the general situation in the mills of today. If, however, the muller is pulled with respect to the board, moving or stationary, grinding will be accomplished effectively. Although grinding in today&apos;s mills is primarily the result of cataracting and/or cascading media, the principal place of grinding at high supercritical speeds will be the attrition zone.&apos; In the mineral dressing laboratory of the State Institute for Technical Research. Helsinki, Finland, large quantities of different ores have been ground in a pilot plant ball mill (3x3 ft) at a top speed about 230 pct of the critical. With the same mill, theoretical investigations concerning the grinding characteristics of ball mills equipped with a smooth lining have been carried out up to the speed of 313 pct&apos; of the critical. With a smaller mill, the grinding characteristics with a variety of grinding media have been investigated at speeds up to 2000 pct of the

Jan 1, 1959

By Haydn H. Murray, Sam H. Patterson

The term clay is somewhat ambiguous unless specifically defined, because it is used in three ways: (1) as a diverse group of fine-grained minerals, (2) as a rock term, and (3) as a particle-size term. Actually, most persons using the term clay realize that it has several meanings, and in most instances they define it. As a rock term, clay is difficult to define because of the wide variety of materials that compose it; therefore, the definition must be general. Clay is a natural earthy, fine-grained material composed largely of a group of crystalline minerals known as the clay minerals. These minerals are hydrous silicates composed mainly of silica, alumina, and water. Several of these minerals also contain appreciable quantities of iron, alkalies, and alkaline earths. Many definitions state that a clay is plastic when wet. Most clay materials do have this property, but some clays are not plastic; for example, halloysite and flint clay. As a particle-size term, clay is used for the category that includes the smallest particles. The maximum-size particles in the clay-size grade are defined differently on various grade scales. Soil investigators and mineralogists generally use 2 micrometers as the maximum size, whereas the widely used scale by Wentworth (1922) defines clay as material finer than approximately 4 micrometers. Some authorities find it convenient to use the term clay for any fine-grained, natural, earthy, argillaceous material (Grim, 1968). When used this way, the term includes clay, shale, or argillite, and some argillaceous soils. Even though no standard definition of the term clay is accepted by geologists, agronomists, engineers, and others, the term is generally understood by those who use it. Clay is an abundant natural raw material, and it has an amazing variety of uses and properties which will be discussed in this chapter. Clays rank among the leading industrial minerals in both tonnages produced and total value. Their importance is indicated in Table 1, which lists the 1978, 1979, and 1980 production and values according to the US Bureau of Mines (Ampian, 1980). Statistical data summarizing world production of kaolin, bentonite, and fuller&apos;s earth are compiled by the US Bureau of Mines (Ampian and Polk, 1981). The total world bentonite production in 1980 was 6,625,204 st of which the United States produced 4,184,619 st. The total fuller&apos;s earth produced in the world in 1980 was 1,952,600 st of which 1,534,000 st was produced in the United States. The total world kaolin production in 1980 was estimated at 22,971,000 st. Approximately 13 million tons of this total was produced in two countries, the United States and the United Kingdom. World production data on ball clay, fire clay, and miscellaneous clays are not available. As industrial minerals, clays are a complex group that consists of several mineral commodities, each having somewhat different mineralogy, geologic occurrence, technology, and uses. In this chapter these commodities are organized as follows: (1) bentonite and fuller&apos;s earth; (2) kaolin, ball clay, halloysite, and refractory clays; and (3) miscellaneous clay and shale. Bentonite and fuller&apos;s earth are grouped together because they are closely interrelated. Though bentonite is a term based on mineral composition and fuller&apos;s earth is a term based on use, the two are virtually inseparable, because much, but by no means all, clay sold as

Jan 1, 1983

By George Rice

TEN years ago, October, 1914, the author had the privilege of giving an-illustrated address on investigations of coal-dust explosions1 to this Institute at one session of its fall meeting in Pittsburgh, Pa. On the following day, the members had the opportunity of seeing a large-scale explosion test at the Experimental Mine near Bruceton, in which the explosion was made to follow a predetermined path by means of rock-dust barriers of various types, which had prevented the explosive waves from reaching the outlets of, the mine by the shortest paths.2 There was also shown a "home-made rock-dusting machine discharging the dust from a flexible nozzle, and a cement gun operated for the quick erection of a fire or ventilation stopping, such as might be put up after an explosion. Following that paper, there was presented a paper by J. Taffanel, Director of the Lievin testing station in the Pas de Calais, which reviewed the French coal-dust investigations.3 Another important paper was by Howard N. Eavenson, on Coal-mine Explosions Caused by Gas or Dust.4 This paper contains complete lists of explosions that occurred in North America and Great Britain, from early in the 19th century to 1912; in France to 1903, and in Belgium to 1909. No one can look over these lists without being struck by the great number of explosions and the, appalling aggregate of lives lost by them. Although they still happen, we-are hopeful that we have entered on a happier period of freedom from these dreaded visitations, as the result of great increase in knowledge; of the causes and means of prevention. Looking back over coal-dust investigations, there appear to have been periods of advance and of stagnation.

Jan 3, 1925

By G. T. Smith, R. C. Moyer

Cadmium, along with other impurities such as lead, gallium, germanium and indium, is characteristically found associated with zinc ores, the average ratio of zinc to cadmium being about 200 to 1. The increasing demand for cadmium has led most zinc producers to develop a means for its recovery. The separation and recovery of this byproduct constitutes an important development in the metallurgical field. Zinc sulphide concentrates, principally from domestic sources, are processed at Donora Zinc Works and they assay approximately 60 pct zinc, 30 pct sulphur, 0.37 pct cadmium, and 0.8 pct lead. Concentrates are roasted to convert zinc sulphide to zinc oxide. Sulphur evolved as sulphur dioxide is used to manufacture 60º Baume sulphuric acid by the lead chamber process. The roasted calcine is sintered to remove the remaining sulphur and volatile impurities. Fume from the sintering machines is collected by Cottrell pre-cipitators and sent to the Cadmium Department for cadmium removal. The sintered product, a crude zinc oxide, is then mixed with coke and salt and charged into horizontal retorts for reduction to zinc metal. Furnace residues are then passed through a Waelz kiln which recovers practically all of the remaining zinc as an oxide. This oxide is collected by Cottrell precipi-tators and returned to the sintering plant for further processing. The following discussion covers operating procedure, and equipment used in the Cadmium Department for the manufacture of cadmium and its byproducts. (See attached Flow Sheet, Fig 1.) The production of cadmium may be divided into several steps, each of which will be discussed separately. These steps are as follows: 1. Raw Materials—Sinter Plant Cottrell dust, acid sludge and sulphuric acid. 2. Sulphating—Separation of lead. 3. Purification—Separation of impurities other than zinc. 4. Precipitation—Separation of cadmium from zinc. 5. Briquetting—Preparation of sponge for charging to furnace. 6. Smelting—Distillation of cadmium metal. 7. Remelting—Casting into commercial shapes. 8. Recovery of Rare Metals—Separation of germanium, gallium and indium. Raw Materials The raw material, or Sinter Plant Cottrell dust, from which the cadmium is manufactured, is recovered by Cottrell units collecting fume from two Dwight-Lloyd sintering machines. An average analysis of this dust is 36 pct zinc, 1.5 pct sulphur, 17 pct lead, and 5.5 pct cadmium, with associated elements in smaller amounts. A lesser tonnage of material removed from the sintering machine fans, and called fan cleanings, is also treated for cadmium. It is lower grade material and analyzes approximately 41 pct zinc, 1.2 pct sulphur, 14 pct lead, and 4 pct cadmium. Cottrell dust and fan cleanings are delivered to the Cadmium Department by monorail crane in bell-bottomed dump buckets. Acid sludge and 60" Bauine sulphuric acid are received from the Acid Department. The acid sludge is a mixture of lead sulphate, sulphuric acid and zinc sulphate, and is recovered mainly from the floors of the acid chambers or storage tanks. The acid sludge is delivered to the Cadmium Plant in a lead lined bucket. The 60º Baume sulphuric acid is delivered through a lead pipe to a lead lined storage tank. Sulphating Four well ventilated lead lined sulphating tanks, 8 1/2 ft in diam by 12 ft deep, are used. These are steel tanks lined with 20 lb lead on the bottom and 16 lb lead on the ides, equipped with Hastelloy side agitators. 15 hp motors drive 24 in. propellers at 450 rpm. There are water connections to stuffing boxes to keep sludge from entering the bearings. The tanks are covered with removable wooden lids and are connected to marine plywood

Jan 1, 1950

By J. B. Morrow, D. H. Davis

THERE are two general approaches to the problem of increasing profits from an operation. One is to lower expense; the other is to raise income. Mechanical preparation of coal may be used for either purpose but a prudent consideration of many details must precede any decision lest the results be negative instead of positive. It is quite possible that any net gain will result from a combination of the two. Since mechanically prepared coal invariably is a better product qualitatively than a hand-picked coal from the same mine, it is a reasonable expectation that the customer will be willing to increase the producer&apos;s income by paying a higher price. Or there may be the possibility that a combination of mechanical mining plus mechanical cleaning will give a lower over-all production cost for the coal in the railroad car. More likely, there will be found a combination of these two factors. From the customer&apos;s point of view, the competitive delivered cost per B.t.u. considered in relation to such incidental factors as dust nuisance, handling properties, ash disposal, and ash fusibility determines what he will pay. In-a bulk tonnage such as coal, freight is a very considerable part of the delivered fuel cost, and obviously freight paid on incombustible ash has no economic attractions. INCENTIVE FOR CLEANING Coal is prepared in four major ways: l (1) by screening or sizing, (2) by mixing or blending, (3) by cleaning, including hand picking and mechanical cleaning, (4) by dustless treatment. By a combination of any or all of these methods, coal can be prepared to standard specifications. It is easily possible to have good cleaning and still get a poor final product because of faulty screening or mixing, while it is possible to produce a very acceptable product from mediocre cleaning if the coal is well screened and mixed.

Jan 1, 1950

By Donald W. Scott, Nathaniel Arbiter, A. C. Richardson

THIS paper describes the application of amine flotation to a specific problem-that of increasing the grade of magnetite concentrates derived from an iron ore requiring extremely fine grinding for mineral liberation. Experiments conducted on an iron ore from Wisconsin had shown that concentrates containing 60 to 62 per cent iron and 12 to 14 per cent silica could be produced by magnetic separation. The residual silica occurred as quartz and hornblende, either entrained or locked with magnetite. Most advantageous utilization of the concentrate, however, necessitated that the silica content be reduced to about 5 per cent, equivalent to an iron content of 67.5 per cent. It had been demonstrated that tabling of the magnetic concentrate removed sufficient quartz and hornblende to yield an acceptable concentrate, but disadvantages inherent in tabling dictated that flotation be investigated as a substitute. The goals set for the flotation investigation were: (I) the production of concentrates of about 68 per cent iron content from the magnetic concentrate; (2) an iron recovery of about 85 per cent of that in the feed to flotation; and (3) minimum reagent cost. Both batch and continuous flotation tests were employed; the former, to establish the procedure and the latter to verify it. Although the data were obtained on a specific ore, and with a commercial application in view, it is believed that they have a bearing on other problems where amine flotation is being used or is anticipated. SAMPLES Two samples, designated "minus 100mesh magnetic concentrate" and "minus 150-mesh magnetic concentrate," were used for the batch experimental work. They differed only in the degree to which the crude ore was ground prior to magnetic separation. They were stored moist in steel drums in quantities sufficient for all the experimental work reported. This procedure had the advantage of allowing all tests to be made on common samples, but had the disadvantage that the individual flotation samples, because of the difference in storage time, were subject to various stages of surface alteration. Previous work had indicated that common samples were desirable for the batch studies, and it was decided that if these data appeared sufficiently promising the effect of surface alteration could be checked best by continuous tests. The size distributions and the assays of the samples are given in Table I. The minus 150-mesh magnetic concentrate, on which most of the flotation tests were made, assayed 60.9 per cent iron, 13.3 per cent silica, and 0.016 per cent phosphorus. The minus 325-mesh portion represented 78.1 per cent of the sample by weight, and assayed 67.9 per cent iron. Thus, the insoluble, mainly silica, was concentrated

Jan 1, 1945

By Bevan Presley

THERE has been developed at Latouche a rather unusual system of mining which, for want of a better name, has been called the "Latouche system of mining." It is a modified form of shrinkage stoping applicable to orebodies of large or fairly large size where the ground is such that timbering would not be required in stoping. Mention has been made of this method of mining by Birch,1 who gave no details as it had been in use only a short time and the final outcome undetermined. The system, however, has proved to be entirely successful and it is thought that a paper covering it might be of general interest. Before proceeding with a detailed description of the "Latouche system" a brief description of the property and the various mining methods previously used will be given. LOCATION The Beatson mine of the Kennecott Copper Corp. is situated on the west coast of Latouche Island-, in Prince William Sound, Southwestern Alaska, 45 miles east of Seward, the coast terminus of the U. S. Government Railroad. It is a regular port of call for ships on the Southwestern Alaska run. The island is about 12 miles long and 3 miles wide. A ridge of mountains runs the entire length with a maximum elevation of 2500 feet. CLIMATE Latouche has to contend with possibly the greatest amount of precipitation on the North American continent. The annual average precipitation for the past 4 years has been 188 in., with 248 in. for the year 1926. A rainfall of 4 in. per day is not uncommon. In the winter the thermometer rarely falls below +20° F. and the snowfall is usually heavy during the months of March and April.

Jan 1, 1927

By W. C. Hagel, H. J. Beattie

Variations in the secondary phase reactions of six nickel-and cobalt-base alloys were determined as a function of solu-tioning from 1700" to 2200°F and aging at 1200" to 1800° F for times up to 1000 hr. Room-temperature impact energies and hardnesses were also measured. Precipitation hardening of these alloys results mainly from the grain-interior formation of ? &apos;; M23C6 appears principally as grazn-boundary cells which can be eliminated by intermediate high-temperature aging treatments. Cellular precipitation of ?&apos; occurs up to 1500°F in cobalt-nickel alloys devoid of chromium, where precipitation by this mode can be attributed to a large degree of lattice disvegistery. THE usefulness of nickel- and cobalt-base alloys is dependent on balancing the strength and ductility provided by the solid-solution matrix, dislocation-type subboundaries, grain-boundary phases and genera1 precipitation within individual grains. Since equilibrium relationships for complex austenitic alloys are not easily fixed, a satisfactory balance

Jan 1, 1960