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By Gerald Sherman

LARGE part of the mining industry is still under the shadow of the depression, and unwilling to undertake changes in plant or methods of operation that require large preliminary expenditures of money. Certain metals command fair prices: nickel, tin, and molybdenum. The precious metals, gold and silver, have been given greater values by natural processes of economics or by proclamation, but are of so much less importance in industry, in total value, and number of men employed, that they have not greatly raised the average for the mining business. The increased value of gold which was established in 1933 has stimulated .the search for new deposits, and aided efforts to revive some of the old mines 'Where it is hoped to find quantities of marginal ore now become profitable. The higher price did not increase production very much for 1934, but two discoveries of major importance, and others yet to be proved, will help later. The two referred to are the Lupa gold field in Tanganyika Territory, and the Silver Queen mine on Soledad Mountain near Mojave in California. The first was recently discovered, and is being developed by the East African Goldfields, Ltd. Uncompleted explorations of the croppings early in the year had exposed for measurement and sampling to a shallow depth, three ore shoots as gregating 7400 ft. in length and 6 ft. in width, containing 0.375 oz. of gold per ton. In the Silver Queen. an ore-

Jan 1, 1935

By Roswell H. Johnson

What becomes of the water which must have filled the oil and gas sands at the time of deposition, has long puzzled students of oil and gas and has found expression in Munn's well-known article on the hydraulic theory. Both Munn and Clapp have pointed out that in the Appalachian field the deeper sands carry increasingly less proportionate amounts of water. It seems to me probable that the principal source of oil and gas has been in the shales in proximity to the sands which now contain these products. The sand spits which mark off the lagoons from the sea comply particularly with the requirements of a limited sand imbedded in shales rich in organic matter. Cunningham Craig has objected to this view that the rich organic muds of lagoons are found only at the surface. That such muds do extend to considerable depth 1 am assured by Prof. Douglas W. Johnson, who has made an extensive study of the Atlantic Coast marshes. As any particular sand body becomes weighted by a heavier and heavier overburden, the result of increasing deposition, a part of the very large percentage of water in the uncompacted sand and mud is forced out. The water percentage of freshly settled mud is vastly higher than that of the resultant shales, or even of a very porous sand. If beds of less compressible material meet or underlie the shales in question, there will frequently be a lateral motion along such beds to some point where the upward movement will be resumed. We find in our laboratory work here that oil, gas, and water have extremely slight capacity for gravitational sorting while in a state of rest, but when moving the gravitational sorting is readily accomplished. As the oil, gas, and water pass a body of larger pores, the gas, owing to its lack of capillary attraction, is retained in the large pores. This has been predicted by Washburne, Blatehley and others on the ground that the water has a higher capillarity and grips the finer pores in such a way that there will be a greater proportion of oil and gas in the large

Jan 1, 1915

By B. A. Rogers

The etching effect that is produced on a piece of polished iron or steel when it is heated in hydrogen or in a vacuum seems to have been observed first by Osmond,' who believed that he could distinguish four systems of grain boundaries on a piece of steel which had been heated in hydrogen. In a number of other investigations, samples of pure iron were found, after heating, to have complex networks in which two or three systems of grain boundaries could be detected. It was further noticed that samples that had been polished plane before being placed in the furnace were, after treatment, roughened and undulating over their entire surfaces. From a comparison of the temperature of heat treatment with that of the A3 transformation, it was concluded that the changed appearance of the samples was definitely related to the latter phenomenon. Certain other deductions were made but these are not of importance here and only observations on the appearance of the samples will be reviewed. Ewen2 heated a strip of polished iron in a vacuum in such a way that one end was maintained at a temperature of 1000" C. and the other at 580" C. On the cooler end there was outlined a simple polyhedral network, and at the hotter there appeared the complex systern of lines ant the undulating surface characteristic of iron which has passed through the A3 transformation. He found that in going from the cooler toward thc hotter end the sample maintained much the same character of surface up to the beginning of the transformed area, but that near this region doublc grain boundaries were of frequent occurrence. Rawdon and Scott concluded that the simple type of network brought out by heating a sample of pure iron in a vacuum was of the same type as that developec by ordinary etching methods. They also confirmed the observations of

Jan 1, 1929

By R. D. Pehlke, J. V. Gluck

A study was made of' the effects of up to five additional solutes on the thermodynamic activity of zinc in dilute solution with molten bismuth in the range 450" to 650°C. The experimental measurements were made in a multielectrode galvanic cell apparatus employing fused LiCl-KCl as the electrolyte. The solute additions included indium, lead, tin, cadmium, copper, silver, antimony, or gold. A range of positice and negative interactiotls with zinc was covered. The experinzer~tal observations were cowlpared with the activity coefficients calculated usitlg either Wagner's first-order Taylor series rnodel or a proposed second-order solution itrteraction model. hi general, the truncated first-order Taylor series proposed by Wagner gaue good results for "dilute" solutions (XBi > 0.90) contaitzing up to six solutes. The second-order model, which includes a second-order cross-interaction term, produced a slight improvement in predictions for solutions with XZn = 0.015 and a significant improvement for solutions with XZn = 0.050 hear the limit of Henry's law region). Seveval of the quaternary solutions studied contained a total solute content of 0.215 mole fraction, and fairly good success was achieved in predicting the activity coefficient 01- zinc. ThE study of thermodynamic interactions between dilute solutes in liquid metallic solutions has occasioned much recent interest. It is useful to recall in this respect that Wagner's well-known expression for the activity coefficient' is a practical application of the problem of representing a given function, i .e., In ?, by means of a sequence of polynomials. No specific physical model of a solution is involved in its use. As suggested by Wagner, a Taylor Series is used to expand In ? about a point of infinite dilution with respect to all solutes. The partial differential coefficients of the series have been termed "interaction parameters". Various authors'-6 have proposed formalisms for parameters, the definitions being designed to meet some specific experimental or physical condition. A usual assumption is that terms above first-order in the Taylor Series may be neglected. In that case, the logarithm of the activity coefficient is expressed as a linear function of solute concentrations. The resulting expression is presumed valid for any number of additional solutes as long as the solution can be regarded as "dilute". This assumption can be termed "the hypothesis of additivity". However, experimental tests of that hypothesis for quaternary or higher-order solutions have been extremely limited. Primarily such tests have been confined to studies of effects of added metallic elements on either the activity of carbon or the solubility of gases in liquid iron.7-13 The only known previous study of an all-metal system is the limited work of Okajima and pehlke14 on the effects of multiple solute additions on the activity of cadmium in liquid lead. The present investigation is a portion of the work to determine the effects of various solute additions on the activity of zinc in dilute solution with molten bismuth in the range 450" to 650C It was shown for such ternary solutions that second-order Taylor Series terms could be evaluated at the same time as first-order terms, with no additional experimentation required. A second-order solution model was described which, under certain conditions, is a rigorous representation of solute activity in a ternary solution. (In the sense employed in this paper, the term "model", as distinguished from "equation", is taken to mean an empirical correlation or formalism, but not a hypothetical physical system per se.) Presumably such a model could be extended to produce a better representation of In ? in solutions of even higher order. The feasibility of a generalized Taylor Series approach to solution interactions and inclusion of second-order terms also has been discussed recently by Lupis and Elliott in independent work concurrent with the present investigation. In addition, they discussed empirical means of estimating certain second -order coefficients.17 The utility of such solution models rests on the ability of a truncated series to represent adequately the experimental facts in multicomponent solutions. Questions that arise include: Do the second-order terms really make a significant contribution? How far away from "dilute" solution may such models be applied? Are the types and varieties of the additional solutes important? among others. In order to provide some answers to these questions, an experimental study was made of the effects of two or more additional solutes on the activity of zinc in dilute solution with molten bismuth. Comparisons were then made with calculated activity coefficients obtained using the previously determined ternary interaction parameters. INTERACTION MODELS As an example of the approach to defining activities in multicomponent solutions, consider the Taylor Series expansion for a quaternary system, i.e., three dilute solutes. Writing terms through second order, the result is:''

Jan 1, 1968

By Arthur Winslow

Location.—The Liberty Bell gold-mine is in the San Juan region, in the southwestern corner of Colorado. It is situated about 2 miles from the town of Telluride, near the summit of the Uncompahgre range, at the head of Cornett basin, at an altitude of 11,000 feet, and in a district of excellent record in the past and of great promise for the future. In the immediate vicinity are such well-known and important mines as the Smuggler Union, with a total production of over $12,000,000; the Virginius and Revenue Tunnel group, with a production of probably $5,000,000; the Tom-Boy, with a production of probably at least $3,000,000; the Japan, the Cimarron, and a number of others. History.—The first prospecting in this district is reported to

Jan 1, 1900

By L. F. Mondolfo

An aluminum-copper 4 pct Cu alloy aged at room temperature for times increasing up to 78,000 hr was annealed at 170°C and the hardness and electrolytic potential determined during retrogression and subsequent aging. It was found that there is a change of behavior with increasing time of aging at room temperature which indicates that, given sufficient time, retrogression disappears and the room-temperature aging tends to progress directly into the high-temperature aging. WHEN an age-hardenable alloy is aged at low temperature after proper quench, changes of properties and structure take place. If this material is then heated to a temperature higher than the previous one, but still well below the solution-treatment temperature, the properties and structure changes produced by the low-temperature aging disappear and the material apparently reverts to the as-quenched condition, ready to undergo aging from the start. This phenomenon is termed reversion or retrogression. First discovered by Cayler3l it has been extensively investigated, as shown by the number of publications listed in the bibliography. From all the information available the following facts emerge: 1) All aeg hardenable alloys can be retrogressed.9 13, 19) 24, 33, 41, 42, 44, 47, 53, 54, 61, 63, 64, 66, 73, 78 2) All the properties changes that take place during aging at low temperature can be retrogressed to a smaller or larger extent.4,5,7,12,19,32,49,50,57,58,60,67,75,76 67, 75, 76 3) Retrogression requires that the temperature be well above the preliminary aging temperature. If the difference between the two temperatures is small, Little or no retrogression takes place.7,20,32,33,41,49 57. 65 4) The larger the difference between the preliminary aging and the retrogression temperature, the faster and more complete is the retrogression.20, 33, 41, 48, 65, 67 5) Retrogression can be produced several times in the same alloy.23, 35,41,57,59 6) The amount of retrogression that can be obtained depends on the aging temperature. Alloys aged at the lower temperatures can be retrogressed the most. The higher the preliminary aging temperature the less retrogression can be produced.20,25,33,37,44,49,54,58 7) Appreciable retrogression after aging at elevated temperatures is possible only if the preliminary aging has lasted a short time. After a certain time of aging at high temerature retrogression does not take place any more,:5,6,9,10,11,21,40,58 8) During retrogression the Guinier-Preston zones redissolve and disappear. The other precipitate

Jan 1, 1960

By A. D. Marriott, J. V. N. Dorr

This paper reviews recent developments in the application of classification practice to the origination of fine-grinding flow sheets and traces the history of the mechanical classifier from its initial application for separating cyanide process sands and slimes down to its present six or more distinctly different applications at copper concentrators; it undertakes to show also, by reference to diagrammatic fine-grinding flow sheets and accompanying operating data from nine copper concentrators in western North America, the advantages gained from improved classi-ficiation flow sheets at these properties in terms of reduced grinding costs, improved flexibility of operation or increased recovery. Comparison is only made between different fine-grinding flow sheets at a given plant and no attempt is made to compare different concentrators, on account of ore variations and differences in metallurgical objectives sought,. The adoption of the flotation process in recent years, and especially the development of selective flotation, has brought a demand for much finer grinding than formerly. This has caused much thought to be given to grinding efficiency, and today there is hardly a mill where the grinding flow sheet is not under close study and subject to frequent changes. When closed-circuit grinding was introduced into metallurgy some years ago, its value was recognized at once, and since then the combination of mills and classifiers has been regarded and operated as a grinding unit. Apart from variations in both the grinding and classifying elements of this unit, there have been many variations in grouping tried by different mills to suit varying conditions of ore and plant limitations. Although operators feel that in most cases their present flow sheets are on trial, and the data on present work are often incomplete, we have felt that a discussion of the progress that has been made and an endeavor to show present trends and their results should be of use to the profession. We have therefore prepared flow sheets of some of the larger mills with which we have been in contact and present them with available data as to their results, in the hope that they may be of service now rather than later when practice may have become more standardized and more complete records and analyses have been made. We believe that the data given,

Jan 1, 1930

By A. S. Hewitt

After an interval of fourteen years, saddened for all of us by the death of David Thomas, the father of the anthracite iron-trade, first president of the Institute, and by the untimely loss of his successor, Alexander L. Holley, whose memory we are about to honor by loving services, the members of the American Institute of Mining Engineers have conferred upon me for the second time the office of president, under circumstances similar to those which led to the choice in 1876. Then the whole world was represented at the great exposition of industry which was held in Philadelphia to celebrate the one hundredth anniversary of our declaration of political independence. In 1890 it is our privilege to receive as guests the members of the British Iron and Steel Institute, who, with singular and graceful felicity, have appointed a meeting in the United States in the year when we pass from the second to the first place in the international column of the production of iron, and thus celebrate our industrial independence. For the honor of being chosen to extend to our distinguished guests the right hand of fellowship and a hearty welcome I return to my associates the grateful acknowledgment of one whose chief claim to your favor is to be found in his love for the professional occupation in which we are all engaged, and in his efforts, public and private, to promote its advancement into new fields of usefulness. In order to indicate the full significance of the visit of our foreign guests at this time, it will be proper to explain briefly the origin, aims and work of the Iron and Steel Institute. It unquestionably owes its birth to the International Expositions held in London in 1851 and 1862, and in Paris in 1867. These expositions served to break down the jealousies of nationality and to diffuse a better knowledge of industrial processes. Trade-secrets, which had been carefully guarded, became common property; manufacturers who had previously regarded themselves as rivals formed bonds of union and ties of friendship, as the results of an intercourse which

Jan 1, 1891

By Oliver Bowles

Two striking events marked the year 1871-the establishment of the A.I.M.E. and the beginning of the portland cement industry, the most spectacular of all the nonmetallics in its development. Just as David Saylor's first portland cement, made in a little mill at Allentown, Pa., in that year was the forerunner of a mighty industry, the products of which in 1942 were made in 155 plants scattered throughout the country (having attained a value of nearly $300,000,000), so the Institute from its small beginning has attained a membership of many thousands, likewise decentralized into a series of individual sections of wide geographical distribution. Concurrent with the establishment of the Institute was also the invention of the steam drill, followed by the compressed-air drill about 1904. These mechanical drills were so immeasurably in advance of the hand drill and hammer used previously that quarrying and mining of present-day magnitude could never have been attained without them. Some outstanding occurrences have marked this eventful three quarters of a century. The concrete age, with its enormous demands for cement, aggregates and steel, is of primary importance. Of interest also is the shift of fertilizers from the organic to the mineral field. Nitrates, primarily obtained

Jan 1, 1947

By T. W. Lippert

CUBA fancies herself the "pearl of the Antilles" and, by many, Jamaica is called "blessed." But far to the southward lies what is seemingly the Caribbean's most glittering jewel, the sparsely-settled, Spanish-speaking United States of Venezuela, indeed blessed by nature to a lavish degree. Not a large country, Venezuela is leaping from the donkey to the airplane under the impact of its natural wonders. Angel Falls, dwarfing Niagara and seldom seen by man, is hidden in the cold, primitive and unexplored Guiana highlands along the southeast border. A few hundred miles northwest are the low and torrid coastal plains from which gush unlimited black-gold streams of oil. About midway are the Llanos-low-lying, savanna-type grasslands, beneath which large deposits of bauxite are as yet barely touched by the explorer's diamond drill. And jutting starkly upward 2000 ft from a surrounding expanse of savanna is a small mountain (see front cover), 11 miles long and 1 mile wide. It is, or was, La Parida.

Jan 2, 1950

THE composition and quality of finished steel depend upon selection and proportioning of the raw materials of the charge as well as upon control of furnace practice. This chapter deals only with the raw materials of the basic open-hearth process that are important in determining the composition of the steel or slay. They are the metallic charge, oxygen-bearing materials, fluxes, alloying and deoxidizing additions, and certain refractory materials used for maintenance of bottoms. Other refractories, which may affect the slag composition, are discussed in Chapter 3. Wide variations are possible in the type and composition of charged materials but certain limiting relations among the elements of the charge must be observed. Since the process consists essentially of refining by the oxidation of undesired elements, a balance must be established between the sources of oxygen and the elements in the charge that are subject to oxidation (see Chapters 2 and 7). For example, if it is desired to use a high ratio of blast-furnace hot metal to scrap, it is necessary to add an oxygen-bearing material such as ore or mill scale to eliminate the excess carbon and silicon that are present in the hot metal. An example of the opposite extreme is the use of a metallic charge composed entirely of steel scrap. With this type of charge, it is common practice to substitute burnt lime for limestone as a flux and to charge some carbonaceous material such as coke to avoid an excess of oxygen in relation to the elements of the charge that are subject to oxidation. Elements such as copper and nickel, which are not oxidized or eliminated by any other reaction, may be introduced into the charge only to the extent to which they are permissible in the finished steel. An example of adjustment of the charge for elements of this type is found in the use of steel scrap high in copper. In this case, metallic components of the charge other than the scrap should be low in copper, or a sufficiently high ratio, of pig iron to scrap should be charged to dilute the copper from the

Jan 1, 1964

By G. H. Clevenger

(Continuing the discussion of the paper of James Johnston, presented at the New York meeting, February, 1914, and printed in Bulletin No. 85, January, 1914, pp. 107 to 133.) This paper cannot fail of being of great interest and value to all who are interested in the cyanide process, on account of the important developments which it records. Mr. Johnston is to be commended for the large amount of detail which he gives, and the company and its management for permitting the publication of data of this character, which while of great value to others could well be considered private property. It might be discussed from a number of standpoints: First, as an example of recent practice in mill and cyanide plant construction; second, the mill practice; third, the cyanide practice; and fourth, the new features in cyanide treatment involved. Perhaps a more vivid way of expressing it would be : First, the equipment or tools with which the various operations are carried on, are they the best and most efficient which could have been selected for their respective uses; and, second, is the best use in every case made of these tools? It may be well inquired is the highest possible recovery of silver made at the lowest cost per ounce recovered? For after all, the making of the greatest ultimate profit is inseparably associated with successful metallurgical practice; there must therefore be at all times a careful balance maintained between recovery and cost of obtaining it. I wish to call attention in a very general way to the equipment used and to an anticipation of questions which are bound to arise in this connection. However, the. bulk of my discussion will be confined to the presentation of certain additional data, together with a more or less general discussion showing the line of development which leads up to the present practice and .the applicability of certain features of it to similar problems elsewhere. There are a number of vital points of broad general interest involved in Nipissing low-grade practice upon which metallurgists will by no means be agreed to which I wish to call particular attention in the hope that it will lead to the presentation of data y others of practice in other districts which will' assist in reconciling this divergence of opinion.

Jan 7, 1914

By Paul M. Tyler, Herbert R. Mosley

Strategically situated in almost the heart of the leading fertilizer-consuming area of the United States, Tennessee long has ranked second only to Florida as a phosphate-producing state. Since 1932 its share of the national output of phosphate rock has increased steadily, and in 1937 its production mounted to an all-time record. More significant even than the increase in tonnage are the forward strides in technology. The Tennessee Valley Authority's research program has led to quasicommer-cia1 operations using hydroelectric power to manufacture concentrated phosphatic fertilizer that is used to further the farmer education program designed to streamline the fertilizer business and halt the appalling waste of farm land by soil erosion. Even more stimulating to chemically minded imaginations is the production of elemental phosphorus by a private company that not only has succeeded in extracting it from the phosphate rock in electric furnaces but actually has contrived to capture it and to transport it safely in tank cars. New values have been created for low-grade phosphate deposits, and the economic life of reserves has been lengthened while the waste of former years goes back into the mills for recovery of its values by modernized methods. Tennessee's phosphate-mining industry dates from the discovery of blue rock in Lewis County in December 1893. Its known reserves are of the order of 101,500,000 tons, which compares with the production of 825,099 tons in 1937; that is, 21 per cent of the phosphate-rock output of the whole nation. The total output reported from 1894 until July 1. 1938, was approximately 19,000,000 tons. Offcial estimates of reserves are overly conservative and evidence submitted before a joint Congressional committee in November 1938 places "probable" reserves at more than 6,000,000,000 tons.

Jan 1, 1942

By Herbert R. Mosley, Paul M. Tyler

Strategically situated in almost the heart of the leading fertilizer-consuming area of the United States, Tennessee long has ranked second only to Florida as a phosphate-producing state. Since 1932 its share of the national output of phosphate rock has increased steadily, and in 1937 its production mounted to an all-time record. More significant even than the increase in tonnage are the forward strides in technology. The Tennessee Valley Authority's research program has led to quasicommer-cia1 operations using hydroelectric power to manufacture concentrated phosphatic fertilizer that is used to further the farmer education program designed to streamline the fertilizer business and halt the appalling waste of farm land by soil erosion. Even more stimulating to chemically minded imaginations is the production of elemental phosphorus by a private company that not only has succeeded in extracting it from the phosphate rock in electric furnaces but actually has contrived to capture it and to transport it safely in tank cars. New values have been created for low-grade phosphate deposits, and the economic life of reserves has been lengthened while the waste of former years goes back into the mills for recovery of its values by modernized methods. Tennessee's phosphate-mining industry dates from the discovery of blue rock in Lewis County in December 1893. Its known reserves are of the order of 101,500,000 tons, which compares with the production of 825,099 tons in 1937; that is, 21 per cent of the phosphate-rock output of the whole nation. The total output reported from 1894 until July 1. 1938, was approximately 19,000,000 tons. Offcial estimates of reserves are overly conservative and evidence submitted before a joint Congressional committee in November 1938 places "probable" reserves at more than 6,000,000,000 tons.

Jan 1, 1942

By Richard L. Ash, J. H. Kelley, W. H. McCracken, William Bellano, J. D. Morgan, D. R. Mitchell

Rubber-tired shuttle cars are finding increased use as gathering units in under-ground mines. As the name implies, they shuttle back and forth between the loading machine and the section transportation system. In many mines their use has in-creased the efficiency of the loading and gathering operations, resulting in increased output per man employed and decreased costs per ton. A car motivated by cable reel is shown in Fig I, and a car with battery power in Fig 2. A brief chronological account of the development of rubber-tired haulage equip-ment follows: 1936. J. H. Fletcher1 installed his first unit for the Blue Bird Coal Co., Carrier Mills, Illinois. This unit consisted of a battery-powered industrial tractor and a trailer with drop-bottom doors. The coal was transported for short distances to a hopper for discharge into mine cars. 1938. A battery-powered self-contained shut-tle car with rubber-tired wheels was built by the Joy Manufacturing Co. Two units were installed for the Katherine Coal Co., Lumberport, West Virginia. The shuttle car consisted of a materials-receiving body with a conveyor in the bottom to move the coal forward during loading and to unload the coal at the discharge station. 1938. A cable-powered shuttle car with four-wheel drive and four-wheel steer was developed by A. L. Lee. Special wheels mounted on king pins on the car permitted all four wheels to be steered. The cable reel was driven by a torque motor to give the cable proper tension during the payout and uniform tension when rewound on the reel. 1940. A Joy shuttle car equipped with trolley poles and a cable reel was developed to operate on a double trolley-wire system.2 This unit was installed at a potash mine of the International Minerals and Chemicals Corporation at Carlsbad, New Mexico. It is believed to have been the first installation of its kind, and the first of shuttle cars for handling material other than coal. 1941. Truck haulage3 was introduced in the Tri State District by the Eagle-Picher Mining and Smelting Company. Storage battery electric trucks were rebuilt to handle a bottom-dump trailer. 1941—Joy shuttle cars were installed in a mine of the United States Gypsum Company, Oakfield, New York. 1943—Joy shuttle cars were installed in several bauxite mines.4,5 1945—Joy shuttle cars installed in a lime-stone mine. Because of the nature of bituminous coal beds trackless equipment has had its greatest application in bituminous coal mining. Usually a shuttle car is filled by a continuous type of loader. In Fig 3 is shown a continuous machine loading coal into a battery-powered shuttle car, 48-in. coal. However, intermittent types of load-

Jan 1, 1949

By T. D. Murphy

The element silicon, with its usual partner, oxygen, plays the same role on this planet relative to inorganic materials as carbon and hydrogen play with respect to living organisms. The crystallographic structure of silicon dioxide (SiO,) consists of one atom of silicon well-nigh inseparably bonded to four contiguous atoms of oxygen, a gas of but slightly more than half its atomic weight, forming a three-dimensional network of SiO, tetrahedra (Dietz, 1968). This wispy arrangement is the fabric of the mineral quartz which is one of the harder, more abrasive, and chemically stable raw materials to be found in Mother Nature's cupboard. Most of us are vaguely familiar with the observation that nearly 60% of the lithosphere to an approximate depth of 10 miles is composed of these two elements, which proportion actually rises to about 75% if the atmosphere, hydrosphere, and biosphere are included (Parker, 1967). Elemental silicon is a brittle steel-gray metalloid with a density of 2.42 and does not occur in nature. In its limited commercial form, which is still brittle and metallic in appearance, its density drops to 2.33. It combines with oxygen to form the gaseous oxide SiO, or the solid dioxide SiO, (analogous to its congener carbon in CO and CO,); a tetrachloride SiCl, (analogous to CC1,); or, combining with oxygen and one or more metal ions, forms the largest rock-making family of all, the silicates. Further, next to the feldspars, quartz is the most abundant known mineral and, in some form or another, accounts for roughly 12% of surficial terrestrial rock. It is this so-called "free silica" to which your attention is chiefly directed in this chapter. In any such consideration of silica, its several crystalline phases with their attendant differing physical properties appear worthy of delineation. Alpha quartz is the only one of this interesting polymorphic family that is thermodynamically stable at normal pressures and temperatures up to about 573°C. The low phases of tridymite and cristobalite can exist in the so-called metastable state below 117°- 200°C but seldom occur in nature in these two different crystal forms (Sosman, 1965). Opaline silica, now considered by most researchers to be a variety of cristobalite, occurs in abundance and is the only exception. The three remaining polymorphs, keatite, coesite, and stishovite, also are metastable under ambient conditions. Keatite, however, is not known to occur naturally and has only been synthesized in the laboratory. The other two have been identified in submicron sizes and in microscopic amounts, occurring naturally as a result of high order shock-wave pressures generating quite elevated temperatures-such as might accompany the impact of a large meteorite on a hard sandstone terrain (Chao, et al., 1962). An intriguing characteristic of these silica minerals, and one which has very practical applications, is their extremely variable densities. The classic 2.65 specific gravity of alpha quartz drops to 2.20 in tridymite, cristobalite, and lechatelierite (natural silica glass), as well as in many man-made glasses of commerce which are merely noncrystalline or amorphous solids in the form of super-cooled liquids which can no longer change their shapes (Pauling, 1950). It rises again to 2.50 and 2.93 for keatite and coesite, respectively, and finally becomes a reported 4.35 for stishovite-nearly a 50% range in density for the known physical combinations that silica naturally assumes (Frondel, 1962; Konnert, et al., 1973; Pecora, 1960).

Jan 1, 1975

By AIME AIME

CONVENTION plans for the A.I.M.E. Regional Meeting to be held on the Minnesota Iron Range Aug. 12 to 1.5 are being completed to give the visiting member?s from all parts of the country a wide variety of technical and recreational features. High spots of the social events are the official dinner, dance, luncheon and golf: and of course, special provision is being, made for the entertainment of visiting ladies. The technical sessions will fit in with scheduled trips to view all phases of mining, beneficiation and transportation of iron ore. Men from the West and Southwest will find much of interest in the detail of the mining operations. A trip to the steel plant of the

Jan 1, 1941

By Lennart Wellenius

LAISVALL - ONE OF THE BOLIDEN MINES Until the Aitik Mine (2,000,000 mtpy) started in 1968 the Laisvall Mine (1,200,000 mtpy) was the biggest unit of about 20 producing mines, belonging to the Boliden Company Ltd. As shown in Fig. 1 the mines are spread over a wide area. Most of them are small complex ore mines (50,000 - 300,000 mtpy), for which reason the total mine production does not exceed 5,500,000 mtpy. When our company was invited to present a paper, Laisvall was chosen because it is the biggest European galena-mine in production today. The Laisvall Mine is situated in the county of Norrbotten, Sweden, at the eastern border of the Caledonian mountain-chain. The road distance to Slagnäs, the nearest railway station, is 60 miles. The railway between Slagnäs and BOLIDEN's smelting plant, the Rönnskär Works, is 140 miles long. PRODUCTION STARTED IN 1943 In the Autumn of 1938 a boulder was discovered, consisting of sandstone with galena, on the shore of the Lake Stor-Laisan. The boulder came from an Eocambrian sandstone formation, which is overlain by Cambrian-Silurian rock.

Jan 1, 1970

IN A broad sense, the subject of slag control includes not only the adjustment of the composition of the slag but also of its relative weight in terms of percentage of the metal-bath weight. The slag is made up essentially of (1) oxides formed by oxidation of silicon, manganese, phosphorus, and iron in the charge, (2) SiO2, MnO, and other oxides charged as such, and (3) lime charged or fed to the heat to neutralize the “acidic”: oxides present (Si02 and P2O5). Obviously, if practically perfect control were possible over the composition of the charge as well as over the oxidation process during the melting period, both slag weight and composition would be very nearly predetermined, and the control problem would be solved. Unfortunately, we have only a somewhat. imperfect control over these factors, so that beginning at about the lime-boil period in the heat, and later in the early refining period, it becomes necessary for the first helper, as the heat progresses, to make quick estimates of the composition and physical state of development of the slag (as well as of the amounts of phosphorus, sulphur, and carbon in the metal) from which he can judge how much extra lime, roll scale, fluorspar, and other additions will be needed not only to give the desired final slag composition, but also to hasten the complete fusion or shaping to a desired viscosity in the liquid state. The discussion in this chapter is limited essentially to those more or less practical rapid methods of slag estimation that have been used, or at least tried, for these purposes under actual open-hearth shop conditions. Another aspect of importance here is the extent to which the freedom of choice to the operator is limited by available charge materials, product specifications, and the oxidation and other chemical- reaction effects which inevitably occur under the conditions of this furnace process. For a better understanding of these control limitations and of the chemical and physical background of the subject, the reader is urged to read at least part of the discussion in Chapters XVII and XIX. Charge materials are discussed in Chapter IV, and many of the details of charging, melting, and refining practice closely related to slag control are given in Chapters VI and VII.

Jan 1, 1944

By Paul Weaver

OF the four papers that comprise this TECHNICAL PUBLICATION, three are case histories of individual geophysical prospects, subsequently tested by drilling. The bibliography of Dr. Barton's published scientific papers† includes investigaions in physiography and surface geological mapping, as well as his geophysical papers, and from this list it is to be observed that he early recognized the place of different types of geophysical prospecting methods in the search for geological structures of economic importance. Moreover, his viewpoint was not merely that the structures should be found, but that the geophysical data should be examined quantitatively to determine the geometry of the structures. In other words, that although these data are insufficient to deduce a unique form for the structure that caused the effects measured in the data, the engineering computations should be carried-out to give as much of a definite configuration to he structure as the data permitted, in order that the testing of the structures could be conducted in the most economical manner and with the idea that the experience so gained could be later incorporated in the study of structures subsequently found. Dr. Barton continually emphasized the quantitative use of geophysical observations, whereas at the time that he began his specialization in geophysics it was considered sufficient to use observations only qualitatively. He, more than any one else, was responsible for -the first volume on geophysical prospecting issued by the Institute in 1929, and his three articles in that volume stressed the quantitative use of geophysical prospecting. The fourth article in this present TECHNICAL PUBLICATION is a further contribution to this branch of geophysical interpretation, and is a supplement to the paper in the 1929 volume, "Calculations in the Interpretation of Observations with .the Eötvös Torsion Balance." From the successful' demonstration by Dr. Barton of the usefulness of quan-

Jan 1, 1944