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By Charles C. Towle, Irving Rapaport

URANIUM mineralization along the north flank of the Zuni Uplift, in the vicinity of Haystack Butte, was discovered by Paddy Martinez, a Navajo Indian, in the spring of 1950. The find was reported to the Santa Fe Railway Co., which initiated a program of exploration upon its holdings in the district in December of 1950. The Anaconda Copper Mining Co. secured numerous leases in January and February, 1951, and began an intensive exploration and development program in March 1951. The district was extended into the Lucero Uplift in August of 1951 by the discovery of uranium mineralization in Todilto limestone by Joy Sinyella, a Supai Indian living on the Laguna Reservation. Initial reconnaissance was performed in the district by the Atomic Energy Commission in November 1950. A field office under the direction of the Denver Exploration Branch of the AEC was established at Prewitt, N. Mex. in January 1951 to study regional and detailed guides to ore, to evaluate the ore deposits, and to promote the development of the district by providing geologic services for the companies and individuals engaged in exploration. With the development of sufficient ore to warrant construction of a mill, the Grants area of New Mexico has come of age as a full fledged uranium mining district. The carnotite-type deposits of Grants, the first of major economic importance found in limestone, have extended the Colorado Plateau carnotite field into the more complex structure of the Basin and Range Province. General Geology The Grants uranium district is in northwestern New Mexico, along the southern flank of the San Juan Basin, between the cities of Gallup and Albuquerque. The region is at a mean altitude of about 6800 ft, vegetation is sparse, and outcrops are excellent. Mt. Taylor volcanic peak, at an elevation of 11,400 ft dominates the surrounding area. The overlying cliff-forming Dakota sandstone is the most resistant formation in the Grants District and characteristically erodes into dissected mesas as much as five miles wide. The principle uranium ore-bearing horizons are found in the underlying Morrison formation, and the Todilto limestone of the San Rafael group. The Morrison weathers into. a series of steep slopes and precipitous cliffs near the lower part of the Dakota-capped rims, while in contrast, the relatively resistant underlying. Todilto [ ] limestone forms broad benches extending out from the base of these Dakota rims as much as five miles wide. The Todilto benches are covered with overburden to an average depth of about 5 ft in the first thousand ft away from the Dakota rim, but increases to about 200 ft at the base of the rim. In many places however, a thick mantle of upper Cretaceous sediments and Tertiary volcanics "obscures the ore-bearing Jurassic, and precludes exploration. . The known uranium deposits of the Grants District are distributed throughout a zone 85 miles long and about 10 miles wide. Stratigraphy Rocks from pre-Cambrian through Tertiary are exposed in the uplifted areas, but uranium appears to be restricted chiefly to two zones in Jurassic sediments. The Jurassic sediments of the Colorado Plateau have been subdivided into three units, in ascending order: (1) Glen Canyon group, (2) San Rafael group, (3) Morrison formation. The Todilto limestone zone within the San Rafael group has produced the bulk of ore to date, but the promise of the Morrison zone is rapidly increasing. The Todilto formation extends about 300 miles east-west and about 100 miles in a north-south direction. It is composed of a lower, extensive, limestone member and a central, more restricted, thick, pure gypsum member. The Todilto is believed to be of lacustrine origin. The Morrison formation in this area is subdivided, rather arbitrarily, into three members: Recapture Creek, Westwater Canyon, and Brushy Basin. Ore

Jan 1, 1952

By T. M. Morris

THE rate of flotation of solid particles determines the percentage recovery of these particles which can be obtained during a given time interval. It is an established fact that the recovery is greatest in the fine sand size range and falls off on either side of this size range. It is also a fact that the history of the development of concentrating devices has been marked by a desire to recover the small particles: tables were developed to treat material too fine to recover in jigs; flotation recovers material too fine to be recovered on tables. As our ores become more complex and require finer grinding, a greater proportion is in the slow-floating size range. It is therefore of economic importance that the effect of size of particle upon rate of flotation be studied. Many studies have been made along this line. The present investigation attempts to quantify the rate of flotation by means of a rate equation, and then compares the effect of size upon the rate of flotation. It was found that the flotation rate constant increases with increase in diameter of particle in the size range smaller than the optimum size particle. The flotation rate constant decreases with an increase in diameter of particle in the size range coarser than the optimum size particle. This suggested two different actions taking place, and these are discussed. Suggestions for further work in order to improve the flotation rate of both fine and coarse particles are made. The usual method of expressing rate is to plot cumulative percent recovery vs time. If we knew the equation of this kind of curve we could replot it as a straight line, and the slope of the line would be an index of the magnitude of the flotation rate. It is easier to compare straight lines than curves. The basis used for obtaining the equation of the recovery vs time curve is the law of mass action. This law states that the "rate of a chemical reaction is proportional to the 'active masses' of the reacting substances present at any given time." This, of course, implies a constant temperature. We can modify this for our use by using the term flotation reaction instead of chemical reaction and the term floatable particle instead of active masses. dC Thus----— kc [1] where C denotes concentration of particles, t denotes time, k denotes a proportionality constant. If the exponent of C is 1, then we have a first order rate reaction. If the exponent of C is 2, then we have a second order rate reaction. For a first order rate reaction, we obtain, after integration, where k is again a proportionality constant and has the dimension of the reciprocal of time. C, is the original concentration or weight or percentage of floatable particles. C, is the concentration or weight or percentage of floatable particles remaining in the flotation cell after time t. If all particles of the mineral to be floated were capable of floating we could take C, as 100 and C, would be 100 - R, where R is the cumulative percentage recovery of mineral at time t. But it is not usual for all of the particles to be capable of floating, because of surface oxidation, etc. Therefore, we must introduce a factor x which is the percentage of un-floatable mineral. Hence the first order equation is It has been proposed by various workers1-' that this equation describes the flotation rate. More recently N. Arbiter4 states that a second order rate equation fits the recovery vs time curve more closely than does a first order rate equation. Morris- as discussed the evidence presented for this statement. It has been concluded that the first

Jan 1, 1953

By M. J. Coolbaugh

Mining of potash more than 3000 ft beneath the water-bearing sediments in Saskatchewan presented the unique challenge of designing stable mine workings and assuring protection from overhead water in a material that was believed to flow plastically, but whose behavior as a plastic material was not sufficiently known. Under the stress conditions ordinarily encountered in mining most rocks behave as elastic materials; that is, they compress slightly under pressure, and rebound when the pressure is released. Salt and potash, however, are different. Even under the relatively low pressures encountered at shallow depths, these materials become slightly plastic and yield to stress by flowing.* The plastic properties become more pronounced at greater depth and pressure, and the question arises as to whether or not the plastic flow will be rapid enough and exert enough pressure to destroy underground structures or interrupt the mining process.

Jan 5, 1967

By R. G. Knickerbocker

A STURDY and consistent expansion of the metal industry occurred in 1947 exemplified by an increase of approximately 30 per cent in steel consumption over 1946. For this major reason, ferroalloy metals have seen their most useful and important peace-time year. The current domestic rate of consumption of high-grade ferroalloy ores, together with added consumption of new foreign producers as well as for eign nationals' restrictions on high-grade exports, makes very evident the increasing difficulties of obtaining sufficient high-grade ores. This accentuates the need for new and less expensive methods of production of ferro-alloy metals of higher purity from lower-grade domestic resources. As an important factor in preparedness, procurement of these high-grade, -critical ferroalloy minerals and metals for our nation's stock piles is a most important task. Also, this stock-piling can be the means of supplying incentive for the industrial development of the new metallurgical processes and plants necessary for the recovery of ferroalloy metals from our domestic low-grade deposits.

Jan 1, 1948

By C. MeCulloch

A NOVEL practice in the bituminous coal industry is the accelerated method of burning coal to ash used in the laboratory of the Fidelity washery of the United Electric Coal Companies, Du Quoin, Ill. Development of this method has supplanted the tedious float-and-sink process for plant control at this plant. In normal operation the plant operators have available within thirty minutes the accurate ash percentage of the coal loaded in the railroad cars and can therefore make adjustments to maintain a practically uniform quality of washed coal, regardless of the variations in washery feed.

Jan 1, 1937

By T. M. Morris

THE rate of flotation of solid particles determines the percentage recovery of these particles which can be obtained during a given time interval. It is an established fact that the recovery is greatest in the fine sand size range and falls off on either side of this size range. It is also a fact that the history of the development of concentrating devices has been marked by a desire to recover the small particles: tables were developed to treat material too fine to recover in jigs; flotation recovers material too fine to be recovered on tables. As our ores become more complex and require finer grinding, a greater proportion is in the slow-floating size range. It is therefore of economic importance that the effect of size of particle upon rate of flotation be studied. Many studies have been made along this line. The present investigation attempts to quantify the rate of flotation by means of a rate equation, and then compares the effect of size upon the rate of flotation. It was found that the flotation rate constant increases with increase in diameter of particle in the size range smaller than the optimum size particle. The flotation rate constant decreases with an increase in diameter of particle in the size range coarser than the optimum size particle. This suggested two different actions taking place, and these are discussed. Suggestions for further work in order to improve the flotation rate of both fine and coarse particles are made. The usual method of expressing rate is to plot cumulative percent recovery vs time. If we knew the equation of this kind of curve we could replot it as a straight line, and the slope of the line would be an index of the magnitude of the flotation rate. It is easier to compare straight lines than curves. The basis used for obtaining the equation of the recovery vs time curve is the law of mass action. This law states that the "rate of a chemical reaction is proportional to the `active masses' of the reacting substances present at any given time." This, of course, implies a constant temperature. We can modify this for our use by using the term flotation reaction instead of chemical reaction and the term floatable particle instead of active masses. [ ] where C denotes concentration of particles, t denotes time, k denotes a proportionality constant. If the exponent of C is 1, then we have a first order rate reaction. If the exponent of C is 2, then we have a second order rate reaction. For a first order rate reaction, we obtain, after integration, [ ] where k is again a proportionality constant and has the dimension of the reciprocal of time. C, is the original concentration or weight or percentage of floatable particles. C, is the concentration or weight or percentage of floatable particles remaining in the flotation cell after time t. If all particles of the mineral to be floated were capable of floating we could take C, as 100 and C, would be 100 - R, where R is the cumulative percentage recovery of mineral at time t. But it is not usual for all of the particles to be capable of floating, because of surface oxidation, etc. Therefore, we must introduce a factor x which is the percentage of unfloatable mineral. Hence the first order equation is [ ] It has been proposed by various workers1-3 that this equation describes the flotation rate. More recently N. Arbiter4 states that a second order rate equation fits the recovery vs time curve more closely than does a first order rate equation. Morris' has discussed the evidence presented for this statement. It has been concluded that the first

Jan 1, 1952

By R. S. Wagner, H. Brown

Criteria for nucleation with the aid of twin planes during crystal growth from the melt are discussed. It is shown experimentally that bismuth crystals can grow from a subercooled melt in a twinned bismdtic form. A mechanism of growth based on the presence of at least me twin plane is proposed. It is well known that faceted growth can be observed in crystals grown from the vapor phase, dilute solutions, or from the melt. Faceted growth, in which the crystal is bounded by its slowest growing faces, will occur if the growth rate is strongly orientation dependent. The addition of atom layers on a facet plane can only occur by two-dimensional surface nucleation or with the aid of an imperfection. Nucleation with the aid of dislocations was proposed by rank' and observed to be of particular importance in crystal growth from the vapor phase. Nucleation with the aid of two-dimensional imperfections, notably twin planes, was suggested by stranski2,3 and Frank.4 A twin plane, terminating at the growth interface, can form a reentrant step at which nucleation can occur at a much smaller super-saturation (or supercooling) than required for two-dimensional surface nucleation. Nucleation by a twin plane usually results in a fast growth rate along a crystallographic direction parallel to the twin plane. Such a nucleation mechanism, based on the presence of a twin plane, has been used by Dawson5 to explain the growth and morphology of sheet-like crystals of paraffin n-hectane. In recent years more evidence was found that nucleation by twin planes occurs frequently in crystal growth from the vapor phase and from dilute solutions, for example, in cadmium,' barium titanate,7 silver,8 silicon9 and gallium arsenide.10 In crystal growth from a supercooled melt, however, nucleation by twin planes has so far only been observed in materials with the diamond or zinc blende structure. Bennett and Longini11 were the first to recognize the important role a single twin plane plays in the growth of germanium dendrites. Subsequently, it was found that a prerequisite for continued propagation of germanium dendrites is the presence of two parallel twin planes which form a self-perpetuating system of nucleation sites.12 Sili- con and some III-V compounds such as InSb also grow dendritically by twin plane nucleation. It appears that the following criteria must be satisfied in order that nucleation with the aid of twin planes can occur: A) The growth form of the material must be faceted." B) The formation of twin boundaries, by a fault in layer sequence during growth, by plastic deformation, or by an accidental meeting of properly oriented crystals, must be possible. C) Twinning must form a reentrant step where the twin boundary terminates at the faceted growth interface. D) These three conditions are necessary, but in certain cases not sufficient for continued crystal growth with the aid of a twin plane. Depending on interface morphology, a combination of more twin planes is sometimes required to form a self-perpetuating system of nucleation sites. This investigation was carried out with the idea in mind that nucleation with the aid of twin planes is a more general phenomenon and should occur in those materials, grown from a supercooled melt, which satisfy the criteria outlined above. It has been found that crystals of high-purity bismuth grown from a supercooled melt can grow by the aid of a twin plane. In the first two sections the faceted growth form and the twinning elements of bismuth are discussed. In the last section prismatic crystals of bismuth, which appear to grow with the aid of a deformation twin are discussed.

Jan 1, 1962

By V. V. J. Sarma

Interpretation of earth resistivity data involves not only obtaining depth to interfaces but also determining the nature of formations from their resistivity characteristics. Moore's method of interpretation envisages obtaining depths to the interfaces alone. A simple method of estimating the true resistivity values of formations by applying Hummel's formula of average resistivities is proposed. The method would increase the interpretative value of Moore's method as originally proposed. For most of the earth resistivity measurements, the four-electrode configuration developed by Wennerl is employed. In principal, the method consists of energizing (Current I) the ground through two outer electrodes and measuring the resultant potential (v) between the two inner electrodes. The configuration is such that the separation (a) between any two successive electrodes is equal. The apparent resistivity (pa) for such a configuration is given by 2p- a (V/I). By increasing the electrode separation (pa vs a) curves are obtained. Ideally, a homogeneous isotropic formation underground has a characteristic resistivity. However, the field conditions do not present such ideal cases. Almost invariably, even in the same geological bed, the physical conditions are widely different at different parts in the bed. It is further shown that the penetration of the current into the ground for a given horizontal electrode separation, a, is roughly down to a depth, equal to a. It is therefore, evident that the apparent resistivity calculated from the field observations is a weighted average of the resistivities of the materials present down to this depth. With some prior knowledge about the relative dispositions of the geological formations and their physical conditions, it would be possible, by resistivity surveys, to obtain characteristic resistivities for these formations. It is, thus, that the apparent resistivity-electrode separation curves enable one to decipher the resis- tivity distribution at various depth levels and therefore the nature of the geological formations present. Both empirical and theoretical methods have been developed for determining resistivity characteristics of the various formations. The theoretical methods proposed by Tagg2 and Roman3 are derived from studies of the potential distribution on the surface due to the presence of layers of widely differing resistivities underground. The more recent methods of Wetzel and McMurry4 and Wetzel and Mooney5 are but extensions of the original Roman method of superposition. These methods suffer from lack of similarity of the actual field conditions with those of assumed conditions in developing the theory. The empirical methods such as the one developed by Gish and rooneY6 depend purely on personal observation and local peculiarities, and are applicable only for those limited areas. Out of the empirical methods, moore's7 cumulative resistivity method is still found to be applicable in several localities of differing conditions. While Reudy in 1945 adduced some theoretical justification for the method (Eve and Keys),8 Muskat9 and Mooney 10 tried to show the lack of theoretical basis for the same. It is, however, observed that the method in practice "forms a valuable means of successfully attacking the apparent resistivity curves which fail to respond to the Gish-Rooney, the Tagg or the Roman logarithmic methods" (Ramachandra Rao). 11 Comparatively good results are also reported by Melbyel2 by employing Moore's method in interpreting the resistivity results obtained for ground water in the city of Gunnison, Colo. MOORE'S METHOD As has already been pointed out, the application of the theoretical methods is time-consuming, laborious and sometimes not applicable for quick and accurate interpretation of the field data. moore7 has developed a quick method for obtaining depths to interfaces by plotting the cumulative sums of resistivities, against the corresponding electrode separations a instead of plotting the usual Pa — a curve. In this process of continuous integration, corrections for small variations in resistivities, arising due to local surface conditions or adjacent layers, are made, while large consistent variations are brought out

Jan 1, 1963

By K. R. Bixby

OPENING of numerous stripping operations in Ohio, Pennsylvania, and other districts, particularly outside the Middle West and Southwest where the large-scale stripping mines predominate, holds the limelight for the year 1940. Several factors are responsible for this expansion. One is the scarcity of untested and undeveloped properties in this central field. Another has been the development of earth-moving and preparation equipment suitable for these smaller tonnage tracts. Draglines of the Walker type, small long-range .hovels, and large-capacity tractor- drawn scrapers have to be considered. Wash boxes, designed for light tonnages, costing a few thousand dollars, have made their contribution.

Jan 1, 1941

By Cleland N. Conwell

APPLICATION of seismic methods to the location of buried channels in placer mining is fairly common knowledge, yet some of the facets of seismic refraction surveys have remained obscure in their application to mining. This description by a member of the U. S. Bureau of Reclamation team investigating bedrock at the Oso Dam site, may offer a lead to wider application of the method for bedrock determinations in engineering of mine and mill plants, tailing disposal, and water supply. It may also offer assistance in planning geological exploration in areas covered by overburden. Pertinent, and perhaps more than passingly significant, is that the seismic survey of the Oso dam site started at noon and was completed the afternoon of the next day. Location Oso dam site is on the Navajo River, Archuleta, County, Colo., 30 miles southeast of Pagosa Springs, Colo., 10 miles northwest of Chama, N. M. Bedrock at the proposed dam site is Mesa Verde Formation, Cretaceous age sandstone. The nearest good sandstone exposure is about 5/8 of a mile upstream from the location of the seismic determinations. The material above bedrock is sand and gravel with sandy loam soil covering benches above the river. The site appeared favorable, after a geologic and topographic reconnaissance, but overburden thickness was unknown. Exploratory drilling was not contemplated in the near future so a short seismic investigation was selected as the most suitable method of determining depth to bedrock. Field Procedure Geophysically, a seismic depth investigation is simply the measurement of depth from ground surface to the top of a layer which transmits seismic waves at a higher velocity. In this case the high-velocity seismic layer tentatively correlates with the Mesa Verde sandstone. Field procedure required a seismic explorationline or "spread" with 12 geophones set at measured intervals. Explosive charges were buried at few feet in the ground and detonated at shotpoints near the ends of the spread, and at intermediate points. The time of travel of the seismic waves from the shotpoints through the ground to each of the geophones along the spread was measured and recorded photographically with equipment housed in a field truck. The seismograph on each spread provided a time-travel graph. From it were computed the speed of seismic waves in various layers below the surface and depth to each different seismic layer below the shotpoint. In the case of the Oso dam site it was possible, in addition, to determine the depths below certain geophones, because there were only two seismic layers involved. Interpretation In seismic exploration waves are refracted from the top of layers which often correspond to divisions between subsurface formations. When drill holes are available the geologic logs offer a means of correlating stratigraphic breaks with seismic layers, improving reliability of seismic interpretation in terms of depth to bedrock or other geologic terms. There were no drill holes available in the case of the work at the Oso dam site. Geologic conditions appeared favorable for seismic technique because of excellent contrast in seismic wave velocity between the overburden and the Mesa Verde formation. The upper layer had a velocity of approximately 2500 fps and was interpreted as overburden, the lower layer had a velocity of approximately 9000 fps and was assumed to be the sandstone. These velocities are of the order expected in these materials. The seismographs obtained at the Oso dam site were excellent. The energy from the shot came in strongly at each geophone, giving an easily read record. Time-travel graphs plotted from wave arrival times were uniform and made interpretation comparatively easy. In Spreads 1 and 2 near the river the lower velocity layer was 12 to 15 ft deep. For the spreads on higher ground, or the bench south of the river, it was from 15 to 29 ft deep.

Jan 1, 1952

By William S. Springer

A NEW preparation plant has been put in - operation to treat coal from the recently opened Concord mine, located about 15 miles west of Birmingham, Ala., by the Tennessee Coal, Iron & Railroad Co., a U. S. Steel subsidiary. The mine produces metallurgical grade coking coal from the American seam for use as coke in the company's blast furnaces at the Fairfield and Enseley works. The capacity of the operation is 1000 tons of run-of-mine per hr, approximately half of which is delivered to the by-product coke plant at Fairfield after beneficiation to metallurgical grade. The remaining portion of the mine run is rock and refuse removed during preparation. No boiler coal or other fuels are produced by this mine. Preparation of the coal is done both under- ground and on the surface. The underground primary crushing station removes some tramp iron, and screens and crushes the oversize, most of which is rock, to protect the main slope conveyor. The surface plant consists of a crushing and screening plant, large blending bins, a two- process washing plant, a water clarification and

Jan 1, 1950

By A. KROENLEIN

THE Cromwell 'Pool has been the outstanding development in Oklahoma during the year 1924. . Tonkawa contributed the deep "Slick Sand" bit apparently its 'peak has been reached and like other pools producing from below the Mississippi lime its decline' mill be rapid. After reaching a daily production of 67,000 bbl., the Cromwell Pool is declining because of a lull in -new completions, but a mile extension has revived activity and an area equal to that of the present producing' area is under development and will cause an increase in the present production of 38,000 bbl. This pool is seven months old, has three dry holes in one hundred twenty completions and is actually defined only on the southern extremity. This area has been one of the chief contributors to the .over-production of high gravity oil in the Mid- continent fields and will be such' for the remainder of ' the year. 1924 and first part of 1925.

Jan 1, 1924

By James S. Baker

LARGER than continental United States but with only about one third the population, Brazil is a land of enormous potential wealth, waiting to be developed. During a recent visit to that country I saw Brazil at war and learned about some of the recent mineral developments. Many engineers and geologists have been sent to Brazil by various U. S. Government agencies to assist the Brazilian producers and co-operate with the Brazilian Government in producing needed war minerals. The Foreign Economic Administration staff of engineers has been active and through their assistance to the Brazilian producers, steadily increasing quantities of strategic minerals were provided to aid the United Nations' war effort. Mineral wealth has been found in almost every state of Brazil. Many mineral deposits have been discovered during the war period. Examples are: barite near Bahia; the tungsten and molybdenum deposits in Rio Grande do Norte; and corundum, beryl, and tungsten ores in Ceara.

Jan 1, 1945

By R. J. Grissom

PHOSPHATE deposits have been worked in many countries of central and south central Tennessee, but only ht ebrown rock deposits of Maury and Giles Counties will be discussed at any length in this articles, as all of the major opeations are now located there. They are: Mt. Pleasant District-Federal Chemical Co., Hoover and Mason Phosphae Co., International Minerals and Chemical Corp. (Maury and Giles Counties), Virginia-Carolina Chemical Corp. (formerly Charleston Mining Co.), and Victor Chemical Co. Columbia District-Armour Fertilizer Works and Monsanto Chemical Co. In the near future, the well-known, extensive deposits of blue rock in Lewis and Hickman Counties,also the brown rock in Hickman, Willamson, Summer and Davidson Counties, will again come into production. Certain physical peculiarities of the Tenessee deposit have played an important part in the design and use of mining and milling equipment.

Jan 1, 1944

By Frederick M. Becket

SHORTLY after the Armistice there appeared a few references to numerous attempts that had been made to produce steel without the aid of manganese, or at least with manganese in abnormally low percentage. Some years later, during two consecutive days of train travel, I had excellent opportunity to read Sir Robert Hadfield's book, entitled "Metallurgy-Its Influence on Modern Progress," and also his paper, "The Metal Manganese and Its Properties : Also the Production of Ferro-Manganese and Its History," presented at the spring meeting of the Iron and Steel Institute, 1927. Both the book and the paper are most interesting historically to makers of alloy steels and

Jan 1, 1931

By Roscoe W. Stensrud

Marcona Mining Company operations are located 500 kilometers south of Lima, Peru, on the Pacific Coast, at approximately 15º-22' latitude south and 75º-11' longitude west. The terrain is sandy rolling hills ranging from sea level at the coast and rising sharply (escarpment) to an elevation of 800 meters at the mine area. The climate is arid and windy with a moderate year-round temperature, ideal for a year-round mining operation. San Juan, a new and modern community of 14,000 inhabitants and developed by Marcona, houses the working forces and their families.

Jan 11, 1968

By AIME AIME

READERS of a technical paper, or the audience if the paper is presented orally, judge the paper on several counts. The September 1940 issue of MINING AND METALLURGY contained an excellent short article by S. Marion Tucker en- titled "Are You Going to Present a Paper," which considered the general subject of presentation. In it Dr. Tucker referred to the large number of poorly prepared and badly delivered papers that are presented annually before the large number of technical and other societies that meet regularly, and he stressed the point that good delivery, length of paper, content, and composition are of great importance. All of Dr. Tucker's points were well taken; however, good illustrations are equally important in explaining certain phases of some papers.

Jan 1, 1941

By Simon D. Strauss

The world appetite for minerals in the, third quarter of this century grew at a higher rate than had been anticipated. To illustrate, consider the experience of four, commodities. Excluding the Communist bloc, sometimes referred to as the centrally planned economies, demand for aluminum increased at a compound rate of 8.6% between 1950 and 1975,; copper rose by 4.4%; iron ore by 5.5%; and tin, the laggard in the group, by 2%. Except for tin, the figures are substantially greater than growth rates anticipated in 1950 in the Paley Commission report and other studies. The growth rate was not evenly distributed in geographical areas. Professor Wilfred Malenbaum of the University of Pennsylvania did an interesting study breaking these figures down as among three principal sources of demand -- the United States, other industrialized nations (which he referred to as the "rich lands"), and the developing world (which he referred to as the "poor lands").

Jan 1, 1982

By J. K. Edgar

For a number of years the production and use of super-purity aluminum (better than 99.99 pct) has been steadily increasing. High-grade lots of. such aluminum show certain outstanding characteristics not found in lower grades containing principally silicon, iron and copper as impurities. One such characteristic is the so-called "self annealing," that is, the re-crystallization of the heavily cold worked metal at room temperature.' Interest therefore is aroused as to the effects of the impurities. It is well known that the amounts of silicon and copper which occur in aluminum of better than 99.95 pct are completely soluble, at least at elevated temperatures (above 200°C). Iron, on the other hand, is known to be fairly insoluble in solid aluminum. Thus, a knowledge of the limits of this solubility would he of considerable use in studying the characteristics of the high purity metal. All investigators have agreed that iron has very low solubility in solid aluminum. Rosenhain, Archbutt and Hanson2 reported traces of an aluminum-iron phase in the "purest samples of aluminum obtainable." Gwyer and Phillips3 reported that an iron constituent was visible under the microscope in metal containing ".0088 per cent iron." Roth4 found that in the solid state the solubility of iron in high purity aluminum was 0.01, 0.01, 0.017 and 0.022 pct at 225, 320, 500 and 600°C respectively. Dix5 working with alloys containing less than 0.03 pct impurities, concluded from microscopic and chemical analyses of eutectic areas that the eutectic composition was close to 1.7 pct iron. Dix placed the eutectic temperature at 65s°C. Archer and Fink,6 using high purity aluminum-iron alloys, found that the hypoeutectic liquidus intersects the eutec-tic horizontal at 1.7 pct. This is in fair agreement with the investigation of the aluminum-iron system by Gwyer and Phillips who placed the eutectic at 1.89 pct iron with a freezing point of 653'C. Preparation and Chemical Analysis oP Alloys Electrolytically refined aluminum (99.991 pct aluminum) and a high purity alumi-num-iron alloy (11.45 Pet iron) were used in the preparation of the alloys for this investigation. To aid in controlling the iron content of the experimental alloys, an alloy of lower iron content was prepared first from these materials. The high purity aluminum was melted and heated to about 700°C in a plumbago crucible coated with alundum cement and the aluminum-iron alloy was then added. The alloy was thoroughly stirred, fluxed and skimmed and then chill-cast into notch bars. The aIlalyses of the three materials are given in Table I. The alloys for the determination of the solid solubility of iron in aluminum were prepared by melting 600 g total of the aluminum plus the required quantity of the aluminum-iron alloy (No. 92531). These

Jan 1, 1949

By David Cole

THE New Cornelia Copper Co. is mining and treating a 'monzonite " porphyry" copper deposit that is all hard rock. The oxidized surface shell, which constitutes the leachable part of the orebody, is measurably more resistent to crushing and comminution processes than is the underlying sulfide portion. The siliceous ribs running through the whole orebody are harder to crush than the main mass and there is no soft crumbly material to furnish the large volume of primary fines that features the crusher feeds of most other porphyry properties. New Cornelia ore reaches the primary crushers with a greater. proportion of large 'pieces. When the New Cornelia company first equipped its 'property, it used the following machines and flow , scheme to reduce the ore to leaching size:

Jan 1, 1925