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By Clarence Wright

THE average lead and zinc content of the ores mined and milled in the Joplin district is low as compared with that of other lead and zinc deposits throughout the United States. Because of this fact and of the high grade of the concentrates, the ratio of concentration is unusually high. Most of the operating companies have aimed to produce as high a grade of concentrate as possible in order to obtain the highest price for their product. They have done this at the sacrifice of the percentage of zinc recovered. The average percentage of zinc recovery is from 60 to 70 per cent. For percentage of recoveries from actual mill tests, see tables. The concentration is commonly effected by crushing the ore to h-in. (12.7 mm.) size and subjecting it to a roughing and cleaning over two or more large Cooley jigs, of the Harz type, the finer sands being treated on the usual types of sand and slime tables. The treatment of slimes by flotation is being tested at several of the larger mills. COARSE CONCENTRATION When the ore. has been hoisted from the mine it is dumped onto a chute leading to a grizzly made of iron bars, usually heavy rails, spaced 4 to -5 in. (101 to 127 mm.) apart. The oversize is caught on the grizzly, the mineralized pieces are broken with sledge hammers so as to pass through, and the boulders that are practically barren are sorted out by hand and trammed to the waste-rock pile. The proportion of waste rock thus sorted out varies from a fraction of 1 per cent to 15 per cent., depending on the nature of the rock.

Jan 10, 1917

By D. G. Westlake

Resistance was measured as a function of temperature, 77° to 350°K,for niobium with hydrogen concentrations up to 3.76 at. pct. Cooling curves exhibited a discontinuity in slope that was attributed to the initiation of hydride formation. A thermal hysteresis was explained in terms of diffusion and the effects of mechanical constraint on nucleation and growth. The heat of solution of hydrogen in saturated Nb-H solid solution was 2. 737 * 0.045 kcal per g-atom, including an unknown stress contribution. The critical ternperatures for hydride formation during cooling and for embrittlement are correlated but not coincident. This, too, has been explained in terms of mechanical constraint and stress-itlduced tratzsfomtation. Nb-H alloys undergo a ductile-brittle transition with decreasing temperature.'-3 Similar behavior has been noted for v-H.1,5 For the latter system, there is evi-dence6 suggesting coincidence of the temperature of minimum ductility and the critical temperature T, for initiation of metal hydride precipitation during cooling. A decrease in ductility due to the presence of brittle hydride particles is readily explainable. The fact that ductility begins to decrease at some temperature higher than T,4,5 has led us6 to suggest that precipitation may be strain-induced locally during tensile testing. Wood and Daniels' have reported that a plot of temperatures for 10 pct reduction in ductility vs hydrogen concentration in niobium is not coincident with, but parallels, the solvus.7,8 They believe this indicates a correlation of precipitation and embrittlement. Unfortunately, the two reported solvuses 7,8 to which Wood and Daniels refer are not in agreement with each other. Furthermore, neither solvus was determined experimentally: each was a plot of calculated solubilities. Thus. neither is highly dependable for determining whether embrittlement coincides with initiation of hydride precipitation. Longson 9 studied phase relations in the Nb-H system between 77° and 473°K by dilatometry. Comparison with metallographic observations convinced him that discontinuities in the slopes of his dilatometric plots were coincident with the initiation of hydride precipitation. Plotting the logarithm of the hydrogen concentration vs the reciprocal of the temperature at which precipitation was initiated during cooling, he obtained a straight line shown in Fig. 1. Walter and chandler,'' using X-ray techniques to detect the for mation of a second phase? have obtained three experimental points in the temperature range 295° to 338°K which fall within Longson's experimental error for this plot. A similar plotg of temperatures at which dissolution was completed during heating was a parallel line shifted toward higher temperatures. A straight-line plot was obtained, also, for the temperatures of the ductile-brittle transitions,9 but it was shifted toward still higher temperatures. Longson calculated an activation energy of 2.980 * 0.300 kcal per mole for the hydrogen embrittlement mechanism, compared with 3.180 * 0.400 kcal per mole for hydride formation. Despite this agreement, he concluded, "It seems unlikely that embrittlement results from hydride formation..." because hydrogen embrittlement was observed at temperatures above the solvus. It is our contention that embrittlement is correlated with precipitation of the hydride.6 Because only Longson has investigated Nb-H phase relations at sub-ambient temperatures, we deemed it advisable to re-determine the temperature dependence of the solubility using the resistometric technique already proven successful for the V-H system.6 Coincidence of our solvus with temperatures for embrittlement would

Jan 1, 1970

By J. T. Ryan

POISONOUS, irritating, or explosive gases are found in almost every industry, and manufacturers of gas masks are called upon to provide gas mask protection for a great variety of conditions, such as operators in horseradish factories, fumigators of homes and ocean liners, and men engaged in the manufacture of tetra-ethyl-lead, the new motor fuel. The modern type of gas mask and respirator, to provide protection against all such industrial gases, is an outgrowth of the gas mask developed during the World War to protect the soldiers against the poisonous war gases. So far, it has been possible to develop ample mask protection from all known noxious gases and fumes present in atmospheres encountered in mines, metallurgical works, and chemical and other industries, so long as there is sufficient oxygen present to support the flame of an oil lamp. The most important development of the gas mask was in providing protection against carbon monoxide- which is the noxious gas that mining men are most concerned with and, in fact, is the noxious gas that man is most frequently exposed to. This paper will be con- fined largely to the discussion of masks for underground use in metal mines. Gases that contaminate the normal air in mines can be divided into two classes: those that are given off normally by the workings, and those that are produced in mine operation.

Jan 1, 1926

During the war period of quicksilver activity there were a number of departures from what may be termed the classical quicksilver metallurgy. Attempts were made to beneficiate low-grade ores by gravity concentration and flotation; mechanical furnaces began to replace the Scott furnace and the vertical coarse-ore furnaces, and condensers of sewer tile and redwood tanks were used in place of the older brick and stone condensing chambers. Other developments that have occurred during the current period of quicksilver activity are mainly in the nature of improvement and further refinement of those started during the war period. Each period of quicksilver activity has been accompanied by the proposal of various new processes, including wet methods for the treatment of quicksilver ores and innovations in furnaces, retorts and condenser equipment. As far as the author knows, nothing of economic significance in the way of "new processes" has been developed. There is in fact no real need for any essentially new process for the treatment of quicksilver ores; the direct furnace treatment is simple and inexpensive. Moreover, with rare exceptions, the quicksilver industry has no complex or refractory ore problems corresponding to those which are receiving more and more attention from metallurgists in other branches of the nonferrous field. Untler these conditions improvements in quicksilver metallurgy must be looked for through the adaptation of current developments in engineering and metallurgy generally to the particular needs of quicksilver practice rather than through the invention of new processes. Preliminary Treatment of Quicksilver Ores At Sulphur Bank, in the treatment of old dump material left by the early operators, wet screening is being used as a preliminary step in concentration ahead of flotation. Power shovels and trucks are used to deliver some 400 tons of ore per day to the lower terminal of a hoist, which in turn discharges the material at the top of the screening plant. Wet screening is carried on in two stages. Depending on the character of the material, 1-in. or 2-in. punched screens are used on the first trommel.

Jan 1, 1930

By F. N. Rhines, B. H. Alexander

MUCH attention has been directed to the effects of grain size upon the properties of alloys, but there has been scant study either of the conditions that determine the pattern and dimensions of den-drites in metal systems, or of the influence of their shape and size upon the overall properties of cast-ings. The aim of the research that is about to be described has been to investigate the effect of vari-ous factors upon the mode of formation of dendrites in alloys by measurements of the distance between adjacent dendrite arms (dendrite spacing). Early investigators, including Grignonl and Tschernoff,2 showed that a metal dendrite is com-posed of a tree-like system of stalks and branches arranged in a simple geometrical pattern. North-cott and Thomas3 demonstrated that, in the face-centered cubic solid solutions of copper-base, these stalks and side arms all lie in (100) directions in the crystal. Several investigators, including Sauveur and Chou,0 Sauveur and Reed,' and Martin and Mar-tina have reported that the addition to steel of alloy-ing elements, such as nickel, chromium, and molybdenum, not only makes the dendrites easier to reveal by etching, but makes them coarser. The latter authors8 proposed that the coarsening of the dendrites is roughly proportional to the increase in the temperature range of freezing, caused by adding the alloying elements. Sauveur and Chou6 showed, in addition, that the dendrites are coarsened by a decreased rate of cooling of the casting. Measurement of Dendrite Arm Spacing Among the physical conditions that could be ex-pected to have an influence upon the dendrite arm spacing, that appears in a cast metal, are: composi-tion, rate of freezing, crystal structure, and type of constitution. The relationships obtaining between these variables and the dendrite dimensions have been examined, in the present research, by measur- ing the arm spacing in a wide variety of alloys, listed in tables II through VI. Alloy compositions are recorded in the tables by showing the symbol of the major metal followed by the percentage and symbol of the alloying agent; thus, "Al-10Ag" is an aluminum-base alloy containing 10 pct of silver. Although none of the alloys were analyzed, an im-pression of their degree of purity may be obtained from that of their component metals given in table I. Five hundred grams of each alloy was made by melting in small clay-graphite crucibles in an elec-tric muffle furnace. After alloying the temperature was adjusted to 50" to 75°C above the liquidus and the melts were poured into cast iron molds, at room temperature, the molds having a wall thickness of 1 in. and a cavity 11/2 in. sq in cross-section. Each ingot, thus cast, was sectioned at mid-height and the sectioned surface was polished and etched for metallographic examination. Dendrite spacing meas-urements were made at three positions, namely, ad-jacent to the mold wall, midway between the wall and the center of the ingot, and at the center (desig-nated e, m, and c respectively, in the tables). A typical series of microstructures is presented in fig. 1. For each measurement, the average was taken of the dendrite spacing of several grains covering a zone about 2 mm wide. Only those grains which had a major dendrite axis nearly in the plane of polish were selected in order to eliminate corrections for orientation differences from grain to grain. Although the dendrite spacings were measured to the nearest thousandth of a millimeter, the values listed in the tables are thought to be significant only to the nearest hundredth of a millimeter. The larg-est difference in readings found, when various ob-servers rated the same specimens, was 0.012 mm; the largest difference between corresponding meas-urements upon duplicate specimens was 0.027 mm.

Jan 1, 1951

By R. Webeler

In order to study the role of work hardening in the fatigue process, use was made of the great sensitivty of the resistivity of AuCu to cold work. A change of the resistivity of AuCu of the order of 1 to 2 pct at the temperature of liquid nitrogen was found to occur as a consequence of severe fatigue. ACCORDING to Orowan's theory,' the process of fatigue In metals 1s associated with the production of a number of small regions which have undergone strain hardening. This phenomenon is supposed to occilr even if the stress applied during fatiguing is always smaller than the yield stress. In an attempt to verity the existence of such regions, Welber and Webeler' undertook to detect the stored energy associated with severe fatigue in copper. Previous experiments" had shown that the energy stored in a sample of copper which has been cold worked by torsion is released in the temperature range between 150" and 250°C when the sample is heated from room temperature and that no more energy is released (or absorbed) between 250" and 450°C. In particular the stored energy amounted to 0.41 cal per g for a case in which the mechanical energy expended in twisting the sample was 11.9 cal per g. In the case of fatigued copper, however, no release of stored energy could be detected between 150" and 250°C, so that the experimental error of &0.02 cal per g represents an upper limit for the amount of energy stored in strain hardening., It seemed desirable to attack the problem in a new fashion. For this purpose, it was decided to make use of the fact that, if an alloy capable of undergoing the order-disorder transition is ordered and then cold worked, the resistivity, p, increases very greatly above the value for the ordered state even if the deformation is very small. Some insight into the nature of the fatigue process may be obtained then by measuring the resistivity of an ordered sample before and after subjecting it to fatigue. For reasons which will become apparent from the following remarks, considerably more can be learned by carrying out the resistivity measurements at two different temperatures. In the case of a material containing impurities, vacancies, dislocations, or other imperfections of essentially atomic dimensions, the resistivity, p, according to Matthiessen's rule, can be represented as a sum of two terms p = p, + p, where p, is the (temperature dependent) resistivity of the pure metal, and p, is the temperature independent contribution of the imperfections. Briefly, the physical basis for this rule is the following: The main contribution of the impurities in question to the resistivity results from the fact that they interrupt the periodicity of the lattice and thus scatter the conduction electrons with a probability which is almost independent of temperature. In order that this be the case, it is necessary that the' extension of the impurities be small enough—roughly less than one electron mean free path—so that their main effect on the resistivity occurs for the foregoing reason. If an alloy like AuCu is partly or completely disordered by quenching from an appropriate temperature, Matthiessen's rule also applies to a very good approximation* with p, representing in this case the resistivity po of the ordered sample and p, the additional (temperature independent) resistivity due to the disorder. In general, the disorder can be represented in terms of atoms which are displaced from their "proper" positions in the superlattice and which thus qualitatively represent the imperfections in the superlattice responsible for the term p,. Since the misplaced atoms are distributed at random throughout the super-lattice, their contribution to the resistivity still can be considered in terms of the scattering of conduction electrons by lattice defects. The situation is somewhat more complex in the case of an alloy disordered by cold work because the process of disordering here does not involve a random redistribution of the atoms; however, Matthiessen's rule also holds in this case. Whenever Matthiessen's rule does apply, the values of the quantity /3 = (p? — /(T, — T,), where p, and p, are the values of the resistivity at two fixed temperatures, T, and T,, respectively, is constant (independent of p,) for a given alloy or metal. In particular, if a sample of AuCu is subjected to ordinary cold work, the value of /3 remains equal to Po, the value for the ordered material. According to Orowan's theory,' as remarked before, a fatigued sample contains a large number of isolated severely cold-worked regions, which make up only a small proportion of the metal. Thus, if a sample of AuCu initially in the ordered state is fatigued, more or less disordered regions will be produced within the ordered material. If these regions are small enough so that Matthiessen's rule applies, then it follows from the previous discussion that /3 again will remain equal to Po. If the effect of fatigue is to produce cold-worked regions which are macroscopic—of the order of at least several electron mean free paths—the effective resistivity, p, has to be computed by use of the ordinary laws of large-scale electrodynamics. For the sake of simplicity, it will be assumed here that the cold-worked regions are completely disordered and have a resistivity, p,. For a given proportion A of disordered regions the effective resistivity, p, for the current in a given direction depends on the geometrical configuration of these regions. In any case, the value of p for such

Jan 1, 1956

By T. Sterry Hunt

WET processes for the extraction of copper from its ores have of late attracted much attention, especially in Europe, where the use of oupriferous iron-pyrites as a' source of sulphur prevails. These processes present an additional interest, when, as is often the case, the copper-ore's to be treated contain one or both of the precious metals, since the complete separation of these from copper, either in the dry or the moist way, is, as is well known, one of the difficult problems of metallurgy. The principal wet processes hitherto in use for the extraction of copper from its ores, may be included under three classes : I. Those in which the copper in snlphuretted ores is rendered soluble in water by calcining them, after a preliminary roasting which removes the greater part of their sulphur, with a portion of common salt, by which the copper is converted into a chloride (Long-maid and Henderson), or with sulphate of soda, by which sulphate of copper is formed (Monnier). Allied to these is the method by which a portion of the copper is got as soluble sulphate by roasting without addition, a process which is sometimes modified and rendered more complete by re-roasting the lixiviated residues with the addition of a portion of raw sulphuretted ore (Bankart). II. Those methods in which free chlorhydric or sulphuric acid is used to dissolve the copper- from oxidized or roasted ores. These, while simple and efficient, are too costly, except in certain localities where chlorhydric acid is a waste product. Related to them is the plan which consists in exposing the oxidized and moistened ores to the slow action of sulphurous acid mixed with air, by which a soluble sulphate of copper is formed. It has been proposed to decompose the solutions of sulphate or chloride of copper by sulphuretted hydrogen, thus separating the copper as sulphide, and using the liberated acid to dissolve fresh portions of oxidized copper. It is, however, the almost universal practice to throw down the copper from its solutions, however obtained, in the metallic state by the use of iron, either scrap-iron or iron-sponge; although in some instances

Jan 1, 1882

By T. Sterry Hunt

Jan 1, 1882

By J. R. Thoenen

The Bureau of Mines has used various sizes of core barrels above 2 in. and below 10 in. in diameter to core manganese, potash, coal, brown iron ore and bauxite. The paper describes in some detail the methods and types of equipment used to obtain maximum sampling accuracy. Introduction On December 11, 1946, R. D. Longyear, in his capacity as Chairman of the Subcommittee on Exploration Drilling, wrote the author requesting him to prepare a paper presenting the collective ideas of engineers in the Bureau of Mines on the design, standardization and application of core barrels using diamonds or other hard cutting media for drilling holes larger than two inches and less than ten inches in diameter. In subsequent correspondence it was indicated that similar papers covering the experience of other government agencies would be solicited and all such papers received would be combined in a symposium on the subject for discussion at the March 1947 meeting of the Mining Methods Committee AIME. In soliciting such information from other Bureau engineers, it developed that most Bureau experience had been confined to standard core size, two inches or less in diameter, and that larger sizes had been used only for special purposes. It is hoped the data contained herein will be of help to other operators in solving problems encountered in the field. Acknowledgments This paper was made possible by the request of Lowell B. Moon, Chief, Mining Division, Bureau of Mines, to all Division engineers to send to the author any data they had on the subject. Engineers of the Mining Division contributing were: M. H. Kline, Chief, Raleigh Branch. Paul T. Allsman, Chief, Salt Lake City Branch. J. H. Hedges, Chief, Tucson Branch. C. H. Johnson, Chief, Rolla Branch. A. M. Evans, Mining Engineer, College Park Branch. Wing Agnew, Engineer in charge, Mount Weather, Virginia. Andrew Brown, Mining Engineer, Tus-caloosa Branch. In addition Albert L. Toenges, Supervising Engineer, Bituminous Coal Mining Section, Pittsburgh, contributed his experience in coring coal beds. The author's experience in the use of cores within the limits stated has been confined to the brown iron-ore work described by Brown and coring bauxite and clay in Arkansas. Design and Standardization of Core Barrels Bureau engineers are primarily interested in obtaining core that will best represent

Jan 1, 1949

By J. R. Thoenen

The Bureau of Mines has used various sizes of core barrels above 2 in. and below 10 in. in diameter to core manganese, potash, coal, brown iron ore and bauxite. The paper describes in some detail the methods and types of equipment used to obtain maximum sampling accuracy. Introduction On December 11, 1946, R. D. Longyear, in his capacity as Chairman of the Subcommittee on Exploration Drilling, wrote the author requesting him to prepare a paper presenting the collective ideas of engineers in the Bureau of Mines on the design, standardization and application of core barrels using diamonds or other hard cutting media for drilling holes larger than two inches and less than ten inches in diameter. In subsequent correspondence it was indicated that similar papers covering the experience of other government agencies would be solicited and all such papers received would be combined in a symposium on the subject for discussion at the March 1947 meeting of the Mining Methods Committee AIME. In soliciting such information from other Bureau engineers, it developed that most Bureau experience had been confined to standard core size, two inches or less in diameter, and that larger sizes had been used only for special purposes. It is hoped the data contained herein will be of help to other operators in solving problems encountered in the field. Acknowledgments This paper was made possible by the request of Lowell B. Moon, Chief, Mining Division, Bureau of Mines, to all Division engineers to send to the author any data they had on the subject. Engineers of the Mining Division contributing were: M. H. Kline, Chief, Raleigh Branch. Paul T. Allsman, Chief, Salt Lake City Branch. J. H. Hedges, Chief, Tucson Branch. C. H. Johnson, Chief, Rolla Branch. A. M. Evans, Mining Engineer, College Park Branch. Wing Agnew, Engineer in charge, Mount Weather, Virginia. Andrew Brown, Mining Engineer, Tus-caloosa Branch. In addition Albert L. Toenges, Supervising Engineer, Bituminous Coal Mining Section, Pittsburgh, contributed his experience in coring coal beds. The author's experience in the use of cores within the limits stated has been confined to the brown iron-ore work described by Brown and coring bauxite and clay in Arkansas. Design and Standardization of Core Barrels Bureau engineers are primarily interested in obtaining core that will best represent

Jan 1, 1949

By E. B. Mayo

David LeCount Evans (Consulting Petroleum and Mining Geologist, Wichita, Kans.)-—Not only E. B. Mayo but also W. C. Lacy, who apparently urged the preparation of this analysis, is to be commended. Regional thinking of this type is needed to assure future success in the never-ending search for new mineralized and petroliferous districts. As is usually the case, here is a regional study that will be read by the mining geologist alone. It is ironic that several of the trends established in this study have suggested themselves in northern mid-continent, detailed, and regional studies. These, where established, have offered new keys to petroleum exploration and have provided a possible basis for unraveling a number of broad generalities. The oil geologists, active in Colorado, Kansas, and Oklahoma, would find much food for thought in Mr. Mayo's projections. To be more specific: 1) The parallelism between E. B. Mayo's Texas Lineament and the Amarillo Uplift, the Wichita Complex and the Arbuckle Complex of the Texas Panhandle and Southern Oklahoma is viewed with interest and appears especially significant when compared with the similar northwest trend of the Central Kansas Uplift, a major trend of production. 2) Considering the various northeast zones of Fig. 2, and with particular reference to Mayo's C-C, the Jemez Zone is on direct line with one of several northeast-southwest controls which the present writer has been using with some success in Kansas subsurface correlations. Considering zones of shearing, with no apparent vertical displacement, but suggesting strike-slip movement, because of the staggered effect on other features which cross such trends, Mayo's philosophy presents regional possibilities for lines of weakness, considered to this time of only local significance. 3) And, finally, in an area as distant from the Southwest as central Kansas, the north-south trends of the Fiarport-Ruggles anticline, the Voshel-Hol-low Nikkel-Burrton structures, the Dayton to Stut-gart trend, the north, slightly east trend of the Ne-maha structural complex, and others all seem to approach the north-south alignments, a through f, of Mayo's Fig. 3. Mayo's employment of structural intersections to pinpoint crustal weakness, to localize igneous activity and its accompanying mineralization is not, perhaps, a new concept, but it is a 1958 model, produced by tools improved from the ever-increasing accumulation of geological observations. The use of intersecting trends in petroleum geology is not a new idea, since much production in earlier days was encountered via the straight line projections of established trends to centers of intersection. A tragedy in this age of specialization is that iron curtains have been raised between groups, all seeking raw materials, all acolytes at the altar of structural geology, but all smugly content in and protected by the ivory towers of petroleum geology, engineering geology, mining geology, and geophysics. Mayo presents basic ideas which can stimulate mid-continent structural thinking and, in the case of cen- tral Kansas. he provides a key to replace the broad and overworked simple monoclinal, sinkhole-dotted, Karst topography credo, which is not finding its share of new oil in a state where the declining discovery ratio is disconcerting. The American Association of Petroleum Geologists would do well to add E. B. Mayo to its list of Distinguished Lecturers. Evans B. Mayo (author's reply)—In reply to David LeCount Evans' comments, it is pleasing to learn that some of the elements discussed in my paper may interest petroleum geologists as well as mining geologists. This should not be surprising, however, because the lineaments make up the framework of the continent, and the oil-bearing sediments must reflect to varying degrees adjustments of basement blocks along their boundaries. A further possibility that petroleum geologists must have considered is that the slow escape of heat from buried lineaments and their intersections has aided the separation of oil from the sediments and started the migration into traps. Regarding the specific points listed by Evans, the following are suggested: 1) The branch of Texas Lineament marked 1' (Fig. 3) is thought to extend eastward through the Capitan Mts., New Mexico, through the long Tertiary dikes east of Roswell, and beyond via the Matador and Electra ranges of the Red River Uplift, Texas. Its further continuation might be the eastern flank of the Ouachita Fold Belt. The Amarillo-Wichita-Arbuckle zone of uplifts appears to continue east-southeastward the Spanish Peaks belt (3-5, Fig. 3). The northwest-trending Central Kansas Uplift would not belong to the above set, except insofar as the Central Kansas Uplift is traversed by west-northwest folds, possible continuations of the Uinta belt (5-5, Fig. 3). 2) The possible continuations into Kansas of the Jemez zone are new to me and are most welcome suggestions. 3) Most of the nearly north-south Kansan structures mentioned by Evans are unfamiliar to me, but the Nemaha Uplift itself appears to be part of a very pronounced structure traceable from the Cerralvo Fault Zone, south of the Rio Grande, through the Bend Arch, Texas, and the Nemaha Uplift, into the Pre-Cambrian of Minnesota (?). This nearly meridional zone is crossed and broken by the Rio Grande Embayment and by the Red River-Wichita Syntaxis. Petroleum geologists realize the economic importance of these features. Perhaps it is inevitable that some papers of general interest be buried in the journals of specialized groups. Moreover, papers dealing with regional, or lineament, tectonics and its applications to exploration for economic mineral deposits are as yet few in the American literature. The opportunity to advance this field is open to all those who are not ultra-conservative and who have a lively curiosity, plenty of patience, and not too many business restrictions. In conclusion, much appreciation is extended to D. L. Evans for his comments.

Jan 1, 1960

By W. L. Falke, A. A. Cochran

Vast deposits of low-grade manganese ore exist in the United States, yet domestic production is insignificant compared to the more than 2 million tons of ore imported yearly into this country.1 A basic problem in connection with manganese is to find economical ways to utilize domestic resources.2 As a part of its program to conserve domestic mineral resources and to reduce dependence on foreign sources, the U.S. Bureau of Mines has conducted extensive research to broaden manganese technology and to find economical processes for recovering manganese from these low-grade resources. Although a great many processes have been proposed for treating domestic manganese resources, a failing of many of them is that too many steps are involved for economical operation.2 Some of the major processes that have been proposed were reviewed by Norman and Kirby.3,4

Jan 3, 1967

By D. Turnbull, J. H. Hollomon

IN the most general sense, solidification refers to the formation of crystalline material from either a gas or a liquid. However, in this symposium, only the formation of crystals from liquids will be considered. Thus, in our present study the problem of solidification becomes that of determining the mechanism of the transition from a liquid to a crystalline solid, and our particular interest is in the transformation of metals from the liquid to the crystalline state. Metal liquids are seldom composed of only one kind of atom. Often solute atoms are added intentionally to make an alloy, or they may be present accidently because of incomplete purification. Furthermore, there may be small solid particles of various other crystals present in the liquid. Such small crystals may persist if their melting points are higher than any temperature to which the liquid is heated. Prior to solidification, the liquid metal usually is poured from one container to another. The second container, called the mold, usually is at a lower temperature than the container, or the crucible, in which the metal is liquified. The first solid that forms upon contact with the mold generally is of a different composition than the liquid, usually containing fewer foreign atoms or dissolved impurities. Heat is evolved upon solidification and is dissipated through the surroundings. Tree-like crystals, or dendrites, grow from the container walls and branch into the melt, enriching the remaining liquid in impurity atoms. In some alloys the remaining, relatively impure liquid continues to solidify until no liquid remains and the branches of the original crystal are cemented together. In other alloys, particles with a second type of crystal structure appear before solidification is complete. First the nature of the liquid and the solid states will be considered and then the mechanism of the initial formation of crystals from pure and alloy liquids. Later the problem of the growth of these crystals and the complexities of solidification in a mold, where the temperatures are not uniform and the composition of the melt changes continuously, will be discussed. LIQUID AND CRYSTALLINE STATES A liquid is an aggregate of atoms arranged with no apparent regularity (over distances of more than a few atom diameters). Nevertheless, any given atom generally has a definite number of nearest neighbors at definite distances, and thus order may be said to exist over a short range. In a crystal, on the other hand, a regular array of atoms continues for many hundreds or thousands of atom diameters, and a long-range order is apparent. Thus, a crystal having long-range order can be reproduced by linear translations for 10-5 cm or more of some fundamental unit possessing short-range order. A crude illustration of the difference between liquid and crystalline structures can be obtained by comparing the possible arrangements of oranges in a crate. If the oranges are simply dumped into the crate haphazardly until it is filled, the oranges will represent a static model of a liquid.

Jan 1, 1951

By E. E. Malouf

Leaching is rapidly becoming an important adjunct to mining operations. A summary of various leaching operations is presented showing the role of these activities to the successful operation of the mining venture. The summary will include recent developments in dump, heap, and in situ leaching of copper and uranium ores. It will include a discussion on the expanding impact of industrial and academic research on leaching as a mining tool, showing the interplay of chemical kinetics and biogenic activity.

Jan 1, 1973

On the preceding pages, operations of the four major producers of nickel today have been described. There are, however, other operations in the world that, while not as large, are still of importance to the over-all picture of the industry. Among these are the Finnish producer, Outokumpu Oy, a state-controlled company that operates the Kotlahti mine 200 miles northeast of Helsinki. The ore from this operation, which began production in 1959, is pentlandite, chalcopyrite and pyrrhotite, occurring as disseminations in the host rock and in breccias. The flowsheet of the 1500-tpd mill at Kotlahti follows standard practices of crushing, grinding, and flotation to produce a pentlandite-pyrrhotite concentrate and a copper concentrate, both of which are shipped to the smelter at Harjavalta.

Jan 10, 1968

By Norman Lamont

The evaluation of certain reser-voir properties, such as porosity and fluid saturation, from electrical well surveys has been widely accepted in petroleum engineering. Various investigators have established relationships between these properties and certain parameters which affect the response of the electrical log. Among these are the resistivities of the mud, its filtrate, and its filter cake. In 1949, Patnode1 established a relationship between the resistivities of the mud and filtrate. The well logging service companies have contributed relationships for the mud-mud cake resistivities2,3 These have been valuable since it was the practice to measure only resistivity of mud at the well site. During the mid-1940's the industry began drilling wells with oil-emulsion drilling fluids. These were conventional aqueous muds with a dispersed oil phase. Since 1950, oil-emulsion muds have been used on an increasing number of wells each year. However, the practice of measuring only the resistivity of the mud at the well site has continued, and the mud filtrate and mud cake resistivities have been determined by the above-mentioned relationships. Service companies are now equipped to measure all three resistivities at the well site. An investigation was conducted on the resistivities of oil-emulsion muds, mud filtrates, and mud cakes to determine if these values conformed to the relationships for aqueous muds. TYPES OF MUDS Fifty-one oil-emulsion mud samples were prepared in the laboratory following a standard manual' published by a leading mud company. The diesel oil in the samples varied from 5 to 50 per cent, the majority of the samples being in the 10 per cent region. The basic aqueous mud types which were converted to oil-emulsion muds were commercial clay and bentonite muds, low pH and high pH, caustic-quebracho treated muds, and lime treated muds. The emulsions were stabilized by dispersed solids, lignins, lignosulfo-nates, sodium carboxymethyl cellulose, or sulfonated petrolatum. It is worthy of note that after a quiescent period of two weeks at room temperature all samples, regardless of emulsifying agent, remained stable. The make-up water for the muds was from the laboratory tap. Resistivities were varied by the addition of table salt to the water. A range of mud resistivities from 0.44 to 3.9 ohm-m was obtained in this way. Twenty-three field muds were tested. These covered the same range of mud types as did laboratory muds. Oil provinces of the Gulf Coast, South Texas, West Texas, Oklahoma, Montana, and Canada were represented. MUD TEST PROCEDURE Each mud was tested for density, viscosity, pH, and filter loss by standard testing techniques. The resistivity measurements were obtained with a Schlumberger EMT meter. This meter required small volumes of sample, e.g., 2 mm. Filtrate was obtained from a Standard Baroid fil-ter press at the end of a 30-minute test. The filter cake from the same test was used for cake resistivity measurements. Mud, filtrate, and cake samples were heated to 100" F in a constant temperature water bath prior to measurement of resistivities. RESULTS The relation between mud resistivity (Rm) and mud filtrate resistivity (Rmf) is shown in Fig. 1. The solid line represents an average for the data. The equation of this line is Rmf =0.876 (Rm) 1.075 . . (1) Arbitrary limits, indicated by the dashed curves, have been set. The majority of the data falls within these limits, but some points do lie outside the limits. The approximate equation Rmt = 0.88 Rm , . . . . (2) will give satisfactory results within these limits. The data on mud cake resistivity Rmc is shown in Fig. 2. The solid line is an average for the data. The equation for the line is Rmc = 1.306 (Rm)0.88 The dashed lines are arbitrary limits on the data. Within these limits, Eq. 3 may be simplified to Rmc = 1.31 Rm . . . . (4) DISCUSSION The limiting curves in Figs. 1 and 2 represent maximum deviations of ±25 per cent. Thus the use of the average curves can introduce considerable error. There is no substitute for accurate measurements of mud, mud cake, and mud filtrate resistivities at the well site. The mud sample tested should be representative of the mud opposite the formation being logged. The average mud filtrate resistivity curve of Fig. 1 is reproduced in Fig. 3 with two curves which have been published for clay-base aqueous muds2,3. The latter curves were determined from average values of a large number of drilling fluids. The three curves have essentially the same slope and the differences between them are from 7 to 22 per cent. Comparison is made only to illustrate the possibility of error

Jan 1, 1958

By AIME AIME

IN view of the approaching visit to Japan and the Imperial Steel Works at Yawata by our members, the following notes on present conditions in the industry there will be of interest. The data were collected by the representatives of the Bureau of Foreign and Domestic Commerce in Japan and are furnished here through the courtesy of the Department. In connection with the proposed suspension of both new and old Government undertakings and the general depression in building, which is expected to result from the retrenchment policy of the Government, some cuts in iron and steel prices have been made by dealers. It is expected that the Yawata Steel Works may reduce its round bar prices for November delivery by 1 yen.

Jan 1, 1929

By A. J. Bartlett

ISLAND Creek conditions are generally referred to as ideal; yet, as at all other properties, there are all known hazards of coal mining. The hardest of these hazards to combat is the human element. The basic thought in the minds of the management of these properties is to produce coal with the utmost safety, and it has impressed upon its supervisory force that it does not want a ton of coal unless it can be produced safely. This company has instituted a mine inspection department, which reports direct to the general manager, and all matters pertaining to safety come under the direction of this department. Through the medium of the inspection department, the management is kept in touch with the actual conditions existing in general at all mines. Inspections are made regularly and continuously; that is, at all times while the mines are in operation some sections of some mines are being examined. These inspections cover all active and inactive workings. Miners are con-tacted in their working places and other employees at their respective work. A thorough check is made to see that the state mining laws are complied with and that company safety rules are being observed. Night shifts receive the same attention as day shifts. All violations and dangerous practices are brought to the attention of the plant supervisory force with suggestions and recommendations; major hazards of emer-gency nature are taken up immediately with the management. Peri-odical inspections are also made of all tipples, preparation plants, dumping and hoisting equipment, to see that all machinery is properly guarded, and walkways and platforms properly fenced; conditions of equipment and mechanical defects are also reported. Reports of inspection are written in letter form and in such a manner as to give the management a picture-of the existing conditions at the time of inspection. Copies of inspection reports are forwarded; to the superintendents with the general manager's comments.

Jan 1, 1937

By Harry L. McNeill

THE Selective Media Process was developed by the author in a laboratory provided by The Steårns-Roger Manufacturing Co. It is the outcome of an [ ] investigation into the possibilities of coarse beneficiation by sink and float without using the conventional heavy media. Commercial work to date has been limited to the treatment of minus 3/8-in. iron ore at the Hill Trumbull washing plant of the Cleveland Cliffs Iron Co., at Calumet, Minnesota. Two cut away prints of the machine are shown (Figs. I and 2). A rotary conical impeller is mounted within a stationary cone (Fig. 2). This impeller is adjustable vertically by a 12-ton screw jack. The speed of the impeller can be varied from 14 to 32 r.p.m. by the Reeves variable-speed motor pulley mounted on the 7 ½ -hp. motor drive. Attached to the bottom of the stationary cone is the automatic control valve for sink product, actuated by a ¼ -hp. gear motor. The sink product is dewatered in a conventional drag driven by a 7 ½ -hp. motor and discharged onto an inclined conveyor containing from 6 to 10 per cent moisture. Two plants are operated at the Hill Trumbull property. All the ore is first treated in a typical washing plant (Fig. 3). When treating "wash ore" a finished concentrate can be produced by the log washers and Akins classifiers, as the separation involves only fine silica (minus 48-mesh) and free iron. However, when "jig ore" is fed to the washing plant the coarse

Jan 1, 1946

By Allan B. Tanner

The effects of radon in drillholes on gamma-ray logs have been described by L. S. Hilpert and C. M. Bunker1 Since these effects may cause drastic error in the evaluation of uranium deposits, it is useful to know the conditions under which significant amounts of radon tend to accumulate in drill- holes. In the studies described here, atmospheric conditions were found to dominate in the control of the behavior of radon in drillholes in the vicinity of a uranium orebody. The site of the investigation was in McKinley County, New Mexico, about 12 miles north of Grants. Drillholes of 4 ¼ -in. diam, on 25-ft and 100- ft centers, penetrate ore in dry rock at a depth of about 100 ft. A geologic log of the drillhole of primary interest is shown in Fig. 1. Gamma-ray logs revealed three zones of ore-grade mineralization in the Todilto limestone. A 6-ft zone, the lowest of the three, assayed 0.20 pct U3O8 by chemical analysis. The limestone ores in this area contain disseminated uraninite and some yellow and orange secondary minerals.

Jan 7, 1959