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By Richard D. Hagni

Abstract-Although the ore microscopist routinely examines polished sections to determine the mineralogy and texture of ores, his importance to the solution of problems peripheral to geology is not always fully realized. The techniques which he uses can be applied with little modification to the solution of a wide variety of beneficiation problem. By extending his studies beyond those normally considered to be of interest to the geologist, he can include examinations of polished sections of selected mill products. This is a logical extension, because the minerals and textures in the polished sections of ores are the same as those in mill Products. The mill dressing engineer should be more aware of the types of beneficiation problems that can be solved by the ore microscopist and what the ore microscopist can do for him. A greater degree of cooperation between the ore microscopist and the mill dressing engineer can be of significant mutual benefit. Ore microscopy holds an advantage over chemical analysis, because the interrelations and combinations of the mineral constituents of an ore or mil1 product can be visually determined. This advantage provides solutions to many beneficiation problems. Locking is a type of beneficiation problem that is particularly amenable to ore microscopy. The percentage, type, and distribution of locked particles can be readily determined with the aid of an ore microscope and an estimate made of the extent of additional grinding required for liberation. The extent of intimately locked types, which no reasonable amount of grinding will liberate, can also be evaluated. Mineral coating conditions, free particles of a deleterious mineral, and free particles of a valuable mineral held in floculated clusters of gangue are other features that can readily be observed. In some instances, visual examination may show that the problem is not one of locking. Photomicrographs illustrate the variety of beneficiation problems for which the ore microscope is applicable. These problems and their resolution demonstrate the importance of the instrument and show the value of close coordination between the mill dressing engineer and the ore microscopist.

Jan 10, 1978

By Nathaniel Arbiter

There is a history in all men's lives, Figuring the nature of the times deceas'd, The which observ'd, a man may prophesy, With a near aim, of the main chance of things. W. Shakespeare, Henry IV; Part 2 Introduction This nation's first century embraced two stages of the Industrial Revolution. During one, what had been a colonial agricultural economy began to industrialize; water power, then steam after 1794, were the energy sources; coal and iron were the essential ingredients. The second stage started after 1850; aided by rich and diverse mineral resources, the country began its transition from the Iron Age to the Age of Metals. Early civilizations had been built on stone, and fairly high levels were sustained on iron. But the spectacular advances in the past century in communication, in construction, in transportation by sea, rail, land and air, and in much that characterizes modern civilization have depended increasingly on the use of the complete metallic and nonmetallic resources of the earth's crust. Thus it was appropriate to define the Industrial Revolution as “the period during which man's relationship to natural resources became utterly changed”, 1 with minerals playing a major and indispensable role. But we are now becoming aware that the relationship of man to natural resources must change again. On every hand the dangers inherent in the contamination of land, sea and air by the wastes of civilization are becoming apparent. And from the growing realization that mineral wealth is finite must eventually come other far reaching changes in mineral use and distribution. For on the scale of centuries we cannot continue to exploit mineral resources even at present rates, let alone at expanded rates, without eventual depletion of the more abundant resources, and early exhaustion of the less abundant. In the past our problems were relatively easily met by the development of new and improved machinery and processes. But the future will

Jan 1, 1971

By P. G. Shewmon

THIS paper is concerned with the redistribution of a second phase when a 2-phase solid alloy is annealed in a temperature gradient. An examplewhich is discussed in detail is the redistribution of carbides in a low-carbon steel annealed in a temperature gradient below the A, temperature. As a result of such a treatment, the carbides at the cooler side disappear, while those at the hotter side grow in size. In a 2-phase zirconium-hydrogen alloy, the amount of hydride will tend to be increased at the cold end and decreased at the hot end. That such an effect can occur in solid metals is not generally appreciated. However, with the trend toward higher operating temperatures in several fields, this phenomenon will become more important in the future. Actually, such effects should be rather common in the core of nuclear power reactors where the op- erating temperatures are high and temperature gradients are an order of magnitude higher than in previous high-temperature applications of alloys. The purpose of this paper is to point out the existence of such an effect, to discuss the manner in which one predicts whether a redistribution of the second phase will occur in a given system, whether the second phase will go to the hot or cold face, and how rapidly the redistribution will occur. One aspect of this problem has been discussed by pfam and Wernick2who considered the migration of a small liquid region through a solid. In their case, the diffusivity in the liquid is much larger than in the solid and they have interpreted their results successfully by using Fick's first law as the flux equation in the liquid, and taking the concentration gradient from the phase diagram. For all the cases they have studied, this type of analysis predicts that the liquid region migrates from the cold end to the hot end, and this is what was found ex-

Jan 1, 1959

By H. C. George

The Wisconsin Zinc District, or the Upper Mississippi Lead and Zinc District as it is often called, lies in the southwestern corner of Wisconsin, in Grant, Iowa and Lafayette Counties, and it includes adjoining parts of Illinois and Iowa. The district is about 70 miles long, north and south, and about 40 miles wide, east and west. It lies wholly within what is geologically known as the non-glaciated area of the Upper Mississippi Valley. HISTORY OF THE DISTRICT The district was first opened up as a lead producer in 1822. From this time until 1860, about 205,000 tons of cog lead (galena) and washed lead (galena) was produced from shallow crevices and openings. From 1860 to 1900, about 74,500 tons was produced, and since that time, from 5000 to 7000 tons has been produced annually. Since 1900, most of the lead concentrate produced has been as a byproduct of the zinc mines. The first zinc ores were mined about 1862. These were the carbonate ores, locally known as "drybone." Very little zinc blende was mined in the district, previous to 1875. The zinc blende ores mined from 1875 to 1900 were mostly of the high-grade, hand-cobbed, sheet-ore class, which usually contained from 45 to 60 per cent. metallic zinc Such mines as the "Sallie Waters," "Quinlin," 'Lead Mine," "Benton Blende," and "Ida Blende," located near Benton, Wis., were mines which produced ores of this type, during this period. The mines located at Highland, the "Coker Mine" located at Livingston, Wis., and the "Opencut Mine" located at Shullsburg, Wis., were mines that were heavy zinc carbonate producers, previous to 1900. The production of zinc ores in the district from 1862 to 1890 was about 283,500 tons, mostly zinc carbonate, with a probable average metallic zinc content of 30 per cent. From 1890 to 1903, the production

Jan 1, 1918

By Samuel Hoyt

THE writer has long been interested in seeking an explanation of the upper heat effect in the copper-tin alloys over the a + ß range, first described in 1913. These notes are offered, not at all as the final explanation of this heat effect, but rather to indicate certain progress which has been made toward establishing what happens over this temperature interval. While working on the thermal analysis of the copper-rich kalchoids (copper-tin-zinc alloys), it was noted that those alloys containing major portions of tin and minor portions of zinc exhibited two marked heat effects, one at about 520° C. and the other at about 600° C., instead of the single effect which is generally observed in either of the two binary series. This matter was discussed with Dr. Guertler, who suggested that a heat effect at about 600° C. in the pure copper-tin alloys might be expected. This led to a more searching examination of the thermal critical points in the pure copper-tin alloys, with the result that a marked, although somewhat weak, heat effect was located at about 600°. Somewhat later, this upper heat effect was discussed with Dr. Burgess, and it was requested that the Bureau of Standards make heating and cooling curves of one of these alloys for the purpose of removing any possible doubt as to the actual presence of the heat effect. Results obtained by the Bureau are given in Plate I. In an earlier paper1 differential curves were published showing that the heat effect occurred at constant temperature over the a + ß range and increased in magnitude with the amount of a up to a point somewhat above 20 per cent. tin. No heat effect was noticed at this temperature in the eutectoid alloy. The existence of this heat effect seems to require a modification of the present copper-tin diagram in the a + ß field, and it has been the object of the work here presented to secure the evidence upon which such a change should be based.

Jan 12, 1918

By Maurice C. Fetzer, Charles R. Austin

It has long been known that plain high-carbon steels may be susceptible to graphiti-zation below the A1 critical, but no data have been available to indicate what factors cause and tend to inhibit graphite formation. Two recent publicationsl,2 have shown that the factors controlling graphitization below the A1 are different from those operating above the A1 inversion where commercial graphitization of malleable iron begins. Furthermore, for plain high-carbon steels graphitization below the critical point does not appear to be related to ordinary chemical analyses. Many years ago it was recorded3 that the rate of graphitization at subeutectoid temperature is not a maximum just below the A1 critical, but at some lower temperature, which Austin and Norris have shown to be about 670°C. Indeed, work done in our laboratory has demonstrated that it is impossible to spheroidize certain steels in the temperature range of 650° to 710°C. without the formation of considerable amounts of graphite. However, if the temperature is maintained just below the A1 (720°C.) these same steels may be completely sphe-roidized at constant temperature. In previous studiesl,2,4 on I per cent plain carbon steels graphitization was encountered during prolonged tempering. The limited number of steels studied did not provide sufficiellt data to permit adequate study of the factors controlling this graphitization. Accordingly, a limited statistical investigation was undertaken, utilizing 18 steels of similar chemical analyses, furnished by four steel companies, who also supplied information regarding the history of manufacture. An extensive program of research is being carried out on these steels, including the effect of pretreatment and atmosphere on the nature and extent of graphitization, and the possible correlation of graphitization with such characteristic properties as hardenability, grain size and mechanical behavior. In the present paper discussion is restricted to a study of the correlation between graphitizing tendency at 670°C. after quenching from several temperatures above the critical, and (I) the minor variations in the chemistry of these steels of "similar" chemical composition, and (2) the deoxida-tion practice employed. The state of the lead bath, oxidized or protected from oxidation by charcoal, used in the tempering treatments is also considered. Materials Eighteen plain carbon steels of about I per cent carbon, and containing similar amounts of each of the other common elements usually found as impurities, were obtained in the form of rods % in, in diameter from four steel manufacturers. The analyses for ordinary and special elements of all the steels were made on the rod stock as received in the laboratory, and the re-

Jan 1, 1941

By P. J. Soltis

Direct as well as indirect evidence of a-phase ordering was found in a "near-a" type titanium alloy, Ti-8Al-1Mo-1V. The annealed alloy showed an anomalous decrease in second-stage creep rate at 950°F (510°C) and 47,500 psi. Anomalous increases were noted in initial yield stress after 500 hr creep exposure and in tensile strength after 1100 hr creep exposure. Debye-Scherrer X-ray diffraction patterns obtained on fine-grained polycrystalline speci-ment showed much line broadening and development of superlattice lines after 500 hr at 510° C. Examination with the light and electron microscopes failed to reveal phase changes in thermally exposed material, but detailed metallography is presented illustrating the plastic and fracture characteristics of the alloy. Electron-metallographic evidence is presented, however, which shows the nature of the nucleation and growth of ordered regions from the disordered a in annealed material. In the original phase diagram of the binary Ti-Al system constructed by Ogden et al.1 aluminum was shown to be soluble in a titanium over a wide temperature range at concentrations up to about 30 pct. Subsequently, a number of papers2-7 have appeared which indicate the existence of either intermetallic compounds and/or ordered phases in the a field up to 25 pct Al. In the most recent of these, Goldak and Gordon paw7 have determined unequivocally the ordered hexagonal D019 structure for Ti3Al in a 25 pct Al alloy. No superlattice lines were observed above 1112°F (600°C). Previously, the embrittle-ment encountered by Crossley and Carew4 in low- temperature heat treatments of binary Ti-Al alloys low in aluminum had been attributed to the appearance of a new phase in light micrographs. In the present work, direct as well as indirect evidence is presented showing the existence of a-phase ordering in what is essentially the binary Ti-8A1 alloy containing small percentages of the ß stabilizers molybdenum and vanadium, i.e., the "near-a" Ti-8Al-1Mo-1V alloy. Although Bohanek and Kessler8 have shown that this alloy has good stability at temperatures up to 1100°F (593°C), the present work shows instability at 950°F (510°C) where long exposure times were used. Light and electron microscopy proved very useful in revealing the mechanical behavior of ordered a and led to the conviction that ordered "near-a" alloys may have remarkably good properties and useful engineering applications.

Jan 1, 1965

By Jasper L. Stuckey

It is not known when kaolin mining was first begun in North carolina, Evidence, in the form of excavations and primitive tools, indicates that some of the deposits were worked in prehistoric times. It has been suggested that the prehistoric mining was for mica, but the workings were all in altered or partly altered pegmatite material and the dumps do not represent the amount of material removed. some of the early openings may have been made in search of kaolin or semi-kaolinized feldspar which was sold to English1 traders along the coast and used in some Of the early English porcelains. In 1744,2 an application was made for an English patent to produce porcelain from an earthy mixture obtained from the Cherokee Nation in North America. It is well established, however, that the occurrence of kaolin in western North Carolina was known in England by 1767. In that year, Josiah Wedgewood sent T. Griffiths3,4 to what is now Macon County, North Carolina, to secure a supply Of kaolin for use in England. Griffiths diary, now in Etruria Museum, Stokes-on-Trent, contains a most interesting account of his experience. Kaolin was discovered at St. Austell, England, shortly after the voyage Of Griffiths, which probably accounts for the lack of further interest in American kaolin. Between 1767 and 1888, there are no records of kaolin mining in North Carolina. In the latter year, however, mining was begun near Webster, Jackson County, and, in the intervening period, has become an important industry. 'Or some 20 years, kaolin mining was carried On chiefly in Jackson, Macon, and Swain Counties. About 1904, it was begun in the Spruce Pine district and for the past 20 Yea's most of the kaolin mined in the State has come from Avery, Mitchell, and Yancey Counties. Distribution The kaolins of North Carolina are limited in occurrence to the Piedmont Plateau and Appalachian Mountain area of the State. While kaolins are widespread in the Piedmont Plateau, having been prospected for in Rutherford, Cleveland, Gaston, Granville, Lincoln, Catawba, Ire-dell, Richmond, Moore, Randolph, and Montgomery Counties, the production from that area has never been important. The known deposits of commercial importance are limited entirely to the mountain area of the State. While kaolins occur widely distributed throughout the mountain area and have been prospected for in many counties of that area, commercial production has come chiefly from two districts. One of these includes Jackson, Macon, Swain, and Haywood Counties. The other includes Avery, Mitchell, and Yancey Counties. Geology With few exceptions, all the known kaolin deposits in North Carolina contain

Jan 1, 1948

By W. R. Hibbard, Ming-Kao Yen

Various rationalizations of preferred orientations in cold worked polycrystalline metals have been based on the operation of at least two three2 five, an indefinite number, and all,6 slip systems of the type occurring in single crystals. Pickus and Mathewson3 suggested that the cold rolling texture in face-centered cubic metals could be rationalized on the basis of two or more operating slip directions symmetrically disposed about the direction of flow in such a manner that the resolved shear stress factor is equal for all operating slip systems and lattice rotations cancel each other. The importance of the direction of flow, the necessity for the operation of slip systems capable of producing the required changes in external dimensions, the maintenance of a common surface between adjacent grains and a symmetrical arrangement of the operating slip systems in order to produce an end orientation which is stable under additional deformation lead to the following rationalization of textures based on the type of slip systems operative in single crystals. The rationalization is intended to explain why certain orientations are suitable for deformational flow without a change in orientation and thus are stable end orientations or ideal texture orientations. It does not attempt to explain how the grains of a randomly oriented polycrystalline aggregate will reach this orientation. The rationalization is based on the following four postulates: 1. The ideal textures for polycrystalline aggregates are the result of reorientations of individual crystals toward the same stable end orientation at which no further reorientation will occur even during additional deformation. Since, in simple slip, the relative orientations of the stress axis and the active slip system determine the change in orientation during slip, it is considered that the orientation of the stress axis with respect to the ideal texture determines what slip systems must be active to retain the stable end orientation. Therefore the stable end orientation should be a symmetrical one around the stress axis with respect to the active slip systems such that lattice rotations resulting from slip will cancel each other and prevent a resultant change in orientation. (Rotational symmetry only—not translation, inversion, nor others—is considered here.) Thus a metal under a pure stress should develop a texture consisting of one or more of the crystallographically symmetrical directions, <100>, <110> or <111> for cubic metals or <0001>, <1010> or <1120> for hexagonal close-packed metals, parallel to the stress axis. 2. Since the active slip direction is the direction of glide during simple slip and thus the direction of maximum shear movement, in the ideal texture the active slip

Jan 1, 1949

By R. M. Brick

Segregation can occur only in cast alloys that solidify over a range of temperatures with a difference in composition of liquid and solid phases within this range (ignoring monotectic systems and chemical reactions as in rimming steels). Thus a pure binary eutectic alloy should show no segregation unless undercooling occurs for one of the solid constituents of the eutectic; e.g., chill-cast Al-I2 per cent Si alloys. The phasial condition implicitly described above—solidification over a range of temperatures with a compositional difference between solid and liquid—is found in nearly all solid solutions or combinations of solid solutions and eutec-tics, Metastable conditions of solidification of these types of alloys cause coring; i.e., a difference in composition between the center of a dendrite and its periphery. This composition gradient can be detected usually only by microscopic examination of etched structures; it is a "micro" effect. The gradient of more immediate industrial concern is that between the center of a cast section and the surface layers. This gross (macro) effect is usually deter-minable only by sampling of the casting at different points, with chemical analyses of each sample. If the compositional difference is of the same type as in coring, the first parts to freeze being enriched in higher-melting-point constituents, and vice versa, the effect is called normal segregation. When what is apparently the first part of the casting to solidify shows a higher concentration of low-melting-point constituents, the effect is called inverse segregation. These macro effects are quite separate from the micro effect, coring, yet the latter must be described first because it is an essential part of the picture. Coring Solid Solution, Ni-Cu The nickel-copper phase diagram is reproduced in Fig. Ia, in which the solid lines represent the equilibrium liquidus I, 3, 7 and solidus 2, 5, 8, and where the vertical I, 4: 8 represents a 55 per cent Cu alloy. Upon moderately rapid solidification, the first dendritic axes of composition 2 (see Fig. Ib) start to form at a temperature somewhat under I. Solidification continues by growth of the dendritic nuclei, but at temperature 4 the increment solidifying is of composition 5. The rapidity of this crystal growth prevents diffusion of nickel and copper atoms from adjusting the composition of the entire dendrite at 5, which it would be under equilibrium conditions. The average composition of a specific dendrite, or the entire solid phase, at temperature 4 might be that indicated

Jan 1, 1945

By James T. Kemp

SOME interesting and, to American eyes, rather unusual processes for refining impure aluminum derived from scraps were found by American and British investigators who went into Germany in 1945 for the Technical Industrial Intelligence Committee Of the Joint Chiefs of Staff. What was found was recorded in a series of reports (see page 14), many of which have been released for general reading. This paper gathers under one title and summarizes the German work in refining light metal scrap. Reference must be made to the original reports for greater detail. Basically, the occasion and stimulus for the German developments in treating light metal scrap were hard necessity. Germany needed the metal for a rapacious war industry. Adequate supplies of new aluminum from reduction works were not assured. Great quantities of airplane and other light metal war scraps were forecast. It was evident that the scrap metal would have to be reabsorbed by the producing industry and would have to be kept of good quality. The normal current production of manufacturing scrap was being and could be consumed as generated. It offered no technical problem. The mixed scraps, especially those arising from crashed and decommissioned airplanes, however, presented problems of another kind. AIRPLANE SCRAP The recovery of usable aluminum alloy from the mixed assemblies that made up the piles of airplane scrap was attacked in different ways by different groups and with differing degrees of success. Three procedures actually were used On a commercial scale, one was in pilot-plant stage and another had come to a halt in the laboratory a year before Germany collapsed. Four of these five processes actually involved "refining"; that is, some measure of purification of the metal after melting. SORTING AND SEPARATION ON A SLOPING HEARTH The simplest procedure for utilizing airplane scrap involved no refining in the strict sense of the word. This was the practice adopted by two representative plants visited by the author, the Leipziger Leichtmetalle Werke, Rackwitz, Saxony, and the Vereinigte Leichtmetalle Werke, Hanover. These firms did essentially the same thing that was done in England but not with equal success, to judge by their shorter experience, the smaller tonnage handled and by the number and quality of alloys produced. The two German firms named rough-sorted scraps by their easily recognizable alloys, essentially by part and shape. They used hand labor to chop and hack and tear apart. The easily separated heavy metal and nonmetallic scraps were discarded as they were found. Steel and the higher-melting-point metal parts riveted to aluminum or built into

Jan 1, 1947

By Maurice C. Fetzer, Charles R. Austin

It has long been known that plain high-carbon steels may be susceptible to graphiti-zation below the A1 critical, but no data have been available to indicate what factors cause and tend to inhibit graphite formation. Two recent publicationsl,2 have shown that the factors controlling graphitization below the A1 are different from those operating above the A1 inversion where commercial graphitization of malleable iron begins. Furthermore, for plain high-carbon steels graphitization below the critical point does not appear to be related to ordinary chemical analyses. Many years ago it was recorded3 that the rate of graphitization at subeutectoid temperature is not a maximum just below the A1 critical, but at some lower temperature, which Austin and Norris have shown to be about 670°C. Indeed, work done in our laboratory has demonstrated that it is impossible to spheroidize certain steels in the temperature range of 650° to 710°C. without the formation of considerable amounts of graphite. However, if the temperature is maintained just below the A1 (720°C.) these same steels may be completely sphe-roidized at constant temperature. In previous studiesl,2,4 on I per cent plain carbon steels graphitization was encountered during prolonged tempering. The limited number of steels studied did not provide sufficiellt data to permit adequate study of the factors controlling this graphitization. Accordingly, a limited statistical investigation was undertaken, utilizing 18 steels of similar chemical analyses, furnished by four steel companies, who also supplied information regarding the history of manufacture. An extensive program of research is being carried out on these steels, including the effect of pretreatment and atmosphere on the nature and extent of graphitization, and the possible correlation of graphitization with such characteristic properties as hardenability, grain size and mechanical behavior. In the present paper discussion is restricted to a study of the correlation between graphitizing tendency at 670°C. after quenching from several temperatures above the critical, and (I) the minor variations in the chemistry of these steels of "similar" chemical composition, and (2) the deoxida-tion practice employed. The state of the lead bath, oxidized or protected from oxidation by charcoal, used in the tempering treatments is also considered. Materials Eighteen plain carbon steels of about I per cent carbon, and containing similar amounts of each of the other common elements usually found as impurities, were obtained in the form of rods % in, in diameter from four steel manufacturers. The analyses for ordinary and special elements of all the steels were made on the rod stock as received in the laboratory, and the re-

Jan 1, 1941

By L. D. Jaffe, J. H. Hollomon

THE effect of tempering temperature and time upon the properties of quenched steel is clearly a subject of great practical importance, as well as of considerable theoretical interest. It would be very desirable to be able to predict the properties of a quenched steel when given any selected tempering cycle, with a minimum of experimental work upon that heat or even type of steel. Two problems are involved: one consists of relating the structure obtained to the physical properties, and will not be discussed here; the other, with which this paper deals, involves the relations of time, temperature and composition with the structure obtained on tempering. Indentation hardness is perhaps the most convenient quantitative measure of the tempered structure, or of what might be called the "degree of tempering." Undoubtedly, it is not an exact measure, and in some cases (as when temper-brittleness occurs) pieces of the same quenched and tempered steel may have widely differing properties at the same hardness. However, hardness has the advantage of being simple to determine and is certainly the most widely used indication of the degree of tempering. Moreover, for fully quenched steels that are not temper-brittle and do not contain retained austenite when quenched, it appears that, in general, if the hardness of the steel is the same, the tensile and impact properties will also be identical, whether a high or a low tempering temperature is used. The tempering charts available in the metallurgical literature usually give the hardness as a function of tempering temperature for only one tempering time. However, in practice, tempering times frequently vary, and a method of converting tempering curves for one time to tempering curves for some other time would be very valuable. It is also advantageous, in determining the tempering treatment necessary for a given part, not to have to temper samples at several temperatures for the time used for the commercial tempering operation. A more satisfactory procedure would be to employ times of the order of 10 to 30 min., rather than 5 or 10 hr., and if possible to use only one temperature. Furthermore, it is frequently desirable, for reasons such as temper-brittleness,* to obtain a given hardness with short times at relatively high temperatures, and it would be convenient to be able to compute without tests the time required to produce this hardness. Remarkably few quantitative studies of the hardness of quenched steel tempered over wide ranges of temperature and time

Jan 1, 1945

By Jasper L. Stuckey

It is not known when kaolin mining was first begun in North carolina, Evidence, in the form of excavations and primitive tools, indicates that some of the deposits were worked in prehistoric times. It has been suggested that the prehistoric mining was for mica, but the workings were all in altered or partly altered pegmatite material and the dumps do not represent the amount of material removed. some of the early openings may have been made in search of kaolin or semi-kaolinized feldspar which was sold to English1 traders along the coast and used in some Of the early English porcelains. In 1744,2 an application was made for an English patent to produce porcelain from an earthy mixture obtained from the Cherokee Nation in North America. It is well established, however, that the occurrence of kaolin in western North Carolina was known in England by 1767. In that year, Josiah Wedgewood sent T. Griffiths3,4 to what is now Macon County, North Carolina, to secure a supply Of kaolin for use in England. Griffiths diary, now in Etruria Museum, Stokes-on-Trent, contains a most interesting account of his experience. Kaolin was discovered at St. Austell, England, shortly after the voyage Of Griffiths, which probably accounts for the lack of further interest in American kaolin. Between 1767 and 1888, there are no records of kaolin mining in North Carolina. In the latter year, however, mining was begun near Webster, Jackson County, and, in the intervening period, has become an important industry. &apos;Or some 20 years, kaolin mining was carried On chiefly in Jackson, Macon, and Swain Counties. About 1904, it was begun in the Spruce Pine district and for the past 20 Yea&apos;s most of the kaolin mined in the State has come from Avery, Mitchell, and Yancey Counties. Distribution The kaolins of North Carolina are limited in occurrence to the Piedmont Plateau and Appalachian Mountain area of the State. While kaolins are widespread in the Piedmont Plateau, having been prospected for in Rutherford, Cleveland, Gaston, Granville, Lincoln, Catawba, Ire-dell, Richmond, Moore, Randolph, and Montgomery Counties, the production from that area has never been important. The known deposits of commercial importance are limited entirely to the mountain area of the State. While kaolins occur widely distributed throughout the mountain area and have been prospected for in many counties of that area, commercial production has come chiefly from two districts. One of these includes Jackson, Macon, Swain, and Haywood Counties. The other includes Avery, Mitchell, and Yancey Counties. Geology With few exceptions, all the known kaolin deposits in North Carolina contain

Jan 1, 1948

By Jasper L. Stuckey

HISTORY IT is not known when kaolin mining was first begun in North Carolina. Evidence, in the form of excavations and primitive tools, indicates that some of the deposits were worked in prehistoric times. It has been suggested that the prehistoric mining was for mica, but the workings were all in altered or partly altered pegmatite material and the dumps do not represent the amount of material removed. Some of the early openings may have been made in search of kaolin or semi-kaolinized feldspar which was sold to English1 traders along the coast and used in some of the early English porcelains. In 1944,2 an application was made for an English patent to produce porcelain from an earthy mixture obtained from the Cherokee Nation in North America. It is well established, however, that the occurrence of kaolin in western North Carolina was known in England by 1767. In that year, Josiah Wedgewood sent T. Griffiths3,4 to what is now Macon County, North Carolina, to secure a supply of kaolin for use in England. Griffiths diary, now in Etruria Museum, Stokes-on-Trent, contains a most interesting account of his experience. Kaolin was discovered at St. Austell, England, shortly after the voyage of Griffiths, which probably accounts for the lack of further interest in American kaolin. Between 1767 and 1888, there are no records of kaolin mining in North Carolina. In the latter year, however, mining was begun near Webster, Jackson County, and, in the intervening period, has become an important industry. For some 20 years, kaolin mining was carried on chiefly in Jackson, Macon, and Swain Counties. About 1904, it was begun in the Spruce Pine district and for the past 20 years most of the kaolin mined in the State has come from Avery, Mitchell, and Yancey Counties. DISTRIBUTION The kaolins of North Carolina are limited in occurrence to the Piedmont Plateau and Appalachian Mountain area of the State. While kaolins are widespread in the Piedmont Plateau, having been prospected for in Rutherford, Cleveland, Gaston, Granville, Lincoln, Catawba, Iredell, Richmond, Moore, Randolph, and Montgomery Counties, the production from that area has never been important. The known deposits of commercial importance are limited entirely to the mountain area of the State. While kaolins occur widely distributed throughout the mountain area and have been prospected for in many counties of that area, commercial production has come chiefly from two districts. One of these includes Jackson, Macon, Swain, and Haywood Counties. The other includes Avery, Mitchell, and Yancey Counties. GEOLOGY With few exceptions, all the known kaolin deposits in North Carolina contain

Jan 1, 1947

By L. Frank, Nason

THE complete statistics of zinc-ore production in the United States for 1916 are not yet available. The following figures are, therefore, only approximate. The total production of concentrates for this year, including New Jersey and Tennessee, amounts to 1,280,000 tons. Of this tonnage, five mines produced approximately 536,000 tons, or about 42 per cent. The remaining concentrates came mainly from the "Valley States," Missouri, Wisconsin, Kansas, Oklahoma, and Arkansas. The 1,280,000 tons of concentrates represent about 25,000,000 tons of crude or run-of-mine ore. Of the five mines producing the 42 per cent., the dimensions of three are approximately 25 by 1,500 by 2,000 ft. (7.6 by 457 by 610, m.) or more. Tour of the five mines are undoubtedly veins in the common acceptance of the term. They are located in great vein systems. The mines of "Valley States" have not, so far, been classed as veins; simply as "secondary deposits." The origin of these secondary deposits has been a warmly debated subject. Many geologists contend that they are the results of leaching from overlying and from adjacent rocks carrying but traces of zinc, these traces leached out and deposited in favorable loci. If this theory is correct, deposition is strictly limited to shallow depths. No volume of ore comparable to that of "true fissure veins" is to be expected. Just what this means to the future of zinc mining in these States is here indicated. The total zinc areas of these States amounts to about 9,124- sq. miles (23,631 sq. km.).- Assuming that 10 per cent. of this total will be more or less productive, there are 912 sq. miles (2,362 sq, km.) of "mineral? ground. The average depth of the operated mines is something like 100 ft. or less. In Bulletin 606, U. S. Geological Survey (1915), p. 202, Siebenthal makes the following statement: "The writer is informed by William Waugh, one of the drillers of the Stone City well, that cuttings from other wells which he drilled in the vicinity of Pittsburgh, Kan., have shown galena and sphalerite taken from a depth of 591 ft. (180.14 m.) and that the showing of ore at some places would be considered good enough to justify the sinking of a shaft had it been found in the Joplin district and at shallower depths." Leaving out of the question the prohibitive cost of such a shaft, there is

Jan 5, 1917

By Ming-Kao Yen, W. R. Hibbard

Various rationalizations of preferred orientations in cold worked polycrystalline metals have been based on the operation of at least two three2 five, an indefinite number, and all,6 slip systems of the type occurring in single crystals. Pickus and Mathewson3 suggested that the cold rolling texture in face-centered cubic metals could be rationalized on the basis of two or more operating slip directions symmetrically disposed about the direction of flow in such a manner that the resolved shear stress factor is equal for all operating slip systems and lattice rotations cancel each other. The importance of the direction of flow, the necessity for the operation of slip systems capable of producing the required changes in external dimensions, the maintenance of a common surface between adjacent grains and a symmetrical arrangement of the operating slip systems in order to produce an end orientation which is stable under additional deformation lead to the following rationalization of textures based on the type of slip systems operative in single crystals. The rationalization is intended to explain why certain orientations are suitable for deformational flow without a change in orientation and thus are stable end orientations or ideal texture orientations. It does not attempt to explain how the grains of a randomly oriented polycrystalline aggregate will reach this orientation. The rationalization is based on the following four postulates: 1. The ideal textures for polycrystalline aggregates are the result of reorientations of individual crystals toward the same stable end orientation at which no further reorientation will occur even during additional deformation. Since, in simple slip, the relative orientations of the stress axis and the active slip system determine the change in orientation during slip, it is considered that the orientation of the stress axis with respect to the ideal texture determines what slip systems must be active to retain the stable end orientation. Therefore the stable end orientation should be a symmetrical one around the stress axis with respect to the active slip systems such that lattice rotations resulting from slip will cancel each other and prevent a resultant change in orientation. (Rotational symmetry only—not translation, inversion, nor others—is considered here.) Thus a metal under a pure stress should develop a texture consisting of one or more of the crystallographically symmetrical directions, <100>, <110> or <111> for cubic metals or <0001>, <1010> or <1120> for hexagonal close-packed metals, parallel to the stress axis. 2. Since the active slip direction is the direction of glide during simple slip and thus the direction of maximum shear movement, in the ideal texture the active slip

Jan 1, 1949

By M. H. Caron

D. C. Ralston—The fact that none of the organizations that have worked on these ammoniacal leaching processes have contributed discussion of Mr. Caron&apos;s papers today is a matter of some disappointment. Adaptations, modifications and improvements have been made by several organizations or individuals and to complete the record I want to document a number of them. The Nicaro Nickel Co. operated a Government owned plant at Nicaro, Oriente, Cuba, during the past war. A report on the project was written for Reconstruction Finance Corp. and is in the document file collected by the Office of Technical Services, Commerce Department and filed with the Library of Congress, where it can be consulted or bibliofilm or photostat copies obtained by asking for copies of PB 97271. Nicaro Nickel Co. has obtained a series of U.S. Patents, my list (probably incomplete) of which bears the following numbers: 2,400,098; 2,400,114; 2,400,115; 2,400,461; 2,400,612; 2,458,902 and 2,473,795. International Nickel Co. has also studied the problem and U.S. Patent 2,478,942 shows that some of the complications involving occasional low extractions have been unraveled. Forward, Samis, and Kudryk, of the University of British Columbia, have also published a study of copper-nickel sulphide concentrate.&apos; Others are interested and it is evident that this type of hydrometallurgy is likely to find a happy application in the not-too-far distant future. Caron&apos;s two papers practically amount to a summation of his life&apos;s work on the important subject of nickeliferous iron ores and the American Institute of Mining and Metallurgical Engineers is fortunate to have been chosen the medium of publication. M. Rey—The ammonia leaching process has been the subject of certain studies in New Caledonia, but at the present time, the conditions are not very favorable to its adoption. The process is a combination of a thermal and a hydrometallurgical process. As a result, the first costs and the operative costs are rather high. To counteract this unfavorable situation, it would be necessary to make a very high extraction. But unfortunately, the process is delicate and in spite of all of Caron&apos;s valuable work, there are still many unknown factors. It is difficult to obtain regularly a high extraction, exceeding 75 to 80 pct. It would be interesting to have the opinion of Inter-national Nickel on the process and to know what the Dutch are doing in Celebes. M. H. Caron (author&apos;s reply)—I am quite familiar with the different types of nickel and cobalt ores as found on New Caledonia, and it may be pointed out that the Celebes ores are quite the same in their properties. Their behavior when treating the ores by the ammonia-leaching process is also alike and in my opinion, there is no reason why a high extraction of the New Caledonian ores could not be obtained if the process is properly applied. For the sake of completeness I may add that one of my patents has not been discussed in the papers. This patent deals particularly with the treatment of serpentine nickel ores. (Netherlands No. 62693 40a, French No. 965.786 April 21. 1948. and Cuban No. 13.625 Jan. 1950.)

Jan 1, 1951

By H. H. Kellogg

0. C. Ralston—The fact that none of the organizations that have worked on these ammoniacal leaching processes have contributed discussion of Mr. Caron&apos;s papers today is a matter of some disappointment. Adaptations, modifications and improvements have been made by several organizations or individuals and to complete the record I want to document a number of them. The Nicaro Nickel Co. operated a Government owned plant at Nicaro, Oriente, Cuba, during the past war. A report on the project was written for Reconstruction Finance Corp. and is in the document file collected by the Office of Technical Services, Commerce Department and filed with the Library of Congress, where it can be consulted or bibliofilm or photostat copies obtained by asking for copies of PB 97271. Nicaro Nickel Co. has obtained a series of U.S. Patents, my list (probably incomplete) of which bears the following numbers: 2,400,098; 2,400,114; 2,400,115; 2,400,461; 2,400,612; 2,458,902 and 2,473,795. International Nickel Co. has also studied the problem and U.S. Patent 2,478,942 shows that some of the complications involving occasional low extractions have been unraveled. Forward, Samis, and Kudryk, of the University of British Columbia, have also published a study of copper-nickel sulphide concentrate.&apos; Others are interested and it is evident that this type of hydrometallurgy is likely to find a happy application in the not-too-far distant future. Caron&apos;s two papers practically amount to a summation of his life&apos;s work on the important subject of nickeliferous iron ores and the American Institute of Mining and Metallurgical Engineers is fortunate to have been chosen the medium of publication. M. Rey—The ammonia leaching process has been the subject of certain studies in New Caledonia, but at the present time, the conditions are not very favorable to its adoption. The process is a combination of a thermal and a hydrometallurgical process. As a result, the first costs and the operative costs are rather high. To counteract this unfavorable situation, it would be necessary to make a very high extraction. But unfortunately, the process is delicate and in spite of all of Caron&apos;s valuable work, there are still many unknown factors. It is difficult to obtain regularly a high extraction, exceeding 75 to 80 pct. It would be interesting to have the opinion of Inter-national Nickel on the process and to know what the Dutch are doing in Celebes. M. H. Caron (author&apos;s reply)—I am quite familiar with the different types of nickel and cobalt ores as found on New Caledonia, and it may be pointed out that the Celebes ores are quite the same in their properties. Their behavior when treating the ores by the ammonia-leaching process is also alike and in my opinion, there is no reason why a high extraction of the New Caledonian ores could not be obtained if the process is properly applied. For the sake of completeness I may add that one of my patents has not been discussed in the papers. This patent deals particularly with the treatment of serpentine nickel ores. (Netherlands No. 62693 40a, French No. 965.786 April 21. 1948. and Cuban No. 13.625 Jan. 1950.)

Jan 1, 1951

THERE has been a lot of talk about the shortage of engineers and we have done our share of it; but recently we heard a spot radio commercial-between broadcasts-urging high school seniors to study engineering. We think this is going too far. Engineering is an exacting profession requiring the highest personal qualifications. Publicity for the purpose of interesting capable young people in choosing courses in engineering should emphasize qualification. The opportunities for a career in a great constructive profession which is the basis of our high standard of living should be properly evaluated. Although there is a need for more engineers today, nobody knows what the employment potential is going to be four years hence. The profession may do itself a grave disservice by attempting mass recruitment in the face of an unpredictable national economy. The mining and metals industries are in a special position as fewer engineers are needed in these fields. Only 10 pct of all engineers are mining and metallurgical engineers. Today&apos;s shortage is not so much in recent graduates, but in trained practicing engineers. The shortage has served the profession to good effect because it directed the talents of engineers into more productive channels. In some areas high school graduates have been put into routine jobs such as, surveying. If there is one thing the mining profession does not want, it is an oversupply of graduates which would relegate college men to years of work and discouragement in routine jobs. The public has a clear cut picture of the legal and medical professions and thus the respect knowledge imparts. But the engineer is variously thought of as a man who pulls the throttle lever on a locomotive, tends a furnace, or builds a bridge. The term engineer is too loosely used. For instance we have heard of "crowd engineers" and "exterminating engineers." In some unions an engineer designation has been established to describe a person doing routine checking or other control job. We do not disparage these positions but they are different from the work done by the man qualified by years of experience and study. Many of these so-called engineers are not engineers at all. The engineering profession has cooperated closely on a program of recruiting high school graduates for engineering study. It should start a cooperative public relations program to enlighten the public on the accomplishments and work of engineers. This type of publicity need not be of the bombastic type. It can be educational and dignified. Radio, television, and the periodicals can be used to convey information. It is time that laymen and interested young people learn to make a distinction between the true engineer and the technician. Such a program would instruct parents and high school students and thereby interest the right type of people in the engineering profession. The Centennial of Engineering sponsored by the American Society of Civil Engineers is a step in the direction of instructive public relations. This fine start should not be allowed to remain as a one pass venture. The engineering profession as a whole should follow this exposition with a sustained, well directed effort to inform the public of the engineer&apos;s work and the possibilities it holds for a constructive career.

Jan 1, 1952