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By Etienne A. Ritter

The Evergreen mine, located at Apex, in the northern part of Gilpin county, Colorado, has opened a very peculiar and interesting copper-deposit, in which both bornite and chalcopyrite occur as rock-minerals. The country-rocks are crystalline schists cut by dikes of granu-lite and of pegmatite. At the Evergreen property they have been cut by a dike of a uew kind of eruptive rock, to which I have given the name " Evergreenite." The rock is composed of quartz, alkali feldspars, orthoclase and albite (often interlocked as microperthite), with augite of the ægirine variety and long needles of enstatite and diallage. For reasons stated below, I believe the dike to be of Tertiary age. It is easily traced on the surface of the ground, from a point in the bottom of Pine creek, about a mile below Apex, to the top of Nevada hill, 1,500 ft. beyond and 600 ft. above it. (See Fig. 1.) It varies from 3 to 12 ft. in width, and is bounded on both sides by contact-zones about 60 ft. wide, in which the crystalline schists have been changed into pseudo-quartzites or pseudo-gneisees, according to the injection of an excess of quartz or of feldspars through the special layer of the schists. The most interesting feature is the presence of the pyroxenes, which are always found, though in very variable proportions from place to place, in the layers of these metamorphosed crystalline schists. The dike has torn from its walls a large number of fragments of the wall-rock. It must have been in a viscous state when that happened, because these fragments of the wall-rock do not show any sign of resorption or of assimilation by the magma. In places they are so distinct and so numerous that the rock looks to the naked eye like a pseudo-breccia, of which, never-

Jan 1, 1908

By Rudolf Gahl

Page Tests Conducted in Small Test Mill................... 577 Demonstration Tests Conducted by Minerals Separation Co....... 577 Flotation Tcsts Conducted by Inspiration Co............. 577 Sampling of Orebody........................ 578 Other Results Obtained in Small Test Mill.............. 580 Tests Conducted in Large Test Mill................... 580 Flow Sheet............................. 580 Discussion of the Value of Preliminary Table Treatment......582 Callow Flotation Installation..................... 585 Flinn-Towne ~nstallation...................... 587 Cole-Bergman Installation...................... 588 Methods Followed in Competitive Tests................ 590 Advantage of Pneumatic Flotation Machines.............. 591 Pneumatic Machines of Minerals Separation Co............. 591 Float Skimming Device......................; 594 Experimental Inspiration Flotation Machine.............. 596 Arrangement of Callow Cells in Series ................ 598 Variations of Flow Sheet....................... 599 Coal Tar as Flotation Agent..................... 600 Experience with Primary Slime.................... 602 Influence of Iron on Flotation..................... 605 Influence of Chemicals on Primary Slime............... 607 Fineness of Crushing Desired.................... 607 Operation of Large Concentrator..................... 608 Flow Sheet of Callow Sections.................... 608 Flow Sheet of Inspiration Sections.................• 609 Inspiration Flotation Machine of Steel Construction.......... 610 Minerals Separation Section..................... 613 Filter Plant............................ 613 Results Obtained in Commercial Concentrator............... 616 Tonnage............................... 616 Air and Power Consumption...................... 616 Floor Space............................ 617 Water Consumption......................... 617 Recovery............................. 618 Oil Consumption.......................... 618 Operating Costs for Flotation..................... 620 Discussion of Results Obtained.................... 620 Prospects for Futurc Development of the Flotation Process......... 621 Porous-Bottom Experiments..................... 622 Raising the Grade of Concentrates.................. 624 Recovering Carbonates by Flotation................. 624 Recovery of Silicates by Flotation.................. 627 General Theory......................... 628 Conclusion............................... 630

Jan 1, 1917

By J. Nutting, J. W. Cahn

WITH the development of thin film techniques for the direct examination of metals in the electron microscope some new problems in quantitative metallography have become apparent. In order to obtain certain contrast effects in the electron optical image when examining thin films from alloys containing dispersed phases, it is essential to use films of a thickness at least two or three times greater than that of the mean particle diameter of the dispersed phase. From micrographs of such specimens it may be desired to obtain the volume fraction of the dispersed phase and the number of particles of the phase in a unit volume of the matrix. Under these conditions the particles sectioned by

Jan 1, 1960

By Albert C. Harding

FOR several years barite (BaSO4) production has topped such better known minerals as feldspar and fluorspar in annual tonnage and is now well established among our foremost nonmetallic industries. DESCRIPTION Of widespread occurrence in the United States, barite is relatively soft (hardness, 2.5 to 3.5), inert, heavy (specific gravity, 4.5), and is also called "barytes" (sometimes pronounced "bear-i-tease"), "heavy spar" and "tiff." It occurs with granular and earthy structure but usually has coarse, orthorhombic crystallization. It is commonly white, and although occurring in various shades of red, yellow, and gray, barite always gives a white streak and can be scratched by the ordinary prospecting pick. Its softness and weight are usually sufficient to establish field identification. Another aid is the "rotten egg" odor of H2S which sometimes emanates from freshly fractured surfaces. Barite can be readily distinguished from two other minerals which have somewhat similar occurrences and characteristics. The relatively rare celestite, strontium sulphate, has a specific gravity slightly less than 4.00 and gives a distinctively crimson color in a flame test. The very rare witherite, barium carbonate, has a specific gravity of 4.3 but readily effervesces with dilute hydrochloric acid. OCCURRENCE All known commercially important barite deposits in the United States occur as re placements or cavity fillings in schists, shales, limestones, dolomites, and quartzites, or as residual deposits from such formations. In Georgia, Tennessee, North Carolina, and Missouri, high-grade barite is recovered as fragments from residual clays covering quartzites and dolomites. In Arkansas, Nevada, and California, barite, usually of lower grade, is mined from replacement deposits. These seven states contributed the entire production reported by the U. S. Bureau of Mines for 1945 as given in Table I. [TABLE 1-Crude Barite Sold or Used by Producers in 1945 STATE SHORT TONS Arkansas260,660 Missouri225,467 Georgia110,393 Tennessee32,812 Nevada28,919 Other States37,811 Total 696,062] "Other States" included only California and North Carolina. Such a large part of this undistributed production came from California that that state probably outranked both Nevada and Tennessee. For the second consecutive year Arkansas was the leading producing state, particularly worthy of note because there was no commercial production of barite there prior to 1941 and because the entire production of Arkansas has come from one large deposit which is being operated by two companies. CONSUMPTION [The 1945 consumption as reported by the Bureau of Mines was: 482,442 tons as ground barite 139,288 tons in making lithopone 99,173 tons in producing barium -- chemicals Total 720,903 tons]

Jan 1, 1947

By Clarence Zener

Contents Page General Principles................................................................. 551 Equilibrium Diagrams......................................................... 551 Nucleation................................................................... 553 Kinetics of Phase-boundary Propagation......................................... 553 Kinetics of Growth of New Phase............................................... 556 Spheroidization............................................................... 560 Pure Iron-carbon System........................................................... 561 Formation of Pearlite.......................................................... 561 Interlamellar Spacing........................................................ 562 Pearlite C-curve............................................................. 563 Bainite Formation............................................................. 565 Formation of Martensite....................................................... 570 Loss of Tetragonality of Martensite.............................................. 570 Effect of Alloys upon Decomposition of Austenite..................................... 572 Pearlite...................................................................... 572 Bainite and Martensite......................................................... 574 Time-temperature-transformation Curves............................................. 576 Appendix A............................................................. ......... 579 Appendix B....................................................................... 580 Appendix C....................................................................... 580 The present investigation started in an attempt to understand certain details of the decomposition of austenite, and of the effect of alloying elements thereon. As the investigation proceeded it became apparent that not only these details, but all the general features of austenite decomposition, could be understood in terms of fundamental physical principles. Since the direct applicability of these physical principles has not been previously recognized, it was decided to incorporate the original results of the investigation into a review of the general subject of the kinetics of austenite decomposition. This review constitutes the present article. An extended summary of the results is given on pages 576 to 579. This article, which deals with the kinetics of phase transformations, may appropriately be considered as a sequel to two recent articles1,2 from this laboratory on the equilibrium relations in medium alloy steels.

Jan 1, 1947

By Clarence Zener

Contents Page General Principles................................................................. 551 Equilibrium Diagrams......................................................... 551 Nucleation................................................................... 553 Kinetics of Phase-boundary Propagation......................................... 553 Kinetics of Growth of New Phase............................................... 556 Spheroidization............................................................... 560 Pure Iron-carbon System........................................................... 561 Formation of Pearlite.......................................................... 561 Interlamellar Spacing........................................................ 562 Pearlite C-curve............................................................. 563 Bainite Formation............................................................. 565 Formation of Martensite....................................................... 570 Loss of Tetragonality of Martensite.............................................. 570 Effect of Alloys upon Decomposition of Austenite..................................... 572 Pearlite...................................................................... 572 Bainite and Martensite......................................................... 574 Time-temperature-transformation Curves............................................. 576 Appendix A............................................................. ......... 579 Appendix B....................................................................... 580 Appendix C....................................................................... 580 The present investigation started in an attempt to understand certain details of the decomposition of austenite, and of the effect of alloying elements thereon. As the investigation proceeded it became apparent that not only these details, but all the general features of austenite decomposition, could be understood in terms of fundamental physical principles. Since the direct applicability of these physical principles has not been previously recognized, it was decided to incorporate the original results of the investigation into a review of the general subject of the kinetics of austenite decomposition. This review constitutes the present article. An extended summary of the results is given on pages 576 to 579. This article, which deals with the kinetics of phase transformations, may appropriately be considered as a sequel to two recent articles1,2 from this laboratory on the equilibrium relations in medium alloy steels.

Jan 1, 1947

Correlation between Metallography and Mechanical Testing By H F MOORE (Henry Marion Howe Memorial Lecture Trans, vol 120 11,000 words ) The lack of effective correlation between metallography and mechanical testing from the days of Reaumur to the present is noted, and two general problems of such cor¬relation are stated (1) the correlation of qualitative test results with quantitative, and (2) the correlation of average results with maximum or minimum results Some correlation has been achieved, notably in the field of heat-treatment and in the study of elastic strength of metals Correlation is in the process of being developed in several other fields, including the quantitative study of the effect of grain size of metal on mechanical properties, of grain size and type of crystalline structure on the sensitivity of metals to weakening at holes, notches and other "stress raisers," and in the study of the starting phases of spreading, "fatigue" cracks Correlation of mechanical test results and metallographic study is needed in the study of such problems as the various theories of failure of metals, the meaning of and tests for service ductility of metals, and the relative damaging effect of defects inherent in metals, such as minute cracks and segregation, as compared with the damaging effect of "imposed" stress raisers, such as screw threads, sharp shoulders, etc The neces¬sity for more correlation of metallography and mechanical testing during student days is emphasized, and also the need of a better understanding on the part of engi¬neers of the significance and limitations of metallographic apparatus and results and of X-ray diffraction This should be matched by a better understanding on the part of metallurgists of the significance and limitations of mechanical tests of metals, of testing machines and strain-measuring apparatus

Jan 1, 1937

By Robert Keeney

Before the outbreak of the war in 1914, the only electric-furnace smelting plant operating on a commercial basis west of the Mississippi River was an electric pig-iron plant in California; rare metal ores were not smelted, concentrates of molybdenum, tungsten, uranium, and vanadium ores being shipped east for reduction. Practically no- chrome ore was being mined, and only comparatively small amounts of manganese ore. Today there are two electric smelting plants in California, one in Washington, one in Iowa, and four in Colorado; two plants are under construction in California, and one in Montana. Ores of manganese, chromium, molybdenum and tungsten are now smelted in the West, and although uranium and vanadium concentrates are still shipped to the East, they will probably be treated in western plants in a short time. The four electric-furnace plants in Colorado are listed in Table 1. TABLE 1.-Electric Smelting Plants in Colorado Capacity, Company, Location Kilowatts Products . Tungsten Products Co Boulder 800 Ferrotungsten, ferromolybdentun. Boulder Tungsten Production Co. . Boulder 400 Ferrotungsten. Ferro Alloy Co Utah Junction 1200 Ferrochrome, ferrotung-sten. Iron Mountain Alloy Co Utah Junction 3000 Ferromanganese. Power for all of these plants is supplied by the Colorado Power Co.

Jan 8, 1918

By J. D. Hunt, R. J. McDonald

It is proposed that extensive fluid motion occurs between the dendrites of a Partially solid casting and it is suggested the A segregates in steel castings are a direct result of this motion. The fluid flow arises because of density differences between liquid ahead of the dendrites and the interdendritic liquid. Experiments are described on a model system investigating this fluid motion. The importance of interdendritic fluid flow is discussed with reference to longitudinal segregation. SERIOUS macro segregation is often found in large killed steel ingots. Among the most common segregates are those known as A and V, Fig. 1. The A segregates are arranged over the surface of cones, the wide parts being at the base of the ingot. The A segregates are pencil like in shape and extend from the columnar into the equiaxed region. The V segregates are distributed over inverted cones but have a less well defined shape. They occur at the center of the ingot. Because of the commercial importance of macro inhomogenities these segregates have attracted wide-scale attention. The segregates contain alloying elements and impurities which depress the freezing temperature and are thus the last liquid to freeze. A number of explanations have been proposed to explain their presence. It has been suggested1'' that the segregates are the result of the equiaxed zone growing towards the columnar region together with the interaction of convection within the bulk liquid. It has also been proposed that the segregates are the result of nucleation and rapid growth ahead of the dendritic front.3 Neither of these explanations is completely satisfactory because A segregates are pencil shaped and are not found as continuous cones. In this paper an alternative mechanism is proposed, and experiments are described on a model system to determine whether the mechanism occurs in practice. It is thought that A and V segregates are not peculiar to steels but should occur in many other large castings. Fluid motion within the bulk liquid region of a casting has been extensively discussed. Little attention has been paid to fluid motion within the partially solid regions. The work415 that has been done has been mainly concerned with the fluid motion which results from the volume contraction on freezing. The volume contraction is used to explain various types of macro segregation. The present authors suggest that in many cases the fluid flow resulting from volume contraction will be small compared with that due to other causes. When the columnar region is growing, the liquid still remaining between the dendrites has a much lower temperature near the ingot walls than at the dendrite tips. The composition of the liquid in contact with solid will vary with temperature. The density of the liquid will thus vary both because of changes in temperature and composition. The layers of different density liquid will give rise to a slow but steady liquid flow through the interdendritic regions. If there is no density change with composition, the temperature gradient within the dendritic region should give rise to a downward flow between the dendrites, shown schematically in Fig. 2. When the liquid density changes appreciably with alloy concentration this motion could either be en-

Jan 1, 1970

By George M. Fowler, F. E. Gregory, William M. Agar, Joseph P. Lyden

The fact that most of the zinc-lead ores of the Tri-State district are associated with abundant chert in the Boone formation has led us to give much consideration to the manner of occurrence of the chert throughout the formation and to its relationship to the structural and other geologic features having bearing upon the sulfide mineralization. Necessarily the question of the source and the manner of deposition of the chert has come up in the course of these studies. We do not pretend to have arrived at the answer to all the questions regarding the chert. However, we have made a very large number of field observations, which present certain facts about the chert in this district that may be worth elaboration. Whatever theories may be drawn upon to explain the presence and distribution of the chert must necessarily be capable of reconciliation to these facts. The more important theories that have been presented are briefly summarized, and some of them discussed, in this paper. This paper is in three distinct parts, each complete in itself, wherein is recorded the evidence gained from three separate methods of attack. In an earlier paper,(3)‡ we briefly described the chert and its relation-ship to the ore deposits. Chertification, as used in this paper, means the replacement of limestone by introduced silicic acid. It is a common phenomenon in many widely distributed limestones. The products of chertification may be chert, cotton rock, or tripoli, depending upon the extent to which the replacement has been carried. Chertification is used instead of silicifica-tion in order to reserve the latter for the siliceous emanations so common in connection with the sulfide ore deposits of this and many other districts. Broadly, it is meant to include all silicification in this district prior to the introduction of the jasperoid, the latter being contemporaneous with the ore-bearing solutions.

Jan 1, 1935

By William M. Agar, F. E. Gregory, Joseph P. Lyden, George M. Fowler

The fact that most of the zinc-lead ores of the Tri-State district are associated with abundant chert in the Boone formation has led us to give much consideration to the manner of occurrence of the chert throughout the formation and to its relationship to the structural and other geologic features having bearing upon the sulfide mineralization. Necessarily the question of the source and the manner of deposition of the chert has come up in the course of these studies. We do not pretend to have arrived at the answer to all the questions regarding the chert. However, we have made a very large number of field observations, which present certain facts about the chert in this district that may be worth elaboration. Whatever theories may be drawn upon to explain the presence and distribution of the chert must necessarily be capable of reconciliation to these facts. The more important theories that have been presented are briefly summarized, and some of them discussed, in this paper. This paper is in three distinct parts, each complete in itself, wherein is recorded the evidence gained from three separate methods of attack. In an earlier paper,(3)‡ we briefly described the chert and its relation-ship to the ore deposits. Chertification, as used in this paper, means the replacement of limestone by introduced silicic acid. It is a common phenomenon in many widely distributed limestones. The products of chertification may be chert, cotton rock, or tripoli, depending upon the extent to which the replacement has been carried. Chertification is used instead of silicifica-tion in order to reserve the latter for the siliceous emanations so common in connection with the sulfide ore deposits of this and many other districts. Broadly, it is meant to include all silicification in this district prior to the introduction of the jasperoid, the latter being contemporaneous with the ore-bearing solutions.

Jan 1, 1935

The fact that most of the zinc-lead ores of the Tri-State district are associated with abundant chert in the Boone formation has led us to give much consideration to the manner of occurrence of the chert throughout the formation and to its relationship to the structural and other geologic features having bearing upon the sulfide mineralization. Necessarily the question of the source and the manner of deposition of the chert has come up in the course of these studies. We do not pretend to have arrived at the answer to all the questions regarding the chert. However, we have made a very large number of field observations, which present certain facts about the chert in this district that may be worth elaboration. Whatever theories may be drawn upon to explain the presence and distribution of the chert must necessarily be capable of reconciliation to these facts. The more important theories that have been presented are briefly summarized, and some of them discussed, in this paper. This paper is in three distinct parts, each complete in itself, wherein is recorded the evidence gained from three separate methods of attack. In an earlier paper,(3)‡ we briefly described the chert and its relation-ship to the ore deposits. Chertification, as used in this paper, means the replacement of limestone by introduced silicic acid. It is a common phenomenon in many widely distributed limestones. The products of chertification may be chert, cotton rock, or tripoli, depending upon the extent to which the replacement has been carried. Chertification is used instead of silicifica-tion in order to reserve the latter for the siliceous emanations so common in connection with the sulfide ore deposits of this and many other districts. Broadly, it is meant to include all silicification in this district prior to the introduction of the jasperoid, the latter being contemporaneous with the ore-bearing solutions.

Jan 1, 1935

By F. E. Gregory, George M. Fowler, William M. Agar, Joseph P. Lyden

The fact that most of the zinc-lead ores of the Tri-State district are associated with abundant chert in the Boone formation has led us to give much consideration to the manner of occurrence of the chert throughout the formation and to its relationship to the structural and other geologic features having bearing upon the sulfide mineralization. Necessarily the question of the source and the manner of deposition of the chert has come up in the course of these studies. We do not pretend to have arrived at the answer to all the questions regarding the chert. However, we have made a very large number of field observations, which present certain facts about the chert in this district that may be worth elaboration. Whatever theories may be drawn upon to explain the presence and distribution of the chert must necessarily be capable of reconciliation to these facts. The more important theories that have been presented are briefly summarized, and some of them discussed, in this paper. This paper is in three distinct parts, each complete in itself, wherein is recorded the evidence gained from three separate methods of attack. In an earlier paper,(3)‡ we briefly described the chert and its relation-ship to the ore deposits. Chertification, as used in this paper, means the replacement of limestone by introduced silicic acid. It is a common phenomenon in many widely distributed limestones. The products of chertification may be chert, cotton rock, or tripoli, depending upon the extent to which the replacement has been carried. Chertification is used instead of silicifica-tion in order to reserve the latter for the siliceous emanations so common in connection with the sulfide ore deposits of this and many other districts. Broadly, it is meant to include all silicification in this district prior to the introduction of the jasperoid, the latter being contemporaneous with the ore-bearing solutions.

Jan 1, 1935

By A. A. Burr, D. G. Ebeling

The effects of casting texture, grain orientation and grain size upon the performance of Alnico permanent magnets is described. Single-crystal specimens were produced by special sintering and grain coarsening techniques to study the effect of crystal orientation. In addition to texture and orientation effects, an analysis of the results indicates that the permanent magnet performance is impaired by a refinement of the grain size. AN excellent historical review of the development of Alnico permanent magnets has been prepared by Bozorth.1 The desirable permanent magnet characteristics of Fe-Ni-A1 alloys were discovered in 1932 by Mishima.2,3 The work of Ruder' showed that the alloys were age-hardenable, and Betteridge5 defined the best composition and heat treatment for the magnetically isotropic alloy known as "Alnico 3." Horsburgh and Tetley0 increased the energy product by the addition of cobalt and copper, "Alnico 2," and Oliver and Sheddon7 demonstrated that cooling in a magnetic field improved the residual induction of this alloy. Jonas8,9 then disclosed the great practical benefits of heat treating an alloy of higher cobalt content in a magnetic field and the resulting alloy, "Alnico 5," has become the standard of the industry. This paper describes the fundamental aspects of a procedure which can be used to further improve the properties of these anisotropic permanent magnet alloys. A study of the casting techniques used in the production of anisotropic Alnico permanent magnets indicated that the magnetic quality was affected by the as-cast macrostructure. Improved performance was observed in magnets containing a high percentage of columnar grains whose long axes were parallel to the magnetic axis of the casting. McCaig10 studied the effect of such columnar grain structures upon the magnetostriction characteristics of similar alloys, however no data was presented showing the effects on other magnetic properties. The following paragraphs describe two experiments which were conducted to determine the effect of various grain orientations upon the energy product. Special composite molds were prepared of highly conductive and highly refractive components to remove the heat of solidification from the casting in a controlled manner. Representative macrostructures produced by these techniques are shown in Fig. 1, along with the relative volumes of favorably oriented columnar grains. The alloy, Alnico 5, has the highest permanent magnet performance of any commercial magnet material. It has the nominal weight composition of 8 pct Al, 14 pct Ni, 24 pct Co, 3 pct Cu, and 51 pct Fe. A heat of this material was cast into molds producing the type A and B grain structures shown in Fig. 1 and pairs of the resulting magnets were placed in heat-treating boats so as to eliminate any biasing effects of boat position. After a standard heat treatment the type A magnets, with 16 pct of the volume composed of favorably aligned grains, had a maximum energy value of 3,940,000 gauss-oersteds, while the type B magnets with 73 pct aligned grains averaged 5,090,000. This large im-

Jan 1, 1954

By D. M. Hausen

This study identifies and describes various crystalline phases of the V205-Na20 system, and relates their properties to metallurgical aspects of vanadium production. Phase equilibria and stability ranges of sodium vanadate phases of varying molar ratios of Na20/V205 were investigated in a variety of plant products, ranging from fused "black cakes" (V20 melts) to "salt roast" calcines. Crystalline compounds, Including vanadium pentoxide, V205; sodium vanadyl vanadate, 6 phase, Na2O.V2O5.5V2O5; sodium vanadyl vanadate, y phase, 5Na20.V204.12V205; sodium metavanadate, Na20 .V 05; sodium pyrovanadate , 2Na20 .V205; and sodium orthovanadate, 4Na20.~2~5, have been characterized with the aid of X-ray diffraction patterns, infrared spectra, and optical properties in addition to chemical analyses, as a guide to mineralogical "troubleshooting" of plant problems and processes in vanadium pyro- and hydrometallurgy.

Jan 1, 1984

By Henry E. Wood

In my opinion, the concentration of minerals by flotation is the most interesting problem in ore-dressing, and will command eventually far more consideration than it has at present. For many ores it furnishes a complete method of concentration absolutely independent of specific gravity, and thus simplifies the milling of many difficult combinations. Not having to recognize the influence of specific gravity, we are also able to dispense with some of the complications resulting from classifying-conditions. Where flotation cannot be used for a complete separation of the minerals from the gangue, it will be found, in nearly all cases, to save those portions which are generally lost by reason of their fine state of division. For this reason, it should be looked upon mainly as an aid to general concentration, although there are many ores so well adapted to flotation that more than 90 per cent. of the valuable metals can be recovered from them in one operation by this process. In presenting the results of my investigations in flotation, I have endeavored to theorize as little as possible. That side of the subject has been extensively discussed by others. My earliest work with flotation was done in 1895, when I used various oils, grease, soap, etc., with results that were remarkable. I did not realize then that with water alone equally good separations could be made. Up to 1906, my endeavors were confined to attempts to keep the concentrates on the tables well wetted and away from exposure to the air. In common with others, I observed that when there mas any obstruction in the wash-water on the table of sufficient size to divert the water to either side, the concentrates collected, and, on exposure to the air, would promptly float away. This convinced me that the sulphides were all good "swimmers," and that if,

Jan 1, 1913

Institute of Metals Division Iron and Steel Division Extractive Metallurgy Division Council A W Thornton (ISD), Chairman, R W Shearman, Secretary, C S Barrett (IMD), J C Kinnear, Jr (EMD), John Chipman (ISD), J S Smart, Jr (IMD), A W Schlechten (EMD), M E Volin (MED), D S Eppelsheimer (MIED) Journal of Metals Editorial Advisory Committee J S Smart, Jr, Chairman, W A Dean, J J Golden,T D Jones, Evan Just, J C Kinnear, Jr, M Tenenbaum Pacific Northwest Regional Conference E R Marble, General Chairman, Marshall Huntting, Assistant General Chairman, W C Douglass, Mining Chairman, H C Hughes, Mining Chairman for British Columbia, W C Douglass, Mining Chair¬man for United States, Paul Billingsley, Geology Chairman, W D Nesbeitt, Miner¬als Beneficiation Chairman, H D Kelley, Industrial Minerals Chairman, J G Johnston, Metals Chairman, Lloyd Banning, Iron and Steel Chairman, W G Rouillard, Extractive Metallurgy Chairman, E C Roberts, Physical Metallurgy Chairman, D A Pifer, Mineral Industry Education Chairman, Frederick Brien, General Arrangements Chairman Metals Branch Membership Committee C M Squarcy, Chairman, R C Cole, Harold Mar¬golin, M E Nickel, S K Scovil Bylaws Committee A W Thornton, Chairman, W R Hibbard, Jr, J S Smart, Jr (IMD), John Chipman, T S Washburn (ISD), T D Jones, J D Sullivan (EMD)

Jan 1, 1956

By J. H. Pratt

In a recent paper* on the origin of corundum associated with the peridotites of North Carolina, attention was called to the constant occurrence of the mineral, chromite, in these rocks. The field-data obtained during the preparation of that paper have been used largely in the present paper. During the past summer the general occurrences of chromite have been carefully studied, and those in North Carolina have been especially examined in the field. It is purposed to give, in this paper, the reasons why the chromite should be regarded as having been formed at the same time with the peridotites, having been held in solution by the molten mass of the peridotite, and crystallizing out among the first minerals as the mass began to cool. This theory is essentially the same as that advanced by me for the origin of the corundum associated with the peridotite rocks, and a similar line of reasoning has been used to substantiate the theory proposed. Investigations concerning the igneous origin of some of the ores have been materially aided, during recent years, by the skillful experiments of Morozewicz and Lagorio,§ and by researches that show us, more clearly, why we should regard a fused mass of rock as a liquid, having similar properties to an ordinary solution. These experiments have shown that a molten basic glass, similar in composition to the basic magnesian rocks, dissolves alumina readily, and that upon cooling, the first minerals to separate out are corundum and spinel.

Jan 1, 1900

By Lillian Erskine

While brass and other copper alloys have long been listed as offering health hazards to their workers, it is questionable if the metals involved are alone responsible for the trades' records of morbidity. The entire science of foundry sanitation is the product of the past two decades; and the best standards now operative would have been regarded as little short of revolutionary prior to 1910. The special handicap to the conservation of the health of the brass founder's employees has been the fact that, unlike the iron founder, his business could be profitably carried on in almost any small and unsanitary quarters. As a result, writers on occupational disease have accepted brass chills or brass founders' ague as an inevitable feature of the trade; and respiratory disabilities, as well as phthisis and disturbances of the nervous system, are also included as prevalent among those employed. While there can be no question as to the basic accuracy of past investigations, there is every reason to doubt the necessity for an undue percentage of ill health among brass molders and casters who are safeguarded by scientific ventilating standards and by improving personal habits of sobriety. There is, however, need for a campaign of education as to the most approved practices and equipment whereby the employer may safeguard the health of his workers, and thereby reduce his labor turnover and increase his productive efficiency. Broadly speaking, copper, tin, and aluminum carry negligible health hazards. The toxic qualities of lead, however, are a menace; especially if scrap lead is recovered or bought for foundry processes. The rapid volatilization of zinc renders its fumes and flocculent condensation the chief problems in conserving the health of the brass worker. The frequent presence in the foundry air of traces of arsenic compounds, lead

Jan 1, 1919

By Walter E. Mingramm

The construction of rescue-apparatus on the principle of furnishing the wearer with air from a tank containing it under high pressure was given up by inventors about 20 years ago. Such an apparatus must supply continuously, for not less than two hours, nearly 50 liters of pure air at atmospheric pressure per minute, or a total of 6,000 liters (210 cu. ft.); and a cylinder containing this amount of air, under 2,000 lb. pressure, would weigh 180 lb. or more. Although apparatus has been recently constructed utilizing liquefied air, no experiments have been made to determine the regularity with which the air is generated, nor has its chemical composition been determined. Moreover, the chief objection to such an apparatus is the difficulty and cost of keeping on hand a large quantity of liquefied air. The system of furnishing the wearer of a breathing-apparatus with air which has given the best results, and has found

Jan 1, 1909