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By Edward P. Chapman

IN the Leadville district toward the close of the "intermediate mesothermal period" of mineralization, there occurred a stage of ore deposition marked by a rather complex mineral association. As bismuth minerals formed in many places during this period, it is here called the "bismuth stage" for convenience of description. The minerals so far identified with this stage, listed roughly in the order of prominence, are: chalcopyrite; several varieties of galena, differing slightly from one another in their small contents of silver, bismuth and tellurium; altaite; hessite; galenobismutite; alaskaite; aikinite; ,gold; tennantite; argentite; and perhaps sphalerite and arsenopyrite. With the exception of gold, the age relations of these minerals are difficult to determine. As shown in their descriptions, they all appear contemporaneous and hypogene. Gold may be in part contemporaneous, but most of it is distinctly later. Where minerals of this stage occur so that they can be mined alone, as at the Tucson mine, they constitute high-grade ore. Elsewhere their presence in small amounts has served to increase greatly the value of what otherwise would be low- grade pyritic or zinc-lead sulphide ore. The distribution of the bismuth ores corresponds closely to the distribution of gold ores, though not so general. It seems probable that most of the gold in the district was deposited during the "bismuth stage." These ores occur relatively near the supposed centers of mineralization in Breece and Printer Boy Hills or deep down along the Tucson-Maid fault, which is one of the well recognized channels of mineralization in the Iron Hill and Graham Park areas. Consideration of the high-grade nature of this mineralization and the fact that it appears to be found relatively close to the source of mineralization suggests that prospecting along some of the known channels, even deeper than they have yet been prospected, may offer hope of commercial success.

Jan 1, 1939

By A. C. Spencer, H. F. Bain, E. C. Harder, Sidney Paige, C. M. Weld, W. Lindgren

At a meeting of the New York Section, on May 23, 1918, the sole subject of discussion was the nature and occurrence of iron ores in certain parts of the world." Owing to the importance of this subject, it has been deemed advisable to publish the remarks made at that meeting in the form of a paper, for presentation at the Milwaukee Meeting. The remarks related to the following districts: Page Brazil. By E. C. Harder................................. 116 Scandinavia. By Waldemar Lindgren..................... 120 Cuba. By C. M. Weld.................................. 124 Southern Europe. By A. C. Spencer...................... 130 China. By H. Foster Bain............................... 132 Alsace-Lorraine. By Sidney Paige......................... 135 Brazil BY E. C. HARDER† During the years immediately preceding the war, the iron ores of Brazil were attracting the attention of iron operators both in Europe and in the United States. This was due to the large quantities of practically undeveloped ore available, and to its great purity. It is reasonably safe to state that had capital not been diverted from the exploitation of these deposits to war purposes, Brazilian iron ores would probably now be offered in European and American markets. It is certain that after the war these ores will play a prominent part in the economic reconstruction of Europe and perhaps in the development of America. The Brazilian iron-ore field ranks among the six great iron-ore districts of the world, the others being: (1) The Lake Superior district of the United States; (2) the Lorraine ore field of northern France and southern Germany; (3) the magnetic deposits of northern Sweden; (4) the ore fields of Oriente, Cuba; and (5) the Wabana ores of Newfoundland. It is doubtless the greatest known undeveloped iron-ore district in the world. The Brazilian iron ores are situated in the State of Minas Geraes, the center of the district being located about 250 miles in a direct line west of

Jan 1, 1920

By N. Mungan, F. W. Smith, J. L. Thompson

Adsorption of polymers and transport, rheology and oil recovery efficiency of their solutions were studied in the laboratory to evaluate the use of polymers in waterflood-ing. While a tenfold mobility reduction was obtained with polymer concentrations as low as 0.05 per cent by weight, the mobility reduction depended on the type of polymer, molecular weight, salinity and pH of water, crude oil and capillary properties of the porous media. Choice of a suitable polymer and a workable concentration will have to be tailored for each application. Little reduction in the residual oil saturation can be expected from polymer flooding. Improvement in the volumetric sweep efficiency is possible hut the extent of the improvement can best be evaluated by properly designed field testing. Some aspects of the field use of polymer floods are discussed. INTRODUCTION Waterflooding is a simple, inexpensive secondary recovery method and is being used widely. Innumerable laboratory studies have been made to unravel the fundamentals of the displacement of oil by water and to find the ways of most efficient oil recovery. These studies and a great many field case histories have revealed that the prime cause of poor oil recovery is the inefficient and incomplete sweep of reservoir volume by the injected water. Sweep efficiency is affected by many factors of which the mobility ratio is an important one. Mobility ratio M is defined here as the ratio of water to oil mobilities: M = (k»/y,r)/(k,JJJJ........(1) In Eq. I, the permeabilities are the effective permeabilities and depend on fluid saturations and, hence, change during the different depletion stages in a flood. A wide practice is to use the effective water permeability at residual oil saturation and the effective oil permeability at interstitial water saturation in Eq. 1. If the mobility ratio is greater than one, the mobility ratio is unfavorable and water, being more mobile than oil, would finger through the oil zone resulting in poor oil recovery efficiency. If the mobility ratio is favorable (one or less) the displacement of oil by water occurs more or less in a pistonlike fashion. In some waterfloods. the mobility ratio is unfavorable and any additives by which the mobility of water can be decreased would favor more efficient oil recovery. The thing to bear in mind, however, is whether or not the improvement in oil recovery is sufficient to more than pay out the cost of the additives needed. For example, materials like sugars, alcohols and glycerine reduce water mobility by thickening the water, but the cost of material requirement precludes any field application. For an additive to be useful in water-flooding, it must bring about a large reduction in water mobility at low concentrations; it must be adsorbed only negligibly; and it must not completely plug up the formation. Some synthetic organic polymers have shown promise of meeting these requirements and have been used in the field.'-W owever, no in-depth studies of the rheological, adsorption and oil displacement characteristics of polymer solutions have been reported. The present work is a study of these properties. EXPERIMENTAL In this work, concentrations are given on a weight per volume basis; 0.5 per cent concentration means 0.5 gm of polymer is dissolved in enough water (or NaCl solution) to make 100 ml. A bactericide, usually 0.1 to 0.2 per cent by volume of 38 per cent formaldehyde solution, was used in the polymer solutions. The NaCl solution was 30,000 ppm. Some properties of the polymers studied are given in Table I. Physical properties of all cores used are in Table 2. Flow behavior of polymer solutions was studied by three consecutive flow tests in cores. First, water (or brine) was injected at constant rate of about 1 ft/D to obtain the water mobility. Then, filtered polymer solution (prepared in water or brine) was flowed through the core. Since the rate was constant, increase in the pressure drop across the core reflects decrease in the mobility. Finally, the core was flooded with water (or brine) to study recovery of mobility. The Alundum cores which were used in

Jan 1, 1967

By Rudolf K. Berkhard

Static soil investigations with more or less heavy loads and extensive borings do not always have efficient results; also, they are very expensive. The new geophysical method of dynamic tests described herein is simple and cheap and avoids several disadvantages of the routine investigation, thus forming a useful supplement to the older methods and even at times replacing various static tests. The fundamental principle of dynamic soil tests consists in the application of artificial vibration. The technique employed is essentially geophysical in nature and in some respects is akin to seismic studies. Artificial vibration may be excited by centrifugal forces resulting from eccentrically supported rotating masses. The reactions of soil and structures caused by these vibrations may be measured. Their dynamic constants, such as amplitudes, phase speeds, damping, reflection, and interference effects, can be investigated. This geophysical method has been used for several years with increasing success. The results of these tests, summarized at the end of the paper, indicate that this method opens a new field for the pkactical engineer in investigating soils (capacity and formation), foundations, dams and structures, and especially buildings that must withstand earthquakes. Methods Static Method.—The first and oldest tests to investigate the bearing capacity of the soil were carried out by static weights. The penetration of these weights, however, depends not only on the soil but also on the size and the form of their lower surface. The length of time the load acts is also important. To imitate actual field conditions, heavy weights and lengthy tests are required, both of which are expensive. Furthermore, the influence of static weights affects only the surface and does not penetrate into deeper strata, therefore substitutes and supplements for static tests have to include the time factor and consequently lead to dynamic investigations. Such dynamic investigations also affect

Jan 1, 1940

By Rudolf K. Berkhard

Static soil investigations with more or less heavy loads and extensive borings do not always have efficient results; also, they are very expensive. The new geophysical method of dynamic tests described herein is simple and cheap and avoids several disadvantages of the routine investigation, thus forming a useful supplement to the older methods and even at times replacing various static tests. The fundamental principle of dynamic soil tests consists in the application of artificial vibration. The technique employed is essentially geophysical in nature and in some respects is akin to seismic studies. Artificial vibration may be excited by centrifugal forces resulting from eccentrically supported rotating masses. The reactions of soil and structures caused by these vibrations may be measured. Their dynamic constants, such as amplitudes, phase speeds, damping, reflection, and interference effects, can be investigated. This geophysical method has been used for several years with increasing success. The results of these tests, summarized at the end of the paper, indicate that this method opens a new field for the pkactical engineer in investigating soils (capacity and formation), foundations, dams and structures, and especially buildings that must withstand earthquakes. Methods Static Method.—The first and oldest tests to investigate the bearing capacity of the soil were carried out by static weights. The penetration of these weights, however, depends not only on the soil but also on the size and the form of their lower surface. The length of time the load acts is also important. To imitate actual field conditions, heavy weights and lengthy tests are required, both of which are expensive. Furthermore, the influence of static weights affects only the surface and does not penetrate into deeper strata, therefore substitutes and supplements for static tests have to include the time factor and consequently lead to dynamic investigations. Such dynamic investigations also affect

Jan 1, 1940

By J. M. Callow

THe results obtained by pneumatic flotation throughout the country on all classes of ore, and the tonnage now being treated by this particular method, speak for themselves. Its advantages over the so-called agitation process are now established by facts and data from practicc. The comparative efficiency of a rapidly revolving paddle, as a means for aerating an ore pulp, and of a cyeloidal or turbine blower for the same purpose, would seem to be so obvious as to leave no room for discussion. Practitioners in this art are to be congratulated on the acquisition of the valuable literary contributions that have recently been made on the theory of flotation by Messrs. Ralston, Van Arsdale, Taggart and Beach, and others, and the very valuable and able articles by Messrs. Laist and Wiggin on "Flotation Concentration at Anaconda, Mont.," by Dr. Rudolf Gahl on the "History of Flotation at Inspiration," and by David Cole on "The Advent of Flotation in the Morenci District." It is not within the province of this article to attempt an answer to the various issues raised in regard to the theory, or to defend the one advanced by me a year ago. But since discussion usually benefits the profession, a reply will be made to some of the statements made by the last-named writers. CoMPABATIVE SENSITIVENESS AND ATTENDANCE Concerning the article, "Flotation Concentration at Anaconda, Mont.," by Laist and Wiggin, a little explanation is in order. It should be stated that, with the exception of about 24 days at the end of the testing period, the Callow experimental plant at Anaconda was not run under my direction. This perhaps accounts for some of the concIusions drawn on page 499 of the descriptive paper. The conclusion that the use of acid seems to be of considerable advantage, calls for some comment. While the tests conducted by the Anaconda Copper Co. do show acid to be of considerable benefit, this is a consequence of using acid sludge as a flotation agent. My belief has always been that the Anaconda

Jan 1, 1917

By Roy Lindgren

SINCE the year 1643, when the first blast furnace in America for treating iron ore was built at Saugus, Mass., out of mica schist quarried in the neighboring district, the procurement of a suitable refractory for furnace lining has been a problem of concern to the operators of furnaces. The stacks built of mica schist continued to smelt iron ore until about 1836, when, according to F. H. Norton, the first firebrick were produced1, at Queens Run, Pa. Other writers speak of brick having been molded and burned in Massachusetts about the year 1834. In 1841, Andrew Russell began to produce medium refractory plastic clay brick near East Liverpool, Ohio, that were used for lining blast furnaces1. The well-known Kentucky clay-producing district was not opened up until the year 1871, but since then it has produced a large percentage of the linings for iron blast furnaces. While some strides have been made by the refractories industry during the 100 years that have passed since the first firebrick were produced, it has been only during the last two decades that any real progress has been made towards bettering the product, even though the method of production had improved. Perhaps the fault lies with the user of the brick rather than with the producer, for not sooner demanding a supe-rior product. During the past 15 years the tonnage produced per lining has increased from 500,000 gross tons to 1,000,000 gross tons, and now some furnaces are producing 1,600,000 gross tons and better on a single lining. It is true that enlarged capacity of furnaces and improved practice have accounted for some of this increase in tonnage, nevertheless better quality in firebrick must be given credit for its share. However, we are not yet ready to say that we have reached a maximum life of furnace lining. We believe that a better product can be produced and that the refractories industries of America will, through their extensive research depart-

Jan 1, 1937

By Hans Allenius, R. T. Hukki

This paper describes in quantitative terms the effect of sharpness of classification on the performance of the closed grinding circuit. The analysis is based on a large number of laboratory experiments designed to simulate the two most common industrial closed grinding systems. The experimental results show quantitatively the degree of improvement achievable by more efficient classification. In an earlier paper1 the senior author has presented a trend showing qualitative analysis of mill and classifier performance in tile closed grinding circuit. According to this analysis, the master key to a major improvement appeared to be effective removal of finished fine material from the classifier sands, or in other words, improved sharpness of classification, leading simultaneously to a substantial reduction of the circulating load. One purpose of this paper is to present the results of a quantitative investigation of the closed grinding circuit. Another is to set forth the essential pertinent variables revealed by the quantitative experiments carried out by the junior author. In the two most common systems of closed-circuit grinding, (1) feed to the circuit is introduced into the grinding unit, normally the ball mill, operating in closed circuit with the classifier; or (2) feed to the grinding circuit is introduced into the primary grinding unit, normally the rod mill, discharging into the classifier in closed circuit with the secondary grinding unit, normally the ball mill. In the following discussion, these two systems are analyzed separately in the indicated order. BALL MILL - CLASSIFIER CIRCUIT The Test Apparatus and Procedure: The test appara- tus included: (1) a F 195 mm x 220 mm laboratory ball mill rotated at a speed 77% of the theoretical critical speed, and a 7-kg batch of F 20 mm-F 50 mm steel balls; (2) a conventional 65-mesh test sieve and a Ro-Tap sieve shaker serving as a classifier; and (3) a Permaran instrument manufactured by Outo-kumpu Co. for surface area determinations by the permeability method. As no continuous closed-circuit experiments could be brought about on a laboratory scale, the process was broken down into alternating grinding and sizing steps in such a way that the new feed plus the returning sands always formed a batch of 1000 gm. For each selected grinding period and for each selected sharpness of classification the basic steps were repeated six times. Steady-state conditions were then reached. Crystalline vein quartz was used as a test material. Feed to the process consisted of -10-mesh fraction of this quartz crushed in rolls. This fraction included 15% of-65-mesh material. Experimental Results: The general flowsheet is shown in Fig. 1. Table I gives the essential data obtained representing steady-state conditions under the indicated set of variables. The table is based on 110 grinding experiments, 440 screen analyses and an equal number of specific surface area determinations. Fig. 2 shows the relationship between the cumulative net energy consumption and the cumulative number of mill rotations as evaluated by separate experiments. Note that this relationship is not linear but is instead represented by a slight curve. The data given in Table I are presented in graphical form as follows: Fig. 3 shows the produced -65-mesh material in grams per minute vs. time of grinding in minutes; the sharpnesses of classification at 65 mesh were 100%, 75% and 50%. It is clearly indicated that the highest-capacity figures call for relatively short grinding times and for the sharpest possible classification. Fig. 4 presents the specific surface area on the final -65-mesh product in square centimeters per gm vs. time of grinding in minutes. In conventional mineral dressing processes, a final product characterized

Jan 1, 1969

By Blamey Stevens

The object of this paper is to present a theory of the formation of fissures, which seems to be supported by all available data. The investigation is, in the main, an exact one, and irregularities of the rock-structure are generalized. From the conclusions drawn a general classification of fissures is made, and this should be of practical use in the comparison of mineral deposits. The theory also throws some light on the equilibrium of the earth's crust and the depth of action of surface-waters. Incidentally, additions are made to the theory of earthquake-slips. Former Theory. It has been previously pointed out that the "jointing" of homogeneous rocks occurs in two sets of planes, at right angles to one another, and making angles of 450 with the directions of greatest and least principal stress.' The theory by which this fact is explained does not, however, account for fissures and faults, because normal faults are usually more vertically, and reverse faults more horizontally, inclined than 450. The "jointing law" is based on the following axiom: In a homogeneous mass under pressure, rupture must take place on the lines of maximum tangential stress."2 This law applies, with fair approximation, to the tests on jointing which can be made in the laboratory, and as nearly as can be expected to the natural jointing-planes in rock-masses, where the stresses are not very great; but it entirely fails to account for fissure-fractures.3

Jan 1, 1910

By Samuel G. Lasky

What the evidence prevails upon the mind to believe, depends upon the mind as well as upon the evidence. M. L. IN a recent discussion of the mineral resource position of the United States, published in the September 1946 issue of MINING AND METALLURGY, I expressed my conviction that ore deposits of major magnitude remain to be found in this country and that they can be found without undue cost or risk. I stated with equally strong conviction, however, that if the search for such deposits is to be notably successful there must be, among other things, a reorientation of philosophy and mental habits on the part of many who would be connected with the search. I would now like to enlarge upon that statement. For such a purpose, we may consider that the search for concealed deposits involves four steps: (I) the selection of areas for further study; (2) the geologic study of those areas in order to verify their general favorableness and in order to choose specific patches worthy of being tested; (3) the decision whether exploration of the patches chosen should actually be undertaken; and (4) the exploration itself. The first two steps and the last rest upon the judgment and skill of geologists. The third step-the decision whether exploration should be undertaken-rests upon management. In my opinion, the philosophies or principles that have guided these steps in the past are now inadequate. PHILOSOPHY OF APPRAISAL If concealed deposits are to be looked for, how are the places of their possible concealment to be recognized? Every known mineralized area still in the prospect stage has already been repeatedly examined and condemned. As for those deposits concealed under later rocks, there may be not even the clue of a near-by outcrop for engineer or geologist to consider. How then, are we to know where to look? Geologic Probability In the early days of our mining industry, ore deposits were found mainly by "following the ore." Later, as such opportunities decreased, and as geologic concepts became accepted, deposits were found more and more through use of the notion of geologic probability. Many instances can be cited wherein a courageous operator ignored the implications of the unsuccessful efforts of predecessors and, solely by "following the ore," converted a discredited prospect into a good mine. Similar experience doubtless will occur in the future, but "following the ore" will no longer in itself find new deposits in the amount needed. Nor can enough new ore be expected from further use of the notion of geologic probability, for, as mentioned above, our known prospects `have already been ex-

Jan 1, 1947

By H. M. Ziesemer

PRIOR to 1909 that mountain of porphyry, known as. Sacramento Hill, had remained hardly touched but had always aroused suspicions as to the presence of ore within.. During that year, exploratory work was started by underground methods; drifting and raising continued until 1913. It was proved that a mineralized zone existed, the limits of which had not been determined; so, because of the lower costs of exploratory work and the greater desirability of vertical sections, it was decided to prove the extent of the ore zone by churn drills. Drilling continued until the year 1917, when it seemed almost certain that the horizontal limits of the orebodies had been determined. Ore continued in depth in one direction beyond a point where it was economical to explore by churn drilling; this extension is still being developed by underground methods. The irregularities of the boundaries of the ore zones, together with the variable grades of ore encountered, made it necessary to drill on the corners of 100-ft. squares. Two ore zones were proved, known as the East and West Orebodies. The Sacramento Hill porphyry stock intruded into the Dividend fault. The fault ran roughly east and west with a dip to the south, having pre-Cambrian schists on the north against Paleozoic limestone on, the south. This intrusion was accompanied by a silica breccia on the south periphery, along the limestone contact side. The ore lay in the silica breccia and in the porphyry, some distance from the breccia. No ore was found in the heart of the porphyry mass on the north side, along the schist contact. The West Orebody is elliptic in shape, having a major axis of 1200 ft. (366 m.) and a minor axis of 800 ft. (244 m.); these diminish with depth until, at 300. ft., the axes are 500 ft. and 300 ft., respectively. The ore consists of chalcocite, some bornite, chalcopyrite, and considerable pyrite in a silicious gangue. About 30 per cent. of the copper is caused by

Jan 2, 1922

By C. V. Corless

We are living at a period of the world's history in which social phenomena are on so vast a scale, are of so profoundly soul-searching a nature, and are occurring in such rapid succession in the great world drama in which we are both actors and spectators, that, in our efforts to obtain a rational point of view in relation to them, our minds may fail to discern the simple in the complex and our understanding is liable to become confused or even overwhelmed. To the social student whose: scientific training has convinced him of the truth of the evolutionary law, Natura non facit salium, it is neither the vast scale of the events, their deeply soul-stirring nature, nor their rapid succession that matters so much, as the discovery of the underlying principle or law in accordance with which the disintegration and reintegration, which are the two aspects of social evolution, or indeed of evolution everywhere, are occurring. He is most deeply concerned in seeking an answer to the question: Have we in the present great and perplexing upheavals in human society, whether regarded in Central Europe, in Russia, in Great Britain, or in America, a really new cause at work, or, have we, though on a very large scale, merely new manifestations of the working out of an old principle? When we think of the appalling struggle in Europe, into which the world's greatest exemplar of democracy was finally drawn, no one has any hesitation in admitting that the great conflict was fundamentally a life-and-death struggle for self-preservation and self-propagation on the part of autocracy. The variations we meet with in the statement of the cause of the war arise mainly from differing distances of perspective; but in the last analysis all agree that the autocratic system of political gov ernment, which found its very soul and center in Prussian despotism, was consciously arrayed in a final "world-power-or-downf all" struggle against a love of freedom which was steadily widening and deepening throughout the world, and particularly throughout those parts of the world where this love of freedom and justice hasfound expressionin democratic institutions. It is not irrelevant to our discussion to recall in passing that this most imposing structure ever conceived by the human mind as an instrument of tyranny is lying today an irretrievable mass of ruins, completely over-

Jan 1, 1920

By C. E. Nelson

THE purpose of this discussion is to outline briefly the practices commonly followed in this country for the melting and refining of magnesium and its alloys. The processes used for the various forms of primary magnesium, as far as there are differences in the physical shape or behavior, will be discussed. The refining of general fine scrap or secondary magnesium was presented in an earlier paper.1 Inasmuch as the use of fluxes is an essential part of all the melting and refining processes, the principal aim of this paper will be to deal with these in sufficient detail to point out their unique characteristics, in order to make their use more effective. TYPES OF MELTING PRACTICE All melting and refining processes for magnesium and its alloys require the use of fluxes. These fluxes have a magnesium chloride base and other halide salts or oxides are added to give a density or behavior exactly suited to the particular melting practice. The successful handling of magnesium depends upon the proper use of the correct fluxes. There are four general methods of melting, summarized in the following paragraphs and treated in more detail in the section on Melting and Refining. Open-pot Method The open-pot method makes use of No. 230 flux.* The flux provides protection during melting and a molten pool of flux into which the solid magnesium melts. It is stirred through the molten metal bath and agglomerates oxide or similar foreign bodies; then on quiet standing separates away, leaving the refined metal ball floating in an encircling layer of molten flux. It forms only a thin fluid film over the surface of the molten metal, which may be parted for hand-ladling processes and tends to cover the metal again after the ladle is removed. A very light dusting of the pot surface with fresh flux immediately after the ladle is removed is usually desirable. The open-pot method is used generally in the following processes: (I) alloying and secondary smelting in the production of ingot, (2) in sand foundries for premelting and to a smaller extent for the production of small castings requiring hand ladling, (3) in permanent-mold founding for premelting and also direct ladling to castings, (4) for continuous methods of preparing metal in the production of billets or ingots from which wrought products are fabricated, (5) in general scrap recovery. Crucible Process The crucible process makes use of No. 310 flux, which has the property of being thinly fluid at the start, to provide protec-

Jan 1, 1944

By W. M. Pierce

THE present work has been done in an endeavor to correlate and complete the data on the constitution of alloys of zinc with other common, metals, dealing exclusively, however, with the zinc-rich alloys in which the zinc content is between 90 and 100 per cent. This investigation has included the systems lead-zinc, cadmium-zinc, iron-zinc, copper-zinc, aluminum-zinc, nickel-zinc, manganese-zinc, cobalt-zinc, tin-zinc, and magnesium-zinc. The important ternary system zinc-lead-cadmium and the zinc corners of other ternary systems have been investigated in connection with this work but will not be dealt with here. Zinc does not form a single homogenous zinc-rich solid solution over any considerable range of concentration with any of the metals mentioned. A limited range of solid solubility is said,; by previous investigators, to occur in several cases and certain effects on the properties of zinc are attributed (with varying degrees of consistency among different writers) to the presence of certain other metals dissolved in zinc. The increasing use of rolled zinc and the possibilities offered by zinc as a casting alloy in certain fields have it made essential to determine precisely these equilibrium relationships. In carrying out this .investigation reliance was placed chiefly on two methods, conductivity measurements and microscopic analysis. The first method proved valuable in determining the existence and extent of solid solubility. The second method stands alone as a means of determining structural characteristics and supplements the first method in the measurement of solid solubility. The scleroscopic hardness of all conductivity specimens was measured partly for its value from the point of view of mechanical properties and partly; as a check on the conductivity curves in indicating the limits of solid solubility. No hardness curves are included in this paper, for in no case were they important in arriving at the constitution of any system.

Jan 2, 1922

By E. A. H. Tays, F. A. Schiertz

In 1893 the Anglo-Mexican Mining Company, Limited, purchased the Guadalupe and adjoining mines, and, after opening up the Guadalupe, constructed a 20-stamp mill, which was started in August, 1894. Although the results were extremely profitable (the ore being very rich and carrying much free gold) they were not satisfactory, because the tailings were found to average about $20 per ton in gold. Early in 1895 the late Mr. James E. Mills made for the company a very thorough study of the subject, and decided that the tailings could be treated most advantageously by the cyanide process. In view of this opinion, Mr. Henry R. Batcheller, of Boston, was sent down in the winter of 1895-96 to experiment on a working scale. Mr. Batcheller was successful; and, during 1896-97, built a cyanide-plant with a capacity for treating 1500 tons per month. This was run until May, 1899, when all the sands suitable for the process had been treated. The mill was stopped about the same time for lack of ore; but no tailings from the mill had gone to the dump since October, 1897, as the values they contained after that date were far too low to warrant further treatment. When the cyanide-plant was stopped there still remained on the dump about 16,000 tons of slimes, consisting of about 75 per cent. of clay-slimes and 25 of sand-slimes. The successful treatment of this very unfavorable material is the theme of this paper. Fig. 1 is a view of the hacienda, taken in 1897.

Jan 1, 1902

By M. F. Hawkes, R. F. Mehl

The rate of isothermal transformation of austenite to pearlite depends upon the rate of nucleation, N, and the rate of growth, G, of pearlite in austenite. Values of N are given in terms of the number of nuclei forming in unit time per unit grain boundary area of unreacted austenite; values of C are given in terms of the linear rate of radial growth. Variations in the isothermal rate with temperature result from variation of N and G with temperature. Depth of hardening of a steel depends fundamentally upon values of N and G; changes in carbon and alloy content effect changes in N and G and thus affect depth of hardening. Quantitative studies are available on N and G for the formation of pearlite in plain carbon eutectoid steels.3 Systematic studies in this field are necessary if the phenomena are to be well enough known to furnish a proper basis for full rationalization and for theory. Accordingly, the studies are continuing, both with respect to the effect of alloying elements upon the values of N and G in the formation of pearlite and to the values of N and G for the formation of ferrite in hypoeutectoid steels. The present paper is the first relating to the effect of alloying elements upon the values of N and G for pearlite. It offers special interest since cobalt is known to have an anomalous effect upon the rate of formation of pearlite, accelerating it, whereas all other elements retard it.4 It will be shown that cobalt increases both N and G for pearlite and that this effect is inherent in the Fe-Co-C system and not dependent upon factors relating to austenite heterogeneity nor upon any recognizable adventitious factor. Inasmuch as the rate of diffusion of carbon in austenite and the interlamellar spacing of pearlite are variables related to G and possibly to N (in a manner not yet certain), measurements of the effect of cobalt upon them are also reported here. In the course of the work, measurements were made on the effect of cobalt upon the marten-site temperature and these are given. COBALT AS AN ALLOYING ELEMENT IN STEEL Properties of Cobalt Cobalt resembles iron more closely than does any other chemical element. Its atomic number is 27, hence it is the element immediately following iron in the periodic system. The two differ in atomic structure only in the fact that cobalt contains seven electrons instead of six in the third, or transition, level of .the third shell. The next shell, which is the

Jan 1, 1948

By M. F. Hawkes, R. F. Mehl

The rate of isothermal transformation of austenite to pearlite depends upon the rate of nucleation, N, and the rate of growth, G, of pearlite in austenite. Values of N are given in terms of the number of nuclei forming in unit time per unit grain boundary area of unreacted austenite; values of C are given in terms of the linear rate of radial growth. Variations in the isothermal rate with temperature result from variation of N and G with temperature. Depth of hardening of a steel depends fundamentally upon values of N and G; changes in carbon and alloy content effect changes in N and G and thus affect depth of hardening. Quantitative studies are available on N and G for the formation of pearlite in plain carbon eutectoid steels.3 Systematic studies in this field are necessary if the phenomena are to be well enough known to furnish a proper basis for full rationalization and for theory. Accordingly, the studies are continuing, both with respect to the effect of alloying elements upon the values of N and G in the formation of pearlite and to the values of N and G for the formation of ferrite in hypoeutectoid steels. The present paper is the first relating to the effect of alloying elements upon the values of N and G for pearlite. It offers special interest since cobalt is known to have an anomalous effect upon the rate of formation of pearlite, accelerating it, whereas all other elements retard it.4 It will be shown that cobalt increases both N and G for pearlite and that this effect is inherent in the Fe-Co-C system and not dependent upon factors relating to austenite heterogeneity nor upon any recognizable adventitious factor. Inasmuch as the rate of diffusion of carbon in austenite and the interlamellar spacing of pearlite are variables related to G and possibly to N (in a manner not yet certain), measurements of the effect of cobalt upon them are also reported here. In the course of the work, measurements were made on the effect of cobalt upon the marten-site temperature and these are given. COBALT AS AN ALLOYING ELEMENT IN STEEL Properties of Cobalt Cobalt resembles iron more closely than does any other chemical element. Its atomic number is 27, hence it is the element immediately following iron in the periodic system. The two differ in atomic structure only in the fact that cobalt contains seven electrons instead of six in the third, or transition, level of .the third shell. The next shell, which is the

Jan 1, 1948

By L. B. Slichter

IT has been estimated that rock exposures in most mining districts aggregate less than 1 per cent. of the total surface area.1 Conclusions concerning the hidden 99 per cent. necessarily have been based on knowledge of only a small fraction of the surface, and from this limited information the geologist has been obliged to deduce the approximate and general nature of the underlying formations. In the search for ore it is necessary to supplement this general picture with greater detail. Fairly accurate knowledge of relatively small zones is required. This knowledge is carefully sought in many different ways-detailed interpretations of geological history, the tracing of float, the use of test pits, of trenching, of drilling, and of other methods. Practical ingenuity, scientific brilliance, great perseverance and patience, and the expenditure. of large sums of money have all been a part of this search. The problem of exploring beneath cover with economy, and of obtaining essential information which this cover hides, is obviously a difficult one. It is also a very important one, for geologists inform us that already the story of the 1 per cent. exposed outcrops has been largely read.2 There remains the nearly virgin field comprised in the hidden 99 per cent., and the importance of this zone is bound to increase continually. In recent years, the problems connected with the exploration of this "99 per cent. zone" have attracted a constantly enlarging group of investigators and at present greater efforts than ever before are being made to resolve then. This work, in its various special aspects, has enlisted, beside geologists, the cooperative efforts of chemists, physicists, and mathematicians. The progress made in this development should be kept before those directing explorations in order that due advantage may be taken of a changing situation.

Jan 1, 1928

By V. F. Hollister

Although it is apparent that porphyry copper deposits may have formed in the Andean orogen from Permian time onward, commercial deposits thus far developed appear to have Cenozoic ages only. Following Chilean usage, the porphyry deposits are divided into either (1) a stockwork or (2) a tourmaline breccia model. As indicated by evidence cited in the paper, stockwork-type deposits tend to be related to major strike-slip structures which may be either transcurrent or transverse faults related to plate movements, while the tourmaline breccia type may more frequently form independently of regional faults. Stockwork types may be conjugate fractures that intersect and ramify as a network of veins and veinlets, cutting altered rock, and genetically related to a major regional fault, or in other cases they may reflect the intersection of two large fault structures. Circular fracture patterns may more rarely occur in stockwork deposits in response to a specific intrusion. Tourmaline breccia types are characterized by circular and radial fractures genetically connected in some way with touramline breccia pipe development or an intrusive piercement that preceded it. Each structural model contains mineralized intrusions which have a close time-space relationship to ore, and in each model mineral paragenesis is similar, regardless of age or location in the plate. Also, each model contains the same type of alteration halos (phyllic, argillic, propylitic) as are developed in intrusive centers in porphyry copper deposits found in North America. The potassic zone is exposed best in the older deposits. Examples of each type of deposit are illustrated, demonstrating the feature evolved.

Jan 1, 1975

By C. G. Bieber, R. F. Decker

The effects of minor constituents on the malleability of nickel alloys are described. These effects are related to the atomic diameter, valence, and position on the Periodic Table. The basic methods for removal or neutralization of deleterious elements are then reviewed. Finally, practical methods for melting nickel alloys are described in detail and related to minor constituent control. L HE first malleable nickel was produced by Fleit-man in about 1870 by the addition of manganese and magnesium to the molten metal to counteract the harmful effects of sulfur. Merica and Waltenbergl explained the mechanism by which these elements accomplished the desired result. They showed that sulfur in concentrations in excess of about 0.005 pct produced films of a brittle low melting eutectic of nickel-nickel sulfide which completely surrounded the grains. When manganese was added to molten nickel it reacted with the sulfur to form manganese sulfide which precipitated as widely scattered globules in the grain boundaries. The further addition of small amounts of magnesium converted the sulfur to a very stable sulfide of magnesium which was relatively insoluble in both the liauid and solid states and therefore occurred as finely divided particles within the grains where it had relatively little detrimental effect upon the malleability of nickel or its alloys. The practice of treating nickel with manganese and magnesium came to be called "deoxidation" and was employed without appreciable modification for the commercial production of wrought nickel and high nickel alloys (in this paper—50 pct or more nickel) until about 1930 even though the results were never entirely satisfactory. At that time a more extensive study was made of the effects of minor constituents on malleability and metallurgical quality. The results, small portions of which have been published,2-4 are presented here with other pertinent data. EFFECTS OF MINOR CONSTITUENTS UPON NICKEL Systematic additions were made of 0.5 pct or less of each of most of the elements of the periodic ta- ble. It was established in this study that some minor constituents other than manganese and magnesium were extremely influential. The malleability, as evaluated by the reduction of area in tension tests, depended roughly on temperature as shown in Fig. 1. Four temperature zones are of interest; the cold malleable zone (up to about 1000° F), the red short zone from roughly 1000° to 1500' F, the hot malleable zone around 2000° F and the incipient melting zone. Most of the malleability problems are associated with the red short zone and the discussion will concern this mainly. The reduction of area in normal tensile tests on high-purity nickel (see curve A of Fig. 1) appeared to have no

Jan 1, 1962