Search Documents

By Karl Fetters

IN the process of making steel in the open-hearth furnace the refining of the metal during the working period of the heat is largely accomplished through the agency of the slag. From the birth of the process until the present day steelmakers have recognized the importance of the slag in determining the composition of the metal and the quality of the product. The general relationships between slag composition and metal analysis have long been known, at least in a qualitative or approximate fashion. For examples, the iron oxide content of the slag is higher on lower carbon heats; the more basic slags are higher in iron oxide for a given carbon content; certain amounts of iron oxide and lime are required for phos-phorus removal and a high lime-silica ratio is needed if the sulphur content of the metal is to be diminished. In recent years a number of quantita-tive relationships involving these and other variables have been developed through plant and laboratory studies by numerous investigators in this country and abroad. The direct comparison of laboratory and open-hearth data involves the question of the degree to which each approaches the conditions of chemical equilibrium, a question which, from the open-hearth standpoint, we are scarcely yet in position to answer. And, although a considerable body of dependable equilibrium data has been obtained in the laboratory, this work has not yet been extended to cover the ranges of slag composi-tion encountered in basic open-hearth practice. In the present study we shall not attempt to draw comparisons between data from the two sources; nor do we attempt to draw conclusions as to the approach to chemical equilibrium in the open-hearth furnace. Many of the operating variables that are likely to be erratic or unrecorded during the earlier stages of the heat become more consistent and are more readily subject to observation and control during later stages. For example, undigested lime or ore gradually goes into solution, the rate of carbon drop levels off, and the temperature of the metal is brought under control. For these and other reasons a greater degree of self-consistency is likely to be found among data obtained during the

Jan 1, 1940

By Erskine Ramsay

The following description of the Alabama coal-,fields is taken (with slight omissions) from the report " On the Warrior CoalField, by Henry McCalley, A.M., C. and M. E., Assistant State Geologist:" The coal lands of Alabama are of the great coal basin of the Ohio, or of the great Appalachian coal-field, and are estimated at 8660 square miles. They formed one connected field prior to the great Appalachian revolution, when there was pushed up through them long, narrow, anticlinal ridges which have been denuded into the present well-known anticlinal valleys, and thus this great field has been divided up into three more or less distinct parts. These parts were named by Prof. Tuomey, in 1849, the Warrior, the Cahaba and the Coosa coal-fields, respectively, from the names of the rivers which drain them. They are of very unequal size, the Warrior, with an area of 7810 square miles, being nearly ten times as large as the other two combined, and about two-thirds as large as the coal-area of Great Britain. This Warrior field is the most northwestern of the three coal-fields of Alabama, and comprises all of the coal-measnres in Alabama, northwest of the Alabama Great Southern railroad, or all of those drained by the Warrior and Tennessee rivers. The greater part of this field, almost all of it away from the present railroad lines, has never received more than a surface-examination. Still, we have in the Warrior coal-field one of the richest coal-basins of this or any other country. As a whole, the Warrior coal-field is a broad, shallow, tray-shaped depression, sloping towards the southwest, and with its southwest end covered by a newer formation and its southeast side, especially, complicated by folds and fractures. As is the case with all of our Coal Measures. it is composed of a series of sandstones. conglomerates, shales, slates and coal-seams, with some little limestone at several horizontal positions, but contains no thick bed of this last rock like the Measures of Pennsylvania and other States. The thickest conglomerates are near the bottom and top of the series, and hence these coals might be said to belong mainly to the

Jan 1, 1891

By William A. West

One manifestation of anelastic properties in solids is the mechanical elastic aftereffect, which may be described briefly as follows: If a stress is applied to a solid body, a deformation or strain is produced. On removal of the stress, this deformation disappears, at least in part. As a first approximation, this appearance or disappearance of deformation usually has been considered instantaneous. Actually, however, for a very wide variety of substances, on application of stress the instantaneous deformation is followed by a further slow yielding, which continues, although at a rapidly diminishing rate, for as long as the stress is applied. Similarly, on removal of the stress, the instantaneous recovery from deformation is followed by a further slow recovery, which continues, although at a rapidly diminishing rate, often for a long time. This latter phenomenon has been called the "elastic after-effect." Experiments upon the elastic after-effect in metals, when properly designed and when properly interpreted, are capable of giving quite precise information regarding the relation between stress and strain in the various constituent parts of the metal. For example, if certain parts of the metal, such as grain boundaries or slip bands, behave in a viscous manner—that is, if therein—the relaxation spectrum will contain lines or bands associated with the relaxation of shear stress within these parts. No attempts have heretofore been made to utilize elastic after-effects for obtaining such detailed information. The purpose of the present paper is to explore the possibilities of properly designed and interpreted experiments on the elastic aftereffect in metals. Since new procedures and principles are employed in this study, an attempt has been made to record each step taken. Elastic after-effect observations are susceptible of simple interpretation only when the stress level employed is so low that all effects are linear with the stress. Just how low the stress level must be can he determined only by experiment. An advnntage, other than simple interpretation, is associated with low stress levels. When all effects are linear, derived quantities, such as the relaxation spectrum, are independent of the stress distribution. It is, furthermore, possible to employ the type of deformation that is most convenient from the experimental standpoint; for example torsion. It appears that in experiments involving both loading and unloading the following would be observed: I. Instantaneous deformation, recoverable instantaneously in whole, or in part. 2. Delayed deformation, recoverable slowly in whole, in part, or not at all. 3. Permanent deformation, the difference between total deformation and total recovery. In the work here described, unloading experiments only were made. Wires were

Jan 1, 1947

By M. E. Wadsworth

The region about the south shore of Lake Superior is to geologists one of the most interesting districts of the United States, embracing as it does, in a limited area, old crystalline rocks, together with forms that are almost in their original condition of a beach sand and mud. In this region was first established the base of the geological column, the Azoic (" without life") System of Foster and Whitney, or the Archæan (" the beginning ") of Dana. Overlying this system are found the sandstones and limestones of the Paleozoic (" ancient life "), and their associated lava-flows (Algonkian ?). These systems possess a strong economic interest, owing to the stores of iron in the Azoic and of copper in the Paleozoic or Eozoic of this district, which forms one of the most important mining regions in America. The geology of this section is so difficult and complicated that, in its general discussion, perhaps no proposition can be stated concerning any portion of it to which exceptions cannot be taken. Indeed, out of the general discussion of different points comes in time the truth, and various geologists, even now, are working over this region in the endeavor to arrive at some consensus, or at least to determine upon what points they can agree, and upon what points difference of opinion will have to exist between them at present, until further evidence can be obtained. The writer will endeavor to give in a brief form that which appears to him at present to be the most correct statement of the geological structure of the region, admitting that from time to time, as more complete evidence shall be obtained, he expects to change his views in the future, as he has done in the past, if that evidence shall cause him to believe that he has been mistaken.

Jan 1, 1898

By Delbert E. Gann, Richard D. Hagni

Ore microscopic study of copper-bearing shale at the Creta mine in southwestern Oklahoma reveals a variety of copper sulfide grains and shows that each has originated by replacement of original constituents In the Permian Flowerpot Shale at Creta. The largest grains, about 120 pm in diameter, are replacements of megaspores with triletes morphology. Their interiors are shown by Auger microprobe analyses to be organic matter. The interior organic matter and the spore exines have been replaced by anilite and djurleite. Digenite and anilite replace collomorphic pyrite averaging 40 pm in diameter. Grains 10 pm or less in d~ameter are mostly euhedral, six-sided, platy crystals that have anllite compositions and are pseudomorphous after pyrrhotzte. Other 10 pm copper sulfide grains are pseudomorphous after octahedra and cubes of pyrite. The results of this study indicate that the copper minerals are epigenetic and were deposited from fluids introduced into the Creta shale when it was relatively uncompacted and permeable. The shale served as a favorable reducing environment that contained a source of sulfur in the form of pyrite and pyrrhotite.

Jan 1, 1985

By Charles Barrett

METALLURGISTS are making use of the stereographic projection to a steadily increasing extent. In the last five years no less than 20 papers in American metallurgical journals alone have employed the stereographic projection; recent books on physical metallurgy, plastic deformation, X-rays and their applications, and crystal structure use it. Mineralogists have used the stereographic projection for many years in the description of symmetry classes and crystal planes, for it presents an accurate, easily understood plot of any angular relations in crystals with all unessential features eliminated (such as the accidentally deter-mined size and shape of crystal faces). In metallography and physical metallurgy the projection is much used for the analysis of markings appearing on polished grains: slip lines, twins, cracks, structures formed by precipitation, magnetic-powder patterns, etch pits, etc. Data from certain types of X-ray photograms are most conveniently analyzed by its use, particularly those for determining the orientation of single crystals or the preferred orientation of grains in an aggregate. Calculations of how to tilt or cut a crystal parallel to a certain crystallographic plane or to reflect X-rays from a certain plane are rapidly carried out. It has been adopted almost universally to the exclusion of other methods by those studying the deformation of metallic crystals, save where the accu-racy required is greater than a few tenths of a degree. Any directional property in a crystal or polycrystalline material can be shown on a stereo-graphic projection; for example, the modulus of elasticity, yield point, etc. It has been repeatedly called to our attention that there is need of all elementary explanation of the principles and methods of stereographic projection, covering all the, common applications in the field of metal-lography and physical metallurgy. The following contribution is an attempt to fill this need. The description of each method is supplemented with references to publications in which the method has been used. For convenience to the reader, these illustrative references are chiefly in American journals, particularly the publications of the American Institute of Mining and

Jan 1, 1937

By William A. West

One manifestation of anelastic properties in solids is the mechanical elastic aftereffect, which may be described briefly as follows: If a stress is applied to a solid body, a deformation or strain is produced. On removal of the stress, this deformation disappears, at least in part. As a first approximation, this appearance or disappearance of deformation usually has been considered instantaneous. Actually, however, for a very wide variety of substances, on application of stress the instantaneous deformation is followed by a further slow yielding, which continues, although at a rapidly diminishing rate, for as long as the stress is applied. Similarly, on removal of the stress, the instantaneous recovery from deformation is followed by a further slow recovery, which continues, although at a rapidly diminishing rate, often for a long time. This latter phenomenon has been called the "elastic after-effect." Experiments upon the elastic after-effect in metals, when properly designed and when properly interpreted, are capable of giving quite precise information regarding the relation between stress and strain in the various constituent parts of the metal. For example, if certain parts of the metal, such as grain boundaries or slip bands, behave in a viscous manner—that is, if therein—the relaxation spectrum will contain lines or bands associated with the relaxation of shear stress within these parts. No attempts have heretofore been made to utilize elastic after-effects for obtaining such detailed information. The purpose of the present paper is to explore the possibilities of properly designed and interpreted experiments on the elastic aftereffect in metals. Since new procedures and principles are employed in this study, an attempt has been made to record each step taken. Elastic after-effect observations are susceptible of simple interpretation only when the stress level employed is so low that all effects are linear with the stress. Just how low the stress level must be can he determined only by experiment. An advnntage, other than simple interpretation, is associated with low stress levels. When all effects are linear, derived quantities, such as the relaxation spectrum, are independent of the stress distribution. It is, furthermore, possible to employ the type of deformation that is most convenient from the experimental standpoint; for example torsion. It appears that in experiments involving both loading and unloading the following would be observed: I. Instantaneous deformation, recoverable instantaneously in whole, or in part. 2. Delayed deformation, recoverable slowly in whole, in part, or not at all. 3. Permanent deformation, the difference between total deformation and total recovery. In the work here described, unloading experiments only were made. Wires were

Jan 1, 1947

By Enid C. Plante, K. L. Sutherland

PRACTICAL metallurgists are unanimous in stating that oxidation of mined sulphide ore adversely affects separation of the constituent minerals under standard conditions in a mill. Frequently, the need for different operating conditions in different plants is attributed either to the extent of oxidation of the mineral surfaces or to soluble oxidation products. The investigations reported in this paper study the effect of oxidation on the primary condition necessary for flotation, namely that of adhesion of an air bubble to the mineral. OXIDATION PRODUCTS FROM SULPHIDE MINERALS Weinig and Carpenter1 state that the relative rates of oxidation of some sulphides are: FeAsS > FeS2 > CuFeS2 > ZnS >PbS > Cu2S tetrahedrite. They also show that oxidation is rapid at first, that sulphides of older geological formations are more stable than those of recent date and that mixtures oxidize more rapidly than any one mineral alone. The more rapid oxidation of mixtures is borne out by results of Gottschalk and Buehler2 who found that PbS, ZnS and CuS oxidized 8 to 20 times faster when pyrite was present. Only the end products of oxidation, sulphate and the metal ion, were identified in these tests. Gaudin3 states that pyrite is difficult to oxidize in the laboratory. Winchell,4 using pyrite containing 99.98 pct FeS2, allowed water to percolate through a bed of this ground material. At the end of three months only a trace of Fe +++and S04- were found. Even after 10 months the quantity of Fe+++ was only 7.8 mg and S04- 25.5 mg per liter of percolating solution. Carmichael5 confirmed Winchell's results on the slow oxidation of pyrite. Usually the oxidation of sulphide surfaces has been conducted in neutral or acid solutions, the acidity being caused by the oxidation products. Eliseev and Nagirnyak6 found that treatment of pure pyrite with lime gave only thiosulphate, but considered it possible that thiosulphate was obtained not by oxidation of the pyrite itself, but by oxidation of calcium disulphide. Mitrofanov7 suggested that thiosulphate was formed by the following process: oxidation of sulphide to give free sulphur (this frequently happens with marcasite), followed by oxidation of the sulphur to sulphur dioxide and reaction of the sulphur dioxide with sulphur to give thiosulphate. Ferric and ferrous hydroxides, or similar compounds, were shown to be present. The Research Staff of the United Verde Copper Co.8 treated ore from the United Verde mine with lime. Thiosulphate, sulphide and polysulphides were stated to be

Jan 1, 1947

By George S. Rice

The increasing use of mechanization at the face of the workings in coal mining and the consequent necessity of special supports of the roof has led, in several countries, to considerable scientific investigation, including physical tests in mines as well as on specimens of roof rocks to obtain data on the behavior of the immediate roof strata and on the effect of its pressure on supports while the coal is being mined. The investigations discussed in this paper do not include studies of the ultimate effect of subsidence and movement of the roof rock over the mine excavation, upon higher strata and the surface, but are confined to the immediate underground effects in the workings. The more recent principal investigations which have been brought to the attention of the writer are as follows: Germany.—The trial of strip packing, the usual method employed in Great Britain in longwall workings, as compared with complete packing heretofore used in Germany and in France to minimize subsidence; the behavior and strength of metal props under load; the testing of the strength of coal measure rocks, in the laboratory of the Technical High School of Breslau; and an investigation, by a special commission, concerning "bumps" as a possible cause of instantaneous outbursts of gas in coal mines of Lower Silesia. France.—The cause of instantaneous outbursts of gas in the Gard mines and tests by the official French experimental organization of the "electrical resistivity" of coal as a possible means of detecting a condition preceding an instantaneous outburst. Great Britain.—The subsidence of the roof and rise of the floor preceding and during excavation of the coal, in longwall and in room-and-pillar or bord-and-pillar workings; the compression and lateral movement of the road packs in longwall back from the face; the extent of separation of the immediate roof layers from the higher strata following mining excavation;

Jan 1, 1932

By L. A. Mekler

The recirculating furnace is primarily a heating apparatus of the convection type in which the heat-absorbing surfaces are heated by a mixture of fresh products of combustion and a portion of the combustion gases that have already given off a part of their heat in their previous passage over the heat-absorbing surfaces. In its basic conception, the recirculating furnace can be considered as a closed thermal system in which the heat-absorbing surfaces are constantly swept by a fixed quantity of products of combustion at a given initial temperature with the gases being constantly returned to the furnace and reheated before they again enter the heating zone. Gases equal in amount to those produced by the fuel burned to reheat the circulating gases are constantly ejected from the system to the stack. The recirculating furnace is the most suitable apparatus for heating by convection where low furnace temperatures must be maintained and where only a small portion of the available heat is taken out of the gases, particularly where the maximum allowable furnace temperature is low and where the final temperature of the gases is only a few hundred degrees below their initial temperature. In such cases, recirculation not only provides a method of reducing the rather high combustion temperatures of the fuel when burned without a large amount of excess air, but, by returning to the furnace the heat content of the gases at their final temperature, recovers a large portion of heat that otherwise would have been lost through the stack. The convection-type oil still is particularly suitable for the application of flue-gas recirculation. In an oil still, the heating of the oil is accomplished by applying to the tube surfaces a given quantity of heat of a certain predetermined quality, usually with the initial temperature of the gases not over 1500" F. as measured by thermocouples placed above the tube bank. To obtain the full benefit of the heating surface of the coil, the final temperature of the gases, after passing over the coil, is kept 200" to 300" higher than the temperature of the incoming oil. This final temperature varies from 500" F. for a topping still with only a slight or no

Jan 1, 1928

By G. L. Oldright, F. S. Wartman, H. E. Keyes

The economic manufacture of sulfuric acid by the ordinary chamber process usually involves production on a large scale and a plant that is costly to construct. The nature of sulfuric acid makes it costly to transport any great distance. For these reasons, the metallurgist has not found it feasible, at times, to beneficiate ores amenable to leaching, and a need exists for a local process that will produce acid cheaply on a small or large scale. To leach ores containing residual sulfides, an oxidizer, such as ferric sulfate, is needed in solution. Precipitation with scrap iron is one of the cheapest methods of removing some metals from solution, giving a plant of low first cost and supplying a source of cheap ferrous sulfate. The other ingredient needed for the process is SO2 roaster gas, the addition of which, as described below, will give both ferric sulfate and sulfuric acid. Where roaster gas is a waste or obnoxious product, the expense for materials is still further lessened. The use of ferric sulfate and sulfuric acid as a solvent lends itself well to the utilization of scrap iron as a precipitant, and the stages of the process fit in well together as an economic whole. Applications The hydrometallurgist usually thinks of ferric sulfate as a partial solvent for some of the sulfides of copper alone, as most work has been done on this metal. The processes of Hannay and Christensen, for leaching unroasted galena with ferric chloride made by anodic oxidation, show the added solvent action given by "ic" salts when added to brine solutions. It was found by R. D. Bradford (in some work to be published soon by the University of Utah) that, by the addition of a ferric salt to a brine solution, the silver as well as the lead in an unroasted semi-oxidized ore could be largely dissolved. The "ic" salt in the case of silver has evidently the same effect as the case of cupric sulfate when

Jan 1, 1926

By W. H. Newhouse

During the past few years the writer has been impressed by the close relation of many epigenetic orebodies with anticlinal structures. In the literature on ore deposits there is occasional mention that an oreshoot or district is on an anticline, but in most of the descriptions no weight or significance is attached to the relation, and usually the fact is concealed in a mass of structural detail. A few writers have stressed the relationship in a few districts or on a certain type of deposit. Church, Spurr, Butler, Stahl and Schuette have called attention to certain features, but the general extent of such a correlation has not been made known in any publication that the author has seen. A recent article1 on the localization of ore deposits, by well-known geologists, does not consider this common association. The author has seen in the field a number of the structural features described, and in addition has made a fairly complete review of the literature. This paper presents enough of the examples found to show the frequency of the relation to anticlines, and since only a few deposits on synclines are known, all of these of any importance of which the writer knows are mentioned. With certain qualifications which are discussed later, epigenetic ore deposits of replacement or vein type are mostly found where local upwarps of the earth's crust have taken place. Where formations antedating the ore deposits are present in the proper attitude to demonstrate vertical warping (i. e., more or less horizontal beds) the structural feature on which a mineral district, or mineralized area is located is almost always anticlinal, or domelike in nature. Some or even most of the ore deposits in a given district may be on the flanks of the upwarp, but few major districts are located definitely on downwarped areas. Synclinal basins within certain limits of size appear to be unfavorable to the type of fracturing that admits ore-bearing solutions. Replacement orebodies frequently are localized in small anticlines or domes, the size of the anticline or roll often being more or less commensurate with that of the enclosed oreshoot. This feature certainly ranks

Jan 1, 1931

By Norman P. Goss

It is generally agreed that cold-working mechanically refines the grains into smaller fragments and with continued working these are oriented with certain crystallographic directions bearing a relation to the direction in which the metal is worked. Some of the energy expended on the metal during plastic deformation appears in the form of heat, but a very small portion remains in the metal as stored energy. The entropy, specific heat capacity, temperature at which recrystallization will just begin, density, ductility, elasticity, tensile strength, and resistance to corrosion are affected. These properties have been studied extensively and some of the changes in the physical properties due to cold-working were attributed to lattice distortion.l-8 The broadening of the Ka lines on the X-ray diffraction diagrams of plastically deformed metals is believed to indicate lattice distortion, and consequently the existence of internal stresses. The evidence supporting this theory rests solely upon the observed experimental fact that the diffraction lines are broadened and the Ka doublets are completely diffused. Elam9 has reviewed the matter of lattice distortion in relationship to the hardening of metals by plastic deformation. The X-ray diagrams of plastically deformed metals differ in general from annealed metals. The hardening of a metal was believed due to lattice distortion.9 The resolution of the doublet is lost when a metal is cold-worked and the Laue spots are elongated. At one time this elongation was thought to indicate the elastic bending of the crystal planes. However, more careful work showed that the asterism was due to new orientations developed within the fragmented grains during plastic deformation. Some theories attributed the hardening to fragmentation of the grains into smaller units. Jeffries and Archer,ll after carefully considering the problem of work-hardening from many angles, came to the conclusion that cold-working mechanically refines the grains into smaller crystal fragments, some of which at least differ in orientation from the parent grain. The increase in

Jan 1, 1940

By F. F. Sharpless

IT IS to be. read in Western newspapers that Hon. S. S. Arentz who introduced H. R. 7736, 'has repudiated it, that certain mining men in Utah and Nevada say that they will fight it "until hell freezes over." It is to be read in more temperate expressions that "the eminent engineers who drafted the bill exhibited a woeful misunderstanding of Western sentiment and opinion." Furthermore, it is averred that there is no need for revising the mining laws, that we have got along pretty well under the existing laws, etc. Such statements are so surprising in view of, the facts of record that it is hard to believe that the oppon-ents of the bill, who make them, are well informed, or that they represent general opinion. It will be useful therefore to review the record of the case. Our GOOD OLD MINING LAWS We have indeed got on well in our mining industry, but that has not been by virtue; of our good old mining laws. Rather has it been in spite of them. Ever since the Richmond-Eureka case in the '70s there has been litigation arising from them. Early in the '80s the apex law was discarded by common consent in Leadville, and it has been ignored in every district of flat-lying ore deposits ever since. The great mines of the present time are the porphyry copper deposits. At Bingham, Ely, Ray, Chino, Miami, Clifton and Ajo the apex law is simply inapplicable. A law that is inapplicable to the modern conditions of mining may be an old law, but it can not properly be characterized as a "good" law. For such reasons, and many others of weight, there has been a demand for revision of the mining laws; dat-ing ,back at least three decades. President Roosevelt appointed a commission to advise respecting the question, said commission comprising. Dr. James Douglas (chairman), John Hays Hammond, D: M. Barringer, Walter B: Devereux, and William B. Mather. This committee was unanimous on the following points:

Jan 1, 1922

By Frederick M. Becket, Russell Franks

WideSpread experimentation has been conducted in recent years to devise a means of preventing intergranular corrosion in austenitic chromium-nickel steels of the 18 per cent chromium-8 per cent nickel type. Additions of titanium to these steels have been used commercially to overcome this dificulty, as advocated by Krupp of Germany, and the latest literature reference concerning improved details of this method is the article by Bain, Aborn and Rutherford.' Extensive work by the present authors has shown columbium also to be a particularly valuable agent for inhibiting intergranular corrosion. This paper does not deal with steels that are largely or wholly austenitic; it is limited to a discussion of the results obtained through the use of titanium and columbium in plain high-chromium steels. For many years titanium has been used commercially by some steelmakers as a cleanser, and to a lesser extent as a hardener, but then in greater percentages. The results of the work to be described disclose that titanium and columbium in proper Proportions act as effective softeners in the high-chromium steels. It is well known that chromium intensifies the hardening effect of carbon in steel; it imparts pronounced air-hardening properties within a rather wide range of chromium content; it provides increased ductility in steels of given strength and hardness; and it enhances resistance to corrosion and oxidation at elevated temperatures to a marked degree. However, in applications requiring a combination of some of these valuable properties great hardness is frequently a detriment rather than a merit. When the objective is a soft and ductile steel having optimurn corrosion resistance, the producer strives for a carbon content as low as commercially practicable. Despite these efforts some of the commercial high-chromium steels low in carbon present considerable difficulties during production, owing to their air-hardening properties, and in consequence the economic result is not favorable. A good example is found in the 5 to 6 per cent chromium steels employed chiefly in the oil-cracking industry. Sleels

Jan 1, 1934

By W. H. Emmons

Although gold is one of the rarer metals, it is widely distributed; it is found on all of the continents and in each of the grand metallogenic provinces of the earth. It is prominent particularly in the shield areas of the earth; these areas have produced a large part of the world's lode gold and in most of them gold lodes are more important than the lodes of other metals. The Scandinavian shield is the only one that has not produced much gold. Nearly all of the world's gold has been derived from lodes and from sands and gravels where gold placers formed by the destruction of lodes. The gold derived from magmatic segregations, from pegmatites and from contact metamorphic deposits is quite subordinate to that derived from auriferous lodes. The lodes include all veins and related deposits that are formed by hot waters that move along fissures or other openings and that deposit vein 'matter :in the fissures and by replacement of the country rocks along the fissures. All of the shield areas of the earth are characterized by large areas of granitic rocks including granitic gneisses, granodiorites and other acid intrusives which here are included in the general term "granite." The granites are intruded into schists, ancient lavas and other rocks which here are designated as the "invaded" rocks. The granites are parts of what once were great batholiths: that is, they are the remaining portions of great deep-seated bodies that slope outward, have very irregular roofs and so far as known have no floors but extend downward to great though unknown depths. Some of them are scores or hundreds of miles across and contain islands or "roof pendants" of the invaded rocks at places where the roofs of the batholiths were low—that is, where erosion has not yet completely unroofed the batholiths. It is in these islands of older rocks and in the narrow marginal belts and cupolas of the batholiths that practically all of the gold lode deposits of the shields are found. Valuable lodes are lacking generally in the granites themselves except in grahite within a mile or less from .the contacts with rocks of the islands (Fig. 1). It is probable that the great areas of granites and gneisses that surround the islands are not all of the same age, and that at places unmapped granite intrudes gneiss or older

Jan 1, 1932

By Edward W. Parker

One of the most important features of the coal-mining industry of the present day is one that is common to the majority of industrial enterprises—the substitution of mechanical methods for hand-labor.

Jan 1, 1900

By James R. Finlay

At first blush one is tempted to say that iron-mines are like any other mines, and that principles governing miniug-property in general will apply to them. But there are certain considerations which seem to repay reflection. Gold and copper are more or less independent of transportation. The proof of this is that those metals are profitably mined and shipped from the remotest corners of the earth. Their value is determined by the cost of production on the ground. This is quite true of gold, not quite so true of copper, not at all true of iron. If New York were a. fishing-village and Chicago a swamp, Calumet & Hecla might still be a bonanza. The main element of its value is the 60 lb. of fine copper per ton which it produced for years. But the Mesabi Range is absolutely dependent upon the industrial activity in the United States. Iron-manu-facture in Europe would give it no value whatever. If Chicago and New York had a population of Peruvians or Hindus, the Hull-Rust mine would be as worthless a bit of landscape as any tundra in Alaska. I have discussed these facts more or less casually and dimly in my book on the cost of mining and in my report to the Tax Commissioners of Michigan.1 I shall try here to bring them out in more detail. I have already referred to some differences in the problem of mining as between the more precious metals, e.g., gold, and the less precious and more abundant minerals, like iron and coal; but it is interesting to note that the literature of the eco-

Jan 1, 1914

By Norman P. Goss

It is generally agreed that cold-working mechanically refines the grains into smaller fragments and with continued working these are oriented with certain crystallographic directions bearing a relation to the direction in which the metal is worked. Some of the energy expended on the metal during plastic deformation appears in the form of heat, but a very small portion remains in the metal as stored energy. The entropy, specific heat capacity, temperature at which recrystallization will just begin, density, ductility, elasticity, tensile strength, and resistance to corrosion are affected. These properties have been studied extensively and some of the changes in the physical properties due to cold-working were attributed to lattice distortion.l-8 The broadening of the Ka lines on the X-ray diffraction diagrams of plastically deformed metals is believed to indicate lattice distortion, and consequently the existence of internal stresses. The evidence supporting this theory rests solely upon the observed experimental fact that the diffraction lines are broadened and the Ka doublets are completely diffused. Elam9 has reviewed the matter of lattice distortion in relationship to the hardening of metals by plastic deformation. The X-ray diagrams of plastically deformed metals differ in general from annealed metals. The hardening of a metal was believed due to lattice distortion.9 The resolution of the doublet is lost when a metal is cold-worked and the Laue spots are elongated. At one time this elongation was thought to indicate the elastic bending of the crystal planes. However, more careful work showed that the asterism was due to new orientations developed within the fragmented grains during plastic deformation. Some theories attributed the hardening to fragmentation of the grains into smaller units. Jeffries and Archer,ll after carefully considering the problem of work-hardening from many angles, came to the conclusion that cold-working mechanically refines the grains into smaller crystal fragments, some of which at least differ in orientation from the parent grain. The increase in

Jan 1, 1940

By William H. Case

The Bertha zinc-mines of the Bertha Zinc and Mineral Company are in that part of the State of Virginia popularly known as Southwest Virginia, and are included in that division of the " Great Valley " named in recent years the " New River-Cripple Creek Mineral-Region of Virginia." The mines lie wholly in the southeast part of Wythe county, two miles from Pulaski county on the east, and three miles from Carroll county on the south. The only other zinc-mines that are opened in the region are those of Manning & Squier, which adjoin the Bertha zinc-mines on the northeast, and the mines of the Wythe Lend and Zinc Company, at Austinville, eight miles to the southwest. A little farther southwest of Austinville, near Ivanhoe, a new company is preparing to mine zinc-ores. The mining properties named are included within a distance of ten miles along a direct line, bearing north 55' east, on the south side of New river, which here flows northeastward in a tortuous course. The greatest distance of any of the mine-openings from the river is a little less than two miles. It is not the magnitude of the operations in zinc-mining in this particular region, as compared with that of other well-known districts, that merits especial notice. Aside from the exceptional purity of the spelter made directly from the Bertha ores, some peculiar features of the zinc-ore deposih, as shown at the Bertha mines, and

Jan 1, 1894