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By Robert H. Richards

The extent to which sizing by sieves should be carried, as a preliminary to the separation, by jigging, of minerals of different specific gravities, has been a matter of controversy for many years. The subject has been investigated by several authorities, yet the ground does not seem to have been completely covered, nor are the questions involved entirely settled. For my present purpose I shall refer to but three investigators—Rittinger, Munroe, and Hoppe. In seeking additional light, I have gone over part of the old ground which has been considered satisfactorily settled; and since these preliminary tests have thrown light on some points, they have been included in this paper. In the investigations here described, I have confined myself, for several reasons, wholly to small sizes—grains of 0.1 inch in diameter and less. Rittinger's work was mainly done upon larger sizes, and there is much need among millmen of information concerning the smaller sizes. Moreover, these sizes brought the investigation within the means at my disposal. The laws that have been claimed as the laws of jigging by the several authorities are: 1. The law of equal-settling particles. 2. The lam of interstitial currents. 3. The law of acceleration. 4. The law of suction. The first of these has been considered by investigators, generally, to be the most important of all, and the larger part of the work of jigging is thought to be governed by it. But that it does not cover the whole of jigging is clear to all; and to account for the increased efficiency which we may call the extra jigging-catch, the other three laws have been advanced. The investigation described in this paper was undertaken to determine, as far as possible, to what extent each of the four laws con-

Jan 1, 1895

Electro-mechanical actuator, self-protected for mechanical and electrical overload, is developed by RACO. Tubular housing consists of squirrel cage motor with hollow rotor shaft and inner threads in the rotor. Features stroke distance of 2-72 in. and wide range of trust (20 lb-10 tons). (100) Agglomeration systems, offered by Ferro-Tech, incorporate pelletizing, briquetting and extrusion systems to agglomerate materials too fine to convey, load or feed to a process. Equipment includes disc and drum pelletizers, briquetter presses, compactors, extruders, pugmills and mixers, dryers, coolers, feeders and conveyors. (101)

Jan 9, 1973

By R. O. Leach, O. W. Wagner

Because of unfavorable wetting conditions much residual oil is left when a porous material is Pushed by water. Methods suggested to change reservoir wetting to improve oil displncernrnt efficiency are generally expensitlr. The present 1aborator.y study was undertaken to gain an under.standinx of the factors which determine reservoir wettability, arid to find out if oil displacement efficiency might be improved by a wettahility change accomplished at low cost in on oil reservoir. Contact angle measurements were made on mineral surfaces using sevc.r~zl sets of reservoir oil and water samp1es. Results of the contact angle studies suggest that reservoir wetta-hility may he primarily determined by natural surface-active substances present in the reservoir fluids. The effect of changing sa1inity and pH of the water phase was studied. The re.suits suggest that gross changes in preferential wettability might be acc~o~npli.shed by injection of water containing simple chernicnls to alter pH or salinity in the reservoir. Such treatment could he much less expensive than injection of commercial surface-active agents. Waterflood tests have also been made using synthetic cores and oil and water having wening characteristics similar to those of reservoir fluids. Cores initially oil-wet were flooded in such a way that they were made prefermtial1y water-wct by the advancing flood water. This reversal in preferential wettability achieved greater oil displacement efficiency than when either oil-wet or water-wet conditions were maintained throughout the flood. For the systems studied, the higher the oil viscosity the greater the percentage improvement obtained over conventional waterflood recovery. This suggests that a flooding process making use of wettability-reversal may extend the oil viscosity range over which water flooding is attractive. Because a precise adjustment of reservoir wettability does not seem to be required, and because altering the pH or salinity in some reservoirs may be inexpensive, it appears that a waterflooding process employing wet-[ability-reversal could find .succesful field application. I NTRODUCTION The efficiency with which water will displace oil from a porous material is related to the nature of the capillary forces present. These in turn are controlled by the preferential wetting of the solid by the two fluids. Because of unfavorable wetting conditions, 30 per cent or more of the original oil in place may remain unrecovered in that portion of a reservoir flushed by water. This paper is concerned with the possibility of improving waterflood oil displacement efficiency by alterations in the wettability of the porous material. A laboratory study was made to gain a better understanding of the factors which control reservoir wettability, and to determine if the oil displacement efficiency could be improved by some inexpensive means of manipulating wettability of the porous medium. Contact angle measurements were made with several natural and synthetic oil, water and solid systems (1) to obtain a better understanding of how to duplicate reservoir wettability in the laboratory, and (2) to discover possible means for changing preferential wettability of natural reservoir systems. Flooding tests were also made in synthetic systems to determine if oil displacement efficiency could be improved by those wettability manipulations suggested by the contact angle measurements. Based on these studies a possible method for improving waterflood oil displacement efficiency is presented. This method involves causing an originally oil-wet porous material to become preferentially water-wet during the course of a water flood. The purpose of this paper is to present results of the laboratory studies. THEORY Rock surfaces in some oil reservoirs are believed to be covered with a firmly attached bituminous or other organic coating. Such surfaces would be preferentially oil-wet in the presence of both oil and water, regardless of composition of reservoir fluids. Other reservoirs are believed to contain rock surfaces not permanently coated with such materials, and which would be preferentially wet by water in the presence of water and oil free from surface-active substances. However, when the reservoir fluids do contain certain natural surface-active materials in sufficient quantity, rock surfaces acquire a degree of preferential oil wettability caused by adsorption of these natural surface-active materials on the solid. The equilibrium amount of these materials adsorbed per unit surface area is believed to depend upon their concentration in the bulk liquid phases.

By John E. Dorn, Oscar E. Harder

The phenomenon of diffusion, according to the most prevalent conceptions at the present time, undoubtedly played an important part in the formation and distribution of metals and minerals in the earth's crust. Apparently there is good evidence that in the geological rate of cooling diffusion caused numerous materials to separate into individual masses or into duplex structures. As is well known, the early steels were made by cementation; that is, by heating wrought ferrous metal in contact with carburizing materials so as to produce a relatively high carbon content on the surface. If the process was continued long enough, the carbon diffused throughout the piece. A more homogeneous product depended upon further heating and forging, so that the carbon diffused to a fairly uniform concentration throughout the metal. In the modern metallurgical industry, diffusion is the basis for many operations; for example, the production of hard surfaces on steels by carburizing, nitriding, cementing with chromium, silicon, boron and beryllium. Castings or ingots as they solidify do not have homogeneous structures, but these structures are made largely homogeneous by suitable process of heat-treating and the resulting diffusion. It is in modern physical metallurgy, however, that we become greatly concerned about the mechanism of the phenomenon of diffusion. The rates of diffusion, effect of temperature and time on diffusion, and the relation of diffusion to the many properties of the parent metal and the diffusing metal have become important; also, we are concerned with the diffusion of a single metal into a complex alloy. For example, what is the mechanism whereby carbon and nitrogen travel into steel? What is the effect of alloying elements in the ferrous material on the rates of diffusions? What is the effect of simultaneous diffusion of carbon and nitrogen? How does chromium, beryllium, boron, or the like, diffuse into the steel, and what are the effects of alloying elements in the steel previous to the cementation process? These inquiries are by no means limited

Jan 1, 1938

By Oscar E. Harder, John E. Dorn

The phenomenon of diffusion, according to the most prevalent conceptions at the present time, undoubtedly played an important part in the formation and distribution of metals and minerals in the earth's crust. Apparently there is good evidence that in the geological rate of cooling diffusion caused numerous materials to separate into individual masses or into duplex structures. As is well known, the early steels were made by cementation; that is, by heating wrought ferrous metal in contact with carburizing materials so as to produce a relatively high carbon content on the surface. If the process was continued long enough, the carbon diffused throughout the piece. A more homogeneous product depended upon further heating and forging, so that the carbon diffused to a fairly uniform concentration throughout the metal. In the modern metallurgical industry, diffusion is the basis for many operations; for example, the production of hard surfaces on steels by carburizing, nitriding, cementing with chromium, silicon, boron and beryllium. Castings or ingots as they solidify do not have homogeneous structures, but these structures are made largely homogeneous by suitable process of heat-treating and the resulting diffusion. It is in modern physical metallurgy, however, that we become greatly concerned about the mechanism of the phenomenon of diffusion. The rates of diffusion, effect of temperature and time on diffusion, and the relation of diffusion to the many properties of the parent metal and the diffusing metal have become important; also, we are concerned with the diffusion of a single metal into a complex alloy. For example, what is the mechanism whereby carbon and nitrogen travel into steel? What is the effect of alloying elements in the ferrous material on the rates of diffusions? What is the effect of simultaneous diffusion of carbon and nitrogen? How does chromium, beryllium, boron, or the like, diffuse into the steel, and what are the effects of alloying elements in the steel previous to the cementation process? These inquiries are by no means limited

Jan 1, 1938

By AIME AIME

THE iron and steel activities of this meeting opened on Monday morning with the steel melting session," with G. B. Waterhouse in the chair and A. L. Feild as vice-chairman. N. A. Zeigler's paper, on "Gases Extracted From Iron Carbon Alloys by Vacuum Melbing," created considerable interest and the discussion in general was most favorable. H. W. Gillett and Louis Jordan of the Bureau questioned the method of analysis for oxygen and C. H. Herty, Jr., and J. M. Gaines, Jr., I , expressed their surprise at the large amount of oxygen with the high ,carbon alloys. Whether the gases found existed as gas in blowholes or as oxide inclusions was also a moot point. A paper by C. D. King, on "Basic Open-Hearth Yields," was an extremely interesting and valuable contribution. It was discussed by C. E.Kinney and A. L. Feild and numerous questions were asked throughout the presentation. Mr. King then presented a critical analysis of the losses together with novel methods of calculating them. A paper by C. H. Herty, Jr., and J. M. Gaines, Jr., on "Unreduced Oxides in Pig Iron and Their Elimination in the Basic Open-Hearth Furnace," followed. The question of silicates and oxides in pig iron created much discussion, notably by Henry Hanson and W. J. MacKenzie, who gave figures on chipping cost as a function of blast-furnace practice.

Jan 1, 1929

By S. F. Emmons

In the yew 1879, Congress, acting tinder the advice of tile National Acdemy of Sciences, discontinued the temporary surveys or explorations under Hayden, powell, and Wheeler, and established as a permanent organization the United States Geological Survey, making it a Bureau of the Interior Department. A great step was thus taken toward obtaining the greatest practical results from the expenditure of the public money for geological purposes. The recommendations of the National Academy also contemplated the consolidation of all the various organizations for the mensuration and mapping of the country—-such as the Coast, Engineer, and Land Office Surveys—under one single head; which, also, should assume the duty of providing the mays necessary as a basis fir the work of the Geological Survey. But this useful measure did not meet the approval of Congress, and the various mensuration surveys were left in statu quo. With the final establishment of a permanent Geological Survey of the United States, it became necessary to adopt a plan of work which would enable it in time to take the prominent rank among the older surveys of other civilized nations of the world, which is justified by the great, wealth and mineral resources of the country it is destintd to study. The somewhat vague wording of the organic law under which it was created, directing an examination of the geological structure, mineral resources, and products of the public domain, left the details of the policy to he pursued very largely a matter of discretion with its director. That adopted by Mr. Clarence King, the first director, as foreshadowed in his Annual Report to the Secretary of the Interior for 1880, was one whose distinguishing feature was the prominence that should be given to economical geology, or the practical application of geological investigations to the development of the mineral resources of the country. In earlier Government Surveys, which were topographical reconnoissances in a practically unknown region, geology occupied a secondary and unimportant position. With the Fortieth Parallel Survey, inaugurated in 1867, and its successors, the Hayden, Powell, and Wheeler Surveys, geology became an essential object of the work, but owing to the want of already existing maps topography

Jan 1, 1882

By M. Guney, A. R. Bell

In Mindola mine on the Zambian Copperbelt, there is a plan to extend the current production level of 1.2- 1.5 km (3,900-4,900 ft) with five additional production levels. Research work indicated that the present total heat output of 38.6 MW will inevitably increase to 63.2 MW in 25 years. Estimated WE and DB temperatures, representing the total heat generation in stope faces and development headings during these same periods are predicted to increase to 33.8/40.2°C (93/104°F) and 35.3/42.1°C (95/108°F) respectively. It is assessed that the nominal refrigeration capacity needs to be progressively increased to 9,000 M W.

Jan 1, 1984

By R. J. Charles, G. Agar

Experiments on single particles show that the amount of material created during impact that is finer than any chosen size is proportional to the energy of the impact. As the underlying principle of comminution, it might be stated that each unit of energy input to a given comminution system tends to add to the system an identical assembly of new particles and subtract an equivalent volume of larger particles. Thus, two of the consequences of the fact that each unit of energy tends to add identical assemblies of new particles to the system are: 1) on continued application of energy the total charge in any batch comminution system tends to assume the characteristics of this assembly, and 2) the process of comminution may be described by a relationship such as E = Ak-a. Recently Schuhmannl presented a theory of comminution which puts rational perspective on the extensive controversy surrounding most of the existent theories of comminution. With hindsight the origin of controversy can be ascribed to a relatively simple circumstance. In general, a progressive shift of a size distribution curve towards finer sizes is observed as energy is added to a comminution system. It is also observed that, with continued grinding, the size distribution curves usually change and appear to approach some constant shape. Inves-tigators generally felt that an appropriate method of relating and generalizing such data would be to consider the hypothetical case where particles in the system were uniformly subjected to comminution such that each of these particles, receiving its proportion of input energy, was transformed into a number of smaller particles of uniform size. Since the changes in shape of the size distribution curves during size reduction were clearly associated with the coarse particles in the system, it was also assumed that these changes accounted for little of the input energy and one could deal solely with the equilibrium shape towards which the size distribution curves tended. Although the unrealistic nature of the foregoing points of view was realized some justification was felt for such treatments since, in most cases, the resulting mathematical formulae could, by the adjustment of at most two parameters, satisfactorily describe experimental observation. Difficulties arose, however, in that the formulae required a specific influence of the feed size on the comminution process. In actual fact, the application of a feed size term in fitting experimental data was often found to be unnecessary or contrary to the above formulae. Secondarily, much discussion arose concerning the appropriate energy number that would relate the size change of one particle to the amount of comminution energy it received. As has been previously shown3 all the above theories that treat comminution as a continuous process of size reduction may be related to a proposition of the following form: dE = -Cfn [1] where dE is the increment of energy, dx is the size change, x is the particle size, and C and n are constants. It is now clear, as pointed out by Schuhmann, that Eq. 1 is inapplicable to comminution processes, since comminution cannot be considered other than as a discontinuous mixing process in which the overall size distribution of the product results from mixing, in various proportions, finished material with unfinished, and sometimes untouched, material. A striking illustration of this mixing phenomena may be obtained by comparing the size distributions of grinds in a typical batch ball mill with size distributions calculated on the basis of mixing various proportions of feed material with a ground material which obeys a power law size distribution relationship. Figs. la and lb illustrate such a comparison and the similarity of these figures indicates that mixing plays an important role in determining the overall shape of the product size distributions. Figs. la and lb illustrate, additionally, the underlying basis of the comminution theory presented by Schuhmann.' In the preliminary grinding of relatively close sized feed particles in a batch ball mill, one may visualize that, when a successful encounter of a ball with a feed particle occurs, then the particle undergoes severe size reduction and the size range in which the resultant particles reside is far removed from the size of the feed particles. After a number of feed particles are reduced by independent but similar impacts and one examines the size dis-

Jan 1, 1961

By N. Mungan, J. L. Thompson

Laboratory displacement tests were performed to study oil recovery elficiency by gravity drainage in fractured systems under miscible conditions. The porous media used were cylindrical Berea and Blue Jacket sandstone cores containing a number of well-defined, artificially formed, vertical and subvertical fractures. Butane and Soltrol 130 were the two miscible fluids used. The purpose of the study was to examine the influences of the displacement rate, fracture density, fracture orientation, fracture permeability, matrix permeability, crossflow, core length and connate water on the oil recovery. It was found that displacement rate, matrix permeability and the subvertical fractures affected oil recovery most. The critical flow rate, based on the matrix permeability, was found to be a significant factor in the process. For displacement rates below the critical flow rate, the oil recovery efficiency appeared to be unaffected by the density of the subvertical fractures. At the high displacement rates, the fracture density becomes important, with the recovery being the most efficient in the core having the greatest number of the subvertical fractures. The magnitude of the fracture permeability, the fracture orientation, the core length and the connate water have little effect on the oil recovery efficiency. INTRODUCTION Gravity drainage under miscible conditions from relatively thick reservoirs can be a very efficient recovery process, especially at low flow rates where the gravity forces are dominant and, consequently, the adverse viscous fingers associated with the unfavorable viscosity ratio are minimized or eliminated. Such a process might involve injection of an LPG or some solvent bank at the crest and then driving the bank with dry gas. For some favorable combination of reservoir temperature, pressure and oil composition, there may be no need to inject any solvent bank, since enrichment of the dry gas by the light ends of the crude creates an in-situ solvent bank. Slobod and Howlett2 have studied the effects of gravity segregation in vertical unconsolidated porous media under miscible conditions in the laboratory. The main variables in their study were the viscosity ratio, the density differences and the rate of flow. In this study, the objective was to find the influence of fractures on gravity drainage under miscible conditions. A greater number of related variables were also studied. LABORATORY STUDY CORE DESCRIPTION Displacement tests were performed mostly in cylindrical Berea sandstone cores. In a few cases in which a much lower matrix permeability was desired, Blue Jacket sandstone cores were used. The vertical fractures were formed by cutting the cores with a thin circular blade or by parting them along a bedding plane. The vertical fracture plane always contained the axis of the cylindrical core. The subvertical fractures, cut with a saw, were inclined 45' from the horizontal. The line of intersection between the planes of the vertical and subvertical fractures was parallel to the circular faces of the cores in all cases except one, as depicted by VF3HF-2 in Fig. 1. Fracture geometry of the other cores is also given in Fig. 1. Tables 1 and 2 give the physical properties of the solid and fractured cores, respectively. The suffixes and prefixes shown for each core have been used throughout the paper so that the reader may discern the fracture geometry from the core numbers.

Jan 1, 1970

By J. Lewis, J. Harper, M. F. Ashby

A grain boundary in a metal interacts with second-phase particles, which exert a pinning force (first estimated by Zener) on the boundary opposing its motion. We have computed the shape of boundaries which interact with more or less spherical second-phase particles and have constructed a soap-film model to reproduce the shape of the boundary surface. An important result is that measurement of this shape allows the pressure, or driving force, on the boundary to be measured. We hare applied this technique to grain boundaries in two alloys and hate measured the pinning force exerted by single second-phase jwrticles on the boundaries. It is in good agreement with Zener's estimate. J\. boundary between two grains, or two bulk phases, interacts with small inclusions or particles of a second phase, whether they are gas or solid. This interaction means that the boundary, forced to migrate by a difference in free energy between the material of the two grains or phases which it separates, exerts a force on a particle which it touches, tending to drag it forward. (The movement of inclusions through metals under the influence of this force, has, in fact, been observed. 1-3) Equally, the particle can be thought of as exerting a pinning force on the boundary, tending to hold it back. Zener (in a celebrated private communication4) first realized that this interaction, and the resulting pinning force, existed. His calculation of its magnitude was crude but adequate: a spherical inclusion of radius r blanks off an area nr2 of the boundary on which it sits; since the boundary has an energy of rMM x per unit area, the blanlung-olf decreases the energy of the system by MM: this energy is returned to the system if the boundary is pulled free from the inclusion— a forward movement of the boundary by a distance r will do this—so that the maximum pinning force is Trrym.M- A similar argument can be made for inter-phase boundaries. The nature of the particle itself did not enter this, or two subsequent treatments.5,6 When it is considered, tic leifthe energyoftheb a) The boundary may enter and pass through the particle if the energy of the boundary is lower within the particle than in the matrix. Fig. l(r/). Certain coherent precipitate particles behave like this. h) More usually, the boundary will bend round the particle, enveloping and bypassing it. Fig. l(b). In doing so, it changes the structure and energy of the interface between the particle and its matrix. This means that the boundary does not touch the particle surface at right angles, as early treatments assumed,5'9 but at some angle a which depends on this change in surface energy of the particle, and can be calculated from the equilibrium of surface tensions. Most precipitate particles and inclusions behave like this. Gas bubbles or liquid drops can be regarded as belonging to either group. The progress of bypassing is conveniently measured by the angle shown in Fig. 1. When the nature of the particle is ignored, its maximum pinning force is exerted when - 45 deg. When it is considered, this critical value of is found to depend on a and thus on the nature of the particle. The maximum pinning force lies between nryMM and 2jtjMM (Appendix 1). not very different from Zener's result. In reality, a boundary between crystals has a specific energy and tension which varies with the orientation of the boundary. Furthermore, recent experiments7 indicate that such a boundary is not atom-ically smooth, but has steps on it: migration of the boundary corresponds to the sweeping of these steps across the boundary surface, like the Frank model of crystal growth from the vapor. This means that the interaction of a boundary with particles should really be considered in terms of the way in which particles hinder the movement of these steps. To suppose a grain boundary or interphase boundary to be smooth, and to ignore the variation of its energy with orientation, is to liken it to a soap film. The advantage of this soap film approximation, which we have used throughout this paper, is that interaction energies and boundary shapes can be calculated easily. We have done this by numerical computation and by using a soap film model, and have compared the results with grain boundaries in an aluminum-based and a copper-based alloy. It turns out that the shape of the boundary which bulges between particles allows the pressure an it to be calculated; that is, the local driving force an the boundary can be measured. This has allowed us to check the Zener relationship experimentally.

Jan 1, 1970

By Thomas L. Kesler

The Cartersville mining district, 35 miles northwest of Atlanta, Ga, has been of varying but continuous importance in the southern mineral industry during the past century. Noted chiefly for its production of brown iron ore, manganese oxide ores, barite, sienna, and magnesian limestone, the district and its environs have produced brick and tile clays, slate, gold, bauxite, and graphitic schist. Minor deposits of serpentine, sericite schist, copper ore, and red iron oxide have been prospected. The obvious deposits of brown iron ore, together with some associated specular hematite, were mined out years ago, although a little ore was left in the workings. Moderately steady production of sienna reached a peak about 1930, then declined rapidly. Manganese mining passed through a relatively active period from the World War to 1931, but has subsided to a small but rather constant output for the Birmingham market. However, the White Manganese Corporation has prepared for possible increased production by constructing a new washer capable of handling about 300 tons of ore per day. Principal activity in the district proper has centered for some years in the production of barite and magnesian limestone. General Geology Geologic relations of the ore deposits of this district are more or less similar to those of many Appalachian districts. The lowermost Cambrian formation, heretofore called Weisnerl in this region, supposedly partly or. wholly equivalent to the Erwin and Hesse quartzites as recognized to the northeast, is overlain conformably by the Shady† formation, also of Lower. Cambrian age. In the Cartersville district, the sedimentary rocks of these formations were folded with increasing intensity eastward, and were recrystallized.

Jan 1, 1941

By J. J. Jakosky

ALL electrical geophysical methods depend for their operation upon the effects produced by the flow of an electric current. By studying these effects it is possible to predict the general axis of current flow. The greater flow of current is in the path of greatest, effective conductivity; and since the effective conductivity of a mineralized zone is different from that of its surrounding envelope (usually much greater), it is possible to locate such a mineralized zone by the distribution of current. Due consideration must be given, of course, to geological structure, to type of mineralization, and to other factors. A number of methods are used to cause this flow of current, and various methods are available for detecting the presence of such current flow and for studying its effects. In a rather detailed way, this paper will discuss the theoretical and practical phases of the inductive methods of geophysical prospecting. ELECTROMAGNETIC GENERATION OF AN ELECTROMOTIVE FORCE The inductive method is so named because the current flowing in the conductor is obtained by electromagnetic induction, instead of by the use of ground electrodes through which a current is passed as in the applied potential systems, or by direct contact with the orebody. An alternating current flowing in a coil will create an electromagnetic field around the coil. This field will have the same frequency as the current and will radiate or travel outward from the coil in closed magnetic or flux circuits: These flux circuits (in air or a homogeneous medium) will be perpendicular to the plane of the coil and will extend or travel outward with uniform velocity in every direction. Maximum field exists in the plane of the coil. Such a coil used for transmitting or as the "energizer" will exhibit similar figure-eight characteristics to those exhibited by the direction-finding coil which will be described in detail later.

Jan 1, 1928

By Thomas L. Kesler

The Cartersville mining district, 35 miles northwest of Atlanta, Ga, has been of varying but continuous importance in the southern mineral industry during the past century. Noted chiefly for its production of brown iron ore, manganese oxide ores, barite, sienna, and magnesian limestone, the district and its environs have produced brick and tile clays, slate, gold, bauxite, and graphitic schist. Minor deposits of serpentine, sericite schist, copper ore, and red iron oxide have been prospected. The obvious deposits of brown iron ore, together with some associated specular hematite, were mined out years ago, although a little ore was left in the workings. Moderately steady production of sienna reached a peak about 1930, then declined rapidly. Manganese mining passed through a relatively active period from the World War to 1931, but has subsided to a small but rather constant output for the Birmingham market. However, the White Manganese Corporation has prepared for possible increased production by constructing a new washer capable of handling about 300 tons of ore per day. Principal activity in the district proper has centered for some years in the production of barite and magnesian limestone. General Geology Geologic relations of the ore deposits of this district are more or less similar to those of many Appalachian districts. The lowermost Cambrian formation, heretofore called Weisnerl in this region, supposedly partly or. wholly equivalent to the Erwin and Hesse quartzites as recognized to the northeast, is overlain conformably by the Shady† formation, also of Lower. Cambrian age. In the Cartersville district, the sedimentary rocks of these formations were folded with increasing intensity eastward, and were recrystallized.

Jan 1, 1941

By Francis F. Lucas

Jan 1, 1931

By R. I. Jaffee, E. S. Bartlett, D. N. Williams

The oxidation resistance and fabricability of molybdenum powder-metallurgy alloys containing up to 20 wt pct nickel in the form of a fine dispersion were studied. The effects of dispersion distribution and of amount and type (pure nickel or nickel compounds) of additive were considered. A definite improvement in oxidation resistance was observed, but the amount of improvement fell far short of requirements for an oxidation-resistant alloy. Fabricability by hot-rolling was limited. INVESTIGATIONS at Ohio State university1 and Battelle Memorial institute2 have indicated that the attainment of a truly oxidation-resistant molybdenum-base alloy for high-temperature service, with the coincident retention of high-temperature strength and toughness, will be a difficult, if not impossible, feat. Among the most promising alloy systems studied was the molybdenum-nickel system shown in Fig. 1. Alloys in this system show good oxidation resistance at temperatures well above the normal melting point of molybdenum trioxide because of the regenerative formation of protective nickel-molyb-date (NiMoO4) on the surface of the alloy during exposure at high temperatures. Unfortunately, the required alloy content to obtain oxidation resistant molybdenum-nickel alloys far exceeds the limits of the narrow terminal solid-solution boundary, and closely approaches the peri-tectic composition involving the brittle intermetal-lic compound, MoNi. Because of the peritectic reaction, fusion alloys are characteristically brittle, since the MoNi phase, being the last to form, tends to occur as a continuous grain-boundary network around each molybdenum grain. An added problem with this system is that the protective nickel-molybdate layer formed at high temperatures is unstable, undergoing one or more allotropic modifications upon cooling. The volume changes associated with this modification during cooling are such as to cause violent expulsion of the protective molybdate coating from the surface of the piece. This is, of course, quite detrimental in material exposed to cyclic temperature during service. The research reported here resulted from an attempt to overcome the aforementioned problems associated with the molybdenum-nickel alloys primarily by controlling the amount, size, and location of the MoNi phase. By using powder-metallurgy techniques of alloy preparation and sintering the blended molybdenum-nickel powder mixtures at a temperature below the peritectic reaction temperature, molybdenum-nickel alloys with a randomly dispersed MoNi phase were produced. MATERIALS The molybdenum powder used in the preparation of alloys for this study was commercial hydrogen reduced, minus 325-mesh (Tyler) material. Master alloys, by which nickel was added, consisted of elemental carbonyl nickel powder (12 average particle size), an alloy of 50 wt pct Ni-50 wt pct Cr, and compounds of MoNi, Ni,Si, and Ni2B. The nickel-chromium powder was prepared by filing a vacuum-arc-melted ingot, separating impurities magnetically, and screening to minus 200-mesh. The MoNi powder was prepared by pulverizing a hydrogen-sintered powder-metallurgy compact to minus 325-mesh material. Further sizing of this powder for study of effects of dispersion distribution was accomplished by air classification of the minus 325-mesh powder. The Ni2Si and Ni2B powders were prepared by crushing vacuum-sintered powder-metallurgy compacts to minus 200-mesh material. EXPERIMENTAL PROCEDURE Specimen Preparation—The general procedure followed in the preparation of alloys for testing is described as follows: 1) Blending. Either hand-blending of the powders in a ceramic mortar and pestle for X 1/2 or mechanical blending was used. Hand-blending seemed preferable for optimum homogeneity. 2) Compacting. Most of the blended powders were pressed to green compacts at pressures of 15 tons per sq in. in a single-action die, although some were pressed at 80 tons per sq in. A 1 X 11/4 X 1/4-in. green compact was the standard size for oxidation test material, and 7 X 1/2 X 1/4-in. compacts were used for fabricability test specimens. 3) Sintering. All green compacts were sinteredat

Jan 1, 1959

By Eric R. Morgan, J. C. Shyne

STRAIN aging is the name given to time-dependent changes which occur in the properties of cold-worked metals and alloys during storage. These changes are best observed through a study of mechanical properties, as illustrated in Fig. I for low-carbon steel. The effects of strain aging are usually regarded as being detrimental, particularly in deep-drawing steels. For example, an increase in yield strength and loss in ductility lead to buckling and tearing during drawing. At the same time the return of the yield point results in the formation of Luders bands or stretcher strains during the pressing operation. As a result of these effects many attempts have been made to eliminate strain aging from low-carbon steel. The problem still remains, however, because all known methods of preventing strain aging result in a more costly steel. The present work is an assessment of the situation in terms of theoretical, practical, and economic factors and suggests a new solution to the problem. Previous Work According to the Cottrell theory,' strain aging in a-iron may be regarded as the migration of interstitial atoms to free dislocations and the anchoring of dislocations by the resulting atmospheres. It may be concluded that the important factors which will govern the degree of strain aging are the diffusivity, the effective amount of interstitial element in solution, and the time of aging. The diffusivities and effective amounts of carbon and nitrogen in solution in low-carbon rimming steel are such that significant aging occurs in a few hours' storage at room temperature. Strain aging in deep-drawing steels cannot be controlled by controlling the time of aging because in commercial practice this is determined by economic factors concerned with inventories and may be several weeks. The diffusivity of nitrogen is twice that of carbon at room temperature but the diffusivities can be controlled by controlling the storage temperature. The retardation produced by only a 25 °C drop in temperature is significant but the cold storage of large steel inventories is an impractical solution to Table I. Analysis of Base Materials Alloy Pet C Yet 0 Pet N Vac 0.0037 0.052 0.0003 H 0.0044 0.013 0.0008 C 0.06 0.0014 0.0001 the problem. By far the most simple and effective ways to control strain aging are through control of the amount of carbon and nitrogen in solution. This may be effected through alloying, controlled precipitation, or by eliminating the carbon and nitrogen. Consider first the control of the amount of carbon in solution. The simplest approach would be alloy -ing in which strong carbide-forming elements are added. Examples of this approach are the additions of titanium' and niobium9 0 steel. These elements also combine with nitrogen and oxygen and when added in sufficient quantity result in a completely killed and non-aging steel. They are, however, impractical additions because they result in a costly steel. Carbon and nitrogen are often removed from iron on a laboratory scale by annealing in wet hydrogen, but because of cost this process has never been adopted on a commercial scale. In practice the amount of carbon in solution is controlled by the rate of cooling from the annealing temperature (710°C or 1310°F). In commercial box

Jan 1, 1958

By S. V. Krusiewski, J. W. Gabelman

Regional metallogenic zones and areas of equal paragenetic range have been interpreted from a compiled metallogenic map. of Mexico. Mineralization gradients of the pattern subsequently identified extend inland from coastal zones of high-temperature mineralization, and join in a central longitudinal zone of relatively low-temperature mineralization, apparently leaving no zonal room for lowest temperature deposits. The striking regional zoning pattern can be correlated with regional deformation gradients of similar position and orientation. The gradients represent at least three major orogenic cycles in two structural belts. Paleozoic structural belts existed along each coast with deformation gradients diminishing inland toward a narrow, central peninsular craton. The Mesozoic-Tertiary Mexican (Cordilleran) belt covered the entire country with a gradient oriented toward the Gulf of Mexico. Most ore deposits in this belt are of Tertiary age, although Tertiary mineralization gradients seem to have "inherited" the pattern left by Paleozoic tectonic gradients. Mineralization gradients can be used to identify the regions most favorable for the occurrence of selected metals. A metallogenic province is characterized by particular proportions of various metals, and the relative proportions can vary from province to province; but within any province the same intensity of mineralization would produce similar deposits in different places. Declining intensity of minetalization produces different kinds and sizes of deposits in zones that are concentrically arranged around sites of strongest rock alteration. On a regional basis, districts of similar average intensity of mineralization occur in zones that generally parallel some tectonic grain with the result that tectonic deformation has been designated a principal cause of mineralization. Variations in the type and intensity of deformation would determine the type as well as size of metal deposits. Mexico is especially favorable for such a study be- cause of its great abundance and variety of epi-genetic mineral deposits in various lithologic, structural and tectonic environments. The concept is also useful in recognizing portions of Mexico favorable for the occurrence of specific metals. METALLOTECTONIC ZONING IN MEXICO Theory: In studies of individual districts and groups of districts throughout North and South America, areal zoning of metal deposits generally seemed to respond to the paragenetic sequence of iron, gold, copper, zinc, lead, silver, antimony and arsenic, gold and fluorite. However, the definition of district zones is greatly obscured by contemporaneous or rhythmic deposition of metals, especially in the middle of the paragenetic range, and by the common superimposi-tions of different generations of metals. Zones could usually be distinguished only for groups of metals, such as early precious metals, base-metal sulfides, sulfosalts and late precious metals. The best defined zoning in a district is normally the spatial separation of the greatest volumes of altered and metallized rocks.' Exceptions are districts representing the high- and low-temperature extremes of the mineralization range where the former creates a matrix for the latter. In most districts the total quantity of alteration products is greatly in excess of, and appears to be roughly proportional to, the total quantity of metallization products. Subsequent to the bicomponent nature of each district, the most important mineralogical feature is the great excess of one to several metals or minerals which results in a district identifiable as one of predominantly gold, copper, lead-zinc, fluorite, etc., although a great variety of other elements may be present. The para-genetic range for the abundant elements in any district is only a portion of the entire possible range for all the elements representing the complete process throughout the region. Early during investigations of this type, it became apparent that the consistent bicomponent character of districts allows two methods for studying epi-genetic mineralization patterns. One is to identify and plot altered rock "pipes,"* which are easily recognizable in the landscape by their anomalous

Jan 1, 1969

Arkansas Geological Survey, Rooms 443-447 State Capitol, Little Rock, Ark George C Branner, State Geologist A list of available publications will be sent upon request Publications issued by the U. S Bureau of Mines, U S Geological Survey and Oklahoma Geological Survey, pertaining to' Arkansas, are also available through this Survey office. Annual Reports may be had for the following years. 1890, 3147, 1891, 81 35; 1892, $1 10 Other available publications: The slates of Arkansas, by A H. Purdue, with a bibliography of the geology of Arkansas by John C Branner (1909), $1.10, Coal mining in Arkansas, pt 1, by A A Steel (1910), 3175, An outline of the physical features of Arkansas, by George C Branner (1927), free, An outline of the metallic minerals of Arkansas, by George C Branner, free, Bulletin 3, The geology of the Arkansas Paleozoic Area, by Carey Croneis (1930), $3 20, Bulletin 4, St Peter and older Ordovician sandstones of northern Arkansas, by A W Giles (1930), $1 95, Bulletin 5, A geomagnetic survey of the bauxite region of Arkansas, by Noel H Stearn (1930), 80 cents, Information Circular 1, A barite deposit in Hot Spring County, by B Parks and George C Branner (1932), $1, Information Circular 2,

Jan 1, 1933

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at Institute headquarters during the period Jan. 10, 1916 to Feb. 10, 1916: William Rettie, Yonkers, N. Y. Wallace E. Pratt, Manila, P. I. R. V. Norris, Wilkesbarre, Pa. T. Skewes Saunders, El Oro, Mex. Fred MacCoy, El Oro, Mex. M. L. Requa, San Francisco, Cal. Reno H. Sales, Butte, Mont. R. W. Schultz, Ravenna, O. R. T. White, Batourn, Russia. H. J. Brown, Chester, Pa. David T. Day, Washington, D: C. A. M. Van Rensselaer, New Rochelle, N. Y. H. M. LaFollette, LaFollette, Tenn. Norman C. Stines, Russia. F. N. Speller, Pittsburgh, Pa. Howard R. Hughes, Houston, Tex. Robert W. Hunt, Chicago, Ill. C. F. Schnepp, Ridgefield Park, N. J. B. E. Fernow, Toronto, Ont., Can. George L. A. Thomson, Elizabeth, N. J. A. F. Bennett, New York City. Jasper T. Robertson, Chicago, Ill. J. C. Ralston, Spokane, Wash. J. B. Tyrrell, Toronto, Ont., Can. George J. Lyon, Schenectady, N. Y. H. G. Officer, New York Cty. Jesse C. Porter is now superintendent of the San Fernando Mine, Hoyo de Manicaragua, Santa Clara Province, Cuba.

Jan 3, 1916