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By W. C. Spence, Burt C. Mariacher

Methods employed to beneficiate ores utilize relatively few fundamental principles to effect size reduction and concentration. In crushing and grinding only impact and compressive forces with a minor amount of shear are employed. In concentration, gravity, magnetic, electrostatic and flotation constitute the major methods of concentration with minor use of sizing, hand picking and adhesion. This industry, as all others, can expect in the near future to see the development of new techniques for improved efficiency, cost reduction, and exploitation of raw materials hitherto considered unmanageable. NATURAL AND INDUCED RADIOACTIVITY At the Canadian Department of Mines in Ottawa in 1946, C. M. Lapointe developed a picker belt system whereby radioactive ores could be concentrated by electromechanical means. This invention ultimately led to development of what is now refer- red to as the Lapointe Picker and which has been used commercially at Port Radium and Port Hope for the upgrading of jig concentrates. Basically, the system consisted of conveying sized uranium ore on a belt under a radioactivity detection device which in turn electronically operated a kicker or plunger that separated the ore from the gangue constituents. Thus, a new principle for mineral concentration, radioactivity, was introduced commercially.

Jan 7, 1962

By AIME AIME

CHARLES A. CHASE, manager of the Shenandoah-Dives Syndicate, operating the Shenandoah Mines in southwestern Colorado, reviewed the current work at that property at a recent meeting of the Colorado Section, in Denver. This operation is a new one, having been in effect only two years, but the properties that were consolidated by Mr. Chase had had certain production in earlier years, since when they had: been inactive. These properties are located. in the high mountains of the San Juan section in Colorado, and although they had had a substantial production of ores of good grade in the upper levels, the project as a whole involved the bold undertaking of driving through the mountain, starting on the Mayflower claim on the Arrastre Gulch side and passing through the Mayflower, Slide, Terrible, North Star, Dives and Shenandoah No. 3 claims. This is a distance of over 8,000 ft. which is known to be mineralized, and the main operating tunnel was started at an elevation of approximately 11,000 ft. The main exploration work has already extended in nearly 4,200 ft. and the present mining production of nearly 550 tons daily is being secured while the main exploration work is being continued. The main heading is now within the North Star claim and the plan of operations involves continuing ahead for a few hundred feet and then starting an upraise which will he 2,200 ft. high and which will connect with the old workings of the North Star mine. The plan of ruining then will he to drive levels along the vein in both, directions to daylight and retreat downward, taking out all the ore and abandoning, the workings after the ore is removed. In this way one level after another progressing downward will be abandoned. The raise will be of two compartments, one of which will carry the 8-ton skip and the other the counterweight and manway. So far the ore has been broken over an average width of more than 11 ft., with an output of 39 tons per machine shift.

Jan 1, 1932

By N. S. Greensfelder

THE firing of explosive charges by electricity dates back to 1745 when a Doctor Watson is said to have used an electric spark for igniting gunpowder. His method failed in practical application because, to ignite blasting powder, heat must be applied for a period longer than the duration of an electrostatic spark; Wheatstone found that this does not exceed 14000 sec. The usual result, therefore, of an electrical discharge in gunpowder is to scatter the grains, without igniting them. Benjamin Franklin partly overcame this difficulty by confining the powder and crushing grains that lay in the line of discharge. In 1822, after the primary cell had been discovered by Volta, Robert Hare, professor of chemistry at the University of Philadelphia, noticed the heating of a short piece of wire placed in the circuit of a voltaic battery. Later work by Oersted, Faraday, Wheatstone, and Henley resulted in the development of the magneto blasting machines. Fulminates of gold and silver are thought to have been discovered by Cornelius Drebbel, about 1600. Pepys, in his diary for November 11, 1663, recounts a conversation with Doctor Allen, who told him about aurium fulminans "of which a grain ... . put in a silver spoon and fired, will give a blow like a musquett and strike a hole through the silver spoon downward, without the least force upward.1," This fallacious belief that explosives act downwards only, is still held by many who should know better. Fulminate of mercury was discovered by Howard in 1799. J. Shaw of Philadelphia is said to have invented a fulminate-of-mercury cap in 1814; his idea was later adopted by gunmakers in England and France. The principal advantages of

Jan 9, 1922

By Norman 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.1-8 The broadening of the K. 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 dif-fraction lines are broadened and the K a 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 resolu-tion of the doublet is lost when a metal is cold-worked and the Lane 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 attrib-uted the hardening to fragmentation of the grains into smaller units.

Jan 1, 1940

By K. S. Lane

As the initial chapter in this section entitled "Role of Fluid Pressure in Rock," this attempts to fulfill an assignment for (1) summarizing the state-of-the-art and (2) illustrating engineering problems resulting from rock pore pressure. Hence, the chapter is presented in two parts: 1) Basic Concepts, and 2) Examples of Engineering Problems, including failures. Neither of these objectives has necessarily been completely met: partly from limitation of space and partly as the case histories have been restricted to the author's own field in civil engineering, and there deemphasizing those applications which will be covered in more detail by subsequent papers in this section. As with any state-of-the-art attempt, contributions of some have undoubtedly been overlooked (or omitted for brevity). Notwithstanding the foregoing limitations, it is hoped that this summary of the situation will at least: 1) Outline current concepts on effects of fluid pressure in rock-both as a pore pressure in interconnected void spaces of the intact rock and as a cleft pressure or hydraulic force acting in the joints or other discontinuities of the rock mass. 2) Indicate the often fragmentary nature of evidence presently available to support these concepts and thus encourage further research. 3) Illustrate the major significance of fluid pressure in several types of engineering problems and thus stimulate its consideration as designers encounter related situations.

Jan 1, 1970

By Edward Wichers

THE purpose of this paper is to set forth the matters of principal interest in connection with work done in the past few years on the purification of the metals of the platinum group, including the study and modification of methods already in the literature and the development of new procedures. For the most part, the results will be given in summary form, reserving the publication of detailed data and directions for a forthcoming paper to be issued by the Bureau of Standards. In recent years increasing interest has been shown in the preparation of the pure platinum metals, both by those concerned with the manufacture of the metals and their alloys for scientific and industrial purposes and those who are engaged in the study of the chemical or physical properties of the elements. The purification of the metals usually has been regarded as a matter so involved and difficult as to require the attention of specialists. It is hoped that this paper will show that any of the metals can be prepared in any desired degree of purity by relatively simple straightforward chemical methods. For the most part, it is thought that the methods given are suitable for small-scale refineries as well as for the laboratory; also, that they will bring the time required for the purification of any of the metals within reasonable limits. The new procedure suggested for purifying platinum should prove to be much shorter than any methods described in the literature.

Jan 1, 1928

By McQuiston. F. W., E. C. Tveter

Sulfide mineral flotation has been applied to all naturally occurring sulfides and several synthetics. Of even more importance is the fact that economic separations are now being made between sulfides of essentially all the different metals. The variety of methods and minerals involved in such practice make it difficult to characterize them except in terms of general factors which influence the practices used. Ore grade and mineral composition are the major factors determining the processing method and the extent to which processing must be carried to achieve optimum economic return for a given ore. Since the choice of treatment is also affected by such factors as mine location, shipping charges, smelter schedules, each ore is a separate problem even though mineralization may be similar; The dissemination of minerals in the ore naturally determines the fineness of grind required for liberation. However, since grinding costs are a major part of most milling costs, emphasis has been placed on means of rejecting gangue minerals at the coarsest size possible. This has led to increased flotation of middling products or bulk concentrates for subsequent regrind and retreatment. Reagent development has also played an important part in present plant practice. Relatively few new frothers and collectors have found application during the past 25 years and many have disappeared. In general practice, re- agent combination choice is now fairly consistent with the type of collector being chosen on the basis of the mineral to be floated, the frother on the basis of pulp alkalinity, and the modifiers primarily on the basis of minerals to be rejected. REPRESENTATIVE FLOTATION PLANTS The milling operations described in this chapter have been selected primarily to illustrate these differences in ores and processing methods for the major types of ore minerals. The compositions of these minerals are shown in Table 1. These concentrators were chosen as representatives, both on the basis of geographic location and mineral content of the ore treated. At least one mill is included from each of the major producers, but the primary object was to show the practice employed for the various ore minerals and the different approaches to the middling problems encountered. The individual plants which have contributed data to this study are listed in Table 2, with a summary of their operating data, and are discussed in the order shown.

Jan 1, 1962

By Chester R. McKee, Robert W. Terhune, Merle E. Hanson

The relationships describing the enhancement of permeability by firing explosives in boreholes have been derived and combined to yield permeability enhancement as, [ ] or the case in which the stress decays asymptotically as a power law kc and nc represent permeability and fracture density at the edge of the pulverized region near the cavity wall, f is a geometric attenuation factor, m is the dissipation due to real material effects, ko is the original permeability and rd is the scaled radius. This relationship has been compared with available measurements from the American nuclear shot "Hardhat", the French nuclear events in Hoggar granite and the chemical explosive shot in coal near Kemmerer, Wyoming. Significant correlation between this theory and the experimental measurement is observed. A comparison between single and multiple detonations shows that permeability enhancement falls off steeply near the shot; however enhancement can be considerable midway between two shots spaced 10 cavity radii apart. The degree to which enhancement, can be significant depends on material properties and fracture density. Porosity distribution from the explosive 1s the dominate parameter in permeability enhancement. Existing theories of permeability enhancement have also been reviewed.

Jan 1, 1976

By Walter H. Ortel, George B. Wallace

INTRODUCTION A greater understanding is required about the factors which control tunneling operations if we are to meet the expected demand for tunnels. Much of the needed information can best be achieved by the proper use of instrumentation and advanced engineering concepts. Tunnel measurements and their analysis may prove to be the key which will give the insight necessary to understand the relationship of rock, tunnel supports, and linings. There are three main areas which can be improved through the use of tunnel instrumentation. First, and of prime importance, is safety for men and the project. When unstable conditions occur, sets become distorted. Even without measurements, it is sometimes possible to tell when trouble is approaching. In effect, the set acts as a load cell. Distortions in the set indicate reinforcements may be required to maintain stability. Additional sets or rock bolts, if they are placed soon enough, may provide this stability. However, when large rock displacements occur in short periods of time, it could be too late. Figure 1 is an example of the difficulties encountered in stopping moving rock. To stop the movement and possible failure, large props were placed above the spring line and the massive concrete gravity buttress was constructed along the legs. Rock bolts from the buttress deep into the rock were also used in an attempt to stabilize the rock mass. However, this work is for a highway tunnel and eventually these props and buttresses must be removed.

Jan 1, 1971

By Samuel M. Cassidy, John A. Garcia

In some districts of the bituminous coal field the problem of constructing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it is felt that a description of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. AS far as the writers know, these three mines are the only ones in the bituminous coal fields of the United States with anything like so large a number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it. General Mining System All three of the mines use the same general panel room-and-pillar system, which consists of rooms turned both ways off room entries and a solid block of coal left on all sides of the completed panel except on the cross-entry side, where a heavier pillar is pierced by two entries for haulage and air. On completion of the panel the two entries arc sealed and the panel is then isolated from the rest of the mine. Owing to water conditions, no pillars are pulled; recovery inside the panel barrier pillars is approximately 65 per cent.

Jan 1, 1938

By Samuel M. Cassidy, John A. Garcia

In some districts of the bituminous coal field the problem of constructing bulkheads to seal off water under pressure is becoming increasingly important. Recently this matter has been brought very much to the front by the loss of a large Illinois mine due to failure of a bulkhead that separated it from several old, flooded mines. As this great misfortune has provoked much inquiry about proper bulkhead design, it is felt that a description of the successful and extensive water-sealing practice at three mines that have different natural conditions will be of considerable interest to those connected with properties having a present or future water problem and to engineers that may have to design safe bulkheads of economical construction. These three mines are the Saxton and Dresser, near Terre Haute, Ind., and the Hegeler, near Danville, Ill. All three have water conditions that make it necessary to regularly seal off all worked-out sections of the mine, and there are considerably over a hundred bulkheads in each. AS far as the writers know, these three mines are the only ones in the bituminous coal fields of the United States with anything like so large a number of water seals and experience, although a number of other mines are known to have a few bulkheads. More detail will be included herein on the Saxton mine than on the others, as the writers are more familiar with it. General Mining System All three of the mines use the same general panel room-and-pillar system, which consists of rooms turned both ways off room entries and a solid block of coal left on all sides of the completed panel except on the cross-entry side, where a heavier pillar is pierced by two entries for haulage and air. On completion of the panel the two entries arc sealed and the panel is then isolated from the rest of the mine. Owing to water conditions, no pillars are pulled; recovery inside the panel barrier pillars is approximately 65 per cent.

Jan 1, 1938

By J. D. Wright

INTRODUCTION The Endako deposit was first explored in 1926, but development waited until the early nineteen sixties. It first came under the control of Placer Development in 1963, and early in 1964 a decision to bring it into production was reached. The deposit is located near the geographic center of British Columbia, and is served by an east-west communication system including a paved highway, mainline railway and good telephone, teletype, and computer facilities. The plant area is shown in Figure 1. The operation is known as the Endako Mines Division of Canex Placer Limited of Vancouver. First production was achieved in June, 1965, at a nominal rate of 10,000 tons per day, but it soon was closer to 15,000 tons per day. In 1967, two new grinding and flotation, sections brought capacity to the present rate of approximately 27,000 tons per day. With mill heads of around 0.15 percent MoS2, production is about 14,000,000 pounds of molybdenum per year. A flowsheet of the operation is given in Figure 2. A legend for this flowsheet is given in Table 1. Published ore reserves are estimated at 214,500,000 tons at an average grade of 0.143 percent MoS2. PRIMARY CRUSHING The 85 or 100-ton haulage trucks dump over a grizzly into a 42 inch x 65 inch C.A.C. (Canadian Allis Chalmers) gyratory crusher. The

Jan 1, 1976

By Volker Weiss, George Sachs, AE. P. Klier

PHYSICAL chemistry contributes to the understanding and efficient operation of hydrometal-lurgical processes in many ways, among them by providing quantitative answers to the following questions. 1) Can a given chemical reaction or process be made to operate and. if so, under what conditions? 2) what are the' factors which determine the rate of the reaction and how can this rate be regulated in practice? Thermodynamics attempts to answer the first of these questions and kinetics the second. The answer

Jan 1, 1958

By H. H. Kaveler

A summary of the reservoir engineering and related geologic data on the Schuler field, Union County, Arkansas, is presented here in a manner intended to interest both technical and nontechnical readers. The Cotton Valley formation and the Reynolds oolite are oil-productive formations in the Schuler field, but the Jones sand pool, at a depth of 7500 ft., developed with 146 wells on zo-acre spacing, is the reservoir of principal interest. The Jones sand sandstone reservoir is an anticlinal trap typically gas-drive or depletion type in performance. The core analyses from 88 per cent of the wells drilled, together with drilling time and electric-log data, yield an accurate estimate of the "productive" sand thickness and its areal distribution over the pool. Accurate production statistics, monthly reservoir-pressure surveys, and bottom-hole sample analyses when correlated by the "material-balance equation" show unusually good agreement with that principle. Estimates of oil initially in place made by the material-balance method and the sand-volume method are in good agreement at 116 to rzo million barrels. The reservoir-pressure history of the pool reflects the reaction of a reservoir to production, proration and secondary-recovery practices. The cost of the extensive program of reservoir study in the Jones sand pool has been estimated, in order to emphasize the value derived from such an investment through better understanding of a reservoir's reaction to production practices. Unit operation of 140 of the 146 Jones sand wells made possible an effective unitized gas-injection pressure-maintenance program. Res-ervoir-pressure decline was arrested, natural flow was maintained, and pumping and lease equipment were conserved. An increased ultimate recovery of zo million barrels beyond the estimated 34 million barrels primary recovery is indicated at present. Extension of the Jones sand unit to include the undeveloped Cotton Valley formation will permit additional recovery of otherwise uneconomic reserves of oil through wells no longer required in the Jones sand operations. Introduction The Schuler field comprises approximately 4000 acres in and about sec. 18, T. 18 S., R. 17 W. in west central Union County, Arkansas. Three reservoirs are procluctive of oil and gas: the Cotton Valley formation, the Jones sand, and the Reynolds oolite section of the Smackover limestone. The Jones sand pool is the most important reservoir from an engineering viewpoint. It possesses the traditional and somewhat classic characteristics usually associated with an anticlinal trap. Development and operations have followed the dictates of advanced engineering practices. The pool has attracted attention because of the unusually detailed reservoir data obtained, its interesting production history, and the success of the unitized gas-injection pres-sure-maintenance operation now being carried out. The purpose of this paper is to present a summary of the engineering data relating to the field, with particular reference to the more interesting general applications of

Jan 1, 1944

By H. H. Kaveler

A summary of the reservoir engineering and related geologic data on the Schuler field, Union County, Arkansas, is presented here in a manner intended to interest both technical and nontechnical readers. The Cotton Valley formation and the Reynolds oolite are oil-productive formations in the Schuler field, but the Jones sand pool, at a depth of 7500 ft., developed with 146 wells on zo-acre spacing, is the reservoir of principal interest. The Jones sand sandstone reservoir is an anticlinal trap typically gas-drive or depletion type in performance. The core analyses from 88 per cent of the wells drilled, together with drilling time and electric-log data, yield an accurate estimate of the "productive" sand thickness and its areal distribution over the pool. Accurate production statistics, monthly reservoir-pressure surveys, and bottom-hole sample analyses when correlated by the "material-balance equation" show unusually good agreement with that principle. Estimates of oil initially in place made by the material-balance method and the sand-volume method are in good agreement at 116 to rzo million barrels. The reservoir-pressure history of the pool reflects the reaction of a reservoir to production, proration and secondary-recovery practices. The cost of the extensive program of reservoir study in the Jones sand pool has been estimated, in order to emphasize the value derived from such an investment through better understanding of a reservoir's reaction to production practices. Unit operation of 140 of the 146 Jones sand wells made possible an effective unitized gas-injection pressure-maintenance program. Res-ervoir-pressure decline was arrested, natural flow was maintained, and pumping and lease equipment were conserved. An increased ultimate recovery of zo million barrels beyond the estimated 34 million barrels primary recovery is indicated at present. Extension of the Jones sand unit to include the undeveloped Cotton Valley formation will permit additional recovery of otherwise uneconomic reserves of oil through wells no longer required in the Jones sand operations. Introduction The Schuler field comprises approximately 4000 acres in and about sec. 18, T. 18 S., R. 17 W. in west central Union County, Arkansas. Three reservoirs are procluctive of oil and gas: the Cotton Valley formation, the Jones sand, and the Reynolds oolite section of the Smackover limestone. The Jones sand pool is the most important reservoir from an engineering viewpoint. It possesses the traditional and somewhat classic characteristics usually associated with an anticlinal trap. Development and operations have followed the dictates of advanced engineering practices. The pool has attracted attention because of the unusually detailed reservoir data obtained, its interesting production history, and the success of the unitized gas-injection pres-sure-maintenance operation now being carried out. The purpose of this paper is to present a summary of the engineering data relating to the field, with particular reference to the more interesting general applications of

Jan 1, 1944

By Chauncey L. Berrien

The United Verde Copper Company's mine is at Jerome, Ariz. The orebodies arc of the schist replacement type, the main sulfide mass being a large lens-shaped body approximately 7 acres in cross-sectional area. In general, the mineralization is found along the iron schist contact, with the orebodies extending about 1000 ft. along this contact and varying from a few feet to 250 ft. in width. Three types of ore are mined; schist porphyry and the so-called "heavy" or "massive sulfide" ore. Approximately 50 per cent. of the total tonnage mined at present is of the latter class. A representative analysis of this ore indicates 42 to 46 per cent. sulfur. Because of the high sulfur content, blasting in this ore is an extremely hazardous operation. not only does it endanger the lives of men who may be in the mine at blasting time but it also becomes a potential fire menace when timber is in close proximity to shots being fired in these massive sulfides. The origin of the fires of 38 years ago, embers of which are glowing to this day, may perhaps be attributed to dust explosions due to blasting in the massive sulfides of those early square-set stopes. Dust Explosions Dust explosions in coal mines are a common source of mine disasters. That such explosions may be of common occurrence in metal mines is not generally known, but it is known that metal-mine dust will explode and such explosions have been investigated by the U. S. Bureau of Mines at the Pittsburgh Experiment Station. Samples of "heavy sulfide" ore from the United Verde mine were used in the tests. After studying the results of the tests it was concluded1 that: 1. Dust explosions were initiated in sulfide ore dust in the gallery with a charge of as low as 75 g. of 60 per cent. gelatin dynamite. 2. The exploding dust generated considerable pressure.

Jan 1, 1930

By F. W. Smith

Within the Northern Pennine Orefield, England, intersections of fluorite veins are generally richest in ore, and their recognition enables investigation of the ore potential of the intersecting bodies. A method, based on routine analysis of fluorite for yttrium, has been used with success in mines of the district to predict the location of intersections in partially developed fluorite-bearing ore bodies. This short note is intended as a brief introduction; the details of United Kingdom applications are to be published at a later date. Geology The Northern Pennine Orefield is the second largest fluorspar-producing region in Britain. The associated minerals galena, sphalerite, chalcopyrite, barite, and witherite have all been extensively worked in the past but, with the exception of a single barytes mine, all of these operations are now abandoned. Galena alone is recovered as a byproduct of fluorspar beneficiation. At the present time two companies are producing about 38,000 tpy of fluorspar from high grade vein ore bodies, and a number of concerns are actively prospecting in old lead workings. The mineralization is localized in veins and replacement flats within favorable lithologies in an alternating limestone, sandstone, shale sequence. Since the thickness of individual beds is not great (generally less than 20 m), vein bodies tend to be ribbon-shaped, with length greatly exceeding width and height (Dunham). They thus present difficult exploration targets for conventional diamond drilling techniques. Ore grade varies greatly along the veins, which can change rapidly in character from mineral stained fault gouge to massive mineral bodies up to 10 m in width. It has been known for a very long time that the richer ore bodies tend to be associated with vein intersections in favorable beds. It is assumed that vein fissure intersections provided vertical channelways through which hot ore-bearing brines were able to ascend from deeper cavities in the sequence. Thus investigation of intersections at other horizons generally yields further ore bodies. Technique The relative concentration of yttrium in fluorite is a good indicator, in the North Pennines, of the direction of flow of mineralizing fluids. In all of the ore bodies so far studied in detail in this region, the concentration of yttrium increases markedly in the direction of vein intersections that are believed to have acted as feeder zones to the remainder of the bodies. The reason for this relationship is probably connected with the degradation of soluble rare earths-fluoride complexes by the changes in various physicochemical parameters of the hydrothermal fluids as they entered the ore body cavities from the feeder zones. The simultaneous release of free fluoride ions also contributed to the increased ore values in these intersection zones. Yttrium values in fluorite taken from a longitudinal traverse of the western ore body, Redburn mine, Rookhope, are plotted in [Fig. 1.] The position of a major vein branch and three cross veins are clearly indicated by yttrium maxima. The cross veins themselves contain up to 2.5 m of low grade fluorspar ore. The exact positions of B and C were unknown previous to the geochemical survey. Similar results have been obtained for several other veins and ore bodies in the area. Clean fluorspar was collected as bulk samples from within 300 mm of the vein wall and, since the vein infilling is simple, with mineral growth from the walls inward, analyses of the samples are considered comparable along the length of the ore body. A number of samples taken from the center of the vein show a

Jan 1, 1975

By Gerhard Derge, J. Warren Stewart

Extrusion processes are used in the commercial production of a wide variety of products, as indicated by the review presented a few years ago by D. K. Crampton.' Most writers have confined themselves to a general description of the equipment and products and the engineering aspects of the process. The few studies that have dealt with the metallurgical side of extrusion have been concerned primarily with an examination of the mode of flow of the metal during extrusion. This has been accomplished by the use of composite billets, by scribing grids on symmetrical sections of billets and observing the change of dimensions in the gridwork, or by examining microstructures in extruded sections.2"8 Ariotlier limitation of these original studies is that they were confined to the extrusion of very simple shapes, usually rods having a diameter of about one-fourth that of the billet. Tin is particularly well suited to the extrusion of collapsible tubes and similar shapes in which the extruded section is very small in comparison to the diameter of the billet or slug. In modern production, impact extrusion methods are generally employed, therefore the thickness of the slug is small compared to its diameter. Under these conditions the process differs considerably from the processes that have been most fully described in the literature, and it is known that the quality of the product is very sensitive to slight variations in any one of the many variable factors involved, such as coinposition and structure of the alloy, rate of extrusion, temperature, shape of punch and die. An exhaustive examination of all of the above-mentioned problems promises to produce so many data that it seems advisable to initiate the reports at this time, even though all of the factors outlined have not been examined fully, and to confine this paper to a description of the apparatus and method. Only tin and its alloys with small amounts of copper have been considered. These are the alloys most commonly used in this country for the production of the type of articles already described.

Jan 1, 1940

By Gerhard Derge, J. Warren Stewart

Extrusion processes are used in the commercial production of a wide variety of products, as indicated by the review presented a few years ago by D. K. Crampton.' Most writers have confined themselves to a general description of the equipment and products and the engineering aspects of the process. The few studies that have dealt with the metallurgical side of extrusion have been concerned primarily with an examination of the mode of flow of the metal during extrusion. This has been accomplished by the use of composite billets, by scribing grids on symmetrical sections of billets and observing the change of dimensions in the gridwork, or by examining microstructures in extruded sections.2"8 Ariotlier limitation of these original studies is that they were confined to the extrusion of very simple shapes, usually rods having a diameter of about one-fourth that of the billet. Tin is particularly well suited to the extrusion of collapsible tubes and similar shapes in which the extruded section is very small in comparison to the diameter of the billet or slug. In modern production, impact extrusion methods are generally employed, therefore the thickness of the slug is small compared to its diameter. Under these conditions the process differs considerably from the processes that have been most fully described in the literature, and it is known that the quality of the product is very sensitive to slight variations in any one of the many variable factors involved, such as coinposition and structure of the alloy, rate of extrusion, temperature, shape of punch and die. An exhaustive examination of all of the above-mentioned problems promises to produce so many data that it seems advisable to initiate the reports at this time, even though all of the factors outlined have not been examined fully, and to confine this paper to a description of the apparatus and method. Only tin and its alloys with small amounts of copper have been considered. These are the alloys most commonly used in this country for the production of the type of articles already described.

Jan 1, 1940

By C. W. EICHRODT

NUMEROUS requests for the suspension of publicity make difficult the preparation of the annual review of copper metallurgy for 1934. In the United States, sales allocations indirectly have set restrictions on the scope of activities of producers and refiners, and necessitated closer cooperation between secondary and primary producers. However, the feeling exists that preparations for a return of intense competition should not he neglected, and careful investigations are being conducted for ways and means of improving industrial positions and production methods. In all probability, efficiency in technique and equipment will prove of far greater importance in the near future than production capacity, and many important developments in copper metallurgy later will be found to have been born during the current year.

Jan 1, 1935