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By Arthur West

IT is the purpose of this paper to describe briefly some recent large power stations for blast furnaces, where the blast is exclusively supplied by gas engines using furnace gas. The stations are given in the chronological order in which they were designed, in order to indicate the various improvements suggested by experience. Fig. 1 shows the blowing-engine station of the Bethlehem Steel Co. at Bethlehem. Although the picture shows only five blowing engines, the house now contains 11 engines. In the diagrammatic. plan the arrow shows the position and direction of camera. This station handles five modern blast furnaces of 450 to 500 tons capacity each. In this, as in all the other stations described in this paper, each furnace is blown by-two single tandem gas engines. Ten engines are thus required for five furnaces, leaving one single tandem spare engine. This spare capacity has been shown by several years' experience at Bethlehem to be adequate to insure continuous operation. The engines in the Bethlehem station are right hand and left hand, arranged in pairs. The outboard bearings of each pair are close together so that there is not room for passageway between them. On the right of the picture are shown the inclined drums communicating with the cold-blast lines outside of building, so that any engine may be operated on any furnace. The illustration shows four cold-blast gate valves with pipes passing through wall, but since the photograph was taken the drums have been extended to take care of a fifth valve for a fifth furnace. At the extreme back of the picture can be seen the tubs of three twin vertical-horizontal Southwark steam blowing engines, which, although of modern design and as good as new, are not operated because of the greatly reduced blowing cost shown by the gas blowing engines.

Jan 6, 1915

By Henry Lloyd Smyth

In 1891-92 1 was entrusted with the geological survey of part of the large area lying between the Marquette and Menominee iron-ranges in the Upper Peninsula of Michigan, and extending from the Republic trough on the north, through portions of the valleys of the Michigamme and Fence rivers, to and including the intermediate Felch mountain range on the south. Until a few years back the larger part of this area has been very difficult of access, and much of it is difficult still. The rock-surface is for the most part covered with swamp, forest and glacial deposits of various kinds, and therefore has not invited geological study. For these reasons the district, as a whole, with the exception of the Felch mountain range, remained almost unknown from a geological standpoint until our work in 1892. Our main object was to map the pre-Cambrian rocks, particularly the iron-bearing formations of Algonkian or Huronian age, and to obtain as much information as possible with reference to their sequence and structure, In carrying out this purpose, the use of simple magnetic instruments was found to be of the greatest assistance, and indeed indispensable. In this paper the results of our experience in tracing magnetic rocks by means of the disturbances produced in these instruments, have been brought together in systematic form, with such references to the particular area as are necessary in order to illustrate general principles, with the hope that they will prove useful to other workers in the same region, or in other regions where similar conditions may be encountered. The writer was efficiently aided in the field-work by Messrs. Samuel Sanford and Charlea N. Fairchild for nearly the whole period, and E. B. Mathews and H. F. Phillips for part of it,

Jan 1, 1897

By Edward Steidle

It has been said that "the command of nature has been put into the hands of man before he knows how to command himself," and what we see about us gives particular emphasis to this observation. If this condition be granted, the vaunted boast of school and college, of the institution that had the training of this generation, and of its fathers, and of its grandfathers, the boast that education is a "preparation for life," stands exposed as a hollow claim, or as a ghastly, cynical conception of life, or else education has fallen far short of its intentions. It has been evident for some time that education was not meeting the fullest expectations of society. In recent years there has been a deal of speculation indulged in by both laity and faculty in regard to American education and American civilization, and some few and sporadic changes have been effected. Today, however, there is no longer time for mere hypothetical considerations; we are faced with certain definite facts and confronted with obvious conditions that will not wait for fine-spun theories. If educators do not put their house in order, someone else will do it for them. The trends in mineral industries education must be in harmony with this general realignment that is today visible on the educational horizon, and only as these trends are in conformity with this movement can they be called sound. Two questions, then, confront mineral industries educators: (1) What are the trends in mineral industries education, and (2) how do these trends correlate with the major educational movements of the day? Scope or Mineral Industries Education Before launching into these particulars, it might be well to define the scope of mineral industries education and to consider its present position. Mineral industries education embraces three main types of work: 1. Earth Sciences and Geography.—Geology, mineralogy, geography— courses basic to all mineral industries and to the humanities. 2. Mineral Engineering.—Mining, petroleum and natural gas—dealing with mineral producing industries. Application of earth sciences and all types of engineering to exploitation of natural mineral resources.

Jan 1, 1934

By Murray Pezim

In the good old days of the folklore of the mining industry, grizzled prospectors obtained a few loose dollars from friends and neighbours then wandered off to eventually return with the great discovery which became the core of the new corporate empires. Alternatively, merchant banking barons obtained exclusive rights to just about anything of future value over hugh nation-size territories. Some of this probably still goes on, likely with about the same ineffectiveness and waste of effort and money as in the past. CURRENT CONCERNS IN MINING In today's difficult climate in the mining industry, for that matter in all industry, effectiveness is the vital consideration. Cost effectiveness -- more bang for the buck -- is especially important in such an area of high risk as mineral exploration. And there are other factors to consider. Since minerals are depleting resources, the mining inddustry is constantly confronted with the reality that those resources extracted today must be immediately replaced if a resource enterprise is to continue. And if growth is to be achieved, even more resources must be found to support future expansion. The current and immediately foreseeable climate internationally for the mining industry creates a special need and urgency for aggressive and successful exploration, certainly in Canada, if not also in the United States. Depressed world markets and prices have turned yesterday's economic reserves into today's waste, hopefully to be converted into economic ore again in some distant time. One way of replenishing reserves and maintaining a viable mining industry is to find and develop mines which are economic under short-term depressed price and market conditions. This probably means higher grades. A new copper discovery with the right combination of characteristics to be an attractive investment even at today's pices for copper would still merit development into production. Exploration is the only way to find such mines for the difficult short-term conditions. Another important consideration is that normally many years stretch from the first thought of conducting exploration to production -- in those rare instances where an economic discovery is made. If discoveries are not made today, then there will not be any projects to develop when business conditions are more attrative. This industry and the vast number of skilled professionals who are part of mining, are faced with two key problems that underlie the need for a junior exploration segment. One consideration is how to maintain exploration during those years, indeed eras, of recession and depression. We are in such a time now. Throughout the world, major companies have sharply cut back, if not eliminated completely, exploration expenditures other than what is vitally necessary and easily and inexpensively done at the known and producing deposits. And related to that consideration, even more important today than during happier times, is how to finance such necessary ongoing exploration if major companies and governments back away because of financial stringency. CANADIAN SUCCESS In Canada, such problems are being tackled with a success which is capturing worldwide attention. The ability of mineral explorers to obtain willing, eager, high-risk capital is achieving even more outstanding results than in the past. These results are reflected in the widespread continuing exploration ativity in Canada which even spreads into the United States, with some outstanding discovery successes. The most notable exploration success from junior mining activity is the discovery of the Hemlo gold camp in northwestern Ontario, a source of gold which promises to rank with the South

Jan 1, 1985

By Albert Williams

A large proportion of the work performed in wet-crushing silver mills is devoted to the handling and re-handling of pulp between the battery and the pans. There seems to be no generally applicable substitute for the settling-tanks, and in the present system of constructing mills the tanks involve an amount of labor which may be regarded as disproportionate and unnecessary, in view of the automatic improvements which have been introduced in other directions. This diffculty has been met, however, by Boss's continuous process, in which the pulp flows directly from the mortars to the first of a series of constantly working overflow-pans. This method has been adopted at the Noonday mill, Bodie, California; the Harshaw, Arizona; the Sierra Grande, New Mexico ; and the Prietas, Sonora. The continuous process, while giving excellent results with special ores, and under peculiar local conditions (such as a deficiency in water supply), is not, I believe, claimed to be available for all raw-amalgamating mills, notwithstanding its well-merited popularity for certain work. Some trouble has been experienced from the tendency to concentration in the pans, though this can be avoided by skilful manipulation. It has also the disadvantage inherent in combinations of distinct operations ; it requires a very nice adjustment of the water supply to obtain full battery efficiency without running the pans too thin, though the latter defect is partially compensated for by the gradual thickening of the pulp as it proceeds through the series of pans. The objection is similar to that which holds in a parallel duplex process, that of combining roasting and smelting in a single furnace, where each operation is injuriously affected by the necessity of fitting it in with another and entirely different one.

Jan 1, 1883

By W. M. Weigel

THE rapid advance, during recent years, in the manufacture of articles that have been in common use for generations and the development of new materials entering into appliances and devices unheard of fifty years ago, have created a demand for some of the more common non-metallic minerals. To supply this demand there has quietly developed a branch of the mining industry of which little is known by most mining engineers the mineral-filler industry. In this paper, and generally in the trade, the term mineral filler is applied to a mineral used, in its natural state after mechanical preparation only (such as. grinding, milling and washing), without undergoing any chemical change and without exerting any chemical action on the substance with which it is incorporated. The consumption of mineral fillers is confined chiefly to large manufacturing centers in the eastern and northern states. Where available, materials originating near the place of consumption are used, as most fillers bring a comparatively low price and, frequently, the freight may equal the cost of the finished filler at the mine. The southern states have abundant deposits of non-metallic minerals suitable for fillers, which supply the manufacturing industries in adjacent states. Many of these deposits are equal to, or superior, in quality to those mined in the north, but they can not compete with them because of the freight rates. The mineral-filler industry has felt the present depression, but it has suffered less than most mining industries for as a rule the mills are simple, the overhead expenses are low, and the labor is entirely local and can revert to farm work when the plant closes down. Many other deposits in the southern district will undoubtedly be developed when business. revives and freight rates are adjusted.

Jan 2, 1922

Problems discussed and research opportunities identified during the workshop in the major areas of 1) flocculation, 2) flotation, 3) leaching and magnetic separation are summarized below. I. FLOCCULATION Problems Practical problems caused by unintentional flocculation or dispersion were described in the papers that dealt with iron ore processing, selective flocculation, fine coal processing, phosphate processing and potash processing. Ideas generated during the discussions ranged from the very practical suggestion that a conscious effort be made to transfer knowhow from the experienced clay industry to the metals and fuels-from-slimes industry. . . , to the familiar appeals for omnipotent theoretical developments. There was surprising recurrence of some questions in many contexts. Recurring questions are emphasized here rather than commodity-specific problems because their answers would serve a wider clientele usage. There is indeed no objection and some advantage to commodity-specific research, however, provided the proposed project is planned with full cognizance of transferable knowledge in other commodities, and of the possible usefulness of these results in other areas. Research Needs Most of the questions or research opportunities can be classified into three groups: a) water chemistry, b) dewatering, and c) flocculation theory. Other classifications are possible and probably useful. In each group there is a clear need for outwardly esoteric theoretical research a clear application of that work to current practical problems. Higher priority should be given to proposals for theoretical research which explicitly show the expected ultimate usefulness of the result. Likewise, proposals for applied research should demonstrate cognizance of applicable theory. Both of these types of projects could profit from collaboration among industrial, university and government personnel.

Jan 1, 1979

By C. P. Proctor, J. T. Crawford

TROUGH washers were among the earliest methods used for concentrating ores; they are referred to by Agricola about the middle of the sixteenth century as already being used while the hand- operated jigging sieve had only recently come into use. For cleaning coal the trough washer apparently was first used in France and Belgium .about 1841. The early trough washers were intermittent and the refuse at least was shoveled out by hand. The invention of a continuous jig washer, by a Frenchman, Berard, in 1848, acted as a stimulus to coal washings in jigs and retarded progress in trough washing' in the nineteenth century. Chapman and Mott describe a number of trough washers developed in England and on the Continent from 1850 to 1900, such as the Bell and Ramsay, Ramsay, Bell and Green, Wunderlich, Scaife, McLellan; Lodge, Elliott, Blackett, and Murton. , The later of these removed the refuse mechanically, either intermittently or continuously, but in ways that interfered with stratification. THE RHEOLAVEUR A Belgian engineer, Antoine France, is responsible for the development of means to remove refuse materials continuously from a trough washer while preserving stratification and preventing the loss of coal with the refuse. The methods and equipment devised, which have become known throughout the world as Rheolaveur, were initiated at the St. Nicholas mine near Liége, Belgium, about 1912. This installation consisted of two units to wash 20 to 8-mm. (13/15 to 5/16 in.) and 8-mm. to 0 (5/16-in. to 0), each having only two superimposed inclined troughs. The first few "Rheo" boxes on the top trough removed refuse directly and the remaining Rheo boxes discharged impure refuse to the lower trough for rewashing. On the lower trough the first few boxes removed refuse and the following boxes removed a middling product

Jan 1, 1943

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

ENGINEERS AVAILABLE (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introduced by members.) Graduate mining engineer, with 10 years' experience, having an office in New York, would like to represent a mining company as selling and purchasing agent, and general supervision if desired. Machinery agency considered. No. 259. Member, technical graduate, with several years' experience as engineer for a pyrites company, and as geologist and engineer for copper, nickel, and silver companies, desires a position as engineer or superintendent of mines. No. 260. Member, technical graduate, aged 29, with experience as draftsman, surveyor, and superintendent of iron and gold mines, and as construction engineer, is open for a position as mine superintendent, or in mine examination or construction. No. 261.

Jan 11, 1915

By F. M. Doyle-Garner, A. J. Monhemius

Hydrolytic stripping is the process whereby metal ions in a loaded solvent extractant are hydrolyzed by water, typically at 130°C to 200°C (265°F to 392°F). Equilibrium hydrolytic stripping tests were done on Versatic 10 solutions containing various metals, singly and in mixtures. Single solutions of Fe, Ni, Cu, Mg, and Mn precipitated [a]Fe2O3 Ni(OH)2 Cu2O + CuO, Mg(OH)2 and [?]Mn203 respectively, during hydrolytic stripping. Several mixtures containing iron precipitated magnetic spinel ferrites, MFe204. No other combinations formed mixed oxides. It is proposed that the mechanisms for hydrolysis and precipitation of iron in loaded Versatic solutions are similar to those for iron hydrolysis in aqueous solutions. Magnetic interactions between mixed carboxylate complexes are thought to be responsible for the homogenous nucleation of magnetic mixed oxides in preference to single oxides.

Jan 1, 1986

By Donald W. Gentry

The recently established SME-AIME Education Board has completed its first full year of operation, and its six constituent committees-Accreditation, Career Guidance, Continuing Education, Educational Statistics, and Scholarship-have been extremely active in identifying and initiating programs to serve the educational needs of the Society of Mining Engineers and its members. The Continuing Education Committee-primarily concerned with the needs and problems associated with providing a continuing education program for SME members-is responsible for: (1) determining the need for short course offerings; (2) developing needed courses, along with new means and opportunities of presentation; and (3) scheduling and evaluating course presentation. In response to this charge, the committee has sponsored two short courses at the SME-AIME Fall Meeting in St. Louis and three short courses at the AIME Annual Meeting in Denver. Its major effort, however, has been directed toward the 1978 SME-AIME Fall Meeting to be held in Orlando, Fla., where 18 days of short-course instruction have been scheduled. A portion of these courses will be presented prior to the meeting, with the remainder to be presented in Nassau, Bahamas, immediately following the meeting.

Jan 7, 1978

By Glenn Keep

THIS paper is not an announcement of the successful conclusion of the Cerro de Pasco Copper Corporation's pacos-pyrite problems, but merely a description of the commercial-scale, intermittent-roasting operations conducted by the writer, J. H. Lucas and others of the staff. It was prepared by request, for presentation at the February meeting of the Institute. The results obtained in Peru confirm the 1-ton-a-day experiments completed about three years ago at Kearny, N. J. by C. C. Gordon and Mr. Lucas, where it was first demonstrated that a mixture of about 80 per cent. pacos ore with 10 per cent. pyrite ore and 10 per cent. salt could be roasted intermittently in a small 1-ton-a-day Holt-Dern furnace without extraneous fuel, producing porous calcine that could be leached rapidly. Mr. Keep and his staff, by successfully introducing improvements in the construction of the commercial furnace and in their handling of material, have established beyond doubt a low cost for roasting. The other steps in the process of treating pacos and pyrite ores have not as yet been demonstrated as sufficiently conclusive to warrant their acceptance for a permanent plant.

Jan 1, 1929

By Duane H. Haley

The century we live in has been an eventful time for the Third World, particularly the country of Peru. Although it will take one or two generations more to see its end and fully evaluate its scope, it is already clear that during the twentieth century, Peru has entered a dynamic industrial, economic, social, and political revolution. This century has seen the end of old governments, and the introduction of reforms which radically change complex traditional patterns. It also has marked the beginning of an era in which the government has elected to undertake, as a national effort, most of the future economic growth of Peru. For the most part, large multinational mining companies, which have helped to discover and put into operation large mineral and ore deposits in Peru, have been sympathetic toward this philosophy. Most big foreign companies, in addition to capital, brought with them to Peru an efficient technology, modern management, and an effective organization for the further processing, sales, and distribution of refined commodities. Nationalization of all basic resources, including mining, is the, trend-not, it is hoped, to the detriment of established technology and production.

Jan 1, 1974

By J. Parke Channing

THE caving system of mining is that method of removing the ore from an underground body in which the top is first attacked and mined out and the capping, or roof, as the case may be, is allowed to fall in or "cave" and fill the space formerly occupied by the mined ore. It is applicable, generally, to large orebodies where the ore is relatively soft. We may say, within moderate limits, that when ore is removed the surrounding ground either caves in or remains open. For example, in mines like the Lake Superior amygda-loid copper mines, when the lode is removed there is left a void which remains open for many years; on the con-trary, mining a Lake Superior soft hematite ore, however carefully it may be done, always produces a caving of the surrounding rocks. We may say, with propriety, therefore, that the caving system is applicable to that type of ore deposit in which the surrounding rock readily caves. Another factor which governs the use of the caving system is the value of the ore itself. Admittedly, any form of caving will not extract 100 per cent. of the ore, and in the case of a very rich orebody it is often desirable to get out every pound of the ore with as little dilution as possible. Under these conditions, some other method of mining, such as that by square sets and filling, is indicated and should be followed. We may say, however, that, looking at it broadly, in the United States the caving system of mining is generally used for the removal of soft hematite and for the so-called "porphyry" coppers. In both cases this method is used where open-pit mining is not possible.

Jan 1, 1922

By H. E. Stauss

THE short-time tensile-strength test, while it has not attained the practical importance of the creep test at elevated temperatures, has the advantage of being rapid and is satisfactory for determining relative strengths. For platinum and its alloys, which frequently are used at high temperatures under ill-defined conditions, the short-time test provides useful data that aid in the selection of the most promising alloy for each use. Measurements have been made upon 13 alloys, using wire 0.0031 in. in diameter, the choice of alloys and of wire size being determined by the requirements of a practical problem. Later the measurements were extended to higher temperatures by the use of heavier wire, 0.010 in, in diameter. APPARATUS The use of fine wire made the necessary equipment very simple, since no effort was made to measure the elongation. A small platinum-wound horizontal furnace was used, ½ in. in internal diameter by 1 ft. long, with the wire threaded through it. The wire, clamped at one end while the other ran over a ball-bearing pulley, of a total length of 29 in., was loaded directly by running sea sand into an attached basket, making the rate of loading and not of elongation constant. The sand flowed from a funnel, under a head of 3 in., into the basket. 3 in. below the orifice, at the rate of 170 grants per minute. Pulley friction and bending resist-ance of the wire as well as the force of impact of the sand could be neg-lected, being 3 grams and 0.5 grams, respectively. Furnace temperature .was uniform within ±5° C. over a length of 3 in., although a drift with time occurred, the largest amount being 20° C. No provision was necessary for a controlled atmosphere.

Jan 1, 1939

By George Boulter

Draglines 8.2-1 Introduction. The nature and characteristics of rock and rock derivatives forming the crust of the earth vary so greatly from place to place that it is impossible to use the same numerical factors to show the, productive ability of excavating equipment on different jobs or projects. Factors for each project must be developed individually and applied as the conditions and requirements dictate. TYPES' OF DRAGLINES. Types of draglines are differentiated by the propelling method used and are generally divided into four classes, as follows: 1. Wagon mounted 3. Crawler mounted 2. Truck mounted 4. Walking Figure 8.2-1 shows a truck-mounted dragline. This type is considered to be the most mobile unit. In order to increase stability over the side, outriggers are installed as part of the truck chassis. This feature is not shown in .this figure. Figure 8.2-2 shows a crawler-mounted dragline. The long, wide crawlers are used to increase the stability and reduce the bearing pressure of this unit. These features allow for use of these units on surfaces too soft for the wagon- or truck-mounted types. Figure 8.2-3 shows a walking-type dragline. The large diameter tub and the well-supported boom through the gantry gives high stability for rugged works over a long life. BASIC PARTS OF A DRAGLINE. The basic parts of a dragline are illustrated in Fig. 8.2-4. A deck layout is shown in Fig. 8.2-5 with the main components named. OPERATION OF A DRAGLINE. Following is a description of the steps and controls present in a typical cycle of operation of a large dragline having independent hoist and drag motors. Starting the cycle with positioning the bucket on the ground under the point of the boom, the next step is

Jan 1, 1968

By Ernest Burchard

A RECONAISSANCE of the chrome and manganese'1ore deposits of Culm was made in the spring of 191s by Albert Burch representative of the U. S. Bureau of Mines and the writer representing the U. S. Geological Survey. The object of the study was to obtain authentic information for use of the: United States Government as to the location, character, size, and availability of the Cuban deposits of the ores of these important steel-alloy metals. The Cuban Government courteously detailed Sr. E. I. Montoulieu, a mining engineer connected with the Treasury Department, to act as escort and associate throughout the work on the Island. Mr. George A. Wright, of Baracoa, Cuba, a mining engineer especially familiar with the chromite deposits of Oriente Province, was a member of the party from Feb. 25 to Mar. 20. It was possible to visit most of, the chrome-ore deposits that seemed to be of promise, but there was not sufficient time to visit all that were brought to our attention, some of which may have merit. Furthermore, no attempt was made to examine the extensive chromiferous iron-ore deposits of the Mayari, Moa, and Cubitas districts, as these deposits cannot be regarded as sources of chromium except indirectly. At the close of the field work the essential data concerning the quantity and quality of ore probably available for shipment during 1918 and 1919, in the event of the continuation of the European war, and of the tonnage of ore in reserve, were furnished to such Government bureaus as were interested, including the Shipping Board and the War Industries Board, and as soon as chemical analyses of the chrome ores could .be obtained, a press bulletin on the subject was published by the Geological Survey. In the present paper the engineering data, and tonnage estimates contained in the unpublished notes of Mr. Burch have been freely used, and their helpfulness is hereby gratefully acknowledged. Many thanks are due Senor Montoulieu and Mr. Wright for their valuable work in the field; to the officials of the Spanish American Iron Co. and of the various other companies; and to individuals holding chromite claims, for courteously facilitating the work of the party. In the study of material for the present paper, chemical analyses have been made by R. C. Wells and petrographic determinations and descriptions were furnished by Miss E. F. Bliss, both of the U. S. Geological Survey.

Jan 9, 1919

By Ursula E. Wolff

Il.lechanica1 twins have been observed in brigsten single crystals of a variety of axial orientations defornzed at room temperature in tension or bending. The twins formed near the final fracture and were up to 3 p thick. The twinning plane was always of the type (113). Twinning at room ternperature occurred only after considerable prior slip. Twins usually preceded fracture and nucleated cracks. The crack surfaces often alternated between a (001) plane and the twin interfaces. Secondary twins could also nucleate from cracks. In the absence of twinning tensile samples failed by shear; twinned samples failed by cleavage. On the assumption that observed sudden load drops in the stress-strain curves are associated with twinning, a critical resolved stress for twinning of 60, 000 to 65, 000 psi was calculated. MeCHANICAL twinning has been observed in iron and iron alloys at low temperature by a number of investigators.'-7 Similarly, for high-purity tungsten, twinning has been reported for deformation temperatures below 211°K.8-10 In W-Re and Mo-Re alloys, 20 pct Re was determined as the lower limit for twin formation at room temperature." Since the twins are generally very narrow, they are usually identified only by etching techniques. The expected (112) habit plane has always been confirmed by angular analysis of the surface traces. Recently, however, a complete identification by X-ray analysis has been performed on twins in a Mo-35 pct Re alloy.12 During an investigation of the deformation charac- teristics of tungsten single crystals, twins were revealed in tensile and bend samples deformed at room temperature. This paper deals with the conditions for such twinning and the relation of twinning to fracture. EXPERIMENTAL PROCEDURE Tungsten single crystals, 1/8 in. in diam, of a variety of axial orientations were grown from un-doped material by four-pass electron-beam zone melting. A representative analysis is given in the following table: From these crqstals, tensile samples with 1 in. gage lengths were made by surface grinding, leaving shoulders for gripping. The diameter after grinding was 0.082 in. The distorted surface layer was then removed by ele1:trolytic polishing which reduced the diameter of the gage length to 0.080 in. Tensile tests were carried out at room temperature in an Instron machine under two different sets of conditions: a) Rigid mounting; strain rate 0.02 in. per in. per min. b) Gimbal mounting; strain rate 0.002 in. per in. per min up to a total strain of approximately 0.2 pct, then 0.01 in. per in. per min to fracture. Stress axis and growth direction coincided in all samples and are subsequently called orientation.

Jan 1, 1962

By Douglas R. Cook

The urgent need for new base metal ore discoveries was discussed by various authoritative exploration personnel at a CIM symposium on the future of the Canadian mineral industry held at Ottawa in 1967. Data presented at this meeting showed that approximately 150 new mines have started or restarted production in Canada since 1955. Over half of these mines were discovered prior to 1950. The distribution of Canadian ore discoveries during the last 15 years (shown in Fig. 1) illustrates a striking reduction in the discovery rate in recent years in spite of increasing exploration expenditures. These data indicate that $20 million is now spent in exploration for every significant metal deposit found, and evidently the cost of discovery is still rising. Even fewer discoveries are being made in some other important continental areas of the world such as Africa, Australia and South America. The discovery record in the U.S. is thought to be more rewarding than in Canada because the new deposits appear to be substantially larger. Fortunately, most good base metal ore deposits have attractive investment re- turns to justify large exploration expenditures. The magnitude of the exploration expenditures and the increasing need to develop additional metal resources justifies a critical review of the procedures used in the search for ore deposits. Of particular concern is the need to improve the use of exploration techniques in the attempt to obtain better discrimination and efficiency. There is a tendency by inexperienced exploration groups to think of any geological, geochemical or geophysical anomaly as an exploration target and ignore the fact that anomalies can result from many factors other than economic concentration of metals. The desire for a unique and favorable explanation of exploration data often results in too rapid a movement from the reconnaissance to the drilling stage without the use of all the relevant information.

Jan 7, 1968