Search Documents

By V. F. STANLEY

THERE is not the slightest doubt that the present recoveries of valuable minerals by the Broken Hill mills could be improved, and that further machinery would be installed for the purpose if it could be assured that a high price of metals would be maintained; but concentration, like all other com¬mercial propositions, is a question of profit and loss, and no sensible metallurgist would carry out his work in such a manner as to obtain high recoveries at a financial loss to his company. There is a point in all concentration at which the added money obtained from the higher recovery of minerals is balanced by the extra cost of obtaining the last part of the recovery; a wise metallurgist will be content with his work before his working-expenditure reaches this point. To a casual observer, the work being done by the various Broken Hill mills is identically the same. A closer investigation will show that this is far from being the case, for it is a remarkable fact that, although the larger mines extend over a length of approximately only 2 miles, such a difference in the physical and chemical properties of the ores exists that, from the first reduction downwards, special treatment is necessary in each case, and hardly any two mills are identical in operation. The details of this paper refer directly- to the work of one . particular mill in Broken Hill, for the reason that the ore from each mine presents special difficulties and requires its own special treatment. I have selected the mill referred to because it has been constructed and modified under my supervision.

Sep 1, 1909

By McHenry Mosier

MeRcuRy is one of the strategic metals of which the supply has been raised from critical uncertainty to more than enough for essential demands. Work by the Bureau of Mines has contributed substantially to increased production of mercury in the United States and to consequent accumulation of Government stocks. Other contributing factors have been higher prices for mercury and Government loans to operators. The Bureau has undertaken 13 exploration projects, 10 of which have been completed. This work has comprised 28,376 ft. of several types of drilling and 23,798 lin. ft. of surface trenching, and has indicated commercial ore containing 34,800 flasks of mercury and marginal ore containing 26,200 flasks, a total of 61,000 flasks; equivalent, respectively, to domestic production for 8 months, 6 months, and 14 months. As Government stocks are now adequate, domestic production (currently at the rate of 50,000 flasks per year) is gradually being curtailed through Government control of labor and operating supplies. Introduction Mercury was one of the seven metals designated as strategic by the Army and Navy Munitions Board in 1939, when Congress appropriated funds for the investigation of domestic sources of supply of war minerals. The Bureau of Mines immediately started a limited search for strategic minerals, but the first mercury project was not begun until December 1940. The U. S. Geological Survey assisted in the search for cinnabar by contributing information on domestic mercury deposits, preparing maps, and making geological studies of exploration projects. The present high rate of production of mercury in the United States was encouraged by the increase in price to $196 per flask at New York (Fig. I) and Government loans to operators for mine development and plant construction. The Bureau of Mines has issued, for restricted distribution subject to wartime controls, 13 War Minerals Reports on individual mercury deposits (listed in appendix A). In March 1942 it also published a Progress Report of the Metallurgical Division, R. I. 3627, Cinnabar-reduction Plants of the Southwestern Arkansas Quicksilver District. Uses of Mercury Mercury and its compounds have more than 3000 uses. Its principal use is as a catalyst in the manufacture of gases for chemical warfare; the next largest is in pharmaceuticals. Mercury is essential also for: (I) certain electrical apparatus, (2) industrial control instruments at many war plants, (3) munitions, including blasting caps, (4) insecticides in agriculture, (5) antifouling paint for ship bottoms, (6) dental preparations, (7) general laboratory use, and (8) amalgamation of free-milling gold ores.

Jan 1, 1949

By McHenry Mosier

MeRcuRy is one of the strategic metals of which the supply has been raised from critical uncertainty to more than enough for essential demands. Work by the Bureau of Mines has contributed substantially to increased production of mercury in the United States and to consequent accumulation of Government stocks. Other contributing factors have been higher prices for mercury and Government loans to operators. The Bureau has undertaken 13 exploration projects, 10 of which have been completed. This work has comprised 28,376 ft. of several types of drilling and 23,798 lin. ft. of surface trenching, and has indicated commercial ore containing 34,800 flasks of mercury and marginal ore containing 26,200 flasks, a total of 61,000 flasks; equivalent, respectively, to domestic production for 8 months, 6 months, and 14 months. As Government stocks are now adequate, domestic production (currently at the rate of 50,000 flasks per year) is gradually being curtailed through Government control of labor and operating supplies. Introduction Mercury was one of the seven metals designated as strategic by the Army and Navy Munitions Board in 1939, when Congress appropriated funds for the investigation of domestic sources of supply of war minerals. The Bureau of Mines immediately started a limited search for strategic minerals, but the first mercury project was not begun until December 1940. The U. S. Geological Survey assisted in the search for cinnabar by contributing information on domestic mercury deposits, preparing maps, and making geological studies of exploration projects. The present high rate of production of mercury in the United States was encouraged by the increase in price to $196 per flask at New York (Fig. I) and Government loans to operators for mine development and plant construction. The Bureau of Mines has issued, for restricted distribution subject to wartime controls, 13 War Minerals Reports on individual mercury deposits (listed in appendix A). In March 1942 it also published a Progress Report of the Metallurgical Division, R. I. 3627, Cinnabar-reduction Plants of the Southwestern Arkansas Quicksilver District. Uses of Mercury Mercury and its compounds have more than 3000 uses. Its principal use is as a catalyst in the manufacture of gases for chemical warfare; the next largest is in pharmaceuticals. Mercury is essential also for: (I) certain electrical apparatus, (2) industrial control instruments at many war plants, (3) munitions, including blasting caps, (4) insecticides in agriculture, (5) antifouling paint for ship bottoms, (6) dental preparations, (7) general laboratory use, and (8) amalgamation of free-milling gold ores.

Jan 1, 1949

By K. Reinhardt

THE idea of burning blast-furnace gases directly in gas-engines, instead of under steam-boilers, as had previously been done, was first put into practice barely ten years ago, almost simultaneously in Great Britain, Germany and Belgium. The pioneers of this movement made their first experiments with small engines. After these experiments had given satisfactory results, and it had been shown that the thermal value of the poor blast-furnace gases, in spite of defective scrubbing, could with safety be directly transformed into mechanical work in the gas-engine, there very soon arose a considerable demand for gas-engines of large power, similar to the large steam-engines employed in metallurgical works. In face of these sudden requirements, the gas-engine builders were placed in a difficult position; for up to that time the gas-motor was considered as suitable for small engines only, and it was generally believed that the limit of size bad been attained with 100 to 150 effective h.p. in a single cylinder. Manufacturers of gas-motors, however, did not underrate the advantages offered by this new field for their manufactures, and it so happened that in Germany the Berlin-Anhaltische Maschinenbau-Gesellschaft, of Dessau, was the first to undertake the construction of a 600-h.p. two-cycle gas-engine, with two cyl¬inders of the Oechelhäuser-Junkers type, for the Hoerder Mining & Smelting Company. The engine was started in 1898, and, with a few improvements and alterations, is still working satisfactorily. This engine worked with astonishingly high of efficiency, considering the period. The builders were therefore

Nov 1, 1906

By Finney, W. R.

MUCH has been said and written of the "Big Inch," of the terrific obstacles encountered in its construction, of the colorful and tough men engaged in its building, but little has been publicized of the engineering and economic problems behind the scenes. Long before Pearl Harbor it was apparent to the petroleum industry that a critical oil shortage could be expected along the Atlantic seaboard, owing to delay in tanker deliveries as a result of convoy movements, and to allocation of vessels for foreign shipments. This area, with a normal consumption of approximately 1,800,000 barrels per day of oil and products, was almost entirely supplied by tanker. Pipe lines supplied an average of only 20,000 barrels per day in 1939, 40,300 barrels per day in 1940, and 55,000 barrels per day in 1941. A small amount of oil and products was also delivered via barge.

Jan 1, 1943

Abadilla, Quirico A. Catanawan, Tayabas, P I '20 Abbey, Robert Graham, District Mgr., The W. W. Sly Mfg. Co, 50 Church St, New York, N. Y. '21 Abbott,-A. N., Mines Supt, Mazapil Copper Co., Ltd .. Concepcion del Oro, Zac., Mexico. '23 Abbott, Clarence E., Mgr, Mines & Quarries, Tenn. Coal, Iron & R R Co. 1242 Brown Marx Bldg, Birmingham, Ala. '04 Abbott, Louis Benjamin, Chief Engr, Consolidation Coal Co, Elkhorn Div . Jenkins, Ky. '15 Abeel, George H., Jr., Cons Min Engr... . Box 427, Santa Monica, Cal. '18 Abel, Albert E., Asst. to Pres., Valley Mould & Iron Corp Hubbard, Ohio. '19 Abel, Raymond L., Asst. Prof., Dept. of Pet. Refin , Univ. of Pittsburgh Pittsburgh, Pa. '28 Abernathy, George Elmer, Prof. of Geol. & Min., Kansas State Teachers College. Pittsburg, Kans '20 ||Abernethy, D. Carl, Jr. Min. Engr., Hudson Coal Co . Scranton, Pa '27 Abey, Hiroshi, Min. & Met. Engr., Min. & Met. Dept, The Higher Technical School, Osaka, Japan. '17 Aborn, Robert H., Instructor in Met, Harvard University Cambridge, Mass. '19 Abozeid, Mahmood, Pet. Production Engr., Marland Oil Co Ponca City, Okla. '20 Abraham, Arthur W., Geol, Richfield Oil Co. Box 788, Bakeisfield, Cal. '20 Abraham, W. E. V., Member, Geol Staff of Burmah Oil Co, Ltd Nyaunghla. Upper Burma, India. '23

Jan 1, 1923

By Gordon E. Frantti

Under the auspices of the Geophysical Committee of Michigan College of Mining and Technology, an investigation was made in Michigan's Upper Peninsula to obtain geophysical data related to the regional subsurface geology in the area covered by Paleozoic sediments. The area surveyed includes that portion of the Upper Peninsula which lies between R18W to R26W and T41N and T49N, covering approximately 1300 square miles. On the index map, Fig. 1, it is represented by the cross-hatched zone west of Munising. Four of the five sites of detailed investigation are indicated by the letters A, B, C, and D. A detailed gravity and magnetic survey had previously been conducted by J. G. Wilson near Perkins, 8 miles north of Rapid River, on a local anomalous area. Results of his work, which showed a large positive magnetic anomaly associated with a gravity anomaly, aroused interest in the possible economic significance of the formations underlying the Paleozoic sediments in this part of the Upper Peninsula.

Jan 1, 1956

By George M. Fowler, J. P. LYDEN

T HE relationship of geological structure to orebodies and to the great masses of chert in the Tri-State mining district is of such significance that it prompts a brief recital of the existing information regarding the various periods of structural deformation. We began to note a relationship between structure and orebodies early in our studies of the field, and further work revealed a like relationship of structure to the great masses of chert so commonly associated with the ore-

Jan 1, 1934

By W. F. Domis, F. von Gemmingen, F. Garofalo

The effect of rain size on the creep behavior of an austenitic iron-base alloy has been studied at 1300° F under conditions of constant stress. The average grain diameter varied between 9 and 190 p (ASTM 10.7-2). The subgrain size and apparent activation energy for creep were not found to depend in any systematic manner on gain size. Grain hozmdary serrations were observed in all specimens tested. The variation of the secondary-creep rate, 2,, with the pain diameter, 1, is given by: es = K(213m + 1 )/l.]; 1, is the grain diameter zohere is reaches a minimum. Results in the literature shoujthat 1,increases as the temperature increases. At low creep temperatures is is therefore proportional to 12, at intermediate temperatures <, exhibits a minimum, and at high creep temperatures is is proportional to 1/1. The dependence ofis on the stress, u, is given by: t, = A" (sinh acrln, a and n show little variation with 1. The dependence of A" on 1 is given by: A" = KA[(21k + 13)/1]. For 1 » >>lmn = 4, and at constant values 01- isat lozu stress levels, the steady-state stress is given by the Hall-Petch relation. The variation of c, with grain size is believed to he associated particularly with grain boundary generation of dislocations which becomes more important with increasing temperatures. SEEMINGLY inconsistent experimental findings have led to a certain amount of confusion concerning the effect of grain size on creep behavior. The confusion is attributed to a lack of test results obtained over sufficiently wide ranges in grain size, stress, and temperature. Experimental results presented in this paper and results available in the literature1-5 show a consistent behavior and lead to a unified concept for the dependence of secondary-or steady-state creep rate on grain size. In accordance with this concept, which is substantiated experimentally, secondary-creep rate should increase with increasing grain diameter at low creep temperatures, leading to greater creep strengths for fine-grained materials. At intermediate temperatures the secondary-creep rate should decrease to a minimum and then increase as the grain size is increased. At high creep temperatures the secondary-creep rate should decrease with increasing grain size, leading to greater creep strengths for coarse-grained materials. Whether a temperature is high or low for creep in a metal or alloy depends primarily on its melting temperature. MATERIAL AND TEST PROCEDURES The material tested was an austenitic iron-base alloy of the following composition (wt pct): C, 0.005; N, 0.017; Mn, 1.26; Ni, 14.21; and Cr, 17.18. Two 15 -lb ingots were forged and hot-rolled to 5/8-in.-diam bars which were then cold-rolled and cold-swaged to a diameter of 0.49 in. These were sectioned into 3-in.-long blanks and heat-treated at various temperatures to obtain different grain sizes. The procedures employed and the results obtained are summarized in Table I. The secondary treatment at 1400° F followed the primary treatment without intermediate cooling to room temperature. This final treatment was employed to minimize various effects arising from heating to different temperatures during the primary treatment, particularly differences in intragranular dislocation structure, segregation of interstitial atoms at grain boundaries, and density of grain boundary ledges. The intragranular dislocation structure was examined by electron transmission metallography after each of the treatments described in Table I. Isolated dislocations and a few tangles were observed but no evidence of subgrains was found after any of the treatments. No grain-size effect was evident on the density and distribution of dislocations. Stabilization of grain boundary structure is particularly important because, as will be discussed later, grain boundaries influence high-temperature creep behavior. Magnetic-permeability measurements after each treatment and

Jan 1, 1964

By John Hall

SOME months ago one of the authors was asked to write a paper on the heat treatment of steel castings that would be more comprehensive than other matter lie had published; this is an attempt to present in condensed form the results of experimental work and actual practice carried out for the most part in 1907, 1908; and 1909. It is not a laboratory research and the work done was carried out for the express purpose of putting in practice the processes discovered as fast as possible. Most of the tests are the result of commercial practice and not of bars annealed in our laboratory; most of the micrographs were made for our own records and not for publication. Certain of the micrographs, therefore, are not as clear as we may wish but they were good enough for our purpose at the time they were made. The tests and micrographs are selected from several thousands in our files. All of these micrographs are magnified 60 diameters. These experiments were conducted almost entirely on steel made in a 3-ton bottom-blown converter, and most of the steel illustrated analyzes about 0.05 in phosphorus and sulfur. Unfortunately, a certain number of specimens are shown of which we do not have the complete analysis, but in most cases in which the phosphorus and sulfur vary much from the figure just given that fact is noted. For purposes of comparison, we have included a certain number of micrographs and tests of steel made in the electric furnace, some of which were from specimens made in other shops and some in our own shop, and some tests of acid open-hearth and tropenas steel.

Jan 9, 1919

By Joachim J. Hauser

William F. Hosford, Jr. (Massachusetts Institute of Technology)—Dr. Hauser has used a very interesting method to study the interaction of dislocations on different slip systems, but it should be pointed out that the analysis of the experiments is subject to a serious criticism. He states that "the effect of the compression can be adequately described by one slip system." The effect of frictional constraint during the compression makes this quite unlikely. When a block of metal is compressed its lateral expansion requires a sliding of the metal over the compression platens. The role of friction in the interface between the deforming metal and the platens is to increase the normal force required for the compression. Analyses1213 have shown that, in general, the additional force, p, required for the compression is a function of l/h where is the coefficient of friction, I is the length of the speci- men in contact with the platens. For a constant COefficient of friction, isho&apos; shows that P should increase exponentially with pl/h for both plane strain and axially symmetric compression. For a compression specimen, Fig. 7, whose cross section perpendicular to the compression axis is a rectangle whith one dimension L, much larger than the other W, a much larger force would be required for appreciable flow parallel to L than for flow parallel to U7. Therefore lateral strain in the W direction, EW, should be much greater than the lateral strain in the L direction EL. Since L/H = 14.5 for Dr. Hauser&apos;s crystals, and since no lubrication was used, it seems questionable that appreciable lengthening of the crystals could occur. Because the theories of frictional constraint have been derived for isotropic polycrystalline materials, it was decided to make experimental measurements on a single crystal. A section 3.590 in. long was sawed from an aluminum single crystal with a square section of 0.249 in., so that L/W= 14.4. This crystal was tested in compression between dry ground steel platens. Fig. 8 shows the orientation of the crystal and the axis of compression. The face for compression was chosen so that the operation of the single-slip system which would be predicted in the absence of friction would lead to a larger strain in the length direction than in the width direction. The dimensional changes of the width and length as well as the height were measured frequently during the compression with micrometers. Width strains were calculated from the average of readings near each end and at the center. A plot of the length strain, EL, against the width strain E w is given in Fig. 9. The slope indicates that the EL amounted to only 2.5 pct of cw. Other compression tests on similar crystals with shorter lengths also showed severely limited elongation. Even for a crystal with L/W = A.0, EL was only about 26 pct of cw. Because of the frequent interruptions of the tests for dimensional measurements should have decreased the frictional constraint by allowing a reseating of the platens, even smaller elongations under continuous testing seem probable. These tests on long narrow crystals show that essentially plane strain conditions prevailed. We may assume that Dr. Hauser&apos;s crystals deformed similarly. That the compression can be described by the

Jan 1, 1962

The economics of aerial survey and the technical processes by the aid of which vertical and oblique aerial photographs are turned into line maps showing the most profuse topographical detail such as contours, rivers, roads, plantations, habitations and cultivated lands do not concern us here. They have been ably and exhaustively described in the publications of the British War Office, handbooks on surveying methods and on photogrammetry and in the South African mining, engineering and geological press. Suffice it to mention that for geological interpretation vertical photographs are used on such scales as 1/5000 to 1/10,000, overlapping each other by 55 to 60 per cent in the direction of flight and some 10 to 20 per cent sideways on to the next sequence or strip. Through this duplication in the overlap the stereoscopic examination becomes possible. The standards by which monochrome aerial photographs are interpreted can be grouped under the following headings: 1. Continuity.—The continuity of topographic relief not obtainable on the ground owing to the smallness of man relative to that relief. Here lies the greatest value of aerial survey with relation to geology. An immediate alignment can often be made of drainages running in different directions on each side of a hill; saddles and gorges in the mountainsides; abrupt termination of outcrop or indubitable signs of faulting. Most conclusive evidence is thus often obtained about faults which may be perfectly visible at one place on the ground but cannot elsewhere be identified because of decreased throw. Similarly, dikes can often be followed notwithstanding frequent interruption and disappearance under the soil. Scattered outcrop in scrub-covered or bush-covered country can be conveniently located and often correlated, with a large saving of time compared with field work. The same applies to geological contacts. Once these have been established at a few points on the ground, the intervening stretches can be drawn in.

Jan 1, 1937

By Arthur V. Corry

GOLD was discovered in Alder Gulch, Virginia. City, Mont., on May 26, 1863. In a short time some 6000 people flocked to the new discovery, and on the banks of Alder Gulch six settlements sprang into existence, the principal one, Virginia City, alone surviving. This town today has a population of 800, and is the county seat of Madison County. It is estimated that between forty and fifty million dollars in gold was produced up to 1904. Virginia City is situated at the mouth of Alder Creek where that stream leaves the narrow canyon that cuts the steep foothills flanking Old Baldy Mountain, elevation 9572 ft., 12 mi. south. Virginia City itself is 5700 ft. above sea level.

Jan 1, 1936

By Max Hebgen

Within the State of Montana the streams rise in the high mountains at. an elevation of from 5,000 to 8,000 ft. These streams leave the State line both east and west at elevations from 3,500 to 2,400 ft. It is, therefore, apparent. that all these streams have an average fall of 3,000 ft. within the confines of the. State, and many opportunities are presented on all streams. for the development of power, by taking advantage of the natural fall. It is probable that 1,000,000 h. p. can :be developed in the State of Montana. I. NATURAL FEATURES OF STATE AFFECTING POWER DEVELOPMENT. The main. range of the Rocky mountains, forming the Continental Divide, cuts the State of Montana into two parts. The eastern part is drained by the Missouri river and its tributaries, the Madison; Jefferson, Gallatin and Yellowstone, rivers. The western part is drained by tributaries to the Columbia river, the Clarks fork and the Kootenai river. The Clarks fork in turn is formed by the junction of Missoula and Flathead rivers, the latter, draining Flathead lake. The western part of the State. is mountainous and the eastern part is comparatively level. As a natural result the rivers in the western part are capable of generating large amounts of power, while in the eastern part of the State natural power sites are much fewer and farther apart. It also follows that in the mountainous districts large amounts of power are required for the mining industry, while in the eastern part of the State, which is principally devoted to agriculture, power is required in smaller quantities. ?

Jan 8, 1913

By Royal Preston Jarvis

minerals of different specific gravities. It is simple in construction, easily operated, capable of treating large quantities in a short time, and highly efficient under various conditions. The question, whether the material to be jigged has first been sized, determines the two principal methods of jigging. Jigging preceded by close sizing, generally known as the Continental or German system, involves a more or less elaborate series of screens or trommels, with attendant cost for installation, operation, and repairs. Jigging without sizing, known as the English system, is, according to Munroe,1 a development of the hand-jigging formerly employed in Cornwall . and introduced by English miners to this country." In its simplest form, the method consists in jigging an ore-mixture previously crushed to some maximum size (although, in some cases, even this preliminary is omitted) oil a relatively coarse sieve, and then jigging again on a filler sieve, the material passing through the first sieve and bedding. While many modifications have been necessary to adapt it for use in mills of large capacity, where hand-work was necessarily, replaced by machines, the principle remains the same; the fact that the English system has been successfully employed, both in this country and abroad, is well known; and arguments have been made for its efficiency and applicability in a wider sphere than it has occupied hitherto. II. REVIEW OF PREVIOUS INVESTIGATIONS. The fact that treating a mixture of minerals under jigging conditions increased the amount of mineral saved, or, as Professor Richards aptly terms it, 1 ?the extra jig-catch," has long been known. To account for this fact a number of theories have been proposed. The work of Rittinger2 in this field has, for many years, been a classic in the literature of ore-dressing. For the purposes of my present paper, however, the work of two American investigators, Prof. H. S. Munroe and Prof. R. H. Richards, is chiefly concerned. Professor Munroe has given the results of an elaborate series of experiments,3 and his deductions, based largely oil theoretical grounds, of this work. After reviewing briefly the two systems of jigging, followed by a discussion of Rittinger&apos;s formulas and

Sep 1, 1908

By Robert S. Nichols

Fording Coal Limited&apos;s mine in the Rocky Mountains near Elkford, B.C. has produced 21.8 million clean tonnes of metallurgical coal from 1971 to 1980, inclusive. This production has come from several pit areas and required the removal of 149.1 million bank cubic meters of waste rock and overburden by truck-shovel and dragline operations. Waste dumps from 30m to 200m in height have been successfully constructed on natural slopes, generally between 10° and 26°. Design considerations for the dumps include foundation and soil conditions, natural slope angles and containment of weak overburden or rehandle materials. Dump control is maintained by monitoring the crest and the face of an active dump area. Crest movement is measured by extensometers locally termed "Spoil Monitors". When crest movement rates progressively increase above normal, dumping operations are temporarily relocated. Some unstable conditions and mass failures have occurred as the result of natural foundation slopes being in excess of 26°, failure of weak water saturated foundation soils or weak material being placed on the dump.

Jan 1, 1983

The Institute has prepared a list of Societies&apos; publications, magazines, . etc., which were duplicates and were discarded at the time of the consolidation of the libraries of the three Founder Societies. These books will be disposed of about March 1, 1916 by the Board of Directors of the Institute through the Library Committee. If, meanwhile, members who have incomplete sets of these books, or for any other reason desire to secure some of them, they are asked to communicate immediately with the Secretary, as this is in unusual opportunity to secure books at a very low price. American Gas Light Journal, viols. 31 to 39. American Institute of Electrical Engineers, Transactions, vols. 5 to 26. American Machinist, vols. 3 to 20, 22 to 29. American Society of Civil Engineers, Transactions, vols. 2 to 10, 21 to 24, 26 to 33, 39 to 49, 52, 55, 58, 74. Index, viols. 1 to 21. American Society of Mechanical Engineers, Transactions, vols. 1 to 28. Index, vols. 1 to 20, vols. 1 to 25.

Jan 1, 1916

The Pueblo Viejo Mine, a 7, 250 mtpd (8,000 stpd) gold-silver cyanidation plant built by Rosario Dominicana S. A., was described in Volume I of this monograph. At the time of writing that volume, Pueblo Viejo had not yet gone on-stream and operating data or costs could not be presented. Since that time this information has been obtained and several interesting modifications and an expansion have been made to the plant. Because Pueblo Viejo is the largest open-pit gold mine in the world and one of the world&apos;s leading gold-silver operations with production of approximately 31 kg (1,000 oz) gold and 125 to 155 kg (4,000 to 5, 000 oz) silver per day, the authors have updated the previous data and flow sheet. The Dominican Government, which held a 4670 interest in Rosario Dominicana S. A., completed purchase of the mine to gain full control in 1979. Rosario Resources will continue to manage the mine, at least until the end of 1980. Gold was produced at Pueblo Viejo almost 500 years ago with initial production in the year 1505. Rosario Resources became interested in the property in 1969 and found surface oxidation had rendered the upper portion of the ore body amenable to direct cyanide treatment. The treatment of the underlying gold-bearing sulfide zone is still undergoing metallurgical studies. The ore is considered to be a laterite; and because there appeared to be few boulders in the ore zone, only a 400 m (16 in. ) square grizzly was initially installed ahead of the mills when the plant went on-stream in late 1974 at a design capacity of 7,250 mtpd (8,000 stpd). Operation also proved the ore to be harder than was originally anticipated. During 1967 a 1. 25 m by 1. 5 m (48 in. by 60 in. ) jaw crusher was installed to -feed the 1, 000 mt (1, 100 st) mill bin. Minus 200 mm (8 in.) crushed ore is fed directly to two 5.5 m by 1. 8 m (18 ft by 6 ft) semi-autogenous mills re-powered with 750 km (1,000 hp) motors and 50 mm (2 in.) grates. Each mill product is screened at 13 mm (1 /2 in.) by a vibrating screen. Screen oversize from each mill is combined on a single return belt equipped with a magnetic head pulley for grinding ball removal. The non-magnetic oversize is then split into two fractions for return to the primary mills. Originally, a minus 6 mm (1/4 in ) product was made on each screen and fed to a 300 kw (400 hp) 2.6 m by 3. 7 m (8-1/2 ft by 12 ft) regrind mill. During a plant expansion in 1978, an intermediate mill of 746 kw (1,000 hp) was installed to operate in open circuit on the combined primary mill

Jan 1, 1981

By W. D. Robertson, D. A. Koss, A. J. Goldman

THE significance of the hcp (E) structure, which appears when Fe-Cr-Ni alloys (stainless steels) are transformed martensitically, has been the subject of considerable study and speculation.&apos;-7 It has been proposed that the hcp structure is an intermediate phase in the transformation: fcc (austenite) — hcp (E) -bcc (0, martensite). However, recent studies by transmission electron microscopy6,7 have indicated that the hcp structure may be a consequence of the large shear strain (10 deg) associated with the fcc to bcc transformation. That is, the transformation to a bcc structure is accompanied by extensive dissociation of dislocations in the parent austenite, which has a low stacking-fault energy.&apos;-&apos;&apos; X-ray diffraction analysis of the transformed alloy reveals a pattern of lines corresponding to an hcp structure, together with the parent austenite and the bcc product. The fact that the hcp structure is observed only in association with the bcc product in these alloys1&apos;4&apos;6&apos;7 lends support to the conclusion that the hcp structure is a secondary product of the transformation. But, the evidence is circumstantial and more definite resolution of the two possibilities mains to be obtained. If the hcp structure is an intermediate product of the transformation, as in 1) above, then two distinct Ms temperatures should be observed, Ms and To evaluate this possibility, three different techniques that are particularly sensitive to the structural changes accompanying such transformations have been used in an attempt to detect two transformation temperatures in an Fe-15.1 Cr-11.7 Ni alloy: 1) high-sensitivity differential thermal analysis, 2) the temperature dependence of resonant frequency (elastic moduli), and 3) internal friction of cylindrical specimens vibrating in either longitudinal or torsional modes. To obtain the necessary sensitivity, a differential thermal analysis technique was developed for the purpose, Fig. 1. The differential temperature between a nickel standard and the specimen was amplified to produce a sensitivity of 0.02OC (0.7 v) in temperature difference. The specimen and the standard were surrounded by a copper block and the entire assembly was immersed in a solution of methyl and ethyl alcohol, freezing point, - 140OC, which provided the necessary thermal stability to reduce temperature fluctuations to negligible proportions. A cooling rate of about 1.5OC per min was obtained by bubbling liquid nitrogen through the liquid bath. In order to calibrate the experiment with respect to the evolution of heat in the transformation from fcc to hcp structures, differential cooling curves were obtained for an Fe-19.8 Mn alloy, which transforms martensitically to E.&apos;"-&apos; a Ms(e) temperature of 145°C was clearly defined by a temperature

Jan 1, 1964

By H. D. Wilde

DURING 1934 conditions in the production division of the petroleum industry were reasonably satisfactory but nevertheless a decided feeling of insecurity existed largely because of the uncertainty of controlling production to consumptive demand. Over-production, especially in the East Texas field, threatened a general collapse of crude prices but in spite of this, posted prices were high. Stimulated by the prevailing posted prices, wildcatting activities were wide-spread. Although a number of small discoveries were made, particularly in the Gulf Coast belt and Oklahoma, no fields of major importance, unless it was the Fitts pool in Southern Oklahoma, were brought in. Meanwhile, the Petroleum Division of the A.I.M.E. continued its activities. It sponsored the collection of production and geological data on both foreign and domestic fields. The data on all but a few producing districts in the world were published in the "Petroleum Development and Technology" volume of the "Transactions" and comprise one of the most complete tabula¬tions of this sort ever published. Work of this kind is being continued.

Jan 1, 1935