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By Wayne E. Hall

The Darwin mining district of California, 160 miles north of Los Angeles, has yielded an estimated $45 million in lead, silver, zinc, and copper since 1875. The deposits are in silicated limestone of Pennsylvanian and Permian age close to a stock of horn- blende-biotite-quartz monzonite. Steep left-lateral strike-slip faults that strike N 50" 70" E served as feeder channels for the ore solutions, and minor folds, favorable beds, and faults close to the feeder channels localized the orebodies. The orebodies are irregular, steep, pipe-like replacements that cut across bedding, bedding replacements, and fissure fillings in a calc-silicate country rock consisting mainly of wollastonite, grossularite-andradite garnet, idocrase, and diopside. Near surface the ore consists of a soft, crumbly mass of cerussite, hemimorphite, jarosite, limonite, and some secondary copper minerals. The primary ore consists of galena, sphalerite, pyrite, pyrrhotite, and chalcopyrite with smaller amounts of andorite, matildite, scheelite, tetrahedrite, and a high silver- lead-bismuth-selenium-bearing galena.

Jan 9, 1959

POSITIONS VACANT (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons.) Superintendent for iron mine operated on the sub-level and caving system. Small output, moderate salary. Location, Southern State. No. 45. Chemist to sample and analyze iron ore. Experience in other branches not essential. Location, Southern State. No. 46. ENGINEERS AVAILABLE (Under this heading will be published notes sent to the Secretary of the Institute by members or other persons introducd by members.) Experienced mine superintendent desires position. Several years' experience in practical management of mining and development work. Has also practiced ass consulting engineer and is thoroughly experienced in the examination and development of mining properties. Mexican experience. Will go anywhere for reliable concern. Salary moderate. References. No. 254. Member, mechanical superintendent, wants position. Has had 12 years' experience as master mechanic of smelting plants in United States and Mexico. Also superintendent of shops doing marine, mining, and general contracting work. . Experienced in manufacture of mining tools and equipment. Up to the minute in copper, lead, and zinc smelting. Has learned a learned a great deal, can forget much, and has the inclination and ability to learn more. Best of references. No. 255.

Jan 10, 1915

Los Angeles may well be host to one of the most historic gatherings of AIME members Feb. 16 to 19, 1953, when the 175th General Meeting is scheduled to take place. Plans in the formulative stage indicate that the meeting will be one of the largest ever held by AIME. Headquarters will be the Hotel Statler, now nearing completion of construction. The hotel will be one of the most modern hostelries of the century. The first technical session, of which there will be more than 75, will take place Monday, February 16. Mineral Industries Education Div. and the Board of Directors meet Sunday, February 15. Sessions will end with a meeting of the Council of Section Delegates on Thursday. Deadline for papers that may be preprinted for presentation at the meeting is Sept. 15, 1952. However, division program committees may list papers for presentation after that date if they choose. Various committees are engaged in formulating final plans for the meeting. Developments will be announced as progress is made.

Jan 1, 1952

By Arthur G. Metcalfe

Arthur G. Metcalfe (SOLAR)—Three explanations to account for mechanical nucleation effects are considered in the paper, viz., theories based on fragmentation, agglomeration, and pressure-wave mechanisms. The authors show that none of these mechanisms will explain the results observed with tin and Sn-Pb alloys. A fourth mechanism of nucleation enhancement was developed during work at Armour Research Foundation on casting of beryllium and, although presented briefly on various occasions, the theory has never been discussed adequately. It is believed that this theory will explain many of the observations. Classical homogeneous nucleation theories assume that embryo nuclei are formed in the melt as a result of compositional and/or thermal fluctuations. Stable nuclei are formed when a critical size is reached such that the decrease in free energy for conversion of this volume of melt to solid offsets the increase of surface, energy. The assumption is made that the average properties of liquid and solid metal can be used. In practice this assumption is invalid and indeed is contrary to the postulation of thermal and compositional fluctuations in the melt. Actually the conditions favoring embryo formation bring the seeds of its own destruction—the thermal and compositional fluctuations leave the embryo surrounded by atoms of higher thermal energies and/or by solute atoms that depress the melting point. Any mechanical method of dispersing this destructive

Jan 1, 1964

By Dever C. Ashmead

Coal companies in the anthracite region are studying various methods of mining, seeking one that will shorten considerably the life of the gangway and thus decrease the maintenance charges. In steep pitching measures, the maintenance charges of the gangways are high because of the cost of replacing timbers and cleaning up falls. Therefore, if the length of the gangways can be decreased and the mining made more concentrated, the life of the coal gangways will be decreased and the maintenance charges per ton of coal produced will be smaller. The practice in the anthracite region is to drive long coal gangways and to work the breasts as the gangway from which they were driven is advanced. In many cases these gangways are from 4000 to 6000 ft. in length; and some are even longer. As these must be maintained not only until they have reached their limit but until second mining begins (which may be some years later), the maintenance charges are high. If the gangway is allowed to close, when the time comes to remove the pillars the cost of re-opening it may be as expensive as the original driving cost. The Lehigh and Wilkes-Barre Coal Co., at its Wanamie Colliery at Wanamie, Pa., has been using a system of mining that, as far as the writer knows, is not used in any other place in the anthracite fields. The

Jan 1, 1925

By R. W. Raymond

Prof. Henry Lours, of Armstrong College, Newcastle-on-Tyne, England, a distinguished member of this Institute and other technical societies, has recently sent to the Institution of Mining Engineers, and to the Institution of Mining and Metallurgy, in Great Britain, a communication, the substance of which is as follows : Professor Louis calls attention to the absence of any recognized English term for the definite description of a frequent phenomenon—namely,the oblique position of an ore-body in the plane in which it lies. In this connection, Professor Louis says that in America the term " pitch " has been occasionally applied to this relation, and proposes that, in the literature of ore-deposits, it shall be hereafter restricted to this particular meaning, the angle of the pitch, like that of the dip, being always measured from the horizontal, and the dip being always taken at right angles to the strike, while the pitch is taken on the plane of the dip, in the direction of the strike. Thus, for example, in a vein or bed striking N-S., and dipping, say, 45' E., there might be an ore-body, the axis of which pitched northward, at an angle of 45O below the horizontal line, as measured on the plane of the inclosing vein or bed. If' the term " pitch " had this universally recognized meaning, the situation could be simply and perfectly expressed by its use, in connection with the general data of strike and dip. As Professor Louis says: "This suggestion has a certain practical value, and is not merely academic. Every mining engineer of practical experience in such types of ore-deposit will have met with cases, in which a vertical shaft has been sunk with the object of cutting the deposit, but has missed it, because the dip alone has been taken into account, while the pitch has been overlooked." He adds the acute observation that such an oversight is much likelier to occur with regard to a condition not definitely desig-

Jan 1, 1909

Through the generosity of Sir Robert Hadfield, Honorary Member, the Directors of the American Institute of Mining Engineers are enabled to announce the Hadfield Research Prize of $1,000 for the best contribution to the publications of the Institute upon the general subject of The Different Forms and Combinations of Carbon with Iron, including those in Iron Alloys. The prize will be awarded at the Annual Meeting of the Institute in February, 1916, to the best paper upon this subject which is presented to the Institute before Nov. 1, 1915, provided such paper is deemed worthy by the Institute's Iron and Steel Committee. The following suggestions are also added for the guidance of those who may take part in this research. While' it is not desired to define closely the exact lines or scope of the proposed research, as it is advisable to make these as broad as possible, the object in mind maybe said to be generally as follows: To elaborate and find out the best methods of determining the forms of carbon in steel or iron, including those in iron alloys. A portion of the work would probably be a continuation of the researches which have in the past been carried out by Jullien, Abel, Muller, Ledebur, T. Sterry Hunt, Akerman, Arnold, Stead, E. D. Campbell, Hogg, Parry, Upton, and others. In a generic way, metallurgists now speak of carbides, sub-carbides, double carbides, special carbides, and other combinations. It is very desirable that these should be accurately defined and understood. It is also desirable to know whether there are other or new forms; if so, can these be separated and their characteristics obtained. It may be interesting to point out that the carbon compounds now definitely known are stated to number over 80,000. It is very probable, therefore, that there is room for much valuable and useful research to be carried out with the object of increasing our knowledge of the various combinations of carbon with iron, as probably some of these are still unknown

Jan 5, 1914

The airplane, while not a product of the war, owes its present very prominent place to the war; if it had not been for the war its development would have been retarded many years. War planes were made for various purposes, but their most important use was for photographing the enemies' lines. The same methods; with some modifications, are now

Jan 6, 1919

By Raymond E. Zimmerman

Abstract-The Swirl Cyclone developed in Japan, although based upon the same principles as the standard cyclones for heavy-media or water-only cyclones for cleaning coal, is novel in that it is invested with the apex on top, discharging rejects at the top, and clean coal at the bottom. It also uses a variable air vent tube for controlling the vortex. Tests conducted indicate that its efficiency is not only as sharp as standard cyclones but it also performs using a much coarser grain magnetite, promising higher magnetite recovery. The author describes the results of tests conducted in Japan on a very difficult coal.

Jan 2, 1978

Discussion of the paper of H. H. STOEK, presented at the St. Louis meeting, October, 1917, and printed in Bulletin 129, September, 1917, pp. 1385 to 1419. J. B. WARRINER, Lansford, Pa. (written discussion*).-The figures on costs given at the end of this paper. are of particular interest and it is unfortunate that they necessarily cover such limited periods, as figures giving the costs over a period of at least a year would be of much greater value; for instance, it seems hardly probable that the performances credited to the various shovels for the months for which the costs are given would represent the average of the performances of these machines over a longer period. It would seem to me that the maximum of 4000 cu. yd. (3058 cu. m.) per clay given for the 225 B shovel is much greater than could be maintained for an entire year's operation. On the other hand, the 1500-yd. figure for the 150 B shovel would seem a low average for this type of shovel. In connection with the drag-line excavators, it will be interesting to know that the Lehigh Coal, and Navigation Co. is about to install one of these machines on a clay stripping at their Nesquehoning colliery to excavate an average depth of. overburden of 65 ft. (19 m.), which, due to local conditions, will require that part of the excavated material be handled a second time and a lesser quantity a third time. The results of this operation will undoubtedly be watched with great interest.

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