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By B. A. Rogers

The etching effect that is produced on a piece of polished iron or steel when it is heated in hydrogen or in a vacuum seems to have been observed first by Osmond,' who believed that he could distinguish four systems of grain boundaries on a piece of steel which had been heated in hydrogen. In a number of other investigations, samples of pure iron were found, after heating, to have complex networks in which two or three systems of grain boundaries could be detected. It was further noticed that samples that had been polished plane before being placed in the furnace were, after treatment, roughened and undulating over their entire surfaces. From a comparison of the temperature of heat treatment with that of the A3 transformation, it was concluded that the changed appearance of the samples was definitely related to the latter phenomenon. Certain other deductions were made but these are not of importance here and only observations on the appearance of the samples will be reviewed. Ewen2 heated a strip of polished iron in a vacuum in such a way that one end was maintained at a temperature of 1000" C. and the other at 580" C. On the cooler end there was outlined a simple polyhedral network, and at the hotter there appeared the complex systern of lines ant the undulating surface characteristic of iron which has passed through the A3 transformation. He found that in going from the cooler toward thc hotter end the sample maintained much the same character of surface up to the beginning of the transformed area, but that near this region doublc grain boundaries were of frequent occurrence. Rawdon and Scott concluded that the simple type of network brought out by heating a sample of pure iron in a vacuum was of the same type as that developec by ordinary etching methods. They also confirmed the observations of

Jan 1, 1929

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Jan 1, 1961

By Norman D. Fitzgerald

IN 1943 the petroleum industry completed a series of practical adjustments to the acute problems which dominated the scene a year earlier. The crisis in petroleum transportation from the Gulf Coast to the East Coast was met by the completion of overland pipe lines supplementing emergency haulage by tank car so pressure on consumers along the Atlantic Seaboard was appreciably relieved. Later in the year when the western Atlantic was largely cleared of submarines, the sharp reduction in the hazards of marine transportation permitted the resumption of coastwise traffic and imports from South America. Nationwide restrictions in the use of gasoline and fuel oils became necessary as military demands for all petroleum products mounted to high levels.

Jan 1, 1944

By L. A. Willey

Although the interierometric method for the determination of length changes was devised by Fizeau more than three quarters of a century ago, it has not achieved the widespread use in the metallurgical field that its precision and simplicity would seem to warrant. The interferometer and the basic principle are both very simple. When optically plane surfaces held at a very slight angle to each other are illuminated by monochromatic light, rectilinear, equally spaced interference fringes arc formed. Each fringe corresponds to a defiuitc thikness of the wedge formed by the optical flat.;. The difference in wedge thickness between two consecutive fringes is cqual to one half the wave length of the illuminating light. Instruments for vicwing the intertero~ncter have passed through a number of modifications. Outstanding among the improvements were those Abbe. in 1884. His improved instrument permitted micrometric mcasurements to the order of one-hundredth of the width of an interference fringe (i.e., lengths were measured to the order of one two-hulldredth of the mave length of light ). It also permitted the consecutive use of light of several wave lengths. which made possible the determination of the order number of any fringe and therefore the absolute thickness of the wedge at any point. The Abbe dilatometer and methods of measuretment, including corrections to he applied for the change of index of refraction with change in tempcrature and barometric pressure in an air wedge, have been thoroughly described by Pulfrich.' Pulfrich2 made further improvements in the interference measuring apparatus. His instrument embodied all the features of the Abbe dilatometer but was made more versatile by its complete mechanical separation from the interferorneter. The introduction of an Amici prism in the piece permitted the simultaneous observ tion of the whole set of fringe systems developed in the interferometer from the visible light of a geisler tulle. .Also, the introduction of a direct-vision, reflecting prism made it possible to set the fringes parallel to the two vertical fiducial line. of the instrument without the necessity of rotating the interierometcr. Interferometric methods employed ill this country have been developed and dcscribed by Priest, Pelers and Cragoe," Austin,5 Merritt,= Saunders,? and Nix and MaNair. Since none of these authors used the type of instrument that was employed in the present investigation, they Will not be discussed here. This paper will be limited to the description of the interfernmetric apparatus and method used at the Aluminum Research Laboratories and to the presentation of data so obtained. Apparatus and Procedure A general view of the dilatometer, not including equipment for controlling and

Jan 1, 1945

By M. R. Geer Olds, H. F. Yancey

THE increase in the number of coal-cleaning plants employing dense-medium processes occurring since 1946 is especially interesting when viewed historically. Both sand and magnetite were introduced as material for heavy mediums at about the same time, sand in the Chance process in 1921 and magnetite in the Conklin process in 1922, but from that point on their records diverge. The Chance process enjoyed a steady growth from its inception, whereas no additional magnetite plants were built in the United States for over 20 years. Then, following the close of the World War 11, magnetite was again introduced, this time with marked success. During the following years some 47 plants employing magnetite medium were built. This rapid growth of dense-medium cleaning has been concurrent with widespread adoption of full-seam mining on one hand and a return to a more competitive market on the other. At a time when changing mining practice has provided cleaning plants with dirtier coal and changing market conditions have simultaneously demanded a cleaner product, the industry has through necessity turned to improved preparation. The inherently greater sharpness with which dense-medium processes can separate coal from impurity is thus helping to hold the line against ever-increasing mining costs and at the same time assisting materially in retaining badly needed markets. Although dense-medium cleaning unquestionably offers a distinct advantage when the washing problem is difficult, other methods can provide almost equally high efficiency when the coal is easy to wash. Moreover, fine coal cannot yet be treated by heavy medium in a proved process, although the Driessen cyclone is in the pilot-plant stage. Most of the present types of dense-medium equipment have been in use only a few years, and the dearth of information in the literature concerning their performance characteristics is entirely understandable, Nevertheless this information is necessary if the process is to be intelligently applied to individual cleaning problems. Without data on the efficiency of a process in a particular type of separation, it is difficult to assess the advantage to be expected from it. Similarly, the role of particle size in heavy-medium separation is important in some cases, yet there is little published information on this aspect. To mention only one more of the numerous points on which essential information is lacking, the bearing of medium characteristics on performance has been discussed only in qualitative terms. It was with the hope of providing information on some of these points that the Bureau of Mines built a dense-medium pilot plant for cleaning coal at its Northwest Experiment Station in Seattle in 1950. The plant has been operated continuously since that time, and over 50 runs have been made on 7 coals exhibiting a wide range of washability characteristics. An idea of the magnitude of this work will be gained from the fact that examination of the plant products has involved some 600 float-and-sink separations and about 2500 ash determinations. A laboratory pilot plant is especially well adapted to investigate many aspects of performance because close control over test conditions can be exercised and because a large number of tests can be made rapidly. On the other hand, factors such as consumption of medium and other cost items can be investigated satisfactorily only in a commercial plant. Actually, the two forms of investigation should be complementary, with the laboratory work pointing the way for confirming tests in commercial units. Pilot Plant The dense-medium pilot plant employed for this work comprises a 24x30-in. drum-type separating vessel, a 12-in. densifier, a 12-in. magnetic separator, a 26-in. x 9-ft vibrating screen, and the necessary pumps and conveyors for handling materials. Arrangement of these units corresponds with the flowsheet used in most commercial plants, except that a thickener is not provided for the feed to the magnetic separator. Coal and refuse discharge from the separating drum to the vibrator, which is divided longitudinally down the center. Medium draining through the first 3 ft of the screen is recirculated directly to the drum. Sprays on the middle 3 ft of the screen rinse medium from the products, and the last 3-ft section is for dewatering. Dilute medium from the rinsing and dewatering sections is pumped to the magnetic separator, where magnetic solids are recovered. These are pumped to the densifier, from which they return to the medium-drainage sump by gravity through a demagnetizing coil. The drum-type separating vessel is a scale model of a commercial unit. Feed enters axially at one end of the drum just below the surface of the bath, and float material overflows through a circular opening at the other end. Particles sinking to the bottom of the bath are picked up by lifting flights bolted to the inner wall of the drum, elevated out of the bath, and sluiced to the vibrating screen. Baffles suspended in the bath prevent float material from entering the sink-lifting flights. About 8 gpm of medium is used to sluice the feed into the drum. An additional 15 to 24 gpm, depending upon operating conditions, is added through two pipes dipping into the bath behind the baffle on the side where the sink-lifting flights enter the bath. The bath available for separation is 2 ft long and 13 in. wide, giving an area of 2.08 sq ft. Depth of bath from the surface to the top of the sink-lifting flights, measured vertically below the axis, is 6 in.

Jan 1, 1954

By AIME AIME

THE Petroleum Division opened its proceedings on Wednesday morning, with two simultaneous sessions on engineering and economics. The first paper at the engineering session, over which A. W. Ambrose presided, was "Underground Surveys of Oil Wells," by Alexander Anderson of Los Angeles, Calif., was presented by John Suman of the Humble Oil & Refining Co., Houston, Texas. Following this, the paper of E.'H. Griswold of the Mailand Oil Co., Houston, Texas, was presented by C. V. Millikan of the Amerada Petroleum Corp., Tulsa, Oklahoma. Following the presentation of these two interesting papers a general discussion followed on the subject of "Crooked Holes." The discussion was entered into by F. H. Lahee, Sun Oil Co., Dallas, Texas;'Messrs. Bigelow of Tulsa, H. W. Hixon of New York City, Van Court Warren of Los Anyeles, Calif; H. L. Wheeler of St. Louis, Mo.; R. R. Brandenthaler, United States Bureau of Mines, Bartlesville, Okla.; H. H. Riggs, Indiana Territory Illuminating Oil Co., Bartlesville, Okla.; C. V. Millikan and John R. Suman

Jan 1, 1929

By G. R. Smithson, John E. Hanway

This paper, the first of two papers covering the development of a metallurgical process for the treatment of a complex ore, describes the bench-scale experimental Program undertaken as a basis for initial process design. The results of using various potentially applicable process steps are detailed and the basis for selecting certain of these steps for Pilot-plant development is outlined. A process consisting of the steps of sulfate roasting, leaching, copper recovery, solution purification, zinc electrolysis, and brine leaching for lead recovery was recommended for further study. THIS paper describes the bench-scale development of a sulfate roasting process designed to recover copper, lead, and zinc from a complex ore. The extrapolation of the bench-scale results to pilot-plant design and the results of pilot-plant operation will be described by Lund, et al.' in a subsequent paper. Several years ago, the research divisions of the St. Joseph Lead Co. became responsible for the development of a metallurgical procedure to treat a complex sulfide ore containing copper, zinc, and lead sulfides. The primary objective was to devise a procedure which would permit economic recovery of the nonferrous values. As could logically be expected, the study of conventional flotation procedures was undertaken; in addition, however, because the physical nature of the mineral association in the complex ore indicated that physical methods of ore beneficiation might not prove to be entirely satisfactory, a program also was established to investigate alternative methods of direct metallurgical treatment for recovery of the metal values. Exploratory test work by the St. Joseph Lead staff led to the conclusion that a sulfate roasting technique represented the most attractive approach for a direct metallurgical process. Sulfate roasting would provide for the selective conversion of the nonferrous values to forms soluble in conventiona1.1 leaching agents and would permit their efficient separation from the insoluble iron and other gangue materials. It should allow efficient utilization of the thermal energy available from oxidation of the sulfide raw material, and might provide an opportunity for recovering byproducts such as iron and sulfur. The decision to evaluate a selective sulfation procedure as a basic processing step also was influenced by the excellent results obtained by the St. Joseph Lead Co. in using this procedure for the recovery of cadmium from zinc sulfide concentrates. The choice of selective sulfation as a major processing step served as a basis for an extended experimental investigation of the process with bench- and pilot-scale equipment to prove its feasibility. St Joseph Lead Co., aware that Battelle Memorial 1nstitute had participated in the development of several fluidized-bed sulfate roasting procedures, asked Battelle to undertake the bench-scale development of a suitable sulfation process. This paper describes the procedure used and the results obtained at Battelle in the treatment of the complex sulfide ore. EXPERIMENTAL WORK Nature of the Raw Material. The sulfide ore deposits of interest are essentially a massive sulfide, with the indivudual ore minerals being extremely fine grained and intimately intergrown with each other and with the associated gangue. The zinc in the ore is present mainly as sphalerite (ZnS), the lead as galena (PbS), and the iron either as pyrite (Fes2) or as pyrrhotite (FeS). Table I shows the chemical analysis of various individual samples of the ore. These analyses illustrate the variability of the ore body and impose a rather severe requirement on any type of metallurgical process—that of being able to tolerate probable wide variations in the assay of the head ore. The tentative flowsheet designed to serve as a guide for the initial experimental investigation of

Jan 1, 1962

By J. F. Poland

B. C. Burgess-—Prior to hearing this paper presented at the San Francisco meeting, I travelled by car from Yuma, Ariz., across south-central California and up through the San Joaquin Valley. After hearing the paper I returned by the coast route to San Diego then along the Mexican border to Yuma. The striking feature of these trips, related to this paper, was the dry river and creek beds at a time of year not the dry season. Contrasted with this was the wasteful use of water in irrigation canals and laterals. Poland says "at least 90 pct of the ground water pumped is used for irrigation." That being the case, it would appear that first consideration should be given to conservation of this use. Probably a small part of this is actually reaching the plants. Some measure of this loss between pump and crops would be revealing. Methods that might be employed to reduce this loss are pipe lines and spraying of some crops such as the banana planters are using in Central America. Another idea which might be investigated is to line canals and ditches with some water-repelling mineral like pyro-phyllite. Perhaps a comparatively thin sprayed-on

Jan 1, 1951

By J. F. Poland

B. C. Burgess-—Prior to hearing this paper presented at the San Francisco meeting, I travelled by car from Yuma, Ariz., across south-central California and up through the San Joaquin Valley. After hearing the paper I returned by the coast route to San Diego then along the Mexican border to Yuma. The striking feature of these trips, related to this paper, was the dry river and creek beds at a time of year not the dry season. Contrasted with this was the wasteful use of water in irrigation canals and laterals. Poland says "at least 90 pct of the ground water pumped is used for irrigation." That being the case, it would appear that first consideration should be given to conservation of this use. Probably a small part of this is actually reaching the plants. Some measure of this loss between pump and crops would be revealing. Methods that might be employed to reduce this loss are pipe lines and spraying of some crops such as the banana planters are using in Central America. Another idea which might be investigated is to line canals and ditches with some water-repelling mineral like pyro-phyllite. Perhaps a comparatively thin sprayed-on

Jan 1, 1951

"The Garfield plant of the American Smelting & Refining Company is situated about seventeen miles west of Salt Lake City, on the Los Angeles & Salt Lake Railroad, and has freight service by the Denver & Rio Grande Western, Western Pacific and Bingham & Garfield Railways.The site lies between the picturesque Great Salt Lake, with its mountain islands, and the northern point of the Oquirrh Range, which forms the western boundary of the Salt Lake Valley.The location includes several hundred acres of land rising from the southern shore of the lake, selected on account of its adaptability to the economical handling of materials by gravity methods.The smelter is a custom smelter, treating copper ores and concentrates produced in Utah and adjoining states.The ores treated consist mainly of oxides from the Tintic and Park City Districts, sulphides from Bingham District, and concentrates from the mills of the Utah Copper Company, from mills in California, and copper precipitates from the Ohio Copper Company. The last product comes from low grade ores of Bingham Canyon.The following figures represent approximately the daily consumption of materials:Ores and Concentrates…2,700 tonsLime sand…100 ""Coal…350 ""Oil for Roasters…240 Bbls."

Jan 1, 1925

The Candelaria deposit was first discovered by Spanish prospectors in 1863; but its silver ore was not exploited on a large scale until 1873, when the Northern Belle mine was opened. The first Northern Belle mill was built at Belleville, 13 km (8 miles) to the northwest. From 1876 to 1886 the Northern Belle paid over $1 million in dividends each year. In 1882 a 43 km (27 miles) pipeline was built to Candelaria from the White Mountains to the west to furnish water for the mills and town at Candelaria; it was 100 mm (4 in.) in diameter, hand- riveted, and made in England. Sections of this pipe are used. as claim posts today. At its terminus at Metallic City, above Candelaria, a large concrete reservoir was built and called Metallic Lake. It is being used today by Candelaria Partners. Production at Candelaria declined after the mid-1980s, revived for a short period in the early 1890s, and during the 1920s a 300 ton mill operated for three years. Candelaria Partners is owned jointly by Occidental Minerals and Congdon and Carey, with Occidental being the operator. An engineering study done in mid-1979 resulted in engineering for the plant commencing in late that year and heap leaching being started in September 1980. Two million tons of ore per year containing 108 g Ag and 0.28 g Au per mt (3.15 oz Ag and 0.008 oz Au per st) will be mined from the Lucky Hill and Mount Diablo .areas about 1.6 km (1 mile) up Pickhandle gulch from the heap leaching operation. Waste -to -ore ratio is about 2:l. Ore is mined by front-end loaders and hauled by 85 ton trucks to the primary crusher, a 1,070 by 1,780 mm (42 by 70 in. ) gyratory. Primary crushed ore is conveyed to a stockpile of 10,000 tons live capacity from which it is reclaimed by hydraulic reciprocating feeders and conveyed to the crushing and agglomeration facility. This unit is composed of a 1.8 m by 2.6. m (6 ft by 12 ft) double deck screen, a 2.1 m (7 ft) standard cone crusher, and three conveyors. At the conveyor transfer points NaOH and NaCN solution is sprayed on the ore as it falls through a row of 75 mm (3 in.) hanging steel bars. During this process of turning and dividing the ore, the fines agglomerate with the coarse ore to give better percolation for the leach solution on the heaps. Provision was made for the later addition of 2 kg per mt (4 lb per st) of cement to aid in the agglomeration. Agglomerated ore at minus 50 mm (2 in.) size is then conveyed to a 390 mt (430 st) loadout bin where it is transferred to 85 ton rear dump trucks for haulage to the leach pads.

Jan 1, 1981

By B. A. Rogers

THE etching effect which is produced on a piece of polished iron or steel when it is heated in hydrogen or in a vacuum seems to have been observed first by Osmond,1 who believed that he could distinguish four systems of grain boundaries on a piece of steel which had been heated in hydrogen. In a number of other investigations, samples of pure iron were found, after heating, to have complex networks in which two or three systems of grain boundaries could be detected. It was further noticed that samples that had been polished plane before being placed in the furnace were, after treatment, roughened and undulating over their entire surfaces. From a comparison of the temperature of heat treatment with that of the A 3 transformation, it was concluded that the changed appearance of the samples was definitely related to the latter phenomenon. Certain other deductions were made but these are not of importance here and only observations on the appearance of the samples will be reviewed. Ewen2 heated a strip of polished iron in a vacuum in such a way that one end was maintained at a temperature of 1000° C. and the other at 580° C. On the cooler end there was outlined a simple polyhedral network, and at the hotter there appeared the complex system of lines and the undulating surface characteristic of iron which has passed through the A3 transformation. He found that in going from the cooler toward the hotter end the sample maintained much the same character of surface up to the beginning of the transformed area, but that near this region double grain boundaries were of frequent occurrence. Rawdon and Scott' concluded that the simple type of network brought out by heating a sample of pure iron in a vacuum was of the same type as that developed by ordinary etching methods. They also confirmed the observations of

Jan 1, 1929

By R. D. Coleman, A. E. McIlhinney, C. E. Capes

Problems of unstable operation in continuous balling circuits may be traced to the random generation of seed agglomerates. This has been verified during the continuous operation of a laboratory balling drum with internal recycle described previously by the authors. The cyclical behavior of a balling circuit was also investigated using a simple numerical computer model. Changes are suggested in the design of balling equipment to improve stability.

Jan 1, 1976

[59H1-Water Law and Its Significance to the Mining Industry by Wells A Hutchins 59H2-Relation of Land Subsidence to Groundwater Withdrawals in the Upper Gulf Coast Region, Texas by Leonard A Wood and A G Winslow 59F3-Hydraulic Mining of Gilsonite and Its Application to Coal Mining by J H Baker 59H4-Recovery of Phosphates by In Situ Fluid Mining by Sylvain J Pirson 59F5-Coal Cleaning Plant Design for Minimum Operating Labor by Wm M Bertholf and John D Price 59F6-Coke Combustibility A Neglected Characteristic by J D Price 59B7-Union Carbide's Uranium Operation at Maybell, Colorado by K W Lentz and F T Temple 59H8-A Rapid Method for Estimating Alumina in Feldspathic Sands by Hugh H Bein 59H9-Water Laws as Related to Dredging in Idaho by Robert A Lothrop, Richard B Porter, and Robert P Porter 58B19-Separation and Washing of Alumina Process Residue by Morton Handelman 59B11-Feed Preparation and Froth Modification for Fatty Acid Flotation by Carl C Martin and Burt C Mariacher 59B12-Design Requirements for Tailing Disposal in the Southwest by E Vern Given 59B13-Semi-Dome Shaped Buildings for Bulk Storage by Edward E Ives and William L Payne]

Jan 1, 1961

CONTENTS PAGE FULTON, CHARLES H., and READ, J. BURNS-A New Roasting Furnace for Zinc Flotation Concentrate. Discussed by Charles H. Fulton, Arthur S. Dwight, B. M. O'Harra, Kurt Stock 1 STOCK, KURT.-Redistillation of Zinc. Discussed by G. E. Dalbey, Kurt Stock.. 3 BEASLEY, F. E.-High Zinc in Lead Blast-furnace Slags. Discussed by R. C. Canby, R. L. Lloyd, C. R. Haywood, G. E. Dalbey, A. S. Dwight, E. P. Mathewson, A. L. Walker, B. M. O'Harra, and C. P. Linville 4 STEELE, E. W.-Application of Pulverized Coal to Copper Refinery Furnaces. Discussed by F. R. Pyne, E. P. Mathewson 11 LINVILLE, C. P.-Recovery of Arsenic and Other Valuable Constituents from Speiss. Discussed by C. R. Hayward, C. P. Linville, G. E. Dalbey, A. S. Dwight, Edward F. Kern, Karl Eilers, E. P. Mathewson 12 A New Roasting Furnace for Zinc Flotation Concentrate Discussion of the paper of CHARLES H. FULTON and J. BURNS READ, presented at the New York Meeting, February, 1925, and issued, as Paper No. 1362-D, with MINING AND METALLURGY,. October, 1924. G. E. DALBEY, East Berlin, Conn. What would be the, effect on the formation of sulfates of an increased water vapor content in the roasting gases? CHARLES H. FULTON.-I cannot answer that from our experience. The question of the formation of sulfate in the roasting of zinc is mainly one of temperature and the concentration of S02 and S03 in the gases. We found we could roast almost completely to sulfate if the concentration was kept at the proper point. We, however, did not care to do this because we wished to make a 5 to 6 per cent. S02 gas for sulfuric-acid work. The sulfating of the zinc oxide in the proper concentration of gases goes on very rapidly. There are certain places in the furnace system such as the Cottrell and in a part of the dust chamber in which the roasted

Jan 6, 1925

By Anson Hayes

FOR the purpose of the following discussion the word "research" is interpreted as including all phases of development work on methods of manufacture, metallurgical characteristics, and uses of iron and steel. Research in the iron and steel industry then includes both plant re- search and laboratory research. Since iron and steel came into being, the steel consumer's plant and the steel producer's plant have been important factors in the development of the steel industry. Good minds have always been associated with both consumer and producer plants, so marked progress was made in the industry even when these were the only types of research and development groups in action.

Jan 1, 1937

By J. F. Smith

ELASTIC constants of yttrium and eleven of the rare earth elements have been measured. This has been accomplished by measuring the propagation velocities of ultrasonic pulses. The velocity measurements were made by noting the elapsed time between an applied pulse and the appearance of successive echoes. The pulse-echo technique has become relatively common, and the basis of the measurement is outlined in several standard tests, e.g., Heuter and Bolt.1 Two important assumptions are made when using this method for the determination of elastic moduli. First, the pulse is assumed to propagate as a plane wave. To justify this assumption, the cross section of the test specimen should be large compared to the wave length of the transmitted pulse. For these measurements on the rare earth elements the minimum cross section wave length ratio was about 20. A second assumption which must be made when using polycrystalline specimens is that the grains are sufficiently numerous and randomly oriented so that the specimen may be approximated as elasti-cally isotopic. The grain size in the as-cast specimens which were used is believed to be sufficiently fine for this approximation, and the degree of preferred orientation is believed to be small. Supporting this viewpoint is the fact that elasticity measurements by the pulse-echo technique on as-cast specimens of other metals give results which are in satisfactory agreement with values obtained by other techniques. Hence, it is believed that the measured elasticity values for the rare earth elements are not apt to be seriously in error due to the assumption of elastic isotopy. The apparatus used in this determination was a modified Sperry Reflectoscope with a precisely calibrated time base circuit. Piezoelectric transducers were used both to generate the pulse and to detect the echoes. X-cut quartz crystals were used for the longitudinal modes, and Y-cut quartz crystals were used for the shear modes. Frequencies of 2.25 and 5 megacycles per sec were employed. Most of the specimens were 2.5 to 5.0 cm in length. Results Table I is a tabulation of the measured propagation velocities of longitudinal waves and of shear waves, together with densities obtained by Sped- ding, Daane, and Herrmann2 from lattice parameter measurements. The shear modulus, Poisson's ratio, and Young's modulus were calculated from the data in Table I through use of the following relationships: µ = pv32 [1] s=2-(vb/vs)2/2[1-(vb/vs)2] [2] and Y= 2µ(l+s) [3] where s is the shear modulus, Y is the Young's modulus, s is Poisson's ratio, p is the density, V0 is the longitudinal wave velocity, and v, is the shear wave velocity. The calculated quantities are shown in Table 11. Compressibility values can be computed from the relationship and the computed values may be compared with measured values obtained by Bridgman.8 Table III lists the data for such a comparison. The agreement is satisfactory, being particularly good for neodymi- um and gadolinium, poor for samarium, and intermediate for the other elements. Some variation is expected since Bridgman's measurements are isothermal, whereas the present measurements are adiabatic. In addition there may be some effect due to small variations in purity. Though most of the rare earth metals measured by Bridgman and all of the metals used in the present measurements were prepared at this laboratory, minor purity variations might exist since the samples came from different lots. Also, any imperfections such as dislocations, vacancies, voids, grain boundaries, microcracks, etc., should contribute to the volume change of a com-

Jan 1, 1958

By Robert B. Fulton

Staurolite, an iron aluminum silicate mineral, is used industrially as a high value-in-use sand-blasting agent, as a premium grade foundry sand, and as the source of aluminum in portland cement manufacture in areas where the aluminum constituent is not economically available from shale or argillaceous limestone. It is produced by E. I. du Pont de Nemours & Co. as a coproduct in titanium mineral production in Florida where it was first recovered on a commercial scale in June 1952 from the Pleistocene sand deposit known as Trail Ridge. In the Trail Ridge deposit it comprises about one-fifth of the heavy minerals, the principal other heavy mineral constituents being ilmenite, leucoxene, rutile, zircon, kyanite, sillimanite, and tourmaline. Staurolite and the other silicate nonconductive heavy minerals are separated from the conductive titanium minerals on high-tension separators. The silicates are then separated from one another magnetically, the staurolite being relatively magnetic. In the total processing, 200 tons of raw sand yield 7 tons of heavy mineral concentrate from which about one ton of staurolite is recovered. This process yields staurolite concentrates of the characteristics given in Table 1. These concentrates are sold as three products with the size distribution of subrounded particles shown in Table 2. All three grades are used in sand-blasting for cleaning metal, for paint removal, and for cleaning buildings. Staurolite compares favorably with lower unit cost abrasives, such as boiler slags and mineral aggregates, in applications where the abrasive is used only one time and is not recovered. Because it is hard, fine, clean, and dense it can reduce blasting time, with less material reportedly being required [ ]

Jan 1, 1983

By R. E. Frounfelker, W. M. Hirthe

INVESTIGATORS in the areas of plasticity, crystal growth, and stress analysis have a need for crys-tallographic data such as the interplanar angles. This information is utilized in the form of a stereo-graphic projection from which orientation determinations can be made. Calculations of mechanical properties, such as the critical resolved shear stress, require values for the angles between directions as well as the interplanar angles. Only a limited amount of this data is available for tetragonal crystals. The equations for these angles are relatively simple but because of the large numbers of angles involved and the infinite number of structures that could be investigated, it was decided to program these calculations on a high speed digital computer. The angle, 8, between two crystal planes (h1 k1 l1)

Jan 1, 1962

By Goodman, Richard E.

A complete rational analysis for design of excavation slopes and loaded rock masses is a desirable but perhaps unattainable goal. Irregular external and internal boundary conditions, poor understanding of failure criteria for large masses of rock, capricious material properties, and the importance of indeterminate forces and inaccessible and virtually un- sampleable rock defects emphasize the importance of experience in this aspect of rock engineering. The experience must be correlated with geological factors. In certain regions the accumulation of such experience through the observation of existing rock slopes in various formations constitutes an important aspect of studies for design of rock excavations.

Jan 1, 1969