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By ALFREDO INTZAUGARAT, MIGUEL BERRO

During the years 1943 through 1945, there was a decrease in the total oil production in Argentina. In the fields of Comodoro Rivadavia (Chubut Territory) and Mendoza and Salta Provinces, the production obtained was as shown in Table I. The only place where there was a small increase was Plaza Huincul, in the Neuquen Territory and Lunlunta, in the Mendoza Province.

Jan 1, 1946

By J. M. de la Garza Cardenas

Mexico's total oil production in 1943 amounted to 35,149,843 bbl. and in 1944 to 38,196,818 bbl., both being substantially larger than in 1942, when production was only 34,71j1547 bbl. Daily average figures are as follows: 95,111 bbl. in 1942; 96,301, bbl. in 1943; and 104,363 bbl. in 1944. The increase of 8062 bbl. in daily output from 1943 to 1944 was due to more refinery Tuns and an expanded volume in exports of refined products, although the export of crude oil decreased somewhat. The increase affected mainly the southern Tampico district (Golden Lane), which in Deccmber

Jan 1, 1945

?Aaronson, Alfred E , Oil Producer, Pres, Tuloma Oil Co Tulsa, Okla '18 ||Abad, Leopoldo F , College of Mm , Univ of California Berkeley, Cal '23 ||Abadilla, Quirico A , Geol Dept, Cia Mexicana de Petroleo "El Agmla," S A , Edifico "El Aguila," Esq, Caller Aurora y Comercio, Tampico, Tamps , Mexico '20 ||Abbey, Robert Graham, Student, Case School of Applied Science Cleveland, O '21 Abbott, Clarence E, Gen'l Supt, Iron Mines Div, Tenn Coal, Iron & R R Co, 1405 Minnesota Ave , Bessemer, Ala '04 Abbott, Louis Benjamin, Chief Engr , Consolidation Coal Co , Elkhorn Div Jenkins, Ky '15 Abbott, Robert R , Met Engr , Peerless Motor Car Co Cleveland, Ohio '12 ||Abbott, Wells Osborn, Student, Univ of Arizona Tucson, Ariz '23 Abe, Asaka Ashiya, Mukogun, Hmyogoken, Japan '14 Abeel, George H, Jr , Cons Min Engr 4612 W 17th St , Los Angeles, Cal '18 Abel, Albert E , Asst to Pres , Valley Mould & Iron Corpn Sharpsville, Pa '19 ?Abeloff, Miran S 322 W 45th St, Ness York, N Y '21

Jan 1, 1923

By N. J. Grant, Hans Brunner

ThE materials used in this investigation were furnished by the Aluminum Co. of America and consisted of high-purity alurhinum (99.995 pct) and two aluminum-magnesium alloys containing approximately 2 and 5 pct Mg. The compositions of these alloys are listed in Table I. The materials were received as hot rolled 3/8-in. diam rods and were made from the same heats as the materials which were previously used in this laboratory.'j3 The rods were cold swaged to 1/4-in. diam by 1 in. long, and then had two parallel flats machined over the gage length 0.085 in. apart. The test bars were annealed for 10 min at 700° F, and strained 1 pct in tension at room temperature. They were electropolished (80 pct acetic acid; 20 pct perchloric acid, 70 pct concentration) at a temperature of 60°F at approximately 20 v. A grid, transverse or square, spaced 0.2 mm apart, was impressed by rolling a fine threaded screw (128 threads per in.) across the flat surfaces. The depth of the grooves was less than 5 p. For final annealing and grain size control the specimens were enclosed in aluminum foil and sealed in Vycor tubes. Annealing conditions varied from 1 hr at 700° F to 5 days at 1050° F, depending on the alloy content, to give for most of the specimens a final grain size of about 1 mm. This treatment was followed by electropol-ishing as described above. For the test series presented in Figs. 4 and 5 round specimens were used instead of flat ones, and fine machining marks served as marker lines instead of the impressed grid lines. Electropolishing was omitted. The major advantage is that the spacing of the machining marks is only about 1 u as compared to the 200 u of the impressed grid lines, permitting higher precision in strain measurements. Unfortunately the strain annealing necessary for grain size control also resulted in some preferred orientation of the grains. The preferred orientation of three arbitrary specimens was measured by X-ray diffraction methods and the averaged results are shown in Fig. 1. The possible effects of the preferred orientation on the test results will be discussed later. The testing temperatures were 410°, 515", 725", and 940° F, with one exception in the case of the 5.1 pct Mg alloy. Since the solubility limit of this alloy is 520°F, a test temperature of 545°F was cho-se sen instead of 515°F. The selection of the test temperature was based on two considerations: 1) at 900°F and above, extensive grain boundary migration made it more difficult to measure grain boundary sliding; 2) at 400°F and below, there was so little grain boundary sliding that it was again difficult to make precise measurements. The stress was chosen to give a creep rate of approximately 2.7 pct per hr in connection with Figs. 2

Jan 1, 1961

By Leo Wolrnan

IN the relations that exist between capital and labor in this country, there is a bright as well as a dark side. After many years of distressing conditions of labor and a plentiful supply of propaganda, it is doubtful that the doctrine of the class struggle, however defined and stated, has been embraced by any influential and numerous elements of our population. Extreme and uncivilized methods of conflict, whether they be the labor spy as used by the employer or the sit-down strike by organized, labor, have come to be abandoned as the result of the pressure of sober and distinterested public opinion. Unwise terms of our law of trade unions and the unbridled zeal of its administrators show some slight signs of being revised in the light of 'experience and the protests of the law's own beneficiaries. At the point where labor policy touches economic conditions, the two powerful factions in the American labor movement appear to look with a less friendly eye on the bewildering succession of economic experiments and to have a deep nostalgia for a simpler and more prosperous economy.

Jan 1, 1938

The following Nominating Committee having been already appointed and approved by the Executive Committee in accordance with authority vested in the Executive Committee by the Board of Directors, was approved by the Directors: John V. N. Dorr, Chairman, Percy G. Beckett, J. W. Hutchinson, Julian Kennedy, William H. Linney, Charles W. Merrill, and E. Gybbon Spilsbury. The question of the purchase of Liberty Bonds, as well as that of bringing to the attention of the members the advisability of the purchase of these bonds, was referred to the Finance Committee. Sixty Members, four Associates, and thirty-six Junior Members were elected. Two Members were reinstated. Eight resignations were accepted.

Jan 7, 1917

By W. B. Plank, A. C. Callen

WAR and normalcy do not walk hand in hand, whether it be in industry, the educational field, or in the daily lives of individuals. Schools and departments offering curricula in mineral engineering have been seriously disrupted, beginning with 1942 and reaching a low during 1944. Selective Service regulations and voluntary enlistments have effectually stopped the flow of college-trained men into the mineral industry, and the flow into the colleges is little more than a dribble. The year just closed has been a most serious one for our institutions. Until March many of our faculties had been kept reasonably intact because of the large training programs of the Army and Navy. Although the number of

Jan 1, 1945

By Eugene McAuliffe

The term "mechanical mining" carries an ambiguity which justifies a preliminary word of explanation. . All mining activity conducted in this day is more or less mechanical; that is to say, power expressed in the form of electricity, steam or compressed air is used in some portion of practically every mining activity of consequence. "Mechanical loading" is more nearly correct than "mechanical mining" in reference to present practice. The first substantial effort made in the direction of mechanical mining, subsequent to the application of steam for hoisting and underground pumping purposes, was that of substituting for hand labor undercutting and shearing by power-driven machines. The undercutting of coal by hand represented at one time the most arduous task confronting the miner. Occupying a kneeling position in the thicker beds, or lying on his side in the thinner coal, the task was tedious and exhausting. The first attempt to substitute crude air-driven, and later electrically driven, "punchers," as the percussion type of machine was called, met with much the same opposition on the part of the workers as was expressed by workers in the other industries when any innovation, whether labor-saving or otherwise, was introduced. We should not be too critical of this attitude of mind shown by the mine workers. The peculiarly isolated character of the work carried on in semidarkness by a class of men who to a large extent lived and held themselves aloof from the other branches of society led long ago to the development of a craft consciousness which they have found difficult to surrender. It was not until 1891 that a definite record of the results obtained by the use of undercutting machines of all types was made available, the quantity undercut in that year totaling 6,211,732 tons of bituminous coal from all American mines. The volume of bituminous coal undercut by machines in 1928 totaled 369,687,007 tons, or 73.8 per cent. of the nation's production. In the light of this experience, we can properly feel that the work of introducing the coal-loading machine as a substitute for hand shoveling is making substantial progress.

Jan 1, 1931

By Francis A. Thomson

DO the curricula of our mineral technology schools prepare their graduates to meet properly the full range of their responsibilities in after life? An unequivocal "no" could be returned to this question, because training and experience in professional work are quite as important as adequate college preparation. Furthermore, a had curriculum with a splendid corps of men doing the teaching and a competent body of students doing the learning will produce a better result than an ideal curriculum in the hands of unqualified teachers and poorly prepared students.

Jan 1, 1937

By R. J. Lloyd

INTRODUCTION The Mount Isa Mine is a large modern underground mine located in North-Western Queensland, Australia. Two ore types are mined and treated separately. Currently silver-lead-zinc ore is mined at the rate of 2.6 million tonnes per annum and copper ore at the rate of 4.6 million tonnes per annum. The silver-lead-zinc orebodies are mined by sub level open stoping and cut and fill methods whilst all copper ore is extracted by various forms of sub level open stoping. The mining operations are highly mechanised and utilise diesel powered load-haul-dump units of various sizes, two and three boom face drilling jumbos, electric-hydraulic rotary-percussive ring drills, in-the-hole hammer drills, rotary blasthole drills, raiseborers, battery/trolley locomotives, a large fleet of rubber tyred service and supply vehicles plus light rockdrills mounted on airlegs, rail mounted overshot shovels and battery and diesel powered locomotives. All stoping production ore is extracted with diesel powered load-haul-dump units. The ore is tipped into orepasses which connect to the main rail haulage levels. On the haulage levels electric battery/trolley locomotives are used to pull rakes of bottom dump or side dump trucks which feed the ore into primary crushers. Following two stage crushing the ore is conveyed to the shaft and hoistod to surface in bottom dump skips. Each ore stream has its own rail transport system, crushing stations and hoisting shaft feeding separate concentrators. This paper will consider some aspects of the role of equipment and machinery in the growth of the mine, will discuss in some detail the machinery and equipment in use today and will conclude with a look at some possible developments in mining equipment for the future, with particular reference to the Mount Isa Mine. A summary of mining equipment in use at Mount Isa is given in the Appendix. THE PAST Silver-lead-zinc ore was discovered at Mount Isa in 1923 and within a very short time many small mines were being developed. However the rich surface ore traces did not continue and by 1928 Mount Isa Mines Limited had acquired sufficient leases to plan for a large scale mine to exploit the low grade orebodies. At this early stage it was recognised that the mine would need to adopt the most mechanised mining techniques then available in order to overcome its twin disadvantages of low graaes and extreme remoteness. The Company introduced bar mounted drifters and overshot shovels to replace hammer and tap and hand shovelling in development work and by 1930 headings were advancing at the rate of 30 metres per week. In keeping with the concept of mechanisation the early engineers designed the Man and Supply shaft with a very large, for those days, cage compartment measuring 3.8 m x 3.4 m. This shaft was the main means of access into the mine for 36 years until the K57 shaft (now R62 shaft) was commissioned in 1966. Man and Supply is still in regular use. Production commenced in 1931 at an annual rate of approximately 660 000 tonnes of silver-lead-zinc ore. The mine was mechanised to an extent which was previously unknown in Australia; whilst the concentrator, smelter and power house utilised the most modern and efficient equipment available. Even so, the mine was very near to closure on several occasions and did not return a dividend to its shareholders for many years. Production levels remained at or slightly below 660 000 tonnes until a separate copper ore streani and mill was commissioned in 1953, doubling the existing production levels. The first underground crushers were installed at this time. Production rates expanded in the years between 1953 and 1973. By 1960 production reached 2740 000 tonnes of ore. In 1965-66 total production was 3650 000 tonnes and in 1973 the production rate plateaued at the current level.

Jan 1, 1981

By Leslie C. Richards

The competitive position of producers of industrial minerals depends upon the delivered price of their product. Freight charges are a major factor in the sales to consumers. A comparison of freight rates on movements of limestone and silica rock in the Pacific Northwest shows a wide variance in mills per ton mile for like hauls, thereby favoring some localities over others.

Jan 1, 1950

By Douglas J. Harvey

The surface tension of lead-tellurium alloys (in the range 0 to 6.70 at. pct Te) ad lead-arsenic alloys (in the range 0 to 10.53 at. pct As) has been examined by the maximum bubble pressure method. The surface tension of high purity lead can be expressed over a range of temperatures (M.P. to 750°C) by the relationship = 512 — 0.133t. Arsenic and lellurium were both found to be surface active in lead. The surface excess concentration at 700°C was .found to be constant at 0.74 x 10-10 moles per sq cm for tellurium. The surface excess of arsenic at 700°C varied between 0.26 x 10-10 moles per sq cm at 0.16 at. pct to 1.5 x 10-10 moles per sq cm at 8.3 at. pet. The surface tension of lead has been investigated sporadically over the last 90 years. The first recorded study was made by Quincke1 who used a rather crude application of the drop-weight method. Hogness2 obtained the first reliable value for the surface tension of lead by measuring the pressure necessary to force the liquid metal from the end of a small capillary of known radius. Hogness gives the empirical formula: ?(surface tension)= 444 - 0.077 (l-327) which describes the relationship between surface tension and temperature ("C); This work was followed by that of Bircumshaw3 who applied the two-capillar maximum bubble pressure method of Sugden.4 The values published by Bircumshaw are in good agreement with those found by Hogness. Matuyama5 examined the surface tension of lead by the drop weight method. However, the values found are somewhat higher than those previously reported. More recent investigations by Greenaway6 and by Melford and oar' have resulted in data which are not in close agreement, but which are well within the expected range at most temperature levels. The study of the surface tension of lead alloys began with Drath and sauerwald8 who examined the lead-bismuth system. They found that the surface tension values of the alloys in this system deviated only slightly from the ideal mixture rule. Matuyarna5 examined the lead-antimony system. Bircumshaw the lead-tin, and the lead-indium system was studied by Hoar and Me1ford.10 The results of these investi- gations are summarized in Fig. 1. It may be seen that the data vary only slightly from the ideal mixture rule. As none of the metals studied and reported in the literature has a very interesting effect on the surface tension of lead,*the next logical step might be to examine the effect of metals of low solubility or nonmetals having some liquid solubility. Baes, and Kellogg11 have pointed out that the elements most likely to be surface active in liquid metals are ones of limited solubility in the liquid state and possessing weak intermolecular bonding forces in the solid state. Therefore, Group V, VI and VII nonmetals are most likely to be surface active. It was decided to examine the effect of a borderline metal, arsenic, and a nonmetal tellurium. Arsenic forms a eutectic with lead having a melting point of 290°C and a composition of 6.9 at. pct As.13 Pure arsenic sublimes when heated above 610°C. Even though alloying with lead lowers the vapor pressure, fumes containing arsenic are evolved at a very noticeable rate when lead-arsenic alloys are heated above 650°C. Tellurium raises the liquidus temperature of lead sharply to 904°C,14 the melting point of PbTe (lead-telluride). The solid solubility of tellurium in lead was determined by Greenwood and worner15 to be 0.0007 at. pct at room temperature. EXPERIMENTAL METHOD Surface Tension Measurement—The two capillary maximum bubble pressure method for measuring surface tension developed by Sugden,4 and used later

Jan 1, 1962

By J. L. Schroeder, W. G. Talman

EXPERIENCE has shown that certain known natural conditions and other indefinite characteristics combine to make a mining area vulnerable to mountain bumps. Some of the known conditions are heavy overburden, an overlying stratum of strong non-elastic rock, a structurally strong coal seam that does not crush easily and yet is the weakest stratum in the series, and a floor stratum of more than ordinary firmness. The indefinite characteristics could include resistance of top or bottom of a coal seam to lateral flow, effect of immediate top and bottom strata, nature of the coal seam, and other factors about which very little is known. It is in this area that exhaustive study is needed to achieve positive control of the dreaded mountain bump hazard. In the Gary district, West Virginia, two of the five operating mines have areas known to be vulnerable to mountain bumps.These are the No. 2 and 6 mines, which are working the Pocahontas No. 4 coal seam. In this area the seam is overlain at a zero to 10-ft interval by the massive Eckman sandstone, which is about 100 ft thick in the vulnerable areas. Total overburden, consisting of shale, coal seams, and sandstones, ranges from 700 to 1400 ft where bumps have occurred (Fig. 1). The coal seam is 4 to 8 ft thick and has a weak columnar structure of very soft and spongy or woody coal. The immediate top is either the Eckman sandstone or hard shale, both of which provide generally good roof conditions for mining operations. The bottom ranges from medium to hard gray shale. The incidence of bumps in the Gary district dates from about 1930 and can be correlated to some degree with the increased rate of extraction attained with mechanical mining. During early years of operation at the No. 2 and 6 mines, most of the work was development and under comparatively light cover. As overburden became heavier, together with an increasing percentage of coal coming from pillar extraction, mountain bumps began to occur. Before 1945 they were much less severe than in later years, and because there were no injuries or fatalities, no records were kept. But by 1951 the incidence of bumps had increased to such extent that it became evident a mining system would have to be designed to eliminate or at least minimize these occurrences. Drawing on experience with modified versions of old systems and certain characteristics peculiar to the Pocahontas No. 4 coal seam, the district mining engineer, Martin Hayduk, outlined the essential factors for bump control in the Gary district. These control factors indicated: 1) The highly stressed area, which lies within the limits of convergence effects, moves at approximately the same rate as the retreating pillar line. 2) There is a decided softening of the periphery of blocks which is greatest and deepest on the gob side. 3) Blocks less than 45 ft wide never have been known to bump in the Pocahontas seams. Fig. 2 shows the mining plan based on these observations—a thin-pillar system with a minimum of secondary development. It was recognized from the start that the Hayduk system had certain limitations. When pillar work backed up to an inevitable surrounded block it was no longer applicable; also, burnt bottom and/or unknown factors reduced the system's effectiveness in certain headings. Since there was no way to eliminate the loaded block, it was decided to experiment with auger drilling to attain controlled release of this stored-up energy. The decision to auger was made after consideration of three separate plants, which were: 1) To cut the solid block into pillars of maximum size by driving away from the fracture line and at such a distance outby that development

Jan 1, 1959

By R. J. Grace

Primarily, this report presents the results of direct efficiency tests which were conducted on the 200-hp Coal-Pak, hot water generator, No. 3 unit, at the Otterbein College heating plant in Westerville, Ohio. Also included is a comparison of fuel consumption of the old plant with that of the new plant, a comparison of efficiencies obtained by the indirect method on a 300-hp Coal-Pak, and the cost of gas vs coal to show the savings effected by the latter. Tests were conducted with ten different bituminous coals selected by Mr. S. A. Frye, business manager at Otterbein College. The coals, of ten different suppliers, from four different states and eight different seams, represented competitive products economically available to the heating plant. The tests were conducted by the usual plant personnel which consisted of the plant superintendent and two assistants. No outside supervision of any kind was given during the tests. The tests were made from Dec. 13, 1960, through Mar. 4, 1961. During this period, 300.03 tons of coal were burned in the No. 3 unit. This tonnage represented 25.5 pct of the total coal requirements for the 1960-61 season. Operation during the period was typical for the comfort heat load which the plant supplies. Of the 78.12 operating days, the boiler was on bank or holdfire 14.31 days, or 18.32 pct of the time. The length of individual bank periods varied from 2 hr to three days. Run periods varied from about 2 hr to 7.26 days. DESCRIPTION OF PLANT AND HEATING EQUIPMENT The new Otterbein College heating plant, completed in the summer of 1957, is located in a 50x50 ft boiler room on the lower level of a combination maintenance building and heating plant. The building is situated away from the main college complex on a hillside, which allows for on-grade delivery of coal to the three bunkers. The bunkers are located directly above and connected with the individual stoker hoppers. Fig. 1 shows an in-plant view of the Coal-Pak installations. The No. 3, hot water, unit is at the extreme right. The heating plant consists of three 200-hp Coal-Paks. Unit No. 1 is operated at 4 psi and carries the steam heating load of 14,000 sq ft EDR (steam) installed in two buildings. Provision has been made to convert these buildings to hot water heating at some future date. Since the unit under maximum load conditions operates only at about 50 pct steaming capacity, a heat exchanger was installed to convert steam to hot water. Thus, during light loads in mild weather the unit can be employed more efficiently to supply both steam and hot water and eliminate the need for operating either of the two hot water units. Units No. 2 and No. 3 serve a hot water heating circuit for a large group of 21 buildings of the College. These boilers deliver hot water at temperatures up to 200°F to the various buildings through distribution lines in tunnels. The present calculated maximum heat loss for the College is 15.195 million Btu per hr. The Coal-Paks have individual design capacities of 6.700 million Btu per hr. Table I lists the design date for the Coal-Paks. The No. 3 unit was chosen as the test unit, primarily because of its bunker location at the far end of the delivery ramp. Because of this location any excess coal above bunker capacity could be conveniently stored and isolated from the adjoining bunkers. Each bunker has a capacity of 30 to 35 tons of coal. The No. 2 and No. 3 hot water generators are equipped with automatic controls which maintain the

Jan 1, 1962

By H. O. Hoffman, C. D. Demond

There are two methods of determining the fusibility or refractoriness of fire-clays, the theoretical and the experimental. In the former, conclusions are drawn from the chemical composition; in the latter, from the changes which the clay undergoes when subjeoted to intense heat. It is well to use both methods, beginning with the actual heat-test and explaining the results obtained from this by the help of the chemical analysis. In discussing the subject, however, it is better to reverse this order. I. The Theoretical Method.* Leaving out the hygroscopic and combined waters and any organic matter, as not directly affecting the fire-resisting property, the refractory constituents of fire-clay are alumina and silica, and the fluxing constituents magnesia, lime, soda, potash and ferric oxide. According to Bischof,† alumina is the least fusible component, and silica follows close upon it. If, however, a mixture of the two be heated, it will be found that its melting-point is much lower than that of alumina, as a silicate will then have been formed. The way in which silica affects the refractoriness of alumina has been strikingly presented by Seger 1 in a diagram reproduced in Fig. 1. The abscissæ represent the melting-points of Seger cones Nos. 26 to 36 (see p. 55); the ordinates, the relative amounts of alumina and

Jan 1, 1895

By L. H. Schwartz, S. K. Lahiri, M. E. Fine, D. Chandra

WHILE the yield stress of solution treated Fe-Cu alloys increases rapidly with aging, a precipitate has only been directly observed in overaged samples.'-" This precipitate is essentially pure fcc copper, the E phase. Hornbogen2 suggested that the initial hardening is due to clustering of copper atoms in a bcc iron matrix. Hornbogen was not able to obtain direct confirmation for such bcc clusters by either X-ray diffraction or electron microscopy; however, he did observe analogous clustering in Fe-Au alloys7 where the scattering factor difference between iron and gold is more favorable than that for iron and copper. Fujii, Nemoto, Suto, and Monma4 recently observed diffuse electron diffraction scattering in a 2.5 pct Cu alloy aged at 500°C: for 30 hr. They suggested that part of the diffuse SCattering was due to a modulated structure of 26 to 42 wavelength parallel to the (110) matrix plane. This disappeared with further aging. However, 30 hr at 500°C is well beyond the peak strengthening in this alloy which occurred at less than I hr at 500oc.4 By transmission electron microscopy they could not distinguish between quenched samples and samples aged to maximum strength. The purpose of the present investigation was to try to obtain further confirming evidence for a precipitation stage preceding the formation of the fcc E phase. Change in Young's modulus was selected for study be- EXPERIMENTAL PROCEDURE The Fe-1.67 at. pct Cu alloy was supplied by the U.S. Steel Corporation in the form of a hot forged rectangular bar. The carbon and nitrogen contents of this alloy were 70 ppm and less than 10 ppm, respectively. The samples for Young's modulus measurements were made by cold swaging to & in. diam and cutting to 2 in. lengths. Tensile test samples 1 in. long were prepared by cold rolling to a thickness of 0.012 in. and then machining to gage dimensions of 0.5 by 0.012 in. For Mijssbauer studies, foils 1 mil thick were prepared by cold rolling. During fabrication the alloy was given intermediate anneals at 845OC followed by quenching. The specimens after preparation were solution treated at 1000°C (y field) or 845°C (a field) for 1 to 2 and 5 to 6 hr, respectively, in a dynamic vacuum of about 2 x lom6 torr. The tensile and modulus specimens were drop-quenched into iced brine through an aluminum foil which vacuum-sealed the bottom of the furnace tube. The MOssbauer foils were drop-quenched into helium gas cooled by passing through N2 (liq) in a copper coil. The grain diameter of the modulus and tensile specimens was between 0.025 and 0.035 mm. The samples were aged from 400" to 500°C in a dynamic vacuum of 2 x 10-6 torr and cooled by pulling into a water-cooled portion of the vacuum system. The dynamic Young's modulus was measured at room temperature using electrostatic excitation and detection of longitudinal vibrations.' Neglecting any length change during the aging, (this is expected to be comparatively small), the fractional change of Young's modulus (?Et)/Eav, is equal to twice the fractional change of the resonant frequency (?ft)/fav . ?ft =ft —fo where fo and ft are the resonant frequencies of a specimen before aging and after aging to time t. The measured f's, approximately 51,000 cps, were corrected to 25°C for any variation in the ambient temperature. The tensile tests reported were carried out at room temperature in an Instron with a 1000 lb full scale load cell. The flow stress reported herein corresponds to a strain of 0.002. The Massbauer spectra were taken in a constant acceleration model AM-1 NSEC spectrometer. The

Jan 1, 1970

By H. B. Menardi

THE history, geology, ore deposits and current mining operations of the Huitzuco district have been described by C. W. Vaupell1 and the current mill operations by David Segura.2 This paper completes the story of Huitzuco with a description of the reduction of the flotation concentrates. The predominant ore mineral in the Huitzuco deposit is livingstonite, a rare, mercury-antimony sulphide (HgS.2Sb2S3). Other associated minerals include cinnabar, stibnite and elemental sulphur. The gangue is largely limestone and gypsum. Former operators mined a selected grade of ore, from which the mercury was recovered by an expensive, inefficient operation. A consid-erable tonnage of rejects and fills, carrying mercury and antimony, was left in the mine. In order to recover both mercury and antimony from these fills and also from newly developed ore, a combination method has been developed, by means of which the livingstonite is concentrated by flotation and the flotation concentrates subsequently reduced to metallic mercury and antimony. An essential part of the flotation treatment, as developed by Segura, is the use of copper sulphate as an activating agent. A typical analysis of concentrates now being produced at the property is as follows: Hg, 7.73 per cent; Sb, 26.40; Fe, 1.20; S, 29.68; CaO, 11.50; MgO, 7.25; Si02, 1.63; A1203, 0.65.

Jan 1, 1939

The high-grade orebody at Miami was mined successively by top-slicing, shrinkage, stoping and under caving. The method described in this paper was developed to enable the low-grade orebody (36,000,000 tons assaying 1.06 per cent copper) to be mined at a low cost without further dilution of the grade. The method is clearly described and illustrated by drawings and photographs, and the original paper should be consulted as it is impracticable to abstract it, beyond noting that the mining cost is just under 40 cents per ton and the average grade of ore now being produced yields less copper than the mill tailing of 1915, the tons mined per day having increased from 4000 to 18,000 in the same period. Vertical and Incline Shaft Sinking at North Star Mine By Arthur B. Foote, Grass Valley, Calif. (Tech. Pub. No. 324: Class A. Metal Mining, No. 36) THE main shaft of the North Star mine is an inclined one following the main vein at an average dip of 26 deg., a vertical shaft intersects it at the 4000-ft. (incline) level, the incline continuing to the 6300-ft. level. At this point the vein was found to give out and a new vein, called the No. 1, was found to dip in exactly the opposite direction.

Jan 1, 1930

By Samuel H. Dolbear

NOT WITHSTANDING the extremely low ebb of business activity, the nonmetallic industries have fared somewhat better than some other branches of mining. The average price level in nonmetallics, although far from satisfactory, has resisted any cataclysmic fall such as has been suffered by copper and other metals. Stocks, also, though too abundant, represent no corresponding overhang of the market, which should result, in some branches, in a more rapid recovery. Research work has continued in some industries with interesting developments.

Jan 1, 1933

By M. S. Seltzer

High temperature steady-state creep rates have been determined jor lead sulfide single crystals whose defect concentrations were fixed by equilibration under controlled sulfur pressure. The activation energy of creep, Qc , for undoped lead sulfide, is a function 01 composilion, decreasing from 2.9 to 2.2 ev as the carrier concentration increases from 9 x 1016 to 8 1018 electrons cm-3 for lead excess crystals, and increasing from 1.7 to 2.3 ev as the concentration of holes increases from 4 x 1017 to 1 x 1018 cm-3 in sulfur excess material. For five different composilions, Qc for undoped and bismuth-doped crystals has been found to be equal to Qpb + Qs, the self-diffusion activation energies for lead and sulfur in PbS. It is well-established1 that high-temperature steady-state creep of pure metals is a diffusion-controlled process, where the activation energy of creep is equal, within experimental error, to the activation energy of self-diffusion. The relationship between the activation energy for steady-state creep and those for self-diffusion in binary compounds is more complicated, however, because two different diffusing species must be considered, and becayse the activation energies may be influenced by compositional variations and by foreign atom additions.2-4 In some cases experimentally determined creep activation energies are correlated with those for self-diffusion of the slower-moving species, but such agreement is by no means universal. Interpretation of experimental results is difficult because few investigations include measurements of creep rates and self-diffusion coefficients of both diffusing species on single crystals of similar composition and foreign atom concentration. The objective of this investigation, therefore, is to determine the influence of stoichiometric defects and foreign atoms on steady-state creep and self-diffusion for a well-characterized binary compound. Lead sulfide, a compound semiconductor which crystallizes in the NaC1-type structure, and whose homogeneity range includes compositions on either side of the 1:l atom ratio, was chosen for study in this investigation. The pressure-temperature-composition relations for PbS are available,5,3 and deviations from stoichiometry may be monitored by electrical measurements.7 Single-crystal specimens are available to allow observation of effects due to bulk phenomena without interference from grain-boundary effects. These crystals have been employed to determine steady-state creep rates under compressive stress for "pure" and bismuth-doped PbS as a function of sulfur pressure and temperature as well as crystal orientation and applied stress in order to establish the relationships between defect concentrations and creep rates. EXPERIMENTAL PROCEDURES Crystal Growth. Lead sulfide crystals, prepared by the Bridgman method, are grown in evacuated quartz crucibles, filled with almost equal atomic proportions of high-purity (99.999 pct) lead and sulfur, and heated to a temperature above the melting point of PbS (about 1127°C) so that the lead and sulfur react to form molten PbS. The crucible and melt are dropped through the hot zone of the crystal-growing furnace at the rate of 1 cm per hr. The maximum melting point of PbS is slightly on the lead-rich side of the 50:50 composition; hence crystals grown from a near stoichiometric melt are usually n-type semiconductors containing excess lead atoms. Typically the lead excess concentration in solid solution with the PbS is 3 x 1018 atoms cm-3. Crystals containing either 1/20 or 1/2 mole pct Bi2S3 were prepared by addition of the foreign atoms prior to crystal synthesis. Preparation of Specimens of Controlled Stoichiom-etry. Since it is difficult to grow crystals of desired composition, the process of crystal growth and control of stoichiometry are separated into two distinct operations. Equilibration of as-grown PbS to a desired composition is most easily accomplished by first annealing the n-type crystals under high sulfur pressure (about 1 atm) at temperatures above 700°C. This process serves to put excess lead precipitates into solution, yielding 0 -type crystals upon quenching to room temperature. Inter diffusion occurs readily in crystals so treated, and the methods described by Bloem may then be employed to obtain crystals of controlled stoi-chiometry. For the creep measurements made in this study, this involves heating crystals in mixtures of H2 and H2S The equilibrium constant for H2S is given by: Thus the sulfur partial pressure is obtained from knowledge of the H2/H2S ratio and Kh2S for the temperature in question. Fig. 1 shows the p-T-x diagram for PbS. It can be seen that, within the stability limits for single-phase lead sulfide, desired compositions may be obtained by equilibrating under a specified sulfur pressure and temperature. Characterization of Crystals. The principal methods for evaluating PbS crystals include measurement of electrical properties and mass-spectrographic analysis. The measured electrical parameters include Hall coefficient, conductivity type, and electrical resistivity Bloem7 has shown that there is a 1:l relation between the defect concentration and carrier concentration obtained. Hence, if the contribution to the carrier con-

Jan 1, 1968