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By Joseph E. Worthington

The present-day Northumberland gold mine is one of the deposits generally characterized as a Carlin-type occurrence. It lies at the crest of the Toquima Range in Nye County near the center of Nevada. Gold mineralization occurs in two modes, in argillaceous and in silicified limestones, and is generally very fine-grained or micron gold. The Northumberland district has had a history that is typical of many western gold districts: minor production prior to World War II and intermittent exploration thereafter until a combination of geological insight, improved economics, and the advent of heap leach technology created the Northumberland gold mine. Nye County, Nevada, was sparsely populated and little explored in the early years of the settlement of the west; the Northumberland district was not established until 1866. Initial interest was in silver and the district operated as a very small producer for the next seventy years. The disseminated gold occurrences in silicified limestones were recognized and Northumberland Mining Co. was organized to develop the property in the late 1930s. Northumberland Mining Co. actually conducted drilling operations (over 200 drill holes) and mined from small open pits in the silicified limestones. They ultimately produced almost 936 kg (33,000 oz) gold before being shut down by War Production Board Order L-208 in 1942. After World War II gold mining activities were essentially nil for over a decade due to the poor economics of gold production. The property was, however, a known gold producer and attracted recurrent exploration attention. About 45 holes were drilled under the direction of Peter Joralemon for private interests between 1959 and 1963. Next Kerr McGee drilled about 25 holes during 1963 and 1964. Some- what later, in 1968, Homestake drilled 20 holes. The property was then acquired by Idaho Mining Co. which drilled about 30 more holes between 1972 and 1974. By this time the Northumberland mine was becoming somewhat shopworn with over 300 holes drilled. Interest in gold prospects was increasing substantially in Nevada, how- ever, due to rising gold prices in late 1974, and several companies were interested in continuing exploration at Northumberland. In 1975 Cyprus Mines Corp. was successful in obtaining a joint venture arrangement with Idaho Mining Co. for further exploration and development of the property. The overall Cyprus exploration program was under the direction of James G. Hansen, Vice President Exploration. The geologist recommending acquisition of Northumberland was Peter E. Chapman who reported to Joseph E. Worthington, Manager of U.S. Exploration for Cyprus. The basis for selection of the Northumberland mine as an exploration target for Cyprus by Chapman was essentially prior knowledge of regional and 16cal geology and of the mine. Exploration for the next few years was directed by Chapman under the supervision of Worthington. During 1975 and 1976 rotary and check core drilling were conducted that indicated that a substantial Carlin-type or disseminated, low-grade gold deposit occurred in two separate bodies. Drilling was based on geologic mapping and rock chip geochemical sampling. Both ore zones were reflected at the surface as gold and arsenic anomalies in rock chips. Heap leach tests attempted in 1977 were aborted by a flash flood, but were completed in 1978. Engineering studies occupied the next couple of years until the property achieved production in the fall of 1981. It is now producing by open-pit mining with gold recovery by heap leaching and cyanide extraction at a rated capacity of approximately 2722 t/d (3000 stpd) ore. Metal recovery has been projected (probably conservatively) at 5 10 kg/a (18,000 oz per year) gold and 1.6 Mg/a (59,000 oz per year) silver. Reserves are reported to be adequate for ten to fifteen years of production. REFERENCES Anon., 1981, "Gold in Nevada," Span Magazine, Vol. 21, No. 3, Standard Oil Co., pp. 6-9. Koschman, A.H. and Bergendahl, M.H., 1968, "Principal Gold- producing Districts of the United States, Professional Paper 610, US Geological Survey, p. 193. Kral, V.E., 195 1, "Minerals Resources of Nye County, Nevada, Bulletin, Vol. 45, No. 3, Geology and Mining Series 50, Nevada University.

Jan 1, 1985

Aamot, Olav Crone, Research Engr., Norsk Elektrokemisk Kongensgt, 18, Oslo, Norway ?29 Abbott, Clarence E., V.P., Charge of Raw Materials, Tenn. Coal, Iron & R. R. Co., 1242 Brown-Marx Bldg., Birmingham, Ala. '04 Abbott, Louis Benjamin, Chief Engr., Consolidation Coal Co., Watson Bldg., Fairmont, W. Va. '15 Abel, Raymond L., Asst. Prof., Dept. of Pet. Refin., Univ. of Pittsburgh Pittsburgh, Pa. '28 Abel, Walter D., Cons. Engr 364 S. Cloverdale Ave., Los Angeles, Calif. '32 Abele, Louis T 1457 Euclid Ave., Zanesville, Ohio. '31 Abell, Leo M Sullivan Concentrator, Chapman Camp, B. C., Canada. '31 Aborn, Robert H., Asst. Met., Research Lab., U. S. Steel Corp., Lincoln Highway, Kearny, N. J. '19 Abraham, W. E. V., East India United Service Club, 16 St. James' Sq., London, S. W. 1, England. '28

Jan 1, 1936

By William L. Langdon

PRELIMINARY COMMENTS Recent years have been difficult for the mining industry, as reported in the most recently published Minerals Yearbook (Volume III), the estimated value of world crude mineral production has been generally declining since an historical peak in 1979 (16).* The costs of mineral extraction have, however, been rising rapidly. Individual project costs are, in general, exceeding the growth rate of mining companies, while operating and technical risks continue to increase (16). Risks resulting from currency flotation and political actions in the host country are also on the increase. Labor difficulties (such as those experienced by Phelps Dodge) and the Reagan Administration's recent rejection of a proposal by the International Trade Commission for higher tariffs and/or quotas on copper imports have also contributed to the mining industry's difficulties. The net result of these factors has been financial difficulties for mining companies with respect to paying for their current financial obligations as well as trouble finding new financing. It may be that one of the main factors in determining the future of the mining industry will be centered upon capital structure, i.e. how its assets are financed. Historical Perspective on Capital Structure In The Mining Industry As discussed by Isreal Borenstein in (4) and Thomas Navin in (7), mining firms typically have used a financial model based upon high financial leverage, i.e. large amounts of debt relative to equity. This has been especially true for American firms developing orebodies discovered overseas. Problems sometimes occurred for those who were forced to commit themselves to completion guarantees in order to obtain bank loans. Mines under these circumstances must be brought into operation regardless of market conditions. Politicians in overseas countries also may use the high profits required by these high risk ventures to argue for nationalization of mines. Coupled with the frequent use of high leverage, mining companies traditionally have paid out a higher percentage of earnings in the form of dividends than manufacturing firms. This is significant, in that such funds paid out in dividends are not available for other uses. Hence, a greater reliance upon debt and/or additional stock issues than would ordinarily be the case for manufacturing firms. Thomas Navin has stated in (7), that the theory behind the high dividend payout was that, "most mining investors thought of themselves as investing in a wasting asset, one that would gradually deplete over time until it ultimately became valueless." Investors, therefore, required a receipt, in the form of dividends, of a percentage of current earnings and a return on original capital. This view of reality, apparently, has not changed in some quarters, even though modern mine management ordinarily replaces depleted mines with new ones. It may be that this practice of high dividend payout coupled with relatively high financial leverage should be reexamined. Current capital structure theory could prove interesting and useful for those concerned with current conditions. Capital structure patterns and related practices in this industry are not, in many cases, congruent with those thought by some to be theoretically optimal. Prelude to Capital Structure Discussion With a few notable exceptions (such as the Guggenheims and Anaconda's chief operating,. officer in 1971) mining companies' chief executives and boards of directors have not been persons with financial backgrounds. This, one could conjecture, might have accounted for the relatively nonsophisticated nature of capital structures of mining companies. In order to appreciate the possibilities with respect to alternative influence on a firm's performance, one must be acquainted with the basics of financial theory. This paper is an attempt to familiarize the reader with (1) capital structure in general, (2) the usual components of this structure, (3) the general theory behind the use of financial leverage, and

Jan 1, 1985

By H. Bartholomew, L. Bernstein

Experirmental bonds of Ag-In SLID to gold, copper, nickel, Kovar, Dumet, nickel-plated molybdenum, ALL-Pt vrzetallizing on ceramic, and nickel-plated Mo-Ti metallizing on Al2O3 ceramic have been made and exalnined. Metallographic taper sections were made of all bonds for Phase identification. In addition, failuve temperatltres were determined for bonds heated undev shear load. Sowe bonds were subjected to electvon-probe microanalysis. The ternary SLID system Ag-In-Sn was similarly evaluated. Plwtonticrogaphs and electron-probe data are discussed and related to over-all phase diagrams , diffusion effects, and wetting properties of the liquid. The rates of diffusion andor compound formation of gold, silver, and copper in indium and In-Sn liquids are found to descend in that order, as measured by the relatzve thickness of phase layers in the interfaces of bonds made at 200to 400°C. It is concluded that the SLID process enables one to produce bonds which are stable at high temperatures, after having been fabricated at low temperatures, and meet most requirements for application in interconnection, silicon bonding, or hermetic sealing of electronic devices. In a previous publication by one of the authors, the theory and principle of SLID bonding in simple binary systems was discussed. SLID bonding can be defined as a joining process using a preform with a laminated structure: a low-melting material clad on a high-melting core. During the bonding cycle a metallurgical transformation occurs such that the resultant structure can withstand, without reliquefying, temperatures higher than those at which the bond was made. The phases present in the joint interface region are high-melting compounds or, if equilibrium is reached, solid solution. Properties will depend on the phases present, ultimately approaching those of the solid substrate core of the SLID preform. The high-temperature strength of bonds made in these systems was correlated to phase identification in the interfacial bond regions from metallographic cross sections and electron-probe X-ray microanalysis data. When complex electronic components are assembled, multiphase systems result at the interfaces of bond regions. In these ternary and higher-order systems very little diffusion and phase-diagram data is available with which to predict the nature of the interfacia1 region that will result from conventional fabrication processes and subsequent field use of the component. Clarke and Rhines did early work in the field using the Al-Mg-Zn system as a vehicle. Guy and co-workers studied a portion of the Cu-Zn-Ni system and some mathematical4 and general5 aspects of multiphase diffusion. irkald' and coworkerse recently studied diffusion in the Cu-Zn-Sn system. No diffusion studies have been made on ternary systems directly applicable to this investigation but some phase diagrams are available: g-u-n, u-i-n, and CU-i-n. I) DESCRIPTION AND EXPERIMENTAL PROCEDURE The elements Au, Ag, Cu, Ni, In, and Sn are found in alloy systems commonly used in fabricating and assembling electronic components. Reference to the appropriate phase diagrams9 and the previous publication will indicate that the binary systems of any of the two low-melting elements, indium and tin, with any one of the other four higher-melting elements are capable of producing SLID bonds. It is not unreasonable to assume that any ternary or higher-order alloy system containing at least one of the elements gold, silver, copper, or nickel and one or both of the elements indium and tin could be used to produce bonds which are stable at high temperatures, after having been fabricated at low temperatures. Indeed, the liquidus contours and isothermal sections of those phase diagrams available7 do so indicate. The parameters affecting the bond and the equipment used in evaluating the bond were described in an earlier paper.' The current investigation used the

Jan 1, 1967

By M. L. Bleiberg, L. J. Jones

THE changes induced in metals by subjecting them to heavy particle bombardment have received widespread attention in recent years and results of such investigations have been reviewed by Slater, Dienes, Seitz, Siegel, and Seitz and Koehler.1-5 Of particular significance are the property changes that occur in uranium-base alloys due to neutron bombardment. These changes are generally very severe since fission occurs within the sample, resulting in the formation of heavy, highly energetic fission fragments, as well as additional neutrons born in fission, which serve to intensify the damage generally associated with fast neutron bombardment of nonfissionable metals. The property changes in uranium and uranium alloys due to neutron bombardment have been summarized by Paine and Kitte16 and Billington.7 It has also been shown that neutron bombardment of

Jan 1, 1959

By Peter H. Fletcher

THE ECONOMIC THEORY It will assist in the understanding of the Resource Rent Tax ("RRT") proposals in Australia if the economic theory behind the tax is briefly explained. The idea goes back to the concept of rent put forward by the nineteenth century economist David Ricardo. His analysis was broadly as follows: A tenant who farms land which is just on the margin of economic viability cannot afford to pay his landlord any rent, because the value of the crop produced by such marginal land is equal to the cost of producing the crop, plus the cost of keeping the tenant alive. There is nothing left out of which to pay rent to landlord. A tenant who farms good land can afford to pay his landlord rent -- but the maximum amount of rent that he can be asked to pay is the excess of the value of the crop produced by the good land over the cost of producing the crop and of keeping the tenant alive. Adapting this theory to the taxation of mining projects, modern economists who favour this system of taxation say that a profitable mining (or resource) project produces rent in the Ricardian sense. The amount of the rent is the excess of the profits by the project over the amount of profit which is required to attract the taxpayer to invest in the project in the first place. This explains why the tax is called "Resource Rent Tax". PAPUA NEW GUINEA PRECEDENT Although Papua New Guinea ("PNG") is now independent of Australia, there are still close links between the two countries, and strong similarities between their respective tax regimes. PNG introduced an Additional Profits Tax ("APT") in 1978. In many respects, Australia's RRT proposals follow the precedent set by PNG1s APT. However, in practical terms, not a great deal can be learned at this stage from PNG's experiences since, according to the writer's understanding, no PNG mining project has yet paid any APT. The Bougainville mine is not liable to APT, being subject to tax under its own separate Act, which contains a different formula. Outline of PNG Additional Profits Tax. PNG has two versions of Additional Profits Tax ("APT) - one applying to general mining, the other to petroleum mining. The two versions are very similar. The general mining version is described below. The tax applies on a licence by licence basis. This means that losses on Licence A cannot be offset against profits on Licence B. Expenditure relating to two or more licences, is apportioned "in such manner as the Chief Controller thinks reasonable". Tax is levied on the "accumulated value of net cash receipts" at the rate of (70 - n)% where n=the rate of income tax. The accumulated value of net cash receipts ("av") is calculated as follows: Calculations commence from the first year in which substantial expenditure was incurred on the construction of facilities for the carrying out of mining operations on the licence. For that year the av consists of the total allowable expenditure to date on that lease. For the second year, the av is the av at the end of year one indexed in accordance with the statutory formula set out below, plus the total allowable expenditure in year 2. For year 3, the av is the av at the end of year 2 adjusted by the index factors, plus the total allowable expenditure in year 3. This process is repeated year after year. When the licence starts to earn revenue, the revenue is deducted from total allowable expenditure for that year. If revenue exceeds total allowable

Jan 1, 1985

By B. R. Berger

The Getchell area in the northern Osgood Range, Humboldt County, Nevada, was first prospected in the late 1800s for silver, copper, and gold; the first recorded mention of mining activity concerned a silver discovery. The September 17, 1874 edition of the Winnemucca Silver State notes that the Crystal Mining District was newly organized in the Fremont Range (as the Osgood Range was then called) to include discoveries of silver, lead, and antimony made on the Louisa claim. The name Crystal was derived from the plentiful quartz crystals found in-cavities near the prospects. This same area, occurring on the northwestern margin of the Osgood granodiorite stock, was later mined as the Richmond tungsten property, and crystals may still be found there in cavities in a massive garnet tactite. By 1878, how-ever, the name Crystal had been abandoned in favor of Potosi. The next flurry of activity in the Osgood Range was reported in 1899 when a copper strike on Granite Creek in the southern portion of the range received attention. The copper occukences were in a granite contact zone on the southeastern edge of the Osgood stock and, in 1916, the first tungsten in the district was discovered in the same deposit. During the last part of the nineteenth century, cattle and sheep were brought into the Kelly Creek Valley east of the Osgood Mountains by various ranchers. Alphonso and Adrian Bernard were among these ranchers, and in the first decade of the twentieth century, one of them recognized the altered rock where the Getchell Center it is now located. A 3-m (10-ft) deep prospect pit was dug on the outcrop, but the highest assay ran about $11/t ($10 per st). No further work was done on the gold-bearing rock. In 1934, Emmet Chase of Battle Mountain and Ed Knight of Golconda prospected in the area of the Bernard prospect pit and located several lode claims. At this time, Noble H. Getchell, a state senator, was looking for new mining opportunities to develop. He held interests in the Gold Circle Consolidated at Midas, which was becoming a losing venture. Chase and Knight brought their discovery to his attention, and he grubstaked them to prospect further in the area. In need of financial backing, Getchell solicited the help of George Wingfield, Sr., who held a minor interest in the Gold Circle. Wingfield was a successful banker and mine operator during the heyday of Tonopah and Goldfield, and he had become good friends with Henry C. Frick and Bernard Baruch. Wingfield let Baruch in on several very successful mining ventures in Goldfield, and Baruch returned the favor by underwriting the financing of the Getchell mine. Eleanor Roosevelt and Jack Dempsey were early stockholders in the Getchell operation. George Wingfield brought his brother-in-law, Roy A. Hardy, a consulting engineer who had constructed the American Flat mill near Virginia City, to look at the property. Upon inspecting the Chase-Knight claims, Hardy declared the whole area to be mineralized. A crosscut was driven to check the extent of the ore, and the results were better than anticipated. The locators were reportedly given $50,000 for the claims. The Getchell Mine, Inc., was organized on November 5, 1936. A small railroad that ran from Battle Mountain to Austin was purchased, and the ties and rails were moved to Getchell to be used in underground exploration. Enough reserves were found in the Center and South pit areas to construct a 40 t/d (44 stpd) mill. The financial and engineering help for the mill was provided by the Newmont Mining Co. for a 17 1/2% interest in the corporation. Newmont set about trying to solve the metallurgical problems with the sulfide ore, and also directed the early development work. Newmont wanted to grind the sulfide ore underground and oxidize it in the atmosphere by spreading salt on it. Detrital Flat in Arizona was purchased to provide salt for

Jan 1, 1985

By R. A. Morse, C. R. Stewart, F. F. Craig

This paper preFents the results of a series of model flow test on a number of large limestone cores, having different pore configurations. For limestone cores having substantially sandstone type porosity, the production characteristics for solution and external gas drives are similar. For cores whose pore spaces were microscopically heterogeneous (i.e., consisted of combinations of solution cavities, matrix. and fissures), the production characteristics lor solution and external gas drives vary widely. The degree of divergence between gas-oil relative permeability relationships calculated from solution or external gas drive tests is an indication of heterogeneity of rock pore structure. The results of water floods on cores depleted by solution gas drive for each of these two general types of limestone porosity are also shown. Generalizations are made on the water flood recovery that could be expected from each of these two types of limestone porosity. The similarity between solution drive field performance and model solution drive performance on cores from the same formation is shown for several cases. This indicate? the feasibility of predetermining limestone field performance from such large core tests. Photomicrographs of plastic-impregnated rock thin sections of the samples tested are presented as an aid in understanding the flow test performances. INTRODUCTION During the past 15 years. reservoir engineers and research workers have developed methods of testing rock and fluid samples and applying the results, through calculation, to allow reasonably satisfactory predictions of oil recoveries and performances to be expected in sandstone oil recervoirs. It has been determined that representative fluid flow data can be obtained on rock samples as small as three-fourths in. in diameter by one in. long in most sandstones. However, little has been accomplished toward the laboratory determination of fluid flow characteristics in limestones. There has been a great deal of speculation as to the influence of variations in pore size, shape, and degree of interconnection upon oil recovery processes, and a great deal of thought has been given to the interpretation of limestone field perfomance. It has been generally recognized that predictions of reservoir performance based on oil displacement tests on small limestone core samples the size of those used for sandstone tests can often be misleading because of the improbability of obtaining a representative sample in such a small core. Obviously, if there are present in the rock, pore openings of the magnitude of 1/16 in., or fractures or solution channels up to one in. or more in length, it will be impossible to cut any sample less than one in. in any dimension which would represent the flow geometry of the gross rock system. In some formations, the individual openings in the rock are of such size that it would be impossible to obtain a good sample of the flow system even in the total core available from conventional-sized well cores. However, by increasing to the maximum the size of the sample used, it should be possible to obtain representative flow data from the majority of limestone reservoir materials which can be used for prediction of future primary production performance or response to be expected from secondary recovery measures. The only alternatives to obtaining good laboratory test data to serve these purposes are extrapolation of primary performance data obtained by partial depletion of a field, or obtaining information from pilot tests. It has been shown previously, and will be demonstrated further by the work reported in this paper, that extrapolation of solution gas drive performance for an estimate of gas injection response can be very misleading in reservoirs of heterogeneous type porosity. Although it cannot be expected that laboratory information can ever eliminate the necessity of small-scale pilot operations, it is expected, as is now the situation with sandstone reservoirs, that laboratory tests should provide reliable information for screening of

Jan 1, 1953

By Ludwig Thomas, Klaus Detert

Klaus Detert and Ludwig Thomas (Westinghouse Electric Gorp.)— The results of C. Panseri and co-workers are quite important. The authors came to the same conclusions about the occurrence of zone formation in A1-Mg alloys as was outlined in previous papers.31'32 Because of the sensitivity of their measurements, it was shown that zone formation could also occur at a much lower range of mag- nesium content than previously observed.31, 33 The idea of strong interaction between magnesium atoms and vacancies, as stressed by the authors, so that all of the quenched-in vacancies are kept in solution at lower temperatures but anneal out completely at 150°C, is in disagreement with our results which clearly indicate that zone formation and annealing out of vacancies occur simultane-

Jan 1, 1964

By Louis Huber

THE Liberty tunnels extend through a very steep hill in Pittsburgh (locally called Mount Washington) for a distance of slightly over a mile. The two tunnels parallel each other and are 59 ft. apart, center to center (Fig. 1). They are for vehicular traffic, and in each there is ample space for two lines of vehicles. Northbound traffic, towards downtown Pitts- FIG. I.-NORTH PORTAL OF LIBERTY TUNNELS. NOTE THE WINDBREAK AT END OFEAST TUNNEL. burgh, is confined to the east tunnel and southbound traffic to the west tunnel. The South Hills residential district is separated from downtown Pittsburgh by Mount Washington, a steeply rising escarpment south of and adjacent to the Monongahela River. The Mount Washington district immediately south of the Monongahela River has been reached, for many

Jan 1, 1927

NEW MEMBERS The following list comprises the names of those persons who became members during the period Jan. 1, 1917 to Feb. 10, 1917. ALLEN, ROBERT SEXTON, Chief Chemist at Concentrator, Inspiration Cons. Copper Co. Globe, Ariz. ALTIO, KARL FREDRIK, Min. Engr., The Sissert Mining District Co., Ltd., Polefskoy Zavod, Perm Government, Russia. ARGALL, PHILIP HENRY, Mgr., Ozark Smelt. & Min. Co., Magdalena, New Mexico. BAILEY, MARC Supt., Wolverine & Arizona Min. Co., Bisbee, Ariz. BAKER, DAVID FRANKLIN, Asst. Supt. of Blast Furnaces, Alan Wood, Iron and Steel Co., Swedeland, Pa. BATES, BENNETT R, Min. Engr 1025 Peoples Gas Bldg., Chicago, Ill. BECK, HOWARD A Shift Foreman, Aurora Cons. Mines Co. Aurora, Nev. BELL, LEO RICHARD Casilla 270, La Paz, Bolivia, South America. BENJAMIN, FLOYD SHAW, District Mgr., Aetna Explosives Co., Inc., 800 Torrey Bldg., Duluth, Minn.

Jan 3, 1917

By J. F. Kemp

Introduction The Bulletin of the Institute for March, 1911, is chiefly devoted to papers upon the iron ores of northeastern Cuba. At that time information about the new developments in the peculiar brown hematites of the region was becoming widely circulated and interest was especially keen. For some years exploration had been conducted with pits and trenches and so great an area had been shown to contain ore in the Mayari, Moa, and Cubitas or San Felipe districts, that the reserves conveniently situated for the consumption of American furnaces were estimated as quite two billions of tons. In the subjoined footnote will be found a list of the principal papers of special interest which have already been published.1 The further remark may, however, be made that the

Jan 2, 1915

NEW MEMBERS The following list comprises the names of those persons who became members during the period Aug. 1, 1916, to Sept. 10, 1916: ALLEN, Louis M., JR., Chief Mine Sampler, Old Dominion Min: & Smelt. Co., Globe, Ariz. ATKINSON, CHESTER, Min. Engr., Asst. Supt., Smelt. Dept., Cerro de Pasco Mining Co., La Fundicion, Peru, South America. BAKER, CLAIR LINCOLN, Genl. Mgr., Mexican Dept., Amer. Smelt. & Ref. Co., 1108 Mills Bldg., El Paso, Tex. BARROWS, WALTER A., 3d, Asst. Supt., Blast Furnaces, Thomas Iron Co., Hellertown, Pa. BARTHOLOMEW, GEORGE POMEROY, Asst. Cons. Engr., Guggenheim Bros., 120 Broadway, New York, N. Y. BILLOW, ELMER E., Pres., National Supply Co., 416 NN-rest Grand Ave., Chicago, 111. BROWN, SAMUEL ROLLINS, Mill Supt., The Plymouth Cons. Gold Mines, Ltd., Plymouth, Cal.

Jan 10, 1916

By George Moore

IN spite of many investigations of the occlusion of hydrogen in iron, the nature of the process and the reasons for the accompanying effects upon the metal are still open questions. This is in large part due to three causes: (1) the difficulty of obtaining iron of adequate purity as starting material; (2) the occurrence of allotropic transformations, which compli-cate the effects; and (3) the fact that the body-centered cubic modifica-tion does not lend itself readily to crystallographic investigation. The present paper attempts a critical review and correlation of the somewhat scattered and disconnected existing observations, and an experimental determination of the extent to which the conclusions that appear to follow from these are applicable to iron of really high purity, studied under well-defined conditions.

Jan 1, 1939

By Lauren A. Wright, A. E. J. Engel

Under the designations "industrial talc" and "soapstone" are included earth materials of widely different chemical and mineral compositions. Talc, the mineral, is a hydrous magnesium silicate, with a suggested theoretical formula H2Mg3(SiO3)4 or H2O.3MgO.4SiO2, which postulates 63.5 pct SiO2, 31.7 pct MgO, and 4.8 pct H20.18 Single grains or leaves of talc, however, seem to have variations in water content that range from 3.5 pct to more than 7 pct, as well as slight differences in the proportions of MgO and Si02.20 Most of the industrial talcs produced in the United States do not approach the composition given above (see Table 1), but are essen- [ ]

Jan 1, 1960

By Mark E. Smith

To allow recovery of gold values from ore which cannot be economically processed by the mill, Pinson Mining Company has developed a run-of-mine heap leaching facility. In order to estimate production scale recovery rates, reagent consumption and percolation problems, a series of pilot scale tests were performed. These tests typically consisted of 3,630 metric tons (mt) (4,000 tons) leach ore at a grade of .94 to 1.56 grams Au per metric ton (g/mt) (.03 to .05 oz. Au/ton). Test heaps were loader stacked to approximately 4.3 meters (14 feet) high. Information from these pilot scale tests was employed in the design and construction of the production scale facility. Parameters such as spray rate, leach cycle, sprinkler placement, and barren solution chemistry were determined by the pilot tests.

Jan 1, 1984

By Lombard Squires, W. K. Lewis, W. I. Thompson

Clays consist predominantly of hydrated silicates of alumina. The formula is frequently assumed to be A1203 . 2Si02 . 2H20,'and certain of I. North Carolina. Low plasticity. 11. Same as I, after washing. Low plasticity. III. Tennessee. Good plasticity. IV. Pennsylvania flint fireclay. Low plasticity. V. Laredo, Texas. Very plastic. CaO/Na2O corrected for GO2. VI. San Antonio, Texas. Fine grained, highly plastic. Moisture and CO2 were determined together at 18.8 per cent. VII. Selected crude bentonite, California. " Data from R. Ries: Clays. John Wiley & Sons, New York, 1927. them undoubtedly have substantially this composition, but in general the ratio of silica to alumina is considerably higher. However, they always contain water of chemical constitution, as shown by Table 1.

Jan 1, 1935

NEW MEMBERS The following list comprises the names of those persons who became members during the period Mar. 1 to 15, 1914: Members ADAMS, JOHN H., Cons. Engr First National Bank Bldg., Birmingham, Ala. ALEXANDER, WILLIAM H., Miner 80 Maiden Lane, New York, N. Y. AUSTIN, EDGAR TAYLOR, Asst. Smelter Supt., Mond Nickel Co., Ltd., Coniston, Ont., Can. BAKER, DANIEL, JR., Asst. Treas., Standard Lime & Stone Co. 524 Equitable Bldg., Baltimore, Md. BALL, MAX WAITE, Geologist U. S. Geological Survey, Washington, D. C. BARREN, HARRY B., Supt. Blast Furnaces, Inland Steel Co., Indiana Harbor, Ind. BAUMANN, HENRY N., JR., Amalgamator 365 Lynn St., Seattle, Wash. BLACK,, THOMAS B., Min. Engr Care Vulture Mines Co., Wickenburg, Ariz. BRADT, HARLAN H 429 West 111th_ St, New York, N. Y.

Jan 4, 1914

By W. B. Agocs

In August 1954 a low altitude test geophysical survey was made in the Green Pond area of Morris County, New Jersey, with a Gulf Research and Development Co. Model I1 total magnetic field variation magnetometer mounted in a Sikorsky S-55 helicopter. The test was made in this area to compare the results of a high precision, very low altitude magnetometer survey with an existing ground magnetic survey in this area having known magnetite concentrations, so that the method could be used in areas of difficult access for the detailing of airborne magnetometer anomalies of interest in place of ground surveys. The load capacity of the Sikorsky S-55 permitted installation of a recording scintillation counter so that a radioactivity survey would be made simultaneously with the magnetometer survey.

Nov 1, 1955

By W. C. Knopf, G. Samsel

For several years International Minerals & Chemical Corp. has used a radiation method to assay potassium content of products from potash and feldspar beneficiation. The procedure is rapid, accurate, and inexpensive and is easily handled, if necessary, by nontechnical personnel. Data are presented to show the accuracies that may be expected if the technique is used for control of pilot plants or large- scale plants. Natural potassium is composed of three isotopes -K39, K40 and K41. Five other isotopes, artificially produced, have been detected. In natural potassium only the K40 isotope, with a half life of 1.4 x 109 years, is radioactive. Its modes of decay are beta and gamma rays, positrons, and x-rays. Only the more abundant beta rays, however, are important in radiation measurements using geiger tubes.

Jan 10, 1958