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By Carl L. Renzoni

INTRODUCTION This paper defines equity as the issuance of a permanent interest in the business on a broadly distributed basis. As such, it excludes the issuance of equity to either a merchant bank or to another corporation. Nearly twenty years ago the equity markets were very simple: The instruments used were primarily common shares, convertible debentures or convertible preferred shares. Another equity-type option often used, especially by junior companies, was the sale of joint venture interests. Issue sizes were generally in the order of $25 - $100 million and issues were syndicated primarily in North America and Europe by one or two investment dealers. Mining corporations today benefit from a market with much more depth. Issues are syndicated by dealers on a truly international basis, and issue sizes now often range up to $300 million. Moreover, dealers are now willing to take significant risk in buying the issues for redistribution. This discussion of trends in equity markets will encompass: 1) common shares 2) warrants to buy common shares 3) convertible debentures 4) commodity backed instruments A review follows of events that affect the mining industry and investment dealers as they have a bearing on the equity markets for the metal producers. FACTORS AFFECTING THE MINING INDUSTRY The current business cycle, up to October 1987, had been characterised by a buoyant stock market and depressed base metal prices. Mining companies entered this period with weak balance sheets and little prospect of cash flows meeting capital needs. The issuance of equity and the sale of assets were used extensively to reduce debt to manageable levels. During this period, the relative high price for gold, and more important, the very high earnings and cash flow multiples afforded to gold producers, caused companies to target gold as the only game in town. The need for capital to acquire and develop gold properties prompted an unprecedented volume of equity issues. (Burns Fry led or co-managed over $1 billion of mining equity issues per year during this period). This high demand for equity capital by the industry prompted an increase in the use of equity instruments, such as commodity backed instruments. In addition, government tax incentive programs in Canada, such as flow-through shares, allowed smaller companies to raise significantly more equity than would otherwise have been possible. Over $1 billion in flow-through equity was raised in 1987 alone. The abundance of flow-through capital in Canada made it easy to form a new company. One flow-through share fund developed a system of providing the working capital required for a company to be eligible to receive flow-through share capital so that an entrepreneur required only a mining property to get started. Many new companies were formed and several flourished in a buoyant stock market environment to the point that market capitalizations grew to $100 million or more. The current period is in stark contrast to that before October 1987. The equity markets are generally available to the resource industry only on a window basis and only for senior companies and for special situations. The industry is benefitting from buoyant metal prices, and bankers are anxious to provide debt capital. Investment dealers previously processing several equity issues

Jan 1, 1990

By J. HUNER

Twenty-four new fields were found in Louisiana during 1945. Of this number 15 were oil fields, eight were gas condensate, and one a dry gas field. None of these fields, with the exception of West Delhi, is as yet of any great consequence. The Weeks Island field in Iberia Parish may eventually develop into a considerable reserve.

Jan 1, 1946

Coal - Surface Mining Coal Preparation Coal Utilization Research and Development Health and Safety

Jan 3, 1976

By G. S. Hume

Production of petroleum and natural .gas increased in Canada in 1940 over the previous year. Alberta produced more than 97 per cent of the total Canadian production of 8,718,053 bbl. of oil, an increase for this province of nearly 12 per cent, whereas in Ontario and New Brunswick, where the production is relatively small, there was a slight decline. In Alberta the main producing field is Turner Valley, on the eastern edge of the foothills southwest of Calgary, and development continued in this field in 1940 with the completion of 36 wells, all of which obtained production. In the Red Coulce field, close to the International Boundary, near Coutts, no new wells were drilled and the seven producing wells showed a decline of 900 bbl. below the previous year. Also, in the Wainwright field of east central Alberta, four wells, yielding heavy crude oil, produced 4000 bbl. less oil than in 1939, owing possibly rather to discontinuous operation than to actual decline in potential yield. This decline was more than offset by production from a new field 40 miles northeast of Wainwright, at Borradaile, producing oil of 14" to I 5° A.P.1. There was a small increase in production during 1940 from the Del Bonita field, in southern Alberta, where the production is from two wells. The outstanding development of the year was the completion of Standard Oil Princess No. 2 well in the Steveville area, on the Plains 100 miles east of Calgary. This well was completed late in December with an initial flow1 of 520 bbl. of 26.3" A.P,I. oil, and 12,750 M cu. ft. of gas from the upper part of the Mississippian limestone. It has opened up a new field and given a further proof of the potentialities of the Southern Plains. The production of petroleum in Canada is shown in Table I. Since most of the yield comes from Alberta, the production is shown from the various fields in Table 2. The sale value of the petroleum produced in Canada in 1940 exceeded 11.1 million dollars, which is still somewhat less than the value of the natural gas production, shown in Table 3. Table i.—Production of Petroleum in Canada" Barrels Province 1939 1940 New Brunswick........ 20,101 21,161 Ontario............... 206,196 186,471 Alberta............... 7,595,000 8,493,237 Northwest Territories. . 17,013 8,493,23717.184 Total............... 7,838,310 8,718,053 Value............... $10,353,351 $11.113,000 0 Bureau of Statistics, Ottawa. Turner Valley, Alberta Turner Valley continues to be by far the largest producing field in Canada (details are given in Table 4), The limits of the Pr in- field are now Known. On the east the oil area is bounded by the gas cap, which in turn is cut off on its east side by a major overthrust fault; on the west, ii is defined by edge water at a level of 4roc

Jan 1, 1941

By G. S. Hume

Production of petroleum and natural .gas increased in Canada in 1940 over the previous year. Alberta produced more than 97 per cent of the total Canadian production of 8,718,053 bbl. of oil, an increase for this province of nearly 12 per cent, whereas in Ontario and New Brunswick, where the production is relatively small, there was a slight decline. In Alberta the main producing field is Turner Valley, on the eastern edge of the foothills southwest of Calgary, and development continued in this field in 1940 with the completion of 36 wells, all of which obtained production. In the Red Coulce field, close to the International Boundary, near Coutts, no new wells were drilled and the seven producing wells showed a decline of 900 bbl. below the previous year. Also, in the Wainwright field of east central Alberta, four wells, yielding heavy crude oil, produced 4000 bbl. less oil than in 1939, owing possibly rather to discontinuous operation than to actual decline in potential yield. This decline was more than offset by production from a new field 40 miles northeast of Wainwright, at Borradaile, producing oil of 14" to I 5° A.P.1. There was a small increase in production during 1940 from the Del Bonita field, in southern Alberta, where the production is from two wells. The outstanding development of the year was the completion of Standard Oil Princess No. 2 well in the Steveville area, on the Plains 100 miles east of Calgary. This well was completed late in December with an initial flow1 of 520 bbl. of 26.3" A.P,I. oil, and 12,750 M cu. ft. of gas from the upper part of the Mississippian limestone. It has opened up a new field and given a further proof of the potentialities of the Southern Plains. The production of petroleum in Canada is shown in Table I. Since most of the yield comes from Alberta, the production is shown from the various fields in Table 2. The sale value of the petroleum produced in Canada in 1940 exceeded 11.1 million dollars, which is still somewhat less than the value of the natural gas production, shown in Table 3. Table i.—Production of Petroleum in Canada" Barrels Province 1939 1940 New Brunswick........ 20,101 21,161 Ontario............... 206,196 186,471 Alberta............... 7,595,000 8,493,237 Northwest Territories. . 17,013 8,493,23717.184 Total............... 7,838,310 8,718,053 Value............... $10,353,351 $11.113,000 0 Bureau of Statistics, Ottawa. Turner Valley, Alberta Turner Valley continues to be by far the largest producing field in Canada (details are given in Table 4), The limits of the Pr in- field are now Known. On the east the oil area is bounded by the gas cap, which in turn is cut off on its east side by a major overthrust fault; on the west, ii is defined by edge water at a level of 4roc

Jan 1, 1941

By Heinrich Ries

Fullers' earth is a clay-like substance, which has the property of decolorizing or clarifying oils. An ultimate chemical analysis shows it to differ from most ordinary clays in having usually a high percentage of combined water and a low amount of alumina. There is probably a large amount of hydrous silica present. Fullers' earth possesses little or no plasticity, and in order to work properly has to be ground very fine. A chemical analysis is of little value at present in determining its quality; only a practical test suffices. Up to about two years ago all of the fullers' earth used in this country was imported from England; but about that time deposits were discovered in Florida, "† and since then rumors of its occurrence have been coming from all parts of the country. Next to the Florida deposits of fullers' earth, those of South Dakota are the most extensive thus far discovered in this country. The earth was first discovered near Fairburn, Custer county, and other deposits have since been prospected at Argyle, Minnekahta and other localities. Fairburn.—One of the first deposits located and opened up is five miles southeast of Fairburn, Custer county. The mine is a mile from the Fremont, Elkhorn and Missouri Valley Railroad, and the section exposed shows, beginning at the top: Feet. Micaceous sandy clay,......... 6 Fullers' earth,..........9 Micaceous sandstone,......... The fullers' earth passes upwards into the sandy clay, but in its purer portions it is a yellowish, gritty clay, with a somewhat

Jan 1, 1898

By Gieskieng, D. H.

Published tables of jaw crusher capacities are compiled for the most part from field performance data, interspersed with interpolations, extrapolations, various safety factors, and other modifications. Such a table attempts to balance and equalize field data from widely different materials, with differences of crushability, efficiency of feeding, sizing of the feed, and so on. The tests described in this paper were undertaken with the objectives of checking previously reported capacities; of studying the effects of various factors upon the capacity, including jaw plate curvature; and, if possible, of deriving a general capacity equation. Such an equation has been derived from the data obtained in these tests. It is given together with factors for its use. While more accuracy than is usually required may be obtained by careful application of the equation, it is of simple form and provides a convenient reference plane upon which the potential capacity of various crushers may be compared, and with which operating adjustments may be made on existing installations. The principal deviation in these tests from the usual approach consists of a laboratory technique which has been developed for the production of selected

Jan 1, 1949

By D. R. de Fontaine

By computing the values of the resolved shear stress for a great many orientations of the tensile axis on all 12 (111) <110> slip systems, Taylor and Elam&apos; were able to map out a stereogram of slip systems, given here, Fig. 1, in Diehl&apos;s notation (see, for example Hauser and Jackson&apos;). The purpose of the present note is to derive such a stereogram by mathematical reasoning and to give a simple method of defining the system with highest resolved shear stress for any direction of the tensile axis, thereby eliminating tedious computation of the Schmid factor. Let the tensile axis, of direction cosines [xyz], make the angles 0 and relative to the slip plane normal [HKL] and the slip direction [hkl] respectively. Fig. 2 shows a simple cubic cell whose edges define a Cartesian coordinate system. Let A be a unit vector of origin 0 supported by the tensile axis. Its end point [xyz] then lies on a sphere of unit radius, on the positive hemisphere of which the planes z = 0, x = y, y = z limit the so called primitive triangle of a standard [loo] stereographic projection. For any point of this triangle, the following hold: 0«2 «y *sx « 1 [l] Now, for given [xpz], the most highly stressed system will be the one for which the following expression of the Schmid factor has the largest possible value: (HKL) belonging to the form (111) and [hkl] to the form <110>, the denominator on the right hand side of Eq. [2] is equal to 1.fi.a. The unknowns H, ... h, . . . can now be determined by correctly distributing +1 and -1 to H, K, L, and +1, -1,O to h,k, 1 giving the numerator of Eq. [2] its greatest positive value (the angles 0 and cpare chosen acute) subject to the condition: Hh+Kk+Ll = 0 [3] since the slip direction must lie in the slip plane. Condition [3] can be satisfied only by having one of its terms vanish and the other two equal to +1 and -1. Taking the case of the tensile axis lying in the primitive triangle, x2y, z and therefore Hh will be chosen equal to +1 with H = h = +1 in order to retain a maximum of + signs. There remain two alternatives: either 1 = 0 or k = 0. 1) take 2 = 0 Then Kk = -1 and the numerator of [2] becomes: Retaining a maximum of + signs gives L = k = +1 and becomes: 2) take k = 0 Then L1 = -1and, likewise, the numerator of [2] becomes: xz - z2 + xy + yz [5] But the difference [5] - [4] can be written: (y - z)(x+y +z) [6] positive or zero by virtue of [I]. If [6] is positive (y > z), then the largest possible value for the numerator of [2] for any xyz inside the primitive triangle is given by [5], i.e., for: That is to say, the active slip system corresponding to an orientat:~on of the tensile axis inside the primitive triangle is:

Jan 1, 1962

By Dick Whittington, W. R. Taylor

GENERAL In mid-1974, a representative of ARCO Petroleum Company walked into our Austin offices and asked for a permit for ARCO&apos;s first Clay West Mine site. This was the first in situ uranium mining permit issued in the United States. That initial permit, issued in January 1975, was for three acres. The four years since have been characterized by growth and change. Today there are 16 permits approved for approximately 1,540 production acres issued to five companies at eight sites in four counties. There are approximately seven additional permit applications being processed or on the verge of being submitted for an estimated 2,000 additional acres of production. As a rough gauge of the financial scope of this activity, at the typical 40 production wells per acre and an estimated $2,000/well, operators hale installed or committed $122 million for production wells. This does not account for the exploration and development wells installed to delineate the ore or the cost of processing facilities for extracting the uranium. HISTORY OF URANIUM MINING IN TEXAS Information I have concerning early in situ uranium mining activities is "sketchy" but the apparent first on-site test of in situ uranium mining was conducted between 1967 and 1971 at the Dueterstat site, north of Yorktown in Gonzales County, by City Service. Others ran tests at the Bruni site in Webb County and the Burns and Clay West sites in Live Oak County in the mid-70&apos;s. During this period, Texas Water Quality Board personnel in the central and district offices maintained a general surveillance of these various test activities. Regulation of in situ uranium mining was formalized with the issuance of a permit in January 1975 with the advent of ARCO&apos;s initial production scale (3 acre) effort in the Clay West area at the Moser mine site. Since 1975, the accelerating rate of mining and exploration activity is noticeable. There were 16 exploratory rigs operating early in 1977. This year, the rig count is averaging 46--a 287% increase. HISTORY OF LEGISLATION Paralleling this mining activity was state and federal legislation which subjected in situ mining to environmental regulation. The following is a brief chronology of the legislation that is directly or indirectly related to uranium mining. As most of you know, disposal wells are an integral part of most in situ uranium mines operating in Texas. They are used both during production and during aquifer restoration following production. The wells are regulated by the Texas Injection Well Act, enacted in 1961 by the Texas Legislature. In 1967, the Water Quality Act established the Texas Water Quality Board, and provided for the regulation of water quality by the so-called permit system. In 1969, the Solid Waste Act was enacted by the Texas Legislature. The legislation provides for control of wastes from manufacturing, mining, and agriculture. This Act regulated uranium surface mining activities until 1975 when the Texas Surface and Mining Reclamation Act placed responsibility with the Railroad Commission for uranium open-pit mining and surface mining of coal and lignite. In 1972, the Federal Water Pollution Control Act (Public Law 92-500) was passed. This legislation forms the legal base for the NPDES (National Pollutant Discharge Elimination System) and the subsequent point source effluent guidelines and standards. The November 6, 1975 issue of the Federal Register published interim final rules for Best Practical Treatment levels for effluent discharges from ore mining and dressing operations. Litigation was immediately initiated by eleven companies against these proposed rules, and they are currently being reconsidered for reissuance in 1979. In 1974, the Federal Safe Drinking Water Act (Public Law 93-523) was enacted. A part of this legislation is the Underground Injection Congrol Program. The regulations implementing this program have undergone various public hearings and it is expected that they will be published in the Federal Register before the end of 1978. In 1975, the Texas Surface Mining and Reclamation Act (Senate Bill 55), providing for the Railroad Commission&apos;s authority to require reclamation of surface mines, was passed. In 1977, an amendment to Senate Bill 55 was introduced that proposed to place regulation of in situ mining of coal, lignite, and

Jan 1, 1979

By M. Hoch

Equations are derived from statistical considerations to represent the activities of each component of an interstitial solution, and of a compound with a wide homogeneity range as a function of composition and temperature, based on the interaction energies between the various components, Eij. The equations are checked on the binary systems Fe-C, Ta-H, and Y-H, the ternary systems Ti-O-H, liquid Fe-C-0, and the compounds TiO, MnO, COO, and YH,. In all cases the present model represents the experimental data well. THE aim of this paper is to derive from statistical considerations the thermodynamic behavior of non-substitutional solid solutions. "Nonsubstitutional solid solution" means either an interstitial solid solution (carbon in iron, oxygen and hydrogen in hexagonal and bcc titanium, and so forth) or deviation from stoichiornetry in compounds (introduction of vacancies—removal of atoms in one or both lattice sites of compounds FeO, MnO, TiO, NbO, YH2). wagnerl and Fowler and Guggenheim considered the theory of compounds with small deviation from stoichiometry; Anderson includes larger deviations from stoichiometry, the defect being present in one component only, as vacancy and interstitial. Rees considers only vacancies in one of the components and introduces various kinds of sites for the component where the defect occurs; the various sites interact with different energies, thus giving isotherms with two or more plateaus. Both Rees and Anderson are mainly occupied in determining the limits of two-phase regions, and the defect interaction energy is determined from the critical point. Darken and Gurry5 gave a brief treatment of carbon solution in iron; Speiser and spretnak calculated the configurational entropy for binary interstitial solid solutions by assuming that each interstitial atom in the solution excludes a certain number of neighboring interstitial sites from occupancy. Use will be made of this concept later. Hoch et al treated transition metal oxides of the NaCl-type structure, and also oxygen solution in titanium.&apos; The main aim was to determine the behavior of the activity of one of the components as a function of the composition in the single-phase region. In the present paper, the various interaction energies are discussed in detail and the similarity between interstitial solid solutions and deviation from stoichiometry in ionic compounds is shown. Both types of systems have in common that at least on one kind of lattice site only one kind of atom occurs; this gives a fixed frame to the system, permitting a much easier statistical treatment than for the substitu-tional solid solutions. (The theory is also applied to ternary systems.) The difference between an interstitial solution and deviation from stoichiometry can be explained as follows. In an interstitial solution in the pure or standard state the host atom or host structure is present alone and all the interstitial sites which are going to be filled when the interstitial atom is introduced are empty. The interstitial solution is now created by introducing atoms into this empty lattice. In the deviation from stoichiometry, both kinds of lattice sites are already occupied in a special fashion (all lattice sites occupied, or the same fraction of lattice sites empty, or one kind completely filled, the other only two-thirds). Deviation from stoichiometry removes atoms from lattice sites, adds them, or removes atoms from one kind of lattice site and introduces them on the other lattice site. Though both cases (interstitial solution and deviation from stoichiometry) lead almost to the same equations, they are treated separately. The treatment given below corresponds to the "regular solution"10 treatment of substitutional solid solutions. Speiser and spretnak&apos;s6 treatment is similar to the athermal solution in the substitutional use. a) INTERSTITIAL SOLID SOLUTIONS Theory. It will be assumed that there are N lat-tice sites occupied by the host atom (denoted by 1). Corresponding to those N lattice sites there are N octahedral and EN tetrahedral interstitial sites. If only one kind of interstitial atom is added, this in-

Jan 1, 1964

Discussion, at the Virginia Beach Meeting, February, 1894, of the Paper of Prof. Posepny. (Trans., xxiii., 197, 587.) Including communications subsequently received. a T. A. Rickard, Denver, Colorado (communication to the Secretary) : The paper of Professor Posepny was printed so short a time

Jan 1, 1895

By J. Mizrahi, A. M. Baniel, A. Mitzmager, S. Star

This article gives an account of the latest developments in the use of TBE for sink-float separation of silicate minerals. A number of minerals for which the process has been tested and found suitable are reviewed. Specific examples are discussed in relation to the particular problems of sink-float separation and recovery of TBE as compared with non-silicate minerals. The economic aspects are outlined. Silica and silicates comprise the most common and abundant group of minerals, and since they are present in variable amounts in most ores, they constitute an appropriate subject for the review and discussion of the recent developments in the use of TBE for mineral concentration. The silicates considered as a group have an extremely wide range of chemical and physical properties. Some of these properties, which are common to all minerals, are of importance to concentration by TBE and are discussed in some detail in this paper, as well as the development of methods and apparatus for concentration and recovery of TBE and several examples of concentration of silicates. PROPERTIES OF MINERALS WITH RESPECT TO CONCENTRATION BY TBE The properties considered as most important to concentration by TBE are specific gravity, structure, surface and shape. The specific gravity of a mineral is a fundamental property and is constant between very close limits for the same species of different sources if particles are pure and free from cavities or cracks. In many species, however, solid inclusions and changes in chemical composition due to replacement of elements cause variations in the specific gravity. The plagio-clase series of feldspars between albite and anorthite illustrate this point (specific gravity from 2.60 to 2.77). Fig. 1 shows the specific gravity distribution of some of the common silicate minerals.&apos; The highest specific gravity is about 4.7 (zircon) and the lowest is 2.0 (sepiolite), with most of them ranging between 2.6 and 3.5. Although most of the silicates given in Fig. 1 are found as constituents of rocks, those generally considered as rock making minerals are comparatively few. They include quartz, feldspars, nephelite, sodalite, leucite, mica, pyroxenes, amphiboles, chrysolite, kaolin, talc and serpentine. These minerals may appear in igneous rocks as coarse crystals in granites, syenites and diorites or as very fine grained dispersions in basalt and felsite. When the latter rocks occur in an ore, their specific gravities depend on the minerals present and structure. The same is true for the sedimentary and metamorphic rocks (sandstones, shales, gneiss, slate, schists). A comparison of specific gravities for the minerals listed in Fig. 1 with that of TBE (see Table I) shows that the important rock-forming minerals, with the exception of pyroxenes, amphiboles and chrysolite (olivine), lie in the specific gravity range of less than 2.96 and can therefore be separated by TBE. The ore structure is important both in determining the apparent specific gravity and the efficiency of TBE recovery. The structure can be compact (as in

Jan 1, 1963

By Robert Linton

AT its meeting on May 21, the Board of Directors approved the recommendations submitted by President Lovejoy and named a nominating committee for the year that is especially well distributed as to major technical interest and as to geography. As may be seen from the list published herewith, two come from the East, two from the Midwest, and three from the far West. Mr. Linton, the chairman, has been a valued member of the Institute for 36 years. A memorandum drawn up by Paul D. Merica, representing the A.I.M.E., and W. R. Barclay, representing The Institute of Metals of Great Britain, setting forth a reciprocal plan for special memberships in each Institute for members of the other, was discussed. Both societies already have formally approved the plan in principle and Dr. Merica was clothed with full authority to agree on a few small details that have not been settled, and conclude the arrangement in behalf of the Institute.

Jan 1, 1936

By W. J. Romanow

RECENT papers by Williams, Sherwood, and Boothby,1 Seybolt et al.2 Heikes; and Roberts4 attest to the increasing importance of the hexagonal ferromagnetic compound MnBi. Since the magnetic properties of MnBi crystals are highly anisotropic, it is useful and necessary to have appropriate aids for determining their orientations—a (00.1) standard stereographic projection and a corresponding table of crystallographic angles for this structure. The tables of crystallographic angles for the hexagonal system available in the literature5 are computed for c/a ratios greater than that of MnBi and cannot satisfactorily be used to find the crystallographic angles of MnBi. A table of angles between the crystallographic planes (HK.L) and (hk.1) was calculated for MnBi from the formula0 F=are cos Hh+Kk+ 1/2(Hk+hK) + 3/4 (a/c)2Ll/v(H2 + K2 + HK + 3/4 (a/c)2L2) (h2+ k2+hk + 3/4 (a/c)2l2) on an IBM Type 650 Magnetic Drum Data Processing machine. The lattice constants used are listed in Table I and are those determined by Willis and Rooksby7 at 20°C. More recently published values obtained by both X-ray and neutron diffraction"&apos; show no difference from these significant to the calculation. From the crystallographic angles between the basal plane (00.1) and the general plane (hk.1) in Table I, an (00.1) standard stereographic projection was made for MnBi which is shown in Fig. 1. Acknowledgments The author wishes to thank R. G. Treuting and J. N. Hobstetter for their technical assistance, and Miss D. P. Booth for programing the IBM machine for the calculations. He appreciates the opportunity to read the paper of B. W. Roberts of General Electric Co. prior to its publication. References 1H. J. Williams, R. C. Sherwood, and 0. L. Boothby: Bulletin Amer. Physical Soc., 1956 vol. 1, p. 132. 2 A. U. Seybolt, H. Hangen, B. W. Roberts, and P. Yurcisin: AIME Trans., 1956, vol. 206, p. 605: Journal oF Metals, May 1956. 3R. R. Heikes: Physical Review, 1955, vol. 99, p. 446. .B. W. Roberts: A Neutron Diffraction Study of the Structures of Manganese B.W.Roberts:ANeutronDiffractionBismuthide, Physical. Review, 1956, vol. 104, p. 607. 5 A. Taylor and S. Leber: AIME Trans., 1954, vol. 200, p. 190; JouRNal of Metals February 1954. « C. S. Barrett: Structure of Metals, 2nd Ed., p. 635. McGraw-Hill Book Co. New York and London, 1952. 7B. T. M. Willis and H. P. Rooksby: Proceedings Physical Soc., London, 1954, vol. 67B, p. 290.

Jan 1, 1958

By Spencer S. Shannon

This chapter is concerned with the uses, geology, exploration, evaluation, preparation for markets, and future of 90thorium and 39yttrium, along with 14 rare-earth elements. The rare-earth metals or lanthanides were divided into three categories by Berzelius. The cerium subgroup is comprised of 57lanthanum, 58cerium, 59praseodymium, 60neodymium, and 62samarium. 61Promethium does not occur naturally. The terbium subgroup includes 63europium, 64gadolinium, and 65terbium. The remaining lanthanides are placed in the yttrium subgroup. Strictly speaking, yttrium is not a rare earth. Because the properties of yttrium resemble those of heavy rare earths, its name has been used as a designating adjective. The yttrium subgroup includes 66dysprosium, 67holmium, 68erbium, 69thulium, 70ytterbium, and 67lutetium. Rare-earth elements, especially those of the same subgroup, tend to occur together rather than in discrete minerals.

Jan 1, 1975

By Robert H. Richards

Tuns truly remarkable machine was built on a preliminary scale in May, 1895. The first full-sized table was built by Mr. A. R. Wilfley, and was used in his own mill in Kokomo in May, 1896. The first table sold for installation was placed&apos; in the Puzzle mill, Breckinridge county, in August, 1896. The mill enthusiasts at first hailed it as the cure for all the ills that flesh is heir to in the milling line. A little later it was found to make losses which were serious, and on this account the table succeeded only to a limited extent in displacing the vanners of the gold-mills. Still later, mill-men in a number of districts throughout the country made special studies of the faults of the machine, and devised a number of ways of grouping supplementary machines to overcome as far as possible the losses, and at the same time retain the benefit of the extraordinarily large capacity accompanied by the production of clean concentrates for which the machine has become so justly famous. I hope to make an exhibit of some of these methods in an appendix to my book on ore-dressing which is now in preparation. These experimenters have not written up the subject, and if they possess all the facts they have not given them out for the benefit of the mining profession at large. The object of this paper is to obtain the facts and to pre¬sent them so clearly that their bearing can be seen by all. To this end two complete series-&apos;of tests have been planned. One (the present paper), to study concentration of galena in presence of quartz; the other (to follow shortly), to study concentration of chalcopyrite in presence of quartz. Some authorities claim that the table does its best work when treating natural products; by this phrase I mean products which have been crushed to pass through a limiting

Jul 1, 1907

By W. J. Helfrich, R. A. Dodd

Binary aluminum solid-solution alloys containing various amounts of silver, magnesium, and zinc were prepared by careful directional solidification, and the hydrostatic and X-ray densities were compared. With the exception of the Al(Ag) alloys, the X-ray densities were consistently greater than the hydrostatic measurements, in agreement with earlier observations by Ellwood. In contrast to Ell-wood&apos;s interpretation in terms of vacant lattice sites associated with Brillouin zone effects, a tentative explanation based on the existence of solidification microshrinkage was favored. This hypothesis was confirmed by an examination of Al(Zn) alloys prepared by vapor diffusion of zinc into aluminum. The hydrostatic and X-ray densities were now in very close agreement, and it was concluded that the filling of Brillouin zones in aluminum solid-solution alloys does not necessarily result in the formation of defect structures containing an excess of vacant lattice sites. ThE existence of defect structures of the vacancy type in alloys in which the excess vacancies have an electronic rather than a thermal or mechanical, and so forth, origin is well recognized. Examples of incomplete lattices of this type are to be found in the Ni-Al,1-3 Fe-Ni-A1,4 c~-Ni-Al,5 Fe-Cu-Al,= and Co-A17 systems. These defect structures are of a special kind in that the intermediate phases possess an ordered atomic arrangement or superlattice, and in some instances the vacancy concentration may be unusually large, e.g., at 45.25 at. pet Ni in NiA1, approximately 8.8 pet of the lattice sites are unoccupied. Ellwood8-10 has reported similar defect structures in the aluminum solid solution alloys of the Al-Zn and A1-Mg systems and in alloys of the Au-Ni system." In Al(Zn) the (apparent) vacancy concentration rose, somewhat irregularly, to a maximum of about 2 pet vacant sites at 25 at. pet Zn, while in Al(Mg) the (apparent) vacancy concentration increased continuously to 1.7 pet at 15 at. pet Mg. An explanation in terms of Brillouin zone overlap was attempted, although Pearson12 has pointed out the difficulty of reconciling the observations with zone theory. However, the possibility of the effect being caused by the Fermi surface just touching a plane of energy discontinuity inside a prominent Brillouin zone has, in general, been accepted. In fact, Massal-ski13 has interpreted Ellwood&apos;s8 observations as confirmation of Leigh&apos;s14 theoretically predicted zone overlap occurring at approximately 2.67 electrons per atom. Unfortunately, Massalski was apparently unaware that Ellwood9 had revised his earlier results considerably, and the revised data did not confirm Leigh&apos;s analysis. Ellwood&apos;s clata were reexamined by the present authors who noted a possible correlation between the percentage defects as a function of alloy composition and the temperature interval of solidification measured from the respective equilibrium diagrams. This suggested an explanation in terms of shrinkage porosity rather than vacant lattice sites, and pointed to the desirability of reexamining appropriate alloy systems using: both Ellwood&apos;s method of specimen preparation (casting followed by wrought fabrication) and alternativ&apos;e methods, i.e., diffusion, which might be expected to minimize, or even completely obviate, microporosity. ALLOY PREPARATION 1) Cast Allolys and Aluminum Single Crystals. Al(Ag), Al(Mg;l, and Al(Zn) alloys of various compositions up to 20 at. pet silver, 13.5 at. pet mg, and 30 at. pet Zn were prepared by melting under helium and casting into graphite molds. In the first two systems, the maximum alloying addition was quite close to the limit of solid solubility, but the possibility of transformation to a&apos; during quenching somewhat restricted the suitable Al(Zn) composition range. The alloys were prepared from high-purity aluminum, a lot analysis showing 0.002 wt pet Cu, 0.002 wt pet Fe, and 99.996 wt pet A1 by difference. The silver, magnesium, and zinc were of 99.99+, 99.98+, and 99.998 wt pet respectively. Each composition was analyzed chemically. The as-cast ingots measured 7/16 in. diam and 5 in. length. One in. was removed from the top of the ingot, and the bottom 3 in. was machined to 0.275 in. diam; a point was also machined on the smaller diameter end. The remainder of the original ingot served as a top riser during subsequent remelting and controlled solidification. The machined ingots were now remelted using a Bridgman soft-mold technique to ensure directional solidification and, therefore, a minimum of micro-shrinkage. Alumina powder was used as mold material contained in an alundum thimble, and this crucible was placed in a helium-filled Vycor tube. The assembly was lowered through a suitable temperature gradient at approximately 0.5 in. min-l, and the risered portion of the casting was subsequently removed by sawing.

Jan 1, 1962

By THOMAS LEONBRD WATSON

I. INTRODUCTION. THE results embodied in this paper are based on a careful field- and laboratory-study of the lead- and zinc-deposits of the Virginia-Tennessee district, begun in the latter part of the summer of 1904 and completed in the spring of 1905, preparatory to the publishing of a State report .on them. A separate description of the individual deposits in Virginia is purposely omitted, since I have already described them in considerable detail in a State report. The Tennessee deposits are described here in some detail for the reason that no detailed record of them has yet been published. Practically, this paper summarizes the results obtained from a study of the geology of the ore-deposits of the district as, a whole. (I had the pleasure of visiting the deposits of Virginia and Tennessee with Dr. H. Foster Bain of the U. S. Geological Survey, in April, 1905. Figs. 21 and 22 are from photographs taken by Dr., Bail.) II. HISTORICAL. . The first authentic records of lead-mining .in Virginia date hack more than 150 years; and the old lead-mines at Austinville, on New river in Wythe county, V a., were the first to be worked. Colonel Chiswell, a native of Wales, and one of the earlier adventurers in southwestern Virginia, was one of the first operators of the Austinville mines. Chiswell&apos;s operations at Austinville commenced in the year 1750, and closed shortly after the beginning of the Revolutionary War, in the&apos; year 1776, covering a period of about 25 years. From that time to the present, mining has been carried on almost continuously in the Virginia area. For many years after the Virginia mines were operated, mining was confined exclusively to the lead-ores. The zinc-ores

Mar 1, 1906

By Robert T. MacMillan

Of all the mineral substances utilized by man, salt or sodium chloride has one of the longest and most varied histories. Because all animal life is descended from marine organisms, sodium and chlorine became necessary to life, and as sodium chloride meets requirements most readily, common salt has been essential to human and animal diets from earliest times. As civilization progressed, man learned to evaporate sea water and brines of saline lakes and springs to obtain salt, and gradually ceased to depend on the flesh of animals and the occasional salt outcrops or "salt licks" they frequented. He also learned that salt had a multitude of uses, particularly as a preservative of meat and other foods. The importance of salt in the minds of early men may be readily seen from many allusions in the Bible and other ancient writings. Expressions such as "not worth his salt," and "the salt of the earth" are deeply embedded in the English language. Salt has symbolized friendship, fidelity, purity, and hospitality. It has been used as currency; had religious significance; caused wars; and has been a favorite commodity for taxation. The English word "salary" stems from the Latin word for salt, in which Roman soldiers received part of their pay. Although salt today retains its dietary importance, it has thousands of other uses. Of each 100 pounds produced in the United States less than three pounds is for table use. The other 97 pounds goes for agricultural, industrial, and chemical uses. Fortunately, reserves of salt are enormous and reasonably well distributed on the face of the earth. The sea is an inexhaustible source of salt which may be had at prices which vary with climate and other factors. In addition, large underground salt deposits and many salt lakes, springs and playas are scattered throughout the world. Most countries have access to a salt supply, although some are more favored than others. Properties Crystallized sodium chloride or common salt is known as halite. Its molecular weight is 58.454 and it contains, by weight, 39.34 pct sodium and 60.66 pct chlorine. Alternate positions in the cubic lattice are occupied, respectively, by negative chloride and positive sodium ions; the crystal form is isometric. Crystallization from water produces concentric shells, and when broken, a crystal shows conchoidal fracture. Salt has a hardness of 2.5; its specific gravity ranges from 2.1 to 2.6 for rock salt and is 2.165 for the pure crystal. The refractive index is 1.554; it melts at 800.8 ± 0.5°C and boils at 1413°C. Its heat of fusion is 123.59 cal/ gram. Salt is transparent or translucent and highly diathermous. It is colorless when pure and has a vitreous luster. Salt containing traces of iron oxides has varying shades of yellow, orange, brown, pink, or red. The peculiar shade of red sometimes found in that produced by solar evaporation of sea water has been attributed to tiny organisms. Blue mottlings sometimes seen in halite crystals have been attributed to colloidal sodium. Salt is soluble in water to the extent of 35.7 parts per 100 parts of water at 0°C and 39.8 parts per 100 of water at 100°C. The small difference in solubility with increasing temperature is important in the economics of producing salt by evaporating brine. Salt has a negative heat of solution which is 1.281 kg-cal/ mole at 18°C in 200 moles of water.

Jan 1, 1960

By R. W. Nash, A. E. Schwaneke, V. R. Miller

The Bureau of Mines developed a detector for controlling sorting devices to separate the copper-bearing fragments from the barren portion of Michigan native copper and western prophyry copper ores. A successful sorter could be used to preconcentrate the ore and eliminate costly hoisting or hauling of waste. An induction balance unit was developed and used in sorting tests on crushed sized - 2.5 + 1. 3-cm (- 1 + 1/2- in.) ores from the Kingston (0.9% Cu) and Centennial (1.6% Cu) mines of Upper Michigan. Concentrates of 4.0% and 7.5% Cu, respectively, were obtained at recoveries of 85 and 80% of

Jan 8, 1978