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By F. W. SUTTER

IN order to have ore available on the completion of the beneficiation plant at Clifton and to provide for continuous production while underground development was carried out, it was decided to develop an open-pit through the crest of a long hill in which the ore outcropped, using 40-ft. vertical benches.

Jan 1, 1943

By David Turnbull

In most reactions involving solids the transformation kinetics may be represented by the combination of two processes —those of nucleation and of growth. For example, Mehl and his coiq-orker in their studies on the transformation of austenite to pearlite in steels have been able to describe the kinetics in terms of the rates of nucleation and of growth. By micrographic examination of their specimens they determined the nucleation rate (rate of appearance of pearlite colonies) as a function of time, of percent transformation, and of temperature. They observed that after an incubation period in which no nuclei are observed, the number of nuclei appearing per unit time per unit of untransformed grain boundary area, increases at an increasng rate with time. When recrystallization rates have been interpreted in terms of rates of nucleation and growth and the rate of nucleation determined, an incubation period followed by an increasing rate of nucleation has also been reported. Among the studies in which this phenomenon has been observed are those of Kornfeld and coworkers3 on cold-drawn aluminum wire, of Anderson and Mehl4 n the recrystallization of aluminum sheet, and of Stanlcy and Meh15 on the recrystallization of silicon ferrite sheet. The existence of an incubation period during which no nuclei are observed does not appear to have been reconciled with the generally accepted Volmer-Becker theory of nucleation in condensed systems. This theory ostensibly requires the rate of appearance of nuclei to be independent of time. Volmer-Becker Theory In order to form a stable nuclcus of a new phase B in a mother phase A, the molecules or atoms of the mother phase must surmount a free energy barrier whose height is determined by the volume free energy change accompanying the transformation and the energy of the surface separating the two phases. The free energy difference between nuclei of various sizes and the molecules or atoms of the mother phase is plotted schematically in Fig I as a function of the radius of the nucleus r. This free energy difference is plotted for two values of the change of free energy per atom, (Jb — ja) accompanying the transformation when the volumes of the two phases are infinite. One of these values of (Jb—Ja) corresponds to a temperature above the temperature To at which the phascs A and B are in equilibrium, and the other to a temperature below To. In order for a nucleus of phase B to be stable at a temperature T² < TO, its radius must be equal to or greater than the critical value r* for which the free energy of formatioil of the nucleus is a maximum, the of phase B having radii equal to or less than r* will be called embryos hfehl and Jetter," in discussing the kinetics of nucleation in solid systems, suppose that embryos of critical size are formed

Jan 1, 1949

Meeting of Feb. 16, 1915.-The Committee on Membership was appointed with the following personnel: John H. Janeway, Chairman; Karl Filers, Lewis W. Francis, Louis D. Huntoon, and Thomas H. Leggett. President Saunders announced the appointment of the Committee on Increase of Membership, as shown on p. xxviii of this Bulletin. The reproduction by the anastatic process of 100 copies of Volume IX of the Institute Transactions was authorized. The sum of $50 and the exchange of the Bulletin. was awarded to the commission publishing the Annual Table of Constants. The sum of $49.07 was contributed to the expense of the John Fritz Medal Board of Award for the year 1914, and the Institute agreed in the future to share the annual expense for the John Fritz Medal Board of Award not to exceed one-quarter of $500 in the year. Upon the recommendation of the Committee on Membership, 36 Members, 1 Associate, and 13 Juniors were elected. The resignations of 26 members were accepted. L. D. Ricketts was elected a Vice-President of the Institute to serve the unexpired term of W. L. Saunders. George D. Barron was elected a Director to serve the unexpired term of L. D. Ricketts.

Jan 4, 1915

By David Turnbull

IN most reactions involving solids the transformation kinetics may be represented by the combination of two processes-those of nucleation and of growth. For example, Mehl and his coworkers 1,2 in their studies on the transformation of austenite to pearlite in steels have been able to describe the kinetics in terms of the rates of nucleation and of growth. By micrographic examination of their specimens they determined the nucleation rate (rate of appearance of pearlite colonies) as a function of time, of percent transformation, and of temperature. They observed that after an incubation period in which no nuclei are observed, the number of nuclei appearing per unit time per unit of untransformed grain boundary area, increases at an increasng rate with time. When recrystallization rates have been interpreted in terms of rates of nucleation and growth and the rate of nucleation determined, an incubation period followed by an increasing rate of nucleation has also been reported. Among the studies in which this phenomenon has been observed are those of Kornfeld and coworkers3 on cold-drawn aluminum wire, of Anderson and Mehl4 on the recrystallization of aluminum sheet, and of Stanley and Mehl5 on the recrystallization of silicon ferrite sheet. The existence of an incubation period during which no nuclei are observed does not appear to have been reconciled with the generally accepted Volmer-Becker theory of nucleation in condensed systems. This theory ostensibly requires the rate of appearance of nuclei to be independent of time. VOLMER-BECKER THEORY In order to form a stable nucleus of a new phase B in a mother phase A, the molecules or atoms of the mother phase must surmount a free energy barrier whose height is determined by the volume free energy change accompanying the transformation and the energy of the surface separating the two phases. The free energy difference between nuclei of various sizes and the molecules or atoms of the mother phase is plotted schematically in Fig I as a function of the radius of the nucleus r. This free energy difference is plotted for two values of the change of free energy per atom, (fB - fA) accompanying the transformation when the volumes of the two phases are infinite. One of these values of (fa-fA) corresponds to a temperature above the temperature To at which the phases A and B are in equilibrium, and the other to a temperature below To. In order for a nucleus of phase B to be stable at a temperature T2 < To, its radius must be equal to or greater than the critical value r* for which the free energy of formation of the nucleus is a maximum, ?f*. Aggregates of phase B having radii equal to or less than r* will be called embryos. Mehl and Jetter,6 in discussing the kinetics of nucleation in solid systems, suppose that embryos of critical size are formed

Jan 1, 1948

By Dennis H. Laubscher

INTRODUCTION The selection of mass mining methods is the situation facing not only planners of new operations, but also those involved with cur- rent operations, including the eventual change from open-pit to underground. Increasing ground control problems on many mines, plus a better understanding of dilution and ore loss problems have meant a review of current mining methods and support techniques. Experiments are only successful if conducted in the right mining environment and on the right scale. Mining personnel have been known for their conservatism and will tend to persevere with an established method rather than change; often, hidden costs will obscure the correct economic assessment. An established mining sequence is not necessarily correct in the long term. However, recommendations to change are usually met with opposition because of inconvenience, temporary production problems and the desire for a trouble-free guarantee. In any planning exercise, care must be taken that time and money are not wasted in trying to achieve the unattainable. During the decision-making period, production personnel must be involved, and, if possible, they should visit similar omrations to that proposed. Co-operative production personnel will help ensure success. Descriptions of mining methods are available in technical papers and books, and it is not intended to discuss this aspect, but, rather, the various factors which must be recognised before arriving at a final selection. In another paper presented at this Conference (Heslop and Laubscher, 1981) factors affecting ore recovery and dilution are discussed in greater detail for various cave mining methods. PRELIMINARY CONSIDERATIONS Comprehensive Geological Data. Geological information is available during the exploration stage, but, often, core from exploration drilling is not analysed with the selection of a mining method in mind. Drilling costs are high, therefore the maximum benefits must be derived from this operation. Holes which have not intersected ore may provide data on possible shaft sites, and 35 mm colour slides of core, sound logging and geomechanics classification, will provide a record which can be used with confidence at a later date. Intersections of the various rock types should be kept for future study; for example, is weathering likely to be a problem, bearing in mind that this can be accelerated in the warm, humid atmosphere of an underground mine. The accumulation of data required to select a mining method starts with initial geological work in the target area, whether this be surface mapping or a diamond drill hole. Publications. As technical papers, reports and books are used in the selection of mining methods, an appeal is made to authors to describe the geological environment so that readers can relate to their own conditions. Not enough emphasis is given to the problems experienced and the techniques employed to overcome them. Follow-up papers are seldom written and we should be prepared to discuss our failures. Diagrams are often misleading, as the ideal and not actual situations are depicted. The caved ore/waste interface is not a straight line, and whereas this may not be significant in a diagram of a 200-117 draw height, it certainly is in sub-level caving with draw zones only 1 - 2 m width but up to 20 m high. SUMMARY OF FACTORS AFFECTING THE SELECTION OF UNDERGROUND MASS MINING METHODS (a) Regional rock stresses and mining geometry. (b) The geomechanics rock mass classification of the orebody and surrounding rock mass. (c) Ratio of the surface area of the ore/unpay interface to the contained ore which determines ore losses and dilution. (d) The cavability and fragmentation data of the ore and hangingwall. (e) The mineral distribution in the orebody and its dilution zone.

Jan 1, 1981

By T. K. Perkins, O. C. Johnston

Because of the influence of dispersion on miscible-displacement processes, diffusion and dispersion phenomena in parous rocks are of current interest in the oil industry. This paper reviews and summarizes a great deal of pertinent information from the literature. Porous media (both unconsolidated packs and consolidated rocks) can be visualized as a network of flow chambers, having random size and flow conductivity, connected together by openings of smaller size. In such a porous medium, the apparent diffusion coefficient D is less than the molecular diffusion coefficient Do, as measured in the absence of a porous medium. For packs of unconsolidated granular material the ratio D/D, is about 0.6 to 0.7. For all porous rocks, both cemented and unconsolidated, the ratio of diffusion coefficients can also be represented as D/Do = 1/FF where F is the for- mation electrical resistivity&apos; factor and 4 is the porosity. If fluids are flowing through the porous medium, dispersion may be greater than that due to diffusion alone. At moderate flow rates the porous medium will create a slightly asymmetrical mix zone (trailing edge stretched out), with the longitudinal dispersion coefficient approximately proportional to the first power of average fluid velocity (if composition is nearly equalized in pore spaces by diffusion). If the velocity in interstices is large enough, there will be insufficient time for diffusion to equalize concentration within pore spaces. In this region, longitudinal dispersion increases more rapidly than fluid velocity. At low velocities in interstices, transverse dispersion is characterized by a region in which transverse diffusion dominates. If the fluid velocity gets high enough, there will be a transition into a region where there is stream splitting with mass transfer but with insufficient residence time to completely damp-out concentration variations within pore spaces. There are several variables that must be con- trolled to get consistent longitudinal and transverse dispersion results, viz., (1) edge effect in packed tubes, (2) particle size distribution, (3) particle shape, (4) packing or permeability heterogeneities, (5) viscosity ratios, (6) gravity forces, (7) amount of turbulence, and (8) effect of an immobile phase. INTRODUCTION Diffusion and dispersion in porous rocks are of current interest to the oil industry. This interest arises because of the influence of dispersion on miscible-displacement processes. In a recovery process utilizing a zone of miscible fluid, there is the possibility of losing miscibility by dissipating the miscible fluid or by channeling or "fingering" through the miscible zone. Diffusion and dispersion are two of the mechanisms that may lead to mixing and dissipation of the slug. On the other hand, dispersion may tend to damp-out viscous fingers which may be channeling through the miscible slug. 58 Hence, dispersion may be detrimental or beneficial (if it prevents fingering through the miscible zone). Therefore, it is doubly important that we understand these processes. In this paper we review, summarize and interpret a great deal of information from the literature. In particular, we will briefly discuss molecular diffusion in miscible fluids. Then we will discuss what differences to expect for diffusion in a porous rock. If there is movement of the fluid through the rock, then there may be an additional mixing or "dispersion". Furthermore, the dispersion longitudinally (in the direction of gross fluid movement) and transverse to the direction of fluid movement will not be equal. We will discuss both types of dispersion as well as several variables which can affect dispersion (viscosity differences, density differences, turbulence, heterogeneity of media, etc.). This group of variables has sometimes led to difficulty when comparing literature data. DIFFUSION OF MISCIBLE FLUIDS If two miscible fluids are in contact, with an initially sharp interface, they will slowly diffuse into one another. As time passes, the sharp interface between the two fluids will become a diffuse

By S. W. Parr, F. B. Hobart

Studies relating to the behavior of coal toward oxygen may have for their purpose the determination of the fundamental factors that underlie spontaneous combustion, weathering and deterioration, and the general topic of storage, as well as those properties that have to do with the underlying principles of carbonization. There is also involved the possibility of developing information relating to the constitution of coal, or at least the chemical properties inherent in the type substances of which the coal is composed. It is the purpose here to record certain results bearing on this latter idea of the chemical properties that characterize the main constituents of bituminous coal. The avidity of freshly mined coal for oxygen has long been known. What happens to the coal or to the oxygen is not so clear. Is the oxygen absorbed or chemically combined, and what are the conditions as to time, temperature, texture, or components that are most involved in the phenomenon? If we subject a weighed quantity of coal maintained at a constant temperature to a current of oxygen, we may obtain three factors of interest—the weight increase of the coal, the weight of the water, and the weight of the carbon dioxide formed in the reactions involved at that

Jan 1, 1925

By E. S. Machlin

The alternate processes by which solute atoms can limit the migration of grain boundaries have been considered. At the lowest solute concentrations the controlling process is "mechanical breakaway" in which the solute atoms affect the driving force and not the mobility. In the next higher range of solute concentration, solute atoms are bound to the boundary and diffuse by boundary diffusion along cusps in the boundary developed at the solute atoms. In this region the boundary velocity is controlled by the component in the direction of boundary migration of the rate at which the bound solute atoms can diffuse along the boundary. At still higher concentrations, it is predicted that boundaries break away from the binding solute atoms by thermal activation. The specific behavior Predicted is consistent with the observations of Aust and Rutter. The most striking agreement between prediction and experiment is that obtained for a range of solute concentration in which the boundary velocity is inversely proportional to the cube power of the solute concentration. MaNY models have been devised for the atomic steps in the motion of a grain boundary. McLean1 has listed some of these models and Aust and utter&apos; have evaluated these and other models. If there are

Jan 1, 1962

The Institute is still in need of additional copies of the Bulletin for January, February and March, and will be glad to pay members the regular price of fifty cents per copy. Copies may be sent express collect, or postage may be used and the amount will be refunded in addition to the fifty cents.

Jan 10, 1916

By Valentin R. Garfias

PRODUCTION AND MARINE TRANSPORTATION OF MEXICAN PETROLEUMS ALTHOUGH the work on which this paper is based was carried on, by the writer as Special Commissioner of the Petroleum Department of the Mexican Government, the opinions expressed are only his personal views for which the Mexican Government can in no way be held responsible. Notwithstanding that the appointment covers all phases of the so-called petroleum question, as the one question of immediate importance was that relating to taxation, it was decided to devote all the time to this phase of the work. The present report has been divided into two closely related parts, .the first dealing with the production and marine transportation of Mexican petroleum, and the second, with the Mexican taxation on petroleum and its products. The writer wishes, to acknowledge the loyal cooperation rendered by Mr. M. C. Ehlen, who had charge of the statistical, work, and by Miss S. Stern and Messrs. E. P. Heiles and J. E. Morrissey. The aim throughout the work has been; to pave the way for a thorough understanding between the Mexican Government and the oil operators and to present a true and clear statement of facts relating to the questions at issue.

Jan 2, 1921

By C. L. Meyers, J. L. Lytton, T. E. Tietz

The recovery of tensile flow stress of 99.995-pct Al and Al-1 pct Mg alloy was investigated using a fractional recovery parameter. Tensile strainirg was conducted at room temperature, and recovery treatments were made in the range from 80° to 200°C. Equal values of fractional flow stress recovery were found to result in equivalent structural states. Identical recovery treatments were found to produce constant values of fractional flow stress re covery, independent of prestrain. The activation energy for recovery of the 99.995-pct A1 between 80" and 200°C was found to be 23,000 +2000 cal per mole, and the activation energy for the Al-1 pct Mg alloy was 27,500 cal per mole. 1 HE degree of recovery of a cold-worked metal may be studied by measuring the changes which take place in any of a number of properties. Some of the properties which have been used by past investigators include X-ray diffraction phenomena, electrical resistivity, hardness, creep strength, elastic limit, and flow stress. Despite the apparent preponderance of such studies, little is known concerning the effect of recovery on the strength of metals except as deduced from changes in various types of hardness measurements. Furthermore, little information is avail- able concerning the effects which specific solute atoms have on the recovery process. Limited studies have indicated that in some cases solid-solution additions greatly decrease the rate of recovery,&apos; whereas in at least the case of magnesium additions to alluminum an increase in the rate has been reported.2 The purpose of this investigation was to determine the effect of a 1 pct Mg addition on the recovery of high-purity aluminum. Because of the particular interest in the effect of solute additions on the recovery behavior as related to mechanical properties, the degree of recovery was evaluated in terms of tensile flow stress. For the purposes of this study, a recovery process shall be defined as any process, short of recrystallization, whereby the properties, of work-hardened metals tend toward their values ill the unstrained state. EXPERIMENTAL PROCEDURE Test Materials. The materials used in this study were a 99.995-3 A1 and an Al-1 pct Mg alloy made from high-purity base metal. The high-purity aluminum contained the following wt pct impurities: 0.001 pct Cu, 0.002 pct Fe, 0.001 pct Si, and 0.0004 pct Mg. The Pil-1 pct Mg alloy contained 0.001 pct Cu, 0.002 pct Fe, 0.003 pct Si, and 0.99 pct Mg. Both materials were obtained in the form of as-rolled 0.125-in.-thick sheets, from the Alcoa Research Laboratories, New Kensington, Penn. Tensile specimens were cut from these sheets with the longitudinal axis in the rolling direction. Both materials were recrystallized in a molten salt bath; the high-purity aluminum at 450° C for 20 min and

Jan 1, 1962

By W. N. Tanner

The wire-rope hoisting conditions at the mines of the Anaconda Coppcr Mining Co. in Butte, Mont, are very severe because of the conditions under which it is necessary to operate. A study was made, in the fall of 1919, for the purpose of changing these conditions in order to obtain longer rope and sheave life. There are at present in Butte hoisting engines equipped with wire rope as follows: 9 main hoists using flat ropes. 7 main hoists using 1 1/2-in. rope. 5 main hoists using 11/4-in. rope. 6 shafts using 11/8-in. rope. 2 chippy hoists using 11/4-in. rope. 9 chippy hoists using 11/8-in. rope. 15 shafts using 1-in. rope. 7 shafts using 7/8-in. rope. 1 shaft using 3/4-in. rope. In addition, there are a number of sinking engines wing 5/8-in, 3/4-in., 7/8-in., and 1-in. (15.9, 10, 22, and 25 mm) rope. THe flat ropes run from 1/2 by 71/2 in. (12.7 by 1905 mm.) to-3/8 by 4 1/2-in (9.5 by 114 mm.) and are used on the older hoisting engines, which arc set comparatively close to the shaft. Because of swelling and moving ground at some of the shafts, these ropes present certain difficulties ill operation that are more pronounced than with round ropes; they are, therefore, being superseded by round ropes as newer engines are being installed. They are, however, much more easily inspected and repaired than round ropes. In general, the practice in Butte is to use hoisting engines equipped with 12-ft. (3 7 m.) cast-iron drums, smooth faced, for 11/2-in. rope and 6-ft. cast-iron drums, smooth faced, lagged with 3/8-in. steel plate for 11/4 l1/8 and 1-in. (31.7, 28.6, 25 mm.) rope in main and chippy shafts. Cast-iron head sheaves, 12, 10, and 6 ft. in diameter, with grooves

Jan 1, 1923

By W. N. Tanner

The wire-rope hoisting conditions at the mines of the Anaconda Coppcr Mining Co. in Butte, Mont, are very severe because of the conditions under which it is necessary to operate. A study was made, in the fall of 1919, for the purpose of changing these conditions in order to obtain longer rope and sheave life. There are at present in Butte hoisting engines equipped with wire rope as follows: 9 main hoists using flat ropes. 7 main hoists using 1 1/2-in. rope. 5 main hoists using 11/4-in. rope. 6 shafts using 11/8-in. rope. 2 chippy hoists using 11/4-in. rope. 9 chippy hoists using 11/8-in. rope. 15 shafts using 1-in. rope. 7 shafts using 7/8-in. rope. 1 shaft using 3/4-in. rope. In addition, there are a number of sinking engines wing 5/8-in, 3/4-in., 7/8-in., and 1-in. (15.9, 10, 22, and 25 mm) rope. THe flat ropes run from 1/2 by 71/2 in. (12.7 by 1905 mm.) to-3/8 by 4 1/2-in (9.5 by 114 mm.) and are used on the older hoisting engines, which arc set comparatively close to the shaft. Because of swelling and moving ground at some of the shafts, these ropes present certain difficulties ill operation that are more pronounced than with round ropes; they are, therefore, being superseded by round ropes as newer engines are being installed. They are, however, much more easily inspected and repaired than round ropes. In general, the practice in Butte is to use hoisting engines equipped with 12-ft. (3 7 m.) cast-iron drums, smooth faced, for 11/2-in. rope and 6-ft. cast-iron drums, smooth faced, lagged with 3/8-in. steel plate for 11/4 l1/8 and 1-in. (31.7, 28.6, 25 mm.) rope in main and chippy shafts. Cast-iron head sheaves, 12, 10, and 6 ft. in diameter, with grooves

Jan 1, 1923

For the convenience of members who may be trawling from place to place, the Secretary has compiled a list of libraries or other places in the United States and foreign countries here MINING AND METALLURGY or the Transactions may he consulted. This list will be sent to members if they so request.

Jan 1, 1923

For the convenience of members who may be traveling from place to place, the Secretary has compiled a list of libraries or other places In the United States and foreign countries where MINING AND METALLURGY or the Transactions may be consulted. This list will be sent to members if they so request

Jan 1, 1923

By Luis A. Fierino, M. Ashraf Mahtab

This paper reviews the background of, and solution techniques for, the major geomechanics problems affecting caving operations, including prediction of cavability, defining size distribution of or fragments, stability and support of production openings, and control of rock bursts and subsidence. Further research is also suggested in the solution of the various geomechanics problems.

Jan 1, 1984

INTO their great Pacific Northwest counting house went the members of the Industrial Minerals Division recently, to count their blessings amidst the scenic grandeur and mineral wealth of the State of Washington. From their vantage point in Seattle, those who attended the IMD&apos;s fourth Pacific Northwest meeting turned their sights to the South and Southeast, scanned Montana, Idaho, Oregon and Utah, and predicted a very healthy economic future for their region. The praises of Idaho&apos;s booming phosphate industry were sung by Earl W. Murphy, secretary of that State&apos;s Chamber of Commerce. He said the establishment of Fort Hall, on the banks of the Snake River near Pocatello, first turned the eyes of the world toward what is now the center of the greatest known deposits of phosphate rock-the section adjacent to the common corners of Idaho, Wyoming and Utah. With the founding of Fort Hall, Mr. Murphy said, historians will also rank the construction of the first electric furnaces for the production of elemental phosphorous as equally significant in the commercial history of the West. Those furnaces were installed only last year by the Westvaco Chemical Div. of the Food Machinery & Chemical Corp. at Pocatello, at a cost of $8 million.

Jan 7, 1950

By Oliver B. Hopkins

During the year 1936, a new high record was established for Peruvian production, the total amounting to 17,594,689 bbl., which brought the cumulative production of the country up to 205 million barrels. The 1936 figure represents an increase of 530,288 bbl. over that of 1935. The property of the International Petroleum Co. contributed 369,577 bbl. of this increase and the Lobitos property 158,233. Exploration work in the country was continued. The Selden Breck Co. examined a strip of the National Reserve in eastern Peru from Tambo del Sur to the Rio Pachitea. This company was granted a concession for a term of four years embracing approximately 50,000 acres near the confluence of the Rio Pachitea and the Rio Ucayali. During the year, the Peruvian Government commenced drilling a well on one of the reserved zones at Zorritos. At the end of the year, this well had reached a depth of 1300 feet. La Rrea-Parinas Estate.—Production on the La Brea-Parinas Estate of the International Petroleum Company, Ltd., reached an all-time high in 1936 of 15,126,491 bbl., an increase of 369,577 bbl. over the 1935 record. The total production from 1890 to 1936 was 163,668,014 barrels.

Jan 1, 1937

By H. R. Spedden, A. M. Gaudin, M. P. Corriveau

A preliminary study of silver ion adsorption by sphalerite in ion exchange column with influent electrolyte marked with radiosilver is described. Rapid ion exchange occurs at first followed by slow reaction controlled perhaps by solid state diffusion. One experiment with radiocopper instead of radiosilver is reported briefly. IT has been known for many years that sphalerite is floated after it has been activated by a metallic cation, particularly copper.&apos; The activation of sphalerite by copper is known to be an exchange of an atom of copper for an atom of zinc at the surface of the sphalerite.2,3 It has been estimated from various guesses of the available mineral surface that the depth of the copper-bearing coating is of the order of thickness of one atom. However, the exact mechanism of the activation process is unknown. A number of metals other than copper act in the same general manner."&apos; " In particular, it has been known that silver replaces zinc at the surface of sphalerite. As copper is usually divalent, whereas silver is monovalent, it may well be assumed that there are differences, perhaps major differences, in the detailed scheme of activation by these two cations. Furthermore, since silver has unusual photoelectric properties and may be a contributor to the fluorescence of sphalerite, a study of its activating mechanism might open up some interesting avenues for exploring these other phenomena. The choice of silver as an activator of sphalerite was suggested also by the fact that its radioactive tracer, silver 110, is particularly convenient in that it has a long half-life and is energetic enough to permit counting through a counter window. The experimental technique selected, therefore, included the preparation of solutions of silver nitrate con- taining a proportion of active silver nitrate sufficient to give convenient counting data. In further considering the method to be used, a desirable choice seemed the use of batch experimentation in which a given solution was allowed to act on a certain lot of mineral for a given length of time at a given temperature, this period of mutual reaction being followed by analyses of the separated solid and solution. But an alternative method seemed more attractive. This is the method now so familiar to the users of ion-exchange resins, which was first made famous by the Russian chromatographer, Tswett.6-8 It consists in forming the mineral into a porous column through which the solution is allowed to flow at a constant rate. The usual method of allowing a batch of solid to react with solution is the equivalent of a single plate distillation operation while the chromatographic or ion-exchange column is a multiple-plate method—the multiplicity of the plates being represented by the reciprocal of the rate of flow of solution through the column. It seemed to us that the chromatographic method had such

Jan 1, 1952

By Ralph Nichols

The mines are near the town of Gilmore, in the Texas mining district. This district was organized in 1880. The present producing mines are near the terminus of the Gilmore & Pittsburg railroad. This railroad connects with the main line of the Oregon Short Line at Armstead, Mont. The distance from Gilmore to Armstead is 70 miles. The town of Gilmore is near the head of the Lemhi river at an elevation of 7,000 ft., while the mines are from 400 to 1,300 ft. higher. The range of mountains upon which the mines are situated forms the water shed for the Little Lost river on the west and the Lemhi river on the east. The winters are severe and the snow fall is heavy, but the mines ship right through the year. There is an abundance of timber suitable for all mining purposes in the immediate vicinity. Water is piped into the camp from a lake about 2.5 miles distant. This lake is about 1,400 ft. above the town of Gilmore. The water is exceptionally good for boiler and domestic purposes. The mining companies now producing are the Pittsburg Idaho Co., Ltd.; the Latest Out Mining & Smelting Co., Ltd.; and the Oilmore Mining Co., Ltd. Besides the above propertiea, there are a number of prospects in different stages of development. The producing mines of the district are fissures in limestone, with a general northeast-southwest course and a dip to the west of from 40&apos; to 70°. These fissures are at about right angles to the bedding of the limestones. The veins are regular and the ore shoots strong, both laterally and in depth, so far as developed. The ore shoots have a rake or pitch to the south. The character of the formation is shown in Fig. 1, a section of the Latest Out mine. Character of Ore. The ores of the district are oxidized, carrying an excess of iron over the silica (insoluble matter). The vein filling is a mixture of limonite and hematite, which is replaced by shoots of lead-silver ores. The lead minerals consist of carbonate of lead principally, but with small quantities of sulphide, sulphate, and other lead minerals.

Jan 1, 1914