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By E. R. Borcherdt

Methods and equipment are subject to study in the Butte district at all times in order that advantage may be taken of any new developments that might serve to increase efficiency and lower costs. Detailed time studies of each operation involved in the entire mining process have been of invaluable assistance in analyzing the individual operation for possible improvement. In other words, the fact that a practice has been in vogue for many years does not exempt it from change provided an easier and cheaper method can be found. Exploration Ore occurs in the Butte district in such manner that structures must be drifted on, no matter how small or unimportant they appear when intersected by a crosscut. Parallel structures also add to the crosscut requirements. This prospecting work, which formerly was done entirely by drifting and crosscutting, is now being supplemented by diamond drilling, to aid in greatly decreasing the amount of waste. In long-shot prospecting, or in second or third class prospecting, where the chances of developing commercial ore are not very great, diamond drilling is of particular value. In prospecting where chances of encountering commercial ore are certain or where crosscuts can be used later for haulage or ventilation, drilling obviously is not applicable. Improvement in drilling machines and bits has contributed greatly to the present success of diamond drilling. For many Years square-set filled stoping was the principal mining method used in the Butte district. Later timbered and untimbered rill stopes were used, also some horizontal cut-and-fill stoping where both Ore and walls were particularly strong. Because of the amount of timber required for square-set stoping, and the relatively low production per stope unit, experiments with horizontal cut-and-fill stopes were begun in Ore bodies of which many had fairly weak walls. It was felt that increase in the speed of the stoping operation, followed closely by filling, to avoid weight being produced by permitting ore and walls to remain insufficiently supported over comparatively long periods, would maintain the walls and backs in safe condition without the use of timber and without ore dilution from wall slough. Cycles of drilling, scraping ore, and filling were devised, which have materially increased stope production and decreased timber consumption, so that both stope labor and supply costs were lowered appreciably without materially affecting grade control. In the larger mines of the district, where wide veins favor this stoping method, half of the total production is now being mined by horizontal cut-and-fill stopes (Fig. I). The increase of the filling rate demanded by the increased stoping rate was the greatest obstacle encountered in the accelerated stoping operations. Finally this problem was solved by replacing the time-honored method of transferring filling waste by small cars, which were hoisted or lowered in the auxiliary shaft, by a transfer

Jan 1, 1943

By E. R. Borcherdt

Methods and equipment are subject to study in the Butte district at all times in order that advantage may be taken of any new developments that might serve to increase efficiency and lower costs. Detailed time studies of each operation involved in the entire mining process have been of invaluable assistance in analyzing the individual operation for possible improvement. In other words, the fact that a practice has been in vogue for many years does not exempt it from change provided an easier and cheaper method can be found. Exploration Ore occurs in the Butte district in such manner that structures must be drifted on, no matter how small or unimportant they appear when intersected by a crosscut. Parallel structures also add to the crosscut requirements. This prospecting work, which formerly was done entirely by drifting and crosscutting, is now being supplemented by diamond drilling, to aid in greatly decreasing the amount of waste. In long-shot prospecting, or in second or third class prospecting, where the chances of developing commercial ore are not very great, diamond drilling is of particular value. In prospecting where chances of encountering commercial ore are certain or where crosscuts can be used later for haulage or ventilation, drilling obviously is not applicable. Improvement in drilling machines and bits has contributed greatly to the present success of diamond drilling. For many Years square-set filled stoping was the principal mining method used in the Butte district. Later timbered and untimbered rill stopes were used, also some horizontal cut-and-fill stoping where both Ore and walls were particularly strong. Because of the amount of timber required for square-set stoping, and the relatively low production per stope unit, experiments with horizontal cut-and-fill stopes were begun in Ore bodies of which many had fairly weak walls. It was felt that increase in the speed of the stoping operation, followed closely by filling, to avoid weight being produced by permitting ore and walls to remain insufficiently supported over comparatively long periods, would maintain the walls and backs in safe condition without the use of timber and without ore dilution from wall slough. Cycles of drilling, scraping ore, and filling were devised, which have materially increased stope production and decreased timber consumption, so that both stope labor and supply costs were lowered appreciably without materially affecting grade control. In the larger mines of the district, where wide veins favor this stoping method, half of the total production is now being mined by horizontal cut-and-fill stopes (Fig. I). The increase of the filling rate demanded by the increased stoping rate was the greatest obstacle encountered in the accelerated stoping operations. Finally this problem was solved by replacing the time-honored method of transferring filling waste by small cars, which were hoisted or lowered in the auxiliary shaft, by a transfer

Jan 1, 1943

By L. S. Castleman, L. L. Seigle

IN a recently reported investigation, J. B. Clark and F. N. Rhines1 used a diffusion couple technique to determine the number of intermetallic phases which should be present in the Al-Mg equilibrium phase diagram. Their method was an application of the following generally accepted principle. If a diffusion couple made up of two metals is annealed at a given temperature for a long time, all the phases of the binary system which exist under equilibrium conditions at the diffusion temperature will form intermetallic layers. It is important that the diffusion temperature be high enough and the diffusion time be long enough to permit the nuclea-tion of all thermodynamically stable phases at the interface of the couples and their growth to observable thicknesses. These simple time-temperature criteria are at times difficult to satisfy, and it is the purpose of this note to point out a situation in which this is the case. The authors are currently studying diffusion bonding in the Al-Ni system." It is well established

Jan 1, 1958

By George Comstock

THESE notes should be considered as a further discussion of Mr. S. W. Miller's paper on "Some Structures in Steel Fusion Welds."1 In that paper and the resulting discussion; several conflicting opinions were expressed as to the identity of the needles or small crystals present in oxyacetylene and electric welds. An interesting specimen of an electric weld examined by the writer seems to afford new evidence regarding the needles, that may be worth presenting at this time. The specimen consisted of a piece of 3/8 -in. (9.5-mm.) steel plate, about 2 ¼ by 1 ¾ in. (5.7 by 4.5 cm.) in size, on which some iron had been deposited by arc-welding to a depth of about 3/16 in. (4.7 mm.). The weld appeared to be a very good one, with no noticeable break or boundary between the plate and the deposited iron. Sections for microscopic examination were cut in three planes at right angles to each other through the deposited metal, two of these sections also extending through the steel base. After polishing in the usual way, the microscope showed that the deposited metal was full of very small, round, gray, oxide spots, while the steel plate contained quite a number of alumina inclusions and a little slag. The sections were etched with nitric acid in ordinary alcohol, and structures similar to those described by Mr. Miller were then displayed. Fig. 1 shows the typical appearance of the deposited metal, which was quite uniform in all three of the planes examined. The round dark-gray spots are oxides, and the pale angular crystals are evidently what, Mr. Miller called cementite and Mr. Jeffries martensite, while Dr. Ruder and Prof. Boylston suggested that they might be nitride. The boundary between this structure and the steel base was sharply defined under the microscope. Fig. 2 shows the structure of the plate just under the weld; this is almost martensitic and resembles a coarse-grained casting. This coarse cast structure soon became finer as the distance from the weld increased, finally, becoming very fine, with numerous small particles of sorbite. This very fine structure, shown in Fig. 3, became coarser in turn and finally merged into the original normal structure of the steel plate, shown

Jan 1, 1919

By J. P. Pritchard, J. T. Pierce, O. G. Slay

This paper discusses the results of a technology-evaluation program to ascertain the feasibility of a piotornask-photoresist technology developed for fabrication of multiple-layer thin-film superconductive circuitry. The uehicle selected for this evaluation was a 120-bil associative data processor requiring a set of nine photomasks to define a similar number of patterned material layers of lead, tin, and polymer insulation. A total circuit area of 4 sq in. involved 2500 actitle and 12,000 passive crossings. Several short-free, electrically continuous specimens were satisfactorily completed under this program. Problems encountered in the preparation and use of the requi-ed set of Photomasks are discussed, as also are the problets of providing suitable external connections. A major retarding factor in the development of the superconducting thin-film cryotron technology for many years was the absence of batch fabrication means yielding necessary device density and count per substrate for practical applications. Early workers in the field desired only limited numbers of devices to permit careful study of discrete devices and representative circuitry integrating logic and memory capabilities. For these purposes mask stencils could be formed to selectively control the placement of materials, sequentially vapor-deposited in vacuum, to form the multilayer structure. In general a distinct pattern was required for each material layer; therefore, mechanical provisions were required to change not only the material source, but the patterning mask as well, before each deposition. All deposition steps were preferably performed in a single evacuation of the deposition chamber. Thus the means for storing, transporting, and registering masks and sources with respect to the substrate existed and were operated within the vacuum environment. In the authors' experience, the approach was and remains serviceable for preliminary device study, but was not extensible to an economical manufacturing method by virtue of the difficulties inherent in mask stencil preparation and use, and the capital investment implicit in the mechanization requirements. Since the commercial attraction of the cryotron technology stems principally from its potential for economical batch fabrication, the authors' program has placed major emphasis on fabrication methods. A highly useful method has evolved through adaptation

Jan 1, 1967

By V. K. Zworykin

THROUGHOUT its development the science of electronics, like so many other branches of science and industry, has been indebted to the metallurgist. Metallurgy has provided the electronic engineer with conductors to furnish passage for electrons outside of his evacuated tubes; it. has developed tungsten and tantalum wires for emitting electrons and various refractory metals and alloys suitable for electrodes, which receive them and guide them within the tube; finally it has supplied ferromagnetic materials both for shielding electronic apparatus from magnetic fields and for forming highly concentrated fields for deflecting electron. Today I hope to show you that electronics has not been altogether ungrateful for this assistance. More specifically, I wish to indicate the role that the electron microscope, a relatively recent product of electronic engineering, is playing even now in the study of metals. Every metallographer is aware that his standard metallographic microscope will not reveal structural detail involving separations smaller than a certain fraction -at the very best a tenth-of a micron. This limitation, he knows, is a consequence of the fact that the wave length of the light employed for forming the image has this order of magnitude. It is, thus, a property of all light microscopes. To overcome it, a different imaging medium must be employed. The existence of such a medium became evident when it was demonstrated' that electrons were affected by magnetic and electric fields with axial symmetry just as light is affected by glass lenses; these fields, or "electron lenses," curve the paths of electrons reaching them from an object located on the axis of symmetry in such a manner that, at some distance from the lens, a true image of the object is formed, Furthermore, although a wave length may be ascribed to electron beams just as to light, this wave length is much shorter; for electrons accelerated through a difference of potential of 50 kilovolts, the wave length is only about one hundred-thousandth of that of visible light: Actually, the electron microscopes of today resolve detail one hundred times as fine as light microscopes; if the maximum useful magnification of the latter is taken to be a thousand, that of electron microscopes is one hundred thousand. THE ELECTRON MICROSCOPE Since electrons are readily scattered and absorbed by matter, specimens to be observed in the electron microscope must be prepared to be less than one micron in thickness; furthermore, the interior of the microscope must be carefully evacuated to prevent collisions between the electrons and the molecules of the air. Finally, as already mentioned, the lenses are formed by axially symmetric magnetic or electric fields, and not by any material medium such as glass. Apart from these basic differences, the electron microscope closely

Jan 1, 1943

By L. W. Pommier, F. B. Brien, A. K. Bhasin

The diflerential movement of solid particles through solid-liquid suspensions is very important to many branches of engineering. The flow of suspensions around immersed bodies is mainly of a turbulent nature. Problems are encountered when attempts are made, as is the general practice, to extrapolate the velocity and resistance relationships of Newton, pertaining to Newtonian systems, into non-Newtonian solid-liquid suspensions. The conventional velocity and resistance relationships for turbulent flow in fluids when applied to suspensions, do not take into consideration the two very important variables: suspension particle size and solid volume fraction. A study of the effect of suspension particle size (dgb) on the velocity of falling balls leads to the concept of a critical particle size (dgc) at which the suspensions will be Newtonian. This leads to the classification of static suspensions into two types: suspensions consisting of particle of diameter dgh > dgt, and those with dgh, < dgr. Separate velocity and resistance equations for these two types of suspensions have been proposed, taking into account both the solid particle size and solid volume fraction. The agreement between the velocities predicted from the proposed equations and the measured velocities, confirms their validity. The resistance force offered by suspensions to the movement of immersed bodies has been calculated from the proposed equations, and the effects of suspension particle size and solid volume fraction on the resistance force and velocity have been examined. The movement of immersed bodies in solid-liquid suspensions is of great importance in many areas of engineering such as minerals processing, oil well drilling, suspension flow in pipelines, and hydrometallurgy. A number of mineral dressing processes deal essentially with the movement of solids in suspensions—in particular, classification, thickening, filtration, ore washing, and gravity concentration—thus a study of the fluid characteristics of suspensions is of theoretical and practical interest.&apos; A rigorous analysis of the mechanisms of momentum transport of a solid-liquid system is complex indeed. The rheological properties of the suspensions deviate from those of liquids, varying, for example, with density, solid volume fraction, size and shape of the solid phase of the suspension, and with the density and viscosity of the liquid phase. The flow of suspensions around immersed bodies is mainly of a turbulent nature and hence studies of the turbulent flow characteristics of suspensions are of par- ticular importance. Problems are encountered when attempts are made to extrapolate the velocity and resistance relationships of Newton, pertaining to Newtonian systems, into non-Newtonian solid-liquid suspensions. Due to the numerous variables present in a suspension, certain limitations and assumptions become necessary in order to produce quantitative relationships for predicting their effects. The solid particle size and the solid volume fraction are two of the more important variables. By comparing the measured and calculated Newtonian velocities of falling balls in simple static suspensions, the existing velocity and resistance relationships have been modified to take these variables into account. In order to keep the study less complex, all other variables such as the characteristics of suspending liquid and shape of the particle are maintained constant. Objective The objective of the present investigation is to modify the Newtonian velocity and resistance equations in order to take into account the suspension particle size and solid volume fraction. Theory Liquids are classified on the basis of viscosity, which may be defined as the relationship between applied shear stress and resulting rate of shear.&apos; pure single-phase fluids composed of small light molecules behave as Newtonian liquids, having a single viscosity pa-

Jan 1, 1971

By Charles T. Holland

IN connection with the problems of bumps in coal mines, much has been written concerning the manner in which roof action and methods of mining enter [ ] into the pressure effects observed but little has been written upon the relationship between the physical properties of coal and associated rocks and the cause of bumps. The question of the strength of bituminous coal, of its elasticity, and the energy it can absorb and store has been neglected to a considerable extent in connection with this problem. STRENGTH OF COAL It is generally agreed that one of the necessary conditions for bumps is a strong [ ] coal.1 Therefore, since the strength of coal is an important factor, a study of this property should be made. Several investigators have conducted laboratory experiments upon the strength of coal, using small cubical or rectangular test pieces. An attempt will not be made to go into all of these investigations, but they are briefly summarized in Table I. Experiments of the U. S. Bureau of Mines8 and of Lawall and Holland (pp. 27 and 34 of ref. 9), however, indicate that regardless of whether the coal is a soft and weak semibituminous (Pocahontas No. 3) or a hard and strong bituminous (Stockton) coal, the maximum ultimate unit stress developed in laboratory tests is higher in small cubes than in larger cubes of the same coal.

Jan 1, 1942

SEVERAL distinctions can rightfully be accorded the Bagdad enterprise. For one thing, it has the most romantic name among the Porphyry Coppers and this is said with all due deference to Copper Queen and Inspiration! Bagdad was one of the richest and most magnificent cities of the glamorous world of the Arabian Nights. The record does not say who was responsible for applying the name Bagdad to the company that in 191 1 took over the property of the Arizona-Nevada Copper Company; but whoever it was must have had visions (or at least hopes) of a fabulously profitable mine. So far as I know, Bagdad is the only Porphyry whose owners, or officials, ran afoul of the law because of alleged sins of omission or commission in vending shares of the company&apos;s stock. E. B. Bronson, of New York, had been interested in Bagdad since 1909; and, during the lean period of the 1930&apos;s he had, as president of the corporation, endeavored to raise needed funds by the sale of 140,000 shares of treasury stock. Some legal questions arose as to the need for registration under the Securities and Exchange Act; but, when Mr. Bronson finally filed a registration statement, the New York office of the Securities and Exchange Commission found 155 "deficiencies" in the document. According to the judge who later heard the criminal case against Bronson, no evidence was introduced to show that he had personally benefited "to the extent of one dollar." However, it was charged that the setup was such that he was in position to profit if he had wanted to! A somewhat quixotic position, it would seem. In any event, he was convicted, on highly technical

Jan 1, 1957

The early history of coal in West Virginia is all included with that of Virginia in the few records available but for present-day readers it is much more convenient that the account of this area prior to the Civil War be grouped with that since then. West Virginia shares with Maryland in the first record of coal noted in the Appalachian fields. This was along the upper Potomac River, in the fall of 1736, and the data about it are given under Maryland, as most&apos; of the development of the area was in that state. The next record of coal was left by John Peter Salley in his account of the expedition he made with Howard and others in 1742. (See p. 17.) The next reference found is that of Dr. Thomas Walker, in 1750, when he passed through the Pocahontas coal field. This has been described on page 18. Six years later, in March 1756, Capt. William Preston, who was with Major Lewis in his expedition down Big Sandy River, wrote in his journal: "Tuesday 2.... Moved down the branch and- came to the main creek where we camped. Put on half rations. Came into the Cole land; crossed the river 8 times."1 The party crossed from the head of Clinch River to Horse Pen Creek, then to Jacob&apos;s Fork and down it to Dry Fork of Tug River; the coal was seen in what is now McDowell County. The early settlers must have known of the presence of the great Pittsburgh bed in the northern part of the state, both along the Monongahela River and elsewhere, because the outcrops could easily be seen along streams in many. places. The report of the Commissioners for Adjusting Claims to Unpatented Lands, made in 1789, contains several references to coal in the names of streams, made years earlier. The earliest is one for 1,000 acres to James Walker, in Monongalia County, "adjoining his settlement on a branch of the right hand fork of Pappaw known by the name of the Stone Cole Lick made in the year 1773."2 Another of 400 acres in the same locality was settled upon in 1777.2 A third spoke of a tract "on the left hand fork of Stone Cole about three miles from the mouth," in 1783.1 Monongalia County then covered all of the northern

Jan 1, 1942

By G. Nabi, W-K. Lu

Cylindrical specimens of natural dense hematite were reduced to magnetite at atmospheric pressure in H2-H2O mixtures of known composition over the temperature range 1084° to 1284°K. The rate of reduction was measured by the rate of movement of the interface between hematite and magnetite. The diffusion of gases through the gaseous boundary layer, the magnetite layer, and the interfacial chemical reaction were all considered in the interpretation of experimental data. The mass transfer coefficient through the boundary layer was calculated using accepted correlations. Values of the chemical reaction rate constant and the diffusivity of hydrogen in the magnetite phase were determined. THE present investigation is concerned with the reduction kinetics of natural hematite to magnetite by H2-H2O mixtures in the temperature range 1084" to 1284°K at atmospheric pressure. This reaction is the first step in the series of topochemical reactions in the process of reducing hematite to iron. Kinetic information of the simple steps such as hematite-magnetite transformation is necessary in order to have a better understanding of the complex processes of hematite reduction in iron-making. It also has direct industrial significance because magnetic roasting is one of the most important methods in benefication of lean ore.&apos; Although many technical papers have been published on the process of magnetic roasting and iron oxide reduction, very little information is available in the literature concerning the fundamental nature of hematite reduction to magnetite by reducing gases. Hansen et al.2 reduced the dense synthetic pellets of high-purity oxide in CO-CO2 mixtures and determined the reaction rate by weight-loss method. They were able to interpret most of their results by applying the interfacial area control theory developed by Mckewan.3 In contrast, Wilhelm and St. Pierre,4 who studied reduction of hematite to magnetite in H2-H2O mixtures by weight-loss method, stressed that the resistance of the porous magnetite layer to the diffusion of gases cannot be neglected in consideration of the overall reaction rate. In the present study the contributions of interfacial chemical reaction, diffusion of gases through the magnetite phase, and the gaseous boundary layer to the overall reaction rate will be considered. APPARATUS AND PROCEDURE Hematite Specimens Preparation. Natural hematite ore from Vermillon range of Northern Minnesota was selected for the present investigation because of its high purity and thermal stability. Chemical analysis of five samples gave the following average values: 67.52 pct total iron (96.62 pct Fe2O3, 0.28 pct FeO, 0.03 pct metallic iron), 2.53 pct SiO2, <0.07 pct MgO, 0.03 pct CaO, 0.05 pct combined mixture, 0.07 pct loss on ignition, and 0.34 pct other. Cylindrical specimens of 0.93 cm in diam and 2.7 cm in length were drilled from slabs of ore with a water-cooled diamond core drill. These specimens were heated to 1000°C and furnace-cooled. Specimens with silica pockets developed large cracks. The uncracked specimens were heated a second time, and their surfaces were carefully examined with a microscope. Those with hairline cracks or surface inhomoaenitv-- were rejected. Preparation of H2-H2O Mixtures. H2-H2O mixtures were prepared by the combustion of H2-O2, mixtures in a pyrex glass chamber in the presence of a catalyst. Alumina pellets coated with palladium, supplied by Englehard Industries, were used as the catalyst. Purified grades of hydrogen and oxygen were used which were repurified by usual techniques. Hydrogen before entering the combustion chamber was passed through an activated alumina H2O absorption bulb, with copper turning at the top. The cover of this bulb was not made pressure-tight so that any pressure development in the hydrogen line would cause the cover to blow off and also the copper turnings would act as a flame arrester in the case of a flashback from the combustion flame. Oxygen flow rates were measured with a bubble flow meter after purification with 1 pct accuracy. Hydrogen flow rates were measured by "precision wet test meter" and the amount of unburnt hydrogen was accurately measured by a bubble flow meter, after condensing water vapor in the gaseous stream. The Pyrex glass bulb contained concentric Vycor glass tubes as shown in Fig. 1. Oxygen was prevented from diffusing into the hydrogen line by threading platinum wire through pores at the combustion end of gas inlet tube. The glass bulb was heated with a Kanthal heating wire pasted in asbestos paper. The surface temperature of the bulb was measured with a thermocouple and adjusted to remain at approximately 350°C. The gaseous reaction chamber also served as a preheater for gases to avoid thermal segregation. The following sequence of operation was adopted. 1) Nitrogen was passed through the outer concentric tube to purge the catalyst bulb of oxygen. 2) Hydrogen was introduced through the inner tube until a steady flow was obtained. 3) Oxygen was then introduced into the nitrogen stream passing through the outer tube. 4) When combustion had commenced and a flame was visible over the platinum wire, the N2 was turned off.

Jan 1, 1969

By E. A. Farrell

A comprehensive survey is made of the status of the asbestos industry as it relates to marketing the product. Included are descriptions of the various types of asbestos and the grading and classification systems used. The uses of asbestos, distribution practices, and types of ore bodies are all related to marketing. World production, the producers and their capacities and world consumption for 1966-67 are summarized and statistical data are included. Asbestos is a general term describing a family of fibrous minerals of the serpentine and amphibole mineral groups. Asbestos has a long history going back to the time of the Egyptians, when it was used as a lamp wick. The commercial mining of asbestos started in Canada, Russia, and Africa in the 1800&apos;s, and the first asbestos products were made in Italy and Russia. The five main types of asbestos are: chrysotile, accounting for 95% of the total mined, amosite, crocido-lite, anthophyllite, and tremolite. Canada, Russia, and Africa are the major producers of asbestos. The commercial utility of asbestos was at first based on the heat resistance of the fibrous mineral in the form of packing, at the start of the industrial revolution. Its current utility is based more on its ability to reinforce binders such as portland cement, rubber, and plastics. Its inertness to the chemical nature of most binders is unique. Most important is its ability to maintain its reinforcing utility when the product is exposed to weather and soil conditions as in asbestos cement boards and pipe, and heat, pressure, and chemical exposure as in brake linings and gaskets and packings. The mineral asbestos is also unique because its fibrous form permits it to be spun and woven to cloth or formed into paper. Many asbestos applications are critical to national defense and at the present time, there are no satisfactory substitutes. Grading and Classification Canadian chrysotile asbestos fiber is graded and priced by length since basically the longer the fiber the higher the utility. The Canadian asbestos industry does not, however, classify the fiber by direct length measurement, but by a dry screening test. The method is called the Quebec Standard Screen (QS) test. One pound of fiber is mechanically shaken in four vertically stacked sieve boxes. The relative proportions remaining on the sieves defines the grade. The longer the fiber, the larger is the amount that stays on the top coarse screens and the less on the lower, finer mesh screens. Other tests can be used to further define the length distribution of fiber such as the wet screen Bauer McNett and the Suter Webb Comb (3 group only). The Canadian grading system divides the milled fibers into 5 main groups: group 3, 4, 5, 6, and 7, with 3 group being the longest, and 7 the shortest. Each group is further divided to subgrades, identified in each group by the letters A to Z, with "A" the longest and "Z" the shortest. See Appendix 1 for the Canadian QS classification system. The Russians also use the QS test on chrysotile. The Africans classify their chrysotile into grades similar to Canadian. The African crocidolite and amosite, however, are classified into actual length groups such as l to 2 in. and 2 to 3 in. Amosite and crocidolite are generally longer than chrysotile but also more brittle. Milled asbestos is not composed of staple length fibers like fiber glass or cotton, but of a mixture or blend of fibers ranging from long to short. Milled asbestos has a fiber length distribution similar to the particle size distribution of a powder. For example, the longest group 3 chrysotile grades have a high percentage of the longest fibers (1/2 to 3/4 in.) and low percentage of short fibers (0.003 in.). The figures in Table 1 give the approximate length distribution of the longest, middle, and shortest groups. A second and further method of classifying fiber is the degree to which the fiber bundles are separated to form a larger number of smaller diameter bundles. This property is normally described as the degree of fiberization, openness or surface area. Air permeability tests are used to measure surface area. Asbestos pro-

Jan 1, 1971

By Robert S. Shoemaker

Receiving the Richards Award is undoubtedly the most memorable event in my entire life. There should, however, be more names engraved on it. These are the names of men who were my teachers (but not all of the academic variety) and my friends, each of whom had a part in my ever continuing education and thus have a part of this award. There was Bill Caldwell who made me into a chemist, and Will Shorey who added a lot of ore dressing. There was Rush Spedden who put me to work in his minerals research lab, Joe Brennan who made me turn my research into plant practice, and Tom Meek who sent me all over the world on metallurgical jobs. Bob Cheatham and Abe Dor taught me to try to give the client what he needs rather than what he wants, while Ed Malouf and Casey Davis always gave their particular brand of advice at exactly the right time. And, lastly, there was Leo Abell and Frank McQuiston, both fine metallurgists and the best friends a man could have. In addition to those I have mentioned, there are literally scores of others I would like to acknowledge with my sincere appreciation.

Jan 6, 1974

By Howland Bancroft

AMERICAN investment in foreign mining interests today faces its greatest task. U. S. dollars must make possible the. steady procurement of the minerals our defense effort consumes in huge quantities. The two most vital factors involved in foreign procurement are time and the continued good will of the nations from which minerals are purchased. The Point IV program was formulated to care for the second item, but it has failed to do the job. Its lack of success has not been from intent or from basic failure in formula. Foreign Investment, Four Eras Foreign mineral development, in so far as participation by private capital from the United States is concerned, may be divided into four main chronological categories: First: The period prior to the first World War when people, capital and products moved with relative freedom across international boundaries, and London was the recognized mining seat of the world. By the end of 1919 the United States direct investments abroad amounted to $3.9 billion of which some $900 million were in mining and smelting and $600 million in petroleum. Investment climate throughout most of the world was excellent. Second: The period between the end of World War I, when the international economy had been shaken from its foundations, and the beginning of the great depression of the 1930&apos;s, which still further disrupted the world economy. By that time the world mining center had moved across the sea and the United States direct investments abroad had increased to $7.7 billion of which mining and smelting accounted for $1.2 billion and petroleum for $1.1 billion. Investment climate was good in most parts of the world. Third: The period of the depression of the 1930&apos;s and the beginning of World War II during which foreign trade was still further disorganized and the international economy collapsed. Nazi barter agreements were initiated in many parts of the world, and Soviet propaganda commenced to make its, influence felt in many countries. During this period United States direct investments abroad decreased to $7.3 billion. Mining and smelting investments during the same period decreased some $200 million, though direct investments in foreign petroleum areas increased an equal amount. Investment climate became less and less hospitable in all parts of the world affected by economic nationalism. Fourth: The period since the beginning of World War II during which total direct investments abroad increased from $7.3 to $13.7 billion. Of this sum, at the beginning of 1950 investment in foreign mining and smelting is reported to have been $1.2 billion-back to where it was in 1929, and in petroleum to have reached $3.7 billion. Investment climate remained favorable in the countries respecting contractual obligations and fair in their treatment of invested capital. [ ] As noted above, the relative freedom of passage across international boundaries by people, capital and products ended with World War I and the situation remains unchanged in a greater part of the world. While this same war upset international economy, the depression of the 1930&apos;s caused the collapse of world trade, and exports from all countries fell to an alarmingly low figure. Some countries almost ceased to export. Chile, for example, reported a drop of 88 pct in exports. Countries with

Jan 1, 1952

By R. P. Dolan, W. M. Shedd, B. L. Buchanan

Analytical expressions are derived from empirical data relating the basic physical device parameters to the radiation dose. To put in perspective and justify the approach taken, the overall problem and methods of attempted solution of radiation damage to transistors in a missile or satellite environment is briefly examined. The main emphasis is on a new criteria for neutron radiation hardness and the device design implications resulting from using this criteria. Contrary to other derived criteria, the derived bipolar hardness relation depends mainly on the initial lifetime rather than the base transit time. It is shown, that contrary to previously accepted beliefs, the inherent attainable radiation tolerance of JFET&apos;s is at least a factor of ten greater than the radiation tolerance ofbipolars. Experimental results on JFET&apos;s designed for maximum neutron radiation tolerance are presented. The accuracy, utility, and range of possible validity of various published lifetime and carrier removal damage constants are discussed. It is well known that transistors are subject to damage due to radiation at much lower radiation levels than those which would cause structural damage to a missile or satellite. The three principal categories of radiation damage to transistors are displacement, ionization, and thermomechanical. The main cause of displacement damage is fast neutrons, and the main effects which permanently degrade transistor operation are minority carrier lifetime reduction and carrier removal. A second-order effect is mobility reduction. The main cause of ionization damage is gamma radiation which results in permanent effects due to charge build-up in the oxide and transient effects due to photo-current generation. The transient effects are usually handled by using circumvention techniques in the electronics system. The extent of the transistor degradation due to displacement and ionization damage depends strongly on the transistor type, whereas the extent of thermomechanical damage does not depend on the transistor type, but depends mainly on packaging and metallization which are common to all transistor types. The standard transistor types are categorized in Fig. 1 and typical cross-sections are shown in Fig. 2. The original reason for the designation of the two classes of transistors was that the unipolar operation depends on only one carrier (majority) and the bipolar operation depends on both minority and majority car- riers. The bipolar is then seriously degraded by minority carrier lifetime reduction, whereas the unipolar or field effect transistor is not. One of the two principle classes of field effect transistors, the junction field effect transistor (JFET), depends strongly on carrier removal. However, the insulated gate (MIS) is little affected by either carrier removal or lifetime changes, but is virtually eliminated as a radiation resistant device because of permanent charge build-up in the insulator caused by ionizing radiation. The bipolar and JFET suffer only minor effects due to charge build-up in the oxide passivation when compared1 to the MOS. This is because the active region of the MOS is adjacent to or part of the oxide layer. It is then the bipolar and JFET which are potentially resistant to permanent radiation damage. DERIVATION OF RADIATION TOLERANCE RELATIONS Criteria. The bipolar is by far the most widely used transistor type. The usual criteria for hardening bipo-

Jan 1, 1970

By Edward H. Robie

In late November and early December a considerable portion of our time was devoted to obtaining a business manager for Institute headquarters. The advisability of creating such a position was suggested in 1949 in the report of the Johnson committee. In that year, however, the Institute had a deficit of $72,000 so every effort was made to minimize expense. At that time most of the duties that normally would be assumed by a business manager were given to Newell Appleton who became office manager, convention manager, purchasing agent, and assistant to the secretary. So many responsibilities were his that he could not devote the necessary time to all of the many things that needed attention. H. H. Vasoll, representing a firm that made a study of Institute head office procedures early last fall, made a recommendation that "a business manager and controller from outside the present organization" be obtained, who would supervise the work of accounting, addressograph, purchasing, book and journal orders, filing, and mailing depts. He further recommended that Mr. Appleton be made administrative secretary, in which position he would act as head of an "Institute Activities Dept." He would devote his time to convention planning, meeting arrangements, travel accommodations, membership control and promotion, and public relations, and would assist the Secretary on special problems. Thus, Mr. Appleton retains some of his former responsibilities and will take more of the load off our shoulders in the conduct of affairs at Institute headquarters. The rest of his former work will be in the province of the newly created "Business Office Dept." Peter J. Apol is the man finally selected for the post of business manager. He is a young man of 32, a native Michigander and a graduate of the University of Michigan where he received a B.S. degree in business administration in 1940. He then spent three years in the Navy and has the rank of Lieutenant in the U. S. Naval Reserve. Three more years were spent in the U. S. Maritime Service as chief purser, and another year as chief paymaster for the Pope & Talbot Steamship Co. The past four years have been spent as head of the Greenland Construction Co., Greenland, N. H., chiefly engaged in building construction. Mr. Apol will endeavor to increase the efficiency of Institute headquarters operations and remove all possible causes for complaints of individual members. He will coordinate as seems advisable the work of various departments and install such modern business office machinery as seems applicable to our needs.

Jan 1, 1952

By H. A. Wheeler

That lead and zinc deposits are the result of prolonged,, slow deposition is the idea of most students of ore deposits, and in many cases, where the ore-bearing solutions have been very weak or the precipitating conditions have been very feeble, the ore accumulations have undoubtedly taken a long period of time. As these two vital conditions have been subject to great variations in the different mining camps, the following example is highly interesting in showing that deposition can be very rapid under favorable conditions, geologically speaking, and also extremely recent. In fact, the writer is inclined to regard most, if not all, of the Mississippi Valley deposits of lead and zinc as probably being very young, at least not older than Tertiary, if not Quarternary, in age. The extensive Joplin lead and zinc district, in southwestern Missouri, which is about 60 years old and has numerous mines that were abandoned from 1 to 50 years ago, shows that the lead and zinc today are in an active condition of solution and redeposition, although these two metals occur in the predominant form of sulfides. The mine waters from the older and more or less abandoned portions of the district are frequently so acid, mainly from the oxidation of associated pyrite, as to necessitate the use of wooden pipes and pumps. The first boom in the Oklahoma zinc fields, which is the southwestern extension of the Joplin district, occurred when ore was accidentally struck in drilling a water well. Among the mines then opened up was the Mission mine, at Lincolnville, Ottawa County, Okla. This mine was opened in 1903 in lean "sheet ground," or a flat blanket formation of chert carrying disseminated zinc blende, or "jack," and galena. Theore-body was very free from iron pyrites and the concentrates were very high grade, the "mineral," or lead concentrates, assayed 80 to 85 per cent. lead and the jack, or sphalerite, assayed 60 to 65 per cent. zinc. The orebody was very shallow, occurring at a depth of 76 to 95 ft. (22 to 28 m.) and very wet, requiring three or four pumps to handle the water. The mine was operated until 1914, when it was closed by litigation and immediately filled with water. The second Oklahoma boom, five years ago, opened up the large, active camps of Picher, Tar River, and Century, which are located 2 to 5 mi. west of Lincolnville. They are considerably deeper, being farther down on the westwardly dipping monocline that emanates from the Ozark

Jan 1, 1920

By W. G. Bearden, P. P. Scott, G. C. Howard

This paper concerns the rupture or breakdown of rock formations as related to drilling, completing, and stimulating production of wells, and comprises data compiled from a study of literature and records of treatment of oil and gas wells. and from tests conducted in bores drilled into rock cores and outcrops of rock. Results of the investigation indicate that the internal pressure to rupture cylinders of rock and to breakdown rock formations surrounding a bore in the earth is dependent upon the extent of intrusion of fluids. the position of bedding planes. the ratio of internal to external diameter, the tensile strength of rock, and magnitude of confining pressure, and is independent of the size of bore, degree of fluid saturation. and temperature of rock within practical limits. It is concluded that the mathematical relationship of pressure in bores and stresses in the surrounding rock must not be limited by the simplifying assumptions of homogeneity. isotropy, and impermeability; that the incidence of lost circulation of drilling fluids to induced fractures may be reduced by preventing intrusion of fluids into the small intrinsic fractures along weak bedding planes; and that the magnitude of the breakdown pressure of wells to be treated may be lowered by removal of mud cake. INTRODUCTION The purpose of this paper is to present and discuss the results of tests which may serve to broaden the understanding of the phenomena of rupture or breakdown of rock and thus contribute to the improvement of the techniques for drilling and completing wells. including such operations as preventing lost circulation, stimulating production, and placing cement. Since the early recognition of the possibility of rupturing rock adjacent to a well by fluid pressure, the distribution and magnitude of stresses around a well and the internal pressure to cause failure have been expressed mathematically by application of the principles defining the elastic and inelastic behavior of thick-walled cylinders of a homogeneous. isotropic, impermeable material. In either the elastic or plastic state, if the conditions of homogeneity. isotropy, and impermeability were the normal characteristics of rock. there would be no reason to question the validity of the above principles when applied to rock. However. since most rock formations are characteristically permeable to some degree, contain bedding planes and small intrinsic fractures. and are heterogeneous, rendering invalid the assumptions of homogeneity, isotropy, and impermeability, the application of the thick-walled cylinder theories to the behavior of rock formations penetrated by a bore appears illogical. Also the failure to consider the effect of the properties of the drilling fluids, which certainly intrude in various degrees into most rock formations. is further cause for questioning the application of these principles. Even in the case of cylinders of hardened chrome-nickel steel, which would he considered relatively homogeneous isotropic. and impermeable, as compared to rock, it has been observed that the internal pressure capable of being withstood by the cylinders varied with the sizes of molecules comprising the rupturing fluid used. Because of these apparent weaknesses in the theories of the behavior of thick-walled cylinders when applied to bores in rock, and the importance of knowing the true behavior of rock under the influence of fluid pressure when planning drilling and completing procedures for wells, tests were undertaken to determine by observation the actual rupturing pressure of cylinders of rock and the effects of such variables as environmental conditions and characteristics of rock formations, fluid properties, and bore dimensions. It was intended that by these tests the validity of the thick-walled cylinder theories when applied to rock would be determined and, if found invalid, mathematical expressions would be derived for predicting stress and rupturing pressure of rock formations under various conditions. Since the derivation of mathematical expressions has been only partially completed, all of the results of the latter phase are not included in this paper. PROCEDURE The investigation was initialed with a study of the theories pertaining to the rupturing of thick-walled cylinders of homogeneous. isotropic, impermeable material and a study of the

Jan 1, 1953

By Dudley Homer

MINAS DE MATAHAMBRE, S.A. is a Cuban mining corporation with mines located in the Matahambre district about 100 miles westerly from Havana in the Province of Pinar del Rio. The port of entry is the subport of Santa Lucia on the north coast of Cuba. The mines are located six miles inland at the town of Minas de Matahambre. Minas de Matahambre and Santa Lucia are connected by a 9-mile automobile road, and a 30,000-ft. Leschen aerial tramway. At the subport of Santa Lucia the company maintains docks, concentrate bins, tugs, lighters, and miscellaneous shipping equipment. The power plant of the company is also located at Santa Lucia. Connection between the power plant and the mine is effected by a 30,000-ft. transmission line. In the town of Minas de Matahambre are located the mines, concentrator, shops, and warehouses. The con-centrates are transported to Santa Lucia by the Leschen aerial tramway. The mines are equipped with three shafts, viz., Nos. 1, 2, and 3. (Fig. 1.) No. 1 Shaft is a three-compartment vertical tim-bered shaft and has reached a depth of 1825 ft. This is the present main hoisting shaft. No. 2 Shaft is a four-compartment vertical shaft lined with steel sets and native hardwood lagging. Certain portions where the ground is heavy have been lined with re-inforced concrete. Practically all production will be hoisted eventually through this shaft. No. 3 Shaft is a three-compartment vertical timbered shaft. It has reached a depth of 1090 ft. Its purpose is for prospecting, ventilation, and handling men and sup-plies through the north section of the mine.

Jan 1, 1933

By AIME AIME

Further details of the 97th meeting of the Institute, at Spokane, have been sent to members in the Special Circular of May 8, 1909, and for convenience a summary of the additional information is given later in this announcement. In spite of the present small number who have joined the party, final arrangements have been made to complete the itinerary given in the circular. It is greatly to be desired, both in behalf of the Institute and in recognition of the special courtesies to be extended on the trip, that the party be made larger. Exceptional facilities to visit the many mines and smelters have been freely provided; and members are requested to make all reasonable effort to attend the meeting at Spokane and participate in the excursions. . For those who cannot take the entire trip, it may be possible to provide special Pullman accommodations after leaving the Yellowstone Park. In order to make the necessary arrangements, however, the names of members and guests contemplating this partial trip should be sent at once to Mr. Theodore Dwight, .39 West 39th St., New York, N. Y. A special train of Pullman cars will leave Chicago September 16. This train will be side-tracked at all places visited, and the sleepers will be available for lodging and the dining-car for meals (luring the entire trip, except while taking the tour through the Yellowstone Park. The general cost of the trip per member will be $300, which includes transportation, berth, and meals for the entire trip from Chicago back to Chicago, almost 6,000 miles, and the tour through Yellowstone Park, occupying in all about 30 days. Special accommodations on the train will be furnished at the following rates

Aug 1, 1909