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By H. Cecil Spicer

The results described in this article are based on field work conducted during the periods APril-May, 1939, and MaY-JulY, 1940. The United States Potash CO. is mining potash on Government land under a permit from the Department of the Interior and the geophysical investigation mas completed under a cooperative arrangemerit made between that company and the Conservation Branch of the Geological Survey. The writer, a member of the Section of Chemistry and Physics of the Geologic Branch, was assigned to this investigation. Four definite objectives were in mind for the geophysical work in the studies over the salt deposits. The first was to determine the measure of success that could be attained in this type of work with the resistivity methods that were to be employed. These methods had been introduced into the work of the Conservation Branch by Benjamin E. Jones for the investigation of dam sites, and have been used under his direction by the author for such work. If the method proved to be applicable, an l was to be made to contour the top of the salt beds and also the other formation boundaries known to be present in this area. Salt-water aquifers were to be studied in an effort to determine their boundaries, and an attempt was to be made to delineate the potash-bearing beds. Others have made, and reported, resistivity studies over saliferous deposits in different areas. Friedell and Messrs. Schlumberger2 reported geophysical work performed in the disrovery of the salt domes of Alsace; Carrette and Kelly3 described the geology of the same area. Leonardon and Kelly4 published a resistivity curve obtained over the Hettenschlag dome, and a further discussion of this same area was given by the Messrs. Schlum-berger5 in a communication. Messrs. Alty6 described studies 0" salt deposits in which the sing[e-probe method was used. Sinerez7 mentions that electrical methods were tried over salt deposits in Spain. Geoffrey and Charrin8 show a resistivity curve obtained over marl, gypsiferous marl and salt which is similar to that obtained over the New Mexico salt deposits. Kelly9 reported resistivity work performetl with the ground comparator of Zuschlag over the salt deposits near Syracuse, N. Y., where the Salina formation is at a depth of 700 to 800 ft. Some structural studies on the potash basin of Alsace are described by Poldini.10 Another single-probe resistivity study, made over salt deposits in New Mexico, is briefly described by Heiland,ll through the courtesy of Harry Aurand, of the Midwest Refining CO.

Jan 1, 1942

I. PRESIDING OFFICER. At all business meetings of the Institute the President, or, in his absence, the First Vice-President, or, in the absence of both of them, any other Vice-President or Director, chosen by the meeting, Shall preside. At all other meetings of the Institute the President, or, in his absence, one of the Vice-presidents, Shall preside. If none of these be present the meeting Shall elect a Chairman. The President Shall do and perform Such other duties as may from time to time be assigned to him by resolution of the Board of Directors of the Institute. IL ORDER OF BUSINESS. At each business meeting of the Institute the order of business Shall be as follows: 1. Reading of minutes of preceding meeting. 2. Report of the President. 3. Report of the Treasurer. 4. Report of the Secretary. 5. Election of Directors. 6. Reports of Standing Committees. 7. Reports of Special Committees. 8. Special Orders. 9. Miscellaneous business. This order of business may be changed at any meeting, by a vote of a majority of the Members and Associates present. At all sessions of the Institute, other than business meetings, the order of proceedings and the time of adjournment Shall rest in the discretion of the presiding officer. III. SECRETARY OF THE INSTITUTE. The Secretary Shall keep a record of the proceedings of all the meetings of the Institute. He Shall be custodian of the corporate Seal, of the minute books and of all the legal documents belonging to the Institute. He Shall have charge on behalf of the Institute of all correspondence. He Shall notify all Officers and Directors and all members of committees of their election and appointment; Shall issue notices of all meetings of the Board, and of the annual and other business meetings of the Institute; and Shall, in calling Special meetings of the Directors, Specify the objects of Such meetings. He Shall act as clerk at all the meetings of the Board of Directors and at all meetings of the Institute. The Secretary Shall be custodian of all technical or Scientific papers Submitted to the Institute for its consideration and Shall have general charge and supervision of the editing and proof-reading of all material published by the Institute, and. of the distribution thereof. The Secretary shall be the custodian of all back numbers of the Transactions and other publications of the Institute. There Shall be kept under his direction an account

Jan 1, 1925

By Earl G. Alexander, W. R. Runyan

The nature of silicon growths which form on amorphous silicon dioxide during epitaxial deposition in unmasked areas was investigated. Octahedral silicon crystals nucleate and grow on the oxide at pinholes, adjacent to foreign matter, and probably at oxygen-deficient sites. Generation of these oxygen-deficient sites on the oxide surface is shown to be thermody-namically favorable under usual deposition conditions. The conditions which affect saturation (SiCl4 concentration, flow rate, temperature) determine the number of sites on which silicon will nucleate and grow. Reaction product HCl is likely responsible for suppressing silicon growths on the oxide near exposed areas of silicon. Evidence is given that the oxide-silicon interaction occurs in hydrogen only and involves water as a transport agent. SINCE shortly after the first epitaxial layers of silicon and germanium were grown over large areas, efforts have been underway to grow selectively on specified portions of the surface. Such selective growth should be particularly applicable to monolithic integrated circuits. Usually the approach has been to use a mask to delineate the desired area,'-7 but the VLS methoda can also be used, and direct programmed atomic beam deposition has been suggested.9 The masking techniques may embody two forms: in one the mask is a material which can later be removed along with any growths attached to it; in the other, attempts are made to prevent growth on the mask, so that over a whole slice the only deposition that will occur is in the unmasked regions. The present work is concerned with only the latter case, and specifically with silicon. Joyce and Baldrey1 suggested the use of thermally grown silicon dioxide as a mask material and showed that for the proper choice of operating conditions (total flow, SiCl4 concentration, total deposition time, and temperature) spurious growth could be minimized and that if the deposition times were not too large, and the criteria not too stringent, a usable process occurred. Later Schnable et al 4 observed that after extended deposition times, during which most of the silicon dioxide became covered with growth, there was always a band of oxide around the exposed silicon area that was quite free of spurious silicon crystallites. This latter observation is particularly intriguing since it extends the hope that with proper precautions masking can be much more versatile than it presently is. EXPERIMENTAL PROCEDURE Silicon substrates oriented to within 1.5 deg of a (111) plane were prepared by etch polishing lapped

Jan 1, 1967

By Frank H. Macpherson

When it became apparent early in 1941 that the United States might be drawn into the war, studies were made of the bauxite situation in Arkansas, principally because 9.5 pct of the known bauxite reserves of the country were located in that State. Bauxite mining was then geared for maximum production to supply ore to meet this country's war requirements and, if necessary, to supply the needs of Canada as well. In view of the comparatively small bauxite reserves, Congress appropriated funds for an extensive exploratory drilling program to be carried out by the Bureau of Mines in cooperation with the Geological Survey. An alumina plant was erected near Bauxite and an aluminum plant near Hot Springs, Ark., by the Defence Plant Corp. The Metals Reserve Co. established a schedule of prices, arranged for stockpile sites and a buying agency. Operators cooperated to step up production and new ones came into the field. Production Record Prior to 1941, the greatest annual production in Arkansas was 562,892 long tons, dry basis in 1918. During the single month of August 1943, 693,596 long tons were mined—130,704 tons more than for the entire year of 1918. In general the Arkansas bauxite deposits are relatively small, irregular in thickness, somewhat scattered and, compared to coal, iron or open-pit copper deposits, are ill-adapted to an expansion in output. Commercial deposits range in horizontal extent from less than an acre to about 40 acres and are usually very irregular in outline. The average thickness of all known workable deposits is between 12 and 15 ft. with a maximum of about 60 ft. The ore bodies are usually somewhat undulating and nearly horizontal although locally some deposits dip as much as IS°. Types of Bauxite Three physical types of bauxite may be recognized: pisolitic, granitic and amorphous. Pisolitic ore is the most common type. It consists of small pebble-like nodules, ranging from the size of a pin head up to several inches in diameter, all set in a fine grained matrix. Transported bauxite is usually- pisolitic. Most residual bauxite is granitic. It is believed not to have moved appreciably from the location where it originally was formed. This is indicated by the fact that it appears to grade into unaltered nephelite syenite, which it overlies. Amorphous ore is the least abundant. It is nonpisolitic and resembles clay, has no characteristic texture, and can be identified definitely only by chemical analysis. Uses of Bauxite Bauxite is chiefly used for, and at the present time is substantially the only

Jan 1, 1948

By Frank H. Macpherson

When it became apparent early in 1941 that the United States might be drawn into the war, studies were made of the bauxite situation in Arkansas, principally because 9.5 pct of the known bauxite reserves of the country were located in that State. Bauxite mining was then geared for maximum production to supply ore to meet this country's war requirements and, if necessary, to supply the needs of Canada as well. In view of the comparatively small bauxite reserves, Congress appropriated funds for an extensive exploratory drilling program to be carried out by the Bureau of Mines in cooperation with the Geological Survey. An alumina plant was erected near Bauxite and an aluminum plant near Hot Springs, Ark., by the Defence Plant Corp. The Metals Reserve Co. established a schedule of prices, arranged for stockpile sites and a buying agency. Operators cooperated to step up production and new ones came into the field. Production Record Prior to 1941, the greatest annual production in Arkansas was 562,892 long tons, dry basis in 1918. During the single month of August 1943, 693,596 long tons were mined—130,704 tons more than for the entire year of 1918. In general the Arkansas bauxite deposits are relatively small, irregular in thickness, somewhat scattered and, compared to coal, iron or open-pit copper deposits, are ill-adapted to an expansion in output. Commercial deposits range in horizontal extent from less than an acre to about 40 acres and are usually very irregular in outline. The average thickness of all known workable deposits is between 12 and 15 ft. with a maximum of about 60 ft. The ore bodies are usually somewhat undulating and nearly horizontal although locally some deposits dip as much as IS°. Types of Bauxite Three physical types of bauxite may be recognized: pisolitic, granitic and amorphous. Pisolitic ore is the most common type. It consists of small pebble-like nodules, ranging from the size of a pin head up to several inches in diameter, all set in a fine grained matrix. Transported bauxite is usually- pisolitic. Most residual bauxite is granitic. It is believed not to have moved appreciably from the location where it originally was formed. This is indicated by the fact that it appears to grade into unaltered nephelite syenite, which it overlies. Amorphous ore is the least abundant. It is nonpisolitic and resembles clay, has no characteristic texture, and can be identified definitely only by chemical analysis. Uses of Bauxite Bauxite is chiefly used for, and at the present time is substantially the only

Jan 1, 1948

By Paul Averitt

The U. S. Geological Survey has been actively engaged in work on coal for more than 50 years. During this long period we have released more than 300 publications containing information about coal and coal reserves, including details on the thickness, distribution, and quality of coal, and the structure and stratigraphy of the coal-bearing rocks. We have also cooperated with state surveys on many similar publications. For many areas these reports are the only reliable published data on our resources of coal. During the last several years we have substantially increased our activities above the wartime low. We now have field work in progress, or reports in preparation, on 13 detailed mapping projects distributed as follows: 1. Pennsylvania anthracite field 2. Casselman Basin, Md. 3. Leslie County, Ky. 4. Deep River field, N. C. 5. Coosa field, Ala. 6. Powder River field, Mont. 7. Spotted Horse field, Wyo. 8. Yampa field, Colo. 9. Paonia field, Colo. 10. Trinidad field, Colo. 11. Durango field, Colo. 12. Chaco River area, N. M. 13. Lewis and Thurston County fields, Wash. For two of these areas; the Paonia field, Colo., and the Coosa field, Ala., we have published recently preliminary reports, and final reports are in preparation. In addition, we are nearing completion of a coal reserve study of Montana, and are beginning similar studies in several other states, as part of a program of revising our estimate of national coal resources on the basis of presently available data. Factors Involved in Making Estimates Our responsibilities include detailed field mapping to secure information on areas of outcrop of coal beds, their range in thickness, nature of roof rock, amount of overburden, correlation of the beds, stratigraphy and structure of the coal-bearing rocks, and the preparation of coal reserve figures based on these data. The computation and estimation of resources of coal in the ground, like that of resources of other mineral commodities, involves consideration of many additional purely geological factors that can be appraised best through such regional studies. Regional variations in the thickness and texture of rocks overlying and underlying coal beds, for example, give evidence as to the probable position of the edges of the basin of coal deposition, or may aid in the delineation of sand-filled channels that sometimes cut out coal beds. It is apparent that the detailed field studies, in which data are gathered, are the basis for coal reserve studies, and in our present program these two phases of work are being carried on together. Previous Coal Reserve Estimates For many years we have been aware

Jan 1, 1950

By Frederic Dewey

BONE-ASH cupels have been used from time immemorial to absorb litharge, and accompanying oxides; in assaying. Doubtless, also, from the earliest days cupels have been most unjustly blamed for much poor assaying. It has long been known that the precious metals go with the litharge into the cupel. This occasions a loss of precious metals and reduces the results of the assay. There have been many investigations of cupels and the most diverse views have been expressed, the extremes being the statements of Lodge 1 that every cupel has some effect upon the loss in assaying telluride ores and of the Campredons2 that coarse and fine and hard and soft cupels all give the same loss of silver when cupelling the same weights. The truth lies between these statements and much nearer the latter. In a vast majority of cases the influence of the cupel is not dominant and is outweighed by other conditions, particularly the temperature of the cupelling bead. At the Spokane meeting of the Institute I presented a paper on the Assay and Valuation of Gold Bullion,3 which recorded the results of many hundreds of assays made in the Mint service under everyday commercial conditions, which of necessity differ from scientific conditions. In following this matter up, for the purpose of increasing the accuracy of our commercial methods of bullion assays, the question of the absorption of gold by the cupel was found to be a most important one and was taken up for investigation. In a lesser degree, the silver absorption is important and interesting, but at present it appears to be far more complicated and, while many figures showing silver absorption may be found through this paper, much further investigation is required to put the subject upon a satisfactory basis.

Jan 11, 1917

By Francisco Cadena

THE construction of Norris Dam, built by the Tennessee Valley Authority on the Clinch River, a tributary of the Tennessee River, involved the production of coarse and fine aggregate for approximately 1,000,000 cu. yd. of concrete. A hammer-mill plant for the manufacture of sand from quarried rock was indicated as the most economical method of providing this material. The abrasive character of the feed as compared to the average hammer-mill feed made it necessary to control operations rather ciosely, and this resulted in the accumulation of many data bearing on production and maintenance. This paper will deal only with three specific sets of data, accompanied by such general infor-mation as may be necessary to explain the conditions under which they were obtained and followed by discussions on the relation of silica content to hammer wear, comparative costs of slugger and stirrup hammers, and comparative costs of tool-steel and manganese-steel grate bars.

Jan 1, 1937

By Robert C. Berggan

The hot-milling process for reconditioning rock-drill bits is not new. It has been employed by a few mines for years and in the past decade it has been widely adopted, as its advantages have become better known. Because of the extensive commercial development in England and Canada of machines to operate on this principle, general acceptance has been largely in the British possessions and until recently has been chiefly in the field of conventional steel. In the past two years there has been a definite trend toward hot-milling of detachable bits in Canada, but only in the past year has any considerable attempt been made to build special machines for this type of work. Generally a machine designed for conventional steel has been used and special holders employed to manipulate the bit. As early as 1934 at least one operator in the United States had adapted hot-milling to conventional steel with a substantial saving in resharpening costs.1 Several other operators have taken it up but there has been no widespread adoption of the method in this country by users of conventional steel. This may be partly explained by the fact that until recently no American manufacturer produced this equipment and operators have been obliged to build their own hot-millers or import them. Several years ago a few machines were built in Seattle, Washington, and operated in some mines in the northwest, but, for reasons not generally known, the effort was abandoned. The Process Hot-milling performs the function of re-dressing the bit at a forging temperature of about 1650°F., by the removal of metal from the flutes with a milling cutter, followed by a similar cut from the bit gauge. Conventional bits are thus treated following the usual forging operation in a sharpener, and usually in the same heat.

Jan 1, 1940

By Robert C. Berggan

The hot-milling process for reconditioning rock-drill bits is not new. It has been employed by a few mines for years and in the past decade it has been widely adopted, as its advantages have become better known. Because of the extensive commercial development in England and Canada of machines to operate on this principle, general acceptance has been largely in the British possessions and until recently has been chiefly in the field of conventional steel. In the past two years there has been a definite trend toward hot-milling of detachable bits in Canada, but only in the past year has any considerable attempt been made to build special machines for this type of work. Generally a machine designed for conventional steel has been used and special holders employed to manipulate the bit. As early as 1934 at least one operator in the United States had adapted hot-milling to conventional steel with a substantial saving in resharpening costs.1 Several other operators have taken it up but there has been no widespread adoption of the method in this country by users of conventional steel. This may be partly explained by the fact that until recently no American manufacturer produced this equipment and operators have been obliged to build their own hot-millers or import them. Several years ago a few machines were built in Seattle, Washington, and operated in some mines in the northwest, but, for reasons not generally known, the effort was abandoned. The Process Hot-milling performs the function of re-dressing the bit at a forging temperature of about 1650°F., by the removal of metal from the flutes with a milling cutter, followed by a similar cut from the bit gauge. Conventional bits are thus treated following the usual forging operation in a sharpener, and usually in the same heat.

Jan 1, 1940

By Gustav S. Preller, A. M. Gaudin

Fox the past 20 years it has been generally accepted that the flotation process is made possible as a result of the action of certain chemical substances on the surface of the mineral particles. In fact, it has been suspected, but never demonstrated, that this action produces on the mineral particles a layer of chemosorbed ions that is of the order of magnitude of a monolayer; that is, of a layer one ion deep. It is the purpose of this paper to present certain initial results on the relationship of mineral surface area and collecting-agent requirements. Up to about eight years ago, all considerations involving the surface area of finely divided solids were-limited by the fact that there was not in existence any general method for determining the extent of such surfaces, especially on mixed materials. However, the method invented by Brunauer, Emmett and Teller1 has changed the situation by providing a general procedure (BET method). This procedure has already been applied to mineral dressing problems2 -4 and has now received confirmation as to accuracy by an entirely independent method.5 This confirmatory or "absolute" method uses a very tedious calorimetric procedure and is not suitable for routine determinations; but still another method6 now is available to relate the results obtained by the BET method to those obtained calorimetrically. This Harkins-Jura method has the advantage that it does not require an assumption concerning the parking area per molecule of adsorbate (nitrogen). In the original work by Brunauer, Emmett and Teller the parking area per nitrogen molecule was calculated to be either 13.8Å2. or 16.2Å2. according as the nitrogen was assumed to be closely packed as in crystalline nitrogen or loosely packed as in liquid nitrogen. The initial experimental work from this laboratory2 supported the 13.8Å2. figure; that work was done on glass spheres of measurable geometric area and it was based on the assumption that the glass spheres were truly smooth; any deviation from this assumption would, of course, have made the calculated parking area higher. Harkins and Jura's results suggest that the parking area is not the same for all substrata; furthermore, the average of the 87 measurements cited indicates a "preferred" parking area for the nitrogen molecule of about 15.2Å2., with extreme values at 13.7 and 16.9Å2. The average of 21 determinations made in connection with this study' gave a parking area of 14.3 ± 0.27Å2. In view of this result and of the Harkins and Jura

Jan 1, 1946

By William Klement

KNELLER' has recently reported that extensive metastable solid solutions may be obtained in Cu-Fe alloys by simultaneous vapor deposition. This note reports that solid solutions, apparently single -phase, can be obtained for Cu-Fe alloys containing 0 to 20 and 85 to 100 at. pct Fe by rapid quenching from the melt; the inability to extend the solid solubilities further is related to the liquid miscibility gap, Fig. 1, as for Cu-Co alloys.2'3 Accurate lattice spacings of the copper-rich fcc and iron-rich bcc solid solutions have been obtained. Homogeneous alloys were prepared by casting4'5 and sintering2 from elements of 99.9+ pct purity. The quenching techniques were as before,' except the iron-rich alloys were liberally covered with argon while at elevated temperatures. Flakes about 1 sq mm in area were obtained and investigated with the Debye-Scherrer technique, as previously described.2,4 All X-ray work was done at 25° 2°C using filtered copper and cobalt K radiation. Relative visual intensities of the diffraction lines for the phases in the quenched alloys are shown in Table I. The lattice spacings of the fcc structure for alloys containing up to 80 at. pct Fe are plotted in Fig. 2. The variation of these lattice parameters with composition is in good agreement with the re- of cementite spots usually present (all hkl reflections are allowed) and the ease of confusing them with ferrite or martensite reflections. Copies of the report can be obtained by writing to the Materials Research Department, Rocketdyne. 6633 Canoga Avenue, Canoga Park, Calif., 91304. A copy is also available at the Engineering Societies Library, 2nd floor, 345 East 47th Street, New York, N.Y., 10017. Photocopies, either full-size or microfilm, may be purchased from the Engineering Societies Library. sults6 of Andersen and Kingsbury, Fig. 2, although there is some disagreement in absolute value. This discrepancy may be due to the different temperatures at which the X-ray measurements were carried out and perhaps to the different extrapolation procedures. Also, Andersen and Kingsbury6 state that their lattice spacings were computed relative to the wavelengths given by Siegbahn in 1933; this reference has not been found and it is assumed that the well-known 1931 wavelengths were used, the lattice spacings then being in kx units which are converted into angstroms by the factor 1.00202. There is no support for the contention that solution of iron decreases the lattice parameter of copper, as con-

Jan 1, 1965

By H. Cecil Spicer

THE results described in this article are based on field work conducted during the periods April-May, 1939, and May-July, 1940. The United States Potash Co. is mining potash on Government land under a permit from the Department of the Interior and the geophysical investigation was completed under a cooperative arrangement made between that company and the Conservation Branch of the Geological Survey. The writer, a member of the Section of Chemistry and Physics of the Geologic Branch, was assigned to this investigation. Four definite objectives were in mind for the geophysical work in the studies over the salt deposits. The first was to determine the measure of success that could be attained in this type of work with the resistivity methods that were to be employed. These methods had been introduced into the work of the Conservation Branch by Benjamin E. Jones for the investigation of dam sites, and have been used under his direction by the author for such work. If the method proved to be applicable, an effort was to be made to contour the top of the salt beds and also the other formation boundaries known to be present in this area. Salt-water aquifers were to be studied in an effort to determine their boundaries, and an attempt was to be made to delineate the potash-bearing beds. EARLIER STUDIES Others have made, and reported, resistivity studies over saliferous deposits in different areas. Friede1 and Messrs. Schlumberger2 reported geophysical work performed in the discovery of the salt domes of Alsace; Carrette and Kelly3 described the geology of the same area. Leonardon and Kelly4 published a resistivity curve obtained over the Hettenschlag dome, and a further discussion of this same area was given by the Messrs. Schlumberger5 in a communication. Messrs. Alty6 described studies on salt deposits in which the single-probe method was used. Sinerez7 mentions that electrical methods were tried over salt deposits in Spain. Geoffrey and Charrin8 show a resistivity curve obtained over marl, gypsiferous marl and salt which is similar to that obtained over the New Mexico salt deposits. Kelly9 reported resistivity work performed with the ground comparator of Zuschlag over the salt deposits near Syracuse, N. Y., where the Salina formation is at a depth of 700 to B00 ft. Some structural studies on the potash basin of Alsace are described by Poldini.10 Another single-probe resistivity study, made over salt deposits in New Mexico, is briefly described by Heiland,11 through the courtesy of Harry Aurand, of the Midwest Refining Co.

Jan 1, 1941

By J. J. Gilman

Examination showed that characteristic cleavage step patterns are observed on the cleavage surfaces of undeformed, slipped, bent, twinned, compressed, and indented zinc crystals; and the effect of temperature is discussed. Dimples were seen to produce cleavage steps in a treelike pattern in otherwise undeformed crystals. The steps seem to originate when cracks intersect screw dislocations. IT has been known for a long time that the path of fracture in polycrystals may be discontinuous (see Jaffe, Reed, and Mannl for review). Recently, Kies, Sullivan, and Irwin2 have proposed, and given evidence, that crack propagation is discontinuous within individual crystals as well. Other evidence has been given by Low.' When discontinuous cracks within a crystal join together to make a macrocrack, the lamellae between each set of two cracks are torn somewhere, forming small cliffs. These cliffs appear as lines when the cleavage surface is observed microscopically.4,5 The lines have been called vein, tree, and riverlike markings by various authors, and they have sometimes been mistaken for fissures. The descriptive term cleavage steps is used in this paper. Cleavage steps vary in height over a wide range of values, from molecular dimensionsG to lor. and larger. Kies, Sullivan, and Irwin,2 as well as George,' have shown that the gross cleavage step patterns for plastics, polycrystalline metals, and for mono-crystals are sometimes similar. Thus, they depend mostly on the mechanical variables that prevail during cleavage and are relatively insensitive to the structure of the material. For example, parabolic markings2,7,8 sometimes result when cracks open up ahead of, and not coplanar with, the main crack front. If the advance crack has the same velocity as the main crack, their intersection line is a parabola, otherwise it is a hyperbola or an ellipse. The patterns are strongly affected by differences in crack velocities. This results in chevron patterns which point to the place of origin of the main crack. It is the purpose of this paper to demonstrate the existence of a mechanism of cleavage step formation which is a continuous rather than a discontinuous process. Also, certain characteristic step patterns are described, and the strong effect of temperature is shown. The specimens were zinc monocrystals (grown from 99.999+ pct pure metal). These were cleaved at room temperature and at — 196°C. Results and Discussion Cleavage step patterns are highly variable from point to point on a given specimen, as well as from one specimen to another. Although the patterns shown in the photographs are typical, they have been selected for graphic illustration. Figs. la and lb compare undeformed crystals that were cleaved at —196 °C and room temperature, respectively. Cleavage at room temperature (Fig. lb) resulted in a higher density of high steps (dark black lines) and enhanced the visibility of the fine background markings. Deformation by simple slip caused no marked change in the step patterns until the glide strain reached about 1.0. But, as Fig. lc shows, the density of high cleavage steps was greatly increased by large glide strains. Corrugations lying perpendicular to the slip direction may also be seen in Fig. lc. These are caused by deformation bands. The cleavage resistance of the crystal of Fig. lc was very high compared to undeformed crystals (estimated by the force on a needle required for cleavage). Striking and varied cleavage step patterns were observed on bent crystals. Two characteristic patterns that were observed on crystals bent at 25°C, and cleaved by reverse bending at —196°C, are shown in Figs. 2a and 2b. The first, Fig. 2a, consists of V-shaped lines similar to the parabolas of other materials2,7 Fig. 2b shows a pattern that is the equivalent of Fig. la, consisting of faint background lines with a few higher step markings. Cleavage of bent crystals at room temperature resulted in Figs. 2c and 2d. Now, the cleavage step lines show a strong tendency to follow one of two perpendicular paths. In Fig. 2c (bent once), many of the cleavage step components that lie parallel to the bend axis are assembled into irregular lines. In Fig. 2d (bent twice), the cleavage steps again tend to consist of two perpendicular components, but neither of the components is assembled into lines. Also, the step density is higher.

Jan 1, 1956

By A. J. Miles, A. D. Topping

in this paper, the theory of elasticity has been applied to the rock about a deep well, It is assumed that the rock has a modulus of . elasticity and a Poisson's ratio and that the theory of elasticity applies. It is necessary to know or assume the state of stress existing in the rock before it is penetrated by the well drill. The application of this theory indicates that stress concentration of shear, tensions, and compressions about the bore hole are of a high order. This is particularly true when a horizontal compressive stress exists in one direction only in the formation before drilling. If such an initial state of stress exists before drilling, then the rock will have stress concentrations of both tension and compression at the same elevation and of such magnitude that failure of the rock is likely. Accompanying these is a shearing stress of large proportion which is likely to produce spalling of the well walls. Internal pressure applied to the well bore will relieve the extreme compression but not the tension and has little effect upon the shear. Plastic deformation of the rock through a geological time tends to mitigate the stress concentrations. IntroductioN It has long been known that the stresses about holes and re-entrant corners of elastic solids under the influence of loads are different and generally more intense than those imposed upon the body else- where. Stress concentration at a re-entrant corner can be reduced by increasing the radius of the fillet at the corner. Stress concentration at the end of a crack in a plate undergoing either tension or compression Can be relieved appreciably by drilling a hole at the very end of the crack. Also, stresses can be increased in an elastic body in tension or compression by making a hole in it. The stress concentration is greatest at the edge of the hole. Considerable knowledge of the stresses which exist about the bore hole of a deep well may be had by applying our knowledge of engineering mechanics; or more particularly the theory of elasticity. It is, of course, necessary to make the assumption that the rock is elastic and behaves as an elastic solid, that is, that it obeys Hooke's law, has a modulus of elasticity, and a Poisson's ratio. It is also necessary to know, Or assume, the state of stress which exists in the rock prior to the penetration of the drill. With this knowledge it is possible to compute the stresses about the bore hole. The problem can be simplified by considering several simple cases separately and then by applying the principle of superposition to solve the more complex cases which are made up of the simpler ones. Case i—Rock Strata in Compression Penetrated by a Hole This case was first worked out by G. Kirsch* for structural material, but applies equally well to a horizontal rock strata in a state of in in one direction

Jan 1, 1949

By T. E. SCHTVARZ

THE publication of the report by Mr. F. L. Ransome was welcomed by many engineers who had mined in the heart of the Sail Juan country, braved its long and snowy winters, climbed its lofty peaks, run the gauntlet of its snow-slides, and studied its problems of geology, while making dividends for their English or American clients. This report helps one to understand why the bonanzas occurred, and why the inevitable borrasca presents itself where least expected. The Red Mountain district of Ouray county, a very productive section from 1884 to 1893, occupies considerable space in the report mentioned.. The character of the ore-occurrence, being distinctive and presenting many features not existing elsewhere, has been deserving of special study. It is to be regretted that Mr. Ransome was .unable to observe the conditions underground, as all the principal properties, many of which I opened and developed, were closed at the time of his investigation: It has been my privilege to have contributed a few brief papers recording my observations in developing these properties ; and it is the object of the present paper to present certain sections of the Yankee Girl mine, which throw additional light on the geology of the section and make the available data more complete. The main Yankee Girl chimney or " stock" was the most productive for the first 500 ft. in depth of any chimney in the district.

Mar 1, 1905

By James E. Hoffmann, John A. Bonucci, Peter D. Parker

A hydrometallurgical process has been developed for the recovery of high-purity silver from sulfated residues. The process eliminates the high temperature operations ordinarily associated with silver recovery and refining. The crux of the process is a metathetical leach which maintains the sulfate ion concentration at a level which both allows silver nitrate to be freely soluble and simultaneously depresses the solubility of lead nitrate. The subsequent hydrolytic purification of the silver nitrate solution, the recovery of high-purity silver by electrowinning in a diaphragm cell, and the final product purity are discussed.

Jan 1, 1981

By R. C. Ku, R. G. Davies

The stress-strain behavior of Fe-C and Fe-Ni solid-solution alloys has been investigated at 25°C. It is found that the rate of solid-solution strengthening is dependent upon the strain at which the yield stress is measured, the macroyield stress being much more concentration-dependent than the microyield stress. In fact the addition of nickel does not lead to any increase in the microyield stress of iron. The primary effect of increasing the carbon or nickel content is to increase the slope of the stress-strain curve in the microyield region; this effect has been correlated, by means of transmission electron microscopy, with a decreased ability of the dislocations to cross-slip. It is concluded that the Mott-Nabarro theory is a good description of true solid-solution hardening in these and other iron-base alloys. A.LL theories of the solid-solution strengthening1-4 indicate that the flow stress of an alloy increases both with solute concentration and "misfit" between the solvent and solute atoms. The functional relationship between strength, solute concentration, C, and misfit depends upon the particular theory. Mott and Nabarro1,2 and Schoeck and Seeger3 both predict a linear increase in strength with concentration, while Fleischer4 indicates that the strength should be proportional to C1/2; there are in the literature experimental observations to support both these compositional dependencies.1'8 The experimental evidence used to support the theories is the change in macroscopic yield stress (strain, e, = 10-3) with composition. However, recent investigations have revealed that solid-solution strengthening in a Cu-Al single crystals7 and in Fe-V polycrystal-line" alloys depends upon the strain at which the flow stress is measured; a flow stress in the microplastic range (e = 10-6 to 10-5) is much less concentration-dependent than the macroyield stress. Since the theories of solid-solution strengthening are concerned in particular with the stress to move a dislocation in a dislocation-free matrix, they should only be compared with microyield-stress data; it will be shown that in a material deforming homogeneously the microyield stress (e = 10-6) is approximately the stress to move through the matrix those dislocations which have been nucleated by stress concentrations such as particles or grain boundary ledges.9-11 In contrast, the macro-yield stress is more complex in that it is affected by several phenomena: dislocation multiplication, dislocation interactions, and the ease of propagating slip across grain boundaries. For example, it is experimentally observed that when long-range order12'13 or solute effects10 restrict cross alip the grain boundary

Jan 1, 1967

The Telfer Project, one of the world's newest gold mines, is located about 300 km (190 miles) northeast of the Mt. Newman iron ore project in the northern part of Western Australia. The first mineral claims were staked in 1972; and by mid-1975 ore reserves of 3. 8 million mt (4. 19 million st) of 9.6 g per mt (0. 28 oz per st) ore had been indicated. It is interesting to note that Newmont spent more than 10 years and A$10 million in Australia for extensive mineral exploration before finding the Telfer deposit, and then spent approximately A$3 million in exploration and feasibility engineering on Telfer. Including this A$3 million, a total of A$27 million was spent to complete construction of the mine, village, gold treatment plant and associated roads, airport, water and services. Over 50% of the capital cost is in the metallurgical facility, or approximately A$10, 000 per ton per day. All economically significant gold mineralization at Telfer occurs in a series of layered quartz-limonite reefs in which the former pyrite has been oxidized to limonite to a depth of 100 m (330 ft). The most important gold reef occurs at the base of the siltstone-shale horizon within the enclosing sandstone dome -like structure. At the Main Dome structure the dipping ore horizons will be mined to a vertical depth of about 60 m (200 ft) by open-cut methods. The waste-to-ore ratio is approximately 12:1. Eventually 44 million mt (48. 5 million st) of ore and waste will be mined. Mining of the waste is by contract; however, the ore and a thin layer of waste is company-mined. Dilution from mining the geological ore reserve is about 10%. The ore is completely oxidized and the gold occurs free within the reef, material as discrete particles of varying but mainly fine grain size. Most of the gold is "free milling"; that is, over 50% of the gold is coarse enough to be recoverable by gravity concentration. Two duplex mineral jigs receive the two cyclone underflows from the grinding circuit. The rougher jig concentrate is up-graded on a continuous strake from which the concentrate is tabled to produce a final free gold product. Jig tailings are returned to the ball mill and the concentrates are amalgamated. Gold amalgam is pressed, retorted, and melted into gold bars. The gravity gold recovery circuit is the same as was used in many of the gold mills in California in the 1930s.

Jan 1, 1981

By R. D. Barer, M. B. Bever

Age hardening alloys are quenched from the solution treatment to room temperature in order to retain a supersaturated solid solution. Some alloys age "naturally" in this condition but in most alloys aging is induced "artificially" by heating to intermediate temperatures. Cold working of the supersaturated solid solution accelerates the aging process and quenching strains have the same effect. The investigation reported here is a study of the progress of aging in specimens quenched directly from the solution treatment to various aging temperatures. This procedure reduces the temperature interval of quenching and the resulting quenching stresses. It also eliminates any changes which would take place in the undercooled sample at room temperature prior to aging at an elevated temperature. Isothermal aging is thus approached and its kinetics may be studied. An aluminum-copper and an aluminum-silicon alloy were chosen for this investigation. The aging mechanism of aluminum-copper alloys is complex while the aging of aluminum-silicon alloys is nearly ideal. As standards of comparison for the samples directly quenched to the aging temperature, specimens were also age hardened by the usual procedure in which solution treated samples are first quenched to room temperature and then reheated to the aging temperature. Review of Previous Work The mechanism of age hardening has been the subject of a controversy which has ranged from the theory of outright precipitation of an equilibrium phase to theories based on subtle changes occurring in the matrix prior to precipitation. A detailed critical review of the literature up to 1939 is available1 and contributions to the general theory of age hardening continue to be made.2,3 Age hardening, whatever its mechanism, involves the nucleation of a second phase within a supersaturated solid solution. Theoretical considerations4,5 indicate that the rate of nucleation reaches a maximum at an intermediate temperature below the temperature at which supersaturation sets in. Studies of precipitation at various subcritical temperatures have demonstrated that the largest property changes in a given time occur at such intermediate temperatures.6,7,8 The precipitation of a phase from supersaturated solid solution is accelerated by strains which may result from quenching or cold work. Phillips and Brick9 established that quenching strains are an essential condition for the age hardening of aluminum-copper alloys at room temperature, at least for aging periods of less than 30 days. They also found that on aging at 300°C the hardness increased faster and reached a higher maximum after quenching into water than after quenching directly to the aging temperatures. Fink and Smith10 observed preferential precipitation on slip bands and grain boundaries in aluminum-

Jan 1, 1950