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By W. R. Finlay, W. R. Jr. Hibbard

The key feature of the lattice coherency theory of precipitation hardening1 is the forced coherence between matrix and precipitate which elastically strains both lattices and is believed to be the major source of strengthening in precipitation hardening. In systems exhibiting age hardening, the atom movements leading to precipitation are not at all extensive and are such as to require the minimum amount of energy to produce the interface; that is, the new lattice forms in such a way as to be as nearly as possible a continuation of the old with a matched, coherent plane at the interface at least during the initiation of the precipitation. The crystallographic sequence whereby regions of the matrix change to the precipitate lattice usually can be resolved into a set of shearing operations.6'6 Conversely, the perhaps novel speculation is made that solution of a second phase is accompanied by shearing movements which are possibly the reverse of the precipitation shearing movements. A basic premise of the investigation reported in this paper is that precipitation and solution shearing movements constitute structural weaknesses which might cooperate with applied stresses to facilitate plastic deformation. Another basic premise of the investigation is that the application of hydrostatic pressure to a precipitation hardening system will significantly alter the degree of disregistry across the matrix-precipitate interface and thereby significantly affect the course of age hardening. Two binary precipitation hardening systems were investigated: rz pct zinc in aluminum which undergoes transformations, both precipitation and solution, by a simple crystallographic mechanism; and 4 pet copper in aluminum which undergoes a complex transformation in precipitating and dissolving a second phase. The effects of the application of uniaxial tensile creep stress during elevated temperature aging of both systems and of hydrostatic pressure during the elevated temperature aging of 12 pct aluminum-zinc were then investigated. Previous Investigations Van Wert in 1935,~ studied the effect of hydrostatic pressure on the room temperature age hardening of a few precipitation hardening systems. The latter were rather unfortunately selected since none is known to exhibit any marked volume change on aging and the majority were complex commercial alloys the precipitation mechanisms of which are not known. Jenkins, Bucknall and Jenkins~n,~ in 1944, applied tensile creep stresses to a complex copper. nickel-silicon alloy at various temperatures. The complexity of the alloy and the industrial objective of the work did not permit an appreciable addition to the theoretical understanding of either deformation or precipitation hardening.

Jan 1, 1949

By S. J. Kidder, G. C. McCartney

THE Helen Mine, of the Algoma Steel Corporation, in the Michipicoten district, Ontario, Canada, has produced more than 6,240,290 tons of iron ore. Prior to and during World War I, 2,823,369 gross tons of brown ore were shipped, and from 1939 to the end of the 1944 season, 3,416,921 gross tons of siderite ore were produced from open-pit operations. Brief descriptions are given of the nature of the ore, the mining methods employed and the manner of treatment of the ore. Shipment of the finished product, known as Algoma sinter, is made to blast furnaces in both Canada and the United States. The iron-ore bodies-i.e., the oxide ores of the Old Helen and the siderite of the New Helen-are a part of a tabular shaped area of iron formation that extends over a length of more than 10,000 ft. and has a maximum width of 1000 ft. The ores are considered to be a product of introduction of iron-bearing material accompanied by replacement of the rocks already present. It is shown that introduction took place subsequent to the development of the major folded structures. It is believed the iron-bearing material emanated from an igneous source.

Jan 1, 1946

By Jim Douglas, H. H. Rachford, D. W. Peaceman

The problem of unsteady-state gas flow through porous media has been solved numerically only for the case of linear or radially symmetric reservoirs. A recently introduced numerical method for solving the unsteady-state heat flow equation in two dimensions is applied to the calculation of the depletion of a square region containing a perfect gas. Solutions are presented in graphical form for various values of dimensionless parameters. The solutions are compared with published .solutions for radial reservoirs. I NTR ODUCTION The problem of unsteady-state flow of gas through porous media gives rise to a second-order non-linear partial differential equation for which no analytical solution has been found. Numerical approximations to solutions of the gas flow problem have been obtained by the stepwise solution of an associated difference equation1,2. However, the methods so far developed have required that the reservoir be either linear or radially symmetric. This restriction in shape has been necessary so that only two independent variables be considered, namely, one distance variable and time. In order to deal with reservoirs having more realistic shapes, it is necessary to develop numerical procedures for the solution of the gas flow problem involving two distance variables. A numerical procedure, denoted as the alternating-direction implicit method, for the solution of the heat-flow problem in two dimensions has recently been introduced" By the use of this procedure, approximate solutions have been obtained for heat-flow problems in a square8, and in regions having various non-rectangular boundariesa. Because of the similarity between the equation for heat conduction in solids and the equation for gas flow in porous media, it is reasonable to expect that the alternating-direction implicit method should also be useful for solving the gas flow problem in various two-dimensional regions. Solutions have been calculated for the simplest two-dimensional region, a square reservoir with a single well in the center. While reservoirs of such simple geometry seldom, if ever, exist, the solution of this problem is of some practical importance because it is also the solution of another problem, that of determining the depletion history about an individual well in an infinite uniform reservoir containing wells spaced throughout on a square lattice and producing equally from each well. Finally, it is of interest to compare solutions for a square reservoir with those for a circular reservoir and to determine the effect of the shape of the boundary for that particular case. METHOD OF CALCULATION Basic Differential Equation By combining the equation of continuity, the perfect gas law,

Jan 1, 1956

Aamot, Olav Crone, Research Engr., Guggenheim Bros. Labs., 3,771 10th Ave., New York, N. Y. '29 Abbott, Clarence E., V.P., Charge of Raw Materials, Tenn. Coal, Iron & R. R. Co., 1242 Brown-Marx Bldg., Birmingham, Ala. '04 Abbott, Louis Benjamin, Chief Engr., Consolidation Coal Co., Watson Bldg., Fairmont, W. Va. '15 Abeel, George H., Jr., Cons. Min. Engr 128/ S. Canon Dr., Beverly Hills, Calif. '18 Abel, Raymond L., Asst. Prof., Dept. of Pet. Refin., Univ. of Pittsburgh Pittsburgh, Pa. '28 Abel, Walter D., Cons. Engr 364 S. Cloverdale Ave., Los Angeles, Calif. '32 Abele, Louis T 1457 Euclid Ave., Zanesville, Ohio. '31 Abell, Leo M Sullivan Concentrator, Chapman Camp, B. C., Canada. '31 Abort, Robert H., Asst. Met., Research Lab., U. S. Steel Corp., Lincoln Highway, Kearny, N. J. '19 Abraham, W. E. V., East India United Service Club, 16 St. James' Sq., London, S. W. 1, England. '28 Abstain, Henry T., Engr. & Mgr., Profile-Tamarack Mines Co Yellow Pine, Idaho. '27 Acker, E. O'C., Met 128 East Washington Late, Germantown, Philadelphia, Pa. '86 Ackermat, D. E., Research Met., International Nickel Co., Inc. Bayonne, N. J. '35 Acres, T. H., Geol. Dept., Valuation & Pet. Engrg., Richfield Oil Co., 555 S. Flower St., Los Angeles, Calif. '29

Jan 1, 1934

By Howard Eavenson

ONE who has been trained in belief in the law of supply and demand and its effect upon prices finds it difficult to adjust himself to the minute regulations imposed by the New Deal, and also to the bewildering changes of government policy as expressed within a short period of time between the antitrust laws and the N.R.A., and later by the Bituminous Coal Conservation Act of 1935. A survey of the coal industry since the World War, both in this country and Great Britain, however, shows that regula-tion of some sort is needed if any stabilization is to be achieved and if the Wage structure and economic welfare of the many communities dependent solely upon coal are to be maintained. Let us look at what has happened to the industry since 1920, which can be considered as the end of the period affected by the war influence. This discussion will be confined solely to bituminous coal, although many of the general conditions are equally applicable to anthracite, the position of which now is at least as bad as that of the softer variety. Since 1920-to the end of 1934-the production of coal has decreased from 568.7 million to 358.4 million tons, or 37 per cent; the number of mines from 14,766 to 6,258, or 58 per cent; the average annual production per mine has changed from 38,512 to 57,425 tons, or 50 per cent. The number of large mines has increased considerably, and the number of men employed has decreased from 639,547 to 458,011, a reduction of 28 per cent, while the average output per employee has changed from 4.0 to 4.4 tons, or an increase of 10 per cent. The average price per ton of coal at the mine has varied from $3.75 to $1.75. During that time wages decreased largely until 1933 and since that time have increased, until now the rates paid are- considerably above those in other occupations, although the actual yearly earnings are low, because of part-time work. From 1920 to the signing of the Jacksonville wage agreement in 1924, about two-thirds of the men were union members and practically all of the nonunion mines were south of the Ohio River; with the fixing., of the high wage scale of that agreement, which soon proved to be an uneco-nomic one, many of the mines found that they could not retain their business, so gradually changed to nonunion. By 1928 the proportion

Jan 1, 1936

By P. G. Dunn

Geologic studies during development at Copper Flat were directed at acquiring the necessary information in evaluating a low-grade porphyry copper deposit. In addition to the geologic mapping and core-logging of a typical exploration project, these studies included: - careful checks on the sampling and assaying, - selection of representative samples used to establish the recoverable amounts of precious metals in the ore, - examination of underground workings driven to provide samples both for metallurgical testing and for assay comparison, - evaluation of plant site and waste dump areas as non-material, including a placer examination of the tailings disposal area, and location of an adequate water supply. All these investigation were carefully documented to provide the necessary data both for the engineering design and, more importantly, for the feasibility studies required for successfully financing the project.

Jan 1, 1985

By K. V. Hoover, D. M. Lapham

In Pennsylvania, 310 sampled sites of clay and shale have been studied with regard to potential use, lithology, physical properties, fired properties, major-element chemical analyses, and quantitative five-component X-ray mineralogy. Approximately 80% of the samples are of some potential use. Binary correlations of test data vs. potential use indicate that certain empirically determined parameters may be critical. These are: lithology, particularly for medium to superduty refractories and lightweight aggregate; kaolinite content for refractories vs. low-temperature fired product sources; quartz analyses with an apparent necessary minimum quantity for brick; quartz content, which is low in high grades of lightweight aggregate; mica content, which is low for refractories and possibly high for lightweight aggregate; total iron, which is low for refractories and shows a 4.0% minimum for lightweight aggregate; carbon dioxide, which is low for refractories, beneficial in lightweight aggregate, and probably restrictive for some tiles; chlorite-vermicalite, which is low for refractories and possibly beneficial in lightweight aggregate. In Pennsylvania, clay and shale materials constitute one of the state's major economic mineral resources. To date, the testing program indicates considerable development potential in brick, tile, and lightweight aggregate industries and perhaps a future potential for aluminum from shales that exceed 20% AID..

Jan 1, 1972

By Bruce W. Gonser, Robert I. Jaffee

Recent work by the authors1 established the constitutional diagram of the gold-germanium system. Of particular interest in the simple euctectiferous system was the eutectic alloy at 12 per cent Ge, which melted at the very low temperature of 356°C and had an unusually fine eutectic structure. It was of interest to investigate the effect of third components on the melting point, microstructure, and strength of this alloy, and in this work the effect of copper is discussed rather completely, with less complete data on the effects of silver, platinum, nickel, and zinc. No reference in the literature has been found on ternary systems with gold-germanium. Materials and Alloying -4s in the work on the binary system, gold-germanium, the germanium used in this investigation was the cyanide-reduced, 99.9 per cent product, produced by the Eagle-Picher Co. Fine gold sheet from Handy and Harmon, pure platinum sheet from the American Platinum Works, copper magnet wire from Anaconda, nickel wire assaying 99.6 per cent Ni. and electrolytic zinc were used for alloying. To make the alloys, charges of the pure metals were put in a graphite crucible and melted in an atmosphere of pure hydrogen. The temperature was brought up to about I050 C, and the metal allowed to freeze in the crucible. Except with alloys containing zinc, melting losses were consistently less than a few milligrams. When zinc was a component, weight losses up to half the weight of the zinc present were incurred, and the alloy compositions were calculated by assuming the entire weight loss to be that of zinc. In all other cases the composition of the alloys could safely be taken as that of the charge. The ingots, as solidified, were segregated, the heavier primary phases being at the bottom and sides of the ingots and the lighter primary phases at the top, but by sectioning the entire ingot vertically for microscopic examination, this factor could be evaluated. Ingots for microscopic examination weighed one gram, and those for thermal analysis weighed three grams. Thermal Analysis In this work, the eutectic line composition and thermal arrests were desired, and, after microscopic exploration had established the position of the eutectic line at a given percentage of the third component, a thermal analysis was run at that composition. The method of thermal analysis used in the work on the binary Au-Ge system,' a method particularly well suited for a small quantity of material, was used in this work. Clearly defined arrests were obtained, although with some alloys containing platinum

Jan 1, 1946

By Robert I. Jaffee, Bruce W. Gonser

Recent work by the authors1 established the constitutional diagram of the gold-germanium system. Of particular interest in the simple euctectiferous system was the eutectic alloy at 12 per cent Ge, which melted at the very low temperature of 356°C and had an unusually fine eutectic structure. It was of interest to investigate the effect of third components on the melting point, microstructure, and strength of this alloy, and in this work the effect of copper is discussed rather completely, with less complete data on the effects of silver, platinum, nickel, and zinc. No reference in the literature has been found on ternary systems with gold-germanium. Materials and Alloying -4s in the work on the binary system, gold-germanium, the germanium used in this investigation was the cyanide-reduced, 99.9 per cent product, produced by the Eagle-Picher Co. Fine gold sheet from Handy and Harmon, pure platinum sheet from the American Platinum Works, copper magnet wire from Anaconda, nickel wire assaying 99.6 per cent Ni. and electrolytic zinc were used for alloying. To make the alloys, charges of the pure metals were put in a graphite crucible and melted in an atmosphere of pure hydrogen. The temperature was brought up to about I050 C, and the metal allowed to freeze in the crucible. Except with alloys containing zinc, melting losses were consistently less than a few milligrams. When zinc was a component, weight losses up to half the weight of the zinc present were incurred, and the alloy compositions were calculated by assuming the entire weight loss to be that of zinc. In all other cases the composition of the alloys could safely be taken as that of the charge. The ingots, as solidified, were segregated, the heavier primary phases being at the bottom and sides of the ingots and the lighter primary phases at the top, but by sectioning the entire ingot vertically for microscopic examination, this factor could be evaluated. Ingots for microscopic examination weighed one gram, and those for thermal analysis weighed three grams. Thermal Analysis In this work, the eutectic line composition and thermal arrests were desired, and, after microscopic exploration had established the position of the eutectic line at a given percentage of the third component, a thermal analysis was run at that composition. The method of thermal analysis used in the work on the binary Au-Ge system,' a method particularly well suited for a small quantity of material, was used in this work. Clearly defined arrests were obtained, although with some alloys containing platinum

Jan 1, 1946

By Robert I. Jaffee, Bruce W. Gonser

RECENT work by the authors1 established the constitutional diagram of the gold-germanium system. Of particular interest in the simple euctectiferous system was the eutectic alloy at 12 per cent Ge, which melted at the very low temperature of 356°C. and had an unusually fine eutectic structure. It was of interest to investigate the effect of third components on the melting point, microstructure, and strength of this alloy, and in this work the effect of copper is discussed rather completely, with less complete data on the effects of silver, platinum, nickel, and zinc. No reference in the literature has been found on ternary systems with gold-germanium. MATERIALS AND ALLOYING As in the work on the binary system, gold-germanium, the germanium used in this investigation was the cyanide-reduced, 99.9 per cent product, produced by the Eagle-Picher Co. Fine gold sheet from Handy and Harmon, pure platinum sheet from the American Platinum Works, copper magnet wire from Anaconda, nickel wire assaying 99.6 per cent Ni, and electrolytic zinc were used for alloying. To make the alloys, charges of the pure metals were put in a graphite crucible and melted in an atmosphere of pure hydrogen. The temperature was brought up to about 1050°C., and the metal allowed to freeze in the crucible. Except with alloys containing zinc, melting losses were consistently less than a few milligrams. When zinc was a component, weight losses up to half the weight of the zinc present were incurred, and the alloy compositions were calculated by assuming the entire weight loss to be that of zinc. In all other cases the composition of the alloys could safely be taken as that of the charge. The ingots, as solidified, were segregated, the heavier primary phases being at the bottom and sides of the ingots and the lighter primary phases at the top, but by sectioning the entire ingot vertically for microscopic examination, this factor could be evaluated. Ingots for microscopic examination weighed one gram, and those for thermal analysis weighed three grams. THERMAL ANALYSIS In this work, the eutectic line composition and thermal arrests were desired, and, after microscopic exploration had established the position of the eutectic line at a given percentage of the third component, a thermal analysis was run at that composition. The method of thermal analysis used in the work on the binary Au-Ge system,1 a method particularly well suited for a small quantity of material, was used in this work. Clearly defined arrests were obtained, although with some alloys containing platinum

Jan 1, 1946

By R. L. Sandefur

Professor Kim's excellent review article1 on ultimate pit planning contains a statement of the apparently widely held but incorrect belief that "kriging provides information on the confidence limits around the estimate which no other extension technique is capable of supplying." If a geostatistical approach is valid, there are several good reasons for using kriging but uniquely provided confidence limits is not among them. If kriging is possible, then confidence limits can be calculated for any other linear estimate. Kriging is the procedure which finds the weighing coefficients which minimize the estimation variance [ ] is the variance of blocks like the one being estimated. wi is the covariance of the estimated block and the i-th sample. oij is the covariance of the i-th sample and the j-th sample. Ai is the weighing coefficient for the i-th sample. N is the number of samples. The formula for estimation variance can also be used to calculate confidence limits on blocks estimated by any linear combination of sample grades including: 1) Polygons a. Hole nearest block centroid is assigned weight 1. All other holes are assigned weight 0. b. Polygonal area weighing. The samples are assigned weights directly proportional to their polygonal areas of influence within the block. The weights sum to 1. 2) Inverse distance weighing. The samples are assigned weights directly proportional to the reciprocal of their distance to some power from the block centriod. The weights sum to 1. Often only holes nearer than a certain distance and/or the nearest hole in each octant is considered. If there is an antisotropy to the ore body, an elliptical transformation often gives more accurate results. The most popular inverse distance weighing function is inverse squared distances (IDS). 3) Simple average. All samples within a certain distance are assigned the same weights which sum to 1. As an example of the applicability of the above formula to any linear estimate an internal verification on copper grade of 665 blast holes on the 1040 bench at Utah's Island Copper mine is presented. Internal verification is simple and applicable to non-linear estimates as well. Any sample (drill hole, bulk, trench, or chip) is dropped out, the value of the dropped sample estimated and compared with the actual value. If this is done for all samples, a measure of confidence limits is obtained. Internal verification is used in Cominco's MEPS system4 and in the BLUEPACK system.5 Comparison of block values against estimates697 is not dissimilar to internal verification. Results of the internal verification are presented below:

Jan 1, 1980

By P. W. Neurath, R. E. Waite

INFORMATION is available on the effect of stress on permeability, coercive force, and hysteresis for a variety of materials' but for the technically important grain-oriented 3 pct Si-Fe' the stress effects are not adequately covered in the literature; in addition, most of the stress data do not permit estimation of what would happen to the 60 cycle watt losses of the material under stress. Direct measurement of these effects therefore has been made and appears to be of considerable theoretical as well as practical interest. Losses were measured on the central 25 cm portion of 40~3~0.035 cm samples which could be stressed in a small tensile machine built for this purpose. Under tension the following effects, illustrated in the figures by a particular example, were observed: 1—"Unstrained" material of commercially acceptable loss level shows no change or a small increase in loss at low elastic stresses. For the sample shown in the figures, this is illustrated during the initial run, where a 7 pct increase is observed (Fig. 1). 2—There is no additional change in loss when the sample is further strained up to the elastic limit (Fig. 1). Within that limit the loss-stress curve is reversible. This is not illustrated in Fig. 1. 3—Even in the plastic range only small increases in loss are observed as long as the sample is kept under stress (Fig. 2, point N); often no increase can be observed (Fig. 1). 4—A large increase in watt losses is observed after removal of the stress subsequent to plastic deformation (Figs. 1 and 2). 5—All, or nearly all, of the foregoing increase in loss due to plastic deformation can be eliminated by a reapplication of tensile stress but returns upon removal of this stress. This is illustrated in the third run (Fig. 3). This run remains within the elastic limit and shows the reversibility of the stress-loss curve under this condition. These findings have been confirmed on large Samples (approximately 200~10~0.035 cm and larger) except that under 1 no initial increase in loss was ever observed on these. The accuracy of the watt loss measurements is of the order of 1 pct. Neither bending of the sample in the tensioning device nor a redistribution of flux along the width of the sample accounts for these results. They therefore must be explained on the basis of either a change in the domain configuration due to stress or a change in the domain wall mobility. Acknowledgment The assistance of Mr. Robert L. TenBroeck with the instrumentation is gratefully acknowledged.

Jan 1, 1956

By J. E. Hilliard

A procedure is described for determining, from measurements on a section, the moments of any degree n (i.e., the mean value of Dn, where D is a linear dimension) of the size distribution of particles (or grains) in an opaque sarnple. The analysis is applicable to particles of alnzost any shape and to any mixture of shapes. However, if absolute values of the wloments are required, it is necessary to know what shapes are present and the relative frequency of their occurrence. In addition, certain shape-dependent parameters have to be evaluated before the formulas can be used. The measurement required is the distribution of intercept lengths. This can be determined either visually or with an automatic scanning instrument. Corrections me derived for the bias due to instrumental end effects. The proposed analysis has the following advantages over existing ones: 1) Confidence limits are easily estimated for the measured properties or, conversely, the number of counts required to achieve a given accuracy can be determined. 2) The analysis is not restricted to particles of a special shape. 3) The error resulting from any known degree of departure of the actual from the assumed particle shape can be estimated. 4) The computations are simple and, apart from a change in constants, are independent of particle shape. 5) The number of particles per unit volume can be determined by a simple counting procedure. MANY procedures have been described for determining the size distribution of particles from measurements on a section (or plane of polish). They differ from one another in the property measured on the section (radius, intercept length, profile area) and in the method used for the numerical solution of the integral equation relating the property to the particle size distribution. However, all existing analyses share at least two of the following disadvantages. 1) They are limited to a particular shape of particle (usually spherical). 2) It is very difficult to determine how the statistical sampling error is propagated into the computed size distribution. The investigator thus has no means of knowing the reliability of his result and, what is of equal concern, he is unable to estimate how many measurements are required to obtain a result of the required accuracy. 3) It is also difficult to assess the error resulting from any deviation between the actual and assumed particle shape. The foregoing limitations stem from the complex relationship between the particle size distribution and the distribution of the property measured on the section. As will be shown, they can be avoided by defining the size distribution in terms of discrete parameters

Jan 1, 1969

By R. L. Ash, R. R. Rollins, C. J. Konya

An investigation was performed to determine conditions for optimizing the spacing of simultaneously initiated multiple explosive columns. This was done by using models of mortar, dolomite, and Plexiglas with 10-grain mild detonating fuse as the explosive charge. It was desired to simulate blastholes with multiple primers initiated by detonating fuse or when high-velocity explosives are used in low-velocity materials. It was found that optimum spacing between multiple charges was strongly influenced by charge length. At less than optimum charge length, the spacing at which complete shearing was possible between adjacent charges decreased exponentially with a subsequent loss of broken material volume. For charges fired simultaneously, larger burdens and spacings were possible as compared to those necessary for single-crater charges. For each material studied, there was a characteristic optimum charge length and a maximum attainable spacing at any given burden. Proper selection of the spacing distance between charges is fundamental to successful blasting. Its value directly affects the cost of drilling and explosives used per unit of broken material. In addition, the choice of a spacing that is Compatible with a given set of blasting conditions aids in the control of fragmentation sizing, ground vibrations, overbreak, and throw which in turn, influence other production costs. For example, normally loaded blastholes that are spaced too closely invariably promote overbreak and usually give coarse fragmentation. Unless care is taken, airblast and violent flyrock will occur and under certain conditions cutoffs and misfires may result. Too large a spacing, on the other hand, frequently leads to conditions that form bootlegs or toes. The choice of a particular spacicg to use, however, is largely a matter of individual experience and judgment, usually based on trial and error. Very little is known or can be found in the literature with regard to how the spacing between charges is related to field conditions and charge geometry. As a general rule, the firing time sequence of adjacent charges and properties of a material are thought to have the most significant influence on the spacing distance best suited for any given field condition. For example, delayed initiation of adjacent charges usually always requires a closer spacing than when charges are fired at the same time. This should be expected if one considers that the energy normally dissipated and lost in the surrounding ground from charges fired independently would be captured and utilized for breaking material between charges when they are initiated together. Spacing can be extended also when charges are aligned with structural planes of a material, such as jointing, along which shearing is relatively easy. It is customary to relate the spacing (S) between charges to their common burden (B) in the form of a spacing ratio, or SIB. The burden normally is considered as the optimum depth or distance from any single charge perpendicular to the nearest free or open face at which the desired fragmentation and maximum crater yield are obtained. For production blasting, value of the ratio is generally considered to vary from 1 to 2, depending on conditions.1-6 When adjacent charges are fired independent of one another, the value varies from 1 to about 1.4, the closer amount being employed to square corners or produce craters having the ideal 90" apex angle. The larger ratio is the geometric balance value for craters having an apex angle of 135". The basic ideal crater forms in the plane of the charge diameter for charges fired independently are shown in Fig. 1. In the event charges are fired simultaneously, geometric balance in the plane of their charge diameters suggests that a spacing ratio near 2 would be appropriate, as illustrated by Fig. 2. In practice, however, some compromise ratio value must be selected to conform with the specific ground conditions. An example would be where the jointing planes tend to produce 60° or 120° crater angles, the appropriate geometrically balanced charge arrangement being given by Fig. 3. In this condition, the spacing ratio is 1.15, not 1 or 1.4 as suggested for the 90° cratering of independently fired adjacent charges. In view of the foregoing, it would seem logical to assume that whenever charges all having the same burden are fired at the same time, spacing distances always can be greater than those permitted by charges fired independently. In practice this is not the case, however.

Jan 1, 1970

The Ashanti mine is located in the Gold Coast region of West Africa in Ghana, where gold is found over a wide area of about 105,000 sq km (40,000 sq miles). Ashanti has been the most productive of all the lode mines and has been one of the world's notable gold producers for over 50 years. The mine is located at Obuasi, 113 km (70 miles) north and east of Tarkwa, which is 80 km (50 miles) inland from the coast. The Ashanti lode is worked on 300 m (1,000 ft) of strike length over a width of 12 m (40 ft), and by 1934 it had attained a depth of 700 m (2, 300 ft). The lode is in pre-Cambrian granite intruding a system- of shists, phyllites, etc., containing fragments of the wall rock with quartz, carbonates, sericite and small amounts of pyrite, arsenopyrite, sphalerite, galena, and gold. The shattered quartz fractures carry sulfides and gold, most of which are invisible. (William Harvey Emmons, "Gold Deposits of the World," McGraw -Hill, 1937.) Because the mill treats an ore composed of refractory sulfides - chiefly arsenopyrite and fine free gold - the flowsheet reflects the complex ore characteristics. Plane tables are used in the grinding, circuit for free gold recovery. After roasting the sulfide flotation concentrates, additional free gold is recovered from the calcines with a rotary belt concentrator and the two concentrates are combined for feed to the amalgamation pans, with the resulting gold amalgam being retorted. Following four-stage crushing to minus 9. 5 mm (318 in.) with two stages of grinding, the cyclone overflow is floated for sulfide recovery. The flotation concentrate is roasted with the calcine reground and roughly cyanided to scalp out the gold readily dissolved in one of two cyanidation circuits. The cyanide residue joins the thickened flotation tailing for cyanidation in a complete CCD circuit using filters. The gold precipitates are calcined before melting in pot-type furnaces. The tonnage to the mill of 3,175 mtpd (3,500 s tpd) with a content of over 14.7 g per mt (0.43 oz per st) places the Ashanti production as one of the top producers in the world; and with its past long life, the total production rates it as one of the world's great mines.

Jan 1, 1981

By Frank A. Wardlaw

MY subject covers the effect that recent metallurgy has had on operations at the Utah-Delaware mine. This mine is the old Highland Boy mine of Bingham Canyon, Utah, one that has now been in operation for about 30 years. It was first operated by Messrs. Weir and Newhouse as a gold mine, under direction of the Highland Boy Gold Mining Co. The ore was oxidized gold ore and it was treated on the property in a cyanidation plant. During the process of development, sulfide ore was found assaying about 5 per cent copper. It proved to be the discovery of what is yet the largest sulfide copper orebody in the State. The first shipment was made in December, 1896. A smelter was built in Salt Lake Valley to treat this ore and not long after the property was sold to the Utah Consolidated Mining Co. From 1900 to 1924, the mine was a large producer of direct-smelting ore which averaged for many years 4.5 per cent. copper, then later dropped to 2 per cent. copper. During the years 1912 to 1920, direct-smelting lead ore was also mined. In 1918'and 1919 ore developments at depth showed a decided increase in silica content and a porphyry sill so closely associated with the ore that it was impossible to mine the ore clean and it was found necessary to build a copper flotation Eoncentrator at Tooele. The mill had a capacity of 1000 tons a day and made a recovery of 90 per cent., and would have been responsible for a continuance of profitable operations had it not been for a slump in the copper market and the necessary high cost of mining ore on the lower levels. RESULTS OF SELECTIVE FLOTATION In 1924 the mine was on the point of a shutdown which had all the earmarks of being permanent; it was being operated at a heavy loss and preparations were made to pull the pumps and salvage the machinery. The plant at Tooele was remodelled for selective flotation by the Inter- national Smelting Co. in order to treat custom ores, and incidentally to clean up a possible 10,000 tons of lead-zinc ore which it was thought possible to get in the Utah-Delaware before shutting the mine down. Results were so encouraging that an effort was made to develop more lead-

Jan 1, 1928

By Frank A. Wardlaw

My subject covers the effect that recent metallurgy has had on operations at the Utah-Delaware mine. This mine is the old Highland Boy mine of Bingham Canyon, Utah, one that has now been in operation for about 30 years. It was first operated by Messrs. Weir and Newhouse as a gold mine, under direction of the Highland Boy Gold Mining Co. The ore was oxidized gold ore and it was treated on the property in a cyanida-tion plant. During the process of development, sulfide ore was found assaying about 5 per cent. copper. It proved to be the discovery of what is yet the largest sulfide copper orebody in the State. The first shipment was made in December, 1896. A smelter was built in Salt Lake Valley to treat this ore and not long after the property was sold to the Utah Consolidated Mining Co. From 1900 to 1924, the mine was a large producer of direct-smelting ore which averaged for many years 4.5 per cent. copper, then later dropped to 2 per cent. copper. During the years 1912 to 1920, direet-smelting lead ore was also mined. In 1918 and 1919 ore developments at depth showed a decided increase in silica content and a porphyry sill so closely associated with the ore that it was impossible to mine the ore clean and it was found necessary to build a copper flotation concentrator at Tooele. The mill had a capacity of 1000 tons a day and made a recovery of 90 per cent., and would have been responsible for a continuance of profitable operations had it not been for a slump in the copper market and the necessary high cost of mining ore on the lower levels. Results of Selective Flotation In 1924 the mine was on the point of a shutadown which had all the earmarks of being permanent; it was being operated at a heavy loss and preparations were made to pull the pumps and salvage the machinery. The plant at Tooele was remodelled for selective flotation by the International Smelting Co. in order to treat custom ores, and incidentally to clean up a possible 10,000 tons of lead-zinc ore which it was thought possible to get in the Utah-Delaware before shutting the mine down. Results were so encouraging that an effort was made to develop more lead-

Jan 1, 1928

JOHN B. HASTINGS, Los Angeles, Cal. (written discussion *).-This, paper is so admirable for its brevity that one hesitates to enter into discussion. The cycle of eruptives makes one wonder, "Where's the basalt?" and the youthfulness of the Idaho flows suggests they may yet come. Veins and Dikes.-Veins and dikes seem to be closely aligned in the minds of some authors, while to me they appear quite distinct, the first representing quiet, long-continued action, typified by metasomatic replacement, far removed from volcanic action; the latter, sudden and cyclonic, emanating from the heart of vulcanism. The rock openings occupied by both types were formed by kindred forces, but in the one they were closed for indefinite periods before invasion by the solfataric solutions, and in the other their formation and occupation were simultaneous. Open Fissures.-I do not believe in the existence of open spaces of discission that may be occupied by veins. Occasionally they occur; I found one with. a machine drill 350 ft. below surface, fortunately in an adit; the water spouted for 12 ft. in a 6-in stream for nearly 24 hr. It was only a flattish fissure, 6 in. wide, crossing the perpendicular vein, and indicating how tabular veins of ore might be formed. The practical absence of open fissures should be a joy to miners. We all know the misgivings with which we feel about for an old winze having only 30 ft. of water in it, in an unsurveyed and inaccessible part of a mine. It is said that veins are sometimes formed in open spaces left by Protuberances of the walls, which meet after having been displaced; but I believe that in such circumstances there would be sufficient attrition and brecciated material to fill the fissure, though perhaps loosely. Parts of veins may possibly have been formed in originally open spaces, but if so, the spaces were made by solution shortly preceding the deposition of the veins. That total solution of rock adjacent to a fissure may occur under favorable conditions is proved by the existence of large bodies of sulphide which contain only a few per cent. of silica; while on the same level, and in other levels above and below, all being within the same ore shoot, assays may show as much as 50 to 60 per cent. of silica, although the gold, silver and copper assays may be almost identical in all the

Jan 1, 1918

By G. F. Comstock

A serious disagreement as to the effect of titanium on the hardenability of steel exists in published references to this subject. Kramer, Hafner and Toleman reported' that acid-soluble titanium decreased creased the hardenability, with multiplying factors less than unity according to [ ] Grossmann's system for calculating hardenability from the composition. Crafts and Lamont, on the other hand, showed2 how titanium increased the hardenability, with multiplying factors up to nearly 1.7 for about o.' per cent titanium, though reducing the hardenability with higher titanium. Their data, however, were obtained almost exclusively from steels containing more than 2.4 per cent manganese, and thus should be considered as applying mainly to manganese steels. Likewise, the results of Kramer, Hafner and, Toleman regarding titanium are subject to the limitation that although they eliminated the effect of the insoluble titanium compounds from their calculations, they did not make a similar correction for the carbon that was combined with titanium and therefore occurred in a similarly ineffective form. It is suggested by the literature referred to that titanium may have different effects on hardenability, depending on the mode of its occurrence in the steel. The different effects on strength, ductility, etc., have already been discussed by the author.3 In the present discussion some comparisons, on the basis of hardenability as revealed by the Jominy end-quench test, are given between three titanium and two non titanium steels heat-treated in the same ways, and between other titanium steels heat-treated in several different ways. COMPARISON OF PLAIN-CARBON, VANADIUM AND TITANIUM STEELS The five steels used for these experiments were commercially melted and rolled products received in the form of 1.5-in. rounds from three different mills. Their analyses are given in Table I. Steels 2, 3, and 4 are from the same basic electric heat, containing 0.009 per cent of phosphorus and the same amount of sulphur. They were made by, adding aluminum and low-carbon ferrotitanium to different ingots. No. I is a plain-carbon coarse-grained S.A.E. 1040 steel made by the basic open-hearth -process. No. 5

Jan 1, 1945

By Ming-Kao Yen

S. E. MADDIGAN*—I think Mr. Yen should be complimented on doing a very excellent and a very comprehensive piece of work. I was particularly pleased to note the use of X rays in a somewhat less tedious technique than pole figures. In the past I think many workers have been diverted away from the use of X rays in such investigations because of the large amount of work involved in pole figures if one is dealing with a great number of specimens. The same thing, I think, applies to the determination of orientations by counting of twins which is also a very tedious procedure; as a result several papers which have otherwise been of excellent quality have depended upon etching techniques for determination of orientation. The present paper indicates that the results reported in those previous papers were correct, but I think the use of etching techniques alone is a rather shaky basis for setting up theories in the literature. W. M. BALDWIN, JR.*—This discussion will be a short note of correction and apology. In my discussion of Brick, Martin and Angier's paper I incorrectly reported the orientation of phosphorus deoxidized copper annealed at temperatures. When I learned that Mr. Yen was preparing the present paper I asked that he correct this previous error, which he most graciously consented to do. However, through my ambiguity the correction noted on p. 59 of Mr. Yen's paper is still not the proper one. For this I take full responsibility. The orientation which I observed in phosphorus deoxidized copper at high temperatures is the (112) [111] which agrees with the pole figure given in Fig 8a, on p. 65 of Mr. Yen's paper. Our observations were made on the basis of twin counts rather than X ray determinations and therefore serve as an independent confirmation of Mr. Yen's data. M. K. YEN (author's reply)—The author wishes to thank Dr. Maddigan for his comments in regard to the application of glancing technique to textures. As a matter of fact, considerable work has been done recently in connection with

Jan 1, 1950