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By Richard M. Foose

MOST of the roofing granules produced in Pennsylvania are made by two companies at three plants. The Advance Industrial Supply Co. has three quarries and a mill at Gladhill Station, in southern Adams County. The Funkhouser Company is actively engaged in mining, quarrying and milling at Charmian, about one mile west of Gladhill Station, and at Delta, in southern York County. These three plants produced approximately 100,000 short tons of granules in 1943. The production of roofing granules in 1937 for the whole country was only about 500,000 tons, generally indicating the large growth of the industry since that time. The fundamentals of producing roofing granules were discussed comprehensively by G. W. Josephson in a paper before the Industrial Minerals Division in October 1943 (Mining Technology, March 1944). The purpose of this paper is to describe the actual methods of mining the rock and milling it to make roofing granules, as practiced by the three Pennsylvania plants. MINING AND MILLING Funkhouser Company (Delta) The Funkhouser Company, near Delta, in southern York County, Pennsylvania, operates three joined quarries and a mine in the Peach Bottom slate. The joined quarries extend 1200 ft. in a northeast southwest direction along the strike of the slate cleavage and are about 200 ft. wide. The working face is about 45 ft. high. The quarrying operation is rather simple: Ingersoll-Rand Jackhamers, 1-in. and 1 1/4-in., with hollow drill steel, are used to undercut the quarry face with10-ft. holes. The face is "blown" and allowed to slump on the quarry floor. Loaded by a Marion electric shovel into trucks, the shattered rock is taken to the primary crusher 2500 ft. away. In addition to the normal quarrying operations, a drift into the northeast wall of the middle quarry was begun about 1935 and has advanced about 2000 ft. since then. Rooms have been driven at angles to the drift along choice beds of slate. The drifts and rooms have a roof more than 35 ft. high and the main drift and rooms are all more than 40 ft. wide. There is no cribbing at any place in the mine. Several of the rooms were driven upward on a 5º slope and in some of them there was stoping. Ingersoll-Rand Jackhamers are used, and only wet drilling is practiced. When visited in January 1940, an electric shovel was operating at the head of the drift, scooping up the slate blasted out of the working face. This, too, is trucked to the primary crusher. Some of the better quality slate is saved for making slate shingles. The primary crusher, which is a No. 30 McCulley gyratory, receives the slate from the trucks and crushes it to about 2-in. size (Fig. I). This product travels by a 30-in. belt conveyor to Niagara vibrating screens with 2-in. holes. The minus 2-in. product moves to a storage silo by bucket

Jan 1, 1945

By J. A. Herrick

For a long time, especially in Europe, heavy pieces of forging, such as cannon, armor plates, marine shafting, etc., have been steadily augmented in size, more particularly since steel has been substituted for wrought iron. To keep pace with these forgings several very large hammers have been, from time to time, erected. The most powerful and thoroughly appointed of all now in operation is that designed and built by Messrs. Schneider & Co. at their' works at Creusot, and it is the design of this communication to give to the members of the Institute a concise description of this remarkable piece of mechanism, which I have taken from an article published in the Annales Industrielles. This hammer is rated nominally at 80-tons power, but its capacity is, in reality, far greater, as will be seen by the comparative figures given later. The complete plant, comprising the hammer, the cranes, the furnaces, and the building which shelters the whole, is distin-

Jan 1, 1880

By J. A. Herrick

FOR a long time, especially in Europe, heavy pieces of forgings, such as cannon, armor plates, marine shafting, etc., have been steadily augmented in size, more particularly since steel has been substituted for wrought iron. To keep pace with these forgings several, very large hammers have been, from time to time, erected. The most powerful and thoroughly appointed of all now in operation is that designed and built by Messrs. Schneider & Co. at their works at Creusot, and it is the design of this communication to give to the members of the Institute a concise description of this remarkable piece of mechanism, which I have taken from an article published in the Annales Industrielles. This hammer is rated nominally at 80-tons power, but its capacity is, in reality, far greater, as will be seen by the comparative figures given later. The complete plant, comprising the hammer, the cranes, the furnaces, and the building which shelters the whole, is distin-

Jan 1, 1880

By Donald M. D. Stuart

It gives me great pleasure to accept the invitation I had the honor of receiving through the Secretary of the Institute, to reply to the criticisms made in discussion of the theory advanced in my work entitled, Coal-Dust an Explosive Agent; and to lay before the Institute a further statement of the views which investigations have led me to form upon this subject,

Jan 1, 1897

By R. E. Reed, C. J. McHargue

Single crystals of aluminurn were reduced 90 pct in diameter by extrusion at 296" and 77°K. The resultant double fiber texture had a strong (111) component with a weak (001) component. The relative anzounts of these components varied with starting orientation. Decreasing the Lemperatuve of defovtnation increased the amount of (001) texture component in crystals with inilia1 orientations near (111). The starting orientation and temperature of deformation strongly affected the morphology of the (001) component. The effects of orientation and Lemperatuve upon the distribution of the (001 ) texture component in extruded aluminum single crystals were rationalized on the basis of deformation band formation and interaction. MANY papers since the early 1920s have discussed the occurrence of the double fiber texture (111) + (001) in wires and rods of deformed fcc metals. Aside from the reporting of experimental results for the various metals under a variety of fabrication conditions, emphasis has been placed on two related problems. One problem deals with the prediction of ideal end orientations based on the glide systems and flow directions. The other problem seeks the reason why different amounts of each component may be produced by the same fabrication schedule for metals apparently having the same deformation systems. Some of the difficulties in developing a satisfactory explanation have their origin in the experiments themselves. One mistake has often been the assumption of an initially randomly oriented specimen or complete ignorance of effects of starting orientation. Recent studies by Grewen and Wassermann,1 Cullity and co-workers,2' and McHargue4 have shown that the initial orientation may be the most important factor in determining the final orientation. Hence only limited comparisons of data from different studies can be made unless all conditions of the initial material are specified. Another question has been the nature of the (001) component. Hibbards suggested that any (001) present was the result of re crystallization during fabrication. Although Fleischer6 found no (001) texture in aluminum swaged at room temperature, and Dayal 7 found that component to disappear at very high reductions, a double fiber texture has usually been reported for aluminum. Vandermeer and McHargue showed that, while some (001) in aluminum may be the result of recrystallization, much of this component has its origin in the deformation process. Ahlborn and Wassermanng found the (001) component in silver deformed at low temperature not to be the product of recrystallization.

Jan 1, 1968

By A. B. Stevens

IN the calculation of oil and gas reserves by volumetric methods, it is necessary to know the volume of the reservoir available for the storage of the oil or gas. To obtain this information, a number of methods for determining both total and effective porosity of reservoir rocks are used. For the determination of the total porosity, or the porosity that considers all of the pore spaces, connected and isolated, the Russell7,8,9 and the Melcher-Nutting1-6 methods are the best known and most- widely used in the petroleum industry. These methods have disadvantages in that they give the total porosity of the samples and in that the samples are reduced to grain size in the determination. In many sands there may be little or no difference between total and effective porosity but in other sands there may be considerable difference between the two. For the estimation of oil-and gas reserves the effective porosity of the reservoir rock always should be used. Of the methods that have been developed for the determination of the effective porosity of reservoir rocks, or the porosity that considers only those pore spaces that are connected, the best known are the so-called Boyle's law6,10-13, and the Washburn-Buntings.5,6,11 methods. The Wash-burn-Bunting method is probably the most widely used because it gives effective porosity, it is rapid, and the apparatus is inexpensive. This method employs a special porosimeter in which the core sample is placed in direct contact with mercury. This method has disadvantages in that, as a result of the high vacuum created in the pore spaces, mercury is drawn into the openings, making it impossible to use the sample for a check determination and also ruining the sample for any further test, such as permeability. The purpose of this paper is to describe an appa-ratus employing the same principle as the Washburn-Bunting method but so designed that the core sample does not come in contact with the mercury in the porosimeter.

Jan 1, 1939

By Frances Jane Cromwell, D. J. McAdam, G. W. Geil

INTRODUCTION IN a series of papers, the authors and their associates have shown that the technical cohesion limit is affected by the same four factors that affect the flow stress, namely, the stress system, plastic deformation, temperature, and the strain rate.16-28 Moreover, each of these factors affects the technical cohesion limit in the same way that it affects the flow stress.‡ The influence of any one of these factors may be represented by a curve of cohesion limits, although only one point on the curve may represent actual fracture. As the term "fracture stress" has come into use with the same significance as "technical cohesion limit," the authors are here using the shorter term with the understanding that it does not always refer to actual fracture. This paper presents the results of an investigation of the flow of notched and unnotched specimens between yield and fracture. A study has thus been made of the flow and fracture of metals as affected by the stress system, and of the ductility of metals as affected by the stress system throughout plastic deformation. Since two of the principal stresses were equal (S2 = S3), the stress systems can be represented in terms of the radial stress ratio, the ratio of the transverse radial stress S3 to the longitudinal stress Sl.* The results of the experiments are represented by a series of complete flow-stress curves for each of the metals investigated, and these diagrams have been used for the development of other diagrams of various types. Ludwik was the first to suggest that fracture occurs when the flow stress becomes equal to a technical cohesion limit. Although Ludwik was incorrect in his view that the technical cohesion limit depends only on the amount of plastic deformation and not on the stress system, he was correct in his view that the flow-stress curve for any stress system terminates at a point representing a technical cohesion limit. The authors have seen some recent references to assertions by other investigators that a point representing the fracture stress need not be on the flow-stress curve. The Ludwik principle, however, would seem to be axiomatic, provided that the flow stress and fracture stress are properly defined and that the fracture stress is properly determined. Disregard of this principle has led to some untenable theories of criteria for fracture. When a metal is very ductile, the conventional method of determining the ductility and fracture stress by dividing the breaking load by the sectional area after fracture, generally gives values that are much too high. With some metals and in some conditions, the fracture stress thus determined may be two or more times the

Jan 1, 1948

By M. S. Seltzer

High temperature steady-state creep rates have been determined jor lead sulfide single crystals whose defect concentrations were fixed by equilibration under controlled sulfur pressure. The activation energy of creep, Qc , for undoped lead sulfide, is a function 01 composilion, decreasing from 2.9 to 2.2 ev as the carrier concentration increases from 9 x 1016 to 8 1018 electrons cm-3 for lead excess crystals, and increasing from 1.7 to 2.3 ev as the concentration of holes increases from 4 x 1017 to 1 x 1018 cm-3 in sulfur excess material. For five different composilions, Qc for undoped and bismuth-doped crystals has been found to be equal to Qpb + Qs, the self-diffusion activation energies for lead and sulfur in PbS. It is well-established1 that high-temperature steady-state creep of pure metals is a diffusion-controlled process, where the activation energy of creep is equal, within experimental error, to the activation energy of self-diffusion. The relationship between the activation energy for steady-state creep and those for self-diffusion in binary compounds is more complicated, however, because two different diffusing species must be considered, and becayse the activation energies may be influenced by compositional variations and by foreign atom additions.2-4 In some cases experimentally determined creep activation energies are correlated with those for self-diffusion of the slower-moving species, but such agreement is by no means universal. Interpretation of experimental results is difficult because few investigations include measurements of creep rates and self-diffusion coefficients of both diffusing species on single crystals of similar composition and foreign atom concentration. The objective of this investigation, therefore, is to determine the influence of stoichiometric defects and foreign atoms on steady-state creep and self-diffusion for a well-characterized binary compound. Lead sulfide, a compound semiconductor which crystallizes in the NaC1-type structure, and whose homogeneity range includes compositions on either side of the 1:l atom ratio, was chosen for study in this investigation. The pressure-temperature-composition relations for PbS are available,5,3 and deviations from stoichiometry may be monitored by electrical measurements.7 Single-crystal specimens are available to allow observation of effects due to bulk phenomena without interference from grain-boundary effects. These crystals have been employed to determine steady-state creep rates under compressive stress for "pure" and bismuth-doped PbS as a function of sulfur pressure and temperature as well as crystal orientation and applied stress in order to establish the relationships between defect concentrations and creep rates. EXPERIMENTAL PROCEDURES Crystal Growth. Lead sulfide crystals, prepared by the Bridgman method, are grown in evacuated quartz crucibles, filled with almost equal atomic proportions of high-purity (99.999 pct) lead and sulfur, and heated to a temperature above the melting point of PbS (about 1127°C) so that the lead and sulfur react to form molten PbS. The crucible and melt are dropped through the hot zone of the crystal-growing furnace at the rate of 1 cm per hr. The maximum melting point of PbS is slightly on the lead-rich side of the 50:50 composition; hence crystals grown from a near stoichiometric melt are usually n-type semiconductors containing excess lead atoms. Typically the lead excess concentration in solid solution with the PbS is 3 x 1018 atoms cm-3. Crystals containing either 1/20 or 1/2 mole pct Bi2S3 were prepared by addition of the foreign atoms prior to crystal synthesis. Preparation of Specimens of Controlled Stoichiom-etry. Since it is difficult to grow crystals of desired composition, the process of crystal growth and control of stoichiometry are separated into two distinct operations. Equilibration of as-grown PbS to a desired composition is most easily accomplished by first annealing the n-type crystals under high sulfur pressure (about 1 atm) at temperatures above 700°C. This process serves to put excess lead precipitates into solution, yielding 0 -type crystals upon quenching to room temperature. Inter diffusion occurs readily in crystals so treated, and the methods described by Bloem may then be employed to obtain crystals of controlled stoi-chiometry. For the creep measurements made in this study, this involves heating crystals in mixtures of H2 and H2S The equilibrium constant for H2S is given by: Thus the sulfur partial pressure is obtained from knowledge of the H2/H2S ratio and Kh2S for the temperature in question. Fig. 1 shows the p-T-x diagram for PbS. It can be seen that, within the stability limits for single-phase lead sulfide, desired compositions may be obtained by equilibrating under a specified sulfur pressure and temperature. Characterization of Crystals. The principal methods for evaluating PbS crystals include measurement of electrical properties and mass-spectrographic analysis. The measured electrical parameters include Hall coefficient, conductivity type, and electrical resistivity Bloem7 has shown that there is a 1:l relation between the defect concentration and carrier concentration obtained. Hence, if the contribution to the carrier con-

Jan 1, 1968

By D. M. McFarland

IN mining, quarrying, and construction, drilling and blasting have an important influence on the operations that follow. If the fragmentation of material being disrupted is inadequate, loading and transportation equipment will not operate at or near full capacity. Any operator faced with this difficulty should not be satisfied until he is convinced by a careful study of his methods of drilling and blasting that no improvement can be made. Rock in a certain quarry in Ohio seemed to defy any grade of explosive or means of detonation that the explosives industry had to offer. The average result of a blast was that a great part of the burden would be pushed out from the face in a number of large sections that would jokingly be referred to as "boxcars." These were no credit to the explosives man and a costly problem for the quarry company. Such blocks retard shovel operation as they have to be uncovered and subjected to secondary drilling and blasting which, if extensive, is an expensive operation. It was an attempt to improve the fragmentation obtained in primary blasts that led to the development of milli-second-delay electric blasting caps. The reasoning that prompted the trial was that even with wide spacing of the drill holes it seemed that the burden was separated too quickly from the face by the cutting action of the explosives from hole to hole. If the time of firing of the holes could be regulated so that

Jan 1, 1948

By C. B. Clark, W. H. Bruckner

Since the end of World War II interest has been increasing in the use of shaped charges in the mining industry and in other industries using explosives for blasting purposes. Shaped charges employ the principle known as the "Munroe effect," which was discovered by Charles E. Mun-roe more than 50 years ago (in 1888). Details of their design have been explained elsewhere.1,2,3 Fig I shows the essential features of design of two types of shaped charges (with conical and hemispherical cavities) and a schematic sketch of their action upon detonation. The following discussion deals with the behavior of the metal in the cavity liners when they are subjected to intense Pressures exerted when the explosive charge is detonated. Among the conclusions reached in research On shaped explosive charges, the following have been established concerning cavity liners:1'2 I. The optimum wall thickness of a conical cavity liner is dependent upon the apex angle of the 'One as well as On the base diameter of the charge. Acute apex angles require thinner walls for optimum perfmnance and more obtuse angles require thicker walls for the same base diameter' 2. Cones were more effective in forming a penetrating jet when the walls were tapered; that is, the thickness of the wall of the cone increased from the apex down. 3. The physical and mechanical properties of metals have a marked effect upon their performance as cavity-liner material. Boiling point, ductility, malleability, tensile strength, and hardness are among the properties that influence the effectiveness of a metal used as a cavity liner. Lead, for example, makes a wide, flat crater in steel plates. Aluminum makes a deeper crater than lead, and an aluminum alloy having a high tensile strength makes a deeper hole, but slightly smaller in diameter. Cast iron makes a deep, narrow hole. These findings, together with the following analysis under Metallographic Survey of slug, offer solutions to many of the problems involved in solving the mechanism of the formation of Munroe jets. It has been fairly well established that cavity liners collapse in a manner similar to that indicated in Fig 2, Conical liners are known to collapse upon themselves while hemispherical liners are believed to turn inside out in the process of jet formation. The first has been definitely proved by recovery of collapsed portions of cones, while liners from partly detonated charges show that hemispheres may turn inside out. Fig 3 shows a sketch of a recovered slug from a 6-in. shaped charge using a 45° cone made of cast iron. (This size of charge drilled holes up to 3 ft in depth in solid granodiorite.)

Jan 1, 1949

By C. B. Clark, W. H. Bruckner

Since the end of World War II interest has been increasing in the use of shaped charges in the mining industry and in other industries using explosives for blasting purposes. Shaped charges employ the principle known as the "Munroe effect," which was discovered by Charles E. Mun-roe more than 50 years ago (in 1888). Details of their design have been explained elsewhere.1,2,3 Fig I shows the essential features of design of two types of shaped charges (with conical and hemispherical cavities) and a schematic sketch of their action upon detonation. The following discussion deals with the behavior of the metal in the cavity liners when they are subjected to intense Pressures exerted when the explosive charge is detonated. Among the conclusions reached in research On shaped explosive charges, the following have been established concerning cavity liners:1'2 I. The optimum wall thickness of a conical cavity liner is dependent upon the apex angle of the 'One as well as On the base diameter of the charge. Acute apex angles require thinner walls for optimum perfmnance and more obtuse angles require thicker walls for the same base diameter' 2. Cones were more effective in forming a penetrating jet when the walls were tapered; that is, the thickness of the wall of the cone increased from the apex down. 3. The physical and mechanical properties of metals have a marked effect upon their performance as cavity-liner material. Boiling point, ductility, malleability, tensile strength, and hardness are among the properties that influence the effectiveness of a metal used as a cavity liner. Lead, for example, makes a wide, flat crater in steel plates. Aluminum makes a deeper crater than lead, and an aluminum alloy having a high tensile strength makes a deeper hole, but slightly smaller in diameter. Cast iron makes a deep, narrow hole. These findings, together with the following analysis under Metallographic Survey of slug, offer solutions to many of the problems involved in solving the mechanism of the formation of Munroe jets. It has been fairly well established that cavity liners collapse in a manner similar to that indicated in Fig 2, Conical liners are known to collapse upon themselves while hemispherical liners are believed to turn inside out in the process of jet formation. The first has been definitely proved by recovery of collapsed portions of cones, while liners from partly detonated charges show that hemispheres may turn inside out. Fig 3 shows a sketch of a recovered slug from a 6-in. shaped charge using a 45° cone made of cast iron. (This size of charge drilled holes up to 3 ft in depth in solid granodiorite.)

Jan 1, 1949

With one shaft almost completed and another shaft being sunk, the scope of the Saskatchewan potash area is beginning to come into focus. Some 18 companies have reportedly leased more than four million acres to explore potash possibilities. PCA, farthest along, is located about 15 miles southeast of Saskatoon, and IMC has its project underway near Esterhazy in the eastern edge of the province. U. S. Borax and Chemical Corp. is also reported exploring the area. The field lies in the middle Devonian geological formation which was probed by oil companies along the 200-mile area across the province. Extensive examination began after World War II and deep drilling was started a few years later.

Jan 5, 1958

By G. L. Oldright, F. W. Schroeder

Very great changes were made in the dimensions of the smelting hearths of the furnaces in the period from about 1800 to 1906, the length increasing from about 11 to 116 ft., and the width from 8 to 19 ft. During this time the tonnage smelted increased from about 9 to 250 tons per 24 hr., and the tons of charge smelted per ton of coal increased from 0.77 to 4.3. Dr. Mathewson3 noted no great difference in the "fuel ratio" (i. e., the amount of charge smelted per ton of coal) as the furnace at Anaconda was increased in length by stages from 85 to 116 ft. (The percentage of copper in the slag, however, was lowered from 0.42 to 0.36 per cent. The other components of the slag were not given.) Lump coal fired on grates was the fuel used during this period. The practice in operating the furnaces over such a length of time naturally varied considerably, and there were differences in composition and nature of the charge, yet it may he considered that the improvements made were due largely to increases in the size of the furnace used. Doubtless some credit should be given to improvements in operating technique, like changes in the methods of firing the lump coal. However, the greater part of the advance was probably due to factors influencing the

Jan 1, 1928

By Thomas Watson

INTRODUCTION THE users of barite in the United States derive their supply partly from the domestic production and partly from the imports from foreign countries. According to the Mineral Resource division of the U. S. Geological Survey, the domestic production of barite in 1913 was 45,298 short tons, valued at $156,275, or $3.45 a ton, and the imports of crude barite were 35,840 short tons, valued at $61,409, or $1.71 a ton. These figures clearly show a decided advantage in cost of the foreign over the domestic barite to users in the United States. The difference in cost is the only advantage to the consumer of foreign barite, for there are large reserves of the mineral in the United States of good grade. The production of many of the operating mines is capable of decided increase, and it is believed that the operating mines together with the large reserves of undeveloped deposits of barite are entirely adequate to meet the demands of the users in the United States. Deposits of barite are known in California, Idaho, Nevada, and Alaska, but most of them are undeveloped because there is, apparently, no market for the .material in that region. The domestic production is derived from Missouri and the Appalachian States, the greater part being obtained from Missouri. Following the outbreak of war in Europe many users of foreign barite in the United States have been forced to seek their supplies at home. It seems opportune at this time, therefore, that a general review be given of the barite industry in the Appalachian States, one of the two areas from which the domestic supply of the mineral is derived, and that attention be directed to the undeveloped deposits in the region. Briefly, then, this paper reviews the barite industry in the Appalachian States, and describes the occurrence, preparation, and uses of the mineral.

Jan 2, 1915

By Quentin D. Singewald, B. S. Butler

Some of the broader relations between structure and ore deposition along the London fault, deduced from a thorough study of the geology of the eastern part of the Mosquito Range, should be of general interest to economic geologists. The first part of this paper is a generalized statement of the geology of the region in which the London fault is located; it may be supplemented by reference to several earlier publications by the writers and to the U. S. Geological Survey's Professional Paper 148, on the Leadville district. The second part deals with the structure of both the fault and the disturbed zone adjoining the fault. The third part discusses the salient features of the ore deposits, particularly emphasizing structural control. The two generalized maps are complementary to one another but contain too many data to show on a single small map. The London fault is between Leadville and Alma, and the ore deposits along it are said to lie in the Alma district. Field work in this district, during six summers since 1927, has been a part of the cooperative work of the U. S. Geological Survey, the State of Colorado, and the Colorado Metal Mining Board. The writers have made use of work by R. D. Butler, J. W. Vanderwilt and R. E. Landon. G. F. Loughlin and C. H. Behre, Jr., who have worked on the west side of the range, have contributed valuable suggestions. Mining men of the district have aided in many ways. General Geology Pre-Cambrian Rocks.—The oldest rocks in the district are schists, correlated with the Idaho Springs formation of the Front Range. Quartz-mica schist predominates, but other types occur locally; almost everywhere the rocks show considerable lit-par-lit injection. Intrusive into the schists are two varieties of granite, only one of which is widespread. It is a fine-grained, porphyritie, gray granite correlated with the Silver Plume granite of the Front Range. Near the head of Buckskin Gulch a

Jan 1, 1937

By John Griffen

THEORY HYDRAULIC classification as explained by Rittinger and others was largely restricted to conditions wherein the free-falling velocities of the particles were conceived as governing the separations effected (see chapter 9). The laws governing classification under free-falling conditions have been summarized by Chapman and Mott as fo1lows:l Nomenclature r represents, in a particle of irregular shape, the round-hole screen through which the particle would pass, or some other linear dimension of the particle equivalent to d, the diameter of a sphere. s, the specific gravity of the particle. 1, the specific gravity of the water used as a medium. K, a constant. W, the velocity of the water. In an Upward Current of water 1. A particle will move upward if [V > K dr(s - 1)] and, by suit- ably regulating the speed of the water current, the larger and heavier particles may be made to fall downward against the current, leaving the smaller, lighter particles in suspension in the current. 2. Particles such that [- = -] cannot be separated in an upward- current classifier with any one velocity of current. Coal particles having a specific gravity of 1.35 cannot be separated from refuse particles of [2.5 - 1 2.5 sp. gr.] unless the ratio of diameters is less than [ 4.3 to 1, 1.35 – 1] and the raw coal must be screened to size limits within this ratio if they are to be separated. Cone-shaped vessels or vessels of other shapes that allow the use of different velocities of current at different points in the flow are used to modify this limitation.

Jan 1, 1943

INTRODUCTION Data available on prophyry copper occurrences in the Andean, Caribbean, Appalachian, and Cordilleran orogens may be categorized in a manner to suggest a hypothetical evolution for deposits that occur in the western hemisphere. A classification of de- posits is also suggested. A classification dependent on internal structure of a porphyry copper deposit would lead to two broad categories, breccia pipe and stockwork models. A classification of this type is examined herein but it is not universally accepted in the literature. Modeling based on igneous petrography as well as metasomatism attendant with the sulfide mineralization is more widely accepted by economic geologists whose evaluation of porphyry systems is influenced by the presence or absence of a phyllic zone. Lowell and Guilbert model deposits ordinarily include a phyllic zone, whereas those of the diorite model do not. Position of the phyllic zone in the alteration sequence is a significant ore guide. Should the phyllic zone be absent, dependence on alteration zoning to identify metallization is weakened. Presence or absence of the phyllic zone therefore is a significant parameter in the economic evaluation of a porphyry copper deposit (Hollister. et al., 1975). The Lowell and Guilbert (1970) model commonly includes a phyllic zone in quartz- bearing rocks. Parameters of both calc-alkalic and the quartz monzonite models mentioned elsewhere in this volume are sufficiently close to the Lowell and Guilbert (1970) model that it should be expanded to encompass them. The diorite model remains separate and distinct because deposits of this type are characterized by an absence of quartz in the pluton, commonly highly gold: copper ratios, low molybdenum content, and regular absence of sericite in the alteration zones. Therefore, for the benefit of those

Jan 1, 1978

By D. K. Crampton

Internal stress and season cracking in brass have been studied for many years and the technical literature contains many data on various phases of the subject. A resume of the literature shows certain fairly well established points upon which various authors are mostly agreed: 1. Season cracking is primarily caused by the presence of relatively high internal stresses, or possibly in some cases by external stresses, or both. 2. A specific corrosion is also essential to season cracking. Certain agents, particularly mercurous salts, mercuric salts and ammonia salts, have such a specific corrosive effect. 3. The tendency to season crack under given conditions increases with increasing zinc content, brass containing less than 20 per cent. zinc being relatively immune. 4. In alpha brass the season cracks are intercrystalline; in alpha-beta brass they lie between the two constituents; and in beta brass they are transcrystalline. 5. The ordinary impurities or added elements in special brasses have little or no effect on the tendency to season crack. 6. Internal stresses can be eliminated, or at least reduced to a safe limit by annealing treatments at temperatures that do not produce visible microstructural changes or appreciable softening of the worked brasses. There are, however, some points in connection with the phenomenon of season cracking which have not been thoroughly investigated, or wherein different authors and investigators are not entirely in agreement. The investigations described in this paper were undertaken to determine: 1. The correlation between mercurous nitrate tests and actual season cracking on long-time atmospheric exposure. 2. The quantitative effect of type and degree of drawing operations on the intensity of internal stress and on the tendency to season crack in brass tubes. 3. The possibility of drawing high-brass tubes in such a manner as to prevent the occurrence of harmful stresses rather than to find a remedy for such stresses once having obtained them.

Jan 1, 1930

By Charles Y. Clayton

A study of the literature shows that the greater part of research work on annealing of cold-worked iron has been for the purpose of studying the effect on grain-size and properties other than hardness. No reference has been found of experimental work of the same nature as that explained in this short paper. The material used throughout was Vismera iron, an iron containing 0.03 carbon and made several years ago by the Inland Steel Co. One-half inch stock was cut into cylinders % in. long. The cylinders were then compressed for 60 sec. in a Reihle testing machine under loads as indicated below: CoMPressiON, Average Length, Series Pounds Inches 1 10,000 0.693 2 15,000 .599 3 20,000 .501 4 25,000 .426 5 30,000 .378 6 35,000 .351 7 40,000 .311 Fig. 1 shows these cylinders after compression. Each series consisted of 17 specimens lettered 0, B, C, D, E, F, G, H, I, J, K, L, M, N, P, Q and R. One specimen of each series was reserved for study of the properties in the cold-worked condition. The other specimens were annealed in a Hump furnace for 1/2 hr. at the following temperatures: TEmpeRa- TempeRa- Letters tuRe,° C. LettERs tuRe °C. B............................... 250 J.............................. 650 C............................... 300 K............................. 700 D............................... 350 L.............................. 750 E............................... 400 M............................. 800 F................................ 450 N............................. 851 G............................... 500 0. . :........................... 900 H............................... 550 P.............................. 950 I................................ 600 Q............................. L000

Jan 1, 1926

By Charles S. Barrett

THE experiments reported in this paper have been fruitful in disclosing the mechanism of the deformation of iron in compression. They have established the nature of "deformation bands," "etch bands," or "X-bands," that have been a recognized but little understood feature in the structure of cold-worked metals since the early days of metallography, and have shown the role of the bands in the development of preferred orientations by cold-working. The work has also shown the relation of the orientation of individual grains to the preferred orientation of the aggregate. Some of the methods previously used in the determination of the indices of slip planes and slip directions are shown to be untrustworthy in the presence of deformation bands. The conclusion is reached that many slip planes and slip directions must operate during each stage in the compression of a single crystal, and that theories failing to take account of this require revision. In conducting the experiments a method of compression has been used by which extreme reductions can easily be reached, even to the limit set by the metal's capacity to deform without fracture. The work is a portion of a research program on the plastic properties of iron and steel. It is being used as a foundation for studies of orientations resulting from recrystallization and is being extended to other metals and other types of deformation. PREVIOUS WORK The previous experiments are few and have given confusing results. Ono1 compressed a polycrystalline alpha-iron specimen between two flat plates of a testing machine and found that severe deformation oriented the crystals into a duplex preferred orientation, one set of crystallites having a cube diagonal of the body-centered cubic lattice parallel to the compression axis, and another set having a cube axis parallel to the compression axis. We shall speak of this structure as a. double fiber texture of the type [111] + [100]. Wever2 also made an X-ray determination of the texture

Jan 1, 1938