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By E. R. Johnson

THE copper concentrator of the Braden Copper Co. is at Sewell, Chile, on the western flank of the main Cordillera of the Andes, at an air distance of approximately 50 miles southeast of Santiago, the capital of Chile. The region is mountainous and space is at a premium because of the rough terrain and the danger of snowslides. The ore, a porphyry copper, is mined by a block-caving method in the El Teniente mine. It is hauled to the crushing plant, a distance of 2.6 miles, through a tunnel because of the severe climatic conditions. The usual large, coarsely set, primary reduction machines found in many ore-treating plants are not required because of the mining method employed and the limiting 12-in. spacing of the grizzlies at the head of each ore pass in the mine. It is the purpose of this paper to describe the numerous improvements made in the crushing section of this large flotation concentrator during the past 15 years to increase the efficiency of the plant and to raise the daily output from around 20,000 to 30,000 tons. The reader should keep in mind that all changes were made within the existing building because of the limited space and the high cost of the heavy mill construction required to withstand the snow loads. The present plant, as well as the former, operates on a 24-hr, 7 days a week basis. FORMER PLANT The crushing plant commenced operations at its present site in 1921, the main equipment being No. 7 1/2 gyratories, followed by 48-in. horizontal Symons disk crushers. Fines were removed by 1-in. stationary grizzlies ahead of each unit. In 1924 a third stage of crushing was provided by the addition of 55 1/2-in. rolls in open circuit. During 1925, the Symons disks were replaced by 73 1/2-in. rolls. All the rolls were changed to closed circuit, with elevators and screens to give a final product of 9 pct plus 3-mesh. The flowsheet of a typical crushing section of this period is shown in Fig I. The ore was withdrawn from a common bin serving the five crushing sections in the plant by means of any number up to six 36-in. wide-apron feeders, which discharged onto a common conveyor belt. This conveyor was equipped with a magnetic head pulley and the crusher attendant was stationed near the discharge end to pick out pieces of mine timber that might be in the ore. The ore was discharged over a 1 3/4-in. spaced bar grizzly and the oversize of this grizzly was crushed by a No. 7 1/2 McCully gyratory crusher set at 1 3/4-in. opening on the closed side. The grizzly undersize joined the gyratory discharge and was conveyed to a set of 73 1/2 by 20-in. Garfield rolls set at I in. These rolls operated in closed circuit with a bucket elevator and two vibrating screens placed in parallel.

Jan 1, 1947

By H. M. Howe

Page 1. Introduction............................514 2. Definitions.............................517 3. Brevity of the Heating........................517 I. THE HARDENING OF THE BORE..............517 4. The Hardening of the Bore.....................517 5. The Thickness of the Hardened Layer.................517 6. Martensitization..........................518 7. The Hardening Repetitive ......................519 8. The Temperature Cycle.......................519 9. The Hardened Layer is the Merged Layer............... 521 10. The Progressiveness of Merging....................521 11. The Progressive Thickening of the Hardened Layer from Round to Round. 523 12. Merging and Hardening are Cumulative................523 13. Three Additional Causes of the Progressive Thickening of the Hardened Layer 525 14. Progressive Roughening of the Bore..................525 15. Avoidance of an Endothermic Transformation.............525 16. Asymptotic Retardation of the Thickening of the Hardened Layer.....527 17. The Troostitic Layer........................ 529 18. The Usual Lack of Martensitic Markings................529 19. The Thickness of the Hardened Layer Should Increase with the Quantity of Heat Taken up by the Walls of the Bore.................530 20. The Decrease of the Thickness of the Hardened Layer from Breech to Muzsle 531 21. Phstic Deformation as a Contributory aCause of Hardening........531 22. In What Way May Plastic Deformation Hasten Hardening?....... 535 23. Possible Need of Coarsening.....................535 24. Carburization as a Cause of Hardening..........:.....536 25. Does Hardening Increase Erosion?..................-538 11. THE CRACKING OF THE BORE ...............539 26. Appearance of the Bore and Cracks in Elevation............539 27. The Cracks in Elevation in the Rear Ring...............539 28. The Cracks in Elevation in the Forward Ring.............540 29. The Copper Network in the Grooves.................540 30. The Cracking of the Lands......................541

Jan 1, 1918

By AIME AIME

T HE Mining Methods Committee held its initial meeting* on Tuesday afternoon, with F. W. Bradley in the chair and W. Y. Westervelt as vice- chairman. The first paper to be presented was "A Plea for a U. S. Court of Patent Appeals," for which Kenneth W. Greenawalt ably pleaded. The paper (which was published in full in last month's issue) is so carefully prepared that no synopsis can do it justice. It discusses the opposed views of some patent lawyers and other lawyers and members of the judiciary as, for example, Chief Justice Taft who is quoted as saying in 1921: "I think it is a great deal better to take a first class lawyer and a first-class judge and make him a good patent expert than it is to take a patent expert and try to make him a first-class lawyer and a good judge." Mr. Greenawalt argued the need for specialized scientific and engineering interest and understanding to enable a lawyer or judge to prepare or interpret patent specifications and decide the originality necessary for a valid invention. He proposed the special U. S. Court of Patent Appeals to also counteract the costly confusion and injustice now ruling where a patent may be declared valid in the courts of certain States and invalid by the courts of other States.

Jan 1, 1930

By Robert S. Dewey

Drilling in West Texas during 1942 was substantially less than in the previous year. In all. 1267 Wells were drilled, as compared with 2325 wells in 1941. Of these 1267 wells, 1052 oil wells, 10 gas wells and 69 dry holes were drilled in proven fields and 36 oil wells, one gas well and 99 dry holes were wildcat operations. Of the 36 wildcat wells completed as oil producers, 16 led to new field discoveries, three found new productive horizons in old fields, and 17 extended the productive limits of established fields. Where semiwildcat drilling took place along established productive trends, there was often no sharp demarcation between wildcat wells that extend field limits and normal development to fulfil lease obligations, other than the arbitrary classification of a well as a wildcat if it was drilled at a distance of 2 miles from a producing oil well. The dry hole drilled on the edge of a field may have proved a more hazardous operation than a semiwildcat drilled several miles from production but favorably located on structure. The percentage of successful wildcatting ranges from 26.5 down to 14 per cent, dependent upon the degree of inclusion of the semiwildcat operations. Irrespective of which figure was used, the West Texas area maintained its better than average exploratory position. No doubt a number of factors may have influenced the extent of the 1942 development. Among those arising from the economic dislocation attendant on the war effort, the following are worthy of note. Owing to inductions into the armed forces and shipyard competition for mechanically trained men, experienced drilling personnel was sharply reduced, thereby increasing drilling costs and well-completion hazards. Replacement labor has not met the same standard of responsibility or workmanship to which the oil industry has grown accustomed. Increased military consumption of aviation gasoline and other crude products, coupled with decreased domestic consumption of lower-octane gasoline, has stimulated the market demand for the types of sweet crude most readily processed with available refinery equipment to meet war requirements, and has depressed the market demand for the sour West Texas crudes. As a majority of the purchasers of West Texas crude normally ship a substantial portion of sour crude to the refineries on the Atlantic seaboard, the loss and diversion of tanker service between Gulf Coast and north Atlantic ports have further curtailed the market demand for this type of crude oil. As some purchasers of crude oil were able to move by pipe line their West Texas trunk-line capacity to Midwestern refining centers, they were not impelled to curtail purchases of West Texas crude. The varying ability of the purchasers of crude oil to market West Texas crude was reflected back to various fields to which they were connected, causing an unequal distribution of production as among fields and operators. The pipe-line runs from the West Texas-New Mexico area decreased from approximately 354,000 bbl. Per day in January to about 265,000 bbl. in December 1942. .Approximately 2,991,000 bbl. of West

Jan 1, 1943

By Robert S. Dewey

Drilling in West Texas during 1942 was substantially less than in the previous year. In all. 1267 Wells were drilled, as compared with 2325 wells in 1941. Of these 1267 wells, 1052 oil wells, 10 gas wells and 69 dry holes were drilled in proven fields and 36 oil wells, one gas well and 99 dry holes were wildcat operations. Of the 36 wildcat wells completed as oil producers, 16 led to new field discoveries, three found new productive horizons in old fields, and 17 extended the productive limits of established fields. Where semiwildcat drilling took place along established productive trends, there was often no sharp demarcation between wildcat wells that extend field limits and normal development to fulfil lease obligations, other than the arbitrary classification of a well as a wildcat if it was drilled at a distance of 2 miles from a producing oil well. The dry hole drilled on the edge of a field may have proved a more hazardous operation than a semiwildcat drilled several miles from production but favorably located on structure. The percentage of successful wildcatting ranges from 26.5 down to 14 per cent, dependent upon the degree of inclusion of the semiwildcat operations. Irrespective of which figure was used, the West Texas area maintained its better than average exploratory position. No doubt a number of factors may have influenced the extent of the 1942 development. Among those arising from the economic dislocation attendant on the war effort, the following are worthy of note. Owing to inductions into the armed forces and shipyard competition for mechanically trained men, experienced drilling personnel was sharply reduced, thereby increasing drilling costs and well-completion hazards. Replacement labor has not met the same standard of responsibility or workmanship to which the oil industry has grown accustomed. Increased military consumption of aviation gasoline and other crude products, coupled with decreased domestic consumption of lower-octane gasoline, has stimulated the market demand for the types of sweet crude most readily processed with available refinery equipment to meet war requirements, and has depressed the market demand for the sour West Texas crudes. As a majority of the purchasers of West Texas crude normally ship a substantial portion of sour crude to the refineries on the Atlantic seaboard, the loss and diversion of tanker service between Gulf Coast and north Atlantic ports have further curtailed the market demand for this type of crude oil. As some purchasers of crude oil were able to move by pipe line their West Texas trunk-line capacity to Midwestern refining centers, they were not impelled to curtail purchases of West Texas crude. The varying ability of the purchasers of crude oil to market West Texas crude was reflected back to various fields to which they were connected, causing an unequal distribution of production as among fields and operators. The pipe-line runs from the West Texas-New Mexico area decreased from approximately 354,000 bbl. Per day in January to about 265,000 bbl. in December 1942. .Approximately 2,991,000 bbl. of West

Jan 1, 1943

By J. Ruzicka

IN creep testing, material is subjected to a constant load, preferably at a constant temperature, and its rate of deformation is measured. The method of loading can be of various types but in this paper only creep testing under tensile load will be considered. The ordinary tensile test is essentially a comparison test in conditions that frequently bear little or no relation to those under which the test material is to be used in service. The purpose of creep tests is to measure the strength of the test material at slow rates of deformation that more nearly approach the rates realized in service. One purpose of this paper is to illustrate that the creep test, in addi-tion to its value as a service test, is superior to the ordinary tensile test as a sensitive tool for the comparison of certain metals in investigative testing. The other purpose is to describe equipment having distinctive features of design that make it especially suitable for such tests. Representative data obtained with this equipment on a group of rolled zinc-base materials are given. These data are compared with those from practical comparison tests of the creep type on weatherstrip fabri-cated from the same group of materials. The comparison illustrates the value of the fast creep test and of the equipment.

Jan 1, 1937

By Y. G. Shiau, J. E. Burke

Several attempts have been made to account for the fact that grains in a fully recrystallized metal will coarsen on annealmg. Two fundamentally different hypotheses have been advanced, with several variations of each. One school considers that the cause of grain growth is the surface energy of the grain boundary. The theory of Jeffriesl that grain size and grain size contrast control growth is an example. The second school considers the primary cause to be a difference in the lattice energy on either side of the grain boundary. The more perfect grains are considered to grow at the expense of their less perfect neighbors, with a decrease in free energy, and a consequent increase in the stability of the system. Burgers2 presents the case for the strain or lattice imperfection theory of grain growth quite completely. The latter theory is attractive, since there is no doubt that differences in lattice energy or lattice perfection can cause grain boundary migration. A recrystallization nucleus grows for this reason as was beautifully demonstrated by van Arkel and Ploos van Amstel.³ Although it is generally stated that grain growth does not precede recrystallization, several workers4-5 have shown that small strains may induce a single crystal in an aggregate to grow, or at least may cause some grain boundary migration. The origin and nature of the imperfections that are considered to be responsible for normal grain growth have never been clearly described, but it is generally agreed that they are a consequence of the difficulty of atomic reorientation in the solid state, and that they do not seriously differ from the type of imperfection that can be introduced by mechanical deformation. An object of the present work was to determine whether the introduction of mechanical deformation would cause grain growth in a specimen which would not otherwise show it under the conditions used. It was also planned to determine the effect of such deformation on the rate of growth in a specimen which would show growth in the unstrained condition. Recently Maddigan and Blank6 have indicated that slightly strained specimens of alpha brass can undergo considerable growth prior to recrystallization if annealed at low temperatures. French7 has reported that at deformations less than 17 pet it is very difficult to detect the beginning of recrystallization in the same material. It was therefore planned to broaden this work to include a complete study of the microscopic behavior of alpha brass under condition~ of temperature, time, grain size and deformation such that recrystallization would not occur or would occur to only a Small extent. Experimental Procedure The brass was prepared by melting cathode copper and commercially pure zinc

Jan 1, 1949

By J. E. Burke, Y. G. Shiau

Several attempts have been made to account for the fact that grains in a fully recrystallized metal will coarsen on annealmg. Two fundamentally different hypotheses have been advanced, with several variations of each. One school considers that the cause of grain growth is the surface energy of the grain boundary. The theory of Jeffriesl that grain size and grain size contrast control growth is an example. The second school considers the primary cause to be a difference in the lattice energy on either side of the grain boundary. The more perfect grains are considered to grow at the expense of their less perfect neighbors, with a decrease in free energy, and a consequent increase in the stability of the system. Burgers2 presents the case for the strain or lattice imperfection theory of grain growth quite completely. The latter theory is attractive, since there is no doubt that differences in lattice energy or lattice perfection can cause grain boundary migration. A recrystallization nucleus grows for this reason as was beautifully demonstrated by van Arkel and Ploos van Amstel.³ Although it is generally stated that grain growth does not precede recrystallization, several workers4-5 have shown that small strains may induce a single crystal in an aggregate to grow, or at least may cause some grain boundary migration. The origin and nature of the imperfections that are considered to be responsible for normal grain growth have never been clearly described, but it is generally agreed that they are a consequence of the difficulty of atomic reorientation in the solid state, and that they do not seriously differ from the type of imperfection that can be introduced by mechanical deformation. An object of the present work was to determine whether the introduction of mechanical deformation would cause grain growth in a specimen which would not otherwise show it under the conditions used. It was also planned to determine the effect of such deformation on the rate of growth in a specimen which would show growth in the unstrained condition. Recently Maddigan and Blank6 have indicated that slightly strained specimens of alpha brass can undergo considerable growth prior to recrystallization if annealed at low temperatures. French7 has reported that at deformations less than 17 pet it is very difficult to detect the beginning of recrystallization in the same material. It was therefore planned to broaden this work to include a complete study of the microscopic behavior of alpha brass under condition~ of temperature, time, grain size and deformation such that recrystallization would not occur or would occur to only a Small extent. Experimental Procedure The brass was prepared by melting cathode copper and commercially pure zinc

Jan 1, 1949

John Duer Irving, who left his post as Professor of Economic Geology at the Sheffield Scientific School, New Haven, Conn., to join the Eleventh Regiment of Engineers shortly after the declaration of war, died in France, July 26, 1918, from an attack of pneumonia. Through the initiative of Mr. Benjamin B. Lawrence, a memorial service to Captain Irving was held at St. Paul's Chapel, Columbia University, on Sunday afternoon, August 4, which was' attended by members of Captain Irving's family, and about four hundred of his friends from Columbia, Yale, the American Institute of Mining Engineers and the Association of the 11th Regiment of Engineers. Professor James F. Kemp delivered the memorial address, and has prepared for the Institute the following account of Captain Irving's life, Professor Kemp and Captain Irving having been associated on the most intimate terms for a number of years. , The war has brought home to friends and kin in the western shores of thc Atlantic many losses whose suddenness has the shock of a blow. Many more will follow, but none can leave a sharper sense of regret than the news that the keen and productive mind; the inspiring teacher; the successful and considerate editor, the fine, true man and friend had all passed away when John Duer Irving made the final great gift to the service of his country, in the cause of decency and right. In the closing days of July, the cable brought the tidings that toward midnight on the twentieth of the month pneumonia had proved too great a tax upon one already worn by excessive labors. John Duer Irving was born in Madison, Wis., August 18, 1874. His father, Roland Duer Irving, was at the time professor of geology, mineralogy and metallurgy in the State University of Wisconsin.' Roland . Irving, the father, had entered Columbia College in 1863, but trouble with his eyes compelled him to suspend his studies in the classical course in his sophomore year, and to replace study with some months of life and travel in England. Ultimately his eyes became stronger, and he entered the School of Mincs, completing the course for the degree of Engineer of Mines in 1869, with the third class graduated. The class of eleven contained other future geologists. It numbered on its roll Henry Newton and Walter P. Jenney of the early survey of the Black Hills, where John, future son of Roland, was in the course of years to make his doctor's dissertation, and with its publication his really serious entrance into the profession. Roland Irving was a favorite student of Professor J. S. Newberry, affectionately known to all of his students as "Uncle John," and after some experience in mining and smelting in Pennsylvania and New Jersey, joined the Ohio Survey under Dr. Newberry. The work in Ohio was largely performed during the vacations of the University of Wisconsin, to whose chair Roland Irving was called in 1870. Later, his residence in Wisconsin led to two events of prime importance in the history of American geology. He began the study of the Gogebic iron range and caught the clue to the origin and stratigraphy of the iron ores of all the Lake Superior ranges; and he later undertook the mapping and description of the copper-bearing rocks of the Lake Superior basin. The formative years of the son, John, were passed in a home where the father.

Jan 1, 1920

By W. M. Corse

AT THE TURN of the century the nonferrous alloy industry was awakening to the value of scientific metallurgy, and brass foundries and rolling mills began to establish their own research laboratories for scientific research and control. As the industry grew and its scope broadened it became apparent that an organization was needed that would stand in the same relation to the nonferrous industry as the American Foundrymen's Association did to the iron foundry business. The brass founders' group of the foundrymen's association discussed the matter and it was finally decided to appoint a com- mittee to draw up a constitution for a new organization to be known as the American Brass Founders' Association. Charles J. Caley was chairman and Dr. Richard Moldenke secretary of this committee. The object of the organization as defined by the constitution was the study of the technological development of alloying and founding non- ferrous metals, and furthering the advance of nonferrous metallurgy and the standardization of materials and operations in cooperation with the Bureau of Standards and engineering societies.

Jan 1, 1932

By C. Hertzler

The difference of means of milling characteristics by rock and ore type is tested in a statistical manner in the paper. The null hypothesis being tested is that the sample means of two different populations are equal. It is assumed that the null hypothesis is true when performing the test. Because of this, acceptance of this hypothesis leads to the conclusion that the sample means of the two different populations are equal (or there is no significant difference between the sample means), not that the samples come from the same population, as the author asserts. Rejection of the null hypothesis leads to the conclusion that the sample means of the two different populations are not equal. A P value for this test is reported in Table 2 and is incorrectly identified as the probability that the two samples came from different populations. Actually, what was recorded was 100(1 - p) where p is the usual p-value. The usual p-value measures, on a scale of zero to one, the extent to which the data agree with the null hypothesis. It is the probability of observi" a value of the test statistic (Z score) that is at least as contradictory to the null hypothesis as the one computed from the sample data (McClave and Dietrich 11, 1982). The author makes no mention of the fact that were these tests to be conducted together, the chances of determining that the null hypothesis is not true when it is really true are increased considerably (Snedecor and Cochran, 1980). This is a multiple comparisons problem and should be dealt with accordingly. The usual methods involve adjusting the level of the individual tests. Table 2 reports an incorrect 100(1 - p) value in the comparison of concentrate grades for other rock types with .30 to .69% Cu vs other rock types with .70 + % Cu; 86% should be 98.6%. Although the article can be criticized for poor data presentation and discussion of that data, the point the author makes regarding the use of these statistics in the ore reserve estimation process is well taken. It does not appear that inaccuracies in the statistical interpretations have hindered that usefulness.

Jan 1, 1985

By John J. Collins

Page Purpose and scope..................... 521 Core sampling......................... 521 Sludge sampling....................... 527 Combining core and sludge assays ...... 533 Deviation and surveying of drill holes. . . . 537 Conclusions........................... 544 Acknowledgments...................... 545 Bibliography.......................... 545 Purpose and Scope The purpose of this paper is to review a few of the problems involved in the interpretation of diamond-drill core and sludge samples, with the hope that it will stimulate discussion and bring forth some of the information on the subject that has been accumulated by various organizations. The release of these data would benefit the mining industry as a whole. Particularly valuable would be the details of drilling programs that have been tested by actual mining operations, as most of the available published material is unsupported by production records. The scope of this paper is limited to a few of the commonest problems of interpreting diamond-drill core and sludge samples and the deviation of holes. It does not include the description of routine operations performed by the drillers, nor the estimation of ore reserves. The methods of calculating reserves have been described,25,26,31,32,50,65 but more informa- tion is needed on the results shown by actual mining operations. Core Sampling The accuracy of diamond-drill-hole Sampling depends in large measure on the percentage of core recovery. As a general rule, the longer the run, the poorer is the recovery. Although the longer runs allow cheaper drilling costs, the determining factor should be the percentage of recovery desired. The problem is one of balancing accuracy against costs. Holes of larger diameter may show improved recovery, except as Joralemon* points out that there are some conditions in which small holes give better core recovery than large holes. This is particularly true, he says; in rocks like shattered quartzite, where larger core tends to break in angular fragments and grind up, while the diameter of smaller core is less than the distance between joint planes and grinding is not so serious. In a large measure the length of the sample run should depend on the type of deposit. Favorable drilling may allow uniform sample runs of 5 ft., 10 ft., or perhaps 20 ft. In veins or beds of relatively narrow widths and changing characteristics, however, the ore zone may be overrun and ground in a core barrel full of waste rock. Generally it is desirable to break the sample at a change in the rock or ore. Such a change; often indicated by a color change in the sludge water, should be a a for the driller to make a "dry" block and to pull out that run regardless of the length. Such a procedure permits the segregation of waste from ore samples so

Jan 1, 1946

By Paul M. Tyler

Mineral raw materials, because they are essential to our industrial prosperity and military strength, must be made available in substantial quantities. regardless of cost. Variations in the cost of procuring minerals, as compared with the cost of obtaining other commodities, and changes in the cost of production of different minerals relative to one another, will naturally influence the quantities of a given mineral item that can be marketed readily. However, in the last analysis, the cost of winning minerals from the ground usually constitutes only a small fraction of the value of the end-use products and services derived from them. The miner's share of the cost of a typewriter, telephone circuit, or even a modem office building, is almost insignificant. Far more important to the ultimate consumer, therefore, than any minor saving in cost is the assurance of ample supplies of the minerals needed to aliment our expanding economy. To create a successful metal mining operation involves ( 1 ) the discovery and systematic development of a mineral deposit, (2) extraction of the ore, (3) the mechanical and metallurgical processing to eliminate worth- less or harmful impurities, and (4) the profitable disposal of the product. The first step of the technological process belongs chiefly in the realm of the geologist, the second is a mining engineer's job, the third is mainly up to the millmen and extractive metallurgists; whereas the fourth and equally important step poses a commercial problem that has aspects in common with the marketing of other products. Ore finding is far from being an exact science. There is no mathematical criterion for evaluating the efficiency of prospecting and exploration. Lady Luck shares the honors or assumes part of the blame along with the prospector and geologist. Marketing like- wise involves factors that seemingly defy engineering analysis. Although the other steps can be measured with some degree of mathematical accuracy, even they tend to vary so widely in basic principle, as well as in

Jan 1, 1959

By D. G. Wilder

D.G. Wilder I found the suggestion that the amount of displacement of a fault can be numerically related to the thickness of gouge or breccia to be both intuitively satisfying and intriguing. I have long agreed that there is some type of relationship between the amount of gouge and the amount of displacement of faults. I congratulate the author for developing a numerical relationship between them. However, I am concerned that the limits for applying this relationship be fully understood. An underlying assumption in this approach is that there is either a uniform thickness of gouge or breccia along a given fault or the thickness does not vary widely. Since it is not always possible to confirm this, the displacements derived by this method should be viewed with caution unless significant fault extent can be observed. At the Nevada Test Site, in drifts constructed in granite for test emplacement of spent nuclear reactor fuel, we found a fault with 0.3 to 0.4 m (12 to 16 in.) of clay gouge. Within a few meters of this location, the fault had no clay gouge, but rather consisted of a highly fractured zone with significantly altered rock and some slickensides. Based on Fig. 1, the 0.3 to 0.4 m (12 to 16 in.) thickness of gouge would indicate a displacement in excess of 30 m (98 ft). However, no gouge thickness would indicate essentially no displacement. Based on a quartz vein that terminated on the fault, and is not identified nearby, an estimated displacement of more than a few meters was made. This estimate is consistent with that obtained using the regression line proposed in the paper if the 0.3 to 0.4 m (12 to 16 in.) thickness for the gouge is used. However, using the regression curves with zero thickness would not yield results consistent with what was observed in the field. Therefore, it is important to recognize that the suggested procedure would properly yield a range of probable displacements. ? *Work performed under the auspices of the US Department of Energy by the Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. Reply by E.C. Robertson It is certainly true that the t (thickness) of gg-bx (gouge and breccia) on a fault does vary along the fault. My observations have been that near the termination of a fault, the displacement d is small and the t is also small, whereas the maximum d and t will usually be found in the central part of the fault. The information on gg-bx and t of the fault found in granite in the NTS tunnel by Mr. Wilder could be interpreted somewhat differently than he does. He speaks of the fault changing within a few meters from 0.3 to 0.4 m (12 to 16 in.) of clay gg to "a highly fractured zone with significantly altered rock and some slickensides," but no gg. The highly fractured rock may be taken to be bx, rock not so finely ground as gg but still crushed by the fault movement, equivalent to the gg in my usage, and probably occupying about the same t. Mr. Wilder's estimates for the fault in the NTS tunnel for t of 0.3 to 0.4 m (12 to 16 in.) and for d of a quartz vein, in excess of "a few meters," would place the point on the low side of the central trend line in my Fig. 1, at the lower limit. There is, of course, a problem with determining d using displacement of only one planar surface. It would be greater or lesser depending on the rake of the movement. Finally, estimating the d of a fault from its t should be made with awareness of our present uncertainties, as pointed out by Mr. Wilder. Although the central trend line in my Fig. 1 has a ratio of d/t of 100, I have put the limiting ratios at 10 and 1000. Understanding of the values of the ratio will be improved only with collection of more data, for which the discussion of Mr. Wilder is much appreciated. ? G.C. Waterman E.C. Robertson's paper provides significant information to a geologist attempting to deduce fault offset by noting the products of structural dislocation. However, considerable mapping in underground and open-pit mines, and examination of structures produced in different geological settings, have convinced me that gouge and breccia thickness are controlled by geological conditions and fault movement. The following paragraphs suggest geological variables that control them. 1. Depth of Loading A near-surface fault resulting from tensional stress has more breccia/gouge than is produced by a similar stress at considerable depth. A deep-loaded compressional stress may produce a linear zone of schist, or structural dislocation may occur along an earlier formed belt of schist. Such "shear zones" are common in Canadian mines in precambrian rocks. In neither case can offset be directly deduced by an analysis of the minimal gouge/breccia in the shistose rocks. At greater depth, stress may be partially to wholly relieved by flowage. I vividly recall first noting the regional "Midas Thrust" in the Lark mine, Bingham Mining District, UT (where we called the structure the North Fault). My recorded notes, as I remember them, showed a narrow gouge streak separated the "Jordan" and "Commercial" limestone units from impure, muddy limestone beds of uncertain stratigraphic position. The visible structure did not indicate the great importance of this premineral fault

Jan 1, 1985

By George Norman

A NUMBER of methods have been developed for the determination of the dust concentration in air, some of which have been reported as very efficient and for research may be more satisfactory than the method about to be described. In practical mine use, however, the accurate research equipment is unwieldy and requires a high degree of technical skill to manipulate it. Also, it gives less general practical information to the operator in the same length of time than the method described here. Moreover, it is doubtful whether at the present stage of affairs the results obtained from the precise methods have any more practical significance than those obtained with simpler and more portable appara-tus, which can rapidly give a sufficiently reliable indication of the rela-tive dust hazard.

Jan 1, 1937

By Albert E. Wiggin, Frederick Laist

Early ill 1914 it was decided to test, on a fairly large scale, the treatment by flotation of Anaconda slime and mill tailing. For this purpose a standard-type Minerals Separation machine was installed at the Washoe Reduction Works during May and June, 1914. This was followed by the installation of a full-size Callow pneumatic machine plant. Experiments were also made, on a smaller scale, with the Froment, the Towne, the Fields, and the Anaconda flotation machines. The last-named machine was developed at this plant. In addition to the tests made in the standard-type Minerals Separation machine some tests were made using a Minerals Separation machine of the sub-aeration type. During the series of experiments a large variety of oils was tested. Experiments were also conducted using both round-table feed and tailing to determine whether it would be better to displace the round tables by flotation for the treatment of the slime, or to supplement the round tables by flotation of the round-table tailing. A series of tests was also made on the treatment of the mill tailing by grinding followed by flotation to determine the relative merits of flotation and leaching for the treatment of this product. In addition, flotation tests were made on mixtures of mill tailing and slime. The round-table feed referred to above is the total slime from the mill. It contains about 35 per cent. colloidal solids and approximately 90 to 95 per cent. of the total solids will pass through 200 mesh (0.067 mm.). It assays from 2.3 to 2.6 per cent. Cu. The mill tailing referred to above is the total discard from the mill, exclusive of the slime. It is all finer than 2 mm. and about 90 to 95 per cent. will remain on 0.25 mm. It assays about 0.60 per cent. Cu. A brief summary of the experimental flotation results follows:

Jan 1, 1917

The General Electric Co., in cooperation with the Montana School of Mines and under a research grant from the Anaconda Co., is presently experimenting on a new non-explosive method of breaking rock with radio-frequency electrical power. The method is known as electrothermal forcing. It must be understood that present equipment has not been designed to perform primary blasting functions. Its conceived use will be restricted to small pieces of rock too large to pass through a chute or grizzly. However, even this use is still far in the future. Experiments to date have been limited mostly to rock smaller than 18 in.

Jan 11, 1961

By J. A. Fellows, Earnshaw Cook, Howard S. Avery

HEAT-RESISTANT alloys of the higher nickel and chromium ranges have been empirically developed through the practical experience of the past two decades to a position of significant industrial importance. Few quantitative metallurgical data have been published, however, that could be related directly to engineering specifications and design. Inadequate information led to the inauguration, in 1934, of a research directed toward a better understanding of the properties and performance of these steels at temperatures between 1400° and 2000°F. Investigation was concentrated upon the 26 per cent Cr:12 per cent Ni type, which owes its extensive application to an excellent combination of economy, strength and surface stability at elevated temperatures. The requirements of the oil-refining industry have been prominent in influencing the scope and evolution of the program. Creep strength at the maximum allowable deformation ranges has been employed to evaluate the merits of these alloys. Permissible elongation rates vary from 1.0 per cent in one million hours for turbine blades to 1.o per cent in ten thousand hours for tube supports and heating-furnace equipment. Throughout this paper, the limiting creep stress (L.C.S.) for a given temperature has been defined as the stress that will produce a uniform elongation rate (stage II) of one per cent in ten thousand hours as extrapolated from rates per hour or tests of less than two thousand hours duration. Certain current specifications require a minimum L.C.S. of 1600 lb. per sq. in. at 1800°F., of 3600 lb. per sq. in. at 1400°F., and include a tensile acceptance test at room temperature, after aging for 24 hr. at 1400°F., as a measure of embrittlement in service. An elongation of 4 per cent is considered satisfactory for general use, while a minimum of 9 per cent is prescribed on occasion. Many differences of opinion concerning the properties and performance of these alloys appear to result from their sensitivity to unappreciated variations of chemical analyses which, for example, may change their L.C.S. from 3500 to 350 lb. per sq. in. at 1800°F. Within broad chemical limits, it is possible to balance the six or more important elements present to attain desirable properties with a number of different combinations. One method for adjusting the composition has been described under the sponsorship of the Alloy Casting Institute,1 in which, by maintaining a substantially austenitic* alloy, optimum creep strength and minimum tendency to embrittle after aging are expected. Unless, however, the limits are undesirably dose, it has not been possible to ensure a moderate range of strength and of ductility by any chemical specification alone. There is a definite need

Jan 1, 1942

Executive JVW REYNOLDS, Chairman SYDNEY H BALL E DEGOLYER WILLIAM H BASSETT SAMUEL A TAYLOR Finance GEORGE D BARRON, Chairman H A GUESS GEORGE OTIS SMITH Membership ] H CALLOW, Chairman GEORGE D BARRON WILBER JUDSON JOHN A CHURCH, JR H N SPICER Alternates LEWIS W FRANCIS LOUIS D HUNTOON F T RUBIDGE

Jan 1, 1923

By R. A. Vandermeer, Paul Gordon

On the basis of a unified concept, theoretical erPressions for grain boundary migration in recrys-tallization are derzved for impurity-controlled and impurity-independent migration. The expression in the former case is analogous to that Previously derived by Lucke and Detert, and in the latter is shown to be equivalent to that usually obtained on the basis of absolute reaction rate theory. The equations are tested with quantitative experimental data for boundary migration obtained for the recrystallization of poly crystalline zone-refined alumimnz and for binary "alloys" of this aluminum with 0.00021, 0.00043, 0.0017, 0.0034, 0.0068, 0.0124, and 0.0256 at. pct Cu, respectively. All the essential characteristics of the e@erimentally determined boundary migration rates check both qualitatively ard quantitatively with the predictions of the theoretical equations. THE rates of transformations are customarily analyzed phenomenologically in terms of the two component rates—N, the rate of nucleation and, G, the rate of growth of the nuclei. The scientific aim of both theory and experiment is to describe the fundamental atomic phemmena involved in these two component processes with the hope that parameters calculated from theoretical equations will check those found experimentally. In solid state transformations, the theoretical and experimental problems are both generally of almost prohibitive complexity, for in addition to changes in composition and in such properties as density which may accompany transformations in amorphous, nonrigid materials, transformations in crystalline substances also involve structural changes, crystal reorientations, and the development of stresses. In studying such transformations it thus becomes; highly desirable, if not essential, to focus on a transformation and a set of conditions which minimize the number of active variables. This principle has been applied with considerable success by Cohen and his associates' in their evaluation of nucleation theories using the martensite transformation as the basis of study. A similar possibility exists for the evaluation of growth theories by the use of recrystallization after cold-deforming. If an unalloyed metal is employed as the subject of investigation, the recrystallization transformation involves basically only a change in strain-conditions and orientations. In spite of this possible simplilfication, however, until recently little quantitative success has attended attempts to correlate recrystal1ization parameters measured experimentally with those calculated theoretically. It seems highly probable that this lack of success may be attributed, both in the experimental and theoretical treatments, to one or more of the following factors: a) conditions have usually been studied under which apparently* both nucleation and growth are active;

Jan 1, 1962