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By C. R. McEwen

The displacement equations of Buckley and Lever-ett' have been successfully applied to the prediction of oil recovery in frontal drives for a number of years. Commonly, the capillary pressure term is omitted from Leverett's fractional flow formula. The resulting satura-tion-vs-distance curves become multi-valued, however. Buckley and Leverett, recognizing that the neglect of capillarity was most likely the cause, proposed that this part of the solution he ignored. An ingenious method of propagating a discontinuity in place of the multi-valued portlon of the curve was devised by Cardwell using "non-capillary displacement theory". However, it would seem that a completc description of the displacement pracess would require the inclusion of capillary forces. Three publications on displacement theory have appeared in which capillary pressure was included. Ter-williger. et al', calculated saturation profiles which matched those which they observed when gas displaced water vertically downward. Based on their study, Jones-Parra and Calhoun5 roposed a method of computing saturation distributions sufficiently removed in time from the initial conditions so that all saturations in the flood front region were assumed to move with the same velocity. This latter assumption corresponds to the tangent construction on the flowing fraction-vs-satura-tion curve proposed by Welge." A numerical solution to the problem of water displacing oil from a water-wet porous medium was recently presented by Blair, ef at'. The initial conditions included a uniform saturation slightly above interstitial water saturation. that is, the permeability to water ahead of the front was not zero. This appeared to result in a region of slowly rising water saturation ahead of the front, at least for the particular set of relative permeability and capillary pressure data used to illustrate the computation. The authors also postulated an "end-effect" at the outflow face of the system, whereby no water could pass out of the system until the water saturation had built up to a high value. The saturation profiles computed under these assumptions show water accumulating at the downstream end of the system while the flood front proper is still traveling toward the outlet. The purpose of this paper is to present the results of a numerical solution to the one-dimensional water-flooding equation in which no outlet end-effect is considered and where there is no flow of water ahead of the flood front. It should be noted that the contemporary paper of Fayers and Sheldon8 deals with the problem under discussion. For a thorough treatment including both capillarity and gravity the reader is referred to their paper.

By J. T. Eash, E. M. Wise

Many of the platinum metal alloys are hot-forged in the early stages of reduction from ingot and substantial quantities of platinum alloys are commercially employed at very high temperatures in ammonia oxidation units, orifices for forming glass rods and fibers and as cathodes in long-life thermionic amplifiers. They are used also for electrical heating resistors, safety blowout disks, thermocouples and crucibles. The tensile properties at elevated temperatures are important in many of these situations but data on the subject are limited. Creep data also are important, but will not be covered at this time. Scope and Conclusions Tensile tests were carried out at room temperature and elevated temperatures up to 1100" C. on previously well annealed samples of platinum. palladium and several of their important alloys with compositions shown in Table 1. The results are presented graphically in Figs. 1 to 4. The tensile strengths of platinum and the platinum-base alloys (with the exception of the 10 per cent rhodium-platinum alloy) at 1100" C. are from 16.6 to 18.8 per cent of the strengths of the same alloys (well annealed) at room temperature. The strength ratio of the 10 per cent rhodium-platinum alloy is 22.3 per cent, which is appreciably higher than that of the other materials tested. The tensile strengths of palladium and the palladium alloy at 1100" C. are from 10 to 11.2 per cent of the room-temperature values. The elongations of platinum and its alloys tend to increase at temperatures above 600" to 800" C., while the two samples of pure palladium show a maximum at 600" C.

Jan 1, 1938

By J. T. Eash, E. M. Wise

Many of the platinum metal alloys are hot-forged in the early stages of reduction from ingot and substantial quantities of platinum alloys are commercially employed at very high temperatures in ammonia oxidation units, orifices for forming glass rods and fibers and as cathodes in long-life thermionic amplifiers. They are used also for electrical heating resistors, safety blowout disks, thermocouples and crucibles. The tensile properties at elevated temperatures are important in many of these situations but data on the subject are limited. Creep data also are important, but will not be covered at this time. Scope and Conclusions Tensile tests were carried out at room temperature and elevated temperatures up to 1100" C. on previously well annealed samples of platinum. palladium and several of their important alloys with compositions shown in Table 1. The results are presented graphically in Figs. 1 to 4. The tensile strengths of platinum and the platinum-base alloys (with the exception of the 10 per cent rhodium-platinum alloy) at 1100" C. are from 16.6 to 18.8 per cent of the strengths of the same alloys (well annealed) at room temperature. The strength ratio of the 10 per cent rhodium-platinum alloy is 22.3 per cent, which is appreciably higher than that of the other materials tested. The tensile strengths of palladium and the palladium alloy at 1100" C. are from 10 to 11.2 per cent of the room-temperature values. The elongations of platinum and its alloys tend to increase at temperatures above 600" to 800" C., while the two samples of pure palladium show a maximum at 600" C.

Jan 1, 1938

By Richard H. Sillitoe

Gold is an important byproduct and, locally, coproduct of porphyry copper deposits, and possesses potential for discovery as the major metal in porphyry deposits in either island arcs or Cordilleran belts. Tungsten and tin occur as major components of several potentially bulk-minable porphyry deposits, as well as being byproducts from the Climax porphyry molybdenum deposit. Whereas porphyry tin systems are localized in Cordilleran back-arc settings, their tungsten counterparts appear to span a range of geotectonic settings, from Cordilleran principal arcs through back arcs to rifts. Although silver is a common byproduct of porphyry cop- per deposits, it tends to be preferentially concentrated with lead and zinc on the fringes of all types of porphyry deposits and/or as late-stage superpositions; the latter situation could be of some interest in the higher parts of porphyry systems. As byproducts, rhenium, uranium, platinoids, and magnetite are exploited occasionally, and rutile and the rare metals, such as tantalum and niobium, merit consideration.

Jan 1, 1983

By Frederick J. McGarry, Fred Moavenzadeh

An experimental investigation of the thermal and mechanical responses of rock materials to laser radiation is described. Specifically, the following three topics have been studied in detail: 1. Temperature measurements on thin discs subjected to laser radiation. 2. Strain measurements on thin discs subjected to laser radiation. 3. Observation and evaluation of cracking and spalling phenomena in constrained and unconstrained thin discs respectively, subjected to laser radiation. In conjunction with the experimental work done, use was made of a heat flow analysis and a stress analysis program developed for this purpose. It was possible to theoretically predict the thermal and mechanical responses of a rock specimen to laser radiation and then compare them with experimental observations. Good correlations were obtained.

Jan 1, 1971

By Samuel Gibson Frantz, G. W. Jarman

The purpose of this paper is to relate briefly the development of magnetic separation and its extension from the separation of iron into its present use in the nonmetallic field, to suggest possible future extensions of its field of usefulness and its possible cooperation with other separating methods. The engineering design of separating machines, and statistics as to the number of machines in operation, types, their location and production are outside the scope of this paper. Specific data will be given, however, on certain selected applications. A large part of human endeavor consists in separating one thing from another; the good from the bad, the desired from the undesired. In fact, a philosopher might plausibly claim that separating things into categories and choosing between them is the object of thought itself. In dealing with matter, separation is nowhere more inherently necessary to attain our objects than in mining and metallurgy. Both our desire and our ability to make separations are results of the physical differences between things. Gross separations such as removing ore from worthless rock or coal from slate are usually made visually and depend upon form and color, which are physical properties. When the desired and the undesired things are intimately mixed, however, it becomes impractical to select visually even if the individual particles are readily recognizable to the eye, and some automatic way of making the particles separate themselves on the basis of their own inherent differences in physical properties must be resorted to. Some of the physical properties which have been used as a basis of separation are: color, shape, hardness, size, density, elasticity, surface propertics (surface tension in contact with liquids, etc.), electrical conductivity, dielectric constant, and magnetic susceptibility. Differences in these properties are used in the following methods of separation: color sorting, sifting, settlement in air and in liquids, float-sink methods, flotation, electrostatic and magnetic separation.

Jan 1, 1932

By R. W. Baldwin

As used in geophysical exploration, the term overvoltage applies to secondary voltages set up by a current into the earth which decay when the current is interrupted. These secondary effects may be measured by pick-up electrodes. The term induced polarization has often been employed to describe this same phenomenon. In its own operations Newmont Exploration Ltd. commonly uses the word pulse. The basis of this method in prospecting is that metallic particles, sulfides in particular, give a high response, whereas barren rock, with certain exceptions, gives a low response. Overvoltage has been tried in searching for many types of mineral occurrence but has been most successful in outlining the widespread disseminated mineralization associated with porphyry coppers. History:' Newmont Mining Corp. has been interested in overvoltage since 1946, when Radio Frequency Laboratories of Boonton, N. J.. drew the company's attention to phenomena observed in the laboratory. At the instigation of A. A. Brant further model studies were undertaken, and the first tests were performed in 1947. Tests at San Manuel, Ariz., in 1948 were very encouraging, clearly demonstrating that the method could be used to distinguish scattered sulfides at depth. H. 0. Seigel followed up the San Manuel work with a study to determine the phenomena involved.'

Jan 1, 1960

By C. S. Anderson

GEORGIA, since 1829, has produced nearly $18,000,000 from her gold mines, but in late years the output has dwindled to insignificance. In view of present universal efforts to increase gold production, it seems pertinent to record some recent observations in that field, briefly review its past and weigh probabilities of reviving gold mining there. Little in this paper can be claimed as new or original, and it does not present results of a detailed or profound investigation of the whole region. The Allatoona gold mine was reopened in January, 1932, and explored at greater depth during the period from January to June of that year. A number of other abandoned mines were visited, but since the workings, in common with most such mines in Georgia, were flooded or caved, underground conditions could not be examined. For a wider knowl-edge of the subject, a search was made through available pertinent literature and statistics, a bibliography of which is appended hereto. To all the sources obligations are gratefully acknowledged.

Jan 1, 1933

By Francisco Cadena

The construction of Norris Dam, built by the Tennessee Valley Authority on the Clinch River, a tributary of the Tennessee River, involved the production of coarse and fine aggregate for approximately 1,000,000 cu. yd. of concrete. A hammer-mill plant for the manufacture of sand from quarried rock was indicated as the most economical method of providing this material. The abrasive character of the feed as compared to the average hammer-mill feed made it necessary to control operations rather closely, and this resulted in the accumulation of many data hearing on production and maintenance. This paper will deal only with three specific sets of data, accompanied by such general information as may be necessary to explain the conditions under which they were obtained and followed by discussions on the relation of silica content to hammer wear, comparative costs of slugger and stirrup hammers, and comparative costs of tool-steel and manganese-steel grate bars. Coarse Aggregate Aggregate for the concrete poured at Norris Dam came from a dolomite quarry within 2000 ft. of the west abutment of the dam. Geologically this rock is known as a Knox dolomite. A typical chemical analysis is given in Table 1. Table 1.—Typical Chemical Analysis Per Cent H2O, 110° F............................................. 0.02 lgnition loss.............................................. 43.56 MgO.................................................... 19.19 CaO ................................................... 29.07 Fe²O³.................................................... 0.39 Al2O³ .................................................. 1.94 SiO2..................................................... 5.75 SO2...................................................... Tr. Rock was carried by 12-yd, dump trucks to a 42-in. gyratory crusher set at 6 1/2in. The product of the primary crusher was taken by a belt conveyor to a double.-deck vibrating screen followed by a 5 1/2-ft. cone

Jan 1, 1938

By C. R. Van Hise

[Concluding Contribution of Prof. Van Hise to the Discussion of his Paper, and Others on the Same General Subject, presented at the Washington Meeting, February, 1900 (see Ram., xxx., 27, 177, 323, 424, 578) ; also of the contributions of Vogt, De Launay, Beck, Lindgren, Kemp, Rickard, Bain, Keyes, Collins and Adams, presented at the Richmond Meeting, February, 1901, and to be printed in the present volume.] In June, 1900, shortly after my paper was published in the Fransactions, I made a briefer statement* before the Western Society of Engineers covering the same ground, which, in certain respects, is somewhat of an improvement. For instance, instead of using the terms descending and ascending &th reference to the waters resulting in the two concentrations, my modified statement is as follows: " The first concentration of many ore-deposits is the work of a relatively deep water-circulation, while the reconcentration is the result of reactions upon an earlier concentration through the agency of a relatively shallow water-circulation. Commonly the deep water-circulation is lacking in free oxygen, and contains reducing agents, and the shallow water contains free oxygen. The deep water is therefore a reducing, and the shallow water an oxidizing agent."† Of the papers upon ore-deposits which, in vol. xxx. of the Fransactions, follow my own, or which were presented at the Richmond meeting, a considerable number are wholly con-

Jan 1, 1902

By John M. Dealy, Robert D. Pehlke

Values for interaction parameters in nonferrous systems, as calculated from published data, are tabulated and discussed. The influence of temperature on the parameter is derived and compared with the results of the literature study. Wagner's relationship between the interaction parameter and the self interaction coefficients is compared with the tabulated data. A problem which has been of considerable interest in the field of metallurgy is the prediction of the effect of one alloying element present in dilute concentration on the thermodynamic properties of another dilute alloying element. Ultimately, the prediction may be accomplished entirely from statistical mechanical considerations. At the present, however, the problem remains unsolved since liquid solution models which are simple enough for analytical treatment are inadequate for such purposes. Thus, we desire some means of organizing the information on dilute systems which will serve as a guide for further study on interactions in dilute alloys, and also provide a basis for the utilization of thermodynamic data in the engineering design of alloys.

Jan 1, 1963

By C. H. Benedict, H. C. Kenny

A 2000-ton ammonia leaching plant has been operated by the Calumet & Hecla Mining Co., at Lake Linden, Mich., continuousl~ since February, 1917, except from April, 1921, to April, 1922, during the period of depression following the European war. A description of this plant has been published elsewhere.1 The present article describes the operation of the plant since 1917, together with the changes in the process that have been found to be advisable. In spite of the fact that this plant and that of the Kennecott Copper Co. are the only ones operating on a large scale, much experimental work is being done on ammonia leaching, as applied to oxidized ores, and it is to aid these and other investigators that this detailed account is given. For the benefit of those unfamiliar with the original article, the following short abstract is given, as an introduction to a more detailed account of the process and the reasons for present practice. Rêsumê of Previous Article Leaching on a commercial scale began in July, 1916, and by Februsry, 1917, the plant of 2000 tons capacity was in commission. The ore treated is a conglomerate containing native copper and no sulfides or oxidized copper minerals. Before leaching, the ore is crushed by steam stamps and Hardinge pebble mills to pass a 28-mesh screen. Free copper is removed, by gravity concentration, on Woodbury jigs and Wilfley tables, and colloidal slime for oil flotation is removed by quadruplex Dorr classifiers. The leaching sand remaining contains about 2 per cent. + 28-mesh material and 15 per cent. — 200-mesh and carries from 8 to 14 lb. of copper per ton, depending on the grade of ore worked. The solvent employed in leaching is a water solution of ammonium carbonate,

Jan 1, 1924

By Charles A. Ashburner

The Bradford Oil District lies in the northern part of McKean County, Pa., and the southern part of Cattaraugus County, N. Y. Although petroleum was first found in the producing sand in 1871, it was not until the early part of the year 1875 that a productive horizon was acknowledged to exist, even by those most largely interested in the production of the crude oil. It has been reported to me that the first well drilled in the valley of the Tuneangewant Creek (commonly called Tuna Creek) was drilled by F. E. Dean and brothers in 1865. This well was located on the Shepherd farm, near the present site of Custer City. One hundred and sixty feet of drive pipe was used, and the hole was drilled to the depth of 900 feet. The producing sand at Custer City is found about 1130 feet below the level of the railroad track. The Shepherd farm well was therefore abandoned over 200 feet above the top of the oil sand. The next well was drilled by the Dean brothers on the Clark farm at Tarport. Drilling was stopped at a depth of 605 feet, or over 400 feet above the top of the oil sand. In the year 1862 the old Bradford well, since known as the Barnsdall well, was drilled to a depth of 200 feet with a spring pole, and then abandoned. In the spring of 1866 the citizens of the village of Bradford concluded to club together and sink the Barnsdall well deeper. It was drilled to a total depth of 875 feet, or to within 150 feet of the Bradford producing sand. All of these wells were drilled with the expectation of finding the Venango County oil, and at

Jan 1, 1879

By Chas. A. Ashburner

THE Bradford Oil District lies in the northern part of McKean County, Pa., and the southern part of Cattaraugus County, N. Y. Although petroleum was first found in the producing sand in 1871, it was not until the early part of the year 1875 that a productive horizon was acknowledged to exist, even by those most largely interested in the production of the crude oil. It has been reported to me that the first well drilled in the valley of the Tuneangewant Creek (commonly called Tuna Creek) was drilled by F. E. Dean and brothers in 1865. This well was located on the Shepherd farm, near the present site of Custer City. One hundred and sixty feet of drive pipe was used, and the hole was drilled to the depth of 900 feet. The producing sand at Custer City is found about 1130 feet below the level of the railroad track. The Shepherd farm well was therefore abandoned over 200 feet above the top of the oil sand. The next well was drilled by the Dean brothers on the Clark farm at Tarport. Drilling was stopped at a depth of 605 feet, or over 400 feet above the top of the oil sand. In the year 1862 the old Bradford well, since known as the Barnsdall well, was drilled to a depth of 200 feet with a spring pole, and then abandoned. In the spring of 1866 the citizens of the village of Bradford concluded to club together and sink the Barnsdall well deeper. It was drilled to a total depth of 875 feet, or to within 150 feet of the Bradford producing sand. All of these wells were drilled with the expectation of finding the Venango County oil, and at

Jan 1, 1879

By Francisco Cadena

The construction of Norris Dam, built by the Tennessee Valley Authority on the Clinch River, a tributary of the Tennessee River, involved the production of coarse and fine aggregate for approximately 1,000,000 cu. yd. of concrete. A hammer-mill plant for the manufacture of sand from quarried rock was indicated as the most economical method of providing this material. The abrasive character of the feed as compared to the average hammer-mill feed made it necessary to control operations rather closely, and this resulted in the accumulation of many data hearing on production and maintenance. This paper will deal only with three specific sets of data, accompanied by such general information as may be necessary to explain the conditions under which they were obtained and followed by discussions on the relation of silica content to hammer wear, comparative costs of slugger and stirrup hammers, and comparative costs of tool-steel and manganese-steel grate bars. Coarse Aggregate Aggregate for the concrete poured at Norris Dam came from a dolomite quarry within 2000 ft. of the west abutment of the dam. Geologically this rock is known as a Knox dolomite. A typical chemical analysis is given in Table 1. Table 1.—Typical Chemical Analysis Per Cent H2O, 110° F............................................. 0.02 lgnition loss.............................................. 43.56 MgO.................................................... 19.19 CaO ................................................... 29.07 Fe²O³.................................................... 0.39 Al2O³ .................................................. 1.94 SiO2..................................................... 5.75 SO2...................................................... Tr. Rock was carried by 12-yd, dump trucks to a 42-in. gyratory crusher set at 6 1/2in. The product of the primary crusher was taken by a belt conveyor to a double.-deck vibrating screen followed by a 5 1/2-ft. cone

Jan 1, 1938

By H. W. Morse

MANY of our largest copper deposits contain both sulfide and oxidized copper minerals. The large porphyry mines, with a total copper content of from 1.3 to 2.0 per cent., send to their mills ore with an oxide content of from 0.2 to 0.4 per cent. While the recoveries of the sulfide minerals are considered satisfactory, using modern flotation practice, the recovery of the oxi- dized portion of the copper is small; better recoveries of oxidized copper were made before flotation methods were adopted. Beside the ores containing copper mainly as sulfide, with a small amount of oxidized copper,, many of the large porphyry mines have oxide orebodies, in which the propor-tion of non-sulfide minerals is so high that 2 present methods of treatment are ineffi-cient. In some of the well-known ore-bodies in the Miami-Inspiration district the copper occurs about equally in sulfide and oxidized forms; and the mixing of minerals is complete throughout the ore-body. There is no possibility of mining the sulfides and the oxides selectively. At the New Cornelia mine, however, the oxide, and sulfide ores are sharply separated, per-haps by an ancient water level, so that the oxide ore may be mined and treated in a plant built for that purpose, and the under-lying sulfide ore may be left for treatment in another plant. If copper is to be made from an ore having a total content of 1.5 per cent., it must be concentrated or removed from the ore by some. hydrometallurgical method. Flotation is generally successful for the sulfide minerals and flotation after filming with sulfide seems to work in many cases on the pure carbonate minerals. Callow has given an extensive report on the results of "sulfidizing" flotation on the ores of the. Magma mine.1 Where such ?a 'method can be applied, it ?may be, the best

Jan 9, 1922

By R. V. Norris

IT was stated in a former paper1 that an intensive study of anthracite costs was being made by the engineers of the United States Fuel Administration. The results of this-study are now available and are offered as a supplement to the former paper. Anthracite costs as reported, for the 6-months period, December, 1917, to May, 1918, inclusive, as compiled by the Federal Trade Commission, were used as a base, and charts similar to those described in the-former paper were made for the standard white ash anthracite and for red ash and Lykens valley coals. ADJUSTMENTS The adjustments of cost from a reported to a price-fixing basis, as described for the bituminous methods, were applied but showed only minor adjustments as necessary. The great spread in anthracite prices on the varying sizes, which for the 6-mo. period under review ranged in average from $5.244 for nut to $2.074 for barley coal, makes the question of the percentage of sizes produced at the different collieries a vital one. The realization with the same prices for each size must be within very wide limits, when it is considered that the percentage of prepared coal reported from different collieries varied from over 80 per cent. to below 30 per. cent. for fresh-mined coal. Hence, as the spread in prices for the various sizes must be predicated on some percentage, it is essential to find some method of adjustment to allow for this variation. The logical method of adjustment is to calculate actual costs to costs as of the standard percentage of sizes, so that the margin between the adjusted costs and the average realization shall be the actual margin for each colliery between its actual costs and actual realization clue to its particular percentage of sizes. As a base for realization the actual percentage of sizes for fresh-mined coal for the 6-mo. period was adopted. This percentage is given in Table 1.

Jan 2, 1919

By J. M. Callow

HISTORICAL SKETCH THE selective action of oils for lustrous minerals was first disclosed by Haynes in 1860. In 1885, Miss Carrie Everson elaborated this idea and also disclosed the fact that acid increased the. so-called selective action. Her patent called for oils, either animal, vegetable or mineral, also for an acid or salt. The process was tried out on a practical scale in Baker City and Leadville, in 1889, and failed: first, because,, as has since been shown, of the unsuitability of the ore to flotation; and second, because the invention was too far in advance of the times. Then followed the Elmore brothers, first with their bulk oil processes and later with their vacuum method. The basic principles of oil flotation were undoubtedly covered by the above inventors, the work done since their time being merely a building up on ground work laid by them. Different kinds of oil, different quantities of oil, and all the varying degrees of agitation, were all exemplified and practiced by them in one phase or another, and the developments that have since been made are but elaborations of the fundamental principles laid down by Haynes, Everson, and the Elmore brothers. In 1902, the Potter-Delprat process was developed in Australia. In this process no oil was used, the mineral being raised by the generation of gas, brought about by the introduction of acid into the pulp. The mineral particles appeared on the surface of the separatory vessel, in the form of a scum or froth, buoyed up-by minute gas bubbles attached to them. This no doubt first gave the suggestion of gaseous flotation. In 1902, also, Fromont, an Italian, was granted a patent in which. he combined violent agitation with oil and gaseous flotation, the gas being generated within the pulp, in much the same way as in the Potter-Delprat process.

Jan 12, 1915

INTRODUCTION Porphyry copper deposits have been reported from the Caribbean area by Pease (1966), Cox, et al. (1973), Guild (1974), Kesler, et al. (1975), and others. This chapter summarizes the most widely known characteristics of those deposits. Only one deposit that conceivably can be classed as a porphyry copper occurrence is in production (Pueblo Viejo, Dominican Republic), but others are known whose tonnage and grade are of economic interest. Deposits in this province may be classified as copper-gold or copper-molybdenum types (Kesler, 1972), but deposits associated with quartz-rich plutons that have high Na2O:K2O and high gold:copper but low molybdenum: copper ratios dominate. Porphyry copper occurrences are reported in the literature from Puerto Rico, Haiti, the Dominican Republic, Jamaica, and Cuba. Only the porphyry copper deposits from Puerto Rico are extensively described in the literature; consequently the Caribbean porphyry copper province in general is not as well documented as the southern Cordilleran orogen. Because past published technical descriptions are incomplete, some data presented here are new to the literature. The Caribbean includes the island arcs between North and South America. Porphyry copper occurrences are known from the Greater Antilles, the generally east-west trending group of islands that lies south of North America. Fig. 48, therefore, only covers the Greater Antilles portion of the Caribbean. Porphyry copper deposits in this area are not described by the Lowell and Guilbert (1970) model in details of metallization (general paucity of molybdenum), alteration (scarcity of orthoclase), or petrography (preponderance of quartz diorite). Therefore, this model should be modified to include deposits associated with quartz-bearing plutons such as those found in the Caribbean. In the Meme deposit on Haiti ore occurs in skarn adjacent to the quartz diorite phase of a composite quartz monzonite-granodio-rite-quartz diorite pluton (Kesler, 1968). This deposit, with a K-Ar 66 m.y. date, is not included in Fig. 48 as a porphyry copper deposit because metallization is restricted largely to the intruded rocks. Although the intrusive rocks at the Meme deposit may contain sulfide near skarn contacts they are otherwise essentially unaltered. Porphyry molybdenum deposits as defined by Clarke (1972) have not been reported in the Caribbean area.

Jan 1, 1978

By Hsun Hu

The formation of annealing textures in high-purity silver, from the various rolling textures obtanled in the course of texture transition, was studied. It was found that from a brass-type rolling texture the recrystallization texture is mainly (120) [211] type, which is quite different from the recrystallization texture of brass. From a predominantly copper-type rolling texture, the reclystallization texture is mainly (100) [001]. The recrystallization texture of silver- varies also with the degree of purity. In each case, however, the reorientation can be expressed as [Ill] rotations of 30° to 40°, which is consistent with the oriented growth theory of the formation of annealing textures. ThE recrystallization textures of rolled silver were studied long ago by Glocker and co-workers (1924-27) and were reported to be (113) [iil] upon annealing at low temperatures.1 Since that time, no further study of the recrystallization textures of silver, particularly with the modern techniques of quantitative texture determinations, has been reported in the literature. In a previous study2y3 it was found that the rolling texture of high-purity silver (99.999 +pct pure) is changed gradually from the common silver- or brass-type to the copper-type by raising the temperature of rolling from 0" to 200°C. The formation of annealing textures from the various rolling textures in the same material is, therefore, of considerable interest. The present paper constitutes the results of such a study. MATERIAL AND METHOD Specimens were taken from the same strips of high-purity silver* that were used previously for

Jan 1, 1962