STATE OF CALIFORNIA EARL WARREN. Governor DEPARTMENT OF NATURAL RESOURCES WARREN T. HANNUM, Director DIVISION OF MINES FERRY BUILDING. SAN FRANCISCO 11 OLAF P. JENKINS. Chief 5AN FRANCISCO SPECIAL REPORT 7-A JUNE 1951 GEM- AND LITHIUM-BEARING PEGMATITES OF THE PALA DISTRICT, SAN DIEGO COUNTY, CALIFORNIA By RICHARD H. JAHNS and LAUREN A. WRIGHT Prepared in Cooperation With the United States Geological Survey Digitized by the Internet Archive in 2012 with funding from University of California, Davis Libraries http://archive.org/details/gemlithiumbearin07jahn GEM- AND LITHIUM-BEARING PEGMATITES OF THE PALA DISTRICT, SAN DIEGO COUNTY, CALIFORNIA! By Richard H. Jahns* and Lauren A. Wright** OUTLINE OF REPORT Page ABSTRACT 4 INTRODUCTION 4 Scope of investigations 5 Acknowledgments 5 PHYSICAL FEATURES 6 HISTORICAL SKETCH 6 GEOLOGY 8 General features 8 Metamorphic rocks 9 Igneous rocks 9 Gabbroic rocks 9 Tonalite 11 Graudiorite 11 Dike rocks 12 Other rocks 12 Structure 13 PEGMATITES 15 Distribution and occurrence 15 General structural features 16 Form, size, and attitude 16 Relations to wallrock structure 16 Principal types of pegmatite 18 Graphic granite 18 Other very coarse-grained pegmatite 19 Pocket pegmatite 21 Fine-grained granitoid rocks 21 Other types 22 Internal structure 24 General features 24 Zones 25 Fracture fillings 26 Other units 27 Composite dikes 29 Mineralogy 30 General features 30 Principal minerals 31 Other minerals 49 Paragenetic sequence of minerals 42 Origin of the pegmatites 44 ECONOMIC FEATURES OF THE PEGMATITE MINERALS 45 Lithium minerals 45 Lepidolite 45 Spodumene and amblygonite 46 Feldspars 46 Gem minerals 47 Tourmaline 47 Spodumene 48 Bervl 49 Quartz 49 Other minerals 49 MINING 49 Prospecting and mining methods 49 Production 50 Future possibilities 52 DESCRIPTIONS OF SELECTED MINES 55 Tourmaline King (Wilke, Schuyler) mine 55 Tourmaline Queen mine 56 Gem Star (Loughbaugh) mine 57 Stewart mine 59 Mission mine 61 Pala Chief mine 62 Katerina (Ashley, Catherina, Katrina) mine 68 El Molino mine 70 INDEX 71 t Published by permission of the Director, Geological Survey, TJ. S. Department of the Interior. Manuscript submitted for publication August 1950. * Professor of geology, California Institute of Technology, Pasa- dena, California, and geologist, U. S. Geological Survey. ** Associate mining geologist, California Division of Mines. Plate 1. 2. ILLUSTRATIONS Geologic map and section of the central and southern parts of the Pala district In pocket Map of northern part of the Pala district, show- ing distribution of pegmatite dikes and principal mines and prospects _ In pocket Geologic map of surface workings, Tourmaline Queen mine In ,„„.,.,,, Cross-section through Stewart mine In pocket Geologic map of surface workings and geologic section, Pala Chief mine i„ pocket 48-49 48-49 10. 11. 12. 13. Fig. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. Color-zoned crystals of gem tourmaline, A, Kunzite crystal. B, Crystal fragments of gem spodumene A, Tourmaline, cut stones. B, Tourmaline, bi-col- ored cut stones Spodumene, cut-stones A, Photo of fine-grained lepidolite. B, Photo of very fine-grained lepidolite .4, Photo of crystal of lithiophilite. B, Photo showing wall zone and line rock. C, Photo show- ing wall zone and very coarse-grained pegmatite .4, Photo of matrix specimen from a gem-hearing pocket. B, Photo of line rock. C, Photo of coarse- grained graphic granite .4, Photo of color-zoned tourmaline crystals. B, Photo of crystal of morganite. C, Photo of short, prismatic crystals of aquamarine 48-49 4S-4I) 48-49 48-49 48-49 48-49 Index map showing locations of principal pegmatite areas 7 Aerial view of the Pala district 10 Aerial view of northern part of Pala district 17 Aerial view of Little Chief and Chief Mountains 20 Aerial view of Hiriart Mountain 23 Section through west tunnel, North Star mine 24 Sketch of pegmatite-gabbro relations, Pala View mine__ 25 Photo of large crystals of perthite, Katerina mine 26 Photo of large graphic-granite mass 28 Diagrammatic sketch showing typical relation between wall zone, and core segment 29 Photo of euhedral crystals of perthite in massive quartz. El Molino mine 30 Photo of coarse perthite and quartz 31 Coarse-grained quartz-spodumene pegmatite, Pala Chief mine 32 Photo of matrix specimen from richest gem-bearing part of dike, Pala Chief mine 33 Photo of fine-grained granitoid rocks 34 Photo of fine-grained granitoid rocks 35 Photo of sharply layered line rock 35 Photo of line rock, adjacent to very coarse-grained ag- gregate of perthite and graphic granite 36 Idealized sections of simply zoned pegmatite dikes in Pala district :!S Idealized sections of pegmatite dikes in the Pala district 39 Photo of quartz-spodumene pegmatite in wall and back of large room. Stewart mine 40 Photo of graphic granite underlain by very coarse- grained perthite-quartz pegmatite. El Molino mine 44 Geologic sketch map of main cut. Xaylor mine .".3 Photo of fracture-controlled replacement masses. White Cloud mine •'* Idealized section of pegmatite dikes in the Pala district ."><; (3) Special Report 7-A ILLUSTRATIONS— Continued Page 26. Photo of composite pegmatite mass, Wist slope of Hiriart Mountain 58 27. Photo of thin prisms of schorl, Gem Star mine _ ."">!) 28. Photo of schorl in gem-bearing central part of Tourma- line King dike 59 2!>. Photo of fragments of gem-quality kunzite, Katerina mine 60 30. Geologic map of surface workings, Tourmaline King mine 0.'? 31. Geologic map and plan of ("anyon workings, Gem Star mine 64 32. Geologic map of Mission mine 6."> 33. Plan of main workings, Katerina mine 66 34. Section through adit, 101 Molino mine 67 35. Geologic map of main workings, El Molino mine 69 ABSTRACT The Pala pegmatite district, in northwestern San Diego County, California, has been a widely known source of gem and lithium minerals. Formal mining operations began in the eighteen- seventies; but the most active period was from 1900 to 1922. By 1947 the district's total recorded mineral output was valued at about three-quarters of a million dollars. This output includes 23,480 short tons of lepidolite, 2,!I80 pounds of tourmaline, and 1,325 pounds of gem spodumene. Small amounts of amblygonite, beryl, feldspar, and quartz also have been mined. Deposits of lepidolite and gem minerals have been extensively worked in six mines, and many addi- tional deposits have been prospected or mined on a small scale. The dominant rocks of the district form parts of the southern California batholith, of probable Cretaceous age. Some older rocks, chiefly schists and quartzites, occur as screens, septa, and pendants. Both these and the igneous rocks are covered in places by surficial deposits of Quaternary age. At least 400 pegmatite dikes are exposed in an area of about 13 square miles. Most of them trend northward and dip gently to moderately westward, and many are marked by broad bends in strike and dip. They are remarkably persistent, and range from small stringers to large dikes with bulges nearly 100 feet thick. In several places they occur as swarms of closely spaced, subparallel dikes. In some swarms these dikes branch and converge along their strike, and in places they form thick, composite bodies in which each member dike commonly retains its identity. The pegmatites occur mainly in gabbroic rocks, and appear to have been emplaced along a well-developed set of fractures. These fractures are independent of the primary structural features of the enclosing rocks, and transect contacts between major crystalline rock units ; they may well have been subhorizontal at the time of pegmatite emplacement. Some of the pegmatites are essentially homogeneous in min- eralogy and texture, but most are composed of units that plainly differ from one another in lithology. Graphic granite is the chief constituent of the outermost units, or border zones, which generally are thin, discontinuous, and fine grained. It also composes most of the adjacent, coarse-grained wall zones, which ordinarily are the thickest and most persistent of the pegmatite units. Graphic granite is particularly common in the hanging-wall parts of the dikes, but constitutes nearly the full thickness of many dikes. It appears as relict masses in the fine-grained lower parts of some dikes, but also occurs as pods and thin stringers in such fine-grained pegmatite. Discoidal masses of coarse-grained pegmatite form the inner- most zones, or cores, of many dikes. Such masses are generally thin and elongate, but more pod-like cores are present in the thick bulges of a few dikes. Some cores are composed of quartz, perthite, or an aggregate of these minerals, and others consist of quartz and giant crystals of spodumene. Spodumene of gem quality occurs wholly within the cores, and represents the relatively small amount of this mineral that has escaped all hydrothermal alteration. Lithiophilite and tripli.\ lite occur in or adjacent to some quartz-spodumene cores, and commonly have been altered to manganese- and iron-phosphate minerals. Some of the cores are separated from nearby wall zones by one or more intermediate /.ones, which form discontinuous or complete envelopes. These units are present only in the largest dikes or in dikes with thick bulges, and generally are rich in coarse-grained perthite. Fracture-filling units are widespread, and consist chiefly of quartz, albite, biotite, fine-grained muscovite, or combinations of these minerals. Some transect, wall zones, but merge with inner zones. Others lie wholly within a single zone, and still others cut across entire pegmatite bodies. There are all gradations between simple open-space fillings and replacement bodies developed along fractures. Fracture-controlled replacement bodies are superimposed upon the zonal pattern of nearly all of the pegmatites. They are composed mainly of albite, quartz, and muscovite, and, less commonly, of lepidolite and tourmaline. Such bodies are most easily recognized where they transect wall-zone graphic granite. Similar mineral aggregates occur in the central parts of many dikes, where they generally corrode the surrounding pegmatite zone. These centrally disposed units, which commonly contain residual masses of earlier minerals, include much of the district's "pocket pegmatite," a rock type composed mainly of fine- to coarse-grained quartz, albite, ortho- clase, microeline, muscovite, lepidolite, and tourmaline. Most of the minerals are euhedral. All the gem tourmaline and beryl, as well as the commercial concentrations of lepidolite, occur in so-called "pocket pegmatite." Such rocks actually contain very little open space, although some cavities are partly or completely filled with a clay through which gem crystals are scattered. Pocket pegmatite occurs in cores and imme- diately adjacent zones, chiefly along the footwalls or in the footwall parts of the cores. Fine-grained granitoid rocks, composed chiefly of quartz and albite, are common in the footwall parts of most dikes, and also occur locally in other parts of many dikes. Some varieties are essen- tially uniform in texture and structure. Others, known collectively as "line rock," are strikingly marked by alternating thin layers of garnet-rich and garnet-poor pegmatite, or of schorl-rich and schorl- poor pegmatite. Layering in some of these rocks also is caused by distinct variations in texture. The Pala dikes are believed to have been formed by crystalliza- tion of pegmatite liquid that was injected along fractures during the final stages of consolidation of the southern California batholith. The pegmatite zones appear to have developed from the walls of the dikes inward, probably by fractional crystallization and incomplete reaction wth residual liquid. Many, if not all, of the relations in the central parts of the most complex pegmatites seem best explainable in terms of progressive accumulation and late-stage crystallization of mineralizing fluids, with accompanying deuteric replacement of earlier-formed minerals. In order to develop a few of the larger replacement bodies, material may have been derived from other parts of the dikes, or possibly from sources farther removed. The fine- grained pegmatite units cut across the zonal structure of some dikes, and appear to have been formed in part at the expense of graphic granite. The pocket pegmatite also is at least in part of replacement origin, and is plainly younger than some of the fine-grained pegma- tite. INTRODUCTION The lithium-bearing pegmatites x of the Pala district, southern California, have aroused widespread and con- tinuing interest since their discovery about half a century ago. They have been best known to prospectors, miners, and mineral collectors as sources of gem crystals, lithium minerals, and mineral specimens of remarkable appear- ance and variety. Although little formal mining has been done in the district feince 1922, the deposits have been visited by thousands of collectors, who have obtained from the area a large tonnage of mineral specimens. The dis- trict also has held an unusual attraction for geologists, who have advanced different theories to explain the development of pegmatites so complex in mineralogy and internal structure. It was largely on the basis of studies made in the Pala area, for example, that Waldemar T. Schaller first proposed the hydrothermal origin of much of the material in lithium-bearing pegmatites. 2 1 The term "pegmatite," as herein applied, is defined as an igne- ous rock, generally irregular in texture, that is at least in part very coarse-grained. 2 Schaller, W. T., The genesis of lithium pegmatites: Am. Jour. Sci. 5th ser., vol. 10, pp. 269-279, 1925. Pegmatites op the Pala District Brief descriptions of the mines and minerals appeared in many journals including Mining Science, Mining and Scientific Press, and Mining World. The first systematic account of the mines themselves was published in 1905 by G. F. Kunz, whose field investigations in the district dated back to 1890. 3 The first comprehensive report on the geol- ogy of the pegmatites and the surrounding rocks was published during the same year by Waring. 4 Observations on the geology of the mines were recorded by Merrill in 1914. 5 W. T. Schaller visited the district in 1903, and sub- sequently studied several of the minerals in the labora- tories of the University of California. In 1904 he began a series of investigations for the U. S. Geological Survey that was to extend over a period of many years. His was the most systematic study of the district, and after his field work in 1924 he prepared three brief but important summaries. 6 Although he did much laboratory work, no general report was published. A comprehensive report on the district, with a map of the areal geology and many sketch maps and sections of individual pegmatites and mines, was prepared in manuscript form but never pub- lished. M. G. Donnelly studied the pegmatites and made a reconnaissance geologic map of the district during the period 1933-35. His reports 7 represent the most recent geologic summaries for the district. Recent field work by the U. S. Geological Survey in the southern California pegmatite region dates from 1943, when D. J. Fisher examined and appraised numerous deposits in Riverside and San Diego Counties as potential sources of beryllium and tantalum-columbium minerals, quartz crystals, and sheet muscovite. This wartime inves- tigation was necessarily very brief, aimed as it was at increasing the known domestic reserves of strategic peg- matite minerals. Following the cessation of hostilities in 1945, plans were made for a thorough reinvestigation of the Pala-Rincon-Mesa Grande pegmatite belt, with special emphasis upon detailed mapping and structural studies to supplement the earlier mineralogic work of Schaller. This project, of which the study of the Pala district is a part, was started in July 1946, and has been carried on under the joint auspices of the Geological Survey and the California State Division of Mines. The field investiga- tions were completed in April 1950. Scope of Investigations The study of the pegmatites and other rocks of the Pala district was made intermittently during the period July 1946-March 1948. A total of 29 weeks was devoted to field work by Jahns, and about 10 weeks to field work 3 Kunz, G. F., Gems, jewelers' materials, and ornamental stones of California : Calif. Min. Bur. Bull. 37, 155 pp., 1905. * Waring, G. A., The pegmatyte veins of Pala, San Diego County : Am. Geologist, vol. 35, pp. 356-369, 1905. 5 Merrill, F. J. H., Mines and mineral resources of San Diego County, California: California Min. Bur., Rept. XIV, pp. 691-700, 706-708, 1914. 6 Schaller, W. T., op. cit., 1925. Schaller, W. T., Mineral replacements in pegmatites : Am. Miner- alogist, vol. 12, pp. 59-63, 1927. Schaller, W. T., Pegmatites, in ore deposits of the western states, pp. 144-151, Am. Inst. Min. Met. Ore, New York, 1933. 7 Donnelly. M. G., The lithia pegmatites of Pala and Mesa Grande, San Diego County, California: California Inst. Tech., unpubl. Ph.D. Thesis, 1935. Donnelly, M. G., Notes on the lithium pegmatites of Pala, Cali- fornia : Pacific Mineralogist, vol. 3, pp. 8-12, 1936. during the fall and winter seasons of 11)46-47 by Wright. Wright was not able to participate in the laboratory work and preparation of this report, but has checked and ap- proved the manuscript. During the course of the field investigations, the dis- trict was mapped geologically, more than 350 pegmatite dikes were examined, one of them was mapped in detail for its entire exposed length of more than half a mile, and large parts of four other dikes were mapped. Detailed maps were made of the surface and underground work- ings of 16 mines, and more than 100 other mines and prospects were visited and studied. The mapping was done on several scales, ranging from 10 feet and 20 feet to the inch for most mines, through 50 feet and 100 feet to the inch for pegmatite dikes, to 660 feet to the inch for the entire district. Enlargements of aerial photographs furnished by the Agricultural Adjustment Administra- tion were used as bases for the geologic map of the district. In the studies of the pegmatites, emphasis was placed upon petrology and structure. Particular attention was given to the recognition and interpretation of distinc- tive rock units within each dike, and to such broader features as the relations between shape and attitude of the dikes and structural features in the adjacent country rock. Many of the broader features were made clearer by means of the areal geologic mapping. The field studies were supplemented by preliminary mineralogic investiga- tions in the laboratories of the California Institute of Technology, where 84 thin-sections and more than 500 samples of crushed pegmatite were examined under the microscope. Most of the microscopic studies were aimed at identification of minerals, especially feldspars, and only preliminary work on small-scale textures and struc- tures was undertaken. The tentative conclusions regard- ing paragenetic relations and the origin of the various pegmatite units are therefore based primarily upon de- tailed megascopic study. The present report is in part economic in scope with emphasis on those features of the pegmatites and country rocks that bear most significantly upon the occurrence of commercially desirable minerals. Detailed descriptive mineralogy, country-rock petrography, and discussions of pegmatite genesis, for example, have been held to a minimum, whereas structure and descriptive petrology are emphasized. Not all controversial questions are ana- lyzed in detail, but an attempt has been made, in present- ing interpretations, to indicate the degree of assurance justified by the data at hand. The eight mines which are described briefly include nearly all those from which substantial commercial pro- duction has been obtained, and were selected to provide a satisfactory coverage of the various types of pegma- tites exposed in the district. Acknowledgments The investigations upon which this report is based were started at the suggestion of Waldemar T. Schaller of the U. S. Geological Survey, and it is a real pleasure to acknowledge his continued interest and hearty coopera- tion in the project, lie generously supplied numerous old maps and mine descriptions, many of them prepared when the mines were in operation, and his willing counsel has been invaluable. Lincoln R. Page, Waldemar T. li Special Report 7-A Schaller, and Ward C. Smith of the U. S. Geological Sur- vey. Olaf P. Jenkins and L. A. Norman, Jr., of the Cali- fornia State Division of Mines, and Roy M. Kepner of the San Diego County Division of Natural Resources, visited the area and contributed many helpful ideas and suggestions. Numerous problems were discussed with John B. Ilanley of the IT. S. Geological Survey, who was working in the adjacent areas and who gave generously of his time in aiding the mapping of several deposits. Able field assistance was contributed from time to time by Laurence F. Gurney and Wayne E. Hall of the U. S. Geological Survey, and by Enver Altinli, Wakefield Dort, Jr., Don M. George, Jr., and Robert M. Greenwood of the California Institute of Technology. The mine and property owners in the district have been actively cooperative. Particular thanks for many personal kindnesses are due to Mr. and Mrs. R. D. Arm- strong, Mr. George Ashley, and Mr. and Mrs. Monta F. Moore, of Pala ; Mrs. Frank A. Salmons of La Jolla ; and Mr. Frederick M. Sickler of Bonsall. Completion of the report was facilitated by Joan T. Rounds, who drafted the maps and sections, and by Flor- ence Wiltse, who aided in the preparation of the manu- script. The colored drawings of gem crystals and cut stones reproduced in plates 13, 14, 16, 17, and 18 were the work of David P. Willoughby. The hand-tinted photo- graph of a kunzite crystal shown in plate 15 was donated by Waldemar T. Schaller. The aerial photographs shown in plates 25-28 were obtained by means of a special grant of funds from the California Institute of Technology. The manuscript was critically reviewed by Lincoln R. Page, John II. Eric, and Waldemar T. Schaller, who made nu- merous helpful suggestions. PHYSICAL FEATURES The Pala district is in northwestern San Diego County, about 45 miles north of San Diego and 80 miles southeast of Los Angeles. It lies 10 miles due east of Fallbrook and 17 miles due north of Escondido, and oc- cupies a part of the San Luis Rey River Valley about midway between the Henshaw Reservoir and the river mouth at Oceanside (fig. 1). Like most of the other peg- matite districts in southern California, the Pala district is in the Peninsular Range province, which consists mainly of a series of mountain masses extending from about the latitude of Los Angeles southeastward into Baja California. This province is characterized by crystal- line rocks, most of which are of igneous origin. Most of the pegmatites discussed in this report are exposed on the crests and along the sides of several small N mountain masses north and northeast of Pala, a mission village on the San Luis Rey River. The remainder of the district flanks the river valley on the south, and lies south- east of Pala. The main, or northern part of the district occupies an area of about 5 square miles. It lies along the southwestern base of the Agua Tibia-Palomar Mountain mass, and is about 5 miles beyond the southeastern end of the elongate Elsinore-Temecula-Pechanga Valley. Topo- graphically it is characterized by steep and locally very irregular slopes in sharp contrast to the broad, alluvial floor and associated fans of the adjacent river valley. The hills are circular to markedly elongate in plan, and show no uniform trend. They rise as much as 1500 feet above Pala, which itself is 410 feet above sea level, and the local relief in most parts of the district exceeds 800 feet. The principal eminences, listed in order from west to east, are Queen Mountain (1922 feet), Big Chief Mountain (1607 feet), Chief Mountain (1504 feet), Little Chief Mountain (1143 feet), Hiriart Mountain (1774 feet), Meadow Mountain (1927 feet), and Slice Mountain (1850 feet). The summit of the much larger Pala Mountain, in the southern part of the district, is 2026 feet above sea level. The major hills north and northeast of Pala are flanked by the alluviated canyons of such high-gradient streams as Pala Creek, Salmons Creek, McGee Creek, and Agua Tibia Creek, all of which drain southward and southwestward into the San Luis Rey River. To the north- east are the bold spurs and deep canyons of Agua Tibia Mountain. Pala is served by the paved highway that extends from Oceanside to Henshaw Reservoir. This road connects with U. S. Highway 395, the Los Angeles-San Diego "Inland Route", 8 miles west of Pala, and with State Highway 79 at the south end of Henshaw Reservoir. Pala can be reached also from the north via the 9-mile Pala Canyon route, a winding paved road that connects with U. S. Highway 395 south of Temecula. The mine areas north and northeast of Pala are served by dirt roads. Some of the roads are no longer maintained and a few are im- passable. Most of the mines can be reached by trail only. Most of the district lies within the boundaries of the Pala Indian Reservation and the Mission Indian Reserve. The fertile valley bottom soils in the vicinity of Pala are tilled by Indian families for corn, alfalfa, and other field crops, and the Agua Tibia fan farther east supports the growth of large citrus orchards. Although most irrigated farms use water from wells, water from the San Luis Rey River and Agua Tibia Creek is used in some places. Some crops are grown also on a few scattered ranches in the highland areas. Vegetation there supports small scale cattle grazing and beekeeping. The annual rainfall in the area is less than 20 inches, and there are few perennial streams. The Agua Tibia Mountain mass to the north, however, receives 25 to 40 inches of precipitation a year, and is the chief source of the ground water in the alluvial valleys near Pala. Where not under cultivation, these valleys support the growth of oak, cottonwood, and sycamore trees. In contrast, the hills on which deposits have been mined are covered with a heavy growth of chaparral interrupted only here and there by burned-over areas, and clusters of oak trees. On some north and east slopes the brush is so dense and tightly intergrown that it interferes seriously with the prospecting and geologic investigation of rock outcrops, which are abundant in most areas. HISTORICAL SKETCH Crystals of gem tourmaline were discovered in south- ern California by Henry Hamilton in June 1872. The occurrence, on the southeast slope of Thomas Mountain in the Coahuila Mountain district of Riverside County, com- prised a few prismatic crystals of pink and green color. Several nearby deposits, discovered shortly thereafter, yielded a small output that included some excellent speci- men and gem material. In 1898 commercial exploitation of the world-famous Himalaya pegmatite in the Mesa Grande Pegmatites op the Pala District Fig. 1. Index map showing locations of principal pegmatite areas and districts in southern California. district was begun, although as pointed out by Kunz, 8 this and other gem-bearing pegmatites in the area must have been known and worked by the local Indians for many years, as tourmaline crystals have been found in many Indian graves. The first specific mention of tourmaline in the Pala district dates from 1892, when C. R. Orcutt announced the occurrence of pink tourmaline and lepidolite in the Stewart dike. Specimens of the fine-grained mica with individual prismatic crystals and radiating crystal clus- ters of rubellite had been known and described nearly ten years previously, but no precise information as to their geologic occurrence or geographic location had been recorded. The deposit is said to have been discovered by an Indian deer hunter. It was first worked by Henry McGee, an old prospector who had incorrectly interpreted the rubellite as an ore of quicksilver ; 9 later it was briefly 8 Kunz, G. F., Gems, jewelers' materials, and ornamental stones of California: California Min. Bur. Bull. 37, pp. 23-24, 1905. 8 Kunz, G. F., op cit., p. 124, 1905. mined as a deposit of unusual marble by Don Tomas Alvarado, a local Spanish landowner. The economic potentialities of the pegmatite minerals were not recog- nized until the lepidolite in a specimen from a New York collection was identified by a German chemist who was familiar with lithia occurrences in Europe. Most of the first lepidolite obtained from the Stewart deposit was sold as specimen material, but some was shipped to Germany for testing as a source of lithium, caesium, and rubidium. Development of the Stewart mine as a source of lepidolite stimulated a search for lithium deposits elsewhere in the district, and this search resulted in several discoveries of both lepidolite and gem minerals. Coarse crystals of gem-quality rubellite and other varie- ties of tourmaline were found in the Tourmaline King, Tourmaline Queen, and Pala Chief pegmatites, as well as in the central and northern parts of the Stewart dike. A little gem beryl and large quantities of clear crystallized quartz also were encountered. 8 Special Report 7-A While doing assessment work during 1902 in the Katerina pegmatite, M. M. Sickler and his son, Frederick, penetrated a concentration of large quartz crystals in a matrix of unusual pinkish clay. Also in this clay were splinters and coarse, nodular to blade-like crystal frag- ments of a clear, colorless to straw-yellow and pale-lilac mineral that neither man could identify. Some of these pieces were similar to colorless fragments that had been picked up as float material on the nearby White Queen claim several years before. A series of similar discoveries was made on Chief Mountain, farther west, by Bernardo lliriart and Pedro Feiletch, two Basque prospectors, and by Frank A. Salmons, who was to become one of the lead- ing figures in the development of the district. Efforts to identify the mineral were unsuccessful until the Sicklers, in December, 1902, sent several specimens to Dr. G. F. Kunz, gem expert for Tiffany and Company in New York City, who recognized it as spodumene and announced its discovery. 10 About the same time, similar material fur- nished bv F. A. Salmons was described in greater detail by Schal'ler." During the mining of these and other deposits of gem spodumene, tourmaline, and lepidolite in the Pala area, fine transparent quartz crystals and colorless, blue, golden, and pink to peach-colored crystals of beryl were recovered. Prospecting for gems was carried on vigorously from 1908 to 1914, and more than 50 deposits were mined. This was the golden era of activity in the district. Produc- tion declined sharply after 1914, as a result of dwindling markets and reduced prices, and never again reached the earlier levels. In 1914 the Tourmaline King mine was sold, and although the new owners spent many thousands of dollars in exploring all promising parts of the pegmatite, few marketable gems were recovered. During the 20 's and 30 's little more than assessment work was done in the largest mines, and the others were idle. By 1940, the quantities of domestic tourmaline, kunz- ite, and pink beryl available on the market had become so small that prices began a distinct rise. This rise continued through the decade, and resulted in some revival of min- ing in the district. George Ashley of Pala purchased the claims on Hiriart Mountain from Fred M. Sickler in July, 1!>47, and subsequently sold three of these claims to Norman E. Dawson of San Marcos. Mr. Ashley reopened the Katerina mine, and recovered small quantities of excellent kunzite from inner parts of the pegmatite. The Fargo and White Queen mines, also on Hiriart Mountain, were worked in 1948 and 1949 by Mr. Dawson. Monta J. Moore of Pala, as representative of the F. A. Salmons estate, was planning to reopen the famous Tourmaline Queen and Pala Chief mines late in 1949. Lepidolite mining in the Pala district centered about the Stewart dike, and small quantities of lithia mica were contributed from time to time by operators in the Tourma- line King, Tourmaline Queen, Pala Chief, Katerina, and Vanderburg mines. GEOLOGY General Features Most of the Pala district is underlain by a series of intrusive rocks of late Mesozoic age which are part of 111 Kunz, G. I' . i)n a new lilac colored spodumene, San Diego County, California: Science, new ser., vol. 18, p. 280, 1903. " Schaller, w. T., Spodumene from San Diego County, Cali- fornia: California Univ. Dept. C3eol. Sci., Bull., vol. :!, pp. 265-275, 1903. the very large and complex southern California batholith of the Peninsular Range province. 12 This batholith com- prises many separate intrusive units, or plutons, that range in exposed diameter from a few hundred feet to ten miles or more. In composition they range from gabbro to granite; representatives of the gabbro, tonalite, and granodiorite groups are especially widespread. Metamorphic rocks of pre-batholith age are exposed in many parts of the province, but form a subordinate part of the crystalline complex. Post-batholithic sedimen- tary rocks cover the crystalline complex in the Elsinore- Temecula-Pechanga Valley, in many smaller valleys, and in a broad belt that fringes the coastline to the west. The sedimentary and metamorphic rocks are much folded, the closeness and complexity of folding increasing with the age of the rocks. Both these and the rocks of the batholith are cut by numerous joints and faults, some of which have distinct topographic expression. The Elsinore fault zone, along which recent activity has been recognized, is the most impressive tectonic feature in the Pala area. It trends northwest, and bounds the district on the northeast. The rocks exposed in the vicinity of Pala have been briefly described by several geologists in the course of studies of the pegmatites. In addition, more general descriptions of the geology have been published by Fair- banks, 13 Merrill, 14 Ellis, 15 Miller, 16 Larsen, and others. Additional investigations have been made in the nearby Cuyamaca area by Hudson, 17 Miller, 18 and Everhart ; 19 the San Jacinto area by Fraser ; 20 the Julian district by Donnelly 21 and Creasey ; 22 the Perris area by Dudley ; 23 and in a part of the Ramona quadrangle by Merriam. 24 The results of numerous studies of specific rock types 12 Larsen, E. S., The batholith of southern California : Science, new ser., vol. 93, pp. 442-443, 1941. Larsen, E. S., Batholith and associated rocks of Corona, Elsi- nore, and San Luis Rey quadrangles, southern California : Geol. Soc. America, Mem. 29, 182 pp., 1948. Larsen, E. S., Time required for the crystallization of the great batholith of southern and Lower California : Am. Jour. Sci., vol. 243-A, pp. 399-416, 1945. Larsen, E. S., and Keevil, N. B., Radioactivity of the rocks of the batholith of southern California: Geol. Soc. America Bull., vol. 58, p. 484, 1947. 13 Fairbanks, H. W., Geology of San Diego County ; also of por- tions of Orange and San Bernardino Counties : California Min. Bur., Kept. 11, pp. 76-120, 1893. 14 Merrill, F. J. H., Geology and mineral resources of San Diego and Imperial Counties, California: California Min. Bur., Rept. 14, pp. 636-722, 1914. 16 Ellis, A. J. and Lee, C. H., Geology and ground waters of the western part of San Diego County, California : U. S. Geol. Survey Water Supply Paper 446, pp. 50-76, 1919. 10 Miller, W. J., Crystalline rocks of southern California : Geol. Soc. America Bull. vol. 57, pp. 476-488, 1946. 17 Hudson, F. S., Geology of the Cuyamaca region of California with special reference to the origin of the nickeliferous pyrrhotite: California Univ., Dept. Geol. Sci., Bull., vol. 13, pp. 175-252, 1922. 15 Miller, W. J., A geologic section across the southern Peninsular Range of California : California Jour. Mines and Geology, vol. 31, pp. 115-142, 1935. 1B Everhart, D. M., Geology of the Cuyamaca Peak quadrangle, San Diego County, California: California Div. Mines Bull. 159, in press, 1951. 20 Fraser, D. M., Geology of the San Jacinto quadrangle south of San Gorgonio pass, California : California Jour. Mines and Geology, vol. 27, pp. 494-540, 1931. !1 Donnelly, M. G., Geology and mineral deposits of the Julian district, San Diego County, California : California Jour. Mines and Geology, vol. 30, pp. 331-370, 1934. 22 Creasey, S. G, Geology and nickel mineralization of the Julian- Cuyamaca area, San Diego County, California: California Jour. Mines and Geology, vol. 42, pp. 15-29, 1946. "■> Dudley, P. H., Geology of a portion of the Perris block, south- ern California: California Jour. Mines and Geology, vol. 31, pp. 487- 506, 1935. 24 Merriam, Richard, Igneous and metamorphic rocks of the southwestern part of the Ramona quadrangle, San Diego County, California: Geol. Soc. America Bull., vol. 57, pp. 223-260, 1946. Pegmatites of the Pala District Table 1. Generalized section of rocks exposed in Pala district. Age General designation Lithologic type Quaternary Surficial deposits- _ Landslide, talus, fan, and valley-fill deposits Late Meso- zoic (prob- ably Creta- ceous)-- Rocks of the south- ern California batholith . Pegmatite Aplite Fine-grained granodiorite Coarse-grained granodiorite Felsic tonalite Mafic tonalite Gabbro and norite Mesozoic and/ or Paleozoic. Pre-batholithic crystalline rocks _ Quartzite, schist, conglomerate, and rare marble from the batholithic complex are also in the published record. 25 Metamorphic Rocky The metamorphic rocks of the Pala district are thin, elongate remnants of a once extensive sedimentary ter- rane. The remnants consist of quartzite, quartz conglom- erate, meta-arkose, quartz-mica schist, quartz-mica-amphi- bole schist, and feldspathic amphibole schist, and are now transected and enclosed by younger igneous rocks. These metamorphic rocks are most abundant in a dis- continuous, broadly curving belt that extends around the west and north slopes of Queen Mountain, the south slopes of Carver and Big Chief Mountains, and the southwest slopes of the hills and ridges that lie north and east of Hiriart Mountain. Quartzite is dominant in the western part of this belt, schist in the eastern part. The belt separates gabbroic rocks on the south from dominantly granodioritic rocks on the north. It tapers out at the southwest corner of Queen Mountain, and also at several places in the eastern part of the district. It is widest along the flanks and crest of the rugged ridge immediately east of Pala Canyon, where quartzite, quartz conglomerate, and associated metamorphic rocks have a maximum outcrop width of about 500 feet. Bedding and schistosity in the quartzitic rocks are essentially parallel. On a larger scale, the trends of schis- tosity, of individual beds of quartzite, and of masses of schist and other metamorphic rocks also are parallel. Linear elements, mainly rows of biotite blades, amphibole needles, or stretched pebbles in conglomerate, are locally very well developed. Their plunges are generally very steep. The rocks are tightly folded on a small scale, as 23 See, for example : Kessler, H. H., and Hamilton, W. R., The orbicular gabbro of Dehesa, California: Am. Geologist, vol. 34, pp. 133-140, 1904. Lawson, A. C, The orbicular gabbro at Dehesa, San Diego County, California: California Univ., Dept. Geol. Sci., Bull., vol. 3, pp. 383-396, 1904. Schaller, W. T., Orbicular gabbro from Pala, San Diego County, California: U. S. Geol. Survey Bull. 490, pp. 58-59, 1911. Miller, F. S., Anorthite from California: Am. Mineralogist, vol. 20, pp. 139-146, 1935. Hurlbut, C. S., Dark inclusions in a tonalite of southern Cali- fornia : Am. Mineralogist, vol. 20, pp. 609-630, 1935. Miller, F. S., The petrology of the San Marcos gabbro, southern California: Geol. Soc. America Bull., vol. 48, pp. 1397-1425, 1937. Miller, F. S., Hornblendes and primary structures of the San Marcos gabbro, southern California : Geol. Soc. America Bull., vol. 49, pp. 1213-1232, 1938. Osborn, E. F., Structural petrology of the Val Verde tonalite, southern California: Geol. Soc. America Bull., vol. 50, pp. 921-950, 1939. Merriam, Richard, A southern California ring-dike : Am. Jour. Sci., vol. 239, pp. 365-371, 1941. Merriam, Richard, Orbicular structures in aplite dikes near Ramona, California: Am. Jour. Sci., vol. 246, pp. 129-137, 1948. shown m many outcrops, but their broad structure appears to be simple. The main quartzite-schist bell is a thin sep turn or screen between plutons or pluton groups, and the other smaller masses of metamorphic rocks are roof pen- dants and inclusions within these plutons. The metamorphic rock series in the Pala area is sim- ilar to parts of the Julian schist sequence in areas farther east, and all these pre-batholithic rocks may well be parts of the same general series. Even in the Pala area the quartzites, though dominant, are associated with much schist. The age of the Julian schist (also called "basement complex," "schist complex," "Julian group," "Julian Schist Series," and "Bedford Canyon formation") is not accurately known, but this complex series has been corre- lated with fossiliferous rocks to the north and northeast, chiefly on the basis of lithology and geographic distribu- tion. It has been suggested by Fairbanks, 26 Hudson, 27 and others, that the schist may correspond, at least in part, to the metamorphic sequence in the Santa Ana Mountains, which includes slate beds that contain Triassie fossils. That it may be in part of late Paleozoic age also seems possible, as pointed out by Hudson, 28 Miller, 2! » and others. Rocks of both ages may well be represented in the series, which is assuredly older than the late Mesozoic rocks of the southern California batholith. Igneous Rocks Gabbroic Rocks Gabbro, norite, and associated intrusive rocks of basic composition are very abundant in the vicinity of Pala, where they occur as composite plutons of circular to roughly elliptical plan. In general they are relatively resistant to erosion, and characteristically form prom- inent hills and ridges with smooth, regular slopes and thin mantles of dark reddish-brown soil. Examples of such eminences are Pala Mountain, Queen Mountain, Chief mountain, and Hiriart Mountain. Individual rock types include medium- to coarse- grained gabbro and norite, olivine gabbro and norite, hornblende-rich gabbro and norite, hornblende-biotite gabbro and norite, and quartz-bearing gabbro and norite. All these types have been included under the general name San Marcos gabbro by Miller, 30 and in some areas to the southeast they have been designated as Cuyamaca basic intrusive by Hudson, 31 Donnelly, 32 and others. The most common rock type in the Pala district is a dark-gray, medium-grained, equigranular, homogeneous olivine-hornblende-hypersthene gabbro. Its principal con- stituents, listed in order of decreasing abundance, are calcic plagioclase, hornblende, olivine, augite, and hypers- thene. Accessory minerals include biotite, ilmenite, mag- netite, pyrite, pyrrhotite, and spinel. All but the most mafic or fine-grained gabbros and norites yield boulders with somewhat light-colored sur- faces. These surfaces are strongly pitted, because of the * Fairbanks, H. W., op. cit, pp. 82, 87, 1893. -• Hudson, F. S., op. cit., pp. 188-190, 1922. m i ip. cit. » Miller, \Y. J., op. cit., pp. 477-485, 1946. *> Miller, F. s., Petrology of the San Marcos gabbro, southern California: Geol. Soc. America Bull., vol. 48, pp. 1399-1400, L9 31 Hudson, F. S., Geology of the Cuyamaca region of California, with special reference to the origin of the niekeliferous pyrrhotite: California Univ., Dept. Geol. Sci., Bull., vol. 13, pp. 193-207, 1922. "Donnelly, M <',., Geology and mineral deposits of the Julian District, San Diego County, California: California Jour. Mines and Geology, vol. 30, pp. 3 11-342, 1934. 10 Special Report 7-A U i O I "5s , K : •O-i S is! 81 CO O t. Is .c fa •oT era 3 C O «J *1 OS j "5 ' hj o w "Ejs -^ bfl ."■«" "5 li gg ~ p. £0 u 5 * 24 Special Report 7-A similar openings have been dug farther to the northwest, in an area underlain chiefly by granodiorite. The pegmatite dikes of intermediate composition are much like those that are truly granitic, as far as general structure is concerned, but are not so continuous along their strike. This lack of continuity is even more char- acteristic of the gabbroic pegmatites. (LiJ^rj?*//,//; ' - >^j L -i r J lJj2M^^~~ ■ ■ S.S.E. tt - much sheared ] g g o ft * j Dump material jtti Quartz - per-thite -albite -muscovite ^ pegmatite \r J l~i| Graphic granite | tt u I Gabbro I 1 1 1 1 '. I ll Quartz - mica, schist ao Scale in feet Fig. 6. Section through west tunnel, North Star mine, showing tapered edge of pegmatite dike in gabbro and quartz-mica schist. Internal Structure General Features Many of the Pala pegmatites consist of two or more units of contrasting lithology, as already shown. The dis- tribution of these units within each dike is essentially systematic, and is related— at least in part — to the overall structure of the dike. The disposition of minerals and the pattern of textural variations also follow certain rules within each unit, although there are many irregularities of detail. Most prospectors and mine operators in the dis- trict have recognized this orderliness, and the distribution of mine workings bears testimony to their thorough explo- ration of contacts between line rock and overlying graphic granite in a search for pocket material. Rock units of contrasting composition and texture have long been recognized in many pegmatites. As early as 1871, for example, T. S. Hunt 45 remarked upon the distinct layering of many "granitic veinstones" in Maine. References to bands, layers, lenses, ribs, segregations, shoots, streaks, and zones of massive quartz and of other minerals or mineral aggregates are common in many early reports. Some investigators were impressed by irregulari- ties of mineral distribution in pegmatites, it is true, but others recognized these as essentially irregularities of detail. During the period 1900-35 it was repeatedly noted that cavities, concentrations of both common and unusual minerals, and concentrations of economically desirable minerals tend to occupy characteristic positions. The attention of most investigators, however, was focused more upon the mineralogy of such contrasting units than upon their structural and petrologic relations. During more recent years, increasing emphasis has been placed upon interpretation of the internal structure ' Hunt, T. S., Notes on granitic rocks: Am. Jour. Sci., 3rd ser., vol. 1, pp. 82-89, 182-191, 1871. of pegmatites, both as a means of determining their genesis and as an aid in planning exploration, develop- ment, and mining. 411 Most workable concentrations of peg- matite minerals are in rock units that differ markedly in one or more respects from adjacent barren units. This has been repeatedly demonstrated by detailed studies in many areas. On the other hand, few homogeneous, or internally structureless pegmatite bodies contain concentrations of commercially desirable minerals sufficiently rich to yield satisfactory returns in mining under present economic conditions. Three fundamental types of pegmatite units have been recently defined and described 4T as follows : 1. Fracture fillings are units, generally tabular, that fill fractures in consolidated pegmatite. 2. Replacement bodies are units formed primarily by re- placement of consolidated pegmatite. Although there are all gradations between simple fracture fillings and fracture-controlled replacement bodies, the structural control for many replacement bodies is not clear. 3. Zones are successive units that ordinarily reflect the shape or structure of the enclosing pegmatite body. In lenslike or podlike pegmatites they have a concen- tric pattern, and in the more tabular bodies they ap- pear as simple layers. Many zones are not completely developed, and form straight or curving lenses, trough- like or hoodlike bodies, or chains of lenses. Contacts between adjacent pegmatite units vary con- siderably in distinctness. Those between units of markedly different composition or texture are commonly of knife- edge sharpness, and often may be mapped on a scale as large as 20 feet or even 10 feet to the inch, whereas some of those between mineralogically similar units are difficult to assign within narrow limits, especially where such units are intergradational or very coarse grained. 46 See, for example : Smith, W. C, and Page, L. R., Tin-bearing pegmatites of the Tinton district. Lawrence County, South Dakota : U. S. Geol. Survey Bull. 922-T, 35 pp., 1941. Olson, J. C, Mica-bearing pegmatites of New Hampshire : U. S. Geol. Survey Bull. 931-P, pp. 373-376, 1942. Bannerman, H. M., Structural and economic features of some New Hampshire pegmatites : New Hampshire State Planning and Dev. Comm., Min. Res. Survey, Part VII, 22 pp., 1943. Page, L. R., Hanley, J. B., and Heinrich, E. Wm., Structural and mineralogical features of beryl pegmatites (abstract) : Econ. Geology, vol. 38, pp. 86-87, 1943. Cameron, E. N., Larrabee, D. M., McNair, A. H., and Stewart, G. W., Characteristics of some New England mica-bearing pegmatites (abstract) : Econ. Geology, vol. 39, p. 89, 1944. Jahns, R. H., and Wright, L. A., The Harding beryllium-tan- talum-lithium pegmatites, Taos County, New Mexico (abstract) : Econ. Geology, vol. 39, pp. 96-97, 1944. Olson, J. C, Parker, J. M. Ill, and Page, J. J., Mica distribution in western North Carolina pegmatites (abstract) : Econ. Geology, vol. 39, p. 101, 1944. de Almeida, S. C, Johnston, W. D., Jr., Leonardoes, O. H., and Scorza, E. P., The beryl-tantalite-cassiterite pegmatites of Paraiba and Rio Grande do Norte, northeastern Brazil : Econ. Geology, vol. 39, pp. 206-223, 1944. Olson, J. C, Economic geology of the Spruce Pine pegmatite district, North Carolina : North Carolina Dept. Conservation and De- velopment, Div. Min. Res., Bull. 43, 1944. Johnston, W. D., Jr., Beryl-tantalite pegmatites of northeastern Brazil: Geol. Soc. America Bull., vol. 56, pp. 1015-1070, 1945. Cameron, E. N., Larrabee, D. M., McNair, A. H., Page, J. J., Shainin, V. E., and Stewart, G. W., Structural and economic character- istics of New England mica deposits : Econ. Geology, vol. 40, pp. 369- 393, 1945. Fisher, D. J., Preliminary report on the mineralogy of some pegmatites near Custer : South Dakota State Geol. Survey Rept. of Investigations No. 50, 89 pp., 1945. Jahns, R. H., Mica deposits of the Petaca district, Rio Arriba County, New Mexico : New Mexico School of Mines, State Bur. Mines and Min. Res., Bull. 25, 1946. Cameron, E. N, and Shainin, V. E., The beryl resources of Con- necticut : Econ. Geology, vol. 42, pp. 353-367, 1947. Pecora, W. T., Klepper, M. R., and Larrabee, D. M., Mica-bearing pegmatites in Minas Gerais, Brazil (abstract) : Washington Acad. Sci. Jour., vol. 37, pp. 370-371, 1947. Cameron, E. N., Jahns, R. H., McNair, A. H., and Page, L. R., The internal structure of granitic pegmatites : Econ. Geology, Mon. 2, 1949. "Cameron, E. N., Jahns, R. H., McNair, A. H., and Page, L. R., op. cit., pp. 14-96, 1949. Pegmatites of the Pala District 25 So varied and uneven are the textures of typical peg- matites that no single term, such as "pegmatitic, " suffices for most descriptions. The following size classification of pegmatitic textures, adopted by the U. S. Geological Survey, is used throughout this report : General grain size Term (in terms of maximum diameter of each grain) Very fine (includes sugary, aplitic) Less than J inch Fine & inch to 1 inch Medium 1 inch to 4 inches Coarse 4 inches to 12 inches Very coarse, or giant Greater than 12 inches Zones A grouping of pegmatite /ones into four main cate- gories has been proposed by Cameron, Jahns, McNair, and Page 4S as follows : 1. Border zones, or outermost zones. 2. Wall zones. 3. Intermediate zones. 4. Cores, or innermost zones. According to this classification, pegmatites that are not homogeneous ordinarily range from simple masses with only a border zone surrounding a core to masses with a border zone, wall zone, core, and several intermediate zones. There is no theoretical limit to the possible number of intermediate zones, but few pegmatites in the Pala dis- trict contain more than three such units. The border zones of most Pala pegmatites are thin, inconspicuous selvages. They consist generally of fine- grained graphic granite in which most of the quartz rods are less than 1 millimeter in diameter. The host perthite crystals rarely are greater than 1 inch in maximum dimen- sion, and most of them are less than \ inch. A few peg- matites are marked by selvages of line rock or other fine- grained material. The border zones pass into typical coarse-grained graphic granite of the adjacent wall zones with an abrupt increase in grain size. They are in even sharper contact with the country rock, and in some pegmatites shearing has juxtaposed thin slices of gabbro and border-zone ma- terial. In general the outermost zones are an inch or less in thickness, and most are markedly discontinuous. Indeed, relatively fine-grained selvages are absent from many dikes, in which coarse-grained graphic granite lies against the gabbroic country rock. In most pegmatites, the border zones are more widespread along the hanging wall than along the footwall contacts. In addition to graphic granite, most of the border zones also contain small quantities of fine-grained albite, muscovite, widespread garnet, and some schorl as tiny scattered specks. In general these minerals are rather evenly disseminated, but in a few pegmatites they are arranged in layers parallel to the nearby wallrock con- tacts. A very regularly layered border zone is well exposed in the workings of the Pala View mine, on the south side of Queen Mountain. Here a selvage of fine-grained graphic granite, i to 2\ inches thick, contains small, scattered flakes of pale-green muscovite, and is marked by thin, subparallel layers rich in quartz and garnet. The garnet occurs as deep-red crystals 2 millimeters in maximum diameter. In places where individual layers are at least 1S Cameron, E. N., Jahns, R. H., McNair, A. H., and Page, L. R., op. cit., pp. 20-21, 1949. 1 inch thick, this mineral forms subgraphic intergrowths in quartz. Most of the garnet-rich layers arc near the inner part of the border zone along both the hanging-wall and footwall contacts of the dike. Wall zones, which represent by far the most abundant pegmatite material in the district, are composed of graphic granite, with or without other minerals. In most pegma- tites, substantial quantities of interstitial quartz are present, commonly with subordinate albite, muscovite, and schorl. The typical graphic granite is most abundant and continuous in the hanging-wall parts of the dikes. There is some evidence, first cited by Schaller, 49 that it was once present in the footwall parts, possibly in great abundance, and that it was subsequently replaced by line rock and other types of fine-grained, albite-rich pegmatite. On the other hand, there are many dikes in which such evidence is rare, or does not seem to be present at all, so that the concept of a graphic-granite wall zone, symmetrically developed with respect to a central plane in each dike, cannot be applied with assurance to all of the pegmatites that contain line rock. Some pegmatites consist almost wholly of graphic granite, and appear to comprise only two zones. In them the typical coarse-grained graphic granite should be termed a core, rather than a wall zone, although it seems probable that quartz-rich core segments are present some- where in nearly all the dikes that appear to consist wholly of graphic granite. aaib7-o xx n n n 12 3 4 5 JJ Scale w feet SE Fig. 7. Sketch of pegmatite-gabbro relations on northeast wall of main tunnel, Pala View mine. Most of the wall zones are continuous. They constitute almost the full thickness of many dikes, in which they are interrupted only here and there by small segments of cores or intermediate zones (fig. 19). Large parts of other dikes, however, contain well-developed cores, which typ- ically appear as discoidal masses of very coarse-grained pegmatite. These are single masses or rows, and ordinarily occupy central positions within the dikes (fig. 20). Most are markedly elongate, as if in reflection of the containing dikes themselves, and some are as much as 50 feet long. Excellent examples of thin, but continuous cores are exposed in the White Cloud, Tourmaline King, and El Molino dikes, and in the northern part of the Stewart dike. The thicknesses of such units rarely exceed 3 feet in the dikes of regular shape, but in sonic of those with prominent bulges or protuberances, the innermost zones are more nearly equidimensional. Such cores and core segments are commonly 5 to 15 feet thick, but strike lengths rarely exceed 35 or 40 feet. 48 Schaller, W. T., The genesis of lithium pegmatites: Am. Jour. Sci., 5th ser., vol. 10, pp. 273-276, 1925. 2G Special Report 7-A The thinnest cores and segments of cores consist gen- erally of massive quartz in very coarse-grained aggregates of anhedral crystals, or of such quartz with scattered large cuhedral crystals of perthite. In some of these perth- ite-bearing units, the quartz is the subordinate constit- uent, Indeed, the cores of a few pegmatites consist almost wholly of very coarse-grained blocky perthite in subhedral to anhedral aggregates. In a few others the cores are massive quartz with scattered lath-shaped crystals of spodumene. The relations of these simple innermost units are shown diagrammatically in figures 19 and 20A. The sub- hedral graphic granite, with its local interstitial aggre- gates of quartz, perthite, and albite of much smaller grain size, typically grades into the central units of coarse, euhedral perthite crystals in massive quartz. Quartz-perthite cores of this type are similar to miarolitic cavities, in that the feldspar crystals seem to have grown into a liquid- or gas-filled cavity, the cavity having been subsequently filled with quartz crystals. Much less common than these tabular cores are the thick, pod-like cores at or near the centers of distinct bulges in several of the pegmatite dikes. Some of these thick cores consist of large euhedral to subhedral perthite crystals with interstitial massive quartz, and grade into the adjacent graphic granite of the wall zone as described above. Others are composed of nearly pure massive quartz, of massive quartz with giant spodumene crystals, or, rarely, of massive quartz, spodumene, and large anhedral crystals or crystal aggregates of amblygonite. Because of the great mineralogic difference involved, such units are very sharply separated from the adjoining wall zones. Still other cores are separated from the wall zones by one or more intermediate zones, which appear as partial or complete envelopes around the cores. Some of the inter- mediate zones are so incompletely developed that they appear only as curving lenses or rows of lenses. In a few pegmatites, distinguished by long, subdued bulges, the cores and intermediate zones have the form of discontin- uous layers, rather than thick pods. The general sequence of essential-mineral assemblages from zone to zone within a single pegmatite dike is remark- ably consistent throughout the district. A consistency in sequence of textures also is present, so that the zonal lithology as a whole follows a well-defined pattern. In terms of fundamental textural and mineralogic charac- teristics, the arrangement of zones from the walls of the Pala pegmatites inward is as follows : 1. Fine-grained graphic granite. 2. Coarse-grained to very coarse-grained graphic granite. 3. Perthite, chiefly in aggregates of very large subhedral crystals. 4. Very coarse anhedral quartz (massive quartz) with scat- tered large euhedral crystals of perthite. 5. Very coarse anhedral quartz (massive quartz). 6. Very coarse anhedral quartz (massive quartz) with large subhedral crystals of amblygonite and euhedral crystals of spodumene. 7. Very coarse anhedral quartz (massive quartz) with large euhedral crystals of spodumene. 8. Very coarse anhedral quartz (massive quartz). All of these units are known to occur together in only three pegmatites in the district, the Stewart, Pala Chief, and Vanderburg-Katerina. Most of the dikes contain only three or four of the units, generally Nos. 1, 2, and 4 ; 1, 2, and 5 ; or 1, 2, 4, and 5. Many of those on Chief and Hiriart Mountains contain No. 7 as well. Units Nos. 3 and 6 are in the thickest dikes only, and No. 6 is rare. Regardless of the number of such units present in a given pegmatite, however, their order conforms to the general sequence outlined above. Albite and muscovite are irregularly distributed in most of the units and are locally abundant. The zones con- tain many other minerals also, but these minerals are either minor accessory constituents or appear to have been introduced after the host zones were formed. If all these minerals were taken into consideration in an analysis of the zones, they would complicate but not alter the basic sequence. Fig. 8. Large crystals of perthite, with long quartz rods (above level of small opening) overlie a very coarse-grained aggregate of perthite and interstitial quartz, muscovite, and albite. Large crystal of pale yellowish-green beryl is crossed by shadow of hammer handle. Katerina mine. Fracture Fillings Most of the fracture fillings consist of quartz, albite, biotite, fine-grained muscovite, or combinations of these minerals, with or without minor accessory constituents. They range in thickness from knife edges to nearly 10 inches, and are most abundant in the outer zones of the pegmatites. Many transect the graphic granite of the wall zones, but merge with inner zones, particularly those very rich in quartz. The exposed parts of others lie wholly within single zones. Still others cut across entire pegmatite bodies, and are plainly younger than all the zones nearby. Pegmatites of the Pala District 27 Three general types of fracture structures appear to have guided mineral-depositing solutions in the pegma- tites. One type, parallel to the pegmatite walls, ordinarily consists of individual subparallel fractures that are spaced \ inch to at least 2 feet apart. Many of them are so regular in their development that they give the pegma- tite a sheeted appearance. A second type, consisting of throughgoing fractures, is somewhat less common. Although these fractures also are regular in their dis- tribution, few of them are very closely spaced. A third type of fracture, irregular but abundant and widespread, includes openings along cleavage directions in feldspar and other minerals, and also less regular openings along boundaries between adjacent mineral grains or through the grains themselves. Some of these fractures contain biotite blades that transect both quartz rods and sur- rounding host feldspar in the graphic granite of many pegmatites. The minerals in most fracture fillings have corroded the fracture walls, and there are all gradations between simple open-space fillings and fracture-controlled replace- ment bodies. In general, the more complex the mineralogy of the fracture-related masses, the more they appear to have been formed by replacement of pre-existing peg- matite. Some of the fracture fillings are composite, and evi- dently are the result of repeated Assuring and filling with new material. These are not abundant, but are in numer- ous pegmatites, notably the White Cloud, Tourmaline Queen, Stewart, Douglass, Ocean View, Little Chief, and several dikes on Hiriart Mountain. The layering is com- monly emphasized by alternations of milky and clear quartz, or clear and smoky quartz, or, rarely, of quartz and other minerals. Other Units Replacement bodies, many of which are obviously fracture-controlled, are present in nearly all the pegma- tites. They are younger than the rock that forms the enclosing zones and their structural pattern is plainly superimposed upon the essentially concentric or layer- like arrangement of the zones. They are composed chiefly of fine- to coarse-grained albite, quartz, and muscovite. Lepidolite and tourmaline also are widespread, but are much less abundant. Numerous accessory species are present in some of the pegmatites, but rarely in more than very small quantities. They include beryl, bismuth minerals, clay minerals, columbite-tantalite, cookeite, manganotantalite, monazite, stibiotantalite, sulfide min- erals, topaz, zeolites, and zinnwaldite. Other accessory minerals appear to have been formed earlier, and may well be indigenous to the zonal units of the pegmatites. Apatite, cassiterite, lithiophilite, triphylite, and some beryl, garnet, and schorl are typical examples of these. The simplest replacement bodies are fracture-related units that have corroded the fracture walls. Perhaps most easily interpreted are those in the hanging-wall zones of graphic granite, in which they are generally parallel to the pegmatite-country rock contacts. They range from 1 millimeter to several inches in thickness, and commonly extend for several tens of feet along the strike. Groups of these units form anastomosing networks where devel- oped along a single set of fractures, and more reticulate networks where their distribution was controlled by two sets of fractures. On. the west face of the south cut of the Stewart mine, excellent examples of fracture-related replacement bodies are near the hanging wall of the pegmatite. Here numerous thinly tabular masses of fine- to medium- grained quartz-albite pegmatite with abundant muscovite and green tourmaline clearly were formed along sub- parallel fractures in coarse-grained graphic granite. These units cut across individual crystals of perthite, and also across quartz rods and groups of such rods in the graphic granite. Thinner and more widely spaced replace- ment bodies are exposed in the main cut of the Tourmaline Queen mine. They are composed mainly of quartz and muscovite, with local concentrations of albite, tourmaline, and lepidolite. Comb structure, with platy to pencil-like crystals oriented normal to the walls, is fairly common in the most tabular fracture fillings. The interiors of these units are marked in many places by sharply terminated crystals of quartz, cleavelandite, muscovite, lepidolite, and totirma- line. Individual crystals are rather small, especially where they are in the outer parts of the host pegmatites. Some of the replacement units contain crude layers, distin- guished mainly by variations in quartz, muscovite, or tourmaline content. Some of this layering seems best ascribed to repeated Assuring and introduction of addi- tional material. Other layers evidently were formed by diffusion processes, as they appear to be superimposed upon a coarser textural pattern. Many of these replace- ment bodies are layered only around a few scattered voids where crystals of tourmaline and lepidolite are more abundant than elsewhere. Fracture-controlled replacement bodies are not con- fined to the hanging-wall parts of the dikes, but are also in line rock and other fine-grained granitoid units that commonly form the footwall parts. Most of them are essentially concordant with the planar structure in the line rock, or with the pegmatite-wall rock contacts or contacts between zonal units within the pegmatites. Many of these concordant units are as much as 50 feet long, but most do not exceed 6 feet in maximum dimension. Like those in the hanging-wall parts of the dikes, they com- monly branch and join. Elsewhere they are connected by markedly discordant masses of similar material, so that the whole represents ladder veins or larger, reticu- late masses. In a few pegmatites, notably the Naylor, replacement units occupy positions in the crests and troughs of warps and tighter folds in line rock. They resemble small phacoliths, with saddlelike or troughlike form. There are all gradations between fracture-controlled replacement bodies that form series of parallel layers and those that form intricate stockworks. The variations are particularly well illustrated by tabular masses of cleave- landite in verv coarse-grained aggregates of quartz. In the White Cloud, Pala Chief, and several other pegma- tites, such cleavelandite aggregates were developed along closely spaced parallel fractures in milky to dark-gray quartz, and the two minerals form a strikingly layered rock known throughout the district as zebra rock, banded rock, or stripe rock. Elsewhere, as in the Stewart and Kate'rina pegmatites, the albite forms reticulate or irreg- ularly ramifying veinlets that transect individual crystals th'e quartz aggregate. All stages of replacement can be ognized, and in some places only remnants of quartz, m rec 28 Special Report 7-A representing the cores of original fracture Mocks, attest the former existence of a massive quartz unit. Similar relations are characteristic of much lepidolite and rnus- covite formed in quartz. Fig. 9. Large graphic-granite mass surrounded by much finer- grained aggregate of Quartz, muscovite, perthite, and albite. Mineral aggregates similar to those that form replace- ment units in the outer parts of the pegmatites are more abundant in the central parts of many dikes, but their origin is not so plain. Almost without exception, they appear to be younger than the rock that surrounds them, and in most places they clearly corrode this rock. Whether or not most of them were formed wholly at the expense of this rock is not readily demonstrated, however, for residual masses of earlier pegmatite are rare in their cen- tral parts. Nevertheless, these mineral aggregates are here provisionally termed replacement units (possibly in large part of deuteric origin), because of differences in age, texture, and structure between them and the typical zonal units. These younger units include much of the pocket pegmatite in the district. They range in form from the thinly tabular tourmaline-quartz pockets of such pegma- tites as the Fargo and Tourmaline Queen to thickly ellipsoidal lepidolite-rich masses like those in the Stewart pegmatite. Thicknesses range from slightly less than 1 millimeter to about 30 feet, lengths from about 1 inch to as much as 200 feet. Typically these masses are discoid in general shape, but they are so irregular in detail that they appear in most exposures as blobs or splotches. This lack of clear-cut form is further emphasized by the wide- spread tendency of such units to grade outward into com- plex systems of fracture-fillings and fracture-guided replacement masses. Whereas the smallest and most nearly tabular replacement units are widespread in their distribution, the largest and more bulbous ones ordinarily are restricted to the central parts of the host dikes. More specifically, masses of this pocket pegmatite occur in cores and immedi- ately adjacent zones, chiefly along the footwalls or in the footwall parts of the cores and core segments. It does not occur simply along contacts between line rock and overly- ing graphic granite, as commonly alleged, although it must be admitted that the tops of the main masses of line rock are near the footwalls of the cores and core segments in many of the dikes. Such pegmatite thus is ordinarily most abundant in the central parts of bulges in single dikes or junctions of two or more merging dikes. It is also localized in the nearly flat, terracelike parts of several dikes, as pointed out by Donnelly. 50 To what extent such correlation with gently-dipping parts of the dikes can be generally applied in the district is not yet known. The structure of the fine-grained granitoid rocks common in the footwall parts of most Pala pegmatites is quite distinct from that of the zones, fracture fillings, and replacement units described above. The masses of fine- grained, albite-rich rock commonly occupy the lower, or footwall, one-fourth to one-half of pegmatite dikes in which the remainder of the rock is graphic granite or graphic granite with small segments of very coarse- grained pegmatite. Some of these masses are composed of line rock and others wholly of aplitic rock without planar structure, but most of them contain both rock types. Indeed, there are all gradations between them, both along and across the strike. As shown in figure 25C, the line rock is commonly separated from the footwall contact of many dikes by 6 inches to nearly 10 feet of aplitic rock that is not layered. These albite-rich rocks are not confined to the lower parts of the pegmatite dikes, although they are most abundant there. They occur also in the upper parts and even along a few hanging-wall contacts, where they form poorly defined tabular masses (fig. 25D). Where such masses are present in the hanging-wall zones of graphic granite, they impart a crudely layered appearance to weathered surfaces of the pegmatites. Line rock occurs within the cores of a few dikes and appears to be in part superimposed upon the very coarse-grained pegmatite that typically forms these innermost units. Thus it is markedly quartzose where best developed, and commonly grades into much coarser pegmatite containing only a few garnet- or albite-rich layers. In many places it appears to have encroached upon the footwall parts of cores and core segments (fig. 25C). Where two subparallel pegmatites branch or join, the distribution of line rock generally is like that indi- cated in figure 8E. The line rock in the lower dike is con- tinuous, whereas that in the upper one fades into the graphic granite or other zonal rock at some distance from 50 Donnelly, M. G., The lithia pegmatites of Pala and Mesa Grande, San Diego County, California : California Inst. Technology, unpublished Ph.D. thesis, p. 56, 1935. Pegmatites of the Pala District the point of junction. This distance ranges from a few inches to many tens of feet, but ordinarily is 10 feet to 30 feet. These relations are characteristic also of the aplitic rocks that lack planar structure. The structural relations of line rock and associated types in the more bulbous pegmatites are not so clear, owing to the rarity of critical exposures. In general, how- ever, the fine-grained units occupy the lower, or footwall, parts of the dikes, and appear to have encroached upon the inner zones. As exposed in the underground workings of the Stewart, Pala Chief, and Katerina mines, the aplitic rocks are much more continuous than the nearby cores and intermediate zones, both along the strike and down the dip. Not only are the fine-grained granitoid rocks quite distinct texturally from the other rock types in the peg- matites, but the thin and regular layering in the line rock is an unusual feature. Moreover, these rocks form tabular units that are not symmetrically disposed with respect to the walls of the enclosing dikes, either broadly or in detail. This is in sharp contrast to the relations of the zones, most of which at least tend to be symmetrical. There seems to be a widespread impression among those who have read reports on the Pala pegmatites that the bulk of the material in these dikes is of replacement origin. This is not correct. In few of the dikes, for exam- ple, do the coarse-grained replacement units appear to constitute more than 1 percent of the total pegmatite material present. Even if the various types of aplitic, albite-rich pegmatite in the district were to be interpreted as having been formed at the expense of pre-existing pegmatite, the sum of replacement material still would be less than the amount of graphic granite and other rock types indigenous to the earlier-formed units. In one way or another, this has been pointed out — although admit- tedly not emphasized — by most previous investigators in the district. In his classic paper on the genesis of the peg- matites, Schaller 51 indicates, for example, that graphic granite is virtually the sole constituent of some dikes and is abundant in most others, and that the graphic-granite pegmatites "have been affected but very little by replac- ing solutions ..." This statement is made despite the fact that he considers little material but the microcline in the graphic granite to have been formed by processes other than replacement. Composite Dikes Many of the Pala pegmatites are sub-parallel dikes that join with or branch from one another. As shown in plate 1, they are particularly common on Hiriart Moun- tain. Many do not actually join, but are separated by screens or partitions of wallrock 6 inches or less in thick- ness. Other juxtaposed dikes are in actual contact, either locally or for considerable distances along their strike, or dip, or in both directions (fig. 34). Their respective identities are preserved over the entire areas of contact, as shown by their individual internal structures, and by the presence here and, there of country-rock films between them. Still other dikes appear to mix, or merge with one another, generally at distances of several tens of feet from the points of junction. The composite nature of many dikes is reflected by repetitions of line rock or other units of aplitic rock 51 Schaller, W. T., op. cit., pp. 271-277, esp. p. 275, 1925. 29 within them, and by the slivers and seams of wallrock separating the individual elements of the .likes Repeti- tion of line rock and associated types is by no means a reliable criterion, however, as these units are in several zones in some pegmatites that plainly are not composite Scale in /eet Coarse anhedraZ quartz \^ / Perthite, dominantly euhedral Quartz - perthite -alblte-muscoviie ;,' T ,- 1 '-, interyrowth /^-V^*Zi^\ Oraphvo grxmite, suiihedral — Approximate boundary between, wall zone and core Fig. 10. Diagrammatic sketch showing typical relation between wall zone rich in graphic granite (outside the dashed line) and core seg- ment of quartz and euhedral perthite ; simply zoned pegmatite dike. Much more certain is the evidence of repeated zoning, such as the occurrence of cores or other inner zones at more than one consistent horizon within a given dike. Many of these dikes, as traced along the strike, split into two or more separate dikes, in each of which is preserved the internal structure of the corresponding part of the composite. Large composite dikes in the district include the Stewart, Pala Chief, San Pedro, Vanderburg, Katerina, and El Molino. In the vicinity of the Gem Star mine, the Stewart dike consists of at least three subparallel branches, or "splits," with intervening septa of gabbro. It is composite also where exposed in the main quarry of the Stewart mine. On the west wall of this quarry a layer of graphic granite 5 to 9 feet thick is overlain by a 5-foot zone of massive quartz with giant euhedral perthite crys- tals. It is underlain by a very thick zone rich in coarse, blocky perthite, and this unit in turn is underlain by rock similar to that overlying the graphic granite. A contact between two juxtaposed pegmatites is present within the graphic-granite mass, and careful inspection of the quarry face indicates the position of this contact along a thin layer of much finer-grained graphic granite. Line rock also is repeated at three different strati- graphic positions within the El Molino pegmatite in the vicinity of the main mine workings. Here two thin dikes lie above a much thicker one, and are separated from it in a down-dip direction by a distinct wedge of granodiorite. Along the outcrop, however, all three dikes are in direct contact for almost the full length of the mine area. 30 Special Report 7-A Another, very widespread type of composite pegma- tite body consists of sills and dikes of graphic granite and other perthite-rich pegmatite in much larger host masses of fine-grained, albite-rich pegmatite. They are particularly abundant on Hiriart Mountain. The masses of younger pegmatite range from thin stringers to sills as much as 8J feet thick. These younger elements of the composite masses are remarkably continuous along their strike. Some are single sills, others in groups or even swarms of subparallel sills. Most of them are simple aggre- gates of graphic granite, commonly with bladed biotite and muscovite, albite, and some garnet. Others, especially the larger ones, have symmetrical internal structure, with wall zones of graphic granite and inner zones of other very coarse-grained pegmatite. In several composite dikes, notably the Fargo on Hiriart Mountain, mining has been successfully carried on in such zoned masses, which are surrounded by earlier fine-grained granitoid rock. In a sense, the composite dikes are merely those in which fracture fillings of later pegmatite are present. Some of these fillings plainly have corroded the fracture walls. The distinction between fracture fillings that are basically minor parts of a single dike, on the one hand, and those that are separate intrusive elements in a com- posite dike, on the other, is necessarily an arbitrary one, as there are all gradations between the two extremes. Fio. mine 11. Euhedral crystals of perthite in massive quartz, Kl Molino . Note the narrow cavities at right-hand margin and lower right corner of large perthite crystal. Mineralogy General Features It is not the purpose of this report to discuss in full detail the minerals of the Pala pegmatites, nor to annotate the voluminous literature on this subject. Descriptions of some of the minerals have been recorded from time to j by time, 52 and much additional information obtained Waldemar T. Schaller awaits publication. The minerals noted and recorded from the Pala pegmatites are listed in table 3. Most abundant and wide- spread among them are albite, biotite, garnet, lepidolite, microcline and orthoclase (generally perthitic), mus- covite, quartz, spodumene, and tourmaline. The most common of the minor constituents are amblygonite, beryl, clay minerals, columbite-tantalite, and lithophilite and associated phosphate species. The relative abundance of the various minerals indicates that the pegmatites are truly granitic in composition, and that many are unusually rich in lithium. Other elements present in noteworthy quan- tities are beryllium, columbium and tantalum, manganese, and phosphorus, and in lesser quantities bismuth, fluorine, iron, caesium, and rubidium. Antimony, copper, and tin are rarer constituents of the pegmatites. The principal minerals of the pegmatites, quartz and potash feldspar, are supplemented in most parts of the district by several other species. Muscovite, albite, and garnet are present in all the pegmatites, and generally are widely scattered through each dike. The black variety of tourmaline, schorl, also is widespread. The gem varieties of tourmaline, though less common, are present in many dikes. Most of the pink tourmaline in the district is on Queen Mountain, where it is associated with blue and green varieties. Gem tourmaline is much less common farther east in the district, where most of it is green or yellow green. Spodumene is abundant in a few dikes, and is a much less common constituent of others. It seems to be rare or absent in most of the dikes west of the Stewart on Queen Mountain, but is exceptionally abundant in the Stewart dike. Large quantities of this mineral are present also in the Pala Chief and Vanderburg-Katerina peg- matites. In general, spodumene makes up a higher pro- portion of the dikes in the central and eastern parts of the district than in the western part. It is very rare in the pegmatites on Pala Mountain, south of the San Luis Rey River. The same generalizations apply to the known dis- tribution of the clear, gem variety of spodumene, and also to amblygonite and other lithium phosphate species. Lepidolite is a characteristic associate of both spod- umene and tourmaline, but is more widely distributed than either of these minerals. It is common in the peg- matites on Queen Mountain, where most of the gem tour- maline mines have been developed, and is found also in the spodumene-bearing pegmatites of Chief Mountain and Hiriart Mountain. Beryl also is widespread, but seems to be more abundant in the central and eastern parts of 52 See for example : Kunz, G. F., Gems, jewelers' materials, and ornamental stones of California: California State Min. Bur. Bull. 37, pp. 46-101, 1905. Murdoch, Joseph, Crystallography of hureaulite : Am. Mineral- ogist, vol. 28, pp. 19-24, 1943. Schaller, W. T., Spodumene from San Diego County, California : California Univ. Dept. Geol. Sci. Bull., vol. 3, pp. 265-275, 1903. Schaller, W. T., Notes on some California minerals : Am. Jour. Sci., 4th ser., vol. 17, pp. 191-194, 1904. Schaller, W. T., Mineralogical notes : U. S. Geol. Survey Bull. 262, pp. 121-122, 139-140, 143-144, 1905. Schaller, W. T., Bismuth ochers from San Diego County, Cali- fornia : Am. Chem. Soc. Jour., vol. 33, pp. 162-166, 1911. Schaller, VV. T., Notes on purpurite and heterosite: U. S. Geol. Survey Bull. 490, pp. 72-79, 1911. Schaller, W. T., New manganese phosphates from the gem tour- maline field of southern California: Washington Acad. Sci., Jour., vol. 2, pp. 143-145, 1912. Sterrett, D. B., Tourmaline from San Diego County, California : Am. Jour. Sci., 4th ser., vol. 17, pp. 459-465, 1904. Pegmatites of the Pala District 31 Table 3. List of minerals in pegmatites of the Pala district (observed by present writers except where otherwise noted! Mineral Albite.. Amblygonite Andalusite Apatite Arsenopy rite Bavenite Bertrandite Beryl Aquamarine Cat's eye Common Golden Goshenite Morganite Beyerite Bioti te Bismite Bismuth Bismuthinite Bismutite Bornite Cassiterite Chalcedony Chalcocite Chrysocolla Clay minerals Endellite Halloysite Kaolinite Montmorillonite Columbite-tantalite Cookeite Epidote Garnet Andradite Grossularite (essonite) Spessartite Helvite Hematite and goethite Heterosite. _ Hureaulite. _. Lepidolite Lithiophilite Loellingite Magnetite Malachite Manganese oxides Manganite Psilomelane Manganotantalite Microcline Microlite Molybdenite Monazite Muscovite _. Oligoclase Opal Orthoclase Palaite Petalite Phenakite Pollucite b Pucherite c Purpurite Pyrite Quartz Salmonsite Sericite Sicklerite Siderite Spinel _ Gahnite Hercynite Pleonaste Spodumene Common Hiddenite Kunzite Triphane Stewartite Stibiotantalite Strengite Topaz Pegmatites on Queen Mountain Pegmatites on Hiriart Mountain Pegmatites on Chief Mountain and elsewhere Mineral Tourmaline Achroite, Emeralite, Indicolite, Rubellitc, Schorl Triphylite Triplite Vivianite Zeolite minerals Heulandite, Laumontite, Stilbite Zinnwaldite Pegmatites on Queen Mountain Pegmatites on Hiriart Mountain Chief Mountain and elsewhere * Very rare. x Not common xx Common, or abundant in at least one pegmatite. X Abundant and widespread. Not observed. ■ Reported by Clifford Krondel in Mineralogy of the oxides and carbonates of bis- muth: Am. Mineralogist, vol. 28, pp. 532-533, 1943. b Reported by Adolpli I'abst in Minerals of California: California State Dlv. Mines, Bull 113. p. 229, 1938. c Reported by W. T. Schaller in Bismutb ochers from San Diego County, California: Am. Chem. Soc. Jour., vol. 33, pp. 162-166. 1911. * — Very rare; x — not common; xx — common, or abundant in at least one pegmatite; X — abundant and widespread; — not observed. the district than elsewhere. Common beryl is locally abundant in the Stewart dike. The minor accessory constituents are sporadic, but in general are more abundant in the complex, multi-zoned pegmatites than elsewhere. The greatest variety and bulk of accessory mineral material have been obtained from such pegmatites as the Stewart, Pala Chief, and Vander- burg-Katerina. The Tourmaline King, Tourmaline Queen, Anita, Senpe, and El Molino pegmatites also have yielded notable quantities of the relatively rare minerals. Fig. 12. Coar.se perthite and quartz. Perthite crystals are fringed with aggregates of muscovite and albite. Schorl crystals are large. Principal Minerals Microcline and Orthoclase. Microcline, the most abundant mineral in the Pala pegmatites, occurs as white, gray, and tan crystals that range from about \ inch to 8 feet in maximum dimension. These crystals arc anhedral tosubhedral in coarse-grained aggregates of graphic gran- ite or in finer-grained quartz-perthite-muscovite-albite pegmatite, and euhedral in most very coarse grained varie- ties of pegmatite. The lighter-colored crystals are especi- ally common in the outer parts of the pegmatites. In 32 Special Report 7-A Fig. 13. Coarse-grained quartz-spodumene pegmatite exposed in wall of low room, Pala Chief mine. general they occupy the full thickness of only those dikes that contain no inner units of very coarse-grained peg- matite or pocket pegmatite. The gray varieties, many of them of very dark shade, are typical of cores and inter- mediate zones that consist of very coarse-grained pegma- tite other than graphic granite. They are most abundant in those dikes that have a very complex internal structure. Nearly all of the microcline contains perthitic inter- growths of albite and albite-oligoclase as subparallel blebs and plates ordinarily less than 1 millimeter thick and 1 centimeter long. Some very thin plates, however, are much longer than this. In general the largest plagioclase indi- viduals are in the coarsest host crystals of microcline, and hence are most common in the inner zones of the pegma- tites. The plagioclase of the perthite also shows a system- atic variation in composition, becoming progressively more sodic from the walls of the pegmatite inward. Orthoclase and microcline are widespread constit- uents of the pocket zones in the pegmatites, where they generally form large, equant crystals with well-developed faces. They are known among miners and mineral collec- tors in the district as pocket spar crystals. They are \ inch to at least 15 inches in diameter, and their faces are char- acteristically flat and meet in sharp lines. Many of the crystals are transparent, and others are white to light- gray. All are coarsely perthitic. The crystal faces are com- monly corroded to depths of \ inch, and the intergrown plagioclase, evidently much more resistant to corrosion than the host potash feldspar, stands out on such surfaces as narrow, sharp ridges. Many of these corroded surfaces are marked bv thin films of iron oxide. The orthoclase is intimately associated with perthite, and is more abundant than the perthite in the pocket pegmatite of some dikes. In general, however, the ortho- clase constitutes only a small fraction of the total potash feldspar within the dikes as a whole. Thin-sections of most orthoclase crystals show irregular patches with the typical gridiron twinning of microcline. In testing the theory that inversion of orthoclase to microcline is commonly caused by strains set up during the grinding of a thin-section, Donnelly 53 prepared several sections by various means, but found no significant variations in the proportion of triclinie feldspar. On the other hand, he did find the typical gridiron twinning of microcline to be more com- mon in thin-sections than in crushed fragments obtained from the same specimen. Many of the pocket spar crystals of perthitic ortho- clase are coated with glassy, transparent, nonperthitic microcline, and the two potash feldspars 54 are in essential crystallographic continuity. Most of these coatings are less than \ inch thick. Like the host crystals of orthoclase, many are deeply corroded. Quartz. Quartz is in virtually all of the pegmatite units, and evidently was formed during all general stages of pegmatite development. It is present as spindles, rods, and other elongate masses in graphic granite, and is a ma- jor constituent of line rock, of other fine-grained alhite- rich types, and of the fine- to coarse-grained aggregates of 53 Donnelly, M. G., The lithia pegmatites of Pala and Mesa Grande, San Diego County, California : California Inst, of Technology, unpublished Ph.D. thesis, pp. 68-70, 1935. 54 Throughout these studies, orthoclase and microcline were dis- tinguished under the microscope on the basis of extinction with respect to the (001) and (010) cleavage traces. Pegmatites of the Pala District 33 albite, muscovite, tourmaline, and other minerals. It forms large groups of very coarse, anhedral crystals in coarse- grained pegmatite of various types. It fills fractures, form- ing veinlike masses in potash feldspar and other minerals, and, finally, it occurs in pocket pegmatite as crystals with well-developed faces. The quartz is milky white to light-gray, but both smoky, and clear, colorless varieties are in the interior parts of many dikes. Its coarsest form is as anhedral crystals 6 inches to at least 6 feet in diameter, and in some pockets as well-formed prismatic crystals that range in length from an inch to as much as 3 feet. Many of them are distinctly smoky. The anhedral crystals are distin- guished by rhombohedral cleavage and coarse, lamellar twinning. Individual lamellae are 0.5 millimeter to 10 millimeters thick. Much of this quartz is separated into crystallographic zones by groups of growth lines and roughly planar aggregates of finely divided impurities. A few appear to be phantom crystals without the outer crys- tal faces. Albite. Albite is very abundant in the pegmatites, both as fine-grained, sugary, crystalline aggregates (Abgo-97) and as parallel or radiating groups of coarse cleavelandite crystals (Abo4-99)- The fine-grained variety of albite is lustrous and white, and is most abundant in line rock and related aplitic units. It is common also in fine- to coarse-grained aggregates of quartz, muscovite, and schorl that are interstitial to graphic granite or to pegmatite composed of coarse euhedral perthite in massive quartz. Much sugary albite occurs along fractures and cleav- age cracks in potash feldspar, and pseudomorphs of albite after such feldspar are not uncommon. Some pseudo- morphs of sugary albite appear to have been formed after graphic granite, through selective replacement of potash feldspar by plagioclase. Most of the quartz rods are residua, and show their original orientation and much of their original shape. A great deal of attention has been devoted to this type of evidence by W. T. Schaller, who has used it to demonstrate large-scale albitization of graphic granite. Fine-grained albite occurs also as perthitic spindles and plates in coarse microcline and orthoclase crystals. Cleavelandite is generally present in cores and other inner units of the pegmatites, and is locally very abun- dant. Most of it is white, but pale apple'green and some bluish varieties are not uncommon. The platy crystals are | inch to as much as 3 inches long, | inch to 2\ inches wide, and 1/32 to | inch thick. Many of them are curved or warped, and others are flat, with broadly curving ends. The mineral is characteristically twinned, and shows very thin lamellae. All varieties of the plagioclase generally form aggre- gates that, where relatively free from other minerals, crumble when struck with a hammer. The coarse albite is present chiefly along fractures in quartz, perthite, spodumene, and other relatively early minerals ; along contacts between such minerals, especially spodumene and quartz; as irregular aggregates with quartz and muscovite ; and as cavity linings in pocket pegmatite. Where it is distributed along fractures or mineral contacts, individual crystals tend to lie with their broad surfaces perpendicular to these planar features. Elsewhere they form sheaflike or rosettelike aggregates. PIG. 14. Matrix specimen from richest gem-bearing part of dike, Pala Chief mine Jihort J*"^ «*»^^™SE/. *88S r ' ght> " cleavelandite and quartz. Large crystals and aggregates of lepidohte flakes at left. Photo by courtesy o; mo 34 Special Report 7-A Beautifully formed groups of coarse cleavelandite blades commonly fringe crystals of quartz, potash feldspar, spodumene, and muscovite in the pocket-rich parts of the pegmatites. Miens. Muscovite is present in all the pegmatites, and is a common constituent of most of them. It is scattered through the line rock and related granulitic types as white to very pale green flakes and foils that rarely exceed 1 millimeter in diameter. Similar thin crystals occur locally in graphic granite and other coarse-grained, perthite-rich pegmatite. Individual crystal plates range in diameter from 0.2 millimeter to 3 millimeters. Much coarser plates are present in aggregates of quartz, albite, and tourmaline that are interstitial to large crystals or crystal groups of graphic granite, perthite, or coarse, anhedral quartz with perthite crystals. The inner parts of many pegmatites contain very coarse-grained muscovite, which is characteristically associated with albite and quartz. The crystals, or books, are well formed in pocket pegmatite, and attain diameters of several inches with thicknesses of as much as an inch. Average dimensions, however, are approximately | inch and i inch, respectively. The mineral characteristically ranges from yellowish green to dull, pale to deep green, and is generally marked by ruling and herringbone struc- ture. Some books are so severely marred by fine, closely spaced crenulations that they appear silvery white and opaque. Many contain inclusions of green to very dark blue-green tourmaline, and some are fringed with lepido- lite. The lithia mica ordinarily is crystallographically continuous with muscovite, so that the two minerals form zoned crystals with pink margins and green centers. Some have intermediate zones that are yellow to white. Muscovite occurs also in the inner pegmatite units as nearly pure aggregates of |-inch to |-inch plates. Most of these aggregates are 3 inches to about 6 feet in maxi- mum dimension. Locally they contain quartz, albite, and scattered prisms of green or black tourmaline. Some of these aggregates fill fractures in other minerals, especially in coarse, anhedral quartz. Tabular to equidimensional masses of extremely fine- grained muscovite occur in a few pegmatites. Some of these masses are distinctly podlike. The mica is very pale green, and is generally so fine-grained that it has a waxy appearance. The aggregates, which are rarely greater than 4 inches in maximum dimension, are most abundant along fractures or at fracture intersections. Biotite is a common, but quantitatively minor min- eral in the outer parts of nearly all the pegmatites. It is typically associated with muscovite, both in graphic granite and in the fine-grained rocks that are so abundant in the footwall parts of the dikes. Individual plates and blades of this mineral generally range from ^ inch to 4 inches in diameter or length. All are very thin, and most of them form mere "skims" in the host rock. Some are slightly altered, and are stained with iron oxides. The biotite occurs as isolated crystals, as dense aggre- gates of small foils, and as subparallel to radiating groups or sprays of broader and thinner crystals. In many places individual crystals transect the quartz rods in graphic granite and also boundaries between mineral grains, and clearly were formed along fractures. Elsewhere they are intergrown with other minerals as if they had crystallized with them. Much of the bladed biotite near the hanging- wall contacts of the dikes is oriented normal or nearly normal to these contacts. Possibly much of this biotite was developed as a result of reaction between pegmatite solutions and the gabbroic country rock. Lepidolite is one of the most characteristic pocket minerals. Where best developed, it forms compact aggre- gates of thick flakes and plates 2 millimeters or less in diameter. These aggregates are present as lenses and pods less than a foot thick in most pegmatites, but in others, notably the Stewart, they are 10 to 15 feet thick and many tens of feet long. They range in color from pale rose to deep lilac or even purple. The coarsest flakes ordinarily are lightest in color, whereas most of the purplish aggregates are extremely fine-grained, with a waxy appearance. Although most masses of fine-grained lepidolite are in the innermost parts of the pegmatites, some markedly tabular aggregates of this mica and albite, quartz, and tourmaline fill fractures in the graphic granite and coarse-grained quartz-perthite units of several pegma- tites. Excellent exposures are in the hanging-wall parts of the Tourmaline King, Tourmaline Queen, and Stewart dikes. Pig. 15. Fine-grained granitoid rocks. Boulder with exposed face nearly perpendicular to garnet-rich layering. Note variations in thick- ness, sharpness, and spacing of layers. South side of Hiriart Mountain. Coarse-grained lepidolite occurs only in the typical pocket pegmatite, where it is most commonly associated with muscovite, albite, quartz, and lithia tourmaline. Most individual crystals are \ inch to 2 inches in diameter, with thicknesses of I inch to 1£ inches. Many are tightly intergrown in a manner similar to the much smaller indi- viduals in the compact aggregates described above. In contrast, some aggregates of lepidolite and cleavelandite are markedly cellular, with numerous irregular voids | inch to f inch in diameter. Elsewhere these two min- erals occur as well-formed crystals that line clay-filled cavities. Plates of lepidolite commonly are attached to earlier crystals or crystal aggregates of cleavelandite and quartz. The lithia mica forms the outer parts also of com- posite muscovite-lepidolite crystals, as already noted. Garnet. Of the several kinds of garnet in the peg- matites, an iron-bearing representative of the manganese- aluminum variety, spessartite, is the most widespread. It forms dodecahedral and trapezohedral crystals that range PEfiMATITKS OF THE PALA DISTRICT 35 Fig. 16. Fine-grained granitoid rocks. Boulder with exposed face nearly parallel to garnet-rich layering. Unusual patterns formed by undulations in layers. South side of Hiriart Mountain. in diameter from 0.1 millimeter to as much as 3 milli- meters. Most crystals are salmon pink to brownish-red in color. They are particularly abundant in the line rock, but are also widely scattered through the other types of fine-grained, albite-rich pegmatite, and through graphic granite and other coarse-grained perthite-rich units. Their distribution appears to be regular only in the line rock. Many of these garnets are slightly altered, and are coated with stains of manganese oxide ; where the altera- tion has been unusually intense, large masses of line rock are stained. Spessartite is present also in the innermost pegma- tite units as well-formed crystals as much as an inch in diameter. Some of these crystals are clear and free from cracks and other imperfections. Most of them, however, are marred by fractures and alteration, in general to a greater degree than the smaller crystals near the walls of the dikes. Most of the crystals with diameters greater than half an inch are so severely fractured that they crumble readily to a brown grit. In contrast, some pocket garnet occurs as flattened inclusions in muscovite, and is commonly pure and unaltered. These crystals are too small to be of use as gem material. Grossularite (essonite), the calcium-aluminum gar- net, is much less abundant in the Pala pegmatites than in those of the Ramona and other southern California districts. A manganesian variety occurs sparingly in the pocket-bearing parts of the Tourmaline King, Stewart, Douglass, and several dikes on Hiriart Mountain, chiefly as well-faced crystals ■£$ inch to £ inch in diameter. These crystals are dodecahedrons and trapezohedrons of excep- tionally attractive honey-yellow to orange-brown color. Most of them are attached to crystals of quartz or cleave- landite. A manganese-bearing variety of andradite, the cal- cium-iron garnet, is a rare constituent of the border zones of several of the pegmatites adjacent to gabbroic country rock, and the mineral may have been derived in part from digested wallrock material. This garnet forms very small crystals of deep-red color, and is generally associ- ated with biotite. Tourmaline. Many varieties of tourmaline are pres- ent in the pegmatites. Schorl, the deep black iron tourma- line, is the most abundant, forming both the characteris- tically striated prisms and columnar aggregates, or bundles of rodlike crystals. The mineral appears lustrous and black in hand specimen, blue to deep violet under the microscope. Some of the crystals are shattered and somewhat chalky, apparently in part because of altera- tion. Many are fractured, especially in a direction parallel to the base, and some of these fractures have been healed with quartz, albite, or aggregates of these minerals and mica. A few broken crystals of schorl have been rece- mented with finer-grained black tourmaline. The schorl is most abundant in the upper parts of a given pegmatite, and the crystals generally increase in number and coarseness from the hanging-wall contact downward toward the horizon of the pocket zone. Excep- tionally rich concentrations occur immediately above pockets in many dikes, and very coarse, well-formed crys- tals are present in most of the pockets themselves. The footwall parts of the pegmatites also contain this mineral chiefly as numerous small crystals that are rather uni- formly scattered through the fine-grained, aplitic units. Such tourmaline-bearing granulite forms much of the lowermost part of the Stewart dike. The schorl is scattered as pencil-like crystals through the perthite-rich pegmatite of the wall zones and outer intermediate zones of many dikes, and in places forms swarms of such crystals. Elsewhere the crystals are nearly parallel, and appear to have developed normal to contacts with the wallrock, to contacts between minerals, or to fractures. The schorl occurs also as sprays and rosettes, some of very large size. Several crude rosettes in the Stewart dike are 7 feet in diameter, and somewhat similar large radial aggregates are found in the Tourmaline King, Tourmaline Queen, and Pala Chief pegmatites. Most of the schorl is associated with muscovite, albite, and quartz, and commonly forms fine- to medium-grained aggregates that are interstitial to much coarser crystals or crystal groups of graphic granite, perthite, or, rarely, anhedral quartz. Graphic intergrowths of quartz and schorl are abundant in places, but rarely form masses greater than 6 inches in maximum dimension. Fig 17. Sharply lavered line rock flanked on lift by massive quartz with euhedral perthite and on ri^ht by flne-grained rock without prominent layering. Garnet-rich layers are Irregular. South side or Hiriart Mountain. 36 Special Report 7-A Other varieties of tourmaline in the Pala pegmatites comprise the medium- to deep-blue indieolite, the pink to pale-red rubellite, the green emeralite, and the colorless achroite. Nearly all intermediate colors, tints, and shades occur also, with only the brown types not well represented. Two or more colors are commonly present in a single crystal, and either are disposed in random fashion or are arranged systematically. Some bicolored and multicolored crystals of prismatic habit are characterized by a concen- tric, or layerlike zoning with respect to their long axes. Deep-blue to black cores with single, double, or triple rims that are colorless, green, blue, or pink are most common, but many other combinations occur. "Water- melon tourmaline ' ' is one attractive type in which an outer rim of green surrounds a colorless layer, and both these layers enclose a pink core. Some pink crystals of excep- tional quality are veneered with a thin black or very dark- blue rim. A different type of color zoning characterizes other crystals, which contain two or more contrasting layers that lie perpendicular or nearly perpendicular to their long axes. Many of these crystals are green on one end and pink on the other, and many others grade from black to green or pink, or even from black to colorless. Nearly all combinations are known, and some crystals show five or more alternations of colors in their length. More than one type of color zoning in a single crystal is not uncommon, especially where schorl is involved. The end of the crystal nearest the pegmatite wall is ordinarily black; the color changes to pink, green, or other alkali-bearing types as the crystal is traced toward its other end. The black material commonly persists farther in this direction in the interior of the crystal than in its outer parts, so that part of the crystal contains a black core and a lighter-colored rim. It should be emphasized that there are numerous exceptions to this generalization, and that many pink- cored crystals, for example, have deep blue or even black rims. The colors in some zoned crystals are very sharply bounded from one another, whereas in others they appear to merge very gradually. In most of them, however, the colors intergrade within distances of 2 millimeters or less. The crystals are rather consistently prismatic, and occur as isolated individuals, as columnar composites, as parallel or radiating groups, and as jackstrawlike aggre- gates. Some blue and pink aggregates of very fine-grained tourmaline form irregular masses in the pocket bearing parts of many pegmatites. They appear to be feltlike, and are very pure. Some crystals are so closely spaced that they form the principal constituent of the rock, but most of them represent less than 5 percent of the pegmatite unit in question. Individuals vary considerably in size, ranging from tiny needles to single prisms 6 inches in diameter and at least 4 feet long. Most of them are less than an inch in diameter and 4 inches long. The crystals are commonly fresh and lustrous, and many are clear. The chief Haws are fractures, cavities, and inclusions, many of which are so small and closely spaced that they appear as a cloudiness or milkiness in the min- eral. Sonic larger fractures are clearly healed with quartz oi- finer-grained aggregates of other tourmaline. Much of the tourmaline is opaque or otherwise of poor quality because of alteration, rather than the presence of mechan- ical imperfections. This alteration is most pronounced in the pink and colorless varieties, in which it causes a pro- gressive decrease in hardness and toughness, loss of luster and transparency, and an increasingly clayey appearance. All stages of this alteration are well shown in the Stewart dike, especially in the underground workings of the Stewart and Gem Star mines. A little of the schorl and nearly all of the other tour- maline occur in pocket pegmatite. They are most abundant in the central parts of the dikes, where they commonly form handsome crystals. They occur also in fracture fill- ings and fracture-controlled replacement bodies, espe- cially in the upper parts of the thickest dikes. The rubel- lite is associated with quartz, cleavelandite, pocket perth- ite, muscovite, and especially with lepidolite. In the Stewart dike crystals of nearly fresh to thoroughly altered pink tourmaline form rosettes in fine-grained lepidolite, and this attractive lepidolite-tourmaline rock has been displayed in museums the world over. Fig. 18. Line rock (top) adjacent to very coarse-grained aggregate of perthite and graphic granite. Note cleavage reflections from large crystals. At bottom is fine-grained quartz-albite-perthite-muscovite pegmatite with less sharply developed layering. South side of Hiriart Mountain. The emeralite, or green tourmaline, is generally asso- ciated with quartz, cleavelandite, and other pocket min- erals, and in many places occurs as inclusions in coarse books of muscovite. It is the most common alkali tour- maline in the fracture-filling and replacement units in perthite-rich pegmatite. The blue and colorless varieties are generally present in the pocket-bearing parts of the pegmatites, and are most abundant in and adjacent to concentrations of lepidolite. Spodumene. Most of the spodumene in the Pala pegmatites has formed as very coarse, lath-shaped crys- tals. In general they are white to gray, and are opaque. Where fresh, they have a nearly pearly luster, but in most exposures they are sufficiently altered to appear dull and even earthy. Individual crystals are as much as 14 inches wide and 9 feet long, but the average dimensions are more nearly 3 inches and 2 feet, respectively. Few are thicker than 2 inches, and in most of them this dimen- sion is less than 1 inch. They are deeply striated in a direc- tion parallel to their elongation. Many crystals are twinned, with the twin planes parallel to their flat sides. Pegmatites op the Pala District :i7 The coarse variety of spodumene almost everywhere occurs with quartz that is also very coarse grained, and aggregates of these two minerals are especially well devel- oped in the Stewart, Pala Chief, and Vanderburg-Kat- erina dikes. Common associates are cleavelandite, musco- vite, and lepidolite. Many of the spodumene crystals are thoroughly altered to white, gray, tan, or pink clay pseu- domorphs. Much of the clay is halloysite, but some is montmorillonite and other species. There are all stages of alteration between nearly fresh spodumene and clay masses with no residuum of the original mineral. A very small proportion of the spodumene is unal- tered, and appears as attractive transparent crystals and crystal fragments. Much of this material is the pale pink to deep bluish-lilac variety kunzite, much is the colorless to yellowish triphane, and a little is the green hiddenite. Some of it is color-zoned, generally with lilac centers and colorless to green rims that are thicker at the ends of the crystals than along their sides. Most of the clear spodu- mene occurs as deeply etched cleavage fragments marked by striations and by triangular pits. These features have been described in detail by Schaller. 55 A little of the clear material forms complete or nearly complete crystals which are typically lathlike in the deposits on Chief Mountain, but are shorter and thicker in many of the deposits on Hiriart Mountain. The kunzite, hiddenite, and triphane are plainly varieties of spodumene that escaped the alteration described above. Many specimens recently obtained from the Pala Chief and Katerina mines show clear spodumene as cleavage-bounded remnants within individual host crystals of partly altered spodumene. All these remnants have the same crystallographic orientation within a given host crystal, and there can be no doubt that they repre- sent those parts of the crystal that were not altered. Most of the clear spodumene fragments are less than 2 inches long, but there are some noteworthy exceptions. A few crystals of gem quality, recovered from the Pala Chief, Vanderburg, and Katerina mines, were at least 15 inches long and weighed 16 to 27 ounces. Several of them yielded flawless cut stones weighing 75 to 250 carats. The gem spodumene occurs within the cores of the pegmatites, generally in a very coarse-grained quartz- spodumene unit. The unaltered or only partly altered crystals are most common along the margins of these innermost zones in at least two pegmatites, but in most others the quartz-spodumene unit is so thin that such details of distribution are of little practical significance. Most of the crystals, whether partly altered or not, are embedded in the quartz, or, locally, in aggregates of quartz, cleavelandite, and micas. The fragments of clear material are characteristically surrounded by white to deep-pink clay, some of which is stained black by man- ganese oxides. Most of the clay appears to have been derived from adjacent spodumene rather than from feld- spars or other aluminum-bearing minerals. Other Minerals Beryllium Minerals. Several kinds of beryl (beryl- lium aluminum silicate) are present in the Pala pegma- tites. Perhaps best known are the alkali-rich varieties in the pocket pegmatite of such dikes as the Tourmaline •"» Schaller, W. T., Spodumene from San Diego County, Cali- fornia : California Univ., Dept. Geol. Sci., Bull., vol. 3, pp. 265-275, 1903. King, Tourmaline Queen. Pala Chief, Senpe, and Vander- burg-Katerina. They are the white to colorless goshenite and the pale-rose to peach-colored morganite. The crystals are equant to tabular, with sharply defined faces. They range from ^ inch to 6 inches in maximum dimension, with an average of 24 inches or slightly less. Many crystals are fairly simple tablets with small prism anil broad basal faces, but most are marked by numerous modifying faces, some of which do not differ greatly in orientation from the base. Groups of complex crystals in parallel growth are common, and where the mineral is clear these aggregates are especially attractive. The white to pinkish beryl is generally associated with cleave- landite, muscovite, lepidolite, and quartz, and in places with spodumene and tourmaline. Pale blue-green, moderately deep-blue, yellow-green, and golden beryl occurs in the quartz-rich cores of several pegmatites, chiefly as equant to prismatic crystals 3 inches or less in diameter. They are commonly well- formed, with sharply defined prism, pyramid, and basal faces, but some crystals are rough and subhedral. Most of them are milky or otherwise marred by inclusions and structural imperfections, but a few are clear. The sub- hedral crystals commonly appear sugary, owing to numerous closely spaced fractures. Some of the smaller, well-formed crystals are markedly chatoyant, and yield excellent cat's eye stones when cut. This core beryl is not particularly abundant in any pegmatite, but is locally common in the central parts of the Stewart, El Molino, and several other dikes. It is gen- erally associated with albite, and in places with muscovite. In the Katerina, El Molino, Pala Chief, and San Pedro mines it occurs with pinkish beryl, and a few crystals con- tain greenish cores and pinkish rims. The distribution of the colors suggests true crystallographic zoning. Irregular masses of gray, yellow-green, and pale- green beryl, generally without obvious crystal form, are locally abundant in very coarse-grained units of the Stewart, San Pedro, and Vanderburg-Katerina pegma- tites. In general this type of beryl is nearer the walls of the dikes than either of the types already described, and it is typically a constituent of quartz-blocky perthite in- termediate zones. The crystals are as much as 14 inches in maximum dimension, although most are less than 5 inches. They are opaque, and ordinarily are marred by numerous fractures. Many of those that are gray or green- ish gray are not easily distinguished from some types of quartz "and feldspar in the pegmatites, although they have a characteristic greasy luster. Still another variety of beryl is also anhedral, and occurs with graphic granite, muscovite. and locally with albite in the outermost parts of several pegmatites, not- ably the Stewart, Pala Chief, and El Molino. It is not abundant, although it is so difficult to recognize that it may well have escaped attention at many places. It forms irregular masses of white to medium-gray color which rarely exceed an inch in maximum dimension. So far as can be ascertained on the basis of refractive-index deter- minations and a few chemical analyses, this type of beryl contains the highest proportion of BeO and the lowest proportion of alkalies, as compared with other types in the pegmatites. The pocket beryl, in contrast, has the high- est indices of refraction and contains the highest pro- portion of alkalies, notably sodium and caesium. The beryl 38 Special Report 7-A formed in the cores and intermediate zones is intermedi- ate in composition between these two extremes. The decrease in beryllium-oxide content of beryl from the walls of the dikes inward is compatible with the findings of geologists working in several pegmatite districts else- where in the United States. Bavenite, a hydrous beryllium-calcium-aluminum silicate, forms clusters of small, radiating prismatic crys- tals, and is a very rare pocket constituent of the Pala Chief pegmatite. The crystals are white to colorless, and resemble those described from the Mesa Grande district by Schaller and Fairchild. 50 It is sporadically distributed on the sides and ends of beryl crystals, and also surrounds small ragged masses of beryl. Evidently it was derived from the beryl by alteration. Scale m feet Very coarse grained, massive quartz _. , , , ,— f— Very coarse qrawecL quartz iviifi /nterrneduzie zone || el ^ sdnd perihUe Wall zone | rj L -)rJ | ^* ( 2 ( «™f»^ border zone Fine- grained graphu: granite Fig. 19. Idealized sections of simply zoned pegmatite dikes in Pala district. Small, tabular crystals of white to light-gray ber- trandite, a hydrous beryllium silicate, show similar rela- tions with respect to beryl. The bertrandite occurs in the Pala Chief and Katerina mines. In at least one specimen from the east end of the Pala Chief open cut, an aggregate of the crystals is a pseudomorph after a very small tablet of beryl, and elsewhere similar aggregates line cavities in corroded crystals of white to pink beryl. Most of the bertrandite crystals are less than 1 millimeter long. Phenakite, beryllium silicate, is a rare constituent of the Vanderburg-Katerina dikes. It forms both flat, colorless crystals with sharply defined faces, and sub- hedral masses that are distinctly milky. It is associated with very small crystals of white to pale-blue topaz, and both minerals are attached to the exposed edges of large cleavelandite aggregates in the pocket pegmatite. None M Schaller, W. T., and Fairchild, J. G., Bavenite, a beryllium mineral, pseudomorphou.s after beryl, from California : Am. Mineral- ogist, vol. 17, pp. 409-422, 1932. of the phenakite crystals exceeds \ inch in maximum dimension. Three tiny crystals of bertrandite were in a small cavity in one phenakite-cleavelandite specimen from the main workings of the Katerina mine. Helvite, a silicate-sulfide of beryllium, manganese, iron, and zinc, is an exceedingly rare constituent of the pegmatite in the Gem Star and Katerina mines. It forms small, honey-colored tetrahedral crystals that are less than 1 millimeter in diameter. They occur on the surfaces of cleavelandite and spodumene crystals, and in general are typical of the pocket-bearing parts of the dikes. Bismuth Minerals. Several bismuth minerals are present in the quartz-rich cores of pegmatites in all parts of the district, but constitute an almost negligible part of the pegmatite material as a whole. In the Stewart mine, an irregular mass of native bismuth weighing more than 100 pounds was encountered in the underground work- ings not far from the West adit. The principal associated minerals were quartz, spodumene, and amblygonite. Ac- cording to Kunz, 57 the bismuth occurred as long, irregular crystals, and as platy crystalline masses as much as 12 or 15 millimeters long. One crystal an inch long was re- ported. Minor quantities of native bismuth occur also in the innermost zones of the Tourmaline King, Pala Chief, and Vanderburg-Katerina pegmatites, chiefly in asso- ciation with quartz, albite, and lepidolite. It generally forms small scales and foils, which are typically pinkish to silvery on freshly broken surfaces. Fibrous gray bismuthinite, bismuth sulfide, is asso- ciated with bismuth in the Stewart and Katerina mines, and with bismutite in the Pala Chief, Margarita, and El Molino workings. The bismuth and bismutite probably have been formed at least in part by alteration of the bis- muthinite. Bismite (bismuth oxide), pucherite (bismuth vana- date), and possibly a bismuth hydroxide form earthy, gray to yellowish-orange coatings on fractures in quartz, bis- muth, and bismuthinite, especially in the Tourmaline King, Tourmaline Queen, Stewart, Pala Chief, and Van- derburg-Katerina pegmatites. "Where individually recog- nizable the pucherite forms minute platy to needlelike crys- tals of gray to yellow-brown color. The bismite in some places has formed very small, tabular crystals, but in gen- eral occurs as a crystalline powder. Bismutite, a bismuth carbonate, is probably the most widespread of the bismuth-bearing minerals. It fills frac- tures in bismuth and bismuthinite, and evidently was formed by the oxidation of these minerals. A few masses of bismutite contain cores of unaltered gray bismuthinite. The carbonate ranges in color from gray through canary yellow to pale orange yellow, and its luster is character- istically dull. It forms thin smears, veinlets, and some nodular masses as much as 2 inches in diameter, and is particularly widespread in the quartz-rich pegmatite of the Katerina mine. Beyerite, a calcium-bismuth carbonate first described by Frondel, 58 forms gray-green to yellow-gray earthy coatings on fracture surfaces in the quartz of the Stewart and Katerina pegmatites. In many specimens it is inti- mately mixed with bismutite, and the two minerals are not readily distinguishable. 57 Kunz, G. F., Native bismuth and bismite from Pala, California : Am. Jour. Sci., 4th ser., vol. 16, pp. 398-399, 1903. 58 Frondel, Clifford, Mineralogy of the oxides and carbonates of bismuth : Am. Mineralogist, vol. 28, pp. 532-533, 1943. Pegmatites of the Pala District 39 Clay Minerals. Clay minerals occur in all the Pala pegmatites, and appear to have been developed in two dis- tinctly different ways. Minerals of the kaolinite group, formed by the weathering of feldspars, are widespread in the near-surface parts of the dikes. They coat feldspar crystals and fractures within them, and also fill larger, more continuous fractures that are traceable for several feet or even tens of feet along their strike. Some of this supergene clay is stained with iron oxides that presumably were derived from weathering of mafic minerals in the overlying gabbroic rocks. Much of this iron-stained clay has been mistaken by mineral collectors and even by some miners for the hypogene pocket clay that characteris- tically encloses the gem minerals in the pegmatites. Several species of clay minerals in the pegmatites ap- pear to be much older, and to have formed under hypogene conditions. This mode of origin is shown by the independ- ence of their distribution with respect to the present sur- face, to postulated older erosion surfaces, to weathered and unweathered parts of the dikes, and to post-dike frac- tures. Moreover, they are associated with unaltered pyrite and other sulfide minerals, and consistently occur with tourmaline, cleavelandite, and other typical pocket min- erals. These clays include representatives of both the montmorillonite and kaolinite groups, and have been dis- cussed briefly by Ross and Hendricks. 59 Individual species thus far noted comprise endellite, halloysite, kaolinite, and montmorillonite. To most of the miners in the district these minerals are known collectively as pocket clay. They are most abundant in the pocket-bearing parts of the dikes, where they commonly form the matrix in which the gem crystals occur. They are earthy to waxy where pure, but in most places are distinctly gritty because of numerous small, angular fragments of quartz and other minerals. They range in color from white and light-gray through yellow- ish and pinkish to raspberry red and bright reddish- brown. Most of the clay is distinctly pinkish, and some is marked by irregular white splotches. In places the clay minerals are stained along irregular fractures by man- ganese oxides. Much of the white and pinkish clay occurs as pseudo- morphs after spodumene. Also derived from spodumene are dense, butter-colored types of endellite and halloysite that are known locally as ' ' turkey-fat clay. ' ' Pale to deep pink clay minerals also were formed by the alteration of tourmaline, and abundant pink to brownish clays by the alteration of feldspars. Not only do they form pseudo- morphs after these minerals where alteration has been complete, but they occur in fractures and shear zones that transect partly altered crystals, as well as large masses of the pegmatite itself. These clays also line cavities formed by the selective corrosion and solution of the quartz rods in graphic granite. Columbium-T ant alum Minerals. Members of the co- lumbite-tantalite series (iron-manganese columbate-tanta- late) are widespread minor constituents of the pegmatites, and are locally abundant in the central parts of the Stew- art and Vanderburg-Katerina dikes. Most common is fer- rocolumbite, in which the iron :manganese ratio is greater than 4 :1 and the columbium :tantalum ratio is greater than 3 :1. This mineral forms tabular crystals, generally 58 Ross, C. S., and Hendricks, S. B., Minerals of the montmoril- lonite group: U. S. Geol. Survey Prof. Paper 205-B, pp. 25-28, 34, 69-70, 1945. no more than $ inch thick and 1 inch by 1 inch in plan. The principal faces of most of the crystals are flat, but some very thin and broad crystals are markedly curved. Many of these platy individuals are ,V ; inch or less in thickness and as much as 4 inches in maximum dimension. They commonly occur in radiating groups. A few crystals are more equant, and appear as subhedral to euhedral "chunks" £ inch to 6 inches in diameter, with an average of about an inch. L -I ' J ■jV- 1 L l 1 r r r ' r i" i -i L n r ij n r j l ' l "I l "I r r- J -i r L ' Ln - n n J l -i -iJL_r_j j ■_] ; I L r .Jl-T i-i V*< *»»»"• ?~:<- a V— -J r T-i r - ■-—-LrLlQ J'r J rj L -i r J L rj -f"r n L l -, r j r jf Iff , r -Jr "ir I'.'Ail Inner zones - i.-;> — i very coarse < grained |c^x~| J° ^ 1 Wall zone Borxier zone 1 L"I|_TJ| 1 ■ 1 Scale in feet Quartz- spodumene pegmatite flassive guariz Massive quark? with euhedral perthite Block/ perthite Coarse-io very coarse grained graphic granite Flne-aramed graphic granite Fig. 20. Idealized sections of pegmatite dikes in the Pala district, showing typical relations of intermediate zones and cores. The columbite is dull black on crystal faces, but has a bright submetallic luster on freshly broken surfaces. In contrast to this is manganotantalite, a closely associ- ated species found in the Katerina and very sparingly in several other mines. This mineral forms rather thickly tabular crystals with slightly brownish outer surfaces and a distinctly resinous, splintery appearance on freshly broken surfaces. It is very rich in manganese, and has a high ratio of tantalum to columbium. Both the columbite and the manganotantalite are in the cores and other inner units of the pegmatites They are characteristically associated with quartz, less com- monly with cleavelandite and sugary albite. Many of them are coated with fine flakes and scales of yellowish muscovite. 40 Special Report 7-A Fig. 21. Quartz-spodumene pegmatite in wall and back of large room, Stewart mine. This unit is overlain by massive quartz (dark, at top), and is underlain by quartz-cleavelandite-perthite-muscovite pegmatite (at top and below level of man's head). Massive lepidolite ore at lower right. Two crystals of stibiotantalite, antimony tantalate- columbate, were observed in the Katerina mine, where they were in close association with coarse-grained cleave- landite, quartz, orthoclase, and colorless to pinkish beryl. The crystals were near several clusters of manganotanta- lite tablets, which they resembled in color and luster. In contrast, however, the antimony mineral showed a per- fect cleavage. Numerous other brownish crystals of tantalum-bearing minerals were tested for antimony, but all were found to be ordinary manganota'ntalite. Small crystals of pale honey-yellow to very dark microlite, essentially a tantalate of calcium, are present in pocket aggregates of quartz, lepidolite, muscovite, albite, and tourmaline, but are known from only two pegmatites, the Tourmaline King and the Stewart. The crystals are octahedral and dodecahedral, with maximum dimensions that rarely exceed 1/16 inch. Lithia Micas. In addition to muscovite, biotite, and lepidolite the pegmatites also contain cookeite, hydrous lithium-aluminum silicate. It is a rather widespread pocket species, and ordinarily forms a coating on crystals and crystal aggregates of quartz, lepidolite, spodumene, albite, and orthoclase. It forms white, buff -colored, and very pale pink aggregates of small plates and flakes. It is most common in some of the gem-bearing parts of the Tourmaline King, Tourmaline Queen, Stewart, Pala Chief, and Vanderburg-Katerina dikes. Zinnwaldite, the lithium-iron mica, is very sparingly present in several pegmatites as dark-gray to deep reddish brown crystals and flakes. It resembles phlogopite in having a bronzelike luster. Most of the crystals are stubby prisms \ inch in maximum length. They are only in the pocket-bearing parts of the pegmatites, where they are most commonly associated with quartz, cleavelandite, and beryl. Phosphate Minerals. Amblygonite, lithium-alum- inum fluo-phosphate, is a common constituent of the spo- il umene-bearing pegmatites, especially those on Hiriart Mountain and in the south part of the Stewart dike. Ordi- narily it forms subhedral to anhedral crystals \ inch to at least IS inches in diameter. Larger individuals commonly appear as subrounded or nodular masses. Many crystals are single, but others are grouped in ovoid to discoidal aggregates several feet or even tens of feet in diameter. The largest of these aggregates, encountered in the under- ground workings of the Stewart mine, was nearly 40 feet long, 2 to 15 feet wide, and 16 feet in maximum thickness. This was exceptional, however, and few of the other aggre- gates in the district exceed 3 feet in maximum dimension. Most of the amblygonite is white and bluish white, and has a typical pearly luster. Cleavage surfaces of the coarse crystals are broadly curved, and in many places are markedly uneven in detail. Most of the masses are cut by irregular networks of fractures and zones of shattering that are 1/32 inch to \ inch wide. The broken material is "healed" with fine-grained, sugary ambly- gonite of pale green to pale blue color. Both individual crystals and the larger crystal aggregates typically occur in massive quartz, but are also associated with albite, lepidolite, muscovite, and spodumene. In a few dikes the amblygonite is in readily distinguishable zones of very coarse-grained pegmatite, composed of quartz and some spodumene. These units characteristically occur along the outer margins of quartz cores, or of quartz-spodumene cores. Associated with the spodumene and amblygonite in the inner parts of many pegmatites are lithiophilite, lithium-manganese phosphate, and triphylite, lithium-iron phosphate. These minerals form equant to thickly tabular crystals with rough but well-defined faces. They occur both singly and in clusters of as many as a dozen crystals. Most of them are so stained by manganese oxides that they appear as black blotches on the walls of the mine workings, and in this respect they resemble the spessar- tite garnet so common in many other pegmatite districts. Individual crystals are \ inch to 17 inches in maxi- mum dimension, with an average of about 4 inches in the pegmatites where they are most abundant. Where fresh, the triphylite is bluish gray, and the much more abundant lithiophilite ranges from flesh colored through pinkish tan to light reddish-brown. Unaltered and only partly altered lithiophilite is fairly abundant, especially in the Stewart dike, but nearly all the triphylite in the pegma- tites has been converted to other, secondary phosphate minerals. The lithiophilite and triphylite are most common in the outer parts of the quartz-spodumene zones and quartz- spodumene-amblygonite zones, and in the inner parts of adjacent perthite-bearing zones of very coarse grain size. They are well exposed in the backs of several drifts and stopes in the Stewart mine, where they occur chiefly in coarse quartz-perthite pegmatite. Although this particu- lar unit lies 5 feet to 20 feet or more above the lepidolite- rich rock that was mined, successive rock falls in some of the larger openings during the past two decades have re- vealed the presence of these phosphate minerals in greater quantities than were apparent during the periods of active operations. Lithiophilite is far more abundant than triphy- lite in the pegmatites on Queen and Hiriart Mountains, but triphylite may be dominant in the Pala Chief and in at least one other dike on Chief Mountain. Both minerals occur sparingly as small crystals in the central parts of a few dikes that do not appear to contain spodumene oi amblygonite. Chief among these dikes are the Tourmaline King, White Cloud, and Tourmaline Queen. Of particular interest to mineralogists is a group oi rare manganese and iron phosphate minerals in severa' of the pegmatites, notably the Stewart, Pala Chief, anc Vanderburg-Katerina. Most of these minerals were f ormec directly or indirectly from lithiophilite and triphylite Pegmatites of the Pala District 41 and pseudomorphs, fracture-filling relations, and other evidence of their secondary origin are widespread. Pro- gressive alteration of the two primary minerals first yielded sicklerite, iron-manganese-lithium phosphate, and then, accompanied by loss of lithium, yielded purpurite and heterosite, iron-manganese phosphates. Hydration of the lithiophilite and triphylite, and locally of the sickler- ite, resulted in development of stewartite, hureaulite, and palaite as a much later result of replacement of pre-existing graphic granite bv soda-rich solutions. The fine-grained, albite-rich rocks are clearly younger than some graphic granite, but are older than the stringers, lenses, and small pods of later graphic "•ranite in them. Wherever the line rock or associated aplitic material is in contact with the main masses of graphic granite that constitute much of a given dike, and the age relations of the rocks can be determined', the graphic granite is the older of the two. ( )n the other hand, the pocket pegmatite is distinctly younger than some aplitic units, as offshoots from masses of such pegmatite transect these finer-grained rocks. The fine-grained granitoid rocks form masses whose shape and distribution generally do not conform to the structure of the pegmatite zones. The zonal structure is the older, and the fine-grained mats appear to have been superimposed upon it, particularly in its footwall parts; they cut across the ends of the concentric units in the bulges of some irregular dikes, and are not oriented in accord with the zonal structure of many other dikes. These features, together with the occurrences of graphic granite residual in the line rock and associated fine- grained types, may mean that many, if not all, of these rocks were derived from graphic granite by replacement processes. Schaller 70 has accumulated widespread evi- dence for the existence in these rocks of not only graphic granite residua, but unreplaced aggregates of quartz rods in a matrix of sugary albite, quartz, and muscovite. Evi- dence thus far obtained during the present investigations does not seem to warrant definite conclusions, but if Schaller 's views are correct, the fine-grained granitoid rocks must have been formed prior to the development of the pocket pegmatite in the dikes, presumably by solu- tions introduced from sources at considerable distances from the areas of replacement. ECONOMIC FEATURES OF THE PEGMATITE MINERALS Lithium Minerals Lepidolite Lepidolite was once used mainly as a source of lithium salts, but during the past three decades the ceramic in- dustry has absorbed the bulk of domestic production. The mineral is used directly in the manufacture of glass, as it not only is an excellent fluxing material, but it in- creases the luster, weather resistance, electrical resistance, and strength of the product. More important, it reduces the coefficient of expansion, thus making the -lass more resistant to thermal shock. Lithium glasses are in great demand for high-pressure i>. 1-17, 1948. depth of its color. Facet-cut stones were marketed at prices of $4.00 to $30.00 per carat, with a probable average cost of not more than $8.00 per carat. Prices gradually dropped during later years, until cut kunzite of top quality was, sold for as little as $5.00 per carat in the middle 30 's. More recently, however, the popularity of gem spodumene has again increased, and current prices for good rough material average about $15.00 per ounce. Facet-cut stones are sold for $2.00 to more than $40.00 per carat, and most flawless stones are priced at $15.00 or more per carat. Gem spodumene ordinarily is facet cut, for maximum brilliance, and most stones are cut very deep, so that the strongest possible color is obtained. The mineral is markedly pleochroic, and the deepest colors are seen when the stones are viewed parallel to the long axis of the crys- tal. Thus the limiting factor for size of top-quality cut stones is the thickness of the bladelike or rodlike source crystals. For optimum color and brilliance, such stones are cut with their tables nearly but not exactly perpen- dicular to the long axes of the crystals. The mineral is not an easy one to prepare as a gem, because of its two direc- tions of perfect cleavage and its consequent tendency to break near the edges during cutting. Very careful sawing of the original gem blanks, however, ordinarily eliminates much of the objectionable chipping and "napping off" during subsequent grinding and polishing. Gem spodu- mene is fairly soft, and when subjected to hard usage its edges gradually lose their sharpness and its facets become somewhat dimmed. The color of some stones fades upon prolonged exposure to sunlight. This is most serious with the green, lavender, and pale-purple to bluish varieties, but the colors of most lilac, pink, and yellow stones appear to be very nearly permanent. Exposure to a source of strong X-rays changes the color of spodumene to an intense light green, but the mineral reverts to its original color when exposed to sunlight. 72 The green color appears to last indefinitely if the mineral is kept in darkness. Gem spodu- mene is thermoluminescent and possibly triboluminescent. It is strongly phosphorescent when exposed to X-rays, ultraviolet rays, radioactive emanations, and high-tension electric currents. The rough crystals of clear spodumene are blade-, lath-, or rod-shaped, and nearly all are deeply striated, grooved, and etch-pitted. Some are twinned, with the twin planes parallel to their flat faces. Multiple twinning, in- volving five or more planes in a single crystal, is known but is not common. In most cut stones the twinning does not appear to be objectionable, and few of the twin planes are visible upon even the most careful scrutiny. Most crys- tals are less than 2 inches long, but some are at least 15 inches long and weigh 24 to 27 ounces. The short, thick crystals, characteristic of several pegmatites on Hiriart Mountain, yield relatively large cut stones, some of which weigh more than 200 carats. Many kunzite crystals are attached to quartz, and most of those that have not been removed from the clay matrix in which they are commonly enclosed are clearly unaltered remnants of larger crystals, which in turn are typical of the coarse, jackstrawlike aggregates of spodu- mene in massive quartz or other minerals. The gem mate- rial thus appears to represent spodumene that is indigen- ous to some of the inner pegmatite zones. 7 - Pough, F. H., and Rogers, T. H., Experiments in X-ray irradi- ation of gem stones : Am. Mineralogist, vol. :i2, pp. :j4-:;r>, l!i47. DIVISION OF AMNIOS SPECIAL REP< iRT 7-A, PLATE I J' 1 3 n i >-.... is* I'ii ""n ._ , COLOR-ZONED CRYSTALS OF GEM TOURMALINE Pala and Mesa Grande districts. Natural size. Don M. George Jr. collection, California Institute. ol I log: 1 i «»»- gp» U~ a) c K.C — u 1 - 3 - i-= /. i ca — - = J - — ■■«■ < j= - I i "■ - = "" mmj - - - A 1 g3§ • '/. A '_ _ _^ 'o -- - K _£ O C c ' 1 LI mS ® -x. /••_ = ■- »•= si K •_ o — - i i " " — DIVISION I IF .MIXES SPECIAL REPORT 7-A, PLATE 9 t£ '^B" jfiHSS'l ■ i3 "I ■▼ |DPW| SIM IDUMENE Facet-cut stones. Approximately 1 natural size. F. G. Mcintosh collection, California Institute ol Technology. DIVISION I IF AIIXKS SPECIAL REP< IR1 , \, PLATE 111 .1, FINE-GRAINEI i L,EPID< U.ITE This pinkish to lilac lepidolite is typical of the best material i btai I from the south ore body ol the Stewa rt mine. This lilac t Of the mate) /;. VERY PINE-GRAINE] o bluish lepidolite \\ ith albit and ah a e material obtained from the i h on bod o LEPIDOLITE ink li >ii li 1 1: i line i tj pica I he Stev art mini fc-Z,£'%'o£ iU I. r. " > rs ^ .. — — — - . — j. ■J eS C S Is 2 OS x * o -T X £z - -t '■'■ IS C • - < Pegmatites of the Pala District 49 Beryl Commercial beryl, which is used mainly in ceramics and as the principal source of beryllium metal and beryl- lium compounds, is so rare in the Pala pegmatites that its potential economic significance seems negligible. Gem beryl, on the other hand, is widespread, and has been re- covered during the mining of numerous pegmatites. It is a minor constituent of some pockets in which it occurs as colorless to white goshenite, blue aquamarine, and pale- pink to peach-colored morganite. The Pala beryl yields excellent cut stones. The mor- ganite is particularly attractive and in general has a peach color that is in marked contrast to the pure pink of the Brazilian morganite. Square, baguette, table, and various types of step-cut stones are most popular. Generally they are cut very deep, in order to preserve as much color of the rough material as possible. Most good crystals yield stones of beautiful transparency, and many are of perfect quality. Others, however, are marred by tiny feathers or by very fine tubular cavities. Quartz Clear quartz is abundant in the pocket-bearing parts of most pegmatites, where it commonly forms large crys- tals. Although they are by no means as attractive as some of the other gem minerals, these crystals have yielded ex- cellent cabochon and facet-cut stones. Colorless, smoky, milky, and rose-colored varieties have been used in this way. In addition, some crystals have been fashioned into polished spheres, and others have been carved. The pale- rose quartz in the cores of several dikes on Pala Mountain has been most popular for such use. A little of this mate- rial is sparsely rutilated. Some of the clear crystals of quartz appear to be of "radio grade," as they meet certain tolerances with re- spect to the amount and distribution of twinning, inclu- sions, gas bubbles, and other flaws. Such material is in considerable demand at present, and commands prices of 50 cents to nearly $40 per pound, depending mainly upon the size and grade of individual pieces. The usable crystals are cut into oscillator plates of specified thickness, and these plates are employed for frequency control in radio, telephone, and special electrical equipment. Qiiartz crys- tals were obtained for this purpose from the Senpe peg- matite during World War II, and small quantities of acceptable material were recovered from them by the Uni- versal Microphone Co. of Inglewood, California. Crystals in other mines also may be satisfactory, but the proportion of clear quartz reasonably free from twinning generally is too small to be of economic interest. Other Minerals Specimen minerals have constituted a significant proportion of the output from the mines of the Pala dis- trict, although few have been mined and sold commer- cially. Most of them have been obtained by mineral col- lectors, who have kept them in their own collections or have exchanged them for other minerals. Matrix specimens from pockets in the pegmatites have been most popular in this connection. They commonly include quartz, tour- maline, spodumene. orthoclase, clcavclandite, muscovite, lepidolite, and other, rarer minerals. In addition, speci- men material from the Stewart mine has achieved wide circulation, chiefly in the form of sprays of opaque but attractive pink tourmaline crystals in massive aggregates of fine-grained lilac to blue-gray lepidolite Some exceptionally fine crystals of gem minerals are valued too highly by their owners to be cut up into stones, and others, although of great value as specimens, do not contain enough unflawed gem material to warrant further treatment. An excellent example is the beautifully crystallized peach-colored beryl obtained during World War II from the Senpe mine, chiefly as a by-product from operations for clear quartz. Few of these beryl crystals contain enough clear material to yield cut stones of very large size, although there are some noteworthy exceptions. Also of considerable value are some rare min- erals, notably the crystals of lithium-bearing phosphates and their pseudomorphs in the Stewart pegmatite. Many of the dumps in the district have been worked and reworked for inadvertently discarded fragments of valuable minerals, and a few of the dumps at the better known mines have been screened as many as eight differ- ent times. Even so, it is possible to collect very small fragments of tourmaline, kunzite, and other gem mate- rial on the surfaces of many dumps after periods of heavy rains. The main dump at the recently reopened Katerina mine was the object of critical scrutiny by hundreds of amateur collectors during the period 1947-49. In connec- tion with guided trips through the mine, such persons have been permitted to collect material from the dump for a nominal fee. In addition to the lithium and gem minerals, a little ornamental and monumental stone has been obtained from the pegmatites at irregular intervals. The graphic granite yields rather attractive patterns on polished sur- faces, and has found favor for garden ornaments and, in rough form, for walls and other decorative structures. The line rock, especially garnet-rich types, has been used locally for fireplaces and monuments. A little quarrying of line rock boulders was done on the south face of Hiriart Mountain, not far from the Ashley Ranch house. MINING Prospecting and Mining Methods Nearly all the deposits of lepidolite and gem min- erals in the district were discovered through the tracing of float material to the source ledges. Loose fragments of lepidolite, tourmaline, and euhedral quartz, which were strewn on some slopes and in numerous gullies, were found to be particularly good indicators of pocket peg- matite higher on the hills. In a few places unusually rich concentrations of coarse, green muscovite flakes were traced to gem-bearing parts of nearby dikes. Rarely was it difficult to find or recognize the dikes themselves, even on the brushiest slopes. Their riblike or bouldery outcrops and their prevailingly light color distinguish them from the adjacent gabbroic rock. The pocket-bearing parts of the dikes formed good outcrops in some places, and yielded concentrations of quartz-rich float in others, but the spodumene-bearing parts of the dikes were nowhere well exposed. Tims most discoveries of kunzite in place were essentially happy accidents involved in the development of the pegmatites for other minerals. Prospecting of the pegmatites themselves was done by means of small open cuts and shallow pits, and in a few places the full width of the Stewart dike was exposed .-)() Special Report 7-A by means of shallow trenches. Most of these prospect open- ings are now obscured by dense growths of brush and by slumped material and other rock debris. Some of the holes were enlarged to form irregular bench-like cuts, and others were extended underground. Where the edges of the dikes were well exposed, as on the east side of Chief Mountain, exploratory drifts were driven along the parts of the pegmatites considered most favorable for pros- pecting. Few of them are longer than 100 feet. Inclines were developed for the same purpose in other dikes, especially on the east slopes of Hiriart and Queen Moun- tains. On most ridges and westerly slopes, in contrast, the prospecting was largely confined to surface openings. Whenever the results of preliminary excavations ap- peared to justify mining operations, open-cut work was carried on as long as the amount of barren overburden was not too great. The largest cuts of this type are those at the Stewart mine, and cuts and groups of cuts with maximum dimensions of 100 feet or more form parts of the Tourmaline King, Tourmaline Queen, Pala Chief, San Pedro, Senpe, Vanderburg, and El Molino mines. Underground work was done mainly from drifts and inclines of gentle to moderate slope. The workings commonly were interconnected, especially in the largest mines. Some represent series of irregular sloping tunnels and rooms between drifts, like those of the Tourmaline King, Tourmaline Queen, and parts of the Stewart mine, whereas others are unsystematic networks of both inclined and level openings. The few shafts sunk in the district were prospect holes or were used for mine ventilation. In four places with favorable topographic situation, efforts were made to tap lower parts of pegmatites by driving adits through the country rock, but none of these workings was con- tinued far enough to accomplish its purpose. Most parts of the pegmatite dikes are hard and un- weathered, so that drilling and blasting were necessary in nearly all mining. The finer-grained, sugary parts of the dikes are particularly tough t and require consider- able effort in their removal. Most of the work was done by hand methods, and maximum advantage was taken of joints and other natural features in breaking up the rock. Compressed-air drilling and otherwise mechanized min- ing were typical only of some operations in the Stewart, Tourmaline King, and in one or two other mines. The softer parts of the pegmatites, particularly the quartz- spodumene units and gem-bearing pockets, were easily handled with pick and shovel in many places, and little blasting was required except in masses of lepidolite and albite-rich rock. The most effective tools for excavating the gem-bearing parts of the pegmatites were the screwdriver, chisel, small pick, bar, and hammer. Indiscriminate blast- ing ruined quantities of gem and specimen material in some mines before more careful methods of hand-tool excavation were worked out. Methods of handling the broken rock were generally very simple. The rock was loaded onto wheelbarrows, skips, or cars, and then lifted or trammed to the portal. Hand windlasses or mule-drawn whims were used for lifting at several mines. Much of the pegmatite in the Tourmaline King and Stewart mines was stoped and then carried by various combinations of tramming and chuting to the portals of lower-level adits. Most of the lepidolite and some of the gem material were sorted underground before tramming or between two stages of tramming, whereas most of the gem material was sorted from other constituents of the pocket pegmatite at the surface. Little timbering was required in most mines, and today surprisingly few of the underground workings are caved or otherwise inaccessible. In most places, single stulls or sets of timber sufficed to support the walls or backs of workings. A notable exception to this is the Stewart mine, where square-set timbers were found neces- sary in some haulage ways and ore passes. This was due in part to badly broken ground, and in part to the mining away of all but a few thin pillars in the lepidolite-rich parts of the pegmatite. Much of this timbering has col- lapsed since the mine was abandoned in 1928, in part be- cause no lagging was placed between it and the intricately fractured back of quartz-rich and spodumene-bearing varieties of pegmatite. The elements of all square sets were alined horizontally and vertically, rather than normal and parallel to the westward sloping pegmatite units, so that some timbering was collapsed by oblique stresses dur- ing large-scale caving. Near some mine portals, at places where the pegma- tite and wall rock are jointed, the weathered gabbroic country rock has caved. The backs of large rooms and other openings without adequate support have also caved, especially where the pegmatite is thoroughly fractured, as in parts of the Stewart and Katerina mines, or where it is cut by joints parallel to the hanging-wall contact, as in the Tourmaline King and Tourmaline Queen mines. In places, caving has progressively removed slabs of hanging- wall pegmatite, and part of the overlying gabbro. Ground water is no problem in the mines, even in the deepest workings. Indeed, it was necessary to haul water into nearly all workings during periods of active mining. Production The recorded annual production of lepidolite and clear spodumene, tourmaline, and other gem minerals from the Pala district during the period 1900-47 is shown in table 5. The total reported output of lepidolite and amblygonite, 23,480 tons valued at $432,800, is undoubt- edly slightly lower than the actual, or combined reported and unreported totals, but is probably substantially cor- rect. The average value of this output was about $18.40 per ton, which probably is slightly lower than the national average for the same period. This fact might be in part attributable to the low grade of the material that was shipped, but in part also reflects production during periods when competition from other domestic deposits was keen. Most of the other deposits are more favorably situated with respect to centers of demand, and some of them have yielded material of higher lithium content. The total recorded production of gem tourmaline, 2,980 pounds valued at $154,500, is incomplete in terms of both quantity and value. Production figures without data on value are available for two years, and value data without corresponding figures on quantity are listed for ten years. The total output comprises both rough gem material and some crystals of little but specimen value. Different mine owners and operators reported their pro- duction in terms of different kinds of material, so that figures for different properties — and even for the district as a whole during different years — have little comparative value. Probably more than two-thirds of the tourmaline Pegmatites op the Pala District 51 production listed in table 5 represents rough gem material. The retail value of such material, in the form of its ultimate yield of cut gem stones, is approximately five times this figure. The data on gem spodumene probably constitute a reasonably complete record of the formal production from the district. Most of the material was obtained from the Pala Chief mine, but some was produced from other parts of the district, particularly from mines on Hiriart Moun- tain. The total yield, 1,325 pounds of rough gem crystals and crystal fragments, was valued at $152,900 or at an average of approximately $115 per pound. The produc- tion figures mean little in terms of year-to-year compari- sons, as much of the spodumene was sold several years or even a decade or more after it was mined. In most instances the value figures are based upon calculation, using the price schedules that were current at the time the material was obtained from the ground. The information on production of other gem materi- als from the district, chiefly quartz and beryl, is far from complete, and the figures undoubtedly represent fairly small fractions of the actual formal production. Also, there is no means of determining the total quantity and value of specimen material taken from the district, although the figures must be large. The total value of all gem material for which there is a record of production from the Pala district is at least $319,200. This amount is less than the value of the lepido- lite taken from the Stewart pegmatite, and is considerably less than the $2,000,000 reported for all recorded pegma- tite-gem production in southern California. All figures for the output of gem material represent only those totals for which there is a written record, and hence they must be minimum figures only. Only incomplete records of production are available for some of the mines, and no records at all are available for others, the operators of which either did not keep or did not release such data. Perhaps even more significant is the total of gem and specimen material removed from the pegmatites by amateur collectors, and — more important — by active high graders. These high graders include miners who withheld for personal use some of the output during regular mining operations, and individuals who carried on informal oper- ations of their own during periods when the mines were shut down. It is impossible to estimate accurately the total loss of gem material during the course of active mining in the district, but it must have been large. Also large has been the output of that picturesque group of energetic indi- viduals who have mined the pegmatites from time to time without benefit of definite agreements with the owners. In many instances these men were remarkably shrewd in their interpretations of the pegmatite structure and the probable positions of desirable pocket material, and there is little question that in some mines they obtained a considerably larger yield of usable material per unit of pegmatite handled than did the actual owners of the mines during more regular operations. In contrast to the high graders, the numerous amateur collectors who have been active in the district Table 5. Recorded production of lepidolite and gem minerals from Pala district, San Diego County, California, 1900-1947- Derived from records of the U. S. Geological Survey, U. S. Bureau of Mines, and the California State Division of Mines. Lepidolite Tourmaline Gem spodumene Other gem minerals Year Quantity (short tons) Value (dollars) Quantity (pounds average) Value (dollars) Quantity (pounds average) Value (dollars) Quantity (pounds average) Value (dollars) 1900 •, b l,200 1,400 '820 30 '780 •, =600 •50 NR NR NR NR •120 NR 30 NR 90 •70 880 4,110 800 10,080 700 670 NR 110 NR 40 500 400 NR NR •29,000 37,500 31,900 100 16,000 •9,500 •700 NR NR NR NR 2,000 NR 500 NR 1,400 •1.000 8,800 74,000 14,400 153,500 10,600 10,200 NR 2.200 NR 1,000 12,500 16,000 NR NR 500 NR NR NR NR •80 •50 80 115 80 140 120 20 60 140 50 65 30 30 NR NR NR NR NR 70 55 NR 20 30 10 10 70 NR NR NR NR •10,000 ■5,000 14,000 13,500 14,500 15,200 32,000 5,500 18,000 9,500 900 2,000 2,000 1,800 NR NR NR NR NR 2,300 600 NR 900 1 ,500 900 900 1,900 NR NR NR NR NR NR 1901 425 », ^JiT J "-in r T -, i ' J u-, LJ-iL r n L -| rj ltj r_, rj LI J L \ir L i l -, p -^ r Jn -, r\_ ~1 r J L ~\ rjLnfj-iLrjL^L r ^ J ^JJS^^^-M Scale feet , *ff X C Z.me rock layered fine-grained, albite-giuzrtz- perthite pegmatite Fine-grained aZbi£e - quartz - per thite pegmatite Very- coarse grained, quartz wiih euhedrat perthite | r j L ~| L-| Coarse - to very coarse grained graphic granite I Fine grained graphic granite Fig. 25. Idealized section of pegmatite dikes in the Pala district, showing typical relations of line rock and associated fine-grained rocks. feet. Shearing is well developed along the pegmatite- wallrock contacts in many places, and numerous closely spaced joints within the hanging-wall part of the dike also are parallel with these contacts. Where exposed in the main surface and underground workings, the pegmatite is rather consistently layered. Pegmatites or the Pala District 57 It ranges in thickness from about 10 feet.to as much as 18 feet, but in most places it is less than 15 feet. The dike is marked by rather gentle terracelike rolls, where the dip becomes less than 10° as traced for distances of 5 to 30 feet in a down-dip direction. These terraces are separated by much more steeply dipping segments. In addition, there are several much broader, more gentle rolls whose axes trend down the dip of the dike. From hanging wall to footwall, the dike is layered as follows : (1) A selvage of muscovite-perthite-quartz-albite pegmatite ranges in thickness from a knife edge to a maximum of 6 inches. This unit is best developed in the north half of the Main cut. In many places the muscovite occurs along fractures in fine-grained graphic granite, and also along the contact between the pegmatite and the gabbro. (2) Graphic granite constitutes most of the dike. It is medium- to coarse-grained, coarsening downward from the hanging- wall selvage. In many places the quartz rods tend to be oriented normal to the pegmatite-gabbro contact, but there are many exceptions. This rock is transected by fractures and i- to 0-inch fracture-controlled masses of muscovite and albite, with or without garnet and schorl. Most of the fractures are parallel to the hanging-wall con- tact of the dike. In some places in the graphic granite there are podlike to discoidal masses of closely intergrown quartz and muscovite, with some garnet and schorl ; they commonly form a relatively fine-grained groundmass in a mosaic of graphic granite crystals. (3) Scattered thin lenses of massive quartz with large euhedral crystals of perthite near the center of the dike are best exposed near the south end of the Main cur. Most of them are less than 10 feet long and 2 feet thick, but the original outcrop of the dike must have contained large segments of this unit. (4) Typical pocket pegmatite is in and immediately beneath the segments of quartz-perthite core. This rock contains abundant quartz, with associated albite, schorl, alkali tourmaline, lepidolite, and other pocket minerals. Such material is exposed for a distance of at least 100 feet along the present trace of the dike, but at no place is it thicker than about three feet. (5) Fine- to medium-grained albite-quartz-perthite pegmatite that contains plumose muscovite and local cleavelandite and schorl underlies the pocket-bearing rock. It may have been formed in part from coarse-grained graphic granite, remnants of which are scattered through it. Much of the muscovite forms thin, delicate sprays of plates 1 inch to 6 inches in maximum dimension. In a few places this rock contains as much as 10 percent schorl. (6) Very crudely layered, sugary, fine- to medium-grained albite-quartz-perthite-muscovite pegmatite forms the foot- wall part of the dike. In some places it is in contact with massive quartz or other inner-zone pegmatite, but else- where it is separated from the quartz by graphic granite or by coarse-grained albite-rich pegmatite. Locally this rock contains sharply defined garnet-rich layers similar to those in the typical line rock farther east in the district, but in most places it is considerably coarser, and has little or no planar structure. The layered and un- layered rock types grade into one another, both along and across the strike of the layering. In general the more homogeneous forms of the rock are richer in fine-grained schorl than the layered types. Much of the coarse, prismatic schorl in the lower part of the hanging-wall graphic-granite zone is clearly frac- ture controlled, as it extends outward from fractures or from planar positions that transect individual crystals and crystal aggregates of graphic granite. Much strip and blade biotite shows the same general relations with respect to the graphic granite and to the fine-grained footwall pegmatite (unit 6 above). Such mica is especially promi- nent where it lies normal to fractures, forming 1-inch to 6-inch stripes on the face of the Main cut. Within the pocket-bearing parts of the dike, some of the coarser crystals of green muscovite are rimmed by pink to lilac lepidolite. Such muscovite also contains abundant inclusions of clear green tourmaline. Sonic crystals of schorl above the pocket horizon extend down- ward into this unit, and most of them grade along their lengths into green, and some into pink tourmaline. The dike splits southward, and two dikes, separated by about 3 feet of gabbro, are poorly exposed in the lower, or south cut. The upper dike consists chiefly of coarse perthite, quartz, muscovite, schorl, and widespread garnet, and is 1£- to 4-feet thick. Although this dike is not well zoned, its central part contains irregular patches and stringers of lepidolite and other pocket minerals. The lower dike, nearly 20 feet thick, is much more sharply zoned, but does not contain abundant pocket material. About 9 feet of graphic granite forms the hang- ing-wall half of the pegmatite, and passes abruptly down- ward into fine- to medium-grained albite-quartz-perthite- muscovite pegmatite, which is crudely layered in places. This rock contains much fine-grained flake muscovite. Both muscovite and biotite are also locally abundant in the overlying graphic granite, particularly near the hanging-wall contact. In the central part of this dike are local discoidal to lenticular masses of quartz-perthite peg- matite, and along the footwalls of these masses are the only stringers of lepidolite observed in the dike. Numerous thin, highly irregular cavities occur in this central dis- continuous unit, particularly along or near contacts between the perthite and quartz. The Tourmaline Queen mine has an impressive rec- ord of production, and according to available reports, gem material was obtained from most parts of the sur- face and underground workings. The total output from the deposit is not known, but a series of sales of gem tour- maline amounting to $48,000 was recorded for one year. Most of this material was marketed to eastern consumers, chiefly Tiffany and Company and the American Gem and Pearl Company of New York City. Assessment work dur- ing recent years has been done in a short, gently sloping incline that lies south of the caved entrance to the old Main adit or incline. Numerous pockets were encountered during the course of this work. It seems likely that additional pocket -bearing ground is present in the pegmatite, not only in unmined areas that are surrounded by existing workings, but in parts of the dike down dip from the limits of the present under- ground workings. The gem-bearing part of the dike ap- pears to extend almost directly down the dip, with pos- sibly a slight component to the south. Most of the pockets appear to have been concentrated along the terracelike features in the pegmatite, and if additional flattenings of dip are encountered, the possibilities for further sub- stantial returns of gem material appear to be fairly good. The pegmatite exposed in the south cut probably docs not warrant much attention, as it is reported to become barren down the dip and to pinch out locally. Gem Star (Loughbaugh) Mine The Gem Star mine is in the thick Stewart dike, which crops out prominently on the cast slope of Queen Moun- tain. It can be reached by trail from the Stewart mine to 58 Special Report 7-A the south, from Salmons City to the north, and more directly from the road that adjoins Salmons Creek imme- diately to the east. The workings comprise several open cuts and appended inclines and drifts that are distributed along the pegmatite outcrop for a strike distance of about 500 feet. The mine was operated chiefly between 1905 and 1912 by a Mr. Loughbaugh, and during more recent years it has been worked intermittently by Francisco Moreno of Los Angeles. It is currently owned by Mr. Moreno. The past operations have yielded large quantities of crystal quartz and a little lepidolite and gem tourmaline. The pegmatite is a thick composite mass that ranges in outcrop breadth from 100 feet to about 150 feet. In most places it clearly consists of three distinct dikes, which are juxtaposed without intervening masses of country rock. As traced from north to south in the mine area, how- ever, the upper dike thins and is separated from the others Fig. 26. Composite pegmatite mass, east slope of Hiriart Mountain. The coarse-grained, lighter-colored pegmatite body is a sill (with some apophyses not shown in picture) in faintly layered, finer-grained albite-quartz-muscovite pegmatite. The coarser rock is rich in graphic granite, and contains local core segments of massive quartz and euhedral perthite (not in picture). by a thickening mass of gabbro. It pinches out entirely at the edge of the mine area. In most places the composite pegmatite mass trends north and dips westward at angles ranging from 20° to as much as 42°. Most of the mine workings are in the middle dike, which is 15 to 25 feet thick in most places. The principal opening in the north end of the mine area is a large, benchlike cut, known as the Whim cut, on the crest of an eastward sloping ridge. A 70-foot incline extends westward and leads to irregular drifts. North of these workings are two smaller cuts and appended short drifts, all of which are in pegmatite. South of the Main, or Whim workings is a series of shallow scratchings along a large clifflike exposure of pegmatite, and higher on the slope are two trenches excavated in the upper pegmatite. The openings from which most of the gem production was obtained are known as the Canyon workings, and lie at the south end of the mine area (pi. 34). They consist of two open cuts, from each of which branching tunnels ex- tend westward and southwestward. The largest, or more southerly cut yields access to drifts and short inclines at two levels. All the mine workings are in pegmatite that is rich in coarse graphic granite. This rock grades downward through a central coarse-grained schorl-rich unit into footwall pegmatite that is distinctly finer-grained and contains abundant albite, muscovite, and schorl. Most of the pocket material encountered in the Whim and nearby workings was beneath the coarse schorl-rich unit and within thin, discontinuous segments of massive quartz and of massive quartz with giant euhedral crystals of perthite. Little but quartz crystals was obtained. The discontinuous segments of quartz core and of perthite-bearing inter- mediate zone are chiefly in the upper dike, but some are present also in the middle dike. Where exposed in the vicinity of the Canyon work- ings, the two lower dikes are 32 to 40 feet in combined thickness. Both are markedly asymmetric, with relatively thick hanging-wall units of coarse graphic granite and much thinner footwall units of fine- to medium-grained albite-quartz-perthite-plumose muscovite pegmatite that contains local concentrations of schorl. Both pegmatite and country rock are cut by a cross fault that is well exposed along the southern edge of the open cut. The middle dike has a thin central unit of quartz- spodumene pegmatite, with accessory lepidolite, albite, and alkali tourmaline. The unit ranges in thickness from 1 inch or 2 inches to as much as 4 feet where exposed in the underground workings, and is characterized by an abundance of pale-pink to light-gray clay minerals. These and the other pocket minerals are scattered through the thin core of quartz-spodumene pegmatite. Above this unit, the graphic granite contains very coarse-grained schorl, which forms numerous sprays or radiating groups that point downward toward the pockets. The tourmaline in the pockets is fairly hard, although much of it is sufficiently altered to be opaque. Many clear fragments of small crystals are present in the dumps, and some clear, gem-quality crystals as much as 4 inches in diameter and 15 inches long were recovered. The chief associates of the tourmaline are crystalline pink to laven- der lepidolite, smoky quartz, apple-green albite, and very rare fragments of clear spodumene. All of these minerals are fringed or surrounded by pink clay. The pocket-bearing pegmatite is fairly continuous throughout the Canyon workings, and is well exposed in the face of the incline that extends southwestward from the northwest end of the drift. Additional material of this Pegmatites of the Pala District 59 sort probably remains to be mined, but the gem-bearing part of the dike is so thin and contains such a low propor- tion of unaltered, usable tourmaline that there might well be doubt as to the possible success of future mining opera- tions. The pegmatite exposed in the workings farther north appears to be virtually barren of commercially desirable minerals. Stewart Mine The Stewart mine, once the most important domestic source of lepidolite, is in the bulbous south part of the Stewart pegmatite, and lies on both sides of a prominent ridge that forms the southeastern corner of Queen Moun- tain (pi. 2). The pegmatite itself is traceable for half a mile along the east slope of the mountain, on which it appears as a well-defined riblike feature. The mine work- ings can be reached over a road that extends eastward from the Pala-Temecula road, and also over several trails that ascend the slopes to the south and east. Approximately 18 tons of lepidolite was taken from the deposit in 1892, the first year of mining, and the output was gradually increased during the following years. A substantial annual production was maintained from 1900 to 1907, when the price of lithium salts dropped as a result of the mining of amblygonite in the Black Hills of South Dakota. Most of the large-scale operations were conducted by the American Lithia and Chemical Company of New York. The mine was virtually idle until World War I. Maximum production was attained in 1920, after which mining activities dwindled, chiefly because of the develop- ment of the Harding lepidolite deposit in northern New Mexico. The National Industrial Chemical Corporation of New York worked the deposit for two or three years prior to its shutdown in 1928, and a little small-scale mining was done by several persons in the middle 30 's. In addition to lepidolite, the output from the deposit includes some gem tourmaline and white, pink, and golden beryl. The mine is owned by Mrs. W. H. Crane of Oceanside. Fig. 27. Thin prisms of schorl in medium-grained perthite-quartz- albite pegmatite, Gem Star mine, Queen Mountain. The deposit was first worked along its outcrop by open-cut methods, with progressive development of the Main cut and the much smaller North and South cuts. The largest exposed mass of lepidolite-rich pegmatite was fol- lowed westward from the Main cut by means of a curving drift, from the inner end of which a short incline was extended downward at a moderate angle. A branch adit, driven southwestward from the same cut, was connected with the Old Main adit at a point not far from its portal. Irregular stopes, some of roomlike proportions, were de- veloped from the inner part of the Main adit, and several drifts and low rooms were extended northwestward from points near the portal of the branch adit. The North adit was driven westward into the dike from a point below and east of the North cut, and an irregular exploratory adit was driven northwestward from a point near the Alvarado workings, in the south part of the mine area. A large mass of amblygonite was encountered in the innermost part of the workings from the Old Main adit in 1903, and soon thereafter these workings were connected with the west slope of the hill by means of the Old West adit. Several irregular stopes and rooms were excavated during the period 1902-05, as shown in plate 6. Another adit was driven northeastward from a point fairly low on the west slope of the hill during World War I, and this opening ultimately provided efficient haulage for lepido- lite recovered from the deposit during the most extensive operations in the wartime and postwar period. Extending eastward and northeastward from this adit and its prin- cipal branch drift is a complex series of irregular rooms and inclines, from which large quantities of high-grade lepidolite ore were recovered. During the middle 20 's and for a short period during the middle 30 's some lepidolite was removed from the North cut and from underground workings lower and to the southwest of this opening. These workings are connected with the surface by means of a steep incline and a vertical shaft. Other workings in the mine area, chiefly of an explor- atory nature, include open cuts in the hanging-wall part of the pegmatite dike low on the west slope of the hill, several small cuts along the pegmatite outcrop on the east side of the hill, a small open cut and 50-foot tunnel south- southeast of the Main adit, and a series of irregular shal- low cuts farther east. The last are known as the Alvarado workings. A long adit was driven westward in the foot- wall gabbro from a point beneath the main lepidolite out- crop on the east slope of the hill, but not far enough to Fig. 28. Schorl in gem-bearing central part of Tourmaline King dike. Irregular mass of crystalline lepidolite appears dark near lower right- hand corner. This schorl, also from Queen Mountain, Is coarser than that shown in figure 27. 60 Special Report 7-A Fig. 29. Fragments of gem-quality kunzite in altered crystals of spodumene, Katerina mine, Hiriart Mountain. penetrate the pegmatite dike. This work was done about 1900. It is reported that several winzes and inclines were sunk to points beneath the level of the Main adit during the middle 30 's, mainly in an effort to find extensions of the known lepidolite shoots or additional shoots. One of these lower-level workings has been broken through to the surface about 50 feet south of the Main entry. Nearly all of the underground workings are in haz- ardous condition, owing in part to caving from extensive unsupported backs of rooms, and in part to more local collapse of badly broken rock from the back, in a few places all the way to the surface. Although the high walls of the Main cut and part of the South cut were blasted down in the early 20 's to eliminate use of the old adits, access to the underground workings was still possible through two small openings near the face of the South cut until the fall of 1948. The Main entry, which was timbered for its entire length, is partly collapsed and no longer accessible, but most of the workings with which it was connected can now be reached through the Old West adit. Many of the oldest workings, dating to the period 1900-05, have been backfilled or have been choked with slumped material. Some of the early stopes north of the large am- blygonite stope near the West adit have completely col- lapsed, with formation of a large, quarrylike surface de- pression that is about 70 feet long and 25 to 35 feet wide. Nearly all of the workings connected with the North cut and the vertical shaft immediately south of this cut also are inaccessible or hazardous. Two principal bodies of lepidolite were mined in the surface and underground workings. One of them, which extended westward from the Main cut, was about 200 feet long and 20 to 110 feet wide. Its thickness ranged from a knife edge to at least 20 feet, and was about 10 feet through much of the mined portions. This lepidolite is gray and bluish-gray to deep-purple in color, and most of it contains albite and abundant prismatic crystals of rubellite. In contrast to this material is the lepidolite typi- cal of the other main ore body, which lies about 50 feet to the south. Most of this lepidolite rock is nearly pure, and only locally does it contain much albite and tourmaline. It is also characteristically coarser-grained and more red- dish to pinkish in color than the material in the north ore body. The south ore body, which was poorly exposed in the South cut and was really discovered during the course of later, underground operations, was approximately 200 feet long, 30 to 180 feet wide, and locally as much as 18 feet thick. It was mined largely during the 20 's. In some places the lepidolite bodies are sharply de- fined from the adjacent rock, and particularly from a large mass of quartz-rich pegmatite that lies between them. In many other places, notably at the north bulge of the north ore body, the lepidolite pegmatite grades into quartz-albite pegmatite with abundant stringers, lenses, Pegmatites of the Pala District 61 and irregular stockworks of lepidolite. Much material of this sort is exposed in the walls of the North cut and the appended underground workings. Additional masses of lepidolite pegmatite, some of them satellitic to the two main masses, are in several other parts of the mine area, but most of them are relatively small. The pegmatite body, which is at least 80 feet thick in much of the mine area, forms a steep-faced outcrop on the east side of the ridge, and appears as a very gentle to mod- erate dip slope of hanging-wall graphic granite over much of the west side of the hill. The contact between pegmatite and overlying gabbro passes beneath the surface in the bottom of a small canyon immediately west of the mine area. Much of the longitudinal section of the dike on the east face of the hill is obscured by dump material and other loose debris, so that the internal structure of the pegmatite is best observed underground. As indicated in the cross-section, the pegmatite com- prises many zones arranged in layers around a discon- tinuous quartz-spodumene zone in its central parts. The spodumene-bearing pegmatite forms lenslike masses as much as 150 feet long and 10 to 15 feet in maximum thick- ness. They are poorly exposed at the surface, but appear in the walls and backs of many of the underground open- ings. Relat ! vely thin lenses of massive quartz overlie the quartz-spoo umene core segments. This discontinuous in- ner intermediate zone thickens enormously beyond the edges of the core segments along the strike of the dike, and is at least 30 feet thick where exposed between the Main cut and North cut at the surface. Much more con- tinuous is a middle intermediate zone of massive quartz with large subhedral to euhedral crystals of perthite, which appears above the massive quartz unit. In a few places this zone consists almost wholly of perthite, with only local interstitial quartz, but elsewhere the quartz is dominant or the two minerals are in nearly equal propor- tions. Lithium-phosphate minerals are locally abundant in this unit. Overlying the middle intermediate zone is a 10- to 15- foot outer intermediate zone composed of coarse, blocky perthite, with some quartz, muscovite, and albite. This zone in turn is overlain in most places by the typical coarse-grained graphic granite (with subordinate albite and muscovite) of the thick hanging-wall zone. Both the graphic granite and other perthite-rich units contain much coarse, prismatic schorl, especially at distances of 15 feet to 25 feet beneath the hanging-wall contact of the dike. Thin but continuous fracture-controlled units of muscovite, albite, and green tourmaline are locally abun- dant. Beneath the quartz-spodumene pegmatite of the core in some places is the inner intermediate zone of massive quartz, and elsewhere are exposed the quartz-perthite pegmatite or the outer intermediate zone of coarse, blocky perthite. Much of the footwall part of the dike, however, consists of coarse-grained albite-quartz-muscovite pegma- tite and sugary, fine- to medium-grained albite-quartz- schorl-muscovite pegmatite. These rocks are not notably marked by any planar structure. Most of the lepidolite-rich pegmatite is in the foot- wall parts of the quartz-spodumene core, and may have been formed largely at the expense of this unit, remnants of which occur above and between the lepidolite lenses. Flanking the lenses themselves— and grading into them— are many masses of pegmatite that contain stringers and irregular networks of lepidolite. The relations among the zones in the hanging-wall part of the pegmatite are somewhat complicated in places by at least one other, much thinner, juxtaposed dike. This dike also is zoned, but its core appears to he quartz- perthite pegmatite analogous to the middle intermediate zone of the main dike. The two dikes split as traced to the south, although in most areas the upper one has been re- moved by erosion. The main dike itself splits in the vicinity of the Alvarado workings. One prong tapers out abruptly, but the other extends for some distance south- eastward down the ridge beyond the workings. No pegmatite is exposed at the surface south of the mine area, but the results of some diamond drilling done in 1903 suggest that pegmatite is present at depth. Too little is known of the relations in the few underground workings beneath the level of the Main adit to permit an estimate of the shape of the dike in a down-dip direc- tion. Several reports concerning the old workings indi- cate that a few septa of gabbro were encountered during the early stages of mining. Perhaps some of them repre- sent screens between individual pegmatite dikes, particu- larly where they were near the hanging-wall parts of the main composite mass. The large bodies of lepidolite-rich pegmatite are along or near a marked benchlike roll in the dike. In most parts of the mine area, this terrace lay between the rela- tively steeply dipping part of the pegmatite at the out- crop and another relatively steeply dipping segment in the lowermost part of the mine. Most of the lepidolite- rich masses taper out, or become markedly discontinuous as traced down their dips into this more steeply dipping part of the dike. Other large lenses of lepidolite-rich peg- matite may well be present in the dike, either north of the extensively stoped block of ground, or farther west and down the dip of the dike. The chances for such lenses in a down-dip direction probably would be enhanced mate- rially if the steeply dipping segment of the dike in the vicinity of the lowermost mine workings should flatten. This possibility might well be tested by means of diamond- drill holes collared at points west of the small canyon that bounds the dip slope of pegmatite. Exploratory work directed northwestward from the North cut failed to reveal additional masses of lepidolite, but such openings were not extended for great distances. The possibility that substantial quantities of lepidolite are north of the present underground workings also might be tested by means of diamond-drill holes. Although the two principal ore-bearing lenses are worked out, it is possible that there are other rich lenses of comparable size. Mission Mine The Mission mine, low on the south slope of Queen Mountain, is in a pegmatite dike that is crossed by the road to the Stewart mine (pi. 2). Both the mine workings and the dike are clearly visible from Pala, about a mile to the south-southwest. The deposit was worked between 1905 and 1925, but operations were intermittent and pro- duction never was large. The principal output was quartz crystals and some lepidolite, with a little tourmaline of gem quality. 62 Special Report 7-A The main mine workings are an open cut 20 by 35 feet in plan and an irregular 45-foot drift that extends northward from this cut. The drift is connected under- ground with another, slightly lower drift that was once reached from a cut immediately south of the road. This second drift is caved at the portal, but its outer part is accessible by means of a break-through immediately north of the road. Another open-cut lies along the trace of the pegmatite higher and to the northeast, and a fourth cut bounds the mine area on the southwest. An 85-foot tunnel, driven through gabbro in an unsuccessful effort to tap lower-level parts of the pegmatite dike, extends north- ward from a small cut in the southeastern part of the mine area. The dike is 2 to 11 feet thick, and has an average thickness of less than 6 feet. It trends north and dips 25° to 35° W., so that its trace is southwesterly down the steep hill slope. The pegmatite-wallrock contacts are sharp, but in some places are complicated by many irregu- larities. A septum of gabbro 3 inches to about 2 feet thick divides the dike into two parts where it is exposed in the main drifts, and similar but even smaller irregularities in the contacts are exposed elsewhere in the underground workings. In the face of the Main cut the hanging-wall gabbro is transected by several steeply dipping apophyses of pegmatite. They appear to follow well-defined frac- tures. Both the pegmatite and the country rock are cut by several faults of small displacement. The most prominent break is exposed in the heading of the main drift, where the dike appears to be cut off by a slip plane. Cross joints, some of them slickensided, are abundant in parts of the pegmatite, and are responsible for heavy ground in sev- eral of the workings. The internal structure of the dike is simple, and indi- vidual units are traceable for distances of at least 100 feet. The upper one-third to one-half of the dike is com- posed of typical coarse-grained graphic granite, and most of the lower part consists of very well-developed garnet- rich line rock. This unit resembles the line rock so com- mon on Hiriart Mountain, in that it contains abundant garnet in sharply defined layers. In most places, how- ever, it is slightly coarser-grained and its garnet-rich layers are slightly farther apart. The central part of the dike in the vicinity of the mine workings consists of medium- to coarse-grained albite- quartz-perthite-muscovite pegmatite, which is locally very rich in coarse-grained quartz. The albite and muscovite are later than the other constituents, and locally are plainly concentrated along fractures. In the best-exposed parts of the dike, this central unit appears to be a partly ablitized composite, which consists of graphic granite in its upper part and discontinuous segments of a quartz- perthite core beneath. Remnants of perthite and graphic- granite aggregates are common. In most places the domi- nant constituents of the unit are coarse-grained albite with some schorl, muscovite, and other late-stage minerals. Only a few concentrations of typical pocket minerals are present, however, and all of them are in the main under- ground workings. Lepidolite occurs as lenticular to stringerlike masses \ inch to 24 inches in maximum dimension. No well-defined gem-bearing unit was encountered during mining of this deposit, and the total production of lepidolite and gem minerals has been small. The mine does not seem to offer great promise for future recovery of these minerals. Pala Chief Mine The Pala Chief mine, not far from Chief Mountain summit, is about 2 miles northeast of Pala (pi. 2). It can be reached from that town over an ungraded road and approximately half a mile of trail. The principal surface workings, several interconnected benchlike open cuts, form a distinct scar along the southwest face of a nearly flat-topped ridge. They are clearly visible from most areas to the south and southwest. The mine was opened in 1903, and was operated most intensively during the following 15 years. Since that time, however, little but assessment work has been done. The pegmatite has yielded gem tourmaline, quartz, beryl, and lepidolite, but undoubtedly it is best known as the world's foremost source of gem spodumene. Most of the material produced was kunzite and triphane, but some green and some colorless material also were included in the output. The property was first located by Frank A. Salmons and associates of Pala, and is now owned by the Salmons Estate, of which Monta J. Moore of Pala is administrator. The Main open cut, or series of cuts, is 280 feet long and 20 to about 65 feet wide. In places the excavation is 25 feet deep at the face, but in most of the mine area this dimension is not more than 15 feet. The series of cuts faces southwest, and is rimmed by a group of extensive dumps. Several irregular, interconnected underground workings extend northeastward from the central and southeastern parts of the cuts. Most of them are drifts or inclines with very gentle slopes, and many irregular rat-hole excava- tions have been developed from their walls. Other open- ings in the area, chiefly of an exploratory nature, include shallow cuts and trenches along the strike of the dike to the northwest and southeast, and also a cut and short tunnel in the footwall part of the deposit. The pegmatite dike is only one part of a complex series of branching and joining dikes that in plan appears somewhat like a braided stream (pi. 2). Some of this branching is true splitting of a single pegmatite or a pair of juxtaposed pegmatites into two dikes separated by country rock. In other places this branching is only appar- ent, and instead is due to pronounced warps or rolls in the hanging- wall or footwall contacts of a single dike, with preservation of elongate masses of hanging-wall gabbro along some troughs and appearance of footwall gabbro through erosion-breached crests. Most of these rolls trend west, plunging directly down the dip of the dikes. The main pegmatite mass is a dike 16 feet to at least 33 feet thick. It can be traced southward from the mine area for a distance of nearly 2000 feet, and extends west- ward for approximately 1200 feet to the valley of Salmons Creek, where it is buried beneath alluvium. Within this distance, the dike joins and diverges from numerous other dikes. It trends north-northwest to northwest and dips 5° to 55° southwest. Coarse-grained graphic granite and subordinate al- bite and muscovite occur in the upper part of the dike as a unit 6 feet to at least 15 feet thick. The lower part of the dike, of equal or slightly lesser thickness, consists of fine-grained quartz-albite-perthite-garnet pegmatite with very poorly to very well-developed layering. In many parts of the mine area this line rock grades along the Pegmatites of the Pala District 63 EXPLANATION Dump material * H a= \i \ Pegmatite, undivided X$c I Ca2>, I Quartette and quarts -mica schist o ; 5S Strike and dip of foliation, shoring trend and plunge of linear element .__ Contact, showing dip, dashed where approximate Edge of open cut or pit 25 ■Scale in feet Contour interval JO feet Datum, is mean sea level Mapped by XHdahns 8/47, sMe Fig. 30. Geologic map of surface workings, Tourmaline King mine. 64 Special Report 7-A 2 O Prnl E ^ 1 "9 -a^ 1; M o s 1 -s Is R l *. g ft. 3 so n i- * 1 Q " rJ ^L _V_ i_n t S N S ' "}> a= a n h oT %_ i A f $1 I II E Si I SI y U « ¥ •o * <*sl e 3 -8 3 H a sqnzm 9ip^cmu6s,j I 3 Pegmatites of the Pala District 65 2 O H < < PL X w D ~*° _r0 ro rC: n , K « ~ so >- 3 so kN *! « fo so fO 3 .§ tt 1 >>> 3 ) S.1 C ,C1 Chief mine, 8, 15. 19, 2G, 27, 29, 30, 31, 35, 37, 38, 39, 4G, 47, 50, 51,52.01-08 pegmatite dike, 29, 37, 38, 40, 42, 40, 67 conglomerate, 12, 13 Creek, Indian Reservation, Mountain, 0, 9, 11, 13, 15, 10. 21, 30, 49 -Rincon-Mesa Grande belt, 5 -Temecula road, 59 View mine, 25, 41 Page, J. J., cited, 24 , Lincoln R., 6 , L. R., cited, 24. 25, 45 Palomar Mountain, Tarker, J. M., Ill, cited, 24 Pegmatite dikes, mines, and prospects, table of, 14-15 Pegmatites, principal types of, 17-24 Peninsular Range province, 0, 8, 17 Pleistocene deposits, 13 Quarternary rocks. 12 Quensel, P., cited, 41 Queen Mountain, 6, 9, 11, 12, 13, 15, 16, 25, 30, 40, 41, 50, 55, 56, 59, 61 , photo of, 17 Ramona district, 35 quadrangle, 8, 45 Riverside Countv, 5, 6 Ross, C. S., cited, 39 Rounds, Joan T., 6 Salmons Creek, 6, 56. 58, 62 City, 55, 56, 58 , photo of, 20 , Frank A., 8, 50, 02 , estate, 62 , Mrs. Frank A., 6 San Diego, 55 County, 6, 45 Division of Natural Resources, 6 Luis Rev River, 6, 12, 30, 68 Valley, 6 Marcos, 69 gabbro, 9 Pedro mine, 37, 50 pegmatite dike, 15, 29, 37, 41, 42, 47 Santa Ana Mountains, 9 Schaller, W. T., 6, 33 , cited, 4, 5, 8, 9, 11, 22, 25, 29, 30, 37, 38, 41, 44, 45 Schuyler, F. B., 55 mine, see Tourmaline King mine Scorza, E. P., cited, 24 Senpe mine, 49, 50 pegmatite dike, 15, 31, 37, 47 Shanin, V. E., cited, 24 Sickler, Frederick M., 0, 8, 69 , M. M., 8, 68 Slice Mountain, 6, 13 , photo of, 17 Smith, Ward C, 6 , cited, 24 Sterrett, D. B., cited, 30 Stewart, G. W., cited, 24 mine, 15, 16, 19, 26, 29, 31, 36, 38, 39, 40, 41, 40, 47, 49, 50, 57, 59-61 , photo of, 17 pegmatite dike, 7, 28, 29, 30, 34, 35, 30, 37, 38, 39, 40, 41, 42, 40, 49, 51, 56 road, 55 Temecula, 46 Thomas Mountain, 6 Tiffany and Company, 57 Tourmaline King ( Wilke, Schuyler) mine, 7, 8, 15, 16, 25, 31, 35, 38, 46, 47, 48, 50, 52, 55-56 , map of surface workings, 63 iwgmatite dike, 34, 37, 38, 40, 46, 55, 59 Queen mine, 52, 56-57 , photo of, 17 pegmatite dike, 7, 15, 16, 27, 28, 31, 34, 35, 37, 3S, 40, 41, 46, 47 Universal Microphone Company, 49 University of California, 5 Upper Cretaceous, 44 United States Geological Survey, 5, 6, 25 Vanderburg dike, 29 mine, 8,37, 50 , photo of, 17, 23 -Katerina pegmatite, see Katerina-Vanderburg pegmatite Varutrask pegmatite, Sweden, 41 Waring, G. A., cited, 5, 45 West Chief pegmatite, photo of, 20 White Cloud mine, photo of, 17 pegmatite dike, 25, 27, 40 Queen mine, 8 Whim workings, 58 Wilke, R. M., 55 mine, see Tourmaline King mine Willoughby, David P., 6 Wiltse, Florence, 6 Woodson Mountain granodiorite, 11, 12, 13, 15, 69 World War I, 59 II, 46, 49 Wright, L. A., cited, 24 :d muacortfe in places y? =fc| regmatUe, undivided UV frl Gabtro ^ Contact; dashed where approximate NE GEOLOGIC SECTION THROUGH THE PALA CHIEF PEGMATITE SAN DIEGO COUNTY, CALIFORNIA