UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Nephrite in British Columbia Fraser, John Ross 1973

You don't seem to have a PDF reader installed, try download the pdf

Item Metadata

Download

Media
UBC_1973_A6_7 F73.pdf [ 11.24MB ]
Metadata
JSON: 1.0093110.json
JSON-LD: 1.0093110+ld.json
RDF/XML (Pretty): 1.0093110.xml
RDF/JSON: 1.0093110+rdf.json
Turtle: 1.0093110+rdf-turtle.txt
N-Triples: 1.0093110+rdf-ntriples.txt
Original Record: 1.0093110 +original-record.json
Full Text
1.0093110.txt
Citation
1.0093110.ris

Full Text

NEPHRITE IN BRITISH COLUMBIA, by JOHN ROSS FRASER B.Sc, University of British Columbia, 1967 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Geology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1972 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver 8, Canada Date v^a^-.5.a.1 \<2>7 3 (i) ABSTRACT Nephrite is a compact, microfibrous variety of actinolite-treraolite in which bundles or tufts of minute fibers of the amphibole are twisted and thoroughly felted or interwoven with one another, producing a characteristic "nephritic" microstructure. In British Columbia, nephrite deposits, both in place and placer, are closely associated with a belt of alpine ultramafic rocks that extends for 1000 miles from the Hope area, east of Vancouver, northwestward to the Yukon border. The three major nephrite producing regions are the Bridge River - lower Fraser River area, the Takla Lake area and the Dease Lake area. The nephrite from British Columbia contains, in addition to essential tremolite, small amounts of chlorite, uvarovite, chrome spinel, diopside, talc, carbonate, sphene, phlogopite and pyrite. Grains of chrome spinel and uvarovite are usually visible in hand specimen. The colour of the majority of the specimens is yellowish green; this colouration is caused by the presence of iron in both the divalent and trivalent states. Polished surfaces of the 2 nephrite have an average Vickers hardness of 950 Kg/mm and an average Mohs hardness of 7. The average specific gravity is 3.00. The unit cell parameters of tremolite from British Columbia nephrite specimens are similar to those of nephritic tremolite from Siberia. X-ray diffraction data for the tremolite from these specimens are also in good agree-(ii) merit with those for nephritic tremolite from other localities. The nephrite specimens contain an average of 3.05 percent iron; small amounts of cobalt, nickel, manganese, copper, lead, zinc, chromium, titanium and vanadium are also present. Significant regional variations in the averages for iron, cobalt, manganese, copper, lead, zinc and vanadium are not observed when the specimens are grouped according to the area of origin; slight varia tions are observed in the average contents of nickel, chromium and titanium. The general similarity of the regional average values for these elements suggests that the nephrites have been formed in similar environments. At the 0»Ne-ell Creek deposit in central British Columbia, nephrite occurs in a zone of tremolite-chlorite rock developed in serpentinite at the contact with metasomatically altered sediments. The nephrite has resulted from the metasomatic alteration, by addition of calcium and silica, of the serpentinite during the process of serpentinization. The calcium was derived from the pyroxenes contained in the original ultramafic rock; the source of the silica was the enclosing sediments. High concentrations of calcium and magnesium and relatively lower concentrations of sodium, iron, aluminum and silicon charact erized the environment in which the nephrite formed. Calcium and sodium were perfectly mobile while the other elements were relatively inert. These condi tions of mobility and concentration account for the fine fibrous nature of the nephritic tremolite. A temperature range of approximately 300°C to 500°C and a pressure in excess of 4 kilobars are suggested for the formation of the nephrite. (iii) TABLE OF CONTENTS Page ABSTRACT i I. INTRODUCTION 1 NOMENCLATURE AND HISTORY 1 NEPHRITE OCCURRENCES 3 PREVIOUS WORK 4 SCOPE OF PRESENT WORK 5 ACKNOWLEDGMENTS 6 II. BRITISH COLUMBIA DEPOSITS 8 ALPINE ULTRAMAFIC ROCKS OF BRITISH COLUMBIA 9 PLACER OCCURRENCES OF NEPHRITE 11 BEDROCK OCCURRENCES OF NEPHRITE 3 PRODUCTION 15 MINING METHODS 8 MARKETS, PRICES AND USES 19 III. PETROLOGY AND PHYSICAL PROPERTIES OF BRITISH COLUMBIA NEPHRITE 21 NEPHRITE CLASSIFICATIONS 2Turner Classification 3 Non-schistose Nephrites 2Schistose NephritesSemi-nephrites 25 Kalkowsky ClassificationPETROLOGY 27 TremoliteChlorite 36 Spinel 8 IlmeniteDiopsideUvarovite 40 Unknown 2 SpheneCarbonatePhlogopite and Talc 4Pyrite 4PHYSICAL PROPERTIES 3 FractureSpecific GravityColour and Lustre 45 Hardness 6 Crushing Strength and Relative Corrosion Hardness 51 IV. THE CHEMISTRY AND CRYSTALLOGRAPHIC STRUCTURE OF NEPHRITE 52 CHEMISTRY 5CRYSTALLOGRAPHIC STRUCTURE 57 (iv) Page V. IRON AND TRACE ELEMENT GEOCHEMISTRY OF BRITISH COLUMBIA NEPHRITES 65 DISCUSSION OF RESULTS 69 Iron 6Cobalt and NickelManganese 71 Copper 3 LeadZincChromium, Titanium and Vanadium 75 Element Distribution in Fresh and Weathered Nephrite 76 REGIONAL CHEMICAL VARIATIONS IN BRITISH COLUMBIA NEPHRITES 78 COLOUR OF NEPHRITES 80 VI. THE O'NE-ELL CREEK NEPHRITE DEPOSIT 83 REGIONAL GEOLOGYGEOLOGY OF THE DEPOSIT 88 General DescriptionLithology 92 Cache Creek Group 9Trembleur Intrusions 6 Miscellaneous Rock Types 99 Amphibole-zoisite rockMeta-diabase 9Albite-amphibole rockMeta-aplite 101 Summary 10PETROGENESIS 2 General Statement 10Origin of the Nephrite 103 Temperature and Pressure Conditions 109 VII. CONCLUSIONS 111 BIBLIOGRAPHYAPPENDIX I Survey of World Deposits 119 APPENDIX II Determinative Methods 132 APPENDIX III Nephrite Analyses Obtained from the Literature 138 (v) ILLUSTRATIONS PLATES Plate Page 1 Scanning electron micrograph of a schistose nephrite 22 transitional to a semi-nephrite illustrating the twisted and interwoven nature of the component tremolite fibers (#37; OtNe-ell Creek), X 300. 2 Scanning electron micrograph of a schistose nephrite 22 transitional to a semi-nephrite illustrating the fine fibrous nature of the tremolite (#37; 0*Ne-ell Creek), X 1270. 3 Photomicrograph of a non-schistose nephrite transitional to 24 a schistose nephrite (#7; Fall River), crossed nicols. 4 Photomicrograph of a schistose nephrite (#10; Kelly Creek), 24 crossed nicols. 5 Photomicrograph of a semi-nephrite, with large sheaves of 26 parallel unfelted fibers (#8$ Fall River), crossed nicols. 6 Photomicrograph of a schistose nephrite transitional to 26 a semi-nephrite (#40; Seywerd Creek), crossed nicols. 7 Photomicrograph of coarse acicular tremolite in a schistose 35 nephrite transitional to a semi-nephrite (#10; Kelly Creek), crossed nicols. 8 Photomicrograph of a radial mass of tremolite fibers set in 35 a fine nephritic base (#45; Dease Lake), crossed nicols. 9 Photomicrograph of an aggregate of chlorite surrounding 37 fragments of chrome spinel (#15; Van Decar Creek), crossed nicols with gypsum plate. 10 Photomicrograph of a fractured chrome spinel grain, 37 partially replaced by chlorite (#15; Van Decar Creek), plane polarized light. 11 Photomicrograph of corroded remnants of diopside 39 (#16; 0»Ne-ell Creek), crossed nicols. 12 Photomicrograph of spindle-shaped diopside crystals 39 (#43; Ogden Mountain), crossed nicols. (vi ) Plate Page 13 Photomicrograph of uvarovite garnet containing corroded 41 grains of chrome spinel (#7; Fall River), plane polarized light. 14 Photomicrograph of anhedral grains of uvarovite garnet 41 (#8; Fall River), plane polarized light. 15 Scanning electron micrograph of a schistose nephrite 60 transitional to a semi-nephrite illustrating the (110) cleavage of tremolite (#37; O'Ne-ell Creek), X 6500. 16 A portion of the nephrite outcrop at O'Ne-ell Creek. 91 17 Photomicrograph of a quartzite from O'Ne-ell Creek, 94 crossed nicols. 18 Photomicrograph of "birds-nesf'-like aggregates of tremo- 94 lite fibers in a quartzite from O'Ne-ell Creek, plane polarized light. 19 Photomicrograph of stilpnomelane (brown) and biotite (green) 95 in fractures in a siliceous argillite from O'Ne-ell Creek, plane polarized light. 20 Photomicrograph of stilpnomelane (brown) and needles of 95 tremolite in an argillite from O'Ne-ell Creek, crossed nicols. 21 Photomicrograph of a serpentinite from O'Ne-ell Creek 98 illustrating the fibro-lamellar structure of the antigor-ite, crossed nicols. 22 Photomicrograph of a quartz-carbonate rock from O'Ne-ell 98 Creek, crossed nicols. FIGURES Figure Page 1 Index map of British Columbia. 10 2 Nephrite production in British Columbia for the period 16 1959 - 1970, inclusive. 3 A graph of Mohs hardness values against the log of Vickers 50 hardness numbers. 4 Curves of weight loss in heating for nephrite and broad- 55 prismatic tremolite from Siberia, U. S. S. R. i (vii) Figure Page 5 MgO-CaO-Fe^O^ + FeO in nephrites from various world local- 56 ities. 6 The structure of tremolite. 58 7 Histograms of the Fe, Co, and Ni contents of British 70 Columbia nephrites. 8 Histograms of the Mn, Cu, and Pb contents of British 72 Columbia nephrites. 9 Histogram of the Zn content of British Columbia nephrites. 74 10 Geology map; Takla Lake-Middle River area, British Columbia. 84 11 Legend for Figure 10. 85 12 Geology; 0»Ne-ell Creek nephrite deposit, O'Ne-ell Creek, In British Columbia. Pocket 13 Diagrammatic representation of mineral zoning at the contact 104 between serpentinite and metasomatized argillite and grey-wacke. 14 Ca (activity) - Si02 (activity) for calcium and magnesium 106 silicates. TABLES Table Page 1 Nephrite production from Mining Divisions, British 17 Columbia. 2 Classification, mineralogy and mode of British Columbia 28 nephrites. 3 Indices of refraction of tremolite in nephrites. 34 4 X-ray diffraction data for kbtschubeite (chromian clino- 36 chlore), clinochlore, kammererite (chromian penninite), pen&inite and for chlorite from British Columbia nephrite specimens. 5 Specific gravity of British Columbia nephrite specimens. 44 6 Specific gravity of weathered and unweathered nephrite from 45 placer boulders. 7 Colour of British Columbia nephrite specimens. 47 (viii) Table Page 8 Vickers hardness number and Mohs hardness of polished 49 specimens of British Columbia nephrite. 9 Unit cell parameters for tremolite from British Columbia 62 nephrite, tremolite from Siberian nephrite- and common tremolite. 10 X-ray diffraction data for tremolite and for nephritic 63 tremolite from British Columbia, New Zealand, Taiwan and Siberia. 11 Iron and trace element analyses of British Columbia 66 nephrite specimens. 12 Iron and trace element contents of fresh and weathered 77 nephrite from alluvial boulders. 13 Average and range of iron and trace element contents of 79 nephrites from the three major nephrite producing areas of British Columbia. 14 Average iron and trace element contents of nephrite and 105 serpentinite from O'Ne-ell Creek. 1 I. INTRODUCTION Nephrite and jadeite are the two minerals that are collectively referred to as jade. Nephrite is a compact, fibrous variety of actinolite-tremolite, an amphibole, and jadeite is a pyroxene. Other minerals such as serpentine, grossularite and vesuvianite are often presented as varieties of jade, usually with a geographical prefix, but should be termed pseudojades. An example is massive vesuvianite from California which is known, in lapidary circles, as California jade, American jade or Feather River jade. NOMENCLATURE AND HISTORY The earliest mention of jade in the European literature is after the return from Central and South America of the early Spanish explorers (Hansford, 1969; Palmer, 1967; Foshag, 1957). They brought with them green stones that were reported to be useful for the cure and prevention of diseases of the kidneys and gave them the name "piedra de yjada" meaning "stone of the loins" or "colic stone". Latin scholars translated this term into its Latin equiva lent, "lapis nephriticus". The French translations of the Spanish and Latin terms became "pierre l'ejade" or simply jade and "pierre nephritique", respectively. In the middle of the nineteenth century, Alexis Damour, a French chemist, studied various jades and distinguished, on the basis of chemical composition, two varieties which he termed nephrite and jadeite. Because of its fine colouration, its peculiar translucency and its ability 2 to take and keep a keen edge, nephrite was worked into tools, weapons and ornaments by prehistoric and later cultures in many parts of the world (Hansford, 1969; Palmer, 1967). Jadeite was also used but to a much lesser extent and was more or less restricted to the indigenous cultures of Mesoameri-ca (Foshag, 1957). The earliest recognized use of nephrite was by the inhabitants of the neolithic lake dwellings in Europe, especially in Switzerland (Hansford, 1969). Nephrite was used extensively by the aboriginal peoples of Oceania, particular ly the Maoris of New Zealand. Explorers in the Amazon River basin in the early sixteenth century found nephrite celts in use by the natives of the region. In northwestern North America, the natives of Alaska and British Columbia employed simple nephrite tools up to the time of the introduction of iron by the first European traders (Emmons, 1923; Dawson, 1887). In China, the history of nephrite is long and may extend as far back as neolithic time. To the Chinese, the true jade is nephrite and jadeite, which was imported from Burma, did not come into use until the end of the eighteenth century. Although nephrite has been worked by the Chinese throughout their long history, the mineral is not known to occur anywhere in the eighteen provinces of China Proper or in Manchuria, Mongolia or Tibet. Since the Han Dynasty (206 B.C. - A.D. 220), most of the nephrite used by the Chinese has been obtained from Turkistan. 3 NEPHRITE OCCURRENCES Deposits of nephrite are not common and it is estimated that there are not more than fifty in the world (Kolesnik, 1970) although this figure should be revised upward in light of recent discoveries in Canada. The nature of the occurrence of nephrite accounts for its relative rarity; it generally occurs in lensoidal or discontinuous vein-like masses seldom exceeding ten feet in width and the appearance of nephrite in outcrop is often very similar to that of the enclosing rocks. Nephrite deposits are known in North America, South America, Europe, Asia, Africa and Oceania. Brief descriptions of a number of occurrences, exclusive of those in British Columbia, are presented in Appendix I. The deposits in North America are located in British Columbia, Yukon, Northwest Territories, California, Washington, Oregon and Wyoming. The only known deposits in South America are situated in Brazil. In Europe, occurrences are known in Switzer land, Poland, Italy, West Germany, East Germany and the Union of Soviet Socialist Republics. The Asiatic deposits are located in Chinese Turkistan, Taiwan and Japan. In Africa, nephrite has been reported from Nyasaland and Southern Rhodesia and in Oceania, from New Zealand and New South Wales, Australia. The majority of nephrite deposits are found within serpentinized alpine ultramafic bodies; nephrite has hot been reported from unserpentinized ultra-4 mafic rocks. The nephrite occurs as vein-like to lens-like segregations in the serpentine, usually at the contact with country rocks, tectonic inclusions and dykes. The rocks in contact with, or contained within, the serpentinites are often metasomatically altered. The nephrite is commonly associated with asbestos, chlorite, coarse fibrous tremolite, talc and diopside. Nephrite also occurs in environments in which ultramafic rocks are absent. Deposits of this type are those in Wyoming and in Chinese Turkistan. The nephrite in Wyoming occurs in amphibolites that are contained in, or cut by, siliceous intrusive rocks and is associated with epidote and clinozoisite. In Chinese Turkistan, nephrite occurs in diabase and gabbro that have been intrud ed into shales, sandstone and syenite and in greenstone bodies contained in mica schists. PREVIOUS WORK The number of previous studies regarding British Columbia nephrite is very limited. The earliest reference is by Dawson (1887) in which he describes the manufacture and use of nephrite implements by the Indians of British Columbia and speculates on the source and origin of the material. A monograph by Emmons (1923) deals with the use of nephrite by the native people of British Columbia and Alaska. The only known reference pertaining to nephrite deposits in the Province is by Holland (1961). 5 SCOPE OF PRESENT WORK This investigation was undertaken to determine the geographical distribu tion of nephrite deposits in British Columbia, to study the petrology, physical properties, chemistry and crystallographie structure of nephrite from a number of British Columbia occurrences and to describe, and propose an origin for, the O'Ne-ell Creek nephrite deposit in central British Columbia. Twenty-six specimens of nephrite were examined by standard petrographic procedures and by X-ray diffraction methods. The physical properties investi gated are fracture, specific gravity, colour and hardness, both Vickers and Mohs, of polished surfaces. The microstructure of three specimens was examined with the aid of a Cambridge Stereoscan MK II-A scanning electron microscope operated by the Department of Biological Sciences, University of British Columbia. The unit cell parameters were calculated for the tremolite from ten nephrite specimens to determine if differences exist between this variety of tremolite and common prismatic tremolite. Thirty-one nephrite specimens were analysed for iron, cobalt, nickel, manganese, copper, lead, zinc, chromium, titanium and vanadium. The reasons for the analyses are two-fold; to ascertain if nephrites from the three major producing areas in British Columbia can be characterized by their trace element content and to determine, in qualitative manner, what elements are responsible 6 for the colouration of nephrite. The analyses were performed using atomic-absorption and emission spectrography techniques. Eight samples of serpentinite from O'Ne-ell Creek and the weathered rind from three alluvial nephrite boulders were also analysed for the same elements. The geology of the O'Ne-ell Creek nephrite deposit was mapped, at 1 inch to 40 feet, in September 1969, using a tripod-mounted Brunton compass and a chain. The map covers an area 700 feet long by 250 feet wide. For this report, the map scale was reduced to 1 inch equals 80 feet. Twenty-nine thin sections were examined. Additional information was obtained from feldspar staining, using the procedures of Bailey and Stevens (1960), and from X-ray diffraction studies. ACKNOWLEDGMENTS The author is indebted to all individuals who provided assistance and encouragement during the collection of data and preparation of this thesis. Special recognition is due Mrs. W. Robertson who arranged for the author to visit the O'Ne-ell Creek deposit and provided many specimens from British Columbia nephrite occurrences. The author is grateful to Professor W. R. Danner, Department of Geology, University of British Columbia, for his guidance during the writing of this thesis. Special thanks are due Dr. H. Wynne-Edwards, Dr. K. Fletcher, Dr. E. P. Meagher and Dr. P. Read for their assistance and discussions concern ing specific sections. 7 Mr. Leslie Veto, Department of Biological Sciences, University of British Columbia, provided generous assistance in the use of the scanning electron microscope and the taking of photographs. Finally, the author would like to thank Miss U. Malachowski for her patience and perseverance while typing the final manuscript. 8 II. BRITISH COLUMBIA DEPOSITS Nephrite, presumably obtained from the Fraser River, was utilized by the Kwakiutl, Salish, Tsimshian, Haida and Tlingit tribes of the coast and south western interior of British Columbia and the coast of southeastern Alaska, for fashioning cutting implements and property pieces (Emmons, 1923). These tools and ornaments were highly valued and were used long before European traders had introduced iron tools. The high value placed on such tools is illustrated by the fact that, among the Tlingit tribe, a nephrite adze several inches long was considered to be worth from one to three slaves. The nephrite was laboriously worked into useful objects by means of slabs of sandstone and sand abrasives. After the Fraser River gold rush, many of thevoriginal gold-bearing river bars were reworked by Chinese miners and numerous shipments of jade were made to China in the years before 1900 (Holland, 1961). In the late 1940's, interest was renewed in Fraser River jade and since that time numerous placer and in place deposits have been found throughout the province. Much of the information presented in this section has been drawn from two annual publications of the British Columbia Department of Mines and Petroleum Resources; these are Geology, Exploration and Mining in British Columbia and the Annual Report of the Minister of Mines and Petroleum Resources. For the sake of brevity, these are referred to as G. E. M. and M. M., respectively. 9 ALPINE ULTRAMAFIC ROCKS OF BRITISH COLUMBIA The nephrite deposits in the province are associated with a belt of alpine ultramafic rocks that extends for 1000 miles from the Hope area, east of Vancouver, northwestward through central and northern British Columbia to the Yukon border (Figure 1). This belt is traceable into Yukon and Alaska. The following brief description of these rocks is taken largely from McTaggart (1971). The ultramafic bodies, most of which are peridotite or dunite, range in size from a few tens of feet across to batholiths with areas greater than 70 square miles. In shape, they are sill-like and lenticular to equidimensional, although elongate bodies are the most common. Many are cut by veins and dykes of dunite, pyroxenite and gabbro. Chromite, in pockets, lenses and vein-like masses, is almost always present. The bodies are commonly serpentinized, the degree of which ranges from incipient or partial in the larger masses to almost complete in the smaller, lenticular bodies. Talc rocks and mariposite bearing quartz-carbonate rocks are common but are usually restricted to shear zones and contacts (Cairnes, 1929; Armstrong, 1949; Leech, 1953; Roots, 1954; Gabrielse, 1963). Zones of hornblende, actinolite-tremolite or chlorite are reported to occur at the contacts of several of the ultramafic bodies (Armstrong, 1949; Roots, 1954; Gabrielse, 1963). Most of the ultramafic rocks are enclosed by sediments and volcanics of the late Paleozoic Cache Creek Group although in a few places in central British 11 Columbia and Yukon, they occur in Upper Triassic or Jurassic rocks. Several of the larger bodies lie along major northwest-trending faults that separate the Cache Creek strata from younger rocks. PLACER OCCURRENCES OF NEPHRITE All of the nephrite produced in British Columbia in the 1950's and the early 1960's was obtained from placer deposits in streams draining areas of ultramafic rocks. The three major regions of placer occurrences are the Bridge River - lower Fraser River area, the Takla Lake area and the Dease Lake area which, in Figure 1, are labelled I, II, and III, respectively. In area I, placer nephrite has been found along the Bridge River from its confluence with the Fraser River to Mission Dam (Holland, 1961) and on its tributaries Marshall Creek (M. M., 1961), Yalakom River (Holland, 1961), Jim Creek (M. M., 1963), Brett Creek (M. M., 1968), Cadwallader Creek (M. M., 1968), Noel Creek (G. E. M., 1969) and Hell Creek (M. M., 1968). On the Fraser River, nephrite has been collected from Chilliwack to the mouth of the Bridge River (Holland, 1961). The Coquihalla River, a tributary of the Fraser River, has yielded nephrite from its junction with the Fraser to the mouth of Dewdney Creek (Holland, 1961). The alluvial nephrite occurs as pebbles, cobbles and boulders ranging in weight from a few tens of pounds to as much as ten tons. The largest boulders occur on the Bridge River and its tributaries; those from the Fraser River are smaller in size, mostly in the range of a few tens of pounds, 12 but many are of the finest quality. Placer boulders of nephrite have been reported from a number of creeks in the Takla Lake area, an area containing extensive outcrops of ultramafic rocks belonging to the pre-Upper Triassic Trembleur intrusions (Armstrong, 1949). In the southern part of the area, O'Ne-ell Greek (M. M., 1968; G. E. M., 1969), Van Decar Creek (M. M., 1963; p. c. Forsythe, 1969) and Baptiste Creek (M. M., 1963) have yielded alluvial boulders of generally poor quality material. To the north, nephrite has been found along Vital Creek (M. M., 1963), Quartz Creek (M. M., 1963), Fall River (p. c. Robertson, 1969), Ogden Creek (M. M., 1968; G. E. M., 1969), Kelly Creek (p. c. Robertson, 1969), Teegee Creek (p. c. Robertson, 1969) and Silver Creek (p. c. Knauer, 1971; p. c. Owen, 1972), all of which are tributaries of the Omineca River, and along Kwanika Creek (M. M., 1963, 1968), a tributary of the Nation River. The boulders from Kwanika Creek are reported to be up to 7 or 8 tons in weight. In the Dease Lake area, nephrite boulders have been found on the Liard River (Holland, 1961), Wheaton Creek (Holland, 1961; M. M., 1968; G. E. M., 1969), Thibert Creek (p. c. Larson, 1969) and Seywerd Creek (M. M., 1963, 1969; p. c. Seywerd, 1970). On the Liard River, boulders are found at the mouth of the Hyland River and Holland (1961), on the basis of glacial movement in this area, suggests that the probable source is the ultramafic rocks at Cassiar and at the head of Blue River. The boulders in Wheaton Creek occur along the lower 13 2 miles of its course and are presumably derived from a band of serpentinized peridotite that crops out some 1.5 miles upstream from the creek mouth. Little is known of the occurrences on Thibert and Seywerd Creeks, except that in the latter, nephrite occurs in place in serpentine. BEDROCK OCCURRENCES OF NEPHRITE In British Columbia, there are at least 10 "in situ" occurrences of nephrite and with one exception, the deposit on O'Ne-ell Creek, very little information is available regarding these deposits (Figure 1). All are intimate ly associated with serpentinized alpine ultramafic rocks. Four bedrock nephrite deposits are known in the Bridge River area and are located on Ama Creek (M. M., 1962), Brett and Marshall Creeks (Saunders, 1969), on the west side of Bridge River near Applespring Creek (Holland, 1961) and on Hell Creek. The deposit on Ama Creek occurs in a 3-foot wide pale green alteration zone in serpentine along the contact of a diorite dyke. The jade, which is associated with pectolite (Uncataloged Sutton-Thompson Collection specimen), consists of subparallel bands of greenish tremolite and grey diopside that enclose irregular shaped masses of serpentine. This material, because of its banded nature and resemblance to intestines, is known locally as "intestin al" or "gut jade" but due to this texture it has little use as a gems tone. A number of small showings and one large deposit are situated in the vicinity of Marshall Creek and its tributary Brett Creek. The large deposit, which has 14 produced nephrite commercially, is located on Brett Creek approximately % mile upstream from its confluence with Marshall Creek. In this deposit, vein-like masses of nephrite occur in a 50 foot wide, N 60° E striking zone of sheared serpentine that is in contact with sediments of the Cache Creek Group to the north and a light grey chert-like rock, which in turn is in contact with a quartz diorite, to the south. The nephrite vein has a strike length of 50 feet, a vertical extent of 30 to 40 feet and a width, over the vertical extent, of 1 foot to 10 feet. The "in situ" deposit near Applespring Creek consists of sheared lenses, nodules and folded layers of waxy, greenish-grey nephrite enclosed in sheared tremolite along a fault in serpentine. Nothing is known of the Hell Creek deposit. Nephrite has been produced from four deposits in the Takla Lake area, three of which are on Ogden Mountain and the fourth is on O'Ne-ell Creek. In the largest of the Ogden Mountain deposits, nephrite lenses occur in serpentine in contact with a dense, light greenish-grey rock composed of radial aggregates of diopside in a matrix of tremolite (p. c. Owen, 1972). Much of the nephrite from this deposit has a bright green colour and is of high quality. Chrome rich varieties containing numerous minute grains of bright green uvarovite garnet are common. Little is known of the other two Ogden Mountain deposits except that the nephrite occurs in serpentine (G. E. M., 1970; p. c. Owen, 1972). On O'Ne-ell Creek, lenses of nephrite occur in a 20 to 25 foot thick, moderately 15 west dipping zone of tremolite, chlorite and minor talc at the contact between serpentine and metasediments and metavolcanics of the Cache Creek Group. This deposit will be described in some detail in a later section of this report. In the Dease Lake area, only two deposits are known. The largest, and sole producer, is situated on Seywerd Creek, a small creek entering the west side of Dease Lake at Steamboat Point. The nephrite occurs in serpentine (M. M., 1963; G. E. M., 1970; p. c. Seywerd, 1970). The second occurrence is in the open-pit asbestos mine on Mount McDame near Cassiar (G. E. M., 1970). PRODUCTION Annual production figures for British Columbia nephrite have been kept since 1959; these are graphically portrayed in Figure 2. During the period 1959 to 1970, a total of 596,394 pounds of nephrite were produced worth $531,670 (M. M., 1962 - 1970). In 1970, due largely to production from recent ly discovered "in situ" deposits, the quantity mined was 262,602 pounds, a ten fold increase over the previous year. Undoubtedly production will continue to increase in future years as the "in situ" deposits are able to produce large quantities of consistent quality material for such potential high volume consumers as the construction industry. Nephrite production data for the Lillooet, Omineca and Liard Mining Divisions, which enclose all or large portions of areas I, II and III, respect ively, for the period 1962 to 1970 are presented in Table 1. 250,000-200.000-150,000-100,000-50,000-Quantity, lbs. Value, $. Source-Ann. Rep. of B.C. Min. of Mines and Pet. Res. 1962 - 1970 -200.000 •250,000 150, 000 - 100,000 - 50,000 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 Fig .2. Nephrite production in British Columbia for the period 1959 —1970, inclusive. 17 Table 1 Nephrite Production from Mining Divisions, British Columbia Year Mining Division Quantity (lb.) Value (?) Total to Date Quantity (lb.) Value ($) 1962 Lillooet 56,935 20,760 1963 Lillooet 16,000 15,529 207,986 72,490 1964 Lillooet 10,337 11,404 218,323 83,894 Omineca 1,200 2,400 1,200 2,400 1965 Liard 2,000 2,000 2,000 2,000 Lillooet 4,129 5,249 222,452 89,143 Omineca 1,000 2,000 2,200 4,400 1966 Liard 8,493 8,648 10,493 10,648 Lillooet 3,140 4,577 225,592 93,720 1967 Liard 14,920 19,714 25,413 30,362 Lillooet 5,240 4,627 230,832 98,347 1968 Liard 1,810 2,125 27,223 32,487 Lillooet 42,095 83,899 272,927 182,246 Omineca 5,110 19,646 7,310 24,046 1969 Liard 5,825 11,960 33,048 44,447 Lillooet 6,060 5,237 278,987 187,483 Omineca 14,447 25,438 21,757 49,484 1970 Liard 5,322 9,099 38,370 53,546 Lillooet 14,280 27,583 293,267 215,066 Omineca 243,000 213,574 264,757 263,058 Source: Annual Reports, British Columbia Minister of Mines and Petroleum Resources, 1962 - 1970. 18 MINING METHODS The methods employed in mining "in situ" nephrite vary from deposit to deposit. As with any gemstone, the ultimate goal is to remove the maximum amount of material with the minimum amount of physical damage to it; this is often a difficult task due to the hardness and extreme toughness of nephrite and the fact that it often occurs as discontinuous lenses and veins in moderately to steeply dipping zones. Factors influencing the choice of extraction method are the geometry of the deposit, the topography of Ithe immediate area, the nature of the enclosing rocks and the accessibility of the mine site. Stripping the overburden and the enclosing rocks from the nephrite pods is usually accomplished by using heavy equipment such as bulldozers although at one deposit in the Takla Lake area, the overburden was washed away with high pressure water jets and the harder material in the hanging wall was broken with pneumatic hammers and very light explosive charges. Due to the potential danger of fracturing the nephrite, explosives must be used sparingly and with caution. Once the nephrite is exposed, individual lenses or large fragments are extracted with heavy equipment or hydraulic jacks or the nephrite is sawn, in place, into easily removed blocks. Several small diameter core samples are usually taken from the large pieces in order to ascertain their quality. The extracted nephrite is sawn into smaller blocks to trim waste or low quality material, to provide an easily handled piece and to provide quality control. The sawing is 19 accomplished by means of large diameter diamond saws, diamond impregnated drag saws or large wire saws. MARKETS. PRICES AND USES The bulk of the nephrite produced in British Columbia is exported in a raw or semi-processed form to Germany, Japan, Taiwan, Hong Kong, the Peoples Republic of China and the United States of America. A smaller though significant amount, generally as thin slabs or small blocks weighing 5 pounds or less, is sold locally through retail outlets to collectors and amateur lapidaries. Prices for nephrite are variable and are dependent upon colour, competency, purity and amount of processing that has gone into preparing the material for sale. High quality nephrite has a uniform green colour, very few fractures and veins of cross fiber tremolite and a low content of impurities such as magne tite, chromite and chlorite. Botryoidal nephrite and "mutton fat" jade or white nephrite, two extremely rare varieties, command exceptionally high prices. Medium and select grades of nephrite range in price from $4.00 to $20.00 per pound and in rare instances the price may be as high as $100.00 per pound. Low grade material has a price range of $0.50 to $2.00 per pound. At present, the major users of nephrite are the manufacturers of jewelry, carvings and novelties. This market will account for a very small percentage of the total nephrite sales if applications can be developed in the construction industry. The nephrite producers envision the use of this material for internal and external building facing, counter tops, floor tiles and, in the crushed form, 20 for terrazzo floors. Its hardness, extreme toughness, and resistance to corrosion and weathering make nephrite an ideal material for construction applications. The discovery of relatively large tonnage in place deposits has made it possible for the producers to supply the large quantities of consistent quality material that would be required by this industry. Research is present ly being conducted in Europe to establish the feasibility of using nephrite for the fabrication of bearings for watches and other instruments (p. c. Owen, 1972; p. c. Smith, 1972). 21 III. PETROLOGY AND PHYSICAL PROPERTIES OF BRITISH COLUMBIA NEPHRITE Jade is a terra that is applied to two mineralogically distinct species, nephrite and jadeite. Nephrite is a compact, dense, raicrofibrous form of tremolite-actinolite (Ca^Mg.Fe^OH^Si^O^^), an amphibole, and jadeite (NaAlCSiO-j^) is a massive, microgranular form of the pyroxene of the same name. True nephrite consists of microscopic bundles of tremolite fibers (Plates 1, 2) that have been completely felted or interwoven with one another, producing the characteristic nephritic structure (Turner, 1935). In poor quality nephrites this structure is poorly developed or even completely absent. NEPHRITE CLASSIFICATIONS The nephrite classification commonly used by North American geologists is one established by Turner (1935) during an investigation of New Zealand green stones. This classification is based on microstructure and consists of five divisions, three of which deal with nephrites and two with tremolite rocks lacking a nephritic structure. The Turner classification is used in this report. European geologists use a classification, consisting of seven divisions, that was devised by Kalkowsky (1906) during his study of the Appenine nephrite deposits in northern Italy. Both classifications are presented below. 22 Plate 1: Scanning electron micrograph of a schistose nephrite transitional to a semi-nephrite illustrating the twisted and interwoven nature of the component tremolite fibers (#37; 0»Ne-ell Creek), X 300. Plate 2: Scanning electron micrograph of a schistose nephrite transitional to a semi-nephrite illustrating the fine fibrous nature of the tremo lite (#37; O'Ne-ell Creek), X 1270. 23 Turner Classification The three varieties of nephritic rocks according to the Turner classifica tion are non-schistose nephrites, schistose nephrites and semi-nephrites, with transitional varieties being rather common. Non-schistose Nephrites Nephrites in this division are characterized by the consistantly small size (0.02 mm to 0.3 mm) and unoriented arrangement of the individual tufts of tremolite fibers (Plate 3). The tufts are twisted and felted forming a perfectly developed nephritic structure. Occasionally, prisms and acicules (up to 1.5 mm x 3.0 mm) of tremolite are present indicating a transition to a semi-nephrite. Transition to the schistose nephrites is indicated by the presence of bundles of mutually parallel coarser than average fibers of tremolite. Schistose Nephrites The schistose nephrites are distinguished by the presence of abundant parallel tufts (0.3 mm to 0.5 mm) of tremolite set in a fine nephritic base, the base often comprising only a small percentage of the specimen (Plate 4). The schistosity is due to the parallelism of the fibrous aggregates although the average orientation of the fibers may be inclined to that of the aggregate. The presence of a small amount of coarse prismatic tremolite indicates a transition to a semi-nephrite. In hand specimen, schistose nephrites may 24 Plate 4: Photomicrograph of a schistose nephrite (#10; Kelly Creek), crossed nicols. 25 exhibit a well-developed schistosity. Semi-nephrites The semi-nephrites are composed partly of nephritic material and partly of abundant coarse crystalline tremolite as acicular crystals (1 mm x 0.05 mm to 3 mm x 0.25 mm) or as large sheaves (4 mm x 2 mm) of parallel unfelted fibers (Plates 5, 6). In some instances, the ends of the coarse prismatic crystals fray out into the enclosing nephritic base. The coarse material is not necessarily parallel throughout the section. Accessory minerals, especially chlorite, are much more abundant in the semi-nephrites than in the non-schistose and the schistose nephrites. In hand specimen, the semi-nephrites are usually somewhat fissile. Kalkowsky Classification The following is the Kalkowsky classification as presented by Kolesnik (1970). "1. Matted fibrous (nephritic), with the individual finest fibers or tufts closely intertwined with a simultaneous extinction. 2. Radial, with the tufts reminiscent of a coxcomb. 3. Spherulite. 4. Fibrous, a long tuft of nearly parallel fibers. 5. Wavy, with parallel fibers in regularly alternating short bands locally visible with naked eye. 6. Fluffy, with the fibers undistinguishable even at highest magnification. The entire mass is reminiscent of coarse fluff with gradually inter changing interference colours. 7. Coarse-grained (mosaic). The grains, 2-3 mm, consist of short and extremely fine fibers with a nearly simultaneous extinction. The grains have smooth faces and often are pierced by narrow bands of similar fibers." 26 0.5 mm Plate 5: Photomicrograph of a semi-nephrite, with large sheaves of parallel unfelted fibers (#8; Fall River), crossed nicols. Plate 6: Photomicrograph of a schistose nephrite transitional to a semi-nephrite (#40; Seywerd Creek), crossed nicols. The transition to a semi-nephrite is indicated by the development of acicular crystals of tremolite. 27 PETROLOGY The twenty-six nephrite specimens examined in thin section are composed largely of tremolite. Accessory minerals include chlorite, diopside, carbonate, uvarovite, picotite, chromite, sphene, pyrite, talc, and phlogopite with chlorite being the most abundant. Present are non-schistose nephrites, schistose nephrites, semi-nephrites and transitional varieties. The classifi cation, mineralogy and visually estimated mode of the specimens are tabulated in Table 2. Tremolite Tremolite is the most abundant mineral present, comprising at least 89 per cent of any section. In thin section the tremolite is colourless and under crossed-nicols the interference colours range from low first order to middle second order. Extinction angle (cAz) determinations on the tufts and crystals of coarser tremolite were between 16° and 19° although in many cases the extinction was either parallel or wavy and indistinct. Indices of refraction were not determined but those obtained from the literature for nephritic tremo lite are presented in Table 3. The individual tufts of fine fibers forming the nephritic base of the specimens generally range in length from 0.01 mm to 0.20 mm, although in one section (#35) the smallest tufts are 0.004 mm long. In the schistose nephrites, the oriented aggregates of interwoven and subparallel fibers are 0.02 mm x 0.10 mm to 0.10 ram x 1.30 mm. The acicular crystals and Table 2 Classification, Mineralogy and Mode of British Columbia Nephrites Specimen No. Locality Classification Mineralogy Percentage 6 Junction of the Schistose nephrite Tremolite 98 Bridge and Yalakom Chlorite 1 Rivers Picotite "1 Carbonate \ 1 Sphene J 7 Fall River Non-schistose nephrite Tremolite 100 transitional to schis Picotite 1 tose nephrite Uvarovite r <l Sphene j 8 Fall River Semi-nephrite Tremolite 99 Picotite Uvarovite Phlogopite Chlorite 1 Pyrite Sphene -9 Ogden Mountain Schistose nephrite Tremolite 99 Diopside T- i Sphene J A 10 Kelly Creek Schistose nephrite Tremolite 99 transitional to Picotite semi-nephrite Uvarovite Chlorite 1 Chromite? Sphene -Table 2 continued Specimen No. Locality Classification Mineralogy Percentage 11 Kelly Creek Schistose nephrite Tremolite Picotite Uvarovite Chlorite Pyrite Sphene 99 1 12 Kwanika Creek Schistose nephrite transitional to semi-nephrite Tremolite Unknown (zoisite?) Picotite Uvarovite Pyrite Sphene 99 < 1 1 14 Dease Lake Non-schistose nephrite Tremolite Chlorite Sphene ] 99 15 Van Decar Creek Schistose nephrite transitional to semi-nephrite Tremolite Picotite Uvarovite Chlorite Pyrite Sphene 99 1 16 O'Ne-ell Creek Schistose nephrite transitional to semi-nephrite Tremolite Diopside Picotite Chlorite Opaques Uvarovite Pyrite Sphene 92 5 1 1 Table 2 continued Specimen No. Locality Classification Mineralogy Percentage 19 Fall River Schistose nephrite Tremolite Chromite Sphene ] 100 < 1 23 Coquihalla River Semi-nephrite Tremolite Diopside Picotite Uvarovite Carbonate Pyrite Sphene ] 95 3 1 1 <1 24 Brett Creek Semi-nephrite Tremolite Chlorite Pyrite Sphene 97 3 26 0»Ne-ell Creek Non-schistose nephrite Tremolite Chlorite Picotite Sphene ] 96 3 30 Cassiar area Semi-nephrite Tremolite Chlorite Uvarovite Picotite Pyrite Sphene Talc 94 4 1 1 Table 2 continued Specimen No. Locality Classification Mineralogy Percentage 33 O'Ne-ell Creek Schistose nephrite Tremolite 98 Chlorite 2 Diopside Picotite r <l Sphene j 35 O'Ne-ell Creek Non-schistose nephrite Tremolite 100 Opaques > <1 Sphene J 36 O'Ne-ell Creek Schistose nephrite Tremolite 97 Chlorite 2 Picotite 1 Pyrite \ 1 Sphene J 37 O'Ne-ell Creek Schistose nephrite Tremolite 89 transitional to Chlorite 10 semi-nephrite Picotite 1 Pyrite Sphene J 39 O'Ne-ell Creek Schistose nephrite Tremolite 98 Chlorite 1 Uvarovite Picotite Chromite i Pyrite Talc Sphene • Table 2 continued Specimen No. Locality Classification Mineralogy Percentage 40 Seywerd Creek Schistose nephrite Tremolite 99 transitional to Chlorite semi-nephrite Chromite Uvarovite I Pyrite Sphene -41 Silver Creek Schistose nephrite Tremolite 96 Chlorite 3 Picotite i Pyrite } i Sphene J 42-B Marshall Creek Schistose nephrite Tremolite 92 transitional to semi- Chlorite 7 nephrite Picotite i- i Uvarovite j L 43 Ogden Mountain Schistose nephrite Tremolite 99 transitional to Picotite semi-nephrite Uvarovite -Diopside I Pyrite Sphene -44 Ogden Mountain Schistose nephrite Tremolite 95 Diopside 4 Uvarovite "l Picotite h i Sphene j Table 2 continued Specimen No. Locality Classification Mineralogy Percentage 45 Dease Lake Semi-nephrite Tremolite 99 Uvarovite 1 Picotite Pyrite r <L Sphene 34 sheaves of coarse parallel fibers present In the semi-nephrites exhibit a size range of 0.008 mm x 0.06 mm to 0.02 mm x 0.60 mm and 0.70 mm x 0.10 mm to 5.40 mm x 1.90 mm, respectively. The ends of the acicular crystals are often frayed in the manner described by Turner (1935), (Plate 7). Thin section #45 is characterized by the presence of large radial masses of tremolite-actinolite fibers set in a much finer nephritic base (Plate 8). Veins of cross-fiber tremolite, up to 0.6 mm wide are observed in a number of sections. Table 3 Indices of Refraction of Tremolite in Nephrites n* n g -n« % Fe Colour in Hand Specimen Reference 1.597 1.625 0.028 0.98 Yellowish grey-green Washington (1922) 1.601 1.621 0.020 4.03 ——— Rose and Fromme (1932) 1.609 1.631 0.022 3.22 Spinach green to yellow green Huang (1966) 1.609 1.632 0.023 4.44 Kolesnik (1970) 1.609 1.629 0.020 3.65 Bluish green Yoshimura et al (1966) 35 Plate 8: Photomicrograph of a radial mass of tremolite fibers set in a fine nephritic base (#45; Dease Lake), crossed nicols. The specimen is classified as a semi-nephrite. 36 Chlorite Chlorite is present in eighteen sections in amounts up to 10 percent. In thin section, it is colourless and has a very low birefringence. The interfer ence colours are usually a peculiar dark olive green, although in several sections, an anomalous blue colour is seen. X-ray diffraction data indicate that the chlorite is very similar to kammererite, a chromian penninite (Table 4). It occurs as aggregates of flakes, the individual flakes not exceeding 0.007 mm x 0.002 mm in size. The aggregates range in shape from roughly circular, up to Table 4 X-ray Diffraction Data for Kotschubeite (chromian clinochlore), Clinochlore, Kammererite (chromian penninite), Penninite, and for Chlorite from British Columbia Nephrite Specimens Sample d(002) a A d(003) A d(004) o A Kotschubeite A.S.T.M.: 12 - 185 7.11 4.757 3.570 Clinochlore A.S.T.M.: 19 - 749 7.12 3.56 Kammererite A.S.T.M.: 12 - 240 7.14 4.774 3.589 Penninite A.S.T.M.: 10 - 183 7.19 4.80 3.60 Nephrite #30 Cassiar area 7.15 4.77 3.56 Nephrite #36 O'Ne-ell Creek 7.15 4.76 3.57 Nephrite #42-B Marshall Creek 7.13 4.75 3.56 37 Plate 10: Photomicrograph of a fractured chrome spinel grain, partially replaced by chlorite (#15; Van Decar Creek), plane polarized light. 38 0.12 mm. in diameter, to elongate and irregular with the long axis generally parallel to the direction of schistosity. The circular aggregates usually have a core of picotite or chromite and, more often than not, uvarovite garnet (Plate 9). Spinel Members of the spinel group of minerals observed in the nephrite are picotite, a chromian variety of hercynite, and chromite. The picotite is dark reddish brown to light yellowish brown and occurs as rounded fractured grains up to 1.3 mm x 0.90 mm (Plate 10). According to MacGregor and Smith (1963), the redness of a chrome spinel in thin section increases with chrome content. The individual picotite fragments are often strongly corroded due to replace ment by garnet or chlorite. The chromite is opaque except on thin edges where it is translucent and dark brown. It occurs as discrete grains up to 0.5 mm in diameter or as partial rims on picotite fragments. Ilmenite In one section, #16, a slightly magnetic, finely disseminated mineral, probably ilmenite, occurs as poorly developed skeletal crystals in diopside. Diopside Diopside is present in six sections, #9, #16, #23, #33, #43, and #44. In thin section it is colourless, optically positive, and has an extinction angle, cAZ, of 41°. It occurs as aggregates of subhedral crystals in narrow bands 0.5 mm Plate 11: Photomicrograph of corroded remnants of diopside (d), (#16; O'Ne-ell Creek), crossed nicols. 0.5 mm Plate 12: Photomicrograph of spindle-shaped diopside crystals (d), (#43; Ogden Mountain), crossed nicols. 40 (to 0.2 mm wide), as corroded remnants (0.1 mm x 0.3 mm to 0.9 mm x 2.8 mm), (Plate 11), as spindle-shaped, often corroded crystals (0.03 mm x 0.5 mm), (Plate 12) and as large subhedral crystals (to 0.1 mm x 1.9 mm). The latter are present in one section only and occur in a vein with coarse tremolite. Twinning is occasionally observed in the diopside, the twin plane being parallel to (100). The spindle shape of the diopside crystals is very similar to that described by Kolesnik (1970) for the diopside in Siberian nephrites. Replace ment of the diopside by tremolite is suggested by the corroded nature of the diopside grains. Kolesnik (1970) has determined, on the basis of 1000 measurements, that the majority of the spindle-shaped diopside crystals in Siberian nephrites are elongated perpendicular to the direction of the tremolite-actinolite fibers. Similar measurements were not made on the specimens examined as diopside crystals of this type are few in number and are restricted to two sections. Uvarovite Fourteen of the sections examined contain uvarovite garnet; in most cases it is visible in hand specimen as bright green grains or clusters of grains. In thin section, this mineral is pale to bright green and often exhibits some degree of anisotropism. It usually forms replacement rims around corroded picotite fragments (Plate 13) but also occurs as minute anhedral grains (Plate 14), often in elongate aggregates that are parallel to the schistosity of the Al 0.5 ram Plate 14: Photomicrograph of anhedral grains of uvarovite garnet (#8; Fall River), plane polarized light. The cores of the garnet grains usually contain phlogopite. specimen. In some sections, the uvarovite surrounding the picotite fragments is, in turn, surrounded by a halo of chlorite. Unknown A mineral thought to be zoisite occurs as an augen-like mass of subhedral crystals in thin section #12. The mineral is colourless, has parallel extinction and a positive optic sign. Contained within the mass are patches of chromite and uvarovite garnet. Sphene Sphene is present in variable amounts in the majority of the sections examined. It occurs as brownish dustings of microlites that are best observed in plane light. Carbonate A carbonate, probably magnesite, is present in two sections (#6, #23). In one section, it occurs in microveinlets and in the other as rare rounded grains up to 0.3 mm in diameter. Phlogopite and Talc A very minor amount of phlogopite, identified by X-ray diffraction, is present in one section (#8) as small, strongly birefringent patches surrounded by uvarovite garnet. Talc, present in two sections (#30, #39), occurs in microveinlets cutting tremolite. Pyrite Small, sparsely disseminated, euhedral to anhedral pyrite grains are 43 present in 13 of the 26 sections examined. The average grain size is 0.03 mm. PHYSICAL PROPERTIES  Fracture Only generalized observations can be made regarding the fracture of the nephrite specimens studied. The non-schistose nephrites usually have an irregular fracture with a fine flaky surface. In the schistose nephrites, surfaces parallel to the schistosity are relatively smooth but are finely to coarsely flaky; surfaces perpendicular to the schistosity are irregular to hackly. The serai-nephrites that exhibit a pronounced foliation have a coarsely flaky to splintery fracture. Turner (1935) described the fracture of non-schistose and schistose nephrites as finely flaky and that of semi-nephrites as coarsely flaky. Specific Gravity The specific gravity was determined, on a Jolly balance at 18°C, for 34 specimens. Four determinations were made on each specimen and averaged; the results are tabulated in Table 5. The average specific gravity is 3.00 with the maximum and minimum being 3.04 and 2.95, respectively. The average of seven determinations obtained from the literature (Washington, 1922; Rose and Fromrae, 1932; Coleman, 1966; Huang, 1966; Kolesnik, 1970) is 2.97. As a generalization, specimens containing several percent chlorite (S.G.: 2.6 to 3.3) have lower than average specific gravities while those containing several 4.4 Table 5 Specific Gravity of British Columbia Nephrite Specimens Specimen Number , Locality Specific Gravity Specimen Number Locality Specific Gravity 4 Marshall Creek 3.01 28 Dease Lake area 3.00 6 Junction of Bridge and Yalakom Rivers 3.01 30 Cassiar area 2.98 7 Fall River 3.00 31 Dease Lake area 2.99 8 Fall River 3.01 33 O'Ne-ell Creek 2.99 9 Ogden Mountain 3.00 34 O'Ne-ell Creek 2.99 10 Kelly Creek 2.98 35 O'Ne-ell Creek 3.00 11 Kelly Creek 3.01 36 O'Ne-ell Creek 2.99 12 Kwanika Creek 3.04 37 O'Ne-ell Creek 2.98 13 Kwanika Creek 3.01 38 O'Ne-ell Creek 2.98 14 Dease Lake 3.00 39 O'Ne-ell Creek 3.00 15 Van Decar Creek 3.00 40 Seywerd Creek 2.98 16 O'Ne-ell Creek 3.02 41 Silver Creek 3.00 19 Fall River 3.01 42-A Marshall Creek 3.00 20 Fall River 3.01 42-B Marshall Creek 2.97 23 Coquihalla River 3.02 43 Ogden Mountain 3.02 24 Brett Creek 3.02 44 Ogden Mountain 3.01 26 O'Ne-ell Creek 2.99 45 Dease Lake area 2.96 Mean specific gravity = 3.00 (34 specimens). 45 percent diopside (S.G.: 3.22 to 3.56) have higher than average specific gravities. The specific gravity was also determined for the weathered rind from three placer specimens and the results, along with those for corresponding unweathered nephrites, are presented in Table 6. The weathered nephrite has a slightly lower specific gravity due to its fractured less compact nature. Table 6 Specific Gravity of Weathered and Unweathered Nephrite from Placer Boulders Sample Number Locality S.G. Unweathered Nephrite S.G. Weathered Nephrite 7 Fall River 3.00 2.93 39 O'Ne-ell Creek 3.00 2.88 41 Silver Creek 3.00 2.96 The tonnage factor for nephrite, based on an average specific gravity of 3.00, is 10.7 cubic feet per ton. Colour and Lustre The colour of the nephrite specimens was measured qualitatively by compar ing a polished slab with the Geological Society of America Rock Colour Chart (G.S.A., 1963). This method appears to be reasonably satisfactory for all samples except one (#19) with a dark blue green colour, a colour not present in the colour chart. 46 Of the 34 specimens examined, more than 60 percent are dusky yellowish green (10GY 3/2) or a mixture of greyish green and dusky yellowish green (10GY 4/2). The remainder of the specimens are various shades of the blue green and green yellow hues. In Table 7, the specimens are grouped according to colour. A number of the specimens contain dark yellowish green (10GY 4/4) lenses and patches of uvarovite garnet. White, yellow and black nephrites have been reported in the literature (Palmer, 1967; Kolesnik, 1970) but none were seen during the course of this study. Upon weathering, nephrite becomes discoloured, either bleached or darkened, and deposits of iron hydroxides are formed along fractures and on external surfaces. An opaque white rind resembling bone is often seen on nephrite artifacts that have been subjected to burning. The original shape of the object is not altered in any way (Palmer, 1967). This fact may be of use to archaeologists, particularly in British Columbia, in recognizing nephrite artifacts in excava tions of old Indian settlements. Fractured surfaces of nephrite have a dull somewhat waxy lustre while polished surfaces have a greasy lustre. Hardness 2 Both the Vickers hardness number (V. H. N.), in Kg/mm , and Mohs hardness 47 Table 7 Colour of British Columbia Nephrite Specimens Nephrite Colour Munsell* Numerical Colour Designation Specimen Nos. Dusky yellowish green 10GY 3/2 6,7,9,10,12, 13,24,38,41, 42-B, 43,44 Mixture of greyish green and dusky yellowish green 10GY 4/2 11,14,28,30,33,36,37,39,40 Greyish olive green 5GY 3/2 4,8,16,26,42-A Greenish grey 5GY 6/1 34,35 Mottled greyish green and dark yellowish green 10GY 5/2 10GY 4/4 15,23 Dark greenish grey 5GY 4/1 20 Greyish blue green 5BG 5/2 31 Pale blue green 5BG 7/2 45 Dark blue green Not covered by G.S.A. Rock Colour Chart 19 * Rock-Colour Chart distributed by the Geological Society of America, reprinted 1963. 48 were determined for fourteen polished specimens mounted in bakelite briquettes. These are tabulated in Table 8. The method of preparing the samples and obtaining the hardness values is outlined in Appendix II. The Vickers hardness number is a measure of hardness which is calculated from the size of the indentation produced by a pyramidal-shaped, diamond-tipped indenter falling, under a given load and over a set period of time, onto a specimen. 2 The mean Vickers hardness number is 950 Kg/mm ; the maximum and minimum 2 2 values are 1115 Kg/mm and 789 Kg/mm , respectively. The range of the hardness values is shown in Figure 3, a graph of Mohs hardness values against the logarithm of Vickers hardness number (Bowie, 1967). From Figure 3, it can be seen that the maximum and minimum values of Vickers hardness correspond to Mohs hardnesses of approximately 6% and slightly greater than 7, respectively. Mohs hardness values of the polished surfaces were determined by comparison with standard hardness points. None of the specimens were scratched by the point with a hardness of 6% but all were readily scratched by the point corresponding to a hardness of 7. Both Turner (1935) and Finlayson (1909) report Mohs hardnesses for polished surfaces of New Zealand nephrite that are slightly lower than those determined in this study. Turner observed that non-schistose and schistose varieties had a hardness of 6 to 6.5 while Finlayson recorded a value of 6.5. Table 8 Vickers Hardness Number and Mohs Hardness of Polished Specimens of British Columbia Nephrite Sample Number Locality Number of Determinations Mean V.H.N. (Kg/mm2) Standard Error of the Mean Measured Mohs Hardness 4 Marshall Creek 5 993 25 7 6 Junction of Bridg< River and Yalakom River 5 950 25 7 7 Fall River 5 861 67 7 9 Ogden Mountain 5 851 58 7 10 Kelly Creek 5 1025 52 7 11 Kelly Creek 4 919 25 7 12 Kwanika Creek 5 1115 50 7 13 Kwanika Creek 5 933 30 7 14 Dease Lake 5 819 40 7 15 Van Decar Creek 5 789 32 7 16 O'Ne-ell Creek 5 1062 32 7 26 O'Ne-ell Creek 5 941 44 7 33 O'Ne-ell Creek 5 1017 14 7 34 O'Ne-ell Creek 5 1018 42 7 5Q Fig. 3 A graph of Mohs hardness values against the log of Vickers hardness numbers, (after Bowie, 1967) 2000 1000 Range of the Vickers hardness numbers of 14 British Columbia nephrite specimens. CO CO to z Q < X CO ui U 100 20 MOHS HARDNESS 51 Polished specimens of semi-nephrite examined by Turner were found to have a hardness of 5.5 to 6.0. The lower hardness of semi-nephrite is readily explained by the poorly developed nephritic microstructure and by the abundant impurities that characterize this variety of nephrite. There does not appear to be any obvious correlation between the hardness of the specimens studied and the microstructure or the mineralogic composition. The observed hardness variations are probably due to minute flaws produced dur ing the process of sawing, mounting and polishing. Crushing Strength and Relative Corrosion Hardness Values for these properties were not determined for the British Columbia specimens; those presented below have been obtained from the European litera ture and are included in this report because of the unavailability of such information. The crushing strength of high quality Siberian nephrite is reported to be 7,759 Kg/cm2 (Kolesnik, 1970). The high value is understandable in light of the characteristic microstructure of this material. Eppler (1941) has determined that the relative mechanical corrosion hardness, or resistance to abrasion, of nephrite is 36 percent higher than that of quartz. 52 IV. THE CHEMISTRY AND CRYSTALLOGRAPHIC STRUCTURE OF NEPHRITE Nephrite possesses an unique microstructure, one in which fine fibers of tremolite occur in tufts which are felted and twisted* This microstructure, which imparts to nephrite its distinctive characteristics, is a function of the limited conditions under which it forms (Kolesnik, 1970). These conditions are quite different to those under which common broad-prismatic tremolite-actinolite forms. This section attempts to outline the chemical and structural features of nephritic tremolite and broad-prismatic tremolite-actinolite. CHEMISTRY The general formula of an amphibole may be expressed as (Ernst, 1968; Whittaker, 1960; Deer et al, 1966; Gibbs, 1966): W0_1X2Y5Zg022(OH,0,F,Cl)2 where W represents ten- to twelve-fold coordinated cations, commonly Na and K, occupying the A structural sites (Figure 6); X refers to six- or eight-fold • • +2 coordinated cations with ionic radii from 0.7 A to 1.1 A, chiefly Ca, Na, Fe and Mn; Y stands for six-fold cations with ionic radii from 0.57 A to 0.91 A, + 2 +3 chiefly Mg, Fe , Fe , Al, Mn, and Ti; and Z refers to small highly charged cations within the tetrahedral groups, largely Si, but may be replaced by Al up to about 25 percent. Hydrogen may be present to balance excess charges. The common cation replacements for the amphibole group are Mg = Fe, Al = Si, (Mg,Fe) = Al and Na = Ca; in the tremolite-actinolite series, the predominant 53 replacement is iron for magnesium. A replacement of the type Al = Si, (Mg,Fe) = Al or Na Ca must be accompanied by an additional replacement of this type to maintain charge balance. The above formula represents one-half of the atoms in the unit cell. The crystallographie formulae of nephritic tremolite and broad-prismatic tremolite-actinolite have been computed by Kolesnik (1970) from the analyses of 57 nephrite specimens and 72 actinolite-tremolite specimens. They are present ed below: Broad-prismatic tremolite-actinolite: (^l.ss^.is^.o^o.ii^.n^A^i^ot^V.io^o.os^.oo <Si7.75Al0.25°22)(OH)1.93°0.07 Nephritic tremolite: + 2 +3 (Ca1.91M80.05K0.03Na0.12)2.11(M84.53Fe0.36Fe0.11)5.00 (Si7.77A10.20°22)(OH)2 °'47 H2° The most notable differences between the broad-prismatic amphiboles and the nephritic amphiboles are the increased Ca content and the almost total absence of Mg in the X position of the latter. Other features of nephritic tremolite 4-3 +2 are the absence of Al in the Y position, a decrease in the Fe content of + 3 the Y position and a decrease in the Al content of the Z position. Also, the amount of water liberated from nephrite at temperatures in excess of 100°C, the so-called crystallographie water, is much higher than that in broad-54 prismatic tremolite. Kolesnik attributes the high magnesium content in the X position of the tremolite-actinolite to mechanical additions of anthophyllite. To explain the higher calcium content and the almost total absence of magnesium in the X +2 +2 position of nephritic tremolite, he suggests that Ca -Mg isomorphism is operative under the conditions at which nephrite forms. Crystallographie and thermal studies indicate that the bulk of the excess water contained in nephrite does not enter the crystal lattice but is probably associated with the extremely fine fibrous structure that is characteristic of the nephrites. This structure would allow nephrite to adsorb a significant amount of water and retain it on heating. The weight loss curves in Figure 4 illustrate that the water in nephrite is liberated at a considerably slower rate and at higher temperatures than in the acicular broad-prismatic tremolite-actinolite. Huang (1966) also found a slight excess of water in the computed formula for nephrite from Taiwan. The analyses, of 42 nephrite specimens, obtained from the literature, are presented in Appendix III and are plotted in Figure 5, a plot of MgO-CaO-FeO + Fe^O^. All of the analyses fall on or close to the tremolite-ferroactinolite line and are grouped at the tremolite end of the line. The compositional field of New Zealand nephrites (Finlayson, 1909; Coleman, 1966) is outlined by a broken line and represents a total of 22 samples (Analyses 1 - 20, 25 - 26; 55 1200 Broad Prismatic Tremolite 1000 -r 800 TEMPERATURE, °C Fig.4. Curves of weight loss in heating for nephrite and broad prismatic tremolite from Siberia, U.S.SR.(after Kolesnik, 1970.) 56 Ca O Tremolite MgO Fig.5 + FeO MgO-CaO—Fe203+FeO in nephrites from various world localities. .Field of New Zealand nephrites (Finlayson, 1909; Coleman, 1966) C--' Field of Wyoming nephrites (Sherer, 1969) A: Granite Mountains; Sage Creek locality, Seminoe Mountains B: Laramie Mountains; Seminoe locality, Seminoe Mountains + Harz area, East Germany (Uhlig, 1910) A Bahia, Brazil (Washington, 1922) © Hauderes, Valais Canton, Switzerland (Preiswerk, 1926) H Koleborn, Harz area, East Germany (Rose and Fromme, 1932) • Fengtien, Taiwan (Huang, 1966) Hakuba-mura, Negano Prefecture, Japan (Yoshimura et al, 1966) A Jordanow, Poland (Heflik, 1968) O East Sayans, Siberia, U. S. S. R. (Kolesnik, 1970) 57 Appendix III). The dotted lines define the compositional fields of Wyoming nephrites (Analyses 31 - 42; Appendix III), (Sherer, 1969). A description of the occurrences of the other specimens is given in Appendix I. Sherer (1969) has determined that trace amounts of Ni, V, Cr, Co, Cu, Sr, Ba, B, Ga, Zr, and Zn are present in the Wyoming nephrites. It is probable that these elements are present, in variable amounts, in the nephrites from other localities but have not been looked for. Possibly the amounts or the ratios of certain of these trace elements could be used to characterize the nephrites from various localities. CRYSTALLOGRAPHIC STRUCTURE The structure of the amphiboles is characterized by the presence of (Si,Al)0^ tetrahedra linked in double chains with the composition (Si^Oj^) . The structure of the monoclinic amphibole, tremolite, projected upon (001) and parallel to c, is shown in Figure 6. The c-cell edge of the unit cell is defined by the repeat of the chain along its length. The sites marked M^, M^ and lij are occupied by the octahedrally coordinated Y cations. The two Si-0 chains with the hydroxy1 groups and the M^, and cations sandwiched in between them is equivalent to a narrow strip of the talc structure (Whittaker, 1960). Intermediate size Y cations are distributed nearly randomly in M^ and M^ and the smallest Y cations tend to be concentrated in M^ (Ernst, 1968). At the edges of the talc strips are the M, or X cations, Ca, Na and Mn, which -o—o -o—a- o a„ M A O O O O M, o M2 o M4 o AO 6- -o—o- o A -J"~V o -o—o- H6 Fig.6. The structure of tremolite. The projection is upon (001) and parallel to c. silicon: d oxygen : Q 59 serve to link the strips together. The cations at also serve this purpose but to a lesser extent than cations. The positions marked A and A* are not occupied in tremolite but in some amphiboles which contain in excess of 2(Ca,Na,K) ions per formula unit, these positions may be partially or complete ly occupied. The tremolite-actinolite amphibole series belongs to the monoclinic crystal syst em; the space group is C 2/m. Amphiboles possess a well-developed prismatic cleavage, the planes of which meet at angles of about 55° and 125°, yielding cleavage fragments which appear diamond-shaped in cross section. This cleavage, which is developed along those surfaces in which a minimum number of bonds are broken, passes through the amphibole structure parallel to the chains by stepping successively along their backs through the A-site and thence to the next layer at the periphery of the octahedral layer (Shappell, 1936). In nephrite, due to the very fine nature of the component tremolite fibers, the cleavage is never observed except at the extreme magnifications offered by the scanning electron microscope (Plate 15). Studies of synthetic monoclinic amphiboles have shown the effects of ionic substitution on the dimensions of the unit cell (Ernst, 1966). The bQ para meter is controlled by the sizes of the cations in and M^, but because the occupancy of M, is constant in any particular synthetic series, the control on 60 Plate 15: Scanning electron micrograph of a schistose nephrite transitional to a semi-nephrite illustrating the (110) cleavage of tremolite. (#37; O'Ne-ell Creek), X 6500. 61 this parameter shifts to the cations occupying M^. With an increase in the mean size of the octahedrally coordinated cations, there is an increase in aQ sin B. A slight increase in the chain length Cq is observed when the size of the cations in and is increased. The cell volume increases with the number of large ions contained within the structure. The unit cell parameters of tremolite from ten British Columbia nephrite specimens are tabulated, with those for tremolite and nephritic tremolite obtained from the literature, in Table 9. Details of the method employed in obtaining the unit cell data are given in Appendix II. As can be seen from this data, the a and c parameters are virtually the same for both broad-o o prismatic tremolite and for nephritic tremolite. The major difference, however, is in the length of the bQ parameter; that in the latter is considerably larger + 2 probably reflecting the increased amount of Fe contained in the position. There does not appear to be any relationship between the length of the CQ-cell edge and the extreme elongation of the nephritic tremolite fibers. X-ray diffraction data for tremolite (A.S.T.M.: 13 - 437) and for nephritic tremolite from British Columbia (#39; 0»Ne-ell Creek), New Zealand (Coleman, 1966), Taiwan (Huang, 1966) and Siberia (Kolesnik, 1970) are presented in Table 10. 62 Table 9 Unit Cell Parameters for Tremolite from British Columbia Nephrite, Tremolite from Siberian Nephrite and Common Tremolite Sample Number Locality o a A o b A o O c A o B Cell , Vol. AJ 7 Fall River 9.883 18.116 5.261 105° 11' 909.2 +0.018 TO.022 TO.004 T10' Tl.7 11 Kelly Creek 9.880 18.112 5.261 105° 11' 908.6 +0.017 +-0.021 +0.004 + 10' Tl.6 12 Kwanika Creek 9.879 18.110 5.259 105° 11' 908.6 +0.017 +-0.020 t0.004 TlO' + 1.6 19 Fall River 9.878 18.127 5.262 105° 9' 909.5 +0.018 +0.023 +0.005 + 11' + 1.7 23 Coquihalla River 9.888 18.130 5.263 105° 11' 910.6 +•0.017 +-0.021 TO.004 + 10' + 1.6 35 O'Ne-ell Creek, 9.886 18.132 5.263 105° 10' 910.6 +0.017 +0.021 +0.004 + 10« + 1.6 36 O'Ne-ell Creek 9.889 18.134 5.267 105° 12» 911.5 +0.016 +0.020 +0.004 T 9' + 1.5 40 Seywerd Creek 9.890 18.131 5.266 105° 12» 911.3 +0.018 TO.022 TO.004 T 10' Tl.7 41 Silver Creek 9.873 18.106 5.259 105° 12' 907.2 +•0.017 TO.021 TO.004 + 10' + 1.6 42-B Marshall Creek 9.885 18.116 5.262 105° 10» 909.5 +0.018 +0.022 +0.004 + 10' + 1.7 Siberian 9.878 18.12 5.29 Nephrite +0.007 T0.005 +0.006 104° 47' _ _ _ (Kolesnik, 1970) Tremolite 9.84 18.02 5.27 104° 57' — A.S.T.M.: 13 -437 63 Table 10 X-ray Diffraction Data for Tremolite (I) and for Nephritic Tremolite from British Columbia (II), New Zealand (III), Taiwan (IV) and Siberia (V) I II J11 IV V hkl d A I d A I d A I d A I d A I 020 8.98 16 9.05 35 9.00 20 9.01 37 9.04 20 110 8.38 100 8.45 90 8.43 100 8.38 95 8.48 100 130, 001 5.07 16 5.10 16 5.06 10 5.07 16 5.09 12 111 4.87 10 4.89 19 4.85 7 4.87 18 4.87 13 200 4.76 20 4.77 10 4.73 7 4.75 15 4.77 15 040 4.51 20 4.53 30 4.50 20 4.52 24 4.53 15 220 4.20 35 4.22 15 4.20 10 4.20 12 4.22 25 131 3.870 16 3.888 17 3.87 5 3.87 13 3.91 8 150, 041 3.376 40 3.387 45 3.38 20 3.38 24 3.391 15 240 3.268 75 3.282 50 3.27 50 3.27 40 3.285 46 310 3.121 100 3.130 100 3.12 100 3.12 100 3.133 100 311, 241 3.028 10 3.037 5 — — — — — — 151 2.938 40 2.944 35 2.94 25 2.940 24 2.940 16 330 2.805 45 2.809 13 2.805 15 2.805 12 2.808 35 421 2.730 16 2.734 30 2.731 10 — — 2.736 22 151 2.705 90 2.710 80 2.702 45 2.702 65 2.709 35 112, 061 2.592 30 2.597 30 2.593 15 2.592 22 2.602 12 64 Table 10 continued I II III IV V hkl d A I d A I d A I d A I d A I 202, 002 2.529 40 2.537 30 2.524 15 2.529 25 2.545 12 132 2.407 8 2.415 7 2.411 3 — — — — 350, 400 2.380 30 2.388 10 2.386 5 2.380 11 2.390 18 351 2.335 30 2.340 30 2.338 18 — — 2.341 26 421 2.321 40 2.328 25 2.327 16 2.321 28 2.307 10 420, 071 2.298 12 2.302 14 2.304 10 2.298 22 2.285 5 112 2.273 16 2.282 20 2.266 6 2.276 18 — — 242, 042 2.206 6 2.238 9 — — — — — — 441 2.181 6 — — — 2.181 7 — — 171, 261 2.163 35 2.167 25 2.161 19 2.161 25 2.167 16 081, 280 2.042 18 2.046 9 2.043 6 2.040 10 2.048 8 202 2.015 45 2.020 19 2.016 15 2.014 15 2.019 16 351, 370 2.002 16 2.001 8 2.001 7 2.002 17 2.007 12 281, 190 1.963 6 1.978 17 1.961 6 1.963 9 1.965 5 152 1.929 6 — — — — 1.933 7 — — 510 1.892 50 1.903 10 1.892 10 1.888 9 1.898 47 Radiation: CuK> I: Tremolite, A.S.T.M.: 13 - 437 II: Nephritic tremolite, British Columbia (#39; O'Ne-ell Creek) III: Nephritic tremolite, New Zealand (Coleman, 1966) IV: Nephritic tremolite, Taiwan (Huang, 1966) V: Nephritic tremolite, Siberia, U.S.S.R. (Kolesnik, 1970) 65 V. IRON AND TRACE ELEMENT GEOCHEMISTRY OF BRITISH COLUMBIA NEPHRITES Thirty one nephrite specimens from British Columbia, five from area I, twenty from area II and six from area III, were analysed for the following elements: iron, cobalt, nickel, manganese, copper, lead, zinc, chromium, titanium and vanadium. The reasons for the analyses are two-fold. The first, and foremost, is to determine if there is any regional variation in the trace element content of the nephrites. Such a variation, if systematic, could prove to be extremely important to archaeologists attempting to trace the sources of the nephrite used by early British Columbia Indians for the fabrica tion of tools. The second is to determine, in a qualitative way, what minor and trace elements are colouring agents. The first seven elements were determined by atomic-absorption spectro photometry. The analytical precision (95% confidence level) of these deter minations, based on duplicate analyses, is: Fe,Mn = +- 4%; Ni,Zn = £10%; Co,Cu,Pb = ± 20%. The last three were analysed with an emission spectrograph and, hence, are semirquantitative. Accessory minerals, because of their small grain size and intergrown nature, were not removed from the nephrites prior to analysis. Details of the analytical procedure are discussed in Appendix II; the results are presented in Table 11. Ionic radii given in the following discussion are obtained from Krauskopf (1967). Table 11 Iron and Trace Element Analyses of British Columbia Nephrite Specimens Sample Number Locality Fe % Co ppm Ni ppm Mn ppm Cu ppm Pb ppm Zn ppm Cr ppm Ti ppm V ppm 4 Marshall Creek 3.63 61 831 1043 23 25 60 4000 1000 200 6 Junction of Bridge and Yalakom Rivers 3.19 45 919 481 15 27 35 10000 400 200 7 Fall River 2.68 36 1100 606 10 22 36 4000 500 200 8 Fall River 3.38 24 719 1243 13 32 82 5000 400 150 9 Ogden Mountain 2.55 87 1181 812 16 30 67 4000 400 200 10 Kelly Creek 2.36 21 750 762 13 11 64 4000 200 100 11 Kelly Creek 2.68 46 1112 1243 16 30 97 5000 150 180 12 Kwanika Creek 3.63 70 1188 962 5 32 74 600 300 100 13 Kwanika Creek 2.49 116 1043 725 13 18 58 4000 400 80 14 Dease Lake 3.00 62 925 885 15 19 50 10000 300 200 Table 11 continued Sample Fe Co Ni Mn Cu Pb Zn Cr TI V Number Locality % ppm ppm ppm ppm ppm ppm ppm ppm ppm 15 Van Decar Creek 2.88 59 1012 575 6 22 22 4500 150 120 16 O'Ne-ell Creek 3.25 65 1393 869 17 19 69 6000 250 150 19 Fall River 3.38 100 919 969 6 20 90 1500 400 150 23 Coquihalla River 2.94 70 787 813 33 33 58 3000 500 150 24 Brett Creek 3.25 64 1038 1537 15 21 89 3000 500 180 26 O'Ne-ell Creek 3.38 47 1630 732 35 22 47 8000 200 180 28 Dease Lake area 2.94 40 325 468 3 32 43 200 350 100 30 Cassiar area 3.06 37 956 1125 5 11 44 1000 200 180 31 Dease Lake area 3.13 28 212 587 4 17 33 100 100 80 34 O'Ne-ell Creek 3.38 41 544 813 10 29 39 200 10000 200 35 O'Ne-ell Creek 3.13 19 134 725 3 12 35 100 2000 180 36 O'Ne-ell Creek 2.94 59 1370 581 13 10 35 3500 350 100 Table 11 continued Sample Fe Co Ni Mn Cu Pb Zn Cr Ti V Number Locality % ppm ppm ppm ppm ppm ppm ppm ppm ppm 37 O'Ne-ell Creek 3.13 50 1394 606 14 21 42 10000 325 100 39 O'Ne-ell Creek 3.13 63 1370 512 7 13 32 3000 300 100 40 Seywerd Creek 3.00 6 562 1212 2 16 39 1000 150 80 41 Silver Creek 2.71 44 1025 380 9 24 32 2500 150 80 42-A Marshall Creek 3.63 37 556 643 6 22 32 5000 800 200 42-B Marshall Creek 2.74 30 1600 725 3 32 43 6000 30 100 43 Ogden Mountain 3.31 19 1207 937 3 10 65 6000 300 180 44 Ogden Mountain 2.90 21 1269 738 3 20 44 5000 150 180 45 Dease Lake area 2.81 47 512 493 4 29 29 1500 250 100 Mean X 3.05 49 954 800 11 22 55 4000 700 150 Fe, Co, Ni, Mn, Cu, Pb, Zn: Atomic absorption analyses; analyst J. R. Fraser. The precision of the analyses, at the 95% confidence level, is: Fe,Mn = T4%; Ni, Zn =*10%; Co, Cu, Pb = + 20%. Cr, Ti, V: Spectrographic analyses, semi-quantitative; analyst, D. Marshall, Department of Geology, University of British Columbia. 69 DISCUSSION OF RESULTS  Iron The average for iron in the nephrites studied is 3.05%; the maximum and minimum values are 3.63% and 2.36%, respectively. The results are shown as a histogram in Figure 7. The histogram approximates a normal distribution. With the exception of the small amount contributed by iron bearing accessory minerals such as chromite, picotite and pyrite, the iron is contained in the actinolite-tremolite structure in octahedrally coordinated positions. The iron content of the nephrites in Appendix III ranges from 0.47% to 9.45%. Cobalt and Nickel The cobalt content of the samples ranges from 6 ppm to 116 ppm, with the average being 49 ppm. The average nickel concentration is 954 ppm and the range is 134 ppm to 1630 ppm. The results are plotted as histograms in Figure 7; cobalt is normally distributed while nickel exhibits a slight negative skewness. A weak positive correlation exists between cobalt and nickel, the correlation coefficient being 0.45 (calculated by the method of Lepeltier, 1969). The average cobalt and nickel contents of four nephrite specimens from Wyoming (Sherer, 1969) are 34 ppm and 650 ppm, respectively. Carr and Turkian (1961) found that the amount of cobalt contained in a mineral is closely correlative with the total concentrations of iron and magnesium. Rankama and Sahama (1950) suggest that nickel, on the basis of 70 10n 2 5-Fe X=3.05^ N=31 2.00 2.50 2.90 ° y S o 3.30 3.70 —I 4.10 10- Co DC u. 5-X= 49 p.p.m. N=31 40 80 p.p.m. 120 —T-160 —I 200 ion IT Ni 400 X=954 p.p.m. N = 31 800 p.p.m. 1200 1600 2000 Fig.7. Histograms of the Fe, Co and Ni contents of British Columbia nephrites. 71 Ionic radius (0.69 A), is closely associated with magnesium (0.66 A). Unfortunately, these hypotheses cannot be tested as the magnesium contents of the nephrites studied were not determined. Both the cobalt and the nickel would be contained in the araphibole as octahedrally coordinated cations occupying Y positions. The average cobalt-nickel ratios for British Columbia and Wyoming nephrites are 0.051 and 0.052, respectively. Manganese The average concentration of manganese in the nephrites is 800 ppm; the range of concentration is 300 ppm to 1537 ppm. A histogram of the results (Figure 8) approximates a normal distribution. The bulk of the manganese is undoubtedly concealed in the actinolite-tremolite structure* Rankama and Sahama (1950) state that because of the large size (0.80 A) of the Mn ion, it is incorporated into calcium and magnesium +• 2 silicates only with difficulty. They suggest that the Mn ion is capable of replacing Fe+2 (0.74 A), Mg+2 (0.66 A) and Ca + 2 (0.99 A). In the tremolite-actinolite series, the manganese could be contained in the octahedrally coord inated Y positions and in the M^ sites with calcium. Of the analyses in Appendix III, 31 of the 42 list the presence of Mn, as an oxide, in amounts ranging from trace to 0.69% MnO. 72 11—I 10-o or 5 Mn X= 800 p.p.m. N=31 400 800 p.p.m. 1200 1600 2000 10T Cu o UJ tt. X=11 p.p.m. N=31 12 p.p.m. 18 24 30 36 10-i Pb X=22 p.p.m. N=31 10 16 22 p.p.m. 28 34 -1 40 Fig.8. Histograms of the Mn, Cu and Pb contents of British Columbia nephrites. 73 i Copper The concentration of copper in the nephrites is very low. the mean being 11 ppm and the range 2 ppm to 35 ppm. A histogram plot of the results (Figure 8) shows a biraodal distribution suggesting the presence of two distinct populations, possibly reflecting the presence of minute grains of copper sulphide. The mean copper content of the four Wyoming nephrite specimens analysed by Sherer (1969) is 9 ppm. Lead The lead values range from 10 ppm to 33 ppm, the mean being 22 ppm. The results are plotted as a histogram in Figure 8. Zinc The average zinc content of the 31 nephrite specimens is 55 ppm and the values range from 22 ppm to 97 ppm. The results are graphically presented in the histogram in Figure 9 which indicates a log normal distribution. Zinc was detected in only one of the nephrites analysed by Sherer (1969), this value being 150 ppm. Zinc, with an ionic radius of 0.74 A, is capable of replacing ferrous iron and magnesium in mineral structures (Rankama and Sahama, 1950) and in the case of the actinolite-tremolite series, it would occupy octahedrally coordinated Y positions. 74 10-, a 5-UJ OH 20 Zn X= 55 p.p.m. N = 31 40 p.p.m. 60 80 100 Fig. 9. Histogram of the Zn content of British Columbia nephrites. 75 Chromium, Titanium and Vanadium Because the analyses for chromium, titanium and vanadium are semi quantitative, histograms are not plotted and only the average values for these elements are presented. The average abundance of chromium is 4000 ppm, titanium 700 ppm and vanadium 150 ppm. The bulk of the chromium present in the nephrites is undoubtedly contained in accessory minerals such as picotite, chromite, uvarovite and kammererite o (chlorite) but since the ionic radius of trivalent chromium (0.63 A) is very similar to that of ferric iron (0.64 A), some may be accommodated in octahedral-ly coordinated sites in the amp hibole structure. The average chromium content of the four Wyoming specimens (Sherer, 1969) is 30 ppm which probably reflects the different geologic environment in which this nephrite was formed compared with that from British Columbia. Two of the analyses, 9 and 14, in Appendix III list chromium as a detectable constituent, the concentrations being 0.42% Or^O^ (approximately 2900 ppm Cr) and 0.30% Cr^ (approximately 2100 ppm Cr), respectively. Both of these samples are from New Zealand and are associated with ultramafic rocks (Finlayson, 1909). The majority of the thin sections examined contained fine dustings of microlites of a brown mineral, identified by X-ray diffraction as sphene, which would account for the bulk of the titanium detected in the analyses. According to Rankama and Sahama (1950), titanium may also be contained in the amphibole 76 structure as replacements of Fe , Mg and Al, but the oxidation state is + 3 +4 unknown due to analytical difficulties in determining Ti and Ti in the presence of ferrous and ferric iron. These authors suggest the possibility + 3 +4 that Ti rather than Ti is present in amphiboles and pyroxenes even though TiC^ is reported in analyses. Most general formulae for the amphiboles indi cate that titanium is contained in the Y positions. The average titanium content of 13 nephrites in Appendix III is approximately 790 ppm. The vanadium content of the nephrites is remarkably uniform. This element is similar to titanium in behaviour and may be concealed in the sphene micro-lites described above although some is probably contained in the actinolite-+ 3 • tremolite. Goldschmidt (1937) considers vanadium to be present as V (0.74 A) in ferromagnesian minerals; as such it would easily be admitted to positions of + 2 six-fold coordination, presumably replacing Fe (0.74 A). Moxham (1965) suggests that the behaviour of vanadium in ferromagnesian minerals is analogous to that of iron. The four Wyoming nephrites analysed by Sherer,(1969) contain ed an average of 93 ppm vanadium. Element Distribution in Fresh and Weathered Nephrite Three of the nephrite specimens examined exhibited a conspicuous, dis coloured weathering rind up to 0.5 cm thick. All three specimens were from alluvial boulders. The weathered material is softer than the unweathered nephrite and is usually fractured, the fractures being subparallel to.the Table 12 Iron and Trace Element Contents of Fresh and Weathered Nephrite from Alluvial Boulders Sample Number and locality Fe % Co ppm Ni ppm Mn ppm Cu ppm Pb ppm Zn ppm Cr ppm Ti ppm V ppm #7; Fall River Fresh Weathered 2.68 3.06 36 41 1100 919 606 725 10 6 22 22 36 33 4000 3000 500 125 200 120 #39; 0»Ne-ell Creek Fresh Weathered 3.13 3.63 63 48 1370 1350 512 612 7 8 13 23 32 38 3000 3500 300 100 100 100 #41; Silver Creek Fresh Weathered 2.71 2.81 44 59 1025 975 380 406 9 6 24 20 32 69 2500 3500 150 2 80 115 78 external surface of the specimen. The results of the analyses of the fresh and weathered nephrite from each specimen are presented in Table 12. From this data, it is seen that there is an increase in the amount of iron and manganese contained in the weathered nephrite and a decrease in nickel and titanium. The results for the other elements are inconclusive. The increase in the amount of iron and manganese is readily explained by the precipitation during weathering of the relatively insoluble hydroxides of ferric iron and quadravalent manganese. These hydroxides are seen as brown earthy deposits on fractures and external surfaces. REGIONAL CHEMICAL VARIATIONS IN BRITISH COLUMBIA NEPHRITES The nephrites were grouped according to area of origin (as in Figure 1) and averages calculated for each element. The values for the nephrites from area II exclude two greenish grey specimens from O'Ne-ell Creek as they are rare and contain anomalously low chromium and high titanium. Significant regional variations of the averages for iron, cobalt, manga nese, copper, lead, zinc and vanadium are not observed; variations are present in the averages for nickel, titanium and chromium, that for the latter being the most pronounced. The lowest average values for these three elements are found in the specimens from area III; the highest average chromium and titanium contents are in the samples from area I while those from area II have the highest average nickel content. Because of the overlapping range of values for Table 13 Average and Range of Iron and Trace Element Contents of Nephrites from the Three Major Nephrite Producing Areas of British Columbia Fe Co Ni Mn Cu Pb Zn Cr Ti V Area % ppm ppm ppm ppm ppm ppm ppm ppm ppm Bridge River- 3.23 49 939 741 16 28 46 5600 500 170 lower Fraser River 2.74- 30- 787- 481- 3- 22- 32- 3000- 30- 100-I 3.63 70 1600 1043 33 33 60 10000 1000 200 5 samples Takla Lake 3.00 55 1151 822 12 21 58 4400 300 140 II 2.36- 19- 719- 380- 3- 10- 22- 600- 150- 80-3.63 116 1630 1537 35 32 97 10000 500 200 18 samples Dease Lake 2.99 37 582 795 6 21 40 2300 230 120 III 2.81- 6- 212- 468- 2- 11- 29- 100- 100- 80-3.13 62 956 1212 15 32 50 10000 350 200 6 samples Note: The averages for nephrites from area II do not include the values for two greenish grey specimens (#34, #35) as they are rare and contain anomalously low chromium and high titanium. 80 each element from each area, it is not possible to state that a nephrite specimen with a given trace element content originated in a particular area. The probable reason for the lack of regional variations is that the nephrites from the three areas have formed in similar geologic environments. However, on a much larger scale, the British Columbia nephrites are distinguishable, by chromium content, from the Wyoming nephrites which have been derived from amphibolites and are not associated with ultramafic rocks. The average concentration of chromium in the former is 4000 ppm while in the latter it is 30 ppm. COLOUR OF NEPHRITES The colour of nephrite is one of its most conspicuous physical properties and is certainly its most valuable. The following discussion of the causes of colour in silicate minerals is presented for this reason and is taken largely from Burns (1970). The majority of silicate minerals owe their colour to the presence, in major or trace amounts, of transition metals such as titanium, vanadium, chromium, manganese, iron, cobalt, nickel and copper or lanthanide elements. The most common cause of colour is the absorption of radiation through electron-o o ic processes and if such absorption is in the visible (4000 A to 7000 A) region of the electromagnetic spectrum, colours are produced in transmitted and reflected light. The two most important colour producing processes are internal 81 electron transitions within transition or lanthanide elements and inter-element electron transitions or charge transfer. Internal electron transitions are produced through the absorption of light by excitation of electrons between d or f orbitals. The actual colours observed are determined by the position of the absorption bands and the intensity of the colours may be correlated with the band intensity. In ferrous iron compounds, absorption, by d electron transitions, of red radiation gives rise to the commonly observed green or blue-green colour. Charge transfer or inter-element electron transitions occur when electrons migrate between neighbouring ions in a crystal structure. These processes are favored when transition metals can exist in two or more oxidation states, such + 2+3 as Fe and Fe , and are facilitated by local misbalance of charge accompany ing isomorphous substitution by multivalent ions. Faye and Nickel (1970) state that the green hues of the calcic amphiboles are a direct consequence of the — 2 +2 absorption of violet-blue light (0 - Fe charge transfer) and red-orange + 2 +3 light (Fe - Fe charge transfer). The complementary colours for violet-blue light and red-orange light are red-green, which appears yellow to the eye, and green-blue (Pauling, 1958; Monk, 1963), respectively. The combination of the two complementary colours produces green or yellow-green. In the tremolite-actinolite series, it is probable that both electronic processes are operative to some degree. This is due to the presence of iron in 82 both divalent and trivalent states, although predominating in the former, and + 4 +3 to the occurrence of isomorphic substitutions such as Si = Al . The colour of the majority (85%) of the British Columbia nephrites examined is a hue of green with a distinct yellowish cast. This colour is due to the presence of multivalent iron and is readily explained in terms of the electronic processes outlined above. The cause of the colour of two anomalous specimens, #34 and #35, from O'Ne-ell Creek is unknown. Both these specimens have low chromium contents (100 ppm - 280 ppm), above average iron contents (3.38% - 3.13%) and are a greenish grey colour (G.S.A. Rock Colour Chart); in general terms, the specimens are grey with a very faint tint of green. The lack of green colouration cannot be explained by the paucity of chromium which is readily accounted for by the lack of picotite, chromite, uvarovite and chlorite; in nephrites most of the chromium is contained in the aforementioned accessory minerals. Another anomalous specimen, #19, is a dark blue green colour and contains much higher than average cobalt (100 ppm) and higher than average iron (3.38%). The probable cause of this colour is a strong charge +2 +3 transfer of the type Fe - Fe , causing absorption in the red-orange part of the spectrum giving rise to the conplementary blue-green colour. 83 VI. THE O'NE-ELL CREEK NEPHRITE DEPOSIT The O'Ne-ell Creek nephrite deposit is located in central British Columbia (Figure 1) near the south end of Takla Lake, approximately 130 air miles N 60° W from Prince George, B. C. Specifically, the showings are situated on the north side of O'Ne-ell Creek, at an elevation of 3400 feet, 3.5 miles upstream from its confluence with Middle River (Figure 10). Roads do not reach the property and access is either by air, generally a helicopter from Smithers or Fort St. James, or by boat from Fort St. James. The deposit was discovered in 1968 by Mrs. W. Robertson. The original find was placer boulders which she traced upstream to the nephrite outcrop. Limited production, from alluvial boulders, took place in 1968 and in 1969, nephrite was produced from both the outcrop and the stream boulders. The property has been inactive since the end of the 1969 field season. The following brief description of the regional geology is taken largely from Armstrong (1949) and Little (1949). REGIONAL GEOLOGY The rocks in the Takla Lake-Middle River area (Figure 10) range in age from Pennsylvanian or mid-Permian to Oligocene or later and comprise a great variety of sedimentary, volcanic and intrusive types. The bulk of the rocks exposed belong to four formations; the Pennsylvanian to Permian Cache Creek Group, the pre-Upper Triassic Trembleur intrusions, the Upper Triassic to Upper 84 85 Fig.11. Legend for Fig. 10. SEDIMENTARY AND VOLCANIC ROCKS TERTIARY OLIGOCENE OR LATER ENDAKO GROUP ~"~ 1 Mainly vesicular and amygdaloidal basalt, andeslte | • and dacite; flow breccia and agglomerate CRETACEOUS OR LATER UPPER CRETACEOUS AND PALEOCENE 11 SUSTUT GROUP Conglomerate, shale,greywackc, and tuff CRETACEOUS LOWER CRETACEOUS 10 USLIKA FORMATION: conglomerate;minor sandstone and shale JURASSIC AND CRETACEOUS HAZELTON GROUP Andesite, rhyolite, trachyte. [ 6 basalt, and related breccia and tuff; minor- etrgiltite, arkose, sand'stone,and lime stone. May include some undifferentiated Triassic rocks JUF*ASSIC OR(?) CRETACEOUS TACHE K GROUP Andesite and andesite breccia; basalt and rhyolite TRIASSIC AND JURASSIC UPPER TRIASSIC AND LATER TAKLA GROUP Andt'sit ic and basaltic flows, tuffs, breccias, and agglomerate; inter-bedded conglomerate, shale, gr-eywacke , limestone, and coal 0 CARBONIFEROUS (?) AND PERMIAN PENNSYLVANIAN (?) AND LATER CACHE CREEK GROUP Andesitic flowst tuffs, and breccias , with minor baste intrusions (greenstone); chlorite and horn blende schists; minor argillite, chert,and limestone. May include s<Jme undifferentiated younger rocks Ribbon chert, argillaceous quartzite, argillite, greenstone similar to 6 t limestone ; minor conglomerate and greywacke. Mainly younger than 4 and older than 6 Massive limestone ; minor argillite, slate , chert , and greenstone; mainly older than 5 and 6 ITVTRUH1VE ROCKM JURASSIC OR CRETACEOUS UPPER JURASSIC OR LOWER CRETACEOUS OMINECA INTRUSIONS Granodiorite , quartz diorite t diorite; granite, syenite , gabbro , pyroxenite JURASSIC .TOPLEY INTRUSIONS IGranite and granodiorite syenite, diorite PErtMlAN (1) ANO/OR LATER POST - MIDDLE PERM IAN , PRE-UPPER TRiASStCtf) TREMBLEUR INTRUSIONS [ . fferidotite , dunite ; minor pyroxenite and 1 gabbro; serpentinized and BteetWz&d equivalents. fault or fault zone (mainly inferred) 86 Jurassic Takla Group and Che Upper Jurassic to Lower Cretaceous Omineca intrusions. Rock units of lesser abundance are the sedimentary and volcanic Tachek and Hazelton groups of Jurassic to Cretaceous age, the sedimentary Uslika Formation of probable Lower Cretaceous age, the sedimentary Upper Cretaceous Sustut Group, the volcanic Endako Group of Oligocene age and the Topley granitic intrusions that were emplaced in Jurassic time. The Cache Creek Group consists of a thick succession of steeply folded and intensely faulted sediments, volcanics and derived metamorphic types that crop out in the map area as a northwest trending belt up to 25 miles wide. Foraminiferal limestones and ribbon cherts are characteristic of the group but other rocks interbedded with them are argillite, slate, quartzite, tuff, breccia andesite and basalt. The andesite and basalt are largely altered to greenstone. There are three major divisions; a lower group of massive recrystallized lime stone, a middle group of slate, argillite and ribbon chert, with minor limestone greenstone and related schists, and an upper group of greenstone, with lesser argillite, slate and minor limestone. The sequence is not less than 22,000 feet thick. The metamorphic grade of these rocks is transitional between the prehnite-pumpellyite metagreywacke facies and the greenschist facies (Monger and Hutchison, 1971). The Trembleur ultramafic intrusions are the oldest intrusive rocks present in the map area and are confined to the Cache Creek Group. They consist of sill 87 stocks and batholiths of peridotite, dunite and pyroxenite and their serpent-inized equivalents. Included with these rocks is a minor amount of gabbro, usually uralitized and saussuritized. Peridotite and dunite are the most abundant rock types, the latter occurring as sills, as irregular zones or bands between similar zones of peridotite in thick, undifferentiated sills or as irregular masses in the Mount Sidney Williams batholith. All the ultramafic rocks have been partially or completely altered to serpentine. Talc-carbonate and lesser quartz-carbonate rocks are abundant; the former are marginal to stocks and batholiths of peridotite and the latter predominate in zones of shearing, faulting and fracturing. Along the contacts of serpentine and siliceous sedimentary rocks, reaction zones have been formed, up to 100 feet wide, that consist of talc, chlorite, actinolite-tremolite and carbonate. Flanking the Cache Creek Group on the west and east is a conformable succession of interbedded volcanic and sedimentary rocks known as the Takla Group. It is at least 10,000 feet thick and in the lower part sediments and volcanic tuffs predominate while in the upper part andesitic and basaltic flows predominate. This rock unit, which unconformably overlies the Cache Creek Group, has also been intensely folded and faulted. The Omineca intrusions of Upper Jurassic or Lower Cretaceous age are exposed in the map area in great abundance. They range in size from small sills and dykes to batholiths and in composition from granite to pyroxenite, with 88 granodiorite predominating. Many of the bodies are elongated in a northwest direction. In the vicinity of O'Ne-ell Creek, the largest body is the stock immediately to the north. This stock consists of a core of grey soda granite surrounded by a border of pink granite and some syenite. Related acidic and basic dykes are fairly common. The rocks of this area have been subjected to at least two periods of deformation, (Armstrong, 1949) one in Jurassic or early Cretaceous time and the other in post-Paleocene, probably Eocene time. It is probable that most of the major faults were formed during the latter disturbance. GEOLOGY OF THE DEPOSIT  General Description The nephrite in this deposit occurs as veins and lenses in a zone of foliated tremolite-chlorite rock developed at the contact between serpentinite of the Trembleur intrusions and cherts, quartzites and argillites of the Cache Creek Group (Figure 12). In the map area, rocks of the Cache Creek Group consist of interbedded chert and quartzite with lesser argillite and minor greenstone, all of which are sheared and crumpled. The cherts and quartzites commonly contain wisps of argillaceous and graphitic material. Acicules and clots of radiating fibers of amphibole and patches of brown stilpnomelane are readily visible in hand speci mens of the argillite. Often, the stilpnomelane forms rims around the clots of 89 atnphibole. Individual beds are discontinuous and are not traceable from out crop to outcrop. The general strike of the bedding is north to north-northwest; dips on the north side of the creek are 29° to 54° to the west and on the south side, 30° to 70° to the east. The serpentinite is generally massive and granular although, locally, it is sheared and partially altered to talc, tremolite, carbonate or chlorite. The shape of the serpentinite body is unknown and unaltered ultramafic rocks such as peridotites and dunites are not observed. The contact between the serpentinite and the country rock is not seen at the surface but is expressed by outcrops of tremolite-chlorite rock. Yellowish orange weathering quartz-carbonate rock crops out along, and is displaced by, a vertical, east-west trending fault in the southern portion of the map area. Talc and talc-carbonate rocks are present at the contact between quartz-carbonate rock and serpentinite and in the tremolite-chlorite zones developed in the serpentinites at the con tact with sedimentary rocks. Foliated tremolite-chlorite rock commonly occurs along the contact between sediments and serpentinite; it is also present in shear zones in the serpenti nite. Because of diamond drill hole information and the relatively good rock exposures brought about by brush clearing operations, the extent of the tremolite-chlorite rock is best known on the north side of the creek. In this area, these rocks occur in a zone at least 25 feet thick that dips, in the 90 vicinity of the drill holes, 15° to 30° to the northwest. The foliation of these rocks has a much steeper dip than does the zone in which they are contain ed. Slab-like inclusions of foliated, highly altered Cache Creek volcanic rock are present in the contact zone and in the adjacent serpentinite. The largest mass of nephrite, and the only one exposed at the surface, is located on the north side of the creek, 40 feet southeast of diamond drill hole #5 (Plate 16). The nephrite exhibits a weak foliation which is parallel to that in the enclosing tremolite-chlorite rock. This body is 23 feet wide and has an average true thickness of 5 feet. Information obtained from the aforementioned drill hole indicates that the nephrite lens continues down dip for at least 30 feet but its thickness is decreased to 1.5 feet. One other vein of nephrite, 6 inches thick, was intersected by this hole and in hole #8, a vein 3 feet thick was intersected; in both cases the nephrite is foliated and should be termed a semi-nephrite. The nephrite in the outcrop contains numerous patches and streaks of picotite and, along fractures, lensoid segregations of greenish grey nephrite. These lensoid masses, which are up to 8 inches x 5 inches x 3 inches, have slickensided surfaces and when the enclosing nephrite is broken along the fracture, they are easily extracted. A light grey, scaly rind, up to 0.5 cm thick, is developed on weathered surfaces of the outcrop. The rind consists of tremolite, chlorite and iron and manganese hydroxides. Much of the chlorite is believed to be a weathering product of the tremolite. At the base of the 91 Plate 16: A portion of the nephrite outcrop at 0»Ne-ell Creek. In this deposit, the nephrite was removed from the outcrop by means of the specially designed diamond saw shown in the foreground. The saw blade is three feet in diameter. 92 nephrite outcrop, and resting on serpentinite, is a large slab of nephrite weighing approximately 150 tons. Undoubtedly, this slab was originally part of the above described nephrite body. Numerous boulders of tremolite-chlorite rock and semi-nephrite are present, in an area some 60 feet in diameter, approximately 30 feet southeast of hole #8. These have been derived, by weathering, from the band of similar rock intersected by this hole. Across the creek from the nephrite showing is an outcrop of a dense, very tough, dark green rock composed largely of amphibole. It is situated between outcrops of quartz-carbonate rock and serpentinite but unfortunately, as contacts are not exposed, the relationship between these rocks is unknown. Four varieties of dyke rock are present in the map area; these are porphyritic diabase, aplite, an amphibole-plagioclase rock and a porphyritic plagioclase-clinozoisite rock. The dykes are later than the Trembleur intru sions and may be related to the Omineca intrusions. With the exception of the aplite, these rocks exhibit chilled, fine-grained phases at contacts. Three major directions of faulting have been recognized; east-west, northwest and northeast. All of the faults appear to be steeply dipping or vertical. Lithology Cache Creek Group In hand specimen, the quartzites are light grey, have a fine sugary 93 texture and are cut by a reticulate network of quartz veins up to 2 mm wide. In thin section they are composed almost entirely of interlocking grains of quartz up to 0.1 mm in diameter. The larger quartz grains exhibit an undulose extinction. Also present are tremolite, in amounts up to 10 percent, and stilpnomelane, up to several percent. The tremolite, in colourless, hairlike fibers, occurs as tufts or "birds-nest" like aggregates (Plates 17, 18). The stilpnomelane occurs as irregular aggregates of minute plates and as fracture fillings. The cherts are generally dark grey to black, have a very fine sugary texture and are cut by numerous veins of white quartz. Under the microscope, they are seen to consist essentially of interlocking grains of cryptocrystalline quartz. Stilpnomelane is present as fracture fillings. The argillites are dark grey to black and weather to a yellowish or reddish orange colour. The lighter coloured specimens are quite siliceous while the darker rocks contain abundant graphite. Tremolite is present in both varieties but is especially conspicuous in the graphitic rocks where it occurs as bundles of radiating fibers in lenses and discontinuous veins. Stilpnomelane, in veinlets and patches, is visible in hand specimen. In thin section, these rocks consist essentially of quartz, albite and argillaceous material with variable amounts of tremolite, stilpnomelane, green biotite, muscovite and iron oxide (Plates 19, 20). Plate 18: Photomicrograph of "birds-nest"-like aggregate of tremolite fibers in a quartzite from O'Ne-ell Creek, plane polarized light. Plate 19: Photomicrograph of stilpnomelane (brown) and biotite (green) in fractures in a siliceous argillite from O'Ne-ell Creek, plane polarized light. 1 mm Plate 20: Photomicrograph of stilpnomelane (brown) and needles of tremolite in an argillite from O'Ne-ell Creek, crossed nicols. 96 Slabs of Cache Creek greenstone contained in the contact zone near the nephrite outcrop are completely altered to a mixture of chlorite, zoisite, phlogopite and minor talc. Trembleur Intrusions The serpentinites are emerald green to black and, locally, weather to a yellowish orange colour. Most of the specimens are strongly magnetic and many contain veins of chrysotile, up to 0.5 cm wide, and patches and lenses of magnesite and talc. They consist almost entirely of antigorite, with a characteristic fibro-lamellar structure, (Plate 21) and lesser serpophite in irregular, almost structureless masses. Other minerals present are magnesite, talc, chlorite, chromite and magnetite. The latter mineral occurs in two forms; as opaque rims on grains of chrome spinel and as trains of grains, with carbo nate, forming a mesh structure. Bastite serpentine or remnants of pyroxene were not observed. When fresh, the quartz-carbonate rocks are medium greenish grey to bluish grey but upon weathering, they assume a conspicuous yellowish orange colour. They are weakly to strongly magnetic and are cut by a network of white quartz-carbonate veins. The largest veins are 6 to 8 inches wide, are open and drusy and consist of alternating layers of chalcedonic and coarsely crystalline quartz and minor carbonate. In thin section, veins and patches of magnesite and ankerite, comprising up to 75 percent of the rock, enclose irregular shaped 97 masses of cryptocrystalline quartz (Plate 22). Minor amounts of chlorite, talc, mariposite, chromite, magnetite and pyrite are also present. Locally, the mariposite is abundant enough to impart a brilliant green colour to the rock. The talc-carbonate rocks are medium to dark green and contain up to 85 per cent talc, and lesser amounts of magnesite, serpentine, either antigorite or serpophite, magnetite, chrome spinel and pyrite. Hand specimens of the very fine grained, greenish grey tremolite-chlorite rock yield little information regarding their mineralogy. Under the microscope, they are seen to consist of tremolite, chlorite (penninite) and minor talc, carbonate and chrome spinel. The amount of tremolite contained in these rocks may reach 95 percent while in some specimens, chlorite may comprise 15 percent of the rock. The tremolite occurs as bundles of parallel to subparallel fibers set in a matrix of fine tufts, much in the manner of a semi-nephrite. The chlorite occurs in irregular, elongate patches and vein-like masses that are parallel to the foliation and in envelopes surrounding fractured grains of reddish-brown chrome spinel. Talc and carbonate occur in fine discontinuous veinlets. The nephrite seen in the outcrop and in the alluvial boulders ranges from a non-schistose variety to a semi-nephrite not far removed from the tremolite-chlorite rock described above. The petrology and microstructure of the specimens from the deposit are described in Chapter III. 98 Plate 21: Photomicrograph of a serpentinite from O'Ne-ell Creek illustrating the fibro-lamellar structure of the antigorite, crossed nicols. Note also the mesh structure formed by magnetite grains. Plate 22: Photomicrograph of a quartz-carbonate rock from O'Ne-ell Creek, crossed nicols. 99 Miscellaneous Rock Types Amphibole-zoisite rock: The previously mentioned dense, tough dark green rock of unknown association is seen, in thin section, to consist of 80 percent pale green to colourless hornblende, 15 percent zoisite and 5 percent sphene, chlor ite and apatite. The hornblende occurs as large, ragged crystals, up to 3 mm by 4 mm, that are altered to chlorite along cleavages. Interstitial to the hornblende is a finer grained, interlocking aggregate of zoisite crystals. Euhedral crystals of sphene are present in both the chloritized hornblende and the zoisite. Meta-diabase: The diabase is light olive grey, porphyrifcic and weathers to a dark yellowish brown colour. Phenocrysts of feldspar, up to 1.5 ram x 3.0 mm, comprise at least 1 percent of the rock. These are set in a finer grained matrix containing abundant laths of feldspar with an average size of 0.1 ram x 0.5 mm. In the chilled selvages, which are 6 to 8 inches wide, the groundmass is aphanitic. The feldspars, both the phenocrysts and the laths, consist of "dusty" albite and contain granules of clinozoisite and scales of white mica. A fine grained mixture of chlorite, clinozoisite, tremolite (?), quartz and carbonate occupies the interstices between the laths. Rod-like to granular opaques are disseminated throughout. Albite-araphibole rock: This rock is greyish olive green, hypidiomorphic granular and medium grained although fine-grained phases are observed at 100 contacts. It is composed essentially of albite (40 to 50 percent) and amphibole (40 to 50 percent). Chlorite (penninite), clinozoisite, sphene, carbonate and red iron oxide are also present. The amphibole grains have cores of pale brown to pale green hornblende and rims of pale green actinolite. The hornblende is altered along cleavages to chlorite. Granules of sphene are present in both the chlorite and the actinolite. The albite is interstitial to the amphibole grains and contains prisms and granules of clinozoisite and, occasionally, wisps of white mica. Quartzites in contact with this dyke rock are metasomatically altered, over a distance of one foot, with the formation of albite, carbonate, muscovite, tremolite, clinozoisite, chlorite, chalcopyrite and pyrrhotite. Porphyritic albite-quartz-clinozoisite rock: In this rock type, phenocrysts of pinkish grey plagioclase, are contained in a fine grained, light greenish "speckled" matrix. The phenocrysts constitute up to 15 percent of the rock, range in size from 0.7 mm x 1.0 mm to 2.0 mm x 3.5 mm and have rather diffuse boundaries. In thin section the rock consists of quartz and albite (75 percent), chlorite (penninite), and clinozoisite (20 percent) and minor muscovite, sphene, and carbonate. The phenocrysts are albite and are set in a fine grained matrix consisting of quartz and albite. Prisms and granules of clinozoisite are present throughout the rock and are largest in the phenocrysts. The muscovite and the chlorite generally occur together in elongate, ragged aggregates. 101 Meta-aplite: Hand specimens of this rock are greyish pink, fine-grained and have a sugary texture. Under the microscope, the rock is seen to be composed of quartz and albite (90 percent), muscovite (5 percent), carbonate, pyrite and iron oxides. The albite occurs both as subhedral laths, up to 0.15 mm x 0.25 mm, and as fine anhedral grains, with quartz, in the matrix in which the laths are contained. Ragged shreds of muscovite that average less than 0.1 mm long are disseminated throughout the rock. Summary The nephrite at O'Ne-ell Creek occurs in a zone, 20 to 25 feet wide, of foliated tremolite-chlorite rock developed in serpentinite at the contact with quartzites, cherts and argillites of the Cache Creek Group. Contained within this zone are slabs of similarly foliated Cache Creek volcanic rock that have been altered to a mixture of zoisite and chlorite. Most of the nephrite from this deposit is classified as either schistose nephrite or semi-nephrite. The nephrite in outcrop exhibits a weak foliation which is parallel to that observed in the altered inclusions and in the enclosing tremolite-chlorite rock. Serpentinite is the only ultramafic rock observed in the map-area. Relat ed rocks, in addition to the nephrite and the foliated tremolite-chlorite rock, are talc and quartz-carbonate rocks; these are restricted to fault zones and contacts. Four varieties of altered dyke rock are present; these are aplite, 102 porphyritic diabase, an amphibole-albite rock and a porphyritic albite-quartz-clinozoisite rock. These dykes are observed in the tremolite-chlorite zones but they are not foliated, suggesting that they post-date the formation of the nephrite. The quartzites, cherts, and argillites adjacent to the serpentinite have been metasomatically altered. New minerals formed in the cherts and quartzites are tremolite and stilpnomelane; those in the argillites include tremolite, stilpnomelane, albite, green biotite and muscovite. These minerals have been observed in the sediments at distances up to 30 feet from the contact with the serpentinite. PETROGENESIS  General Statement Nephrite is often associated with serpentinized ultramafic rocks and usually occurs in the serpentinite at the contact with country rock, dykes or tectonic inclusions (Coleman, 1966; Coleman, 1967; Kolesnik, 1970). The rocks in contact with the serpentinite are metasomatically altered, usually with the formation of calcium silicates. Altered basic igneous rocks are characterized by the presence of hydrogrossular, which predominates, prehnite, idocrase, diopside, tremolite-actinolite and chlorite. The alteration of sedimentary rocks produces albite, potassium feldspar, fibrous tremolite-actinolite and prehnite. The serpentinites at the contacts are altered to rocks containing 103 actinolite-tremolite and chlorite. The alteration of the serpentinite and the inclusions, dykes and country rocks involves the movement of calcium and, in some cases, magnesium away from the serpentine, the movement of alkalis away from the contact into the country rock or inclusions and the movement of silica towards the serpentine. Rocks in the reaction zone generally have a higher specific gravity than the unaltered rocks and the altered sedimentary and igneous rocks generally contain more water than do the unaltered equivalents. Coleman (1966) has described mineral zoning at the contact between serp entinite and metasomatized argillite and greywacke in New Zealand (Figure 13). At the contact, a monomineralic zone of actinolite-tremolite is developed. This zone may contain small amounts of prehnite, chlorite or diopside. Away from the contact, into the sediments, the amphibole zone gradually changes to an albite-araphibole rock characterized by the predominance of amphibole over albite. This amphibole-rich rock then changes to a hard, flinty albite-amphibole-quartz rock. Accessory minerals that may be present in the albite-amphibole zones are chlorite, diopside, prehnite and stilpnomelane. This zoning is very similar to the situation that occurs at O'Ne-ell Creek. Origin of the Nephrite The nephrite and the tremolite-chlorite rock have been formed by the metasomatic alteration of the serpentinite. This is suggested by the presence of chrome spinel in all three rock types, and by the similarity in the average 104 Serpentine S.G. - 2.55 Wl. 7o Si02=43.5 MgO=43.5 'CaO= — H20 = 13.0 Contact Argillite- Grey wacke SC.- 2.65 SiO2=65.0 MgO= 1.5 CaO= 2.3 H20= 1.0 Mg Ca T No.K Si02= 53.2 MgO= 17.7 CaO= 15.4 H20= 23 Si02 = 43.8 MgO= 8.9 CaO= 10.7 Fig.13. Diagrammatic representation of mineral zoning at the contact between serpentinite and metasomatized argillite and greywacke.(after Coleman, 1966) 105 amounts of nickel, manganese, lead, zinc and chromium contained in the nephrites and the serpentinites (Table 14). Table 14 Average Iron and Trace Element Contents of Nephrite and Serpentinite from O'Ne-ell Creek Fe Co Ni Mn Cu Pb Zn Cr Ti V % ppm ppm ppm ppm ppm ppm ppm ppm ppm Nephrite 3.17 57 1431 660 17 17 45 6100 285 126 (5 samples) Serpentinite 6.05 91 1597 680 35 20 34 5750 41 14 (8 samples) Note: The averages for nephrite do not include the values for two greenish grey specimens (#34, #35) as they are rare and contain anomalously low chromium and high titanium. The metasomatic alteration of serpentinite is dependent upon the activities of silica and calcium, (Coleman, 1967). An activity diagram showing the stability fields of serpentine, diopside, tremolite and talc is presented in Figure 14. Several assumptions are made concerning this diagram; the activity of water is high and constant and the activity of magnesium is constant. Also, temperature and pressure are constant but not specified. From the diagram, it can be seen that if the activities of calcium and silica are increased, serp entine will react to form tremolite. A possible reaction of this type is given below (Coleman, 1966). 5(3MgO-2Si02- 2H20) + 14 Si02 +• 6CaO —»• 3(2CaO-5MgO-8Si02« H^O) + 7^0 chrysotile added tremolite lost 106 Temperature and pressure constant but not specified. The activity of water is high and constant; the activity of magnesium is constant. Fig.14. Ca(activity) — Si02(activity) for calcium and magnesium silicates.(after Coleman,1967) 107 Coleman suggests that the serpentinite becomes unstable as silica moving towards the ultramafic body meets calcium migrating away, forming tremolite at the boundary. The products of this reaction have a smaller volume than the react-ants (AV = 13 percent) and, hence, is favored by high pressure. The source of the calcium is the pyroxenes that are altered during the process of serpentinization. The average CaO content for 23 peridotites and 19 dunites is 3.5 weight percent and 0.75 weight percent, respectively (Polder-vaart, 1955). The average CaO content of 26 serpentinites investigated by Faust and Fahey (1962) is 0.08 weight percent. This considerable difference in the amount of CaO contained in peridotite-dunites and serpentinites indicates that calcium is liberated during serpentinization. Much of the calcium may combine with CO^ to produce carbonate but some could migrate to contacts and raise the activity of calcium in the reaction zone. The silica required for the reaction is readily obtained from the quartz ites, cherts and argillites in the surrounding country rock. The origin of the fine fibrous habit, characteristic of nephrite, is explained by Kolesnik (1970) in the following manner. Crystals of actinolite-tremolite have two types of faces with very different structures. One type of face corresponds to lattices made up of similar ions, that is a cation layer superimposed on an anion layer. The second type of face corresponds to lattices with a maximum total density of anions and cations. If the actinolite-tremolite 108 forms in an environment in which calcium and sodium are perfectly mobile, and magnesium, silicon, aluminum and iron are relatively inert, the crystal form is dependent upon the availability of ions. Under these conditions, growth of the faces corresponding to lattices made up of similar ions is hampered by the low mobility of magnesium, silicon, aluminum and iron. Faces corresponding to a lattice of maximum total density of ions grow more rapidly because they require fewer of the less mobile ions. The resulting amphiboles have a prismatic habit. Elongation along the c-axis is variable but is markedly higher for a high activity of calcium and, hence, prismatic forms give way to fine fibers. Shearing stress has been considered to be the critical factor in produc ing the characteristic nephritic microstructure (Finlayson, 1909; Turner, 1935; Crippen, 1951) but recent studies by Kolesnik (1970) and Sherer (1969) suggest that this is not the case. Kolesnik reports that in many of the European and Siberian nephrite deposits, the tremolite fibers exhibit a preferential orientation that is perpendicular to the walls bounding the nephrite body. Sherer describes euhedral crystals of quartz in Wyoming nephrite; if shearing stress had been operative during the nephrite formation, the crystals would not have retained their form. The foliation observed in many specimens is a result of the environment in which most nephrite forms. The majority of occurrences are situated in alpine serpentinites at or near the contact with the enclosing rocks. The contacts of these serpentinite bodies are sheared and mylonitized 109 due Co Che tectonic events that followed the initial emplacement of the ultra mafic mass and continued during serpentinization. Reaction rocks formed at the contacts, including nephrite, are usually involved in these tectonic movements and, as a result, are foliated and brecciated. The foliation in the tremolite contact rocks at O'Ne-ell Creek has provided channel-ways for the migration of the aluminum bearing solutions that have caused the partial alteration of the tremolite to chlorite. The source of the solutions is either the dyke rocks or the ultramafic body. Temperature and Pressure Conditions At O'Ne-ell Creek, the tremolite-chlorite rock containing the nephrite is in direct contact with serpentinite. In other nephrite deposits associated with ultramafic rocks the metasomatites are always in contact with or are surrounded by serpentinite. Such rocks in contact with unserpentinized ultra mafic rocks have not been reported. This suggests that the metasomatic reactions take place at temperatures below the breakdown of olivine and/or pyroxene to serpentine. Bowen and Tuttle (1949) have determined that, at a pressure of 1 kilobar, pure magnesium serpentine cannot exist at temperatures above 500°C; at higher pressures the breakdown temperature increases only a few degrees. In New Zealand, semi-nephrite often occurs at the contact between serpen tine and hydrogrossular bearing inclusions of altered gabbro (Coleman, 1966). 110 The temperature of formation of the garnet has been determined by Coleman (1967), on the basis of the relative hydration state, to range from 290°C to 450°C. Although hydrogrossular was not observed at O'Ne-ell Creek, the presence of this mineral in other nephrite occurrences also suggests that the metasomatism takes place in the temperature range where serpentine is stable. Minerals, such as aragonite or jadeite, that could be used to estimate the pressure during metasomatism were not observed in the O'Ne-ell Creek deposit. Because of the general increase in the density of the rocks in the reaction zones and the substantial water content of the metasomatized country rock, Coleman (1967) postulates that the total pressure is high, probably in excess of 4000 bars, and that the water pressures are nearly equal to the total pressure. Ill VII. CONCLUSIONS In British Columbia, deposits of nephrite are closely associated with a belt of alpine ultramafic rocks that extends for 1000 miles from the Hope area, east of Vancouver, northwestward to the Yukon border. The nephrite from these deposits contains, in addition to essential trem olite, small amounts of chlorite, uvarovite, chrome spinel, diopside, talc, carbonate, sphene, phlogopite and pyrite. The felted and twisted nature of the component tremolite fibers accounts for the high hardness and extreme toughness of nephrite. Iron, which is present in both the divalent and trivalent states, is responsible for the yellowish green colour observed in most specimens. The average amounts of iron, cobalt, manganese, copper, lead, zinc, and vanadium contained in the nephrites do not exhibit regional variations when the samples are grouped according to area of origin; slight variations are observed in the average contents of nickel, chromium and titanium. The general similarity of the regional average values for these elements suggests that the nephrites have been formed in similar environments. This assumption is supported by the constant association of nephrite deposits with alpine ultra mafic rocks. At the O'Ne-ell Creek deposit, the nephrite has resulted from the metasom-atic alteration, by the addition of calcium and silica, of serpentine during the process of serpentinization. The source of the calcium was the pyroxenes 112 contained in the original ultramafic rock; the source of the silica was the sediments enclosing the ultramafic body. High concentrations of calcium and magnesium and relatively low concentrations of sodium, iron, aluminum and silicon characterized the environment in which the nephrite formed. Calcium and sodium were perfectly mobile while magnesium, iron, aluminum and silicon were relatively inert. These conditions of mobility and concentration account for the fine fibrous habit of the nephritic tremolite. Shearing stress is not considered to be the critical factor in producing the nephritic microstructure. A temperature range of approximately 300°C to 500°C and a pressure in excess of 4 kilobars are suggested for the formation of nephrite. 113 BIBLIOGRAPHY American Society for Testing Materials (A. S. T. M.), 1964, Index (inorganic) to the powder diffraction file; Philadelphia. Anderson, E., 1945, Asbestos and jade occurrences in the Kobuk River region, Alaska; Terr, of Alaska, Dept. of Mines, Pamphlet 3-R, 26 p. Anderson, R. B., 1961, The mineral resources of Southern Rhodesia: in The Mining Industry of Southern Rhodesia; Seventh Commonwealth Mining and Metallurgical Congress, Salisbury, Southern Rhodesia, 138 p. Armstrong, J. E., 1949, Fort St. James map-area, Cassiar and Coast Districts, British Columbia; Geol. Survey, Canada, Mem. 252, 210 p. Bailey, E.H., and Stevens, R. H., 1960, Selective staining of K-feldspar and plagioclase on rock slabs and thin sections; Am. Min., v. 45, p. 1020 - 1025. Beck, R. J., 1970, New Zealand Jade - The Story of Greenstone; A. H. and A. W. Reed Ltd., Wellington, N.Z., 106 p. Bloomfield, K., 1958, The Chimwadzulu Hill ultrabasic body, Southern Nyasaland; Trans. Geol. Soc. South Africa, v. 51, p. 263 - 282. Bowen, N. L. and Tuttle, 0. F., 1949, The system MgO-SiO -HO; Geol. Soc. America Bull., v. 60, n. 3, p. 439 - 460. Bowie, S. H. U., 1967, Microscopy, reflected light: in Physical Methods in Determinative Mineralogy; Academic Press, London, p. 103 - 159. British Columbia Department of Mines and Petroleum Resources, 1962 - 1970, Annual Reports, Minister of Mines. British Columbia Department of Mines and Petroleum Resources, 1969 - 1970, Geology, exploration and mining in British Columbia. Burns, R. G., 1970, Mineralogical Applications of Crystal Field Theory; Cambridge Univ. Press, 224 p. Butler, B. C. M., 1963, An occurrence of nephrite jade in West Pakistan; Min. Mag., v. 33, p. 385 - 393. Caimes, C.E., 1929, The serpentine belt of Coquihalla region, Yale District, British Columbia; Geol. Survey, Canada, Sum. Rept., pt. A, p. 144 - 197. Carr, M. H., and Turekian, K., 1961, The geochemistry of cobalt; Geochim. Cosmochim. Acta., v. 23, n. 1 - 2, p. 9 - 60. Chalmers, R. 0., 1967, Australian Rocks, Minerals and Gemstones; Angus and Robertson, Sydney, 398 p. 114 Chesterman, G. W., 1951, Nephrite in Marin County, California; California Div. Mines Spec. Rept. 10-B, 11 p. Chesterman, C. W., 1965, Nephrite and associated rocks at Leech Lake Mountain, Mendocino County, California (abst.); Geol. Soc. America Bull., v. 63, n. 12, pt. 2, p. 1323. Coleman, R. C, 1966, New Zealand serpentinites and associated metasomatic rocks; New Zealand Geol. Survey Bull. 76, 102 p. Coleman, R. C, 1967, Low temperature reaction zones and alpine ultramafic rocks of California, Oregon and Washington; U. S. Geol. Survey Bull. 1247, 49 p. Crippen, R. A., 1951, Nephrite jade and associated rocks of the Cape San Martin region, Monterey County, California; California Div. Mines Spec. Rept. 10-A, 14 p. Danner, W. R., 1972, Private communication. Dawson, G. M., 1887, Annual Report (New Series); Geol. Survey, Canada, v. 3, p. 38B. Dawson, G. M., 1887, Occurrence of jade in British Columbia; Canadian Record of Science, v. 2, no. 6, p. 364 - 378. Deer, W. A., Howie, R. A., Zussman, J., 1966, An Introduction to the Rock-Forming Minerals; John Wiley and Sons, New York, 528 p. Emmons, G.T., 1923, Jade in British Columbia and Alaska; Monograph 35, Museum of the American Indian, Heye Foundation, New York. Eppler, W. Fr., 1941, The relative corrosion hardness of agate and some other minerals (Chen. Abst., 37: 6598-5); Zentr. Mineral., Geol., Abt. A, p. 1 - 10. Ernst, W. G., 1966, Amphibole phase relations: in Short course lecture notes on chain silicates; American Geol. Inst., Washington D. C, p. El - E41. Ernst, W. G., 1968, Amphiboles; Springer-Verlag New York Inc., New York, 125 p. Evans, H. T., Jr, Appelman, D. E., and Handwerker, D. S., 1963, The least squares refinement of crystal unit cells with powder diffraction data by an automatic computer indexing method (abst.); Amer. Crystallogr. Assoc. Ann. Meet., March 28, 1963, Cambridge, Mass., Progr. Abstr. 42. Evans, J. R., 1966, Nephrite jade in Mariposa County; California Div. Mines Mineral Information Service, v. 19, n. 9, p. 135 - 147. Faust, G. T., and Fahey, J. J., 1962, The serpentine-group minerals; U. S. Geol. Survey Prof. Paper 384-A, 92 p. .115 Faye, G. H. and Nickel, E. H., 1970, The effects of charge transfer processes on the colour and pleochroism of amphiboles; Can. Min., v. 10, p. 616 -635. Finlayson, A. M., 1909, The nephrite and magnesian rocks of the South Island of New Zealand; Geol. Soc. London Quart. Jour., v. 65, p. 351 - 381. Forsythe, J., 1969, Private communication. Foshag, W.F., 1957, Mineralogical studies on Guatemalan jade; Smithsonian Misc. Collection, v. 135, n. 5, 60 p. Gabrielse, H., 1963, McDame map area, Cassiar District, British Columbia; Geol. Survey, Canada, Mem. 319, 138 p. Gawel, A., 1949, Nephrite (Chem. Abst., 44:3848a); Wiadomosci Muzeum Ziemi, v. 4, p. 65 - 76. Geological Society of America, 1963, Rock colour chart; New York. Gibbs, G. V., 1966; Short course lecture notes on chain silicates; American Geol. Inst., Washington, D. C., 263 p. Goldschmidt, V. M., 1937, The principles of distribution of chemical elements in minerals and rocks; Jour. Chem. Soc. (London), p. 655 - 673. Hansford, S. H., 1969, Jade - Essence of Hills and Streams; American Elsevier Publishing Co., Inc., New York, 200 p. Heflik, W., 1968, Mineralogy and genesis of nephrite from Jordanow, Lower Silesia, Poland (Min. Abst.: 70-607); Zap. Vses. Min. Obshch., v. 97, p. 96 - 99. Henley, R. F., 1947, Jade in California; Rocks and Minerals, v. 22, n. 2, p. 1114 - 1115. Holland, S. S., 1961, Jade in British Columbia; Minister of Mines, B. C. Annual Rept., p. 119 - 126. Huang, C. K., 1966, Nephrite and blue chalcedony from Taiwan; Proc. Geol. Soc. China, n. 9, p. 11 - 19. Kalkowsky, E., 1906, Geologie des Nephrites im sudlichen Ligurien; Zeitschr. Deutsch Geol. Ges., v. 3, p. 3 - 74. Kindle, E. D., 1952, Dezadeash map-area, Yukon Territory; Geol. Survey, Canada, Mem. 268, 68 p. Knauer, J. D., 1971, Private communication. Kolesnik, Yu. N., 1970, Nephrites of Siberia: in International Geology Review, Book Section; v. 12, 107 p. 116 Krauskopf, K. B., 1967, Introduction to Geochemistry; McGraw-Hill Book Company, 721 p. Larson, C., 1969, Private communication. Leech, G. B., 1953, Geology and mineral deposits of the Shulaps Range; British Columbia Dept. Mines and Petroleum Resources, Bull, v. 32, 54 p. Lepeltier, C, 1969, A simplified statistical treatment of geochemical data by graphical representation; Econ. Geol., v. 64, n. 5, p. 538 - 550. Little, H. W. 1949, The ultra-basic rocks of Middle River Range, B. C; Am. Jour. Sci., v. 247, p. 802 - 823. MacGregor, I. D., and Smith, C. H., 1963, The use of chrome spinels in petro-graphic studies of ultramafic intrusions; Can. Min., v. 7, pt. 3, p. 403 - 412. McLeod, D. L., 1968, Nephrite jade has been discovered in Washington; Lapidary Journal, v. 22, n. 8, p. 1034 - 1037. McTaggart, K. C, 1971, On the origin of ultramafic rocks; Geol. Soc. America Bull., v. 82, p. 23 - 42. Monger, J. W. H., and Hutchison, W. W., 1971, Metamorphic map of the Canadian Cordillera; Geol. Survey, Canada, Paper 70-33, 61 p. Monk, George S., 1963, Light - Principles and Experiments; Dover Publications, Inc., New York, 489 p. Moxham, R. L., 1965, Distribution of minor elements in coexisting hornblendes and biotites; Can. Min., v. 8, pt. 2, p. 204 - 240. Murdoch, J. and Webb, Robert W., 1956, Minerals of California; California Div. of Mines Bull. 173, p. 43. Owen, L., 1972, Private communication. Palmer, J. P., 1967, Jade; Spring Books, Middlesex, England, 44 p. Pauling, L., 1958, General Chemistry; W. H. Freeman and Co., San Francisco, 710 p. Poldervaart, A., 1955, Chemistry of the earths crust; in Crust of the earth -a symposium (A. Poldervaart, ed.); Geol. Soc. America Spec. Paper 62, p. 119 - 145. Preiswerk, H., 1926, Nephrite from Hauderes, Wallis (Chem. Abst., 22:45); Schweiz. Mineralog. Petrog. Mitt., v. 6, p. 267 - 277. Rankama, K. and Sahama, T. G., 1950, Geochemistry; University of Chicago Press, Chicago, 912 p. 117 Rice, H. M. A., 1948, Smithers-Fort St. James; Geol. Survey, Canada, Map 971A. Rimann, E., 1938, Nephrite, carcaro and asbestos in the East Thuringian Vogtland schistose hills (Chem. Abst., 34:2290); S. B. u. Abh. naturu. Ges. Isis., Dresden, n. 9. Robertson, W., 1969, Private communication. Rodgers, A. F., 1940, Nephrite jade from Monterey County, California (abst.); Geol. Soc. America Bull,, v. 51, p. 1941. Roots, E. F., 1954, Geology and mineral deposits of Aiken Lake map-area, British Columbia; Geol. Survey, Canada, Mem. 274, 246 p. Rose, H. and Fromme, J., 1932, A new occurrence of nephrite (Chem. Abst., 27:247); Centr. Mineral. Geol., p. 301 - 307, 308 - 313. Saunders, C. R., 1969, Marshall Creek jade deposit, Lillooet, B. C; unpublished report, International Jade Ltd., 24 p. Schmidt, C, 1917, Asbestos and nephrite from Poschiavo, Graubunden (Chem. Abst. 16:40); Zeitschr. prakt. Geologie, p. 77 - 81. Schneider, A., 1912, Der Diallag-Peridotit und seine Umwandlungs produkte auf Gigestaffel sudlich andermatt; Schweiz. Mineralog. Petrog. Mitt., p. 47. Seywerd, J., 1970, Private communication. Shappel, M. D., 1936, Cleavage of ionic minerals; Am. Min., v. 21, p. 99. Sherer, Richard L., 1969, Nephrite deposits of the Granite, the Seminoe and the Laramie Mountains, Wyoming; unpublished Ph. D. Thesis, Univ. of Wyoming, 194 p. Sinkankas, J., 1966, Gemstones of North America; D. Van Nostrand, Inc., Princeton, N. J., 674 p. Smith, R. L., 1972, Private communication. Staub, R., 1925, Nephrit als Gang im Maiencoserpentin; Schweiz. Mineralog. Petrog. Mitt, v. 5, p. 435. Stemple, I. S. and Brindley, G. W., 1960, A structural study of talc and talc-tremolite relations; Jour. American Ceramic Soc, v. 43, n. 1, p. 34 - 42. Sutton-Thompson Mineral Collection, Department of Geology, University of British Columbia. 118 Thompson, G., and Bankston, D. C., 1970, Sample contamination from grinding and sieving determined by emission spectrometry; Applied Spectroscopy, v. 24, n. 2, p. 210 - 219. Turner, F. J., 1935, Geological investigation of the nephrites, serpentines and related "greenstones" used by the Maoris of Otago and South Canterbury; Tran. Roy. Soc. New Zealand, v. 65, p. 187 - 210. Uhlig, J., 1910, Nephrite from the Harz (Chem. Abst., 5:1384); Neues. Jahrb. Min. Geol., v. 2, p. 80 - 103. Washington, H. S., 1922, Nephrite celt from Bahia, Brazil; Pan-American Geologist, v. 37, p. 198 - 202. Webster, R., 1970, Gems - Their Sources, Descriptions and Identification; Archon Books, Hamden, Conn., 836 p. Welter, 0. A., 1911, The nephrite of the Alps and Franconia (Chem. Abst., 6:729); Neues. Jahrb. Min. Geol., v. 2, p. 68 - 106. Whittaker, E. J. W., 1960, The crystal chemistry of the amphiboles; Acta. Cryst., v. 13, p. 291 - 298. Wilson, M. E., 1926, Talc deposits of Canada; Geol. Survey, Canada, Econ. Geol. Ser., n. 2, p. 52 - 53. Yoshimura, T., Hayashi, M. and Honishi, 0., 1966, Prehnite and nephrite from Hakuba-mura, Nagano Prefecture (Min. Abst., 18:308); Jour. Min. Soc. Japan, v. 8, p. 84 - 93. 119 APPENDIX I SURVEY OF WORLD DEPOSITS 120 APPENDIX I SURVEY OF WORLD DEPOSITS EUROPE Switzerland Small deposits of nephrite are known at Salux (Welter, 1911), Val de Faller (Welter, 1911), Poschiavo, Canton Graubunden (Schmidt, 1917; Staub, 1925), Hauderes, Valais Canton (Preiswerk, 1926) and in the Gotthard Range (Schneider, 1912). The deposits at Salux, Val de Faller and Hauderes occur at the contact between spilites or saussuritized gabbro and serpentine. The nephrite is usually schistose and partially altered to chlorite. At Salux, it contains garnet, picotite and magnetite. In the Gotthard Range and at Poschiavo, the nephrite occurs as lenses and veins in serpentine. East Germany Rimann (1938) describes small bodies of nephrite and fibrous diopside (carcaro) formed in a transition zone between Paleozoic sediments and serpentinized picrites in the Thuringian Hills area. At Koleborn in the Harz (Uhlig, 1910; Rose and Fromme, 1932), nephrite occurs at the contact between a partly serpentinized harzburgite and inclusions of chloritized, tremolitized and prehnitized hornblende gabbro. The nephrite is associated with fibrous diopside and forms as vein-like to 121 lenticular bodies 20 to 30 cm. thick. West Germany Near Frankenwalde, Bavaria (Welter, 1911) sheared and chloritized lenses of nephrite are present at the contact between saussuritized gabbro and serpentinite. Poland Deposits of nephrite are known at Jordanow and Zloty Stok, in southwest Poland (Gawel, 1949; Heflik, 1968). At Jordanow, the large deposit of nephrite is situated in lenses of white altered rock between the Sobotka gabbro massif and serpentinite. The altered rock consists of albite, hornblende, garnet, epidote, zoisite, quartz, prehnite and biotite and is considered to be the result of the calcium metasomatism of the gabbro (Kolesnik, 1970). The partially serpentinized and chloritized nephrite contains numerous small spindle shaped crystals of diopside that are locally replaced by coarse grained, colourless tremolite. Often present in the nephrite are fine grains of sulphides, arsenides, hematite and magnetite. No information is available on the deposit at Zloty Stok. Italy The largest European deposit of nephrite is situated in northern Italy between Sestri Levanto and Monterosso (Kalkowsky, 1909). In this area flysch deposits contain large massifs of serpentinite with subordinate gabbro. The 122 nephrite occurs as lenses and vein-like bodies in the serpentine and at the serpentine-gabbro contacts. Accessory minerals observed in the nephrite include garnet, picotite, magnetite, hematite, iron hydroxides, apatite, sphene and spindle-shaped diopside crystals which locally merge to form carcaro. Also present are relicts of diallage. The nephrite is almost always somewhat sheared with the development of chlorite and carbonate. Union of Soviet Socialist Republics Nephrite deposits are known in two widely separated areas in the Soviet Union; in the southern Urals near the village of Kundrava and in Siberia in the East Sayan Mountains, east of Lake Baikal (Kolesnik, 1970). In the southern Urals, the nephrite occurs in a gabbro massif surrounded by serpentinite. The gabbro is altered to an aggregate of zoisite, albite and hornblende and contains relicts of diopside and saussurite. The nephrite, which is slightly chloritized and replaced by acicules of broad prismatic tremolite is in contact with a zoisite-bearing diopside rock. Two similar nephrite deposits are known in the East Sayan Mountains, one in the watershed of the Khusha-Gol and Ilchir Rivers and the other is situated in the upper course of the Khara-Zhalga River, approximately 40 km northwest of the aforementioned deposit. The former deposit, the larger of the two, is associated with serpentinites of the Ospinsk-Kitoy ultrabasic massif that have been intruded by gabbros and diorites. These basic rocks and the adjacent 123 ultrabasic rocks have been metasomatically altered to garnetite and rodingite-type calcium-silicate rocks and varieties of albitites. Veins and lenses of nephrite are developed along the contact between the serpentinites and the altered basic rocks. In the Khara-Zhalga deposit, nephrite occurs at the contact between albitite and serpentinized peridotites. The albitite in this deposit is thought to have been derived from a gabbro. . An unusual feature of the Siberian nephrites is the presence of inclusions of graphite, a mineral not recorded as occurring in nephrites from other localities. The Khara-Zhalga deposit contains 3 to 4 tons of low grade nephrite while the Ospinsk-Kitoy deposit has reserves of approximately 100 tons. ASIA Peoples Republic of China The nephrite deposits of Chinese Turkistan in western China have been known since ancient times, at least since the Han dynasty (206 B.C. - A.D. 220) (Palmer, 1967). The deposits are situated on the northern and southern slopes of the K'un Lun Mountains. On the northern slopes, the area of outcrops and boulders extends from the valley of the Yarkand River to Lake Lop Nor (Kolesnik, 1970). In one deposit, on the Lyushtag River, the nephrite occurs in diabase and gabbro that have been intruded into Devonian shales, sandstone and syenite. Near the nephrite, individual zones of serpentine, wollastonite, 124 epidote and calcite are developed. Surrounding the nephrite body is a zone composed of serpentine, radial hornblende, wollastonite, calcite, augite and pyrite. The deposits on the Kara-Kash or Black Jade River, a tributary of the Yarkand River, consist of small bodies of nephrite bearing greenstone contained in mica schists. The nephrite bodies are surrounded by a zone of friable talc. Taiwan The only known deposit of nephrite is located in eastern Taiwan, near Fengtien, in the province of Hualien (Huang, 1966). The nephrite, which is slightly schistose, occurs with asbestos and talc in serpentinized peridotite and pyroxenite sills near the contact with graphite schists. Accessory minerals in the nephrite are picotite, chromite, magnetite, chlorite, and chrome garnet. Japan Greenish blue nephrite has been observed in amphibolite with prehnite, calcite and feldspar at Hakuba-mura, Nagano Prefecture, Japan (Yoshimura et al, 1966). West Pakistan Two pebbles of good quality nephrite have been reported from the bed of the Teri-Toi River near Kohat in West Pakistan (Butler, 1963). Butler suggests that the pebbles have been derived from late Pliocene to Pleistocene conglomer ates that occur in the southeastern part of the Teri-Toi basin. 125 AFRICA Nyasaland Nephrite, with coarse tremolite and actinolite, occurs in association with amphibolites in a serpentinized peridotite at Chimwadzulu Hill, southern Nyasaland (Bloomfield, 1958). Bloomfield believes that the amphibolites have been derived from pyroxenites and that the tremolite-nephrite-actinolite rocks have been formed directly from the amphibolite by retrograde metamorphism accompanied by metasomatism and shearing stress. Rhodesia Good quality nephrite has been found in the Mashaba area (Anderson, 1961) approximately 35 miles west of Fort Victoria. The nephrite occurs in Precambrian serpentinites that have been altered to talc schists and talc-carbonate rocks. OCEANIA Australia Two nephrite localities are known in Australia, both in eastern New South Wales, one at Lucknow and the other near Nundle, east of the Dungowan Dam (Chalmers, 1967). At Lucknow, poor quality nephrite occurs at the contact between serpentine and andesite. The nephrite from Nundle is dark bluish green and is associated with silicified serpentine. 126 New Zealand Nephrite has been known and used in New Zealand for at least 1000 years (Beck, 1970). It was used extensively by the Maori tribes for the fashioning of tools, weapons and decorative objects and was even used as currency. To date, commercially viable "in situ" deposits have not been found and present production is from placer deposits formed in streams draining the ultramafic rocks of the South Island. A number of small occurrences of poor quality nephritic material have been reported in the literature. In the Griffin Range area, Westland, nephritic amphibole is reported to occur as nodules and veins in a serpentine-talc-carbonate rock (Finlayson, 1909; Coleman, 1966). In the Wakatipu Lake area of northwest Otago, semi-nephrite occurs in serpentine, in association with talc and actinolite-tremolite, near the contact with the enclosing greywackes and schists (Turner, 1935; Coleman, 1966). Coleman mentions the numerous occurrences of semi-nephritic amphibole along the borders of rodingites, tectonic inclusions and at serpentine-country rock contacts. These amphibole segrega tions also occur as veins extending into the serpentinite. Turner (1935) has studied the petrology of a number of nephrite specimens from Otago and South Canterbury, South Island. In addition to tremolite, the major constituent, these specimens contained accessory amounts of chlorite, serpentine, garnet, diopside, chromite and picotite. 127 NORTH AMERICA United States of America Alaska Large "in situ" and placer deposits of nephrite are located on the northern side of the Kobuk River in northwestern Alaska, north of the Arctic Circle (Anderson, 1945). These deposits occur over a distance of approximately 35 miles between Jade Mountain and the Kogoluktuk River, a tributary of the Kobuk River. The Eskimos have known and made use of the nephrite from this area for at least several hundred years; the deposits were discovered by white men in 1898. The nephrite, some of which is of excellent quality, occurs in veins and lenses in serpentinized peridotites in association with chrysotile asbestos and fibrous tremolite. The ultramafic rocks are enclosed by schists and limestone. The constant association of nephrite and asbestos prompted the original placer miners in the area to give the name "asbestos rock" to nephrite boulders observed in the creeks. California Nephrite deposits have been reported in nine counties; the largest and best described deposits are in Marin, Monterey, Mariposa and Mendocino Counties. The deposit in Marin County (Chesterman, 1951) is located on the east side of Massa Hill, 5 miles southwest of Petaluma, California. The nephrite occurs as short lenses and veins, up to 6 inches wide and several feet long, in sheared 128 and massive serpentine near the contact with albite-clinozoisite-muscovite schist. Both the schist and the serpentine belong to the Upper Jurassic to Upper Cretaceous Franciscan Group. The veins and lenses of nephrite cut narrow veins containing a mixture of actinolite, talc and chrysotile. In southern Monterey County pebbles and boulders of nephrite are found on beaches adjacent to bedrock occurrences of nephrite near Cape San Martin, mid way between Monterey and Morro Bay (Crippen, 1951; Coleman, 1967). At the Plaskett-Jade Cove deposit, the nephrite occurs as a large lens, with an apparent width of ten feet, and a number of smaller pods in sheared and recrys-tallized sediments near the contact with a sill of serpentinized peridotite. The altered sediments consist of albite, quartz and tremolite, and locally, are replaced by talc. The nephrite is of poor quality, with a flaky or schistose structure, and is termed a semi-nephrite. Both the serpentinite and the sediments are assigned to the Upper Jurassic to Upper Cretaceous Franciscan Group. At Cape San Martin, approximately two miles south of Jade Cove, massive and botryoidal nephrite occurs at the contact between serpentinite and a large inclusion of greywacke and shale. At the contact, over a width of 2 feet, the greywacke is altered to a light grey calcium metasomatite consisting pre dominantly of prehnite and varying amounts of diopside and actinolite. Good quality nephrite is reported to occur both in serpentine and in beach deposits between Point Sur and the Salmon Creek Ranger Station (Rogers, 1940). Beaches 129 near Cambria Pines, San Simeon Creek and Salmon Creek are reported to yield pebbles of nephrite (Sinkankas, 1966). A number of "in situ" nephrite occurrences are located north of the town of Bagby in Mariposa County (Evans, 1966). The nephrite is generally found in irregularly shaped, discontinuous bodies of talc-rich rock contained entirely within serpentine or along the contacts between serpentine and country rocks or dykes. At Leech Lake Mountain in Mendocino County, approximately 12 miles north east of Covelo, nephrite occurs as irregular bodies and veins in serpentine sills and at the contact between the serpentine and greywacke (Chesterman, 1952). The nephrite is associated with idocrase, hydrogrossular, pectolite and a diopsidic pyroxene. The greywacke adjacent to the serpentine is weakly meta morphosed to a 'dark-grey, dense, hard rock and contains round grains of glaucophane rimmed hornblende. Nephrite has also been found in Santa Barbara, Siskiyou, Trinity, Tulare, and Eldorado Counties (Murdock and Webb, 1959; Sinkankas, 1967). The nephrite in Tulare County occurs in serpentine at Lewis Hill, 2 miles north of Porter-ville. Oregon Lenses and stringers of nephrite occur in serpentine underlying Sugarloaf Peak in Curry County, southeastern Oregon (Sinkankas, 1967). 130 Washington Boulders of nephrite have been reported from an undisclosed locality near Darrington (McLeod, 1968; p. c. Danner, 1972). The description of the boulders occurring in a "jumble of soil and countryrock" suggests a nearby source. Wyoming A number of nephrite deposits are known in the Precambrian rocks of the Granite, Seminoe and Laramie Mountains, Wyoming (Sherer, 1969). In the Granite Mountains, the deposits are found associated with amphibolite inclu sions in a quartzofeldspathic gneiss of quartz diorite composition. Those in the Laramie Mountains occur where quartz veins are eraplaced in orthoamphibolite dykes. Deposits in the Seminoe Mountains are associated with amphibolite inclusions contained in quartz diorite and amphibolite dykes that are cut by quartz veins. In all deposits, epidote and clinozoisite are abundant in the immediate vicinity of the nephrite. Canada Only three occurrences of nephrite are known outside of British Columbia and all are located in northern Canada. Yukon Territory Nephrite pebbles have been found in the gravels of the Lewes River, the best specimens being obtained near Miles Canyon, about 4 miles south of 131 Whitehorse (Dawson, 1887). Specimens of apple-green nephrite have been report ed from the mountain slope east of the south end of Klukshu Lake, south of Dezadeash Lake (Kindle, 1952). Northwest Territories On the Rae River, near the Coronation Gulf, nephrite is reported to occur in a deposit of soapstone (Wilson, 1926). CENTRAL AND SOUTH AMERICA Nephrite has not been found in either Mexico or Central America although jadeite was used extensively for carving by the native races of this area prior to the Spanish conquest in the early sixteenth century (Palmer, 1967). In South America, the only country in which nephrite artifacts or deposits have been found is Brazil (Washington, 1922). Nephrite deposits, both in place and placer, and numerous nephrite artifacts are found in Amargoza, in the state of Bahia. Geological information regarding the nephrite deposits is not available. 132 APPENDIX II DETERMINATIVE METHODS 133 APPENDIX II DETERMINATIVE METHODS Vickers Hardness Number Determinations The nephrite samples were prepared in the following manner: 1. A small slab, approximately \ inches x \ inches x 1/8 inches was ground flat with #240 carborundum powder on an iron lap. 2. The specimen was hot mounted in a bakelite briquette measuring Ik, inches in diameter by an average of \ inches thick. 3. The mounted sample was ground with #600 carborundum powder on an iron lap for 1 minute. 4. This was followed by 1 minute of grinding with #950 carborundum on a glass plate and then by 1 minute of rough polishing with the same abrasive on a high-speed rubber-faced lap. 5. The final polish was imparted with tin oxide on a high-speed lap surfaced with felt. The instrument used for the hardness determinations is a Leitz Mini-load Pol Hardness Tester equipped with a built in analyser and a rotating polarizer. This instrument employs a diamond-tipped indenter that is allowed to fall onto the specimen under a given load over a set period of time; in this study the load was 15 grams and the period approximately 20 seconds. The diamond tip of the indenter is a square pyramid with a 136° included angle between opposite 134 faces. This produces a square pit, the diagonals of which are seven times the depth of penetration. The instrument was calibrated against a steel plate 2 having a hardness of 625 Kg/mm . Each sample was indented five times; for each indentation, the hardness was calculated from the average diagonal length using the following equation taken from the instruction manual for this instrument: Vickers hardness number = (1854.4)(P) d2 where P = load = 15 grams d = average diagonal length in ^m. A correction factor was applied to each hardness and an average hardness calculated for each specimen. Unit Cell Parameter Calculations Four x-ray diffraction records, two up scan and two down scan, were obtained for each of the nephrite samples investigated. The records were obtained with a Philips X-ray diffractometer using nickel filtered CuKw rad iation. The scan speed was 1° 28 /minute and the chart speed was 120 cm/hour. Quartz was used as an internal standard. The average interplaner spacings of the following reflections were used in the calculations: (110), (130), (001), (111), (040), (131), (240), (310), (151), (151), (112), (061), (202) and (002). The parameter computations were done on the I.B.M. 360 computer at the University of British Columbia; the program is one devised by Evans, Appelman and Handwerker (1963). Data for the parameter card was obtained from A.S.T.M. 135 card #13 - 437 (tremolite). Chemical Analyses Crushing and Grinding Small pieces of each of the 31 nephrite specimens analysed were crushed with a hammer on a steel plate. The crushed fragments were hand picked to eliminate any visible iron contamination. A tungsten carbide lined grinding vial containing a tungsten carbide ball was used to reduce the crushed material to a -100 mesh powder. The grinding time for each sample was 15 minutes. Both the vial and the ball are manufactured by Spex Industries, Inc., New Jersey. The serpentine specimens and the weathered nephrite specimens were crushed in the manner described above but were reduced to powder, by hand, in a mullite mortar. Four nephrite specimens were also ground in a mullite mortar in order to provide a correction factor for cobalt contamination introduced by the tungsten carbide vial. Atomic Absorption Analysis (Fe,Co,Ni,Cu,Pb,Zn) The powdered samples were decomposed in a teflon dish using a perchloric acid-hydrofluoric acid digestion. The sample weight was 0.4 grams. To ensure complete digestion of the powders, each sample was treated with the acid mixture twice. The procedure followed is given below: 1. To each powdered sample, 3 ml of distilled water, 5 ml of hydrofluoric acid and 0.5 ml of perchloric acid were added. This mixture was allowed to 136 evaporate to dryness at 180° C. This process was repeated twice. 2. The digestion residue was cooled and dissolved in 3 ml of distilled water and 3 ml of concentrated hydrochloric acid. This solution was transferred to a 25 ml volumetric flask and was made up to the mark with distilled water. The final solutions were stored in polythene bottles. 3. A blank solution containing only the reagents was prepared for each batch of samples dissolved. The samples were analysed for iron, manganese, copper and zinc with a Techtron AA-4 atomic absorption spectrophotometer. A Perkin-Elmer 303 atomic absorption spectrophotometer was used for the cobalt, nickel and lead analyses. The Perkin-Elmer instrument was equipped with a hydrogen lamp to simultaneous ly correct for background absorption. The standards used were prepared by the Department of Geology, University of British Columbia. Spectrographic Analysis (Cr,Ti,V) For the spectrographic analyses, 0.10 gram of each sample was weighed and placed in a small plastic vial with 0.10 gram of graphite containing 30 ppm indium. The graphite-indium mixture was used as an internal standard for the spectrograph. After agitation to ensure thorough mixing of the sample and the indium bearing graphite, the prepared samples were placed in cup electrodes and analysed in a Hilger Automatic Quartz Spectrograph. Spex Mix (Spex Catalogue 137 #1000) diluted to the approximate concentration of the elements being detected was used as a standard. The spectrographic plates were read on an ARL Spectro-line Scanner. Both the analyses and the plate readings were performed by Mr. David Marshall of the Department of Geology, University of British Columbia. Correction for Cobalt Contamination The four nephrite samples ground by hand in the mullite mortar were found to contain an average of 34 ppm less cobalt than the corresponding samples ground in the tungsten carbide vial. The cobalt contents of the nephrite specimens were reduced by this amount. This figure is in good agreement with the 32 ppm obtained by Thompson and Bankston (1970) for the cobalt contamina tion of pure quartz when ground in a similar vial. 138 APPENDIX III NEPHRITE ANALYSES OBTAINED FROM THE LITERATURE 139 APPENDIX III Nephrite Analyses Obtained from the Literature Si02 58.14 57.78 56.41 56.63 56.73 57.35 57.38 56.55 55.99 TI02 A12°3 0,98 2,35 0,91 2,14 3,22 0,22 0,22 °*21 Fe203 3.39 1.60 3.84 3.99 — FeO 0.85 2.83 1.92 — 5.96 5.94 3.50 6.21 5.20 Cr2°3 " -- 0.42 MnO 0.22 — 0.15 MgO 22.38 14.80 19.09 21.69 19.42 20.70 22.32 19.78 21.67 CaO 12.53 15.02 12.81 13.41 13.24 13.47 13.68 13.60 14.18 Na20 0.36 1.63 2.64 0.20 K20 — 1.00 -- 0.69 0.69 1.69 2.75 2.56 1.67 0.83 3.13 2.78 2.81 2.56 H20+ H20-P2°5 " C°2 NiO ign. Totals 100.54 99.76 100.33 100.42 99.40 100.81 100.57 99.16 100.02 — Not looked for Nd Not detected 140 APPENDIX III CONTINUED 10 11 12 13 14 15 16 17 18 S102 55.59 57.96 52.38 57.75 51.70 56.34 56.25 56.01 55.89 T102 A1203 1.43 — 2.07 0.90 0.65 1.60 0.42 0.65 2.34 Fe203 — — — 0.38 — — 1.67 1.88 2.39 FeO 6.15 6.40 4.36 4.79 7.62 4.86 5.61 5.02 2.34 Cr203 — — — — 0.30 MnO — — — 0.46 Tr. — 0.33 0.29 0.41 MgO 21.24 22.15 20.74 19.86 23.50 20.23 20.55 20.65 18.72 CaO 12.93 13.49 15.73 14.89 13.09 13.51 12.67 13.41 13.97 Na20 — -- — — — 0.35 0.45 0.51 0.58 K20 — — — — — — 0.28 2.35 2.77 0.68 2.42 3.57 1.89 2.03 2.21 H20+ H20-P2°5 C°2 NiO — — — 0.22 ign. Totals 99.86 100.00 98.05 99.93 99.28 100.69 99.74 100.67 98.78 Note: Analysis #10 includes 0.17% Cu. 141 APPENDIX III CONTINUED 19 20 21 22 23 24 25 26 27 Si02 57.45 58.28 56.51 59.79 56.02 54.43 51.90 55.00 55.28 TI02 — 0.02 0.23 0.02 0.01 0.45 0.40 0.17 A1203 1.09 0.88 1.80 0.88 1.15 1.58 5.50 0.90 1.43 Fe203 0.24 0.29 — 0.33 1.66 1.31 1.30 1.60 0.67 FeO 1.35 0.35 4.38 0.96 3.69 4.00 5.80 3.80 3.53 Cr203 — -- Tr. MnO 0.28 Tr. 0.06 0.10 0.26 0.69 0.20 0.19 0.11 MgO 20.61 22.08 21.32 24.31 23.54 21.54 15.75 21.80 21.99 CaO 15.41 14.98 12.72 12.52 11.64 11.70 14.90 11.80 12.91 Na20 — 0.42 — 0.35 0.29 -- 0.18 0.20 0.34 K20 0.51 0.38 — 0.06 0.34 — 0.04 0.02 0.02 H 0+ 1.33 2.10 1.43 4.05 3.04 3.16 2.95 1 2.65 1.98 H20- 0.28 0.32 0.05 0.30 0.44 1.16 0.51 P205 — — — — — — 0.10 0.06 C02 — — — — — — 0.09 0.02 NiO — 0.03 ign. — — 1.37 Totals 99.59 99.64 99.82 99.95 100.07 99.61 99.69 99.75 99.91 142 APPENDIX III CONTINUED 28 29 30 31 32 33 34 35 36 Si02 56.20 56.76 57.58 57.30 56.70 56.70 55.90 57.00 57.10 Ti02 — Tr. 0.10 0.06 0.05 0.06 0.10 0.10 0.10 A1203 1.40 1.12 1.35 1.60 1.40 1.40 2.80 1.50 3.00 4.80 4.50 4.50 Fe203 0.06 0.81 0.15 0.38 1.60 0.69 FeO 5.65 3.96 4.02 3.20 6.50 7.10 MnO 0.18 0.02 0.15 0.04 0.08 0.09 0.10 0.10 0.10 MgO 21.09 22.50 20.65 22.40 20.20 19.80 23.10 21.30 21.40 CaO 13.22 11.83 13.10 13.00 11.80 12.40 12.80 14.50 12.80 Na20 0.14 0.21 0.12 0.02 0.30 0.40 Nd. K20 0.21 0.18 Tr. 0.11 0.04 0.08 0.30 0.10 0.10 HO+ 2.09 2.54 0.12 0.20 0.04 — 2.61 H20- Nd. 0.24 0.53 1.30 0.60 P205 — — -- 0.02 0.04 0.05 C02 — — — 0.65 0.05 0.68 NiO 0.24 ign. Totals 100.48 100.17 99.83 99.43 100.26 100.09 99.90 100.00 99.10 143 APPENDIX III CONTINUED 37 38 39 40 41 42 Si02 55.50 57.00 54.10 53.30 51.20 55.50 Ti02 0.10 0.05 0.10 0.10 0.10 0.10 A1203 3.60 1.70 3.30 3.60 3.00 1.00 Fe 0 0.75 9.60 12.30 11.30 13.50 10.70 FeO 4.60 Cr2°3 MnO 0.10 0.07 0.20 0.20 0.20 0.10 MgO 20.00 21.30 20.30 21.30 21.40 21.20 CaO 11.60 12.90 10.30 9.60 10.60 11.50 Na20 — 0.03 K20 0.20 0.10 0.20 0.20 0.20 0.20 H20+ — 0.05 H20- — 0.56 P205 ~ 0.03 C02 — 0.05 NiO ign. Totals 100.70 99.19 100.80 99.60 100.20 100.30 144 APPENDIX III CONTINUED Analyses Locality 1-20 New Zealand 21 Harz area, East Germany 22 Bahia, Brazil 23 Hauderes, Valais Canton, Switzerland 24 Koleborn, Harz area, East Germany 25 - 26 New Zealand 27 Fengtien, Taiwan 28 Siberia, U. S. S. R. 29 Hakuba-mura, Nagano Prefecture, Japan 30 Jordanow, Poland 31-36 Granite Mountains, Wyoming 37 Semi noe locality, Seminoe Mountains, Wyoming 38 Sage Creek locality, Seminoe Mountains, Wyoming 39 - 42 Laramie Mountains, Wyoming Reference Finlayson, 1909 Uhlig, 1910 Washington, 1922 Preiswerk, 1926 Rose and Fromme, 1932 Coleman, 1966 Huang, 1966 Kolesnik, 1970 Yoshimura et al, 1966 Heflik, 1968 Sherer, 1969 Sherer, 1969 Sherer, 1969 Sherer, 1969 LEGEND LITHOLOGY SYMBOLS AA»ro - opllra •^orphyrttK OIJM*# - MMWl • ctin©f#^W# rock Amphibofe-olbrt* rock Moto-dmba** MornbU^ci. - ro.nl. reck j{ Folioiion(incline, vertical) »• dd.no Contact ( defined mlt.r.d •«limot»d ) PERMIAN (?) AND/ OR LATER POST-MIDDLE PERMIAN, PRE - UPPER TRIASSIC (T) TREMBLEUR INTRUSIONS FooH (defined, eiti mated ) •»*- ? M« Os * Dromond drill hole Mot. Brg Dip DeptMft) 5 126° -60* 65 6 ?i5° -60° 52 • 130° -67° 97 Nepnrite Tremor*,-(r*or ml rodr Tak-carbonate-terpentine rock Quart I-cor bona t« rock PENNSYLVANIAN (?) AND PERMIAN CACHE CREEK GROUP Chert quorti.te argillrte nana green, tor » Boutderi of »«mi- nephrite and tremolite- chlorite ichrtl FIG.12. GEOLOGY O'NE-ELL CREEK NEPHRITE DEPOSIT O'NE-ELL CREEK,BRITISH COLUMBIA BO 40 80 160 Mopped by i « f-ow. S.pf.mber. 1969 

Cite

Citation Scheme:

    

Usage Statistics

Country Views Downloads
Canada 92 22
United States 26 11
China 16 13
Australia 6 1
New Zealand 4 1
United Kingdom 3 0
Sweden 3 0
Poland 3 0
Indonesia 3 0
Georgia 2 0
Pakistan 2 0
Japan 2 0
Puerto Rico 1 0
City Views Downloads
Unknown 47 7
Viking 23 0
Ashburn 9 0
Prince Rupert 9 10
Vancouver 6 2
Beijing 5 3
Shenzhen 4 10
Canberra 4 1
Shanghai 4 0
Oshawa 3 0
Stockholm 3 0
Surrey 3 0
Calgary 3 0

{[{ mDataHeader[type] }]} {[{ month[type] }]} {[{ tData[type] }]}
Download Stats

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0093110/manifest

Comment

Related Items