"Arts, Faculty of"@en . "Geography, Department of"@en . "DSpace"@en . "UBCV"@en . "Fraser, John Ross"@en . "2011-03-17T19:08:45Z"@en . "1973"@en . "Master of Science - MSc"@en . "University of British Columbia"@en . "Nephrite is a compact, microfibrous variety of actinolite-tremolite 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.\r\nIn 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.\r\nThe 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 nephrite have an average Vickers hardness of 950 Kg/mm\u00C2\u00B2 and an average Mohs hardness of 7. The average specific gravity is 3.00.\r\nThe 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 agreement with those for nephritic tremolite from other localities.\r\nThe 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 variations\r\nare 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.\r\nAt the O\u00E2\u0080\u0099Ne-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 characterized the environment in which the nephrite formed. Calcium and sodium were perfectly mobile while the other elements were relatively inert. These conditions of mobility and concentration account for the fine fibrous nature of the nephritic tremolite. A temperature range of approximately 300\u00C2\u00B0C to 500\u00C2\u00B0C and a pressure in excess of 4 kilobars are suggested for the formation of the nephrite."@en . "https://circle.library.ubc.ca/rest/handle/2429/32553?expand=metadata"@en . "NEPHRITE IN BRITISH COLUMBIA, by JOHN ROSS FRASER B . S c , U n i v e r s i t y of B r i t i s h Columbia, 1967 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Geology We accept t h i s t h e s i s as conforming to the r e q u i r e d standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1972 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n p e r m i s s i o n . Department o f The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date v^a^-.5.a.1 \<2>7 3 ( i ) ABSTRACT Nephrite i s 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 B r i t i s h 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 Br i t i s h Columbia contains, i n 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 v i s i b l e in hand specimen. The colour of the majority of the specimens i s yellowish green; this colouration i s 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 i s 3.00. The unit c e l l parameters of tremolite from B r i t i s h 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-( i i ) merit with those for nephritic tremolite from other l o c a l i t i e s . 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\u00C2\u00BBNe-ell Creek deposit in central B r i t i s h 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 s i l i c a , of the serpentinite during the process of serpentinization. The calcium was derived from the pyroxenes contained i n the original ultramafic rock; the source of the s i l i c a was the enclosing sediments. High concentrations of calcium and magnesium and relatively lower concentrations of sodium, iron, aluminum and si l i c o n 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\u00C2\u00B0C to 500\u00C2\u00B0C and a pressure in excess of 4 kilobars are suggested for the formation of the nephrite. ( i i i ) 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 13 PRODUCTION 15 MINING METHODS 18 MARKETS, PRICES AND USES 19 III. PETROLOGY AND PHYSICAL PROPERTIES OF BRITISH COLUMBIA NEPHRITE 21 NEPHRITE CLASSIFICATIONS 21 Turner Classification 23 Non-schistose Nephrites 23 Schistose Nephrites 23 Semi-nephrites 25 Kalkowsky Classification 25 PETROLOGY 27 Tremolite 27 Chlorite 36 Spinel 38 Ilmenite 38 Diopside 38 Uvarovite 40 Unknown 42 Sphene 42 Carbonate 42 Phlogopite and Talc 42 Pyrite 42 PHYSICAL PROPERTIES 43 Fracture 43 Specific Gravity 43 Colour and Lustre 45 Hardness 46 Crushing Strength and Relative Corrosion Hardness 51 IV. THE CHEMISTRY AND CRYSTALLOGRAPHIC STRUCTURE OF NEPHRITE 52 CHEMISTRY 52 CRYSTALLOGRAPHIC STRUCTURE 57 (iv) Page V. IRON AND TRACE ELEMENT GEOCHEMISTRY OF BRITISH COLUMBIA NEPHRITES 65 DISCUSSION OF RESULTS 69 Iron 69 Cobalt and Nickel 69 Manganese 71 Copper 73 Lead 73 Zinc 73 Chromium, 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 GEOLOGY 83 GEOLOGY OF THE DEPOSIT 88 General Description 88 Lithology 92 Cache Creek Group 92 Trembleur Intrusions 96 Miscellaneous Rock Types 99 Amphibole-zoisite rock 99 Meta-diabase 99 Albite-amphibole rock 99 Meta-aplite 101 Summary 101 PETROGENESIS 102 General Statement 102 Origin of the Nephrite 103 Temperature and Pressure Conditions 109 VII. CONCLUSIONS 111 BIBLIOGRAPHY 113 APPENDIX 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 i l l u s t r a t i n g 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 il l u s t r a t i n g 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; F a l l 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$ F a l l 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 pa r t i a l l y replaced by chlorite (#15; Van Decar Creek), plane polarized light. 11 Photomicrograph of corroded remnants of diopside 39 (#16; 0\u00C2\u00BBNe-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; F a l l River), plane polarized li g h t . 14 Photomicrograph of anhedral grains of uvarovite garnet 41 (#8; F a l l River), plane polarized light. 15 Scanning electron micrograph of a schistose nephrite 60 transitional to a semi-nephrite i l l u s t r a t i n g 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 l i t e fibers i n a quartzite from O'Ne-ell Creek, plane polarized light. 19 Photomicrograph of stilpnomelane (brown) and biotite (green) 95 in fractures i n a siliceous a r g i l l i t e from O'Ne-ell Creek, plane polarized light. 20 Photomicrograph of stilpnomelane (brown) and needles of 95 tremolite in an a r g i l l i t e from O'Ne-ell Creek, crossed nicols. 21 Photomicrograph of a serpentinite from O'Ne-ell Creek 98 il l u s t r a t i n g the fibro-lamellar structure of the antigor-i t e , crossed nicols. 22 Photomicrograph of a quartz-carbonate rock from O'Ne-ell 98 Creek, crossed nicols. FIGURES Figure Page 1 Index map of Br i t i s h Columbia. 10 2 Nephrite production in Br i t i s h 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 i n 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 i t i e s . 6 The structure of tremolite. 58 7 Histograms of the Fe, Co, and Ni contents of Bri t i s h 70 Columbia nephrites. 8 Histograms of the Mn, Cu, and Pb contents of Bri t i s h 72 Columbia nephrites. 9 Histogram of the Zn content of Br i t i s h Columbia nephrites. 74 10 Geology map; Takla Lake-Middle River area, B r i t i s h Columbia. 84 11 Legend for Figure 10. 85 12 Geology; 0\u00C2\u00BBNe-ell Creek nephrite deposit, O'Ne-ell Creek, In Br i t i s h Columbia. Pocket 13 Diagrammatic representation of mineral zoning at the contact 104 between serpentinite and metasomatized a r g i l l i t e and grey-wacke. 14 Ca (activity) - Si02 (activity) for calcium and magnesium 106 si l i c a t e s . TABLES Table Page 1 Nephrite production from Mining Divisions, British 17 Columbia. 2 Classification, mineralogy and mode of B r i t i s h Columbia 28 nephrites. 3 Indices of refraction of tremolite i n nephrites. 34 4 X-ray diffraction data for kbtschubeite (chromian clino- 36 chlore), clinochlore, kammererite (chromian penninite), pen&inite and for chlorite from B r i t i s h Columbia nephrite specimens. 5 Specific gravity of Br i t i s h Columbia nephrite specimens. 44 6 Specific gravity of weathered and unweathered nephrite from 45 placer boulders. 7 Colour of Bri t i s h Columbia nephrite specimens. 47 ( v i i i ) Table Page 8 Vickers hardness number and Mohs hardness of polished 49 specimens of B r i t i s h Columbia nephrite. 9 Unit c e l l parameters for tremolite from B r i t i s h Columbia 62 nephrite, tremolite from Siberian nephrite- and common tremolite. 10 X-ray diffraction data for tremolite and for nephritic 63 tremolite from Br i t i s h Columbia, New Zealand, Taiwan and Siberia. 11 Iron and trace element analyses of B r i t i s h Columbia 66 nephrite specimens. 12 Iron and trace element contents of fresh and weathered 77 nephrite from a l l u v i a l boulders. 13 Average and range of iron and trace element contents of 79 nephrites from the three major nephrite producing areas of B r i t i s h Columbia. 14 Average iron and trace element contents of nephrite and 105 serpentinite from O'Ne-ell Creek. 1 I. INTRODUCTION Nephrite and ja d e i t e are the two minerals that are c o l l e c t i v e l y r e f e r r e d to as jade. Nephrite i s a compact, fibrous v a r i e t y of a c t i n o l i t e - t r e m o l i t e , an amphibole, and jadei t e i s a pyroxene. Other minerals such as serpentine, g r o s s u l a r i t e and vesuvianite are often presented as v a r i e t i e s of jade, usually with a geographical p r e f i x , but should be termed pseudojades. An example i s massive vesuvianite from C a l i f o r n i a which i s known, i n lapidary c i r c l e s , as C a l i f o r n i a jade, American jade or Feather River jade. NOMENCLATURE AND HISTORY The e a r l i e s t mention of jade i n the European l i t e r a t u r e i s a f t e r 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 f o r the cure and prevention of diseases of the kidneys and gave them the name \"piedra de yjada\" meaning \"stone of the l o i n s \" or \" c o l i c stone\". L a t i n scholars translated t h i s term into i t s L a t i n equiva-l e n t , \" l a p i s n e p h r i t i c u s \" . The French t r a n s l a t i o n s of the Spanish and L a t i n terms became \"p i e r r e l'ejade\" or simply jade and \" p i e r r e nephritique\", r e s p e c t i v e l y . In the middle of the nineteenth century, A l e x i s Damour, a French chemist, studied various jades and distinguished, on the basis of chemical composition, two v a r i e t i e s which he termed nephrite and j a d e i t e . Because of i t s f i n e colouration, i t s p e c u l i a r translucency and i t s a b i l i t y 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 Br i t i s h Columbia employed simple nephrite tools up to the time of the introduction of iron by the f i r s t European traders (Emmons, 1923; Dawson, 1887). In China, the history of nephrite i s long and may extend as far back as neolithic time. To the Chinese, the true jade i s 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 i s not known to occur anywhere i n 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 i t i s estimated that there are not more than f i f t y i n the world (Kolesnik, 1970) although t h i s f i g u r e should be revised upward i n l i g h t of recent discoveries i n Canada. The nature of the occurrence of nephrite accounts f o r i t s r e l a t i v e r a r i t y ; i t generally occurs i n le n s o i d a l or discontinuous v e i n - l i k e masses seldom exceeding ten feet i n width and the appearance of nephrite i n outcrop i s often very s i m i l a r to that of the enclosing rocks. Nephrite deposits are known i n North America, South America, Europe, A s i a , A f r i c a and Oceania. B r i e f descriptions of a number of occurrences, exclusive of those i n B r i t i s h Columbia, are presented i n Appendix I. The deposits i n North America are located i n B r i t i s h Columbia, Yukon, Northwest T e r r i t o r i e s , C a l i f o r n i a , Washington, Oregon and Wyoming. The only known deposits i n South America are s i t u a t e d i n B r a z i l . In Europe, occurrences are known i n Switzer-land, Poland, I t a l y , West Germany, East Germany and the Union of Soviet S o c i a l i s t Republics. The A s i a t i c deposits are located i n Chinese Turkistan, Taiwan and Japan. In A f r i c a , nephrite has been reported from Nyasaland and Southern Rhodesia and i n Oceania, from New Zealand and New South Wales, A u s t r a l i a . The majority of nephrite deposits are found within serpentinized alpine ultramafic bodies; nephrite has hot been reported from unserpentinized u l t r a -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 i s commonly associated with asbestos, chlorite, coarse fibrous tremolite, talc and diopside. Nephrite also occurs i n 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 i n , or cut by, siliceous intrusive rocks and i s associated with epidote and clinozoisite. In Chinese Turkistan, nephrite occurs i n 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 i s very limited. The earliest reference i s by Dawson (1887) in which he describes the manufacture and use of nephrite implements by the Indians of B r i t i s h 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 Br i t i s h Columbia and Alaska. The only known reference pertaining to nephrite deposits in the Province i s by Holland (1961). 5 SCOPE OF PRESENT WORK This investigation was undertaken to determine the geographical distribu-tion of nephrite deposits i n B r i t i s h Columbia, to study the petrology, physical properties, chemistry and crystallographie structure of nephrite from a number of B r i t i s h Columbia occurrences and to describe, and propose an origin for, the O'Ne-ell Creek nephrite deposit in central B r i t i s h 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 B r i t i s h Columbia. The unit c e l l parameters were calculated for the tremolite from ten nephrite specimens to determine i f 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 i f nephrites from the three major producing areas in B r i t i s h 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 a l l u v i a l 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 a l l individuals who provided assistance and encouragement during the collection of data and preparation of this thesis. Special recognition i s due Mrs. W. Robertson who arranged for the author to v i s i t the O'Ne-ell Creek deposit and provided many specimens from British Columbia nephrite occurrences. The author i s 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 B r i t i s h 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 fi n a l manuscript. 8 II. BRITISH COLUMBIA DEPOSITS Nephrite, presumably obtained from the Fraser River, was u t i l i z e d by the Kwakiutl, Salish, Tsimshian, Haida and Tl i n g i t tribes of the coast and south-western interior of Br i t i s h 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 i s illustrated by the fact that, among the T l i n g i t 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 B r i t i s h 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 i n the province are associated with a b e l t of alpine ultramafic rocks that extends for 1000 miles from the Hope area, east of Vancouver, northwestward through c e n t r a l and northern B r i t i s h Columbia to the Yukon border (Figure 1). This b e l t i s traceable into Yukon and Alaska. The following b r i e f d e s c r i p t i o n of these rocks i s taken l a r g e l y from McTaggart (1971). The ultramafic bodies, most of which are p e r i d o t i t e or dunite, range i n s i z e from a few tens of feet across to b a t h o l i t h s with areas greater than 70 square miles. In shape, they are s i l l - l i k e and l e n t i c u l a r to equidimensional, although elongate bodies are the most common. Many are cut by veins and dykes of dunite, pyroxenite and gabbro. Chromite, i n pockets, lenses and v e i n - l i k e masses, i s almost always present. The bodies are commonly serpentinized, the degree of which ranges from i n c i p i e n t or p a r t i a l i n the larger masses to almost complete i n the smaller, l e n t i c u l a r bodies. Talc rocks and mariposite bearing quartz-carbonate rocks are common but are usually r e s t r i c t e d to shear zones and contacts (Cairnes, 1929; Armstrong, 1949; Leech, 1953; Roots, 1954; Gabrielse, 1963). Zones of hornblende, a c t i n o l i t e - t r e m o l i t e or c h l o r i t e 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 l a t e Paleozoic Cache Creek Group although i n a few places i n central B r i t i s h 11 Columbia and Yukon, they occur i n Upper T r i a s s i c or J u r a s s i c rocks. Several of the larger bodies l i e along major northwest-trending f a u l t s that separate the Cache Creek s t r a t a from younger rocks. PLACER OCCURRENCES OF NEPHRITE A l l of the nephrite produced i n B r i t i s h Columbia i n the 1950's and the early 1960's was obtained from placer deposits i n 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, i n Figure 1, are l a b e l l e d I, I I , and I I I , r e s p e c t i v e l y . In area I, placer nephrite has been found along the Bridge River from i t s confluence with the Fraser River to Mission Dam (Holland, 1961) and on i t s t r i b u t a r i e s 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 H e l l Creek (M. M., 1968). On the Fraser River, nephrite has been c o l l e c t e d from Chilliwack to the mouth of the Bridge River (Holland, 1961). The Coquihalla River, a t r i b u t a r y of the Fraser River, has y i e l d e d nephrite from i t s junction with the Fraser to the mouth of Dewdney Creek (Holland, 1961). The a l l u v i a l nephrite occurs as pebbles, cobbles and boulders ranging i n weight from a few tens of pounds to as much as ten tons. The largest boulders occur on the Bridge River and i t s t r i b u t a r i e s ; those from the Fraser River are smaller i n s i z e , mostly i n 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 a l l u v i a l boulders of generally poor quality material. To the north, nephrite has been found along Vital Creek (M. M., 1963), Quartz Creek (M. M., 1963), F a l l 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), a l l 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 i s 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 i t s course and are presumably derived from a band of serpentinized p e r i d o t i t e that crops out some 1.5 miles upstream from the creek mouth. L i t t l e i s known of the occurrences on Thibert and Seywerd Creeks, except that i n the l a t t e r , nephrite occurs i n place i n serpentine. BEDROCK OCCURRENCES OF NEPHRITE In B r i t i s h Columbia, there are at least 10 \" i n s i t u \" occurrences of nephrite and with one exception, the deposit on O'Ne-ell Creek, very l i t t l e information i s a v a i l a b l e regarding these deposits (Figure 1). A l l are intimate-l y associated with serpentinized alpine ultramafic rocks. Four bedrock nephrite deposits are known i n 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 H e l l Creek. The deposit on Ama Creek occurs i n a 3-foot wide pale green a l t e r a t i o n zone i n serpentine along the contact of a d i o r i t e dyke. The jade, which i s associated with p e c t o l i t e (Uncataloged Sutton-Thompson C o l l e c t i o n specimen), c o n s i s t s of s u b p a r a l l e l bands of greenish tremolite and grey diopside that enclose i r r e g u l a r shaped masses of serpentine. This material, because of i t s banded nature and resemblance to i n t e s t i n e s , i s known l o c a l l y as \" i n t e s t i n -a l \" or \"gut jade\" but due to t h i s texture i t has l i t t l e use as a gems tone. A number of small showings and one large deposit are situated i n the v i c i n i t y of Marshall Creek and i t s t r i b u t a r y Brett Creek. The large deposit, which has 14 produced nephrite commercially, i s located on Brett Creek approximately % mile upstream from i t s confluence with Marshall Creek. In this deposit, vein-like masses of nephrite occur in a 50 foot wide, N 60\u00C2\u00B0 E striking zone of sheared serpentine that i s i n contact with sediments of the Cache Creek Group to the north and a light grey chert-like rock, which in turn i s 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 si t u \" 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 ric h varieties containing numerous minute grains of bright green uvarovite garnet are common. L i t t l e i s 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 w i l l 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, i s situated on Seywerd Creek, a small creek entering the west side of Dease Lake at Steamboat Point. The nephrite occurs i n serpentine (M. M., 1963; G. E. M., 1970; p. c. Seywerd, 1970). The second occurrence i s in the open-pit asbestos mine on Mount McDame near Cassiar (G. E. M., 1970). PRODUCTION Annual production figures for Br i t i s h 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 s i t u \" deposits, the quantity mined was 262,602 pounds, a ten-fold increase over the previous year. Undoubtedly production w i l l continue to increase in future years as the \" i n s i t u \" 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 a l l 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, $. Source-Ann. Rep. of B.C. Min. of Mines and Pet. Res. 1962 - 1970 -200.000 \u00E2\u0080\u00A2250,000 150, 000 - 100,000 - 50,000 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 Fig .2 . Nephrite production in British Columbia for the period 1959 \u00E2\u0080\u0094 1 9 7 0 , inclusive. 17 Table 1 Nephrite Production from Mining D i v i s i o n s , B r i t i s h Columbia Year Mining D i v i s i o n Quantity ( l b . ) Value (?) T o t a l to Date Quantity ( l b . ) Value ($) 1962 L i l l o o e t 56,935 20,760 1963 L i l l o o e t 16,000 15,529 207,986 72,490 1964 L i l l o o e t 10,337 11,404 218,323 83,894 Omineca 1,200 2,400 1,200 2,400 1965 L i a r d 2,000 2,000 2,000 2,000 L i l l o o e t 4,129 5,249 222,452 89,143 Omineca 1,000 2,000 2,200 4,400 1966 L i a r d 8,493 8,648 10,493 10,648 L i l l o o e t 3,140 4,577 225,592 93,720 1967 L i a r d 14,920 19,714 25,413 30,362 L i l l o o e t 5,240 4,627 230,832 98,347 1968 L i a r d 1,810 2,125 27,223 32,487 L i l l o o e t 42,095 83,899 272,927 182,246 Omineca 5,110 19,646 7,310 24,046 1969 L i a r d 5,825 11,960 33,048 44,447 L i l l o o e t 6,060 5,237 278,987 187,483 Omineca 14,447 25,438 21,757 49,484 1970 L i a r d 5,322 9,099 38,370 53,546 L i l l o o e t 14,280 27,583 293,267 215,066 Omineca 243,000 213,574 264,757 263,058 Source: Annual Reports, B r i t i s h Columbia Minister of Mines and Petroleum Resources, 1962 - 1970. 18 MINING METHODS The methods employed i n mining \" i n s i t u \" nephrite vary from deposit to deposit. As with any gemstone, the ultimate goal i s to remove the maximum amount of material with the minimum amount of p h y s i c a l damage to i t ; t h i s i s often a d i f f i c u l t task due to the hardness and extreme toughness of nephrite and the f a c t that i t often occurs as discontinuous lenses and veins i n moderately to steeply dipping zones. Factors i n f l u e n c i n g 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 a c c e s s i b i l i t y of the mine s i t e . S t r i p p i n g the overburden and the enclosing rocks from the nephrite pods i s u sually accomplished by using heavy equipment such as bulldozers although at one deposit i n the Takla Lake area, the overburden was washed away with high pressure water j e t s and the harder material i n the hanging wall was broken with pneumatic hammers and very l i g h t explosive charges. Due to the p o t e n t i a l danger of f r a c t u r i n g the nephrite, explosives must be used sparingly and with caution. Once the nephrite i s exposed, i n d i v i d u a l lenses or large fragments are extracted with heavy equipment or hydraulic jacks or the nephrite i s sawn, i n place, into e a s i l y removed blocks. Several small diameter core samples are usually taken from the large pieces i n order to a s c e r t a i n t h e i r q u a l i t y . The extracted nephrite i s sawn into smaller blocks to t r i m waste or low q u a l i t y material, to provide an e a s i l y handled piece and to provide q u a l i t y c o n t r o l . The sawing i s 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 B r i t i s h Columbia i s 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, i s sold locally through r e t a i l 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-t i t e , 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 w i l l account for a very small percentage of the total nephrite sales i f 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 t i l e s 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 i t 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 f e a s i b i l i t y of using nephrite for the fabrication of bearings for watches and other instruments (p. c. Owen, 1972; p. c. Smith, 1972). 21 I I I . PETROLOGY AND PHYSICAL PROPERTIES OF BRITISH COLUMBIA NEPHRITE Jade i s a terra that i s applied to two mi n e r a l o g i c a l l y d i s t i n c t species, nephrite and j a d e i t e . Nephrite i s a compact, dense, raicrofibrous form of t r e m o l i t e - a c t i n o l i t e ( C a ^ M g . F e ^ O H ^ S i ^ O ^ ^ ) , an amphibole, and j a d e i t e (NaAlCSiO-j^) i s a massive, microgranular form of the pyroxene of the same name. True nephrite consists of microscopic bundles of tremolite f i b e r s (Plates 1, 2) that have been completely f e l t e d or interwoven with one another, producing the c h a r a c t e r i s t i c n e p h r i t i c structure (Turner, 1935). In poor q u a l i t y nephrites t h i s structure i s poorly developed or even completely absent. NEPHRITE CLASSIFICATIONS The nephrite c l a s s i f i c a t i o n commonly used by North American geologists i s one established by Turner (1935) during an i n v e s t i g a t i o n of New Zealand green-stones. This c l a s s i f i c a t i o n i s based on microstructure and consists of f i v e d i v i s i o n s , three of which deal with nephrites and two with tremolite rocks lacking a n e p h r i t i c structure. The Turner c l a s s i f i c a t i o n i s used i n t h i s report. European geologists use a c l a s s i f i c a t i o n , c o n s i s t i n g of seven d i v i s i o n s , that was devised by Kalkowsky (1906) during h i s study of the Appenine nephrite deposits i n northern I t a l y . Both c l a s s i f i c a t i o n s are presented below. 22 P l a t e 1: Scanning e l e c t r o n micrograph of a s c h i s t o s e n e p h r i t e t r a n s i t i o n a l to a semi-nephrite i l l u s t r a t i n g the t w i s t e d and interwoven nature of the component t r e m o l i t e f i b e r s (#37; 0\u00C2\u00BBNe-ell Creek), X 300. P l a t e 2: Scanning e l e c t r o n micrograph of a s c h i s t o s e n e p h r i t e t r a n s i t i o n a l to a semi-nephrite i l l u s t r a t i n g the f i n e f i b r o u s nature of the tremo-l i t e (#37; O'Ne-ell Creek), X 1270. 23 Turner Classification The three varieties of nephritic rocks according to the Turner c l a s s i f i c a -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 i s 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 i s 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 i s 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 f i s s i l e . Kalkowsky Classification The following i s 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 i s reminiscent of coarse f l u f f 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 p a r a l l e l unfelted f i b e r s (#8; F a l l R i v e r ) , crossed n i c o l s . P l a t e 6: Photomicrograph of a schistose nephrite t r a n s i t i o n a l to a semi-nephrite (#40; Seywerd Creek), crossed n i c o l s . The t r a n s i t i o n to a semi-nephrite i s indicated by the development of a c i c u l a r c r y s t a l s 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 c l a s s i f i -cation, mineralogy and visually estimated mode of the specimens are tabulated in Table 2. Tremolite Tremolite i s the most abundant mineral present, comprising at least 89 per-cent of any section. In thin section the tremolite i s colourless and under crossed-nicols the interference colours range from low f i r s t order to middle second order. Extinction angle (cAz) determinations on the tufts and crystals of coarser tremolite were between 16\u00C2\u00B0 and 19\u00C2\u00B0 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-l i t e 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 B r i t i s h 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 Fa l l River Non-schistose nephrite Tremolite 100 transitional to schis- Picotite 1 tose nephrite Uvarovite r < l Sphene j 8 Fa l l 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 F a l l 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\u00C2\u00BBNe-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 \u00E2\u0080\u00A2 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. L o c a l i t y C l a s s i f i c a t i o n Mineralogy Percentage 45 Dease Lake Semi-nephrite T r e m o l i t e 99 U v a r o v i t e 1 P i c o t i t e P y r i t e 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 i n 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\u00C2\u00AB % 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 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 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 i s classified as a semi-nephrite. 36 Chlorite Chlorite i s present in eighteen sections in amounts up to 10 percent. In thin section, i t i s 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 i s seen. X-ray diffraction data indicate that the chlorite i s 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, pa r t i a l l y 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 i s 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 i s opaque except on thin edges where i t i s 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 i s present in six sections, #9, #16, #23, #33, #43, and #44. In thin section i t is colourless, optically positive, and has an extinction angle, cAZ, of 41\u00C2\u00B0. 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 i n 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 i s very similar to that described by Kolesnik (1970) for the diopside in Siberian nephrites. Replace-ment of the diopside by tremolite i s 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 i t i s v i s i b l e in hand specimen as bright green grains or clusters of grains. In thin section, this mineral i s 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 i n elongate aggregates that are parallel to the schistosity of the A l 0.5 ram Plate 14: Photomicrograph of anhedral grains of uvarovite garnet (#8; F a l l River), plane polarized light. The cores of the garnet grains usually contain phlogopite. specimen. In some sections, the uvarovite surrounding the picotite fragments i s , 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 i s colourless, has parallel extinction and a positive optic sign. Contained within the mass are patches of chromite and uvarovite garnet. Sphene Sphene i s 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, i s present in two sections (#6, #23). In one section, i t 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, i s 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 i s 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\u00C2\u00B0C, for 34 specimens. Four determinations were made on each specimen and averaged; the results are tabulated in Table 5. The average specific gravity i s 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) i s 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 Br i t i s h 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 F a l l River 3.00 31 Dease Lake area 2.99 8 F a l l 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 F a l l River 3.01 42-A Marshall Creek 3.00 20 F a l l 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 i s often seen on nephrite artifacts that have been subjected to burning. The original shape of the object i s not altered in any way (Palmer, 1967). This fact may be of use to archaeologists, particularly in B r i t i s h 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 i n Table 8. The method of preparing the samples and obtaining the hardness values i s outlined in Appendix II. The Vickers hardness number i s a measure of hardness which i s calculated from the size of the indentation produced by a pyramidal-shaped, diamond-tipped indenter f a l l i n g , under a given load and over a set period of time, onto a specimen. 2 The mean Vickers hardness number i s 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 i s shown in Figure 3, a graph of Mohs hardness values against the logarithm of Vickers hardness number (Bowie, 1967). From Figure 3, i t 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 a l l 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 B r i t i s h 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 F a l l 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) 2 0 0 0 1 0 0 0 Range of the Vickers hardness numbers of 14 British Columbia nephrite specimens. CO CO to z Q < X CO ui U 1 0 0 2 0 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 i s 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 l i t e r a -ture and are included in this report because of the unavailability of such information. The crushing strength of high quality Siberian nephrite i s reported to be 7,759 Kg/cm2 (Kolesnik, 1970). The high value i s 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 i n which f i n e f i b e r s of tremolite occur i n t u f t s which are f e l t e d and twisted* This microstructure, which imparts to nephrite i t s d i s t i n c t i v e c h a r a c t e r i s t i c s , i s a function of the li m i t e d conditions under which i t forms (Kolesnik, 1970). These conditions are quite d i f f e r e n t to those under which common broad-prismatic t r e m o l i t e - a c t i n o l i t e forms. This s e c t i o n attempts to o u t l i n e the chemical and s t r u c t u r a l features of n e p h r i t i c tremolite and broad-prismatic t r e m o l i t e - a c t i n o l i t e . CHEMISTRY The general formula of an amphibole may be expressed as (Ernst, 1968; Whittaker, 1960; Deer et a l , 1966; Gibbs, 1966): W 0_ 1X 2Y 5Z g0 2 2(OH,0,F,Cl) 2 where W represents ten- to twelve-fold coordinated cations, commonly Na and K, occupying the A s t r u c t u r a l s i t e s (Figure 6); X r e f e r s to s i x - or e i g h t - f o l d \u00E2\u0080\u00A2 \u00E2\u0080\u00A2 +2 coordinated cations with i o n i c r a d i i from 0.7 A to 1.1 A, c h i e f l y Ca, Na, Fe and Mn; Y stands f o r s i x - f o l d cations with i o n i c r a d i i from 0.57 A to 0.91 A, + 2 +3 c h i e f l y Mg, Fe , Fe , A l , Mn, and T i ; and Z r e f e r s to small highly charged cations within the tetrahedral groups, l a r g e l y S i , but may be replaced by A l up to about 25 percent. Hydrogen may be present to balance excess charges. The common cat i o n replacements f o r the amphibole group are Mg = Fe, A l = S i , (Mg,Fe) = A l and Na = Ca; i n the t r e m o l i t e - a c t i n o l i t e s e r i e s , the predominant 53 replacement i s iron for magnesium. A replacement of the type Al = S i , (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 c e l l . 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 . s s ^ . i s ^ . o ^ o . i i ^ . n ^ A ^ i ^ o t ^ V . i o ^ o . o s ^ . o o < S i7.75 A l0.25\u00C2\u00B022 ) ( O H )1.93\u00C2\u00B00.07 Nephritic tremolite: + 2 +3 ( C a1.91 M 80.05 K0.03 N a0.12 )2.11 ( M 84.53 F e0.36 F e0.11 )5.00 ( S i7.77 A 10.20\u00C2\u00B022 ) ( O H )2 \u00C2\u00B0 ' 4 7 H2\u00C2\u00B0 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\u00C2\u00B0C, the so-called crystallographie water, i s 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 i s 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 i s characteristic of the nephrites. This structure would allow nephrite to adsorb a significant amount of water and retain i t on heating. The weight loss curves in Figure 4 il l u s t r a t e that the water in nephrite i s 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^. A l l of the analyses f a l l on or close to the tremolite-ferroactinolite line and are grouped at the tremolite end of the line. The compositional f i e l d 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, \u00C2\u00B0C 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 M g O Fig.5 + FeO M g O - C a O \u00E2\u0080\u0094 F e 2 0 3 + F e O in n e p h r i t e s f r o m v a r i o u s w o r l d local i t ies. . F i e l d of New Zealand nephrites (Finlayson, 1909; Coleman, 1966) C--' F i e l d of Wyoming nephrites (Sherer, 1969) A: Granite Mountains; Sage Creek l o c a l i t y , Seminoe Mountains B: Laramie Mountains; Seminoe l o c a l i t y , Seminoe Mountains + Harz area, East Germany (Uhlig, 1910) A Bahia, B r a z i l (Washington, 1922) \u00C2\u00A9 Hauderes, V a l a i s Canton, Switzerland (Preiswerk, 1926) H Koleborn, Harz area, East Germany (Rose and Fromme, 1932) \u00E2\u0080\u00A2 Fengtien, Taiwan (Huang, 1966) Hakuba-mura, Negano Prefecture, Japan (Yoshimura et a l , 1966) A Jordanow, Poland ( H e f l i k , 1968) O East Sayans, S i b e r i a , 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 i s 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 i s probable that these elements are present, in variable amounts, in the nephrites from other lo c a l i t i e s 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 l o c a l i t i e s . CRYSTALLOGRAPHIC STRUCTURE The structure of the amphiboles i s 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, i s shown in Figure 6. The c-cell edge of the unit c e l l i s defined by the repeat of the chain along i t s 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 i s 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 \u00E2\u0080\u0094 o -o\u00E2\u0080\u0094a- o a\u00E2\u0080\u009E M A O O O O M , o M 2 o M 4 o A O 6- - o \u00E2\u0080\u0094 o - o A -J\"~V o - o \u00E2\u0080\u0094 o - H 6 Fig.6. The s t ructure of t remol i te . The project ion is upon (001) and para l le l to c. s i l i c o n : 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 i n 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 i s C 2/m. Amphiboles possess a well-developed prismatic cleavage, the planes of which meet at angles of about 55\u00C2\u00B0 and 125\u00C2\u00B0, yielding cleavage fragments which appear diamond-shaped in cross section. This cleavage, which i s 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 i s 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 c e l l (Ernst, 1966). The b Q para-meter i s controlled by the sizes of the cations in and M^ , but because the occupancy of M, i s constant i n any particular synthetic series, the control on 60 P l a t e 15: Scanning e l e c t r o n micrograph of a s c h i s t o s e n e p h r i t e t r a n s i t i o n a l to a semi-nephrite i l l u s t r a t i n g the (110) cleavage of t r e m o l i t e . (#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 i s an increase in a Q sin B. A slight increase i n the chain length C q i s observed when the size of the cations in and i s increased. The c e l l volume increases with the number of large ions contained within the structure. The unit c e l l parameters of tremolite from ten Br i t i s h 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 c e l l 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, i s in the length of the b Q parameter; that in the latter i s 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 C Q - c e l l 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\u00C2\u00BBNe-ell Creek), New Zealand (Coleman, 1966), Taiwan (Huang, 1966) and Siberia (Kolesnik, 1970) are presented in Table 10. 62 Table 9 Unit C e l l Parameters f o r Tremolite from B r i t i s h Columbia Nephrite, Tremolite from S i b e r i a n Nephrite and Common Tremolite Sample Number L o c a l i t y o a A o b A o O c A o B C e l l , Vol . A J 7 F a l l River 9.883 18.116 5.261 105\u00C2\u00B0 11' 909.2 +0.018 TO.022 TO.004 T10' T l . 7 11 K e l l y Creek 9.880 18.112 5.261 105\u00C2\u00B0 11' 908.6 +0.017 +-0.021 +0.004 + 10' T l . 6 12 Kwanika Creek 9.879 18.110 5.259 105\u00C2\u00B0 11' 908.6 +0.017 +-0.020 t0.004 Tl O ' + 1.6 19 F a l l River 9.878 18.127 5.262 105\u00C2\u00B0 9' 909.5 +0.018 +0.023 +0.005 + 11' + 1.7 23 Coquihalla River 9.888 18.130 5.263 105\u00C2\u00B0 11' 910.6 +\u00E2\u0080\u00A20.017 +-0.021 TO.004 + 10' + 1.6 35 O'Ne-ell Creek, 9.886 18.132 5.263 105\u00C2\u00B0 10' 910.6 +0.017 +0.021 +0.004 + 10\u00C2\u00AB + 1.6 36 O'Ne-ell Creek 9.889 18.134 5.267 105\u00C2\u00B0 12\u00C2\u00BB 911.5 +0.016 +0.020 +0.004 T 9' + 1.5 40 Seywerd Creek 9.890 18.131 5.266 105\u00C2\u00B0 12\u00C2\u00BB 911.3 +0.018 TO.022 TO.004 T 10' Tl . 7 41 S i l v e r Creek 9.873 18.106 5.259 105\u00C2\u00B0 12' 907.2 +\u00E2\u0080\u00A20.017 TO.021 TO.004 + 10' + 1.6 42 - B Marshall Creek 9.885 18.116 5.262 105\u00C2\u00B0 10\u00C2\u00BB 909.5 +0.018 +0.022 +0.004 + 10' + 1.7 Si b e r i a n 9.878 18.12 5.29 Nephrite +0.007 T0.005 +0.006 104\u00C2\u00B0 47' _ _ _ (Kolesnik, 1970) Tremolite 9.84 18.02 5.27 104\u00C2\u00B0 57' \u00E2\u0080\u0094 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 J 1 1 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 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 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 \u00E2\u0080\u0094 \u00E2\u0080\u0094 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 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 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 \u00E2\u0080\u0094 \u00E2\u0080\u0094 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 \u00E2\u0080\u0094 \u00E2\u0080\u0094 242, 042 2.206 6 2.238 9 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 441 2.181 6 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 2.181 7 \u00E2\u0080\u0094 \u00E2\u0080\u0094 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 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 \u00E2\u0080\u0094 1.933 7 \u00E2\u0080\u0094 \u00E2\u0080\u0094 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, B r i t i s h 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 f i r s t , and foremost, i s to determine i f there is any regional variation in the trace element content of the nephrites. Such a variation, i f systematic, could prove to be extremely important to archaeologists attempting to trace the sources of the nephrite used by early B r i t i s h Columbia Indians for the fabrica-tion of tools. The second i s to determine, i n a qualitative way, what minor and trace elements are colouring agents. The f i r s t seven elements were determined by atomic-absorption spectro-photometry. The analytical precision (95% confidence level) of these deter-minations, based on duplicate analyses, i s : Fe,Mn = +- 4%; Ni,Zn = \u00C2\u00A310%; Co,Cu,Pb = \u00C2\u00B1 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 r a d i i 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 T i 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 F a l l River 2.68 36 1100 606 10 22 36 4000 500 200 8 F a l l 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 N i Mn Cu Pb Zn Cr TI V Number L o c a l i t y % 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 F a l l R i v e r 3.38 100 919 969 6 20 90 1500 400 150 23 C o q u i h a l l a River 2.94 70 787 813 33 33 58 3000 500 150 24 B r e t t 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 Ca s s i a r 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 T i 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, i s : Fe,Mn = T4%; Ni, Zn =*10%; Co, Cu, Pb = + 20%. Cr, T i , V: Spectrographic analyses, semi-quantitative; analyst, D. Marshall, Department of Geology, University of Bri t i s h Columbia. 69 DISCUSSION OF RESULTS Iron The average for iron in the nephrites studied i s 3.05%; the maximum and minimum values are 3.63% and 2.36%, respectively. The results are shown as a histogram i n 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 i s contained in the actinolite-tremolite structure i n 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 i s 954 ppm and the range i s 134 ppm to 1630 ppm. The results are plotted as histograms in Figure 7; cobalt i s 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 i s 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 . 0 5 ^ N=31 2.00 2.50 2.90 \u00C2\u00B0 y S o 3.30 3.70 \u00E2\u0080\u0094I 4.10 10-Co DC u. 5-X= 49 p.p.m. N=31 40 80 p.p.m. 120 \u00E2\u0080\u0094 T -160 \u00E2\u0080\u0094I 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 i n the araphibole as octahedrally coordinated cations occupying Y positions. The average cobalt-nickel ratios for Bri t i s h Columbia and Wyoming nephrites are 0.051 and 0.052, respectively. Manganese The average concentration of manganese in the nephrites i s 800 ppm; the range of concentration i s 300 ppm to 1537 ppm. A histogram of the results (Figure 8) approximates a normal distribution. The bulk of the manganese is undoubtedly concealed i n the actinolite-tremolite structure* Rankama and Sahama (1950) state that because of the large size (0.80 A) of the Mn ion, i t i s incorporated into calcium and magnesium +\u00E2\u0080\u00A2 2 s i l i c a t e s only with d i f f i c u l t y . They suggest that the Mn ion i s capable of replacing F e + 2 (0.74 A), M g + 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 l i s t the presence of Mn, as an oxide, in amounts ranging from trace to 0.69% MnO. 72 11\u00E2\u0080\u0094I 1 0 -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 i s 55 ppm and the values range from 22 ppm to 97 ppm. The results are graphically presented in the histogram i n 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, i s capable of replacing ferrous iron and magnesium in mineral structures (Rankama and Sahama, 1950) and in the case of the actinolite-tremolite series, i t 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 i s 4000 ppm, titanium 700 ppm and vanadium 150 ppm. The bulk of the chromium present in the nephrites i s 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) i s very similar to that of f e r r i c 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 B r i t i s h Columbia. Two of the analyses, 9 and 14, in Appendix III l i s t chromium as a detectable constituent, the concentrations being 0.42% Or^O^ (approximately 2900 ppm Cr) and 0.30% C r ^ (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 i s + 3 +4 unknown due to analytical d i f f i c u l t i e s in determining T i and T i in the presence of ferrous and f e r r i c iron. These authors suggest the possibility + 3 +4 that T i rather than T i i s present in amphiboles and pyroxenes even though TiC^ i s reported in analyses. Most general formulae for the amphiboles indi-cate that titanium i s contained in the Y positions. The average titanium content of 13 nephrites i n Appendix III i s approximately 790 ppm. The vanadium content of the nephrites i s remarkably uniform. This element i s similar to titanium in behaviour and may be concealed in the sphene micro-l i t e s described above although some i s probably contained in the actinolite-+ 3 \u00E2\u0080\u00A2 tremolite. Goldschmidt (1937) considers vanadium to be present as V (0.74 A) in ferromagnesian minerals; as such i t 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 i s 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. A l l three specimens were from a l l u v i a l boulders. The weathered material i s softer than the unweathered nephrite and i s 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 T i ppm V ppm #7; Fal l 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\u00C2\u00BBNe-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, i t i s 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 i s readily explained by the precipitation during weathering of the relatively insoluble hydroxides of f e r r i c 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 I r o n and Trace Element Contents of Nephrites from the Three Major Nephrite Producing Areas of B r i t i s h Columbia Fe Co N i Mn Cu Pb Zn Cr T i V Area % ppm ppm ppm ppm ppm ppm ppm ppm ppm Bridge R i v e r - 3.23 49 939 741 16 28 46 5600 500 170 lower F r a s e r R i v e r 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 T a k l a Lake 3.00 55 1151 822 12 21 58 4400 300 140 I I 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 I I I 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 f o r nep h r i t e s from area I I do not i n c l u d e the values f o r two greenish grey specimens (#34, #35) as they are r a r e and contain anomalously low chromium and high t i t a n i u m . 80 each element from each area, i t i s not p o s s i b l e to s t a t e that a n e p h r i t e specimen w i t h a given t r a c e element content o r i g i n a t e d i n a p a r t i c u l a r area. The probable reason f o r the l a c k of r e g i o n a l v a r i a t i o n s i s th a t the n e p h r i t e s from the three areas have formed i n s i m i l a r g e o l o g i c environments. However, on a much l a r g e r s c a l e , the B r i t i s h Columbia n e p h r i t e s are d i s t i n g u i s h a b l e , by chromium content, from the Wyoming n e p h r i t e s which have been de r i v e d from amphibolites and are not a s s o c i a t e d w i t h u l t r a m a f i c r o c k s . The average c o n c e n t r a t i o n of chromium i n the former i s 4000 ppm w h i l e i n the l a t t e r i t i s 30 ppm. COLOUR OF NEPHRITES The c o l o u r of n e p h r i t e i s one of i t s most conspicuous p h y s i c a l p r o p e r t i e s and i s c e r t a i n l y i t s most v a l u a b l e . The f o l l o w i n g d i s c u s s i o n of the causes of co l o u r i n s i l i c a t e minerals i s presented f o r t h i s reason and i s taken l a r g e l y from Burns (1970). The m a j o r i t y of s i l i c a t e minerals owe t h e i r c o l o u r to the presence, i n major o r t r a c e amounts, of t r a n s i t i o n metals such as t i t a n i u m , vanadium, chromium, manganese, i r o n , c o b a l t , n i c k e l and copper o r lanthanide elements. The most common cause of c o l o u r i s the absor p t i o n of r a d i a t i o n through e l e c t r o n -o o i c processes and i f such absorption i s i n the v i s i b l e (4000 A to 7000 A) r e g i o n of the electromagnetic spectrum, c o l o u r s are produced i n t r a n s m i t t e d and r e f l e c t e d l i g h t . The two most important c o l o u r producing processes are i n t e r n a l 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 faci l i t a t e d 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 \u00E2\u0080\u0094 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, i t i s 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 S i = Al . The colour of the majority (85%) of the B r i t i s h Columbia nephrites examined i s a hue of green with a distinct yellowish cast. This colour i s due to the presence of multivalent iron and i s 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 i s 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 i s readily accounted for by the lack of picotite, chromite, uvarovite and chlorite; i n nephrites most of the chromium i s contained in the aforementioned accessory minerals. Another anomalous specimen, #19, i s 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 i s 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 i s located in central British Columbia (Figure 1) near the south end of Takla Lake, approximately 130 air miles N 60\u00C2\u00B0 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 i t s confluence with Middle River (Figure 10). Roads do not reach the property and access i s either by a i r , 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 all u v i a l 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 f i e l d season. The following brief description of the regional geology i s taken largely from Armstrong (1949) and L i t t l e (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. S E D I M E N T A R Y A N D V O L C A N I C R O C K S T E R T I A R Y O L I G O C E N E OR L A T E R ENDAKO GROUP ~\"~ 1 Mainly vesicular and amygdaloidal basalt, andeslte | \u00E2\u0080\u00A2 and dacite; flow breccia and agglomerate C R E T A C E O U S OR L A T E R UPPER C R E T A C E O U S AND P A L E O C E N E 11 SUSTUT GROUP Conglomerate, shale,greywackc, and tuff C R E T A C E O U S LOWER C R E T A C E O U S 10 USLIKA FORMATION: conglomerate;minor sandstone and shale JURASSIC AND C R E T A C E O U S H A Z E L T O N G R O U P 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(?) C R E T A C E O U S TACHE K GROUP Andesite and andesite breccia; basalt and rhyolite TRIASSIC AND JURASSIC U P P E R TRIASSIC AND L A T E R TAKLA GROUP Andt'sit ic and basaltic flows, tuffs, breccias, and agglomerate; inter-bedded conglomerate, shale, gr-eywacke , limestone, and coal 0 C A R B O N I F E R O U S (?) AND P E R M I A N PENNSYLVANIAN (?) AND L A T E R 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 "Thesis/Dissertation"@en . "10.14288/1.0093110"@en . "eng"@en . "Geography"@en . "Vancouver : University of British Columbia Library"@en . "University of British Columbia"@en . "For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use."@en . "Graduate"@en . "Nephrite in British Columbia"@en . "Text"@en . "http://hdl.handle.net/2429/32553"@en .