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A study of barium minerals from the Yukon Territory Montgomery, Joseph Hilton 1960

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A STUDY OP BARIUM MINERALS PROM THE YUKON TERRITORY by JOSEPH HILTON MONTGOMERY B.Sc, University of B r i t i s h Columbia, 19^9 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of Geology We accept th i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , I960 I n 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 o f t h e r e q u i r e m e n t s 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 C o l u m b i a , I agree t h a t t h e 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 s t u d y . 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 g r a n t e d by t h e Head o f my Department o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f 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 a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f GEOLOGY 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 APRIL 13, I960, i ABSTRACT A study of rare barium minerals from the Yukon T e r r i t o r y has resulted i n the discovery of at le a s t one and possibly f i v e new species. The present in v e s t i g a t i o n i s concerned with one of these, a barium-calcium-iron-alumino-silicate, which i s te n t a t i v e l y classed as an I n o s i l i c a t e and named k e e l e i t e . The op t i c a l and physical properties, a chemical analysis, and the c a l c u l a t i o n of i t s formula are presented. The mineral has also been successfully synthesized. An X-ray study of some supergene and a l t e r a t i o n products present i n the rocks revealed the presence of an i n t e r -esting mixture of barium-calcium carbonate s a l t s , s i m i l a r to those obtained as laboratory products. A paragenesis Is also presented. i i TABLE OF CONTENTS Acknowledgments ,v Introduction 1 Regional Geology . . . 2 Mineralized Zones 3 Petrograph Description of the Quartz Monzonite. i | Keeleite . 5> Occurrence f? Physical Properties . . . . . . . . . . . . $ Optical Properties • . . . . . . 6 Chemical Analysis and Cal c u l a t i o n of Formula 7 Synthesis of Keeleite . 1 1 A l t e r a t i o n Products of Keeleite 20 Associated Minerals . . 3 1 Faragenesis . . . . . . . « ^ 2 Conclusions i|7 Bibliography . . . . . . . . . . . . . . . . . . 1*9 ILLUSTRATIONS Figure 1 . Optic Orientation of Keeleite . . . . 1 Figure 2. Possible Optic Orientation of Mineral C 22 Table 1 . Spectrographic Analysis of Keeleite 8 Table 2. Chemical Analysis and Cal c u l a t i o n of Formula for Keeleite . 9 Table 3 « X-ray Data for Natural Keeleite, Fused-Annealed Keeleite, and Synthetic Keeleite l£ Table I4. Revised Calculation of Keeleite Formula . . . . . . . . . . . . . . . 1 7 i i i Table 5» Comparison of Oxide Percentages i n the Two Calculated Formulas . . . 18 Table 6» X-ray Data for Ba^Fe^Fe^SiO^JlO * . 19 Table 7 . X-ray Data for Mineral C . . . . . . 2 2 Table 8 . Spectrographs Analysis of Mineral C 2 3 Table 9 . Spectrographs Analysis of Mineral E 2$ Table 10. X-ray Data for Mineral E 26 Table 1 1 . Comparison of X-ray Data of White Goating, Synthetic Baryto-c a l c i t e , and Synthetic A l s t o n i t e . . 2 9 Table 12. Spectrographic Analysis of Taramellite (Ross River, Y.T.) . . . 3 3 Table 1 3 . X-ray Data f o r Taramellite 3k Table Chemical Analysis of Tara-mel l i t e and Calcul a t i o n of i t s Formula 3 6 Table 1$, X-ray Data for G i l l e s p i t e 3 8 Table 16. Spectrographic Analysis of G i l l e s p i t e 3 9 Table 1 7 . Spectrographic Analysis of Sanbornite I4O Table 18. X-ray Data f o r Sanbornite I4I Plate I. Laths of Keeleite (crossed nicols) . . . . . l l i -Plate I I . X-ray Powder Photographs of Keeleite . . . . . . . . . . . . . . . 16 Plate I I I . X-ray Powder Photograph of the Compound, 5Ba0.2FeO.FegO^.lOSiOg Plate IV. Mineral C, g l l l e s p i t e , keeleite Plate V. X-ray Powder Photograph of Mineral C Plate VI. Mineral E and keeleite Plate VII. Mineral E and sanbornite . . . . Plate VIII. X-ray Powder Photographs of Mineral E . Plate IX. X-ray Powder Photographs of Barium-Calcium Carbonates . . . Plate X. Taramellite . . Plate XI. X-ray Powder Photographs of Taramellite . Plate XII. G l l l e s p i t e , Keeleite, and ' Taramellite . . . . . . . . . . Plate XIII. X-ray Powder Photographs of Sanbornite Map 1. Key map showing l o c a t i o n of mineral deposit . . . . . . Map 2. Map of regional geology • . V ACKNOWLEDGMENTS I am greatly Indebted to Dr. R.M. Thompson of the Unive r s i t y of B r i t i s h Columbia f o r his many sug-gestions and guidance throughout the course of this work. I would also l i k e to thank the Department of Mining and Metallurgy for the loan of equipment neces-sary f o r the synthesis of keeleite, and the s t a f f members of that department, a l l of whom offered t h e i r w i l l i n g co-operation. In addition, I would l i k e to express my gratitude to Dr. K.C. McTaggart of the University of B r i t i s h Columbia for proof-reading the f i r s t d r a f t , and for his many he l p f u l suggestions. I would l i k e to thank Dr. R.E. Delavault of the University of B r i t i s h Columbia f o r preparing the ferrous oxide used i n the synthesis of keeleite, and for his generous help during the course of preparing this t h e s i s . I would also l i k e to thank Dr. J.O. Wheeler and Dr. J.A. Roddick of the Geological Survey of Canada, Mr. S. Sandner, Mr. Pat Clay, and the Newmont Mining Corporation of Canada for t h e i r various assistances. I am al so indebted to the Royal Ontario Museum for the loan of type specimens f o r comparison. M A P 2 I N C H = 4 M I L E S G R A N I T I C S T O C K S M E T A S E D I M E N T S D R I F T C O V E R E D K E E L E I T E < 1 INTRODUCTION The purpose of t h i s i n v e s t i g a t i o n i s to des-cribe a new barium mineral, keeleite, which occurs i n a contact metasomatic deposit i n the Yukon T e r r i t o r y . The mineral deposit i s located on the Sheldon Lake Sheet (Map 10£J) near the head-waters of Ross River and about two miles southwest of G i l l e s p i t e Lake on the Gun group of claims. These claims were staked for t h e i r zinc con-tent f o r the Newmont Mining Corporation of Vancouver, B.C. i n 1957* Map 1 shows the general l o c a t i o n of the deposit and Map 2 i t s exact l o c a t i o n and regional geology. Previous geological work i n the area consists only of several reconnaissance operations. Joseph Keele^" explored the Upper P e l l y and Ross Rivers i n 1 9 0 7 and 1 9 0 8 . No further work was done u n t i l 19kk when E.D. Kindle made a geological reconnaissance along the Canol Road. In 1 9 5 8 , J.A. Roddick and J.O. Wheeler of the Geological Survey of Canada i n i t i a t e d "Operation P e l l y " , a geologi-c a l reconnaissance which includes the Sheldon Lake sheet. It was while In the employ of the Geological Survey of Canada during the 1 9 5 8 f i e l d season that the author c o l -lected the specimens on which the present work i s based. The present invest i g a t i o n was suggested by Dr. R.M. Thompson of the University of B r i t i s h Columbia, who i d e n t i f i e d g i l l e s p i t e ( BaPeSi ^ 0 1 0 ) i n a specimen sub-2 mitted by Mr. Scotty Alan of Newmont Mining Corporation i n 1957-The laboratory work was done at the University of B r i t i s h Columbia i n 1959 and I960 . REGIONAL GEOLOGY The area, as shown i n Map 2, i s characterized by several int r u s i v e stocks which vary In composition from granodiorite to granite. At the contacts of these Igneous bodies, the metasediments, which consist of a r g i l l i t e s , shales, s l a t e s , quartzites, and limestone, have been con-verted to hornfelses and skarns. Many mineralized zones have been reported associated with some of these g r a n i t i c stocks. Most of them are simply pyrrhotite Impregnations of the thermally metamorphosed rocks, but values i n gold, s i l v e r , copper and zinc have been obtained i n a few. The contact aureole from which the present suite of specimens was c o l l e c t e d surrounds a quartz monzonite stock which i s exposed over an area of approximately f i v e square miles. The intruded rocks are steeply dipping to the east, and along the western contact, the bedding i s almost v e r t i c a l . The contact on the north and west sides of the stock dips outward from the stock at an angle of 80 to 85 degrees. The contact aureole i s r e l a t i v e l y narrow and has an apparent width of 50 to 75 feet. i 3 Mineralized Zones The mineralized zones are lens^e-shaped and concordant with the bedding i n the metamorphic rocks, and are probably derived from l o c a l l i m e - r i c h bodies. Two main outcrops of the skarn zone were examined. The f i r s t outcrop i s at an elevation of 5>,1{00 feet and i s exposed on the west wall of a small cirque. It Is a concordant body (0°/60°E) and consists e s s e n t i a l l y of f i n e to medium-grained witherite, sanbornite, and hedenbergite. The lens^ i s about 200 feet long and 30 feet thick at i t s thickest point. The rock on the hanging wall consists of s l a t e , and on the footwall of slat e and quartzite. Compositional banding i s prominent i n the lense, with i n d i v i d u a l bands varying from l/2 to 2 inches i n thickness and composed of varying concentrations of sanbornite, witherite, and hedenbergite. The other mineralized zone Is i n the cirque f l o o r and i s exposed larg e l y by open p i t s which were excavated by Newmont Mining Corporation. This body shows no d e f i n i t e attitude, but i n some places, appears almost f l a t - l y i n g . It consists mostly of f i n e to medium-grained skarn which contains hedenbergite, g l l l e s p i t e , k eeleite, taramellite, and other s i l i c a t e s plus small amounts of sphalerite, chalcopyrite, and py r r h o t i t e . k Fetrographic Description of the Quartz Monzonite In hand specimens, the quartz monzonite i s leu c o c r a t i c , medium-grained phaneritic, homophanous, and very s l i g h t l y p o r p h y r i t i c . In t h i n section, plagioclase, orthoclase, quartz, b i o t i t e , c h l o r i t e , and accessory apatite are evident. The plagioclase Is almost a l l zoned, and oc-casion a l l y twinned (Carlsbad and Albit e twinning). The zoning i s normal and covers a rather wide range, varying from c a l c i c labrador Ite (An^) i n the cores to oligoclase ( An£Q) on the outside. Orthoclase i s present as large anhedral c r y s t a l s (f>mra.) of a s l i g h t l y porphyritic nature, and which contain many inclusions of small plagioclase cry s t a l s and b i o t i t e fragments. Both feldspars have been p a r t i a l l y s e r i c i t i z e d . Quartz occurs as anhedral grains i n t e r s t i t i a l to the feldspars, and contains inclusions of plagioclase and b i o t i t e . A small amount of b i o t i t e occurs as subhedral cr y s t a l s which have been s l i g h t l y c h l o r i t i z e d . Apatite, the only accessory mineral found, i s present as minute euhedral c r y s t a l s . Mode: Plagioclase - 30% Orthoclase - 30% Quartz - 30% B i o t i t e - 8% Chlorite - 2% Apatite - present. The wide range of zoning i n the plagioclase i s indi c a t i v e of a very rapid change i n temperature and/or pressure• 5 KEELEITE Keeleite (pronounced k e e l - i t e ) i s named i n memory of Joseph Keele, a former o f f i c e r of the Geological Survey of Canada who made a geological reconnaissance from Ross River Post to the MacKenzie River i n 1907-1908. Occurrence; Keeleite (Ba^Ca^e^-Pe,'Al^(SiO^)]^) i s found i n a contact metasomatic deposit adjacent to a porphyritic quartz monzonite stock. It occurs as a massive, c r y s t a l -l i n e constituent of skarns which have developed i n o r i g i n a l limestone bodies adjacent to the igneous contact. The mineral assemblage includes ke e l e i t e , b a r i t e , hedenbergite, quartz, andradite, taramellite ( (Ba,Ca,Na)lj. (Fe',Mg) Pe'2 T i ( S I ^ 0 l 2 ) (OH)^, g i l l e s p i t e (BaPeSii|0 1 0), sanbornite (BaSi20cj), chalcopyrite, witherite, double carbonate s a l t s of barium and calcium, and four other minerals which may be new species. Physical Properties; In hand specimen, keeleite i s massive, c r y s t a l -l i n e , and intimately mixed with i t s associated minerals and a l t e r a t i o n products. It possesses three poorly devel-oped cleavages which are usually evident only i n t h i n section. The mineral i s colorless to pale yellow, has a hardness of 6, a s p e c i f i c gravity of 3*5>1, and fuses at 3 to a weakly magnetic bead. It possesses a vitreous l u s t r e 6 and conchoidal fracture very si m i l a r to that of quartz. The a l t e r a t i o n products of keeleite include a fibrous blue pleochroic mineral, a s e r i c i t i c mineral, a pale yellow fibrous pleochroic mineral, a yellow i s o t r o p i c mineral, and a yellow-brown mineral. These minerals also r e s u l t from the a l t e r a t i o n of g l l l e s p i t e or sanbornite and are more f u l l y described i n the section on a l t e r a t i o n products. Specimens which were c o l l e c t e d from the surface are coated with a yellow, earthy material and a white crust of barium-calcium carbonate s a l t s and opal. Optical Properties: The indices of r e f r a c t i o n of keeleite were determined with immersion o i l s and the o p t i c a l orienta-t i o n by the universal stage method. The values given f o r the optic angle and cleavage angles were corrected using Federow's diagram. The o p t i c a l orientation i s represented i n Figure 1 and the o p t i c a l properties are as follows: Color - co l o r l e s s i n t h i n section. Form and Cleavage - subhedral to euhedral tabular c r y s t a l s with two p r i s -matic cleavages which make an angle of with each other, and one pinacoidal cleavage. A l l the cleav-ages are poorly developed. Indices of Refraction -n x = 1.61*3 - .003 n Y = 1.61*5 * .003 4 = 1.61*9 * .003 Birefringence - h z - n x = .006 7 E x t i n c t i o n - P a r a l l e l to elongation of c r y s t a l s . Orientation - length, f a s t or length slow Because of the tabular nature of the c r y s t a l s . Twinning - The twin plane i s p a r a l l e l to the elongation of the c r y s t a l . Optic Angle and Sign - the figure i s b i a x i a l p o s i t i v e with 2V = i| 7 ° . Dispersion - rhombic, very strong with r y v. Figure 1. Optic Orientation of Keeleite. Chemical Analysis and Calculation of Formula; Keeleite i s intimately mixed with i t s a l t e r a t i o n products and the minerals g i l l e s p i t e , quartz, taramellite, hederibergite, andradite, s u l f i d e minerals, and carbonates. I t was therefore impossible to f i n d any specimens pure enough for analysis. Consequently, i t was necessary to 8 resort to grinding, screening, magnetic separation, heavy' l i q u i d separation and f i n a l l y , hand-picking under the binocular microscope. The following procedure was found to be s a t i s f a c t o r y . Hand specimens which contained r e l a t i v e l y large amounts of keeleite were crushed to l / i * inch s i z e . The cleanest of these fragments were ground and screened to obtain a +80 and -60 mesh f r a c t i o n . This f r a c t i o n was then passed through a Pranz Isodynamic Separator set at a 25 degree t i l t and a 15 degree cant. An amperage of 0.i|25 removed most of the g l l l e s p i t e , the blue a l t e r a t i o n product, and the s u l f i d e s while the keeleite and mixed grains remained behind i n the non-magnetic f r a c t i o n . The mixed grains were removed by hand-picking under the bino-cular microscope. A very small amount of quartz was re-moved by gravity separation i n broraoform. The re s u l t s of a spectrographic analysis made on a portion of the sample are presented i n Table 1. Major Intermediate Minor Trace Ba Ca Mg B S i A l Zn Be Pe Mn T i Na Zn Sr Table 1. Spectrographic Analysis of Keeleite. 9 A sample of keeleite weighing about 0 . 8 grams was submitted for chemical analysis to H.V* Sharpies, G»S. Eldridge & Go., Vancouver, B.C. The r e s u l t s appear i n Table 2 with calculations f o r a chemical formula. Mol. Th.$ Oxide % Corr.$ Mol. Wt. Mol.P. Ratio BaO 31*. 16 31*. 3 3 1 5 3 . 3 6 . 2 2 3 6 . 0 2 1 3 ! * . 0 7 CaO 6 . 2 5 6 . 2 8 5 6 . 0 8 . 1 1 2 3 . 0 2 1 * 6 . 2 3 S i 0 2 1 * 0 . 5 0 1*0.70 60.06 . 6 6 7 1 8 . 0 0 9 1*0.03 A 1 2 ° 3 3 . 5 3 3 . 5 5 101 .91* .031*8 0.91*9 3 . 7 7 PeO * 1 1 . 9 7 1 2 . 0 3 7 1 . 5 8 . 1 6 6 5 ) MnO 0 . 5 7 0 . 5 7 7 0 . 9 0 .0080 1 5 . 9 0 . 0 3 6 5 76 .01*8 MgO 1.1*6 1.1+8 1 * 0 . 3 2 ZnO 1 . 0 5 1 . 0 6 8 1 . 3 8 . 0 1 3 0 SOr> t r . -j 99 .1*9 1 0 0 . 0 0 -xTotal i r o n calculated to PeO Table 2 . Chemical Analysis and Calcula-t i o n of Formula:, f o r Keeleite. In c a l c u l a t i n g the formula, the following pro-cedure was used. Neglecting the trace of sulfur, the metal oxide percentages were corrected to bring the t o t a l to 1 0 0 $ . and th e i r molecular proportions calculated by div i d i n g the corrected percentages by t h e i r appropriate molecular weights. It was then necessary to decide which elements were substituting f o r others and which were es s e n t i a l 10 to the c r y s t a l structure. Since barium and s i l i c o n oxides are the major components, they were considered e s s e n t i a l ions. The alumina could have been added to the s i l i c a , as aluminum commonly replaces s i l i c o n i n many s i l i c a t e struc-tures. It was, however, retained as an e s s e n t i a l con-stituent because there are not s u f f i c i e n t monovalent cations present to compensate f o r the deficiency i n p o s i t i v e charge which would r e s u l t , and also because the near perfect b a l -ance of Si02:BaO = 3 : 1 would be upset. The oxides of ferrous iron, manganese, magnesium, and zinc when added together gave a molecular proportion of 0 .221* which i s equivalent to that of barium oxide and one-third that of s i l i c a . High valence manganese might substitute f o r aluminum, but again the balance of molecular proportions would be destroyed i f MnO were calculated i n with alumina. Calcium oxide i s also considered an essential constituent. Although the i o n i c radius of calcium ( 0 . 9 9 ) i s s u f f i c i e n t l y small to enable i t to substitute f o r barium (1 .31+), the size difference i s greater than the \$% l i m i t generally accepted f o r ion substitution. Furthermore, the r a t i o CaOrBaO = 1:2 suggests that calcium occupies an essential p o s i t i o n i n the l a t t i c e . Calcium might also substitute i n part f o r ferrous i r o n (O . 7 I 4 ) , but t h i s p o s s i b i l i t y i s re-jected f o r the same reasons stated above. The smallest near whole numbers are obtained when the molecular proportions are m u l t i p l i e d by a factor of 2 7 . The derived formula i s thus 6BaO„3Ca0.6FeO.Al 2 03. 18S102, or i n the more conventional manner - Ba^Ca^e^A^ ( S i 0 3 ) l 8 . 11 Although m i c r o l i t e s of keeleite were obtained from a mixture of th i s composition, the formula, Ba^Ca^Fe^Al^SiO^JlS i s not the correct formula. The reasons for this statement w i l l be discussed f u l l y i n the section on synthesis. Synthesis of Keeleite: In order to test the p o s s i b i l i t y of synthesizing keeleite by dire c t fusion of the constituent oxides, the natural mineral was fused to a glass. An X-ray powder photograph of the fused material showed that the structure had been completely destroyed. The mineral was then placed i n an evacuated s i l i c a tube and annealed at 850°C for 21* hours. The resultant product was not completely c r y s t a l -l i z e d , probably owing to the r e l a t i v e l y short annealing period, but m i c r o l i t e s i n rad i a t i n g groups were scattered throughout the glass. An X-ray powder photograph of this product proved the c r y s t a l s to be k e e l e i t e . Thus, no hydrous or gaseous constituents are present. The main d i f f i c u l t i e s encountered i n synthesizing keeleite were the i n s t a b i l i t y of i t s constituent oxides, the problem of a suitable container, and the necessity of maintaining a neutral atmosphere during fusion and c r y s t a l -l i z a t i o n to prevent the oxidation of ferrous i r o n . Bowen and Schairer-^ experienced d i f f i c u l t y i n c o n t r o l l i n g and defining the state of oxidation of i r o n i n the i r work on 12 the system PeO - S i 0 2 . They found that even i n vacuums to O.GOOI4 mm. Hg, the ferrous i r o n oxidized. A solution was obtained by using Iron crucibles i n a nitrogen atmo-sphere. The i r o n crucibles served to keep the i r o n i n the ferrous state, but small amounts of i r o n were added to the melt by reaction with the c r u c i b l e . Schairer and Yagi^ successfully c r y s t a l l i z e d s i l i c a t e s i n the system PeO-Al203~Si02 by folding pieces of the glass i n i r o n f o i l , sealing them i n evacuated s i l i c a tubes, and heating at temperatures below the solidus for several days or weeks. Several charges of keeleite composition were fused i n i r o n c r u c i b l e s , but without success. ^ Barium oxide i s available as chemically pure material, but i s somewhat hygroscopic and consequently does not keep w e l l . Ferrous oxide i s very unstable and oxidizes ra p i d l y to a mixed material on standing. The product used i n the synthesis of keeleite was obtained by heating ferrous oxalate (FeC^O^.SB^O) under vacuum to expel the carbon dioxide and water. The return to atmospheric pressure must be gradual to prevent combustion of the unstable product. It appeared to be homogeneous and composed e n t i r e l y of black ferrous oxide. Since calcium oxide Is very hygro-scopic, calcium was added i n the form of CaSiC^ which was made by fusing calcium carbonate and s i l i c a . Alumina and s i l i c a were e a s i l y obtained i n pure form and offered no problem. 13 The containers with which the writer was most successful were V i t r e o s i l tubes which were sealed under vacuum to obtain an atmosphere as close to neutral as pos-s i b l e . The oxides were weighed out i n appropriate amounts to make a 10 gram charge. Only 2 grams were r e -quired f o r the fusion, but greater accuracy i s obtained by weighing the larger amounts. The oxides were ground i n a mortar and thoroughly mixedr The mixture was then placed i n a s i l i c a tube and heated gently under vacuum to expel any moisture which may have been picked up during grinding and mixing. The tube and contents were gradually heated to a red heat, then sealed by melting i n an oxygen-gas flame and twisting off the end of the tube. The charge was then fused at 1350°C i n a "Glow-Bar" furnace and kept i n the fused state f o r one hour. Some corrosion took place on the inside wall of the tube, but apparently a small amount of excess s i l i c a i s not detrimental to the formation of k e e l e i t e . The s t a b i l i t y of keeleite i n excess s i l i c a i s suggested by the occurrence together of keeleite and quartz i n nature. The tube was then opened. A piece of the charge, now a s i l i c a t e glass, was chosen from the center of the melt and placed i n another s i l i c a tube, which was evacuated and heated at 8£0°C for 1*8 hours. The purpose of the change was to allow most of the surface area of the s i l i c a t e glass to be out of contact with the tube i n order Ik to prevent reaction during the long period of annealing. The product obtained was apparently e n t i r e l y c r y s t a l l i n e and composed of fine prismatic c r y s t a l s . An X-ray powder photograph of this material proved i t to be keeleite with a small amount of contaminating quartz. A comparison of X-ray data for synthetic keeleite, natural k e e l i t e and and fused, annealed natural keeleite i s presented i n Table 3» Optical determinations were not made on the synthetic product because of i t s extremely f i n e grain, and a sp e c i f i c gravity determination was not made because of the possible presence of undetected glass or free s i l i c a . Plate I. Laths of keeleite (crossed n i c o l s ) . X7£ 15 Table 3 . X-ray Bata f o r Natural Keeleite, Fused-Annealed Keeleite, and Synthetic Keeleite. Natural Keeleite Fused-Annealed Synthetic Keeleite Natural Keeleite (UBC X2528) (UBC X2701*) (UBC X29i*7) I d I d I d 6.51 - — 1 2 6.51 k 5 . 9 9 1 5 . 9 9 3 5 . 9 5 - - - 3 1+.65 5 • 1**21 2 14.25 3 1*.23 q - - - - 5 i*.08 3 3 . 8 8 1 3 . 9 0 6 3 . 8 3 - - 2 3.60 - — 10 3.1*5 10 3.1*5 10 3.1*8 - - - - 8 3 . 3 0 q 10 3.16 10 3.16 7 3.16 1 3.00 - - 1 3 . 0 3 1 2.86 i 2.85 1 2 .92 - - - - 1 2.80 7 2.62 I s 2 . 6 5 8 2.61 1 2.1*6 2.147 1 2.I46 2 2 . 3 6 3 2 . 3 7 2 2 . 3 6 2 2 . 3 0 - - 2 . 3 1 2 2.21* 1 2.21* 1 2.21* l 2 2.18 - - 1 2.19 2 2.11 - — 1 2.12 2 2 . 0 7 - - 1 2.08 2 2.02 - 2 2.02 3 1.953 1 1 . 9 6 5 3 1.91*9 1 1.899 - - - -2 1.831* 2 1.838 - -- - - - k 1.8l7q 3 1.778 1 1.778 2 1.781 2 I . 7 0 7 - - 1 2 1 . 7 0 7 2 I.678 - - 1 I.678 1.6l6b 2 1.610 1 2 1.631* - - - 2 1.588 3 1 . 5 3 5 1 S i.5l*o 3 1.537 X 2 1 . 5 0 6 - - 3 1.512 5 1 .1*80 2 1.1*80 1* 1.1*78 3 1.1*33 *•" mm 2 1.1*33 q - possible quartz l i n e s . Plate II X-ray Powder Photographs of Keeleite. Top - Keeleite, Y.T. - UBC X 2 5 2 9 Cu/NiO. Center - Pused-Annealed Keeleite, Y.T.-UBC X2701* Cu/NlO. Bottom - Synthetic Keeleite - UBC X2968 Cu/NiO. The data above show that almost every l i n e on the X-ray f i l m for natural keeleite i s also present f o r the synthetic material. The extra l i n e s marked (q) are attributed to the presence of a small amount of quartz. The remaining discrepancies i n spacing and i n t e n s i t i e s are believed due to preferred orientation of mic r o l l t e s i n the synthetic material. Levin and U g r i n i c ^ were con-fronted by a si m i l a r problem i n t h e i r work on the system Ba0-B203-Si0 2. They found that X-ray d i f f r a c t i o n data 17 for t h e i r s i l i c a t e s varied both i n the l i n e s present or absent, and i n t h e i r r e l a t i v e i n t e n s i t i e s . They a t t r i -buted the discrepancies to preferred orientation. I t was stated previously that, although crystals were obtained from a melt of composition Ba^Ca^Fe^AlgCSIO^JlS, that t h i s formula was incorrect. In the analysis given i n Table 2, only t o t a l i r o n was determined and that calculated to FeO. However, a l a t e r sample submitted to the same analyst for the determination of ferrous and f e r r i c i r o n showed that 8.32$ FeO and 4.16$ Fe203 are present i n the mineral k e e l e i t e . A new chemical formula was calculated on the basis of these r e s u l t s as shown i n Table 1*. Oxide BaO CaO S102 AI2O3 FepOo FeO J MnO MgO ZnO 314.16 6.25 ij0.50 3.53 I|.16 8.32 0.57 1.1+6 1.05 t r . 100.00 Mol.Wt. 153.36 56.08 60.06 101.91+ 159.16 71.58 70.90 1+0.32 81.38 Mol. Prop, .223 .111 .671+ .035 .026 .116 .008 .036 .013 Mol.Ratio 1+.011+ 1.998 12.132 } 1.098 3.111+ Table 1+. Revised Calculation of Keeleite Formula. The c a l c u l a t i o n of the formula was done i n the same manner as shown i n Table 2, except that Fe203 was added to AI2O3. A factor of 18 was used to obtain the molecular r a t i o s . The r e s u l t i n g formula i s !+Ba0.2Ca0. 18 3PeO. (PeAl) 20 3.12Si0 2 or Ba.Ca Pe'»(P8f,Al) (SiO )12. The question of how keeleite c r y s t a l s could be obtained from the o r i g i n a l formula may be answered r e a d i l y by comparing the percentages of oxides contained In the two formulas as shown In Table 5* Oxide Ba 6Ca3Pe 6Al 2(.SI0 3 ) l 8 Ba^C &2Fe^ (Pe', A l j 2 ( S i 0 3 ) 12 BaO 34-07 % 33.70 CaO 6.23 6.16 PeO 15.9 11.80 AloOo 8.7*1 3.77 Fe 20-j SI0 2 1*0.03 39.59 Table 5« Comparison of Oxide Percentages i n the Two Calculated Formulas. The percentages of the oxides of barium, calcium and s i l i c o n are close enough i n the two formulas to allow c r y s t a l l i z a t i o n of keeleite from ei t h e r . The discrepancy between FeO and (Al,Fe ) 2 0 2 i n the two formulas indicates that oxidation of the ferrous i r o n must c e r t a i n l y have taken place to allow the development of keeleite c r y s t a l s i n the melt. Any oxides i n excess over those required f o r the formation of the compound may have combined with s i l i c a and remained i n the glassy state. In the course of syntheses of keeleite, one additional compound was obtained from the composition 5Ba0.2FeO.Pe 203.10Si0 2. The c r y s t a l s obtained were dark 19 brown, platy, and dis t r i b u t e d i n coarse r a d i a l groups. X-ray powder d i f f r a c t i o n data for this compound i s given i n Table 6. It does not resemble any known mineral or previously reported s i l i c a t e compound. UBC X 2 8 5 2 Pe/MnO I d I d 10 3.98 i a 2 . 1 2 9 3.73 T 5 1.989 7 3.28 1 1.961* 2 3.08 2 1.870 6 2.98 k 1.803 3 2.77 1 1.706 1 2.67 i 2 1.61*0 2.28 1 1.595 2 2 . 2 2 k 1.1*95 1 2.16 Table 6. X-ray Data for Ba^Pe^e^SiO^JlO Plate III X-ray Powder Photograph of the Compound 5Ba0.2PeO. Pe 20o.l0Si0p. UBC X 2 8 5 8 20 A l t e r a t i o n Products of Keeleite: The a l t e r a t i o n products of keeleite include several minerals which are of hydrothermal o r i g i n and several which have been i d e n t i f i e d as carbonates of barium and c a l -cium. The hydrothermal replacement minerals have been designated by l e t t e r s . The most abundant a l t e r a t i o n product i s Mineral C, a f i n e l y fibrous blue mineral which i s s t r i k i n g l y pleochroic i n b r i l l i a n t blues and pale yellows. This mineral also appears as an a l t e r a t i o n of g i l l e s p i t e and was f i r s t r e-ported by Schaller^ i n 1 9 2 9 i n association with g i l l e s p i t e from Dry Delta, Alaska. It i s also found In the g i l l e s p i t e from Mariposa County, C a l i f o r n i a . This occurrence was des-cribed by Pabst 7 i n 19U3-Plate IV Mineral C (blue) which has re-placed g i l l e s p i t e (pink) and keeleite (white). X 7 £ . 21 Its o p t i c a l properties are as follows. Color - blue, strongly pleochroic with x - c o l o r l e s s to pale yellow, y - pale blue, z - dark blue. Form - Fibrous aggregates, intimately mixed with a s e r i c i t i c mineral. Cleavage - one cleavage p a r a l l e l to the length of the c r y s t a l , and one poorly developed cleavage or parting perpendicular to the f i r s t . Indices of Refraction -= 1.659 ± .005 ny = 1.70i* ± .005 nz = 1.70i| ± .005 Birefringence - n z - n x = .045» E x t i n c t i o n - p a r a l l e l . Orientation - the f a s t ray i s p a r a l l e l Eo the length of the c r y s t a l . Twinning - no twinning observed. Optic Angle and Sign - the figure i s b i a x i a l negative with 2V X~ 4 5 ° * Dispersion - strong, with r < v. A possible o p t i c a l o rientation f o r Mineral C Is presented i n Figure 2. 22 Figure 2. Possible Optic Orientation of Mineral C.,. Several X-ray powder photographs were taken on picked grains, and although the mineral i s f i n e l y divided and intimately mixed with keeleite and g i l l e s p i t e , thus making i t d i f f i c u l t to obtain pure material, the same X-ray pattern was obtained on d i f f e r e n t material. X-ray data i s presented i n Table 7. Mineral C - UBC X261+6 3 1 0 k I s I 2 k k u 5 k 3.62 . 3 . 3 5 3.21 3 . 0 I | 2.81 2 . 5 9 2.1+7 2.26 2.11 2.04 1.888 1.821 3 I 2 i 2 2 1 i 2 1 1 . 6 8 9 1.661+ 1 . 6 0 5 1 .51+0 1 . 5 0 8 1.1+82 1.1+17 1 . 3 7 7 1 . 3 1 8 1 . 2 9 1 1 . 2 5 8 Table 7 . X-ray Data f o r Mineral C Plate V X-ray Powder Photograph of Mineral C, Yukon Territory, UBC X26i|6 Cu/NiO. A closed tube test of Mineral C yielded a small amount of water. The blue color of the mineral disappeared and a yellow-brown, granular residue remained i n the tube. A spectrographic analysis of Mineral C showed the presence of minor boron and li t h i u m i n addition to those elements detected i n keeleite and g l l l e s p i t e . The resu l t s are tabulated i n Table 8. Major Minor Trace SI B Mn Pe L i Mg Ba Al Ca Cu Zn Table 8. Spectrographic Analysis of Mineral C. Mineral C, as stated previously, replaces both keeleite and g i l l e s p i t e . In g i l l e s p i t e , i t follows the prominent basal cleavage, but i n keeleite, the replacement has no preferred d i r e c t i o n . The a l t e r a t i o n product i s commonly a heterogeneous product consisting of Mineral C and f i n e l y fibrous aggregates of a s e r i c i t i c - l o o k i n g material. Another a l t e r a t i o n product of keeleite, which has been designated Mineral D, i s a b r i l l i a n t yellow, i s o -tropic mineral or mineraloid which also replaces g i l l e s p i t e . It may be the mineral mentioned by Rogers i n 1 9 3 2 as occurring with sanbornite from Mariposa County, C a l i f o r n i a . This mineral occurs only i n very small amounts and con-sequently, s u f f i c i e n t material for X-ray or spectrographic analyses was unavailable. Another yellow mineral, which occurs as fibrous aggregates cutting through k e e l e i t e , has a s l i g h t birefringence and may be s t i l l another d i s -t i n c t species. This mineral Is designated Mineral P and i s shown i n Plate VI. Plate VI Mineral P(yellow) cutting keeleite (white). The dark brown mineral i s sphalerite. X 7 5 -25 A fourth nineral, which has been designated Mineral E, i s r e l a t i v e l y common as scattered anhedral grains throughout the mineral, sanbornite. Plate VII Mineral E (yellow) which has formed by a l t e r a t i o n of san-bornite (white). X 7 5 It also occurs i n small amounts i n minute cracks traversing keeleite and i t s associated minerals. I t i s s t r i k i n g l y pleochroic i n b r i l l i a n t orange and yellow. A spectrographic analysis showed the presence of major quantities of manganese and titanium i n addition to those elements contained i n keeleite, g l l l e s p i t e , and sanbornite. The results of the spectrographic analysis are presented i n Table 9. Major Minor Trace Ba Ca Mg S i Sn Pe A l Mn T i Table 9. Spectrographic Analysis of Mineral E. 26 A closed tube test of Mineral E yielded detect-able amounts of water. No color change took place as i n the blue mineral. X-ray powder photographs of the mineral occurring with sanbornite and of that occurring i n cracks traversing keeleite gave i d e n t i c a l patters. The re s u l t s are tabulated i n Table 10 . Mineral E - UBC X25l*8 Cu/NiO I d I d 10 2 2.16 2 3.75 2 2.09 k 3 . 5 5 2 2.0i* 2 3.31 I 1.965 8 2.91 2 1.910 2 2.83 2 1.821* 2 2.74 2 1.71*9 3 2.60 3 1.650 1 2.1*9 3 1.1*27 1 2.21 Table 10 . X-ray Data f o r Mineral E. 27 • Plate VIII X-ray Powder Photographs of Mineral E. (Top) Mineral E associated with sanbornite, Yukon Territory, UBC X2548 Cu/NiO (Bottom) Mineral E associated with keeleite, Yukon Terr i t o r y , UBC X2976 Cu/NiO In addition to the replacement minerals des-cribed i n the foregoing section, several unusual supergene minerals are present on the specimens which were exposed to weathering. The f i r s t of these commonly occurs as a very fine-grained ocherous powder i n t h i n coatings on keeleite. Where keeleite i s mixed with appreciable quan-t i t i e s of g l l l e s p i t e , i t gives an unusual red and yellow mottled appearance to the rocks. An X-ray powder photo-graph of this material showed only a few very weak li n e s 28 i n d i c a t i n g a p o o r l y c r y s t a l l i n e m a t e r i a l . The s u r f a c e s of many of the specimens are coated w i t h l a y e r s of b o t r y o i d a l w h i t e m a t e r i a l , most of which was determined as w i t h e r i t e and o p a l . Some of i t i s a p p a r e n t l y a more complex m i x t u r e of b a r i u m - c a l c i u m c a r -bonates . A comparison of an X - r a y powder photograph of t h i s m a t e r i a l w i t h those of a l s t o n i t e , the orthorhombic b a r i u m - c a l c i u m carbonate and o f b a r y t o c a l c i t e , i t s mono-c l i n i c dimorph, showed t h a t the supergene product was n e i t h e r of these m i n e r a l s . However, a comparison w i t h 9 X - r a y d i f f r a c t i o n da ta of s y n t h e t i c a l s t o n i t e and b a r y t o c a l c i t e " ^ proved almost c e r t a i n l y tha t the supergene product i s a m i x t u r e of b o t h these carbonate s a l t s . A comparison of X - r a y d i f f r a c t i o n data f o r the whi te s u p e r -gene c o a t i n g , s y n t h e t i c b a r y t o c a l c i t e , and s y n t h e t i c a l s t o n i t e i s given i n Table 11. \ 29 White Coating UBC X 2 9 7 3 Synthetic Baryto-c a l c i t e . A.S.T.M, Index Car I - O 7 7 O Synthetic Alston-i t e . A.S.T.M. Index Card 3 - 0 3 2 2 1 7 3 1 0 6 6 6 5 3 1 1 1*.1*8 3 .99 3 .69 3.11+ 2.56 2.15 1.991+ 1 .933 1.61+2 1 . 5 6 3 1.1*75 1 . 3 3 7 1 . 3 1 8 50 100 1*0 30 30 25 13 13 3 5 3 k 3.96 3.16 2.51* 2.11+ 2.00 1.91+ 1.61* 1.57 1.51 1.1*7 1 .39 1.31* 1 . 3 2 1 .29 1 .28 7 25 1 0 0 6 2 3 1 1 0 k 3 7 1 7 3 1 2 1 2 7 5 2 5 7 2 5 l * . 5 i 3 .93 3.68 3.12 2 .60 2.51* 2.27 2.13 2 .00 1.92 1.81+ 1.61* 1 .56 1.1*9 1.1*6 1 .36 1 .33 1.27 1.22 Table 1 1 . Comparison of X-ray d i f f r a c t i o n data of White Coating, Synthetic Barytocalcite and Synthetic A l s t o n i t e . 30 A. B, D. Plate IX X-ray Powder Photographs of Barium-Calcium Carbonates. A. Witherite, Yukon Te r r i t o r y - UBC X 2 ^ 9 2 Cu/NiO. B. Mixed Carbonates, Yukon Ter r i t o r y - UBC X 2 9 7 3 Cu/NiO. C. Barytocalcite, Cumberland - UBC X 2 9 8 2 Cu/NiO. D. Alst o n i t e , Cumberland - UBC X 2 9 8 8 , Cu/NiO. A comparison of X-ray patterns B, C, and D i n Plate IX shows that the supergene mixed carbonates (B) bear no s i m i l a r i t y to either barytocalcite (C) or als t o n i t e (D). However, the X-ray data for synthetic a l s t o n i t e and barytocalcite are s t r i k i n g l y close to that of the supergene coatings. 31 This anomoly is explained later in the section on paragenesis. Associated Minerals: The minerals which occur in association with keeleite include the minerals which are found usually In contact limestones such as garnet, quartz, and hedenbergite. The latter mineral occurs commonly in such mineral deposits with chalcopyrite. It is present in the keeleite assemb-lage with pyrrhotite and marcasite. Occasional very small grains of magnetite were noted In some thin sections. The remaining minerals found in the keeleite assemblage are very rare barium silicate minerals, most of which are known only in one or two localities, and many of which are pro-bably new species. Those minerals which occur as altera-tion products have been described in the section on that subject. Three additional minerals which occur with keeleite are taramellite ( B a ^ F e F ^ T i C S ^ ^ C O H ) ^ gillespite (BaPeSi^010), and sanbornite (BaSi20£). Taramellite occurs as small equant grains or relict crystals disseminated throughout keeleite, quartz, g i l -lespite, and Mineral C. A new formula which is proposed for the mineral taramellite and which is based on a chemical analysis published by Mazzi 1 1 in 1957. Plate X R e l i c t c r y s t a l s of taramellite i n quartz and keeleite X7£. Taramellite (yellow) i n g l l l e s p i t e (Pink) X 7 5 . 3 3 The following o p t i c a l properties were deter-mined i n t h i n sections or on i n d i v i d u a l grains i n immersion o i l s : Color -Pleochroic yellow to deep brown, x - l i g h t yellow, y - l i g h t yellow, z - dark brown. Form and Cleavage -short prismatic grains with square cross-sections"; one poor cleavage p a r a l l e l to the length of the c r y s t a l . Indices of Refraction - n ~ I.76 Birefringence -not determined, strong pleochroism int e r f e r e d . E x t i n c t i o n - p a r a l l e l . Twinning - no twinning observed. Optic Angle and Sign -the f i g u r e i s b i a x i a l p o s i t i v e with 2V = 3 5 ° . Dispersion - strong, with r > v . These properties compare c l o s e l y with those of taramellite from the type l o c a l i t y , Candoglia, I t a l y . A spectrographic analysis of taramellite from the Yukon l o c a l i t y gave the re s u l t s which are presented i n Table 12. Major Minor Trace Ba Mg Mn Fe Ca Sn T i B Cu Si Ag Pb Zn Ha A l Table 12. Spectrographic Analysis of Taramellite, (Ross River, Y.T.) 31*. Taramellite also occurs i n sanbornite (BaSi20^) specimens from Mariposa County, C a l i f o r n i a . In 1932, Rogers^ mentioned an unknown brown pleochrolc mineral which occurred i n that assemblage. In addition, Schaller , i n 1929, described a pleochrolc yellow to deep brown mineral occurring i n g i l l e s p i t e specimens from Dry Delta, Alaska. Specimens from the l o c a l i t y were examined by the author, and i t i s believed that this mineral i s also taramellite. The X-ray d i f f r a c t i o n data for material from Mariposa and Yukon i s compared to that for taramellite from the type l o c a l i t y i n Table 1 3 . Candoglia, I t a l y Ross River, Y.T. UBC X 2 i * 7 9 Pe/MnO Mariposa C t y , C a l i f . UBC X 2 6 8 9 Pe/MnO UBC X25i|6 Pe/MnO I d I d I d 1 7 . 0 0 1 6 . 9 2 _ — 2 6 . 1 2 1 6 . 1 9 1 2 6 . 0 9 8 3 . 8 6 8 3 . 9 0 7 3 .88 1 f 2 3 . 6 9 1 3 . 6 9 2 3 . 7 1 3.1*8 - - 1 3 . 5 0 5 3 .33 1* 3 .33 6 3.31* 2 3 . 1 6 1 3 .18 1 3 . 1 9 1 0 3 . 0 2 1 0 3 . 0 3 1 0 3.01* 6 2 . 7 9 3 2 . 8 0 5 2 . 8 1 6 2 . 5 9 5 2 . 6 1 6 2 . 6 0 3 2.1^8 1 2.1*9 3 2 . 5 0 3 2.1*0 1 2.1*0 3 . 2.1*1 2 2 . 3 1 1 2 . 3 2 2 2 . 3 3 ii 2 . 1 8 1* 2 . 1 8 1* 2 . 1 8 2 2 . 0 6 1 2 . 0 8 2 2 . 0 8 2 1 . 9 8 9 1 1 . 9 9 8 1 1 . 9 9 8 1 I . 8 7 8 1 1 . 8 8 1 1 1 . 8 8 6 - • - .. - 3 1 . 8 1 5 ? 3 1 . 7 9 8 2 1.791* 3 1 . 7 9 8 3 1.71*1* 1 I . 7 5 2 2 1 . 7 5 3 1 2 1 . 6 9 9 - - 1 2 1 . 7 0 8 2 1 . 6 3 8 1 1.61*2 2 1 . 6 5 8 1* 1 . 5 2 1 * 3 1 . 5 3 3 1* 1 . 5 3 8 plus several more diffuse l i n e s Table 1 3 . X-ray data for Taramellite. 35 Plate XI X-ray Powder Photographs of Taramellite. (Top) Taramellite, Candoglia, UBC X251+6 Fe/MnO. (Center) Taramellite, C a l i f o r n i a , UBC X2689 Fe/Mno. (Bottom) Taramellite, Y.T., UBC X 2 5 7 0 Fe/MnO. 1 1 In 1957, Florenzo Mazzi calculated the formula, (Ba,Ca, Ua) i |(Fe,Mg)Fe 2Ti(Si^C L 2) (OH)^ for the mineral tara-m e l l i t e from a chemical analysis on material dried at 1 1 0°C. A r e c a l c u l a t i o n by the author based on the same analysis gave the formula Ba^FeFe 2Ti(Si03)g.(OH)^. This formula f i t s the analysis better, and i s suggested as the correct one. The method of c a l c u l a t i o n i s presented In Table 11+. 36 Oxide % Mol.Wt. Mol.P. Mol. Ratio S i 0 2 33.9 60.06 .565 7.91 T i o | 7-7 79.9 .096 1.34 Pe20o 12.2 159.7 .076 1.06 PeO 3.7 71.58 .052 | 1.01 MgO 0.8 i+0.32 .020 BaO 37.5 153.36 .245 CaO 1.1 56.08 .020 > 3.90 Ng20 0.8 62.0 .013 K 20 0.1 9i|.2 .001 1.65 H 20 2.1 18.0 .117 Table 14« Chemical Analysis of Tara-m e l l i t e and Calcu l a t i o n of i t s Formula. A factor of 14 was used to obtain the molecular r a t i o s . The formula which resulted from the above c a l -culations i s 4BaO.FeO.Fe2O3.TiO2.8SiO2.2H2O or i n the more conventional manner, Ba^FeFe^TIfSIO^^OH^. The mineral taramellite i s therefore classed as an i n o s i l i c a t e . G l l l e s p i t e (BaFeSih.O^Q) occurs as c r y s t a l l i n e masses i n a skarn consisting of hedenbergite, andradite, quartz, keeleite, and l e s s e r amounts of the other minerals described under other sections. G l l l e s p i t e i s a deep rose red color, has a prominent micaceous cleavage, a pearly l u s t r e , a hardness of 3, and a s p e c i f i c gravity of 3«33» Its a l t e r a t i o n products are the same minerals which occur with k e e l e i t e . 37 Plate XII G l l l e s p i t e (pink), keeleite (white), and taramellite (brown). X75 The o p t i c a l properties of g l l l e s p i t e are as follows:-Color - strongly pleochroic 0 = pale pink to colorless E = deep rose red. Form and Cleavage - anhedral grains with a perfect basal cleavage. Indices of Refraction - n ~ 1 . 6 2 . Birefringence - very weak. Ext i n c t i o n - p a r a l l e l . Twinning - no twinning observed. Optic Angle and Sign - the figure i s u n i a x i a l negative. These properties compare clos e l y with those obtained for g l l l e s p i t e from the two l o c a l i t i e s , Dry Delta, Alaska and Mariposa County, C a l i f o r n i a . The mineral was f i r s t discovered by W.T. Schaller (1929)^ i n a single specimen from a g l a c i a l moraine at the head of Dry Delta, Alaska Range, Alaska. The mineral assemblage i n the Alaska specimen i s very s i m i l a r to that i n the 3 8 Ross River specimens except that keeleite i s absent i n the former. The only other previously reported l o c a l i t y for g l l l e s p i t e i s near Incline, Mariposa County, C a l i f . No keeleite has been reported from that l o c a l i t y , but the remainder of the assemblage i s almost i d e n t i c a l to that of the Ross River specimens. Table 15, which follows, presents a comparison of X-ray data of specimens from C a l i f o r n i a and Yukon T e r r i t o r y . Ross River, Y.T. UBC X2188 Pe/MnO Mariposa Cty., C a l i f , UBC X2187 Pe/MnO 10 8 k 2 8 8 2 3 1 ? ¥ s 1 £ 2 1 2 3 7-89 10 4.42 8 3.9-9 3 3.55 2 3 . 4 0 8 3 .19 7 - 1 2.71* 2 2 . 6 6 3 2.52 1 2 2.1*0 5 2 . 2 9 2 2.22 2.05 -1.998 1 1.91*0 1 1.875 2 1.771 I 1.531* S 2 1.1*78 3 7 . 9 5 1* .03 3 . 5 5 3.1*0 3 . 2 0 3 . 1 0 2 . 7 5 2 . 6 7 2 . 5 2 2 . 3 9 2 . 2 9 2 . 0 0 1.937 1*881 1.771* 1.656 1.51*3 1.1*79 Table 15. X-ray Data for G l l l e s p i t e . 39 A spectrographic analysis of g i l l e s p i t e from the Yukon occurrence i s presented i n Table 16. Major Minor Trace Ba A l Mg Pe B S i Ca Mn Cu Zn T i Na Table 16. Spectrographic Analysis of G i l l e s p i t e . Sanbornite (BaSi 20^) occurs as fine-grained c r y s t a l s (0 .5 to 2.0 mm.) associated with Mineral E, quartz, hedenbergite, and witherite. It was not found with ke e l e i t e , but occurred i n an outcropping lense' about 100 feet away from the igneous contact. Sanbornite was recognized i n t h i n section by Its c h a r a c t e r i s t i c o p t i c a l properties which are as follows:-Color - colorless i n thi n section. Form and Cleavage - anhedral grains with a perfect basal cleavage. Indices of Refraction -n x = 1.60 Z .005 n y = 1.62 ± ,005 nz = 1.62 + .005 Birefringence - n 2 - n x = .020. E x t i n c t i o n - i n c l i n e d extinction, small angle. Orientation - the fast ray i s p a r a l l e l to the cleavage. Twinning - no twinning observed. 1*0 Optic Angle and Sign - the figure i s b i a x i a l negative with 2V = 6£ . Dispersion - not observed. A spectrographic analysis of sanbornite from the Yukon T e r r i t o r y i s presented i n Table 17. Major Minor Trace Ba Na Fe S i Al Cu Ca Mn Mg Table 17» Spectrographic Analysis of Sanbornite. Sanbornite was f i r s t described by Rogers (1932) from specimens found i n Mariposa County, C a l i f o r n i a , and the c r y s t a l structure was determined by Douglass (195>8) using specimens from the same l o c a l i t y . X-ray powder data on specimens from Yukon T e r r i t o r y i s compared with that obtained by Douglass on Mariposa sanbornite i n Table 18 . 8 12 Table 18. X-ray Data f o r Sanbornite. Ross River, Y.T. Mariposa C t y . , C a l i f . UBC X2£57 Cu/NiO R.M. Douglass I d 1 d 1* 6.81 30 6.79 3 5.01| 30 5 .08 8 3.97 100 3.97 - - 10 3.82 - - 50 3.1*22 8 3.38 70 3.31*2 1 3.21 20 3.226 10 3.09 75 3.095 - - 5 2.980 - - 5 2.888 7 2.72 55 2.720 2 2.57 15 2.571* — — 5 2.5141 - - .5 2.391* — — .5 2.327 2 2.30 15 2.317 — — 5 2.281 - - 10 2.236 3 2.23 30 2.226 — — 15 2.193 5 2.15 25 2.162 - l*o 2.130 — — 10 2.109 - - 5 2.038 1* 2.02 15 2.025 -- 10 1.990 2 1.911+ 10 1.921 - - 10' 1.903 2 1.81*8 20 1.850 - - 5 1.815 3 1.791* 20 1.793 — — 5 1.736 - 5 1.709 1* 1.689 15 1.690 Plus several more l i n e s . 42 Plate XIII X-ray Powder Photographs of Sanbornite. (Top) Sanbornite, C a l i f o r n i a , UBC X 2 5 5 6 Cu/NiO. (Bottom) Sanbornite, Y.T., UBC X 2 5 5 7 Cu/NIO. Paragenesis: The mineral deposit i s of the contact meta-soraatic class and has resulted from the in t r u s i o n of a quartz monzonite stock into country rock consisting of slates, p h y l l i t e s , limestones, and other low grade region-a l l y metamorphosed types. The metasomatic replacement was favoured i n lim e - r i c h lenses present i n the o r i g i n a l metasediments. High temperatures are indicated by textural relationships i n the s u l f i d e s , and rapid cooling i s suggested by the presence of r e l i c t mineral crystals and pseudomorphs i n the skarn assemblage. Rapid changes 4 3 i n temperature and/or pressure are also suggested by the extreme zoning i n plagioclase feldspars ( A n ^ to An 2o) within the intru s i v e body. Relationships between a l l the minerals i n the assemblage were not observed i n t h i n section, but suf-f i c i e n t evidence was present to allow some conclusions to be drawn regarding the paragenesis of the deposit. For convenience, the paragenetic sequence i s divided into three parts or phases. This d i v i s i o n does not necessarily imply that there were three separate periods of mineralization. It i s quite probable that deposition was continuous, and that the various minerals were de-posited i n a d e f i n i t e sequence con t r o l l e d by rapid changes i n pressure, temperature and the composition of the meta-somatic f l u i d s . The f i r s t phase was one of temperature increase which resulted i n the formation of garnet and pyroxene. Some specimens consist e s s e n t i a l l y of euhedral crystals of pyroxene and anhedral garnet i n keeleite and i t s a l t e r a t i o n products. The garnet has p a r t i a l l y replaced hedenbergite, but the relat i o n s h i p of these minerals to keeleite i s obscured by the a l t e r a t i o n of keeleite and the l a t e r addition of s u l f i d e minerals which replace a l l s i l i c a t e s . The second phase consisted of the metasomatic addition of barium, titanium, s i l i c a , iron, and minor boron, lithium, a id manganese. This metasomatism resulted kk i n the formation of g l l l e s p i t e , keeleite, sanbornite, and taramellite. Taramellite i s believed to be early because i t commonly occurs as r e l i c t c r ystals which have been p a r t l y replaced by other minerals. In one specimen, where taramellite occurs with keeleite and quartz, almost every grain of the taramellite i s so badly corroded as to leave only a bare network of the o r i g i n a l mineral. Keeleite and g i l l e s p i t e may have been contemporaneous, but i n one section, the former mineral was seen to cut across a c r y s t a l of g i l l e s p i t e , and further, g i l l e s p i t e c r ystals are sometimes seen to butt up against the more euhedral keeleite grains. The r e l a t i v e p o s i t i o n i n the paragenesis of sanbornite i s not known because i t occurs separately i n a lense-shaped bed about 100 feet from the main deposit. The a l t e r a t i o n products are also included i n t h i s phase although they are a l l obviously l a t e r . The presence of water and such elements as boron and lithium, which were detected i n Mineral C, suggests a rather l a t e stage i n the process, quite probably follow-ing even the deposition of s u l f i d e s . Mineral C, the blue fibrous mineral, has replaced g i l l e s p i t e along i t s prominent basal cleavage and i t s grain boundaries. In some instances, i t has completely replaced that mineral. Keeleite i s apparently l e s s susceptible to replacement by Mineral C, but has also been replaced to a r e l a t i v e l y moderate extent. Mineral 3D has replaced keeleite i n many sections, p a r t i c u l a r l y In those sections containing 45 s u l f i d e minerals. This relationship suggests that the replacement of g i l l e s p i t e and keeleite by Mineral D was contemporaneous with s u l f i d e emplacement. The only mineral seen to replace sanbornite was Mineral E. The l a t t e r occurs as anhedral grains along the grain boun-daries of sanbornite. I t also occurs i n small quantity i n minute fractures i n the k e e l e i t e - g i l l e spite rocks. The t h i r d phase i s considered to embrace the emplacement of the s u l f i d e minerals. Chalcopyrite sphalerite, pyrrhotite, and marcasite have replaced a l l s i l i c a t e s . Chalcopyrite occurs as exsolved rims and blebs within and around sphalerite grains giving an "emulsion" or "mottled" texture. Some laths of chalco-pyrite are oriented i n the (111) or ( 100) planes of sphalerite. According to Edwards^^ these textures r e -present a l l stages i n the arrested d i f f u s i o n of ex-solution chalcopyrite to the g r a i n boundaries of i t s sphalerite host. He states also that t h i s texture i s the r e s u l t of high temperature deposition and rapid cool-ing, and that the temperature of unmixing i s 350 - 450 degrees C. Pyrrhotite exhibits mutual boundaries with the other sulfid e s and i s probably contemporaneous with them, possibly deposited from a complex s o l i d s o l u t i o n with complete segregation of pyrrhotite from the other s u l f i d e s . Marcasite has replaced pyrrhotite to a con-siderable extent along fractures. Edwards states that replacement of pyrrhotite by marcasite may be caused by 1*6 a change i n the pH and temperature of the r e s i d u a l mineralizing solutions. A number of ba r i t e veins occur i n the immediate v i c i n i t y of the mineral deposit. They range i n width from two or three Inches to one foot and may be up to several hundred feet long. The ba r i t e occurs i n very well-formed c r y s t a l s up to three inches i n length or i n plates forming a boxwork. These veins cut across the country rock and the mineralized zones, and are probably the r e s u l t of a very l a t e stage i n the paragenesis. The formation of white, supergene barium-calcium carbonates as coatings on the surface rocks i s attributed to p r e c i p i t a t i o n from solutions at or very near the surface. The reason for t h i s b e l i e f i s found i n the very close resemblance of the supergene carbonates to synthetic barium-calcium carbonates. The synthetic sal t s were pr e c i p i t a t e d from solutions of CaCl2, BaCl2» and and c a l l e d synthetic barytocalclte and alston-i t e even though t h e i r X-ray patterns do not resemble those of the natural minerals. It i s therefore suggested that the synthetic materials and those natural minerals occur-r i n g as supergene coatings on keeleite are polymorphs of al s t o n i t e and barytocalcite with the composition BaCa(C0.2)2. It i s further suggested that natural a l s t o n i t e and baryto-c a l c i t e may form only under considerable pressures of COo. hi CONCLUSIONS A new mineral, keeleite, is described. The chemical formula, based on chemical analysis and syn-thesis, is Ba^Ca2Fe^(Al,Fe)2(SiQ2)l2. The mineral is tentatively classed as an inosilicate. Optical pro-perties suggest that the mineral is orthorhombic. The minerals designated by the letters C, D, and E are probably new species. Three new localities for taramellite have been proven by X-ray and optical determinations. In addition to the type locality, Candoglia, Italy, taramellite occurs in the Yukon Territory, in Mariposa County, California, and in the material from Dry Delta, Alaska. Sanbornite, previously a one-locality mineral, has also been shown to occur in the Yukon Territory. The presence of supergene barium-calcium car-bonates in the deposit, which are similar to salts ob-tained synthetically, suggests a natural occurrence of minerals of composition BaCafCO^^* If this assumption is true, the minerals are probably polymorphs of alstonite and barytocalcite. A new formula, Ba, FeFe' Ti(SiO.) n(0H)• , is sug-gested for the mineral taramellite. A paragenetic sequence based on present evidence has been presented. It is quite possible that this para-genesis wi l l be revised with a more exhaustive examination 48 of the f ie ld relationships. The author had the oppor-tunity to spend only one day on the property, and it is probable that careful investigation would reveal better crystallized material, additional mineral species, and more evidence for a paragenetic sequence. 1+9 BIBLIOGRAPHY 1. Kindle, E.D. (191*5), "Geological Reconnaissance along the C'anolRoad from Teslin River to MacMillan Pass Yukon", Geological Survey of Canada, Paper 1*5 * 21. 2. Wheeler, J.O. and Roddick, J.A. (1958) - the geological report of Operation Pelly is in preparation. 3. Bowen, N.L. and Schairer, J.P. (1932), "The System FeO-Si02", Am. Jour, of Science, vols. 23-21*, 1932. 1*. Schairer, J.P. and Yagi, Kenzo (1952), "The System Pe0-Al203 - S i 0 2 " , Am. Jour.-of  Science, Bowen volume, 1952. 5. Levin, and Ugrinic, (1951), "Journal of Research of the National Bureau of  Standards," vol. 5 1 , pp. 37-56. 6 . Schaller, W.T. (1929), "The Properties and Associated Minerals of Gillespite," American Mineralogist, vol . l l* , pp.319-322. 7. Pabst, A. (191*3), "Crystal Structure of Glllespite, BaFeSl),Q>i A , " -American Mineralogist, vol. 28, PP. 372-390. 8. Rogers, A.P. (1932), "Sanbornite, a new barium silicate mineral from Mariposa County, C a l i f . , " American Mineralogist, vol . 17, PP. i6i-i72~: — 9. A.S.T.M. X-ray Index Card 3-0322. 10. A.S.T..M. X-ray Index Card I-O77O. 11. Mazzi, Plorenzo (1957), "RIesame della taramellite," Atti Soc.tosc.sci. ~nat., ser.A, vol . 61*, 1957, PP. 237-245. ; 1 2 . Douglass, R.M. (1958) "The Crystal Structure of Sanbornite, BaSi205," American Mineralogist, vol . 1*3, 1958. 13. Edwards, A.B. , Textures of the Ore Minerals and Their Significance, Revised 195U. Aus. Inst. M.M., p. 100. 

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