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Un des symboles suivants apparaitra sur la derni^re image de chaque microfiche, selon le cas: le symbole —^ signifie "A SUIVRE ", le symboie V signifie "FIN". Les cartes, planches, tableaux, etc., peuvent dtre filmds d des taux de reduction diffdrents. Lorsque le document est trop grand pour §tre reproduit en un set! clich6, il est film6 d partir de Tangle sup^rieur gauche, de gauche d droite, et de haut en bas, en prenant le nombre d'images ndcessaire. Les diagrammes suivants illustrent la mdthode. 4 32X 7hH I:) [Fr*»m thb AMERICA^f Journal of Sciknce, Vol. I, March, 1896.1 ON A NEW ALKALI HORNBLENDE AND A " TITANIFEROUS ANDRADITE FROM THE NEPHELINE-SYENITE OF DUNGANNON, HASTINGS COUNTY, ONTARIO. By Frank D. Adams and B. J. Harrington, Mc Gtll College, Montreal. ,■1 '^ i [P'ROM THK AMKRICAN JoURNAI, of ScIKNCR. Vol.. I, Maiuii, ISOfi.l ON A NEW ALKALI HORNBLENDE AND A TITANIFEROUS ANDRADITE FROM THE NEPHELINE-SYENITE OF DUNGANNON, HASTINGS COUNTY, ONTARIO. (1 By Frank D. Auams and li. J. Harrington, Mc Gil, I, Cou.KGK, M()ntrf:al. 210 Adams and Harrington — Alhali Ilornhlende and Art. XXII. — 0)i a new Alkali Hornblende and a titaniferous Andradlte from the NephHine-Si/enite of Dungannon, Hastings County^ Ontario; l)y Frank D. Adams and B. J, Harrington, McGill College, Montreal. In a paper which appeared in the number of this Journal for July, 1894, the discovery of a large area of nepheline- syenite in the township of Dungannon, in the Province of Ontario, was announced and the "geological relations and miu- eralogical characters of the mass briefly described. One of the many peculiarities of this rock is the absence from it of the mineral pyroxene, which is usually the chief iron-magnesia constituent in rocks of this class, its place being taken by hornblende and mica, but even these minerals are present in comparatively small amount. Of the hornblende two varieties, occurring in different parts of the mass, were distinguished. Th.^ first, from near the York river, has a large axial angle with strong pleochroism in tints varying from psile yellow to deep green, and altliough containing a considerable amount of soda, probably approaches common green hornblende in composition. The second variety, which occurs in a series of exposures about two miles to the east of the village of Ban- croft, is (piitc different in character, having a small axial angle with high extinction and a much stronger pleochi'oism in the bluish tints suggestive of arfvedsonite. A number of additional thin sections have been prepared and in the present paper the results of a further investigation of the o])tical properties and chemical composition of this second variety of hornblende are presented. Hornhlende — The mineral occurs in hypidiomorphic grains, which show the usual hornblende cleavages ; it is optically negative, a being the acute bisectrix, but the double refraction is weak. It possesses, as has been mentioned, a strong pleochroism as follows : a = yellowish green, b and c = deep bluish green. The absorption is c = b> a. b and c, if not quite equal in absorption, are nearly so, hence sections cut at right angles to the acute bisectrix show but little pleochroism and are nearly isotropic, c lies nearest the vertical axis, but whether toward the acute angle /9 or on the opposite side cannot be determined as the mineral does not possess a good crystalline form ; it makes with the vertical axis a large angle the extinction amounting to 30°. The plane of the optic axes is the clinopina- I Titaniferous Amh'adite fnmi Ontario. 211 in to coid, and there is a strong dispersion —red greater than violet. What drew especial attention to this hornhletide in the first instance was tlie fact tliat it appeared to he nearly uniaxial. Wiien a section, cut at ri^ht an«i:;les to the acute hisectrix, is examined between crossed nicols in convcrsjfent li^ht, a black cross is seen somewhat thickened toward the intersection of the arms. This cross, on revolving the stage, divides into two hyperbolas, but these separate from one another but very little, and appear to separate less thnii they really do, on account of the fact that the low doul)le refraction and deep color of these sections causes the hyperbolas to be ill-detined, while the whole iield is very dark. The dispersion, however, makes itself evident in the varying colors on the sides of the hyper- bolas. When, however, a gypsum plate giving a red of the first order is inserted above the objective the hyperbolas become a little better defined, altl'.ough still not sufficiently definite to allow the axial angle '„o be ac(uirately measured. The axial angle is found to be over 30°, possibly as much as 45°, which, however, is still very small for hornblende, being about one-half the usual value. Our thanks are dne to Pro- fessor Rosenbusch for his assistance in working out these optical relations. On examining a large series of thin sections of ncpheline- syenites rej)resenting most of the important occurrences hith- erto discovered, only two rocks were found which contain a hornblende at all similar to that above descril>ed. The first of these is the nepheline-syenite from the Cor|)oration Quarry at Montreal, in which hornblende with the same small axial angle, low double refraction, intense color and pleochroism, large extinction angle and high specific gravity, occurs intergrown with the augite. The second is the hornblende described by Hackman under the name of arfvedsonite and which occurs intergrown with acgerine in the nepheline-syenite from Umptek in the Kola peninsula.* This mineral, however, differs from tyj)ieal arfvedsonite in having an extinction of about 40° as well as in several other iini)ortant respects. It possesses more- over a very small axial angle, although this fact is not noted by Hackman, while in true arfvedsonite the axial angle is very large. This Kohv hornblende is much lighter in color than the hornblende from either of the above mentioned Canadian localities. In order to determine the chemical composition of this somewhat remarkable variety of hornblende from the Dungan- non I'ock, it was decided to separate a portion for analysis. A considerable quantity of the rock was accordingly reduced to * " Petrosrrapliische Besclireibimg fles Nepheliusyenites voiu Umptek," von Victor Hackman. Kuopio, 1894, p. 14. 212 AdiUiia and Harrington — Alkali Hornhletuh and powder and passed through a fiieve of 48 incslies to tlie inch — the rocK beiiij; rather coarse in ii;rain — and after liavinjij been freed from dust was treated with ThouU't's solution, Iiavii.g a specific f^ravity of 3'18, in a large separatin<; funnel. In this way an almost compU^te separation of the colored constituents was effected. These latter, which sank in Tiioulet's solution, were 8ubjecte?gest llastingslte as a varietal name for this hornblende, con- necting it with the region where it occurs. TUitniferoHH AndradiU from Ontario. 213 Silica 34 Titaiiiuni dioxide .... 1 Alainiiia 11 Ferric oxide 12 Ferrous oxide . - '-'1 Maiiganou8 oxide Lime 9 Majifnesia 1 Potasli 2 Soda 3 Water* 184 '527 ■517 021 •62 !» •807 •353 •286 •290 ■348 Specific gravity 9n-0()l 3-433 The atomic and qrantivaleiit ratios dediicible from the above analysis are as follows: Atomic. 570X4 = 2280 Si. Ti Al 19X4 = 226X-'^ = Fe'" 158X3: Fe" 305x2: Mn Ca. Mg K.. Na 9X2 = 176X2 = 34X2 = 48 106 76 078 474 610 18 352 68 48 106 Quantivalent. 2356 2356 j. 1152^1 1 I ^2354 The ratio of (R,0 + RO) : K./), : SiO, is 601 : 192 : 589, or approximately 3:1:3, and obviously the mineral is a true I II III orthosilicate agreelni; fairly with the formula (R3U)3 R^SijO,,, or, more fully, (Fe, Mn, Ca, Mjj:, K,, Xa,), (Fe, Al), (Si, Ti), O., — a constitution analofirous to that of i^arnet. So fi'r as we are aware no other hornblende containmg so small a proportion of silica has been analyzed ; but the small percentage of silica is explained by the large proportions of ferrous and ferric oxides. This is made plain by the following formulae and the corresponding percentages of silica deduced from them : Formula. 3FeO, Fe.O,, 3SiO, 3Ca(), Fe^O,, 3SiO, 3FeO, AI.P3, 3SiO, 3Na,0, Ai„0,, 3SiO, 3CaO, Ai;03, 3SiO, C. of SiOa. 32-19 35-43 30-14 38-38 40-00 * Loss after igniting for about llfteen minutes. On furtlier ignition the powder gained in weight owing to oxidation of tlie ferrous oxide. 214 Adams and Jl- tal)le gives the analyses of these four minerals and the molecular ratios deducihle froin them : • Stet)/,cl Dimgaii Jau Mayeu. Molec. R. Bohemia. Mol. 11. berg. i Mol. U. QOQ. 1 Mol. R. RiO, 39167 TiO, .... 653 653 39-66 0-89 661 11 39-62 ► 672 „.,,) 660 ) „,.„ 34-184 2 \ *^"2 1-527 ™J-CS, AliiO, 14-370 Fe,Oa 12-423 140 78 • 218 14-83 12-37 145 77 2,„ H-f»2 146? 210 '^■•^'' 04 f ^'" 12-621 ■i^fm FoO 5-856 811 1-97 27] 767 106] 21-979 305 1 MnO 1-505 21 .. 0-24 3 0-629 9 MgO 10-521 263 14-23 356 11-32 283 1-353 34 \ CaO 11-183 200 \- 648 12-74 227 \- 663 12 65 226 j. 685 9-867 176 )■ 620 KaO 2-013 21 1-25 13 2-18 23 2-286 24 NuaO 2-478 40 2-47 40 112 18 3-290 53 HaO -396 22J --. 0-48 26 J 0-348 19J 99-912 100-43 il0067 99 601 In all four analyses the ratios for (R,/) + RO) : 11,0, : SiO, (including TiO^ when present) are practically 3:1 : 8, or, to give the exact figures (excluding water): (RoO + RO) : R^C Jan Mayen -2-87 : Bohemia. 2-99 : Stenzelberg 3-1 4 : Dungannon 3-l'2 : The ratio (R,0-f-CaO) : (Mg, Mn, Fe)0 is, as observed by Scharizer in the case of the Jan Mayen and IJohemian horn- blendes, approximately 3 : 4, thus : Oa : SiOa I 2-99 1 3-02 1 3-15 1 3-07 *N. .lahrb. f. Mia., 1884, ii, p. 143. f loc. cit. X Min. Mitlh, iv, 23, 1831. g Pogg. Ann., 1858, ciii, 454. \- 192 Tttaniferoim AntJrndiiefrom Ontario. 215 Includiiig Water. KxeludiD« Water. (R,0 + CuO) : (Mk, Mn, Ke)(). (R.,0 + CaO) : (Mfir, Mo, Fe)0. Jan Mayen 3 : 387 3 : 4-17 Bohemia 3 : 4-10 3 : 4-10 Stcn/A'lberg 3 ; 4-02 3 : 438 Diuiganiion 3 ; 3-84 3 : 411 Scluirizer adopts the fore<;oiTig ratios (3 : 1 I -5 and 8 ', 4) as those of syntagmatite in calcnhitinn foreign matter. With the pycnometer their specific gravity at lb _0. was found to be 3-739. Chemical analysis gave the following results : Silica ----- =^6-H04 Titanium dioxide ^ !!l^ • Alumina..- ^ oop Fei-ric oxide 15-996 ferrous oxide 3-852 Manganous oxide 1-301 Lim" 29-m Magnesia.. 1 3b4 Loss on ignition - '^^^ -" 99-57Y . The atomic and cpiantivalent ratios deduced from the above analysis are as follows : ♦SeeScharizer's paper, loc. cit., p. 156. ••-.„„„ a n Hncbom f " Ueber das Noplielinsyenitgebiet auf der Insel Alao, von A. G. Hogbom. Geol. FiJren. i. Stockholm Forb., 1895, p. U4. 218 Adams and llarvin(jton — Alkali Hornblende, etc. 1176 Atomic. Si 610X4 = 2440 Ti iaX4= 52 Al 192X3 = 576 Fe"' 200 X 3 = 600 Fe" 5-^,X2 = 106 ^ Mn .- 18X2 = 36 I Ca 523X2 = 1046 J>i290 Ms; 35X2= 70 I 32 J Qiiantivalent. I 2492 2492 ] ^2466 II 32 The ratio for RO : R,0, : (SiTi)O, is OSl) : IIMI : 623, or, calculating the titanimn as Ti,0„ 629 : 203 : 610 = 3:1:3. The analysis therefore accords well with the ordinary garnet II III formula 3Tl(), R^O,, 3810, or RgR^SijO,,, and the mineral may be regarded as a ti^aniferous andradite, with a consideral)le proportion of the ferric oxide replaced by alumina. In com- position it resembles somewhat the brown garnet from the Island of Stoko, analyzed by Lindstrom.^ By way of comparison the analysis of the Stoko garnet and also one of a garnet from the nepheline-syenite of the Island of Alnof are included in the following table. Stoko. Molec. R. SiOa 2G-63 TiOa AlaOa ... 997 FeaO, ... 13-45 FeO 2-28 MnO -63 CaO 35-90 MgO -28 Na»0 Ign -16 99-30 610 610 98 ) 84 f 32^ 9 I 641 ( ^ r ... I 9J 182 698 Aliio. Molec. R. Dungannon. Molec. R. 31-15 6-73 3-14 23 83 '-58 33-44 •68 99-55 G03 180 597 V 616 36-604 1-078 9-771 15-996 3-852 1-301 29-306 1-384 •285 99-577 *Zeitschr. fur KryHt. u. Mm., xvi, ICO. 1890. f Sahlboin, ia tlie paper by Ilogboin already cited. 610 ) 13 f 96 I 100 J I 63 18 523 I 35 16 623 196 )■ 645