[ADAMS A BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 2S 



distinct, with no hint of decomposition in any of the surrounding 

 minerals. The individual grains show the usual perfect rhombohedral 

 cleavages often with well marked twinning lamellae. Comparatively 

 large individuals occur in the pegmatitic phases as noticed in the ex- 

 posures west of the bridge over the York river in Dungannon township. 



Garnet. — This mineral is of common occurrence and is occasionally 

 so abundant, especially at certain exposures near the York river in the 

 northern part of Dungannon, as to characterize the rock. In the hand 

 specimen it exhibits a dark reddish brown colour. In thin sections it is, 

 of course, much paler in tint, assuming a deep brownish tint, fading to a 

 yellowish towards the interior of the larger grains. It shows the usual 

 high index of refraction and consequent very pronounced relief. It is 

 quite isotropic. The individuals and especially the larger grains usually 

 possess a very irregular outline, with irregular arms and intricate in- 

 dentations and hold abundant inclusions of most, if not of all, of the 

 other constituent minerals of the rock. In some instances it exhibits well 

 developed crystallographic l)oundaries. It is especially al)undant in those 

 varieties of the syenite which contain hornblende, and is for the most part 

 developed in immediate association with tliis mineral. It resembles a 

 garnet found in small amount in the nepheline syenite of the Corpora- 

 tion Quarry at ]\rontreal, and also the melanite in the nepheline syenite 

 of Alno.^ 



A chemical analj^sis by Dr. B. J. Harrington- of the variety asso- 

 ciated with Hastingsite about two miles east of the town of Bancroft in 

 the township of Dungannon afforded the following results, showing the 

 garnet to be a titaniferous andradite: — 



SiO, .. 36.604 



TiO, 1.078 



A1Â 9.771 



Fe,0, 15.996 



FeO 3.852 



MnO 1.301 



CaO 39.306 



MgO 1.384 



Loss on ignition .'285 



99.577 

 Specific gravity at 16° C 3.739 



1 Geol. Foren. i. Stockholm, Forh. 1895. p. 144. 



'Can. Rec. Sc, Vol. VI., 1894-95, pp. 480-481; al.so Vol. VII., 1896-97, pp. 

 87-88. 



