ADAMS à BARLOW] ALKALI SYENITES OF EASTERN ONTARIO 85 



This gives a plagioclase of the albite series having a composition 

 Abio-8 An., which is the proper composition as shown by the Ihoulet 

 separation. The composition assumed for the nepheline is that of the 

 nepheline of the Dungannon nepheline syenite, the analysis of which 

 is given on page 15. This arrangement of results leaves an excess of 

 1.25 per cent of lime and a deficit of 1.40 per cent of ferric oxide. 



The dark brown or black lepidomelane present in the rock was iso- 

 lated by means of a Wetheral Electric Separator, followed by the use of 

 Thoulet's solution, and was analysed by J. C. Egleson, M.Sc, of McGill 

 University. It was found to have the following composition: — (^) 



SiO, 31.48 



TiO, 2.50 



AI2O3 17.23 



Fe203 5.85 



FeO 27.96 



MnO 1.61 



CaO 1.33 



MgO 2.99 



K2O 4.17 



N a,0 1.68 



Li.O .00 



Water (combined) 3.94 



Fl -. .00 



100.74 



The specific gravity of tliis mica is 3.25. 



Another very interesting occurrence in this township is that pre- 

 sented by the lenticular shaped mass of nepheline rocks, occupying por- 

 tions of lots 9, 10, 11 and 12, cons. VI and VIII. This consists of 

 nepheline syenite associated with rocks of the urtite group. The in- 

 trusion breaks through the crystalline limestone of the Grenville Series, 

 by which it is entirely surrounded, and of which it holds many inclu- 

 sions. These included masses of the limestone are coarsely crystalline 

 and have a variety of silicates developed in them. The nepheline syenite 

 presents the appearance of eating into these masses. It might be sup- 

 posed that the limestone was in course of solution by the magma, but 

 there is no sign of an increase of lime-bearing silicates near the contact, 

 for while in some places the nepheline syenite near the contact is rich 

 in hastingsite, elsewhere about the border of the mass this and other 

 lime-bearing minerals are absent. Scapolite in this occurrence is com- 

 paratively rare. It is probable that the mass of the limestone was carried 



'An Examination of some Canadian Micas— Trans. Koy. Sec. of Canada, 2nd 

 Ser., Vol. X, Sec. 3, p. 57 (1904). 



