[ADAMS A BARLOW] ALKALI SYENITES OF E.\STERN ONTARIO 69 



regular or ragged scales, with strongly marked pleochroism and absorp- 

 tion. This brownish biotite has a distinct greenish tinge. The various 

 cracks and fissures are filled with reddish brown iron oxide which also 

 stains the lorthoclase and microcline. The rock is younger than the 

 nepheline syenite which it isometimes intersects, and decidedly later than 

 the surrounding crystalline limestone. Its association with the nephe- 

 line syenite, however, strongly suggests that both are the products of the 

 differentiation of a single magma. 



A similar type of rock prevails along the southern slope of the hill 

 at Craigmont in Eaglan township. Its mode of occuiTenoe, association 

 and relations to the Laurentian gneisses as well as to the nepheline 

 syfenite have already been described. This reddish or pinkish 

 rock frequently contains bands of a dark coloured, highly micaceous rock 

 which may represent deformed and altered dykes of basi^ composition. 

 In places masses and patches of almost pure hornblende occur. A 

 specimen of the reddish highly feldspathic variety of the rock, with a 

 distinct streaked appearance, owing to small ragged scales of biotite with 

 more or less parallel arrangement, was analyzed by Mr. M. F. Connor, 

 B.Sc. with the following results: — 



SiO, 56.05 



TiO, 0.47 



AUO, 17.02 



Fe,0,.. 9.10 



FeO 4.30 



MnO 0.08 



CaO 0.72 



MgO 0.12 



K.0 5.12 



Na,0 G.IO 



PA, •• 0-04 



ÏÏ2O 0.36 



99.38 



