[ADAMS & BARLOW] ALKALI SYENITES OF EASTERN ONTARIO S3 



The rock thus has the following position in the Quanti tatire Clas- 

 sification : — 



Class I Persalane. 



Order 6 Russare. 



Rang 1 MiaskavSe. 



Sub-rang 4 Miaskose. 



The mode of the rock, that is to say, its actual quantitative mineralo- 

 gical composition when calculated out ]s found to he as follows: — 



Orthoclase 16.12 percent. 



Albite 53.45 \ r^ ^q 



Anorthite. .. 1.25/ 



Nepheline 18.18 



Biotite 1.27 



Muscovite 7.95 



Magnetite .93 



99.15 

 Water 28 



99.43 



Tlie Reddish Alkali Syenite. — The reddish syenite is typically 

 developed about a quarter of a mile to the west of the locality 

 from which the v/hite syenite, whose analysis has been given 

 above, was obtained. The syenite is here traversed by the 

 veins which are being worked for corundum. It is first seen to occur 

 as streaks or schlieren in the white syenite, and then on going west it 

 replaces the latter. The syenite here has a pale reddish or pinkish 

 colour and is rather fine and even in grain. The iron-magnesia con- 

 stituents, which are very subordinate in amount, occur in the form of 

 little elongated dashes, giving a species of foliation to the rock. It is 

 chiefly confined to the sides of the Blue Mountain mass, although not 

 continuously developed about it. 



Under the microscope the rock is seen to be composed essentially of 

 albite and microcline. The twinning of the microcline is \ery narrow, 

 and there is some untwinned feldspar which is apparently orthoclase. 

 The only other minerals present are biotite, magnetite, pyrite, calcite 

 and quartz. These occur intimately associated and form the little dark 

 coloured dashes seen on the surface of fracture. They are all present 

 in small amount, the magnetite often having a rude crystalline form. 

 The calcite occurs in irregular-shaped individuals and is ocfcasionally 

 seen away from the dashes, lying between the feldspar grains. The 

 quartz, like the calcite, does not occur in all sections, and when present, 

 is found with the calcite in the form of rather large irregular-shaped 

 grains. These two constituents may be secondary, although not ordinary 

 decomposition products, for the rock is very fresh. 



