SOUTH WESTERN NOVA SCOTIA. POWERS. 303 



sufficient abundance for the rock to be called a quartz mon- 

 zonite. 



Rosiwal measurements of the mineral composition by weight 

 of this quartz diorite and of the Shelburne granite are given 

 for comparison: 



Harrington quartz diorite Shelburne granite 



Oligoclase 54.6 Oligoclase 35.2 



Albite-oligoclase 8 Microperthite 3.1 



Quartz 21 . 2 Albite-oligoclase. . . 17 . 1 



Biotite 23 . 1 Quartz 33.6 



Muscovite 3 Biotite 7.8 



Muscovite 3.1 



100.0 Apatite 1 



100.0 



From these measurements the chemical composition has 

 been calculated: 



SiO 



A1 2 O 



Fe 2 O 



FeO 



MgO 



CaO 



Na 2 ( 



K 2 O 



Rest 



100.0 100 



The most important characteristic of the granite and quartz 

 diorite is the high soda content. The two rocks are petro- 

 graphically related, the feldspar being of the same composition 

 and differing only in amounts as do the other constituents. 



