70 ROYAL SOCIETY OF CANADA 



If the norm of tljis rock be calculated, it will be found to be as 

 follows : — 



Orthoclase 30.02 



Albite 51.35 



Anorthite 3.62 



Corundum .20 



Magnetite 12.30 



Ibnenite .91 



Hematite .64 



Olivine .31 



99.35 



Phosphoric Acid .04 



Water .36 



99.75 

 Deficit in Silica .27 



99.48 



The position of the rock in the Quantitative Classification is accord- 

 ingly as follows: — 



Class II Dosalane 



Order V Germanare 



Rang 1 Umptekase 



Sub-rang IV Umptekose 



The mode of the rock, that is to say, its actual raineralogical com- 

 position, does not differ essentially from the norm, the rock being made 

 up of orthoclase, microcline, albite (about Ab^An^) and magnetite, with 

 a little biotite, which latter mineral in the norm is represented by other 

 mineial combinations. No quartz is present, .27 per cent of additional 

 silica being required to satisfy the feldspars in the norm. 



The rock, which contains the largest and most abundant crystals and 

 masses otf corundum at Craigmont, and thus the richest " ore " of this 

 mineral, is the corundum-syenite-pegmatite, which occurs in the form 

 of dykes or veins, varying from six to eighteen feet in width. These 

 dykes intersect the medium grained or normal type of red syenite just 

 described, which also contains corundum although in less abundance and 

 in smaller individuals. They are made up almost wholly of a deep flesh- 

 red to very pale salmon-pink feldspar, which, in thin sections under the 



