88 ROYAL SOCIETY OF CANADA 



Tlie corundum is of a greenish-grey colour, often changing to blue 

 in the centre of the crystal. The colour suggests sapphire, but the 

 mineral is opaque or at best only translucent. 



\I. The Nephellne and associated Alkali Syenites of the townships of 

 Faraday, Dungannon, Carloiu and' Monteagle. 



It is unnecessary to describe in detail the numerous and often more 

 or less isolated occurrences of the nepheline and alkali syenites in this 

 portion of the belt. They, however, present one point of especial in- 

 terest, namely, the presence in them in many places and often in large 

 amount of the mineral corundum. 



This mineral, while known to occur in considerable quantity in 

 several localities, has been actually worked in two places only, of which 

 The more important is' Craigmont. This occurrence, therefore, merits a 

 special reference. 



Craigmont (formerly Eobillard Mountain) is a well marked topo- 

 graphical feature rising abruptly from Campbell's marsh (an expansion 

 of the York river) and extending as far west as the post road between 

 Combermere and Fort Stewart. It covers most of the first four lots in 

 the eighteenth and nineteenth concessions of the township of Kaglan in 

 the county of Eenfrew, the line between these two concessions running 

 along the southern slope of the mountain. According to the mean of 

 eeveral observations with two aneroid barometers, the " mountain " 

 rises to a height of 500 feet above the dam at the old mill on the creek, 

 which latter is ninety-five feet above Campbell's Marsh. This, added 

 to 931 feet, the height given by White' for the Junction of the York 

 and Madawaska rivers, gives 1426 feet as the height of the top of Craig- 

 mont above mean tide-level. 



The rock composing the mass of the mountain is a rather dark 

 coloured homblende-granitite-gneiss, evidently representative of the 

 gneisses of the great Laurentian bathylith. 



The corundum-bearing rocks form a layer or mass of comparatively 

 small thickness which occupies the whole face of the hill lying on the 

 barren gneiss of the Laurentian and coinciding in strike and 

 dip with the direction of the hill's face. This strike is 

 N75°E with a southerly dip at an angle of 10° to 12°. 

 The main body of the hill behind this layer is therefore 



•Altitudes In Canada, 1901, p. 199. 



