40 



ROYAL SOCIETY OF CANADA 



If this rock possessed about oue-lialf of one per cent less iron-mag- 

 nesia constituents, it would fall into the class of persalanes and would 

 constitute the first dosodic donialkalic tasmanare known. 



The mode or actual mineralogieal composition of the rock is as 

 follows : — 



Albite.. .. 

 Nepheline . 

 Pyroxene. . 

 Garnet. . . 

 Iron Ore . 

 Apatite. . 

 Calcite. . . 



Water. 



19.39 per 

 50.57 

 18.35 



1.45 



1.86 

 .34 



6.80 



98.76 



cent. 



99.64 



Nepheline Rock (Monmouthite) — Township of Monmouth — Lot 10, 

 Con. Vlfl. {Third Variety). 



This consists essentially of nepheline and hornblende, the rock be- 

 ing practically free from feldspar. It is found in bands six feet or more 

 in width, which bands may be traced for long distances on the strike. 

 The rock is coarse in grain, the white nepheline and black hornblende 

 being strongly contrasted on the surface of fracture. The hornblende 

 in the case of the nepheline syenite has a tendency to lam in streaks 

 parallel to the course of the bands. On the weathered surface the rock 

 is pale grey in colour and' presents the smooth surface assumed by nephe- 

 line when exposed to the weather, th3 black hornblende standing out 

 from it. 



Tinder the microscope the rock is seen to consist essentially of 

 nepheline and hornblende, with plagioclase, cancrinite, and calcite as 

 accessory constituents, as well as sodalite, apatite, sphcne, biotite, pyrite 

 and iron ores, these latter minerals being present in extremely small 

 ampunts.^ 



The nepheline occurs in large well-defined grains, presenting the 

 usual characters displayed by the species. It is clear and fresh. 



• F. D. Adams. — On a New Nepheline Rock from the Province of Ontario, 

 Canada. Am. Jour, of Sci., April, 1904. 



