268 



Canadian Record of Science. 



Orthoclase is the most abundant mineral found and is 

 present in almost every case. It is generally fairly fresh. 

 Twinning after the Carlsbad law is quite common while the 

 rarer twins after the Baveno law are found in one thin section 

 examined. The pyroxenes, which, with a few exceptions, are 

 all remarkably fresh, include the interesting soda varieties 

 mentioned above; these are recognized by their grass green 

 color, low extinction angles — less than 6° — and the fact that 

 the greatest axis of elasticity lies next the vertical axis. The 

 aegirite-augite has of course higher extinction angles than 

 acmite or aegirite. The plafFioclase felspar present is andesine, 

 determined by the statistical method and also by measuring 

 extinction angles on crystals twinned according to both the 

 Carlsbad and Albite laws. This lime-soda felspar w r as only 

 found in two sections, however, and the entire series of tuffs 

 and breccias is characteristically an alkaline one, of trachytic 

 tendency. Biotite occurs, but it is rare. 





Analcite. 



Fig. 1. Analcite-tuff; ordinary light ; actual field 2-5 mm. The large white 

 crystals are analcite showing some of the crystal faces still preserved. Inclusions 

 arranged parallel to the octagonol outline of the mineral are seen in the 

 lower left hand crystal. 



