16 Canadian Record of Science. 



clase, which is oligoclase, is abundant. It shows Albite 

 and Pericline twinning, cleavage is often seen, and the 

 extinction is inclined ; it tends to be turbid along the 

 cleavages. Biotite occurs in considerable amount, in 

 irregular individuals : it is brown and strongly pleochroic. 

 Hornblende occurs in about equal amount, generally in 

 irregular individuals of medium size, but some show a 

 tendency toward rough crystallographic outline. It is 

 very deep green and intensely pleochroic ; the scheme of 

 absorbtion is C>b>a. In the zone of co P co and ooPa, 

 the maximum extinction angle observed was 22 c . The 

 sphene is in irregular grains, much cracked. It has a 

 high refractive index, giving a dark border, and a 

 roughened appearance to the surface, and high double 

 refraction, polarizing in colors ranging from brilliant to 

 almost white. Owing to its great dispersion of the axes 

 of elasticity, extinction is never complete. Enclosed in it, 

 or closely associated, are several grains of black iron ore 

 which show a bluish metallic lustre in reflected light, and 

 which are without doubt ilmenite. 



The structure is granular, resembling that seen so often 

 in granite gneisses. 



ALTERED LIMESTONES. 



These constitute the dark basic rocks interbanded with 

 the limestones near the granite contact. In the field they 

 are conveniently divided into two classes depending on 

 the predominance of pyroxene or of hornblende, and are 

 called respectively pyroxene gneisses and amphibolites. 

 Bands of them are very much mixed up, with one another, 

 and with veins or dykes of the granite. 



Pyroxenite, Toivnship of Glamorgan, Lot 27 between Ranges 

 IX. and X. (Sections 1269 A.B.C.D.) 



This is one of the pyroxene gneisses. It is a very fine- 

 grained, friable rock, of greenish gray color. It is very 



