14 Canadian Record of Science. 



biotite is dark brown, and shows good cleavage. It is 

 strongly pleochroic, and the absorbtion is a > £. Ex- 

 tinction is parallel. The grains are of medium size, and 

 allotriomorphic, showing a tendency to skeleton structure, 

 and thus interlocking with other minerals. Hornblende 

 occurs somewhat more abundantly, in deep, yellowish- 

 green individuals ; cleavage excellent. Extinction in the 

 clinopinacoidal sections is inclined, giving a maximum 

 extinction angle of 33°, which indicates a basic composition. 

 The pleochroism is very pronounced, as follows : — 



a = pale yellow, 



h = yellowish green, 



C = deep green. 

 Or to state it in the " absorption scheme," 



c > b > a. 



A comparatively small number of fairly fresh grains of an 

 untwinned feldspar of low specific gravity, about 2.56, 

 are probably orthoclase. The apatite is in small distorted 

 crystals of hexagonal outline. Magnetite occurs in irreg- 

 ular grains of varying size, alone, and also inclosing grains 

 of pyrite. The former shows a characteristic steel-blue 

 color and metallic lustre in reflected light, and under the 

 same conditions the pyrite looks brass-yellow. The mag- 

 netite is sometimes altered at the edge to hematite, which, 

 in reflected light, appears red. 



The structure of the rock is granular, inclining, where 

 individuals of the basic constituents adjoin, to a mosaic 

 structure, and pointing to a partial recrystallization. 



Quartz Diorite Gneiss, Township of Glamorgan, Corner 

 of Lots 25 and 26, Ranges VII. and VIII. (Section 

 1271.) 

 This is a fine grained, rather light reddish gray gneiss, 

 with foliation not very distinct. 



Examined microscopically, it is seen to have as essential 



