104 C. H. GORDON — SYENITE-GNEISS (lEOPARD ROCk) FROM CANADA. 



An analysis of the microline by William Hoskins, of Chicago, gave 

 the following results : 



SiO, 64.54 



AlA 20.55 



Fe,03 -15 



CaO 99 



MgO trace. 



NaaO 1.62 



K2O 10.78 



BaO 32 



Loss by ignition .49 



99.74 



The pyroxene is of a dark green color, and occurs botli in well formed 

 prisms and as irregular aggregates of considerable size. The prisms are 

 long and slender, and occur chiefly inclosed in the microcline, though 

 they are associated sometimes with the quartz in the granular areas. In 

 the latter case, however, they are usually shorter and sometimes show 

 evidence of breaking. The prisms are elongated in the direction of the 

 vertical axis and have a very nearl}^ equal development of the faces 

 00 P ^ (100), GO P"go (010), P (110). The pyroxene is more abundant 

 in places, forming aggregates, inclosing a varjdng amount of feldspar, 

 pyrites, and titanite. In these areas the p3'roxene is coarsely crystallized 

 and of a lighter green than the idiomorphic individuals. 



An analysis of the crystals inclosed in the microcline by jNIr Hoskins 

 gave the following results : 



SiO.^ 49.79^ 



AlA 2.93 



FeO 18.95 



CaO 21.76 



MgO 5.()0 



Na.,0 61 



K,0 36 



100.00 



The analysis shows a high i)ercentage of iron, while alumina and mag- 

 nesium are correspondingly low. Taken in connection with its physical 

 characters, the analysis seems to indicate an augite closely allied to 

 diallage. 



Quartz occurs chiefly in nests and strings, associated with the inter- 

 stitial granular areas. Titanite is present as grains disseminated through 

 the rock, but is more abundant along the granular areas. A fine grained 



*The per cent of silica was rendered doubtfully low by an accident, and is put in by difference. 



