PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 861 



Muscovadyte. Granite. Hyenyto.] 



No. 2209. MUSCOVADYTE. 



Still in the line of strike from Cheadle's cabin, but a little further north, at the extremity of the point. 

 Ref. Annual Report, xxiv, page 64. 



Meg. Gray, micaceous. 



Mic. With the prevailingly new feldspathic groundmass in this slide are several 

 ijiiartz grains. The old feldspars are more numerous and hence more contrasted 

 with the granulitic groundmass. The hornblendes are larger than in the last and 

 sometimes surround grains of quartz, biotite and feldspar. One section. 



Age. Archean (Keewatin). N. H. w. 



No. 2211. GRANITE. 



Head of the rapids at the outlet of Sucker lake, on the Canadian side ; Prairie portage. Intrusive on 

 fine schists. 



Ref. Annual Report, xxiv, page 66. 



A medium-grained granite. 



Mic, The original granite, whatever its nature, shows evidence of having 

 expei'ienced one or more epochs of dynamic stress. The feldspars are much decayed, 

 but rebuilt by small deposits of peripheral, cementing, fresher feldspar, which was 

 perhaps the time of deposition of microcline, which occurs in larger crystals. Quartz 

 is quite abundant, and was last to take the present pose, but also has a shadowy 

 extinction, indicating a later mountain crushing. Muscovite is common. A little 

 hornblende and some chlorite are the only dark minerals. One section. 



Age. Archean. N. H. w. 



No. 2215. SYENYTE(?) 



N. E. % N. W. % sec. 5, T. 62-10, on the south side of the large triangular island surrounded by the 

 Kawishiwi river. 



Ref. Annual Report, xxiv, page 67. 



Meg. Rather coarse-grained mass of hornblende and feldspar, making a dark 

 speckled rock. 



Mic. The larger hornblendes spread rather irregularly so as to embrace 

 poikilitically several other minerals, but they are broken and regenerated by new 

 growths. The minerals thus embraced are usually globular, and consist of feldspar 

 (often much altered), epidote, sphene, apatite and other hornblendes. 



The feldspar is much crushed and kaolinized. It appears to be wholly of 

 orthoclase; at least no striated twin-lines are visible. One section. 



Age. Archean. 



Remark. This rock seems to be of the age of the surrounding granite. It is 

 fresher than the greenstones of the Keewatin, and is probably a variant of the granite 

 of the region. N. H. w. 



