PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 



Sericite schist. Tuff.] 



the same thickness. Hence we are disposed to consider that a portion of the higher 

 polarizing mineral may be epidote. Such grains are abundant and not fibrous, but 

 subangular and constitute an important element in the rock. N. H. w. 



No. 357. SERICITE SCHIST. 



"A chloritic slate, running nearly southwest and sloping to the southeast." Fall lake, at end of portage 

 to Long lake; N. E. M sec. 24, T. 63-12 W. 

 Ref. Annual Report, ix, page 92. 



Meg. A soft, fine-grained, fissile, greenish-gray, sericite schist. 



Mic. The section does not show any schistose structure and was thus cut parallel 

 to the cleavage. The rock is very fine grained, being composed essentially of very 

 minute grains (most probably both quartz and feldspar) and of flakes of sericite and 

 chlorite. There is also considerable epidote in minute grains and crystals, and also a 

 few hornblende fibres, and calcite. A number of larger quartz and feldspar grains 

 occur in the rock; these are not sharply angular, nor rounded, but they interlock 

 with the minute surrounding grains. The rock in general is quite similar to No. 351, 

 but the feldspars are more numerous and do not so much suggest that one larger 

 grain has been broken up to form smaller ones. 



One section. 



Age. Archean (Keewatin). u. s. G. 



No. 358. TUFF(?) ( " Greenstone. " ) 



Island near the west end of Long lake. Perhaps N. W. Y sec. 29, T. 63-12 W. 



Ref. Annual Report, ix, page 93; Annual Report, x, pages 89, 95; Bulletin ii, page 119. 



Meg. Light green, scarcely schistose, evidently decayed deeply, fine-grained, 

 with veins of quartz, resembling No. 356. 



Mic. This rock is one of the tuffaceous parts of the Kawishiwin, the minerals 

 being very indefinite. Still, there may be seen a considerable amount of calcite, a 

 secondary feldspar, which shows no cleavage and can hardly be distinguished from 

 quartz, quartz broken by pressure and with shadowy extinction, an isotropic substance, 

 and a leucojrene-gmy sub-isotropic substance. The only brightly polarizing mineral 

 is calcite. 



Two sections. 



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



No. 359. TUFF(?) ("Greenstone.") 



Prom the hill range running on the north side of Fall and Long lakes, taken on the portage from Burnt- 

 side river to Burntside lake; S. E. ^ sec. 23, T. 63-13 W. 

 Ref. Annual Report, ix, pages 93, 94. 



Meg. Firm, tough, dark gray or greenish, fine-grained, appearing gray and 

 granite-like at a distance when weathered. 



