PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 727 



Granite. Amphiboly te.] 



Mfg. Medium grained, granitic or gneissic. 



Mic. This rock, in the same manner as No. 1427, is made up of old feldspars and 

 new generations, with biotite and hornblende, all embraced in a coarse, granitic, 

 interlocking, new generation of quartz and feldspar. The old feldspars are com- 

 pletely permeated by quartzes and by new-grown feldspar and are sometimes almost 

 lost by the new invasion, but very frequently they remain as cloudy nuclei surrounded 

 by fresh borders. There is also in the section a light-yellow pyroxene resembling 

 epidote, but differs from epidote in not having the axial plane perpendicular to the 

 main cleavage, but forming an angle of 30 in the section exposed. This is 

 probably diopside. This diopside is developed in a spreading, straggling manner, 

 often in scattered small granules, in the midst of one of the old feldspars. One section. 



Age. Archean granite. 



Remark. Coming upon this rock after the details of the examination of the 

 Kekequabic lake granite, the comparison is vivid and complete. It suggests the 

 question whether all the Bassimenan lake granite is not of the same sort, a regen- 

 eration of elastics. As to the cause of that regeneration, it is not possible here to 

 enquire. But that the process seen commenced in some of the gray wackes or green 

 schists and carried out to an imperfect degree in the granitic rocks about Kekequabic 

 lake, is completed here in the Bassimenan lake granite (or gneiss), is as palpable 

 as any petrogenetic process can be made. N. H. w. 



No. 1437. AMPHIBOLYTE. 



S. W. J4 sec ' 5, T. 64-10. Long peninsula in Bassimenan lake. 

 Ref. Annual Report, xvi, page 126. 



Meg. Dark, micaceous and hornblendic. 



Mic. Hornblende, much of it zoned by second growths is the chief coloring 

 matter, but biotite is common, also sphene, which indeed is unusually common. The 

 hornblendes are earlier than the quartz and than most of tiae feldspar, being idiomor- 

 phic toward all the rest and unbroken except by their own interference and by an 

 occasional biotite. There are a few nuclei of the old feldspars still visible, but most 

 of the feldspar and all of the quartz is of secondary granitic origin and structure. 

 One section. 



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



No. 1439. AMPHIBOLYTE. (Greenstone.) 



Bluff on the right bank, just below the Pipestone rapids, southwest extremity of Bassimenan lake. 

 Ref. Annual Report, xvi, pages 111, 126. 



Meg. Even-grained, schistose greenstone. 



Mic. The hornblendes are rather small and prevailingly elongated in the same 

 direction. It is green or bluish-green with variation to yellowish on rotation. 



