Muscovadyte. Cainptonyte.] 



PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 



785 



Remark. This rock is now believed to be a metamorphic condition of the 

 Keewatin greenstone. A chemical examination by Meeds gave a strong test for 

 titanium. N. H. w. 



No. 1785. MUSCOVADYTE. 



North shore of Bashitanequeb lake. 

 Ref, Annual Report, xxi, pages 150, 160. 



Meg. Finegrained. 



Mic. Identical with No. 1784, but with less magnetite. One section. 



Age. Cabotian (metamorphosed Keewatin). N. H. w. 



No. 1786. CAMPTONYTE. 



Branching conspicuous dike, or bleb, which crosses, in part at least, the townsite of Ely, in the highest 

 portion of the town, cutting the bouldery graywacke near the Catholic church. 

 Ref. Annual Report, xxii, page 5. 



Meg. Coarsely granular or sub-porphyritic. 



Mic. Idiomorphic crystals of dark hornblende are the most conspicuous part 

 of this rock. They were older than the feldspars, as they sometimes cut across the 

 feldspars. They are also generally slightly zoned, giving different colors of double 

 refraction in a manner similar to the hornblendes in the dike of Stuntz island (No. 

 872), but this feature is much less noticeable. Occasionally can also be seen a 

 green hornblende, which is doubtless a secondary development, since the brown(?) 

 hornblendes have occasionally green borders and fibrous appendages. Throughout 

 the slide are also numerous irregular grains of epidote, which are enclosed uniformly, 

 and often numerously, in the feldspars. They are also enclosed within the large 

 phenocrysts of pyroxene. They are usually, but not invariably, absent from the idio- 

 morphic hornblendes. They have the peculiarity of presenting different colors and 

 different angles of extinction within the same grain. 



Pyroxene, probably augite, exists as skeletons of phenocrysts, which have been 

 replaced in a micro-pegmatitic manner byfeldspar( ? ) and by a growth of hornblende. 

 These are larger than any of the feldspars, and evidently date from the first 

 consolidation. The feldspar has extinction on n e (acute bisectrix) at 19 to 20, 

 indicating albitc or (tndexine. Zoisite is common, and sphene is rare. Pennine also 

 fills some irregular spaces which were probably once occupied by an older feldspar. 

 One section. 



Age. Archean (dike). 



Remark. The appearances suggest that this rock in its present state is not only 

 altered by weathering, but that the magma fi - om which it was formed suffered some 

 change before it finally consolidated. There were at first some augites and some 

 feldspars. These are now largely replaced and in their stead are epidote, calcite 



