PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 637 



Biotitc schist. Gabhro.] 



Mic. There are a few small plagioclases(1} which still are. so much larger than 

 the rest of the grain of the rock that microscopically they appear like porphyritic 

 crystals, though they are not idiomorphic, and they may be conlierite instead. The 

 most of the rock is micro-crystalline interlocking quartz, with bands and clusters of 

 hint He scales. One section. 



.l;/c. Keewatiu metamorphosed by the gabbro revolution. N. H. w. 



No. 1036. BIOTITE SCHIST C with Itm-nblendeJ. 



From Illusion lake, sec. 13, T. G4-8. 

 Ref. Annual Report, xv, pages 359, 394. 



Mc<j. Fine grained. Similar to the last, evidently arenaceous, at least siliceous. 

 Mic. Quartz grains, as in the last, are the most abundant element of this rock. 

 llnnililcndc, liotilc and magnetite are scattered amongst them. One (thick) section. 

 Age. Keewatin metamorphosed by the gabbro revolution. N. H. w. 



No. 1037. GABBUO. (Musuovadyte.) 



East side of Illusion lake, sec. 13, T. (>4 8. 



Ref. Annual Report, xv, pages 359, 395; Annual Report, xxi, page 152. 



Mi-g. Finely granular, gray or yellowish. 



Mic. The rock is finely granular, with a tendency to globular outlines for all 

 the minerals. There is no evidence of difference of date in the generation of the 

 various minerals, except that the plagioclase in some cases was apparently the last 

 to take form. These *XQ plagioclase, hyjpersthene, augite,the hypersthene being most 

 abundant and frequently embracing minute globules of the same mineral. One 

 (thick) section. 



Age. Oabotian; modification of the Keewatiu. 



Remark. The slightly rusty condition of the hypersthene and the thickness of 

 the slide gives an appearance of olivine to much of the hypersthene, but, as no jelly 

 was formed in HC1, it is presumed that no olivine is in the rock. N. H. w. 



No. 1038. GABBRO. 



South shore of Illusion lake, sec. 13, T. 64-8, south shore, and on a small island. 

 Ref. Annual Report, xv, pages 359, 395. 



Meg. Coarse gabbro. 



Mic, The most of the slide is occupied by a single plate of feldspar, but it sur- 

 rounds several small areas of altered augite and olivine. This plate is cut nearly 

 perpendicular to as acute bisectrix, and has extinction at 24 from cleavage, 

 indicating labradorite. The augite shows an alteration resembling the lamellation 

 of diallage, but it is to be considered uralUic. One section. 



Aye. Cabotian. N. H. w. 



