PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 609 



Gneiss. Graywacke. Chlorite schist.] 



No. 945. GNEISS. (Dioritic.) 



S. W. J< sec. 23, T. 63-16 W.; north shore of Vermilion lake. 

 Ref. Annual Report, xv, pages 301, 390. 



Meg. A medium-grained, dark-gray rock, composed mainly of hornblende and 

 feldspar. The specimen is somewhat banded by bands in which the relative propor- 

 tion and size of the grains of the two constituents vary. 



Mic. The section shows a granitoid rock, composed almost entirely of green 

 hornblende (in great abundance ), feldspar (common and usually much kaolinized) and 

 quartz (in small amount). 



One section. 



Age. Archean. u. s. G. 



No. 946. GNEISS. (Granitic.) 



N. E. J4 sec. 27, T. 63-16 W.; north shore of Vermilion lake. 

 Ref. Annual Report, xv, pages 301, 390. 



Fine grained, red, and composed of feldspar, quartz and a dark micaceous 

 mineral, whose flakes are arranged with their cleavage planes nearly parallel, thus 

 giving a gneissic structure to the rock. 



Mic. An ordinary granitic rock, composed essentially of feldspar (commonly 

 clouded, and in part acid plagioclase), quartz and chlorite. 

 One section. 



Age. Archean. u. s. G. 



No. 947. GRAYWACKE (?) 



N. E. M sec. 3, T. 62-15 W. ; northeast shore of Vermilion lake. 

 Ref. Annual Report, xv, pages 301, 390. 



Meg. A greenish-gray rock of fine grain. There are small hornblendes and 

 feldspars scattered through the rock. 



Mic. This section is quite similar to No. 920. 

 One section. 



Age. Keewatin. u. s. G. 



No. 948. CHLORITE SCHIST. 



"On the N. W. J4 sec. 28, T. 63-11 [Garden lake], a diabasic green rock (No. 949) cuts a greenish, hard, 

 finely schistose rock (No. 948), the contact being well exposed on the south side for a distance of a few feet." 

 Ref. Annual Report, xv, pages 329, 390. 



Meg. A soft, green, fine-grained schist. 



Mir. The section shows chlorite, calcite, quartz (and perhaps also feldspar) and 

 epidote. There is much fine, granular material which is perhaps epidote. 

 One section. 

 Age. Keewatin. u. s. G. 



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