PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 607 



Granite. Schist. Chlorite schist.] 



Mic. The rock is an ordinary granite; the essential minerals are feldspar, 

 quartz and Motite. The feldspar is apparently orthoclase and oligodase, with a little 

 microcline. The quartz often shows undulatory extinction. The following accessory 

 minerals occur in varying amounts: chlorite, muscovite, epidote, magnetite and sphene. 



Two sections. i 



Aqe. Archean. u. s. G. 



i 



No. 937. GRANITE. (Biotitic.) 



From a small island just east of Big island, Vermilion lake; N. W. J sec. 22, T. 63-18 W. 

 Ref. Annual Report, xv, pages 297, 390. 



Meg. A medium-grained, light-gray granite, composed of quartz, white feldspar 

 and a comparatively small amount of biotite. 



Mic. An ordinary granite, in general similar to No. 936, the essential minerals 

 being quartz, feldspar (apparently orthoclase, oligodase and a little microcline) and 

 biotite. 



One section. 



Age. Archean. i). s. G. 



No. 938. SCHIST (with zoisite). 



West side of Oak island, Vermilion lake; S. W. J sec. 23, T. 63-17 W. 

 Ref. Annual Report, xv, pages 294, 390. 



Meg. A hard, gray, compact, fine-grained, but little schistose, rock looking like 

 a graywacke or impure quartzyte. 



Mic. The section is composed mainly of quartz, feldspar (considerably altered) 

 and a mineral of high index of refraction and weak double refraction, which is 

 thought to be zoisite; this is very abundant. Other minerals are hornblende, chlorite, 

 muscovite, magnetite and sphene. 



One section. 



Age- Archean. u. s. G. 



No. 939. CHLORITE SCHIST. 



Small island in S. E. % sec. 31, T. 63-16 W.; Vermilion lake. 

 Ref. Annual Report, xv, pages 299, 390. 



Meg. A soft, fine-grained, green schist. The specimen contains part of a lentic- 

 ular mass of coarse, white vein quartz. 



Mic. The section is fine grained, and consists essentially of calcite, chlorite, 

 cpiilote and quartz. One section. 



Age. Archean. u. s. G. 



No. 940. PEGMATYTE. 



North shore of a bay of Vermilion lake, north of Pine island; S. W. J4 sec. 23, T. 63-16 W. 

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



