PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 327 



Mica schist. Granite or gneiss.] 



Mic. The section consists largely of non-striated and striated feldspars, one of 

 the latter giving on n f an extinction of 79, indicating a feldspar between amlesine- 

 oligoclase and oligodase. The non-striated feldspar is probably ainlcsine, and would 

 show striations if the section were thinner and the grains were properly cut. The 

 presence of evident grains of microdine, however, rather favors orthoclase instead of 

 andesine. Quartz is quite common, and hornblende is sufficient simply to warrant the 

 name hornblende-granite. 



One section. 



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



No. 346. MICA SCHIST (with epidote. }. 



"Passing to the north side of this bay, within a half mile, or perhaps more, the whole changes to a fine, 

 tough gneiss, which has a coarse schistose structure that makes it resemble the schists, being probably only a 

 variation of the schists." Bassimenan (Basswood) lake; perhaps in sec. 11, T. 04 11 W. 



-Re/. Annual Report, ix, page 90. 



Meg. A fine-grained, dark greenish schistose rock, composed of much biotite 

 (with some chlorite) and gray to pink feldspar. 



Mic. The section shows a decided schistose structure due to the approximately 

 parallel "streams" of biotite and epidote. Besides these minerals there are feldspar, 

 quartz, chlorite, calcite and a micaceous mineral due to alteration of the feldspar. 

 The feldspar is often much altered, and this and the quartz are often in very fine 

 grains. 



One section. 



Age. Archean (Coutchiching). u. s. G. 



No. 347. GRANITE OR GNEISS nmth hm^nblendej. 



"A little further along, across the bay, the syenyte returns; but here a schistose structure can be seen on 

 weathering, parallel to that seen all along. This forms the coast for some distance on the north side, at least to 

 within one-half mile of the next portage." Bassimenan (Basswood) lake; perhaps in sec. 11, T. 64-11 W. 



Ref. Annual Report, ix, page 90. 



Meg. A gray, rather fine-grained, granitic rock, consisting of hornblende, gray 

 to pinkish feldspar, quartz and epidote. 



Mic. The section shows feldspar, hornblende, quartz and epidote. Part of the 

 feldspar is very highly altered ; a large part of that which is fresh shows the character- 

 istic microdine grating in polarized light. One of these grains, showing but one set 

 of twinning strise and thus cut parallel to the brachypinacoid, gave a positive bisectrix 

 and an extinction angle of 9, all of which corresponds closely to microdine. Some- 

 times the larger feldspars include the other minerals poikilitically. The epidote is 

 abundant, especially in minute grains and crystals in the immediate vicinity of the 

 hornblende. 



One section. 



Age. Archean (Coutchiching). r. s. G, 



