772 THE GEOLOGY OP MINNESOTA. 



[Quartz-feldspar, hornblende 

 and mica schist . 



with considerable hornblende, gives a greenish coloration to this rock. ( 'a/cite is also 

 common. Some of the quartz seems to be in its original clastic state, but most of it 

 is of secondary origin. One section. 



Age. Archean. > w. 



No. 1731. QUAKTZ-FELDSPAK SCHIST. 



Same place as No. 1729. 



Ref. Annual Report, xxi, page 137. 



Meg. Part of the conglomerate, a phase of No. 1730. These are both intimately 

 associated with characters pertaining to the Kee'watin greenstone, of which they 

 seem to be conditions more feldspathic and coarser. 



Mic. The feldspars are all smaller, roundish, altered in the same way but usually 

 also containing chlorite as one of their products of decay. The same chlorite is 

 distributed sparsely, moreover, throughout the slide, result of alteration of hornblende, 

 in clastic, angular grains of considerable size, considerable epidote and a little 



e should also be noted. One section. 



Age. Archean. N. H. w. 



No. 1732. HORNBLENDE SCHIST. 



S. W. 4 sec. 24, T. G4-9, shore of Snowbank lake. 

 Ref. Annual Report, xxi, page 157. 



Meg. The conglomerate grades into this. It is cut by many dikes of red granite. 



Mic. This rock differs from No. 1724 in the following points: The old feldspars 

 were all small and have nearly disappeared; hornblende is abundant and is arranged 

 in sheets of greater and of less abundance; a powder of hematite is sprinkled every- 

 where in the slide; quartz is almost wanting. One section. 



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



No. 1733. MICA SCHIST. 



Sec. 24, T. 64-9, shore of Snowbank lake. 

 Ref, Annual Report, xxi, page 157. 



Meg. The conglomerate grades into this; fine grained. 



Mic. With a strong schistose structure this rock consists of biotifc, tjnartz, feld- 

 spar, in which last are included microcline and oligoclase. Microcline encloses the 

 biotite and the quartz and interlocks with itself, while the biotite was earlier or 

 cotemporary with the quartz. There are but slight traces of the original clastic 

 grains, still in many places some of the old grains are visible in the presence of dirty 

 and minutely finely crystalline spots, in which frequently many globular feldspars 

 appear along with sericite. 



Judged by its contents and its crystalline grain this might be called a granite, 

 but it is distinctly schistose. One section. 



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



