728 THE GEOLOGY OF MINNESOTA. 



[Amphibolyte. Chlorite schist. Granite. 



Xji/it>ne is rather common mainly in the form of irregular groups of small globules or 

 grains, but occasionally in isolated crystals. These groups have an elongation 

 parallel with the hornblendes. With an occasional large quartz the foregoing consti- 

 tute the colored elements. These elements lie in an interlocking fine network which 

 is in the main feldspathic, but somewhat quartzose, wholly of fresh and secondary 

 date, the ijitniiz sometimes becoming coarser and forming nests of interlocking grains 

 from which feldspar is wholly excluded. There is occasionally a trace of an older 

 feldspar, shown by its decayed state. This network of quartz and feldspar is also 

 interlocked in the margins of the hornblendes and encloses innumerable small 

 hornblende shreds. The horublendic fragments here differ noticeably from those at 

 Kekequabic lake. They are not sharp nor idiomorphically crystalline, but rounded 

 at their extremities. They do not show crystal boundaries, but appear to be shreds 

 or remnants (though fresh still) of hornblendes left after some destroying action 

 had passed over them, without any secondary growths. They surround the sphenes 

 and they sometimes embrace feldspar grains. They probably originated about 

 cotemporary with the surrounding network. One section. 



Age. Archean (Keewatin). x. H. \v. 



No. 1440. CHLORITE SCHIST. (Grc.cnutinic.J 



From the same bluff as No. 1439. 



Ref. Annual Report, xvi, pages 111, 126. 



Metj. Very fine grained. 



Mic. The rock embraces the same elements in about the same structure as No. 

 1489, but all much finer, and in place of sphene is a dark colored leucoxene. There 

 is also a much greater pi'oportionate amount of decayed feI</*/i<ir. which is accom- 

 panied by the generation of considerable calcite and by needles arrd scales of musco- 

 vite(?). Throughout the slide there is also much isotropic chloritic(?) substance. 

 Indeed the green element which takes the place of hornblende is in the main in this 

 condition. One section. 



Age. Archean (Keewatin). N. H. \v. 



No. 1441. GRANITE. 



Cuts Nos. 1439 and 1440. 



Ref. Annual Report, xvi, pages 111, 126. 



Meg. Ohloritic granite. 



Mir. The structure is granitic, with quartz, orlltoclasc and wicrorlim: The 

 small amount of chlorite and of hornblende is hardly worthy of notice in giving name 

 to the rock. The feldspars (except the microcline) are not much altered, though 

 interspersed with fine calcite and Muscovite. In the rock is a large percentage of 

 quartz. One section. 



Age. Archean. N. H. w. 



