856 THE GEOLOGY OF MINNESOTA. 



[Conglomerate. Granite. Dioryte. Syenyte. 



No. 2191. CONGLOMERATE. 



Same place as No. 2190, but about 150 feet from the shore. 

 Ref. Annual Report, xxiv, page 59. 



Meg. The matrix of the rock is hard, green and rather fine grained; it contains 

 fragments and crystals of hornblende and of feldspar. There is one large pebble of 

 a very fine-grained, gray, pink-weathering, granitic rock, and also one of a diabase- 

 like rock holding small, little-elongated feldspars in a dark background. No section. 



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



No. 2194. GRANITE (with augite). 



N. E. % S. W. J4 sec. 19, T. 64-8, Snowbank lake. Small island. 

 Ref. Annual Report, xxiv, page 60. (Compare No. 271E.) 



Meg. Granite. 



Mic. This beautiful rock is porphyritic with an (egyrine augite which has its 

 idiomorphic forms. These crystals lie in a coarsely crystalline interlocking granite 

 of microcline, oligodase( ?) and orthoclase, in which is much sphene and also a little 

 biotite. The microcline appears to have intergrown jinn' pnxxu in some instances, 

 with another feldspar (oligoclase?), and in other cases to have served simply as a 

 cement to regenerate a decrepit old crystal. Frequently also these two feldspars 

 together form such cement, the only sign remaining of the original crystal being a 

 central area now so crowded with alteration products, chiefly mica, that it cannot 

 be studied. One section. 



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



No. 2195. DIORYTE. 



Just east of .the section line between sees. 19 and 20, T. 64-8, at the shore of Snowbank lake. 



Ref. Annual Report, xxiv, page 61. Compare Nos. 271E and 591E, Annual Report, xxii, page 189. 



Meg. Granitic. 



Mic. The feldspars (triclinic) are very much decayed, and the ferromagnesian 

 minerals are hornblende and biotite, largely altered to clinochlore. Epidote is abundant 

 especially in the clinochlore and also associated closely with magnetite. One section. 



Age. Archean (intrusive). 



Remark. Mr. Elftman obtained rocks near the same place which he found were 

 augite granite. If this rock were ever augite granite, which is possible, it has lost 

 that nature probably by weathering. N. H. w. 



No. 2196. SYENYTE. (Porphyritic.) 



North shore of Snowbank lake, at line between sees. 19 and 20, T. 64-8 W. 

 Ref. Annual Report, xxiv, page 62. 



Meg. A very fine-grained reddish rock, composed largely of feldspar. There 

 are some feldspars which are porphyritic, but the fact that these feldspars on fresh 



