672 THE GEOLOGY OP MINNESOTA. 



[Micro-granite. Amphibolyte. Gabbro. 



Mey. Hornblendic and gneissic. 



Mir. This rock, microscopically, is like No. 1128. It is wholly crystalline and 

 granitic in structure. Hornblende constitutes somewhat more than one-half of the 

 mass. One section. 



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



No. 1138. MICRO-GRANITE. (Aplyte.) 



Meander line between sees. G and 7, T. 62-11, White Iron lake. 

 Bef. Annual Report, xv, pages 331, 399. 



Meg. Fine grained, granitic. From dikes cutting granite. 



Mic. Quartz, microcline, oligoclase in rather fine, interlocking allotriomorphic 

 grains make up the bulk of this rock, but there is also a little hornblende, xjt/triie and 

 epidote. One section. 



Age. Archean. N. H. \v. 



No. 1134. AMPHIBOLYTE. 



Lake shore in sec. 12, T. 62-12, White Iron lake. 



Ref. Annual Report, xv, pages 331, 338, 399 ; Annual Report, xvii, pages 198, 207. 



Meg. Granitic, dark colored, cut by veins of granite. 



Mic. Hornblende is the most conspicuous element, but shares the rock liberally 

 vt\\\\"biotitp. These constitute perhaps one-half of the rock, the rest being mainly of 

 feldspar, but yet with a little quartz and a few scattered Nplicnes. One section. 



Age. Archean (changed Keewatin). 



Remark. This rock is petrographically like Nos. 112S and 1132, and probably 

 has the same origin. N. n. \v. 



No. 1135. AMPHIBOLYTE. (Chnnyed Kenc/itin. ) 



Prom small dikes cutting the granite vein above mentioned. 

 Ref. Annual Report, xv, pages 331, 399. 



Meg. Dark, hornblendic. 



Mic. Similar to the last, but has no biotite and less hornblende, with evident 

 epidote. One section. 



A(je. Archean (changed Keewatin). x. H. \\. 



No. 1136. GABBRO. 



From a point about half a mile west of the line between sec. 31, T. G2-11, and sec. 0, T. 01-11, in town 61, 

 Birch lake. 



Ref. Annual Report, xv, pages 332, 399. 



(Jray, granitic in structure, with much feldspar. 

 Mir. Feldspar has extinction angle of 62 on n f , and is hence labradorile. 

 The angite is sometimes crowded with interlamellar inclusions. The magnetite is not 

 infrequently bordered by biotite. The d-iallngie augite was about cotemporary with 



