724 THE GEOLOGY OF MINNESOTA. 



[Gneiss. Ainphibolyte. 



No. 1420. GNEISS. 



West end of Animikie island, Kekequabic lake. 

 Ref. Annual Report, xvi, pages 105, 125. 



Meg. Similar to Nos. 1417, 1418, 1419. 



Mic. The largest feldspars are reconstructed by a microperthitic intergrowth 

 of a fresh feldspar, which sometimes composes more than a half of the whole. The 

 rock also contains more calcite and coarser qnariz than the others. One section. 



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



No. 1421. AMPHIBOLYTE. ( Greemvacke,. ) 



Southwest end of Kekequabic lake ; sec. 4, T. 64-7. 

 Ref. Annual Report, xvi, pages 105, 125. 



Meg. Somewhat conglomeritic. 



Mic. The most conspicuous feature is the abundance of hornblende, which is 

 not only in distinct crystals, often showing its prismatic cleavages in basal sections, 

 but in minute fibres scattered everywhere. The old feldspars are in remnants, in 

 the main, from their original sizes, being eaten up by the prevalent alteration of the 

 micro-granulitic substance mentioned in the description of No. 1419. In some cases 

 a considerable portion of the feldspar substance remains and extinguishes uniformly. 

 In other cases parts of it remain, contiguous, but extinguishing at slightly different 

 angles, those parts being permeated at their borders by the same granulitic alteration, 

 and in still other feldspars the entire crystal is sufficiently intact to show its form 

 and its size, with complete and simultaneous extinction (though still varying in a 

 shadowy manner). These most intact feldspars are still sprinkled throughout with 

 en/cite. /ii/r>ixi'iie and zoisite, so that their albite twinning is scarcely visible. 



The hornblendes are supplied with slight secondary growths. In some places 

 they are bent, and certain branching ramifications, which enclose the large horn- 

 blendes, are composed of a yellowish and dirty granulated substance, which is appar- 

 ently hornblendic and has resulted from a crushing of the hornblende crystals along 

 their mutual contacts. These all lie, as in numerous other instances, in a very fine 

 plexus of feldspar, actinolite and quartz, with a little Ici/m/'c/ie and magnetite, the 

 amount of quartz being small and uncertain. One section. 



Age. Archean (modified Upper Keewatiu). N. H. w. 



No. 1422. GNEISS. 



From a small island south of the point, west part of sec. ,'i, T. (!1 7, Kekequabic lake. 

 Ref. Annual Report, xvi, pages 105, 12.") 



Meg. Greenish, with sparsely disseminated red crystals. 



Mic. There is much calcite in this rock. The old feldspars are very much 

 permeated and replaced and zoned by secondary feldspars, and very much of the rest 



