698 THE GEOLOGY OP MINNESOTA. 



[Quartzyte. Gabbro. Muscovadyte. 



a layer of basic sediments interstratified in the jaspilyte, and not as an intrusive of 

 the nature of the Logan sills of the Animikie. The general globular forms of the 

 minerals show the incompleteness of the fusion, and the occasional ophitic growths 

 of the augite show what would have been the rock had the recrystallization been 

 unimpeded. This interstratiflcation of basic and acid sediments in the iron lodes 

 of the Keewatin is illustrated by figures 1 and 2, page 48, of Bulletin vi. One section 

 examined. 



Age. Cabotian muscovadyte (modified Keewatin). N. H. w. 



No. 1343. QUARTZYTE (with fayalite, etc.; perulotyte). 



Sec. 25, T. 65-5, north of Flying Cloud lake. 



Ref. Annual Report, xvi, pages 87, 88, 122 ; Annual Report, six, pages 199, 201, 204. 



Meg. Quartz, with ferro-magnesian minerals. 



Mic. This is somewhat like No. 1340, but is in general coarser grained. It has 

 augite (diallagic), grunerite, fayalite. The quartz holds many globular inclusions of 

 the other minerals. Such small globules are also disseminated in the olivine and in 

 the hypersthene. The minerals are all fresh and perfectly intact as to chemical per- 

 fection, with abrupt boundaries but rounded outlines. There is a little also of the 

 orange-yellow mineral resembling what has been mentioned as bowlingite. One 

 section. 



Age. Pewabic (modified jaspilyte of the Keewatin). 



Remark. This is a remarkable rock, and is worthy of a special name, but the 

 horizon containing it does not always show all these minerals. It is stratigraphi- 

 cally in the place of some jaspilyte rocks. The question that arises as to its origin 

 can be stated thus: Is it the result of silicification of the gabbro, or is it the result 

 of the metamorphism of the jaspilyte? (See Part III.) If there be no irregularities 

 in the structure, the horizontal distance north and south over which it is exposed, 

 would give it a thickness of 300 to 500 feet, including interbedding gabbro. N. H. w. 



No. 1344. GABBRO (with biotite). 



Sec. 25, T. 65-5. Interbedded in No. 1343. 

 Ref. Annual Report, xvi, pages 87, 88, 122. 



Meg. Granular, like muscovadyte. Interbedded in No. 1343; eight feet thick. 



Mic. Playioclase, olivine, augite, biotite, magnetite. In the augite and in the 

 olivine are numerous globular inclusions, and these are occasionally seen in the 

 plagioclase. See the description of Nos. 1341 and 1365. One (thick) section. 



Age. Cabotian (regenerated Keewatin). N. H. w. 



No. 1345. MUSCOVADYTE. (Dioritic. ) 



Prom a hill south of Bingoschick lake, north from the last. 



Ref. Annual Report, xvi, pages 87-89, 94, 98, 122 ; Annual Report, xix, pages 199-201. 



