370 THE GEOLOGY OP MINNESOTA. 



[Slate. Shale. Conglomerate. 



Mic. The principal ingredient is quartz, in rounded grains which have iron 

 rust about their borders. But itiicrocline, orthoclase, Muscovite and micro-granulitic 

 quartzyte are common. Some of the pebbles are cloudy, being an imperfectly devit- 

 rih'ed glass. The quartzes are to some extent enlarged by secondary quartz, and in some 

 of the interspaces is a fresh interlocking fine-grained quartz of secondary origin. 



Age. Cambrian (in other places associated with the Manitou trap sheets). 



N. H. W. 



No. 446. SLATE. (Black.) 



Near the centre of the south side of S. E. % sec. 30, T. 49-15 W. The exposure is in the bottom of a branch 

 of Mission creek. Slaty cleavage strikes east and west. 

 Ref. Annual Report, x, pages 11, 30. 



Meg. A very dark gray or black slate. It cleaves rather roughly and apparently 

 is not so fine grained as most slates, but its constituent grains cannot be distinguished. 

 Crossing the slaty cleavage, at an angle of about 20, is a rough, schistose structure. 



No section. 



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



No. 447. SHALE. (Gray.) 



Near centre of south side of S. E. % S. E. % sec. 31, T. 49-15 W. In Mission creek. Slaty cleavage strikes 

 in the same direction as in No. 446. 



Ref. Annual Report, x, pages 11, 30. 



Meg. A very fine-grained, light greenish-gray, soft slate or perhaps more 

 probably a shale. 

 No section. 

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



No. 448. CONGLOMERATE. (Red. ) 



Near same place as No. 445. 

 Ref. Annual Report, x, page 11. 



Meg. Specimen missing. 



No section. 



Age. Cambrian (i, e., " Upper" Cambrian.) u. s. G. 



No. 449. CONGLOMERATE. (Pyritifemiix. ) 



S. W. X N. E. X sec. 1, T. 48-16 W.; St. Louis valley. 



Ref. Annual Report, x, pages 11, 12, 17, 30. (Compare No. 1975.) 



Meg. Hard, pebbly with vein quartz, with much pyrite, and having in general 

 a light-gray color. Dips with the red beds about 10 E. of S. Some of the pebbles 

 are two or three inches across. In some places nearly one-half of the pebbles are of 

 the underlying slate formation. Nothing of a Keweenawan origin can be found in 



