BLACKHOOF AND MOOSE RIVER VALLEY EXPOSURES 351 



the rock. Rarely in the vicinity of tlie veins the quartzite schists seem 

 to be greatly shattered and receniented, thus having the appearance of 

 a breccia. 



In such localities the quartz is generally associated with siderite, 

 when fresh, and with a spongy, rusty condition when weathered. This 

 rusted, porous condition extends in places into the schist for many feet. 

 It gives evidence of the earlier presence of some accessory mineral, prob- 

 ably iron-carbonate. It occurs in zones of well defined distribution. 



MoosE River Valley 



MAHTOWA EXPOSURES 



Around Mahtowa are several exposures of the quartzite-schists stretch- 

 ing westward from the Blackhoof valley. In section 5, township 47, 

 range 18, is a ledge of rather massive rock, with schistose structure 

 locally developed. The slaty cleavage characteristic at Thomson and 

 Cloquet is lacking. The rock breaks coarsely, and carries evidence of 

 much pyrite or iron carbonate below its zone of weathering in the cubical 

 and rhombohedral cavities so frequently seen. 



Pressure has resulted in a folding, quite clearly shown in some hand 

 specimens. Wells give evidence of wide distribution of these rocks 

 slightly below the surface. 



BARNUM EXPOSURES 



The schists are widely exposed over miles of almost level surface 

 around Barnum. At the railway depot there is some contortion, a 

 gentle dip southward, an alternation of foliated and quartzose phases, a 

 collection of quartz lenses, and an absence of slaty cleavage. The foliated 

 is the dominant structure, and the southerly the dominant attitude of 

 these rocks. Half a mile west of the station the rocks are more uniform, 

 lithologically and structurally, and some quarrying has been done on 

 that account. The dip southerly is slight, probably not over 5 to 10 

 degrees and interfoliated bands of glossy schist are only an inch or two 

 thick at a maximum. 



Northwest of the station, in section 15, township 47, range 19, there is 

 an exposure in which a pyrite-bearing vein and diabase dike afford 

 lithologic diversity. The badly weathered schists possess the same gen- 

 eral characters as the rocks beside the railway. The locality is in the 

 bank of a stream, and so covered that directions are difficult to deter- 

 mine with exactness. The vein has been assayed for gold ; a good trace 

 was found. 



L— rJuLL. Geol. Soc. Am., Vol. 12, 1900 



