354 ■ THE VERMILION IRON-BEARING DISTRICT. 



or 6 miles across, at a point south of White • Iron Lake. The portion in 

 the area described in this report is rarely more than 2 miles wide and 

 usually less than that. Indeed, that part of the granite which was actually 

 studied represents merely the border of the granite, for the reason that in 

 most cases our traverses were ended at the northern border, as the prime 

 object of the survey was the delimitation and study of the formations in 

 the iron-bearing district proper. 



Exposures. — The exposures of granite are good, as the area in which 

 it lies is well dissected by streams and contains a number of lakes. The 

 exposures are especially good on White Iron Lake, in T. 62 N., Rs. 11 

 and 12 W. 



Topography. — The topography is that usually seen in the granitic areas 

 of the Lake Superior region, consisting of low rounded to oval hills with 

 lakes here and there in the intervening valleys. The range of hills formed 

 by the Giants Range granite is the topographic continuation to the north- 

 east of the Mesabi or Giants range of the Mesabi district. The hills are 

 nowhere high, however, and do not show very well the character of a hill 

 range. 



About 2 miles southeast of Ely and extending from sec. 11, T. 62 N., 

 R. 12 W., to sec. 26, T. 62 N., R. 13 W., there is an area underlain by this 

 granite which is very similar to that occurring north of the district on Iron 

 Lake (see p. 259). This area is almost base-leveled, the lakes into which 

 it is drained representing the level to which the surrounding land has been 

 very nearly reduced. This area is very much larger than that occumng 

 near the international boundary before referred to. Here the swamps are 

 extensive and the elevations are very slight, being flat hillocks of granite 

 rising as a rule only a few feet above the adjacent low ground. 



PETROGRAPHIC CHARACTERS. 



Macroscopic characters. — The Giants Range granite includes a series of 

 granites ranging in color from light gray to very dark gray, to flesh color, 

 pink, and red. • The grain varies also very materially, the rock passing from 

 very dense fine-grained granites through medium to coarse-grained ones. 

 While this rock is, as a rule, granitic in texture, there are also variations 

 to granite-porphyries and exceptionally to some that can be spoken of as 

 rhyolite-porphyries. These granite- and rhyolite-porphyry dikes are nor- 



