GUNFLINT LAKE PLATE OP THE MESABI IRON RANGE, 1899. U. S. GRANT. 



The iron was probably in the same manner precipitated, in part, from the ocean. 

 Still, both silica and iron were doubtless supplied by the obsidian itself. 



Whenever the cotemporary lava was not cooled rapidly, but became crystallized, 

 it must have constituted, and probably constitutes to this day, igneous rock. If it 

 was submarine it probabLy was affected by more or less impregnation by iron and 

 silica. Such may be the cause of much of the aporhyolytes and so-called red rock, 

 though perhaps not at this date. Yet it is not known what may be the date of the 

 red granites, etc., of the Misquah hills which cross the southern part of this and the 

 Akeley Lake plates. 



The stratified flints of the region of Gunflint lake are probably derived from 

 fine clastic, mostly igneous, sediments, mingled with chemical sediments, and are 

 comparable to the sedimentary jaspilytes of the Vermilion Iron range (see the Ver- 

 milion Lake plate). They should not be confounded with the silicified apobsidian 

 breccia mentioned above. N. H. w. 



