(B) 



ADDITIONAL PETROGRAPHIC DESCRIPTIONS. 



No. 1527. HEMATITE. (Taconitic. ) 



sec. 34, T. 56-25 W. 



Ref. Annual Report, xviii, pages 15, 60 ; Bulletin vi, pages 120, 422 ; Final Report, v, pages 737, 991; also, 

 plate IV, figure 1. 



Meg. Basaltic hematite. 



Mic. The globular structure characteristic of taconyte is very evident. It 

 becomes less evident in the crystalline massive hematite, but still it can be seen 

 both in transmitted and in reflected light that the globular structure pervades 

 the whole. The fine, scattered, angular spaces lying between the original grains, 

 even in the massive hematite, are occupied by the usual fine quartz mosaic, showing 

 that the same oceanic precipitate penetrated even amongst those grains which were 

 converted entirely to hematite. One section. 



Age. Animikie (iron-bearing member). N. H. w. 



No. 1689. TUFF. 



From the Cincinnati property, Mesabi Iron range, sec. 2, T. 58-16 W. 

 . Ref. Annual Report, xxi, pages 118, 155 ; Final Report, v, page 760. 



Meg. Coarsely tuffaceous; generally dark, or greenish-black, some of the 

 original angular fragments being about an inch in longest diameter and of a flinty 

 fineness. From this size these flinty pieces graduate downward in size and become 

 the taconitic globular masses characteristic of the rock bearing the Mesabi soft ores. 

 In some parts these taconitic globules compose the most of the rock, though with a 

 liberal supply of magnetite. 



Mic. The section made is so thick that the taconitic globules are for the most 

 part wholly non-transparent. It serves to outline the globules, and to show the 

 inter-granular quartz mosaic which is in part replaced, in a narrow border about 

 each globule apparently by fibrous rusty actinolite. 



Age. Animikie; iron-bearing member. One section. 



Remark. This rock reveals the former activity of volcanoes in the region now 

 occupied by the most valuable mines of the Mesabi Iron range. Connected with 

 similar evidences presented for the extreme western and eastern ends of the Mesabi 

 range, it is apparent that the chief feature of the whole range consists in the agency 

 of volcanoes in the production of the rock that carries the ore. N. H. w. 



