PETROGRAPHIC GEOLOGY AND DESCRIPTIONS. 1005 



Flimt. Conglomerate.] 



No. 433H. FLINT. (Taconitic.) 



Gunflint lake, north shore, a few rods west of the entrance of a small creek which flows into the lake from 

 the north just north of the mouth of the Boundary (Gunflint) river, about an eighth of a mile up the creek. 

 This rock appears to be vertically bedded, and when collected was supposed to belong to the Keewatin. 



Ref. Annual Report, xvii, page 104. This rock is of the same character as No. 1277, which occurs at the 

 lake shore and lies nearly horizontal. 



Meg, Black or greenish black, fine as flint, with conchoidal fracture, frequently 

 jointed, but with a band of coarser grain running like a sedimentary layer through 

 the middle, parallel with the sides. Petrographically this grades into rock No. 

 436H, below. 



Mic. Plainly taconitic. The interstices between the globules are completely 

 filled with the usual quartz mosaic, but the globules are only partly so occupied. 

 Some are wholly replaced by quartz, but the majority are still rather amorphous or 

 are crowded with dirty impurities through which, between crossed nicols, but faint 

 light can be seen to pass. It is yellowish, and distributed in a mosaic fashion 

 throughout the globules, showing probably the initial establishment of the same 

 quartzose background. In other globules the circumferential iron rim is conspicuous, 

 though rarely entire. The globules are all subangular, some are club-shaped, and 

 some are crescentic. The intraglobular quartz mosaic is finer than the interglobular. 

 Plate v, figure 10. One section. 



Age. Animikie; iron-bearing (flinty) member. 



Remark. There is a notable difference in the appearance of the different glob- 

 ules, as to coarseness and completeness of silicification, as well as between the matrix 

 and all the globules. These contrasts can be explained by supposing that the sand 

 itself was not a homogeneous substance, but contained grains ofsilicified rhyolyte 

 as well as non-silicified, and that the oceanic precipitation of silica formed a coarser 

 matrix which embraced them all alike. N. H. w. 



No. 436H. CONGLOMERATE. (Taconitic.) 



Near the same place as the last, but about an eighth of a mile further up the same creek. Here the creek 

 spreads out into a marshy lake. At the head of rapid water on the east side of the stream are thick beds of 

 horizontal Animikie of the nature of a somewhat decomposed, fine, dark conglomerate, some of the pebbles, how- 

 ever, being about an inch long, but flattened horizontally. This conglomerate is unquestionably the same as 

 rock' No. 1294. 



Ref. Annual Report, xvii, page 104. 



Meg. A rusty conglomerate, but cemented by quartz, becoming finer and 



grit-like. 



Mic. This is simply a coarse phase of the taconyte of the Animikie. It presents 

 nearly every aspect mentioned under Nos. 1294 and 1530, and in addition has the 

 character of being a conglomerate. One section. 



Aye. Animikie. 



Remark. It is evident that these pebbles, when they were gathered into these 

 conglomeratic beds, must have been harder than ordinary glauconite, and that they 



