SOUDAN FORMATION. 



231 



ore continue into the jasper, grower fewer and thinner, until finally the iron 

 formation consists almost exclusivel)^ of jasper and chert, with but isolated 

 narrow layers of ore in it. The banding of the jasper is seen to be con- 

 tinuous with that of the ore, which still possesses a banding, though an 

 imperfect one. 



At one place on Soudan Hill, north of open pit No. 6, a contorted 

 banded iron formation is cut by a dike which runs nearly north and south, 

 cutting across the bands of the formation (fig. 12). On the east side of 



Fig. 12.— Reproduction of sketch showing replacement o£ jasper by iron ore. After Smyth and Finlay.a 



the dike and between the dike and the jaspers and cherts there has been 

 formed a small ore deposit. Here the banding in the adjacent jaspers and 

 cherts appears to run right on through the ore, and although interrupted by 

 the dike is found to be continuous beyond this. 



At Ely the rock has been very much brecciated, but even there the 

 banding in the ores and their intimate mixture with the bands of jasper 

 seem to show very conclusively that their relation is essentially the same 

 as that of the ores and jaspers at Tower and Soudan which have been 



« Eeproduced from The geological structure of the western part of the Vermilion range, Minne- 

 sota, by Smyth and Fiulay: Trans. Am. Inst. Min. Eng., Vol. XXV, October, 1895, p. 643. 



