212 THE VERMILION IRON-BEARING DISTRICT. 



There are some large exposures of jasper in the NE. ^ of sec. 25, 

 T. 63 N., R. 12 W., and this locality has been prospected thoroughly by 

 means of diamond-drill borings. The way in which the iron-bearing 

 formation is closely infolded in the Ely greenstone is well shown upon 

 Sheet XXVI of the accompanying atlas, the data for the construction of 

 which have been obtained from the Minnesota Iron Company. 



CXiASTICS ASSOCIATED WITH THE IROlSr-BBAIlIlS^G FOEMATIOK. 



There is only one place in the Vermilion district at which the clastic 

 rocks are associated with the iron formation in such a way that no question 

 can be raised that the}^ belong together and that there is a gradation from the 

 one into the other. This place is just south of the north quarter post 

 of sec. 7, T. 62 N., R. 13 W., on the south slope of a hill. At this place the 

 narrow bands of iron formation are interbanded with bands of conglomerate 

 and slate. There are evidently several series of these bands, although it is 

 possible that there may be in places a reduplication due to the close folding. 

 The conglomerate is made up of fragments derived from the immediately 

 subjacent greenstones, and as these fragments grow smaller the sediments 

 grade upward through graywackes into finely banded greenish slates, next 

 to which occurs the iron-bearing formation, consisting of chert, jasper, iron 

 ore, and an occasional band of material that may correspond to the finer- 

 grained slates adjacent. 



Somewhat similar conditions were observed on the hill in the NW. 

 I of the SE. J of sec. 10, T. 62 N'., R. 14 W., which overlooks the large 

 swamp to the northwest, although the proof of the relationship is, perhaps, 

 not quite so clear. Here there is a large exposure of jasper in which a shaft 

 has been sunk and through which a considerable quantity of pyritiferous ore 

 has been hoisted. The jasper is followed to the south by a fragmental rock 

 made up of fragments of greenstone. This is about 10 feet distant from 

 the jasper. The fragmental rock is thoroughly impregnated with partial 

 pseudomorphs of limonite after jDyrite. South of this fragmental occurs an 

 amygdaloidal lava. The sediments and the greenstone are both slightly 

 schistose, the schistosity striking about; ^^^t and west. South and west of 

 this locality a number of other exposures of greenstone, associated with a 

 fragmental rock made up of greenstone fragments, was observed. In none 

 of the sediments could well-marked sedimentary banding be found. 



