﻿266 R. D. Irving — ferruginous Schists and 



which are to be subsequently rioted. The iron ore bodies of 

 the region lie within these cherty schists, not in iens-shaped 

 masses around whioh the schist bends, but in irregular bodies 

 directly in the course of the schistose banding, or in more defi- 

 nite layers within the schist, and seem to have arisen from two 

 causes, or from a combination of them, viz: from direct oxi- 

 dation of the bands of the carbonate in place and from the de- 

 position within the schist, from percolating waters, of oxide of 

 iron. In short, we have, in this region, except that no con- 

 siderable body of unsilicified carbonate has as yet been met 

 with, all of the indications found in the Animike and Penokee 

 formations, of a derivation of both ferruginous rocks and iron 

 deposits by a process of silicification from stratiform shales im- 

 pregnated with carbon and iron carbonate. 



The differences between the ferruginous horizons of the Mar- 

 quette and Menominee regions appear to lie chiefly in the 

 greater development in the first-named region of thejaspery 

 schists, and in the prevalence in it also of more thoroughly 

 crystalline ores, which are chiefly specular hematite, but also in 

 minor degree magnetite. In addition to the contortion of 

 the jasper-schist, which is at times carried to an extreme, 

 there is often to be seen in places evidence of a more or 

 less complete shattering and brecciation, in which cases the 

 substance filling the interstices may be specular iron alone 

 or specular iron along with jaspery or cherty silica. This 

 is a phenomenon which is met with in yet more striking 

 development in the Vermilion Lake region. It should also be 

 said that in portions of the Marquette region there are develop- 

 ments of actinolitic magnetite-schists which are somewhat dif- 

 ferent, in habit at least, from the usual actinolitic magnetite- 

 slates already described, which occur in abundance in this dis- 

 trict also. Bat notwithstanding these differences the chief fer- 

 ruginous horizons of the Marquette region have manifestly 

 had an identical origin with those of the Menominee and 

 Penokee districts. Not only do they show all of the litholog- 

 ical varieties met with in these regions, but at the same time 

 they present equally strong evidence of a sedimentary origin. 

 This is particularly the case in those portions of the series 

 which are least crumpled and disturbed, in which case there is 

 often no more alteration than in the iron belt of the Penokee 

 series, while for long distances there is an equally simple 

 structure. 



Our material from the Marquette country is unfortunately 

 not as abundant as I could wish. All of the principal local- 

 ities have been visited and somewhat carefully examined, but 

 the collections made at the time of these visits have since all 



