454 THE MAEQUETTE IKON-BEARING DISTRICT. 



At several places within the area under consideration mining has been 

 done on a small scale. These places are located as follows: In sec. 29 a 

 number of pits are a short distance north of the center of the section; 

 others are about one-fourth mile south of the center; and still others some- 

 thing less than one-half mile to the east. In sec. 30 only one small pit is 

 known, and this is about one-fourth mile south of the center of the section. 

 In the south part of sec. 31 is the North Champion mine. At all of these 

 places the country rock is the black carbonaceous and pyritiferous slate. 

 The ores are .strongly limonitic. Associated with these ores are sideritic 

 slates, ferruginous cherts, and griineritic slates. The griineritic .slates are 

 usually finer-grained thaii those of the Negaunee formation, and most of 

 them appear to contain a considerable amount of carbonaceous material. 

 The majority of the ferruginous cherts also have a somewhat different 

 appearance from those of the Negaunee formation, and the amount of this 

 material is small. Where the small ore bodies occur the original carbon- 

 aceous formation appears to have been sideritic. By its oxidation and the 

 concentration of iron oxide griineritic rocks and ferruginous clierts devel- 

 oped, by processes analogous to those by which similar rocks formed in 

 the Negaunee formation. 



The thin sections of the ferruginous rocks of the mines are, in all 

 essential particulars, the same as the similar rocks in the Negaunee forma- 

 tion, described on pages 366-375. Like them, thev show the development 

 of the different varieties of the rock from a sideritic slate. However, there 

 are minor differences, as follows: The chert is usually very fiinely crystal- 

 line, and sometimes has a semiamorphous appearance. The griinerite is at 

 most places finely crystalline. The iron oxide is very largely limonite, and 

 all of the minerals are everywhere impregnated with black carbonaceous 

 material. At the mines the amount of mingled fragmental material is small. 



Eastern area._(Atlas Shcets XV, XVI, XIX, XXII, aud XXV.)— lu sec. 35 

 are pits which contain iron-bearing rocks similar to those in the pits north of 

 Champion. Adjacent to these pits there are the usual black carbonaceous 

 and pyritiferous slates. 



To the east, between Mount Humboldt and the Clarksburg forma- 

 tion slates are found at various localities. However, north of the belt 



