54 THE MAEQUETTE IKON-BE AlUNG DISTRICT. 



After the rapid survey of the most important mines is concluded, the 

 author writes as follows (p. 143): 



Looking back over the field we have now hastily surveyed, * * * it will be 

 seen that, while there are many irregularities, on the whole the ore basin gradually 

 widens toward the west, from a mere point at the Jackson mine to a width fully 5 

 miles at the west end of Michigamme Lake, beyond which too little is known to 

 enable us to accurately define its limits. It follows, therefore, that all the Huronian 

 rocks north, east, and south from the Jackson mine are below, or older than the ore 

 formation (XIII), and all the rocks to the westward and inside of the ore basin are 

 youiKjir, hence above it. 



The country southeast of the Jackson mine produces dark-colored, 

 eaithy hematite. 



I believe these ores all belong to one formation, No. X, in which, up to this time, 

 no merchantable ores, e.Kcept the Lake Augeliiie hematite, have been mentioned as 

 occurring. It is at least certain that they are older thau Formation XII, which 

 embraces the Lake Superior and Winthrop deposits. (P. 143.) 



The Cascade range lies south and east of Negaunee, extending east 

 and west through the southern portion of T. 47 N., R 26 W. The ores here 

 are jasperv oxides with a "flagg}" structure." They are near the Laurentian, 

 and the whole series is overlain by a talcose quartzite, believed by the author 

 to be the equivalent of No. V of the Republic series, and to be a continuation 

 of the same bed that forms the hills north of Teal Lake and becomes calca- 

 reous at Morgan furnace. On this supposition the Cascade ores are older 

 than those of Repu]:)lic, and are the equivalents of the ores of the Magnetic, 

 Cannon, and Chippewa mines. The absence of ores north of the Teal Lake 

 quartzite is thought to require investigation, since the ores of the Cascade 

 range are supposed to be inmiediateb' beneath the continuation of this 

 quartzite. 



The most prominent of all the formations of the Marquette district is 

 this lower quartzite. It is so uniformly present and at such a constant 

 horizon that an account of its distrihutiou is largely an account of the 

 structiu'e of the entire iron-bearing series. 



A brief description * * * of the great geological basin Ibrmed by this 

 quartzite, which embraces within its folds the great mass of the Huronian rocks, and 

 uineteeu-twcutieths of all the ore. will possess interest. Like the ore horizon (XIII), 



