INTEEESTING LOCALITIES OF ISIIPEMING FOEMATION. 439 



Kioman area. — -To tlie iiortliwest of RepubHc, along tlie east side of tlie 

 Republic trough, at the Kloiuau raiue the contact Ijetween the Negaunee 

 formation and the conglomerate of the Ishpeming formation is ])eautifully 

 exposed (Atlas Sheet XI). The Negaunee formation has its typical char- 

 acters. Resting upon this is recomposed ore. The recomposed material 

 near the base of the Ishpeming formation very closely sinmlates the Negau- 

 nee jasper in appearance. However, minute roundi.sli granules of (piartz 

 and pebbles of jasper show the character of the rock when closelv examined. 

 At one place, where the ore welds tlie two formations together, it is impossible 

 to state where the Ishpeming formation ends and the Negaunee formation 

 begins. The ore taken from the mine seems to occur about equally in the 

 two fonnations. As usual, in the ore two kinds of iron oxide are discrimi- 

 nated, the original, detrital, mashed hematite and the secondary crystalline 

 magnetite. In cross fracture the latter is more evident; in specimens ])aral- 

 lel to the lamination the micaceous hematite appeal's to be predominant, 

 presenting its usual lustrous, slickensided surfaces. The heavilv ferruginous 

 material passes up into a quartzite containing numerous fragments of ore 

 and jasjier. Layers of conglomerate and of quartzite, comparativeh' free 

 from jasper jiebbles, are interstratitied. This rock ])asses uj) into a fine- 

 grained gray quartzite, like that at Republic. In thin section the rocks do 

 not differ from the similar rocks at Republic, except that the dynamic 

 effects are less severe. In the quartzose ore the coarse, well-rounded, little- 

 distorted grains of fragmental quartz derived from the Archean show dis- 

 tinct enlargements. All, however, show undulatory extinction, and many 

 are fractured. 



Northern Republic and Western troughs. At a llUmber of plaCCS betweeil tllC Klo- 



man mine and the northwest end of the Republic trough there are exposures 

 of the Ishpeming- formation. The majority of these are at the mines along 

 the trough, but at various other places important outcrops occur. The more 

 important localities are as follows: the S. h sec. 1, T. 46 N., R. 30 W., the 

 Metropolitan mine, the Chippewa mine, the Riverside mine, the Standard 

 mine, the Cannon mine, the Erie mine, the Magnetic jnine, and various 

 places to the east and west in sec. 20, T. 47 N., R. 30 W. In the Western 

 tongue there are exposures of the Ishpeming formation in sec. 30, T. 47 N., 



