INTERESTINC LOCALITIES OF ISHPE.MINCt FORMATION. 441 



prevents it Iroui Ijeiu^- cleaved piirallel to tlic haiuliiiL;-, wliilc tIic .similar 

 rock of the Negamiee fonnatiou has a regular lamination, is brittle, and 

 parts readily along- the lamination; also, the layers of" the tornier are 

 thicker, and many of them have more of the appearance of a crvstalline 

 schist than the similar rock of the Neg-aunee formation. The schist is 

 folded in a most complicated fashion. On the horizontal exposure the 

 layers are seen to turn back upon themselves in re2)eated sharp V folds. 



Upoir the whole, the rocks of the Ishpeining formation in this area are 

 the most extremely metamorphosed of all in the district. While occasional 

 conglomei-atic schists have been discovered and the coarser quartz-schists 

 are not completely crystalline, the iiner-grained rocks have been changed 

 to completely crystalline schists. The evidence of xniconformity between 

 the Negaunee and Ishpeming formations, which is so marked at Republic 

 and other localities in the district, is wholly obliterated. From the proxim- 

 ity to these places one can not doubt that the two are here unconformable, 

 and that there was an irregular erosion contact between them; but if this 

 be true, the mashing was so severe as to wholly destroy the evidence of this. 

 The schistosity of the Ishpeming formation and the bedding of the Negaunee 

 formation are in apparent conformity. Where the Ishpeming formation is 

 in contact with the Archean, somewhat similar relations obtain. The basal 

 horizon of the Ishpeming formation is a coarse micaceous quartz-schist. It 

 is not always possible to tell exactly where this recomposed rock begins 

 and the mashed granite ends. At two localities only, one between the 

 Erie and Magnetic mines and the other southeast of the former, does this 

 basal rock distinctly show by pebbles its fragmental character. 



Under the microscope a few of the slides of the recomposed materials 

 at the mines so closely resemble the original Negaunee jasper that the two 

 could not be discriminated. However, there is usually present muscovite 

 in small or large flakes, and biotite and chlorite are found, in some places 

 abundantly. In certain cases lenticular areas of jasper suggest that the len- 

 ticules represent mashed pebbles. While the quartz of the siliceous lavers 

 vanes considerably in coarseness, there is usually no such range in size as 

 at Republic, where each of the coarse grains derived from the granite can 

 be readily discriminated from the small grains derived from the Negaunee 



