370 THE PENOKEE IRON BEARING SERIES. 



described, .lust south of tlie place of tlieir occurrence is a high east and 

 west ridge of diorite-porphyrite, which is a part of a flow outcropping at 

 various places for a distance of two miles east and west. At the northern 

 foot of this hill, dipping to the north, is the jasper-conglomerate, having a 

 slaty matrix. The specimens frt)m the test pits a few paces to the north 

 are the nonfragmental sediments of the iron l)elt. In the matrix of 

 this jasper-conglomerate are very numerous irregular compact frag- 

 ments, which contain tabular plagioclases and which appear to be frag- 

 ments of the fine grained basic eruptive just to the south. These 

 fragments are often vaguely defined; they are extraordinarily irregular in 

 form; they are very much altered. Besides these complex fragments there 

 are found quite numerous angular particles of feldsiiar of moderate size. 

 These may have been furnished by tlie porphyritic plagioclases of the 

 underlying porphyrite. These two varieties of fragments are cemented l)y 

 a groundmass which consists largely of chei'ty silica. This silica is around 

 and between the tragments in narrow belts, just as it is found in a wide- 

 spread phase of the greenstone-conglomerate. Contained in the above 

 matrix are very numerous angular blood-red jasper pebbles of varying 

 sizes, some of them being large enough to be classed as liowlders. These 

 bright red jasper pebbles give the rock a very striking appearance. The 

 only essential ditference between this conglomerate and certain phases 

 of the greenstone-conglomerates is in the presence of these jasper pebbks, 

 and whether it ought to be cdassed here or with the greenstone-congloia- 

 erates is a somewhat doubtful question It is placed here because it is 

 certainly a water-deposited fragmental rock, and is also certainly below 

 the rocks of the iron-bearing belt. 



The third phase of rock is the chloritic and clay-slates, which ai:e 

 plentifully interstratitied with the nonfragmental iron-bearing sediments in 

 Sees. 20, 21, 22, and 23, T. 47 N., R. 43 W., Michigan. Macroscopically, 

 these rocks are soft, green or brown, aphanitic, finely Jaminated ones. 

 Their constituents are difficult to make out with certainty. Some of the 

 chief ones an; quartz, chlorite, sericife, brown ii-on oxide, iiyrite, and 

 perhaps kaolin. How far the.se rocks niv fragmental and how far nonfrag- 

 mental sediments it is difHcult to determine, so fine grained are they. In 



