PETEOGRAPHICAL CHAKACTEE OF TDE WEWE SLATE. 263 



At one exposure the veins of hematite are Liter than the white ([uartz, 

 and the jasper is hxter than the hematite; and some ot' the fragments have 

 around them, in concentric parallel zones, quartz, hematite, and jasper, 

 although even at this place the quartz entirely fill« some of the spaces. 

 Where the veins of hematite and jasper are of considerable size they 

 can not be discriminated from the hematitic jasper of the iron-bearing* 

 formation. In places the amount of hematite is so great in the breccia 

 that the material has l)een prospected for ore. The secondary charac- 

 ter of the )as[)er and hematite in the case of tliese breccias can not be 

 doubted, and this has a bearing upon the origin of the jasper and hematite 

 of the iron-bearino' formation. These breccias are discriminated from true 



Fig. 12. — Shattered slate cemented by vein ([uartz, from Flo. 13. — llrecciateil si m- ■ i i i. ,1 liyvein qnnrtz, from 



NE. i .sec. 21, T. 47 N., K. 26 "W. samu l.n alil j .is li;;. 12. 



conglomerates b}' the fact that all of the fragments are deri^'ed from the 

 slate. Also, the breccias vary into slate 1)A' imperceptible stages, both 

 along the strike and across it; and finally, while many of the fragments 

 have been rounded so as to resemble those produced li-s' water action, others 

 have an irregular character which is not consonant with a water origin. 



Microscopical. — Tlie malu varieties of rock discriminated in thin section 

 are basal conglomerates and quartzites, graywackes, no^'aculites, slates, and 

 slate-congh )merates. 



The quartzites and conglomerates differ from each other only in that the 

 conglomerates ha^'e large fragments. In other words, the conglomerates 



