Crosby.] 492 [March 7, 



Newer or Eastern Series. 



The eastern or slate series occupies probably a larger portion 

 of the Archaean area than do the schists of the western series. Its 

 predominant rocks are distinguished by their fine and uniform 

 slaty texture. Perhaps the most important type is a fine grained, 

 variously colored clay slate or argillite, which usually splits read- 

 ily parallel with the bedding. This is often lustrous on the flat 

 surfaces or perceptibly hydromicaceous, and frequently passes 

 insensibly into a distinct phyllite or argillaceous schist, and even 

 into a true hydromica schist. The slates also pass into harder, 

 siliceous varieties ; and these often become distinctly arenaceous, 

 changing to quartzite, which is one of the most prominent and 

 characteristic rocks of this series. It resembles the quartzite of 

 the western series, but is much more abundant, occurring in beds 

 from 50 to 500 feet in thickness. In both series the erosion of 

 the soft schists and slates leaves the quartzites in bold and ragged 

 relief, huge dyke-like ledges trending across the country for miles, 

 now bristling suddenly in peaks, and again outcropping in the 

 canons of the creeks as sharply defined walls (Newton). 



The quartzite usually contains some hydromica and, like the 

 slates, passes into hydromica schist. It also becomes coarser in 

 some localities, passing into coarse grits and conglomerate, which 

 have, in the aggregate, a very large development. The pebbles of 

 the conglomerate have suffered extensive deformation by compres- 

 sion, and the whole rock is highly metamorphic. The rocks of this 

 series, including the slates, schists, quartzites and conglomerate, 

 are sometimes highly ferruginous ; the iron occurring chiefly in 

 the form of specular hematite. On Box Elder Creek, a ridge some 

 400 feet in height is composed largely of this crystalline siliceous 

 hematite. Occasional bands of almost pure specular hematite 

 several inches in thickness are found in the mass, but the rock is 

 as a whole so highly siliceous as to be entirely useless as an iron 

 ore. In some cases the hematite is so regularly interlaminated 

 with the slates and quartzites as to recall the siliceous banded 

 hematite of the Lake Superior region. On the other hand, the 

 ferruginous schists are often typical itabarite, specular and mica- 

 ceous hematite taking the place of mica in the rock. 



The eastern series is also traversed by numerous veins of 

 quartz, which usually coincide with the bedding in the more schis- 



