Geology of the Rarz Mountains. 



217 



compact, very hard, infusible, hornstone-like siliceous rock, 

 with splintery fracture and dark colour, and is impregnated 

 with carbonaceous material and iron oxide. It occurs in 

 beds made up of layers from 1 to 4 inches in thickness, and 

 is traversed by numerous joints, and veined with quartz. 

 The kieselschiefer, whet slates, and adinole beds of the Upper 

 Harz have been described minutely by Dr F. Wunderlich,^ 

 who has given an elaborate account of their chemical and 

 mineralogical characters. The following analyses of these 

 three rocks made by him (loc. cit., pp. 30, 31) give a good 

 idea of their average composition : 



SiO,, . 



Fe^Og, . 

 FeO, 



AI2O3, . 



MnO, . 



CaO, 



MgO, . 



K,0, . . 



Na^O, . 



P2O5, . . 



CuFeSg (copper pyrites 



CI,. . . 



C, . 



H,0, . . 



101-430 



101-430 



100-423 



Besides these constituents, traces of TiOg, FeSa (iron 

 pyrites), and SbgSg occur in each rock. SO3 occurs in a few 

 cases, and some of the specimens of b and c contained 

 a large quantity of CaCOg. A is the average of five, and 

 B and c of six analyses. Figures in brackets indicate 

 that the material in question has not been found in all 

 cases. 



The adinoles are distinguished chemically from the kiesel- 

 schiefer by the larger quantity of alkali they contain, which 

 renders them easily fusible before the blowpipe, while the 

 kieselschiefer are infusible. The variegated banded appear- 



1 Mittheilungen des Berg- u. Huttenmannischen Vereins "Maja" zu 

 Clausthal, 1880, pp. 1-95. 



