62 GEOLOGY OF THE SON VALLEY, ETC. 



In addition to quartz the sandstone i^ T contains felspar and 



a great deal of muscovite giving it a distinct schistosity. The mica 



plates are seen bending round the quartz -grains which shows that 



they are not of secondary origin, The rock is further remarkable for 



containing a great many grains of tour- 

 Fragments of tourmaline. _. „ , . 



maline. All its constituents are such as 



might be derived from a gneiss quite similar to that which is found 



n many neighbouring regions, and we may conclude that the 



rock from which the Bijawar beds were derived 



Age of gneiss. . . . 



was no other than the gneiss exposed at the 

 present day. 



We find all gradations from these impure sandstones down to 

 the finest slates. Some of those that have been more particularly 

 studied present many points resembling the specimen y 1 ^. They 

 are principally from the hilly region where the Agori jaspers and 

 lavas are profusely exposed. But as it has not been possible 

 to unravel the distribution of the folds, it is not possible to tell 

 whether the places where the rocks were collected are portions of 

 synclines or anticlines, and we cannot tell whether they belong to 

 the beds immediately overlying or underlying the principal jasper 

 horizon or to those associated with that horizon. 



The specimen -fife was collected a short way north-east of 



Deori. The slates accompanying it have the 

 Deori. , . , . , . , , 



same facies- as those associated with the 



specimen T Vj from Bagra and probably belong also to the upper 

 stage. The sandstone /-^ is very similar to y^ in the hand- 

 specimen, only with a more earthy appearance. The same also 

 holds good for the microscopical section which is very similar : 

 the quartz-grains are about the same size and show the same strain - 

 shadows, but they are separated by a greater proportion of fine- 

 grained material much of which appears to be decomposed mica. 

 There is magnetite together with rusty ferruginous products 

 which may be products of superficial weathering. The rock also 

 contains a great deal of felspar which is somewhat altered. 

 ( 62 ) 



