142 NERBUDDA DISTRICT. 



acteristic red color is the most striking lithological feature of the Vin- 

 dhyan group : and speaking of the formation ge- 

 nerally, its most marked characteristic certainly is 

 the persistency of this lithological aspect over great areas. This sameness 

 of texture is strongly in contrast with the prevailing character of all 

 those more recent sandstone formations to the south, to be hereafter 

 described. 



This general constancy in lithological character does not, of course, 



imply the entire absence of varieties among the 



arie y * beds of the series : instead of clear quartz grits 



slightly earthy sandstones are found, and in many places ferruginous clay 



has been so largely accumulated as to form a considerable ingredient in 



the mass. 



This earthy matter most commonly occurs at the partings of the 

 arenaceous beds, and sometimes exists as irregular 

 aggregations through the mass of the beds them- 

 selves : less commonly the argillaceous and sandy ingredients have been 

 mixed together, producing an earthy, or a shaley sandstone. 



In many places the sandstone is mottled, and spotted, at the surface, 



from the decomposition of grains of magnetic iron, 



which is often abundantly scattered through the 



rock, and may on a fresh fracture, generally be detected in its undecom- 



posed condition. 



Mica is not a common ingredient of the Vindhyan sandstones, yet 



occasionally this mineral is present in quantities 

 Fissile Sandstone. ■ . ' . 



sufficient to constitute the rock a micaceous flao-, 



and it seems generally to cause, or accompany, a laminated, and fissile 



structure. 



Ripple marking may be considered as a phenomenon characteristic 



of the Vindhyan series ; almost totally absent in all the other groups of 



Sandstone of Central India it is almost every, where, throughout them, 



