220 NERBUDDA DISTRICT. 



are frequently very vescicular. Essides agate, which is the most common 



occupant of the cavities, Heulandite is very corn- 

 Accidental minerals. 



mon; immense masses of this mineral sometimes 



occurring, as at Saoligurh, and again near the base of Richera on the west 



side. The cavities which have been filled with it are very frequently 



lined with soft green earth. 



Cavities so lined often contain fine small crystals of quartz, which 

 seldom fill the cavity completely, but are themselves as it were a second 

 or inner lining. Frequently the vescicles of the trap are filled with this 

 green earth unaccompanied by any other mineral, in which case they 

 are generally quite spherical, of very uniform size (about Jth inch) 

 and regularly dispersed throughout the mass. Fine crystals of calcspar 

 occur in the trap (c) near Kappa village, on the Nursingpur and Chind- 

 warra road, and in many other places. Natrolite is also not uncommon, 

 and Thomsonite occurs at the west foot of Deodungri hill. These last miner- 

 als have been found also in other varieties of the trap besides the one re- 

 ferred to (c). As has been already stated none of these lithological 

 peculiarities nor the presence of any of these minerals, can be used to 

 identify different parts of the same layer of the trap. On the contrary 

 all the lithological characters and many of the minerals may be found in 

 what are certainly parts of the same flow (although this is seldom the 

 case) within a short distance. 



The third variety we have mentioned (c ) often appears to be the result 

 of the decomposition of the harder and more solid (b) or even of (a). 



Columnar structure is common in the dense trap (b). Hexagonal and 



pentagonal columns have been measured with a 

 Columnar structure. _ , 



diameter of 22 inches, in the hill east of Buddi 



village. And near Burardo village a very peculiar minute columnar struc- 

 ture was noticed ; the columns are triangular, and the sides measure less 

 than half an inch across, giving the mass a fibrous look ; nor do these 

 columns appear regularly jointed in their length; a piece was obtained 19 



