GEOLOGY. 25 



of large crater-like holes proving its presence now or formerly imme- 

 diately beneath, while throughout the district it is frequently exposed, 

 generally forming precipitous outcrops within the elliptical boundaries 

 of the nummulitic limestone* 



The exposures vary in size from the enormous one at Bahadur Khel 

 to others of a few feet and less. 



Colour and character of the salt. — The salt possesses a characteristic 

 whitish or gray colour all over this region, its texture varying from a 

 highly crystalline mass, the most common form, to a somewhat earthy 

 salt intermingled with some blue or grayish finely divided clay. It often 

 contains blotches of transparent crystalline salt (shishi nimtth Qf the 

 natives), giving it a conglomeratic appearance and rarely minute frag-' 

 ments of gypsum projecting from the weathered surface of the rock. 



The earthy impurities are most common in the western part of the 

 district, where the largest exposures of salt occur, but even here only a 

 few subordinate bands are considered unfit for working, nor is it at all 

 certain that if such large exposures of salt occurred elsewhere, these 

 slightly earthy bands would not be found, for in some of the eastern 

 exposures, as at the Zaino quarries, there are also layers of salt less pure 

 than usual. 



The impurities at both ends of the district, slight though they be, 

 would have some importance if they might be taken as any indications 

 of original limits of the deposit in these directions. 



Much the greater portion of the salt is remarkably pure, and, so 

 far as is yet known, without a trace of contained or associated salts of 

 another class, such as the potassa salts of greater economic value. 



In the eastern parts of the district, besides the foreign matter pre- 

 viously noted, the uppermost portion of the salt, which is also the most 

 impure, is frequently bituminous and sometimes slightly pyritous, this 



* The various places at which rock-salt is seen or known will be mentioned in detail 

 further on. See Part II and Appendix, 



d ( 129 ) 



