84 MALLET : GEOLOGY OF DARJILING AND WESTERN DUARS. 



The rock, therefore, contains an excess of lime over that in normal 

 dolomite, and is almost quite free from impurity. A high range of hills 

 is entirely formed of it, so that the supply is inexhaustible ; but the 

 dolomite hills west of the Tursa are just beyond the British boundary 

 in Bhutan, the authorities of which would no doubt demand a royalty 

 for working the mineral. For the supply of Jalpigori the most advan- 

 tageous locality is a ravine a little east of the Rekti naddi (north of the 

 21st boundary mark). The rock in the lower part is black slate, above 

 which is dolomite, forming a naked precipice at the head of the ravine, 

 from which numberless large and small blocks are washed down every 

 rains, so that there is no necessity to quarry. A considerable quantity 

 of gravel, and small lumps of a convenient size for burning, is washed 

 across the frontier. 



The dolomite east of Baxa is within the British boundary. 



The clunch beds of the Nahan group are very frequently more or 

 less calcareous. Sometimes the calcareous matter 



Tertiary limestone. . , _ . - , , _ . . 



is segregated into nodules, and these even pass 



into short irregular beds of impure grey or yellowish limestone. Mr. 



Dejoux, Executive Engineer in charge of the Sealdah experimental 



cement works, has kindly analysed some rock of this kind from the 



Chirankhola naddi with the following result : — 



Carbonate of lime ... 

 „ „ magnesia 



Oxide of iron and alumina 

 Clay ... 

 Sand 

 Loss 



68-7 



1-7 



1-3 



27'4 



•6 



•3 



100-0 



Mr. Dejoux is of opinion that the stone would yield a kind of 

 natural cement, more especially a kind containing rather more clay than 

 the above. The beds, however, are thin, not very frequent, and irre- 

 gularly scattered through the clunch, so that no quarries, beyond per- 



( 84 ) 



