.1853.] Report on the Geological Structure of the Salt Range. 251 



t 



means uncommon. Eed varieties also occur and beds of a dark grey 

 earthy gypsum are generally associated with the saccharine kind. 



It is a nearly pure sulphate of lime and appears to be free of any 

 admixture of carbonate of lime. 



When calcined it yields a pure plaster of Paris, which sets rapid- 

 ly when mixed with water. Gypsums, however, in which carbonate 

 of lime is absent, form, when calcined, a less coherent cement than 

 those where it occurs to the extent of 10 or 12 per cent. By a due 

 admixture therefore of quick lime with the calcined Salt Eange gyp- 

 sum, its hardness as a cement or mortar will probably be increased. 



The natives do not appear to be aware of the properties of gyp- 

 sum when calcined, though they use it in fine powder mixed up with 

 pure lime into a mortar, to produce the shining marbly appearance, 

 so often noticed in their finer chunam work. 



In the department of public works, the use of gypsum might be 

 successfully introduced for various building purposes, and a supply 

 to any extent might be procured from around Pind Dadun Khan. 



In the gypsum of Maree and Kalibagh and also at Surdee, very 

 perfect rock crystals occur generally in the form of six-sided prisms 

 terminated by six sided pyramids. After rain these spangle in a 

 most striking manner, and hence have acquired the name of Maree 

 diamonds. Transparent, red and milky varieties occur, the former 

 being the most abundant. The longer and more perfect crystals are 

 much esteemed by the natives, who manufacture them into necklaces. 



Yery perfect crystals of iron pyrites also occur in gypsum in the 

 Keila Wan above the village of Khond, from beds, of which a sul- 

 phur spring issues at a natural temperature, depositing sulphur on 

 the gypsum over which it flows. 



In proceeding along the Salt Eange from E. to W., the first indi- 

 cations of salt marl occur in the S. E. or scarped side of mount 

 Tillah, where it is very indistinct, being in great part concealed by 

 Tertiary sands and clays. From the West end of mount Tillah it may 

 be traced along the foot of the scarped or West side of the Chumbul 

 ridge to Jelalpore where it is considerably developed, but in the 

 midst of such great disturbance that its relative position can with 

 difficulty be made out. To the West of Jelalpore there is no distinct 

 outcrop of the marl seen. along the escarpment of the Eange under 



