276 



SYSTEMATIC DESCRIPTION OF PRECIOUS STONES 



the nature of basalt, which is the principal, if not the sole, constituent of the hill ranges. 

 The gem-gravels are made up of fragments of this rock, and the separating layer of 

 tenacioUvS grey, brown, or yellow clay is also, in all probability, a decomposition product of 





rs «9 CART ROAOa ^'^- 



PATHS' -■' BOUNOARIES*-^**..-* 

 QAN(aJVILLAaG KLONO (M) RIVER 

 WAT, TEKIPLE 



t/ULr leaS HXNRY LOUIS 



Fig. 56. Euby and sapphire mines of Muang Klung in Siam. 



the same rock. On these grounds it is concluded that the basaltic trap-rock is here the 

 mother-rock of the ruby ; this conclusion, however, requires the support of further evidence. 

 The gem-bearing layer varies in thickness from 10 inches to 5 feet, and is overlain by a 

 sandy and clayey deposit from 2| to 12 feet thick, containing no precious stones. In the 

 clayey gravel are found ruby and sapphire, as well as common corundum ; quartz, in good 

 transparent crystals, and crystals of zircon and ilmenite are abundant, while topaz is very 

 rare. Of these minerals, the first two only are commercially valuable and sought after by 

 the miners. Rubies are much more frequently met with than are sapphires, the 



