GEMS, NATURAL AND ARTIFICIAL 



of supply. The coveted "cornflower blue" sapphires, 

 which were formerly found only in Burma, Ceylon, 

 and Siam, are now found in the Montana mines; and 

 the uniformity of color and peculiar brilliancy of the 

 American sapphires have made them favorites with 

 many European dealers. 



For many years sapphires of pale tints of yellow, 

 pink, and bluish-green have been found in the Mon- 

 tana gold-mining region, but these stones have very 

 little commercial value. In 1895, however, blue sap- 

 phires of fine quality were discovered, quite by acci- 

 dent. A gold-mining company in the Judith River 

 district, after installing an expensive plant, found that 

 the gravel contained such a low percentage of gold 

 that it would not pay the expense of mining and work- 

 ing. But certain blue stones were found in the sluice- 

 boxes, and were soon identified as sapphires. The 

 gems occur in a dike of trap-rock which cuts through 

 the limestone in this region. This dike is several miles 

 long, showing as a depression covered with vegetation 

 running through the limestone ledges. Pocket-gophers 

 find it an excellent place for their subterranean opera- 

 tions, and in the mounds thrown up by these little 

 miners many valuable gems have been found. The 

 animals follow the course of the trap-rock, since the 

 surrounding rocks are too hard for burrowing, so that 

 the mounds they throw up serve as a guide to the pros- 

 pectors in locating the sapphire-bearing vein. 



The material in which these sapphires are found 

 varies in hardness in different localities and positions. 

 A hard clay, not unlike the diamond-bearing clay of 

 VOL. ix. 21 [321 ] 



