GEMS, NATURAL AND ARTIFICIAL 



recently supposed to be a ruby, is said to be a red 

 spinel. 



The finest spinels are found in Brazil, India, and Cey- 

 lon. Those somewhat inferior in quality are mined 

 in Burma, Siam, and Afghanistan from limestone, 

 gneiss, or volcanic rocks. A certain number have 

 been found in the United States, mostly in New York 

 and New Jersey. 



Reference was made in the early pages of this chapter 

 to the chrysoberyl, one variety of which is that re- 

 markable gem, the cat's-eye. Quite as extraordinary 

 as this kind of chrysoberyl is another variety known as 

 alexandrite. This gem, so called because of its dis- 

 covery in the Ural Mountains on the birthday of Czar 

 Alexander II, has the remarkable quality of changing 

 color from a rich green by daylight to a raspberry red 

 by artificial light. Only the better quality of gems 

 give this distinct change of color, and as these are rare, 

 and difficult to obtain, this gem has never had the 

 vogue that it probably would otherwise have attained. 



Quite as remarkable, but much more common, are 

 the group of gem stones which have the property of 

 dichroism appearing in different colors when viewed 

 from different directions. The tourmalines, having 

 a wide range of colors and shades, are the best exam- 

 ples of this. Thus a crystal of tourmaline when viewed 

 along the length of the crystal may be almost black, 

 while the same crystal if viewed across may be a bright 

 green, or some other color quite as striking. The 

 finest tourmalines come from Brazil, but more or less 

 valuable gems are found on every continent. 



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