424 NATURAL HISTORY. 



to one hundred, the rock crystal is very valuable ; in 

 ancient times it was made into cups and vases. Nero, 

 on hearing of the revolt that caused his ruin is said to 

 have dashed to pieces two cups of this kind, one of which 

 cost him a sum equal to three thousand dollars. They 

 are of various colors ; the yellow is called Citrin or 

 False Topaz ; the brown or smoky quartz, Cairngorm 

 Stone; the black Morion. The pure specimens are cut, 

 set in gold, and used as jewelry ; the imperfect or lower 

 varieties are employed in glass making. 



The Amethyst, a beautiful variety of rock crystal, is 

 transparent ; color purple or bluish-violet, sometimes 

 pearl-gray or greenish-white, is often, like the above- 

 mentioned, found in mountain regions ; the most valuable 

 of this family of gems, however, are native of Siberia, 

 Persia, India, and Ceylon. The amethyst received its 

 name on account of its supposed powers against intoxica- 

 tion. It is always set in gold and used for ornament, as 

 seal rings, etc., and very frequently counterfeited by a 

 substitution of colored glass. 



Common Quartz, of foul color, less transparent and 

 vitreous, is found everywhere, and together with sand- 

 stone, is the principal element of the primary rock for- 

 mation. The most remarkable variety is the Oafs eye, 

 a translucent chalcedony of a light greenish-gray or yel- 

 lowish-brown color. It presents a peculiar opalescence 

 or glaring internal reflections when cut, which reminds 

 one of the eyes of a cat, which effect is owing to fila- 

 ments of asbestos. Found in Ceylon and Hindostan, 

 also in Treseburg in the Hartz Mountains and other 

 places in the elevated portion of Germany. Also used 

 for jewelry. 



Chalcedony is of several varieties, and is found 



