CHRYSOBERYL. 



This mineral is like beryl in contain- 

 ing the element beryllium, but in other 

 respects it is a distinct species. Chryso- 

 beryl has no silica in its composition, as 

 has berv'l, but is composed of glucina, 

 beryllium oxide and alumina, the the- 

 oretical percentages being glucina 19.8. 

 alumina 80.2. In nature, however, some 

 other oxides are usually present as im- 

 purities or replacing the alumina. Such 

 are iron and chromium oxides. Chrvso- 

 beryl is remarkable for its hardness, this 

 being 8.5, and thus near that of corun- 

 dum. The cut stones therefore retain a 

 polish well. The specific gravity of the 

 mineral is somewhat greater than that 

 of the diamond, being 3.5 to 3.8. It 

 crystallizes in the orthorhombic system 

 and often forms twins which are so 

 united as to make a six-rayed stellate 

 crystal or six-sided prisms. An illustra- 

 tion of one of these crystals may be seen 

 in the colored plate of Birds and Na- 

 ture for Janua^\^ Chrysoberyl has a 

 prismatic cleavage and conchoidal frac- 

 ture. Its luster is vitreous, tending to 

 oily, and is brilliant. The mineral is 

 infusible and is not attacked by acids. In 

 color Chrysoberyl usually presents some 

 shade of green, tending at times to brown 

 or yellow. The name Chrysoberyl means 

 literally golden beryl and suggests a yel- 

 low stone. While this is a common 

 color, grass-green and emerald-green are 

 frequent and characteristic in occurrence. 

 Among jewelers Chrysoberyl, especially 

 the Brazilian ChrysoberN'l, is often known 

 as chrysolite, a custom which has doubt- 

 less arisen through the similarity in 

 color of the two minerals. Three kinds 

 of Chrysoberyl are employed in jewelry 

 and being given different names may be 

 considered separately. These are. ( i ) or- 

 dinary Chrysoberyl, (2) cymophane, or 

 cat's-eye, and (3) alexandrite. Ordinary 

 Chrysoberyl, also called Oriental chryso- 

 lite or chrysolite, is greenish-yellow to 

 smoky brown in color and is employed as 



a gem only when transparent. It is for 

 the most part obtained in Brazil and Cey- 

 lon, occurring in the gem gravels of both 

 these countries. The Brazilian Chryso- 

 beryls are rolled pebbles, scarcely larger 

 than beans and occur together with to- 

 paz, garnet, tourmaline, quartz, etc., m 

 the beds of streams chiefly in the north- 

 ern part of the province of Minas Geraes. 

 The stones occur in the neighborhood 

 of granite and gneiss and were there- 

 fore probably originally formed in these 

 rocks. The Ceylonese Chrysoberyls are 

 likewise found in stream beds and come 

 from Safifragam and the neighborhood 

 of Matura in the southern part of the 

 island. In North America, Clirysoberyl 

 has been found in Maine, Connecticut 

 and North Carolina, but few stones suffi- 

 ciently transparent for cutting occur. 

 Cymophane, or "cat's-eye," is a name 

 given to a translucent, opalescent variety 

 of Chrysoberyl, across a polished surface 

 of which may be seen to play a single 

 long, narrow ray of light, changing posi- 

 tion with ever}' movement of the stone. 

 The phenomenon is like that of the star 

 sapphires, except that but a single ray 

 is seen instead of several. The cause of 

 the appearance is believed to be multi- 

 tudes of minute tube-like cavities in the 

 stone arranged in parallel position, which 

 reflect the light which falls upon them. 

 In .cutting the stone the best effect is pro- 

 duced by giving it the form of a long 

 oval, over the middle of which a light 

 ray runs and produces a resemblance to 

 the eye of a cat. Such stones are the 

 true "cat's-eyes" of jewelry, the 

 quartz cat's-eye being much inferior. 

 The name cymophane, also applied to 

 these stones, comes from two Greek 

 words meaning wavy appearance. The 

 cat's-eye variety of Chrysoberyl occurs 

 together with the transparent kind above 

 described in the alluvial deposits of Cey- 

 lon and Brazil. The stones are not large, 

 rarely exceeding 100 carats in weight. 



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