ON THE TOPAZ OF SCOTLAND; 



449 



tuent parts. Besides forming an essential ingredi- 

 ent of topaz- rock, it also occurs in it in drusy ca- 

 vities, along with quartz crystals, and lithomarge. 

 In Bohemia and Saxony, it occurs in veins that 

 traverse gneiss and mica-slate. These veins are 

 generally narrow, intimately connected with the 

 rock they traverse, of very old formation, and con- 

 tain, besides topaz, also tin-stone, arsenic py- 

 rites, sometimes copper pyrites, apatite, fluor-spar, 

 quartz, and steatite. The Siberian topaz appears 

 to occur in veins in primitive mountains, and pro- 

 bably also in large drusy cavities, in rocks of a ve- 

 ry old formation. 



About 25 leagues north from Gatharinenburgh, 

 in the Uralian Mountains, topaz is found in con- 

 siderable quantity in a kind of granite, resembling 

 that variety known under the name of pierre gra- 

 pbique. There, it is said to occur in drusy cavities, 

 along with quartz and precious beryl. It is also found 

 in the opposite extremity of Siberia, in a moun- 

 tain named Odcn-Tschelon, in the province of 

 Dauria, where it occurs in druses along with pre- 

 cious beryl. The topazes of Odon-Tschelon, and, 

 indeed, of Siberia in general, are generally snow 

 white, frequently celandine-green, and very rare- 

 ly of a beautiful blue, resembling the sapphire ; 

 and some varieties exhibit a kind of opalescence. 



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