119 



lustre. It is supposed to be the hardest substance known, 

 excepting Diamond and Corundum. Their hardness, frac- 

 ture, and brilliancy may have confounded them with Dia- 

 monds ; and it is said that Saxon Topazes are heated to give 

 them a white transparency*, and are then actually sold for 

 Diamonds — it is even suspected by some that the reputed 



Portuguese Diamond may be only a Topaz. Spec. Grav. 

 3-464—3-564. 



The Saxon Topaz analysed by Vauquelin afforded him 



Alumina ... 49 



Silica .... 29 



Fluoric Acid . . 20 



Loss .... 2 





100 



The Brazilian gave 





Alumina 



. 47 



Silica 



. 28 



Fluoric Acid 



. 17 



Oxide of Iron 



4 



Loss 



4 





100 



* 1 believe the same i« clone with some Diamonds. It is very usual with the 

 dark Cairn-Gorum Crystals. See Descr. tab. 102. 



