NOME IX. TOPAZ ROCK. 



ing this singular substance, which has never been 

 carefully examined, and concerning which so 

 many errors have been propagated both at home 

 and abroad. 



NOME IX. TOPAZ ROCK. 



This beautiful anomaly is hitherto only known 

 to exist in Saxony; and Mr. Jameson's descrip- 

 tion shall be copied, as it is probably the most 

 authentic. 



" 1. The remaining primitive rocks we have 

 now to describe, are less important than those 

 we have already described, because they occur 

 less abundantly, and not so widely extended. 

 One of the most remarkable of these is the topaz 

 rock, which is not only remarkable on account 

 of its constituent parts, but also its structure. 

 It is composed of quartz, topaz, schorl, and a 

 small portion of lithomarge. The quartz is fine 

 granular; the schorl thin prismatic ; the topaz 

 usually coarse and iine granular, and has com- 

 monly a grey colour, which is to be attended to 

 in its discrimination. These three fossils are 

 disposed in layers, and thus form a slaty struc- 

 ture; "but this slaty structure occurs only in the 

 small ; for these layers are collected into parti- 



