Siliceous Genus. 149 



quartz from cracking or fplitingj and hence 

 its infufibility and ufe in furnaces* 



II. VARIETY. 



Feltfpar and Mica> 

 Granltone. 



This ftone is mentioned by Ferber, in his 

 letters from Italy, p, 1 1 8. A ftone of this 

 fort which moulders by expofures to the air, 

 is found in Finland, and is faid to contain 

 fometimes faltpetre, and fometimes common 

 fait, it is there called Rapakivi^ I Linne von 

 Gmelin, 621. 



III. VARIETY. 

 Quartz and Horn-Jlonc. 



In fmall diftinft grains compacted together, 

 this is found plentifully in the mountain of 

 Penmaumaure in Wales. It exhales an earthy 

 fmell, gives fire with fteel, and is of a thick 

 lamellar texture: its fpecific gravity is 2,811. 

 the quartz is white, and the horn-ftone black, 

 which gives the ftone a bluifh appearance. 



IV. VARIETY. 



l^itartz, Feltfpar^ and Mica^ or Quartz, Shocrl 

 and Mica. 



Granite^ Moor-Jione. 



This ftone confifts of diftin<3 mafles of 



each, firmly compacted together, their pro- 



L 3 portion 



