VEINSTONES. 



575 



bole ; a red unctuous ferruginous clay ; with other 

 kinds and colours, especially that called gur by Gur. 

 the Germans, of various tints of brown, and re- 

 sembling rappee, and sometimes Spanish snuff. 

 The peach of the Cornish miners, chlorite, or 

 green bole, is also frequent. 



From the account which Williams gives of the Rider. 

 rider, in the very imperfect mineralogical language 

 of that period, it would appear that he means to 

 indicate a vein of ferruginous quartz, generally 

 found to accompany metallic ores. By his de- 

 scription it is very rough and irregular, and full 

 of little cavities, containing a ferruginous powder 

 like snuff. The whitest parts have some resem- 

 blance to what is called a bur-stone, chiefly used 

 for mill-stones, their irregular surface serving the 

 purpose of trituration : but the rider generally 

 contains heterogenous substances, as ores, pyrites, 

 spar, fluor, &c.* It seems often to approach 

 keralite, or the hornstein of the Germans, which 

 sometimes even forms mountains, replete with 

 silver and other ores. 



It would seem that the cavities containing druses 

 of small crystals, chiefly occur in the purer por- 

 tions of the rock ; and his account of this beautiful 

 kind of veinstones merits transcription. 



* Will. i. 379. 



