of Devonshire and Cormvall. 177 



Dodecahedral hyaline quartz is frequently found among the veln- 

 Ktones of the lead mines at Beer-alston in Devonshire. 



Swimming quartz is met with in the copper mine of Huel Gor- 

 land, and in that of Suit and Cloak, or Pednandrae, united with 

 tin and calcedony. The same quartz is said to be met with at 

 Nancothan. 



Compact quartz, passing to quartz-agate and calcedony, is very 

 common in the old mines of Beer-alston. It may be said to form the 

 principal part of the vein-stones. It is combined with fluor, galena, 

 and blende, w^hich are disseminated through it in small masses. 



Calcedony, in the form of stalactites, is found at Huel Sparnan 

 and Trevascus. In the former place, it is combined with chloro- 

 phane, a variety of fluor, which was thought to be peculiar to 

 Siberia.* 



In the copper and tin mineof Tol-carn in the parish of Gwennap, 

 a kind of flint, commonly known in England by the name of chert^ 

 has been found with semi-opal in a decomposed granite ; and jasper- 

 agate has been found in the tin mine called Ding-dong in the parish 

 of Gulvall. 



Pitchstone has been met with in the copper mine of Carrarach, 

 one of the consolidated mines. -\ 



* Fluate of lime does not usually enter into the composition of primitive rocks ; it is 

 said howcTcr, that the riolet variety called clorophane is found disseminated in a granitic 

 rock, in eastern Siberia ; and Dandrada mentions having seen in Sweden, in the district 

 of Norberg, extensive strata of mica-slate mixed with fluate of lime in compact masses, and 

 with nodules of quartz. Brongniart, Traite Elem. de Miner, tome i. p: 246. 



+ In the island of Arran, there are appearances of pitch-stone in tbe form of veins 

 traversing the granite, but as all veins are of posterior formation to the rocks which they 

 traverse, this cannot be equally old with the granite or pthjer rocks reckoned primitive. 



Z 



