MODE XII. PITCH-STONE. 



nia ; and in other mountains of that country it 

 forms large strata, that alternate with porphyry*; 

 and as they contain abundance of quartz and 

 felspar, may be called pitchstone-porphyry, for 

 which see the Siliceous Intrites. 



Pitch-stone is universally regarded as a pri- 

 mitive rock ; but it is also often found second- 

 ary, and constituting the substance of petrified 

 wood. In the island of Arran it forms large 

 veins in sand-stone; and it also occurs in Mull 

 and Eig. This curious and important substance 

 seems unknown to Wallerius ; but Gmelin, in 

 his edition of Linnaeus, has called it opalus piceus, 

 and mentioned many of its sites, as Iceland, the 

 isle of Elba, Auvergne, Transylvania, Hungary, 

 the Reisgeberg mountains in Germany, and New 

 Spain. It sometimes occurs in basalt. 



STRUCTURE I. COMPACT. 



Pitch-stone, from Meissen in Saxony, where it 

 was first observed. 



The same, dark red, from Korbetz in Saxony. 



The same, spotted with black, from Upper 

 Hungary. 



The same, deep red, mingled with greenish 



* Kirwan Geol. Es&. 180. 



