MODE V. GRANITE. ]$3 



forms, full of a rust, or brown dust. In breaking 

 these granites, we find in their interior small 

 pyrites, brown and dull on the outside, but bril- 

 liant and of a very pale yellow within, and whose 

 fragments are attracted by the magnet. It is 

 from the decomposition of these pyrites, that the 

 cavities arise. My guides found fragments of 

 these granites, wherein were cubical pyrites from 

 three to four lines in thickness, whose fracture 

 is very brilliant, and of a very lively brassy yel- 

 low : these do not decompose in the air. 



" We also find in these rocks quartz, with 

 veins and nests of delphinite, or green schorl of 

 Dauphiny (actinote) ; it is but confusedly crys- 

 tallised, but easily known by its puffing up un- 

 der the blow-pipe, and by the black and refrac-^ 

 tory scoria into which it is changed. 



" In some parts these granites degenerate into 

 irregularly schistose rocks, composed of quartz 

 and felspar, without any mixture of mica, and 

 whose layers are separated and covered with 

 an argillaceous, nut-brown, ferruginous earth, 

 which melts into a black glass. 



" These same rocks of granite contain a vein 

 of granitel almost entirely composed of laminar 

 black and brilliant hornblende, and of grey 

 translucent felspar, which assumes outwardly a 

 rusty colour. 



