MODE V. PORPHYRY. 



of an unctuous felspar, a little compact, and of a 

 greenish tint*. 



1539- F. " Grey porphyry with a cement of 

 petrosilexj of a greenish grey, enclosing a number 

 of crystals of unctuous felspar of the same colour, 

 though a little whiter, some pyrites, and some 

 black ferruginous spots. 



1539- G. " Schistose porphyry with a blackish 

 cement the colour of iron, with a scaly atid bril- 

 liant fracture, hard, containing crystals of dry 

 white felspar, opake, which bubbles and readily 

 melts under the blow-pipe, and other crystals of 

 hornblende, pretty hard, of a blackish green." 



Add porphyry with black chalcedony, from 

 Chemnitz, in Saxony. (Linn, a Gmelin, 206.) 



Aspect 4. Blue. Dark indigo blue porphyry, 

 with crystals of yellowish felspar, from the isle of 

 Rasay, Scotland. 



'See Mr. Jameson's Mineralogy of the Scotish 

 Isles, ii. 117. He. says the base is betwixt clay 

 and hornstone, so it is only placed here to excite 

 further enquiry concerning so beautiful and un- 

 common a rock. 



* Verd d'oeillet. The French of Swiss and German authors is 

 ften peculiar. 



