NOME VI. OBSIDIAN. 46l 



lied trap or basaltin. The white fibrous veins 

 sometimes observable seem also to be of felspar, 

 which when heated assumes a fibrous form. 



But obsidian also occurs of other colours, such 

 as bluish, dark green, yellowish, and grey ; nay, 

 Troil says that in Iceland it is sometimes found 

 colourless, like crystal. Dolomieu mentions a 

 yellow vitreous lava, with black mica and white 

 quartz, somewhat resembling pitch-stone, and 

 which seems a granite in a particular period of 

 fusion. In the eruption of Etna, 1787, a vitreous 

 lava appeared, interspersed with particles of talc*. 



The volcanoes of New Spain sometimes present 

 a beautiful obsidian, in which a spangled light 

 plays upon a brown base, with an effect resem- 

 bling aventurine. 



Micronome 1. Entire. Common black ob- 

 sidian, from Iceland, commonly called Icelandic 

 agate. 



The same, from Peru, piedra de Galinazzo. 



Bluish obsidian, from Iceland, Teneriffe, &c. 



Yellowish, from Lipari. 



Crystalline, from Iceland. 



Refulgent, from New Spain. 



* Dolomieu Ponces, Q3, Etna, 509, 



