DOMAIN II. SILICEOUS. 



green basalt, are really of granitin with particles 

 of siderite, as micfa is never so much comminuted, 

 Granitin also often forms nodules, or veins, in 

 large or small grained granite, in almost every 

 country where that substance occurs ; but this 

 substance being rather of microscopic observa- 

 Green basalt, tion, the specimens are not common. Green 

 basalt, properly so called, should be homoge- 

 neous, or present only spangles of siderite ; but 

 may contain occasionally very minute particles 

 of quartz only. The Isis of the Capitol, Ferber, 

 231, is of granitin. 



MODE VII. GRANITON. 



When the crystals, especially those of felspar, 

 are extremely large, that is, from two to six 

 inches or more in length, the substance may 

 well be called a graniton. It is common in the 

 Alps, and other granitic mountains; and exam- 

 ples may be seen in the foot pavement of West- 

 minster bridge*. Graniton presents the com- 

 mon colours of granite, that is, white, grey, and 

 red. 



* Mr. Smeaton says it came from Llanlivery, near Fovvey, in 

 Cornwall. 



