DOMAIN If. SILICEOUS. 



mica is also in small spangles, some black, but 

 chiefly of a beautiful silver white. 



STRUCTURE IV. MINGLED. 



Some of this kind have already been incidentally 

 mentioned. Besides schorl and garnets, Saussure 

 observed chalcedony in granite, for which see the 

 Composite Rocks. Chlorite and actinote are not 

 uncommon in granite; and the talc sometimes 

 passes into steatite. Even calcareous spar has 

 been found in granite ; and, when decomposed, 

 porcelain earth, for which see the Decomposed 

 Rocks. Not to mention the metals ; primitive 

 gypsum, anthracite, gneiss, basalt, and other sub- 

 stances, also occur in granite. 



Granite, in veins in schistus, Saussure, 599, 

 from Valorsine. He describes it as passing through 

 his roche de corne, which is generally a magnesian 

 basalt; the granite is of grey quartz, white fel- 

 spar, and grey mica, and is regarded by him as 

 formed by infiltration. 



Granite, in veins in primitive slate, from Scot- 

 land. 



Granite, with veins of granular quartz, from 

 Forez, France. 



This account of one of the most important and 

 interesting rocks, shall be terminated by Zoega's 



