GRANITE. 239 



D. Quartz, felspar, hornblende, chlorite. 



E. Quartz, felspar, hornblende, steatite. 



F. Quartz, felspar, mica, porcelain clay, 



It is doubtful whether the apparent steatite of 

 E is not decomposed talc or chlorite. The por- 

 celain clay of F appears also to be the result of 

 the decomposition of one variety of the felspar in 

 its structure. When the mixture is ternary 

 alone, or of quartz, mica, and clay, it is evidently 

 a decomposed rock and has lost its compactness. 

 This rock occurs in Cornwall. 



The remarks respecting variations of aspect, 

 made on var. A. Div. 2d. are applicable to all 

 the other modifications of granite. In some rare 

 instances, it offers other varieties of a very pecu- 

 liar character, in consequence of a spheroidal 

 concretionary structure, of which the orbicular 

 granite of Corsica is a well known example. 

 Many varieties of granite contain other minerals 

 imbedded, as already noticed ; and the following 

 catalogue contains those of most usual oc- 

 currence. 



Garnet. Zircon. 



Cyanite. Fluor spar. - 



