232 



GUANITE. 



either so imperfect or so inaccessible, that it ap- 

 pears preferable to leave this question open for 

 future correction. Those minerals therefore 

 which are found entering into granite so as to 

 modify its character, are enumerated in an ap- 

 pended list; in which are also contained all those 

 which enter into it in smaller proportions, or of 

 \vhich granite is the natural repository. 



Finally, there are certain compounds of 

 minerals, of a granitic character, the claims of 

 which are not yet determined in a satisfactory 

 manner. It seemed desirable to place them in 

 an appendix for future correction, rather than to 

 ran the risk of misleading the student by a pre- 

 mature decision. 



The colours of granite are infinitely varied. 

 That of the hornblende, where it exists, being 1 

 invariably black, or an extremely dark green, it 

 only contributes to modify that of the rock, by 

 the proportion which it may bear to the other in- 

 gredients. When in great excess, it forms com- 

 pounds nearly black. In other cases it produces 

 various tints of grey. Grey and black tints also 

 arise from the presence of black mica. But this 



