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GRANITE. 



subject, that each of the three preceding minerals 

 may exist of different colours in the same com- 

 pound. 



SYNOPSIS OF GRANITE. 



FIRST DIVISION. 

 Of two ingredieats. 



A. Felspar, and mica. 



This variety does not seem to constitute ex- 

 tensive masses. 



B. Quartz, and felspar. 



a. An uniform mixture of these ingredients. 



b. The quartz, or felspar, or both, imperfectly 

 tsrystallized and influencing each other's forms. Gra- 

 phic granite. 



This remarkable variety seems to occur ex- 

 clusively in veins, particularly in those which 

 traverse gneiss. The quartz and felspar which 

 compose it, are aggregated in lengthened parallel 

 prisms. The prismatic structure therefore is 

 seen in one direction ; while, in the reverse, the 

 peculiar appearance whence the term is derived, 

 becomes visible. That appearance is produced 



