HORNBLENDE SCHIST. 307 



are felspar, either compact or common, and born- 

 blende ; but the latter often occurs alone. Jn 

 this respect it differs from micaceous and chlorite 

 schists, in which the characteristic minerals sel- 

 dom exist without some quartz. The less essen- 

 tial minerals which sometimes occur in this rock 

 to such an extent as to modify its general charac- 

 ters, are mica aud chlorite; but the latter is rare, 

 nor is the former very common. 



As an imbedded mineral, garnet sometimes 

 abounds in this rock, as it does in micaceous 

 schist, but much more rarely; and the general 

 character and aspect of the hornblende schist pre- 

 sent corresponding variations. The other, and 

 more rare imbedded minerals, will be noticed in 

 a more appropriate place. 



As the colour of hornblende is almost inva- 

 riably either black, or a green so dark as scarcely 

 to be distinguished from it, the only varieties of 

 tint in the rock depend on the proportion and 

 colours of the felspar. A large proportion of that 

 mineral produces a grey hue, which varies in in- 

 tensity according to that proportion, and, in tone, 

 us it approximates to white, green or red. 



