PLAGIOCLASE ROCKS. 



Family of Quartzless Plagioclase Rocks. 



These rocks were formerly included partly as greystones, partly as 

 greenstones, the oligoclase series, except diorite, belonging to the 

 former ; while the labradorite rocks with diorite formed the green- 

 stones. Diorite is the deep-seated condition of the andesites, just as 

 gabbro is the plutonic condition of dolerite. 



