184: Washington — Igneous Rocks from Eastern Siberia. 



through incipient decomposition. Quartz occurs in anhedra, 

 but its total amount is very small. It carries minute liquid 

 inclusions. 



The hornblende is olive-green, and shows the usual characters 

 of this mineral in the dioritic rocks. It is occasionally epidoti- 

 sized, and some actinolite is also present, derived apparently 

 from the normal hornblende. There are also a few grains of 

 magnetite, which are occasionally, when embedded in ortho- 

 clase, surrounded by a zone of biotite. Some grains of titanite 

 are also present. 



Although no analysis was made of this rock, yet its system- 

 atic position is quite clear. It obviously belongs to the mon- 

 zonites of Brogger, and indeed much resembles type specimens 

 of this from Predazzo, being slightly finer in grain. The 

 amount of quartz is also a little greater, and the Siberian rock 

 may possibly belong to the banatites or quartz-monzonites. 



Locust, N. J., December, 1901. 



