396 University of California Publications. [Geology 



and even quartz are idioblastie elements. Sometimes the structure 

 of the glaueophane schists is ophitoblastic. 



2. The statement of Rosenbuseh*, "die Arfvedsonitamphi- 

 bole treten nur in Eruptivgesteinen, die Glaukamphibole dagegen 

 nie als urspriingliehe Gemengtheile solcher, auf ", is quite true. 



3. The glaucamphiboles rich in Fe 2 3 (crossite, rhodusite, etc.) 

 are in general characteristic of the most acid schists (quartzites, 

 albite schists, gneiss, mica schist with muscovite, just as arfved- 

 sonite amphiboles rich in Fe 2 3 (riebeckite, etc.) are character- 

 istic of acid eruptive rocksf (pegmatites of granites, quartz 

 syenites, etc. 



4. The origin of the glaueophane schists is very complicated, 

 and nothing but detailed investigations in the field will solve the 

 problem. The phenomenon of the metamorphism of various 

 rocks into glaueophane schists seems to be a kind of piezometa- 

 morphism (Weinschenk) , as stated by S. Franchi. 



5. Many kinds of amphiboles, glaueophane, karinthine, actino- 

 lite, etc., may be formed synchronously in the same rock and 

 crystal. 



6. During the metamorphism of the eruptive rocks into glau- 

 eophane schists, many changes of the homogenous mixtures into 

 non-homogenous rocks take place. Besides the formation of rutile 

 and titanite from brown amphiboles, of lawsonite (epidote, 

 zoisite, lotrite (?), etc.) and albite from a basic plagioclase, the 

 occurence of various amphiboles (glaueophane, karinthine, actino- 

 lite, etc.) can also be explained in this way from katophorite, 

 barkevikite, etc., or a similar complicated amphibole. 



* Loc. cit. 



t 6. Murgoei. The Genesis of Eiebeckite and Riebeckite Eoeks, Amer. 

 Journal of Sci., 1905. 



Bitkarest, 



March, 1906. 



