BY H. I. JENSEN. 



703 



For the sake of being able to compare these two rocks, I 

 calculated tlieir norms, first in terms of such minerals as usually 

 occur in glaucopha,ne schists, next in terms of such minerals as 

 occur in igneous rocks. The chemical symbols for the minerals 

 were taken from Dana's 'Text-Book of Mineralogy.' The follow- 

 ing results were obtained : — 



1. Glaucophane Schist, Conandale Range. 

 Glaucophane 32-91% 



Epidote ... 



Perofskite 



Actinolite 



Anorthite 



Oi-thoclase 



Omphacite 



Akermannite 



Magnetite 



2-20 

 3-81 

 27-49 

 21 41 

 2-78 

 2-23 

 212 

 3-78 



Water 



Total 



98-73 

 9-64 



99-37 



The composition of glaucophane was taken as SiOo, 57*6 %; 

 AUO3, 16-3; FeO, 7*7; Mg, 8-5; and NasO, 9-9; and, in the 

 epidote, the ratio of AlgO- to FeoO.3 was taken to be 5 : 1 (for 

 formulre, see Dana, op cit.). 



The glaucophane was calculated on the formula KaoO, AI0O3, 

 2(FeMg)0, GSiO. with the ratio of Mg to Fe as 2 : 1. 



