Diopside — Forsterite — Silica. 



239 



as will be shown in the optical part of this paper, characteristic 

 of pyroxenes of intermediate composition. There is no doubt, 

 then, that Zinke obtained intermediate pyroxene of varying 

 composition as we have stated should be obtained with the 

 procedure followed. 



It is obvious from the foregoing discussion that in describing 

 any experiment performed on a mixture belonging to such a 

 system it is necessary to state the initial condition of the 



Fig. 20. 



1560 



1500 



1440 



1380 



A<* 



& 



FORSTERITE 

 PYROXENES 

 & LIQUID 



P Y R 



X * 



CaMgSi 2 6 



50 



h- 



<-CaSi0 5O 



20 



40 



60 

 -h- 



40 



70 

 -h- 

 30 



60 

 80 



80 



90 



-+- 



MgSiO, 



20 



material used. For nearly all mixtures it is necessary to use 

 material prepared by crystallizing a glass at a low temperature. 

 Any composition lying in the area AEF (fig. 5) including the 

 pyroxene mixtures E to F can, however, be crystallized to an 

 'equilibrium mixture' simply by cooling from the liquid 

 condition. 



The Pyroxenes, Diopside-Clmo-enstatite. 



By using the results of the ternary system a diagram may 

 be constructed for the pyroxenes which exhibits their behavior 

 with change of temperature in a more striking manner than 

 does the triangular diagram where temperature can be 



