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JOURNAL OF GEOLOGY— SUPPLEMENT 



Crystallization with perfect equilibrium.— Crystallization of a 

 liquid of composition M (Fig. 3) takes place in the following manner 

 when perfect equilibrium prevails. At the temperature of the point 

 M the liquid becomes saturated with olivine (forsterite), and crys- 

 tals of that substance begin to separate. The composition of the 

 liquid then changes along the line AMK toward K with continued 

 separation of forsterite. When the temperature of the point K is 



CAMcSi^Og 



Mg^SiO, MeSiO, SiOj 



Fig. I. — Field diagram of the system: diopside, forsterite, silica 



reached, the liquid becomes saturated with pyroxene, and pyroxene 

 of composition L begins to separate, i.e., pyroxene rich in magnesia. 

 At the same time forsterite begins to redissolve and the composition 

 of the liquid begins to change along the boundary curve from K 

 toward TV. Meantime the composition of the pyroxene separating, 

 as well as that of the pyroxene which has already separated, changes 

 from L toward P (becomes more calcic) . When the temperature of 



