56 Buddington — Natural and Synthetic Melilites. 



10 2CaO.Al 2 3 .Si0 2 — 50 



Temperature Time 

 1110° 1 hr. 



1125° 1 hr. 



1358' 

 1363' 



1/3 hr. 



1/3 hr. 



orAMA()Q .. ..(90 3CaO.Al 2 3 .3Si0 2 

 2CaO.Mg0.2Si0 2 — 40 j 10 3N a 2 O.Al 2 3 .3Si0 2 



Phases 

 Homogeneous crystal aggregate. 

 Trace of beginning of dissociation. 



ww = 1.634 w e = 1.635 

 Glass plus trace of crystal. 

 All glass. 



10 2CaO.Al 2 3 .Si0 2 — 10 2CaO.Mg0.2Si0 2 



SO 



Temperature Time 

 980° 10 hrs. 



1050° 



1100° 

 1150° 



4 hrs. 



40 hrs. 

 1 hr. 



90 3CaO.ALO s .3SiO, 

 10 3Na^O.A"l 2 3 .3Si6 2 



Phases 



Homogeneous medium grained fibrous aggregate 

 and lath shaped crystals in a finer ground 

 mass. 

 Ww = 1.634 we =1.623 



Homogeneous fine grained fibrous granular ag- 

 gregate. 



Homogeneous crystal phase. 



A little dissociation. 



Tables II, VI, VII, VIII give the optical characters 

 and thermal data for the preparations examined. Fig- 

 ures 1, 5, and 6 show the indices of refraction plotted 

 against composition in weight percent. In fig. 7 the com- 

 positions of the mixtures investigated are plotted in 



Fig. 5: 



*5 

 ■-§ 1-640, 



g 

 V> 1-630 



„ 1-020 



«£=c 











JSalli^^ 





< 



^ 























l-64-O 



1-630 



1-62 O 



I-GIO 



O 20 <4-0 CO SO IOO 



2<EaO-MgO-<2<SlO i ? WT- RERCENT 3o[^3CaO'Al z Oj-JSL0 2 ] 



/o[jNa 2 O-A l 2 Oj • J\J I O e J 



5. — Curves for refractive indices plotted against composition in weight 

 percent for mixtures crystallized above 1000° and .below the point of 

 dissociation. 



triangular coordinates together with the isotherms for the 

 temperatures of complete melting. As in the case _ of 

 fig. 4, a significant point is that those compositions which 

 approximate most closely to the natural minerals lie in 

 the zone of mixtures with the lowest temperatures of com- 

 plete melting. In fig. 8 the indices of refraction are 



