1200° 



1 hr. 



1428° 



% hr. 



1430° 



1/3 hr. 



50 Buddington — Natural and Synthetic Melilites. 



Table VI. 



Optical and thermal data for mixtures of 2CaO.Mg0.2Si0 2 ; and [(90 

 3CaO.Al 2 3 .3Si0 2 ) (10 3Na 2 O.Al 2 Q 3 3Si0 2 )] Compositions^ expressed 

 in weight percent, and temperatures in degrees Centigrade. 

 90 2CaO.Mg0.2Si0 2 — 10 J 90 3CaO.Al 2 3 .3Si0 2 

 1 10 3Na 2 O.Al 2 3 3Si0 2 



Temperature Time Phases 



1180° 16 hrs. Essentially homogeneous very fine grained 



fibrous aggregate, with sutured texture. 

 Trace of minute grains of much higher index 

 of refraction. 

 w w - 1.634 n € =1.639 



Trace of dissociation in some grains. 

 Glass plus trace of crystals. 

 All glass. 



80 2CaO.Mg0.2Si0 2 — 20 [ (90 3CaO.Al 2 3 .3Si0 2 ) (10 3Na 2 O.Al 2 3 .3Si0 2 ) ] 



Temperature Time Phases 



900° 16 hrs. Essentially homogeneous fibrous granular aggre- 



gate. Trace of minute grains of much higher 

 index of refraction and low birefringence. 



1100° 1 hr. Same as above. 



1150° 1 hr. Same as above. Ww = 1.632 n e = 1.637 



1175° 2 hrs. Trace of dissociation. 



1300° 45 hrs. Conspicuous poikilitic texture. Second phase 



occurring as minute inclusions in the major 

 crystal phase. 



1320° % hr. Single crystal phase plus trace of glass. 



1409° 1/3 hr. Glass plus trace crystals; crystal habit tabular 



parallel to base. 



1414° 1/3 hr. All glass. 



60 2CaO.Mg0.2Si0 2 — 40 [ ( 90 3CaO.Al 2 3 .3Si0 2 ) ( 10 3Na 2 O.AL0 3 .3Si0 2 ) ] 



Temperature Time Phases 



1100° 2 hrs. Homogeneous bladed aggregate, full of minute 



air bubbles. 

 1130° 3 hrs. Minute trace dissociation. Fine grained, ribbed 



and bladed aggregate. Anomalous interfer- 

 ence colors, 

 ww = 1.632 ne =1.632 



1361° 1/3 hr. Glass plus trace crystals. 



1366° 1/3 hr. All glass. 



50 2CaO.Mg0.2Si0 2 — 50 [ ( 90 3CaO. Al 2 3 .3Si0 2 ) ( 10 3Na 2 O.AL0 3 .3Si0 2 ) ] 



Temperature Time Phases 



1100° 16 hrs. Homogeneous bladed aggregate full of minute 



air bubbles. ww = 1.631 n e = 1.630 



1130° 3 hrs. Trace of dissociation; interstitial strongly 



birefringent material. 

 1170° 40 hrs. Distinct dissociation; 2d phase interstitial. 



1200° 40 hrs. 2d phase in well-formed rods. 



1341° 1/3 hr. Glass plus trace crystals; crystal habit thick 



tabular to pseudo-cubic with and without 



modification by 2d order prism. 

 1346° 1/3 hr. All glass. 



