Buddington — Natural and Synthetic Melilites. 55 



Temperature Tim e Pliases 



1360° 16 hrs. Glass plus few crystals. Crystal habit, thin to 



thick tabular parallel base, combination of 1st 

 order prism and base modified by 2d order 

 prism. 



1375° % hr. Glass plus trace of crystals. 



1378° y 2 hr. All glass. 



20 2CaO.Al 2 3 .Si0 2 — 40 2CaO.Mg0.2Si0 2 — 40 j Jjj 3§J^^3^i 



Temperature Time Phases 



900° 16 hrs. Very fine grained fibrous granular aggregate. 



1130° 1 hr. Homogeneous single crystal phase. 



n» = 1.640 ne = 1.638 

 1150° 1 hr. Trace of dissociation. 2d crystal phase occurs 



as interstitial material. 

 1388° y% hr. Glass plus trace of crystals. 



1395° y 2 hr. AU glass. 



20 2CaO.AL0 3 .Si0 2 — 30 2CaO.Mg0.2Si0 2 — 50 j ^ 3Na°OAi?0 ffsiO, 



Temperature Time Pliases 



1100° 1 hr. Homogeneous single crystal phase, 



ww =1.639 ne =1.635 

 Bare trace of dissociation. 

 Glass plus trace of crystals. 

 All glass. 



20 2CaO.ALO,SiO s - 20 2CaO.Mg0.2SiO s - 60 { «> ^^^ 



Temperature Time Phases 



1125° 1 hr. Homogeneous crystal aggregate with ribbed 



structure and coarse laths. 

 raw — 1.639 ne =1.632 



1150° 1 hr. Trace of beginning of dissociation. 



1360° 16 hrs. Glass plus few crystals. Crystal habit; tabular 



to pseudo-cubic; combination of base and 1st 

 order prism usually modified by 2d order 

 prism. 2d order pyramid present on an occa- 

 sional crystal. 



1389° y 2 hr. Glass plus trace of crystals. 



1395° % hr. All glass. 



10 2CaO.Al 2 3 .Si0 2 — 80 2CaO.Mg0.2Si0 2 — 10 j ®° s^OALof 3SiO, 



Temperature Time Phases 



1160° 16 hrs. Large clear crystal plates obtained by first melt- 



ing material and undercooling rapidly. 

 raw = 1.636 n e = 1.641 

 Homogeneous fibrous granular aggregate. 

 Trace of dissociation; poikilitic texture. 

 Glass plus trace of crystals. 

 All glass. 



1150° 



1 hr. 



1390° 



1/3 hr. 



1400° 



1/3 hr. 



1200° 



1 hr. 



1225° 



1 hr. 



1397° 



% hr. 



1405° 



y 2 hr. 



