1125° 



1 hr. 



1150° 



1 hr 



1415° 



16 hrs. 



Buddington — Natural and Synthetic Melilites. 53 



Temperature Time Phases 



1250° 1 hr. Crystals plus trace of glass, the glass occurring 



as minute droplets in the crystals. 



1524° % hr. Glass plus trace of crystals. Crystal habit is 



medium tabular parallel to base ; combination 

 of 1st order prism and base, usually modified 

 by the 2d order prism. 2d order pyramid 

 rare. 



1533° y 2 hr. All glass. 



40 2CaO.Al 2 3 .Si0 2 — 60[(90 3CaO.Al 2 3 .3Si0 2 ) (10 SNaAALA.SSiO,) ] 



Temperature Time Phases 



1085° 2 hrs. Perfectly homogeneous radiating fibrous aggre- 



gate with some plates and ribbed structure. 

 1110° 1 hr. Perfectly homogeneous. 



iiw = 1.645 ne = 1.633 

 Beginning of trace of dissociation. 

 Trace of dissociation. 



Glass plus few crystals. Crystal habit predomi- 

 nantly tabular parallel to base; combination 

 of base and 1st order prism modified by 2d 

 order prism. 2d order pyramid and ditetra- 

 gonal noted on a few crystals. A few equidi- 

 mensional crystals present. 

 1485° 1/3 hr. Glass plus trace crystals. 



1490° 1/3 hr. All glass. 



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



Temperature Time Phases 



1000° 16 hrs. Homogeneous ribbed and bladed aggregate. 



Much coarser grain than 16 hrs. at 1175°. 

 n w = 1.637 ne= 1.625 

 1150° 16 hrs. Minute trace of dissociation. Some aggregates 



seem homogeneous. 

 1418° y 2 hr. Glass plus trace crystals. 



1422° y 2 hr. AU glass. 



Table VIII. 



Optical and thermal data for mixtures of 2CaO.Mg0.2Si0 2 ; 2CaO.Al 2 3 .Si0 2 ; 



and [(90 3CaO.Al 2 3 .3Si0 2 ) (10 SNa-CALOsSSiO,) ] Composition 



in weight percent and temperatures in degrees Centigrade. 



70 2CaO.MO.SiO, - 15 2CaO.Mg0.2Si0 2 - 15 { «j g ^« 



Temperature 



Time 



Phases 





1200° 



1 hr. 



Homogeeous single crystal phase. 

 Ww = 1.658 n € = 1.652 





1205° 



16 hrs. 



Trace of beginning of dissociation, 

 texture. 



Poikilitic 



1537° 



1/3 hr. 



Glass plus trace of crystals. 





1542° 



1/3 hr. 



All glass. 





