JV. L. Bowen — The Binary System. 



559 



to indicate the hexagonal form of Na 2 Al 2 Si 2 8 and also the 

 isomorphous hexagonal mix-crystals with 0—35 per cent CaAl 2 

 Si 2 8 . Carnegieite is used to indicate the triclinic form of 

 Na 2 Al 2 Si 2 8 and also the isomorphous triclinic mix -crystals 

 with — 5 per cent Ca 2 Al 2 Si 2 8 . Anorthite indicates triclinic 



Diagram II. 



IA60' 



neiphll ite: g; / northite: 



ANDRTHITE. 







ME1LT 



j,, 



rfi. 



IO 



LO 



so ao so eo 



Na i Al t Si.,O e> 





%OaAI 4 Si 4 O e weight 



EQU(LIBR/Un DIAGRAM 



CaAl 2 Si 2 8 and also the isomorphous triclinic mix-crystals with 

 0-2 per cent E"a 2 Al 2 Si 2 O s . 



Throughout the text abbreviations are used : Ne to indi- 

 cate nephelite (NaAlSi0 4 hex.) ; Cg to indicate carnegieite 

 NaAlSi0 4 triclinic) ; An to indicate anorthite (CaAl 2 Si 2 8 tri- 

 clinic). Nephelite mix-crystals are indicated, Ne 65 An 35 or Ne 80 - 

 An 20 , the subscript numbers indicating the weight percentage 

 of NaAlSi0 4 and of CaAl 2 Si 2 8 present in the mix-crystal. In 

 like manner, carnegieite mix-crystals are referred to, -Cg 95 An 5 

 and anorthite mix-crystal -An 98 Ne 2 . NaAlSi0 4 and Na 2 Al 2 

 Si 2 8 are used interchangeably. The purpose in using the 



