Ferguson and WIerwin — The Ternary System. 91 



Charges within the monticellite (CaO.MgO.Si0 2 ) field, 

 and in the forsterite field near it, crystallized with such 

 rapidity that great difficulty was experienced in quench- 

 ing them. The resorption of magnesia did not occur 

 readily and charges selected for a study of this phenome- 

 non were prepared in such a manner as to prevent the 

 formation of large crystals of magnesia which if formed 

 would not then dissolve in a reasonable time. The 

 microscopic examinations were in part very troublesome. 

 It often happened that the crystalline phases were not 

 only very similar optically but also had nearly the same 

 refractive index as the glass in which they were im- 

 bedded, thus making the positive identification of traces 

 of either almost impossible. 



The Crystalline Phases. 



The following crystalline phases 34 are found in the ter- 

 nary system stable in contact with a suitable melt : 



1. Lime, CaO. 



2. Periclase, MgO. 



3. Cristobalite and tridymite, Si0 2 . 



4. Pseudowollastonite, aCaO.SiO,. 



5. 3Ca0.2Si0 o . 



6. a2CaO.SiO, and /?2Ca0.Si0 o . 



7. Clino-enstatite, MgO.SiO,. 



8. Forsterite, 2MgO.SiO,. 



9. Diopside, CaO.MgO.2SiO.,. 



11. Akermanite, 2CaO.MgO.2SiO,. 



11. 5Ca0.2Mg0.6Si0 o . 



12. Monticellite (CaO.MgO.SiOJ— forsterite solid solutions. 



13. Wollastonite-diopside solid solutions. 



14. Wollastonite-5Ca0.2Mg0.6Si0 2 solid solutions. 



The significant properties of all of these phases with 

 the exception of the compounds 5Ca0.2Mg0.6Si0 2 , and 

 2CaO.Mg0.2SiO ; > and the solid .solutions of wollastonite, 

 of 5Ca0.2Mg0.6Si0 2 , and of monticellite, have been given 

 earlier in this paper and only corrections and such addi- 

 tional information as we have obtained will be given here. 



Pseudowollastonite grows in remarkably large crystals 

 as it forms during the inversion of wollastonite in the 



34 The general temperature-concentration relations of wollastonite, pseu- 

 dowollastonite and 5Ca0.2Mg0.6SiOo will be discussed in detail in a subse- 

 quent paper. 



