38 Buddington — Natural and Synthetic Melilites. 



Schaller, from a study of the natural gehlenites, showed 

 that the major components are gehlenite, akermanite, 

 and 3CaO.Al 2 3 .3Si0 2 . Accordingly, these three com- 

 pounds were chosen as end members and their relations 

 were studied. They were found to have a limited field 

 of solid solution. The composition 90% 3CaO.Al 2 3 . 

 3SiO + 10% 3Na 2 O.Al 2 3 .3Si0 2 , corresponding to the 

 composition of sarcolite, was then taken as another 

 end member, and its relations in mixtures of 2CaO.MgO. 

 2Si0 2 and 2CaO.Al 2 3 .SiQ 2 were studied. A field of 

 complete solid solution was found for these mixtures, 

 with the exception of a doubtful zone close to the 2CaO. 

 Mg0.2Si0 2 end. 



Schaller, from a study of the humboldtilites and the 

 original melilites of Capo di Bove, had shown that the 

 major components of these minerals were the compounds 

 3CaO.Al 2 3 .3Si0 2 , 2CaO.Mg0.2Si0 2 , and 3CaO.Fe 2 3 . 

 3Si0 2 , with minor amounts of 3Na 2 O.Al 2 3 .3Si0 2 and 

 2CaO~. Al 2 3 .Si0 2 . The soda compound varies from 8 to 

 12 percent, averaging about 9 percent. Accordingly, 

 a system was studied in which the percentage of 3Na 2 0. 

 Al 2 3 .3Si0 2 was maintained constant at 10 percent, and 

 the percentages of the compounds 2CaO.Mg0.2Si0 2 , 

 2CaO.AL0 3 .Si0 2 , and 3CaO.Fe 2 8 .3Si0 2 were varied. 



Another system was studied in which all five com- 

 pounds were introduced, the percentage of the soda com- 

 pound being maintained constant at 10 percent and 2CaO. 

 Al 2 3 .Si0 2 at 20 percent, while the percentages of the 

 other three compounds were varied. 



The compositions of all the analyzed natural minerals 

 of the melilite group, except one, approximate to com- 

 positions embraced within or between the systems thus 

 studied. A synthetic preparation corresponding in com- 

 position to the mineral fuggerite, which is classed with 

 the melilites but falls outside these compositions, was 

 studied separately. 



Three analyses of natural humboldtilites made for the 

 writer by Dr. H. S. Washington showed that a ferrous 

 iron compound was an accessory component constituting 

 up to 15 percent or more of this mineral. Apparatus 

 for dealing with ferrous iron compounds must be devel- 

 oped before this component can be studied; it is there- 

 fore not considered in this work. 



