Bucldington — Natural and Synthetic Melilites. 71 



Monzoni gehlenite. — A specimen of limestone, labeled 

 Monzoni (Fassathal), with minute disseminated crystals 

 of gehlenite. was obtained by Dr. Wright from the U. S. 

 National Museum. The indices of refraction were deter- 

 mined on this mineral, and rough tests made for the loca- 

 tion of the solidus and liquidus. If we assume this 

 material to be essentially the same as that analyzed by 

 Banmielsberg from this locality, and recalculate the 

 analysis in terms of constituent compounds, we find that 

 the mineral consists of about 58 percent gehlenite, 28 per- 

 cent akermanite, and 14 percent ferric and ferrous iron 

 compounds. The results of the study of the natural 

 mineral and a comparison of its properties with those of 

 an artificial preparation having the same ratio of gehlen- 

 ite to akermanite, but free of iron compounds, are given 

 in Table XX. If the relatively large percentage of iron 

 compounds in the mineral is taken into account, the 



agreement is goo 



:1. 



Table 

 Gehlenite fi 



XXII. 



om Monzoni. 







Original 



Analysis 





Calculated 





analysis 



reduced 



Mol. 



molecules 



Differen 



SiO, 29.78 



30.20 



500S 



5218 



—210 



Al,6 3 22.02 



22.33 



2155 



2109 



— 46 



CaO 87.90 



38.43 



6S50 



750S 



—342 



AT<?0 3.8S 



3.93 



975 



1025 



— 50 



Fe.O, 3.22 



3.27 



205 



181 



— 24 



Feb 1.63 



MnO 19 



1.65 

 .19 



230 | 

 2 "1 



262 



— 5 



Ign. by dif- 











ference .. . 1.3S 











100.00 



100.00 





Table XXII gives the analysis by Kammelsberg of 

 gehlenite from Monzoni, stated in terms of its constituent 

 molecules and compared with the calculated molecules 

 in a mixture composed of 58 percent 2CaO.AloOo.SiOo, 

 28 percent 2CaO.Mg0.2Si0 2 , 8 percent 2CaO.Fe0.2SiOo, 

 and 6 percent 2CaO.Fe 2 3 .Si0 2 . 



The agreement between the properties of the artificial 

 preparations and the corresponding minerals is so close 

 that we feel warranted in concluding that the artificial 

 series of 2CaO.Mg0.2SiOo-2CaO.Alob 3 .SiOo solid solu- 

 tions are pure synthetic analogues of the akermanite- 



