16 W. M. Bradley — Analysis of the Mineral Neptunite. 



in a mixture of hydrofluoric and sulphuric acids and finally 

 titrating with KMn0 4 . 



The analyses agree essentially with those obtained by the 

 previous investigators on the Greenland material with the 

 exception that the percent of MnO present is much smaller 

 while the amounts of lime and magnesia show a corresponding 

 increase. The mineral is therefore a silico-titanate of iron 

 and the alkalies. The results of the analyses are as follows : 



Si0 2 52-91 



Ti0 2 17-77 



MnO -82 



CaO 1-59 



MgO 1*41 



FeO 11*54 



K 2 5-11 



NaO 9-83 



II 



52*83 



17-89 



•88 



1-53 



1-48 



11-83 



5-06 



9-28 



Average 



52-87 



17-83 



•85 



1-56 



1-44 



11-69 



5-08 



9-56 



Ratio 



•875 



4013 



•222 



1-017 



•Oil "J 





'° 27 1-235 

 •035 ( 23D 



1-077 



•162 J 





•?" [ -208 

 •lo4 j 



•954 



100-98 100-78 100-88 

 The ratios derived from the analysis yield very closely the 

 following formula — 4Si0 2 .lTi0 2 .lR0.1R 2 0, which can be ex- 



i ir 



pressed by the general formula R 2 RTiSi 4 12 or (Na,K) (Fe, Ca 

 Mg,Mn) Ti Si 4 O la . 



This is the same as that given by Flink* as a formula for the 

 Greenland material. 



In conclusion the author here makes known his indebtedness 

 to Prof. W. E. Ford, who so kindly furnished the material for 

 this investigation. 



Mineralogical Laboratory of the Sheffield Scientific School of Yale Univer- 

 sity, New Haven, Conn., April 3, 1909. 



;: Loc. cit. 



