213 



the perfectly unaltered form. If some of the trivalent metals 

 are placed together with phosphoric and niobic acid, and 

 fluorine combined with calcium , the following composition is 

 arrived at: 



(Si, Th)^._0.^e [La, Di, Г, Fe)^ [Mn, Ca, Mg).^ (Na, H)^., 

 • A(P,Nb)0, Ce- CaF^.AH^O. 



According to this, the steenstrupite should naturally be a 

 metasilicate, but as the quantity of water and possibly several 

 other circumstances besides must be taken into consideration 

 the classification becomes very uncertain. It would perhaps be 

 most natural to classify the steenstrupite with eudialyte, as the 

 axial ratios of these minerals as proved by Mob erg, show a 

 great equality; type III of the steenstrupite has also a con- 

 siderable similarity in form to the usual Greenlandic eudialyte. 

 However it must be mentioned, that the close relation between 

 these two minerals becomes somewhat improbable, especially 

 when considering that the eudialyte contains a much larger 

 quantity of silica; still at present I do not beheve , that it is 

 possible to classify the steenstrupite in any better place in 

 the system. 



