119 



Pyrochlore iR{Ti, Th]0^- ъ'ЕШ.^О^ +ANaF 

 ov\R(Ti, Th]0.,-bRNb^O^ + ANaF 

 (R = Ce, Ca, Fe) 



Chalcolamprite RSi O3 • RNb .^ O^F.^ 



{R = Ce, Ca, Fe, Na etc.) 



En de i о li te RSiO ., - RM .,0 r, {OH)^ 

 (R as in Chalcolamprite) 



Lewisite 2СаТгО^- Z CaSb^Og 



Mauzeliite RTiO^-2RSb^Of, 

 {R = Pb, Ca, CaF, Ca {OH) etc.) 



B. The ratio between the number of ВОо and R^O^ 

 equal to or greater than 2. 



1. Orthorhombic. 



a :b : с = 



\{TiO,),.'R{NbO,),.-^H,0 



0-364 : 1 : 0-303 



{R = Y, Er, Ce, и etc.) 



2R(TiO.,).,-R{NbO.^)., -ЪН.О 



0-3638 : 1 : 0-3422 

 {R as in Euxenite) 



R,{Ti,Th),0,,.RM,0,, 



0-3612 : 1 : 0-3362 



[R = Ce, La, Di, Fe, Ca etc.) 



bRSiO^ . h'RZrO.^ • R(Nb, Ta),0^ 



0-38408 : 1 : 0-35602 



(R = Ce, La, Di, Fe, Fe, Ca etc.) 



used Brøgger' s axial ratio for polycrase (a:b:c = 34619 : 1 : 031843) 

 and the just named axial ratio of columbite by Schrauf. 



Euxenite 



Polycrase 



Aeschvnite 



P 1 y m i g n i t e 



