Ill 



siderably more complicated , as these ingredients may be put, 

 and have been put, on very different places in the formula. 

 As will be seen from the following the formula, with regard to 

 most of the minerals, agrees rather well with the above common 

 combination. The following formulae are given: 



Euxenite: R.,{TiO.^)^ • È{NbO.^).^ • ЧгН.^О 

 Polycrase: 2Л,,{ТгО.^)., M • ШЬО.^)^ • ЪН.О 



(from Brevik) lÈ{TiT}i)0^ . bRM.ß^ -y 4NaF 

 Pyrochlore (from Miask) \R[TiTh)0^ . bÈNb^^ -\-\NaF 

 \ (from Frederiksværn) RTiO^ • R^Nb^^O.^ + \NaF 



Here only the last formula deviates from the common com- 

 position; according to Brögger^) the occurrence of the pyro- 

 niobate is due, however, to an alteration in the mineral. 



MauzeUite has been analysed by Sjögren^) who has 

 established three different formulae. If no regard is paid to the 

 fluorine we get: 



(1) Ti(SbO^È), 

 which may also be written 



RTiO.^ .2RSb.^^ Л -RO 



In this case the amount of basic ingredients becomes so 

 large, that the mineral cannot be a compound of a metatita- 

 nate and a metaniobate. 



If we take F and [OH] to be connected with Ca we get: 



(2) [Sb oO .;) ^R ^TiO i.e. a pyroantimonate. 



When this formula is written 



RTiO.^.lRSb.O^ 

 it is seen to correspond exactly to the common composition. 



^) hi Dana (Mineralogy, t892 p. 745) is wriUen 2В(Т10^).^ 



^) Zeitschr. f. Kryst. XVI. p. 511. 



3) Geol. Foren. Förh. Stockholm. XVII. p. 316. 



