105 



The composition shown above , answers tolerably well to 

 the empiric formula: 



SSiO^. AF^O^. A[Ce,La,Di)^Os. ZAh_0.^. CaO. ZNa.^O. 



It is scarcely to be decided with anything like certainty, 

 how the chemical composition of the erikite is to be inter- 

 preted. First its pseudomorphous-like structure shows that 

 the mineral must have been transformed, and secondly it is 

 found intimately mixed up with another mineral, probably hydro- 

 nephelite, which cannot be separated from the erikite, and the 

 relative amount of which cannot be decided. 



Neither is it possible to tell to how high a degree the 

 mineral has been transformed ; other minerals containing cerium, 

 especially steenstrupite which is, as to composition, tolerably 

 nearly allied to erikite , are generally transformed in such a 

 way that the substance becomes single-refracting, without this 

 fact being accompanied by any specially great alteration of the 

 chemical composition M- Contrary to this the erikite has be- 

 come an aggregate of exceedingly strongly double-refracting 

 small parts. 



Although the structure might perhaps indicate that a 

 thorough transformation of the original erikite has taken place, 

 the peculiar chemical composition would rather indicate a con- 

 trary fact; as is to be mentioned hereafter, there are in this 

 composition some peculiarities especially characteristic of several 

 of the pegmatitic minerals from the district of Julianehaab; 

 as all the other minerals are known in their original state, we 

 have some reason to suppose that the erikite has originally 

 contained the principal ones of the elements now found in it, 

 viz. SiO.^i P^^bi (^^5 L'^4 ^^)2^3? and NuoO, even if their 

 respective amount may be somewhat altered. 



■) Comp, the above quoted paper on steenstrupite by 0. B. Bøggild. 



