171 



Compared with each other, the two minerals agree in most 

 respects. With regard to the composition they differ only in 

 the fact that chalcohimprite contains fluorine Hke the previously 

 known pyrochlore minerals, whereas endeiolite chiefly contains 

 hydroxyl. In specific gravity the two minerals differ con- 

 siderably, and also in hardness. Another point of difference 

 deserving of attention lies in the fact that endeiolite often 

 occurs in twins, whereas twinning is unknown on chalcolaraprite 

 as well as on other pyrochlore minerals. 



33. Microlite. 



As has already been mentioned, G. Nordenskiöld dis- 

 covered in the Liitzen collection a mineral which on examina- 

 tion he found to be microlite. The mineral, which occurred 

 implanted on aegirine individuals, formed microscopical brow'nish 

 yellow octahedrons. For an analysis no more than 0,0303 grams 

 could be obtained. After deducting silicic acid, ferric oxide and 

 lime for the aegirine mixed with it, the result of the analysis 

 was as follows : 



{Nh, Ta)., 0, 74 



SnO,_ 4 



CaO., : 12,1 • 



(Oe, La,Di).> 0.^ 4,2 



Loss 0,7 



The metallic acids were considered chiefly to be tantalic 

 acid, and the loss fluorine and, possibly, alkalies. From this 

 is calculated the following formula for microlite : 



Ca.,Ta.,0,. 



In the Mineralogicai department of the Riksmuseum at 

 Stockholm, for which the Liitzen collection was purchased, 

 1 have had an opportunity of seeing the mineral examined by 



