B—O — SiO — O — B 



That the ratios for niobic acid and for water and fluorine 

 are somewhat too high may also in this instance be explained 

 as due to the niobic acid not being quite free from tantalic 

 acid and to the determination of the water having given too 

 high a result. 



Endeiolite has only been found at the locality No. 2 on 

 INarsarsuk. As mentioned above, the crystals occur implanted 

 on aegirine crystals. These lay imbedded in a porous mass of 

 elpidite prisms and needles, which mass, moreover, contained 

 a number of uncommon minerals such as leucosphenite, epidi- 

 dymite , zinnwaldite , etc. The aegirine crystals in this elpidite 

 formation were rather numerous , but it was only on compara- 

 tively few of them that endeiolite crystals were implanted. In 

 some places endeiolite was also deposited on the elpidite needles 

 in the immediate neighbourhood of the aegirine crystal. How- 

 ever, the occurrence of the mineral on elpidite is so subordinate 

 that it may be said to occur almost exclusively on aegirine. 



The two minerals chalcolamprite and endeiolite now de- 

 scribed are to be considered as species belonging to the pyro- 

 chlore group. In chemical constitution they differ from the 

 previously known members of this group by containing SiO., 

 instead of Гг'О.,, ThO^, etc. Owing to this difference of com- 

 position the new minerals also have a considerably lower spe- 

 cific gravity than the iiitherto known minerals of the group. 



