174 



mineral is opaque, and only in thin splinters translucent. Even 

 in microscopical sections its diaphaneity is rather slight. Like 

 other apatite it has tolerably weak negative double refraction. 



The specific gravity of the mineral has been found by 

 weighing in benzole to be 3,24. This determination has been 

 made byMauzelius, who has also analyzed the mineral. The 

 analysis gave the following result. 



P,0, 41,12 



F 3,59 



CaO 47,67 



Y^ O3 etc 3,36 



Ce^ O3 etc 1 ,52 



MgO 0,79 



Mn 0, FeO trace 



H.,0 . 0,22 



Insoluble 2,63 



i00;90 

 — = F., ...... . 1,51 



99,37 



The insoluble residue probably consists chiefly of aegirine 

 and neptunite, with which the mineral is often so intimately 

 associated that it can hardly be perfectly separated from them. 

 After deducting this insoluble portion, the values found cor- 

 respond very well with the usual composition of apatite. Part 

 of the lime is, however, here replaced by rare earths, especially 

 yttrium earths. As far as I know this is the first time that 

 the presence of yttrium earths in apatite has been ascertained. 

 Cerium earths, on the other hand, have been found in apatite 

 from Norway by Th. Schere r 4- The largest percentage of 

 cerium earths found by him amounts to 5 %. The above 



1) Nyt Magazin f. Nat. Vol. 5, 1S48, p. 308. 



