MANUAL OF NATURAL HISTORY. 613 



18. Family. — Didymiides. Minerals containing 



compounds of Didymium. Occurs with 

 cerium in " Parisite/' also in " Tschewki- 

 nite/' Symb. D. 



19. Family. — Lanthaniides. Minerals containing 



compounds of Lanthanium. Occur as Car- 

 bonate or " Lanthanite," in thin 4-sided 

 plates, H. =2-5-3, grayish, coating "cerite " 

 in Sweden ; also in " Cerium-ochre/' in 

 "Monazite," and in "Mosandrite." Symb. La. 



20. Family. — Ceriides. Minerals containing com- 



pounds of Cerium. Occur 1, as Silicate or 

 "Cerite," in short 6-sided prisms, H. =5*5 ; 

 sp. gr. 4*9 ; also in " Gadolinite/' " Mosan- 

 drite/' " Muromontile," &c. Symb. Ce. 



Y. ORDER— Uranexides. 



Minerals containing metals of the Uranium series, 

 either native or in different states of composition ; 

 solid. 



1. Family. — Uraniides. Minerals containing com- 



pounds of Uranium. Occur 1, as Oxide, or 

 " Pitch-blende/' octahedral, H. = 5*5, sp. gr. 

 = 6-7, black ; also in " Urinite," " Medjidite," 

 " Liebigite/' &c. Compounds of the peroxide 

 afford permanent yellow colours. Symb. U. 



2. Family. — Columbiides. Minerals containing 



compounds of Columbium. Occur ] , as Co- 

 Iambic acid, with Yttrium in " Yttro-tanta- 

 lite/' H. = 45 — 5*5, greenish-black, or with 



