612 MANUAL OF NATURAL HISTORY. 



and gneiss rocks ; 2, with alumina or " Chry- 

 soberyl," in right rectangular prisms, sp. gr. 

 3-5 3*8, H. = 8*5, yellowish-green, in alluvial 

 fluviatile deposits in Brazil and Ceylon. Glu- 

 cina is precipitated from its salts by pure 

 potassa or soda ; it is soluble in a cold solu- 

 tion of sesqui-carbonate of ammonia. Symb. 

 G., sometimes Be. 



13. FAMILY. Zirconiides. Minerals containing 



compounds of Zirconium. Occur 1, as Sili- 

 cate, or " Zircon " or " Hyacinth/' in square 

 prisms, sp. gr. 4*5 4*7, H. = 7*5, red, brown, 

 yellow, or gray, in fluviatile sand and allu- 

 vial deposits in Ceylon, also in Syenite. Zir- 

 conia is precipitated from solutions of its 

 salts as an insoluble sub-sulphate on being 

 boiled with sulphate of potassa. Symb. Zr. 



14. FAMILY. Noriides. Minerals containing com- 



pounds of Norium. Symb. Nr. 



15. FAMILY. Yttriides. Minerals containing com- 



pounds of Yttrium. Occur 1, as Silicate, or 

 " Gadolinite," monoclinic, sp. gr. 4--4'5, H. 

 =6'5 7, blackish, in Sweden; 2, as "Tan- 

 talate " or " Yttrotantalite," not crystalline, 

 brownish-black, sp. gr. 5 '3 =5*8, H. = 4'5 5 '5. 

 Yttria is precipitated from solutions of its 

 salts by ferrocyanide of potassium. Symb. Y. 



] 6. FAMILY. Erbiides. Minerals containing com- 

 pounds of Erbium. Symb. Eb. 



17. FAMILY. Terbiides. Minerals containing com- 

 pounds of Terbium. Symb. Tb. 



