612 MANUAL OF NATUKAL HISTOBY. 



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, EL 

 =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. — T erbiides. Minerals containing com- 

 pounds of Terbium. Symb. Tb. 



