YTTROTANTALITE. 

 yellow glass ; with a smaller quantity, a 

 dark yellowish-brown glass. Does not dis- 

 solve in carbonate of soda. 



2. Black Variety. Presents indistinct 

 traces of four- or six-sided irregular prisms 

 and plates. Colour black. Opaque. Lustre 

 metallic. Streak grey. H. scratches glass. 

 S.G. 5-395. 



Comp. 3 (Ca, Y, Fe) (Ta, W). 



Analysis by Nordenskiold : 



Oxide of tantalum , . 56-56 

 Tungstic acid . . . 3-87 

 Yttria . . . .19 56 



Lime 4*47 



Protoxide of iron . . 8-90 

 Protoxide of uranium . 0-8-2 

 Oxide of copper . . traces 



Water .... 6-68 



10066 

 BB decrepitates slightly, and becomes 

 dark brown, but does not fuse. With borax 

 yields a transpai-ent, colourless or yellowish 

 glassjwhich when it contains a compai-atively 

 small proportion of the Yttro-Tantalite, is 

 rendered opaque by flaming; but when it 

 contains a larger quantity, becomes opaque 

 without flaming. With carbonate of soda 

 swells up, and remains in the form of a 

 white mass after the soda has been absorbed 

 by the charcoal. 



3. Yellow Variety. Occurs in laminae in 

 fissures in Felspar. Colour brownish-yellow. 

 Opaque. Streak white. Not crystalline. 

 Softer than glass. S.G. 5-882. 



Comp. The same as No. 2 or 3 (Ca, Y, 



Fe) (fa, W), 



BB decrepitates slightly, and becomes 

 pale yellow, but does not fuse. With borax, 

 in the inner flame, yields a transparent, 

 yellow glass, which becomes darker yellow 

 on cooling, and is rendered milk-white by 

 flaming. 



All three varieties are insoluble in aque- 

 ous acids, but are completely decomposed by 

 fused bisulphate of potash. 



Yttrotantalitehas recently been stated by 

 Nordenskiold to be isomorphous with Poly- 

 crase and Polymignite. 



Localities. — Sweden: Ytterby in flesh- 

 red Felspar with Gadolinite ; Broddbo, 

 Finbo, and Kararfvet, near Fahlun, in gra- 

 nite veins ; associated with Garnet, JMica, and 

 Pyrophysalite. The Ilmen Mountains, near 

 Miask in the Ural. 



Name. From its composition: chiefly of 

 Yttria and Tantalum. 



ZEOLITE. 415 



Brit. Mus,, Case 38. 

 Yttrotitanite, Scheerer. See Keil- 



HAULITE. 



Yu. The Chinese name for Jade. 



z. 



Zala, See Borax. 



Zavalite. Probably hydrated carbonate 

 of Nickel, resembling Nickel-Emerald. Does 

 not occur crystallized. Lustre waxy, in- 

 clining to vitreous. Streak apple-green. 

 Yields to the knife. 



Locality. Spain. 



Zeagonite, Gismondi. AYesuvian mineral 

 occurring in rhombic crystals on Somma, 

 and identical with Gisjnondine (which see). 



Zeasitk. See Opal, 



Zeilanit, JFerwer, or Candite. A variety 

 of Pleonaste, in which part of the magnesia 

 is replaced by protoxide of iron. It occurs 

 in black octahedrons which are harder than 

 Quartz. Translucent to opaque. Powder 

 greyish -green. S.G. 3-6 to 38. 



Comp. (Mg2 Fe) Al^. 



Analysis, by Gmelin ; 



Alumina .... 67*28 

 Magnesia .... 17-45 

 Protoxide of iron . . 15*27* 



100-00 



BB infusible. With borax, or microcos- 

 mic salt, dissolves, forming a glass coloured 

 by iron. 



Scarcely acted on by acids. 



Locality. Near Candy, in Ceylon (whence 

 the name). 



Zellkies, Werner. See Cellular Py- 

 rites. 



Zeolite or Zeolith, Hausmann. A term 

 under which are comprised several minerals, 

 all of which possess, in common, the ten- 

 dency to form a jelly with acids. 



The ditferent varieties of Zeolitic minerals 

 may be divided into six groups, viz, : — 



1. Etfloi-escing Zeolite, or Laumonite. 



2. Feather Zeolite, or Natrolite, Scolecite. 



3. Foliated Zeolite, or Heulandite and 

 Stilbite. 



4. Needle Zeolite, or Scolecite and Na- 

 trolite ; including Mesolite, 



5. Pyramidal Zeolite, or Apophyllite ; in- 

 cluding Ichthyophthalmite, Oxhaverite,Tes- 

 selite. 



6. Radiated Zeolite, or Mesot^^pe. 



