Z 1 R 



According to Klaproth, the conftituent parts are, 



Zircon - - 69 63 



Silex - - 26.50 33 



Z 1 R 



Oxyd of iron 



96. 



97 



Hyacinth : Zircon Hyacinth, Brongniart. — The prevail- 

 ing colour of this mineral is orange-red ; it is fometimes 

 yellow, grey, and green, and very rarely white. It occurs 

 in angular grains, but more frequently in fmall cryftals, 

 which have the following forms. A reftangular four-fided 

 prifm, terminated by four rhomboidal faces at each end, 

 fet on the lateral edges of the prifm ; the prifm is fome- 

 times truncated on the edges. Sometimes it occurs in an 

 irregular garnet-fhaped dodecahedron, and fometimes in a 

 flat oftahedron. The ftrufture is foliated ; it has a double 

 reftangular cleavage, and the folia are parallel with the dia- 

 gonal of the prifm. Hyacinth is tranfparent or tranflucent, 

 and refrafts doubly : the luftre is refino-vitreous and 

 fplendent. It is very hard, fcratching quartz with eafe. 

 The fpecific gravity varies from 4.3 to 4.7. Before the 

 blow-pipe it lofes its colour, but not its tranfparency, and 

 is infufible. According to Klaproth, the conftituent parts 

 of hyacinth of Ceylon are. 



According to Vauquelin, the conftituent parts of hyacinth 

 of ExpaiUy are. 



99 



Zirconite does not appear to differ from zircon, except 

 in the fituation in which it is found. It occurs in fmall 

 cryftals of a reddifh-brown colour, imbedded in fienite. 

 According to Klaproth, its conftituent parts are. 



Zircon - . - . 65 



Silex - - - - ' 33 

 Oxyd of iron - - - i 



99 



Zircon and hyacinth, as we have ftated, were originally 

 found in Ceylon ; they have fince been found in various 

 parts of Afia and Europe. 



Zircon occurs in confiderable quantities along with 

 fapphire and iron-fand in volcanic fand, in a rivulet near 

 Expailly in Auvergne ; alfp near Pifa, and in the volcanic 

 fand of the Vicentine. It has been found in trap-rocks in 

 Bohemia, and in the vicinity of Lifbon. It was iirft found 

 in its native fituation at Freidrickfchwarn, in the diftrift of 

 Chriftiana, in Norway, imbeddfd in fienite. It was alfo 

 found in bafalt near Expailly, and in the mountain of 

 Anife in Auvergne, and alfo in volcanic fcoria in the fame 



country. It has been found in rolled maffes of fienite by 

 profetTor Jamefon in Scotland, in the county of Galloway ; 

 and has fince been met with in granite near Cuffel, in 

 Dumfriesfhire. 



Zircon has been found in South America, and in the 

 province of New Jerfey, in the United States. 



Zircon and hyacinth are charafterized by their great 

 fpecific gravity. Common zircon has been frequently con- 

 founded with the diamond, but the fpecific gravity alone 

 would be fufficient to diftinguifh them ; that of the dia- 

 mond not exceeding i-^. The hyacinth has often been 

 confounded with other minerals. The oriental hyacinth of 

 Rome de Lifle is orange-coloured fapphire. The occi- 

 dental hyacinth of Dutens is yellow-coloured topaz. 



Cruciform hyacinth is crofs-itone ; brown volcanic hya- 

 cinth is vefuvian ; white hyacinth of Somma is meionite. 



The hyacinth of Deflentis, mentioned by Sauffure, is » 

 variety of garnet. 



Common zircon is frequently cut and poliftied by the 

 jewellers as a gem. The greyifh-white and yellowifh-white 

 varieties are the moft prized, on account of their refemblance 

 to the diamond. The darker coloured varieties may be 

 deprived of their colour by heat. It is cut into the fame 

 forms as the diamond, and exhibits faintly the fame play of 

 colours, and is not unfrequently fold as an inferior kind of 

 diamond. The hyacinth is alfo employed by jewellers in 

 various kinds of ornaments ; but pale garnets and rock 

 cryftals are frequently fold- for hyacinths. 



ZIRCONIA, or Zircon, in Chemiflry, the name of a 

 peculiar earth, hitherto only met with in the minerals termed 

 hyacinth, and zircon or jargon. See the preceding article. 



Zirconia exifts in the form of a fine white powder, which 

 feels rather harfti when rubbed between the fingers. It ha» 

 neither tafte nor fmell. It is infufible before the blow-pipe ; 

 but when heated violently in a charcoal crucible it under- 

 goes a fort of imperfeft fufion, and acquires a greyifli 

 colour and porcelanious appearance. In this ftate it is very 

 hard, and its fpecific gravity is 4.3. 



Zirconia is infoluble in water, but has a confiderable af- 

 finity for that Hquid. It does not combine with oxygen, 

 azote, or any of the fimple combuftibles, but appears to 

 have a ftrong affinity for many metallic oxyds, efpecially 

 for that of iron. 



It is infoluble in alkaline folutions, neither can it be 

 fufed with them by the affiftance of heat ; but it is fo- 

 luble in the alkaline carbonates. Sir H. Davy fubjefted 

 this earth to the aAion of galvanifm, and obtained evi- 

 dences of its containing a metal as its bafis. To this metal 

 he gave the name of zirconium. Nothing fatisfaftory is 

 known refpeding its nature. 



No verj' accurate analyfis of the falts of this earth have 

 been yet made. From fome experiments of Klaproth and 

 Vauquelin, Dr. Thomfon fixes the weight of its atom at 

 46.25, though it is probable that this is not to be abfo- 

 lutely relied upon. 



Salts of Zirconia : Nitrate of Zirconia. — This fait may be 

 formed by pouring nitric acid on newly precipitated zirco- 

 nia. It always contains an excefs of acid, and does not 

 cryftallize. It is decompofed by heat, and moft of the 

 vegetable acids, except perhaps the acetic. 



Carbonate of Zirconia is a white infoluble powder. It 

 may be formed by double decompoCtion with the alkaline 

 carbonates, and folutions of zirconia in acids. 



Sulphate of Zirconia This fait exifts in the form of a 



white powder, but may be obtained in fmall needle-formed 



cryftals. It has no tafte, and is infoluble in water. It is 



eafily decompofed by heat. 



/iceiate 



