Z I R

Z I R.

( 507 )

Zinc and tin combine by fufion, forming athi£Hie alloy, harder than zinc and of a bettercolour.

Zinc and Mercury ; fee Mercury , alloys of.

Zinc forms with filver a bluifli-white brittlealloy of a granular texture.

The ufes of zinc in its various forms areconfiderable. In its metallic date it is employedby the Chinefe for coins, and has been propofedin this country as a fubftitute for lead and tinin forming and lining various culinary veflels :this however is extremely. injudicious aszinc is remarkably foluble in all acids, and allits falts are violent emetics. In combinationwith copper it forms brafs and all the ufefuland ornamental gold coloured alloys. Its fub-limed oxyd has been ufed-in oil painting as afubftitute for white lead: it has not indeed thedcnfity of common white paint, and thereforeone or two more coatings are required of theformer than of the latter, but in return it is notliable to be blackened by fulphureous vapours,and is entirely free from the deleterious effectsof lead paint. Of the falts of zinc the fulphatis largely ufed by varnifhers, &c. to make oildrying, and this together with the acetite isemployed in medicine. In the laboratory thechief ufe of zinc is to procure hydrogen gasby the folution of it in the fulphuric or muriaticacids.

ZIRCON. Jargon or Jargoon. Hyacinth.

Werner and his difciples make two feparatefpecies of the zircon or jargon, and hyacinth 5but from the analyfes of Klaproth and Vauque-lin, and the cryftallographical refearches ofHauy, it is evident that the two fpecies oughtto be confoiidated into one. The colour ofthis mineral is pale greyifh-white, fmoke-grey,and greenifh-grey, leek-green and olive-brown,alfo pale wine-yellow, orange-yellow, bluifli-red,

blood-red, and reddifh-brown. It occurs infmall rounded pieces and cryftallized. Its pri-mitive form is an octahedron with ifofcelestriangular faces: the angle formed at thecommon bafe of the pyramids is — 82°: 5c 7 ..It prefents alfo the following varieties of crys-tallization.

t. The rhomboidal dodecahedron.

2. The fame as the preceding except thatthe fides of the prifm are hexagons inltead ofrhombs.

3. Var. 2. with the common edges of theprifm and terminating pyramids truncated.

4. Var. 2. with the lateral edges of the prifmtruncated.

5. A combination of the two precedingvarieties, that is var. 2. with all the edges ofthe hexagonal faces truncated.

6. A ftrait tetrahedral prifm terminated bytetrahedral pyramids.

7. The preceding with the folid angles atthe bafe of the pyramids truncated.

8. Var. 6. with both the folid angles andcommon edges of the prifm, and terminatingpyramids truncated.

The cryftals are fmall and very fmall; exter-nally they are fmooth and fhining; internallyboth the cryftals and rounded pieces have abrightly fhining luftre, between adamantine andvitreous. The fracture is foliated palling intoflat conchoidal: the fragments are indetermi-nate and fharp edged. It varies from tranflu-cent to tranfparent, and is doubly refracting ina high degree. It is hard enough to Scratchquartz, though with difficulty. It is brittleand eafily frangible. Sp. gr. 4.38—4.62.

It lofes its colour but is infufible per fe beforethe blow-pipe. The following are the analyfesthat have been made of this mineral.

Jargon of Ceylon.

Hyacinth of Ceylon.

Do.

Klaproth

Klapr.

Vauquelin

68. —

— 70. —

64.5

3 r -5 —

— 25. —

32 -

0.5 —

— 0.5 —

2.

IOO.

95-5

98.5

Hyacinth of Expailly.Vauquel.

— 66. Zircon

— 31. Silex

— 2. Oxyd of Iron

99.

It occurs in the beds of rivers in Ceylonmixed with magnetic fand, ruby, tourmaline,Sapphire, &c. alfo in the fand of the brookExpailly in Auvergne ; near Meronitz andHohenftein in Saxony ; at Schelkowitz inBohemia imbedded in trap ; and at Friedrich-fchwarn in Norway .

The yellow and fmoke coloured varietiesare called by the jewellers jargoons, and arenot unfrequently paffed off as diamonds: the-orange-red varieties are called hyacinths. - Thecommercial value both of one and the other isconfiderably inferior to that of the diamondand all the oriental gems.

3 s 2