Z I N

Z I N

( 497 )

I Sub/p. Cryftallized C.

Its colour is greyifh-white and yellowifh-grey. It occurs in rhomboids approachingvery nearly to the cube, and in longifh quadri-lateral tables: the cryftals are fmall and veryfmall; both externally and internally they areufually {hilling with a luftre between refinousand vitreous. Its fradture is fmall and imper-fe£tly foliated. It is tranfparent, palling intotranflucent; It yields eafily to the knife but notto the nail. Sp.gr. 4.33.

By ignition in a covered crucible it lofesabout 34 per cent. It ditlblves totally and witheffcrvefcencc in the mineral acids, and the folu-tion does not gelatinize.

It is compofed, according to an analyfis bySmithfon, a of

'65.2 Oxyd of zinc,

34.8 Carbonic acid.

100.

It occurs in veins in fecondary Iimeftone,accompanied by the other ores of this metal, bygalena, calcareous fpar, quartz, &c. It is foundin Derbyfhire,

2 Sub/p. Compact C.

Its colours are greyifh, greenifh and yellowilhwhite, ochre yellow and yellowilh brown, thetwo latter colours however indicate a contami-nation of iron. It occurs mallive, cellular,botryoidal, mamillated, reniform and ftaladtitic.Its internal luftre is gliftening, between vitreousand refinous. Its fradfure is imperfectly fibrouspalling to fplintery and granular uneven. Itprefents granular and curved-lamellar diftindtconcretions : the lighter coloured are tranflucentat the edges. In hardnefs, fpecific gravity, andchemical charadters it differs but little from thepreceding fubfpecies.

It has been analyfed by Smithfon and Berg-man b with the following refult.

Sm. Berg.

64.8 — 64. Oxyd of zinc,

35.2 — 28. Carbonic acid,

o. — 6. Water,

o. — 1. Oxyd of iron.

too. 101.

Concerning Bergman’s analyfis it may be re-marked, that the oxyd of iron is merely acci-dental, and that the exiftence of the water is

rather inferred than proved, fo that probablythe amount of carbonic acid is ftated too low.

It occurs in the fame geological fituations asthe preceding, and is very abundant in Cumber-land, Derbyshire , Flintfliire, and Somerfetfhirein England, and in a multitude of other places.

3 Sub/p. Earthy C.

Its colour is greyifh or yeflowifh white. Itoccurs in mafs, and encrufting the furface ofother minerals. It is dull; its fradlure is veryfine grained earthy. It may be fcraped by thenail; is opake, and adheres to the tongue. Sp.gf- 3-5 8 -

It confifts, according to Smithfon, of

71.4 Oxyd of zinc,

13.5 Carbonic acid,

15.1 Water.

100..

In its other properties it agrees with the pre-ceding fubfpecies.

It is found in Derbyfhire, in Bleyberg i*Carinthia, and elfewhere.

Sp. 2. Electric Calamine.

Its colour is greyifh, bluifh or yellowifh white:it occurs in mafs or cryftallized. The form ofits cryftals is a comprefl'ed hexahedral prifin,terminated by low, bevilled, and truncated hex-ahedral pyramids. The cryftals are fmall andvery fmall, either folitary or grouped in diver-gent rays, like zeolite. The luftre of the cryf-tals is fhining, vitreous ; their fradlure is imper-fedtly foliated; that of the maffive variety isgenerally diverging fibrous. It varies fromtranfparent to opake according as it is cryftal-lized or not. It may be fcratched by a knife,but is eonftderably harder than common cala-mine. Sp. gr. 3.43. When gently heated itbecomes ftrongly eledtrical, nor is this propertydeftroyed even by a red heat. By ignition itslofs does not exceed 12 per cent, and the cryf-tals though they beeome opake and decrepitatea little, do not fall to powder. It is foluble inthe mineral acids without effervefcence, con-fiderable heat is extricated, and the folutiongelatinizes on cooling.

The maffive variety from Hungary was ana-lyfed by Bergman, and another fpecimen fromWanlock-Head by Klaproth ; that in radiatedcryftals, like zeolite, fromFribourg, byPelletier; cand that in folitary cryftals, from Regbania inHungary , by Smithfon, with the following re-fults.

» Phil, Tranf, for 1803, p, 17, * Opufcvila, ii. p. 3*4. « Memolres, i. p. 49,

3 »

VOL. II.