COP

COP

( 320 }

be the only neceflary ingredients of this ore,yet it is moft frequently found to contain alfoantimony, filver and lead, though in extremelyvariable proportions. Some varieties from Tran-filvania, Allace, the Hartz, Saxony , Heffia andDauphine, examined by Mr. Chenevix, werefound to contain, befides the fubftances abovementioned, a portion of antimony varying from5 to 38 per cent, but neither lead nor filver.Two of th» more complicated fpecimens, onefrom Cremnitz and the other from Andreafberg,have been analyfed by Klaproth with the fol-lowing refults:

Copper 31.36

— 16.

Iron 3.30

— i3-

Sulphur 11.5

— 10.

Antimony 34*09

— 16.

Silver 14.77

— 2.25

Lead 0

— 34*

Silex 0

— 2*5

95.02

93*75

■ 1.5.1 -

r

Finally, a fpecimen from Piedmont has '

examined by Napione, and found to confift

Copper

29.3

Iron

12.1

Sulphur

12.7

Antimony

36.9

Silver

0.7

Arfenic

4-

Alumine

i.r

96.8 •

It occurs in veins in date and fome other ofthe neweft primitive rocks, and in beds in thetranfition and floetz-rocks. It is accompaniedby copper-pyrites, galena, manganefe, fpathofeiron, quartz, heavy fpar and fluor, alfo, thoughrarely, with malachite and azure copper. Whenit co.ntains a notable proportion of filver, it isworked as an ore of that metal, and will accord-ingly be mentioned again under filver.

It is found in Cornwall and Ayrfhire, and intnany parts of the Continent.

Sp. VII. Copper Pyrites . ¥sllow Copper ore ,Kirw. Kupferkies , Werner. Pyrite cuivreufe ,Hauy and Brochant.

Its colour is a deep brafs-yellow verging intogold-yellow: its furface is often iridefcently tar-aiftied. It occurs in mafs, difleminated, fuper-ficial, in particular fhapes fuch as ftala&itical,cluttered, dendritical and reniform: alfo cryf-tallized in tetrahedrons and the derivative octa-hedron and dodecahedron. The cryftals are

fmall and very fmall, and generally difficult toafcertain. The furface of the cryftals is fmoothand fhining, the other varieties are rough andglimmering, The fracture is commonly unevenwith coarfe or fine grains; the coarfe-grainedpaffes into imperfect and fmall conchoidal, andthence into imperfectly foliated; the fine-grainedpaffes into uneven, even, and fiat-conchoidal;the colour of the foliated is gold-yellow, and ithas alfo the ftrongeft luftre. It is brittle, andwith difficulty gives a few feeble fparks withthe fteel: it is eafily frangible. Sp. gr. 4. to 4.1.

When expofed to the blowpipe on charcoalit decrepitates, emits a fulphureous vapour, andmelts into a black globule, which by continuingthe heat acquires the colour and luftre of me-tallic copper.

It does not appear that the cryftallized va-rieties of this ore have as yet been fubjedted toanalyfis, and the proportion of its conftituentparts cannot be eftimated from the other va-rieties on account of the iron pyrites which isalways blended with them in greater or lefsquantity. A fpecimen examined by Lampadiusafforded 41. Copper,

17.1 Iron,

45.1 Sulphur.

103.2

In this analyfis the copper and ir6n were re-duced to the metallic ftate, fo that the fulphur(probably for want of fufficient drying) is efti-mated too high. In general however the pro-duce of copper from this ore does not exceedmore than about 20 per cent, and in favourablefituations it is reckoned worth working when itdoes not yield more than 5 or 6 per cent. Agood deal of confufion is obfervable amongmineralogical writers in treating of copperpyrites, fome confidering it as a peculiar fpecies,while others reckon it only as a variety of ironpyrites holding a variable proportion of copper ;and this confufion has been ftill further increafedby affayers and metallurgifts, who rank as yel-low copper ore every fpecimen of a yellowcolour and metallic luftre, from which a notableproportion of copper can be extracted. It ishowever neceflary to diftinguifh between copperpyrites, which appears to be a proper doublefulphuret of copper and iron, and of which inthe cryftallized varieties the proportions of thethree ingredients are probably permanent; andiron pyrites holding an accidental and variableproportion of copper. Of the former the pri-mitive figure is a regular tetrahedron, its colour