COP
COP
( 319 )
It effervefces with nitrous acid, and whenexpofed to the blowpipe it gives a metallic but-ton generally of a fteel grey colour and attract-able by the magnet.
When pure it appears to be a Ample fulphu-ret of copper, and is found occafionally in thisftate in Cornwall , when it confifts, according toChenevix, of 81 Copper,
19 Sulphur.
100
It is generally however mixed with iron inthe proportion of from 3 to 6 per cent. Klaproth analyfed a fpecimen from Siberia , which con-tained 78.5 Copper,
18.5 Sulphur,
2.25 Iron,
0.75 Silex,
100.00
It occurs in veins and beds in primitive andfloetz mountains, accompanied by copper pyritesand other ores of this metal. It is not veryabundant, but is found in various places, efpe-cially Cornwall, Hungary, Saxony, Norway andSiberia .
Sp. V. Purple Copper. Buntiupfererz , Wer,Cuivre pyriteux hepatique , Hauy.
Its colour is intermediate between copper-redand tombac-brown •, on expofure to the air itbecomes firft reddifh, then violet azure andIky-blue, and laftly green; its general tingehowever is blue, and the green only occurs infpots. It is found in mafs or diffeminated, orfuperficial, or, according to fome writers, crys-tallized in octohedrons. Internally it is fhining,with a metallic lultre. Its fracture is fmall andimperfect conchoidal, palling into fine-graineduneven. It takes a polifh by friction, and whenpulverized is of a reddilli colour. It is fo foftas in fome degree to yield to the nail; and iseafily frangible. Sp. gr. about 5.
It effervefces with nitrous acid, though by nomeans fo ltrongly as the preceding fpecies, andmelts readily before the blowpipe without vapouror fmell.
It is looked upon by Bournon as a properdouble lulphuret of copper and iron. From theanalyfis by Chenevix of feveral Cornilh fpeci-mens of a nickel-red colour, it appears to confift°f 60 to 65 Copper,
15 — 18 Iron,.
*7 —25 Sulphur.
69.5
— 58 Copper,
19
— 19 Sulphur,
7-5
— x 8 Iron,
4
— 5 Oxygen.
100.0
100
It is to be obferved however that the oxygenin thefe analyfes was only inferred from thedeficiency of the three firft ingredients whencompared with the whole quantity previous toanalyfis.
This ore occurs in beds, veins, and diffemi-nated in rocks of different formations : it appearshowever to be molt frequent in primitive beds.It is ufually accompanied by vitreous copperand copper-pyrites, and not unfrequently bygarnet. It is found in Cornwall , and in moltof the copper-mines on the Continent.
Sp. VI. Grey Copper. Fahlerz, Werner.Cuivre gris , Hauy.
Its ufual colour is Heel-grey of more or lefsintenfity, which often pafles into iron-black andlead-grey; feme varieties incline towards yellow,and others again prefent fuperficial iridefcentcolours. It occurs in mafs or diffeminated, orinvelting, and is then often fpecular, or cryf-tallized in regular tetrahedrons and their modi-fications. The cryftals are fmall and rarelymiddle-fized, with fhining furfaces. Internallyit is gliftening or fhining, with a metallic lultre.The fra£ture is coarfe and fmall grained uneven,inclining to imperfect-conchoidal. It gives ablack powder palling into reddilh-brown. It ismoderately hard, brittle and eafily frangible.Sp. gr. when pure 4.46 to 4.56, that of themore compound varieties rifes to 4.86.
It is confidered by Bournon as a proper doublefulphuret of copper and iron, and differs fromthe preceding fpecies in colour, cryftalline form,fpecific gravity, and proportion of componentparts. Some brilliant cryftals of this fpecies, inthe form of tetrahedrons with doubly bevillededges and.the folid angles truncated, from Corn-wall , were analyfed by Chenevix, and found toconfift of 52 Copper,
33 Ir ° n > .
14 Sulphur,
99
. A fimilar refult was alfo obtained from theanalyfis of fome fpecimens of the fame in mafs.But though copper, iron and fulphur appear to