COPPER 909 



Pure copper may be obtained in the solid state either by the reduction of the pure 

 oxide by a stream of hydrogen gas passed over it in an ignited tube, or by the elec- 

 trotype process. See ELECTRO-METAILURGY. 



ORES OF COPPER. Copper ores do not possess any one general physical character by 

 which they may be recognised ; but they are readily distinguished by chemical reagents. 

 Ammonia digested upon any of the cupreous ores in a pulverised state, after they have 

 been calcined either alone or -with nitre, assumes an intense blue colour, indicative of 

 copper. Few copper ores are to be met with which do not betray the presence of this 

 metal by more or less of a greenish film. 



The following are the principal minerals which contain copper : 



Native or Virgin Copper (Cuivre natif, Fr. ; Gediegen Kupfer, Ger.) This metal 

 commonly occurs in dendritic and arborescent masses, or is indistinctly crystallised in 

 complex and distorted forms of the cubic system. It is a frequent associate of the 

 ordinary ores of copper, and appears to have been formed in mest cases by reduction 

 from some of these ores. Native copper is found not only in copper-bearing veins, 

 but in the fissures and cavities of certain trappean rocks, in deposits in serpentine, 

 and occasionally in sandstones and conglomerate. The native metal is not uncommon 

 in some of the Cornish copper-mines, and is found abundantly in certain copper- 

 bearing deposits in Siberia, Chili, Bolivia, and South Australia. But the most im- 

 portant occurrence of native copper yet recorded is that at Keewenaw Point, Lake 

 Superior, where certain amygdaloidal trap-rocks hold large quantities of copper, in 

 association with calcite and zeolitic minerals. The native copper of Lake Superior 

 also occurs as the cementing materials of a conglomerate, and in a finely-divided form 

 disseminated through sandstone. Some of this copper is remarkable for containing 

 silver, which appears in distinct masses sharply separated from the copper in which 

 it is embedded, the two metals not having formed an alloy. Masses of native copper 

 have been found at Lake Superior, weighing upwards of 400 tons. 



Copper Glance, Vitreous Copper Ore, Chalcocite, Eedruthite, or Bisulphide of Copper, 

 (Cuivre vitreux, Fr. ; Kupferglanz, Ger.). This mineral, which forms a most valuable 

 ore, occurs both crystallised and massive. Some of the composite crystals from St. 

 Just, in Cornwall, are known, from their form, as nail-head copper ore. The fracture 

 of copper-glance is conchoidal ; surface sometimes dull ; colour, iron-black or lead- 

 grey, often bluish, iridescent, or reddish from a mixture of oxide. It is easily melted 

 even by the heat of a candle ; but is more difficult of reduction than protoxide. This 

 ore yields to the knife, assuming a metallic lustre when cut. Its density varies from 

 4'8 to 5'34. Copper-glance is a disulphide (cuprous sulphide), containing when pure 

 Cu 2 S, corresponding to 79'8 per cent, of copper and 20'2 of sulphur ; but as found in 

 nature it generally contains more or less iron. This is, therefore, one of the richest 

 ores, and forms very important veins. It is to be found in all considerable copper 

 districts ; in Siberia, Saxony, Sweden, and especially Cornwall, where the finest 

 crystals occur. 



Copper Pyrites, Chalcopyrite, Towanite, or Yellow Copper Ore, (Cuivre pyriteux, Fr. ; 

 Kupferkies, Ger.). This is the common ore of copper in Cornwall and many other 

 copper-mining districts. It resembles in its metallic yellow hue bisulphide of iron 

 (iron pyrites); but the latter is paler, harder, and strikes fire easily with steel. 

 Copper pyrites sometimes presents the most lively rainbow colours, and is then known, 

 from this iridescence, as Peacock ore. Its specific gravity is 4 - 3. 



Copper pyrites is a double sulphide of copper and iron, containing theoretically 34'5 

 per cent, of copper, 30'5 of iron, and 35 of sulphur, corresponding to the formula 

 Cu 2 S,Fe 2 S 3 , or, as sometimes expressed, CuS,FeS. Copper pyrites occurs in vast 

 masses and extended veins, in primitive and transition districts ; and is commonly 

 accompanied with grey copper, iron pyrites, sparry iron, galena, and zinc blende. 



Somite, Erubescite, Phillipsite, Purple Copper Ore, Variegated Ore, or Horse-flesh 

 Ore, (Cuivre panache, Fr. ; Buntkupfererz, Ger.). A double sulphide of copper and 

 iron. A Cornish specimen, analysed by Plattner, yielded copper, 56'76 ; iron, 

 14 - 84 ; sulphur, 28'24. The composition of the crystallised mineral appears to be 

 reducible to the formula 3Cu 2 S,Fe 2 S 3 . The ore usually occurs massive, presenting a 

 colour between copper-red and pinchbeck-brown, but often obscured by a purple 

 tarnish. Its specific gravity varies from 4'4 to 5'5. Horse-flesh ore is abundant in 

 some of the copper-mines of Chili and Canada. It is also found in Cornwall and in 

 Ireland. It occurs with serpentine at Monte Catini in Tuscany, and forms thin 

 seams in the copper-slates of Mansfeld in Prussia. 



Fahl Ore, Tetrahedrite, or Grey Copper Ore, (Fahlerz, Ger.). An ore of variable 

 composition, generally containing between 30 and 40 per cent, of copper. It is 

 essentially an antimonio-sulphido or arsenio-sulphide of copper, but the copper may 

 be partially replaced by iron, zinc, silver, or mercury. Fahlerz is a steel-grey mineral, 

 with a metallic lustre, and frequently assumes well-defined tctrahedral forms. The 



