COPPER 



447 



used by the button-makers of Birmingham, under the 

 name of platina, by adding five pounds of zinc to 

 eight of brass. The brothers Keller, who were very 

 celebrated statue-founders, used an alloy, 10,000 

 parts of which containing 9140 of copper, 553 of 

 zinc, 170 of tin, and 137 of lead. Their castings are 

 famous, and some are of very large size, as the eques- 

 trian statue of Louis XIV., cast at a single jet, by 

 Balthazar Keller, in 1699, which is twenty-one feet 

 high, and weighs 53,263 French pounds. These 

 statues are usually called bronze statues, although 

 made of brass. Brass was well known to the Ro- 

 mans, under the name of orichalcum, who took ad- 

 vantage of its resemblance to gold, in robbing the 

 temples, and other public places, of that precious 

 metal. Thus Julius Caesar robbed the capital of 

 3000 pounds' weight of gold, and Vitellius despoiled 

 the temples of then- gifts and ornaments, and re- 

 placed them with this inferior compound. 



The art of tinning copper consists in covering that 

 metal with a thin layer of tin, in order to protect its 

 surface from rusting. For this purpose, pieces of 

 tin are placed upon a well-polished sheet of copper, 

 which, if the process is skilfully conducted, adhere 

 mtiformly to its surface. The oxidation of the tin 

 a circumstance which would entirely prevent the 

 success of the operation is avoided by employing 

 fragments of resin, or muriate of ammonia, and re- 

 gulating the temperature with great care. 



ORES OF COPPER. 1. Native copper, like the me- 

 tal, is of a red colour, but frequently tarnished. Its 

 lustre is metallic : it is flexible, ductile, and malle- 

 able : its fracture is hackly. It occurs in branched 

 pieces, dendritic, in thin plates, and rarely in regular 

 crystals, under the form of the cube or octoedron. It 

 is found in the veins of primitive rocks, and of the 

 older secondary. It is occasionally accompanied by 

 several of the ores of copper, and sometimes those of 

 other metals. One of the largest masses of this sub- 

 stance ever noticed was discovered by School- 

 craft, in the North West Territory, about thirty miles 

 from lake Superior, on the west bank of the river 

 Ontonagon. It weighs, by estimation, 2200 pounds. 

 It lies near the water's edge, at the foot of an elevat- 

 ed bank of alluvion. Native copper is frequently 

 found in connexion with the secondary greenstone 

 and red sandstone formation in America. Its 

 greatest known depositories, however, are the mines 

 of Cornwall in England. 



2. Sulphuret of Copper. Under this name may be 

 described a series of ores containing copper, sulphur, 

 and variable proportions of other metals, which, by 

 some mineralogists, are conceived to pass into each 

 other, and, of course, are improperly arranged as 

 distinct species. Its principal varieties are the vi- 

 treous copper ore, the purple copper, grey copper, 

 and yellow copper pyrites. 



a. Vitreous Copper is of a lead or iron-grey colour. 

 It occurs crystallized in regular six-sided prisms, 

 mostly modified on the terminal edges, and in acute, 

 double, six-sided pyramids, with triangular planes. It 

 also occurs massive. The cross-fracture of the crys- 

 tallized is often conchoidal, with a vitreous lustre : 

 the massive varies greatly in respect of hardness and 

 colour. It is sometimes sectile and soft. The frac- 

 ture is even, or flat conchoidal. Specific gravity, 

 4-8 to 5-4. It consists, according to Chenevix, of 

 81 copper and 19 sulphur. It occurs in veias and 

 beds, in primitive and early secondary rocks, and is 

 found with other ores of copper. In the United 

 States, it has been met with very often in the old red 

 sandstone, but is nowhere wrought as yet, to advan- 

 tage. It abounds in Cornwall, and many European 

 countries. 



b. Purple Copper occurs both massive and crystal- 



lized. Its colour is between copper-red, and tombac- 

 brown. It is often possessed of an iridescent tarnish, 

 in which blue is apt to prevail. The general form of 

 the crystal is that of a cube, of which the solid angles 

 are replaced. It is soft, easily frangible, and sectile 

 in a slight degree. Specific gravity, 5-033. That of 

 Norway consists of copper 69-50, sulphur 19, iron 

 7-50, and oxygen 4. It is fusible into a globule, 

 which acts powerfully upon the magnetic needle. 

 The purple copper is found hi Norway, Saxony, and 

 England, and occurs under similar circumstances 

 with the other ores of copper. 



c. The Grey Copper, or Fahlerz, is of a steel-grey 

 or iron-black colour. It occurs crystallized in the 

 form of the tetraedron, in which no regular structure 

 is visible ; it also occurs massive and disseminated. 

 Ua fracture is uneven or imperfectly conchoidal, with 

 a shining or glistening metallic lustre. It is brittle. 

 Specific gravity, 4-5. It consists of 52 copper, 23 

 iron, and 14 sulphur; but it also contains, mixed 

 with these constituents, various other metals, in very 

 variable proportions, as lead, antimony, and silver. It 

 occurs in Russia, France, Spain, England, Chile, and 

 Mexico. 



d. Yellow Copper Ore, or Copper Pyrites, occurs of 

 various shades or yellow, crystallized in the form of 

 the tetraedron, having the solid angles replaced, 

 and massive. It is also stalactitic and botryoidal. It 

 is brittle, yields to the knife, and may thereby easily 

 be distinguished from iron pyrites, which it often 

 much resembles. Specific gravity, 4-3. It contains 

 copper 30, iron 32 '20, sulphur 35-16, earthy matter 

 0-50, lead, arsenic, and loss, 2-14. It is the most 

 abundant of all the ores of copper, and affords almost 

 exclusively, the copper of commerce. It exists both 

 in primitive and secondary rocks, and is accompanied 

 by most of the other ores of copper, sometimes ga- 

 lena, oxide of tin, and several of the ores of iron. It 

 is found in North and South America, most Euro- 

 pean countries, in Japan, and Africa. In the year 

 ending June 30, 1817, 73,727 tons of copper ore 

 (principally copper pyrites), which sold for 4 10,93 6, 

 and yielded 6425 tons of pure copper, were raised 

 from the mines of Cornwall only ; being more than 

 three-fourths of the quantity raised from the British 

 mines. 



3. Red Oxide of Copper is of a red colour, varying 

 greatly in its shades, and, by transmitted light, often 

 of a crimson red. It occurs crystallized in the form 

 of the octoedron, and its varieties, which are very nu- 

 merous. The crystals are externally splendent, but 

 sometimes of a lead-grey colour, with a metallic lus- 

 tre. The cross-fracture is sometimes uneven ; oftener 

 conchoidal with a splendent and somewhat adaman- 

 tine lustre. It is transparent, or translucent, yields 

 easily to the knife, and is brittle. Specific gravity, 

 4-9 to 5-6. It consists, according to Chenevix, of 

 88-5 copper, and 11-5 of oxygen. Red oxide of cop- 

 per is also found in delicate capillary crystals, as well 

 as massive, when it is opaque, and frequently granu- 

 lar in its fracture. The brick-red, or tile copper ore, 

 which occurs earthy, or a little indurated, appears to 

 be a mixture of oxide of copper and oxide of iron. 

 This species is found in the primitive and transition 

 rocks, associated with the other ores of copper. It is 

 found finely crystallized in the English mines, and at 

 Chessy in France. It also occurs in the Hartz, the 

 Bannat, Hungary, Chile, and Peru, but, hitherto, has 

 not been found, except in very limited quantities, ic 

 the United States. 



4. Carbonate of Copper. Oxide of copper, combin- 

 ed with carbonic acid, forms two species the blue, 

 and the green carbonate ; the differences between 

 which arise either from different states of oxidation, 

 or in part from the combination of water. 



