14 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



These works are situated at a distance from auy mining operation, and 

 obtain their supplies wherever they can to the best advantage. The 

 ores therefore are generally quite rich and vary constantly. As a conse- 

 quence, the operations are somewhat complicated. 



A suitable mixture of ore is made up, and with the proper lluxes sub- 

 mitted to a fusion, whereby the earthy material of the ore is separated 

 into a slag, which is thrown away ; while the metals are concentrated 

 into a matte which contains most of the copper, with some of the iron of 

 the ore, in the form of sulphides, and also the gold and silver. 



This matte is further concentrated by roasting and fusing to a second 

 matte, and this process of refining goes on until nearly pure metallic 

 copper is obtained. Through all these operations the gold and silver 

 remain with the copper. 



The metallic copper is now subjected to an electric current in a suit- 

 able bath, generally of sulphate of cop]>er, whereby the copper is dis- 

 solved at the anode, leaving the impurities containing the gold and 

 silver behind, while pure copper is deposited on the cathode. This 

 pure electrolytic copper is now ready to be worked up into mer- 

 chantable forms. The residues, by a very simple operation, yield metal- 

 lic gold and silver, which are readily separated. 



Ores. 



(1) GoUl-beariiig quartz. (5566B.) 



(2) Gold-bearing sulphurets, consisting of a mixture oJ; pyrite and cbaicopyrite 

 with a little quartz. (55667.) 



Fluxes. 



(1) Limestone. (55671.) 



(2) Fluorspar. (.5.5672.) 



(3) Cinder, from an iron puddle furnace. (55673.) 



Intermediaie jiroducts. 



(1) First matte, obtained by smelting the ore, contains gold, silver, copper, and 

 iron combined with sulphur. (55674.) 



(2) Slag, obtained in smelting first matte, is practically free from gold, silver, and 

 copper and is rejected. (55675.) 



(3) Second matte, obtained by roasting and fusing Hrst matte, whereby large 

 amounts of 8ul{)hur and iron are removed. (55676.) 



(4) Black copper, obtained by roasting and fusing second matte, whereby nearly all 

 the sulphur and iron are removed. (5^677.) 



(5) Metallic copper, nearly pure, obtained by refining black copper. (55665.) 



(6) Sulphate of copper, obtained as a by-product and used in making up the bath 

 for the electrolytic separation. (5.5670.) 



(7) Residues, remaining from dissolving the copper, No. 55665, in the electrolytic 

 process, and containing the gold, silver, and other impurities of the copper. (55662.) 



Final products. 



(1) Metallic copiier, a sheet of pure copper deposited by the electrolytic proce.ss. 

 (5.5661.) 



(2) Gold, tine metal, separated from the residues from the electrolytic process; 

 weight, 1.3 ounces ; value, §27. (5.^681.) 



(3) Silver, fiiu? metal, separated from the residues from the electrolytic process; 

 weight, lOi ounces ; value, $11. .50. (.55680.) 



