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THE AMERICAN MUSEUM JOURNAL 



places by dikes and bosses of granite por- 

 phyry, an igneous rock. The fault zones 

 and intrusions were probably the chan- 

 nels through which the ore reached the 

 limestones. Subsequent to their depo- 

 sition, these zones and adjacent rocks 

 have been altered and converted into 

 masses of highly ferruginous and man- 

 ganiferous c\a.ys and other products, lo- 

 cally known as "ledge matter," within 

 which the profitable ores have been rede- 

 posited by a process of natural concentra- 

 tion as secondary oxydized (malachite, 

 azurite, cuprite) and secondary sulphide 

 (chalcocite) minerals. This extensive 

 alteration is confined to the carbonifer- 

 ous limestones, but as the model shows, 

 masses of unaltered ore (sulphides) have 

 been met with, imbedded in the Devo- 

 nian and even in the Cambrian strata. 



The ore is raised to the surface through 

 one central shaft, the Sacramento, 

 though access to the different sections of 

 the mine is obtained through six subsidi- 

 ary shafts, four of which are shown in 

 the model: the Holbrook, Spray, Gard- 

 ner and Lowell. The mine is opened by 

 fifteen levels one hundred feet apart 

 vertically, the ore bodies between the 

 various levels being reached by upraises, 

 or by descending passages called winzes. 

 As the ore is extracted, the exposed 

 ground must be supported by timbers 

 and the vacant space filled with waste 

 rock to insure safety. The ore as ex- 

 tracted is thrown down to the next 

 lower level through chutes, from which 

 it is transported in small cars drawn by 

 electric locomotives to the central shaft. 



From the Sacramento shaft the ore 

 is dumped onto a belt-conveyor which 

 ■distributes it into waiting trains of rail- 

 road cars. This operation mixes the 

 ores from different stopes to some ex- 

 tent. The trains take the ore to Doug- 

 las, Arizona, twenty miles away where 



the great smelter is located. There the 

 ore is dumped into long pits or " beds " 

 between the railroad tracks, further 

 mixing of the material being accom- 

 plished during this operation. Hither, 

 are brought also sulphide ores as concen- 

 trates from the mines at Nacozari, So- 

 nora, Mexico, for admixture with the 

 Bisbee ores, which are too largely car- 

 bonates and oxides for economical 

 smelting by themselves. Steam shovels 

 transfer the mixed ores from the beds to 

 cars for the final journey to the smelter, 

 where together with the proper amounts 

 of coke and limestone they go into the 

 blast furnaces and thence into the con- 

 verters. The copper ingots which re- 

 sult from this treatment are brought to 

 New York to be refined, the final 

 products being pure copper and con- 

 siderable quantities of silver and gold. 



The first claim actively worked was 

 the Copper Queen, on which operations 

 were begun in the summer of 1880 by 

 the Copper Queen Mining Company, 

 In the following year, exploration was 

 begun in the neighboring claims by the 

 Atlanta Mining Company. In 1885, 

 the two companies consolidated as the 

 Copper Queen Consolidated Mining 

 Company. Subsequently, the proper- 

 ties of the Holbrook and Cave Mining 

 Company, the Neptune Mining Com- 

 pany and the Lowell and Arizona Min- 

 ing Company were acquired and other 

 claims bought. 



From the time when mining was be- 

 gun in 1880 up to the end of the year 

 1912, there were extracted from these 

 mines 7,729,922 tons of ore of an average 

 copper content of 7.16 per cent. The 

 metal production in this period was as 

 follows : copper, 1,106,605,774 pounds 

 (553,303 tons); gold, 104,775 ounces 

 Troy (8,731 pounds) ; silver, 6,107,421 

 ounces Troy (508,952 pounds). 



