COLLECTIONS IN ECONOMIC GEOLOGY AND METALLURGY. 31 



STAMP MILL SAMPLES. 

 Ore. 



(1) Free silver aud argeutite, ou crystallized quartz, with a little pyrite. Very rich 

 specimen. (65146.) 



(2) Various sulphides, in quartz. (55560.) 



(3) Galena aud blende, in quartz, with a little rhodochrosite. (55561.) 



(4) Pyrite and chalcopyrite, in crystals, with galena aud blende, in quartz. (5556"-i. ) 



(5) Surface ore, showing large amounts of oxides of manganese. From the None- 

 such mine. (55564. ) 



(6) Average sample of the lump ore, showing sulphides in (puirtz and rhodochro- 

 site. (55563.) 



Salt. 



(1) Used for chloridizing, obtained by solar evaporation of the water of Great Salt 

 Lake, Utah. (55565.; 



Furnace charge. 



(1) Consisting of ore containing 55 to 60 ounces of silver, and salt, stamped together. 

 (55566.) 



FVRXACE SAMPLES. 



Roasted ore. 



(I) From Howell roaster. (55567.) 



Flue (lusts. 



(1) First chamber. (.55568.) 



(2) Second chamber. (55,569.) 



(3) Third chamber. (55570.) 



(4) Fourth chamber. (55571.) 



(5) Main flue, 100 feet from fourth chamber. (55572.) 



MILL SAMPLES. 



(1; Mercury, used in the pans to amalgamate the silver. (55573.) 



(2) Silver amalgam, taken from the strainer. (55574.) 



(3) Silver bullion, from the retort. (55836.) 



THE ZIERVOGEL PROCESS. 



This is an exceedingly interesting compound process for the treatment 

 of argentiferous copper ores,an(l is frequently modified so as to include 

 gold ores. Frequently, also, gold and silver ores free from copper are 

 used in the process, the gold and silver in them being gathered and 

 concentrated by means of the copper in the copper ores. The process 

 depends upon the fact, that when a mixture of sulphide of iron, copper, 

 and silver, such as an ordinary argentiferous copper matte produced 

 by a series of preliminary roasting fusions, is exposed to the action of 

 air at the proper temperature the iron is readily converted into sul- 

 phate, at a somewhat higher temperature this will decompose, giving 



