586 



UNITED STATES MINERAL RESOURCES 



no more than several feet in limestone and dolomite 

 host rocks but that it is as mobile as zinc in unreac- 

 tive host rocks such as quartzite and shale. In oxi- 

 dized lead-silver limestone replacement deposits 

 silver commonly occurs as cerargyrite (AgCl), em- 

 bolite (AgClBr), native silver, sooty argentite 

 (AgsS) or acanthite (pAgS) , the ruby silvers 

 (proustite, pyrargyrite), silver-bearing lead sulfate, 

 argentian plumbojarosite, argentiferous anglesite, 

 silver-bearing lead carbonate (argentiferous cerus- 

 site) , various hydrous argentiferous lead-manganese 

 oxides (for example, argentian todorokite), and sil- 

 ver sulfide minerals or sulfosalts precipitated by 

 reaction of silver-bearing solutions with primary sul- 

 fide minerals. This supergene enriched ore may carry 

 hundreds or thousands of ounces of silver per ton 

 of ore, but one will be disappointed if one expects 

 such values to continue downward into the primary 

 ore. 



MINERALOGY 



There are few active mines in the United States 

 whose principal product is silver. Most silver is 

 obtained as a byproduct or coproduct from ores of 

 copper, lead, zinc, gold, manganese, cobalt, nickel, 

 or uranium. There are, however, all gradations from 

 deposits that are mined chiefly for silver to those 

 in which silver is a minor byproduct. 



The principal silver minerals are as follows: 

 Native elements and alloys: 



Electrum (Ag, Au) 



Silver Ag 



Carbonate : 



Cerussite PbCoa, commonly silver-bearing 



Sulfides, sulfosalts, selenides, and tellurides: 



Andorite PbAgSbsSs 



Acanthite iSAgjS 



Argentite Ag2S 



Diaphorite PbzAgaSbaSa 



Dyscrasite AgsSb 



Fizelyite Pbs Ag^SbsSis 



Galena (argentiferous) _(Pb,Ag)S 



Hessite AgjTe 



Matildite AgBiSa 



Miargyrite AgSbS2 



Naumannite AgsSe 



Pearceite AgieAssSn 



Petzite AgaAuTes 



Proustite (Ag,Cu)i6Sb2Sii 



Polybasite AgaAsSa 



Pyrargyrite AgaSbSa 



Stephanite AgjSbSi 



Strom eyerite CuAgS 



Sylvanite Ag2Au2Te8 



Tennantite (argenti- 

 ferous) (Cu,Fe,Ag)i2As4Si3 



Tetrahedrite (argenti- 

 ferous) (Cu,Fe,Ag),2Sb4Sia 



Halides : 



Bromyrite AgBr 



Cerargyrite AgCl 



Embolite Ag(Cl,Br) 



lodyrite Agl 



Oxides : 



Aurorite _ _ ( Ag2Ba,Ca,Pb,K2CuMn + =) Mn + *0r 



•3H2O 

 Argentian 

 todoro- 

 kite (Ag2K2Ca,Ba,Na,Cu,Pb)Mn+^09 



•5H2O 

 Silver-bearing lead-manganese oxides 

 Sulfates : 



Anglesite PbSoj, commonly silver-bearing 



Argentian 

 plumbo- 

 jarosite _ _ (Pb,Ag) Fee (SO4) 4 (OH) 12 

 Argento- 



jarosite __Ag2Fe6(S04)4(OH)a2 

 Where silver is a byproduct or coproduct it may 

 occur either as discrete silver minerals or it may 

 substitute for other metals in minerals of base- 

 metal ores. Argentiferous tetrahedrite and tennan- 

 tite are exceptionally rich in silver in some base- 

 metal deposits, and either one may be the economi- 

 cally important ore mineral. In many lead-silver de- 

 posits, silver occurs in tiny inclusions of argentite, 

 tetrahedrite, tennantite, or other silver-antimony or 

 silver-bismuth sulfosalts in argentian galena. Silver 

 may also occur in solid solution in galena. Some 

 galena may be relatively free of silver but accom- 

 panied by silver-rich sphalerite, chalcopyrite, and 

 pyrite as in the southeast Missouri lead district 

 (Hall and Heyl, 1968, p. 666). Some sphalerite en- 

 riched in silver contains inclusions of argentian 

 tennantite. 



Most newly mined gold contains some alloyed 

 silver, the quantity ranging from a trace to as much 

 as 60 percent. Gold from the Mother Lode Belt of 

 California commonly contains 10-20 percent silver; 

 that from the Homestake mine in South Dakota an 

 average of 20 percent. The epithermal precious- 

 metal deposits commonly contain the highest pro- 

 portion of silver to gold, such as in the Comstock 

 Lode of Nevada. 



Placer gold contains less silver than the gold in 

 the lode from which it was derived. Placer gold in 

 California commonly contains 2-7 percent silver, as 

 much as an order of magnitude less than that in the 



