Native Silver

Silver, Native

 

a mineral, one of the native elements. The chemical composition of native silver varies from nearly pure Ag, with admixtures constituting no more than 1.5 percent, to natural solid solutions of Au, Hg, Sb, Bi, or Cu in Ag. Varieties of native silver include küstelite (up to 10 percent Au), kongs-bergite, arquerite, and bordosite (up to 5, 13, and 30 percent Hg, respectively), animikite and allargentum (up to 11 and 15 percent Sb), chilenite (up to 5 percent Bi), and copper-bearing silver (up to tenths of a percent Cu). Native silver has a face-centered cubic structure. Although it occasionally occurs in the form of cubes and octahedrons, it is usually found as thin, irregular plates and scales, filiform or dendriform growths, irregular grains, or larger compact aggregates or nuggets. One plate-shaped nugget, found in Chañarcillo in northern Chile, weighed 1,420 kg. A freshly made fracture is white in color, and sometimes the surface is covered with a black film. Polished sections exhibit very high reflectivity. Native silver is soft and ductile; it has a hardness of 2.5 on Mohs’ scale and a density of 10,500 kg/m3.

Native silver occurs rarely in nature. It is formed in hydrothermal vein deposits in association with silver-bearing sulfides, calcite, quartz, fluorite, adularia, the minerals of Ag, Co, Ni, Bi, and U, and arsenides of cobalt and nickel. Commercial deposits of native silver are located in Kongsberg (Norway), Cobalt (Canada), and Schneeberg and Annaberg (German Democratic Republic) and in low-temperature veins in zones containing young volcanic rocks. Such veins can be found in North America (Cordilleras), Europe (Carpathians), Japan, and New Zealand.

Native silver associated with native gold occurs in the oxidation zone of, for example, lead-zinc, pyrite, and silver deposits (Rudnyi Altai, the Urals, and Dzhezkazgan in the USSR; Potosí in Bolivia).

REFERENCES

Mineraly: Spravochnik, vol. 1. Moscow, 1960.
Maksimov, M. M. Ocherk oserebre. Moscow, 1974. [23–883–]
References in periodicals archive ?
The dominant sulfide minerals include sphalerite and galena along with argentite and native silver, and they occur as disseminations, bands, or zones of massive sulfide.
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Hypogene ba-rich todorokite and associated nanometric native silver in the san miguel tenango mining area, Zacatlan, Puebla, Mexico.
The mineralisation occurs as Co-Fe-Ni Arsenides, argentite, niccolite and native Silver. Silver grades up to 261 g/t, and Cobalt grades up to 14.75% have been reported from the property, concluded the company.
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The most important mineral is native silver followed by cobaltite, niccolite, ruby silver, argentite, bismuth and chalcopyrite.
Apart from argentiferous (silver bearing) lead minerals, the district also hosts numerous occurrences and deposits containing silver sulfosalts and in some cases, native silver," said Nauman of Alexco.
The drilling has confirmed the presence and continuity of relatively narrow, very high grade native silver zones below and southwest of the historical workings.
Each drill hole returned encouraging mineralisation, including native silver, sphalerite and significant sulphide-rich quartz veining and brecciation.
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