naumannite

naumannite

[′nau̇·mə‚nīt]
(mineralogy)
Ag2Se An iron-black mineral that crystallizes in the isometric system; consists of silver selenide, and occurs massive or in crystals; specific gravity is 8.
References in periodicals archive ?
Kunkar was lucky in finding an ore pocket of 300 kg of silver selenides with a grade of about 40% silver, which must have been pure naumannite.
Assays have shown the selenides from the West Vein to be dominated by penroseite and to include clausthalite, tiemannite and naumannite with possible krutaite (although the Cu may be chalcopyrite).
Polished sections show that clausthalite and naumannite cut across earlier-formed penroseite along brittle fractures (C.
Naumannite occurs intimately mixed with penroseite and is responsible for the high silver content of the penroseite analyses.
The presence of naumannite at Pacajake was first noticed by Herzenberg and Ahlfeld (1935).
Polished sections show that it is heavily fractured and cemented by clausthalite and naumannite (C.
They considered that inclusions of naumannite, recognized optically and by X-ray, caused part of the variation in the silver and lead content, but that penroseite contained combined lead and silver and that "the true composition of penroseite still remains uncertain" (Bannister and Hey, 1937).
High grade ore found along this vein is comprised of multi-phase, banded quartz-chalcedony veining with the principal economic minerals consisting of naumannite, pyrargyrite, miargyrite, tetrahedrite, and electrum.
These include: annabergite, aragonite, argentopentlandite (Sirka, 1988), brochantite, chlorite (group), covellite, devilline, erythrite, gadolinite, gahnite, goethite, gold-silver (electrum), illite, kaolinite, langite, malachite, montmorillonite, natrojarosite, naumannite (Frigstad, 1972), palygorskite, posnjakite, scheelite, sepiolite (van der Wel, 1972), stilpnomelane, sulfur, tetrahedrite and tremolite-actinolite.
1972) Naumannite from Kongsberg silver deposit, south Norway.
The only specimen of naumannite investigated was from the uppermost level of the San Carlos mine, while the large, lustrous Rayas mine acanthites (with nearly zero selenium) are from the deepest levels of that mine.
WolEgang has also identified naumannite from the location.