What is "nagyagite"

Nagyagite \Nag"yag*ite\, n. [So called from Nagyag, in Transylvania.] (Min.) A mineral of blackish lead-gray color and metallic luster, generally of a foliated massive structure; foliated tellurium. It is a telluride of lead and gold.

n. (context mineralogy English) A dark grey to black sulfide, formula (lead₅gold(tellurium,antimony)₄sulfur_5-8).

Nagyágite ( Pb Au( Te, Sb) S) is a rare sulfide mineral with known occurrence associated with gold ores. Nagyágite crystals are opaque, monoclinic and dark grey to black coloured.

It was first described in 1845 for an occurrence at the type locality of the Nagyág mine, Săcărâmb, Hunedoara County, Romania.

It occurs in gold–tellurium epithermal hydrothermal veins. Minerals associated with nagyágite include: altaite, petzite, stutzite, sylvanite, tellurantimony, coloradoite, krennerite, native arsenic, native gold, proustite, rhodochrosite, arsenopyrite, sphalerite, tetrahedrite, calaverite, tellurobismuthite, galena and pyrite.