Nagyágite

{{infobox mineral }} Nagyágite is a rare sulfide mineral with known occurrence associated with gold ores. Nagyágite crystals are opaque, monoclinic and dark grey to black coloured.
 * name    = Nagyágite
 * category = Sulfosalt mineral
 * image      = Nagyagite-163939.jpg
 * imagesize  = 260px
 * alt        =
 * caption    = Nagyágite from Nagyág (Săcărâmb), Romania (image width: 1.5 mm)
 * formula    = {{chem|Pb|5|Au(Te,Sb)}|4|S|(5–8)}} or  or (Te,Au)Pb(Pb,Sb)S2
 * IMAsymbol  = Ngy
 * molweight  =
 * strunz     = 2.HB.20a
 * dana       = 02.11.10.01
 * system     = Monoclinic
 * class      = Prismatic (2/m) (same H-M symbol)
 * symmetry   = P21/m
 * color      =
 * colour     = Blackish lead-grey; pale grey in polished section
 * habit      = Tabular crystals (often bent), also massive granular, pseudotetragonal
 * twinning   = Crossed twin lamellae observed on (001) sections
 * cleavage   = Perfect on {010}, excellent on {101}
 * fracture   = Hackly
 * tenacity   = Flexible, slightly malleable
 * mohs       = 1.5
 * lustre     = Metallic, bright on fresh cleavage
 * streak     = Blackish lead-grey
 * diaphaneity = Opaque
 * gravity    = 7.35–7.49
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 * pleochroism = Weak
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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.