Nagyágite

{{Short description|Sulfide mineral}}

{{infobox mineral

| 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 {{chem|AuPb(Sb,Bi)Te|(2–3)|S|6|}} or {{chem2|(Te,Au)Pb(Pb,Sb)S2}}

| IMAsymbol = Ngy{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |s2cid=235729616 |doi-access=free}}

| 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

| 2V =

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| references = {{mindat|id=2830|title=Nagyágite|access-date=6 August 2022}}{{Cite web|last1=Barthelmy|first1=David|year=2014|url=http://www.webmineral.com/data/Nagyagite.shtml|access-date=6 August 2022|title = Nagyagite Mineral Data|website=Webmineral.com}}{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Nagyágite |url=http://www.handbookofmineralogy.org/pdfs/nagyagite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=6 August 2022 |date=2005}}

}}

Nagyágite ({{chem|Pb|5|Au(Te,Sb)|4|S|(5–8)}}) 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.