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Nagyágite

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Nagyágite
Nagyágite from Nagyág (Săcărâmb), Romania (image width: 1.5 mm)
General
CategorySulfosalt mineral
Formula
(repeating unit)
Pb
5
Au(Te,Sb)}
4
S
(5–8)
[1] or AuPb(Sb,Bi)Te
(2–3)
S
6
[2] or (Te,Au)Pb(Pb,Sb)S2[3]
IMA symbolNgy[4]
Strunz classification2.HB.20a
Dana classification02.11.10.01
Crystal systemMonoclinic
Crystal classPrismatic (2/m)
(same H-M symbol)
Space groupP21/m
Identification
ColourBlackish lead-grey; pale grey in polished section
Crystal habitTabular crystals (often bent), also massive granular, pseudotetragonal
TwinningCrossed twin lamellae observed on (001) sections
CleavagePerfect on {010}, excellent on {101}
FractureHackly
TenacityFlexible, slightly malleable
Mohs scale hardness1.5
LustreMetallic, bright on fresh cleavage
StreakBlackish lead-grey
DiaphaneityOpaque
Specific gravity7.35–7.49
PleochroismWeak
References[1][2][3]

Nagyágite (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.[1][2]

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.[3]

References

[edit]
  1. ^ a b c Nagyágite, Mindat.org, retrieved 6 August 2022
  2. ^ a b c Barthelmy, David (2014). "Nagyagite Mineral Data". Webmineral.com. Retrieved 6 August 2022.
  3. ^ a b c Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Nagyágite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 6 August 2022.
  4. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.