Nagyágite | |
---|---|
General | |
Category | Sulfosalt mineral |
Formula (repeating unit) | Pb 5Au(Te,Sb)} 4S (5–8) [1] or AuPb(Sb,Bi)Te (2–3)S 6 [2] or (Te,Au)Pb(Pb,Sb)S2 [3] |
IMA symbol | Ngy [4] |
Strunz classification | 2.HB.20a |
Dana classification | 02.11.10.01 |
Crystal system | Monoclinic |
Crystal class | Prismatic (2/m) (same H-M symbol) |
Space group | P21/m |
Identification | |
Colour | Blackish lead-grey; pale grey in polished section |
Crystal 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 scale hardness | 1.5 |
Lustre | Metallic, bright on fresh cleavage |
Streak | Blackish lead-grey |
Diaphaneity | Opaque |
Specific gravity | 7.35–7.49 |
Pleochroism | Weak |
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]