Nagyagite
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| Nagyagite | |
|---|---|
 Nagyagite from Nagyag (Săcărâmb), Romania (image width: 1.5 mm) |
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| General | |
| Category | Sulfosalt mineral |
| Chemical formula | Pb5Au(Te,Sb)4S5-8[1] or AuPb(Sb,Bi)Te2-3S6[2] or (Te, Au)Pb(Pb, Sb)S2[3] |
| Strunz classification | 02.HB.20a |
| Dana classification | 02.11.10.01 |
| Identification | |
| Colour | Blackish lead-grey; pale grey in polished section |
| Crystal habit | Tabular crystals (often bent), also massive granular |
| Crystal system | Monoclinic, pseudotetragonal. Point Group: 2/m. |
| 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 |
| Luster | Metallic, bright on fresh cleavage |
| Streak | Blackish lead-grey |
| Diaphaneity | Opaque |
| Specific gravity | 7.35–7.49 |
| Pleochroism | Weak |
| References | [3][1][2] |
Nagyagite (Pb5Au(Te,Sb)4S5-8) is a rare sulfide mineral with known occurrence associated with gold ores. Nagyagite 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 Nagyag mine, Sacarîmb, Hunedoara, Romania.[1][2]
It occurs in gold–tellurium epithermal hydrothermal veins. Minerals associated with nagyagite include: altaite, petzite, stutzite, sylvanite, tellurantimony, coloradoite, krennerite, native arsenic, native gold, proustite, rhodochrosite, arsenopyrite, sphalerite, tetrahedrite, calaverite, tellurobismuthite, galena and pyrite.[3]
[edit] References
- ^ a b c http://www.mindat.org/min-2830.html Mindat.org
- ^ a b c http://webmineral.com/data/Nagyagite.shtml Webmineral data
- ^ a b c http://rruff.geo.arizona.edu/doclib/hom/nagyagite.pdf Handbook of Mineralogy
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