Posnjakite

Posnjakite
Posnjakite from Špania Dolina in Slovakia
General
Category Copper minerals
Formula
(repeating unit)		 Cu4[(OH)6|SO4] • H2O
Strunz classification 7.DD.10
Dana classification 31.4.1.1
Crystal system Monoclinic
Crystal class Domatic (m)
(same H-M symbol)
Space group Pa
Unit cell a = 10.578 Å,
b = 6.345 Å,
c = 7.863 Å;
β = 117.98°; Z = 2[1]
Identification
Formula mass 488.32 g/mol
Color Sky-blue to dark-blue
Crystal habit Crystals scaly, or as crusts; earthy
Mohs scale hardness 2 to 3
Luster Vitreous
Refractive index nα = 1.625 nβ = 1.680 nγ = 1.706 [1]
References [2]

Posnjakite is a hydrated copper sulfate mineral. It was discovered in the Tungsten deposit of Nura-Taldy[3] in Karaganda Region in Kazakhstan and described in 1967 by Aleksandr Ivanovich Komkov (1926–1987) and Yevgenii Ivanovich Nefedov (1910–1976)[4] and named after geochemist Eugene Valdemar Posnjak (1888–1949).[5]

Occurrence

Posnjakite is an uncommon but widespread secondary mineral in the oxidised zone of copper sulfide deposits, which may be of post-mine formation. It is associated with brochantite, langite, devilline, serpierite, woodwardite, wroewolfeite, aurichalcite, azurite, malachite and chalcopyrite.[3]

References

  1. 1 2 Mindat - Posnjakite
  2. ↑ Mineralienatlas
  3. 1 2
  4. ↑
  5. ↑ MINER Database, (c) Jacques Lapaire - Minéraux et étymologie Archived 2014-10-06 at the Wayback Machine.
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