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 symmetry Monoclinic domatic
H-M symbol: (m)
Space group: Pm
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
Color Sky-blue to dark-blue
Crystal habit Crystals scaly, or as crusts; earthy
Crystal system Monoclinic
Mohs scale hardness 2 to 3
Luster Vitreous
Refractive index nα = 1.625 nβ = 1.680 nγ = 1.706 [1]

Posnjakite is a hydrated copper sulfate mineral. It was discovered in the Tungsten deposit of Nura-Taldy[2] in Karaganda Region in Kazakhstan and described in 1967 by Aleksandr Ivanovich Komkov (1926–1987) and Yevgenii Ivanovich Nefedov (1910–1976)[3] and named after geochemist Eugene Valdemar Posnjak (1888–1949).[4]

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.[2]

References