Retgersite Locality: Ragra Mine (Minasragra), Junín, Cerro de Pasco, Daniel Alcides Carrión Province, Pasco Department, Peru Emerald-green Retgersite from the TL. Field of view 4 mm. Specimen and photo Leon Hupperichs. — Photo: Leon Hupperichs · CC BY-SA 3.0
Retgersite
Retgersite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Ni(SO₄)·6H₂O.
It crystallizes in the tetragonal crystal system (space group P4_12_12).
Key properties: Mohs hardness 2.5; specific gravity 2.04; Pale green streak; Vitreous luster; optically uniaxial.
IMA symbol Rtg, grandfathered status — known before the IMA’s founding, named in 1949.
Occurs as an uncommon secondary mineral in the oxidization zone of nickel-bearing hydrothermal mineral deposits, formed from H2O solution between 31.5 ° C and 53.5 ° C.
It is found associated with Nickeline, gersdorffite, nickelian pyrite, morenosite, chalcanthite, annabergite.
The mineral was named to honor Jan Willem Retgers (1856–1896), Dutch physical chemist and chemical crystallographer, who studied the crystallography of many synthetic compounds.