Voltaite Locality: Rio Tinto Mines, Minas de Riotinto , Huelva , Andalusia , Spain ( Locality at mindat.org ) Picture width 0,8 mm. Collection and photograph Christian Rewitzer — Photo: Christian Rewitzer · CC BY-SA 3.0
Voltaite
Voltaite is an IMA-recognized mineral species in the sulfate class, with the chemical formula K₂Fe²⁺₅Fe³⁺₃Al(SO₄)₁₂·18H₂O.
It crystallizes in the cubic crystal system (space group Fd3c). It is a member of the Voltaite structural group.
Key properties: Mohs hardness 3; specific gravity 2.645; Grayish green streak; Resinous luster.
IMA symbol Vlt, grandfathered status — known before the IMA’s founding, named in 1841.
Found in volcanic fumaroles, solfataras, and mud volcanos; an alteration product in mineral deposits high in pyrite, especially in arid climates, where it may also be a post-mining product.
It is found associated with Halotrichite, pickeringite, alunogen, metavoltine, römerite, hexahydrite, coquimbite, copiapite, rhomboclase, krausite, jarosite, goldichite, botryogen.
The mineral was named to honor Alessandro Giuseppe Antonio Anastasio Volta (1745–1827), Italian physicist, early experimenter with electricity.