Magnesiovoltaite
Magnesiovoltaite is an IMA-recognized mineral species in the sulfate class, with the chemical formula K₂Mg₅Fe³⁺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 2.5; specific gravity 2.51; optically uniaxial.
IMA symbol Mvlt, IMA status: approved, named in 2015.
Found in the oxidized zone of a hydrothermal, polymetallic, sulfide vein deposit hosted by volcanic rocks in an arid region.
It is found associated with On coquimbite: tamarugite, alum-(Na), rhomboclase, yavapaiite, voltaite, opal; on botryogen and opal: tamarugite, alum-(K), pickeringite, magnesiocopiapite.
As an analog of voltaite and zincovoltaite with Mg dominant at the M1 structural position.