Pertlikite
Pertlikite is an IMA-recognized mineral species in the sulfate class, with the chemical formula K₂(Fe²⁺,Mg)₂(Mg,Fe³⁺)₄Fe³⁺₂Al(SO₄)₁₂·18H₂O.
It crystallizes in the tetragonal crystal system (space group I4_1/acd). It is a member of the Voltaite structural group.
Key properties: specific gravity 2.59; Grayish green streak; optically uniaxial.
IMA symbol Plk, IMA status: approved, named in 2005.
Found in a pyrite-bearing trachytic eruptive rock, and probably formed after the oxidation of pyrite.
It is found associated with Metavoltine, botryogen, pyrite, alunite.
The mineral was named to honor Franz Pertlik (b. 1943), Professor of Mineralogy and Crystallography, University of Vienna, Austria, for his contributions to the crystal chemistry of minerals.