Erssonite
Erssonite is an IMA-recognized mineral species in the sulfate class, with the chemical formula CaMg₇Fe³⁺₂(OH)₁₈(SO₄)₂·12H₂O.
It crystallizes in the hexagonal crystal system (space group P-3c1). It is a member of the Hydrotalcite structural group.
Key properties: specific gravity 2.02; Vitreous luster; optically uniaxial.
IMA status: approved, named in 2021.
Found in a late-stage, low-temperature assemblage likely formed by hydrothermal alteration in cavities of magnetite-bearing dolomitic rock.
It is found associated with Dolomite, calcite, members of the magnetite-magnesioferrite solid solution series, phlogopite, chrysotile, pyroaurite, norbergite.
The mineral was named to honor chemist and amateur mineralogist, Dr. Anders Ersson (b. 1971), Senior Engineer, Materials Technology section at Scania AB, Södertälje, Sweden.