Ungemachite
A rare potassium-sodium-iron sulfate-nitrate known from only two copper deposits worldwide.
Intro adapted from Wikipedia (CC BY-SA).
Ungemachite is an IMA-recognized mineral species in the nitrate class, with the chemical formula K₃Na₈Fe³⁺(SO₄)₆(NO₃)₂·6H₂O.
It crystallizes in the hexagonal crystal system (space group R-3).
Key properties: Mohs hardness 2.5; specific gravity 2.287; Vitreous luster; optically uniaxial.
IMA symbol Ugm, grandfathered status — known before the IMA’s founding, named in 1938.
Rarely formed by the oxidation of pyrite in an arid climate, in veins and cavities in other massive iron sulfates.
It is found associated with Clinoungemachite, jarosite, sideronatrite, metasideronatrite, metavoltine, fibroferrite.
The mineral was named to honor Henri Léon Ungemach (1879–1936), Belgian crystallographer who studied the natural sulfates of Chile.