Klaprothite
Klaprothite is an IMA-recognized mineral species in the sulfate class, with the chemical formula Na₆(UO₂)(SO₄)₄(H₂O)₄.
It crystallizes in the monoclinic crystal system (space group P2_1/c).
Key properties: Mohs hardness 2.5; specific gravity 2.9; Pale yellow-green streak; Vitreous luster; optically biaxial.
IMA symbol Kpr, IMA status: approved, named in 2015.
Occurs as efflorescent crusts on mine walls, formed by hydration-oxidation weathering of primary uranium minerals (mainly uraninite) by acidic solutions from the decomposition of sulfides.
It is found associated with Blödite, bluelizardite, bobcookite, epsomite, gypsum, hexahydrite, konyaite, plášilite, tamarugite.
The mineral was named to honor German chemist Martin Heinrich Klaproth (1743-1817), the discoverer of uranium (1789), zirconium (1789) and cerium (1803).