Widenmannite
Widenmannite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Pb₂(OH)₂[(UO₂)(CO₃)₂].
It crystallizes in the orthorhombic crystal system (space group Pnmm).
Key properties: Mohs hardness 2; specific gravity 6.89; Pale yellow streak; Pearly to silky luster; optically biaxial.
IMA symbol Wdm, IMA status: approved, named in 1961.
A rare secondary mineral found in the oxidized zone of a hydrothermal As–Pb-bearing deposit (Michael mine, Germany); an alteration product of sulfides by sea water (Loe Warren zawn, England).
It is found associated with Hügelite, hallimondite, cerussite, galena, quartz (Michael mine, Germany); dewindtite, uraninite (Loe Warren zawn, England).
The mineral was named to honor Johann Friedrich Wilhelm Widenmann (1764–1798), German mineralogist who discovered uranium in the Black Forest.