Uranosphaerite
Uranosphaerite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Bi(UO₂)O₂(OH).
It crystallizes in the monoclinic crystal system (space group P2_1/n).
Key properties: Mohs hardness 2–3; specific gravity 6.36; Yellow streak; Greasy luster; optically biaxial.
IMA symbol Us, grandfathered status — known before the IMA’s founding, named in 1873.
An oxidation product of uraninite in a Co-Ni-Bi-bearing hydrothermal vein (Schneeberg, Germany).
It is found associated with Walpurgite, uranospinite, uranospathite, asselbornite, trögerite, zeunerite, erythrite, cobaltian wad (Schneeberg, Germany); uraninite, wölsendorfite.
The name refers to URANium in the composition, and the Greek for sphere, for the typical habit.