Botryoidal Čejkaite with prismatic Grimselite (specimen width 4.7cm) Locality: Rovnost Mine (Werner Mine), Jáchymov (St Joachimsthal), Karlovy Vary Region, Bohemia (Böhmen; Boehmen), Czech Republic — Photo: Weirdmeister · CC BY-SA 3.0
Grimselite
Grimselite is an IMA-recognized mineral species in the carbonate class, with the chemical formula K₃Na(UO₂)(CO₃)₃·H₂O.
It crystallizes in the hexagonal crystal system (space group P-62c).
Key properties: Mohs hardness 2–2.5; specific gravity 3.3; Pale yellow streak; [Vitreous.] luster; optically uniaxial.
IMA symbol Gsl, IMA status: approved, named in 1971.
Found as a rare secondary mineral in veins in mineralized granodiorite.
It is found associated with Schrockingerite, baylissite, monohydrocalcite, calcite.
The name refers to the Grimsel region of Switzerland, which produced the first specimens.