Yellow crystal aggregates of the rare U-Mo mineral iriginite from Mexico (Picacho, Bacoachi, Bacoachi Municipality, Sonora, Mexico). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Iriginite
Iriginite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (UO₂)Mo⁶⁺₂O₇·3H₂O.
It crystallizes in the orthorhombic crystal system (space group Pbcm).
Key properties: Mohs hardness 4–5; specific gravity 3.84; Vitreous to dull luster; optically biaxial.
IMA symbol Irg, grandfathered status — known before the IMA’s founding, named in 1957.
Found in granulated albite, in part replacing brannerite (Aleksandrovskii Golets deposit, Russia); in a stream channel in sandstone (Hart Table, South Dakota, USA); may be of post-mining origin.
It is found associated with Ferrimolybdite, ilsemannite, metauranocircite, uranyl sulfates, gypsum.
A euphonious construction, devoid of connotation.