Yellow green crystals of the rare vanadium mineral fervanite from Joe Dandy Mine (Montrose County, Colorado, United States of America). — Photo: David Hospital · CC BY-SA 4.0
Fervanite
Fervanite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Fe³⁺₄V⁵⁺₄O₁₆·5H₂O.
Key properties: specific gravity 3.28; Brilliant luster; optically biaxial.
IMA symbol Fvn, grandfathered status — known before the IMA’s founding, named in 1931.
Occurs as an impregnation in sandstone (Colorado Plateau-type U–V deposits).
It is found associated with Hewettite, metahewettite, carnotite, steigerite, tyuyamunite, gypsum, other vanadium oxides (Colorado Plateau deposits); hewettite, duttonite, schoderite.
The name refers to its content of FERric iron and VANadium.