Very dark green , almost black, crystal aggregates of the rare vanadium mineral corvusite from Utah (Temple Mountain, San Rafael, Emery County, Utah, United States of America). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Corvusite
Corvusite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula (Na,Ca,K)₁₋ₓ(V⁵⁺,V⁴⁺,Fe²⁺)₈O₂₀·4H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Straczekite structural group.
Key properties: Mohs hardness 2.5–3; specific gravity 2.82; Purplish blue-black streak; “Lusterous”. n = [2.05] (rule of Gladstone and Dale) luster.
IMA symbol Cvu, grandfathered status — known before the IMA’s founding, named in 1933.
Found in roll-front uranium deposits in sandstone.
It is found associated with Carnotite, fervanite, roscoelite, gypsum.
The name comes from the Latin word for raven, in allusion to the similarity of the mineral’s color to that of a raven.