Dark green almost black crystals of the very rare vanadium mineral bariandite from the type locality in Mounana (Mounana Mine, Franceville, Haut-Ogooue, Gabon). Bariandite has only been found in 5 localities worldwide. — Photo: David Hospital · CC BY-SA 4.0
Bariandite
Bariandite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Al₀.₆(V⁵⁺,V⁴⁺)₈O₂₀·9H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c). It is a member of the Straczekite structural group.
Key properties: specific gravity 2.7; optically biaxial.
IMA symbol Brd, IMA status: approved, named in 1970.
Found in the oxidation zone of a uranium mineral deposit (Mounana mine, Gabon); in the oxidation zone of a vanadium deposit (Minasragra, Peru).
It is found associated with Duttonite, lenoblite (Mounana mine, Gabon); roscoelite, gypsum (Minasragra, Peru).
The mineral was named to honor Dr. Pierre Bariand (1933–), Curator of Mineralogy, University of Paris, Paris, France.