Francevillite , Mounanaite , Curienite Locality: Mounana Mine (Mouana Mine), Franceville , Haut-Ogooué Province , Gabon ( Locality at mindat.org ) A rich CABINET-sized specimen that is incredible for both its aesthetic and scientific qualities. This piece features INDIVIDUAL and ISOLATED , RELATIVELY LARGE crystals of Francevillite to several mm in size, on an attractive matrix plate! Tiny yellow-gemmy crystals of mounanaite are so abundant and rich on this specimen that they are easily eye-visible against the larger francevillites, as shown in my pics. Characteristically powdery microcrystals of orangey-yellow curienite are in association , as well, in scattered crystals and as a thick matte on the rightmost edge of the specimen. This mine closed in 1999 after 40 years of production, and this is, for quality if not size, pretty much as good as the mineral gets. Note that this its the type locality of ALL THREE species! 12.5 x 7 x 2.25 cm — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Mounanaite
Mounanaite is an IMA-recognized mineral species in the vanadate class, with the chemical formula PbFe³⁺₂(VO₄)₂(OH)₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Natrochalcite structural group.
Key properties: Mohs hardness 4.5; specific gravity 4.85; optically biaxial.
IMA symbol Mun, IMA status: approved, named in 1968.
A rare mineral found in the oxidized zone of a sediment-hosted U–V deposit.
It is found associated with Francevillite, curienite, vanuralite, goethite.
The name refers to the Mounana mine, Gabon, the locality that produced the first specimens.