Francevillite
Image: <a href="//commons.wikimedia.org/wiki/User:Archaeodontosaurus" title="User:Archaeodontosaurus">Didier Descouens</a> (CC BY-SA 3.0)
Mineral NameFrancevillite
Chemical Formula(Ba,Pb)(UO₂)₂(VO₄)₂·5H₂O
Mohs Hardness2.5
Crystal Systemorthorhombic
Lusterearthy
Streak Coloryellowish-orange
Cleavageperfect on {001}
Fractureuneven
Specific Gravity4.5
Colorsorange, reddish-orange, yellow
Transparencytranslucent
Type LocalityMounana Mine, Franceville, Haut-Ogooué, Gabon
Mineral GroupVanadates
Usescollector
Associated Mineralscurienite
Rarityuncommon
Description
This specimen displays a vibrant orange to reddish-orange crust of Francevillite, composed of numerous small, granular crystals, with some brighter yellow areas, all on a darker rock matrix.
Geological Context
Francevillite is a secondary uranium mineral that forms in the oxidized zones of uranium-vanadium deposits, resulting from the alteration of primary uranium minerals in the presence of barium, lead, and vanadium.
