Francevillite

Francevillite , Mounanaite , Curienite Locality: Mounana Mine (Mouana Mine), Franceville, Haut-Ogooué Province, Gabon Dimensions: 4 cm x 3.5 cm x 1 cm”Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”

Chemical Formula: (Ba,Pb)(UO2)2V2O8·5(H2O)
Locality: Mounana mine, Franceville, Haut-Ogooue, Gabon.
Name Origin: Named for the locality

Francevillite is a uranyl-group vanadate mineral in the tyuyamunite series. Its chemical formula is (Ba,Pb)(UO2)2V2O8·5(H2O). Francevillite is a strongly radioactive mineral. It is typically orange, yellow or brownish yellow. It forms a series with curienite.

Occurrence

Francevillite occurs in the oxidized zone of a lead-bearing uranium–vanadium deposits. Francevillite was first described in 1957 for an occurrence in its type locality of the idle Mounana uranium mine, near Franceville, Haut-Ogooué, Gabon and was named for the city.

At its type locality it is associated with curienite (a closely related uranyl vanadate), chevetite (a lead vanadate), and mounanaite (another lead vanadate). At other localities, francevillite is associated with duttonite, vanuralite, mottramite, carnotite, dewindtite, torbernite, uranopilite, johannite and kasolite.

Physical Properties

Cleavage: {001} Perfect
Color: Brownish yellow, Yellow, Yellow green.
Density: 4.55
Hardness: 3 – Calcite
Luster: Adamantine – Pearly
Streak: light yellow

Photo :

This sample of francevillite is displayed in the Smithsonian Museum of Natural History. The sample  is about 12 cm across and is from Mounana, Gabon.
Mounana Mine (Mouana Mine), Franceville, Haut-Ogooué Province, Gabon
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