Francevillite is really a barium that is rare uranyl vanadate mineral that is strongly radioactive due to its uranium content. Francevillite does occur in the zone that is oxidized of uranium–vanadium deposits. It absolutely was first described in 1957 from an occurrence during the Mounana (uranium) Mine, near Franceville, Haut-Ogooué, Gabon and was named for the city that is nearby of. Francevillite occurs as crystals to about 8 mm, and also as aggregates, massive, in veinlets and as impregnations. Its colors range from lemon-yellow to orange and yellow-orange, greenish yellow, green and brown. Francevillite is semi-transparent with adamantine to luster that is pearly strong dispersion and Mohs hardness of 3.

Francevillite circulation: exceptional crystals from the Mounana uranium Mine, Franceville, Gabon. At Kambove as well as in the Musonoi mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire). On the edge that is southwest of Chimeja Range, about four km north of Lubimbi Spring, Zimbabwe. From Bertholène and Lussagues, Aveyron, and Saint-Pierre, Cantal, France. In Germany, on the Donnersberg, near Imsbach, Rhineland-Palatinate; in the Ebony Forest, at Nussbach, near Triberg, and from the Clara mine, near Oberwolfach. In the South Terras mine, St. Stephen-in-Brannel, Cornwall, England. At the Tyuya-Muyun Cave, Fergana Valley, Alai Range, Kyrgyzstan. Through the Otish Mountains, Quebec, Canada. Within the United States Of America, at Jim Thorpe, Carbon County, Pennsylvanis.

Category: Vanadate mineral
Chemical Formula: (Ba,Pb)(UO2)2(V2O8) · 5H2O
Hydrated Barium Lead Uranyl Vanadate
Molecular Weight: 978.77 gm
Composition: Barium 10.52 % Ba 11.75 % BaO
Uranium 48.64 % U 55.18 % UO2
Vanadium 10.41 % V 18.58 % V2O5
Hydrogen 0.62 % H 5.52 % H2O
Lead 5.29 % Pb 5.70 % PbO
Oxygen 24.52 % O
  100.00 % 96.73 % = TOTAL OXIDE


Crystallography: Orthorhombic – Dipyramidal
Crystal Habit: Commonly as crystals, dominantly {111}, rare {100}, {010}, a few other forms, to 8 mm, in aggregates and crusts. Also massive, in veinlets and as impregnations.
Twinning: None


Cleavage: Perfect on {001}
Fracture: n/a
Tenacity: Brittle
Moh’s Hardness: 3.0
Density: 4.55 (g/cm3)
Luminescence: None
Radioactivity: Very Strong; GRapi = 3,545,303.50 (Gamma Ray American Petroleum Institute Units)
Health Warning: Contains uranium – always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest. Avoid prolonged exposure in proximity of the body. Store away from inhabited areas.


Color: Lemon-yellow, yellow-orange, orange, greenish yellow; green, brown.
Transparency: Semi-transparent
Luster: Adamantine, pearly
Refractive Index: 1.750 – 2.002  Biaxial ( – )
Birefringence: 0.195 – 0.217
Dispersion: Strong
Pleochroism: X = colorless; Y = Z = yellow