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Francevillite

 

Francevillite

 

Discovered in 1957; IMA status: Valid (pre-IMA; Grandfathered)

 

 

Chemistry

 

 

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

 

 

Classification

   

   

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

7/E.11-100

Nickel-Strunz 10th Ed. ID:

4.HB.15

 

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
H : V[5,6] Vanadates
B : Uranyl Sorovanodates

Related to:

Curienite-Francevillite Series.

Varieties:

None

Synonyms:

Barium-Francevillite

 

 

Crystal Data

   

   

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

 

 

Physical Properties

   

 

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.

 

 

Optical Properties

   

   

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

 

 

Occurances

   

   

Geological Setting:

In the oxidized zone of a Pb-bearing U–V deposit (Mounana mine, Gabon).

Common Associations:

Curienite, Duttonite, Vanuralite, Chervetite, Mottramite, Mounanaite, Carnotite, Dewindtite, Torbernite, Uranopilite, Johannite, Kasolite (Mounana mine, Gabon)

Common Impurities:

None

Type Locality:

Mounana Mine (Mouana Mine), Franceville, Haut-Ogooué Province, Gabon

Year Discovered:

1957

View mineral photos:

Francevillite Mineral Photos and Locations

 

 

Unusual Gem Categories

   

   

 

Radioactive Gems

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 

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

Francevillite distribution: exceptional crystals from the Mounana uranium Mine, Franceville, Gabon. At Kambove and in the Musonoi mine, near Kolwezi, Katanga Province, Congo (Shaba Province, Zaire). On the southwest edge of the 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 Black 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. From the Otish Mountains, Quebec, Canada. In the USA, at Jim Thorpe, Carbon County, Pennsylvania.

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