Francevillite

Francevillite
IMA-GP
Uranium 40.2a.27.1
(Dana Classification Number)
(Images) 7/E.11-100
(Strunz ID)

Property Data Remarks
Named for: Franceville, Haut-Ogooué, Gabon, its type locality
Alternate
Name(s):

Mineral Class:

Phosphates, Arsenates and Vanadates
Uranylphosphates and uranylvanadates with:
[UO₂]²⁺ - [PO₄ | AsO₄]^3- and
uranyl-group vanadates with [UO₂]²⁺ - [V₂O₈]^6-
Tyuyamunite series

Chemical
Formula: (Ba,Pb)(UO₂)₂V₂O₈ · 5(H₂O
Chemical
Composition:

Barium: (Ba) 10.52%
Hydrogen: (H) 0.62%
Lead: (Pb) 5.29%
Oxygen: (O) 24.52%
Vanadium: (V) 10.41%
Uranium: (U) 48.64%

by weight
Molecular
Weight: 978.77 daltons (amu)
Specific
Radioactivity:
(All radiation is for a 1 gram, fully aged specimen)

Specific Activity Dose Rate
Becquerels Curies milliRems/hour microSieverts/hour
8.7062 × 10⁰⁴ 2.35 × 10^-06 1.17 116.56

Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)

Crystalography:

System: Orthorhombic - Dipyramidal
Axial Ratios: a: 1.2232
b: 1
c: 1.9694
Cell Dimensions: a: 10.41 Å
b: 8.51 Å
c: 16.76 Å
Z: 4
V: 1,484.75 Å³
Den_Calc: 4.38
H-M Symbol: 2/m 2/m 2/m
Space Group: Pcan
X-Ray Diffraction:
By Intensity ( ^I/_{I_o} ) (1): 2.996 Å
(1): 8.4 Å
(0.6): 5.2 Å
Francevillite
Crystal

(as observed)
Habit:

Cleavage:

[001] Perfect
[010]
[100]

Fracture:
Moh's
Hardness: 3
Density: 4.55 grams/cm³
Color: Orange
Streak: Light yellow
Luster: Adamantine - Pearly
Diaphaneity: Translucent to Transparent Twinned crystals usually translucent

Single crystals usually transparent
Pleochroism:

(x):
(y:)
(z:)

Ultra Violet
Fluorescence:

Long Wave:
Short Wave:

Magnetism: Non-magnetic
Occurance:
Weathering zone of pegmatites

Associated
Minerals:
Autunite, Azurite, Barite, Brochantite, Calcite, Carnotite, Cerussite, Chalcocite, Chalcopyrite, Coffinite, Copper, Covellite, Curienite, Galena, Gersdorffite, Hematite, Illite, Kasolite, Malachite, Metatorbernite, Metazeunerite, Mixite, Mottramite, Pharmacosiderite, Pitchblende, Pyrite, Safflorite, Scorodite, Skutterudite, Torbernite, Tyuyamunite, Uraninite, Uranophane, Wulfenite, Zeunerite

Mineral - > 50% of sites
Mineral - > 25% of sites
Mineral - > 15% of sites
Minerals - Uranium & Thorium
mineral links

In some locations, Chervetite (Pb₂V₂O₇) is closely associated with Francevillite.
These are minerals known to be found with Francevillite
Localities:
Uncommon
Francevillite Localities
Notes:
Strongly radioactive a- and b-particles, g-rays.

Crystals are probably metamict.

Francevillite Images

Specimen #1

(001a)

(001)

(001b)

Mounana mine, Franceville, Haut-Ogooué, Gabon

Specimen Notes

Occurrence - The Francvillite occurs on a substrate that is a mixture of quartz grains and a minor amount of Vanuranylite microcrystals. The host rock is quartz grains bonded by lime (calcium carbonate).

The primary crystaline mineral on the specimen is Chevetite (Lead Vanadate - Pb₂V₂O₇).

Crystals - The Francevillite crystals are in the 'seashell' shape that is typical of its twinned crystals. There are no solitary crystals on the specimen. Most of the Francevillite is so intergrown as to be massive.

Appearence - The Francevillite's overall appearence is heavily textured in parallel corregations. The diaphaneity of the Francevillite is translucent to nearly transparent. Its luster is vitreous.

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