Francevillite
A valid IMA mineral species - grandfathered
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About Francevillite
Franceville, Gabon
Formula:
Ba(UO2)2(VO4)2 · 5H2O
Colour:
Lemon-yellow, yellow-orange, orange, greenish yellow, green, brown
Hardness:
3
Specific Gravity:
4.55
Crystal System:
Orthorhombic
Member of:
Name:
Named in 1957 by G. Branche, M.E. Ropert, F. Chantret, B. Morignat, and R. Pouget for Franceville, the city nearest the type locality.
Unique Identifiers
Mindat ID:
1589
Long-form identifier:
mindat:1:1:1589:5
Classification of Francevillite
Francevillite sheet topology
Francevillite contains the francevillite sheet topology.
IMA Classification of Francevillite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ba(U6+O2)2(V5+O4)2·5H2O
First published:
1957
Type description reference:
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
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
H : V[5,6] Vanadates
B : Uranyl Sorovanodates
40.2a.27.1
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
2a : AB2(XO4)2·xH2O, containing (UO2)2+
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
2a : AB2(XO4)2·xH2O, containing (UO2)2+
21.4.10
21 : Vanadates (and vanadates with arsenate or phosphate)
4 : Vanadates of U, Mn, Fe or Ni
21 : Vanadates (and vanadates with arsenate or phosphate)
4 : Vanadates of U, Mn, Fe or Ni
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Fvl | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Francevillite
Transparency:
Translucent
Colour:
Lemon-yellow, yellow-orange, orange, greenish yellow, green, brown
Streak:
Light yellow
Hardness:
3 on Mohs scale
Cleavage:
Perfect
On {001}
On {001}
Density:
4.55 g/cm3 (Measured) 4.56 g/cm3 (Calculated)
Optical Data of Francevillite
Type:
Biaxial (-)
RI values:
nα = 1.750 - 1.785 nβ = 1.910 - 1.952 nγ = 1.945 - 2.002
2V:
Measured: 52° , Calculated: 46° to 52°
Max. Birefringence:
δ = 0.195 - 0.217
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
Dispersion:
strong
Optical Extinction:
X = c; Y = b; Z = a.
Pleochroism:
Visible
Comments:
X = colorless; Y = Z = yellow.
Chemistry of Francevillite
Mindat Formula:
Ba(UO2)2(VO4)2 · 5H2O
Element Weights:
Crystallography of Francevillite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Cell Parameters:
a = 10.419(1) Å, b = 8.510(1) Å, c = 16.763(2) Å
Ratio:
a:b:c = 1.224 : 1 : 1.97
Unit Cell V:
1,486.30 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Dominant {111}, rare {100}, {010}.
Comment:
Space Group: P can
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0014807 | Francevillite | Mereiter K (1986) Crystal structure refinement of two francevillites, (Ba,Pb)[(UO2)2V2O8]*5H2O Neues Jahrbuch fur Mineralogie, Monatshefte 1986 552-560 | 1986 | Mounana, near Franceville, Gabon | 0 | 293 | |
| 0014806 | Francevillite | Mereiter K (1986) Crystal structure refinement of two francevillites, (Ba,Pb)[(UO2)2V2O8]*5H2O Neues Jahrbuch fur Mineralogie, Monatshefte 1986 552-560 | 1986 | Mounana, near Franceville, Gabon | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Loading XRD data...
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.30 Å | (100) |
| 2.98 Å | (80) |
| 4.17 Å | (60) |
| 2.57 Å | (60) |
| 2.10 Å | (50) |
| 3.27 Å | (40) |
| 2.01 Å | (40) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47e : [Vanadates, chromates, manganates] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Type Occurrence of Francevillite
General Appearance of Type Material:
Impregnations, cryptocrystalline veinlets, and crystal-plates several millimeters in thickness.
Place of Conservation of Type Material:
National School of Mines, Paris, France.
The Natural History Museum, London, England, 1958,597.
The Natural History Museum, London, England, 1958,597.
Geological Setting of Type Material:
Sandstone
Associated Minerals at Type Locality:
Synonyms of Francevillite
Other Language Names for Francevillite
Relationship of Francevillite to other Species
Member of:
Other Members of Francevillite Group:
| Curienite | Pb(UO2)2(VO4)2 · 5H2O | Orth. mmm(2/m2/m2/m) |
| Finchite | Sr(UO2)2(V2O8) · 5H2O | Orth. mmm(2/m2/m2/m) |
| Fritzscheite | Mn2+(UO2)2(VO4,PO4)2 · 4H2O | Tet. |
Forms a series with:
Common Associates
Associations Based on Photo Data:
| 83 photos of Francevillite associated with Curienite | Pb(UO2)2(VO4)2 · 5H2O |
| 73 photos of Francevillite associated with Chervetite | Pb2(V2O7) |
| 54 photos of Francevillite associated with Mounanaite | PbFe3+2(VO4)2(OH)2 |
| 6 photos of Francevillite associated with Mottramite | PbCu(VO4)(OH) |
| 5 photos of Francevillite associated with Vanuralite | Al(UO2)2(V2O8)(OH) · 11H2O |
| 5 photos of Francevillite associated with Quartz | SiO2 |
| 5 photos of Francevillite associated with Carnotite | K2(UO2)2(VO4)2 · 3H2O |
| 3 photos of Francevillite associated with 'Pitchblende' | UO2 |
| 3 photos of Francevillite associated with Pandoraite-Ba | BaV4+5V5+2O16 · 3H2O |
| 3 photos of Francevillite associated with Autunite | Ca(UO2)2(PO4)2 · 10-12H2O |
Related Minerals - Strunz-mindat Grouping
| 4.HB.X | Spanoite | Tl2[(UO2)2(V2O8)] |
| 4.HB.05 | Margaritasite | (Cs,K,H3O)2(UO2)2(VO4)2 · H2O |
| 4.HB.05 | Carnotite | K2(UO2)2(VO4)2 · 3H2O |
| 4.HB.10 | Sengierite | Cu2(UO2)2(VO4)2 · 6H2O |
| 4.HB.15 | Fritzscheite | Mn2+(UO2)2(VO4,PO4)2 · 4H2O |
| 4.HB.15 | Curienite | Pb(UO2)2(VO4)2 · 5H2O |
| 4.HB.15 | Finchite | Sr(UO2)2(V2O8) · 5H2O |
| 4.HB.20 | Vanuralite | Al(UO2)2(V2O8)(OH) · 11H2O |
| 4.HB.20 | Metavanuralite | Al(UO2)2(VO4)2(OH) · 8H2O |
| 4.HB.25 | Metatyuyamunite | Ca(UO2)2(VO4)2 · 3H2O |
| 4.HB.25 | Tyuyamunite | Ca(UO2)2(VO4)2 · 5-8H2O |
| 4.HB.30 | Strelkinite | Na2(UO2)2(VO4)2 · 6H2O |
| 4.HB.35 | Uvanite | U6+2V5+6O21 · 15H2O (?) |
| 4.HB.40 | Rauvite | Ca(UO2)2(V10O28) · 16H2O |
| 4.HB.45 | Vandermeerscheite | K2[(UO2)2V2O8] · 2H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 47.7329% | 11,933,225 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 0.0000% | 0 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Fluorescence of Francevillite
Does not fluoresce.
Other Information
Thermal Behaviour:
The mineral loses 7.8% H2O up to 225° and 8.7% up to 520°, but heating for three hours at 225° drove off 8.6%. X-ray patterns of material heated at 520° show no change, and the mineral rehydrates on being allowed to stand in the room atmosphere. A DTA curve shows a large endothermal effect at about 150-200°, and smaller ones at 680° and 900°.
Notes:
Radioactive
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Francevillite
mindat.org URL:
https://www.mindat.org/min-1589.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Francevillite
Reference List:
Branche, Georges, Ropert Marie-Edith, Chantret, Francis, Morignat, Bernard, Pouget, Robert (1957) La francevillite, nouveau minéral uranifère [Francevillite, a new uranium mineral]. Comptes rendus de l’Académie des sciences de Paris, 245. 89-91
Localities for Francevillite
Showing 49 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Argentina | |
| Rainoldi et al. (2024) |
Australia | |
| Henry et al. (2005) |
| |
Canada | |
| Rose (1973) |
| SASSANO et al. (1987) |
China | |
| National Geological Archives of China ... |
Czech Republic | |
| Pauliš et al. (1990) |
| Sejkora et al. (2026) |
| Sejkora et al. (2019) |
DR Congo | |
| KMMA +1 other reference |
| Gauthier et al. (1989) |
| Wilson (2018) |
France | |
| Cuchet et al. (2000) |
| J.-J. Périchaud: "Les Minéraux ... |
| Agrinier et al. (1967) |
| Wittern et al. (1997) +1 other reference |
| - (1998) |
| - (1998) |
| - (1998) +1 other reference |
Gabon | |
| |
| Branche et al. (1957) +1 other reference |
| Janusz Janeczek (1999) | |
Germany | |
| Walenta (1992) +4 other references |
| |
| Lorenz (1998) +1 other reference |
| Weiß (1990) |
| Gröbner et al. (2007) +1 other reference |
Italy | |
| Campostrini I. (2013) |
Kazakhstan | |
| Pavel M. Kartashov (n.d.) |
Mauritania | |
| Marsh et al. (2015) |
| Marsh et al. (2015) | |
| Marsh et al. (2015) |
Morocco | |
| W.Paar (1974) |
Niger | |
| Roux et al. (1987) |
Russia | |
| Pavel M. Kartashov (n.d.) |
| Pavel M. Kartashov (n.d.) |
Slovenia | |
| Dolenec (1985) |
South Korea | |
| Cheong et al. (2003) |
Spain | |
| Joan Abella i Creus specimen |
| Calvo Rebollar (2009) |
UK | |
| Embrey (1978) +1 other reference |
USA | |
| Anita Moore-Nall and David R. Lageson (2015) |
| Anita Moore-Nall and David R. Lageson (2015) |
| |
| Peter Chin |
| |
Zimbabwe | |
| Gallagher M. J. (1966) |
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Mounana Mine, Mounana, Léboumbi-Leyou Department, Haut-Ogooué Province, Gabon