Françoisite-(Nd)
A valid IMA mineral species
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About Françoisite-(Nd)
Formula:
(Nd,Ce,Sm)(UO2)3(PO4)2O(OH) · 6H2O
Colour:
Yellow
Lustre:
Vitreous
Hardness:
3
Specific Gravity:
4.06
Crystal System:
Monoclinic
Member of:
Name:
Named in 1988 by P. Piret, M. Deliens, and J. Piret-Meunier in honor of Dr. Armand François (Aljustrel, Portugal, December 28th 1922 - ), Belgian geologist and former director of the Geology Department of Gécamine, a Zaïrian mining company.
Type Locality:
Isostructural with:
This page provides mineralogical data about Françoisite-(Nd).
Name Encoding
ASCII-7:
Francoisite-(Nd)
Unique Identifiers
Mindat ID:
1594
Long-form identifier:
mindat:1:1:1594:9
Similar Names
| Francisite | A valid IMA mineral species | Cu3Bi(SeO3)2O2Cl |
| Françoisite | ||
| Françoisite-(Ce) | A valid IMA mineral species | (Ce,Nd,Ca)(UO2)3(PO4)2O(OH) · 6H2O |
Classification of Françoisite-(Nd)
Phosphuranylite sheet topology
The sheet topology exhibited by members of the phosphuranylite group.
IMA Classification of Françoisite-(Nd)
Approved
IMA Formula:
Nd(U6+O2)3(PO4)2O(OH)·6H2O
Approval year:
1987
First published:
1988
Type description reference:
8.EC.05
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
C : UO2:RO4 = 3:2
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
C : UO2:RO4 = 3:2
42.4.14.1
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
4 : (AB)5(XO4)2Zq·xH2O
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
4 : (AB)5(XO4)2Zq·xH2O
19.11.34
19 : Phosphates
11 : Phosphates of U
19 : Phosphates
11 : Phosphates of U
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 |
|---|---|---|
| Frç-Nd | 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 Françoisite-(Nd)
Vitreous
Transparency:
Translucent
Colour:
Yellow
Streak:
White, yellow
Hardness:
3 on Mohs scale
Cleavage:
Distinct/Good
{010}
{010}
Fracture:
Irregular/Uneven
Density:
4.06 g/cm3 (Measured) 4.63 g/cm3 (Calculated)
Optical Data of Françoisite-(Nd)
Type:
Biaxial (-)
RI values:
nα = 1.65 nβ = 1.74 nγ = 1.75
2V:
Measured: 35° , Calculated: 34°
Max. Birefringence:
δ = 0.100
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:
relatively strong
Chemistry of Françoisite-(Nd)
Mindat Formula:
(Nd,Ce,Sm)(UO2)3(PO4)2O(OH) · 6H2O
Element Weights:
Crystallography of Françoisite-(Nd)
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 9.298(2) Å, b = 15.605(4) Å, c = 13.668(2) Å
β = 112.77(1)°
β = 112.77(1)°
Ratio:
a:b:c = 0.596 : 1 : 0.876
Unit Cell V:
1,828.61 ų (Calculated from Unit Cell)
Z:
4
Twinning:
Twinned on (100)
Comment:
space groupP2/c
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.79 Å | (100) |
| 5.76 Å | (50) |
| 4.44 Å | (40) |
| 4.33 Å | (40) |
| 3.88 Å | (50B) |
| 3.13 Å | (50) |
| 2.874 Å | (40) |
| 2.840 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] | |
| 47c : [Carbonates, phosphates, borates, nitrates] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Type Occurrence of Françoisite-(Nd)
Place of Conservation of Type Material:
Royal Belgian Institute of Natural Sciences, Brussels
Geological Setting of Type Material:
Copper cobalt deposit
Associated Minerals at Type Locality:
Synonyms of Françoisite-(Nd)
Françoisite (in part)
Other Language Names for Françoisite-(Nd)
Relationship of Françoisite-(Nd) to other Species
Member of:
Other Members of Phosphuranylite Group:
| Althupite | AlTh(UO2)7(PO4)4(OH)5O2 · 15H2O | Tric. 1 : P1 |
| Bergenite | Ca2Ba4(UO2)9(PO4)6O6 · 16H2O | Mon. 2/m : P21/b |
| Dewindtite | H2Pb3(UO2)6O4(PO4)4 · 12H2O | Orth. mmm(2/m2/m2/m) : Cmma |
| Dumontite | Pb2(UO2)3O2(PO4)2 · 5H2O | Mon. 2/m : P21/m |
| Françoisite-(Ce) | (Ce,Nd,Ca)(UO2)3(PO4)2O(OH) · 6H2O | Mon. 2/m : P21/b |
| Hügelite | Pb2(UO2)3(AsO4)2O2 · 5H2O | Mon. 2/m : P21/m |
| Phosphuranylite | KCa(H3O)3(UO2)7(PO4)4O4 · 8H2O | Orth. mmm(2/m2/m2/m) : Cmcm |
| Phuralumite | Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9 | Mon. 2/m |
| Phurcalite | Ca2(UO2)3(PO4)2O2 · 7H2O | Orth. mmm(2/m2/m2/m) : Pbca |
| Upalite | Al(UO2)3(PO4)2O(OH) · 7H2O | Mon. 2/m : P21/b |
| Vanmeersscheite | U6+(UO2)3(PO4)2(OH)6 · 4H2O | Orth. mmm(2/m2/m2/m) |
| Yingjiangite | K2Ca(UO2)7(PO4)4(OH)6 · 6H2O | Orth. mmm(2/m2/m2/m) : Cmcm |
Common Associates
Associations Based on Photo Data:
| 5 photos of Françoisite-(Nd) associated with Metatorbernite | Cu(UO2)2(PO4)2 · 8H2O |
| 4 photos of Françoisite-(Nd) associated with Françoisite-(Ce) | (Ce,Nd,Ca)(UO2)3(PO4)2O(OH) · 6H2O |
Related Minerals - Strunz-mindat Grouping
| 8.EC.05 | Upalite | Al(UO2)3(PO4)2O(OH) · 7H2O |
| 8.EC.05 | Françoisite-(Ce) | (Ce,Nd,Ca)(UO2)3(PO4)2O(OH) · 6H2O |
| 8.EC.05 | Phuralumite | Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9 |
| 8.EC.10 | Yingjiangite | K2Ca(UO2)7(PO4)4(OH)6 · 6H2O |
| 8.EC.10 | Renardite | Pb(UO2)4(PO4)2(OH)4 · H2O |
| 8.EC.10 | Phosphuranylite | KCa(H3O)3(UO2)7(PO4)4O4 · 8H2O |
| 8.EC.10 | Arsenuranylite | Ca(UO2)4(AsO4)2(OH)4 · 6H2O |
| 8.EC.10 | 'Kivuite' | Th(UO2)4(PO3OH)2(OH)8 · 7H2O |
| 8.EC.10 | Dewindtite | H2Pb3(UO2)6O4(PO4)4 · 12H2O |
| 8.EC.15 | Dumontite | Pb2(UO2)3O2(PO4)2 · 5H2O |
| 8.EC.15 | Hügelite | Pb2(UO2)3(AsO4)2O2 · 5H2O |
| 8.EC.20 | Vanmeersscheite | U6+(UO2)3(PO4)2(OH)6 · 4H2O |
| 8.EC.20 | Arsenovanmeersscheite | U6+(UO2)3(AsO4)2(OH)6 · 4H2O |
| 8.EC.20 | Metavanmeersscheite | U6+(UO2)3(PO4)2(OH)6 · 2H2O |
| 8.EC.25 | Althupite | AlTh(UO2)7(PO4)4(OH)5O2 · 15H2O |
| 8.EC.30 | Mundite | Al(UO2)3(PO4)2(OH)3 · 5.5H2O |
| 8.EC.35 | Phurcalite | Ca2(UO2)3(PO4)2O2 · 7H2O |
| 8.EC.40 | Bergenite | Ca2Ba4(UO2)9(PO4)6O6 · 16H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 55.5551% | 13,888,775 | 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
Other Information
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 Françoisite-(Nd)
mindat.org URL:
https://www.mindat.org/min-1594.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Françoisite-(Nd)
Reference List:
Piret, Paul, Deliens, Michel, Piret-Meunier, Jacqueline (1988) La françoisite-(Nd), nouveau phosphate d'uranyle et de terres rares ; propriétés et structure cristalline. Bulletin de Minéralogie, 111 (5) 443-449 doi:10.3406/bulmi.1988.8091
Janeczek, Janusz, Ewing, Rodney (1996) Phosphatian coffinite with rare earth elements and Ce-rich françoisite-(Nd) from sandstone beneath a natural fission reactor at Bangombé, Gabon. Mineralogical Magazine, 60 (401) 665-669 doi:10.1180/minmag.1996.060.401.14
Localities for Françoisite-(Nd)
Showing 7 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.
Australia | |
| Brugger et al. (2003) |
DR Congo (TL) | |
| European Journal of Mineralogy (1990) +3 other references |
Gabon | |
| MinMag 60:665 +3 other references |
Germany | |
| Noller et al. (01/21) |
Italy | |
| Campostrini et al. (2006) |
Japan | |
| Uehara et al. (2022) |
Switzerland | |
| In Philippe Roth's collection. XRD and SEM/EDX determination by N. Meisser (MGL Lausanne) |
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Krunkelbach Valley Uranium deposit, Menzenschwand, St Blasien, Waldshut, Freiburg Region, Baden-Württemberg, Germany