Dumontite
A valid IMA mineral species - grandfathered
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About Dumontite
André Dumont
Formula:
Pb2(UO2)3O2(PO4)2 · 5H2O
Colour:
Golden yellow to ocher yellow
Specific Gravity:
5.65
Crystal System:
Monoclinic
Member of:
Name:
Named in 1924 by Alfred Schoep (1881-1966) in honor of André Hubert Dumont (15 February 1809, Liège, Belgium - 28 February 1857, Liège, Belgium), geologist. He travelled 90,000 km on foot and horseback to publish a geological map of Belgium on 1/160,000. He was also awarded the Wollaston Medal in 1840.
A secondary uranium mineral.
Unique Identifiers
Mindat ID:
1328
Long-form identifier:
mindat:1:1:1328:0
Classification of Dumontite
Phosphuranylite sheet topology
The sheet topology exhibited by members of the phosphuranylite group.
IMA Classification of Dumontite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Pb2+2(U6+O2)3(PO4)2O2·5H2O
First published:
1924
Type description reference:
8.EC.15
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
42.4.5.1
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
19.11.38
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 |
|---|---|---|
| Dmt | 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 Dumontite
Transparency:
Translucent
Colour:
Golden yellow to ocher yellow
Streak:
Light yellow
Density:
5.65(4) g/cm3 (Measured) 5.666 g/cm3 (Calculated)
Optical Data of Dumontite
Type:
Biaxial (+)
RI values:
nα = 1.85 nβ = 1.87 nγ = 1.89
Max. Birefringence:
δ = 0.040
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.
No measured or calculated 2V is on file for this mineral, so the value used here (91°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
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.
No measured or calculated 2V is on file for this mineral, so the value used here (91°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
strong r < v
Pleochroism:
Visible
Comments:
X = a = Pale yellow
Y = c =
Z = b = Deep yellow
Y = c =
Z = b = Deep yellow
Chemistry of Dumontite
Mindat Formula:
Pb2(UO2)3O2(PO4)2 · 5H2O
Element Weights:
Crystallography of Dumontite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/m
Cell Parameters:
a = 8.118(6) Å, b = 16.819(8) Å, c = 6.983(3) Å
β = 109.03(5)°
β = 109.03(5)°
Ratio:
a:b:c = 0.483 : 1 : 0.415
Unit Cell V:
901.33 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals small, elongated [001] and flattened {010} to 1.5 mm. May form stellate aggregates.
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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CIF File Best | x | y | z | a | b | c
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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) |
|---|---|---|---|---|---|---|---|
| 0012090 | Dumontite | Piret P, Piret-Meunier J (1988) Nouvelle determination de la structure cristalline de la dumonite Pb2[(UO2)3O2(PO4)2]*5H2O Bulletin de Mineralogie 111 439-442 | 1988 | Shinkolobwe, Shaba, Zaire | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.27 Å | (very strong) |
| 3.00 Å | (strong to very strong) |
| 2.95 Å | (strong to very strong) |
| 3.48 Å | (strong) |
| 6.14 Å | (moderately strong) |
| 4.20 Å | (moderately strong) |
| 3.74 Å | (moderately strong) |
Comments:
Shinkolobwe, DR Congo. Data from Thoreau et al. (1958).
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] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Geological Setting:
Secondary uranium deposits
Type Occurrence of Dumontite
Place of Conservation of Type Material:
Muséum national d'Histoire naturelle, Paris.
Associated Minerals at Type Locality:
Other Language Names for Dumontite
Relationship of Dumontite 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 |
| Françoisite-(Ce) | (Ce,Nd,Ca)(UO2)3(PO4)2O(OH) · 6H2O | Mon. 2/m : P21/b |
| Françoisite-(Nd) | (Nd,Ce,Sm)(UO2)3(PO4)2O(OH) · 6H2O | Mon. 2/m |
| 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:
| 11 photos of Dumontite associated with Metatorbernite | Cu(UO2)2(PO4)2 · 8H2O |
| 2 photos of Dumontite associated with Torbernite | Cu(UO2)2(PO4)2 · 12H2O |
| 1 photo of Dumontite associated with Uranophane | Ca(UO2)2(SiO3OH)2 · 5H2O |
| 1 photo of Dumontite associated with Parsonsite | Pb2(UO2)(PO4)2 |
| 1 photo of Dumontite associated with Kolbeckite | ScPO4 · 2H2O |
| 1 photo of Dumontite associated with Dewindtite | H2Pb3(UO2)6O4(PO4)4 · 12H2O |
Related Minerals - Strunz-mindat Grouping
| 8.EC.05 | Upalite | Al(UO2)3(PO4)2O(OH) · 7H2O |
| 8.EC.05 | Françoisite-(Nd) | (Nd,Ce,Sm)(UO2)3(PO4)2O(OH) · 6H2O |
| 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 | 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) | 46.4749% | 11,618,725 | 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 Dumontite
Greenish (UV).
Other Information
Notes:
Soluble in acids.
Health Risks:
Radioactive
Internet Links for Dumontite
mindat.org URL:
https://www.mindat.org/min-1328.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Dumontite
Reference List:
Billiet, Valère (1926) Détermination des indices de réfraction de la becquerélite, de la curite, de la kasolite, de la fourmariérite, de la parsonsite, de la dumontite, et de l'ianthinite. Bulletin de la Société française de Minéralogie, 49 (3). 136-140 doi:10.3406/bulmi.1926.4309
Thoreau, J.; Van Meerssche, Maurice; Protas, Jean (1958) Sur la Dumontite de Shinkolobwe (Katanga). Bulletin de la Société française de Minéralogie, 81 (1). 63-65 doi:10.3406/bulmi.1958.5229
Piret, Paul, Piret-Meunier, Jacqueline (1988) Nouvelle détermination de la structure cristalline de la dumontite Pb2[(UO2)3O2(PO4)2]·5H2O. Bulletin de Minéralogie, 111 (5) 439-442 doi:10.3406/bulmi.1988.8090
Jambor, John L., Burke, Ernst A. J. (1989) New Mineral Names. American Mineralogist, 74 (11-12) 1399-1404
Localities for Dumontite
Showing 28 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 | |
| Mineralogical Society of America - ... |
| Henry et al. (1999) | |
| Henry et al. (2005) |
Austria | |
| Auer (2005) |
Belgium | |
| Dejonghe et al. (1982) +1 other reference |
China | |
| Carnegie Museum of Natural History ... |
DR Congo (TL) | |
| Schoep (1924) +2 other references |
| Wilson (2018) |
| Dunn et al. (1985) |
France | |
| XRD & EDS probed - M.E. Ciriotti collection (2005) +1 other reference |
Germany | |
| Weiß (1990) |
| Dill et al. (2010) | |
| Gröbner et al. (2007) +1 other reference |
India | |
| Deepthi et al. (2015) |
Italy | |
| Campostrini et al. (2005) |
Portugal | |
| Alves et al. (2017) |
Slovenia | |
| Dolenec (1985) |
Tajikistan | |
| Soboleva et al. (1957) +1 other reference |
USA | |
| Granger (1962) +1 other reference |
| Eckel et al. (1997) |
| Harrison & Wells (1955) +1 other reference | |
| U.S. Geological Survey Bulletin 1032-B +1 other reference | |
| Sims (1963) +1 other reference | |
| Sims (1963) +1 other reference |
| Eckel et al. (1997) |
| Longwell et al. (1965) |
| Page et al. (1956) +2 other references |
| Peter Chin Collection |
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Shinkolobwe Mine, Shinkolobwe, Kambove Territory, Haut-Katanga, DR Congo