Sklodowskite
A valid IMA mineral species - grandfathered
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About Sklodowskite
Marie Skłodowska Curie
Formula:
Mg(UO2)2(SiO3OH)2 · 6H2O
Colour:
Light yellow to green-yellow
Lustre:
Adamantine, Vitreous, Silky
Hardness:
2 - 3
Specific Gravity:
3.54
Crystal System:
Monoclinic
Member of:
Name:
Named after Marie Skłodowska-Curie (7 November 1867, Warsaw, Russian Empire (now Poland) – 4 July 1934, Passy, Haute-Savoie, France), who, with her husband Pierre, was a pioneer in the study of radioactivity. She was given many awards, including the 1903 Nobel Prize in Physics and the 1911 Nobel Prize in Chemistry.
Unique Identifiers
Mindat ID:
3681
Long-form identifier:
mindat:1:1:3681:4
IMA Classification of Sklodowskite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Mg(U6+O2)2(SiO3OH)2·6H2O
First published:
1924
Classification of Sklodowskite
9.AK.10
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
53.3.1.3
53 : NESOSILICATES Insular SiO4 Groups and Other Anions or Complex Cations
3 : Insular SiO4 Groups and Other Anions of Complex Cations with (UO2)
53 : NESOSILICATES Insular SiO4 Groups and Other Anions or Complex Cations
3 : Insular SiO4 Groups and Other Anions of Complex Cations with (UO2)
14.16.9
14 : Silicates not Containing Aluminum
16 : Silicates of U
14 : Silicates not Containing Aluminum
16 : Silicates 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 |
|---|---|---|
| Sds | 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 Sklodowskite
Adamantine, Vitreous, Silky
Transparency:
Transparent, Translucent
Comment:
Earthy when massive
Colour:
Light yellow to green-yellow
Streak:
Yellow
Hardness:
2 - 3 on Mohs scale
Cleavage:
Perfect
on {100}
on {100}
Density:
3.54 g/cm3 (Measured) 3.51 g/cm3 (Calculated)
Optical Data of Sklodowskite
Type:
Biaxial (+)
RI values:
nα = 1.613 - 1.615 nβ = 1.635 - 1.642 nγ = 1.656 - 1.657
Max. Birefringence:
δ = 0.042 - 0.043
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:
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 (100°) 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 (100°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
strong r > v
Pleochroism:
Visible
Comments:
X= colorless
Y= yellow
Z= pale yellow
Y= yellow
Z= pale yellow
Chemistry of Sklodowskite
Mindat Formula:
Mg(UO2)2(SiO3OH)2 · 6H2O
Element Weights:
Common Impurities:
Te,Ni,Na,K
Crystallography of Sklodowskite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
a = 17.4078(6) Å, b = 7.0428(3) Å, c = 6.6080(2) Å
β = 105.882(14)°
β = 105.882(14)°
Ratio:
a:b:c = 2.472 : 1 : 0.938
Unit Cell V:
779.21 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Acicular crystals.
Twinning:
With {001} or {100} as twin plane.
Comment:
Cell parameters from Plášil (2018) with R1=1.96%
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
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View
CIF File Best | x | y | z | a | b | c
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Rotation
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Labels
Console Off | On | Grey | Yellow
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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) |
|---|---|---|---|---|---|---|---|
| 0012337 | Sklodowskite | Ryan R R, Rosenzweig A (1977) Sklodowskite, MgO*2UO3*2SiO2*7H2O Crystal Structure Communications 6 611-615 | 1977 | Naica, Chihuahua, Mexico | 0 | 293 | |
| 0015548 | Sklodowskite | Mokeeva V I (1964) The structure of sklodowskite Soviet Physics Crystallography 9 217-218 | 1964 | 0 | 293 | ||
| 0015594 | Sklodowskite | Mokeeva V I (1959) The crystal structure of sklodowskite Soviet Physics Doklady 4 27-29 | 1959 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.42 Å | (100) |
| 4.19 Å | (80) |
| 3.27 Å | (70) |
| 3.52 Å | (60) |
| 3.00 Å | (60) |
| 5.91 Å | (50) |
| 4.00 Å | (50) |
Comments:
Katanga, D.R. Congo.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Geological Setting:
Silica bearing waters acting on earlier deposited uranium minerals (uraninite)
Type Occurrence of Sklodowskite
General Appearance of Type Material:
Spherulites of fibers, 6-7 mm in diameter.
Place of Conservation of Type Material:
No designated type material.
Geological Setting of Type Material:
Uranium deposit; found in cracks in a talcose siliceous breccia.
Associated Minerals at Type Locality:
Synonyms of Sklodowskite
Other Language Names for Sklodowskite
Dutch:Sklodowskiet
German:Sklodowskit
Japanese:スクロドフスカ石
Russian:Склодовскит
Simplified Chinese:硅镁铀矿
Spanish:Sklodowskita
Traditional Chinese:矽鎂鈾礦
Relationship of Sklodowskite to other Species
Member of:
Other Members of Sklodowskite Group:
| Cuprosklodowskite | Cu(UO2)2(SiO3OH)2 · 6H2O | Tric. 1 : P1 |
| Oursinite | Co(UO2)2(SiO3OH)2 · 6H2O | Orth. mmm(2/m2/m2/m) : Cmca |
Common Associates
Associations Based on Photo Data:
| 59 photos of Sklodowskite associated with Cuprosklodowskite | Cu(UO2)2(SiO3OH)2 · 6H2O |
| 50 photos of Sklodowskite associated with Gypsum | CaSO4 · 2H2O |
| 30 photos of Sklodowskite associated with Malachite | Cu2(CO3)(OH)2 |
| 30 photos of Sklodowskite associated with Heterogenite | Co3+O(OH) |
| 20 photos of Sklodowskite associated with Soddyite | (UO2)2SiO4 · 2H2O |
| 18 photos of Sklodowskite associated with Rutherfordine | (UO2)CO3 |
| 13 photos of Sklodowskite associated with Uranophane | Ca(UO2)2(SiO3OH)2 · 5H2O |
| 11 photos of Sklodowskite associated with Metatorbernite | Cu(UO2)2(PO4)2 · 8H2O |
| 10 photos of Sklodowskite associated with Saléeite | Mg(UO2)2(PO4)2 · 10H2O |
| 9 photos of Sklodowskite associated with Calcite | CaCO3 |
Related Minerals - Strunz-mindat Grouping
| 9.AK. | 'Orlite' | Pb3(UO2)3(Si2O7)2 · 6H2O |
| 9.AK.05 | Soddyite | (UO2)2SiO4 · 2H2O |
| 9.AK.10 | Cuprosklodowskite | Cu(UO2)2(SiO3OH)2 · 6H2O |
| 9.AK.10 | Oursinite | Co(UO2)2(SiO3OH)2 · 6H2O |
| 9.AK.15 | Parauranophane | Ca(UO2)2(SiO3OH)2 · 5H2O |
| 9.AK.15 | Uranophane | Ca(UO2)2(SiO3OH)2 · 5H2O |
| 9.AK.15 | Natroboltwoodite | Na(UO2)(SiO3OH) · H2O |
| 9.AK.15 | Kasolite | Pb(UO2)(SiO4) · H2O |
| 9.AK.15 | Boltwoodite | (K,Na)(UO2)(SiO3OH) · 1.5H2O |
| 9.AK.20 | Swamboite-(Nd) | Nd0.333[(UO2)(SiO3OH)](H2O)~2.5 |
| 9.AK.25 | Haiweeite | Ca(UO2)2[Si5O12(OH)2] · 6H2O |
| 9.AK.25 | Metahaiweeite | Ca(UO2)2Si6O15 · nH2O |
| 9.AK.30 | Weeksite | K2(UO2)2(Si5O13) · 4H2O |
| 9.AK.30 | Coutinhoite | ThxBa(1-2x)(UO2)2Si5O13 · (H2O)1+y (0 < x < 0.5 and 0 < y < (2+x)) |
| 9.AK.30 | Barronite | (◻0.5Ba0.5)(UO2)2Si5O12(OH) · 2H2O |
| 9.AK.35 | Magnioursilite | Mg4(UO2)4(Si2O5)5(OH)6 · 20H2O |
| 9.AK.35 | Calcioursilite | Ca4(UO2)4(Si2O5)5(OH)6 · 15H2O |
| 9.AK.40 | Uranosilite | UO3 · 7SiO2 |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 55.4436% | 13,860,900 | 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:
Radioactive
Internet Links for Sklodowskite
mindat.org URL:
https://www.mindat.org/min-3681.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Sklodowskite
Reference List:
Schoep, Alfred (1924) Sur la sklodowskite, un nouveau minéral uranifère ; ses analogies avec l'uranotile. Bulletin de Minéralogie, 47 (5) 162-172 doi:10.3406/bulmi.1924.3946
Schoep, Alfred (1924) Sur la sklodowskite, un nouveau minéral uranifère ; ses analogies avec l'uranotile. Bulletin de Minéralogie, 47 (5) 162-172 doi:10.3406/bulmi.1924.3946
Gorman, D. H. (1957) Studies of radioactive compounds; IX - Sklodowskite. The Canadian Mineralogist, 6 (1) 52-60
Stohl, Frances V., Smith, Deane K. (1981) The crystal chemistry of the uranyl silicate minerals. American Mineralogist, 66 (5-6) 610-624
Burns, Peter C. (2005) U6+ minerals and inorganic compounds: insights into an expanded structural hierarchy of crystal structures. The Canadian Mineralogist, 43 (6) 1839-1894 doi:10.2113/gscanmin.43.6.1839
Localities for Sklodowskite
Showing 79 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 | |
| Angelelli (1984) |
Australia | |
| Geosciences +1 other reference |
| Economic Geology of Australia and papua ... |
| Isobe et al. (1992) +1 other reference | |
| Giblin (2005) |
| Econ Geol (1987) +1 other reference | |
Brazil | |
| Cassedanne et al. (1978) |
| A.M.D.V. Chaves (2005) | |
| Pires et al. (2014) | |
Canada | |
| Paul (1984) |
| Knipping (1974) |
| Watkinson et al. (1975) | |
| Rich et al. (1977) | |
China | |
| Shen (n.d.) |
Czech Republic | |
| Pauliš P. et al. (Kutna Hora, issue 1) |
| Hloušek et al. (2002) |
| Möhn et al. (12/2021) | |
| Sejkora et al. (2013) |
| Bradna |
DR Congo (TL) | |
| Stohl et al. (1981) +1 other reference |
| KMMA | |
| KMMA |
| KMMA |
| Mandarino (1997) +1 other reference |
| Lhoest (1992) | |
| Wilson (2018) |
Egypt | |
| Hussein et al. (1988) |
| Bahr et al. (2026) |
| Bisher (2012) |
France | |
| R. Pierrot |
| - (1998) |
| - (1998) |
| Bariand et al. (1993) +2 other references |
Germany | |
| Kolitsch et al. (2019) |
| Desor (04/2020) +1 other reference |
| Färber (n.d.) |
| Weiß (1990) |
| Dill et al. (2010) | |
| Aufschluss 69/ (7+8) +1 other reference |
| Desor (05/2020) |
| King (n.d.) |
| Gröbner et al. (2007) +1 other reference |
| Witzke et al. (1998) |
Greece | |
| analysed by Michalis Fitros - personal ... +3 other references |
Iran | |
| Iranmanesh et al. (2018) |
Japan | |
| Matsubara et al. (2013) |
Mexico | |
| Megaw (2023) |
| Panczner (1987) |
New Zealand | |
| Christie et al. (2000) |
Poland | |
| Syczewski et al. (2023) +1 other reference |
| Mochnacka et al. (2000) +1 other reference | |
| Syczewski et al. (2023) |
Romania | |
| Hîrtopanu P. et al. (2004) |
Russia | |
| Eremin et al. (2023) |
Spain | |
| Arrufat et al. (2017) |
Sweden | |
| Löfvendahl (1981) |
Switzerland | |
| Stalder et al. (1998) |
Tajikistan | |
| Pekov (1998) |
USA | |
| - (2008) +1 other reference |
| Scarborough (1981) |
| W. Wise - X-ray work at U.C. Santa ... |
| Eckel et al. (1997) |
| Travis Olds collection |
| No reference known. Particularly NOT ... |
| Northrop et al. (1996) |
| NMBMMR Memoir 15 Geology and Technology ... | |
| Northrop et al. (1996) | |
| RRUFF R050445 |
| Patrick Haynes |
| Jensen (1978) |
| Robinson et al. (2007) | |
| Lapham et al. (1976) |
| USGS Prof Paper 455 p57 +1 other reference |
| Richardson et al. (1993) | |
| Bullock (1981) |
| Vochten et al. (2001) |
| Bullock (1981) |
| George E. Becraft and Paul L. Weis (1963) +1 other reference |
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Musonoi Mine, Kolwezi, Mutshatsha, Lualaba, DR Congo