Soddyite
A valid IMA mineral species - grandfathered
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About Soddyite
Frederick Soddy
Formula:
(UO2)2SiO4 · 2H2O
Colour:
Canary-yellow, amber-yellow
Lustre:
Vitreous, Greasy, Dull
Hardness:
3 - 4
Specific Gravity:
4.63 - 4.70
Crystal System:
Orthorhombic
Name:
Named in honor of Frederick Soddy (2 September 1877, Eastbourne, Sussex, England – 22 September 1956, Brighton, Sussex, England), physicist and radiochemist. He received the 1921 Nobel Prize in chemistry for his work on radioactive decay and isotopes.
See also: http://www.mindat.org/article.php/2163/Note+on+soddyite
See also: http://www.mindat.org/article.php/2163/Note+on+soddyite
A triclinic(?) uranyl silicate mineral with a powder XRD pattern close to soddyite was reported by Stohl & Smith (1981).
Unique Identifiers
Mindat ID:
3702
Long-form identifier:
mindat:1:1:3702:6
Similar Names
| Sodaite | A synonym of 'Wernerite' | |
| Sudoite | A valid IMA mineral species | Mg2Al3(AlSi3O10)(OH)8 |
IMA Classification of Soddyite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
(U6+O2)2SiO4(H2O)2
First published:
1922
Classification of Soddyite
9.AK.05
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
53.3.3.1
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)
14.16.3
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 |
|---|---|---|
| Sod | 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 Soddyite
Vitreous, Greasy, Dull
Transparency:
Transparent, Translucent, Opaque
Colour:
Canary-yellow, amber-yellow
Streak:
Pale yellow
Hardness:
3 - 4 on Mohs scale
Cleavage:
Perfect
Perfect on {001}, good on {111}
Perfect on {001}, good on {111}
Density:
4.63 - 4.70 g/cm3 (Measured) 5.09 g/cm3 (Calculated)
Optical Data of Soddyite
Type:
Biaxial (-)
RI values:
nα = 1.65 - 1.654 nβ = 1.685 nγ = 1.699 - 1.715
2V:
Measured: 70° to 84°
Max. Birefringence:
δ = 0.049 - 0.061
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:
r > v; negligible to strong
Pleochroism:
Weak
Comments:
X = colorless; Y = very pale yellow; Z = pale yellow-green
Chemistry of Soddyite
Mindat Formula:
(UO2)2SiO4 · 2H2O
Element Weights:
Elements listed:
Crystallography of Soddyite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Fddd
Setting:
Fddd
Cell Parameters:
a = 8.3097(3) Å, b = 11.2205(4) Å, c = 18.6576(11) Å
Ratio:
a:b:c = 0.741 : 1 : 1.663
Unit Cell V:
1,739.62 ų (Calculated from Unit Cell)
Comment:
Cell parameters from Plášil (2018) with R1=1.92%.
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
Remove metal-metal sticks
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0010268 | Soddyite | Demartin F, Gramaccioli C M, Pilati T (1992) The importance of accurate crystal structure determination of uranium minerals. II. Soddyite (UO2)2(SiO4)*2H2O Acta Crystallographica C48 1-4 |  | 1992 | Democratic Republic of the Congo | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.32 Å | (100) |
| 4.48 Å | (90) |
| 6.14 Å | (80) |
| 2.69 Å | (70) |
| 2.47 Å | (60) |
| 1.855 Å | (50) |
| 2.09 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] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Type Occurrence of Soddyite
General Appearance of Type Material:
Minute prismatic crystals.
Place of Conservation of Type Material:
Natural History Museum, Paris, France, 122.122/3.
Associated Minerals at Type Locality:
Synonyms of Soddyite
Other Language Names for Soddyite
Common Associates
Associations Based on Photo Data:
| 49 photos of Soddyite associated with Curite | Pb3(H2O)2[(UO2)4O4(OH)3]2 |
| 38 photos of Soddyite associated with Cuprosklodowskite | Cu(UO2)2(SiO3OH)2 · 6H2O |
| 37 photos of Soddyite associated with Rutherfordine | (UO2)CO3 |
| 23 photos of Soddyite associated with Swamboite-(Nd) | Nd0.333[(UO2)(SiO3OH)](H2O)~2.5 |
| 20 photos of Soddyite associated with Sklodowskite | Mg(UO2)2(SiO3OH)2 · 6H2O |
| 20 photos of Soddyite associated with Uranophane | Ca(UO2)2(SiO3OH)2 · 5H2O |
| 19 photos of Soddyite associated with Malachite | Cu2(CO3)(OH)2 |
| 19 photos of Soddyite associated with Heterogenite | Co3+O(OH) |
| 15 photos of Soddyite associated with Uraninite | UO2 |
| 13 photos of Soddyite associated with Metatorbernite | Cu(UO2)2(PO4)2 · 8H2O |
Related Minerals - Strunz-mindat Grouping
| 9.AK. | 'Orlite' | Pb3(UO2)3(Si2O7)2 · 6H2O |
| 9.AK.10 | Sklodowskite | Mg(UO2)2(SiO3OH)2 · 6H2O |
| 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) | 71.2481% | 17,812,025 | 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
Notes:
Before the blowpipe it is infusible; in the closed tube it blackens, losing H2O and O. It dissolves in HCl with gelatinization.
Health Risks:
Contains uranium - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest. Avoid prolonged exposure in proximity of the body. Store away from inhabited areas.
Internet Links for Soddyite
mindat.org URL:
https://www.mindat.org/min-3702.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Soddyite
Reference List:
Gorman, D. H. (1952) Studies of radioactive compounds: V--Soddyite. American Mineralogist, 37 (5-6) 386-393
Stohl, Frances V., Smith, Deane K. (1981) The crystal chemistry of the uranyl silicate minerals. American Mineralogist, 66 (5-6) 610-624
Biwer, Bruce M., Ebert, William L., Bates, John K. (1990) The Raman spectra of several uranyl-containing minerals using a microprobe. Journal of Nuclear Materials, 175 (3). 188-193 doi:10.1016/0022-3115(90)90205-2
Demartin, F., Gramaccioli, C. M., Pilati, T. (1992) The importance of accurate crystal structure determination of uranium minerals. II. Soddyite (UO2)2(SiO4).2H2O. Acta Crystallographica Section C Crystal Structure Communications, 48 (1). 1-4 doi:10.1107/s0108270191004481
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
Frost, Ray L., Čejka, Jiří, Weier, Matt L., Martens, Wayde, Kloprogge, J. Theo (2006) A Raman and infrared spectroscopic study of the uranyl silicates—Weeksite, soddyite and haiweeite. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 64 (2) 308-315 doi:10.1016/j.saa.2005.07.028
Frost, Ray L., Čejka, Jiří, Weier, Matt L., Martens, Wayde (2006) A Raman and infrared spectroscopic study of the uranyl silicates—Weeksite, soddyite and haiweeite: Part 2. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 63 (2) 305-312 doi:10.1016/j.saa.2005.05.015
Sureda, R.; Casas, I.; Giménez, J.; de Pablo, J.; Quiñones, J.; Zhang, J.; Ewing, R. C. (2011) Effects of Ionizing Radiation and Temperature on Uranyl Silicates: Soddyite (UO2)2(SiO4)(H2O)2 and Uranophane Ca(UO2)2(SiO3OH)2·5H2O. Environmental Science & Technology, 45 (6). 2510-2515 doi:10.1021/es1041496
Localities for Soddyite
Showing 62 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 | |
| E. Linares y R. O. Toubes (1960) | |
| E. Linares y R. O. Toubes (1960) | |
| E. Linares y R. O. Toubes (1960) | |
| E. Linares y R. O. Toubes (1960) | |
Australia | |
| Anenburg et al. (2018) |
| Henry et al. (2005) |
| Henry et al. (2005) | |
| Brugger et al. (2003) +1 other reference |
| Bottrill (2021) |
Brazil | |
| Pires et al. (2014) |
Bulgaria | |
| Kalaidjiev et al. (2009) |
Canada | |
| Wilson (1991) |
| Robertson (1976) |
Czech Republic | |
| Hloušek et al. (2002) |
| Pauliš P. et al. (Kutna Hora, issue 1) |
| Pauliš P. et al. (Kutna Hora, issue 1) |
| věd. Brno. +1 other reference |
DR Congo | |
| KMMA +1 other reference |
| Schoep (1922) +1 other reference |
| KMMA +1 other reference | |
| KMMA +1 other reference |
| KMMA |
| Anthony et al. (2003) |
| Anthony et al. (2003) | |
| Deliens (1992) | |
| Wilson (2018) |
Egypt | |
| El-Naby (2009) |
| Yehia H. Dawood (2011) |
| Hussein et al. (1988) | |
| Kamar et al. (2022, August) |
| Abd El-Moghny et al. (2026) |
France | |
| Collection Frédéric Bonnet |
| Henriot et al. (1998) |
Germany | |
| Walenta (1989) +1 other reference |
| Wittern (2001) |
| Wittern (2001) |
Iran | |
| Iranmanesh et al. (2018) |
Italy | |
| Olmi F. |
Japan | |
| Matsubara and Miyawaki (2006) |
Mexico | |
| Murphy (2006) |
| Wong et al. (1999, January) +2 other references | |
Romania | |
| Hîrtopanu P. et al. (2004) |
Russia | |
| Pavel M. Kartashov (n.d.) |
South Africa | |
| Gevers +2 other references |
Spain | |
| www.foro-minerales.com (n.d.) |
| www.foro-minerales.com (n.d.) | |
| www.foro-minerales.com (n.d.) |
USA | |
| Frondel (1958) +1 other reference |
| Eckel et al. (1997) |
| Gross (1965) +1 other reference |
| Cook (1978) |
| Cook (1978) | |
| Nevada Bureau of Mines and Geology NBMG ... +1 other reference |
| Korzeb +3 other references |
| Northrop et al. (1996) |
| NMBMMR Memoir 15 Geology and Technology ... | |
| Northrop et al. (1996) |
| McLemore et al. (2009) | |
| USGS Prof Paper 455A p57 |
| Mineralogical Society of America - ... |
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Shinkolobwe Mine, Shinkolobwe, Kambove Territory, Haut-Katanga, DR Congo