Oursinite
A valid IMA mineral species
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About Oursinite
Formula:
Co(UO2)2(SiO3OH)2 · 6H2O
All material so far seems to contain minor Mg replacing Co.
Colour:
Pale yellow
Hardness:
3 - 3½
Specific Gravity:
3.674 (Calculated)
Crystal System:
Orthorhombic
Member of:
Name:
From the french oursin, in allusion to its appearance like a sea urchin
This page provides mineralogical data about Oursinite.
Unique Identifiers
Mindat ID:
3047
Long-form identifier:
mindat:1:1:3047:8
IMA Classification of Oursinite
Approved
IMA Formula:
Co2+(U6+O2)2(SiO3OH)2(H2O)4·2H2O
Approval year:
1982
First published:
1983
Classification of Oursinite
9.AK.10
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
53.3.1.7
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)
14.16.19
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 |
|---|---|---|
| Osn | 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 Oursinite
Transparency:
Transparent
Colour:
Pale yellow
Hardness:
3 - 3½ on Mohs scale
Cleavage:
Distinct/Good
on {hk0}
on {hk0}
Density:
3.674 g/cm3 (Calculated)
Optical Data of Oursinite
Type:
Biaxial (-)
RI values:
nα = 1.624 nβ = 1.64 nγ = 1.65
2V:
Measured: 76° , Calculated: 76°
Max. Birefringence:
δ = 0.026
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.
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:
weak
Chemistry of Oursinite
Mindat Formula:
Co(UO2)2(SiO3OH)2 · 6H2O
All material so far seems to contain minor Mg replacing Co.
All material so far seems to contain minor Mg replacing Co.
Element Weights:
Common Impurities:
Ni
Crystallography of Oursinite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Cmca
Cell Parameters:
a = 7.0457(4) Å, b = 17.5445(8) Å, c = 12.7231(2) Å
Ratio:
a:b:c = 0.402 : 1 : 0.725
Unit Cell V:
1,572.74 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Radiating aggregates of acicular crystals to 1mm.
Comment:
Cell parameters from Plášil (2018) with R1=2.03%.
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
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View
CIF File Best | x | y | z | a | b | c
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Rotation
Stop | Start
Stop | Start
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) |
|---|---|---|---|---|---|---|---|
| 0004122 | Oursinite | Kabatko K A, Burns P C (2006) A novel arrangement of silicate tetrahedra in the uranyl silicate sheet of oursinite, (Co0.8Mg0.2)[(UO2)(SiO3OH)]2(H2O)6 American Mineralogist 91 333-336 |  | 2006 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.73 Å | (100) |
| 7.20 Å | (70) |
| 5.16 Å | (50) |
| 4.55 Å | (35) |
| 4.141 Å | (70) |
| 3.528 Å | (40) |
| 3.267 Å | (30) |
| 2.853 Å | (90) |
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 Oursinite
General Appearance of Type Material:
Radial aggregates of pale yellow acicular crystals, with maximum dimensions 1 x 0.02 x 0.02 mm.
Place of Conservation of Type Material:
Royal Museum of Central Africa, Tervuren, Belgium, RGM1321.
Geological Setting of Type Material:
Uranium deposit; brecciated dolomite.
Associated Minerals at Type Locality:
Synonyms of Oursinite
Other Language Names for Oursinite
Relationship of Oursinite to other Species
Member of:
Other Members of Sklodowskite Group:
| Cuprosklodowskite | Cu(UO2)2(SiO3OH)2 · 6H2O | Tric. 1 : P1 |
| Sklodowskite | Mg(UO2)2(SiO3OH)2 · 6H2O | Mon. 2/m : B2/m |
Common Associates
Associations Based on Photo Data:
| 1 photo of Oursinite associated with Wölsendorfite | Pb7(UO2)14O19(OH)4 · 12H2O |
| 1 photo of Oursinite associated with Uranophane | Ca(UO2)2(SiO3OH)2 · 5H2O |
| 1 photo of Oursinite associated with Uraninite | UO2 |
| 1 photo of Oursinite associated with Sklodowskite | Mg(UO2)2(SiO3OH)2 · 6H2O |
| 1 photo of Oursinite associated with Rutherfordine | (UO2)CO3 |
| 1 photo of Oursinite associated with Becquerelite | Ca(UO2)6O4(OH)6 · 8H2O |
| 1 photo of Oursinite associated with Heterogenite | Co3+O(OH) |
Related Minerals - Strunz-mindat Grouping
| 9.AK. | 'Orlite' | Pb3(UO2)3(Si2O7)2 · 6H2O |
| 9.AK.05 | Soddyite | (UO2)2SiO4 · 2H2O |
| 9.AK.10 | Sklodowskite | Mg(UO2)2(SiO3OH)2 · 6H2O |
| 9.AK.10 | Cuprosklodowskite | Cu(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) | 53.2943% | 13,323,575 | 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 Oursinite
mindat.org URL:
https://www.mindat.org/min-3047.html
Please feel free to link to this page.
Please feel free to link to this page.
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Mineral Dealers:
References for Oursinite
Reference List:
Deliens, Michel, Piret, Paul (1983) L'oursinite (Co0,86Mg0,10Ni0,04)O.2UO3. 2SiO2.6H2O, nouveau minéral de Shinkolobwe, Shaba, Zaïre. Bulletin de Minéralogie, 106 (3) 305-308 doi:10.3406/bulmi.1983.7710
Dunn, Pete J., Chao, George Y., Grice, Joel D., Ferraiolo, James A., Fleischer, Michael, Pabst, Adolf, Zilczer, Janet A. (1984) New mineral names. American Mineralogist, 69 (5-6) 565-569 p.567
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 Oursinite
Showing 2 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.
DR Congo (TL) | |
| edit.africamuseum.be (n.d.) +2 other references |
| Wilson (2018) |
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Shinkolobwe Mine, Shinkolobwe, Kambove Territory, Haut-Katanga, DR Congo