Natroboltwoodite
A valid IMA mineral species
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About Natroboltwoodite
Formula:
Na(UO2)(SiO3OH) · H2O
Colour:
Light yellow
Lustre:
Dull
Specific Gravity:
4.1
Crystal System:
Orthorhombic
Member of:
Name:
The name reflects its sodium content and similarity to boltwoodite. It was originally named sodium boltwoodite, but changed to the current form in 2008.
Uranophane Group.
The Na analogue of boltwoodite.
The crystal structure of the synthetic analog of natroboltwoodite has been published by Plášil et al. (2022); it is orthorhombic (Pbcn) with the unit-cell volume ~8 times larger as for boltwoodite. The structural formula can be simplified as Na4(UO2)4(SiO3OH)4(H2O)3, Z = 4.
The Na analogue of boltwoodite.
The crystal structure of the synthetic analog of natroboltwoodite has been published by Plášil et al. (2022); it is orthorhombic (Pbcn) with the unit-cell volume ~8 times larger as for boltwoodite. The structural formula can be simplified as Na4(UO2)4(SiO3OH)4(H2O)3, Z = 4.
Unique Identifiers
Mindat ID:
3692
Long-form identifier:
mindat:1:1:3692:0
IMA Classification of Natroboltwoodite
Approved
IMA status notes:
Renamed by the IMA
IMA Formula:
Na(U6+O2)(SiO3OH)(H2O)
First published:
1975
Classification of Natroboltwoodite
9.AK.15
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
9 : SILICATES (Germanates)
A : Nesosilicates
K : Uranyl neso- and polysilicates
53.3.1.6
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)
14.16.7
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 |
|---|---|---|
| Nbwd | 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 Natroboltwoodite
Dull
Transparency:
Translucent
Colour:
Light yellow
Cleavage:
Perfect
{010} perfect, {001} imperfect.
{010} perfect, {001} imperfect.
Density:
4.1 g/cm3 (Measured) 4.4 g/cm3 (Calculated)
Optical Data of Natroboltwoodite
Type:
Biaxial (-)
RI values:
nα = 1.692 nγ = 1.6585
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:
weak to distinct
Pleochroism:
Visible
Comments:
X = colorless; Z = pale yellow.
Comments:
Anomalous interference colors.
Chemistry of Natroboltwoodite
Mindat Formula:
Na(UO2)(SiO3OH) · H2O
Element Weights:
Crystallography of Natroboltwoodite
Crystal System:
Orthorhombic
Class (H-M):
222 - Disphenoidal
Space Group:
P212121
Cell Parameters:
a = 27.40(5) Å, b = 7.02 Å, c = 6.65(2) Å
Ratio:
a:b:c = 3.903 : 1 : 0.947
Unit Cell V:
1,279.11 ų (Calculated from Unit Cell)
Z:
8
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.71 Å | (100) |
| 2.92 Å | (100) |
| 4.70 Å | (80) |
| 3.49 Å | (80) |
| 3.37 Å | (80) |
| 3.10 Å | (80) |
| 6.92 Å | (70) |
Comments:
Kyzylsai Mo-U deposit, Kazakhstan. The data are from Chernikov et al. (1975).
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 Natroboltwoodite
General Appearance of Type Material:
Powdery pale yellow crusts and platy radiating fibrous aggregates.
Place of Conservation of Type Material:
No designated type material.
Geological Setting of Type Material:
A secondary mineral formed near-surface in an arid region.
Associated Minerals at Type Locality:
Synonyms of Natroboltwoodite
Other Language Names for Natroboltwoodite
Relationship of Natroboltwoodite to other Species
Member of:
Other Members of Uranophane Group:
| Boltwoodite | (K,Na)(UO2)(SiO3OH) · 1.5H2O | Mon. 2 : P21 |
| Parauranophane | Ca(UO2)2(SiO3OH)2 · 5H2O | Mon. 2/m : P21/b |
| Uranophane | Ca(UO2)2(SiO3OH)2 · 5H2O | Mon. 2 : P21 |
Common Associates
Associations Based on Photo Data:
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.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 | 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) | 58.9000% | 14,725,000 | 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:
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 Natroboltwoodite
mindat.org URL:
https://www.mindat.org/min-3692.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
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References for Natroboltwoodite
Reference List:
Fleischer, Michael, Pabst, Adolf, Cabri, Louis J. (1976) New Mineral Names. American Mineralogist, 61 (9-10) 1053-1056 pp.1054-1055
Vochten, R., Blaton, N., Peeters, O., Van Springel, K., Van Haverbeke, L. (1997) A new method of synthesis of boltwoodite and of formation of sodium boltwoodite, uranophane, sklodowskite and kasolite from boltwoodite. The Canadian Mineralogist, 35 (3) 735-741
Burns, P. C. (1998) The structure of boltwoodite and implications of solid-solution towards sodium boltwoodite. The Canadian Mineralogist, 36 (4) 1069-1075
Localities for Natroboltwoodite
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.
Egypt | |
| Abd El-Moghny et al. (2026) |
Kazakhstan (TL) | |
| Chernikov et al. (1975) +1 other reference |
Namibia | |
| Swakop Uranium |
Russia | |
| ... |
USA | |
| Gunnar Farber analyses |
| Luetcke (n.d.) |
| King (n.d.) |
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Alluaiv Mountain, Lovozersky District, Murmansk Oblast, Russia