Bassetite
A valid IMA mineral species - grandfathered
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About Bassetite
Formula:
Fe2+(UO2)2(PO4)2 · 10H2O
Colour:
brownish yellow, olive-green, yellow, bronze-yellow.
Lustre:
Sub-Vitreous, Waxy
Hardness:
2½
Specific Gravity:
3.40 - 3.63
Crystal System:
Monoclinic
Member of:
Name:
Named in 1915 by Arthur Francis Hallimond after the Basset Mine group, Cornwall, England, UK, from which the mineral was first described.
Isostructural with:
An uncommon secondary mineral occurring in the oxidized zones of uranium-bearing hydrothermal mineral deposits.
Crystal structure details (Dal Bo et al., 2016): (1) autunite-type sheets, [(UO2)(PO4)]-, built of corner-sharing UO6 square bipyramids and tetrahedral phosphate groups; (2) interlayer Fe(H2O)6 octahedra; (3) 2 isolated interlayer water molecules.
See also Unnamed (Oxidised bassetite).
Crystal structure details (Dal Bo et al., 2016): (1) autunite-type sheets, [(UO2)(PO4)]-, built of corner-sharing UO6 square bipyramids and tetrahedral phosphate groups; (2) interlayer Fe(H2O)6 octahedra; (3) 2 isolated interlayer water molecules.
See also Unnamed (Oxidised bassetite).
Unique Identifiers
Mindat ID:
558
Long-form identifier:
mindat:1:1:558:8
Similar Names
| Bastite | A variety of Serpentine Subgroup | D3[Si2O5](OH)4 D= Mg, Fe, Ni, Mn, Al, Zn |
Classification of Bassetite
The autunite-type sheet
The autunite-type sheet found in members of the autunite group.
IMA Classification of Bassetite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Fe2+(U6+O2)2(PO4)2(H2O)10
First published:
1915
Type description reference:
8.EB.10
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
B : UO2:RO4 = 1:1
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
B : UO2:RO4 = 1:1
40.2a.16.1
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
2a : AB2(XO4)2·xH2O, containing (UO2)2+
40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
2a : AB2(XO4)2·xH2O, containing (UO2)2+
19.11.41
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 |
|---|---|---|
| Bas | 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 Bassetite
Sub-Vitreous, Waxy
Transparency:
Transparent
Colour:
Brownish yellow, olive-green, yellow, bronze-yellow.
Comment:
Observed as sectored in transmitted light due to twinning
Streak:
Pale yellow to greenish white
Hardness:
2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
On {010}, perfect; on {100} and {001}, good/distinct.
On {010}, perfect; on {100} and {001}, good/distinct.
Fracture:
Micaceous
Density:
3.40 - 3.63 g/cm3 (Measured) 3.63 g/cm3 (Calculated)
Optical Data of Bassetite
Type:
Biaxial (-)
RI values:
nα = 1.603 nβ = 1.610 nγ = 1.617
2V:
Measured: 90° , Calculated: 88°
Birefringence:
0.014
Max. Birefringence:
δ = 0.014
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:
strong r > v
Optical Extinction:
Y^c = 18.5°, X=b
Pleochroism:
Visible
Comments:
X = b = Pale yellow
Y = Deep yellow
Z = ^c -4° = Deep yellow (sometimes dark olive brown to brownish black)
Y = Deep yellow
Z = ^c -4° = Deep yellow (sometimes dark olive brown to brownish black)
Comments:
Biaxial negative property probable.
Chemistry of Bassetite
Mindat Formula:
Fe2+(UO2)2(PO4)2 · 10H2O
Element Weights:
Crystallography of Bassetite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 6.961(1) Å, b = 20.039(2) Å, c = 6.974(1) Å
β = 90.46(1)°
β = 90.46(1)°
Ratio:
a:b:c = 0.347 : 1 : 0.348
Unit Cell V:
972.78 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Crystals thin tablets, flattened on [010], with a square or rectangular outline, and exhibiting {111}, {101}, {110}, {001}, and {010}. Commonly in parallel or fanlike groups.
Twinning:
Common, with two or more individuals at ~90° with [001] of one individual parallel to [100] of the other, with the contact surface being (010) in some instances, and (110) against (011) in other instances.
Comment:
Space group P21/n (previous one: P21/m). Pseudotetragonal; synthetic material. Originall given cell: a = 6.98, b = 17.07, c = 7.01 Å, β = 90.53°.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.59 Å | (60) |
| 4.89 Å | (100) |
| 4.24 Å | (30) |
| 4.05 Å | (30) |
| 3.46 Å | (100) |
| 2.96 Å | (30) |
| 2.20 Å | (60) |
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] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Geological Setting:
Oxdized zones of uranium-bearing hydrothermal deposits.
Type Occurrence of Bassetite
General Appearance of Type Material:
Fan-like groups of almost parallel tabular crystals.
Place of Conservation of Type Material:
Mineralogical Museum, Cambridge: #1297. Harvard University, Cambridge, Massachusetts, USA.
Associated Minerals at Type Locality:
Other Language Names for Bassetite
Relationship of Bassetite to other Species
Member of:
Other Members of Autunite Group:
| Autunite | Ca(UO2)2(PO4)2 · 10-12H2O | Orth. mmm(2/m2/m2/m) : Pnma |
| Heinrichite | Ba(UO2)2(AsO4)2 · 10H2O | Mon. 2/m : P2/b |
| Hydronováčekite | Mg(UO2)2(AsO4)2 · 12H2O | Tric. 1 : P1 |
| Kahlerite | Fe2+(UO2)2(AsO4)2 · 12H2O | Tet. 4/m : P42/n |
| Nováčekite | Mg(UO2)2(AsO4)2 · 10H2O | Mon. 2/m |
| Rauchite | Ni(UO2)2(AsO4)2 · 10H2O | Tric. 1 : P1 |
| Sabugalite | HAl(UO2)4(PO4)4 · 16H2O | Mon. 2/m : B2/m |
| Saléeite | Mg(UO2)2(PO4)2 · 10H2O | Mon. 2/m |
| Torbernite | Cu(UO2)2(PO4)2 · 12H2O | Tet. 4/mmm(4/m2/m2/m) : I4/mmm |
| Uranocircite | Ba(UO2)2(PO4)2 · 10H2O | Tet. |
| Uranospinite | Ca(UO2)2(AsO4)2 · 10H2O | Tet. 4/mmm(4/m2/m2/m) : P4/nmm |
| Zeunerite | Cu(UO2)2(AsO4)2 · 12H2O | Tet. 4/mmm(4/m2/m2/m) : I4/mmm |
Common Associates
Associations Based on Photo Data:
| 9 photos of Bassetite associated with Autunite | Ca(UO2)2(PO4)2 · 10-12H2O |
| 6 photos of Bassetite associated with Torbernite | Cu(UO2)2(PO4)2 · 12H2O |
| 5 photos of Bassetite associated with 'Opal-AN' | SiO2 · nH2O |
| 3 photos of Bassetite associated with Quartz | SiO2 |
| 3 photos of Bassetite associated with Chalcocite | Cu2S |
| 2 photos of Bassetite associated with Uranospathite | (Al,◻)(UO2)2(PO4)2F · 20(H2O,F) |
| 1 photo of Bassetite associated with Chalcopyrite | CuFeS2 |
| 1 photo of Bassetite associated with 'Stink-Fluss' | CaF2 |
| 1 photo of Bassetite associated with Kahlerite | Fe2+(UO2)2(AsO4)2 · 12H2O |
| 1 photo of Bassetite associated with Saléeite | Mg(UO2)2(PO4)2 · 10H2O |
Related Minerals - Strunz-mindat Grouping
| 8.EB. | Meta-autunite Group | A1-2(UO2)2(TO4)2 · 5-10H2O |
| 8.EB.05 | Rauchite | Ni(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Uranocircite | Ba(UO2)2(PO4)2 · 10H2O |
| 8.EB.05 | Uranospinite | Ca(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Zeunerite | Cu(UO2)2(AsO4)2 · 12H2O |
| 8.EB.05 | Metarauchite | Ni(UO2)2(AsO4)2 · 8H2O |
| 8.EB.05 | Heinrichite | Ba(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Kahlerite | Fe2+(UO2)2(AsO4)2 · 12H2O |
| 8.EB.05 | Hydronováčekite | Mg(UO2)2(AsO4)2 · 12H2O |
| 8.EB.05 | Torbernite | Cu(UO2)2(PO4)2 · 12H2O |
| 8.EB.05 | Nováčekite | Mg(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Autunite | Ca(UO2)2(PO4)2 · 10-12H2O |
| 8.EB.05 | Saléeite | Mg(UO2)2(PO4)2 · 10H2O |
| 8.EB.05 | Xiangjiangite | (Fe3+,Al)(UO2)4(PO4)2(SO4)2(OH) · 22H2O |
| 8.EB.10 | Lehnerite | Mn2+(UO2)2(PO4)2 · 8H2O |
| 8.EB.10 | Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
| 8.EB.10 | Metasaléeite | Mg(UO2)2(PO4)2 · 8H2O |
| 8.EB.10 | Metauranocircite | Ba(UO2)2(PO4)2 · 7H2O |
| 8.EB.10 | Metauranospinite | Ca(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metaheinrichite | Ba(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metakahlerite | Fe2+(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metakirchheimerite | Co(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metanováčekite | Mg(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metanatroautunite | Na(UO2)(PO4)(H2O)3 |
| 8.EB.10 | Metatorbernite | Cu(UO2)2(PO4)2 · 8H2O |
| 8.EB.10 | Metazeunerite | Cu(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Przhevalskite | Pb2(UO2)3(PO4)2(OH)4 · 3H2O |
| 8.EB.10 | 'Pseudo-autunite' | (H3O)4Ca2(UO2)2(PO4)4 · 5H2O |
| 8.EB.15 | Abernathyite | K(UO2)(AsO4) · 3H2O |
| 8.EB.15 | Uramphite | (NH4)2(UO2)2(PO4)2 · 6H2O |
| 8.EB.15 | Meta-ankoleite | K2(UO2)2(PO4)2 · 6H2O |
| 8.EB.15 | Natrouranospinite | Na2(UO2)2(AsO4)2 · 5H2O |
| 8.EB.15 | Trögerite | (H3O)(UO2)(AsO4) · 3H2O |
| 8.EB.15 | Chernikovite | (H3O)2(UO2)2(PO4)2 · 6H2O |
| 8.EB.15 | Uramarsite | (NH4)(UO2)(AsO4) · 3H2O |
| 8.EB.20 | Chistyakovaite | Al(UO2)2(AsO4)2(F,OH) · 6.5H2O |
| 8.EB.20 | Threadgoldite | Al(UO2)2(PO4)2(OH) · 8H2O |
| 8.EB.25 | Uranospathite | (Al,◻)(UO2)2(PO4)2F · 20(H2O,F) |
| 8.EB.25 | Arsenuranospathite | Al(UO2)2(AsO4)2F · 20H2O |
| 8.EB.30 | Vochtenite | (Fe2+,Mg)Fe3+(UO2)4(PO4)4(OH) · 12-13H2O |
| 8.EB.35 | Coconinoite | Fe3+2Al2(UO2)2(PO4)4(SO4)(OH)2 · 20H2O |
| 8.EB.40 | Ranunculite | HAl(UO2)(PO4)(OH)3 · 4H2O |
| 8.EB.45 | Triangulite | Al3(UO2)4(PO4)4(OH)5 · 5H2O |
| 8.EB.50 | Furongite | Al13(UO2)7(PO4)13(OH)14 · 58H2O |
| 8.EB.55 | Arsenosabugalite | H0.5Al0.5(UO2)2(AsO4)2 · 8H2O |
| 8.EB.55 | Sabugalite | HAl(UO2)4(PO4)4 · 16H2O |
| 8.EB.60 | Horákite | (Bi7O7OH)[(UO2)4(PO4)2(AsO4)2(OH)2] · 3.5H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 49.2816% | 12,320,400 | 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 Bassetite
Not fluorescent in UV.
Other Information
Notes:
Radioactive.
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 Bassetite
mindat.org URL:
https://www.mindat.org/min-558.html
Please feel free to link to this page.
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Mineral Dealers:
References for Bassetite
Reference List:
Hallimond, A. F. (1915) On Bassetite and Uranospathite, new species hitherto classed as Autunite. Mineralogical Magazine and Journal of the Mineralogical Society, 17 (81) 221-236 doi:10.1180/minmag.1915.017.81.11
Frondel, Clifford (1954) Bassetite and uranospathite. Mineralogical Magazine and Journal of the Mineralogical Society, 30 (225) 343-353 doi:10.1180/minmag.1954.030.225.02
Frondel, Clifford (1958) Systematic mineralogy of uranium and thorium. Bulletin 1064. US Geological Survey doi:10.3133/b1064 pp.200-204
Localities for Bassetite
Showing 70 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.
Belgium | |
| Mineralogical Society of America - ... +1 other reference |
Brazil | |
| Revista Brasileira de Geociências 24 (1) +1 other reference |
| Fosfatos e Silicatos Secundários de ... | |
Bulgaria | |
| Kalaidjiev et al. (2009) |
Canada | |
| Chatterjee (1977) |
China | |
| National Geological Archives of China ... |
| Dahlkamp (2009) |
| Dahlkamp (2009) | |
Czech Republic | |
| Pittauerová et al. (2002) |
| Pauliš P. et al. (Kutna Hora, issue 1) |
| Viktor Goliáš et al. (2016) |
| Pauliš P. et al. (Kutna Hora, issue 1) |
Egypt | |
| Abd El-Moghny et al. (2026) |
| Bisher (2012) |
France | |
| R. Pierrot |
| R. Pierrot +1 other reference | |
| - (1998) |
| Lièvre et al. (2002) |
| - (1998) |
| - (1998) |
| - (1998) |
| - (1998) |
Gabon | |
| Jensen et al. (2002) |
| Lena Z. Evins | |
Germany | |
| Walenta (1995) |
| Walenta (1992) |
| Keck (1989) |
| Weiß (1990) |
| Weiß (1990) |
| Weiß (1990) | |
| Dill et al. (2010) | |
| Gröbner et al. (2007) +1 other reference |
Italy | |
| Savia et al. (2026) |
| Brizzi et al. (1987) +1 other reference |
| Campostrini et al. (2005) |
| Bonifazi (2021) |
Poland | |
| Siuda R. et al. (2010) |
| Syczewski et al. (2023) +1 other reference |
| Syczewski et al. (2023) |
Slovakia | |
| Kopáčik R. et al. (2024) |
| Ferenc Š. et al. (2019) |
Spain | |
| Joan Rosell (2021) |
| Anthony et al. (2000) |
| |
| www.foro-minerales.com (n.d.) |
| www.foro-minerales.com (n.d.) | |
| www.foro-minerales.com (n.d.) |
| Anthony et al. (2000) |
Switzerland | |
| Meisser (2012) |
| |
| Stalder et al. (1998) +1 other reference |
UK (TL) | |
| Hallimond (1915) +2 other references |
| Mineralogical Society of America - ... | |
| Golley et al. (1995) |
| Alysson Rowan collection |
USA | |
| - (2008) +1 other reference |
| Anthony et al. (1995) |
| Anthony et al. (1995) | |
| Granger (1959) +2 other references |
| Anthony +3 other references |
| Eckel et al. (1997) |
| Mineralogical Society of America - ... |
| Heinrich et al. (2004) |
| Morris (1983) |
| Heinrich et al. (2004) |
| Northrop et al. (1996) |
| |
| Anthony et al. (2000) |
| Anthony et al. (2000) |
Uzbekistan | |
| Pavel M. Kartashov (n.d.) |
Quick NavTopAbout BassetiteUnique IdentifiersSimilar NamesClassification IMA Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesRelationshipsCommon AssociatesStrunz-MindatRadioactivityFluorescence Other InformationInternet Links References Localities Locality List
Hagendorf South Pegmatite, Hagendorf, Waidhaus, Neustadt an der Waldnaab District, Upper Palatinate, Bavaria, Germany