Guilleminite
A valid IMA mineral species
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About Guilleminite
Claude Guillemin in the field in Congo
Formula:
Ba(UO2)3(SeO3)2O2 · 3H2O
Colour:
Bright yellow
Lustre:
Waxy, Greasy, Dull, Earthy
Hardness:
2
Specific Gravity:
4.88
Crystal System:
Orthorhombic
Name:
Named by R. Pierrot, J. Toussaint, and T. Verbeek in 1965 in honor of Jean Claude Guillemin [September 13, 1923 France - April 6, 1994 France], chemist and mineralogist, 1957-1969 he was professor at the Ecole des Mines in Paris and curator of the mineral collection of the Ecole des Mines. Guillemin was director general of the Union Miniere du Haut-Katanga and co-founder of the International Mineralogical Association.
Type Locality:
Unique Identifiers
Mindat ID:
1771
Long-form identifier:
mindat:1:1:1771:4
IMA Classification of Guilleminite
Approved
IMA Formula:
Ba(U6+O2)3(Se4+O3)2O2·3H2O
Approval year:
1964
First published:
1965
Classification of Guilleminite
4.JJ.10
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
J : Arsenites, antimonites, bismuthites, sulfites, selenites, tellurites; iodates
J : Selenites with additional anions, with H2O
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
J : Arsenites, antimonites, bismuthites, sulfites, selenites, tellurites; iodates
J : Selenites with additional anions, with H2O
34.7.3.1
34 : SELENITES, TELLURITES AND SULFITES
7 : Hydrated Selenites, Tellurites and Sulfites containing Hydroxyl or Halogen
34 : SELENITES, TELLURITES AND SULFITES
7 : Hydrated Selenites, Tellurites and Sulfites containing Hydroxyl or Halogen
28.1.9
28 : Selenites, Selenates, Tellurites, and Tellurates
1 : Selenites
28 : Selenites, Selenates, Tellurites, and Tellurates
1 : Selenites
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 |
|---|---|---|
| Gul | 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 Guilleminite
Waxy, Greasy, Dull, Earthy
Transparency:
Translucent
Colour:
Bright yellow
Streak:
Light yellow
Hardness:
2 on Mohs scale
Hardness Data:
Estimated
Tenacity:
Brittle
Cleavage:
Perfect
{100} perfect, {010} good.
{100} perfect, {010} good.
Density:
4.88(2) g/cm3 (Measured) 5.08 g/cm3 (Calculated)
Optical Data of Guilleminite
Type:
Biaxial (-)
RI values:
nα = 1.720 nβ = 1.798 nγ = 1.805
2V:
Measured: 35° , Calculated: 32°
Birefringence:
0.085
Max. Birefringence:
δ = 0.085
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 strong
Optical Extinction:
Parallel. X = c; Y = b; Z = a.
Pleochroism:
Strong
Comments:
X = bright yellow; Y = yellow; Z = colorless.
Chemistry of Guilleminite
Mindat Formula:
Ba(UO2)3(SeO3)2O2 · 3H2O
Element Weights:
Crystallography of Guilleminite
Crystal System:
Orthorhombic
Class (H-M):
mm2 - Pyramidal
Space Group:
Pmn21
Cell Parameters:
a = 7.29 Å, b = 16.87 Å, c = 7.07 Å
Ratio:
a:b:c = 0.432 : 1 : 0.419
Unit Cell V:
869.48 ų (Calculated from Unit Cell)
Z:
2
Morphology:
As rectangular crystals, tabular on {010}. Forms include {001}, {010}, {001}, and minor {101}.
Comment:
Space group is P21nm
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
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
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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) |
|---|---|---|---|---|---|---|---|
| 0005466 | Guilleminite | Cooper M A, Hawthorne F C (1995) The crystal structure of guilleminite, a hydrated Ba-U-Se sheet structure The Canadian Mineralogist 33 1103-1109 |  | 1995 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.39 Å | (100) |
| 7.29 Å | (100) |
| 6.68 Å | (60) |
| 6.51 Å | (20) |
| 3.55 Å | (80) |
| 3.17 Å | (40) |
| 3.04 Å | (60) |
| 2.80 Å | (60) |
Comments:
ICDD 18-582.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Type Occurrence of Guilleminite
General Appearance of Type Material:
Canary-yellow coatings and silky masses up to 1 cm2. In geodes, it forms tablets up to 0.4 x 0.2 mm.
Place of Conservation of Type Material:
National School of Mines, Paris, France.
National Museum of Natural History, Washington, D.C., USA, 119360.
National Museum of Natural History, Washington, D.C., USA, 119360.
Geological Setting of Type Material:
Oxidized zone of a uranium-selenium-copper deposit.
Associated Minerals at Type Locality:
Synonyms of Guilleminite
Other Language Names for Guilleminite
Common Associates
Associations Based on Photo Data:
| 59 photos of Guilleminite associated with Malachite | Cu2(CO3)(OH)2 |
| 26 photos of Guilleminite associated with Vandenbrandeite | Cu(UO2)(OH)4 |
| 24 photos of Guilleminite associated with Digenite | Cu9S5 |
| 20 photos of Guilleminite associated with Cuprosklodowskite | Cu(UO2)2(SiO3OH)2 · 6H2O |
| 13 photos of Guilleminite associated with Marthozite | Cu2+(UO2)3(SeO3)2O2 · 8H2O |
| 12 photos of Guilleminite associated with Demesmaekerite | Pb2Cu5(UO2)2(SeO3)6(OH)6 · 2H2O |
| 5 photos of Guilleminite associated with Wulfenite | Pb(MoO4) |
| 5 photos of Guilleminite associated with Kasolite | Pb(UO2)(SiO4) · H2O |
| 5 photos of Guilleminite associated with Torbernite | Cu(UO2)2(PO4)2 · 12H2O |
| 4 photos of Guilleminite associated with Derriksite | Cu4(UO2)(SeO3)2(OH)6 |
Related Minerals - Strunz-mindat Grouping
| 4.JJ. | Kristekite | Cu2(H2O)4(UO2)(SeO3)3 · 4H2O |
| 4.JJ.X | Larisaite | Na(H3O)(UO2)3(SeO3)O2 · 4H2O |
| 4.JJ. | Borzęckiite | Pb(UO2)3(SeO3)2O2 · 3H2O |
| 4.JJ. | Petermegawite | Al6(Se4+O3)3[SiO3(OH)](OH)9 · 10H2O |
| 4.JJ. | Amurselite | (NH4)2(UO2)5(SeO3)3O2(OH)2(H2O) · 8H2O |
| 4.JJ.05 | Marthozite | Cu2+(UO2)3(SeO3)2O2 · 8H2O |
| 4.JJ.15 | Piretite | Ca(UO2)3(SeO3)2(OH)4 · 4H2O |
| 4.JJ.20 | Demesmaekerite | Pb2Cu5(UO2)2(SeO3)6(OH)6 · 2H2O |
| 4.JJ.25 | Haynesite | (UO2)3(Se4+O3)2(OH)2 · 5H2O |
| 4.JJ.30 | Favreauite | PbBiCu6O4(SeO3)4(OH) · H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 55.4686% | 13,867,150 | 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 Guilleminite
Not fluorescent.
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Guilleminite
mindat.org URL:
https://www.mindat.org/min-1771.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Guilleminite
Reference List:
Pierrot, Roland, Toussaint, J., Verbeek, Théodore (1965) La guilleminite, une nouvelle espèce minérale. Bulletin de Minéralogie, 88 (1) 132-135 doi:10.3406/bulmi.1965.5815
Pierrot, Roland, Toussaint, J., Verbeek, Théodore (1965) La guilleminite, une nouvelle espèce minérale. Bulletin de Minéralogie, 88 (1) 132-135 doi:10.3406/bulmi.1965.5815
Cooper, M. A., Hawthorne, F. C. (1995) The crystal structure of guilleminite, a hydrated Ba-U-Se sheet structure. The Canadian Mineralogist, 33 (5) 1103-1109
Cooper, M. A., Hawthorne, F. C. (2001) Structure topology and hydrogen bonding in marthozite, Cu2+[(UO2)3(SeO3)2O2](H2O)8, a comparison with guilleminite, Ba[(UO2)3(SeO3)2O2](H2O)3. The Canadian Mineralogist, 39 (3) 797-807 doi:10.2113/gscanmin.39.3.797
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 Guilleminite
Showing 5 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.
Czech Republic | |
| Plášil et al. (2026) |
DR Congo | |
| KMMA +1 other reference |
| Pierrot et al. (1965) +2 other references |
France | |
| - (1998) +1 other reference |
Spain | |
| Castillo-Oliver et al. (2019) |
Quick NavTopAbout GuilleminiteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatRadioactivityFluorescence Other InformationInternet Links References Localities Locality List
Musonoi Mine, Kolwezi, Mutshatsha, Lualaba, DR Congo