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Kroupaite
A valid IMA mineral species
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About Kroupaite
Formula:
KPb0.5[(UO2)8O4(OH)10] · 10H2O
Colour:
Orange-yellow
Lustre:
Vitreous
Hardness:
2
Specific Gravity:
5.058 (Calculated)
Crystal System:
Orthorhombic
Name:
The new mineral is named after mining engineer Gustav Kroupa (born 30 August 1857 in Mutějovice near Rakovník, Bohemia, died 31 May 1935 in Vienna, Austria), mining engineer, in 1896 he became the head of the k.k. Uranfarbenfabrik in St. Joachimsthal (Jáchymov) until 1900. He approved and sent 10 tons of leachates after processing of uranium ore for uranium pigments to Marie-Curie Sklodowska and Pierre Curie, who were the first to discover and isolate 3 grams of RaCl2 from them.
Structurally related to leesite and metaschoepite.
Belongs to a group of minerals that may be important in uptaking radionuclides like 90Sr or 135Cs.
Belongs to a group of minerals that may be important in uptaking radionuclides like 90Sr or 135Cs.
Unique Identifiers
Mindat ID:
51971
Long-form identifier:
mindat:1:1:51971:7
IMA Classification of Kroupaite
Approved
IMA Formula:
KPb2+0.5[(U6+O2)8O4(OH)10]·10H2O
Approval year:
2017
First published:
2020
Type description reference:
Plášil, Jakub, Kampf, Anthony R., Olds, Travis A., Sejkora, Jiří, Škoda, Radek, Burns, Peter C., Čejka, Jiří (2020) The new K, Pb-bearing uranyl-oxide mineral kroupaite: Crystal-chemical implications for the structures of uranyl-oxide hydroxy-hydrates. American Mineralogist, 105 (4) 561-568 doi:10.2138/am-2020-7311
Classification of Kroupaite
4.GB.85
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
G : Uranyl Hydroxides
B : With additional cations (K, Ca, Ba, Pb, etc.); with mainly UO2(O,OH)5 pentagonal polyhedra
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
G : Uranyl Hydroxides
B : With additional cations (K, Ca, Ba, Pb, etc.); with mainly UO2(O,OH)5 pentagonal polyhedra
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 |
|---|---|---|
| Kpa | 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 Kroupaite
Vitreous
Transparency:
Translucent
Colour:
Orange-yellow
Streak:
Light yellow
Hardness:
2 on Mohs scale
Hardness Data:
Measured
Comment:
Scratch tests
Tenacity:
Brittle
Cleavage:
Perfect
{100}
{100}
Fracture:
Irregular/Uneven
Density:
5.058 g/cm3 (Calculated)
Comment:
Not measured due to limited amount of materal. Calculated from empirical formula.
Optical Data of Kroupaite
Type:
Biaxial (-)
RI values:
nα = 1.691(2) nβ = 1.752(2) nγ = 1.768(2)
2V:
Measured: 53° (1), Calculated: 52.7°
Max. Birefringence:
δ = 0.077
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.
Pleochroism:
Visible
Comments:
X = colorless, Y = yellow, Z = yellow; X < Y ≈ Z
Comments:
X = a, Y = c, Z = b
Chemistry of Kroupaite
Mindat Formula:
KPb0.5[(UO2)8O4(OH)10] · 10H2O
Element Weights:
Crystallography of Kroupaite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Pbca
Setting:
Pbca
Cell Parameters:
a = 14.8201(8) Å, b = 14.0958(8) Å, c = 16.765(1) Å
Ratio:
a:b:c = 1.051 : 1 : 1.189
Unit Cell V:
3,502.23 ų (Calculated from Unit Cell)
Morphology:
Tablets flattened on {100}, with prominent forms {100}, {013} and {021}.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.407 Å | (100) |
| 3.602 Å | (59) |
| 3.224 Å | (78) |
| 2.572 Å | (16) |
| 2.035 Å | (21) |
| 1.978 Å | (11) |
| 1.798 Å | (10) |
| 1.747 Å | (7) |
Reference:
Plášil, Jakub, Kampf, Anthony R., Olds, Travis A., Sejkora, Jiří, Škoda, Radek, Burns, Peter C., Čejka, Jiří (2020) The new K, Pb-bearing uranyl-oxide mineral kroupaite: Crystal-chemical implications for the structures of uranyl-oxide hydroxy-hydrates. American Mineralogist, 105 (4) 561-568 doi:10.2138/am-2020-7311
Comments:
From Type Description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 27 : Radioactive decay; auto-oxidation | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47g : [Halogen-bearing surface weathering minerals] |
Type Occurrence of Kroupaite
General Appearance of Type Material:
Radial aggregates of thick platy, orange-yellow crystals, up to 1 mm, growing in interstices of gypsum crystals
Place of Conservation of Type Material:
Type material is deposited in the mineralogical collections of the National Museum in Prague, Czech Republic, catalogue number no. P1P 16/ 2017, and the Natural History Museum of Los Angeles County, Los Angeles, CA, USA, catalogue number 66572.
Associated Minerals at Type Locality:
Reference:
Plášil, Jakub, Kampf, Anthony R., Olds, Travis A., Sejkora, Jiří, Škoda, Radek, Burns, Peter C., Čejka, Jiří (2020) The new K, Pb-bearing uranyl-oxide mineral kroupaite: Crystal-chemical implications for the structures of uranyl-oxide hydroxy-hydrates. American Mineralogist, 105 (4) 561-568 doi:10.2138/am-2020-7311
Synonyms of Kroupaite
Other Language Names for Kroupaite
Common Associates
Associations Based on Photo Data:
| 2 photos of Kroupaite associated with Jáchymovite | (UO2)8(SO4)(OH)14 · 13H2O |
| 1 photo of Kroupaite associated with Fourmarierite | Pb(UO2)4O3(OH)4 · 4H2O |
| 1 photo of Kroupaite associated with Compreignacite | K2(UO2)6O4(OH)6 · 7H2O |
| 1 photo of Kroupaite associated with Sklodowskite | Mg(UO2)2(SiO3OH)2 · 6H2O |
| 1 photo of Kroupaite associated with Uraninite | UO2 |
| 1 photo of Kroupaite associated with Uranopilite | (UO2)6(SO4)O2(OH)6 · 14H2O |
| 1 photo of Kroupaite associated with Gypsum | CaSO4 · 2H2O |
Related Minerals - Strunz-mindat Grouping
| 4.GB. | Leishmanite | Ba(H2O)4[(UO2)3O2(OH)3]2 · 3H2O |
| 4.GB.05 | Rameauite | K2Ca(UO2)6O6(OH)4 · 6H2O |
| 4.GB.05 | Agrinierite | K2(Ca,Sr)[(UO2)3O3(OH)2]2 · 5H2O |
| 4.GB.05 | Compreignacite | K2(UO2)6O4(OH)6 · 7H2O |
| 4.GB.10 | Becquerelite | Ca(UO2)6O4(OH)6 · 8H2O |
| 4.GB.10 | Billietite | Ba(UO2)6O4(OH)6 · 4-8H2O |
| 4.GB.10 | Protasite | Ba(UO2)3O3(OH)2 · 3H2O |
| 4.GB.15 | Richetite | (Fe3+,Mg)Pb 8.6(UO2)36O36(OH)24 · 41H2O |
| 4.GB.20 | Calciouranoite | (Ca,Ba,Pb)U2O7 · 5H2O |
| 4.GB.20 | Bauranoite | Ba(UO2)2(OH)6 · 1-2H2O |
| 4.GB.20 | Metacalciouranoite | (Ca,Ba,Pb,K2)U2O7 · 2H2O |
| 4.GB.25 | Fourmarierite | Pb(UO2)4O3(OH)4 · 4H2O |
| 4.GB.30 | Wölsendorfite | Pb7(UO2)14O19(OH)4 · 12H2O |
| 4.GB.35 | Masuyite | Pb(UO2)3O3(OH)2 · 3H2O |
| 4.GB.40 | Vandendriesscheite | PbU7O22 · 12H2O |
| 4.GB.40 | Metavandendriesscheite | PbU7O22 · nH2O n < 12 |
| 4.GB.45 | Vandenbrandeite | Cu(UO2)(OH)4 |
| 4.GB.50 | Sayrite | Pb2(UO2)5O6(OH)2 · 4H2O |
| 4.GB.55 | Curite | Pb3(H2O)2[(UO2)4O4(OH)3]2 |
| 4.GB.60 | Iriginite | (UO2)Mo2O7 · 3H2O |
| 4.GB.65 | Uranosphaerite | Bi(UO2)O2(OH) |
| 4.GB.70 | Holfertite | CaxU6+2-xTi(O8-xOH4x) · 3H2O |
| 4.GB.75 | Carlosbarbosaite | (UO2)2Nb2O6(OH)2 · 2H2O |
| 4.GB.80 | Gauthierite | KPb[(UO2)7O5(OH)7] · 8H2O |
| 4.GB.90 | Leesite | K(H2O)2[(UO2)4O2(OH)5] · 3H2O |
| 4.GB.95 | Shinkolobweite | Pb1.333[U5+O(OH)(UO2)5O4.67(OH)5.33](H2O)5 |
| 4.GB.95 | Nollmotzite | Mg[U5+(U6+O2)2O4F3] · 4H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 70.0821% | 17,520,525 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 1.4389% | 446 | 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 Kroupaite
Not fluorescent
Other Information
Notes:
Soluble in dilute HCl, with no effervescence
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 Kroupaite
mindat.org URL:
Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic