Sharpite
A valid IMA mineral species - grandfathered
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About Sharpite
Robert R. Sharp
Formula:
Ca(UO2)3(CO3)4 · 3H2O
According to the single-crystal X-ray study (Plášil 2018), an idealized formula of sharpite is Ca(H2O)3[(UO2)3(CO3)3.6O0.2],where the content of (CO3) lies most probably within 4 > xCO3 > 3.5 apfu range.
Colour:
Greenish-yellow, olive-green
Hardness:
2½ - 3
Specific Gravity:
4.412 (Calculated)
Crystal System:
Orthorhombic
Name:
Named after Major Robert Rich Sharp (25 September 1881 Gateshead, Durham County, England - 25 August 1960 Bulawayo, Zimbabwe), discoverer of the uranium deposit at Shinkolobwe, Zaire in 1915.
Sharpite represents a unique sheet-based structure derived from the rutherfordine topology, where one of the hexagons within that topology accomodates Ca2+.
Unique Identifiers
Mindat ID:
3633
Long-form identifier:
mindat:1:1:3633:3
IMA Classification of Sharpite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ca(U6+O2)3(CO3)4·3H2O
First published:
1938
Classification of Sharpite
5.EA.35
5 : CARBONATES (NITRATES)
E : Uranyl Carbonates
A : UO2:CO3 > 1:1
5 : CARBONATES (NITRATES)
E : Uranyl Carbonates
A : UO2:CO3 > 1:1
16b.7.10.1
16b : HYDRATED CARBONATES CONTAINING HYDROXYL OR HALOGEN
7 : Miscellaneous
16b : HYDRATED CARBONATES CONTAINING HYDROXYL OR HALOGEN
7 : Miscellaneous
11.11.10
11 : Carbonates
11 : Carbonates of Cr and U
11 : Carbonates
11 : Carbonates of Cr and 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 |
|---|---|---|
| Shp | 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 Sharpite
Transparency:
Translucent
Colour:
Greenish-yellow, olive-green
Hardness:
2½ - 3 on Mohs scale
Density:
4.412 g/cm3 (Calculated)
Comment:
measured > 4.55
Optical Data of Sharpite
Type:
Biaxial (+)
RI values:
nα = 1.632 - 1.638 nγ = 1.720 - 1.722
Max. Birefringence:
δ = 0.084 - 0.088
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.
No measured or calculated 2V is on file for this mineral, so the value used here (92°) 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 (92°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
Weak to distinct
Optical Extinction:
Y ⊥ laths; Z ‖ elongation. Positive elongation, parallel extinction.
Pleochroism:
Visible
Comments:
X = Y = pale brown, very pale yellow-green; Z = pale yellow-green.
Comments:
Pale yellow in transmitted light.
Chemistry of Sharpite
Mindat Formula:
Ca(UO2)3(CO3)4 · 3H2O
According to the single-crystal X-ray study (Plášil 2018), an idealized formula of sharpite is Ca(H2O)3[(UO2)3(CO3)3.6O0.2],where the content of (CO3) lies most probably within 4 > xCO3 > 3.5 apfu range.
According to the single-crystal X-ray study (Plášil 2018), an idealized formula of sharpite is Ca(H2O)3[(UO2)3(CO3)3.6O0.2],where the content of (CO3) lies most probably within 4 > xCO3 > 3.5 apfu range.
Element Weights:
Crystallography of Sharpite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Cmcm
Cell Parameters:
a = 4.9032(4) Å, b = 15.6489(11) Å, c = 22.0414(18) Å
Ratio:
a:b:c = 0.313 : 1 : 1.408
Unit Cell V:
1691.2 ų
Z:
4
Morphology:
Occurs as crusts of thin, radiating fibers.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 4.497 Å | (100) |
| 3.910 Å | (48) |
| 7.82 Å | (40) |
| 5.34 Å | (35) |
| 2.996 Å | (33) |
| 11.02 Å | (30) |
| 6.37 Å | (28) |
Comments:
Shinkolobwe Mine, DR Congo. Data from Čejka (1984).
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] |
Type Occurrence of Sharpite
General Appearance of Type Material:
Radially fibrous crust.
Place of Conservation of Type Material:
University of Liege, Liege, Belgium, 6280, 16905.
Geological Setting of Type Material:
Secondary mineral in oxide zone of hydrothermal uranium deposit.
Associated Minerals at Type Locality:
Other Language Names for Sharpite
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 5.EA.05 | 'UM1997-24-CO:CaCuHU' | Ca2Cu(UO2)2(CO3)2O3 · 3H2O |
| 5.EA.10 | Urancalcarite | Ca(UO2)3(CO3)(OH)6 · 3H2O |
| 5.EA.15 | Wyartite | CaU5+(UO2)2(CO3)O4(OH) · 7H2O |
| 5.EA.20 | Oswaldpeetersite | (UO2)2(CO3)(OH)2 · 4H2O |
| 5.EA.25 | Roubaultite | Cu2(UO2)3(CO3)2O2(OH)2 · 4H2O |
| 5.EA.30 | Kamotoite-(Y) | Y2(UO2)4(CO3)3O4 · 14H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 62.4069% | 15,601,725 | 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
Notes:
Soluble in dilute acids with effervescence.
Radioactive.
Radioactive.
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 Sharpite
mindat.org URL:
https://www.mindat.org/min-3633.html
Please feel free to link to this page.
Please feel free to link to this page.
Search Engines:
External Links:
Mineral Dealers:
References for Sharpite
Reference List:
Dunn, Pete J., Chao, George Y., Fleischer, Michael, Ferraiolo, James A., Langley, Richard H., Pabst, Adolf, Zilczer, Janet A. (1985) New mineral names. American Mineralogist, 70 (1-2) 214-221 p.220
Localities for Sharpite
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.
DR Congo (TL) | |
| KMMA +3 other references |
France | |
| Mineralogical Society of America - ... +1 other reference |
| - (1998) |
Germany | |
| Aufschluss 69/ (7+8) +1 other reference |
Iran | |
| Khoshnoodi et al. (2025) |
Poland | |
| Eligiusz Szełęg collection (SEM/EDS identification) |
| pl.wikipedia.org (2006) |
Quick NavTopAbout SharpiteUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography X-Ray Powder DiffractionGeological EnvironmentType Occurrence Other LanguagesCommon AssociatesStrunz-MindatRadioactivityOther InformationInternet Links References Localities Locality List
Shinkolobwe Mine, Shinkolobwe, Kambove Territory, Haut-Katanga, DR Congo