Phurcalite
A valid IMA mineral species
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About Phurcalite
Formula:
Ca2(UO2)3(PO4)2O2 · 7H2O
Colour:
Yellow
Lustre:
Adamantine, Vitreous
Hardness:
3
Specific Gravity:
4.22
Crystal System:
Orthorhombic
Member of:
Name:
Named by M. Deliens and P. Piret in 1978 for the composition, that includes PHosphate, URanyl, and CAlcium.
Type Locality:
This page provides mineralogical data about Phurcalite.
Unique Identifiers
Mindat ID:
3202
Long-form identifier:
mindat:1:1:3202:1
Classification of Phurcalite
Phosphuranylite sheet topology
The sheet topology exhibited by members of the phosphuranylite group.
IMA Classification of Phurcalite
Approved
IMA Formula:
Ca2(U6+O2)3O2(PO4)2·7H2O
Approval year:
1977
First published:
1978
Type description reference:
8.EC.35
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
C : UO2:RO4 = 3:2
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
C : UO2:RO4 = 3:2
42.4.7.1
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
4 : (AB)5(XO4)2Zq·xH2O
42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
4 : (AB)5(XO4)2Zq·xH2O
19.11.17
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 |
|---|---|---|
| Phu | 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 Phurcalite
Adamantine, Vitreous
Transparency:
Transparent, Translucent
Colour:
Yellow
Streak:
Pale yellow.
Hardness:
3 on Mohs scale
Hardness:
VHN5=86 - 95 kg/mm2 - Vickers
Tenacity:
Brittle
Cleavage:
Perfect
{001} and {010}, perfect. Also {100}.
{001} and {010}, perfect. Also {100}.
Fracture:
Conchoidal
Density:
4.22(4) g/cm3 (Measured) 4.220 g/cm3 (Calculated)
Optical Data of Phurcalite
Type:
Biaxial (-)
RI values:
nα = 1.690 nβ = 1.730(1) nγ = 1.749(1)
2V:
Measured: 68° , Calculated: 66°
Max. Birefringence:
δ = 0.059
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:
weak to moderate, r > v.
Optical Extinction:
Parallel. X = b; Y = a; Z = c.
Pleochroism:
Strong
Comments:
X = colorless to pale yellow; Y = very pale yellow to pale yellow; Z = bright yellow to golden yellow.
Comments:
α calculated.
Absorption: X < Y < Z.
Elongation positive.
Absorption: X < Y < Z.
Elongation positive.
Chemistry of Phurcalite
Mindat Formula:
Ca2(UO2)3(PO4)2O2 · 7H2O
Element Weights:
Chemical Analysis
Oxide wt%:
| 1 | |
|---|---|
| UO3 | 65.2 % |
| CaO | 7.3 % |
| P2O5 | 16.8 % |
| H2O | 10.3 % |
| Total: | 99.6 % |
Sample references:
| ID | Locality | Reference | Notes |
|---|---|---|---|
| 1 | Putholi, Chittorgarh District, Udaipur Division, Rajasthan, India | Anhedral encrustation from fractures in quartzite. Method used for chemical analysis is not given. |
Crystallography of Phurcalite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Pbca
Setting:
Pbca
Cell Parameters:
a = 17.3785(8) Å, b = 15.9864(6) Å, c = 13.5477(6) Å
Ratio:
a:b:c = 1.087 : 1 : 0.847
Unit Cell V:
3763.8 ų
Z:
8
Morphology:
Tablets flattened on [010] and elongated on [001].
Comment:
As-enriched material from Jáchymov
Crystal Structure
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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) |
|---|---|---|---|---|---|---|---|
| 0005255 | Phurcalite | Atencio D, Neumann R, Silva A J G C, Mascarenhas Y P (1991) Phurcalite from Perus, San Paulo, Brazil, and redetermination of its crystal structure The Canadian Mineralogist 29 95-105 |  | 1991 | Perus, San Paulo, Brazil | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 8.05 Å | (100) |
| 3.10 Å | (80) |
| 3.09 Å | (80) |
| 2.878 Å | (70) |
| 3.39 Å | (50) |
| 4.24 Å | (30) |
| 4.00 Å | (30) |
Comments:
Bergen, Germany. The data are from the type description.
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 Phurcalite
General Appearance of Type Material:
Tablets, flattened on [010] and elongated on [001], with crystals up to 1 mm long.
Place of Conservation of Type Material:
Royal Museum of Central Africa, Tervuren, Belgium, number RMG13388.
National Museum of Natural History, Washington, D.C., USA, number 144187.
National Museum of Natural History, Washington, D.C., USA, number 144187.
Associated Minerals at Type Locality:
Synonyms of Phurcalite
Other Language Names for Phurcalite
Relationship of Phurcalite to other Species
Member of:
Other Members of Phosphuranylite Group:
| Althupite | AlTh(UO2)7(PO4)4(OH)5O2 · 15H2O | Tric. 1 : P1 |
| Bergenite | Ca2Ba4(UO2)9(PO4)6O6 · 16H2O | Mon. 2/m : P21/b |
| Dewindtite | H2Pb3(UO2)6O4(PO4)4 · 12H2O | Orth. mmm(2/m2/m2/m) : Cmma |
| Dumontite | Pb2(UO2)3O2(PO4)2 · 5H2O | Mon. 2/m : P21/m |
| Françoisite-(Ce) | (Ce,Nd,Ca)(UO2)3(PO4)2O(OH) · 6H2O | Mon. 2/m : P21/b |
| Françoisite-(Nd) | (Nd,Ce,Sm)(UO2)3(PO4)2O(OH) · 6H2O | Mon. 2/m |
| Hügelite | Pb2(UO2)3(AsO4)2O2 · 5H2O | Mon. 2/m : P21/m |
| Phosphuranylite | KCa(H3O)3(UO2)7(PO4)4O4 · 8H2O | Orth. mmm(2/m2/m2/m) : Cmcm |
| Phuralumite | Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9 | Mon. 2/m |
| Upalite | Al(UO2)3(PO4)2O(OH) · 7H2O | Mon. 2/m : P21/b |
| Vanmeersscheite | U6+(UO2)3(PO4)2(OH)6 · 4H2O | Orth. mmm(2/m2/m2/m) |
| Yingjiangite | K2Ca(UO2)7(PO4)4(OH)6 · 6H2O | Orth. mmm(2/m2/m2/m) : Cmcm |
Common Associates
Associations Based on Photo Data:
| 20 photos of Phurcalite associated with Brochantite | Cu4(SO4)(OH)6 |
| 10 photos of Phurcalite associated with Malachite | Cu2(CO3)(OH)2 |
| 9 photos of Phurcalite associated with Torbernite | Cu(UO2)2(PO4)2 · 12H2O |
| 7 photos of Phurcalite associated with Autunite | Ca(UO2)2(PO4)2 · 10-12H2O |
| 6 photos of Phurcalite associated with Quartz | SiO2 |
| 5 photos of Phurcalite associated with Metatorbernite | Cu(UO2)2(PO4)2 · 8H2O |
| 3 photos of Phurcalite associated with 'Manganese Oxides' | |
| 3 photos of Phurcalite associated with Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
| 2 photos of Phurcalite associated with 'Sandstone' | |
| 2 photos of Phurcalite associated with Haiweeite | Ca(UO2)2[Si5O12(OH)2] · 6H2O |
Related Minerals - Strunz-mindat Grouping
| 8.EC.05 | Upalite | Al(UO2)3(PO4)2O(OH) · 7H2O |
| 8.EC.05 | Françoisite-(Nd) | (Nd,Ce,Sm)(UO2)3(PO4)2O(OH) · 6H2O |
| 8.EC.05 | Françoisite-(Ce) | (Ce,Nd,Ca)(UO2)3(PO4)2O(OH) · 6H2O |
| 8.EC.05 | Phuralumite | Al2[(UO2)3(PO4)2O(OH)](OH)3(H2O)9 |
| 8.EC.10 | Yingjiangite | K2Ca(UO2)7(PO4)4(OH)6 · 6H2O |
| 8.EC.10 | Renardite | Pb(UO2)4(PO4)2(OH)4 · H2O |
| 8.EC.10 | Phosphuranylite | KCa(H3O)3(UO2)7(PO4)4O4 · 8H2O |
| 8.EC.10 | Arsenuranylite | Ca(UO2)4(AsO4)2(OH)4 · 6H2O |
| 8.EC.10 | 'Kivuite' | Th(UO2)4(PO3OH)2(OH)8 · 7H2O |
| 8.EC.10 | Dewindtite | H2Pb3(UO2)6O4(PO4)4 · 12H2O |
| 8.EC.15 | Dumontite | Pb2(UO2)3O2(PO4)2 · 5H2O |
| 8.EC.15 | Hügelite | Pb2(UO2)3(AsO4)2O2 · 5H2O |
| 8.EC.20 | Vanmeersscheite | U6+(UO2)3(PO4)2(OH)6 · 4H2O |
| 8.EC.20 | Arsenovanmeersscheite | U6+(UO2)3(AsO4)2(OH)6 · 4H2O |
| 8.EC.20 | Metavanmeersscheite | U6+(UO2)3(PO4)2(OH)6 · 2H2O |
| 8.EC.25 | Althupite | AlTh(UO2)7(PO4)4(OH)5O2 · 15H2O |
| 8.EC.30 | Mundite | Al(UO2)3(PO4)2(OH)3 · 5.5H2O |
| 8.EC.40 | Bergenite | Ca2Ba4(UO2)9(PO4)6O6 · 16H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 57.6673% | 14,416,825 | 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 Phurcalite
Not fluorescent in UV.
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 Phurcalite
mindat.org URL:
https://www.mindat.org/min-3202.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Phurcalite
Reference List:
Deliens, Michel, Piret, Paul, Deliens, Michel, Piret, Paul (1978) La phurcalite, Ca2(UO2)3(PO4)2(OH)4·4H2O, nouveau minéral. Bulletin de Minéralogie, 101 (3) 356-358 doi:10.3406/bulmi.1978.7197
Piret, P., Declercq, J.-P. (1978) Phurcalite. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 34 (5) 1677-1679 doi:10.1107/s0567740878006317
Deliens, Michel, Piret, Paul, Deliens, Michel, Piret, Paul (1978) La phurcalite, Ca2(UO2)3(PO4)2(OH)4·4H2O, nouveau minéral. Bulletin de Minéralogie, 101 (3) 356-358 doi:10.3406/bulmi.1978.7197
Fleischer, Michael, Chao, George Y., Pabst, and Adolf (1979) New Mineral Names. American Mineralogist, 64 (1-2) 241-245
Braithwaite, R. S. W., Paar, W. H., Chisholm, J. E. (1989) Phurcalite from Dartmoor, Southwest England, and its identity with ‘nisaite’ from Portugal. Mineralogical Magazine, 53 (373) 583-589 doi:10.1180/minmag.1989.053.373.09
Jambor, John L.; Puziewicz, Jacek (1990) New Mineral Names. American Mineralogist, 75 (9-10). 1209-1216
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
Čejka, Jiří, Sejkora, Jiří, Scholz, Ricardo, López, Andrés, Xi, Yunfei, Frost, Ray L. (2014) Raman and infrared spectroscopic studies of phurcalite from Red Canyon, Utah, USA – Implications for the molecular structure. Journal of Molecular Structure, 1068. 14-19 doi:10.1016/j.molstruc.2014.03.040
Plášil, Jakub, Kiefer, Boris, Ghazisaeed, Seyedat, Philippo, Simon (2020) Hydrogen bonding in the crystal structure of phurcalite, Ca2[(UO2)3O2(PO4)2]·7H2O: single-crystal X-ray study and TORQUE calculations. Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials, 76 (3) 502-509 doi:10.1107/s2052520620005739
Localities for Phurcalite
Showing 39 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.
Argentina | |
| O. Morello y C. N. Reyes Encinas (1990) |
| O. Morello y C. N. Reyes Encinas (1990) | |
| M. E. Saulnier y F. Greco (1988) | |
| Personally collected by Günter Frenz |
Australia | |
| Haupt (2003) |
| Elliott et al. (2019) |
| The mines & minerals of the Olary ... | |
Austria | |
| Brandstätter et al. (1987) +1 other reference |
Brazil | |
| D Atencio & R Hypolito () +1 other reference |
| Fosfatos e Silicatos Secundários de ... | |
Chile | |
| A.Molina & M. Dini collections - based ... |
| samples identified by Gerhard Möhn |
China | |
| Guang Fan et al. (2014) |
Czech Republic | |
| J. Plasil (SC-XRD) |
| Collected by Jan Hloušek +1 other reference |
DR Congo | |
| Deliens (1996) |
Egypt | |
| Ehab K. Abu Zeid (2020) |
| Ismail (2017) +1 other reference | |
France | |
| Chollet Pascal Collection - SEM-EDS ... |
| - (1998) |
Germany | |
| Steen et al. (2024) |
| Walenta (1994) +1 other reference |
| Habel et al. (1994) +1 other reference |
| https://www.mineralienatlas.de/?l=5281 |
| www.mineralienatlas.de (n.d.) |
| Deliens et al. (1978) |
| Witzke (2018) |
India | |
| Saini +3 other references |
| Singh et al. (1999) | |
Namibia | |
| Schnaitmann et al. (2009) |
Portugal | |
| Luis Casinhas collection |
| Cesar Menor Salvan |
UK | |
| Braithwaite et al. (1989) +1 other reference |
USA | |
| Braithwaite et al. (1989) |
| Pemberton (1983) +1 other reference |
| Excalibur Mineral Corp. - Mineral News |
| Caldwell (2018) |
| Min News 3:9 p5-6 |
Zambia | |
| Randabel et al. (2018) |
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Posey Mine, Red Canyon Mining District, San Juan County, Utah, USA