Piretite
A valid IMA mineral species
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About Piretite
Formula:
Ca(UO2)3(SeO3)2(OH)4 · 4H2O
Colour:
Lemon-yellow
Lustre:
Pearly
Hardness:
2½
Specific Gravity:
4.00
Crystal System:
Orthorhombic
Name:
For Dr. Paul Piret (born Tournai, Belgium May 13th 1932 and passed away in Ottignies, Belgium on March 22nd 1999), Professor of Crystallography, University of Louvain-la-Neuve, Belgium. Described about 30 new mineral species, in co-authorship with Michel Deliens.
This page provides mineralogical data about Piretite.
Unique Identifiers
Mindat ID:
7238
Long-form identifier:
mindat:1:1:7238:6
Similar Names
| Peretaite | A valid IMA mineral species | Ca(SbO)4(SO4)2(OH)2 · 2H2O |
| Perettiite-(Y) | A valid IMA mineral species | Y2Mn4FeSi2B8O24 |
| Pierrotite | A valid IMA mineral species | Tl2(Sb,As)10S16 |
| Pirrotita | A synonym of Pyrrhotite | |
| Portite | A synonym of Natrolite |
IMA Classification of Piretite
Approved
IMA Formula:
Ca(U6+O2)3(Se4+O3)2(OH)4·4H2O
Approval year:
1996
Classification of Piretite
4.JJ.15
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
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 |
|---|---|---|
| Pir | 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 Piretite
Pearly
Transparency:
Transparent, Translucent
Colour:
Lemon-yellow
Streak:
Pale yellow
Hardness:
2½ on Mohs scale
Cleavage:
Distinct/Good
{001}, good.
{001}, good.
Fracture:
Irregular/Uneven
Comment:
Tenacity - weak
Density:
4.00 g/cm3 (Measured) 3.87 g/cm3 (Calculated)
Optical Data of Piretite
Type:
Biaxial (-)
RI values:
nα = 1.54 nβ = 1.73 nγ = 1.75
2V:
Measured: 33° (5), Calculated: 32°
Max. Birefringence:
δ = 0.210
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
Chemistry of Piretite
Mindat Formula:
Ca(UO2)3(SeO3)2(OH)4 · 4H2O
Element Weights:
Crystallography of Piretite
Crystal System:
Orthorhombic
Cell Parameters:
a = 7.010(3) Å, b = 17.135(7) Å, c = 17.606(4) Å
Ratio:
a:b:c = 0.409 : 1 : 1.027
Unit Cell V:
2,114.77 ų (Calculated from Unit Cell)
Z:
4
Comment:
Point Group: 2/m 2/m 2/m or mm2.; Space group is Pmnm or Pmn21
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.50 Å | (100) |
| 3.033 Å | (100) |
| 8.80 Å | (80) |
| 3.095 Å | (50) |
| 8.57 Å | (40) |
| 1.924 Å | (40) |
| 4.29 Å | (30) |
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 Piretite
Place of Conservation of Type Material:
Royal Belgian Institute of Natural Sciences, Brussels
Associated Minerals at Type Locality:
Synonyms of Piretite
Other Language Names for Piretite
Common Associates
Associations Based on Photo Data:
| 3 photos of Piretite associated with Naumannite | Ag2Se |
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.10 | Guilleminite | Ba(UO2)3(SeO3)2O2 · 3H2O |
| 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) | 57.3947% | 14,348,675 | 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
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 Piretite
mindat.org URL:
https://www.mindat.org/min-7238.html
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Please feel free to link to this page.
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References for Piretite
Localities for Piretite
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.
Argentina | |
| Morello (2016) |
Czech Republic | |
| Plášil et al. (2026) |
| In the collection of Brent Thorne. ... |
DR Congo (TL) | |
| Can Min (1996) |
| Desor (12/2023) |
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Zálesí uranium deposit, Zálesí, Javorník, Jeseník District, Olomouc Region, Czech Republic