Jáchymovite
A valid IMA mineral species
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About Jáchymovite
Formula:
(UO2)8(SO4)(OH)14 · 13H2O
Colour:
Yellow
Lustre:
Vitreous
Specific Gravity:
4.79 (Calculated)
Crystal System:
Monoclinic
Name:
Named for the type locality.
This page provides mineralogical data about Jáchymovite.
Name Encoding
ASCII-7:
Jachymovite
Unique Identifiers
Mindat ID:
7117
Long-form identifier:
mindat:1:1:7117:4
Similar Names
| Jachymovite (of Novácek) | A synonym of Cuprosklodowskite |
IMA Classification of Jáchymovite
Classification of Jáchymovite
7.EA.10
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
E : Uranyl sulfates
A : Without cations
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
E : Uranyl sulfates
A : Without cations
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 |
|---|---|---|
| Jác | 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 Jáchymovite
Vitreous
Colour:
Yellow
Streak:
Pale yellow.
Tenacity:
Brittle
Cleavage:
Very Good
on {010}
on {010}
Fracture:
Conchoidal
Density:
4.79 g/cm3 (Calculated)
Optical Data of Jáchymovite
Type:
Biaxial (-)
RI values:
nα = 1.715(2) nβ = 1.718(2) nγ = 1.720(2)
2V:
Calculated: 78°
Max. Birefringence:
δ = 0.005
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
Pleochroism:
Visible
Comments:
Y = pale yellow; Z = yellow.
Chemistry of Jáchymovite
Mindat Formula:
(UO2)8(SO4)(OH)14 · 13H2O
Element Weights:
Elements listed:
Crystallography of Jáchymovite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/m
Cell Parameters:
a = 18.553(8) Å, b = 9.276(2) Å, c = 13.532(7) Å
β = 125.56(2)°
β = 125.56(2)°
Ratio:
a:b:c = 2 : 1 : 1.459
Unit Cell V:
1,894.52 ų (Calculated from Unit Cell)
Z:
2
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.56 Å | (100) |
| 7.13 Å | (48) |
| 3.771 Å | (34) |
| 3.554 Å | (20) |
| 3.234 Å | (10) |
| 3.206 Å | (13) |
Comments:
Jáchymov, Czech Republic. 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] | |
| 47b : [Sulfates and sulfites] | |
| 47f : [Uranyl (U⁶⁺) minerals] | |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 55 : Anthropogenic mine minerals |
Type Occurrence of Jáchymovite
General Appearance of Type Material:
As crusts of acicular crystals, to 0.1 mm
Place of Conservation of Type Material:
Natural History Museum, Prague, Czech Republic.
Geological Setting of Type Material:
Oxidation zone of a uranium deposit.
Associated Minerals at Type Locality:
Synonyms of Jáchymovite
Other Language Names for Jáchymovite
Common Associates
Associations Based on Photo Data:
| 2 photos of Jáchymovite associated with Kroupaite | KPb0.5[(UO2)8O4(OH)10] · 10H2O |
| 1 photo of Jáchymovite associated with Uranopilite | (UO2)6(SO4)O2(OH)6 · 14H2O |
| 1 photo of Jáchymovite associated with Rabejacite | Ca(UO2)4(SO4)2(OH)6 · 6H2O |
| 1 photo of Jáchymovite associated with Johannite | Cu(UO2)2(SO4)2(OH)2 · 8H2O |
| 1 photo of Jáchymovite associated with Redcanyonite | (NH4)2Mn[(UO2)4O4(SO4)2](H2O)4 |
Related Minerals - Strunz-mindat Grouping
| 7.EA. | Scenicite | [(UO2)(H2O)2(SO4)]2 · 3H2O |
| 7.EA.05 | Uranopilite | (UO2)6(SO4)O2(OH)6 · 14H2O |
| 7.EA.05 | Metauranopilite | (UO2)6(SO4)(OH)10 · 5H2O |
| 7.EA.15 | Shumwayite | (UO2)2(SO4)2 · 5H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 69.7882% | 17,447,050 | 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 Jáchymovite
Yellow under both SW and LW UV.
Other Information
Health Risks:
Radioactive.
Internet Links for Jáchymovite
mindat.org URL:
https://www.mindat.org/min-7117.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
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References for Jáchymovite
Reference List:
Localities for Jáchymovite
Showing 9 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 (TL) | |
| Čejka et al. (1996) +1 other reference |
| Möhn et al. (12/2021) | |
| Škácha et al. (2014) |
| Desor (04/2022) |
| 70 (in German) +2 other references |
Germany | |
| Mangold et al. (10/21) |
| Gerstenberg et al. (11/21) +1 other reference |
Switzerland | |
| Brugger et al. (2003) |
USA | |
| Caldwell (2018) |
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Johanngeorgenstadt, Erzgebirgskreis, Saxony, Germany