Horákite
A valid IMA mineral species
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About Horákite
Formula:
(Bi7O7OH)[(UO2)4(PO4)2(AsO4)2(OH)2] · 3.5H2O
Colour:
Greenish-yellow to pale yellow
Lustre:
Vitreous
Hardness:
2
Specific Gravity:
6.358 (Calculated)
Crystal System:
Monoclinic
Name:
Horákite is named after Ing. František Horák (1882–1919) served from 1916 to 1918 as bergadjunkt and the responsible head of the Radium factory in St. Joachimsthal (Jáchymov) and his grandson MUDr. (M.D.) Vladimír Horák (born 1964) is an amateur mineral collector and historian, focused on the history of mining in Jáchymov.
New structure type. Quite unique with phosphate and arsenate groups occurring separately.
Formed by supergene alteration.
Formed by supergene alteration.
Name Encoding
ASCII-7:
Horakite
Unique Identifiers
Mindat ID:
51973
Long-form identifier:
mindat:1:1:51973:5
IMA Classification of Horákite
Approved
IMA Formula:
(Bi3+7O7OH)[(U6+O2)4(PO4)2(As5+O4)2(OH)2]·3.5H2O
Approval year:
2017
First published:
2018
Classification of Horákite
8.EB.60
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
B : UO2:RO4 = 1:1
8 : PHOSPHATES, ARSENATES, VANADATES
E : Uranyl phosphates and arsenates
B : UO2:RO4 = 1:1
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 |
|---|---|---|
| Hor | 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 Horákite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Greenish-yellow to pale yellow
Streak:
Light yellow
Hardness:
2 on Mohs scale
Hardness Data:
Estimated
Cleavage:
Perfect
on {100}
on {100}
Density:
6.358 g/cm3 (Calculated)
Optical Data of Horákite
Type:
Biaxial (+)
RI values:
nα = 1.81 nβ = 1.81 nγ = 1.88
2V:
Measured: 78° , Calculated: 83°
Max. Birefringence:
δ = 0.070
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:
Non-pleochroic
Comments:
Optical orientation is X = b, Z ≈ c
Chemistry of Horákite
Mindat Formula:
(Bi7O7OH)[(UO2)4(PO4)2(AsO4)2(OH)2] · 3.5H2O
Element Weights:
Crystallography of Horákite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/b
Setting:
C2/c
Cell Parameters:
a = 21.374(2) Å, b = 15.451(3) Å, c = 12.168(2) Å
β = 122.26(1)°
β = 122.26(1)°
Ratio:
a:b:c = 1.383 : 1 : 0.788
Unit Cell V:
3398.1 ų
Z:
4
Morphology:
Prismatic crystals; clusters of acicular aggregates
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 11.77 Å | (100) |
| 6.21 Å | (23) |
| 5.55 Å | (23) |
| 4.185 Å | (27) |
| 3.543 Å | (61) |
| 3.287 Å | (20) |
| 3.144 Å | (58) |
| 3.017 Å | (98) |
Reference:
Comments:
From 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] | |
| 47d : [Arsenates, antimonates, selenates, bismuthinates] | |
| 47f : [Uranyl (U⁶⁺) minerals] |
Type Occurrence of Horákite
General Appearance of Type Material:
Greenish-yellow to pale yellow prismatic crystals clustering to acicular aggregates, up to 1 mm across.
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 17/2017, and the Natural History Museum of Los Angeles County, Los Angeles, CA, USA, catalogue number 66575
Empirical Formula of Type Material:
(Bi7.01Pb0.14)O7OH[(U1.01O2)4(P1.03O4)2(As0.74Si0.23O4)2(OH)2]·3.5H2O
Associated Minerals at Type Locality:
Synonyms of Horákite
Other Language Names for Horákite
Related Minerals - Strunz-mindat Grouping
| 8.EB. | Meta-autunite Group | A1-2(UO2)2(TO4)2 · 5-10H2O |
| 8.EB.05 | Rauchite | Ni(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Uranocircite | Ba(UO2)2(PO4)2 · 10H2O |
| 8.EB.05 | Uranospinite | Ca(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Zeunerite | Cu(UO2)2(AsO4)2 · 12H2O |
| 8.EB.05 | Metarauchite | Ni(UO2)2(AsO4)2 · 8H2O |
| 8.EB.05 | Heinrichite | Ba(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Kahlerite | Fe2+(UO2)2(AsO4)2 · 12H2O |
| 8.EB.05 | Hydronováčekite | Mg(UO2)2(AsO4)2 · 12H2O |
| 8.EB.05 | Torbernite | Cu(UO2)2(PO4)2 · 12H2O |
| 8.EB.05 | Nováčekite | Mg(UO2)2(AsO4)2 · 10H2O |
| 8.EB.05 | Autunite | Ca(UO2)2(PO4)2 · 10-12H2O |
| 8.EB.05 | Saléeite | Mg(UO2)2(PO4)2 · 10H2O |
| 8.EB.05 | Xiangjiangite | (Fe3+,Al)(UO2)4(PO4)2(SO4)2(OH) · 22H2O |
| 8.EB.10 | Bassetite | Fe2+(UO2)2(PO4)2 · 10H2O |
| 8.EB.10 | Lehnerite | Mn2+(UO2)2(PO4)2 · 8H2O |
| 8.EB.10 | Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
| 8.EB.10 | Metasaléeite | Mg(UO2)2(PO4)2 · 8H2O |
| 8.EB.10 | Metauranocircite | Ba(UO2)2(PO4)2 · 7H2O |
| 8.EB.10 | Metauranospinite | Ca(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metaheinrichite | Ba(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metakahlerite | Fe2+(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metakirchheimerite | Co(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metanováčekite | Mg(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Metanatroautunite | Na(UO2)(PO4)(H2O)3 |
| 8.EB.10 | Metatorbernite | Cu(UO2)2(PO4)2 · 8H2O |
| 8.EB.10 | Metazeunerite | Cu(UO2)2(AsO4)2 · 8H2O |
| 8.EB.10 | Przhevalskite | Pb2(UO2)3(PO4)2(OH)4 · 3H2O |
| 8.EB.10 | 'Pseudo-autunite' | (H3O)4Ca2(UO2)2(PO4)4 · 5H2O |
| 8.EB.15 | Abernathyite | K(UO2)(AsO4) · 3H2O |
| 8.EB.15 | Uramphite | (NH4)2(UO2)2(PO4)2 · 6H2O |
| 8.EB.15 | Meta-ankoleite | K2(UO2)2(PO4)2 · 6H2O |
| 8.EB.15 | Natrouranospinite | Na2(UO2)2(AsO4)2 · 5H2O |
| 8.EB.15 | Trögerite | (H3O)(UO2)(AsO4) · 3H2O |
| 8.EB.15 | Chernikovite | (H3O)2(UO2)2(PO4)2 · 6H2O |
| 8.EB.15 | Uramarsite | (NH4)(UO2)(AsO4) · 3H2O |
| 8.EB.20 | Chistyakovaite | Al(UO2)2(AsO4)2(F,OH) · 6.5H2O |
| 8.EB.20 | Threadgoldite | Al(UO2)2(PO4)2(OH) · 8H2O |
| 8.EB.25 | Uranospathite | (Al,◻)(UO2)2(PO4)2F · 20(H2O,F) |
| 8.EB.25 | Arsenuranospathite | Al(UO2)2(AsO4)2F · 20H2O |
| 8.EB.30 | Vochtenite | (Fe2+,Mg)Fe3+(UO2)4(PO4)4(OH) · 12-13H2O |
| 8.EB.35 | Coconinoite | Fe3+2Al2(UO2)2(PO4)4(SO4)(OH)2 · 20H2O |
| 8.EB.40 | Ranunculite | HAl(UO2)(PO4)(OH)3 · 4H2O |
| 8.EB.45 | Triangulite | Al3(UO2)4(PO4)4(OH)5 · 5H2O |
| 8.EB.50 | Furongite | Al13(UO2)7(PO4)13(OH)14 · 58H2O |
| 8.EB.55 | Arsenosabugalite | H0.5Al0.5(UO2)2(AsO4)2 · 8H2O |
| 8.EB.55 | Sabugalite | HAl(UO2)4(PO4)4 · 16H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 29.4151% | 7,353,775 | 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 Horákite
mindat.org URL:
https://www.mindat.org/min-51973.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 Horákite
Reference List:
Hålenius, U., Hatert, F., Pasero, M., Mills, S. J. (2017) New minerals and nomenclature modifications approved in 2017, CNMNC Newsletter No 38. Mineralogical Magazine, 81 (4) 1033-1038 doi:10.1180/minmag.2017.081.062
Localities for Horákite
Showing 1 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) | |
| Hålenius et al. (2017) +2 other references |
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Jáchymov, Karlovy Vary District, Karlovy Vary Region, Czech Republic