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Horákite

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About HorákiteHide

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.


Classification of HorákiteHide

Approved
Approval Year:
2017
First Published:
2018

Physical Properties of HorákiteHide

Vitreous
Transparency:
Transparent, Translucent
Colour:
Greenish-yellow to pale yellow
Streak:
Light yellow
Hardness:
Hardness Data:
Estimated
Cleavage:
Perfect
on {100}
Density:
6.358 g/cm3 (Calculated)

Optical Data of HorákiteHide

Type:
Biaxial (+)
RI values:
nα = 1.810 nβ = 1.810 nγ = 1.880
2V:
Measured: 78° , Calculated: 83°
Max Birefringence:
δ = 0.070
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Very High
Pleochroism:
Non-pleochroic
Comments:
Optical orientation is X = b, Z ≈ c

Chemical Properties of HorákiteHide

Formula:
(Bi7O7OH)[(UO2)4(PO4)2(AsO4)2(OH)2] · 3.5H2O

Crystallography of HorákiteHide

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)°
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 DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
11.77(100)
6.21(23)
5.55(23)
4.185(27)
3.543(61)
3.287(20)
3.144(58)
3.017(98)
Comments:
From Type Description.

Type Occurrence of HorákiteHide

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:
Reference:
Plášil, J., Kampf, A.R., Sejkora, J., Čejka, J., Škoda, R., Tvrdý, J. (2018): Horákite, a new hydrated bismuth uranyl-arsenate-phosphate mineral from Jáchymov (Czech Republic) with a unique uranyl-anion topology. Journal of Geosciences, 63: 265-276.

Synonyms of HorákiteHide

Other InformationHide

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for HorákiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Plášil, J., Kampf, A.R., Sejkora, J., Škoda, R. and Tvrdý, J. (2017) Horákite, IMA 2017-033. CNMNC Newsletter No. 38, August 2017, page 1036; Mineralogical Magazine: 81: 1033–1038.
Plášil, J., Kampf, A.R., Sejkora, J., Čejka, J., Škoda, R., Tvrdý, J. (2018): Horákite, a new hydrated bismuth uranyl-arsenate-phosphate mineral from Jáchymov (Czech Republic) with a unique uranyl-anion topology. Journal of Geosciences, 63: 265-276.

Internet Links for HorákiteHide

Localities for HorákiteHide

ⓘ - Click for 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). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Czech Republic (TL)
 
  • Karlovy Vary Region
    • Krušné Hory Mts (Erzgebirge)
      • Jáchymov District (St Joachimsthal)
        • Jáchymov (St Joachimsthal)
Plášil, J., Kampf, A.R., Sejkora, J., Škoda, R. and Tvrdý, J. (2017) Horákite, IMA 2017-033. CNMNC Newsletter No. 38, August 2017, page 1036; Mineralogical Magazine: 81: 1033–1038 ;Plášil, J., Kampf, A.R., Sejkora, J., Čejka, J., Škoda, R., Tvrdý, J. (2018): Horákite, a new hydrated bismuth uranyl-arsenate-phosphate mineral from Jáchymov (Czech Republic) with a unique uranyl-anion topology. Journal of Geosciences, 63, 265-276.
Mineral and/or Locality  
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