Journal of Geosciences, 60 (2015), 113–121

DOI: 10.3190/jgeosci.192

Original paper

Svornostite, K2Mg[(UO2)(SO4)2]2∙8H2O, a new uranyl sulfate mineralfrom Jáchymov, Czech Republic
Jakub PLÁŠIL1*, Jan Hloušek2,†, Anatoly V. Kasatkin3, Milan Novák4, Jiří Čejka5,
Ladislav Lapčák6
1

Institute of Physics, Academy of Sciences of the Czech Republic v.v.i., Na Slovance 2, 182 21 Prague 8, Czech Republic; plasil@fzu.cz
U Roháčových kasáren 24, 100 00 Prague 10, Czech Republic
3
Fersman Mineralogical Museum of the Russian Academy of Sciences, Leninsky Prospekt 18-2, 119071 Moscow, Russia
4
Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
5
Department of Mineralogy and Petrology, National Museum, Cirkusová 1740, 193 00 Prague 9, Czech Republic
6
Institute of Chemical Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic†deceased on April 27, 2014
* Corresponding author
2

Svornostite (IMA2014-078), K2Mg[(UO2)(SO4)2]2∙8H2O, is a new uranyl sulfate mineral from Jáchymov, Western Bohemia,
Czech Republic. The new mineral was found in material originating from the Geschieber vein in the Svornost mine. It
occurs as crystalline crusts composed of yellow prismatic crystals on a gangue along with geschieberite, adolfpateraite
and gypsum. It is a low-temperature, supergene mineral formed by the post-mining weathering of uraninite. Svornostite
is orthorhombic, the space group Pmn21, with the unit-cell parameters a = 12.7850(3), b = 8.2683(4), c = 11.2163(3) Å,
V= 1185.68(7) Å3 and Z = 2. Crystals are long prisms elongated on [001] and flattened on {100}. Crystals exhibit theforms {100}, {010} and {011}, usually forming multiple intergrowths. Svornostite is light yellow and has a very pale yellow streak. It exhibits a strong yellowish-green fluorescence under both long-wave and short-wave UV. It is translucent
to transparent with strong vitreous luster. The mineral has a Mohs hardness ~2; it is brittle, with uneven fracture and aperfect cleavage, on {100} and {010}. The calculated density based on the empirical formula is 3.268 g/cm3. The mineralis optically biaxial (+), with α = 1.548(2), β = 1.556(3) and γ = 1.585(2) (measured at 590 nm). The 2V was not measured,calculated value is 56°. Birefringence is 0.037. No dispersion or pleochroism was observed. The optical orientation isZ = c. Chemical analysis (EDS, 6 spots) is K2O 7.93, MgO 3.11, CuO 0.79, SO3 28.13, UO3 48.94, H2O (calc.) 12.53, total
101.43 wt. %, which yields the empirical formula K1.94(Mg0.89Cu0.11)Σ1.00(U0.99O2)2(S1.01O4)4(H2O)8 (based on 28 O apfu).
Prominent features in the Raman spectrum include the O–H stretching vibrations, symmetric stretching vibrations of(UO2)2+ ion, and stretching and bending vibrations of symmetrically non-equivalent SO4 groups. The eight strongest
powder X-ray diffraction lines are [dobs Å (Irel.) (hkl)]: 8.279(50)(010), 6.398(100)(200), 5.060(55)(210), 4.645(40)(012),
4.610(38)(211), 3.881(34)(021), 3.318(44)(221), 3.009(44)(213). The crystal structure of svornostite (R = 0.023 for 2745
reflections with Iobs > 3σ[I]) contains infinite uranyl sulfate chains of composition [(UO2)(SO4)2(H2O)]2– parallel to (001).
The adjacent chains are linked through the Mg2+-octahedra linked to the apical O atoms of the SO4 groups with the chains
and additionally by the K–O bonds and also H-bonds involving H2O molecules. The uranyl sulfate chains are the same
as found in the structures of several others uranyl sulfate minerals.
Keywords: svornostite, new mineral, uranyl sulfate, crystal structure, bond-valence, Jáchymov
Received: 10 February 2015; accepted: 24 March 2015; handling editor: F. Laufek
The online version of this article (doi: 10.3190/jgeosci.192) contains supplementary electronic material.

1. Introduction
Uranyl sulfates typically occur as supergene alteration
products after hydration-oxidation weathering of uraninite (Plášil 2014). They are relatively common sinceuraninite is often associated with sulfides such as pyrite,
marcasite or chalcopyrite (Finch and Murakami 1999;
Krivovichev and Plášil 2013). Uranyl sulfates usuallyform during oxidizing weathering of sulfides and U oresin the old mining workings by the process connected tothe acid mine drainage (AMD) (Fernandes et al. 1995;

Brugger et al. 2003; Johnson 2003; Johnson and Hallberg
2005), generating highly mobile acid solutions containing
dissolved UO22+.
Svornostite is further new uranyl sulfate mineral foundin Jáchymov (Joachimsthal), Czech Republic. The newmineral and the name were approved by the Commission
for the new Minerals, Names and Classification of International Mineralogical Association (IMA2014-078). The
new mineral was named after the type locality, abandoned
Svornost mine (also known as Einigkeit in German). The
holotype specimen is deposited in the collections of the
www.jgeosci.org

Jakub Plášil, Jan Hloušek, Anatoly V. Kasatkin, Milan Novák, Jiří Čejka, Ladislav Lapčák

Fersman Mineralogical Museum of the Russian Academyof Sciences, Moscow, Russia, registration number 4537/1.

2. Occurrence
Svornostite was found on a single specimen collectedfrom Geschieber vein on the 5th level of the Svornost
mine, Jáchymov, Western Bohemia, Czech Republic by
one of the authors (JH). The description of the locality and its geological setting has been already given indetail elsewhere (e.g., Ondruš et al. 1997, 2003; Tvrdý
and Plášil 2010; Hloušek et al. 2014). The Jáchymov ore
district is a classic example of the Variscan hydrothermalvein type of deposit, so-called five-elements formation,
Ag–Bi–Co–Ni–(U). Jáchymov is the type locality for
43 minerals and more than 430 minerals have been identified from there.
Minerals found in direct spatial association withsvornostite include geschieberite, K2(UO2)(SO4)2·2H2O(IMA2014–006; Plášil et al. 2014a) and adolfpateraite(Plášil et al. 2012). Minerals are of supergene origin andformed during alteration during post-mining processes.

Tab. 1 Results of chemical analyses (in wt. %) of svornostite
Mean (n = 6)
Range
7.93
7.34–8.71
K 2O
MgO
3.11
2.75–3.93
CuO
0.79
0.00–2.40
SO3
28.13
25.44–30.70
UO3
48.94
44.99–51.72
H 2O
12.53*
Total
101.43* calculated from the structure
SD – standard deviation

SD
0.48
0.45
1.23
2.51
2.74

Standard
Microcline
OlivineCu (metal.)BaSO4 (synth.)
UO2 (synth.)and {010}, and uneven fracture. The Mohs hardness isestimated at 2. A density of 3.268 g/cm3 was calculated
based on the unit-cell dimensions from single-crystal
X-ray data and on the empirical formula from electron
microprobe results. Svornostite shows strong yellowishgreen fluorescence under both long- and short-wave UV
radiation. The mineral is optically biaxial positive, with
α = 1.548(2), β = 1.556(3) and γ = 1.585(2) (measured
at 590 nm), birefringence of 0.037 and 2Vcalc. = 56°. No
dispersion or pleochroism was observed. The opticalorientation is Z = c. The Gladstone-Dale compatibility,
1 – (Kp/Kc), is good (0.039) for the empirical formula andthe single-crystal unit-cell.

3. Physical and optical properties
Svornostite forms markedly elongated prisms (Fig. 1)
in multiple intergrowths. Crystals, up to 0.2 mm across,are flattened on {100} and elongated parallel to [001].
It is light yellow in crystals and bright yellow in larger
aggregates with a very pale yellow streak. Crystals aretransparent to translucent (if thicker) with a vitreous
luster. They are brittle, with a perfect cleavage on {100}4. Chemical composition
The chemical composition of svornostite was determinedusing a CamScan4D scanning electron microscope (SEM)
equipped with an Oxford Link ISIS energy-dispersive Xray spectrometer. An operating voltage of 20 kV was usedwith a beam current of 500 pA and a 1 μm beam diameter.
The EDS mode on the SEM was chosen for the analysis
instead of the WDS mode on
the electron microprobe (EMP)
because svornostite was foundto be less stable under the highvacuum and higher probe current. A special attention was
paid to the overlap of the U andK lines in the EDS spectrum,
thus to the good resolution of
the KK α and UM α analyticallines during measurement ofK; the U content was measured
using the ULα line. The content
of molecular H2O was not deterFig. 1 Bright-yellow prismatic crystalsof svornostite in association with greenish geschieberite (IMA2014-006) andcoatings of white gypsum on alteredgangue from Jáchymov. Width of imageis 2.5 mm (photo P. Škácha).

114

Svornostite, a new uranyl sulfate mineralmined directly, because of the paucity of pure material forthermal analysis. The H2O content was calculated fromstoichiometry obtained from the structure model. Presenceof H2O was independently proven by Raman spectroscopy.
The empirical formula of svornostite, calculated as
the mean of 6 representative spot analyses (Tab. 1),
is K 1.94 (Mg 0.89 Cu 0.11 ) Σ1.00 (U 0.99 O 2 ) 2 (S 1.01 O 4 ) 4 (H 2 O) 8
(based on 28 O apfu). The simplified formula,
K2Mg(UO2)2(SO4)4(H2O)8, requires K2O 8.05, MgO 3.43,
UO3 48.89, SO3 27.32, H2O 12.31, total 100 wt. %.

5. Raman spectroscopy
A Raman spectrum of svornostite (Fig. 2) was collected in
the range 50–3500 cm–1 using a DXR dispersive Raman
spectrometer (Thermo Scientific) mounted on a confocal Olympus microscope (100× objective). The Raman
signal was excited by a 532 nm diode-pumped solid-statelaser and detected by a CCD detector. The experimental
parameters were: 5 s exposure time, 32 exposures, 400
lines/mm grating, 50 mm slit spectrograph aperture and2.5 mW laser power level. The instrument was set up bya software-controlled calibration procedure using multiple
neon emission lines (wavelength calibration), multiple
polystyrene Raman bands (laser frequency calibration)and standardized white-light sources (intensity calibration).
The general features of the vibration spectra of uranylsulfate minerals and their characteristics were thoroughly
reviewed by Čejka (1999). Recently, Raman spectra ofseveral structurally related uranyl sulfates, among others
bobcookite, NaAl(UO2)2(SO4)4·18H2O (IMA2013-030,
Kampf et al. 2014) were investigated. We based the assignment and interpretation of the Raman spectrum ofsvornostite on the similarities with the spectra of bobcookite and oppenheimerite, and also on the well-resolved
Raman spectrum of natural zippeite (Plášil et al. 2010).
Interestingly, svornostite spectrum contains wellresolved O–H stretching vibrations, which is uncommon
in case of unpolarized Raman spectroscopy. However,similarly well-resolved bands in the O–H stretchingregion were observed in the spectrum of bluelizardite(Plášil et al. 2014b) or plášilite (Kampf et al. 2015a). Raman bands at 3622, 3545 and 3496 cm–1 in the svornostite

Fig. 2 The Raman spectrum of svornostite.

115

Jakub Plášil, Jan Hloušek, Anatoly V. Kasatkin, Milan Novák, Jiří Čejka, Ladislav Lapčák

spectrum are attributed to υ O–H stretching vibrations ofsymmetrically distinct H2O molecules. The O–H...O hydrogen bond lengths, inferred using the empirical relation
given by Libowitzky (1999), vary in the range ~3.2 to
2.9 Å. These values are consistent with the O…O interatomic distances of the corresponding hydrogen- bonded
H2O molecules inferred from the X-ray structure study.
Bands at 1220, 1200, 1155 and 1110 cm–1 are attributed
to triply degenerate υ3 (SO4)2– antisymmetric stretchingvibrations and those at 1028 and 989 cm–1 to υ1 (SO4)2–
symmetric stretching vibrations. A very weak band at
951 and a very strong one at 854 cm–1 are assigned to υ3(UO2)2+ antisymmetric and υ1 (UO2)2+ symmetric stretching vibrations, respectively. The approximate U–O bondlength inferred from the respective wavenumbers of the(UO2)2+ vibrations after Bartlett and Cooney (1989) is~1.76 Å, which is in line with the bond lengths obtained
from the structure refinement. A very weak band at
725 cm–1 is probably connected with libration of H2O
molecules. Bands at 643 and 610 cm–1 are attributed totriply degenerate υ4 (δ) (SO4)2– bending vibrations, andthose at 458 and 438 cm–1 to υ2 (δ) (SO4)2– bending vibrations. A weak band at 322 cm–1 can be assigned to the υ(U–Oligand) vibration. A weak band at 268 cm–1 together
with a shoulder at 207 cm–1 may probably be assigned to
split, doubly degenerate υ2 (δ) (UO2)2+ bending vibrations.
However, the shoulder may be related to a set of lattice
vibrations at 186, 132 and 75 cm–1. From the number ofobserved bands of (SO4)2– vibrations it may be inferredthat structurally (symmetrically) distinct (SO4)2– groups
are present in the structure of svornostite.

6. X-ray crystallography andstructure determination

6.1. Powder diffraction
X-ray powder diffraction data (Tab. 2) were obtained
from a hand-picked sample using a PANalytical Empy-

Tab. 2 Powder diffraction data for svornostite
Irel
dobs
50
8.279
2
6.901
32
6.661
100
6.398
20
5.613
55
5.060
40
4.645
38
4.610
1
4.359
23
4.217
5
4.137
2
3.983
34
3.881
29
3.757
7
3.588
24
3.409
6
3.330
44
3.318
6
3.218
22
3.197
44
3.009
4
2.986
14
2.955
5
2.884
6
2.800
19
2.776
4
2.758
16
2.679
10
2.658
5
2.634
3
2.602
6
2.570
d values quoted in Å

116

dcalc

Icalc

h

k

l

Irel

dobs

dcalc

Icalc

h

k

l

8.275
6.947
6.660
6.393
5.611
5.059
4.644
4.612
4.365
4.217
4.137
3.985
3.882
3.757
3.590
3.409
3.330
3.318
3.222
3.197
3.008
2.982
2.953
2.882
2.806
2.775
2.758
2.679
2.657
2.633
2.601
2.569

48
<1
27
100
18
52
40
37
2
24
3
2
35
30
2
27
5
49
1
27
50
7
15
8
8
17
1
17
10
10
1
8

0
1
0
2
0
2
0
2
1
2
0
3
0
2
3
0
0
2
1
4
2
4
2
4
0
0
0
0
0
4
1
2

1
1
1
0
0
1
1
1
1
0
2
0
2
1
1
1
2
2
2
0
1
1
2
1
0
2
3
3
1
1
1
0

0
0
1
0
2
0
2
1
2
2
0
1
1
2
1
3
2
1
2
0
3
0
2
1
4
3
0
1
4
2
4
4

11
5
5
15
10
6
1
1
3
3
3
6
3
5
17
1
3
3
11
2
4
2
4
5
2
6
6
7
6
6
13

2.546
2.533
2.476
2.470
2.467
2.454
2.431
2.385
2.331
2.308
2.236
2.220
2.206
2.109
2.097
2.090
2.068
2.063
2.053
2.045
2.030
1.99381.9736
1.96781.95691.94081.93581.88611.8704
1.86671.8574

2.545
2.533
2.475
2.470
2.468
2.454
2.430
2.387
2.332
2.308
2.240
2.220
2.211
2.109
2.095
2.088
2.069
2.064
2.053
2.043
2.030
1.9923
1.97281.9682
1.9572
1.94101.93691.88511.8703
1.8681
1.8573

13
5
5
11
10
6
<1
1
6
3
1
7
1
7
16
1
3
6
13
6
6
6
6
3
3
6
5
11
6
9
17

2
2
0
2
4
2
1
5
4
2
5
0
1
4
4
4
0
6
4
4
6
6
0
2
4
0
6
2
0
6
2

2
3
3
3
2
1
3
1
1
3
1
3
0
0
2
3
4
1
3
1
1
0
2
4
3
4
1
2
0
2
4

3
0
2
1
1
4
2
1
3
2
2
3
5
4
3
0
0
0
1
4
1
2
5
0
2
2
2
5
6
1
2

Svornostite, a new uranyl sulfate mineralrean diffractometer equipped with a
PIXcel3D detector using CuKα radiation (45 kV, 40 mA) and operating in
Debye-Scherrer geometry provided
by focusing Göbel mirror optics.
Data were collected in the range
3–50° 2θ, with the step size of 0.01°
and counting time of 2 s per step, using an accumulation of 20 scans toimprove the intensity statistics. Positions and intensities of diffractions
were refined using a pseudo-Voigt
shape function with the High-Score(PANalytical) program. Unit-cellparameters were refined by leastsquares with the Celref program(Laugier and Bochu 2003). The
theoretical pattern, used for indexing the experimental dataset, wascalculated from the structure datausing PowderCell (Kraus and Nolze
1996). Refined unit-cell parametersof svornostite obtained from powder
data are a = 12.787(3), b = 8.275(2),c = 11.222(3) Å, with V = 1187.5(5)Å3 and Z = 2.

6.2.	Single-crystal X-ray
diffraction and structure solution
A prismatic single crystal ofsvornostite, with dimensions
0.24 × 0.07 × 0.05 mm, was selectedunder the microscope and examined using an Oxford Diffraction
Gemini single-crystal diffractometer with an Atlas CCD detector
using monochromatized MoKα radiation, with a fibre-optic Mo-Enhance collimator. The unit-cell dimensions were refined from 10483
reflections by least-squares with
the CrysalisPro package (Agilent
Technologies 2014). According toTab. 3 Crystallographic data and refinement details for svornostite
Crystal data
FormulaCrystal system
Space group
Unit-cell parameters: a, b, c [Å]Unit-cell volume [Å3]Z
Calculated density [g/cm3]
Crystal size [mm]K2Mg[(UO2)(SO4)2]2(H2O)8
orthorhombic
Pmn21
12.7850(3), 8.2683(4), 11.2163(3)1185.68(7)23.280
0.235 × 0.068 × 0.052

Data collection
Diffractometer
Temperature [K]Radiation, wavelength [Å]θ range for data collection [º]Limiting Miller indicesAxis, frame width (º), time per frame (s)Total reflections collected
Unique reflections
Unique observed reflections, criterion
Absorption coefficient [mm–1], type
Tmin/Tmax
Rint
F000

Oxford Diffraction Gemini with Atlas detector
300
MoKα, 0.71073 (50 kV, 30 mA)
2.9029.30
h = –17→16, k = –11→11, l = –14 → 14
ω, 0.8, 350
19142
3108
2745, [I > 3σ(I)]14.492; multi-scan
0.574/1
0.047
1044Structure refinement by Jana2006
No. of ref. param., restraints, constraints
R, wR (obs)
R, wR (all)
GOF obs/all
Weighting scheme, weights
Largest diff. peak and hole (e–/Å3)
Absolute structure parameter, Friedel pairs

Full-matrix least-squares on F2
179, 1, 00.0230, 0.0567
0.0280, 0.0587
1.38, 1.34
σ, w =1/(σ2(I)+0.0004I2)–0.98, 1.40
0.018(9), 1410

Twin matrix

 -1 0 0 
 0 -1 0 
 0 0 - 1Fig. 3 The crystal structure of svornostite
viewed down c. Infinite uranyl sulfate chains(blue and yellow, respectively) run parallelto the viewing direction. Adjacent chains arelinked by Mg-octahedra (orange), the K–O
bonds (K atoms are violet) and a H-bondnetwork (not displayed); O atoms are red
spheres. Unit-cell edges are outlined by thesolid black line.

117

118

x/a

y/b

z/c

U1
0.755069(14)0.61283(2)0.85798(4)K1
0.5
0.2719(3)0.8707(3)K2
10.8826(4)1.0339(4)Mg
10.1579(4)0.6665(3)S10.74623(12)0.2420(3)0.6685(2)S20.77026(15)0.2595(3)1.0488(2)O110.1964(12)0.8516(10)O2
0.6640(4)0.1643(6)0.7344(5)O3
0.6577(4)0.2552(6)1.0454(5)O40.8137(4)0.3955(5)0.9763(5)O50.8405(4)0.1447(6)0.6649(5)O60.8206(5)0.1104(5)1.0052(5)O70.8086(4)0.2879(6)1.1735(4)O8
0.7089(4)0.9027(5)0.8698(7)O90.7065(4)0.2736(6)0.5468(4)O10
10.9163(9)0.6856(7)O11
0.5
0.4422(10)0.6289(7)O120.8850(3)0.6619(6)0.8231(4)O13
0.6239(3)0.5657(6)0.8945(4)O14
10.1207(16)1.2173(10)O1511.0993(12)0.4828(9)O160.7725(5)0.4015(7)0.7218(6)O171
0.4055(8)0.6389(6)* − refined with isotropic atomic displacement parameters

Atom0.01161(6)0.0351(7)0.0475(11)0.0288(11)0.0156(6)0.0127(5)0.061(3)0.0320(17)0.0274(16)0.0221(17)0.0257(16)0.0307(19)0.0230(15)0.0265(15)0.0216(15)0.0145(17)*0.041(3)0.0231(15)0.0231(15)0.071(5)0.041(3)0.038(2)0.023(2)

Ueq/Uiso0.00883(10)0.0118(10)0.0078(9)0.0323(14)0.074(2)0.0316(19)0.027(4)0.031(3)0.028(3)0.024(3)0.036(3)0.035(3)0.014(2)0.024(3)0.007(2)0.052(5)0.024(3)0.027(3)0.046(7)0.043(6)0.028(3)0.030(4)0.039(5)0.030(3)0.026(2)0.089(10)0.067(7)0.021(3)0.028(4)0.032(5)0.015(2)0.017(2)0.076(10)0.012(4)0.064(5)0.010(3)U33

0.01179(11)0.0133(11)0.0116(10)0.0527(14)0.0395(19)0.030(2)0.134(8)0.037(3)0.034(3)0.019(3)0.022(3)0.020(3)0.027(3)0.011(2)0.026(3)U220.01420(11)0.0217(11)0.0186(8)0.0203(10)0.0288(16)0.0248(19)0.023(4)0.029(3)0.021(3)0.024(3)0.019(3)0.038(4)0.028(3)0.045(3)0.032(3)U11

Tab. 4 Atom coordinates and displacement parameters for the crystal structure of svornostite. The O10 atom refined isotropically.

0−0.004(2)−0.004(2)000.008(3)0−0.00062(8)0.0014(7)−0.0008(8)00000.009(2)−0.005(2)−0.002(2)0.006(2)0.007(2)0.006(2)0.0012(18)0.001(2)U1200.0044(17)−0.0009(17)00−0.008(3)00.00013(18)−0.0004(6)0.0003(8)00000.016(2)−0.003(2)−0.001(2)0.002(2)−0.008(3)0.002(2)−0.006(3)−0.002(2)U13−0.003(4)0.0032(18)0.0075(18)0.018(5)0.024(4)−0.015(2)0.002(3)0.0000(2)−0.0003(8)0.0000(7)−0.0038(14)0.0004(15)0.0017(15)−0.020(7)0.019(2)0.009(2)0.0127(19)−0.005(2)−0.011(2)−0.0063(19)0.005(2)0.0019(18)U23

Jakub Plášil, Jan Hloušek, Anatoly V. Kasatkin, Milan Novák, Jiří Čejka, Ladislav Lapčák

single-crystal X-ray data, svornostite
is orthorhombic with a = 12.7850(3),b = 8.2683(4), c = 11.2163(3) Å,V = 1185.68(7) Å3 and Z = 2. Of the 19142
collected reflections, 3108 were independent and 2745 were classified as observed
based on the criterion [Iobs > 3σ(I)]. Data
were corrected for Lorentz effect, polarization factor and background and an
empirical (multi-scan) correction for absorption was applied to the dataset using
the ABSPACK3 algorithm implemented in
the RED routine of the CrysAlis software(Agilent Technologies 2014), leading to
Rint of 0.047. Other details of the data collection are given in Tab. 3.
The crystal structure of svornostite
was solved by the charge-flipping algorithm implemented in the Superflip program (Palatinus and Chapuis 2007) andsubsequently refined using the software
Jana2006 (Petříček et al. 2006, 2014) withthe full-matrix least-squares refinement
based on F2. The reflection conditions andstatistics indicated orthorhombic primitive
cell and the non-centrosymmetric spacegroup Pnm21 was confirmed by the refinement of the structure. Nearly all atoms
with the unit-cell were found by the solution, some of the O atoms were localized
by the difference Fourier syntheses. Nearly
all atoms were refined using harmonic
atomic-displacement parameters. Attempts
to localize hydrogen atoms from the difference Fourier maps failed. The refinement
converged smoothly with final indices ofagreement R = 0.0230 and wR = 0.0567
for 2745 observed reflections with GOF= 1.34 (Tab. 3). The atom coordinates andthe displacement parameters are given in
Tab. 4 and selected interatomic distancesin Tab. 5. Bond-valences are shown in
Tab. 6.

6.3. Description of the crystal   structure

The structure of svornostite (Fig. 3) contains one U, two S, one Mg, two K andeighteen O sites in the asymmetric unit.
The U site, occupied by U6+, is coordinated by 7 O atoms, two of which form
the uranyl ion, UO22+, and five more forma squat pentagonal bipyramid. This shares

Svornostite, a new uranyl sulfate mineralfour of the equatorial vertices with sulfate tetrahedra suchthat each tetrahedron is linked to two uranyl bipyramids
to form an infinite chain (Fig. 4). The free, non-linking
equatorial vertex of the uranyl bipyramid is occupied byan H2O molecule. The Mg site is coordinated octahedrally
by six ligands including two O atoms and four H2O molecules. The O atoms of the Mg octahedra belong to SO4
tetrahedra of the chains. Therefore, Mg octahedra linkadjacent chains (Fig. 3). Additional linkage is provided
by the K–O bonds, involving either O atoms of the SO4groups or OUranyl atoms. Acceptors of the H–bonds (Tab.
6) within the structural units are the O12Uranyl atom,which can accept two H–bonds, the O3Sulphur atom, which
can accept one H–bond, O6 Sulphur, which can accept
two H–bonds and O13Uranyl and O12Uranyl atoms, which
also can accept one H–bond. The structural formula ofsvornostite obtained from the refinement is K2Mg[(UO2)(SO4)2(H2O)]2(H2O)6. The EDS showed possibly Cu2+ tobe entering most probably the octahedrally coordinatedMg site; however, this theory was not substantiated by
the structure refinement.

7. Discussion – structure topology andstructure relations
The infinite uranyl sulfate chains present in the structureof svornostite are a well-known structural feature foundin other uranyl sulfates, e.g., in bobcookite (IMA2014030), NaAl(UO2)2(SO4)4·18H2O (Kampf et al. 2014), or
the synthetic compounds K2[(UO2)(SO4)2(H2O)](H2O)(Ling et al. 2010) and Mn(UO2)(SO4)2(H2O)5 (Tabachenko et al. 1979).
It should be noticed here that svornostite is structurally
very similar to the group of synthetic compounds preparedby Serezhkin and Serezhkina (1977, 1978, 1982) and by
Tabachenko et al. (1979). These synthetic uranyl sulfate
hydrates M2+[(UO2)(SO4)2].xH2O have layered structures(x ~ 11) or chain structures (x ~ 5); in all of them the[(UO2)(SO4)2(H2O)]2– units are present. The structural
relations among these units were studied in detail especially in case of the Mg2+-containing compounds. Uranium coordination polyhedra
are pentagonal [(UO2)O4(H2O)]
bipyramids. Each uranyl ion
coordinates four monodentate
sulfate groups and one watermolecule as in svornostite. Layer structures (x ~ 11H2O), where
the [M2+(H2O)6]2+ octahedra andremaining water molecules are

Tab. 5 Selected interatomic distances (Å) and angles (°) in the structureof svornostite
U–O12
U–O13
U–O4
U–O7i
U–O8
U–O9ii
U–O16<U–OUr><U–Oeq>
K1–O2
K1–O2iii
K1–O3
K1–O3iii
K1–O11
K1–O13
K1–O13iii
K1–O15ii<K1–O>
O1–O4
O1–O4iv
O1–O5
O1–O5iv
O1–O6
O1–O6iv
O1–O10v
O1–O17
O2–O5
O2–O8vO2–O9
O2–O11O2–O14vi
O2–O16
O3–O4

1.754(4)1.770(4)2.356(5)2.370(5)2.472(4)2.368(5)2.331(6)
1.762
2.379
2.743(6)2.743(6)2.815(5)2.815(5)3.056(9)2.912(5)2.912(5)3.317(10)2.914
3.216(9)3.216(9)2.954(9)2.954(9)2.955(9)2.955(9)2.971(13)2.946(13)2.392(7)2.704(7)2.354(7)3.329(8)3.160(11)2.406(8)2.434(7)

S1–O2
S1–O5
S1–O9
S1–O16<S1–O>

1.436(6)1.449(5)1.480(5)1.486(6)
1.463

S2–O3
S2–O4
S2–O6
S2–O7
<S2–O>

1.440(5)1.495(5)1.474(5)1.501(5)1.478

K2–O1v
K2–O2iK2–O6v
K2–O9iK2–O11i
K2–O12
K2–O14ix<K2–O>

3.304(11)3.099(6)2.985(6)2.943(5)2.889(9)3.329(5)2.847(13)
3.057

Mg–O1
Mg–O5
Mg–O5iv
Mg–O10ix
Mg–O15ix
Mg–O17<Mg–O>

2.100(11)2.042(5)2.042(5)2.009(8)2.117(10)2.070(7)2.063

O4–O9ii
O4–O11ii
O4–O12O4–O13O4–O16O4–O18v
O5–O8iO5–O9
O5–O10v
O5–O15v
O5–O16O5–O17
O6–O7
O6–O8v
O6–O9vii

2.860(6)3.225(7)2.939(6)2.952(7)2.903(8)2.851(3)3.392(9)2.413(7)2.789(7)2.910(9)2.381(8)2.982(7)2.397(7)2.701(8)3.227(6)O8–O9ii
2.690(8)O8–O12 3.050(7)O8–O13 3.004(6)O8–O14i 3.178(9)O8–O15viii 2.957(7)O9–O11 3.125(6)O9–O12i 2.819(6)O9–O13i 3.064(6)O9–O16 2.384(8)O10–O12 2.994(8)O10–O12iv 2.994(8)O10–O15 2.732(12)O12–O12iv 2.941(6)O12–O16 2.828(8)O12–O17 3.305(7)
O13–
O3–O6
2.445(7) O6–O14 3.305(10)3.167(6)O13iiiO13–
2.717(8)3.341(10)O3–O7
2.421(7) O7–O8ii
O15viii
ii
ii
O3–O10 2.924(7) O7–O11 3.349(7) O13–O16 3.034(8)O3–O12ii 3.235(7) O7–O12ii 3.019(6) O13–O17ii 3.175(7)O3–O13 3.106(7) O7–O13ii 2.890(6) O14–O15x 2.984(15)O4–O6
2.381(6) O7–O14 2.853(8) O15–O17ix 3.078(12)O4–O7
2.385(7) O7–O16ii 2.822(8) O14–O15x 2.984(15)Symmetry codes: (i) −x+3/2, −y+1, z−1/2; (ii) −x+3/2, −y+1, z+1/2;(iii) −x+1, y, z; (iv) −x+2, y, z; (v) x, y−1, z; (vi) −x+3/2, −y, z−1/2;(vii) −x+3/2, −y, z+1/2; (viii) −x+3/2, −y+2, z+1/2; (ix) x, y+1, z;(x) x, y−1, z+1.

Fig. 4 Infinite uranyl sulfate chain foundin the structure of svornostite; O8 marks
the site occupied by H2O.

119

Jakub Plášil, Jan Hloušek, Anatoly V. Kasatkin, Milan Novák, Jiří Čejka, Ladislav Lapčák

Tab. 6 The bond-valence analysis for svornostite
U S1 S2
K1
K2
Mg ∑BV Species +H
O1
0.04
0.33
0.37 H2O
+1.6
O2
1.66
0.19×2↓ 0.07×2↓
1.92 O
O3
1.64 0.16×2↓
1.80 O
+0.2
O4
0.54
1.42
1.96 OO5
1.60
0.39×2↓ 1.99 O
O6
1.50
0.10×2↓1.60 O
+0.4
O7
0.53
1.37
1.90 OO8
0.43
0.43 H2O+1.6
O9
0.53 1.48
0.11×2↓2.12 OO10
0.43
0.43 H2O
+1.6
O11
0.08
0.13
0.21 H2O+1.8
O12 1.77
0.04×2↓
1.81 O+0.2
O13 1.71
0.12×2↓
1.83 O
+0.2
O14
0.14
0.14 H2O
+1.8
O15
0.04
0.32
0.36 H2O+1.6
O16 0.57 1.45
2.02 OO17
0.36
0.36 H2O+1.6∑BVC 6.08 6.19 5.93 1.06
0.95
2.22
All values are in valence units (vu); ×2↓ – multiplicity; ∑BVC – sumof the bond-valences of cations; ∑BVA – sum of the bond-valences ofanions; +H+ – inferred contribution of the H-bonds; an average H-bondstrength is of 0.2 vu, Odonor–H is equivalent to ~0.8 vu (Schindler and
Hawthorne 2008). Values of +0.2 and +0.4 correspond thus to the acceptance of one or two H-bonds. A value of +1.6 is characteristic of
the transformer H2O group 2*0.8 vu. A value of +1.8 corresponds tothe non-transformer H2O group = ∆ + 2*0.8 + 0.2 vu. Bond valence
parameters are taken from Burns et al. (1997), for U6+–O, and from
Brown and Altermatt (1985) for K+–O, S6+–O and Mg2+–O.
A+

located between the layers, transform in chain structures(x ~ 5H2O) during the partial irreversible dehydration.
During such dehydration process, all H 2O molecules
non-coordinated to metal cations and the two H2O molecules in trans positions of [M2+(H2O)6]2+ octahedra arereleased from the structure. In structures of pentahydrates, the coordination polyhedra involving M2+ consistof four H2O and two terminal O atoms adhering to SO4groups, as in case of svornostite. Chemical formulae ofboth type of compounds are therefore [Mg(H2O)6][(UO2)(SO4)2(H2O)].4H2O and [Mg(H2O)4[(UO2)(SO4)2(H2O)],
respectively.
Acknowledgements. We appreciate kind cooperationof Pavel Škácha, who provided photomicrographs ofsvornostite. Professor V. N. Serezhkin (University ofSamara) is highly acknowledged for e-prints of several
papers of his. The current text benefited from the constructive comments of Nicolas Meisser and Stuart Mills.
František Laufek is thanked for editorial handling of
the manuscript. This research was financially supportedby the post-doctoral grant of the GAČR no. 13-31276P
to JP and by the long-term project DKRVO 2015-02 of
the Ministry of Culture of the Czech Republic (National
Museum 00023272) to J. Č.

120

Electronic supplementary material. Supplementary crystallographic data for this paper are available online at the
Journal web site (http://dx.doi.org/10.3190/jgeosci.192).

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