American Mineralogist, Volume 91, pages 929–936, 2006

Pseudojohannite from Jáchymov, Musonoï, and La Creusaz: A new member of thezippeite-groupJOËL BRUGGER,1,2,* KIA SHEREE WALLWORK,3,† NICOLAS MEISSER,4 ALLAN PRING,1
PETR ONDRUŠ,5 AND JIŘÍ ČEJKA6
1South Australian Museum, North Terrace, Adelaide, South Australia 5000, Australia
School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
3
Bragg Institute, ANSTO, PMB 1, Menai, New South Wales 2234, Australia
4
Museum of Geology and Institute of Mineralogy and Geochemistry, University, UNIL-BFSH-2, CH 1015 Lausanne, Switzerland
5
Czech Geological Survey, Geologická 6, CZ–15200 Prague, Czech Republic
6
National Museum, Václavské nám. 68, CZ–11579 Prague 1, Czech Republic
2

ABSTRACT
Pseudojohannite is a hydrated copper(II) uranyl sulfate described from Jáchymov, Northern
Bohemia, Czech Republic (type locality). Pseudojohannite also occurs at the Musonoï quarry near
Kolwezi, Shaba, Congo, and the La Creusaz prospect, Western Swiss Alps. At all three localities,
pseudojohannite formed through the interaction of acid sulfate mine drainage waters with uraninite(Jáchymov and La Creusaz) or uranyl silicates (Musonoï). Pseudojohannite forms moss green, non
UV-ßuorescent aggregates consisting of irregularly shaped crystals measuring up to 25 μm in length–and displaying an excellent cleavage parallel to (101). dmeas is 4.31 g/cm3, dcalc 4.38 g/cm3, and therefractive indices are nmin = 1.725 and nmax = 1.740.
A high-resolution synchrotron powder diffraction pattern on the material from Musonoï shows that–pseudojohannite is triclinic (P1 or P1), with a = 10.027(1) Å, b = 10.822(1) Å, c = 13.396(1) Å, α =87.97(1)°, β = 109.20(1)°, γ = 90.89(1)°, V = 1371.9(5) Å3. The location of the uranium and sulfur
atoms in the cell was obtained by direct methods using 1807 reßections extracted from the powder–
diffractogram. Pseudojohannite contains zippeite-type layers oriented parallel to (101). The empiricalchemical formula calculated for a total of 70 O atoms is Cu6.52U7.85S4.02O70H55.74, leading to the simpliÞed
chemical formula Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O. The distance of 9.16 Å between the uranylsulfate sheets in pseudojohannite shows that neighboring layers do not share O atoms with the same
CuΦ6 [Φ = (O,OH)] distorted octahedrons, such as in magnesium-zippeite. Rather, it is expected thatCuΦ6 forms a layer bound to the zippeite-type layers by hydrogen bonding, as in marécottite, or one
apex of the CuΦ6 polyhedron only is shared with a zippeite-type layer, as in synthetic SZIPPMg. The
higher number of cations in the interlayer of pseudojohannite (Cu:S = 1.6:1) compared to marécottite(3:4) and SZIPPMg (1:1) indicates that pseudojohannite has a unique interlayer topology.
Ab-initio powder structure solution techniques can be used to obtain important structural information on complex micro-crystalline minerals such as those found in the weathering environment.
Pseudojohannite represents a new member of the zippeite group of minerals, and further illustrates
the structural complexity of zippeite-group minerals containing divalent cations, which have diverse
arrangements in the interlayer. Peudojohannite and other divalent zippeites are common, easily overlooked minerals in acid drainage environments around uranium deposits and wastes.
Keywords: New mineral, pseudojohannite, uranyl sulfate, XRD data, IR spectroscopy, Jáchymov,
La Creusaz, Musonoï

INTRODUCTION
Pseudojohannite (IMA-2000-019) was described as a newmineral from Jáchymov (St. Joachimsthal), Northern Bohemia,
Czech Republic (Ondruš et al. 1997, 2003), with chemical formula Cu5(UO2)6(SO4)3(OH)16·14H2O and a triclinic unit cell witha = 13.754(2) Å, b = 9.866(1) Å, c = 8.595(2) Å, α = 103.84(2)°,β = 90.12(2)°, γ = 106.75(2)°, V = 1081.3 (4) Å3. The mineral* E-mail: joel.brugger@adelaide.edu.au† Current Address: Australian Synchrotron, 800 Blackburn Road,
Clayton, Victoria 3168, Australia.
0003-004X/06/0506–929$05.00/DOI: 10.2138/am.2006.1885

929

name acknowledges the chemical and paragenetical relationshipwith johannite Cu(UO2)2(SO4)2(OH)2·8H2O (Mereiter 1982).
This paper describes two new occurrences of this rare uranyl
sulfate mineral at Musonoï, Shaba, Congo, and La Creusaz, Western Swiss Alps. Based on analysis of the synchrotron powder diffraction patterns obtained on pseudojohannite from Musonoï, weredeÞne the unit cell, and consequently the chemical formula ofpseudojohannite, and demonstrate that pseudojohannite belongs
to the zippeite-group of minerals. Because the mineralogical dataon pseudojohannite are only brießy described in two separate
publications (Ondruš et al. 1997, 2003), we also present a complete description of the holotype material.

930

BRUGGER ET AL.: PSEUDOJOHANNITE, A NEW MEMBER OF THE ZIPPEITE-GROUP

The holotype of pseudojohannite from Jáchymov has been
split and part is deposited in the mineralogical collection of the
National Museum Prague (Czech Republic) under number P1p
1/2000 and the other part at the Geological Museum of Lausanne(Switzerland) under sample number MGL 79290. Pseudojohannite samples from Musonoï and La Creusaz are deposited at the
Geological Museum of Lausanne (Switzerland) under sample
numbers MGL 54110 and 58324, respectively.

OCCURRENCES
To date, only one sample from the Rovnost (Werner) shaft
at Jáchymov (Northern Bohemia, Czech Republic) is known
to contain pseudojohannite. In this sample, pseudojohannite
grows directly on strongly weathered uraninite containing pyrite,
tennantite, and chalcopyrite (Ondruš et al. 1997, 2003) and isassociated with johannite, uranopilite, and gypsum. Pseudojohannite forms earthy moss green, brittle aggregates up to 5 mm or
coatings with an uneven surface, which are composed of very
Þne crystals with sizes between 1 and 10 μm. Pseudojohannite
shows no ßuorescence under UV light. The measured density ofpseudojohannite from Jáchymov is 4.31 g/cm3, dcalc= 4.38 g/cm3(using the pseudo-monoclinic zippeite cell), and the refractive
indices are: nmin = 1.725 and nmax = 1.740 (Ondruš et al. 1997,
2003).
At the Musonoï quarry near Kolwezi (Shaba, Congo), lightgreen pseudojohannite appears in association with yellow uranopilite and orange-yellow metaschoepite on a saccharoidal
quartz matrix containing many crosscutting veins of kasolite,
α-uranophane, and cuprosklodowskite (sample MGL 54110).
Other associated mineral species are relic Se-bearing digenite,malachite, and a pale blue brochantite. The excellent cleavageof pseudojohannite is visible on SEM photographs (Fig. 1). The
crystals measure up to 25 μm in length, and are ßattened along
the cleavage plane. They coat several cm2 of tiny open veins.
Three specimens of this unique mineral association were bought
in 2002 by the Geological Museum of Lausanne from the Swiss
mineral dealer François Pahud. These samples were collectedby local miners in 1998–2002.
At the La Creusaz U-deposit near Les Marécottes village(canton Valais, Western Alps, Switzerland), pseudojohannite is
directly associated with gypsum, johannite, ktenasite, marécottite (type locality; Brugger et al. 2003), and uranopilite in a
broader paragenesis that also contains Al-bearing coconinoite,
jáchymovite, jarosite, rabejacite, schröckingerite, zippeite s.s.,magnesium-zippeite, and zeunerite (Meisser 2003; Meisser et al.
2002). These minerals encrust blocks of primary ore consisting
mainly of uraninite and quartz. Pseudojohannite forms moss
green earthy aggregates up to 3 mm in size; these aggregates areconstituted by poorly shaped crystals ~10 μm in length.
La Creusaz was explored by drilling, surface scratching,and galleries between 1973–1981 (Meisser 2003; Meisser et al.
2002). Since the end of the underground exploration in 1981, outcropping veins and stockpiled U-ore have been exposed to acidmine drainage water and atmospheric oxygen in the abandoned
galleries. The oxidation of the sulÞdes (mainly pyrite and chalcopyrite) resulted in the production of acid (pH ≥ 3.1), sulfate-richwaters. These waters reacted with uraninite, chamosite, calcite,and siderite to form a rich assemblage of secondary uranyl min-

FIGURE 1. SEM microphotograph of pseudojohannite crystals from
Musonoï (sample MGL 54110). Image width: 50 μm.

erals, including several sulfates. Pseudojohannite samples werecollected among the ore stockpiled in the exploration gallery at
La Creusaz, which remained undisturbed since 1981.
Hence, at La Creusaz, pseudojohannite forms through theinteraction of acid sulfate water resulting from the oxidationof pyrite and chalcopyrite, with uraninite. A similar genesis isprobable at Jáchymov. At Musonoï, the acid drainage waters
probably result mainly from the oxidation of Se-digenite, andpseudojohannite subsequently forms through the reaction withoxidized U-bearing minerals such as kasolite, α-uranophane,and cuprosklodowskite.
The identiÞcation of the material is based on qualitative
chemical analyses showing that the three minerals consist onlyof U, O, S, and Cu, and on the similarity in the X-ray powder
diffraction patterns (Table 1).

X-RAY POWDER DIFFRACTION (MUSONOÏ)Experimental methods
An almost pure sample was loaded into a 0.3 mm diameter silica glass capillary
without further crushing. The diffraction pattern was recorded using synchrotron
radiation in the high-resolution powder diffractometer at the Australian National
Beamline Facility (ANBF) BL-20B at the Photon Factory (KEK), Tsukuba, Japan,(Garrett et al. 1995). Partial diffraction rings were collected on three adjacent image
plates, located 573 mm from the axially spinning sample. Data were collected ata wavelength of 1.4985(2) Å, calibrated by using an alumina reference standard(NBS 674). The data were extracted from the image plates and processed using
the program Python PDA (Hester et al. 1999). The angular range of the data was
6.00–43.00°, 43.23–83.10°, 83.50–120.00°, in steps of 0.010° of 2θ. Even though
the image plates are butted together a small gap (~0.3°) occurs. For structure
analysis and reÞnement the RIETICA (Hunter 1998) and SIRPOW.92 (Altomare
et al. 1994) packages were used.

Unit-cell determination
Attempts to index the pattern using the cell data of Ondruš etal. (2003) were unsuccessful and a new triclinic cell was obtainedusing the program ITO (Visser 1969). This cell, where a = 8.880

BRUGGER ET AL.: PSEUDOJOHANNITE, A NEW MEMBER OF THE ZIPPEITE-GROUPTABLE 1. X-ray powder diffraction pattern of pseudojohannite

931

TABLE 1. —Continued

Musonoï1
Jáchymov2
Musonoï1
Jáchymov2
No.
h k l
dcalc
Icalc
dobs (Å)
Iobs
dobs (Å) Iobs
No.
h k l
dcalc
Icalc
dobs (Å)
Iobs
dobs (Å) Iobs
–
67.
3 2 1
2.852
0.9
2.851
7.7
2.845
10
1.
20.487
1
3 0 1
2.850
6
2.
0 0 1
12.6
<0.1
13.2
7
–
–
68.
3 2 1
2.820
1
2.820
1.1
3.
1 0 1
9.16
100
9.18
100
9.13
100
69.
0 3 3
2.784
7
2.784
11.9
4.
0 1 1
8.35
12
8.37
6
8.33
7
70.
0 2 4
2.768
0.1
2.767
0.7
5.
8.188
2
–
2 2 4
2.764
1
6.
7.921
2
71.
0 4 0
2.704
1
2.704
2.0
7.
1 1 0
7.11
8
7.121
22
7.09
26
72.
2 3 1
2.693
6
2.694
6.7
2.687
13
8.
1 0 1
6.609
0.3
6.625
0.9
–
73.
2 2 4
2.682
1
2.682
2.7
9.
0 0 2
6.322
0.5
6.332
0.8
6.308
1
–
74.
2.672
5
2.673
8.7
2.667
13
10.
1 0 2
6.300
<0.1
6.26
0.1
–1 0 –5
75.
3 1 4
2.663
0.7
2.663
3.8
2.66
13
11.*
6.087
0.2
2 1 3
2.662
0.8
12.
0 1 2
5.536
<0.1
5.535
13
5.511
22
–
–
76.
1 1 –4
2.640
<0.1
2.636
0.3
1 1 2
5.528
5
77.
3 2 3
2.628
0.5
2.629
0.9
2.622
5
13.
0 2 0
5.408
<0.1
5.43
0.4
–
–
78.
3 1 4
2.624
0.3
2.624
0.7
14.
1 1 2
5.364
0.4
5.369
1.2
5.351
3
–
79.
1 4 1
2.613
0.8
2.613
0.7
15.*
4.843
0.4
–
80.
2 3 3
2.585
4
2.585
2.1
2.580
4
16.*
4.820
0.4
–
81.
1 4 1
2.574
0.6
2.574
0.5
17.*
4.795
0.1
–
82.
2 1 5
2.564
0.4
2.564
0.8
2.560
2
18.
2 0 0
4.735
2
4.739
2
4.721
6
–
–
83.
2 1 5
2.525
0.2
2.523
1.4
19.
1 2 1
4.713
0.2
4.717
0.2
–
–
84.
3 2 1
2.518
0.1
2.517
0.3
2.517
3
20.
1 2 1
4.602
0.2
4.615
0.5
–
–
85.
4 0 2
2.504
2
2.504
2.1
21.
2 0 2
4.580
20
4.584
53.2
4.566
80
–
–
86.
1 3 4
2.497
5
2.497
5.7
2.495
12
22.
2 1 1
4.514
2
4.518
1.2
–
87.
2.480
0.8
2.480
0.3
23.
1 0 3
4.429
2
4.433
2.9
4.419
8
–0 1 5
88.
3 3 2
2.455
4
2.455
3.4
2.4518
5
24.*
4.293
0.4
–
89.
0 1 5
2.445
0.1
2.443
0.1
25.
1 1 2
4.270
<0.1
4.273
0.7
–
3 1 2
2.443
0.1
26.
1 2 1
4.214
3
4.215
5.9
4.200
10
–
–
90.
1
2.429
0.2
2.429
0.6
1 1 2
4.205
3
– 2 5
91.
4 1 1
2.422
0.6
2.422
1.5
2.4183
4
27.
0 2 2
4.176
3
4.179
4.2
4.166
8
–
–
92.
3 3 2
2.405
1
2.405
1.3
28.
1 2 1
4.157
3
4.158
0.9
–
–
93.
2.394
2
2.395
2.1
2.3990
5
29.
1 1 3
4.151
<0.1
4.147
2.2
–3 0 5
94.
4 1 3
2.386
0.5
2.386
0.7
2.3905
8
30.*
4.090
0.9
–
95.
3 3 0
2.370
4
2.370
7.8
2.3659
13
31.
0 2 2
4.046
3
4.048
7.7
4.036
8
2.367
3
32.
0 1 3
3.970
0.1
3.973
1.0
3.963
2
–4 0 0
96.
3 3 3
2.361
0.1
2.363
1.1
33.*
3.956
0.9
–
34.
0 1 3
3.885
2
3.887
4.4
3.874
6
–
–
97.
2 –4 2
2.357
0.5
2.357
0.5
36.
2 1 1
3.761
2
3.763
6.5
3.752
7
98.
2 4 0
2.352
0.1
2.352
0.4
2.3408
5
37.*
3.739
1.1
–
–
99.
1 4 3
2.345
0.1
2.344
2.6
38.
2 1 3
3.653
2
3.654
1.2
3.645
4
–
100. –2 4 2
2.301
0.4
2.301
0.3
39.
0 3 0
3.605
<0.1
3.601
0.1
–
101. 4
2.290
2
2.290
4.7
2.2857
14
40.
2 2 0
3.569
2
3.571
4.7
3.560
9
– 0 4
102. 4 2 2
2.287
0.5
2.286
0.5
41.
2 2 0
3.555
2
3.556
2.0
–
–
103. 1 4 3
2.272
0.1
2.272
1.0
42.
2 2 2
3.543
0.4
3.544
0.5
–
104. 4 2 2
2.257
0.6
2.257
0.3
2.2537
2
43.*
3.527
<1
–
2.214
3
2.215
2.8
2.2112
6105. 2 0 6
44.*
3.511
<1
106. –3 3 4
2.208
1
2.208
0.8
45.
0 3 1
3.497
<0.1
3.497
0.6
–
107. 3 0 3
2.203
0.2
2.203
1.3
46.
1 2 3
3.488
2
3.489
3.2
3.480
6
–
108. 2 3 3
2.198
<0.1
2.198
0.2
47.
1 2 2
3.470
<0.1
3.474
2.2
–
109. 1 1 6
2.187
0.5
2.187
1.0
2.1836
2
48.
1 0 3
3.452
12
3.454
18.0
3.443
17
–
–
110. 1 3 5
2.183
<0.1
2.183
<0.1
2 2
3.449
0.4
–
– 2
111. 3 –2 5
2.163
0.5
2.162
0.3
49.
0 3
3.438
12
3.439
12.6
– 1
112. 2 3
2.159
3
2.159
8.9
50.
1 3 0
3.374
11
3.375
18.9
3.367
15
– 3
–
113. 1 3 4
2.154
6
2.154
11
2.151
12
51.
1 2 3
3.368
2
3.367
1.3
–
114. 3 3 4
2.142
2
2.143
5.2
2.1387
8
1 3 0
3.365
0.2
–
0 5 1
2.143
0.7
52.
3 0 1
3.330
2
3.332
3.1
3.321
11
115. –2 2 4
2.135
0.7
2.135
2.0
53.
2 0 2
3.304
10
3.306
16.4
3.298
13
–
116. 4
2.130
0.3
2.130
0.7
54.
1 1 4
3.230
0.3
3.208
0.9
– 2 4
117. 3
2.112
0.2
2.112
0.4
55.
0 0 4
3.161
9
3.162
15.8
3.154
15
– 4 1
–
118. 3 4 2
2.110
0.6
2.110
1.9
56.
2 0 4
3.150
2
3.151
2.8
–
119. 1 –5 0
2.107
0.8
2.107
6.5
2.104
8
57.
3 1 2
3.128
0.9
3.129
1.5
3.122
8
–
120. 1 4 3
2.103
0.4
2.103
4.7
58.
1 3 2
3.083
8
3.084
16.7
–
–
2 2 4
2.102
0.6
59.
3 0 3
3.053
6
3.054
9.1
3.046
26
121.
3 lines ≤ 0.5
2.088
2.9
2.0845
6
60.
3 1 0
3.027
0.2
3.028
0.7
–
122. –2 3 –5
2.083
0.8
2.082
1.4
62.
2 1 4
2.997
<0.1
2.994
1.0
–
4 –1 5
2.081
0.3
63.
2 3 1
2.950
7
2.950
9.6
2.945
10
123. –2 4 2
2.078
0.4
2.078
0.6
64.
1 2 3
2.943
<0.1
2.930
0.6
–
124. 3 1 6
2.075
0.4
2.075
2.7
2.073
4
65.
3 1 3
2.918
<0.1
2.912
0.3
–
125. 1 2 5
2.069
0.6
2.068
3.9
66.
1 3 2
2.869
7
2.869
18.8
2.862
20
Notes: (1) Synchrotron radiation, λ = 1.4985(2) Å; (2) Diffractometer Phillips X’Pert System, CuKα -Ni- filtered radiation, 40 kV, 40 mA. Data from Ondruš et al. (1997)
on holotype. Unindexed line in the Musonoï pattern are starred (*); their intensities are ≤1.1%.

932

BRUGGER ET AL.: PSEUDOJOHANNITE, A NEW MEMBER OF THE ZIPPEITE-GROUP

Å, b = 10.025 Å, c = 8.686 Å, α = 109.467°, β = 103.994°, and γ= 72.115°, V = 684.7 Å3, was transformed into a pseudo-monoclinic cell and the cell parameters were reÞned by Þtting thewhole data set: a = 10.027(1) Å, b = 10.822(1) Å, c = 13.396(1)Å, α = 87.97(1)°, β = 109.20(1)°, γ = 90.89(1)°, V = 1371.9(5)Å3. A cell of higher metric symmetry could not be found by cell
reduction (Le Page and Flack 1995). The pseudo-monoclinic cell,with a volume about twice that of the reduced cell, was preferred
for easy comparison with zippeite-type minerals (see below).
The powder data on pseudojohannite from different localities
were indexed using this pseudo-monoclinic cell (Table 1). This
cell allows all the major lines on the powder diffractogram ofMusonoï to be indexed; a few low intensity (≤1.1%) lines are
unexplained, and are probably related to impurities: for example,
the line at 4.293/0.4 may be gypsum (100%). The original unit
cell given by Ondruš et al. (2003) for pseudojohannite is listed
in Table 2; this cell does not account for all the signiÞcant lines
observed in the synchrotron powder diffraction pattern for theMusonoï specimen. The new pseudo-monoclinic cell accounts
for all lines in the holotype specimen from Jáchymov. Thereis no relationship between the unit cell of Ondruš et al. (2003)
and the new pseudo-monoclinic cell found in this study, and theformer probably represents an artifact of the quality of the datathat could be obtained on the holotype.
Structure model and topology
Intensity data were extracted from the powder pattern in theform of F2obs values using the Le Bail proÞle Þt within RIETICA.
The cell parameters, zero error, scale factor, and peak proÞle
parameters for each of the three histograms were reÞned. A
pseudo-Voigt function was used to model the proÞle shape. The
coefÞcients were reÞned simultaneously but constrained to beequal for all histograms. Space group P1 was chosen for the
reßection extraction. This data extraction afforded 4402 reßections, the Þrst 1807 of which were subsequently input into thedirect methods program SIRPOW.92 in the form: hkl, FWHM,
F2obs. Of the atomic coordinates given in the direct methods
program output, the Þrst eight atoms were found to be U atoms,
and the next three atoms were assigned as S atoms. Due to thesymmetry observed in the coordinates of the U and S atoms, theseatoms were placed at the positions deÞned by a body-centeredcell. Consequently, the space group I1 was assigned; the result-ing Þnal atomic coordinates are given in Table 3. Using thisprocedure, the missing, 4th S position that could not be found in
the P1 reÞnement was located. The residuals were similar forreÞnements in P1 (9.90%) and I1 (9.78%). Note that the body
centering (I1) relates only to the U and S atomic positions; the–mineral itself is triclinic with space group P1 or P1. Althoughthe “heavy” copper atoms were expected to be observed in the
direct method solution, they could not be conclusively assigned,
despite numerous empirical attempts. Fourier difference maps
also failed to reveal the location of the copper atoms.
The topology of the U and S atoms in the structural model
presented herein is such that they occur in layers oriented parallel–to (101); the distance between each layer is 9.16 Å. Within thelayers, the U atoms form inÞnite double chains extending along– –[1 1 1], separated by a single row of sulfur atoms (Fig. 2). This
topology corresponds to the zippeite-type layer (Fig. 2). The
case for the zippeite-type structure is also supported by the U:
S ratio of 2:1 (Table 4), as in other zippeite structures (Brugger
et al. 2003; Burns et al. 2003). IR spectroscopy further supports
this conclusion (see below).

INFRARED SPECTROSCOPY
The IR spectrum of pseudojohannite was recorded using the
KBr technique on the type material from Jáchymov (Fig. 3; Table
5). A strong band at 874 cm–1 is assigned to the antisymmetricstretching vibration ν3 (UO2)2+. The wavenumber of this vibration is lower than the wavenumbers observed in the IR spectraof johannite (911 cm–1 with a shoulder at 936 cm–1; Čejka et al.
1988), jáchymovite (902–904 cm–1; Čejka et al. 1996), uranopilite (895–900 and 929–931 cm–1; Čejka et al. 1996), rabejacite(901–906 cm–1; Sejkora et al. 2000), and of one of two zippeite
groups (~910 cm–1; Čejka 1999). However, the wavenumber ofthe ν3 (UO2)2+ of pseudojohannite is comparable with that of
the second zippeite group (870 to 883 cm–1; Čejka 1999), which
includes zippeite sensu stricto, NH+4 -zippeite, Co-zippeite, andZn-zippeite. The close relationship between pseudojohannite andthe zippeite-group is further emphasized by the similarity of the
IR spectra of pseudojohannite and zippeite (Fig. 3).
The symmetric stretching vibration ν1 (UO2)2+ may be observed at 831 cm–1; however, there may be a coincidence with theδ U-OH bending vibration. The uranyl bond lengths calculatedwith the available empirical relations are:

TABLE 2. Comparison of the chemical formulas and unit-cells parameters of pseudojohannite, marécottite, and magnesium-zippeite
Details
Diffractometer (CuKα),cell based on 20 lines.
Synchrotron, λ = 1.4985(2) Å,
4402 lines used in refinement.
Gandolfi Camera (CuKα),cell based on 11 lines.*
Ondruš et al. 1997.†

Locality

S. G.
a (Å)
b (Å)
c (Å)
Pseudojohannite, Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O–
Jáchymov, Czech Republic
P1 or P1 10.0277
10.8175 13.3955
Musonoï, Congo–
P1 or P1

α (°)

β (°)

γ (°)

V (Å3)

88.005109.21190.8641362.4(8)10.027(1)10.822(1) 13.396(1) 87.97(1) 109.20(1) 90.89(1) 1371.9(5)La Creusaz, Switzerland

10.03(4)10.86(3)Jáchymov, Czech Republic

8.595(2)9.866(1) 13.754(2) 106.75(2)13.42(7)88.0(2)109.2(4)91.1(2) 1380(6)90.12(2) 103.84(2) 1081.2

Marécottite Mg3(H2O)18[(UO2)4O3(OH)(SO4)2]2(H2O)10–
La Creusaz, Switzerland
P1
10.815(4) 11.249(4) 13.851(6) 66.224(7) 72.412(7) 69.95(2) 1422.1(9)Magnesium-zippeite Mg(H2O)3.5(UO2)2(SO4)O2
Synthetic (structure on Zn-isomorph) C 2/m
8.654(3) 14.182(6) 17.714(7)103.92*Unit cells refined using the program UnitCell (Holland and Redfern 1997), based on lines clearly indexed from the proposed structural model (Table 3).
† a and c inverted.

BRUGGER ET AL.: PSEUDOJOHANNITE, A NEW MEMBER OF THE ZIPPEITE-GROUPTABLE 3.

Atomic coordinates for U and S atoms in the pseudojohannite structure, in space group I1

Atom
x
y
Z
U1
0.050(6)0.589(5)0.747(5)U2
0.352(5)0.336(5)0.978(4)U30.064(5)0.924(5)0.746(4)U40.348(6)0.677(5)0.977(5)
S1
0.540
0.740
0.240
S2
0.820
0.500
0.500
Note: The coordinates in P1 can be obtained by adding positions with (+1/2,+1/2, +1/2).

TABLE 4.

Chemical analyses of holotype pseudojohannite from
JáchymovConstituent
Wt%Standard deviation
Probe Standard
CuO
14.4
0.49
lammerite
62.4
0.77
metallic U
UO3
8.9
0.15
bariteSO3
13.95
one TG analysis (Table 7)
H2O
Total
99.65
Notes: Average of 15 electron microprobe analyses; empirical formula assuming
marécottite-type uranyl-sulfate layers, and 70 O atoms pfu: Cu6.52U7.85S4.02O70H55.74;
simplified empirical fomula: Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O.

TABLE 5.

FIGURE 2. Uranyl-sulfate layers in pseudojohannite compared withthe layers in zippeite (Burns et al. 2003).

933

Infrared spectrum of pseudojohannite from Jáchymov (KBr
disk) and Musonoï (Diamond cell)

Jáchymov*(cm–1) Intensity
3520
m,sh
3453
s
3375
S
3310 m, sh, b
3200 m, sh, bMusonoï†(cm–1)
Intensity
~3496
m, sh
3446
s
3364
s
3092

s, b

1665
1627

m, sh
m

1654
1618

m, sh
m

1457
1390

vw
vw

1151
1077

vs
vs

1142
1071

vs
vs

ν3 (SO4)2– antisymmetricstretching vibrations

975

w

1000
926

s
w

ν1 (SO4)2- symmetricstretching vibration874s

852 to 820s, bν3 (UO2)2+ antisymmetricstretching vibration831w

ν1 (UO2)2+ symmetric stretchingvibration or δ U-OH bending
vibration

765

w,b

L H2O libration mode orδ U-OH bending vibration

674
625
583

w
w
m

ν4 (SO4)2– bending vibrations

Tentative assignmentν OH stretching vibrations ofhydrogen-bonded watermolecules and hydroxyl ions

δ H2O bending vibrationsof water moleculesδ U-OH bending vibrations
and/or overtones and/or
combination bands497
w-m
ν2 (SO4)2– bending vibrations
475
w-m
Notes: Intensity scale: vs = very strong, s = strong, m = medium, w = weak, vw =very weak, character of absorption maxima: sh = shoulder, b = broad.
* Nicolet 740 spectrophotometer; KBr tablets (range 400–4000 cm–1).
† Diamond anvil cell GRAESEBY SPECAC coupled with a Perkin-Elmer PARAGON
1000 FT-IR spectrometer on ground material (range 650–4000 cm–1).

1.804 Å using (R = 91.41 ν3,874 cm–1–2/3 + 0.804 Å; Barlett and Cooney 1989)
1.796 Å using (R = 68.2 ν3,874 cm–1–2/3 + 1.05 Å; Glebov 1989)
1.780 Å using (R = 106.5 ν1,831 cm–1–2/3 + 0.575 Å; Barlett and Cooney 1989)

FIGURE 3. Infrared absorption spectrum of pseudojohannite from
Jáchymov, Musonoï, and La Creusaz measured with a diamond anvil cell(DAC) compared with the spectra of pseudojohannite from Jáchymov
and of synthetic zippeite (Čejka 1999) measured using KBr pellets. See
Table 5 for line positions, tentative line assignment and analytical details
for the Jáchymov and Musonoï samples.

All these lengths correspond to U-O bond lengths in various other uranyl sulfates and in general agree with uranyl bonddistances found in uranyl minerals with U6+ in pentagonal bipyramidal coordination (Burns 1999).
The symmetric stretching vibration ν1 (SO4)2– appears as a
weak band at 975 cm–1, the doubly degenerate ν2 (SO4)2– bending vibration bands are observed at 497 and 475 cm–1, the triply
degenerate ν3 (SO4)2– antisymmetric stretching vibration at 1151
and 1077 cm–1, and the triply degenerate ν4 (SO4)2– bending vibra-

934

BRUGGER ET AL.: PSEUDOJOHANNITE, A NEW MEMBER OF THE ZIPPEITE-GROUP

tion bands at 674, 625, and 583 cm–1. This indicates a loweringof the Td symmetry of the (SO4)2– tetrahedron to C2v or lower.
Note that a coincidence of the ν4 (SO4)2–, H2O libration modes,and δ U-OH is possible.
The ν OH stretching vibrations of water molecules and hydroxyl ions are observed in the range 3520–3200 cm–1. A bandat 1627 cm–1 with a shoulder at 1665 cm–1 may be attributed tothe δ H2O bending vibrations and shows that at least two typesof structurally nonequivalent water molecules are present in the
crystal structure of pseudojohannite. Very weak and weak bands
at 1457 and 1390 cm–1 may be assigned to the δ U-OH bending
vibrations and/or overtones and/or combination bands. A weakbroad band at 765 cm–1 may be connected with the δ U-OH
vibration or a H2O libration mode. Wavenumbers of the ν OH
and δ H2O vibrations indicate that hydrogen bonds of different
strengths are involved in the crystal structure of pseudojohannite
and a hydrogen-bonding network is established with lengths ofthe hydrogen bonds approximately 2.70, 2.75, 2.77, 2.85, and2.95 Å (Libowitzky 1999).
The IR spectra of pseudojohannite from La Creusaz, Musonoï, and part of the holotype from Jáchymov were recorded
using a diamond anvil cell (Fig. 3; Table 5). Overall, the spectra
are similar to each other, and they closely match the IR spectrum
recorded on the Jáchymov material in a KBr tablet. A signiÞcant
difference, however, appears in the region of stretching vibrations ν1 and ν3 of the uranyl ion. The pseudojohannite from La
Creusaz and Musonoï exhibits only one broad band in the region
852 to 820 cm–1, while the pseudojohannite from Jáchymov
displays well-resolved ν1 and ν3 bands. Moreover, the position
at which the ν3 (UO2)2+ band is expected is shifted from 874
cm–1 at Jáchymov to 852 cm–1 at Musonoï. This difference may
indicate slight differences in the hydrogen-bonding network andthus also in the way the interlayer is bound to the zippeite-layers
in the pseudojohannite from Jáchymov and La Creusaz/Musonoï.
The assignment of the broad band at 852 cm–1 to the ν3 (UO2)2+
is supported by its strong intensity. A weak band at 926 cm–1
(Musonoï) is more probably associated with the H2O libration
modes or the δ U-OH bending vibration than with the ν3 (UO2)2+
vibration.

position); also, the unit cell is likely to contain an integer numberof U and S atoms. Following these considerations, we conclude
that pseudojohannite contains 70 O atoms per unit cell, leading
to the empirical formula Cu6.52U7.85S4.02O70H55.74. Introducing azippeite-type layer (Brugger et al. 2003; Burns et al. 2003), thesimpliÞed structural formula becomes Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O.
The presence of H2O and OH groups is conÞrmed by thethermo-gravimetric analysis (Fig. 4; Table 7). Pseudojohannite
dehydrates and dehydroxylates in the range 55–625 °C in several
steps. The mineral looses 9.10 wt% corresponding to ~18H2O
between 20 and 210 °C, and 4.85 wt% corresponding to ~10H2O
between 210 and 625 °C. A further 4.6 wt% weight loss occurring
between 625 and 800 °C is attributed to SO3 and, possibly O2,
released from the thermal decomposition of anhydrous uranyl
sulfate and copper uranates, probably resulting from the dehydration reactions. The IR spectrum shows that pseudojohannite
contains non-equivalent groups of H2O molecules (see above).

DISCUSSION
The zippeite group of minerals is named after the mineralzippeite, K3(H2O)3[(UO2)4(SO4)2O3(OH)] (Burns et al. 2003;
Frondel et al. 1976). The zippeite group is deÞned by a characteristic topology of the uranyl sulfate layers (Brugger et al.
2003; Burns et al. 2003). Both monovalent and bivalent cations
can occur in the interlayer, and pseudojohannite belongs to thesecond category. Zippeite containing the divalent cations Mg,
Co, Ni, and Zn have been reported and/or synthesized (Burns etal. 2003; Frondel et al. 1976). Frondel et al. (1976) attempted tosynthesize Cu-bearing zippeites, but obtained only johannite or

CHEMICAL FORMULA OF PSEUDOJOHANNITE
The simpliÞed chemical formula of pseudojohannite has
been reported as Cu5(UO2)6(SO4)3(OH)16·14H2O in the original
publications (Ondruš et al. 1997, 2003), based upon the chemical
analysis reported in Table 4 and the unit-cell volume of 1081.2
Å3. The number of O atoms in the unit cell can be estimated bycomparison with the average volume of oxygen ions in somezippeite-group minerals and in johannite (Table 6). The numberof anions is likely to be a multiple of 2 (no O atom on special

FIGURE 4. Thermogravimetric (TG) and differential thermogravimetric(DTG) curves of pseudojohannite from Jáchymov. TG-750 StantonRedcroft microthermobalance, sample weight 1.957 mg, 10 °C/min,
dynamic air atmosphere, 10 mL/min.

TABLE 6. Comparison of the average volume occupied by anions in some zippeite-group minerals and in johannite
MineralFormulaZ
1
Marécottite
Mg3(H2O)18[(UO2)4O3(OH)(SO4)2]2(H2O)108
Magnesium-zippeite
Mg(H2O)3.5(UO2)2(SO4)O2
4
SZIPPMg
Mg2(H2O)11[UO2)2(SO4)O2]2
1
Johannite
Cu(UO2)2(SO4)2(OH)2·8H2O
1
Pseudojohnannite
Cu6.5[(UO2)4O4(SO4)2]2(OH)5·25H2O
Note: References are (1) Brugger et al. (2003); (2) Burns et al. (2003); (3) Mereiter (1982).

V (Å3)
1422.1(9)2110.2(2)2684.6(2)469.851371.9(5)Z*Nanions
68
108
124
22
70

V (Å3/Ox)
20.91
19.54
21.65
21.36
19.46

Ref
1
2
2
3

BRUGGER ET AL.: PSEUDOJOHANNITE, A NEW MEMBER OF THE ZIPPEITE-GROUPTABLE 7. Thermogravimetric analysis of pseudojohannite from Jáchymov
Temperature
Mass loss
Mass loss
Attribution
range (°C)
(mg)
(wt%)
55–2100.178
9.10
18.34 H2O
210–625
0.095
4.85
9.79 H2O
55–6250.273
13.95
28.13 H2O
625–800
0.090
4.60
2.61 SO3
Note: Decomposition process proceeds continuously at temperatures higher
than 800 °C.

Magnesium-zippeite Mg(H2O)3.5[(UO2)2(SO4)O2]
U

Mg:S = 1:1

7.10 ÅS

Mg

SZIPPMg Mg2(H2O)11[(UO2)2(SO4)]2
U

Mg:S = 1:1

Mg

9.03 ÅS

H 2O

Marecottite Mg3(H2O)18[(UO2)4O3(OH)(SO4)2]2

Mg:S = 3:4

SU

9.47 ÅMg
H2O

Johannite Cu[(UO2)2(SO4)2(OH)2]•8H2O

Cu:S = 1:2

7.72 Å

S

U
Cu
H2O

Pseudojohannite Cu6.5[(UO2)4O4(SO4)2]2•25H2O

Cu:S = 1.6:1

US
9.16 Å

basic copper sulfates together with sodium-zippeite or zippeite.
The name “cuprozippeite” has been given by Boldyrev (1935) toa mineral containing 5 wt% CuO, but it is not known whether thematerial is related to the zippeite group (Frondel et al. 1976).
Until recently, the nature of the zippeite group was the subjectof great confusion, especially regarding the divalent members of
the group. Crystal structure reÞnements on natural (marécottite;
Brugger et al. 2003) and synthetic zippeites (Burns et al. 2003)
have revealed that the confusion is due to a great variability inthe arrangement of the interlayer cations, resulting in different
unit cells and cell volumes for zippeites containing divalentcations (Table 6).
Some level of disorder is common in the interlayers ofzippeite-group minerals. The different conÞgurations result indifferent distances between the zippeite-type layers (Fig. 5).
In the crystal structure of magnesium-zippeite, two O atoms at
opposite apices of each Mg-octahedron are shared with uranylgroups ([UO2]2+) from two adjacent zippeite-type layers (Fig. 5).
This arrangement results in a relatively short distance between
two uranyl-sulfate layers (dz = 7.10 Å). In contrast, marécottite contains a hydrated layer of Mg(H2O)6 octahedra, and thezippeite-type layers are bound only by hydrogen bonding. This
arrangement results in an increase in dz to 9.47 Å. The synthetic
phase SZIPPMg (Burns et al. 2003) has an intermediate conÞguration where Mg-octahedra share only one oxygen with a uranylgroup (dz = 9.03 Å). The size of the Mg- and Jahn-Teller distorted
Cu-octahedrons are similar (Mg-O 1.9 to 2.5 Å in zippeites; Cu-O
1.9 to 2.4 Å in johannite). Hence, we can assume that the CuΦ6
polyhedra (Φ = O,H2O,OH) in pseudojohannite do not directly
connect to two adjacent uranyl-sulfate layers, because of the longdz of 9.16 Å. The metal:S ratio in pseudojohannite is higher thanin other zippeite-group minerals, indicating that some, or all, of
the CuΦ6 polyhedrons are linked together.
The failure to locate the Cu atoms in pseudojohannite illustrates the fundamental difÞculty of ab-initio structure solution from powder diffraction data, which originates from the
1-dimensional nature of the data, compared with 3-dimensional
single-crystal data. This problem is particularly acute for minerals
containing heavy atoms such as uranium, for which the X-ray
diffraction patterns are dominated by scattering from the U atoms.
The topology of the uranyl-sulfate layers plays a fundamental role
not only for the classiÞcation of uranium minerals, but also incontrolling their physical and chemical properties (Burns 1999).
Hence, the ability of powder diffraction methods to reveal the
topology of the uranyl framework opens new means to study thecomplex, and often Þne grained uranyl minerals that are prevalent
in areas where acid drainage waters interact with U-bearing ores
or wastes (Finch and Murakami 1999).

935

FIGURE 5. Comparison of the stacking and interlayer topology in the
crystal structures of magnesium-zippeite (Spitsyn et al. 1982; Brugger
et al. 2003), SZIPPMg (Burns et al. 2003), marécottite (Brugger et al.
2003), and johannite (Mereiter 1982) with pseudojohannite.

ACKNOWLEDGMENTS
We are grateful to Sergey Krivovichev and an anonymous reviewer for helpfulcomments. This work was partly funded by an Australian Research Council QEII
fellowship to J.B. The synchrotron work was performed at the Australian National
Beamline Facility with support from the Australian Synchrotron Research Program,which is funded by the Commonwealth of Australia under the Major National
Research Facilities Program.

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MANUSCRIPT ACCEPTED DECEMBER 29, 2005
MANUSCRIPT HANDLED BY PETER BURNS