Mineralogical Magazine, August 2017, Vol. 81(4), pp. 895–907

Alwilkinsite-(Y), a new rare-earth uranyl sulfate mineral fromthe Blue Lizard mine, San Juan County, Utah, USA
ANTHONY R. KAMPF1,*, JAKUB PLÁŠIL2, JIŘÍ ČEJKA3, JOE MARTY4, RADEK ŠKODA5 AND LADISLAV LAPČÁK6
1

Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard,
Los Angeles, CA 90007, USA
2
Institute of Physics ASCR, v.v.i., Na Slovance 1999/2, 18221 Prague 8, Czech Republic
3
Department of Mineralogy and Petrology, National Museum, Cirkusová 1740, 193 00, Prague 9, Czech Republic
45199 East Silver Oak Road, Salt Lake City, UT 84108, USA
5
Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37, Brno,
Czech Republic
6
Institute of Chemical Technology, Prague, Technická 5, 166 28, Prague 6, Czech Republic[Received 20 April 2016; Accepted 28 July 2016; Associate Editor: Michael Rumsey]
ABSTR ACTThe new mineral alwilkinsite-(Y) (IMA2015-097), Y(H2O)7[(UO2)3(SO4)2O(OH)3]·7H2O, was found in
the Blue Lizard mine, San Juan County, Utah, USA, where it occurs as a secondary alteration phase. The
mineral is slightly flexible before brittle failure with splintery fracture and perfect cleavage parallel to [010],
has Mohs hardness of ∼2–2½, exhibits dull greenish-grey fluorescence and has a calculated density of
3.371 g cm–3. Alwilkinsite-(Y) occurs as yellowish-green needles, elongate on [010], with domatic
terminations and exhibits the forms {102}, {301} and {124}. It is optically biaxial (+) with α = 1.573(1),β = 1.581(1), γ = 1.601(1) (white light), the measured 2V is 65.3(1)°, the dispersion is r < v (weak), theoptical orientation is X = c, Y = a, Z = b and there is no pleochroism. Electron microprobe analyses
yieldedtheempirical
formula(Y0.66Dy0.08Gd0.06Er0.05Nd0.03Yb0.03Sm0.02Ce0.01)Σ0.94(H2O)7[(UO2)3(S1.01O4)2O(OH)3]·7H2O. The eight strongest powder X-ray diffraction lines are [dobs Å(I)(hkl)]:
9.88(100)(101,002), 7.47(13)(102), 5.621(17)(103,201), 4.483(18)(104), 3.886(14)(130,222), 3.322(46)(multiple), 3.223(13)(multiple) and 3.145(16)(034). Alwilkinsite-(Y) is orthorhombic, P212121,
a = 11.6194(5), b = 12.4250(6), c = 19.4495(14) Å, V = 2807.9(3) Å3 and Z = 4. The structure ofalwilkinsite-(Y) (R1 = 0.042 for 4244 Fo > 4σF ) contains edge-sharing chains of uranyl bipyramids with
outlying sulfate tetrahedra that are similar to the chain linkages within the uranyl sulfate sheets of thezippeite structure. Short segments of the uranyl sulfate chains in the alwilkinsite-(Y) structure have the same
topology as portions of the uranyl sulfate linkages in uranopilite. Alwilkinsite-(Y) is named for Alan (Al)J. Wilkins, MD (born 1955), the discoverer of the mineral.
K E Y WO R D S : alwilkinsite-(Y), new mineral, uranyl sulfate, crystal structure, Blue Lizard mine, Utah, USA.

Introduction
ALWILKINSITE-(Y) is the twelfth new uranyl sulfate
and the fourteenth new mineral overall to be firstdescribed from the Blue Lizard uranium mine in*E-mail: akampf@nhm.org
https://doi.org/10.1180/minmag.2016.080.139© 2017 The Mineralogical Society

southeast Utah (Table 1). In an accompanying
paper, the fifteenth new mineral from thisdeposit, chinleite-(Y) NaY(SO4)2·H2O is described(Kampf et al., 2017a). Alwilkinsite-(Y) is the only
new mineral from the Blue Lizard mine that does
not contain essential Na and is one of only two new
rare-earth-bearing phases to be described from themine, the other being chinleite-(Y). It is only
the second known rare-earth uranyl sulfate mineral,

ANTHONY R. KAMPF ET AL.

TABLE 1. New mineral species described from the Blue Lizard mine.
Mineral

Structural Formula

Referencecobaltoblödite
manganoblödite
meisserite
belakovskiite
bluelizardite
plášilite
bobcookite
wetherillite
fermiite
oppenheimerite
klaprothite
péligotite
ottohahnite
alwilkinsite-(Y)chinleite-(Y)Na2Co(SO4)2(H2O)4
Na2Mn(SO4)2(H2O)4
Na5(SO3OH)(H2O)[(UO2)(SO4)3]Na7(SO3OH)(H2O)3[(UO2)(SO4)4(H2O)]
Na7Cl(H2O)2[(UO2)(SO4)4]
Na(H2O)2[(UO2)(SO4)(OH)]
Na(H2O)2Al(H2O)6[(UO2)2(SO4)4(H2O)2]·8H2O
Na2(H2O)6(Mg,Zn)(H2O)6[(UO2)2(SO4)4(H2O)2]·4H2O
Na4(H2O)3[(UO2)(SO4)3]
Na2(H2O)2[(UO2)(SO4)2(H2O)]
Na6(H2O)4[(UO2)(SO4)4]
Na6(H2O)4[(UO2)(SO4)4]
Na6(H2O)7[(UO2)2(SO4)5]·1.5H2O
Y(H2O)7[(UO2)3(SO4)2O(OH)3]·7H2O
NaY(SO4)2·H2O

Kasatkin et al. (2013)
Kasatkin et al. (2013)
Plášil et al. (2013)
Kampf et al. (2014)
Plášil et al. (2014)
Kampf et al. (2015a)
Kampf et al. (2015b)
Kampf et al. (2015b)
Kampf et al. (2015c)
Kampf et al. (2015c)
Kampf et al. (2017b)
Kampf et al. (2017b)
Kampf et al. (2017b)
This study
Kampf et al. (2017a)

the first being the zippeite-group mineralsejkoraite-(Y), described by Plášil et al. (2011)
from Jáchymov, Czech Republic.
Alwilkinsite-(Y) is named in honour of Alan
(Al) J. Wilkins, MD (born 1955) of Coto de Caza,
California. Dr. Wilkins has had a keen interest in
microminerals for nearly 20 years and has beenvery active in the amateur mineral community. He is
one of a group of sophisticated and dedicatedcollectors who in recent years have provided many
specimens for scientific research, especially fromthe Blue Bell claims and Otto Mountain in
California (USA), the Silver Coin mine in Nevada(USA) and the Blue Lizard mine in Utah (USA),
which have resulted in the descriptions of

numerous new mineral species. Dr. Wilkins
collected and provided the only specimen knownof the new mineral described herein. He has given
permission for the naming of the mineral in hishonour. Note that the compound name ‘alwilkinsite’ is proposed rather than the simpler ‘wilkinsite’ to avoid possible confusion with the existingmineral species wilkinsonite.
The new mineral and name were approved by theCommission on New Minerals, Nomenclature andClassification of the International Mineralogical
Association (IMA2015-097). The description isbased on one holotype specimen deposited in thecollections of the Natural History Museum of Los
Angeles County, 900 Exposition Boulevard, Los
Angeles, CA 90007, USA, catalogue number
65629.

Occurrence

FIG. 1. Alwilkinsite-(Y) with gypsum and natrozippeite onquartz; field of view: 1 mm across.

896

Alwilkinsite-(Y) was found underground in theBlue Lizard mine, Red Canyon, White Canyon
district, San Juan County, Utah, USA (37°33′26″N110°17′44″W). The Blue Lizard mine is located∼72 km west of the town of Blanding, Utah, and∼22 km southeast of Good Hope Bay on Lake
Powell. Information on the history and geology ofthe deposit is taken largely from Chenoweth (1993).
Mineralized channels are in the Shinarump
member of the Chinle Formation. The Shinarump
member consists of medium- to coarse-grainedALWILKINSITE-(Y), A NEW RARE-EARTH URANYL

FIG. 3. Bundles of alwilkinsite-(Y) needles with gypsum
and natrozippeite on quartz; field of view: 1 mm across.

FIG. 2. Crystal drawing of alwilkinsite-(Y), clinographic
projection in nonstandard orientation, [010] vertical.

sandstone, conglomeratic sandstone beds and thicksiltstone lenses. Ore minerals were deposited as
replacements of wood and other organic material andas disseminations in the enclosing sandstone. Since
the mine closed in 1978, oxidation of primary ores in
the humid underground environment has produced avariety of secondary minerals, mainly sulfates, as
efflorescent crusts on the surfaces of mine walls.
Alwilkinsite-(Y) is a very rare mineral, known
only from one micromount specimen. On thatspecimen there are only a few groupings of crystals,
as described below. The other secondary minerals
found in direct association with alwilkinsite-(Y) are
calcite, dickite, gypsum, johannite, natrozippeite
and zinczippeite. The bulk of the matrix is897

comprised of subhedral to euhedral, equant quartz
crystals that are recrystallized counterparts of theoriginal grains of the sandstone. Other minerals
remaining from the original sandstone include
feldspar and rare detrital almandine andzircon. An exhaustive list of other secondary
minerals found in our studies of the Blue Lizard
secondary assemblages can be found in Kampf
et al. (2017b).
Alwilkinsite-(Y) and the other minerals in thesecondary assemblages in the Blue Lizard mine
formed at ambient temperature by evaporative
processes at the surface of a rock with high relativeporosity. The environment is relatively oxidizing(high Eh) and solutions are generally acidic (lowpH). The high molar proportion of H2O inalwilkinsite-(Y) suggests that it formed at moderately high relative humidity. A detailed discussionof the origin and conditions of formation of theuranyl sulfate assemblages at the Blue Lizard mine
was provided by Plášil et al. (2014) and was more
recently summarized by Kampf et al. (2017b).
As noted above, the only Y-bearing phases thus
far observed are the very rare new minerals
alwilkinsite-(Y) and chinleite-(Y). The Y, as wellas other rare-earth elements (REEs) found in lesser
amounts, in these minerals probably existed in thesandstones of the Chinle Formation prior to thedeposition of the U ores. Shoemaker et al. (1959)
noted that Y is intrinsic to the rocks of the Chinle
Formation and Newman (1962) suggested that thesource of the above-average concentrations of Y incertain areas may be Precambrian rocks of theancestral Uncompahgre highland. It is also likelythat some Y and other REEs were introduced alongwith U in the ore-forming solutions.

ANTHONY R. KAMPF ET AL.

FIG. 4. The Raman spectrum of alwilkinsite-(Y) measured with a red (NIR) laser.

Physical and optical properties

typically exhibit very similar fluorescence under the
405 nm laser, as they do under both longwave andshortwave ultraviolet radiation. For sparsely distributed microscopic crystals, the 405 nm laser is themost practical tool for observing fluorescence.) The
Mohs hardness is estimated to be between 2 and 2½,
based upon the behaviour of crystals when broken.
Crystals are slightly flexible before brittle failure
with at least one perfect cleavage parallel to [010],
possibly {102}, and have splintery fracture. The
mineral is insoluble in H2O, but easily soluble indilute HCl, in both cases at room temperature. The

Alwilkinsite-(Y) crystals are long, thin prisms(Fig. 1), elongate on [010], with domatic terminations and exhibit the forms {102}, {301} and{124} (Fig. 2). Prisms are up to ∼0.5 mm long andare sometimes intergrown in subparallel bundles(Fig. 3). No twinning was observed.
Crystals are yellow green and transparent with avitreous lustre. The streak is pale yellow green. The
mineral fluoresces greenish grey under a 405 nm
laser. (Note that the Blue Lizard uranyl sulfates

TABLE 2. Chemical composition (in wt.%) for alwilkinsite-(Y).
Constituent

Mean

Range

Stand. Dev.

Probe standard (Line)

CaO
Y2O3
Ce2O3
Nd2O3
Sm2O3
Gd2O3
Dy2O3
Er2O3
Yb2O3
SO3
UO3
H2O*
Total

0.01
5.49
0.15
0.38
0.29
0.76
1.11
0.67
0.37
11.97
63.25
20.59
105.040.00–0.07
5.11–5.69
0.12–0.17
0.33–0.42
0.20–0.36
0.61–0.94
1.10–1.17
0.45–0.76
0.27–0.50
10.31–12.41
61.06–64.94

0.03
0.21
0.02
0.03
0.06
0.11
0.06
0.06
0.06
0.77
1.48

Wollastonite (Kα)
YPO4 (Lα)
CePO4 (Lα)
NdPO4 (Lβ)
SmPO4 (Lα)
GdPO4 (Lα)
DyPO4 (Lα)
ErPO4 (Lα)
YbPO4 (Lα)
SrSO4 (Kα)
uranophane (Mα)*Based on the structure.

898

ALWILKINSITE-(Y), A NEW RARE-EARTH URANYLTABLE 3. Powder X-ray data (d in Å) for alwilkinsite-(Y).
Iobs

dobs

dcalc

10.4708
9.97499.72487.82
7.77847.47
7.4575
6.38
6.3942n
5.66155.621
5.56675.27345.26285.252
5.23545.151
5.15194.98754.654
4.62854.483
4.48554.314
4.3267
4.137
4.14584.0860n3.9012
3.886
3.8892n3.8251
3.807
3.8105
3.6976n3.63663.639
3.6208n3.59823.580
3.57143.55053.49033.34273.32293.322
3.29693.28673.24083.23233.223
3.21203.19713.18633.145
3.15293.1224
3.11373.04293.029
3.0295n2.99192.978
2.96582.94332.905
2.90492.8739n2.86742.848
2.8289n

100 9.88
3
13
9
17
7
11
2
18
6
3
14
7
8
8

46

13

16

12
11
3
6

f

f
f

Icalc h k l
1
63
37
4
11
8
12
6
3
2
1
10
1
3
16
7
2
1
8
1
5
1
2
2
4
2
3
2
1
9
21
3
4
3
4
3
2
1
9
1
2
3
7
7
2
1
2
1
3
4

011
101
002
111
102
112
103
201
121
210
022
113
202
212
104
203
221
213
130
222
131
032
310
124
132
302
214
223
033
133
231
025
320
321
205
313
224
232
034
106
322
134
304
233
141
314
400
026
225
330

Iobs

dobs

dcalc
n

2.57602.55272.53642.50662.495
2.49372.48582.47802.43822.43122.41132.412
2.40762.40462.38662.35762.3513n2.33722.336
2.32752.31422.28792.28482.27552.275
2.26922.2632n2.22372.218
2.22132.16882.16312.15452.13642.1291
2.124
2.12402.12192.1095n
2.09662.08392.09232.07082.06792.05962.06332.06092.03872.02762.02542.01952.01642.0103
1.99911.9953
1.98661.9823
1.98201.9722
1.96983 2.563

4

3

3

8

3

8

3
9

9

9

f
f

f
f
f
f
f

Icalc h k l
1
1
1
3
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
2
2
2
1
1
1
1
3
1
1
2
1
1
1
2
1
3
1
1
2
1
3
1
1
1
1
5
1
1

226
036
027
207
404
306
127
423
008
151
052
341
244
152
342
118
405
424
335
250
153
251
137
512
317
344
521
513
434
019
522
327
228
038
246
060
254
138
155
160
161
062
443
129
219
162
524
337
056
515

Iobs

dobs

dcalc

9 1.8605

f

5

f

7

4
5

7

7

4

3

10

1.8672
1.86261.8523
1.84381.8421
1.82761.8262
1.82811.8182
1.81631.81301.81041.80691.80701.80571.7973
1.78571.7806n1.76811.76781.76471.75781.74371.74561.74061.73791.72811.72581.7192
1.71871.7172
1.70961.7001
1.6987
1.6934
1.69181.69091.6862n
1.66471.66271.6614
1.64201.6394
1.6374n1.63171.63081.63071.61381.61281.60851.60371.60271.59651.59471.59581.59301.59191.58871.5859

f
f

f
f

f

Icalc h k l
4
1
2
1
1
1
1
1
1
1
1
1
2
1
1
1
2
1
2
1
1
1
2
1
2
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
1
1

516
445
057
338
355
542
347
361
622
453
264
526
329
535
428
614
2 2 10257
363
265
1 3 10
544
624
166
158
419
364
438
455
633
551
460
518
462
553
711
537
456
059
546
349
3 0 11
720
274
267
713
643
372
607
2 4 10(continued)

899

ANTHONY R. KAMPF ET AL.

TABLE 3. (contd.)
Iobs

dobs

dcalc
n

8

10

6

2.799

2.751

2.698

f

f

2.79912.78982.78332.76002.75462.74462.73932.71632.71152.70232.68002.63672.5926

Icalc h k l
3
3
1
3
3
1
1
3
1
1
3
1
2

411
126
402
216
135
305
240
332
017
107
315
242
413

Iobs

dobs

6 1.9408
6 1.9111

5 1.8828

f
f
f

dcalc

Icalc h k l

Iobs

1.9546
1.94481.94091.9343
1.9213
1.91751.9135
1.8994
1.89581.88871.8801
1.8775

1
3
1
1
2
2
1
1
2
1
2
1

1.57591.57001.56601.56416 1.5603
1.56181.55711.5346n1.5275
3 1.5233
1.51851.51004 1.5034
1.50561.5039density could not be measured because the mineralis soluble in Clerici solution. The calculated density
is 3.371g cm–3 based on the empirical formula andsingle-crystal cell parameters.

328
163
261
533
354
436
610
525
1 1 10
506
164
612

dobs

dcalc

f
f

V
Z
Density (for above formula)
Absorption coefficientF(000)
Crystal size (μm)
θ range
Index ranges
Reflections collected/unique
Reflections with F > 4σ(F )Completeness to θ = 25.03°
Refinement method
Restraints/parameters
Goof
Final R indices [F > 4σ(F )]R indices (all data)
Absolute structure parameter
Largest diff. peak/hole

Rigaku R-Axis Rapid II
MoKα (λ = 0.71075Å)/50 kV, 40 mA
298(2) K(Y0.66Dy0.34)[(UO2)3(SO4)2O(OH)3](H2O)7·7H2O
P212121a = 11.6194(5) Å
b = 12.4250(6) Åc = 19.4495(14) Å
2807.9(3) Å3
4
3.401 g cm–3
19.781 mm–1
2576.55 × 5 × 100
3.19 to 25.03°–10 ≤ h ≤ 13, –14 ≤ k ≤ 13, –23 ≤ l ≤ 23
12598/4893; Rint = 0.074
4244
99.5%
Full-matrix least-squares on F 2
0/344
1.024
R1 = 0.0422, wR2 = 0.0830
R1 = 0.0535, wR2 = 0.0876–0.002(11)+1.72/–1.75 e A–3*Rint = Σ|Fo2–Fo2(mean)|/Σ[Fo2]. Goof = S = {Σ[w(Fo2–F2c )2]/(n–p)}1/2. R1 = Σ||Fo|–|
Fc||/Σ|Fo|. wR2 = {Σ[w(Fo2–F2c )2]/Σ[w(Fo2)2]}1/2; w = 1/[σ2(Fo2) + (aP)2 + bP] where ais 0.0302, b is 0 and P is [2F2c + Max(Fo2,0)]/3.

900

1
1
1
1
1
1
1
1
1
1
1
1

617
259
2 3 114 2 10457
3 2 11181
650
1 5 10471
4 3 10563

Optically, alwilkinsite-(Y) is biaxial (+), with
α = 1.573(1), β = 1.581(1), γ = 1.601(1) (measured
in white light). The 2V measured using spindlestage extinction data with EXCALIBR (Gunter

TABLE 4. Data collection and structure refinement details for alwilkinsite-(Y).*Diffractometer
X-ray radiation/power
Temperature
Structural formulaSpace group
Unit-cell dimensions

Icalc h k lTABLE 5. Atom coordinates and displacement parameters (Å2) for alwilkinsite-(Y).
y/b

z/c

Ueq

U 11

U 22

U 33

U 23

U 13

U 12

0.14324(14)0.61542(7)0.35441(7)0.55600(7)0.7905(5)0.8680(5)0.8717(15)0.8442(15)0.7381(14)0.6950(13)0.9221(14)0.8205(15)0.7770(13)0.9515(12)0.7164(13)0.5167(12)0.4343(13)0.2678(14)0.4618(13)0.6516(14)0.5009(12)0.6331(10)0.4805(12)0.6670(12)0.0691(16)0.1074(18)0.1434(12)0.2364(16)0.2844(15)0.3240(15)0.0615(18)0.9899(16)0.0921(15)0.9005(17)0.9026(16)0.17466(13)0.34108(6)0.48448(6)0.63142(6)0.7794(5)0.1883(4)0.7484(13)0.7839(13)0.8857(12)0.6996(11)0.2081(13)0.0798(13)0.2662(12)0.1976(12)0.3910(12)0.2856(11)0.5491(11)0.4188(13)0.6114(11)0.6620(13)0.4855(12)0.1567(10)0.3232(11)0.4787(11)0.0774(13)–0.0023(14)0.1910(12)0.3391(15)0.1780(17)0.1043(16)0.3051(12)0.4294(14)0.8077(12)0.6164(15)0.5281(13)0.42601(8)0.28129(4)0.19984(4)0.32771(4)0.4039(3)0.3340(3)0.3499(9)0.4720(8)0.3888(8)0.4081(7)0.2686(8)0.3344(10)0.3478(7)0.3917(7)0.2210(8)0.3420(8)0.1343(8)0.2635(8)0.3989(7)0.2569(8)0.2712(7)0.2361(6)0.1809(7)0.3616(7)0.5165(8)0.3879(8)0.3054(7)0.3990(8)0.5149(7)0.3878(9)0.5069(8)0.2362(11)0.4564(8)0.5655(9)0.3537(9)0.0201(6)0.0170(2)0.0163(2)0.0158(2)0.0239(14)0.0193(12)0.040(5)0.038(4)0.032(4)0.020(3)0.033(4)0.043(5)0.024(4)0.024(4)0.028(4)0.024(4)0.025(4)0.033(4)0.023(4)0.032(4)0.021(3)0.014(3)0.024(4)0.020(3)0.038(4)0.051(5)0.029(4)0.044(5)0.047(5)0.049(6)0.043(5)0.049(5)0.037(4)0.048(5)0.047(5)0.0181(10)0.0179(4)0.0166(4)0.0183(4)0.029(4)0.015(3)0.031(11)0.033(10)0.027(10)0.026(9)0.024(9)0.036(11)0.023(9)0.007(7)0.028(9)0.020(9)0.012(8)0.021(9)0.018(9)0.031(9)0.0243(10)0.0133(4)0.0138(4)0.0133(4)0.017(3)0.018(3)0.036(10)0.036(10)0.023(9)0.014(8)0.045(10)0.025(9)0.036(9)0.036(9)0.030(9)0.013(8)0.014(8)0.037(10)0.023(8)0.034(10)0.0180(9)0.0198(4)0.0185(4)0.0157(4)0.025(3)0.025(3)0.053(11)0.044(11)0.044(10)0.019(8)0.032(9)0.068(13)0.014(8)0.029(9)0.026(9)0.039(10)0.051(10)0.040(11)0.027(8)0.032(9)0.0009(7)–0.0007(4)0.0001(3)–0.0001(4)0.000(3)0.001(2)–0.007(9)0.004(9)0.022(8)0.002(7)0.007(8)0.016(10)–0.004(7)0.000(8)–0.005(8)–0.008(7)–0.001(7)–0.004(8)0.001(7)0.015(8)0.0001(7)–0.0031(4)–0.0025(3)–0.0010(4)–0.009(3)0.000(2)0.018(9)–0.023(9)–0.013(8)–0.002(7)–0.002(8)–0.015(10)–0.006(7)0.000(7)–0.008(7)0.001(7)–0.003(8)–0.005(8)–0.001(7)0.001(8)0.0010(8)0.0014(4)–0.0006(3)–0.0002(3)–0.002(3)–0.002(2)0.002(8)–0.012(9)0.000(7)0.005(7)0.006(8)–0.006(8)0.011(7)–0.003(7)–0.006(7)–0.005(6)0.001(7)0.000(8)–0.008(7)–0.006(9)0.010(7)0.030(9)0.022(8)0.048(12)0.087(16)0.016(7)0.050(12)0.045(11)0.020(10)0.068(13)0.033(11)0.049(12)0.055(13)0.052(13)0.012(7)0.018(8)0.012(7)0.044(11)0.037(11)0.050(11)0.042(11)0.091(16)0.077(15)0.031(10)0.037(11)0.025(10)0.057(12)0.029(10)0.021(7)0.025(9)0.026(8)0.021(9)0.030(10)0.021(8)0.041(10)0.007(8)0.050(12)0.032(10)0.077(15)0.036(10)0.034(10)0.059(12)0.006(6)0.005(7)0.004(7)0.010(8)0.003(9)0.004(7)0.012(10)–0.003(9)0.000(11)–0.006(8)0.008(11)0.005(8)0.008(9)0.005(9)0.001(6)–0.005(7)0.005(6)0.000(8)0.012(10)0.003(7)0.001(9)–0.005(8)0.009(8)–0.003(9)0.008(10)0.000(9)–0.019(9)0.001(10)0.004(6)0.008(7)0.009(6)–0.002(9)0.009(11)0.010(7)–0.004(10)–0.017(11)0.025(10)0.017(9)0.000(8)0.000(8)–0.012(10)0.000(9)(continued)

ALWILKINSITE-(Y), A NEW RARE-EARTH URANYL

901

Y*
U1
U2
U3
S1
S2
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
O15
OH1
OH2
OH3
OW1
OW2
OW3
OW4
OW5
OW6
OW7
OW8
OW9
OW10
OW11

x/a

–0.013(12)0.017(13)–0.011(9)0.020(10)0.011(12)0.016(9)et al., 2004) is 65.3(1)°; the calculated 2V is 65.3°.
Dispersion is r > v, weak. No pleochroism wasobserved. The optical orientation is X = c, Y = a,
Z = b.

Raman spectroscopy
The Raman spectrum of alwilkinsite-(Y) is shownin Fig. 4. The strong fluorescence of the material(due to the presence of Y and REEs) required theuse of a 780 nm laser for collection of the Raman
data. As a result, it was not possible to acquire theO–H stretching region of the spectrum. The broad
bands at ∼1600 cm–1 are the result of thefluorescence; assignment of some of them asν2 (δ) H2O is unlikely. A similar effect wasobserved in sejkoraite-(Y) (Plášil et al., 2011). A
broader Raman band of medium intensity at
1265 cm–1 and also weak bands at 1135 and1080 cm–1 are attributed to the split triply degenerate ν3 antisymmetric stretching vibrations of the(SO4) tetrahedra. The Raman band at 1325 cm–1 isprobably an overtone or a combination band. Sharp
Raman bands at 1035, 1015 and 990 cm–1 are
attributed to the ν1 symmetric stretching vibrationsof (SO4) tetrahedra.
A very weak Raman band at 900 cm–1 isattributed to the ν3 antisymmetric stretchingvibration of the uranyl ion, (UO2)2+. The verystrong Raman band at 840 cm–1 is attributed to theν1 symmetric stretching vibration of the uranyl ion.
The inferred U–O bond lengths (after Bartlett andCooney, 1989) for the uranyl ion of 1.77 Å (ν1) and1.79 Å (ν3) are consistent with those obtained in the
structure determination (see below).
Medium-weak Raman bands at 605, 555 and530 cm–1 are attributed to the ν4 (δ) triply degenerate
antisymmetric stretching vibrations of the (SO4)
tetrahedra. Weak bands at 465 and 455 cm–1 and abroader band at ∼380 cm–1, consisting of at least two
overlapping bands centred at 395 and 378 cm–1, arerelated to the split ν2 (δ) doubly degenerate bending
vibrations of the (SO4). A suite of overlapping bands
below 300 cm–1 (320, 288, 268, 240 cm–1) is
associated with the ν2 (δ) doubly degeneratebending vibrations of the UO2þ2 (e.g. Bullock andParret, 1970; Ohwada, 1976; Brittain et al., 1985;
Plášil et al., 2010). The high number of bands
reflects the large number of symmetrically nonequivalent U sites in the structure. More intense
splitting bands at 200 and 170 cm–1 are assigned
to the U–Oeq–ligand stretching (Bullock andParret, 1970; Plášil et al., 2010). Weak bands at*Refined occupancy of Y site is Y/Dy = 0.661/0.339(10)

OW12
OW13
OW14

0.1874(17)0.046(2)0.3338(15)0.6498(17)0.5147(16)0.4818(14)0.3608(9)0.4677(11)0.4959(9)0.056(5)0.066(6)0.042(5)0.059(13)0.073(15)0.042(11)0.067(14)0.049(13)0.037(11)0.042(11)0.076(15)0.048(11)0.004(11)0.000(12)–0.012(9)

U 12
x/a

TABLE 5. (contd.)

y/b

z/c

Ueq

U 11

U 22

U 33

U 23

U 13

ANTHONY R. KAMPF ET AL.

902

ALWILKINSITE-(Y), A NEW RARE-EARTH URANYLTABLE 6. Selected bond distances (Å) for alwilkinsite-(Y).
U1–O9
U1–O10U1–O15
U1–OH3
U1–OH1
U1–O7
U1–OH2<U–OUr><U–Oeq>1.771(16)1.784(15)2.243(13)2.392(14)2.462(13)2.463(14)2.514(14)
1.778
2.415

Y–OW1
Y–O8
Y–OW3
Y–OW2
Y–OW4
Y–OW5
Y–OW6
Y–OW7
<Y–O>

2.303(16)2.343(15)2.355(14)2.357(18)2.371(18)2.384(16)2.393(16)2.451(16)
2.370

U2–O11
U2–O12
U2–O15
U2–O3
U2–O6
U2–OH1U2–OH2<U–OUr><U–Oeq>1.770(16)1.792(17)2.196(13)2.373(14)2.445(16)2.480(12)2.509(14)
1.781
2.401

S1–O1
S1–O2
S1–O3
S1–O4
<S1–O>

1.463(17)1.465(16)1.484(16)1.490(16)
1.461

U3–O13U3–O14U3–O15
U3–OH3
U3–O4
U3–OH2
U3–OH1<U–OUr><U–Oeq>1.783(15)1.809(15)2.215(14)2.387(13)2.402(14)2.426(14)2.543(12)
1.796
2.395

S2–O5
S2–O6
S2–O7
S2–O8
<S2–O>

1.439(16)1.457(16)1.459(15)1.488(15)1.476145, 135, 108, 90, 72 and 60 cm–1 are attributed to–Oeq–U–Oeq– bending (Ohwada, 1976) and to
unclassified lattice modes, most probably skeletal
vibrations of the entire chains of polyhedra.

Composition
Chemical analyses (seven points on several crystals)
were undertaken using a Cameca SX100 electron
microprobe (WDS mode, 15 kV, 10 nA, 10 μm
beam diameter). Because insufficient material isavailable for a direct determination of H2O, it wascalculated by stoichiometry. As is typical of highly
hydrated phases with weakly held H2O, alwilkinsite(Y) partially dehydrates under vacuum during
carbon coating and in the microprobe chamber.
This H2O loss results in higher concentrations for theremaining constituents than are to be expected for the903

Hydrogen bonds
OH1–OW12
OH2–OW10
OH3–OW11OW1–OH3OW1–OW14OW2–OW8
OW2–OW9OW3–O5OW3–O14OW4–O12OW4–OW14OW5–O8OW5–OW7
OW6–O11
OW6–O14OW7–O10OW7–O11OW8–O1OW8–O9OW9–O2OW9–O4OW10–O2OW10–OW13
OW11–O1OW11–OW13
OW12–O5
OW12–OW9OW13–OW10OW13–OW11
OW14–O2OW14–O13

2.81(2)2.74(2)2.81(2)2.72(2)2.84(3)2.80(3)2.72(2)2.68(2)2.70(2)2.84(2)2.83(2)3.08(2)
3.26(3)2.92(2)2.92(2)
3.19(2)3.07(2)
3.23(2)
3.23(2)2.91(2)2.90(2)2.84(2)2.84(3)2.76(2)2.78(3)2.91(3)2.92(3)2.84(3)2.78(3)2.98(2)2.89(2)

fully hydrated phase; hence, the high analytical
total when the calculated H2O is included.
Lanthanum, Pr, Tb, Ho, Tm and Lu weresought, but their contents were below the detection
limit of the electron microprobe. No other elementswith Z > 8 were observed. Analytical data are given
in Table 2.
The empirical formula (calculated on the basis of
3 U and 32 O atoms per formula unit) is(Y0.66Dy0.08Gd0.06Er0.05Nd0.03Yb0.03Sm0.02Ce0.01)Σ0.94(H2O)7[(UO2)3(S1.01O4)2O(OH)3]·7H2O.
The
ideal structural formula is Y(H2O)7[(UO2)3(SO4)2O(OH)3]·7H2O, which requires Y2O3
8.01, UO3 60.84, SO3 11.35 and H2O 19.80, total
100 wt.%.
The Gladstone-Dale compatibility index 1 –(KP/KC) for the empirical formula is –0.015,
in the superior range (Mandarino, 2007), usingk(UO3) = 0.118, as provided by Mandarino (1976).

ANTHONY R. KAMPF ET AL.

TABLE 7. Bond-valence analysis for alwilkinsite-(Y). Values are expressed in valence units.*
Y
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
O15
OH1
OH2
OH3
OW1
OW2
OW3
OW4
OW5
OW6
OW7
OW8
OW9
OW10
OW11
OW12
OW13
OW14
Σ

U1

U2

U3

S1

0.51

1.55
1.54
1.46
1.44

0.54

S2

1.65
1.57
1.56
1.44

0.47
0.45
0.41
1.72
1.67
1.72
1.65
0.69
0.45
0.41
0.52

0.76
0.44
0.41

5.91

5.99

1.68
1.59
0.73
0.39
0.49
0.52

5.91

Σ

+0.20, +0.10+0.15, +0.17, +0.13

1.85
1.99
2.00
2.10
2.04
2.04
2.01
1.97
1.82
1.77
1.99
1.82
1.83
1.97
2.18
1.10
1.11
1.08
0.07
–0.01
–0.08
0.04
0.14
0.05
0.18
–0.02
0.07
0.03
–0.02
–0.12
0.00
0.06

+0.15
+0.24, +0.15
+0.12
+0.10
+0.10
+0.15, +0.12
+0.17
+0.15
+0.23, +0.15
–0.18
–0.20
+0.22, –0.18–0.22, –0.17–0.18, –0.22–0.24, –0.23–0.17, –0.17–0.10, –0.12–0.15, –0.15+0.10, –0.12, –0.10+0.18, –0.10, –0.10+0.22, +0.15, –0.15, –0.15+0.20, +0.17, –0.17, –0.17+0.18, +0.19, –0.20, –0.19+0.18, –0.15, –0.15+0.19, +0.17, –0.17, –0.19+0.17, +0.17, –0.13, –0.15

0.46
0.39
0.39
0.38
0.36
0.35
0.30

3.04

Hydrogen bonds

5.99

6.22

*S6+–O bond-valence parameter from Brown and Altermatt (1985); Y3+–O from Krivovichev (2012); U6+–O from
Burns et al. (1997); hydrogen-bond strengths based on O–O bond lengths from Ferraris and Ivaldi (1988).

X-ray crystallography and structurerefinement
Powder X-ray studies were done using a Rigaku
R-Axis Rapid II curved imaging plate microdiffractometer, with monochromatized MoKα
radiation (λ = 0.71075 Å). A Gandolfi-like motion
on the j and ω axes was used to randomize thesample and observed d-values and intensities were
derived by profile fitting using JADE 2010 software(Materials Data, Inc.). The powder data presented
in Table 3 show good agreement with the patterncalculated from the structure determination.
904

Unit-cell parameters refined from the powder datausing JADE 2010 with whole pattern fitting are: a= 11.5874(10), b = 12.4171(10), c = 19.4242(17) Åand V = 2794.8(4) Å3.
The single-crystal structure data for alwilkinsite(Y) were collected at room temperature on a Rigaku
R-Axis Rapid II curved imaging plate microdiffractometer, also using monochromatized MoKα
radiation. The data were processed using the
Rigaku CrystalClear software package and an
empirical (multi-scan) absorption correction wasapplied using the ABSCOR program (Higashi,2001) in the CrystalClear software suite. The

ALWILKINSITE-(Y), A NEW RARE-EARTH URANYL

FIG. 5. The [(UO2)3O5(OH)5]9– uranyl trimer in the
structure of alwilkinsite-(Y).

structure was solved by direct methods using
SIR2011 (Burla et al., 2012). SHELXL-2013(Sheldrick, 2008) was used for the refinement of
the structure. The Y site was refined with joint
occupancy by Y and Dy, yielding a site scatteringvalue of 192.61 electrons per formula unit (epfu).
While significantly higher than that expected basedon the chemical analysis, 175.92 epfu, it is still
consistent with strong dominance of Y in this site.
A difference-Fourier synthesis failed to locate the Hatom positions. All atoms were refined withanisotropic-displacement parameters, except for
O15 which yielded a negative displacement
parameter along the c axis; consequently, it was
refined with an isotropic displacement parameter inthe final cycles. Data collection and refinement
details are given in Table 4, atom coordinates anddisplacement parameters in Table 5, selected bonddistances in Table 6, and a bond-valence analysis in
Table 7. For the bond-valence analysis, calculations
are based upon full occupancy of the Y site byY. (Note that the weighted average of the bondvalence parameters for the REEs are close to thebond-valence parameters for Y.)

FIG. 6. The edge-sharing uranyl chain decorated by sulfate
groups in the structure of alwilkinsite-(Y) compared to thecluster ( part of the infinite chain) in the uranopilite
structure and the chain in the zippeite structure.

Description and discussion of the structure
The three U sites in the structure of alwilkinsite-(Y)are each surrounded by seven O atoms, forming
squat UO7 pentagonal bipyramids. This is the mosttypical coordination for U6+, particularly in uranyl
sulfates. The two apical O atoms of each bipyramid
form short bonds with the U, and this unit
uranyl group. The fivecomprises the UO2þ2
equatorial O atoms complete each of the U905

coordinations. The three different UO7 bipyramidsin the structure share a single O atom (O15) andeach bipyramid shares two edges (O15–OH1, O15–
OH2 and/or O15–OH3) with each of the two otherbipyramids to form a [(UO2)3O5(OH)5]9– trimer(Fig. 5). The trimers are linked to one anotherthrough OH1–OH2 shared edges between U1 andU3 polyhedra in adjacent trimers to form a chain
along [010]. The chain is decorated by two different
SO4 tetrahedra (S1O4 and S2O4), which each sharecorners with UO7 bipyramids in adjacent trimers.
This decorated chain (Fig. 6) has the formula[(UO2)3(SO4)2O(OH)3]3–. The S1O4 tetrahedronhas two unshared corners, while the S2O4 tetrahedron shares one corner with the YO(H2O)7
polyhedron and has one unshared corner. The
decorated chain with linked Y polyhedron forms a

ANTHONY R. KAMPF ET AL.

Although uranopilite has not been recognizedin the secondary assemblages at the Blue Lizard
mine, it is worth noting that uranyl sulfates,
including uranopilite, zippeite-related phases andalwilkinsite-(Y), can be involved in complexhydrolysis reactions. Later phases can be derived
from earlier ones by dissolution and hydrolysis inwhich structures are broken down and reassembled,
preserving some distinctive structural features.
Acknowledgements
Two anonymous reviewers and Editorial Board
Member Mike Rumsey are thanked for their constructive comments on the manuscript. A portion ofthis study was funded by the John Jago Trelawney
Endowment to the Mineral Sciences Department of
the Natural History Museum of Los Angeles County.
This research was also financially supported by GACR
post-doctoral Grant no. 13-31276P to J.P. and by thelong-term project DKRVO 2016-02 of the Ministry of
Culture of the Czech Republic (National Museum
00023272) to J.Č.

FIG. 7. The structure of alwilkinsite-(Y) viewed along[010], the chain direction. The O atoms of isolated H2Ogroups are shown as white spheres. Unit-cell outlines areshown as dashed lines. The complicated hydrogen bond
network is not shown; the scheme proposed (Table 6) was
based upon a detailed evaluation of O–O distances andgeometries, and using an analysis of bond-valencebalance (Table 7).

References
neutral unit of formula Y(H2O)7[(UO2)3(SO4)2O(OH)3] (Fig. 7). Seven additional isolated H2Ogroups complete the complement of structuralcomponents. The Y(H2O)7[(UO2)3(SO4)2O(OH)3]
units and isolated H2O groups are linked only via
hydrogen bonds. The hydrogen bonding scheme
proposed in Table 6 should be considered tentative
because, lacking H atom locations, the choices ofmany of the hydrogen bonds are ambiguous.
There are numerous structures of uranyl sulfatesthat are based upon chains of polyhedra (cf. Burns,
2005); however, none contain chains with a
topology identical to that in the structure ofalwilkinsite-(Y). As noted above, the only otherknown rare-earth uranyl sulfate mineral, sejkoraite(Y), belongs to the zippeite group. The uranyl
sulfate sheet of the zippeite topology contains edgesharing chains of UO7 pentagonal bipyramids with
outlying SO4 tetrahedra that somewhat resemble
the chain in the alwilkinsite-(Y) structure (Fig. 6);
however, the zippeite-type chains do not containuranyl trimers. The uranyl sulfate chain in theuranopilite structure (in which the chain linkage isthrough SO4 tetrahedra) contains a cluster consisting of two uranyl trimers sharing an edge andfurther decorated by SO4 tetrahedra. The topologyof this cluster is the same as the topology of asection of the alwilkinsite-(Y) chain (Fig. 6).

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