Mineralogical Magazine, October 2018, Vol. 82(5), pp. 1089–1100

Markeyite, a new calcium uranyl carbonate mineral from theMarkey mine, San Juan County, Utah, USA
ANTHONY R. KAMPF1,*, JAKUB PLÁŠIL2, ANATOLY V. KASATKIN3, JOE MARTY4 AND JIŘÍ ČEJKA5
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
Fersman Mineralogical Museum of the Russian Academy of Sciences, Leninsky Prospekt, 18-2, 119071, Moscow,
Russia4
5199 East Silver Oak Road, Salt Lake City, UT 84108, USA
5
Department of Mineralogy and Petrology, National Museum, Cirkusová 1740, 193 00, Prague 9, Czech Republic[Received 3 July 2017; Accepted 19 October 2017; Associate Editor: Ian Graham]
ABSTR ACTThe new mineral markeyite (IMA2016-090), Ca9(UO2)4(CO3)13·28H2O, was found in the Markey mine,
San Juan County, Utah, USA, where it occurs as a secondary phase on asphaltum in association with calcite,
gypsum and natrozippeite. The mineral is pale yellowish-green with white streak and fluoresces brightbluish white under a 405 nm laser. Crystals are transparent and have vitreous to pearly lustre. It is brittle,
with Mohs hardness 1½ to 2, irregular fracture and three cleavages: perfect on {001}; good on {100} and{010}. The measured density is 2.68 g cm–3. Crystals are blades, flattened on {001} and elongate on [010],
exhibiting the forms {100}, {010}, {001}, {110}, {101}, {011} and {111}. Markeyite is optically biaxial(–) with α = 1.538(2), β = 1.542(2) and γ = 1.545(2) (white light); the measured 2V is 81(2)°; the dispersion
is r < v (weak); the optical orientation is X = c, Y = b, Z = a; and pleochroism is X = light greenish yellow, Y
and Z = light yellow (X > Y  Z). Electron microprobe analyses (energy-dispersive spectroscopy mode)yielded CaO 18.60, UO3 42.90, CO2 21.30 (calc.) and H2O 18.78 (calc.), total 101.58 wt.% and theempirical formula Ca8.91(U1.01O2)4(CO3)13·28H2O. The six strongest powder X-ray diffraction lines are[dobs Å(I)(hkl)]: 10.12(69)(001), 6.41(91)(220,121), 5.43(100)(221), 5.07(33)(301,002,131), 4.104(37)(401,141) and 3.984(34)(222). Markeyite is orthorhombic, Pmmn, a = 17.9688(13), b = 18.4705(6), c =10.1136(4) Å, V = 3356.6(3) Å3 and Z = 2. The structure of markeyite (R1 = 0.0435 for 3427 Fo > 4σF)
contains uranyl tricarbonate clusters (UTC) that are linked by Ca–O polyhedra forming thick corrugatedheteropolyhedral layers. Included within the layers is an additional disordered CO3 group linking the Ca–O
polyhedra. The layers are linked to one another and to interlayer H2O groups only via hydrogen bonds. The
structure bears some similarities to that of liebigite.
K E Y WO R D S : markeyite, new mineral, uranyl tricarbonate, crystal structure, liebigite, Markey mine, Utah, USA.
Introduction
IN recent years, mines in the Red Canyon portion of
the White Canyon district in south-eastern Utah
have yielded many new minerals. Our investigationof the secondary mineralization at the Blue Lizard*E-mail: akampf@nhm.org
https://doi.org/10.1180/minmag.2017.081.085

mine has already resulted in the description of
sixteen new minerals, most of which are Na uranyl
sulfates. As we have expanded our efforts to othernearby uranium mines in Red Canyon, additional
new species are being revealed. The new Na–Mg
uranyl carbonate leószilárdite (Olds et al., 2016)
was recently described from the Markey mine and,herein, we describe another new uranyl carbonate,markeyite, from this mine.

Copyright © Mineralogical Society of Great Britain and Ireland 2018
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ANTHONY R. KAMPF ET AL.

Markeyite (/ma:r ’ki: ait/) is named for the
locality, the Markey mine. The new mineral andname were approved by the International
Mineralogical Association Commission on New
Minerals, Nomenclature and Classification (IMA
2016-090). After the initial approval of the mineraland its publication in the CNMNC Newsletter No.
35 (Kampf et al., 2017), a change in the formulafrom Ca9(UO2)4(CO3)12(OH)2·28H2O to Ca9(UO2)4(CO3)13·28H2O was approved by the officers of the CNMNC (Hålenius et al., 2017). The
description is based on one holotype and fivecotype specimens. The holotype and four cotypes
are deposited in the collections of the Natural
History Museum of Los Angeles County, 900
Exposition Boulevard, Los Angeles, CA 90007,
USA, catalogue numbers 67091 (holotype), 67092,
67093, 67094 and 69095, respectively. One cotype
specimen is housed in the collections of theFersman Mineralogical Museum of the Russian
Academy of Sciences, Moscow, Russia, withregistration number 4932/1.

Lower Triassic Moenkopi Formation. The
Shinarump member consists of medium- tocoarse-grained sandstone, conglomeratic sandstone
beds and thick siltstone lenses. Ore minerals were
deposited as replacements of wood and otherorganic material and as disseminations in theenclosing sandstone. Since the mine closed in
1982, oxidation of primary ores in the humid
underground environment has produced a variety of
secondary minerals, mainly carbonates and sulfates, as efflorescent crusts on the surfaces of minewalls.
Markeyite is a rare mineral in the secondary
mineral assemblage. It occurs on asphaltum inassociation with calcite, gypsum and natrozippeite.
Other secondary minerals in the general assemblage include: ammoniozippeite, andersonite,anglesite, aragonite, arsenuranospathite, atacamaite, bayleyite, bluelizardite, bobcookite, brochantite, čejkaite, chalcanthite, chalconatronite,chinleite-(Y), covellite, cuprosklodowskite, cyanotrichite, deliensite, devilline, erythrite, eugsterite,
fermiite,jarosite,johannite,klaprothite,leószilárdite, leydetite, magnesioleydetite, mahnertite, malachite, marécottite, melanterite, metakahlerite, metasideronatrite, natrojarosite, plášilite,
posnjakite,
pseudojohannite,
redcanyonite,römerite, sabugalite, schröckingerite, sideronatrite,
sulfur, thénardite, thérèsemagnanite, uramarsite,uranospathite, wetherillite, zippeite and otherpotentially new minerals currently underinvestigation.

OccurrenceMarkeyite was found underground in the Markey
mine, Red Canyon, White Canyon District, San JuanCounty, Utah, USA (37°32′57″N, 110°18′08″W).
The Markey mine is located ∼1 km southwest of theBlue Lizard mine, on the east-facing side of Red
Canyon, ∼72 km west of the town of Blanding, Utah,and ∼22 km southeast of Good Hope Bay on Lake
Powell. The geology of the Markey Mine is quite
similar to that of the Blue Lizard mine (Chenoweth,
1993; Kampf et al., 2016), although the secondary
mineralogy of the Markey mine is notably richer incarbonate phases. The information following is taken
largely from Chenoweth (1993).
Jim Rigg of Grand Junction, Colorado began
staking claims in Red Canyon in March of 1949.
The Markey group of claims, staked by Rigg andothers, was purchased by the Anaconda Copper
Mining Company on June 1, 1951. After limited
exploration and production, the mine closed in
1955. The mine was subsequently acquired from
Anaconda by Calvin Black of Blanding, Utah underwhose ownership the mine operated from 1960 to1982 and was a leading producer in the district fornearly that entire period.
The uranium deposits in Red Canyon occur
within the Shinarump member of the Upper
Triassic Chinle Formation, in channels incised
into the reddish-brown siltstones of the underlying

Physical and optical properties
Markeyite crystals are blades and tablets (Fig. 1) up
to ∼1 mm in maximum dimension, flattened on{001} and elongate on [010]. Measurements on a
Huber Reflection Goniometer 302 confirmed the
crystal forms {100}, {010}, {001}, {110}, {101},{011} and {111} (Fig. 2). No twinning wasobserved.
Crystals are pale yellowish green and transparent
with vitreous lustre. The streak is white. The
mineral fluoresces bright bluish white under a405 nm laser. The Mohs hardness is between 1½
and 2, based upon scratch tests. Crystals are brittle
with irregular fracture and three cleavages: perfecton {001}, good on {100} and {010}. At room
temperature, the mineral dissolves very slowly in
H2O (minutes) and dissolves immediately witheffervescence in dilute HCl. The density measured
by flotation in a mixture of methylene iodide and1090
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MARKEYITE, A NEW CALCIUM URANYL CARBONATE

FIG. 1. Markeyite (blades in centre) with similar new Ca
uranyl carbonate (tapering crystals along bottom) andcalcite (brown and grey balls) on asphaltum; field of view:
1.6 mm across.

toluene is 2.68(2) g/cm3. The calculated density
based on the empirical formula and unit-cellparameters obtained from single-crystal X-ray
diffraction data is 2.699 g/cm3.
Optically, markeyite is biaxial (–), with α =1.538(1), β = 1.542(1) and γ = 1.545(1) (measured
in white light). The 2V measured directly on aspindle-stage is 81(2)°; the calculated 2V is 81.6°.
Dispersion is r < v, weak. The mineral is weakly
pleochroic: X = light greenish yellow, Y  Z = lightyellow; X > Y  Z. The optical orientation is X = c,
Y = b, Z = a.

FIG. 2. Crystal drawing of markeyite; clinographic
projection in nonstandard orientation, [010] vertical.

Raman spectroscopy
Raman spectroscopy was conducted on a Horiba
XploRA PLUS using a 532 nm diode laser. A
background correction was applied using the
Horiba software. The Raman spectrum of markeyite is shown in Fig. 3.
The broad multiple bands in the 3700–3300 and
2800–2300 cm–1 ranges are attributed to ν O–H
stretching vibrations of structurally nonequivalent/symmetrically distinct hydrogen-bonded OH andH2O groups. The 3700–3300 cm–1 range corresponds to weak hydrogen bonds and the 2800–
2300 cm–1 range to strong hydrogen bonds(Libowitzky, 1999). A weak, broad band centredat ∼1600 cm–1 is attributed to the ν2 (δ) bending
vibrations of H2O.
The aforementioned H2O band partly overlaps
with a very weak broad band associated with the
split doubly degenerate ν3 (CO3)2– antisymmetricstretching vibrations of the (CO3)2– units, with amore distinct weak band at 1412 cm–1. Medium tostrong bands at 1095, 1086, 1078 and 1067 cm–1
are connected with the ν1 (CO3)2– symmetricstretching vibrations. These bands are consistent
with the presence of four structurally nonequivalentcarbonate units (Koglin et al., 1979; Anderson
et al., 1980; Čejka, 1999 and 2005; and references
therein), but do not preclude the presence of a fifthcarbonate unit.
Aweak band at 882 cm–1 may be due to the ν2 (δ)(CO3)2– bending vibrations or to the ν3 (UO2)2+
antisymmetric stretching vibration corresponding
with the U–O bond length in uranyl at ∼1.80 Å; anoverlap/coincidence of these two bands is possible.
Avery strong band at 825 cm–1 is assigned to the ν1(UO2)2+ symmetric stretching vibrations and provides an inferred U–O bond length of ∼1.79 Å(Bartlett and Cooney, 1989). Also a coincidence ofthe ν2 (δ) (CO3)2– bending vibration and ν1 (UO2)2+
symmetric stretching vibration is likely.
Weak to strong bands at 772, 751, 733 and694 cm–1 are assigned to the doubly degenerate ν4(δ) (CO3)2– bending vibrations. A medium broadband at 238 cm–1 is assigned to the split doubly
degenerate ν2 (δ) (UO2)2+ bending vibrations andweak to medium bands at 170, 155 and 128 cm–1 tothe lattice modes (Koglin et al., 1979; Anderson
et al., 1980; Čejka, 1999 and 2005).

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ANTHONY R. KAMPF ET AL.

FIG. 3. The Raman spectrum of markeyite.

Chemical composition
Chemical analyses (nine) were performed using a
CamScan 4D electron microprobe in energydispersive spectroscopy mode (20 kV, 5 nA and3 µm beam diameter). Attempts to use wavelengthdispersive spectroscopy with a higher beam current
were made, but resulted in partial dehydration andtotals significantly higher than 100 wt.%. H2O and
CO2 were not determined directly because of
extreme paucity of material. The H2O and CO2
contents were calculated by stoichiometry on thebasis of 75 O atoms per formula unit and confirmedby the crystal-structure refinement and Raman
spectroscopy. No other elements with atomic
numbers higher than 8 were observed. Analytical
data are given in Table 1.
The empirical formula is Ca8.91(U1.01O2)4(CO3)13·28H2O. The ideal formula is Ca9(UO2)4(CO3)13·28H2O which requires CaO 18.52, UO3
41.98, CO2 20.99 and H2O 18.51, total 100 wt.%.
The Gladstone-Dale compatibility index 1 –(KP/KC) for the empirical formula is –0.027, inthe excellent range (Mandarino, 2007), using k(UO3) = 0.118, as provided by Mandarino (1976).

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-likemotion on the φ and ω axes was used to randomize
the sample and observed d values and intensities

TABLE 1. Chemical composition (in wt.%) for
markeyite.
Constituent

Mean

Range

CaO
UO3
CO2*
H2O*
Total

18.60 17.87–19.34 0.52 wollastonite
42.90 41.10–44.60 1.07 syn. UO2
21.30
18.78
101.58* Based on the structure.
S.D. – Standard deviation.

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S.D.

Standard

MARKEYITE, A NEW CALCIUM URANYL CARBONATE

were derived by profile fitting using JADE 2010
software (Materials Data, Inc.). The powder data
presented in Table 2 show good agreement withthe pattern calculated from the structure determination. Unit-cell parameters refined from thepowder data using JADE 2010 with whole pattern
fitting are: a = 17.9688(13), b = 18.4705(6), c =10.1136(4) Å and V = 3356.6(3) Å3.
The single-crystal structure data were collected atroom temperature using the same diffractometer

TABLE 2. Powder X-ray diffraction data (d in Å) for markeyite. Only calculated lines with I ≥ 2 are listed.
Iobs

dobs

dcalc

Icalc

hkl

69

10.12

13
6

8.77
8.11

91

6.41

23

5.75

100

5.43

33

5.07

10.11369.23538.98447.95436.71686.43986.37605.8244
5.69755.4321
5.15365.05685.04734.96404.86774.61764.53864.50034.49224.43544.40674.30624.20054.10544.0902
3.9772
3.86393.81853.8052
3.78203.61843.58343.56453.40993.40693.35843.35013.33083.3164
3.21993.16683.11873.10373.07843.06823.00242.99482.98672.9671

100
2
3
3
3
42
16
6
13
68
9
6
18
3
7
10
3
2
7
2
2
6
19
25
6
27
8
3
2
5
6
3
4
5
2
8
3
3
3
6
5
3
5
2
3
6
4
4
4

001
020
200
111
201
220
121
130
310
221
301
002
131
311
102
040
231
321
400
022
202
122
041
401
141
222
302
132
241
312
150
232
322
042
151
402
142
511
013
440
023
123
530
060
441
351
600
223
531

9

4.920

25

4.618

13

4.488

9
22

4.301
4.199

37

4.104

34

3.984

15

3.827

11

3.591

11

3.383

12

3.344

5
7

3.217
3.161

11

21

3.086

2.987

f
f

f
f

f

f
f

f
f
f

f

Iobs

dobs

22

2.921

f

7

2.876

f

23

2.806

25

7

19

2.732

2.651

2.521

f
f
f

f
f

11

2.469

3

2.436

3

2.375

8

2.318

f

15

2.265

f

f

12

2.190

f

9

2.134

f

19

2.091

f

dcalc

Icalc

hkl

2.94502.93782.91222.90622.90142.89322.87152.84882.83102.80872.79962.79232.74612.74212.71602.69212.64522.62952.53942.52782.52362.50372.48202.46582.45592.43722.41652.37602.32852.31972.28892.27162.26932.26382.25862.22172.21772.20382.18342.17792.15312.14322.12692.10802.10032.08612.08142.0726

3
6
5
4
2
2
3
3
3
2
11
2
2
11
7
2
3
3
3
5
5
2
4
2
2
4
3
4
4
3
3
3
2
5
3
2
2
3
2
4
2
3
2
5
2
2
5
2

061
303
260
161
313
512
601
620
252
233
323
522
451
621
442
143
532
062
460
171
262
104
622
711
271
513
124
523
443
172
702
712
462
272
324
722
044
263
281
453
244
424
570
750
082
182
571
154

Iobs

dobs

f

21

2.0518192.0198f

22

1.9794f

18

1.945512

1.907414

1.86658

1.843113

1.810118

1.786911

1.75418

1.68897

1.66587

1.612616

1.58971093
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91.56915

1.54778

1.52176
71.49991.4746

f
f

f
f

f
f
f

f
f

f
f
f

dcalc

Icalc

hkl

2.06562.05502.04682.04512.04232.02992.02442.01791.99881.99411.98071.97591.97331.9605
1.9457
1.94151.93191.90671.90491.8692
1.86781.8665
1.8635
1.84711.84331.81461.80871.7943
1.79281.78901.78731.75301.7512
1.68891.6844
1.67501.6582
1.65671.6202
1.60301.59401.59211.59091.5832
1.57281.5594
1.5556
1.52801.51861.5003
1.4779

2
3
2
3
3
3
3
2
3
2
3
3
3
4
2
3
2
2
2
2
2
3
2
3
2
2
2
3
2
3
2
3
2
2
2
2
2
2
2
2
2
2
2
3
2
2
2
2
2
2
3

831
514
553
282
703
713
273
524
191
723
841
025
205
572
752
390
604
391
083
803
743
931
283
0 10 0
634
245
425
852
714
274
753
093
492
923
4 10 1
284
026
206
872
790
484
970
555
791
971
246
426
792
972
2 12 1
11 5 1ANTHONY R. KAMPF ET AL.

and radiation noted above. The data were processedusing the Rigaku CrystalClear software package
and an empirical (multi-scan) absorption correction
was applied using the ABSCOR program (Higashi,2001) in the CrystalClear software suite. The
structure was solved by direct methods using
SIR2011 (Burla et al., 2012). SHELXL-2013(Sheldrick, 2015) was used for the refinement of
the structure.
Determining the locations of most atoms wasstraightforward. The initial structure determination
showed that the O15 site, nearly fully occupied by
O, is only 2.28 Å from an equivalent O15 site. We
first thought that the short O15–O15 distance could
be indicative of a very strong hydrogen bond;however, the distance is typical for an O–O edge ofa CO3 group. Closer examination of differenceFourier maps revealed that two partially-occupied
CO3 groups (centred by C5) share this O15–O15
edge and are completed by a partially occupiedO site, O16. In subsequent refinements, theFIG. 4. The grouping of Ca2 polyhedra in markeyite,
viewed down [001], showing the linkage by the partiallyoccupied C5 carbonate group, OH and OW7.

TABLE 3. Data collection and structure refinement details for markeyite.*
Diffractometer
X-ray radiation/power
Temperature (K)Structural formulaSpace group
Unit-cell dimensions
VZ
Density (for above formula)
Absorption coefficientF(000)
Crystal size (μm)
θ range (°)
Index ranges
Reflections collected/unique
Reflections with F > 4σFCompleteness to θ = 27.49°
Max./min. transmission
Refinement method
Restraints/parameters
GoF
Final R indices [F > 4σ(F)]R indices (all data)
Largest diff. peak/hole (e·A–3)

Rigaku R-Axis Rapid II
MoKα (λ = 0.71075 Å)/50 kV, 40 mA
293(2)
Ca9(UO2)4(CO3)12.71(OH)0.50·28.25H2O
Pmmn
a = 17.9688(13) Å
b = 18.4705(6) Åc = 10.1136(4) Å3356.6(3) Å3
2
2.692 g cm–3
10.45 mm–1
2561
110 × 80 × 10
3.16 to 27.49−23 ≤ h ≤ 22, –23 ≤ k ≤ 22, –13 ≤ l ≤ 13
22,867/4045; Rint = 0.062
3427
98.8%
0.903/0.393
Full-matrix least-squares on F 2
3/280
1.054
R1 = 0.0435, wR2 = 0.0987
R1 = 0.0544, wR2 = 0.1034+3.60/–2.28*Rint = Σ|Fo2–Fo2(mean)|/Σ[Fo2]. GoF = 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 a = 0.0420, b =40.5434 and P = [2F2c +Max(Fo2,0)]/3.

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TABLE 4. Atom coordinates and displacement parameters (Å2) for markeyite.
y/b

z/c

Ueq

U 11

U 22

U 33

U 23

U 13

U 12

0.47538(2)0.250.44024(8)0.37570(10)0.25
0.4296(4)0.6094(4)0.25
0.4235(6)0.25
0.4097(3)0.4704(3)0.4096(3)0.5499(3)0.6721(3)0.3866(3)0.25
0.3100(3)0.3792(4)0.4483(3)0.3970(5)0.5540(5)0.25
0.25
0.3137(5)0.25
0.25
0.3281(4)0.4080(3)0.25
0.3994(5)0.4729(7)0.4990(4)
0.25
0.25
0.25
0.6245(10)
0.25
0.25

0.75
0.46729(2)0.43680(8)0.63955(10)0.250.6138(4)0.4956(4)0.4050(6)0.25
0.7230(15)0.5575(3)0.6158(3)0.6771(3)0.4702(3)0.4931(4)0.4730(3)0.3731(4)0.4211(4)0.25
0.3088(3)0.75
0.75
0.3777(5)0.5564(5)0.75
0.6690(18)0.6531(18)0.5260(4)0.4127(3)0.6746(7)0.6575(4)0.75
0.5848(5)0.6261(7)0.75
0.25
0.6744(10)0.250.174(3)0.98772(4)0.07707(4)0.87250(15)0.61086(18)0.6838(4)0.8744(8)0.8050(8)0.8168(11)0.7923(12)0.576(3)0.8153(6)0.9798(5)0.8283(6)0.7577(6)0.7421(6)0.0800(5)0.7068(8)0.8783(6)0.6935(9)0.8460(6)0.0941(9)0.8808(10)0.1403(9)0.0134(9)0.5822(10)0.489(4)0.628(4)0.5243(6)0.6367(6)0.2409(15)0.3744(7)0.5764(15)0.5845(7)0.7475(13)0.9025(19)0.9269(15)0.6682(16)0.462(2)0.455(5)0.02223(12)0.02281(12)0.0195(3)0.0346(4)0.0347(8)0.0244(16)0.0240(16)0.025(2)0.026(2)0.030(9)0.0270(12)0.0286(13)0.0336(14)0.0287(13)0.0371(15)0.0298(13)0.0276(17)0.0335(14)0.034(2)0.0351(14)0.038(2)0.042(2)0.039(2)0.035(2)0.045(4)0.082(16)0.037(13)0.0416(16)0.0330(14)0.084(4)0.0533(19)0.074(4)0.061(2)0.042(4)0.067(5)0.063(5)0.120(9)0.075(11)0.09(2)0.0223(2)0.01450(18)0.0151(6)0.0363(9)0.0196(15)0.027(4)0.020(3)0.023(5)0.024(5)0.027(18)0.032(3)0.035(3)0.044(4)0.017(3)0.015(2)0.020(3)0.026(4)0.018(3)0.026(4)0.040(3)0.031(5)0.036(5)0.033(5)0.030(4)0.029(6)0.043(19)0.028(18)0.047(4)0.035(3)0.091(10)0.075(5)0.057(7)0.058(5)0.033(6)0.043(9)0.115(15)0.109(14)0.084(19)0.0189(2)0.0305(2)0.0205(7)0.0376(10)0.0254(17)0.024(4)0.031(4)0.032(6)0.022(5)0.022(14)0.018(3)0.023(3)0.020(3)0.038(3)0.071(4)0.045(3)0.032(4)0.052(4)0.034(4)0.024(3)0.035(5)0.039(5)0.038(5)0.033(5)0.058(8)0.08(3)0.024(18)0.045(4)0.039(3)0.052(7)0.055(4)0.059(8)0.077(6)0.054(8)0.068(11)0.032(7)0.158(17)0.10(3)0.0255(2)0.0234(2)0.0228(8)0.0298(9)0.059(3)0.023(4)0.021(4)0.022(6)0.034(6)0.04(2)0.031(3)0.028(3)0.036(3)0.030(3)0.026(3)0.025(3)0.024(4)0.030(3)0.043(5)0.042(4)0.049(6)0.050(6)0.044(5)0.042(5)0.049(7)0.12(4)0.06(3)0.033(3)0.025(3)0.109(12)0.030(4)0.105(11)0.046(5)0.040(8)0.089(14)0.043(9)0.095(13)0.039(14)0−0.00413(16)0.0009(6)−0.0053(7)0−0.002(3)0.004(3)−0.006(5)0−0.012(13)−0.002(2)0.002(2)−0.001(2)0.000(2)−0.013(3)−0.008(3)−0.008(3)−0.015(3)00.000(3)000.003(4)−0.001(4)0−0.02(3)−0.012(17)−0.008(3)−0.002(3)−0.016(7)−0.009(3)00.026(4)0.011(6)000.008(11)0−0.00475(16)0−0.0009(5)−0.0032(7)00.001(3)−0.004(3)0−0.010(5)0−0.007(2)−0.013(2)−0.020(3)−0.001(2)0.004(2)0.000(2)00.001(2)−0.016(4)−0.020(3)−0.001(4)0.007(4)00−0.005(4)000.001(3)−0.002(2)00.000(4)0.009(7)0.020(4)0000.010(10)000−0.0001(6)0.0061(8)0−0.005(3)−0.003(3)0000.001(2)0.004(2)0.000(3)−0.007(2)−0.005(3)0.002(3)0−0.002(3)00.001(3)
0
0
0
0
0
0
0
0.005(3)−0.009(3)00.013(4)00.030(4)0000.026(12)0* Occupancies: C5/O16: 0.35(3); O15: 0.93(4); OH/OW7: 0.25/0.75(3); OW10: 0.75(3); OW11/OW12: 0.71/0.29(5).

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MARKEYITE, A NEW CALCIUM URANYL CARBONATE

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U1
U2
Ca1
Ca2
Ca3
C1
C2
C3
C4
C5
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
O15
O16
OH
OW1
OW2
OW3
OW4
OW5
OW6
OW7
OW8
OW9
OW10
OW11
OW12

x/a

ANTHONY R. KAMPF ET AL.

occupancies of the C5 and O16 sites were refined as
equivalent. Another partially occupied O site (OH)was located 1.43 Å from the O16 site and 1.31 Åfrom OW7 on the opposite side. The OH site cannot
be occupied when either the O16 or OW7 site is
occupied. In subsequent refinements, the occupancies of the OW7 and OH sites were refined with a
combined occupancy of 1.0. The aforementioned
sites are shown in Fig. 4. There are three otherpartially occupied O sites, OW10, OW11 andOW12. The OW11 and OW12 sites are separated
by only 1.41 Å; consequently, their occupancies
were refined with a combined occupancy of 1.0. In
the final refinement, soft distance restraints wereplaced on the distances between the atoms in the
C5O3 group, which slightly improved the refinement and bond-valence sums. All sites, except the
low-occupancy OW12 site, were refined withanisotropic displacement parameters.

Data collection and refinement details are given
in Table 3, atom coordinates and displacement
parameters in Table 4, selected bond distances inTable 5 and a bond-valence analysis in Table 6. The
crystallographic information files have been deposited with the Principal Editor of Mineralogical
Magazine and are available as Supplementarymaterial (see below).

Description and discussion of the structure
Two U sites (U1 and U2) in the structure ofmarkeyite are each surrounded by eight O atoms
forming a squat UO8 hexagonal bipyramid. Thesebipyramids are each chelated by three CO3 groups,
forming uranyl tricarbonate clusters (UTC) of
formula [(UO2)(CO3)3]4– (Burns 2005; Fig. 5).
There are three different Ca–O polyhedra in the

TABLE 5. Selected bond distances (Å) for markeyite.
Ca1–O8
Ca1–O1
Ca1–O4
Ca1–O10
Ca1–O2
Ca1–O6
Ca1–OW2<Ca1–O>

2.360(5)2.368(5)2.369(6)2.383(6)2.399(5)2.404(6)2.494(6)2.397

Ca2–OH
Ca2–O15
Ca2–O3
Ca2–OW1
Ca2–OW6
Ca2–OW4
Ca2–O16
Ca2–O1Ca2–OW7
Ca2–OW5<Ca2–O>*2.279(5)2.343(5)2.384(6)2.428(7)2.450(7)2.451(7)2.63(2)2.635(6)2.660(7)2.708(8)2.503

Ca3–OW11(×2)
Ca3–O7(×2)
Ca3–O9(×2)
Ca3–OW9
Ca3–OW12(×2)<Ca3–O>*

2.24(3)2.286(8)2.324(8)2.459(16)2.71(6)
2.347

U1–O11
U1–O12
U1–O3(×2)
U1–O10(×2)
U1–O2(×2)<U1–Oap><U1–Oeq>1.773(9)1.779(9)2.411(5)2.427(6)2.481(5)
1.776
2.440

U2–O14U2–O13U2–O5(×2)
U2–O8(×2)
U2–O6(×2)<U2–Oap><U2–Oeq>1.768(9)1.773(9)2.416(6)2.436(6)2.457(5)
1.771
2.436

C1–O1
C1–O2
C1–O3
<C1–O>

1.250(9)1.295(9)1.309(9)
1.285

C2–O4
C2–O5
C2–O6
<C2–O>

1.261(9)1.296(9)1.301(9)
1.286

C3–O7
C3–O8(×2)<C3–O>

1.258(13)1.279(8)1.272

Hydrogen bonds
OW1···O5
OW1···OH
OW2···O7
OW2···O9
OW3···O11
OW4···O4
OW6···O1
OW6···O4
OW7···O14
OW8···O11
OW9···O13
OW10···O12
OW10···O13

2.717(9)2.93(3)3.017(6)3.103(6)3.334(12)2.859(9)2.876(9)2.896(9)2.981(16)3.276(15)3.197(17)2.861(19)3.124(18)

C4–O9
C4–O10(×2)<C4–O>

1.278(13)1.294(8)1.289

C5–O15(×2)
C5–O16<C5–O>

1.250(13)1.33(2)
1.277

Hydrogen bonds to
H2O groups are notincluded.

* Weighted average based on partial occupancies of OH, O15, O16, OW7, OW11 and OW12 sites; the effective
coordination of Ca2 is 8.27 and that of Ca3 is 7.00.

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TABLE 6. Bond-valence analysis for markeyite. Values are expressed in valence units.*
Ca1
0.32
0.29

Ca3

U1

U2

0.15

0.32
0.40 × 2↓
0.33

C3

Hydrogen bonds

Sum

0.16

2.09
2.02
2.04
2.05
2.00
2.02
1.96
2.16
1.94
2.08
1.98
1.85
1.92
1.86
2.29
1.82
1.12

0.16, 0.15
0.22

0.36 × 2↓

0.13
1.36
1.30 × 2↓

0.48 × 2↓
1.71
1.69

0.11, 0.11
0.09, 0.09, 0.09
0.16
0.11, 0.10
0.13

1.71
1.73
0.49
0.49

0.34 × 0.93↓
0.15 × 0.34↓
0.41 × 2→, ×0.25↓
0.27

C5

1.43
1.35 × 2↓

0.48 × 2↓

0.30

C4

1.42
1.29
1.27

0.49 × 2↓
0.46 × 2↓

0.29

C2

1.46
1.29
1.24

0.44 × 2↓
0.50 × 2↓

0.30

C1

1.46
1.18
0.15, 0.15

0.22
0.25
0.12
0.25
0.14 × 0.75↓

Hydrogen bondcontributions
to OW sites andbond-valence sumsfor OW sites are
not included.

0.25

2.07

1.92

0.46 × 0.71↓
0.12 × 0.58↓
2.17

6.24

6.29

4.00

3.98

4.13

3.95

4.10

* Multiplicity is indicated by ×↓→. Bond strength contributions to Ca sites from partially occupied O sites are adjusted for their occupancies. Ca2+–O and C4+–O bondvalence parameters from Brown and Altermatt (1985); U6+–O bond valence parameters from Burns et al. (1997); hydrogen-bond strengths based on O–O bond lengths
from Ferraris and Ivaldi (1988).

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MARKEYITE, A NEW CALCIUM URANYL CARBONATE

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O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
O15
O16
OH
OW1
OW2
OW3
OW4
OW5
OW6
OW7
OW8
OW9
OW10
OW11
OW12
Sum

Ca2

ANTHONY R. KAMPF ET AL.

FIG. 5. The uranyl tricarbonate cluster (UTC) of formula[(UO2)(CO3)3]4–.

structure: Ca1 bonds to seven fully occupied O
sites; Ca2 bonds to five fully occupied and five
partially occupied O sites (Fig. 4) for a total
effective coordination of 8.27; and Ca3 bonds tofive fully occupied and four partially occupied O
sites for a total effective coordination of 7. The
three Ca–O polyhedra share edges and corners with

the UTCs in very different ways. The Ca1
polyhedra share edges with U1 and U2 bipyramids
and corners with C1 and C2 triangles in different
UTCs. Pairs of Ca2 polyhedra share an edge toform a dimer, which is linked to a second dimer
through the partially occupied C5 triangles and OH
and OW7 sites. The group of four Ca2 polyhedra(and C5 triangle) is linked to two U1 UTCs by edge
sharing between Ca2 polyhedra and C1 triangles.
The Ca3 polyhedra share corners with two C3 andtwo C4 triangles, each being in a different UTC.
The linkages between UTCs and Ca polyhedra
form thick corrugated heteropolyhedral layers
parallel to {010} (Fig. 5) and these layers link to
one another and to interlayer H2O groups (OW3,OW8 and OW10) only via hydrogen bonds (Fig. 6).
The formula based upon the refined structure is
The
Ca9(UO2)4(CO3)12.71(OH)0.50·28.25H2O.
ideal formula assumes full occupancy of the O15
site and half occupancy of the C5 and O16 sites,
providing one CO3 group per formula unit. The OH
site, with an occupancy of 0.25, is combined with
the nearby OW7 site, with a refined occupancy of
0.75. The resultant ideal formula is Ca9(UO2)4(CO3)13·28H2O.

FIG. 6. The heteropolyhedral layer in markeyite.

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MARKEYITE, A NEW CALCIUM URANYL CARBONATE

FIG. 7. The structures of markeyite and liebigite viewed parallel to the heteropolyhedral layers. UO8 hexagonal
bipyramids are dark blue, CO3 triangles are yellow and Ca–O polyhedra are light blue; O atoms of isolated H2O groups
are white balls. Unit cell outlines are shown as dashed black lines.

The structure of liebigite, Ca2(UO2)(CO3)3·
11H2O (Mereiter, 1982), contains the same structural components as that of markeyite. The sametypes of polyhedral linkages occur in both
structures. As in the structure of markeyite, theCa–O polyhedra link the UTCs in the structure ofliebigite forming thick corrugated heteropolyhedral layers and these layers link to one
another and to interlayer H2O groups only via
hydrogen bonds (Fig. 7). However, topologies of
the two structures are quite different. Of particularnote, in the liebigite structure, one of the Ca–O
polyhedra shares an edge with a CO3 group of theUTC, but there is no such linkage in the markeyite
structure.
Acknowledgements
Igor Pekov and an anonymous reviewer are thanked
for their constructive comments on the manuscript. An
anonymous CNMNC member is thanked for pointing
out the likelihood that the short O15–O15 distancecorresponds to the edge of an additional CO3 group. A
portion of this 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 the long-term project
DKRVO 2016-02 of the Ministry of Culture of the
Czech Republic (National Museum 00023272) to J.Č.

Supplementary material
To view supplementary material for this article, please
visit https://doi.org/10.1180/minmag.2017.081.085
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