15
The Canadian Mineralogist
Vol. 52, pp. 15-25 (2014)
DOI : 10.3749/canmin.52.1.15

KOKINOSITE, Na2Ca2(V10O28)•24H2O, A NEW DECAVANADATEMINERAL SPECIES FROM THE ST. JUDE MINE, COLORADO:
CRYSTAL STRUCTURE AND DESCRIPTIVE MINERALOGY
Anthony R. KAMPF§
Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard,
Los Angeles, CA 90007, U.S.A.

John M. HUGHES
Department of Geology, The University of Vermont, Burlington, VT 05405, U.S.A.

Barbara Nash
Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, U.S.A.

Joe MARTY
5199 E. Silver Oak Rd., Salt Lake City, UT 84108, U.S.A.

Abstract
Kokinosite, Na2Ca2(V10O28)•24H2O, is a new mineral species from the St. Jude mine, Slick Rock district, San Miguel County,
Colorado, USA. Kokinosite typically occurs as tablets or blades up to 0.05 mm thick, with stepped faces, and 1 mm in maximum
dimension. Crystals are yellow orange, although sometimes they are tinted orange brown; the streak of the phase is yellow. The
luster of kokinosite is subadamantine, and the mineral is transparent; it does not fluoresce in short- or long-wave radiation. The
Mohs hardness is ca. 1½. Kokinosite possesses a brittle tenacity, and displays one good cleavage on {011}. No parting wasobserved, and fracture is irregular. Density (calc.) = 2.353 g cm–3 on the basis of the empirical formula and the single-crystal celldata. Kokinosite is biaxial (–), with α 1.725(3), β 1.770(5), and γ 1.785(3). The 2V was measured as 56.6(3)° from extinction data,
and 2Vcalc = 58.7°. Dispersion is r < v, moderate. The optic orientation was incompletely determined, with X ^ a = 15°, Y ≈ b. The
mineral is pleochroic: X, Z = orange yellow, Y = orange, and X = Z < Y. Electron probe microanalysis and the crystal structure
solution gave the empirical formula (based on V = 10 and O = 52 apfu) (Na1.88K0.01)Σ1.89(Ca1.81Sr0.12)Σ1.93(V10O28)•24H2O.
The simplified structural formula is Na2Ca2(V10O28)•24H2O. Kokinosite is triclinic, P1, with a 8.74899(19), b 10.9746(3), c
12.8216(9)Å, α 114.492(8), β 105.093(7), γ 91.111(6)°, V 1070.25(11) Å3, and Z = 1. The strongest four lines in the diffraction
pattern are [d in Å(I)(hkl)]: 9.88(100)(010, 011), 7.92(36)(101), 8.42(33)(100), and 6.01(31)(111, 110). The atomic arrangementof kokinosite was solved and refined to R1 = 0.0379 for 3806 Fo > 4σF reflections. The structural unit is a decavanadate polyanion,(V10O28)6–; charge balance in the structure is maintained by the [Na2Ca2(H2O)24]6+ interstitial unit that exists as Na(H2O)6octahedra and Ca(H2O)8 polyhedra that link into chains by edge- and corner-sharing. The linkage between the structural unit
and the interstitial unit occurs solely by hydrogen bonding. The new mineral is named in honor of Michael Kokinos (b. 1927) of
Shingle Springs, California, a well-known mineral collector and member of the Micromounters’ Hall of Fame.
Keywords: kokinosite, new mineral species, decavanadate, crystal structure, St. Jude mine, Gypsum Valley, San Miguel County,
Colorado, USA

Introduction
The U and V (Uravan) deposits of Colorado andUtah have been a rich source of ore for the productionof uranium, vanadium, and radium. Throughout the§Corresponding author e-mail address: akampf@nhm.org

Colorado Plateau Uravan Mineral Belt, uranium andvanadium minerals occur together in bedded or rollfront deposits in the sandstone of the Salt Wash memberof the Jurassic Morrison Formation (Carter & Gualtieri
1965, Shawe 2011). The first production of uranium

16

the canadian mineralogist

from the Colorado Plateau took place in the SlickRock district, beginning around 1900; Shawe (2011)provides a comprehensive summary of the deposits of
the Slick Rock district, and some of those details arerecounted here.
Mining activity for uranium, vanadium, and radiumin the Slick Rock district has been episodic, dependinglargely on the demand for the various ores. The last
major period of mining occurred from 1949 to 1983,
when uranium mining ended due to the large decline
in the price of uranium ores. By the time mining
activities ceased in the mid-1980s, 4,839,300 tons ofuranium-vanadium ore had been produced in the SlickRock district (Shawe 2011). With the resurgence of theprice of uranium ore in 2007, several of the Slick Rockdistrict mines reopened.
Collecting at the mines of the Slick Rock districtby one of the authors (JM) has revealed numerous
secondary vanadium minerals that result from oxidationof vanadium ore bodies that are exposed to near-surface
conditions in the mining process. With the exceptionof martyite, Zn3(V2O7)(OH)2•2H2O (Kampf & Steele
2008a), which contains the (V2O7) 4– divanadate group,and dickthomssenite, Mg(V2O6)•7H2O (Hughes et al.
2001), and calciodelrioite, Ca(VO3)2(H2O)4 (Kampf etal. 2012a), which contain (VO3) – vanadate chains, allof the recently described species contain the decavanadate anionic complex, (V10O28) 6–, found in the pascoite
family of minerals. All known minerals that containthe (V10O28)6– decavanadate unit are listed in Table 1.
In addition to those minerals that contain the(V10O28)6– decavanadate unit sensu stricto, the firstminerals that contain protonated decavanadate groups
have also been discovered in mines of the Colorado
Plateau. The deposits have also yielded the first mineralthat contains a mixed-valence (V10O28) polyanion,
the vanadylnonovanadate {(V4+V5+9)O28} group. The
minerals that contain these variants of the decavanadategroup and references thereto are also listed in Table 1.
Herein, we describe another new secondary mineralfrom the Uravan deposits. The new species was
discovered in the St. Jude mine, Slick Rock district,
San Miguel County, Colorado, USA. The mineralis named in honor of Michael (Mike) Kokinos (b.
1927) of Shingle Springs, California, U.S.A. Mike is acharter member of both the Southern California MicroMineralogists (SCMM) and the Northern California
Mineralogical Association (NCMA), and is a member ofthe Micromounters’ Hall of Fame; his collecting and his
mentoring of others in the collecting community have
led to the description of many new mineral species,
and the naming of a new mineral in his honor is mostappropriate.
The new mineral and name were approved by theCommission on New Minerals, Nomenclature and Classification of the International Mineralogical Association(IMA 2013–099). Six cotype specimens of kokinosite
are deposited in the collections of the Natural History
Museum of Los Angeles County, Los Angeles, California, USA, catalogue numbers 64004 (also a cotype
for wernerbaurite), 64074, 64075, 64076, 64077, and
64078.

Occurrence
Kokinosite was found in the St. Jude mine, Gypsum
Valley, Slick Rock district, San Miguel County, Colorado, USA. The discovery site is a stope not far fromthe interconnected West Sunday and Sunday mines. All
three mines are currently inactive and their entrances

TABLE 1. THE PASCOITE FAMILY OF MINERALS
A. {V10O28}6– Decavanadates
huemulite
hughesitehummeritekokinosite
lasalitemagnesiopascoite
pascoitepostiteschindlerite
wernerbaurite

Na4 Mg(V10O28) •24(H2O)
Na3Al(V10O28) •22(H2O)
K2Mg2(V10O28) •16H2O
Na2Ca2(V10O28)•24H2O
Na2Mg2 (V10O28) •20H2O
MgCa2(V10O28) •16H2O
Ca3(V10O28) •17H2O
MgAl2(V10O28)(OH)2•27H2O
Na2(H3O)4(V10O28) •10H2O
Ca2(H3O)2(V10O28) •16H2O

Colombo et al. 2011
Rakovan et al. 2011
Hughes et al. 2002
This work
Hughes et al. 2008
Kampf & Steele 2008b
Hughes et al. 2005
Kampf et al. 2012b
Kampf et al. 2013b
Kampf et al. 2013b

B. {HxV10O28}(6–x)– Protonated Decavanadates
gunterite
rakovanite

Na4(H2V10O28) •22H2O
Na3(H3V10O28) •15H2O

Kampf et al. 2011b
Kampf et al. 2011aC. Mixed-Valence {(V4+xV5+10–x)O28}(6+x)– VanadylvanadatenashiteNa3Ca2[(V4+V5+9)O28] •24H2O

Kampf et al. 2013a

KOKINOSITE, A NEW DECAVANADATE MINERAL SPECIES FROM THE ST. JUDE MINE, COLORADO

are sealed. Kokinosite is rare; the mineral was foundgrowing on a corvusite-montroseite-bearing sandstone
block and is closely associated with gypsum, huemulite,
metarossite, pascoite, rossite, and wernerbaurite (Kampf
et al. 2013b). Other minerals found in the same area in
the St. Jude mine include calciodelrioite (Kampf et al.
2012a), delrioite, hendersonite, hughesite (Rakovan
et al. 2011), nashite (Kampf et al. 2013a), powellite,
postite (Kampf et al. 2012b), and schindlerite (Kampf
et al. 2013b). Other minerals found nearby in adjacentareas of the West Sunday mine are andersonite, gunterite(Kampf et al. 2011b), hewettite, munirite, natrozippeite,
pyrite, rakovanite (Kampf et al. 2011a), sherwoodite,and tyuyamunite.
The mineral forms from the oxidation of montroseite-corvusite assemblages in a moist environment.
Mining operations have exposed unoxidized andoxidized phases. Under ambient temperatures andgenerally oxidizing near-surface environments, water
reacts with pyrite in the deposit to form aqueous solutions with relatively low pH. The various secondary
vanadate phases that formed depend upon the Eh-pH
and the presence of other cations (Na+, Ca2+, Mg2+,
Al3+) (e.g., Evans & Garrels 1958).

17

ultra-violet radiation. The Mohs hardness of kokinosite
is ca. 1½. Kokinosite possesses a brittle tenacity, one
good cleavage on {011}, and irregular fracture. The
density of kokinosite could not be measured because themineral dissolves in available aqueous density liquids
and there is insufficient material for direct measurement. Density (calc.) = 2.35 g cm–3 on the basis of theempirical formula and 2.352 g cm –3 on the basis of theideal formula, both using single-crystal unit cell data.

Optical Properties
The optical properties of kokinosite were determinedin white light. Kokinosite is biaxial (–), with α 1.725(3),β 1.770(5), and γ 1.785(3). The 2V was measured
as 56.6(3)° from extinction data using EXCALIBR(Gunter et al. 2004), and 2Vcalc = 58.7°. Dispersion is r
< v, moderate. The optic orientation was incompletely
determined, with X ^ a = 15°, Y ≈ b. The mineral ispleochroic: X, Z = orange-yellow, Y = orange, and X = Z< Y. Compatibility [1 – (Kp/Kc) = 0.003], as calculated
from the empirical formula using the density derived
from the single-crystal unit cell, is superior (Mandarino1981).

Appearance and Physical Properties
Kokinosite typically occurs as tablets or blades up to
0.05 mm thick, with stepped faces, and 1 mm maximum
dimension (Figs. 1 and 2). Crystals sometimes form
larger, irregularly stepped crystal masses up to several
mm across. Kokinosite is yellow orange, although it issometimes tinted orange-brown; the streak of the phaseis yellow, typical of decavanadate-bearing minerals. The
luster of kokinosite is subadamantine, and the mineral istransparent; it does not fluoresce in short- or long-wave

Fig. 1. Kokinosite crystals from the St. Jude mine. Field ofview = 2 mm.

Fig 2. Crystal drawing of kokinosite; clinographic projection
in nonstandard orientation, a vertical.

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the canadian mineralogist

The Composition of Kokinosite
Analyses of kokinosite (10 analyses from three
crystals) were obtained at the University of Utah usinga Cameca SX-50 electron microprobe with four wavelength dispersive spectrometers. Analytical conditions
were 15 keV accelerating voltage, 10 nA beam current,
and a beam diameter of 10 µm. Counting times were
10 seconds for each element except Na, which wasanalyzed with five second count times. In the analyticalroutine, Na, Ca, and V were counted simultaneously,
i.e., first on their respective spectrometers. Raw X-ray
intensities were corrected for matrix effects with a φρ(z)algorithm (Pouchou & Pichoir 1991).
There was no visible damage from the electron beam;
however, as is typical of decavanadate phases (i.e.,
postite, rakovanite, hughesite, gunterite, and lasalite),kokinosite partially dehydrates under the vacuum of the
microprobe chamber. This H2O loss results in higher
concentrations for the remaining constituents than are
to be expected for the fully hydrated phase. Because
insufficient material is available for a direct determination of H2O, the H2O content was calculated basedon stoichiometry. The analyzed constituents were thennormalized to provide a total of 100% when combinedwith the calculated H2O.
The results of the chemical analysis of kokinosite arecontained in Table 2. The empirical formula of kokinosite (based on V = 10 and O = 52 apfu) is (Na1.88K0.01)
Σ1.89(Ca1.81Sr0.12)Σ1.93(V10O28)·24H2O. The simplified
structural formula is Na2Ca2(V10O28)·24H2O, which
requires Na2O 4.09, CaO 7.40, V2O5 59.99, H2O 28.52,
total 100.00 wt.%.

Crystal Structure: Experimental
Powder and single-crystal X-ray diffraction data for
kokinosite were obtained with a Rigaku R-Axis Rapid
II curved imaging plate microdiffractometer using
monochromatized MoKα radiation. The powder data
presented in Table 3 are in good agreement with those
calculated from the structure data. Observed d values

and intensities were derived by profile fitting using
JADE 2010 software (Materials Data Inc.).
The Rigaku Crystal Clear software package wasused for processing of the structure data, including
the application of an empirical multi-scan absorption correction using ABSCOR (Higashi 2001). The
structure was solved by direct methods using SIR2004(Burla et al. 2005). SHELXL-97 software (Sheldrick2008) was used, with neutral atom scattering factors,
for the refinement of the structure. O–H distances wererestrained to be 0.90(2)Å, and H–H distances for each
H2O were restrained to be 1.45(3)Å. The Ueq for each H
was set to 1.2× that of O to which it is bonded. Detailsof the sample, data collection, and structure refinement
are provided in Table 4, final atom coordinates andequivalent isotropic temperature factors in Table 5, andselected bond distances are given in Table 6. Table 7
contains bond valences for selected bonds in kokinosite.
A Table of structure factors, a CIF file, and a Tableof anisotropic displacement parameters are available
from the Depository of Unpublished Data on the MAC
website [document Kokinosite CM52_15].

Atomic Arrangement of Kokinosite
Minerals that contain the decavanadate groupcan be considered members of the pascoite family,
pascoite (Ca3V10O28•17H2O) being the first-describeddecavanadate mineral (Hillebrand et al. 1914). All of
the minerals of the pascoite family possess bipartite
structures that contain a structural unit and an interstitialunit, as elucidated by Schindler & Hawthorne (2001).
Those authors noted that the structural unit is an arrayof high-bond-valence polyhedra that is usually anionicin character, and in kokinosite that unit is the (V10O28)6–
decavanadate polyanion. The structural units are linked
by the interstitial unit, an array of large, low-valence
cations, simple anions, and H2O groups that is usuallycationic in character. Interstitial units link the structuralunits with weak cation-anion and hydrogen bonds into
a continuous structure; in kokinosite the interstitial unit
has a composition of (Na2Ca2•24H2O)6+.

TABLE 2. ANALYTICAL RESULTS FOR KOKINOSITE
Oxide

wt.%

Range

S.D.

Norm. wt.%

FormulaProbe Standard

Na2O
K2 O

4.64
0.04

3.78–5.95
0.02–0.07

0.71
0.02

3.85
0.03

4.09

albitesanidine

CaO
SrO

8.08
1.01

6.39–9.91
0.52–2.54

1.09
0.70

6.70
0.84

7.40

diopside
Sr titanate (syn)

V2O5*

72.43

70.66–74.08

1.29

60.06

59.99

Y vanadate (syn)

H2O*
Total

–
86.20

28.52
100.00

28.52
100.0

*Based upon crystal structure with V = 10 and O = 52 apfu.

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KOKINOSITE, A NEW DECAVANADATE MINERAL SPECIES FROM THE ST. JUDE MINE, COLORADO

In all the pascoite family minerals, the (V10O28)6–
decavanadate polyanion or its chemical variants(Table 1) form the structural unit of the mineral; thedecavanadate polyanion, formed of ten distorted VO6octahedra, is depicted in Figure 3. The decavanadate
unit is a polyoxometalate that has received considerable attention by the community of chemists andbiologists over many decades (Aureliano 2011, Tracey
et al. 2007).

The interstitial unit in kokinosite
In all decavanadate sensu stricto minerals [i.e.,
those minerals containing the unprotonated (V10O28)6–
group with pentavalent vanadium], the 6– charge ofthe structural unit is balanced by the 6+ charge of theinterstitial unit. In Table 1-A, the compositions of theinterstitial units are evident for all the decavanadatebearing minerals.

TABLE 3. POWDER X-RAY DIFFRACTION DATA FOR KOKINOSITE
Iobs

dobs

dcalc

Icalc

hkl

11.148644

9.881749

9.80818.35807.8987

30

11.24

100

9.88

33
35

8.42
7.92

14

6.80

31

6.01

3

5.46

6

4.942

8

4.531

15

4.144

2

4.032

7

3.920

4
2

3.695
3.607

8

12

9

3.378

3.285

3.117

Iobs

dcalc

Icalc

hkl

001

2.9234

1

130

010

2.9146

2

104

51
43
36

011
100
101

2.87452.87072.8559

1
4
4

214
131
222

6.893051102.85101302

6.75936.1806
6.1267
6.0266

17
2
5
15

111
011
012
111

2.84112.82042.79502.7871

2
3
2
4

031
134
312
004

5.969291102.76543311

5.90355.43664.9408

4
3
4

101
102
020

2.74302.73302.7183

1
4
2

042
233
204

4.90413022

2.68501

122

4.55354.46724.35854.21274.14494.11774.03104.01583.90463.8246
3.69363.6037

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

121
112
201
112
012
013
122
211
212
123
211
032

2.66942.65782.64312.60442.60202.59282.55772.55182.53952.51512.46842.4520

4
2
7
2
1
2
1
1
1
3
3
5

041
043
113
231
311
221
125
321
131
115
321
044

3.44651220

2.44238313

3.37978222

2.43701

104

3.35782112

2.42191230

3.34993.29943.29393.28873.26943.2385
3.2282
3.17183.16383.1279

3
1
1
2
2
1
2
3
1
2

221
221
030
121
033
221
130
133
114
212

2.39392.23022.22862.21482.19712.18952.18632.17442.16752.1573

5
1
5
2
4
4
1
2
3
1

322
123
222
145
045
213
132
323
314
231

3.12251124

2.13211

241

3.11403.06683.0513

2
2
2

211
013
014

2.10602.08892.0808

1
1
1

403
245
332

28

dobs

2.814

17

2.659

3

2.608

8

2.540

13

2.447

3

2.399

2

2.237

22

2.189

6

2.090

Iobs

dobs

3

2.059

26

1.96133

1.923011

1.86565

1.81707

1.69196

1.64533

1.61763

1.56176

1.47228

1.43274

1.40955

1.388941.36486

1.3450

dcalc

Icalc

hkl

2.06041312

2.05562204

2.04912.00391.9802

1
1
4

141
154
422

1.960912155

1.9244
1.88461.87571.8709

5
1
1
7

223
136
414
423

1.84873322

1.8173
1.76831.7123

3
1
1

156
351
426

1.69851262

1.69481.68891.6781
1.67161.64671.63011.62181.61711.61411.6126
1.58591.5723

2
1
1
1
1
1
2
1
1
1
1
1

337
510
226
500
137
127
262
511
135
235
501
427

1.56211362

1.47411362

1.46491353

1.4553
1.43651.43531.43411.43051.42651.4104
1.39301.38591.3781

1
1
1
1
1
1
1
1
1
1

138
126
601
438
245
145
530
600
373
605

1.35651177

1.35001.34351.3421

1
1
1

184
373
238

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the canadian mineralogist

F ig 3. [V 10 O 28 ] 6– structural unit in
kokinosite.

TABLE 4. DATA COLLECTION AND STRUCTURE
REFINEMENT DETAILS FOR KOKINOSITE
Diffractometer
X-ray radiation/power
Temperature
Ideal FormulaSpace group
Unit cell dimensions

VZ
Density (for above formula)
Absorption coefficientF(000)
Crystal sizeθ range
Index ranges
Reflections collected/unique
Reflections with Fo > 4σFCompleteness to θ = 27.47°
Refinement method
Parameters refined
GoF
Final R indices [Fo > 4σ(F)]R indices (all data)
Largest diff. peak/hole

Rigaku R-Axis Rapid II
MoKα (λ = 0.71075 Å)/50 kV, 40 mA
298(2) K
Na2Ca2(V10O28) •24H2O
P1
a 8.74899(19) Åb 10.9746(3) Åc 12.8216(9) Åα 114.492(8)°β 105.093(7)°γ 91.111(6)°1070.25(11) Å3
12.352 g cm–3
2.479 mm–1
756
120 x 80 x 30 µm
3.01 to 27.47°
11 ≤ h ≤ 9, 14 ≤ k ≤ 14, 16 ≤ ℓ ≤ 16
20535/4885; Rint = 0.041
3806
99.6%
Full-matrix least-squares on F2
371
1.055
R1 = 0.0379, wR2 = 0.0933
R1 = 0.0529, wR2 = 0.1009+1.15/–0.65 e A–3*Rint = Σ|Fo2–Fo2(mean)|/Σ[Fo2]. GoF = S = {Σ[w(Fo2–Fc2)2]/(n–p)}1/2. R1 = Σ||Fo|–|Fc||/Σ|Fo|.
wR2 = {Σ[w(Fo2–Fc2)2]/Σ[w(Fo2)2]}1/2; w = 1/[σ2(Fo2) + (aP)2 + bP] where a is 0.0503, b is0.9223 and P is [2Fc2 + Max(Fo2,0)]/3

KOKINOSITE, A NEW DECAVANADATE MINERAL SPECIES FROM THE ST. JUDE MINE, COLORADOTABLE 5. COORDINATES AND EQUIVALENT ISOTROPIC DISPLACEMENTPARAMETERS§ (Å2) OF ATOMS IN KOKINOSITE
Atom
V1
V2
V3
V4
V5
Na
Ca
O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
OW1

OW2

OW3

OW4

OW5

OW6

OW7

OW8

OW9

H1a
H1b
H2a
H2b
H3a
H3b
H4a
H4b
H5a
H5b
H6a
H6b
H7a
H7b
H8a
H8b

H9a
H9b
OW10
H10a
H10b
OW11
H11a
H11b
OW12
H12a
H12b

x/a

y/b

z/c

U(eq)

0.80250(6)0.99343(6)0.99148(6)0.82947(7)0.80443(7)0.5210(2)0.32122(9)0.0075(2)0.8517(2)0.8527(2)0.6901(3)0.1481(3)0.1475(3)0.6752(3)0.8277(3)0.8269(3)0.0175(3)0.9925(3)0.6942(3)0.6594(3)0.0128(3)0.5575(4)0.482(4)0.482(4)0.4723(4)0.377(3)0.550(4)0.6999(3)0.790(4)0.745(4)0.7456(3)0.787(5)0.819(4)0.3774(3)0.450(4)0.300(3)0.4855(6)0.560(6)0.480(7)0.0909(4)0.100(7)0.086(7)0.1337(4)0.137(5)0.092(5)0.3551(3)0.310(5)0.294(4)0.4256(3)0.513(3)0.348(3)0.2414(8)0.270(10)0.261(10)0.8861(5)0.930(6)0.948(6)0.47931(5)0.24235(5)0.51228(5)0.72650(6)0.23481(5)0.1387(1)0.32248(7)0.6077(2)0.6002(2)0.3721(2)0.5781(2)0.4111(2)0.1888(2)0.3604(2)0.1560(2)0.3793(2)0.8267(2)0.1471(2)0.7998(3)0.1333(2)0.3894(2)0.3016(4)0.343(5)0.343(5)0.9660(3)0.908(4)0.911(4)0.9971(3)1.038(4)0.937(3)0.2575(3)0.201(4)0.295(4)0.3281(3)0.394(3)0.326(4)0.1541(4)0.151(6)0.082(5)0.3804(4)0.293(3)0.407(5)0.1336(3)0.048(3)0.145(4)0.5686(3)0.614(4)0.579(4)0.4199(3)0.409(4)0.423(4)0.1424(5)0.057(5)0.156(7)0.0970(4)0.029(4)0.174(3)0.46000(4)0.47322(4)0.29221(4)0.69749(5)0.22879(5)0.6354(1)0.93686(6)0.6031(2)0.3948(2)0.5470(2)0.5410(2)0.25020(19)0.39888(19)0.33217(19)0.33586(19)0.18775(18)0.81227(19)0.5410(2)0.7534(2)0.1177(2)0.7732(2)0.5709(3)0.545(5)0.545(5)0.6947(3)0.661(4)0.695(4)0.5364(2)0.532(4)0.562(4)0.8106(3)0.840(4)0.795(4)0.7602(2)0.781(3)0.699(3)0.9129(3)0.972(3)0.840(3)0.0099(3)–0.012(4)0.086(3)0.7663(2)0.743(4)0.701(3)0.9940(2)1.052(3)0.930(3)0.1656(2)0.210(3)0.199(3)0.0012(4)–0.033(6)0.079(3)0.9242(3)0.885(4)0.965(5)0.0191(1)0.0210(1)0.0222(1)0.0266(1)0.0264(1)0.0385(3)0.0312(2)0.0187(4)0.0200(4)0.0205(4)0.0261(5)0.0270(5)0.0258(5)0.0260(5)0.0260(5)0.0265(5)0.0291(5)0.0295(5)0.0385(6)0.0405(6)0.0327(5)0.0622(10)
0.075
0.075
0.0577(8)
0.069
0.069
0.0386(6)
0.046
0.046
0.0445(7)
0.053
0.053
0.0322(5)
0.039
0.039
0.0908(15)
0.109
0.109
0.0698(11)
0.084
0.084
0.0445(7)
0.053
0.053
0.0376(6)
0.045
0.045
0.0370(6)
0.044
0.044
0.069(2)
0.083
0.083
0.0718(10)
0.086
0.086

§U(eq) is defined as one third of the trace of the orthogonalized U

ij tensor.

21

22

the canadian mineralogist

Fig 4. Atomic arrangement of kokinosite
viewed down [100]. Large white spheres
are O atoms of isolated H2O groups.
Small white spheres are H atoms. The
unit cell outline is shown by a dashedblack line.

TABLE 6. SELECTED BOND DISTANCES AND ANGLES IN KOKINOSITE
V1–O7
V1–O4
V1–O3
V1–O2
V1–O1
V1–O1
<V1–O>

1.688(2)1.692(2)1.917(2)1.931(2)2.110(2)2.148(2)1.914

V2–O11
V2–O6
V2–O8
V2–O2
V2–O3
V2–O1
<V2–O>

1.614(2)1.818(2)1.826(2)1.994(2)
1.999(2)2.235(2)
1.914

V3–O14
V3–O9
V3–O5
V3–O2
V3–O3
V3–O1
<V3–O>

1.614(2)1.814(2)1.829(2)1.997(2)2.005(2)2.235(2)1.916

V4–O12V4–O10
V4–O6
V4–O5
V4–O4
V4–O1
<V4–O>

1.601(2)1.846(2)1.873(2)1.885(2)2.026(2)2.311(2)
1.924

V5–O13
V5–O10
V5–O8
V5–O9
V5–O7
V5–O1
<V5–O>

1.603(2)1.826(2)1.876(2)1.887(2)2.064(2)2.300(2)1.926

Na–OW1Na–OW2Na–OW3Na–OW4Na–OW3Na–OW5<Na–O>

2.308(3)2.384(3)2.399(3)2.405(3)2.443(3)2.617(3)2.426

Ca–OW6
Ca–OW7
Ca–OW8Ca–OW5Ca–OW9Ca–OW10
Ca–OW11
Ca–OW9<Ca–O >

Hydrogen bonds
D–H...A
D–H
H...A
...
OW1–H1A O4
0.89(3)2.05(3)OW1–H1B...O3
0.86(3)
1.96(3)OW2–H2A...O8
0.92(3)
1.93(3)OW2–H2B...O120.91(3)2.00(3)OW3–H3A...O11
0.92(2)2.07(3)OW3–H3B...O6
0.91(2)
1.84(3)OW4–H4A...OW12 0.89(2)1.95(3)OW4–H4B...O14
0.86(3)2.11(3)OW5–H5A...OW10 0.86(2)2.04(3)OW5–H5B...O2
0.89(2)
1.97(3)OW6–H6A...O13
0.88(3)
1.93(3)...
OW6–H6B OW2
0.93(3)1.75(3)OW7–H7A...OW11 0.89(3)2.12(4)OW7–H7B...O5
0.91(3)2.02(3)OW8–H8A...O8
0.87(2)2.10(3)OW8–H8B...O11
0.88(2)2.02(3)OW9–H9A...OW4
0.90(2)
1.94(3)OW9–H9B...O9
0.91(2)
1.84(3)...
OW10–H10A O7 0.87(2)2.08(3)OW10–H10B...O5 0.88(2)2.05(2)OW11–H11A...O13 0.92(3)2.11(3)OW11–H11B...O12 0.92(3)1.92(3)OW12–H12A...O10 0.87(3)2.26(3)OW12–H12B...OW7 0.87(3)2.34(3)2.331(4)2.425(3)2.452(3)2.464(2)2.476(3)2.559(3)2.583(5)2.814(3)
2.513

D...A
2.925(4)2.810(3)2.779(4)2.859(4)2.991(3)2.750(3)2.830(5)2.970(4)2.881(4)2.805(3)2.773(4)2.672(6)2.921(7)2.861(4)2.958(3)2.897(3)2.818(4)2.739(3)2.922(3)2.921(3)3.033(6)2.834(5)3.105(4)3.165(6)<DHA
171(5)
178(5)
153(4)
156(5)
174(4)
172(4)
173(4)
174(4)
165(4)
157(3)
160(6)
171(6)
149(5)
155(4)
168(4)
173(4)
167(4)
173(4)
164(4)
172(4)
178(6)
173(7)
164(5)
160(5)

23

KOKINOSITE, A NEW DECAVANADATE MINERAL SPECIES FROM THE ST. JUDE MINE, COLORADOTABLE 7. SELECTED BOND VALENCES AND BOND VALENCE SUMS (vu) IN KOKINOSITE

O1
O2
O3
O4
O5
O6
O7
O8
O9
O10
O11
O12
O13
O14
OW1
OW2
OW3

V1

V2

V3

V4

V5

0.44
0.39
0.71
0.73
1.35

0.31

0.31

0.25

0.26

0.60

0.59

+0.15

2.05

0.59

0.58

+0.17
+0.13
+0.14 +0.14
+0.19
+0.13
+0.12 +0.15
+0.19
+0.09
+0.11 +0.14+0.14 +0.16+0.17 +0.10+0.12–0.13 –0.17–0.15 –0.14 +0.21–0.11 –0.19

2.07
2.03
2.01
1.98
1.99
2.03
1.96
1.92
1.92
2.03
1.99
1.79
–0.08
0.10
0.03

–0.16 –0.12 +0.16

0.05–0.14 –0.15–0.17 –0.21–0.11 –0.14 +0.08–0.12 –0.14–0.16 –0.19

0.07
–0.01
0.12
0.01
0.01

–0.13 –0.14 +0.14

0.07–0.10 –0.16 +0.11–0.09 –0.08 +0.16

0.04
–0.01

1.36

0.96
0.94

0.93

0.97

1.67

0.55
0.80
0.83

0.89
1.73

1.67

Na

1.72
0.22
0.18
0.18
0.16
0.17
0.10

OW5
OW6
OW7
OW8
OW9
OW10

4.99

5.06

5.05

5.05

5.03

hydrogen bonds

∑
1.97

0.49
0.82
0.80
0.94

OW4

OW11
OW12
∑

Ca

1.01

0.26
0.37
0.29
0.27
0.25
0.10
0.20
0.19
1.94

Na+–O bond strengths from constants of Wood & Palenik (1999); V5+–O, and Ca2+–O, and hydrogen bond strengths based on H…Obond lengths from constants of Brown & Altermatt (1985).

In kokinosite, the interstitial unit has a compositionof Na2Ca2•24H2O; the atomic arrangement is formedof the aforementioned (V10O28)6– structural units thatare linked by Na(H2O)6 octahedra and Ca(H2O)8 polyhedra that link into chains by edge- and corner-sharing(Fig. 4). Adjacent Na(H2O)6 octahedra share OW3–OW3 edges and adjacent Ca(H2O)8 polyhedra share
OW9–OW9 edges, in each case forming edge-sharing
dimers, and these adjacent Na- and Ca-centered dimers
share OW5 corners. Indicating each polyhedron by
its cation (Na or Ca), shared edges by “=” and sharedcorners by “–”, the chain is thus (–Na=Na–Ca=Ca–)∞.
The interstitial unit also includes one isolated H2Ogroup.
Table 1-A lists the formulas of the pascoite-family
minerals, which illustrates the composition of the interstitial unit in each phase. The contents of the interstitial
units include Na, Mg, Ca, Al, H2O, and hydronium ions;no interstitial O atom exists that is not fully hydrated.
The interstitial cations occur in monomers, dimers,
trimers, and infinite chains; in any given pascoite

mineral more than one type of coordination can occur.
Kokinosite is the only pascoite-family mineral in which
all the interstitial cations are linked in infinite chains andno other interstitial polymer type is present; it may bethat the similar size of the interstitial cations (Na, Ca)facilitates such polymerization in the interstitial group.
The linkage between the (V10O28)6– structural units
and the Na2Ca2•24H2O interstitial unit is attained byhydrogen bonding alone; there are no bonds between
the interstitial group cations (Na, Ca) and the O atomsof the decavanadate group. Table 7 lists the hydrogenbonds that link the interstitial unit and structural unit
in kokinosite.

Acknowledgments
The manuscript was greatly improved by reviewsby Associate Editor Jim Evans, Henrik Friis, and an
anonymous reviewer, for which we express our thanks.
This study was funded by the John Jago Trelawney
Endowment to the Mineral Sciences Department of the24

the canadian mineralogist

Natural History Museum of Los Angeles County andby grant NSF-MRI 1039436 from the National Science
Foundation to JMH.

Hughes, J.M., Schindler, M., & Francis, C.A. (2005) The
C2/m disordered structure of pascoite, Ca3(V10O28)•17H2O.
The Canadian Mineralogist 43, 1379–1386.

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Received November 24, 2013, revised manuscript accepted
February 21, 2014.