1275
TheCanadianMineralogist
Vol. 37,pp. 1275-1282(1999)

pb2+4(56+0352-)
THE STRUCTURETOPOLOGYOF S|DP|ETERS|TE,
02 (OH)2,
A NOVELTHIOSULFATESTRUCTURE
MARK A. COOPER aro FRANK C. HAWTHORNES
Depanmentof GeologicalSciences,
Universityof Manitoba,Winnipeg,ManitobaR3T2N2, Canada
ABSTRACTThe crystal structure of sidpietersite.Pb2*4(56*0152-) 02 (OH)2, ticlinic, a'/ .455(2), b 6.496(2), c 11.207(4)A, a 114.33(2),B 89.65(2),1 88.69(2)', V 494.3\3113 , Z = 2. spacegroup Pl, has been solved by djrect methodsand refined to an R index of
3 07o fot 1292 observed (l Fo | > 5o I Fo l) reflections measuredwith MoKo X-radiation. There are four symmetrically distinct Pbsites occupied by P!'* in-very asymmetric coordinations typical of stereoactive lone-pair behavior. Sidpietersiti contains athiosulfate group, (56+0352-)^,and is the first thiosulfate mineral to be characterizedstructurally. The <56*-0; distanceis 1.48 A,
the 56+-52 distance is 1.98 A, and the four anions form a distorted tetrahedral arangement about the central cation. A ladder of
Pb2nand O atoms (a motif from the structure of PbO) extends along the a axis; thisladder is decoratedby peripheral Pb atoms,
and the resultant ribbons are c-ross-linkedby thiosulfate groups to form a thick slab orthogonal to t0011. These slabs are linked
along the c axis by weak Pb-Sz bonds. The structureof sidpietersiteis unrelated to any synthetic thiosulfate structures.The latter
have cation:thiosulfate ratios between l:I and 2:1, and the structures consist of thiosulfate groups linked by weak bonds. In
sidpietersite, the cation:thiosuifate ratio is 4:1, and the cations form extended polymerized anays that are cross-linked bythiosulfate groups. There seemsno intrinsic reason why more complex structues such as sidpietersite should not occur, at leastas synthetic materials.
Keywords: sidpietersite,thiosulfate, crystal structure, Pb mineral, Tsumeb, Namibia.

Soulrarnr
Nous avons r6solu la structure cristalline de la sidpietersite,Pb2*q156*0352) 02 (OH)2, triclinique, a7.455(2), b 6.496(2), c
11.207(4)A, a 114.33(2),B 89.65(2),^y88.69(2)', V-4g4.3(3) L3,Z ='2, group" rputiut Pi, par m6thodesdirecteset affinementj u s q u ' d u n r d s i d u R d e 3 . 0 T o p o u r l 2 9 2 r 6 f l e x i o n s o b s e r v 6 e s ( l F o l > 5 o l F o l ) e t m e s u r 6 e s a v e c r a y o n n e m e n t M oLKaostructurecontient quatre sites Pb sym6triquementdistincts, oi sont log6s les atomesPb2+dans une coordinence assym6triquetypique d'uncomportement impliquant une paire d'6lectrons isolds st6rdoactifs.La sidpietersitecontient un groupe thiosulf-ate,(56*0352-), et
en serait le premier exemple dans le rbgne min6ral d etre structuralementd6crit. La distance <56*-0> est 1.48 A, la distance 56*Sr- est 1.98 .1, et les quatre anions sont dispos6sdans un agencementt6ha6drique difforme autour du cation central. Une 6chelled'atomes Pbz+et O (motif retrouv6 dans la structure de PbO) longe I'axe rz,et est ddcor6 par des atomes p6riph6riques de Pb, etlesrubansquienr6sultentsontinterli6spardesgroupesthiosulfat6spourformerunedpaissecoucheperpendiculaired[001]Ces
couchessont li6es le long de I'axe c par de faibles liaisons Pb-S2-. Du point de vue structural, la sidpietersitene ressembled aucun
compos6 thiosulfat6 synth6tique.Ce groupe de compos6spossbdeun rapport cation:thiosulfate entre l:1 et2:1, et leurs structures
compoftent des agencementsde groupes thiosulfate li6s par de faibles liaisons. Dans la sidpietersite,le rapport cation:thiosulfate
est 4:1, et les cations forment des agencementsallong6s polym6ris6s, interli6s par des groupes thiosulfat6s. Il ne semble pas yavoir une raison intrinsdque pour empOcherla formation de structuresplus complexes, comme celle de la sidpietersite,au morns
parmi les mat6riaux synth6tiques.
(Traduit par la R6daction)
Mots-clds: sidpietersite, thiosulfate, structure cristalline, min6ral de plomb, Tsumeb, Namibie.

IE-mail address: frank_hawthorne@umanitoba ca

l2'76

THE CANADIAN MINERALOGISTFORSIDPIETERSITEINFORMATIONTABLE1, MISCELLANEOUS

INrnooucrroN
Sidpietersite is a new mineral described by Roberts
et al. (1999) from the Tsumeb mine, Namibia. It occurs
in three different habits, one of which is as free-stand-ing to radiating bladed-crystaraggregatesand hence
susceptibleto crystal-structureanalysis. Sidpietersite
was the last mineral to crystallizein an assemblageof
smithsonite,zincite, galena,sphalerite,minor quartz andgreenockite. The mineral species was identified as"new" by determination of its unit cell (which did notcorrespond to any known species)and solution and refinement of the crystal structure;the results are presentedhere.

0.015x 0 04x 0.04
7.455(2) crystalsize(mm)MoKc/Graphite
6.4e6(2) Radiation
3044
11207(41 roralno.ot |11433(2)
I?:!l-l"ltll,11^,.^^ 21ft

a (A)
b
c
c (')

nJ::;'"**n'"*""".on,rro
33.ii[ii
i
y(A.)
12s2
oro.rrai' NooflF.l>5opi
11.7-2.2E(aimurhat)%
spGr.
1.3
F (merge)%
2z
30
F(obs)%
Dd(scmi) 6.765
s2
wF(obs)%,,m(mm-') 68'3(oH),I(s6'o3s'?-)o,unitcellsntents:2[Pb4F=Egql-lF"l)/:lF"lFfrh,w=1
w1=Ir.wllF.l-lF"D,t

ExpnnrvpNteL
The crystals used in this work are from the type locality. The crystal used for collection of the intensity
data is a thin plate, flattened on (001). It was attachedto
a sharpenedglass fiber and mounted on a Siemens P4
automated four-circle diffractometer equipped withmonochromatedMoKct X-radiation. Thirty-four reflections were detectedon a 3 h rotation photograph (6 < 20
< 25') and centered, and the unit-cell dimensions(Table 1) and orientation matrix were determined fromthe resulting setting angles.Intensity data were collected
in 0:20 scan-modeat a fixed scan-rateof 1o20lmin. A
total of 3044 reflections was collected over the range
4 <20 < 60', with index ranges10 < h < lO,9 <k <9,
9 < I < 15. Two standard reflections were monitored
every fifty-eight reflections; there were no significant
changesin their intensities during data collection. Data
for an empirical absorption-correctionwere collected in
psi-scan mode at intervals of 5o for eight reflections
distributed over the range 4 to 60"20. The crystal wasmodeled as a plate, and all reflections with a plate-glancing angle less than l5o were discarded, reducing
R(azimuthal) from 11.7 to 2.2Vo;the same model wasthen used to correct the 0-20 data, the standardcorrections were done. and intensities were reduced to structure factors; of the 1974 unique reflection:s,1292 wereconsideredas observed (l F. I > 5o I F" l).

Srnucrune Soluuott ervo Ret INeN4BNI
Scattering curryesfor neutral atoms were taken fromthe International Tables for X-ray Crystallography(1992); R indices are ofthe form given in Table 1, andare expressedas percentages.The Siemens SHELXTL
PLUS (PC version) system of programs was used forthis work.
The structure was solved by direct methods, the solution with the highest figure-of-merit resulting in thecorrect structure.All atom locations and identities were
derived by successivecycles ofleast-squaresrefinementand difference-Fourier synthesis,.The S(1) site was interpreted as being occupied by Sb*, and the surrounding(tetrahedral arrangement of) sites were assigned to O
atoms. However, least-squaresrefinement resulted in
one very inappropriate S(1)-O distance,a displacement
factor of zero and a large negative residual in the difference-Fouriermap at the anomalousO site. Careful electron-microprobe analysisrevealedno constituentsapartfrom Pb and S (and hence Cl could not be assignedto
the anomalous O site); thus 52- was the only possible
constituent ofthis site. Insertion ofthe S scatteringfactor at this site resulted in a stable refinement and a sensible solution consisting of two fully occupied S sites
with stereochemistry consistent with S(1) - So+ andTABLE 2 ATOMICPOSITIONSAND DISPLACEMENTFAoTOBS {x 10r) FOR SIDPIETERSITE
x
Pb(1)
PA4

U.'

Un

0 74s3(1)0 0063(r)1s9(3)

1s2(3)

06198(1)0.5932(1)062620)0 7487(1)o 1253(8)o 204(1)0.3116(1)030480)0,027s(1)0-3160(6)O 4275(81168(4)

311(4)
309(4)

O18s(3)0246(3)-O 127(2)O390(3)022912|'

olO3O(1)0.627s0)
03704(7)0 1so9(9)

o(1)
o(2)
o(3)
o(4)

o530(2)oH(2)zO 1221(1)

Pb(3)
Pb(4)
s(1)
s(2)

o(5)
oH0)

y

0352(3)o 373(2)o 128(2)0615(2)O 47512\0450(2)0.874(2)O 357(3)0.841(2)0.7s8(3)0.231121
O 0850)O084(2)0.245(2:)
0.256(2)

180(4)
146(3)
236(22)289(28)262(87)4"
255(5)
219(5)
200(5)

Us

U,"

7S(3)

-2(41

104(4)

22(4)-11(4)

94(4)
77\3)

U12
7(3)

191(3)0(3)-30(3)-3(3)16(4)-26(23) -19(16)235(3)

239{s)
155(3)
38(20)
13s(18) 181(31)56(30)
33(25)
130(30)422131l' 314(41)580(112) 607(18S) 292(125) 142(106) 13(86)-79(77)55(108)542(114) 25s(75) 438(155) 180(93)-75(83) -69(58)376(89) 103(55) 227(103) -85(62)245(70\s7\76)

340(83)326(114) 88(64132(M)
154(70)122(64)108(79)223(63\2sO(70) 130{5s)198(66) 397(79)339(75)1s(58)

Uq

52(64t86(s6)
31(73) 74(53)41(67)
21(62)-104(74) -e5(66)233(3)
182(3)
193(18)350(2s)
46s(102)400(85)285(s9)191(50)238(60)228(56)2s1(56)

1277

THE STRUCTURE OF SIDPIETERSITE(A} ANDTABLE3 SELECTEDINTEFATOMICDISTANCES
ANGLES(") FORSIDPIETEHSITETABLE 4 BOND.VALENCE(vU)TABLE FOR SIDPIETERSITE
Pb(1)Pb(1Fo(3)aPb(1)-O(4)Pb(1Fo(a)ePb(1FO(5)dP41I-OH(1)d.Pb(1)+r

2 9s(2)2.28(2)2 35(1)2 31(1)
2.6'le\2.51

Pb(3)4(212.88(2)
Pb(3)-o(3)a2.52(2)225(2)
Pb(3)-o(4)Pb(3)-OH(1)f 237(2)Pb(3)-OH(2)f 2.40(2)Pb(3)-S(2)c3.303(8)Pb(3)-S(2)a3.451(7)Pb(3)-s(2)@apL.P43Hr
2.89

Pb(2rc(r)Pq2)-O(r)b
Pq2lol2't
Pb(2Fo(3)aP42)-O(5)P42rcH(1)Pb{2)-OH(2)Pbt2)-s(2)b<Pb(2)+>
Pi/\414(2\dP44)-o(3)aP44J4l4)dPb(4)-O(s)Pb(4)-O(s)dP44l4H(2).P44fr,3.20(3)3.23(3)2.e1(212.95(2')2.3312t2.33(1)237(2)
cl-g4igL
2 A1
2 8e(3)
2 8o(2J
2 32(1)2.28(2J2.30(1)s(l )-s(2)s(1)-o(1)s(1)-o(2)s(1)-o(3).S(1)-0r

1.e8(1)142(2)
1 4e(3)13?t!.L
1.60

oH(l) OH(2) 2.81(3)s(2F-o(1)s(2)-o(2)s(2)-o(3)o(1)-o(2)o(2)-o(3)o(1)-o(3)<0-.o>

2 85(2)278(3128s(2)
2 41(41
2 44(31?,!2!2L
2.63

s(2)-s(1)-o(1) 1 1 3 ( 1 )s(2)-s(1)-o(2) 1 0 6 ( 1 )s(2)-s(1)-o(3) 1 0 8 0 )o(1Fs(1Fo(2) 111 ( 1 )o(2Fs(rFo(3) 1 0 8 ( 1 )o(rFs(1Fo(3) 11 0 ( 1 )<0-S(1}4r
109oH(2) s(2)s

P0(3)

Pb(4)

S(1)

H(1)

128

o(r)

008
008

174

190

o14 015 015o(2)o(3) o12 0 1 3 0 1 4 0 1 8
0,59 0 50
o(4) 0.55
o6

144

188

o,sl

0 49

oH(1)026

049

O4

oH(2)

044

o4't

014

r,90 203

202

204

o20

1.89

207

0.80

BrM

loE

2.10

0 55
052

Bond-valencecurues:PH:
O'Keeffe(1991)

574

199

o.20

o 80

100

100

199

(1981); $-O, PFS, S--S:Brese &3.4s(2)

S(2) = 5z-. Full-matrix least-squaresrefinement withunit weights and anisotropic-displacementparametersconverged to an R index of 3.07o. Positional and displacement parameters are given in Table 2, selectedinteratomic distancesand anglesin Table 3, and a bondvalence analysis in Table 4. Observed and calculated
structure-factors are available from The Depository of; i A + 1 y, + l , 2 ,a t x ,y + l , 2 , b : t + 1 , t + l , 2 + 1 c; : 7 , y + 1 , 2 + 1 d
e: x, t+1, 2t l: x-1,y, z, g. x+1,y+l, zoH(1)d

O(4)e

Pb(1)

Pb(4)

o(5)d
o(4)

x5)

Pb(2)

H(2)

0.18 0 13
0,09
0,07

o(s)

?,9!!A_
2.59

Pb(2)

s(2)

(2)

Pb(3)

Frc. 1. The coordination of the Pb sites in sidpietersite; large cross-hatchedcircles: Pb,
large black circles: S(2), medium unshadedcircles: OH, small unshadedcircles: O atoms, heavy lines: short bonds (< 2.4 A) involving Pb, thin lines: long bonds (> 2.6 A)
involving Pb

1278

THE CANADIAN MINERALOGIST

Unpublished Data, CISTI, National ResearchCouncil,
Ottawa, Ontario K1A 0S2, Canada.
CerroN CoonowarroN
The Pb sites
There are four symmetrically distinct Pb sites; thelocal stereochemistryat each site, plus considerationof
the overall electroneutrality, indicate that Pb is present
at each site as Pb2*.Each Pb atom bonds to three O atoms at distancesbetween2.25 and2.4OL, and theseO
atoms all lie to one side of the cation (Fig. 1). The otheranions lie at much longer distances from the central
cations (<<Pb-+>> - 3.055 A; $: unspecifiedanion).
This type of arrangementis characteristicof Pb2*with astereoactivelone-pair of electrons.There is a considerable variation in <Pb-6> distances,from 2.51 to 2.89
A. ttris variation is partly a result of variation in coordination mrmber,from [5] and 2.51 A for Pb(l) to [8]and2.89 Afor Pb(2), and partly the result of an unusually wide dispersion in anion size, from 1.34 A for OHto 1.84 A for 52 (Shannon1976).

Ftc.2. Thecoordinationof theS(1)site,shownasatoms(left)(right)in which the,l(2) atomis idenandasa tetrahedrontified asa largeblack circle;legendasin Figure1, with acircle astheS(l) sitelargerandom-dot-shaded

1.98 A, the four anions forming a very distorted tetrahedron. Despite the large dispersion in the S(1)-$ (S:O2-, S2-) distances,the angular distortion ofthe tetrahedron is not particularly large, and the mean tetrahedral
angle, 109.3', is close to the ideal value, 109.47'(Table 3).
As sidpietersiteis the first thiosulfate mineral to be
characterizedstructurally, the geomeffy of the thiosulfate group is of more than passing interest; this geometry is compared with the range in geometry fromseventeen synthetic structures (R in the range 2-9Vo)

The thiosulfate group
Details of the.l(1) coordination are shown in Figure
2. The central S(1) is linked to three O atoms at a mean
distance of 1.48 A and the S(2) anion at a distance of

1.49

1.48

1.47

S r.+o
o
+
.a

1.45

1.44

1.43

1.42
190

195

2.00

2.05

2.10

2.15

s6*-s2-(A)Frc. 3. The <56+-0> distance as a function of 56+-52 distance in thiosulfate groups fromthe synthetic compounds listed in Table 5 and ammonium thiosulfates (black circles),and sidpietersite (black triangle) The line shows the relation for ideal bond-valencesatisfaction at the central 56+cation.

THE STRUCTIJRE OF SIDPIETERSITE

Cation/S2o3 Ratio Rsf
Na,
Na,
Nq
Na.
2Na

Au1*
Ag*

S.O"
SrO,
SrO"
(SrO")zIll(HzO)za(HzO)c(HzO)z
HrO

"K,

$o,
Qoe

"19
tg
s2*
.Rb, TelTT-,$o"(s.o").
(szo"),
S,O,(HzO)ta(H,O)*(H,O)*

Mg
Ni&
cd
Ba
Ba
,Pb

SzO"
sro"
$o"
SrO"
(qOJ,
s"o"

(HzO)"

Tea(H,o)"(t-!oL
H.o(H,O)"

l1)

2
2
2
1
2
15
15

t3l
t4l
t5l
t6l
t7l
t81
tel
n0l
tt 1l
112l
t13l
114l
[15]
r't6l

Refergnces:[1] Tsng efat (1984); [2] Hess6 efaf (1993);[3] Uraz & Armagan ( 1977);[4] Ruben et al. (1974);[5] Cavalca ef ar. (1970); [6JChristidis&RenEeperis(1985); [7] Csordas (1969); [El Marsy (1971a);[9] Maroy (1971b); [10] Andsrsson & Bosson (1976);'tl[1 Eleman ef ar- (1983); [12] El€man et al. (197E);[13] Baggioefal (1997);[14]Aka efar (1980);[15] Gjerrestad& Matsy ('1973):[16] Christenssnefal,(1991)
1 excluding ammonium-bearingcompounds;' strucduraldat6 not includEdin Figure 3;
3 contains O.Se-Sts-S&O, groupcontaining twenty-three distilct thiosulfate groups(Table 5). The variation in <So*-O> as a function of
56+-52- is shown in Figure 3; there is a negative correlation, as expected from the valence-sum rule (Brown
1981,Hawthorne 1994,1997). The data for sidpietersite
lie on the general trend, albeit near the lower end of therange of 56+-52-distances.The curve in Figure 3 shows
ideal agreement with the valence-sum rule calculatedusing the observed <S-O> distances.There is reasonable agreementbetween the slopes of the curve and of
the data, but the curve is displaced approximately 0.02
A below the trend of the data. The bond-valence curvefor 56+-0 can be considered as reliable. The value reported by Brese & O'Keeffe (1991) is the sameas thatreported by Brown (1981), and gives close-to-idealbond-valencesums at So+in (SOa)groups.The problem
must therefore be with the 56+-52- bond-valence curveof Brese & O'Keeffe (1991).
Srnucrune Topor-ocy
The basic features of the sidpietersite structure areshown in Figure 4. A ladder of Pb [Pb(l) and Pb@)]
and O atoms extends along the a axis; note that this is amotif from the PbO structure (Cooper & Hawthorne
1994,Fr5.4). This ladder is decoratedon either side bya staggeredarrangementotPb lPb(2) and Pb(3)l and O
atoms to form a ribbon that extends along the a axis.
These ribbons are linked in the c direction by (S6*O3S2J

r279

groups such that the S'- anions [S(2)] form an almost
linear array in projection (Fig. a).
This linkage forms thick slabs orthogonal to [001].
In Figure 5, the "Pb-O" ladders are seen"end-on"; they
are linked into slabs orthogonal to [001] by thiosulfate
groups and Pb-O bonds. These slabs are linked in the cdirection by long weak Pb-S(2) bonds; note that in thisorientation, the Pb(2), Pb(3) andS(2) atoms form a ladder resembling the Pb-O ladder in Figure 4.
CorupenrsoNwITH OrHER Srnucrunrs
Sidpietersite is a unique structure both with regard
to minerals and to synthetic compounds. Inspection of
Table 5 shows that all the structureshave cation:S2O3
ratios between 1 and 2, and the structural arrangements
all involve thiosulfate tetrahedra floating in a networkof weak cation-oxygen bonds, usually involving H or
alkali cations. Sidpietersitehas a cation:S2O3ratio of4,and contains relatively strongly bonded and polymerized fragments of the PbO structure. However, there
does not seem to be anything particularly exotic about
the structure of sidpietersite,except for the occurrenceof the thiosulfate group in a mineral, and there seemsto
be no intrinsic reason why structureswith cation:S2O3
ratios higher than 2 should not be common. In this regard, Kucha et al. (1996) reported that viaeneite,(Fe,Pb)aSsO,containsboth 52- and 56+,and can be written as (Fe,Pb)rz (Sz2-)rr (S2O3),although there are no
structural data available for this mineral.
Trm Fonvar- Ver-nNcss or S
GROTIP
IN THETHIOSULFATE
On the basis of XANES spectroscopy,Vairavamurthy et al. (1993) proposed that the valencesof S
in thiosulfate are 5+ and 1- instead of the conventionally assigned6' and 2-. This proposal may be tested lna very simple marner using structural data and bondvalence theory. The bond-valence incident at the O anions of the thiosulfate group from the rest of the structure
is calculated independently of the formal charges of S
in the structure.Hence the S(l)-O bond-valencecan becalculated from the valence-sum rule, and the totalbond-valence incident at S(1) from the O anions of thethiosulfate group can be derived; the value is 4.83 vu(valence units). If the formal charge on ,5(l) were 5*,
the bond-valence for S(1)-S(2) [56+-52-] bond would
be 0. 17 va. This result seemsunlikely from severalperspectives.First, the four long Pb-S(2) bonds would be
required to supply 0.83 vu, at a mean p62+-52- 6on6valence of 0.21 vu. This requirement is not in accord
with the incident bond-valencesumsaroundthe Pb sites,
as it would require a bond-valencesum around Pb(3) of-2.36 vu. Second,it is unlikely that the thiosulfate groupwould be a prominent complex in aqueoussolutions at
a range of pH (and Eh) values if it were defined by sucha weak S6+-S2-bond.Third. it seemsintuitively unlikely

1280

THE CANADIAN MINERALOGIST

Pb(2,3)
Pb(1,4)Pb(2,3)

Frc.4.

The crystal structure ofsidpietersite viewed down an axis 5o from [010]; legend as in Figures I and 2.

that a group involving such a weak bond would occur
with such reproducible stereochemistry in a range ofstructures.Thus it does not seem possible that the formal valencesof S in the thiosulfate group are 5+ and 1-.
Ac<NowLeocBlreNrs
We thank Andy Roberts for bringing this material to
our attention, Charles L. Key for supplying us withmaterial, and John Hughes and one anonymousreviewer
for their comments on the manuscript. This work was
supported by Natural Sciences and Engineering ResearchCouncil of Canadagrants to FCH.
ReEBnBNces

Beccro, S., Penno, M.I , BAGGro,R. & GoNzAr-nz,O (1997):
Cadmium thiosulfate dihydrate. Acta Crystallogr. C53,
1521-r523.
Bnsse, N.E & O'Knprre, M. (1991): Bond-valenceparameters
for solids. Acta Crystallogr. B,47, 192-197.
BRowN, I D. (1981): The bond-valence method: an empiricalapproach to chemical structure and bonding. 1n Structure
and Bonding in Crystals II (M. O'Keeffe and A. Navrotsky,eds ) Academic Press,New York, N.Y. (1-30).
Crvrrcr, L , MANGTA,A., PelurBnr, C. &Pnuzzt, G. (1970):
The crystal and molecular structure of NaAgS2O3.H2O.
Inorg. Chim Acta 4, 299-3O4.
CHnrsrsr,rsBN,
N.A., HAZELL,R.G , HEwAr, A.W. & O'RsLrv,
K.P.J. (1991): The crystal structure ofPbS2O3.Acta Chem.
Scand 45,469-473.

Ar,r, Y., ARMA6AN,
N. & Unez,A.A (1980):An X-ray diffraction study of barium thiosulphatemonohydrate,BaS2O3.|1r9.
Z Kristallogr.151,6l-66
Cnnrsrus, P.C. & RrNrzBpBnrs, P.J. (1985): Experimental
ANDERSSoN,
J.-E.& Bossor,r,B (1976):Thallium(I)rhiosulphate.Acta Crystallogr.B.32,22252227.

charge density in polythionate anions. L X-ray study ofelectron density distribution in potassium trithionate,
K2$O6 Z. Kristallogr 173,59-14-

THE STRUCTURE OF SIDPIETERSITE

1281

F\c 5 The crystal structure of sidpietersite viewed down an axis 3o from [100]; legend as in Figures I and 2; the broken lines
indicate H bonds

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Received January 28, 1999, revised mnnu;cript acceptedAugust28,1999,