American Mineralogist, Volume 91, pages 1378–1384, 2006

Crystal chemistry and polytypism of tyrolite
SERGEY V. KRIVOVICHEV,1,2,* DMITRII YU. CHERNYSHOV,3,4 NICOLA DÖBELIN,5THOMAS ARMBRUSTER,5 VOLKER KAHLENBERG,2 REINHARD KAINDL,2 GIOVANNI FERRARIS,6
RICHARD TESSADRI,2 AND GERARD KALTENHAUSER2
1

Department of Crystallography, Faculty of Geology, St.Petersburg State University, St.Petersburg 199034, Russia
2
Institut für Mineralogie und Petrographie, Universität Innsbruck, Innrain 52, A-6020 Innsbruck, Austria
3
Swiss-Norwegian beamline, European Synchrotron Radiation Facility, BP 220, Grenoble 38043, France
4
Petersburg Nuclear Physics Institute, St. Petersburg, Gatchina, 188350, Russia
5
Laboratorium für chemische und mineralogische Kristallographie, Universität Bern,
Freiestrasse 3, CH-3102 Bern, Switzerland
6
Dipartimento di Scienze Mineralogiche e Petrologiche Università di Torino, 10125 Torino, Italy

ABSTRACTThe crystal structures of the 1M and 2M polytypes of tyrolite have been solved from single-crystal
X-ray diffraction data. The structure of tyrolite-1M [monoclinic, P2/c, a = 27.562(3), b = 5.5682(7),c = 10.4662(15) Å, β = 98.074(11)°, V = 1590.3(3) Å3] has been refined to R1 = 0.086 on the basisof 2522 unique observed reflections collected using synchrotron radiation at the Swiss-Norwegian
beamline BM01 of the European Synchrotron Research Facility (SNBL at the ESRF). The structure oftyrolite-2M [monoclinic, C2/c, a = 54.520(6), b = 5.5638(6), c = 10.4647(10) Å, β = 96.432(9)°, V =3154.4(6) Å3] has been refined to R1 = 0.144 on the basis of 2666 unique observed reflections obtained
from a non-merohedrally twinned crystal using in-house X-ray radiation and a STOE IPDS II imageplate diffractometer. The structures are based upon complex nanolayers consisting of Cu, As, and Ca
coordination polyhedra. The core of the nanolayer is a copper arsenate substructure consisting of A
and B sublayers. The B sublayer consists of chains of edge-sharing Cu octahedra running along theb axis. The A sublayer contains trimeric units of Cu octahedra sharing corners with AsO4 tetrahedra.
Two adjacent A sublayers are linked by the octahedral chains of the B sublayer resulting in formationof the 18 Å thick ABA slab. The ABA slab is sandwiched between sublayers of Ca2+ cations and H2O
molecules. Adjacent nanolayers are connected by hydrogen bonds to the interlayer species (carbonate anions and H2O molecules). The structures of tyrolite-1M and tyrolite-2M differ by the stacking
sequence of the nanolayers only. The adjacent nanolayers in tyrolite-2M are shifted by b/2 = 2.8 Å incomparison to the relative position of the nanolayers in tyrolite-1M. The structural formula of tyrolite
can be written as [Ca2Cu9(AsO4)4(OH)8(CO3)(H2O)11](H2O)x where x = 0–1.
Keywords: Tyrolite, “clinotyrolite,” crystal structure, copper arsenate, nanolayers, polytypes

INTRODUCTION
Copper arsenates are common minerals in oxidation zones
of sulfide ore deposits. There are more than 70 different copper
arsenate mineral species reported so far (see, e.g., recent papers:
Pushcharovskii et al. 2000; Zubkova et al. 2003; Locock andBurns 2003). The restricted stability of As-bearing mineralssuch as the copper arsenates may play a significant role in themobility of arsenic in the near-surface environment. Structuralinvestigations of secondary As-bearing phases may lead to a better understanding of the geochemical behavior of As and thereby
help to elucidate mechanisms of transportation and accumulationof As under natural conditions.
Tyrolite, a complex copper arsenate carbonate hydrate, was firstdescribed by A.G. Werner in 1817 (published in Haidinger 1845;
cf. Blackburn and Dennen 1997) from Schwaz-Brixlegg, Tyrol,
Austria. The mineral is widely distributed (Anthony et al. 2000)
and has been reported at more than 128 localities worldwide.
* E-mail: skrivovi@mail.ru
0003-004X/06/0809–1378$05.00/DOI: 10.2138/am.2006.2040

On the basis of wet chemical analysis of material from
Falkenstein, Austria, Church (1895) assigned the formula CaCu5(AsO4)2(CO3)(OH)4·6H2O to tyrolite. Berry (1948) reported tyrolite as orthorhombic, probable space group Pmma, a = 10.50,
b = 54.71, c = 5.59 Å, V = 3211 Å3, with Z = 4 and formula
Cu9Ca2(AsO4)4(OH)10⋅10H2O (notably lacking any carbonate).
Palache et al. (1951) considered the formula of tyrolite to be
uncertain, particularly with respect to the presence or absenceof carbonate and/or sulfate, and reported both previously cited
formulae along with supporting chemical data. Guillemin (1956)
assigned the formula CaCu5(AsO4)2(CO3)(OH)4⋅6H2O to tyroliteand considered the mineral as orthorhombic, space group Pmma,a = 10.212, b = 55.510, c = 5.602 Å, V = 3175.6 Å3. Li et al.
(2004) reported 0.73 wt% SO3 in tyrolite from China. Castillo andMallego (1972) provided chemical analysis of tyrolite with 7.17
wt% Fe2O3 and refined unit-cell dimensions as a = 10.48(5), b =55.04(5), c = 5.57(5) Å. In 1980, Ma et al. reported occurence
and properties of clinotyrolite, a tyrolite-like mineral with thecomposition Cu9Ca2[(As,S)O4]4(OH,O)10·10H2O and monoclinic
symmetry, space group Pa or P2/a, a = 10.513, b = 5.56, and c

1378

KRIVOVICHEV ET AL.: CRYSTAL CHEMISTRY OF TYROLITE

1379= 27.61 Å, β = 94.01°. Ma et al. (1980) pointed out that clinotyrolite is a monoclinic polymorph of tyrolite. Later, Liao et al.
(1996) investigated the {001} surface structure of clinotyroliteusing atomic force microscopy (AFM). Note that two varieties
of tyrolite were first recognized by Müller (1979) in samples
from Schwaz-Brixlegg, e.g., type locality of tyrolite. Schnorrer
and Poeverlein (2002) described these two varieties as tyroliteand clinotyrolite and pointed out some differences in their colorand crystal morphology.
Crystal structures of both tyrolite and clinotyrolite werepreviously unknown, primarily due to the poor quality of theirplaty and flexible crystals. Kloprogge and Frost (2000) reported a
Raman spectrum of tyrolite from Schwaz-Brixlegg and reviewed
the available spectroscopic data. Both the infrared and the Raman spectra of tyrolite suggest two symmetrically independent–
AsO3–
4 tetrahedra, OH groups, and H2O molecules. Kloprogge
and Frost (2000) assigned the bands around 1035 and 1088 cm–1
to the v1 modes of the CO2–
3 groups, but noted that this assignment
is difficult because of overlap with the OH– bending vibrations.
Details of the crystal chemistry of tyrolite and clinotyrolite haveremained unknown. The purpose of this study is to report the
crystal structures of two tyrolite polytypes, which were solved
using the experimental advantages provided by modern area
detector technologies and high-intensity synchrotron radiation.

EXPERIMENTAL METHODS
The samples of tyrolite used in this study originate from the tyrolite type locality (Brixlegg, Schwaz, Tyrol). Sample T1 is from the personal collection of G.K.,
whereas sample T2 was taken from the mineralogical collections of the Instituteof Mineralogy and Petrography of the University of Innsbruck.
Sample T1 represents a dolomite rock covered by greenish-blue flexible tyrolite
crystals (Fig. 1a). All attempts to collect indexable X-ray diffraction data from
relatively large crystals extracted from this sample were unsuccessful. In all cases,
only two unit-cell parameters could be reliably determined, whereas the third could
not be found. Close inspection of the sample T1 revealed two visually different aggregates: light blue plates and aggregates of greenish-blue elongated platy crystals.
One of the greenish-blue aggregates was split and several strongly birefringent plates
were selected under a polarizing microscope. X-ray diffraction experiments were
performed under ambient conditions at the Swiss-Norwegian beamline BM01 of
the European Synchrotron Research Facility (ESRF) using an imaging plate area
detector (Mar345; 2300 × 2300 pixels) with a crystal-to-detector distance of 150
mm. Data were collected for the crystal with dimensions of 11 × 14 × 2 µm3. Diffraction data were measured using monochromatized radiation (λ = 0.80000 Å) inan oscillation mode by rotating the crystal in ϕ by 2° in 2 min per frame; 179 frames
were measured. The unit-cell parameters for the crystal T1 (Table 1) were found to
be in general agreement with the unit-cell parameters reported by Ma et al. (1980)
for clinotyrolite (see Introduction). The intensities were integrated and merged withthe program CrysAlis. Lorentz and polarization corrections were applied; absorption
effects were corrected using SADABS (based on the method of Blessing 1995).
The structure was solved using SHELXS program. The agreement factor for the
final model is R1 = 0.089 for 2522 unique observed reflections with |Fo| ≥ 4σF. The
atomic coordinates and displacement parameters are given in Table 2.
Sample T2 represents a limestone with a small cavity filled with rectangularplates of tyrolite (Fig. 1b). One of the crystals was mounted on a glass fiber. X-ray
diffraction data were collected by means of a STOE IPDS II diffractometer using
monochromated MoKα radiation and framewidths of 1° in ω. The unit-cell dimensions (Table 1) were refined by a least-squares technique. The unit-cell dimensions
differ from those observed for the crystal extracted from sample T1. During data
treatment, it was realized that the obtained diffraction pattern represents an overlapof two diffraction patterns corresponding to two twin components related by reflection on the (100) mirror plane. Figure 2a shows the reconstructed h0l reciprocal
space plot. Figure 2b provides the pattern obtained by superimposing two monoclinic reciprocal lattices related to each other by the (100) mirror plane. In bothexperimental pattern and calculated superimposed image, a pseudo-orthorhombic
B-centered unit cell can be chosen; it corresponds to a supercell of the untwinned

FIGURE 1. SEM photos of crystals of tyrolite-1M (a) and tyrolite2M (b). Scale bars in the upper right parts of the photos correspond to
50 µm.

TABLE 1.

Crystallographic data and refinement parameters fortyrolite-1M and tyrolite-2M

tyrolite-1M
tyrolite-2M
a (Å)
27.562(3)54.520(6)b (Å)
5.5682(7)5.5638(6)c (Å)
10.4662(15)10.4647(10)β (°)
98.074(11)96.432(9)31590.3(3)3154.4(6)V (Å )Space group
P2/c
C2/c
10.477
10.570µ (cm–1)
Z
2
4
3.302
3.327
Dcalc (g/cm3)
Crystal size (µm)
0.014 × 0.011 × 0.002
0.18 × 0.12 × 0.03
λ (Å)
0.80000.71073
Total ref.
7795
11238
Unique ref.
2557
3116
2522
2666
Unique |Fo| ≥ 4σF
0.059
0.109
Rint
0.061
0.076
Rσ
0.086
0.144
R1
0.241
0.359
wR2
S
1.128
1.085
Notes: 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 P = (Fo2 + 2Fc2)/3; s = {Σ[w(Fo2 – Fc2)]/(n – p)}1/2 where n is the numberof reflections and p is the number of refined parameters.

1380

KRIVOVICHEV ET AL.: CRYSTAL CHEMISTRY OF TYROLITETABLE 2. Atomic coordinates and displacement parameters for tyrolite-1M
Atom
x
y
As1
0.86524(6)–0.2818(3)As2
0.69328(6)–0.6964(3)Cu1
0.76399(8)–0.1650(4)Cu2
0.85745(8)–0.1824(4)Cu3
0.94819(8)–0.5359(4)Cu4
0.76470(8)–0.4692(4)Cu5
0.00000.0000Ca
0.65147(13) –0.2505(7)O10.8339(4)–0.294(2)O20.8329(4)–0.573(2)O30.9197(5)–0.585(2)O40.5928(5)–0.423(3)O5
0.6363(6)0.104(3)O6
0.8764(4)–0.011(2)O7
0.5876(6)–0.095(4)O80.7032(4)–0.326(2)O90.6352(5)–0.617(2)O100.9807(5)–0.697(2)O110.9251(4)–0.270(2)O120.7270(5)–0.498(2)O130.7023(5)0.016(2)O14
0.7496(4)–0.210(2)O15
0.9704(5)–0.844(2)O16
0.7863(4)–0.155(2)O17*
0.8715(12)0.207(6)O18*
0.8060(8)0.215(4)O19*
0.5057(16)–0.075(8)O20*0.4945(15)–0.333(8)O21*0.5303(16)0.068(9)C1‡
0.5417(18)–0.050(9)* s.o.f. = 0.50.
† Fixed during refinement.
‡ s.o.f. = 0.38(9).

z0.71749(16)0.79980(16)0.84020(19)0.02406(19)0.9187(2)0.0984(2)0.00000.9456(3)0.8477(12)0.0938(12)0.2544(11)0.0623(14)0.0679(16)0.1880(12)0.7893(16)0.1443(11)0.8116(12)0.0700(11)0.0219(12)0.8955(12)0.8505(13)0.6559(10)0.8322(12)0.0259(12)0.915(3)0.820(2)0.702(4)0.018(4)0.885(4)0.791(4)Ueq
0.0098(5)0.0119(5)0.0121(5)0.0135(5)0.0132(5)0.0123(5)0.0183(8)0.0153(8)0.012(2)0.016(3)0.015(3)0.029(3)0.034(4)0.014(3)0.050(5)0.014(3)0.019(3)0.015(3)0.016(3)0.020(3)0.017(3)0.010(2)0.018(3)0.012(2)0.037(7)0.014(5)0.062(11)0.056(10)0.070†
0.022(18)U110.0205(9)0.0238(10)0.0222(11)0.0216(11)0.0258(12)0.0231(12)0.0387(19)0.0248(19)0.019(6)0.016(6)0.030(7)0.037(8)0.045(9)0.024(6)0.047(10)0.019(5)0.030(7)0.028(7)0.017(6)0.040(8)0.025(7)0.024(5)0.033(7)0.017(6)0.040(10)crystal. Within this cell, non-space group absences occur if at the same time H +2K + L = 4n + 2 and H + 2K + 3L = 4n + 2, where HKL are indices referred to thetwin pseudo-orthorhombic cell. In direct space, this cell has approximate dimensionof a ≈ 54.5, b ≈ 5.6, c ≈ 10.4 Å, which is in general agreement with the parameters
determined for tyrolite by Guillemin (1956). Thus, it is very likely that Guillemin(1956) has also studied a twinned crystal of tyrolite with the unit-cell dimensions
similar to those of the crystal 2. Consequently, the unit cells given in the ICCD
powder diffraction cards 2-0032 and 11-348 have to be revised. According to Ferraris et al. (2004), the twin observed in this sample of tyrolite can be described as
twinning by reticular pseudomerohedry, obliquity 0.92°, twin index = 2. The twoorientation matrices for the monoclinic twin components were used for intensity
integration; however, it was impossible to separate diffraction patterns from thetwo twin components. Special care was taken to manually prepare a reflection fileby selecting reflections, which could unambiguously be indexed and did not suffer from partial overlap, but all attempts failed to obtain better refinement quality.
It should be noted that an exact overlap of the two monoclinic cells would occur
if acosβ = c/2; this condition is satisfied for β = 95.51°. The data were correctedfor Lorentz, polarization, absorption, and background effects. The structure wassolved by direct methods and refined by means of the program SHELX-97. At
the final stage of the refinement, an additional twin model was introduced using
the [–10–1/0–10/001] matrix, which improved the refinement. However, becauseof the numerous partial overlaps, the refinement quality was not perfect. A final
agreement index (R1) is 0.144, calculated for the 2666 unique observed reflections(|Fo| > 4σF). The atomic coordinates and displacement parameters are given in
Table 3. Selected bond lengths are listed in Table 4.
The structure models obtained for the crystals 1 and 2 have many featuresin common and differ only by the stacking sequence of the identical layers (seebelow). This allowed us (Guinier et al. 1984) to identify the studied species as
two polytypes, tyrolite-1M (sample T1) and tyrolite-2M (sample T2). In the
final refinements, atomic positions in both structures were renumbered to allow
comparison of geometrical parameters of the two structures. As can be seen from
Table 4, the bond lengths between the corresponding sites in the two structures
are identical within 0.09 Å.
Raman spectra of tyrolite samples were recorded using the Jobin-Yvon Labpah-HR 800 spectrometer. The spectra were found to be in close agreement withthose reported by Kloprogge and Frost (2000) and showed presence of carbonate
and lack of any sulfate anions.

U22
0.0037(8)0.0042(9)0.0096(11)0.0124(11)0.0069(11)0.0049(10)0.0088(15)0.0090(17)0.007(6)0.012(6)0.012(6)0.032(8)0.016(7)0.003(5)0.078(14)0.014(5)0.019(7)0.012(6)0.015(6)0.009(6)0.007(6)0.005(5)0.009(6)0.003(5)0.037(11)U33
0.0062(9)0.0085(9)0.0051(10)0.0074(10)0.0073(10)0.0102(11)0.0081(15)0.0129(18)0.012(6)0.021(7)0.004(6)0.021(7)0.043(10)0.015(6)0.026(9)0.011(5)0.011(6)0.006(6)0.017(6)0.009(6)0.022(7)0.002(5)0.014(6)0.018(6)0.036(11)U23–0.0003(6)0.0000(6)–0.0007(8)–0.0039(8)0.0002(8)0.0025(8)0.0002(12)–0.0003(14)–0.007(5)0.002(5)0.000(5)–0.003(7)0.007(7)–0.003(4)0.014(9)–0.006(5)0.000(5)0.004(5)–0.006(5)–0.002(5)0.002(5)0.001(4)0.007(5)0.002(5)0.012(9)U130.0052(7)0.0053(7)0.0041(8)0.0049(8)0.0041(8)0.0065(8)0.0055(13)0.0052(14)0.006(5)0.006(5)0.007(5)0.014(6)0.012(7)0.003(4)0.003(7)0.013(4)0.013(5)0.007(5)0.004(5)0.002(5)0.015(5)0.006(4)0.007(5)0.004(5)0.010(8)U120.0000(6)–0.0007(7)0.0015(8)0.0014(8)0.0035(8)0.0013(8)0.0070(13)–0.0026(14)0.000(5)0.002(5)–0.007(5)–0.010(7)0.002(7)0.004(4)0.026(10)–0.001(4)–0.002(6)0.000(5)0.002(5)–0.010(6)0.000(5)–0.002(4)–0.001(5)–0.002(5)0.000(8)RESULTS
Cation coordination
There are five independent Cu positions in both structures.
The Cu2+ cations are octahedrally coordinated by anions (ϕ =O2–, OH–, H2O). The Cu2+ϕ6 octahedra are strongly distortedwith four short (1.88–2.13 Å) and two long (2.21–2.91 Å) Cu2+ϕ bonds. This type of bond-length distortion is typical for the
Cu2+ oxysalts owing to the Jahn-Teller effect (Jahn and Teller
1937; Burns and Hawthorne 1995); however, the observed
distortions are also a function of ϕ as one can see from the different degree of distortion for the different Cu sites. The roleof coordination is best illustrated for the most irregular Cu2+ϕ6octahedron observed for the Cu4 site. In both structures, thetwo apical (long) Cu2+-ϕ bonds are highly irregular with one
bond [Cu4-ϕ = O2– (O12): 2.24 Å] being significantly shorter
than the other [Cu4-ϕ = H2O (O18): 2.82 Å]. It should be notedthat the O17 and O18 sites represent H2O molecules that are
half-occupied. Thus coordinations of the Cu1, Cu2, Cu3, andCu4 sites locally vary between distorted octahedral and squarepyramidal.
Both tyrolite-1M and tyrolite-2M contain two symmetricallyindependent As sites tetrahedrally coordinated by four O atoms.
The AsO43– tetrahedra show typical geometries with the As1O4
tetrahedron in the structure of tyrolite-2M being essentiallycompressed. However, it is not obvious whether this compression is due to structural effects or just a result of poor qualityof the structure refinement.
Each structure contains one symmetrically independent Ca2+
site coordinated by five O atoms and two H2O molecules.

KRIVOVICHEV ET AL.: CRYSTAL CHEMISTRY OF TYROLITE

1381

FIGURE 3. Projection of the crystal structure of tyrolite-1M along theb axis (perspective view). Legend: Cu octahedra = gray; As tetrahedra =lined; Ca polyhedra = cross-hatched. Note that in projections parallel tob, the 1M and 2M polytypes look very similar. However, both polytypes
are distinct due to b/2 shifts of adjacent nanolayers.

linked by the octahedral chains from the B sublayer resulting information of the 18 Å thick ABA slab. The ABA copper arsenateslab is sandwiched between the sublayers of the Ca2+ cationsand H2O molecules. The adjacent nanolayers are connected byhydrogen bonds to the interlayer species (see below).
The structure of tyrolite-2M is very similar to that of tyrolite-1M and differs from the latter by the stacking sequence ofthe nanolayers.
Bond-valence analysis, interlayer species, and structural
formulaFIGURE 2. Reconstructed h0l reciprocal space plot from tyrolite-2M(a) and calculated pattern obtained by superposition of two monoclinic
reciprocal lattices of tyrolite-2M related to each other by the (100)
mirror plane (b). Empty circles correspond to the extinctions due to the
C-centered monoclinic cells of the twin components.

Structure description
Figure 3 shows projection of the structure of tyrolite-1M along
the b axis. It is based upon complex slabs consisting of Cu, As,
and Ca coordination polyhedra. The slabs are about 26 Å = 2.6 nm
thick and thus can be considered as nanolayers. This feature of thestructure of tyrolite is very specific and has not been previously
observed in oxysalt minerals. The architecture of the nanolayers
can be understood in terms of separate sublayers. The core of thenanolayer is a copper arsenate substructure consisting of the A
and B sublayers specified in Figure 3. The B sublayer represents
a series of chains of edge-sharing Cu octahedra running along theb axis. Within the chain, three Cu2+ϕ6 octahedra form trimers by
sharing the common OH10 group (Fig. 4). Similar trimeric units
constitute an important part of the A sublayer (Fig. 5). However,in this case, the trimers do not form chains but share corners with
AsO4 tetrahedra to produce complex 2-dimensional topology.
The copper arsenate substructure consists of two A sublayers

Bond-valence analysis of the two structures was performed
using bond-valence parameters taken from Brese and O’Keeffe(1991). The obtained bond-valence sums are listed in Table 5
together with the assignment of the anion positions to the O2– and
OH– anions and H2O molecules. The assignment made requires
some additional comments.
The structure of the interlayer species has been resolved in
the case of tyrolite-1M only. Even in this case, the interlayercomponents are significantly disordered. The interlayer contains approximately 50% occupied carbonate groups attachedto the O7 site. For this reason, the occupancy of this site has
been defined as O0.5H2O0.5 (Table 5). There are also additional
disordered positions that were assigned to the H2O molecules,
which most likely participate in hydrogen bonding between the
nanolayers. We were unable to locate carbonate groups in the
structure of tyrolite-2M. Instead, this structure contains a “ghost”
peak Q (3.2 e–) located at 1.47 Å from the O7 site. However, theinterlayer sites may in fact correspond to low-occupied cationicspecies (e.g., low occupied Ca and/or Cu positions). However,the data quality does not allow unambiguous resolution of theinterlayer content.
It should be noted that the bond-valence sum obtained
for the O15 site is rather high for H2O molecule (expectedvalues for the H2O-occupied site would be 0.00–0.40 v.u.). We
suggest that the O15 site in fact accommodates OH-for-H2O
substitution that can be balanced by (1) H2O-for-CO3 substitution at the O7 site or (2) introduction of low-occupied cationic

1382

KRIVOVICHEV ET AL.: CRYSTAL CHEMISTRY OF TYROLITETABLE 3. Atomic coordinates and displacement parameters for tyrolite-2M
Atom
x
y
As1
0.06789(7)0.2812(6)As2
0.15439(7)0.3026(7)Cu1
0.11904(9)0.1678(8)Cu2
0.07185(9)0.8170(8)Cu3
0.02610(9)0.5363(7)Cu4
0.11848(9)0.5278(9)Cu5
0.00000.0000Ca
0.1753(2)0.7487(15)O10.0831(4)0.295(5)O2
0.0841(5)0.431(5)O30.0404(4)0.417(4)O40.2056(7)0.582(7)O5
0.1829(7)0.106(7)O6
0.0624(5)0.003(5)O7
0.2086(8)0.892(9)O80.1495(5)0.320(5)O90.1836(6)0.379(6)O10
0.0092(6)0.299(6)O11
0.0378(5)0.273(5)O120.1372(5)0.500(6)O13
0.1500(5)0.011(5)O14
0.1265(4)0.211(4)O15
0.0147(5)0.146(5)O16
0.1078(5)0.843(5)O17*
0.0678(11)0.195(11)O18*
0.0981(10)–0.207(10)O19*0.247(3)0.56(3)O20*
0.248(2)0.17(2)O21†
0.256(5)0.79(5)Q‡
0.2352(17)0.852(17)* s.o.f. = 0.50.
† s.o.f. = 0.21(11).
‡ Peak height = 3.2(1) e–.
§ Fixed during refinement.

z0.3059(4)0.0030(5)0.4956(5)0.1189(5)0.4526(5)0.2534(6)0.00000.1761(9)0.455(3)0.201(3)0.300(3)0.338(4)0.286(4)0.270(3)0.053(5)–0.163(3)0.062(3)0.073(4)0.576(3)0.075(3)0.049(3)0.323(3)–0.151(3)0.167(3)0.012(6)0.455(6)0.091(19)0.149(12)0.06(3)0.043(11)Ueq
0.0123(9)0.0180(10)0.0158(10)0.0151(10)0.0141(10)0.0195(12)0.0205(16)0.0231(19)0.012(5)0.017(6)0.009(5)0.043(9)0.043(9)0.020(6)0.057(12)0.014(5)0.028(7)0.029(7)0.022(6)0.025(7)0.019(6)0.011(5)0.019(6)0.015(6)0.024(13)0.018(12)0.14(6)0.08(3)0.080§
0.050

U11
0.015(2)0.020(2)0.017(2)0.019(2)0.024(2)0.017(2)0.032(4)0.035(5)species into the interlayer. Once again, this problem cannot
be resolved using the present data quality.
Taking into account the results of structural investigation andthe discussion presented above, the structural formula of tyrolite
can be written as [Ca2Cu9(AsO4)4(OH)8(CO3)(H2O)11](H2O)xwhere x = 0–1. This formula is in good agreement with the H2Oamount determined for tyrolite by Guillemin (1956) as 12 H2Omolecules per 4 As atoms. However, the Ca:Cu:As ratio wasdetermined by Guillemin (1956) as 1:5:2, whereas the correct
ratio is 2:9:4, as found by Berry (1948) for tyrolite and by Ma
et al. (1980) for clinotyrolite.
Presumably the clinotyrolite of Ma et al. (1980) corresponds
to tyrolite-1M described in this paper; however, without a structural study of the holotype samples, which contain S as well, it
is impossible to reach a firm conclusion.

DISCUSSION
The structures of tyrolite-1M and tyrolite-2M differ by thestacking sequence of the nanolayers. In both structures, adjacentnanolayers are translationally equivalent. The adjacent nanolayers in tyrolite-2M are shifted by b/2 = 2.8 Å in comparison to
the relative position of the nanolayers in tyrolite-1M. This shift
is quite subtle compared to the thickness of the nanolayers (26Å). Perhaps, this feature of the tyrolite polytypes explains thedifficulties associated with the structural characterization ofthis mineral. Most of the tyrolite crystals that we studied wereunindexable along the direction perpendicular to the nanolayers.
This could be the result of the loss of periodicity along the aaxis due to the presence of extensive stacking faults or the loss

U22
0.007(2)0.009(2)0.015(2)0.018(2)0.004(2)0.013(2)0.011(3)0.015(4)TABLE 4.

U33
0.014(2)0.026(2)0.016(2)0.009(2)0.014(2)0.028(3)0.019(4)0.020(5)U23–0.0002(14)–0.0005(16)0.0027(19)–0.0044(18)–0.0006(17)0.002(2)–0.003(3)0.006(3)U130.0007(15)0.0063(18)0.006(2)0.0044(19)0.001(2)0.001(2)0.005(3)0.005(4)U12–0.0005(13)0.0016(14)0.0016(18)–0.0018(18)0.0046(17)0.0003(19)–0.010(3)0.002(3)Selected bond lengths (Å) in the structures of tyrolite-1M
and tyrolite-2M

As1-O3As1-O2As1-O6
As1-O1<As1-O>

1M
1.670(12)1.674(12)1.694(12)1.715(12)1.69

2M
1.67(2)1.70(3)
1.62(3)
1.69(3)
1.67

As2-O12As2-O9As2-O13
As2-O8<As2-O>

1.681(12)1.682(13)1.692(12)1.693(11)1.69

1.67(3)1.70(3)
1.72(3)
1.73(3)1.70

Cu1-O14
Cu1-O16
Cu1-O13
Cu1-O1
Cu1-O12
Cu1-O18<Cu1-ϕ>1.930(11)1.955(12)1.995(12)2.046(12)2.231(13)2.43(2)
2.10

1.91(3)
1.96(3)
1.99(3)2.08(2)2.21(3)2.39(6)2.09

Cu2-O11
Cu2-O16
Cu2-O1
Cu2-O6
Cu2-O2Cu2-O17<Cu2-ϕ>1.932(12)1.969(12)1.969(12)1.970(12)2.420(13)2.51(3)
2.13

1.93(3)
1.97(3)
1.98(3)2.00(3)2.38(3)2.38(7)
2.11

Cu3-O31.910(12)
Cu3-O101.927(12)
Cu3-O111.989(13)
Cu3-O15
2.071(13)
Cu3-O102.339(13)
Cu3-O172.55(3)<Cu3-ϕ>2.13
Note: ϕ = O, OH, H2O.

1.97(3)
1.88(3)2.01(3)2.13(3)2.32(3)2.73(6)
2.17

Cu4-O14
Cu4-O2
Cu4-O8
Cu4-O16
Cu4-O12
Cu4-O18<Cu4-ϕ>1M
1.951(12)1.972(12)1.991(12)2.029(12)2.235(13)2.82(2)
2.17

2M
1.94(3)
1.97(3)2.00(3)2.03(3)2.23(3)2.90(6)
2.18

Cu5-O10
Cu5-O10
Cu5-O15
Cu5-O15
Cu5-O11
Cu5-O11<Cu5-ϕ>1.945(13)1.945(13)2.026(12)2.026(12)2.589(13)2.589(13)2.19

1.88(3)
1.88(3)2.02(3)2.02(3)2.61(3)2.61(3)
2.17

Ca-O13
Ca-O4
Ca-O8
Ca-O7
Ca-O5
Ca-O9
Ca-O12<Ca-ϕ>

2.356(12)2.365(14)2.388(13)2.392(16)2.420(16)2.483(14)2.611(15)2.43

2.32(3)2.42(4)2.34(3)2.47(5)2.31(4)2.45(3)2.62(3)
2.42

C-O21
C-O19
C-O7
<C-O>

1.26(2)
1.27(7)1.29(5)
1.27

n/d
n/d
n/d

KRIVOVICHEV ET AL.: CRYSTAL CHEMISTRY OF TYROLITETABLE 5.

FIGURE 4. Ball-and-stick (a) and polyhedral (b) representations of
the chain of edge-sharing Cu octahedra that constitute the B sublayer ofthe structure of tyrolite polytypes.

1383

Bond-valence sums for atoms in the structures of tyrolite1M and tyrolite-2M

Atom
1M
2M
Site assignment
As1
5.26
5.57
As
As2
5.27
5.06
As
Cu1
2.13
2.16
Cu
Cu2
2.11
2.09
Cu
Cu3
2.09
2.01
Cu
Cu4
2.02
2.00
Cu
Cu5
1.93
2.06
Cu
Ca
2.05
2.12
Ca
O1
2.05
2.11
O
O2
1.94
1.88
O
O3
1.92
1.84
O
O4
0.34
0.30
H2O
O5
0.29
0.39
H2O
O6
1.75
2.00
O
O7*
0.32/1.63
0.25
O0.5H2O0.5
O8
1.85
1.98
O
O9
1.59
1.54
O
O10
1.17
1.33
OH
O11
1.02
1.01
OH
O12
1.96
2.01
O
O13
1.73
2.04
O
O14
0.99
1.03
OH
O15†
0.74
0.69
H2O
O16
1.32
1.32
OH
O17
0.20
0.19
H2O
O18
0.18
0.19
H2O
O19
1.38*
–
O in 1M; H2O in 2M
O20
–
–
H2O
O21
1.42*
–
O in 1M; H2O in 2M* Attached to the 50% occupied C4+ site.
† The bond-valence sum is rather high. See text for details.

that physical properties of nanosized particles are enhanced incomparison to the macroscopic crystals [see, e.g., recent reportof Sigman and Korgel (2005) on optical anisotropy of mendipite(Pb3O2Cl2) nanobelts].

ACKNOWLEDGMENTS

FIGURE 5. Sublayer A projected onto (100) plane (a) (Cu polyhedra= dark gray; As tetrahedra = light gray) and polyhedral (b) and ball-andstick (c) representations of trimeric unit of Cu octahedra.

of structural integrity.
The unique character of the structures of tyrolite polytypes
described here (nanometer-sized layers linked by weak hydrogen bonds) makes it interesting from the viewpoint of material science. Recently, layered materials with weak interlayer
bonding have attracted considerable attention. These materials
can be exfoliated into nanosheets with subsequent fabricationof nanomaterials (e.g., by rolling nanosheets into nanotubes orby intercalating of organic molecules in between the layers andfabrication of organic/inorganic nanocomposites) (Ma et al.
2004). Tyrolite polytypes are especially interesting in this regard
owing to the magnetism of the Cu2+ cations. In tyrolites, a 2-dimensional nanosized substructure of transition metal ions (Cu2+)
is sandwiched between the layers of dielectric Ca2+ cations andH2O molecules. This peculiarity of the tyrolite structure makes itvery interesting from the viewpoint of physical properties, which
are currently under investigation. It is also generally known

We thank Andrew Locock (Toronto) and Natalia V. Zubkova (Moscow) for
many useful and detailed comments that significantly improved the manuscript.
S.V.K. thanks the Austrian Science Fund (FWF) (grant no. M771-N10) and Russian
Ministry of Science and Education (grant 2.1.1.3077) for financial support. We
are grateful to L. Liao (China University of Geosciences, Beijing) for providing
us with the reprint of the paper on the AFM study of clinotyrolite. We thank V.
Dmitriev and P. Pattison for the assistance during synchrotron experiments in
Grenoble. Thilo Arlt (formerly Bern) is thanked for making X-ray single-crystal
photographs of twinned tyrolite-2M available to us.

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