1229
The Canadian Mineralogist
Vol. 45, pp. 1229-1245 (2007)
DOI : 10.2113/gscanmin.45.5.1229

PIZGRISCHITE, (Cu,Fe)Cu14PbBi17S35, A NEW SULFOSALT FROM THE SWISS ALPS:DESCRIPTION, CRYSTAL STRUCTURE AND OCCURRENCENICOLAS MEISSER§
Musée Cantonal de Géologie and Institut de Minéralogie et Géochimie, Université-Dorigny, CH–1015 Lausanne, Switzerland

KURT SCHENKLaboratoire de Cristallographie 1, EPFL, Dorigny, CH–1015 Lausanne, Switzerland

PETER BERLEPSCH
Heinrichsgasse 8, CH–4055 Basel, SwitzerlandJOËL BRUGGER
School of Earth and Environmental Sciences, The University of Adelaide, North Terrace, 5005 Adelaide, South Australia,
and Division of Mineralogy, South Australian Museum, North Terrace, 5000 Adelaide, South Australia

MICHEL BONIN
Laboratoire de Cristallographie 1, EPFL, Dorigny, CH–1015 Lausanne, Switzerland

ALAN J. CRIDDLE†
Department of Mineralogy, Natural History Museum, Cromwell Road, London SW7 580, U.K,

PHILIPPE THÉLIN AND FRANÇOIS BUSSY
Institut de Minéralogie et Géochimie, Université-Dorigny, CH–1015 Lausanne, Switzerland

ABSTRACT
Pizgrischite, (Cu,Fe)Cu14PbBi17S35, is a new mineral species named after the type locality, Piz Grisch Mountain, Val Ferrera,
Graubünden, Switzerland. This sulfosalt occurs as thin, striated, metallic lead-grey blades measuring up to 1 cm in length,
embedded in quartz and associated with tetrahedrite, chalcopyrite, pyrite, sphalerite, emplectite and derivatives of the aikinite–
bismuthinite series. In plane-polarized light, the new species is brownish grey with no perceptible pleochroism; under crossed
nicols in oil immersion, it presents a weak anisotropy with dark brown tints. Minimum and maximum reßectance values (in %) in
air are: 40.7–42.15 (470 nm), 41.2–43.1 (546 nm), 41.2–43.35 (589 nm) and 40.7–43.3 (650 nm). Cleavage is perfect along {001}and well developed on {010}. Abundant polysynthetic twinning is observed on (010). The mean micro-indentation hardness
is 190 kg/mm2 (Mohs hardness 3.3), and the calculated density is 6.58 g/cm3. Electron-microprobe analyses yield (wt%; mean
result of seven analyses): Cu 16.48, Pb 2.10, Fe 0.77, Bi 60.70, Sb 0.35, S 19.16, Se 0.04, total 99.60. The resulting empiricalchemical formula is (Cu15.24Fe0.80Pb0.60)⌺16.64(Bi17.07Sb0.17)⌺17.24(S35.09Se0.03)⌺35.12, in accordance with the formula derived fromthe single-crystal reÞnement of the structure, (Cu,Fe)Cu14PbBi17S35. Pizgrischite is monoclinic, space group C2/m, with thefollowing unit-cell parameters: a 35.054(2), b 3.91123(1), c 43.192(2) Å, ␤ 96.713(4)°, V 5881.24 Å3, Z = 4. The strongest seven
X-ray powder-diffraction lines [d in Å (I)(hkl)] are: 5.364(40)(604), 4.080(50)(805), 3.120(40)(118), 3.104(68)(318), 2.759(53)(911), 2.752(44)(910) and 1.956(100)(020). The crystal structure is an expanded monoclinic derivative of kupčikite. Pizgrischite
belongs to the cuprobismutite series of bismuth sulfosalts but, sensu stricto, it is not a homologue of cuprobismutite. At the type§†E-mail address: nicolas.meisser@unil.ch
Deceased 2nd May 2002.

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THE CANADIAN MINERALOGIST

locality, pizgrischite is the result of the Alpine metamorphism under greenschist-facies conditions of pre-Tertiary hydrothermal
Cu–Bi mineralization.
Keywords: pizgrischite, new mineral species, sulfosalt, crystal structure, kupčikite, Alps, Switzerland.

SOMMAIRE
La pizgrischite, (Cu,Fe)Cu14PbBi17S35, est une nouvelle espèce minérale nommée d’après son lieu de découverte dans les
Alpes, le Piz Grisch, montagne située dans le Val Ferrera, canton des Grisons, Suisse. Ce sulfosel se présente en Þnes lames striéesà l’éclat métallique gris acier et qui mesurent jusqu’à 1 cm. Ces cristaux sont inclus dans du quartz et associés à la tétraédrite,
la chalcopyrite, la pyrite, la sphalérite, l’emplectite et à des sulfosels de la série aïkinite–bismuthinite. Optiquement, en lumière
simplement polarisée, le nouveau minéral est brun grisâtre sans pléochroïsme visible. Sous immersion dans l’huile et en lumière
doublement polarisée, il présente une faible anisotropie optique avec des teintes brun foncé. Le clivage est excellent selon {001}et bien marqué selon {010}. Les valeurs minimales et maximales du pouvoir réßecteur dans l’air, en fonction de la longueurd’onde incidente, sont (en %): 40.7–42.15 (470 nm), 41.2–43.1 (546 nm), 41.2–43.35 (589 nm) et 40.7–43.3 (650 nm). Un abondant maclage polysynthétique s’observe dans le plan (010). La dureté par micro-indentation est de 190 kg/mm2 (ce qui correspondà une dureté selon Mohs de 3.3), et la densité calculée, de 6.58. L’analyse chimique par microsonde électronique donne (en %poids; résultat moyen de sept analyses): Cu 16.48, Pb 2.10, Fe 0.77, Bi 60.70, Sb 0.35, S 19.16, Se 0.04, total 99.60. La formule
chimique empirique est: (Cu15.24Fe0.80Pb0.60)⌺16.64(Bi17.07Sb0.17)⌺17.24(S35.09Se0.03)⌺35.12 et qui correspond bien avec celle obtenue
par résolution de la structure cristalline: (Cu,Fe)Cu14PbBi17S35. La pizgrischite est un sulfosel monoclinique, de groupe spatial
C2/m, qui présente les paramètres réticulaires suivants: a 35.054(2), b 3.91123(1), c 43.192(2) Å, ␤ 96.713(4)°, V 5881.24 Å3,
Z = 4. Les sept raies les plus intenses du cliché de diffraction par la méthode des poudres sont [d en Å (I)(hkl)]: 5.364(40)(604),
4.080(50)(805), 3.120(40)(118), 3.104(68)(318), 2.759(53)(911), 2.752(44)(910) et 1.956(100)(020). La structure cristalline est
plus fortement expansée que celle de la kupčikite. La pizgrischite appartient à la série des sulfosels bismuthifères apparentésà la cuprobismutite; toutefois, il ne s’agit pas au sens strict d’un homologue de la cuprobismutite. Dans sa localité-type, lapizgrischite résulte du métamorphisme régional, en faciès schistes vert, d’un produit de minéralisation hydrothermale à cuivre
et bismuth d’âge pré-Tertiaire.
Mots-clés: pizgrischite, nouvelle espèce minérale, sulfosel, structure cristalline, kupčikite, Alpes, Suisse.

INTRODUCTION
The sulfosalt pizgrischite, (Cu,Fe)Cu14PbBi17S35, isa new mineral species from an Alpine metamorphosed
pre-Tertiary Cu–Bi quartz vein situated in the steep
northern face of Piz Grisch, Val Ferrera, Graubünden,
eastern Swiss Alps. Small stratabound Mn-deposits(e.g., Fianel and Starlera) located in Triassic carbonates on the northwestern and southwestern face of Piz
Grisch, are well known because of the occurrence of
new or rare mineral species, in some cases in striking
samples, described during the last decade (i.e., Þanelite, manganlotharmeyerite, ansermetite, sailauÞte,wallkilldellite, romeite, tilasite, medaite, palenzonaite,and långbanite; Brugger & Berlepsch 1996, Brugger& Gieré 1999, 2000, Brugger et al. 2003a, b, Meisser
et al. 2004).
The occurrence of an acicular sulfosalt at Piz Grisch
was mentioned already by Grünenfelder (1956), who
identiÞed it as “wittichenite” on the basis of its opticalproperties. A new sampling was made in July 1988, andsubsequent XRD analysis showed that the “wittichenite”
is indeed an unknown mineral species.
The new mineral is named after the type locality, Piz
Grisch mountain. The mineral was approved by the IMA
Commission on New Minerals and Mineral Names (voteno. 2001–002). Two holotype specimens are depositedat the Museum of Geology, Lausanne (MGL), Switzer-

land: sample MGL 58622 consists of crystals isolatedby dilute hydroßuoric acid and used for the singlecrystal study, chemical analysis and synchrotron X-ray
powder diffraction. Sample MGL 53660 is a polishedsection used for the measurement of optical data, forchemical analysis and a study of its paragenesis. A
cotype sample is deposited at the British Museum of
Natural History, London (BM–NH). All three specimens are fragments of a single hand-sized specimen.

OCCURRENCE AND GEOLOGICAL SETTING
Occurrence
The Cu–Bi quartz vein containing pizgrischite
is located in the face under the ridge extending to
the northwest of Piz Grisch (3062 m), Val Ferrera,
Graubünden, eastern Swiss Alps. The coordinates of thetype locality according to the Swiss federal system are:755.400/155.700; 2950 m. The access to this mineraloccurrence is made difÞcult by its location in a cliff
face, and climbing is necessary.
Mineral association
Sprays of pizgrischite crystals are embedded in Þnegrained saccharoidal quartz. Other associated sulÞdes
and sulfosalts form mm-sized masses dispersed in

PIZGRISCHITE, A NEW SULFOSALT FROM THE SWISS ALPS

1231

quartz. Xenomorphic Bi-bearing tetrahedrite, Cu11.07
Ag 0.01Fe 1.29Zn 0.08Sb 2.88As 0.64Bi 0.48S 12.54 with 6.10
wt.% Bi (two analyses) is commonly partially replacedby flame-like inclusions of emplectite, Cu0.99Fe0.03
Bi0.97Sb0.01S2.00Se0.01 (four analyses) and idiomorphic
hammarite ± friedrichite, Pb2.28Cu2.53Bi3.43Sb0.02S8.70(two analyses). Some isolated grains, also embedded
in quartz, consist of krupkaite ± lindströmite,
Pb1.03Cu1.17Bi2.82Sb0.03S5.95 (two analyses) admixed
with minor emplectite. Chalcopyrite, pyrite and rare
sphalerite complete the primary association of metallic
minerals. The Þrst stage of alteration by meteoric water
led to the formation of covellite and digenite alongcleavages and cracks of pizgrischite or associated sulfosalts. Bismutite and malachite are common and azurite
is rare in the second stage of alteration. Some crystalsof pizgrischite are completely replaced by a mixture of
bismutite and malachite.
Geological setting
Pizgrischite is the main metallic mineral in dm-size
pods within a massive to saccaroidal quartz vein (0.5–2
m in thickness) that runs semiparallel to a siderite vein
(up to 5 m in thickness; Fig. 1). Both veins can befollowed along strike for about 80 m, and are embedded
in augen gneisses belonging to the pre-Triassic basement of the Surreta nappe. Similar veins of siderite wereactively mined until the second half of the 19th century
in Val Ferrera. Grünenfelder (1956) considered thehost augen gneiss to be a variety of the early Permian
Roffna rhyolite, dated by Marquer et al. (1998) at 268.3± 0.6 Ma. Marquer et al. (1996) suggested that thesemineralized augen gneisses represent pre-Carboniferous
gneisses that underwent a pre-Alpine high-temperature
event. The augen gneiss is overlain by Triassic dolomitic carbonates hosting numerous small stratabound(i.e., Fe–Mn ± As, V, Be, Sb, Mo deposits), which wereinterpreted to share a syngenetic exhalative origin by
Brugger & Gieré (1999, 2000).
Strong siliciÞcation is observed in the augen gneissat the contact of the veins on Piz Grisch (Fig. 1). Boththe quartz and siderite veins are discordant relative
to the main regional Alpine schistosity (S1), which
formed under greenschist-facies conditions during acomplex but still poorly constrained P–T path in the
Tertiary, leading from near-blueschist-facies to lowergreenschist-facies conditions (e.g., Baudin et al. 1995,
Brugger & Gieré 2000). The D1 episode of folding of
the veins and remobilization of siderite in the S1 foliation unambiguously indicate a pre-D1 emplacement of
the siderite and quartz veins (Fig. 1).
The mineralogy of the siderite veins at Val Ferrera ismonotonous, and mostly consists of manganoan sideriteand ankerite with accessory hematite. Alkaline skarnlike quartz + green aegirine + hematite or magnetite
rocks occur as lenses and layers at the contact between
some veins and the hosting gneiss, as lenses within the

FIG. 1. Synthetic proÞle through the thickest part of the vein
system at Piz Grisch.

1232

THE CANADIAN MINERALOGISTore, or as veinlets cross-cutting the ore; such rocks havenot been observed at Piz Grisch. Pyrite and chalcopyrite
are rare accessories in the siderite ores.
The quartz vein at Piz Grisch is one of the few
pre-Alpine base-metal occurrences known in the
Briançonnais domain of the Eastern Swiss Alps. Other
occurrences include: 1) stratabound sulfide mineralization (tetrahedrite, chalcopyrite, galena, bornite,
pyrite, covellite) in the basal Triassic quartzite at
Ursera and Traversa (Surreta nappe, Escher 1935)
and in the Triassic marbles near Piz Grisch (Swisscoordinates 754.540/156.060); 2) dolomite – calcite –quartz – barite veinlets with pyrite, uraninite, Se-richgalena, tetrahedrite, sphalerite, chalcopyrite, bornite,
covellite, molybdenite in the dolomitic marbles of the
Suretta nappe in the hydroelectric tunnel “Valle di Lei– Ferrera” (Dietrich et al. 1967) and 3) barite, quartz,
carbonate, albite veins with galena, sphalerite, Ag-richtetrahedrite, chalcopyrite, bornite, pyrite, arsenopyrite,
covellite, siegenite, stannite and polybasite–pearceite(Sommerauer 1972) in Mesozoic breccias of the Schams
nappe (Escher 1935).
However, the quartz vein at Piz Grisch appears to
be unique in Val Ferrera, not only owing to its highBi-content and mineralogy, but also by its association
with a siderite vein. Pizgrischite originated from theremobilization of a primary, pre-Tertiary, hydrothermal
quartz–sulÞde assemblage during the Alpine regional
metamorphism.

APPEARANCE AND PHYSICAL PROPERTIESThe new mineral species occurs as blades up to 1
cm in length. They are metallic lead grey, thin, opaqueand striated, forming sprays in quartz (Fig. 2). The poor
quality (microfractures, rough surface) and abundant
twinning of the crystals chemically extracted fromthe quartz preclude a complete morphological study.
Pizgrischite is brittle, with an uneven fracture, and it
possesses a grey-black streak. Cleavage is perfect along{001}, and well developed on {010}; microscopically(Fig. 3), abundant polysynthetic twinning is observedon (010). Vickers micro-indentation hardness, VHN100,
measured with a Leitz Durimet (Miniload 2) hardness
tester, gave a mean value of 190 and a range of 174–202
kg/mm2 (n = 10), which corresponds to a Mohs hardness of 3.3(2). These values are comparable to thoseobtained for the related sulfosalts hodrušhite (200 kg/
mm2; Kodĕra et al. 1970) and kupčíkite (192 kg/mm2;
Topa et al. 2003a).
On the basis of the unit-cell volume, 5881.24 Å3,and using the average result of seven chemical analyses
obtained with an electron microprobe, the calculated
density Dx is 6.58 g/cm3.
If observed in reßected light, pizgrischite is not
perceptibly bireßectant or pleochroic; it has straight
extinction, but is only weakly anisotropic in darkbrown. Rotation of the analyzer by a few degrees

from full extinction lightens the brown color. In someareas, between crossed polars, irregular lamellae ofdifferent shades of brown are perceptible: these may be
deformation twins related to late Alpine deformation.
Reßectance values in air and oil (Zeiss nD = 1.515),
measured at 23°C from 400 to 700 nm with a Zeiss
MPM800 spectrophotometer on a freshly polishedgrain, are presented in Table 1. As shown in Figure 4,
the measured Rmax values (in air) coincide with those oftype hodrušhite from the Rosalia vein, Banská Hodruša,
Slovakia (Koděra et al. 1970), whereas the Rmax values(in air) are on average 1.5% higher than those of typekupčíkite from Felbertal, Austria (Topa et al. 2003a) andcuprobismutite from Baicolliou, Wallis, Switzerland(Picot & Johan 1977).

CHEMICAL ANALYSES
Quantitative electron-microprobe analyses of four
crystals were carried out with a CAMECA SX 50
instrument. The results are summarized in Table 2,
together with operating conditions and the standards
used. Pizgrischite is not damaged by the electron beam.
The empirical chemical formula, calculated on the basisof 69 atoms per formula unit (apfu) from the average
results of seven analyses, is: (Cu15.24Fe0.80Pb0.60)⌺16.64(Bi17.07Sb0.17)⌺17.24 (S35.09Se0.03)⌺35.12.
The resulting imbalance in charges is –0.47 electrons
per formula unit, i.e., 0.7% of the negative charges.
The simpliÞed formula, in accordance with the crystalstructure refinement reported below, is: (Cu+,Fe2+)
Cu+14PbBi17S35.

X-RAY-DIFFRACTION STUDY
Preliminary powder diagrams were obtained on aconventional laboratory diffractometer in 1988. As thismaterial turned out to be unsuitable for classical singlecrystal X-ray study (Weissenberg and Buerger precession techniques), we decided to wait for better material
or technical improvements. The accessibility to XRD
powder synchrotron method (European Synchrotron
Radiation Facility 2005) and the development of imageplate CCD detectors for single-crystal diffractometers(e.g., Burns 1998) Þnally enabled us to complete thecharacterization of this mineral and to solve its crystal
structure. Because the mineral cannot be easily distinguished visually from other associated related phases(emplectite and aikinite–bismuthinite-series sulfosalts),
each sample used for further studies was Þrst identiÞed
by the GandolÞ method.

POWDER DIFFRACTION
A quartz-rich sample containing unaltered domainsof the new mineral was partially dissolved in 5%
aqueous hydroßuoric acid. The pizgrischite crystals
were carefully hand-picked from the residue, gently

PIZGRISCHITE, A NEW SULFOSALT FROM THE SWISS ALPS

ground in an agate mortar, and placed in a capillary
tube 0.3 mm in diameter, containing about 0.14 mm3of powder.
The X-ray synchrotron powder data (Table 3) was
measured in Debye–Scherrer geometry, with a distanceof 664 mm between the capillary-hosting sample andthe receiving slit. Data acquisition was made at the
Swiss–Norwegian Beam Line, European Synchrotron

1233

Research Facility in Grenoble, with a wavelength ␭ =1.09816(1) Å, and a step size of 0.01° 2␪.
The pattern was decomposed into individual intensities using the XND program (Bérar & Baldinozzi 1998)
to give a Rwp of 0.038. Relative intensities are given
with the respect to the strongest line (020). The unit-cellparameters were reÞned from a Le Bail Þt on the powder
pattern, using the space group C2/m. The ensuing lattice
parameters and the complete set of powder data arereported in Table 3.
It should be noted that the lattice parameters fromthe powder are more trustworthy, as they are not biasedby the presence of the other twin individual (those from

FIG. 2. Pizgrischite crystals spray partially altered into malachite (green) and bismutite(yellow) in a Þne-grained quartz matrix. Horizontal Þeld of view is 5 cm. Holotype
sample MGL #58622. Photo and courtesy S. Ansermet.

1234

THE CANADIAN MINERALOGIST

FIG. 3. a, b. SEM images of twinned pizgrischite crystals extracted from quartz matrix bytreatment with dilute hydroßuoric acid. Part of holotype sample MGL #58622.

the image-plate data tend toward those from the powder
with increasing distance of crystal to image plate).
Structure determination and reÞnement
The structure of pizgrischite was solved by direct
methods (program SHELXS, Sheldrick 1997). An apparently monocrystalline splinter was extracted from apolished section under polarized light (reßecting lightmicroscope). A full hemisphere was collected on a IPDS
I instrument equipped with Mo radiation, using the datacollection parameters listed in Table 4. Unfortunately,
the measured crystal turned out to be a pseudomerohedral twin. Nevertheless, we were able to determine
the unit cell and space group (C2/m) unequivocally.
The reßections from the dominant individual could be
integrated, but may contain some contribution from theother individual (this might partly explain the higher

PIZGRISCHITE, A NEW SULFOSALT FROM THE SWISS ALPS

1235

FIG. 4. Maximal and minimal reßectance data in air of pizgrischite (䡺), compared to those of kupčíkite (䡬), hodrušhite (〫)and cuprobismutite ().

than usual Rint value). The absorption correction was
based on the habit of the measured crystal ({100} and{001} pinacoids, partial {111} prism and the (911)bevel face). The occupancy of the lead, bismuth andcopper atoms was reÞned anisotropically, whereas thesulfur atoms were treated isotropically. The atom Cu9
required a split position, and the atoms Cu15 and Fe1
occupy the same site: their populations were made to
add up to 1.0, and the same x, y and z coordinates aswell as the same Uij were imposed on them.
In Table 5, we present the coordinates of the atoms
in the structure of pizgrischite, and in Table 6, we list
selected interatomic distances. A table of observedand calculated structure-factors is available from the
Depository of Unpublished Data on the MAC web site
[document Pizgrischite CM45_xxx].

DESCRIPTION OF THE CRYSTAL STRUCTURE
Modular elements
Pizgrischite is related to the cuprobismutite homologous series, as similar structural units occur inpizgrischite and in the cuprobismutite-group minerals.
However, pizgrischite does not belong to the cuprobismutite homologues. Three members of the cuprobismutite homologous series are known so far: kupčíkite
Cu3.4Fe0.6Bi5S10 (Fig. 5), cuprobismutite Cu10Bi12S23(Fig. 6), and hodrushite Cu8Bi12S22 (not shown here).

The crystal structures of cuprobismutite homologues
can be described in terms of regular 1:1 intergrowths
on the unit-cell scale of two types of slabs: (a) (311)PbS
slabs of a galena-like structure, i.e., kupčíkite-like(simpliÞed in Fig. 5), cuprobismutite-like (Fig. 6) orboth (in hodrushite; not shown here), and (b) complex
slabs with columns of paired BiS5 pyramids and CuS4
coordination tetrahedra (Makovicky 1989, Topa etal. 2003b); they are grey-shaded in Figures 5 and 6.
The (a) slabs consist of BiS6 coordination octahedra,
coordination pyramids BiS5 ßanking them, and of theÞtting parts of the trigonal coordination bipyramids ofCu(Fe). The (b) layers are identical in all homologues,
i.e., homologous accretion takes place in the galena-like
portions. In kupčíkite, N = 1, two coordination pyramidsof BiS5 attach themselves to the appropriate sides of the
Bi coordination octahedron (Fig. 5); in cuprobismutite,N = 2, there are pairs of such pyramids (Fig. 6). The
PbS-like slab is then two and three octahedra (or pyramids) wide, respectively (Figs. 5, 6). Hodrushite is aregular 1:1 combination of these two slab thicknesses,
N = 1, 2 (Topa et al. 2003b).
The principle of the pizgrischite structure can becompared to that of sartorite homologues. In modular
description, the sartorite homologues are composedof slices of SnS-like structure cut parallel to (301)SnSor (301)SnS. Similarly, the pizgrischite structure iscomposed of slices of kupčíkite-like structure cut
parallel to (201)kpk (Fig. 5). In the sartorite homo-

1236

THE CANADIAN MINERALOGIST

logues, the known slab-widths are exclusively threeand four square coordination pyramids if measured
diagonally along [001] SnS. In pizgrischite, similarcounting units are missing. An attempt is made here to
use the number of “unbroken” columns of paired BiS5
pyramids and CuS4 coordination tetrahedra in the thinlayers measured diagonally along [100]kpk (Fig. 5). In
doing so, the structure of pizgrischite (Fig. 7) can be
described as composed of slices of a kupčíkite-likestructure cut parallel to (201)kpk (Fig. 5). The slabs areÞve and seven columns thick, respectively, and alternate
along [001]pgr. They are symmetry-related to each otherby rotation around a two-fold axis [203]kpk. Along thecomposition zone (001)pgr, the slabs apparently transform into cuprobismutite, as described in the following
section. Thus, pizgrischite can be considered the Þrstknown homologue N = 5, 7 of a possible pizgrischite
homologous series.

PIZGRISCHITE, A NEW SULFOSALT FROM THE SWISS ALPS

FIG. 5. Crystal structure of kupčíkite projected along [010]. Small, medium and large
circles indicate Cu, Bi, and S atoms, respectively. The white and grey colors indicate
a relative difference in height of about 2 Å. Four different clusters of Cu–S and Bi–S
polyhedra are shown consisting of CuS4: tetrahedron, BiS6: octahedron, BiS5: squarepyramid (completed by two additional atoms of S into BiS5+2: monocapped trigonal
prism). Gray shading indicates the b slab of cuprobismutite homologues (thin layer).
A tiling pattern is derived from the clusters and a thin layer according to Topa et al.
(2003a) is shown. Two slabs, Þve and seven columns thick, and the corresponding cutting direction [201]kpk, are illustrated. These slabs are the basic building units of the
pizgrischite structure. Details are provided in the text.

1237

1238

THE CANADIAN MINERALOGISTPIZGRISCHITE, A NEW SULFOSALT FROM THE SWISS ALPS

Tiles and tiling patterns
In order to better understand how the structure of
pizgrischite is derived from that of the cuprobismutite
homologues, it is necessary to further decompose theabove-introduced N = 5 and N = 7 slabs (modules) into
submodular clusters of coordination polyhedra. It is thenpossible to use the projection of these clusters and todescribe the structure in terms of tiling patterns.
Figure 5 shows the structure of kupčíkite andthe tiles derived from it: in the (a) slab (cf. previous
section), pairs of CuS4 tetrahedra are represented byyellow rhombi, and the BiS6 octahedra as pink rhombi
flanked by the BiS 5 pyramids indicated as mauve
triangles; in the (b) slabs (“thin layers”), pairs of CuS4
tetrahedra are represented by beige rhombi, and thepairs of BiS5 pyramids as turquoise rhombi. The fourindividual tiles and their composition as tiling pattern
are shown. One thin layer is shaded in grey. In addition,
the cutting direction [201] and two slabs, N = 5 and N= 7, are shown.
Figure 6 shows the structure of cuprobismutite andthe tiles derived from it: in the (a) slabs, CuS4 tetrahedra are represented by yellow triangles, and the BiS6
octahedra as pink rhombi ßanked by the pairs of BiS5
pyramids indicated as mauve rhombi; the (b) slabs are
identical to those in Figure 5. The four individual tiles
and their composition as a tiling pattern as well as one
grey-shaded thin layer are shown.
Figure 7 shows the structure of pizgrischite. We
show the (001) composition zones of the N = 5 and N= 7 slabs in dark grey, and the thin layers within the
kupčíkite-like slabs in light grey. A herringbone-likepattern becomes clearly visible. The small unit-cell of
kupčíkite is indicated, and a comparison with Figure
5 shows the identity of the two sections of the structure. The colored tiles underline this aspect. It is very
interesting to observe the lateral transformation of the1239

kupčíkite-like slabs into cuprobismutite in, or close to,the composition zone. As real hinges connecting the
N = 5 and N = 7 slabs serve the Cu(1)S4 tetrahedra(beige triangles within the dark grey-shaded composition zones; Fig. 7): they can be interpreted either asa continuation of the kupčíkite-like tiling pattern (iflooking at the N = 7 slab) or part of the cuprobismutitelike tiling pattern (if looking at the N = 5 slab).
If one looks close to the tiles of pizgrischite, one cansee that they are more distorted compared to those of
kupčíkite and cuprobismutite. This aspect is discussed
further in the next section in the context of individual
coordination-polyhedra.
Coordination polyhedra
The Bi sites. In cuprobismutite homologues, Topa etal. (2003a) distinguished two types of BiS6 octahedra:
unsubstituted and substituted ones. In pizgrischite(Fig. 7), only unsubstituted BiS6 octahedra are present(Bi1; Bi3, Bi10). As described above, BiS5 pyramids(and one PbS5 pyramid) ßank the BiS6 octahedra on
appropriate sides (Fig. 7): Bi(4)S5–Bi(1)S6–Bi(2)S6,
Pb(1)S5–Bi(3)S6–Bi(12)S6, Bi(14)S5–Bi(10)S6–Bi(17)S6. As in kupčíkite, the coordination polyhedra of allßanking BiS5 pyramids is completed by two distant S
atoms. Thus, for example, Bi(4)S5 can alternatively bedescribed as Bi(4)S5+2, a monocapped trigonal prism.
In cuprobismutite, however, these ßanking BiS5 pyramids are each completed by one additional S atom into
distorted BiS6 octahedra. In, or close to, the domainzone (001)pgr, kupčíkite transforms into cuprobismutite
by attaching monocapped trigonal prisms Bi(15)S5+2
to Pb(1)S5+2 and Bi(9)S5+2 to Bi(17)S5+2, respectively(Fig. 7). It is very interesting to observe that Pb(1)S5+2 and Bi(17)S5+2 retain their original coordination(kupčíkite-like, i.e., monocapped trigonal prisms) and1240

THE CANADIAN MINERALOGIST

FIG. 6. Crystal structure of cuprobismutite projected along [010]. Small, medium andlarge circles indicate Cu, Bi, and S atoms, respectively. The white and grey colors
indicate a relative difference in height of about 2 Å. Four different clusters of Cu–S
and Bi–S polyhedra are shown (cf. caption of Fig. 5; BiS5+1: octahedron) and a tiling
pattern is derived as well. A thin layer, identical to the one in Figure 5, is shown. Details
are provided in the text.

PIZGRISCHITE, A NEW SULFOSALT FROM THE SWISS ALPS

1241

FIG. 7. Crystal structure of pizgrischite projected along [010]. Small, medium and large circles indicate Cu, Bi (Pb), and S
atoms, respectively. The white and grey colors indicate a relative difference in height of about 2 Å. Dark grey shaded bands
indicate the composition zones of the slices of kupčíkite-like structure (small unit-cell) cut parallel to (201)kpk. The thin layersof kupčíkite are shown in light grey (cf. Fig. 5) and underline the herringbone-like pattern of the pizgrischite structure.

1242

THE CANADIAN MINERALOGIST

do not form distorted octahedra, as one would expect
in comparing kupčíkite and cuprobismutite.
The remaining Bi atoms, except Bi16, form pairs of
BiS5+2 monocapped trigonal prims in the thin layers of
the kupčíkite-like slabs: Bi5–Bi8, Bi6–Bi13, Bi7–Bi11.
Polyhedron Bi(16)S5+2 is an isolated monocapped trigonal prism in the composition zone (001)pgr (Fig. 7). The
location of this coordination polyhedron fully corresponds to the tiling pattern of the cuprobismutite.
The Cu sites. In all structures of the cuprobismutite
homologues, the tetrahedral coordination of copper
is asymmetrical, transitional to trigonal–planar or,considering more distant ligands, trigonal–bipyramidal(Topa et al. 2003a). The same is true for pizgrischite(Fig. 7). In kupčíkite, Topa et al. (2003a) reÞned split
Cu,Fe positions (not shown in the simpliÞed Fig. 5). As
discussed by Topa et al. (2003a) for kupčíkite, the splitting of the position is not automatically a consequenceof Fe-for-Cu substitution. In pizgrischite, the Cu9 site is
split and may contain some Fe. ReÞning the ratio Cu/Feof all other sites resulted in full Cu occupancies for allsites except Cu15, which contains 23(10)% Fe.
All Cu atoms except Cu1 form pairs of CuS 4
tetrahedra sensu lato. Some of them are monotype(Cu2–Cu2, Cu4–Cu4, Cu8–Cu8, Cu10–Cu10), whereas
the remaining pairs are not (Cu3–Cu9, Cu5–Cu7,
Cu6–Cu14, Cu11–Cu12, Cu13–Cu15). The polyhedra
containing Cu1 forms isolated Cu(1)S4 tetrahedra in thecomposition zone (beige triangle in Fig. 7). The role of

PIZGRISCHITE, A NEW SULFOSALT FROM THE SWISS ALPS

Cu(1)S4 as hinges between the N = 5 and 7 slabs has
been discussed in a previous section. The coordinationof four S atoms around Cu8 is distinctly tetrahedral,
whereas Cu5 has three close ligands in a clear trigonal–
planar arrangement [parallel to the (001) compositionzone] and Cu9 has Þve ligands forming a distorted but
Þne trigonal bipyramid. All remaining CuS4 tetrahedra
show transitions in the sense described above.
The Cu(13)S4 tetrahedron is attached to the Bi(3)S6 octahedron (Fig. 7), as observed in cuprobismutite.
The location of Cu(15)S4, the counterpart of Cu(13)S4
within the dark-grey-shaded composition zone (Fig. 7),
is exactly where it has to be in the kupčíkite structure.
The Pb site. The isoelectronic Pb2+ and Bi3+ cannot
be distinguished with the chosen experimental setup.
Bond-valence estimates indicate substantial underbonding of “Bi18”. Coordination polyhedra of bismuth
in cuprobismutite homologues follow closely a hyperbolic correlation of opposing bonds, investigated originally by Trömel (1981) for Sb3+, Te4+, I5+ bonds withoxygen, and by Berlepsch et al. (2001) for bismuthinite
derivatives (meneghinite homologues). Inspection ofpairs of opposing Bi–S bonds of pizgrischite reveals that
all except one fall on, or close to, the Bi–S hyperbola
as deÞned by Berlepsch et al. (2001). Only “Bi18”,
with pairs of opposing Bi–S bonds of 2.996(7) Å and3.026(7) Å, matches almost perfectly the intersection of
the Pb–S hyperbola with the median line (x = y). Consequently, “Bi18” is regarded as the Pb site in pizgrischite,
and accordingly has been labeled Pb1.

CHEMICAL STRUCTURAL MINERAL CLASSIFICATION
According to the Chemical Structural Mineral
ClassiÞcation System of Strunz & Nickel (2001) andconsidering the chemical and structural features of the
new PbS archetype sulfosalt, pizgrischite could be classiÞed as a related mineral (pizgrischite subgroup) in the
cuprobismutite series (2.JA.10).

CU–BI SULFOSALTS IN METAMORPHOSED PRE-ALPINEDEPOSITS OF CENTRAL EUROPE
In unmetamorphosed examples of polymetallic veintype mineralization, emplectite is the most common
Cu–Bi sulfosalt; wittichenite and cuprobismutite areless common. During metamorphism, however, a more
complex paragenesis develops, and single phases suchas emplectite or wittichenite rarely survive (Table 7).
Complex Cu–Bi sulfosalts, such as pizgrischite, arecharacteristic of metamorphosed Cu–Bi vein-type
deposits with a low content of Pb, which precludes
the formation of minerals of the aikinite–bismuthinite
series. These complex Cu–Bi sulfosalts can be very
common at one locality, but rare elsewhere; this probably results partly from the difÞculty in identifying
these minerals, but also it reßects the fact that small

1243

variations in physical (cooling rate, P, T) and chemicalvariables [e.g., f(S2) and Cu/Bi] can stabilize different
phases. “Dry” and “wet” experiments in the system
Cu–Bi–S made by Sugaki et al. (1981) and Wang (1994)
show that complex sulfosalts like cuprobismutite,
hodrushite and kupčíkite are not stable below ~300°C.
For example, Sugaki et al. (1981) clearly demonstrated
that below 316°C, cuprobismutite decomposes toemplectite and synthetic monoclinic CuBi3S5.

ACKNOWLEDGEMENTS
The manuscript greatly beneÞtted from an insightfulreview by Daniela Pinto and editorial care of Robert
F. Martin. We are grateful to Stefan Ansermet andStéphane Cuchet for their help during Þeld work. We
further thank Peter O. Baumgartner (SEM/EDS laboratory, Institute of Geology and Paleontology, UNIL,
Lausanne) for help with the SEM. Special thanks to
Gervais Chapuis (Laboratoire of Crystallography,
EPFL, Lausanne) for single-crystal XRD facilities.
Portions of this research were funded by the European
Synchrotron Research Facility, Swiss–Norwegian BeamLine (project 01–01–30 to N. Meisser).

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Received May 26, 2006, revised manuscript accepted March 8,
2007.