467
The Canadian Mineralogist
Vol. 48, pp. 467-481 (2010)
DOI : 10.3749/canmin.48.3.467

DANTOPAITE, Ag5Bi13S22, THE 6P NATURAL MEMBER
OF THE PAVONITE HOMOLOGOUS SERIES, FROM ERZWIES, AUSTRIA
Emil MAKOVICKY§
Department of Geography and Geology, University of Copenhagen, Østervoldgade 10, DK–1350 Copenhagen K, Denmark

Werner H. PAAR, Hubert PUTZ and Georg ZAGLER
Department of Materials Research and Physics, Paris-Lodron University of Salzburg,
Hellbrunnerstr. 34, A–5020 Salzburg, Austria

Abstract
Dantopaite, Ag5Bi13S22, is the 6P natural member of the pavonite homologous series. It is a very rare mineral in a quartz
vein hosted by Variscan metagranitoids at the abandoned mining district at Erzwies, Gasteiner Valley, province of Salzburg,
Austria. The associated sulfosalts are lillianite–gustavite, heyrovskyite, eskimoite, vikingite, ourayite, bismuthinite, krupkaite,
benjaminite, pavonite, and cosalite. Traces of pyrite, tetradymite and native gold also are present. The new species occurs
as isolated grains intimately intergrown with pavonite or benjaminite or both. The grain size does not exceed 250–300 mm.
Dantopaite has a greyish white color and is opaque. It has a metallic luster and a grey streak. Its hardness (VHN50) is ~190 kg/
mm2 (3½ on the Mohs scale). In plane-polarized light, and compared to galena, it is weakly bireflectant, and distinctly pleochroic
in shades of grey. The anisotropy is distinct in air and oil, and the rotation tints change from greyish blue to brownish grey. The
reflectances (in air) are tabulated. The average result of electron-microprobe analysis is: Cu 1.68, Ag 11.56, Pb 4.64, Bi 63.82,
Te 0.34, S 17.52, total 99.57 wt.%, which gives Cu1.06Ag4.24,Pb0.9Bi12.23S21.89Te0.11. The ideal formula is Ag5Bi13S22. Dantopaite
is monoclinic with a 13.380(3), b 4.0492(9), c 18.690(4) Å, V 975.8(4) Å3, space group C2/m and Z = 1. The calculated density
is 6.74 g/cm3. The strongest eight lines in the (calculated) powder-diffraction pattern [d in Å(I)(hkl)] are: 3.578(58)(205),
3.452(90)(112), 3.331(36)(401), 3.301(40)(204), 2.861(100)(313), 2.225(24)(117), 2.025(25)(020) and 2.013(24)(512). The
crystal structure, based on 1051 observed reflections (R1 = 7.3%), is that of N = 6 pavonite homologue, consisting of thick slabs
with a width of six octahedra on a diagonal, in alternation with thin slabs composed of foreshortened octahedra and pairs of Bi
coordination pyramids. The central columns of the thin structural slabs are populated by octahedrally coordinated Ag sites andtetrahedrally coordinated Cu1 and Cu2 sites; all of them are only partly occupied. In the thick slabs, with distorted octahedral
bismuth sites, silver partly replaces bismuth in the centrally placed octahedra. The name honors Dr. Dan Topa (University ofSalzburg), ore mineralogist and crystallographer.
Keywords: dantopaite, sulfosalt, new mineral species, pavonite homologue (6P), silver, bismuth, crystal structure, Erzwies,
Austria.

Sommaire
Nous décrivons la dantopaïte, Ag5Bi13S22, le membre 6P naturel de la série d’homologues de la pavonite. Il s’agit d’unminéral rarissime découvert dans une veine de quartz recoupant un métagranite d’âge varisque dans le camp minier abandonné deErzwies, vallée de Gasteiner, province de Salzburg, en Autriche. Lui sont associés les sulfosels lillianite–gustavite, heyrovskyite,eskimoïte, vikingite, ourayite, bismuthinite, krupkaïte, benjaminite, pavonite, et cosalite. Des traces de pyrite, tétradymite et or
natif sont aussi présentes. La nouvelle espèce minérale se présente en grains isolés en intercroissance intime avec la pavonite ou labenjaminite ou les deux. La taille des grains ne dépasse pas 250–300 mm. La dantopaïte est blanc grisâtre et opaque. Elle possède
un éclat métallique et une rayure grise. La dureté (VHN50) est ~190 kg/mm2 (3½ sur l’échelle de Mohs). En lumière réfléchie,et comparée à la galène, la dantopaïte est faiblement biréflectante, et pléochroïque en teintes de gris. L’anisotropie est distinctedans l’air et dans l’huile, et les teintes de rotation changent du bleu grisâtre au gris brunâtre. Nous fournissons les réflectances
dans l’air. En moyenne, les analyses avec une microsonde électronique ont donné Cu 1.68, Ag 11.56, Pb 4.64, Bi 63.82, Te 0.34,
S 17.52, pour un total de 99.57% (poids), ou Cu1.06Ag4.24,Pb0.9Bi12.23S21.89Te0.11. La formule idéale est Ag5Bi13S22. La dantopaïte
est monoclinique, avec a 13.380(3), b 4.0492(9), c 18.690(4) Å, V 975.8(4) Å3, groupe spatial C2/m et Z = 1. La densité calculée§

E-mail address: emilm@geol.ku.dk

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est 6.74 g/cm3. Les huit raies les plus intenses du spectre de diffraction (calculé) d’une poudre [d en Å(I)(hkl)] sont: 3.578(58)(205), 3.452(90)(112), 3.331(36)(401), 3.301(40)(204), 2.861(100)(313), 2.225(24)(117), 2.025(25)(020) et 2.013(24)(512).
La structure cristalline, fondée sur 1051 réflexions observées (R1 = 7.3%), est celle d’un homologue N = 6 de la pavonite, avecd’épais modules d’une largeur de six octaèdres en diagonale, en alternance avec des modules plus minces d’octaèdres plus trappus
et de paires de pyramides où logent les atomes de Bi. Les colonnes centrales de ces modules plus minces sont peuplées de sites Agà coordinence octaédrique et des sites Cu1 et Cu2 à coordinence tétraédrique. Tous ces sites ont un taux d’occupation incomplet.
Dans les modules plus épais, ayant les sites octaédriques difformes de Bi, les atomes de Ag remplacent le Bi dans les octaèdres
centraux. Le nom honore Dan Topa, de l’Université de Salzburg, minéralogiste des minerais et cristallographe.
(Traduit par la Rédaction)
Mots-clés: dantopaïte, sulfosel, nouvelle espèce minérale, homologue de la pavonite (6P), argent, bismuth, structure cristalline,
Erzwies, Autriche.

Introduction
In homologous series of minerals, members withcertain values of the order number N may be very
common, whereas other members, with N values
interspersed between the common ones, may be rareor unknown. This has been the situation of the N = 6
homologue of the pavonite homologous series, situatedcrystal-chemically between the most common members,
N = 5 (pavonite) and N = 7 (benjaminite). Therefore,
the find of a natural N = 6 member, dantopaite, in the
Siglitz – Bockhart – Erzwies ore district, Gasteinertal,
province of Salzburg, Austria, provides evidence ofthe exceptional character of this sulfosalt occurrence.
Dantopaite was found during field studies that constitutepart of a larger project concerning the ore petrology andthe conditions of formation of Alpine-type mesothermal
gold mineralization (Paar 2006, Günther et al. 2000,
Weber 1997). During the mapping of the structurally
controlled mineralization at Erzwies (“ore meadow”),
numerous outcrops of quartz veins were located, whichcontain a widespread distribution of patchy sulfosalts
in association with high-grade gold and silver ore. In
only one of the exposed veins, dantopaite occurs as rareinclusions in quartz in association with native gold andother sulfosalts and sulfides.
The new mineral species is named after Dr. Dan
Topa (born 1955), in recognition of his outstanding
contributions to the crystal chemistry and structures of
sulfosalts, especially in regard to the pavonite series
and bismuthinite derivatives. The new species andits name have been approved by the CNMNC of the
IMA (2008–058). The holotype material (one polishedsection and a single-crystal mount) were deposited in
the reference collection of the Department of Materials Research and Physics (Division of Mineralogy),
University of Salzburg.

Location and Geology
The area of Erzwies, where mining for precious andbase metals probably began long before the Middle
Ages, is located in the Hohe Tauern region west of the

Gasteinertal, in the province of Salzburg, Austria. It issituated in the direct northern continuation of the districtof Siglitz–Bockhart which, together with other districtsin the same region (Radhausberg, Hoher Goldberg,
Goldzeche), were economically the most importantcenters of gold mining in the Alps. The mining area at
Erzwies (Fig. 1) reaches from the Bockhartscharte in
the south (2450 m above sea level) for more than 2 km
toward the Angertal, where one encounters the lowermost adit (2200 m a.s.l.) used for drainage of the mine.
Signs of old mining activities, which lasted forseveral centuries, occur in a strip 500 m wide in a NNE
direction, roughly parallel with the main ore-hosting
structure (the “Kupelwieser” structure). The host rocks
are metamorphosed Jurassic limestone and dolostone,
which show widespread karstification. The extent of
the mineralized system along strike is more than 4 km;
the width of the veins, which pinch and swell, varies
strongly. The ore assemblage of the prominent veins istypically composed of silver-rich native gold, arsenopyrite, pyrite, variable amounts of sphalerite, galena,
Ag-rich tetrahedrite, acanthite and rare pyrargyrite.
The gangue may be quartz, ankerite and intermediate
Mn-bearing members of the magnesite–siderite solid
solution.
In contrast to this type of mineralization is a systemof numerous (~70) east–west-trending quartz veins.
Outcrops can be observed at an elevation between 2440
and 2200 m above sea level. These veins penetrate
Variscan granitoids (the “Central gneiss”), and have athickness varying between a few centimeters and almost
half a meter. Their continuation along strike and dip isstrongly reduced, and is in the range of a few tens ofmeters (strike) and only meters (dip). They are cut by
the above-described NNE-trending systems of veins,
and thus older than it. At least five of these east–weststriking veins carry a very distinctive, and in places, richsulfosalt mineralization. The striking indicator of thissulfosalt mineralization is pyrite in modified cubes up to
10 cm across, as well as irregular sandy accumulationsof the same mineral. In superficially weathered portionsof the veins, pyrite leaves hollow casts displaying its
typical habit.

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469

Fig. 1. The geological map of the Erzwies area and the location of the dantopaite
occurrence.

Occurrence of Dantopaite
The type locality of the new sulfosalt species is asmall exploration trench and a tunnel (20 m long) drivena few meters below the trench to explore the expected
downward continuation of the mineralization. The location is situated on the orographic left-hand side of asteep flank that parallels the Kupelwieser main structure
at an elevation of 2275 m a.s.l. The quartz vein exposed
just above the nearly collapsed entrance of the tunnel
contains gold-bearing arsenopyrite and pyrite. The
thickness of the quartz vein is 0.2 m, the ore is concentrated in a massive band 2–5 cm wide. A parallel quartz
veinlet less than 6 cm in thickness contains a sporadic
sulfosalt mineralization in quartz, which in its richest

part is composed of prismatic crystals reaching several
centimeters. This subtype of sulfosalt mineralization(denoted as SS1 in the above studies) is represented
by traces of dantopaite and members of the lillianite
homologous series (LHS) such as gustavite, eskimoite,
and ourayite, among others.
A few meters below the adit of the tunnel, loose
blocks of another type of quartz occur, whose primarysource could not be located. This is a smoky quartz
variety, more coarse-grained than the quartz of the vein.
It contains small vugs and carries plenty of muscovite.
Dantopaite and other sulfosalts are concentrated insmall amounts near the boundary with gneiss, whichhosts the quartz vein. The mineralogy of this type of
sulfosalt mineralization is distinctly different from470

the canadian mineralogistthat present in SS1. Here, dantopaite is accompanied
by derivatives of the bismuthinite–aikinite series(bismuthinite, krupkaite), by members of the pavonite
homologous series (PHS below) (pavonite, benjaminite), and also members of the lillianite homologous
series (gustavite, heyrovskyite), cosalite, traces oftetradymite, native gold and pyrite. All the minerals
mentioned in this section have been identified by ore
microscopy and electron-microprobe analyses.

Appearance and Physical Properties
In polished sections, dantopaite is a relatively rare
constituent. It occurs as independent grains (200–300mm) embedded in quartz, and as a component of intergrowths with pavonite and benjaminite (Fig. 2). The
latter occur as irregular, elongate polyphase grains withpavonite at one end, one or more grains of dantopaitein the central parts, and benjaminite grains at the otherend (Figs. 2a, b). They are enclosed in quartz and appear
slightly corroded on most surfaces, making genetic
interpretations uncertain. Pavonite and benjaminite
may be polysynthetically twinned. A grain of dantopaitewith lamellae of benjaminite has been located as well(Fig. 2c).
Benjaminite associated with dantopaite is limited
to its copper-poor variety, whereas in an elongate grain
associated with lillianite, benjaminite exsolved into
an intergrowth of benjaminite matrix and lamellae of
a hitherto undescribed, copper-rich variety (Fig. 2d).
These aggregates are fully analogous to the mako­
vickyite – cupromakovickyite intergrowths (Topa &Paar 2008), pavonite – cupropavonite intergrowths(Karup-Møller & Makovicky 1979) and mummeite– cuprian mummeite intergrowths (Karup-Møller &Makovicky 1992).
In hand specimen, the mineral is greyish white incolor, has a metallic luster and is opaque. It is brittle andhas an uneven fracture. The mean VHN50, determinedon three identations on only one grain, is 190 kg/mm2.
This corresponds to Mohs hardness of 3½, very similar
to that of other members of the PHS. The density of thenatural material could not be measured because of thesmall size of the crystals, their scarcity and pervasive
intergrowths with other phases. Using the empiricalformula and Z = 1, the calculated density is 6.74 g/cm3,
thus very close to that of pavonite (6.75 g/cm3), mako­
vickyite (6.70 g/cm3) and other members of the PHS.
In polished sections, in plane-polarized light,
dan­topaite is greyish white and lacks internal reflections. No reflection pleochroism can be discerned in
the few grains available for this study. The bireflectanceis perceptible in air and moderate in oil. Anisotropy is
distinct in air and becomes enhanced in oil. Between
crossed polars, bluish grey to brownish grey rotationtints are common.
The reflectance data for dantopaite were obtainedin air within the visible spectrum (400–700 nm) usinga Leitz MPV–SP microscope-spectrophotometer. A
WTiC reflectance standard (Zeiss 314) was used as areference for the measurements. No measurements in
oil were performed. The results are presented in Table
1. The Rmax reflectance curve has a distinct maximum
in the broad region of 450 nm, and the reflectancevalues decrease continuously toward 700 nm (Table
1). A corresponding maximum on the Rmin curve andthe decrease in reflectance toward 700 nm are barely
perceptible. Still, the differences in reflectance on bothcurves are small, leading to a light grey colour of themineral. In terms of reflectance and overall optical properties, there are only very minor differences between
dantopaite and the other chemically closely related
members of the PHS.

Chemical Data
Chemical analyses of dantopaite and associatedphases were carried out in a polished section bymeans of an electron microprobe (JEOL JXA–8600
in WDS mode). The acceleration voltage was 25 kV,and the beam current, 30 nA; the correction procedure
employed was on-line ZAF. Analytical results represent
average of 37 analyses on two mineral grains. In Table
2, we give data for Cu, Ag, Pb, Bi, Te and S; no otherelements with Z greater than 11 were detected. The
empirical formula of dantopaite, based on (S + Te) =22 atoms per formula unit, is Cu1.06Ag4.24Pb0.90Bi12.23(Te0.11S21.89)S22. A simplified formula of this mineral is
Ag5Bi13S22. It requires Ag 13.61 wt.%, Bi 68.58 wt.%,
and S 17.81 wt.%, in conformity with the theoreticalcomposition of the N = 6 homologue of the pavonite
series (Makovicky et al. 1977).
A small surplus of cations (~0.43 apfu) in the empirical formula, in comparison with the ideal formula, isdue especially to the accumulation of Cu in the columnof octahedra in the thinner structural slabs (see section
on Crystal Structure), possibly supplemented by apartial replacement of Bi in some octahedral Bi sites.
Karup-Møller & Makovicky (1979) called the
portion of copper fitting into the ideal formula together
with silver (i.e., occupying potentially the octahedral
cation sites of the ideal structure) “substitutional sCu”,
whereas the surplus copper they called “interstitial iCu”.
For calculation of the order number N of the pavonite
homologue analyzed by means of an electron microprobe, Karup-Møller & Makovicky (1979) proposed
to normalize the atomic proportions according to therelationPb + Bi + Ag + sCu = 1
and to calculate the homologue order N applying theequation
N = [7 – 6Bi – 3(Pb + sCu)] / [2Bi + (Pb + sCu) – 1].

dantopaite, a new pavonite homologue from erzwies, austria

471

Fig. 2. The back-scattered electron images (b, c, d) and reflected-light photograph (a) of the dantopaite assemblage (a–b) andof the benjaminite exsolution pair (d). The mineral association, dantopaite (dant), pavonite (pav), benjaminite (benj), lillianite(lill), krupkaite (krup), and bismutinite (bism), is embedded in quartz.

It might be noted that Ag is involved in the latter
expression indirectly, via the normalization procedure.
It is impossible to distribute copper a priori between
the iCu and sCu categories in a pavonite homologue

with an unknown order-number N. Therefore, KarupMøller & Makovicky (1979) proposed to use threecompromise formulae to help bracket the right valueof N: calculation of the value called NP1, in which all

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copper is taken to be iCu (i.e., Cu is not considered in
the normalization and is zero in the above equation),
NP2, in which all copper is considered sCu (i.e., all Cu
is included in normalization and the equation), andNP3, for which copper is distributed equally between
interstitial and substitutional modes. Table 2 shows thatthe latter compromise gives the best results, closest to
the integer values of N confirmed for dantopaite by
structure determination.
In the formula Cu 1.06Ag 4.24Pb 0.90Bi 12.23(S 21.89 +Te0.11)S22, 0.43 Cu apfu is “interstitial”, whereas 0.63
Cu apfu is “substitutional”. If we convert interstitial
Cu plus the equivalent amount of Pb into Bi plus aninterstitial vacancy (iCu+ + Pb2+ ! □ + Bi3+), 0.90 Pb
apfu reduces to 0.47 Pb apfu, whereas iCu is eliminated.
Redistributing this remaining Pb into ½ Ag + ½ Bi, andrenaming sCu as Ag, we obtain Ag5.11Bi12.90S22, close
to ideal Ag5Bi13S22.
Figure 3 and Table 2 show that the closely associated pavonite, dantopaite and benjaminite from Erzwies
are varieties with a moderate content of Cu and Pb andadopt approximately the same Ag : (Cu + Pb) ratio. This
figure also shows the extent of Cu-for-Pb substitution in
the exsolved, Cu–Pb-poor and Cu–Pb-rich componentsof the isolated benjaminite intergrowth described above.

For pavonite, Cu0.87Ag3.51Pb0.72Bi11.38S19.93Te0.07,
iCu is 0.49 atoms apfu. Subtraction of this and theequivalent amount of Pb leaves 0.23 Pb apfu to beconverted into 0.11 Ag and 0.11 Bi. The resulting“substitution-free” composition Ag 4.01 Bi 12.0 S 20 isnearly the ideal formula of pavonite. The associatedbenjaminite, Cu1.16Ag5.03Pb1.15Bi13.16S23.83Te0.17, with
iCu equal to 0.50 atoms apfu, will have 0.65 Pb atoms
apfu available for conversion into Ag + Bi, and theresulting “substitution-free formula” is Ag6.02Bi13.99S24,
again close to the ideal formula, Ag6Bi14S24. The two
products of exsolution in the isolated benjaminite pair
have sCu values equal to 0.40 and 0.91 atoms Cu apfu.
The amount of interstitial copper exceeds the amountof Pb in the formula unit of the latter phase.

Crystallography and Crystal Structure
A fragment of dantopaite of irregular shape andmeasuring 0.05 3 0.07 3 0.09 mm was mounted on a
Bruker AXS three-circle diffractometer equipped witha CCD area detector at the University of Salzburg. The
crystal was separated from an acicular intergrowth of
the sulfosalt species mentioned above. Similar to theother homologues of pavonite, dantopaite is monoclinic,

Fig. 3. Triangular diagram Ag – Bi – (Pb + Cu) showing the compositional data of thepavonite homologues from the Erzwies area plotted. Np = 5, 6, and 7 denote pavonite,
dantopaite and benjaminite, in this order. The data for the Cu–Pb-enriched benjaminite
exsolution pair represent average results of the best analyses. Deviations of all three
analyzed phases from the ideal composition lines (drawn in red) are due to the contentsof “interstitial copper” in them (see text). Only the phases with no copper or with all
copper of “substitutional type” will plot onto these lines. Ideal gustavite is a copper-freephase, whereas the substituted benjaminite is rich in copper, i.e., the “overlap” observed
is a product of projection from a quaternary system.

dantopaite, a new pavonite homologue from erzwies, austria

and the space group is C2/m. Cell dimensions are a
13.380(3), b 4.0492(9), c 18.690(4) Å, b 105.494(4)°, V
975.8(4) Å3 and Z = 1 for Ag5Bi13S22. The a:b:c ratio is3.3044:1:4.6157 (from unit-cell parameters). Twinningwas not observed.
Experimental details of data acquisition and crystalstructure determination are described in Table 3. We
used the S mart system of programs for unit-celldetermination and data collection, and Saint+ for the
calculation of integrated intensities and for the structure
solution. From the systematic reflection conditions hkl:
h + k = 2n; h0l: h = 2n; 0kl: k = 2n; hk0: h + k = 2n;0k0: k = 2n; h00: h = 2n, the space group was found473

to be C2/m (No. 12). The structure was solved bydirect methods and refined with the Shelxtl packageof programs (Bruker AXS, 1997). On the basis ofinteratomic distances, Bi, Ag, S and Cu were directly
assigned in subsequent difference-Fourier maps.
The final refinement was performed with anisotropic
displacement parameters for all positions except thoseof copper. The final R1 value is 7.3% (Fo > 4s [Fo]).
Refined positional and displacement parameters
are listed in Table 4, selected interatomic distancesin Table 5, and coordination-polyhedron characteristics calculated with IVTON program (Balić-Žunić
& Vicković 1996) in Table 6. The crystal structure
is illustrated in Figures 4, 5 and 6. A table of struc-Fig. 4. Atom labeling in the unit cell of dantopaite. Atoms Ag1 and Cu2 are at different y levels; Bi2 and Ag2 substitute for
one another at the same y level.

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ture factors may be obtained from the Depository of
Unpublished Data on the Mineralogical Association of
Canada website [document Dantopaite CM48_467].
The crystal structure of dantopaite (Table 4, Figs.
4, 5 and 6) follows a structural scheme considered to
be classical for pavonite homologues. The first one of
the two alternating types of structural slabs is a thin
one that contains a single column of edge-sharing
octahedra. The latter are flanked and interconnected
within the slab by double columns of Bi coordination
pyramids. These thin slabs alternate with thick slabs
composed of coordination octahedra of Bi and (Bi, Ag,
Pb). The crystal-structure determination of dantopaite
confirmed unambiguously its order number, N = 6, i.e.,there are six octahedra present in a diagonal row acrossthe thicker slab (Fig. 6). With the C2/m space group, thestructure contains three distinct coordination octahedra
occupied by cations in the thick slab. A single site wasrefined as a mixed site, defined as (Bi2, Ag2) (Table 4).
This is the most centrally located site in the thick slab

(Fig. 6). The octahedral Bi1 site and the pyramidal Bi4
site in the thin slabs were found to be fully occupied
by bismuth.
The marginal octahedra Bi1 and Bi3 are distinguished by typical short Bi–S bonds toward sulfur
atoms, S3 and S6 respectively, situated on interslab
surfaces. The Bi3 site has two additional short bonds(2.78 Å) to S3, whereas Bi1, sandwiched between Bi2
and Bi3, has four intermediate, almost equally longbonds, 2 3 2.84 Å and 2 3 2.85 Å, to S5 and S2, in thatorder (Table 5). On the basis of cation–anion distances
observed, Pb is assumed to be concentrated at the Bi2
site, which flanks the central S4 atom in the thicker
slab. According to the refinement, this site also hosts
0.18 Ag in a slightly asymmetric coordination (Ag2 in
Fig. 4). Eccentricity of coordination octahedra in the
thick slab (Table 6) increases progressively toward themore marginal Bi1, and further toward the protruding
Bi3 position.
The Bi2–Ag2 octahedron in dantopaite is substantially larger than the analogous centrally located octahedron in the structure of substitution-free pavonite N= 5, which was refined as an Ag site (Makovicky et al.
1977). As already mentioned, the Bi2 octahedron is
the site accumulating lead. The analogously positioned
Me4 site in benjaminite (N = 7; Makovicky & Mumme
1979) was refined as 0.7 Ag and 0.3 Bi(Pb), again withinteratomic distances somewhat shorter than those forBi2 in dantopaite. In benjaminite, bismuth, with somePb, is concentrated in the adjacent central Me3 site of
the thicker slab.
The lone coordination-octahedron in the columnof octahedra of the thin slab is foreshortened andskewed, with low sphericity (Table 6), analogous

dantopaite, a new pavonite homologue from erzwies, austria

475

to the corresponding octahedra in the structures ofpavonite homologues N = 4, 5, and 7 (Makovicky
et al. 1977, Makovicky & Mumme 1979, Herbert &Mumme 1981, Mumme 1990, Topa et al. 2008). Only
partial occupancy of this octahedral Ag1 site by 0.68
Ag is observed (Fig. 5). The coordination octahedron isflanked by partially occupied tetrahedrally coordinatedcopper Cu1 sites (each with 0.20 Cu), situated along thecolumn, between two adjacent octahedra (Figs. 4, 5).
In addition, about 0.08 Cu2 occupies flat-tetrahedral
positions above and below Ag1 in the coordinationoctahedron itself (Fig. 5). Thus, in Figures 4 and 6, thenearly overlapping, mutually exclusive Cu2 and Ag1
sites actually are at two different y heights, although
only approximately 0.6 Å apart. The Cu2 position
corresponds closely to those observed in the pavonite
N = 3 homologues Cu1.57Bi4.57S8 (Tomeoka et al. 1980)
and Cu1.78Bi4.73Se8 (Makovicky et al. 2006).
Two “adjacent” Cu2 sites in the same coordinationoctahedron are mutually exclusive, situated at a distanceof only 1.23 Å. The acceptable Cu2 neighbor is situatedin the next coordination octahedron along the [010]
direction, at a distance of 2.82 Å. In a similar manner,
the Cu2–Cu1 distances are 1.93 Å (too close) and 2.95
Å, respectively. The Cu1–Ag1 distance is 2.42 Å; it
can become a cation–cation contact common in the
crystal chemistry of these elements only where theseatoms deviate somewhat from their average position,
extending this distance to a tolerable length. Both the
Cu1 site and the silver site have the highest values ofdisplacement factors of all cations (Table 4), whereas
the displacement factor of Cu2 lies within the range
seen for other cations in the structure of dantopaite.
The bond-valence sum for Cu2 in Table 6 is influenced
by the fact that the dimensions of the coordination
polyhedron are in principle determined by the requirements of Ag1.

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Fig. 5.  Atom labeling for an oblique projection of the columns of octahedra occupied by silver and copper and the intervening
columns of coordination pyramids of bismuth in the thin layer of the crystal structure of dantopaite.

The partially (~70%) occupied, linearly coordinatedAg1 site in the present structure has two short bonds,
2.50 Å; the remaining four bonds in the foreshortenedoctahedron are 2.90 Å. The partly occupied Ag2 position appears to represent silver, with the minimum
cation–anion distance equal to 2.59 Å. This value,dantopaite, a new pavonite homologue from erzwies, austria

however, is influenced by the presence of Pb as wellas the predominance of Bi in the “Bi2” coordination
polyhedron, in which Ag2 is a minority site. The
distances observed for Ag1 and Ag2 can be comparedwith a distance encountered for the linearly coordinated,fully occupied Ag site in neyite (2.416 Å; Makovicky
et al. 2001).
Occupancy of a potential triangularly coordinatedCu position spanning the free, outwardly oriented wallof the Bi3 coordination octahedron has been checked,
especially because of its analogy to the corresponding
Cu positions in pure synthetic Cu–Bi pavonite homologues N = 3. This position in dantopaite would
correspond to the Cu2 site in the marginal octahedraof the synthetic selenide Cu1.78Bi4.73Se8 [the pavonite
homologue N = 3] (Makovicky et al. 2006), with site
occupancy equal to 0.03 Cu, and to the same site in
Cu1.57Bi4.57S8 [the synthetic sulfide homologue N =3] with site occupancy equal to 0.12 (Tomeoka et al.
1980). Although traces of Cu or Ag persist at this location during the refinement process (up to 0.04 Cu persite combined with 0.97 Bi in the adjacent Bi3 site),these amounts are considered to lie below the error
threshold of the current refinement, and the site was477

considered to be unoccupied. In makovickyite andcupromakovickyite, the marginal Bi2 polyhedra of the
thick slab (Topa et al. 2008) resemble closely the Bi3
polyhedron in dantopaite. They were refined as a pure
Bi site in both structures.
The reader should be attentive to the inferior qualityof diffraction data that yield relatively high standard
deviations of the occupancy values and of positionalparameters for the Cu and Ag sites. Refinement resultson the little-occupied copper and silver sites in thepresence of an array of bismuth atoms will absorb thebulk of experimental errors. Furthermore, comparison
with the results of the chemical analysis shows thatthe contents of heavy cations (Bi and Pb) are overestimated in relation to those of Ag. These problems
probably are a reflection of the ubiquitous intimate
intergrowths of two or several sulfosalts in practicallyeach grain extracted, as also seen in the high value ofRint. Positional parameters of fully occupied sites aremuch less strongly influenced. Correlations between thedisplacement parameters of Ag1 and the occupancy of
the adjacent Cu2 site, as well as the occupancy of theAg1 site itself, reflect negatively upon the reliabilityof these values and result in high standard deviations.

Fig. 6. The crystal structure of dantopaite projected along the b axis (~4 Å). A unit-cell is shown. In order of increasing size,
circles represent Cu (red), Ag (green), Bi plus (Bi, Ag), and S positions. Void and filled circles represent atoms at two y levels,
2 Å apart. Thick slabs with rows of six Bi and (Bi, Ag) octahedra are shaded; thin layers are left unshaded.

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the canadian mineralogist

The relatively large residual maximum close to the Bi4
site (Table 3) might reflect the presence of subsidiary
7P lamellae in the diffracting dantopaite (6P) material.
The sum of monovalent cations in the thin slab is2.50 M+ apfu, which amounts to 1.25 M+ per octahedron of the thin slab. Comparison with chemical
data shows that the bulk of excess cations is locatedhere. The spatial distribution of the Ag1, Cu1 and Cu2
sites follows closely the usual pattern observed in thepavonite homologues, e.g., in makovickyite (Topa etal. 2008), which has 1.34 M+ per octahedron of the thinslab. This justifies further the structure model presented.
The orientation of the short and long bonds in themarginal Bi3 coordination octahedron coincides withthat observed in synthetic Cu–Bi pavonite homologues
N=3, i.e., the shortest Bi–S bond bridges the gap
between the two kinds of slabs and is oriented outward
from the thicker slab. This agrees with conclusionsby Makovicky et al. (2006), who suggested that theorientation of the short and long “horizontal” bondin this polyhedron is a function of the valence of theoctahedrally coordinated cation in the thin slab. The
short bond is oriented outward, as in the present case,where the coordination octahedra of the thin slab areoccupied by monovalent cations, and inward, into thethicker slabs, where these octahedra are occupied bydivalent cations.
As already mentioned, the cell parameters given
were refined from single-crystal data. The amount ofmaterial was not sufficient for experimentally obtained
X-ray powder data. A theoretical pattern (Table 7)
was calculated with PowderCell 2.3 software (Kraus& Nolze 1999) in Debye–Scherrer configuration
employing Cu Ka radiation (l = 1.540598 Å), a fixed
slit, and no anomalous dispersion. Cell parameters,

space group, atom positions, site-occupancy factors andisotropic displacement factors from the crystal-structure
determination were used.

The Place of Dantopaite
among Pavonite Homologues
Since its definition by Makovicky et al. (1977), thepavonite homologous series (PHS) of Ag–Cu–Pb–Bi
sulfosalts became one of the most prolific homologous
series, with an ever-increasing number of members. The

dantopaite, a new pavonite homologue from erzwies, austria

original definition is based on the structure of pavonite(N = 5) (Makovicky et al. 1977) and on the structure ofbenjaminite refined somewhat later (N = 7) (Mako­vicky& Mumme 1979, Herbert & Mumme 1981) (Table 8);these minerals were originally defined by Nuffield(1954) and Shannon (1925) [modern definition by Nuffield (1953)], respectively. Subsequently, Karup-Møller
& Makovicky (1979) found cupropavonite (N = 5) witha unit cell doubled compared to that of pavonite.
In 1992, Karup-Møller & Makovicky definedmummeite (N = 8) and Žák et al. (1994) describedmakovickyite (N = 4); their structures were resolved
by Mumme (1990). Further refinement of the structureof makovickyite and description of the structure of anew phase with a doubled unit-cell, cupromakovickyite(defined by Topa & Paar 2008), was published by Topaet al. (2008). There exist naturally occurring lower
members of the series, N = 3, with somewhat exotic
compositions: grumiplucite, a Hg–Bi sulfosalt (Orlandi
et al. 1998; structure by Mumme & Watts 1980), andkudriavite, a Cd sulfosalt (Chaplygin et al. 2005, structure by Balić-Žunić & Makovicky 2007).
The crystal structure of a synthetic, Cu–Bi, N = 3
member was determined first by Ohmasa & Nowacki(1973), then refined by Tomeoka et al. (1980); thecorresponding Cu–Bi (N = 3) selenide was published by
Makovicky et al. (2006). The synthetic N = 4 member isrepresented by a Cu–Bi sulfide as well (Ohmasa 1973),
whereas synthetic Cd–Bi members have N values equal
to 2 and 3, as do their regular intergrowths (Choe etal. 1997). The crystal structure of the synthetic N =8 member, Ag3.5Bi7.5S13, was described by Poudeu &Ruck (2005). A synthetic N = 4 selenide homologue
combining In, Sn and Bi was described by Wang etal. (2009). The synthetic member N = 1, MnSbSe2I(Tougait et al. 2003), as well as the monoclinic form of
MnSbS2Br (Doussier et al. 2006), represent an extension of the series to halogen sulfides. This approachproved very prolific as well, and a series of pavonite
homologues with N = 1, 2, 3, 4, 5, and 7 was synthetizedin the systems Ag–Bi–S–Cl or Br. For chlorine, N = 1
turned out to be a lillianite homologue. A conditional
N = 0 member with a composition AgBi2S2Cl3 was
obtained as well (Poudeu & Ruck 2002, Poudeu et al.
2004, Ruck & Poudeu 2008a, b).
What has been conspicuously missing in thisinventory, both among minerals and among synthetic
compounds, and even in the series of recently synthetized halogen sulfides, is the sixth member of thepavonite homologous series. The only reference weknow of describes a somewhat unusual N = 6 homologue, a synthetic selenide with Pb in interslab positions, synthetized and structurally analyzed by Mumme(1990). Unlike the latter compound, dantopaite is a“classical” pavonite homologue, close to the ideal
composition Ag5Bi13S22, with bismuth situated in thethin structural slabs.

479

Note on the Formation of Dantopaite
According to the present state of knowledge,
dantopaite is apparently a rare mineral. Its formation in the Erzwies deposit might be due to a rapidly
and constantly changing composition of ore-forming
solutions that resulted, in addition to the formation ofcomplex aggregates of sulfosalts, in the simultaneouspresence of three distinct pavonite homologues in thebunches of subparallel elongate sulfosalt crystals and in
the same elongate composite grains. Another proof ofthis fluid regime are the corroded grains of ourayite in
the decomposed PbS–AgBiS2 aggregates and the presence of aggregates in which the composition of lillianite
homologues varies along the vikingite–heyrovskyite
line, similar to the “schirmerite” aggregates analyzed
and described by Makovicky & Karup-Møller (1977).

Epilogue
Dantopaite is a new member of pavonite homologous
series. As an answer to queries about the definition of a
new mineral, raised by some members of the Commission for New Minerals, we should like to reiterate thatmembers of a homologous series of accretionary typeare independent chemical compounds, each with its own
structure, unit cell, physical properties and chemicalcomposition, as is the case of dantopaite relatively topavonite and benjaminite (Table 8). They are individual
mineral species (Makovicky 1989) and should be notconfused with members of a solid-solution series. A
distinct mineral (i.e., a given structure) can even be amember of more than one homologous series, lying at
the intersection of two series (e.g., the pavonite homologous series and the proudite–felbertalite homologous
series intersect in the structure of makovickyite). In
cases of a complicated chemical composition, crystalstructure determination gives a final, unambiguous
answer whether the mineral is a new species, as is in
the present case.

Acknowledgements
EM acknowledges financial support by the projectno. 272–08–0227 of the Research Council for Natureand Universe (Denmark). The Austrian team was financially supported by the Austrian Academy of Sciences(“Kommission für Grundlagen der Mineralrohstofforschung”), the present investigation being a part of
the above-mentioned regional project. Suggestions of
Dr. Yves Moëlo and an anonymous reviewer, as well as
the editorial care of Prof. Robert F. Martin, were helpful
in improving the present paper.

480

the canadian mineralogist

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Received October 23, 2009, revised manuscript accepted
April 11, 2010.