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THE CRYSTAL STRUCTURE OF SULFOSALTS WITH THE BOXWORK ARCHITECTURE AND THEIR NEW REPRESENTATIVE, Pb_15–2xSb_14+2xS₃₆O_x

Emil Makovicky^1, and Dan Topa²

¹ Department of Geography and Geology, University of Copenhagen, Østervoldgade 10, DK–1350 Copenhagen, Denmark
² Department of Material Research & Physics, University of Salzburg, Hellbrunnerstrasse 34, A–5020 Salzburg, Austria

E-mail address: emilm{at}geol.ku.dk

	ABSTRACT

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
The new monoclinic phase with a structure-determined formula Pb_15–2xSb_14+2xS₃₆O_x (Z = 4) was found only as a single grain in a micro-intergrowth of sulfosalts in the Klaianka Sb deposit, Low Tatra Mountains, Slovakia. Unit-cell dimensions are a 48.293(15), b 4.1107(13), c 34.223(11) Å, β 106.168(5)°, space group C2/m. There are 11 independent lead sites, 13 antimony sites, and five mixed (Pb, Sb) sites, 36 sulfur positions, and a single, approximately half-occupied oxygen site. Some coordination polyhedra of antimony exhibit split Sb sites, with positional parameters refined independently. Because of the intergrowth, the final R₁ value remained at 23.5%. It does not reflect visibly upon positional parameters, but has an adverse influence on the occupancy of mixed positions. Until further occurrences are documented, it remains an unnamed mineral. It is a typical sulfosalt representative of the category of boxwork structures. Other structures of this category comprise pellouxite, marrucciite, vurroite, neyite, and several synthetic sulfosalts. Sulfosalts with a boxwork structure are formed by a combination of three types of structural modules: continuous walls with a complex structure of rod-layer type; these walls are interconnected by partitions, and the resulting boxlike channels are filled by another type of structure rods. In its entirety, this group demonstrates a number of types for each of these kinds of module. The "core" group of Pb–Sb sulfosalts, scainiite, pillaite, pellouxite, rouxelite, a synthetic Mn–Pb sulfosalt, and Pb_15–2xSb_14+2xS₃₆O_x described in this study, depend on the presence of minor amounts of oxygen in the structures. Oxygen forms a part of a kermesite-like configuration that generates a pronounced change of the local structural arrangement and, in this way, makes the boxwork framework possible. Several REE sulfides form boxwork structures as well.

Keywords: boxwork structures, sulfosalts, unnamed Pb–Sb oxysulfosalt, crystal structure, Klaianka deposit, Low Tatra Mountains, Slovakia.

	INTRODUCTION

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
Since the solution of the crystal structure of Sb₂S₃ by Hofmann (1933), which clarified the coordination properties of Sb³⁺, the complexity of sulfosalt structures treated has been growing steadily. Examples of stepping stones on this path are jamesonite (Niizeki & Buerger 1957), robinsonite (Petrova et al. 1978) and kobellite (Miehe 1971). The challenge of solving the structure of izoklakeite, a member of the kobellite–izoklakeite family (Makovicky & Mumme 1986) has been superseded in 2000–2001 by structure determinations on scainiite, Pb₁₄Sb₃₀S₅₄O₅ (Moëlo et al. 2000), neyite Ag₂Cu₆Pb₂₅Bi₂₆S₆₈ (Makovicky et al. 2001) and pillaite (Meerschaut et al. 2001). Makovicky et al.(2001) introduced the name of boxwork structures to refer to their architecture. The number of boxwork structures of sulfosalts published is growing every year, as is also the variety of principles involved in their construction. A literature search revealed analogous structures among synthetic sulfosalts, e.g., In₄Bi₂S₉ (Chapuis et al. 1972) and rare-earth sulfides.

The structures of this category can be understood as an extension of the principle of rod-based structures (rod layers, rod chessboards, etc.), which was worked out by Makovicky (1993, 1997) for less complex families of sulfosalts and then applied to a number of new structures. This principle was also applied to several Pb–Sb–S–O sulfosalts (such as scainiite and pillaite) by the Nantes – Pisa research group but, starting with their study of scainiite, they favored an alternative approach to modular analysis of the Pb–Sb sulfosalts that is based primarily on the kinship with cyclically twinned sulfosalt structures. Spurred by a discovery of a new Pb–Sb sulfosalt, Pb_15–2xSb_14+2xS₃₆O_x, the boxwork structure of which is documented here, we have summarized the boxwork structures known today and made some generalizations that can be obtained by considering the boxwork approach, including the observations presented by the Nantes–Pisa group. We expect that the conclusions obtainable by the cyclic approach (see listing in Moëlo et al. 2008) will one day complete the understanding of the dual nature of this group. Our boxwork approach also differs from the approach of "couches gaufrées" (or palisade-like layers) developed by Moëlo et al. (2000) and Doussier et al.(2007), respectively, and discussed in more detail below.

	THE OCCURRENCE OF PB15–2xSB14+2xS36Ox

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
The material examined comes from the abandoned dumps of a small sulfide deposit of Klaianka in the old antimony mining region on the northern slopes of the Low Tatra Mountains, Slovakia. A single fragment of quartz matrix with aggregates of needle-like sulfosalt crystals yielded crystals of boulangerite, jamesonite, dadsonite and the hitherto unknown sulfosalt. We found it as a single tiny grain with domains in two orientations and in intimate intergrowth with other phases, while looking for a suitable crystal of dadsonite (Makovicky et al. 2006). Fundamental features of the new crystal structure were determined in 2003. Since then, neither examination of concentrates nor electron-microprobe examination of the material collected in Klaianka gave an indication of more material of the same kind. Therefore, the structure determination was carried out to its possible limits and the results are presented here.

	EXPERIMENTAL DATA

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
Experimental and crystal data are presented in Table 1. Reflections of the reciprocal lattice of the new compound were separated as much as possible from those of the admixtures, but still the principal problem encountered with the structure determination stems from the numerous random overlaps with the reflections of minor phases present. In the final stage of refinement, fifty manifestly wrong intensities were rejected, but many reflections still suffer from non-removable overlaps, arresting the R₁ value of an obviously right structure solution at 23.5%. The current sulfosalt is not the only boxwork structure with high R values; for example, marrucciite (Orlandi et al. 2007) has R₁ equal to 9.6%, and in rouxelite (Orlandi et al. 2005), R₁ is equal to 16.9% because of the quality of the material available.

	DESCRIPTION OF COORDINATION POLYHEDRA IN PB15–2xSB14+2xS36Ox

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

The coordination polyhedra of lead are mono- and bicapped trigonal coordination prisms, positioned typically on the outer surfaces of Pb–Sb rods (i.e., acting as envelopes of lone-electron-pair micelles of Sb); they are intermeshed with the coordination pyramids of antimony, which are concentrated in the rod interior. Eight of them are "standing prisms" with the (approximate) three-fold axes parallel to the rods (i.e., b axis), and three are "lying-down prisms" with three-fold axes at 90° to the rod elongation. A three-fold group of bicapped coordination prisms, Pb2–Pb4–Pb5, and the only tricapped trigonal prismatic Pb site, Pb 7, respectively, bind together three adjacent rods (micelles) at two different points of the structure. The Pb–S distances are recorded in Table 3.

The coordination polyhedra of antimony are square coordination pyramids completed by two additional S atoms under the base to monocapped trigonal prisms. The Sb atom is situated in the prism wall, and the lone electron-pair of Sb, in the volume of the prism. The distance of the additional S from Sb may exceed 4 Å, but the shape of the prism is only rarely distorted: this happens for Sb8 and Sb11 by a partial closure of the lone-electron-pair micelle, and especially for Sb10, which faces the Sb14 site (Figs. 1, 2). The Sb14 atom is bound to oxygen and has an entirely reorganized scheme of Sb–S bonds. An even distribution between "standing" and "lying-down" coordination prisms of Sb is observed.

View larger version (56K): [in this window] [in a new window]   FIG. 1. Labeling of cations and anions in one asymmetric unit of the crystal structure of Pb15–2xSb14+2xS36Ox. Note the oxygen position below Sb14.

View larger version (118K): [in this window] [in a new window]   FIG. 2. The crystal structure of Pb15–2xSb14+2xS36Ox. Here and in the remaining figures, Pb is dark blue, Sb red, Hg, Ag or Mn (where applicable) are green, S and Bi are colorless, O is light blue, and Cl is yellow. Two kinds of rods forming walls (vertical in the figure) and their lone-electron-pair micelles (lighter, along median planes), and those forming partitions (horizontal) and boxwork fill, respectively, are delineated by increasingly dark shading. Non-commensurate interspaces between rods are left unshaded. Note the (capped) standing and lying-down trigonal coordination prisms of Pb.

As already stated, anisotropic displacement parameters indicate that Sb16 and, to a lesser degree, also Sb14 and Sb5, might be positions split along the 4 Å b axis. In the case of Sb14, this might be connected with bond formation to oxygen because, with a lack of visible superstructure, Sb14 might be bonding randomly to the ligand below, or above, its level. The bond-length scheme (Table 3) suggests a similar disorder along the b direction for Sb19 as well.

The mixed sites are concentrated in a rod of SnS-like structure, which fills the box-like void of the boxwork structure (Fig. 2). Three such sites, Sb1–Pb1, Sb2–Pb3 and Sb17–Pb15, were refined as split sites, with every fractional atom having its own coordinates and a label. Two more sites, Sb3 and Sb20, could only be refined as unsplit sites in which Sb and Pb have the same set of coordinates. In all cases, complete occupancy of a coordination polyhedron was assumed. The Pb atoms protrude from the base of the pyramid and, for well-split cases, the relevant bond-distances approximate those of pure Pb and Sb (not forgetting, however, that their ligands represent mixed positions in such a case). All mixed sites form standing, monocapped trigonal coordination prisms.

The Sb14 site is a specific antimony site of decisive importance for oxysulfosalts of Pb and Sb (Moëlo et al. 2000). The three nearly perpendicular short Sb–anion bonds are: (1) Sb14–S25 (2.464 Å) to the vertex of the configuration, which remained from the "reduction" of the coordination pyramid SbS₅, analogous to those of the Sb neighbors, (2) Sb14–S22 (2.499 Å) to a new S position with the same y height as Sb14, and (3) S14–O (2.128 Å), which is oriented along +y or –y with equal probability. Two additional distances, Sb14–S21, are 3.264 Å. The Sb–O distance is an average distance because both Sb14 and O display a pronounced (oriented) displacement parallel to [010]. The half-occupied O site suggests that each Sb14 atom has only one oxygen neighbor. Doussier et al.(2007) modeled this coordination as a mean of 2.02 Å for the Sb–O bond and 2.36 Å for the Sb–vacancy distance; these differences are obtained by displacements of Sb toward oxygen and away from vacant sites, similar to our displacements. Doussier et al.(2007) assumed a half-filled oxygen site in the synthetic Mn sulfosalt they studied, similar to our direct refinement results. The oxygen positions in scainiite (Moëlo et al. 2000) were refined as two full and one half-occupied site, in pillaite (Meerschaut et al. 2001) and pellouxite (Palvadeau et al. 2004) as a half-occupied site, and in rouxelite (Orlandi et al. 2005) as a ~2/3 occupied position.

	MODULAR DESCRIPTION AND AFFINITIES

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
A modular description of Pb_15–2xSb_14+2xS₃₆O_x requires a prior definition of what is a boxwork structure (configuration), what are the individual module categories involved, and what are their mutual relationships.

Boxwork structures: definition and architecture

Boxwork structures are the most complex modular category of structures of sulfosalts and other complex sulfides known to date. Their name (Makovicky et al. 2001) comes from the arrangement of structural elements into a framework of walls interconnected by partitions, which together delimit large quadrilateral channels filled by structural elements that are crystal-chemically similar to, although not identical with, the elements that constitute the channel walls. The boxwork structures thus are not a category of micro- or mesoporous structures, in which the channel fill is profoundly different from the structure framework and even may be exchanged under certain conditions (Makovicky 2005).

This definition allows for a variety of principles in wall and partition construction as well as in the box fill, but the majority of sulfosalt structures known to date, those determined chiefly by the members of the Nantes–Pisa research group, follow a rather narrow set of principles, making possible a unified description of this "principal" Pb–Sb subgroup of (primarily) oxysulfosalts. The "aberrant" cases can generally be interpreted as related to definite groups of sulfosalts lying outside the boxwork category. Prominent cases of boxwork structures also exist among the chalcogenides of rare-earth elements.

As already mentioned, the category of boxwork structures overlaps partly with another large category of complex sulfides, the derivatives of the cyclically twinned structures, known among sulfosalts and other complex sulfides (Moëlo et al. 2000, 2008). Thus, several important boxwork sulfosalts, e.g., pillaite, scainiite and the present sulfosalt, can be described with equal validity as structures derived from cyclically twinned sulfosalt structures of zinckenite or barium– bismuth sulfide type (Makovicky 1985); they were classified as such by Moëlo et al.(2008). The duality of description is the best expression of the dual nature of these structures. However, not all important cases of the boxwork category are "cyclic derivatives", e.g., neyite (Makovicky et al. 2001) and La₁₀Er₉S₂₇ (Carré & Laruelle 1973, Makovicky 1992), whereas structures like (Mn_1–xPb_x)Pb_10–ySb_12–yS_26–yCl_4+yO (Doussier et al. 2007) are a boundary case. Besides the boxwork structures, the derivatives of cyclically twinned structures encompass other important groups of sulfosalts, such as the kobellite-type structures in the broadest sense. Treatment of the cyclic aspect of complex sulfosalts will not be taken up here, except for a short mention of its application to our new compound.

The structural elements of boxwork structures

The continuous walls in "typical" boxwork structures (drawn vertically in all figures) can be based on the SnS archetype, in a smaller number of cases on the PbS archetype or, being just a double layer, the archetype remains ambiguous (Makovicky 1997). In most cases, they represent an alternation of two types or rods along the layer. They are interconnected by a double layer (100)_SnS; this layer-building principle corresponds in principle to "Layer Type 1" observed in boulangerite (Makovicky 1993). In neyite, based on the PbS principle, the interconnection proceeds via a triple layer (100)_PbS.

The double layers discernible in the wall structures based on SnS archetype take part in two adjacent rods. They are sinuous, as is also the layer in neyite, and start on one side of the wall, ending on its opposite side. Sinuosity is materialized via insertion of modified "kermesite-like fragments"(Moëlo et al. 2000) (in scainiite, Fig. 3), or by insertion of Hg (in marrucciite, Fig. 4), and by insertion of Pb [in pillaite (Fig. 5), which has three types of rods, although these layers (in "walls") can also be interpreted as Layer-type 11 of Makovicky (1993) with an extended "interconnecting" region between two adjacent rods, as well as in the present structure (Fig. 2)]. Finally, sinuosity can also be produced by the presence of slightly inflated lone-electron- pair micelles (in pellouxite, Fig. 6; for all references see Table 4). These sinuous double layers may have two types of termination: either both terminations end in Sb, which is coordinated to S and O in a "kermesite-type" arrangement defined by Moëlo et al.(2000) (see below), or they have one termination by a SbS₅ pyramid and another one of the "kermesite type". Each structure has only one type of double layers.

View larger version (103K): [in this window] [in a new window]   FIG. 3. The crystal structure of scainiite (Moëlo et al. 2000) with a high concentration of "kermesite-like configurations" along (001) planes, in continuation of "horizontal" interspaces. Oxygen is shown in light blue.

View larger version (125K): [in this window] [in a new window]   FIG. 4. The crystal structure of marrucciite (Orlandi et al. 2007) Note the two distinct flat-octahedron Hg sites in the vertical walls; it was left unshaded.

View larger version (91K): [in this window] [in a new window]   FIG. 5. The crystal structure of pillaite (Meerschaut et al. 2001). For conventions, see Figure 2. Rods of the walls (vertical) are terminated by "kermesite-like configurations", and box-fill rods are completed by chlorine atoms (yellow).

View larger version (126K): [in this window] [in a new window]   FIG. 6. The crystal structure of pellouxite (Palvadeau et al. 2004). Note the two distinct ways in which rods in the walls are terminated: by SbS5 pyramids and by "kermesitelike" configurations, respectively. The latter allow deep insertion of rods forming horizontal partitions into the spaces created.

View larger version (100K): [in this window] [in a new window]   FIG. 7. The crystal structure of the synthetic Mn–Pb oxychlorosulfosalt (Doussier et al. 2007). Note the "kermesite-like configurations" in the walls and single-octahedron columns of (Mn,Pb)Cl4 stoichiometry in the box interior.

The configuration of the partitions between the walls varies much less. In most cases, they are lozenge-shaped rods based on the SnS archetype, four atomic layers thick and with [001]_SnS as the rod axis. The maximum width observed involves four pseudotetragonal subcells (pyramids) (pillaite); more common are three pyramids (e.g., scainiite and the present compound), and a two-pyramid width is observed in the synthetic Mn sulfosalt. Their pseudohexagonal, anion-lined surfaces face the walls just described, the pseudotetragonal surfaces face the "fill" of the channels. The only other type observed are partitions in marrucciite; these are based on the PbS archetype and can be interpreted as truncated, with an additional Pb atom at the corner of the partition.

In neyite (Fig. 8) and in La₁₀Er₉S₂₇, dealt with in detail below, the partitions are pseudotetragonal layers, two atomic layers thick. In neyite, they contain a unique lateral offset in the form of a column of empty octahedra flanked by tetrahedrally coordinated Cu sites, fully analogous to the configurations observed in the sheared-layer structures of proudite-group minerals.

View larger version (112K): [in this window] [in a new window]   FIG. 8. The crystal structure of neyite (Makovicky et al. 2001). The Ag atom in the walls has a linear coordination, whereas Cu has tetrahedral and triangular coordination, respectively. Partitions (grey) and box-fill (dark grey) underwent crystallographic shear midway between walls.

The SnS-based "fill elements" are [001]_SnS rods in most structures. In neyite (Makovicky et al. 2001), the synthetic Pb–La–Bi sulfosalt (Iordanidis & Kanatzidis 2001, Doussier et al. 2007) and the synthetic Mn sulfosalt (Doussier et al. 2007), as well as vurroite (Pinto et al. 2008) (the latter two examples contain single-octahedron rods), they are [011]_PbS. Because of different cross-sections, comparison of the size of fill elements in different structures can be best performed counting the number of cations and anions per cross-section in the projections illustrated. They start with MS₄ for single-octahedron columns and end with M₁₈S₂₆ for the present compound. For scainiite, the fill is M₉S₁₄, whereas in pillaite, the complete "fill" represents M₆S₁₀Cl₂, because chlorine completes the lozenge-shaped fill-rod. The same stoichiometry, M₆S₁₂, occurs in the PbS-like fragments, terminated by trigonal prisms, in Pb₂La_xBi_8–xS₁₄ (Iordanidis & Kanatzidis 2001, Doussier et al. 2007). In terms of an SnS-like arrangement, the rods of Sb sulfosalts contain between two fragments and four fragments of tightly bonded double layers, respectively seen in scainiite and in the new structure.

The different types of rods described here were already defined and illustrated by Moëlo et al.(2000) and Palvadeau et al.(2004) as rods A (defined as partitions in the present contribution), B (channel fill) and C₁–C₂ rods (Moëlo et al. 2000) or type-C ribbon layers (Palvadeau et al. 2004) (our walls). In the paper on marrucciite, Orlandi et al.(2007) altered the assignment of the A, B, C notation to the three rod types mentioned, and in the paper by Doussier et al. (2007), this notation was abandoned in favor of "palisade-like layers" discussed further below. A brief discussion of boxwork structures and illustration of the rods involved was also given by Ferraris et al.(2004) and Makovicky (2006).

Modular character of Pb_15–2xSb_14+2xS₃₆O_x

The structure of Pb_15–2xSb_14+2xS₃₆O_x is a typical rod-based structure of a Pb–Sb boxwork type, broadly similar to those of pillaite or pellouxite, with the largest channels or "boxes" and most voluminous channel fill known to this day (Table 4). Typically, rods of the box walls and partitions are primarily rods with extensive pseudotetragonal surfaces. Sheared pseudohexagonal surfaces 3³.4² form only portions of rod terminations. Correspondingly, the box contents consist of an enclosed rod with all surfaces of a sheared pseudohexagonal type, with only single-corner pyramids as intervals of pseudotetragonal type (Fig. 2).

The combined (100) walls in Pb_15–2xSb_14+2xS₃₆O_x consist of two alternating types of rods arranged en échelon in a way similar to the rod-layers in boulangerite: (1) smaller rods, with four combined layers of cations–anions that are three coordination pyramids wide [these are pseudotetragonal pyramids that have also been described as Q subcells by Makovicky (1993)]. They are interconnected with (2) larger rods via tightly bonded double-layers. The latter rods are 3 pyramids wide, 4 atomic layers thick, and they end in "kermesite-like portions", instead of the classical 3³.4² (101)_SnS endings [a mathematical notation for surfaces in which three triangular and two quadratic configurations of sulfur atoms meet in every S atom, defined as sheared pseudohexagonal anionic surfaces by Makovicky (1993)], seen in the classical rod-based sulfosalts (Makovicky 1993). In this "kermesite-like" configuration, the horizontal, outwardly oriented short Sb–S bond and that to the vertex of the pyramid are accompanied by a short bond to oxygen above or below the Sb atom.

The partition (quoted as rod category 3 below) is a rod that is three pseudotetragonal coordination pyramids wide; it has a regular rod aspect and a lozenge-like cross-section. The encapsulated "fill" rods (category 4) are eight atomic layers thick, and in their principal portions, they are three pyramids wide, with terminal double-layers reduced to a width of two, and finally only one coordination pyramid (Fig. 2). The anionic surfaces are of the 3³.4² configuration; the rod is truncated in two opposing corners by pseudotetragonal intervals only one Pb pyramid wide.

Rods of the categories (1) and (2) are infinite along [010]_SnS, whereas the category (3), i.e., the transversal rod (i.e., the partition) and (4) the boxwork infill, are infinite along [001]_SnS. In the projection along [010] of the present structure, the cases (1) and (2) exhibit "lying-down" monocapped trigonal coordination prisms, whereas the configurations (3) and (4) are composed of "standing" monocapped trigonal coordination prisms (Fig. 2). The Sb–S–O configuration of rods (2) forms an embayment into which a corner of the transversal rod (3) is inserted.

The degenerate cyclic character (Makovicky 1985, Moëlo et al. 2000) of the structure of Pb_15–2x Sb_14+2xS₃₆O_x is produced by the arrangement of three distinct rods around a local three-fold axis in each of the acute corners of a "boxwork" channel. On a local scale, they form groups of three edge-sharing bicapped trigonal coordination prisms of Pb. The rods involved are of the category (1) and (3) defined above, both of 3Q type, but with different external connections, as well as the corner portions of the large rod (4). As mentioned above, the rods (1) and (3) display an orientation of the SnS archetype at 90° to that in rod (4). All this limits the size of the region that obeys the local three-fold axis.

Surfaces of the first three types of rods in Pb_15–2x Sb_14+2xS₃₆O_x are occupied by Pb in standing and lyingdown trigonal coordination prisms, which are mono-, bi-, and tricapped, according to the local match requirement on rod interfaces. The longest match is ~4 Q : 2 H in terms of primitive pseudotetragonal (Q) and centered orthohexagonal (H) subcells (mesh), followed by ~2 Q : 1 H and ~1 Q : 1 H. Rods of category (1) and (2) together compose a (100) rod-layer that approximates the Type-1 rod-layer of Makovicky (1993), although modified by the insertion of a "kermesite-like configuration" at selected edges. The configurations resulting from this arrangement allow insertion of an unmodified transversal 3Q rod (a partition) and a formation of a "box", in which the cation–anion contacts between the walls and "fill" satisfy the coordination requirements of lead.

	STRUCTURAL AFFINITIES OF PB15–2xSB14+2xS36Ox

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
If we consider the number of strongly bonded double-layers present in the box-fill of the Pb–Sb sulfosalts, the new oxysulfosalt presents four, rouxelite three, and scainiite, marrucciite and pellouxite only two double-layers each, separated in all cases by lone-electron interspaces. The situation in pellouxite is modified by the "termination" of the lozenge-like infill by columns of chlorine atoms. These are situated in those portions of the structure already occupied by the framework of the walls and partitions in scainiite and marrucciite. In this context, the columns of octahedra in vurroite and in the synthetic Mn sulfosalt can be interpreted as one double-layer plus one interspace.

This concept leads to the question of possible homologous series in this group of compounds. All representatives of the Pb–Sb sulfosalts of the "core" oxysulfosalt group, related to zinkenite, have variously large local environments in common, as illustrated in the original descriptions by the Nantes–Pisa research group. However, the misfit between the dimensions of the arrays of pseudotetragonal subcells in the walls and the dimensions of the n x (101)_SnS subperiodicity of pseudohexagonal surfaces means that practically all attempts to produce a homologous expansion or contraction are frustrated, demanding excessive concentrations of kermesite-like elements in order to compensate for the lack of fit.

The new sulfosalt, Pb_15–2xSb_14+2xS₃₆O_x, however, represents a case close to homology. In the structure of pellouxite (Palvadeau et al. 2004), a large complex rod (Fig. 9) can be defined, which also describes large portions of the structure of Pb_15–2xSb_14+2xS₃₆O_x. The latter structure contains additional elements that form a zig-zag layer cutting diagonally through the walls and the box-fill and displacing the complex rods as well (Fig. 9). In addition, however, when we proceed along the [100] and [001] directions of pellouxite, the adjacent complex rods are invariably displaced by Q (~2 Å) parallel to [010] in the new compound. Therefore, these two structures are not two homologues in an exact sense but plesiotypes (Makovicky 1997).

View larger version (96K): [in this window] [in a new window]   FIG. 9. Rod configurations common to Pb15–2xSb14+2xS36Ox (left) and pellouxite (right). Note the mutual shifts in the heights of rods by 2 Å, when proceeding along either crystallographic direction. They are different in the two phases and are expressed by coloring of atoms (light and dark). Note also the additional structure portions present in Pb15–2xSb14+2xS36Ox.

	FROM THE ROD -BASED TO BOXWORK STRUCTURES: THE IMPORTANCE OF THE "KERMESITE -LIKE " CONFIGURATION

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

View larger version (80K): [in this window] [in a new window]   FIG. 10. Two distinct "kermesite-like configurations" in the crystal structure of scainiite. In the order of decreasing size, spheres indicate S, Pb, Sb, and O. The Sb–S, Pb–S and Sb–O bonds are indicated, the long Sb–S bonds (interactions) are shown using a smaller diameter. Chains are parallel to [010]. Modified from Moëlo et al.(2000).

Kupík 1967

urovi & Hybler 2006

Both the apically or internally situated "kermesite configurations" shorten the pseudotetragonal subperiodicity of cation–anion configurations (and their surfaces) by about a half-width of the coordination pyramid of Sb, in the direction perpendicular to the rod orientation. Thus, the structural element that follows, and is attached into the embayment of the structure wall, can be positioned "earlier", and yield structural configurations not considered possible with the above-mentioned "classical matches" in rod-based sulfosalts. In addition, as already mentioned by Moëlo et al.(2000), the paired "kermesite-like" elements in the centers of double layers in scainiite shift the two portions of the double layer by ~2 Å against one another. For the Pb–Sb sulfosalts, along the wall direction, the position of the next partition thus fits with the dimensions and position of the fill element and can follow after it. It would be situated too far for any contact with the fill element without the intervention of the "kermesite fragment". Furthermore, the "horizontally situated" apical S atom of the "kermesite configuration" becomes a regular corner-component of the partition (Figs. 2, 3), and determines its shift along the rod axis to such a level that the coordinations of Pb atoms on the partition surfaces fit with the heights of S atoms on the pseudohexagonal surfaces of the fill element. All this would not exist without the small islands of "kermesite configuration" in the structure.

Is oxygen invariably present? Light (1997) described a structure of "Pb_8.67Sb_11.33S₂₃", with a nonstoichiometric formula derived from structure determination, with unit-cell dimensions (Table 4) marginally larger than those of pillaite (Meerschaut et al. 2001) and a crystal structure virtually identical with that of pillaite. Light placed an Sb atom (with 5% Pb) into the Cl site of pillaite; all metal and metalloid sites were refined as mixed sites. These crystals are a product of vapor transport with iodine and H₂O vapor as a transport medium. Thus, we interpret this "trigonal prismatic Sb position" as the iodine position, the "5% Pb content" being in full agreement with the difference between the atomic numbers of Sb and I. The I–cation distances are 3.514 Å, 3.546 Å, and 3.610 Å, to be compared with the Cl-cation distances in pillaite itself, 3.250 Å, 3.329 Å, and 3.399 Å. The marginal Sb atom in the rods of the continuous walls in Light’s structure has a coordination identical to that in the "kermesite configurations" of pillaite, except for the unidentified oxygen.

Our interpretation of the phase synthesized by Light (1997) has been corroborated by the syntheses of Kryukova et al.(2005), who prepared a phase with unit-cell parameters nearly identical with those of pillaite (Table 4), a composition estimated by a combination of WDS and EDS as Cu_0.51Pb_8.73Sb_8.15I_1.6S₂₀ (no data on the analysis given; the phase was obtained by vapor transport from a natural, mixed sulfosalt material), and a pillaite-like structure that was verified by HRTEM and comparison of calculated and observed powder-diffraction patterns. Therefore, both sets of investigations describe apparently the same phase, a synthetic "iodo-pillaite", and left some problems unsolved, especially the presence of oxygen in the "kermesite-like fragments", which seems inevitable from the coordination found by Light (1997).

	PALISADE -LIKE LAYERS ("COUCHES GAUFRÉES")

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
As already mentioned, Moëlo et al.(2000) and the authors of later publications of the Nantes–Pisa group used another type of layer definition than used here. They drew a "complex rod layer", in which rods are the above-mentioned boxes with their fill, and include the adjacent halves of walls. Boundaries of these layers (called by them "couches gaufrées") pass wherever possible through lone-electron-pair micelles and through interfaces between archetype rods as defined by us. Doussier et al.(2007) calls such a layer "a palisade-like layer with a waffle structure". Layers so defined follow the presumed easy cleavage of these Pb–Sb sulfosalts. This principle of structure slicing, which preserves tightly bonded elements, reflects yet another aspect of the Pb–Sb subfamily of boxwork sulfosalts. It uses a quite different definition of a "rod", and the channel infill becomes a "lozenge heart". The concept of Doussier et al. does not lead to the recognition of the SnS-based character of the structure. The extension of the waffle layer concept by Doussier et al.(2007) to channel structures with tightly bonded walls, where a waffle layer is not individualized [such as Pb₄La_2x Bi_16–2xS₂₈ (Iordanidis & Kanatzidis 2001), treated further below] and has to be cut out of the strong, three-dimensionally continuous porous framework, gives a definition of waffle structures that differs from the one given at the beginning of their paper.

The paper by Doussier et al. (2007) contains an attempt to classify boxwork structures according to the complex palisade-like layers in them, distancing them in this way from the large body of rod-based structures of layer, chessboard, and even cyclic types. One of the aims of the present paper is to re-establish this connection, preserving the unity of the family of rod-based structures on a higher level of complexity.

	STRUCTURE TYPES OTHER THAN PB–SB OXYSULFOSALTS RELATED TO ZINKENITE

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
Vurroite, Pb₁₀Sn(Bi,As)₁₁S₂₇Cl₃ (Pinto et al. 2008) is a boxwork structure with single octahedron columns (Sn,Bi)₄ in boxes of lozenge-like cross-section (Fig. 11). The walls consist of rods, two and three (As,Bi) pyramids wide, arranged into tiers by intercalated planes of trigonally coordinated Pb and mixed-cation positions. These levels also act as mirror planes of the motif, so that no clear distinction into walls and partitions can be made.

View larger version (119K): [in this window] [in a new window]   FIG. 11. The crystal structure of vurroite (Pinto et al. 2008). Two kinds of walls, respectively composed of rods, two and three pyramids wide (indicated by two kinds of shading), enclose boxes with a single-octahedron (Sn, Bi) fill.

View larger version (125K): [in this window] [in a new window]   FIG. 12. The crystal structure of rouxelite (Orlandi et al. 2005). Note the flattened octahedron of Hg and the tetrahedrally coordinated Cu atoms. There are three kinds of modules, which lead to a local but not a global kinship to the kobellite structure-type. Details are in the text.

Neyite, Ag₂Cu₆Pb₂₅Bi₂₆S₆₈ (Makovicky et al. 2001), is a type structure of the boxwork concept (Fig. 8). The clearly outlined box-fill is of the PbS type, with the composition M₂₆S₃₆ and with pseudohexagonal surfaces, disturbed only by two short Q intervals at the acute corners. The boxfill faces the pseudotetragonal surfaces of the sinuous walls, three atomic planes thick, as well as those of the tightly bonded double-layers serving as partitions. In analogy to rouxelite, the straight portions of the sinuous walls are locally extended by insertion of broad, foreshortened Ag octahedra, and the four surrounding polyhedra are rotated and thus fitted to the periodicity of the adjacent pseudohexagonal surface (Fig. 8).

One of the smallest boxwork frameworks among sulfosalts is the structure of Bi₂In₄S₉ (Chapuis et al. 1972). Ribbons with a composition Bi₂In₂S₆ form porous walls; other such ribbons, stabilized in place by In–S bonds, form partitions, and fragments of octahedrally coordinated In layers are the box fill (Fig. 13). The marginal atoms of five-coordinated indium in the latter fragments can be assigned either to the framework or to the fill.

View larger version (96K): [in this window] [in a new window]   FIG. 13. The crystal structure of Bi2In4S9 (Chapuis et al. 1972) with six- and five-coordinated indium, and square-pyramidal Bi. Three kinds of elements are present: "porous" walls (vertical), partitions and double-octahedron chains as a fill.

View larger version (106K): [in this window] [in a new window]   FIG. 14. The crystal structure of the synthetic Pb–La–Bi sulfosalt (Iordanidis & Kanatzidis 2001). The boxwork consists of two-sheet-thick pseudotetragonal walls with no obvious division into walls and partitions, and a seven-coordinated cation in wall intersections.

View larger version (102K): [in this window] [in a new window]   FIG. 15. The crystal structure of Er9La10S27 (Carré & Laruelle 1973). Walls underwent a homologous expansion in comparison to those in Figure 14, partitions have greater length, and the filling elements are three-strand ribbons of octahedra. A conspicuous configurational affinity exists to the sulfosalt structure in Figure 14.

View larger version (116K): [in this window] [in a new window]   FIG. 16. The crystal structure of CeTmS3 (Rodier 1973). It has complex walls (see text), simple partitions, and octahedron elements of the boxfill similar to, but narrower than, those in Figure 14. Cerium prefers a bicapped trigonal prismatic coordination, whereas Tm prefers coordination by six and seven ligands.

	CONCLUSIONS

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

	AKNOWLEDGEMENTS

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
This research was supported by grant no. 21–03– 0519 of the State Research Council for Natural Sciences (Denmark) and by Christian Doppler Forschungsgesellschaft (Austria). Thorough reviews by Dr. Yves Moëlo and Dr. Allan Pring, as well as the editorial care of Prof. R.F. Martin, are gratefully acknowledged.

	References

Top Abstract Introduction The Occurrence of Pb15... Experimental Data Description of Coordination... Modular Description and... Structural Affinities of Pb15... From the Rod -Based... Palisade -Like Layers ("Couches... Structure Types Other than... Conclusions Aknowledgements References

 
BERLEPSCH, P., MAKOVICKY, E. & BALIC-UNIC, T. (2001): Crystal chemistry of sartorite homologues and related sulfosalts. Neues Jahrb. Mineral., Abh. 176, 45–66.

BONAZZI, P., MENCHETI, S. & SABELLI, C. (1987): Structure refinement of kermesite: symmetry, twinning and comparison with stibnite. Neues Jahrb. Mineral., Monatsh., 557–567.

CARRE, D. & LARUELLE, P. (1973): Structure cristalline du sulfure d’erbium et de lanthane, Er₉La₁₀S₂₇. Acta Crystallogr. B29, 70–73.

CHAPUIS, G., GNEHM, C. & KRAMER, V. (1972): Crystal structure and crystal chemistry of bismuth indium sulfide, Bi₂ In₄ S₉. Acta Crystallogr. B28, 3128–3130.[CrossRef]

DOUSSIER, C., MOELO, Y., LEONE, P. & MEERSCHAUT, A. (2007): (Mn_1–xPb_x)Pb_10+ySb_12–yS_26–yCl_4+yO, a new oxychloro- sulfide with ~2 nm-spaced (Mn,Pb)Cl₄ single chains within a waffle-type structure. J. Solid State Chem. 180, 2323–2334.[CrossRef]

UROVIC, S. & HYBLER, J. (2006): OD structures in crystallography – basic concepts and suggestions for practice. Z. Kristallogr. 221, 63–76.[CrossRef]

ECREPONT, C., GUITTARD, M. & FLAHAUT, J. (1988): Système La_4/2S₃–Bi₂S₃: phases intermédiaires; diagramme de phase. Mater. Res. Bull. 23, 37–42.[CrossRef]

FERRARIS, G., MAKOVICKY, E. & MERLINO, S. (2004): Crystallography of Modular Materials. Oxford University Press, Oxford, U.K.

HOFMANN, W. (1933): Die Struktur der Minerale der Antimonitgruppe. Z. Kristallogr. 86, 225–245.

IORDANIDIS, L. & KANATZIDIS, M.G. (2001): Novel quaternary lanthanum bismuth sulfides Pb₂ La_x Bi_8–x S₁₄, Sr₂La_x Bi_8–x S₁₄, and Cs₂ La_x Bi_10–x S₁₆ with complex structures. Inorg. Chem. 40, 1878–1887.[CrossRef][Medline]

KRYUKOVA, G.N., HEUER, M., WAGNER, G., DOERING, T. & BENTE, K. (2005): Synthetic Cu_0.507(5)Pb_8.73(9)Sb_8.15(8) I_1.6S_20.0(2) nanowires. J. Solid State Chem. 178, 376–381.[CrossRef]

KUPCIK, V. (1967): Die Kristallstruktur des Kermesits, Sb₂S₂O. Naturwiss. 54, 114.

LAUFEK, F., SEJKORA, J., FEJFAROVA, K., DUSEK, M. & OZDIN, D. (2007): The mineral marrucciite: monoclinic Hg₃Pb₁₆Sb₁₈S₄₆. Acta Crystallogr. E63, i190 [doi:10.1107/S1600536806040980].[CrossRef]

LIGHT, M.E. (1997): Structural Studies of Mineral Silicates and Synthetic Sulfosalts Characterised by Mixed Occupancies. Ph.D. thesis, Univ. of Wales, Cardiff, U.K.

MAKOVICKY, E. (1985): Cyclically twinned sulfosalt structures and their approximate analogues. Z. Kristallogr. 173, 1–23.

MAKOVICKY, E. (1992): Crystal structures of complex lanthanide sulfides with built-in non-commensurability. Aust. J. Chem. 45, 1451–1472.

MAKOVICKY, E. (1993): Rod-based sulphosalt structures. Eur. J. Mineral. 5, 545–591.[Abstract/Free Full Text]

MAKOVICKY, E. (1997): Modular crystal chemistry of sulphosalts and other complex sulphides. In Modular Aspects of Minerals (S. Merlino, ed.). Eur. Mineral. Union, Notes in Mineralogy 1, 237–271.

MAKOVICKY, E. (2005): Micro- and mesoporous sulfide and selenide structures. In Micro- and Mesoporous Mineral Phases (G. Ferraris & S. Merlino, eds.). Rev. Mineral. Geochem. 57, 403–433.[Free Full Text]

MAKOVICKY, E. (2006): Crystal structures of sulfides and other chalcogenides. In Sulfide Mineralogy and Geochemistry (D.J. Vaughan, ed.). Rev. Mineral. Geochem. 61, 7–125.

MAKOVICKY, E., BALIC-UNIC, T. & TOPA, D. (2001): The crystal structure of neyite, Ag₂Cu₆ Pb₂₅ Bi₂₆ S₆₈. Can. Mineral. 39, 1365–1376.[Abstract/Free Full Text]

MAKOVICKY, E. & MUMME, W.G. (1986): The crystal structure of izoklakeite, Pb_{51. 3}Sb_20.4 Bi_19.5 Ag_1.2Cu_2.9 Fe_0.7 S₁₁₄. The kobellite homologous series and its derivatives. Neues Jahrb. Mineral., Abh. 153, 121–145.

MAKOVICKY, E., TOPA, D. & MUMME, W.G. (2006): The crystal structure of dadsonite. Can. Mineral. 44, 1499–1512.[Abstract/Free Full Text]

MEERSCHAUT, A., PALVADEAU, P., MOELO, Y. & ORLANDI, P. (2001): Lead–antimony sulfosalts from Tuscany (Italy). IV. Crystal structure of pillaite, Pb₉Sb₁₀S₂₃ClO_0.5, an expanded monoclinic derivative of hexagonal Bi(Bi₂S₃)₉I₃, from the zinkenite group. Eur. J. Mineral. 13, 779–790.[Abstract/Free Full Text]

MIEHE, G. (1971): Crystal structure of kobellite. Nature Phys. Sci. 231, 133–134.

MOELO, Y., MAKOVICKY, E., MOZGOVA, N.N., JAMBOR, J.L., COOK, N., PRING, A., PAAR, W., NICKEL, E.H., GRAESER, S., KARUP-MOLLER, S., BALIC-UNIC, T., MUMME, W.G., VURRO, F., TOPA, D., BINDI, L., BENTE, K. & SHIMIZU, M. (2008): Sulfosalt systematics: a review. Report of the sulfosalt sub-committee of the IMA Commission on Ore Mineralogy. Eur. J. Mineral. 20, 7–62.[Abstract/Free Full Text]

MOELO, Y., MEERSCHAUT, A., ORLANDI, P. & PALVADEAU, P. (2000): Lead–antimony sulfosalts from Tuscany (Italy). II. Crystal structure of scainiite, Pb₁₄ Sb₃₀ S₅₄ O₅, an expanded monoclinic derivative of Ba₁₂ Bi₂₄ S₄₈ hexagonal sub-type (zinkenite group). Eur. J. Mineral. 12, 835–846.[Abstract/Free Full Text]

MUMME, W.G. (1989): The crystal structure of Pb_5.05(Sb_3.75 Bi_0.28)S_10.72Se_0.28: boulangerite of near ideal composition. Neues Jahrb. Mineral., Monatsh., 498–512.

NIIZEKI, W.& BUERGER, M.J. (1957): The crystal structure of jamesonite, FePb₄Sb₆S₁₄. Z. Kristallogr. 109, 161–183.

ORLANDI, P., MEERSCHAUT, A., MOELO, Y., PALVADEAU, P. & LEONE, P. (2005): Lead–antimony sulfosalts from Tuscany (Italy). VIII. Rouxelite, Cu₂Hg Pb₂₂ Sb₂₈ S₆₄ (O, S)₂, a new sulfosalt from Buca Della Vena mine, Apuan Alps: definition and crystal structure. Can. Mineral. 43, 919–933.[Abstract/Free Full Text]

ORLANDI, P., MOELO, Y., CAMPOSTRINI, I. & MEERSCHAUT, A. (2007): Lead–antimony sulfosalts from Tuscany (Italy). IX. Marrucciite, Hg₃Pb₁₆Sb₁₈S₄₆, a new sulfosalt from Bucca della Vena mine, Apuan Alps: definition and crystal structure. Eur. J. Mineral. 19, 267–279.[Abstract/Free Full Text]

PALVADEAU, P., MEERSCHAUT, A., ORLANDI, P. & MOELO, Y. (2004): Lead–antimony sulfosalts from Tuscany (Italy). VII. Crystal structure of pellouxite, ~(Cu,Ag)₂ Pb₂₁ Sb₂₃ S₅₅ Cl O, an expanded monoclinic derivative of Ba₁₂ Bi₂₄ S₄₈ hexagonal sub-type (zinkenite group). Eur. J. Mineral. 16, 845–855.[Abstract/Free Full Text]

PETROVA, I.V., KAPLUNNIK, L.N., BORTNIKOV, N.S., POBEDIMSKAYA, E.A. & BELOV, N.V. (1978): The crystal structure of synthetic robinsonite. Dokl. Akad. Nauk SSSR 241, 88–90.

PINTO, D., BONACCORSI, E., BALIC-UNIC, T. & MAKOVICKY, E. (2008): The crystal structure of vurroite, Pb₂₀Sn₂(Bi,As)₂₂S₅₄Cl₆: OD-character, polytypism, twinning and modular description. Am. Mineral. 93, 713–727.[Abstract/Free Full Text]

RODIER, N. (1973): Structure cristalline du sulfure mixte de thulium et de cérium TmCeS₃. Bull. Soc. fr. Minéral. Cristallogr. 96, 350–355.

SHELDRICK, G.M. (1997a): SHELXS-97. A Computer Program for Crystal Structure Determination. University of Göttingen, Göttingen, Germany.

SHELDRICK, G.M. (1997b): SHELXL-97. A Computer Program for Crystal Structure Refinement. University of Göttingen, Göttingen, Germany.

Received December 11, 2007 ,revised manuscript received January 18, 2009

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