The crystal structure of grumiplucite: its OD characterand structural relationships

Stefano Merlino • Cristian Biagioni •

Paolo Orlandi

Received: 23 October 2012 / Accepted: 15 November 2012 / Published online: 4 December 2012

� Accademia Nazionale dei Lincei 2012

Abstract A new single-crystal X-ray diffraction study of

grumiplucite, HgBi2S4, from Levigliani mine, Apuan Alps,

Tuscany, Italy, has allowed the refinement of its crystal

structure, confirming its identity with the synthetic ana-

logue. Its crystal structure was refined up to R1 = 0.116 in

the space group C2/m, with a 14.1690(16), b 4.0508(4),

c 13.9751(14) A, b 118.292(6)�, V 706.29(13) A3. The

crystal structure is formed by (001) layers, built up by

Bi2S4 rods running along b, connected through Hg2? ions

in the [100] direction. Each rod is built up by chains of

edge-sharing square-pyramidal BiS5 polyhedra, paired

through the apical Bi–S bonds. Adjacent layers are con-

nected through weaker Bi–S bonds, in agreement with the

good {001} cleavage of grumiplucite. Grumiplucite has an

order–disorder (OD) character and can be described as

formed by equivalent layers having a layer symmetry C 1

2/m 1, with translation vectors a = 14.161, b = 4.051,

c0 = 6.18 A, b 90�. Applying the OD theory, two Maxi-

mum Degree of Order (MDO) polytypes were derived.

MDO1 polytype is orthorhombic, with space group Ccm21,

with a 14.16, b 4.05, c 12.36 A, whereas the MDO2

polytype, corresponding to the refined structure, is mono-

clinic, space group C2/m, with a 14.16, b 4.05, c 14.2 A,

b 119.9�, in satisfying agreement with experimental data.

Grumiplucite is a member of the pavonite homologous

series and is structurally related to kudriavite (Cd,Pb)Bi2S4,

and some synthetic compounds. In addition, appealing

structural relationships occur also with livingstonite,

HgSb4S8.

Keywords Grumiplucite � Crystal structure �Order–disorder (OD) � Sulfosalt � Pavonite �Kudriavite � Livingstonite

1 Introduction

Grumiplucite has been defined as a new mineral phase by

Orlandi et al. (1998). It was found in the small Hg deposit

of Levigliani, Apuan Alps, Tuscany, Italy, hosted within

phyllitic and metavolcanic rocks of Middle to Upper

Ordovician age. The ore deposit was deformed and meta-

morphosed to the greenschist facies (about 0.3–0.4 GPa

and 350–370 �C) during both the Hercynian and Tertiary

Alpine orogenies (Dini et al. 2001).

Chemical analyses pointed to the ideal composition

HgBi2S4. The X-ray crystallographic studies were carried

on through rotation, Weissenberg, and precession photo-

graphs, as well as through data collected with a four-circle

automatic diffractometer, pointing to the following unit-

cell parameters: a 14.164(5), b 4.053(1), c 13.967(3) A,

b 118.28(3)�, V 706.1(6) A3, with possible space groups

C2/m, C2, or Cm.

The chemical composition and the results of the X-ray

crystallographic investigations indicated that grumiplucite

is identical with the compound firstly synthesized by

Brower et al. (1973) and subsequently by Mumme and

Watts (1980) who defined its structural arrangement.

The present study aims not only to confirm this struc-

tural identity, comparing the structural results obtained

with the natural phase with those obtained on the synthetic

material, but also to describe the order–disorder (OD)

character of the compound and to discuss its relationships

with other natural and synthetic sulfosalts.

S. Merlino (&) � C. Biagioni � P. Orlandi

Dipartimento di Scienze della Terra,

Universita di Pisa, Via S. Maria 53, 56126 Pisa, Italy

e-mail: merlino@dst.unipi.it

123

Rend. Fis. Acc. Lincei (2013) 24:47–52

DOI 10.1007/s12210-012-0213-1

2 Experimental

As described by Orlandi et al. (1998), grumiplucite ‘occurs

as very slender grey-black prismatic crystals…with a

metallic luster and almost micaceous (001) cleavage’. Due

to this micaceous character, the crystals present poor-

quality diffraction patterns. The best results were obtained

with new diffraction data collected from a crystal with size

of 1.11 9 0.07 9 0.07 mm3, using a Bruker Smart Breeze

diffractometer with an air-cooled CCD detector, with Mo

Ka radiation. The detector to crystal working distance was

50 mm. 1,115 frames were collected using x scan mode, in

0.5� slices, with an exposure time of 10 s per frame. The

data were corrected for the Lorentz and polarization factors

and absorption using the package of software Apex2

(Bruker AXS Inc 2004).

The refined cell parameters, in the standard setting, are

a 14.1690(16), b 4.0508(4), c 13.9751(14) A, b 118.292(6),

V 706.29(13) A3.

The crystal structure was refined using SHELX-97

(Sheldrick 2008) starting from the atomic coordinates

given in Mumme and Watts (1980) in the space group

C2/m. Scattering curves for neutral atoms were taken from

the International Tables for X-ray crystallography (1992).

Crystal data and details of the intensity data collection and

refinement are reported in Table 1.

After ten cycles of isotropic refinement, the R1 con-

verged to *0.17; refining the anisotropic thermal

parameters for the cations only, the refinement yielded a R1

value of *0.13, thus confirming the correctness of the

structural model. The OD character of the structure (see

Sect. 4) suggested the presence of a (001) twin plane

(pseudo metric merohedry with obliquity of 2.14�) and by

adding a twin according to the matrix [-1 0 0 | 0 1 0 | 1 0

1], a R1 = 0.116 was achieved for 1,376 unique reflections.

The highest and deepest residuals are located around Hg2

(Table 1). Atomic coordinates, equivalent or isotropic

displacement parameters, and selected bond distances are

reported in Table 2. The bad quality of the crystals of

grumiplucite explains the relatively high R1 value, as well

as the high residual maxima in the difference Fourier

synthesis, as reported in Table 1.

A list of Fo/Fc factors may be obtained from the authors

on request.

3 Description of the crystal structure

Grumiplucite is isostructural with the synthetic compound

HgBi2S4. The structure of this last compound has been

determined and discussed by Mumme and Watts (1980)

who stressed its relationships with the members of the

pavonite homologous series. To this aim, those authors

described the coordination of the two Hg and one of the Bi

atoms as ‘octahedral’, with the second Bi atom in ‘a dis-

torted trigonal-prismatic coordination capped on one face’.

Table 1 Crystal data and

summary of parameters

describing data collection and

refinement for grumiplucite

Crystal data

X-ray formula HgBi2S4

Crystal size (mm3) 1.11 9 0.07 9 0.07

Cell setting, space group Monoclinic, C2/m

a, b, c (A) 14.1690(16), 4.0508(4), 13.9751(14)

a, b, c (�) 90.00, 118.292(5), 90.00

V (A3) 706.29(13)

Z, Dc (g/cm3) 4, 7.022

Data collection and refinement

Radiation, wavelength (A) Mo Ka, k = 0.71073

Temperature (K) 293

Maximum observed 2h 65.22

Measured reflections 3764

Unique reflections 1,376

Rint after absorption correction 0.061

Range of h, k, l -15 B h B 20, -6 B k B 5, -21 B l B 20

R (all data) 0.116

wR (on Fo2) 0.315

Goof 1.173

Number of least-squares parameters 35

Maximum and minimum residual peak (e/A3) 16.11 (at 1.06 A from Hg2)

-8.19 (at 2.03 A from Hg2)

48 Rend. Fis. Acc. Lincei (2013) 24:47–52

123

Actually, the bond distances presented in Table 2 suggest a

linear coordination of the two Hg atoms, with bond dis-

tances Hg1–S1 and Hg2–S2 of 2.36 A, disregarding the

metal–sulfide contacts with distances longer than 3 A. The

same configuration occurs also in cinnabar, with Hg–S

bond distances of 2.37 A and S–Hg–S almost linear

(172.8�) (Auvray and Genet 1973) and in some other

sulfosalts.

Similarly, the two Bi atoms may be described as

characterized by a square-pyramidal (1 ? 4) coordination,

with one apical (Bi1–S4 2.62 A, Bi2–S3 2.58 A) and four

longer basal distances in the range 2.82–2.87 A. The

structural arrangement is illustrated in Figs. 1 and 2, as

consisting of structural a, b layers, built up by Bi2S4 rods

running along b and connected through Hg2? ions in the

a direction. Each rod is built up by chains of edge-sharing

square-pyramidal BiS5 polyhedra, paired through the

apical Bi–S bonds.

Adjacent layers are connected through weak Bi1–S1

(3.06 A) and Bi2–S2 (3.38 A) interactions, in agreement

with the almost micaceous {001} cleavage observed by

Orlandi et al. (1998). Considering these weaker bonds, the

coordination numbers of Bi1 and Bi2 increase up to six and

seven, respectively.

4 OD character of grumiplucite

Figure 1 suggests also that grumiplucite has OD character,

which could be guessed on the basis of peculiarities of the

diffraction pattern, in particular the non-space group con-

dition (0kl reflections present only for l = 2n) indicated by

Brower et al. (1973) in their X-ray crystallographic study

of the synthetic product HgBi2S4.

In fact, we may describe the structure of grumiplucite as

an OD structure built up with equivalent layers presenting

layer symmetry C 1 2/m 1, with translation vectors a, b,

and third basic vector (not a translation vector) c0

(a = 14.161, b = 4.051, c0 = 6.18 A, b = 90�).

The single layer is indicated in Fig. 1. By looking

for the possible r operations (partial operations relating

adjacent layers) which are in keeping with the set of koperations (partial operations of the single OD layer)

(Dornberger-Schiff and Fichtner 1972; Ferraris et al. 2008

(Appendix 2.1)), we found the OD groupoid family

Table 2 Atomic positions,

equivalent or isotropic

displacement parameters, and

selected bond distances (in A)

for grumiplucite

a �-x, -�-y, -zb �-x, -� -y, 1-zc � ? x, � ? y, z

Atom Wyckoff site x y z Ueq/iso (A2)

Hg1 2a 0 0 0 0.017(1)

Hg2 2a 0 0 � 0.016(1)

Bi1 4i 0.2254(2) 0 0.3677(2) 0.010(1)

Bi2 4i 0.3501(2) 0 0.1373(2) 0.012(1)

S1 4i 0.0025(11) 0 0.1701(11) 0.005(2)

S2 4i -0.1543(13) 0 0.3285(13) 0.010(3)

S3 4i 0.3126(12) 0 -0.0625(12) 0.007(2)

S4 4i 0.3744(11) 0 0.5718(11) 0.005(2)

Hg1 Bond length Bi1 Bond length Bi2 Bond length

S1 9 2 2.360(14) S4 2.623(14) S3 2.583(15)

S3a 9 4 3.117(11) S4b 9 2 2.820(10) S1c 9 2 2.835(10)

S2c 9 2 2.864(11) S3a 9 2 2.868(10)

S1 3.055(14) S2c 9 2 3.375(13)

Hg2

S2 9 2 2.359(16)

S4b 9 4 3.157(11)

Fig. 1 Structure of grumiplucite, drawn down b, with the projection

vector slightly inclined (6�), just to consent a better appreciation of

the three-dimensional arrangement. The single OD layer as well as

the r operations transforming each layer into the subsequent one are

indicated. Small black circles Hg atoms, small grey circles Bi atoms,

large light grey circles S atoms

Rend. Fis. Acc. Lincei (2013) 24:47–52 49

123

C 1 2=m ð1Þf2r=ns;2 1 ð22=nr;sÞg

which, assuming r = -1/2, s = 2, gives

C 1 2=m ð1Þf2�1=2=c2 1 ð22=a�1=2Þg

ðAÞ

with a set of r operations just describing the sequence of

layers in the OD family of grumiplucite.

The symbol (A) indicates that layers with symmetry C 1 2/m

1 may follow each other in the direction normal to the layers,

related by the operators a-1/2 (or a1/2) normal to c0 [and 2-1/2

(or 21/2) parallel to a]. It seems proper to indicate that the set of

r operations relating adjacent layers do not cause perfect

superposition, with displacements from the ideal positions in

the actual structural arrangement up to 0.2 A for the Hg atoms.

There are two MDO polytypes in this family:

MDO1: it corresponds to the sequence of OD layers in

which the operators a-1/2 and a1/2 regularly alternate;

MDO2: it corresponds to the sequence of layers in which

the operator a-1/2 is constantly applied (the constant

application of the operator a1/2 gives rise to the structure

MDO20, in twin relation with MDO2). The twinning was

actually found: its relatively high obliquity is due to the fact

that the r operations in (A) are only approximately valid.

4.1 Symmetry and parameters of the two MDO

polytypes

MDO1, sequence a-1/2/a1/2/a-1/2/a1/2…

1. The k operator [– m –] is a total one, valid for the

whole structure, whereas the operators [– 2 –] and

[– 21 –] are not valid for the whole structure.

2. The C centring operator a/2 ? b/2 is valid for all the

layers.

3. The r operator [– – 22] is continuing in the sequence

of layers and becomes a [– – 21] axis in a structure

with c = 2 c0.

4. The r operator [c2 – –] is continuing, becoming a glide

c in the structure with c = 2 c0.

The space group is therefore Ccm21, with a = 14.16,

b = 4.05, c = 2c0 = 12.36 A. The crystal structure of the

orthorhombic MDO1 polytype of grumiplucite is illustrated

in Fig. 3, as seen down [0 1 0], with a slight inclination of

the projection axis. The atomic coordinates in the MDO1

polytype may be easily calculated from the corresponding

coordinates of a single layer in grumiplucite (MDO2

Fig. 2 The structure of a single

layer of grumiplucite, as seen in

the direction normal to (001).

Small black circles Hg atoms,

small grey circles Bi atoms,

large light grey circles S atoms

Table 3 Atomic positions in the structure of the MDO1 polytype

Atom x y z

Hg 0.125 0 0

Bi2 0.3436 � -0.1373

Bi20 0.4065 0 0.1373

S1 0.2076 0 -0.1701

S10 0.0425 0 0.1701

S3 0.2812 � 0.0625

S30 0.4689 0 -0.0625

Fig. 3 Crystal structure of the MDO1 polytype of grumiplucite as

seen down [010]. The OD layers follow each to the other according to

the regular alternation of a1/2 and a-1/2 operations. Small blackcircles Hg atoms, small grey circles Bi atoms, large light grey circlesS atoms

50 Rend. Fis. Acc. Lincei (2013) 24:47–52

123

polytype) and are reported in Table 3. The atoms are

denoted as the corresponding atoms in the structure of

grumiplucite; Bi2–Bi20, S1–S10, S3–S30 are pairs of atoms

which are symmetry related in the structure of grumiplu-

cite, whereas they are independent atoms in the structure of

the MDO1 polytype.

No indications for the presence of the orthorhombic

polytype in the studied sample have been actually detected.

MDO2, sequence a-1/2/a-1/2 …

1. The r operator [– – 22] does not continue in the

successive layers; similarly the operator [c2 - -] does

not continue.

2. The C centring operator a/2 ? b/2 is valid for all the

layers.

3. Also the [- 2/m -] operations are valid for the whole

structure.

It is proper to observe that the displacement by –a/4 of

the position of the twofold axis [and of the origin as well]

in subsequent layers is reflected in the c vector of the

MDO2 structure, with c = 2c0-a/2.

The space group symmetry is therefore C 1 2/m 1, with

a = 14.16, b = 4.05, c = [(2c0)2 ? (a/2)2]1/2 = 14.2 A,

b = 90� ? arctg [(a/2)/2c0] = 119.9�, which can be

compared with the experimentally determined parameters

of grumiplucite. The discrepancy between the cell param-

eters of the theoretically derived MDO2 polytype and the

actual structural arrangement are obviously due to the

‘ideal’ character of the r operations in symbol (A).

5 Structural relationships of grumiplucite

Grumiplucite belongs to the pavonite homologous series

(Moelo et al. 2008). Structurally, it is correlated with

kudriavite (Cd,Pb)Bi2S4 (Balic-Zunic and Makovicky

2007) and with some synthetic compounds (Table 4). It

seems useful to complete the comparison by indicating the

cationic positions in the various isostructural compounds

and discuss their coordinations, so to appreciate, together

with the similarities, also the relevant distinctions. To this

aim, Table 5 presents the occupancies of the four cation

sites in the different phases.

In carrying on the comparison, it was observed that the

structures of kudriavite and synthetic CdBi2S4 are descri-

bed in a setting different from that of grumiplucite (and

synthetic HgBi2S4). Therefore to present a consistent

comparison, with cations of the various compounds dis-

tributed over the same Wyckoff sites, the unit cell of

Table 4 Natural and synthetic phases structurally related to grumiplucite

Phase Chemical formula a (A) b (A) c (A) b (�) S.G. Refs.

Grumiplucite HgBi2S4 14.16 4.05 13.95 118.28 C2/m This work

Synthetic HgBi2S4 14.17 4.06 13.99 118.27 C2/m Mumme and Watts (1980)

Kudriavite (Cd,Pb)Bi2S4 13.10 4.00 14.71 115.59 C2/m Balic-Zunic and Makovicky (2007)

Synthetic CdBi2S4 13.10 4.00 14.61 116.30 C2/m Choe et al. (1997)

Synthetic MnBi2S4 12.87 3.95 14.77 116.61 C2/m Lee et al. (1993)

Synthetic MnSb2S4 12.75 3.80 15.11 113.91 C2/m Pfitzner and Kurowski (2000)

Table 5 Occupancies by cations in the corresponding Wyckoff sites

of the different isostructural compounds

Phase Wyckoff position

2a 2c 4i(1) 4i(2)

Grumiplucite Hg Hg Bi Bi

Synth. HgBi2S4 Hg Hg Bi Bi

Kudriavite Cd Bi0.6In0.3 Bi Bi0.5Pb0.5

Synth. CdBi2S4 Cd Cd0.6Bi0.4 Bi0.8Cd0.2 Bi

Synth. MnBi2S4 Mn0.8 Mn0.6Bi0.4 Bi Bi

Synth. MnSb2S4 Mn Mn Sb Sb

The two sites denoted 4i(1) and 4i(2) correspond to the positions of

Bi1 and Bi2, respectively, in the structure of grumiplucite

Fig. 4 Comparison of the HgSb2S4 and HgBi2S4 layers in the crystal

structures of livingstonite and grumiplucite respectively. Small blackcircles Hg atoms, small grey circles Sb atoms, large light grey circlesS atoms

Rend. Fis. Acc. Lincei (2013) 24:47–52 51

123

kudriavite and CdBi2S4 has been transformed through the

matrix [-1 0 0/0 -1 0/1 0 1].

The three bismuth-containing compounds, namely

kudriavite, synthetic CdBi2S4, and MnBi2S4, present octa-

hedrally coordinated cations in both 2a and 2c sites, which

in grumiplucite are occupied by linearly coordinated Hg2?

cations. Whereas the 2a site displays ordered occupancy by

Cd (in kudriavite and synthetic CdBi2S4), and Mn in

MnBi2S4, the 2c site presents mixed occupancies by bis-

muth, plus indium, cadmium, and manganese, in kudria-

vite, CdBi2S4, and MnBi2S4, respectively.

As regards the two 4i sites, Bi3? is the largely domi-

nant cation, apart from the 4i(2) site of kudriavite, which

hosts nearly equal amounts of bismuth and lead. The

cations of these two sites display distinct coordinations,

namely octahedral coordination for those located at 4i(1)

and square-pyramidal coordination for those located at

4i(2).

The closest similarity with grumiplucite is found in the

compound MnSb2S4 (Pfitzner and Kurowski 2000), with Sb

and Mn atoms substituting for Bi and Hg, respectively. The

last substitution is accompanied by a change of coordina-

tion from the linear to the octahedral one.

Particularly appealing are the structural relationships of

grumiplucite with livingstonite. The structure of livings-

tonite, HgSb2S8, has been solved by Niizeki and Buerger

(1957), redetermined by Srikrishnan and Nowacki (1975)

and more recently refined by Borisov et al. (2010). Its

structure may be described as built up by two distinct

layers, one of them closely corresponding to the a, b layer

of grumiplucite and characterized by Sb2S4 rods running

along b and connected, as the similar Bi2S4 rods of

grumiplucite, through Hg2? ions. Figure 4 compares the

layers displayed in the two distinct structures. In livings-

tonite, the HgSb2S4 layers alternate with layers in which

the Sb2S4 rods are directly connected with formation of

short S–S bonds (disulphide bond, 2.078 A long).

Acknowledgments This work was supported by MIUR (Ministero

dell’Istruzione, dell’Universita e della Ricerca) through a grant to the

National project PRIN 2009 ‘Structures, microstructures and prop-

erties of minerals’. The suggestions of an anonymous referee helped

us in improving the paper.

References

Auvray P, Genet F (1973) Affinement de la structure crystalline du

cinabre a-HgS. Bull Soc fr Mineral 96:218–219 (in French)

Balic-Zunic T, Makovicky E (2007) The crystal structure of

kudriavite (Cd, Pb)Bi2S4. Can Mineral 45:437–443

Borisov SV, Pervukhina NV, Magarill SA, Kuratieva NV, Vasil’ev VI

(2010) Crystallographic analysis of the structure of livingstonite

HgSb4S8 from refined data. Crystallogr Rep 55:224–228

Brower WS, Parker HS, Roth RS (1973) Synthesis of mercury

bismuth sulfide. Mat Res Bull 8:859–862

Bruker AXS Inc (2004) APEX 2. Bruker advanced X-ray solutions,

Madison

Choe W, Lee S, O’Connell P, Covey A (1997) Synthesis and structure

of new Cd-Bi-S homologous series: a study in intergrowth and

the control of twinning patterns. Chem Mater 9:2025–2030

Dini A, Benvenuti M, Costagliola P, Lattanzi P (2001) Mercury

deposits in metamorphic settings: the example of Levigliani and

Ripa mines, Apuane Alps (Tuscany, Italy). Ore Geol Rev

18:149–167

Dornberger-Schiff K, Fichtner K (1972) On the symmetry of OD

structures consisting of equivalent layers. Kristall und Technik

7:1035–1056

Ferraris G, Makovicky E, Merlino S (2008) Crystallography of

modular materials. IUCr Monographs on Crystallography 15,

Oxford University Press, New York

International Tables for X-ray Crystallography (1992) Volume C.

Kluwer Academic Publishers, Dordrecht

Lee S, Fischer E, Czerniak J, Nagasundaram N (1993) Synthesis and

structure of two phases with both extended and point defects:

Mn1-xBi2?xS4 and Mn1-xBi2?xSe4. J All Comp 197:1–5

Moelo Y, Makovicky E, Mozgova NN, Jambor JL, Cook N, Pring A,

Paar WH, Nickel EH, Graeser S, Karup-Møller S, Balic-Zunic T,

Mumme WG, 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 20:7–46

Mumme WG, Watts JA (1980) HgBi2S4: crystal structure and

relationship with the pavonite homologous series. Acta Crystal-

logr B36:1300–1304

Niizeki N, Buerger MJ (1957) The crystal structure of livingstonite,

HgSb4S8. Z Kristallogr 109:129–157

Orlandi P, Dini A, Olmi F (1998) Grumiplucite, a new mercury—

bismuth sulfosalt species from the Levigliani mine, Apuan Alps,

Tuscany, Italy. Can Mineral 36:1321–1326

Pfitzner A, Kurowski D (2000) A new modification of MnSb2S4

crystallizing in the HgBi2S4 structure type. Z Kristallogr 215:

373–376

Sheldrick GM (2008) A short history of SHELX. Acta Crystallogr

A64:112–122

Srikrishnan T, Nowacki W (1975) A redetermination of the crystal

structure of livingstonite, HgSb4S8. Z Kristallogr 141:174–192

52 Rend. Fis. Acc. Lincei (2013) 24:47–52

123