Eur. J. Mineral.
2003, 15, 177-180

Tillmannsite, (Ag3Hg)(V,As)O4, a new mineral:its description and crystal structure
HALIL SARP1, DMITRY YU. PUSHCHAROVSKY2,*, ELIZABETH J. MACLEAN3, SIMON J. TEAT3
and NATALIA V. ZUBKOVA21)Département de Minéralogie du Museum d’Histoire naturelle de Genève, 1, route de Malagnou,CH-1208 Geneve, Switzerland
2)Geology Department, Moscow State University, 119899 Moscow Russia
3)CCLRC Daresbury Laboratory, Daresbury, Warrington. Cheshire WA4 4AD, UK

Abstract: Tillmannsite, (Ag3Hg)(V,As)O4, was found in the old copper mines of Roua (Alpes-Maritimes, France), associated withpecoraite, vésigniéite, olivenite, kolfanite, janggunite, chlorargyrite, cuprite, native copper, native silver, native silver containing
2 % of mercury, domeykite, djurleite and algodonite. It forms aggregates (0.2 mm diameter) consisting of pseudooctahedral crys–tals (50 mm maximum dimension). The crystals are red, brownish red. The mineral is tetragonal, I 4, a = 7.727(7) Å, c = 4.648(5)Å, V = 277.5(5) Å3, Z = 2 and Dcalc = 7.733(3) g/cm3 . The strongest lines in the X-ray powder diffraction pattern (dobs in Å, (hkl),Ivis) are: 5.45, (110), 25; 2.772, (211), 100; 2.324, (002), 30; 2.254, (301), 20. Luster is adamantine translucent, streak is brownish
red; crystals are uniaxial (+) with w – 2.3, e – 2.5 at 589 nm. Pleochroism is intense with e = red orange intense, w = orange brown.
The crystal structure was solved from data collected using synchrotron radiation by traditional direct methods and refined using
350 observed unique reflections to R(F) = 0.037, Rw(F2) = 0.075. The structure of tillmannsite containes isolated tetrahedra(V,As)O4 and tetrahedral clusters (Ag3Hg) formed by metallic atoms. Each (Ag,Hg) metallic atom is coordinated by 3 metallic
neighbors and by 3 oxygens.
Key-words: tillmannsite, crystal structure, vanadate, silver, mercury, Roua (France).

Introduction
Tillmannsite, (Ag3Hg)(V,As)O4, is a new mineral
discovered in samples collected by Danielle Mari, Gilbert
Mari and Pierre Rolland in the old copper mines of Roua,which are situated in the northwestern part of the AlpesMaritimes department (France). The mineral name honors
Professor Ekkehart Tillmanns (born 1941) from Institute ofMineralogy and Crystallography of Wien, Austria. Themineral and mineral name have been approved by theCommission on New Minerals and Mineral Names of theInternational Mineralogical Association. Type material ispreserved in the Department of Mineralogy of the NaturalHistory Museum of Geneva, Switzerland, under reference
no. 478.006.

Occurrence
The new mineral herewith described occurs in the Rouacopper occurrences in the upper part of the Var valley (theDaluis gorge) at the western margin of the Barrot Dome.

The metallogeny and geology of this Dome have beenstudied by Vinchon (1984) and Mari (1992). In the Rouaore deposit, the cupriferous mineralisation is hosted in agangue formed by dolomite, calcite and aragonite, andconsists of native copper, cuprite, domeykite, algodonite,koutekite and native silver. Detailed mineralogical study ofthis ore deposit produced several secondary, rare andunknown mineral species (Sarp et al., 1994, 1995, 1996).
The new mineral described here occurs in small geodes inassociation with pecoraite, vésigniéite, olivenite, kolfanite,janggunite, chlorargyrite, cuprite, native copper, nativesilver, native silver containing 2 % of mercury, domeykite,djurleite and algodonite. It is a secondary alteration
mineral.

Physical and optical properties
Tillmannsite occurs as aggregates of maximum size
0.2 mm in diameter, which are formed by pseudooctahedral
crystals of maximum size 50 mm. The crystals are occasionally twinned by contact on (100) and they do note-mail: dmitp@geol.msu.ru

DOI: 10.1127/0935-1221/2003/0015-0177

0935-1221/03/0015-0177 $ 1.80
© 2003 E. Schweizerbart’sche Verlagsbuchhandlung. D-70176 Stuttgart

178

H. Sarp, D. Y. Pushcharovsky, E. J. MacLean, S. J. Teat, N. V. Zubkova

could not be measured because of the small grain size.
Calculated density is 7.769 (based on the empiricalformula) and 7.733(3) g/cm3 (based on the ideal formula).
The mineral is not soluble in HC1. It is nonfluorescent andhas intense pleochroism: e = red orange intense, w =orange brown. Tillmannsite is uniaxial positive. The refractive indices, which are high, could not be measured byindex oils. They were determined by reflectance measurements on oriented crystals in a polished section and yielded
w –2.3, e – 2.5 (at 589 nm).

Chemical composition

Fig. 1. SEM image of tillmannsite crystals of pseudooctahedralhabitus.

possess a cleavage. The most developed forms are (111),(110), (100), (101) and minor (001) (Fig. l). The crystals
are red, brownish red, translucent, with adamantine luster
and brownish red streak. The mineral is very brittle withconchoidal fracture. The Mohs’ hardness and the density
Table 1. Chemical analysis (wt.%) of tillmannsite.

Table 2. X-ray powder diffraction data for tillmannsite (in Å).

Tillmannsite was analyzed with a Cameca SX 50 electron microprobe, using operating voltage of 20 kV, beam
current of 30 nA, and a beam diameter of 5 mm. Qualitative
examination showed only Ag, Hg, V, As and O. For quantitative analysis, AgAsS (Ag, As), HgTe (Hg), V metal (V) andvanadinite (O) were used as standards. The results are given
in Table 1. The empirical formula based on (Ag + Hg) = 4 is:Ag3.01Hg0.99V0.68 As0.36O4.03 and the idealized formula,(Ag3Hg)(V,As)O4, was confirmed by the structure determination. The Gladstone-Dale calculation (Mandarino, 1981)
give the excellent compatibility: 1- KP/KC = -0.034.

X-ray crystallography
Powder diffraction data for tillmannsite (Table 2) wereobtained using a Gandolfi camera (114.6 mm diameter, Nifiltered CuKa ). The relative intensities of the reflections
were estimated visually. A single crystal with dimensions
40 x 20 x 10 mm3 was first tested by the precession method(Ni-filtered CuKa ) and the same crystal was used for thestructure determination at room temperature. Details of thesingle crystal X-ray data collection and structure refinement of tillmannsite are given in Table 3. The data werecollected at l = 0.6941 Å using a Bruker AXS SMART
CCD area detector diffractometer on station 9.8 of theSynchrotron Radiation Source located at the CCLRC
Daresbury Laboratory (Cernik et al., 1997). A nominal fullsphere of diffraction data was collected with w-rotations
and processed (Clegg et al., 1998). This yielded refined
tetragonal cell constants of a = 7.727(7) Å, c = 4.648(5) Å,V = 277.5(5) Å3 are in accordance with the unit cell parameters calculated from powder data: a = 7.731(2) Å,c = 4.647(2) Å, V = 277.8(2) Å3.
SHELXTL (Sheldrick, 2000) was used for structure–solution and refinement (space group I 4) by using 919
reflections merged to 363 independent reflections, ofwhich 350 reflections have I > 2s(I) with R(int) = 0.05. A
difference Fourier map with residual peaks around (Ag,Hg)
and (V,As) atoms showed that their positions should berefined using the anharmonic thermal displacement factors(Gram-Charlier expansion of tensors F(ijklmn)). The
program JANA98 (Petricek & Dusek, 1998) was used in
the structure refinement using full-matrix least-squares
refinement on F2. The Ag/Hg and V/As ratio in cationicsites indicated by the refinement are in good agreement

Crystal structure of tillmannsite, (Ag3Hg)(V,As)O4179

Table 3. Crystal data, structure solution and refinement for tillmannsite.,with the results of chemical analysis (Table 1). The final
difference Fourier map was featureless: dr maximum andminimum were 1.80 e/Å3 and -1.78 e/Å3. The atomic coordinates, displacement parameters, selected interatomic
distances and bond angles are presented in Tables 4 and 5.
The value of density calculated on the basis of the structural formula is 7.733(3) g/cm3. The intensity calculations(Yvon et al., 1977) for tillmannsite (Table 2) demonstrated
Table 4. Final positional and displacement parameters (Å2) for tillmannsite.

Table 5. Selected interatomic distances (Å) and angles (o) for tillmannsite.

the agreement between the X-ray powder diffraction andthe single-crystal data. The figures were obtained with theuse of the program ATOMS (Dowty, 1995).

Description of the structure
The structure of tillmannsite contains isolated (V,As)O4tetrahedra and tetrahedral clusters (Ag3Hg) formed bymetallic atoms (Fig. 2). A disordered distribution of Ag andHg atoms within the latter structural units, revealed on thebasis of XRD data, can be considered as a specific featureof tillmannsite in respect to chemically related synthetic
AgHg2PO4 and AgHg2AsO4 (Masse et al., 1978) where Agand Hg atoms are completely ordered and form the dimers
O2Ag-AgO 2 and O3Hg-HgO 3. In tillmannsite, each(Ag,Hg) metallic atom is coordinated by 3 metallic neighbours and by 3 oxygens (Fig. 2).
The analysis of the metal-metal bond lengths in mercury
and silver compounds (Table 6) confirms the conclusion
about disordered distribution of Ag and Hg atoms in tillmannsite. Tetrahedral clusters (Ag3Hg)3+ revealed in tillmannsite are unique in spite of the fact that mercury ischaracterized by the low-valence state in many minerals(Pervukhin et al., 1999). From the almost 100 Hg-minerals
known so far, about 20 contain the dimers [Hg2]2+: forexample, halogenides – calomel, Hg2Cl2, moschelite, Hg2I2;
oxides–poyarkovite,
Hg3ClO,
hanawaltite,
Hg6Hg[Cl,(OH)]2O3 or shakhovite, Hg4Sb(OH)3O3 etc.
Triangles of [Hg3]4+ have been observed only in a few

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H. Sarp, D. Y. Pushcharovsky, E. J. MacLean, S. J. Teat, N. V. Zubkova

Fig. 2. Projection of tillmannsite along [001] with marked bonds
between Ag,Hg atoms and surrounding O atoms.

minerals, namely in kuznetsovite, Hg2HgCl(AsO4), andterlinguaite, Hg2ClO, and there are no known minerals withtetrahedral clusters formed by Hg atoms. However thediscrete Ag3Sn heteroclusters were recently reported insynthetic Ag3SnP7 (Shatruk et al., 2000).
Acknowledgments: The authors are grateful to Prof. A.A.
Ul’yanov for the electron microprobe analysis of tillmannsite and to Dr. J. Wuest for the scanning electron
microscope photographs. The authors thank M. Pasero, F.
Marchetti and F. Hatert for their helpful suggestions.Thiswork was supported in part by the Russian ScientificFoundation (grants 00-05-65399 and 00-15-96633) and by
the Russian Universities Program.

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Received 28 January 2002
Modified version received 9 May 2002
Accepted 18 June 2002