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Eur. J. . 1996,8,487-492

Rosiaite, PbSb206, a new mineral from the Cetine mine, Siena, Italy

RICCARDO BASSOI, GABRIELLALUCCHETTII, LIVIa ZEFlROI and ANDREA PALENZONA2

1 Dipartimento di Scienze della Terra dell'Universita, Corso Europa 26, 1-16132 Genova, Italy 2 Istituto di Chimica Fisica dell'Universita, Corso Europa 26, 1-16132 Genova, Italy

Abstract: Rosiaite occurs at the Cetine di Cotomiano mine, formerly named Rosia mine, associated with valen- tinite, tripuhyite, bindheimite and a phase corresponding to the synthetic B-Sb204 polymorph of cervantite. Rosiaite, appearing generally as aggregates of minute tabular {OOOl}crystals with hexagonal outline, is colour1ess to pale yellow, transparent, optically uniaxial negative and nonpleochroic with co= 2.092(2) and I::= 1.920(10). Microprobe analyses reveal a good compositional homogeneity and a quasi-ideal composition. The strongest lines in the powder pattern are dlOl = 3.49 A and dllO = 2.648 A. The , described in the P3 1m with a = 5.295(1) A, c = 5.372(1) A and Z = 1, has been refined to R = 0.033, confirming the new mineral to be the natural analogue of synthetic PbSb206 studied previously. The approximately hexagonal close-packed structure of rosiaite shows a pattern of occupied octahedral sites identical to that of synthetic compounds such as Li:zZrF6, Li2MJOFs and several double hexaoxides, containing Sb or As.

Key-words: rosiaite, new mineral, physical and chemical data, powder pattern, structure refinement.

Introduction Recently rosiaite has been recognized also in material coming from the abandoned Tafone Rosiaite, PbSb206, is a new mineral found in mine, Grosseto, Tuscany, Italy. the Cetine mine, central Tuscany, Italy. It is the natural phase corresponding to the synthetic com- pound PbSb206 known for many years (Magneli, Occurrence 1941). The name of the new mineral is after the vil- The Cetine mine, eastern flank of the CoUine lage of Rosia, near to the Cetine di Cotorniano MetaUifere, province of Siena, Italy, was active mine, formerly named Rosia mine. Both mineral from 1878 for antimony exploitation; the active and its name have been approved by the Com- mining was finally terminated in 1948. mission on New and Mineral Names of The mineralization, previously described by the International Mineralogical Association (ref. many authors (Pelloux, 1901; Lotti, 1910; Des- 95-021). Type material is preserved at the Dipar- sau, 1952; Sabelli & Brizzi, 1984), occurs in timento di Scienze della Terra, Sezione di Min- brecciated dolomitic limestones developed in eralogia, Universita di Genova, Italy. evaporitic deposits of Triassic age known as

0935-1221/96/0008-0487 $ 1.50 @ 1996 E. Schweizerbart'sche Verlagsbuchhandlung. D-70176 Stuttgart 488 R. Basso, G. Lucchetti, L. Zefiro, A. Palenzona

"Calcare Cavernoso". The "Calcare Cavernoso" acterized by a dominant pinacoid {000l} as- overlies a quartzitic phyllitic basement, Paleozoic sociated with subordinated forms: hexagonal to Triassic in age, and in turn is tectonically over- dipyramid {lOTI}, hexagonal prism {lOTO} and lain by shales and argillaceous limestones. Hy- a not indexed scalenohedron. The crystals are drothermal fluids, originating from magmatic colourless to pale yellow, transparent, with re- Pliocene-Pleistocene intrusions, were active sinous and white ; no is pre- along fault systems; the circulating fluids sent, only a possible {000l} parting has been ob- strongly silicified the "Calcare Cavernoso" and served. The mineral is brittle with conchoidal deposited the mineralization, mainly consisting . Due to the small size of the crystals, it of as disseminated small pods (Sabelli & was impossible to measure density and hardness. Brizzi, 1984). The calculated density is 6.96 g/cm3. The mineral The Cetine mine is a well known site for min- does not fluoresce under short- and long-wave eral collectors and mineralogists, because of the light. Optically, rosiaite is non- presence of numerous rare minerals and new spe- pleochroic, uniaxial negative, with 0) = 2.092(2) cies, such as onoratoite (Belluomini et al., 1968), and E = 1.920(10), for 589 nm at 2YC using cetineite (Sabelli & Vezzalini, 1987), coquandite Cargille's liquids. (Sabelli et al., 1992), rosenbergite (Olmi et al., The chemical composition of rosiaite was de- 1993) and brizziite (Olmi & Sabelli, 1994). termined by an electron microprobe (PHILIPSSEM Rosiaite, to the best of our knowledge, is the 515 electron microscope equipped with EDAX first Pb mineral found in the antimony deposit of pv9100 spectrometer) in energy dispersive mode, the Cetine mine. It occurs in little cavities of a with an accelerating voltage of 15 kV and a beam rock fragment found in the debris derived from current of about 2.10 nA. mining operations, associated with , Spot analyses show neither significant varia- Sb203, tripuhyite, FeSb203, bindheimite, Pb2Sb2 tions nor compositional zoning in single crystals. 06(O,OH), and a phase corresponding to the syn- Microprobe analysis, average of 3 measurements, thetic B-Sb204 polymorph of cervantite, at pre- gives PbO 40.88 (ranging from 40.65 to 41.18) sent under study. Rosiaite generally occurs as and Sb20s 58.67 (ranging from 58.46 to 58.82) aggregates, not exceeding 2 mm in size, of wt%, corresponding to the empirical formula minute crystals up to 0.3 mm in size. PbI.()()8Sb1.99706,calculated on the basis of six atoms.

Physical properties and chemical composition X-ray powder diffraction Rosiaite crystals show tabular habit with hex- The powder pattern was obtained by a Guinier agonal outline (Fig. 1). The morphology is char- STOE camera using graphite-monochromatized

Fig. 1. SEM images showing: (a) aggregate of rosiaite crystals, (b) octahedra of bindheimite and acicular crystals of valentinite overgrown on a hexagonal tablet of rosiaite. Rosiaite 489

Table 1. X-ray powder-diffraction data for rosiaite (d in A).

Calculated Measured Calculated Measured h k 1 d I d I h k 1 d I d I

0 0 1 5.372 4 5.37 VVW 2 1 1 1.650 13 } 1.651 W 1 0 0 4.586 3 4.60 VVW 2 1 I 1.650 9

1 0 1 3.488 100 3.49 VS 3 0 0 1.529 11 1.531 W

0 0 2 2.686 10 2.688 VW 2 0 3 1.411 8 1.412 VVW

1 1 0 2.648 35 2.648 M 3 0 2 1.329 9 1.330 VW

1 1 1 2.375 2 2 2 0 1.324 5 1.325 VW } 2.376 VVW 1 1 I 2.375 2 1 3 1.245 5 } 1.246 VW 1 0 2 2.318 2 2.319 VVW 2 1 3 1.245 6 2 0 0 2.293 2 2.293 VVW 3 1 1 1.238 4 } 1.239 VW 2 0 1 2.109 22 2.110 W 3 1 I 1.238 6 1 1 2 1.886 22 1 1 4 1.198 3 } 1.887 W } 1.198 VVW 1 1 2" 1.886 16 1 1 4 1.198 5 1 0 3 1.668 11 1.671 VW 2 2 2 1.187 4 } 1.188 VW 2 2 4 1.187 5

CuKa radiation and silicon as an internal stand- input data the structural model resulting from the ard. The relative intensities of the reflections X-ray single-crystal analysis. In Table 1 calcu- were estimated visually and the indices were in- lated and measured diffraction data are com- ferred from the pattern calculated by the LAZY pared. The cell parameters refined from powder PULVERIXprogram (Yvon et al., 1977), using as data are a = 5.301(1) A and c = 5.375(1) A.

Table 2. Crystal structure data for rosiaite.

Formula used for refinement

Space group Z

a(1I.) 5.295(1) c(1I.J 5.372(1) v(1I.) 130.4 p(MoKa, mm-I) 42.77

Reflections measured (-7~h~7. -7~~7, -7~ 1~7) 1508 Unique reflections 153 Observed reflections (1)301) 151

R (observed) 0.033 R (all) 0.033 Extinction parameter (x10~) 1. 2( 3) 490 R. Basso, G. Lucchetti, L. Zefiro, A. Palenzona

Table 3. Atomic coordinates and equivalent isotropic temperature factors (A2) for rosiaite.

Atom x/a y/b z/c Beq

Pb 0.0 0.0 0.0 1.33 Sb 1/3 2/3 0.5 0.95 0 0.3770(16) 0.0 0.2965(22) 1.36

Table 4. Interatomic distances (A) and angles n in rosiaite.

M-O 0-0 0- M-O distance distance angle

Pb06 octahedron

6 Pb-O 2.554(9) 6 0-0' 3.457(15) 85.21(36) 6 -0" 3.759(20) 94.79(36)

Average 2.554 3.608 90.0

Sb06 octahedron

6 Sb-O 1.989(7) 3 0-0' 2.545(21) 79.56(46) 6 -0" 2.878(6) 92.68(40) 3 -0'" 2.960(19) 96.18(57)

Average 1.989 2.815 90.28

Refinement of the crystal structure and refined using 25 reflections within the angu- lar range 24 < e < 28°. The diffraction intensities A near hexagonal tablet, measuring 0.20 x 0.11 were measured up to e = 30°, using graphite- x 0.04 mm, was used for the X-ray single-crystal monochromatized MoK a radiation and operating analysis. The data collection was performed by in the (J)- e scan mode. An absorption correction means of an ENRAF-NONIUSCAD-4 automatic dif- was applied using the", scan method (North et fractometer. The cell parameters were determined al., 1968).

c

a

Fig. 2. Layers of edge-sharing Sb06 octahedra alternating with layers of isolated Pb06 octahedra in the rosiaite structure; the Pb atoms are positioned midway along [001] between the centers of Sb06 octahedra rings. Rosiaite 491

The crystal structure was refined in the space factors were introduced after the fourth cycle. group P31m starting with the coordinates result- Tables 2, 3 and 4 summarize experimental details ing from the structural analysis of the corre- and results of the crystal structure refinement. sponding syntheticcompound (Hill,1987). Eight These results confirm rosiaite to be the natural cycles of least squares refinement were carried analogue of the synthetic PbSb206 studied by out by a modified version of the ORFLSprogram Magneli (1941) and Hill (1987). (Busing etal.,1962), using the scattering factors According to the description given by the for neutral atoms from the International Tables above authors, the structure of rosiaite is based for X-ray Crystallography, vol. IV (1974). Total on an approximately hexagonal close-packed site occupancy was fixed for all atoms; scale fac- array of oxygen atoms. The polyhedral frame- tor, secondary extinction coefficient, oxygen work consists of gibbsite-like layers, with 2/3 of coordinates and temperature factors were simul- the octahedral interstices occupied by Sb, alter- taneously derived. The anisotropic temperature nating with layers where 1/3 of the octahedral

Table 5. Synthetic MSb206 and natural MM' 206 compounds related to rosiaite.

Name Chemical Space group or References formula

CuSbP6 P2/c SR 8,153;PDF

~-MnSbp6 P3 SR 54A,152 r-MnSb206 P321 SR 56A,128;PDF BaSb206 P31m SR 8,157jPDF PbSbP6 P31m SR 54A,152jPDF SrSb206 P31m SR 8,157 HgSb206 P31m SR 8,157 CaSb206 P31m SR 8,157;PDF Synthetic CdSb206 P31m SR 8,157j55A,153jPDF

ZnSb206 P4/mnm SR 8,153;PDF FeSb206 tet. SR 8,155jPDF CoSb206 P4/mnm SR 8,155;56A,128;PDF NiSb206 tet. SR 8,155jPDF MgSbP6 tet. SR 8,155jPDF

Ludlockite (Fe,Pb)As206 tric. C,FM,NN.PDF

Foordite (Sn, Pb) (Nb, Ta )206 mon. C,FM,NN,PDF Thoreaulite SnTa206 mon. C,FM,NN,PDF Columbite group aeschynite subgroup orth. PDF columbite subgroup orth. PDF Tantalite (Fe, Mn) (Ta, Nb )206 orth. C,FM,NN,PDF

Changbaiite PbNbP6 trig. C,FM,NN,PDF Ferrotapiolite group FM or tet. group trirutile subgroup PDF

C Nickel & Nichols = Clark (1993), FM = Fleischer & Mandarino (1991), NN = (1991), PDF = Powder Diffraction File, SR = Structure Reports. 492 R. Basso, G. Lucchetti, L. Zefiro, A. Palenzona interstices, located above and below the vacant Dessau, G. (1952): Antimony deposits of Tuscany. holes of the Sb layers, are occupied by Pb (Fig. 2). Econ. Geol., 47, 397-411. The deviation of the arrangement of oxygen Fleischer, M. & Mandarino, J. A. (1991): Glossary of atoms from the ideal close packing is related to Mineral Species, The Mineralogical Record Inc., the strongly different sizes of Pb06 and Sb06 Tucson. Galy, J., Andersson, S., Portier, J. (1969): in "Structure octahedra. Reports", 41A, 416. Synthetic MSbz06 and natural compounds Hill, R. J. (1987): Structure of PbSbz06 and its rela- with the same atomic ratios of rosiaite are re- tionships to the crystal chemistry of PbOz in anti- ported in Table 5. From the structural point of moniallead-acid batteries. 1. Solid State Chem., 71, view, synthetic or natural complex halides and 12-18. , containing two kinds of cations occupy- Lotti, 8. (1910): Geologia delia Toscana. Mem. Descr. ing one-half of the octahedral sites in close- Carta Geol. Italia, 13. packed structures, show different patterns of oc- Magneli, A. (1941): The crystal structure of tahedral sites occupied. The four recognized metantimonate and isomorphous compounds. Ark. kinds of approximately hexagonal close-packed Kemi. Min. Geol., 815, 1-6. structures for these MM' zX6 compounds are re- Nickel, E. H. & Nichols, M. C. (1991): Mineral refer- ported by Wells (1975): trirutile-, columbite-, ence manual. Van Nostrand Reinhold ed., New LizZrF6- and NazSiF6-type structures. As sug- York. North, A. C. T., Phillips, D. c., Scott Mathews, F. gested by Hill (1987), in the structure of MM'z06 (1968): A semiempirical method of absorption cor- compounds the segregation of M from M' cations rection. Acta Cryst., A24, 351-359. into separate layers is favoured by a strong differ- Olmi, F. & Sabelli, C. (1994): Brizziite, NaSb03, a new ence between the respective cationic radii. Rosi- mineral from the Cetine mine (Tuscany, Italy) : aite, some MSbz06 and MAsz06 compounds description and crystal structure. Eur. 1. Mineral., (Hill, 1987) as well as LizNbOFs (Galy et al., 6, 667-672. 1969) and LizNbF6 (de Bournoville et al., 1986) Olmi, F., Sabelli, C. Trosti-Ferroni, R. (1993): show a LizZrF6 structure type (Brunton, 1973), Rosenbergite, AIF[Fo.s(HzO)o.sJ4.HzO, a new min- with distinct M and M' layers. The other syn- erai from the Cetine mine (Tuscany, Italy): descrip- tion and crystal structure. Eur. 1. Mineral., 5, 1167- thetic MSbz06, with M = Cu, Mn, Zn, Fe, Co, Ni and Mg, and the known minerals referenced in 1174. Table 5 show different structures characterized Pelloux, A. (1901): Appunti sopra alcuni minerali delle by mixed M M' layers. Cetine di Cotorniano presso Rosia (in provincia di Siena). Rend. Regia Ace. Lincei, 10, 10-14. Acknowledgements: This study was supported Powder Diffraction File (1994): Inorganic Phases. by the Ministero dell 'Universita e della Ricerca JCPDS ed., U.S.A.. Scientifica e Tecnologica. Thanks are due to Mr. Sabelli, C. & Brizzi, G. (1984): Alteration minerals of C. Bianchi and Mr. P. Prandoni, local mineral the Cetine mine, Tuscany, Italy. Mineral. Rec., 15, collectors who provided the studied sample. 27-36. Sabelli, C. & Vezzalini, G. (1987): Cetineite, a new antimony -sulfide mineral from Cetine mine, References Tuscany, Italy. N. Jb. Mineral. Mh., 1987,419-425. Sabelli, C., Orlandi, P., Vezzalini, G. (1992): Coquan- Belluomini, G., Fornaseri, M., Nicoletti, M. (1968): dite, Sb60S(S04).HzO, a new mineral from Pereta, Onoratoite, a new antimony oxychloride from Tuscany, Italy and two other localities. Mineral. Cetine di Cotorniano, Rosia (Siena, Italy). Min. Mag., 56, 599-603. Mag., 36, 1037-1044. Structure Reports: and Inorganic Compounds. Brunton, G. (1973): LilZrF6. Acta Cryst., 829, 2294- Ferguson & Trotter ed., Dordrecht. 2296. Wells, A. F. (1975): Structural inorganic chemistry. Busing, W. R., Martin, K. 0., Levi, H. A. (1962): Clarendon Press ed., Oxford, 147 p. ORFLS,a FORTRANcrystallographic least-squares re- Yvon, K., Jeitschko, W., Parthe, E. (1977): LAZY finement program. U. S. Nat!. Tech. Inform. Serv., PULVERIX,a computer program, for calculating X- ORNTL- TM-305. ray and neutron diffraction powder patterns. 1. Clark, A. M. (1993): Hey's Mineral Index. Chapman Appl. Cryst., 10,73-74. & Hall ed., London. de Bournoville, M.B., Bizot, D., Chassaing, J., Quar- ton, M. (1986): Structures et proprietes magne- tiques de LizNbF6 et N azNbF6. 1. Solid State Received 14 November 1995 Chem., 62, 212-219. Accepted 31 January 1996