162 New Data on . 2011. Vol. 46

BILIBINSKITE, (Au56Cu32)8(Te,Pb,Sb)5, FROM THE CEMENTATION ZONE OF THE AGINSKOE, KAMCHATKA AND PIONERSKOE, SAYAN MOUNTAINS -TELLURIDE DEPOSITS Ernst M. Spiridonov Geology Department, Lomonosov Moscow State University, @geol.msu.ru

The mineral assemblages and conditions of formation of bilibinskite are reported. The color photos, without which this unique Au-rich mineral is difficult to be determined, are shown for the first time. The photos illustrate extreme- ly strong bireflectance and anisotropy of bilibinskite. The chemical composition of bilibinskite from the cementa- tion zone of the Aginskoe and Ozernovskoe, Kamchatka, and Pionerskoe, Sayan Mountains gold-telluride deposits is refined. The chemical composition of the bilibinskite from the Aginskoe and Ozernovskoe deposits is close to Au5Cu3(Te,Pb)5; while that of Pionerskoe is close to Au6Cu2(Te,Pb,Sb)5; generalized formula (Au56Cu32)8(Te,Pb,Sb)5. Bilibinskite in the oxidation zone is the direct prospecting guide to rich endogenic gold- telluride mineralization. Figures 4, references 16. Keywords: bilibinskite, gold-telluride mineralization, Aginskoe deposit, Ozernovskoe deposit, Pionerskoe deposit.

Rickardite, Cu7Te5В and , Cu2Te as ores. Bilibinskite occurs as partial or complete pseudomorphs after gold tellurides were pseudomorphs after Au3(Ag,Au)Te8, reported from the oxidation zone of the Au(Ag,Au)Te4, kostovite Au(Cu, Kalgoorlie, Australia (Stillwell, 1931; Mark - Ag,Au)Te4, AuTe2, altaite PbTe, and ham, 1960), Pervomaiskoe, Northern Kazakh - nagyagite AuPb5(Te,Sb,Bi)4S6, and rim hypo- stan (Boris hanskaya, 1946), Pionerskoe, Sayan genic gold. It is associated with Cu-Pb and Fe- Mountains (Gromova, 1959; Sindeeva, 1959), Cu-Pb tellurites. The pockets of bilibinskite are and Aginskoe, Kamchatka (Andrusenko and up to a few millimeters in size; radiated aggre- Shchepot'ev, 1974) hydrothermal gold depo - gated of the mineral are frequent. Megascopally, sits. In reflected light, and weissite bilibinskite is dark brown and brown, similar to are characterized by the extremely wide range . This mineral is well polished. The cleav- of colors, strong bireflectance and anisotropy. age is absent. Conduction is metallic. The rela-

Therefore, the optical parameters were consid- tive relief is higher than gold. VHN20 = 380 ered to be adequate for qualitative determina- (330–420) kg/mm2 (n = 6). In reflected light, tion of these minerals. Hypogenic gold tel- this mineral is looks like bornite in one sections, lurides were unlike to be replaced by super- whereas in the other sections, it is unique due to gene copper tellurides elsewhere. The study of color changed from grey-violet to beige-cream gold ores for the cementation zone of the and blood red that results in strong color bire- Aginskoe, Pervomaiskoe, and Pionerskoe de - flectance (Fig. 1). Extremely strong colored posits did not support the presence of copper anisotropy ranges from grey and dove-color to tellurides. It was established that these are Au- canary yellow and fiery-red (Fig. 2). The ref - dominated intermetallic compounds (Spiri- lectance spectra are unique, complex, and donov et al., 1978; Spiridonov, Chvileva, 1979, crossed (Fig. 3). According to optical parame- 1982; Chvileva et al., 1988; Spiridonov, 1991, ters, the symmetry of bilibinskite is low, not high 2010). The most abundant mineral among these that orthorhombic. compounds is bilibinskite named in memory of The chemical composition of bilibinskite Yurii Alexandrovich Bilibin (1901-1952), the (determined with a Camebax electron micro- outstanding Russian geologist, who investigat- probe) from the Aginskoe, Ozernovskoe, and ed geology of gold deposits. Pionerskoe deposits is as follows, wt.%: 49.6, 50.8, In addition to the listed deposits, bilibinskite 58.1 Au; 1.57, 0.99, 2.81 Ag; 9.35; 9.29, 4.53 Cu; and related minerals were described form the 0.21, 0.02, 0.17 Fe; 24.6, 24.0, 23.6 Te; 12.8, 13.9, Ozernovskoe (Kamchatka), Zod (Armenia), Zha- 6.35 Pb; 0.18, 0, 1.53 Bi; 0.23, 0, 3.53 Sb; and 0.34, na-Tyube, Zholymbet, Solnyshko, and Almaly 0, 0.13 Se, respectively; total is 98.88, 99.00, and (Kazakhstan), and Manka (Altai) deposits. In 98.75 (n = 13, 5, 6), respectively. The electron some places of the cementation zone of the microprobe data, high color strength (color puri- Aginskoe and Zod deposits, bilibinskite and ty) (close to native gold and three times more related minerals contain up to 10% of gold in the than that of rickardite), and metallic conduction Bilibinskite, (Au5-6Cu3-2)8(Te,Pb,Sb)5, from the cementation zone of the Aginskoe, Kamchatka and Pionerskoe, Sayan Mountains gold-telluride deposits 163

Fig. 1. Photomicrograph of bilibinskite with bright col- ored bireflectance inter- grown with Fe-Cu-Pb tellurite. Cementation zone, Agin skoe deposit, Kam chat - ka. Reflected light. Width of image 120 microns.

Fig.2. Photomicrograph of bilibinskite with bright color anisotropy. Cementation zo- ne, Aginskoe deposit, Kam- chatka. Reflected light, cros- sed polars. Width of image 80 microns.

Fig.3. Reflectance spectra of bilibinskite and Sb-rich bili- binskite in the range of 400 to 700 nm from (1) Aginskoe deposit, Kamchatka, and (2) Pionerskoe deposit, Sayan Mountains, respectively.

Fig. 4. X-ray diffraction pow- der patterns of gold, bog- danovite, bilibinskite, and moschellandsbergite. are not consistent with assumption of a signifi- permits the similarity to moschellandsbergite cant oxygen in bilibinskite. Hg8Ag5 with the same relation of atoms of differ- Due to small monoblocks (less than 10–15 ent species. The structure of moschellandsber- microns), the X-ray single crystal study and gite is similar to the disordered defect body-cen- determination of the structure of the mineral tered cubic superlattice of g-br a ss Zn 8Cu5 (Pe - were failed. The X-ray diffraction patterns of bili- arson, 1972). The X-ray diffraction data, elevated binskite and related bogdanovite (Fig. 4) are dif- hardness, and insignificant anisotropy of hard- ferent from that of gold (Berry, Thompson, 1962) ness are not consistent with the assumption of in additional reflections. On the basis of this fact, the layered structure of the mineral. these minerals are suggested to have superstruc- According the X-ray diffraction data of bog- tures produced from face-centered cubic lattice danovite, Au, Cu, Fe, and Ag are combined at of gold. The dimension of the primitive one structural site Me (core of the face-centered pseudocubic subcell of bilibinskite is ао' = cubic lattice), while Te, Pb, Sb, and Bi occupy 4.10 Å. The X-ray powder diffraction pattern of another site X (interstitial atoms) (Spiridonov et bilibinskite shows many additional weak and al., 1991). The chemical composition of bog- medium reflections in comparison with gold that danovite corresponds to the formula Au5(Cu,Fe)3 164 New Data on Minerals. 2011. Vol. 46

(Te,Pb)2, in other words Ме4Х. Therefore, bilibin- Chvileva, T.N., Bezsmertnaya, M.S., Spirido - skite is considered as plumbotelluride – stibio- nov, E.M. et al. Handbook-identification plumbotelluride of Au and Cu with the composi- guide of ore minerals in reflected light. tion of Ме8Х5. Nedra, Moscow. 1988 (In Russian). The formulae of bilibinskite from the Gromova, E.I. The composition of ores of one Aginskoe, Ozernovskoe, and Pionerskoe de - gold deposit. // Tr. Eastern Siberian Geol. posits calculated on the basis of 13 atoms are as Inst. 1959 V. 1. P. 1–112 (in Russian). follows: Harris D.C., Sinclar W.D., Thorpe R.J. Telluride

(Au4.82Cu2.82Ag0.28Fe0.07)7.99(Te3.69Pb1.18Se0.08Sb0.04Bi0.02)5.01; minerals from the Ashley deposit, Ban- (Au5.01Cu2.84Ag0.18Fe0.01)8.04(Te3.66Pb1.30)4.96; nockburn Township, Ontario. // Canad. (Au5.91Cu1.43Ag0.52Fe0.06)7.92(Te3.71Pb0.61Sb0.58Bi0.15Se0.03)5.08. Mineral. 1983. Vol. 21. P. 137–143. respectively. The composition of bilibinskite Markham, N.L. Synthetic and natural phases in from Aginskoe and Ozernovskoe is close to the system Au-Ag-Te. // Econ. Geol. 1960.

Au5Cu3(Te,Pb)5; from Pionerskoe, to Au6Cu2 Vol. 55. P. 1148–1178, 1460–1477. (Te,Pb,Sb)5; the generalized formula of the Pearson, W.B. Crystal chemistry and physics of mineral is (Au56Cu32)8 (Te,Pb,Sb)5. metals and alloys. Willey-Interscience, New A mineral, AuTeO3, with optical parameters York. 1972. similar to bilibinskite occurs in the cementation Sindeeva, N.D. , deposit types, and zone of the Aginskoe and Ozernovskoe deposits, major geochemical features of selenium and Kamchatka. The minerals similar to bilibinskite . Izd. AN SSSR, Moscow, 1959 (in but are different in composition and X-ray dif- Russian). fraction pattern occur at the Ashley deposit, Spiridonov, E.M. A review of mineralogy of gold Canada (Harris et al., 1983). in the leading types of Au mineralization. // In the oxidation zone bilibinskite (Au-Cu In: Gold of Kola Peninsula and neighbor plumbotelluride and stibiplumbotelluride) is areas. Kola Scientific Center, Russian unstable. It is replaced by the aggregates of fine- Academy of Sciences, Apatity. 2010. lamellar and sponge gold, balyakinite СuTeO3, P. 143–171 (in Russian). plumbotellurite PbTeO3, Cu-Pb oxytellurites, Spiridonov, E.M. Iron-rich bogdanovite, the cupriferous gold group minerals, and iron Au5CuFe2(Te,Pb)2, form the cementation hydroxides. zone of the aginskoe gold-telluride deposit, The bilibinskite group minerals in the Kamchatka. // New Data on Minerals. 2008. weathering profile are the direct prospecting V. 43. P. 143–145. guide to rich endogenic gold-telluride miner- Spiridonov, E.M. The composition and structure alization. of the bilibinskite-bogdanovite group miner- This study has been supported by the Russian als. // New Data on Minerals. 1991. V. 37. Foundation for Basic Researches (project no. P. 138–145 (in Russian). 10-05-0674). Spiridonov, E.M., Bezsmertnaya, M.S., Chvileva, T.N. Bilibinskite, a new mineral of gold-tel- References luride deposits. // Zap. VMO. 1978. V. 107, V. 3. P. 310–315 (in Russian). Andrusenko, N.I., Schepot'ev, Yu.M. Tem pe - Spiridonov, E.M., Chvileva, T.N. Antimony-rich rature and stages of formation of Au-Ag sub- bilibinskite (second finding of bilibinskite). volcanic deposits in the Central Kamchatka. // Dokl. AN SSSR. 1982. V. 265(6). Geokhimiya. 1974. No. 2. P. 179–186 (in P. 1243–1247 (in Russian). Russian). Spiridonov, E.M., Chvileva, T.N. Bezsmertnovite, Berry, L.G., Thompson, R.M. X-ray powder data Au4Cu(Te,Pb), a new mineral from the oxida- for ore minerals: the Peacock atlas. // Geol. tion zone of deposit in the Russian Far East. Soc. Amer. New York. 1962. Mem. 85. // Dokl. AN SSSR. 1979. V. 240(1). Borishanskaya, S.S. Tellurides in gold deposits of P. 185–189 (in Russian). the USSR and diagnostics of these minerals. Stillwell F.L. The occurence of telluride minerals Candidate diss. TSINIGRI, Moscow. 1946 (in at Kalgoorlie // Proc. Austral. Inst. Mining Russian). and Metall. 1931. № 84. P. 115–190.