• journal_title：The Canadian Mineralogist
• Contributor：Stanislav V. Borisov ; Natalie V. Pervukhina ; Svetlana A. Magarill ; Natalia V. Kuratieva ; Igor A. Bryzgalov ; Nadezhda N. Mozgova ; Ilya V. Chaplygin
• Publisher：Mineralogical Association of Canada
• Date：2012-
• Format：text/html
• Language：en
• Identifier：10.3749/canmin.50.2.387
• journal_abbrev：Can Mineral
• issn：0008-4476
• volume：50
• issue：2
• firstpage：387
• section：Articles

A (Cd,In)-rich variety of cannizzarite has been found in sublimates from high-temperature fumaroles of the Kudriavy volcano, on Iturup Island, Kurile Archipelago, Russia. An electron-microprobe analysis gave the unit formula (calculated on the basis of 14 anions): (Pb_3.54Cd_1.06)_∑4.60(Bi_5.45In_0.29)_∑5.74(S_13.30Se_0.70)_∑14. A single-crystal X-ray-diffraction study indicates a monoclinic symmetry, space group P2₁/m, with unit-cell parameters a 15.4172(9), b 4.0582(2), c 20.8071(12) Å, β 98.031(2)°, V 1289.05(12) ų, and Z = 2. Its crystal structure has been solved and refined to R₁ = 0.0504 on the basis of 3158 unique reflections. There are 25 atom positions, corresponding to 11 cations and 14 anions. Among cations, bond-valence calculations allow us to distinguish three Pb sites, two Bi sites, and six mixed sites. Selenium seems to concentrate at two specific S positions of the H layer. In the cannizzarite variable-fit series of the composite layer type, the two H and Q sublattices are here in the ratio 3H : 5Q, like in the synthetic isotypic selenide Pb₅Bi₆Se₁₄. The structural features of H and Q layers and the common pseudotranslational sublattices of cations and anions are examined. The distribution of Pb, Bi, Cd and In among the mixed sites is discussed; cadmium and In could not be differentiated. In the final proposal, the Q layer contains the three Pb sites, with two mixed (Pb,Bi) sites; the H layer contains the two Bi sites, one [Pb,Bi,(Cd,In)] site, and three [Bi,(Cd,In)] sites.