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The crystal structure of 7h:12Q cannizzarite from Vulcano, Italy

Dan Topa, Emil Makovicky and Herbert Dittrich
The crystal structure of 7h:12Q cannizzarite from Vulcano, Italy
The Canadian Mineralogist (June 2010) 48 (3): 483-495


The crystal structure of cannizzarite, ideally Pb (sub 48) Bi (sub 56) (S (sub 124) Se (sub 8) ) (sub 132) , a fumarole sublimate from the La Fossa crater, on the island of Vulcano, Italy, with a nominal composition Pb (sub 47.9) Bi (sub 55.8) (S (sub 121.8) Se (sub 10.5) ) (sub Sigma 132.3) and unit-cell parameters a 38.86(3), b 4.090(3), c 39.83(3) Aa, beta 102.30(3) degrees , Z=1, has been solved and refined in space group P2 (sub 1) /m from X-ray single-crystal diffraction data, to an R (sub 1) of 10.7% on the basis of 3612 unique reflections with [F (sub o) >4sigma (F (sub o) )]; the data were collected on a Bruker P3 diffractometer with a CCD detector and MoKalpha radiation. The cannizzarite crystal studied has 104 cations and 132 anions in a unit cell. Refinement shows that about eight anions per cell contents are selenium, the bulk being sulfur. The crystal structure is composed of pseudotetragonal layers (Q layers), two cation-anion planes thick, of the (100) (sub PbS) type that alternate with double-octahedron pseudohexagonal layers (H layers) of the (111) (sub PbS) type. Both types of layer contain Pb and Bi; their distribution was studied by means of bond-valence calculations, polyhedron characteristics and bond-length ratios of the opposing Me-anion bonds. The unit-cell contents are Me (sub 48) X (sub 48) for the Q layers, and Me (sub 56) X (sub 84) for the H layers. Selenium was found only in H layers. The structure determined represents the shorter of the two modules, Pb (sub 12) Bi (sub 14) S (sub 33) and Pb (sub 17) Bi (sub 20) S (sub 47) , found in the structure of synthetic cannizzarite proposed earlier, and proves their independent existence.

ISSN: 0008-4476
EISSN: 1499-1276
Coden: CAMIA6
Serial Title: The Canadian Mineralogist
Serial Volume: 48
Serial Issue: 3
Title: The crystal structure of 7h:12Q cannizzarite from Vulcano, Italy
Affiliation: Paris-Lodron University of Salzburg, Department of Materials Research and Physics, Salzburg, Austria
Pages: 483-495
Published: 201006
Text Language: English
Publisher: Mineralogical Association of Canada, Ottawa, ON, Canada
References: 33
Accession Number: 2010-080780
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
N38°19'60" - N38°25'00", E14°52'00" - E15°00'00"
Secondary Affiliation: University of Copenhagen, DNK, Denmark
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Association of Canada. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201043
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