2010/06/01 by Dan Topa, Emil Makovicky, H. Dittrich · 1 citation
Materials Science · Earth and Planetary Sciences · #Crystal Structures and Properties #Mineralogy and Gemology Studies #High-pressure geophysics and materials
paper · doi:10.3749/canmin.48.3.483
openalex publication_date 2010/06/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/07
The crystal structure of cannizzarite, ideally Pb 48 Bi 56 (S 124 Se 8 ) 132 , a fumarole sublimate from the La Fossa crater, on the island of Vulcano, Italy, with a nominal composition Pb 47.9 Bi 55.8 (S 121.8 Se 10.5 ) ∑132.3 and unit-cell parameters a 38.86(3), b 4.090(3), c 39.83(3) A, β 102.30(3)°, Z = 1, has been solved and refined in space group P 2 1 / m from X-ray single-crystal diffraction data, to an R 1 of 10.7% on the basis of 3612 unique reflections with [ F o > 4σ( F o )]; the data were collected on a Bruker P3 diffractometer with a CCD detector and Mo K α 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) PbS type that alternate with double-octahedron pseudohexagonal layers (H layers) of the (111) 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 48 X 48 for the Q layers, and Me 56 X 84 for the H layers. Selenium was found only in H layers. The structure determined represents the shorter of the two modules, Pb 12 Bi 14 S 33 and Pb 17 Bi 20 S 47 , found in the structure of synthetic cannizzarite proposed earlier, and proves their independent existence.