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THE CRYSTAL STRUCTURE OF KAMPFITE

Laurel C. Basciano and Lee A. Groat^¶

Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada

^¶ E-mail address: lgroat{at}eos.ubc.ca

The crystal structure of kampfite, ideally Ba₁₂(Si₁₁Al₅)O₃₁(CO₃)₈Cl₅, a 31.2329(7), b 5.2398(1), c 9.0966(3) Å, β 106.933(2)°, V 1424.2(1) ų, Cc, Z = 1, has been solved by direct methods and refined to an R index of 2.3% for 2938 observed (|F_o| > 4F) reflections collected with a four-circle diffractometer using MoK radiation and a CCD detector. The kampfite structure is based on double layers of tetrahedra, [T₄O₈] , consisting of six-membered rings oriented parallel to (100). The layers of tetrahedra are connected by slabs of Ba polyhedra composed of a layer of BaO₆Cl₆ polyhedra, with all of the Ba and Cl atoms sharing a common plane parallel to (100), flanked on either side by a layer of BaO₉Cl polyhedra. The CO₃ groups lie between the layers of Ba polyhedra and are oriented approximately parallel to (100). The layering of TO₄ tetrahedra and Ba polyhedra is responsible for the perfect {100} cleavage of kampfite. Kampfite is part of the monteregianite-(Y) – wickenburgite series and is structurally and chemically similar to cymrite.

Keywords: kampfite, crystal structure, chemical formula, barium mineral.