Crystal structure and physical properties of sophiite, Zn2(Se03)C12, a new mineral

• Main Authors: T. F. Semenova, I. V. Rozhdestvenskaya, S. K. Filatov, L. P. Vergasova
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: tenorite; CuO; cotunnite; PbCl2 (Semenova; Pyramid; Pyramid The; Tolbachik; Kamchatka
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.606.5089; http://www.minersoc.org/pages/Archive-MM/Volume_56/56-383-241.pdf

The crystal structure of sophiite, Zn2(SeO3)Cl 2 (a = 10.251(4), b = 15.223(2), c = 7.666(5) A, Z = 8) was solved in space group Pccn from single crystal X-ray data, and refined to R = 0.053 for 666 Fo> 4op,. The mineral belongs to layer compounds. The threefold coordinated Se atom is at the apex of a pyramid, the base of which is formed by three O atoms; Se-O = 1.69 ~. Zn cations occupy two positions with distorted tetrahedral nd octahedral coordinations. In the tetrahedra, Zn cations are surrounded by two O (2.02 A) and two Ci (2.224 ~) atoms. Zn octahedra contain four O atoms (2.07 A) and two CI atoms (2.701 ~). The atomic arrangement is characterized byrings containing two Se pyramids linked by their corners to two Zn tetrahedra. The rings are linked by their edges and corners to Zn octahedra toform layers parallel to (010). The layers are interconnected byresidual Van der Waals bonds. Experimental results on thermal phase transformations and deformations, crystal optics and other physical properties of sophiite are presented. A structural aspect of their anisotropy is discussed. KEYWOROS: sophiite, crystal structure, Tolbachik volcano, Kamchatka. Occurrence and paragenesis SOPHIITE is the first selenium-bearing mineral occurring as a result of fumarolic activity of the Tolbachik Main Fracture Eruption, Kamchatka, Russia (Fedotov, 1984). The mineral occurs at a temperature of 180-230 ~ on lava flows in the second slag cone of the North Break as well as in a fumarolic field of a slag cone of the South Break (Vergasova et al., 1989). Associated minerals are cotton-like hygroscopic emanations bearing zinc and chlorine which, together with sophiite, fill small fractures and interstices between clasts of igneous rocks. Besides ophiite and white cotton-like emanations, in products of fumarolic activity confined to linear subsidences in the second cone